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Kitaguchi S, Imai K, Hashimoto N, Fujii K, Yamauchi-Kawaura C, Mizutani T. Devising a novel evaluation method for computed tomography images containing metal artifacts from titanium seed implants: Application to virtual monochromatic imaging energy optimization. Radiography (Lond) 2025; 31:102944. [PMID: 40199192 DOI: 10.1016/j.radi.2025.102944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2024] [Revised: 03/18/2025] [Accepted: 03/21/2025] [Indexed: 04/10/2025]
Abstract
INTRODUCTION Metal artifact reduction (MAR) technology cannot fully eliminate metal artifacts from metallic devices in computed tomography (CT) images. Hence, it is important to investigate the optimal acquisition parameters and post-processing techniques. This study aimed to devise a novel evaluation method for images containing metal artifacts from titanium seed implants and identify the optimal energy level for virtual monochromatic imaging (VMI) to reduce metal artifacts and enhance signal detectability. METHODS Post-brachytherapy CT scans are a clinical example of the effects of metal artifacts. Therefore, we focused on the pelvic region, including the prostate, and created a phantom with simulated radioactive seeds that were inserted into the prostate region. We investigated the relationship between metal artifacts and monochromatic energy levels (35-200 keV at 5 keV intervals) using a dual-energy CT system with deep learning (DL) and MAR algorithms. Metal artifacts were investigated using the Gumbel evaluation method, which quantitatively evaluates artifacts, and contrast detectability was assessed using the contrast-to-noise ratio (CNR) and a newly devised contrast-to-artifact ratio (CAR). RESULTS The location parameter, representing the physical index of metal artifacts, was the lowest at 65 keV. CNR and CAR achieved the highest signal detectability at 70 and 65 keV, respectively. VMI at 65 keV provided an optimal balance. When two images with similar CNR values were assessed using CAR, the resulting difference aligned consistently with the visual evaluation findings. CONCLUSIONS VMI at 65 keV with DL and MAR reconstructions is the optimal acquisition parameter for reducing metal artifacts and improving signal detectability. Additionally, CAR can be used to evaluate images affected by metal artifacts. IMPLICATIONS FOR PRACTICE CAR is useful for evaluating the effect of metal artifacts on signal detection.
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Affiliation(s)
- S Kitaguchi
- Department of Integrated Health Sciences, Nagoya University Graduate School of Medicine, 1-1-20, Daiko-Minami, Higashi-ku, Nagoya, Aichi 461-8673, Japan; Department of Central Radiology, Kindai University Hospital, 377-2 Ohno-Higashi, Osakasayama, Osaka 589-8511, Japan.
| | - K Imai
- Department of Integrated Health Sciences, Nagoya University Graduate School of Medicine, 1-1-20, Daiko-Minami, Higashi-ku, Nagoya, Aichi 461-8673, Japan.
| | - N Hashimoto
- Department of Central Radiology, Kindai University Hospital, 377-2 Ohno-Higashi, Osakasayama, Osaka 589-8511, Japan.
| | - K Fujii
- Department of Integrated Health Sciences, Nagoya University Graduate School of Medicine, 1-1-20, Daiko-Minami, Higashi-ku, Nagoya, Aichi 461-8673, Japan.
| | - C Yamauchi-Kawaura
- Department of Integrated Health Sciences, Nagoya University Graduate School of Medicine, 1-1-20, Daiko-Minami, Higashi-ku, Nagoya, Aichi 461-8673, Japan.
| | - T Mizutani
- Department of Central Radiology, Kindai University Hospital, 377-2 Ohno-Higashi, Osakasayama, Osaka 589-8511, Japan.
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Lam FC, Guru S, AbuReesh D, Hori YS, Chuang C, Liu L, Wang L, Gu X, Szalkowski GA, Wang Z, Wohlers C, Tayag A, Emrich SC, Ustrzynski L, Zygourakis CC, Desai A, Hayden Gephart M, Byun J, Pollom EL, Rahimy E, Soltys S, Park DJ, Chang SD. Use of Carbon Fiber Implants to Improve the Safety and Efficacy of Radiation Therapy for Spine Tumor Patients. Brain Sci 2025; 15:199. [PMID: 40002531 PMCID: PMC11852773 DOI: 10.3390/brainsci15020199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2024] [Revised: 01/22/2025] [Accepted: 02/13/2025] [Indexed: 02/27/2025] Open
Abstract
Current standard of care treatment for patients with spine tumors includes multidisciplinary approaches, including the following: (1) surgical tumor debulking, epidural spinal cord decompression, and spine stabilization techniques; (2) systemic chemo/targeted therapies; (3) radiation therapy; and (4) surveillance imaging for local disease control and recurrence. Titanium pedicle screw and rod fixation have become commonplace in the spine surgeon's armamentarium for the stabilization of the spine following tumor resection and separation surgery. However, the high degree of imaging artifacts seen with titanium implants on postoperative CT and MRI scans can significantly hinder the accurate delineation of vertebral anatomy and adjacent neurovascular structures to allow for the safe and effective planning of downstream radiation therapies and detection of disease recurrence. Carbon fiber-reinforced polyetheretherketone (CFR-PEEK) spine implants have emerged as a promising alternative to titanium due to the lack of artifact signals on CT and MRI, allowing for more accurate and safe postoperative radiation planning. In this article, we review the tenants of the surgical and radiation management of spine tumors and discuss the safety, efficacy, and current limitations of CFR-PEEK spine implants in the multidisciplinary management of spine oncology patients.
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Affiliation(s)
- Fred C. Lam
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA 94305, USA; (F.C.L.); (S.G.); (D.A.); (Y.S.H.); (A.T.); (S.C.E.); (L.U.); (A.D.); (M.H.G.); (D.J.P.)
| | - Santosh Guru
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA 94305, USA; (F.C.L.); (S.G.); (D.A.); (Y.S.H.); (A.T.); (S.C.E.); (L.U.); (A.D.); (M.H.G.); (D.J.P.)
| | - Deyaldeen AbuReesh
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA 94305, USA; (F.C.L.); (S.G.); (D.A.); (Y.S.H.); (A.T.); (S.C.E.); (L.U.); (A.D.); (M.H.G.); (D.J.P.)
| | - Yusuke S. Hori
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA 94305, USA; (F.C.L.); (S.G.); (D.A.); (Y.S.H.); (A.T.); (S.C.E.); (L.U.); (A.D.); (M.H.G.); (D.J.P.)
| | - Cynthia Chuang
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305, USA; (C.C.); (L.L.); (L.W.); (X.G.); (G.A.S.); (Z.W.); (C.W.); (J.B.); (E.L.P.); (E.R.); (S.S.)
| | - Lianli Liu
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305, USA; (C.C.); (L.L.); (L.W.); (X.G.); (G.A.S.); (Z.W.); (C.W.); (J.B.); (E.L.P.); (E.R.); (S.S.)
| | - Lei Wang
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305, USA; (C.C.); (L.L.); (L.W.); (X.G.); (G.A.S.); (Z.W.); (C.W.); (J.B.); (E.L.P.); (E.R.); (S.S.)
| | - Xuejun Gu
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305, USA; (C.C.); (L.L.); (L.W.); (X.G.); (G.A.S.); (Z.W.); (C.W.); (J.B.); (E.L.P.); (E.R.); (S.S.)
| | - Gregory A. Szalkowski
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305, USA; (C.C.); (L.L.); (L.W.); (X.G.); (G.A.S.); (Z.W.); (C.W.); (J.B.); (E.L.P.); (E.R.); (S.S.)
| | - Ziyi Wang
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305, USA; (C.C.); (L.L.); (L.W.); (X.G.); (G.A.S.); (Z.W.); (C.W.); (J.B.); (E.L.P.); (E.R.); (S.S.)
| | - Christopher Wohlers
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305, USA; (C.C.); (L.L.); (L.W.); (X.G.); (G.A.S.); (Z.W.); (C.W.); (J.B.); (E.L.P.); (E.R.); (S.S.)
| | - Armine Tayag
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA 94305, USA; (F.C.L.); (S.G.); (D.A.); (Y.S.H.); (A.T.); (S.C.E.); (L.U.); (A.D.); (M.H.G.); (D.J.P.)
| | - Sara C. Emrich
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA 94305, USA; (F.C.L.); (S.G.); (D.A.); (Y.S.H.); (A.T.); (S.C.E.); (L.U.); (A.D.); (M.H.G.); (D.J.P.)
| | - Louisa Ustrzynski
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA 94305, USA; (F.C.L.); (S.G.); (D.A.); (Y.S.H.); (A.T.); (S.C.E.); (L.U.); (A.D.); (M.H.G.); (D.J.P.)
| | - Corinna C. Zygourakis
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA 94305, USA; (F.C.L.); (S.G.); (D.A.); (Y.S.H.); (A.T.); (S.C.E.); (L.U.); (A.D.); (M.H.G.); (D.J.P.)
| | - Atman Desai
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA 94305, USA; (F.C.L.); (S.G.); (D.A.); (Y.S.H.); (A.T.); (S.C.E.); (L.U.); (A.D.); (M.H.G.); (D.J.P.)
| | - Melanie Hayden Gephart
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA 94305, USA; (F.C.L.); (S.G.); (D.A.); (Y.S.H.); (A.T.); (S.C.E.); (L.U.); (A.D.); (M.H.G.); (D.J.P.)
| | - John Byun
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305, USA; (C.C.); (L.L.); (L.W.); (X.G.); (G.A.S.); (Z.W.); (C.W.); (J.B.); (E.L.P.); (E.R.); (S.S.)
| | - Erqi Liu Pollom
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305, USA; (C.C.); (L.L.); (L.W.); (X.G.); (G.A.S.); (Z.W.); (C.W.); (J.B.); (E.L.P.); (E.R.); (S.S.)
| | - Elham Rahimy
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305, USA; (C.C.); (L.L.); (L.W.); (X.G.); (G.A.S.); (Z.W.); (C.W.); (J.B.); (E.L.P.); (E.R.); (S.S.)
| | - Scott Soltys
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305, USA; (C.C.); (L.L.); (L.W.); (X.G.); (G.A.S.); (Z.W.); (C.W.); (J.B.); (E.L.P.); (E.R.); (S.S.)
| | - David J. Park
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA 94305, USA; (F.C.L.); (S.G.); (D.A.); (Y.S.H.); (A.T.); (S.C.E.); (L.U.); (A.D.); (M.H.G.); (D.J.P.)
| | - Steven D. Chang
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA 94305, USA; (F.C.L.); (S.G.); (D.A.); (Y.S.H.); (A.T.); (S.C.E.); (L.U.); (A.D.); (M.H.G.); (D.J.P.)
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Suzuki C, Matsubara K, Ujihara Y, Isogai K. Dual-energy metal artefact reduction for iodine-125 seed identification in postimplant CT after prostate brachytherapy. Br J Radiol 2025; 98:271-279. [PMID: 39495147 DOI: 10.1093/bjr/tqae225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2024] [Revised: 10/25/2024] [Accepted: 10/29/2024] [Indexed: 11/05/2024] Open
Abstract
OBJECTIVES To assess the metal artefact reductions of dual-energy CT high-energy virtual monochromatic images (VMI) combined with the Single-Energy Metal Artifact Reduction (SEMAR) (CANON MEDICAL SYSTEMS, Otawara, Japan) processing techniques for iodine (I)-125 seed identification in postimplant CT after prostate brachytherapy. METHODS Dual-energy acquisition with fast tube voltage switching was performed on a prostate phantom with simulated seeds and six clinical cases treated with I-125 prostate brachytherapy. The images were retrospectively reconstructed at VMI energy levels of 65-200 keV and with and without SEMAR (SEMAR and non-SEMAR images). To estimate seed swelling, the calibre of iodine-125 seed was calculated as the full width at half maximum. The metal artefacts were evaluated using the artefact index (AI). The dose distributions were calculated and were compared among the high-energy VMI (SEMAR and non-SEMAR images) and low-energy VMI (SEMAR images). RESULTS The blooming artefacts decreased at higher energy levels. In addition, the SEMAR process markedly reduced AI, which helped reduce overestimation of high dose ranges in the treatment planning dose map. CONCLUSIONS The locations and number of iodine-125 seed were clearly identified in the dose distribution map of the treatment planning using 200 keV VMI with SEMAR. ADVANCES IN KNOWLEDGE The high-energy VMI of the dual-energy CT in combination with SEMAR is appropriate for the postimplant planning process of I-125 prostate brachytherapy.
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Affiliation(s)
- Chiaki Suzuki
- Department of Diagnostic Radiology, Seirei Mikatahara Hospital, Seirei Social Welfare Community, Hamamatsu, 4338558, Japan
- Division of Health Sciences, Graduate School of Medical Science, Kanazawa University, Kanazawa, 920-0942, Japan
| | - Kosuke Matsubara
- Faculty of Health Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa UniversityKanazawa, 920-0942, Japan
| | - Yuta Ujihara
- Department of Diagnostic Radiology, Seirei Mikatahara Hospital, Seirei Social Welfare Community, Hamamatsu, 4338558, Japan
| | - Kenta Isogai
- Department of Diagnostic Radiology, Seirei Mikatahara Hospital, Seirei Social Welfare Community, Hamamatsu, 4338558, Japan
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Kleber CEJ, Karius R, Naessens LE, Van Toledo CO, A C van Osch J, Boomsma MF, Heemskerk JWT, van der Molen AJ. Advancements in supervised deep learning for metal artifact reduction in computed tomography: A systematic review. Eur J Radiol 2024; 181:111732. [PMID: 39265203 DOI: 10.1016/j.ejrad.2024.111732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2024] [Revised: 08/23/2024] [Accepted: 09/05/2024] [Indexed: 09/14/2024]
Abstract
BACKGROUND Metallic artefacts caused by metal implants, are a common problem in computed tomography (CT) imaging, degrading image quality and diagnostic accuracy. With advancements in artificial intelligence, novel deep learning (DL)-based metal artefact reduction (MAR) algorithms are entering clinical practice. OBJECTIVE This systematic review provides an overview of the performance of the current supervised DL-based MAR algorithms for CT, focusing on three different domains: sinogram, image, and dual domain. METHODS A literature search was conducted in PubMed, EMBASE, Web of Science, and Scopus. Outcomes were assessed using peak signal-to-noise ratio (PSNR) and structural similarity index measure (SSIM) or any other objective measure comparing MAR performance to uncorrected images. RESULTS After screening, fourteen studies were selected that compared DL-based MAR-algorithms with uncorrected images. MAR-algorithms were categorised into the three domains. Thirteen MAR-algorithms showed a higher PSNR and SSIM value compared to the uncorrected images and to non-DL MAR-algorithms. One study showed statistically significant better MAR performance on clinical data compared to the uncorrected images and non-DL MAR-algorithms based on Hounsfield unit calculations. CONCLUSION DL MAR-algorithms show promising results in reducing metal artefacts, but standardised methodologies are needed to evaluate DL-based MAR-algorithms on clinical data to improve comparability between algorithms. CLINICAL RELEVANCE STATEMENT Recent studies highlight the effectiveness of supervised Deep Learning-based MAR-algorithms in improving CT image quality by reducing metal artefacts in the sinogram, image and dual domain. A systematic review is needed to provide an overview of newly developed algorithms.
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Affiliation(s)
- Cecile E J Kleber
- Department of Clinical Technology, Faculty of Mechanical Engineering, Delft University of Technology, Delft, the Netherlands
| | - Ramez Karius
- Department of Clinical Technology, Faculty of Mechanical Engineering, Delft University of Technology, Delft, the Netherlands
| | - Lucas E Naessens
- Department of Clinical Technology, Faculty of Mechanical Engineering, Delft University of Technology, Delft, the Netherlands
| | - Coen O Van Toledo
- Department of Clinical Technology, Faculty of Mechanical Engineering, Delft University of Technology, Delft, the Netherlands
| | | | | | - Jan W T Heemskerk
- Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Aart J van der Molen
- Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands.
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Isabelle Choi J, Wojcieszynski A, Amos RA, Giap H, Apisarnthanarax S, Ashman JB, Anand A, Perles LA, Williamson T, Ramkumar S, Molitoris J, Simone CB, Chuong MD. PTCOG Gastrointestinal Subcommittee Lower Gastrointestinal Tract Malignancies Consensus Statement. Int J Part Ther 2024; 11:100019. [PMID: 38757077 PMCID: PMC11095104 DOI: 10.1016/j.ijpt.2024.100019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Accepted: 01/02/2024] [Indexed: 05/18/2024] Open
Abstract
Purpose Radiotherapy delivery in the definitive management of lower gastrointestinal (LGI) tract malignancies is associated with substantial risk of acute and late gastrointestinal (GI), genitourinary, dermatologic, and hematologic toxicities. Advanced radiation therapy techniques such as proton beam therapy (PBT) offer optimal dosimetric sparing of critical organs at risk, achieving a more favorable therapeutic ratio compared with photon therapy. Materials and Methods The international Particle Therapy Cooperative Group GI Subcommittee conducted a systematic literature review, from which consensus recommendations were developed on the application of PBT for LGI malignancies. Results Eleven recommendations on clinical indications for which PBT should be considered are presented with supporting literature, and each recommendation was assessed for level of evidence and strength of recommendation. Detailed technical guidelines pertaining to simulation, treatment planning and delivery, and image guidance are also provided. Conclusion PBT may be of significant value in select patients with LGI malignancies. Additional clinical data are needed to further elucidate the potential benefits of PBT for patients with anal cancer and rectal cancer.
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Affiliation(s)
- J. Isabelle Choi
- Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, New York, USA
- New York Proton Center, New York, New York, USA
| | | | - Richard A. Amos
- Department of Medical Physics & Biomedical Engineering, University College London, London, UK
| | - Huan Giap
- Medical University of South Carolina, Charleston, South Carolina, USA
| | - Smith Apisarnthanarax
- Department of Radiation Oncology, University of Washington, Seattle, Washington, USA
| | | | - Aman Anand
- Department of Radiation Oncology, Mayo Clinic, Scottsdale, Arizona, USA
| | - Luis A. Perles
- Department of Radiation Physics, UT MD Anderson Cancer Center, Houston, Texas, USA
| | - Tyler Williamson
- Department of Radiation Physics, UT MD Anderson Cancer Center, Houston, Texas, USA
| | | | - Jason Molitoris
- Department of Radiation Oncology, University of Maryland Medical Center, Baltimore, Maryland, USA
| | - Charles B. Simone
- Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, New York, USA
- New York Proton Center, New York, New York, USA
| | - Michael D. Chuong
- Department of Radiation Oncology, Miami Cancer Institute, Miami, Florida, USA
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Li B, Huang J, Ruan J, Peng Q, Huang S, Li Y, Li F. Dosimetric impact of CT metal artifact reduction for spinal implants in stereotactic body radiotherapy planning. Quant Imaging Med Surg 2023; 13:8290-8302. [PMID: 38106297 PMCID: PMC10721987 DOI: 10.21037/qims-23-442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Accepted: 09/14/2023] [Indexed: 12/19/2023]
Abstract
Background Metal artifacts due to spinal implants may affect the accuracy of dose calculation for radiotherapy. However, the dosimetric impact of metal artifact reduction (MAR) for spinal implants in stereotactic body radiotherapy (SBRT) plans has not been well studied. The objective of this study was to evaluate the dosimetric impact of MAR in spinal SBRT planning with three clinically common dose calculation algorithms. Methods Gammex phantom and 10 patients' computed tomography (CT) images were studied to investigate the effects of titanium implants. A commercial orthopedic MAR algorithm was employed to reduce artifacts. Dose calculations for SBRT were conducted on both artifact-corrected and uncorrected images using three commercial algorithms [analytical anisotropic algorithm (AAA), Acuros XB (AXB), and Monte Carlo (MC)]. Dose discrepancies between artifact-corrected and uncorrected cases were appraised using a dose-volume histogram (DVH) and 3-dimensional (3D) gamma analysis with different distance to agreement (DTA) and dose difference criteria. The gamma agreement index (GAI) was denoted as G(∆D, DTA). Statistical analysis of t-test was utilized to evaluate the dose differences of different algorithms. Results The phantom study demonstrated that titanium metal artifacts can be effectively reduced. The patient cases study showed that dose differences between the artifact-corrected and uncorrected datasets were small evaluated by gamma index and DVH. Gamma analysis found that even the strict criterion local G(1,1) had average values ≥93.9% for the three algorithms. For all DVH metrics, average differences did not exceed 0.7% in planning target volume (PTV) and 2.1% in planning risk volume of spinal cord (PRV-SC). Statistical analysis showed that the observed dose differences of MC method were significantly larger than those of AAA (P<0.01 for D98% of PTV and P<0.001 for D0.1cc of spinal cord) and AXB methods (P<0.001 for D98% and P<0.0001 for D0.1cc). Conclusions Dosimetric impact of artifacts caused by titanium implants is not significant in spinal SBRT planning, which indicates that dose calculation algorithms might not be very sensitive to CT number variation caused by titanium inserts.
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Affiliation(s)
- Bin Li
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Jiexing Huang
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
- Department of Radiation Oncology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Junjie Ruan
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Qinghe Peng
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Sijuan Huang
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Yunfei Li
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Fanghua Li
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
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Clunk MJ, Gonzalez MR, Denwood HM, Werenski JO, Sodhi A, Hoffman BA, Merchan N, Lozano-Calderon SA. A PEEK into carbon fiber: A practical guide for high performance composite polymeric implants for orthopaedic oncology. J Orthop 2023; 45:13-18. [PMID: 37822644 PMCID: PMC10562613 DOI: 10.1016/j.jor.2023.09.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Accepted: 09/25/2023] [Indexed: 10/13/2023] Open
Abstract
Introduction The use of carbon fiber implants in orthopaedic oncology has increased within recent years. The most widely used type of polymer is carbon fiber polyether ether ketone (CF-PEEK). Its radiolucency enables targeted radiotherapy and artifact-free tumor surveillance, which provides major advantages over metallic hardware. We aim to summarize the unique benefits within orthopaedic oncology, clinical pitfalls, and recent advancements. Methods Four representative patient cases from a single tertiary academic medical center were treated with carbon fiber implants (n = 2 nails, n = 2 plates) from 2021 to 2022. Results There were no adverse events noted during intraoperative implantation or postoperative follow up. All patients reported improvements in pain and no difficulties in ambulation. There were no instances of catastrophic failure or implant loosening. Conclusion CF implants offer a diverse array of advantages regarding its radiolucency, low scatter density, and bioinert profile. Nonetheless, further research is required to understand the long-term surgical outcomes and robustness of CF implants. Multi institutional trials could address important aspects of durability and stability over extended periods, feasibility and ease-of-use for different anatomical sites and bone quality, as well as cost-effectiveness in post-operative imaging, healthcare resource utilization, and revision rates. Providing orthopaedic surgeons with valuable insight will enable thorough clinically supported, informed decision making regarding optimal use of implants.
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Affiliation(s)
- Marilee J. Clunk
- Musculoskeletal Oncology Service, Department of Orthopaedic Surgery, Massachusetts General Hospital Boston, MA, 02114, USA
- University of Toledo College of Medicine and Life Sciences Toledo, OH, 43614, USA
| | - Marcos R. Gonzalez
- Musculoskeletal Oncology Service, Department of Orthopaedic Surgery, Massachusetts General Hospital Boston, MA, 02114, USA
| | - Hayley M. Denwood
- Musculoskeletal Oncology Service, Department of Orthopaedic Surgery, Massachusetts General Hospital Boston, MA, 02114, USA
- Boston University Chobanian and Avedisian School of Medicine Boston, MA, 02118, USA
| | - Joseph O. Werenski
- Musculoskeletal Oncology Service, Department of Orthopaedic Surgery, Massachusetts General Hospital Boston, MA, 02114, USA
| | - Alisha Sodhi
- Musculoskeletal Oncology Service, Department of Orthopaedic Surgery, Massachusetts General Hospital Boston, MA, 02114, USA
| | - Brett A. Hoffman
- University of Toledo College of Medicine and Life Sciences Toledo, OH, 43614, USA
| | - Nelson Merchan
- Musculoskeletal Oncology Service, Department of Orthopaedic Surgery, Massachusetts General Hospital Boston, MA, 02114, USA
| | - Santiago A. Lozano-Calderon
- Musculoskeletal Oncology Service, Department of Orthopaedic Surgery, Massachusetts General Hospital Boston, MA, 02114, USA
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Anhaus JA, Killermann P, Mahnken AH, Hofmann C. A nonlinear scaling-based normalized metal artifact reduction to reduce low-frequency artifacts in energy-integrating and photon-counting CT. Med Phys 2023; 50:4721-4733. [PMID: 37202918 DOI: 10.1002/mp.16461] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Revised: 04/01/2023] [Accepted: 04/30/2023] [Indexed: 05/20/2023] Open
Abstract
BACKGROUND Metal within the scan plane can cause severe artifacts when reconstructing X-ray computed tomography (CT) scans. Both in clinical use and recent research, normalized metal artifact reduction (NMAR) has established as the reference method for correcting metal artifacts, but NMAR introduces inconsistencies within the sinogram, which can cause additional low-frequency artifacts after image reconstruction. PURPOSE This paper introduces an extension to NMAR by applying a nonlinear scaling function (NLS-NMAR) to reduce low-frequency artifacts, which get introduced by the reconstruction of interpolation-edge-related sinogram inconsistencies in the normalized sinogram domain. METHODS After linear interpolation of the metal trace, an NLS function is applied in the prior-normalized sinogram domain to reduce the impact of the interpolation edges during filtered backprojection. After sinogram denormalization and image reconstruction, the low frequencies of the NLS image are combined with different high frequencies to restore anatomic details. An anthropomorphic dental phantom with removable metal inserts was utilized on two different CT systems to quantitatively assess the artifact reduction performance in terms of HU deviations and the root-mean-square-error within relevant regions of interest. Clinical dental examples were assessed to qualitatively demonstrate the problem of the interpolation-related blooming as well as to demonstrate the performance of the NLS function to reduce respective artifacts. To quantitatively prove HU consistency, HU values were assessed in central ROIs in the clinical cases. In addition, single clinical cases of a hip replacement and pedicle screws in the spine are shown to demonstrate the method's results in other body regions. RESULTS The NLS-NMAR can minimize the effect of interpolation-related sinogram inconsistencies and thus reduce resulting hyperdense blooming artifacts. In the phantom results, the reconstructions with the NLS-NMAR-corrected low frequencies demonstrate the lowest error. In the qualitative assessment of the clinical data, the NLS-NMAR shows a tremendous enhancement in image quality, also performing best within all assessed images series. CONCLUSION The NLS-NMAR provides a small yet effective extension to conventional NMAR by reducing low-frequency hyperdense metal trace-interpolation-related artifacts in computed tomography.
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Affiliation(s)
- Julian A Anhaus
- Siemens Healthineers, CT Physics, Forchheim, Germany
- Philipps-University Marburg, Marburg, Germany
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Selles M, Slotman DJ, van Osch JAC, Nijholt IM, Wellenberg RHH, Maas M, Boomsma MF. Is AI the way forward for reducing metal artifacts in CT? development of a generic deep learning-based method and initial evaluation in patients with sacroiliac joint implants. Eur J Radiol 2023; 163:110844. [PMID: 37119708 DOI: 10.1016/j.ejrad.2023.110844] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 04/13/2023] [Accepted: 04/17/2023] [Indexed: 05/01/2023]
Abstract
PURPOSE To develop a deep learning-based metal artifact reduction technique (dl-MAR) and quantitatively compare metal artifacts on dl-MAR-corrected CT-images, orthopedic metal artifact reduction (O-MAR)-corrected CT-images and uncorrected CT-images after sacroiliac (SI) joint fusion. METHODS dl-MAR was trained on CT-images with simulated metal artifacts. Pre-surgery CT-images and uncorrected, O-MAR-corrected and dl-MAR-corrected post-surgery CT-images of twenty-five patients undergoing SI joint fusion were retrospectively obtained. Image registration was applied to align pre-surgery with post-surgery CT-images within each patient, allowing placement of regions of interest (ROIs) on the same anatomical locations. Six ROIs were placed on the metal implant and the contralateral side in bone lateral of the SI joint, the gluteus medius muscle and the iliacus muscle. Metal artifacts were quantified as the difference in Hounsfield units (HU) between pre- and post-surgery CT-values within the ROIs on the uncorrected, O-MAR-corrected and dl-MAR-corrected images. Noise was quantified as standard deviation in HU within the ROIs. Metal artifacts and noise in the post-surgery CT-images were compared using linear multilevel regression models. RESULTS Metal artifacts were significantly reduced by O-MAR and dl-MAR in bone (p < 0.001), contralateral bone (O-MAR: p = 0.009; dl-MAR: p < 0.001), gluteus medius (p < 0.001), contralateral gluteus medius (p < 0.001), iliacus (p < 0.001) and contralateral iliacus (O-MAR: p = 0.024; dl-MAR: p < 0.001) compared to uncorrected images. Images corrected with dl-MAR resulted in stronger artifact reduction than images corrected with O-MAR in contralateral bone (p < 0.001), gluteus medius (p = 0.006), contralateral gluteus medius (p < 0.001), iliacus (p = 0.017), and contralateral iliacus (p < 0.001). Noise was reduced by O-MAR in bone (p = 0.009) and gluteus medius (p < 0.001) while noise was reduced by dl-MAR in all ROIs (p < 0.001) in comparison to uncorrected images. CONCLUSION dl-MAR showed superior metal artifact reduction compared to O-MAR in CT-images with SI joint fusion implants.
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Affiliation(s)
- Mark Selles
- Department of Radiology, Isala, 8025 AB Zwolle, the Netherlands; Department of Radiology & Nuclear medicine, Amsterdam University Medical Centre, 1105 AZ Amsterdam, the Netherlands; Amsterdam Movement Sciences, 1081 BT Amsterdam, the Netherlands.
| | - Derk J Slotman
- Department of Radiology, Isala, 8025 AB Zwolle, the Netherlands
| | | | | | - Ruud H H Wellenberg
- Department of Radiology & Nuclear medicine, Amsterdam University Medical Centre, 1105 AZ Amsterdam, the Netherlands; Amsterdam Movement Sciences, 1081 BT Amsterdam, the Netherlands
| | - Mario Maas
- Department of Radiology & Nuclear medicine, Amsterdam University Medical Centre, 1105 AZ Amsterdam, the Netherlands; Amsterdam Movement Sciences, 1081 BT Amsterdam, the Netherlands
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Meng Q, Li J, Jiang W, Hu B, Xu F, Shi X, Zhong R. Prediction of proton beam range in phantom with metals based on monochromatic energy CT images. JOURNAL OF RADIATION RESEARCH 2022; 63:828-837. [PMID: 36109316 PMCID: PMC9726739 DOI: 10.1093/jrr/rrac051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 05/30/2022] [Indexed: 06/15/2023]
Abstract
The purpose of the study was to evaluate the accuracy of monochromatic energy (MonoE) computed tomography (CT) images reconstructed by spectral CT in predicting the stopping power ratio $( SP{R}_w)$ of materials in the presence of metal. The CIRS062 phantom was scanned three times using spectral CT. In the first scan, a solid water insert was placed at the center of the phantom $(C{T}_{no\ metal})$. In the second scan, the solid water insert was replaced with a titanium alloy femoral head $(C{T}_{metal})$. The metal artifact reduction (MAR) algorithm was used in the last scan $(C{T}_{metal+ MAR})$. The MonoE-CT images of 40 keV and 80 keV were reconstructed. Finally, the single-energy CT method (SECT) and the dual-energy CT method (DECT) were used to calculate the $SP{R}_w$. The mean absolute error (MAE) of the $SP{R}_w$ of the inner layer inserts calculated by the SECT method were 3.19%, 13.88% and 2.71%, corresponding to $C{T}_{no\ metal}$, $C{T}_{metal}$ and $C{T}_{metal+ MAR}$, respectively. For the outer layer inserts, the MAE of $SP{R}_w$ were 3.43%, 5.42% and 2.99%, respectively. Using the DECT method, the MAE of the $SP{R}_w$ of the inner layer inserts was 1.30%, 3.69% and 1.46% and the MAE of the outer layer inserts- was 1.34%, 1.36% and 1.05%. The studies shows that, compared with the SECT method, the accuracy of the DECT method in predicting the $SP{R}_w$ of a material is more robust to the presence of metal. Using the MAR algorithm when performing CT scans can further improve the accuracy of predicting the SPR of materials in the presence of metal.
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Affiliation(s)
- Qianqian Meng
- Radiophysical Technology Center, Cancer Center, West China Hospital, Sichuan University, Chengdu, 610041, China
| | - Jing Li
- Radiophysical Technology Center, Cancer Center, West China Hospital, Sichuan University, Chengdu, 610041, China
| | - Wei Jiang
- Department of Radiotherapy, Yantai Yuhuangding Hospital, Yantai, 264000, China
- Academy of Medical Engineering and Translational Medicine, Department of Biomedical Engineering, School of Precision Instrument and Opto-electronics Engineering, Tianjin University, Tianjin, 300072, China
| | - Birong Hu
- Department of Radiotherapy, Chengdu Second People’s Hospital, Chengdu, 610021, China
| | - Feng Xu
- Lung Cancer Center & Institute, West China Hospital, Sichuan University, Chengdu, 610041, China
| | - Xiaomeng Shi
- CT Imaging Research Center, GE Healthcare China, Shanghai, 201203, China
| | - Renming Zhong
- Radiophysical Technology Center, Cancer Center, West China Hospital, Sichuan University, Chengdu, 610041, China
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King J, Whittam S, Smith D, Al-Qaisieh B. The Impact of a Metal Artefact Reduction Algorithm on Treatment Planning for Patients Undergoing Radiotherapy of the Pelvis. Phys Imaging Radiat Oncol 2022; 24:138-143. [DOI: 10.1016/j.phro.2022.11.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 11/08/2022] [Accepted: 11/08/2022] [Indexed: 11/13/2022] Open
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Yang XZ, Li PY, Zhang BH, Yan ZG, Niu GC, Yang M. Contrast-enhanced magnetic resonance angiography for monitoring an embolized renal artery aneurysm: A case report and literature review. J Int Med Res 2022; 50:3000605221136711. [DOI: 10.1177/03000605221136711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
This case report describes a 69-year-old male patient with a renal artery aneurysm that was followed up with contrast-enhanced magnetic resonance angiography at 8 months after coil embolization treatment. Due to the disappearance of residual lumen with few metal artifacts, the therapeutic effect was satisfactory. At present, the indications for the treatment of renal artery aneurysms are still controversial and there are very few reports of postembolization images of renal artery aneurysms, with no criteria for reintervention and few reports for monitoring the embolized aneurysms. Further reports and research are still needed for the treatment of this rare disease.
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Affiliation(s)
- Xin-Zhi Yang
- Department of Interventional Radiology and Vascular Surgery, Peking University First Hospital, Beijing, China
| | - Peng-Yu Li
- Department of Interventional Radiology and Vascular Surgery, Peking University First Hospital, Beijing, China
| | - Bi-Hui Zhang
- Department of Interventional Radiology and Vascular Surgery, Peking University First Hospital, Beijing, China
| | - Zi-Guang Yan
- Department of Interventional Radiology and Vascular Surgery, Peking University First Hospital, Beijing, China
| | - Guo-Chen Niu
- Department of Interventional Radiology and Vascular Surgery, Peking University First Hospital, Beijing, China
| | - Min Yang
- Department of Interventional Radiology and Vascular Surgery, Peking University First Hospital, Beijing, China
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Anhaus JA, Killermann P, Sedlmair M, Winter J, Mahnken AH, Hofmann C. Non-linearly scaled (NLS) prior image-controlled frequency split for high-frequency metal artifact reduction in Computed Tomography. Med Phys 2022; 49:5870-5885. [PMID: 35866263 DOI: 10.1002/mp.15879] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 05/03/2022] [Accepted: 07/18/2022] [Indexed: 11/10/2022] Open
Abstract
PURPOSE This paper introduces a new approach for the dedicated reduction of high-frequency metal artifacts, which applies a non-linear scaling transfer function (NLS) on the high-frequency projection domain to reduce artifacts, while preserving edge information and anatomic detail by incorporating prior image information. METHODS A non-linear scaling function is applied to suppress high-frequency streak artifacts, but to restrict the correction to metal projections only, scaling is performed in the sinogram domain. Anatomic information should be preserved and is excluded from scaling by incorporating a prior image from tissue-classification. The corrected high-frequency sinogram is reconstructed and combined with the low-frequency component of an NMAR image. Scans of different anthropomorphic phantoms were acquired (unilateral hip, bilateral hip, dental implants, and embolization coil). Multiple ROIs were drawn around the metal implants and HU deviations were analyzed. Clinical datasets including single image slices of dental fillings, a bilateral hip implant, spinal fixation screws, and an aneurysm coil were reconstructed and assessed. RESULTS The prior image-controlled non-linear scaling function can remove streak artifacts while preserving anatomic detail within the bone and soft tissue. The qualitative analysis of clinical cases showed a tremendous enhancement within dental fillings and neuro coils, and a significant enhancement within spinal screws or hip implants. The phantom scan measurements support this observation. In all phantom setups, the NLS-corrected result showed lowest HU derivation and the best visualization of the data. CONCLUSIONS The prior image-controlled NLS provides a method to reduce high-frequency streaks in metal-corrupted CT data. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Julian A Anhaus
- Siemens Healthineers, CT Physics, Forchheim, D-91031, Germany.,Philipps-University Marburg, Marburg, D-35037, Germany
| | | | - Martin Sedlmair
- Siemens Healthineers, CT Physics, Forchheim, D-91031, Germany
| | - Jonas Winter
- Siemens Healthineers, CT Physics, Forchheim, D-91031, Germany
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Kuah T, Vellayappan BA, Makmur A, Nair S, Song J, Tan JH, Kumar N, Quek ST, Hallinan JTPD. State-of-the-Art Imaging Techniques in Metastatic Spinal Cord Compression. Cancers (Basel) 2022; 14:3289. [PMID: 35805059 PMCID: PMC9265325 DOI: 10.3390/cancers14133289] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 06/24/2022] [Accepted: 06/28/2022] [Indexed: 12/23/2022] Open
Abstract
Metastatic Spinal Cord Compression (MSCC) is a debilitating complication in oncology patients. This narrative review discusses the strengths and limitations of various imaging modalities in diagnosing MSCC, the role of imaging in stereotactic body radiotherapy (SBRT) for MSCC treatment, and recent advances in deep learning (DL) tools for MSCC diagnosis. PubMed and Google Scholar databases were searched using targeted keywords. Studies were reviewed in consensus among the co-authors for their suitability before inclusion. MRI is the gold standard of imaging to diagnose MSCC with reported sensitivity and specificity of 93% and 97% respectively. CT Myelogram appears to have comparable sensitivity and specificity to contrast-enhanced MRI. Conventional CT has a lower diagnostic accuracy than MRI in MSCC diagnosis, but is helpful in emergent situations with limited access to MRI. Metal artifact reduction techniques for MRI and CT are continually being researched for patients with spinal implants. Imaging is crucial for SBRT treatment planning and three-dimensional positional verification of the treatment isocentre prior to SBRT delivery. Structural and functional MRI may be helpful in post-treatment surveillance. DL tools may improve detection of vertebral metastasis and reduce time to MSCC diagnosis. This enables earlier institution of definitive therapy for better outcomes.
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Affiliation(s)
- Tricia Kuah
- Department of Diagnostic Imaging, National University Hospital, 5 Lower Kent Ridge Rd, Singapore 119074, Singapore; (A.M.); (S.N.); (J.S.); (S.T.Q.); (J.T.P.D.H.)
| | - Balamurugan A. Vellayappan
- Department of Radiation Oncology, National University Cancer Institute Singapore, National University Hospital, Singapore 119074, Singapore;
| | - Andrew Makmur
- Department of Diagnostic Imaging, National University Hospital, 5 Lower Kent Ridge Rd, Singapore 119074, Singapore; (A.M.); (S.N.); (J.S.); (S.T.Q.); (J.T.P.D.H.)
- Department of Diagnostic Radiology, Yong Loo Lin School of Medicine, National University of Singapore, 10 Medical Drive, Singapore 117597, Singapore
| | - Shalini Nair
- Department of Diagnostic Imaging, National University Hospital, 5 Lower Kent Ridge Rd, Singapore 119074, Singapore; (A.M.); (S.N.); (J.S.); (S.T.Q.); (J.T.P.D.H.)
| | - Junda Song
- Department of Diagnostic Imaging, National University Hospital, 5 Lower Kent Ridge Rd, Singapore 119074, Singapore; (A.M.); (S.N.); (J.S.); (S.T.Q.); (J.T.P.D.H.)
| | - Jiong Hao Tan
- University Spine Centre, Department of Orthopaedic Surgery, National University Health System, 1E Lower Kent Ridge Road, Singapore 119228, Singapore; (J.H.T.); (N.K.)
| | - Naresh Kumar
- University Spine Centre, Department of Orthopaedic Surgery, National University Health System, 1E Lower Kent Ridge Road, Singapore 119228, Singapore; (J.H.T.); (N.K.)
| | - Swee Tian Quek
- Department of Diagnostic Imaging, National University Hospital, 5 Lower Kent Ridge Rd, Singapore 119074, Singapore; (A.M.); (S.N.); (J.S.); (S.T.Q.); (J.T.P.D.H.)
- Department of Diagnostic Radiology, Yong Loo Lin School of Medicine, National University of Singapore, 10 Medical Drive, Singapore 117597, Singapore
| | - James Thomas Patrick Decourcy Hallinan
- Department of Diagnostic Imaging, National University Hospital, 5 Lower Kent Ridge Rd, Singapore 119074, Singapore; (A.M.); (S.N.); (J.S.); (S.T.Q.); (J.T.P.D.H.)
- Department of Diagnostic Radiology, Yong Loo Lin School of Medicine, National University of Singapore, 10 Medical Drive, Singapore 117597, Singapore
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Chen J, Cao G, Li L, Cai Q, Dunne N, Li X. Modification of polyether ether ketone for the repairing of bone defects. Biomed Mater 2022; 17:042001. [PMID: 35395651 DOI: 10.1088/1748-605x/ac65cd] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 04/08/2022] [Indexed: 11/12/2022]
Abstract
Bone damage as a consequence of disease or trauma is a common global occurrence. For bone damage treatment-bone implant materials are necessary across three classifications of surgical intervention (i.e. fixation, repair, and replacement). Many types of bone implant materials have been developed to meet the requirements of bone repair. Among them, polyether ether ketone (PEEK) has been considered as one of the next generation of bone implant materials, owing to its advantages related to good biocompatibility, chemical stability, x-ray permeability, elastic modulus comparable to natural bone, as well as the ease of processing and modification. However, as PEEK is a naturally bioinert material, some modification is needed to improve its integration with adjacent bones after implantation. Therefore, it has become a very hot topic of biomaterials research and various strategies for the modification of PEEK including blending, 3D printing, coating, chemical modification and the introduction of bioactive and/or antibacterial substances have been proposed. In this systematic review, the recent advances in modification of PEEK and its application prospect as bone implants are summarized, and the remaining challenges are also discussed.
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Affiliation(s)
- Junfeng Chen
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, 37 Xueyuan Rd, Haidian District, Beijing, 100083, People's Republic of China
| | - Guangxiu Cao
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, 37 Xueyuan Rd, Haidian District, Beijing, 100083, People's Republic of China
| | - Linhao Li
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, 37 Xueyuan Rd, Haidian District, Beijing, 100083, People's Republic of China
| | - Qiang Cai
- Key Laboratory of Advanced Materials of Ministry of Education, Tsinghua University, Beijing 100084, People's Republic of China
| | - Nicholas Dunne
- Centre for Medical Engineering Research, School of Mechanical and Manufacturing Engineering, Dublin City University, Dublin 9, Ireland
| | - Xiaoming Li
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, 37 Xueyuan Rd, Haidian District, Beijing, 100083, People's Republic of China
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Le Fèvre C, Lacornerie T, Noël G, Antoni D. Management of metallic implants in radiotherapy. Cancer Radiother 2021; 26:411-416. [PMID: 34955412 DOI: 10.1016/j.canrad.2021.11.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The number of patients with metallic implant and treated with radiotherapy is constantly increasing. These hardware are responsible for the deterioration in the quality of the CT images used at each stage of the radiation therapy, during delineation, dosimetry and dose delivery. We present the update of the recommendations of the French society of oncological radiotherapy on the pros and cons of the different methods, existing and under evaluation, which limit the impact of metallic implants on the quality and safety of radiation treatments.
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Affiliation(s)
- C Le Fèvre
- Service de radiothérapie, Institut de cancérologie Strasbourg Europe (ICANS), 17, rue Albert-Calmette, BP 23025, 67033 Strasbourg, France
| | - T Lacornerie
- Département de physique médicale, centre Oscar-Lambret, 3, rue Frédéric-Combemale, 59000 Lille, France
| | - G Noël
- Service de radiothérapie, Institut de cancérologie Strasbourg Europe (ICANS), 17, rue Albert-Calmette, BP 23025, 67033 Strasbourg, France; Université de Strasbourg, CNRS, IPHC UMR 7178, centre Paul-Strauss, Unicancer, 67000 Strasbourg, France
| | - D Antoni
- Service de radiothérapie, Institut de cancérologie Strasbourg Europe (ICANS), 17, rue Albert-Calmette, BP 23025, 67033 Strasbourg, France; Université de Strasbourg, CNRS, IPHC UMR 7178, centre Paul-Strauss, Unicancer, 67000 Strasbourg, France.
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17
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Selles M, Stuivenberg VH, Wellenberg RHH, van de Riet L, Nijholt IM, van Osch JAC, van Hamersvelt RW, Leiner T, Boomsma MF. Quantitative analysis of metal artifact reduction in total hip arthroplasty using virtual monochromatic imaging and orthopedic metal artifact reduction, a phantom study. Insights Imaging 2021; 12:171. [PMID: 34817722 PMCID: PMC8613319 DOI: 10.1186/s13244-021-01111-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 10/18/2021] [Indexed: 11/17/2022] Open
Abstract
Objective To quantify metal artifact reduction using 130 keV virtual monochromatic imaging (VMI) with and without orthopedic metal artifact reduction (O-MAR) in total hip arthroplasty. Methods Conventional polychromatic images and 130 keV VMI of a phantom with pellets representing bone with unilateral or bilateral prostheses were reconstructed with and without O-MAR on a dual-layer CT. Pellets were categorized as unaffected, mildly affected and severely affected. Results When 130 keV VMI with O-MAR was compared to conventional imaging with O-MAR, a relative metal artifact reduction in CT values, contrast-to-noise (CNR), signal-to-noise (SNR) and noise in mildly affected pellets (67%, 74%, 48%, 68%, respectively; p < 0.05) was observed but no significant relative metal artifact reduction in severely affected pellets. Comparison between 130 keV VMI without O-MAR and conventional imaging with O-MAR showed relative metal artifact reduction in CT values, CNR, SNR and noise in mildly affected pellets (92%, 72%, 38%, 51%, respectively; p < 0.05) but negative relative metal artifact reduction in CT values and noise in severely affected pellets (− 331% and -223%, respectively; p < 0.05), indicating aggravation of metal artifacts. Conclusion Overall, VMI of 130 keV with O-MAR provided the strongest metal artifact reduction. Supplementary Information The online version contains supplementary material available at 10.1186/s13244-021-01111-5.
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Affiliation(s)
- Mark Selles
- Department of Radiology, Isala, 8025 AB, Zwolle, The Netherlands.
| | | | - Ruud H H Wellenberg
- Department of Radiology, Amsterdam University Medical Centre, 1105 AZ, Amsterdam, The Netherlands
| | - Loes van de Riet
- Department of Radiology, Isala, 8025 AB, Zwolle, The Netherlands.,Department of Radiology, University Medical Centre Utrecht, 3584 CX, Utrecht, The Netherlands
| | - Ingrid M Nijholt
- Department of Radiology, Isala, 8025 AB, Zwolle, The Netherlands
| | | | | | - Tim Leiner
- Department of Radiology, University Medical Centre Utrecht, 3584 CX, Utrecht, The Netherlands
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Taniguchi T, Hara T, Shimozato T, Hyodo F, Ono K, Nakaya S, Noda Y, Kato H, Tanaka O, Matsuo M. Effect of computed tomography value error on dose calculation in adaptive radiotherapy with Elekta X-ray volume imaging cone beam computed tomography. J Appl Clin Med Phys 2021; 22:271-279. [PMID: 34375008 PMCID: PMC8425939 DOI: 10.1002/acm2.13384] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 06/03/2021] [Accepted: 07/12/2021] [Indexed: 11/30/2022] Open
Abstract
Purpose We evaluated the effect of changing the scan mode of the Elekta X‐ray volume imaging cone beam computed tomography (CBCT) on the accuracy of dose calculation, which may be affected by computed tomography (CT) value errors in three dimensions. Methods We used the electron density phantom and measured the CT values in three dimensions. CT values were compared with planning computed tomography (pCT) values for various materials. The evaluated scan modes were for head and neck (S‐scan), chest (M‐scan), and pelvis (L‐scan) with various collimators and filter systems. To evaluate the effects of the CT value error of the CBCT on dose error, Monte Carlo calculations of dosimetry were performed using pCT and CBCT images. Results The L‐scan had a CT value error of approximately 800 HU at the isocenter compared with the pCT. Furthermore, inhomogeneity in the longitudinal CT value profile was observed in the bone material. The dose error for ±100 HU difference in CT values for the S‐scan and M‐scan was within ±2%. The center of the L‐scan had a CT error of approximately 800 HU and a dose error of approximately 6%. The dose error of the L‐scan occurred in the beam path in the case of both single field and two parallel opposed fields, and the maximum error occurred at the center of the phantom in the case of both the 4‐field box and single‐arc techniques. Conclusions We demonstrated the three‐dimensional CT value characteristics of the CBCT by evaluating the CT value error obtained under various imaging conditions. It was found that the L‐scan is considerably affected by not having a unique bowtie filter, and the S‐scan without the bowtie filter causes CT value errors in the longitudinal direction. Moreover, the CBCT dose errors for the 4‐field box and single‐arc irradiation techniques converge to the isocenter.
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Affiliation(s)
- Takuya Taniguchi
- Department of Radiation Oncology, Asahi University Hospital, Gifu, Japan.,Department of Radiology, Gifu University, Gifu, Japan
| | - Takanori Hara
- Department of Medical Technology, Nakatsugawa Municipal General Hospital, Gifu, Japan
| | - Tomohiro Shimozato
- Faculty of Radiological Technology, School of Health Sciences, Gifu University of Medical Science, Seki, Japan
| | - Fuminori Hyodo
- Department of Radiology Frontier Science for Imaging, School of Medicine, Gifu University, Gifu, Japan
| | - Kose Ono
- Department of Radiation Oncology, Asahi University Hospital, Gifu, Japan
| | - Shuto Nakaya
- Department of Radiation Oncology, Asahi University Hospital, Gifu, Japan
| | | | - Hiroki Kato
- Department of Radiology, Gifu University, Gifu, Japan
| | - Osamu Tanaka
- Department of Radiation Oncology, Asahi University Hospital, Gifu, Japan
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Koutsouvelis N, Dipasquale G, Rouzaud M, Dubouloz A, Nouet P, Jaccard M, Miralbell R, Tsoutsou P, Zilli T. Bilateral metallic hip implants: Are avoidance sectors necessary for pelvic VMAT treatments? Z Med Phys 2021; 31:420-427. [PMID: 34210536 DOI: 10.1016/j.zemedi.2021.05.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 03/29/2021] [Accepted: 05/26/2021] [Indexed: 11/29/2022]
Abstract
PURPOSE Metallic hip implants (MHI) are common in elderly patients. For pelvic cancers radiotherapy, conventional approaches consist of MHI avoidance during treatment planning, which leads, especially in case of bilateral MHI, to a decreased quality or increased complexity of the treatment plan. The aim of this study is to investigate the necessity of using avoidance sectors (AvSe) using a 2-arcs coplanar pelvic volumetric modulated arc-therapy (VMAT) planning. METHODS We evaluated: (1) The dose calculation error of a static 6MV open beam traversing a MHI; (2) The magnitude of an error's decrease within the planning target volume (PTV) for a 360° VMAT treatment without AvSe as compared to the static open beam; (3) The dosimetric influence of MHI misalignment generated by patient's repositioning rolls during image-guided radiotherapy (IGRT). RESULTS (1) In the static 6MV beam configuration, for distances between 0.5cm and 6cm from the MHI, the median (maximum, number of points) dose calculation error was -1.55% (-2.5%, 11); (2) Compared to the static open beam, in the 360° VMAT treatment without AvSe a simulated error was decreased by a factor of 4.4/2.4 (median/minimum); (3) MHI anterior-posterior misalignment exceeding 0.6cm, resulted in error at PTV surface of >2%. CONCLUSIONS A standard 2 coplanar arcs 360° VMAT treatment, with dedicated artifact reduction algorithms applied, decreased the error of static beam traversing MHI, in patients presenting a bilateral MHI and might be used to treat the pelvic region without MHI avoidance.
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Affiliation(s)
| | - Giovanna Dipasquale
- Department of Radiation Oncology, Geneva University Hospital, Geneva, Switzerland
| | - Michel Rouzaud
- Department of Radiation Oncology, Geneva University Hospital, Geneva, Switzerland
| | - Angele Dubouloz
- Department of Radiation Oncology, Geneva University Hospital, Geneva, Switzerland
| | - Philippe Nouet
- Department of Radiation Oncology, Geneva University Hospital, Geneva, Switzerland
| | - Maud Jaccard
- Department of Radiation Oncology, Geneva University Hospital, Geneva, Switzerland
| | - Raymond Miralbell
- Department of Radiation Oncology, Geneva University Hospital, Geneva, Switzerland; Faculty of Medicine, Geneva University, Geneva, Switzerland
| | - Pelagia Tsoutsou
- Department of Radiation Oncology, Geneva University Hospital, Geneva, Switzerland; Faculty of Medicine, Geneva University, Geneva, Switzerland
| | - Thomas Zilli
- Department of Radiation Oncology, Geneva University Hospital, Geneva, Switzerland; Faculty of Medicine, Geneva University, Geneva, Switzerland
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Nakamura M, Nakao M, Imanishi K, Hirashima H, Tsuruta Y. Geometric and dosimetric impact of 3D generative adversarial network-based metal artifact reduction algorithm on VMAT and IMPT for the head and neck region. Radiat Oncol 2021; 16:96. [PMID: 34092240 PMCID: PMC8182914 DOI: 10.1186/s13014-021-01827-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 05/28/2021] [Indexed: 11/26/2022] Open
Abstract
Background We investigated the geometric and dosimetric impact of three-dimensional (3D) generative adversarial network (GAN)-based metal artifact reduction (MAR) algorithms on volumetric-modulated arc therapy (VMAT) and intensity-modulated proton therapy (IMPT) for the head and neck region, based on artifact-free computed tomography (CT) volumes with dental fillings. Methods Thirteen metal-free CT volumes of the head and neck regions were obtained from The Cancer Imaging Archive. To simulate metal artifacts on CT volumes, we defined 3D regions of the teeth for pseudo-dental fillings from the metal-free CT volumes. HU values of 4000 HU were assigned to the selected teeth region of interest. Two different CT volumes, one with four (m4) and the other with eight (m8) pseudo-dental fillings, were generated for each case. These CT volumes were used as the Reference. CT volumes with metal artifacts were then generated from the Reference CT volumes (Artifacts). On the Artifacts CT volumes, metal artifacts were manually corrected for using the water density override method with a value of 1.0 g/cm3 (Water). By contrast, the CT volumes with reduced metal artifacts using 3D GAN model extension of CycleGAN were also generated (GAN-MAR). The structural similarity (SSIM) index within the planning target volume was calculated as quantitative error metric between the Reference CT volumes and the other volumes. After creating VMAT and IMPT plans on the Reference CT volumes, the reference plans were recalculated for the remaining CT volumes. Results The time required to generate a single GAN-MAR CT volume was approximately 30 s. The median SSIMs were lower in the m8 group than those in the m4 group, and ANOVA showed a significant difference in the SSIM for the m8 group (p < 0.05). Although the median differences in D98%, D50% and D2% were larger in the m8 group than the m4 group, those from the reference plans were within 3% for VMAT and 1% for IMPT. Conclusions The GAN-MAR CT volumes generated in a short time were closer to the Reference CT volumes than the Water and Artifacts CT volumes. The observed dosimetric differences compared to the reference plan were clinically acceptable.
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Affiliation(s)
- Mitsuhiro Nakamura
- Division of Medical Physics, Department of Information Technology and Medical Engineering, Human Health Sciences, Graduate School of Medicine, Kyoto University, 53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, 606-8507, Japan. .,Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
| | - Megumi Nakao
- Department of Systems Science, Graduate School of Informatics, Kyoto University, Kyoto, Japan
| | | | - Hideaki Hirashima
- Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Yusuke Tsuruta
- Division of Medical Physics, Department of Information Technology and Medical Engineering, Human Health Sciences, Graduate School of Medicine, Kyoto University, 53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, 606-8507, Japan.,Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto, Japan
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21
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Accuracy of digital model generated from CT data with metal artifact reduction algorithm. Sci Rep 2021; 11:10332. [PMID: 33990637 PMCID: PMC8121776 DOI: 10.1038/s41598-021-89298-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 04/22/2021] [Indexed: 11/08/2022] Open
Abstract
This study investigated whether metal artifact reduction (MAR) applied computed tomography (CT) scans could be used to generate precise digital models and explored possible correlations between the amount of metal artifact and model accuracy. Thirty maxillofacial CT scans were randomly selected and a MAR algorithm was applied. By subtracting the original and MAR-applied CT images, the amount of metal artifact was quantified. Digital models were generated from the original and the MAR-applied CT data. Paired digital models were superimposed and shape deviation in planar surface was measured at 10 points in 4 planes. Statistical analyses were performed to compare deviations and to assess correlations between the amount of artifact and deviation. The MAR algorithm reduced metal artifact in all cases. The overall mean deviation of the MAR-applied models was 0.0868 mm, with no significant difference according to the reference plane. The amount of artifact did not significantly influence the accuracy of the digital models. MAR-applied CT is a convenient source for digital modeling with clinically acceptable accuracy. The MAR algorithm can be used regardless of the amount of metal artifact, which are generated by dental prostheses, for the quick and convenient manipulation of dental digital models.
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22
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Branco D, Kry S, Taylor P, Rong J, Zhang X, Frank S, Followill D. Evaluation of image quality of a novel computed tomography metal artifact management technique on an anthropomorphic head and neck phantom. PHYSICS & IMAGING IN RADIATION ONCOLOGY 2021; 17:111-116. [PMID: 33898789 PMCID: PMC8058027 DOI: 10.1016/j.phro.2021.01.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 01/22/2021] [Accepted: 01/25/2021] [Indexed: 11/27/2022]
Abstract
Background and purpose Artefacts caused by dental amalgam implants present a common challenge in computed tomography (CT) and therefore treatment planning dose calculations. The goal was to perform a quantitative image quality analysis of our Artifact Management for Proton Planning (AMPP) algorithm which used gantry tilts for managing metal artefacts on Head and Neck (HN) CT scans and major vendors’ commercial approaches. Materials and methods Metal artefact reduction (MAR) algorithms were evaluated using an anthropomorphic phantom with a removable jaw for the acquisition of images with and without (baseline) metal artifacts. AMPP made use of two angled CT scans to generate one artifact-reduced image set. The MAR algorithms from four vendors were applied to the images with artefacts and the analysis was performed with respective baselines. Planar HU difference maps and volumetric HU differences were analyzed. Results AMPP algorithm outperformed all vendors’ commercial approaches in the elimination of artefacts in the oropharyngeal region, showing the lowest percent of pixels outside +− 20 HU criteria, 4%; whereas those in the MAR-corrected images ranged from 26% to 67%. In the region of interest within the affected slices, the commercial MAR algorithms showed inconsistent performance, whereas the AMPP algorithm performed consistently well throughout the phantom’s posterior region. Conclusions A novel MAR algorithm was evaluated and compared to four commercial algorithms using an anthropomorphic phantom. Unanimously, the analysis showed the AMPP algorithm outperformed vendors’ commercial approaches, showing the potential to be broadly implemented, improve visualizations in patient anatomy and provide accurate HU information.
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Key Words
- AMPP, Artifact Management for Proton Planning
- Algorithm
- Artifacts
- CT, Computed tomography
- Computed X ray tomography
- Gantry tilts
- HU, Hounsfield Unit
- Head and neck neoplasms
- MAR, metal artifact reduction
- OAR, Organs at Risk
- OMAR, orthopedic metal artifact reduction
- SEMAR, single-energy metal artifact reduction
- SmartMAR, Smart metal artifact reduction
- iMAR, iterative metal artifact reduction
- kVp, Kilovoltage peak
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Affiliation(s)
- Daniela Branco
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Unit 607, Houston, TX 77030, United States
| | - Stephen Kry
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Unit 607, Houston, TX 77030, United States
| | - Paige Taylor
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Unit 607, Houston, TX 77030, United States
| | - John Rong
- Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Unit 607, Houston, TX 77030, United States
| | - Xiaodong Zhang
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Unit 607, Houston, TX 77030, United States
| | - Steven Frank
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Unit 607, Houston, TX 77030, United States
| | - David Followill
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Unit 607, Houston, TX 77030, United States
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Branco D, Kry S, Taylor P, Zhang X, Rong J, Frank S, Followill D. Dosimetric impact of commercial CT metal artifact reduction algorithms and a novel in-house algorithm for proton therapy of head and neck cancer. Med Phys 2020; 48:445-455. [PMID: 33176003 DOI: 10.1002/mp.14591] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 09/16/2020] [Accepted: 11/04/2020] [Indexed: 11/05/2022] Open
Abstract
PURPOSE To compare the dosimetric impact of all major commercial vendors' metal artifact reduction (MAR) algorithms to one another, as well as to a novel in-house technique (AMPP) using an anthropomorphic head phantom. MATERIALS AND METHODS The phantom was an Alderson phantom, modified to allow for artifact-filled and baseline (no artifacts) computed tomography (CT) scans using teeth capsules made with metal amalgams or bone-equivalent materials. It also included a cylindrical insert that was accessible from the bottom of the neck and designed to introduce soft tissue features into the phantom that were used in the analysis. The phantom was scanned with the metal teeth in place using each respective vendor's MAR algorithm: OMAR (Philips), iMAR (Siemens), SEMAR (Canon), and SmartMAR (GE); the AMPP algorithm was designed in-house. Uncorrected and baseline (bone-equivalent teeth) image sets were also acquired using a Siemens scanner. Proton spot scanning treatment plans were designed on the baseline image set for five targets in the phantom. Once optimized, the proton beams were copied onto the different artifact-corrected image sets, with no reoptimization of the beams' parameters, to evaluate dose distribution differences in the different MAR-corrected and -uncorrected image sets. Dose distribution differences were evaluated by comparing dose-volume histogram (DVH) metrics, including planning target volume D95 and clinical target volume D99 coverages, V100, D0.03cc, and heterogeneity indexes, along with a qualitative and water equivalent thickness (WET) analysis. RESULTS Uncorrected CT metal artifacts and commercial MAR algorithms negatively impacted the proton dose distributions of all five target shapes and locations in an inconsistent manner, sometimes overdosing by as much as 11.1% (D0.03) or underdosing by as much as 11.7% (V100) the planning target volumes. The AMPP-corrected images, however, provided dose distributions that consistently agreed with the baseline dose distribution. The dosimetry results also suggest that the commercial MAR algorithms' performances varied more with target location and less with target shape. Once relocated further from the metal, the target showed dose distributions that agreed more with the baseline for all commercial solutions, improving the overdosing by as much as 6%, implying inadequate HU correction from commercial MAR algorithms. In comparison to the baseline, HU profile shapes were considerably altered by commercial algorithms and reference values showed differences that represent stopping power percentage differences of 2.7-10%. The AMPP algorithm plans showed the smallest WET differences with the baseline (0.06 cm on average), while the commercial image sets created differences that ranged from 0.11 to 0.54 cm. CONCLUSIONS Computed tomography metal artifacts negatively impacted proton dose distributions on all five targets analyzed. The commercial MAR solutions performed inconsistently throughout all targets compared to the metal-free baseline. A lack of CTV coverage and an increased number of hotspots were observed throughout all commercial solutions. Dose distribution errors were related to the proximity to the artifacts, demonstrating the inability of commercial techniques to adequately correct severe artifacts. In contrast, AMPP consistently showed dose distributions that best matched the baseline, likely because it makes use of accurate HU information, as opposed to interpolated data like commercial algorithms.
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Affiliation(s)
- Daniela Branco
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, 77054, USA
| | - Stephen Kry
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, 77054, USA
| | - Paige Taylor
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, 77054, USA
| | - Xiaodong Zhang
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, 77054, USA
| | - John Rong
- Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, 77054, USA
| | - Steven Frank
- Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77054, USA
| | - David Followill
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, 77054, USA
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Koike Y, Anetai Y, Takegawa H, Ohira S, Nakamura S, Tanigawa N. Deep learning-based metal artifact reduction using cycle-consistent adversarial network for intensity-modulated head and neck radiation therapy treatment planning. Phys Med 2020; 78:8-14. [DOI: 10.1016/j.ejmp.2020.08.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 08/17/2020] [Accepted: 08/18/2020] [Indexed: 01/27/2023] Open
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Feldhaus FW, Böning G, Kahn J, Fehrenbach U, Maurer M, Renz D, Streitparth F. Improvement of image quality and diagnostic confidence using Smart MAR - a projection-based CT protocol in patients with orthopedic metallic implants in hip, spine, and shoulder. Acta Radiol 2020; 61:1421-1430. [PMID: 32122149 DOI: 10.1177/0284185120903446] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND In computed tomography (CT) scans, artifacts caused by metallic orthopedic implants still hamper the visualization of important, periprosthetic tissues. Smart MAR metal artifact reduction tool is a promising three-stage, projection-based, post-processing algorithm. PURPOSE To determine whether the Smart MAR tool improves subjective and objective image quality and diagnostic confidence in patients with orthopedic implants of the hip, spine, and shoulder. MATERIAL AND METHODS Seventy-two patients with orthopedic screws, hip/shoulder replacement, or spine spondylodesis were included. CT scans were performed on a single-source multislice CT scanner, raw data were post-processed using Smart MAR. Image quality was evaluated both quantitatively (ROI-based) and qualitatively (rater-based) and compared to iterative reconstructions (ASIR V). As comparative standard for artificial prosthetic breaks or loosening, follow-up examinations were used. RESULTS Smart MAR reconstructions of the hip (n = 23), spine (n = 26), and shoulder (n = 23) showed a significantly reduced attenuation and noise of regions adjacent to metallic implants (P<0.002). Subjective image quality (P<0.005, shoulder P = 0.038/P = 0.046) and overall diagnostic confidence were higher in Smart MAR (all regions P<0.002). Signal-to-noise ratio (SNR; P = 0.72/P = 0.96) was not improved. Compared to standard ASIR V new, artificial metal extinctions (up to 50%) or periprosthetic hem lines (48%-73%) were introduced by Smart MAR. CONCLUSION Smart MAR improved image quality of the hip, spine, and shoulder CT scans resulting in higher diagnostic confidence in evaluation of periprosthetic soft tissues. As shown for spine implants, it should be used with caution and as a complementary tool for evaluation of periprosthetic loosening or integrity of metal implant, as in many cases it introduced new artifacts.
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Affiliation(s)
| | | | | | | | - Martin Maurer
- Department of Diagnostic, Interventional and Pediatric Radiology, Inselspital, University of Bern, Bern, Switzerland
| | - Diane Renz
- Department of Radiology, University of Jena, Jena, Germany
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Kubo Y, Ito K, Sone M, Nagasawa H, Onishi Y, Umakoshi N, Hasegawa T, Akimoto T, Kusumoto M. Diagnostic Value of Model-Based Iterative Reconstruction Combined with a Metal Artifact Reduction Algorithm during CT of the Oral Cavity. AJNR Am J Neuroradiol 2020; 41:2132-2138. [PMID: 32972957 DOI: 10.3174/ajnr.a6767] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Accepted: 07/07/2020] [Indexed: 12/28/2022]
Abstract
BACKGROUND AND PURPOSE Metal artifacts reduce the quality of CT images and increase the difficulty of interpretation. This study compared the ability of model-based iterative reconstruction and hybrid iterative reconstruction to improve CT image quality in patients with metallic dental artifacts when both techniques were combined with a metal artifact reduction algorithm. MATERIALS AND METHODS This retrospective clinical study included 40 patients (men, 31; women, 9; mean age, 62.9 ± 12.3 years) with oral and oropharyngeal cancer who had metallic dental fillings or implants and underwent contrast-enhanced ultra-high-resolution CT of the neck. Axial CT images were reconstructed using hybrid iterative reconstruction and model-based iterative reconstruction, and the metal artifact reduction algorithm was applied to all images. Finally, hybrid iterative reconstruction + metal artifact reduction algorithms and model-based iterative reconstruction + metal artifact reduction algorithm data were obtained. In the quantitative analysis, SDs were measured in ROIs over the apex of the tongue (metal artifacts) and nuchal muscle (no metal artifacts) and were used to calculate the metal artifact indexes. In a qualitative analysis, 3 radiologists blinded to the patients' conditions assessed the image-quality scores of metal artifact reduction and structural depictions. RESULTS Hybrid iterative reconstruction + metal artifact reduction algorithms and model-based iterative reconstruction + metal artifact reduction algorithms yielded significantly different metal artifact indexes of 82.2 and 73.6, respectively (95% CI, 2.6-14.7; P < .01). The latter algorithms resulted in significant reduction in metal artifacts and significantly improved structural depictions(P < .01). CONCLUSIONS Model-based iterative reconstruction + metal artifact reduction algorithms significantly reduced the artifacts and improved the image quality of structural depictions on neck CT images.
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Affiliation(s)
- Y Kubo
- From the Department of Diagnostic Radiology (Y.K., K.I., M.S., H.N., Y.O., N.U., T.H., M.K.), National Cancer Center Hospital, Tokyo, Japan .,Department of Cancer Medicine (Y.K., T.A.), Jikei University Graduate School of Medicine, Tokyo, Japan
| | - K Ito
- From the Department of Diagnostic Radiology (Y.K., K.I., M.S., H.N., Y.O., N.U., T.H., M.K.), National Cancer Center Hospital, Tokyo, Japan
| | - M Sone
- From the Department of Diagnostic Radiology (Y.K., K.I., M.S., H.N., Y.O., N.U., T.H., M.K.), National Cancer Center Hospital, Tokyo, Japan
| | - H Nagasawa
- From the Department of Diagnostic Radiology (Y.K., K.I., M.S., H.N., Y.O., N.U., T.H., M.K.), National Cancer Center Hospital, Tokyo, Japan
| | - Y Onishi
- From the Department of Diagnostic Radiology (Y.K., K.I., M.S., H.N., Y.O., N.U., T.H., M.K.), National Cancer Center Hospital, Tokyo, Japan
| | - N Umakoshi
- From the Department of Diagnostic Radiology (Y.K., K.I., M.S., H.N., Y.O., N.U., T.H., M.K.), National Cancer Center Hospital, Tokyo, Japan
| | - T Hasegawa
- From the Department of Diagnostic Radiology (Y.K., K.I., M.S., H.N., Y.O., N.U., T.H., M.K.), National Cancer Center Hospital, Tokyo, Japan
| | - T Akimoto
- Department of Cancer Medicine (Y.K., T.A.), Jikei University Graduate School of Medicine, Tokyo, Japan.,Division of Radiation Oncology and Particle Therapy (T.A.), National Cancer Center Hospital East, Kashiwa, Japan
| | - M Kusumoto
- From the Department of Diagnostic Radiology (Y.K., K.I., M.S., H.N., Y.O., N.U., T.H., M.K.), National Cancer Center Hospital, Tokyo, Japan
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Transperineal ultrasound for aiding target volume delineation and monitoring during prostate cancer radiotherapy in men with bilateral hip prostheses. JOURNAL OF RADIOTHERAPY IN PRACTICE 2020. [DOI: 10.1017/s1460396920000758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractAims:To investigate the use of co-registration of the computerised tomography (CT) planning scan with transperineal ultrasound (TPUS) as an aid to the delineation of the clinical target volume (CTV), and the use of TPUS as a tool for inter- and intra-fractional monitoring in men with bilateral hip prostheses (b-P) undergoing prostate radiotherapy.Materials and methods:We marked the CTV of three patients with and without the co-registered TPUS images. A metal artefact reduction algorithm was utilised. Two patients were treated with intensity-modulated radiotherapy (IMRT) and one with volumetric-modulated arc therapy (VMAT). The inter- and intra-fractional monitoring details were reviewed retrospectively.Results:Clinician marking with TPUS/CT fusion improved the confidence of prostate CTV delineation leading to a consistent change in volumes across two observers. Inter- and intra-fractional monitoring was possible using TPUS as image guidance, as it is for those patients with non-prosthetic hips.Findings:Using TPUS in the radiotherapy workflow has enabled us to more confidently plan, treat and monitor patients with b-HP. Due to transperineal image acquisition, the ultrasound images are not affected by the presence of hip prostheses, which are outside the field of view.
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Rousselle A, Amelot A, Thariat J, Jacob J, Mercy G, De Marzi L, Feuvret L. Metallic implants and CT artefacts in the CTV area: Where are we in 2020? Cancer Radiother 2020; 24:658-666. [PMID: 32859465 DOI: 10.1016/j.canrad.2020.06.022] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Revised: 06/25/2020] [Accepted: 06/25/2020] [Indexed: 12/18/2022]
Abstract
Radiation therapy (RT) is one of the main modalities of cancer treatment worldwide with computed tomography (CT), as the most commonly used imaging method for treatment planning system (TPS). Image reconstruction errors may greatly affect all the radiation therapy planning process, such as target delineation, dose calculation and delivery, particularly with particle therapy. Metallic implants, such as hip and spinal implants, and dental filling significantly deteriorate image quality. These hardware structures are often very complex in geometry leading to geometric complex artefacts in the clinical target volume (CTV) area, rendering the delineation of CTV challenging. In our review, we focus on the methods to overcome artefact consequences on CTV delineation: 1- medical approaches anticipating issues associated with imaging artefacts during preoperative multidisciplinary discussions while following standard recommendations; 2- common metal artefact reduction (MAR) methods such as manually override artefact regions, ballistics avoiding beam paths through implanted materials, megavoltage-CT (MVCT); 3- prospects with radiolucent implants, MAR algorithms and various methods of dual energy computed tomography (DECT). Despite substantial and broad evidence for their benefits, there is still no universal solution for cases involving implanted metallic devices. There is still a high need for research efforts to adapt technologies to our issue: "how do I accurately delineate the ideal CTV in a metal artefact area?"
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Affiliation(s)
- A Rousselle
- Department of Radiation Oncology, Sorbonne Université, AP-HP, hôpitaux universitaires La Pitié Salpêtrière-Charles-Foix, 75013 Paris, France
| | - A Amelot
- Department of Neurosurgery, CHRU de Tours, 37000 Tours, France
| | - J Thariat
- Department of Radiation Oncology, centre François-Baclesse/ARCHADE, Laboratoire de physique corpusculaire IN2P3-UMR6534 - Normandie Université, 1400 Caen, France
| | - J Jacob
- Department of Radiation Oncology, Sorbonne Université, AP-HP, hôpitaux universitaires La Pitié Salpêtrière-Charles-Foix, 75013 Paris, France
| | - G Mercy
- Department of Medical Imaging, Sorbonne Université, AP-HP, hôpitaux universitaires La Pitié Salpêtrière-Charles-Foix, 75013 Paris, France
| | - L De Marzi
- Institut Curie, PSL Research University, Radiation Oncology Department, Proton Therapy Centre, Centre universitaire, 91898 Orsay, France
| | - L Feuvret
- Department of Radiation Oncology, Sorbonne Université, AP-HP, hôpitaux universitaires La Pitié Salpêtrière-Charles-Foix, 75013 Paris, France.
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Inal A, Sarpün IH. Dosimetric evaluation of phantoms including metal objects with high atomic number for use in intensity modulated radiation therapy. RADIATION AND ENVIRONMENTAL BIOPHYSICS 2020; 59:503-510. [PMID: 32488311 DOI: 10.1007/s00411-020-00851-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Accepted: 05/25/2020] [Indexed: 06/11/2023]
Abstract
The dosimetric effect of artefacts caused by metal hip prostheses in computed tomography imaging is most commonly encountered in the planning of prostate cancer treatment. In this study, a phantom, containing a metal with high atomic number, was prepared for intensity-modulated radiotherapy (IMRT) treatment plans to be used in quality assurance (QA) procedures. Two sets of image files, one without metal artefact correction (ORG) and another with MAR correction (MAR+), were sent to the treatment planning system. In this study, 12 IMRT treatment plans with different fields and segment numbers were calculated. The normal tissue complication probability (NTCP) values of imaginary organs at risk (OARs), such as the rectum and bladder, were investigated, as was the difference in dose maps for ORG and MAR+ derived by calculating gamma passing rates (GPRs). The MatriXX was used for the gamma evaluation of patient-specific IMRT QA measurements. The gamma evaluation was repeated, based on the measurements using an EBT3 gafchromic film, for the plan showing the lowest GPR. The mean relative difference in NTCP values between the two sets of image files was found to be 2.5, 2.1 and 1.4 for the rectum; and 5.33, 6.80 and 9.82 for the bladder, for the investigated 5-, 7- and 9-field beam arrangements, respectively. The relative differences and the standard deviations in GPRs for the standard and metal-containing phantoms were calculated for the MAR+ and ORG sets. The maximum difference found was 7.69% ± 0.88 for the 9-field beam arrangement calculated without metal artefact correction. In the IMRT QA procedures for prostate patients with hip prostheses, the application of a metal-containing phantom that is both easy and inexpensive to prepare, is considered to be a useful method for examining any dose changes involved in introducing a hip prosthesis. Therefore, it is recommended for use in clinics that do not have MAR correction algorithms.
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Affiliation(s)
- Aysun Inal
- Antalya Training and Research Hospital, Radiation Oncology, University of Health Sciences, Antalya, Turkey.
| | - Ismail Hakki Sarpün
- Physics Dept., Science Faculty, Akdeniz University, Antalya, Turkey
- Nuclear Sciences Application and Research Center, Akdeniz University, Antalya, Turkey
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Sun X, Zhao Q, Sun P, Yao Z, Wang R. Metal artifact reduction using mono-energy images combined with metal artifact reduction software in spectral computed tomography: a study on phantoms. Quant Imaging Med Surg 2020; 10:1515-1525. [PMID: 32676369 DOI: 10.21037/qims-19-936] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND This study aimed to evaluate the effectiveness of spectral computed tomography (CT) mono-energy imaging combined with metal artifact reduction software (MARs) for metal implant artifact reduction using a phantom. METHODS A quantitative standard phantom with 9 cylinders was used to simulate the attenuation of the different tissues of the human body around the metal implant. Groups A and B were divided according to conventional CT scan mode and spectral CT scan mode. Three sets of reconstructed images, including 120 kVp-like + MARs images, mono-energy images (MonoE), and MonoE + MARs images, were generated after spectral CT scanning. High-attenuation artifacts and low-attenuation artifacts were observed around the coil in the images of groups A and B. The CT values (Hounsfield unit) and standard deviation (SD) values of the artifacts were measured, and the artifact index and hardening artifact removal rate were calculated. RESULTS Compared to conventional poly-energy CT images, for high-attenuation and low-attenuation artifacts, the artifact indices of 120 kVp-like + MARs, MonoE, and MonoE + MARs images were all reduced significantly. The hardening artifact removal rates of the high-attenuation and low-attenuation artifacts of 120 kVp-like + MARs images were 82% and 92%, respectively. The hardening artifact removal rate of the high-attenuation and low-attenuation artifacts of MonoE and MonoE + MARs images increased with the mono-energy level. CONCLUSIONS Spectral CT using the 120 kVp-like + MARs, 110-140 keV MonoE, and MonoE + MARs reconstruction methods can reduce metal implant artifacts in varying degrees. MonoE + MARs reconstruction was the best method for reducing metal artifacts.
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Affiliation(s)
- Xiaoli Sun
- Department of Radiology, Beijing Shijitan Hospital, Peking University Ninth School of Clinical Medicine, Capital Medical University, Beijing, China
| | - Qingqing Zhao
- Department of Radiology, Beijing Shijitan Hospital, Peking University Ninth School of Clinical Medicine, Capital Medical University, Beijing, China
| | - Pengtao Sun
- Department of Radiology, Beijing Shijitan Hospital, Peking University Ninth School of Clinical Medicine, Capital Medical University, Beijing, China
| | - Zhipeng Yao
- Department of Radiology, Beijing Shijitan Hospital, Peking University Ninth School of Clinical Medicine, Capital Medical University, Beijing, China
| | - Rengui Wang
- Department of Radiology, Beijing Shijitan Hospital, Peking University Ninth School of Clinical Medicine, Capital Medical University, Beijing, China
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Beyer T, Bidaut L, Dickson J, Kachelriess M, Kiessling F, Leitgeb R, Ma J, Shiyam Sundar LK, Theek B, Mawlawi O. What scans we will read: imaging instrumentation trends in clinical oncology. Cancer Imaging 2020; 20:38. [PMID: 32517801 PMCID: PMC7285725 DOI: 10.1186/s40644-020-00312-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 04/17/2020] [Indexed: 12/16/2022] Open
Abstract
Oncological diseases account for a significant portion of the burden on public healthcare systems with associated costs driven primarily by complex and long-lasting therapies. Through the visualization of patient-specific morphology and functional-molecular pathways, cancerous tissue can be detected and characterized non-invasively, so as to provide referring oncologists with essential information to support therapy management decisions. Following the onset of stand-alone anatomical and functional imaging, we witness a push towards integrating molecular image information through various methods, including anato-metabolic imaging (e.g., PET/CT), advanced MRI, optical or ultrasound imaging.This perspective paper highlights a number of key technological and methodological advances in imaging instrumentation related to anatomical, functional, molecular medicine and hybrid imaging, that is understood as the hardware-based combination of complementary anatomical and molecular imaging. These include novel detector technologies for ionizing radiation used in CT and nuclear medicine imaging, and novel system developments in MRI and optical as well as opto-acoustic imaging. We will also highlight new data processing methods for improved non-invasive tissue characterization. Following a general introduction to the role of imaging in oncology patient management we introduce imaging methods with well-defined clinical applications and potential for clinical translation. For each modality, we report first on the status quo and, then point to perceived technological and methodological advances in a subsequent status go section. Considering the breadth and dynamics of these developments, this perspective ends with a critical reflection on where the authors, with the majority of them being imaging experts with a background in physics and engineering, believe imaging methods will be in a few years from now.Overall, methodological and technological medical imaging advances are geared towards increased image contrast, the derivation of reproducible quantitative parameters, an increase in volume sensitivity and a reduction in overall examination time. To ensure full translation to the clinic, this progress in technologies and instrumentation is complemented by advances in relevant acquisition and image-processing protocols and improved data analysis. To this end, we should accept diagnostic images as "data", and - through the wider adoption of advanced analysis, including machine learning approaches and a "big data" concept - move to the next stage of non-invasive tumour phenotyping. The scans we will be reading in 10 years from now will likely be composed of highly diverse multi-dimensional data from multiple sources, which mandate the use of advanced and interactive visualization and analysis platforms powered by Artificial Intelligence (AI) for real-time data handling by cross-specialty clinical experts with a domain knowledge that will need to go beyond that of plain imaging.
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Affiliation(s)
- Thomas Beyer
- QIMP Team, Centre for Medical Physics and Biomedical Engineering, Medical University Vienna, Währinger Gürtel 18-20/4L, 1090, Vienna, Austria.
| | - Luc Bidaut
- College of Science, University of Lincoln, Lincoln, UK
| | - John Dickson
- Institute of Nuclear Medicine, University College London Hospital, London, UK
| | - Marc Kachelriess
- Division of X-ray imaging and CT, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120, Heidelberg, DE, Germany
| | - Fabian Kiessling
- Institute for Experimental Molecular Imaging, University Clinic and Helmholtz Institute for Biomedical Engineering, RWTH Aachen University, Pauwelsstrasse 20, 52074, Aachen, DE, Germany
- Fraunhofer Institute for Digital Medicine MEVIS, Am Fallturm 1, 28359, Bremen, DE, Germany
| | - Rainer Leitgeb
- Centre for Medical Physics and Biomedical Engineering, Medical University Vienna, Vienna, AT, Austria
| | - Jingfei Ma
- Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Lalith Kumar Shiyam Sundar
- QIMP Team, Centre for Medical Physics and Biomedical Engineering, Medical University Vienna, Währinger Gürtel 18-20/4L, 1090, Vienna, Austria
| | - Benjamin Theek
- Institute for Experimental Molecular Imaging, University Clinic and Helmholtz Institute for Biomedical Engineering, RWTH Aachen University, Pauwelsstrasse 20, 52074, Aachen, DE, Germany
- Fraunhofer Institute for Digital Medicine MEVIS, Am Fallturm 1, 28359, Bremen, DE, Germany
| | - Osama Mawlawi
- Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
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Vaishnav JY, Ghammraoui B, Leifer M, Zeng R, Jiang L, Myers KJ. CT metal artifact reduction algorithms: Toward a framework for objective performance assessment. Med Phys 2020; 47:3344-3355. [PMID: 32406534 PMCID: PMC7496341 DOI: 10.1002/mp.14231] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 04/05/2020] [Accepted: 04/29/2020] [Indexed: 12/26/2022] Open
Abstract
Purpose Although several metal artifact reduction (MAR) algorithms for computed tomography (CT) scanning are commercially available, no quantitative, rigorous, and reproducible method exists for assessing their performance. The lack of assessment methods poses a challenge to regulators, consumers, and industry. We explored a phantom‐based framework for assessing an important aspect of MAR performance: how applying MAR in the presence of metal affects model observer performance at a low‐contrast detectability (LCD) task This work is, to our knowledge, the first model observer–based framework for the evaluation of MAR algorithms in the published literature. Methods We designed a numerical head phantom with metal implants. In order to incorporate an element of randomness, the phantom included a rotatable inset with an inhomogeneous background. We generated simulated projection data for the phantom. We applied two variants of a simple MAR algorithm, sinogram inpainting, to the projection data, that we reconstructed using filtered backprojection. To assess how MAR affected observer performance, we examined the detectability of a signal at the center of a region of interest (ROI) by a channelized Hotelling observer (CHO). As a figure of merit, we used the area under the ROC curve (AUC). Results We used simulation to test our framework on two variants of the MAR technique of sinogram inpainting. We found that our method was able to resolve the difference in two different MAR algorithms’ effect on LCD task performance, as well as the difference in task performances when MAR was applied, vs not. Conclusion We laid out a phantom‐based framework for objective assessment of how MAR impacts low‐contrast detectability, that we tested on two MAR algorithms. Our results demonstrate the importance of testing MAR performance over a range of object and imaging parameters, since applying MAR does not always improve the quality of an image for a given diagnostic task. Our framework is an initial step toward developing a more comprehensive objective assessment method for MAR, which would require developing additional phantoms and methods specific to various clinical applications of MAR, and increasing study efficiency.
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Affiliation(s)
- J Y Vaishnav
- Diagnostic X-Ray Systems Branch, Office of In Vitro Diagnostic Devices and Radiological Health, Center for Devices and Radiological Health, United States Food & Drug Administration, 10903 New Hampshire Ave., Silver Spring, MD, 20993, USA.,Canon Medical Systems, USA, Inc., 2441 Michelle Drive, Tustin, CA, 92780, USA
| | - B Ghammraoui
- Division of Imaging, Diagnostics, and Software Reliability, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, United States Food & Drug Administration, 10903 New Hampshire Ave., Silver Spring, MD, 20993, USA
| | - M Leifer
- Division of Imaging, Diagnostics, and Software Reliability, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, United States Food & Drug Administration, 10903 New Hampshire Ave., Silver Spring, MD, 20993, USA
| | - R Zeng
- Division of Imaging, Diagnostics, and Software Reliability, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, United States Food & Drug Administration, 10903 New Hampshire Ave., Silver Spring, MD, 20993, USA
| | - L Jiang
- Diagnostic X-Ray Systems Branch, Office of In Vitro Diagnostic Devices and Radiological Health, Center for Devices and Radiological Health, United States Food & Drug Administration, 10903 New Hampshire Ave., Silver Spring, MD, 20993, USA
| | - K J Myers
- Division of Imaging, Diagnostics, and Software Reliability, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, United States Food & Drug Administration, 10903 New Hampshire Ave., Silver Spring, MD, 20993, USA
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Hoellwarth JS, Weiss K, Goodman M, Heyl A, Hankins ML, McGough R. Evaluating the reoperation rate and hardware durability of three stabilizing implants for 105 malignant pathologic humerus fractures. Injury 2020; 51:947-954. [PMID: 32143857 DOI: 10.1016/j.injury.2020.02.124] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 02/23/2020] [Accepted: 02/24/2020] [Indexed: 02/02/2023]
Abstract
INTRODUCTION Many patients sustaining a malignant pathologic humerus fracture (MPHF) elect for surgical stabilization. Complications prompting reoperation can occur, leading to additional quality of life and financial cost. One common event preceding reoperation is a broken implant (BI). The purpose of this study was to identify the rate of reoperation following surgical stabilization of MPHF with three techniques - photodynamic bone stabilization (PBS), intramedullary nail (IMN), and cemented plate fixation (CPF) - and estimate to what extent improved implant durability might prevent reoperation. MATERIALS AND METHODS Retrospective data collection was performed, identifying 105 procedures (100 patients) who underwent non-articular MPHF surgery from 2010-2016: 19 PBS, 65 IMN, 21 CPF. All patients were followed for at least two years or until death. RESULTS Reoperation rates were similar at one year (10.5%,6.2%,4.8%, p = 737), two years (15.8%,6.2%,9.5%, p = 375), and final evaluation (15.8%,7.7%,14.3%, p = 248). The rate of BI for PBS, IMN, and CPF was 10.5%,0%, and 4.8% (p = 049 PBS/IMN) at one year, 15.8%,0%, and 9.5% (p = 010 PBS/IMN) at two years, and 15.8%,0%, and 14.3% (p = 010 IMN/PBS, p = 013 IMN/CPF) at final evaluation. CONCLUSIONS Reoperation rate was not significantly different at any time point. However, IMN surgery resulted in the lowest rate of broken implants (zero), statistically significant versus PBS at all time periods and versus CPF at final follow-up. PBS may eventually offer selected advantages for MPHF management, but current data suggests fragility must be thoughtfully considered.
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Affiliation(s)
- Jason S Hoellwarth
- Department of Orthopaedic Surgery, University of Pittsburgh Medical Center Shadyside, 5200 Centre Ave, Suite 415 Pittsburgh, PA 15232, USA.
| | - Kurt Weiss
- Department of Orthopaedic Surgery, University of Pittsburgh Medical Center Shadyside, 5200 Centre Ave, Suite 415 Pittsburgh, PA 15232, USA
| | - Mark Goodman
- Department of Orthopaedic Surgery, University of Pittsburgh Medical Center Shadyside, 5200 Centre Ave, Suite 415 Pittsburgh, PA 15232, USA
| | - Alma Heyl
- Department of Orthopaedic Surgery, University of Pittsburgh Medical Center Shadyside, 5200 Centre Ave, Suite 415 Pittsburgh, PA 15232, USA
| | - Margaret L Hankins
- Department of Orthopaedic Surgery, University of Pittsburgh Medical Center Shadyside, 5200 Centre Ave, Suite 415 Pittsburgh, PA 15232, USA
| | - Richard McGough
- Department of Orthopaedic Surgery, University of Pittsburgh Medical Center Shadyside, 5200 Centre Ave, Suite 415 Pittsburgh, PA 15232, USA
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Welch ML, McIntosh C, Purdie TG, Wee L, Traverso A, Dekker A, Haibe-Kains B, Jaffray DA. Automatic classification of dental artifact status for efficient image veracity checks: effects of image resolution and convolutional neural network depth. Phys Med Biol 2020; 65:015005. [PMID: 31683260 DOI: 10.1088/1361-6560/ab5427] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Enabling automated pipelines, image analysis and big data methodology in cancer clinics requires thorough understanding of the data. Automated quality assurance steps could improve the efficiency and robustness of these methods by verifying possible data biases. In particular, in head and neck (H&N) computed-tomography (CT) images, dental artifacts (DA) obscure visualization of structures and the accuracy of Hounsfield units; a challenge for image analysis tasks, including radiomics, where poor image quality can lead to systemic biases. In this work we analyze the performance of three-dimensional convolutional neural networks (CNN) trained to classify DA statuses. 1538 patient images were scored by a single observer as DA positive or negative. Stratified five-fold cross validation was performed to train and test CNNs using various isotropic resampling grids (643, 1283 and 2563), with CNN depths designed to produce 323, 163, and 83 machine generated features. These parameters were selected to determine if more computationally efficient CNNs could be utilized to achieve the same performance. The area under the precision recall curve (PR-AUC) was used to assess CNN performance. The highest PR-AUC (0.92 ± 0.03) was achieved with a CNN depth = 5, resampling grid = 256. The CNN performance with 2563 resampling grid size is not significantly better than 643 and 1283 after 20 epochs, which had PR-AUC = 0.89 ± 0.03 (p -value = 0.28) and 0.91 ± 0.02 (p -value = 0.93) at depths of 3 and 4, respectively. Our experiments demonstrate the potential to automate specific quality assurance tasks required for unbiased and robust automated pipeline and image analysis research. Additionally, we determined that there is an opportunity to simplify CNNs with smaller resampling grids to make the process more amenable to very large datasets that will be available in the future.
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Affiliation(s)
- Mattea L Welch
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada. The Techna Institute for the Advancement of Technology for Health, Toronto, Ontario, Canada. Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada
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Reduction of Metal Artifacts and Improvement in Dose Efficiency Using Photon-Counting Detector Computed Tomography and Tin Filtration. Invest Radiol 2019; 54:204-211. [PMID: 30562270 DOI: 10.1097/rli.0000000000000535] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
OBJECTIVES The aim of this study was to investigate the impact on metal artifacts and dose efficiency of using a tin filter in combination with high-energy threshold (TH) images of a photon-counting detector (PCD) computed tomography (CT) system. MATERIALS AND METHODS A 3D-printed spine with pedicle screws was scanned on a PCD-CT system with and without tin filtration. Image noise and severity of artifacts were measured for low-energy threshold (TL) and TH images. In a prospective, institutional review board-approved, Health Insurance Portability and Accountability Act-compliant study, 20 patients having a clinical energy-integrating detector (EID) CT were scanned on a PCD-CT system using tin filtration. Images were reviewed by 3 radiologists to evaluate visualization of anatomic structures, diagnostic confidence, and image preference. Artifact severity and image noise were measured. Wilcoxon signed rank was used to test differences between PCD-CT TH and EID-CT images. RESULTS Phantom TH images with tin filtration reduced metal artifacts and had comparable noise (32 HU) to TL images (29 HU) acquired without tin filtration. Visualization scores for the cortex, trabeculae, and implant-trabecular interface from PCD-CT TH images (4.4 ± 0.9, 4.4 ± 1.0, and 4.4 ± 1.0) were significantly higher (P < 0.0001) than EID-CT images (3.3 ± 1.3, 3.3 ± 1.2, and 3.3 ± 1.6). A strong preference was shown for PCD-CT TH images due to improved diagnostic confidence and decreased artifact severity. Noise in PCD-CT TH images (93 ± 41 HU) was significantly lower than that in EID-CT images (133 ± 92 HU, P < 0.05). CONCLUSIONS Threshold high images acquired with tin filtration on PCD-CT demonstrated a substantial decrease in metal artifacts and an increase in dose efficiency compared with EID-CT.
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Abstract
Abstract
Biomedical accelerators used in radiotherapy are equipped with detector arrays which are commonly used to obtain the image of patient position during the treatment session. These devices use both kilovolt and megavolt x-ray beams. The advantage of EPID (Electronic Portal Imaging Device) megavolt panels is the correlation of the measured signal with the calibrated dose. The EPID gives a possibility to verify delivered dose. The aim of the study is to answer the question whether EPID can be useful as a tool for interfraction QC (quality control) of dose and geometry repeatability.
The EPID system has been calibrated according to the manufacturer’s recommendations to obtain a signal and dose values correlation. Initially, the uncertainty of the EPID matrix measurement was estimated. According to that, the detecting sensitivity of two parameters was checked: discrepancies between the planned and measured dose and field geometry variance. Moreover, the linearity of measured signal-dose function was evaluated.
In the second part of the work, an analysis of several dose distributions was performed. In this study, the analysis of clinical cases was limited to stereotactic dynamic radiotherapy. Fluence maps were obtained as a result of the dose distribution measurements with the EPID during treatment sessions. The compatibility of fluence maps was analyzed using the gamma index. The fluence map acquired during the first fraction was the reference one. The obtained results show that EPID system can be used for interfraction control of dose and geometry repeatability.
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Lim P, Barber J, Sykes J. Evaluation of dual energy CT and iterative metal artefact reduction (iMAR) for artefact reduction in radiation therapy. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2019; 42:1025-1032. [PMID: 31602593 DOI: 10.1007/s13246-019-00801-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 08/19/2019] [Accepted: 09/16/2019] [Indexed: 11/27/2022]
Abstract
Metal artefacts pose a common problem in single energy computed tomography (SECT) images used for radiotherapy. Virtual monoenergetic (VME) images constructed with dual energy computed tomography (DECT) scans can be used to reduce beam hardening artefacts. Dual energy metal artefact reduction is compared and combined with iterative metal artefact reduction (iMAR) to determine optimal imaging strategies for patients with metal prostheses. SECT and DECT scans were performed on a Siemens Somatom AS-64 Slice CT scanner. Images were acquired of a modified CIRS pelvis phantom with 6, 12, 20 mm diameter stainless steel rods and VME images reconstructed at 100, 120, 140 and 190 keV. These were post-reconstructed with and without the iMAR algorithm. Artefact reduction was measured using: (1) the change in Hounsfield Unit (HU) with and without metal artefact reduction (MAR) for 4 regions of interest; (2) the total number of artefact pixels, defined as pixels with a difference (between images with metal rod and without) exceeding a threshold; (3) the difference in the mean pixel intensity of the artefact pixels. DECT, SECT + iMAR and DECT + iMAR were compared. Both SECT + iMAR and DECT + iMAR offer successful MAR for phantom simulating unilateral hip prosthesis. DECT gives minimal artefact reduction over iMAR alone. Quantitative metrics are advantageous for MAR analysis but have limitations that leave room for metric development.
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Affiliation(s)
- P Lim
- School of Physics, University of Sydney, Sydney, Australia.
| | - J Barber
- School of Physics, University of Sydney, Sydney, Australia
- Radiation Oncology, Blacktown Hospital, Sydney West Cancer Network, Sydney, Australia
| | - J Sykes
- School of Physics, University of Sydney, Sydney, Australia
- Radiation Oncology, Blacktown Hospital, Sydney West Cancer Network, Sydney, Australia
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Kaposi PN, Youn T, Tóth A, Frank VG, Shariati S, Szendrői A, Magyar P, Bérczi V. Orthopaedic metallic artefact reduction algorithm facilitates CT evaluation of the urinary tract after hip prosthesis. Clin Radiol 2019; 75:78.e17-78.e24. [PMID: 31590913 DOI: 10.1016/j.crad.2019.08.027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 08/29/2019] [Indexed: 11/28/2022]
Abstract
AIM To examine the improvement in the visualisation of bladder and ureteric pathologies next to a hip prosthesis with metallic artefact reduction for orthopaedic implants (O-MAR). MATERIALS AND METHODS Thirty-four patients who underwent pelvic computed tomography (CT) for non-prosthesis-related causes were enrolled retrospectively. Portal venous phase scans were reconstructed both with standard iterative reconstruction (ITR) and with O-MAR. The density of the ureters and the bladder was measured at both sides in the plane of the prosthesis. A semi-quantitative score was also used to assess visibility. The R (version 3.4.1) package was used for statistical analysis. RESULTS The average (μ) density of the 41 prosthesis side ureters was significantly lower on ITR images (μ=-94.76±150.48 [±SD] HU) than on O-MAR images (μ=-13.40±36.37 HU; p<0.0004). The difference between the ITR and O-MAR (μ=-138.62±182.64 versus -35.55±40.21 HU; p<0.0003) was also significant at the prosthesis side of the bladder. The visibility of the prosthesis side ureters was improved: 53.7% was obscured on ITR series compared to 4.9% on O-MAR. The visibility score was also better across all levels (p<0.001) with O-MAR. In four cases (13%), the O-MAR images significantly changed the diagnosis: in two cases ureteric stones, in one case each a bladder stone and a bladder tumour were discovered. CONCLUSIONS O-MAR reconstruction of CT images significantly improves the visibility of the urinary tract adjacent to metallic hip implants. Thus, O-MAR is essential for detecting ureteric and bladder pathologies in patients with a hip prosthesis.
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Affiliation(s)
- P N Kaposi
- Department of Radiology, Semmelweis University, Budapest, Hungary.
| | - T Youn
- Department of Radiology, Semmelweis University, Budapest, Hungary
| | - A Tóth
- Department of Radiology, Semmelweis University, Budapest, Hungary
| | - V G Frank
- Department of Radiology, Semmelweis University, Budapest, Hungary
| | - S Shariati
- Department of Radiology, Semmelweis University, Budapest, Hungary
| | - A Szendrői
- Department of Urology, Semmelweis University, Budapest, Hungary
| | - P Magyar
- Department of Radiology, Semmelweis University, Budapest, Hungary
| | - V Bérczi
- Department of Radiology, Semmelweis University, Budapest, Hungary
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Sillanpaa J, Lovelock M, Mueller B. The effects of the orthopedic metal artifact reduction (O-MAR) algorithm on contouring and dosimetry of head and neck radiotherapy patients. Med Dosim 2019; 45:92-96. [PMID: 31375297 DOI: 10.1016/j.meddos.2019.07.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 06/25/2019] [Accepted: 07/09/2019] [Indexed: 12/20/2022]
Abstract
Metallic objects, such as dental fillings, cause artifacts in computed tomography (CT) scans. We quantify the contouring and dosimetric effects of Orthopedic Metal Artifact Reduction (O-MAR), in head and neck radiotherapy. The ease of organ contouring was assessed by having a radiation oncologist identify the CT data set with or without O-MAR for each of 28 patients that was easier to contour. The effect on contouring was quantified further by having the physician recontour parotid glands, previously drawn by him on the O-MAR scans, on uncorrected scans, and calculating the Dice coefficent (a measure of overlap) for the contours. Radiotherapy plans originally generated on scans reconstructed with O-MAR were recalculated on scans without metal artifact correction. The study was done using the Analytical Anisotropic Algorithm (AAA) dose calculation algorithm. The 15 patients with a planning target volume (PTV) extending to the same slice as the artifacts were used for this part of the study. The normal tissue doses were not significantly affected. The PTV mean dose and V95 were not affected, but the cold spots became less severe in the O-MAR corrected plans, with the minimum point dose on average being 4.1% higher. In 79% of the cases, the radiation oncologist identified the O-MAR scan as easier to contour; in 11% he chose the uncorrected scan and in 11% the scans were judged to have equal quality. A total of nine parotid glands (on both scans-18 contours in total) in 5 patients were recontoured. The average Dice coefficient for parotids drawn with and without O-MAR was found to be 0.775 +/- 0.045. The O-MAR algorithm does not produce a significant dosimetric effect in head and neck plans when using the AAA dose calculation algorithm. It can therefore be used for improved contouring accuracy without updating the critical structure tolerance doses and target coverage expectations.
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Affiliation(s)
- Jussi Sillanpaa
- Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NJ 07748, USA.
| | - Michael Lovelock
- Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NJ 07748, USA
| | - Boris Mueller
- Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NJ 07748, USA
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Feldhaus F, Böning G, Jonczyk M, Kahn J, Fehrenbach U, Maurer M, Renz D, Hamm B, Streitparth F. Metallic dental artifact reduction in computed tomography (Smart MAR): Improvement of image quality and diagnostic confidence in patients with suspected head and neck pathology and oral implants. Eur J Radiol 2019; 118:153-160. [PMID: 31439235 DOI: 10.1016/j.ejrad.2019.07.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Revised: 07/09/2019] [Accepted: 07/14/2019] [Indexed: 10/26/2022]
Abstract
PURPOSE We determined whether the Smart MAR metal artifact reduction tool - a three-stage, projection-based, post processing algorithm - improves subjective and objective image quality and diagnostic confidence in patients with dental artifacts and suspected head and neck pathology compared to standard adaptive statistical iterative reconstructions (ASIR V) alone. METHOD The study included 100 consecutive patients with nonremovable oral implants or dental fillings and suspected oropharyngeal cancer or abscess. CT raw data of a single-source multislice CT scanner were postprocessed using ASIR V alone and with additional Smart MAR reconstruction. Image quality of baseline ASIR V and Smart MAR-based reconstruction series was compared both quantitatively (5 regions of interest, ROIs) and qualitatively (two independent raters). RESULTS Additional Smart MAR reconstruction significantly seems to improve both attenuation and noise adjacent to implants and in more distant areas (all p < 0.001) compared to standard ASIR V reconstructions alone. Signal-to-noise ratio (SNR; p = 0.001) and contrast-to-noise ratio were improved significantly (CNR; p = 0.001). Smart MAR improved visualization of tumor/abscess (detected in 36 of 100 patients, 36%) and representative oropharyngeal tissue (p < 0.001). In 8 of 36 patients (22%), tumor was only detected in Smart MAR series. Mean total DLP was 506.8mGy*cm; average CTDIvol was 5.5 mGy. CONCLUSIONS The supplementary use of the Smart MAR post-processing tool seems to significantly improve both subjective and objective image quality as well as diagnostic confidence and lesion detection in CT of the head and neck. In 22% of cases, the tumor was detected only in Smart MAR reconstructed images.
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Affiliation(s)
- Felix Feldhaus
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Radiology, Augustenburger Platz 1, 13353 Berlin, Germany.
| | - Georg Böning
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Radiology, Augustenburger Platz 1, 13353 Berlin, Germany.
| | - Martin Jonczyk
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Radiology, Augustenburger Platz 1, 13353 Berlin, Germany.
| | - Johannes Kahn
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Radiology, Augustenburger Platz 1, 13353 Berlin, Germany.
| | - Uli Fehrenbach
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Radiology, Augustenburger Platz 1, 13353 Berlin, Germany.
| | - M Maurer
- Department of Diagnostic, Interventional and Pediatric Radiology, Inselspital, University of Bern, CH-3010 Bern, Switzerland.
| | - D Renz
- Department of Radiology, University of Jena, Am Klinikum 1, 07747, Germany.
| | - Bernd Hamm
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Radiology, Augustenburger Platz 1, 13353 Berlin, Germany.
| | - Florian Streitparth
- Department of Radiology, Ludwig-Maximilians-University, Marchioninistr. 15, 81377 München, Germany.
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Wellenberg RHH, van Osch JAC, Boelhouwers HJ, Edens MA, Streekstra GJ, Ettema HB, Boomsma MF. CT radiation dose reduction in patients with total hip arthroplasties using model-based iterative reconstruction and orthopaedic metal artefact reduction. Skeletal Radiol 2019; 48:1775-1785. [PMID: 31016340 PMCID: PMC6776565 DOI: 10.1007/s00256-019-03206-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 02/08/2019] [Accepted: 03/07/2019] [Indexed: 02/02/2023]
Abstract
OBJECTIVE To evaluate the impact of radiation dose reduction on image quality in patients with metal-on-metal total hip arthroplasties (THAs) using model-based iterative reconstruction (MBIR) combined with orthopaedic metal artefact reduction (O-MAR). MATERIALS AND METHODS Patients with metal-on-metal THAs received a pelvic CT with a full (FD) and a reduced radiation dose (RD) with -20%, -40%, -57%, or -80% CT radiation dose respectively, when assigned to group 1, 2, 3, or 4 respectively. FD acquisitions were reconstructed with iterative reconstruction, iDose4. RD acquisitions were additionally reconstructed with iterative model-based reconstruction (IMR) levels 1-3 with different levels of noise suppression. CT numbers, noise and contrast-to-noise ratios were measured in muscle, fat and bladder. Subjective image quality was evaluated on seven aspects including artefacts, osseous structures, prosthetic components and soft tissues. RESULTS Seventy-six patients were randomly assigned to one of the four groups. While reducing radiation dose by 20%, 40%, 57%, or 80% in combination with IMR, CT numbers remained constant. Compared with iDose4, the noise decreased (p < 0.001) and contrast-to-noise ratios increased (p < 0.001) with IMR. O-MAR improved CT number accuracy in the bladder and reduced noise in the bladder, muscle and fat (p < 0.01). Subjective image quality was rated lower on RD IMR images than FD iDose4 images on all seven aspects (p < 0.05) and was not related to the applied radiation dose reduction. CONCLUSION In RD IMR with O-MAR images, CT numbers remained constant, noise decreased and contrast-to-noise ratios between muscle and fat increased compared with FD iDose4 with O-MAR images in patients with metal-on-metal THAs. Subjective image quality reduced, regardless of the degree of radiation dose reduction.
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Affiliation(s)
- Ruud H. H. Wellenberg
- grid.452600.50000 0001 0547 5927Department of Radiology, Isala, Dokter van Heesweg 2, 8025 AB Zwolle, The Netherlands ,grid.7177.60000000084992262Department of Radiology and Nuclear Medicine, Amsterdam UMC, University of Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands
| | - Jochen A. C. van Osch
- grid.452600.50000 0001 0547 5927Department of Radiology, Isala, Dokter van Heesweg 2, 8025 AB Zwolle, The Netherlands
| | - Henk J. Boelhouwers
- grid.452600.50000 0001 0547 5927Department of Radiology, Isala, Dokter van Heesweg 2, 8025 AB Zwolle, The Netherlands
| | - Mireille A. Edens
- grid.452600.50000 0001 0547 5927Department of Innovation and Science, Isala, Zwolle, The Netherlands
| | - Geert J. Streekstra
- Department of Biomedical Engineering and Physics, Amsterdam UMC, Amsterdam, The Netherlands
| | - Harmen B. Ettema
- grid.452600.50000 0001 0547 5927Department of Orthopedic Surgery, Isala, Zwolle, The Netherlands
| | - Martijn F. Boomsma
- grid.452600.50000 0001 0547 5927Department of Radiology, Isala, Dokter van Heesweg 2, 8025 AB Zwolle, The Netherlands
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Ade N, Oderinde O, du Plessis F. Monte Carlo dose in a prosthesis phantom based on exact geometry vs streak artefact contaminated CT data as benchmarked against Gafchromic film measurements. Phys Med 2018; 54:94-102. [DOI: 10.1016/j.ejmp.2018.09.124] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2018] [Revised: 09/10/2018] [Accepted: 09/28/2018] [Indexed: 11/26/2022] Open
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Andersson KM, Dahlgren CV, Reizenstein J, Cao Y, Ahnesjö A, Thunberg P. Evaluation of two commercial CT metal artifact reduction algorithms for use in proton radiotherapy treatment planning in the head and neck area. Med Phys 2018; 45:4329-4344. [PMID: 30076784 DOI: 10.1002/mp.13115] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Revised: 07/19/2018] [Accepted: 07/26/2018] [Indexed: 12/19/2022] Open
Abstract
PURPOSE To evaluate two commercial CT metal artifact reduction (MAR) algorithms for use in proton treatment planning in the head and neck (H&N) area. METHODS An anthropomorphic head phantom with removable metallic implants (dental fillings or neck implant) was CT-scanned to evaluate the O-MAR (Philips) and the iMAR (Siemens) algorithms. Reference images were acquired without any metallic implants in place. Water equivalent thickness (WET) was calculated for different path directions and compared between image sets. Images were also evaluated for use in proton treatment planning for parotid, tonsil, tongue base, and neck node targets. The beams were arranged so as to not traverse any metal prior to the target, enabling evaluation of the impact on dose calculation accuracy from artifacts surrounding the metal volume. Plans were compared based on γ analysis (1 mm distance-to-agreement/1% difference in local dose) and dose volume histogram metrics for targets and organs at risk (OARs). Visual grading evaluation of 30 dental implant patient MAR images was performed by three radiation oncologists. RESULTS In the dental fillings images, ΔWET along a low-density streak was reduced from -17.0 to -4.3 mm with O-MAR and from -16.1 mm to -2.3 mm with iMAR, while for other directions the deviations were increased or approximately unchanged when the MAR algorithms were used. For the neck implant images, ΔWET was generally reduced with MAR but residual deviations remained (of up to -2.3 mm with O-MAR and of up to -1.5 mm with iMAR). The γ analysis comparing proton dose distributions for uncorrected/MAR plans and corresponding reference plans showed passing rates >98% of the voxels for all phantom plans. However, substantial dose differences were seen in areas of most severe artifacts (γ passing rates of down to 89% for some cases). MAR reduced the deviations in some cases, but not for all plans. For a single patient case dosimetrically evaluated, minor dose differences were seen between the uncorrected and MAR plans (γ passing rate approximately 97%). The visual grading of patient images showed that MAR significantly improved image quality (P < 0.001). CONCLUSIONS O-MAR and iMAR significantly improved image quality in terms of anatomical visualization for target and OAR delineation in dental implant patient images. WET calculations along several directions, all outside the metallic regions, showed that both uncorrected and MAR images contained metal artifacts which could potentially lead to unacceptable errors in proton treatment planning. ΔWET was reduced by MAR in some areas, while increased or unchanged deviations were seen for other path directions. The proton treatment plans created for the phantom images showed overall acceptable dose distributions differences when compared to the reference cases, both for the uncorrected and MAR images. However, substantial dose distribution differences in the areas of most severe artifacts were seen for some plans, which were reduced by MAR in some cases but not all. In conclusion, MAR could be beneficial to use for proton treatment planning; however, case-by-case evaluations of the metal artifact-degraded images are always recommended.
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Affiliation(s)
- Karin M Andersson
- The Skandion Clinic, 752 37, Uppsala, Sweden.,School of Health and Medical Sciences, Örebro University, 70182, Örebro, Sweden
| | | | - Johan Reizenstein
- Department of Oncology, Faculty of Medicine and Health, Örebro University, 70182, Örebro, Sweden
| | - Yang Cao
- Clinical Epidemiology and Biostatistics, School of Medical Sciences, Örebro University, 70182, Örebro, Sweden.,Unit of Biostatistics, Institute of Environmental Medicine, Karolinska Institutet, 17177, Stockholm, Sweden
| | - Anders Ahnesjö
- Medical Radiation Sciences, Department of Immunology, Genetics and Pathology, Uppsala University, 751 85, Uppsala, Sweden
| | - Per Thunberg
- Department of Medical Physics, Faculty of Medicine and Health, Örebro University, 70182, Örebro, Sweden
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Bolstad K, Flatabø S, Aadnevik D, Dalehaug I, Vetti N. Metal artifact reduction in CT, a phantom study: subjective and objective evaluation of four commercial metal artifact reduction algorithms when used on three different orthopedic metal implants. Acta Radiol 2018; 59:1110-1118. [PMID: 29310445 DOI: 10.1177/0284185117751278] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Background Metal implants may introduce severe artifacts in computed tomography (CT) images. Over the last few years dedicated algorithms have been developed in order to reduce metal artifacts in CT images. Purpose To investigate and compare metal artifact reduction algorithms (MARs) from four different CT vendors when imaging three different orthopedic metal implants. Material and Methods Three clinical metal implants were attached to the leg of an anthropomorphic phantom: cobalt-chrome; stainless steel; and titanium. Four commercial MARs were investigated: SmartMAR (GE); O-MAR (Philips); iMAR (Siemens); and SEMAR (Toshiba). The images were evaluated subjectively by three observers and analyzed objectively by calculating the fraction of pixels with CT number above 500 HU in a region of interest around the metal. The average CT number and image noise were also measured. Results Both subjective evaluation and objective analysis showed that MARs reduced metal artifacts and improved the image quality for CT images containing metal implants of steel and cobalt-chrome. When using MARs on titanium, all MARs introduced new visible artifacts. Conclusion The effect of MARs varied between CT vendors and different metal implants used in orthopedic surgery. Both in subjective evaluation and objective analysis the effect of applying MARs was most obvious on steel and cobalt-chrome implants when using SEMAR from Toshiba followed by SmartMAR from GE. However, MARs may also introduce new image artifacts especially when used on titanium implants. Therefore, it is important to reconstruct all CT images containing metal with and without MARs.
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Affiliation(s)
- Kirsten Bolstad
- Department of Oncology and Medical Physics, Haukeland University Hospital, Bergen, Norway
| | - Silje Flatabø
- Department of Oncology and Medical Physics, Haukeland University Hospital, Bergen, Norway
| | - Daniel Aadnevik
- Department of Oncology and Medical Physics, Haukeland University Hospital, Bergen, Norway
| | - Ingvild Dalehaug
- Department of Oncology and Medical Physics, Haukeland University Hospital, Bergen, Norway
| | - Nils Vetti
- Department of Radiology, Haukeland University Hospital, Bergen, Norway
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Katsura M, Sato J, Akahane M, Kunimatsu A, Abe O. Current and Novel Techniques for Metal Artifact Reduction at CT: Practical Guide for Radiologists. Radiographics 2018. [PMID: 29528826 DOI: 10.1148/rg.2018170102] [Citation(s) in RCA: 188] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Artifacts caused by metallic implants appear as dark and bright streaks at computed tomography (CT), which severely degrade the image quality and decrease the diagnostic value of the examination. When x-rays pass through a metal object, depending on its size and composition, different physical effects negatively affect the measurements in the detector, most notably the effects of photon starvation and beam hardening. To improve image quality and recover information about underlying structures, several artifact reduction methods have been introduced in modern CT systems. Projection-based metal artifact reduction (MAR) algorithms act in projection space and replace corrupted projections caused by metal with interpolation from neighboring uncorrupted projections. MAR algorithms primarily suppress artifacts that are due to photon starvation. The dual-energy CT technique is characterized by data acquisition at two different energy spectra. Dual-energy CT provides synthesized virtual monochromatic images at different photon energy (kiloelectron volt) levels, and virtual monochromatic images obtained at high kiloelectron volt levels are known to reduce the effects of beam hardening. In clinical practice, although MAR algorithms can be applied after image acquisition, the decision whether to apply dual-energy CT for the patient usually needs to be made before image acquisition. Radiologists should be more familiar with the clinical and technical features of each method and should be able to choose the optimal method according to the clinical situation. ©RSNA, 2018.
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Affiliation(s)
- Masaki Katsura
- From the Department of Radiology, Graduate School of Medicine (M.K., J.S., O.A.), and the Department of Radiology, Institute of Medical Science (A.K.), the University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan; and the Department of Radiology, School of Medicine, International University of Health and Welfare, Chiba, Japan (M.A.)
| | - Jiro Sato
- From the Department of Radiology, Graduate School of Medicine (M.K., J.S., O.A.), and the Department of Radiology, Institute of Medical Science (A.K.), the University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan; and the Department of Radiology, School of Medicine, International University of Health and Welfare, Chiba, Japan (M.A.)
| | - Masaaki Akahane
- From the Department of Radiology, Graduate School of Medicine (M.K., J.S., O.A.), and the Department of Radiology, Institute of Medical Science (A.K.), the University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan; and the Department of Radiology, School of Medicine, International University of Health and Welfare, Chiba, Japan (M.A.)
| | - Akira Kunimatsu
- From the Department of Radiology, Graduate School of Medicine (M.K., J.S., O.A.), and the Department of Radiology, Institute of Medical Science (A.K.), the University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan; and the Department of Radiology, School of Medicine, International University of Health and Welfare, Chiba, Japan (M.A.)
| | - Osamu Abe
- From the Department of Radiology, Graduate School of Medicine (M.K., J.S., O.A.), and the Department of Radiology, Institute of Medical Science (A.K.), the University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan; and the Department of Radiology, School of Medicine, International University of Health and Welfare, Chiba, Japan (M.A.)
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Wellenberg RHH, Hakvoort ET, Slump CH, Boomsma MF, Maas M, Streekstra GJ. Metal artifact reduction techniques in musculoskeletal CT-imaging. Eur J Radiol 2018; 107:60-69. [PMID: 30292274 DOI: 10.1016/j.ejrad.2018.08.010] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Revised: 07/02/2018] [Accepted: 08/11/2018] [Indexed: 01/02/2023]
Abstract
It is known that metal artifacts can be reduced by modifying standard acquisition and reconstruction, by modifying projection data and/or image data and by using virtual monochromatic imaging extracted from dual-energy CT. In this review we focus on the origin of metal artifacts, technical background of commercially available metal artifact reduction (MAR) algorithms and the value of dual-energy CT and MAR software for different metal hardware in current clinical practice. Virtual monochromatic imaging reduces beam-hardening artifacts, where metal artifact reduction software effectively reduces artifacts caused by extensive photon-starvation. Both techniques have their advantages and disadvantages, and the combination of both techniques is often but not always the best solution regarding metal artifact reduction. Advances in prosthetic imaging are reinforced by advances in prosthetic design. Providing implant specific information prior to scanning is important in order to adjust the metal artifact reduction approach, minimize artifacts and optimize image quality and diagnostic value of CT.
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Affiliation(s)
- R H H Wellenberg
- Department of Radiology and Nuclear Medicine, Amsterdam University Medical Center, location AMC, University of Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands; Department of Radiology, Isala, Zwolle, The Netherlands.
| | - E T Hakvoort
- Department of Biomedical Engineering and Physics, Amsterdam University Medical Center, location AMC, Amsterdam, The Netherlands.
| | - C H Slump
- MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands.
| | - M F Boomsma
- Department of Radiology, Isala, Zwolle, The Netherlands.
| | - M Maas
- Department of Radiology and Nuclear Medicine, Amsterdam University Medical Center, location AMC, University of Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands.
| | - G J Streekstra
- Department of Biomedical Engineering and Physics, Amsterdam University Medical Center, location AMC, Amsterdam, The Netherlands.
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Long Z, Bruesewitz MR, DeLone DR, Morris JM, Amrami KK, Adkins MC, Glazebrook KN, Kofler JM, Leng S, McCollough CH, Fletcher JG, Halaweish AF, Yu L. Evaluation of projection- and dual-energy-based methods for metal artifact reduction in CT using a phantom study. J Appl Clin Med Phys 2018; 19:252-260. [PMID: 29749048 PMCID: PMC6036383 DOI: 10.1002/acm2.12347] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Revised: 03/11/2018] [Accepted: 03/27/2018] [Indexed: 12/30/2022] Open
Abstract
Objectives Both projection and dual‐energy (DE)‐based methods have been used for metal artifact reduction (MAR) in CT. The two methods can also be combined. The purpose of this work was to evaluate these three MAR methods using phantom experiments for five types of metal implants. Materials and Methods Five phantoms representing spine, dental, hip, shoulder, and knee were constructed with metal implants. These phantoms were scanned using both single‐energy (SE) and DE protocols with matched radiation output. The SE data were processed using a projection‐based MAR (iMAR, Siemens) algorithm, while the DE data were processed to generate virtual monochromatic images at high keV (Mono+, Siemens). In addition, the DE images after iMAR were used to generate Mono+ images (DE iMAR Mono+). Artifacts were quantitatively evaluated using CT numbers at different regions of interest. Iodine contrast‐to‐noise ratio (CNR) was evaluated in the spine phantom. Three musculoskeletal radiologists and two neuro‐radiologists independently ranked the artifact reduction. Results The DE Mono+ at high keV resulted in reduced artifacts but also lower iodine CNR. The iMAR method alone caused missing tissue artifacts in dental phantom. DE iMAR Mono+ caused wrong CT numbers in close proximity to the metal prostheses in knee and hip phantoms. All musculoskeletal radiologists ranked SE iMAR > DE iMAR Mono+ > DE Mono+ for knee and hip, while DE iMAR Mono+ > SE iMAR > DE Mono+ for shoulder. Both neuro‐radiologists ranked DE iMAR Mono+ > DE Mono+ > SE iMAR for spine and DE Mono+ > DE iMAR Mono+ > SE iMAR for dental. Conclusions The SE iMAR was the best choice for the hip and knee prostheses, while DE Mono+ at high keV was best for dental implants and DE iMAR Mono+ was best for spine and shoulder prostheses. Artifacts were also introduced by MAR algorithms.
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Affiliation(s)
- Zaiyang Long
- Department of Radiology, Mayo Clinic, Rochester, MN, USA
| | | | - David R DeLone
- Department of Radiology, Mayo Clinic, Rochester, MN, USA
| | | | | | - Mark C Adkins
- Department of Radiology, Mayo Clinic, Rochester, MN, USA
| | | | - James M Kofler
- Department of Radiology, Mayo Clinic, Rochester, MN, USA
| | - Shuai Leng
- Department of Radiology, Mayo Clinic, Rochester, MN, USA
| | | | | | | | - Lifeng Yu
- Department of Radiology, Mayo Clinic, Rochester, MN, USA
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Ali AM. Evaluation of Orthopedic Metal Artifact Reduction Application in Three-Dimensional Computed Tomography Reconstruction of Spinal Instrumentation: A Single Saudi Center Experience. J Clin Imaging Sci 2018; 8:11. [PMID: 29619282 PMCID: PMC5868229 DOI: 10.4103/jcis.jcis_92_17] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2017] [Accepted: 02/11/2018] [Indexed: 11/06/2022] Open
Abstract
Aim of the Study: The aim of the study was to evaluate the commercially available orthopedic metal artifact reduction (OMAR) technique in postoperative three-dimensional computed tomography (3DCT) reconstruction studies after spinal instrumentation and to investigate its clinical application. Materials and Methods: One hundred and twenty (120) patients with spinal metallic implants were included in the study. All had 3DCT reconstruction examinations using the OMAR software after obtaining the informed consents and approval of the Institution Ethical Committee. The degree of the artifacts, the related muscular density, the clearness of intermuscular fat planes, and definition of the adjacent vertebrae were qualitatively evaluated. The diagnostic satisfaction and quality of the 3D reconstruction images were thoroughly assessed. Results: The majority (96.7%) of 3DCT reconstruction images performed were considered satisfactory to excellent for diagnosis. Only 3.3% of the reconstructed images had rendered unacceptable diagnostic quality. Conclusion: OMAR can effectively reduce metallic artifacts in patients with spinal instrumentation with highly diagnostic 3DCT reconstruction images.
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Affiliation(s)
- Amir Monir Ali
- Department of Radiodiagnosis, Faculty of Medicine, Mansoura University, Egypt.,Department of Medical Imaging, Sultan Bin Abdulaziz Humanitarian City, Riyadh 13571-6262, Kingdom of Saudi Arabia
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Metal Artifact Reduction in X-ray Computed Tomography Using Computer-Aided Design Data of Implants as Prior Information. Invest Radiol 2018; 52:349-359. [PMID: 28106615 DOI: 10.1097/rli.0000000000000345] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES The performance of metal artifact reduction (MAR) methods in x-ray computed tomography (CT) suffers from incorrect identification of metallic implants in the artifact-affected volumetric images. The aim of this study was to investigate potential improvements of state-of-the-art MAR methods by using prior information on geometry and material of the implant. MATERIALS AND METHODS The influence of a novel prior knowledge-based segmentation (PS) compared with threshold-based segmentation (TS) on 2 MAR methods (linear interpolation [LI] and normalized-MAR [NORMAR]) was investigated. The segmentation is the initial step of both MAR methods. Prior knowledge-based segmentation uses 3-dimensional registered computer-aided design (CAD) data as prior knowledge to estimate the correct position and orientation of the metallic objects. Threshold-based segmentation uses an adaptive threshold to identify metal. Subsequently, for LI and NORMAR, the selected voxels are projected into the raw data domain to mark metal areas. Attenuation values in these areas are replaced by different interpolation schemes followed by a second reconstruction. Finally, the previously selected metal voxels are replaced by the metal voxels determined by PS or TS in the initial reconstruction. First, we investigated in an elaborate phantom study if the knowledge of the exact implant shape extracted from the CAD data provided by the manufacturer of the implant can improve the MAR result. Second, the leg of a human cadaver was scanned using a clinical CT system before and after the implantation of an artificial knee joint. The results were compared regarding segmentation accuracy, CT number accuracy, and the restoration of distorted structures. RESULTS The use of PS improved the efficacy of LI and NORMAR compared with TS. Artifacts caused by insufficient segmentation were reduced, and additional information was made available within the projection data. The estimation of the implant shape was more exact and not dependent on a threshold value. Consequently, the visibility of structures was improved when comparing the new approach to the standard method. This was further confirmed by improved CT value accuracy and reduced image noise. CONCLUSIONS The PS approach based on prior implant information provides image quality which is superior to TS-based MAR, especially when the shape of the metallic implant is complex. The new approach can be useful for improving MAR methods and dose calculations within radiation therapy based on the MAR corrected CT images.
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