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Yilmaz B, Guo X, Schimmel M, Abou-Ayash S. Effect of industrial scanner and framework material interaction on the marginal gaps of CAD-CAM complete arch implant frameworks. J Prosthet Dent 2023; 130:723-730. [PMID: 34998580 DOI: 10.1016/j.prosdent.2021.10.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2021] [Revised: 10/18/2021] [Accepted: 10/18/2021] [Indexed: 12/27/2022]
Abstract
STATEMENT OF PROBLEM Structured-light and computed tomography industrial scanners have been used as reference scanners to measure marginal gaps between implants and superstructures. However, the effect of framework material on the scanners' ability to detect gaps and on precision has not yet been evaluated. PURPOSE The purpose of this in vitro study was to investigate the interaction between the industrial scanner and framework material on measured marginal gaps of implant-supported fixed complete arch frameworks made from titanium and polymethylmethacrylate and on the precision of scans. MATERIAL AND METHODS A completely edentulous maxillary model with 4 implants and multiunit abutments at the first molar and canine sites was digitized by using a laboratory scanner. Implant-supported frameworks were milled from titanium and polymethylmethacrylate (n=5). Each framework was secured on the left molar site abutment. The marginal gaps between the frameworks and abutment sites without a screw were measured by using an industrial structured-light scanner and an industrial computed tomography scanner. The effect of the scanner, the framework material, and their interaction on measured gaps was analyzed by applying linear regressions and weighted least square methods. The F-statistics was used with Bonferroni corrections for precision analysis (α=.05). RESULTS No significant effect of scanner, material, or their interaction was found on the marginal gaps at the canine sites. The titanium framework gaps detected by using the computed tomography scanner were greater than those detected by using the structured-light scanner at the right molar site (estimated difference in means=0.054 mm; P=.003) and overall (estimated difference in means=0.023 mm; P=.033). The structured-light scanner's precision was higher than that of the computed tomography scanner when titanium frameworks were scanned (P=.001). The computed tomography scanner's precision was higher when scanning polymethylmethacrylate frameworks than when scanning titanium frameworks (P=.03). CONCLUSIONS Framework material and industrial scanner interaction affected the measured gaps. The computed tomography scanner detected greater marginal gaps with low precision when scanning titanium frameworks than the structured-light scanner. The sample size, the use of only 2 types of materials, and a laboratory scanner to obtain the computer-aided design file should be considered when interpreting the results.
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Affiliation(s)
- Burak Yilmaz
- Associate Professor, Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland; Associate Professor, Department of Restorative, Preventive and Pediatric Dentistry, School of Dental Medicine, University of Bern, Bern, Switzerland; Adjunct Professor, Division of Restorative and Prosthetic Dentistry, The Ohio State University College of Dentistry, Columbus, Ohio
| | - Xiaohan Guo
- PhD student, Division of Biostatistics, College of Public Health, The Ohio State University, Columbus, Ohio
| | - Martin Schimmel
- Department Head, Department of Reconstructive Dentistry and Gerodontology, University of Bern, Bern, Switzerland; Senior Lecturer, Extra muros, Division of Gerodontology and Removable Prosthodontics, University Clinics of Dental Medicine, University of Geneva, Geneva, Switzerland
| | - Samir Abou-Ayash
- Senior Lecturer and Head of the Section of Digital Implant and Reconstructive Dentistry, Department of Reconstructive Dentistry and Gerodontology, University of Bern, Bern, Switzerland.
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Klein L, Liu C, Steidel J, Enzmann L, Knaup M, Sawall S, Maier A, Lell M, Maier J, Kachelrieß M. Patient-specific radiation risk-based tube current modulation for diagnostic CT. Med Phys 2022; 49:4391-4403. [PMID: 35421263 DOI: 10.1002/mp.15673] [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: 04/25/2021] [Revised: 03/11/2022] [Accepted: 03/29/2022] [Indexed: 11/08/2022] Open
Abstract
PURPOSE Modern CT scanners use automatic exposure control (AEC) techniques, such as tube current modulation (TCM), to reduce dose delivered to patients while maintaining image quality. In contrast to conventional approaches that minimize the tube current time product of the CT scan, referred to as mAsTCM in the following, we herein propose a new method referred to as riskTCM which aims at reducing the radiation risk to the patient by taking into account the specific radiation risk of every dose-sensitive organ. METHODS For current mAsTCM implementations, the mAs-product is used as a surrogate for the patient dose. Thus they do not take into account the varying dose sensitivity of different organs. Our riskTCM framework assumes that a coarse CT reconstruction, an organ segmentation and an estimation of the dose distribution can be provided in real time, e.g. by applying machine learning techniques. Using this information riskTCM determines a tube current curve that minimizes a patient risk measure, e.g. the effective dose, while keeping the image quality constant. We retrospectively applied riskTCM to 20 patients covering all relevant anatomical regions and tube voltages from 70 kV to 150 kV. The potential reduction of effective dose at same image noise is evaluated as a figure of merit and compared to mAsTCM and to a situation with a constant tube current referred to as noTCM. RESULTS Anatomical regions like the neck, thorax, abdomen and the pelvis benefit from the proposed riskTCM. On average, a reduction of effective dose of about 23 % for the thorax, 31 % for the abdomen, 24 % for the pelvis, and 27% for the neck have been evaluated compared to today's state-of-the-art mAsTCM. For the head, the resulting reduction of effective dose is lower, about 13 % on average compared to mAsTCM. CONCLUSIONS With a risk-minimizing tube current modulation, significant higher reduction of effective dose compared to mAs-minimizing tube current modulation is possible. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Laura Klein
- Division of X-Ray Imaging and CT, German Cancer Research Center (DKFZ), Heidelberg, Germany.,Department of Physics and Astronomy, Ruprecht-Karls-University Heidelberg, Heidelberg, Germany
| | - Chang Liu
- Pattern Recognition Lab, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Jörg Steidel
- Division of X-Ray Imaging and CT, German Cancer Research Center (DKFZ), Heidelberg, Germany.,Department of Physics and Astronomy, Ruprecht-Karls-University Heidelberg, Heidelberg, Germany
| | - Lucia Enzmann
- Division of X-Ray Imaging and CT, German Cancer Research Center (DKFZ), Heidelberg, Germany.,Department of Physics and Astronomy, Ruprecht-Karls-University Heidelberg, Heidelberg, Germany
| | - Michael Knaup
- Division of X-Ray Imaging and CT, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Stefan Sawall
- Division of X-Ray Imaging and CT, German Cancer Research Center (DKFZ), Heidelberg, Germany.,Medical Faculty, Ruprecht-Karls-University Heidelberg, Heidelberg, Germany
| | - Andreas Maier
- Pattern Recognition Lab, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Michael Lell
- Department of Radiology and Nuclear Medicine, Klinikum Nürnberg, Paracelsus Medical University, Nürnberg
| | - Joscha Maier
- Division of X-Ray Imaging and CT, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Marc Kachelrieß
- Division of X-Ray Imaging and CT, German Cancer Research Center (DKFZ), Heidelberg, Germany.,Medical Faculty, Ruprecht-Karls-University Heidelberg, Heidelberg, Germany
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Chumak VV, Petrenko NP, Bakhanova OV, Voloskyi VM, Treskunova TV. USE OF ANTHROPOMORPHIC HETEROGENEOUS PHYSICAL PHANTOMS FOR VALIDATION OF COMPUTATIONAL DOSIMETRY OF MEDICAL PERSONNEL AND PATIENTS. PROBLEMY RADIAT︠S︡IĬNOÏ MEDYT︠S︡YNY TA RADIOBIOLOHIÏ 2020; 25:148-176. [PMID: 33361833 DOI: 10.33145/2304-8336-2020-25-148-176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Indexed: 11/10/2022]
Abstract
In the dosimetry of ionizing radiation, the phantoms of the human body, which are used as a replacement for thehuman body in physical measurements and calculations, play an important, but sometimes underestimated, role.There are physical phantoms used directly for measurements, and mathematical phantoms for computationaldosimetry. Their complexity varies from simple geometry applied for calibration purposes up to very complex, whichsimulates in detail the shapes of organs and tissues of the human body. The use of physical anthropomorphic phantoms makes it possible to effectively optimize radiation doses by adjusting the parameters of CT-scanning (computed tomography) in accordance with the characteristics of the patient without compromising image quality. The useof phantoms is an indispensable approach to estimate the actual doses to the organs or to determine the effectivedose of workers - values that are regulated, but cannot be directly measured.The article contains an overview of types, designs and the fields of application of anthropomorphic heterogeneousphysical phantoms of a human with special emphasis on their use for validation of models and methods of computational dosimetry.
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Affiliation(s)
- V V Chumak
- State Institution «National Research Center for Radiation Medicine of the National Academy of Medical Sciences of Ukraine», 53 Yuriia Illienka St., Kyiv, 04050, Ukraine
| | - N P Petrenko
- State Institution «National Research Center for Radiation Medicine of the National Academy of Medical Sciences of Ukraine», 53 Yuriia Illienka St., Kyiv, 04050, Ukraine
| | - O V Bakhanova
- State Institution «National Research Center for Radiation Medicine of the National Academy of Medical Sciences of Ukraine», 53 Yuriia Illienka St., Kyiv, 04050, Ukraine
| | - V M Voloskyi
- State Institution «National Research Center for Radiation Medicine of the National Academy of Medical Sciences of Ukraine», 53 Yuriia Illienka St., Kyiv, 04050, Ukraine
| | - T V Treskunova
- State Institution «National Research Center for Radiation Medicine of the National Academy of Medical Sciences of Ukraine», 53 Yuriia Illienka St., Kyiv, 04050, Ukraine
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Davoudi M, Khoramian D, Abedi-Firouzjah R, Ataei G. STRATEGY OF COMPUTED TOMOGRAPHY IMAGE OPTIMISATION IN CERVICAL VERTEBRAE AND NECK SOFT TISSUE IN EMERGENCY PATIENTS. RADIATION PROTECTION DOSIMETRY 2019; 187:98-102. [PMID: 31135908 DOI: 10.1093/rpd/ncz145] [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: 10/31/2018] [Revised: 04/27/2019] [Accepted: 05/03/2019] [Indexed: 06/09/2023]
Abstract
INTRODUCTION With regards to the use of ionisation radiation in the computed tomography (CT), optimal parameters should be used to reduce the risk of incidence of secondary cancers in patients who are constantly exposed to X-rays. The aim of this study was to optimise the parameters used in CT scan of cervical vertebrae and neck soft tissue with minimal loss of image quality in emergency patients. MATERIALS AND METHODS In this study, the patients were divided into two groups. The first group consisted of patients scanned with default parameters and the second group scanned with optimised parameters. All the study has been implemented in emergency settings. The cases included cervical vertebrae and soft tissue protocols. Common CT dose descriptors including weighted computed tomography dose index (CTDIw), volumetric CTDI (CTDIvol), dose length product (DLP), effective dose (ED) and image noise were measured for each group. The ImpactDose program was used to estimate the organs doses. Statistical analysis was performed using Kruskal-Wallis test using SPSS software. RESULTS There was no significant quality reduction in the optimised images. Decreasing in radiation dose parameters for the soft tissue was: kVp=16.7%, mAs=64.3% and pitch=24.1%, and for the cervical vertebrae was: kVp=16.7%, mAs=54.2% and pitch=48.3%. Consequently, decreasing these parameters reduced CTDIw=81.0%, CTDIvol=90.0% and DLP = 90.2% in the cervical vertebral protocol, as well as CTDIw=75.5%, CTDIvol=81.3% and DLP = 81.4% in the soft tissue protocol. CONCLUSION Regarding the results, the optimised parameters in the mentioned organ scan reduce the radiation dose in the target area and the organs surrounding. Therefore, these protocols can be used for reducing the risk of cancer.
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Affiliation(s)
- Mohammad Davoudi
- MSc of Medical Radiation Engineering, Department of Medical Imaging Center, Babol University of Medical Sciences Babol, Iran
| | - Daryoush Khoramian
- The Advocate Center for Clinical Research, Ayatollah Yasrebi Hospital, Kashan, Iran
| | - Razzagh Abedi-Firouzjah
- Department of Medical Physics Radiobiology and Radiation Protection, Babol University of Medical Sciences, Babol, Iran
| | - Gholamreza Ataei
- Department of Radiology Technology, Faculty of Paramedical Sciences, Babol University of Medical Science, Babol, Iran
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Chian TC, Nassir NM, Ibrahim MI, Yusof AKM, Sabarudin A. Quantitative assessment on coronary computed tomography angiography (CCTA) image quality: comparisons between genders and different tube voltage settings. Quant Imaging Med Surg 2017; 7:48-58. [PMID: 28275559 DOI: 10.21037/qims.2017.02.02] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND This study was carried out to quantify and compare the quantitative image quality of coronary computed tomography angiography (CCTA) between genders as well as between different tube voltages scan protocols. METHODS Fifty-five cases of CCTA were collected retrospectively and all images including reformatted axial images at systolic and diastolic phases as well as images with curved multi planar reformation (cMPR) were obtained. Quantitative image quality including signal intensity, image noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of right coronary artery (RCA), left anterior descending artery (LAD), left circumflex artery (LCx) and left main artery (LM) were quantified using Analyze 12.0 software. RESULTS Six hundred and fifty-seven coronary arteries were evaluated. There were no significant differences in any quantitative image quality parameters between genders. 100 kilovoltage peak (kVp) scanning protocol produced images with significantly higher signal intensity compared to 120 kVp scanning protocol (P<0.001) in all coronary arteries in all types of images. Higher SNR was also observed in 100 kVp scan protocol in all coronary arteries except in LCx where 120 kVp showed better SNR than 100 kVp. CONCLUSIONS There were no significant differences in image quality of CCTA between genders and different tube voltages. Lower tube voltage (100 kVp) scanning protocol is recommended in clinical practice to reduce the radiation dose to patient.
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Affiliation(s)
- Teo Chee Chian
- Diagnostic Imaging & Radiotherapy Program, School of Diagnostic and Applied Health Sciences, Faculty of Health Sciences, Universiti Kebangsaan Malaysia, 50300 Kuala Lumpur, Malaysia
| | - Norziana Mat Nassir
- Diagnostic Imaging & Radiotherapy Program, School of Diagnostic and Applied Health Sciences, Faculty of Health Sciences, Universiti Kebangsaan Malaysia, 50300 Kuala Lumpur, Malaysia
| | - Mohd Izuan Ibrahim
- Diagnostic Imaging & Radiotherapy Program, School of Diagnostic and Applied Health Sciences, Faculty of Health Sciences, Universiti Kebangsaan Malaysia, 50300 Kuala Lumpur, Malaysia
| | | | - Akmal Sabarudin
- Diagnostic Imaging & Radiotherapy Program, School of Diagnostic and Applied Health Sciences, Faculty of Health Sciences, Universiti Kebangsaan Malaysia, 50300 Kuala Lumpur, Malaysia
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Introduction of an Effective Method for the Optimization of CT Protocols Using Iterative Reconstruction Algorithms: Comparison With Patient Data. AJR Am J Roentgenol 2014; 203:W434-9. [DOI: 10.2214/ajr.13.11973] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Strauss KJ. Developing patient-specific dose protocols for a CT scanner and exam using diagnostic reference levels. Pediatr Radiol 2014; 44 Suppl 3:479-88. [PMID: 25037975 DOI: 10.1007/s00247-014-3088-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 06/04/2014] [Accepted: 06/12/2014] [Indexed: 11/30/2022]
Abstract
The management of image quality and radiation dose during pediatric CT scanning is dependent on how well one manages the radiographic techniques as a function of the type of exam, type of CT scanner, and patient size. The CT scanner's display of expected CT dose index volume (CTDIvol) after the projection scan provides the operator with a powerful tool prior to the patient scan to identify and manage appropriate CT techniques, provided the department has established appropriate diagnostic reference levels (DRLs). This paper provides a step-by-step process that allows the development of DRLs as a function of type of exam, of actual patient size and of the individual radiation output of each CT scanner in a department. Abdomen, pelvis, thorax and head scans are addressed. Patient sizes from newborns to large adults are discussed. The method addresses every CT scanner regardless of vendor, model or vintage. We cover adjustments to techniques to manage the impact of iterative reconstruction and provide a method to handle all available voltages other than 120 kV. This level of management of CT techniques is necessary to properly monitor radiation dose and image quality during pediatric CT scans.
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Affiliation(s)
- Keith J Strauss
- Department of Radiology, Cincinnati Children's Hospital Medical Center, MLC 5031, 3333 Burnet Ave., Cincinnati, OH, 45229-3026, USA,
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Utility of additional CT examinations driven by completion of a standard trauma imaging protocol in patients transferred for minor trauma. Emerg Radiol 2014; 21:341-7. [PMID: 24532129 DOI: 10.1007/s10140-014-1200-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Accepted: 01/28/2014] [Indexed: 10/25/2022]
Abstract
Many clinicians order focused computed tomography (CT) examinations for trauma patients based on history and physical examinations. Trauma patients transferred to our level I trauma center undergo an extensive, nonfocused standard trauma CT protocol. We hypothesize that the use of the standard trauma CT protocol does not contribute significant clinical information for patient care when compared with CT examinations based on history and physical examination. We aim to quantify the utility of the additional CT examinations required by our institution's trauma protocol compared with emergent CT examinations dictated by the patient's history and physical examination findings. In this IRB-approved study, we retrospectively evaluated 132 trauma patients transferred to our center who underwent additional CT examinations as determined by fulfillment of our institution's standard trauma CT protocol. The emergency radiologist evaluated the CT examinations acquired after the patient's transfer to determine if there were any additional acute findings that were identified on these additional examinations compared with the initial assessment undertaken at the outside institution. A total of 101 patients transferred to our trauma center met inclusion criteria. The majority of these patients sustained minor trauma. The standard trauma protocol generated 474 negative CT examinations in 101 patients. In seven patients, there were unexpected acute findings. However, these unexpected acute findings did not change clinical management in any of the patients. After initial evaluation, the acquisition of additional nonfocused CT examinations based on the standard trauma CT protocol provides little useful clinical information in patients who are transferred for minor trauma. Rather, CT utilization should be based on clinical findings. Replacement of standard trauma CT protocol with focused CT examinations in trauma patients is a way to curtail overutilization, thereby decreasing health care cost and the amount of patient radiation exposure.
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Bernstine H, Sopov V, Yefremov N, Nidam M, Gabbai M, Sosna J, Groshar D. Comparison of 80 and 120 kVp contrast-enhanced CT for attenuation correction in PET/CT, using quantitative analysis and reporter assessment of PET image quality. Clin Radiol 2013; 69:e17-24. [PMID: 24156801 DOI: 10.1016/j.crad.2013.08.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 07/24/2013] [Accepted: 08/06/2013] [Indexed: 12/13/2022]
Abstract
AIM To determine the effect of low tube voltage on positron-emission tomography (PET) image quality, quantitative analysis, and radiation dose in a combined PET/computed tomography (CT) study in patients with normal body mass index (BMI). MATERIALS AND METHODS One hundred and twenty-nine examinations performed in 46 patients (mean age 57 years), who had at least two separate studies were retrospectively evaluated; at least one with 120 kVp and one with 80 kVp. Three independent readers reviewed all PET images and graded the image quality. PET signal and noise were recorded on the liver, spleen, fat, bone marrow, and aorta. CT dose index (CTDI) and the dose-length product (DLP) were used for CT radiation dose estimation. A mixed-effects model analysis was used for comparison of estimated radiation dose and PET data. RESULTS There was a significant decrease of 15% in the radiation dose estimates between 80 and 120 kVp (DLP 946.2 ± 189 versus 1157.0 ± 236, respectively; p < 0.001). There was an increase of 12% in PET signal in the normal liver with 80 kVp. The average score of PET image quality obtained between 80 and 120 kVp was 4.85 ± 0.42 versus 4.90 ± 0.27, respectively (p = 0.47). CONCLUSION PET/80 kVp CT has no statistically significant difference in the PET image quality and quantitative analysis compared to PET/120 kVp and may be used in selected patients to reduce the radiation dose.
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Affiliation(s)
- H Bernstine
- Department of Nuclear Medicine, Rabin Medical Center, Petah Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - V Sopov
- Department of Nuclear Medicine, Rabin Medical Center, Petah Tikva, Israel
| | - N Yefremov
- Department of Nuclear Medicine, Rabin Medical Center, Petah Tikva, Israel
| | - M Nidam
- Department of Nuclear Medicine, Rabin Medical Center, Petah Tikva, Israel
| | - M Gabbai
- Department of Radiology, Hadassah Hebrew University Medical Center, Jerusalem, Israel
| | - J Sosna
- Department of Radiology, Hadassah Hebrew University Medical Center, Jerusalem, Israel; Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - D Groshar
- Department of Nuclear Medicine, Rabin Medical Center, Petah Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; Department of Nuclear Medicine, Assuta Medical Center, Tel Aviv, Israel.
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Automatic selection of tube potential for radiation dose reduction in vascular and contrast-enhanced abdominopelvic CT. AJR Am J Roentgenol 2013; 201:W297-306. [PMID: 23883244 DOI: 10.2214/ajr.12.9610] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVE The purpose of this study is to assess the ability of a novel automatic tube potential selection tool to reduce radiation dose while maintaining diagnostic quality in CT angiography (CTA) and contrast-enhanced abdominopelvic CT. MATERIALS AND METHODS One hundred one CTA examinations and 90 contrastenhanced abdominopelvic examinations were performed using an automatic tube potential selection tool on a 128-MDCT scanner. Two vascular radiologists and two abdominal radiologists evaluated the image quality for sharpness, noise, artifact, and diagnostic confidence. In a subset of patients who had undergone prior studies (CTA, 28 patients; abdominopelvic CT, 25 patients), a side-by-side comparison was performed by a separate radiologist. Dose reduction and iodine contrast-to-noise ratio resulting from use of the tool were calculated. RESULTS For CTA, 80 or 100 kV was selected for 73% of the scans, with a mean dose reduction of 36% relative to the reference 120-kV protocol. For abdominopelvic CT examinations, 80 or 100 kV was used for 55% of the scans, with a mean dose reduction of 25%. Overall dose reduction relative to the reference 120-kV protocol was 25% and 13% for CTA and abdominopelvic CT scans, respectively. Over 98% of scans had acceptable sharpness, noise texture, artifact, and diagnostic confidence for both readers and diagnostic tasks; 94-100% of scans had acceptable noise. Iodine contrast-to-noise ratio was significantly higher than (p < 0.001) or similar to (p = 0.11) that of prior scans, and equivalent quality was achieved despite the dose reduction. CONCLUSION Automatic tube potential selection provides an efficient and quantitativeway to guide the selection of the optimal tube potential for CTA and abdominopelvic CT examinations.
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Brady SL, Yee BS, Kaufman RA. Characterization of adaptive statistical iterative reconstruction algorithm for dose reduction in CT: A pediatric oncology perspective. Med Phys 2012; 39:5520-31. [PMID: 22957619 DOI: 10.1118/1.4745563] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
PURPOSE This study demonstrates a means of implementing an adaptive statistical iterative reconstruction (ASiR™) technique for dose reduction in computed tomography (CT) while maintaining similar noise levels in the reconstructed image. The effects of image quality and noise texture were assessed at all implementation levels of ASiR™. Empirically derived dose reduction limits were established for ASiR™ for imaging of the trunk for a pediatric oncology population ranging from 1 yr old through adolescence∕adulthood. METHODS Image quality was assessed using metrics established by the American College of Radiology (ACR) CT accreditation program. Each image quality metric was tested using the ACR CT phantom with 0%-100% ASiR™ blended with filtered back projection (FBP) reconstructed images. Additionally, the noise power spectrum (NPS) was calculated for three common reconstruction filters of the trunk. The empirically derived limitations on ASiR™ implementation for dose reduction were assessed using (1, 5, 10) yr old and adolescent∕adult anthropomorphic phantoms. To assess dose reduction limits, the phantoms were scanned in increments of increased noise index (decrementing mA using automatic tube current modulation) balanced with ASiR™ reconstruction to maintain noise equivalence of the 0% ASiR™ image. RESULTS The ASiR™ algorithm did not produce any unfavorable effects on image quality as assessed by ACR criteria. Conversely, low-contrast resolution was found to improve due to the reduction of noise in the reconstructed images. NPS calculations demonstrated that images with lower frequency noise had lower noise variance and coarser graininess at progressively higher percentages of ASiR™ reconstruction; and in spite of the similar magnitudes of noise, the image reconstructed with 50% or more ASiR™ presented a more smoothed appearance than the pre-ASiR™ 100% FBP image. Finally, relative to non-ASiR™ images with 100% of standard dose across the pediatric phantom age spectrum, similar noise levels were obtained in the images at a dose reduction of 48% with 40% ASIR™ and a dose reduction of 82% with 100% ASIR™. CONCLUSIONS The authors' work was conducted to identify the dose reduction limits of ASiR™ for a pediatric oncology population using automatic tube current modulation. Improvements in noise levels from ASiR™ reconstruction were adapted to provide lower radiation exposure (i.e., lower mA) instead of improved image quality. We have demonstrated for the image quality standards required at our institution, a maximum dose reduction of 82% can be achieved using 100% ASiR™; however, to negate changes in the appearance of reconstructed images using ASiR™ with a medium to low frequency noise preserving reconstruction filter (i.e., standard), 40% ASiR™ was implemented in our clinic for 42%-48% dose reduction at all pediatric ages without a visually perceptible change in image quality or image noise.
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Affiliation(s)
- S L Brady
- Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, TN, USA.
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Borrás C, Huda W, Orton CG. Point/counterpoint. The use of effective dose for medical procedures is inappropriate. Med Phys 2010; 37:3497-500. [PMID: 20831055 DOI: 10.1118/1.3377778] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- Caridad Borrás
- Radiological Physics and Health Services Consultant, Washington, DC 20007, USA.
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Image gently: Ten steps you can take to optimize image quality and lower CT dose for pediatric patients. AJR Am J Roentgenol 2010; 194:868-73. [PMID: 20308484 DOI: 10.2214/ajr.09.4091] [Citation(s) in RCA: 190] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Yu L, Li H, Fletcher JG, McCollough CH. Automatic selection of tube potential for radiation dose reduction in CT: a general strategy. Med Phys 2010; 37:234-43. [PMID: 20175486 DOI: 10.1118/1.3264614] [Citation(s) in RCA: 181] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
PURPOSE To optimize radiation dose efficiency in CT while maintaining image quality, it is important to select the optimal tube potential. The selection of optimal tube potential, however, is highly dependent on patient size and diagnostic task. The purpose of this work was to develop a general strategy that allows for automatic tube potential selection for each individual patient and each diagnostic task. METHODS The authors propose a general strategy that allows automatic adaptation of the tube potential as a function of patient size and diagnostic task, using a novel index of image quality, "iodine contrast to noise ratio with a noise constraint (iCNR_NC)," to characterize the different image quality requirements by various clinical applications. The relative dose factor (RDF) at each tube potential to achieve a target image quality was then determined as a function of patient size and the noise constraint parameter. A workflow was developed to automatically identify the optimal tube potential that is both dose efficient and practically feasible, incorporating patient size and diagnostic task. An experimental study using a series of semianthropomorphic thoracic phantoms was used to demonstrate how the proposed general strategy can be implemented and how the radiation dose reduction achievable by the tube potential selection depends on phantom sizes and noise constraint parameters. RESULTS The proposed strategy provides a flexible and quantitative way to select the optimal tube potential based on the patient size and diagnostic task. The noise constraint parameter alpha can be adapted for different clinical applications. For example, alpha = 1 for noncontrast routine exams; alpha = 1.1- 1.25 for contrast-enhanced routine exams; and alpha = 1.5-2.0 for CT angiography. For the five thoracic phantoms in the experiment, when alpha = 1, the optimal tube potentials were 80, 100, 100, 120, 120, respectively. The corresponding RDFs (relative to 120 kV) were 78.0%, 90.9%, 95.2%, 100%, and 100%. When alpha = 1.5, the optimal tube potentials were 80, 80, 80, 100, 100, respectively, with corresponding RDFs of 34.7%, 44.7%, 54.7%, 60.8%, and 89.5%. CONCLUSIONS A general strategy to automatically select the most dose efficient tube potential for CT exams was developed that takes into account patient size and diagnostic task. Dependent on the patient size and the selection of noise constraint parameter for different diagnostic tasks, the dose reduction at each tube potential, quantified explicitly with the RDF, varies significantly.
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Affiliation(s)
- Lifeng Yu
- Department of Radiology, Mayo Clinic, Rochester, Minnesota 55905, USA.
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Hellinger JC, Epelman M, Rubin GD. Upper Extremity Computed Tomographic Angiography: State of the Art Technique and Applications in 2010. Radiol Clin North Am 2010; 48:397-421, ix. [DOI: 10.1016/j.rcl.2010.02.022] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Hellinger JC, Pena A, Poon M, Chan FP, Epelman M. Pediatric Computed Tomographic Angiography: Imaging the Cardiovascular System Gently. Radiol Clin North Am 2010; 48:439-67, x. [DOI: 10.1016/j.rcl.2010.03.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Alessio AM, Kinahan PE, Manchanda V, Ghioni V, Aldape L, Parisi MT. Weight-Based, Low-Dose Pediatric Whole-Body PET/CT Protocols. J Nucl Med 2009; 50:1570-7. [DOI: 10.2967/jnumed.109.065912] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Opreanu RC, Samaraweera R, Kepros JP. Effective Dose to Dose-Length Product Coefficients for Calculation of CT Effective Dose. Radiology 2009; 252:315; author reply 315. [DOI: 10.1148/radiol.2521090245] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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