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Pouymayou B, Perez-Haas Y, Allemann F, Saguner AM, Andratschke N, Guckenberger M, Tanadini-Lang S, Wilke L. Characterization of spatial integrity with active and passive implants in a low-field magnetic resonance linear accelerator scanner. Phys Imaging Radiat Oncol 2024; 30:100576. [PMID: 38644933 PMCID: PMC11031795 DOI: 10.1016/j.phro.2024.100576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 04/02/2024] [Accepted: 04/05/2024] [Indexed: 04/23/2024] Open
Abstract
Background and Purpose Standard imaging protocols can guarantee the spatial integrity of magnetic resonance (MR) images utilized in radiotherapy. However, the presence of metallic implants can significantly compromise this integrity. Our proposed method aims at characterizing the geometric distortions induced by both passive and active implants commonly encountered in planning images obtained from a low-field 0.35 T MR-linear accelerator (LINAC). Materials and Methods We designed a spatial integrity phantom defining 1276 control points and covering a field of view of 20x20x20 cm3. This phantom was scanned in a water tank with and without different implants used in hip and shoulder arthroplasty procedures as well as with active cardiac stimulators. The images were acquired with the clinical planning sequence (balanced steady-state free-precession, resolution 1.5x1.5x1.5 mm3). Spatial integrity was assessed by the Euclidian distance between the control point detected on the image and their theoretical locations. A first plane free of artefact (FPFA) was defined to evaluate the spatial integrity beyond the larger banding artefact. Results In the region extending up to 20 mm from the largest banding artefacts, the tested passive and active implants could cause distortions up to 2 mm and 3 mm, respectively. Beyond this region the spatial integrity was recovered and the image could be considered as unaffected by the implants. Conclusions We characterized the impact of common implants on a low field MR-LINAC planning sequence. These measurements could support the creation of extra margin while contouring organs at risk and target volumes in the vicinity of implants.
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Affiliation(s)
- Bertrand Pouymayou
- Department of Radiation Oncology, University Hospital Zurich and University of Zurich, Zurich, Switzerland
| | - Yoel Perez-Haas
- Department of Radiation Oncology, University Hospital Zurich and University of Zurich, Zurich, Switzerland
| | - Florin Allemann
- Department of Traumatology, University Hospital Zurich and University of Zurich, Zurich, Switzerland
| | - Ardan M. Saguner
- Department of Cardiology, University Hospital Zurich and University of Zurich, Zurich, Switzerland
| | - Nicolaus Andratschke
- Department of Radiation Oncology, University Hospital Zurich and University of Zurich, Zurich, Switzerland
| | - Matthias Guckenberger
- Department of Radiation Oncology, University Hospital Zurich and University of Zurich, Zurich, Switzerland
| | - Stephanie Tanadini-Lang
- Department of Radiation Oncology, University Hospital Zurich and University of Zurich, Zurich, Switzerland
| | - Lotte Wilke
- Department of Radiation Oncology, University Hospital Zurich and University of Zurich, Zurich, Switzerland
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2
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Cheong SCW, Yan YY, Sheikh A, Ouellette HA, Munk PL, Murray N, Mallinson PI. Dual-energy CT applications in musculoskeletal disorders. Br J Radiol 2024; 97:705-715. [PMID: 38291893 PMCID: PMC11027318 DOI: 10.1093/bjr/tqae023] [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: 07/30/2023] [Revised: 01/06/2024] [Accepted: 01/24/2024] [Indexed: 02/01/2024] Open
Abstract
Dual-energy CT (DECT) is an exciting application in CT technology conferring many advantages over conventional single-energy CT at no additional with comparable radiation dose to the patient. Various emerging and increasingly established clinical DECT applications in musculoskeletal (MSK) imaging such as bone marrow oedema detection, metal artefact reduction, monosodium urate analysis, and collagen analysis for ligamentous, meniscal, and disc injuries are made possible through its advanced DECT post-processing capabilities. These provide superior information on tissue composition, artefact reduction and image optimization. Newer DECT applications to evaluate fat fraction for sarcopenia, Rho/Z application for soft tissue calcification differentiation, 3D rendering, and AI integration are being assessed for future use. In this article, we will discuss the established and developing applications of DECT in the setting of MSK radiology as well as the basic principles of DECT which facilitate them.
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Affiliation(s)
- Sook Chuei W Cheong
- Musculoskeletal section, Department of Radiology, Vancouver General Hospital, University of British Columbia, Vancouver, BC, V5Z 1M9 Canada
- Department of Radiology, Changi General Hospital, Singapore 529889, Singapore
| | - Yet Yen Yan
- Musculoskeletal section, Department of Radiology, Vancouver General Hospital, University of British Columbia, Vancouver, BC, V5Z 1M9 Canada
- Department of Radiology, Changi General Hospital, Singapore 529889, Singapore
| | - Adnan Sheikh
- Musculoskeletal section, Department of Radiology, Vancouver General Hospital, University of British Columbia, Vancouver, BC, V5Z 1M9 Canada
| | - Hugue A Ouellette
- Musculoskeletal section, Department of Radiology, Vancouver General Hospital, University of British Columbia, Vancouver, BC, V5Z 1M9 Canada
| | - Peter L Munk
- Musculoskeletal section, Department of Radiology, Vancouver General Hospital, University of British Columbia, Vancouver, BC, V5Z 1M9 Canada
| | - Nicolas Murray
- Musculoskeletal section, Department of Radiology, Vancouver General Hospital, University of British Columbia, Vancouver, BC, V5Z 1M9 Canada
| | - Paul I Mallinson
- Musculoskeletal section, Department of Radiology, Vancouver General Hospital, University of British Columbia, Vancouver, BC, V5Z 1M9 Canada
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3
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Zaid Alkilani A, Çukur T, Saritas EU. FD-Net: An unsupervised deep forward-distortion model for susceptibility artifact correction in EPI. Magn Reson Med 2024; 91:280-296. [PMID: 37811681 DOI: 10.1002/mrm.29851] [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: 03/10/2023] [Revised: 07/18/2023] [Accepted: 08/15/2023] [Indexed: 10/10/2023]
Abstract
PURPOSE To introduce an unsupervised deep-learning method for fast and effective correction of susceptibility artifacts in reversed phase-encode (PE) image pairs acquired with echo planar imaging (EPI). METHODS Recent learning-based correction approaches in EPI estimate a displacement field, unwarp the reversed-PE image pair with the estimated field, and average the unwarped pair to yield a corrected image. Unsupervised learning in these unwarping-based methods is commonly attained via a similarity constraint between the unwarped images in reversed-PE directions, neglecting consistency to the acquired EPI images. This work introduces a novel unsupervised deep Forward-Distortion Network (FD-Net) that predicts both the susceptibility-induced displacement field and the underlying anatomically correct image. Unlike previous methods, FD-Net enforces the forward-distortions of the correct image in both PE directions to be consistent with the acquired reversed-PE image pair. FD-Net further leverages a multiresolution architecture to maintain high local and global performance. RESULTS FD-Net performs competitively with a gold-standard reference method (TOPUP) in image quality, while enabling a leap in computational efficiency. Furthermore, FD-Net outperforms recent unwarping-based methods for unsupervised correction in terms of both image and field quality. CONCLUSION The unsupervised FD-Net method introduces a deep forward-distortion approach to enable fast, high-fidelity correction of susceptibility artifacts in EPI by maintaining consistency to measured data. Therefore, it holds great promise for improving the anatomical accuracy of EPI imaging.
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Affiliation(s)
- Abdallah Zaid Alkilani
- Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey
- National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey
| | - Tolga Çukur
- Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey
- National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey
- Neuroscience Graduate Program, Bilkent University, Ankara, Turkey
| | - Emine Ulku Saritas
- Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey
- National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey
- Neuroscience Graduate Program, Bilkent University, Ankara, Turkey
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4
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Alkemade A, Großmann R, Bazin PL, Forstmann BU. Mixed methodology in human brain research: integrating MRI and histology. Brain Struct Funct 2023; 228:1399-1410. [PMID: 37365411 PMCID: PMC10335951 DOI: 10.1007/s00429-023-02675-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 06/20/2023] [Indexed: 06/28/2023]
Abstract
Postmortem magnetic resonance imaging (MRI) can provide a bridge between histological observations and the in vivo anatomy of the human brain. Approaches aimed at the co-registration of data derived from the two techniques are gaining interest. Optimal integration of the two research fields requires detailed knowledge of the tissue property requirements for individual research techniques, as well as a detailed understanding of the consequences of tissue fixation steps on the imaging quality outcomes for both MRI and histology. Here, we provide an overview of existing studies that bridge between state-of-the-art imaging modalities, and discuss the background knowledge incorporated into the design, execution and interpretation of postmortem studies. A subset of the discussed challenges transfer to animal studies as well. This insight can contribute to furthering our understanding of the normal and diseased human brain, and to facilitate discussions between researchers from the individual disciplines.
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Affiliation(s)
- Anneke Alkemade
- Integrative Model-Based Cognitive Neuroscience Unit, Department of Psychology, University of Amsterdam, Amsterdam, The Netherlands.
| | - Rosa Großmann
- Integrative Model-Based Cognitive Neuroscience Unit, Department of Psychology, University of Amsterdam, Amsterdam, The Netherlands
| | - Pierre-Louis Bazin
- Integrative Model-Based Cognitive Neuroscience Unit, Department of Psychology, University of Amsterdam, Amsterdam, The Netherlands
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
- Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Birte U Forstmann
- Integrative Model-Based Cognitive Neuroscience Unit, Department of Psychology, University of Amsterdam, Amsterdam, The Netherlands
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5
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Haskell MW, Nielsen JF, Noll DC. Off-resonance artifact correction for MRI: A review. NMR IN BIOMEDICINE 2023; 36:e4867. [PMID: 36326709 PMCID: PMC10284460 DOI: 10.1002/nbm.4867] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 09/25/2022] [Accepted: 11/01/2022] [Indexed: 06/06/2023]
Abstract
In magnetic resonance imaging (MRI), inhomogeneity in the main magnetic field used for imaging, referred to as off-resonance, can lead to image artifacts ranging from mild to severe depending on the application. Off-resonance artifacts, such as signal loss, geometric distortions, and blurring, can compromise the clinical and scientific utility of MR images. In this review, we describe sources of off-resonance in MRI, how off-resonance affects images, and strategies to prevent and correct for off-resonance. Given recent advances and the great potential of low-field and/or portable MRI, we also highlight the advantages and challenges of imaging at low field with respect to off-resonance.
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Affiliation(s)
- Melissa W Haskell
- Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan, USA
- Hyperfine Research, Guilford, Connecticut, USA
| | | | - Douglas C Noll
- Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
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6
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Magnetic Resonance Visibility, Artifacts, and Overall Safety of the Self-Locating Peritoneal Dialysis Catheter with a Tungsten Tip. Int J Nephrol 2023; 2023:7901413. [PMID: 36733472 PMCID: PMC9889163 DOI: 10.1155/2023/7901413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 12/19/2022] [Accepted: 12/20/2022] [Indexed: 01/26/2023] Open
Abstract
Background The self-locating peritoneal dialysis (PD) catheter, contains a tungsten tip. The effects of magnetic resonance (MR) on the catheter were evaluated, emphasizing its MR signal, artifacts, ferromagnetism, and possible heating production during the MR sequences. Methods The catheter was studied in an ex vivo model using a 1.5T MR system and placed into a plastic box containing saline solution. Acquisitions on coronal and axial planes were obtained on fast gradient-echo T1-weighted and fast spin-echo T2-weighted. In vivo abdominal MR exams were also carried out. Results Overall, the catheter had good visibility. In all sequences, an extensive paramagnetic blooming artifact was detected at the level of the tip tungsten ballast, with a circular artifact of 5 cm in diameter. The catheter showed no magnetic deflection, rotation, or movements during all MR sequences. After imaging, the temperature of the saline solution did not change compared to the basal measurement. Patients safely underwent abdominal MR. Conclusions The results point to the possibility of safely performing MR in PD patients carrying the self-locating catheter. The self-locating PD catheter is stable when subjected to a 1.5T MR system. However, it creates some visual interference, preventing an accurate study of the tissues surrounding the tungsten tip.
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7
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Espiritu J, Berangi M, Yiannakou C, Silva E, Francischello R, Kuehne A, Niendorf T, Könneker S, Willumeit-Römer R, Seitz JM. Evaluating metallic artefact of biodegradable magnesium-based implants in magnetic resonance imaging. Bioact Mater 2022; 15:382-391. [PMID: 35386351 PMCID: PMC8958470 DOI: 10.1016/j.bioactmat.2021.11.035] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 11/12/2021] [Accepted: 11/28/2021] [Indexed: 11/13/2022] Open
Abstract
Magnesium (Mg) implants have shown to cause image artefacts or distortions in magnetic resonance imaging (MRI). Yet, there is a lack of information on how the degradation of Mg-based implants influences the image quality of MRI examinations. In this study, Mg-based implants are analysed in vitro, ex vivo, and in the clinical setting for various magnetic field strengths with the aim to quantify metallic artefact behaviour. In vitro corroded Mg-based screws and a titanium (Ti) equivalent were imaged according to the ASTM F2119. Mg-based and Ti pins were also implanted into rat femurs for different time points and scanned to provide insights on the influence of soft and hard tissue on metallic artefact. Additionally, MRI data of patients with scaphoid fractures treated with CE-approved Mg-based compression screws (MAGNEZIX®) were analysed at various time points post-surgery. The artefact production of the Mg-based material decreased as implant material degraded in all settings. The worst-case imaging scenario was determined to be when the imaging plane was selected to be perpendicular to the implant axis. Moreover, the Mg-based implant outperformed the Ti equivalent in all experiments by producing lower metallic artefact (p < 0.05). This investigation demonstrates that Mg-based implants generate significantly lower metallic distortion in MRI when compared to Ti. Our positive findings suggest and support further research into the application of Mg-based implants including post-operative care facilitated by MRI monitoring of degradation kinetics and bone/tissue healing processes. Mg-based implants produce lower metallic artefact than Ti in MRI. Metallic artefact production of Mg reduces as degradation increases. Mg implants provide sufficient visualisation in MRI for better postoperative care.
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Affiliation(s)
| | - Mostafa Berangi
- MRI.TOOLS GmbH, Berlin, Germany.,Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt Universität zu Berlin, Berlin, Germany.,Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrueck Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | | | - Eduarda Silva
- Institute of Clinical Physiology, National Research Council, Pisa, Italy
| | - Roberto Francischello
- Chemistry and Industrial Chemistry Department, Università di Pisa, Via Moruzzi 13, Pisa, Italy.,Fondazione Toscana Gabriele Monasterio, Via Moruzzi 1, Pisa, Italy
| | | | - Thoralf Niendorf
- MRI.TOOLS GmbH, Berlin, Germany.,Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt Universität zu Berlin, Berlin, Germany.,Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrueck Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Sören Könneker
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt Universität zu Berlin, Berlin, Germany
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8
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Guallart-Naval T, Algarín JM, Pellicer-Guridi R, Galve F, Vives-Gilabert Y, Bosch R, Pallás E, González JM, Rigla JP, Martínez P, Lloris FJ, Borreguero J, Marcos-Perucho Á, Negnevitsky V, Martí-Bonmatí L, Ríos A, Benlloch JM, Alonso J. Portable magnetic resonance imaging of patients indoors, outdoors and at home. Sci Rep 2022; 12:13147. [PMID: 35907975 PMCID: PMC9338984 DOI: 10.1038/s41598-022-17472-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 07/26/2022] [Indexed: 12/25/2022] Open
Abstract
Mobile medical imaging devices are invaluable for clinical diagnostic purposes both in and outside healthcare institutions. Among the various imaging modalities, only a few are readily portable. Magnetic resonance imaging (MRI), the gold standard for numerous healthcare conditions, does not traditionally belong to this group. Recently, low-field MRI technology companies have demonstrated the first decisive steps towards portability within medical facilities and vehicles. However, these scanners' weight and dimensions are incompatible with more demanding use cases such as in remote and developing regions, sports facilities and events, medical and military camps, or home healthcare. Here we present in vivo images taken with a light, small footprint, low-field extremity MRI scanner outside the controlled environment provided by medical facilities. To demonstrate the true portability of the system and benchmark its performance in various relevant scenarios, we have acquired images of a volunteer's knee in: (i) an MRI physics laboratory; (ii) an office room; (iii) outside a campus building, connected to a nearby power outlet; (iv) in open air, powered from a small fuel-based generator; and (v) at the volunteer's home. All images have been acquired within clinically viable times, and signal-to-noise ratios and tissue contrast suffice for 2D and 3D reconstructions with diagnostic value. Furthermore, the volunteer carries a fixation metallic implant screwed to the femur, which leads to strong artifacts in standard clinical systems but appears sharp in our low-field acquisitions. Altogether, this work opens a path towards highly accessible MRI under circumstances previously unrealistic.
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Affiliation(s)
| | - José M Algarín
- Institute for Molecular Imaging and Instrumentation, Spanish National Research Council, 46022, Valencia, Spain
- Institute for Molecular Imaging and Instrumentation, Universitat Politècnica de València, 46022, Valencia, Spain
| | - Rubén Pellicer-Guridi
- PhysioMRI Tech S.L., 46022, Valencia, Spain
- Asociación de investigación MPC, 20018, San Sebastián, Spain
| | - Fernando Galve
- Institute for Molecular Imaging and Instrumentation, Spanish National Research Council, 46022, Valencia, Spain
- Institute for Molecular Imaging and Instrumentation, Universitat Politècnica de València, 46022, Valencia, Spain
| | - Yolanda Vives-Gilabert
- PhysioMRI Tech S.L., 46022, Valencia, Spain
- Intelligent Data Analysis Laboratory, Department of Electronic Engineering, Universitat de València, 46100, Burjassot, Spain
| | | | - Eduardo Pallás
- Institute for Molecular Imaging and Instrumentation, Spanish National Research Council, 46022, Valencia, Spain
- Institute for Molecular Imaging and Instrumentation, Universitat Politècnica de València, 46022, Valencia, Spain
| | | | | | | | | | | | | | | | - Luis Martí-Bonmatí
- Medical Imaging Department, Hospital Universitari i Politècnic La Fe, 46026, Valencia, Spain
| | | | - José M Benlloch
- Institute for Molecular Imaging and Instrumentation, Spanish National Research Council, 46022, Valencia, Spain
- Institute for Molecular Imaging and Instrumentation, Universitat Politècnica de València, 46022, Valencia, Spain
| | - Joseba Alonso
- Institute for Molecular Imaging and Instrumentation, Spanish National Research Council, 46022, Valencia, Spain.
- Institute for Molecular Imaging and Instrumentation, Universitat Politècnica de València, 46022, Valencia, Spain.
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9
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Meneses BP, Amadon A. Physical limits to human brain B0 shimming with spherical harmonics, engineering implications thereof. MAGMA (NEW YORK, N.Y.) 2022; 35:923-941. [PMID: 35829793 DOI: 10.1007/s10334-022-01025-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Revised: 06/17/2022] [Accepted: 06/22/2022] [Indexed: 01/07/2023]
Abstract
OBJECTIVE As the MRI main magnetic field rises for improved signal-to-noise ratio, susceptibility-induced B0-inhomogeneity increases proportionally, aggravating related artifacts. Considering only susceptibility disparities between air and biological tissue, we explore the topological conditions for which perfect shimming could be performed in a Region of Interest (ROI) such as the human brain or part thereof. MATERIALS AND METHODS After theoretical considerations for perfect shimming, spherical harmonic (SH) shimming simulations of very high degree are performed, based on a 100-subject database of 1.7-mm-resolved brain fieldmaps acquired at 3T . In addition to the whole brain, shimmed ROIs include slabs targeting the prefrontal cortex, both or single temporal lobes, or spheres in the frontal brain above the nasal sinus. RESULTS AND DISCUSSION We show "perfect" SH shimming is possible only if the ROI can be contained in a sphere that does not enclose sources of magnetic field inhomogeneity, which are gathered at the air-tissue interface. We establish a [Formula: see text]Hz inhomogeneity hard shim limit at 7T for whole brain SH shimming, that can only be attained at shimming degree higher than 90. On the other hand, under limited power and SH degree resources, 3D region-specific shimming is shown to greatly improve homogeneity in critical zones such as the prefrontal cortex and around ear canals.
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Affiliation(s)
- Bruno Pinho Meneses
- Université Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, 91191, Gif-sur-Yvette, France
| | - Alexis Amadon
- Université Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, 91191, Gif-sur-Yvette, France.
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10
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Abdala-Junior R, No-Cortes J, Arita ES, Ackerman JL, da Silva RLB, Kim JH, Cortes ARG. Influence of receiver bandwidth on MRI artifacts caused by orthodontic brackets composed of different alloys. Imaging Sci Dent 2022; 51:413-419. [PMID: 34988002 PMCID: PMC8695464 DOI: 10.5624/isd.20210099] [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: 04/23/2021] [Revised: 05/13/2021] [Accepted: 05/14/2021] [Indexed: 11/18/2022] Open
Abstract
Purpose The aim of this in vitro study was to assess the role of bandwidth on the area of magnetic resonance imaging (MRI) artifacts caused by orthodontic appliances composed of different alloys, using different pulse sequences in 1.5 T and 3.0 T magnetic fields. Materials and Methods Different phantoms containing orthodontic brackets (ceramic, ceramic bracket with a stainless-steel slot, and stainless steel) were immersed in agar gel and imaged in 1.5 T and 3.0 T MRI scanners. Pairs of gradient-echo (GE), spin-echo (SE), and ultrashort echo time (UTE) pulse sequences were used differing in bandwidth only. The area of artifacts from orthodontic devices was automatically estimated from pixel value thresholds within a region of interest (ROI). Mean values for similar pulse sequences differing in bandwidth were compared at 1.5 T and 3.0 T using analysis of variance. Results The comparison of groups revealed a significant inverse association between bandwidth values and artifact areas of the stainless-steel bracket and the self-ligating ceramic bracket with a stainless-steel slot (P<0.05). The areas of artifacts from the ceramic bracket were the smallest, but were not reduced significantly in pulse sequences with higher bandwidth values (P<0.05). Significant differences were also observed between 1.5 T and 3.0 T MRI using SE and UTE, but not using GE 2-dimensional or 3-dimensional pulse sequences. Conclusion Higher receiver bandwidth might be indicated to prevent artifacts from orthodontic appliances in 1.5 T and 3.0 T MRI using SE and UTE pulse sequences.
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Affiliation(s)
- Reinaldo Abdala-Junior
- Department of Oral Radiology, School of Dentistry, University of São Paulo, São Paulo, SP, Brazil.,Department of Radiology, Martinos Center of Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA
| | - Juliana No-Cortes
- Department of Dental Surgery, Faculty of Dental Surgery, University of Malta, Msida, Malta
| | - Emiko Saito Arita
- Department of Oral Radiology, School of Dentistry, University of São Paulo, São Paulo, SP, Brazil
| | - Jerome L Ackerman
- Department of Radiology, Martinos Center of Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA
| | | | - Jun Ho Kim
- Department of Oral Radiology, School of Dentistry, University of São Paulo, São Paulo, SP, Brazil.,Department of Oral and Maxillofacial Radiology, School of Dentistry, Seoul National University, Seoul, Korea
| | - Arthur Rodriguez Gonzalez Cortes
- Department of Oral Radiology, School of Dentistry, University of São Paulo, São Paulo, SP, Brazil.,Department of Radiology, Martinos Center of Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA
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11
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Schmidt VF, Arnone F, Dietrich O, Seidensticker M, Armbruster M, Ricke J, Kazmierczak PM. Artifact reduction of coaxial needles in magnetic resonance imaging-guided abdominal interventions at 1.5 T: a phantom study. Sci Rep 2021; 11:22963. [PMID: 34824361 PMCID: PMC8617285 DOI: 10.1038/s41598-021-02434-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 11/10/2021] [Indexed: 11/12/2022] Open
Abstract
Needle artifacts pose a major limitation for MRI-guided interventions, as they impact the visually perceived needle size and needle-to-target-distance. The objective of this agar liver phantom study was to establish an experimental basis to understand and reduce needle artifact formation during MRI-guided abdominal interventions. Using a vendor-specific prototype fluoroscopic T1-weighted gradient echo sequence with real-time multiplanar acquisition at 1.5 T, the influence of 6 parameters (flip angle, bandwidth, matrix, slice thickness, read-out direction, intervention angle relative to B0) on artifact formation of 4 different coaxial MR-compatible coaxial needles (Nitinol, 16G–22G) was investigated. As one parameter was modified, the others remained constant. For each individual parameter variation, 2 independent and blinded readers rated artifact diameters at 2 predefined positions (15 mm distance from the perceived needle tip and at 50% of the needle length). Differences between the experimental subgroups were assessed by Bonferroni-corrected non-parametric tests. Correlations between continuous variables were expressed by the Bravais–Pearson coefficient and interrater reliability was quantified using the intraclass classification coefficient. Needle artifact size increased gradually with increasing flip angles (p = 0.002) as well as increasing intervention angles (p < 0.001). Artifact diameters differed significantly between the chosen matrix sizes (p = 0.002) while modifying bandwidth, readout direction, and slice thickness showed no significant differences. Interrater reliability was high (intraclass correlation coefficient 0.776–0.910). To minimize needle artifacts in MRI-guided abdominal interventions while maintaining optimal visibility of the coaxial needle, we suggest medium-range flip angles and low intervention angles relative to B0.
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Affiliation(s)
- Vanessa Franziska Schmidt
- Department of Radiology, University Hospital, LMU Munich, Marchioninistr. 15, 81377, Munich, Germany.
| | - Federica Arnone
- Department of Radiology Sciences, University of Palermo, Palermo, Italy
| | - Olaf Dietrich
- Department of Radiology, University Hospital, LMU Munich, Marchioninistr. 15, 81377, Munich, Germany
| | - Max Seidensticker
- Department of Radiology, University Hospital, LMU Munich, Marchioninistr. 15, 81377, Munich, Germany
| | - Marco Armbruster
- Department of Radiology, University Hospital, LMU Munich, Marchioninistr. 15, 81377, Munich, Germany
| | - Jens Ricke
- Department of Radiology, University Hospital, LMU Munich, Marchioninistr. 15, 81377, Munich, Germany
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12
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Lahti K, Parkkola R, Jääsaari P, Haataja L, Saunavaara V. The impact of susceptibility correction on diffusion metrics in adolescents. Pediatr Radiol 2021; 51:1471-1480. [PMID: 33893847 PMCID: PMC8266789 DOI: 10.1007/s00247-021-05000-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 09/16/2020] [Accepted: 02/03/2021] [Indexed: 11/06/2022]
Abstract
BACKGROUND Diffusion tensor imaging is a widely used imaging method of brain white matter, but it is prone to imaging artifacts. The data corrections can affect the measured values. OBJECTIVE To explore the impact of susceptibility correction on diffusion metrics. MATERIALS AND METHODS A cohort of 27 healthy adolescents (18 boys, 9 girls, mean age 12.7 years) underwent 3-T MRI, and we collected two diffusion data sets (anterior-posterior). The data were processed both with and without susceptibility artifact correction. We derived fractional anisotropy, mean diffusivity and histogram data of fiber length distribution from both the corrected and uncorrected data, which were collected from the corpus callosum, corticospinal tract and cingulum bilaterally. RESULTS Fractional anisotropy and mean diffusivity values significantly differed when comparing the pathways in all measured tracts. The fractional anisotropy values were lower and the mean diffusivity values higher in the susceptibility-corrected data than in the uncorrected data. We found a significant difference in total tract length in the corpus callosum and the corticospinal tract. CONCLUSION This study indicates that susceptibility correction has a significant effect on measured fractional anisotropy, and on mean diffusivity values and tract lengths. To receive reliable and comparable results, the correction should be used systematically.
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Affiliation(s)
- Katri Lahti
- Department of Pediatric Neurology, University of Turku and Turku University Hospital, P.O. Box 52, 20521, Turku, Finland.
- Department of Adolescent Psychiatry, Turku University Hospital, Turku, Finland.
| | - Riitta Parkkola
- Department of Radiology, University of Turku and Turku University Hospital, Turku, Finland
| | - Päivi Jääsaari
- Department of Oral and Maxillofacial Diseases, Turku University Hospital, Turku, Finland
| | - Leena Haataja
- Children's Hospital, and Pediatric Research Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Virva Saunavaara
- Department of Medical Physics, Turku University Hospital, Turku, Finland
- Turku PET Centre, Turku University Hospital, Turku, Finland
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Gassenmaier S, Herrmann J, Nickel D, Kannengiesser S, Afat S, Seith F, Hoffmann R, Othman AE. Image Quality Improvement of Dynamic Contrast-Enhanced Gradient Echo Magnetic Resonance Imaging by Iterative Denoising and Edge Enhancement. Invest Radiol 2021; 56:465-470. [PMID: 33645949 DOI: 10.1097/rli.0000000000000761] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVES The aim of this study was to investigate the impact of a novel edge enhancement and iterative denoising algorithm in 1.5-T T1-weighted dynamic contrast-enhanced (DCE) gradient echo (GRE) magnetic resonance imaging of the abdomen on image quality, noise levels, diagnostic confidence, and lesion detectability. MATERIALS AND METHODS Fifty patients who underwent a clinically indicated magnetic resonance imaging with DCE imaging of the abdomen between June and August 2020 were included in this retrospective, monocentric, institutional review board-approved study. For DCE imaging, a series of 3 volume interpolated breath-hold examinations (VIBEs) was performed. The raw data of all DCE imaging studies were processed twice, once using standard reconstruction (DCES) and again using an edge enhancement and iterative denoising approach (DCEDE). All imaging studies were randomly reviewed by 2 radiologists independently regarding noise levels, arterial contrast, sharpness of vessels, overall image quality, and diagnostic confidence using a Likert scale ranging from 1 to 4, with 4 being the best. Furthermore, lesion detectability was evaluated using the same ranking system. RESULTS All 50 imaging studies were successfully reconstructed with both methods. Interreader agreement (Cohen κ) was substantial to perfect for both readers. Arterial contrast and sharpness of vessels were rated superior by both readers with a median of 4 in DCEDE versus a median of 3 in DCES (P < 0.001). Furthermore, noise levels as well as overall image quality were rated higher with a median of 4 in DCEDE compared with a median of 3 in DCES (P < 0.001). Lesion detectability was evaluated to be superior in DCEDE with a median of 4 versus DCES with a median of 3 (P < 0.001). Consequently, diagnostic confidence was also rated to be superior in DCEDE with a median of 4 versus DCES with a median of 3 (P < 0.001). CONCLUSIONS Iterative denoising and edge enhancement are feasible in DCE imaging of the abdomen providing superior arterial contrast, noise levels, and overall image quality. Furthermore, lesion detectability and diagnostic confidence were significantly improved using this novel reconstruction method. Further reduction of acquisition time might be possible via reduction of increased noise levels using this presented method.
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Affiliation(s)
- Sebastian Gassenmaier
- From the Department of Diagnostic and Interventional Radiology, Eberhard-Karls-University Tuebingen, Tuebingen
| | - Judith Herrmann
- From the Department of Diagnostic and Interventional Radiology, Eberhard-Karls-University Tuebingen, Tuebingen
| | - Dominik Nickel
- MR Applications Predevelopment, Siemens Healthcare GmbH, Erlangen, Germany
| | | | - Saif Afat
- From the Department of Diagnostic and Interventional Radiology, Eberhard-Karls-University Tuebingen, Tuebingen
| | - Ferdinand Seith
- From the Department of Diagnostic and Interventional Radiology, Eberhard-Karls-University Tuebingen, Tuebingen
| | - Rüdiger Hoffmann
- From the Department of Diagnostic and Interventional Radiology, Eberhard-Karls-University Tuebingen, Tuebingen
| | - Ahmed E Othman
- From the Department of Diagnostic and Interventional Radiology, Eberhard-Karls-University Tuebingen, Tuebingen
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Stanescu T, Mousavi SH, Cole M, Barberi E, Wachowicz K. Quantification of magnetic susceptibility fingerprint of a 3D linearity medical device. Phys Med 2021; 87:39-48. [PMID: 34116316 DOI: 10.1016/j.ejmp.2021.05.023] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 05/13/2021] [Accepted: 05/14/2021] [Indexed: 02/03/2023] Open
Abstract
PURPOSE The study investigates the numerical modelling as well as experimental validation of magnetic susceptibility effects with respect to a 3D linearity phantom used for the quantification of MR image distortions. METHODS Magnetic field numerical simulations based on finite difference methods were conducted to generate the susceptibility (χ) model of the MRID3D phantom. Experimental data was acquired and analyzed for eight different MR scanners to include a wide range of scanning parameters. Distortion vector fields were generated by applying a harmonic analysis based on finite elements methods. Phantom scans for the same setup but with opposite polarities of the frequency encoding gradient were processed in conjunction with the susceptibility modelling to separately quantify three field components due to gradient non-linearities (GNL), B0 inhomogeneities and χ perturbations. RESULTS The numerical modelling showed a significant range of χ value of up to 8.23 ppm, with a mean value of 2.9 ppm. The χ perturbations were found to be mostly present at the end plates of the cylindrical phantom design. The simulations also showed that setup rotations of up to 10° introduced only negligible variations in the χ model of less than 0.1 ppm. This allows for a straightforward practical implementation of the modelling as a single lookup table. After correcting for the χ perturbations, the B0 inhomogeneities were derived and found to be in good agreement with either the MR system manufacturer specifications or experimental data available in the literature. CONCLUSIONS It is possible to accurately model the magnetic susceptibility signature of a 3D linearity device and remove it as a post-processing correction step. This is important as the procedure unlocks the ability of determining both the GNL field and B0 map of the scanner without the need of extra acquisitions or phantoms.
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Affiliation(s)
- T Stanescu
- Princess Margaret Cancer Centre, University Health Network, Department of Radiation Oncology, University of Toronto, 610 University Avenue, Toronto, Ontario M5G 2M9, Canada.
| | - S H Mousavi
- Princess Margaret Cancer Centre, University Health Network, Department of Radiation Oncology, University of Toronto, 610 University Avenue, Toronto, Ontario M5G 2M9, Canada
| | - M Cole
- Modus QA, London, Ontario N6H 5L6, Canada
| | - E Barberi
- Modus QA, London, Ontario N6H 5L6, Canada
| | - K Wachowicz
- Cross Cancer Institute, Alberta Health Services, Department of Radiation Oncology, University of Alberta, 11560 University Avenue, Edmonton, AB T6G 1Z2, Canada
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Zhang F, Jiang C, Li Y, Niu X, Long T, He C, Ding J, Li L, Li L. Investigation of Artifacts and Optimization in Proton Resonance Frequency Thermometry Towards Heating Risk Monitoring of Implantable Medical Devices in Magnetic Resonance Imaging. IEEE Trans Biomed Eng 2021; 68:3638-3646. [PMID: 34003743 DOI: 10.1109/tbme.2021.3081599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
OBJECTIVE Artifacts limit the application of proton resonance frequency (PRF) thermometry for on-site, individualized heating evaluations of implantable medical devices such as deep brain stimulation (DBS) for use in magnetic resonance imaging (MRI). Its properties are unclear and the research on how to choose an unaffected measurement region is insufficient. METHODS The properties of PRF signals around the metallic DBS electrode were investigated through simulations and phantom experiments considering electromagnetic interferences from material susceptibility and the radio frequency (RF) interactions. A threshold method on phase difference Δϕ was used to define a measurement area to estimate heating at the electrode surface. Its performance was compared to that of the Bayesian magnitude method and probe measurements. RESULTS The B0 magnetic field inhomogeneity due to the electrode susceptibility was the main influencing factor on PRF compared to the RF artifact. Δϕ around the electrode followed normal distribution but was distorted. Underestimation occurred at places with high temperature rises. The noise was increased and could be well estimated from magnitude images using a modified NEMA method. The Δϕ-threshold method based on this knowledge outperformed the Bayesian magnitude method by more than 42% in estimation error of the electrode heating. CONCLUSION The findings favor the use of PRF with the proposed approach as a reliable method for electrode heating estimation. SIGNIFICANCE This study clarified the influence of device artifacts and could improve the performance of PRF thermometry for individualized heating assessments of patients with implants under MRI.
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Liu Y, Ye Q, Zeng F, Jiang X, Cai B, Lv W, Wen J. Library-driven approach for fast implementation of the voxel spread function to correct magnetic field inhomogeneity artifacts for gradient-echo sequences. Med Phys 2021; 48:3714-3720. [PMID: 33914914 DOI: 10.1002/mp.14904] [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: 12/08/2020] [Revised: 03/15/2021] [Accepted: 04/12/2021] [Indexed: 11/10/2022] Open
Abstract
PURPOSE Previously developed Voxel Spread Function (VSF) method (Yablonskiy, et al, MRM, 2013;70:1283) provides solution to correct artifacts induced by macroscopic magnetic field inhomogeneity in the images obtained by multi-Gradient-Recalled-Echo (mGRE) techniques. The goal of this study was to develop a library-driven approach for fast VSF implementation. METHODS The VSF approach describes the contribution of the magnetic field inhomogeneity effects on the mGRE signal decay in terms of the F-function calculated from mGRE phase and magnitude images. A pre-calculated library accounting for a variety of background field gradients caused by magnetic field inhomogeneity was used herein to speed up the calculation of F-function. Quantitative R2* maps from the mGRE data collected from two healthy volunteers were generated using the library as validation. RESULTS As compared with direct calculation of the F-function based on a voxel-wise approach, the new library-driven method substantially reduces computational time from several hours to few minutes, while, at the same time, providing similar accuracy of R2* mapping. CONCLUSION The new procedure proposed in this study provides a fast post-processing algorithm that can be incorporated in the quantitative analysis of mGRE data to account for background field inhomogeneity artifacts, thus can facilitate the applications of mGRE-based quantitative techniques in clinical practices.
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Affiliation(s)
- Ying Liu
- Department of Radiology, The First Affiliated Hospital of USTC (Anhui Provincial Hospital), Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China
| | - Qiong Ye
- High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, Anhui, China
| | - Feiyan Zeng
- Department of Radiology, The First Affiliated Hospital of USTC (Anhui Provincial Hospital), Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China
| | - Xiaohua Jiang
- The First Affiliated Hospital of USTC (Anhui Provincial Hospital), Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China
| | - Bin Cai
- Department of Radiation Oncology, Washington University in St. Louis, St. Louis, MO, USA
| | - Weifu Lv
- Department of Radiology, The First Affiliated Hospital of USTC (Anhui Provincial Hospital), Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China
| | - Jie Wen
- Department of Radiology, The First Affiliated Hospital of USTC (Anhui Provincial Hospital), Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China
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17
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Gassenmaier S, Afat S, Nickel D, Kannengiesser S, Herrmann J, Hoffmann R, Othman AE. Application of a Novel Iterative Denoising and Image Enhancement Technique in T1-Weighted Precontrast and Postcontrast Gradient Echo Imaging of the Abdomen: Improvement of Image Quality and Diagnostic Confidence. Invest Radiol 2021; 56:328-334. [PMID: 33214390 DOI: 10.1097/rli.0000000000000746] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
OBJECTIVES The aim of this study was to investigate the impact of a novel iterative denoising and image enhancement technique in T1-weighted precontrast and postcontrast volume-interpolated breath-hold examination (VIBE) of the abdomen on image quality, noise levels, and diagnostic confidence without change of acquisition parameters. MATERIALS AND METHODS Fifty patients were included in this retrospective, monocentric, institutional review board-approved study after clinically indicated magnetic resonance imaging of the abdomen including T1-weighted precontrast and postcontrast imaging. After acquisition of the standard VIBE (VIBES), images were processed with a novel reconstruction algorithm using the same raw data as for VIBES, resulting in a denoised and enhanced dataset (VIBEDE). Two different radiologists evaluated both datasets in a randomized order regarding sharpness of organs as well as vessels, noise levels, artifacts, overall image quality, and diagnostic confidence using a Likert scale ranging from 1 to 4 with 4 being the best. Furthermore, in the presence of focal liver lesions, the largest lesion was measured in the postcontrast dataset, and lesion detectability was analyzed using a Likert scale (1-4). RESULTS Precontrast and postcontrast sharpness of organs and sharpness of vessels were rated significantly superior by both readers in VIBEDE with a median of 4 (interquartile range, 0) compared with VIBES with a median of 3 (1) (all P's < 0.0001). Precontrast and postcontrast noise levels were also rated superior by both readers in VIBEDE with a median of 4 (0) compared with VIBES with a median of 3 (1) for precontrast and a median of 3 (0) (median of 3 [1] for reader 2) for postcontrast imaging (all P's < 0.0001).Overall image quality was also rated higher with a median of 4 (0) in VIBEDE versus 3 (1) in VIBES (P < 0.0001). Twenty-seven imaging studies contained liver lesions. There was no difference regarding the number and localization between the readers and between VIBES and VIBEDE. Lesion detectability was rated by both readers significantly better in VIBEDE with a median of 4 (0) compared with a median of 4 (1) for reader 1 and a median of 3 (1) for reader 2 (P = 0.001 for reader 1; P < 0.001 for reader 2). Consequently, diagnostic confidence was also significantly superior in VIBEDE versus VIBES with a median of 4 (0) for both (P = 0.001). Interreader agreement resulted in a Cohen κ of 0.76 for precontrast analysis as well as of 0.76 for postcontrast analysis. CONCLUSIONS Application of a novel iterative denoising and image enhancement technique in T1-weighted VIBE precontrast and postcontrast imaging of the abdomen is feasible, providing superior image quality, noise levels, and diagnostic confidence.
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Affiliation(s)
- Sebastian Gassenmaier
- From the Department of Diagnostic and Interventional Radiology, Eberhard-Karls-University Tuebingen, Tuebingen
| | - Saif Afat
- From the Department of Diagnostic and Interventional Radiology, Eberhard-Karls-University Tuebingen, Tuebingen
| | - Dominik Nickel
- MR Applications Predevelopment, Siemens Healthcare GmbH, Erlangen, Germany
| | | | - Judith Herrmann
- From the Department of Diagnostic and Interventional Radiology, Eberhard-Karls-University Tuebingen, Tuebingen
| | - Rüdiger Hoffmann
- From the Department of Diagnostic and Interventional Radiology, Eberhard-Karls-University Tuebingen, Tuebingen
| | - Ahmed E Othman
- From the Department of Diagnostic and Interventional Radiology, Eberhard-Karls-University Tuebingen, Tuebingen
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Steidle G, Schick F. A new concept for improved quantitative analysis of reversible transverse relaxation in tissues with variable microscopic field distribution. Magn Reson Med 2020; 85:1493-1506. [PMID: 33000529 DOI: 10.1002/mrm.28534] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 09/03/2020] [Accepted: 09/03/2020] [Indexed: 12/12/2022]
Abstract
PURPOSE The intravoxel distribution of the magnetic field strongly influences signal dephasing after RF excitation and the resulting signal decay in gradient echo-based MRI. In this work, several different field distribution models were applied and tested for analysis of microscopic field characteristics within pixels. THEORY A flexible model for improved pixel-wise characterization of the underlying field distribution is introduced. The proposed symmetric alpha-stable (SαS) distribution covers Lorentzian, Gaussian, and intermediate field distributions in a continuous way using a two-parametric (width and shape) function. METHODS The new model was applied on human brain, potatoes (homogeneous isotropic tissue), and stems of pineapple (anisotropic fibrous tissue). Effects of microscopic structure and background gradients on the shape and the widths of the microscopic field distribution were analyzed using gradient echo sampling of the spin echo and multigradient-echo sequences. Effects of non-Lorentzian shapes of microscopic field distributions on the results of common T 2 ∗ measurements with mono-exponential fitting of signal values were tested. RESULTS Many pixels of the examined objects showed field characteristics in between Lorentzian and Gaussian shapes. Microscopic field inhomogeneities caused by microscopic susceptibility effects and background gradients sometimes led to rather Gaussian than Lorentzian field distribution. In cases with nearly Gaussian field distribution, mono-exponential fitting of the signal decay resulted in different T 2 ∗ values, depending on the sampling points. CONCLUSIONS Using the concept of more flexible distributions for characterization of microscopic susceptibility effects in tissue provides better fitting of data and nearly sampling point-independent results than common T 2 ∗ measurements with mono-exponential fitting.
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Affiliation(s)
- Günter Steidle
- Section of Experimental Radiology, Department of Diagnostic and Interventional Radiology, Universitätsklinikum Tübingen, Tübingen, Germany
| | - Fritz Schick
- Section of Experimental Radiology, Department of Diagnostic and Interventional Radiology, Universitätsklinikum Tübingen, Tübingen, Germany
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Li Y, Buch S, He N, Zhang C, Zhang Y, Wang T, Li D, Haacke EM, Yan F. Imaging patients pre and post deep brain stimulation: Localization of the electrodes and their targets. Magn Reson Imaging 2020; 75:34-44. [PMID: 32961237 DOI: 10.1016/j.mri.2020.09.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 07/27/2020] [Accepted: 09/17/2020] [Indexed: 12/27/2022]
Abstract
PURPOSE Deep brain stimulation (DBS) has become a widely performed surgical procedure for patients with medically refractory movement disorders and mental disorders. It is clinically important to set up a MRI protocol to map the brain targets and electrodes of the patients before and after DBS and to understand the imaging artifacts caused by the electrodes. METHODS Five patients with DBS electrodes implanted in the habenula (Hb), fourteen patients with globus pallidus internus (GPi) targeted DBS, three pre-DBS patients and seven healthy controls were included in the study. The MRI protocol consisted of magnetization prepared rapid acquisition gradient echo T1 (MPRAGE T1W), 3D multi-echo gradient recalled echo (ME-GRE) and 2D fast spin echo T2 (FSE T2W) sequences to map the brain targets and electrodes of the patients. Phantom experiments were also run to determine both the artifacts and the susceptibility of the electrodes. Signal to noise ratio (SNR) on T1W, T2W and GRE datasets were measured. The visibility of the brain structures was scored according to the Rose criterion. A detailed analysis of the characteristics of the electrodes in all three sequence types was performed to confirm the reliability of the postoperative MRI approach. In order to understand the signal behavior, we also simulated the corresponding magnitude data using the same imaging parameters as in the phantom sequences. RESULTS The mean ± inter-subject variability of the SNRs, across the subjects for T1W, T2W, and GRE datasets were 20.1 ± 8.1, 14.9 ± 3.2, and 43.0 ± 7.6, respectively. High resolution MPRAGE T1W and FSE T2W data both showed excellent contrast for the habenula and were complementary to each other. The mean visibility of the habenula in the 25 cases for the MPRAGE T1W data was 5.28 ± 1.11; and the mean visibility in the 20 cases for the FSE T2W data was 5.78 ± 1.30. Quantitative susceptibility mapping (QSM), reconstructed from the ME-GRE sequence, provided sufficient contrast to distinguish the substructures of the globus pallidus. The susceptibilities of the GPi and globus pallidus externa (GPe) were 0.087 ± 0.013 ppm and 0.115 ± 0.015 ppm, respectively. FSE T2W sequences provided the best image quality with smallest image blooming of stimulator leads compared to MPRAGE T1W images and GRE sequence images, the measured diameters of electrodes were 1.91 ± 0.22, 2.77 ± 0.22, and 2.72 ± 0.20 mm, respectively. High resolution, high bandwidth and short TE (TE = 2.6 ms) GRE helped constrain the artifacts to the area of the electrodes and the dipole effect seen in the GRE filtered phase data provided an effective mean to locate the end of the DBS lead. CONCLUSION The imaging protocol consisting of MPRAGE T1W, FSE T2W and ME-GRE sequences provided excellent pre- and post-operative visualization of the brain targets and electrodes for patients undergoing DBS treatment. Although the artifacts around the electrodes can be severe, sometimes these same artifacts can be useful in identifying their location.
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Affiliation(s)
- Yan Li
- Department of Radiology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Sagar Buch
- Department of Radiology, Wayne State University, Detroit, MI, USA
| | - Naying He
- Department of Radiology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Chencheng Zhang
- Department of Neurosurgery, Center for Functional Neurosurgery, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Yingying Zhang
- Department of Neurosurgery, Center for Functional Neurosurgery, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Tao Wang
- Department of Neurosurgery, Center for Functional Neurosurgery, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Dianyou Li
- Department of Neurosurgery, Center for Functional Neurosurgery, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Ewart Mark Haacke
- Department of Radiology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China; Department of Radiology, Wayne State University, Detroit, MI, USA
| | - Fuhua Yan
- Department of Radiology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
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Duong STM, Phung SL, Bouzerdoum A, Schira MM. An unsupervised deep learning technique for susceptibility artifact correction in reversed phase-encoding EPI images. Magn Reson Imaging 2020; 71:1-10. [PMID: 32407764 DOI: 10.1016/j.mri.2020.04.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 03/17/2020] [Accepted: 04/11/2020] [Indexed: 10/24/2022]
Abstract
Echo planar imaging (EPI) is a fast and non-invasive magnetic resonance imaging technique that supports data acquisition at high spatial and temporal resolutions. However, susceptibility artifacts, which cause the misalignment to the underlying structural image, are unavoidable distortions in EPI. Traditional susceptibility artifact correction (SAC) methods estimate the displacement field by optimizing an objective function that involves one or more pairs of reversed phase-encoding (PE) images. The estimated displacement field is then used to unwarp the distorted images and produce the corrected images. Since this conventional approach is time-consuming, we propose an end-to-end deep learning technique, named S-Net, to correct the susceptibility artifacts the reversed-PE image pair. The proposed S-Net consists of two components: (i) a convolutional neural network to map a reversed-PE image pair to the displacement field; and (ii) a spatial transform unit to unwarp the input images and produce the corrected images. The S-Net is trained using a set of reversed-PE image pairs and an unsupervised loss function, without ground-truth data. For a new image pair of reversed-PE images, the displacement field and corrected images are obtained simultaneously by evaluating the trained S-Net directly. Evaluations on three different datasets demonstrate that S-Net can correct the susceptibility artifacts in the reversed-PE images. Compared with two state-of-the-art SAC methods (TOPUP and TISAC), the proposed S-Net runs significantly faster: 20 times faster than TISAC and 369 times faster than TOPUP, while achieving a similar correction accuracy. Consequently, S-Net accelerates the medical image processing pipelines and makes the real-time correction for MRI scanners feasible. Our proposed technique also opens up a new direction in learning-based SAC.
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Affiliation(s)
- Soan T M Duong
- School of Electrical, Computer and Telecommunications Engineering, University of Wollongong, Australia.
| | - Son L Phung
- School of Electrical, Computer and Telecommunications Engineering, University of Wollongong, Australia
| | - Abdesselam Bouzerdoum
- School of Electrical, Computer and Telecommunications Engineering, University of Wollongong, Australia; ICT Division, College of Science and Engineering, Hamad Bin Khalifa University, Qatar
| | - Mark M Schira
- School of Psychology, University of Wollongong, Australia
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Duong STM, Phung SL, Bouzerdoum A, Boyd Taylor HG, Puckett AM, Schira MM. Susceptibility artifact correction for sub-millimeter fMRI using inverse phase encoding registration and T1 weighted regularization. J Neurosci Methods 2020; 336:108625. [PMID: 32061690 DOI: 10.1016/j.jneumeth.2020.108625] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 01/13/2020] [Accepted: 02/03/2020] [Indexed: 11/27/2022]
Abstract
BACKGROUND Functional magnetic resonance imaging (fMRI) enables non-invasive examination of both the structure and the function of the human brain. The prevalence of high spatial-resolution (sub-millimeter) fMRI has triggered new research on the intra-cortex, such as cortical columns and cortical layers. At present, echo-planar imaging (EPI) is used exclusively to acquire fMRI data; however, susceptibility artifacts are unavoidable. These distortions are especially severe in high spatial-resolution images and can lead to misrepresentation of brain function in fMRI experiments. NEW METHOD This paper presents a new method for correcting susceptibility artifacts by combining a T1-weighted (T1w) image and inverse phase-encoding (PE) based registration. The latter uses two EPI images acquired using identical sequences but with inverse-PE directions. In the proposed method, the T1w image is used to regularize the registration, and to select the regularization parameters automatically. The motivation is that the T1w image is considered to reflect the anatomical structure of the brain. RESULTS Our proposed method is evaluated on two sub-millimeter EPI-fMRI datasets, acquired using 3T and 7T scanners. Experiments show that the proposed method provides improved corrections that are well-aligned to the T1w image. COMPARISON WITH EXISTING METHODS The proposed method provides more robust and sharper corrections and runs faster compared with two other state-of-the-art inverse-PE based correction methods, i.e. HySCO and TOPUP. CONCLUSIONS The proposed correction method used the T1w image as a reference in the inverse-PE registration. Results show its promising performance. Our proposed method is timely, as sub-millimeter fMRI has become increasingly popular.
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Affiliation(s)
- S T M Duong
- School of Electrical, Computer and Telecommunications Engineering, University of Wollongong, Australia.
| | - S L Phung
- School of Electrical, Computer and Telecommunications Engineering, University of Wollongong, Australia
| | - A Bouzerdoum
- School of Electrical, Computer and Telecommunications Engineering, University of Wollongong, Australia; College of Science and Engineering, Hamad Bin Khalifa University, Qatar
| | | | - A M Puckett
- School of Psychology, University of Queensland, Australia; Queensland Brain Institute, University of Queensland, Australia
| | - M M Schira
- School of Psychology, University of Wollongong, Australia.
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What You Need to Know Before Reading Multiparametric MRI for Prostate Cancer. AJR Am J Roentgenol 2020; 214:1211-1219. [PMID: 32255689 DOI: 10.2214/ajr.19.22751] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE. Multiparametric MRI (mpMRI) has become the main imaging modality for the detection, localization, and local staging of prostate cancer over the past decade. For radiologists to achieve consistent and reproducible reporting of prostate mpMRI, a comprehensive evaluation of the gland including detailed knowledge of anatomy, pathology, and clinical data is required. This article familiarizes radiologists with common pitfalls and conditions that affect mpMRI performance during readouts. CONCLUSION. Consistent, accurate, and reproducible reporting of prostate mpMRI is vital. Additionally, radiologists should be aware of common diagnostic pitfalls that can hinder mpMRI performance.
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Zijlstra F, Viergever MA, Seevinck PR. SMART tracking: Simultaneous anatomical imaging and real-time passive device tracking for MR-guided interventions. Phys Med 2019; 64:252-260. [DOI: 10.1016/j.ejmp.2019.07.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2019] [Revised: 07/18/2019] [Accepted: 07/24/2019] [Indexed: 11/27/2022] Open
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Shiina R, Ogura A, Takeuchi T, Nakano H. [Improvement of Fat Suppressing Effect for Finger and Neck MRI by Using Small Glass Beads]. Nihon Hoshasen Gijutsu Gakkai Zasshi 2019; 75:446-453. [PMID: 31105093 DOI: 10.6009/jjrt.2019_jsrt_75.5.446] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The defectiveness of the fat suppression becomes the factor of the decrease of the quality of the diagnosis of magnetic resonance imaging. It is reported that the use of magnetic field uniformity adjuvant pad is effective for reduce poor fat suppression. The ball bullets, polystyrene balls, and polished rice are used for pad packing material, in recently, it was reported that fat suppression effect was good by the use of the small glass beads. Therefore, we tested the utility of small glass beads pad in the neck and fingers in this study. Neck and the fingers of subjects were imaged with T1-weighted image with fat suppression and T1-high resolution isotropic volume excitation image. The fat suppression effect of each image was compared with the polished rice and glass beads as material of pad used by physical, observation, and contact evaluation. In the result, satisfactory results were obtained by using glass beads, and it is suggested that fat suppression effect is improved by using glass beads as a filling material of pad in clinical study as a conclusion.
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Affiliation(s)
- Ryosuke Shiina
- School of Radiological Technology, Gunma Prefectural College of Health Sciences (Current address: Yokohama Municipal Citizen's Hospital)
| | - Akio Ogura
- Graduate School, Gunma Prefectural College of Health Sciences
| | - Tomokazu Takeuchi
- School of Radiological Technology, Gunma Prefectural College of Health Sciences (Current address: Graduate School, Gunma Prefectural College of Health Sciences)
| | - Hiroki Nakano
- School of Radiological Technology, Gunma Prefectural College of Health Sciences (Current address: Ishii Hospital)
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Hilgenfeld T, Prager M, Schwindling FS, Nittka M, Rammelsberg P, Bendszus M, Heiland S, Juerchott A. MSVAT-SPACE-STIR and SEMAC-STIR for Reduction of Metallic Artifacts in 3T Head and Neck MRI. AJNR Am J Neuroradiol 2018; 39:1322-1329. [PMID: 29794233 DOI: 10.3174/ajnr.a5678] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2017] [Accepted: 03/30/2018] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE The incidence of metallic dental restorations and implants is increasing, and head and neck MR imaging is becoming challenging regarding artifacts. Our aim was to evaluate whether multiple-slab acquisition with view angle tilting gradient based on a sampling perfection with application-optimized contrasts by using different flip angle evolution (MSVAT-SPACE)-STIR and slice-encoding for metal artifact correction (SEMAC)-STIR are beneficial regarding artifact suppression compared with the SPACE-STIR and TSE-STIR in vitro and in vivo. MATERIALS AND METHODS At 3T, 3D artifacts of 2 dental implants, supporting different single crowns, were evaluated. Image quality was evaluated quantitatively (normalized signal-to-noise ratio) and qualitatively (2 reads by 2 blinded radiologists). Feasibility was tested in vivo in 5 volunteers and 5 patients, respectively. RESULTS Maximum achievable resolution and the normalized signal-to-noise ratio of MSVAT-SPACE-STIR were higher compared with SEMAC-STIR. Performance in terms of artifact correction was dependent on the material composition. For highly paramagnetic materials, SEMAC-STIR was superior to MSVAT-SPACE-STIR (27.8% smaller artifact volume) and TSE-STIR (93.2% less slice distortion). However, MSVAT-SPACE-STIR reduced the artifact size compared with SPACE-STIR by 71.5%. For low-paramagnetic materials, MSVAT-SPACE-STIR performed as well as SEMAC-STIR. Furthermore, MSVAT-SPACE-STIR decreased artifact volume by 69.5% compared with SPACE-STIR. The image quality of all sequences did not differ systematically. In vivo results were comparable with in vitro results. CONCLUSIONS Regarding susceptibility artifacts and acquisition time, MSVAT-SPACE-STIR might be advantageous over SPACE-STIR for high-resolution and isotropic head and neck imaging. Only for materials with high-susceptibility differences to soft tissue, the use of SEMAC-STIR might be beneficial. Within limited acquisition times, SEMAC-STIR cannot exploit its full advantage over TSE-STIR regarding artifact suppression.
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Affiliation(s)
- T Hilgenfeld
- From the Department of Neuroradiology, (T.H., M.P., M.B., S.H., A.J.)
| | - M Prager
- From the Department of Neuroradiology, (T.H., M.P., M.B., S.H., A.J.).,Section of Experimental Radiology (M.P., S.H.), University of Heidelberg, Heidelberg, Germany
| | - F S Schwindling
- Department of Prosthodontics (F.S.S., P.R.), Heidelberg University Hospital, Heidelberg, Germany
| | - M Nittka
- Siemens Healthcare (M.N.), Erlangen, Germany
| | - P Rammelsberg
- Department of Prosthodontics (F.S.S., P.R.), Heidelberg University Hospital, Heidelberg, Germany
| | - M Bendszus
- From the Department of Neuroradiology, (T.H., M.P., M.B., S.H., A.J.)
| | - S Heiland
- From the Department of Neuroradiology, (T.H., M.P., M.B., S.H., A.J.).,Section of Experimental Radiology (M.P., S.H.), University of Heidelberg, Heidelberg, Germany
| | - A Juerchott
- From the Department of Neuroradiology, (T.H., M.P., M.B., S.H., A.J.)
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Ma Y, Zuo P, Nittka M, Cheng X, Shao H, Wang C. Comparisons of slice-encoding metal artifact correction and view-angle tilting magnetic resonance imaging and traditional digital radiography in evaluating chronic hip pain after total hip arthroplasty. J Orthop Translat 2017; 12:45-54. [PMID: 29662778 PMCID: PMC5866482 DOI: 10.1016/j.jot.2017.11.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 11/15/2017] [Accepted: 11/29/2017] [Indexed: 11/20/2022] Open
Abstract
Purpose The aims of this study were (1) to compare the areas of metal-induced artifacts and definition of periprosthetic structures between patients scanned with the slice-encoding metal artifact correction and view-angle tilting (SEMAC-VAT) turbo-spin-echo (TSE) prototype and those scanned with the standard TSE magnetic resonance (MR) sequences and (2) to further clarify the superiority of the SEMAC-VAT MR imaging technique at detecting lesions in patients after total hip arthroplasty (THA), compared with digital radiography (DR). Materials and methods A total of 38 consecutive patients who underwent THA were referred to MR imaging at our institution. All patients suffered from chronic hip pain postoperatively. Twenty-three patients of the 38 were examined with a 1.5-T MR scanner using a SEMAC-VAT TSE prototype and standard TSE sequence, and the remaining 15 patients were examined with the same 1.5-T MR scanner, but using the SEMAC-VAT TSE prototype only. The traditional DR imaging was also performed for all patients. Two radiologists then independently measured the area of metal-induced artifacts and evaluated the definition of both the acetabular and femoral zones based on a three-point scale. Finally, the positive findings of chronic hip pain after THA based on SEMAC-VAT TSE MR imaging and traditional DR imaging were compared and analysed. Results The areas of metal-induced artifacts were significantly smaller in the SEMAC-VAT TSE sequences than those in the standard TSE sequences for both the T1-weighted (p < 0.001) and T2-weighted (p < 0.001) turbo inversion recovery magnitude images. In addition, 28 patients showed a series of positive signs in the SEMAC-VAT images that were not observed in the traditional DR images. Conclusion Compared with the standard TSE MR imaging, SEMAC-VAT MR imaging significantly reduces metal-induced artifacts and might successfully detect most positive signs missed in the traditional DR images. Translational potential of this article The main objective of this research was to show that MR sequences from the SEMAC-VAT TSE prototype provide a significant advantage at detecting lesions in patients after THA because of the excellent soft-tissue resolution of the MR imaging. SEMAC-VAT MR can evaluate chronic hip pain after THA and determine the cause, which can help the clinician decide on whether a surgical revision is needed.
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Affiliation(s)
- Yimin Ma
- Department of Radiology, Jishuitan Hospital, Beijing, China
- Corresponding author.
| | - Panli Zuo
- Siemens Healthcare, MR Collaborations NE Asia, Beijing, China
| | | | | | - Hongyi Shao
- Department of Orthopedics, Jishuitan Hospital, Beijing, China
| | - Chen Wang
- Department of Radiology, Jishuitan Hospital, Beijing, China
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Baldelomar EJ, Charlton JR, Beeman SC, Bennett KM. Measuring rat kidney glomerular number and size in vivo with MRI. Am J Physiol Renal Physiol 2017; 314:F399-F406. [PMID: 29092847 DOI: 10.1152/ajprenal.00399.2017] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
number is highly variable in humans and is thought to play an important role in renal health. Chronic kidney disease (CKD) is the result of too few nephrons to maintain homeostasis. Currently, nephron number can only be determined invasively or as a terminal assessment. Due to a lack of tools to measure and track nephron number in the living, the early stages of CKD often go unrecognized, preventing early intervention that might halt the progression of CKD. In this work, we present a technique to directly measure glomerular number ( Nglom) and volume in vivo in the rat kidney ( n = 8) using MRI enhanced with the novel contrast agent cationized ferritin (CFE-MRI). Adult male rats were administered intravenous cationized ferritin (CF) and imaged in vivo with MRI. Glomerular number was measured and each glomerulus was spatially mapped in 3D in the image. Mean apparent glomerular volume (a Vglom) and intrarenal distribution of the individual glomerular volume (IGV), were also measured. These metrics were compared between images of the same kidneys scanned in vivo and ex vivo with CFE-MRI. In vivo Nglom and a Vglom correlated to ex vivo metrics within the same kidneys and were within 10% of Nglom and a Vglom previously validated by stereologic methods. This is the first report of direct in vivo measurements of Nglom and a Vglom, introducing an opportunity to investigate mechanisms of renal disease progression and therapeutic response over time.
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Affiliation(s)
| | - Jennifer R Charlton
- University of Virginia , Department of Pediatrics, Charlottesville, Virginia
| | - Scott C Beeman
- Washington University School of Medicine , Mallinckrodt Institute of Radiology, St. Louis, Missouri
| | - Kevin M Bennett
- University of Hawaii at Manoa, Department of Biology , Honolulu, Hawaii
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Cipriano AF, Lin J, Miller C, Lin A, Cortez Alcaraz MC, Soria P, Liu H. Anodization of magnesium for biomedical applications - Processing, characterization, degradation and cytocompatibility. Acta Biomater 2017; 62:397-417. [PMID: 28818688 DOI: 10.1016/j.actbio.2017.08.017] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 07/17/2017] [Accepted: 08/12/2017] [Indexed: 01/05/2023]
Abstract
This article reports anodization of Mg in KOH electrolyte and the associated surface, degradation, and biological properties for bioresorbable implant applications. The preparation procedures for electrodes and anodization setup significantly enhanced reproducibility of samples. The results of anodization performed at the applied potentials of 1.8, 1.9, or 2.0V showed that the sample anodized at 1.9V and annealed, referred to as the 1.9 AA sample, had homogenous surface microstructure and elemental composition, and a reduction in corrosion current density in the electrochemical testing. In comparison with Mg control, the 1.9 AA sample showed a distinct mode of degradation, e.g., continuous growth of a passivation layer enriched with Ca and P instead of typical localized pitting and undermining, and a greater release rate of Mg2+ ions when immersed in physiologically relevant media. In the direct culture with bone marrow derived mesenchymal stem cells (BMSCs) in vitro, the 1.9 AA sample did not affect BMSC adhesion and morphology under indirect contact; however, the 1.9 AA sample showed a reduction in cell spreading under direct contact. The change in surface topography/composition at the dynamic interface of the anodized-annealed Mg sample might have contributed to the change in BMSC morphology. In summary, this study demonstrated the potential of anodic oxidation to modulate the degradation behaviors of Mg-based biomaterials and BMSC responses in vitro, and confirmed the value of direct culture method for studying cytocompatibility of Mg-based biomaterials for medical implant applications. STATEMENT OF SIGNIFICANCE Magnesium (Mg)-based biomaterials have been specifically designed and actively explored for biodegradable implant applications since the early 2000s. To realize the benefits of Mg-based materials for medical implant applications, it is critical to control the rate of Mg degradation (i.e. corrosion) in the body. We investigated an environmentally friendly anodization process using KOH electrolyte for modifying the surface of Mg-based materials, and the resulted surface, degradation, and biological properties for biomedical applications. This study reported critical considerations that are important for repeatability of anodization process, homogeneity of surface microstructure and composition, and in vitro evaluations of the degradation and biological properties of surface treated Mg samples. The details in preparation of electrodes, anodization setup, annealing, and sample handling before and after surface treatment (e.g. re-embedding) reported in this article are valuable for studying a variety of electrochemical processes for surface treatment of Mg-based metals, because of enhanced reproducibility.
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Affiliation(s)
- Aaron F Cipriano
- Department of Bioengineering, University of California, Riverside, CA 92521, USA; Materials Science & Engineering, University of California, Riverside, CA 92521, USA
| | - Jiajia Lin
- Department of Bioengineering, University of California, Riverside, CA 92521, USA; Materials Science & Engineering, University of California, Riverside, CA 92521, USA
| | - Christopher Miller
- Department of Bioengineering, University of California, Riverside, CA 92521, USA
| | - Alan Lin
- Department of Bioengineering, University of California, Riverside, CA 92521, USA
| | | | - Pedro Soria
- Department of Bioengineering, University of California, Riverside, CA 92521, USA; Department of Biology, California State University, San Bernardino, CA 92407, USA; Stem Cell Center, University of California, Riverside, CA 92521, USA
| | - Huinan Liu
- Department of Bioengineering, University of California, Riverside, CA 92521, USA; Materials Science & Engineering, University of California, Riverside, CA 92521, USA; Stem Cell Center, University of California, Riverside, CA 92521, USA; Cell, Molecular and Developmental Biology Program, University of California, Riverside, CA 92521, USA.
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Comparative study of fat-suppression techniques for hip arthroplasty MR imaging. Skeletal Radiol 2017; 46:1209-1217. [PMID: 28540521 DOI: 10.1007/s00256-017-2670-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 04/18/2017] [Accepted: 05/02/2017] [Indexed: 02/02/2023]
Abstract
OBJECTIVES The goal of this study was to evaluate different fat-suppressed fluid-sensitive sequences in association with different metal artifacts reduction techniques (MARS) to determine which combination allows better fat suppression around metallic hip implants. METHODS An experimental study using an MRI fat-water phantom quantitatively evaluated contrast shift induced by metallic hip implant for different fat-suppression techniques and MARS. Then a clinical study with patients addressed to MRI unit for painful hip prosthesis compared these techniques in terms of fat suppression quality and diagnosis confidence. RESULTS Among sequences without MARS, both T2 Dixon and short tau inversion recuperation (STIR) had significantly lower contrast shift (p < 0.05), Dixon offering the best fat suppression. Adding MARS (view-angle tilting or slice-encoding for metal artifact correction (SEMAC)) to STIR gave better results than Dixon alone, and also better than SPAIR and fat saturation with MARS (p < 0.05). There were no statistically significant differences between STIR with view-angle tilting and STIR with SEMAC in terms of fat suppression quality. CONCLUSIONS STIR sequence is the preferred fluid-sensitive MR sequence in patients with metal implant. In combination with MARS (view-angle tilting or SEMAC), STIR appears to be the best option for high-quality fat suppression.
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Schleicher KE, Bock M, Düring K, Kroboth S, Krafft AJ. Radial MRI with variable echo times: reducing the orientation dependency of susceptibility artifacts of an MR-safe guidewire. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2017; 31:235-242. [PMID: 28770356 DOI: 10.1007/s10334-017-0645-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 07/20/2017] [Accepted: 07/21/2017] [Indexed: 11/26/2022]
Abstract
OBJECTIVES Guidewires are indispensable tools for intravascular MR-guided interventions. Recently, an MR-safe guidewire made from a glass-fiber/epoxy compound material with embedded iron particles was developed. The size of the induced susceptibility artifact, and thus the guidewire's visibility, depends on its orientation against B 0. We present a radial acquisition scheme with variable echo times that aims to reduce the artifact's orientation dependency. MATERIALS AND METHODS The radial acquisition scheme uses sine-squared modulated echo times depending on the physical direction of the spoke to balance the susceptibility artifact of the guidewire. The acquisition scheme was studied in simulations based on dipole fields and in phantom experiments for different orientations of the guidewire against B 0. The simulated and measured artifact widths were quantitatively compared. RESULTS Compared to acquisitions with non-variable echo times, the proposed acquisition scheme shows a reduced angular variability. For the two main orientations (i.e., parallel and perpendicular to B 0), the ratio of the artifact widths was reduced from about 2.2 (perpendicular vs. parallel) to about 1.2 with the variable echo time approach. CONCLUSION The reduction of the orientation dependency of the guidewire's artifact via sine-squared varying echo times could be verified in simulations and measurements. The more balanced artifact allows for a better overall visibility of the guidewire.
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Affiliation(s)
- Katharina E Schleicher
- Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Breisacher Strasse 60a, 79106, Freiburg, Germany.
| | - Michael Bock
- Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Breisacher Strasse 60a, 79106, Freiburg, Germany
| | | | - Stefan Kroboth
- Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Breisacher Strasse 60a, 79106, Freiburg, Germany
| | - Axel J Krafft
- Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Breisacher Strasse 60a, 79106, Freiburg, Germany
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Kose R, Kose K. BlochSolver: A GPU-optimized fast 3D MRI simulator for experimentally compatible pulse sequences. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2017; 281:51-65. [PMID: 28550818 DOI: 10.1016/j.jmr.2017.05.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2017] [Revised: 05/15/2017] [Accepted: 05/15/2017] [Indexed: 06/07/2023]
Abstract
A magnetic resonance imaging (MRI) simulator, which reproduces MRI experiments using computers, has been developed using two graphic-processor-unit (GPU) boards (GTX 1080). The MRI simulator was developed to run according to pulse sequences used in experiments. Experiments and simulations were performed to demonstrate the usefulness of the MRI simulator for three types of pulse sequences, namely, three-dimensional (3D) gradient-echo, 3D radio-frequency spoiled gradient-echo, and gradient-echo multislice with practical matrix sizes. The results demonstrated that the calculation speed using two GPU boards was typically about 7 TFLOPS and about 14 times faster than the calculation speed using CPUs (two 18-core Xeons). We also found that MR images acquired by experiment could be reproduced using an appropriate number of subvoxels, and that 3D isotropic and two-dimensional multislice imaging experiments for practical matrix sizes could be simulated using the MRI simulator. Therefore, we concluded that such powerful MRI simulators are expected to become an indispensable tool for MRI research and development.
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Affiliation(s)
- Ryoichi Kose
- MRTechnology Inc, 2-1-6 B5 Sengen, Tsukuba 3050047, Japan
| | - Katsumi Kose
- Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 3058573, Japan.
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Shokrollahi P, Drake JM, Goldenberg AA. Ultrasonic motor-induced geometric distortions in magnetic resonance images. Med Biol Eng Comput 2017; 56:61-70. [PMID: 28670659 DOI: 10.1007/s11517-017-1665-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Accepted: 06/10/2017] [Indexed: 10/19/2022]
Abstract
Ultrasonic motors (USMs) are common actuators that can be safely used in the magnetic resonance imaging (MRI) environment. However, lack of MRI compatibility results in issues such as image distortion. This fact led researchers to shift focus from USMs to pneumatic and hydraulic actuators in development of surgical robots. The aim is to quantify and compensate the geometric distortion of MR images as generated by the presence of USMs. An ultrasonic motor was positioned in three orientations with respect to the bore axis. The induced distortions were compared across four image sequences. To reduce the distortions, three artifact reduction methods were employed. Geometric distortion is the only artifact in image slices farther from the motor. The various motor orientations lead to different distortions, with the lowest distortion for the z orientation. The maximum measured distortion of ten pixels occurred. This maximal distortion is equal to a 1-cm displacement of the displayed points relative to their actual locations and it is beyond the acceptable level for medical display standards. Bandwidth reduction reduced the distortion, with a 50% reduction for a doubled bandwidth. In conclusion, USMs can be preferred alternative because accurate targeting of pathologies can occur in free distorted images.
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Affiliation(s)
- P Shokrollahi
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Rosebrugh Building, 164 College Street, Room 407, Toronto, ON, M5S3G9, Canada. .,Division of Neurosurgery, The Hospital for Sick Children, 555 University Avenue, Room 1504, Toronto, ON, M5G1X8, Canada.
| | - J M Drake
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Rosebrugh Building, 164 College Street, Room 407, Toronto, ON, M5S3G9, Canada.,Division of Neurosurgery, The Hospital for Sick Children, 555 University Avenue, Room 1504, Toronto, ON, M5G1X8, Canada
| | - A A Goldenberg
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Rosebrugh Building, 164 College Street, Room 407, Toronto, ON, M5S3G9, Canada.,Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Road, Room 106, Toronto, ON, M5S3G8, Canada
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Mavroidis P, Boci N, Kostopoulos S, Ninos C, Glotsos D, Oikonomou G, Bakas A, Roka V, Sakkas GK, Tsagkalis A, Chatzigeorgiou V, Batsikas G, Zaimis G, Cavouras D, Lavdas E. Investigation of the Possibility to Reduce Susceptibility Artifacts in MRI Knee Examination. J Med Biol Eng 2017. [DOI: 10.1007/s40846-017-0260-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Chaput A, Robin P, Podeur F, Ollivier M, Keromnes N, Tissot V, Nonent M, Salaün PY, Rousset J, Abgral R. Diagnostic performance of 18
fluorodesoxyglucose positron emission/computed tomography and magnetic resonance imaging in detecting T1-T2 head and neck squamous cell carcinoma. Laryngoscope 2017; 128:378-385. [DOI: 10.1002/lary.26729] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Revised: 04/26/2017] [Accepted: 05/09/2017] [Indexed: 11/11/2022]
Affiliation(s)
- Anne Chaput
- Department of Nuclear Medicine; University Hospital of Brest; Brest France
| | - Philippe Robin
- Department of Nuclear Medicine; University Hospital of Brest; Brest France
- Thrombosis Study Group in Western Brittany; Research's Federative Institute 148, European University of Brittany; Brest France
| | - Fabien Podeur
- Department of Radiology; University Hospital of Brest; Brest France
| | - Morgan Ollivier
- Department of Radiology; University Hospital of Brest; Brest France
| | - Nathalie Keromnes
- Department of Nuclear Medicine; University Hospital of Brest; Brest France
| | - Valentin Tissot
- Department of Radiology; University Hospital of Brest; Brest France
| | - Michel Nonent
- Department of Radiology; University Hospital of Brest; Brest France
| | - Pierre-Yves Salaün
- Department of Nuclear Medicine; University Hospital of Brest; Brest France
- Thrombosis Study Group in Western Brittany; Research's Federative Institute 148, European University of Brittany; Brest France
| | - Jean Rousset
- Department of Radiology; University Hospital of Brest; Brest France
- Department of Radiology; Military Hospital of Brest; Brest France
| | - Ronan Abgral
- Department of Nuclear Medicine; University Hospital of Brest; Brest France
- Thrombosis Study Group in Western Brittany; Research's Federative Institute 148, European University of Brittany; Brest France
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Hua J, Miao X, Agarwal S, Bettegowda C, Quiñones-Hinojosa A, Laterra J, Van Zijl PCM, Pekar JJ, Pillai JJ. Language Mapping Using T2-Prepared BOLD Functional MRI in the Presence of Large Susceptibility Artifacts-Initial Results in Patients With Brain Tumor and Epilepsy. ACTA ACUST UNITED AC 2017; 3:105-113. [PMID: 28804779 PMCID: PMC5552052 DOI: 10.18383/j.tom.2017.00006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
At present, presurgical functional mapping is the most prevalent clinical application of functional magnetic resonance imaging (fMRI). Signal dropouts and distortions caused by susceptibility effects in the current standard echo planar imaging (EPI)-based fMRI images are well-known problems and pose a major hurdle for the application of fMRI in several brain regions, many of which are related to language mapping in presurgical planning. Such artifacts are particularly problematic in patients with previous surgical resection cavities, craniotomy hardware, hemorrhage, and vascular malformation. A recently developed T2-prepared (T2prep) fMRI approach showed negligible distortion and dropouts in the entire brain even in the presence of large susceptibility effects. Here, we present initial results comparing T2prep- and multiband EPI-fMRI scans for presurgical language mapping using a sentence completion task in patients with brain tumor and epilepsy. In all patients scanned, T2prep-fMRI showed minimal image artifacts (distortion and dropout) and greater functional sensitivity than EPI-fMRI around the lesions containing blood products and in air-filled cavities. This enhanced sensitivity in T2prep-fMRI was also evidenced by the fact that functional activation during the sentence completion task was detected with T2prep-fMRI but not with EPI-fMRI in the affected areas with the same statistical threshold, whereas cerebrovascular reactivity during a breath-hold task was preserved in these same regions, implying intact neurovascular coupling in these patients. Although further investigations are required to validate these findings with invasive methods such as direct cortical stimulation mapping as the gold standard, this approach provides an alternative method for performing fMRI in brain regions with large susceptibility effects.
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Affiliation(s)
- Jun Hua
- F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland.,Neurosection, Division of MRI Research, Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Xinyuan Miao
- F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland.,Neurosection, Division of MRI Research, Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Shruti Agarwal
- Division of Neuroradiology, Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Chetan Bettegowda
- Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | | | - John Laterra
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Peter C M Van Zijl
- F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland.,Neurosection, Division of MRI Research, Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - James J Pekar
- F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland.,Neurosection, Division of MRI Research, Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Jay J Pillai
- Division of Neuroradiology, Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland
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Mallinson PI, Coupal TM, McLaughlin PD, Nicolaou S, Munk PL, Ouellette HA. Dual-Energy CT for the Musculoskeletal System. Radiology 2017; 281:690-707. [PMID: 27870622 DOI: 10.1148/radiol.2016151109] [Citation(s) in RCA: 153] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The principal advantages of dual-energy computed tomography (CT) over conventional CT in the musculoskeletal setting relate to the additional information provided regarding tissue composition, artifact reduction, and image optimization. This article discusses the manifestations of these in clinical practice-urate and bone marrow edema detection, metal artifact reduction, and tendon analysis, with potential in arthrography, bone densitometry, and metastases surveillance. The basic principles of dual-energy CT physics and scanner design will also be discussed. © RSNA, 2016.
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Affiliation(s)
- Paul I Mallinson
- From the Department of Radiology, Vancouver General Hospital/University of British Columbia, Jim Pattison Pavilion, 899 W 12th Ave, Vancouver, BC, Canada V5Z 1M9
| | - Tyler M Coupal
- From the Department of Radiology, Vancouver General Hospital/University of British Columbia, Jim Pattison Pavilion, 899 W 12th Ave, Vancouver, BC, Canada V5Z 1M9
| | - Patrick D McLaughlin
- From the Department of Radiology, Vancouver General Hospital/University of British Columbia, Jim Pattison Pavilion, 899 W 12th Ave, Vancouver, BC, Canada V5Z 1M9
| | - Savvas Nicolaou
- From the Department of Radiology, Vancouver General Hospital/University of British Columbia, Jim Pattison Pavilion, 899 W 12th Ave, Vancouver, BC, Canada V5Z 1M9
| | - Peter L Munk
- From the Department of Radiology, Vancouver General Hospital/University of British Columbia, Jim Pattison Pavilion, 899 W 12th Ave, Vancouver, BC, Canada V5Z 1M9
| | - Hugue A Ouellette
- From the Department of Radiology, Vancouver General Hospital/University of British Columbia, Jim Pattison Pavilion, 899 W 12th Ave, Vancouver, BC, Canada V5Z 1M9
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37
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Probst M, Richter V, Weitz J, Kirschke JS, Ganter C, Troeltzsch M, Nittka M, Cornelius CP, Zimmer C, Probst FA. Magnetic resonance imaging of the inferior alveolar nerve with special regard to metal artifact reduction. J Craniomaxillofac Surg 2017; 45:558-569. [DOI: 10.1016/j.jcms.2017.01.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 12/08/2016] [Accepted: 01/09/2017] [Indexed: 11/30/2022] Open
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Jones BG, Fosgate GT, Green EM, Habing AM, Hettlich BF. Magnetic resonance imaging susceptibility artifacts in the cervical vertebrae and spinal cord related to monocortical screw-polymethylmethacrylate implants in canine cadavers. Am J Vet Res 2017; 78:458-464. [PMID: 28346006 DOI: 10.2460/ajvr.78.4.458] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To characterize and compare MRI susceptibility artifacts related to titanium and stainless steel monocortical screws in the cervical vertebrae and spinal cord of canine cadavers. SAMPLE 12 canine cadavers. PROCEDURES Cervical vertebrae (C4 and C5) were surgically stabilized with titanium or stainless steel monocortical screws and polymethylmethacrylate. Routine T1-weighted, T2-weighted, and short tau inversion recovery sequences were performed at 3.0 T. Magnetic susceptibility artifacts in 20 regions of interest (ROIs) across 4 contiguous vertebrae (C3 through C6) were scored by use of an established scoring system. RESULTS Artifact scores for stainless steel screws were significantly greater than scores for titanium screws at 18 of 20 ROIs. Artifact scores for titanium screws were significantly higher for spinal cord ROIs within the implanted vertebrae. Artifact scores for stainless steel screws at C3 were significantly less than at the other 3 cervical vertebrae. CONCLUSIONS AND CLINICAL RELEVANCE Evaluation of routine MRI sequences obtained at 3.0 T revealed that susceptibility artifacts related to titanium monocortical screws were considered mild and should not hinder the overall clinical assessment of the cervical vertebrae and spinal cord. However, mild focal artifacts may obscure small portions of the spinal cord or intervertebral discs immediately adjacent to titanium screws. Severe artifacts related to stainless steel screws were more likely to result in routine MRI sequences being nondiagnostic; however, artifacts may be mitigated by implant positioning.
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Zhou DB, Wang SG, Wang SP, Ai HJ, Xu J. MRI compatibility of several early transition metal based alloys and its influencing factors. J Biomed Mater Res B Appl Biomater 2017; 106:377-385. [PMID: 28160410 DOI: 10.1002/jbm.b.33832] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 07/15/2016] [Accepted: 10/02/2016] [Indexed: 11/06/2022]
Abstract
Magnetic resonance imaging (MRI) compatibility of three early transition metal (ETM) based alloys was assessed in vitro with agarose gel as a phantom, including Zr-20Nb, near-equiatomic (TiZrNbTa)90 Mo10 and Nb-60Ta-2Zr, together with pure tantalum and L605 Co-Cr alloy for comparison. The artifact extent in the MR image was quantitatively characterized according to the maximum area of 2D images and the total volume in reconstructed 3D images with a series of slices under acquisition by fast spin echo (FSE) sequence and gradient echo (GRE) sequence. It was indicated that the artifacts extent of L605 Co-Cr alloy with a higher magnetic susceptibility (χv ) was approximately 3-fold greater than that of the ETM-based alloys with χv in the range of 160-250 ppm. In the ETM group, the MRI compatibility of the materials can be ranked in a sequence of Zr-20Nb, pure tantalum, (TiZrNbTa)90 Mo10 and Nb-60Ta-2Zr. In addition, using a rabbit cadaver with the implanted tube specimens as a model for ex vivo assessment, it was confirmed that the artifact severity of Nb-60Ta-2Zr alloy is significantly reduced in comparison with the L605 alloy. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 377-385, 2018.
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Affiliation(s)
- Da-Bo Zhou
- School of Stomatology, China Medical University, Shenyang, 110002, China
| | - Shao-Gang Wang
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, 110016, China
| | - Shao-Ping Wang
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, 110016, China
| | - Hong-Jun Ai
- School of Stomatology, China Medical University, Shenyang, 110002, China
| | - Jian Xu
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, 110016, China
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Zijlstra F, Bouwman JG, Braškutė I, Viergever MA, Seevinck PR. Fast Fourier-based simulation of off-resonance artifacts in steady-state gradient echo MRI applied to metal object localization. Magn Reson Med 2016; 78:2035-2041. [PMID: 27928834 PMCID: PMC5655717 DOI: 10.1002/mrm.26556] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 10/28/2016] [Accepted: 10/28/2016] [Indexed: 12/23/2022]
Abstract
PURPOSE To accelerate simulation of off-resonance artifacts in steady-state gradient echo MRI by using fast Fourier transforms and demonstrate its applicability to metal object localization. THEORY AND METHODS By exploiting the repetitive nature of steady-state pulse sequences it is possible to use fast Fourier transforms to calculate the MR signal. Based on this principle, a method for fast simulation of off-resonance artifacts was designed. The method was validated against Bloch simulations and MRI scans. Its clinical relevance was demonstrated by employing it for template matching-based metal object localization, as applied to a titanium cylinder, an oxidized zirconium knee implant, and gold fiducials. RESULTS The fast simulations were accurate compared with actual MRI scans of the objects. The differences between the fast simulations and Bloch simulations were minor, while the acceleration scaled linearly with the number of phase-encoding lines. The object localization method accurately localized the various metal objects. CONCLUSION The proposed simulation methodology provided accurate 3D simulations of off-resonance artifacts with a lower computational complexity than Bloch simulations. The speed of the simulations opens up possibilities in image reconstructions involving off-resonance phenomena that were previously infeasible due to computational limitations, as demonstrated for metal object localization. Magn Reson Med 78:2035-2041, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
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Affiliation(s)
- Frank Zijlstra
- Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Job G Bouwman
- Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Ieva Braškutė
- Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Max A Viergever
- Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Peter R Seevinck
- Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands
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Kabil J, Belguerras L, Trattnig S, Pasquier C, Felblinger J, Missoffe A. A Review of Numerical Simulation and Analytical Modeling for Medical Devices Safety in MRI. Yearb Med Inform 2016:152-158. [PMID: 27830244 DOI: 10.15265/iy-2016-016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
OBJECTIVES To review past and present challenges and ongoing trends in numerical simulation for MRI (Magnetic Resonance Imaging) safety evaluation of medical devices. METHODS A wide literature review on numerical and analytical simulation on simple or complex medical devices in MRI electromagnetic fields shows the evolutions through time and a growing concern for MRI safety over the years. Major issues and achievements are described, as well as current trends and perspectives in this research field. RESULTS Numerical simulation of medical devices is constantly evolving, supported by calculation methods now well-established. Implants with simple geometry can often be simulated in a computational human model, but one issue remaining today is the experimental validation of these human models. A great concern is to assess RF heating on implants too complex to be traditionally simulated, like pacemaker leads. Thus, ongoing researches focus on alternative hybrids methods, both numerical and experimental, with for example a transfer function method. For the static field and gradient fields, analytical models can be used for dimensioning simple implants shapes, but limited for complex geometries that cannot be studied with simplifying assumptions. CONCLUSIONS Numerical simulation is an essential tool for MRI safety testing of medical devices. The main issues remain the accuracy of simulations compared to real life and the studies of complex devices; but as the research field is constantly evolving, some promising ideas are now under investigation to take up the challenges.
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Affiliation(s)
| | | | | | | | - J Felblinger
- Jacques Felblinger, Ph.D, Prof., Laboratoire IADI (UL-INSERM U947), CHRU Nancy Brabois, Rue du Morvan, 54511 Vandoeuvre Cedex, France, Tel: + 33 3 83 15 49 76, E-Mail:
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Alanen A, Bondestam S, Komu M. Artifacts in MR Imaging Caused by Small Quantities of Powdered Iron. Acta Radiol 2016. [DOI: 10.1177/028418519503600117] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The MR image artifacts caused by minute metallic particles were investigated by imaging small powdered iron quantities from 0.01 mg to 1.7 mg in water phantoms. Images with T1-weighted GRE 3-D and T2-weighted SE 2-D sequences were reconstructed with 5 MR imagers: at 0.04 T., 0.1 T (2 scanners), 1.0 T and 1.5 T. In GRE 3-D images the artifacts were round, clearly demarcated black areas, whereas in SE 2-D images artifact areas were elliptic and surrounded by a bright irregular rim with ghost veils in the direction of frequency encoding. The area of the artifact increased slightly up to 0.1 mg of iron, but grew clearly with larger samples. It appeared to behave independently on the MR imager system for all iron samples. This study shows that even microscopic magnetic particles cause a notable distortion in the MR image independently of the MR equipment used.
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43
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Lönnemark M, Hemmingsson A, Ericsson A, Gundersen HG, Bach-Gansmo T. Oral Superparamagnetic Particles for Magnetic Resonance Imaging. Acta Radiol 2016. [DOI: 10.1177/028418519003100316] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
As a potential gastrointestinal MR contrast medium magnetic particles have been evaluated in preclinical studies as well as in healthy volunteers. The main problem was to achieve an even distribution of the aqueous suspension of magnetic particles in the entire intestine. To improve the distribution of the contrast medium, a viscosity-increasing agent was added to the preparation. In the plain aqueous suspension the magnetic particles sedimented rapidly and caused artifacts, whereas no such sedimentation occurred in the viscous preparation. The contrast effect, as well as the presence of artifacts, increased with particle concentration. The general contrast effect was good in all 5 volunteers, and the contrast medium was well distributed in the small intestine, including the duodenum. There were no artifacts observed, and the contrast medium was well tolerated. The viscosity-increasing agent will thus be introduced in further clinical studies.
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44
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Holtås S, Wallengren NO, Ericsson A, Bach-Gansmo T. Signal Alterations, Artifacts and Image Distortion Induced by a Superparamagnetic Contrast Medium; a Phantom Study in a 0.3 Tesla MR System. Acta Radiol 2016. [DOI: 10.1177/028418519003100220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In a phantom study using a 0.3 tesla MR system the signal alterations, artifacts and image distortion induced by a bowel contrast medium containing superparamagnetic magnetite particles were evaluated. A concentration of 20 mg iron/1 was most useful because it caused a significant signal reduction without disturbing artifacts and image distortion. The signal reduction was most pronounced on long TR/TE spin echo sequences. The appearance and distribution of artifacts are related to the direction of the static magnetic field and frequency encoding gradient. The size of artifacts is related to the concentration of the contrast medium and the band width used.
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Ericsson A, Lönnemark M, Hemmingsson A, Bach-Gansmo T. Effect of Superparamagnetic Particles in Agarose Gels. Acta Radiol 2016. [DOI: 10.1177/028418519103200119] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The effect of different preparations of superparamagnetic particles, designed as potential MR contrast media for the gastrointestinal tract (oral magnetic particles, OMP, diameter of 3.5 μm, iron content 20% by weight) and for the reticuloendothelial system (intravenous magnetic particles, IMP, mean diameter of 0.3 μm, iron content 30% by weight), were evaluated in agarose gels in vitro, using a 0.5 T whole body MR system. The iron content ranged from 2.1 × 10−4 to 2.1 × 10−1 mg Fe/ml in both preparations. Both preparations reduced the signal intensities substantially over a range of concentrations in spin echo sequences. Generally, the signal intensity decreased monotonously with concentration, except for IMP at low concentrations, at which a minor signal intensity increase was observed on T1 and proton density weighted images. The reduction of the signal intensity was stronger in gradient echo and phase contrast sequences, as compared to corresponding spin echo sequences with similar timing. Both IMP and OMP had a pronounced T2 effect, the effect of IMP being stronger than that of OMP. IMP had a relatively smaller T1 effect, whereas T1 was almost unaffected by OMP. Susceptibility artifacts occurred at higher concentrations of both OMP and IMP, in all sequences used. Thus, OMP reduced the signal intensity, without causing significant artifacts, on both T1 and T2 weighted images over a relatively wide range of concentrations.
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46
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Lönnemark M, Hemmingsson A, Bach-Gansmo T, Hagberg H, Magnusson A, Gundersen HG, Nyman R. Superparamagnetic Particles as Oral Contrast Medium in MR Imaging of Malignant Lymphoma. Acta Radiol 2016. [DOI: 10.1177/028418519103200309] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Non-biodegradable superparamagnetic particles, in plain and viscous aqueous suspensions, were used as an oral contrast medium in 34 patients with known or suspected malignant lymphoma. The contrast effect, the occurrence of artifacts, and the distribution were evaluated in the plain and the viscous aqueous suspensions, and the diagnostic information received from abdominal MR examinations performed without bowel contrast medium was compared with that of post-contrast examinations. Magnetic particles in the concentration of 0.5 g/l displayed a good contrast effect at 0.5 T, and helped in differentiating the intestine from adjacent tissues, resulting in increased diagnostic information in abdominal MR imaging. In the patients given the viscous aqueous suspension the occurrence of artifacts caused by the magnetic particles decreased considerably, and the distribution was homogeneous and improved compared with that in patients given the plain aqueous suspension.
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Chiang CH, Tseng YC, Chen AC, Huang YL, Chen DYT, Chen CJ, Lin YK, Hsu HL. In vitro comparison of intracranial stent visibility using various concentrations of gadolinium contrast agent under 1.5 T and 3 T MR angiography. J Neurointerv Surg 2016; 9:399-404. [DOI: 10.1136/neurintsurg-2016-012490] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 07/12/2016] [Accepted: 07/21/2016] [Indexed: 11/03/2022]
Abstract
Background and purposeMR angiography (MRA) is an increasingly used evaluation method following intracranial stenting. However, the various artifacts created by the stent limit this technique. The purpose of this study was to investigate the effects of various concentrations of gadolinium contrast agent on the visibility and signal characteristics of two stents using the a contrast enhanced MRA technique.Material and methodTwo intracranial stents (Enterprise and Helistent) were placed in polyvinyl chloride tubes as vascular phantoms. They were filled with six different doses of gadolinium contrast agent (1.0, 2.0, 4.0, 6.0, 8.0, and 10.0 mmol/L dimeglumine gadopentetate, respectively) and imaged using 3 T and 1.5 T MR systems. Relative in-stent signal (RIS) was calculated and artificial luminal narrowing (ALN) was obtained using pixel by pixel analysis.ResultThe Enterprise stent, performed in both 1.5 T and 3 T MR systems, showed mean RIS values much less than those for the Helistent for all different doses of gadolinium solution. Increased gadolinium concentration resulted in a gradual reduction in RIS values in the Enterprise group. Also, ALN in the Enterprise group showed no or little change with various gadolinium doses.ConclusionsThe Enterprise stent demonstrated good luminal visibility regardless of gadolinium concentration. The relative in-stent signals were more predictable in the Enterprise stent with various doses of gadolinium. Therefore, the Enterprise stent has been shown to provide better in-stent visibility compared with the Helistent using various gadolinium doses.
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Otazo R, Nittka M, Bruno M, Raithel E, Geppert C, Gyftopoulos S, Recht M, Rybak L. Sparse-SEMAC: rapid and improved SEMAC metal implant imaging using SPARSE-SENSE acceleration. Magn Reson Med 2016; 78:79-87. [PMID: 27454003 DOI: 10.1002/mrm.26342] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Revised: 05/27/2016] [Accepted: 06/21/2016] [Indexed: 02/03/2023]
Abstract
PURPOSE To develop an accelerated SEMAC metal implant MRI technique (Sparse-SEMAC) with reduced scan time and improved metal distortion correction. METHODS Sparse-SEMAC jointly exploits the inherent sparsity along the additional phase-encoding dimension and multicoil encoding capabilities to significantly accelerate data acquisition. A prototype pulse sequence with pseudorandom ky -kz undersampling and an inline image reconstruction was developed for integration in clinical studies. Three patients with hip implants were imaged using the proposed Sparse-SEMAC with eight-fold acceleration and compared with the standard-SEMAC technique used in clinical studies (three-fold GRAPPA acceleration). Measurements were performed with SEMAC-encoding steps (SES) = 15 for Sparse-SEMAC and SES = 9 for Standard-SEMAC using high spatial resolution Proton Density (PD) and lower-resolution STIR acquisitions. Two expert musculoskeletal (MSK) radiologists performed a consensus reading to score image-quality parameters. RESULTS Sparse-SEMAC enables up to eight-fold acceleration of data acquisition that results in two-fold scan time reductions, compared with Standard-SEMAC, with improved metal artifact correction for patients with hip implants without degrading spatial resolution. CONCLUSION The high acceleration enabled by Sparse-SEMAC would enable clinically feasible examination times with improved correction of metal distortion. Magn Reson Med 78:79-87, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Ricardo Otazo
- Department of Radiology, NYU School of Medicine, New York, New York, USA
| | | | - Mary Bruno
- Department of Radiology, NYU School of Medicine, New York, New York, USA
| | | | | | | | - Michael Recht
- Department of Radiology, NYU School of Medicine, New York, New York, USA
| | - Leon Rybak
- Department of Radiology, NYU School of Medicine, New York, New York, USA
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Merkle EM, Klein S, Wisianowsky C, Boll DT, Fleiter TR, Pamler R, Görich J, Brambs HJ. Magnetic Resonance Imaging versus Multislice Computed Tomography of Thoracic Aortic Endografts. J Endovasc Ther 2016. [DOI: 10.1177/15266028020090s202] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Purpose: To compare the potential of magnetic resonance imaging (MRI) to multislice computed tomography (CT) for evaluating stent-graft placement in the thoracic aorta. Methods: Susceptibility artifacts in 2 different stent-graft systems (Talent and Excluder) were evaluated in vitro in 2 angulations (straight and 33° curved) using 3 different MRI gradient echo sequences (True FISP, 2-dimensional FLASH, and 3-dimensional Turbo FLASH). The size of the stent-related artifact was measured, and the relative stent lumen was calculated. In vivo stent demarcation, stent patency, and additional findings were determined in 13 patients (3 Talent, 9 Excluder, and 1 combined) and compared to CT findings. Results: In vitro, both endograft systems proved to be MR compatible, with the relative stent lumen value ranging from 82% to 100% in the straight configuration; in a curved model, the relative stent lumen value ranged from 56% to 92% with the 3D Turbo FLASH sequence, which provided the smallest susceptibility artifacts. The Excluder endoprosthesis caused significant signal inhomogeneity within the stent in a curved configuration. In vivo, MRI and multislice CT showed similar results, with CT imaging slightly superior in stent demarcation and MRI better in demonstrating thrombus. CT beam hardening artifacts were pronounced in the Talent system, while the Excluder device caused significant signal inhomogeneity within the stent on magnetic resonance angiography. Conclusions: Multislice CT and contrast-enhanced MRI are fast, reliable means of providing all relevant information for surveillance of fully MR-compatible stent-grafts in the thoracic aorta.
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Affiliation(s)
| | | | | | | | | | - Reinhard Pamler
- Department of Thoracic and Vascular Surgery, University Hospitals of Ulm, Germany
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Dillenseger JP, Molière S, Choquet P, Goetz C, Ehlinger M, Bierry G. An illustrative review to understand and manage metal-induced artifacts in musculoskeletal MRI: a primer and updates. Skeletal Radiol 2016; 45:677-88. [PMID: 26837388 DOI: 10.1007/s00256-016-2338-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Revised: 01/13/2016] [Accepted: 01/17/2016] [Indexed: 02/02/2023]
Abstract
This article reviews and explains the basic physical principles of metal-induced MRI artifacts, describes simple ways to reduce them, and presents specific reduction solutions. Artifacts include signal loss, pile-up artifacts, geometric distortion, and failure of fat suppression. Their nature and origins are reviewed and explained though schematic representations that ease the understanding. Then, optimization of simple acquisition parameters is detailed. Lastly, dedicated sequences and options specifically developed to reduce metal artifacts (VAT, SEMAC, and MAVRIC) are explained.
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Affiliation(s)
- J P Dillenseger
- Medical imaging department, University Hospital of Strasbourg, 10 Av. Molière, F- 67098, Strasbourg, France.,Icube, CNRS, University of Strasbourg, Strasbourg, France.,Translational Medicine Research Federation, Strasbourg Medical School, University of Strasbourg, Strasbourg, France
| | - S Molière
- Medical imaging department, University Hospital of Strasbourg, 10 Av. Molière, F- 67098, Strasbourg, France
| | - P Choquet
- Medical imaging department, University Hospital of Strasbourg, 10 Av. Molière, F- 67098, Strasbourg, France.,Icube, CNRS, University of Strasbourg, Strasbourg, France.,Translational Medicine Research Federation, Strasbourg Medical School, University of Strasbourg, Strasbourg, France
| | - C Goetz
- Medical imaging department, University Hospital of Strasbourg, 10 Av. Molière, F- 67098, Strasbourg, France.,Icube, CNRS, University of Strasbourg, Strasbourg, France.,Translational Medicine Research Federation, Strasbourg Medical School, University of Strasbourg, Strasbourg, France
| | - M Ehlinger
- Icube, CNRS, University of Strasbourg, Strasbourg, France.,Translational Medicine Research Federation, Strasbourg Medical School, University of Strasbourg, Strasbourg, France.,Department of orthopedic surgery, University Hospital of Strasbourg, Strasbourg, France
| | - G Bierry
- Medical imaging department, University Hospital of Strasbourg, 10 Av. Molière, F- 67098, Strasbourg, France. .,Icube, CNRS, University of Strasbourg, Strasbourg, France. .,Translational Medicine Research Federation, Strasbourg Medical School, University of Strasbourg, Strasbourg, France.
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