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Wang D, Stirnberg R, Stöcker T. Improved gradient echo magnitude- and phase-based mapping of T 2 $$ {\mathrm{T}}_2 $$ using multiple RF spoiling increments at 3T and 7T. Magn Reson Med 2024; 92:2328-2342. [PMID: 38987985 DOI: 10.1002/mrm.30217] [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: 12/12/2023] [Revised: 05/23/2024] [Accepted: 06/25/2024] [Indexed: 07/12/2024]
Abstract
PURPOSE The transverse relaxation time T 2 $$ {}_2 $$ holds significant relevance in clinical applications and research studies. Conventional T 2 $$ {}_2 $$ mapping approaches rely on spin-echo sequences, which require lengthy acquisition times and involve high radiofrequency (RF) power deposition. An alternative gradient echo (GRE) phase-based T 2 $$ {}_2 $$ mapping method, utilizing steady-state acquisitions at one small RF spoil phase increment, was recently demonstrated. Here, a modified magnitude- and phase-based T 2 $$ {}_2 $$ mapping approach is proposed, which improvesT 2 $$ {\mathrm{T}}_2 $$ estimations by simultaneous fitting ofT 1 $$ {\mathrm{T}}_1 $$ and signal amplitude (A ∝ P D $$ A\propto PD $$ ) at three or more RF spoiling phase increments, instead of assuming a fixedT 1 $$ {\mathrm{T}}_1 $$ value. METHODS The feasibility of the magnitude-phase-based method was assessed by simulations, in phantom and in vivo experiments using skipped-CAIPI three-dimensional-echo-planar imaging (3D-EPI) for rapid GRE imaging.T 2 $$ {\mathrm{T}}_2 $$ ,T 1 $$ {\mathrm{T}}_1 $$ and PD estimations obtained by our method were compared toT 2 $$ {\mathrm{T}}_2 $$ of the phase-based method andT 1 $$ {\mathrm{T}}_1 $$ and PD of spoiled GRE-based multi-parameter mapping using a multi-echo version of the same sequence. RESULTS The agreement of the proposedT 2 $$ {\mathrm{T}}_2 $$ with ground truth and referenceT 2 $$ {\mathrm{T}}_2 $$ values was higher than that of phase-basedT 2 $$ {\mathrm{T}}_2 $$ in simulations and in phantom data. While phase-basedT 2 $$ {\mathrm{T}}_2 $$ overestimation increases with actualT 2 $$ {\mathrm{T}}_2 $$ andT 1 $$ {\mathrm{T}}_1 $$ , the proposed method is accurate over a large range of physiologically meaningfulT 2 $$ {\mathrm{T}}_2 $$ andT 1 $$ {\mathrm{T}}_1 $$ values. At the same time, precision is improved. In vivo results were in line with these observations. CONCLUSION Accurate magnitude-phase-based T 2 $$ {}_2 $$ mapping is feasible in less than 5 min scan time for 1 mm nominal isotropic whole-head coverage at 3T and 7T.
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Affiliation(s)
- Difei Wang
- MR Physics, German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Rüdiger Stirnberg
- MR Physics, German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Tony Stöcker
- MR Physics, German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
- Department of Physics & Astronomy, University of Bonn, Bonn, Germany
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Li X, Kim J, Yang M, Ok AH, Zbýň Š, Link TM, Majumdar S, Ma CB, Spindler KP, Winalski CS. Cartilage compositional MRI-a narrative review of technical development and clinical applications over the past three decades. Skeletal Radiol 2024; 53:1761-1781. [PMID: 38980364 PMCID: PMC11303573 DOI: 10.1007/s00256-024-04734-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 06/11/2024] [Accepted: 06/13/2024] [Indexed: 07/10/2024]
Abstract
Articular cartilage damage and degeneration are among hallmark manifestations of joint injuries and arthritis, classically osteoarthritis. Cartilage compositional MRI (Cart-C MRI), a quantitative technique, which aims to detect early-stage cartilage matrix changes that precede macroscopic alterations, began development in the 1990s. However, despite the significant advancements over the past three decades, Cart-C MRI remains predominantly a research tool, hindered by various technical and clinical hurdles. This paper will review the technical evolution of Cart-C MRI, delve into its clinical applications, and conclude by identifying the existing gaps and challenges that need to be addressed to enable even broader clinical application of Cart-C MRI.
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Affiliation(s)
- Xiaojuan Li
- Program of Advanced Musculoskeletal Imaging (PAMI), Cleveland Clinic, 9500 Euclid Avenue, ND20, Cleveland, OH, 44195, USA.
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.
- Department of Diagnostic Radiology, Cleveland Clinic, Cleveland, OH, USA.
| | - Jeehun Kim
- Program of Advanced Musculoskeletal Imaging (PAMI), Cleveland Clinic, 9500 Euclid Avenue, ND20, Cleveland, OH, 44195, USA
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Mingrui Yang
- Program of Advanced Musculoskeletal Imaging (PAMI), Cleveland Clinic, 9500 Euclid Avenue, ND20, Cleveland, OH, 44195, USA
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Ahmet H Ok
- Program of Advanced Musculoskeletal Imaging (PAMI), Cleveland Clinic, 9500 Euclid Avenue, ND20, Cleveland, OH, 44195, USA
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
- Department of Diagnostic Radiology, Cleveland Clinic, Cleveland, OH, USA
| | - Štefan Zbýň
- Program of Advanced Musculoskeletal Imaging (PAMI), Cleveland Clinic, 9500 Euclid Avenue, ND20, Cleveland, OH, 44195, USA
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
- Department of Diagnostic Radiology, Cleveland Clinic, Cleveland, OH, USA
| | - Thomas M Link
- Department of Radiology and Biomedical Imaging, University of California San Francisco (UCSF), San Francisco, CA, USA
| | - Sharmilar Majumdar
- Department of Radiology and Biomedical Imaging, University of California San Francisco (UCSF), San Francisco, CA, USA
| | - C Benjamin Ma
- Department of Orthopaedic Surgery, UCSF, San Francisco, CA, USA
| | - Kurt P Spindler
- Program of Advanced Musculoskeletal Imaging (PAMI), Cleveland Clinic, 9500 Euclid Avenue, ND20, Cleveland, OH, 44195, USA
- Department of Orthopaedic Surgery, Cleveland Clinic, Cleveland, OH, USA
| | - Carl S Winalski
- Program of Advanced Musculoskeletal Imaging (PAMI), Cleveland Clinic, 9500 Euclid Avenue, ND20, Cleveland, OH, 44195, USA
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
- Department of Diagnostic Radiology, Cleveland Clinic, Cleveland, OH, USA
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Aghaeifar A, Bosch D, Heule R, Williams S, Ehses P, Mauconduit F, Scheffler K. Intra-scan RF power amplifier drift correction. Magn Reson Med 2024; 92:645-659. [PMID: 38469935 DOI: 10.1002/mrm.30078] [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: 09/14/2023] [Revised: 12/18/2023] [Accepted: 02/21/2024] [Indexed: 03/13/2024]
Abstract
PURPOSE The drift in radiofrequency (RF) power amplifiers (RFPAs) is assessed and several contributing factors are investigated. Two approaches for prospective correction of drift are proposed and their effectiveness is evaluated. METHODS RFPA drift assessment encompasses both intra-pulse and inter-pulse drift analyses. Scan protocols with varying flip angle (FA), RF length, and pulse repetition time (TR) are used to gauge the influence of these parameters on drift. Directional couplers (DICOs) monitor the forward waveforms of the RFPA outputs. DICOs data is stored for evaluation, allowing calculation of correction factors to adjust RFPAs' transmit voltage. Two correction methods, predictive and run-time, are employed: predictive correction necessitates a calibration scan, while run-time correction calculates factors during the ongoing scan. RESULTS RFPA drift is indeed influenced by the RF duty-cycle, and in the cases examined with a maximum duty-cycle of 66%, the potential drift is approximately 41% or 15%, depending on the specific RFPA revision. Notably, in low transmit voltage scenarios, FA has minimal impact on RFPA drift. The application of predictive and run-time drift correction techniques effectively reduces the average drift from 10.0% to less than 1%, resulting in enhanced MR signal stability. CONCLUSION Utilizing DICO recordings and implementing a feedback mechanism enable the prospective correction of RFPA drift. Having a calibration scan, predictive correction can be utilized with fewer complexity; for enhanced performance, a run-time approach can be employed.
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Affiliation(s)
- Ali Aghaeifar
- High-Field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany
| | - Dario Bosch
- High-Field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany
- Department of Biomedical Magnetic Resonance, University of Tuebingen, Tuebingen, Germany
| | - Rahel Heule
- High-Field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany
- Department of Biomedical Magnetic Resonance, University of Tuebingen, Tuebingen, Germany
- Center for MR Research, University Children's Hospital, Zurich, Switzerland
| | - Sydney Williams
- Imaging Centre of Excellence, University of Glasgow, Glasgow, UK
| | - Philipp Ehses
- MR Physics, German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | | | - Klaus Scheffler
- High-Field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany
- Department of Biomedical Magnetic Resonance, University of Tuebingen, Tuebingen, Germany
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4
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Coronado R, Castillo-Passi C, Besa C, Irarrazaval P. Fast and accessible T2 mapping using off-resonance corrected DESPOT2 with application to 3D prostate. Magn Reson Imaging 2024; 109:227-237. [PMID: 38508291 DOI: 10.1016/j.mri.2024.03.018] [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: 01/24/2024] [Revised: 03/12/2024] [Accepted: 03/13/2024] [Indexed: 03/22/2024]
Abstract
PURPOSE Most T1 and T2 mapping take long acquisitions or needs specialized sequences not widely accessible on clinical scanners. An available solution is DESPOT1/T2 (Driven equilibrium single pulse observation of T1/T2). DESPOT1/T2 uses Spoiled gradient-echo (SPGR) and balanced Steady-State Free Precession (bSSFP) sequences, offering an accessible and reliable way for 3D accelerated T1/T2 mapping. However, bSSFP is prone to off-resonance artifacts, limiting the application of DESPOT2 in regions with high susceptibility contrasts, like the prostate. Our proposal, DESPO+, employs the full bSSFP and SPGR models with a dictionary-based method to reconstruct 3D T1/T2 maps in the prostate region without off-resonance banding. METHODS DESPO+ modifies the bSSFP acquisition of the original variable flip angle DESPOT2. DESPO+ uses variable repetition and echo times, employing a dictionary-based method of the full bSSFP and SPGR models to reconstruct T1, T2, and Proton Density (PD) simultaneously. The proposed DESPO+ method underwent testing through simulations, T1/T2 phantoms, and on fourteen healthy subjects. RESULTS The results reveal a significant reduction in T2 map banding artifacts compared to the original DESPOT2 method. DESPO+ approach reduced T2 errors by up to seven times compared to DESPOT2 in simulations and phantom experiments. We also synthesized in-vivo T1-weighted/T2-weighted images from the acquired maps using a spin-echo model to verify the map's quality when lacking a reference. For in-vivo imaging, the synthesized images closely resemble those from the clinical MRI protocol, reducing scan time by around 50% compared to traditional spin-echo T1-weighted/T2-weighted acquisitions. CONCLUSION DESPO+ provides an off-resonance insensitive and clinically available solution, enabling high-resolution 3D T1/T2 mapping and synthesized T1-weighted/T2-weighted images for the entire prostate, all achieved within a short scan time of 3.6 min, similar to DESPOT1/T2.
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Affiliation(s)
- Ronal Coronado
- Biomedical Imaging Center, Pontificia Universidad Católica de Chile, Santiago, Chile; Department of Electrical Engineering, Pontificia Universidad Católica de Chile, Santiago, Chile; Millennium Institute for Intelligent Healthcare Engineering, Santiago, Chile
| | - Carlos Castillo-Passi
- Millennium Institute for Intelligent Healthcare Engineering, Santiago, Chile; School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom; Institute for Biological and Medical Engineering, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Cecilia Besa
- Millennium Institute for Intelligent Healthcare Engineering, Santiago, Chile; Department of Radiology, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Pablo Irarrazaval
- Biomedical Imaging Center, Pontificia Universidad Católica de Chile, Santiago, Chile; Department of Electrical Engineering, Pontificia Universidad Católica de Chile, Santiago, Chile; Millennium Institute for Intelligent Healthcare Engineering, Santiago, Chile; Institute for Biological and Medical Engineering, Pontificia Universidad Católica de Chile, Santiago, Chile.
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5
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Bieri O, Weidensteiner C, Ganter C. Robust T 2 estimation with balanced steady state free precession. Magn Reson Med 2024; 91:2257-2265. [PMID: 38411351 DOI: 10.1002/mrm.30037] [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: 09/15/2023] [Revised: 01/12/2024] [Accepted: 01/15/2024] [Indexed: 02/28/2024]
Abstract
PURPOSE To develop a novel signal representation for balanced steady state free precession (bSSFP) displaying its T2 independence on B1 and on magnetization transfer (MT) effects. METHODS A signal model for bSSFP is developed that shows only an explicit dependence (up to a scaling factor) on E2 (and, therefore, T2) and a novel parameter c (with implicit dependence on the flip angle and E1). Moreover, it is shown that MT effects, entering the bSSFP signal via a binary spin bath model, can be captured by a redefinition of T1 and, therefore, leading to modification of E1, resulting in the same signal model. Various sets of phase-cycled bSSFP brain scans (different flip angles, different TR, different RF pulse durations, and different number of phase cycles) were recorded at 3 T. The parameters T2 (E2) and c were estimated using a variable projection (VARPRO) method and Monte-Carlo simulations were performed to assess T2 estimation precision. RESULTS Initial experiments confirmed the expected independence of T2 on various protocol settings, such as TR, the flip angle, B1 field inhomogeneity, and the RF pulse duration. Any variation (within the explored range) appears to directly affect the estimation of the parameter c only-in agreement with theory. CONCLUSION BSSFP theory predicts an extraordinary feature that all MT and B1-related variational aspects do not enter T2 estimation, making it a potentially robust methodology for T2 quantification, pending validation against existing standards.
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Affiliation(s)
- Oliver Bieri
- Department of Biomedical Engineering, University of Basel, Allschwil, Switzerland
- Department of Radiology, Division of Radiological Physics, University Hospital Basel, Basel, Switzerland
| | - Claudia Weidensteiner
- Department of Biomedical Engineering, University of Basel, Allschwil, Switzerland
- Department of Radiology, Division of Radiological Physics, University Hospital Basel, Basel, Switzerland
| | - Carl Ganter
- Department of Radiology, Klinikum rechts der Isar, Technical University Munich, Munich, Germany
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Guan X, Lancione M, Ayton S, Dusek P, Langkammer C, Zhang M. Neuroimaging of Parkinson's disease by quantitative susceptibility mapping. Neuroimage 2024; 289:120547. [PMID: 38373677 DOI: 10.1016/j.neuroimage.2024.120547] [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: 02/02/2024] [Accepted: 02/17/2024] [Indexed: 02/21/2024] Open
Abstract
Parkinson's disease (PD) is a common neurodegenerative disease, and apart from a few rare genetic causes, its pathogenesis remains largely unclear. Recent scientific interest has been captured by the involvement of iron biochemistry and the disruption of iron homeostasis, particularly within the brain regions specifically affected in PD. The advent of Quantitative Susceptibility Mapping (QSM) has enabled non-invasive quantification of brain iron in vivo by MRI, which has contributed to the understanding of iron-associated pathogenesis and has the potential for the development of iron-based biomarkers in PD. This review elucidates the biochemical underpinnings of brain iron accumulation, details advancements in iron-sensitive MRI technologies, and discusses the role of QSM as a biomarker of iron deposition in PD. Despite considerable progress, several challenges impede its clinical application after a decade of QSM studies. The initiation of multi-site research is warranted for developing robust, interpretable, and disease-specific biomarkers for monitoring PD disease progression.
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Affiliation(s)
- Xiaojun Guan
- Department of Radiology, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China; Joint Laboratory of Clinical Radiology, the Second Affiliated Hospital, Zhejiang University School of Medicine, No.88 Jiefang Road, Shangcheng District, Hangzhou 31009, China
| | - Marta Lancione
- Laboratory of Medical Physics and Magnetic Resonance, IRCCS Stella Maris Foundation, Pisa, Italy
| | - Scott Ayton
- Florey Institute, The University of Melbourne, Australia
| | - Petr Dusek
- Department of Neurology and Center of Clinical Neuroscience, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czechia; Department of Radiology, First Faculty of Medicine, Charles University and General University Hospital in Prague, Auenbruggerplatz 22, Prague 8036, Czechia
| | | | - Minming Zhang
- Department of Radiology, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China; Joint Laboratory of Clinical Radiology, the Second Affiliated Hospital, Zhejiang University School of Medicine, No.88 Jiefang Road, Shangcheng District, Hangzhou 31009, China.
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7
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Mickevicius NJ. Magnetic resonance coherence pathway unraveling. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2024; 358:107613. [PMID: 38134509 DOI: 10.1016/j.jmr.2023.107613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 12/08/2023] [Accepted: 12/15/2023] [Indexed: 12/24/2023]
Abstract
Efficiently acquiring multi-contrast magnetic resonance imaging data is crucial for patient comfort and clinical throughput. Developing scan acceleration methods tailored for specific applications drastically improves the value of an MRI examination. Here, we propose a novel method to control the aliasing of simultaneously acquired images of multiple spin echo coherence pathways with the goal of producing high quality multi-contrast images from a single acquisition. Modulating the radiofrequency phase of several pulses applied in brief succession also uniquely modulates the phase of spin echo coherence pathways. A method, termed magnetic resonance coherence pathway unraveling (MR-CPU), to control the aliasing of simultaneously acquired coherence pathway images is developed here along with parallel imaging-based reconstruction methods to separate them. MR-CPU was validated in phantom experiments and tested in vivo. High levels of correlation between reference pathway images and MR-CPU-derived coherence pathway images were found from the phantom experiments. Minimal artifacts arising from the separation of the overlapped coherence pathway images were observed in vivo. MR-CPU provides a novel mechanism through which to acquire and separate multiple overlapped coherence pathway images, thus adding to the diagnostic potential of an MRI exam without the penalty of additional scan time.
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8
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Li T, Wang J, Yang Y, Glide-Hurst CK, Wen N, Cai J. Multi-parametric MRI for radiotherapy simulation. Med Phys 2023; 50:5273-5293. [PMID: 36710376 PMCID: PMC10382603 DOI: 10.1002/mp.16256] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 09/10/2022] [Accepted: 12/06/2022] [Indexed: 01/31/2023] Open
Abstract
Magnetic resonance imaging (MRI) has become an important imaging modality in the field of radiotherapy (RT) in the past decade, especially with the development of various novel MRI and image-guidance techniques. In this review article, we will describe recent developments and discuss the applications of multi-parametric MRI (mpMRI) in RT simulation. In this review, mpMRI refers to a general and loose definition which includes various multi-contrast MRI techniques. Specifically, we will focus on the implementation, challenges, and future directions of mpMRI techniques for RT simulation.
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Affiliation(s)
- Tian Li
- Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hong Kong, China
| | - Jihong Wang
- Department of Radiation Physics, Division of Radiation Oncology, MD Anderson Cancer Center, Houston, Texas, USA
| | - Yingli Yang
- Department of Radiology, Ruijin Hospital, Shanghai Jiaotong Univeristy School of Medicine, Shanghai, China
- SJTU-Ruijing-UIH Institute for Medical Imaging Technology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Carri K Glide-Hurst
- Department of Radiation Oncology, University of Wisconsin, Madison, Wisconsin, USA
| | - Ning Wen
- Department of Radiology, Ruijin Hospital, Shanghai Jiaotong Univeristy School of Medicine, Shanghai, China
- SJTU-Ruijing-UIH Institute for Medical Imaging Technology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
- The Global Institute of Future Technology, Shanghai Jiaotong University, Shanghai, China
| | - Jing Cai
- Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hong Kong, China
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9
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Ganter C. Approximate B 1 + scaling of the SSFP steady state. Magn Reson Med 2023; 89:2264-2269. [PMID: 36705048 DOI: 10.1002/mrm.29598] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 01/09/2023] [Accepted: 01/09/2023] [Indexed: 01/28/2023]
Abstract
PURPOSE It is shown that the steady state of rapid, TR-periodic steady-state free precession (SSFP) sequences at small to moderate flip angles exhibits a universal, approximate scaling law with respect to variations of B 1 + $$ {B}_1^{+} $$ . Implications for the accuracy and precision of relaxometry experiments are discussed. METHODS The approximate scaling law is derived from and numerically tested against known analytical solutions. To assess the attainable estimator precision in a typical relaxometry experiment, we calculate the Cramér-Rao bound (CRB) and perform Monte Carlo (MC) simulations. RESULTS The approximate universal scaling holds well up to moderate flip angles. For pure steady state relaxometry, we observe a significant precision penalty for simultaneous estimation of R 1 $$ {R}_1 $$ and B 1 + $$ {B}_1^{+} $$ , whereas good R 2 $$ {R}_2 $$ estimates can be obtained without even knowing the correct actual flip angle. CONCLUSION Simultaneous estimation of R 1 $$ {R}_1 $$ and B 1 + $$ {B}_1^{+} $$ from a set of SSFP steady states alone is not advisable. Apart from separate B 1 + $$ {B}_1^{+} $$ measurements, the problem can be addressed by adding transient state information, but, depending on the situation, residual effects due to the scaling may still require some attention.
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Affiliation(s)
- Carl Ganter
- School of Medicine, Department of Diagnostic and Interventional Radiology, Klinikum rechts der Isar der TUM, Technical University of Munich, Munich, Germany
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10
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Eck BL, Yang M, Elias JJ, Winalski CS, Altahawi F, Subhas N, Li X. Quantitative MRI for Evaluation of Musculoskeletal Disease: Cartilage and Muscle Composition, Joint Inflammation, and Biomechanics in Osteoarthritis. Invest Radiol 2023; 58:60-75. [PMID: 36165880 PMCID: PMC10198374 DOI: 10.1097/rli.0000000000000909] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
ABSTRACT Magnetic resonance imaging (MRI) is a valuable tool for evaluating musculoskeletal disease as it offers a range of image contrasts that are sensitive to underlying tissue biochemical composition and microstructure. Although MRI has the ability to provide high-resolution, information-rich images suitable for musculoskeletal applications, most MRI utilization remains in qualitative evaluation. Quantitative MRI (qMRI) provides additional value beyond qualitative assessment via objective metrics that can support disease characterization, disease progression monitoring, or therapy response. In this review, musculoskeletal qMRI techniques are summarized with a focus on techniques developed for osteoarthritis evaluation. Cartilage compositional MRI methods are described with a detailed discussion on relaxometric mapping (T 2 , T 2 *, T 1ρ ) without contrast agents. Methods to assess inflammation are described, including perfusion imaging, volume and signal changes, contrast-enhanced T 1 mapping, and semiquantitative scoring systems. Quantitative characterization of structure and function by bone shape modeling and joint kinematics are described. Muscle evaluation by qMRI is discussed, including size (area, volume), relaxometric mapping (T 1 , T 2 , T 1ρ ), fat fraction quantification, diffusion imaging, and metabolic assessment by 31 P-MR and creatine chemical exchange saturation transfer. Other notable technologies to support qMRI in musculoskeletal evaluation are described, including magnetic resonance fingerprinting, ultrashort echo time imaging, ultrahigh-field MRI, and hybrid MRI-positron emission tomography. Challenges for adopting and using qMRI in musculoskeletal evaluation are discussed, including the need for metal artifact suppression and qMRI standardization.
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Affiliation(s)
- Brendan L. Eck
- Program of Advanced Musculoskeletal Imaging, Cleveland Clinic, Cleveland, OH, USA
- Imaging Instute, Cleveland Clinic, Cleveland, OH, USA
| | - Mingrui Yang
- Program of Advanced Musculoskeletal Imaging, Cleveland Clinic, Cleveland, OH, USA
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
| | - John J. Elias
- Program of Advanced Musculoskeletal Imaging, Cleveland Clinic, Cleveland, OH, USA
- Department of Research, Cleveland Clinic Akron General, Akron, OH, USA
| | - Carl S. Winalski
- Program of Advanced Musculoskeletal Imaging, Cleveland Clinic, Cleveland, OH, USA
- Imaging Instute, Cleveland Clinic, Cleveland, OH, USA
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Faysal Altahawi
- Program of Advanced Musculoskeletal Imaging, Cleveland Clinic, Cleveland, OH, USA
- Imaging Instute, Cleveland Clinic, Cleveland, OH, USA
| | - Naveen Subhas
- Program of Advanced Musculoskeletal Imaging, Cleveland Clinic, Cleveland, OH, USA
- Imaging Instute, Cleveland Clinic, Cleveland, OH, USA
| | - Xiaojuan Li
- Program of Advanced Musculoskeletal Imaging, Cleveland Clinic, Cleveland, OH, USA
- Imaging Instute, Cleveland Clinic, Cleveland, OH, USA
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
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11
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Jara H, Sakai O, Farrher E, Oros-Peusquens AM, Shah NJ, Alsop DC, Keenan KE. Primary Multiparametric Quantitative Brain MRI: State-of-the-Art Relaxometric and Proton Density Mapping Techniques. Radiology 2022; 305:5-18. [PMID: 36040334 PMCID: PMC9524578 DOI: 10.1148/radiol.211519] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 05/01/2022] [Accepted: 05/24/2022] [Indexed: 11/11/2022]
Abstract
This review on brain multiparametric quantitative MRI (MP-qMRI) focuses on the primary subset of quantitative MRI (qMRI) parameters that represent the mobile ("free") and bound ("motion-restricted") proton pools. Such primary parameters are the proton densities, relaxation times, and magnetization transfer parameters. Diffusion qMRI is also included because of its wide implementation in complete clinical MP-qMRI application. MP-qMRI advances were reviewed over the past 2 decades, with substantial progress observed toward accelerating image acquisition and increasing mapping accuracy. Areas that need further investigation and refinement are identified as follows: (a) the biologic underpinnings of qMRI parameter values and their changes with age and/or disease and (b) the theoretical limitations implicitly built into most qMRI mapping algorithms that do not distinguish between the different spatial scales of voxels versus spin packets, the central physical object of the Bloch theory. With rapidly improving image processing techniques and continuous advances in computer hardware, MP-qMRI has the potential for implementation in a wide range of clinical applications. Currently, three emerging MP-qMRI applications are synthetic MRI, macrostructural qMRI, and microstructural tissue modeling.
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Affiliation(s)
- Hernán Jara
- From the Department of Radiology, Boston University, 670 Albany St,
Boston, Mass 02118 (H.J., O.S.); Institute of Neuroscience and Medicine-4,
Forschungszentrum Jülich, Jülich, Germany (E.F., A.M.O.P.,
N.J.S.); Department of Radiology, Beth Israel Deaconess Medical Center, Harvard
Medical School, Boston, Mass (D.C.A.); and Physical Measurement Laboratory,
National Institute of Standards and Technology, Boulder, Colo (K.E.K.)
| | - Osamu Sakai
- From the Department of Radiology, Boston University, 670 Albany St,
Boston, Mass 02118 (H.J., O.S.); Institute of Neuroscience and Medicine-4,
Forschungszentrum Jülich, Jülich, Germany (E.F., A.M.O.P.,
N.J.S.); Department of Radiology, Beth Israel Deaconess Medical Center, Harvard
Medical School, Boston, Mass (D.C.A.); and Physical Measurement Laboratory,
National Institute of Standards and Technology, Boulder, Colo (K.E.K.)
| | - Ezequiel Farrher
- From the Department of Radiology, Boston University, 670 Albany St,
Boston, Mass 02118 (H.J., O.S.); Institute of Neuroscience and Medicine-4,
Forschungszentrum Jülich, Jülich, Germany (E.F., A.M.O.P.,
N.J.S.); Department of Radiology, Beth Israel Deaconess Medical Center, Harvard
Medical School, Boston, Mass (D.C.A.); and Physical Measurement Laboratory,
National Institute of Standards and Technology, Boulder, Colo (K.E.K.)
| | - Ana-Maria Oros-Peusquens
- From the Department of Radiology, Boston University, 670 Albany St,
Boston, Mass 02118 (H.J., O.S.); Institute of Neuroscience and Medicine-4,
Forschungszentrum Jülich, Jülich, Germany (E.F., A.M.O.P.,
N.J.S.); Department of Radiology, Beth Israel Deaconess Medical Center, Harvard
Medical School, Boston, Mass (D.C.A.); and Physical Measurement Laboratory,
National Institute of Standards and Technology, Boulder, Colo (K.E.K.)
| | - N. Jon Shah
- From the Department of Radiology, Boston University, 670 Albany St,
Boston, Mass 02118 (H.J., O.S.); Institute of Neuroscience and Medicine-4,
Forschungszentrum Jülich, Jülich, Germany (E.F., A.M.O.P.,
N.J.S.); Department of Radiology, Beth Israel Deaconess Medical Center, Harvard
Medical School, Boston, Mass (D.C.A.); and Physical Measurement Laboratory,
National Institute of Standards and Technology, Boulder, Colo (K.E.K.)
| | - David C. Alsop
- From the Department of Radiology, Boston University, 670 Albany St,
Boston, Mass 02118 (H.J., O.S.); Institute of Neuroscience and Medicine-4,
Forschungszentrum Jülich, Jülich, Germany (E.F., A.M.O.P.,
N.J.S.); Department of Radiology, Beth Israel Deaconess Medical Center, Harvard
Medical School, Boston, Mass (D.C.A.); and Physical Measurement Laboratory,
National Institute of Standards and Technology, Boulder, Colo (K.E.K.)
| | - Kathryn E. Keenan
- From the Department of Radiology, Boston University, 670 Albany St,
Boston, Mass 02118 (H.J., O.S.); Institute of Neuroscience and Medicine-4,
Forschungszentrum Jülich, Jülich, Germany (E.F., A.M.O.P.,
N.J.S.); Department of Radiology, Beth Israel Deaconess Medical Center, Harvard
Medical School, Boston, Mass (D.C.A.); and Physical Measurement Laboratory,
National Institute of Standards and Technology, Boulder, Colo (K.E.K.)
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12
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Seginer A, Schmidt R. Phase-based fast 3D high-resolution quantitative T 2 MRI in 7 T human brain imaging. Sci Rep 2022; 12:14088. [PMID: 35982143 PMCID: PMC9388657 DOI: 10.1038/s41598-022-17607-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 07/28/2022] [Indexed: 12/04/2022] Open
Abstract
Magnetic resonance imaging (MRI) is a powerful and versatile technique that offers a range of physiological, diagnostic, structural, and functional measurements. One of the most widely used basic contrasts in MRI diagnostics is transverse relaxation time (T2)-weighted imaging, but it provides only qualitative information. Realizing quantitative high-resolution T2 mapping is imperative for the development of personalized medicine, as it can enable the characterization of diseases progression. While ultra-high-field (≥ 7 T) MRI offers the means to gain new insights by increasing the spatial resolution, implementing fast quantitative T2 mapping cannot be achieved without overcoming the increased power deposition and radio frequency (RF) field inhomogeneity at ultra-high-fields. A recent study has demonstrated a new phase-based T2 mapping approach based on fast steady-state acquisitions. We extend this new approach to ultra-high field MRI, achieving quantitative high-resolution 3D T2 mapping at 7 T while addressing RF field inhomogeneity and utilizing low flip angle pulses; overcoming two main ultra-high field challenges. The method is based on controlling the coherent transverse magnetization in a steady-state gradient echo acquisition; achieved by utilizing low flip angles, a specific phase increment for the RF pulses, and short repetition times. This approach simultaneously extracts both T2 and RF field maps from the phase of the signal. Prior to in vivo experiments, the method was assessed using a 3D head-shaped phantom that was designed to model the RF field distribution in the brain. Our approach delivers fast 3D whole brain images with submillimeter resolution without requiring special hardware, such as multi-channel transmit coil, thus promoting high usability of the ultra-high field MRI in clinical practice.
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Affiliation(s)
| | - Rita Schmidt
- Department of Brain Sciences, Weizmann Institute of Science, Rehovot, Israel. .,The Azrieli National Institute for Human Brain Imaging and Research, Weizmann Institute of Science, Rehovot, Israel.
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13
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Madore B, Jerosch-Herold M, Chiou JYG, Cheng CC, Guenette JP, Mihai G. A relaxometry method that emphasizes practicality and availability. Magn Reson Med 2022; 88:2208-2216. [PMID: 35877783 DOI: 10.1002/mrm.29394] [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: 05/05/2022] [Revised: 06/17/2022] [Accepted: 06/29/2022] [Indexed: 11/08/2022]
Abstract
PURPOSE Although many methods have been proposed to quantitatively map the main MRI parameters (e.g., T1 , T2 , C × M0 ), these methods often involve special sequences not readily available on clinical scanners and/or may require long scan times. In contrast, the proposed method can readily run on most scanners, offer flexible tradeoffs between scan time and image quality, and map MRI parameters jointly to ensure spatial alignment. METHODS The approach is based on the multi-shot spin-echo (SE) EPI sequence. The corresponding signal equation was derived and strategies for solving it were developed. As usual with multi-shot EPI, scan time can readily be traded-off against image quality by adjusting the echo train length. Validation was performed against reference relaxometry methods, in gel phantoms with varying concentrations of gadobutrol and gadoterate meglumine contrast agents. In vivo examples are further presented, from 3 neuroradiology patients. RESULTS Bland-Altman analysis was performed: for T2 , as compared to 2D SE, bias was 0.29 ms and the 95% limits of agreement ranged from -1.15 to +1.73 ms. For T1 , compared to inversion-recovery SE (and MOLLI), bias was -20.2 ms (and -14.5 ms) and the limits of agreement ranged from -62.4 to +22.0 ms (and -53.8 to +24.9 ms). The mean relative T1 error between the proposed method and each of the 2 reference methods was similar to that of the reference methods among themselves. CONCLUSION In the constellation of existing relaxometry methods, the proposed method is meant to stand out in terms of its practicality and availability.
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Affiliation(s)
- Bruno Madore
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Michael Jerosch-Herold
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Jr-Yuan George Chiou
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Cheng-Chieh Cheng
- Department of Computer Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan
| | - Jeffrey P Guenette
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Georgeta Mihai
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
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14
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So S, Park HW, Kim B, Fritz FJ, Poser BA, Roebroeck A, Bilgic B. BUDA-MESMERISE: Rapid acquisition and unsupervised parameter estimation for T 1 , T 2 , M 0 , B 0 , and B 1 maps. Magn Reson Med 2022; 88:292-308. [PMID: 35344611 DOI: 10.1002/mrm.29228] [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: 08/12/2021] [Revised: 02/21/2022] [Accepted: 02/22/2022] [Indexed: 11/10/2022]
Abstract
PURPOSE Rapid acquisition scheme and parameter estimation method are proposed to acquire distortion-free spin- and stimulated-echo signals and combine the signals with a physics-driven unsupervised network to estimate T1 , T2 , and proton density (M0 ) parameter maps, along with B0 and B1 information from the acquired signals. THEORY AND METHODS An imaging sequence with three 90° RF pulses is utilized to acquire spin- and stimulated-echo signals. We utilize blip-up/-down acquisition to eliminate geometric distortion incurred by the effects of B0 inhomogeneity on rapid EPI acquisitions. For multislice imaging, echo-shifting is applied to utilize dead time between the second and third RF pulses to encode information from additional slice positions. To estimate parameter maps from the spin- and stimulated-echo signals with high fidelity, 2 estimation methods, analytic fitting and a novel unsupervised deep neural network method, are developed. RESULTS The proposed acquisition provided distortion-free T1 , T2 , relative proton density (M0), B0 , and B1 maps with high fidelity both in phantom and in vivo brain experiments. From the rapidly acquired spin- and stimulated-echo signals, analytic fitting and the network-based method were able to estimate T1 , T2 , M0 , B0 , and B1 maps with high accuracy. Network estimates demonstrated noise robustness owing to the fact that the convolutional layers take information into account from spatially adjacent voxels. CONCLUSION The proposed acquisition/reconstruction technique enabled whole-brain acquisition of coregistered, distortion-free, T1 , T2 , M0 , B0 , and B1 maps at 1 × 1 × 5 mm3 resolution in 50 s. The proposed unsupervised neural network provided noise-robust parameter estimates from this rapid acquisition.
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Affiliation(s)
- Seohee So
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Republic of Korea
| | - Hyun Wook Park
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Republic of Korea
| | - Byungjai Kim
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Republic of Korea
| | - Francisco J Fritz
- Institute of Systems Neuroscience, Center for Experimental Medicine, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany
| | - Benedikt A Poser
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - Alard Roebroeck
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - Berkin Bilgic
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA.,Department of Radiology, Harvard Medical School, Charlestown, Massachusetts, USA.,Harvard-MIT Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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15
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Juras V, Szomolanyi P, Schreiner MM, Unterberger K, Kurekova A, Hager B, Laurent D, Raithel E, Meyer H, Trattnig S. Reproducibility of an Automated Quantitative MRI Assessment of Low-Grade Knee Articular Cartilage Lesions. Cartilage 2021; 13:646S-657S. [PMID: 32988236 PMCID: PMC8808824 DOI: 10.1177/1947603520961165] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
OBJECTIVE The goal of this study was to assess the reproducibility of an automated knee cartilage segmentation of 21 cartilage regions with a model-based algorithm and to compare the results with manual segmentation. DESIGN Thirteen patients with low-grade femoral cartilage defects were included in the study and were scanned twice on a 7-T magnetic resonance imaging (MRI) scanner 8 days apart. A 3-dimensional double-echo steady-state (3D-DESS) sequence was used to acquire MR images for automated cartilage segmentation, and T2-mapping was performed using a 3D triple-echo steady-state (3D-TESS) sequence. Cartilage volume, thickness, and T2 and texture features were automatically extracted from each knee for each of the 21 subregions. DESS was used for manual cartilage segmentation and compared with automated segmentation using the Dice coefficient. The reproducibility of each variable was expressed using standard error of measurement (SEM) and smallest detectable change (SDC). RESULTS The Dice coefficient for the similarity between manual and automated segmentation ranged from 0.83 to 0.88 in different cartilage regions. Test-retest analysis of automated cartilage segmentation and automated quantitative parameter extraction revealed excellent reproducibility for volume measurement (mean SDC for all subregions of 85.6 mm3), for thickness detection (SDC = 0.16 mm) and also for T2 values (SDC = 2.38 ms) and most gray-level co-occurrence matrix features (SDC = 0.1 a.u.). CONCLUSIONS The proposed technique of automated knee cartilage evaluation based on the segmentation of 3D MR images and correlation with T2 mapping provides highly reproducible results and significantly reduces the segmentation effort required for the analysis of knee articular cartilage in longitudinal studies.
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Affiliation(s)
- Vladimir Juras
- High-Field MR Centre, Department of
Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna,
Austria,Institute of Measurement Science, Slovak
Academy of Sciences, Bratislava, Slovakia,Vladimir Juras, High-Field MR Centre,
Department of Biomedical Imaging and Image-Guided Therapy, Medical University of
Vienna, Waehringer Guertel 18-20, Vienna, 1090, Austria.
| | - Pavol Szomolanyi
- High-Field MR Centre, Department of
Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna,
Austria,Institute of Measurement Science, Slovak
Academy of Sciences, Bratislava, Slovakia
| | - Markus M. Schreiner
- Department of Orthopedics and Trauma
Surgery, Medical University of Vienna, Vienna, Austria
| | - Karin Unterberger
- Department of Orthopedics and Trauma
Surgery, Medical University of Vienna, Vienna, Austria
| | - Andrea Kurekova
- High-Field MR Centre, Department of
Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna,
Austria
| | - Benedikt Hager
- High-Field MR Centre, Department of
Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna,
Austria,CD Laboratory for Clinical Molecular MR
Imaging, Vienna, Austria
| | - Didier Laurent
- Novartis Institutes for Biomedical
Research, Department of Translational Medicine, Basel, Switzerland
| | | | | | - Siegfried Trattnig
- High-Field MR Centre, Department of
Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna,
Austria,CD Laboratory for Clinical Molecular MR
Imaging, Vienna, Austria,Austrian Cluster for Tissue
Regeneration, Vienna, Austria
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16
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Guenthner C, Amthor T, Doneva M, Kozerke S. A unifying view on extended phase graphs and Bloch simulations for quantitative MRI. Sci Rep 2021; 11:21289. [PMID: 34711847 PMCID: PMC8553818 DOI: 10.1038/s41598-021-00233-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 10/05/2021] [Indexed: 12/16/2022] Open
Abstract
Quantitative MRI methods and learning-based algorithms require exact forward simulations. One critical factor to correctly describe magnetization dynamics is the effect of slice-selective RF pulses. While contemporary simulation techniques correctly capture their influence, they only provide final magnetization distributions, require to be run for each parameter set separately, and make it hard to derive general theoretical conclusions and to generate a fundamental understanding of echo formation in the presence of slice-profile effects. This work aims to provide a mathematically exact framework, which is equally intuitive as extended phase graphs (EPGs), but also considers slice-profiles through their natural spatial representation. We show, through an analytical, hybrid Bloch-EPG formalism, that the spatially-resolved EPG approach allows to exactly predict the signal dependency on off-resonance, spoiling moment, microscopic dephasing, and echo time. We also demonstrate that our formalism allows to use the same phase graph to simulate both gradient-spoiled and balanced SSFP-based MR sequences. We present a derivation of the formalism and identify the connection to existing methods, i.e. slice-selective Bloch, slice-selective EPG, and the partitioned EPG. As a use case, the proposed hybrid Bloch-EPG framework is applied to MR Fingerprinting.
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Affiliation(s)
- Christian Guenthner
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland.
- Philips Research, Hamburg, Germany.
| | | | | | - Sebastian Kozerke
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
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17
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Leitão D, Teixeira RPAG, Price A, Uus A, Hajnal JV, Malik SJ. Efficiency analysis for quantitative MRI of T1 and T2 relaxometry methods. Phys Med Biol 2021; 66:15NT02. [PMID: 34192676 PMCID: PMC8312556 DOI: 10.1088/1361-6560/ac101f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 05/12/2021] [Accepted: 06/30/2021] [Indexed: 11/11/2022]
Abstract
This study presents a comparison of quantitative MRI methods based on an efficiency metric that quantifies their intrinsic ability to extract information about tissue parameters. Under a regime of unbiased parameter estimates, an intrinsic efficiency metricηwas derived for fully-sampled experiments which can be used to both optimize and compare sequences. Here we optimize and compare several steady-state and transient gradient-echo based qMRI methods, such as magnetic resonance fingerprinting (MRF), for jointT1andT2mapping. The impact of undersampling was also evaluated, assuming incoherent aliasing that is treated as noise by parameter estimation.In vivovalidation of the efficiency metric was also performed. Transient methods such as MRF can be up to 3.5 times more efficient than steady-state methods, when spatial undersampling is ignored. If incoherent aliasing is treated as noise during least-squares parameter estimation, the efficiency is reduced in proportion to the SNR of the data, with reduction factors of 5 often seen for practical SNR levels.In vivovalidation showed a very good agreement between the theoretical and experimentally predicted efficiency. This work presents and validates an efficiency metric to optimize and compare the performance of qMRI methods. Transient methods were found to be intrinsically more efficient than steady-state methods, however the effect of spatial undersampling can significantly erode this advantage.
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Affiliation(s)
- David Leitão
- School of Biomedical Engineering and Imaging Sciences, King’s College London, London, United Kingdom
- Communication Address: Perinatal Imaging and Health 1st Floor South Wing, St Thomas’ Hospital London SE1 7EHUK, United Kingdom
| | - Rui Pedro A. G. Teixeira
- School of Biomedical Engineering and Imaging Sciences, King’s College London, London, United Kingdom
- Centre for the Developing Brain, King’s College London, London, United Kingdom
| | - Anthony Price
- School of Biomedical Engineering and Imaging Sciences, King’s College London, London, United Kingdom
- Centre for the Developing Brain, King’s College London, London, United Kingdom
| | - Alena Uus
- School of Biomedical Engineering and Imaging Sciences, King’s College London, London, United Kingdom
| | - Joseph V. Hajnal
- School of Biomedical Engineering and Imaging Sciences, King’s College London, London, United Kingdom
- Centre for the Developing Brain, King’s College London, London, United Kingdom
| | - Shaihan J. Malik
- School of Biomedical Engineering and Imaging Sciences, King’s College London, London, United Kingdom
- Centre for the Developing Brain, King’s College London, London, United Kingdom
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18
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Zijlstra F, Seevinck PR. Multiple-echo steady-state (MESS): Extending DESS for joint T 2 mapping and chemical-shift corrected water-fat separation. Magn Reson Med 2021; 86:3156-3165. [PMID: 34270127 PMCID: PMC8596862 DOI: 10.1002/mrm.28921] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 06/21/2021] [Accepted: 06/21/2021] [Indexed: 12/21/2022]
Abstract
Purpose To extend the double echo steady‐state (DESS) sequence to enable chemical‐shift corrected water‐fat separation. Methods This study proposes multiple‐echo steady‐state (MESS), a sequence that modifies the readouts of the DESS sequence to acquire two echoes each with bipolar readout gradients with higher readout bandwidth. This enables water‐fat separation and eliminates the need for water‐selective excitation that is often used in combination with DESS, without increasing scan time. An iterative fitting approach was used to perform joint chemical‐shift corrected water‐fat separation and T2 estimation on all four MESS echoes simultaneously. MESS and water‐selective DESS images were acquired for five volunteers, and were compared qualitatively as well as quantitatively on cartilage T2 and thickness measurements. Signal‐to‐noise ratio (SNR) and T2 quantification were evaluated numerically using pseudo‐replications of the acquisition. Results The water‐fat separation provided by MESS was robust and with quality comparable to water‐selective DESS. MESS T2 estimation was similar to DESS, albeit with slightly higher variability. Noise analysis showed that SNR in MESS was comparable to DESS on average, but did exhibit local variations caused by uncertainty in the water‐fat separation. Conclusion In the same acquisition time as DESS, MESS provides water‐fat separation with comparable SNR in the reconstructed water and fat images. By providing additional image contrasts in addition to the water‐selective DESS images, MESS provides a promising alternative to DESS.
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Affiliation(s)
- Frank Zijlstra
- Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.,Department of Radiology and Nuclear Medicine, St Olav's University Hospital, Trondheim, Norway
| | - Peter R Seevinck
- Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.,MRIGuidance BV, Utrecht, The Netherlands
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19
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Khajehim M, Christen T, Tam F, Graham SJ. Streamlined magnetic resonance fingerprinting: Fast whole-brain coverage with deep-learning based parameter estimation. Neuroimage 2021; 238:118237. [PMID: 34091035 DOI: 10.1016/j.neuroimage.2021.118237] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 05/26/2021] [Accepted: 06/02/2021] [Indexed: 01/02/2023] Open
Abstract
Magnetic resonance fingerprinting (MRF) is a quantitative MRI (qMRI) framework that provides simultaneous estimates of multiple relaxation parameters as well as metrics of field inhomogeneity in a single acquisition. However, current challenges exist in the forms of (1) scan time; (2) need for custom image reconstruction; (3) large dictionary sizes; (4) long dictionary-matching time. This study aims to introduce a novel streamlined magnetic-resonance fingerprinting (sMRF) framework based on a single-shot echo-planar imaging (EPI) sequence to simultaneously estimate tissue T1, T2, and T2* with integrated B1+ correction. Encouraged by recent work on EPI-based MRF, we developed a method that combines spin-echo EPI with gradient-echo EPI to achieve T2 in addition to T1 and T2* quantification. To this design, we add simultaneous multi-slice (SMS) acceleration to enable full-brain coverage in a few minutes. Moreover, in the parameter-estimation step, we use deep learning to train a deep neural network (DNN) to accelerate the estimation process by orders of magnitude. Notably, due to the high image quality of the EPI scans, the training process can rely simply on Bloch-simulated data. The DNN also removes the need for storing large dictionaries. Phantom scans along with in-vivo multi-slice scans from seven healthy volunteers were acquired with resolutions of 1.1×1.1×3 mm3 and 1.7×1.7×3 mm3, and the results were validated against ground truth measurements. Excellent correspondence was found between our T1, T2, and T2* estimates and results obtained from standard approaches. In the phantom scan, a strong linear relationship (R = 1-1.04, R2>0.96) was found for all parameter estimates, with a particularly high agreement for T2 estimation (R2>0.99). Similar findings are reported for the in-vivo human data for all of our parameter estimates. Incorporation of DNN results in a reduction of parameter estimation time on the order of 1000 x and a reduction in storage requirements on the order of 2500 x while achieving highly similar results as conventional dictionary matching (%differences of 7.4 ± 0.4%, 3.6 ± 0.3% and 6.0 ± 0.4% error in T1, T2, and T2* estimation). Thus, sMRF has the potential to be the method of choice for future MRF studies by providing ease of implementation, fast whole-brain coverage, and ultra-fast T1/T2/T2* estimation.
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Affiliation(s)
- Mahdi Khajehim
- Department of Medical Biophysics, University of Toronto, 101 College St Suite 15-701, Toronto, ON M5G 1L7, Canada.
| | - Thomas Christen
- Grenoble Institute of Neuroscience, Inserm, Grenoble, France
| | - Fred Tam
- Hurvitz Brain Sciences Research Program, Sunnybrook Research Institute, Toronto, ON, Canada
| | - Simon J Graham
- Department of Medical Biophysics, University of Toronto, 101 College St Suite 15-701, Toronto, ON M5G 1L7, Canada; Hurvitz Brain Sciences Research Program, Sunnybrook Research Institute, Toronto, ON, Canada
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20
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Raudner M, Schreiner MM, Hilbert T, Kober T, Weber M, Szelényi A, Windhager R, Juras V, Trattnig S. Clinical implementation of accelerated T 2 mapping: Quantitative magnetic resonance imaging as a biomarker for annular tear and lumbar disc herniation. Eur Radiol 2021; 31:3590-3599. [PMID: 33274406 PMCID: PMC8128819 DOI: 10.1007/s00330-020-07538-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 10/20/2020] [Accepted: 11/17/2020] [Indexed: 11/26/2022]
Abstract
OBJECTIVES This study evaluates GRAPPATINI, an accelerated T2 mapping sequence combining undersampling and model-based reconstruction to facilitate the clinical implementation of T2 mapping of the lumbar intervertebral disc. METHODS Fifty-eight individuals (26 females, 32 males, age 23.3 ± 8.0 years) were prospectively examined at 3 T. This cohort study consisted of 19 patients, 20 rowers, and 19 volunteers. GRAPPATINI was conducted with the same parameters as a conventional 2D multi-echo spin-echo (MESE) sequence in 02:27 min instead of 13:18 min. Additional T2 maps were calculated after discarding the first echo (T2-WO1ST) and only using even echoes (T2-EVEN). Segmentation was done on the four most central slices. The resulting T2 values were compared for all four measurements. RESULTS T2-GRAPPATINI, T2-MESE, T2-EVEN, and T2-WO1ST of the nucleus pulposus of normal discs differed significantly from those of bulging discs or herniated discs (all p < 0.001). For the posterior annular region, only T2-GRAPPATINI showed a significant difference (p = 0.011) between normal and herniated discs. There was a significant difference between T2-GRAPPATINI, T2-MESE, T2-EVEN, and T2-WO1ST of discs with and without an annular tear for the nucleus pulposus (all p < 0.001). The nucleus pulposus' T2 at different degeneration states showed significant differences between all group comparisons of Pfirrmann grades for T2-GRAPPATINI (p = 0.000-0.018), T2-MESE (p = 0.000-0.015), T2-EVEN (p = 0.000-0.019), and T2-WO1ST (p = 0.000-0.015). CONCLUSIONS GRAPPATINI facilitates the use of T2 values as quantitative imaging biomarkers to detect disc pathologies such as degeneration, lumbar disc herniation, and annular tears while simultaneously shortening the acquisition time from 13:18 to 2:27 min. KEY POINTS • T2-GRAPPATINI, T2-MESE, T2-EVEN, and T2-WO1ST of the nucleus pulposus of normal discs differed significantly from those of discs with bulging or herniation (all p < 0.001). • The investigated T2 mapping techniques differed significantly in discs with and without annular tearing (all p < 0.001). • The nucleus pulposus' T2 showed significant differences between different stages of degeneration in all group comparisons for T2-GRAPPATINI (p = 0.000-0.018), T2-MESE (p = 0.000-0.015), T2-EVEN (p = 0.000-0.019), and T2-WO1ST (p = 0.000-0.015).
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Affiliation(s)
- Marcus Raudner
- Department of Biomedical Imaging and Image-guided Therapy, High Field MR Center, Medical University of Vienna, Lazarettgasse 14, 1090, Vienna, Austria
- Christian Doppler Laboratory for Clinical Molecular MR Imaging (MOLIMA), Department of Biomedical Imaging and Image-guided Therapy, High Field MR Center, Medical University of Vienna, Vienna, Austria
| | - Markus M Schreiner
- Department of Orthopaedics and Trauma Surgery, Medical University of Vienna, Vienna, Austria
| | - Tom Hilbert
- Advanced Clinical Imaging Technology, Siemens Healthcare, Lausanne, Switzerland
- Department of Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
- LTS5, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Tobias Kober
- Advanced Clinical Imaging Technology, Siemens Healthcare, Lausanne, Switzerland
- Department of Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
- LTS5, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Michael Weber
- Department of Biomedical Imaging and Image-guided Therapy, High Field MR Center, Medical University of Vienna, Lazarettgasse 14, 1090, Vienna, Austria
| | - Anna Szelényi
- Department of Biomedical Imaging and Image-guided Therapy, High Field MR Center, Medical University of Vienna, Lazarettgasse 14, 1090, Vienna, Austria
| | - Reinhard Windhager
- Department of Orthopaedics and Trauma Surgery, Medical University of Vienna, Vienna, Austria
| | - Vladimir Juras
- Christian Doppler Laboratory for Clinical Molecular MR Imaging (MOLIMA), Department of Biomedical Imaging and Image-guided Therapy, High Field MR Center, Medical University of Vienna, Vienna, Austria
- Department of Imaging Methods, Institute of Measurement Science, Bratislava, Slovakia
| | - Siegfried Trattnig
- Department of Biomedical Imaging and Image-guided Therapy, High Field MR Center, Medical University of Vienna, Lazarettgasse 14, 1090, Vienna, Austria.
- Christian Doppler Laboratory for Clinical Molecular MR Imaging (MOLIMA), Department of Biomedical Imaging and Image-guided Therapy, High Field MR Center, Medical University of Vienna, Vienna, Austria.
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21
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Lee H, Wehrli FW. Alternating unbalanced SSFP for 3D R 2 ' mapping of the human brain. Magn Reson Med 2020; 85:2391-2402. [PMID: 33331076 DOI: 10.1002/mrm.28637] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 11/11/2020] [Accepted: 11/16/2020] [Indexed: 11/10/2022]
Abstract
PURPOSE Measuring the transverse-relaxation rate R 2 ' provides valuable information in quantitative evaluation of tissue microstructure, for example, in terms of oxygenation levels. Here, we propose an alternating unbalanced SSFP pulse sequence for rapid whole-brain 3D R 2 ' mapping. METHODS Unlike currently practiced, spin echo-based R 2 ' measurement techniques, the proposed method alternates between SSFP-FID and SSFP-ECHO modes for rapid 3D encoding of transverse relaxation rates expressed as R2 + R 2 ' and R2 - R 2 ' . Z-shimming gradients embedded into multi-echo trains of each SSFP module are designed to achieve relative immunity to large-scale magnetic-field variations (ΔB0 ). Appropriate models for the temporal evolution of the two groups of SSFP signals were constructed with ΔB0 -induced modulations accounted for, leading to ΔB0 -corrected estimation of R2 , R 2 ' , and R 2 ∗ (= R2 + R 2 ' ). Additionally, relative magnetic susceptibility (Δχ) maps were obtained by quantitative susceptibility mapping of the phase data. Numerical simulations were performed to optimize scan parameters, followed by in vivo studies at 3 T in 7 healthy subjects. Measured parameters were evaluated in six brain regions, and subjected to interparameter correlation analysis. RESULTS The resultant maps of R 2 ' and additionally derived R2 , R 2 ∗ , and Δχ all demonstrated the expected contrast across brain territories (eg, deep brain structures versus cortex), with the measured values in good agreement with previous reports. Furthermore, regression analyses yielded strong linear relationships for the transverse relaxation parameters ( R 2 ' , R2 , and R 2 ∗ ) against Δχ. CONCLUSION Results suggest feasibility of the proposed method as a practical and reliable means for measuring R 2 ' , R2 , R 2 ∗ , and Δχ across the entire brain.
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Affiliation(s)
- Hyunyeol Lee
- Laboratory for Structural, Physiologic, and Functional Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Felix W Wehrli
- Laboratory for Structural, Physiologic, and Functional Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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22
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Abstract
Regulatory approval of ultrahigh field (UHF) MR imaging scanners for clinical use has opened new opportunities for musculoskeletal imaging applications. UHF MR imaging has unique advantages in terms of signal-to-noise ratio, contrast-to-noise ratio, spectral resolution, and multinuclear applications, thus providing unique information not available at lower field strengths. But UHF also comes with a set of technical challenges that are yet to be resolved and may not be suitable for all imaging applications. This review focuses on the latest research in musculoskeletal MR imaging applications at UHF including morphologic imaging, T2, T2∗, and T1ρ mapping, chemical exchange saturation transfer, sodium imaging, and phosphorus spectroscopy imaging applications.
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23
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Iyyakkunnel S, Schäper J, Bieri O. Configuration-based electrical properties tomography. Magn Reson Med 2020; 85:1855-1864. [PMID: 33107082 DOI: 10.1002/mrm.28542] [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: 04/09/2020] [Revised: 09/09/2020] [Accepted: 09/14/2020] [Indexed: 11/07/2022]
Abstract
PURPOSE To introduce phase-based conductivity mapping from a configuration space analysis. METHODS The frequency response function of balanced SSFP (bSSFP) is used to perform a configuration space analysis. It is shown that the transceive phase for conductivity mapping can be directly obtained by a simple fast Fourier transform of a series of phase-cycled bSSFP scans. For validation, transceive phase and off-resonance mapping with fast Fourier transform is compared with phase estimation using a recently proposed method, termed PLANET. Experiments were performed in phantoms and for in vivo brain imaging at 3 T using a quadrature head coil. RESULTS For fast Fourier transform, aliasing can lead to systematic phase errors. This bias, however, decreases rapidly with increasing sampling points. Interestingly, Monte Carlo simulations revealed a lower uncertainty for the transceive phase and the off-resonance using fast Fourier transform as compared with PLANET. Both methods, however, essentially retrieve the same phase information from a set of phase-cycled bSSFP scans. As a result, configuration-based conductivity mapping was successfully performed using eight phase-cycled bSSFP scans in the phantoms and for brain tissues. Overall, the retrieved values were in good agreement with expectations. Conductivity estimation and mapping of the field inhomogeneities can therefore be performed in conjunction with the estimation of other quantitative parameters, such as relaxation, using configuration theory. CONCLUSIONS Phase-based conductivity mapping can be estimated directly from a simple Fourier analysis, such as in conjunction with relaxometry, using a series of phase-cycled bSSFP scans.
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Affiliation(s)
- Santhosh Iyyakkunnel
- Division of Radiological Physics, Department of Radiology, University Hospital Basel, Basel, Switzerland.,Department of Biomedical Engineering, University of Basel, Basel, Switzerland
| | - Jessica Schäper
- Division of Radiological Physics, Department of Radiology, University Hospital Basel, Basel, Switzerland.,Department of Biomedical Engineering, University of Basel, Basel, Switzerland
| | - Oliver Bieri
- Division of Radiological Physics, Department of Radiology, University Hospital Basel, Basel, Switzerland.,Department of Biomedical Engineering, University of Basel, Basel, Switzerland
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24
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Aringhieri G, Zampa V, Tosetti M. Musculoskeletal MRI at 7 T: do we need more or is it more than enough? Eur Radiol Exp 2020; 4:48. [PMID: 32761480 PMCID: PMC7410909 DOI: 10.1186/s41747-020-00174-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Accepted: 07/01/2020] [Indexed: 12/18/2022] Open
Abstract
Ultra-high field magnetic resonance imaging (UHF-MRI) provides important diagnostic improvements in musculoskeletal imaging. The higher signal-to-noise ratio leads to higher spatial and temporal resolution which results in improved anatomic detail and higher diagnostic confidence. Several methods, such as T2, T2*, T1rho mapping, delayed gadolinium-enhanced, diffusion, chemical exchange saturation transfer, and magnetisation transfer techniques, permit a better tissue characterisation. Furthermore, UHF-MRI enables in vivo measurements by low-γ nuclei (23Na, 31P, 13C, and 39K) and the evaluation of different tissue metabolic pathways. European Union and Food and Drug Administration approvals for clinical imaging at UHF have been the first step towards a more routinely use of this technology, but some drawbacks are still present limiting its widespread clinical application. This review aims to provide a clinically oriented overview about the application of UHF-MRI in the different anatomical districts and tissues of musculoskeletal system and its pros and cons. Further studies are needed to consolidate the added value of the use of UHF-MRI in the routine clinical practice and promising efforts in technology development are already in progress.
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Affiliation(s)
- Giacomo Aringhieri
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Via Risorgimento, 36, Pisa, Italy.
| | - Virna Zampa
- Diagnostic and Interventional Radiology, University Hospital of Pisa, Via paradisa, 2, Pisa, Italy
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25
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Tendler BC, Foxley S, Cottaar M, Jbabdi S, Miller KL. Modeling an equivalent b-value in diffusion-weighted steady-state free precession. Magn Reson Med 2020; 84:873-884. [PMID: 31922283 PMCID: PMC7216928 DOI: 10.1002/mrm.28169] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 12/13/2019] [Accepted: 12/18/2019] [Indexed: 11/26/2022]
Abstract
PURPOSE Diffusion-weighted steady-state free precession (DW-SSFP) is shown to provide a means to probe non-Gaussian diffusion through manipulation of the flip angle. A framework is presented to define an effective b-value in DW-SSFP. THEORY The DW-SSFP signal is a summation of coherence pathways with different b-values. The relative contribution of each pathway is dictated by the flip angle. This leads to an apparent diffusion coefficient (ADC) estimate that depends on the flip angle in non-Gaussian diffusion regimes. By acquiring DW-SSFP data at multiple flip angles and modeling the variation in ADC for a given form of non-Gaussianity, the ADC can be estimated at a well-defined effective b-value. METHODS A gamma distribution is used to model non-Gaussian diffusion, embedded in the Buxton signal model for DW-SSFP. Monte-Carlo simulations of non-Gaussian diffusion in DW-SSFP and diffusion-weighted spin-echo sequences are used to verify the proposed framework. Dependence of ADC on flip angle in DW-SSFP is verified with experimental measurements in a whole, human postmortem brain. RESULTS Monte-Carlo simulations reveal excellent agreement between ADCs estimated with diffusion-weighted spin-echo and the proposed framework. Experimental ADC estimates vary as a function of flip angle over the corpus callosum of the postmortem brain, estimating the mean and standard deviation of the gamma distribution as 1.50 · 10 - 4 mm2 /s and 2.10 · 10 - 4 mm2 /s. CONCLUSION DW-SSFP can be used to investigate non-Gaussian diffusion by varying the flip angle. By fitting a model of non-Gaussian diffusion, the ADC in DW-SSFP can be estimated at an effective b-value, comparable to more conventional diffusion sequences.
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Affiliation(s)
- Benjamin C. Tendler
- Wellcome Centre for Integrative NeuroimagingFMRIBNuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUnited Kingdom
| | - Sean Foxley
- Department of RadiologyUniversity of ChicagoChicagoIllinois
| | - Michiel Cottaar
- Wellcome Centre for Integrative NeuroimagingFMRIBNuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUnited Kingdom
| | - Saad Jbabdi
- Wellcome Centre for Integrative NeuroimagingFMRIBNuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUnited Kingdom
| | - Karla L. Miller
- Wellcome Centre for Integrative NeuroimagingFMRIBNuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUnited Kingdom
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26
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Accelerated T2 Mapping of the Lumbar Intervertebral Disc: Highly Undersampled K-Space Data for Robust T2 Relaxation Time Measurement in Clinically Feasible Acquisition Times. Invest Radiol 2020; 55:695-701. [PMID: 32649331 DOI: 10.1097/rli.0000000000000690] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
T2 mapping of the intervertebral disc (IVD) can depict quantitative changes reflecting biochemical change due to loss of glycosaminoglycan content. Conventional T2 mapping is usually performed using a 2-dimensional multi-echo-spin echo sequence (2D-MESE) with long acquisition times that are generally not compatible with clinical routine. This study investigates the applicability of GRAPPATINI, a T2 mapping sequence combining undersampling, model-based reconstruction, and parallel imaging, to offer clinically feasible acquisition times in T2 mapping of the lumbar IVD. MATERIALS AND METHODS Fifty-eight individuals (26 female; mean age, 23.3 ± 8.1 years) were prospectively studied at 3 T. GRAPPATINI was conducted with the same parameters as the 2D-MESE while shortening the acquisition time from 13:18 to 2:27 minutes. The setup was also validated in a phantom experiment using a 6.48-hour-long single echo-spin echo sequence as reference. The IVDs were manually segmented on 4 central slices. RESULTS The median nucleus pulposus showed a strong Pearson correlation coefficient between T2GRAPPATINI and T2MESE (rp = 0.919; P < 0.001). There was also a significant correlation for the ventral (rp = 0.241; P < 0.001) and posterior (rp = 0.418; P < 0.001) annular regions.In the single spin-echo phantom experiment, the most accurate T2 estimation was achieved using T2GRAPPATINI with a median absolute deviation of 15.3 milliseconds as compared with T2MESE with 26.5 milliseconds. CONCLUSIONS GRAPPATINI facilitates precise T2 mapping at 3 T in accordance with clinical standards and reference methods using the same parameters while shortening acquisition times from 13:18 to 2:27 minutes with the same parameters.
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27
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Leroi L, Gras V, Boulant N, Ripart M, Poirion E, Santin MD, Valabregue R, Mauconduit F, Hertz‐Pannier L, Le Bihan D, Rochefort L, Vignaud A. Simultaneous proton density, T
1
, T
2
, and flip‐angle mapping of the brain at 7 T using multiparametric 3D SSFP imaging and parallel‐transmission universal pulses. Magn Reson Med 2020; 84:3286-3299. [DOI: 10.1002/mrm.28391] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Revised: 05/28/2020] [Accepted: 06/02/2020] [Indexed: 12/15/2022]
Affiliation(s)
- Lisa Leroi
- Université Paris‐Saclay, CEA, CNRS, BAOBAB, NeuroSpin Gif‐sur‐Yvette France
| | - Vincent Gras
- Université Paris‐Saclay, CEA, CNRS, BAOBAB, NeuroSpin Gif‐sur‐Yvette France
| | - Nicolas Boulant
- Université Paris‐Saclay, CEA, CNRS, BAOBAB, NeuroSpin Gif‐sur‐Yvette France
| | - Mathilde Ripart
- Université Paris‐Saclay, CEA, CNRS, BAOBAB, NeuroSpin Gif‐sur‐Yvette France
| | - Emilie Poirion
- Université Paris‐Saclay, CEA, CNRS, BAOBAB, NeuroSpin Gif‐sur‐Yvette France
- ICM, Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Université Paris 06 UMR S1127, Institut du Cerveau et de la Moelle Épinière Paris France
| | - Mathieu D. Santin
- ICM, Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Université Paris 06 UMR S1127, Institut du Cerveau et de la Moelle Épinière Paris France
- CENIR, ICM, Hôpital Pitié‐Salpêtrière Paris France
| | - Romain Valabregue
- ICM, Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Université Paris 06 UMR S1127, Institut du Cerveau et de la Moelle Épinière Paris France
- CENIR, ICM, Hôpital Pitié‐Salpêtrière Paris France
| | - Franck Mauconduit
- Université Paris‐Saclay, CEA, CNRS, BAOBAB, NeuroSpin Gif‐sur‐Yvette France
| | | | - Denis Le Bihan
- Université Paris‐Saclay, CEA, CNRS, BAOBAB, NeuroSpin Gif‐sur‐Yvette France
| | - Ludovic Rochefort
- Aix‐Marseille University, CNRS, CRMBM (Center for Magnetic Resonance in Biology and Medicine‐UMR 7339) Marseille France
| | - Alexandre Vignaud
- Université Paris‐Saclay, CEA, CNRS, BAOBAB, NeuroSpin Gif‐sur‐Yvette France
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28
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Heule R, Bause J, Pusterla O, Scheffler K. Multi-parametric artificial neural network fitting of phase-cycled balanced steady-state free precession data. Magn Reson Med 2020; 84:2981-2993. [PMID: 32479661 DOI: 10.1002/mrm.28325] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 04/22/2020] [Accepted: 04/27/2020] [Indexed: 12/16/2022]
Abstract
PURPOSE Standard relaxation time quantification using phase-cycled balanced steady-state free precession (bSSFP), eg, motion-insensitive rapid configuration relaxometry (MIRACLE), is subject to a considerable underestimation of tissue T1 and T2 due to asymmetric intra-voxel frequency distributions. In this work, an artificial neural network (ANN) fitting approach is proposed to simultaneously extract accurate reference relaxation times (T1 , T2 ) and robust field map estimates ( B 1 + , ΔB0 ) from the bSSFP profile. METHODS Whole-brain bSSFP data acquired at 3T were used for the training of a feedforward ANN with N = 12, 6, and 4 phase-cycles. The magnitude and phase of the Fourier transformed complex bSSFP frequency response served as input and the multi-parametric reference set [T1 , T2 , B 1 + , ∆B0 ] as target. The ANN predicted relaxation times were validated against the target and MIRACLE. RESULTS The ANN prediction of T1 and T2 for trained and untrained data agreed well with the reference, even for only four acquired phase-cycles. In contrast, relaxometry based on 4-point MIRACLE was prone to severe off-resonance-related artifacts. ANN predicted B 1 + and ∆B0 maps showed the expected spatial inhomogeneity patterns in high agreement with the reference measurements for 12-point, 6-point, and 4-point bSSFP phase-cycling schemes. CONCLUSION ANNs show promise to provide accurate brain tissue T1 and T2 values as well as reliable field map estimates. Moreover, the bSSFP acquisition can be accelerated by reducing the number of phase-cycles while still delivering robust T1 , T2 , B 1 + , and ∆B0 estimates.
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Affiliation(s)
- Rahel Heule
- High Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Jonas Bause
- High Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Orso Pusterla
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland.,Division of Radiological Physics, Department of Radiology, University Hospital Basel, Basel, Switzerland.,Department of Biomedical Engineering, University of Basel, Basel, Switzerland
| | - Klaus Scheffler
- High Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.,Department of Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany
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29
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Strijkers GJ, Araujo EC, Azzabou N, Bendahan D, Blamire A, Burakiewicz J, Carlier PG, Damon B, Deligianni X, Froeling M, Heerschap A, Hollingsworth KG, Hooijmans MT, Karampinos DC, Loudos G, Madelin G, Marty B, Nagel AM, Nederveen AJ, Nelissen JL, Santini F, Scheidegger O, Schick F, Sinclair C, Sinkus R, de Sousa PL, Straub V, Walter G, Kan HE. Exploration of New Contrasts, Targets, and MR Imaging and Spectroscopy Techniques for Neuromuscular Disease - A Workshop Report of Working Group 3 of the Biomedicine and Molecular Biosciences COST Action BM1304 MYO-MRI. J Neuromuscul Dis 2020; 6:1-30. [PMID: 30714967 PMCID: PMC6398566 DOI: 10.3233/jnd-180333] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Neuromuscular diseases are characterized by progressive muscle degeneration and muscle weakness resulting in functional disabilities. While each of these diseases is individually rare, they are common as a group, and a large majority lacks effective treatment with fully market approved drugs. Magnetic resonance imaging and spectroscopy techniques (MRI and MRS) are showing increasing promise as an outcome measure in clinical trials for these diseases. In 2013, the European Union funded the COST (co-operation in science and technology) action BM1304 called MYO-MRI (www.myo-mri.eu), with the overall aim to advance novel MRI and MRS techniques for both diagnosis and quantitative monitoring of neuromuscular diseases through sharing of expertise and data, joint development of protocols, opportunities for young researchers and creation of an online atlas of muscle MRI and MRS. In this report, the topics that were discussed in the framework of working group 3, which had the objective to: Explore new contrasts, new targets and new imaging techniques for NMD are described. The report is written by the scientists who attended the meetings and presented their data. An overview is given on the different contrasts that MRI can generate and their application, clinical needs and desired readouts, and emerging methods.
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Affiliation(s)
| | - Ericky C.A. Araujo
- NMR Laboratory, Neuromuscular Investigation Center, Institute of Myology & NMR Laboratory, CEA/DRF/IBFJ/MIRCen, Paris, France
| | - Noura Azzabou
- NMR Laboratory, Neuromuscular Investigation Center, Institute of Myology & NMR Laboratory, CEA/DRF/IBFJ/MIRCen, Paris, France
| | | | - Andrew Blamire
- Institute of Cellular Medicine, Newcastle University, Newcastle-upon-Tyne, UK
| | - Jedrek Burakiewicz
- Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Pierre G. Carlier
- NMR Laboratory, Neuromuscular Investigation Center, Institute of Myology & NMR Laboratory, CEA/DRF/IBFJ/MIRCen, Paris, France
| | - Bruce Damon
- Vanderbilt University Medical Center, Nashville, USA
| | - Xeni Deligianni
- Department of Radiology, Division of Radiological Physics, University Hospital Basel, Basel, Switzerland & Department of Biomedical Engineering, University of Basel, Basel, Switzerland
| | | | - Arend Heerschap
- Radboud University Medical Center, Nijmegen, the Netherlands
| | | | | | | | | | | | - Benjamin Marty
- NMR Laboratory, Neuromuscular Investigation Center, Institute of Myology & NMR Laboratory, CEA/DRF/IBFJ/MIRCen, Paris, France
| | - Armin M. Nagel
- Institute of Radiology, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany & Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | | | | | - Francesco Santini
- Department of Radiology, Division of Radiological Physics, University Hospital Basel, Basel, Switzerland & Department of Biomedical Engineering, University of Basel, Basel, Switzerland
| | - Olivier Scheidegger
- Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Switzerland
| | - Fritz Schick
- University of Tübingen, Section on Experimental Radiology, Tübingen, Germany
| | | | | | | | - Volker Straub
- Institute of Cellular Medicine, Newcastle University, Newcastle-upon-Tyne, UK
| | | | - Hermien E. Kan
- Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands
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30
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Guenthner C, Sethi S, Troelstra M, van Gorkum RJ, Gastl M, Sinkus R, Kozerke S. Unipolar MR elastography: Theory, numerical analysis and implementation. NMR IN BIOMEDICINE 2020; 33:e4138. [PMID: 31664745 PMCID: PMC7003474 DOI: 10.1002/nbm.4138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Revised: 06/10/2019] [Accepted: 06/14/2019] [Indexed: 06/10/2023]
Abstract
In MR elastography (MRE), zeroth moment balanced motion-encoding gradients (MEGs) are incorporated into MRI sequences to induce a phase shift proportional to the local displacement caused by external actuation. To maximize the signal-to-noise ratio (SNR), fractional encoding is employed, i.e., the MEG duration is reduced below the wave period. Here, gradients encode primarily the velocity of the motion-reducing encoding efficiency. Thus, in GRE-MRE, T2 * decay and motion sensitivity have to be balanced, imposing a lower limit on repetition times (TRs). We propose to use a single trapezoidal gradient, a "unipolar gradient", to directly encode spin displacement. Such gradients cannot be used in conventional sequences as they exhibit a large zeroth moment and dephase magnetization. By time-reversing a spoiled SSFP sequence, the spoiling gradient becomes an efficient unipolar MEG. The proposed "unipolar MRE" technique benefits from this approach in three ways: first, displacement encoding is split over multiple TRs increasing motion sensitivity; second, spoiler and MEG coincide, allowing a reduction in TR; third, motion sensitivity of a typical unipolar lobe is of an order of magnitude higher than a bipolar MEG of equal duration. In this work, motion encoding using unipolar MRE is analyzed using the extended phase graph (EPG) formalism with a periodic motion propagator. As an approximation, the two-transverse TR approximation for diffusion-weighted SSFP is extended to incorporate cyclic motion. A complex encoding efficiency metric is introduced to compare the displacement fields of unipolar and conventional GRE-MRE sequences in both magnitude and phase. The derived theoretical encoding equations are used to characterize the proposed sequence using an extensive parameter study. Unipolar MRE is validated against conventional GRE-MRE in a phantom study showing excellent agreement between measured displacement fields. In addition, unipolar MRE yields significantly increased octahedral shear strain-SNR relative to conventional GRE-MRE and allows for the recovery of high stiffness inclusions, where conventional GRE-MRE fails.
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Affiliation(s)
- Christian Guenthner
- Institute for Biomedical EngineeringUniversity and ETH ZurichZurichSwitzerland
| | - Sweta Sethi
- Division of Research OncologyGuy's and Saint Thomas' NHS Foundation TrustLondonUK
| | - Marian Troelstra
- Division for Imaging Sciences & Biomedical EngineeringKing's College LondonLondonUK
- Department of Radiology and Nuclear MedicineUniversity Medical Center AmsterdamAmsterdamThe Netherlands
| | | | - Mareike Gastl
- Institute for Biomedical EngineeringUniversity and ETH ZurichZurichSwitzerland
| | - Ralph Sinkus
- Division for Imaging Sciences & Biomedical EngineeringKing's College LondonLondonUK
| | - Sebastian Kozerke
- Institute for Biomedical EngineeringUniversity and ETH ZurichZurichSwitzerland
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31
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Wang X, Hernando D, Reeder SB. Phase-based T 2 mapping with gradient echo imaging. Magn Reson Med 2019; 84:609-619. [PMID: 31872470 DOI: 10.1002/mrm.28138] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2019] [Revised: 10/31/2019] [Accepted: 11/27/2019] [Indexed: 12/12/2022]
Abstract
PURPOSE Transverse relaxation time (T2 ) mapping with MRI has a plethora of clinical and research applications. Current T2 mapping techniques are based primarily on spin-echo (SE) relaxometry strategies that rely on the signal magnitude, and often suffer from lengthy acquisition times. In this work, we propose a phase-based T2 mapping technique where T2 information is encoded into the signal phase of rapid gradient echo (GRE) acquisitions. THEORY Bloch equation simulations demonstrate that the phase of GRE acquisitions obtained with a very small inter-repetition RF phase increment has a strong monotonic dependence on T2 , resulting from coherent transverse magnetization. This T2 -dependent phase behavior forms the basis of the proposed T2 mapping technique. To isolate T2 -dependent phase from background phase, at least 2 data sets with different RF phase increments are acquired. The proposed method can also be combined with chemical shift encoded MRI to separate water and fat signals. METHODS The feasibility of the proposed technique was validated in a phantom experiment. In vivo feasibility was demonstrated in the brain, knee, abdomen, and pelvis. Comparisons were made with SE-based T2 mapping, spectroscopy, and T2 values from the literature. RESULTS The proposed method produced accurate T2 maps compared with SE-based T2 mapping in the phantom. Good qualitative agreement was observed in vivo between the proposed method and the reference. T2 measured in various anatomies agreed well with values reported in the literature. CONCLUSION A phase-based T2 mapping technique was developed and its feasibility demonstrated in phantoms and in vivo.
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Affiliation(s)
- Xiaoke Wang
- Department of Radiology, University of Wisconsin, Madison, Wisconsin.,Department of Biomedical Engineering, University of Wisconsin, Madison, Wisconsin
| | - Diego Hernando
- Department of Radiology, University of Wisconsin, Madison, Wisconsin.,Department of Medical Physics, University of Wisconsin, Madison, Wisconsin
| | - Scott B Reeder
- Department of Radiology, University of Wisconsin, Madison, Wisconsin.,Department of Biomedical Engineering, University of Wisconsin, Madison, Wisconsin.,Department of Medical Physics, University of Wisconsin, Madison, Wisconsin.,Department of Medicine, University of Wisconsin, Madison, Wisconsin.,Department of Emergency Medicine, University of Wisconsin, Madison, Wisconsin
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32
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Bauman G, Bieri O. Balanced steady‐state free precession thoracic imaging with half‐radial dual‐echo readout on smoothly interleaved archimedean spirals. Magn Reson Med 2019; 84:237-246. [DOI: 10.1002/mrm.28119] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 10/22/2019] [Accepted: 11/19/2019] [Indexed: 12/15/2022]
Affiliation(s)
- Grzegorz Bauman
- Division of Radiological Physics Department of Radiology University of Basel Hospital Basel Switzerland
- Department of Biomedical Engineering University of Basel Basel Switzerland
| | - Oliver Bieri
- Division of Radiological Physics Department of Radiology University of Basel Hospital Basel Switzerland
- Department of Biomedical Engineering University of Basel Basel Switzerland
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Cheng CC, Preiswerk F, Madore B. Multi-pathway multi-echo acquisition and neural contrast translation to generate a variety of quantitative and qualitative image contrasts. Magn Reson Med 2019; 83:2310-2321. [PMID: 31755588 DOI: 10.1002/mrm.28077] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2019] [Revised: 10/21/2019] [Accepted: 10/22/2019] [Indexed: 11/11/2022]
Abstract
PURPOSE Clinical exams typically involve acquiring many different image contrasts to help discriminate healthy from diseased states. Ideally, 3D quantitative maps of all of the main MR parameters would be obtained for improved tissue characterization. Using data from a 7-min whole-brain multi-pathway multi-echo (MPME) scan, we aimed to synthesize several 3D quantitative maps (T1 and T2 ) and qualitative contrasts (MPRAGE, FLAIR, T1 -weighted, T2 -weighted, and proton density [PD]-weighted). The ability of MPME acquisitions to capture large amounts of information in a relatively short amount of time suggests it may help reduce the duration of neuro MR exams. METHODS Eight healthy volunteers were imaged at 3.0T using a 3D isotropic (1.2 mm) MPME sequence. Spin-echo, MPRAGE, and FLAIR scans were performed for training and validation. MPME signals were interpreted through neural networks for predictions of different quantitative and qualitative contrasts. Predictions were compared to reference values at voxel and region-of-interest levels. RESULTS Mean absolute errors (MAEs) for T1 and T2 maps were 216 ms and 11 ms, respectively. In ROIs containing white matter (WM) and thalamus tissues, the mean T1 /T2 predicted values were 899/62 ms and 1139/58 ms, consistent with reference values of 850/66 ms and 1126/58 ms, respectively. For qualitative contrasts, signals were normalized to those of WM, and MAEs for MPRAGE, FLAIR, T1 -weighted, T2 -weighted, and PD-weighted contrasts were 0.14, 0.15, 0.13, 0.16, and 0.05, respectively. CONCLUSIONS Using an MPME sequence and neural-network contrast translation, whole-brain results were obtained with a variety of quantitative and qualitative contrast in ~6.8 min.
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Affiliation(s)
- Cheng-Chieh Cheng
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Frank Preiswerk
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Bruno Madore
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
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Juras V, Mlynarik V, Szomolanyi P, Valkovič L, Trattnig S. Magnetic Resonance Imaging of the Musculoskeletal System at 7T: Morphological Imaging and Beyond. Top Magn Reson Imaging 2019; 28:125-135. [PMID: 30951006 PMCID: PMC6565434 DOI: 10.1097/rmr.0000000000000205] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In 2017, a whole-body 7T magnetic resonance imaging (MRI) device was given regulatory approval for clinical use in both the EU and United States for neuro and musculoskeletal applications. As 7 Tesla allows for higher signal-to-noise , which results in higher resolution images than those obtained on lower-field-strength scanners, it has attracted considerable attention from the musculoskeletal field, as evidenced by the increasing number of publications in the last decade. Besides morphological imaging, the quantitative MR methods, such as T2, T2∗, T1ρ mapping, sodium imaging, chemical-exchange saturation transfer, and spectroscopy, substantially benefit from ultrahigh field scanning. In this review, we provide technical considerations for the individual techniques and an overview of (mostly) clinical applications for the assessment of cartilage, tendon, meniscus, and muscle. The first part of the review is dedicated to morphological applications at 7T, and the second part describes the most recent developments in quantitative MRI at 7T.
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Affiliation(s)
- Vladimir Juras
- High-field MR Center, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria.,Department of Imaging Methods, Institute of Measurements Science, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Vladimir Mlynarik
- High-field MR Center, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria.,Karl Landsteiner Society, St. Pölten, Austria
| | - Pavol Szomolanyi
- High-field MR Center, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria.,Department of Imaging Methods, Institute of Measurements Science, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Ladislav Valkovič
- High-field MR Center, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria.,Oxford Centre for Clinical Magnetic Resonance Research, BHF Centre of Research Excellence, University of Oxford, Oxford, UK.,Department of Imaging Methods, Institute of Measurements Science, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Siegfried Trattnig
- High-field MR Center, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria.,Austrian Cluster for Tissue Regeneration, Vienna, Austria.,Christian Doppler Laboratory for Clinical Molecular MR Imaging, Vienna, Austria
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Shcherbakova Y, van den Berg CAT, Moonen CTW, Bartels LW. Investigation of the influence of B 0 drift on the performance of the PLANET method and an algorithm for drift correction. Magn Reson Med 2019; 82:1725-1740. [PMID: 31317584 PMCID: PMC6772029 DOI: 10.1002/mrm.27860] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 04/26/2019] [Accepted: 05/23/2019] [Indexed: 01/03/2023]
Abstract
Purpose The PLANET method was designed to simultaneously reconstruct maps of T1 and T2, the off‐resonance, the RF phase, and the banding free signal magnitude. The method requires a stationary B0 field over the course of a phase‐cycled balanced SSFP acquisition. In this work we investigated the influence of B0 drift on the performance of the PLANET method for single‐component and two‐component signal models, and we propose a strategy for drift correction. Methods The complex phase‐cycled balanced SSFP signal was modeled with and without frequency drift. The behavior of the signal influenced by drift was mathematically interpreted as a sum of drift‐dependent displacement of the data points along an ellipse and drift‐dependent rotation around the origin. The influence of drift on parameter estimates was investigated experimentally on a phantom and on the brain of healthy volunteers and was verified by numerical simulations. A drift correction algorithm was proposed and tested on a phantom and in vivo. Results Drift can be assumed to be linear over the typical duration of a PLANET acquisition. In a phantom (a single‐component signal model), drift induced errors of 4% and 8% in the estimated T1 and T2 values. In the brain, where multiple components are present, drift only had a minor effect. For both single‐component and two‐component signal models, drift‐induced errors were successfully corrected by applying the proposed drift correction algorithm. Conclusion We have demonstrated theoretically and experimentally the sensitivity of the PLANET method to B0 drift and have proposed a drift correction method.
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Affiliation(s)
- Yulia Shcherbakova
- Center for Image Sciences, Imaging Division, University Medical Center Utrecht, Utrecht, Netherlands
| | - Cornelis A T van den Berg
- Department of Radiotherapy, Imaging Division, University Medical Center Utrecht, Utrecht, Netherlands
| | - Chrit T W Moonen
- Center for Image Sciences, Imaging Division, University Medical Center Utrecht, Utrecht, Netherlands
| | - Lambertus W Bartels
- Center for Image Sciences, Imaging Division, University Medical Center Utrecht, Utrecht, Netherlands
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Roccia E, Vidya Shankar R, Neji R, Cruz G, Munoz C, Botnar R, Goh V, Prieto C, Dregely I. Accelerated 3D T 2 mapping with dictionary-based matching for prostate imaging. Magn Reson Med 2019; 81:1795-1805. [PMID: 30368900 DOI: 10.1002/mrm.27540] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 08/28/2018] [Accepted: 08/28/2018] [Indexed: 01/17/2023]
Abstract
PURPOSE To develop a fast and accurate method for 3D T2 mapping of prostate cancer using undersampled acquisition and dictionary-based fitting. METHODS 3D high-resolution T2 -weighted images (0.9 × 0.9 × 3 mm3 ) were obtained with a multishot T2 -prepared balanced steady-state free precession (T2 -prep-bSSFP) acquisition sequence using a 3D variable density undersampled Cartesian trajectory. Each T2 -weighted image was reconstructed using total variation regularized sensitivity encoding. A flexible simulation framework based on extended phase graphs generated a dictionary of magnetization signals, which was customized to the proposed sequence. The dictionary was matched to the acquired T2 -weighted images to retrieve quantitative T2 values, which were then compared to gold-standard spin echo acquisition values using monoexponential fitting. The proposed approach was validated in simulations and a T1 /T2 phantom, and feasibility was tested in 8 healthy subjects. RESULTS The simulation analysis showed that the proposed T2 mapping approach is robust to noise and typically observed T1 variations. T2 values obtained in the phantom with T2 prep-bSSFP and the acquisition-specific, dictionary-based matching were highly correlated with the gold-standard spin echo method (r = 0.99). Furthermore, no differences were observed with the accelerated acquisition compared to the fully sampled acquisition (r = 0.99). T2 values obtained in prostate peripheral zone, central gland, and muscle in healthy subjects (age, 26 ± 6 years) were 97 ± 14, 76 ± 7, and 36 ± 3 ms, respectively. CONCLUSION 3D quantitative T2 mapping of the whole prostate can be achieved in 3 minutes.
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Affiliation(s)
- Elisa Roccia
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Rohini Vidya Shankar
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Radhouene Neji
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
- Siemens Healthcare Limited, Frimley, United Kingdom
| | - Gastão Cruz
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Camila Munoz
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - René Botnar
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Vicky Goh
- Cancer Imaging, King's College London, London, United Kingdom
| | - Claudia Prieto
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Isabel Dregely
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
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Roeloffs V, Rosenzweig S, Holme HCM, Uecker M, Frahm J. Frequency-modulated SSFP with radial sampling and subspace reconstruction: A time-efficient alternative to phase-cycled bSSFP. Magn Reson Med 2018; 81:1566-1579. [PMID: 30357904 DOI: 10.1002/mrm.27505] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 07/05/2018] [Accepted: 08/03/2018] [Indexed: 11/11/2022]
Abstract
PURPOSE A novel subspace-based reconstruction method for frequency-modulated balanced steady-state free precession (fmSSFP) MRI is presented. In this work, suitable data acquisition schemes, subspace sizes, and efficiencies for banding removal are investigated. THEORY AND METHODS By combining a fmSSFP MRI sequence with a 3D stack-of-stars trajectory, scan efficiency is maximized as spectral information is obtained without intermediate preparation phases. A memory-efficient reconstruction routine is implemented by introducing the low-frequency Fourier transform as a subspace which allows for the formulation of a convex reconstruction problem. The removal of banding artifacts is investigated by comparing the proposed acquisition and reconstruction technique to phase-cycled bSSFP MRI. Aliasing properties of different undersampling schemes are analyzed and water/fat separation is demonstrated by reweighting the reconstructed subspace coefficients to generate virtual spectral responses in a post-processing step. RESULTS A simple root-of-sum-of-squares combination of the reconstructed subspace coefficients yields high-SNR images with the characteristic bSSFP contrast but without banding artifacts. Compared to Golden-Angle trajectories, turn-based sampling schemes were superior in minimizing aliasing across reconstructed subspace coefficients. Water/fat separated images of the human knee were obtained by reweighting subspace coefficients. CONCLUSIONS The novel subspace-based fmSSFP MRI technique emerges as a time-efficient alternative to phase-cycled bSFFP. The method does not need intermediate preparation phases, offers high SNR and avoids banding artifacts. Reweighting of the reconstructed subspace coefficients allows for generating virtual spectral responses with applications to water/fat separation.
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Affiliation(s)
- Volkert Roeloffs
- Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany
| | - Sebastian Rosenzweig
- Institute for Diagnostic and Interventional Radiology, University Medical Center, Göttingen, Germany.,German Centre for Cardiovascular Research (DZHK), Göttingen, Germany
| | - H Christian M Holme
- Institute for Diagnostic and Interventional Radiology, University Medical Center, Göttingen, Germany.,German Centre for Cardiovascular Research (DZHK), Göttingen, Germany
| | - Martin Uecker
- Institute for Diagnostic and Interventional Radiology, University Medical Center, Göttingen, Germany.,German Centre for Cardiovascular Research (DZHK), Göttingen, Germany
| | - Jens Frahm
- Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany.,German Centre for Cardiovascular Research (DZHK), Göttingen, Germany
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Ozdemir S, Ider YZ. bSSFP phase correction and its use in magnetic resonance electrical properties tomography. Magn Reson Med 2018; 81:934-946. [PMID: 30357891 DOI: 10.1002/mrm.27446] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 06/06/2018] [Accepted: 06/12/2018] [Indexed: 11/05/2022]
Abstract
PURPOSE Balanced steady-state free precession (bSSFP) sequence is widely used because of its high SNR and high speed. However, bSSFP images suffer from "banding artifact" caused by B0 inhomogeneity. In this article, we propose a method to remove this artifact in bSSFP phase images and investigate the usage of the corrected phase images in phase-based magnetic resonance electrical properties tomography (MREPT). THEORY AND METHODS Two bSSFP phase images, obtained with different excitation frequencies, are collaged to get rid of the regions containing banding artifacts. Phase of the collaged bSSFP image is the sum of the transceive phase of the RF system and an error term that depends on B0 and T2 . By using B0 and T2 maps, this error is eliminated from bSSFP phase images by using pixel-wise corrections. Conductivity maps are obtained from the uncorrected and the corrected phase images using the phase-based cr-MREPT method. RESULTS Phantom and human experiment results of the proposed method are illustrated for both phase images and conductivity maps. It is shown that uncorrected phase images yield unacceptable conductivity images. When only B0 information is used for phase correction conductivity, reconstructions are substantially improved, and yet T2 information is still needed to fully recover accurate and undistorted conductivity images. CONCLUSIONS With the proposed technique, B0 sensitivity of the bSSFP phase images can be removed by using B0 and T2 maps. It is also shown that corrected bSSFP phase images are of sufficient quality to be used in conductivity imaging.
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Affiliation(s)
- Safa Ozdemir
- Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey
| | - Yusuf Ziya Ider
- Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey
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Cheng CC, Preiswerk F, Hoge WS, Kuo TH, Madore B. Multipathway multi-echo (MPME) imaging: all main MR parameters mapped based on a single 3D scan. Magn Reson Med 2018; 81:1699-1713. [PMID: 30320945 DOI: 10.1002/mrm.27525] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 08/15/2018] [Accepted: 08/18/2018] [Indexed: 12/27/2022]
Abstract
PURPOSE Quantitative parameter maps, as opposed to qualitative grayscale images, may represent the future of diagnostic MRI. A new quantitative MRI method is introduced here that requires a single 3D acquisition, allowing good spatial coverage to be achieved in relatively short scan times. METHODS A multipathway multi-echo sequence was developed, and at least 3 pathways with 2 TEs were needed to generate T1 , T2 , T2 * , B1 + , and B0 maps. The method required the central k-space region to be sampled twice, with the same sequence but with 2 very different nominal flip angle settings. Consequently, scan time was only slightly longer than that of a single scan. The multipathway multi-echo data were reconstructed into parameter maps, for phantom as well as brain acquisitions, in 5 healthy volunteers at 3 T. Spatial resolution, matrix size, and FOV were 1.2 × 1.0 × 1.2 mm3 , 160 × 192 × 160, and 19.2 × 19.2 × 19.2 cm3 (whole brain), acquired in 11.5 minutes with minimal acceleration. Validation was performed against T1 , T2 , and T2 * maps calculated from gradient-echo and spin-echo data. RESULTS In Bland-Altman plots, bias and limits of agreement for T1 and T2 results in vivo and in phantom were -2.9/±125.5 ms (T1 in vivo), -4.8/±20.8 ms (T2 in vivo), -1.5/±18.1 ms (T1 in phantom), and -5.3/±7.4 ms (T2 in phantom), for regions of interest including given brain structures or phantom compartments. Due to relatively high noise levels, the current implementation of the approach may prove more useful for region of interest-based as opposed to pixel-based interpretation. CONCLUSIONS We proposed a novel approach to quantitatively map MR parameters based on a multipathway multi-echo acquisition.
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Affiliation(s)
- Cheng-Chieh Cheng
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Frank Preiswerk
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
| | - W Scott Hoge
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Tai-Hsin Kuo
- Department of Imaging Systems, Philips Healthcare, Taipei, Taiwan
| | - Bruno Madore
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
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Colotti R, Omoumi P, van Heeswijk RB, Bastiaansen JAM. Simultaneous fat-free isotropic 3D anatomical imaging and T 2 mapping of knee cartilage with lipid-insensitive binomial off-resonant RF excitation (LIBRE) pulses. J Magn Reson Imaging 2018; 49:1275-1284. [PMID: 30318667 DOI: 10.1002/jmri.26322] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2018] [Revised: 08/13/2018] [Accepted: 08/13/2018] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Improved knee cartilage morphological delineation and T2 mapping precision necessitates isotropic 3D high-resolution and efficient fat suppression. PURPOSE To develop and assess an isotropic 3D lipid-insensitive T2 mapping technique of the knee for improved cartilage delineation and precise measurement of T2 relaxation times. STUDY TYPE Prospective. PHANTOM/SUBJECTS Phantoms (n = 6) used in this study were designed to mimic the T1 and T2 relaxation times of cartilage and fat. The study cohort comprised healthy volunteers (n = 7) for morphometry and T2 relaxation time measurements. FIELD STRENGTH/SEQUENCE A high-resolution isotropic 3D T2 mapping technique that uses sequential T2 -prepared segmented gradient-recalled echo (Iso3DGRE) images and lipid-insensitive binomial off-resonant radiofrequency (RF) excitation (LIBRE) at 3T. ASSESSMENT Numerical simulations and phantom experiments were performed to optimize the LIBRE pulse. Phantom studies were carried out to test the accuracy of the technique against reference standard spin-echo (SE) T2 mapping. Subsequently, T2 maps with and without LIBRE pulses were acquired in knees of healthy volunteers and the T2 relaxation time values in different cartilage compartments were compared. STATISTICAL TESTS A two-tailed paired Student's t-test was used to compare the average T2 values and the relative standard deviations (inverse measurement of the precision) obtained with and without LIBRE pulses. RESULTS A LIBRE pulse of 1 msec suppressed fat with an RF excitation frequency offset of 1560 Hz and optimal RF excitation angle of 35°. These results were corroborated by phantom and knee experiments. Robust and homogeneous fat suppression was obtained (a fat signal-to-noise ratio (SNR) decrease of 86.4 ± 2.4%). In phantoms, T2 values were found in good agreement when comparing LIBRE-Iso3DGRE with SE (slope 0.93 ± 0.04, intercept 0.11 ± 1.6 msec, R2 >0.99). In vivo, LIBRE excitation resulted in more precise T2 estimation (23.7 ± 7.4%) than normal excitation (30.5 ± 9.9%, P < 0.0001). DATA CONCLUSION Homogeneous LIBRE fat signal suppression was achieved with a total RF pulse duration of 1 msec, allowing for the removal of chemical shift artifacts and resulting in improved cartilage delineation and precise T2 values. LEVEL OF EVIDENCE 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;49:1275-1284.
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Affiliation(s)
- Roberto Colotti
- Department of Radiology, University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
| | - Patrick Omoumi
- Department of Radiology, University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
| | - Ruud B van Heeswijk
- Department of Radiology, University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland.,Centre for Biomedical Imaging (CIBM), Lausanne, Switzerland
| | - Jessica A M Bastiaansen
- Department of Radiology, University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
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Shcherbakova Y, van den Berg CAT, Moonen CTW, Bartels LW. On the accuracy and precision of PLANET for multiparametric MRI using phase-cycled bSSFP imaging. Magn Reson Med 2018; 81:1534-1552. [PMID: 30303562 PMCID: PMC6585657 DOI: 10.1002/mrm.27491] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Revised: 07/17/2018] [Accepted: 07/19/2018] [Indexed: 11/09/2022]
Abstract
Purpose In this work we demonstrate how sequence parameter settings influence the accuracy and precision in T1, T2, and off‐resonance maps obtained with the PLANET method for a single‐component signal model. In addition, the performance of the method for the particular case of a two‐component relaxation model for white matter tissue was assessed. Methods Numerical simulations were performed to investigate the influence of sequence parameter settings on the accuracy and precision in the estimated parameters for a single‐component model, as well as for a two‐component white matter model. Phantom and in vivo experiments were performed for validation. In addition, the effects of Gibbs ringing were investigated. Results By making a proper choice for sequence parameter settings, accurate and precise parameter estimation can be achieved for a single‐component signal model over a wide range of relaxation times at realistic SNR levels. Due to the presence of a second myelin‐related signal component in white matter, an underestimation of approximately 30% in T1 and T2 was observed, predicted by simulations and confirmed by measurements. Gibbs ringing artifacts correction improved the precision and accuracy of the parameter estimates. Conclusion For a single‐component signal model there is a broad “sweet spot” of sequence parameter combinations for which a high accuracy and precision in the parameter estimates is achieved over a wide range of relaxation times. For a multicomponent signal model, the single‐component PLANET reconstruction results in systematic errors in the parameter estimates as expected.
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Affiliation(s)
- Yulia Shcherbakova
- Center for Image Sciences, Imaging Division, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Cornelis A T van den Berg
- 2Department of Radiotherapy, Imaging Division, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Chrit T W Moonen
- Center for Image Sciences, Imaging Division, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Lambertus W Bartels
- Center for Image Sciences, Imaging Division, University Medical Center Utrecht, Utrecht, the Netherlands
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Juras V, Schreiner M, Laurent D, Zbýň Š, Mlynarik V, Szomolanyi P, Hager B, Scotti C, Goldhahn J, Heule R, Bieri O, Trattnig S. The comparison of the performance of 3 T and 7 T T 2 mapping for untreated low-grade cartilage lesions. Magn Reson Imaging 2018; 55:86-92. [PMID: 30244140 DOI: 10.1016/j.mri.2018.09.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Revised: 09/17/2018] [Accepted: 09/18/2018] [Indexed: 11/17/2022]
Abstract
OBJECTIVE To investigate T2 mapping as a possible marker for low-grade human articular cartilage lesions during a one-year follow-up, possible changes during the follow-up and compare the reliability and sensitivity of these measurements on high-field (3 T) and ultra-high-field (7 T) MRI scanners. DESIGN Twenty-one patients with femoral, tibial and patellar cartilage defect in the knee joint participated in the study. The MRI protocol consisted of morphological, as well as three-dimensional triple-echo steady-state (3D-TESS) T2 mapping sequences with similar parameters at 3T and 7T. Patients were scanned at five time-points up to 12 months. T2 values were evaluated in the lesion and healthy-appearing regions for superficial and deep cartilage zone. The repeated ANOVA was used to determine differences in T2 values at various time points. RESULTS A significant decrease in T2 values was observed between baseline and six months in the superficial layer of the lesion in patients at 3 T (decrease from 41.89 ± 9.3 ms to 31.21 ± 7.2 ms, which is a difference of -5.67 ± 2.2 ms (p = 0.031)), and at 12 months in the superficial layer of the lesion in patients at 3 T (decrease from 41.89 ± 9.3 ms to 35.28 ± 4.9 ms, which is a difference of -6.60 ± 4.4 ms (p = 0.044). No significant differences were recorded at 7 T. CONCLUSION The change in T2 values acquired with 3 T 3D-TESS appears to be reflecting subtle changes of cartilage composition in the course of low-grade lesion development. 7 T T2 mapping does not reflect these changes probably due to completely decayed short T2 component.
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Affiliation(s)
- Vladimir Juras
- High-Field MR Centre, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria; Institute of Measurement Science, Slovak Academy of Sciences, Bratislava, Slovakia.
| | - Markus Schreiner
- High-Field MR Centre, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria; Department of Orthopaedics, Medical University of Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria.
| | - Didier Laurent
- Novartis Institutes for Biomedical Research, Department of Translational Medicine, CH-4056 Basel, Switzerland.
| | - Štefan Zbýň
- High-Field MR Centre, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria; Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, Minnesota, USA.
| | - Vladimir Mlynarik
- High-Field MR Centre, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria; Karl-Landsteiner Gesselschaft, St. Pölten, Austria.
| | - Pavol Szomolanyi
- High-Field MR Centre, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria; Institute of Measurement Science, Slovak Academy of Sciences, Bratislava, Slovakia.
| | - Benedikt Hager
- High-Field MR Centre, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria.
| | - Celeste Scotti
- Novartis Institutes for Biomedical Research, Department of Translational Medicine, CH-4056 Basel, Switzerland.
| | - Jörg Goldhahn
- ETH Zurich, Institute of Translational Medicine, Leopold-Ruzicka-Weg 4, CH-8093 Zurich, Switzerland.
| | - Rahel Heule
- High Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
| | - Oliver Bieri
- Division of Radiological Physics, Department of Radiology, University of Basel Hospital, Basel, Switzerland.
| | - Siegfried Trattnig
- High-Field MR Centre, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria; Christian Doppler Laboratory for Clinical Molecular MR Imaging, Vienna, Austria; Austrian Cluster for Tissue Regeneration, Austria.
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A G Teixeira RP, Malik SJ, Hajnal JV. Fast quantitative MRI using controlled saturation magnetization transfer. Magn Reson Med 2018; 81:907-920. [PMID: 30257044 PMCID: PMC6492254 DOI: 10.1002/mrm.27442] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2018] [Revised: 06/04/2018] [Accepted: 06/10/2018] [Indexed: 01/31/2023]
Abstract
Purpose This study demonstrates magnetization transfer (MT) effects directly affect relaxometry measurements and develops a framework that allows single‐pool models to be valid in 2‐pool MT systems. Methods A theoretical framework is developed in which a 2‐pool MT system effectively behaves as a single‐pool if the RMS RF magnetic field (B1rms{\text{B}}_{1}^{{{\text{rms}}}}) is kept fixed across all measurements. A practical method for achieving controlled saturation magnetization transfer (CSMT) using multiband RF pulses is proposed. Numerical, Phantom, and in vivo validations were performed directly comparing steady state (SS) estimation approaches that under correct single‐pool assumptions would be expected to vary in precision but not accuracy. Results Numerical simulations predict single‐pool estimates obtained from MT model generated data are not consistent for different SS estimation methods, and a systematic underestimation of T2 is expected. Neither effect occurs under the proposed CSMT approach. Both phantom and in vivo experiments corroborate the numerical predictions. Experimental data highlights that even when using the same relaxometry method, different estimates are obtained depending on which combination of flip angles (FAs) and TRs are used if the CSMT approach is not used. Using CSMT, stable measurements of both T1 and T2 are obtained. The measured T1(T1CSMT)) depends on B1rms{\text{B}}_{1}^{{{\text{rms}}}}, which is therefore an important parameter to specify. Conclusion This work demonstrates that conventional single pool relaxometry, which is highly efficient for human studies, results in unreliable parameter estimates in biological tissues because of MT effects. The proposed CSMT framework is shown to allow single‐pool assumptions to be valid, enabling reliable and efficient quantitative imaging to be performed.
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Affiliation(s)
- Rui Pedro A G Teixeira
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom.,Centre for the Developing Brain, King's College London, London, United Kingdom
| | - Shaihan J Malik
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Joseph V Hajnal
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom.,Centre for the Developing Brain, King's College London, London, United Kingdom
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44
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Leroi L, Coste A, de Rochefort L, Santin MD, Valabregue R, Mauconduit F, Giacomini E, Luong M, Chazel E, Valette J, Le Bihan D, Poupon C, Boumezbeur F, Rabrait-Lerman C, Vignaud A. Simultaneous multi-parametric mapping of total sodium concentration, T 1, T 2 and ADC at 7 T using a multi-contrast unbalanced SSFP. Magn Reson Imaging 2018; 53:156-163. [PMID: 30055291 DOI: 10.1016/j.mri.2018.07.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 07/23/2018] [Accepted: 07/23/2018] [Indexed: 01/10/2023]
Abstract
PURPOSE Quantifying multiple NMR properties of sodium could be of benefit to assess changes in cellular viability in biological tissues. A proof of concept of Quantitative Imaging using Configuration States (QuICS) based on a SSFP sequence with multiple contrasts was implemented to extract simultaneously 3D maps of applied flip angle (FA), total sodium concentration, T1, T2, and Apparent Diffusion Coefficient (ADC). METHODS A 3D Cartesian Gradient Recalled Echo (GRE) sequence was used to acquire 11 non-balanced SSFP contrasts at a 6 × 6 × 6 mm3 isotropic resolution with carefully-chosen gradient spoiling area, RF amplitude and phase cycling, with TR/TE = 20/3.2 ms and 25 averages, leading to a total acquisition time of 1 h 18 min. A least-squares fit between the measured and the analytical complex signals was performed to extract quantitative maps from a mono-exponential model. Multiple sodium phantoms with different compositions were studied to validate the ability of the method to measure sodium NMR properties in various conditions. RESULTS Flip angle maps were retrieved. Relaxation times, ADC and sodium concentrations were estimated with controlled precision below 15%, and were in accordance with measurements from established methods and literature. CONCLUSION The results illustrate the ability to retrieve sodium NMR properties maps, which is a first step toward the estimation of FA, T1, T2, concentration and ADC of 23Na for clinical research. With further optimization of the acquired QuICS contrasts, scan time could be reduced to be suitable with in vivo applications.
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Affiliation(s)
- Lisa Leroi
- NeuroSpin, CEA, DRF/JOLIOT, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Arthur Coste
- NeuroSpin, CEA, DRF/JOLIOT, Université Paris-Saclay, Gif-sur-Yvette, France
| | | | - Mathieu D Santin
- CENIR, Centre de NeuroImagerie de Recherche, Paris, France; ICM, Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Université Paris 06 UMR S1127, Institut du Cerveau et de la Moelle épinière, Paris, France
| | - Romain Valabregue
- CENIR, Centre de NeuroImagerie de Recherche, Paris, France; ICM, Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Université Paris 06 UMR S1127, Institut du Cerveau et de la Moelle épinière, Paris, France
| | | | - Eric Giacomini
- NeuroSpin, CEA, DRF/JOLIOT, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Michel Luong
- NeuroSpin, CEA, DRF/JOLIOT, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Edouard Chazel
- NeuroSpin, CEA, DRF/JOLIOT, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Julien Valette
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Direction de la Recherche Fondamentale (DRF), Institut de Biologie François Jacob, MIRCen, Fontenay-aux-Roses, France
| | - Denis Le Bihan
- NeuroSpin, CEA, DRF/JOLIOT, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Cyril Poupon
- NeuroSpin, CEA, DRF/JOLIOT, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Fawzi Boumezbeur
- NeuroSpin, CEA, DRF/JOLIOT, Université Paris-Saclay, Gif-sur-Yvette, France
| | | | - Alexandre Vignaud
- NeuroSpin, CEA, DRF/JOLIOT, Université Paris-Saclay, Gif-sur-Yvette, France.
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45
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Qiao Y, Zou C, Cheng C, Wan Q, Tie C, Liang D, Zheng H, Liu X, Chung YC. Diffusion effect on T2 relaxometry in triple-echo steady state free precession sequence. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2018; 292:25-35. [PMID: 29758451 DOI: 10.1016/j.jmr.2018.04.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Revised: 04/28/2018] [Accepted: 04/29/2018] [Indexed: 06/08/2023]
Abstract
PURPOSE The purpose of this study is to evaluate the effect of diffusion on SSFP (Steady-state Free Precession) signals in triple-echo steady state (TESS) sequence and ultimately on the accuracy of T2 relaxometry. METHODS The extended phase graph (EPG) algorithm was used to study the effect of diffusion on SSFP signals and T2 relaxometry. The simulation results were verified by a commercial phantom and in vivo studies. Based on the simulation results, a correction scheme was proposed to correct the estimated T2 values. RESULTS T2 underestimation in TESS was evident in case of small flip angle and large unbalanced gradient moment on objects with large T2 and D values. The T2 underestimation mainly originated from the diffusion sensitivity of SSFP-echo. It was also observed that SSFP-FID (Free Induction Decay) signals increased with increasing diffusion weighting under some specific conditions. The proposed correction scheme corrected the T2 underestimation, which verified that the underestimation was due to the neglect of diffusion effect. For clinical practice of TESS in tissues with short T2 such as cartilage and muscle, the diffusion effect of TESS is negligible. CONCLUSION The effect of diffusion cannot be neglected during TESS T2 quantification as it is the main source of T2 underestimation when small flip angle and large unbalanced gradient moment is used, especially for objects with large T2 and D values.
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Affiliation(s)
- Yangzi Qiao
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, People's Republic of China
| | - Chao Zou
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, People's Republic of China
| | - Chuanli Cheng
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, People's Republic of China; University of Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Qian Wan
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, People's Republic of China
| | - Changjun Tie
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, People's Republic of China
| | - Dong Liang
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, People's Republic of China
| | - Hairong Zheng
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, People's Republic of China
| | - Xin Liu
- Paul C Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, People's Republic of China; Chongqing Collaborative Innovation Center, Chongqing, People's Republic of China.
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46
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Menon RG, Chang G, Regatte RR. The Emerging Role of 7 Tesla MRI in Musculoskeletal Imaging. CURRENT RADIOLOGY REPORTS 2018. [DOI: 10.1007/s40134-018-0286-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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47
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Carlier PG, Marty B, Scheidegger O, Loureiro de Sousa P, Baudin PY, Snezhko E, Vlodavets D. Skeletal Muscle Quantitative Nuclear Magnetic Resonance Imaging and Spectroscopy as an Outcome Measure for Clinical Trials. J Neuromuscul Dis 2018; 3:1-28. [PMID: 27854210 PMCID: PMC5271435 DOI: 10.3233/jnd-160145] [Citation(s) in RCA: 132] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Recent years have seen tremendous progress towards therapy of many previously incurable neuromuscular diseases. This new context has acted as a driving force for the development of novel non-invasive outcome measures. These can be organized in three main categories: functional tools, fluid biomarkers and imagery. In the latest category, nuclear magnetic resonance imaging (NMRI) offers a considerable range of possibilities for the characterization of skeletal muscle composition, function and metabolism. Nowadays, three NMR outcome measures are frequently integrated in clinical research protocols. They are: 1/ the muscle cross sectional area or volume, 2/ the percentage of intramuscular fat and 3/ the muscle water T2, which quantity muscle trophicity, chronic fatty degenerative changes and oedema (or more broadly, “disease activity”), respectively. A fourth biomarker, the contractile tissue volume is easily derived from the first two ones. The fat fraction maps most often acquired with Dixon sequences have proven their capability to detect small changes in muscle composition and have repeatedly shown superior sensitivity over standard functional evaluation. This outcome measure will more than likely be the first of the series to be validated as an endpoint by regulatory agencies. The versatility of contrast generated by NMR has opened many additional possibilities for characterization of the skeletal muscle and will result in the proposal of more NMR biomarkers. Ultra-short TE (UTE) sequences, late gadolinium enhancement and NMR elastography are being investigated as candidates to evaluate skeletal muscle interstitial fibrosis. Many options exist to measure muscle perfusion and oxygenation by NMR. Diffusion NMR as well as texture analysis algorithms could generate complementary information on muscle organization at microscopic and mesoscopic scales, respectively. 31P NMR spectroscopy is the reference technique to assess muscle energetics non-invasively during and after exercise. In dystrophic muscle, 31P NMR spectrum at rest is profoundly perturbed, and several resonances inform on cell membrane integrity. Considerable efforts are being directed towards acceleration of image acquisitions using a variety of approaches, from the extraction of fat content and water T2 maps from one single acquisition to partial matrices acquisition schemes. Spectacular decreases in examination time are expected in the near future. They will reinforce the attractiveness of NMR outcome measures and will further facilitate their integration in clinical research trials.
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Affiliation(s)
- Pierre G Carlier
- Institute of Myology, Pitie-Salpetriere University Hospital, Paris, France.,CEA, DSV, I2BM, MIRCen, NMR Laboratory, Paris, France.,National Academy of Sciences, United Institute for Informatics Problems, Minsk, Belarus
| | - Benjamin Marty
- Institute of Myology, Pitie-Salpetriere University Hospital, Paris, France.,CEA, DSV, I2BM, MIRCen, NMR Laboratory, Paris, France
| | - Olivier Scheidegger
- Institute of Myology, Pitie-Salpetriere University Hospital, Paris, France.,Support Center for Advanced Neuroimaging (SCAN), Institute of Diagnostic and Interventional Neuroradiology, Inselspital, Bern University Hospital, and University of Bern, Switzerland
| | | | | | - Eduard Snezhko
- National Academy of Sciences, United Institute for Informatics Problems, Minsk, Belarus
| | - Dmitry Vlodavets
- N.I. Prirogov Russian National Medical Research University, Clinical Research Institute of Pediatrics, Moscow, Russian Federation
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48
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Heule R, Celicanin Z, Kozerke S, Bieri O. Simultaneous multislice triple-echo steady-state (SMS-TESS) T 1 , T 2 , PD, and off-resonance mapping in the human brain. Magn Reson Med 2018; 80:1088-1100. [PMID: 29468727 DOI: 10.1002/mrm.27126] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Revised: 01/12/2018] [Accepted: 01/19/2018] [Indexed: 12/27/2022]
Affiliation(s)
- Rahel Heule
- Division of Radiological Physics, Department of Radiology, University Hospital Basel, University of Basel, Basel, Switzerland.,Department of Biomedical Engineering, University of Basel, Basel, Switzerland
| | - Zarko Celicanin
- Division of Radiological Physics, Department of Radiology, University Hospital Basel, University of Basel, Basel, Switzerland.,Department of Biomedical Engineering, University of Basel, Basel, Switzerland
| | - Sebastian Kozerke
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
| | - Oliver Bieri
- Division of Radiological Physics, Department of Radiology, University Hospital Basel, University of Basel, Basel, Switzerland.,Department of Biomedical Engineering, University of Basel, Basel, Switzerland
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49
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[When is cartilage repair successful?]. Radiologe 2017; 57:907-914. [PMID: 28929186 DOI: 10.1007/s00117-017-0305-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Focal cartilage lesions are a cause of long-term disability and morbidity. After cartilage repair, it is crucial to evaluate long-term progression or failure in a reproducible, standardized manner. This article provides an overview of the different cartilage repair procedures and important characteristics to look for in cartilage repair imaging. Specifics and pitfalls are pointed out alongside general aspects. After successful cartilage repair, a complete, but not hypertrophic filling of the defect is the primary criterion of treatment success. The repair tissue should also be completely integrated to the surrounding native cartilage. After some months, the transplants signal should be isointense compared to native cartilage. Complications like osteophytes, subchondral defects, cysts, adhesion and chronic bone marrow edema or joint effusion are common and have to be observed via follow-up. Radiological evaluation and interpretation of postoperative changes should always take the repair method into account.
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50
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Shcherbakova Y, van den Berg CAT, Moonen CTW, Bartels LW. PLANET: An ellipse fitting approach for simultaneous T 1 and T 2 mapping using phase-cycled balanced steady-state free precession. Magn Reson Med 2017; 79:711-722. [PMID: 28543430 PMCID: PMC5811804 DOI: 10.1002/mrm.26717] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 03/23/2017] [Accepted: 03/26/2017] [Indexed: 11/09/2022]
Abstract
Purpose To demonstrate the feasibility of a novel, ellipse fitting approach, named PLANET, for simultaneous estimation of relaxation times T1 and T2 from a single 3D phase‐cycled balanced steady‐state free precession (bSSFP) sequence. Methods A method is presented in which the elliptical signal model is used to describe the phase‐cycled bSSFP steady‐state signal. The fitting of the model to the acquired data is reformulated into a linear convex problem, which is solved directly by a linear least squares method, specific to ellipses. Subsequently, the relaxation times T1 and T2, the banding free magnitude, and the off‐resonance are calculated from the fitting results. Results Maps of T1 and T2, as well as an off‐resonance and a banding free magnitude can be simultaneously, quickly, and robustly estimated from a single 3D phase‐cycled bSSFP sequence. The feasibility of the method was demonstrated in a phantom and in the brain of healthy volunteers on a clinical MR scanner. The results were in good agreement for the phantom, but a systematic underestimation of T1 was observed in the brain. Conclusion The presented method allows for accurate mapping of relaxation times and off‐resonance, and for the reconstruction of banding free magnitude images at realistic signal‐to‐noise ratios. Magn Reson Med 79:711–722, 2018. © 2017 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‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.
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Affiliation(s)
- Yulia Shcherbakova
- Center for Image Sciences, Imaging Division, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Cornelis A T van den Berg
- Department of Radiotherapy, Imaging Division, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Chrit T W Moonen
- Center for Image Sciences, Imaging Division, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Lambertus W Bartels
- Center for Image Sciences, Imaging Division, University Medical Center Utrecht, Utrecht, The Netherlands
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