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Samsonov AA, Yarnykh VL. Accurate actual flip angle imaging (AFI) in the presence of fat. Magn Reson Med 2024; 91:2345-2357. [PMID: 38193249 PMCID: PMC10997465 DOI: 10.1002/mrm.30000] [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: 09/07/2023] [Revised: 11/30/2023] [Accepted: 12/19/2023] [Indexed: 01/10/2024]
Abstract
PURPOSE To investigate the effect of incomplete fat spoiling on the accuracy of B1 mapping with actual flip angle imaging (AFI) and to propose a method to minimize the errors using the chemical shift properties of fat. THEORY AND METHODS Diffusion-based dephasing is the main spoiling mechanism exploited in AFI. However, a very low diffusion in fat may make the spoiling insufficient, leading to ghosts in the B1 maps. As the errors retain the chemical-shift signature of fat, their impact can be minimized using chemical-shift-based fat signal removal from AFI acquisition modified to include multi-echo readout. The source of the errors and the proposed correction were studied in simulations and phantom and in-vivo imaging experiments. RESULTS Our results support that AFI artifacts are caused by the incomplete fat spoiling present in clinically attractive short TR acquisition regimes. The correction eliminated the ghosting and significantly improved the B1 mapping accuracy as well as the accuracy of R1 mapping performed with AFI-derived B1 maps. CONCLUSIONS The incomplete fat signal spoiling may be a source of AFI B1 mapping errors, especially in subjects with high fat content. Achieving complete fat spoiling requires longer TR, which is undesirable in clinical applications. The proposed approach based on fat signal removal can reduce errors without significant prolongation of the AFI pulse sequence. We propose that, when attaining complete fat spoiling is not feasible, AFI mapping should be performed in a multi-echo regime with appropriate fat separation or suppression to minimize these errors.
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Affiliation(s)
- Alexey A Samsonov
- Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Vasily L Yarnykh
- Department of Radiology, University of Washington, Seattle, Washington, USA
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2
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Zampini MA, Sijbers J, Verhoye M, Garipov R. A preparation pulse for fast steady state approach in Actual Flip angle Imaging. Med Phys 2024; 51:306-318. [PMID: 37480220 DOI: 10.1002/mp.16624] [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: 02/23/2023] [Revised: 05/26/2023] [Accepted: 06/20/2023] [Indexed: 07/23/2023] Open
Abstract
BACKGROUND Actual Flip angle Imaging (AFI) is a sequence used for B1 mapping, also embedded in the Variable flip angle with AFI for simultaneous estimation of T1 , B1 and equilibrium magnetization. PURPOSE To investigate the design of a preparation module for AFI to allow a fast approach to steady state (SS) without requiring the use of dummy acquisitions. METHODS The features of a preparation module with a B1 insensitive adiabatic pulse, spoiler gradients, and a recovery timeT r e c $T_{rec}$ were studied with simulations and validated via experiments and acquired with different k-space traveling strategies. The robustness of the flip angle of the preparation pulse on the acquired signal is studied. RESULTS When a 90° adiabatic pulse is used, the forthcomingT r e c $T_{rec}$ can be expressed as a function of repetition times and AFI flip angle only asTR 1 ( n + cos α ) / ( 1 - cos 2 α ) $\mathrm{TR_1}(n+\cos \alpha )/(1-\cos ^2\alpha )$ , where n represents the ratio between the two repetition times of AFI. The robustness of the method is demonstrated by showing that using the values further away from 90° still allows for a faster approach to SS than the use of dummy pulses. CONCLUSIONS The preparation module is particularly advantageous for low flip angles, as well as for AFI sequences that sample the center of the k-space early in the sequence, such as centric ordering acquisitions, and for ultrafast EPI-based AFI methods, thus allowing to reduce scanner overhead time.
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Affiliation(s)
- Marco Andrea Zampini
- MR Solutions Ltd., Ashbourne House, Guildford, Surrey, UK
- Bio-Imaging Lab, Department of Biomedical Sciences, University of Antwerp, Belgium
| | - Jan Sijbers
- imec-Vision Lab, Department of Physics, University of Antwerp, Belgium
- μNEURO Research Centre of Excellence, University of Antwerp, Belgium
| | - Marleen Verhoye
- Bio-Imaging Lab, Department of Biomedical Sciences, University of Antwerp, Belgium
- μNEURO Research Centre of Excellence, University of Antwerp, Belgium
| | - Ruslan Garipov
- MR Solutions Ltd., Ashbourne House, Guildford, Surrey, UK
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3
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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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4
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Balbastre Y, Brudfors M, Azzarito M, Lambert C, Callaghan MF, Ashburner J. Model-based multi-parameter mapping. Med Image Anal 2021; 73:102149. [PMID: 34271531 PMCID: PMC8505752 DOI: 10.1016/j.media.2021.102149] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 05/07/2021] [Accepted: 06/24/2021] [Indexed: 12/29/2022]
Abstract
Quantitative MR imaging is increasingly favoured for its richer information content and standardised measures. However, computing quantitative parameter maps, such as those encoding longitudinal relaxation rate (R1), apparent transverse relaxation rate (R2*) or magnetisation-transfer saturation (MTsat), involves inverting a highly non-linear function. Many methods for deriving parameter maps assume perfect measurements and do not consider how noise is propagated through the estimation procedure, resulting in needlessly noisy maps. Instead, we propose a probabilistic generative (forward) model of the entire dataset, which is formulated and inverted to jointly recover (log) parameter maps with a well-defined probabilistic interpretation (e.g., maximum likelihood or maximum a posteriori). The second order optimisation we propose for model fitting achieves rapid and stable convergence thanks to a novel approximate Hessian. We demonstrate the utility of our flexible framework in the context of recovering more accurate maps from data acquired using the popular multi-parameter mapping protocol. We also show how to incorporate a joint total variation prior to further decrease the noise in the maps, noting that the probabilistic formulation allows the uncertainty on the recovered parameter maps to be estimated. Our implementation uses a PyTorch backend and benefits from GPU acceleration. It is available at https://github.com/balbasty/nitorch.
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Affiliation(s)
- Yaël Balbastre
- Wellcome Center for Human Neuroimaging, Queen Square Institute of Neurology, University College London, London, UK; Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Boston, USA.
| | - Mikael Brudfors
- Wellcome Center for Human Neuroimaging, Queen Square Institute of Neurology, University College London, London, UK; School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK
| | - Michela Azzarito
- Spinal Cord Injury Center Balgrist, University Hospital Zurich, University of Zurich, Switzerland
| | - Christian Lambert
- Wellcome Center for Human Neuroimaging, Queen Square Institute of Neurology, University College London, London, UK
| | - Martina F Callaghan
- Wellcome Center for Human Neuroimaging, Queen Square Institute of Neurology, University College London, London, UK
| | - John Ashburner
- Wellcome Center for Human Neuroimaging, Queen Square Institute of Neurology, University College London, London, UK
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Mickevicius NJ, Kim JP, Zhao J, Morris ZS, Hurst NJ, Glide-Hurst CK. Toward magnetic resonance fingerprinting for low-field MR-guided radiation therapy. Med Phys 2021; 48:6930-6940. [PMID: 34487357 DOI: 10.1002/mp.15202] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 08/17/2021] [Accepted: 08/25/2021] [Indexed: 12/14/2022] Open
Abstract
PURPOSE The acquisition of multiparametric quantitative magnetic resonance imaging (qMRI) is becoming increasingly important for functional characterization of cancer prior to- and throughout the course of radiation therapy. The feasibility of a qMRI method known as magnetic resonance fingerprinting (MRF) for rapid T1 and T2 mapping was assessed on a low-field MR-linac system. METHODS A three-dimensional MRF sequence was implemented on a 0.35T MR-guided radiotherapy system. MRF-derived measurements of T1 and T2 were compared to those obtained with gold standard single spin echo methods, and the impacts of the radiofrequency field homogeneity and scan times ranging between 6 and 48 min were analyzed by acquiring between 1 and 8 spokes per time point in a standard quantitative system phantom. The short-term repeatability of MRF was assessed over three measurements taken over a 10-h period. To evaluate transferability, MRF measurements were acquired on two additional MR-guided radiotherapy systems. Preliminary human volunteer studies were performed. RESULTS The phantom benchmarking studies showed that MRF is capable of mapping T1 and T2 values within 8% and 10% of gold standard measures, respectively, at 0.35T. The coefficient of variation of T1 and T2 estimates over three repeated scans was < 5% over a broad range of relaxation times. The T1 and T2 times derived using a single-spoke MRF acquisition across three scanners were near unity and mean percent errors in T1 and T2 estimates using the same phantom were < 3%. The mean percent differences in T1 and T2 as a result of truncating the scan time to 6 min over the large range of relaxation times in the system phantom were 0.65% and 4.05%, respectively. CONCLUSIONS The technical feasibility and accuracy of MRF on a low-field MR-guided radiation therapy device has been demonstrated. MRF can be used to measure accurate T1 and T2 maps in three dimensions from a brief 6-min scan, offering strong potential for efficient and reproducible qMRI for future clinical trials in functional plan adaptation and tumor/normal tissue response assessment.
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Affiliation(s)
- Nikolai J Mickevicius
- Department of Human Oncology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Joshua P Kim
- Department of Radiation Oncology, Henry Ford Cancer Institute, Detroit, Michigan, USA
| | - Jiwei Zhao
- Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Zachary S Morris
- Department of Human Oncology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Newton J Hurst
- Department of Human Oncology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Carri K Glide-Hurst
- Department of Human Oncology, University of Wisconsin-Madison, Madison, Wisconsin, USA
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6
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Wei Z, Jang H, Bydder GM, Yang W, Ma YJ. Fast T 1 measurement of cortical bone using 3D UTE actual flip angle imaging and single-TR acquisition (3D UTE-AFI-STR). Magn Reson Med 2021; 85:3290-3298. [PMID: 33404142 DOI: 10.1002/mrm.28655] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 12/02/2020] [Accepted: 12/03/2020] [Indexed: 12/16/2022]
Abstract
PURPOSE To describe a new method for accurate T1 measurement of cortical bone that fits the data sets of both 3D UTE actual flip angle imaging (UTE-AFI) and UTE with a single TR (UTE-STR) simultaneously (UTE-AFI-STR). THEORY AND METHODS To make both the constant values and longitudinal mapping functions in the signal equations for UTE-AFI and UTE-STR identical, the same RF pulses and flip angles were used. Therefore, there were three unknowns in the three equations. This was sufficient to fit the data. Numerical simulation as well as ex vivo and in vivo cortical bone studies were performed to validate the T1 measurement accuracy with the UTE-AFI-STR method. The original UTE-AFI variable TR (VTR) (ie, combined UTE-AFI and UTE with VTR) and simultaneous fitting (sf) of UTE-AFI and UTE-VTR (sf-UTE-AFI-VTR) methods were performed for comparison. RESULTS The numerical simulation study showed that the UTE-AFI-STR method provided accurate value of T1 when the SNR of the UTE-STR image was higher than 40. The ex vivo study showed that the UTE-AFI-STR method measured the T1 of cortical bone accurately, with difference ratios ranging from -5.0% to 0.4%. The in vivo study showed a mean T1 of 246 ms with the UTE-AFI-STR method, and mean difference ratios of 2.4% and 5.0%, respectively, compared with the other two methods. CONCLUSION The 3D UTE-AFI-STR method provides accurate mapping of the T1 of cortical bone with improved time efficiency compared with the UTE-AFI-VTR/sf-UTE-AFI-VTR methods.
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Affiliation(s)
- Zhao Wei
- Department of Radiology, University of California San Diego, San Diego, California, USA
- Institute of Electrical Engineering Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Hyungseok Jang
- Department of Radiology, University of California San Diego, San Diego, California, USA
| | - Graeme M Bydder
- Department of Radiology, University of California San Diego, San Diego, California, USA
| | - Wenhui Yang
- Institute of Electrical Engineering Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Ya-Jun Ma
- Department of Radiology, University of California San Diego, San Diego, California, USA
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Desmond KL, Xu R, Sun Y, Chavez S. A practical method for post-acquisition reduction of bias in fast, whole-brain B1-maps. Magn Reson Imaging 2020; 77:88-98. [PMID: 33338561 DOI: 10.1016/j.mri.2020.12.009] [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: 08/25/2020] [Revised: 11/22/2020] [Accepted: 12/13/2020] [Indexed: 12/24/2022]
Abstract
Large consistent differences have been observed between maps of the flip angle correction factor (commonly called "B1-maps") produced with different fast methods in the human brain. We present an empirical procedure for first-order multiplicative bias correction that can be applied when more than one B1-mapping method is available. We use a B1-map measurement in a calibration phantom as a reference and the voxel-wise histogram mode between ratios of B1-maps produced from different methods to calculate determine the bias as a multiplicative correcting scale factor. Institutional implementations of four common methods of B1-mapping were assessed: Method of Slopes, FSE and EPI double angle methods (DAM), and Bloch-Siegert. In human subjects, the multiplicative bias used to correct for each of the four methods was: Method of Slopes = 1.005, FSE-DAM = 0.956, EPI-DAM = 1.080, and Bloch-Siegert = 1.128. Scaling to remove this bias between methods produces more consistent B1-maps which enable more consistent values for any computations requiring flip angle correction. In addition, we present evidence that the corrected B1 maps, using our calibration method, are also more accurate.
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Affiliation(s)
- Kimberly L Desmond
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Toronto, Ontario M5T 1R8, Canada; Department of Psychiatry, University of Toronto, Toronto, Ontario M5T 1R8, Canada.
| | - Ruiyang Xu
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Toronto, Ontario M5T 1R8, Canada
| | - Yutong Sun
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Toronto, Ontario M5T 1R8, Canada
| | - Sofia Chavez
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Toronto, Ontario M5T 1R8, Canada; Department of Psychiatry, University of Toronto, Toronto, Ontario M5T 1R8, Canada
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Isaacs BR, Keuken MC, Alkemade A, Temel Y, Bazin PL, Forstmann BU. Methodological Considerations for Neuroimaging in Deep Brain Stimulation of the Subthalamic Nucleus in Parkinson's Disease Patients. J Clin Med 2020; 9:E3124. [PMID: 32992558 PMCID: PMC7600568 DOI: 10.3390/jcm9103124] [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: 08/24/2020] [Revised: 09/17/2020] [Accepted: 09/25/2020] [Indexed: 12/17/2022] Open
Abstract
Deep brain stimulation (DBS) of the subthalamic nucleus is a neurosurgical intervention for Parkinson's disease patients who no longer appropriately respond to drug treatments. A small fraction of patients will fail to respond to DBS, develop psychiatric and cognitive side-effects, or incur surgery-related complications such as infections and hemorrhagic events. In these cases, DBS may require recalibration, reimplantation, or removal. These negative responses to treatment can partly be attributed to suboptimal pre-operative planning procedures via direct targeting through low-field and low-resolution magnetic resonance imaging (MRI). One solution for increasing the success and efficacy of DBS is to optimize preoperative planning procedures via sophisticated neuroimaging techniques such as high-resolution MRI and higher field strengths to improve visualization of DBS targets and vasculature. We discuss targeting approaches, MRI acquisition, parameters, and post-acquisition analyses. Additionally, we highlight a number of approaches including the use of ultra-high field (UHF) MRI to overcome limitations of standard settings. There is a trade-off between spatial resolution, motion artifacts, and acquisition time, which could potentially be dissolved through the use of UHF-MRI. Image registration, correction, and post-processing techniques may require combined expertise of traditional radiologists, clinicians, and fundamental researchers. The optimization of pre-operative planning with MRI can therefore be best achieved through direct collaboration between researchers and clinicians.
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Affiliation(s)
- Bethany R. Isaacs
- Integrative Model-based Cognitive Neuroscience Research Unit, University of Amsterdam, 1018 WS Amsterdam, The Netherlands; (A.A.); (P.-L.B.); (B.U.F.)
- Department of Experimental Neurosurgery, Maastricht University Medical Center, 6202 AZ Maastricht, The Netherlands;
| | - Max C. Keuken
- Municipality of Amsterdam, Services & Data, Cluster Social, 1000 AE Amsterdam, The Netherlands;
| | - Anneke Alkemade
- Integrative Model-based Cognitive Neuroscience Research Unit, University of Amsterdam, 1018 WS Amsterdam, The Netherlands; (A.A.); (P.-L.B.); (B.U.F.)
| | - Yasin Temel
- Department of Experimental Neurosurgery, Maastricht University Medical Center, 6202 AZ Maastricht, The Netherlands;
| | - Pierre-Louis Bazin
- Integrative Model-based Cognitive Neuroscience Research Unit, University of Amsterdam, 1018 WS Amsterdam, The Netherlands; (A.A.); (P.-L.B.); (B.U.F.)
- Max Planck Institute for Human Cognitive and Brain Sciences, D-04103 Leipzig, Germany
| | - Birte U. Forstmann
- Integrative Model-based Cognitive Neuroscience Research Unit, University of Amsterdam, 1018 WS Amsterdam, The Netherlands; (A.A.); (P.-L.B.); (B.U.F.)
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Hilbert T, Xia D, Block KT, Yu Z, Lattanzi R, Sodickson DK, Kober T, Cloos MA. Magnetization transfer in magnetic resonance fingerprinting. Magn Reson Med 2020; 84:128-141. [PMID: 31762101 PMCID: PMC7083689 DOI: 10.1002/mrm.28096] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 10/18/2019] [Accepted: 11/04/2019] [Indexed: 01/28/2023]
Abstract
PURPOSE To study the effects of magnetization transfer (MT, in which a semi-solid spin pool interacts with the free pool), in the context of magnetic resonance fingerprinting (MRF). METHODS Simulations and phantom experiments were performed to study the impact of MT on the MRF signal and its potential influence on T1 and T2 estimation. Subsequently, an MRF sequence implementing off-resonance MT pulses and a dictionary with an MT dimension, generated by incorporating a two-pool model, were used to estimate the fractional pool size in addition to the B 1 + , T1 , and T2 values. The proposed method was evaluated in the human brain. RESULTS Simulations and phantom experiments showed that an MRF signal obtained from a cross-linked bovine serum sample is influenced by MT. Using a dictionary based on an MT model, a better match between simulations and acquired MR signals can be obtained (NRMSE 1.3% vs. 4.7%). Adding off-resonance MT pulses can improve the differentiation of MT from T1 and T2 . In vivo results showed that MT affects the MRF signals from white matter (fractional pool-size ~16%) and gray matter (fractional pool-size ~10%). Furthermore, longer T1 (~1060 ms vs. ~860 ms) and T2 values (~47 ms vs. ~35 ms) can be observed in white matter if MT is accounted for. CONCLUSION Our experiments demonstrated a potential influence of MT on the quantification of T1 and T2 with MRF. A model that encompasses MT effects can improve the accuracy of estimated relaxation parameters and allows quantification of the fractional pool size.
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Affiliation(s)
- Tom Hilbert
- Advanced Clinical Imaging Technology, Siemens Healthcare AG, Lausanne, Switzerland
- Department of Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
- LTS5, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Ding Xia
- Center for Advanced Imaging Innovation and Research (CAIR), Department of Radiology, New York University School of Medicine, New York, NY, USA
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, USA
| | - Kai Tobias Block
- Center for Advanced Imaging Innovation and Research (CAIR), Department of Radiology, New York University School of Medicine, New York, NY, USA
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, USA
- Department of Radiology, University Hospital Basel, Basel, Switzerland
| | - Zidan Yu
- Center for Advanced Imaging Innovation and Research (CAIR), Department of Radiology, New York University School of Medicine, New York, NY, USA
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, USA
- The Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine, New York, NY, USA
| | - Riccardo Lattanzi
- Center for Advanced Imaging Innovation and Research (CAIR), Department of Radiology, New York University School of Medicine, New York, NY, USA
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, USA
- The Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine, New York, NY, USA
| | - Daniel K Sodickson
- Center for Advanced Imaging Innovation and Research (CAIR), Department of Radiology, New York University School of Medicine, New York, NY, USA
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, USA
- The Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine, New York, NY, USA
| | - Tobias Kober
- Advanced Clinical Imaging Technology, Siemens Healthcare AG, Lausanne, Switzerland
- Department of Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
- LTS5, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Martijn A Cloos
- Center for Advanced Imaging Innovation and Research (CAIR), Department of Radiology, New York University School of Medicine, New York, NY, USA
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, USA
- The Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine, New York, NY, USA
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10
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Watts JJ, Garani R, Da Silva T, Lalang N, Chavez S, Mizrahi R. Evidence That Cannabis Exposure, Abuse, and Dependence Are Related to Glutamate Metabolism and Glial Function in the Anterior Cingulate Cortex: A 1H-Magnetic Resonance Spectroscopy Study. Front Psychiatry 2020; 11:764. [PMID: 32973572 PMCID: PMC7468488 DOI: 10.3389/fpsyt.2020.00764] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 07/20/2020] [Indexed: 02/06/2023] Open
Abstract
There is evidence that long-term cannabis use is associated with alterations to glutamate neurotransmission and glial function. In this study, 26 long-term cannabis users (males=65.4%) and 47 non-cannabis using healthy controls (males=44.6%) underwent proton magnetic resonance spectroscopy (1H-MRS) of the anterior cingulate cortex (ACC) in order to characterize neurometabolite alterations in cannabis users and to examine associations between neurometabolites, cannabis exposure, and cannabis use behaviors. Myo-inositol, a marker of glial function, and glutamate metabolites did not differ between healthy controls and cannabis users or cannabis users who met criteria for DSM5 cannabis use disorder (n=17). Lower myo-inositol, a putative marker of glial function, was related to greater problematic drug use (F1,22 = 11.95, p=.002; Cohen's f=0.59, large effect; Drug Abuse Screening Test) and severity of cannabis dependence (F1,22 = 6.61, p=.17; Cohen's f=0.44, large effect). Further, past-year cannabis exposure exerted different effects on glutamate and glutamate+glutamine in males and females (glutamate: F1,21 = 6.31, p=.02; glutamate+glutamine: F1,21 = 7.20, p=.014), such that greater past-year cannabis exposure was related to higher concentrations of glutamate metabolites in male cannabis users (glutamate: F1,14 = 25.94, p=.00016; Cohen's f=1.32, large effect; glutamate+glutamine: F1,14 = 23.24, p=.00027, Cohen's f=1.24, large effect) but not in female cannabis users (glutamate: F1,6 = 1.37, p=0.78; glutamate+glutamine: F1,6 = 0.001, p=.97). The present results extend existing evidence of altered glial function and glutamate metabolism with cannabis use by providing evidence linking problematic drug use behaviors with glial function as measured with myo-inositol and recent chronic cannabis exposure to alterations in glutamate metabolism. This provides novel directions for the interrogation of the impact of cannabis use on brain neurochemistry.
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Affiliation(s)
- Jeremy J Watts
- Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada.,Department of Pharmacology & Toxicology, University of Toronto, Toronto, ON, Canada
| | - Ranjini Garani
- Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada.,Department of Pharmacology & Toxicology, University of Toronto, Toronto, ON, Canada
| | - Tania Da Silva
- Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada
| | - Nittha Lalang
- Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada.,Department of Pharmacology & Toxicology, University of Toronto, Toronto, ON, Canada
| | - Sofia Chavez
- Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada.,Department of Psychiatry, University of Toronto, Toronto, ON, Canada.,Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, ON, Canada
| | - Romina Mizrahi
- Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada.,Department of Pharmacology & Toxicology, University of Toronto, Toronto, ON, Canada.,Department of Psychiatry, University of Toronto, Toronto, ON, Canada.,Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, ON, Canada
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11
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Rivera-Rivera LA, Schubert T, Johnson KM. Measurements of cerebral blood volume using quantitative susceptibility mapping, R 2 * relaxometry, and ferumoxytol-enhanced MRI. NMR IN BIOMEDICINE 2019; 32:e4175. [PMID: 31482602 PMCID: PMC6868300 DOI: 10.1002/nbm.4175] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 07/30/2019] [Accepted: 08/13/2019] [Indexed: 05/08/2023]
Abstract
Ferumoxytol-enhanced MRI holds potential for the non-invasive assessment of vascular architecture using estimates of cerebral blood volume (CBV). Ferumoxytol specifically enables steady-state imaging with extended acquisition times, for substantial improvements in resolution and contrast-to-noise ratio. With such data, quantitative susceptibility mapping (QSM) can be used to obtain images of local tissue magnetic susceptibility and hence estimate the increase in blood susceptibility after administration of a contrast agent, which in turn can be correlated to tissue CBV. Here, we explore the use of QSM for CBV estimation and compare it with R2 * (1/T2 *)-based results. Institutional review board approval was obtained, and all subjects provided written informed consent. For this prospective study, MR images were acquired on a 3.0 T scanner in 19 healthy subjects using a multiple-echo T2 *-weighted sequence. Scanning was performed before and after the administration of two doses of ferumoxytol (1 mg FE/kg and 4 mg FE/kg). Different QSM approaches were tested on numerical phantom simulations. Results showed that the accuracy of magnetic susceptibility measurements improved with increasing image resolution and decreasing vascular density. In vivo changes in magnetic susceptibility were measured after the administration of ferumoxytol utilizing QSM, and significantly higher QSM-based CBV was measured in gray matter compared with white matter. QSM- and R2 *-based CBV estimates correlated well, with similar average values, but a larger variance was found in QSM-based estimates.
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Affiliation(s)
- Leonardo A Rivera-Rivera
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, 1111 Highland Ave, Madison, WI 53705-2275, USA
| | - Tilman Schubert
- Department of Radiology and Nuclear Medicine, Basel University Hospital, Petersgraben 4, 4031 Basel, Switzerland
| | - Kevin M Johnson
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, 1111 Highland Ave, Madison, WI 53705-2275, USA
- Department of Radiology, University of Wisconsin School of Medicine and Public Health, 600 Highland Ave, Madison, WI 53705-2275, USA
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12
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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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13
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Bouhrara M, Rejimon AC, Cortina LE, Khattar N, Spencer RG. Four-angle method for practical ultra-high-resolution magnetic resonance mapping of brain longitudinal relaxation time and apparent proton density. Magn Reson Imaging 2019; 66:57-68. [PMID: 31730882 DOI: 10.1016/j.mri.2019.11.013] [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: 08/23/2019] [Revised: 11/09/2019] [Accepted: 11/10/2019] [Indexed: 10/25/2022]
Abstract
Changes in longitudinal relaxation time (T1) and proton density (PD) are sensitive indicators of microstructural alterations associated with various central nervous system diseases as well as brain maturation and aging. In this work, we introduce a new approach for rapid and accurate high-resolution (HR) or ultra HR (UHR) mapping of T1 and apparent PD (APD) of the brain with correction of radiofrequency field, B1, inhomogeneities. The four-angle method (FAM) uses four spoiled-gradient recalled-echo (SPGR) images acquired at different flip angles (FA) and short repetition times (TRs). The first two SPGR images are acquired at low-spatial resolution and used to accurately map the active B1+ field with the recently introduced steady-state double angle method (SS-DAM). The estimated B1+ map is used in conjunction with the two other SPGR images, acquired at HR or UHR, to map T1 and APD. The method is evaluated with numerical, phantom, and in-vivo imaging measurements. Furthermore, we investigated imaging acceleration methods to further shorten the acquisition time. Our results indicate that FAM provides an accurate method for simultaneous HR or UHR mapping of T1 and APD in human brain in clinical high-field MRI. Derived parameter maps without B1+correction suffer from large inaccuracies, but this issue is well-corrected through use of the SS-DAM. Furthermore, the use of SPGR imaging with short TR and phased-array coil acquisition permits substantial imaging acceleration and enables robust HR or UHR T1 and APD mapping in a clinically acceptable time frame, with whole brain coverage obtained in less than 2 min or 5 min, respectively. The method exhibits high reproducibility and benefits from the use of the conventional SPGR sequence, available in all preclinical and clinical MRI machines, and very simple modeling to address a critical outstanding issue in neuroimaging.
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Affiliation(s)
- Mustapha Bouhrara
- Laboratory of Clinical Investigation, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA.
| | - Abinand C Rejimon
- Laboratory of Clinical Investigation, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
| | - Luis E Cortina
- Laboratory of Clinical Investigation, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
| | - Nikkita Khattar
- Laboratory of Clinical Investigation, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
| | - Richard G Spencer
- Laboratory of Clinical Investigation, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
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14
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Taylor AJ, Kim JH, Singh V, Halfen EJ, Pfeuffer J, Ress D. More than BOLD: Dual-spin populations create functional contrast. Magn Reson Med 2019; 83:681-694. [PMID: 31423634 DOI: 10.1002/mrm.27941] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 07/16/2019] [Accepted: 07/21/2019] [Indexed: 11/06/2022]
Abstract
PURPOSE Functional MRI contrast has generally been associated with changes in transverse relaxivity caused by blood oxygen concentration, the so-called blood oxygen level dependent contrast. However, this interpretation of fMRI contrast has been called into question by several recent experiments at high spatial resolution. Experiments were conducted to examine contrast dependencies that cannot be explained only by differences in relaxivity in a single-spin population. METHODS Measurements of functional signal and contrast were obtained in human early visual cortex during a high-contrast visual stimulation over a large range of TEs and for several flip angles. Small voxels (1.5 mm) were used to restrict the measurements to cortical gray matter in early visual areas identified using retinotopic mapping procedures. RESULTS Measurements were consistent with models that include 2 spin populations. The dominant population has a relatively short transverse lifetime that is strongly modulated by activation. However, functional contrast is also affected by volume changes between this short-lived population and the longer-lived population. CONCLUSION Some of the previously observed "nonclassical" behaviors of functional contrast can be explained by these interacting dual-spin populations.
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Affiliation(s)
- Amanda J Taylor
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas
| | - Jung H Kim
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas
| | | | | | - Josef Pfeuffer
- Siemens Healthcare, Application Development, Erlangen, Germany
| | - David Ress
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas
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15
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He D, Fan X, Chatterjee A, Wang S, Medved M, Pineda FD, Yousuf A, Antic T, Oto A, Karczmar GS. A compact solution for estimation of physiological parameters from ultrafast prostate dynamic contrast enhanced MRI. Phys Med Biol 2019; 64:155012. [PMID: 31220816 PMCID: PMC7227457 DOI: 10.1088/1361-6560/ab2b62] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The Tofts pharmacokinetic model requires multiple calculations for analysis of dynamic contrast enhanced (DCE) MRI. In addition, the Tofts model may not be appropriate for the prostate. This can result in error propagation that reduces the accuracy of pharmacokinetic measurements. In this study, we present a compact solution allowing estimation of physiological parameters K trans and v e from ultrafast DCE acquisitions, without fitting DCE-MRI data to the standard Tofts pharmacokinetic model. Since the standard Tofts model can be simplified to the Patlak model at early times when contrast efflux from the extravascular extracellular space back to plasma is negligible, K trans can be solved explicitly for a specific time. Further, v e can be estimated directly from the late steady-state signal using the derivative form of Tofts model. Ultrafast DCE-MRI data were acquired from 18 prostate cancer patients on a Philips Achieva 3T-TX scanner. Regions-of-interest (ROIs) for prostate cancer, normal tissue, gluteal muscle, and iliac artery were manually traced. The contrast media concentration as function of time was calculated over each ROI using gradient echo signal equation with pre-contrast tissue T1 values, and using the 'reference tissue' model with a linear approximation. There was strong correlation (r = 0.88-0.91, p < 0.0001) between K trans extracted from the Tofts model and K trans estimated from the compact solution for prostate cancer and normal tissue. Additionally, there was moderate correlation (r = 0.65-0.73, p < 0.0001) between extracted versus estimated v e. Bland-Altman analysis showed moderate to good agreement between physiological parameters extracted from the Tofts model and those estimated from the compact solution with absolute bias less than 0.20 min-1 and 0.10 for K trans and v e, respectively. The compact solution may decrease systematic errors and error propagation, and could increase the efficiency of clinical workflow. The compact solution requires high temporal resolution DCE-MRI due to the need to adequately sample the early phase of contrast media uptake.
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Affiliation(s)
- Dianning He
- College of Medicine and Biological Information Engineering, Northeastern University, Shenyang, People’s Republic of China,Department of Radiology, University of Chicago, Chicago, IL 60637, United States of America
| | - Xiaobing Fan
- Department of Radiology, University of Chicago, Chicago, IL 60637, United States of America
| | - Aritrick Chatterjee
- Department of Radiology, University of Chicago, Chicago, IL 60637, United States of America
| | - Shiyang Wang
- Department of Radiology, University of Chicago, Chicago, IL 60637, United States of America
| | - Milica Medved
- Department of Radiology, University of Chicago, Chicago, IL 60637, United States of America
| | - Federico D Pineda
- Department of Radiology, University of Chicago, Chicago, IL 60637, United States of America
| | - Ambereen Yousuf
- Department of Radiology, University of Chicago, Chicago, IL 60637, United States of America
| | - Tatjana Antic
- Department of Pathology, University of Chicago, Chicago, IL 60637, United States of America
| | - Aytekin Oto
- Department of Radiology, University of Chicago, Chicago, IL 60637, United States of America
| | - Gregory S Karczmar
- Department of Radiology, University of Chicago, Chicago, IL 60637, United States of America,Author to whom any correspondence should be addressed.
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16
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Smaragdi A, Chavez S, Lobaugh NJ, Meyer JH, Kolla NJ. Differential levels of prefrontal cortex glutamate+glutamine in adults with antisocial personality disorder and bipolar disorder: A proton magnetic resonance spectroscopy study. Prog Neuropsychopharmacol Biol Psychiatry 2019; 93:250-255. [PMID: 30959086 DOI: 10.1016/j.pnpbp.2019.04.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 03/20/2019] [Accepted: 04/03/2019] [Indexed: 02/06/2023]
Abstract
As the main excitatory neurotransmitter in the central nervous system, glutamate, as measured in combination with glutamine (Glx), is implicated in several psychopathologies when levels are aberrant. One illness that shows heightened Glx levels is bipolar disorder (BD), an illness characterized by high impulsivity. In addition, although animal studies have reported elevated levels of Glx in aggressive and impulsive phenotypes, no study, to our knowledge, has reported Glx in the human cortex in relation to aggression. Here, we addressed the question of whether elevated levels of Glx would be present in patients with BD and antisocial personality disorder (ASPD), a condition associated with aggression and, like BD, also presents high impulsivity. We recruited individuals with ASPD (n = 18), individuals with BD (n = 16), and a healthy control group (n = 24). We used proton magnetic resonance spectroscopy to measure relative neurometabolite concentrations in the left dorsolateral prefrontal cortex (dlPFC) and supra-genual anterior cingulate cortex (ACC), two brain regions associated with impulsivity and behavior control. We found significantly elevated levels of Glx in the ASPD group relative to the BD and healthy control groups in the dlPFC (p = .014), and a positive correlation between Glx levels and aggression in the dlPFC in the ASPD group alone (r = .59, p = .026). These findings suggest a link between aggression in ASPD and Glx levels.
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Affiliation(s)
- Areti Smaragdi
- Research Imaging Centre, Campbell Family Mental Health Research Institute, and Centre for Addiction and Mental Health (CAMH), Toronto, ON, Canada; Violence Prevention Neurobiological Research Unit, Forensic Psychiatry, CAMH, Toronto, ON, Canada; Child Development Institute, Toronto, ON, Canada
| | - Sofia Chavez
- Research Imaging Centre, Campbell Family Mental Health Research Institute, and Centre for Addiction and Mental Health (CAMH), Toronto, ON, Canada; Faculty of Medicine, Department of Psychiatry, University of Toronto, Toronto, ON, Canada
| | - Nancy J Lobaugh
- Research Imaging Centre, Campbell Family Mental Health Research Institute, and Centre for Addiction and Mental Health (CAMH), Toronto, ON, Canada; Faculty of Medicine, Department of Medicine, Division of Neurology, University of Toronto, Toronto, ON, Canada
| | - Jeffrey H Meyer
- Research Imaging Centre, Campbell Family Mental Health Research Institute, and Centre for Addiction and Mental Health (CAMH), Toronto, ON, Canada; Faculty of Medicine, Department of Psychiatry, University of Toronto, Toronto, ON, Canada
| | - Nathan J Kolla
- Research Imaging Centre, Campbell Family Mental Health Research Institute, and Centre for Addiction and Mental Health (CAMH), Toronto, ON, Canada; Violence Prevention Neurobiological Research Unit, Forensic Psychiatry, CAMH, Toronto, ON, Canada; Faculty of Medicine, Department of Psychiatry, University of Toronto, Toronto, ON, Canada; Faculty of Arts and Science, Department of Criminology and Sociological Studies, University of Toronto, Toronto, ON, Canada; Waypoint Centre for Mental Health Care, Penetanguishene, ON, Canada.
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17
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Ma YJ, Zhao W, Wan L, Guo T, Searleman A, Jang H, Chang EY, Du J. Whole knee joint T 1 values measured in vivo at 3T by combined 3D ultrashort echo time cones actual flip angle and variable flip angle methods. Magn Reson Med 2019; 81:1634-1644. [PMID: 30443925 PMCID: PMC6347520 DOI: 10.1002/mrm.27510] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 07/06/2018] [Accepted: 08/07/2018] [Indexed: 02/06/2023]
Abstract
PURPOSE To measure T1 relaxations for the major tissues in whole knee joints on a clinical 3T scanner. METHODS The 3D UTE-Cones actual flip angle imaging (AFI) method was used to map the transmission radiofrequency field (B1 ) in both short and long T2 tissues, which was then used to correct the 3D UTE-Cones variable flip angle (VFA) fitting to generate accurate T1 maps. Numerical simulation was carried out to investigate the accuracy of T1 measurement for a range of T2 values, excitation pulse durations, and B1 errors. Then, the 3D UTE-Cones AFI-VFA method was applied to healthy volunteers (N = 16) to quantify the T1 of knee tissues including cartilage, meniscus, quadriceps tendon, patellar tendon, anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), marrow, and muscles at 3T. RESULTS Numerical simulation showed that the 3D UTE-Cones AFI-VFA technique can provide accurate T1 measurements (error <1%) when the tissue T2 is longer than 1 ms and a 150 μs excitation RF pulse is used and therefore is suitable for most knee joint tissues. The proposed 3D UTE-Cones AFI-VFA method showed an average T1 of 1098 ± 67 ms for cartilage, 833 ± 47 ms for meniscus, 800 ± 66 ms for quadriceps tendon, 656 ± 43 ms for patellar tendon, 873 ± 38 ms for ACL, 832 ± 49 ms for PCL, 379 ± 18 ms for marrow, and 1393 ± 46 ms for muscles. CONCLUSION The 3D UTE-Cones AFI-VFA method allows volumetric T1 measurement of the major tissues in whole knee joints on a clinical 3T scanner.
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Affiliation(s)
- Ya-Jun Ma
- Department of Radiology, University of California, San Diego, CA
| | - Wei Zhao
- Department of Radiology, University of California, San Diego, CA
| | - Lidi Wan
- Department of Radiology, University of California, San Diego, CA
| | - Tan Guo
- Department of Radiology, University of California, San Diego, CA
| | - Adam Searleman
- Department of Radiology, University of California, San Diego, CA
| | - Hyungseok Jang
- Department of Radiology, University of California, San Diego, CA
| | - Eric Y Chang
- Department of Radiology, University of California, San Diego, CA
- Radiology Service, VA San Diego Healthcare System, San Diego, CA
| | - Jiang Du
- Department of Radiology, University of California, San Diego, CA
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18
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Rivera-Rivera LA, Johnson KM, Turski PA, Wieben O, Schubert T. Measurement of microvascular cerebral blood volume changes over the cardiac cycle with ferumoxytol-enhanced T 2 * MRI. Magn Reson Med 2019; 81:3588-3598. [PMID: 30756424 DOI: 10.1002/mrm.27670] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Revised: 12/28/2018] [Accepted: 01/04/2019] [Indexed: 12/24/2022]
Abstract
PURPOSE This feasibility study investigates the non-invasive measurement of microvascular cerebral blood volume (BV) changes over the cardiac cycle using cardiac-gated, ferumoxytol-enhanced T 2 ∗ MRI. METHODS Institutional review board approval was obtained and all subjects provided written informed consent. Cardiac gated MR scans were prospectively acquired on a 3.0T scanner in 22 healthy subjects using T 2 ∗ -weighted sequences with 2D-EPI and 3D spiral trajectories. Images were collected before and after the intravenous administration of 2 doses of ferumoxytol (1 mg FE/kg and 4 mg FE/kg). Cardiac cycle-induced R 2 ∗ (1/ T 2 ∗ ) changes (Δ R 2 ∗ ) and BV changes (ΔBV) throughout the cardiac cycle in gray matter (GM) and white matter (WM) were quantified and differences assessed using ANOVA followed by post hoc analysis. RESULTS Δ R 2 ∗ was found to increase in a dose-dependent fashion. A significantly larger increase was observed in GM compared to WM in both 2D and 3D acquisitions (P < 0.050). In addition, Δ R 2 ∗ increased significantly (P < 0.001) post versus pre-contrast injection in GM in both T 2 ∗ MRI acquisitions. Mean GM Δ R 2 ∗ derived from 2D-EPI images was 0.14 ± 0.06 s-1 pre-contrast and 0.33 ± 0.13 s-1 after 5 mg FE/kg. In WM, Δ R 2 ∗ was 0.19 ± 0.06 s-1 pre-contrast, and 0.23 ± 0.06 s-1 after 5 mg FE/kg. The fractional changes in BV throughout the cardiac cycle were 0.031 ± 0.019% in GM and 0.011 ± 0.008% in WM (P < 0.001) after 5 mg FE/kg. CONCLUSION Cardiac-gated, ferumoxytol-enhanced T 2 ∗ MRI enables characterization of microvascular BV changes throughout the cardiac cycle in GM and WM tissue of healthy subjects.
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Affiliation(s)
- Leonardo A Rivera-Rivera
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
| | - Kevin M Johnson
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin.,Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
| | - Patrick A Turski
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin.,Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
| | - Oliver Wieben
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin.,Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
| | - Tilman Schubert
- Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin.,Department of Radiology and Nuclear Medicine, Basel University Hospital, Petersgraben 4, 4031, Basel, Switzerland
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19
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Ramos-Llorden G, Vegas-Sanchez-Ferrero G, Bjork M, Vanhevel F, Parizel PM, San Jose Estepar R, den Dekker AJ, Sijbers J. NOVIFAST: A Fast Algorithm for Accurate and Precise VFA MRI Mapping. IEEE TRANSACTIONS ON MEDICAL IMAGING 2018; 37:2414-2427. [PMID: 29993537 PMCID: PMC6277233 DOI: 10.1109/tmi.2018.2833288] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In quantitative magnetic resonance mapping, the variable flip angle (VFA) steady state spoiled gradient recalled echo (SPGR) imaging technique is popular as it provides a series of high resolution weighted images in a clinically feasible time. Fast, linear methods that estimate maps from these weighted images have been proposed, such as DESPOT1 and iterative re-weighted linear least squares. More accurate, non-linear least squares (NLLS) estimators are in play, but these are generally much slower and require careful initialization. In this paper, we present NOVIFAST, a novel NLLS-based algorithm specifically tailored to VFA SPGR mapping. By exploiting the particular structure of the SPGR model, a computationally efficient, yet accurate and precise map estimator is derived. Simulation and in vivo human brain experiments demonstrate a twenty-fold speed gain of NOVIFAST compared with conventional gradient-based NLLS estimators while maintaining a high precision and accuracy. Moreover, NOVIFAST is eight times faster than the efficient implementations of the variable projection (VARPRO) method. Furthermore, NOVIFAST is shown to be robust against initialization.
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20
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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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21
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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: 38] [Impact Index Per Article: 6.3] [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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22
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Ma YJ, Lu X, Carl M, Zhu Y, Szeverenyi NM, Bydder GM, Chang EY, Du J. Accurate T 1 mapping of short T 2 tissues using a three-dimensional ultrashort echo time cones actual flip angle imaging-variable repetition time (3D UTE-Cones AFI-VTR) method. Magn Reson Med 2018; 80:598-608. [PMID: 29314235 PMCID: PMC5912804 DOI: 10.1002/mrm.27066] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 11/14/2017] [Accepted: 12/11/2017] [Indexed: 02/04/2023]
Abstract
PURPOSE To develop an accurate T1 measurement method for short T2 tissues using a combination of a 3-dimensional ultrashort echo time cones actual flip angle imaging technique and a variable repetition time technique (3D UTE-Cones AFI-VTR) on a clinical 3T scanner. METHODS First, the longitudinal magnetization mapping function of the excitation pulse was obtained with the 3D UTE-Cones AFI method, which provided information about excitation efficiency and B1 inhomogeneity. Then, the derived mapping function was substituted into the VTR fitting to generate accurate T1 maps. Numerical simulation and phantom studies were carried out to compare the AFI-VTR method with a B1 -uncorrected VTR method, a B1 -uncorrected variable flip angle (VFA) method, and a B1 -corrected VFA method. Finally, the 3D UTE-Cones AFI-VTR method was applied to bovine bone samples (N = 6) and healthy volunteers (N = 3) to quantify the T1 of cortical bone. RESULTS Numerical simulation and phantom studies showed that the 3D UTE-Cones AFI-VTR technique provides more accurate measurement of the T1 of short T2 tissues than the B1 -uncorrected VTR and VFA methods or the B1 -corrected VFA method. The proposed 3D UTE-Cones AFI-VTR method showed a mean T1 of 240 ± 25 ms for bovine cortical bone and 218 ± 10 ms for the tibial midshaft of human volunteers, respectively, at 3 T. CONCLUSION The 3D UTE-Cones AFI-VTR method can provide accurate T1 measurements of short T2 tissues such as cortical bone. Magn Reson Med 80:598-608, 2018. © 2018 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Ya-Jun Ma
- Department of Radiology, University of California, San Diego, CA
| | - Xing Lu
- Department of Radiology, University of California, San Diego, CA
| | | | - Yanchun Zhu
- Department of Radiology, University of California, San Diego, CA
| | | | - Graeme M Bydder
- Department of Radiology, University of California, San Diego, CA
| | - Eric Y Chang
- Department of Radiology, University of California, San Diego, CA
- Radiology Service, VA San Diego Healthcare System, San Diego, CA
| | - Jiang Du
- Department of Radiology, University of California, San Diego, CA
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23
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Mazor G, Weizman L, Tal A, Eldar YC. Low-rank magnetic resonance fingerprinting. Med Phys 2018; 45:4066-4084. [PMID: 29972693 DOI: 10.1002/mp.13078] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 04/24/2018] [Accepted: 05/23/2018] [Indexed: 02/28/2024] Open
Abstract
PURPOSE Magnetic resonance fingerprinting (MRF) is a relatively new approach that provides quantitative MRI measures using randomized acquisition. Extraction of physical quantitative tissue parameters is performed offline, without the need of patient presence, based on acquisition with varying parameters and a dictionary generated according to the Bloch equation simulations. MRF uses hundreds of radio frequency (RF) excitation pulses for acquisition, and therefore, a high undersampling ratio in the sampling domain (k-space) is required for reasonable scanning time. This undersampling causes spatial artifacts that hamper the ability to accurately estimate the tissue's quantitative values. In this work, we introduce a new approach for quantitative MRI using MRF, called magnetic resonance fingerprinting with low rank (FLOR). METHODS We exploit the low-rank property of the concatenated temporal imaging contrasts, on top of the fact that the MRF signal is sparsely represented in the generated dictionary domain. We present an iterative recovery scheme that consists of a gradient step followed by a low-rank projection using the singular value decomposition. RESULTS Experimental results consist of retrospective sampling that allows comparison to a well defined reference, and prospective sampling that shows the performance of FLOR for a real-data sampling scenario. Both experiments demonstrate improved parameter accuracy compared to other compressed-sensing and low-rank based methods for MRF at 5% and 9% sampling ratios for the retrospective and prospective experiments, respectively. CONCLUSIONS We have shown through retrospective and prospective experiments that by exploiting the low-rank nature of the MRF signal, FLOR recovers the MRF temporal undersampled images and provides more accurate parameter maps compared to previous iterative approaches.
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Affiliation(s)
- Gal Mazor
- Department of Electrical Engineering, Technion - Israel Institute of Technology, Haifa, Israel
| | - Lior Weizman
- Department of Electrical Engineering, Technion - Israel Institute of Technology, Haifa, Israel
| | - Assaf Tal
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Yonina C Eldar
- Department of Electrical Engineering, Technion - Israel Institute of Technology, Haifa, Israel
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24
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Ma D, Jiang Y, Chen Y, McGivney D, Mehta B, Gulani V, Griswold M. Fast 3D magnetic resonance fingerprinting for a whole-brain coverage. Magn Reson Med 2018; 79:2190-2197. [PMID: 28833436 PMCID: PMC5868964 DOI: 10.1002/mrm.26886] [Citation(s) in RCA: 103] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 07/19/2017] [Accepted: 08/03/2017] [Indexed: 12/24/2022]
Abstract
PURPOSE The purpose of this study was to accelerate the acquisition and reconstruction time of 3D magnetic resonance fingerprinting scans. METHODS A 3D magnetic resonance fingerprinting scan was accelerated by using a single-shot spiral trajectory with an undersampling factor of 48 in the x-y plane, and an interleaved sampling pattern with an undersampling factor of 3 through plane. Further acceleration came from reducing the waiting time between neighboring partitions. The reconstruction time was accelerated by applying singular value decomposition compression in k-space. Finally, a 3D premeasured B1 map was used to correct for the B1 inhomogeneity. RESULTS The T1 and T2 values of the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology MRI phantom showed a good agreement with the standard values, with an average concordance correlation coefficient of 0.99, and coefficient of variation of 7% in the repeatability scans. The results from in vivo scans also showed high image quality in both transverse and coronal views. CONCLUSIONS This study applied a fast acquisition scheme for a fully quantitative 3D magnetic resonance fingerprinting scan with a total acceleration factor of 144 as compared with the Nyquist rate, such that 3D T1 , T2 , and proton density maps can be acquired with whole-brain coverage at clinical resolution in less than 5 min. Magn Reson Med 79:2190-2197, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Dan Ma
- Department of Radiology, Case Western Reserve University, Cleveland, OH
| | - Yun Jiang
- Department of Radiology, Case Western Reserve University, Cleveland, OH
| | - Yong Chen
- Department of Radiology, Case Western Reserve University, Cleveland, OH
| | - Debra McGivney
- Department of Radiology, Case Western Reserve University, Cleveland, OH
| | - Bhairav Mehta
- Department of Radiology, Case Western Reserve University, Cleveland, OH
| | - Vikas Gulani
- Department of Radiology, Case Western Reserve University, Cleveland, OH
| | - Mark Griswold
- Department of Radiology, Case Western Reserve University, Cleveland, OH
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25
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Rivera-Rivera LA, Schubert T, Knobloch G, Turski PA, Wieben O, Reeder SB, Johnson KM. Comparison of ferumoxytol-based cerebral blood volume estimates using quantitative R 1 and R2* relaxometry. Magn Reson Med 2017; 79:3072-3081. [PMID: 29096054 DOI: 10.1002/mrm.26975] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Revised: 08/24/2017] [Accepted: 09/28/2017] [Indexed: 12/11/2022]
Abstract
PURPOSE Cerebral perfusion is commonly assessed clinically with dynamic susceptibility contrast MRI using a bolus injection of gadolinium-based contrast agents, resulting in semi-quantitative values of cerebral blood volume (CBV). Steady-state imaging with ferumoxytol allows estimation of CBV with the potential for higher precision and accuracy. Prior CBV studies have focused on the signal disrupting T2* effects, but ferumoxytol also has high signal-enhancing T1 relaxivity. The purpose of this study was to investigate and compare CBV estimation using T1 and T2*, with the goal of understanding the contrast mechanisms and quantitative differences. METHODS Changes in R1 (1/T1 ) and R2* (1/ T2*) were measured after the administration of ferumoxytol using high-resolution quantitative approaches. Images were acquired at 3.0T and R1 was estimated from an ultrashort echo time variable flip angle approach, while R2* was estimated from a multiple gradient echo sequence. Twenty healthy volunteers were imaged at two doses. CBV was derived and compared from relaxometry in gray and white matter using different approaches. RESULTS R1 measurements showed a linear dependence of blood R1 with respect to dose in large vessels, in contrast to the nonlinear dose-dependence of blood R2* estimates. In the brain parenchyma, R2* showed linear dose-dependency whereas R1 showed nonlinearity. CBV calculations based on R2* changes in tissue and ferumoxytol blood concentration estimates based on R1 relaxivity showed the lowest variability in our cohort. CONCLUSIONS CBV measurements were successfully derived using a combined approach of R1 and R2* relaxometry. Magn Reson Med 79:3072-3081, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Leonardo A Rivera-Rivera
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Tilman Schubert
- Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
- Clinic of Radiology and Nuclear Medicine, Basel University Hospital, Basel, Switzerland
| | - Gesine Knobloch
- Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
- Departments of Biomedical Engineering, Medicine and Emergency Medicine, University of Wisconsin, Madison, Wisconsin, USA
| | - Patrick A Turski
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
- Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Oliver Wieben
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
- Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Scott B Reeder
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
- Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
- Departments of Biomedical Engineering, Medicine and Emergency Medicine, University of Wisconsin, Madison, Wisconsin, USA
| | - Kevin M Johnson
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
- Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
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26
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Wang Y, Chen Y, Wu D, Wang Y, Sethi SK, Yang G, Xie H, Xia S, Haacke EM. STrategically Acquired Gradient Echo (STAGE) imaging, part II: Correcting for RF inhomogeneities in estimating T1 and proton density. Magn Reson Imaging 2017; 46:140-150. [PMID: 29061370 DOI: 10.1016/j.mri.2017.10.006] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 10/16/2017] [Accepted: 10/18/2017] [Indexed: 11/19/2022]
Abstract
PURPOSE To develop a method for mapping the B1 transmit (B1t) and B1 receive (B1r) fields from two gradient echo datasets each with a different flip angle and from these two images obtain accurate T1 and proton density (PD) maps of the brain. METHODS A strategically acquired gradient echo (STAGE) data set is collected using two flip angles each with multiple echoes. The B1t field extraction was based on forcing cortical gray matter and white matter to have specific T1 values and fitting the resulting B1t field to a quadratic function. The B1r field extraction was based on synthesizing isointense images despite there being two or three tissue types present in the brain. This method was tested on 10 healthy volunteers and 20 stroke patients from data acquired at 3.0Tesla. RESULTS With the knowledge of the B1t and B1r fields, the uniformity of tissue T1 and PD maps was considerably improved. T1 values were measured for both the midbrain and basal ganglia and found to be in good agreement with the literature. DISCUSSION AND CONCLUSIONS STAGE provides a practical way to assess the B1t and the B1r fields which can then be used to correct for spatial variations in the images.
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Affiliation(s)
- Yu Wang
- Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai, China
| | - Yongsheng Chen
- Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang, China; The MRI Institute for Biomedical Research, Detroit, MI, USA; Department of Radiology, School of Medicine, Wayne State University, Detroit, MI, USA
| | - Dongmei Wu
- Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai, China
| | - Ying Wang
- Department of Biomedical Engineering, Wayne State University, Detroit, MI 48201, USA
| | - Sean K Sethi
- The MRI Institute for Biomedical Research, Detroit, MI, USA; Magnetic Resonance Innovations, Inc., Detroit, MI 48202, USA
| | - Guang Yang
- Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai, China
| | - Haibin Xie
- Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai, China
| | - Shuang Xia
- Tianjin First Central Hospital, Tianjin, China
| | - E Mark Haacke
- Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai, China; Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang, China; The MRI Institute for Biomedical Research, Detroit, MI, USA; Department of Radiology, School of Medicine, Wayne State University, Detroit, MI, USA; Department of Biomedical Engineering, Wayne State University, Detroit, MI 48201, USA; Magnetic Resonance Innovations, Inc., Detroit, MI 48202, USA.
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27
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Lankford CL, Does MD. Propagation of error from parameter constraints in quantitative MRI: Example application of multiple spin echo T 2 mapping. Magn Reson Med 2017; 79:673-682. [PMID: 28426147 DOI: 10.1002/mrm.26713] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 03/21/2017] [Accepted: 03/23/2017] [Indexed: 12/20/2022]
Abstract
PURPOSE Quantitative MRI may require correcting for nuisance parameters which can or must be constrained to independently measured or assumed values. The noise and/or bias in these constraints propagate to fitted parameters. For example, the case of refocusing pulse flip angle constraint in multiple spin echo T2 mapping is explored. METHODS An analytical expression for the mean-squared error of a parameter of interest was derived as a function of the accuracy and precision of an independent estimate of a nuisance parameter. The expression was validated by simulations and then used to evaluate the effects of flip angle (θ) constraint on the accuracy and precision of T⁁2 for a variety of multi-echo T2 mapping protocols. RESULTS Constraining θ improved T⁁2 precision when the θ-map signal-to-noise ratio was greater than approximately one-half that of the first spin echo image. For many practical scenarios, constrained fitting was calculated to reduce not just the variance but the full mean-squared error of T⁁2, for bias in θ⁁≲6%. CONCLUSION The analytical expression derived in this work can be applied to inform experimental design in quantitative MRI. The example application to T2 mapping provided specific cases, depending on θ⁁ accuracy and precision, in which θ⁁ measurement and constraint would be beneficial to T⁁2 variance or mean-squared error. Magn Reson Med 79:673-682, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Christopher L Lankford
- Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.,Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA
| | - Mark D Does
- Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.,Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA.,Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA.,Electrical Engineering, Vanderbilt University, Nashville, Tennessee, USA
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28
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Tisdall MD. Bias and SNR of T1 estimates derived from joint fitting of actual flip-angle and FLASH imaging data with variable flip angles. PROCEEDINGS OF THE INTERNATIONAL SOCIETY FOR MAGNETIC RESONANCE IN MEDICINE ... SCIENTIFIC MEETING AND EXHIBITION. INTERNATIONAL SOCIETY FOR MAGNETIC RESONANCE IN MEDICINE. SCIENTIFIC MEETING AND EXHIBITION 2017; 25:1445. [PMID: 29643746 PMCID: PMC5891138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Previous work has suggested fitting joint AFI/FLASH data for T1 and B1+ by minimizing the 2-norm of the difference between the signal model and measurements will produce unbiased estimates of T1. We demonstrate that, contrary to previous results, the estimator has a substantial bias that varies with both the true T1 and B1+, and the receive channel count. We also demonstrate that the correct ML estimator removes the effect of channel count, and that the choice of AFI protocol has a larger impact of the quality of estimates than the addition of an extra FLASH scan.
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Affiliation(s)
- M Dylan Tisdall
- Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
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29
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Ma D, Coppo S, Chen Y, McGivney DF, Jiang Y, Pahwa S, Gulani V, Griswold MA. Slice profile and B 1 corrections in 2D magnetic resonance fingerprinting. Magn Reson Med 2017; 78:1781-1789. [PMID: 28074530 DOI: 10.1002/mrm.26580] [Citation(s) in RCA: 125] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 11/17/2016] [Accepted: 11/21/2016] [Indexed: 11/12/2022]
Abstract
PURPOSE The goal of this study is to characterize and improve the accuracy of 2D magnetic resonance fingerprinting (MRF) scans in the presence of slice profile (SP) and B1 imperfections, which are two main factors that affect quantitative results in MRF. METHODS The SP and B1 imperfections are characterized and corrected separately. The SP effect is corrected by simulating the radiofrequency pulse in the dictionary, and the B1 is corrected by acquiring a B1 map using the Bloch-Siegert method before each scan. The accuracy, precision, and repeatability of the proposed method are evaluated in phantom studies. The effects of both SP and B1 imperfections are also illustrated and corrected in the in vivo studies. RESULTS The SP and B1 corrections improve the accuracy of the T1 and T2 values, independent of the shape of the radiofrequency pulse. The T1 and T2 values obtained from different excitation patterns become more consistent after corrections, which leads to an improvement of the robustness of the MRF design. CONCLUSION This study demonstrates that MRF is sensitive to both SP and B1 effects, and that corrections can be made to improve the accuracy of MRF with only a 2-s increase in acquisition time. Magn Reson Med 78:1781-1789, 2017. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Dan Ma
- Department of Radiology, Case Western Reserve University, Cleveland, Ohio, USA
| | - Simone Coppo
- Department of Radiology, Case Western Reserve University, Cleveland, Ohio, USA
| | - Yong Chen
- Department of Radiology, Case Western Reserve University, Cleveland, Ohio, USA
| | - Debra F McGivney
- Department of Radiology, Case Western Reserve University, Cleveland, Ohio, USA
| | - Yun Jiang
- Biomedical Engineering Department, Case Western Reserve University, Cleveland, Ohio, USA
| | - Shivani Pahwa
- Department of Radiology, Case Western Reserve University, Cleveland, Ohio, USA
| | - Vikas Gulani
- Department of Radiology, Case Western Reserve University, Cleveland, Ohio, USA
| | - Mark A Griswold
- Department of Radiology, Case Western Reserve University, Cleveland, Ohio, USA
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30
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Lewis CM, Hurley SA, Meyerand ME, Koay CG. Data-driven optimized flip angle selection for T1 estimation from spoiled gradient echo acquisitions. Magn Reson Med 2015; 76:792-802. [PMID: 26361720 DOI: 10.1002/mrm.25920] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Revised: 08/12/2015] [Accepted: 08/14/2015] [Indexed: 11/06/2022]
Abstract
PURPOSE Define criteria for selection of optimal flip angle sets for T1 estimation and evaluate effects on T1 mapping. THEORY AND METHODS Flip angle sets for spoiled gradient echo-based T1 mapping were selected by minimizing T1 estimate variance weighted by the joint density of M0 and T1 in an initial acquisition. The effect of optimized flip angle selection on T1 estimate error was measured using simulations and experimental data in the human and rat brain. RESULTS For two-point acquisitions, optimized angle sets were similar to those proposed by other groups and, therefore, performed similarly. For multipoint acquisitions, optimal angle sets for T1 mapping in the brain consisted of a repetition of two angles. Implementation of optimal angles reduced T1 estimate variance by 30-40% compared with a multipoint acquisition using a range of angles. Performance of the optimal angle set was equivalent to that of a repetition of the two-angle set selected using criteria proposed by other researchers. CONCLUSION Repetition of two carefully selected flip angles notably improves the precision of resulting T1 estimates compared with acquisitions using a range of flip angles. This work provides a flexible and widely applicable optimization method of particular use for those who repeatedly perform T1 estimation. Magn Reson Med 76:792-802, 2016. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Christina M Lewis
- Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Samuel A Hurley
- Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - M Elizabeth Meyerand
- Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA.,Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Cheng Guan Koay
- Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA
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31
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Dokumaci AS, Pouymayou B, Kreis R, Boesch C. Motion-insensitive determination of B1+ amplitudes based on the bloch-siegert shift in single voxels of moving organs including the human heart. Magn Reson Med 2015; 75:1867-74. [PMID: 26185908 DOI: 10.1002/mrm.25763] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Revised: 04/10/2015] [Accepted: 04/15/2015] [Indexed: 11/08/2022]
Abstract
PURPOSE To reliably determine the amplitude of the transmit radiofrequency ( B1+) field in moving organs like the liver and heart, where most current techniques are usually not feasible. METHODS B1+ field measurement based on the Bloch-Siegert shift induced by a pair of Fermi pulses in a double-triggered modified Point RESolved Spectroscopy (PRESS) sequence with motion-compensated crusher gradients has been developed. Performance of the sequence was tested in moving phantoms and in muscle, liver, and heart of six healthy volunteers each, using different arrangements of transmit/receive coils. RESULTS B1+ determination in a moving phantom was almost independent of type and amplitude of the motion and agreed well with theory. In vivo, repeated measurements led to very small coefficients of variance (CV) if the amplitude of the Fermi pulse was chosen above an appropriate level (CV in muscle 0.6%, liver 1.6%, heart 2.3% with moderate amplitude of the Fermi pulses and 1.2% with stronger Fermi pulses). CONCLUSION The proposed sequence shows a very robust determination of B1+ in a single voxel even under challenging conditions (transmission with a surface coil or measurements in the heart without breath-hold).
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Affiliation(s)
- Ayse Sila Dokumaci
- Department of Clinical Research and Department of Radiology, University of Bern, Switzerland
| | - Bertrand Pouymayou
- Department of Clinical Research and Department of Radiology, University of Bern, Switzerland
| | - Roland Kreis
- Department of Clinical Research and Department of Radiology, University of Bern, Switzerland
| | - Chris Boesch
- Department of Clinical Research and Department of Radiology, University of Bern, Switzerland
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32
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Pineda FD, Medved M, Fan X, Karczmar GS. B1 and T1 mapping of the breast with a reference tissue method. Magn Reson Med 2015; 75:1565-73. [PMID: 26014575 DOI: 10.1002/mrm.25751] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Revised: 03/20/2015] [Accepted: 04/03/2015] [Indexed: 11/07/2022]
Abstract
PURPOSE To develop a method for mapping the B1 field using a reference signal from a tissue with known T1. METHODS Flip angle correction factors were calculated in a region with a known "gold standard" T1; by comparing T1 values from a variable flip angle (VFA) sequence to the "gold standard" and correcting the value of the Ernst angle. The resulting partial B1 map was interpolated for all other regions. In the breast, fat is an ideal reference tissue because its T1 is spatially homogeneous and interpatient variability is low. This method was tested with scans of phantoms and patients (n = 4) on a 3T magnet. The performance of the method was evaluated by comparing the results of VFA T1 mapping with and without B1 correction to inversion recovery (IR) T1 maps. RESULTS Phantom data determined that a linear inverse distance weighted interpolation accurately recovered the full B1 map. Use of interpolated maps to correct the VFA data in vivo, reduced the average difference in the T1 of parenchyma between VFA and IR results from 58% to 8%. CONCLUSION This proof-of-principle study showed that it is possible to recover a full and accurate map of the B1 field in the breast by using a reference tissue (fat) with an accurately measured T1.
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Affiliation(s)
- Federico D Pineda
- Department of Radiology, University of Chicago, Chicago, Illinois, USA
| | - Milica Medved
- Department of Radiology, University of Chicago, Chicago, Illinois, USA
| | - Xiaobing Fan
- Department of Radiology, University of Chicago, Chicago, Illinois, USA
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Heule R, Ganter C, Bieri O. Variable flip angle T1 mapping in the human brain with reduced T2 sensitivity using fast radiofrequency-spoiled gradient echo imaging. Magn Reson Med 2015; 75:1413-22. [PMID: 25980525 DOI: 10.1002/mrm.25668] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Revised: 01/08/2015] [Accepted: 02/02/2015] [Indexed: 11/06/2022]
Abstract
PURPOSE Variable flip angle (VFA) T1 quantification using three-dimensional (3D) radiofrequency (RF) spoiled gradient echo imaging offers the acquisition of whole-brain T1 maps in clinically acceptable times. However, conventional VFA T1 relaxometry is biased by incomplete spoiling (i.e., residual T2 dependency). A new postprocessing approach is proposed to overcome this T2-related bias. METHODS T1 is quantified from the signal ratio of two spoiled gradient echo (SPGR) images acquired at different flip angles using an analytical solution for the RF-spoiled steady-state signal in combination with a global T2 guess. T1 accuracy is evaluated from simulations and in vivo 3D SPGR imaging of the human brain at 3 Tesla. RESULTS The simulations demonstrated that the sensitivity of VFA T1 mapping to T2 can considerably be reduced using a global T2 guess. The method proved to deliver reliable and accurate T1 values in vivo for white and gray matter in good agreement with inversion recovery reference measurements. CONCLUSION Based on a global T2 estimate, the accuracy of VFA T1 relaxometry in the human brain can substantially be improved compared with conventional approaches which rely on the generally wrong assumption of ideal spoiling.
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Affiliation(s)
- Rahel Heule
- Division of Radiological Physics, Department of Radiology, University of Basel Hospital, Basel, Switzerland
| | - Carl Ganter
- Department of Radiology, Klinikum rechts der Isar, Technische Universität München, Munich, Germany
| | - Oliver Bieri
- Division of Radiological Physics, Department of Radiology, University of Basel Hospital, Basel, Switzerland
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Kecskemeti S, Samsonov A, Hurley SA, Dean DC, Field A, Alexander AL. MPnRAGE: A technique to simultaneously acquire hundreds of differently contrasted MPRAGE images with applications to quantitative T1 mapping. Magn Reson Med 2015; 75:1040-53. [PMID: 25885265 DOI: 10.1002/mrm.25674] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 02/02/2015] [Accepted: 02/04/2015] [Indexed: 12/29/2022]
Abstract
PURPOSE To introduce a new technique called MPnRAGE, which produces hundreds of images with different T1 contrasts and a B1 corrected T1 map. THEORY AND METHODS An interleaved three-dimensional radial k-space trajectory with a sliding window reconstruction is used in conjunction with magnetization preparation pulses. This work modifies the SNAPSHOT-FLASH T1 fitting equations for radial imaging with view-sharing and develops a new rapid B1 correction procedure. MPnRAGE is demonstrated in phantoms and volunteers, including two volunteers with eight scans each and eight volunteers with two scans each. T1 values from MPnRAGE were compared with those from fast spin echo inversion recovery (FSE-IR) in phantoms and a healthy human brain at 3 Tesla (T). RESULTS The T1 fit for human white and gray matter was T1MPnRAGE = 1.00 · T1FSE-IR + 24 ms, r(2) = 0.990. Voxel-wise coefficient of variation in T1 measurements across eight time points was between 0.02 and 0.08. Region of interest-based T1 values were reproducible to within 2% and agree well with literature values. CONCLUSION In the same amount of time as a traditional MPRAGE exam (7.5 min), MPnRAGE was shown to produce hundreds of images with alternate T1 contrasts as well as an accurate and reproducible T1 map that is robust to B1 errors.
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Affiliation(s)
- Steven Kecskemeti
- Waisman Center and Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Alexey Samsonov
- Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Samuel A Hurley
- Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Douglas C Dean
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Aaron Field
- Department of Radiology and Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Andrew L Alexander
- Waisman Center, Department of Medical Physics and Department of Psychiatry, University of Wisconsin-Madison, Madison, Wisconsin, USA
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Droby A, Lukas C, Schänzer A, Spiwoks-Becker I, Giorgio A, Gold R, De Stefano N, Kugel H, Deppe M, Wiendl H, Meuth SG, Acker T, Zipp F, Deichmann R. A human post-mortem brain model for the standardization of multi-centre MRI studies. Neuroimage 2015; 110:11-21. [DOI: 10.1016/j.neuroimage.2015.01.028] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Revised: 12/11/2014] [Accepted: 01/07/2015] [Indexed: 10/24/2022] Open
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Hernandez D, Cho MH, Lee SY. Iterative multi-channel radio frequency pulse calibration with improving B1 field uniformity in high field MRI. Biomed Eng Online 2015; 14:15. [PMID: 25884219 PMCID: PMC4340295 DOI: 10.1186/s12938-015-0010-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 02/09/2015] [Indexed: 11/21/2022] Open
Abstract
Background In high field MRI capable of multi-channel radio frequency (RF) transmission, B1 shimming is a time-consuming job because conventional B1 shimming techniques require B1 mapping for each channel. After acquiring the complex-numbered B1 field maps, the optimal amplitude and phase of the driving RF pulse are determined for each channel to maximize the B1 field uniformity in conventional B1 shimming. However, time-consuming B1 shimming procedures at the pre-scan may not be tolerated in the clinical imaging in which patient throughput is one of the important factors. Methods To avoid the time-consuming B1 mapping, the first spin echo and the stimulated echo were repeatedly acquired in the slice-selective stimulated echo sequence without imaging gradients. A cost function of the amplitudes and phases of the driving RF pulse for every channel was defined in a way that the ratio between the spin echo and stimulated echo amplitudes rapidly converged to √ 2. The amplitude and phase of the driving RF pulse were iteratively modified over the repeating RF pulse sequence so that the cost function was minimized. Results From the finite-difference-time-domain (FDTD) electromagnetic field simulations with a human body model placed in a birdcage coil operating at 3 T, it was observed that the RF pulse calibration with iterative cost function minimization can give improvement of B1 field uniformity as well as flip-angle calibration. The experiments at 3 T also showed improvement of RF field uniformity in the phantom imaging studies. Conclusions Since the proposed RF pulse calibration is not based on B1 mapping, the RF pulse calibration time could be much shorter than the B1-mapping based methods. The proposed method is expected to be a practical substitute for the B1-mapping-based B1 shimming methods when long pre-scan time is not tolerable.
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Affiliation(s)
- Daniel Hernandez
- Department of Biomedical Engineering, Kyung Hee University, Yongin-si, Gyeonggi-do, 446-701, Korea.
| | - Min Hyoung Cho
- Department of Biomedical Engineering, Kyung Hee University, Yongin-si, Gyeonggi-do, 446-701, Korea.
| | - Soo Yeol Lee
- Department of Biomedical Engineering, Kyung Hee University, Yongin-si, Gyeonggi-do, 446-701, Korea.
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Using high-resolution quantitative mapping of R1 as an index of cortical myelination. Neuroimage 2014; 93 Pt 2:176-88. [DOI: 10.1016/j.neuroimage.2013.06.005] [Citation(s) in RCA: 253] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 06/03/2013] [Accepted: 06/04/2013] [Indexed: 01/19/2023] Open
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Wang G, El-Sharkawy AMM, Bottomley PA. Minimum acquisition methods for simultaneously imaging T(1), T(2), and proton density with B(1) correction and no spin-echoes. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2014; 242:243-55. [PMID: 24705365 PMCID: PMC4058094 DOI: 10.1016/j.jmr.2014.02.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 02/10/2014] [Accepted: 02/12/2014] [Indexed: 05/25/2023]
Abstract
The spin lattice (T(1)) and spin-spin (T(2)) relaxation times, along with the proton density (PD) contain almost all of the information that (1)H MRI routinely uses in clinical diagnosis and research, but are seldom imaged directly. Here, three methods for directly imaging T(1), T(2), and PD with the least possible number of acquisitions - three, are presented. All methods utilize long 0° self-refocusing adiabatic pre-pulses instead of spin-echoes to encode the T(2) information prior to a conventional gradient-echo MRI sequence. T(1) information is encoded by varying the flip-angle (FA) in the 'Dual-τ Dual-FA' and 'Four-FA' methods, or the sequence repetition period, TR, in the 'Dual-τ Dual-TR' method. Inhomogeneity in the FA distribution and slice-selection profile are recognized as the main error sources for T(1) measurements. The former is remedied by integrating an extra FA-dependent acquisition into the 'Four-FA' method to provide self-corrected T(1), T(2), PD, and FA in just four acquisitions - again, the minimum possible. Slice profile errors - which manifest as differences between 2D and 3D T(1) measurements, can be addressed by Bloch equation analysis and experimental calibration. All three methods are validated in phantom studies, and the 'Dual-τ Dual-FA' and 'Four-FA' methods are validated in human brain studies using standard partial saturation and spin-echo methods for reference. The new methods offer a minimum-acquisition option for imaging single-component T(1), T(2), and PD. 'Four-FA' performs best overall in accuracy, with high efficiency per unit accuracy vs. existing methods when B(1)-inhomogeneity is appropriately addressed.
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Affiliation(s)
- Guan Wang
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, USA; Russell H. Morgan Dept. of Radiology and Radiological Sciences, Johns Hopkins University, Baltimore, MD, USA
| | - AbdEl-Monem M El-Sharkawy
- Russell H. Morgan Dept. of Radiology and Radiological Sciences, Johns Hopkins University, Baltimore, MD, USA
| | - Paul A Bottomley
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, USA; Russell H. Morgan Dept. of Radiology and Radiological Sciences, Johns Hopkins University, Baltimore, MD, USA.
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Kang LH, Kim DE, Lee SY. Fast B1 mapping based on interleaved-three-flip-angle (ITFA) excitation. Med Phys 2013; 40:112301. [PMID: 24320457 DOI: 10.1118/1.4824151] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Fast B1 mapping based on short-TR sequences is prone to T1-induced errors. The purpose of this study is to develop a novel fast B1 mapping method that is less prone to T1-induced errors. METHODS The authors acquired three gradient echoes by applying three RF pulses of different flip angles in an interleaved manner. The new method, named interleaved-three-flip-angle (ITFA) method, employs a short TR for fast scan. Since the pixel intensity of the gradient echo images is dependent on both B1 and T1, the authors could compute a B1 map from the three gradient echo images with excluding the T1-effects. The authors simulated the proposed B1 mapping method for various T1 values, and they found optimal flip angles for ITFA experiments for a given repetition time. To evaluate the B1 mapping performance, the authors made a human-brain-mimicking phantom that had six compartments with different T1 and T2. The authors performed B1 mapping experiments at 3T on the phantom and a volunteer using the ITFA method, the actual flip angle imaging (AFI) method, and the double angle method (DAM), and then, the authors compared the B1 mapping results. RESULTS Using a birdcage coil as a transceiver at 3T, the authors performed ITFA scans of the phantom and a volunteer with TR of 60 ms and the nominal flips angles of (25°, 70°, 80°). The authors also performed AFI scans with TR1/TR2 of 30/150 ms and the nominal flip angle of 60°. In both the phantom and human head imaging performed with the same scan times for ITFA and AFI, ITFA showed smaller average B1 errors than AFI when they were compared to DAM. CONCLUSIONS ITFA excitations made it possible to reduce the T1-effects on B1 mapping of the human-brain-mimicking phantom and the human brain at 3T. The authors expect the ITFA method can be used for B1 shimming once the optimal flip angles have been predetermined for the target imaging region and for the preferred TR.
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Affiliation(s)
- Lae Hoon Kang
- Department of Biomedical Engineering, Kyung Hee University, 1 Seochun, Yongin-si, Gyeonggi-do 446-701, South Korea
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Jankiewicz M, Gore JC, Grissom WA. Improved encoding pulses for Bloch-Siegert B1(+) mapping. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 226:79-87. [PMID: 23220183 PMCID: PMC3561618 DOI: 10.1016/j.jmr.2012.11.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Revised: 11/06/2012] [Accepted: 11/08/2012] [Indexed: 05/31/2023]
Abstract
A new family of optimized encoding pulses for Bloch-Siegert (BS) |B(1)(+)| mapping is introduced, as well as an algorithm to design them. The pulses are designed by numerical maximization of BS sequence sensitivity, subject to constraints that ensure low on-resonance excitation. The pulses are in all cases characterized by a constant envelope and U-shaped frequency sweep. They are validated in simulations, 7T in vivo experiments, and an experiment to measure their on-resonance excitation, and are compared to a Fermi pulse conventionally used in the BS method. The pulses are shown to produce larger phase shifts in a shorter time and with lower on-resonance excitation than the Fermi pulse, which results in lower SAR and improved |B(1)(+)| accuracy in areas of the body with large main field inhomogeneities.
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Affiliation(s)
- Marcin Jankiewicz
- Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA
| | - John C. Gore
- Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - William A. Grissom
- Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
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Velikina JV, Alexander AL, Samsonov A. Accelerating MR parameter mapping using sparsity-promoting regularization in parametric dimension. Magn Reson Med 2012; 70:1263-73. [PMID: 23213053 DOI: 10.1002/mrm.24577] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Revised: 10/17/2012] [Accepted: 11/09/2012] [Indexed: 11/05/2022]
Abstract
MR parameter mapping requires sampling along additional (parametric) dimension, which often limits its clinical appeal due to a several-fold increase in scan times compared to conventional anatomic imaging. Data undersampling combined with parallel imaging is an attractive way to reduce scan time in such applications. However, inherent SNR penalties of parallel MRI due to noise amplification often limit its utility even at moderate acceleration factors, requiring regularization by prior knowledge. In this work, we propose a novel regularization strategy, which uses smoothness of signal evolution in the parametric dimension within compressed sensing framework (p-CS) to provide accurate and precise estimation of parametric maps from undersampled data. The performance of the method was demonstrated with variable flip angle T1 mapping and compared favorably to two representative reconstruction approaches, image space-based total variation regularization and an analytical model-based reconstruction. The proposed p-CS regularization was found to provide efficient suppression of noise amplification and preservation of parameter mapping accuracy without explicit utilization of analytical signal models. The developed method may facilitate acceleration of quantitative MRI techniques that are not suitable to model-based reconstruction because of complex signal models or when signal deviations from the expected analytical model exist.
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Affiliation(s)
- Julia V Velikina
- Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA
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