1
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Vejdani Afkham B, Alonso-Ortiz E. On the impact of B0 shimming algorithms on single-voxel MR spectroscopy. Magn Reson Med 2024. [PMID: 39188098 DOI: 10.1002/mrm.30257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2024] [Revised: 07/27/2024] [Accepted: 07/31/2024] [Indexed: 08/28/2024]
Abstract
PURPOSE To assess the impact of different B0 shimming algorithms on MRS. METHODS B0 field maps and single-voxel MR spectroscopy were acquired in the prefrontal cortex of five volunteers at 3 T using five different B0 shimming approaches. B0 shimming was achieved using Siemens' proprietary shim algorithm, in addition to the Pseudo-Inverse (PI), Quadratic Programming (QuadProg), Least Squares (LSq), and Gradient optimization (Grad) algorithms. The standard deviation of the shimmed B0 field, as well as the SNR and FWHM of the measured metabolites, was used to evaluate the performance of each B0 shimming algorithm. RESULTS Compared to Siemens's shim, significant reductions (p < 0.01) in the standard deviation of the B0 field distribution within the MRS voxel were observed for the PI, QuadProg, and Grad algorithms (3.8 Hz, 7.3 Hz, and 3.9 Hz respectively, compared to 11.5 Hz for Siemens), but not for the LSq (12.9 Hz) algorithm. Moreover, significantly increased SNR and reduced FWHM for the N-acetylaspartate metabolite were consistent with the improvement in B0 homogeneity for the aforementioned shimming algorithms. CONCLUSION Here, we demonstrate that the choice of B0 shimming algorithm can have a significant impact on the quality of MR spectra and that significant improvements in spectrum quality could be achieved by using alternatives to the default vendor approach.
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Affiliation(s)
- Behrouz Vejdani Afkham
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montréal, Montréal, Quebec, Canada
| | - Eva Alonso-Ortiz
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montréal, Montréal, Quebec, Canada
- Centre de recherche du CHU Sainte-Justine, Montréal, Quebec, Canada
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2
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Yang H, Wang G, Li Z, Li H, Zheng J, Hu Y, Cao X, Liao C, Ye H, Tian Q. Artificial intelligence for neuro MRI acquisition: a review. MAGMA (NEW YORK, N.Y.) 2024; 37:383-396. [PMID: 38922525 DOI: 10.1007/s10334-024-01182-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Revised: 06/11/2024] [Accepted: 06/14/2024] [Indexed: 06/27/2024]
Abstract
OBJECT To review recent advances of artificial intelligence (AI) in enhancing the efficiency and throughput of the MRI acquisition workflow in neuroimaging, including planning, sequence design, and correction of acquisition artifacts. MATERIALS AND METHODS A comprehensive analysis was conducted on recent AI-based methods in neuro MRI acquisition. The study focused on key technological advances, their impact on clinical practice, and potential risks associated with these methods. RESULTS The findings indicate that AI-based algorithms have a substantial positive impact on the MRI acquisition process, improving both efficiency and throughput. Specific algorithms were identified as particularly effective in optimizing acquisition steps, with reported improvements in workflow efficiency. DISCUSSION The review highlights the transformative potential of AI in neuro MRI acquisition, emphasizing the technological advances and clinical benefits. However, it also discusses potential risks and challenges, suggesting areas for future research to mitigate these concerns and further enhance AI integration in MRI acquisition.
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Affiliation(s)
- Hongjia Yang
- School of Biomedical Engineering, Tsinghua University, Beijing, China
| | - Guanhua Wang
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Ziyu Li
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Haoxiang Li
- School of Biomedical Engineering, Tsinghua University, Beijing, China
| | - Jialan Zheng
- School of Biomedical Engineering, Tsinghua University, Beijing, China
| | - Yuxin Hu
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Xiaozhi Cao
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
- Department of Radiology, Stanford University, Stanford, CA, USA
| | - Congyu Liao
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
- Department of Radiology, Stanford University, Stanford, CA, USA
| | - Huihui Ye
- State Key Laboratory of Extreme Photonics and Instrumentation, College of Optical Science and Engineering, Zhejiang University, Hangzhou, China
| | - Qiyuan Tian
- School of Biomedical Engineering, Tsinghua University, Beijing, China.
- Tsinghua Laboratory of Brain and Intelligence, Tsinghua University, Beijing, China.
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Xu J, Yang B, Kelley D, Magnotta VA. Automated High-Order Shimming for Neuroimaging Studies. Tomography 2023; 9:2148-2157. [PMID: 38133072 PMCID: PMC10748357 DOI: 10.3390/tomography9060168] [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: 10/25/2023] [Revised: 11/28/2023] [Accepted: 11/29/2023] [Indexed: 12/23/2023] Open
Abstract
B0 inhomogeneity presents a significant challenge in MRI and MR spectroscopy, particularly at high-field strengths, leading to image distortion, signal loss, and spectral broadening. Existing high-order shimming methods can alleviate these issues but often require time-consuming and subjective manual selection of regions of interest (ROIs). To address this, we proposed an automated high-order shimming (autoHOS) method, incorporating deep-learning-based brain extraction and image-based high-order shimming. This approach performs automated real-time brain extraction to define the ROI of the field map to be used in the shimming algorithm. The shimming performance of autoHOS was assessed through in vivo echo-planar imaging (EPI) and spectroscopic studies at both 3T and 7T field strengths. AutoHOS outperforms linear shimming and manual high-order shimming, enhancing both the image and spectral quality by reducing the EPI image distortion and narrowing the MRS spectral lineshapes. Therefore, autoHOS demonstrated a significant improvement in correcting B0 inhomogeneity while eliminating the need for additional user interaction.
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Affiliation(s)
- Jia Xu
- Department of Radiology, University of Iowa, Iowa City, IA 52242, USA
| | | | - Douglas Kelley
- GE Corporate Consultant, Contracted through Kelly Services, Fairfax, CA 94930, USA;
| | - Vincent A. Magnotta
- Department of Radiology, University of Iowa, Iowa City, IA 52242, USA
- Department of Psychiatry, University of Iowa, Iowa City, IA 52242, USA
- Department of Biomedical Engineering, University of Iowa, Iowa City, IA 52242, USA
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Pan JW, Terpstra MJ, Moon CH, Hetherington HP. Map-based B 0 shimming for single voxel brain spectroscopy at 7T. NMR IN BIOMEDICINE 2023; 36:e5021. [PMID: 37586403 DOI: 10.1002/nbm.5021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 07/18/2023] [Accepted: 07/20/2023] [Indexed: 08/18/2023]
Abstract
While B0 shimming is an important requirement for in vivo brain spectroscopy, for single voxel spectroscopy (SVS), the role for advanced shim methods has been questioned. Specifically, with the small spatial dimensions of the voxel, the extent to which inhomogeneities higher than second order exist and the ability of higher order shims to correct them is controversial. To assess this, we acquired SVS from two loci of neurophysiological interest, the rostral prefrontal cortex (rPFC; 8 cc) and hippocampus (Hc; 9 cc). The rPFC voxel was placed using SUsceptibility Managed Optimization (SUMO) and an initial B0 map that covers the entire cerebrum to cerebellum. In each location, we compared map-based shimming (Bolero) with projection-based shimming (FAST(EST)MAP). We also compared vendor-provided spherical harmonic first- and second-order shims with additional third- and fourth-order shim hardware. The 7T SVS acquisition used stimulated echo acquisition mode (STEAM) TR/TM/TE of 6 s/20 ms/8 ms, a tissue water acquisition for concentration reference, and LCModel for spectral analysis. In the rPFC (n = 7 subjects), Bolero shimming with first- and second-order shims reduced the residual inhomogeneity σ B 0 from 9.8 ± 4.5 Hz with FAST(EST)MAP to 6.5 ± 2.0 Hz. The addition of third- and fourth-order shims further reduced σ B 0 to 4.0 ± 0.8 Hz. In the Hc (n = 7 subjects), FAST(EST)MAP, Bolero with first- and second-order shims, and Bolero with first- to fourth-order shims achieved σ B 0 values of 8.6 ± 1.9, 5.6 ± 1.0, and 4.6 ± 0.9 Hz, respectively. The spectral linewidth,Δ v σ B 0 , was estimated with a Voigt lineshape using σ B 0 and T2 = 130 ms.Δ v σ B 0 significantly correlated with the Cramer-Rao lower bounds and concentrations of several metabolites, including glutamate and glutamine in the rPFC. In both loci, if the B0 distribution is well described by a Gaussian model, the variance of the metabolite concentrations is reduced, consistent with the LCModel fit based on a unimodal lineshape. Overall, the use of the high order and map-based B0 shim methods improved the accuracy and consistency of spectroscopic data.
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Affiliation(s)
- Jullie W Pan
- Department Radiology, University of Missouri Columbia, Columbia, Missouri, USA
| | - Melissa J Terpstra
- Department Radiology, University of Missouri Columbia, Columbia, Missouri, USA
- Chemical and Biomedical Engineering, University of Missouri Columbia, Columbia, Missouri, USA
| | - Chan-Hong Moon
- Department Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Hoby P Hetherington
- Department Radiology, University of Missouri Columbia, Columbia, Missouri, USA
- Resonance Research Inc., Billerica, Massachusetts, USA
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5
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Ding B, Dragonu I, Rua C, Carlin JD, Halai AD, Liebig P, Heidemann R, Correia MM, Rodgers CT. Parallel transmit (pTx) with online pulse design for task-based fMRI at 7 T. Magn Reson Imaging 2022; 93:163-174. [PMID: 35863691 DOI: 10.1016/j.mri.2022.07.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 06/17/2022] [Accepted: 07/11/2022] [Indexed: 10/31/2022]
Abstract
PURPOSE Parallel transmission (pTx) is an approach to improve image uniformity for ultra-high field imaging. In this study, we modified an echo planar imaging (EPI) sequence to design subject-specific pTx pulses online. We compared its performance against EPI with conventional circularly polarised (CP) pulses. METHODS We compared the pTx-EPI and CP-EPI sequences in a short EPI acquisition protocol and for two different functional paradigms in six healthy volunteers (2 female, aged 23-36 years, mean age 29.2 years). We chose two paradigms that are typically affected by signal dropout at 7 T: a visual objects localiser to determine face/scene selective brain regions and a semantic-processing task. RESULTS Across all subjects, pTx-EPI improved whole-brain mean temporal signal-to-noise ratio (tSNR) by 11.0% compared to CP-EPI. We also compared the ability of pTx-EPI and CP-EPI to detect functional activation for three contrasts over the two paradigms: face > object and scene > object for the visual objects localiser and semantic association > pattern matching for the semantic-processing paradigm. Across all three contrasts, pTx-EPI showed higher median z-scores and detected more active voxels in relevant areas, as determined from previous 3 T studies. CONCLUSION We have demonstrated a workflow for EPI acquisitions with online per-subject pulse calculations. We saw improved performance in both tSNR and functional acquisitions from pTx-EPI. Thus, we believe that online calculation pTx-EPI is robust enough for future fMRI studies, especially where activation is expected in brain areas liable to significant signal dropout.
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Affiliation(s)
- Belinda Ding
- Wolfson Brain Imaging Centre, University of Cambridge, UK.
| | | | - Catarina Rua
- Wolfson Brain Imaging Centre, University of Cambridge, UK; Department of Clinical Neurosciences, University of Cambridge, UK; Invicro, Invicro London, UK
| | | | - Ajay D Halai
- MRC Cognition and Brain Science Unit, Cambridge, UK
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Koush Y, Rothman DL, Behar KL, de Graaf RA, Hyder F. Human brain functional MRS reveals interplay of metabolites implicated in neurotransmission and neuroenergetics. J Cereb Blood Flow Metab 2022; 42:911-934. [PMID: 35078383 PMCID: PMC9125492 DOI: 10.1177/0271678x221076570] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2021] [Revised: 12/26/2021] [Accepted: 01/05/2022] [Indexed: 01/28/2023]
Abstract
While functional MRI (fMRI) localizes brain activation and deactivation, functional MRS (fMRS) provides insights into the underlying metabolic conditions. There is much interest in measuring task-induced and resting levels of metabolites implicated in neuroenergetics (e.g., lactate, glucose, or β-hydroxybutyrate (BHB)) and neurotransmission (e.g., γ-aminobutyric acid (GABA) or pooled glutamate and glutamine (Glx)). Ultra-high magnetic field (e.g., 7T) has boosted the fMRS quantification precision, reliability, and stability of spectroscopic observations using short echo-time (TE) 1H-MRS techniques. While short TE 1H-MRS lacks sensitivity and specificity for fMRS at lower magnetic fields (e.g., 3T or 4T), most of these metabolites can also be detected by J-difference editing (JDE) 1H-MRS with longer TE to filter overlapping resonances. The 1H-MRS studies show that JDE can detect GABA, Glx, lactate, and BHB at 3T, 4T and 7T. Most recently, it has also been demonstrated that JDE 1H-MRS is capable of reliable detection of metabolic changes in different brain areas at various magnetic fields. Combining fMRS measurements with fMRI is important for understanding normal brain function, but also clinically relevant for mechanisms and/or biomarkers of neurological and neuropsychiatric disorders. We provide an up-to-date overview of fMRS research in the last three decades, both in terms of applications and technological advances. Overall the emerging fMRS techniques can be expected to contribute substantially to our understanding of metabolism for brain function and dysfunction.
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Affiliation(s)
- Yury Koush
- Magnetic Resonance Research Center, Department of Radiology & Biomedical Imaging, Yale University, New Haven, CT, USA
| | - Douglas L Rothman
- Magnetic Resonance Research Center, Department of Radiology & Biomedical Imaging, Yale University, New Haven, CT, USA
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA
| | - Kevin L Behar
- Magnetic Resonance Research Center, Department of Radiology & Biomedical Imaging, Yale University, New Haven, CT, USA
- Department of Psychiatry, Yale University, New Haven, CT, USA
| | - Robin A de Graaf
- Magnetic Resonance Research Center, Department of Radiology & Biomedical Imaging, Yale University, New Haven, CT, USA
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA
| | - Fahmeed Hyder
- Magnetic Resonance Research Center, Department of Radiology & Biomedical Imaging, Yale University, New Haven, CT, USA
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA
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7
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Scheenen TWJ. Dual-purpose coils in MRSI of brain tumours. NMR IN BIOMEDICINE 2022; 35:e4660. [PMID: 34816524 DOI: 10.1002/nbm.4660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Affiliation(s)
- Tom W J Scheenen
- Department of Medical Imaging, Radboud University Medical Center, Nijmegen, The Netherlands
- Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen, Germany
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8
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Strasser B, Arango NS, Stockmann JP, Gagoski B, Thapa B, Li X, Bogner W, Moser P, Small J, Cahill DP, Batchelor TT, Dietrich J, van der Kouwe A, White J, Adalsteinsson E, Andronesi OC. Improving D-2-hydroxyglutarate MR spectroscopic imaging in mutant isocitrate dehydrogenase glioma patients with multiplexed RF-receive/B 0 -shim array coils at 3 T. NMR IN BIOMEDICINE 2022; 35:e4621. [PMID: 34609036 PMCID: PMC8717863 DOI: 10.1002/nbm.4621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2021] [Revised: 08/27/2021] [Accepted: 08/30/2021] [Indexed: 06/13/2023]
Abstract
MR spectroscopic imaging (MRSI) noninvasively maps the metabolism of human brains. In particular, the imaging of D-2-hydroxyglutarate (2HG) produced by glioma isocitrate dehydrogenase (IDH) mutations has become a key application in neuro-oncology. However, the performance of full field-of-view MRSI is limited by B0 spatial nonuniformity and lipid artifacts from tissues surrounding the brain. Array coils that multiplex RF-receive and B0 -shim electrical currents (AC/DC mixing) over the same conductive loops provide many degrees of freedom to improve B0 uniformity and reduce lipid artifacts. AC/DC coils are highly efficient due to compact design, requiring low shim currents (<2 A) that can be switched fast (0.5 ms) with high interscan reproducibility (10% coefficient of variation for repeat measurements). We measured four tumor patients and five volunteers at 3 T and show that using AC/DC coils in addition to the vendor-provided second-order spherical harmonics shim provides 19% narrower spectral linewidth, 6% higher SNR, and 23% less lipid content for unrestricted field-of-view MRSI, compared with the vendor-provided shim alone. We demonstrate that improvement in MRSI data quality led to 2HG maps with higher contrast-to-noise ratio for tumors that coincide better with the FLAIR-enhancing lesions in mutant IDH glioma patients. Smaller Cramér-Rao lower bounds for 2HG quantification are obtained in tumors by AC/DC shim, corroborating with simulations that predicted improved accuracy and precision for narrower linewidths. AC/DC coils can be used synergistically with optimized acquisition schemes to improve metabolic imaging for precision oncology of glioma patients. Furthermore, this methodology has broad applicability to other neurological disorders and neuroscience.
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Affiliation(s)
- Bernhard Strasser
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Radiology, Boston, Massachusetts, USA
- High-Field MR Centre, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Vienna, Austria
| | - Nicolas S. Arango
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Jason P. Stockmann
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Radiology, Boston, Massachusetts, USA
- Harvard Medical School, Boston, Massachusetts, USA
| | - Borjan Gagoski
- Fetal Neonatal Neuroimaging and Developmental Science Center, Boston Children’s Hospital, Boston, Massachusetts, USA
- Department of Radiology, Harvard Medical School, Boston, Massachusetts, USA
| | - Bijaya Thapa
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Radiology, Boston, Massachusetts, USA
| | - Xianqi Li
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Radiology, Boston, Massachusetts, USA
| | - Wolfgang Bogner
- High-Field MR Centre, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Vienna, Austria
| | - Philipp Moser
- High-Field MR Centre, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Vienna, Austria
| | - Julia Small
- Department of Neurosurgery, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Daniel P. Cahill
- Department of Neurosurgery, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Tracy T. Batchelor
- Department Neurology, Division of Neuro-Oncology, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Jorg Dietrich
- Department Neurology, Division of Neuro-Oncology, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Andre van der Kouwe
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Radiology, Boston, Massachusetts, USA
- Harvard Medical School, Boston, Massachusetts, USA
| | - Jacob White
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Elfar Adalsteinsson
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Ovidiu C. Andronesi
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Radiology, Boston, Massachusetts, USA
- Harvard Medical School, Boston, Massachusetts, USA
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9
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Shi Y, Clare S, Vannesjo SJ. Shim optimization with region of interest-specific Tikhonov regularization: Application to second-order slice-wise shimming of the brain. Magn Reson Med 2021; 87:1218-1230. [PMID: 34783374 DOI: 10.1002/mrm.28951] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Revised: 06/18/2021] [Accepted: 07/18/2021] [Indexed: 11/12/2022]
Abstract
PURPOSE Slice-wise shimming can improve field homogeneity, but suffers from large noise propagation in the shim calculation. Here, we propose a robust shim current optimization for higher-order dynamic shim updating, based on Tikhonov regularization with a variable regularization parameter, λ . THEORY AND METHODS: λ was selected for each slice separately in a fully automatic procedure based on a combination of boundary constraints and an L-curve search algorithm. Shimming performance was evaluated for second order slice-wise shimming of the brain at 7T, by simulation on a database of field maps from 143 subjects, and by direct measurements in 8 subjects. RESULTS Simulations yielded on average 36% reduction in the shim current norm for just 0.4 Hz increase in residual field SD as compared to unconstrained unregularized optimization. In vivo results yielded on average 34.0 Hz residual field SD as compared to 34.3 Hz with a constrained unregularized optimization, while simultaneously reducing the shim current norm to 2.8 A from 3.9 A. The proposed regularization also reduced the average step in the shim current between slices. CONCLUSION Slice-wise variable Tikhonov regularization yielded reduced current norm and current steps to a negligible cost in field inhomogeneity. The method holds promise to increase the robustness, and thereby the utility, of higher-order shim updating.
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Affiliation(s)
- Yuhang Shi
- Wellcome Centre for Integrative Neuroimaging, FMRIB, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Stuart Clare
- Wellcome Centre for Integrative Neuroimaging, FMRIB, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Signe Johanna Vannesjo
- Wellcome Centre for Integrative Neuroimaging, FMRIB, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
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10
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Pan JW, Antony A, Tal A, Yushmanov V, Fong J, Richardson M, Schirda C, Bagic A, Gonen O, Hetherington HP. MR spectroscopic imaging at 3 T and outcomes in surgical epilepsy. NMR IN BIOMEDICINE 2021; 34:e4492. [PMID: 33751687 PMCID: PMC8122073 DOI: 10.1002/nbm.4492] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 01/23/2021] [Indexed: 05/09/2023]
Abstract
For the spectroscopic assessment of brain disorders that require large-volume coverage, the requirements of RF performance and field homogeneity are high. For epilepsy, this is also challenging given the inter-patient variation in location, severity and subtlety of anatomical identification and its tendency to involve the temporal region. We apply a targeted method to examine the utility of large-volume MR spectroscopic imaging (MRSI) in surgical epilepsy patients, implementing a two-step acquisition, comprised of a 3D acquisition to cover the fronto-parietal regions, and a contiguous parallel two-slice Hadamard-encoded acquisition to cover the temporal-occipital region, both with TR /TE = 2000/40 ms and matched acquisition times. With restricted (static, first/second-order) B0 shimming in their respective regions, the Cramér-Rao lower bounds for creatine from the temporal lobe two-slice Hadamard and frontal-parietal 3D acquisition are 8.1 ± 2.2% and 6.3 ± 1.9% respectively. The datasets are combined to provide a total 60 mm axial coverage over the frontal, parietal and superior temporal to middle temporal-occipital regions. We applied these acquisitions at a nominal 400 mm3 voxel resolution in n = 27 pre-surgical epilepsy patients and n = 20 controls. In controls, 86.6 ± 3.2% voxels with at least 50% tissue (white + gray matter, excluding CSF) survived spectral quality inclusion criteria. Since all patients were clinically followed for at least 1 year after surgery, seizure frequency outcome was available for all. The MRSI measurements of the total fractional metabolic dysfunction (characterized by the Cr/NAA metric) in FreeSurfer MRI gray matter segmented regions, in the patients compared with the controls, exhibited a significant Spearman correlation with post-surgical outcome. This finding suggests that a larger burden of metabolic dysfunction is seen in patients with poorer post-surgical seizure control.
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Affiliation(s)
- Jullie W Pan
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania
- Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Arun Antony
- Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Assaf Tal
- Department of Chemical and Biological Physics, Weizmann Institute, Rehovot, Israel
| | - Victor Yushmanov
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Joanna Fong
- Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Mark Richardson
- Department of Neurosurgery, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Claud Schirda
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Anto Bagic
- Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Oded Gonen
- Department of Radiology, New York University, New York, New York
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11
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Tal A, Zhao T, Schirda C, Hetherington HP, Pan JW, Gonen O. Fast, regional three-dimensional hybrid (1D-Hadamard 2D-rosette) proton MR spectroscopic imaging in the human temporal lobes. NMR IN BIOMEDICINE 2021; 34:e4507. [PMID: 33754420 PMCID: PMC8122085 DOI: 10.1002/nbm.4507] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 02/03/2021] [Accepted: 02/25/2021] [Indexed: 05/05/2023]
Abstract
1 H-MRSI is commonly performed with gradient phase encoding, due to its simplicity and minimal radio frequency (RF) heating (specific absorption rate). Its two well-known main problems-(i) "voxel bleed" due to the intrinsic point-spread function, and (ii) chemical shift displacement error (CSDE) when slice-selective RF pulses are used, which worsens with increasing volume of interest (VOI) size-have long become accepted as unavoidable. Both problems can be mitigated with Hadamard multislice RF encoding. This is demonstrated and quantified with numerical simulations, in a multislice phantom and in five healthy young adult volunteers at 3 T, targeting a 2-cm thick temporal lobe VOI through the bilateral hippocampus. This frequently targeted region (e.g. in epilepsy and Alzheimer's disease) is subject to strong, 1-2 ppm.cm-1 regional B0, susceptibility gradients that can dramatically reduce the signal-to-noise ratio (SNR) and water suppression effectiveness. The chemical shift imaging (CSI) sequence used a 3-ms Shinnar-Le Roux (SLR) 90° RF pulse, acquiring eight steps in the slice direction. The Hadamard sequence acquired two overlapping slices using the same SLR 90° pulses, under twofold stronger gradients that proportionally halved the CSDE. Both sequences used 2D 20 × 20 rosette spectroscopic imaging (RSI) for in-plane spatial localization and both used RF and gradient performance characteristics that are easily met by all modern MRI instruments. The results show that Hadamard spectroscopic imaging (HSI) suffered dramatically less signal bleed within the VOI compared with CSI (<1% vs. approximately 26% in simulations; and 5%-8% vs. >50%) in a phantom specifically designed to test these effects. The voxels' SNR per unit volume per unit time was also 40% higher for HSI. In a group of five healthy volunteers, we show that HSI with in-plane 2D-RSI facilitates fast, 3D multivoxel encoding at submilliliter spatial resolution, over the bilateral human hippocampus, in under 10 min, with negligible CSDE, spectral and spatial contamination and more than 6% improved SNR per unit time per unit volume.
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Affiliation(s)
- Assaf Tal
- Department of Chemical and Biological Physics, The Weizmann Institute of Science, Rehovot, Israel
| | - Tiejun Zhao
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine, New York, New York, USA
- Siemens Medical Solutions USA Inc., Malvern, Pennsylvania, USA
| | - Claudiu Schirda
- Departments of Radiology and Neurology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Hoby P. Hetherington
- Departments of Radiology and Neurology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Jullie W. Pan
- Departments of Radiology and Neurology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Oded Gonen
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine, New York, New York, USA
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12
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Juchem C, Cudalbu C, de Graaf RA, Gruetter R, Henning A, Hetherington HP, Boer VO. B 0 shimming for in vivo magnetic resonance spectroscopy: Experts' consensus recommendations. NMR IN BIOMEDICINE 2021; 34:e4350. [PMID: 32596978 DOI: 10.1002/nbm.4350] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Revised: 05/14/2020] [Accepted: 05/19/2020] [Indexed: 05/07/2023]
Abstract
Magnetic resonance spectroscopy (MRS) and spectroscopic imaging (MRSI) allow the chemical analysis of physiological processes in vivo and provide powerful tools in the life sciences and for clinical diagnostics. Excellent homogeneity of the static B0 magnetic field over the object of interest is essential for achieving high-quality spectral results and quantitative metabolic measurements. The experimental minimization of B0 variation is performed in a process called B0 shimming. In this article, we summarize the concepts of B0 field shimming using spherical harmonic shimming techniques, specific strategies for B0 homogenization and crucial factors to consider for implementation and use in both brain and body. In addition, experts' recommendations are provided for minimum requirements for B0 shim hardware and evaluation criteria for the primary outcome of adequate B0 shimming for MRS and MRSI, such as the water spectroscopic linewidth.
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Affiliation(s)
- Christoph Juchem
- Departments of Biomedical Engineering and Radiology, Columbia University, New York, New York
| | - Cristina Cudalbu
- Centre d'Imagerie Biomedicale (CIBM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Robin A de Graaf
- Department of Radiology and Biomedical Imaging, Yale University, New Haven, Connecticut
| | - Rolf Gruetter
- Laboratory for Functional and Metabolic Imaging, Center for Biomedical Imaging, Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland
| | - Anke Henning
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas
- Max Planck Institute for Biological Cybernetics, Tuebingen, Germany
| | | | - Vincent O Boer
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark
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13
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Tinnermann A, Büchel C, Cohen-Adad J. Cortico-spinal imaging to study pain. Neuroimage 2020; 224:117439. [PMID: 33039624 DOI: 10.1016/j.neuroimage.2020.117439] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 09/21/2020] [Accepted: 10/01/2020] [Indexed: 12/15/2022] Open
Abstract
Functional magnetic resonance imaging of the brain has helped to reveal mechanisms of pain perception in health and disease. Recently, imaging approaches have been developed that allow recording neural activity simultaneously in the brain and in the spinal cord. These approaches offer the possibility to examine pain perception in the entire central pain system and in addition, to investigate cortico-spinal interactions during pain processing. Although cortico-spinal imaging is a promising technique, it bears challenges concerning data acquisition and data analysis strategies. In this review, we discuss studies that applied simultaneous imaging of the brain and spinal cord to explore central pain processing. Furthermore, we describe different MR-related acquisition techniques, summarize advantages and disadvantages of approaches that have been implemented so far and present software that has been specifically developed for the analysis of spinal fMRI data to address challenges of spinal data analysis.
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Affiliation(s)
- Alexandra Tinnermann
- Department for Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; Max Planck School of Cognition, Leipzig, Germany.
| | - Christian Büchel
- Department for Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; Max Planck School of Cognition, Leipzig, Germany
| | - Julien Cohen-Adad
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, Quebec, Canada; Functional Neuroimaging Unit, CRIUGM, Université de Montréal, Montreal, Quebec, Canada.
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14
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Esmaeili M, Stockmann J, Strasser B, Arango N, Thapa B, Wang Z, van der Kouwe A, Dietrich J, Cahill DP, Batchelor TT, White J, Adalsteinsson E, Wald L, Andronesi OC. An integrated RF-receive/B 0-shim array coil boosts performance of whole-brain MR spectroscopic imaging at 7 T. Sci Rep 2020; 10:15029. [PMID: 32929121 PMCID: PMC7490394 DOI: 10.1038/s41598-020-71623-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Accepted: 06/16/2020] [Indexed: 12/03/2022] Open
Abstract
Metabolic imaging of the human brain by in-vivo magnetic resonance spectroscopic imaging (MRSI) can non-invasively probe neurochemistry in healthy and disease conditions. MRSI at ultra-high field (≥ 7 T) provides increased sensitivity for fast high-resolution metabolic imaging, but comes with technical challenges due to non-uniform B0 field. Here, we show that an integrated RF-receive/B0-shim (AC/DC) array coil can be used to mitigate 7 T B0 inhomogeneity, which improves spectral quality and metabolite quantification over a whole-brain slab. Our results from simulations, phantoms, healthy and brain tumor human subjects indicate improvements of global B0 homogeneity by 55%, narrower spectral linewidth by 29%, higher signal-to-noise ratio by 31%, more precise metabolite quantification by 22%, and an increase by 21% of the brain volume that can be reliably analyzed. AC/DC shimming provide the highest correlation (R2 = 0.98, P = 0.001) with ground-truth values for metabolite concentration. Clinical translation of AC/DC and MRSI is demonstrated in a patient with mutant-IDH1 glioma where it enables imaging of D-2-hydroxyglutarate oncometabolite with a 2.8-fold increase in contrast-to-noise ratio at higher resolution and more brain coverage compared to previous 7 T studies. Hence, AC/DC technology may help ultra-high field MRSI become more feasible to take advantage of higher signal/contrast-to-noise in clinical applications.
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Affiliation(s)
- Morteza Esmaeili
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
- Department of Diagnostic Imaging, Akershus University Hospital, Lørenskog, Norway
| | - Jason Stockmann
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Bernhard Strasser
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Nicolas Arango
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Bijaya Thapa
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Zhe Wang
- Siemens Medical Solutions, USA, Charlestown, MA, USA
| | - Andre van der Kouwe
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Jorg Dietrich
- Division of Neuro-Oncology, Department Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Daniel P Cahill
- Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Tracy T Batchelor
- Department Neurology, Brigham's and Women Hospital, Harvard Medical School, Boston, MA, USA
| | - Jacob White
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Elfar Adalsteinsson
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Lawrence Wald
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Ovidiu C Andronesi
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
- Athinoula A. Martinos Center for Biomedical Imaging, Building 149, Room 2301 13th Street, Charlestown, MA, 02129, USA.
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15
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Hetherington HP, Moon CH, Schwerter M, Shah NJ, Pan JW. Dynamic B 0 shimming for multiband imaging using high order spherical harmonic shims. Magn Reson Med 2020; 85:531-543. [PMID: 32857424 DOI: 10.1002/mrm.28438] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2020] [Revised: 06/25/2020] [Accepted: 06/29/2020] [Indexed: 11/05/2022]
Abstract
PURPOSE To describe and implement a strategy for dynamic slice-by-slice and multiband B0 shimming using spherical harmonic shims in the human brain at 7T. THEORY For thin axial slices, spherical harmonic shims can be divided into pairs of shims (z-degenerate and non-z-degenerate) that are spatially degenerate, such that only ½ of the shims (non-z-degenerate) are required for single slice optimizations. However, when combined, the pairs of shims can be used to simultaneously generate the same in-plane symmetries but with different amplitudes as a function of their z location. This enables multiband shimming equivalent to that achievable by single slice-by-slice optimization. METHODS All data were acquired at 7T using a spherical harmonic shim insert enabling shimming up through 4th order with two additional 5th order shims (1st-4th+). Dynamic shim updating was achieved using a 10A shim power supply with 2 ms ramps and constrained optimizations to minimize eddy currents. RESULTS In groups of eight subjects, we demonstrated that: 1) dynamic updating using 1st-4th+ order shims reduced the SD of the B0 field over the whole brain from 32.4 ± 2.6 and 24.9 ± 2 Hz with 1st-2nd and 1st-4th+ static global shimming to 15.1 ± 1.7 Hz; 2) near equivalent performance was achieved when dynamically updating only the non-z-degenerate shims (14.3 ± 1.5 Hz), or when a using multiband shim factor of 2, MBs = 2, and all shims (14.4 ± 2.0 Hz). CONCLUSION High order spherical harmonics provide substantial improvements over static global shimming and enable dynamic multiband shimming with near equivalent performance to that of dynamic slice-by-slice shimming. This reduces distortion in echo planar imaging.
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Affiliation(s)
- Hoby P Hetherington
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Chan Hong Moon
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Michael Schwerter
- Institute of Neuroscience and Medicine 4, Forschungszentrum, INM-4, Jülich, North Rhine-Westphalia, Germany
| | - Nadim Joni Shah
- Institute of Neuroscience and Medicine 4, Forschungszentrum, INM-4, Jülich, North Rhine-Westphalia, Germany.,Institute of Neuroscience and Medicine 11, JARA, Forschungszentrum, INM-11, Jülich, North Rhine-Westphalia, Germany.,JARA - BRAIN - Translational Medicine, Aachen, North Rhine-Westphalia, Germany.,Department of Neurology, RWTH Aachen University, Aachen, North Rhine-Westphalia, Germany
| | - Jullie W Pan
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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16
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Geiger Y, Tal A. Optimal echo times for multi-gradient echo-based B 0 field-mapping. NMR IN BIOMEDICINE 2020; 33:e4316. [PMID: 32339348 DOI: 10.1002/nbm.4316] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 03/28/2020] [Accepted: 04/05/2020] [Indexed: 06/11/2023]
Abstract
B0 field maps are used ubiquitously in neuroimaging, in disciplines ranging from magnetic resonance spectroscopy to temperature mapping and susceptibility-weighted imaging. Most B0 maps are acquired using standard gradient-echo-based vendor-provided sequences, often comprised of two echoes spaced a few milliseconds apart. Herein, we analyze the optimal spacing of echo times, defined as those maximizing precision-minimizing the standard deviation-for a fixed total acquisition time. Field estimation is carried out using a weighted least squares estimator. The standard deviation is shown to be approximately inversely proportional to the total acquisition time, suggesting a law of diminishing returns, whereby substantial gains are obtained up to a certain point, with little improvement beyond that point. Validations are provided in a phantom and a group of volunteers. Multi-gradient echo sequences are readily available on all manufacturer platforms, making our recommendations straightforward to implement on any modern scanner.
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Affiliation(s)
- Yasmin Geiger
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Israel
| | - Assaf Tal
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Israel
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17
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Schwerter M, Hetherington H, Moon CH, Pan J, Felder J, Tellmann L, Shah NJ. Interslice current change constrained B 0 shim optimization for accurate high-order dynamic shim updating with strongly reduced eddy currents. Magn Reson Med 2019; 82:263-275. [PMID: 30883909 PMCID: PMC8168441 DOI: 10.1002/mrm.27720] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 01/14/2019] [Accepted: 02/09/2019] [Indexed: 01/07/2023]
Abstract
PURPOSE To overcome existing challenges in dynamic B0 shimming by implementing a shim optimization algorithm which limits shim current amplitudes and their temporal variation through the application of constraints and regularization terms. THEORY AND METHODS Spherical harmonic dynamic B0 shimming is complicated by eddy currents, ill-posed optimizations, and the need for strong power supplies. Based on the fact that eddy current amplitudes are proportional to the magnitude of the shim current changes, and assuming a smoothness of the B0 inhomogeneity variation in the slice direction, a novel algorithm was implemented to reduce eddy current generation by limiting interslice shim current changes. Shim degeneracy issues and resulting high current amplitudes are additionally addressed by penalizing high solution norms. Applicability of the proposed algorithm was validated in simulations and in phantom and in vivo measurements. RESULTS High-order dynamic shimming simulations and measurements have shown that absolute shim current amplitudes and their temporal variation can be substantially reduced with negligible loss in achievable B0 homogeneity. Whereas conventional dynamic shim updating optimizations improve the B0 homogeneity, on average, by a factor of 2.1 over second-order static solutions, our proposed routine reached a factor of 2.0, while simultaneously providing a 14-fold reduction of the average maximum shim current changes. CONCLUSIONS The proposed algorithm substantially reduces the shim amplitudes and their temporal variation, while only marginally affecting the achievable B0 homogeneity. As a result, it has the potential to mitigate the remaining challenges in dynamic B0 shimming and help in making its application more readily available.
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Affiliation(s)
- Michael Schwerter
- Institute of Neuroscience and Medicine (INM-4), Forschungszentrum Jülich, Jülich, Germany
| | - Hoby Hetherington
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Chan Hong Moon
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Jullie Pan
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Jörg Felder
- Institute of Neuroscience and Medicine (INM-4), Forschungszentrum Jülich, Jülich, Germany
| | - Lutz Tellmann
- Institute of Neuroscience and Medicine (INM-4), Forschungszentrum Jülich, Jülich, Germany
| | - N. Jon Shah
- Institute of Neuroscience and Medicine (INM-4), Forschungszentrum Jülich, Jülich, Germany
- Institute of Neuroscience and Medicine (INM-11), JARA, Forschungszentrum Jülich, Jülich, Germany
- JARA - BRAIN - Translational Medicine, Aachen, Germany
- Department of Neurology, RWTH Aachen University, Aachen, Germany
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18
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Gaspar AS, Nunes RG, Ferrazzi G, Hughes EJ, Hutter J, Malik SJ, McCabe L, Baruteau KP, Rutherford MA, Hajnal JV, Price AN. Optimizing maternal fat suppression with constrained image-based shimming in fetal MR. Magn Reson Med 2019; 81:477-485. [PMID: 30058204 PMCID: PMC6282825 DOI: 10.1002/mrm.27375] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 05/02/2018] [Accepted: 05/03/2018] [Indexed: 12/21/2022]
Abstract
PURPOSE Echo planar imaging (EPI) is the primary sequence for functional and diffusion MRI. In fetal applications, the large field of view needed to encode the maternal abdomen leads to prolonged EPI readouts, which may be further extended due to safety considerations that limit gradient performance. The resulting images become very sensitive to water-fat shift and susceptibility artefacts. The purpose of this study was to reduce artefacts and increase stability of EPI in fetal brain imaging, balancing local field homogeneity across the fetal brain with longer range variations to ensure compatibility with fat suppression of the maternal abdomen. METHODS Spectral Pre-saturation with Inversion-Recovery (SPIR) fat suppression was optimized by investigating SPIR pulse frequency offsets. Subsequently, fetal brain EPI data were acquired using image-based (IB) shimming on 6 pregnant women by (1) minimizing B0 field variations within the fetal brain (localized IB shimming) and (2) with added constraint to limit B0 variation in maternal fat (fat constrained IB shimming). RESULTS The optimal offset for the SPIR pulse at 3 Tesla was 550 Hz. Both shimming approaches had similar performances in terms of B0 homogeneity within the brain, but constrained IB shimming enabled higher fat suppression efficiency. CONCLUSION Optimized SPIR in combination with constrained IB shimming can improve maternal fat suppression while minimizing EPI distortions in the fetal brain.
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Affiliation(s)
- Andreia S. Gaspar
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
- Institute for Systems and Robotics/Department of Bioengineering, Instituto Superior TécnicoUniversidade de LisboaLisbonPortugal
- Instituto de Biofísica e Engenharia BiomédicaFaculdade de Ciências da Universidade de LisboaCampo GrandeLisbonPortugal
| | - Rita G. Nunes
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
- Institute for Systems and Robotics/Department of Bioengineering, Instituto Superior TécnicoUniversidade de LisboaLisbonPortugal
- Instituto de Biofísica e Engenharia BiomédicaFaculdade de Ciências da Universidade de LisboaCampo GrandeLisbonPortugal
| | - Giulio Ferrazzi
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
| | - Emer J. Hughes
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
| | - Jana Hutter
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
| | - Shaihan J. Malik
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
| | - Laura McCabe
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
| | - Kelly P. Baruteau
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
- Lysholm Department of Neuroradiology, National Hospital for Neurology and NeurosurgeryUniversity College London Hospitals NHS Foundation TrustLondonUnited Kingdom
| | - Mary A. Rutherford
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
| | - Joseph V. Hajnal
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
| | - Anthony N. Price
- Centre for the Developing Brain, School of Biomedical Engineering & Imaging SciencesKing's College London, St Thomas' HospitalLondonUnited Kingdom
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19
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Winkler SA, Schmitt F, Landes H, de Bever J, Wade T, Alejski A, Rutt BK. Gradient and shim technologies for ultra high field MRI. Neuroimage 2018; 168:59-70. [PMID: 27915120 PMCID: PMC5591082 DOI: 10.1016/j.neuroimage.2016.11.033] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Revised: 10/06/2016] [Accepted: 11/12/2016] [Indexed: 02/08/2023] Open
Abstract
Ultra High Field (UHF) MRI requires improved gradient and shim performance to fully realize the promised gains (SNR as well as spatial, spectral, diffusion resolution) that higher main magnetic fields offer. Both the more challenging UHF environment by itself, as well as the higher currents used in high performance coils, require a deeper understanding combined with sophisticated engineering modeling and construction, to optimize gradient and shim hardware for safe operation and for highest image quality. This review summarizes the basics of gradient and shim technologies, and outlines a number of UHF-related challenges and solutions. In particular, Lorentz forces, vibroacoustics, eddy currents, and peripheral nerve stimulation are discussed. Several promising UHF-relevant gradient concepts are described, including insertable gradient coils aimed at higher performance neuroimaging.
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Affiliation(s)
| | | | | | | | - Trevor Wade
- Imaging Research Laboratories, Robarts Research Institute, Canada
| | - Andrew Alejski
- Imaging Research Laboratories, Robarts Research Institute, Canada
| | - Brian K Rutt
- Department of Radiology, Stanford University, USA
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20
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Stockmann JP, Wald LL. In vivo B 0 field shimming methods for MRI at 7T. Neuroimage 2018; 168:71-87. [PMID: 28602943 PMCID: PMC5760477 DOI: 10.1016/j.neuroimage.2017.06.013] [Citation(s) in RCA: 85] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2016] [Revised: 05/19/2017] [Accepted: 06/06/2017] [Indexed: 01/12/2023] Open
Abstract
Functional MRI (fMRI) at 7T and above provides improved Signal-to-Noise Ratio and Contrast-to-Noise Ratio compared to 3T acquisitions. In addition to the beneficial effects on spin polarization and magnetization of deoxyhemoglobin, the increased applied field also further magnetizes air and tissue. While the magnets themselves typically provide a static B0 field with sufficient spatial homogeneity, the diamagnetism of tissue and the paramagnetism of air causes local field deviations inside the human head. These spatially-varying field offsets (ΔB0) cause image artifacts, especially in single shot EPI, including geometric distortion, signal dropout, and blurring. These effects are particularly strong near air-tissue interfaces such as the frontal sinus, and ear canals. Furthermore, if the field offsets are dynamically modulated through physiological processes such as respiration or motion, then the effect on the image time-series can be even more problematic. While post-processing methods have been developed to mitigate these effects, the ideal solution would be to reduce the ΔB0 variations at their source. Typically 7T scanners contain 2nd and some 3rd order spherical harmonic shim coil terms to cancel static ΔB0 variations of low spatial order. In this article, we will motivate the need for improved, higher-order compensation for B0 inhomogeneity and potentially add dynamic control of these fields. We discuss and compare several promising hardware approaches for static and dynamic B0 shimming using either higher-order spherical harmonic shim coils or multi-coil shim arrays as well as passive shimming approaches, and active variants such and adaptive current networks.
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Affiliation(s)
- Jason P Stockmann
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, United States.
| | - Lawrence L Wald
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, United States; Harvard Medical School, Boston, MA, United States
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21
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Uğurbil K. Imaging at ultrahigh magnetic fields: History, challenges, and solutions. Neuroimage 2018; 168:7-32. [PMID: 28698108 PMCID: PMC5758441 DOI: 10.1016/j.neuroimage.2017.07.007] [Citation(s) in RCA: 86] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Revised: 07/05/2017] [Accepted: 07/07/2017] [Indexed: 01/06/2023] Open
Abstract
Following early efforts in applying nuclear magnetic resonance (NMR) spectroscopy to study biological processes in intact systems, and particularly since the introduction of 4 T human scanners circa 1990, rapid progress was made in imaging and spectroscopy studies of humans at 4 T and animal models at 9.4 T, leading to the introduction of 7 T and higher magnetic fields for human investigation at about the turn of the century. Work conducted on these platforms has provided numerous technological solutions to challenges posed at these ultrahigh fields, and demonstrated the existence of significant advantages in signal-to-noise ratio and biological information content. Primary difference from lower fields is the deviation from the near field regime at the radiofrequencies (RF) corresponding to hydrogen resonance conditions. At such ultrahigh fields, the RF is characterized by attenuated traveling waves in the human body, which leads to image non-uniformities for a given sample-coil configuration because of destructive and constructive interferences. These non-uniformities were initially considered detrimental to progress of imaging at high field strengths. However, they are advantageous for parallel imaging in signal reception and transmission, two critical technologies that account, to a large extend, for the success of ultrahigh fields. With these technologies and improvements in instrumentation and imaging methods, today ultrahigh fields have provided unprecedented gains in imaging of brain function and anatomy, and started to make inroads into investigation of the human torso and extremities. As extensive as they are, these gains still constitute a prelude to what is to come given the increasingly larger effort committed to ultrahigh field research and development of ever better instrumentation and techniques.
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Affiliation(s)
- Kamil Uğurbil
- Center for Magnetic Resonance Research (CMRR), University of Minnesota Medical School, Minneapolis, MN 55455, USA.
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22
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Winkler SA, Warr PA, Stockmann JP, Mareyam A, Keil B, Watkins RD, Wald LL, Rutt BK. Comparision of new element designs for combined RF-Shim arrays at 7 T. CONCEPTS IN MAGNETIC RESONANCE. PART B, MAGNETIC RESONANCE ENGINEERING 2018; 48B:e21364. [PMID: 30613196 PMCID: PMC6317377 DOI: 10.1002/cmr.b.21364] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Accepted: 05/10/2018] [Indexed: 06/09/2023]
Abstract
PURPOSE To identify novel concepts for RF-shim loop architectures suitable for 7T made of two concentric conducting loops fulfilling RF and DC functions, respectively, and to determine their relative SNR performance. The goal is to minimize interference between the two systems while making efficient use of the space closest to the body. THEORY We show by means of theoretical derivation of the frequency spectrum that the proposed two-loop structure exhibits an anti-resonant null and a resonant peak in the frequency domain. METHODS The proposed structure is comprised of two concentric wire loops either arranged as nested loops or in the form of a coaxial cable, in which the two conductors carry the RF and shim signals, respectively. We use theory, simulation, and phantom measurements to obtain frequency spectra and SNR maps for the proposed structures. RESULTS Retained SNR is found to be 75% in the coaxial loop and ranges from 57% to 67% in three different coaxial configurations. We have found both implementations to be a viable concept for the use in RF-shim devices if remaining SNR limitations can be overcome. CONCLUSIONS We have investigated two new design modalities in 7T RF-shim coil design that separate the RF and shim conductors such that the previously proposed toroidal chokes are eliminated - thereby removing undesired additional loss, bulk, and design complexity.
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Affiliation(s)
- Simone A. Winkler
- Department of Radiology, Stanford University, Stanford, California, USA., Grant sponsor: NIH K99 EB24341., Grant sponsor: NIH P41 EB015891., Grant sponsor: NSERC., Grant sponsor: BWF
| | - Paul A. Warr
- Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA
| | - Jason P. Stockmann
- Department of Electrical and Electronic Engineering, University of Bristol, UK
| | - Azma Mareyam
- Department of Electrical and Electronic Engineering, University of Bristol, UK
| | - Boris Keil
- Technische Hochschule Mittelhessen, Germany
| | - Ronald D. Watkins
- Department of Radiology, Stanford University, Stanford, California, USA., Grant sponsor: NIH K99 EB24341., Grant sponsor: NIH P41 EB015891., Grant sponsor: NSERC., Grant sponsor: BWF
| | - Lawrence L. Wald
- Department of Electrical and Electronic Engineering, University of Bristol, UK
| | - Brian K. Rutt
- Department of Radiology, Stanford University, Stanford, California, USA., Grant sponsor: NIH K99 EB24341., Grant sponsor: NIH P41 EB015891., Grant sponsor: NSERC., Grant sponsor: BWF
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Kirov II, Kuzniecky R, Hetherington HP, Soher BJ, Davitz MS, Babb JS, Pardoe HR, Pan JW, Gonen O. Whole brain neuronal abnormalities in focal epilepsy quantified with proton MR spectroscopy. Epilepsy Res 2018; 139:85-91. [PMID: 29212047 PMCID: PMC6411059 DOI: 10.1016/j.eplepsyres.2017.11.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 11/20/2017] [Accepted: 11/28/2017] [Indexed: 12/31/2022]
Abstract
OBJECTIVE To test the hypothesis that localization-related epilepsy is associated with widespread neuronal dysfunction beyond the ictal focus, reflected by a decrease in patients' global concentration of their proton MR spectroscopy (1H-MRS) observed marker, N-acetyl-aspartate (NAA). METHODS Thirteen patients with localization-related epilepsy (7 men, 6 women) 40±13 (mean±standard-deviation)years old, 8.3±13.4years of disease duration; and 14 matched controls, were scanned at 3 T with MRI and whole-brain (WB) 1H MRS. Intracranial fractions of brain volume, gray and white matter (fBV, fGM, fWM) were segmented from the MRI, and global absolute NAA creatine (Cr) and choline (Cho) concentrations were estimated from their WB 1H MRS. These metrics were compared between patients and controls using an unequal variance t test. RESULTS Patients' fBV, fGM and fWM: 0.81±0.07, 0.47±0.04, 0.31±0.04 were not different from controls' 0.79±0.05, 0.48±0.04, 0.32±0.02; nor were their Cr and Cho concentrations: 7.1±1.1 and 1.3±0.2 millimolar (mM) versus 7.7±0.7 and 1.4±0.1mM (p>0.05 all). Patients' global NAA concentration: 11.5±1.5 mM, however, was 12% lower than controls' 13.0±0.8mM (p=0.004). CONCLUSIONS These findings indicate that neuronal dysfunction in localization-related epilepsy extends globally, beyond the ictal zone, but without atrophy or spectroscopic evidence of other pathology. This suggests a diffuse decline in the neurons' health, rather than their number, early in the disease course. WB 1H-MRS assessment, therefore, may be a useful tool for quantification of global neuronal dysfunction load in epilepsy.
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Affiliation(s)
- Ivan I Kirov
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, USA.
| | - Ruben Kuzniecky
- Comprehensive Epilepsy Center, New York University School of Medicine,New York City, NY, USA.
| | - Hoby P Hetherington
- Department of Radiology and Neurology, University of Pittsburgh School of Medicine,Pittsburgh, PA, USA.
| | - Brian J Soher
- Department of Radiology, Duke University Medical Center, Durham NC, USA.
| | - Matthew S Davitz
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, USA.
| | - James S Babb
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, USA.
| | - Heath R Pardoe
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, USA.
| | - Jullie W Pan
- Department of Radiology and Neurology, University of Pittsburgh School of Medicine,Pittsburgh, PA, USA.
| | - Oded Gonen
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, USA.
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24
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Kirov II, Wu WE, Soher BJ, Davitz MS, Huang JH, Babb JS, Lazar M, Fatterpekar G, Gonen O. Global brain metabolic quantification with whole-head proton MRS at 3 T. NMR IN BIOMEDICINE 2017; 30:10.1002/nbm.3754. [PMID: 28678429 PMCID: PMC5609859 DOI: 10.1002/nbm.3754] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 05/04/2017] [Accepted: 05/05/2017] [Indexed: 06/07/2023]
Abstract
Total N-acetyl-aspartate + N-acetyl-aspartate-glutamate (NAA), total creatine (Cr) and total choline (Cho) proton MRS (1 H-MRS) signals are often used as surrogate markers in diffuse neurological pathologies, but spatial coverage of this methodology is limited to 1%-65% of the brain. Here we wish to demonstrate that non-localized, whole-head (WH) 1 H-MRS captures just the brain's contribution to the Cho and Cr signals, ignoring all other compartments. Towards this end, 27 young healthy adults (18 men, 9 women), 29.9 ± 8.5 years old, were recruited and underwent T1 -weighted MRI for tissue segmentation, non-localizing, approximately 3 min WH 1 H-MRS (TE /TR /TI = 5/10/940 ms) and 30 min 1 H-MR spectroscopic imaging (MRSI) (TE /TR = 35/2100 ms) in a 360 cm3 volume of interest (VOI) at the brain's center. The VOI absolute NAA, Cr and Cho concentrations, 7.7 ± 0.5, 5.5 ± 0.4 and 1.3 ± 0.2 mM, were all within 10% of the WH: 8.6 ± 1.1, 6.0 ± 1.0 and 1.3 ± 0.2 mM. The mean NAA/Cr and NAA/Cho ratios in the WH were only slightly higher than the "brain-only" VOI: 1.5 versus 1.4 (7%) and 6.6 versus 5.9 (11%); Cho/Cr were not different. The brain/WH volume ratio was 0.31 ± 0.03 (brain ≈ 30% of WH volume). Air-tissue susceptibility-driven local magnetic field changes going from the brain outwards showed sharp gradients of more than 100 Hz/cm (1 ppm/cm), explaining the skull's Cr and Cho signal losses through resonance shifts, line broadening and destructive interference. The similarity of non-localized WH and localized VOI NAA, Cr and Cho concentrations and their ratios suggests that their signals originate predominantly from the brain. Therefore, the fast, comprehensive WH-1 H-MRS method may facilitate quantification of these metabolites, which are common surrogate markers in neurological disorders.
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Affiliation(s)
- Ivan I. Kirov
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY 10016, USA
| | - William E. Wu
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY 10016, USA
| | - Brian J. Soher
- Department of Radiology, Duke University Medical Center, Durham NC 27710, USA
| | - Matthew S. Davitz
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY 10016, USA
| | - Jeffrey H. Huang
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY 10016, USA
| | - James S. Babb
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY 10016, USA
| | - Mariana Lazar
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY 10016, USA
| | - Girish Fatterpekar
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY 10016, USA
| | - Oded Gonen
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY 10016, USA
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25
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Nassirpour S, Chang P, Fillmer A, Henning A. A comparison of optimization algorithms for localized in vivo B 0 shimming. Magn Reson Med 2017; 79:1145-1156. [PMID: 28543722 DOI: 10.1002/mrm.26758] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 04/05/2017] [Accepted: 04/29/2017] [Indexed: 01/06/2023]
Abstract
PURPOSE To compare several different optimization algorithms currently used for localized in vivo B0 shimming, and to introduce a novel, fast, and robust constrained regularized algorithm (ConsTru) for this purpose. METHODS Ten different optimization algorithms (including samples from both generic and dedicated least-squares solvers, and a novel constrained regularized inversion method) were implemented and compared for shimming in five different shimming volumes on 66 in vivo data sets from both 7 T and 9.4 T. The best algorithm was chosen to perform single-voxel spectroscopy at 9.4 T in the frontal cortex of the brain on 10 volunteers. RESULTS The results of the performance tests proved that the shimming algorithm is prone to unstable solutions if it depends on the value of a starting point, and is not regularized to handle ill-conditioned problems. The ConsTru algorithm proved to be the most robust, fast, and efficient algorithm among all of the chosen algorithms. It enabled acquisition of spectra of reproducible high quality in the frontal cortex at 9.4 T. CONCLUSIONS For localized in vivo B0 shimming, the use of a dedicated linear least-squares solver instead of a generic nonlinear one is highly recommended. Among all of the linear solvers, the constrained regularized method (ConsTru) was found to be both fast and most robust. Magn Reson Med 79:1145-1156, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Sahar Nassirpour
- Max Planck Institute for Biological Cybernetics, Tuebingen, Germany.,IMPRS for Cognitive and Systems Neuroscience, Eberhard-Karls University of Tuebingen, Germany
| | - Paul Chang
- Max Planck Institute for Biological Cybernetics, Tuebingen, Germany.,IMPRS for Cognitive and Systems Neuroscience, Eberhard-Karls University of Tuebingen, Germany
| | | | - Anke Henning
- Max Planck Institute for Biological Cybernetics, Tuebingen, Germany.,Institute for Biomedical Engineering, UZH and ETH Zürich, Zürich, Switzerland
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26
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Chang P, Nassirpour S, Henning A. Modeling real shim fields for very high degree (and order) B 0 shimming of the human brain at 9.4 T. Magn Reson Med 2017; 79:529-540. [PMID: 28321902 DOI: 10.1002/mrm.26658] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Revised: 02/06/2017] [Accepted: 02/06/2017] [Indexed: 01/07/2023]
Abstract
PURPOSE To describe the process of calibrating a B0 shim system using high-degree (or high order) spherical harmonic models of the measured shim fields, to provide a method that considers amplitude dependency of these models, and to show the advantage of very high-degree B0 shimming for whole-brain and single-slice applications at 9.4 Tesla (T). METHODS An insert shim with up to fourth and partial fifth/sixth degree (order) spherical harmonics was used with a Siemens 9.4T scanner. Each shim field was measured and modeled as input for the shimming algorithm. Optimal shim currents can therefore be calculated in a single iteration. A range of shim currents was used in the modeling to account for possible amplitude nonlinearities. The modeled shim fields were used to compare different degrees of whole-brain B0 shimming on healthy subjects. RESULTS The ideal shim fields did not correctly shim the subject brains. However, using the modeled shim fields improved the B0 homogeneity from 55.1 (second degree) to 44.68 Hz (partial fifth/sixth degree) on the whole brains of 9 healthy volunteers, with a total applied current of 0.77 and 6.8 A, respectively. CONCLUSIONS The necessity of calibrating the shim system was shown. Better B0 homogeneity drastically reduces signal dropout and distortions for echo-planar imaging, and significantly improves the linewidths of MR spectroscopy imaging. Magn Reson Med 79:529-540, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Paul Chang
- Max Planck Institute for Biological Cybernetics, Tuebingen, Germany.,IMPRS for Cognitive and Systems Neuroscience, Eberhard-Karls University of Tuebingen, Germany
| | - Sahar Nassirpour
- Max Planck Institute for Biological Cybernetics, Tuebingen, Germany.,IMPRS for Cognitive and Systems Neuroscience, Eberhard-Karls University of Tuebingen, Germany
| | - Anke Henning
- Max Planck Institute for Biological Cybernetics, Tuebingen, Germany
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27
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Davitz MS, Wu WE, Soher BJ, Babb JS, Kirov II, Huang J, Fatterpekar G, Gonen O. Quantifying global-brain metabolite level changes with whole-head proton MR spectroscopy at 3T. Magn Reson Imaging 2017; 35:15-19. [PMID: 27580518 PMCID: PMC5125897 DOI: 10.1016/j.mri.2016.08.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 07/21/2016] [Accepted: 08/20/2016] [Indexed: 01/24/2023]
Abstract
BACKGROUND AND PURPOSE To assess the sensitivity of non-localized, whole-head 1H-MRS to an individual's serial changes in total-brain NAA, Glx, Cr and Cho concentrations - metabolite metrics often used as surrogate markers in neurological pathologies. MATERIALS AND METHODS In this prospective study, four back-to-back (single imaging session) and three serial (successive sessions) non-localizing, ~3min 1H-MRS (TE/TR/TI=5/104/940ms) scans were performed on 18 healthy young volunteers: 9 women, 9 men: 29.9±7.6 [mean±standard deviation (SD)] years old. These were analyzed by calculating a within-subject coefficient of variation (CV=SD/mean) to assess intra- and inter-scan repeatability and prediction intervals. This study was Health Insurance Portability and Accountability Act compliant. All subjects gave institutional review board-approved written, informed consent. RESULTS The intra-scan CVs for the NAA, Glx, Cr and Cho were: 3.9±1.8%, 7.3±4.6%, 4.0±3.4% and 2.5±1.6%, and the corresponding inter-scan (longitudinal) values were: 7.0±3.1%, 10.6±5.6%, 7.6±3.5% and 7.0±3.9%. This method is shown to have 80% power to detect changes of 14%, 27%, 26% and 19% between two serial measurements in a given individual. CONCLUSIONS Subject to the assumption that in neurological disorders NAA, Glx, Cr and Cho changes represent brain-only pathology and not muscles, bone marrow, adipose tissue or epithelial cells, this approach enables us to quantify them, thereby adding specificity to the assessment of the total disease load. This will facilitate monitoring diffuse pathologies with faster measurement, more extensive (~90% of the brain) spatial coverage and sensitivity than localized 1H-MRS.
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Affiliation(s)
- Matthew S Davitz
- Center for Advanced Imaging Innovation and Research, Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY 10016, USA
| | - William E Wu
- Center for Advanced Imaging Innovation and Research, Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY 10016, USA
| | - Brian J Soher
- Department of Radiology, Duke University Medical Center, Durham, NC, 27710, USA
| | - James S Babb
- Center for Advanced Imaging Innovation and Research, Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY 10016, USA
| | - Ivan I Kirov
- Center for Advanced Imaging Innovation and Research, Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY 10016, USA
| | - Jeffrey Huang
- Center for Advanced Imaging Innovation and Research, Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY 10016, USA
| | - Girish Fatterpekar
- Center for Advanced Imaging Innovation and Research, Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY 10016, USA
| | - Oded Gonen
- Center for Advanced Imaging Innovation and Research, Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY 10016, USA.
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28
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Kim T, Lee Y, Zhao T, Hetherington HP, Pan JW. Gradient-echo EPI using a high-degree shim insert coil at 7 T: Implications for BOLD fMRI. Magn Reson Med 2016; 78:1734-1745. [PMID: 27910126 PMCID: PMC6084307 DOI: 10.1002/mrm.26563] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Revised: 11/04/2016] [Accepted: 11/04/2016] [Indexed: 12/27/2022]
Abstract
Purpose To quantitatively assess the effects of high degree and order (1st–4th+) relative to 1st–2nd degree B0 shimming at 7 Tesla (T) on gradient‐echo echo planar imaging (GE‐EPI) and blood‐oxygen‐level dependent (BOLD) activation. Methods Simulations and GE‐EPI were performed at (2mm)3 and (3mm)3 resolution, evaluating the temporal signal‐to‐noise ratio (tSNR), transverse relaxivity (
R2*), BOLD % signal change and activated pixel counts in a breath‐hold task. Results Comparing the 1st–4th+ degree with 1st–2nd degree shimmed B0 maps generated spatially varying regions of
Δ|B0|=|B01−2|−|B01−4+|. As binned in 10‐Hz intervals, the two center Δ|B0| (±10 Hz) bins maintained the B0 offset of 48.6% of gray‐matter pixels. In the positive Δ|B0| bins greater than 10 Hz, the 1st–4th+degree shimming improved the B0 offset in 41.1%; in negative Δ|B0| bins less than −10 Hz, the offset worsened in 10.2% of the pixels. In the positive Δ|B0| bins, we found variable but significant increases in BOLD sensitivity; the negative Δ|B0| bins showed significant decreases. In the breath‐hold studies, positive bins showed significantly increased activated pixel numbers (+5–29%), whereas negative bins showed −18 to 0% decline. Conclusion 1st–4th+ degree shimming maintained B0 homogeneity over central brain regions while improving most of the other regions, including the inferior frontal lobe. Magn Reson Med 78:1734–1745, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
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Affiliation(s)
- Tae Kim
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Yoojin Lee
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Tiejun Zhao
- Siemens Healthineers, USA, Siemens Medical Solution USA, Pittsburgh, Pennsylvania, USA
| | - Hoby P Hetherington
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Jullie W Pan
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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29
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Meyer EJ, Kirov II, Tal A, Davitz MS, Babb JS, Lazar M, Malaspina D, Gonen O. Metabolic Abnormalities in the Hippocampus of Patients with Schizophrenia: A 3D Multivoxel MR Spectroscopic Imaging Study at 3T. AJNR Am J Neuroradiol 2016; 37:2273-2279. [PMID: 27444940 DOI: 10.3174/ajnr.a4886] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 06/03/2016] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Schizophrenia is well-known to be associated with hippocampal structural abnormalities. We used 1H-MR spectroscopy to test the hypothesis that these abnormalities are accompanied by NAA deficits, reflecting neuronal dysfunction, in patients compared with healthy controls. MATERIALS AND METHODS Nineteen patients with schizophrenia (11 men; mean age, 40.6 ± 10.1 years; mean disease duration, 19.5 ± 10.5 years) and 11 matched healthy controls (5 men; mean age, 33.7 ± 10.1 years) underwent MR imaging and multivoxel point-resolved spectroscopy (TE/TR, 35/1400 ms) 1H-MRS at 3T to obtain their hippocampal GM absolute NAA, Cr, Cho, and mIns concentrations. Unequal variance t tests and ANCOVA were used to compare patients with controls. Bilateral volumes from manually outlined hippocampal masks were compared by using unequal variance t tests. RESULTS Patients' average hippocampal GM Cr concentrations were 19% higher than that of controls, 8.7 ± 2.2 versus 7.4 ± 1.2 mmol/L (P < .05); showing no differences, concentrations in NAA were 8.8 ± 1.6 versus 8.7 ± 1.2 mmol/L; in Cho, 2.3 ± 0.7 versus 2.1 ± 0.3 mmol/L; and in mIns, 6.1 ± 1.5 versus 5.2 ± 0.9 (all P > .1). There was a positive correlation between mIns and Cr in patients (r = 0.57, P = .05) but not in controls. The mean bilateral hippocampal volume was ∼10% lower in patients: 7.5 ± 0.9 versus 8.4 ± 0.7 cm3 (P < .05). CONCLUSIONS These findings suggest that the hippocampal volume deficit in schizophrenia is not due to net loss of neurons, in agreement with histopathology studies but not with prior 1H-MR spectroscopy reports. Elevated Cr is consistent with hippocampal hypermetabolism, and its correlation with mIns may also suggest an inflammatory process affecting some cases; these findings may suggest treatment targets and markers to monitor them.
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Affiliation(s)
- E J Meyer
- From the Department of Radiology (E.J.M., I.I.K., M.S.D., J.S.B., M.L., O.G.), Center for Advanced Imaging Innovation and Research, Bernard and Irene Schwartz Center for Biomedical Imaging
| | - I I Kirov
- From the Department of Radiology (E.J.M., I.I.K., M.S.D., J.S.B., M.L., O.G.), Center for Advanced Imaging Innovation and Research, Bernard and Irene Schwartz Center for Biomedical Imaging
| | - A Tal
- Department of Chemical Physics (A.T.), Weizmann Institute of Science, Rehovot, Israel
| | - M S Davitz
- From the Department of Radiology (E.J.M., I.I.K., M.S.D., J.S.B., M.L., O.G.), Center for Advanced Imaging Innovation and Research, Bernard and Irene Schwartz Center for Biomedical Imaging
| | - J S Babb
- From the Department of Radiology (E.J.M., I.I.K., M.S.D., J.S.B., M.L., O.G.), Center for Advanced Imaging Innovation and Research, Bernard and Irene Schwartz Center for Biomedical Imaging
| | - M Lazar
- From the Department of Radiology (E.J.M., I.I.K., M.S.D., J.S.B., M.L., O.G.), Center for Advanced Imaging Innovation and Research, Bernard and Irene Schwartz Center for Biomedical Imaging
| | - D Malaspina
- Department of Psychiatry (D.M.), Institute for Social and Psychiatric Initiatives, New York University School of Medicine, New York, New York
| | - O Gonen
- From the Department of Radiology (E.J.M., I.I.K., M.S.D., J.S.B., M.L., O.G.), Center for Advanced Imaging Innovation and Research, Bernard and Irene Schwartz Center for Biomedical Imaging
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30
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Henning A, Koning W, Fuchs A, Raaijmakers A, Bluemink JJ, van den Berg CAT, Boer VO, Klomp DWJ. (1) H MRS in the human spinal cord at 7 T using a dielectric waveguide transmitter, RF shimming and a high density receive array. NMR IN BIOMEDICINE 2016; 29:1231-1239. [PMID: 27191947 DOI: 10.1002/nbm.3541] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Revised: 03/22/2016] [Accepted: 03/23/2016] [Indexed: 06/05/2023]
Abstract
Multimodal MRI is the state of the art method for clinical diagnostics and therapy monitoring of the spinal cord, with MRS being an emerging modality that has the potential to detect relevant changes of the spinal cord tissue at an earlier stage and to enhance specificity. Methodological challenges related to the small dimensions and deep location of the human spinal cord inside the human body, field fluctuations due to respiratory motion, susceptibility differences to adjacent tissue such as vertebras and pulsatile flow of the cerebrospinal fluid hinder the clinical application of (1) H MRS to the human spinal cord. Complementary to previous studies that partly addressed these problems, this work aims at enhancing the signal-to-noise ratio (SNR) of (1) H MRS in the human spinal cord. To this end a flexible tight fit high density receiver array and ultra-high field strength (7 T) were combined. A dielectric waveguide and dipole antenna transmission coil allowed for dual channel RF shimming, focusing the RF field in the spinal cord, and an inner-volume saturated semi-LASER sequence was used for robust localization in the presence of B1 (+) inhomogeneity. Herein we report the first 7 T spinal cord (1) H MR spectra, which were obtained in seven independent measurements of 128 averages each in three healthy volunteers. The spectra exhibit high quality (full width at half maximum 0.09 ppm, SNR 7.6) and absence of artifacts and allow for reliable quantification of N-acetyl aspartate (NAA) (NAA/Cr (creatine) 1.31 ± 0.20; Cramér-Rao lower bound (CRLB) 5), total choline containing compounds (Cho) (Cho/Cr 0.32 ± 0.07; CRLB 7), Cr (CRLB 5) and myo-inositol (mI) (mI/Cr 1.08 ± 0.22; CRLB 6) in 7.5 min in the human cervical spinal cord. Thus metabolic information from the spinal cord can be obtained in clinically feasible scan times at 7 T, and its benefit for clinical decision making in spinal cord disorders will be investigated in the future using the presented methodology. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- A Henning
- Max Plank Institute for Biological Cybernetics, Tübingen, Germany
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
| | - W Koning
- University Medical Center Utrecht, Utrecht, The Netherlands
| | - A Fuchs
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
| | - A Raaijmakers
- University Medical Center Utrecht, Utrecht, The Netherlands
| | - J J Bluemink
- University Medical Center Utrecht, Utrecht, The Netherlands
| | | | - V O Boer
- University Medical Center Utrecht, Utrecht, The Netherlands
| | - D W J Klomp
- University Medical Center Utrecht, Utrecht, The Netherlands
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31
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Bisdas S, Chadzynski GL, Braun C, Schittenhelm J, Skardelly M, Hagberg GE, Ethofer T, Pohmann R, Shajan G, Engelmann J, Tabatabai G, Ziemann U, Ernemann U, Scheffler K. MR spectroscopy for in vivo assessment of the oncometabolite 2-hydroxyglutarate and its effects on cellular metabolism in human brain gliomas at 9.4T. J Magn Reson Imaging 2016; 44:823-33. [PMID: 26970248 DOI: 10.1002/jmri.25221] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 02/22/2016] [Indexed: 12/27/2022] Open
Abstract
PURPOSE To examine in vivo metabolic alterations in the isocitrate dehydrogenase (IDH) mutated gliomas using magnetic resonance spectroscopy (MRS) at magnetic field 9.4T. MATERIALS AND METHODS Spectra were acquired with a 9.4T whole-body scanner with the use of a custom-built head coil (16 channel transmit and 31 channel receive). A modified stimulated echo acquisition mode (STEAM) sequence was used for localization. Eighteen patients with brain tumors of probable glial origin participated in this study. The study was performed in accordance with the guidelines of the local Ethics Committee. RESULTS The increased spectral resolution allowed us to directly address metabolic alterations caused by the specific pathophysiology of IDH mutations including the presence of the oncometabolite 2-hydroxglutarate (2HG) and a significant decrease of the pooled glutamate and glutamine (20%, P = 0.024), which probably reflects an attempt to replenish α-ketoglutarate lost by conversion to 2HG. We also observed significantly reduced glutathione (GSH) levels (39%, P = 0.019), which could be similarly caused by depletion of dihydronicotinamide-adenine dinucleotide phosphate (NADPH) during this conversion in IDH mutant gliomas. CONCLUSION We demonstrate that MRS at 9.4T provides a noninvasive measure of 2HG in vivo, which may be used for therapy planning and prognostication, and may provide insights into related pathophysiologic metabolic alterations associated with IDH mutations. J. MAGN. RESON. IMAGING 2016;44:823-833.
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Affiliation(s)
- Sotirios Bisdas
- Department of Neuroradiology, Eberhard-Karls University Tübingen, Tübingen, Germany.,Department of Neuroradiology, National Hospital for Neurology and Neurosurgery, University College London Hospitals, London, UK.,Center for CNS tumors, Comprehensive Cancer Center Tübingen-Stuttgart, University Hospital Tübingen, Eberhard Karls University Tübingen, Tübingen, Germany
| | - Grzegorz L Chadzynski
- Department of Biomedical Magnetic Resonance, Eberhard-Karls University Tübingen, Tübingen, Germany. .,High-field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
| | - Christian Braun
- Center for CNS tumors, Comprehensive Cancer Center Tübingen-Stuttgart, University Hospital Tübingen, Eberhard Karls University Tübingen, Tübingen, Germany.,Department of Neurology & Stroke, Hertie Institute for Clinical Brain Research, Eberhard-Karls University Tübingen, Tübingen, Germany.,Interdisciplinary Division of Neuro-Oncology, University Hospital Tübingen, Hertie Institute for Clinical Brain Research, Eberahrd Karls University, Tübingen, Germany
| | - Jens Schittenhelm
- Center for CNS tumors, Comprehensive Cancer Center Tübingen-Stuttgart, University Hospital Tübingen, Eberhard Karls University Tübingen, Tübingen, Germany.,Interdisciplinary Division of Neuro-Oncology, University Hospital Tübingen, Hertie Institute for Clinical Brain Research, Eberahrd Karls University, Tübingen, Germany.,Department of Neuropathology, Eberhard-Karls University Tübingen, Tübingen, Germany.,Center for Personalized Medicine, Eberhard Karls University, Tübingen, Germany
| | - Marco Skardelly
- Center for CNS tumors, Comprehensive Cancer Center Tübingen-Stuttgart, University Hospital Tübingen, Eberhard Karls University Tübingen, Tübingen, Germany.,Interdisciplinary Division of Neuro-Oncology, University Hospital Tübingen, Hertie Institute for Clinical Brain Research, Eberahrd Karls University, Tübingen, Germany.,Center for Personalized Medicine, Eberhard Karls University, Tübingen, Germany.,Department of Neurosurgery, Eberhard-Karls University Tübingen, Tübingen, Germany
| | - Gisela E Hagberg
- Department of Biomedical Magnetic Resonance, Eberhard-Karls University Tübingen, Tübingen, Germany.,High-field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Thomas Ethofer
- Department of Biomedical Magnetic Resonance, Eberhard-Karls University Tübingen, Tübingen, Germany.,Clinic for Psychiatry and Psychotherapy, Eberhard-Karls University Tübingen, Tübingen, Germany
| | - Rolf Pohmann
- High-field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - G Shajan
- High-field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Jörn Engelmann
- Department of Biomedical Magnetic Resonance, Eberhard-Karls University Tübingen, Tübingen, Germany.,High-field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Ghazaleh Tabatabai
- Center for CNS tumors, Comprehensive Cancer Center Tübingen-Stuttgart, University Hospital Tübingen, Eberhard Karls University Tübingen, Tübingen, Germany.,Department of Neurology & Stroke, Hertie Institute for Clinical Brain Research, Eberhard-Karls University Tübingen, Tübingen, Germany.,Interdisciplinary Division of Neuro-Oncology, University Hospital Tübingen, Hertie Institute for Clinical Brain Research, Eberahrd Karls University, Tübingen, Germany.,Center for Personalized Medicine, Eberhard Karls University, Tübingen, Germany.,German Cancer Consortium (DKTK), DKFZ partner site Tübingen, Tübingen, Germany
| | - Ulf Ziemann
- Center for CNS tumors, Comprehensive Cancer Center Tübingen-Stuttgart, University Hospital Tübingen, Eberhard Karls University Tübingen, Tübingen, Germany.,Department of Neurology & Stroke, Hertie Institute for Clinical Brain Research, Eberhard-Karls University Tübingen, Tübingen, Germany.,Center for Personalized Medicine, Eberhard Karls University, Tübingen, Germany
| | - Ulrike Ernemann
- Department of Neuroradiology, Eberhard-Karls University Tübingen, Tübingen, Germany.,Center for CNS tumors, Comprehensive Cancer Center Tübingen-Stuttgart, University Hospital Tübingen, Eberhard Karls University Tübingen, Tübingen, Germany.,Center for Personalized Medicine, Eberhard Karls University, Tübingen, Germany
| | - Klaus Scheffler
- Department of Biomedical Magnetic Resonance, Eberhard-Karls University Tübingen, Tübingen, Germany.,High-field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
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32
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Ratai EM, Gilberto González R. Clinical magnetic resonance spectroscopy of the central nervous system. HANDBOOK OF CLINICAL NEUROLOGY 2016; 135:93-116. [PMID: 27432661 DOI: 10.1016/b978-0-444-53485-9.00005-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Proton magnetic resonance spectroscopy (1H MRS) is a noninvasive imaging technique that can easily be added to the conventional magnetic resonance (MR) imaging sequences. Using MRS one can directly compare spectra from pathologic or abnormal tissue and normal tissue. Metabolic changes arising from pathology that can be visualized by MRS may not be apparent from anatomy that can be visualized by conventional MR imaging. In addition, metabolic changes may precede anatomic changes. Thus, MRS is used for diagnostics, to observe disease progression, monitor therapeutic treatments, and to understand the pathogenesis of diseases. MRS may have an important impact on patient management. The purpose of this chapter is to provide practical guidance in the clinical application of MRS of the brain. This chapter provides an overview of MRS-detectable metabolites and their significance. In addition some specific current clinical applications of MRS will be discussed, including brain tumors, inborn errors of metabolism, leukodystrophies, ischemia, epilepsy, and neurodegenerative diseases. The chapter concludes with technical considerations and challenges of clinical MRS.
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Affiliation(s)
- Eva-Maria Ratai
- Division of Neuroradiology, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, and Athinoula A. Martinos Center for Biomedical Imaging, Boston, MA, USA.
| | - R Gilberto González
- Division of Neuroradiology, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, and Athinoula A. Martinos Center for Biomedical Imaging, Boston, MA, USA
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Chadzynski GL, Pohmann R, Shajan G, Kolb R, Bisdas S, Klose U, Scheffler K. In vivo proton magnetic resonance spectroscopic imaging of the healthy human brain at 9.4 T: initial experience. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2014; 28:239-49. [PMID: 25248946 DOI: 10.1007/s10334-014-0460-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Revised: 08/22/2014] [Accepted: 08/22/2014] [Indexed: 11/26/2022]
Abstract
OBJECT In this study, the feasibility of in vivo proton magnetic resonance spectroscopic imaging ((1)H MRSI) of the healthy human brain at a field strength of 9.4 T, using conventional acquisition techniques, is examined and the initial experience is summarized. MATERIALS AND METHODS MRSI measurements were performed on a 9.4 T MR scanner (Siemens, Erlangen, Germany) equipped with head-only gradient insert (AC84, Siemens) and custom-developed, 8-channel transmit/24-channel receive, and 16-channel transmit/31-channel receive coils. Spectra were acquired from the superior part of the human brain with a modified STEAM sequence. Spectral quantification was done with LCModel software. RESULTS Reasonable quality and signal-to-noise ratio of the acquired spectra allowed reliable quantification of 12 metabolites (Cramer-Rao lower bounds < 20 %), some of which may be difficult to quantify at field strengths below 7 T due to overlapping resonances or low concentrations. CONCLUSION While further developments are necessary to minimize chemical shift displacement and homogeneity of the transmit field, it is demonstrated that in vivo (1)H MRSI at a field strength of 9.4 T is possible. However, further studies applying up-to-date techniques to overcome high-field specific problems are needed in order to assess the potential gain in sensitivity that may be offered by MRSI at 9.4 T.
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Affiliation(s)
- Grzegorz L Chadzynski
- Biomedical Magnetic Resonance, University Hospital Tuebingen, Hoppe-Seyler-Str. 3, 72076, Tübingen, Germany,
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Zhang N, Song X, Bartha R, Beyea S, D’Arcy R, Zhang Y, Rockwood K. Advances in high-field magnetic resonance spectroscopy in Alzheimer's disease. Curr Alzheimer Res 2014; 11:367-88. [PMID: 24597505 PMCID: PMC4108086 DOI: 10.2174/1567205011666140302200312] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 02/21/2014] [Accepted: 02/25/2014] [Indexed: 12/20/2022]
Abstract
Alzheimer's disease (AD) affects several important molecules in brain metabolism. The resulting neurochemical changes can be quantified non-invasively in localized brain regions using in vivo single-voxel proton magnetic resonance spectroscopy (SV 1H MRS). Although the often heralded diagnostic potential of MRS in AD largely remains unfulfilled, more recent use of high magnetic fields has led to significantly improved signal-to-noise ratios and spectral resolutions, thereby allowing clinical applications with increased measurement reliability. The present article provides a comprehensive review of SV 1H MRS studies on AD at high magnetic fields (3.0 Tesla and above). This review suggests that patterned regional differences and longitudinal alterations in several neurometabolites are associated with clinically established AD. Changes in multiple metabolites are identifiable even at early stages of AD development. By combining information of neurochemicals in different brain regions revealing either pathological or compensatory changes, high field MRS can be evaluated in AD diagnosis and in the detection of treatment effects. To achieve this, standardization of data acquisition and analytical approaches is needed.
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Affiliation(s)
- Ningnannan Zhang
- National Research Council Canada, Institute for Biodiagnostics – Atlantic, Halifax, Nova Scotia, Canada
- Department
of Radiology, General Hospital of Tianjin Medical University, Tianjin, China
| | - Xiaowei Song
- National Research Council Canada, Institute for Biodiagnostics – Atlantic, Halifax, Nova Scotia, Canada
- Division of Geriatric Medicine,
Department of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
- Neuroimaging Research Laboratory,
Biomedical Translational Imaging Centre, Halifax, Nova Scotia, Canada
| | - Robert Bartha
- Centre for Functional and Metabolic
Mapping, Robarts Research Institute, University of Western Ontario, London, Ontario, Canada
- Department of
Medical Biophysics, University of Western Ontario, London, Ontario, Canada
| | - Steven Beyea
- National Research Council Canada, Institute for Biodiagnostics – Atlantic, Halifax, Nova Scotia, Canada
- Neuroimaging Research Laboratory,
Biomedical Translational Imaging Centre, Halifax, Nova Scotia, Canada
- Department of Physics, Dalhousie
University, Halifax, Nova Scotia, Canada
| | - Ryan D’Arcy
- National Research Council Canada, Institute for Biodiagnostics – Atlantic, Halifax, Nova Scotia, Canada
- Department of Applied Science, Simon Fraser University, Surrey, British
Columbia, Canada
- Surrey Memorial Hospital, Fraser Health Foundation Innovation, Surrey, British Columbia,
Canada
| | - Yunting Zhang
- Department
of Radiology, General Hospital of Tianjin Medical University, Tianjin, China
| | - Kenneth Rockwood
- Division of Geriatric Medicine,
Department of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
- Centre for Health Care of the Elderly, Queen Elizabeth II Health Sciences Centre, Halifax, Canada
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Reynaud O, Gallichan D, Schaller B, Gruetter R. Fast low-specific absorption rate B0
-mapping along projections at high field using two-dimensional radiofrequency pulses. Magn Reson Med 2014; 73:901-8. [DOI: 10.1002/mrm.25217] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 02/13/2014] [Accepted: 02/13/2014] [Indexed: 12/24/2022]
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Fillmer A, Kirchner T, Cameron D, Henning A. Constrained image-based B0 shimming accounting for "local minimum traps" in the optimization and field inhomogeneities outside the region of interest. Magn Reson Med 2014; 73:1370-80. [PMID: 24715495 DOI: 10.1002/mrm.25248] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Revised: 03/17/2014] [Accepted: 03/19/2014] [Indexed: 01/09/2023]
Abstract
PURPOSE To improve B0 shimming for applications in high- and ultrahigh-field magnetic resonance imaging and magnetic resonance spectroscopy. METHODS An existing image-based constrained B0 shimming algorithm was enhanced using two techniques: (1) A region of less interest was introduced to control B0 field inhomogeneities in the vicinity of the region of interest; (2) multiple sets of starting values were used for the fitting routine, to avoid "getting trapped" in a local minimum of the optimization function. The influence of constraints during the fitting procedure, due to hardware limitations, on the B0 shim result was investigated. The performance of this algorithm was compared to other B0 shim algorithms for typical shim problems in head and body applications at 3T and 7T. RESULTS Utilization of a weighted region of less interest lead to a significant gain in B0 homogeneity adjacent to the region of interest. The loss of B0 quality due to the enlarged total shim volume within the region of interest remained minimal, allowing for improved artifact reduction in magnetic resonance spectroscopic imaging. Multiple sets of starting values and consideration of shim field constraints led to an additional gain in B0 shim quality. CONCLUSION The proposed algorithm allows for more flexible control of B0 inhomogeneities and, hence, enables gains in image and spectral quality for MR applications. RO1AR050597
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Affiliation(s)
- Ariane Fillmer
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
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37
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Hetherington HP, Hamid H, Kulas J, Ling G, Bandak F, de Lanerolle NC, Pan JW. MRSI of the medial temporal lobe at 7 T in explosive blast mild traumatic brain injury. Magn Reson Med 2014; 71:1358-67. [PMID: 23918077 PMCID: PMC4117409 DOI: 10.1002/mrm.24814] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 04/02/2013] [Accepted: 04/29/2013] [Indexed: 11/06/2022]
Abstract
PURPOSE Up to 19% of veterans returning from the wars in Iraq and Afghanistan have a history of mild traumatic brain injury with 70% associated with blast exposure. Tragically, 20-50% of this group reports persistent symptoms, including memory loss. Unfortunately, routine clinical imaging is typically normal, making diagnosis and clinical management difficult. The goal of this work was to develop methods to acquire hippocampal MRSI at 7 T and evaluate their sensitivity to detect injury in veterans with mild traumatic brain injury. METHODS At 7 T, hippocampal MRSI measurements are limited by: (1) poor B(0) homogeneity; (2) insufficient B(1)(+) strength and homogeneity; and (3) chemical shift dispersion artifacts. To overcofme these limitations we: (1) used third degree B(0) shimming; (2) an inductively decoupled transceiver array with radiofrequency shimming; and (3) a volume localized single slice sequence using radiofrequency shimming-based outer volume suppression. RESULTS In 20 controls and 25 veterans with mild traumatic brain injury due to blast exposure with memory impairment, hippocampal N-acetyl aspartate to choline (P < 0.001) and N-acetyl aspartate to creatine (P < 0.001) were decreased in comparison to control subjects. CONCLUSION With the appropriate methods robust spectroscopic imaging of the hippocampus can be carried out at 7 T. MRSI at 7 T can detect hippocampal injury in veterans with mild traumatic brain injury.
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Affiliation(s)
- Hoby P Hetherington
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; Department of Neurosurgery, Yale University School of Medicine, New Haven, Connecticut, USA
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Abstract
Since the introduction of 4 T human systems in three academic laboratories circa 1990, rapid progress in imaging and spectroscopy studies in humans at 4 T and animal model systems at 9.4 T have led to the introduction of 7 T and higher magnetic fields for human investigation at about the turn of the century. Work conducted on these platforms has demonstrated the existence of significant advantages in SNR and biological information content at these ultrahigh fields, as well as the presence of numerous challenges. Primary difference from lower fields is the deviation from the near field regime; at the frequencies corresponding to hydrogen resonance conditions at ultrahigh fields, the RF is characterized by attenuated traveling waves in the human body, which leads to image nonuniformities for a given sample-coil configuration because of interferences. These nonuniformities were considered detrimental to the progress of imaging at high field strengths. However, they are advantageous for parallel imaging for signal reception and parallel transmission, two critical technologies that account, to a large extend, for the success of ultrahigh fields. With these technologies, and improvements in instrumentation and imaging methods, ultrahigh fields have provided unprecedented gains in imaging of brain function and anatomy, and started to make inroads into investigation of the human torso and extremities. As extensive as they are, these gains still constitute a prelude to what is to come given the increasingly larger effort committed to ultrahigh field research and development of ever better instrumentation and techniques.
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Abstract
Magnetic resonance spectroscopy (MRS) is indicated in the imaging protocol of the patient with epilepsy to screen for metabolic derangements such as inborn errors of metabolism and to characterize masses that may be equivocal on conventional magnetic resonance imaging for dysplasia versus neoplasia. Single-voxel MRS with echo time of 35 milliseconds may be used for this purpose as a quick screening tool in the epilepsy imaging protocol. MRS is useful in the evaluation of both focal and generalized epilepsy.
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40
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Verma T, Cohen-Adad J. Effect of respiration on the B0field in the human spinal cord at 3T. Magn Reson Med 2014; 72:1629-36. [DOI: 10.1002/mrm.25075] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 11/01/2013] [Accepted: 11/19/2013] [Indexed: 02/01/2023]
Affiliation(s)
- Tanya Verma
- Institute of Biomedical Engineering, Polytechnique Montreal; Montreal Quebec Canada
- Birla Institute of Technology and Science Pilani; Pilani Rajasthan India
| | - Julien Cohen-Adad
- Institute of Biomedical Engineering, Polytechnique Montreal; Montreal Quebec Canada
- Functional Neuroimaging Unit, CRIUGM, Université de Montreal, Montreal; Quebec Canada
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41
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The neurochemical profile quantified by in vivo 1H NMR spectroscopy. Neuroimage 2012; 61:342-62. [DOI: 10.1016/j.neuroimage.2011.12.038] [Citation(s) in RCA: 168] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Accepted: 12/15/2011] [Indexed: 12/13/2022] Open
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Pan JW, Duckrow RB, Spencer DD, Avdievich NI, Hetherington HP. Selective homonuclear polarization transfer for spectroscopic imaging of GABA at 7T. Magn Reson Med 2012; 69:310-6. [PMID: 22505305 DOI: 10.1002/mrm.24283] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2011] [Accepted: 03/13/2012] [Indexed: 12/29/2022]
Abstract
We develop and implement a selective homonuclear polarization transfer method for the detection of 3.0 ppm C-4 GABA resonance by spectroscopic imaging in the human brain at 7T. This single shot method is demonstrated with simulations and phantoms, which achieves comparable efficiency of detection to that of J-difference editing. The macromolecule resonance that commonly co-edits with GABA is suppressed at 7T through use of a narrow band preacquisition suppression pulse. This technique is implemented in humans with an eight channel transceiver array and high degree B(0) shimming to measure supplementary motor area and thalamic GABA in controls (n = 8) and epilepsy patients (n = 8 total). We find that the GABA/N-acetyl aspartate ratio in the thalamus of control volunteers, well controlled and poorly controlled epilepsy patients are 0.053 ± 0.012 (n = 8), 0.090 ± 0.012 (n = 2), and 0.038 ± 0.009 (n = 6), respectively.
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Affiliation(s)
- J W Pan
- Department of Neurosurgery, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
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43
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The road to functional imaging and ultrahigh fields. Neuroimage 2012; 62:726-35. [PMID: 22333670 DOI: 10.1016/j.neuroimage.2012.01.134] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Revised: 01/24/2012] [Accepted: 01/30/2012] [Indexed: 11/23/2022] Open
Abstract
The Center for Magnetic Resonance (CMRR) at the University of Minnesota was one of the laboratories where the work that simultaneously and independently introduced functional magnetic resonance imaging (fMRI) of human brain activity was carried out. However, unlike other laboratories pursuing fMRI at the time, our work was performed at 4T magnetic field and coincided with the effort to push human magnetic resonance imaging to field strength significantly beyond 1.5T which was the high-end standard of the time. The human fMRI experiments performed in CMRR were planned between two colleagues who had known each other and had worked together previously in Bell Laboratories, namely Seiji Ogawa and myself, immediately after the Blood Oxygenation Level Dependent (BOLD) contrast was developed by Seiji. We were waiting for our first human system, a 4T system, to arrive in order to attempt at imaging brain activity in the human brain and these were the first experiments we performed on the 4T instrument in CMRR when it became marginally operational. This was a prelude to a subsequent systematic push we initiated for exploiting higher magnetic fields to improve the accuracy and sensitivity of fMRI maps, first going to 9.4T for animal model studies and subsequently developing a 7T human system for the first time. Steady improvements in high field instrumentation and ever expanding armamentarium of image acquisition and engineering solutions to challenges posed by ultrahigh fields have brought fMRI to submillimeter resolution in the whole brain at 7T, the scale necessary to reach cortical columns and laminar differentiation in the whole brain. The solutions that emerged in response to technological challenges posed by 7T also propagated and continues to propagate to lower field clinical systems, a major advantage of the ultrahigh fields effort that is underappreciated. Further improvements at 7T are inevitable. Further translation of these improvements to lower field clinical systems to achieve new capabilities and to magnetic fields significantly higher than 7T to enable human imaging is inescapable.
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44
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Pan JW, Lo KM, Hetherington HP. Role of very high order and degree B0 shimming for spectroscopic imaging of the human brain at 7 tesla. Magn Reson Med 2011; 68:1007-17. [PMID: 22213108 DOI: 10.1002/mrm.24122] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Revised: 11/21/2011] [Accepted: 11/23/2011] [Indexed: 01/19/2023]
Abstract
With the advent of ultrahigh field systems (7 T), significant improvements in spectroscopic imaging (SI) studies of the human brain have been anticipated. These gains are dependent upon the achievable B0 homogeneity, both globally (σB0Global, over the entire regions of interest or slice) and locally (σB0Global, influencing the linewidth of individual SI voxels within the regions of interest). Typically the B0 homogeneity is adjusted using shim coils with spatial distributions modeled on spherical harmonics which can be characterized by a degree (radial dependence) and order (azimuthal symmetry). However, the role of very high order and degree shimming (e.g., 3rd and 4th degree) in MRSI studies has been controversial. Measurements of σB0Global and σB0Local were determined from B0 field maps of 64×64 resolution. In a 10 mm thick slice taken through the region of the subcortical nuclei, we find that in comparison to 1st-2nd degree shims, use of 1st-3rd and 1st-4th degree shims reduces σB0Global by 29% and 55%, respectively. Using a SI voxel size of ∼1cc with an estimate of σB0Local from 3×3×3 B0 map pixels in this subcortical region, the number of pixels with σB0Local of less than 5 Hz increased from 24 to 59% with 1st-3rd and 1st-4th over 1st-2nd degree shims, respectively.
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Affiliation(s)
- Jullie W Pan
- Department of Neurosurgery, Yale University, New Haven, Connecticut 06511-0820, USA.
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45
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Rothman DL, De Feyter HM, de Graaf RA, Mason GF, Behar KL. 13C MRS studies of neuroenergetics and neurotransmitter cycling in humans. NMR IN BIOMEDICINE 2011; 24:943-57. [PMID: 21882281 PMCID: PMC3651027 DOI: 10.1002/nbm.1772] [Citation(s) in RCA: 187] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Revised: 06/09/2011] [Accepted: 06/14/2011] [Indexed: 05/05/2023]
Abstract
In the last 25 years, (13)C MRS has been established as the only noninvasive method for the measurement of glutamate neurotransmission and cell-specific neuroenergetics. Although technically and experimentally challenging, (13)C MRS has already provided important new information on the relationship between neuroenergetics and neuronal function, the energy cost of brain function, the high neuronal activity in the resting brain state and how neuroenergetics and neurotransmitter cycling are altered in neurological and psychiatric disease. In this article, the current state of (13)C MRS as it is applied to the study of neuroenergetics and neurotransmitter cycling in humans is reviewed. The focus is predominantly on recent findings in humans regarding metabolic pathways, applications to clinical research and the technical status of the method. Results from in vivo (13)C MRS studies in animals are discussed from the standpoint of the validation of MRS measurements of neuroenergetics and neurotransmitter cycling, and where they have helped to identify key questions to address in human research. Controversies concerning the relationship between neuroenergetics and neurotransmitter cycling and factors having an impact on the accurate determination of fluxes through mathematical modeling are addressed. We further touch upon different (13)C-labeled substrates used to study brain metabolism, before reviewing a number of human brain diseases investigated using (13)C MRS. Future technological developments are discussed that will help to overcome the limitations of (13)C MRS, with special attention given to recent developments in hyperpolarized (13)C MRS.
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Affiliation(s)
- Douglas L Rothman
- Department of Diagnostic Radiology, Magnetic Resonance Research Center, Yale University School of Medicine, New Haven, CT 06520-8043, USA.
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46
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Dreher W, Erhard P, Leibfritz D. Fast three-dimensional proton spectroscopic imaging of the human brain at 3 T by combining spectroscopic missing pulse steady-state free precession and echo planar spectroscopic imaging. Magn Reson Med 2011; 66:1518-25. [PMID: 21574181 DOI: 10.1002/mrm.22963] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2010] [Revised: 02/18/2011] [Accepted: 03/19/2011] [Indexed: 12/24/2022]
Abstract
The combination of the principles of two fast spectroscopic imaging (SI) methods, spectroscopic missing pulse steady-state free precession and echo planar SI (EPSI) is described as an approach toward fast 3D SI. This method, termed missing pulse steady-state free precession echo planar SI, exhibits a considerably reduced minimum total measurement time T(min), allowing a higher temporal resolution, a larger spatial matrix size, and the use of k-space weighted averaging and phase cycling, while maintaining all advantages of the original spectroscopic missing pulse steady-state free precession sequence. The minor signal-to-noise ratio loss caused by using oscillating read gradients can be compensated by applying k-space weighted averaging. The missing pulse steady-state free precession echo planar SI sequence was implemented on a 3 T head scanner, tested on phantoms and applied to healthy volunteers.
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47
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Pan JW, Avdievich N, Hetherington HP. J-refocused coherence transfer spectroscopic imaging at 7 T in human brain. Magn Reson Med 2011; 64:1237-46. [PMID: 20648684 DOI: 10.1002/mrm.22534] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Short echo spectroscopy is commonly used to minimize signal modulation due to J-evolution of the cerebral amino acids. However, short echo acquisitions suffer from high sensitivity to macromolecules which make accurate baseline determination difficult. In this report, we describe implementation at 7 T of a double echo J-refocused coherence transfer sequence at echo time (TE) of 34 msec to minimize J-modulation of amino acids while also decreasing interfering macromolecule signals. Simulation of the pulse sequence at 7 T shows excellent resolution of glutamate, glutamine, and N-acetyl aspartate. B(1) sufficiency at 7 T for the double echo acquisition is achieved using a transceiver array with radiofrequency (RF) shimming. Using an alternate RF distribution to minimize receiver phase cancellation in the transceiver, accurate phase determination for the coherence transfer is achieved with rapid single scan calibration. This method is demonstrated in spectroscopic imaging mode with n = 5 healthy volunteers resulting in metabolite values consistent with literature and in a patient with epilepsy.
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Affiliation(s)
- J W Pan
- Department of Neurosurgery, Yale University School of Medicine, New Haven, Connecticut 06520-0882, USA.
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Boska M, Liu Y, Uberti M, Sajja BR, Balkundi S, McMillan J, Gendelman HE. Registered bioimaging of nanomaterials for diagnostic and therapeutic monitoring. J Vis Exp 2010:2459. [PMID: 21178969 PMCID: PMC3052268 DOI: 10.3791/2459] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nanomedications can be carried by blood borne monocyte-macrophages into the reticuloendothelial system (RES; spleen, liver, lymph nodes) and to end organs. The latter include the lung, RES, and brain and are operative during human immunodeficiency virus type one (HIV-1) infection. Macrophage entry into tissues is notable in areas of active HIV-1 replication and sites of inflammation. In order to assess the potential of macrophages as nanocarriers, superparamagnetic iron-oxide and/or drug laden particles coated with surfactants were parenterally injected into HIV-1 encephalitic mice. This was done to quantitatively assess particle and drug biodistribution. Magnetic resonance imaging (MRI) test results were validated by histological coregistration and enhanced image processing. End organ disease as typified by altered brain histology were assessed by MRI. The demonstration of robust migration of nanoformulations into areas of focal encephalitis provides '"proof of concept" for the use of advanced bioimaging techniques to monitor macrophage migration. Importantly, histopathological aberrations in brain correlate with bioimaging parameters making the general utility of MRI in studies of cell distribution in disease feasible. We posit that using such methods can provide a real time index of disease burden and therapeutic efficacy with translational potential to humans.
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Affiliation(s)
- Michael Boska
- Department of Radiology, University of Nebraska Medical Center, USA.
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Dong Z, Dreher W, Leibfritz D, Peterson BS. Challenges of using MR spectroscopy to detect neural progenitor cells in vivo. AJNR Am J Neuroradiol 2009; 30:1096-101. [PMID: 19357383 DOI: 10.3174/ajnr.a1557] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A recent report of detection of neural progenitor cells (NPCs) in living human brain by using in vivo proton MR spectroscopy ((1)H-MR spectroscopy) has sparked great excitement in the field of biomedicine because of its potential influence and utility in clinical neuroscience research. On the other hand, the method used and the findings described in the report also caused heated debate and controversy. In this article, we will briefly detail the reasons for the debate and controversy from the point of view of the in vivo (1)H-MR spectroscopy methodology and will propose some technical strategies in both data acquisition and data processing to improve the feasibility of detecting NPCs in future studies by using in vivo (1)H-MR spectroscopy.
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Affiliation(s)
- Z Dong
- Department of Psychiatry, Columbia University, New York, NY 10032, USA.
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Mangia S, Giove F, Tkác I, Logothetis NK, Henry PG, Olman CA, Maraviglia B, Di Salle F, Uğurbil K. Metabolic and hemodynamic events after changes in neuronal activity: current hypotheses, theoretical predictions and in vivo NMR experimental findings. J Cereb Blood Flow Metab 2009; 29:441-63. [PMID: 19002199 PMCID: PMC2743443 DOI: 10.1038/jcbfm.2008.134] [Citation(s) in RCA: 126] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Unraveling the energy metabolism and the hemodynamic outcomes of excitatory and inhibitory neuronal activity is critical not only for our basic understanding of overall brain function, but also for the understanding of many brain disorders. Methodologies of magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) are powerful tools for the noninvasive investigation of brain metabolism and physiology. However, the temporal and spatial resolution of in vivo MRS and MRI is not suitable to provide direct evidence for hypotheses that involve metabolic compartmentalization between different cell types, or to untangle the complex neuronal microcircuitry, which results in changes of electrical activity. This review aims at describing how the current models of brain metabolism, mainly built on the basis of in vitro evidence, relate to experimental findings recently obtained in vivo by (1)H MRS, (13)C MRS, and MRI. The hypotheses related to the role of different metabolic substrates, the metabolic neuron-glia interactions, along with the available theoretical predictions of the energy budget of neurotransmission will be discussed. In addition, the cellular and network mechanisms that characterize different types of increased and suppressed neuronal activity will be considered within the sensitivity-constraints of MRS and MRI.
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Affiliation(s)
- Silvia Mangia
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, Minnesota 55455, USA.
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