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Storey P, Novikov DS. Signatures of microstructure in gradient-echo and spin-echo signals. Magn Reson Med 2024; 92:269-288. [PMID: 38520259 DOI: 10.1002/mrm.30022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Revised: 01/06/2024] [Accepted: 01/08/2024] [Indexed: 03/25/2024]
Abstract
PURPOSE To determine whether the spatial scale and magnetic susceptibility of microstructure can be evaluated robustly from the decay of gradient-echo and spin-echo signals. THEORY AND METHODS Gradient-echo and spin-echo images were acquired from suspensions of spherical polystyrene microbeads of 10, 20, and 40 μm nominal diameter. The sizes of the beads and their magnetic susceptibility relative to the medium were estimated from the signal decay curves, using a lookup table generated from Monte Carlo simulations and an analytic model based on the Gaussian phase approximation. RESULTS Fitting Monte Carlo predictions to spin-echo data yielded acceptable estimates of microstructural parameters for the 20 and 40 μm microbeads. Using gradient-echo data, the Monte Carlo lookup table provided satisfactory parameter estimates for the 20 μm beads but unstable results for the diameter of the largest beads. Neither spin-echo nor gradient-echo data allowed accurate parameter estimation for the smallest beads. The analytic model performed poorly over all bead sizes. CONCLUSIONS Microstructural sources of magnetic susceptibility produce distinctive non-exponential signatures in the decay of gradient-echo and spin-echo signals. However, inverting the problem to extract microstructural parameters from the signals is nontrivial and, in certain regimes, ill-conditioned. For microstructure with small characteristic length scales, parameter estimation is hampered by the difficulty of acquiring accurate data at very short echo times. For microstructure with large characteristic lengths, the gradient-echo signal approaches the static-dephasing regime, where it becomes insensitive to size. Applicability of the analytic model was further limited by failure of the Gaussian phase approximation for all but the smallest beads.
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Affiliation(s)
- Pippa Storey
- Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, New York, USA
| | - Dmitry S Novikov
- Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, New York, USA
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2
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Elschot EP, Backes WH, van den Kerkhof M, Postma AA, Kroon AA, Jansen JFA. Cerebral Microvascular Perfusion Assessed in Elderly Adults by Spin-Echo Dynamic Susceptibility Contrast MRI at 7 Tesla. Tomography 2024; 10:181-192. [PMID: 38250960 PMCID: PMC10819808 DOI: 10.3390/tomography10010014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 01/15/2024] [Accepted: 01/15/2024] [Indexed: 01/23/2024] Open
Abstract
Perfusion measures of the total vasculature are commonly derived with gradient-echo (GE) dynamic susceptibility contrast (DSC) MR images, which are acquired during the early passes of a contrast agent. Alternatively, spin-echo (SE) DSC can be used to achieve specific sensitivity to the capillary signal. For an improved contrast-to-noise ratio, ultra-high-field MRI makes this technique more appealing to study cerebral microvascular physiology. Therefore, this study assessed the applicability of SE-DSC MRI at 7 T. Forty-one elderly adults underwent 7 T MRI using a multi-slice SE-EPI DSC sequence. The cerebral blood volume (CBV) and cerebral blood flow (CBF) were determined in the cortical grey matter (CGM) and white matter (WM) and compared to values from the literature. The relation of CBV and CBF with age and sex was investigated. Higher CBV and CBF values were found in CGM compared to WM, whereby the CGM-to-WM ratios depended on the amount of largest vessels excluded from the analysis. CBF was negatively associated with age in the CGM, while no significant association was found with CBV. Both CBV and CBF were higher in women compared to men in both CGM and WM. The current study verifies the possibility of quantifying cerebral microvascular perfusion with SE-DSC MRI at 7 T.
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Affiliation(s)
- Elles P. Elschot
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Center+, P. Debyelaan 25, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands; (E.P.E.)
- MHeNs School for Mental Health and Neuroscience, Maastricht University, Minderbroedersberg 4-6, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Walter H. Backes
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Center+, P. Debyelaan 25, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands; (E.P.E.)
- MHeNs School for Mental Health and Neuroscience, Maastricht University, Minderbroedersberg 4-6, P.O. Box 616, 6200 MD Maastricht, The Netherlands
- CARIM School for Cardiovascular Diseases, Maastricht University, Minderbroedersberg 4-6, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Marieke van den Kerkhof
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Center+, P. Debyelaan 25, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands; (E.P.E.)
- MHeNs School for Mental Health and Neuroscience, Maastricht University, Minderbroedersberg 4-6, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Alida A. Postma
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Center+, P. Debyelaan 25, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands; (E.P.E.)
- MHeNs School for Mental Health and Neuroscience, Maastricht University, Minderbroedersberg 4-6, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Abraham A. Kroon
- CARIM School for Cardiovascular Diseases, Maastricht University, Minderbroedersberg 4-6, P.O. Box 616, 6200 MD Maastricht, The Netherlands
- Department of Internal Medicine, Maastricht University Medical Center+, P. Debyelaan 25, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands
| | - Jacobus F. A. Jansen
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Center+, P. Debyelaan 25, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands; (E.P.E.)
- MHeNs School for Mental Health and Neuroscience, Maastricht University, Minderbroedersberg 4-6, P.O. Box 616, 6200 MD Maastricht, The Netherlands
- Department of Electrical Engineering, Eindhoven University of Technology, De Rondom 70, P.O. Box 513, 5612 AP Eindhoven, The Netherlands
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van Horen T, Siero J, Bhogal A, Petridou N, Báez-Yáñez M. Microvascular Specificity of Spin Echo BOLD fMRI: Impact of EPI Echo Train Length. bioRxiv 2023:2023.09.15.557938. [PMID: 37745507 PMCID: PMC10516014 DOI: 10.1101/2023.09.15.557938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
A spatially specific fMRI acquisition requires specificity to the microvasculature that serves active neuronal sites. Macrovascular contributions will reduce the microvascular specificity but can be reduced by using spin echo (SE) sequences that use a π pulse to refocus static field inhomogeneities near large veins. The microvascular specificity of a SE-echo planar imaging (SE-EPI) scan depends on the echo train length (ETL)-duration, but the dependence is not well-characterized in humans at 7T. To determine how microvascular-specific SE-EPI BOLD is in humans at 7T, we developed a Monte Carlo voxel model that computes the signal of a proton ensemble residing in a vasculature subjected to a SE-EPI pulse sequence. We characterized the ETL-duration dependence of the microvascular specificity by simulating the BOLD signal as a function of ETL, the range adhering to experimentally realistic readouts. We performed a validation experiment for our simulation observations, in which we acquired a set of SE-EPI BOLD time series with varying ETL during a hyperoxic gas challenge. Both our simulations and measurements show an increase in macrovascular contamination as a function of ETL, with an increase of 30% according to our simulation and 60% according to our validation experiment between the shortest and longest ETL durations (23.1 - 49.7 ms). We conclude that the microvascular specificity decreases heavily with increasing ETL-durations. We recommend reducing the ETL-duration as much as possible to minimize macrovascular contamination in SE-EPI BOLD experiments. We additionally recommend scanning at high resolutions to minimize partial volume effects with CSF. CSF voxels show a large BOLD response, which can be attributed to both the presence of large veins (high blood volume) and molecular oxygen-induced T1-shortening (significant in a hyperoxia experiment). The magnified BOLD signal in a GM-CSF partial volume voxel reduces the desired microvascular specificity and, therefore, will hinder the interpretation of functional MRI activation patterns.
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Affiliation(s)
- T.W.P. van Horen
- Department of Radiology, Centre for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - J.C.W. Siero
- Department of Radiology, Centre for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
- Spinoza Center for Neuroimaging, Amsterdam, The Netherlands
| | - A.A. Bhogal
- Department of Radiology, Centre for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
| | - N. Petridou
- Department of Radiology, Centre for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
| | - M.G. Báez-Yáñez
- Department of Radiology, Centre for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
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Maklakov A, Dvoyashkin N, Khozina E. Features of Self-Diffusion of Tridecane Molecules in a Porous Medium of Kaolinite Used as a Model of a Chemically Inert Membrane. Membranes (Basel) 2023; 13:221. [PMID: 36837723 PMCID: PMC9966625 DOI: 10.3390/membranes13020221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 01/22/2023] [Accepted: 02/07/2023] [Indexed: 06/18/2023]
Abstract
The present work focused on the experimental study of the specific features of self-diffusion of tridecane molecules in macroporous kaolinite, which is used as a raw material for the production of chemically inert membranes. The measurements of self-diffusion coefficients by pulsed magnetic field gradient nuclear magnetic resonance (PMFG NMR) revealed an increased translational mobility of tridecane molecules in kaolinite with incomplete filling of the pore space. This effect was accompanied by a sharp change in the slope of the Arrhenius plot of the self-diffusion coefficients of tridecane molecules in kaolinite. An analysis of the diffusion spin echo decay in the tridecane-kaolinite system revealed a discrepancy between the experimental data and the theoretical predictions, considering the effect of the geometry of porous space on molecular mobility. It was shown that the experimental results could be interpreted in terms of a model of two phases of tridecane molecules in the pores of kaolinite, in the gaseous and adsorbed state, coexisting under the fast-exchange conditions. Within the framework of the model, the activation energies of self-diffusion were calculated, which agreed satisfactorily with the experimental data. Additionally, the effects of the internal magnetic field gradients arising in a porous medium loaded with a gas or liquid on the data of the PFG NMR measurements were calculated. It was shown that the effect of magnetic field inhomogeneities on the measured self-diffusion coefficients of tridecane in kaolinite is small and could be neglected.
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Affiliation(s)
| | | | - Elena Khozina
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry of Russian Academy of Science, 119071 Moscow, Russia
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5
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Kern AL, Gutberlet M, Rumpel R, Bruesch I, Hohlfeld JM, Wacker F, Hensen B. Absolute thermometry using hyperpolarized 129 Xe free-induction decay and spin-echo chemical-shift imaging in rats. Magn Reson Med 2022; 89:54-63. [PMID: 36121206 DOI: 10.1002/mrm.29455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 07/21/2022] [Accepted: 08/22/2022] [Indexed: 11/12/2022]
Abstract
PURPOSE To implement and test variants of chemical shift imaging (CSI) acquiring both free induction decays (FIDs) showing all dissolved-phase compartments and spin echoes for specifically assessing 129 $$ {}^{129} $$ Xe in lipids in order to perform precise lipid-dissolved 129 $$ {}^{129} $$ Xe MR thermometry in a rat model of general hypothermia. METHODS Imaging was performed at 2.89 T. T 2 $$ {T}_2 $$ of 129 $$ {}^{129} $$ Xe in lipids was determined in one rat by fitting exponentials to decaying signals of global spin-echo spectra. Four rats (conventional CSI) and six rats (turbo spectroscopic imaging) were scanned at three time points with core body temperature 37/34/37 ∘ $$ {}^{\circ } $$ C. Lorentzian functions were fit to spectra from regions of interest to determine the water-referenced chemical shift of lipid-dissolved 129 $$ {}^{129} $$ Xe in the abdomen. Absolute 129 $$ {}^{129} $$ Xe-derived temperature was compared to values from a rectal probe. RESULTS Global T 2 $$ {T}_2 $$ of 129 $$ {}^{129} $$ Xe in lipids was determined as 251 . 3 ms ± 81 . 4 ms $$ 251.3\;\mathrm{ms}\pm 81.4\;\mathrm{ms} $$ . Friedman tests showed significant changes of chemical shift with time for both sequence variants and both FID and spin-echo acquisitions. Mean and SD of 129 $$ {}^{129} $$ Xe and rectal probe temperature differences were found to be - 0 . 1 5 ∘ C ± 0 . 9 3 ∘ C $$ -0.1{5}^{\circ}\mathrm{C}\pm 0.9{3}^{\circ}\mathrm{C} $$ (FID) and - 0 . 3 8 ∘ C ± 0 . 6 4 ∘ C $$ -0.3{8}^{\circ}\mathrm{C}\pm 0.6{4}^{\circ}\mathrm{C} $$ (spin echo) for conventional CSI as well as 0 . 0 3 ∘ C ± 0 . 7 7 ∘ C $$ 0.0{3}^{\circ}\mathrm{C}\pm 0.7{7}^{\circ}\mathrm{C} $$ (FID) and - 0 . 0 6 ∘ C ± 0 . 7 6 ∘ C $$ -0.0{6}^{\circ}\mathrm{C}\pm 0.7{6}^{\circ}\mathrm{C} $$ (spin echo) for turbo spectroscopic imaging. CONCLUSION 129 $$ {}^{129} $$ Xe MRI using conventional CSI and turbo spectroscopic imaging of lipid-dissolved 129 $$ {}^{129} $$ Xe enables precise temperature measurements in the rat's abdomen using both FID and spin-echo acquisitions with acquisition of spin echoes enabling most precise temperature measurements.
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Affiliation(s)
- Agilo L Kern
- Institute for Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany.,Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), German Center for Lung Research, Hannover, Germany
| | - Marcel Gutberlet
- Institute for Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany.,Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), German Center for Lung Research, Hannover, Germany
| | - Regina Rumpel
- Institute for Laboratory Animal Science and Central Animal Facility, Hannover Medical School, Hannover, Germany
| | - Inga Bruesch
- Institute for Laboratory Animal Science and Central Animal Facility, Hannover Medical School, Hannover, Germany
| | - Jens M Hohlfeld
- Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), German Center for Lung Research, Hannover, Germany.,Clinical Airway Research, Fraunhofer Institute for Toxicology and Experimental Medicine, Hannover, Germany.,Department of Respiratory Medicine, Hannover Medical School, Hannover, Germany
| | - Frank Wacker
- Institute for Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany.,Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), German Center for Lung Research, Hannover, Germany
| | - Bennet Hensen
- Institute for Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany
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6
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Meloche R, Vučković I, Mishra PK, Macura S. Transverse relaxation in fixed tissue: Influence of temperature and resolution on image contrast in magnetic resonance microscopy. NMR Biomed 2022; 35:e4747. [PMID: 35467776 DOI: 10.1002/nbm.4747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 04/19/2022] [Accepted: 04/20/2022] [Indexed: 06/14/2023]
Abstract
To describe transverse relaxation of water in fixed tissue, we propose a model of transverse relaxation accelerated by diffusion and exchange (TRADE) that assumes exchange between free (visible) and bound (invisible) water, which relax by the dipole-dipole interaction, chemical exchange, and translation in the field gradient. Depending on the prevailing mechanism, transverse relaxation time (T2 ) of water in fixed tissue could increase (when dipole-dipole interaction prevails) or decrease with temperature (when diffusion in the field gradient prevails). Chemical exchange can make T2 even temperature independent. Also, variation of resolution from 100 to 15 μm/pxl (or less) affects effective transverse relaxation. T2 steadily decreases with increased resolution ( T 2 ∝ ∆ x 2 , ∆ x is the read direction resolution). TRADE can describe all of these observations (semi)quantitatively. The model has been experimentally verified on water phantoms and on formalin-fixed zebrafish, mouse brain, and rabbit larynx tissues. TRADE could help predict optimal scanning parameters for high-resolution MRM from much faster measurements at lower resolution.
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Affiliation(s)
- Ryan Meloche
- Metabolomics Core, Mayo Clinic, Rochester, Minnesota, USA
| | - Ivan Vučković
- Metabolomics Core, Mayo Clinic, Rochester, Minnesota, USA
| | | | - Slobodan Macura
- Metabolomics Core, Mayo Clinic, Rochester, Minnesota, USA
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota, USA
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7
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Doyle EK, Thornton S, Ghugre NR, Coates TD, Nayak KS, Wood JC. Effects of B 1 + Heterogeneity on Spin Echo-Based Liver Iron Estimates. J Magn Reson Imaging 2021; 55:1419-1425. [PMID: 34555245 PMCID: PMC8940739 DOI: 10.1002/jmri.27928] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 09/07/2021] [Accepted: 09/10/2021] [Indexed: 01/19/2023] Open
Abstract
BACKGROUND Liver iron concentration (LIC) measured by MRI has become the clinical reference standard for managing iron overload in chronically transfused patients. Transverse relaxivity (R2 or R2 * ) measurements are converted to LIC units using empirically derived calibration curves. HYPOTHESIS That flip angle (FA) error due to B1 + spatial heterogeneity causes significant LIC quantitation error. B1 + scale (b1 , [FAactual /FAspecified ]) variation is a major problem at 3 T which could reduce the accuracy of transverse relaxivity measurements. STUDY TYPE Prospective. POPULATION Forty-seven subjects with chronic transfusional iron overload undergoing clinically indicated LIC assessment. FIELD STRENGTH/SEQUENCE 5 T/3 T dual-repetition time B1 + mapping sequence ASSESSMENT: We quantified the average/standard deviation b1 in the right and left lobes of the liver from B1 + maps acquired at 1.5 T and 3 T. The impact of b1 variation on spin echo LIC estimates was determined using a Monte Carlo model. STATISTICAL TESTS Mean, median, and standard deviation in whole liver and right and left lobes; two-sided t-test between whole-liver b1 means. RESULTS Average b1 within the liver was 99.3% ± 12.3% at 1.5 T versus 69.6% ± 14.6% at 3 T and was independent of iron burden (P < 0.05). Monte Carlo simulations demonstrated that b1 systematically increased R2 estimates at lower LIC (<~25 mg/g at 1.5 T, <~15 mg/g at 3 T) but flattened or even inverted the R2 -LIC relationship at higher LIC (≥~25 mg/g to 1.5 T, ≥~15 mg/g to 3 T); changes in the R2 -LIC relationship were symmetric with respect to over and under excitation and were similar at 1.5 T and 3 T (for the same R2 value). The R2 * -LIC relationship was independent of b1 . CONCLUSION Spin echo R2 measurement of LIC at 3 T is error-prone without correction for b1 errors. The impact of b1 error on current 1.5 T spin echo-based techniques for LIC quantification is large enough to introduce measurable intersubject variability but the in vivo effect size needs a dedicated validation study. LEVEL OF EVIDENCE 1. TECHNICAL EFFICACY STAGE 2.
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Affiliation(s)
- Eamon K Doyle
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California, USA.,Division of Cardiology and Radiology, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Samuel Thornton
- Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, California, USA
| | - Nilesh R Ghugre
- Schulich Heart Research Program, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.,Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Ontario, Canada.,Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
| | - Thomas D Coates
- Division of Hematology, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Krishna S Nayak
- Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, California, USA
| | - John C Wood
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California, USA.,Division of Cardiology and Radiology, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
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Barghoorn A, Riemenschneider B, Hennig J, LeVan P. Improving the sensitivity of spin-echo fMRI at 3T by highly accelerated acquisitions. Magn Reson Med 2021; 86:245-257. [PMID: 33624352 DOI: 10.1002/mrm.28715] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 01/14/2021] [Accepted: 01/14/2021] [Indexed: 11/11/2022]
Abstract
PURPOSE Spin-echo (SE) functional MRI (fMRI) can be highly advantageous compared to gradient-echo (GE) fMRI with respect to magnetic field-inhomogeneity artifacts. However, at 3T, the majority of blood oxygenation level-dependent (BOLD) fMRI experiments are performed using T 2 ∗ -weighted GE sequences because of their superior sensitivity compared to SE-fMRI. The presented SE implementation of a highly accelerated GE pulse sequence therefore aims to improve the sensitivity of SE-fMRI while profiting from a reduction of susceptibility-induced signal dropout. METHODS Spin-echo MR encephalography (SE-MREG) is compared with the more conventionally used spin-echo echo-planar imaging (SE-EPI) and spin-echo simultaneous multislice (SE-SMS) at 3T in terms of capability to detect neuronal activations and resting-state functional connectivity. For activation analysis, healthy subjects underwent consecutive SE-MREG (pulse repetition time [TR] = 0.25 seconds), SE-SMS (TR = 1.3 seconds), and SE-EPI (TR = 4.4 seconds) scans in pseudorandomized order applied to a visual block design paradigm for generation of t-statistics maps. For the investigation of functional connectivity, additional resting-state data were acquired for 5 minutes and a seed-based correlation analysis using Stanford's FIND (Functional Imaging in Neuropsychiatric Disorders) atlas was performed. RESULTS The increased sampling rate of SE-MREG relative to SE-SMS and SE-EPI improves the sensitivity to detect BOLD activation by 33% and 54%, respectively, and increases the capability to extract resting-state networks. Compared with a brain region that is not affected by magnetic field inhomogeneities, SE-MREG shows 2.5 times higher relative signal strength than GE-MREG in mesial temporal structures. CONCLUSION SE-MREG offers a viable possibility for whole-brain fMRI with consideration of brain regions that are affected by strong susceptibility-induced magnetic field gradients.
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Affiliation(s)
- Antonia Barghoorn
- Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Bruno Riemenschneider
- Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Jürgen Hennig
- Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.,Center for Basics in NeuroModulation (NeuroModul Basics), University of Freiburg, Freiburg, Germany
| | - Pierre LeVan
- Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.,Departments of Radiology and Paediatrics, Cumming School of Medicine, University of Calgary, Calgary, Canada.,Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Canada
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Wiggermann V, Vavasour IM, Kolind SH, MacKay AL, Helms G, Rauscher A. Non-negative least squares computation for in vivo myelin mapping using simulated multi-echo spin-echo T 2 decay data. NMR Biomed 2020; 33:e4277. [PMID: 32124505 DOI: 10.1002/nbm.4277] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 01/20/2020] [Accepted: 01/26/2020] [Indexed: 06/10/2023]
Abstract
Multi-compartment T2 mapping has gained particular relevance for the study of myelin water in the brain. As a facilitator of rapid saltatory axonal signal transmission, myelin is a cornerstone indicator of white matter development and function. Regularized non-negative least squares fitting of multi-echo T2 data has been widely employed for the computation of the myelin water fraction (MWF), and the obtained MWF maps have been histopathologically validated. MWF measurements depend upon the quality of the data acquisition, B1+ homogeneity and a range of fitting parameters. In this special issue article, we discuss the relevance of these factors for the accurate computation of multi-compartment T2 and MWF maps. We generated multi-echo spin-echo T2 decay curves following the Carr-Purcell-Meiboom-Gill approach for various myelin concentrations and myelin T2 scenarios by simulating the evolution of the magnetization vector between echoes based on the Bloch equations. We demonstrated that noise and imperfect refocusing flip angles yield systematic underestimations in MWF and intra-/extracellular water geometric mean T2 (gmT2 ). MWF estimates were more stable than myelin water gmT2 time across different settings of the T2 analysis. We observed that the lower limit of the T2 distribution grid should be slightly shorter than TE1 . Both TE1 and the acquisition echo spacing also have to be sufficiently short to capture the rapidly decaying myelin water T2 signal. Among all parameters of interest, the estimated MWF and intra-/extracellular water gmT2 differed by approximately 0.13-4 percentage points and 3-4 ms, respectively, from the true values, with larger deviations observed in the presence of greater B1+ inhomogeneities and at lower signal-to-noise ratio. Tailoring acquisition strategies may allow us to better characterize the T2 distribution, including the myelin water, in vivo.
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Affiliation(s)
- V Wiggermann
- Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada
- Department of Pediatrics, University of British Columbia, Vancouver, Canada
- UBC MRI Research Center, University of British Columbia, Vancouver, Canada
| | - I M Vavasour
- UBC MRI Research Center, University of British Columbia, Vancouver, Canada
- Department of Radiology, University of British Columbia, Vancouver, Canada
| | - S H Kolind
- Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada
- UBC MRI Research Center, University of British Columbia, Vancouver, Canada
- Department of Radiology, University of British Columbia, Vancouver, Canada
- Department of Medicine (Division Neurology), University of British Columbia, Vancouver, Canada
| | - A L MacKay
- Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada
- UBC MRI Research Center, University of British Columbia, Vancouver, Canada
- Department of Radiology, University of British Columbia, Vancouver, Canada
| | - G Helms
- Department of Clinical Sciences Lund (IKVL), Medical Radiation Physics, Lund University, Lund, Sweden
| | - A Rauscher
- Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada
- Department of Pediatrics, University of British Columbia, Vancouver, Canada
- UBC MRI Research Center, University of British Columbia, Vancouver, Canada
- Department of Radiology, University of British Columbia, Vancouver, Canada
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Han S, Liao C, Manhard MK, Park DJ, Bilgic B, Fair MJ, Wang F, Blazejewska AI, Grissom WA, Polimeni JR, Setsompop K. Accelerated spin-echo functional MRI using multisection excitation by simultaneous spin-echo interleaving (MESSI) with complex-encoded generalized slice dithered enhanced resolution (cgSlider) simultaneous multislice echo-planar imaging. Magn Reson Med 2020; 84:206-220. [PMID: 31840295 PMCID: PMC7083698 DOI: 10.1002/mrm.28108] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 10/29/2019] [Accepted: 11/14/2019] [Indexed: 12/14/2022]
Abstract
PURPOSE Spin-echo functional MRI (SE-fMRI) has the potential to improve spatial specificity when compared with gradient-echo fMRI. However, high spatiotemporal resolution SE-fMRI with large slice-coverage is challenging as SE-fMRI requires a long echo time to generate blood oxygenation level-dependent (BOLD) contrast, leading to long repetition times. The aim of this work is to develop an acquisition method that enhances the slice-coverage of SE-fMRI at high spatiotemporal resolution. THEORY AND METHODS An acquisition scheme was developed entitled multisection excitation by simultaneous spin-echo interleaving (MESSI) with complex-encoded generalized slice dithered enhanced resolution (cgSlider). MESSI uses the dead-time during the long echo time by interleaving the excitation and readout of 2 slices to enable 2× slice-acceleration, while cgSlider uses the stable temporal background phase in SE-fMRI to encode/decode 2 adjacent slices simultaneously with a "phase-constrained" reconstruction method. The proposed cgSlider-MESSI was also combined with simultaneous multislice (SMS) to achieve further slice-acceleration. This combined approach was used to achieve 1.5-mm isotropic whole-brain SE-fMRI with a temporal resolution of 1.5 s and was evaluated using sensory stimulation and breath-hold tasks at 3T. RESULTS Compared with conventional SE-SMS, cgSlider-MESSI-SMS provides 4-fold increase in slice-coverage for the same repetition time, with comparable temporal signal-to-noise ratio. Corresponding fMRI activation from cgSlider-MESSI-SMS for both fMRI tasks were consistent with those from conventional SE-SMS. Overall, cgSlider-MESSI-SMS achieved a 32× encoding-acceleration by combining Rinplane × MB × cgSlider × MESSI = 4 × 2 × 2 × 2. CONCLUSION High-quality, high-resolution whole-brain SE-fMRI was acquired at a short repetition time using cgSlider-MESSI-SMS. This method should be beneficial for high spatiotemporal resolution SE-fMRI studies requiring whole-brain coverage.
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Affiliation(s)
- SoHyun Han
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts
- Department of Radiology, Harvard Medical School, Boston, Massachusetts
| | - Congyu Liao
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts
- Department of Radiology, Harvard Medical School, Boston, Massachusetts
| | - Mary Kate Manhard
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts
- Department of Radiology, Harvard Medical School, Boston, Massachusetts
| | - Daniel Joseph Park
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts
| | - Berkin Bilgic
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts
- Department of Radiology, Harvard Medical School, Boston, Massachusetts
| | - Merlin J. Fair
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts
- Department of Radiology, Harvard Medical School, Boston, Massachusetts
| | - Fuyixue Wang
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts
- Medical Engineering & Medical Physics, Harvard-MIT Division of Health Sciences and Technology, Cambridge, Massachusetts
| | - Anna I. Blazejewska
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts
- Department of Radiology, Harvard Medical School, Boston, Massachusetts
| | - William A. Grissom
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
| | - Jonathan R. Polimeni
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts
- Department of Radiology, Harvard Medical School, Boston, Massachusetts
- Harvard-MIT Division of Health Sciences and Technology, Cambridge, Massachusetts
| | - Kawin Setsompop
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts
- Department of Radiology, Harvard Medical School, Boston, Massachusetts
- Harvard-MIT Division of Health Sciences and Technology, Cambridge, Massachusetts
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Howe PWA. Is perfection ever attainable? Strong coupling effects in the Perfect Echo. Magn Reson Chem 2020; 58:77-83. [PMID: 31348542 DOI: 10.1002/mrc.4927] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 07/17/2019] [Accepted: 07/18/2019] [Indexed: 06/10/2023]
Abstract
The Perfect Echo sequence, originally proposed in the late 1980s, has recently been popularised with many applications in the field of small-molecule proton NMR spectroscopy. The Perfect Echo refocuses all homonuclear J-couplings for AX spin systems and refocuses magnetization in-phase for more complex weakly coupled spin systems, albeit with some intensity reduction. In contrast to suggestions in previous publications, spectra acquired in our laboratory showed that the Perfect Echo caused intensity distortions in strongly coupled systems where the chemical shift difference between the coupled spins was not large compared to the J-coupling. This paper reports experimental observations and theoretical analysis of strongly coupled spins to confirm the distortions are real and that they originate principally from transfer of magnetization caused by the final inversion pulse of the Perfect Echo. The intensity changes are not large, but because of them, identifications of coupling partners based on resonance intensities ("roofing") can no longer be relied on when the Perfect Echo is used. However, theory and experiment confirm that adding an orthogonal excitation pulse at the end of the Perfect Echo greatly reduces the distortions.
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Abstract
STUDY DESIGN An in vitro magnetic resonance imaging (MRI) study. OBJECTIVE Investigate the potential of high-field MRI for producing higher quality images of the intervertebral disc (IVD) to better distinguish structural details. SUMMARY OF BACKGROUND DATA Higher spatial and contrast resolution are important advantages when imaging the complex tissue structures in the spine such as the IVDs. However, at present it is challenging to capture the substructural details in the IVD such as the lamellae. METHODS Three MRI sequences; two-dimensional proton-density-weighted Turbo-Spin-Echo (PD-TSE), 2D T2-weighted Turbo-Spin-Echo (T2W-TSE) with fat-saturation (FS), and 3D Spoiled-Gradient-Echo (3D-GE), were modified based on the image quality and scan duration. IVDs of three intact cadaveric lumbar-spines (T12-S1, Age 83-94 yr) were imaged using these optimized sequences. Thereafter each IVD was transversely sectioned and the exposed surfaces were photographed. Landmark observations from corresponding MRI slices and photographs were compared to confirm the MRI captured morphology. The image quality was evaluated using signal-to-noise ratio (SNR), and relative-contrast values. Finally, the underlying tissue structures, including specific pathological features, were qualitatively compared between the MR images and photographs. RESULTS Observations from photographs and corresponding MRI slices matched well. The PD-TSE sequence had better overall SNR, but the relative contrast between the tissue types was relatively poor. The 3D-GE sequence had higher relative contrast between the IVD and bone, but not between annulus and nucleus regions. The T2W images provided the best relative contrast between the annulus and nucleus, however the standard deviations here were high. Structural details including fissures, vascular and granular tissue proliferation, and pathologies in the endplate region, were identifiable from the MR images obtained using the optimized sequences. CONCLUSION The results demonstrate the potential of high-field MRI to capture the IVD structural details. Since the acquisition durations were within clinically acceptable levels, these methodological improvements have the potential to enhance clinical diagnostics. LEVEL OF EVIDENCE 4.
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Matsushita T, Fujii S, Kurozumi A, Nagano A, Ichiba Y, Ohno S, Tahara S. [Improvement of Brain Contrast Using Spin Echo T 1-weighted Image at 3 T MRI]. Nihon Hoshasen Gijutsu Gakkai Zasshi 2019; 75:46-53. [PMID: 30662032 DOI: 10.6009/jjrt.2019_jsrt_75.1.46] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Brain T1-weighted images using spin echo (SE) sequence has poor contrast at 3.0 Tesla magnetic resonance imaging (3.0 T MRI) systems from the influence of crosstalk and magnetized transfer (MT) effect, and prolongation of the T1 value. Therefore, improving of scan parameters has been reported such as excitation flip angle (FA) and interleave data acquisition. The purpose of this study was to show the effects of alterations of presaturation pulse amplitude and chemical shift selective (CHESS) pulse amplitude. Gray-to-white matter contrast increased with decreasing amplitude of presaturation pulse in whole brain imaging. Presaturation and CHESS pulse consist of radio frequency pulse. Therefore, both pulses have a similar effect on MT pulse. Manual alteration of presaturation pulse amplitude for each scan lacks versatility on clinical use. However, decreasing amplitude of presaturation pulse is equal to decreasing thickness of presaturation pulse. About CHESS pulse, it requires no manual alteration for each scan. For example, switching fat suppression mode from strong to weak increase T1 contrast. Our study demonstrated that using not only low excitation FA and interleave date acquisition but also low amplitude of presaturation and CHESS pulse increase the contrast in T1 SE brain scans at 3.0 T MRI.
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Affiliation(s)
- Toshi Matsushita
- Department of Radiology, Division of Medical Technology, Okayama University Hospital
| | - Shunsuke Fujii
- Department of Radiology, Division of Medical Technology, Okayama University Hospital
| | - Akira Kurozumi
- Department of Radiology, Division of Medical Technology, Okayama University Hospital
| | - Akira Nagano
- Department of Radiology, Division of Medical Technology, Okayama University Hospital
| | - Yoshito Ichiba
- Customer Service Division, Application Service Department, Siemens Healthcare K.K
| | - Seiichiro Ohno
- Department of Radiology, Division of Medical Technology, Okayama University Hospital
| | - Seiji Tahara
- Department of Radiology, Division of Medical Technology, Okayama University Hospital
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Lee H, Kim EY, Sohn CH, Park J. Rapid whole-brain gray matter imaging using single-slab three-dimensional dual-echo fast spin echo: A feasibility study. Magn Reson Med 2017; 78:1691-1699. [PMID: 28921660 DOI: 10.1002/mrm.26910] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 08/15/2017] [Accepted: 08/18/2017] [Indexed: 11/07/2022]
Abstract
PURPOSE To achieve rapid, high resolution whole-brain gray matter (GM) imaging by developing a novel, single-slab three-dimensional dual-echo fast-spin-echo pulse sequence and GM-selective reconstruction. METHODS Unlike conventional GM imaging that uses time-consuming double-inversion-recovery preparation, the proposed pulse sequence was designed to have two split portions along the echo train, in which the first half was dedicated to yield short inversion recovery (IR)-induced white matter suppression and variable-flip-angle-induced two-step GM signal evolution while the second half cerebrospinal fluid-only signals. Multi-step variable-flip-angle schedules and sampling reordering were optimized to yield high GM signals while balancing cerebrospinal fluid signals between ECHOes. GM-selective images were then reconstructed directly from the weighted subtraction between ECHOes by solving a sparse signal recovery problem. In vivo studies were performed to validate the effectiveness of the proposed method over conventional double-inversion-recovery. RESULTS The proposed method, while achieving one millimeter isotropic, whole-brain GM imaging within 5.5 min, showed superior performance than conventional double-inversion-recovery in producing GM-only images without apparent artifacts and noise. CONCLUSION We successfully demonstrated the feasibility of the proposed method in achieving whole-brain GM imaging in a clinically acceptable imaging time. The proposed method is expected to be a promising alternative to conventional double-inversion-recovery in clinical applications. Magn Reson Med 78:1691-1699, 2017. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Hyunyeol Lee
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea
| | - Eung Yeop Kim
- Department of Radiology, Gachon University Gil Medical Center, Incheon, Republic of Korea
| | - Chul-Ho Sohn
- Department of Radiology, Seoul National University Hospital, Seoul, Republic of Korea
| | - Jaeseok Park
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea
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Cao P, Hyder F, Zhou IY, Zhang JW, Xie VB, Tsang A, Wu EX. Simultaneous spin-echo and gradient-echo BOLD measurements by dynamic MRS. NMR Biomed 2017; 30:e3745. [PMID: 28574615 DOI: 10.1002/nbm.3745] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 03/22/2017] [Accepted: 04/10/2017] [Indexed: 06/07/2023]
Abstract
This study aimed to dissociate the intravascular and extravascular contributions to spin-echo (SE) and gradient-echo (GE) blood oxygenation level-dependent (BOLD) signals at 7 T, using dynamic diffusion-weighted MRS. We simultaneously acquired SE and GE data using a point-resolved spectroscopy sequence with diffusion weightings of 0, 600, and 1200 s/mm2 . The BOLD signals were quantified by fitting the free induction decays starting from the SE center to a mono-exponential decay function. Without diffusion weighting, BOLD signals measured with SE and GE increased by 1.6 ± 0.5% (TESE = 40 ms) and 5.2 ± 1.4% (nominal TEGE = 40 ms) during stimulation, respectively. With diffusion weighting, the BOLD increase during stimulation measured with SE decreased from 1.6 ± 0.5% to 1.3 ± 0.4% (P < 0.001), whereas that measured by GE was unaffected (P > 0.05); the post-stimulation undershoots in the BOLD signal time courses were largely preserved in both SE and GE measurements. These results demonstrated the feasiblity of simultaneous SE and GE measurements of BOLD signals with and without interleaved diffusion weighting. The results also indicated a predominant extravascular contribution to the BOLD signal time courses, including post-stimulation undershoots in both SE and GE measurements at 7 T.
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Affiliation(s)
- Peng Cao
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
- Department of Radiology and Biomedical Imaging, University of California at San Francisco, San Francisco, CA, USA
| | - Fahmeed Hyder
- Departments of Diagnostic Radiology and Biomedical Engineering, Yale University, New Haven, CT, USA
| | - Iris Y Zhou
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
| | - Jevin W Zhang
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
| | - Victor B Xie
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
| | - Adrian Tsang
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
| | - Ed X Wu
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, SAR, China
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Assländer J, Glaser SJ, Hennig J. Application of spin echoes in the regime of weak dephasing to T 1 -mapping of the lung. Magn Reson Med 2017; 79:960-967. [PMID: 28419591 DOI: 10.1002/mrm.26719] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 03/23/2017] [Accepted: 03/24/2017] [Indexed: 11/09/2022]
Abstract
PURPOSE This work presents an approach to mapping the entire lung's proton density and T1 within a single breath-hold and analyzes the apparent T1 when exciting with a spin echo generating pulse in comparison to a standard gradient echo acquisition. METHODS An inversion-recovery SNAPSHOT-FLASH sequence with a stack-of-stars k-space readout with a golden angle increment was modified to use a spin echo generating radiofrequency-pulse for excitation. Data of five volunteers were acquired on a 3T scanner and image reconstruction was performed by an iterative algorithm adopted from MR-Fingerprinting. RESULTS The feasibility of acquiring quantitative maps of the entire lung with a resolution of 5 × 5 × 10 mm within 7.5 s is demonstrated. It is shown that the proposed spin echo forming radiofrequency-pulse increases the apparent proton density compared to a rectangular pulse. Further, the apparent T1 is reduced in the spin echo case compared to the gradient echo sequence. CONCLUSION The proposed spin echo based method results in T1 maps that are comparable to the ones that were acquired with ultra-short echo time sequences elsewhere. The T1 shortening is believed to originate from increased signal contributions of the extra vascular compartment, which has a short T2∗ and T1 . Magn Reson Med 79:960-967, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Jakob Assländer
- Faculty of Medicine, Department of Radiology, Medical Physics, Medical Center - University of Freiburg, University of Freiburg, Freiburg, Germany.,Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, New York, USA.,Center for Advanced Imaging Innovation and Research (CAI2R), Department of Radiology, New York University School of Medicine, New York, New York, USA
| | - Steffen J Glaser
- Department of Chemistry, Technische Universität München, Munich, Germany
| | - Jürgen Hennig
- Faculty of Medicine, Department of Radiology, Medical Physics, Medical Center - University of Freiburg, University of Freiburg, Freiburg, Germany
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Lan G, Yunmin L, Pu W, Haili H. [Contrastive analysis of artifacts produced by metal dental crowns in 3.0 T magnetic resonance imaging with six sequences]. Hua Xi Kou Qiang Yi Xue Za Zhi 2016; 34:277-280. [PMID: 27526453 PMCID: PMC7030840 DOI: 10.7518/hxkq.2016.03.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 03/05/2016] [Indexed: 06/06/2023]
Abstract
OBJECTIVE This study aimed to observe and evaluate six 3.0 T sequences of metallic artifacts produced by metal dental crowns. METHODS Dental crowns fabricated with four different materials (Co-Gr, Ni-Gr, Ti alloy and pure Ti) were evaluated. A mature crossbreed dog was used as the experimental animal, and crowns were fabricated for its upper right second premolar. Each crown was examined through head MRI (3.0 T) with six sequences, namely, T₁ weighted-imaging of spin echo (T₁W/SE), T₂ weighted-imaging of inversion recovery (T₂W/IR), T₂ star gradient echo (T₂*/GRE), T2 weighted-imaging of fast spin echo (T₂W/FSE), T₁ weighted-imaging of fluid attenuate inversion recovery (T₂W/FLAIR), and T₂ weighted-imaging of propeller (T₂W/PROP). The largest area and layers of artifacts were assessed and compared. RESULTS The artifact in the T₂*/GRE sequence was significantly wider than those in the other sequences (P < 0.01), whose artifact extent was not significantly different (P > 0.05). CONCLUSION T₂*/GRE exhibit the strongest influence on the artifact, whereas the five other sequences contribute equally to artifact generation.
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Khatamian YB, Golestani AM, Ragot DM, Chen JJ. Spin-Echo Resting-State Functional Connectivity in High-Susceptibility Regions: Accuracy, Reliability, and the Impact of Physiological Noise. Brain Connect 2016; 6:283-97. [PMID: 26842962 DOI: 10.1089/brain.2015.0365] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Gradient-echo (GE) echo-planar imaging (EPI) is the method of choice in blood-oxygenation level-dependent (BOLD) functional MRI (fMRI) studies, as it demonstrates substantially higher BOLD sensitivity than its spin-echo (SE) counterpart. However, it is also well known that the GE-EPI signal is prone to signal dropouts and shifts due to susceptibility effects near air-tissue interfaces. SE-EPI, in contrast, is minimally affected by these artifacts. In this study, we quantify, for the first time, the sensitivity and specificity of SE and GE EPI for resting-state fMRI functional connectivity (fcMRI) mapping, using the 1000-brain fcMRI atlas (Yeo et al., 2011 ) as the pseudoground truth. Moreover, we assess the influence of physiological processes on resting-state BOLD measured using both regular and ultrafast GE and SE acquisitions. Our work demonstrates that SE-EPI and GE-EPI are associated with similar sensitivities, specificities, and intersubject reproducibility in fcMRI for most brain networks, generated using both seed-based analysis and independent component analysis. More importantly, SE-based fcMRI measurements demonstrated significantly higher sensitivity, specificity, and intersubject reproducibility in high-susceptibility regions, spanning the limbic and frontal networks in the 1000-brain atlas. In addition, SE-EPI is significantly less sensitive to prominent sources of physiological noise, including low-frequency respiratory volume and heart rate variations. Our work suggests that SE-EPI should be increasingly adopted in the study of networks spanning susceptibility-affected brain regions, including those that are important to memory, language, and emotion.
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Affiliation(s)
| | | | - Don M Ragot
- 1 Rotman Research Institute , Baycrest, Toronto, Canada .,2 Department of Medical Biophysics, University of Toronto , Toronto, Canada
| | - J Jean Chen
- 1 Rotman Research Institute , Baycrest, Toronto, Canada .,2 Department of Medical Biophysics, University of Toronto , Toronto, Canada
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Wijayathunga VN, Ridgway JP, Ingham E, Treanor D, Carey D, Bulpitt A, Magee D, Damion R, Wilcox RK. A Nondestructive Method to Distinguish the Internal Constituent Architecture of the Intervertebral Discs Using 9.4 Tesla Magnetic Resonance Imaging. Spine (Phila Pa 1976) 2015; 40:E1315-22. [PMID: 26244404 PMCID: PMC4684101 DOI: 10.1097/brs.0000000000001075] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN An in vitro study of the intervertebral disc (IVD) structure using 9.4T magnetic resonance imaging (MRI). OBJECTIVE Investigate the potential of ultrahigh-field strength MRI for higher quality 3-dimensional (3D) volumetric MRI datasets of the IVD to better distinguish structural details. SUMMARY OF BACKGROUND DATA MRI has the advantages of being nondestructive and 3D in comparison to most techniques used to obtain the structural details of biological tissues, however, its poor image quality at higher resolution is a limiting factor. Ultrahigh-field MRI could improve the imaging of biological tissues but the current understanding of its application for spinal tissue is limited. METHODS 2 ovine spinal segments (C7-T1, T2-T3) containing the IVD were separately imaged using 2 sequences; 3D spin echo (multislice-multiecho) pulse sequence for the C7-T1 sample and 3D gradient echo (fast-low-angle-shot) pulse sequence for the T2-T3 sample. The C7-T1 sample was subsequently decalcified and imaged again using the same scanning parameters. Histological sections obtained from the decalcified sample were stained followed by digital scanning. Observations from corresponding MRI slices and histological sections were compared as a method of confirmation of morphology captured under MRI. The signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and relative-contrast values were calculated for quantitative evaluation of image quality. RESULTS Measurements from histology sections and corresponding MRI slices matched well. Both sequences revealed finer details of the IVD structure. Under the spin echo sequence, the annulus lamellae architecture was distinguishable and the SNR and CNR values were higher. The relative contrast was considerably higher between high (nucleus) and low (bone) signal constituents, but between the nucleus and the annulus the relative contrast was low. Under the gradient echo sequence, although the relative contrasts between constituents were poor, the fiber orientation was clearly manifested. CONCLUSION The obtained positive results demonstrate the potential of ultrahigh-field strength MRI to nondestructively capture the IVD structure. LEVEL OF EVIDENCE N/A.
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Affiliation(s)
| | - John P. Ridgway
- Division of Medical Physics, University of Leeds, Leeds, United Kingdom
| | - Eileen Ingham
- Institute of Medical and Biological Engineering, University of Leeds, Leeds, United Kingdom
| | - Darren Treanor
- The Leeds Institute of Cancer and Pathology, Leeds Teaching Hospitals NHS Trust, St James's University Hospital, Beckett Street, Leeds, United Kingdom
| | - Duane Carey
- School of Computing, University of Leeds, Leeds, United Kingdom
| | - Andy Bulpitt
- School of Computing, University of Leeds, Leeds, United Kingdom
| | - Derek Magee
- School of Computing, University of Leeds, Leeds, United Kingdom
| | - Robin Damion
- School of Physics and Astronomy, University of Leeds, Leeds, United Kingdom
| | - Ruth K. Wilcox
- Institute of Medical and Biological Engineering, University of Leeds, Leeds, United Kingdom
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Feldman RE, Islam HM, Xu J, Balchandani P. A SEmi-Adiabatic matched-phase spin echo (SEAMS) PINS pulse-pair for B1 -insensitive simultaneous multislice imaging. Magn Reson Med 2015; 75:709-17. [PMID: 25753055 DOI: 10.1002/mrm.25654] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Revised: 01/13/2015] [Accepted: 01/21/2015] [Indexed: 12/24/2022]
Abstract
PURPOSE Simultaneous multislice (SMS) imaging is a powerful technique that can reduce image acquisition time for anatomical, functional, and diffusion weighted magnetic resonance imaging. At higher magnetic fields, such as 7 Tesla, increased radiofrequency (RF) field inhomogeneity, power deposition, and changes in relaxation parameters make SMS spin echo imaging challenging. We designed an adiabatic 180° Power Independent of Number of Slices (PINS) pulse and a matched-phase 90° PINS pulse to generate a SEmi-Adiabatic Matched-phase Spin echo (SEAMS) PINS sequence to address these issues. METHODS We used the adiabatic Shinnar Le-Roux (SLR) algorithm to generate a 180° pulse. The SLR polynomials for the 180° pulse were then used to create a matched-phase 90° pulse. The pulses were sub-sampled to produce a SEAMS PINS pulse-pair and the performance of this pulse-pair was validated in phantoms and in vivo. RESULTS Simulations as well as phantom and in vivo results, demonstrate multislice capability and improved B1 -insensitivity of the SEAMS PINS pulse-pair when operating at RF amplitudes of up to 40% above adiabatic threshold. CONCLUSION The SEAMS PINS approach presented here achieves multislice spin echo profiles with improved B1 -insensitivity when compared with a conventional spin echo.
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Affiliation(s)
- Rebecca E Feldman
- Translational and Molecular Imaging Institution, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Haisam M Islam
- Bioengineering Department, Stanford University, Stanford, California, USA
| | - Junqian Xu
- Translational and Molecular Imaging Institution, Icahn School of Medicine at Mount Sinai, New York, New York, USA.,Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA
| | - Priti Balchandani
- Translational and Molecular Imaging Institution, Icahn School of Medicine at Mount Sinai, New York, New York, USA
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Abstract
Colloidal impurity-doped quantum dots (QDs) are attractive model systems for testing the fundamental spin properties of semiconductor nanostructures relevant to future spin-based information processing technologies. Although static spin properties of this class of materials have been studied extensively in recent years, their spin dynamics remain largely unexplored. Here we use pulsed electron paramagnetic resonance (pEPR) spectroscopy to probe the spin relaxation dynamics of colloidal Mn(2+)-doped ZnO, ZnSe, and CdSe quantum dots in the limit of one Mn(2+) per QD. pEPR spectroscopy is particularly powerful for identifying the specific nuclei that accelerate electron spin relaxation in these QDs. We show that the spin-relaxation dynamics of these colloidal QDs are strongly influenced by dipolar coupling with proton nuclear spins outside the QDs and especially those directly at the QD surfaces. Using this information, we demonstrate that spin-relaxation times can be elongated significantly via ligand (or surface) deuteration or shell growth, providing two tools for chemical adjustment of spin dynamics in these nanomaterials. These findings advance our understanding of the spin properties of solution-grown semiconductor nanostructures relevant to spin-based information technologies.
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Affiliation(s)
- Alina M Schimpf
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
| | - Stefan T Ochsenbein
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
| | - Daniel R Gamelin
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
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Assländer J, Glaser SJ, Hennig J. Spin echoes in the regime of weak dephasing. Magn Reson Med 2015; 75:150-60. [PMID: 25640051 DOI: 10.1002/mrm.25579] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Revised: 11/05/2014] [Accepted: 11/22/2014] [Indexed: 11/10/2022]
Abstract
PURPOSE This article analyzes possibilities and limits of spin echoes beyond Hahn's theory. The regime of weak dephasing is explored with the purpose of combining the enhanced signal and reduced artifacts of spin echoes with the speed and flexibility of the fast low angle shot sequence. METHODS In the regime of weak dephasing, an upper boundary of the echo time is derived analytically. This limit is verified with optimal control pulses, which are also used to heuristically examine the transition to Hahn's regime of complete dephasing. The potential of the proposed pulses is demonstrated in proof-of-concept spin echo fast low angle shot images of a volunteer's lung and head. RESULTS It was found that the time between the end of the pulse and the spin echo can exceed the duration of the composite radio frequency-pulse, which stands in contrast to Hahn echoes where those measures are at most equal. The maximum echo time was found to mainly depend on the total amount of dephasing. In vivo spin echo fast low angle shot images show an increased pulmonary signal as well as reduced artifacts in areas affected by susceptibility differences. CONCLUSION The spin dynamics in the regime of weak dephasing was investigated and the feasibility of spin echo fast low angle shot imaging was demonstrated in vivo.
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Affiliation(s)
- Jakob Assländer
- Department of Radiology-Medical Physics, University Medical Center Freiburg, Freiburg, Germany
| | - Steffen J Glaser
- Department of Chemistry, Technische Universität München, Munich, Germany
| | - Jürgen Hennig
- Department of Radiology-Medical Physics, University Medical Center Freiburg, Freiburg, Germany
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Tal A, Gonen O. Spectroscopic localization by simultaneous acquisition of the double-spin and stimulated echoes. Magn Reson Med 2014; 73:31-43. [PMID: 24664399 DOI: 10.1002/mrm.25112] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 12/11/2013] [Accepted: 12/12/2013] [Indexed: 12/17/2022]
Abstract
PURPOSE To design a proton MR spectroscopy ((1) H-MRS) localization sequence that combines the signal-to-noise-ratio (SNR) benefits of point resolved spectroscopy (PRESS) with the high pulse bandwidths, low chemical shift displacements (CSD), low specific absorption rates (SAR), short echo times (TE), and superior radiofrequency transmit field (B1+) immunity of stimulated echo acquisition mode (STEAM), by simultaneously refocusing and acquiring both the double-spin and stimulated echo coherence pathways from the volume of interest. THEORY AND METHODS We propose a family of (1)H-MRS sequences comprising three orthogonal spatially selective pulses with flip angles 90° < α, β, γ < 128°. The stimulated and double-spin echo are refocused in-phase simultaneously by altering the pulses' phases, flip angles and timing, as well as the interpulse gradient spoiling moments. The ≈ 90° nutations of α, β, γ provide STEAM-like advantages (lower SAR, in-plane CSD and TE; greater B1+ immunity), but with SNRs comparable with PRESS. RESULTS Phantom and in vivo brain experiments show that 83-100% of the PRESS SNR (metabolite-dependent) is achieved at under 75% of the SAR and 66% lower in-plane CSD. CONCLUSION The advantages of STEAM can be augmented with the higher SNR of PRESS by combining the spin and stimulated echoes. Quantification, especially of J-coupled resonances and intermediate and long TEs, must be carefully considered.
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Affiliation(s)
- Assaf Tal
- Department of Radiology, New York University School of Medicine, New York, New York, USA
| | - Oded Gonen
- Department of Radiology, New York University School of Medicine, New York, New York, USA
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Halai AD, Welbourne SR, Embleton K, Parkes LM. A comparison of dual gradient-echo and spin-echo fMRI of the inferior temporal lobe. Hum Brain Mapp 2014; 35:4118-28. [PMID: 24677506 DOI: 10.1002/hbm.22463] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Revised: 10/17/2013] [Accepted: 01/06/2014] [Indexed: 11/11/2022] Open
Abstract
Magnetic susceptibility differences at tissue interfaces lead to signal loss in conventional gradient-echo (GE) EPI. This poses a problem for fMRI in language and memory paradigms, which activate the most affected regions. Two methods proposed to overcome this are spin-echo EPI and dual GE EPI, where two EPI read-outs are serially collected at a short and longer echo time. The spin-echo method applies a refocusing pulse to recover dephased MR signal due to static field inhomogeneities, but is known to have a relatively low blood oxygenation level dependant (BOLD) sensitivity. In comparison, GE has superior BOLD sensitivity, and by employing an additional shorter echo, in a dual GE sequence, it can reduce signal loss due to spin dephasing. We directly compared dual GE and spin-echo fMRI during a semantic categorization task, which has been shown to activate the inferior temporal region-a region known to be affected by magnetic susceptibility. A whole brain analysis showed that the dual GE resulted in significantly higher activation within the left inferior temporal fusiform (ITF) cortex, compared to spin-echo. The inferior frontal gyrus (IFG) was activated for dual GE, but not spin-echo. Regions of interest analysis was carried out on the anterior and posterior ITF, left and right IFG, and part of the cerebellum. Dual GE outperformed spin-echo in the anterior and posterior ITF and bilateral IFG regions, whilst being equal in the cerebellum. Hence, dual GE should be the method of choice for fMRI studies of inferior temporal regions.
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Affiliation(s)
- Ajay D Halai
- Neuroscience and Aphasia Research Unit, School of Psychological Sciences, University of Manchester, Zochonis Building, Manchester, United Kingdom
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De Martino F, Schmitter S, Moerel M, Tian J, Ugurbil K, Formisano E, Yacoub E, de Moortele PFV. Spin echo functional MRI in bilateral auditory cortices at 7 T: an application of B₁ shimming. Neuroimage 2012; 63:1313-20. [PMID: 22917678 PMCID: PMC3472083 DOI: 10.1016/j.neuroimage.2012.08.029] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 07/21/2012] [Accepted: 08/11/2012] [Indexed: 11/17/2022] Open
Abstract
Ultra high fields (UHF) permit unprecedented explorations of functional organizations and insight into basic neuronal processes. Increases in the signal and contrast to noise ratios have allowed increases in the spatial resolution of T(2) weighted gradient echo (GE) echo planar imaging (EPI). Furthermore, while the use of T(2) weighted imaging methods at UHF (e.g. spin echo (SE) EPI, gradient and spin echo (GRASE) EPI) can also permit higher resolution images, they in addition allow for increased spatial specificity of functional responses, permitting the in-vivo study of functional organizations down to the columnar level of the cortex. The study of the visual cortex has, thus far, benefitted the most from higher resolution T(2) weighted studies as achieving the required transmit B(1) magnitude at 7T is more challenging in other brain regions, such as the auditory cortex. As such, auditory fMRI studies at UHF have been limited to T(2) weighted GE sequences. Recent advances in multi-channel RF transmission (e.g. B(1) shimming) have enabled procedures to efficiently address deficiencies in transmit B(1) profiles. However, these techniques, shown to be advantageous in anatomical imaging at UHF, are not generally utilized to facilitate T(2) weighted fMRI studies. Here we investigate the feasibility of applying B(1) shimming to achieve efficient RF transmission in the human auditory cortex. We demonstrate that, with B(1) shimming, functional responses to simple tones and to complex sounds (i.e. voices, speech, animal cries, tools and nature) can be efficiently measured with T(2) weighted SE-EPI in the bilateral human auditory cortex at 7T without exceeding specific absorption rate (SAR) limits.
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Affiliation(s)
- Federico De Martino
- Center for Magnetic Resonance Research, University of Minnesota Medical School, Minneapolis, MN 55455, USA.
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Cheung JS, Wang E, Zhang X, Mandeville E, Lo EH, Sorensen AG, Sun PZ. Fast radio-frequency enforced steady state (FRESS) spin echo MRI for quantitative T2 mapping: minimizing the apparent repetition time (TR) dependence for fast T2 measurement. NMR Biomed 2012; 25:189-194. [PMID: 21755552 PMCID: PMC3712835 DOI: 10.1002/nbm.1729] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2010] [Revised: 02/21/2011] [Accepted: 03/16/2011] [Indexed: 05/31/2023]
Abstract
Transverse relaxation time (T(2)) is a basic but very informative MRI parameter, widely used in imaging to examine a host of diseases, including multiple sclerosis, stroke, and tumor. However, short repetition time (TR) is often used to minimize scan time, which may introduce non-negligible errors in T(2) measurement. Specifically, due to the use of refocusing pulse, the steady state magnetization depends not only on TR but also on the TE. Hence, if the TE dependence is not properly accounted for, it may be mistaken as T(2)-induced signal attenuation, leading to non-negligible T(2) underestimation. Our study proposed a fast radio-frequency enforced steady state (FRESS) spin echo (SE) MRI sequence, which saturates the magnetization after the echo and ensures a TE-independent steady state. The proposed FRESS-SE MRI was evaluated with numerical simulation, implemented with echo planar imaging readout, and validated by both phantom and in vivo experiments. In summary, FRESS-SE T(2) MRI technique was developed for fast and accurate T(2) imaging, suitable for in vivo applications.
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Affiliation(s)
- Jerry S. Cheung
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Enfeng Wang
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
- Department of Radiology, 3rd Affiliated Hospital, Zhengzhou University, PR China
| | - XiaoAn Zhang
- Department of Radiology, 3rd Affiliated Hospital, Zhengzhou University, PR China
| | - Emiri Mandeville
- Neuroprotection Research Laboratory, Department of Radiology and Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Eng H. Lo
- Neuroprotection Research Laboratory, Department of Radiology and Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - A. Gregory Sorensen
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Phillip Zhe Sun
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
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Shemesh N, Özarslan E, Komlosh ME, Basser PJ, Cohen Y. From single-pulsed field gradient to double-pulsed field gradient MR: gleaning new microstructural information and developing new forms of contrast in MRI. NMR Biomed 2010; 23:757-80. [PMID: 20690130 PMCID: PMC3139994 DOI: 10.1002/nbm.1550] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
One of the hallmarks of diffusion NMR and MRI is its ability to utilize restricted diffusion to probe compartments much smaller than the excited volume or the MRI voxel, respectively, and to extract microstructural information from them. Single-pulsed field gradient (s-PFG) MR methodologies have been employed with great success to probe microstructures in various disciplines, ranging from chemistry to neuroscience. However, s-PFG MR also suffers from inherent shortcomings, especially when specimens are characterized by orientation or size distributions: in such cases, the microstructural information available from s-PFG experiments is limited or lost. Double-pulsed field gradient (d-PFG) MR methodology, an extension of s-PFG MR, has attracted attention owing to recent theoretical studies predicting that it can overcome certain inherent limitations of s-PFG MR. In this review, we survey the microstructural features that can be obtained from conventional s-PFG methods in the different q regimes, and highlight its limitations. The experimental aspects of d-PFG methodology are then presented, together with an overview of its theoretical underpinnings and a general framework for relating the MR signal decay and material microstructure, affording new microstructural parameters. We then discuss recent studies that have validated the theory using phantoms in which the ground truth is well known a priori, a crucial step prior to the application of d-PFG methodology in neuronal tissue. The experimental findings are in excellent agreement with the theoretical predictions and reveal, inter alia, zero-crossings of the signal decay, robustness towards size distributions and angular dependences of the signal decay from which accurate microstructural parameters, such as compartment size and even shape, can be extracted. Finally, we show some initial findings in d-PFG MR imaging. This review lays the foundation for future studies, in which accurate and novel microstructural information could be extracted from complex biological specimens, eventually leading to new forms of contrast in MRI.
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Affiliation(s)
- Noam Shemesh
- School of Chemistry, The Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Israel
| | - Evren Özarslan
- Section on Tissue Biophysics and Biomimetics, NICHD, National Institutes of Health, Bethesda, Maryland, USA
| | - Michal E Komlosh
- Section on Tissue Biophysics and Biomimetics, NICHD, National Institutes of Health, Bethesda, Maryland, USA
| | - Peter J Basser
- Section on Tissue Biophysics and Biomimetics, NICHD, National Institutes of Health, Bethesda, Maryland, USA
| | - Yoram Cohen
- School of Chemistry, The Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Israel
- Corresponding author: Prof. Yoram Cohen, School of Chemistry, The Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel, , Tel/fax- 972 3 6407232/972 3 6407469
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Azuah RT, Kneller LR, Qiu Y. DAVE: A Comprehensive Software Suite for the Reduction, Visualization, and Analysis of Low Energy Neutron Spectroscopic Data. J Res Natl Inst Stand Technol 2009; 114:341-58. [PMID: 27504233 PMCID: PMC4646530 DOI: 10.6028/jres.114.025] [Citation(s) in RCA: 456] [Impact Index Per Article: 30.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 10/16/2009] [Indexed: 05/18/2023]
Abstract
National user facilities such as the NIST Center for Neutron Research (NCNR) require a significant base of software to treat the data produced by their specialized measurement instruments. There is no universally accepted and used data treatment package for the reduction, visualization, and analysis of inelastic neutron scattering data. However, we believe that the software development approach adopted at the NCNR has some key characteristics that have resulted in a successful software package called DAVE (the Data Analysis and Visualization Environment). It is developed using a high level scientific programming language, and it has been widely adopted in the United States and abroad. In this paper we describe the development approach, elements of the DAVE software suite, its usage and impact, and future directions and opportunities for development.
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Affiliation(s)
- Richard Tumanjong Azuah
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899
- Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742
| | - Larry R. Kneller
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899
- Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742
| | - Yiming Qiu
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899
- Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742
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