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Zhipei Liang - One of the best experts on this subject based on the ideXlab platform.
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variable slew rate Spiral design theory and application to peak b 1 amplitude reduction in 2d rf pulse design
Magnetic Resonance in Medicine, 2007Co-Authors: Kevin F King, Zhipei LiangAbstract:A new class of Spiral trajectories called variable slew-rate Spirals is proposed. The governing differential equations for a variable slew-rate Spiral are derived, and both numeric and analytic solutions to the equations are given. The primary application of variable slew-rate Spirals is peak B(1) amplitude reduction in 2D RF pulse design. The reduction of peak B(1) amplitude is achieved by changing the gradient slew-rate profile, and gradient amplitude and slew-rate constraints are inherently satisfied by the design of variable slew-rate Spiral gradient waveforms. A design example of 2D RF pulses is given, which shows that under the same hardware constraints the RF pulse using a properly chosen variable slew-rate Spiral Trajectory can be much shorter than that using a conventional constant slew-rate Spiral Trajectory, thus having greater immunity to resonance frequency offsets.
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variable slew rate Spiral design theory and application to peak b 1 amplitude reduction in 2d rf pulse design
Magnetic Resonance in Medicine, 2007Co-Authors: Dan Xu, Kevin F King, Zhipei LiangAbstract:A new class of Spiral trajectories called variable slew-rate Spirals is proposed. The governing differential equations for a variable slew-rate Spiral are derived, and both numeric and analytic solutions to the equations are given. The primary application of variable slew-rate Spirals is peak B1 amplitude reduction in 2D RF pulse design. The reduction of peak B1 amplitude is achieved by changing the gradient slew-rate profile, and gradient amplitude and slew-rate constraints are inherently satisfied by the design of variable slew-rate Spiral gradient waveforms. A design example of 2D RF pulses is given, which shows that under the same hardware constraints the RF pulse using a properly chosen variable slew-rate Spiral Trajectory can be much shorter than that using a conventional constant slew-rate Spiral Trajectory, thus having greater immunity to resonance frequency offsets. Magn Reson Med 58:835–842, 2007. © 2007 Wiley-Liss, Inc.
Yi Wang - One of the best experts on this subject based on the ideXlab platform.
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combining quantitative susceptibility mapping with automatic zero reference qsm0 and myelin water fraction imaging to quantify iron related myelin damage in chronic active ms lesions
American Journal of Neuroradiology, 2017Co-Authors: Thanh D Nguyen, Yi Wang, Sneha Pandya, Yan Zhang, Ilhami Kovanlikaya, Amy Kuceyeski, Susan A GauthierAbstract:BACKGROUND AND PURPOSE: A hyperintense rim on susceptibility in chronic MS lesions is consistent with iron deposition, and the purpose of this study was to quantify iron-related myelin damage within these lesions as compared with those without rim. MATERIALS AND METHODS: Forty-six patients had 2 longitudinal quantitative susceptibility mapping with automatic zero reference scans with a mean interval of 28.9 ± 11.4 months. Myelin water fraction mapping by using fast acquisition with Spiral Trajectory and T2 prep was obtained at the second time point to measure myelin damage. Mixed-effects models were used to assess lesion quantitative susceptibility mapping and myelin water fraction values. RESULTS: Quantitative susceptibility mapping scans were on average 6.8 parts per billion higher in 116 rim-positive lesions compared with 441 rim-negative lesions ( P P P P CONCLUSIONS: Quantitative susceptibility mapping rim-positive lesions maintained a hyperintense rim, increased in susceptibility, and had more myelin damage compared with rim-negative lesions. Our results are consistent with the identification of chronic active MS lesions and may provide a target for therapeutic interventions to reduce myelin damage.
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rapid whole brain myelin water content mapping without an external water standard at 1 5 t
Magnetic Resonance Imaging, 2017Co-Authors: Thanh D Nguyen, Pascal Spincemaille, Susan A Gauthier, Yi WangAbstract:Abstract The objective of this study is to develop rapid whole brain mapping of myelin water content (MWC) at 1.5 T. The Fast Acquisition with Spiral Trajectory and T2prep (FAST-T2) pulse sequence originally developed for myelin water fraction (MWF) mapping was modified to obtain fast mapping of T1 and receiver coil sensitivity needed for MWC computation. The accuracy of the proposed T1 mapping was evaluated by comparing with the standard IR-FSE method. Numerical simulations were performed to assess the accuracy and reliability of the proposed MWC mapping. We also compared MWC values obtained with either cerebrospinal fluid (CSF) or an external water tube attached to the subject's head as the water reference. Our results from healthy volunteers show that whole brain MWC mapping is feasible in 7 min and provides accurate brain T1 values. Regional brain WC and MWC measurements obtained with the internal CSF-based water standard showed excellent correlation (R > 0.99) and negligible bias within narrow limits of agreement compared to those obtained with an external water standard.
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rapid whole brain myelin water content mapping without an external water standard at 1 5 t
Magnetic Resonance Imaging, 2017Co-Authors: Thanh D Nguyen, Pascal Spincemaille, Susan A Gauthier, Yi WangAbstract:Abstract The objective of this study is to develop rapid whole brain mapping of myelin water content (MWC) at 1.5 T. The Fast Acquisition with Spiral Trajectory and T2prep (FAST-T2) pulse sequence originally developed for myelin water fraction (MWF) mapping was modified to obtain fast mapping of T1 and receiver coil sensitivity needed for MWC computation. The accuracy of the proposed T1 mapping was evaluated by comparing with the standard IR-FSE method. Numerical simulations were performed to assess the accuracy and reliability of the proposed MWC mapping. We also compared MWC values obtained with either cerebrospinal fluid (CSF) or an external water tube attached to the subject's head as the water reference. Our results from healthy volunteers show that whole brain MWC mapping is feasible in 7 min and provides accurate brain T1 values. Regional brain WC and MWC measurements obtained with the internal CSF-based water standard showed excellent correlation (R > 0.99) and negligible bias within narrow limits of agreement compared to those obtained with an external water standard.
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feasibility and reproducibility of whole brain myelin water mapping in 4 minutes using fast acquisition with Spiral Trajectory and adiabatic t2prep fast t2 at 3t
Magnetic Resonance in Medicine, 2016Co-Authors: Thanh D Nguyen, Pascal Spincemaille, Yi Wang, Kofi Deh, Elizabeth Monohan, Sneha Pandya, Ashish Raj, Susan A GauthierAbstract:Purpose To develop and measure the reproducibility of 4-min whole brain myelin water fraction (MWF) mapping using fast acquisition with Spiral Trajectory and T2prep (FAST-T2) sequence at 3T. Methods Experiments were performed on phantoms, 13 volunteers, and 16 patients with multiple sclerosis. MWF maps were extracted using a spatially constrained non-linear algorithm. The proposed adiabatic modified BIR-4 (mBIR-4) T2prep was compared with the conventional composite T2prep (COMP). The effect of reducing the number of echo times (TEs) from 15 to 6 (reducing scan time from 10 to 4 min) was evaluated. Reproducibility was assessed using correlation analysis, coefficient of variation (COV), and Bland–Altman plots. Results Compared with COMP, mBIR-4 provided more accurate T2 in phantoms and better MWF maps in human brains. Reducing the number of TEs had a negligible effect on MWF map quality, with a regional MWF difference of <0.8%. Regional MWFs obtained by repeated scans showed excellent correlation (R = 0.99), low COV (1.3%–2.4%), and negligible bias within ±1% limits of agreement. On a voxel-wise basis, the agreement remained strong (correlation R = 0.89 ± 0.03, bias = 0.01% ± 0.29%, limits of agreement = [−3.35% ± 0.73%, 3.33% ± 0.61%]). Conclusion Whole brain MWF mapping with adiabatic FAST-T2 is feasible in 4 min and provides good intrasite reproducibility. Magn Reson Med, 2015. © 2015 Wiley Periodicals, Inc.
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highly accelerated 3d dynamic contrast enhanced mri from sparse Spiral sampling using integrated partial separability model and jsense
Proceedings of SPIE, 2014Co-Authors: Jingyuan Lyu, Pascal Spincemaille, Yi Wang, Yihang Zhou, Fuquan Ren, Leslie YingAbstract:Dynamic contrast enhanced MRI requires high spatial resolution for morphological information and high temporal resolution for contrast pharmacokinetics. The current techniques usually have to compromise the spatial information for the required temporal resolution. This paper presents a novel method that effectively integrates sparse sampling, parallel imaging, partial separable (PS) model, and sparsity constraints for highly accelerated DCE-MRI. Phased array coils were used to continuously acquire data from a stack of variable-density Spiral Trajectory with a golden angle. In reconstruction, the sparsity constraints, the coil sensitivities, spatial and temporal bases of the PS model are jointly estimated through alternating optimization. Experimental results from in vivo DCE liver imaging data show that the proposed method is able to achieve high spatial and temporal resolutions at the same time.
Chrit T W Moonen - One of the best experts on this subject based on the ideXlab platform.
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automatic spatial and temporal temperature control for mr guided focused ultrasound using fast 3d mr thermometry and multiSpiral Trajectory of the focal point
Magnetic Resonance in Medicine, 2004Co-Authors: C Mougenot, Rares Salomir, Jean Palussiere, N Grenier, Chrit T W MoonenAbstract:Of the different modalities to induce local hyperthermia, focused ultrasound is the only noninvasive technology available at the moment. In addition to the 3D localization of the target region, it has been shown that MRI can provide real-time thermometry and allows online, automatic control of temperature evolution of the focal point. Treatment of a large tissue volume (as compared to the focal spot size, i.e., the ultrasound wavelength) can be achieved rapidly by moving the focal point along an inside-out Spiral Trajectory. It has been shown previously that under linear conditions of energy deposition versus temperature, the spatial profile of the temperature within a large area can be controlled. In this study, a proportional, integral, and derivative (PID) spatial-and-temporal controller is described for the control of the temperature evolution within the target region under more variable conditions. The aim was to reach a predefined temperature profile after a few successive trajectories. Heat conduction in tissue is exploited to obtain a uniform temperature increase in a volume using discrete sonications without any waiting time. Input data sets consisted of 3D temperature maps provided online by a MR scanner. For each new Trajectory, the controller recalculates the number of sonications per surface unit (spatial density of points describing the Trajectory) and the applied power. Its performance was tested ex vivo and in vivo. Diameters of the target region ranged from 9 mm to 19 mm. Targeted temperature increase ranged from +8°C to +18°C. Spatiotemporal temperature control showed good stability and fast convergence, for both circular and elliptic ROIs. Magn Reson Med 52:1005–1015, 2004. © 2004 Wiley-Liss, Inc.
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automatic spatial and temporal temperature control for mr guided focused ultrasound using fast 3d mr thermometry and multiSpiral Trajectory of the focal point
Magnetic Resonance in Medicine, 2004Co-Authors: C Mougenot, Rares Salomir, Jean Palussiere, N Grenier, Chrit T W MoonenAbstract:Of the different modalities to induce local hyperthermia, focused ultrasound is the only noninvasive technology available at the moment. In addition to the 3D localization of the target region, it has been shown that MRI can provide real-time thermometry and allows online, automatic control of temperature evolution of the focal point. Treatment of a large tissue volume (as compared to the focal spot size, i.e., the ultrasound wavelength) can be achieved rapidly by moving the focal point along an inside-out Spiral Trajectory. It has been shown previously that under linear conditions of energy deposition versus temperature, the spatial profile of the temperature within a large area can be controlled. In this study, a proportional, integral, and derivative (PID) spatial-and-temporal controller is described for the control of the temperature evolution within the target region under more variable conditions. The aim was to reach a predefined temperature profile after a few successive trajectories. Heat conduction in tissue is exploited to obtain a uniform temperature increase in a volume using discrete sonications without any waiting time. Input data sets consisted of 3D temperature maps provided online by a MR scanner. For each new Trajectory, the controller recalculates the number of sonications per surface unit (spatial density of points describing the Trajectory) and the applied power. Its performance was tested ex vivo and in vivo. Diameters of the target region ranged from 9 mm to 19 mm. Targeted temperature increase ranged from +8 degrees C to +18 degrees C. Spatiotemporal temperature control showed good stability and fast convergence, for both circular and elliptic ROIs.
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feasibility of mr guided focused ultrasound with real time temperature mapping and continuous sonication for ablation of vx2 carcinoma in rabbit thigh
Magnetic Resonance in Medicine, 2003Co-Authors: Jean Palussiere, Rares Salomir, Bruno Quesson, N Grenier, Brigitte Le Bail, Rabia Fawaz, Chrit T W MoonenAbstract:The efficiency of MRI-guided focused ultrasound (FUS) hyperthermia with continuous sonication was investigated for the treatment of VX2 carcinoma implanted in rabbit thigh muscle. Six rabbits were treated with a single session of FUS when the tumor diameter exceeded 2 cm (10-21 days after implant). The FUS treatment method was based on a Spiral Trajectory of the focal point that allows continuous sonication under automatic, real-time MR guidance. The total heating time was approximately 1000 sec. Efficacy of treatment was evaluated twice a week based on clinical (weight) and MRI data. Treated animals were sacrificed 5 weeks after the heating procedure and histological analysis was performed. Tumor regression was observed in each treated animal. Complete ablation of tumor, with confirmation by histological analysis, was obtained in five of six treated cases. Tumor regrowth occurred in one animal. Thermal injury was limited to the targeted region in three cases, but ablation also reached some healthy muscle around the tumor in the other three cases. A good correlation was found between postmortem histological analysis and premortem MRI data. Efficacy of MR-controlled hyperthermia using FUS heating with Spiral trajectories was demonstrated for successful local control of intramuscular VX2 tumor.
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local hyperthermia with mr guided focused ultrasound Spiral Trajectory of the focal point optimized for temperature uniformity in the target region
Journal of Magnetic Resonance Imaging, 2000Co-Authors: Rares Salomir, Jean Palussiere, Frederic Vimeux, Jacco A De Zwart, Bruno Quesson, Maurice Gauchet, Pierre Lelong, Jean Pergrale, N Grenier, Chrit T W MoonenAbstract:The objective of hyperthermia treatment is to deliver a similar therapeutic thermal dose throughout the target volume within a minimum amount of time. We describe a noninvasive approach to this goal based on magnetic resonance imaging (MRI)-guided focused ultrasound (FUS) with a spherical transducer that can be moved along two directions inside the bed of a clinical MR imager and that has an adjustable focal length in the third dimension. Absorption of FUS gives rise to a highly localized thermal buildup, which then spreads by heat diffusion and blood perfusion. A uniform temperature within a large target volume can be obtained using a double Spiral Trajectory of the transducer focal point together with constant and maximum FUS power. Differences between the real and target temperatures during the first Spiral are evaluated in real time with temperature MRI and corrected for during the second Spiral Trajectory employing FUS focal point velocity modulation. Once a uniform temperature distribution is reached within the entire volume, FUS heating is applied only at the region's boundaries to maintain the raised temperature levels. Heat conduction, together with the design and timing of the trajectories, therefore ensures a similar thermal dose for the entire target region. Good agreement is obtained between theory and experimental results in vitro on gel phantoms, ex vivo on meat samples, and in vivo on rabbit thigh muscle. Edema in muscle was visible 1 hour after hyperthermia as a spatially uniform rise of the signal intensity in T2-weighted images. J. Magn. Reson. Imaging 2000;12:571–583. © 2000 Wiley-Liss, Inc.
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local hyperthermia with mr guided focused ultrasound Spiral Trajectory of the focal point optimized for temperature uniformity in the target region
Journal of Magnetic Resonance Imaging, 2000Co-Authors: Rares Salomir, Jean Palussiere, Frederic Vimeux, Jacco A De Zwart, Bruno Quesson, Maurice Gauchet, Pierre Lelong, Jean Pergrale, N Grenier, Chrit T W MoonenAbstract:The objective of hyperthermia treatment is to deliver a similar therapeutic thermal dose throughout the target volume within a minimum amount of time. We describe a noninvasive approach to this goal based on magnetic resonance imaging (MRI)-guided focused ultrasound (FUS) with a spherical transducer that can be moved along two directions inside the bed of a clinical MR imager and that has an adjustable focal length in the third dimension. Absorption of FUS gives rise to a highly localized thermal buildup, which then spreads by heat diffusion and blood perfusion. A uniform temperature within a large target volume can be obtained using a double Spiral Trajectory of the transducer focal point together with constant and maximum FUS power. Differences between the real and target temperatures during the first Spiral are evaluated in real time with temperature MRI and corrected for during the second Spiral Trajectory employing FUS focal point velocity modulation. Once a uniform temperature distribution is reached within the entire volume, FUS heating is applied only at the region's boundaries to maintain the raised temperature levels. Heat conduction, together with the design and timing of the trajectories, therefore ensures a similar thermal dose for the entire target region. Good agreement is obtained between theory and experimental results in vitro on gel phantoms, ex vivo on meat samples, and in vivo on rabbit thigh muscle. Edema in muscle was visible 1 hour after hyperthermia as a spatially uniform rise of the signal intensity in T(2)-weighted images.
Thanh D Nguyen - One of the best experts on this subject based on the ideXlab platform.
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impact of lesion location on longitudinal myelin water fraction change in chronic multiple sclerosis lesions
Journal of Neuroimaging, 2020Co-Authors: Sneha Pandya, Thanh D Nguyen, Ulrike W Kaunzner, Sandra Hurtado M Rua, Nancy Nealon, Jai Perumal, Timothy Vartanian, Susan A GauthierAbstract:BACKGROUND AND PURPOSE To examine the impact of lesion location on longitudinal myelin water fraction (MWF) changes in chronic multiple sclerosis (MS) lesions. Relative hypoxia, due to vascular watershed regions of the cerebrum, has been implicated in lesion development but impact on ongoing demyelination is unknown. METHODS Forty-eight patients with relapsing-remitting and secondary progressive MS had two MWF scans with fast acquisition, Spiral Trajectory, and T2prep (FAST-T2) sequence, at an interval of 2.0 (±.3) years. Lesion location was identified based upon cerebral lobe and relation to the ventricles. Change in MWF was assessed using a mixed effects model, controlling for lesion location and patient covariates. RESULTS Average age was 42.3 (±12) years, mean disease duration was 9.7 (±9.1) years, and median Expanded Disability Status Score (EDSS) was 2.5 (±2.3). The majority of 512 chronic lesions was located in the frontal and parietal lobes (75.6%) and more often periventricular (44.7%). All occipital lesions were periventricular. The average lesion MWF decreased from baseline (.07 ± .03) to 2 years (.06 ±.03) P < .01. Lesions within the occipital lobe showed a significant reduction in MWF as compared to other lobes. CONCLUSIONS Chronic lesions in the occipital lobe showed the greatest reduction in MWF. Neuroanatomical localization of lesions to the occipital horns of the lateral ventricles, a watershed region, may contribute to ongoing demyelination in this lesion type.
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combining quantitative susceptibility mapping with automatic zero reference qsm0 and myelin water fraction imaging to quantify iron related myelin damage in chronic active ms lesions
American Journal of Neuroradiology, 2017Co-Authors: Thanh D Nguyen, Yi Wang, Sneha Pandya, Yan Zhang, Ilhami Kovanlikaya, Amy Kuceyeski, Susan A GauthierAbstract:BACKGROUND AND PURPOSE: A hyperintense rim on susceptibility in chronic MS lesions is consistent with iron deposition, and the purpose of this study was to quantify iron-related myelin damage within these lesions as compared with those without rim. MATERIALS AND METHODS: Forty-six patients had 2 longitudinal quantitative susceptibility mapping with automatic zero reference scans with a mean interval of 28.9 ± 11.4 months. Myelin water fraction mapping by using fast acquisition with Spiral Trajectory and T2 prep was obtained at the second time point to measure myelin damage. Mixed-effects models were used to assess lesion quantitative susceptibility mapping and myelin water fraction values. RESULTS: Quantitative susceptibility mapping scans were on average 6.8 parts per billion higher in 116 rim-positive lesions compared with 441 rim-negative lesions ( P P P P CONCLUSIONS: Quantitative susceptibility mapping rim-positive lesions maintained a hyperintense rim, increased in susceptibility, and had more myelin damage compared with rim-negative lesions. Our results are consistent with the identification of chronic active MS lesions and may provide a target for therapeutic interventions to reduce myelin damage.
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rapid whole brain myelin water content mapping without an external water standard at 1 5 t
Magnetic Resonance Imaging, 2017Co-Authors: Thanh D Nguyen, Pascal Spincemaille, Susan A Gauthier, Yi WangAbstract:Abstract The objective of this study is to develop rapid whole brain mapping of myelin water content (MWC) at 1.5 T. The Fast Acquisition with Spiral Trajectory and T2prep (FAST-T2) pulse sequence originally developed for myelin water fraction (MWF) mapping was modified to obtain fast mapping of T1 and receiver coil sensitivity needed for MWC computation. The accuracy of the proposed T1 mapping was evaluated by comparing with the standard IR-FSE method. Numerical simulations were performed to assess the accuracy and reliability of the proposed MWC mapping. We also compared MWC values obtained with either cerebrospinal fluid (CSF) or an external water tube attached to the subject's head as the water reference. Our results from healthy volunteers show that whole brain MWC mapping is feasible in 7 min and provides accurate brain T1 values. Regional brain WC and MWC measurements obtained with the internal CSF-based water standard showed excellent correlation (R > 0.99) and negligible bias within narrow limits of agreement compared to those obtained with an external water standard.
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rapid whole brain myelin water content mapping without an external water standard at 1 5 t
Magnetic Resonance Imaging, 2017Co-Authors: Thanh D Nguyen, Pascal Spincemaille, Susan A Gauthier, Yi WangAbstract:Abstract The objective of this study is to develop rapid whole brain mapping of myelin water content (MWC) at 1.5 T. The Fast Acquisition with Spiral Trajectory and T2prep (FAST-T2) pulse sequence originally developed for myelin water fraction (MWF) mapping was modified to obtain fast mapping of T1 and receiver coil sensitivity needed for MWC computation. The accuracy of the proposed T1 mapping was evaluated by comparing with the standard IR-FSE method. Numerical simulations were performed to assess the accuracy and reliability of the proposed MWC mapping. We also compared MWC values obtained with either cerebrospinal fluid (CSF) or an external water tube attached to the subject's head as the water reference. Our results from healthy volunteers show that whole brain MWC mapping is feasible in 7 min and provides accurate brain T1 values. Regional brain WC and MWC measurements obtained with the internal CSF-based water standard showed excellent correlation (R > 0.99) and negligible bias within narrow limits of agreement compared to those obtained with an external water standard.
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feasibility and reproducibility of whole brain myelin water mapping in 4 minutes using fast acquisition with Spiral Trajectory and adiabatic t2prep fast t2 at 3t
Magnetic Resonance in Medicine, 2016Co-Authors: Thanh D Nguyen, Pascal Spincemaille, Yi Wang, Kofi Deh, Elizabeth Monohan, Sneha Pandya, Ashish Raj, Susan A GauthierAbstract:Purpose To develop and measure the reproducibility of 4-min whole brain myelin water fraction (MWF) mapping using fast acquisition with Spiral Trajectory and T2prep (FAST-T2) sequence at 3T. Methods Experiments were performed on phantoms, 13 volunteers, and 16 patients with multiple sclerosis. MWF maps were extracted using a spatially constrained non-linear algorithm. The proposed adiabatic modified BIR-4 (mBIR-4) T2prep was compared with the conventional composite T2prep (COMP). The effect of reducing the number of echo times (TEs) from 15 to 6 (reducing scan time from 10 to 4 min) was evaluated. Reproducibility was assessed using correlation analysis, coefficient of variation (COV), and Bland–Altman plots. Results Compared with COMP, mBIR-4 provided more accurate T2 in phantoms and better MWF maps in human brains. Reducing the number of TEs had a negligible effect on MWF map quality, with a regional MWF difference of <0.8%. Regional MWFs obtained by repeated scans showed excellent correlation (R = 0.99), low COV (1.3%–2.4%), and negligible bias within ±1% limits of agreement. On a voxel-wise basis, the agreement remained strong (correlation R = 0.89 ± 0.03, bias = 0.01% ± 0.29%, limits of agreement = [−3.35% ± 0.73%, 3.33% ± 0.61%]). Conclusion Whole brain MWF mapping with adiabatic FAST-T2 is feasible in 4 min and provides good intrasite reproducibility. Magn Reson Med, 2015. © 2015 Wiley Periodicals, Inc.
Susan A Gauthier - One of the best experts on this subject based on the ideXlab platform.
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impact of lesion location on longitudinal myelin water fraction change in chronic multiple sclerosis lesions
Journal of Neuroimaging, 2020Co-Authors: Sneha Pandya, Thanh D Nguyen, Ulrike W Kaunzner, Sandra Hurtado M Rua, Nancy Nealon, Jai Perumal, Timothy Vartanian, Susan A GauthierAbstract:BACKGROUND AND PURPOSE To examine the impact of lesion location on longitudinal myelin water fraction (MWF) changes in chronic multiple sclerosis (MS) lesions. Relative hypoxia, due to vascular watershed regions of the cerebrum, has been implicated in lesion development but impact on ongoing demyelination is unknown. METHODS Forty-eight patients with relapsing-remitting and secondary progressive MS had two MWF scans with fast acquisition, Spiral Trajectory, and T2prep (FAST-T2) sequence, at an interval of 2.0 (±.3) years. Lesion location was identified based upon cerebral lobe and relation to the ventricles. Change in MWF was assessed using a mixed effects model, controlling for lesion location and patient covariates. RESULTS Average age was 42.3 (±12) years, mean disease duration was 9.7 (±9.1) years, and median Expanded Disability Status Score (EDSS) was 2.5 (±2.3). The majority of 512 chronic lesions was located in the frontal and parietal lobes (75.6%) and more often periventricular (44.7%). All occipital lesions were periventricular. The average lesion MWF decreased from baseline (.07 ± .03) to 2 years (.06 ±.03) P < .01. Lesions within the occipital lobe showed a significant reduction in MWF as compared to other lobes. CONCLUSIONS Chronic lesions in the occipital lobe showed the greatest reduction in MWF. Neuroanatomical localization of lesions to the occipital horns of the lateral ventricles, a watershed region, may contribute to ongoing demyelination in this lesion type.
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combining quantitative susceptibility mapping with automatic zero reference qsm0 and myelin water fraction imaging to quantify iron related myelin damage in chronic active ms lesions
American Journal of Neuroradiology, 2017Co-Authors: Thanh D Nguyen, Yi Wang, Sneha Pandya, Yan Zhang, Ilhami Kovanlikaya, Amy Kuceyeski, Susan A GauthierAbstract:BACKGROUND AND PURPOSE: A hyperintense rim on susceptibility in chronic MS lesions is consistent with iron deposition, and the purpose of this study was to quantify iron-related myelin damage within these lesions as compared with those without rim. MATERIALS AND METHODS: Forty-six patients had 2 longitudinal quantitative susceptibility mapping with automatic zero reference scans with a mean interval of 28.9 ± 11.4 months. Myelin water fraction mapping by using fast acquisition with Spiral Trajectory and T2 prep was obtained at the second time point to measure myelin damage. Mixed-effects models were used to assess lesion quantitative susceptibility mapping and myelin water fraction values. RESULTS: Quantitative susceptibility mapping scans were on average 6.8 parts per billion higher in 116 rim-positive lesions compared with 441 rim-negative lesions ( P P P P CONCLUSIONS: Quantitative susceptibility mapping rim-positive lesions maintained a hyperintense rim, increased in susceptibility, and had more myelin damage compared with rim-negative lesions. Our results are consistent with the identification of chronic active MS lesions and may provide a target for therapeutic interventions to reduce myelin damage.
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rapid whole brain myelin water content mapping without an external water standard at 1 5 t
Magnetic Resonance Imaging, 2017Co-Authors: Thanh D Nguyen, Pascal Spincemaille, Susan A Gauthier, Yi WangAbstract:Abstract The objective of this study is to develop rapid whole brain mapping of myelin water content (MWC) at 1.5 T. The Fast Acquisition with Spiral Trajectory and T2prep (FAST-T2) pulse sequence originally developed for myelin water fraction (MWF) mapping was modified to obtain fast mapping of T1 and receiver coil sensitivity needed for MWC computation. The accuracy of the proposed T1 mapping was evaluated by comparing with the standard IR-FSE method. Numerical simulations were performed to assess the accuracy and reliability of the proposed MWC mapping. We also compared MWC values obtained with either cerebrospinal fluid (CSF) or an external water tube attached to the subject's head as the water reference. Our results from healthy volunteers show that whole brain MWC mapping is feasible in 7 min and provides accurate brain T1 values. Regional brain WC and MWC measurements obtained with the internal CSF-based water standard showed excellent correlation (R > 0.99) and negligible bias within narrow limits of agreement compared to those obtained with an external water standard.
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rapid whole brain myelin water content mapping without an external water standard at 1 5 t
Magnetic Resonance Imaging, 2017Co-Authors: Thanh D Nguyen, Pascal Spincemaille, Susan A Gauthier, Yi WangAbstract:Abstract The objective of this study is to develop rapid whole brain mapping of myelin water content (MWC) at 1.5 T. The Fast Acquisition with Spiral Trajectory and T2prep (FAST-T2) pulse sequence originally developed for myelin water fraction (MWF) mapping was modified to obtain fast mapping of T1 and receiver coil sensitivity needed for MWC computation. The accuracy of the proposed T1 mapping was evaluated by comparing with the standard IR-FSE method. Numerical simulations were performed to assess the accuracy and reliability of the proposed MWC mapping. We also compared MWC values obtained with either cerebrospinal fluid (CSF) or an external water tube attached to the subject's head as the water reference. Our results from healthy volunteers show that whole brain MWC mapping is feasible in 7 min and provides accurate brain T1 values. Regional brain WC and MWC measurements obtained with the internal CSF-based water standard showed excellent correlation (R > 0.99) and negligible bias within narrow limits of agreement compared to those obtained with an external water standard.
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feasibility and reproducibility of whole brain myelin water mapping in 4 minutes using fast acquisition with Spiral Trajectory and adiabatic t2prep fast t2 at 3t
Magnetic Resonance in Medicine, 2016Co-Authors: Thanh D Nguyen, Pascal Spincemaille, Yi Wang, Kofi Deh, Elizabeth Monohan, Sneha Pandya, Ashish Raj, Susan A GauthierAbstract:Purpose To develop and measure the reproducibility of 4-min whole brain myelin water fraction (MWF) mapping using fast acquisition with Spiral Trajectory and T2prep (FAST-T2) sequence at 3T. Methods Experiments were performed on phantoms, 13 volunteers, and 16 patients with multiple sclerosis. MWF maps were extracted using a spatially constrained non-linear algorithm. The proposed adiabatic modified BIR-4 (mBIR-4) T2prep was compared with the conventional composite T2prep (COMP). The effect of reducing the number of echo times (TEs) from 15 to 6 (reducing scan time from 10 to 4 min) was evaluated. Reproducibility was assessed using correlation analysis, coefficient of variation (COV), and Bland–Altman plots. Results Compared with COMP, mBIR-4 provided more accurate T2 in phantoms and better MWF maps in human brains. Reducing the number of TEs had a negligible effect on MWF map quality, with a regional MWF difference of <0.8%. Regional MWFs obtained by repeated scans showed excellent correlation (R = 0.99), low COV (1.3%–2.4%), and negligible bias within ±1% limits of agreement. On a voxel-wise basis, the agreement remained strong (correlation R = 0.89 ± 0.03, bias = 0.01% ± 0.29%, limits of agreement = [−3.35% ± 0.73%, 3.33% ± 0.61%]). Conclusion Whole brain MWF mapping with adiabatic FAST-T2 is feasible in 4 min and provides good intrasite reproducibility. Magn Reson Med, 2015. © 2015 Wiley Periodicals, Inc.