Publications

2014
Wei-Tang Chang, Kawin Setsompop, Jyrki Ahveninen, John W Belliveau, Thomas Witzel, and Fa-Hsuan Lin. 2014. “Improving the spatial resolution of magnetic resonance inverse imaging via the blipped-CAIPI acquisition scheme.” Neuroimage, 91, Pp. 401-11.Abstract
Using simultaneous acquisition from multiple channels of a radio-frequency (RF) coil array, magnetic resonance inverse imaging (InI) achieves functional MRI acquisitions at a rate of 100ms per whole-brain volume. InI accelerates the scan by leaving out partition encoding steps and reconstructs images by solving under-determined inverse problems using RF coil sensitivity information. Hence, the correlated spatial information available in the coil array causes spatial blurring in the InI reconstruction. Here, we propose a method that employs gradient blips in the partition encoding direction during the acquisition to provide extra spatial encoding in order to better differentiate signals from different partitions. According to our simulations, this blipped-InI (bInI) method can increase the average spatial resolution by 15.1% (1.3mm) across the whole brain and from 32.6% (4.2mm) in subcortical regions, as compared to the InI method. In a visual fMRI experiment, we demonstrate that, compared to InI, the spatial distribution of bInI BOLD response is more consistent with that of a conventional echo-planar imaging (EPI) at the level of individual subjects. With the improved spatial resolution, especially in subcortical regions, bInI can be a useful fMRI tool for obtaining high spatiotemporal information for clinical and cognitive neuroscience studies.
WT Chang, K Setsompop, and J Ahveninen. 2014. “Improving the spatial resolution of magnetic resonance inverse imaging via the blipped-CAIPI acquisition scheme.” NeuroImage. Publisher's Version
Stephen F. Cauley, Jonathan R. Polimeni, Himanshu Bhat, Lawrence L. Wald, and Kawin Setsompop. 2014. “Interslice leakage artifact reduction technique for simultaneous multislice acquisitions.” Magnetic Resonance in Medicine, 72, Pp. 93–102. Publisher's VersionAbstract
PURPOSE: Controlled aliasing techniques for simultaneously acquired echo-planar imaging slices have been shown to significantly increase the temporal efficiency for both diffusion-weighted imaging and functional magnetic resonance imaging studies. The "slice-GRAPPA" (SG) method has been widely used to reconstruct such data. We investigate robust optimization techniques for SG to ensure image reconstruction accuracy through a reduction of leakage artifacts. METHODS: Split SG is proposed as an alternative kernel optimization method. The performance of Split SG is compared to standard SG using data collected on a spherical phantom and in vivo on two subjects at 3 T. Slice-accelerated and nonaccelerated data were collected for a spin-echo diffusion-weighted acquisition. Signal leakage metrics and time-series SNR were used to quantify the performance of the kernel fitting approaches. RESULTS: The Split SG optimization strategy significantly reduces leakage artifacts for both phantom and in vivo acquisitions. In addition, a significant boost in time-series SNR for in vivo diffusion-weighted acquisitions with in-plane 2× and slice 3× accelerations was observed with the Split SG approach. CONCLUSION: By minimizing the influence of leakage artifacts during the training of SG kernels, we have significantly improved reconstruction accuracy. Our robust kernel fitting strategy should enable better reconstruction accuracy and higher slice-acceleration across many applications. Magn Reson Med, 2013. © 2013 Wiley Periodicals, Inc.
Stephen F Cauley, Jonathan R Polimeni, Himanshu Bhat, Lawrence L Wald, and Kawin Setsompop. 2014. “Interslice leakage artifact reduction technique for simultaneous multislice acquisitions.” Magn Reson Med, 72, 1, Pp. 93-102.Abstract
PURPOSE: Controlled aliasing techniques for simultaneously acquired echo-planar imaging slices have been shown to significantly increase the temporal efficiency for both diffusion-weighted imaging and functional magnetic resonance imaging studies. The "slice-GRAPPA" (SG) method has been widely used to reconstruct such data. We investigate robust optimization techniques for SG to ensure image reconstruction accuracy through a reduction of leakage artifacts. METHODS: Split SG is proposed as an alternative kernel optimization method. The performance of Split SG is compared to standard SG using data collected on a spherical phantom and in vivo on two subjects at 3 T. Slice-accelerated and nonaccelerated data were collected for a spin-echo diffusion-weighted acquisition. Signal leakage metrics and time-series SNR were used to quantify the performance of the kernel fitting approaches. RESULTS: The Split SG optimization strategy significantly reduces leakage artifacts for both phantom and in vivo acquisitions. In addition, a significant boost in time-series SNR for in vivo diffusion-weighted acquisitions with in-plane 2× and slice 3× accelerations was observed with the Split SG approach. CONCLUSION: By minimizing the influence of leakage artifacts during the training of SG kernels, we have significantly improved reconstruction accuracy. Our robust kernel fitting strategy should enable better reconstruction accuracy and higher slice-acceleration across many applications.
Cornelius Eichner, Lawrence L. Wald, and Kawin Setsompop. 2014. “A low power radiofrequency pulse for simultaneous multislice excitation and refocusing.” Magnetic Resonance in Medicine, 72, Pp. 949–58. Publisher's VersionAbstract
PURPOSE: Simultaneous multislice (SMS) acquisition enables increased temporal efficiency of MRI. Nonetheless, MultiBand (MB) radiofrequency (RF) pulses used for SMS can cause large energy deposition. Power independent of number of slices (PINS) pulses reduce RF power at cost of reduced bandwidth and increased off-resonance dependency. This work improves PINS design to further reduce energy deposition, off-resonance dependency and peak power. THEORY AND METHODS: Modifying the shape of MB RF-pulses allows for mixing with PINS excitation, creating a new pulse type with reduced energy deposition and SMS excitation characteristics. Bloch Simulations were used to evaluate excitation and off-resonance behavior of this "MultiPINS" pulse. In this work, MultiPINS was used for whole-brain MB = 3 acquisition of high angular and spatial resolution diffusion MRI at 7 Tesla in 3 min. RESULTS: By using MultiPINS, energy transmission and peak power for SMS imaging can be significantly reduced compared with PINS and MB pulses. For MB = 3 acquisition in this work, MultiPINS reduces energy transmission by up to ∼50% compared with PINS pulses. The energy reduction was traded off to shorten the MultiPINS pulse, yielding higher signal at off-resonances for spin-echo acquisitions. CONCLUSION: MB and PINS pulses can be combined to enable low energy and peak power SMS acquisition. Magn Reson Med 72:949-958, 2014. © 2014 Wiley Periodicals, Inc.
Cornelius Eichner, Lawrence L Wald, and Kawin Setsompop. 2014. “A low power radiofrequency pulse for simultaneous multislice excitation and refocusing.” Magn Reson Med, 72, 4, Pp. 949-58.Abstract
PURPOSE: Simultaneous multislice (SMS) acquisition enables increased temporal efficiency of MRI. Nonetheless, MultiBand (MB) radiofrequency (RF) pulses used for SMS can cause large energy deposition. Power independent of number of slices (PINS) pulses reduce RF power at cost of reduced bandwidth and increased off-resonance dependency. This work improves PINS design to further reduce energy deposition, off-resonance dependency and peak power. THEORY AND METHODS: Modifying the shape of MB RF-pulses allows for mixing with PINS excitation, creating a new pulse type with reduced energy deposition and SMS excitation characteristics. Bloch Simulations were used to evaluate excitation and off-resonance behavior of this "MultiPINS" pulse. In this work, MultiPINS was used for whole-brain MB = 3 acquisition of high angular and spatial resolution diffusion MRI at 7 Tesla in 3 min. RESULTS: By using MultiPINS, energy transmission and peak power for SMS imaging can be significantly reduced compared with PINS and MB pulses. For MB = 3 acquisition in this work, MultiPINS reduces energy transmission by up to ∼50% compared with PINS pulses. The energy reduction was traded off to shorten the MultiPINS pulse, yielding higher signal at off-resonances for spin-echo acquisitions. CONCLUSION: MB and PINS pulses can be combined to enable low energy and peak power SMS acquisition.
Y Rathi, O Michailovich, F Laun, K Setsompop, PE Grant, and C-F Westin. 2014. “Multi-shell diffusion signal recovery from sparse measurements.” Med Image Anal, 18, 7, Pp. 1143-56.Abstract
For accurate estimation of the ensemble average diffusion propagator (EAP), traditional multi-shell diffusion imaging (MSDI) approaches require acquisition of diffusion signals for a range of b-values. However, this makes the acquisition time too long for several types of patients, making it difficult to use in a clinical setting. In this work, we propose a new method for the reconstruction of diffusion signals in the entire q-space from highly undersampled sets of MSDI data, thus reducing the scan time significantly. In particular, to sparsely represent the diffusion signal over multiple q-shells, we propose a novel extension to the framework of spherical ridgelets by accurately modeling the monotonically decreasing radial component of the diffusion signal. Further, we enforce the reconstructed signal to have smooth spatial regularity in the brain, by minimizing the total variation (TV) norm. We combine these requirements into a novel cost function and derive an optimal solution using the Alternating Directions Method of Multipliers (ADMM) algorithm. We use a physical phantom data set with known fiber crossing angle of 45° to determine the optimal number of measurements (gradient directions and b-values) needed for accurate signal recovery. We compare our technique with a state-of-the-art sparse reconstruction method (i.e., the SHORE method of Cheng et al. (2010)) in terms of angular error in estimating the crossing angle, incorrect number of peaks detected, normalized mean squared error in signal recovery as well as error in estimating the return-to-origin probability (RTOP). Finally, we also demonstrate the behavior of the proposed technique on human in vivo data sets. Based on these experiments, we conclude that using the proposed algorithm, at least 60 measurements (spread over three b-value shells) are needed for proper recovery of MSDI data in the entire q-space.
Y Rathi, O Michailovich, F Laun, K Setsompop, PE Grant, and C-F Westin. 2014. “Multi-shell diffusion signal recovery from sparse measurements.” Medical image analysis, 18, 7, Pp. 1143–56. Publisher's VersionAbstract
For accurate estimation of the ensemble average diffusion propagator (EAP), traditional multi-shell diffusion imaging (MSDI) approaches require acquisition of diffusion signals for a range of b-values. However, this makes the acquisition time too long for several types of patients, making it difficult to use in a clinical setting. In this work, we propose a new method for the reconstruction of diffusion signals in the entire q-space from highly undersampled sets of MSDI data, thus reducing the scan time significantly. In particular, to sparsely represent the diffusion signal over multiple q-shells, we propose a novel extension to the framework of spherical ridgelets by accurately modeling the monotonically decreasing radial component of the diffusion signal. Further, we enforce the reconstructed signal to have smooth spatial regularity in the brain, by minimizing the total variation (TV) norm. We combine these requirements into a novel cost function and derive an optimal solution using the Alternating Directions Method of Multipliers (ADMM) algorithm. We use a physical phantom data set with known fiber crossing angle of 45° to determine the optimal number of measurements (gradient directions and b-values) needed for accurate signal recovery. We compare our technique with a state-of-the-art sparse reconstruction method (i.e., the SHORE method of Cheng et al. (2010)) in terms of angular error in estimating the crossing angle, incorrect number of peaks detected, normalized mean squared error in signal recovery as well as error in estimating the return-to-origin probability (RTOP). Finally, we also demonstrate the behavior of the proposed technique on human in vivo data sets. Based on these experiments, we conclude that using the proposed algorithm, at least 60 measurements (spread over three b-value shells) are needed for proper recovery of MSDI data in the entire q-space.
Wei Zhao, Julien Cohen-Adad, Jonathan R. Polimeni, Boris Keil, Bastien Guerin, Kawin Setsompop, Peter Serano, Azma Mareyam, Philipp Hoecht, and Lawrence L Wald. 2014. “Nineteen-channel receive array and four-channel transmit array coil for cervical spinal cord imaging at 7T.” Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine, 72, 1, Pp. 291–300. Publisher's VersionAbstract
PURPOSE: To design and validate a radiofrequency (RF) array coil for cervical spinal cord imaging at 7T. METHODS: A 19-channel receive array with a four-channel transmit array was developed on a close-fitting coil former at 7T. Transmit efficiency and specific absorption rate were evaluated in a B1 (+) mapping study and an electromagnetic model. Receive signal-to-noise ratio (SNR) and noise amplification for parallel imaging were evaluated and compared with a commercial 3T 19-channel head-neck array and a 7T four-channel spine array. The performance of the array was qualitatively demonstrated in human volunteers using high-resolution imaging (down to 300 $μ$m in-plane). RESULTS: The transmit and receive arrays showed good bench performance. The SNR was approximately 4.2-fold higher in the 7T receive array at the location of the cord with respect to the 3T coil. The g-factor results showed an additional acceleration was possible with the 7T array. In vivo imaging was feasible and showed high SNR and tissue contrast. CONCLUSION: The highly parallel transmit and receive arrays were demonstrated to be fit for spinal cord imaging at 7T. The high sensitivity of the receive coil combined with ultra-high field will likely improve investigations of microstructure and tissue segmentation in the healthy and pathological spinal cord.
Wei Zhao, Julien Cohen-Adad, Jonathan R Polimeni, Boris Keil, Bastien Guerin, Kawin Setsompop, Peter Serano, Azma Mareyam, Philipp Hoecht, and Lawrence L Wald. 2014. “Nineteen-channel receive array and four-channel transmit array coil for cervical spinal cord imaging at 7T.” Magn Reson Med, 72, 1, Pp. 291-300.Abstract
PURPOSE: To design and validate a radiofrequency (RF) array coil for cervical spinal cord imaging at 7T. METHODS: A 19-channel receive array with a four-channel transmit array was developed on a close-fitting coil former at 7T. Transmit efficiency and specific absorption rate were evaluated in a B1 (+) mapping study and an electromagnetic model. Receive signal-to-noise ratio (SNR) and noise amplification for parallel imaging were evaluated and compared with a commercial 3T 19-channel head-neck array and a 7T four-channel spine array. The performance of the array was qualitatively demonstrated in human volunteers using high-resolution imaging (down to 300 μm in-plane). RESULTS: The transmit and receive arrays showed good bench performance. The SNR was approximately 4.2-fold higher in the 7T receive array at the location of the cord with respect to the 3T coil. The g-factor results showed an additional acceleration was possible with the 7T array. In vivo imaging was feasible and showed high SNR and tissue contrast. CONCLUSION: The highly parallel transmit and receive arrays were demonstrated to be fit for spinal cord imaging at 7T. The high sensitivity of the receive coil combined with ultra-high field will likely improve investigations of microstructure and tissue segmentation in the healthy and pathological spinal cord.
Benedikt A Poser, Robert J Anderson, Bastien Guerin, Kawin Setsompop, Weiran Deng, Azma Mareyam, Peter Serano, Lawrence L Wald, and Andrew V Stenger. 2014. “Simultaneous Multislice Excitation by Parallel Transmission.” Magnetic Resonance in Medicine, 71, Pp. 1416–1427.
Benedikt A Poser, Robert James Anderson, Bastien Guérin, Kawin Setsompop, Weiran Deng, Azma Mareyam, Peter Serano, Lawrence L Wald, and Andrew V Stenger. 2014. “Simultaneous multislice excitation by parallel transmission.” Magn Reson Med, 71, 4, Pp. 1416-27.Abstract
PURPOSE: A technique is described for simultaneous multislice (SMS) excitation using radiofrequency (RF) parallel transmission (pTX). METHODS: Spatially distinct slices are simultaneously excited by applying different RF frequencies on groups of elements of a multichannel transmit array. The localized transmit sensitivities of the coil geometry are thereby exploited to reduce RF power. The method is capable of achieving SMS-excitation using single-slice RF pulses, or multiband pulses. SMS-pTX is demonstrated using eight-channel parallel RF transmission on a dual-ring pTX coil at 3 T. The effect on B(1)(+) homogeneity and specific absorption rate (SAR) is evaluated experimentally and by simulations. Slice-GRAPPA reconstruction was used for separation of the collapsed slice signals. RESULTS: Phantom and in vivo brain data acquired with fast low-angle shot (FLASH) and blipped-controlled aliasing results in higher acceleration (CAIPIRINHA) echo-planar imaging are presented at SMS excitation factors of two, four, and six. We also show that with our pTX coil design, slice placement, and binary division of transmitters, SMS-pTX excitations can achieve the same mean flip angles excitations at ∼30% lower RF power than a conventional SMS approach with multiband RF pulses. CONCLUSION: The proposed SMS-pTX allows SMS excitations at reduced RF power by exploiting the local B(1)(+) sensitivities of suitable multielement pTX arrays.
Cornelius Eichner, Kawin Setsompop, Peter J Koopmans, Ralf Lützkendorf, David G Norris, Robert Turner, Lawrence L Wald, and Robin M Heidemann. 2014. “Slice accelerated diffusion-weighted imaging at ultra-high field strength.” Magn Reson Med, 71, 4, Pp. 1518-25.Abstract
PURPOSE: Diffusion magnetic resonance imaging (dMRI) data with very high isotropic resolution can be obtained at 7T. However, for extensive brain coverage, a large number of slices is required, resulting in long acquisition times (TAs). Recording multiple slices simultaneously (SMS) promises to reduce the TA. METHODS: A combination of zoomed and parallel imaging is used to achieve high isotropic resolution dMRI data with a low level of distortions at 7T. The blipped-CAIPI (controlled aliasing in parallel imaging) approach is used to acquire several slices simultaneously. Due to their high radiofrequency (RF) power deposition and ensuing specific absorption rate (SAR) constraints, the commonly used multiband (MB) RF pulses for SMS imaging are inefficient at 7T and entail long repetition times, counteracting the usefulness of SMS acquisitions. To address this issue, low SAR multislice Power Independent of Number of Slices RF pulses are employed. RESULTS: In vivo dMRI results with and without SMS acceleration are presented at different isotropic spatial resolutions at ultra high field strength. The datasets are recorded at a high angular resolution to detect fiber crossings. CONCLUSION: From the results and compared with earlier studies at these resolutions, it can be seen that scan time is significantly reduced, while image quality is preserved.
Cornelius Eichner, Kawin Setsompop, Peter J Koopmans, Ralf Lützkendorf, David G Norris, Robert Turner, Lawrence L Wald, and Robin M Heidemann. 2014. “Slice accelerated diffusion-weighted imaging at ultra-high field strength.” Magnetic Resonance in Medicine, 71, 4, Pp. 1518–25. Publisher's VersionAbstract
PURPOSE: Diffusion magnetic resonance imaging (dMRI) data with very high isotropic resolution can be obtained at 7T. However, for extensive brain coverage, a large number of slices is required, resulting in long acquisition times (TAs). Recording multiple slices simultaneously (SMS) promises to reduce the TA. METHODS: A combination of zoomed and parallel imaging is used to achieve high isotropic resolution dMRI data with a low level of distortions at 7T. The blipped-CAIPI (controlled aliasing in parallel imaging) approach is used to acquire several slices simultaneously. Due to their high radiofrequency (RF) power deposition and ensuing specific absorption rate (SAR) constraints, the commonly used multiband (MB) RF pulses for SMS imaging are inefficient at 7T and entail long repetition times, counteracting the usefulness of SMS acquisitions. To address this issue, low SAR multislice Power Independent of Number of Slices RF pulses are employed. RESULTS: In vivo dMRI results with and without SMS acceleration are presented at different isotropic spatial resolutions at ultra high field strength. The datasets are recorded at a high angular resolution to detect fiber crossings. CONCLUSION: From the results and compared with earlier studies at these resolutions, it can be seen that scan time is significantly reduced, while image quality is preserved.
Cornelius Eichner, Kourosh Jafari-Khouzani, Stephen Cauley, Himanshu Bhat, Pavlina Polaskova, Ovidiu C Andronesi, Otto Rapalino, Robert Turner, Lawrence L Wald, Steven Stufflebeam, and Kawin Setsompop. 2014. “Slice accelerated gradient-echo spin-echo dynamic susceptibility contrast imaging with blipped CAIPI for increased slice coverage.” Magn Reson Med, 72, 3, Pp. 770-8.Abstract
PURPOSE: To improve slice coverage of gradient echo spin echo (GESE) sequences for dynamic susceptibility contrast (DSC) MRI using a simultaneous-multiple-slice (SMS) method. METHODS: Data were acquired on 3 Tesla (T) MR scanners with a 32-channel head coil. To evaluate use of SMS for DSC, an SMS GESE sequence with two-fold slice coverage and same temporal sampling was compared with a standard GESE sequence, both with 2× in-plane acceleration. A signal to noise ratio (SNR) comparison was performed on one healthy subject. Additionally, data with Gadolinium injection were collected on three patients with glioblastoma using both sequences, and perfusion analysis was performed on healthy tissues as well as on tumor. RESULTS: Retained SNR of SMS DSC is 90% for a gradient echo (GE) and 99% for a spin echo (SE) acquisition, compared with a standard acquisition without slice acceleration. Comparing cerebral blood volume maps, it was observed that the results of standard and SMS acquisitions are comparable for both GE and SE images. CONCLUSION: Two-fold slice accelerated DSC MRI achieves similar SNR and perfusion metrics as a standard acquisition, while allowing a significant increase in slice coverage of the brain. The results also point to a possibility to improve temporal sampling rate, while retaining the same slice coverage.
Cornelius Eichner, Kourosh Jafari-Khouzani, Stephen Cauley, Himanshu Bhat, Pavlina Polaskova, Ovidiu C Andronesi, Otto Rapalino, Robert Turner, Lawrence L Wald, Steven Stufflebeam, and Kawin Setsompop. 2014. “Slice accelerated gradient-echo spin-echo dynamic susceptibility contrast imaging with blipped CAIPI for increased slice coverage.” Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine, 72, 3, Pp. 770–8. Publisher's VersionAbstract
PURPOSE: To improve slice coverage of gradient echo spin echo (GESE) sequences for dynamic susceptibility contrast (DSC) MRI using a simultaneous-multiple-slice (SMS) method. METHODS: Data were acquired on 3 Tesla (T) MR scanners with a 32-channel head coil. To evaluate use of SMS for DSC, an SMS GESE sequence with two-fold slice coverage and same temporal sampling was compared with a standard GESE sequence, both with 2× in-plane acceleration. A signal to noise ratio (SNR) comparison was performed on one healthy subject. Additionally, data with Gadolinium injection were collected on three patients with glioblastoma using both sequences, and perfusion analysis was performed on healthy tissues as well as on tumor. RESULTS: Retained SNR of SMS DSC is 90% for a gradient echo (GE) and 99% for a spin echo (SE) acquisition, compared with a standard acquisition without slice acceleration. Comparing cerebral blood volume maps, it was observed that the results of standard and SMS acquisitions are comparable for both GE and SE images. CONCLUSION: Two-fold slice accelerated DSC MRI achieves similar SNR and perfusion metrics as a standard acquisition, while allowing a significant increase in slice coverage of the brain. The results also point to a possibility to improve temporal sampling rate, while retaining the same slice coverage.
Cornelius Eichner, Kourosh Jafari-Khouzani, Stephen F. Cauley, Himanshu Bhat, Pavlina Polaskova, Ovidiu C Andronesi, Otto Rapalino, Robert Turner, Lawrence L Wald, Steven Stufflebeam, and Kawin Setsompop. 2014. “Slice accelerated gradient-echo spin-echo dynamic susceptibility contrast imaging with blipped CAIPI for increased slice coverage.” Magnetic Resonance in Medicine, 778, 3, Pp. 770–778. Publisher's VersionAbstract
PURPOSE: To improve slice coverage of gradient echo spin echo (GESE) sequences for dynamic susceptibility contrast (DSC) MRI using a simultaneous-multiple-slice (SMS) method. METHODS: Data were acquired on 3 Tesla (T) MR scanners with a 32-channel head coil. To evaluate use of SMS for DSC, an SMS GESE sequence with two-fold slice coverage and same temporal sampling was compared with a standard GESE sequence, both with 2× in-plane acceleration. A signal to noise ratio (SNR) comparison was performed on one healthy subject. Additionally, data with Gadolinium injection were collected on three patients with glioblastoma using both sequences, and perfusion analysis was performed on healthy tissues as well as on tumor. RESULTS: Retained SNR of SMS DSC is 90% for a gradient echo (GE) and 99% for a spin echo (SE) acquisition, compared with a standard acquisition without slice acceleration. Comparing cerebral blood volume maps, it was observed that the results of standard and SMS acquisitions are comparable for both GE and SE images. CONCLUSION: Two-fold slice accelerated DSC MRI achieves similar SNR and perfusion metrics as a standard acquisition, while allowing a significant increase in slice coverage of the brain. The results also point to a possibility to improve temporal sampling rate, while retaining the same slice coverage. Magn Reson Med, 2013. © 2013 Wiley Periodicals, Inc.
2014. “Wave‐CAIPI for highly accelerated 3D imaging.” Magnetic łdots}. Publisher's Version
2013
Boris Keil, James N Blau, Stephan Biber, Philipp Hoecht, Veneta Tountcheva, Kawin Setsompop, Christina Triantafyllou, and Lawrence L Wald. 2013. “A 64-channel 3T array coil for accelerated brain MRI.” Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine, 70, 1, Pp. 248–58. Publisher's VersionAbstract
A 64-channel brain array coil was developed and compared to a 32-channel array constructed with the same coil former geometry to precisely isolate the benefit of the 2-fold increase in array coil elements. The constructed coils were developed for a standard clinical 3T MRI scanner and used a contoured head-shaped curved former around the occipital pole and tapered in at the neck to both improve sensitivity and patient comfort. Additionally, the design is a compact, split-former design intended for robust daily use. Signal-to-noise ratio and noise amplification (G-factor) for parallel imaging were quantitatively evaluated in human imaging and compared to a size and shape-matched 32-channel array coil. For unaccelerated imaging, the 64-channel array provided similar signal-to-noise ratio in the brain center to the 32-channel array and 1.3-fold more signal-to-noise ratio in the brain cortex. Reduced noise amplification during highly parallel imaging of the 64-channel array provided the ability to accelerate at approximately one unit higher at a given noise amplification compared to the sized-matched 32-channel array. For example, with a 4-fold acceleration rate, the central brain and cortical signal-to-noise ratio of the 64-channel array was 1.2- and 1.4-fold higher, respectively, compared to the 32-channel array. The characteristics of the coil are demonstrated in accelerated brain imaging.
Boris Keil, James N Blau, Stephan Biber, Philipp Hoecht, Veneta Tountcheva, Kawin Setsompop, Christina Triantafyllou, and Lawrence L Wald. 2013. “A 64-channel 3T array coil for accelerated brain MRI.” Magn Reson Med, 70, 1, Pp. 248-58.Abstract
A 64-channel brain array coil was developed and compared to a 32-channel array constructed with the same coil former geometry to precisely isolate the benefit of the 2-fold increase in array coil elements. The constructed coils were developed for a standard clinical 3T MRI scanner and used a contoured head-shaped curved former around the occipital pole and tapered in at the neck to both improve sensitivity and patient comfort. Additionally, the design is a compact, split-former design intended for robust daily use. Signal-to-noise ratio and noise amplification (G-factor) for parallel imaging were quantitatively evaluated in human imaging and compared to a size and shape-matched 32-channel array coil. For unaccelerated imaging, the 64-channel array provided similar signal-to-noise ratio in the brain center to the 32-channel array and 1.3-fold more signal-to-noise ratio in the brain cortex. Reduced noise amplification during highly parallel imaging of the 64-channel array provided the ability to accelerate at approximately one unit higher at a given noise amplification compared to the sized-matched 32-channel array. For example, with a 4-fold acceleration rate, the central brain and cortical signal-to-noise ratio of the 64-channel array was 1.2- and 1.4-fold higher, respectively, compared to the 32-channel array. The characteristics of the coil are demonstrated in accelerated brain imaging.

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