ISMRM 25th Annual Meeting & Exhibition • 22-27 April 2017 • Honolulu, HI, USA

Electronic Poster Session: MR Spectroscopy
 5465 -5488 MRS Processing 5489 -5512 MRS Acquisition Methods 5513 -5536 MRSI Methods 5585 -5608 NMR & ESR & Education 5609 -5632 Non-Proton MRI & MRS 5633 -5655 MRS Applications

MRS Processing
Electronic Poster
MR Spectroscopy

Thursday, 27 April 2017
 Exhibition Hall 13:00 - 14:00

MRS Acquisition Methods
Electronic Poster
MR Spectroscopy

Thursday, 27 April 2017
 Exhibition Hall 13:00 - 14:00

MRSI Methods
Electronic Poster
MR Spectroscopy

Thursday, 27 April 2017
 Exhibition Hall 13:00 - 14:00

 Computer # 5520. 80 Comparison of different acceleration methods for high-resolution metabolite mapping using 1H FID MRSI at 9.4T Sahar Nassirpour, Paul Chang, Anke Henning Reliable metabolite mapping of the human brain using ultra-short TE and TR 1H FID-MRSI is possible at ultra-high fields. However, MRSI studies with high spatial resolutions and brain coverage suffer from long scan times. To make these studies clinically relevant, different acceleration methods are used at the price of losing SNR. The aim of this study is to implement and compare different in-plane acceleration methods: SENSE, GRAPPA and compressed sensing for high-resolution metabolite mapping of the human brain at 9.4T without lipid suppression. 5518. 78 Macromolecule Mapping with Ultrashort-TE Acquisition and Metabolite Spectral Prior Fan Lam, Yudu Li, Bryan Clifford, Zhi-Pei Liang This work presents a novel method for macromolecule mapping and quantification. The proposed method integrates an FID-based MRSI acquisition with a generalized series (GS) model based extrapolation scheme. The FID acquisition allows for the use of ultrashort echoes and short repetition times for fast imaging with improved SNR efficiency. The GS model effectively makes use of the spectral priors from single voxel spectroscopy and allows for reformulating the back-extrapolation of metabolite signals as a linear problem (in contrast to conventional nonlinear methods). Results from in vivo experiments demonstrate that MM signals estimated by the proposed method are consistent with an inversion recovery based method and lead to better metabolite quantification. 5519. 79 Covariance Five Dimensional Echo Planar J-resolved Spectroscopic Imaging Zohaib Iqbal, M. Albert Thomas Chemical shift imaging is a very important method used to investigate several pathologies in vivo. A recent technological development incorporating an echo planar readout, a non-uniform sampling scheme, and an iterative, non-linear reconstruction is the five dimensional echo planar J-resolved spectroscopic imaging (5D EP-JRESI) method. While this technique is capable of obtaining 3 spatial and 2 spectral dimensions in vivo, the indirect spectral dimension has a low spectral resolution, which may hinder accurate metabolite quantitation. In this study, a novel approach using a covariance transformation after reconstruction is assessed and compared to the 5D EP-JRESI method. 5530. 90 A Minimum-Phase Shinnar-Le Roux Spectral-Spatial Excitation RF Pulse for Water and Lipid Suppression in 1H MRSI of Body Extremities Kexin Deng, Chao Ma, Kui Ying, Georges El Fakhri It is challenging to remove nuisance water and lipid signals in 1H-MRSI of body extremities. Strong lipid signals exist both in the subcutaneous layer and bone marrow but also in the muscle, i.e., intramyocellular and extramyocellular lipids.  This work presents a novel minimum-phase Shinnar-Le Roux (SLR) spectral-spatial excitation RF pulse for both water and lipid suppression in 1H-MRSI of body extremities. We have validated the proposed method using Bloch equation simulation, phantom, and in vivo studies. 5532. 92 Spatial Hadamard encoding of J-edited spectroscopy using slice-selective editing pulses Kimberly Chan, Georg Oeltzschner, Michael Schär, Peter Barker, Richard Edden A new approach for simultaneous dual-voxel J-difference spectral editing is described, that uses spatially selective spectral-editing pulses and Hadamard encoding. The theoretical framework for Spatial Hadamard Editing and Reconstruction for Parallel Acquisition (SHERPA) was developed, applying gradient pulses during the frequency selective editing pulses. SHERPA was simulated for GABA, tested in a two-compartment GABA phantom, and applied to the left and right hemispheres of ten normal subjects. SHERPA was successfully implemented with results in close agreement with conventional MEGA-PRESS scans.  Compared to conventional single-voxel single-metabolite J-difference editing, two-fold acceleration is possible without significant loss of SNR using the SHERPA method. 5528. 88 Motion Correction for 1H-MRSI of the Brain Using Unsuppressed Water Signals Bryan Clifford, Xi Peng, Yudu Li, Zhi-Pei Liang, Fan Lam Head motion poses a significant problem in MRSI experiments, especially for 1H-MRSI of the brain performed without water or lipid suppression. In this work we propose a practical method specifically designed to track head motion and correct for its effects on 1H-MRSI data acquired without water suppression. By using the companion spectroscopic water signals, we are able to track head motion with navigators collected in circular and linear trajectories. A specialized data processing scheme is also proposed for processing the navigator data along with the unsuppressed spectroscopic water signals to determine the motion parameters. 5514. 74 semi-adiabatic SPECIAL-based 1H MRSI at 9.4T: Implementation and preliminary validation in a rat brain Hyeong-Hun Lee, Hyeonjin Kim Given the issues of chemical shift displacement error, B1 inhomogeneity and short T2 at high field, a semi-adiabatic SPECIAL-based MRSI sequence was implemented at 9.4T, which is equipped with a pair of broad-band hyperbolic secant adiabatic full passage pulses for refocusing, and yet, allows a minimum TE of as short as 4.98 ms. In phantom, the effect of the prolonged minimum TE on the J-evolution of coupled spins is negligible. In a rat brain, preliminary quantitative results are in close agreement with the previous results obtained by using single-voxel MRS. 5515. 75 High resolution MRSI using compartmental low rank algorithm: demonstration using undersampled EPSI Ipshita Bhattacharya, Ralph Noeske, Baolin Yang, Rolf Schulte, Mathews Jacob Improved spatial resolution is the need of the hour for MRSI. In this work we propose an algorithm which provides a comprehensive and automatic approach to recover high resolution metabolite maps from highly undersampled acquisitions; the improved spatial resolution translates to improved spectral quality and reduced leakage artifacts. The proposed algorithm is also quite flexible and can be readily used in a variety of sequences, including EPSI, CSI, and spirals acquisition schemes. 5513. 73 S-ESPIRiT: Estimation of Coil Sensitivity Maps from MR Spectroscopic Imaging Data Using ESPIRiT Namgyun Lee, Vincent Boer, Esben Petersen, Gyunggoo Cho Estimating a set of coil sensitivity maps that is consistent with the low-resolution SENSE model is challenging in SENSE spectroscopic imaging. Recently, ESPIRiT, an autocalibrating approach to estimate sensitivity maps for MR imaging, that combines both advantages of SENSE and GRAPPA has been developed. In this work, we propose a spectroscopic extension of ESPIRiT, referred to as S-ESPIRiT, to estimate sensitivity maps from Cartesian 2D spectroscopic k-space data.  The proposed method was demonstrated using 2D spectroscopic imaging data of a brain metabolite phantom acquired with a semi-LASER pulse sequence and a 32-channel receive head coil on a 7T MRI scanner. 5523. 83 Full-field of view GM and WM spectroscopy in vivo using spatial lipid pattern estimation and BASE-SLIM localization - permission withheld Peter Adany, In-Young Choi, Phil Lee The presence lipids of several orders of magnitude higher concentrations than metabolites in the extracranial tissues present significant challenges for the reliable acquisition and quantification of 1H MRSI, especially in the outer perimeter areas of the brain.  We developed a novel spatial lipid reconstruction technique to remove nuisance lipid signals in 1H MRS. We applied lipid reconstruction to MRSI data and performed BASE-SLIM localization on the lipid-subtracted signal. Using this method, high quality compartment spectra of GM and WM could be obtained. 5516. 76 Evaluation of Compressed Sensing reconstructions of 3D Echo Planar Spectroscopic Imaging using TV, Wavelet-$$\ell_{1}$$$, and TV+Wavelet-$$\ell_{1}$$$ based regularization. Andres Saucedo, Zohaib Iqbal, Manoj Sarma, M. Albert Thomas Magnetic Resonance Spectroscopic Imaging (MRSI) is a valuable tool to characterize metabolic concentrations and changes in several spatial locations in a single recording. However, the long acquisition time of conventional three-dimensional (3D) MRSI limits its practical application. Non-uniformly sampled 3D echo planar spectroscopic imaging (EPSI) has been proposed to accelerate the scan time, combined with compressed sensing (CS) to retain reconstruction fidelity.  We apply the novel approach of reconstructing 3D EPSI data by applying TV, Wavelet-$$\ell_{1}$$$, and TV + Wavelet-$$\ell_{1}$$$ CS-based regularization on both the combined spectral and two undersampled spatial dimensions. These three reconstruction methods were evaluated in both simulated and in retrospectively undersampled data of a brain phantom. 5517. 77 Low-Rank TGV Reconstruction of High-Resolution 1H-FID-MRSI of whole brain slices Antoine Klauser, Dimitri Van De Ville, Franc¸ois Lazeyras High resolution MRSI data were acquired with 2D FID-MRSI at 3T and a post-processing including lipid suppression, low-rank approximation and TGV-reconstruction is proposed. The resulting metabolic images of tNAA, tCre, Cho, Ins and Glx showed a substantial gain in quality, CRLB values associated and the SNR. This effect was particularly marked for lower signal metabolite: Ins and Glx. In addition, the proposed post-processing reconstructed efficiently under-sampled data allowing a 2- or 4-fold acquisition acceleration. 5525. 85 IRREGULAR SPIRAL ACQUISITION FOR COMPRESSIVE SENSING IN MRSI Jabrane Karkouri, Fabien Millioz, Magalie Viallon, Rémy Prost, Hélène Ratiney Magnetic resonance spectroscopic imaging (MRSI) has multiple interests in clinical practice but it faces quite long acquisition time in practice which limits their use in a clinical environment. In this work, a new fast Magnetic Resonance Spectroscopic image acquisition method, based on Compressed Sensing and the a priori known support of the metabolites chemical shift, is introduced and evaluated based on a k-t space spiral sampling.  In the real-world noisy scenario the error in the recovered spectrum highly depends on the acquired samples. We reduce this error to an acceptable level by selecting irregularly the samples using the Sequential Backward Selection algorithm. Our method has been applied on an in vivo 31P acquisition, to prove the feasibility of the proposed approach. 5524. 84 Multi-region Semi-Adiabatic Spectral-Spatial Spectroscopic Imaging (SASSI) sequence for accelerated MRSI at 7T Rebecca Feldman, Priti Balchandani High field MRI permits us to leverage increased signal-to-noise ratio (SNR) and spectral separation between metabolite peaks for more sensitive metabolite detection at higher spatial resolutions. However, the acquisition of high-resolution spectral grids can be prohibitively time intensive. Accelerated MRSI acquisitions are challenged by the limitations at 7T. We develop a multi-region SPSP excitation pulse and use it to create a novel low power, B1 insensitive multi-region SASSI sequence with minimal chemical shift to enable accelerated MRSI. 5527. 87 Rigid Motion Correction in MRSI Using Wireless Active Markers Yibo Zhao, Chao Ma, Chang Gao, Kui Ying, Jinsong Ouyang, Georges El Fakhri For brain imaging, even with head restraints, maximum translations in the range of 5-10 mm and rotations of 1-4 degrees are sometimes observed.  The rigid body motion of the subject during MRSI acquisition can degrade both the spatial resolution and spectral quality. In this work, we developed a wireless active marker based method to track and correct motion in MRSI. 5526. 86 Prospective frequency correction using outer volume suppression-localized navigator for MR Spectroscopic Imaging Chu-Yu Lee, In-Young Choi, Phil Lee Data acquisitions for magnetic resonance spectroscopic imaging (MRSI) require a long scan time to increase SNR and for spatial encoding. During the prolonged scan time, maintaining a constant static magnetic field (B0) is important for a robust MRSI measurement. However, frequency drifts occur over time even in advanced MR systems and become larger when high shim currents or rapidly switched gradients are applied. The frequency drift causes broad and distorted spectral lineshapes, reduced SNR, and quantification errors. These effects can be mitigated retrospectively and prospectively. However, in MRSI measurements, these effects can only be mitigated using the prospective frequency correction, because each spectrum is phase-encoded. The prospective frequency correction is typically achieved by incorporating a PRESS-based interleaved reference scan (PRESS-IRS) as a navigator, termed as PRESS-IRS navigator. A small excitation flip angle (10-20°) is used for the PRESS-IRS navigator to reduce the saturation-induced SNR loss on metabolite signals. Nonetheless, the SNR loss remains unavoidable and becomes notable when the imperfect refocusing pulses or a short repetition time (TR) are used in MRSI. In this study, a new prospective frequency correction method is introduced. The new method utilizes the outer volume suppression-localized navigator, termed OVS-localized navigator, resulting in no perturbations of metabolite signals and thus no saturation-induced SNR losses. Meanwhile, a precise measurement of the frequency drift and the effective correction is achieved. The presented method was demonstrated in two-dimensional (2-D) MRSI measurements under the large frequency drift induced by a fMRI experiment. 5521. 81 Density Weighted Concentric Circle Trajectories for Brain MRSI at 7T Lukas Hingerl, Bernhard Strasser, Philipp Moser, Gilbert Hangel, Siegfried Trattnig, Wolfgang Bogner A density weighted concentrically circular echo-planar trajectories readout scheme is presented for brain MRSI at 7 T. We give an analytic solution for the variable radii distribution in order to intrinsically measure a Hamming weighted k-space. A comparison with post acquisition filtered equidistant concentric circles is done. Invivo metabolic maps and spectra are shown. 5531. 91 High resolution cortical spectroscopy at 7T using lipid signal crushing and a high density receive array. Alex Bhogal, Carrie Wismans, Christiaan Vinckers, Peter Luijten, Dennis Klomp, Jannie Wijnen In this work we attempt to overcome MRSI limitations associated with extra-cranial lipid signal leakage and low SNR at high resolution. We use a dedicated crusher coil for lipid signal removal, in combination with a high density receive array and an  7T MR scanner for boosted SNR. 5522. 82 Metabolite-Cycling Short-Echo Time Magnetic Resonance Spectroscopic Imaging using a Concentric Ring k-space Trajectory Uzay Emir, Brian Burns, Mark Chiew, Peter Jezzard, Albert Thomas In this study, the feasibility of acquiring and quantifying short-echo (TE = 14 ms), two-dimensional (2D) STEAM MRSI spectra from the motor cortex was demonstrated by utilizing a non-water-suppressed metabolite-cycling technique. The increase in measurement time by the metabolite-cycling is counterbalanced by a time-efficient concentric ring k-space trajectory. High quality spectra were acquired from 36 localized 2mL voxels in 8 minutes. The metabolite spectra and estimated concentrations were in agreement between non-water-suppressed and water-suppressed MRSI techniques.  Findings of this study demonstrate that a non-water-suppressed metabolite-cycling MRSI technique can perform robustly on clinical MRI scanners and within a clinically feasible acquisition time. 5529. 89 Lipid Suppression in 3D Magnetic Resonance Spectroscopic Imaging Mohammed Goryawala, Andrew Maudsley, Sulaiman Sheriff Proton MR spectroscopic imaging (MRSI) is complicated by the presence of subcutaneous lipids, which, if not suppressed before Fourier reconstruction, cause ringing in metabolite maps due to limited k-space sampling. In this study inversion recovery (IR) based lipid suppressed acquisition was compared to non-lipid suppressed acquisition combined with two methods for reducing lipid ringing in whole brain MRS imaging. Results indicate non-lipid suppressed acquisition using the l2-regularization or Papoulis-Gerchberg algorithm for reconstruction is possible without significant ringing artifacts, however, can have a detrimental effect on spectral linewidth and baseline, resulting in smaller spatial coverage than IR based lipid-suppressed acquisition. 5536. 96 Accelerated 3D Echo Planar Spectroscopic Imaging of HIV: Metabolite Changes Correlation with CD4 count and Number of Years of Treatment Rajakumar Nagarajan, Eric Daar, Zohaib Iqbal, Manoj Sarma, Mario Guerrero, Michael Thomas In vivo proton magnetic resonance spectroscopy studies of HIV-infected humans have demonstrated region-specific changes in brain metabolites including N-acetylaspartate, creatine, choline, glutamate/ glutamine, and myo-inositol. Using a 3D EPSI technique, we examined metabolite ratios with respect to creatine in several regions of brain in 18 HIV adults (mean age 46.2 years) and 15 healthy controls (mean age 43.4 years). We have demonstrated for the first time the feasibility of a novel accelerated 3D EPSI method in HIV-infected adults compared to age matched healthy controls and correlated with CD4 counts and number of years of treatment. 5535. 95 Assessment of Neurochemical changes in HIV adults Using Accelerated MR Spectroscopic Imaging and Compressed Sensing Reconstruction Rajakumar Nagarajan, Eric Daar, Ebrahim Haroon, Zohaib Iqbal, Neil Wilson, Sathya Arumugam, Mario Guerrero, Michael Thomas In this work, we have successfully evaluated the accelerated 5D EP-JRESI sequence in 16 adult HIV-infected  patients and 15 healthy subjects. Compared to healthy subjects, significant neurochemical changes were observed in HIV+ patients on ART: elevated Ch/Cr ratios in frontal gray, right frontal white and right basal ganglia locations, decreased Glx ratios in the left frontal white, right basal ganglia, occipital gray and white and right insular cortical regions. There was also decreased NAA/Cr in the left basal ganglia and right occipital white regions. In the HIV+ patients, a positive correlation was recorded between the left basal ganglia NAA/Cr and the number of years of ART treatment (r=0.58, p<0.02). 5534. 94 Using 3D MEGA-LASER MRSI to study the role of basal ganglia GABA and Glx in response selection in Manganese neurotoxicology Ruoyun Ma, Sandy Snyder, Ann-Kathrin Stock, Wolfgang Bogner, Ovidiu Andronesi, Christian Beste, Ulrike Dydak This pilot study on manganese (Mn) neurotoxicity investigates the association between deficits in response selection and GABA and Glx levels in basal ganglia structures using MEGA-LASER 3D MRSI. Using a novel automated brain-structure-specific quantification approach for GABA+ and Glx, we studied three basal ganglia structures and the thalamus in Mn-exposed welders and controls. A modified Simon task was used to measure selection inhibition. GABA+ and Glx in putamen and globus pallidus were associated with response times in the most complicated experimental scenario in Mn-exposed subjects; whereas thalamic Glx levels were associated with response time for all subjects. 5533. 93 A Vendor-Agnostic MRSI Acquisition and Reconstruction XML Descriptor Format Marram Olson, Jason Crane, Peder Larson, Sarah Nelson The evaluation of MRSI data is complex because data files are encoded with vendor specific file formats and there is a lack of standardized tools for reconstruction. A standard way to describe raw MRSI data is necessary for the reconstruction of sequences utilizing parallel and non-Cartesian sampling strategies. In this work we are developing a vendor neutral data format to define MRSI sequences with arbitrary k-space trajectories that can be used by reconstruction software to understand the data acquisition scheme. This file format is XML-based and uses the ISMRMRD header as a basis for its scheme.

NMR & ESR & Education
Electronic Poster
MR Spectroscopy

Thursday, 27 April 2017
 Exhibition Hall 14:00 - 15:00

Non-Proton MRI & MRS
Electronic Poster
MR Spectroscopy

Thursday, 27 April 2017
 Exhibition Hall 14:00 - 15:00

MRS Applications
Electronic Poster
MR Spectroscopy

Thursday, 27 April 2017
 Exhibition Hall 14:00 - 15:00