REPRODUCIBILITY STUDY OF WHOLE-BRAIN SPECTRO IMAG WITH AUTOMATED QUANTIFICATION

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Introduction: Brain H-MRSI has become an important clinical tool Although widely used, most brain MRSI sequences suffer from drawbacks including limited spatial coverage, insufficient water and lipid suppression, long scan times, low SNR and lack of robust automated spectral quantification. To address these limitations, we implemented a fast 3D whole-brain 1.5T MRSI sequence with efficient and robust water and lipid suppression, spiral k-space readout trajectories, and an 8-channel phased-array coil. In this work, we assessed the reliability and reproducibility of the sequence and the data processing methods. Methods and Discussion: A spectral-spatial 90 degree RF pulse and two identical dualband spectral-spatial 180 degree pulses were incorporated into a PRESS sequence for localization, partial excitation of water and excitation of Cho, Cre and NAA. In-plane spatial and spectral information (kx, ky,kf ) was encoded using repeated spiral k-space trajectories. Encoding in z direction (kz) was performed using standard phase encoding. Phased spectra for each voxel and coil were then combined, weighted by water signal, to achieve maximum SNR. Concentrations of Cho, Cr and NAA and concentrations ratios of Cho and NAA to Cr were generated for each voxel. Eight subjects were recruited for a reproducibility study. Seven subjects were each scanned once while one subject was scanned 6 times. Regions of interest covering the frontal, parietal, temporal, and occipital lobes and basal ganglia and thalamus, were drawn on the high-resolution structural images. Final metabolite values were obtained by averaging signals from all voxels within each ROI. The inter-subject CVs of the five ROIs ranged from 6.1-11% for NAA/Cr and 7.2-12.1% for Cho/Cr. The intra-subject CVs of five ROIs ranged from 4.7-12.7% for NAA/Cr and 2.7-7.1% for Cho/Cr.