Automatic repositioning of MRSI voxels in longitudinal studies: Impact on reproducibility of metabolite concentration measurements

Abstract

To study an automatic repositioning method to reduce variability in longitudinal MRSI exams based on a priori image registration. Longitudinal proton MR spectroscopic imaging ((1)H MRSI) exams to study the effects of disease or treatment are becoming increasingly common. However, one source of variability in such exams arises from imperfect relocalization of the MRSI grid in the follow-up exams. Six healthy subjects were each scanned three times during the course of 1 day. In each follow-up exam a manually placed MRSI grid was acquired in addition to the automatically repositioned MRSI grid. Then coefficients of variance between baseline and follow-up scans were calculated for N-acetylaspartate, creatine, and choline. In addition, the overall MRSI grid overlap and individual voxel overlaps were also calculated for both the visually and automatically repositioned voxels. Streamlined workflow, reduced variability of metabolite concentration measurements, and increased voxel overlaps are noted when this automatic repositioning procedure is compared to the visual MRSI grid repositioning approach. Our results suggest that this approach is able to improve reproducibility in longitudinal MRS exams.