Motion-Corrected Structural Realignment and Quantitative Voxel Targeting in Magnetic Resonance Spectroscopy

Abstract

Magnetic resonance spectroscopy (MRS) non-invasively quantifies neurochemical metabolites within a prescribed voxel in the brain, but is highly sensitive to head motion that displaces the voxel from its intended anatomical location, and introduces spectral contamination as well as tissue estimation errors. In particular, voxel displacement into bone tissue severely degrades spectral quality due to lipid contamination, often rendering the data unusable. While promising solutions exist to address motion-related issues, many rely on specialized infrastructure and expertise available only at a limited number of research centers. To address inter-acquisition motion, we combine automatic voxel repositioning using an updated 18 s head scout MRI, acquired immediately before MRS, with realignment of the structural MRI to ensure that tissue correction is based on the updated voxel location. Furthermore to quantify anatomical targeting accuracy, we introduced a voxel-ROI overlap metric that measures the percentage intersection between the prescribed voxel and atlas-defined target regions, enabling objective evaluation of voxel positioning accuracy. Using voxels prescribed across three brain regions (prefrontal cortex, thalamus, left superior temporal gyrus; N = 31), realignment on average increased voxel-ROI overlap by 24%, reduced inter-subject variability in tissue composition by 8.1%, and eliminated bone contamination in all six affected cases. Our computationally efficient method executes in < 35 s per participant and requires no specialized hardware, offering an accessible solution that integrates inter-acquisition motion correction with quantitative assessment to achieve accurate voxel targeting.