Comparing single-shot EPI and 2D-navigated, multi-shot EPI diffusion tensor imaging acquisitions in the lumbar spinal cord at 3T

Abstract

Diffusion tensor imaging (DTI) can provide insights into spinal cord microstructure in health and disease; however, its application has been largely limited to cervical spinal segments using single-shot echo-planar imaging (EPI) diffusion-weighted MRI acquisitions. In this work, we evaluate a multi-shot EPI diffusion-weighted acquisition with reduced field-of-view (FOV) and 2D-navigated motion correction applied in the lumbar spinal cord of healthy volunteers, and compare image quality, geometric distortions, and quantitative DTI indices to those obtained with conventional, single-shot EPI diffusion-weighted MRI in a distinct, age/sex-matched healthy cohort. At 3 Tesla, 25 and 27 healthy participants were imaged using the single-shot and multi-shot EPI readouts with diffusion weighting, respectively, with matching resolution and comparable scan time. Seven participants underwent both diffusion acquisitions and were included in both cohorts. DTI indices were compared between the multi-shot and single-shot cohorts. Image signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) between gray and white matter, geometric distortions, and within-subject bias between the acquisitions were also assessed. The lumbar spinal cord diffusion indices derived from both cohorts were comparable to those in previous studies using single-shot EPI, though within-subject analysis demonstrated a systematic bias between the acquisitions in gray and white matter DTI measures, indicating these acquisitions are not interchangeable within a study. The multi-shot quantitative DTI maps demonstrated a significant reduction in image artifacts (i.e., distortions and blurring) and higher SNR and CNR compared to single-shot images. Overall, the reduced FOV, 2D-navigated, motion-corrected multi-shot acquisition demonstrated improved DTI quality metrics compared to single-shot, supporting its application for the lumbar spinal cord region.