Advancing high-resolution 7 T diffusion MRI: Evaluating phase-encoding correction strategies for distortion correction from basic to four-way acquisitions

Summary

At 0.9 mm resolution on a NexGen 7T scanner, this study compares 11 time-matched diffusion acquisition and correction strategies. Four-direction phase encoding provides the strongest geometric fidelity and repeatability in five adults scanned twice. The findings inform high-resolution protocols for both fine superficial connections and long-range pathways.

Study overview

High-resolution diffusion MRI at 7T offers detailed tissue measurements but also amplifies geometric distortion. Five healthy adults were scanned twice with a highly sampled, four-direction phase-encoding protocol on the NexGen 7T system. The authors derived 11 time-equivalent, ten-minute acquisition strategies and compared their alignment with anatomical images and the reproducibility of diffusion tensor measurements. Full reversed-direction diffusion acquisitions outperformed correction using a single reversed non-diffusion-weighted image, and four-direction acquisition performed best among the tested strategies. The results provide practical guidance for this high-resolution setting, with the small cohort and specialized scanner defining the scope of the evidence.

Main findings

• Compared 11 time-matched strategies using repeated scans in five adults.
• Full reversed-encoding diffusion data outperformed a single reversed b=0 image.
• Four-direction encoding gave the best geometry and reproducibility among tested strategies.