Longitudinal analysis of diffusion-weighted MRI with a ball-and-sticks model

Abstract

Purpose: To increase the sensitivity in longitudinal analysis of DW-MRI data with the ball-and-sticks model. Methods: Longitudinal DW-MRI data (baseline and two follow-up scans) of 25 middle-aged subjects (47 to 61 years at base line) were acquired. After coregistering all the diffusion-weighted images (DWIs) from the baseline and follow-up scans to a subject-specific intermediate space, an extended ball-and-sticks model was fitted. Stick orientations were constrained such that they did not change over time. The stick fractions were warped and projected onto the TBSS (tract-based spatial statistics) skeleton, and were compared to a reference framework in which all scans were processed independently. Results: Compared to the reference framework, the standard deviation of the apparent noise on the primary stick fractions on the TBSS skeleton was reduced with approximately a factor two. Conclusion: The use of the proposed longitudinal DW-MRI pipeline may significantly increase the precision compared to a default cross-sectional image processing pipeline.