Validation of diffusion tensor imaging in the central nervous system using light microscopy

Abstract

Diffusion tensor imaging (DTI) provides an indirect measure of tissue structure on microscopic scales. To date, DTI is the only imaging method that provides such information in vivo, and it has proven to be a valuable tool in both research and clinical settings. In this study, A multi-step procedure was developed to register diffusion tensor imaging (DTI) and histological data in the light microscopy image space, with the ultimate goal of allowing quantitative comparisons of the two datasets. The registration procedure was utilized to investigate the relationship between white matter structures and diffusion parameters measured by DTI. We used micrographs from light microscopy of fixed, myelin stained brain sections as a gold standard for direct comparison with data from DTI. Relationships between microscopic tissue properties observed with light microscopy - fiber orientation, density, and coherence - and fiber properties observed by DTI – tensor orientation and fractional anisotropy (FA) - were investigated. Agreement between the major eigenvector of the tensor and myelinated fibers was excellent in voxels with high fiber coherence. However, the diffusion tensor was not a reliable indicator of fiber geometry where fibers crossed or diverged.