Spatial resolution dependence of DTI tractography in human occipito-callosal region

Diffusion tensor imaging (DTI) and fiber tracking have been used to measure the fiber structural connectivity in humans in a non-invasive manner. However, low sensitivity is a principal limitation of these methods, causing a large number of possibly missing fiber tracts (FTs). Here we studied how the spatial resolution affects the sensitivity of the fiber tracing by rescaling data to different resolutions. Our data suggest that the spatial resolution can change the degree of the asymmetric cross-callosal connections in the lower visual field (loVF) compared to the upper visual field (upVF). Among connections from loVF, a larger voxel size resulted in a smaller number of FTs that was not commensurate to the number of seed points, while the number of connections from upVF was not significantly affected by variation in seeding point numbers. We conclude from our study that the spatial resolution of the acquired data will have to be taken into consideration in interpreting DTI fiber tracking data. Our results further suggest that the acquisition resolution of around 2 mm iso-voxel in the conventional DTI scheme can reconstruct the asymmetric upper and lower white matter structure in occipito-callosal region.