Feasibility of 1.6-mm isotropic voxel diffusion tensor tractography in depicting limbic fibers.

INTRODUCTION: We attempted to assess the feasibility of a 1.6-mm isotropic voxel diffusion tensor imaging (DTI) tractography at 3T in visualizing nerve bundles in the limbic system.
METHODS: We examined 20 healthy volunteers by conventional DTI with a voxel size of 1.6 x 1.6 x 3.0 mm and by high-resolution DTI with a voxel size of 1.6 x 1.6 x 1.6 mm and generated tractographs of three limbic nerve bundles: the fornix, cingulum, and uncinate fasciculus. We visually assessed whether these bundles reached their targets and compared their diffusion parameters between the two techniques.
RESULTS: The entire pathways of the fornix, cingulum, and uncinate fasciculus were more readily visualized by high-resolution DTI than by conventional DTI. Among these, the fimbria of the fornix and the uncinate fasciculus adjacent to the temporal pole were identified more frequently by high-resolution DTI (visualization rate 83 and 100%, respectively) than by conventional DTI (visualization rate 63 and 83%, respectively) at a statistical significance of P < 0.05 and P < 0.01, respectively). Fractional anisotropy values in the fornix, cingulum, and uncinate fasciculus by high-resolution DTI were significantly higher than those by conventional DTI (P < 0.01); in contrast, the apparent diffusion coefficient values of all these fibers except that of the fornix remained unchanged between the two techniques.
CONCLUSION: The 1.6-mm istropic voxel DTI at 3T is a feasible visualization tool and can improve the precision of tracking nerve bundles of the limbic system.