Improved human brain tractographs using multi-shell q-ball diffusion magnetic resonance imaging compared with DTI

Recently, it has been proven that assuming the Gaussian model in DTImethod is inappropriate for propagation in a complex substrate such as human braintissue. High Angular Resolution Diffusion Imaging (HARDI) (or so called q-ball imaging)is known as a model free method that allows to more accurately detect changes in diffusionwith different orientations. In this study, after finding the best angle threshold at the OpticRadiation (OR) level, the length and number of reconstructed nerve fibers in this anglewere measured using q-ball imaging and were compared with DTI. Tractographs of q-ball images from the human brains of 10healthy volunteers (30 to 50 years old) were studied using a 3-Tesla scanner. 64 directionsof diffusion encoding in two b-values (1000 and 2000 s/mm2), were used for q-ballimaging and in routine b-value of 1000 s/mm2 for DTI. The tractographs were comparedat the OR level with the tractography based on q-ball and DTI images. The results wereanalyzed using t-test. The angle threshold for tractography was selected at 45 degrees bycomparing the tractographs in 13 angles. Consequently, the number and length of nerve fibers of OR, measured usingthe q-ball imaging, were significantly higher than those using the DTI. Finally, the betterquality of the tractographs as well as the analyzed quantities, are indicators of larger signalto-noise ratio in q-ball imaging and indicate that q-ball imaging compared to DTI plays animportant role in the development of brain nerve mapping.