Document Type : Original Article
Medical Physics Department, College of Medical Science, Tarbiat Modares University, 7 Jalal Al Ahmad Street, Tehran, Iran
Department of Radiology, Upstate Medical University, State University of New York, 750 E Adams st., Syracuse, NY 13210
Medical Physics and Biomedical Engineering Department, Tehran University of Medical Sciences (TUMS), Tehran, Iran
Introduction: Recently, it has been proven that assuming the Gaussian model in DTI
method is inappropriate for propagation in a complex substrate such as human brain
tissue. 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 diffusion
with different orientations. In this study, after finding the best angle threshold at the Optic
Radiation (OR) level, the length and number of reconstructed nerve fibers in this angle
were measured using q-ball imaging and were compared with DTI.
Materials and Method: Tractographs of q-ball images from the human brains of 10
healthy volunteers (30 to 50 years old) were studied using a 3-Tesla scanner. 64 directions
of diffusion encoding in two b-values (1000 and 2000 s/mm2), were used for q-ball
imaging and in routine b-value of 1000 s/mm2 for DTI. The tractographs were compared
at the OR level with the tractography based on q-ball and DTI images. The results were
analyzed using t-test. The angle threshold for tractography was selected at 45 degrees by
comparing the tractographs in 13 angles.
Conclusion: Consequently, the number and length of nerve fibers of OR, measured using
the q-ball imaging, were significantly higher than those using the DTI. Finally, the better
quality 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 an
important role in the development of brain nerve mapping.