A Macro-Structural Dispersion Characteristic of Brain White Matter and Its Application to Bipolar Disorder

Objective: Our goal is to find distinct characteristics of brain white matter in bipolar disorder, of which the development of diagnostic imaging measures is necessary for early diagnosis and prospective studies. Methods: Given a tractogram dataset which is a dense set of white matter fiber pathways of the whole brain obtained from diffusion magnetic resonance imaging, we propose to compute a global measure for a voxel from the dispersion statistics of a set of fibers which indicates the complexity of the white matter voxel not locally but at macroscopic scales. Results: Our findings demonstrate that macro-structural dispersion information is significant for discrimination of the bipolar patients from the healthy controls, particularly in the frontally associative bundles such as cingulum and inferior occipito-frontal fascicles. Conclusion: The proposed measure is as informative as the local diffusion measures for the detection of changes in the white matter regions. Significance: Our findings show that the proposed measure is a potential diagnostic imaging marker in bipolar disorder and the proposed novel dispersion map of the brain could be used for other neurological applications.