Tract analysis to identify brain biomarker
of neurological diseases and psychiatric disorders
4.1 Tract level analysis
DTI-derived metrics, fractional anisotropy (FA), has been widely used to detect subtle structural white matter abnormalities. Conventional VBM (voxel-based-morphometry) approaches delineate the abnormality at the voxel level. However, information reflected from a single voxel of the brain image cannot be used to evaluate the clinical condition of the patient.
It is the whole white matter tracts connecting different brain regions that have clinical importance. In this study, the targeted unit is the functional white matter tract incorporating continuous and multiple voxels rather than the individual voxel in a brain image. We developed a method to survey all white matter tracts by mapping the labeling of a digital atlas to the core white matter of the subjects and applied it to Alzheimer disease (AD). With no a priori information, this novel tract analysis approach has been used to examine all 50 major white matter tracts of AD patients and age-matched controls at the tract level. The proposed method is highly efficient, accurate, makes comprehensive examination of all major tracts and allows comparison of disruption level of these tracts. With the analysis of AD results, we found that white matter disruption in AD brains is heterogeneous, widespread, and affects the fornix most severely.
For details, please see our Publication (Huang et al., Neurobiology of Aging 2012).
4.2 Along-the-tract analysis
In another study to detect abnormality of white matter integrity of maltreated subjects, along-the-tract analysis of superior longitudinal fasciculus has been conducted, as shown below. For details, please see our Publication (Huang et al., Neuropyschopharmacology 2012).