Project 5

Mean FA (gray scale) and skeleton of all subjects overlaid by the atlas labels in the ICBM-DTI-81 space. Colored regions indicate major white matter tracts. The skeleton from averaged FA maps is shown as white solid curve. Abbreviations of white matter tracts are as follows. ACR: Anterior corona radiata; ALIC: Anterior limb of internal capsule; BCC: Body of corpus callosum; CGC: Cingulum; CGH: Cingulum (hippocampus); CST: Corticospinal tract; EC: External capsule; FX: Fornix FX-B: Body of fornix; GCC: Genu of corpus callosum; IFO: Inferior fronto-occipital fasciculus left; ILF: Inferior longitudinal fasciculus; PCR: Posterior corona radiate; PLIC: Posterior limb of internal capsule; PTR: Posterior thalamic radiation; RLIC: Retrolenticular part of internal capsule; SCC: Splenium of corpus callosum; SCR: Superior corona radiate; SLF: Superior longitudinal fasciculus; ST: Stria terminalis; UNC: Uncinate fasciculus.

Tract analysis to identify brain biomarker
of neurological diseases and psychiatric disorders
with DTI

5.1 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).

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5.2 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).

Fractional anisotropy (FA) profiles
Fractional anisotropy (FA) profiles of the two segments of left superior longitudinal fasciculus of the brains of control (blue FA lines) and maltreated (red FA lines) subjects. Dramatic FA differences between maltreated and control group in the FA profile coincide with the locations of disrupted clusters (C1, C2, C3 and C4). The three-dimensionally reconstructed fiber bundles of left superior longitudinal fasciculus and four disrupted clusters of this tract are also shown on the left panel.

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