White matter changes in primary dystonia determined by 2D distribution analysis of diffusion tensor images.

PURPOSE: To determine brain tissue affected by dystonia by making group comparison of parameter-based diffusion tensor imaging (DTI) distributions of patients with control subjects. A 2D distribution analysis of mean diffusivity and fractional anisotropy index was used for modeling brain tissues according to the inherent diffusion characteristics. MATERIALS AND METHODS: Seven affected carriers of the DYT1 dystonia mutation and eight healthy control subjects were imaged for a previous study. We employed a 2D distribution analysis of all the diffusion voxels and a four compartmental brain model for group comparison of the dystonia subjects and controls. RESULTS: Our analysis showed disease involvement in the white matter of the patients. Excellent tissue characterization was achieved automatically using the 2D distribution analysis based on a physical brain model. CONCLUSION: This 2D analysis implicated white matter in dystonia and could be useful as a screening tool in diseases with unknown pathologies.

Early registration of diffusion tensor images for group tractography of dystonia patients.

PURPOSE: To make a group comparison of diffusion tensor imaging (DTI) results of dystonia patients and controls to reveal occult pathology. We propose using an early registration method that produces sharper group images and enables us to do group tractography. MATERIALS AND METHODS: Twelve dystonia patients manifesting the disease, seven nonmanifesting dystonia mutation carriers (DYT1 and DYT6 gene mutations), and eight age-matched normal control subjects were imaged for a previous study. Early and late registration methods for DTI were compared. An early registration technique for a super set was proposed, in which the diffusion-weighted images were registered to a template, gradient vectors were reoriented for each subject, and they were combined into a super set before tensor calculation. The super set included images from all subjects and was useful for group comparisons. We used results obtained from the early registration of a super set for group analysis of tracts using the deterministic fiber-tracking technique. RESULTS: In dystonia mutation carriers, we detected fewer fibers in the cerebello-thalamo-cortical pathways. This result agrees well with the findings of a previous study that utilized a probabilistic tractography method and demonstrated that gene carriers have less fiber tracts in the disease-involved pathway. CONCLUSION: This analysis visualized group level white matter fractional anisotropy and tract differences between dystonia patients and controls, and can be useful in understanding the pathophysiology of other nonfocal white matter diseases.