Cluster analysis of diffusion tensor magnetic resonance images in human head injury

OBJECTIVE: issues surrounding the nature of the edema associated with traum atic brain injury in humans, and its evolution in the acute phase, remain u nresolved. This study aimed to characterize the topographical nature of the pathophysiological changes in human traumatic brain injury with diffusion tensor magnetic resonance imaging. METHODS: Multislice diffusion-weighted magnetic resonance imaging data were acquired from five patients undergoing elective ventilation for management of traumatic focal contusion or hematomas. The diffusion tensor and the Ta -weighted intensity were then computed for every voxel in the image data se t for each patient The topographical distribution of abnormalities in the t race of the diffusion tensor and T2-weighted images were characterized by c luster analysis. RESULTS: In four patients with technically satisfactory data, a narrow band of tissue was observed in the periphery of focal lesions, which was charac terized by selective reduction in the trace of the diffusion tensor, withou t any associated increase in the T2-weighted signal intensity. CONCLUSION: This change is interpreted as indicating either a partial redis tribution of water from the extra- to intracellular compartment, or a reduc tion in the diffusivity of water in the intracellular or cytosolic environm ent. These diffusion and T2-weighted characteristics are also found in earl y ischemic change, hence, such regions may represent potentially salvageabl e tissue at risk of permanent damage. The study illustrates the advantage o f using information contained within the diffusion tensor in addition to mo re conventional imaging sequences.