Magnetic resonance imaging studies with cluster algorithm for characterization of brain edema after controlled...

Objective of this study was the characterization of traumatic brain injury induced by a "Controlled Cortical Impact" with magnetic resonance imaging techniques. The impact was applied to the intact dura of the left hemisphere in Sprague-Dawley rats. The pneumatic impactor was accelerated to a velocity of 7 m/s contusing the left temporo-parietal hemisphere to a depth of 2 mm. Posttraumatic hemispheric swelling and water content were determined gravimetrically, Evans Blue extravasation photometrically, and volume of ischemia by TTC-staining and planimetry. Magnetic resonance imaging was performed by a Bruker biospec 24/40, 90 min, 24 and 72 h post trauma using a T2w RARE sequence, a T1w sequence, before and after application of contrast agent, and a set of diffusion weighted images for calculation of ADC-maps. Data analysis was performed using a cluster algorithm enabling to interpret corresponding image pairs simultaneously. T2w imaging indicates the maximum edema about 24 h post trauma. Blood-brain barrier damage, detected by T1w imaging, is more predominant in the early posttraumatic phase. The cluster algorithm detects different edema components: from the necrotic core to the perifocal vasogenic rim. MRI in combination with the cluster algorithm will hopefully be a valuable tool in testing neuroprotective agents.