E-081 Susceptibility – Weighted imaging findings in experimental acute ischemic stroke model

Purpose Assessment of the ischemic penumbra is essential in the treatment of acute ischemic stroke. This work sought to study the hyperacute changes on ischemic regions on the susceptibility-weighted imaging (SWI) using a controlled large animal experimental middle cerebral artery (MCA) occlusion model. Methods Eleven mongrel canines (20-30kg) underwent permanent endovascular occlusion of the M1 segment of MCA. Magnetic resonance imaging (MRI) was acquired on a 3T unit (Achieva, Philips Healthcare, Best, Netherlands) and included SWI and DTI starting one-hour post-MCA occlusion (MCAO). DSC perfusion MRI was subsequently acquired. Regions of interest (ROIs) were manually drawn using the Image J software (National Institutes of Health, Bethesda, Maryland) corresponding to the MCA territory of each hemisphere based on previously reported canine anatomic studies. An independent samples t-test was conducted to compare the mean signal intensity on the MCA territory of the ischemic region and the contralateral non-ischemic region. The Mean diffusivity maps and DSC perfusion were compared to the SWI images. Results Signal intensity was consistently lower in the ischemic territory compared to the non-ischemic territory. There was a significant difference in the mean signal intensity on the ischemic region (M=1,517.51, SD=104.50) vs. the non-ischemic region (M=1,676.54, SD=81.91); P-value= 0.0007. Qualitatively, the images revealed larger cortical and medullary veins in the ischemic territory. Mean diffusivity images, cerebral blood volume, and cerebral blood flow maps did not consistently match the extent of the SWI signal loss, whereas MTT and Tmax maps consistently matched the area of signal loss on SWI. Conclusion In the hyperacute stages of MCAO, SWI images display a consistent and significant signal drop relative to the unaffected side. This signal drop is suspected to result from the paramagnetic effect of deoxyhemoglobin and venodilation and thus an indirect means of visualizing tissue hypoxia. Disclosures N. Saadat: None. G. Christoforidis: 1; C; NIH. M. Niekrasz: None. S. Roth: 1; C; NIH. T. Carroll: 1; C; NIH.