Abstract
1115
Objectives: The middle cerebral artery occlusion (MCAO) rat model has been widely used to induce focal cerebral ischemia. It has been reported that regional cerebral hematocrit is altered under ischemic conditions. No studies have been done in the acute phase (<24hrs) making it difficult to determine when the alteration of cerebral hematocrit occurs. To this end, focal cerebral ischemia was induced in rats using the MCAO model. MicroSPECT could be used to measure hematocrit levels in lieu of direct sampling. Preliminary experiments will establish a relationship between the distribution of blood components measured via SPECT and cerebral blood flow (CBF) measured via MR. Methods: Hematocrit measurements require labeling of both erythrocytes and plasma with SPECT agents. ROI analysis is then performed to isolate the individual signals and obtain a hematocrit value. For plasma measurements 10mCi Tc-99m labeled human-serum-albumin (HSA) was injected prior to MCAO and pinhole microSPECT was performed. Following SPECT, the MR arterial spin labeling approach was employed to obtain cerebral blood flow under similar conditions. A final HMPAO pinhole SPECT scan (10mCi HMPAO) was performed to provide a perfusion image to identify the ischemic region in the SPECT images. The procedure for erythrocyte imaging was similar. Erythrocytes were harvested from donor rats and labeled with 10mCi Tc-99m and injected into the model rat. Results: Preliminary control rats with no infarct have shown cerebral hematocrit to be 44. For 4 rats injected with Tc-99m HSA, images show little difference between the healthy and ischemic hemispheres suggesting no alteration of plasma level during MCAO. HMPAO images show lower perfusion in the lesion area relative to the healthy tissue. MR analysis clearly shows location of lesion and reduced CBF in infarct. Conclusions: SPECT imaging shows potential to identify infarct location and provide measurement for hematocrit in ischemic tissue.
Research Support (if any): This work supported by NIH RO1NS054079-01.
- Society of Nuclear Medicine, Inc.