CALCIUM-45 AUTORADIOGRAPHY AND DUAL-ISOTOPE SINGLE-PHOTON EMISSION CTIN A CANINE MODEL OF CEREBRAL-ISCHEMIA AND MIDDLE CEREBRAL-ARTERY OCCLUSION

PURPOSE: To determine whether transient ischemia can be separated from permanent ischemia via calcium 45 autoradiography and to assess the a pplicability of dual isotope single-photon emission CT (SPECT) in the evaluation of cerebral blood flow. METHODS: We examined calcium influx in 12 dogs (group A) by using whole-brain calcium 45 autoradiography: Animals received 250 mu Ci/kg 24 hours after 30-minute (n = 6) or per manent (n = 6) middle cerebral artery (MCA) occlusion. Forty-eight hou rs after MCA occlusion, 5-mm coronal brain sections were fixed for eit her autoradiography or pathologic examination. In a separate study, 9 mongrel dogs (group B) were given 250 mu Ci/kg calcium 45 and a mean d ose of 700 mu Ci/kg technetium Tc 99m hexamethyl-propyleneamine oxime intravenously. A silicone plug was then injected into the internal car otid artery and angiography was performed to verify MCA occlusion. A 1 0th (control) animal did not undergo occlusion. In an 11th animal, pla cement of the plug could not be achieved and a slurry of microfibrilla r collagen was injected into the carotid artery. No angiography was pe rformed in animals 10 and 11. After occlusion, each animal was injecte d with a mean dose of 126 mu Ci/kg I-123-iodoamphetamine. The control animal was also injected, SPECT was performed using a simultaneous acq uisition for technetium 99m and I-123-iodoamphetamine. RESULTS: In gro up A, all animals who had permanent MCA occlusion showed infarction an d increased calcium 45 uptake in infarcted territories. None of the an imals who had 30-minute occlusion had either increased calcium 45 upta ke or infarction at 48 hours. In group B, 7 of 10 dogs had SPECT findi ngs that were consistent with the calcium autoradiographic marker for ischemia. One animal died during the procedure and 1 dog served as a c ontrol. CONCLUSION: Calcium 45 autoradiography allowed distinction bet ween areas of temporary and permanent occlusion. Iodoamphetamine imagi ng was not consistently sensitive to that level of ischemia. Timing of calcium influx may lead to insight that could impact timing of pharma cologic or endovascular intervention.