EVALUATION OF ABNORMAL HEMODYNAMICS IN INTRACRANIAL ARTERY OCCLUSION USING DYNAMIC SPECT
We evaluated the hemodynamics under ischemic state to examine cerebral blood flow tracer processing toward equilibrium using Tc-99m ethyl cysteinate dimer (Tc-99m ECD) dynamic SPECT. Dynamic SPECT studies were performed in 32 patients with unilateral chronic internal carotid artery or middle cerebral artery occlusion and 16 controls in the absence of arterial stenosis on MR angiography. Dynamic SPECT data (30sec′24frames) were acquired immediately after the administration of Tc-99m ECD. Although the radioactivity of both cerebral hemispheres reached plateau phase within 180sec after the injection based on time-activity curve, the radioactivity of affected cerebral hemisphere showed slower build-up than that of contralateral unaffected hemisphere. The build-up (0–180sec) and plateau phase (540–720sec) images were analyzed statistically. Twenty of 32 patients demonstrated reduced accumulation of the affected hemisphere on the build-up phase images, although all patients showed normal accumulation on plateau phase images. In 17 of 32 patients, the discrepancy of the accumulation on the affected hemisphere between the build-up and plateau phase images was corresponded to that with reduced reactivity to acetazolamide, reflecting the impairment of vasucular reseve in brain tissue. We speculate that the reduced accumulation of the affected hemisphere in the build-up phase image was derived from flow delay due to arterial occlusion and the collateral flow. Our finding suggests that dynamic SPECT allow detecting the compensatory vasodilatation by means of the evaluation of tracer s equilibrium process in brain tissue where ischemic change such as misery perfusion is present. In conclusion, not only tracer extraction (plateau phase) image but also intra-vascular tracer delivery (build-up phase) image would provide important information of abnormal hemodynamics.