TEMPORAL CORRELATION-ANALYSIS OF PENUMBRAL DYNAMICS IN FOCAL CEREBRAL-ISCHEMIA

A novel temporal correlation technique was used to map the first-pass transit of iodinated contrast agents through the brain. Transit profil es after bolus injections were measured with dynamic computed tomograp hy (CT) scanning (1 image/s over 50 s). A rabbit model of focal cerebr al ischemia(n = 6) was used, and dynamic CT scans were performed at 30 , 60, 90, and 120 min postocclusion. Within the ischemic core, no bolu s transit was detectable, demonstrating that complete ischemia was pre sent after arterial occlusion. In the periphery of the ischemic distri bution, transit dynamics showed smaller peaks, broadened profiles, and overall delay in bolus transit. A cross-correlation method was used t o generate maps of delays in ischemic transit profiles compared with n ormal transit profiles from the contralateral hemisphere. These maps s howed that penumbral regions surrounding the ischemic core had signifi cantly delayed bolus transit profiles. Enlargement of the ischemic cor e over time (from 30 to 120 min postocclusion) was primarily accomplis hed by the progressive deterioration of the penumbral regions. These r esults suggest that (a) temporal correlation methods can define region s of abnormal perfusion in focal cerebral ischemia, (b) peripheral reg ions of focal cerebral ischemia are characterized by delays in bolus t ransit profiles, and (c) these regions of bolus transit delay deterior ate over time and thus represent a hemodynamic penumbra.