Quantitative Analysis of Intracranial Circulation Using Rapid-Sequence DSA

Abstract

Using a high-frame-rate technique, intravenous digital subtraction angiography (IVOSA) of the intracranial circulation was performed in patients with transient ischemic attacks and asymptomatic bruits. Twenty patients with normal carotid arteries or mild stenosis of no hemodynamic significance were selected as a control group to evaluate the effect of carotid stenosis on the difference between hemispheres in the peak arrival time (Δ TMAX) of the contrast bolus. Data were obtained for the anterior (ACA), middle (MCA), and posterior (PCA) cerebral artery distributions. Raw data of the time-density curve in a region of interest were analyzed by polynomial curve-fitting techniques to obtain the peak arrival time (TMAX). The Δ TMAXs for normal middle, anterior, and posterior distributions were 0.140 ± 0.119 sec, 0.152 ± 0.146 sec, and 0.189 ± 0.187 sec, respectively. Eleven patients with tight carotid stenosis or occlusion whose Δ TMAX fell outside the normal range as established from the 20 control patients were analyzed with regard to ischemic symptoms. The Δ TMAXs of the MCA, ACA distributions in the asymptomatic patients with tight carotid stenosis or occlusion were 0.653 ± 0.379 sec and 0.118 ± 0.159 sec, respectively; p < 0.001 in the MCA when compared with controls. The Δ TMAXs of the MCA, ACA distribution in the symptomatic patients with tight carotid stenosis or occlusion were 1.31 ± 0.13 sec and 0.525 ± 0.079 sec, respectively; p < 0.001 in the MCA and ACA distributions when compared with controls. Quantitative analysis of this type of physiologic data may enable the detection of patients with carotid stenosis who are well compensated by collateral flow from those who are poorly compensated and at risk for possible infarction on a hemodynamic basis. Serial follow-up DSA studies in patients with asymptomatic bruits may help to correlate the progression of extracranial carotid stenosis and the status of intracranial collateral reserves.