The Susceptibility Vessel Sign of the Middle Cerebral Artery on the T2*-Weighted Gradient Echo Imaging: Semi-quantification to Predict the Response to Multimodal Intra-Arterial Thrombolysis

Abstract

Purpose: We wanted to determine whether or not the “susceptibility asymmetry index” (SAI) of acute stroke on the T2*-weighted image is related with successful recanalization using multimodal intra-arterial thrombolysis (IAT). Materials and Methods: The 81 patients who underwent multimodal IAT for middle cerebral artery (MCA) territory acute stroke were included in this retrospective study. The multimodal IAT included intra-arterial urokinase infusion, clot disruption by a microwire, microcatheter and balloon manipulation, and balloon angioplasty and/or stenting for the flow-limiting stenosis. The diameter of the susceptibility vessel sign was measured on the T2*-weighted gradient echo imaging (GRE), and the diameter of the contralateral normal MCA at the corresponding level was measured on magnetic resonance angiography (MRA); the ratio between these two diameters was defined as the susceptibility asymmetry index. The relation between the TICI (Thrombolysis In Cerebral Infarction) score of 2-3 after multimodal IAT and the SAI was assessed. The receiver operating characteristic (ROC) curve analysis was performed on the SAI to predict a TICI score of 2-3 after multimodal IAT. Results: The mean SAI of 81 patients was 1.66 ± 0.66. Seventy nine percent of the patients had a TICI of 2-3 after multimodal IAT. According to the ROC curve analysis, an SAI less than 1.3 was optimal for predicting the presence of stenotic lesion after recanalization (area under the curve: 0.821, sensitivity: 88.2%, specificity: 69.8%, p=0.0001), and the SAI ≤1.61 (area under the curve: 0.652, sensitivity: 60.9%, specificity: 70.6%, p=0.0226) could predict a TICI score of 2-3. The TICI score of 2-3 after multimodal IAT was achieved in 88.6% of the cases with a SAI ≤ 1.61 and in 67.6% of the cases with a SAI >1.61 (p=0.028). Conclusion: The lower SAI on T2*-GRE could predict stenotic lesion and successful recanalization after performing IAT.