Abstract TP39: High Accuracy of Magnetic Resonance T2*- Weighted Sequences for Detection of Intracranial Arterial Thrombus

Abstract

Introduction: Rapid detection and location of vessel occlusion are pivotal in the intra-arterial management of patients with acute stroke in the emergency room. MRI has demonstrated to detect intravascular thrombus but its accuracy compared to CT angiography has not been well established. Hypothesis: Our purpose is to determine the accuracy of 1.5 T MRI T2*-weighted (W) sequences compared to immediate CT angiography as the standard reference imaging modality, for detection of intra-arterial thrombus in patients with suspected acute MCA infarction. Methods: Consecutive patients with suspected middle cerebral artery (MCA) territory stroke were selected from 2008 to 2009. The inclusion criteria for the study subjects: CTA, T2*W sequences included on MRI protocol and restricted diffusion in MCA territory on DWI within 12 hrs of clinical onset. Two investigators reviewed DWI and T2*W sequences for the presence of infarction and thrombus. Intracranial internal carotid artery (ICA), M1 and M2 segments of the MCA were accessed. Consensus was reached with a third reviewer for data analyses. Accuracy, sensitivity, specificity, positive and negative predictive values (PPV/NPV) were calculated. Results: Fifty-one patients were included in the study, of which 40 patients had confirmed arterial thrombus and 11 patients had normal studies on CTA. Of the subjects with arterial occlusion on CTA, the mean time interval from stroke onset to CTA was 4.2 h +/- 2.3 h (range, 0.4-12h). The mean time interval from CTA to MRI was 29.5 min +/- 11.1 min. Twenty-six cases showed M1 thrombus on CTA, of these, 22 cases had corresponding thrombus and 4 cases had no abnormality in T2*W sequences on MRI. Nevertheless, 25 patients demonstrated no M1 thrombus, either on CTA or MRI. After statistical analyses, we observed an accuracy of 92%, sensitivity of 85%, specificity of 100%, PPV 100% and NPV of 86% for M1 occlusion. The Kappa obtained was 0.79. Conclusion: In conclusion, T2*W sequences demonstrated overall high accuracy and specificity for detection of arterial thrombus in the M1 segment of the MCA in patients with suspected acute MCA ischemic stroke.