Acute Ischemic Stroke Assessment on CT-Angiography That Derived from CT-Perfusion Images

PURPOSE: To assess the diagnostic accuracy of timing-invariant CT angiography (TI-CTA) that is derived from CT perfusion (CTP) data for acute ischemic stroke assessment. METHOD AND MATERIALS: We selected 73 consecutive patients with suspected acute ischemic stroke. Standard CT angiography (CTA) and CT perfusion images were obtained at admission, and timing-invariant CTA was automatically derived from the CTP data. Two experienced radiologists were individually presented with a blinded and randomized sequence of scans. All images were scored for the presence of occlusion in the following artery segments: internal carotid artery (ICA), middle cerebral artery (MCA) segment 1 (M1) and trifurcation to segment 2 (M2), anterior cerebral artery segments 1 (A1) and 2 (A2), basilar artery (BA), posterior cerebral artery segments 1 (P1) and 2 (P2). Sensitivity and specificity of timing-invariant CTA were determined relative to standard CTA (unanimous occlusions). RESULTS: Timing-invariant CTA provided high sensitivity and specificity for arterial occlusion assessment. Specificity per segment was: ICA: 99%, A1: 98%, A2: 100%, M1: 96%, M2: 98%, BA: 100%, P1: 100%, P2: 100%. Sensitivity per segment was: ICA: 88%, M1: 94% and M2: 89%. Sensitivity could not be calculated for the other segments since those had two or less occlusions. There was one false negative score in the ICA that was missed by one observer only, the false negatives in the MCA were never solitary occlusions but were assigned to other MCA segments. CONCLUSION: Timing-invariant CTA that is derived from CT perfusion data provides a diagnostic accuracy that is similar to standard CTA. These findings suggest that a separate cerebral CTA scan can be omitted if CT perfusion imaging is performed. CLINICAL RELEVANCE/APPLICATION: If CT perfusion has been performed, a separate standard CTA of the brain can be omitted, thereby reducing the total radiation dose and the amount of contrast material needed.