Timing-Invariant CT Angiography Derived from CT Perfusion Imaging in Acute Stroke: A Diagnostic Performance Study

Abstract

BACKGROUND AND PURPOSE: Timing-invariant (or delay-insensitive) CT angiography derived from CT perfusion data may obviate a separate cranial CTA in acute stroke, thus enhancing patient safety by reducing total examination time, radiation dose, and volume of contrast material. We assessed the diagnostic accuracy of timing-invariant CTA for detecting intracranial artery occlusion in acute ischemic Stroke, to examine whether standard CIA can be omitted. MATERIALS AND METHODS: Patients with suspected ischemic stroke were prospectively enrolled and underwent CIA and CTP imaging at admission. Timing-invariant CIA was derived from the CTP data. Five neuroradiologic observers assessed all images for the presence and location of intracranial artery occlusion in a blinded and randomized manner. Sensitivity and specificity of timing-invariant CTA and standard CIA were calculated by using an independent expert panel as the reference standard. Interrater agreement was determined by using kappa statistics. RESULTS: We included 108 patients with 47 vessel occlusions. Overall, standard CIA and timing-invariant CIA provided similar high diagnostic accuracy for occlusion detection with a sensitivity of 96% (95% Cl, 90%-100%) and a specificity of 100% (99%-100%) for standard CIA and a sensitivity of 98% (95% Cl, 94%-100%) and a specificity of 100% (95% Cl, 100%-100%) for timing-invariant CIA. For proximal large-vessel occlusions, defined as occlusions of the ICA, basilar artery, and M1, the sensitivity and specificity were 100% (95% Cl, 100% 100%) for both techniques. Interrater agreement was good for both techniques (mean kappa value, 0.75 and 0.76). CONCLUSIONS: Timing-invariant CIA derived from CTP data provides diagnostic accuracy similar to that of standard CIA for the detection of artery occlusions in acute stroke.