Multiphase CT angiography increases detection of anterior circulation intracranial occlusion

Abstract

Objective: To evaluate whether the use of multiphase CT angiography (CTA) improves interrater agreement for intracranial occlusion detection between stroke neurology trainees and an expert neuroradiologist.

Methods: A neuroradiologist and 2 stroke neurology fellows independently reviewed 100 prospectively collected single-phase and multiphase CTA scans from acute ischemic stroke patients with mild symptoms (NIH Stroke Scale score ≤5). The presence and location of a vascular occlusion(s) were documented. Interrater agreement single- and multiphase CTA was quantified using unweighted κ statistics. We assessed for any occlusions, anterior vs posterior occlusions, and pial vessel asymmetry.

Results: Using multiphase CTA, the neuroradiologist detected 50 scans with anterior circulation occlusions and 15 scans with posterior circulation occlusions. Median reading time was 2 minutes per scan. Median reading time for the neurologists was 3 minutes per multiphase CTA scan. Interrater agreement was fair between the 2 neurologists and neuroradiologist when using single-phase CTA (κ = 0.45 and 0.32). Agreement improved minimally when stratified by anterior vs posterior circulation. When using multiphase CTA, agreement was high for detection of occlusion or asymmetry of pial vessels in the anterior circulation (κ = 0.80 and 0.84).

Conclusions: Multiphase CTA improves diagnostic accuracy in minor ischemic stroke for detection of anterior circulation intracranial occlusion.

Classification of evidence: This study provides Class II evidence that multiphase CTA, compared to single-phase CTA, improves the interrater agreement between stroke neurology trainees and an expert neuroradiologist for detecting anterior circulation intracranial vascular occlusion in patients with minor acute ischemic strokes.

Figure 1. Case study 1

Axial multiphase CT angiography showing 3 phases as P1 (late arterial phase), P2 (midvenous phase), and P3 (late-venous phase). P1 images are degraded by motion artifacts. There is evidence of a right MCA mid-M1 loss of contrast opacification, indicating an occlusion (blue arrow). P2 and P3 show asymmetry in pial arteries in the right MCA distribution with delayed washout of the contrast, confirming the vascular occlusion despite motion artifact. MCA = middle cerebral artery.

Figure 2. Case study 2

(A) Multiphase CT angiography with right MCA occlusion in the distal branches, made evident by delayed washout of contrast in the right MCA vascular distribution in P2 and P3. (B) Magnified axial maximum intensity projection of P1 showing gradual loss of contrast opacification of a distal M2 branch of the MCA in the sylvian fissure indicating a vascular occlusion (blue arrows). MCA = middle cerebral artery.

Figure 3. Case study 3

(A) Multiphase CT angiography with left MCA-M2 branch occlusion in P1 and delayed contrast washout in the left MCA vascular distribution (P2, P3). (B) Magnified axial maximum intensity projection of P1 showing abrupt vessel cutoff with distal vessel opacification, either through slow anterograde or retrograde collateral filling (blue arrow). MCA = middle cerebral artery.