Improved Detection of Anterior Circulation Occlusions: The "Delayed Vessel Sign" on Multiphase CT Angiography

Area of Science:

• Neuroradiology
• Vascular Imaging
• Acute Ischemic Stroke

Background:

• Multiphase CT angiography (CTA) is a dynamic imaging technique primarily used for assessing collateral circulation in acute ischemic stroke.
• A novel observation, termed the "delayed vessel sign," identifies distal anterior circulation occlusions by delayed opacification on multiphase CTA.

Purpose of the Study:

• To evaluate the diagnostic utility of the "delayed vessel sign" identified on multiphase CTA.
• To compare the effectiveness of multiphase CTA with single-phase CTA in detecting distal anterior circulation occlusions.

Main Methods:

• Retrospective analysis of 23 distal anterior circulation occlusions, 10 M1-segment occlusions, and 10 control cases over a 2-year period.
• Initial blinded interpretation of noncontrast CT and first-phase multiphase CTA by neuroradiologists and radiology trainees.
• Re-examination of multiphase CTA after reader education on the "delayed vessel sign" to assess occlusion detection, confidence, and interpretation time.

Main Results:

• Multiphase CTA demonstrated a significant improvement in the sensitivity of detecting distal anterior circulation occlusions (P < .001).
• Reader confidence (P < .001) and interpretation speed (P < .001) were significantly enhanced with multiphase CTA.
• Maximum intensity projection (MIP) images were preferred over source images in over 90% of cases.

Conclusions:

• The "delayed vessel sign" is a reliable indicator for anterior circulation vessel occlusions, especially in distal branches.
• Utilizing later phases of multiphase CTA to identify the "delayed vessel sign" substantially improves interpretation speed and confidence.
• Multiphase CTA offers superior diagnostic performance compared to single-phase CTA for identifying distal anterior circulation occlusions.