Blinded pairwise review — synthetic chest CT.
Compare the nine target arteries. Assess their presence, origins, course, continuity, branching, and caliber. Choose the CT with more anatomically plausible arterial anatomy. Do not base the decision on nonvascular organs or general image attractiveness. Do not classify a plausible anatomic variant or low contrast alone as an anatomic error. A missing or distorted vessel is a study finding, not a reason to skip the scan.
A major error is an absent expected artery within the imaged region, an implausible origin or connection, a complete interruption, or a clearly impossible course or caliber. Use Uncertain when visibility prevents a confident major-error judgment. No means no clear major error identified, not proven normal anatomy.
This saves the issue without a preference and leaves the assignment incomplete. The same pair returns after the problem is corrected.