Fig. 1

The schematic diagram of the circle of Willis (CoW) and the measurement formulas of lesions. A Methodology used to measure the normalized wall index, arterial remodeling ratio, and stenosis percentage. B Evaluation of the CoW. The CoW was divided into anterior- and posterior-CoW (A-CoW and P-CoW, respectively) sections. A-CoW consists of bilateral A1 segments and the anterior communicating artery. P-CoW consists of the bilateral P1 segments and the bilateral posterior communicating arteries. P-CoW was further categorized into incomplete and complete symptomatic sides