Supplementary Material

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Purpose: To determine whether the age-related change occurs in the arterial segments of the circle of Willis (CoW).

Materials and Methods: Patients (n = 100) who underwent time-of-flight MR angiography (TOF-MRA) were grouped according to age, 10–20 years old (n = 50) or 50–60 years old (n = 50). MRA images were retrospectively analyzed and the diameters of segments of the CoWweremeasured, and the patency of the CoW and the half circles was estimated. The CoW patterns according to the patency of each vessel segment were recorded.

Results: Most segments of the CoW in adult group revealed significant decrease in vessel diameter except for bilateral posterior communicating arteries. The number of vascular patterns of the CoW in the adult groupwas higher than in the adolescent group. Therewas significant decrease in the patency rate of the posterior, left, and right half-circles.

Conclusion: The CoW showed age-related change, resulting in markedly decreased vessel diameters in most segments.