Abstract
To establish normal reference values for the presence of the anatomic variants of the circle of Willis and to compare anatomic pattern of the circle of Willis of our results with foreign one, 61 healthy volunteers of young adults (male 18, female 43, age 19-25 years, mean age 22.3 years) were examined with 3-dimensional time-of-flight MR angiography (3D-TOF-MRA) of the circle of Willis at 1.5T MRJ equipment. On MR angiography, the presence of entirely complete circle of Willis, incomplete circle of the anterior or posterior part, incomplete circle of the anterior and posterior parts were 53%, 37%, 10% respectively. The presence of entirely complete circle of Willis was higher in women (64%) than men (24%) (P<0.05). Statistically signfficant differences were also found in 4 subtypes of the entirely complete circle of Willis between Japanese and Western country young people. 3D-TOF-MRA is the superb modality for evaluation of blood-flow-based functional anatomic variation of the circle of Willis.
