Uz, AysunKarataş, Ayşe2022-06-282022-06-282012http://hdl.handle.net/20.500.12575/82343Circulus arteriosus cerebri was described by Thomas Willis in 1664. Willis Polygon, of which function is to protect the brain ischemia, is an arterial polygon. The aim of this study is to define structural characteristics of the Willus polygon belonging to the Turkish adult population, variations and arteries involved in the measurement of diameters and lengths on cadavers and cranial computed tomography angiography. Two groups took place in the study. Willis polygon was evaluated in 100 adult fresh human brain obtained from autopsies in the Group 1 and in 100 adult cranial computed tomography angiography in Group 2. As a result, all arteries forming the Willis polygon as 91% in Group 1 and as 71% in Group 2 were anatomically seen. The typical structure in which hypoplasia arteries is not involved was obtained as 8% in Group 1 and 28% in Group 2. The atypical Willis polygon with aplasia was seen as 9% in Group 1 and 29% in Group 2. In Group 1, 87% of adult, 9% fetal, and 4% transitional configuration in the samples were detected. In Group 2, 82% adult, 17% fetal, and 1% transitional configuration were found. The variations of the Circle of Willis in both groups were more common in the posterior portion. Hypoplasia was found to be the most common variation and seen maximum in AComP (85% in Group 1, 32% in Group 2). Aplasia was found as the second most common variation after hypoplasia and again the most common in AComP (5% in Group 1, 22% in Group 2). According to the literature, hypoplasia of AComP was high and hypoplasia of P1 was low. According to the findings obtained in this study, although computed tomography angiography is useful clinical method for demonstrating the vascular structure, because of technical difficulties for imaging of some vessels, cadaver studies is still important for evaluation of occlusive cerebrovascular disease and procedures such as bypass surgery, aneurysm.trCirculus arteriosus cerebrianatomidoctoralThesis