Background Our goal was to provide measurements of the posterior cerebral circulation using non-invasive imaging and advanced software analysis tools.

Methods 100 consecutive patients aged ≥40 years (50 men and 50 women) who had undergone CT angiography (CTA) but had no vascular abnormality were analyzed. Specific software was used to make vessel measurements along the center line. The length of the intracranial vertebral artery (VA), the basilar artery (BA) and the distance from the mid-basilar artery to the posterior cerebral artery (mBA-PCA) was recorded. Vessel diameter was measured at the proximal and distal ends of these vessel lengths. Vessel taper was calculated as the change in diameter in millimeters per centimeter of length.

Results The mean lengths of the intracranial VA, the BA and the mBA-PCA were 40±10.6 mm, 27.3±5.7 mm and 25.6±4.3 mm, respectively. The proximal and distal diameters were 3.9±0.8 mm and 2.8±0.6 mm for the VA and 3.6±0.6 mm and 3.1±0.5 mm for the BA, respectively. The mean mid-BA diameter and the proximal PCA diameter were 3.2±0.5 mm and 2.2±0.4 mm, respectively. There was a significant increase in arterial caliber in patients aged ≥60 years compared with those aged 40–59 years. Men also tended to have longer vessels with a larger diameter than women.

Conclusions Advanced software and non-invasive imaging can be used to perform accurate vessel analysis. The posterior circulation measurements showed an increase in arterial caliber with age. This baseline information may be useful in planning neurovascular procedures and endovascular device development.