[Three dimensional CT angiography using helical scanning].

Thirty-seven intracranial aneurysms were examined with three dimensional CT angiography (3D-CTA) using helical scanning. The raw data were acquired using a helical CT scanner (X vigor, Toshiba). The collimation was 1 mm or 2 mm, and the table speed was 1 mm or 2 mm/rotation. The contrast medium (iohexol 350) of 1.2-1.5 ml/body weight kg was intravenously injected at an initial rate of 1.5 ml/sec and a second rate of 1.0 ml/sec. The scan delay time was 40-45 sec after the injection of the contrast medium. The 3D-CTA was compared with cerebral angiography (CAG) in the detectability of aneurysms. The 3D-CTA was equal or superior to CAG in 22 aneurysms. The 3D-CTA was less useful in the most aneurysms adjacent to the bone such as aneurysms of internal carotid artery. The subtraction 3D-CTA was useful in the detection of those aneurysms which could not clearly be detected on the 3D-CTA.