With 2mm-thick CT scanning during the rapid infusion of contrast material (TICT), cerebral aneurysms arising from the circle of Willis and adjacent vessels can be directly visualized. Twenty-five patients who had cerebral aneurysm confirmed by surgery were examined with TICT and digital subtraction angiography. The authors examined TICT prospectively to assess the detection rate of the cerebal aneurysms and to evaluate the clinical usefulness of TICT. The detection rates of aneurysms by TICT and digital subtraction angiography suspected cerebral aneurysm. permitting direct visualization of the aneurysm.