Three-dimensional images by helical CT scan with intra-arterial injection of diluted contrast medium.

Eighty-seven patients with primary or metastatic brain tumors who were admitted to the National Cancer Center Hospital since April 1996, underwent a helical CT scan during cerebral angiography using the IVR-CT system (Toshiba Medical Systems, Tokyo, Japan), which comprised a digital subtraction angiography system (KXO-80C/DFP-2000A) and a helical CT scanner (X-Vision, Toshiba Medical Systems, Tokyo, Japan) (2). An angiographic catheter was introduced into the carotid or vertebral artery, the main feeding artery of the tumor, and 100 ml of a 1:5 diluted contrast medium was injected at a rate of 2 rnl/s, The couchtop of the CT scanner was shifted at a speed of 2 mm/s during injection. Axial images obtained from helical CT were reconstructed to produce 3-D images on a shaded surface display using accessory software of the helical CT scanner (3,4). In order to distinguish the vessels from the tumor, red color was applied to the vessels and orange color to the tumors, according to their CT attenuation numbers. Most of the malignant brain tumors were enhanced with the contrast medium and could be outlined on the display to create clearer images. Two of these 3-D images which were horizontally rotated by 7 0 from each other were placed side by side to yield a virtual 3-D image by staring at the left image with the right eye and the right image with the left eye.