Three-dimensional CT angiographyを用いた未破裂脳動脈瘤手術のプランニング

Abstract

Recent technical advancements in spiral computerized tomography (CT) imaging allow exellent three-dimensional visualization of the intracranial larger vessels. In the present study, we compared three-dimensional CT angiography (3D-CTA) with digital subtraction angiography (DSA) to clarify the clinical usefulness of this new imaging technique for surgical planning in patients with unruptured cerebral aneurysms, referring to intraoperative findings. 3D-CTA was performed on 15 patients with 21 unruptured aneurysms who underwent operation for these aneurysms, using a SOMATOM PLUS-S scanner. We employed the shaded surface rendering method for three-dimensional reconstruction with the threshold of 80-150 HU and maximum intensity projection (MIP) processing. In 11 out of 21 aneurysms, images obtained from 3D-CTA were superior to those from DSA for surgical planning, while in only 3 aneurysms 3D-CTA was considered to be less useful due to overlapping with bony and vascular structures. 3D-CTA provided valuable information for surgical simulation as follows: 1) Good delineation of actual shape of the dome and the neck, 2) better understanding of the direction of the aneurysm and its anatomical relationship with surrounding major arteries and bony structures, 3) easy visualization of intramural calcification around the neck using MIP technique. In cases with cavernous sinus aneurysms, the intradural projection of the aneurysm can be made visible by elevating the threshold up to 250 HU. On the other hand, several potential limitations to the use of 3D-CTA such as poor demonstration of small branches and perforators and overlapping with venous and bony structures existed. In conclusion, although further improvement and adequate clinical experience of 3D-CTA are needed, this noninvasive method has proved to be valuable for planning in aneurysm surgery.