Fusion imageを用いた前脈絡叢動脈の解剖学的variationの術前評価

Efficacy of Fusion Image for the Preoperative Assessment of Anatomical Variation of the Anterior Choroidal Artery

Ⅰ．はじめに

　前脈絡叢動脈（anterior choroidal artery：AchoA）には，豊富な解剖学的variationが存在する^{2,10,12-14,17)}．AchoA脳動脈瘤の外科治療では，虚血性合併症が4.4～16%に生じると報告され^5,7,8)，虚血領域はその解剖学的variationに依存すると考えられる^{1,2,10,12-14,17,18)}．したがって，術前に解剖学的variationおよび灌流領域を把握する必要があるが，AchoAに過形成や低形成，起始異常がある場合には，後交通動脈（posterior communicating artery：PcomA）との血管撮影上の鑑別が困難な場合もある^12,13)．今回，AchoAの解剖学的variationの術前評価に血管撮影とmagnetic resonance imaging（MRI）のfusion imageが有用だった未破裂脳動脈瘤2例を報告する．

　We report two cases with internal carotid artery（ICA）aneurysms, in which fusion image effectively indicated the anatomical variations of the anterior choroidal artery（AchoA). Fusion image was obtained using fusion application software（Integrated Registration, Advantage Workstation VS4, GE Healthcare). When the artery passed through the choroidal fissure, it was diagnosed as AchoA. Case 1 had an aneurysm at the left ICA. Left internal carotid angiography（ICAG）showed that an artery arising from the aneurysmal neck supplied the medial occipital lobe. Fusion image showed that this artery had a branch passing through the choroidal fissure, which was diagnosed as hyperplastic AchoA. Case 2 had an aneurysm at the supraclinoid segment of the right ICA. AchoA or posterior communicating artery（PcomA）were not detected by the right ICAG. Fusion image obtained from 3D vertebral angiography（VAG）and MRI showed that the right AchoA arose from the right PcomA. Fusion image obtained from the right ICAG and the left VAG suggested that the aneurysm was located on the ICA where the PcomA regressed. Fusion image is an effective tool for assessing anatomical variations of AchoA. The present method is simple and quick for obtaining a fusion image that can be used in a real-time clinical setting.