未破裂小脳動脈瘤の診断におけるthree-dimensional MR angiographyの有用性 Utility of Three-dimensional Magnetic Resonance Angiography in the Detection of Small Unruptured Cerebral Aneurysms

【目的】未破裂小脳動脈瘤(SUCA)の診断におけるthree-dimensional (3-D)MRAの有用性について報告する.【対象および方法】MRA MIPにて10mm以下のSUCAと診断,あるいは疑われた76例(女性54例,男性22例,42-85歳)を対象とした.MRIはSigna Infinity Excite 1.5 Tを用いた.約10分間で3-D time-of-flight MRAの元画像から3-D MRAを作成し,MIPと比較検討した.【結果】1)76例中3D-MRAにて88個のSUCAが認められ,その形状は全例saccular typeであった.2)部位はMCA 31, ICA 30, AcomA 15, ACA 4, BA tip 3, VA 3, SCA 2個で,その最大径は1.7-9.8mmで平均4.0mmであった.3-D MRAではSUCAの形状,大きさ,親動脈や娘動脈との位置関係などがよく把握でき,有用であった.3)MIPでは44個(50%)のSUCAについて診断できたが,SUCAのサイズ別の診断率は1.7-2.9mm:12%,3.0-4.9mm:69%,5.0-9.8mm:90%であった.MIPではSUCAの存在を診断できてもその形状,親動脈や娘動脈との位置関係などの把握は困難な場合が多かった.【結論】3-D MRAはMIPに比べ,SUCAの診断に有用である.3-D MRAはSUCAの診断率の向上に寄与するものと考えられた.

We describe the utility of three-dimensional (3-D) magnetic resonance (MR) angiography in the detection of small unruptured cerebral aneurysms (SUCA). Seventy-six patients with suspected or detected unruptured cerebral aneurysms smaller than 10mm by maximum intensity projection images using 3-D time-of-flight MR angiography were investigated by surface rendered 3-D MR angiography. About 10 minutes were required to reconstruct 3-D display images from source images of MR angiography. A total of 88 SUCA in 76 patients were detected on 3-D MR angiography. A majority of aneurysms were located at the anterior part of the circle of Willis, and the maximum diameter of the aneurysms ranged from 1.7 to 9.8mm with a mean of 4.0mm. 3-D MR angiography provided important information regarding the configuration of the aneurysm sac, its size, and its relationship to the surrounding vessels. These results indicate that 3-D MR angiography will make a contribution as a new supporting method in the detection of patients with SUCA.