Color-coded 3D MRA による個々の未破裂脳動脈瘤における瘤内MR信号強度分布パターンの画像解析

Assessment of the Signal Intensity Distribution Pattern within the Unruptured Cerebral Aneurysms Using Color-coded 3D MR Angiography

Ⅰ．はじめに

　脳動脈瘤の発生，成長，破裂には，血液の流れによる血行力学的負荷が深くかかわっていると考えられ，脳動脈瘤内の流れの解明にはこれまで多くの研究がなされてきた^2-4,12-14)．しかしながら，そのほとんどはin vitro model，computer simulationあるいは実験脳動脈瘤を用いた基礎的検討であり，臨床例でのまとまった報告はみられない．今回われわれは，MR angiography（MRA）で得られる血流情報に着目して，MRA volume dataの信号強度分布を3次元（three-dimensional, 3D）カラー表示するcolor-coded 3D MRAを新たに創作した⁹⁾．本論文では，color-coded 3D MRAを用いて，未破裂脳動脈瘤50例において個々の脳動脈瘤での瘤内MR信号強度分布パターンとbleb形成・domeの変形など瘤形態との関連を3D画像解析し，新たな知見を得たので報告する．

To evaluate the interaction between the MR signal intensity distribution pattern and bleb formation/ deformation of the aneurysmal dome,fifty cases of the unruptured cerebral aneurysms were investigated with the color-coded 3D MR angiography. Patterns were categorized into central-type,neck-type and peripheral-type according to the distribution of MR signals with low-,moderate- and high signal intensity areas. Imaging analysis revealed the significant relationship (P＜0.02) of the peripheral-type aneurysms to the bleb formation and deformation of the dome,compared with those of central- and neck-type. Additionally,peripheral-type signal intensity distribution pattern was shown with aneurysms harboring relatively large dome size and lateral-type growth including internal carotid aneurysms. Prospective analysis of intraaneurysmal flow pattern with the color-coded 3D MR angiography may provide patient-specific analysis of intraaneurysmal flow status in relation to the morphological change of the corresponding aneurysmal dome in the management of unruptured cerebral aneurysms.