頸部内頸動脈狭窄における横断面画像および断面積狭窄率測定について

Three-Dimensional DSA Imaging and 3-Dimensional Measurement of Cross Section for Internal Carotid Artery Stenosis

　要旨　頸部内頸動脈（ICA）狭窄28例において回転digital subtraction angiography（DSA）を行って横断面画像を検討し，さらに断面積狭窄率（ASR）：〔1－（ICA最狭窄部断面積/ICA遠位部断面積）〕×100とNASCET法による狭窄率，頸動脈エコーによるICAと総頸動脈（CCA）の収縮期血流速度比（PSVRICA/CCA）を比較検討した。断面画像が構成できなかった症例は不穏状態の1例のみで，それ以外は断面画像により狭窄部の形態把握が可能であった。またASRはNASCET法と高い相関を示し，（ASR＝12.886＋1.037×NASCET法狭窄率）により求められた。狭窄の偏在症例ではNASCET法により狭窄を過度に評価する可能性が示唆された。PSVRICA/CCAにより狭窄率の推測はある程度可能であり，特に3.1以上は全て高度狭窄例であった。ただし高位の高度狭窄の1例はエコーでは検出できなかった。

　ICA狭窄において回転DSAにより1回の撮影で狭窄の状態，および断面積狭窄率をとらえることができ，ルーチン検査として有用な方法と考えられた。

We have performed rotational DSA for internal carotid aretry（ICA）stenosis and examined cross sectional imaging of the stenosis. Then, we compared the area stenosis rate（ASR）with stenosis rate by NASCET method and with results of duplex carotid ultrasonography.

Of consecutive 451 patients who underwent digital subtraction angiography, 28 patients with ICA stenosis were selected for this study. Imaging data were transmitted to a workstation, and three-dimension（3-D）images were prepared, and cross sectional images of the highest-grade stenotic portion were obtained. ASRs were calculated 〔1-（the area of highest stenotic portion of ICA/the area of distal ICA）〕×100, which were compared with stenosis rates by NASCET method, as well as peak systolic velocity ratios （PSVR）of ICA to common carotid artery（CCA）determined by duplex carotid ultrasonography（USG）.

Cross sectional images in all patients were made except for restless patients, thereby morphology of the stenosis was feasible and measurements of cross section and diameter were possible. ASR and stenosis rate by NASCET method showed a very high correlation, and ASR was obtained by formula of（12.886＋1.037×stenosis rate by NASCET method）. In patients with distorted stenosis, the stenosis rate was overestimated by NASECT method. ICA/CCA PSVR could predict stenosis to some extent, and in particular, all the patients with ICA/CCA PSVR of 3.1 or greater were found to have high grade stenosis. However duplex carotid USG failed to detect stenosis in a patient with high-grade stenosis at high position.

In conclusion, as to ICA stenosis, 3-D image could show the stenosis precisely, and was considered to be useful as a routine examination.