運動負荷ECTの検討

A study of exercise ECT

　²⁰¹Tlを用いた心筋シンチグラムは，非侵襲的な心筋虚血部確認の方法として有用とされてきたが^1〜3），そのbackgroundの問題や，二次元画像であることの欠点のため，その臨床的応用に限界がありた。そのため，臨床的応用の有用性，客観性，定量性を向上させるために，backgroundの処理^4），ROIを決めてのwashout法^5），circumferential profile curveの応用^6）などが考えられた。今回我々は，回転型ガンマカメラを用いたemission CT（ECT）を使用し^7），運動負荷前後の心筋シンチグラムの検討により，²⁰¹Tl運動負荷シンチグラフィーの客観性，定量性において診断能力の向上を確認したので報告する。

Twenty-five patients with angina pectoris, 18 patients with post-myocardial infarction angina and 2 normal patients (mean age of 57 years, male/ female=40/5) were examined by exercise thal-lium-201 emission computed tomography (ECT). The results were compared to those of planar scintigraphy. A large-field-of-view gamma camera with a high resolution pallarel-hole collimator supported by gantry was rotated 180°around the long axis of the patient. Thirty-two different views every 5.8°with sampling time of 20 seconds each were obtained. Total acquisition time was 11 minutes. Data collection started from the left posterior oblique view and ended at the right anterior oblique view. Exercise was performed by graded bicycle ergometer. Post exercise ECT was compared to that of reperfusion imaging 2 3 hours after exercise. Sensitivity and specificity to detect involved coronary arteries by identifying myocardial perfusion defect were 96 & 86% ; 84 & 92% ; 81 & for the right corollary artery (RCA), the left anterior descending artery (LAD) and the left circumflex artery (LCX), respectively. These data surpassed to those of planar scintigraphy (83 & 86% ; 66 & 85% ; 38 & 100% for RCA, LAD and LCX. respectively). Especially in 3 vessel disease, ECT revealed better sensitivity (100%,, 86%, 79% for RCA, LAD and LCX, respectively) than that to planar imaging (86%, 29% respectively). For 1. 2 and 0 vessel disease sensitivity and spec-ificity of both techniques were comparable, though specificity of ECT tended to he a little better than planar's one. In conclusion, exercise ECT was very useful for detection of coronary lesions, especially in 3 vessel disease.