A Quantitative Method for the Assessment of Myocardial Function using the Polar Analysis of Tc-99m-MIBI Myocardial SPECT

Tc-99m-MIBI 심근 SPECT 극성지도 분석에 의한 심근 기능의 정량적 평가

As the Tc-99m-MIBI myocardial SPECT demonstrated wide application in the diagnosis of myocardial function, the quantitative and severity-dependent information is currently re quired. In this study, we proposed a computerized method for scoring the fixed defects in terms of extent-weighted severity and for identifying the reversibility in ischemic regions. At the first stage of this method, the transverse slices were reconstructed with 0.4 Nyquist freq. and order 5 Butterworth filter. From the oblique/sagittal slices, maximal count per pixel circumferential profiles were extracted for each sector, and then stress/redist. polar maps were normalized and plotted. For reversibility, the stress polar map was subtracted from the de-layed image and positive-valued pixels were categorized into three grades. The extent-weight-ed severity scores were calculated using the assigned grades and their number of pixels. This procedure was done automatically and the reversibility and severity scores were produced for each of the coronary territories (LAD, RCA, LCX) or any combination of these. Clinical ap-plication has shown that the changes In reversibility scores after PTCA were correlated linearly with the pre PTCA scores(r>0.8) in postinfarct cases as well as in angina, and severity scores of persistent defects in stress/rest SPECT study matched to the regional ejection fraction and visual analysis of regional wall motion of gated blood pool scan(r>0.6). We conclude that the computerized severity scoring method for the analysis of myocardial SPECT could be useful in the assessment of the myocardial ischemia and fixed defect.

심근 SPECT에 의한 심근질환의 심도 및 허혈부위를 평가하는 방법으로 정상인의 극성지도와의 비교에 의한 결손지도 평가방법이 상용화되었으나 본 연구에서는 결손부위의 범위만을 산출할 수 있었던 종래의 방법을 개선할 수 있는 관류회복정도 및 심도성적 산출 방법을 시도하여 보았다. 허혈 및 심도성적의 산출에서 부하 및 휴식기 극성지도의 차이를 3등급으로 분할하여 각 등급에 해당되는 화소의 수를 가중하므로서 관류결손부위의 면적이 반영된 허혈 및 심도성적 산출방법을 제안하고자 하였으며, 등급 및 가중치의 할당은 정상인의 잔상동맥영역별 관류분포를 반영하여 고른 등급 할당방법보다 상관도가 개선된 결과를 얻을 수 있었다.