title: Functional imaging of thallium-201 myocardial washout and the clinical utility of this method.
abstract: In exercise testing with Thallium-201 myocardial scintiscan, we developed a quantitative myocardial Tl-201 washout image, a washout ratio and a washout index to detect ischemic segments. The washout value was measured with a pixel by pixel calculation between counts of the initial image and images that were delayed for three hours after the initial image. We compared the color displayed functional washout images with the original image in the detection of ischemic segments which had been confirmed by coronary angiography. A study of 22 patients showed 20 cases of coronary artery disease (with MI 8, but without MI 12) and two cases of normal control. The sensitivity for detection of a diseased vessel was 81% in the washout ratio imaging method and 79% in the washout index method, and both were superior to the sensitivity of the original image, which was 69%. As concerns MI cases, eight out of nine infarcted segments showed a lower washout, which represented partial redistribution on the delayed image. Six out of seven ischemic but not infarcted segments could be detected by the washout image, but only three were detected by the original image. These results indicate the washout image could provide not only transient ischemia but also additional ischemia of MI. We conclude that the washout image will be useful in producing a visual indication of ischemic areas.
mesh_terms: D000328:Adult; D000368:Aged; D000790:Angiocardiography; D003327:Coronary Disease / Q000000981:diagnostic imaging*; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011868:Radioisotopes; D011877:Radionuclide Imaging; D013793:Thallium
chemical_list: D011868:Radioisotopes; D013793:Thallium