A comparative study between a new, 50-degree right-semidecubital scanning and usual supine scanning of thallium-201 myocardial tomography for evaluation of coronary artery disease.

Images of thallium-201 cardiac tomography in the 50-degree right-lateral-semidecubital vs. usual supine positions were compared after a single dose of the isotope in 225 patients with or suspected of coronary artery diseases. Compared with the supine position method, the semidecubital position method enabled 25% shortening of the orbital radius (20.0 +/- 0.9 cm to 15.3 +/- 0.6 cm, n = 174, p less than 0.05), higher posteroinferior wall counts in both exercise and 3-hour-delayed images by up to 18%, better image sharpness and contrast, less motion artifact, more marked redistribution in the ischemic walls, and significantly higher specificity (57% vs. 78%, p less than 0.05) and accuracy (63% vs. 79%, p less than 0.05) for inferior wall lesions. The results indicate that the thallium cardiac scan is significantly affected by patient position during scanning, i.e., artifactual inferior wall defects due to photon attenuation in the supine position method. The semidecubital position method is recommended to minimize this artifact. The method is simple, easy to perform, well tolerated, feasible in any 1-headed tomography system, inexpensive, and free of running costs.