RESUMO
In a series of 12 patients presenting with a single-vessel coronary artery disease and who were injected with 370 MBq of 99mTc-2-methoxyisobutylisonitrile at peak exercise, two consecutive single photon emission computed tomography (SPECT) data collections, i.e., 32 views of 30 sec during a 180 degrees rotation and 64 views of 15 sec during a 360 degrees rotation, were performed 1 hr later. In both cases, transverse sections were reconstructed using (a) a backprojection method with a ramp filter, (b) a correction for downscatter, (c) a correction for depth attenuation by the Chang method, or (d) both corrections. Each reconstructed myocardium was then divided into four short-axis sections which were radially divided into nine sectors. Sectors with an activity below 80% of the maximum were considered as abnormal. Sensitivity and specificity were calculated relative to a sector-by-sector theoretical anatomic distribution of the perfusion abnormalities. Results demonstrate that, of all situations, the best balance between sensitivity and specificity was achieved with the 180 degrees data collection and no correction at reconstruction. Using the 360 degrees data sampling technique mainly lowered the sensitivity in the patients with a circumflex or right coronary artery disease. It is concluded that there does not seem to be any definite advantage in performing a 360 degrees rather than a 180 degrees data collection in 99mTc myocardial SPECT.
