The Importance of Technical Aspects in the Evaluation of Supplementary Indicators on Thallium-201 Myocardial Perfusion Scintigraphs Using Planar Imaging

We previously evaluated the usefulness of visual abnormalities on myocardial stress-perfusion scintigraphy (SPS) not related to the pattern of cardiac perfusion (1). These supplementary indicators (Sf) included: increased lung and ventricular basal uptake and a stress related increase in left ventricular size. In a study population of 72 randomly selected patients, artifac­ tual production of Sf was achieved by changes in our imaging parameters. Through increases in imaging intensities and time of acquisition, all Sf were created. Similar effects were ob­ served with increased count rates. Acquiring images at greater distances than direct patient contact affected ventricular si:.e and basal uptake. Angulation differences affected both these Sf and the interpretation of the extent of existing perfusion defects. Ventricular si:.e differences were seen when compari­ sons of stress images were done with the same redistribution projections acquired on a different camera system. Unless technical accuracy is assured there is risk in using Sf to help identify patients with coronary artery disease (CAD).