COMPARISON OF IMAGING PROPERTIES OF TECHNETIUM 99M Q12 AND TECHNETIUM 99M Q3 IN HUMANS

Background: This study was a direct comparison of the imaging characteristics of Tc-99m-labeled Q12 (Tc-99m-Q12) and Tc-99m-labeled Q3 (Tc-99m-Q3) in the same patients. Methods and Results: In 10 patients with known angiographic coronary artery anatomy, Tc-99m-Q12 and Tc-99m-Q3 myocardial imaging were performed. Tomographic myocardial imaging was started 15 minutes after tracer injection at rest and with treadmill exercise, Ratios of heart-to-lung and heart-to-liver activity were calculated from the anterior plane projections of the tomograms at 20 minutes after tracer injection, The presence or absence of angiographic coronary artery disease was correctly determined from Tc-99m-Q12 images in 10 of 10 patients with Tc-99m-Q12 and in 9 of 10 patients with Tc-99m-Q3. The presence or absence of a greater than 50% stenosis in an individual coronary vessel was correctly predicted for 26 of 30 vessels with Tc-99m-Q12 (87%) and in 27 of 30 vessels with Tc-99m-Q3 (90%, p = NS vs Tc-99m-Q12), Mean heart-to-lung activity ratio at rest was 1.50 for Tc-99m-Q12 and 1.93 for Tc-99m-Q3 (p < 0.01). Mean heart-to-liver activity ratio at rest for Tc-99m-Q12 was 0.78 versus 0.54 for Tc-99m-Q3 (p < 0.0001). Conclusions: In 10 patients with chest pain and angiographically defined coronary anatomy, Tc-99m-Q12 and Tc-99m-Q3 provided similar detection of coronary artery stenoses, At 20 minutes after tracer injection, heart-to-liver activity ratios were more favorable for Tc-99m-Q12 than for Tc-99m-Q3, but Tc-99m-Q3 resulted in a more favorable ratio of heart-to-lung activity.