COMPARISON OF IMAGING PROPERTIES OF TECHNETIUM 99M Q12 AND TECHNETIUM99M Q3 IN HUMANS

Background: This study was a direct comparison of the imaging characte ristics of Tc-99m-labeled Q12 (Tc-99m-Q12) and Tc-99m-labeled Q3 (Tc-9 9m-Q3) in the same patients. Methods and Results: In 10 patients with known angiographic coronary artery anatomy, Tc-99m-Q12 and Tc-99m-Q3 m yocardial imaging were performed. Tomographic myocardial imaging was s tarted 15 minutes after tracer injection at rest and with treadmill ex ercise, Ratios of heart-to-lung and heart-to-liver activity were calcu lated from the anterior plane projections of the tomograms at 20 minut es after tracer injection, The presence or absence of angiographic cor onary artery disease was correctly determined from Tc-99m-Q12 images i n 10 of 10 patients with Tc-99m-Q12 and in 9 of 10 patients with Tc-99 m-Q3. The presence or absence of a greater than 50% stenosis in an ind ividual coronary vessel was correctly predicted for 26 of 30 vessels w ith 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 angio graphically defined coronary anatomy, Tc-99m-Q12 and Tc-99m-Q3 provide d similar detection of coronary artery stenoses, At 20 minutes after t racer injection, heart-to-liver activity ratios were more favorable fo r Tc-99m-Q12 than for Tc-99m-Q3, but Tc-99m-Q3 resulted in a more favo rable ratio of heart-to-lung activity.