RAPID BACK-TO-BACK ADENOSINE STRESS REST TC-99M TEBOROXIME MYOCARDIALPERFUSION SPECT USING A TRIPLE-DETECTOR CAMERA

Technetium-99m-teboroxime is characterized by a high extraction fracti on over a wide range of blood flow rates, rapid myocardial clearance a nd avid hepatic uptake. This study determined the imaging parameters a nd examined the clinical efficacy of a rapid back to back adenosine st ress/rest teboroxime myocardial perfusion SPECT protocol using a tripl e-detector camera. Acquisition parameters were determined using cardia c phantom studies which were then applied in SPECT studies of 51 cathe terized patients (22 with prior myocardial infarction) and 20 patients with a ''low'' (7.9% +/- 4.3%) likelihood of coronary artery disease. Technetium-99m-teboroxime (20-25 mCi) was injected at the third minut e of adenosine infusion. Teboroxime (20-25 mCi) was also injected at r est, 15 min later. Stress followed by rest SPECT were completed within 25 min using a triple-detector camera and sequential, 1-min continuou s rotations in alternating directions. Summed raw data from the first to second (1-2 min), second to third (2-3 min) and second to fifth (2- 5 min) minutes of imaging following stress teboroxime injection were r econstructed and compared for image quality, degree of liver interfere nce, and accuracy for diagnostic efficacy. In a subgroup of 30 patient s, 2-8-min summed images were also reconstructed to compare this more conventional imaging protocol with our rapid acquisition. Image qualit y was fair to good in 75% of the 1-2-min, 84% of the 2-3-min and 2-5-m in studies and 53% of the 2-8-min scans. The frequency of severe liver interference appeared to increase with the duration of imaging time ( 1-2 min: 3%; 2-3 min: 7%; 2-5 min: 8%) and was greatest (30%, p = 0.08 ) with 2-8-min images. Three patients (4%) had uninterpretable studies due to intense hepatic uptake. Overall sensitivity (95%) and specific ity (71%) were equal for the 2-3-min and 2-5-min stress images and app eared better than in the 1-2-min images (84% and 57%, respectively). F or the 2-8-min scans, vessel sensitivity (69%) and specificity (63%) a ppeared poorer than with 2-3-min studies (83% and 81%, respectively). Normalcy rates were 89% for the 2-3-min and 2-min and 79% for 1-2-min images. The back to back adenosine stress/rest teboroxime SPECT can be performed in 30 min using a triple-detector camera. Although overall high sensitivity and normalcy rates were achieved, the protocol is tec hnically demanding. Interference due to intense liver uptake remains p roblematic.