Rubidium-82 generator yield and efficiency for PET perfusion imaging: Comparison of two clinical systems
Ali Ahmadi, Ran Klein, Howard C. Lewin, Rob Beanlands, Robert A. deKemp
Abstract
Strontium-82/Rubidium-82 ( 82 Sr/ 82 Rb) generators are used widely for positron emission tomography (PET) imaging of myocardial perfusion. In this study, the 82 Rb isotope yield and production efficiency of two FDA-approved 82 Sr/ 82 Rb generators were compared. N = 515 sequential daily quality assurance (QA) reports from 9 CardioGen-82 ® and 9 RUBY-FILL ® generators were reviewed over a period of 2 years. A series of test elutions was performed at different flow-rates on the RUBY-FILL ® system to determine an empirical correction-factor used to convert CardioGen-82 ® daily QA values of 82 Rb activity (dose-calibrator ‘maximum’ of 50 mL elution at 50 mL·min −1 ) to RUBY-FILL ® equivalent values (integrated ‘total’ of 35 mL elution at 20 mL·min −1 ). The generator yield ( 82 Rb) and production efficiency ( 82 Rb yield/ 82 Sr parent activity) were measured and compared after this conversion to a common scale. At the start of clinical use, the system reported 82 Rb activity from daily QA was lower for CardioGen-82 ® vs RUBY-FILL ® (2.3 ± 0.2 vs 3.0 ± 0.2 GBq, P < 0.001) despite having similar 82 Sr activity. Dose-calibrator ‘maximum’ (CardioGen-82 ® ) values were found to under-estimate the integrated ‘total’ (RUBY-FILL ® ) activity by ~ 24% at 50 mL·min −1 . When these data were used to convert the CardioGen-82 values to a common measurement scale (integrated total activity) the CardioGen-82 ® efficiency remained slightly lower than the RUBY-FILL ® system on average (88 ± 4% vs 95 ± 4%, P < 0.001). The efficiency of 82 Rb production improved for both systems over the respective periods of clinical use. 82 Rb generator yield was significantly under-estimated using the CardioGen-82 ® vs RUBY-FILL ® daily QA procedure. When generator yield was expressed as the integrated total activity for both systems, the estimated 82 Rb production efficiency of the CardioGen-82 ® system was ~ 7% lower than RUBY-FILL ® over the full period of clinical use.