Rubidium-82 generator yield and efficiency for PET perfusion imaging: Comparison of two clinical systems

Strontium-82/Rubidium-82 (⁸²Sr/⁸²Rb) generators are used widely for positron emission tomography (PET) imaging of myocardial perfusion. In this study, the ⁸²Rb isotope yield and production efficiency of two FDA-approved ⁸²Sr/⁸²Rb 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 ⁸²Rb 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 (⁸²Rb) and production efficiency (⁸²Rb yield/⁸²Sr parent activity) were measured and compared after this conversion to a common scale.

At the start of clinical use, the system reported ⁸²Rb 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 ⁸²Sr 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 ⁸²Rb production improved for both systems over the respective periods of clinical use.

⁸²Rb 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 ⁸²Rb production efficiency of the CardioGen-82^® system was ~ 7% lower than RUBY-FILL^® over the full period of clinical use.