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

INTRODUCTION

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

METHODS

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 Rb activity (dose-calibrator 'maximum' of 50 mL elution at 50 mL·min) to RUBY-FILL equivalent values (integrated 'total' of 35 mL elution at 20 mL·min). The generator yield (Rb) and production efficiency (Rb yield/Sr parent activity) were measured and compared after this conversion to a common scale.

RESULTS

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

CONCLUSIONS

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