Multicentre quantitative Ga-68 PET/CT performance harmonisation

Abstract

Purpose Performance standards for quantitative F-18-FDG PET/CT studies are provided by the EANM Research Ltd. (EARL) to enable comparability of quantitative PET in multicentre studies. Yet, such specifications are not available for Ga-68. Therefore, our aim was to evaluate Ga-68-PET/CT quantification variability in a multicentre setting. Methods A survey across Dutch hospitals was performed to evaluate differences in clinical Ga-68 PET/CT study protocols. Ga-68 and F-18 phantom acquisitions were performed by 8 centres with 13 different PET/CT systems according to EARL protocol. The cylindrical phantom and NEMA image quality (IQ) phantom were used to assess image noise and to identify recovery coefficients (RCs) for quantitative analysis. Both phantoms were used to evaluate cross-calibration between the PET/CT system and local dose calibrator. Results The survey across Dutch hospitals showed a large variation in clinical Ga-68 PET/CT acquisition and reconstruction protocols. Ga-68 PET/CT image noise was below 10%. Cross-calibration was within 10% deviation, except for one system to overestimate F-18 and two systems to underestimate the Ga-68 activity concentration. RC-curves for F-18 and Ga-68 were within and on the lower limit of current EARL standards, respectively. After correction for local Ga-68/F-18 cross-calibration, mean Ga-68 performance was 5% below mean EARL performance specifications. Conclusions Ga-68 PET/CT quantification performs on the lower limits of the current EARL RC standards for F-18. Correction for local Ga-68/F-18 cross-calibration mismatch is advised, while maintaining the EARL reconstruction protocol thereby avoiding multiple EARL protocols