Multicentre quantitative 68Ga PET/CT performance harmonisation

Abstract

Purpose: Performance standards for quantitative 18F-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 68Ga. Therefore, our aim was to evaluate 68Ga-PET/CT quantification variability in a multicentre setting. Methods: A survey across Dutch hospitals was performed to evaluate differences in clinical 68Ga PET/CT study protocols. 68Ga and 18F 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 68Ga PET/CT acquisition and reconstruction protocols. 68Ga PET/CT image noise was below 10%. Cross-calibration was within 10% deviation, except for one system to overestimate 18F and two systems to underestimate the 68Ga activity concentration. RC-curves for 18F and 68Ga were within and on the lower limit of current EARL standards, respectively. After correction for local 68Ga/18F cross-calibration, mean 68Ga performance was 5% below mean EARL performance specifications. Conclusions: 68Ga PET/CT quantification performs on the lower limits of the current EARL RC standards for 18F. Correction for local 68Ga/18F cross-calibration mismatch is advised, while maintaining the EARL reconstruction protocol thereby avoiding multiple EARL protocols.