The 68Ge phantom-based FDG-PET site qualification program for clinical trials adopted by FIL (Italian Foundation on Lymphoma)

Purpose: The quantitative assessment of Positron Emission Tomography (PET) scans using standardized uptake value and derived parameters proved to be superior to traditional qualitative assessment in several retrospective or mono-centric prospective reports. Since different scanners give different quantitative readings, a program for clinical trial qualification (CTQ) is mandatory to guarantee a reliable and reproducible use of quantitative PET in prospective multi-centre clinical trials and in every-day clinical life. Methods: We set up, under the auspices of Italian Foundation on Lymphoma (FIL), a CTQ program consisting of the PET/CT scan acquisition and analysis of 18F and 68Ge NEMA/IEC image quality phantoms for the reduction of inter-scanner variability. Variability was estimated on background activity concentration (BAC) and sphere to background ratio (SBR). Results: The use of a 68Ge phantom allowed reducing the inter-scanner variability among different scanners from 74.0% to 20.5% in BAC and from 63.3% to 17.4% in SBR compared to using the 18F phantom. The CTQ criteria were fulfilled at first round in 100% and 28% of PET scanners with 68Ge and 18F respectively. Conclusions: The 68Ge phantom proved a reliable tool for PET scanner qualification, able to significantly reduce the potential sources of error while increasing the reproducibility of PET derived quantitative parameter measurement.