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

• Quantitative Positron Emission Tomography (QPET) could be used as a biomarker.
• Clinical trial qualification (CTQ) of PET scanners is mandatory for reliable use of QPET.
• Variability in activity measurements at 95% CI was 74.0% (18F) and 20.5% (68Ge).
• 100% (with 68Ge) and 28% (with 18F) of PET scanners passed CTQ at first round.
• CTQ with 68Ge vs 18F filled phantom assure lower variability and eases the process.

PurposeThe 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.MethodsWe 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).ResultsThe 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.ConclusionsThe 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.