PET scanner clinical trial qualification with 68Ge-filled NEMA/IEC image quality phantom outperforms with respect to 18F

Introduction: The quantitative reading of Positron Emission Tomography (PET) scan by standardized uptake value and derived parameters is experimentally studied in several clinical trials. Since 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-center clinical trials and in every-day clinical life. Materials and Methods: Under the auspices of Italian Foundation on Lymphoma (FIL) we set-up a CTQ program consisting on 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: Seventy-four sites equipped with 83 PET/CT scanners participated in the 18F phantom CTQ program. Sixty-three out of 83 (76%) scanners fulfilled the CTQ requirements, 14 (17%) did not because of a lack of phantoms or trained personnel, while CTQ is still ongoing on 6 (7%) scanners. For qualified scanners the CTQ was reached at the first round in 28% of the cases, while in 18%, 17% and 13%, two, three or more than three iterations were required, respectively. The use of 68Ge phantom allowed reducing the inter-scanner variability at 95% confidence level among different scanners from 39.2% to 10.6% in BAC and from 23.6% to 9.4% in SBR with respect to the one based on 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-filled phantom is a reliable tool for CTQ and permits to reduce inter-scanner variability with respect to 18F-filled one.