Operational Reliability of an Automated ¹⁷⁶Lu-Based Daily Quality Control System: A Five-Month Continuous Monitoring Study in Digital PET/CT.

This study aimed to evaluate the feasibility of background quality control (QC) as a novel approach for monitoring time-of-flight (TOF) and energy drift in uMI 550 positron emission tomography-computed tomography (PET/CT) systems. Methods: Three experiments were conducted to compare 176Lu background QC with conventional radioactive source QC. These included multi-system validation, long-term clinical tracking, and anomaly detection. System performance was assessed by calculating TOF drift, energy drift, TOF deviation, and energy deviation. The Wilcoxon signed-rank test compared energy and TOF drift between 176Lu background QC and 18F-FDG rod phantom QC, while the Friedman rank sum test compared parameters among 176Lu background QC, 18F-FDG rod phantom, and 68Ge cylinder phantom QC. Results: Long-term tracking and anomaly detectts showed, TOF deviation remained below 7.6 ps and energy deviation below 1%. Over the five-month period, TOF drift remained stable, whereas energy drift showed a slight decrease under both 176Lu background and radioactive source QC. 176Lu Background, 18F-FDG rod phantom, and 68Ge cylinder phantom QC methods all reliably detected variations in system energy and TOF drift. Conclusions: 176Lu Background QC offers a feasible and reliable alternative to ¹⁸F-FDG rod phantom QC for daily PET/CT quality control. It reduces radiation exposure and simplifies operation, while periodic cross-validation with ¹⁸F-FDG rod phantom QC every six to twelve months remains advisable to ensure long-term system stability.&#xD.