[Evaluation of Residual Ratio and Optimization of Residual Setting in Automated Infusion Device for 18F-florbetapir Administration].

Abstract

Purpose: This study aimed to quantify residual radioactivity in medical devices used during ¹⁸F-florbetapir administration with the UG-02 automated infusion device and to identify the optimal residual setting for accurate dose calculation.

Methods: We analyzed 52 amyloid positron emission tomography (PET) examinations performed at our institution. After radiotracer administration, residual radioactivity was measured in the drug vial, infusion circuit, route, residual solution, and individual circuit components. Administration rates and residual ratios were calculated after decay correction to the injection time. Residual ratios estimated by the UG-02 system were compared with measured values, and the optimal residual setting was determined using least-squares optimization. Statistical analyses were performed using paired t-tests, with statistical significance set at P<0.05.

Results: The mean administered dose was 348.0±33.3 MBq, whereas the mean residual activity was 93.1±12.6 MBq, corresponding to an administration rate of 77.8% and a residual ratio of 22.2%. The infusion circuit exhibited the highest residual ratio (18.0%), primarily attributable to the air vent filter (13.5%) and infusion set (4.0%). The UG-02 system significantly overestimated the residual ratio in the drug vial compared with the measured value (1.5% vs. 0.9%, P<0.01). The optimal residual setting was 16.1%, reducing the relative error of the displayed dose from 17.1% to 0.08%.

Conclusion: This study characterized residual distribution within the UG-02 automated infusion system and identified an optimal residual setting for ¹⁸F-florbetapir administration. Implementing this setting improves dose calculation accuracy, reduces underdosing risk, and may contribute to improving the quantitative reliability of amyloid PET imaging.