Exploring the Gamma Counting Function in PET for Sample Activity Measurement

With the widespread availability of small animal PET scanners globally, there exists a significant opportunity to enhance their operational utility. Our research introduces a novel utilization pathway by integrating gamma-counting functionalities within PET systems. This approach leverages the shared gamma counting technology between PET systems and traditional gamma counters, enabling direct radioactivity measurement from PET-derived raw count data. We established a correlation between the raw data from all-digital PET and the radioactivity of samples, conducting experiments to assess the system's measurement capabilities. The system demonstrated high accuracy and stability across a detectable range of 25.53-1900.69 kBq in single-photon mode and 19.61-1107.04 kBq in coincidence mode, with the difference between the sample activity and the linear function being no more than 5 %. Due to the multi-channel characteristic of PET detectors, our system exhibits a tenfold higher upper detection limit than that of gamma counters, without dead-time correction. This study demonstrates that all-digital PET can directly measure radioactivity, simplifying nuclear medicine procedures by integrating gamma counting within PET systems. This strategy not only reduces the need for multiple instruments but also has the potential to improve quantitative accuracy by minimizing cross-calibration errors, thereby maximizing the operational utility of existing all-digital PET scanners.