Imaging of Ir-192 source using a high energy gamma camera for high-dose-rate brachytherapy

We developed a small field-of-view (FOV) high energy gamma camera and measured the gamma photons from an Ir-192 source for imaging of the source. The developed gamma camera consists of a 10 mm thick GAGG pixel scintillator block optically coupled to a position sensitive photomultiplier (PSPMT). It was encased in a 2 cm thick tungsten shield and a 1 mm diameter pinhole collimator was mounted in its head. The gamma camera was positioned 1 m from the Ir-192 source delivered from the brachytherapy system and imaged the Ir-192 source while the source changed dwell positions in the FOV of the gamma camera. We could image the source with 1 s interval and observed the source changed its position in the images. The spatial resolution of the gamma camera system at 1 m from the Ir-192 source was 28 mm FWHM and position accuracy was 5 mm. With the 10 cm thick water phantom positioned between the source and gamma camera, the counts were decreased to half, but the Ir-192 source images could still be observed clearly. We conclude that the developed gamma camera system is promising for the imaging of the Ir-192 source during high-dose-rate brachytherapy pending future improvements in spatial resolution.