Feasibility study of real-time imaging of an Ir-192 source using compact gamma camera with curved diverging collimator for brachytherapy

Abstract

Brachytherapy is a treatment method that requires the accurate positioning of a radioactive source to deliver high doses to a tumor while minimizing exposure to surrounding tissues. Herein, we propose a compact gamma camera system based on a diverging collimator for real-time source positioning during brachytherapy. In the process of developing and fabricating such a gamma camera system, Monte Carlo simulations for diverging and pinhole collimators are performed under conditions that are similar to the actual detection environment, with the camera-to-source distance set at 50 cm to verify the feasibility of the gamma camera. Full width at half maximum (FWHM) and signal-to-noise ratio (SNR) values are analyzed based on the horizontal and vertical profiles at each location as the source shifts stepwise from the center to the right and diagonal direction. On average, the diverging collimator had FWHM values of 18 and 13 mm and SNR values of 30 and 31, while the pinhole collimator had FWHM values of 26 and 25 mm and SNR values of 47 and 46 when profiled horizontally and vertically. The diverging collimator has a lower SNR than pinhole collimator but performs better in terms of spatial resolution. Additionally, to test the performance of the manufactured gamma camera, the distance between the camera and the source was set to 100 cm and an experiment was conducted. The experimental results exhibit a trend similar to the simulation. Numerically, the average FWHM value were 39 mm in the vertical direction and 71 mm in the horizontal direction. Additionally, the average SNR values were 27 for the vertical direction and 17 for the horizontal direction. Based on these results, we confirm the possibility of Ir-192 source imaging.