New method for obtaining position and time structure of source in HDR remote afterloading brachytherapy unit utilizing light emission from scintillator

When using a HDR remote afterloading brachytherapy unit, results of treatment can be greatly influenced by both source position and treatment time. The purpose of this study is to obtain information on the source of the HDR remote afterloading unit, such as its position and time structure, with the use of a simple system consisting of a plastic scintillator block and a charge-coupled device (CCD) camera. The CCD camera was used for recording images of scintillation luminescence at a fixed rate of 30 frames per second in real time. The source position and time structure were obtained by analyzing the recorded images. For a preset source-step-interval of 5 mm, the measured value of the source position was 5.0 +/- 1.0 mm with a pixel resolution of 0.07 mm in the recorded images. For a preset transit time of 30 s, the measured value was 30.0 +/- 0.6 s, when the time resolution of the CCD camera was 1/30 s. This system enables us to obtain the source dwell time and movement time. Therefore, parameters such as 192Ir source position, transit time, dwell time, and movement time at each dwell position can be determined quantitatively using this plastic scintillator-CCD camera system.