Abstract
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±1.0mm, 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 enabled us to obtain the source dwell time and movement time. Therefore, parameters such as I192r source position, transit time, dwell time, and movement time at each dwell position can be determined quantitatively using this plastic scintillator‐CCD camera system.PACS number: 87.53.Jw
Highlights
Brachytherapy, a type of modern radiotherapy for cancer treatment, usually uses a high-dose rate (HDR) 192Ir source
Because the preset source-step-interval was 5 mm, this value satisfied the tolerance of quality assurance (QA) for the source position of HDR remote afterloading units in TG40
The decision precision was such that it allowed us to estimate source position and source movement distance, because this was equal to the pixel resolution (0.069 mm) of the scintillation luminescence image
Summary
Brachytherapy, a type of modern radiotherapy for cancer treatment, usually uses a high-dose rate (HDR) 192Ir source. Accurate control of source position and time using a HDR remote afterloading unit is critical to ensure the effectiveness of the treatment. The estimation of source position and time of the HDR remote afterloading unit is included in the QA test (as reported in AAPM Radiation Therapy Committee Task Group 40 (TG40)).(1) The tolerance at the source position is 1 mm, and the test is conducted every week. Many studies have been conducted to obtain information on the source for QA checks of remote afterloading units. These studies involved the use of a film,(2) a well-type ionization chamber,(3-4) a radiochromic film,(5-6) and a fluorescent screen.[7] Li et al[8] designed a QA test tool consisting of two concentric disks
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