(Thursday, 7/18/2019) 10:00 AM - 12:00 PM
Room: 301
Purpose: Verification of delivery is especially important in dynamic delivery such as volumetric modulated arc therapy and scanned particle therapy. Therefore, final objective of our study is to measure the four-dimensional (4D) dose distribution. In this study, we developed the system to measure the three-dimensional (3D) dose distribution using a scintillator and CCD camera and examined the performance.
Methods: Measurement system was composed of a column-shaped plastic scintillator (CoPS), a Gd2O2S: Tb intensifier screen (IS), a truncated cone-shaped mirror (TCsM) and a cooled CCD camera. The CoPS was covered by the IS. The CoPS-IS detection unit was irradiated with 6MV photon beams. Low-level visible lights that generated by CoPS and IS were measured using the CCD camera. Shape of the irradiated field was the square shape (10 mm, 16 mm and 20 mm) and the step shape. Each measured image indicated the irradiated field shape and the depth dose distribution in the CoPS. In performance test, a dose linearity was acquired and a relative dose profiles by measurement were compared with that by radiation treatment planning system (RTPS).
Results: It was found that the relationship between the dose and the light intensity had a good linearity. The field size of the measured 3D dose distribution was in good agreement with that of the calculated data by RTPS. In penumbra region of the lateral dose profiles, the difference between the measured data and the calculated data was within 10 %.
Conclusion: We succeeded in developing the system using the CoPS-IS detection unit for the measurement of 3D dose distribution. Therefore, we suggested that the 4D dose distribution can be calculated from the measured images with timestamp. In future plan, we will correct the spread-out of the scintillation light in the CoPS.
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