Characterization of a practically designed plastic scintillation plate dosimeter

Background

Advancements in radiotherapy have enabled the use of high-definition irradiation, leading to more precise and finely adjusted treatments in clinical settings. Nevertheless, the attainment of high resolution, an extensive measurement area, and the repeatability of dose distribution measurements persist as challenges in clinical practice, thereby often requiring multiple dosimetry systems to overcome measurement constraints. Consequently, there is a significant need to develop a dosimeter that offers both a high resolution and a capability for repeated use.

Purpose

A practical scintillation plate dosimeter was designed and its dosimetric characteristics were evaluated using x-ray beams from a linear accelerator.

Methods

A practical scintillation plate dosimeter comprised a 0.2 cm-thick scintillation plate sandwiched between a pair of 2.0 cm-thick Polymethyl methacrylate (PMMA) plates. A Complementary Metal Oxide Semiconductor (CMOS) camera was used to detect the scintillation light emitted from the scintillation plate when the x-ray beams were delivered to the plate. Measurements were made at 6 MV to test the dose linearity, reproducibility, and dependencies on the camera temperature and angles of incidence. The dose-rate dependency was also measured using 6 and 10 MV flattening filter-free (FFF) beams. The x-ray energy dependency was further tested using 4 MV, 6 MV, 10 MV, 6 MV FFF, and 10 MV FFF beams.

Results

A maximum linearity error of 0.4% was observed for doses ranging from 10 to 1000 MU. The coefficient of variation for the dose reproducibility was ± 0.062%, the temperature dependency was 0.07%/°C, and the angular variations were within ± 1.3% after the removal of Cherenkov light. The dose output decreased by 5.0% at 45 MU/min, compared with that at 1300 MU/min with the 6 MV FFF beams, and by 2.0% at 160 MU/min, compared to 1900 MU/min with the 10 MV FFF beams. The dependency of x-ray energy ranged from −2.1% to +1.4%.

Conclusions

The practical scintillation plate dosimeter showed favorable dose characteristics that can be applied in patient-specific quality assurance for volumetric modulated arc therapy.