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KMID : 1038720190300040112
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Progress in Medical Physics
2019 Volume.30 No. 4 p.112 ~ p.119
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Therapeutic Proton Beam Range Measurement with EBT3 Film and Comparison with Tool for Particle Simulation
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Lee Nu-Ri
Kim Chan-Kyu
Song Mi-Hee
Lee Se-Byeong
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Abstract
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Purpose: The advantages of ocular proton therapy are that it spares the optic nerve and delivers the minimal dose to normal surrounding tissues. In this study, it developed a solid eye phantom that enabled us to perform quality assurance (QA) to verify the dose and beam range for passive single scattering proton therapy using a single phantom. For this purpose, a new solid eye phantom with a polymethyl-methacrylate (PMMA) wedge was developed using film dosimetry and an ionization chamber.
Methods: The typical beam shape used for eye treatment is approximately 3 cm in diameter and the beam range is below 5 cm. Since proton therapy has a problem with beam range uncertainty due to differences in the stopping power of normal tissue, bone, air, etc, the beam range should be confirmed before treatment. A film can be placed on the slope of the phantom to evaluate the Spread-out Bragg Peak based on the water equivalent thickness value of PMMA on the film. In addition, an ionization chamber (Pin-point, PTW 31014) can be inserted into a hole in the phantom to measure the absolute dose.
Results: The eye phantom was used for independent patient-specific QA. The differences in the output and beam range between the measurement and the planned treatment were less than 1.5% and 0.1 cm, respectively.
Conclusions: An eye phantom was developed and the performance was successfully validated. The phantom can be employed to verify the output and beam range for ocular proton therapy.
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KEYWORD
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Proton therapy, Melanoma, Radiotherapy setup errors, Radiotherapy computer-assisted, Film dosimetry
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