Purpose: The aims of this study were to investigate the characteristics of contact lens in vivo ocular dosimeter (CLOD) which directly measured the in vivo dose delivered by treatment beam in ocular tumor for proton therapy.
Methods: The proton beam irradiation was carried out using IBA cyclotron PROTEUS 235 at National Cancer Center in Korea. CLOD was composed of biocompatible materials such as LiPCDA, Tartrazine and Sorta clear 40. It was analyzed using an EPSON Expression 10000XL scanner in reflective mode. The analysis of CLODs was used to RIT software (Radiological Imaging Technology, Inc., Colorado Springs, CO, USA). For characteristics evaluation, we had investigated the dose response for RGB channels, linearity, energy & dose-rate dependence, angular dependence and sensitivity.
Results: For RGB channels, the red channel is the most sensitive one among the RGB channels. The results of linearity showed that the CLOD is linearly related to the irradiated dose in the range from 0 to 15 Gy. The energy response obtained for the 122.9, 159.9, 206.9 MeV/u were 0.2%, 1.6% and 1.6% compared to the 147.3 MeV/u. In the range from 1 to 5 Gy/min, the dose rate responses differ by up to 1.8% compared to the 3 Gy/min. The angular dependence normalized to the response at 0 obtained for different angle was also observed to be <2.0% for all angle.
Conclusion: The CLOD has been proven to be an in vivo dosimeter which verify the delivered dose compared to the planned dose for proton therapy. The evaluation of dose characteristics in open field condition shows that the CLOD can be applied to an in vivo dosimeter for ocular tumor in proton therapy.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. NRF-2019R1F1A1063078).