Purpose: To evaluate the dosimetric characteristics and applications of a
dosimetry system composed of a flexible amorphous silicon thin-film solar cell
and scintillator screen (STFSC-SS) for therapeutic X-rays.
Methods: The real-time dosimetry system was composed of a flexible a Si thin-film solar cell (0.2-mm thick), a scintillator screen to increase its efficiency, and an electrometer to measure the generated charge. The dosimetric
characteristics of the developed system were evaluated including its energy
dependence, dose linearity, and angular dependence. Calibration factors for the
signal measured by the system and absorbed dose-to-water were obtained
by setting reference conditions. The application and correction accuracy of
the developed system were evaluated by comparing the absorbed dose-to water measured using a patient treatment beam with that measured using
the ion chamber.
Results: The responses of STFSC-SS to energy, field size, depth, and sourceto-surface distance (SSD) were more dependent on measurement conditions than were the responses of the ion chamber, although the former
dependence was due to the scintillator screen, not the solar cell. The signals of STFSC-SS were also dependent on dose rate, while the responses
of solar cell alone and scintillator screen were not dependent on dose
rate. The scintillator screen reduced the output of solar cell at 6 and 15
MV by 0.60 and 0.55%, respectively. The different absorbed dose-to-water
measured using STFSC-SS for patient treatment beam differed by 0.4%
compared to those measured using the ionization chamber. The uncertainties of the developed system for 6 and 15 MV photon beams were 1.8
and 1.7%, respectively, confirming the accuracy and applicability of this
system.
Conclusions: The thin-film solar cell-based detector developed in this study
can accurately measure absorbed dose-to-water. The increased signal resulting from the use of the scintillator screen is advantageous for measuring low doses and stable signal output. In addition, this system is flexible,
making it applicable to curved surfaces, such as a patient’s body, and is
cost-effective.
Seonghoon Jeong, Wonjoong Cheon, Dongho Shin, Young Kyung Lim, Jonghwi Jeong, Haksoo Kim, Se Byeong Lee
Proton Therapy Center, National Cancer
Center, Goyang, Korea
Myonggeun Yoon
Department of Bioconvergence Engineering,
Korea University, Seoul, Korea
Med Phys. 2022;49:4768–4779