Speaker
Description
- Purpose
Lead halide perovskites (such as CsPbX₃) have been highly spotlighted in the field of solar cells due to their outstanding optoelectronic properties, including excellent charge-carrier mobility and high stopping power.[1] Recently, leveraging these exceptional radiation-responsive characteristics, they have begun to be investigated as novel real-time dosimetric materials in the field of radiotherapy quality assurance (QA), which strictly requires high dosimetric accuracy. Accordingly, this study introduces chlorine-containing mixed-halide perovskites (CsPbX₂Cl) –materials not yet explored in the QA of high-dose-rate brachytherapy (HDR-BT), where the dose gradient changes drastically with distance–to evaluate their clinical feasibility. Notably, a commercial ion chamber (34013, PTW) was employed as a reference dosimeter for comparative evaluation.
- Materials and Methods
The experiments were conducted using an ¹⁹²Ir source (~380 keV) embedded in a clinical HDR-BT system (Flexitron, Elekta). CsPbI₂Cl and CsPbBr₂Cl were selected to fabricate sensors using interdigitated electrodes (IDEs) with an active area of 0.5×0.4 cm² each. To evaluate their feasibility as QA dosimeters, the dose linearity over a range of 1-1000 cGy and the repeatability under 10 repeated irradiations of an identical dose were analyzed for the fabricated sensors and the reference ion chamber. The evaluation criteria were set to a coefficient of determination (R²) > 0.99 and a coefficient of variation (CV) < 1.5%.
- Results and Discussion
The evaluation results demonstrated that all sensors, including the ion chamber, successfully satisfied the established clinical criteria. In the linearity assessment, the ion chamber exhibited R² = 0.9983, while CsPbI₂Cl and CsPbBr₂Cl sensors exhibited excellent dose proportionality with R² = 0.99864 and 0.99997, respectively, fulfilling the criterion. In the repeatability assessment, the ion chamber showed a CV of 0.875%, and the perovskite sensors showed highly stable signal reproducibility with CV values of 0.942% and 0.317%, respectively, proving their suitability as HDR-BT QA dosimeters.
Furthermore, the slope of the linearity graph and the mean Y-axis value of the repeatability graph indicate the sensor's response to the dose, serving as effective indicators of sensitivity. In both metrics, CsPbI₂Cl exhibited higher values, demonstrating superior sensitivity compared to CsPbBr₂Cl. These results are interpreted as the CsPbI₂Cl sensor exhibiting higher responsiveness to ¹⁹²Ir γ-rays due to its relatively higher effective atomic number (Z_eff) which elevates the photoelectric effect, whereas the CsPbBr₂Cl sensor demonstrated a more stable output (higher R² and lower CV) by suppressing background noise through its relatively wider bandgap.[2]
- Conclusion
In conclusion, this study is highly significant as it confirms the clinical feasibility of Cl-containing perovskite materials, which have not been previously addressed in the HDR-BT QA field. Based on these findings, future research will focus on developing customized real-time dosimetry systems optimized for specific clinical purposes—such as high-sensitivity measurements or extreme stability—through halide compositional engineering, ultimately extending their application to actual patient QA environments.
[1] Yakunin, S., Sytnyk, M., Kriegner, D. et al. Detection of X-ray photons by solution-processed lead halide perovskites. Nature Photon 9, 444–449 (2015).
[2] Akkerman, Q. A., D’Innocenzo, V., Accornero, S. et al. Tuning the optical properties of cesium lead halide perovskite nanocrystals by anion exchange reactions. Nano Lett 15, 3691–3696 (2015).
This work was supported by a National Research Foundation of Korea (NRF) grants funded by the Korean government (RS-2025-16066841)