2201 - Dosimetric Characterization and Experimental Validation for the Flat-Panel X-Ray Source, An Electronic Brachytherapy System
Presenter(s)
M. Qi1, Q. Ling2, J. Kang3, S. Luo3, S. Kang4, T. He3, J. Chen4, Y. Xu3, L. Zhou3, and X. Huang5; 1Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Guangdong Key Laboratory of Nasopharyngeal Carcinoma Diagnosis and Therapy, Guangzhou, China, 2Department of Medical Engineering, Nanfang Hospital, Southern Medical University, Guangzhou, China, 3School of Biomedical Engineering, Southern Medical University, Guangzhou, China, 4State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Province Key Laboratory of Display Material and Technology, School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou, China, 5State Key Laboratory of Oncology in South China, Guangdong Key Laboratory of Nasopharyngeal Carcinoma Diagnosis and Therapy, Guangdong Provincial Clinical Research Center for Cancer, Department of Radiation Oncology, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong, China
Purpose/Objective(s): The flat-panel X-ray source (FPXS) is an innovative radiation source that delivers low-kV X-rays with arbitrarily adjustable intensity and customizable radiation fields. These properties position FPXS as a promising candidate for applications in electronic brachytherapy (EB). This study aims to analyze the dosimetric characteristics of FPXS and to verify the feasibility of using FPXS for brachytherapy by conducting irradiation experiments.
Materials/Methods: A low-kV FPXS EB system was constructed for dosimetry measurements and experimental validation, in which the FPXS can be immobilized directly or in insulating oil. The physical beam characteristics of FPXS were quantified using a multimeter, while the surface dose characteristics were measured using a 34013 Chamber, Unidos E electrometer, and RW3 slab phantom. A dose rate-current relationship and the FPXS-based EB workflow were established based on the measured dosimetry characteristics, enabling the calculation of surface dose rates and required exposure times for FPXS at a given prescription dose. The accuracy of the delivered dose and the therapeutic efficacy of FPXS irradiation were verified through brachytherapy experiments conducted on murine models with breast cancer.
Results: The maximum voltage of FPXS is up to 50 kV, the operating current is up to 1 mA, and the surface dose rate is 2.42 Gy/min at the voltage of 50 kV. The surface dose rate and current increase exponentially with the voltage, and the dose rate exhibits a linear correlation with the current. The calculated cumulative dose delivered to mice in the experimental group was slightly higher than the average in-field dose measured by film (21.88±0.61 Gy vs 20.83 ± 1.03 Gy). Following FPXS irradiation, the weight of mice in the experimental group (10 Gy×2 and 20 Gy×1) decreased and then increased, while the weight of mice in the control group (0 Gy) demonstrated minimal fluctuation. The tumor volume of mice in the control group exhibited a significantly faster growth rate compared to the experimental group, and the average volume of the control group on day 29 was approximately 1.5 times that of the experimental group. The survival rate of mice in the experimental group over time was significantly higher than that of the control group, which was 58.33% vs 12.50% at day 29. The dose fraction also affected the survival rate, which was 83.33% vs 33.33% for group 1 (10 Gy×2) and group 2 (20 Gy×1) at day 29.
Conclusion: The physical characteristics of FPXS are comparable to current EB devices and the surface dose rate is adequate. Animal irradiation experiments validate the accuracy of FPXS-delivered doses and the effectiveness of tumor irradiation. This work presents a novel electronic brachytherapy system, which will further promote the clinical application of FPXS for brachytherapy.