Qi Mengke, Luo Sifu, Wu Wangjiang, Kang Jing, He Ting, Dai Jiancong, Kang Song, Chen Jun, Song Ting, Li Yongbao, Ouyang Bin, Zhou Linghong, Xu Yuan
School of Biomedical Engineering, Southern Medical University, Guangzhou, Guangdong, China.
Department of Radiation Oncology, State Key Laboratory of Oncology in South China, Sun Yat-sen University Cancer Center, Collaborative Innovation Center for Cancer Medicine, Guangzhou, Guangdong, China.
Med Phys. 2025 Jul;52(7):e17988. doi: 10.1002/mp.17988.
The flat-panel x-ray source (FPXS) is an innovative x-ray source comprising millions of micro sources that emit low-energy x-rays. To date, the dosimetric characteristics of FPXS remain unclear, limiting its clinical applications.
This study aims to characterize the physical and dosimetric characteristics of FPXS through Monte Carlo (MC) dose calculation and experimental dosimetry measurements and to analyze the feasibility of FPXS as an electronic brachytherapy (EB) unit.
A measurement setup and two specialized measurement platforms were developed. By using an energy spectrometer, ionization chamber, and Gafchromic film, a measurement procedure for physical beam characteristics and dosimetric characteristics of FPXS was established, and a series of experimental measurements were conducted. A previously in-house developed MC simulation toolkit, designated gFPDMC, was employed to perform FPXS structure simulation and parallel dose calculation. The measured dose distributions were compared with the gFPDMC-calculated dose distributions, thereby validating the accuracy of gFPDMC.
The measured energy spectra are consistent with the MC-simulated spectra with mean relative error (MRE) values < 9% and an average energy difference < 1.40%. The measured surface dose rate of FPXS increases exponentially with the operating voltage, with a maximum dose rate of 2.45 Gy/min at 40 kV; the depth dose rate decreases exponentially with the measurement depth and increases with the operating voltage. The doses calculated by gFPDMC, DOSXYZnrc, and Geant4 exhibit excellent consistency, with mean absolute error (MAE) values of 0.31% and 0.40%. The gFPDMC-calculated percentage depth dose (PDDs) exhibit identical voltage-dependent depth dose characteristics as measured PDDs, with deviations < 4%.
The precision of gFPDMC was rigorously validated through comparison with DOSXYZnrc, Geant4, and experimentally measured dose. Adequate operating voltage and suitable dose rate demonstrate the feasibility of FPXS as an EB unit.
平板X射线源（FPXS）是一种创新的X射线源，由数百万个发射低能X射线的微源组成。迄今为止，FPXS的剂量学特性仍不明确，限制了其临床应用。
本研究旨在通过蒙特卡罗（MC）剂量计算和实验剂量学测量来表征FPXS的物理和剂量学特性，并分析FPXS作为电子近距离治疗（EB）装置的可行性。
开发了一种测量装置和两个专门的测量平台。通过使用能谱仪、电离室和Gafchromic薄膜，建立了FPXS物理束流特性和剂量学特性的测量程序，并进行了一系列实验测量。使用先前在内部开发的MC模拟工具包gFPDMC进行FPXS结构模拟和并行剂量计算。将测量的剂量分布与gFPDMC计算的剂量分布进行比较，从而验证gFPDMC的准确性。
测量的能谱与MC模拟的能谱一致，平均相对误差（MRE）值<9%，平均能量差<1.40%。FPXS测量的表面剂量率随工作电压呈指数增加，在40 kV时最大剂量率为2.45 Gy/min；深度剂量率随测量深度呈指数下降，并随工作电压增加。gFPDMC、DOSXYZnrc和Geant4计算的剂量表现出极好的一致性，平均绝对误差（MAE）值为0.31%和0.40%。gFPDMC计算的百分深度剂量（PDDs）与测量的PDDs表现出相同的电压依赖性深度剂量特性，偏差<4%。
通过与DOSXYZnrc、Geant4和实验测量剂量进行比较，严格验证了gFPDMC的精度。足够的工作电压和合适的剂量率证明了FPXS作为EB装置的可行性。
