A low-pressure ionization chamber for real-time dose monitoring in electron FLASH radiotherapy

Jrong Zhao^1,2Yiwei Yang²Luyan Tao¹Yi Zhang^2,3Baoqian Li¹Peng Luan¹Jing Liu¹Shilan Wang²Yinghong Tang²Song Feng^1*

• ¹School of Nuclear Science and Technology, University of South China, Hengyang, Hunan Province, China
• ²Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang, China
• ³School of Nuclear Science and Technology, Lanzhou University, Lanzhou, Gansu Province, China

Electron FLASH radiotherapy has emerged as a promising modality for next-generation cancer treatment, while accurate real-time monitoring the delivering dose is a challenging mission in both preclinical and clinical applications. To reduce the ion recombination in gasous detectors resulted by intensive beams, a low-pressure ionization chamber (LPIC) has been designed and constructed. The LPIC consisted of two independent and sealed chambers at a pressure of about 300 Pa for simultaneous beam monitoring to avoid cross interference. The performance of the LPIC has been tested using a dedicated electron FLASH accelerator to assess its response of dose linearity and reproducibility. The dose rate was about from 2 Gy/s to 500 Gy/s at the normal treatment distance and the LPIC was placed at the beam exit window of the accelerator. The dose response of the LPIC was found with an excellent linearity. The reproducibility of measuring same condition pulses has been performed, and the coefficient of variation has been found within 0.5%.The developed LPIC has been proved as reliable dosimeter capable of quantifying accelerator performance and electron beam pulses, and meets the criterion of clinical applications. This type of gasous detector provides a practical solution for real-time dose monitoring in electron FLASH radiotherapy.