Speakers
Description
Jyun-Wei Jheng1, Shih-Yao, Chiou1, Tsz-Yui Chan2, Sen-Hao Lee3, Tsi-Chian Chao1,2,3,4,5, I-Chun Cho1,5
1 Radiation Research Core Laboratory, Chang Gung Memorial Hospital Linkou Branch, Taoyuan, Taiwan.
2 Department of Medical Imaging and Radiological Sciences, Chang Gung University, Taoyuan, Taiwan.
3 Department of Radiation Oncology, Chang Gung Memorial Hospital Linkou Branch, Taoyuan, Taiwan.
4 Department of Radiation Oncology, New Taipei Municipal Tucheng Hospital, New Taipei City, 236, Taiwan
5 Medical Physics Research Center, Institute for Radiological Research, Chang Gung University, Taoyuan, Taiwan.
E-mail: afsgf65445550@gmail.com
Objective: The aim of this study was to develop an irradiation system for small-field (< 2×2 cm²) proton FLASH mouse studies. This technique, characterized by its ability to administer radiation at extremely high dose rates (> 40 Gy/s), presents unique challenges in ensuring dose accuracy, maintaining consistent subject positioning, and achieving homogenous dose distribution within the target area.
Methods: To ensure accurate real-time dose monitoring, a Transmission Ionization Chamber (TIC) was employed, meticulously calibrated with a PTW Pinpoint Ionization Chamber for precision. To precisely target the designated area on the mouse model, the irradiation field was defined using four secondary brass collimators—two circular, with diameters of 1 cm and 2 cm, and two square, with dimensions of 1 cm and 2 cm—positioned subsequent to a lead scatter and a primary brass collimator. The beam's energy consistency and qualitative integrity were verified through Integrator Depth Dose (IDD) measurements utilizing a chamber and water tank configuration, complemented by the application of EBT3 film to evaluate the dose distribution at the mouse immobilization site.
Results: The TIC, crucial for the FLASH application, showed significant stability and accuracy with a dose monitoring uncertainty of less than 3%. The average proton energy was measured at 231.7 MeV, with the R80d depth in water—indicative of the proton dose's penetration—recorded at 315.57 mm.
Conclusions: The irradiation platform developed in this study reliably produces a 1cm x 1cm square proton beam for FLASH irradiation experiments, with dose monitoring effectively managed by a specially designed TIC. This advancement provides a robust foundation for precise and controlled small-field irradiation research, with potential implications for the future of radiobiological and oncological studies.
Keyword
Proton, FLASH, irradiation platform, dosimetry
