Development and Advanced Characterization of an X-Ray Flash Benchtop
Abstract
Purpose
Ultra-high dose rate (FLASH) irradiation has demonstrated the potential to spare normal tissue while maintaining tumor control, yet its underlying mechanisms remain unclear, particularly for low-energy X-rays where radiation quality and linear energy transfer (LET) vary strongly with beam energy and depth. The purpose of this work is to develop and dosimetrically characterize an improved benchtop kV X-ray FLASH system based on a commercial small-animal irradiator, enabling systematic investigation of FLASH irradiation under both constant and variable LET conditions using conventional X-ray tube technology.
Methods
A commercial orthovoltage irradiator was upgraded to a high-power configuration, 6kW, and equipped with a newly developed fast mechanical shutter optimized for ultra-short irradiation times. Dosimetric characterization was performed for filtered and unfiltered beams at tube potentials of 119–200kVp. Absolute dose and dose-rate measurements were conducted using synthetic diamond detectors, newly commissioned ionization chambers, and radiochromic films. Percentage depth dose measurements were performed in water-equivalent material at millimeter-scale depths. Monte Carlo modeling of the X-ray tube and dosimeters was performed using BEAMnrc, EGSnrc, and egs++, including explicit modeling of ionization chamber components and backscatter effects. Spectral verification was additionally performed using SpekPy. Initial in-vitro clonogenic assays were conducted using HaCaT-keratinocytes and SAS oral squamous cell carcinoma cells.
Results
The upgraded system achieved dose rates exceeding 40Gy/s under filtered conditions and up to 66Gy/s for unfiltered beams at short source-to-sample distances. Percentage depth dose measurements demonstrated dose rates above 37Gy/s at 1mm water-equivalent depth. Monte Carlo simulations agreed with experimental dose and HVL measurements within 5% for filtered configurations. The new shutter design enabled reproducible high-power irradiations with minimal temporal uncertainty.
Conclusion
A high-power benchtop X-ray FLASH system was successfully developed and rigorously characterized, providing a robust platform for future investigations of the role of radiation quality in the FLASH effect using conventional X-ray sources.