FLASH Radiation Therapy Using High-Energy X-Rays: Validation of the Flash Effect Triggered by a Compact Device.

PURPOSE: This study investigated whether the Flash effect could be triggered using a compact single high-energy x-ray source (CHEXs) FLASH radiation therapy with or without two 30-second pauses during irradiation in mice.

METHODS AND MATERIALS: The integral dose and beam time structure of the CHEXs were measured using an EBT-XD radiochromic film and a beam current transformer. Healthy C57BL/6J female mice and subcutaneous tumor models were irradiated under different conditions: sham, FLASH radiation therapy (FLASH1: delivering the total dose in 1 delivery; FLASH3: the total dose was split into 3 identical deliveries with two 30-second pauses, simulating gantry rotation time requirements in 3-field conformal radiation therapy), and conventional dose rate radiation therapy. Various total doses were administered to the corresponding normal tissues (whole body, whole thorax, whole abdomen, and skin) and tumors (CT26 and Lewis lung carcinoma). Survival status, normal tissue damage, and tumor growth suppression were recorded.

RESULTS

The average dose rate of the CHEXs ranged from 244 to 388 Gy/s. For whole-body, whole-thorax, and skin irradiation, both FLASH1 and FLASH3 demonstrated protective effects. For whole-abdomen irradiation, FLASH1 exhibited a superior protective effect. No significant differences in tumor growth responses were observed between the FLASH1, FLASH3, and conventional dose rate radiation therapy groups (P > .05).

CONCLUSIONS

Both CHEXs with or without two 30-second pauses during irradiation can trigger the Flash effect. This suggests that CHEXs may be beneficial for 3-dimensional conformal radiation therapy.