Beam intensity and stability control on a modified clinical linear accelerator for FLASH irradiation

Area of Science:

• Radiation oncology
• Radiobiology
• Medical physics

Background:

• The FLASH effect, utilizing ultra-high dose-rate (UHDR) irradiations, shows promise for improving cancer treatment outcomes.
• Understanding UHDR biological mechanisms is crucial for biodosimetry and developing radiological medical countermeasures.
• Achieving stable, reproducible UHDR electron beams with modified clinical linear accelerators (Linacs) remains a significant challenge.

Purpose of the Study:

• To investigate the impact of key parameters on electron beam intensity stability in a modified Varian Clinac 2100 C.
• To develop a parameter-tuning method for adjusting beam intensity and enhancing stability in UHDR electron beams.
• To improve pulse-by-pulse stability and trial-by-trial reproducibility for preclinical FLASH irradiators.

Main Methods:

• Systematic investigation of standing-wave linear accelerator parameters: electron gun current, pulse-forming network voltage, and auto-frequency control.
• Development and application of a parameter-tuning methodology for UHDR electron beam intensity adjustment.
• Validation of beam stability and reproducibility through multiple biological experiments.

Main Results:

• Enabled fine-tuning of dose-per-pulse without physical modifications to the Linac.
• Significantly reduced beam fluctuations, especially during cold starts.
• Achieved enhanced pulse-by-pulse stability and trial-by-trial reproducibility, validated biologically.

Conclusions:

• The study provides practical methods for enhancing UHDR electron beam stability and reproducibility in modified clinical Linacs.
• The developed techniques allow for intensity tuning, crucial for preclinical FLASH irradiator development.
• This work supports the advancement of FLASH radiotherapy research by enabling more reliable preclinical studies.