Online Verification for a Vhee Flash Beam
Abstract
Purpose
Numerous studies have shown that Very High Energy Electrons (VHEE), in conjunction with Ultra High Dose Rate (UHDR) delivery, could effectively treat deep-seated tumors. This combination has the potential to enhance the treatment plan's efficacy while reducing overall treatment duration. However, UHDR poses risks, as any misalignment of the patient can lead to significant exposure of surrounding healthy tissues to radiation. This study aims to develop a method for Online Verification (OV) of treatment by detecting the emission of secondary particles.
Methods
Similar to what has been achieved in proton therapy, we identified relevant secondary particles for OV. We quantified the relative contributions of three particle types: neutrons, gamma rays from annihilation processes (GAP), and prompt gamma rays (PG). Monte Carlo simulations were conducted to calculate the fluence of these particles outside a cylindrical water phantom, comparing VHEE and proton beams. Subsequently, we evaluated different methods for determining the maximum dose depth and assessed the sensitivity of the calculations to the detected signal (secondary particle fluence). We then introduced various heterogeneities (e.g., lungs) into the phantom to test their effects.
Results
Our findings indicate that GAP and PG are the most promising secondary particles for OV of VHEEs. VHEE beams also demonstrated a higher number of emitted PG and GAP compared to proton beams. We confirmed that the location of the depth-dose profile maximum can be verified by the maximum fluence measured in a water phantom. The lung insert altered the fluence profile, enabling us to detect heterogeneity effectively.
Conclusion
This preliminary study demonstrates the feasibility of an online verification for VHEE beams using secondary particle emissions. Further research is needed to explore advanced detection methods and test more realistic treatment plans.