Simulation and experimental detection of radiation-induced acoustic waves from a radiotherapy linear accelerator

Acoustic waves are generated in objects irradiated with megavoltage photon beams produced by a clinical linear accelerator. The detection of such induced acoustic waves (IAWs) has potential applications in radiation therapy dosimetry. This work developed a novel simulation platform to model IAWs by combining radiotherapy Monte Carlo and acoustic wave transport simulation techniques. Simulations and experimental measurements were performed to assess the IAWs when a lead block suspended in a water tank was irradiated with a photon beam produced by a clinical linear accelerator. Simulations correctly predicted the frequency of such IAWs, which allowed improved experimental detection through the development of a custom band-pass filter and signal amplification system. Photon beam energy, lead block depth, and lead block distance from the transducer were varied, and experimental and simulated signals showed the same trends for such set-up changes. These results demonstrate the ability of our simulation platform to accurately predict the frequency spectrum and relative amplitude trends of IAWs. The simulation platform can be applied to assess IAWs in clinically relevant radiotherapy dosimetry situations.