Analysis of experimental acoustic waves induced by high energy pulsed X-ray beams*

X-ray induced acoustic tomography has recently gained attention for its potential use for 3D dose distribution imaging in radiation therapy and for low dose high resolution 3D imaging in diagnostic therapy. X-ray acoustic waves are produced by the temperature rise following the energy absorption from a pulsed photon beam. While the theory for X-ray acoustics is well established, there is little known about how the X-ray source properties affect the acoustic signal strength and frequency. Here, we present current experimental results of the X-ray acoustic signals obtained by two types of X-ray sources; megavoltage energy with a long pulse width (4 us) and kilovoltage energy with short pulse width (10 ns). The effect of the pulse length and the X-ray source energy on the acoustic signals are investigated. Experimental acoustic signals with high signal to noise ratio are generated when the X-rays strike thin sheets (between 0.1-3 mm) of a high Z material in a water tank. The experimental signals are compared to simulated acoustic waves using Monte Carlo modeling combined with a numerical solver for time domain acoustic wave propagation (kWave).