Room: Exhibit Hall | Forum 6
Purpose: Our goal is to investigate the dependence of the X-ray acoustic waves on the absorption parameters.
Methods: We first obtained the pressure waveform due to a point dose absorption using a thermo-acoustic equation governing the heat absorption-pressure induction process. Then, X-ray induced acoustic signal at the detection point was obtained by generalizing point-dose-gradient induced acoustic signal to surface-dose-gradient of a uniform spherical 3D dose distribution. We used the reciprocity principle for pressure waves in fluid media. Therapeutic range of X-ray beam parameters dose rate, spot-size, pulse duration and repetition frequency are obtained from the literature to simulate the induced acoustic signal.
Results: X-ray beam of 1.7 mGy/pulse pulses each with duration of 1 Î¼s with 5x5 cm2 field size on the water medium induces a pressure profile of two crest and troughs with the maximum pressure amplitude of 0.1 Pa at a 10 cm distance from the center of the assumed 3D spherical uniform dose distribution. Based on the power spectrum of the signal, the central frequency is determined as 45.8 kHz.
Conclusion: X-ray induced acoustic signals are observable in conventional cancer radiotherapy and the proposed analytic model achieves a very simple and practical way of predicting and interpreting these signals.