Chinh Nguyen, “Pre-Amplifier Characterization and K-Wave Simulations”
Mentor: Sarah Patch, Physics

In cancer treatment, most patients will go through a “CatScan” before undergoing proton therapy. In the days between the “CatScan” and proton therapy, patients’ organs may move several centimeters. Our research focuses on range verification with a direct correlation to the underlying anatomy. Although there are procedures to stop the treatment when equipment failure is detected, there is no safety net when it comes to the changes in anatomy. Modified K – wave software used the initial pressure distribution taken from Monte Carlo simulations of dose deposited by a clinical proton beam to model thermoacoustic measurements at select receiver positions.A hydrophone can be used to observe thermoacoustic pulses generated by a proton beam scattering through a phantom. Simulations of thermoacoustic pulses generated by clinical proton beams are bandlimited below 100kHz, with amplitudes below 1 mV so preamplifiers are needed. We tested a commercial preamplifier by conducting a pitch-catch experiment, using the same piezoelectric element models for both hydrophones to transmit and “listen”. The experiment was conducted in different media such as water, oil and coconut milk to mimics the different layers in human anatomy. The results indicated that the commercial product was bandlimited below 50 kHz. Hence, we ordered a custom preamp and repeated the experiments to confirm bandwidth exceeding 100 kHz, which suffices for proton therapy. Whether this preamplifier would suffice for carbon ion therapy remains to be determined. Furthermore, the preamplifiers were grounded to avoid electrical noise that could corrupt the data.