Thermoacoustic range verification during conventional dose rate delivery by a synchrocyclotron

Area of Science:

• Medical Physics
• Radiation Oncology
• Ultrasound Technology

Background:

• Proton therapy requires precise range verification to ensure effective treatment delivery.
• Minimizing range uncertainties is critical for maximizing therapeutic outcomes and minimizing off-target radiation.
• Thermoacoustic range verification presents a promising non-invasive method for accurately locating the Bragg peak.

Purpose of the Study:

• To verify a prototype wireless thermoacoustic range verification device.
• To assess the device's minimal disruption to clinical workflows in proton therapy.
• To evaluate the device's performance with a synchrocyclotron-based proton therapy system.

Main Methods:

• A wireless thermoacoustic range verifier with an onboard radiation detector captured emissions from a gelatin ultrasound phantom.
• Proton beams were delivered using a Mevion Hyperscan S250i system with varying energy layers and lateral separations.
• Finite element acoustic simulations, informed by dose maps from RayStation 12A, were used to model beam current and analyze range shifts.

Main Results:

• The wireless range verification system achieved millimeter accuracy, with errors as low as -0.1 ± 1.3 mm when averaging 16 thermoacoustic pulses.
• Best- and worst-case errors across all spots were within ±1.6 mm, demonstrating robust performance.
• Analysis of single-layer data also showed high precision, with errors averaging 0.0 ± 1.3 mm in the best case.

Conclusions:

• A wireless research device for thermoacoustic range verification can be rapidly set up in under 10 minutes.
• The device demonstrated millimeter-level range accuracy in an ultrasound quality assurance phantom.
• This technology holds potential for improving the precision and efficiency of proton therapy.