In vivo 3D Dose Mapping of Cranial Proton Irradiation Using Proton Acoustic Imaging In a Human Cadaver Model
Abstract
Purpose
While Proton Acoustic (PA) imaging has shown promise for range verification, its application in complex transcranial environments remains under-explored. This study aims to demonstrate the feasibility of in situ 3D dose mapping and localization of pulsed proton beams within a human cadaver head.
Methods
A human cadaver was positioned in a clinical proton therapy system (Hyerscan S250i, Mevion Medical Systems). Proton beam spots were delivered to the brain with a prepared treatment at varying energies (103.23 MeV – 107.66 MeV). The generated PA signals were acquired using a 256-channel matrix array ultrasound transducer positioned on the temporal window. The pressure map was reconstructed with time-reversal (TR) algorithm and the dose map was optimized with a physics-informed neural network (PINN).
Results
The system successfully detected PA signals originating from the brain tissue, demonstrating sufficient signal-to-noise ratio despite transcranial attenuation after hundreds average. The 3D reconstruction visualized the Bragg peak location after PINN training. Gamma analysis with 10%/10 mm between the measured PA dose and the treatment plan revealed high concordance. Furthermore, the system distinguished between different proton beam energies with high temporal resolution, where distinct ultrasound time delays corresponded accurately to the shifts in Bragg peak depth.
Conclusion
This study demonstrates the successful application of 3D proton acoustic dose mapping in a human cadaver brain. The results confirm that PA signals can be detected through the intact skull to accurately reconstruct 3D dose distributions and verify range in real-time. This technology holds significant potential for clinical translation, offering a non-invasive solution for in-patient localization and in vivo dosimetry during cranial proton radiotherapy.