Performance analysis of ionoacoustic signal reconstruction algorithms for proton-beam range verification in heterogeneous medium

Proton therapy requires precise range verification to ensure accurate dose delivery within the tumor and to minimize irradiation of surrounding healthy tissues. Ionoacoustic imaging has emerged as a promising technique for in-vivo range monitoring, exploiting acoustic signals generated at the Bragg peak. In this study, we evaluate three acoustic image reconstruction methods—Time Reversal (TR), Synthetic Aperture (SA), and Delay-and-Sum (DAS)—using anatomically realistic simulations based on a prostate CT slice extracted from a patient DICOM dataset. The Bragg peak dose distribution was used as the initial acoustic source, and acoustic wave propagation was simulated in k-Wave with spatially varying acoustic properties mapped from the CT. Acoustic signals recorded by sensor arrays placed along the prostate boundary were reconstructed with TR, SA, and DAS algorithms. Reconstruction quality was quantified using Full Width at Half Maximum (FWHM), localization error, signal-to-noise ratio (SNR), and computation time. TR yielded the best spatial accuracy and SNR but required higher computational time. DAS provided the fastest reconstruction but with reduced resolution and noise robustness. SA demonstrated intermediate performance, balancing accuracy and efficiency. These results demonstrate the feasibility of ionoacoustic imaging for proton range verification in anatomically realistic prostate tissue and provide guidance on algorithm selection for clinical translation.