Wavelet-based Protoacoustic Signal Denoising for Proton Range Verification

Protoacoustics, the measurement of the pressure waves emitted by thermal expansion resulting from proton dose deposition, may be used to obtain the depth of the Bragg-peak (BP) by measuring the time-of-flight of the pressure wave. However, using the method in the clinic has a drawback since numerous measured signals were averaged to identify the accurate signal peak from the indistinguishable noises. We proposed a wavelet-based denoising method to significantly reduce noise in collected protoacoustic signals and improve the BP identification accuracy with fewer signal averages. The average 1024 signal, which has been used in the published study, was used as the reference to identify the accurate acoustic location. We used Daubechies (db) 4 wavelet transform to decompose the collected signals to recover the useful protoacoustic signals. Our approach was able to identify the BP signal up to the average 8 signals that correspond to the dose (<1.5 Gy). This denoising technique would be useful for future 2D/3D protoacoustic imaging and make protoacoustic clinically useful for proton range verification.