Ionoacoustics for range monitoring of proton therapy

Proton beams exhibit favourable interaction properties for highly conformal tumour dose delivery with better sparing of surrounding healthy tissue and critical structures in comparison to widely established photon beams. However, full clinical exploitation of these advantages is still hampered by treatment uncertainties, particularly related to the stopping position of protons in tissue, determining the so called Bragg peak, where protons release most of their energy. Hence, several approaches are currently investigated to enable an in-vivo, ideally real-time verification of the proton beam range in the patient. While most of the considered techniques aim at exploiting secondary emissions from nuclear interactions, interest is being regained for alternative, cost-effective solutions exploiting acoustic emissions originating from ion interaction in tissue. This contribution will thus address the basics and recent experiments of this so called ⁱonoacoustics for pre-clinical and clinical beam energies.