Proton therapy is a promising cancer treatment modality with the ability to concentrate the deposited dose (Bragg peak) on the tumour while minimising collateral damage due to low dose to healthy surrounding tissue. However, uncertainties in the Bragg peak position limit clinical utility. Especially due to range uncertainties, patient movement and tissue deformation, the localisation accuracy is restricted to ca. 0.5-1.0 cm.

To exploit full advantage of proton therapy, real-time dosimetry is crucial to enable precise dose deposition with accuracies down to ~1 mm. Real-time dosimetry could significantly improve the clinical outcome of proton therapy of irregularly shaped tumours near vital organs and in moving anatomies. The objective is to develop a real-time accurate localisation technology based on ionoacoustics, by measuring thermoacoustic waves emitted at the Bragg peak during pulsed proton irradiation with an innovative ultra-sensitive Optical Micromachined Ultrasound Sensor (OMUS).