Bragg Peak Live Monitoring

Testbeam in Cracow Karim Laihem Krakow experiment: Test-beam experimental setup.

The optimization of a hadron therapy for clinical cancer treatment needs a real-time monitoring of the longitudinal Bragg-peak position inside the patient body (PTV). Several non-invasive techniques have been proposed that exploit the detection of prompt gamma-rays issued from nuclear interactions of the irradiated region. A precise determination of the ion range in the patient tissue can be reached by exploiting the prompt-gamma emission with an imaging device using a Compton Camera principle. This device would allow to monitor and control the Bragg-peak position and the delivered dose in the target volume already during treatment.

The main goal of the current project is in a first step the investigation of the correlation between prompt-γ emission and longitudinal dose distribution during proton therapy. This is done by systematic measurements of the γ emission cross section for reactions induced by protons interacting with phantoms simulating human tissue. The measurements are carried out at Krakow Hadron-therapy center with proton kinetic energies of 70 MeV and will be extended for higher energies around 150 and 230 MeV. The angular distributions for strong γ transitions between discrete states as well as the continuum spectra will be measured. The experiments will be performed for three different target materials, with the thickness increasing from 1.5 cm up to several millimeters above the proton range in the material.

Obtained data will allow to search for a correlation between the characteristics of γ spectra and a place in the target, where the reaction occurred. Parametrized distributions of γ-ray emission will be made available to researchers implementing the cross sections to advanced simulation tools as GEANT4 or programs like TALYS. This will allow to perform a more precise calculations applied e.g. in hadron therapy. Known correlation between the depth of penetration of the beam in thick targets (i.e. the Bragg peak position) and the spectral and angular distribution of the emitted γ radiation will be very important in the development of methods for monitoring of absorbed dose in hadron therapy. The development of these methods based on the results of the current project will have a strong influence on the accuracy of hadron therapy, thereby minimizing side effects for the patient.