Gamma emission in hadron therapy : towards new tools of quality assurance

The Gamma-CCB experiment is focused on investigation of gamma emission in experiments modeling the course of hadron therapy. The main goal is to search for manifestation of the Bragg peak in the prompt gamma spectra. Experimental program comprises a series of measurements at different proton beam energies and for various phantom materials. In the two beam times performed by the group so far in CCB Cracow and HIT Heidelberg, data were taken with proton beam energy of 70 and 130 MeV and with three phantom materials: graphite, poly(methyl methacrylate) PMMA and polyoxymethylene POM, in order to study effects from different elements forming human tissue. Two different measurement modes were tested. In the first mode the gamma spectrum integrated over the whole beam penetration path in the phantom was registered, in the other mode only the gamma quanta originating in a phantom slice at a certain depth. In both measurement modes we observe strong correlation of the intensity of the carbon and oxygen excitation lines (4.44 and 6.13 MeV, respectively) with the Bragg peak position. Moreover, the correlation was found to be far more pronounced at backward angles than at the 90° polar angle studied so far.