Therapeutic proton beams: LET, RBE and microdosimetric spectra with gas and silicon detectors

A sealed mini-TEPC able to work in gas-steady modality, a monolithic silicon device composed by a matrix of micrometric cylindrical diodes and a residual energy measurement stage and the silicon MicroPlus Bridge detector were used to perform microdosimetric measurements at the 62 MeV proton clinical SOBP of CATANA at the Southern National Laboratories of INFN (LNS – INFN, Catania, Italy). Measurements were taken at the same different positions in a PMMA phantom, in order to analyse the detector response differences. Finally, a weighting function was applied to the spectra to see if the microdosimetric detectors are able to monitor RBE data for glioma cells (U87) irradiated at six positions along the same modulated 62-MeV proton beam. The results obtained with the three microdosimeters are compared and discussed.