Dosimetric characteristics of active solid state detectors in a 60 MeV proton radiotherapy beam

The solid state active detectors, widely used for conventional radiotherapy, such as diamond detectors (DD) and diodes may be attractive tools also in dosimetry of therapeutic proton beams. Diodes are broadly applied in oncology clinics and routinely used for in-vivo dosimetry [1, 8]. These real-time detectors are rugged, relatively inexpensive and provide on-line readings, what allows for quick correction of errors encountered during dose delivery. Since a long time, diamonds have been considered as a promising tool for clinical dosimetry, but the dosimeters based on natural diamonds are expensive and hardly available. Synthetic diamond (CVD) is potentially one of the most interesting materials in the field of detectors applicable in dosimetry. Diamond detectors, working as solid state ionization chambers, are considered to be tissue equivalent which is an advantage for clinical dosimetry. Commercially available DD offered by PTW are currently produced from natural diamonds. It was reported that the sensitivity of PTW DD was independent of the photon beam quality, and in the electron beam energy in the therapeutic range [5]. Similarly, the CVD diamond, tested in photon, electron and proton beams, has sufficient sensitivity to be used as a dosimeter [3]. One of the problem is the effect of dose rate dependence which needs to be corrected, e.g. using Fowler’s model, which introduce the Δ parameter, describing the deviation from the linearity [3, 5]. In proton beam dosimetry the Dosimetric characteristics of active solid state detectors in a 60 MeV proton radiotherapy beam Urszula Sowa, Tomasz Nowak, Barbara Michalec, Gabriela Mierzwińska, Jan Swakoń, Paweł Olko