Dose verification in HDR brachytherapy and IMRT with Fricke gel-layer dosimeters

During the last years, the implementation of highly conformal radiotherapeutic techniques which use high dose gradients has brought the demand of new dosimetric methods for dose distribution measurements. Among the various proposals, gel dosimetry represents a possible dosimetric technique applicable in radiotherapy [1,2]. At the Department of Physics of the Universita degli Studi di Milano in collaboration with the Medical Physics Unit and the Radiotherapy Unit of the Fondazione IRCCS Istituto Nazionale dei Tumori di Milano the research of a dosimetric technique based on Fricke gel layers and optical analysis is under study [3]. In fact, Fricke gel layer dosimeters (FGLD) have various advantages such as the tissue-equivalence for photons in the clinical energy interval [4], the possibility to obtain the spatial information about continuous dose distribution [5] and not only a point dose distribution as it is for example in the case of ionization cambers, TLD or diodes and the possibility to obtain the information about 3D dose distributions [6,7]. In this work, specific applications of FGLD to absolute dosimetry in radiotherapy have been studied, i.e. in-phantom measurements of complex intensity modulated radiation therapy (IMRT) fields and complex brachytherapy fields.