Sophisticated techniques employed in radiotherapy for irradiation of tumours require comprehensive dosimetry allowing for precise, high resolution measurements of radiation dose distribution in three dimensions and verication of treatment planning systems. Polymer gel dosimetry has been shown to be a unique technique for such the purpose. If exposed to ionizing radiation, radical polymerisation and crosslinking of monomeric components take place in a 3D polymer gel dosimeter, leading to the formation of large polymeric structures that scatter visible light. This feature allows for optical observation of the eects of the absorbed dose and its distribution. Presently, magnetic resonance imaging is employed most often for the analysis of the 3D polymer gel dosimeters. However, much attention is also being given to the development of optical computed tomography since this technique is hoped to serve as a substitute for expensive and not easily available magnetic resonance imaging. The optical scanner presented in this work consists of a laser diode, a scanning system and a signal detector. A 3D polymer gel dosimeter is measured in an immersion liquid in order to reduce deection of the light from the dosimeter phantom. The very rst results were obtained with the newly constructed scanner and PABIG nx 3D polymer gel dosimeter, which was inhomogeneously irradiated with 192 Ir brachytherapy source. The results have been contrasted with those for the magnetic resonance imaging and are presented in this work together with the description of the developed instrument. Currently, the optimization of the optical scanner is performed
