Gel dosimetry by magnetic resonance imaging

VEDELAGO J; PARABUÉ M; VALENTE M; CHACÓN D; MARANGONI A; ARNUZ A; MATTEA F

Pucón

Conferencia; VI Conference on Medical Physics at La Frontera; 2018

Gel dosimetry is a versatile tool for determining three dimensional dose distribution in radiation therapy applications. These dosimeters consist mainly of a gelatin matrix and some chemical species that make energy deposition quantification possible. Post-irradiation readout methods may differ according to gel type. Nevertheless, optical transmission and magnetic resonance are the two most commonly used techniques, which are capable of determining three dimensional dose distributions thanks to optical density or proton density difference in the material, respectively. The present study is focused on magnetic resonance imaging of irradiated gel dosimeters. Irradiations were carried out with a 6 MV photon beam from a clinical linear accelerator. Quantitative magnetic resonance images were acquired with a Philips Intera 1.5 T scanner using an eight-element neurovascular head coil. The obtained magnetic resonance signal was fitted according to previously reported models in order to calculate relaxation maps, then these maps were correlated to the absorbed dose values in the gels. The proposed protocols and calibration methods proved to be suitable for absolute dose distribution determination.