PHANTOM DOSIMETERS EXAMINED BY NMR ANALYSIS - A PROMISING TECHNIQUE FOR 3-D DETERMINATION OF ABSORBED DOSE

Fricke-infused agarose gels examined by nuclear magnetic resonance (NM R) analysis are inspected, and their response to gamma-rays, thermal n eutrons and protons, at radiotherapy dose levels, is examined. The gel composition is chosen with attention to the tissue equivalence for th e radiation fields of interest; this problem is crucial, in particular , for thermal neutrons. The feasibility of three-dimensional determina tion of absorbed dose in Fricke-gel phantoms is investigated, and the possibility of employing the technique in conformal therapies, such as boron neutron capture therapy (BNCT) and proton therapy, is tested. I sodose curve determination in a cylindrical gel phantom exposed to the rmal neutrons is presented. A method for depth-dose profiling in tissu e exposed to protons is described, and some results are reported which show that the depth-dose data are determinable with millimetric preci sion. Results obtained with a spectrophotometer from gel augmented wit h a metal indicator are reported and discussed also. These results sho w the possibility of obtaining a very sensitive dosimetry technique co nsisting of spectrophotometric analysis of such a Fricke-gel. (C) 1997 Elsevier Science Ltd. All rights reserved.