Phantom dosimeters examined by NMR analysis: a promising technique for 3-D determinations of absorbed dose.

Fricke-infused agarose gels examined by nuclear magnetic resonance (NMR) analysis are inspected, and their response to gamma-rays, thermal neutrons and protons, at radiotherapy dose levels, is examined. The gel composition is chosen with attention to the tissue equivalence for the radiation fields of interest; this problem is crucial, in particular, for thermal neutrons. The feasibility of three-dimensional determination 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. Isodose curve determination in a cylindrical gel phantom exposed to thermal neutrons is presented. A method for depth-dose profiling in tissue exposed to protons is described, and some results are reported which show that the depth-dose data are determinable with millimetric precision. Results obtained with a spectrophotometer from gel augmented with a metal indicator are reported and discussed also. These results show the possibility of obtaining a very sensitive dosimetry technique consisting of spectrophotometric analysis of such a Fricke-gel.