title: Preliminary studies on the role and reactions of tetrakis(hydroxymethyl)phosphonium chloride in polyacrylamide gel dosimeters.
abstract: A major source of dosimetric inaccuracy in normoxic polymer gel dosimeters is local variations in the concentration of oxygen scavenger. Currently, a phosphorus compound, tetrakis(hydroxymethyl)phosphonium chloride (THPC), is the oxygen scavenger of choice in most polymer gel dosimetry studies. Reactions of THPC in a gel dosimeter are not limited to oxygen. It can possibly be consumed in reacting with gelling agent, water free-radicals and polymer radicals before, during and after irradiation, hence affecting the dose response of the dosimeter in several ways. These reactions are not fully known or understood. It is our hypothesis that THPC not only scavenges radical species but also modifies the morphology of the gelatin network and of the polymer, possibly by intervening in the polymerization of monomers. These hypotheses are investigated in an anoxic acrylamide-based gel dosimeter. Scanning electron microscopy results indicate gelatin pores decreasing from 70 to 40 µm and a very different radiation-induced polymer structure in samples containing THPC; Fourier-transform Raman spectroscopy shows a two-fold reduction in the dose constants of monomer consumption; however, a significant change in the relative dose constants of monomer consumption as a function of dose could not be detected.
authors.affiliation: Centre d'imagerie moléculaire de Sherbrooke, Département de médecine nucléaire et radiobiologie, Université de Sherbrooke, Sherbrooke, QC, Canada.
authors.forename: Mahbod
authors.initials: M
authors.lastname: Sedaghat
authors.forename: Rachel
authors.initials: R
authors.lastname: Bujold
authors.forename: Martin
authors.initials: M
authors.lastname: Lepage
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D005782:Gels; D006863:Hydrogen-Ion Concentration; D009943:Organophosphorus Compounds / Q000737:chemistry*; D011874:Radiometry; D000099166:Polyacrylamides
chemical_list: D000180:Acrylic Resins; D005782:Gels; D009943:Organophosphorus Compounds; D000099166:Polyacrylamides; C014850:tetramethylolphosphonium chloride