title: Magnetic resonance imaging of radiation dose distributions using a polymer-gel dosimeter.
abstract: A new formulation of a tissue-equivalent polymer-gel dosimeter for the measurement of three-dimensional dose distributions of ionizing radiation has been developed. It is composed of aqueous gelatin infused with acrylamide and N, N'-methylene-bisacrylamide monomers, and made hypoxic by nitrogen saturation. Irradiation of the gel, referred to as BANG, causes localized polymerization of the monomers, which, in turn, reduces the transverse NMR relaxation times of water protons. The dose dependence of the NMR transverse relaxation rate, R2, is reproducible (less than 2% variation) and is linear up to about 8 Gy, with a slope of 0.25 s(-1)Gy(-1) at 1.5 T. Magnetic resonance imaging may be used to obtain accurate three-dimensional dose distributions with high spatial resolution. Since the radiation-induced polymers do not diffuse through the gelatin matrix, the dose distributions recorded by BANG gels are stable for long periods of time, and may be used to measure low-activity radioactive sources. Since the light-scattering properties of the polymerized regions are different from those of the clear, non-irradiated regions, the dose distributions are visible, and their optical densities are dependent on dose.
authors.affiliation: Department of Diagnostic Radiology, Yale University, New Haven, CT 06510, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Maryanski
authors.forename: R J
authors.initials: RJ
authors.lastname: Schulz
authors.forename: G S
authors.initials: GS
authors.lastname: Ibbott
authors.forename: J C
authors.initials: JC
authors.lastname: Gatenby
authors.forename: J
authors.initials: J
authors.lastname: Xie
authors.forename: D
authors.initials: D
authors.lastname: Horton
authors.forename: J C
authors.initials: JC
authors.lastname: Gore
mesh_terms: D000180:Acrylic Resins / Q000032:analysis / Q000528:radiation effects*; D001822:Body Burden; D001918:Brachytherapy / Q000379:methods*; D002588:Cesium Radioisotopes / Q000032:analysis* / Q000627:therapeutic use; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D012062:Relative Biological Effectiveness; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D000180:Acrylic Resins; D002588:Cesium Radioisotopes; C016680:polyacrylamide gels