A new method for dosimetry standardization using 137Cs biological irradiator based on Fricke solution

Abstract

Radiobiological experiments such as small animal whole or partial body irradiation, cell culture irradiation, tissue culture irradiation, require accurate and reproducible irradiation dosimetry to allow the work to be interpreted and repeated and for valid comparisons to be made by other laboratories. Limited standardized protocols are available for small animal dosimetry when using 137Cs irradiators.Methods for mapping dose distributions and to determine the regions of isodose such as Gafchromic film, ionization chambers or arrays of Thermoluminescent Dosimeters (TLDs) may result in low-resolution mappings, is very laborious, time-consuming and allows for dosimeter placement inaccuracies in regions of high-dose gradients. Our new approach takes advantage of Fricke solution properties and has been adapted so that it can be performed in 96-well plates. Fricke dosimetry depends on the oxidation of ferrous ions (Fe2+) to ferric ions (Fe3+) by ionizing radiation. The increased concentration of ferric ions is measured spectrophotometrically at 304nm. The Fricke dosimeter is 96% water by weight; therefore, it lends itself well to a determination of absorbed dose to water. This dosimeter is used in a dose range of 5–400Gy and for dose rates of up to 106Gy/s.This new methodology approach allow us to have an absolute dosimetry system, with proven performance, having 96 independent dosimeters on plates of small dimensions. A 3D array of hundreds of independent dosimeters analyzed with a mathematical software to create 3D-surface plots lead that absorbed dose can be estimated in virtually any area of the chamber.Our method could be used for standardization of dosimetry within and between laboratories and for intercomparison programs, which is becoming clear that is needed to be implemented for the radiobiology research procedures.