A Radio-Fluorogenic Polymer-Gel Makes Fixed Fluorescent Images of Complex Radiation Fields

Abstract

We review the development and application of an organic polymer-gel capable of producing fixed, three-dimensional fluorescent images of complex radiation fields. The gel consists for more than 99% of γ-ray-polymerized (~15% conversion) tertiary-butyl acrylate (TBA) containing ~100 ppm of a fluorogenic compound, e.g., maleimido-pyrene (MPy). The radio-fluorogenic effect depends on copolymerization of the MPy into growing chains of TBA on radiation-induced polymerization. This converts the maleimido residue, which quenches the pyrene fluorescence, into a succinimido moeity (SPy), which does not. The intensity of the fluorescence is proportional to the yield of free-radicals formed and hence to the local dose deposited. Because the SPy moieties are built into the polymer network, the image is fixed. The method of preparing the gel and imaging the radiation-induced fluorescence are presented and discussed. The effect is illustrated with fluorescent images of the energy deposited in the gel by beams of X-rays, electrons, and protons as well as a radioactive isotope.

A Polymer-Gel Eye-Phantom for 3D Fluorescent Imaging of Millimetre Radiation Beams

“…Precise agreement might not be expected because of the superlinear dependence found for the fluorescence intensity on dose and the sublinear dependence found on dose rate [22]. These compensatory effects are the object of ongoing research into methods of making corrections to the experimental data required for dosimetry applications.…”

“…The RFG gel preparation procedure has been described in full previously [21,22]. In summary, the gel is preformed in the cell by 60 Co γ -irradiation (~15 Gy at ~1 Gy/min) of pure, de-aerated, and inhibitor-free TBA to ~15% monomer conversion.…”

“…In this report, we show how a radio-fluorogenic (RFG) polymer-gel [21,22] can be used to provide a 3D image of the track of a narrow (3 mm diameter) X-ray beam in a volume as small as the human eye. An RFG gel is a two-component mixture whose components are commercially available, inexpensive, and whose composition can be accurately determined by optical spectroscopy.…”

A Polymer-Gel Eye-Phantom for 3D Fluorescent Imaging of Millimetre Radiation Beams

“…The RFG gel preparation procedure has been described in full previously [21,22]. Briefly, the gel is preformed in the cell by 60 Co γ-irradiation (~15 Gy at ~1 Gy/min) of pure, de-aerated, inhibitor-free TBA to ~15% monomer conversion.…”

“…This is close to the value of 0.67 that would be expected for the decrease in dose rate across the gel based on the value of [Mρδ]gel = 0.296 determined in section 3.2 and a conical expansion by 10%. Precise agreement might not be expected because of the superlinear dependence found for the fluorescence intensity on dose and the sublinear dependence found on dose rate [22]. These compensatory effects are the object of ongoing research into methods of making corrections to the experimental data required for dosimetry applications.…”