AbstractID: 9282 Title: A novel polymerizing radiochromic gel
We present a novel three-dimensional radiochromic gel, which uses an active component similar to that of GAFCHROMIC® film. The
GAFCHROMIC®dosimetry films provide a sensitive, tissue equivalent medium for high-spatial resolution mapping of dose
distributions. As the films are thin sheets of gelatin containing microcrystalline active monomers, we sought to make 3D gels out of
them. However, when observed macroscopically the gel is milky white. The microcrystals cause diffuse scattering of light as they are
insoluble in gelatin and of different refractive index. Since the gelatin layer is very thin in the film medium (10s of microns), the film
appears transparent. We modified the radiochromic gel compound such that at elevated temperatures, the microcrystals dissolve in the
gelatin making it transparent. The temperature has to be high enough to dissolve the monomers but not so high that the gel melts and
the dose pattern is not stable. We measured the gel absorption spectrum using a Beckman UV-VIS spectrophotometer with a
temperature controlled water circulator. Measurements of the gel absorbance were made at 70 ºC with and without irradiation. We
observed an optical density change of 1.15 for 200 cGy at the peak wavelength of 545 nm. The spectrum shows a peak in absorbance
at 545 nm and another broader peak around 505 nm, requiring green lasers for readout. The gel is not sensitive to oxygen and nonhazardous. This gel appears to be a good candidate for 3D dosimetry by optical tomographic methods.
Research Support in Part by International Specialty Products, Inc.