Assessment of dosimetric sensitivity enhancement of xylenol orange Fricke gel by AuNPs: optical and MR imaging investigation.

Metallic nanoparticles, such as gold and silver nanoparticles (AuNPs and AgNPs, respectively),possess strong surface plasmonic resonance (SPR) and high atomic number, which makes them ideal candidates for enhancing dosimeter sensitivity. In this study, we have inserted different mass percentages (from 0 to 0.015%) of AuNPs into a gelatinous Fricke-Xylenol-Orange (FXO-f) gel matrix and irradiated it with doses ranging from 0 to 32Gy, using a source of X-ray of low energy. Optical absorption increased significantly; sensitivity gains of up to 50% were achieved for the FXO-f gel matrix containing 0.011% AuNPs. To elucidate the mechanism underlying this increased sensitivity, we also evaluated FXO-f gel matrixes containing AgNPs. AgNPs insertion into the FXO-f gel matrix did not enhance sensitivity, which suggested that the AgNPs plasmonic absorption band and the FXO-f gel matrix absorption band at 441nm overlapped, to increase absorption even after the gel matrix was irradiated. To visualize the dose distribution, we recorded optical tomography and acquired 3D reconstruction maps. In addition, we analyzed the dose enhancement factor (DEF) by using magnetic resonance images. AuNPs insertion into the FXO-f gel matrix resulted in a DEF gain of 1.37, associated with the photoelectric effect originating from the increased number of free radicals.