Leuco crystal violet-Pluronic F-127 3D radiochromic gel dosimeter

摘要

This work reports results related to the manufacturing and optimisation of a leuco crystal violet (LCV)-Pluronic F-127 radiochromic gel dosimeter suitable for 3D radiotherapy dosimetry. A feature of this gel is that the natural gelatine polymer, which is most often used as a matrix in 3D dosimeters, is substituted with Pluronic F-127 synthetic copolymer (poly(ethylene oxide)-blockpoly(propylene oxide)-block-poly(ethylene oxide). Pluronic F-127 ensures a higher transparency than gelatine, which may be beneficial for optical computed tomography readout, and improves the thermal properties in the temperature range above similar to 30 degrees C at which the gelatine physical gel converts to a solution. The optimal composition obtained comprises 2 mM LCV, 4 mM 4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol (Triton X-100),17 mM trichloroacetic acid (TCAA) and 25% Pluronic F-127. Its main dose-response features are 4-150 Gy linear dose range (150 Gy was the maximal dose applied to gels in this work), 0.0070 Gy(-1) cm(-1) dose sensitivity (derived from absorbance (600 nm) = f(dose) for 6 MeV electrons, 0.88(3) Gy s(-1) and 0.0156 Gy(-1) cm(-1) derived from optical density (Delta mu = f(dose) for 6 MV x-rays, 0.1010 Gy s(-1)), low initial colour (initial absorbance = 0.0429) and a diffusion coefficient of crystal violet (CV) in LCV-Pluronic of 0.054 +/- 0.023 mm(2) h(-1). Raman spectroscopy was used to characterize LCV-Pluronic chemical changes after irradiation. Differential scanning calorimetry (DSC) revealed that LCV-Pluronic is stable in temperatures between approximately 11 degrees C and 56 degrees C. Irradiation of LCV-Pluronic gel impacts on its first sol-gel transition temperature and the thermal effect of this process-both increased with absorbed dose, which might be related to the degradation of Pluronic. LCV-Pluronic is a promising 3D dosimeter for ionising radiation applications. Further work is needed to improve LCV-Pluronic response in the low dose region, and characterize potential effects of pH, temperature during irradiation, and radiation quality/dose rate on dose response characteristics.