Radiochromic leuco dye micelle hydrogels: II. Low diffusion rate leuco crystal violet gel

Abstract

Radiation-sensitive hydrogels offer the capability of verifying intricate dose distributions in three-dimensional (3D) space conveniently in a single measurement with sub-millimetre spatial resolution. In this study, a new radiochromic hydrogel called leuco crystal violet (LCV) micelle gel is introduced. Upon irradiation, LCV converts to crystal violet (CV(+)). Triton X-100 micelles are used to provide the required hybrid-interfacing environment to dissolve LCV. The diffusion coefficient of the LCV gel has been measured to be 0.036 +/- 0.001 mm(2) h(-1), which is a factor of 25 times less than the standard radiochromic ferrous xylenol-orange (FX) gel; LCV gels without Triton X-100 micelles have a diffusion coefficient of 0.33 +/- 0.02 mm(2) h(-1). The LCV gel formulation contains: 1 mM LCV, 25 mM trichloroacetic acid, 4 mM Triton X-100 and 4% w/w gelatin. The primary innovative feature of this 3D hydrogel is that the radiation-induced CV(+) dye is more soluble in the Triton X-100 micelles than in the surrounding water which consequently leads to more stable post-irradiation dose distributions. A dosimetric characterization revealed that the dose response is reproducible to within 1% over three separate batches, independent of energy, dose rate and dose fractionation but is affected by the temperature ( approximately 4% per degree C) during irradiation. LCV micelle gels scanned optically with a yellow light source are a promising system for 3D dose verification. They may prove to be, especially, useful for scanning large volume dosimeters (i.e. 20 cm) since they are easily manufactured, transparent and near colourless prior to irradiation.

Leuco-crystal-violet micelle gel dosimeters: Component effects on dose-rate dependence

“…However, batches do show a large amount of variance and further work reproducing these results is necessary. The proposed gel has a dose sensitivity 80% higher than the original LCV micelle gel developed by Babic et al [1] while still at a similar initial absorbance. In future, we will explore the possibility to develop gels with lower dose-rate dependence and even higher dose sensitivity by expanding the bounds used for recipe optimization, and attempt to modify the preparation methods to produce more consistent results.…”

“…Radio-chromic LCV micelle gels manufactured with CTAB surfactant exhibit improved dose sensitivity and comparable initial absorbance when compared to the LCV gel proposed by Babic et al [1]. Unfortunately, these new gels can exhibit undesirable dose-rate dependence (as high as 32% between dose rates of 100 and 600 cGy min -1 ).…”

“…Leucocrystal violet (LCV) micelle gel dosimeters developed by Babic et al [1] can be read optically and produce accurate 3-D dosimetry with excellent spatial stability, but have low dose sensitivity compared to alternatives such as Fricke gel dosimeters which use ferric ions as their reporter molecule [2]. LCV gels are preferable to leucomalachite green (LMG) gels, also developed by Jordan's research group, because LCV is less soluble in water causing it to preferentially dissolve in micelles, thereby reducing diffusion [1,3,4].…”

“…LCV gels are preferable to leucomalachite green (LMG) gels, also developed by Jordan's research group, because LCV is less soluble in water causing it to preferentially dissolve in micelles, thereby reducing diffusion [1,3,4]. Nasr et al attempted to optimize Jordan's LCV gel recipe by adjusting concentrations of LCV and Triton X-100 (Tx100) surfactant and adding 2,2,2-trichloroethanol (TCE) as a sensitizing agent [5,6].…”

3D dosimetry fundamentals: gels and plastics

“…This approach is general and is an active area of research on an industrial scale as society migrates from hydrocarbon solvents to "green chemical syntheses". The initial reports have demonstrated that insoluble leuco dyes can be incorporated into gelatin hydrogels with nonionic surfactants [16,24]. Diffusion measurements revealed that the more water soluble, cationic dye Malachite Green had a higher diffusion coefficient.…”