Abstract
A modification to the PVA-FX hydrogel whereby the chelating agent, xylenol orange, was partially bonded to the gelling agent, poly-vinyl alcohol, resulted in an 8% reduction in the post irradiation Fe3+ diffusion, adding approximately 1 hour to the useful timespan between irradiation and readout. This xylenol orange functionalised poly-vinyl alcohol hydrogel had an OD dose sensitivity of 0.014 Gy−1 and a diffusion rate of 0.133 mm2 h−1. As this partial bond yields only incremental improvement, it is proposed that more efficient methods of bonding xylenol orange to poly-vinyl alcohol be investigated to further reduce the diffusion in Fricke gels.
Highlights
Fricke gels are based on adding gelling agents to the Fricke solution; an acidic oxygenated aqueous solution of ferrous ion (Fe2+)
Formation of gel using XO-poly-vinyl alcohol (PVA) resulted in increased scatter and more noise was encountered in its optical densities (ODs) profiles
The diffusion coefficient, measured for the PVA-FX hydrogel matched results reported by Chu et al, with D = 0.144 ± 0.002 mm2 h-1
Summary
Fricke gels are based on adding gelling agents to the Fricke solution; an acidic oxygenated aqueous solution of ferrous ion (Fe2+). A dose dependant transformation of ferrous (Fe2+) to ferric ions (Fe3+) occurs, which is detectable via MRI or optical CT scanning. The poor spatial stability of Fricke gels due to diffusion of Fe3+ ions constrains the permissible time between irradiation and read-out [1, 2]. This introduces an obvious practical inconvenience inhibiting the routine use of gels a clinical environment. Limited success in reducing Fe3+ diffusion rates is obtained using different gelling agents (gelatin, agarose, sephadex and poly-vinyl alcohol) and chelating agents such as xylenol orange [3, 4]
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