Technical Note: Preliminary investigations into the use of a functionalised polymer to reduce diffusion in Fricke gel dosimeters

• Published in: Medical physics (Lancaster) 2015-12, Vol.42 (12), p.6798-6803
• Main Authors: Smith, S. T., Masters, K.‐S., Hosokawa, K., Blinco, J. P., Crowe, S. B., Kairn, T., Trapp, J. V.
• Format: Article
• Language: English
• Subjects: Acids; APPROXIMATIONS; biodiffusion; Cations - chemistry; CHELATING AGENTS; Computed tomography; Diffusion; Dose-Response Relationship, Drug; DOSEMETERS; Dose‐volume analysis; dosimeters; DOSIMETRY; Dosimetry/exposure assessment; Ferrous Compounds - chemistry; Fricke gel dosimeter; functionalised polymer; gelatin; GELS; Gels and sols; hydrogels; Hydrogels - chemical synthesis; Hydrogels - chemistry; Hydrogels - radiation effects; Image scanners; INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; Iron - chemistry; Molecular Structure; oxidation; Oxidation-Reduction; Phenols - chemistry; polymers; Polyvinyl Alcohol - chemistry; PVA; radiation therapy; Radiometry - instrumentation; Radiometry - methods; READOUT SYSTEMS; Scintigraphy; Silica; Solution processes; Sulfoxides - chemistry; Sulfuric Acids - chemistry; Therapeutic applications, including brachytherapy; Ultrafast optical diffusion tomography; XYLENOL ORANGE
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.4934827

Purpose: A modification of the existing PVA‐FX hydrogel has been made to investigate the use of a functionalised polymer in a Fricke gel dosimetry system to decrease Fe3+ diffusion. Methods: The chelating agent, xylenol orange, was chemically bonded to the gelling agent, polyvinyl alcohol (PVA) to create xylenol orange functionalised PVA (XO‐PVA). A gel was created from the XO‐PVA (20% w/v) with ferrous sulfate (0.4 mM) and sulfuric acid (50 mM). Results: This resulted in an optical density dose sensitivity of 0.014 Gy−1, an auto‐oxidation rate of 0.0005 h−1, and a diffusion rate of 0.129 mm2 h−1; an 8% reduction compared to the original PVA‐FX gel, which in practical terms adds approximately 1 h to the time span between irradiation and accurate read‐out. Conclusions: Because this initial method of chemically bonding xylenol orange to polyvinyl alcohol has inherently low conversion, the improvement on existing gel systems is minimal when compared to the drawbacks. More efficient methods of functionalising polyvinyl alcohol with xylenol orange must be developed for this system to gain clinical relevance.