Fricke gel as a tool for dose distribution verification: optimization and characterization

Area of Science:

• Medical Physics
• Radiation Oncology
• Dosimetry

Background:

• Gel dosimetry is crucial for 3D dose verification in radiation therapy.
• Polymer gels offer advantages but are costly; Fricke gels are less expensive but require further investigation.
• Dose resolution is a key metric for comparing gel dosimeter performance.

Purpose of the Study:

• To investigate the dose resolution and diffusion characteristics of Fricke gels.
• To evaluate the impact of gelatine concentration, Fe2+ concentration, and pH on Fricke gel performance.
• To assess the clinical relevance of diffusion in Fricke gels for IMRT verification.

Main Methods:

• Systematic variation of gelatine concentration (6-10 wt%), Fe2+ concentration (1.0 mM), and pH (1.5-2.0).
• Measurement of diffusion coefficients and dose resolution.
• Evaluation of dose distribution impact using the gamma-method.

Main Results:

• Increasing gelatine concentration significantly reduced the diffusion coefficient.
• Lowering pH from 2.0 to 1.5 most effectively improved dose resolution.
• Optimal Fricke gel formulation (10 wt% gelatine, 1.0 mM Fe2+, pH 1.5) yielded a diffusion coefficient of 1.5 mm2/h and 4.1% dose resolution at 40 Gy.
• Diffusion had no clinically significant impact on dose distribution within 3 hours post-irradiation.

Conclusions:

• Fricke gels can be optimized for improved dose resolution and acceptable diffusion.
• The optimized Fricke gel formulation shows potential for routine clinical use in IMRT verification.
• Further research may establish Fricke gels as a viable alternative for 3D dose verification in conformal radiation therapy.