Development and optimization of a 2-hydroxyethylacrylate MRI polymer gel dosimeter

Area of Science:

• Materials Science
• Medical Physics
• Polymer Chemistry

Background:

• Polymer gel dosimeters are crucial for accurate radiation dose measurement.
• Understanding radiation-induced changes in polymer structure is key to improving dosimeter performance.
• Magnetic Resonance Imaging (MRI) and FT-Raman spectroscopy offer complementary insights into gel dosimeter properties.

Purpose of the Study:

• To investigate radiation-induced changes in 2-hydroxyethylacrylate (HEA) and N,N'-methylene-bisacrylamide (BIS) polymer gel dosimeters.
• To model the relationship between absorbed radiation dose and magnetic resonance relaxation time (T2).
• To optimize HEA gel composition for enhanced relative dosimetry applications by introducing percentage dose resolution (Dp delta, %).

Main Methods:

• Fabrication of polymer gel dosimeters using HEA and BIS.
• Investigation of radiation-induced changes using Magnetic Resonance Imaging (MRI) and FT-Raman spectroscopy.
• Modeling of T2 variation with absorbed dose, considering proton exchange with water.
• Application of percentage dose resolution (Dp delta, %) to evaluate gel compositions.

Main Results:

• A model for T2 variation with absorbed dose showed good agreement with experimental data.
• FT-Raman data suggested not all polymer protons contribute to the relaxation process.
• Optimized HEA gels demonstrated superior percentage dose resolution compared to standard polyacrylamide gel (PAG) dosimeters.
• The optimal HEA gel (4% HEA, 4% BIS) achieved Dp delta, % < 2.3%, significantly better than PAG's 3.8%.

Conclusions:

• The T2 value in HEA/BIS polymer gel dosimeters is influenced by polymer composition and topology.
• Optimized HEA gel formulations offer improved performance for relative dosimetry applications.
• HEA-based polymer gel dosimeters represent a significant advancement over traditional PAG dosimeters for clinical radiation therapy.