A Novel Approach to Evaluating HEMA Polymer Gel Dosimeters Using Molecular Vibrational Features

A polymer Gel Dosimeter (PGD) provides essential three-dimensional (3D) radiation dose distribution for the radiotherapy planning system (TPS). This study investigates the use of infrared absorption spectrum as a novel and more cost-effective alternative to Magnetic Resonance Imaging (MRI), Nuclear Magnetic Resonance (NMR), and Optical Computed Tomography (Optical CT) for reading out PGDs. The PGDs were fabricated using 2-Hydroxyethyl methacrylate (HEMA), maltose, N’N, methylene(bis)acrylamide (Bis), gelatin, deionized water (DI Water), and Tetrakis (hydroxymethyl) phosphonium chloride (THPC), and were irradiated using a Linear Accelerator (LINAC) within the range of 0–30 Gy. The possibility of translating molecular vibrational frequency, amplitude, and energy of vibration into absorbed dose was explored by analyzing the absorption spectra in the near-infrared region (NIR) with wavelengths between 750–1100 nm. The findings reveal that these vibrational properties can be employed to interpret irradiated PGDs. Furthermore, an increase in maltose concentration within the 0–520 mM range widens the linear dose range and enhances sensitivity. The PGDs exhibit temporal stability up to 7 days post-irradiation, and the span of their response remains relatively unaffected by scanning temperature. In conclusion, NIR spectroscopy offers a cost-effective method for interpreting PGDs, potentially improving the affordability and efficiency of PGD dosimetry in clinical radiotherapy. This holds particularly promising for less developed countries, aligning with the sustainable development goal (SDG) of ensuring affordable healthcare for all. We finally recommend further research into translating the molecular vibrational parameters into 3D images.