Characteristics of a novel poly (methyl methacrylate-gel) dosimeter doped with copper oxide nanoparticles for radiotherapy applications

Abstract

This study investigates the characteristics of a novel poly (methyl methacrylate-gel) (PMMAG) dosimeter doped with copper oxide nanoparticles (CuO NPs) for radiotherapy applications. The dosimeter was evaluated based on its optical density, mass density, dose resolution, thermal stability, and toxicity. Irradiation was performed using a 6-MV photon beam and a dose range of 0–10 Gy from a medical linear accelerator (LINAC). Measurements were conducted using UV–Vis spectrophotometry, a digital density meter, and thermal analysis techniques (DSC and TGA). The addition of CuO NPs enhanced the optical density linearly with increase in radiation dose, with the greatest enhancement observed at an optimal concentration of 3 × 10⁻² mg/L. This was attributed to increased free radical production via Compton scattering. The same concentration also corresponded to the highest measured mass density, indicating a dual role in enhancing both optical and physical dosimetric response. Dose resolution was optimized at 1% CuO NPs, based on the analysis of the dose–response curve slope and the standard deviation of absorbance measurements obtained via UV–Vis. This concentration achieved improved radiation sensitivity while minimizing signal noise and avoiding absorbance saturation effects. TGA and DSC results indicated that CuO NPs enhanced the gel's thermal stability by delaying weight loss and increasing the decomposition temperature, while only slightly reducing the glass transition and melting temperatures. Replacing acrylamide with methyl methacrylate (MMA) significantly decreased toxicity (LD50 = 7872 mg/kg) and eliminated carcinogenic concerns, making the PMMAG/CuO NP dosimeter a safer and more environmentally friendly alternative.