Optical characterization of NIPAM and PAGAT polymer gels for radiation dosimetry

Introduction: The purpose of the current study was to determine optical sensitivity of N-isopropyl acrylamide NIPAM and polyacrylamide gelatin and tetrakis hydroxymethyl phosphoniun chloride (PAGAT) polymer gels for different wavelength of visible light spectrum applied in optical computed tomography method. Materials and Methods: NIPAM and PAGAT polymer gels with conventional formulations used for polymer gel dosimetry in radiation therapy were prepared. Using a laboratory spectrophotometer, light absorbance against wavelength of light spectrum from 400 to 700 nm was measured. The optical absorbance-dose response curves were obtained for different wavelengths and the results were compared to find the wavelength where the highest sensitivity of polymer gels is occurred. Results: The results showed light wavelength dependency for polymer gels optical absorbance-dose sensitivity. The highest sensitivity was seen in the blue part of visible light at wavelengths of 440 and 460 nm for PAGAT and NIPAM, respectively. Moreover, the sensitivity of NIPAM gel was higher than PAGAT for all studied wavelengths. Conclusion: The sensitivity of both gels varied considerably with light wavelength and was higher in shorter wavelength of visible light. It is recommended to study optical absorbance-dose sensitivity of polymer gels for selecting the optimum light wavelength for optical measurements and optical computed tomography applications.