Optical and NMR dose response of N-isopropylacrylamide normoxic polymer gel for radiation therapy dosimetry

Abstract

Background: Application of less toxic normoxic polymer gel of N-isopropyl acrylamide (NIPAM) for radiation therapy has been studied in recent years. Aim: In the current study the optical and NMR properties of NIPAM were studied for radiation therapy dosimetry application. Materials and methods: NIPAM normoxic polymer gel was prepared and irradiated by 9MV photon beam of a medical linac. The optical absorbance was measured using a conventional laboratory spectrophotometer in different wavelengths ranging from 390 to 860nm. R2 measurements of NIPAM gels were performed using a 1.5T scanner and R2-dose curve was obtained. Results: Our results showed R2 dose sensitivity of 0.193ط¢آ±0.01s-1Gy-1 for NIPAM gel. Both R2 and optical absorbance showed a linear relationship with dose from 1.5 to 11Gy for NIPAM gel dosimeter. Moreover, absorbance-dose response varied considerably with light wavelength and highest sensitivity was seen for the blue part of the spectrum. Conclusion: Our results showed that both optical and NMR approaches have acceptable sensitivity and accuracy for dose determination with NIPAM gel. However, for optical reading of the gel, utilization of an optimum optical wavelength is recommended. ط¢آ© 2012 Greater Poland Cancer Centre, Poland.