Asghar Mesbahi1, Vahid Jafarzadeh2, Nahideh Gharehaghaji3. 1. Medical Physics Department, Medical School, Tabriz University of Medical Sciences, Tabriz, Iran ; Radiation Oncology Department, Imam Hospital, Tabriz, Iran. 2. Electronic Department, Islamic Azad University, Ahar, Iran. 3. Radiology Department, Paramedical School, Tabriz University of Medical Sciences, Tabriz, Iran.
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 9 MV photon beam of a medical linac. The optical absorbance was measured using a conventional laboratory spectrophotometer in different wavelengths ranging from 390 to 860 nm. R 2 measurements of NIPAM gels were performed using a 1.5 T scanner and R 2-dose curve was obtained. RESULTS: Our results showed R 2 dose sensitivity of 0.193 ± 0.01 s(-1) Gy(-1) for NIPAM gel. Both R 2 and optical absorbance showed a linear relationship with dose from 1.5 to 11 Gy 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.
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 9 MV photon beam of a medical linac. The optical absorbance was measured using a conventional laboratory spectrophotometer in different wavelengths ranging from 390 to 860 nm. R 2 measurements of NIPAM gels were performed using a 1.5 T scanner and R 2-dose curve was obtained. RESULTS: Our results showed R 2 dose sensitivity of 0.193 ± 0.01 s(-1) Gy(-1) for NIPAM gel. Both R 2 and optical absorbance showed a linear relationship with dose from 1.5 to 11 Gy 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.
Entities:
Keywords:
Gel dosimetry; Optical absorbance; Polymer gel
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