title: 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.
  
  
  OBJECTIVE
  In the current study the optical and NMR properties of NIPAM were studied for radiation therapy dosimetry application.
  
  
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Medical Physics Department, Medical School, Tabriz University of Medical Sciences, Tabriz, Iran ; Radiation Oncology Department, Imam Hospital, Tabriz, Iran.
authors.forename: Asghar
authors.initials: A
authors.lastname: Mesbahi
authors.affiliation: Electronic Department, Islamic Azad University, Ahar, Iran.
authors.forename: Vahid
authors.initials: V
authors.lastname: Jafarzadeh
authors.affiliation: Radiology Department, Paramedical School, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Nahideh
authors.initials: N
authors.lastname: Gharehaghaji
keywords: Gel dosimetry; Optical absorbance; Polymer gel