title: Effect of Gold Nanoparticles on Prostate Dose Distribution under Ir-192 Internal and 18 MV External Radiotherapy Procedures Using Gel Dosimetry and Monte Carlo Method.
abstract: BACKGROUND
  Gel polymers are considered as new dosimeters for determining radiotherapy dose distribution in three dimensions.
  
  
  OBJECTIVE
  The ability of a new formulation of MAGIC-f polymer gel was assessed by experimental measurement and Monte Carlo (MC) method for studying the effect of gold nanoparticles (GNPs) in prostate dose distributions under the internal Ir-192 and external 18MV radiotherapy practices.
  
  
  METHODS
  A Plexiglas phantom was made representing human pelvis. The GNP shaving 15 nm in diameter and 0.1 mM concentration were synthesized using chemical reduction method. Then, a new formulation of MAGIC-f gel was synthesized. The fabricated gel was poured in the tubes located at the prostate (with and without the GNPs) and bladder locations of the phantom. The phantom was irradiated to an Ir-192 source and 18 MV beam of a Varian linac separately based on common radiotherapy procedures used for prostate cancer. After 24 hours, the irradiated gels were read using a Siemens 1.5 Tesla MRI scanner. The absolute doses at the reference points and isodose curves resulted from the experimental measurement of the gels and MC simulations following the internal and external radiotherapy practices were compared.
  
  
  RESULTS
  The mean absorbed doses measured with the gel in the presence of the GNPs in prostate were 15% and 8 % higher than the corresponding values without the GNPs under the internal and external radiation therapies, respectively. MC simulations also indicated a dose increase of 14 % and 7 % due to presence of the GNPs, for the same experimental internal and external radiotherapy practices, respectively.
  
  
  CONCLUSIONS
  There was a good agreement between the dose enhancement factors (DEFs) estimated with MC simulations and experiment gel measurements due to the GNPs. The results indicated that the polymer gel dosimetry method as developed and used in this study, can be recommended as a reliable method for investigating the DEF of GNPs in internal and external radiotherapy practices.
authors.affiliation: Ph.D. Candidate, Department of Medical Physics, Tarbiat Modares University, Tehran, Iran;
authors.forename: H
authors.initials: H
authors.lastname: Khosravi
authors.affiliation: Associate Professor, Department of Medical Physics, Tarbiat Modares University, Tehran, Iran;
authors.forename: B
authors.initials: B
authors.lastname: Hashemi
authors.affiliation: Assistant Professor, Department of Medical Physics, Iran University of Medical Sciences, Tehran, Iran;
authors.forename: S R
authors.initials: SR
authors.lastname: Mahdavi
authors.affiliation: Assistant Professor, Department of Medical Physics, Semnan University of Medical Sciences, Semnan, Iran;
authors.forename: P
authors.initials: P
authors.lastname: Hejazi
keywords: Brachytherapy; Ir-192; MAGIC-f Polymer Gel Dosimeters; Monte Carlo Method; Nanoparticles; Prostate; Radiotherapy