title: Calibration of (192)Ir high dose rate brachytherapy source using different calibration procedures.
abstract: OBJECTIVE
  To calibrate Ir-192 high dose rate (HDR) brachytherapy source using different calibration methods and to determine the accuracy and suitability of each method for routine calibrations.
  
  
  BACKGROUND
  The source calibration is an essential part of the quality assurance programme for dosimetry of brachytherapy sources. The clinical use of brachytherapy source requires an independent measurement of the air kerma strength according to the recommendations of medical physics societies.
  
  
  METHODS
  The Ir-192 HDR brachytherapy source from Gammamed plus machine (Varian Medical Systems, Palo Alto, CA) was calibrated using three different procedures, one using the well-type ionization chamber, second by the in-air calibration method and third using solid water phantoms. The reference air kerma rate (RAKR) of the source was determined using Deutsche Gesellschaft fur Medizinische Physik (DGMP) recommendations.
  
  
  RESULTS
  The RAKR determined using different calibration methods are in good agreement with the manufacturer stated value. The mean percentage variations of 0.21, -0.94, -0.62 and 0.58 in RAKR values with respect to the manufacturer quoted values were observed with the well-type chamber, in-air calibration, cylindrical phantom and slab phantom measurements, respectively.
  
  
  CONCLUSIONS
  Measurements with a well-type chamber are relatively simple to perform. For in-air measurements, the indigenously designed calibration jig provides an accurate positioning of the source and chamber with minimum scatter contribution. The slab phantom system has an advantage that no additional phantom and chamber are required other than those used for external beam therapy dosimetry. All the methods of calibration discussed in this study are effective to be used for routine calibration purposes.
authors.affiliation: Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Hosur Road, Bangalore 560 029, India.
authors.forename: Shwetha
authors.initials: S
authors.lastname: Bondel
authors.affiliation: Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Hosur Road, Bangalore 560 029, India.
authors.forename: Manickham
authors.initials: M
authors.lastname: Ravikumar
authors.affiliation: Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Hosur Road, Bangalore 560 029, India.
authors.forename: Sanjay Sudhakar
authors.initials: SS
authors.lastname: Supe
authors.affiliation: Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Hosur Road, Bangalore 560 029, India.
authors.forename: Buchuppudi Rekha
authors.initials: BR
authors.lastname: Reddy
keywords: High dose rate brachytherapy; In-air calibration; Reference air kerma rate; Well-type chamber