title: Experience from long-term monitoring of RAKR ratios in (192)Ir brachytherapy.
abstract: BACKGROUND
  Ratios of values of brachytherapy source strengths, as measured by hospitals and vendors, comprise constant differences as, e.g., systematic errors in ion chamber calibration factors and measurement setup. Such ratios therefore have the potential to reveal the systematic changes in routines or calibration services at either the hospital or the vendor laboratory, which could otherwise be hidden by the uncertainty in the source strength values.
  
  
  METHODS
  The RAKR of each new source in 13 afterloading units at five hospitals were measured by well-type ion chambers and compared to values for the same source stated on vendor certificates.
  
  
  RESULTS
  Differences from unity in the ratios of RAKR values determined by hospitals and vendors are most often small and stable around their mean values to within +/- 1.5%. Larger deviations are rare but occur. A decreasing ratio, seen at two hospitals for the same source, was useful in detecting an erroneous pressure gauge at the vendor's site.
  
  
  CONCLUSIONS
  Establishing a mean ratio of RAKR values, as measured at the hospital and supplied on the vendor certificate, and monitoring this as a function of time are an easy way for the early detection of problems with equipment or routines at either the hospital or the vendor site.
authors.affiliation: Radiation Physics, Department of Medical and Health Sciences (IMH), Linköping University, Linköping, Sweden. asa.carlsson-tedgren@imv.liu.se
authors.forename: Asa
authors.initials: A
authors.lastname: Carlsson Tedgren
authors.forename: Emil
authors.initials: E
authors.lastname: Bengtsson
authors.forename: Håkan
authors.initials: H
authors.lastname: Hedtjärn
authors.forename: Asa
authors.initials: A
authors.lastname: Johansson
authors.forename: Leif
authors.initials: L
authors.lastname: Karlsson
authors.forename: Inger-Lena
authors.initials: IL
authors.lastname: Lamm
authors.forename: Marie
authors.initials: M
authors.lastname: Lundell
authors.forename: Younes
authors.initials: Y
authors.lastname: Mejaddem
authors.forename: Per
authors.initials: P
authors.lastname: Munck Af Rosenschöld
authors.forename: Josef
authors.initials: J
authors.lastname: Nilsson
authors.forename: Elinore
authors.initials: E
authors.lastname: Wieslander
authors.forename: Jeanette
authors.initials: J
authors.lastname: Wolke
mesh_terms: D001918:Brachytherapy / Q000295:instrumentation*; D002138:Calibration; D006801:Humans; D007496:Iridium Radioisotopes / Q000627:therapeutic use*; D011874:Radiometry / Q000295:instrumentation*; D011879:Radiotherapy Dosage
chemical_list: D007496:Iridium Radioisotopes