title: Usefulness of specific calibration coefficients for gamma-emitting sources measured by radionuclide calibrators in nuclear medicine.
abstract: OBJECTIVE
  In nuclear medicine, the activity of a radionuclide is measured with a radionuclide calibrator that often has a calibration coefficient independent of the container type and filling.
  
  
  METHODS
  To determine the effect of the container on the accuracy of measuring the activity injected into a patient, The authors simulated a commercial radionuclide calibrator and 18 container types most typically used in clinical practice. The instrument sensitivity was computed for various container thicknesses and filling levels. Monoenergetic photons and electrons as well as seven common radionuclides were considered.
  
  
  RESULTS
  The quality of the simulation with gamma-emitting sources was validated by an agreement with measurements better than 4% in five selected radionuclides. The results show that the measured activity can vary by more than a factor of 2 depending on the type of container. The filling level and the thickness of the container wall only have a marginal effect for radionuclides of high energy but could induce differences up to 4%.
  
  
  CONCLUSIONS
  The authors conclude that radionuclide calibrators should be tailored to the uncertainty required by clinical applications. For most clinical cases, and at least for the low-energy gamma and x-ray emitters, measurements should be performed with calibration coefficients specific to the container type.
authors.affiliation: Institute of Radiation Physics, University Hospital and University of Lausanne, Rue du Grand-Prd 1, CH-1007 Lausanne, Switzerland. francois.bochud@chuv.ch
authors.forename: François O
authors.initials: FO
authors.lastname: Bochud
authors.forename: Jean-Pascal
authors.initials: JP
authors.lastname: Laedermann
authors.forename: Sébastien
authors.initials: S
authors.lastname: Baechler
authors.forename: Marek
authors.initials: M
authors.lastname: Kosinski
authors.forename: Claude J
authors.initials: CJ
authors.lastname: Bailat
mesh_terms: D016477:Artifacts; D002138:Calibration; D005720:Gamma Rays; D011829:Radiation Dosage; D011868:Radioisotopes / Q000032:analysis* / Q000592:standards*; D011874:Radiometry / Q000379:methods* / Q000592:standards*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013048:Specimen Handling / Q000295:instrumentation* / Q000592:standards*
chemical_list: D011868:Radioisotopes