title: Comparison of methods to determine accurate dose calibrator activity measurements.
abstract: BACKGROUND
  In nuclear medicine, liquid radiopharmaceuticals for diagnostic or therapeutic purposes are administered to patients by using various types of syringes with different volumes. The activity of each "dose" must be carefully measured and documented prior to administration using an activity calibrator.
  
  
  METHODS
  Calibrator response is a function of the measurement geometry and, in particular, it depends on the syringe type and filling volume. To minimize the uncertainty associated with the measured activity of the syringe, it is necessary to calculate a calibration curve depending on filling volume for each syringe type. This curve can be obtained by fitting experimentally determined volume correction factors.
  
  
  RESULTS
  A theoretical evaluation of volume correction factors for syringes is reported for three different experimental methods. The aim is to determine the most accurate experimental method among those considered, by examining the expression of uncertainty for the correction factor. This theoretical analysis was then tested experimentally.
  
  
  CONCLUSIONS
  The agreement between the experimental data obtained in the constant activity method and gravimetric method at constant specific activity and the small associated uncertainties show the accuracy of these two procedures; while the volumetric method at constant specific activity could lead to a wrong evaluation of the correction factors.
authors.affiliation: Laboratory of Medical Physics and Expert Systems, National Cancer Institute Regina Elena, Rome, Italy. strigari@ifo.it
authors.forename: Lidia
authors.initials: L
authors.lastname: Strigari
authors.forename: Marcello
authors.initials: M
authors.lastname: Benassi
authors.forename: Pierino
authors.initials: P
authors.lastname: De Felice
authors.forename: Marco
authors.initials: M
authors.lastname: D'Andrea
authors.forename: Aldo
authors.initials: A
authors.lastname: Fazio
authors.forename: Sandro
authors.initials: S
authors.lastname: Nocentini
authors.forename: Annelisa
authors.initials: A
authors.lastname: d'Angelo
authors.forename: Alessia
authors.initials: A
authors.lastname: Ceccatelli
mesh_terms: D002138:Calibration / Q000592:standards; D008962:Models, Theoretical; D009683:Nuclear Medicine / Q000295:instrumentation* / Q000379:methods / Q000592:standards; D019275:Radiopharmaceuticals / Q000008:administration & dosage*; D013594:Syringes / Q000592:standards; D014894:Weights and Measures
chemical_list: D019275:Radiopharmaceuticals