title: [Constancy check of system linearity for dose calibrators. Effect of molybdenum impurities at high start activities of 99mTc].
abstract: Dose calibrators are one of the most important and most frequently used instruments for the determination of activities in nuclear medicine. For guaranteeing a constant quality of the dose calibrators' measurements, constancy checks including the examination of the system linearity have to be performed regularly, usually measured using 99mTc. The 99mTc eluate extracted from a 99Mo/99mTc generator is contaminated with molybdenum. Not accounting for the molybdenum impurity might lead to an exceed of the tolerance limit of 5% deviation to the reference value for this constancy check. The reason for this effect is the contamination of the 99mTc eluate with 99Mo, whose impact depends on both the amount of the impurity and on the total measurement time (high start activities).
  
  
  RESULTS
  In this work, the influence of the molybdenum impurity on the results of the constancy check of the system linearity was investigated and maximum start activities for certain impurities were determined providing that the deviation to the reference values is below 5%.
  
  
  CONCLUSIONS
  Provided that certain boundary conditions are observed, a correction of the results with respect to the molybdenum contamination is not necessary.
authors.affiliation: Christian Schütze, Stabsstelle Strahlenschutz und Abteilung Medizinische Physik, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625 Hannover, Tel. 05 11/532-30 83, Fax -26 76, Schuetze.Christian@mh-hannover.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Schütze
authors.forename: Bernd O
authors.initials: BO
authors.lastname: Knoop
authors.forename: Iris
authors.initials: I
authors.lastname: Vehrenkamp
authors.forename: Frank
authors.initials: F
authors.lastname: Rudolf
authors.forename: Lilli
authors.initials: L
authors.lastname: Geworski
mesh_terms: D002138:Calibration / Q000592:standards; D004340:Drug Contamination; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005858:Germany; D008982:Molybdenum / Q000032:analysis* / Q000737:chemistry; D009683:Nuclear Medicine / Q000592:standards; D011874:Radiometry / Q000295:instrumentation* / Q000592:standards*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013667:Technetium / Q000032:analysis* / Q000737:chemistry*
chemical_list: D013667:Technetium; D008982:Molybdenum
keywords: Dose calibrator; constancy check; impurity; nuclear medicine; system linearity