Determination of the efficiency of commercially available dose calibrators for beta-emitters.
OBJECTIVE
The goals of this investigation are to determine whether commercially available dose calibrators can be used to measure the activity of beta-emitting radionuclides used in pain palliation and to establish whether manufacturer-supplied calibration factors are appropriate for this purpose.


METHODS
Six types of commercially available dose calibrators were studied. Dose calibrator response was controlled for 5 gamma-emitters used for calibration or typically encountered in routine use. For the 4 most commonly used beta-emitters ((32)P, (90)Sr, (90)Y, and (169)Er) dose calibrator efficiency was determined in the syringe geometry used for clinical applications. Efficiency of the calibrators was also measured for (153)Sm and (186)Re, 2 beta-emitters with significant gamma-contributions. Source activities were traceable to national standards.


RESULTS
All calibrators measured gamma-emitters with a precision of +/-10%, in compliance with Swiss regulatory requirements. For beta-emitters, dose calibrator intrinsic efficiency depends strongly on the maximal energy of the beta-spectrum and is notably low for (169)Er. Manufacturer-supplied calibration factors give accurate results for beta-emitters with maximal beta-energy in the middle-energy range (1 MeV) but are not appropriate for use with low-energy ((169)Er) or high-energy ((90)Y) beta-emitters. beta-emitters with significant gamma-contributions behave like gamma-emitters.


CONCLUSIONS
Commercially available dose calibrators have an intrinsic efficiency that is sufficient for the measurement of beta-emitters, including beta-emitters with a low maximum beta-energy. Manufacturer-supplied calibration factors are reliable for gamma-emitters and beta-emitters in the middle-energy range. For low- and high-energy beta-emitters, the use of manufacturer-supplied calibration factors introduces significant measurement inaccuracy.
Valley
Jean-François
JF
Institute for Applied Radiophysics, Lausanne, Switzerland. Jean-Francois.Valley@inst.hospvd.ch
Bulling
Shelley
S
Leresche
Michel
M
Wastiel
Claude
C
D001610:Beta Particles / Q000627:therapeutic use; D001859:Bone Neoplasms / Q000532:radiotherapy / Q000556:secondary; D004871:Erbium; D006801:Humans; D010166:Palliative Care; D010761:Phosphorus Radioisotopes; D011834:Radiation Monitoring / Q000295:instrumentation*; D011868:Radioisotopes; D011874:Radiometry / Q000295:instrumentation*; D011878:Radiotherapy; D013326:Strontium Radioisotopes; D015021:Yttrium Radioisotopes
D010761:Phosphorus Radioisotopes; D011868:Radioisotopes; D013326:Strontium Radioisotopes; D015021:Yttrium Radioisotopes; D004871:Erbium