68(Ge+Ga) activity standardization by 4πβ(LS)-γ(NaI(Tl)) anticoincidence counting measurements

• Published in: Applied radiation and isotopes 2018-04, Vol.134, p.307-311
• Main Authors: da Silva, C.J., da Cruz, P.A.L., Iwahara, A., de Oliveira, E.M., Loureiro, J. dos S., Tauhata, L., da Silva, Ronaldo L., Poledna, R., Lopes, R.T.
• Format: Article
• Language: English
• Subjects: 68(Ge+Ga); Activity standardization; Anticoincidence; Coincidence; TDCR
• ISSN: 0969-8043; 1872-9800
• DOI: 10.1016/j.apradiso.2017.10.009

In this work, a 68(Ge+Ga) solution has been standardized at the National Institute of Ionizing Radiation Metrology (LNMRI), in Brazil, in the frame of an international key comparison CCRI(II)-K2.Ge-68 piloted by National Institute of Standards and Technology (NIST/USA). The 4πβ(LS)-γ(NaI(Tl)) anticoincidence method with live-time and extended dead-time was used and its result was validated by 4πβ(LS)-γ(NaI(Tl)) coincidence counting and liquid scintillation counting using the Triple to Double Coincidence Ratio (TDCR) method. The deviations of the activity concentration values of coincidence and TDCR measurements from the anticoincidence result were 1.7% and 0.63%, respectively, which were within experimental evaluated uncertainties at ~95% level of confidence (coverage factor k = 2). The combined relative standard uncertainties were 0.65%, 0.70% and 0.53% for anticoincidence, coincidence and TDCR methods, respectively. These values are consistent with the results reported by Cessna at the ICRM2017 conference. •Participation in BIPM international key-comparison of activity measurements of 68(Ge + Ga) piloted by NIST.•The agreement between comparison reference value and LNMRI/IRD value is better than 0.3 %.•Activity results determined by three methods were consistent with k = 2.•LNMRI/IRD, as Designed Metrology Institute, is able to provide certificated solution 68(Ge + Ga), with uncertainty better than 1.3 %.•68(Ge + Ga) can be used as a surrogate for 18F in quality control of radiation measurements equipment of nuclear medicine.