Abstract
A 68(Ge+Ga) commercial solution has been standardized in LNMRI in Brazil, by sum-peak method, in which a 3”x3” NaI(Tl) gamma-ray detector is positioned at the top of a well-type 5”x5” NaI(Tl) gamma-ray detector, resulting in a set up approximately 4p geometry. In this work the known germanium volatility was tested using three dried sources and three liquid sources in the sum-peak method measurements and the activity results showed a standard deviation of 0.41%. The activities were compared with another primary method: 4pb-g live-timed anti-coincidence counting. The two methods gave activity concentration values with differences from the certified value of +0.8 % (anticoincidence method) and -3.4% (sum-peak method).
Highlights
IntroductionThe 68(Ge + Ga) standardization generally is done using liquid scintillation methods [1] to avoid losses of 68Ge by volatility, if dry sources are done [4]
68Ge in equilibrium with its daughter, 68Ga, is a potential surrogate of 18F in the checking of the radionuclide calibrators, and another practices in nuclear medicine [1] because his half-life (270.95 ± 0.16) d [2] is much longer than the 18F half-life (1.8288 ± 0.0003) h [3].The 68(Ge + Ga) standardization generally is done using liquid scintillation methods [1] to avoid losses of 68Ge by volatility, if dry sources are done [4]
Despite the presence many gamma rays in the decay scheme of 68Ga, there is just one that follows up the β+ decay and it has a low intensity, causing a little interference in measurements
Summary
The 68(Ge + Ga) standardization generally is done using liquid scintillation methods [1] to avoid losses of 68Ge by volatility, if dry sources are done [4]. The purpose of this work was to standardize a 68(Ge + Ga) solution by sum-peak method, which uses solid sources. Because of the setup system that requires dry sources, a study for the loss of 68(Ge + Ga) by volatility was done with dry and liquid sources. The 68Ge disintegrates 100% by electron capture to 68Ga, producing x-rays and Auger electrons with energies smaller than 10 keV. Despite the presence many gamma rays in the decay scheme of 68Ga, there is just one that follows up the β+ decay and it has a low intensity, causing a little interference in measurements. Correction due to detection of 1077 keV photons u (%)
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