Kossert Karsten, Nähle Ole J, Ott Oliver, Dersch Rainer
Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany.
Appl Radiat Isot. 2012 Sep;70(9):2215-21. doi: 10.1016/j.apradiso.2012.02.104. Epub 2012 Mar 4.
The activity concentration of a (177)Lu solution was measured within the scope of the international comparison CCRI(II)-K2.Lu-177, starting in 2009. At PTB, the solution was measured by means of 4πβ-γ coincidence counting using a proportional counter and a NaI detector. In addition, liquid scintillation counting using the CIEMAT/NIST efficiency tracing method as well as the triple-to-double coincidence ratio (TDCR) method was applied. The efficiency computation for the TDCR method was realized by means of the MICELLE2 program, applying a stochastic model for the computation of electron emission spectra. The activity concentrations derived from the three methods were found to be in good agreement and the relative standard uncertainty of the combined result was found to be 0.19%. At PTB, the combined result was used to calibrate a 4π ionization chamber for future calibrations of this isotope which is frequently used in nuclear medicine. In addition, activity standardizations were combined with gamma-ray spectrometry to determine photon emission probabilities. To this end, the comparison solution as well as another (177)Lu solution was used. The results are in good agreement with previous measurements at PTB but show a considerable discrepancy to recently published values from Deepa et al. (2011). The decay curve of a third solution was followed by liquid scintillation counting for about 66 days to determine the half-life of (177)Lu, which was found to be T(1/2)=6.639(9) d.
自2009年起，在国际比对CCRI(II)-K2.Lu-177的范围内对一种¹⁷⁷Lu溶液的活度浓度进行了测量。在德国物理技术研究院（PTB），使用正比计数器和碘化钠探测器通过4πβ-γ符合计数法对该溶液进行测量。此外，还应用了使用CIEMAT/NIST效率追踪法以及三对双符合比（TDCR）法的液体闪烁计数法。TDCR法的效率计算通过MICELLE2程序实现，应用随机模型计算电子发射光谱。发现由这三种方法得出的活度浓度吻合良好，合并结果的相对标准不确定度为0.19%。在PTB，合并结果用于校准一个4π电离室，以供未来对这种在核医学中常用的同位素进行校准。此外，将活度标准化与伽马射线能谱法相结合以确定光子发射概率。为此，使用了比对溶液以及另一种¹⁷⁷Lu溶液。结果与PTB之前的测量结果吻合良好，但与迪帕等人（2011年）最近发表的值存在相当大的差异。通过液体闪烁计数法对第三种溶液的衰变曲线进行了约66天的跟踪，以确定¹⁷⁷Lu的半衰期，结果发现其半衰期为T(1/2)=6.639(9)天。
