Miyaji Noriaki, Miwa Kenta, Wagatsuma Kei, Umeda Takuro, Murata Taisuke, Takiguchi Tomohiro, Koizumi Mitsuru
Department of Nuclear Medicine, Cancer Institute Hospital of Japanese Foundation for Cancer Research.
Nihon Hoshasen Gijutsu Gakkai Zasshi. 2013 Dec;69(12):1379-86. doi: 10.6009/jjrt.2013_jsrt_69.12.1379.
Accurate calibration of dose calibrators (DC) is required for quantitative positron emission tomography (PET) studies to generate meaningful information. Values measured by DC depend not only on the radioactive nuclide but also the environment where measurements are taken. Therefore, DC must be calibrated at each location. The present study aimed to determine appropriate calibration values, and evaluate the performance of DC using a traceable (68)Ge/(68)Ga calibration source that is available as a surrogate (18)F source.
We used a (68)Ge/(68)Ga calibration source to determine the optimal DC value for measuring (18)F activity in the operating environment. Variations in sensitivity and geometry as well as measurement uncertainty were evaluated using the (68)Ge/(68)Ga source. We adopted the criteria of the Guide for the expression of uncertainty in measurement (GUM) to evaluate DC performance.
Although the manufacturer's recommended (18)F calibration number for the CRC-25PET is 480, we found that the optimal number was 482. Over a period of one year, the sensitivity of the DC varied <0.1%, and the expanded uncertainty of DC measurements was 2.2%.
Measurements of the certified activity of a traceable national standard were corrected, and the uncertainty of measurements as well as the accuracy of a DC were determined. Calibration numbers for DC should be regularly determined using (68)Ge/(68)Ga calibration sources at each location to ensure the most accurate results.
定量正电子发射断层扫描（PET）研究需要对剂量校准仪（DC）进行精确校准，以生成有意义的信息。DC测量的值不仅取决于放射性核素，还取决于测量所处的环境。因此，DC必须在每个位置进行校准。本研究旨在确定合适的校准值，并使用可作为替代（18）F源的可溯源（68）Ge/（68）Ga校准源评估DC的性能。
我们使用（68）Ge/（68）Ga校准源来确定在操作环境中测量（18）F活度的最佳DC值。使用（68）Ge/（68）Ga源评估灵敏度、几何形状的变化以及测量不确定度。我们采用《测量不确定度表示指南》（GUM）的标准来评估DC性能。
尽管CRC - 25PET制造商推荐的（18）F校准值为480，但我们发现最佳值为482。在一年的时间里，DC的灵敏度变化<0.1%，DC测量的扩展不确定度为2.2%。
对可溯源国家标准的认证活度测量进行了校正，确定了测量不确定度以及DC的准确性。应在每个位置定期使用（68）Ge/（68）Ga校准源确定DC的校准值，以确保获得最准确的结果。
