Sorenson J A
J Nucl Med. 1979 Dec;20(12):1286-93.
We have investigated a technique for measuring stable iodine concentrations by absorption-edge transmission measurements using a Ce 139 radiation source. The lanthanum daughter emits characteristic x-rays whose energies just bracket the absorption edge of iodine at 33.2 keV. Relative transmission of these x-rays is sensitive to iodine concentration in the sample, but is relatively insensitive to other elements. By applying energy-selective beam filtration, it is possible to determine the relative transmission of these closely spaced x-ray energies with NaI(Tl) detectors. Optimizations of sample thickness, detector thickness, and Ce-139 source activity are discussed. Using sample volumes of about 10 ml, one can determine iodine concentration to an uncertainty (standard deviation) of +/- 5 microgram/ml with a 5-mCi source in a measurement time of 400 sec. Potential clinical applications of the in vitro technique are discussed, along with comparative aspects of the Ce-139 technique and other absorption and fluorescence techniques for measuring stable iodine.
我们研究了一种通过使用Ce 139辐射源进行吸收边透射测量来测量稳定碘浓度的技术。镧子体发射特征X射线，其能量刚好涵盖碘在33.2 keV处的吸收边。这些X射线的相对透射率对样品中的碘浓度敏感，但对其他元素相对不敏感。通过应用能量选择性束流过滤，使用NaI(Tl)探测器可以确定这些间隔很近的X射线能量的相对透射率。讨论了样品厚度、探测器厚度和Ce-139源活度的优化。使用约10 ml的样品体积，在400秒的测量时间内，使用5毫居里的源，可以将碘浓度测定到±5微克/毫升的不确定度（标准偏差）。讨论了该体外技术的潜在临床应用，以及Ce-139技术与其他用于测量稳定碘的吸收和荧光技术的比较方面。
