Collins S M, Keightley J D, Ivanov P, Arinc A, Fenwick A J, Pearce A K
National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW, United Kingdom.
National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW, United Kingdom.
Appl Radiat Isot. 2019 Mar;145:251-257. doi: 10.1016/j.apradiso.2018.10.023. Epub 2018 Dec 1.
At the time of publication, radiopharmaceuticals labelled with thorium-227 are in clinical trials in Europe for the treatment of various types of cancer. In part I of this two-part series the primary standardisation of an aqueous solution of Th was reported. In part II, the activity derived from the recommended absolute γ-ray emission intensities have been compared to that from the primary standardisation techniques. This comparison showed a negative bias of 4% in the determined activity per unit mass with an 11% spread in the activities determined for the eight most intense γ-ray emissions (I > 1%) from the Th α decay. Using the standardised Th, measurements of the characteristic γ-ray emissions from the Ra excited states were made using a calibrated HPGe γ-ray spectrometer. This has enabled the absolute intensities of 70 γ ray emissions from the Th α-decay to be experimentally determined. A significant improvement over the precision of the recommended normalisation scaling factor has been made, with a value of 12.470 (35) % determined. Typically, the precision of the intensities has been improved by an order of magnitude or greater than current recommended values. The correlation matrices for pairs of the most intense γ-ray emission intensities are presented.
在本文发表之时，标记有钍 - 227的放射性药物正在欧洲进行各类癌症治疗的临床试验。在这个两部分系列的第一部分中，报道了钍水溶液的初级标准化。在第二部分中，将源自推荐的绝对γ射线发射强度的活度与初级标准化技术得出的活度进行了比较。该比较显示，每单位质量的测定活度存在4%的负偏差，对于钍α衰变产生的八个最强γ射线发射（I > 1%）所测定的活度，其偏差范围为11%。使用标准化的钍，利用校准后的高纯锗γ射线光谱仪对镭激发态的特征γ射线发射进行了测量。这使得能够通过实验确定钍α衰变产生的70条γ射线发射的绝对强度。相对于推荐的归一化比例因子的精度有了显著提高，测定值为12.470 (35) %。通常，强度的精度提高了一个数量级或比当前推荐值更高。给出了最强γ射线发射强度对的相关矩阵。
