Quantification of manganese in human hand bones: a feasibility study
Quantification of manganese in human hand bones: a feasibility study
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DOI：
10.1088/0031-9155/53/15/005
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发表时间：
2008-08-07
影响因子：
3.5
通讯作者：
McNeill, F. E.
中科院分区：
文献类型：
--
作者：
Aslam;Pejovic-Milic, A.;McNeill, F. E.
锰是调节人体神经和骨骼功能所必需的营养物质，但当人类过度接触锰时，它也是有毒的。血液(或血清/血浆)和其他体液仅反映最近一次接触，并迅速恢复到正常范围内，即使对暴露有短暂的反应。在此背景下，我们一直在开发一种非侵入性的测量储存在骨骼中的锰，使用体内中子激活分析。在可行性研究之后，在相关研究伦理委员会的批准下，进行了第一项初步研究，即使用中子活化分析来测量10名健康男性受试者手部骨骼中的锰。这项研究的参与者没有已知的接触锰的历史。由于测量的技术问题，两名志愿者被排除在这项研究之外。本研究受试者锰/钙的逆方差加权平均值为0.12+/-0.68微克锰/克钙，与身体资料估算的0.16-0.78微克锰/克钙和0.63+/-0.30微克锰/克钙的平均值在不确定度范围内可比。建议使用体内诊断技术对职业性接触过量锰的工人进行体内测量，这些工人的骨骼中的锰水平可能会增加许多倍，这是通过各种动物研究证明的。这项技术需要进一步开发，以提高在非暴露人群中体内测量的精确度。锰既是人类健康的必需元素，当人类暴露在过量水平下，特别是通过吸入的方式时，也是有毒的。对锰暴露的生物监测是有问题的。它受动态平衡的影响；血液(或血清/血浆)中的水平仅反映最近的暴露，并迅速恢复到正常范围内，即使在对暴露的反应出现暂时偏离的情况下也是如此。在这种背景下，我们一直在开发一种非侵入性的技术来测量储存在骨骼中的锰，使用体内中子激活分析。在初步可行性研究之后，这项技术因两项重大的基础设施进步而得到加强。一种特别设计的辐照设施用于根据电离辐射的剂量最大限度地激活锰。其次，由8个NaI(Tl)晶体组成的阵列提供了一个非常接近4pi几何形状的检测系统。这项可行性研究使用中子活化分析来测量手骨中的锰，考虑到了两个特点。首先，骨骼中有相当多的镁，这会对锰产生光谱干扰。镁-26(n，伽马)镁-27反应从镁-27的衰变中产生0.843 MeV的伽马射线，这干扰了由锰-55(n，伽马)锰-56反应产生的0.847 MeV的锰-56衰变的伽马射线。其次，这项工作提供了对参照受试者预期的锰水平的估计。从最新的文献中修订了一项估计，以探索该技术作为一种合适的手段的潜力，以筛查患者和暴露于过量锰的人，这些患者和人的骨骼中的锰水平可能会增加许多倍，这是通过各种动物研究证明的。本文介绍了对中子活化系统的改进，利用该系统可以测量锰，从而使受试者手中的检出限达到1.6微克/克钙。它还提供了骨中锰的预期参考水平的修订估计，目前估计为0.63微克/克钙，并强调了需要在多大程度上改进技术，以进一步扩大该技术在非暴露人体受试者体内测量的应用。
Manganese (Mn) is a nutrient essential for regulating neurological and skeletal functions in the human body, but it is also toxic when humans are excessively exposed to Mn. Blood (or serum/plasma) and other body fluids reflect only the most recent exposure and rapidly return to within normal ranges, even when there has been a temporary excursion in response to exposure. In this context, we have been developing a non-invasive measurement of Mn stored in bone, using in vivo neutron activation analysis. Following feasibility studies, a first pilot study, using neutron activation analysis to measure Mn in the bones of the hand of ten healthy male human subjects, was conducted with the approval of the concerned research ethics boards. The participants of this study had no known history of exposure to Mn. Two volunteers were excluded from this study due to technical problems with their measurements. The inverse variance weighted mean value of Mn/Ca for the participants of this study is 0.12 +/- 0.68 mu g Mn/g Ca which is comparable within uncertainties with the estimated range of 0.16-0.78 mu g Mn/g Ca and mean value of 0.63 +/- 0.30 mu g Mn/g Ca derived from cadaver data. It is recommended to investigate the use of the diagnostic technique for in vivo measurements of workers exposed occupationally to excessive amounts of Mn who could develop many-fold increased levels of Mn in bones as demonstrated through various animal studies. The technique needs further development to improve the precision of in vivo measurements in the non-exposed population.Manganese is both an essential element to human health and also toxic when humans are exposed to excessive levels, particularly by means of inhalation. Biological monitoring of manganese exposure is problematic. It is subject to homeostasis; levels in blood (or serum/plasma) reflect only the most recent exposure and rapidly return to within normal ranges, even when there has been a temporary excursion in response to exposure. In this context, we have been developing a non-invasive technique for measurement of manganese stored in bone, using in vivo neutron activation analysis. Following preliminary feasibility studies, the technique has been enhanced by two significant infrastructure advances. A specially designed irradiation facility serves to maximize the activation of manganese with respect to the dose of ionizing radiation. Secondly, an array of eight NaI(Tl) crystals provides a detection system with very close to 4 pi geometry. This feasibility study, using neutron activation analysis to measure manganese in the bones of the hand, takes two features into account. Firstly, there is considerable magnesium present in the bone and this produces a spectral interference with the manganese. The Mg-26(n, gamma)Mg-27 reaction produces gamma-rays of 0.843 MeV from the decay of Mg-27, which interfere with the 0.847 MeV gamma-rays from the decay of Mn-56, produced by the Mn-55(n, gamma)Mn-56 reaction. Secondly, this work provides estimates of the levels of manganese to be expected in referent subjects. A revised estimate has been made from the most recent literature to explore the potential of the technique as a suitable means of screening patients and people exposed to excessive amounts of Mn who could develop many-fold increased levels of Mn in bones as demonstrated through various animal studies. This report presents the enhancements to the neutron activation system, by which manganese can be measured, which resulted in a detection limit in the hand of human subjects of 1.6 mu g/g Ca. It also provides a revised estimate of expected referent levels of manganese in bone, now estimated to be 0.63 mu g/g Ca and highlights the extent to which technical improvements will be required to further extend the application of the technique for in vivo measurements in non-exposed human subjects.