Lopez M A, Navarro T
CIEMAT-Internal Dosimetry Group, Avda Complutense 22, 28040 Madrid, Spain.
Radiat Prot Dosimetry. 2003;105(1-4):477-82. doi: 10.1093/oxfordjournals.rpd.a006285.
In in vivo detection of internal contamination by actinides the minimum detectable activities (MDAs) correspond to significant doses, so the sensitivity of the detection system is the key to establishing adequate individual monitoring programmes for internal exposure to these radionuclides. The whole body counting (WBC) faculty at CIEMAT uses a low-energy Ge detector system with different available counting geometries to estimate the retention of actinides in the lungs and evaluate 125I in thyroid and 241Am in bone (skull and knee). A study of the factors and uncertainties involved in estimations of MDA is presented for lung and thyroid monitoring. The dependence of detection limits on counting efficiency in the measurement of low-energy emitters in the lungs has been carefully studied, carrying out a comparison among different biometric equations obtained by ultrasound techniques for estimations of chest wall thickness. Dosimetric implications of the estimated MDAs are taken into account in the framework of ICRP 78 application and considering Spanish regulations. The main interest in lung measurements is for the assessment of occupational exposure. This work confirms the low-energy Ge detector system to be an adequate in vivo technique for the routine monitoring of internal exposure to most insoluble uranium compounds (detection of 3% enriched uranium in lungs), and also to be useful in special monitoring programmes or in the case of incidents when the detection of 241Am is required.
在对锕系元素体内污染的检测中，最小可探测活度（MDA）对应着显著剂量，因此检测系统的灵敏度是为这些放射性核素的内照射建立适当个人监测计划的关键。CIEMAT的全身计数（WBC）设备使用具有不同可用计数几何结构的低能锗探测器系统，以估计锕系元素在肺部的滞留情况，并评估甲状腺中的125I和骨骼（颅骨和膝盖）中的241Am。本文针对肺部和甲状腺监测，介绍了MDA估计中涉及的因素和不确定性研究。仔细研究了肺部低能发射体测量中探测限对计数效率的依赖性，对通过超声技术获得的用于估计胸壁厚度的不同生物计量方程进行了比较。在ICRP 78应用框架内并考虑西班牙法规的情况下，考虑了估计的MDA的剂量学影响。肺部测量的主要目的是评估职业暴露。这项工作证实，低能锗探测器系统是一种适用于常规监测大多数不溶性铀化合物内照射（检测肺部3%富集铀）的体内技术，并且在特殊监测计划或需要检测241Am的事故情况下也很有用。
