Pérez López B, Navarro J F, López Ponte M A, Nogueira P
Whole Body Counting Laboratory - Internal Dosimetry Service (CIEMAT), Avda. Complutense, 40, 28040 Madrid, Spain
Whole Body Counting Laboratory - Internal Dosimetry Service (CIEMAT), Avda. Complutense, 40, 28040 Madrid, Spain.
Radiat Prot Dosimetry. 2016 Sep;170(1-4):231-6. doi: 10.1093/rpd/ncv404. Epub 2015 Sep 28.
(241)Am incorporation due to an incident or chronic exposure causes an internal dose, which can be evaluated from the total activity of this isotope in the skeleton several months after the intake. For this purpose, it is necessary to perform in vivo measurements of this bone-seeker radionuclide in appropriate counting bone geometries with very low attenuation of surrounded tissue and to extrapolate to total activity in the skeleton (ICRP 89, Basic anatomical and physiological data for use in radiological protection: reference values. 2001. 265). The work here presented refers to direct measurements of americium in the Cohen skull phantom at the CIEMAT Whole Body Counter (WBC) using low-energy germanium (LEGe) detectors inside a shielding room. The main goal was to determinate the most adequate head counting geometry for the in vivo detection of americium in the bone. The calibration of the in vivo LEGe system was performed with four detectors with 2 cm of distance to Cohen phantom. Two geometries were measured, on junction of frontal to parietal bones and frontal bone. The efficiencies are very similar in both geometries, the preferred counting geometry is the most comfortable for the person, with the LEGe detectors in the highest part of the frontal bone, near the junction with the parietal bone, CIEMAT WBC participated in a skull intercomparison exercise organised by WG7 of EURADOS (European Radiation Dosimetry Group e.V.). Efficiencies using three different skull phantoms were obtained. Measurements were performed for different head counting positions, four of them in the plane of symmetry and others over the temporal bone. The detector was placed in parallel with the calibration phantom at a distance of 1 cm. The main gamma emission of (241)Am, 59.5 keV (36 %), was used for comparing efficiency values. The lower efficiency was obtained over the frontal and occipital bones. Measurement with one LEGe detector over the parietal bone is the most efficient. The activity of each skull phantom was calculated using CIEMAT head calibration. Results of the EURADOS intercomparison are presented here for discussion.
因事故或长期暴露导致的镅摄入会造成体内剂量，摄入数月后可根据骨骼中该同位素的总活度对其进行评估。为此，有必要在周围组织衰减极低的合适的骨骼计数几何条件下对这种亲骨性放射性核素进行体内测量，并外推至骨骼中的总活度（国际放射防护委员会第89号出版物，《用于放射防护的基本解剖和生理数据：参考值》，2001年，第265页）。此处介绍的工作涉及在CIEMAT全身计数器（WBC）的科恩颅骨模型中，使用屏蔽室内的低能锗（LEGe）探测器直接测量镅。主要目标是确定用于体内检测骨骼中镅的最合适的头部计数几何条件。体内LEGe系统的校准是使用四个与科恩模型距离为2厘米的探测器进行的。测量了两种几何条件，即额骨与顶骨交界处和额骨。两种几何条件下的效率非常相似，首选的计数几何条件是让人感觉最舒适的，LEGe探测器位于额骨的最高处，靠近与顶骨的交界处。CIEMAT WBC参与了由欧洲辐射剂量测定组织（EURADOS）第7工作组组织的颅骨比对实验。获得了使用三种不同颅骨模型的效率。针对不同的头部计数位置进行了测量，其中四个在对称平面内，其他的在颞骨上方。探测器与校准模型平行放置，距离为1厘米。镅的主要γ发射线59.5 keV（36%）用于比较效率值。在额骨和枕骨上方获得的效率较低。在顶骨上方使用一个LEGe探测器进行测量效率最高。每个颅骨模型的活度是使用CIEMAT头部校准计算得出的。此处给出了EURADOS比对的结果以供讨论。
