California State University, Fresno, CA, United States of America.
Physiol Meas. 2018 Mar 29;39(3):035007. doi: 10.1088/1361-6579/aaad5a.
L-shell x-ray fluorescence (LXRF) is a non-invasive approach to lead (Pb) concentration measurements in the human bone. The first studies were published in the early 1980s. In the same period the K-shell x-ray fluorescence (KXRF) method using a Cd-109 radionuclide source was developed and later improved and refined. Lower sensitivity and calibration difficulties associated with the LXRF method led the KXRF to be the most adopted method for in vivo human bone Pb studies. In the present study a microbeam-based grazing-incidence approach to Pb LXRF measurements was investigated.
The microbeam produced by an integrated x-ray tube and polycapillary x-ray lens (PXL) unit was used to excite cylindrical plaster-of-Paris (poP) bone phantoms doped with Pb in seven concentrations: 0, 8, 16, 29, 44, 59, and 74 µg g. Two 1 mm- and 3 mm-thick cylindrical shell soft tissue phantoms were made out of polyoxymethylene (POM) plastic. Three bone-soft tissue phantom sets corresponding to the 0, 1, and 3 mm POM thickness values resulted. Each phantom was placed between the microbeam and the detector; its position was controlled using a positioning stage. Small steps (0.1-0.5 mm) and short 30 s x-ray spectra acquisitions were used to find the optimal phantom position according to the maximum observed Sr Kα peak height. At the optimal geometry, five 180 s x-ray spectra were acquired for each phantom set. Calibration lines were obtained using the fitted peak heights of the two observed Pb Lα and Pb Lβ peaks.
The lowest detection limit (DL) values were (2.9 ± 0.2), (4.9 ± 0.3), and (23 ± 3) µg g, respectively. The order of magnitude of the absorbed radiation dose in the POM plastic for the 180 s irradiation was estimated to be <1 mGy.
The results are superior to a relatively recently published LXRF phantom study and show promise for future designs of in vivo LXRF measurements.
L 壳层 X 射线荧光（LXRF）是一种非侵入性方法，可用于测量人体骨骼中的铅（Pb）浓度。最早的研究发表于 20 世纪 80 年代初。同期，利用 Cd-109 放射性核素源开发了 K 壳层 X 射线荧光（KXRF）方法，后来该方法得到了改进和完善。由于 LXRF 方法灵敏度较低且校准困难，因此 KXRF 成为体内人类骨骼 Pb 研究中最常用的方法。本研究采用基于微束的掠入射方法对 Pb LXRF 测量进行了研究。
采用集成 X 射线管和多晶 X 射线透镜（PXL）单元产生的微束，激发 7 种浓度的 Pb 掺杂石膏（poP）骨标本：0、8、16、29、44、59 和 74μg/g。用聚甲醛（POM）塑料制作了两个 1mm 和 3mm 厚的圆柱形壳软组织标本。根据 0、1 和 3mm POM 厚度值，制作了三组对应的骨-软组织标本。每个标本都放置在微束和探测器之间；使用定位台控制其位置。采用小步距（0.1-0.5mm）和 30s 短 X 射线光谱采集，根据观察到的最大 Sr Kα 峰高，找到最佳的标本位置。在最佳几何位置，每个标本集采集 5 个 180s X 射线光谱。通过拟合观察到的两个 Pb Lα 和 Pb Lβ 峰的峰高，获得校准线。
最低检测限（DL）值分别为（2.9±0.2）、（4.9±0.3）和（23±3）μg/g。180s 辐照时，POM 塑料中吸收辐射剂量的数量级估计为<1mGy。
结果优于最近发表的 LXRF 体模研究，为未来体内 LXRF 测量的设计提供了希望。
