A novel calibration for L-shell x-ray fluorescence measurements of bone lead concentration using the strontium Kβ/Kα ratio

Abstract

Objective. Lead (Pb) is a well-known toxic element. In vivo bone Pb concentration measurement is a long-term exposure metric complementary to blood Pb concentration measurement which is a metric of recent exposure. In vivo human tibia bone Pb measurements using Pb K-shell or L-shell x-ray fluorescence (KXRF or LXRF) emissions were developed in the 1980s. KXRF bone Pb measurements using Cd-109 gamma rays and coherent-to-fluorescence ratio to account for differences between phantom and in vivo measurements, was employed in human studies. Bone Pb LXRF method employed x-ray tubes. However, calibration procedures using ultrasound measurements of the soft tissue thickness (STT) proved inaccurate. Approach. In this study, bone and soft tissue (ST) phantoms simulated in vivo bone Pb measurements. Seven plaster-of-Paris cylindrical bone phantoms containing 1.01 mg g−1 of strontium (Sr) were doped with Pb in 0, 8, 16, 29, 44, 59, and 74 μg g−1 concentrations. Polyoxymethylene (POM), resin, and wax were each used to fabricate four ST phantoms in the approximate 1–4 mm thickness range. Pb LXRF measurements were performed using a previously developed optimal grazing incidence position method. Main results. Linear attenuation coefficients measurements of ST materials indicated that POM and resin mimicked well attenuation of Pb x-rays in skin and adipose tissue, respectively. POM and resin data indicated a bone Pb detection limit of 20 μg g−1 for a 2 mm STT. Derived relationships between the Pb concentration, Pb LXRF and Sr K β /K α ratio data did not require STT knowledge. Applied to POM and resin data, the new calibration method yielded unbiased results. Significance. In vivo bone Pb measurements in children were suggested following considerations of radiation dose, STT, detectability and distribution of Pb and Sr in bone. This research meets with the concerns regarding the negative effects of low levels of Pb exposure on neurodevelopment of children.

A Two-Dimensional K-Shell X-ray Fluorescence (2D-KXRF) Model for Soft Tissue Attenuation Corrections of Strontium Measurements in a Cortical Lamb Bone Sample

“…The experimental equipment was presented in our previous publications [59][60][61]. For clarity, the main experimental equipment is described in this section.…”

“…In both cases, the sample was positioned at 15 mm from the PXL end as indicated in Figure 1a. At this position, the lateral size of the X-ray beam expressed as FWHM was 1.7 mm [60]. The XRF procedure titled the optimal grazing-incidence position (OGIP) [58][59][60], was applied to both samples.…”

“…At this position, the lateral size of the X-ray beam expressed as FWHM was 1.7 mm [60]. The XRF procedure titled the optimal grazing-incidence position (OGIP) [58][59][60], was applied to both samples. The OGIP was obtained from data analysis of sequential 10-s duration X-ray spectra acquired at positions separated by equal 0.5 mm steps which brought the sample closer to the X-ray beam while the detector-sample distance was constant as explained in the previous Section 2.1.1.…”

“…The X-ray linear attenuation coefficients of lamb bone slice, leather sample, and Al were measured by employing a procedure described in our previous publication [60]. Comparison of the linear attenuation coefficient measurements of Al to the corresponding values of the XCOM database [63] was used to ensure procedural reliability.…”

Atomic spectrometry update: review of advances in the analysis of clinical and biological materials, foods and beverages

“…Overall, the study demonstrated the potential of the system for large scale population studies though further consideration for accuracy and precision is still required, especially at lower Pb concentrations. A paper by Gherase et al 129 described developments for the calibration of L-shell KXRF spectrometry for the determination of in vivo Pb in bone. In this work, the effect of soft tissue thickness was addressed with bone phantoms doped with various levels of Pb and a fixed amount of Sr and coated in polyoxymethylene, resin and wax to mimic the soft tissue at four different thicknesses between 1–4 mm.…”