Ex vivo quantification of lanthanum and gadolinium in post-mortem human tibiae with estimated barium and iodine concentrations using K x-ray fluorescence

Abstract

Objectives: Lanthanum (La) and gadolinium (Gd) are known to deposit in bone of exposed populations, namely those who are orally administered lanthanum carbonate (LaC, La 2 (CO 3 ) 3 ) or are injected with Gd-based contrast agents, respectively. In this work, bone La and Gd concentrations from the environment and diet were measured using x-ray fluorescence in ten post-mortem human tibiae. As a secondary objective, bone barium (Ba) and iodine concentrations were estimated. Approach: Two calibration lines were produced for La and Gd and the minimum detection limits (MDLs) of the system were determined using a 180° irradiation-detection geometry. Main results: The MDLs of the system were 0.4 µg La g −1 bone mineral and 0.5 µg Gd g −1 bone mineral. The mean concentrations were −0.02 ± 0.1 µg La g −1 bone mineral and 0.1 ± 0.2 µg Gd g −1 bone mineral in tibiae. The average Ba and iodine concentrations estimated from the experimental La calibration line and Monte-Carlo derived sensitivity factors were determined to be 3.4 ± 0.8 µg Ba g −1 bone mineral and −0.5 ± 0.3 µg iodine g −1 bone mineral. Since it was discovered that four donors previously received an iodine-based contrast agent, the mean concentrations in these donors was 27.8 ± 28.4 µg iodine g −1 bone mineral. Significance: The XRF system has determined baseline concentrations of these four heavy metals in trace quantities from natural exposure pathways (with the exception of iodine in four donors). This indicates that the system can measure low levels in ex vivo tibiae samples and can potentially be further developed for in vivo studies involving live subjects who are directly exposed to these metals.

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

“…This review would not be complete without mention of XRF spectrometry for the analysis of bone . Nguyen et al 105 focussed on the quantification of La and Gd by KXRF spectrometry, with Ba and I inferred from sensitivity factors derived from the La calibration line and Monte Carlo simulations. Tibiae from human cadavers were obtained from individuals with no known exposure to either La ( e.g.…”

Investigating coherent normalization and dosimetry for the 241Am-La K XRF system

“…All experimental coherently normalized data points are shown as an average of three independent measurements. Peak fitting was performed in OriginPro 2019 (OriginLab Corp., Northampton, MA, USA) with the fitting function described in our previous work (Nguyen et al 2019).…”

“…A sample XRF spectrum of the bare hydroxyapatite phantom is shown in figure 5 where the inset graph illustrates the four term Gaussian function used to fit the La Kα 1,2 x-ray signals at 33.4 keV and 33.0 keV, in addition to Ba Kα x-ray peaks that originated from the powders used to create the hydroxyapatite phantom and the fourth Gaussian peak was used to fit a 33.2 keV gamma emission from the 241 Am source (Nguyen et al 2019).…”

“…Previously, it was determined that the minimum detection limit for the 241 Am-La XRF system for a 2000 s measurement while accounting for a 0.55 cm overlying tissue thickness was 3.9 µg La g −1 bone mineral (Nguyen et al 2019). This detection limit is comparable to the highest concentration of 5.5 µg La g −1 bone reported after one year of LaC administration (D'Haese et al 2003), while in another study a concentration of 9.5 µg La g −1 of wet weight of bone was measured following four and a half years of LaC usage (Persy et al 2006).…”

“…A summary of other XRF systems has been reviewed extensively in (Chettle and McNeill 2019). Previously, our group developed an XRF system capable of measuring La in a series of hydroxyapatite-based phantoms and post-mortem human tibiae (Nguyen et al 2019). Lanthanum is orally ingested through LaC [La 2 (CO 3 ) 3 ], a phosphate-binding drug used to reduce serum phosphate concentrations in individuals with end-stage renal disease (Damment and Pennick 2008).…”