Fast and automated monitoring of gadolinium-based contrast agents in surface waters

Quantification of [99Tc]TcO4- in urine by means of anion-exchange chromatography-aerosol desolvation nebulization-inductively coupled plasma-mass spectrometry

To sensitively determine 99Tc, a new method for internal quantification of its most common and stable species, [99Tc]Tc O 4 - , was developed. Anion-exchange chromatography (IC) was coupled to inductively coupled plasma-mass spectrometry (ICP-MS) and equipped with an aerosol desolvation system to provide enhanced detection power. Due to a lack of commercial Tc standards, an isotope dilution-like approach using a Ru spike and called isobaric dilution analysis (IBDA) was used for internal quantification of 99Tc. This approach required knowledge of the sensitivities of 99Ru and 99Tc in ICP-MS. The latter was determined using an in-house prepared standard manufactured from decayed medical 99mTc-generator eluates. This standard was cleaned and preconcentrated using extraction chromatography with TEVA resin and quantified via total reflection X-ray fluorescence (TXRF) analysis. IC coupled to ICP-MS enabled to separate, detect and quantify [99Tc]Tc O 4 - as most stable Tc species in complex environments, which was demonstrated in a proof of concept. We quantified this species in untreated and undiluted raw urine collected from a patient, who previously underwent scintigraphy with a 99mTc-tracer, and determined a concentration of 19.6 ± 0.5 ng L-1. The developed method has a high utility to characterize a range of Tc-based radiopharmaceuticals, to determine concentrations, purity, and degradation products in complex samples without the need to assess activity parameters of 99(m)Tc.

Contrast Media-driven Anthropogenic Gadolinium: Knowns and Unknowns

Gadolinium-based contrast agents (GBCAs) have augmented the capabilities of MRI, which has led to their widespread and increasing use in radiology practice. GBCAs are introduced into the environment through disposal of unused product and elimination after intravenous injection, both primarily via liquid dispersion into the environment. This human introduction of gadolinium into the environment, referred to as anthropogenic gadolinium, is associated with the detection of gadolinium in water systems, raising concerns for potential adverse impact and prompting certain mitigation actions. This article summarizes the existing knowledge and problem scope, conveys the relevant underlying chemical principles of chelate dissociation, and offers an inferred perspective that the magnitude of the problem is most unlikely to cause human harm. The merits and limitations regarding possible mitigation tactics, such as collecting urine after GBCA administration, use of lower-dose high-relaxivity macrocyclic GBCAs, and the option for virtual contrast-enhanced examinations, will be discussed. Finally, the potential for monitoring gadolinium uptake in bone will be presented, and recommendations for future research will be offered. © RSNA, 2024 See also the article by Ibrahim et al in this issue. See also the article by McKee et al in this issue.

Review of strategies to reduce the contamination of the water environment by gadolinium-based contrast agents

Gadolinium-based contrast agents (GBCA) are essential for diagnostic MRI examinations. GBCA are only used in small quantities on a per-patient basis; however, the acquisition of contrast-enhanced MRI examinations worldwide results in the use of many thousands of litres of GBCA per year. Data shows that these GBCA are present in sewage water, surface water, and drinking water in many regions of the world. Therefore, there is growing concern regarding the environmental impact of GBCA because of their ubiquitous presence in the aquatic environment. To address the problem of GBCA in the water system as a whole, collaboration is necessary between all stakeholders, including the producers of GBCA, medical professionals and importantly, the consumers of drinking water, i.e. the patients. This paper aims to make healthcare professionals aware of the opportunity to take the lead in making informed decisions about the use of GBCA and provides an overview of the different options for action.In this paper, we first provide a summary on the metabolism and clinical use of GBCA, then the environmental fate and observations of GBCA, followed by measures to reduce the use of GBCA. The environmental impact of GBCA can be reduced by (1) measures focusing on the application of GBCA by means of weight-based contrast volume reduction, GBCA with higher relaxivity per mmol of Gd, contrast-enhancing sequences, and post-processing; and (2) measures that reduce the waste of GBCA, including the use of bulk packaging and collecting residues of GBCA at the point of application.Critical relevance statement This review aims to make healthcare professionals aware of the environmental impact of GBCA and the opportunity for them to take the lead in making informed decisions about GBCA use and the different options to reduce its environmental burden.Key points• Gadolinium-based contrast agents are found in sources of drinking water and constitute an environmental risk.• Radiologists have a wide spectrum of options to reduce GBCA use without compromising diagnostic quality.• Radiology can become more sustainable by adopting such measures in clinical practice.

Species-dependent uptake of gadolinium in Chlamydomonas reinhardtii algae

Single cell-inductively coupled plasma-mass spectrometry (sc-ICP-MS) was used in this study as a valuable tool to assess the species-dependent uptake of metallopharmaceuticals into algal cells. Chlamydomonas reinhardtii algae were incubated for 24 h with four Gadolinium-based contrast agents (GBCAs) and GdCl3. A species dependency towards the uptake of the tested Gd species was observed. Using single cell-ICP-MS, a Gd signal corresponding to single cell events was detected for GdCl3 and the linear GBCAs Omniscan® (Gadodiamide, Gd-DTPA-BMA) and Magnevist® (Gadodiamide, Gd-DTPA). For the macrocyclic complexes Dotarem® (Gadoteric acid, Gd-DOTA) and Gadovist® (Gadobutrol, Gd-BT-DO3A), no such Gd signal was visible. Total Gd analysis via ICP-MS confirmed the presence of Gd in the cells only after incubation with GdCl3 and the linear GBCAs, while only small amounts of Gd were detected for the incubations with macrocyclic GBCAs. Furthermore, the results showed that more Gd is bound to cell structures or macromolecules, while smaller amounts are present in the lysate. Using hydrophilic interaction liquid chromatography (HILIC)-ICP-MS, the soluble Gd species in the lysate were analyzed to determine if the initial Gd complexes were still intact. Surprisingly, no intact GBCAs were detected in the lysates of any incubation solution, possibly due to a change in Gd speciation. Further research is needed to assess which Gd species are present in the lysate, while "free" Gd ions or adducts with cell constituents are the most likely explanation. This study highlights the need for species-dependent investigation of elements in aquatic organisms. Moreover, the uptake of linear GBCAs and their species alteration raises the question of a potential accumulation of Gd in the food chain.

Analysis of the elemental species-dependent uptake of lanthanide complexes in Arabidopsis thaliana plants by LA-ICP-MS

Gadolinium-based contrast agents (GBCAs) are found increasingly in different water bodies, making the investigation of their uptake and distribution behavior in plants a matter of high interest to assess their potential effects on the environment. Depending on the used complexing agent, they are classified into linear or macrocyclic GBCAs, with macrocyclic complexes being more stable. In this study, by using TbCl3, Gd-DTPA-BMA, and Eu-DOTA as model compounds for ionic, linear, and macrocyclic lanthanide species, the elemental species-dependent uptake into leaves of Arabidopsis thaliana under identical biological conditions was studied. After growing for 14 days on medium containing the lanthanide species, the uptake of all studied compounds was confirmed by means of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Furthermore, the uptake rate of TbCl3 and the linear Gd-DTPA-BMA was similar, with Tb and Gd hotspots colocated in the areas of hydathodes and the trichomes of the leaves. In contrast, in the case of the macrocyclic Eu-DOTA, Eu was mainly located in the leaf veins. Additionally, Eu was colocated with Tb and Gd in the hydathode at the tip of the leave. Removal of the lanthanide species from the medium led to a decrease in signal intensities, indicating their subsequent release to some extent. However, seven days after the removal, depositions of Eu, Gd, and Tb were still present in the same areas of the leaves as before, showing that complete elimination was not achieved after this period of time. Overall, more Eu was present in the leaves compared to Gd and Tb, which can be explained by the high stability of the Eu-DOTA complex, potentially leading to a higher transport rate into the leaves, whereas TbCl3 and Gd-DTPA-BMA could interact with the roots, reducing their mobility.

Analytical strategies to measure gadolinium as a wastewater marker in surface and groundwater systems

The increasing use of gadolinium (Gd)-based contrast agents in magnetic resonance imaging and the recalcitrant behavior of Gd during municipal wastewater treatment have led to increased concentrations of the tracer in aquatic environments. These anthropogenic Gd emissions to wastewater and, subsequently, to surface and groundwater systems can be exploited to calculate groundwater travel times and mixing ratios, identify wastewater inputs, and calibrate groundwater models. However, analytical complexity, costs, and the time needed to directly measure anthropogenic inputs hinder the practical use of Gd. While direct measurements with inductively coupled plasma-mass spectrometry (ICP-MS) are highly efficient and feasible, only total Gd can be detected with this approach. In unknown hydrogeological systems, the differentiation between total, anthropogenic, and geogenic Gd by interpolating rare earth element patterns requires complex sample pre-treatment and pre-concentration. Direct measurements of Gd can be obtained using anion-exchange chromatography coupled to ICP-MS but the limit of quantification will be higher. Here we provide guidelines for selecting the optimal method for the analysis of Gd as a wastewater tracer in surface-groundwater systems.•The cost-effectiveness of existing analytical strategies to measure Gd when used as a wastewater tracer in surface-groundwater systems is addressed•A novel analytical strategy for direct determination of total Gd is presented.

Gadolinium based contrast agents (GBCAs): Uniqueness, aquatic toxicity concerns, and prospective remediation

The current toxicity concerns of gadolinium-based contrast agents (GBCAs) have birthed the need to regulate and, sometimes restrict its clinical administration. However, tolerable concentration levels of Gd in the water sector have not been set. Therefore, the detection and speedy increase of the anthropogenic Gd-GBCAs in the various water bodies, including those serving as the primary source of drinking water for adults and children, is perturbing. Nevertheless, the strongly canvassed risk-benefit considerations and superior uniqueness of GBCAs compared to the other ferromagnetic metals guarantees its continuous administration for Magnetic resonance imaging (MRI) investigations regardless of the toxicity concerns. Unfortunately, findings have shown that both the advanced and conventional wastewater treatment processes do not satisfactorily remove GBCAs but rather risk transforming the chelated GBCAs to their free ionic metal (Gd ³⁺) through inadvertent degradation processes. This unintentional water processing-induced GBCA dechelation leads to the intricate  pathway for unintentional human intake of Gd ion. Hence exposure to its probable ecotoxicity and several reported inimical effects on human health such as; digestive symptoms, twitching or weakness, cognitive flu, persistent skin diseases, body pains, acute renal and non-renal adverse reactions, chronic skin, and eyes changes. This work proposed an economical and manageable remediation technique for the potential remediation of Gd-GBCAs in wastewater, while a precautionary limit for Gd in public water and commercial drinks is advocated.

Facets of ICP-MS and their potential in the medical sciences-Part 1: fundamentals, stand-alone and hyphenated techniques

Since its inception in the early 80s, inductively coupled plasma–mass spectrometry has developed to the method of choice for the analysis of elements in complex biological systems. High sensitivity paired with isotopic selectivity and a vast dynamic range endorsed ICP-MS for the inquiry of metals in the context of biomedical questions. In a stand-alone configuration, it has optimal qualities for the biomonitoring of major, trace and toxicologically relevant elements and may further be employed for the characterisation of disrupted metabolic pathways in the context of diverse pathologies. The on-line coupling to laser ablation (LA) and chromatography expanded the scope and application range of ICP-MS and set benchmarks for accurate and quantitative speciation analysis and element bioimaging. Furthermore, isotopic analysis provided new avenues to reveal an altered metabolism, for the application of tracers and for calibration approaches. In the last two decades, the scope of ICP-MS was further expanded and inspired by the introduction of new instrumentation and methodologies including novel and improved hardware as well as immunochemical methods. These additions caused a paradigm shift for the biomedical application of ICP-MS and its impact in the medical sciences and enabled the analysis of individual cells, their microenvironment, nanomaterials considered for medical applications, analysis of biomolecules and the design of novel bioassays. These new facets are gradually recognised in the medical communities and several clinical trials are underway. Altogether, ICP-MS emerged as an extremely versatile technique with a vast potential to provide novel insights and complementary perspectives and to push the limits in the medical disciplines. This review will introduce the different facets of ICP-MS and will be divided into two parts. The first part will cover instrumental basics, technological advances, and fundamental considerations as well as traditional and current applications of ICP-MS and its hyphenated techniques in the context of biomonitoring, bioimaging and elemental speciation. The second part will build on this fundament and describe more recent directions with an emphasis on nanomedicine, immunochemistry, mass cytometry and novel bioassays.