Iron-mobilizing properties of the gadolinium-DTPA complex: clinical and experimental observations

Real-Time Deformability Cytometry Detects Leukocyte Stiffening After Gadolinium-Based Contrast Agent Exposure

OBJECTIVES

Reports on gadolinium (Gd) retention in soft tissues after administration of Gd-based contrast agents (GBCAs) raise concerns about Gd-induced changes in the biophysical properties of cells and tissues. Here, we investigate if clinical GBCAs of both classes of linear and macrocyclic structure cause changes in the mechanical properties of leukocytes in human blood samples.

MATERIAL AND METHODS

Real-time deformability cytometry was applied to human blood samples from 6 donors. The samples were treated with 1 mM gadoteric acid (Dotarem), gadopentetic acid (Magnevist), gadobutrol (Gadovist), or Gd trichloride at 37°C for 1 hour to mimic clinical doses of GBCAs and exposure times. Leukocyte subtypes-lymphocytes, monocytes, and neutrophils-were identified based on their size and brightness and analyzed for deformability, which is inversely correlated with cellular stiffness.

RESULTS

We observed significant stiffening (3%-13%, P < 0.01) of all investigated leukocyte subtypes, which was most pronounced for lymphocytes, followed by neutrophils and monocytes, and the effects were independent of the charge and steric structure of the GBCA applied. In contrast, no changes in cell size and brightness were observed, suggesting that deformability and cell stiffness measured by real-time deformability cytometry are sensitive to changes in the physical phenotypes of leukocytes after GBCA exposure.

CONCLUSIONS

Real-time deformability cytometry might provide a quantitative blood marker for critical changes in the physical properties of blood cells in patients undergoing GBCA-enhanced magnetic resonance imaging.

Stability of MRI contrast agents in high-energy radiation of a 1.5T MR-Linac

BACKGROUND

Gadolinium-based contrast is often used when acquiring MR images for radiation therapy planning for better target delineation. In some situations, patients may still have residual MRI contrast agents in their tissue while being treated with high-energy radiation. This is especially true when MRI contrast agents are administered during adaptive treatment replanning for patients treated on MR-Linac systems.

PURPOSE

The purpose of this study was to analyze the molecular stability of MRI contrast agents when exposed to high energy photons and the associated secondary electrons in a 1.5T MR-Linac system. This was the first step in assessing the safety of administering MRI contrast agents throughout the course of treatment.

MATERIALS AND METHODS

Two common MRI contrast agents were irradiated with 7 MV photons to clinical dose levels. The irradiated samples were analyzed using liquid chromatography-high resolution mass spectrometry to detect degradation products or conformational alterations created by irradiation with high energy photons and associated secondary electrons.

RESULTS

No significant change in chemical composition or displacement of gadolinium ions from their chelates was discovered in samples irradiated with 7 MV photons at relevant clinical doses in a 1.5T MR-Linac. Additionally, no significant correlation between concentrations of irradiated MRI contrast agents and radiation dose was observed.

CONCLUSION

The chemical composition stability of the irradiated contrast agents is promising for future use throughout the course of patient treatment. However, in vivo studies are needed to confirm that unexpected metabolites are not created in biological milieus.

Gadolinium-based contrast agents: did we miss something in the last 25 years?

In the last 24 months, several clinical and experimental studies, suggested first and demonstrated later, a progressive concentration of Gadolinium in the brain of normal renal function patients, following repeated injections of some of the commercially approved Gadolinium-Based Contrast Agents. Although, till now, Gadolinium brain deposits have not been associated to any kind of neurological signs or symptoms, they oblige the radiology community to modify the actual approach in using Gadolinium contrast media in daily practice, to reduce unknown possible risks for patients.

The effect of MRI contrast agents on hepatic and splenic uptake in the rabbit during (99m) Tc-MDP bone scintigraphy

The objective of this study was to investigate the effects of Omniscan® and Magnevist® on (99m) Tc-MDP uptake in rabbits during (99m) Tc-MDP bone scintigraphy. In Experiment Group 1, 30 healthy adult rabbits were randomized into six subgroups (n = 5); each subgroup experienced a different time interval between injections (30 min, 60 min, 120 min, 240 min, 360 min, 24 h). All six subgroups were injected first with Omniscan®, then with (99m) Tc-MDP. After 7 days, the same six subgroups were injected with normal saline followed by (99m) Tc-MDP at the same time intervals. In Experiment Group 2, 20 healthy adult rabbits were allocated randomly to four subgroups (n = 5); each subgroup experienced a different time interval between injections (30 min, 60 min, 120 min, 240 min). All four subgroups were injected first with Magnevist®, then with (99m) Tc-MDP. After 7 days, the same four subgroups were injected with normal saline followed by (99m) Tc-MDP. In all experiments, whole-body skeletal imaging was performed. Liver, spleen, and background were delineated to determine the target-to-background (T/B) ratio. Diffusely increased intake of the imaging agent was seen in the liver and spleen when the injection-time interval between Omniscan® and (99m) Tc-MDP varied from 30 min to 240 min and when the time interval between Magnevist® and (99m) Tc-MDP was 30 min-60 min. The imaging findings are consistent with the results of L/B and S/B ratios in each experiment group. Both Omniscan® and Magnevist® have an effect on (99m) Tc-MDP uptake during bone scanning; the main effect is diffusely increased hepatic and splenic activity.

Evaluation of a quercetin–gadolinium complex as an efficient positive contrast enhancer for magnetic resonance imaging

The quercetin–gadolinium complex showing superior contrast than the commercially used gadopentetate dimeglumine.

A feasibility study to determine the potential of in vivo detection of gadolinium by x-ray fluorescence (XRF) following gadolinium-based contrast-enhanced MRI

The feasibility of using a (109)Cd γ-ray induced K x-ray fluorescence (K-XRF) system for the in vivo detection of gadolinium (Gd) in bone has been investigated. The K-XRF bone measurement system employs an array of four detectors, and is normally used for the non-invasive study of bone lead levels. The system was used to measure bone simulating phantoms doped with varying levels of gadolinium and fixed amounts of sodium (Na), chlorine (Cl) and calcium (Ca). The detection limits for bare bone phantoms, using a source of activity 0.17 GBq, were determined to be 3.9 ppm and 6.5 ppm (µg Gd per gram phantom) for the Kα1 and Kα2 Gd x-ray peaks, respectively. This leads to an overall detection limit of 3.3 ppm (µg Gd per gram phantom). Layers of plastic were used to simulate overlying soft tissue and this permitted prediction of a detection limit, using the current strength of our radioisotope source, of 6.1 ppm to 8.6 ppm (µg Gd per gram phantom) for fingers with 2-4 mm of overlying tissue. With a new source of activity 5 GBq, we predict that this system could achieve a detection limit of 4-5.6 µg Gd g(-1) Ca. This is within the range of levels (2-30 µg Gd g(-1) Ca) previously found in the bone of patients receiving Gd based contrast imaging agents. The technique is promising and warrants further investigation.

Trace element analysis of human urine collected after administration of Gd-based MRI contrast agents: characterizing spectral interferences using inorganic mass spectrometry

Analysis of human urine is commonly used in biomonitoring studies to assess exposure to essential (e.g., Cu, Zn, Se) and non-essential (Pb, Cd, Pt) trace elements. These data are also used in epidemiological studies to evaluate potential associations between trace element exposure and various health outcomes within a population. Today most trace element analyses are typically performed using quadrupole-based inductively coupled plasma mass spectrometry (Q-ICP-MS). However, there is always the potential for spectral interferences with Q-ICP-MS instrumentation, especially when analyzing human specimens that may contain medications and other exogenous substances. Moreover, such xenobiotics may be unknown to the investigators. In a recent study focusing on environmental exposures and endometriosis: Endometriosis: Natural History, Diagnosis, and Outcomes (ENDO Study), urine specimens (n=619) were collected from participating women upon enrollment into the study or prior to surgery or pelvic magnetic resonance imaging (MRI), and analyzed for 21 trace elements by Q-ICP-MS. Here we report on some anomalous results observed for Se and Pt with elevated concentrations up to several orders of magnitude greater than what might be expected based on established reference intervals. Further investigations using Sector Field (SF-) ICP-MS instrumentation led to identification of doubly charged and polyatomic gadolinium (Gd) species traced to a Gd-based contrast agent that was administered to some subjects just prior to urine collection. Specifically, interferences from Gd2+ and several minor polyatomics were identified as interferences on all of the major isotopes of Se including 74Se, 76Se, 77Se, 78Se, 80Se, and 82Se. While trace amounts of Pt were present in the urine, a number of Gd-containing polyatomic species were also evident as major interferences on all isotopes of Pt (190Pt, 192Pt, 194Pt, 195Pt, 196Pt, and 198Pt), including Gd-chlorides, Gd-argides, and Gd-oxides. These observations underscore the importance of considering potential isobaric interferences when interpreting unusual trace element results for clinical specimens.

Myelin imaging compound (MIC) enhanced magnetic resonance imaging of myelination

The vertebrate nervous system is characterized by myelination, a fundamental biological process that protects the axons and facilitates electric pulse transduction. Damage to myelin is considered a major effect of autoimmune diseases such as multiple sclerosis (MS). Currently, therapeutic interventions are focused on protecting myelin integrity and promoting myelin repair. These efforts need to be accompanied by an effective imaging tool that correlates the disease progression with the extent of myelination. To date, magnetic resonance imaging (MRI) is the primary imaging technique to detect brain lesions in MS. However, conventional MRI cannot differentiate demyelinated lesions from other inflammatory lesions and therefore cannot predict disease progression in MS. To address this problem, we have prepared a Gd-based contrast agent, termed MIC (myelin imaging compound), which binds to myelin with high specificity. In this work, we demonstrate that MIC exhibits a high kinetic stability toward transmetalation with promising relaxometric properties. MIC was used for in vivo imaging of myelination following intracerebroventricular infusion in the rat brain. MIC was found to distribute preferentially in highly myelinated regions and was able to detect regions of focally induced demyelination.

Strategies for the preparation of bifunctional gadolinium(III) chelators

The development of gadolinium chelators that can be easily and readily linked to various substrates is of primary importance for the development high relaxation efficiency and/or targeted magnetic resonance imaging (MRI) contrast agents. Over the last 25 years a large number of bifunctional chelators have been prepared. For the most part, these compounds are based on ligands that are already used in clinically approved contrast agents. More recently, new bifunctional chelators have been reported based on complexes that show a more potent relaxation effect, faster complexation kinetics and in some cases simpler synthetic procedures. This review provides an overview of the synthetic strategies used for the preparation of bifunctional chelators for MRI applications.

Nephrogenic systemic fibrosis and gadolinium-based contrast agents

The strong association between nephrogenic systemic fibrosis (NSF) and exposure to gadolinium-based contrast agents (GBCAs) has greatly affected the care of patients with kidney disease. NSF has been reported in patients with ESRD, CKD, and acute kidney injury (AKI). The majority of cases have occurred in patients with ESRD, but about 20% have been reported in patients with AKI or CKD stages 4 and 5. There is also a risk difference among GBCAs, with the Food and Drug Administration contraindicating 3 linear agents in patients at risk. Given the significant morbidity and mortality of NSF, it is imperative to identify individuals at risk. Although there are no data to support a role for hemodialysis (HD) in reducing the risk for NSF after administration of GBCAs, immediate HD is still recommended within 2 hours. Patients maintained on peritoneal dialysis seem to be at high risk and immediate HD is also recommended. However, this is not the current recommendation for CKD stages 4 and 5, especially with suspected lower risk of noncontraindicated agents. Individualized assessment is important and especially in those patients close to dialysis initiation. Instituting policies is important to address the imaging needs of patients with CKD and AKI while ensuring a balance between benefits and risks.

Gadodiamide contrast agent 'activates' fibroblasts: a possible cause of nephrogenic systemic fibrosis

Nephrogenic systemic fibrosis (NSF) is a fibrotic disease generating intense interest due to its recent discovery, and unknown cause. It appears confined to patients with renal disease and presents as grossly thickened, indurated, tight skin that is woody to palpation. Histologically, the dermis contains thickened collagen bundles, numerous plump fibroblast-like cells, and elevated hyaluronan expression. Recent data suggest a link between the use of gadolinium chelate as an MRI contrast agent and the onset of the disease. Fibroblasts from the lesions of six NSF patients, all of whom were exposed to gadodiamide, were compared with control fibroblasts for hyaluronan and collagen synthesis. Serum from NSF patients was assessed for fibroblast hyaluronan-stimulating activity, collagen synthesis, and gadodiamide for its effect on fibroblast proliferation and matrix synthesis. NSF fibroblasts synthesized excess levels of hyaluronan and collagen compared with control fibroblasts, with up to 2.8-fold and 3.3-fold increases, respectively. NSF patient serum stimulated control fibroblast hyaluronan synthesis by up to 7-fold, and collagen synthesis by up to 2.4-fold. 1 mM gadodiamide added to culture medium stimulated fibroblast growth in a dose-dependent manner, decreasing their doubling time from 28 h to 22 h, and increasing the maximum cell density. Even a short exposure to gadodiamide stimulated cell growth, suggesting that the cells were activated by the gadodiamide. The growth of fibroblasts within contracted collagen lattices was also significantly stimulated by gadodiamide, while fibroblasts exposed to gadodiamide synthesized increased levels of hyaluronan. Control fibroblasts exposed to gadodiamide, and NSF fibroblasts exhibited an extensive pericellular coat of hyaluronan, and expressed alpha-smooth muscle actin. Gadolinium chloride did not affect fibroblast growth. This report demonstrates that NSF fibroblasts synthesize excess levels of hyaluronan and collagen, and that gadodiamide stimulates control fibroblast growth, matrix synthesis, and differentiation into myofibroblasts, suggesting a possible role for gadodiamide in the pathophysiology of NSF.

Gadolinium-containing magnetic resonance imaging contrast and nephrogenic systemic fibrosis: a case-control study

BACKGROUND

Nephrogenic systemic fibrosis (NSF) is a newly described disorder occurring in persons with renal failure. Gadolinium-based contrast used in magnetic resonance imaging (MRI) has been suggested as a cause. A cluster of patients with NSF was investigated to identify risk factors. Limited preliminary findings from this investigation were presented in the Morbidity and Mortality Weekly Report.

STUDY DESIGN

Matched case-control.

SETTING & PARTICIPANTS

Dialysis patients with and without a diagnosis of NSF treated at an academic medical center.

PREDICTOR

Exposure to gadolinium-based contrast.

OUTCOMES & MEASUREMENTS

Laboratory and clinical characteristics of NSF.

RESULTS

19 of 28 cases identified at the hospital from December 2002 to August 2006 met inclusion criteria and were matched to 57 controls. In univariate analysis, receipt of gadolinium-containing MRI contrast in the preceding year (odds ratio [OR], 7.99; 95% confidence interval, 2.22 to 28.8) was associated with NSF; the measure of association increased as cumulative dose increased. Gadodiamide exposure (OR, 9.83; 95% confidence interval, 2.09 to 46.2) was associated more strongly with NSF than gadoversetamide (OR, 1.82; 95% confidence interval, 0.33 to 10.2). Although not statistically significant, cases were more likely than controls to have undergone primarily peritoneal dialysis in the preceding 6 months. There was no significant difference in receipt of high-dose recombinant erythropoietin between cases and controls. In multivariable analysis, gadolinium contrast exposure (OR, 8.97; 95% confidence interval, 1.28 to 63.0) remained significantly associated with NSF.

LIMITATIONS

Retrospective design, small sample size, inability to completely evaluate erythropoietin.

CONCLUSIONS

Receipt of gadolinium-containing MRI contrast is associated with NSF in a dose-dependent manner. The risk associated with gadolinium may differ by contrast agent and dialysis modality. Use of gadolinium-based contrast agents should be avoided when possible in patients with renal failure.

Patient characteristics and risk factors for nephrogenic systemic fibrosis following gadolinium exposure

Nephrogenic systemic fibrosis (NSF) is a systemic illness, which only affects patients with kidney failure. NSF risk increases with progressively lower levels of kidney function. It is characterized by red skin areas or plaques that develop over several weeks to painful thickened skin with a "woody" texture, resembling "peau d'orange." It may ultimately cause flexion contractures of joints. Skin biopsy reveals thickened collagen bundles, mucin deposition, proliferation of fibroblasts and elastic fibers, without inflammation. Originally described as nephrogenic fibrosing dermopathy (NFD), because of its primarily cutaneous manifestation, it was renamed NSF because of the involvement of various organs like the lungs, myocardium, or striated muscles. The pathogenesis of the disease is not known yet, but recently we suggested a strong association between development of NSF and exposure to gadolinium-based contrast (GBC) agents, thereafter confirmed by other authors. As a consequence of our recent observations, medical authorities imposed restrictions that exclude patients with advanced levels of renal insufficiency from potentially important magnetic resonance imaging studies with gadolinium. Unfortunately, the only alternatives in many situations (examination of brain, lungs, vasculature) are imaging modalities using iodinated radiocontrast agents. Thus, clinicians are faced with weighing the potential risk of NSF from GBC exposure against the risk of acute kidney injury-associated with radiocontrast media. In this dilemma, clinicians must identify patients at high-risk to develop NSF. Known risk factors critical for the development of NSF after exposure to GBC agents (certain chelates and higher doses) are end-stage renal disease requiring dialysis, especially those with little or no residual renal function, and advanced kidney disease not on dialysis. Other potential risk factors include metabolic acidosis, iron overload/intravenous iron, divalent ion disturbances, endothelial/vascular injury, and high erythropoietin doses. Further studies are required.

Nephrogenic systemic fibrosis with multiorgan involvement in a teenage male after lymphoma, Ewing's sarcoma, end-stage renal disease, and hemodialysis

Nephrogenic systemic fibrosis (NSF) is a rare condition that always occurs after acute or chronic renal failure with or without dialysis. The vast majority of cases in the literature are adults, and postmortem findings have been reported in only 5 cases. We report a 15-year-old male who developed NSF with multiorgan involvement after successful treatment of renal lymphoma and a subsequent sacral Ewing's sarcoma, and end-stage renal disease treated with hemodialysis. At autopsy, he was found to have diffuse dural osseous metaplasia, transmural bronchiolar fibrosis, diaphragmatic central tendon fibrosis, and fibrous plaques of the mitral valve. These previously unreported findings expand the spectrum of multiorgan involvement in NSF providing additional evidence that it is an emerging systemic disorder.

Gadolinium and nephrogenic systemic fibrosis

Nephrogenic systemic fibrosis (NSF) is characterized by red skin areas or plaques that over several weeks successively develop to painful thickened skin with a 'woody' texture, resembling 'peau d'orange'. Starting at the extremities, it may spread to the trunk, and may progressively inhibit flexion of adjacent joints. In skin biopsies of affected areas, thickened collagen bundles, mucin deposition, and proliferation of fibroblasts and elastic fibers are seen. Originally described as nephrogenic fibrosing dermopathy (NFD) because of its primarily cutaneous manifestation, this entity was then named NSF because of systemic involvement of other organs like lungs, myocardium, or striated muscles. The pathogenesis of the disease is not yet known, but our observations suggest a close association between development of NSF and exposure to gadolinium-containing contrast agents, thereafter confirmed by other authors. Recently, gadolinium was demonstrated to be detectable in skin tissue samples of affected patients. In this short review, the development of NSF and its sequential association with the exposure to gadolinium-containing contrast agents is presented. The mechanisms likely to cause NFD/NSF are discussed.

Clinical and biological consequences of transmetallation induced by contrast agents for magnetic resonance imaging: a review

Gadolinium-based contrast agents (CAs) are widely used to enhance the contrast of images in magnetic resonance imaging procedures. Two categories of gadolinium chelates exist: the macrocyclic molecules where Gd3+ is caged in the pre-organized cavity of the ligand and the linear molecules. Gadolinium chelates differ in their thermodynamic stability constants and in their kinetic stability. In general, macrocyclic chelates such as Gd-DOTA or Gd-HP-DO3A are more stable than linear molecules. Even among linear agents, differences can be found. There is increasing evidence that transmetallation can be found in vivo, in the case of certain CAs (especially linear chelates), with body cations such as zinc, calcium or iron. Furthermore, analytical interference with colorimetric determination of calcium has been clinically evidenced with two linear chelates, Gd-DTPA-BMA and Gd-DTPA-BMEA. Clinical cases of spurious hypocalcaemia have been reported with these molecules. Such interference with some colorimetric assays for calcium is clinically relevant in that it can lead to unnecessary and potentially harmful treatment for hypocalcaemia.

Gadolinium is detectable within the tissue of patients with nephrogenic systemic fibrosis

BACKGROUND

Nephrogenic systemic fibrosis (NSF) is a disease of unknown etiology that affects a subset of patients with renal insufficiency. Recent publications suggested an association between exposure to gadolinium-containing contrast agents and subsequent development of NSF. We sought to detect gadolinium within the skin and soft tissue of patients with NSF who were exposed to gadolinium-based contrast.

METHODS

Paraffin-embedded skin and soft tissue from NSF patients exposed to gadolinium, and from negative controls, was provided by the NSF Registry (New Haven, Conn). The tissue was searched for metals using a field emission scanning electron microscope that was equipped with energy dispersive spectroscopy. The presence of gadolinium and other metals was verified through identification of unique and requisite X-ray emission spectra.

RESULTS

Gadolinium was detected in 4 of 13 tissue specimens from 7 patients with documented NSF who were exposed to gadolinium-based radiographic contrast. No gadolinium was detected in a paraffin-embedded specimen from a negative control. Based upon the known exposure history of patients with detectable gadolinium, a tissue residence time of 4 to 11 months was observed.

LIMITATIONS

As this was a pilot investigation, only a single control specimen and a single histological section from each block of tissue were utilized.

CONCLUSION

In this pilot investigation, gadolinium was detected in the tissue of a number of patients with NSF. Although neither dispositive of a pathophysiologic mechanism, nor proof of causation, the detection of gadolinium within tissue of NSF patients is supportive of an epidemiologic association between exposure to gadolinium-containing contrast material and development of disease.