Diffusion Of Gadolinium Research Articles

Giant widening of interface magnetic layer in almost compensated iron garnet

A two-sublattice ferrimagnet undergoes a transition from a collinear to the canted magnetic phase at magnetic field oriented along an easy magnetization direction. In this work, we study the transition by means of the magneto-optical Faraday effect in a thin film of compensated iron garnet (Lu3−xBix)(Fe5−y−zGayAlz)O12 grown on the Gd3Ga5O12 substrate. In the immediate vicinity of the compensation temperature, a precursor of the transition with a complex shape was observed. Using a special sample with variable thickness, we demonstrate an interfacial origin of the precursor. Diffusion of gadolinium from the substrate into the film forms a thin intermixed layer with enhanced magnetization. It induces an extended inhomogeneous magnetic structure in the film. A two-step shape of the precursor appears due to an easy-plane anisotropy of the intermixed magnetic layer. We emphasize that an effective width of the inhomogeneous magnetization distribution in the film grows enormously while approaching the compensation temperature.

Long-Term Follow-Up of Hematopoietic Stem-Cell Gene Therapy for Cerebral Adrenoleukodystrophy.

In 2009, cerebral adrenoleukodystrophy (c-ALD) became the first brain disease to be treated with lentiviral (LV)-based hematopoietic stem cell gene therapy with the ABCD1 gene in four boys (P1-P4) who had demyelinating lesions expected to be lethal in the short term and no bone marrow donor. We report the clinical and magnetic resonance imaging (MRI) follow-up over a mean of 8.8 years posttransplant. In parallel, vector genome copies, expression of transgenic ALD protein (ALDP), and viral integration sites were determined in peripheral blood cells. Prior to transplant, the four patients had a normal or near normal neurocognitive status but gadolinium-enhanced demyelination in various brain regions. Gadolinium diffusion disappeared during the first year posttransplant. P3 kept a near normal status until 8.3 years of follow-up, but P1, P2, and P4 showed major cognitive degradation around 9, 28, and 60 months posttransplant. Neurological status and demyelination stabilized until last evaluation in P2, but deteriorated in both P1 at 10 years and P4 at 3 years posttransplant. The proportion of myeloid and lymphoid cells expressing transgenic ALDP decreased by half within 5 years then stabilized around 5% to 10%. Integration site analysis revealed a durable polyclonal distribution of genetically corrected hematopoietic cells. No adverse effects were observed. The long-term arrest of demyelination at MRI and persistence of transduced hematopoietic progenitors support that LV gene therapy may be a safe and durable treatment of c-ALD. However, the neurological degradation observed in three out of four patients mitigates the benefit of this therapy, calling for an earlier intervention, more potent vectors, and additional therapeutic strategies.

Oxysterols and multiple sclerosis: Physiopathology, evolutive biomarkers and therapeutic strategy

Multiple sclerosis is an autoimmune disease that affects the central nervous system. Dysfunction of the immune system leads to lesions that cause motor, sensory, cognitive, visual and/or sphincter disturbances. In the long term, these disorders can progress towards an irreversible handicap. The diagnosis takes time because there are no specific criteria to diagnose multiple sclerosis. To realize the diagnosis, a combination of clinical, biological, and radiological arguments is therefore required. Hence, there is a need to identify multiple sclerosis biomarkers. Some biomarkers target immunity through the detection of oligoclonal bands, the measurement of the IgG index and cytokines. During the physiopathological process, the blood-brain barrier can be broken, and this event can be identified by measuring metalloproteinase activity and diffusion of gadolinium in the brain by magnetic resonance imaging. Markers of demyelination and of astrocyte and microglial activity may also be of interest as well as markers of neuronal damage and mitochondrial status. The measurement of different lipids in the plasma and cerebrospinal fluid can also provide suitable information. These different lipids include fatty acids, fatty acid peroxidation products, phospholipids as well as oxidized derivatives of cholesterol (oxysterols). Oxysterols could constitute new biomarkers providing information on the form of multiple sclerosis, the outcome of the disease and the answer to treatment.

A first principles kinetic Monte Carlo investigation of the adsorption and mobility of gadolinium on the (100) surface of tungsten

An accurate characterization of lanthanide adsorption and mobility on tungsten surfaces is important for pyroprocessing. In the present study, the adsorption and diffusion of gadolinium on the (100) surface of tungsten was investigated. It was found that the hollow sites were the most energetically favorable for the adsorption. It was further observed that a magnetic moment was induced following the adsorption of gadolinium on the tungsten surface and that the system with adsorbed hollow sites had the largest magnetization. A pathway for the surface diffusion of gadolinium was determined to occur by hopping between the nearest neighbor hollow sites via the bridge site and the activation energy for the hop was calculated to be 0.75 eV. The surface diffusion process was further assessed using two distinct kinetic Monte Carlo models; one that accounted for lateral adsorbate interactions up to the second nearest neighbor and one that did not account for such interatomic interactions in the adlayer. When the lateral interactions were included in the simulations, the diffusivity was observed to have a strong dependence on coverage (for the coverage values being studied). The effects of lateral interactions were further observed in a one-dimensional simulation of the diffusion equation where the asymmetry in the surface coverage profile upon its approach to a steady state distribution was clear in comparison with the simulations which did not account for those interactions.

Tolerance and long-term MRI imaging of gadolinium-modified meshes used in soft organ repair.

BackgroundSynthetic meshes are frequently used to reinforce soft tissues. The aim of this translational study is to evaluate tolerance and long-term MRI visibility of two recently developed Gadolinium-modified meshes in a rat animal model.Materials and MethodsGadolinium-poly-ε-caprolactone (Gd-PCL) and Gadolinium-polymethylacrylate (Gd-PMA) modified meshes were implanted in Wistar rats and their tolerance was assessed daily. Inflammation and biocompatibility of the implants were assessed by histology and immunohistochemistry after 30 days post implantation. Implants were visualised by 7T and 3T MRI at day 30 and at day 90. Diffusion of Gadolinium in the tissues of the implanted animals was assessed by Inductively Coupled Plasma Mass Spectrometry.ResultsOverall Gd-PMA coated implants were better tolerated as compared to those coated with Gd-PCL. In fact, Gd-PMA implants were characterised by a high ratio collagen I/III and good vascularisation of the integration tissues. High resolution images of the coated mesh were obtained in vivo with experimental 7T as well as 3T clinical MRI. Mass spectrometry analyses showed that levels of Gadolinium in animals implanted with coated mesh were similar to those of the control group.ConclusionsMeshes coated with Gd-PMA are better tolerated as compared to those coated with Gd-PCL as no signs of erosion or significant inflammation were detected at 30 days post implantation. Also, Gd-PMA coated meshes were clearly visualised with both 7T and 3T MRI devices. This new technique of mesh optimisation may represent a valuable tool in soft tissue repair and management.

Magnetic Resonance Characteristics and Susceptibility Weighted Imaging of the Brain in Gadolinium Encephalopathy

To report the brain imaging features on magnetic resonance imaging (MRI) in inadvertent intrathecal gadolinium administration. A 67-year-old female with gadolinium encephalopathy from inadvertent high dose intrathecal gadolinium administration during an epidural steroid injection was studied with multisequence 3T MRI. T1-weighted imaging shows pseudo-T2 appearance with diffusion of gadolinium into the brain parenchyma, olivary bodies, and membranous labyrinth. Nulling of cerebrospinal fluid (CSF) signal is absent on fluid attenuation recovery (FLAIR). Susceptibility-weighted imaging (SWI) demonstrates features similar to subarachnoid hemorrhage. CT may demonstrate a pseudo-cerebral edema pattern given the high attenuation characteristics of gadolinium. Intrathecal gadolinium demonstrates characteristic imaging features on MRI of the brain and may mimic subarachnoid hemorrhage on susceptibility-weighted imaging. Identifying high dose gadolinium within the CSF spaces on MRI is essential to avoid diagnostic and therapeutic errors.

Variability in the perilymphatic diffusion of gadolinium does not predict the outcome of intratympanic gentamicin in patients with ménière's disease

To assess the utility of imaging in planning intratympanic (IT) gentamicin (Gent) treatment in Ménière's disease (MD), we compared the dosage and outcomes of ITGent with the severity and extent of endolymphatic hydrops (EH), as evaluated by three-dimensional fluid-attenuated inversion recovery (3D-FLAIR) sequence in a 3-T magnetic resonance imaging (MRI) unit, after IT gadolinium administration. Retrospective review. A total of 18 patients (10 males and 8 females; age, 28-78 years; median age, 53.2 years) with definite MD participated in the investigation. The duration of the disease ranged from 8 months to 9 years (median, 2 years), with a prevalence of vertigo spells ranging from 0.8 to 8 per month (median, 2.2), as calculated in the last 6 months. A 3D-FLAIR MRI was performed 24 hours after IT injection of diluted gadobutrol. ITGent injection was performed within a variable period of time, from 1 week to 3 weeks after 3D-FLAIR MRI. The degree and extension of EH as evaluated by 3D-FLAIR MRI were compared with the number of injections necessary to cure vertigo attacks. Vertigo results, functional level scale modifications, variations in caloric excitability, and pure-tone average modifications. No statistically significant correlation was observed between severity of EH and outcomes of ITGent administration. The hypothesis of a reduced effect of Gent administered intratympanically in the presence of severe EH, owing to obstacled diffusion along the perilymphatic compartments, has not been confirmed in the present investigation.

Electron magnetic resonance investigation of gadolinium diffusion in zircon powders

The electron magnetic resonance (EMR) technique was used to investigate the diffusion of gadolinium in zircon (ZrSiO 4) powders. The EMR absorption intensity was measured for several annealing times and three different temperatures of isothermal annealing: 1273, 1323 and 1373 K. The activation energy for diffusion, calculated from the experimental data using a theoretical model based on the Fick equation, was found to be E A =506±5 kJ mol −1. This value is close to the ones for the diffusion of Gd in UO 2 and CeO 2, but much larger than for the diffusion of gadolinium in a compound with the same crystal structure as zircon, YVO 4. This is attributed to a difference in the relative sizes of the ions involved in the diffusion process.

Formation of nanoclusters of gadolinium atoms in silicon

A technology of stagewise low-temperature diffusion of gadolinium into silicon that makes it possible to form nanoclusters of impurity atoms with a significant magnetic moment distributed throughout the volume of the material has been developed. It is shown that, unlike the samples obtained by high-temperature diffusion doping, the samples prepared by the new technology do not have surface erosion, and alloys and silicides are not formed in the near-surface region. Nanoclusters of impurity atoms of gadolinium in the volume of the crystal lattice of the silicon are studied using an MIK-5 infrared microscope. It is found that, in the stagewise low-temperature diffusion, the temperature and time of the diffusion have an effect not only on the depth of penetration of the impurities but also on the sizes of the resulting clusters; these factors can also prevent the formation of clusters. The study of the effect of low-temperature treatments on the size and distribution of clusters shows that, upon annealing in the temperature range of 500–700°C, the ordering of the clusters of gadolinium impurity atoms is observed. A further increase in the annealing temperature leads to the destruction of gadolinium clusters in the silicon bulk.

Features of simultaneous diffusion of boron and gadolinium in silicon from nanoscale hybrid organic-inorganic films

Nanoscale organic-inorganic films were grown using the sol-gel technology and were used as advanced sources of boron and gadolinium diffusion into silicon. Features of boron depth profiles in the case of its separate diffusion and simultaneous diffusion with gadolinium from grown films were studied by secondary ion mass spectrometry. A program was developed and numerical simulation was performed, which provided adequate description of complex portions of experimentally measured boron diffusion profiles. A model was proposed, which considers the boron redistribution between the glassy film and oxide layer. This model allowed determination of the optimum boron diffusivities providing the best agreement between experimental and calculated results.

Electron Magnetic Resonance Investigation of Gadolinium Diffusion in Ceria Powders

The electron magnetic resonance (EMR) technique was used to investigate the diffusion of gadolinium in ceria (CeO2) powders. The EMR absorption intensity was measured for several annealing times and three different temperatures of isothermal annealing: 1273, 1323, and 1373 K. The activation temperature for diffusion, calculated from the experimental data using a theoretical model based on the Fick equation, was found to be EA=485±5 kJ/mol. This value is very close to the one obtained for the diffusion of gadolinium in an oxide with a similar crystal structure, UO2, using the secondary ion mass spectrometry technique, EA=492 kJ/mol. On the other hand, it is much larger than the one obtained for the diffusion of gadolinium in yttrium vanadate (YVO4), EA=177 kJ/mol, a compound with a different crystal structure.

Investigation of the parameters of layers prepared through diffusion of boron and gadolinium from silicate and hybrid films into silicon wafers

This paper reports on the results of investigations into the main electrical parameters of diffusion layers formed in silicon due to the annealing of films containing boron and gadolinium. The sources for boron and gadolinium diffusion are silicate and hybrid organic-inorganic films prepared by the sol-gel method. It is demonstrated that small amounts (0.5–2.0 wt %) of organic additives, i.e., polyols with different structures and different molecular weights, favor the formation of layers with the highest possible concentration of the boron dopant at a level of the boron solubility limit in silicon (Ns = 5−7 × 1020 cm−3) with a diffusion layer depth ≥4 μm. The electrical parameters determined for the diffusion layers with the use of the Irwin concentration curves and the data obtained by secondary ion mass spectrometry are compared. The diffusion coefficients of boron and gadolinium are calculated. These data for gadolinium are obtained for the first time. It is revealed that the process of boron diffusion is retarded when boron is introduced in combination with gadolinium.

Difusão do gadolínio no combustível nuclear UO2

Coeficientes de difusão do gadolínio foram medidos em volume e em contornos de grão de pastilhas do combustível nuclear UO2. Entre 1505 e 1703 ºC, em atmosfera de hidrogênio, o coeficiente de difusão em volume pode ser descrito pela seguinte equação de Arrhenius: D (cm²/s) = 5,3x10-3 exp (-5,1(eV)/kT). Na mesma faixa de temperaturas e na mesma atmosfera, o coeficiente de difusão do gadolínio em contornos de grão do UO2 pode ser descrito pela expressão: D' delta (cm³ / s) = 1,1x1,0-2 exp (-6,3 (eV) / kT), onde D´ é o coeficiente de difusão em contornos de grão e delta é a largura do contorno de grão. Nossos resultados mostram que a difusão em contornos de grão é cerca de quatro ordens de grandeza maior do que a difusão em volume nas mesmas condições experimentais. Para os diferentes isótopos do gadolínio utilizados nas experiências não foi observado efeito isotópico para a difusão do gadolínio no UO2. Não há na literatura dados sobre a difusão do gadolínio no UO2 para comparação com os resultados obtidos neste trabalho.

Gadolinium encephalopathy in a patient with renal failure

Gadolinium chelates are extensively used in MRI studies. Neurotoxicity due to gadolinium chelates is minimal and uncommon. A 57-year-old woman in renal failure developed a subacute encephalopathy after inadvertent repetitive gadolinium contrast administration. An unusual MRI appearance with CSF hyperintensity due to gadolinium diffusion into the CSF is also shown.

Characterization and thermal and electromagnetic behaviour of gadolinium-doped calcium tartrate crystals grown by the solution technique

Energy dispersive analysis by X-rays (EDAX), X-ray diffraction (XRD), infrared (IR), thermogravimetric (TG), differential thermogravimetric (DTG), differential scanning calorimetric (DSC) and electromagnetic studies carried out on crystalline materials obtained by diffusion of gadolinium and calcium ions through silica gel impregnated with tartaric acid and grown by means of slow cooling between 72°C and 40°C are reported. EDAX confirmed the presence of gadolinium. X-ray diffraction data did not show any appreciable differences between the structures of doped and undoped calcium tartrate. IR in the range of 500–4000 cm −1 and the description of peaks recorded for the material are given. Results of thermal analysis (TG, DTG and DSC) indicated that the material is thermally unstable. Dielectric and magnetic measurements were determined in the frequency range 45 MHz to 2 GHz.

Gd-DOTA

The pharmacokinetics of Gd-DOTA meglumine in humans were evaluated in six healthy male volunteers. The agent was injected intravenously at 0.1 mmol/kg over approximately 2 minutes. Its behavior was found to be similar to that of urographic and angiographic iodinated contrast media with a plasma elimination half-life of 91 +/- 14 minutes (mean +/- standard deviation [SD]), a small distribution volume of 171.0 +/- 19.7 mL/kg and rapid urinary excretion. The results suggest rapid passive extravascular diffusion of gadolinium (Gd)-DOTA in the interstitial space without intracellular penetration, followed by a rapid urinary excretion via glomerular filtration. Furthermore, the results are consistent with animal data that showed that the compound does not cross the normal blood brain barrier. Its plasma pharmacokinetics appeared to be similar to those reported for Gd-DTPA. No relevant biological effects were seen with Gd-DOTA, especially in regard to serum iron and bilirubin levels.

Sticking coefficient determination and study of gadolinium-tantalum interfaces

Results have been obtained on the sticking coefficients of gadolinium on gadolinium or glass and on the behaviour of the gadolinium-tantalum interface for various annealing temperatures. The preliminary values of the sticking coefficients measured at room temperature are the following: ξ( Gd Gd ) = 0.98 and ξ( Gd glass ) = 0.94 . For temperatures up to 600° C the Gd-Ta interface is abrupt and no interdiffusion occurs after two minutes annealing, whereas a diffusion of gadolinium about 10 nm into tantalum is observed for annealing at 1200°C.

Epitaxial crystal growth of gadolinium on tungsten

Field electron microscopy is used to measure activation energies for multilayer diffusion of gadolinium over several different surfaces of tungsten and to prepare crystal layers of gadolinium by epitaxy on tungsten substrates. Nucleation, crystal growth and epitaxial relations are described.

Epitaxial crystal growth of gadolinium on tungsten

Field electron microscopy is used to measure activation energies for multilayer diffusion of gadolinium over several different surfaces of tungsten and to prepare crystal layers of gadolinium by epitaxy on tungsten substrates. Nucleation, crystal growth and epitaxial relations are described.