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MRI Contrast Agents (mri + contrast_agent)

Distribution by Scientific Domains

Medical Sciences	57%
Polymers and Materials Science	23%
Chemistry	19%

Selected Abstracts

Cyclodextrin-Based Bimodal Fluorescence/MRI Contrast Agents: An Efficient Approach to Cellular Imaging

CHEMISTRY - A EUROPEAN JOURNAL, Issue 33 2010
Zuzana Kotková Dr.
Abstract A novel bimodal fluorescence/MRI probe based on a cyclodextrin scaffold has been synthesized and characterized. The final agent employs the fluorescein (F) functionality as a fluorescence marker and the GdIII complex of a macrocyclic DOTA-based ligand (GdL) having one aminobenzyl-phosphinic acid pendant arm as an MRI probe, and has a statistical composition of (GdL)6.9 -F0.1 -,-CD. Slow rotational dynamics (governed by a very rigid cyclodextrin scaffold) combined with fast water exchange (ensured by the chosen macrocyclic ligand) resulted in a high relaxivity of ,22,s,1,mM,1 per GdIII or ,150,s,1,mM,1 per molecule of the final conjugate (20,MHz, 25,°C). In vitro labelling of pancreatic islets (PIs) and rat mesenchymal stem cells has been successfully performed. The agent is not cytotoxic and is easily internalized into cells. The labelled cells can be visualized by MRI, as proved by the detection of individual labelled PIs. A fluorescence study performed on mesenchymal stem cells showed that the agent stays in the intracellular space for a long time. [source]

Fluorinated Polymer Nanoparticles as a Novel 19F MRI Contrast Agent Prepared by Dendrimer-Initiated Living Radical Polymerization

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 12 2010
Michihiro Ogawa
Abstract Novel fluorinated polymer nanoparticles (PNPs) for 19F MRI were prepared by living radical polymerization initiated by a dendrimer. The dendritic macroinitiator with Br substituents was synthesized from hydroxy-group-terminated G2 polyamidoamine dendrimers. The arborescent fluorinated polymers of 2,2,3,3-tetrafluoropropyl methacrylate and 2,2,2-trifluoroethyl methacrylate were characterized in molecular weight, the number of arms, the degree of polymerization per arm, and the diameter as a whole. The PNP diameter was precisely controlled by the molecular weight in the range of 3,25,nm. In addition, the fluorinated PNP gave a narrow resonance by 19F NMR spectroscopy. These results indicate that the fluorinated PNP can be used as a new type of 19F MRI agent. [source]

Potential MRI Contrast Agents Based on Micellar Incorporation of Amphiphilic Bis(alkylamide) Derivatives of [(Gd,DTPA)(H2O)]2,

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2003
Kristof Kimpe
Abstract DTPA-bisamide derivatives with alkyl chains containing 14, 16 and 18 carbon atoms were synthesized and complexes of various trivalent lanthanide ions (Ln = Gd, La, Pr, Eu) were formed. Variable temperature proton NMR spectroscopy of paramagnetic praseodymium(III) and europium(III) complexes revealed that long aliphatic substituents considerably increase the energy barrier for the intramolecular rearrangement around the lanthanide ion. The gadolinium(III) complexes were incorporated into mixed micelles, and photon correlation spectroscopy showed that the mean sizes of all the micelles were within the same range. The NMRD curves of all three DTPA-bisamide-gadolinium complexes incorporated in mixed micelles display higher relaxivity values than the commercially available Gd,DTPA contrast agent. The higher relaxivity obtained for the micellar DTPA-bisamide-gadolinium complexes with C14 and C16 chains relative to the micellar DTPA-bisamide-GdIII C18 chain complex could be attributable to the fact that the alkyl chain containing 18 carbon atoms is longer than the alkyl chain of the major component of the micelles, DPPC, in which it is inserted. This would allow increased mobility of the polar head and hence a lower relaxivity. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Porous Polymersomes with Encapsulated Gd-Labeled Dendrimers as Highly Efficient MRI Contrast Agents

ADVANCED FUNCTIONAL MATERIALS, Issue 23 2009
Zhiliang Cheng
Abstract The use of nanovesicles with encapsulated Gd as magnetic resonance (MR) contrast agents has largely been ignored due to the detrimental effects of the slow water exchange rate through the vesicle bilayer on the relaxivity of encapsulated Gd. Here, the facile synthesis of a composite MR contrast platform is described; it consists of dendrimer conjugates encapsulated in porous polymersomes. These nanoparticles exhibit improved permeability to water flux and a large capacity to store chelated Gd within the aqueous lumen, resulting in enhanced longitudinal relaxivity. The porous polymersomes, ,130,nm in diameter, are produced through the aqueous assembly of the polymers, polyethylene oxide- b -polybutadiene (PBdEO), and polyethylene oxide- b -polycaprolactone (PEOCL). Subsequent hydrolysis of the caprolactone (CL) block resulted in a highly permeable outer membrane. To prevent the leakage of small Gd-chelate through the pores, Gd was conjugated to polyamidoamine (PAMAM) dendrimers via diethylenetriaminepentaacetic acid dianhydride (DTPA dianhydride) prior to encapsulation. As a result of the slower rotational correlation time of Gd-labeled dendrimers, the porous outer membrane of the nanovesicle, and the high Gd payload, these functional nanoparticles are found to exhibit a relaxivity (R1) of 292 109,mM,1,s,1 per particle. The polymersomes are also found to exhibit unique pharmacokinetics with a circulation half-life of >3.5,h and predominantly renal clearance. [source]

Inorganic Nanoparticles for MRI Contrast Agents

ADVANCED MATERIALS, Issue 21 2009
Hyon Bin Na
Abstract Various inorganic nanoparticles have been used as magnetic resonance imaging (MRI) contrast agents due to their unique properties, such as large surface area and efficient contrasting effect. Since the first use of superparamagnetic iron oxide (SPIO) as a liver contrast agent, nanoparticulate MRI contrast agents have attracted a lot of attention. Magnetic iron oxide nanoparticles have been extensively used as MRI contrast agents due to their ability to shorten T2* relaxation times in the liver, spleen, and bone marrow. More recently, uniform ferrite nanoparticles with high crystallinity have been successfully employed as new T2 MRI contrast agents with improved relaxation properties. Iron oxide nanoparticles functionalized with targeting agents have been used for targeted imaging via the site-specific accumulation of nanoparticles at the targets of interest. Recently, extensive research has been conducted to develop nanoparticle-based T1 contrast agents to overcome the drawbacks of iron oxide nanoparticle-based negative T2 contrast agents. In this report, we summarize the recent progress in inorganic nanoparticle-based MRI contrast agents. [source]

Gadolinium(III)-Loaded Nanoparticulate Zeolites as Potential High-Field MRI Contrast Agents: Relationship Between Structure and Relaxivity

CHEMISTRY - A EUROPEAN JOURNAL, Issue 16 2005
Éva Csajbók Dr.
Abstract The effects of dealumination, pore size, and calcination on the efficiency (as expressed in the relaxivity) of Gd3+ -loaded zeolites for potential application as magnetic resonance imaging (MRI) contrast agents were studied. Partial dealumination of zeolites NaY or NaA by treatment with (NH4)2SiF6 or diluted HCl resulted in materials that, upon loading with Gd3+, had a much higher relaxivity than the corresponding non-dealuminated materials. Analysis of the 1H NMR dispersion profiles of the various zeolites showed that this can be mainly ascribed to an increase of the amount of water inside the zeolite cavities as a result of the destruction of walls between cavities. However, the average residence time of water inside the Gd3+ -loaded cavities did not change significantly, which suggests that the windows of the Gd3+ -loaded cavities are not affected by the dealumination. Upon calcination, the Gd3+ ions moved to the small sodalite cavities and became less accessible for water, resulting in a decrease in relaxivity. The important role of diffusion for the relaxivity was demonstrated by a comparison of the relaxivity of Gd3+ -loaded zeolite NaY and NaA samples. NaA had much lower relaxivities due to the smaller pore sizes. The transversal relaxivities of the Gd3+ -doped zeolites are comparable in magnitude to the longitudinal ones at low magnetic fields (<60 MHz). However at higher fields, the transversal relaxivities steeply increased, whereas the longitudinal relaxivities decreased as field strength increased. Therefore, these materials have potential as T1 MRI contrast agents at low field, and as T2 agents at higher fields. [source]

CMR2009: 3.04: Mn loaded apoferritin(Mn-Apo): an improved MRI contrast agent for liver imaging

CONTRAST MEDIA & MOLECULAR IMAGING, Issue 6 2009
S. Aime
No abstract is available for this article. [source]

Manganese cell labeling of murine hepatocytes using manganese(III)-transferrin,

CONTRAST MEDIA & MOLECULAR IMAGING, Issue 3 2008
Christopher H. Sotak
Abstract Manganese(III)-transferrin [Mn(III),Tf] was investigated as a way to accomplish manganese-labeling of murine hepatocytes for MRI contrast. It is postulated that Mn(III),Tf can exploit the same transferrin-receptor-dependent and -independent metabolic pathways used by hepatocytes to transport the iron analog Fe(III),Tf. More specifically, it was investigated whether manganese delivered by transferrin could give MRI contrast in hepatocytes. Comparison of the T1 and T2 relaxation times of Mn(III),Tf and Fe(III),Tf over the same concentration range showed that the r1 relaxivities of the two metalloproteins are the same in vitro, with little contribution from paramagnetic enhancement. The degree of manganese cell labeling following incubation for 2,7,h in 31.5,µm Mn(III),Tf was comparable to that of hepatocytes incubated in 500,µm Mn2+ for 1,h. The intrinsic manganese tissue relaxivity between Mn(III),Tf-labeled and Mn2+ -labeled cells was found to be the same, consistent with Mn(III) being released from transferrin and reduced to Mn2+. For both treatment regimens, manganese uptake by hepatocytes appeared to saturate in the first 1,2,h of the incubation period and may explain why the efficiency of hepatocyte cell labeling by the two methods appeared to be comparable in spite of the ,16-fold difference in effective manganese concentration. Hepatocytes continuously released manganese, as detected by MRI, and this was the same for both Mn2+ - and Mn(III),Tf-labeled cells. Manganese release may be the result of normal hepatocyte function, much in the same way that hepatocytes excrete manganese into the bile in vivo. This approach exploits a biological process,namely receptor binding, endocytosis and endosomal acidification,to initiate the release of an MRI contrast agent, potentially conferring more specificity to the labeling process. The ubiquitous expression of transferrin receptors by eukaryotic cells should make Mn(III),Tf particularly useful for manganese labeling of a wide variety of cells both in culture and in vivo. Published in 2008 by John Wiley & Sons, Ltd. [source]

Kinetic analysis of hyaluronidase activity using a bioactive MRI contrast agent

CONTRAST MEDIA & MOLECULAR IMAGING, Issue 3 2006
Liora Shiftan
Abstract One of the attractions of molecular imaging using ,smart' bioactive contrast agents is the ability to provide non-invasive data on the spatial and temporal changes in the distribution and expression patterns of specific enzymes. The tools developed for that aim could potentially also be developed for functional imaging of enzyme activity itself, through quantitative analysis of the rapid dynamics of enzymatic conversion of these contrast agents. High molecular weight hyaluronan, the natural substrate of hyaluronidase, is a major antiangiogenic constituent of the extracellular matrix. Degradation by hyaluronidase yields low molecular weight fragments, which are proangiogenic. A novel contrast material, HA-GdDTPA-beads, was designed to provide a substrate analog of hyaluronidase in which relaxivity changes are induced by enzymatic degradation. We show here a first-order kinetic analysis of the time-dependent increase in R2 as a result of hyaluronidase activity. The changes in R2 and the measured relaxivity of intact HA-GdDTPA-beads (r2B) and HA-GdDTPA fragments (r2D) were utilized for derivation of the temporal drop in concentration of GdDTPA in HA-GdDTPA-beads as the consequence of the release of HA-GdDTPA fragments. The rate of dissociation of HA-GdDTPA from the beads showed typical bell-shaped temperature dependence between 7 and 36 °C with peak activity at 25 °C. The tools developed here for quantitative dynamic analysis of hyaluronidase activity by MRI would allow the use of activation of HA-GdDTPA-beads for the determination of the role of hyaluronidase in altering the angiogenic microenvironment of tumor micro metastases. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Manganese-guided cellular MRI of human embryonic stem cell and human bone marrow stromal cell viability

MAGNETIC RESONANCE IN MEDICINE, Issue 4 2009
Mayumi Yamada
Abstract This study investigated the ability of MnCl2 as a cellular MRI contrast agent to determine the in vitro viability of human embryonic stem cells (hESC) and human bone marrow stromal cells (hBMSC). Basic MRI parameters including T1 and T2 values of MnCl2 -labeled hESC and hBMSC were measured and viability signal of manganese (Mn2+)-labeled cells was validated. Furthermore, the biological activity of Ca2+ -channels was modulated utilizing both Ca2+ -channel agonist and antagonist to evaluate concomitant signal changes. Metabolic effects of MnCl2 -labeling were also assessed using assays for cell viability, proliferation, and apoptosis. Finally, in vivo Mn2+ -guided MRI of the transplanted hESC was successfully achieved and validated by bioluminescence imaging. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc. [source]

Chromium(VI) as a novel MRI contrast agent for cerebral white matter: Preliminary results in mouse brain in vivo

MAGNETIC RESONANCE IN MEDICINE, Issue 1 2006
Takashi Watanabe
Abstract This work demonstrates that intraventricular microinjections of a low dose of potassium dichromate (0.4 ,L of 10 mM solution) yield a specific contrast enhancement of white matter (WM) tracts in T1 -weighted 3D MRI of mouse brain in vivo. Pronounced and persistent signal increases (40,100% at 24 hr after injection) were observed in the corpus callosum, anterior commissure, fornix, and stria medullaris, as well as in the mammillothalamic tract and fasciculus retroflexus. These results suggest that the extracellular diffusion of diamagnetic chromium(VI) (Cr(VI)) after injection is followed by a tissue-specific reduction to paramagnetic Cr(V) and (III), which relies predominantly on the oxidation of myelin lipids. Because Cr(VI)-induced contrast leads to only a mild unspecific enhancement (10,20%) of gray matter (GM) structures, such as the hippocampal formation, the method reveals novel information that differs from that obtainable using other paramagnetic ions, such as manganese. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc. [source]

Magnetic resonance imaging and biological properties of pancreatic islets labeled with iron oxide nanoparticles

NMR IN BIOMEDICINE, Issue 8 2009
Hoe Suk Kim
Abstract This study was undertaken to investigate the in vitro effect of islet labeling with iron oxide nanoparticles for MRI on islet viability, insulin secretion, and gene expression. Isolated rat islets were labeled with Resovist (25,200,µg Fe/mL, a clinically approved MRI contrast agent) in the presence or absence of poly- l -Lysine (PLL, 1.5,µg/mL) for 48,h. The iron content of labeled islets was found to increase in a dose-dependent manner. More than 90% of the islets were labeled with 100,µg Fe/mL. We confirmed the localizations of iron oxide nanoparticles within islet , -cells by insulin immunostaining. As the concentration of Resovist increased, T2 values as determined by T2 -weighted MRI on a 1.5,Tesla MR scanner decreased. Labeling of 100 islets in a medium containing 100,µg Fe/mL of Resovist in the absence of PLL provided sufficient contrast for islet visualization on T2 -weighted MRI. MTT assays showed that the viability of labeled islets was not different from that of unlabeled islets. No statistical difference was observed between labeled (2.91,±,0.36) and unlabeled islets (2.83,±,0.61) in terms of the ability to secrete insulin, as determined by the glucose stimulation index. We also evaluated the effect of iron oxide incorporation on the gene expressions in islet cells using RT-PCR (reverse transcriptase PCR). Insulin expression in labeled islets was significantly elevated (1.83,±,0.25 fold vs. unlabeled; p,=,0.005), but not the expression of somatostatin (1.39,±,0.18 fold vs. unlabeled; p,=,0.085) or glucagons (1.28,±,0.13 fold vs. unlabeled; p,=,0.09). Expression of an important transcription factor for insulin gene transcription, BETA2 (beta-cell E-box trans-activator), was increased in labeled islets (1.67,±,0.15 fold vs. unlabeled; p,=,0.029). The findings of this study indicate that Resovist provides a satisfactory means to image islets and has no deleterious effect on islet function or gene expression. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Gd(III)-EPTPAC16, a new self-assembling potential liver MRI contrast agent: in vitro characterization and in vivo animal imaging studies,

NMR IN BIOMEDICINE, Issue 4 2008
Suzana Torres
Abstract The recently reported amphiphilic chelate, [Gd(EPTPAC16)(H2O)]2,, forms supramolecular aggregates in aqueous solution by self-assembly of the monomers with a relaxometrically determined critical micellar concentration (CMC) of 0.34,mM. The effect of sonication on the aggregate size was characterized by dynamic light scattering and relaxometry, indicating the presence of premicellar aggregates and an overall decrease in aggregate size and polydispersity upon sonication, slightly below the CMC. {[153Sm](EPTPAC16)(H2O)}2, radiotracer was evaluated in vivo from , scintigraphy and biodistribution in Wistar rats. It was found to depend strongly on the sample concentration, below or above the CMC, and its sonication, in a way that correlates with the effect of the same factors on the size of the aggregates formed in solution. Below CMC, the very large aggregates of the [153Sm]3+ -labeled chelate were persistently and mainly taken up by the lungs, and also by the macrophage-rich liver and spleen. Sonication of this solution led to loss of the lung uptake. Above CMC, the metal chelate was mainly taken up by the liver, with very little uptake by the spleen and lungs. In vivo, dynamic contrast-enhanced (DCE)-MRI evaluation of the micellar [Gd(EPTPAC16)(H2O)]2, compound in Wistar rats showed a persistent hepatic positive-contrast effect in T1 -weighted images, qualitatively similar to the clinically established GdIII -based hepatobiliary-selective agents. No enhancement effect was observed in the lungs because of the scarcity of mobile protons in this organ, despite the scintigraphic evidence of significant lung retention of the [153Sm]3+ -labeled chelate at concentrations below the CMC. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Evaluation of Gd(III)DTPA-terminated poly(propylene imine) dendrimers as contrast agents for MR imaging

NMR IN BIOMEDICINE, Issue 1 2006
Sander Langereis
Abstract Different generations of Gd(III)DTPA-terminated poly(propylene imine) dendrimers {G1 [n,=,4 Gd(III) ions per molecule], G3 (n,=,16) and G5 (n,=,64)} and reference Gd(III)DTPA complex [G0 (n,=,1)] were characterized in terms of (i) longitudinal (r1) and transverse (r2) relaxivities in mouse blood plasma, (ii) concentration detection limits in vitro and (iii) in vivo contrast-enhanced MR imaging (CE-MRI) in mice at 1.5,,,T. Serial and dynamic CE-MRI were performed to monitor the distribution of MRI contrast agent in the heart, arteries, renal system, liver, spleen, bladder and tumor periphery. The relaxivities increased non-linearly with molecular weight (for G0 ionic r1,=,8.1,mM,1,s,1 and ionic r2,=,8.6,mM,1,s,1 to G5 19.3 and 25.0, respectively). The minimal detectable dendrimer concentration was more than two orders of magnitude lower for G5 (8.1,×,10,8,M) than for G0 (3.1,×,10,5,M). Sub-millimeter-sized blood vessels were well visualized with serial CE-MRI with each contrast agent. Dynamic CE-MRI showed timely renal clearance for all contrast agents, but a stronger and a prolonged blood signal enhancement for the higher generations of the dendritic contrast agent. Moreover, G0 and G1 showed a rapid tumor wash-in and wash-out, whereas G3 and G5 displayed a more gradual and prolonged tumor wash-in. In conclusion, both G0 and dendritic contrast agents G1, G3 and G5 are well suited for non-tissue-specific MRI of sub-millimeter-sized blood vessels and evaluating tumor microcirculatory characteristics in mice. Higher generations of dendritic contrast agents display lower concentration detection limits, which suggests their future use for molecular imaging. Copyright © 2006 John Wiley & Sons, Ltd. [source]

A new method for the aqueous functionalization of superparamagnetic Fe2O3 nanoparticles

CONTRAST MEDIA & MOLECULAR IMAGING, Issue 6 2008
Fernando Herranz
Abstract A new methodology for the synthesis of hydrophilic iron oxide nanoparticles has been developed. This new method is based on the direct chemical modification of the nanoparticles' surfactant molecules. Using this methodology both USPIO (ultrasmall super paramagnetic iron oxide) (hydrodynamic size smaller than 50,nm) and SPIO (super paramagnetic iron oxide) (hydrodynamic size bigger than 50,nm) were obtained. In addition, we also show that it is possible to further functionalize the hydrophilic nanoparticles via covalent chemistry in water. The magnetic properties of these nanoparticles were also studied, showing their potential as MRI contrast agents. Copyright © 2008 John Wiley & Sons, Ltd. [source]

A physiologically based pharmacokinetic model of vascular,extravascular exchanges during liver carcinogenesis: application to MRI contrast agents

CONTRAST MEDIA & MOLECULAR IMAGING, Issue 5 2007
Muriel Mescam
Abstract The extraction of physiological parameters by non-invasive imaging techniques such as dynamic magnetic resonance imaging (MRI) or positron emission tomography requires a knowledge of molecular distribution and exchange between microvascularization and extravascular tissues. These phenomena not only depend on the physicochemical characteristics of the injected molecules but also the pathophysiological state of the targeted organ. We developed a five-compartment physiologically based pharmacokinetic model focused on hepatic carcinogenesis and MRI contrast agents. This model includes physical characteristics of the contrast agent, dual specific liver supply, microvessel wall properties and transport parameters that are compatible with hepatocarcinoma development. The evolution of concentrations in the five compartments showed significant differences in the distribution of three molecules (differentiated by their diameters and diffusion coefficients ranging, respectively, from 0.9 to 62,nm and from 68.10,9 to 47.10,7,cm2,s,1) in simulated regeneration nodules and dysplastic nodules, as well as in medium- and poorly differentiated hepatocarcinoma. These results are in agreement with known vascular modifications such as arterialization that occur during hepatocarcinogenesis. This model can be used to study the pharmacokinetics of contrast agents and consequently to extract parameters that are characteristic of the tumor development (like permeability), after fitting simulated to in vivo data. Copyright © 2007 John Wiley & Sons, Ltd. [source]

A new temperature-sensitive contrast mechanism for MRI: Curie temperature transition-based imaging

CONTRAST MEDIA & MOLECULAR IMAGING, Issue 1 2007
F. Settecase
Abstract A temperature-sensitive MRI contrast mechanism is proposed based on the physical property, the Curie temperature (Tc), at which a ferromagnetic material transitions to paramagnetic state and vice versa. To evaluate the feasibility of this new contrast mechanism, experiments were performed with solid gadolinium metal, which has a Tc of 20°C. In phantom and ex vivo experiments, the magnetic susceptibility artifact area decreased with increasing temperature transitioning across Tc (p,<,0.05). Similar results would be expected for a variety of ferromagnetic substances with substance-specific Tc values. Temperature-sensitive MRI contrast agents harnessing this mechanism may be used to (1) indicate regional attainment of specific temperatures in thermotherapy, (2) render an accumulated contrast agent more or less visible by the external application of appropriate heating or cooling, or (3) quantify tissue temperature based on MR image characteristics and magnetic susceptibility artifact caused by a ferromagnetic,paramagnetic transitioning substance. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Surface Modification of Exfoliated Layered Gadolinium Hydroxide for the Development of Multimodal Contrast Agents for MRI and Fluorescence Imaging

ADVANCED FUNCTIONAL MATERIALS, Issue 21 2009
Young-su Yoon
Abstract A novel method for modifying the surface of magnetic-resonance-contrasting layered gadolinium hydroxide (LGdH) is developed providing them with water- and bio-compatibility and acid-resistance, all of which are essential for medical applications. A stable colloid of exfoliated layers is synthesized by exchanging interlayer anions of LGdH with oleate ions. The delaminated layers are successively coated with phospholipids with poly(ethylene glycol) tail groups, and their effectiveness as a contrast agent for magnetic resonance imaging (MRI) is demonstrated. The adaptability of this surface modification approach for incorporating functional molecules and fabricating a fluorescent colloid of LGdH, which has the potential utility as a multimodal probe, is also demonstrated. This result provides a novel approach for expanding the applications of layered inorganic materials and developing a new class of MRI contrast agents. [source]

Inorganic Nanoparticles for MRI Contrast Agents

Functionalization of PAMAM dendrimers with nitronyl nitroxide radicals as models for the outer-sphere relaxation in dentritic potential MRI contrast agents

MAGNETIC RESONANCE IN CHEMISTRY, Issue 2 2003
Giancarlo Francese
Abstract PAMAM dendrimers functionalized with nitronyl nitroxide radicals were characterized. Quantitative determination of substitution with radicals was performed using EPR and electrochemical methods. The study of the 1H NMR relaxation of the surrounding water showed how the outer-sphere contribution to the relaxivity may be limited by the presence of the dendrimer core. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Gadolinium and nephrogenic systemic fibrosis: Association or causation (Review Article)

NEPHROLOGY, Issue 3 2008
JAGADEESH KURTKOTI
SUMMARY: With widespread availability of magnetic resonance imaging (MRI), it has become standard practice for patients with severe renal impairment or previous severe reactions to iodine-containing contrast media to receive gadolinium-based MRI contrast agents instead of traditional radiographic contrast agents, particularly for magnetic resonance angiography. However, there is growing concern about the use of gadolinium contrast agents in the presence of severe renal insufficiency, because of increasing reports of nephrogenic fibrosing dermopathy (NFD)/nephrogenic systemic fibrosis (NSF), associated with the exposure to certain gadolinium-containing contrast agents. In this review we explore the causal link between gadolinium exposure and NSF, using an established system of epidemiological criteria proposed by Bradford Hill. Though the current evidence makes gadolinium a strong suspect as an aetiologic agent for NSF in the presence of severe renal failure, the die is not cast yet. At this stage there needs to be cautious approach to the use of gadolinium-containing contrast agents in the presence of severe renal failure (glomerular filtration rate <30 mL/min per 1.73 m2). [source]

Measuring SPIO and Gd contrast agent magnetization using 3,T MRI

NMR IN BIOMEDICINE, Issue 8 2009
Pádraig Cantillon-Murphy
Abstract Traditional methods of measuring magnetization in magnetic fluid samples, such as vibrating sample magnetometry (VSM), are typically limited to maximum field strengths of about 1,T. This work demonstrates the ability of MRI to measure the magnetization associated with two commercial MRI contrast agents at 3,T by comparing analytical solutions to experimental imaging results for the field pattern associated with agents in cylindrical vials. The results of the VSM and fitted MRI data match closely. The method represents an improvement over VSM measurements since results are attainable at imaging field strengths. The agents investigated are Feridex, a superparamagnetic iron oxide suspension used primarily for liver imaging, and Magnevist, a paramagnetic, gadolinium-based compound used for tumors, inflammation and vascular lesions. MR imaging of the agents took place in sealed cylindrical vials in the presence of a surrounding volume of deionized water where the effects of the contrast agents had a measurable effect on the water's magnetization in the vicinity of the compartment of contrast agent. A pair of phase images were used to reconstruct a B0 fieldmap. The resultant B0 maps in the water region, corrected for shimming and container edge effects, were used to predict the agent's magnetization at 3,T. The results were compared with the results from VSM measurements up to 1.2,T and close correlation was observed. The technique should be of interest to those seeking quantification of the magnetization associated with magnetic suspensions beyond the traditional scope of VSM. The magnetization needs to be sufficiently strong (Ms , 50 Am2/kg Fe for Feridex and Xm , 5 × 10,5 m3/kg Gd for Magnevist) for a measurable dipole field in the surrounding water. For this reason, the technique is mostly suitable for undiluted agents. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Non-invasive temperature imaging with thulium 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethyl-1,4,7,10-tetraacetic acid (TmDOTMA,)

NMR IN BIOMEDICINE, Issue 1 2006
Sait Kubilay Pakin
Abstract Non-invasive thermometry using hyperfine-shifted MR signals from paramagnetic lanthanide complexes has attracted attention recently because the chemical shifts of these complexes are many times more sensitive to temperature than the water 1H signal. Among all the lanthanide complexes examined thus far, thulium tetramethyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (TmDOTMA,) appears to be the most suitable for MR thermometry. In this paper, the feasibility of imaging the methyl 1H signal from TmDOTMA, using a frequency-selective radiofrequency excitation pulse and chemical shift-selective (CHESS) water suppression is demonstrated. A temperature imaging method using a phase-sensitive spin-echo imaging sequence was validated in phantom experiments. A comparison of regional temperature changes measured with fiber-optic probes and the temperatures calculated from the phase shift near each probe showed that the accuracy of imaging the temperature with TmDOTMA, is at least 0.1,0.2°C. The feasibility of imaging temperature changes in an intact rat at 0.5,0.6,mmol/kg dose in only a few minutes is demonstrated. Similar to commonly used MRI contrast agents, the lanthanide complex does not cross the blood,brain barrier. TmDOTMA, may prove useful for temperature imaging in many biomedical applications but further studies relating to acceptable dose and signal-to-noise ratio are necessary before clinical applications. Copyright © 2006 John Wiley & Sons, Ltd. [source]