Relaxation induced by ferritin and ferritin-like magnetic particles: The role of proton exchange

Gossuin, Yves; Roch, Alain; Müller, Robert N.; Gillis, Pierre

doi:10.1002/(sici)1522-2594(200002)43:2<237::aid-mrm10>3.0.co;2-5

Cited by 98 publications

(124 citation statements)

References 28 publications

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“…33,34 Taking into account that the protons in the layer between the spheres with radii of r p and r diff do not contribute to the relaxivity, we consider the…”

Section: Resultsmentioning

confidence: 99%

NMR Transversal Relaxivity of Suspensions of Lanthanide Oxide Nanoparticles

et al. 2007

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Aqueous suspensions of paramagnetic lanthanide oxide nanoparticles have been studied by NMR relaxometry. The observed R 2 * relaxivities are explained by the static dephasing regime (SDR) theory. The corresponding R 2 relaxivities are considerably smaller and are strongly dependent on the interval between the two refocusing pulses. The experimental data are rationalized by assuming the value of the diffusion correlation time, τ D , to be very long in a layer with adsorbed xanthan on the particle's surface. In this layer, the refocusing pulses are fully effective and R 2 ≈ 0. Outside this layer, the diffusion model for weakly magnetized particles was applied. From the fit of the experimental relaxation data with this model, both the particle radii (r p ) and the radii of the spheres, within which the refocusing pulses are fully effective (r diff ), were estimated. The values of r p obtained are in agreement with those determined by dynamic light scattering. Because the value of r diff depends on the external magnetic field B and on the magnetic moment of the lanthanide of interest (µ eff 2 ), the R 2 relaxivity was found to be proportional to B and to µ eff 2 .

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“…33,34 Taking into account that the protons in the layer between the spheres with radii of r p and r diff do not contribute to the relaxivity, we consider the…”

Section: Resultsmentioning

confidence: 99%

NMR Transversal Relaxivity of Suspensions of Lanthanide Oxide Nanoparticles

et al. 2007

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“…For our simulation we set the background tissue to be gray matter (GM) of the central nervous system (CNS) and relied on published values of relaxation times in humans at 1.5T (16) and mice at 11.7T (18,19). For GM, we used T 1 /T 2 ϭ 1900/31.4 ms at 11.7T (16), and T 1 /T 2 ϭ 1200/80 ms at 1.5T (17). For GdHP-DO3A, we use a T 1 relaxivity value at 37°C given by 3.7 s -1 mM Ϫ1 (Gd) at 1.5T (20), and we measured a value of 3.40 s -1 mM -1 (Gd) at 11.7T.…”

Section: Resultsmentioning

confidence: 99%

Theoretical MRI contrast model for exogenous T₂ agents

Mills

Ahrens

2007

Magnetic Resonance in Med

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The rational development of new generations of MRI contrast agents (CAs) requires a scheme for predicting contrast enhancement. Previous contrast predictions have been based largely on empirical results in specific systems. Here we present a general theoretical model for evaluating the minimum concentration of T 2 CA required for satisfactory image contrast. This analytic contrast model is applicable to a wide range of T 2 -type agents and delivery scenarios, and requires only a few readily evaluated parameters. We demonstrated the model by predicting contrast produced by superparamagnetic ferumoxide and the iron storage protein, ferritin. We then experimentally verified the predictions using suspensions of Feridexா and ferritin in phantoms. The model was also used to compare the contrast efficacy of the metal ions in two clinically approved T 1 -and T 2 -type CAs. In the Appendix we present a numerical formalism that is useful for relating image contrast and agent concentration when gradient-echo (GRE) T* 2 -weighted (T There is great interest in developing new generations of MRI contrast agents (CAs) that can be used for diagnostic purposes, therapeutic monitoring, and to further our understanding of diseases. New generations of agents can often provide MRI contrast for specific cell types, detect the presence of specific molecules, such as enzymes and nucleic acids (1-3), and be responsive to physiology.Superparamagnetic iron oxide (SPIO) CAs are widely used as a platform for many of these emerging cellularmolecular applications (1). SPIO agents typically consist of an iron-oxide nanocrystal that is coated with dextran or polymer and have a net median diameter of 10 -100 nm. SPIO particles perturb the static magnetic field out to a distance on the order of ϳ50 2 times its diameter, resulting in a dramatic reduction in T 2 of nearby water molecules. The resulting images exhibit hypointense regions, indicating agent accumulation. Unmodified SPIO particles, such as Resovist, Feridex, and Combidex, have been used for cellular imaging (4) and are FDA-approved for detecting liver lesions and distinguishing between normal and cancerous lymph nodes. SPIO particles with surfaces conjugated to targeting entities, such as peptides or antibodies, have also been described (4). Intracellular applications of SPIO for cell-tracking in animal models is a rapidly evolving research area (5), and the clinical translation of these techniques is already in the early stage (6).In addition, T 2 -type CAs are included in a new category of intracellular labeling approaches that utilize genetically-encoded metalloproteins (2,7). In this approach, metalloproteins from the ferritin family are expressed in specific host tissues. These iron-storage metalloproteins effectively become a superparamagnetic CA by sequestering endogenous iron from the organism and thus imparting MRI contrast to targeted tissues.For useful images to be generated, CAs must accumulate in cells or tissues in adequate concentrations. Moreover, too high of a concentra...

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“…The dual spin echo imaging protocol, combined with Eq. [26], offers two advantages over the method of Imai et al (23). First, it is rooted in a quantitative theory that predicts how the signal intensity data is related to the Kupffer cell density.…”

Section: Discussionmentioning

confidence: 99%

“…For ferumoxides, experimental relaxivity measurements agree well with numerical calculations based on the iron susceptibility effect (25), pointing to this effect as the predominant source of relaxation. In ferritin solutions, on the other hand, Gossuin et al (26) have shown that magnetic field inhomogeneities are insufficient to account for the measured transverse relaxation rates and have argued that proton binding plays a key role. However, for hemosiderin, proton binding, or any similar process that requires short-range interaction with water molecules, is probably unimportant, since hemosiderin is not water-soluble.…”

Section: Discussionmentioning

confidence: 99%

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Theory of nonexponential NMR signal decay in liver with iron overload or superparamagnetic iron oxide particles

Jensen

Chandra

2002

Magnetic Resonance in Med

111

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A quantitative theory is proposed for the nonexponential NMR proton signal decay observed in liver with iron overload or superparamagnetic iron oxide particles. This effect occurs for Carr-Purcell-Meiboom-Gill (CPMG) sequences and is argued to be a direct consequence of the strong magnetic field inhomogeneities generated by the iron, rather than being due to tissue compartments. An approximate mathematical form is given for the signal decay, which is fit to experimental data for samples of rat liver with iron oxide particles, for samples of marmoset liver with hemosiderosis, and for in vivo human liver with hereditary hemochromatosis. The fitting parameters obtained are consistent with the pattern of iron deposition determined from histology. For the case of hereditary hemochromatosis, a good correlation is found between a parameter characterizing the nonexponential decay and the iron concentration. Implications for practical MR quantification of hepatic iron are discussed. Magn

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Relaxation induced by ferritin and ferritin-like magnetic particles: The role of proton exchange

Cited by 98 publications

References 28 publications

NMR Transversal Relaxivity of Suspensions of Lanthanide Oxide Nanoparticles

NMR Transversal Relaxivity of Suspensions of Lanthanide Oxide Nanoparticles

Theoretical MRI contrast model for exogenous T₂ agents

Theory of nonexponential NMR signal decay in liver with iron overload or superparamagnetic iron oxide particles

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Relaxation induced by ferritin and ferritin-like magnetic particles: The role of proton exchange

Cited by 98 publications

References 28 publications

NMR Transversal Relaxivity of Suspensions of Lanthanide Oxide Nanoparticles

NMR Transversal Relaxivity of Suspensions of Lanthanide Oxide Nanoparticles

Theoretical MRI contrast model for exogenous T2 agents

Theory of nonexponential NMR signal decay in liver with iron overload or superparamagnetic iron oxide particles

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Product

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Theoretical MRI contrast model for exogenous T₂ agents