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- Title
Hindered diffusion of MRI contrast agents in rat brain extracellular micro-environment assessed by acquisition of dynamic T<sub>1</sub> and T<sub>2</sub> maps.
- Authors
Marty, B.; Djemaï, B.; Robic, C.; Port, M.; Robert, P.; Valette, J.; Boumezbeur, F.; Le Bihan, D.; Lethimonnier, F.; Mériaux, S.
- Abstract
The knowledge of brain tissues characteristics (such as extracellular space and tortuosity) represents valuable information for the design of optimal MR probes for specific biomarkers targeting. This work proposes a methodology based on dynamic acquisition of relaxation time maps to quantify in vivo MRI contrast agent concentration after intra-cerebral injection in rat brain. It was applied to estimate the hindered diffusion in brain tissues of five contrast agents with different hydrodynamic diameters (Dotarem® ≈ 1 nm, P846 ≈ 4 nm, P792 ≈ 7 nm, P904 ≈ 22 nm and Gd-based emulsion ≈ 170 nm). In vivo apparent diffusion coefficients were compared with those estimated in an obstacle-free medium to determine brain extracellular space and tortuosity. At a 2 h imaging timescale, all contrast agents except the Gd-based emulsion exhibited significant diffusion through brain tissues, with characteristic times compatible with MR molecular imaging (<70 min to diffuse between two capillaries). In conclusion, our experiments indicate that MRI contrast agents with sizes up to 22 nm can be used to perform molecular imaging on intra-cerebral biomarkers. Our quantification methodology allows a precise estimation of apparent diffusion coefficients, which is helpful to calibrate optimal timing between contrast agent injection and MRI observation for molecular imaging studies. Copyright © 2012 John Wiley & Sons, Ltd.
- Publication
Contrast Media & Molecular Imaging, 2013, Vol 8, Issue 1, p12
- ISSN
1555-4309
- Publication type
Article
- DOI
10.1002/cmmi.1489