Transverse NMR relaxation as a probe of mesoscopic structure

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  • 8 October 2002
Abstract
We show that transverse NMR signal relaxation averaged over a macroscopic volume is extremely sensitive to structure of mesoscopic paramagnetic inhomogeneities. Such a sensitivity is proposed as a novel kind of contrast in the NMR measurements. We model the medium by a suspension of arbitrary shaped mesoscopic paramagnetic objects, and find transverse relaxation without adjustable parameters in the case when the dephasing effect of an individual object is small. Results indicate a strong relaxation rate dependence on the shape of the objects. As a major application we consider transverse spin relaxation in the whole blood, for which our theory agrees well with experiments and Monte-Carlo simulations. Applications to a wide range of problems in complex systems (porous media, biological systems, diffusion limited reaction rates) are discussed.

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