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Magnetic field dependence of proton relaxation rates in tissue with added Mn 2+ : Rabbit liver and kidney
Author(s) -
Koening Seymour H.,
Brown Rodney D.,
Goldstein Edward J.,
Burnett Keith R.,
Wolf Gerald L.
Publication year - 1985
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910020206
Subject(s) - ion , relaxation (psychology) , proton , chemistry , paramagnetism , nuclear magnetic resonance , kidney , proton magnetic resonance , spin–lattice relaxation , magnetic field , electron paramagnetic resonance , chelation , inorganic chemistry , condensed matter physics , medicine , psychology , social psychology , physics , organic chemistry , quantum mechanics , endocrinology
Abstract Since contrast in magnetic resonance imaging (MRI) is so sensitive to the magnetic relaxation rates of tissue protons, the use of paramagnetic ions to alter contrast in a tissue‐specific fashion is an alluring prospect. The influence of these ions on the proton relaxation rates in homogeneous solutions is known to vary dramatically according to whether the ions are present as hydrated aquoions, in solute chelate, or immobilized in macromolecules. In tissue, there is the additional complication of access of water to the ions. In the present study, Mn 2+ ions were introduced into rabbits both orally and intravenously in various chemical complexes. Accumulation of these ions in rabbit liver is demonstrated here, qualitatively, by MRI. The quantitation of the change in relaxation rates is investigated in excised samples of liver and kidney by study of the magnetic field dependence (dispersion) of the relaxation rates of the protons (NMRD profiles) of tissue water. Results are presented for several sets of experiments, including doseresponse data for weakly chelated Mn 2+ and time‐response data for free and complexed Mn 2+ . The general findings are that, for liver, the response (the increment in the NMRD profile) is relatively rapid (<2 m); that it is relatively independent of how, or in what form, the Mn 2+ is introduced; that it persists for several hours (at least); and that it saturates with increasing body load of Mn 2+ . Moreover, from the form of the NMRD profiles of liver, it is clear that the Mn 2+ ions are bound irrotationally, perhaps to cell membrane, and, when introduced in chelated form, can become separated even from strongly associated chelate complexes. For kidney, the results are qualitatively similar, though different in detail.