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Magnetic field dependence of solvent proton relaxation in aqueous solutions of Fe 3+ complexes
Author(s) -
Koenig Seymour H.,
Baglin Coral M.,
Brown Rodney D.
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.1910020311
Subject(s) - chemistry , relaxation (psychology) , solvent , aqueous solution , ion , methemoglobin , proton , nuclear magnetic resonance , chemical physics , organic chemistry , hemoglobin , physics , psychology , social psychology , quantum mechanics
It might appear that the Fe 3+ ion would be particularly useful as an agent for enhancing contrast in NMR images since it has a relatively large magnetic moment and occurs in vivo in a variety of forms. Moreover, the concentration of Fe 3+ changes locally in certain disease states (e. g., β‐thalassemia) and in trauma (formation of methemoglobin), and can be altered in the gastrointestinal tract by the ingestion of readily available dietary supplements. However, the Fe 3+ ion is insoluble above pH ∼ 4, and soluble chelate and protein complexes of Fe 3+ tend to sequester the ions from solvent; hence, the efficacy of Fe 3+ ions for relaxing water protons ought to be low under typical physiological conditions. We report the magnetic field dependence of the relaxation rate of solvent protons (NMRD profiles) for solutions of a variety of Fe 3+ complexes to demonstrate the phenomenology relevant to NMR imaging. From these data we make some estimates to show that, deposite the low relaxation rates of solvent protons in solutions of Fe 3+ complexes, certain observed changes in image contrast are consistent, quantitatively, with inferences that can be drawn from solution data.