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Theory of heterogeneous relaxation in compartmentalized tissues
Author(s) -
Barsky Daniel,
Pütz Benno,
Schulten Klaus
Publication year - 1997
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.1910370507
Subject(s) - relaxation (psychology) , computer science , neuroscience , nuclear magnetic resonance , biology , physics
A new model of compartmentalized relaxation—that which occurs for spins (protons) exchanging between compartments of different relaxation rates—is presented. This model generalizes previous ones by allowing spatially dependent relaxation within compartments. Solutions for the diffusion‐Bloch equations are found via an efficient numerical technique known as the generalized moment expansion, and they agree well with the solutions to the standard two‐site exchange equations (TSEE) for many typical situations. Specific models are developed for liposomes, red blood cells, capillaries, and arteries with respect to applied contrast agents. A parameter derived from tissue characteristics is introduced to predict the nature of the solutions. A new method is proposed for using contrast agents to detect capillaries, which exploits their high surface‐to‐volume ratio relative to the other elements of the vasculature.