Grant Support: NIH RO1-NS40801, EB-11687, UO1-CA154602, and Philips Healthcare
Magnetic Resonance in Medicine
PURPOSE: Accurate characterization of contrast reagent (CR) longitudinal relaxivity in whole blood is required to predict arterial signal intensity in contrast-enhanced MR angiography (CE-MRA). This study measured the longitudinal relaxation rate constants (R1 ) over a concentration range for non-protein-binding and protein-binding CRs in ex vivo whole blood and plasma at 1.5 and 3.0 Tesla (T) under physiologic arterial conditions.
METHODS: Relaxivities of gadoteridol, gadobutrol, gadobenate, and gadofosveset were measured for [CR] from 0 to 18 mM [mmol(CR)/L(blood)]: the latter being the upper limit of what may be expected in CE-MRA.
RESULTS: In plasma, the 1H2 O R1 [CR]-dependence was nonlinear for gadobenate and gadofosveset secondary to CR interactions with the serum macromolecule albumin, and was well described by an analytical expression for effective 1:1 binding stoichiometry. In whole blood, the 1H2 O R1 [CR]-dependence was markedly non-linear for all CRs, and was well-predicted by an expression for equilibrium exchange of water molecules between plasma and intracellular spaces using a priori parameter values only.
CONCLUSION: In whole blood, 1H2 O R1 exhibits a nonlinear relationship with [CR] over 0 to 18 mM CR. The nonlinearity is well described by exchange of water between erythrocyte and plasma compartments, and is particularly evident for high relaxivity CRs.
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Published as: Wilson, G.J., Woods, M., Springer, C.S., Jr., Bastawrous, S., Bhargava, P. and Maki, J.H. (2014), Human whole‐blood 1H2O longitudinal relaxation with normal and high‐relaxivity contrast reagents: Influence of trans‐cell‐membrane water exchange. Magn. Reson. Med., 72: 1746-1754. doi:10.1002/mrm.25064