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Assessment of T 1 and T * 2 effects in vivo and ex vivo using iron oxide nanoparticles in steady state—dependence on blood volume and water exchange
Author(s) -
Bjørnerud Atle,
Johansson Lars O.,
BrileySæbø Karen,
Ahlström Håkan K.
Publication year - 2002
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.10066
Subject(s) - ex vivo , in vivo , chemistry , relaxation (psychology) , perfusion , renal cortex , blood volume , biophysics , kidney , in vitro , medicine , biochemistry , biology , microbiology and biotechnology
Accurate knowledge of the relationship between contrast agent concentration and tissue relaxation is a critical requirement for quantitative assessment of tissue perfusion using contrast‐enhanced MRI. In the present study, using a pig model, the relationship between steady‐state blood concentration levels of an iron oxide nanoparticle with a hydrated diameter of 12 nm (NC100150 Injection) and changes in the transverse and longitudinal relaxation rates (1/ T * 2and 1/ T 1 , respectively) in blood, muscle, and renal cortex was investigated at 1.5 T. Ex vivo measurements of 1/ T * 2and 1/ T 1 were additionally performed in whole pig blood spiked with different concentrations of the iron oxide nanoparticle. In renal cortex and muscle, 1/ T * 2increased linearly with contrast agent concentration with slopes of 101 ± 22 s −1 mM −1 and 6.5 ± 0.9 s −1 mM −1 (mean ± SD), respectively. In blood, 1/ T * 2increased as a quadratic function of contrast agent concentration, with different quadratic terms in the ex vivo vs. the in vivo experiments. In vivo, 1/ T 1 in blood increased linearly with contrast agent concentration, with a slope ( T 1 ‐relaxivity) of 13.9 ± 0.9 s −1 mM −1 . The achievable increase in 1/ T 1 in renal cortex and muscle was limited by the rate of water exchange between the intra‐ and extravascular compartments and the 1/ T 1 ‐curves were well described by a two‐compartment water exchange limited relaxation model. Magn Reson Med 47:461–471, 2002. © 2002 Wiley‐Liss, Inc.