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On the use of R 1 and R 2 * for measurement of contrast agent concentration in isolated perfused rat liver
Author(s) -
Dimicoli JeanLuc,
Patry Jacqueline,
Poupon Joël,
Volk Andreas
Publication year - 2003
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.846
Subject(s) - bolus (digestion) , chemistry , in vivo , intravenous bolus , nuclear magnetic resonance , analytical chemistry (journal) , nuclear medicine , chromatography , endocrinology , medicine , physics , microbiology and biotechnology , biology
We present experimental MRI protocols at 4.7 T for quantitative determination of the Dotarem® distribution volume in isolated perfused rat liver. The procedures involved either constant contrast agent (CA) concentration or bolus administration conditions. R 1 and R 2 * effects of the CA in liver and perfusate were measured using gradient echo fast imaging (GEFI) experiments by varying either the excitation angle or the echo time. CA concentrations in liver and perfusate were also measured after MRI by inductively coupled plasma atomic emission spectroscopy, in order to determine in situ relaxivities in the perfusate ( r 1 =4.2±0.1 s −1 m m −1 , r 2 *=17±2 s −1 m m −1 ) and in the liver ( r 1 =7.2±0.2 s −1 m m −1 , r 2 *=99±5 s −1 m m −1 ). When CA concentrations were estimated from R 1 measurements and r 1 , the CA distribution volume estimations in liver resulting from bolus (0.31±0.01) and stationary (0.32±0.05) experiments were not significantly different. In contrast, after a bolus, CA concentrations derived from R 2 * and r 2 * were overestimated in liver and even more in perfusate. However, with R 1 and R 2 * being measured before CA bolus administration, zero echo time signal intensities computed from multiple TE measurements during multiple boli yielded good estimations of R 1 and thus correct CA concentrations in liver and in perfusate. Under these conditions, a single multi‐echo GEFI acquisition should be sufficient to determine the concentration–time curves. Consequently, this protocol should be appropriate to rapidly estimate the distribution volume in vivo when multiple boli have to be avoided. Copyright © 2001 John Wiley & Sons, Ltd.