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In vivo measurements of relaxivities in the rat kidney cortex
Author(s) -
Pedersen Michael,
Mørkenborg Jan,
Jensen Finn Taagehøj,
StødkildeJørgensen Hans,
Djurhuus Jens Christian,
Frøkioer Jørgen
Publication year - 2000
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/1522-2586(200008)12:2<289::aid-jmri11>3.0.co;2-o
Subject(s) - in vivo , bolus (digestion) , chemistry , gadolinium , kidney , renal cortex , cortex (anatomy) , nuclear magnetic resonance , medicine , biology , microbiology and biotechnology , organic chemistry , physics , neuroscience
The aim of this study was to implement a novel noninvasive method to derive the in vivo T1 relaxivity (R1) and T2 relaxivity (R2) in the rat kidney cortex. A two‐compartment gadolinium diethylene triamine pentaacetic acid (Gd‐DTPA) distribution model was established to estimate the bolus and infusion dosages of Gd‐DTPA necessary for obtaining the required steady‐state concentration levels. After a single bolus injection of 99m Tc‐DTPA, several blood samples were collected. Based on considerations from the applied two‐compartment model, a steady‐state concentration was predicted approximately 5–10 minutes after the bolus injection. The plasma concentration levels of Gd‐DTPA were measured by simultaneous injection of 99m Tc‐DTPA. Three regions in the cortex (upper, central, and lower) of both rat kidneys were used. A statistical evaluation resulted in the following in vivo relaxivities found at 7 T: R1 = 1.04 ± 0.08 mM −1 s −1 and R2 = 10.78 ± 0.83 mM −1 s −1 . Using a 95% confidence interval, no intracortical differences were detected. The relaxivities R1 and R2 calculated in the intact rat kidney cortex were distinctly different from relaxivities found in human plasma: (22°C) 4.42 ± 0.07 mM −1 s −1 (r2> 0.98) and R2 = 5.75 ± 0.17 mM −1 s −1 (r2> 0.98), respectively. The measurements showed a marked difference between in vitro and in vivo relaxivities. Comparison of the distribution rates in pig, human, and rats shows a distinct proportionality between size and renal function. J. Magn. Reson. Imaging 2000;12:289–296. © 2000 Wiley‐Liss, Inc.