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The MRI‐measured arterial input function resulting from a bolus injection of Gd‐DTPA in a rat model of stroke slightly underestimates that of Gd‐[ 14 C]DTPA and marginally overestimates the blood‐to‐brain influx rate constant determined by Patlak plots
Author(s) -
Nagaraja Tavarekere N.,
Karki Kishor,
Ewing James R.,
Divine George W.,
Fenstermacher Joseph D.,
Patlak Clifford S.,
Knight Robert A.
Publication year - 2010
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.22339
Subject(s) - gadolinium , medicine , nuclear medicine , diethylenetriaminepentaacetic acid , bolus (digestion) , cohort , nuclear magnetic resonance , chemistry , physics , organic chemistry , chelation
The hypothesis that the arterial input function (AIF) of gadolinium‐diethylenetriaminepentaacetic acid injected by intravenous bolus and measured by the change in the T 1 ‐relaxation rate (Δ R 1 ; R 1 = 1/ T 1 ) of superior sagittal sinus blood (AIF‐I) approximates the AIF of 14 C‐labeled gadolinium‐diethylenetriaminepentaacetic acid measured in arterial blood (reference AIF) was tested in a rat stroke model ( n = 13). Contrary to the hypothesis, the initial part of the Δ R 1 ‐time curve was underestimated, and the area under the normalized curve for AIF‐I was about 15% lower than that for the reference AIF. Hypothetical AIFs for gadolinium‐diethylenetriaminepentaacetic acid were derived from the reference AIF values and averaged to obtain a cohort‐averaged AIF. Influx rate constants (K i ) and proton distribution volumes at zero time (V p + V o ) were estimated with Patlak plots of AIF‐I, hypothetical AIFs, and cohort‐averaged AIFs and tissue Δ R 1 data. For the regions of interest, the K i s estimated with AIF‐I were slightly but not significantly higher than those obtained with hypothetical AIFs and cohort‐averaged AIF. In contrast, V p + V o was significantly higher when calculated with AIF‐I. Similar estimates of K i and V p + V o were obtained with hypothetical AIFs and cohort‐averaged AIF. In summary, AIF‐I underestimated the reference AIF; this shortcoming had little effect on the K i calculated by Patlak plot but produced a significant overestimation of V p + V o . Magn Reson Med 63:1502–1509, 2010. © 2010 Wiley‐Liss, Inc.