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-[14C]DTPA and marginally overestimates the blood-to-brain influx rate constant determined by Patlak plots
✍ Scribed by Tavarekere N. Nagaraja; Kishor Karki; James R. Ewing; George W. Divine; Joseph D. Fenstermacher; Clifford S. Patlak; Robert A. Knight
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 172 KB
- Volume
- 63
- Category
- Article
- ISSN
- 0740-3194
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
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.