Modeling of Look-Locker Estimates of the Magnetic Resonance Imaging Estimate of Longitudinal Relaxation Rate in Tissue After Contrast Administration

Ramesh Paudyal¹, Hassan Bagher-Ebadian¹, Robert A. Knight^1,2, Tavarekere N. Nagaraja³, Joseph D. Fenstermacher³, James R. Ewing^1,2

In this study, we evaluate the effects of equilibrium intercompartmental water exchange kinetics in a monoexponential estimate of tissue water protons relaxation rate R1 using an experimentally measured plasma concentration vs. time, an arterial input function (AIF), of a paramagnetic contrast agent like Gd-DTPA via a Look-Locker measurement in a three site two exchange [3S2X] model. The observable change in R1 was used in a Patlak graphical plot to asses the influence of protons of water exchange on the measured cerebrovascular parameters.