Gd-DTPA relaxivity depends on macromolecular content

Gd-DTPA T-1 relaxivity of water protons was measured at 1.5 T and room temp erature as a function of macromolecular content in model systems. Gd-DTPA r elaxivity was found to increase with macromolecular concentration. The resu lts of this study indicate that the Gd-DTPA relaxivity in tissue extracellu lar compartment could be as much as 30-70% higher than that of Gd-DTPA in s aline. Quantitative MR analyses that use T-1 as an estimation of local Gd-D TPA concentration require a priori determination of the Gd relaxivity in ti ssue. (C) 2000 Wiley-Liss, Inc.