Jeffrey H. Maki1, Charles S. Springer, Jr. 2, Mark Woods2, 3, Sarah Bastawrous, 14, Puneet Bhargava, 14, Miles A. Kirchin5, Gregory J. Wilson1
1Radiology, University of Washington, Seattle, WA, United States; 2Advanced Imaging Research Center, Oregon Health and Science University, Portland, OR, United States; 3Chemistry, Portland State University, Portland, OR, United States; 4Radiology, Puget Sound VAHCS, Seattle, WA, United States; 5Medical Affairs, Bracco Diagnostics, Milan, Italy
Dynamic contrast-enhanced MRA (CE-MRA) makes use of Gd-based contrast agents (GBCA) during first pass. Optimizing CE-MRA requires, among other things, an understanding of GBCA relaxation (R1 and R2*) properties in whole blood. We examined relaxation of four GBCAs in whole blood under physiologic conditions. R1 relaxivity is very non-linear; secondary to both RBC finite water exchange kinetics and (for protein-binding agents) albumin binding. Furthermore, R2* in whole blood is much greater than in plasma. Both of these effects combine to give less signal than might be expected for the CE-MRA sequence, particularly with higher injection rates. This will be explored.