Abstract #1272

T1 and T2* Relaxation Rates of Four Gadolinium Based Contrast Agents in Whole Human Blood at First-Pass Concentrations: Non-Linearities and Their Impact on Optimizing Contrast-Enhanced MRA

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.