Relaxivities of Conventional and Protein-Binding Gd-Based Contrast Agents in Human Blood and Their Implications for Dosing in CE-MRA

Jeffrey Harold Maki¹, ², Gregory J. Wilson³, Miles A. Kirchin⁴, Sarah Bastawrous², Puneet Bhargava²

High-relaxivity protein-binding contrast agents are believed to improve contrast-enhanced MRA. To effectively use these agents, knowing their true r1 and r2 relaxivities in human blood at MRA concentrations is vital. In Vitro relaxivity measurements (gadoteridol, gadobenate, gadofosveset) were performed in human blood at concentrations to 20 mmol (1.5, 3T). R1 and R2* were non-linear vs. [Gd] such that relaxivities r1 and r2* depended highly on [Gd]. At low concentrations r1 relaxivity behaved approximately per labeling data, but >3mmol the r1 of all agents decreased and became similar. This and r2* effects suggest higher Gd doses may be detrimental for CE-MRA.