A serial dilution study of gadolinium-based MR imaging contrast agents

BACKGROUND AND PURPOSE: With the approval of gadobenate dimeglumine, higher relaxivity MR contrast agents were introduced into the clinical environment, and multiple in vivo studies compared the efficacy and safety with the previously approved agents. An in vitro study was conducted to demonstrate differences between the various agents to confirm published values and for imaging-sequence optimization. MATERIALS AND METHODS: A contrast phantom was made with serial dilutions of commercially available formulations of 5 US Food and Drug Administration-approved gadolinium-based MR imaging contrast agents in human serum substitute. Dilution factors ranging from 1:8 to 1:4096 were included in the phantom. Spin-echo sequences were performed at 1.5T and 3T with varying TRs and TEs. RESULTS: At physiologic concentrations and by using short TRs and TEs, gadobenate demonstrated the highest signal intensities, confirming greater R1 relaxivity. At higher concentrations and with longer TR and TE values, the greatest signal intensity loss was appreciated for gadobenate, confirming greater R2 relaxivity. CONCLUSION: Using rigorous in vitro methodology and serial dilution techniques, this study confirms the reported higher R1 and R2 relaxivities of gadobenate relative to the other agents at 1.5T and 3T.