NMR relaxation studies with MnDPDP

Abstract

Purpose: Our studies were designed to compare the efficacy of mangafodipir triso-dium (MnDPDP, Teslascan) as a tissue-specific MR agent with that of manganese chloride (MnCl₂), to compare the efficacy of different doses and rates of administration of MnDPDP, and to collect the data needed for predicting optimum pulse sequences.

Material and Methods: The dose response for the relaxation rates R1 and R2 at 0.47 T, and the manganese (Mn) concentrations in rat liver and in the liver, pancreas, heart and adrenals of pigs was determined for both MnDPDP and MnCl₂ administered i.v. Computer simulations were carried out to model the effects of different tissue Mn concentrations and TR on signal intensities and contrast-to-noise ratios.

Results: In rat liver and pig organs both compounds produced a positive dose-response in R1 and tissue Mn concentration, and only small or no response in R2. The Mn concentration in rat liver was positively correlated with R1, regardless of the form in which Mn was given, or the rate of administration. Optimal imaging parameters are therefore expected to be different pre- and post-MnDPDP administration.

Conclusion: The added cardiovascular safety of MnDPDP compared with MnCl₂ does not result in loss of efficacy in increasing R1 at the intended clinical dose of 5 μmol/kg MnDPDP. The changes in R2 were too small to affect T2-weighted images. The data give the basis for choosing the appropriate pulse sequences for MnDPDP-en-hanced MR imaging.