Purpose: Our studies were designed to compare the efficacy of mangafod
ipir trisodium (MnDPDP, Teslascan) as a tissue-specific MR agent with
that of manganese chloride (MnCl2), to compare the efficacy of differe
nt doses and rates of administration of MnDPDP, and to collect the dat
a needed for predicting optimum pulse sequences. Material and Methods:
The dose response for the relaxation rates R1 and R2 at 0.47 T, and t
he manganese (Mn) concentrations in rat liver and in the liver, pancre
as, heart and adrenals of pigs was determined for both MnDPDP and MnCl
2 administered i.v. Computer simulations were carried out to model the
effects of different tissue Mn concentrations and TR on signal intens
ities and contrast-to-noise ratios. Results: In rat liver and pig orga
ns both compounds produced a positive dose-response in R1 and tissue M
n concentration, and only small or no response in R2. The Mn concentra
tion in rat liver was positively correlated with R1, regardless of the
form in which Mn was given, or the rate of administration. Optimal im
aging 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 incr
easing R1 at the intended clinical dose of 5 mu mol/kg, MnDPDP. The ch
anges in R2 were too small to affect T2-weighted images. The data give
the basis for choosing the appropriate pulse sequences for MnDPDP-enh
anced MR imaging.