Influence of Mn-DPDP on MRI and Proton MR Spectroscopy of the Liver

ABSTRACT

PURPOSE: To determine the influence of manganese dipyridoxyl diphosphate (Mn-DPDP) on MRI and proton MRS. MATERIALS AND METHODS: In an in-vitro study designed to determine changes in the lipid peak at 1.3 ppm, 4.7T MR equipment was used to obtain proton MR spectrographic images of a lipid solution of varying concentration, with and without Mn-DPDP. Before; at 10, 20, and 30 minutes; and at 1, 2, 4, and 24 hours after the IV injection of Mn-DPDP (10umol, 1ml/kg), the concentration of Mn in liver tissue was measured by atomic absorption spectrometry. At the same intervals, T1-weighted MR images were obtained, the signal intensity ofthe liver was thus determined, and the relative enhancement ratio was calculated. MRS of rabbit liver was performed serially at the same intervals, and the peak areas of metabolites, as well as their peak areas relative to lipids, were calculated. The findings were correlated with tissue Mn concentration. RESULTS: At 1.3 ppm with Mn-DPDP, MRS showed that the peak area of the lipid had decreased. Tissue Mn concentration increased just after Mn-DPDP injection and peaked after 20 minutes, decreasing to a level within the normal range after 24 hours. Serial changes in the signal intensity of the liver, as seen at MRI, showed a similar pattern to that of Mn concentration. There was reverse correlation between serial change in the peak area of lipids at 1.3 ppm and Mn concentration after Mn-DPDP injection. CONCLUSION: At T1-weighted MR imaging, the injection of Mn-DPDP led to the enhancement of liver tissue, and at MRS, the lipid peak at 1.3 ppm decreased. There was close correlation between these effects and tissue Mn concentration.