Preclinical evaluation of manganese carbonate particles for magnetic resonance imaging of the liver

Rationale and Objectives.: We characterized the physical, biological, and imaging properties of a manganese (Mn) carbonate particle suspension, a contrast agent for hepatic magnetic resonance (MR) imaging. Methods.: Mn carbonate suspensions were produced by controlled precipitation and characterized using light microscopy, transmission electron microscopy, and in vitro relaxivity studies. Efficacy of the agent was studied in normal and tumor-bearing rats using T1-weighted MR imaging. Results.: Following intravenous injection of Mn carbonate particles at doses ranging from 10 to 100 μmol Mn/kg, peak hepatic contrast enhancement of approximately 35% occurred from about 125 min until the termination of the MR imaging studies that varied from 125 to 305 min. Lesion conspicuity was increased because of relative intensity differences between normal liver and tumor. Data also showed that Mn carbonate particle dissolved on delivery to the liver, allowing Mn to interact with intrahepatic macromolecular complexes to provide positive contrast enhancement. Conclusion.: Mn carbonate particles produce significant and sustained hepatic enhancement and should improve detection of small or isointense liver lesions.