PRECLINICAL EVALUATION OF MANGANESE CARBONATE PARTICLES FOR MAGNETIC-RESONANCE-IMAGING OF THE LIVER

Rationale and Objectives. We characterized the physical, biological, a nd imaging properties of a manganese (Mn) carbonate particle suspensio n, a contrast agent for hepatic magnetic resonance (MR) imaging. Metho ds. Mn carbonate suspensions were produced by controlled precipitation and characterized using light microscopy, transmission electron micro scopy, and in vitro relaxivity studies. Efficacy of the agent was stud ied in normal and tumor-bearing rats using T1-weighted MR imaging. Res ults. Following intravenous injection of Mn carbonate particles at dos es ranging from 10 to 100 mu mol Mn/kg, peak hepatic contrast enhancem ent of approximately 35% occurred from about 125 min until the termina tion of the MR imaging studies that varied from 125 to 305 min. Lesion conspicuity was increased because of relative intensity differences b etween normal liver and tumor. Data also showed that Mn carbonate part icles dissolved on delivery to the liver, allowing Mn to interact with intrahepatic macromolecular complexes to provide positive contrast en hancement. Conclusion. Mn carbonate particles produce significant and sustained hepatic enhancement and should improve detection of small or isointense liver lesions.