The uptake of manganese dipyridoxal–diphosphate by chemically induced hepatocellular carcinoma in rats: A correlation between contrast–media-enhanced magnetic resonance imaging, tumor differentiation, and vascularization

OBJECTIVES AND RATIONALE. Negative enhancement of implanted liver tumors has been achieved in preclinical studies on manganese dipyridoxal-diphosphate (Mn-DPDP), a new hepatobiliary specific contrast agent for magnetic resonance imaging (MRI). The authors investigated the effects of Mn-DPDP on primary liver cancer and its possible mechanisms. METHODS. Magnetic resonance imaging was performed in 15 rats with chemically induced hepatocellular carcinoma (HCC) before and after Mn-DPDP injection. Both tumor-liver contrast-to-noise ratio and absolute tumor enhancement were evaluated and compared with the MRI results of a nonspecific contrast agent, gadolinium-DOTA, and correlated with corresponding microangiographic and histologic findings. RESULTS. Mn-DPDP injection led to a persistent positive enhancement in differentiated solid HCCs (22/23) with maximal conspicuity at 24 hours. Undifferentiated HCCs were all delineated by a prompt negative enhancement (20/20) with maximal conspcuity within 30 minutes.