MRI in focal liver disease: A comparison of small and ultra-small superparamagnetic iron oxide as hepatic contrast agents

The purpose of this study was to compare small and ultrasmall superparamagn etic iron oxide particles (SPIO and USPIO, respectively) as MR contrast age nts for the evaluation of focal hepatic disease. In two different patient g roups (SPIO [n = 53], USPIO [n = 27]), with focal liver disease (metastases , hepatocellular carcinoma [HCC], hepatocellular adenoma [HCA], and focal n odular hyperplasia FNH]), spin-echo T1- and T2-weighted images (T1WI, T2WI) were obtained at 1.0T, before and after intravenous contrast administratio n. The percentage signal-to-noise ratio (SNR) change and lesion-to-liver co ntrast (LLC) were measured and statistically compared. The liver decreased in signal intensity (SI) after SPIO administration (-28%) and increased aft er USPIO administration (+16%) on T1WI, On T2WI, the liver decreased in SI on postcontrast images with both agents (-78% SPIO, -73% USPIO), This diffe rence was not statistically significantly different (P less than or equal t o .07). Both SPIO and USPIO provided >500% improvement in LLC on T2WI. On T 1WI, LLC was increased in metastases (120%) and HCC (325%) with SPIO, Post- USPIO, LLC was increased on T1WI only in metastases (>500%). Both SPIO and USPIO show excellent hepatic uptake, presumed secondary to reticuloendothel ial activity, based on the degree of %SI change seen hn the liver after adm inistration of contrast on T2WI, However, USPIO preparations exhibit blood pool activity that may aid in further characterization of focal liver lesio ns, as is evidenced by their greater T1 effect in the liver and in some foc al liver lesions.