Magnetic Particle Imaging of liver tumors in small animal models

Abstract

In vivo liver visualization can be realized with Magnetic Particle Imaging (MPI) since a major part of the iron oxide nanoparticles – intravenously injected and imaged with MPI – is finally taken up by the mononuclear phagocytic system (MPS) of the liver. In this study, the possibility to detect and characterize liver tumors with MPI was analyzed. Genetically modified mice developing hepatocellular carcinoma (HCC) were continuously screened with high-field MRI. In case of liver lesions with diameters larger 5 mm, the mice were sequentially imaged with MRI and MPI after the intravenous injection of ferucarbotran (Resovist^®). For comparison of liver morphologies represented by MPI and MRI, image data of both modalities were fused assisted by external MPI and MRI fiducial markers. A good correlation between MPI and MRI images was found with image analysis-based 2-D correlation coefficients of around 0.7. Liver lesions – characterized by a missing accumulation of ferucarbotran – led to signal gaps or drops in the MPI signal depending on their actual size and location. While lesions with diameters larger than 5 mm caused visible effects in the MPI signal, smaller sized lesions could not be detected. This was mainly attributed to the comparable low MPI resolution of a few millimeters in this study. The principle feasibility of liver tumor visualizations with MPI was demonstrated motivating more detailed studies on liver MPI for diagnostic and interventional applications.