In Vivo Dual-Modality Terahertz/Magnetic Resonance Imaging Using Superparamagnetic Iron Oxide Nanoparticles as a Dual Contrast Agent

Molecular imaging is one of the most promising tools for diagnosis of cancer. We assessed whether commercially available superparamagnetic iron oxide nanoparticles (SPIO; Feridex
^®
) could be utilized as a dual modality contrast agent for terahertz (THz) imaging as well as magnetic resonance (MR) imaging. Feridex particles were transfected into SKOV3 cancer cells, at concentrations of 0, 0.35, 0.70, and 1.38 mM, and the magnetic and optical properties of the particles were examined by MR and THz reflection imaging. Mice were inoculated with Feridex-labeled SKOV3 cells, and in vivo MR and THz images were taken 1, 3, 7, and 14 days after inoculation. THz images and T2*-weighted MR images of Feridex-labeled SKOV3 tumors showed similar patterns; the signal intensities of both image sets increased with Feridex concentration. The signal intensity of in vivo MR and THz images from mice decreased over time. H&E and Prussian blue staining results correlated with imaging data. Dual-modality molecular MR and THz imaging of Feridex-labeled cells may be used to identify cancer cells both in vivo and in vitro. Such a noninvasive multimodal imaging method may be valuable in future cellular and molecular studies.