Dual Contrast Method for Cellular MRI using Positive and Negative Contrast Agents

Introduction: MR contrast agents (CAs) are important elements for cellular MRI. Gadolinium (Gd) chelates are used in T1-weighted production of positive signal contrast while superparamagnetic iron oxide particles (SPIOs) produce T2-weighted signal reduction. Although SPIOs provide more sensitivity toward cell labeling compared to Gd-chelates, the negative contrast generated by the SPIOs may be confused with signal voids from tissue inhomogeneity, edema, or local hemorrhage. Combination of both Gd-based and SPIO-based CAs may provide unique opportunity in creating user-tunable contrast mechanism. We examined the utility of using combination of these two CAs in MRI for concurrent cell-labeling and dual contrast visualization.