Bo Zhu1, 2, Thomas Witzel1, Shan Jiang3, Daniel G. Anderson3, Robert S. Langer3, Bruce R. Rosen1, 2, Lawrence L. Wald1
1Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States; 2Harvard-MIT Health Sciences and Technololgy, Massachusetts Institute of Technology, Cambridge, MA, United States; 3Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States
Detailed characterization of a contrast mechanism for imaging iron oxide contrast agents is presented, whereby the rotary saturation effect produces tunable signal changes as oscillating magnetic fields generated from vibrating iron oxide nanoparticles resonantly alter the signal in the spin-lock sequence. These signal changes only occur near the vibrating iron oxide agents, selectively localizing their presence. We characterize the the signal changes as a function of vibrational displacement of the contrast agent, duration of spin-lock time, and spin-lock frequency. The measured dependencies indicate desirable regimes of operation for any system using rotary saturation to detect vibrating agents.