Magnetomotive contrast for in vivo optical coherence tomography

Molecularly-specific contrast can greatly enhance the biomedical utility of optical coherence tomography (OCT). We describe a contrast mechanism, magnetomotive OCT (MMOCT), where a modulated magnetic field induces motion of magnetic nanoparticles. The motion of the nanoparticles modifies the amplitude of the OCT interferogram. High specificity is achieved by subtracting the background fluctuations of the specimen, and sensitivity to 220 μg/g magnetite nanoparticles is demonstrated. Optically and mechanically correct tissue phantoms elucidate the relationships between imaging contrast and nanoparticle concentration, imaging depth, tissue optical scattering, and magnetic field strength. MMOCT is demonstrated in a living Xenopus laevis tadpole where the results were consistent with corresponding histology.