Spectral-domain magnetomotive OCT imaging of magnetic nanoparticle biodistribution

Magnetomotive optical coherence tomography (MMOCT) is a method for imaging the distribution of magnetic nanoparticles in tissue by applying an external dynamic magnetic field gradient during B-mode scanning. We present a new method for spectral-domain MMOCT imaging which affords increased sensitivity and frame rates compared to previous work, with a demonstrated sensitivity to <100 ppm iron oxide nanoparticles and imaging time of 5 s. Agarose phantoms embedded with iron oxide nanoparticles (~20 nm) also provide negative T2 contrast in magnetic resonance imaging (MRI) with sensitivity <10 ppm, which is promising for multi-modality applications where MRI and MMOCT provide whole-body and microscopic imaging, respectively. To demonstrate the biomedical potential of this technique, rats are injected with the same nanoparticles as those used in MRI, and uptake into the spleen is detected and imaged post mortem by MMOCT. This illustrates a potentially powerful multi-modal platform for molecular imaging using targeted magnetic nanoparticles.