Magneto-motive detection of tissue-based macrophages by differential phase optical coherence tomography

Background and Objectives A novel method to detect tissue‐based macrophages using a combination of superparamagnetic iron oxide (SPIO) nanoparticles and differential phase optical coherence tomography (DP‐OCT) with an external oscillating magnetic field is reported. Study Design/Material and Methods Magnetic force acting on iron‐laden tissue‐based macrophages was varied by applying a sinusoidal current to a solenoid containing a conical iron core that substantially focused and increased magnetic flux density. Results Nanoparticle motion was detected with DP‐OCT, which can detect tissue movement with nanometer resolution. Frequency response of iron‐laden tissue movement was twice the modulation frequency since the magnetic force is proportional to the product of magnetic flux density and gradient. Conclusions Results of our experiments indicate that DP‐OCT can be used to identify tissue‐based macrophage when excited by an external focused oscillating magnetic field. Lasers Surg. Med. 39:266–272, 2007. © 2007 Wiley‐Liss, Inc.