Barium Titanate Nanoparticles as Exogenous Contrast Agents in Second Harmonic Optical Coherence Tomography

I propose and demonstrate a method by which barium titanate nanoparticle clusters can be used as exogenous contrast agents in Second Harmonic Optical Coherence Tomography imaging systems to localize and highlight desired regions of tissue. SH-OCT has previously been used to identify collagen within OCT images. However, SH-OCT signals from collagen are highly susceptible to inferior reflector artifacts because most of the second harmonic generated light is forward scattered. Second harmonic generating nanoparticle clusters exhibit high scattering properties, which can give them the advantage of backscattering a large quantity of second harmonic light while attenuating the forward scattered light. In this research project, a mathematical model is proposed in which the backward to forward scattering ratio of second harmonic generated light from nanoparticle layers is exponentially proportional to the thickness of the layer. This model was supported by measurements of the backward to forward scattering ratio of second harmonic light in barium titanate nanoparticles layers. This indicates that nanoparticle clusters can be designed and manufactured with the proper thickness so that they generate a large second harmonic signal without creating inferior reflector artifacts.