Computational and experimental investigation of nanoparticle effects on tissue optical properties and optical coherence tomography imaging.

Optical coherence tomography (OCT) is a widely used biomedical imaging modality due to its simplicity, low cost, and high spatial resolution; however, its performance is fundamentally limited by low intrinsic image contrast, particularly at increased imaging depths. Nanoparticle-based contrast agents have been proposed as an effective strategy to overcome this limitation by modifying tissue optical properties and enhancing OCT signal formation. Despite advances in nanoparticle design, a systematic understanding of how nanoparticles influence tissue optical properties and OCT image contrast remains limited, partly due to the high computational cost of conventional simulation approaches. In this study, a combined computational and experimental framework is developed to investigate the effects of nanoparticles on tissue optical properties and OCT imaging. A hybrid numerical approach integrating finite difference time domain (FDTD) simulations, performed using Lumerical FDTD Solutions, with Monte Carlo (MC) light transport modeling, is employed to quantify nanoparticle-induced changes in tissue absorption, scattering, and anisotropy parameters. These modified optical properties are then incorporated into OCT simulations without explicitly resolving nanoparticles within the MC domain. The computational framework is experimentally validated through optical property measurements and OCT imaging of nanoparticle-embedded gelatin-based tissue phantoms. Both numerical and experimental results demonstrate that the presence of nanoparticles significantly enhances OCT image contrast, with nanoparticle shape playing a critical role. In particular, triangular nanoparticles provide a more pronounced contrast enhancement compared to nanorods and nanospheres, which is attributed to their stronger scattering efficiency and enhanced plasmonic response. The proposed framework substantially reduces computational runtime relative to conventional methods while maintaining adequate physical accuracy, offering an efficient and reliable tool for evaluating nanoparticle-mediated contrast enhancement in OCT imaging.