Designing Tissue Phantoms for Optical Coherence Tomography and Two-Photon Excited Fluorescence Imaging

Abstract

Optical imaging systems are constantly being developed, which creates a need for objects to be used for initial testing and quality control. Long lasting tissue phantoms can fulfill this need. Optical tissue phantoms can mimic the absorption coefficient (µa), reduced scattering coefficient (µ’s), and fluorescence excitation/emission spectra of human tissue. For this study, I fabricated a polydimethylsiloxane (PDMS) based phantom to be used as a resolution target for optical coherence tomography (OCT) and two-photon excited (2PEF). Titanium dioxide (TiO2) was used as the scattering agent for OCT and polystyrene fluorescence microspheres with known excitation/emission properties were used for 2PEF. The TiO2 particles and microspheres are sub-resolution elements. I used a double integrated sphere and inverse adding-doubling program to observe the µa and µ’s of a phantom with a relatively high TiO2 concentration. After imaging the phantoms, I performed point spread function (PSF) measurements of the sub-resolution elements with the assistance of others in the lab. For OCT, we measured the axial and lateral resolution, and for 2PEF, the lateral resolution. Additionally, I fabricated a cylindrical phantom to be used with a fire-siding miniature endoscope. I successfully designed OCT and 2PEF phantoms with varying concentrations and geometries to meet specific needs of different imaging modalities.