Tailored-Reflectivity Microstructures for Measuring Signal Sensitivity of Optical Coherence Tomography Medical Imaging Systems.

Optical coherence tomography (OCT) is a medical imaging technique that has transformed the practice of ophthalmology via high-resolution visualization and measurement of numerous ocular structures, the retina in particular. Despite its widespread use, the development of tools that help ensure high-quality diagnostic outcomes from OCT systems has not kept pace with the technology's rapid advancements. In this work, a novel microstructure array phantom is presented capable of directly evaluating OCT sensitivity: its ability to distinguish meaningful signal from background noise. Through a combination of two-photon direct laser writing (DLW) and thermally activated selective topographic equilibrium (TASTE), optically smooth microstructures are fabricated and shown to be effective in directly quantifying OCT sensitivity threshold, an advancement over the current practice of extrapolating system sensitivity in the high-signal regime. This phantom serves as proof-of-concept for an easily disseminated regulatory science tool that will increase the consistency of performance reporting anywhere OCT is used. The advanced fabrication techniques used in this study also serve as demonstration of what future retinal phantoms could contain, helping to close the gap between the planar, largely two-dimensional phantoms typically used for OCT systems and the geometrically complex, biomimetic phantoms common to other biomedical imaging modalities.