qtOCT: quantitative transmission optical coherence tomography

Transmission optical coherence tomography (OCT) enables analysis of biological specimens in vitro through the detection of forward-scattered light. Up to now, transmission OCT has been considered a technique that cannot directly retrieve quantitative phase and is thus a qualitative method. In this paper, we present qtOCT, a novel quantitative transmission optical coherence tomography method. Unlike existing approaches, qtOCT allows for a direct, easy, fast, and rigorous retrieval of 2D integrated phase information from transmission full-field swept-source OCT measurements. Our method is based on coherence gating and allows user-defined temporal measurement range selection, making it potentially suitable for analyzing multiple-scattering samples. In the weak-scattering regime, we demonstrate high consistency between qtOCT and digital holographic microscopy phase images, whereas in the multiple-scattering regime, we show the superiority of qtOCT. This approach enhances transmission OCT capabilities, positioning it as a viable alternative to existing quantitative phase imaging techniques.