Doppler velocity detection limitations in spectrometer and swept-source Fourier-domain optical coherence tomography

Recent advances in Doppler and variance techniques have enabled high sensitivity imaging in regions of biological flow to measure blood velocities and vascular perfusion. In recent years, the sensitivity and imaging speed benefits of Fourier domain OCT have become apparent. Spectrometer-based and wavelength-swept implementations have both undergone rapid development. Comparative analysis of the potential benefits and limitations for the various configurations would be useful for matching technology capabilities to specific clinical problems. Here we take a first step in such a comparative analysis by presenting theoretical predictions and experimental results characterizing the lower and upper observable velocity limits in spectrometer-based versus swept-source Doppler OCT. Furthermore, we characterize the washout limit, the velocity at which signal degradation results in loss of flow information. We present comparative results from phantom flow data as well as retinal data obtained with a commercial spectrometer OCT system and a custom high-speed swept-source retinal OCT system.