Doppler flow imaging of cytoplasmic streaming using spectral domain phase microscopy

Spectral domain phase microscopy (SDPM) is a function extension of spectral domain optical coherence tomography. SDPM achieves exquisite levels of phase stability by employing common-path interferometry. We discuss the theory and limitations of Doppler flow imaging using SDPM, demonstrate monitoring the thermal contraction of a glass sample with nanometer per second velocity sensitivity, and apply this technique to measurement of cytoplasmic streaming in an pseudopod. We observe reversal of cytoplasmic flow induced by extracellular , and report results that suggest parabolic flow of cytoplasm in the pseudopod.