 The author of that article measured the 1-dimensional velocity of the flow of particles, which blazed away in coherence gating measurements.Scientists continue to find ways to measure 2-dimensional velocity, and the first result was reported in 1997, where it reported using spectrogram in doing in vivo DOCT.The same disadvantages occur when using the spectrogram method to do in vivo tissue structure and flow velocity imaging, as spectral-domain OCT is limited to fast imaging.