The second experiment was made on the velocity-dependence to illustrate our imaging theory further. In the experiment, the artificial flow phantom, 1% intralipid solution, was used to simulate the blood flow. The solution was pushed into a polyethene tube () by a single-channel syringe pump with the flow velocity varying from 0 to . Figure 3 shows the dependence of MD for LSI-IFM and, as comparison, speckle contrast for tLSCA on the flow velocity. Here the MD curve does not vary dramatically as the function of the velocity, but the contrast curve does as has already been known.14 It means that our imaging method does not take the directional motion of scatterers as the physical basis of its imaging parameter. In fact, the scatterers in the flow make the Brownian motion overlapped with the directional motion. For the LSI-IFM, what is imaged reflects the information of the speckle concentration fluctuation, which is closely related to Brownian motion, and for LSCA, it is the blurring degree that is mainly decided by the directional velocity. Therefore, the imaging mechanisms of the two methods are totally different. It is because MD responds to the flow of high velocity in a big vessel similarly as it responds to the flow of low velocity in a thin vessel, so that microvessels can be imaged if big vessels can.