Fig. 4.

Results from flow phantom experiments for channels whose upper edge were (a) 7 mm, (b) 19 mm, and (c) 28 mm below the background phantom surface. Only 850 nm data are shown. The first column, labeled “Channel $\mathrm{\Delta }{\mu }_{\mathrm{a}}$,” depicts the mean $\mathrm{\Delta }{\mu }_{\mathrm{a}}$ values as a function of time across all S-D pairs that probe the width of the channel. Flow began after $\sim 0.5\min$. For each S-D separation (going from 22 to 50 mm), the sample sizes (number of S-D pairs within channel) were as follows: $n=28$, 12, 20, 20, 18. The second column, labeled “Final $\mathrm{\Delta }{\mu }_{\mathrm{a}}$,” shows the mean and standard deviation of channel $\mathrm{\Delta }{\mu }_{\mathrm{a}}$ values at the final time point of the flow experiment. The third column, labeled “Channel Contrast,” depicts spatial contrast as a function of S-D separation. The final column shows a topographic reconstruction of the final $\mathrm{\Delta }{\mu }_{\mathrm{a}}$ values (in $x\text{-}y$ space) for each channel depth, each shown for the S-D separation that corresponded to the highest final $\mathrm{\Delta }{\mu }_{\mathrm{a}}$. For panel (a), this was 22 mm; for panel (b), this was 41 mm; and for panel (c), this was 50 mm. The colorbar represents $\mathrm{\Delta }{\mu }_{\mathrm{a}}$ in units of ${\mathrm{mm}}^{-1}$, and the horizontal dashed lines indicate the true boundaries of the channel (Video 1, mp4, 420 KB [URL: https://doi.org/10.1117/1.JBO.26.6.062708.1]; Video 2, mp4, 500 KB [URL: https://doi.org/10.1117/1.JBO.26.6.062708.2], Video 3, mp4, 457 KB [URL: https://doi.org/10.1117/1.JBO.26.6.062708.3]).