Detecting and quantifying dynamics of broad protrusion. (A) Cell boundary. Filopodia skeletons are shown in black, and the cell body is shown in gray. (B and C) The cell is partitioned into filopodia (B) and cell body (C). (D and D′) Changes in cell body shape can be tracked over time. The cell body at time t (blue) and t + 1 (red) with regions of protrusion in white and retraction in black. (D′) Expanded view of the red box in D. Red arrows highlight broad, lamellipodial protrusions. (E) Screenshot of the ProActive module for detecting and quantifying broad protrusions. The cell body with filopodia removed is loaded in the left section above a scroll bar for selecting individual frames. The image on the right shows the change in cell body as in D with a scroll bar for selecting time lag. Protrusion, retraction, or both can be analyzed and normalized to cell perimeter or area (green curve). A smoothed curve through the data is shown in blue. (F) To correct for small cell body fluctuations, the velocity controls (blue arrow) allow users to set a minimum threshold for boundary velocity (indicated in red). (G and G′) Selecting Run the Range graphs data for the mean and maximum activity for every time lag (G) or for every filter value (G′) from 1 to the number typed in the up to box.