Fig. 4: iCLOTS adapts feature finding and tracking algorithms to calculate cell suspension velocity measurements in microfluidic devices.

a Cell suspension velocity applications rely on algorithms that find patterns within images, typically a cluster of cells, and algorithms that track these detected patterns from one frame to the next. To quantify cell suspension velocity, users must adjust window size (a region of interest in which a detected pattern is searched for in the subsequent frame), a minimum distance traveled, and an approximate feature/cell size for best quantification. Trajectories of individual cell patterns are labeled on the provided video data, seen here as cyan lines. Data generated includes a velocity measurement for each cell pattern tracked and mean and maximum velocity for each frame. Mean and maximum velocity measurements of sickle cell patient RBCs in suspension approach zero as oxygen tension is lowered from physiologic oxygen concentrations of 160 mm Hg O₂ to deoxygenated conditions of 0 mm Hg O₂ (n = 1 experiment). Data taken at ×40 magnification, all scale bars represent 10 μm. b Users may also indicate a bin size for automatic generation of channel-wise velocity profiles (representative data from n = 1 experiment). taken at ×20 magnification, all scale bars represent 50 μm. c Representative time course data shows a consistent mean and maximum velocity over the time course of videos of sepsis patient and healthy control whole blood samples at a shear rate of 350 s⁻¹_, chosen to recapitulate venous shear rate of a vessel of similar dimensions. d Representative profile data shows a blunted velocity profile in sepsis patient whole blood as compared to healthy control whole blood at a shear rate of 350 s⁻¹ indicating changes in blood viscosity. e Sepsis patient whole blood (n = 6 experiments) had a higher ratio of mean wall velocity to frame maximum velocity values as compared to healthy control whole blood (n = 3 experiments), indicating a blunted velocity profile, at a shear rate of 350 s⁻¹ (*p = 0.047 via two-sided Mann–Whitney test). Error bars = standard deviation. Source data are provided as a Source data file.