Table 1 Definitions of single-cell migratory parameters.
Parameter | Definition | Significance | Unit | Value range |
|---|---|---|---|---|
y-FMI | Forward migration index in the y-direction. The y-coordinate of the ending position of a given trajectory after setting the starting position as (0,0) divided by the accumulated distance | Efficiency of cell migration or attraction toward the chemoattractant source | Unitless | [− 1,1] |
Mean velocity | Accumulated distance divided by time duration of a given trajectory | Overall speed of cell migration | µm/min | (0, ∞) |
Maximum velocity | The highest instantaneous velocity during a given trajectory | Highest speed of cell migration | µm/min | (0, ∞) |
Displacement | The length of the straight line between the starting and the ending positions of a given trajectory; Euclidean distance | Effective distance of cell migration | µm | [0, ∞) |
Directionality | The ratio of the Euclidean distance and the accumulated distance between the starting and the ending positions of a given trajectory | Straightness or directional persistence of cell migration. Irrelevant of the location of the chemoattractant source | Unitless | [0,1] |
