Figure 6.

Illustrating the fact that with an un-normalized center-to-edge distance measure, thymocytes of different sizes may have the same center-to-edge distance to a DC. Panel A illustrates a true positive: the case when Thymocyte A (green) with a distance ${\text{D}}_A^t$ indeed touches its neighboring DC body (red). Panel B illustrates a false positive, the case when Thymocyte B having the same distance measure ${\text{D}}_B^t={\text{D}}_A^t$ is incorrectly classified as contacting with the DC. Normalizing the distances by the radii of the thymocytes yields a distance measure that avoids the above problem and compensates for variations in thymocyte volumes between and within populations of various types of cells.