Tracking motile algal cells with a deformable model

Abstract

Phototaxis is a natural locomotor response of many mobile algal unicells either towards or away from a light stimulus. A novel, non‐contact and non‐invasive cell‐tracking technique is described which can be used to monitor cell movement. This is the first step towards developing an understanding of the organism's phototactic movement control system. A “deformable” modelling method has the potential to contribute significantly to tracking the motion of deformable cell types. We propose a segmenting and continuous tracking method based on a gradient vector flow (GVF) deformable model. To avoid the manual initialisation step of the earlier deformable models, a fast Hough transform method for detecting circles is used to obtain the whole contour of single and discrete cells and the watershed algorithm is used to obtain the initial contour of adjacent cells, even when in contact with one another. For the small capture range of the GVF edge energy, the deformable curves are easily bulged outward to the object boundary. This edge enhancing algorithm combined with the GVF deformable model could solve this problem. We present the tracking performance with real sequence images of Chlamydomonas reinhardtii cells under bright‐field microscopy and indicate the validation of the method.