Particle tracking and TILLvisTRAC package

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Automated particle tracking − the TILLvisTRAC approach

The TILLvisTRAC solution is a fully integrated TILLvisION module that uses a three−step dialogue to guide the user through each sequential, independent stage of the tracking and trajectory analysis. These are:

• Automated multi−object detection
• Automated dynamic object tracking
• 3D visualisation and quantitative evaluation of object trajectories

Automated multi−object detection: Poor signal to noise ratio hampers accurate object detection. Thus, this stage is a two step procedure which first uses an anisotropic diffusion filter to remove noise without disturbing essential edge information. Objects are then detected using a segmentation based algorithm that detects candidate edge pixels within the image and assigns them such that closed borderlines are produced around homogeneous areas. These detected objects can then be filtered with respect to their size and mean intensity. All parameters for the automated multi−object detection can be adjusted under visual control on a single image before processing the entire image sequence.

Automated dynamic object tracking: This sophisticated algorithm uses a fuzzy logic-based system to analyse the image sequence on the assumption that object features are conserved in an indistinct (fuzzy) sense. Features taken into account include more than just position information − differences in size, intensity, velocity, and travelled distances are also considered to produce the object tracks.

3D visualisation and quantitative evaluation of object trajectories: By interpolating between object gravity centres tracks are transformed into continuous trajectories. These can be visualised in 3D (x, y, time) for a detailed inspection of individual events. In addition the interpolated data allows for a quantitative analysis of morphological and dynamic parameters e.g. track length, velocity, acceleration, mean squared distances, diffusion coefficients, degree of colocalisation between two sets of trajectories, etc. are all calculated in an automated way to produce an evaluation file.

TrajectoryNr	Length	Velocity	Acceleration	DiffusionConst	dTotal/|pEnd-pStart|
2	19.900.000	10.094.795	124.296.858	1.083.437	21.462.240
3	3.200.00	14.957.743	157.004.230	2.934.094	5.505.319
5	4.400.000	8.457.362	102.345.297	0.845375	13.763.957
6	3.100.000	14.625.881	168.671.269	1.608.662	10.471.300