F. Raisch, H. Scharr, N. Kirchgeßner, B. Jähne, R.H.A Fink, and D. Uttenweiler (Germany)
Active Contours, Fluorescence Microscopy, Image Sequence Processing, Noise, Optical Flow Estimation
We present a new approach for determining particle features such as length, curvature and hence ﬂexibility in addition to the velocity of moving single actin ﬁlaments in
noisy ﬂuorescence image sequences. The reliable determination of these features is essential for the analysis of
the elementary force generation process of single motor
molecules including heart and skeletal muscle myosins.
First, the image sequence is preprocessed with the 3D
structure tensor - where the third dimension is the time in the image sequence - in order to eliminate noise and to
obtain a measure for extracting coherently moving particles. Secondly, we determine the contour of the actin
ﬁlaments with subpixel accuracy using active contours.
Thereafter, we readjust a local coordinate system to eliminate inner movements of the active contour. In the fourth
step, we estimate the initial position of the active contour
in the next frame from the displacement vector ﬁeld calculated by the 3D structure tensor. The accuracy of the
method is veriﬁed on synthetic test data, a prerequisite
for the quantitative use of this method on experimentally
obtained data. Finally this is demonstrated for ﬂuorescence image sequences of actin ﬁlament movement in the
in vitro motility assay.