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. Author manuscript; available in PMC: 2012 Sep 6.
Published in final edited form as: IEEE Trans Med Imaging. 2011 Aug 22;31(1):117–130. doi: 10.1109/TMI.2011.2165554

Fig. 3.

Fig. 3

Modeling the axon using cubic spline interpolation. Two examples are shown, one in panels (a), (c), and (e) and the other in panels (b), (d), and (f). These are the same axons shown in Fig. 1. (a), (b) Single frame from each video image sequence showing the moving neurofilaments within the gaps in the neurofilament array (white arrowheads). (c), (d) Maximum intensity projection of each image of the entire video sequence, revealing the paths of the moving filaments, and thus the axons, within the gaps in the neurofilament array. The blue line represents the medial axis of this projection. (e), (f) The resulting curve fit obtained by cubic spline interpolation (white line) overlaid on the image of the maximum intensity projection. The solid white points along the white lines are the knots, which are placed manually. The number of knots required to achieve a good fit depends on the extent of curvature of the axon; more knots are needed when the axon bends sharply, and fewer when it bends more gradually. Eight knots were sufficient for the axon in (e) but 14 knots were required for the axon in (f).