Dear Haim,
the problem can be approached by either smoothing the centerlines
or locally fitting a low-degree polynomial through each point and deriving
the curvature and torsion analytically.
Probably, for what you need to do, the second approach is a better one.
Indeed, both approaches lead to a regularization of a noisy centerline, where
the noise is for a large part unavoidable and due to the discrete and noisy
nature
of the images. The current smoothing scheme can lead to shifts in the centerline
position if a large number of iterations is employed. In fact, there are no
terms constraining
the centerline where it is initially. Better smoothing schemes could be
adopted,
but local polynomial fitting could be enough (i.e. you won't obtain a globally
smooth centerline, but you would estimate of a smooth approximation of the
centerline one point at a time around the point neighborhood).
Currently there is no script that does that in vmtk right now, although it
would not
be particularly hard to implement. I can provide you with directions if you
have someone with development skills to rely on.
Hope this helps,
Luca
On Jan 18, 2013, at 6:41 PM, Haim Ezer wrote:
> Dear Luca, everybody
>
> I would like to compare the arterial geometry (e.g. Curvature ant torsion) in
> a very accurate manner. The problem is that the amount of smoothing of the
> digital data, determines how flat the centerline result is. Since my data is
> from different modalities (MRI and DSA) a different amount of smoothing is
> required for both modalities. Hence, similar curvature, as proven to be by
> rigid registration of two arteries have different curvature, since different
> amount of smoothing have been performed.
>
> I will appreciate any help.
>
> Thank you!
>
> Haim
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