[vtkusers] Recognize a screw in a CT

David Gobbi david.gobbi at gmail.com
Tue Nov 11 08:52:01 EST 2014

Hi Igor,

This is something that connected component labelling can do fairly well.
The procedure is as follows (roughly):

1) Find the brightness of the voxels within the screw.  Find the brightness
of the voxels surrounding the screw.  Choose a threshold that separates
them.  Apply that threshold to the image to make a binary image.

2) Apply a 3D connected component labelling filter to label the objects in
the binary image.

3) Identify the object that is most likely to be the screw, based on size,
shape, or other characteristics.

See the following website for a quick description of connected component
labelling (the site describes it in 2D, but the methods works just as well
in 3D):

ITK has a ConnectedComponentImageFilter.  For VTK, I have a
vtkImageConnectivityFilter in one of my own repositories:

 - David

On Tue, Nov 11, 2014 at 4:52 AM, igorznt <igorznt at gmail.com> wrote:

> I have to recognize a screw in a CT an locate the point on its bases and
> head. Does anyone knows how or could indicate a good material about?
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