Extract shell of certain thickness from 3d image

Hi,

I am working with a stack of dicom images that represents a volume and I would like to extract shells of a certain thickness from this volume. Has anyone have any idea how to do it or have done before?

Thanks in advance.

[Sean de Wolski]

So you want to keep 3d objects in it that rare a certain size? Please elaborate on the question and provide a sample image.

[Siddharth]

Thank you for your reply, so i have this 3d image volume (created by stacking dicoms) and now I am trying to extract concentric shells of thickiness 4 voxel from this volume.

I am attaching picture of 2d projection of the volume and the concentric rings for that image. I want to do similar thing on volume. Please let me know.

[Muthu Annamalai]

If you have X-Y data and Y-Z data then finding blobs in each of projects, and linking them in a data structure via rigid rotations should give you an algorithm to find spheroid structures from their 2 projections.

Once you have these structures you may find their volumes, by assuming rotational symmetry, by intersection of the two.

This is probably a somewhat hard algorithm to implement.

Answer 1

[Image Analyst]

See the last chunk of code in the FAQ for how to create a sphere. http://matlab.wikia.com/wiki/FAQ#How_do_I_create_a_circle.3F Just create two of them and subtract the smaller one from the larger on then use it as a mask against your original data volume.

[Siddharth]

Hi thanks for your reply. I am not sure if i explained it correctly, but the shell should be similar to 3D volume shape and not spherical. If you see hollow shells in my third figure, the shape isn't spherical.

The outer-most shell will be like a boundary for that 3D volume with 4voxel thickness.

Anyway, I have already made a code to trace boundary for my 3D volume and certainly I can use the boundary indices to create those shells now.

Thanks all -Sid