Volume rendering of actors

[fmri]

Dear VTK users,

when visualizing 3D reconstructions from head MRI and CT data I came
accross the following problems, which I should appreciate to discuss
with You:

After data segmentation I obtain an atlas volume of object labels (e.g.
bone object, tumor object etc.). Generating a surface mesh from the
atlas then results in unrealistic staircase effects, whereas smoothing
and decimating seriously distort the anatomy resulting in 2-3mm
shortened distances. Additionally, the whole scene is far from the
reality, which I see intraoperatively. Thus I left this strategy and
experimented with volume rendering of the raw data. I do not possess a
real deep technical understanding of the internal workings of the volume
renderer and so I wonder if You could inform me regarding the following
issues:

1.) Does it make sense to perform volume rendering on the labelled atlas
volume and what would be the most convenient way to do it in VTK ?
2.) Is it reasonable to abandon the atlas concept and for instance
define actors corresponding to the objects (e. g. skin actor is assigned
the voxels within a certain greylevel range to define its geometry)
provided it is possible to map parts of the volume to the actor ?
3.) Is it then still possible to perform ray casting/volume rendering of
the resulting scene/individual actors ?

Thank You very much for discussing this issue with me.

Arno R. Schleich, MS, MD

Dpt. of Otorhinolaryngology
Freie Universitaet Berlin

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