Info-Volumizer Mailing List Archives: Re: Fly-through suggesti

Re: Fly-through suggestions

Angus Bond (bond@stereosgi.neur.cwru.edu)
Thu, 14 Oct 1999 13:22:02 -0400 (EDT)

> Message-ID: <38061800.A98BE7D5@medphys.ucl.ac.uk>
> Date: Thu, 14 Oct 1999 10:50:56 -0700
> From: Mark Davey <mkd@medphys.ucl.ac.uk>
> To: info-volumizer <info-volumizer@corp.sgi.com>
> Subject: Fly-through suggestions
>
> Hi..
> I am looking to use Volumizer to effectively 'fly-through' a CT or MRI
> volume. For instance, this could be used as a teaching aid for
> endoscopic surgery. Does anyone have any ideas concerning steps that
> should be taken to do this using Volumizer. My initial attempts have
> been less than satisfactory resulting in quite blurred, very aliased
> images.
> Regards
> Mark
>
> --
> From: Mark Davey
> Dept. of Medical Physics, UCL.
>
> TEL: +44 (0)171 915 1673.
> FAX: +44 (0)171 837 9279.
>
> Institute of Laryngology and Otology,
> 330 Gray's Inn Road,
> London.
> WC1X 8GE.

Hello Mark,

I do not have the answer you seek, but I can tell you that, if you
are emulating an endoscope, you can expect to see blurred and/or
aliased images.

The problem has to do with image resolution. CT and MR scans are
usually 512 pixels across a field-of-view of 240 mm and the slices
are usually 1 to 2 mm apart. That means that each voxel is about
0.5x0.5x1.0 mm at best. An endoscope usually has a field-of-view
of about 10 to 20 mm, so you will be looking at a field of about
40x40 voxels at best and 20x10 voxels at worst. I can guarantee
that the result will be blurred and/or aliased.

A good rendering system will produce an anti-aliased image so that
you get an understanding of what you are seeing. You may also be
able to get a crude surface rendering. The rendering system cannot
create data that was not in the original CT or MR scan, so the very
best it can do is approximate reality. Once you understand this,
you can find a rendering system that will give you a good
representation of the volume. For that, you will have to talk to
the other members of this mailing list.

Good luck!
Angus
-----------------------------------
Angus Bond
bond@stereosgi.neur.cwru.edu
bond@modex.com
+1 216 844-8963 lab/office
+1 440 834-1414 answering machine/fax

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