[Rtk-users] trouble projecting phantom

[Simon Rit]

Hi Micah,
I have given it a try and I think I obtain the expected result if you use
the SheppLogan file that we provide here
http://midas3.kitware.com/midas/download?items=27326
However, the result might surprise you because your source is in the
phantom (sid=65.93 vs largest ellipsoid which is A=88.32 B=115.2 C=117.76).
You can scale the shepp logan phantom using the following command
rtkprojectshepploganphantom -g geo.xml -o proj.mha --spacing 1 --dimension
1024 --phantomscale 10
You will then obtain more meaningful results, i.e., the full phantom will
be in the beam.
Note by the way that if you use rtkfdk afterwards, you will have to be
careful to have the source outside the volume as well. I have recently
noticed that there was a bug when the source was in the volume, I will fix
it as soon as possible.
Simon

On Tue, Feb 26, 2013 at 2:23 AM, M Miller <croow at yahoo.com> wrote:

> I've been unable to project a phantom, or anything else, at high
> magnification. Here's the steps I've think should work, but don't.
>
> "rtksimulatedgeometry.exe --output=geo.xml --nproj=1600 --arc=360
> --sdd=870.86 --sid=65.93"
>
> These are the values from my actual CT system. Next I try using
> rtkprojectgeometricphantom to create some projections.
>
> "rtkprojectgeometricphantom -g geo.xml -o projs\projections1024.mha
> --spacing 1 --dimension 1024 --phantomfile
> SheppLogan.txt"
>
> Inspecting the output projections shows they're mostly unrecognizable.
> Repeating these steps with a higher SID does produce the expected phantom
> projections. I've had no luck using real data, so I thought I'd try a
> simple phantom, but it's turned out to be not so simple.
>
> Is RTK limited somehow with respect to magnification, or are my
> expectations unrealsitic? Am I missing a command-line switch?
>
> Thanks
> Micah
>
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