[Rtk-users] trouble projecting phantom

[M Miller]

Scaling the phantom worked perfectly.
You mentioned that a reconstruction will need to specify the source outside of the volume. How can I specify that? What parameters would you pass to rtkfdk.exe to reconstruct the phantom?
 
Thanks
Micah

--- On Tue, 2/26/13, Simon Rit <simon.rit at creatis.insa-lyon.fr> wrote:


From: Simon Rit <simon.rit at creatis.insa-lyon.fr>
Subject: Re: [Rtk-users] trouble projecting phantom
To: "M Miller" <croow at yahoo.com>
Cc: rtk-users at openrtk.org
Date: Tuesday, February 26, 2013, 12:36 AM


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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