[Rtk-users] Helical cone-beam reconstruction with RTK

[vahid ettehadi]

Hello,Thank you Robert, Louie and Simon, for your tips and recommendations. I will work on it and I will share the result or potential problems. I found the RTK more accurate and easy to use in compare with other open-source reconstruction tools such as Oscar and NiftyRec. 
Thank you RTK team!Vahid

 

     On Friday, February 27, 2015 4:42 AM, Simon Rit <simon.rit at creatis.insa-lyon.fr> wrote:
   

 Hi,
We haven't worked on helical (CB)CT and I haven't heard of anyone working on it. Others answers are correct:
- it's easy to simulate helical CBCT by playing with the geometry. I guess compared to a circular geometry where only source-to-detector and source-to-isocenter distances matter, you'll have to adjust the SourceOffsetY and the ProjectionOffsetY. That should work for shepp logan type of simulations and forward projections of 3D images.
- iterative reconstruction should work since we don't have any prior on the geometry except we use the displaced detector for weighting the central area when required. You probably want to do something similar in the direction of the axis of rotation to have smooth transitions between projections but it's theoretically not mandatory (we found the result is better in practice).
- there is no analytical reconstruction available.
Good luck and don't hesitate to contribute if you do some tests.
Simon

On Thu, Feb 26, 2015 at 10:33 PM, louie L <ghostcz at hotmail.com> wrote:

Hi,
You can change the geometry. If changed correctly, most, if not all, the iterative cone beam reconstruction will work. 
Best regards,Louie

Greetings from my iOS!
On 26 Feb 2015, at 21:19, Robert Calließ <robert.calliess at gmx.de> wrote:


Hello Vahid,I think you need to add a new reconstruction filter for it. For the first projection the object usually is placed so that theresulting projection image covers the upper half of the detector. And you will need some additional handling (z-increment).I guess you could do a little work around with the current rtk. If you only reconstruct an rectangular roi aroundthe detector’s center where the perspective distortion (because of the cone) is minimal. And then you add theseseperate volumes to a final volume. This is just an idea. I do not know how the result will look like. Think of it like a TDIbut with a wider sensor array. I do not know the code in detail, but if it were possible to have seperate geometry settings for every projection image it would be possible to model the helical trajectory by the changing geometry without changing /adding code. But let’s see what grandmasters of RTK will suggest. Best regards,Robert                 Von: Rtk-users [mailto:rtk-users-bounces at public.kitware.com] Im Auftrag von vahid ettehadi via Rtk-users
Gesendet: Donnerstag, 26. Februar 2015 20:35
An: rtk-users at public.kitware.com
Betreff: [Rtk-users] Helical cone-beam reconstruction with RTK Dear RTK users,  I am using the RTK code to reconstruct the image for a bench-top micro-CT in a circular cone-beam geometry. It works well with FDK algo. Thanks RTK.I would like to change the current source trajectory from circular to helical. I was wondering is it possible to use the RTK for helical reconstruction only with some simple modification?I don't know well about reconstruction process and I don't know which type of modification is necessary to use RTK for a helical cone beam geometry. So, any suggestion and recommendation would be appreciated. Sincerely,Vahid  

_______________________________________________
Rtk-users mailing list
Rtk-users at public.kitware.com
http://public.kitware.com/mailman/listinfo/rtk-users


_______________________________________________
Rtk-users mailing list
Rtk-users at public.kitware.com
http://public.kitware.com/mailman/listinfo/rtk-users




_______________________________________________
Rtk-users mailing list
Rtk-users at public.kitware.com
http://public.kitware.com/mailman/listinfo/rtk-users


   
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://public.kitware.com/pipermail/rtk-users/attachments/20150227/63d31de5/attachment-0009.html>