Hi Simon, Thanks for your kind reply and information provided. Basically the problem i encountered is that without changing any geometry (i.e., sid, sdd, detector physical size), if i downsample my original projection images, how can i reconstruct corresponding volume correctly. In RTK, it seems that i just need to change the input projection file and newspacing parameter (as same as the factor of downsample), then i got promising results. but in my own application, i simulate the situation, but got some aliasing. So i really want to know how it work behind our RTK. I thought that this parameter is to simulate the detector's spacing size. And in my experiment, i set the detector physical size as 256mm*256mm, and i got projection images P1.mha with size of 256^2 , now i downsample these images with factor of 2( i.e., the images size change from 256^2 to 128^2 ), from which i got P2.mha in our rtkfdk, after the dowmsample. i just need change input projections from P1.mha to P2.mha, besides, i need change flag newspacing from 1 to 2. both of the results from RTK are pretty good. my questions are: 1) can i just regard the newspacing as the upsample operation with nearest neighbor filter?? 2) how many rays RTK generated in forward projecion (i.e. ray tracing part ) for each image in P2.mha??? is it 256^2????
To sum up,in my own application, can i reproduce the result from RTK for flag "newspacing as 2" by doing: upsample image by factor of 2 (got a 256mm*256mm image ) and just generate half number of rays in raytracing (forward priject ) part??? Thanks for your time and help in advance, -Regards Guangming On Sat, Feb 20, 2016 at 1:15 AM, Simon Rit <[email protected]> wrote: > Hi Guangming, > The parameter is processed in rtkGgoFunctions > <https://github.com/SimonRit/RTK/blob/master/code/rtkGgoFunctions.h>.h. > It's passed to an itk::ChangeInformationFilter > <http://www.itk.org/Doxygen/html/classitk_1_1ChangeInformationImageFilter.html> > at the beginning of the rtk::ProjectionsReader.h > <http://www.openrtk.org/Doxygen/classrtk_1_1ProjectionsReader.html>. But > in the end, there is nothing to explain, it's simply changes the spacing of > the input projections. > I hope this helps, > Simon > > On Fri, Feb 19, 2016 at 8:52 PM, Guangming Zang < > [email protected]> wrote: > >> >> ---------- Forwarded message ---------- >> From: Guangming Zang <[email protected]> >> Date: Fri, Feb 19, 2016 at 10:49 PM >> Subject: About the newspacing flag >> To: [email protected], Chao Wu <[email protected]>, >> Simon Rit <[email protected]>, "[email protected]" >> <[email protected]>, [email protected] >> >> >> Dear RTK community, >> i have a question about the parameter "newspacing " in rtkFDK and rtkSART >> algorithm. >> it says:--newspacing new spacing of input projections (before >> pre-processing). >> I checked in the code, and it seems not easy to find the correct part >> in the code about the newspacing . >> So could anyone help me and explain about this parameter?? i want to >> simulate this preprocess step in my own project and compare to our RTK. >> -best regards Guangming >> >> -- >> *Guangming Zang (Alex)* >> *King Abdullah University of Science and Technology(KAUST)* >> *University of Chinese Academy of Sciences(UCAS)* >> >> >> >> >> >> >> -- >> *Guangming Zang (Alex)* >> *King Abdullah University of Science and Technology(KAUST)* >> *University of Chinese Academy of Sciences(UCAS)* >> >> >> >> >> ------------------------------ >> This message and its contents, including attachments are intended solely >> for the original recipient. If you are not the intended recipient or have >> received this message in error, please notify me immediately and delete >> this message from your computer system. Any unauthorized use or >> distribution is prohibited. Please consider the environment before printing >> this email. >> >> _______________________________________________ >> Rtk-users mailing list >> [email protected] >> http://public.kitware.com/mailman/listinfo/rtk-users >> >> > -- *Guangming Zang (Alex)* *King Abdullah University of Science and Technology(KAUST)* *University of Chinese Academy of Sciences(UCAS)* -- ------------------------------ This message and its contents, including attachments are intended solely for the original recipient. If you are not the intended recipient or have received this message in error, please notify me immediately and delete this message from your computer system. Any unauthorized use or distribution is prohibited. Please consider the environment before printing this email.
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