Please stick to the mailing list. The DivideImageFilter is part of OSEM so that doesn't explain it. I did a quick test and that works for me: rtksimulatedgeometry -n 100 -o g rtkprojectshepploganphantom -g g -o proj.mha --spacing 1.5 rtkosem -p . -r proj.mha -v -o osem.mha -n 5 -g g --nprojpersubset 100 and I obtain 5.7e6 in the osem.mha file and 5.9e8 in the proj.mha file.
On Tue, Jun 27, 2023 at 4:07 PM Nathan Sinsoilliez <n.sinsoill...@gmail.com> wrote: > Hi, > I'm not using any attenuation correction currently. The total counts of > the reconstructed images is still too low compared to the total average in > one projection. It looks like the pixel values are divided (which can > explain why they're decimals). After checking the > OSEMConeBeamReconstructionFilter on the wiki, I saw that there is a > DivideImageFilter, maybe it can explain why but I don't really get how it > works and why it is necessary so maybe I'm speaking nonsense here. > > Sinsoilliez Nathan > > > > > Le mar. 27 juin 2023 à 10:18, Simon Rit <simon....@creatis.insa-lyon.fr> > a écrit : > >> Hi, >> I'm not sure we actually ever checked this but it's a good check. Are you >> using attenuation correction? If not, I expect that the total number of >> counts in one projection should be equal to the integral of the SPECT image >> as this is the Radon transform model. So you may want to average the number >> of counts and not sum it (i.e., divide 8E+6 by your number of projections). >> Can you check this? >> Simon >> >> On Tue, Jun 27, 2023 at 8:48 AM Nathan Sinsoilliez < >> n.sinsoill...@gmail.com> wrote: >> >>> Hello everyone, >>> >>> I'm currently using rtk to reconstruct SPECT images using OSEM and I >>> have an issue after the reconstruction. The total count of the image is >>> completely changed (like 8E+6 in the projections VS 2E+4 when >>> reconstructed). Also most of the pixels now have decimal values. >>> Graphically everything seems to be alright though. >>> >>> Do you have an idea about what could cause this problem ? >>> >>> Best Regards >>> Sinsoilliez Nathan >>> _______________________________________________ >>> Rtk-users mailing list >>> rtk-us...@openrtk.org >>> https://www.creatis.insa-lyon.fr/mailman/listinfo/rtk-users >>> >>
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