[Rtk-users] FirstReconstruction questions

[Simon Rit]

Hi lyh,
I had a look at what you've sent. I obtain a first result with the
following command lines:
rtksimulatedgeometry -n 100 -o g --sid 278.044 --sdd $(echo 278.044+372.528
| bc -l) -f 6.3
rtkfdk -p images -r p_[0-9]*.tif -o fdk.mha -g g --newspacing 0.2
--neworigin $(echo -0.5*1951*0.2 | bc -l) --spacing 0.25 --dimension 512
The newspacing and neworigin options set the projections spacing and origin
with the ChangeInformationImageFilter. The result is not perfect, I believe
the geometry is not right yet. Maybe there is a detector offset you're not
aware of? But your text file indicate no offset so I don't know what's
wrong. Attached is a snapshot. There are also some dead pixels which you
could try to prefilter.
I hope this helps. Cheers,
Simon

On Tue, Jan 5, 2021 at 5:35 PM Lai Yao Hao <yao_hao777 at hotmail.com> wrote:

> Hi,
> I cannot send the projections via email as the projections are too big in
> size. Instead, I am sharing the files on Drive, with the hyperlink as
> below. In the folder, there is a subset of 100 projections out of the 800
> projections, with the angle between each projection being 3.6 degrees.
> There are other details on the projects as listed in report.txt file in the
> folder.
>
> Google drive share link:
>
> https://drive.google.com/drive/folders/1wMRo3Rmr6HszUVil0vEsLPtLSLftFyfQ?usp=sharing
>
> Regards
> lyh
> ------------------------------
> *From:* Simon Rit <simon.rit at creatis.insa-lyon.fr>
> *Sent:* Tuesday, January 5, 2021 5:21 PM
> *To:* Lai Yao Hao <yao_hao777 at hotmail.com>
> *Cc:* rtk-users at public.kitware.com <rtk-users at public.kitware.com>
> *Subject:* Re: [Rtk-users] FirstReconstruction questions
>
> Hi,
> I think the issue is that your projection images are given in the TIFF
> file format which does not contain important meta information such as the
> origin and the spacing of the projections. You should use
> ChangeInformationFilter
> <https://itk.org/Doxygen/html/classitk_1_1ChangeInformationImageFilter.html>
> to set these. I'm guessing that the origin is currently (0,0) and since you
> do not set any offsets when using AddProjection, it comes down to having
> the corner of your projection aligned with the central ray (line defined by
> the source and the center of rotation).
> You can share projections or a subset of them if you'd like us to give it
> a try with your code.
> Good luck!
> Simon
>
> On Mon, Jan 4, 2021 at 4:35 PM Lai Yao Hao <yao_hao777 at hotmail.com> wrote:
>
> Hi,
>
> The code is as attached. Just for further reference, I am given images as
> attached, and there are 800 of them, with 0.45 degrees separating each
> frame. The naming of the screenshots depicts the frame that it is in.
>
> Thanks in advance for the advice and help!! I really appreciate this
> community 🙂
>
> Regards
> lyh
> ------------------------------
> *From:* Simon Rit <simon.rit at creatis.insa-lyon.fr>
> *Sent:* Wednesday, December 30, 2020 9:35 PM
> *To:* Lai Yao Hao <yao_hao777 at hotmail.com>
> *Cc:* rtk-users at public.kitware.com <rtk-users at public.kitware.com>
> *Subject:* Re: [Rtk-users] FirstReconstruction questions
>
> Hi,
> RTK cone beam reconstruction filters expect line integrals but the
> projection that you are showing seems to have the highest value in air. RTK
> automatically processes such projections with log and normalization if the
> pixels are unsigned short. Otherwise, you need to do it yourself.
> It is not clear if the geometry is correct from the reconstruction screen
> shot. The best would be to share your code if you want us to have a look.
> Simon
>
> On Mon, Dec 28, 2020 at 8:34 AM Lai Yao Hao <yao_hao777 at hotmail.com>
> wrote:
>
> Dear Simon and the RTK community
>
> Really thank you for the answer, and really sorry for the late reply. I am
> trying to reconstruct a 3d model using 800 images, rotating an object 360
> degrees using rtk::ThreeDCircularProjectionGeometry,
> rtk::ConstantImageSource and rtk:: FDKConeBeamReconstructionFilter from the
> FirstReconstruction example as well as itk::ImageSeriesReader.
>
> However, the reconstruction created is shown above in the screenshot and
> after checking all the parameters, I have no idea on how to move forward
> from here. From reading the forums, I think that I should do one more image
> filter before applying the cone beam reconstruction? However, I am not too
> sure. Please advise on the next steps that can enable me to get the 3d
> reconstruction.
>
> Thanks so much in advance and look forward to everyone's reply!!
>
> PS: the tif file is just 1 of the 800 images I am given to reconstruct the
> object
>
> Regards
> lyh
>
> ------------------------------
> *From:* Simon Rit <simon.rit at creatis.insa-lyon.fr>
> *Sent:* Wednesday, December 9, 2020 4:23 PM
> *To:* Lai Yao Hao <yao_hao777 at hotmail.com>
> *Cc:* rtk-users at public.kitware.com <rtk-users at public.kitware.com>
> *Subject:* Re: [Rtk-users] FirstReconstruction questions
>
> Hi,
> constantImageSource creates a constant volume. In the example, one is used
> as input of the simulation of projections of an ellipsoid (rei) and one as
> input of the reconstruction algorithm (feldkamp). fieldofview masks out
> (i.e., set to 0) voxels which are not in the field of view.
> I don't understand your screenshot either but if you use the tiff format,
> make sure you use a viewer capable of dealing with 3D tiff images (e.g.,
> vv <http://vv.creatis.insa-lyon.fr> or ImageJ).
> Simon
>
> On Wed, Dec 9, 2020 at 8:59 AM Lai Yao Hao <yao_hao777 at hotmail.com> wrote:
>
> Hi to all the rtk-users
>
> I am a new user of rtk, and I have some questions regarding the
> FirstReconstruction example given in github. I have generated an image as
> attached, with 4 tiny ball-like drawing hanging from the top. Can anyone
> explain to me why do I get such image and what are the implications of
> constantImageSource, rei, constantImageSource2, feldkamp and fieldofview?
>
> Your explanation will be much appreciated. Thanks in advance!
>
> Regards
> lyh
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