[Rtk-users] Using rtkfdk to reconstruct CBCT

[Simon Rit]

Hi,
Sorry for my late reply.
1. The Hann parameter is a fraction of the Nyquist frequency. If set to 0,
there is no Hann windowing. If you set it to 0.5, a Hann windowing is used
with a cut-off at 50% of the Nyquist frequency.
2. The reconstructed values are attenuation coefficient assuming that the
input projections are line integrals of this coefficient. Small values are
typical, yes. For HU conversion, you need to normalize them using the
attenuation coefficient of air and water.
3. For denoising, you could use the TV denoiser
<http://www.openrtk.org/Doxygen/classrtk_1_1TotalVariationDenoisingBPDQImageFilter.html>
but there are probably other options in ITK (e.g., Gaussian smoothing). For
scatter, we only have the Boellaard algorithm
<http://www.openrtk.org/Doxygen/classrtk_1_1BoellaardScatterCorrectionImageFilter.html>.
For binarizing, you can threshold your image.
Simon

On Sun, Oct 29, 2023 at 11:23 AM 小哈 <2310447681 at qq.com> wrote:

> Hello,
> I think RTK packets are very useful in reconstructing CBCT. When using the
> FDK algorithm with RTK packets, I encountered the following issues:
> 1.How should I set the parameters if I want to achieve a truncation
> frequency of 5 for reconstruction? What is the function of the Hann
> parameter?
> 2. For the reconstructed 3D image in mha format (512 * 256 * 512), I use
> simpleITK to read the code as follows:
>
> Image=sitk ReadImage (path)
> Vol=sitk GetArrayFromImage (image)
>
> But the obtained three-dimensional array vol, but each value in the array
> is very small, is this normal? The results of the array are shown in the
> figure:
>
> 3. If I want to further denoise, scatter correct, and binarize the
> reconstructed image, how should I achieve it？
> If you could help me, I would be very grateful. Thank you.
>
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> rtk-users at openrtk.org
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>
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