[Rtk-users] Does rtkbackprojections handle half-beam data?

[Andy Shieh]

Hi Simon,

Thanks. I tried disabling ramp filter in rtkFDKConeBeamReconstructionFilter.txx
with the new line, but then gets a runtime error as this:

ExceptionObject caught with writer->Update()
itk::ExceptionObject (0000000000AFE978)
Location: "void __cdecl itk::DataObject::PropagateRequestedRegion(void)
throw(cl
ass itk::InvalidRequestedRegionError)"
File: ..\..\..\Code\Common\itkDataObject.cxx
Line: 397
Description: Requested region is (at least partially) outside the largest
possible region.

which I don't get if I use the original line. I tried lowering the
reconstructed region, but it didn't help.
My projection size is 1024*768, 0.388 mm in both directions. It's half beam
data, detector being displaced by 14.8 cm.
The reconstructed region I always use is 512*100*512, spacing being
0.88,2,0.88 mm.

Cheers,
Andy.



2012/12/17 Simon Rit <simon.rit at creatis.insa-lyon.fr>

> Hi Andy,
> Handling of the half-beam data (we call it displaced detector in RTK
> if I understand you correctly) is done on the projection level with
> the following filter :
>
> http://www.openrtk.org/Doxygen/classrtk_1_1DisplacedDetectorImageFilter.html
>
> You an check in rtkfdk.cxx how to use it.
>
> If you want to disable the ramp filter during reconstruction, a
> "simple" way would be to change the internal pipeline connections in
> rtk::FDKConeBeamReconstructionFilter. Replace in
> rtkFDKConeBeamReconstructionFilter.txx the line
>   m_BackProjectionFilter->SetInput( 1, m_RampFilter->GetOutput() );
> with
>   m_BackProjectionFilter->SetInput( 1, m_WeightFilter->GetOutput() );
> I hope this helps,
> Simon
>
>
> On Sat, Dec 15, 2012 at 2:44 PM, Andy Shieh <hsieandy at gmail.com> wrote:
> > Hi Simon,
> >
> > I've been using rtkfdk to reconstruct and noticed that it handles
> half-beam
> > data.
> > In some situation, I want to use rtkbackprojections (for cases I don't
> want
> > to include ramp filtering). Does rtkbackprojections handle half-beam data
> > correctly, too? I gave it a try and it seems like rtkbackprojections
> would
> > result in some kind of voxel accumulation in the middle, which probably
> > means it doesn't handle half-beam data correctly like rtkfdk?
> > If that's the case, is it possible to make rtkbackproejctions support
> > half-beam data in the next patch (if it's not some massive work)? Thanks!
> >
> > Cheers,
> > Andy
>
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