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

[Simon Rit]

Hi Andy,
Indeed, you also need to comment the update of the ramp filter:
m_RampFilter->Update();
This time, I tested it and it works!
Simon

On Thu, Dec 20, 2012 at 2:03 PM, Andy Shieh <hsieandy at gmail.com> wrote:
> 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
>
>