[Rtk-users] Parker weighting

[Simon Rit]

Hi,
The geometry files look ok to me. What is the projection information? If
you're still getting the same message as before, I think it's because you
don't have enough data. If you send the mhd file of the projections (just
the mhd, not the raw data), I can try to test it on simulated data to let
you know my feeling.
Simon

On Tue, Dec 8, 2015 at 5:41 PM, Shiras Abdurahman <shiraska at gmail.com>
wrote:

> Dear Simon,
>
> I tried this option and unfortunately it did not work. I added zero
> projections and modified geometry files. However, I am getting same
> artifacts in the volume. Voxel values changed a little bit that indicates
> during backprojection it still considers extreme projections. I am also
> getting an output message same as before.
>
> I am attaching geometry files.
>
> With regards,
> Shiras
>
> On Tue, Dec 8, 2015 at 10:15 AM, Simon Rit <simon.rit at creatis.insa-lyon.fr
> > wrote:
>
>> So calling AddProjection before and after the loop with an adequate
>> gantry_angle should work.
>> Simon
>>
>> On Tue, Dec 8, 2015 at 9:52 AM, Shiras Abdurahman <shiraska at gmail.com>
>> wrote:
>>
>>> Drear Simon,
>>>
>>> I generate the geometry with system geometry parameters and using
>>> AddProjection method.
>>>
>>> Here is the code
>>>
>>>
>>> rtk::ThreeDCircularProjectionGeometry::Pointer rtk_sys_geometry_;
>>> rtk_sys_geometry_ = rtk::ThreeDCircularProjectionGeometry::New();
>>> for (uint16_t proj_index = 0; proj_index < num_projections_;
>>> proj_index++)
>>> {
>>> rtk_sys_geometry_->AddProjection(rtk_geom_params_.at(proj_index).sid_mm,
>>> rtk_geom_params_.at(proj_index).sdd_mm,
>>> rtk_geom_params_.at(proj_index).gantry_angle_deg,
>>> rtk_geom_params_.at(proj_index).proj_offset_x_mm,
>>> rtk_geom_params_.at(proj_index).proj_offset_y_mm,
>>> rtk_geom_params_.at(proj_index).out_plane_angle_deg,
>>> rtk_geom_params_.at(proj_index).in_plane_angle_deg,
>>> rtk_geom_params_.at(proj_index).src_offset_x_mm,
>>> rtk_geom_params_.at(proj_index).src_offset_y_mm);
>>> }
>>>
>>>  And then write to xml file.
>>>
>>> Shiras
>>>
>>>
>>>
>>> On Tue, Dec 8, 2015 at 9:23 AM, Simon Rit <
>>> simon.rit at creatis.insa-lyon.fr> wrote:
>>>
>>>> Hi,
>>>> rtkfdk.cxx just read the geometry from a file so the best is to modify
>>>> the geometry file. How do you generate the geometry?
>>>> For example, if you use rtksimulated geometry, let's say that you were
>>>> using:
>>>> rtksimulatedgeometry -n 200 -a 200 -o g.xml
>>>> then you'll have to replace it with
>>>> rtksimulatedgeometry -n 202 -a 202 -o g.xml -f -1
>>>> Don't forget to add dummy projection at the beginning and the end. If
>>>> you use a more complex geometry, maybe SimpleRTK
>>>> <http://wiki.openrtk.org/index.php?title=SimpleRTK> can be helpful
>>>> (I'd use that) or you'd have to modify the cxx code to add these additional
>>>> projections in the geometry and the projection stack.
>>>> Simon
>>>>
>>>>
>>>> On Tue, Dec 8, 2015 at 8:51 AM, Shiras Abdurahman <shiraska at gmail.com>
>>>> wrote:
>>>>
>>>>> Dear Simon,
>>>>>
>>>>> Thanks a lot for the reply. Can you please inform me how can I set
>>>>> where the arc starts?
>>>>> Do I need to modify geometry also?
>>>>> If you can point the line of code rtkfdk.cxx, it will be really
>>>>> helpful.
>>>>>
>>>>> With regards,
>>>>> Shiras
>>>>>
>>>>> On Tue, Dec 8, 2015 at 7:56 AM, Simon Rit <
>>>>> simon.rit at creatis.insa-lyon.fr> wrote:
>>>>>
>>>>>> Dear Shiras,
>>>>>> Yes, for practical reasons the first and the last projections are set
>>>>>> to 0 and the arc used in the Parker weighting starts between the first two
>>>>>> projections and ends between the lasts two projections. There is a simple
>>>>>> solution: add a projection at the beginning and the end of the arc, which
>>>>>> can contain any pixel values but should be set where you want this arc to
>>>>>> start. In the future, I think someone should once take the time to correct
>>>>>> this but I haven't so far. I'll keep you posted on the mailing list when
>>>>>> it's corrected.
>>>>>> Simon
>>>>>>
>>>>>> On 07/12/2015 12:04, Shiras Abdurahman wrote:
>>>>>>
>>>>>> Hi all,
>>>>>>
>>>>>> I am trying to reconstruct a volume from projection data generated
>>>>>> with C-arm CT. There are 248 projections with an angular range of 199
>>>>>> degree. Technically, parker weighting should run without any problems.
>>>>>> However, I am getting an output message that "You do not have enough data
>>>>>> for proper parker weighting". After parker weighting, the two extreme
>>>>>> projections (projection number 1 and 248) were completely zero and thus
>>>>>> reconstructed volume contained artifacts. When I increased the angular
>>>>>> range, this problem did not happen. How can I solve this problem without
>>>>>> increasing angular range? Is there any threshold constant that I can change
>>>>>> in command line  or in my code?
>>>>>>
>>>>>> I really appreciate any help you can provide.
>>>>>>
>>>>>> With regards,
>>>>>> Shiras
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> Rtk-users mailing listRtk-users at public.kitware.comhttp://public.kitware.com/mailman/listinfo/rtk-users
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
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