[Rtk-users] Parker weighting

[Shiras Abdurahman]

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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