[Insight-users] ring artifacts in CT

[Luis Ibanez]

Hi Somi,

For (a) , please look at the example:

Insight/Examples/Filtering
    FFTImageFilterFourierDomainFiltering.cxx


For (b), please look at the class:

itkAzimuthElevationToCartesianTransform.h
http://www.itk.org/Doxygen312/html/classitk_1_1AzimuthElevationToCartesianTransform.html


    Regards,


         Luis


------------------------------------------------------------------
On Wed, Apr 28, 2010 at 9:40 AM, somi <seesomi at gmail.com> wrote:
> Hi Sergio, Mario ,
> Thanks for the reply. Unfortunately these images were given to me by someone
> and I don't have access to scanners directly.
> Median filtering seemed to suppress the noise to some extent, I would try
> out Fourier analysis. I think converting the image to cylindrical
> co-ordinates might help before Fourier analysis.
>
> a) Does ITK have any frequency domain High/Low/notch etc filters ? or do I
> have to create mask images depending on what type of filter I am applying ?
>
> b) Does ITK have any Cartesian to cylindrical/spherical co-ordinate
> transformation ?  Or do I have to create my own transform and pass it to
> resample image filter ?
>
> Regards,
> Somi
>
>
> On Wed, Apr 28, 2010 at 3:52 AM, Mario Ceresa <mrceresa at gmail.com> wrote:
>>
>> Hello Somi,
>> rings artefacts happen in a CT scan if one of the detectors is faulty
>> or out of calibration. The detector then gives the same erroneous
>> reading at each angle and the result is a visible circle in the image.
>>
>> You can read about some methods to reduce them here:
>>
>> http://www.iop.org/EJ/article/0031-9155/54/12/018/pmb9_12_018.pdf
>>
>> I'm sorry but I'm not aware of any "pluggable" solution, and the
>> scanner will probably need a repair/recalibration.
>>
>> Hope this helps,
>>
>> Mario
>>
>>
>> On 28 April 2010 09:27, Sergio Vera <sergio.vera at alma3d.com> wrote:
>> > It seems to me,
>> > after seeing that image, my first thought is that some filtering based
>> > on
>> > fourier analysis might help.
>> > At least when dealing with 2D images.
>> >
>> > Regards
>> >
>> > On Tue, Apr 27, 2010 at 9:27 PM, somi <seesomi at gmail.com> wrote:
>> >>
>> >> Hi,
>> >> I have some CT images which are severely degraded by ring artifacts
>> >> during
>> >> acquisition .
>> >> The ring artifact looks something like :
>> >> http://www.upstate.edu/radiology/rsna/ct/images/artifact4.jpg (not my
>> >> image)
>> >> , its more severe in my images.
>> >>
>> >> Has anybody encountered similar artifacts ? Is there is any out of the
>> >> box
>> >> way to remove them ?
>> >>
>> >> Regards,
>> >> Somi
>> >>
>> >> _____________________________________
>> >> Powered by www.kitware.com
>> >>
>> >> Visit other Kitware open-source projects at
>> >> http://www.kitware.com/opensource/opensource.html
>> >>
>> >> Kitware offers ITK Training Courses, for more information visit:
>> >> http://www.kitware.com/products/protraining.html
>> >>
>> >> Please keep messages on-topic and check the ITK FAQ at:
>> >> http://www.itk.org/Wiki/ITK_FAQ
>> >>
>> >> Follow this link to subscribe/unsubscribe:
>> >> http://www.itk.org/mailman/listinfo/insight-users
>> >>
>> >
>> >
>> >
>> > --
>> > Sergio Vera
>> >
>> > Alma IT Systems
>> > C/ Vilana, 4B, 4º 1ª
>> > 08022 Barcelona
>> > T. (+34) 932 380 592
>> > www.alma3d.com
>> >
>> > _____________________________________
>> > Powered by www.kitware.com
>> >
>> > Visit other Kitware open-source projects at
>> > http://www.kitware.com/opensource/opensource.html
>> >
>> > Kitware offers ITK Training Courses, for more information visit:
>> > http://www.kitware.com/products/protraining.html
>> >
>> > Please keep messages on-topic and check the ITK FAQ at:
>> > http://www.itk.org/Wiki/ITK_FAQ
>> >
>> > Follow this link to subscribe/unsubscribe:
>> > http://www.itk.org/mailman/listinfo/insight-users
>> >
>> >
>
>
> _____________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
>
> Kitware offers ITK Training Courses, for more information visit:
> http://www.kitware.com/products/protraining.html
>
> Please keep messages on-topic and check the ITK FAQ at:
> http://www.itk.org/Wiki/ITK_FAQ
>
> Follow this link to subscribe/unsubscribe:
> http://www.itk.org/mailman/listinfo/insight-users
>
>