[Rtk-users] About Kaiser-Bessel Filter

[Guangming Zang]

Oh, I did not notice that.
Thanks for pointing out.
Best
Guangming

*Guangming Zang (Alex)*
*King Abdullah University of Science and Technology(KAUST)*
*University of Chinese Academy of Sciences(UCAS)*


2014-11-18 19:47 GMT+03:00 Simon Rit <simon.rit at creatis.insa-lyon.fr>:

> The trilinear version is available with CUDA:
>
> http://www.openrtk.org/Doxygen/classrtk_1_1CudaForwardProjectionImageFilter.html
> Simon
>
> On Tue, Nov 18, 2014 at 5:43 PM, Guangming Zang <
> guangming.zang at kaust.edu.sa> wrote:
>
>> Hi Chao,
>> Thanks very much for your prompt and so kind reply.
>> I will recheck the process of setting carefully with your suggestions and
>>  a short report may be given later.
>>  BTW, do you have any plan recently to add other interpolation filter(e.g.Kaiser-Bessel
>> or Trilinear)??
>> Thanks for your time.
>> Regards
>> Guangming
>>
>>
>>
>> 2014-11-18 19:09 GMT+03:00 Chao Wu <wuchao04 at gmail.com>:
>>
>>> Hi Guangming,
>>>
>>> To reconstruct a volume from a series of tiff files you have to let the
>>> algorithm know the geometrical relationship among the source, the volume
>>> and the projections stored in the tiffs. The idea is the same: RTK uses
>>> projection matrices and image coordinates to understand the positioning of
>>> those projections. The projection matrices are based on a lot of
>>> geometrical parameters like gantry angle, source position, detector
>>> position, in-plane and out-of-plane rotation angles of the detector etc. I
>>> won't go though all since most of them have no differences if you use tiff
>>> files or whatever format as input. I focus on some tiff tips.
>>>
>>> In the simplest situation, the tiff files contain correct resolution
>>> (DPI) information, then you need to do nothing on these files. You have to
>>> specify the correct detector offset though, since in the tiff image
>>> coordinates the origin is the first pixel (corner pixel) which is
>>> apparently not the intersection of the central ray and the detector. The
>>> detector offsets in x and y actually mean the position of the image origin
>>> (the first pixel) in the coordinate system centred at the intersection.
>>> Since the direction cosines is an identity matrix and pixel sizes are
>>> positive, the detector offsets in x and y will be negative.
>>>
>>> If the resolution information of the tiff files is not correct, you have
>>> to rewrite this information. You can of course perform a pre-processing to
>>> change the DPI of all tiff files with a third-party software, or you can
>>> alter the RTK code to allow such changes after reading the images, by using
>>> a itk::ChangeInformationImageFilter filter.
>>>
>>> Another non-geometrical issue with tiff files is that when their integer
>>> pixel values are converted into attenuation, the maximum possible integer
>>> is used as the reference value. This may not be correct in practice, e.g.
>>> in your 16-bit tiffs you use 62000 to represent air (no attenuation)
>>> leaving the integer range from 62001 to 65535 for statistical fluctuation.
>>> If for instance you only use the lower 14 bits for your data then this
>>> problem is more severe. For sure you can correct this by changing the code
>>> and specify the correct reference value.
>>>
>>> Hope these can help.
>>>
>>> Regards,
>>> Chao
>>>
>>> 2014-11-18 15:09 GMT+01:00 Guangming Zang <guangming.zang at kaust.edu.sa>:
>>>
>>>> Thanks
>>>>
>>>> *Guangming Zang (Alex)*
>>>> *King Abdullah University of Science and Technology(KAUST)*
>>>> *University of Chinese Academy of Sciences(UCAS)*
>>>>
>>>>
>>>> 2014-11-18 16:46 GMT+03:00 Guangming Zang <guangming.zang at kaust.edu.sa>
>>>> :
>>>>
>>>>> Hi,
>>>>> I am using the sart reconstruction in RTK, it works well.Thanks for
>>>>> your great work.
>>>>> and i was wondering do you have any plan to add other filters except
>>>>> Joseph, such as Kaiser-Bessel???  ( described here
>>>>> http://wscg.zcu.cz/wscg2003/papers_2003/herman.pdf)
>>>>> BTW, i have read the messages sent by other users(
>>>>> http://public.kitware.com/pipermail/rtk-users/2014-October/000573.html
>>>>> )
>>>>> but i still can not make it. can u help me and explain again about
>>>>> using a series of .tiff images ans sart algorithms to get the volume.
>>>>> Thanks in advance
>>>>> Best
>>>>> *King Abdullah University of Science and Technology(KAUST)*
>>>>> *University of Chinese Academy of Sciences(UCAS)*
>>>>>
>>>>>
>>>>
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