[Rtk-users] Hounsfield Unit Conversion - New User

[Chao Wu]

This way you have correct_pixel_value = 100 + 0 * original_pixel_value
Then you have all your projections flat with value 100.

If you set --wpc=a,b,c,d,... it means correct_pixel_value = a + b *
original_pixel_value + c * original_pixel_value^2 + d *
original_pixel_value^3 + ...
You have to figure out proper values yourself.

2018-02-23 18:25 GMT+01:00 muhammad waqar <muhammad.s.waqar at gmail.com>:

> Hello,
>
> I'm still having a hard time using --wpc in the rtkfdk tool.
> This is how im using it, could you please tell me how im doing it wrong?
>
> /RTK-bin/bin/rtkfdk \
>       --lowmem \
>       --geometry $RtkGeoOutLoc \
>       --path $IMGLOC \
>       --regexp '.*.his' \
>       --output /Sorted_4DCBCT_Data/$FileName/sorted/wpcTest/WPCtest100b.mha'
> \
>       --verbose \
> -spr=24 \
> --wpc= 100 0 \
>       --spacing $Space,$Space,$Space \
>       --dimension $Dim,$Dim,$Dim
>
> Thank you very kidnly,
> ᐧ
>
>
>   Phone: (647)885-5292
>
> On Mon, Feb 19, 2018 at 6:00 AM, Chao Wu <wuchao04 at gmail.com> wrote:
>
>> And be aware that --wpc receives polynomial coefficients, and if you only
>> specify one number this will become the constant term only, which is
>> probably not your intent.
>> Regards, Chao
>>
>>
>> 2018-02-19 7:39 GMT+01:00 Simon Rit <simon.rit at creatis.insa-lyon.fr>:
>>
>>> Hi,
>>> To convert to HU, you need to measure a phantom with water and air and
>>> to apply the formula for HU conversion (see wikipedia
>>> <https://en.wikipedia.org/wiki/Hounsfield_scale>). Note that due to
>>> scatter in (Elekta) cone-beam CTs, you will have difficulties in doing this
>>> conversion due to strong artifacts.
>>> The --wpc coefficients can allow you to apply the slope of this formula
>>> but the intercept must be subtracted after reconstruction. We illustrate
>>> here <http://wiki.openrtk.org/index.php/WaterPreCorrection> how to use
>>> wpc.
>>> Good luck,
>>> Simon
>>>
>>> On Mon, Feb 19, 2018 at 1:01 AM, muhammad waqar <
>>> muhammad.s.waqar at gmail.com> wrote:
>>>
>>>> Hello all,
>>>>
>>>> I'm a new user to ITK/RTK and I'm having a few issues:
>>>>
>>>> Following the ElektaReconstruction steps on the wiki, I was able to
>>>> reconstruct my scan. However, the window and level are still in attenuation
>>>> coefficients. How can I convert my scan to Hounsfield Units?
>>>>
>>>> Whenever I put in any value for --wpc in RTKFDK (I've tried values from
>>>> 0.015-150) my recon results in a 'blank' as is attached below.
>>>>
>>>> Any help in resolving this would be great.
>>>>
>>>> Kindly,
>>>> -Waqar Muhammad
>>>> Carleton University
>>>>
>>>>
>>>> ​
>>>> ᐧ
>>>>
>>>> _______________________________________________
>>>> Rtk-users mailing list
>>>> Rtk-users at public.kitware.com
>>>> https://public.kitware.com/mailman/listinfo/rtk-users
>>>>
>>>>
>>>
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>>>
>>>
>>
>
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