[Insight-users] rescale

[Andreas Schuh]

Hi Ismail,

as the name and the methods of the filter imply does this filter rescale 
the intensities of the input image linearly such that the intensities of 
the output image range from OutputMinimum to OutputMaximum. So, the 
minimum value of the input image is mapped to OutputMinimum and the 
maximum value of the input image to OutputMaximum. The intensities in 
between are scaled linearly, which means that the relative intervals of 
the intensities remain the same. The scale is just shrinked or 
stretched. This may be necessary if you attempt to cast the intensities 
afterwards to another pixel type, for instance, before passing the image 
to an WriteImageFilter.

In case of CT images, you have intensities that range from -1024 HU up 
to 3071 HU. By just shifting the intensities by 1024 HU, you can store 
the values as unsigned short, which is usually done. However, if you 
would like to store the CT image as unsigned char, you would have to 
rescale the intensities, whereby you loose information due to the  
poorer quantization. Consider using the ShiftScaleImageFilter instead 
for CT images.

--
regards
Andreas

saheb ismail schrieb:
> Dear all,
>
>
>          I want to know about rescaleintensityimagefilter, why it is 
> used, and its effect on ct image
>
> -- 
> With Regards
> S.Ismail Saheb
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