How can I modify the pixel value of output files of fdk method to CT value?

[Onishi]

 Hello. I am now working with the images acquired from fdk method, and I do not know how to modify the pixel value in the outcome .mha file to ct value. 

 I used this code to make the image using fdk method.

plastimatch drr -t pfm -o "0 0 0"-a 900 -N 0.4 -r "1024 768" --sad 1000 --sid 1500 -z "397 298" -s 262144 -I c023_20.mha -O PK020/

plastimatch fdk -f ramp -r "512 512 120" -z "300 300 150" -I PK020 -O out.mha

I would like to compare the outcome data (out.mha) to original ct data (c023_20.mha) in range of the CT values -1000 to 1000, and the value 0 is set as water index.

 I want to know how to change the pixel values in (out.mha) to CT value.

 If there are general technique to do this, I want to know it. Could someone help me?

 Thank you.

 Regards,