dicom window center, window width

Question

I'm trying to implement the dicom veiwer. And i thought i'm almost done. But some CT images different with MATLAB. So i checked tags. Then i found something.

These images have two value of window center and window width.

window center = [2000], window width = [8000]

Then i calculate yMin, yMax.

yMin = (winCenter - 0.5 * winWidth)
yMax = (winCenter + 0.5 * winWidth)

if(inPixel <= yMin)
  outpixel = 0;
else if (inPixel > yMax) 
  outPixel = 255;  
else  
  outPixel = (((i - (winCenter - 0.5)) / (winWidth - 1)) + 0.5) * 255;

But the problem is this case.

window center = [-600;40], window width = [400;1200]

How can i calculate this values? Anyone know how i can implement this.

Answer 1

It's not uncommon for CT images to be viewed using multiple window settings in order to see different features of the image. For example, you would use one window setting to look at bones and another to look at soft tissue. This is likely the reason that the modality equipment sent the window center (0028, 1050) and window width (0028, 1051) with a value multiplicity greater than one. So, your window setting in this case (center, width) is (-600, 400) or (40, 1200) and you can display using either setting.