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RadiAnt DICOM Viewer - Discussion Forum
Adjust Image Window - Negative

Jan 11, 2020 10:26 AM
by DrPaul

From my understanding, dicom images are displayed to the screen using the following logic:

ModalityValue = RescaleSlope * StoredValue + RescaleIntercept

n = number of output gray levels (usually 256 or 1024)
w = WindowWidth - 1.0
c = WindowCenter - 0.5

if (ModalityValue <= c - 0.5*w), then WindowedValue = 0
else if (ModalityValue > c + 0.5*w), then WindowedValue = n - 1
else WindowedValue = ((ModalityValue - c)/w + 0.5) * (n - 1)

I know that changing the image window (for e.g., from abdomen to angio) changes the WindowWidth and WindowCenter values to produce the right image. How is negative mode (by pressing F11) produced in RadiAnt? I have tried multiplying StoredValue and ModalityValue by -1, but that does not work in all cases.
Jan 11, 2020 04:51 PM
by RadiAnt
NegativeValue = n - 1 - WindowedValue
Jan 11, 2020 05:13 PM
by DrPaul
Got it right! Thank you :)
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