CT and MRI dicom images can be viewed using multiple window settings in order to see different features of the image. For example, there would be different window settings to look at Abdominal / soft tissues, Bone, Brain, Liver, Lung, Subdural brain.
The Window Center (0028,1050), Window Width (0028,1051) and VOI LUT Function (0028,1056) Attributes are used only for Images with Photometric Interpretation (0028,0004) values of MONOCHROME1 and MONOCHROME2. They have no meaning for other Images. If any VOI LUT Table is included by an Image, a Window Width and Window Center or the VOI LUT Table, but not both, may be applied to the Image for display. Inclusion of both indicates that multiple alternative views may be presented.