To change window width and center values for an image, study, or specified region, use the ROI with W/L tool in the toolbox tool bar (or click Settings/Cursor/ROI). Follow these steps:
Click the cursor on the starting point
Drag the mouse to define the area.
Release the cursor, and the calculations are automatically applied to the images in the frame.
The region defining the area remains on the screen. Drag it around to change the W/L settings. Each time you release the mouse button new window/level values are applied.