Select one of the options shown below to measure HU for CT.

Point probe is for a single pixel.

Average probe averages a small area.

Region of interest e.g., ellipse, rectangle, averages HU over a larger area.

You may “grab” with the mouse and drag the overlayed text away from the actual image if necessary.

Press delete button on your keyboard or the “X” icon in viewer to remove the annotations.

Note that in some very old PCs (manufactured before 2013), HU feature my not function properly because PC hardware does not support this feature. In such computers, Volume rendering and thick slab modes (e.g. MIP) may also not work.