Measuring a Hounsfield Unit Value
On multi-slice CT images, this tool measures the average Hounsfield unit value of a sphere with a defined diameter around the indicated point.
On cone beam (CB)CT data, the average gray value of a sphere (with a diameter of 2 mm) will be measured. In the latter case, a warning will be shown before the first measurement.
To measure the HU or gray value of a point:
Click Measure on the menu bar.
Click 
HU Value.
Click a point in the scene.
The gray value is added in the viewer and shown in the smart panel 
Visibility tab.
Note
In case of cone beam (CB)CT data, a warning will be shown when performing the first measurement during a session. For this type of scan, the gray value is measured instead of the HU value.