(ROI) Keyboard controlled identification of a given area of an image for numerical analysis and the area of anatomy being scanned that is of particular importance in the image. This area can also be a volume, than called (VOI) volume of interest.
A ROI can be used for purposes such as calculation of pixel statistics. ROI measurements should be made with the smallest area and away from boarders and edges to avoid partial volume averaging.

Zooming increases scale factors of images within a window. Zooming takes a selected region and extends it over the entire matrix of the displayed CT image. Usually, a zoom reconstruction increases the accuracy of the CT numbers by decreasing the overall size of the displayed image pixels, which decreases the possibility of many tissues occupying a single pixel (partial volume averaging).
Zooming or targeting is not the same as image magnification.

See also Banding.