Roi; Modify Active (Red) Annotation - GE Revolution CT User Manual

3.2 ROI

The Region of Interest (ROI) tools exist in 2D and 3D. Several shapes are available to measure
a region of interest in any view plane/volume: circle, elliptic, rectangle, and cubic for 3D ROIs.
You can use the ROI tools to obtain information, volumes, areas and statistics of anatomy or
pathology. The ROI tools allow you to:
•
measure the pixel intensity value at a specific point on the image
•
display the area or volume
• display the mean, standard deviation and minimum and maximum pixel values within the
ROI
In order to perform measurements on an image that can be expressed in absolute values (mm),
the image must be calibrated, i.e. the relationship between image pixels and true anatomical
distance in the patient's body (the scale factor) must be known. For images such as CT and MR
this information is automatically recorded during image acquisition and stored with the image.
Measurements on such images can therefore be expressed directly in mm, using the patient-
based Right Anterior Superior (RAS) coordinate system.

3.3 Modify active (red) annotation

All active (red) annotations on the image indicate adjustable fields. Red Numerical values can
also be adjusted with left/right-click to decrease/increase values. Other red annotations can be
modified selecting options from a menu. The selections vary based on the application launched
and the selected view.
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