There are two specific types of overlays. The type is specified in this Attribute.
A Region of Interest (ROI) is a specific use of an Overlay. The overlay bits corresponding to all the pixels included in the ROI shall be set to 1. All other bits are set to 0. This is used to specify an area of the image of particular interest.
A Graphics overlay may express reference marks, graphic annotation, or bit mapped text, etc. A Graphics overlay may be used to mark the boundary of a ROI. If this is the case and the ROI statistical parameters are used, they will only refer to the pixels under the boundaries, not those in the included regions.
The overlay bits corresponding to all the pixels included in the Graphics shall be set to 1. All other bits are set to 0.
These Attributes contain the statistical parameters of the ROI. The values of these parameters are for the overlay pixel values set to 1.
Two Defined Terms are specified:
USER - User created graphic annotation (e.g. operator)
AUTOMATED - Machine or algorithm generated graphic annotation, such as output of a Computer Assisted Diagnosis algorithm.
Note: Additional or alternative Defined Terms may be specified in modality specific Modules, such as in the Ultrasound Image Module, C.220.127.116.11.11.