Grouping ROIs

You may want to "group" several ROIs together in order to:

  • Logically link the ROIs if together they form a particular anatomical structure.
  • More easily change the annotation or colour of all the ROIs in the group.
  • Create 3-D connected volumes-of-interest (VOIs) from ROIs in different slices.

Forming a group

An ROI group can be formed in one of two ways:

  • Select all the ROIs to be grouped together. You can select ROIs in several slices, as long as all the slices are displayed. Then either use the keyboard accelerator CONTROL-G or select Group ROIs from the ROI Toolkit's Edit menu: Menu item to group ROIs
  • Select Create VOI Groups from the ROI Toolkit's Edit menu: Menu item to group ROIs as VOIs. This will automatically create ROI groups from ROIs that form 3-D structures by connecting overlapping ROIs across slices. This could be used, for example, if you have outlined anatomical regions that stretch across multiple slices, and want to form each individual region into a group. The result will be one or more groups of ROIs, each outlining a structure that is connected in 3-D.

Editing a group

You can select all the ROIs in a group by selecting any of the ROIs in the group.
Note: care is required. If the group's ROIs extends across multiple slices, and those slice are not visible on-screen, they other ROIs will still be selected. Changing a group's ROIs can therefore have hidden consequences.

Once a group is selected, changing the annotation or colour will change the annotation or colour of all ROIs in the group. However, the shape of individual ROIs in a group cannot be changed: if shape changes are needed, the ROIs must be ungrouped first.

To ungroup ROIs, either use the keyboard accelerator CONTROL-U or select Ungroup ROIs from the ROI Toolkit's Edit menu: Menu item to ungroup ROIs

When you save ROIs to disk, any groupings that exist will be saved, and those groupings restored when you load the ROIs again.