# Support:Documents:Manual:COMKAT Image Tools

# COMKAT Image Tool topics

# Volume of interest (VOI) operations of COMKAT

COMKAT Image Tools support the volume of interest operations. It is simple to draw a VOI and find it's statistics. We also provide functions for user to extend the capabilities.

## Definition of a volume of interest

A volume of interest is defined as 'a collection of regions of interest (ROI or ROIs)'. It contains at least one ROI.

A region of interest (ROI) is defined as 'a list of vertices's that creates an image mask to find the pixels within this mask'.

ROIs in a VOI do not necessarily have to be on the same plane or be of the same size.

### VOI and ROI

VOI with multiple ROIs is usually used to find statistics or time-activity curve over a volume. If you want to look at individual regions, create several VOIs with one ROI per VOI.

### COMKAT VOI object

A VOI is defined and stored as a 'VOI' object. You may go to '@VOI' folder under COMKAT root to find its constructor and properties.

### Properties of a VOI

Here are some important properties of a VOI:

- Name - VOI name.
- NumberOfROIs - how many ROIs are in this VOI
- TAC - the time activity curve of this VOI. If there are two image volume data, it will be a 2 element cell array.