Background Group

The Small Animal Image application requires a user-defined background shape to be placed and assigned prior to defining the region to be quantified.

1. In the Shapes group, click Draw Ellipse .

   The cursor will become a cross-hair .

2. Use the cross-hair cursor to draw a background shape on the image by clicking and dragging to form the shape.

   Best practices for where to place the background shape.

   • The background shape should be placed on a shaved part of the animal, ideally in the same location but on the contralateral side of the feature to be quantified.
   • If the background shape cannot be placed on the animal's contralateral side, place it close to the feature to be quantified.
   • Some organs may retain probe after 24 hours. Be careful not to place the background shape on these bright areas.
   • If the region drawn by the Define New feature encompasses too much area, the background shape can be moved so it incorporates a small region of bright space surrounding a feature to be quantified. This will raise the average background value and decrease the area of the region after the region is redrawn using the Define New feature. However, only try moving the background shape this close to the feature of interest if adjusting the St. Dev. Multiplier and Search Limit does not produce the desired boundary.
3. Once the shape has been drawn and while it is still selected (shown as a dashed line), click Assign Shape in the Background group.