User guide

Volume Tools
16-9
16.4 Volume Background Subtraction
When you draw a volume, you will probably include some non-data
background pixels inside the volume. These background pixels will usually
have an intensity value that you do not want to include in your volume
quantitation. There are two ways of calculating this background intensity for
your volumes: local and global.
The background subtraction method is selected in the Volume Report Options
dialog box (section 19.5.a).
Local Background Subtraction
Local background subtraction calculates a separate background intensity for
each unknown and standard volume you create. For each volume, the
intensities of the pixels in a 1-pixel border around the volume are added
together and divided by the total number of border pixels. This gives an
average intensity for the background around each volume, which is then
subtracted from the intensity of each pixel inside the volume.
Fig. 16-7. Local background is calculated from a one-pixel border around the volume
One-pixel border
around the volume