The size of region-of-interest (ROI)
The volume of ROIs (or VOIs) is saved in regional TAC files (*.dft) in units mm3 (=0.001 mL). If regions drawn on several image planes are averaged, the volumes are usually summed up. The volumes can be listed on screen e.g. using dftlist.
Volumes can be converted to areas by dividing them by image plane width (ECAT 931 6.75 mm, GE Advance 4.25 mm, HR+ 2.425 mm, HRRT 1.21875 mm). In ECAT 7 images the plane width can be seen using lshdr.
If regions are circular in shape, the diameter of region can be calculated as 2 * square root of (Area/Pi).
