ecatcalc can perform arithmetic calculations on ECAT files. Image1 and image2 must be in the same format, and they must have same matrix size and plane numbers. Data is not interpolated or corrected for physical decay, and thus it is on the responsibility of the user to check that PET frame times are similar and that physical decay and other corrections are appropriately considered.

Usage:
ecatcalc [Options] <Image1> <Operation> <Image2|Const> <Output img>

where
Operation = +, -, x , /
Const = Image1 is operated with this value

Options:
-f or -frames
All frames in image1 are processed with 1st frame of image2
-m=<value> or -max=<value>
Upper limit for output pixels
-h or --help
Print this message and exit
--version, or --build
Print software build information and exit
--silent
Program works silently, printing only warnings and error messages.

The license of this software is Freeware, you can free download and free use this calculator software.