Digital Picture Processing, 2nd Edition

References 427

the same for all the rays in the projection data, which is usually not the case.

A more general expression (not using this assumption) for the noise variance

was derived by Kak [34] who has also introduced the concept of the relative-

uncertainty image.

The algebraic approaches to image reconstruction have been studied in

great detail by Gordon et al [22-25], Herman et al [27, 29] and Budinger

and Gullberg [10]. To somewhat improve the noise properties of the alge-

braic techniques, a simultaneous iterative reconstruction technique was

proposed by Gilbert [21].

The reconstruction implementations that we presented in this chapte ...