Zero-order moment of the Radon transform in tomography: some further remarks

It is well known that the integral of a tomographic projection (zero-order moment) represents the total irradiance absorption of an object. Therefore, it must be rotational invariant. In this paper it is shown that the filtered projections must obey the same condition. Numerical examples are presented to illustrate the usefulness of the invariance property to judge the filtering process performance. Furthermore, the possibility to inspect the fulfilment of the invariance with experimental data is discussed, and the development of a rejection criterion for projection data in experimental tomography is suggested.