  The inverse Radon transform allows to obtain partonic double distributions
from (extended) generalized parton distributions. We express the extension of
generalized parton distributions by their dual parts, generalized distribution
amplitudes and study some aspects of the filtered backprojection (inverse Radon
transform). We also show that single integral transforms, previously obtained
in the context of wave function overlap representation, are valid for
generalized parton distributions that do not possess such a representation.
Utilizing Radyushkin`s double distribution ansatz, we study and compare the
numerical evaluation of double distributions within the filtered backprojection
and single integral transforms along the imaginary and real axes.
