The Radon transform for discretely given points of a g function at points
in sinogram space:

Approxiomately:

where

With this notation for each i we need to interpolate the function g in 2D. If we choose the step size such that in dimension x we match grid points we can spare the interpolation step. Let us do the integration according to x:

thus:

With that:

From this from we see that if the angle falls around 0 or 1800,the expression renders unstable, and we should rather swith to mathcing grid lines in the y dimension.