algorithm for iradon in matlab

Hello everyone:

According to fourier slice theorem, fourier transform of a 1D projection equals to the corresponding "line" in fourier transform of the 2D object. In the try of adding the 1D fourier line in to the 2D fourier domain, I find the difficulty dealing with the fourier value in same lacation in the fourier domain. And afterwards I thought of iradon in matlab, the algorithm of iradon shows in help document:

iradon uses the filtered back projection algorithm to perform the inverse Radon transform. The filter is designed directly in the frequency domain and then multiplied by the FFT of the projections. The projections are zero-padded to a power of 2 before filtering to prevent spatial domain aliasing and to speed up the FFT.

so, iradon in matlab isn't realized by direct fourier trasform but filtered backprojection? and is there someone knows that is there any CT reconstruction algorithm according to fourier slice theorem but not filtered backprojection?