Sinogram Fourier Analysis Doesn't Show Clear Bow Tie Shape
Try imtool() and adjust the contrast to show ft similar as in the paper. I set eliminate outliers to 5%, then (contrast) window minimum to 0.0. May I suggest to ask the author about the settings for the display range in his paper.



Now to the signal processing.

The mentioned paper by Vo is public available. Moreover Vo published the algorithm in mathematica code. Note that the code by Vo does a gaussian filtering, i.e. a lowpass of the sinogram. IMHO to achieve similar results as in a real scan.

Generally a real scan shows lowpass behaviour, i.e. the high frequencies in the projections in the sinogram are lost due to the size of the focal point inside the x-ray tube, the detector system and radiation scatter inside the object. In contrast the forward projection algoritm: Those may keep high frequencies in the projections, depending on their base algorithm.

sinogram1 = GaussianFilter[ sinogram1, {{3,2}}];
(* Apply smooth filter: recommend blur more in the vertical direction *)


The Mathematica help tells, that those 3 and 2 steer the xy-sigma of the GaussianFilter(). One can go theroretically through that to find the values of the matrix, but I prefer to run the above filter over a dirac impulse to see the resulting filtermatrix and establish it similar in matlab for use in imfilter(). But I have no access to mathematica. May be s.o can translate the Mathematica GaussianFilter() into a matlab fspecial().

So let's filter the sinogram with a lowpass to ged rid of the high frequencies introduced by radon() :

imtool(ft); %% eliminate 5% outliers and set min to 0.0
h=fspecial('gaussian',[2 3]); %% wider in projection direction
sino_lp = imfilter(sinogram,h,'replicate');
ft_lp=real(fftshift(fft2(sino_lp)));
imtool(ft_lp);


Such a fourier transformed sinogram has lower values in the high frequencies.