i = Import["http://i.imgur.com/zxKkFP9.png"];(* Sinogram from InverseRadon Documentation *)
filter = {{Automatic, "Default"}, {#1&, "ramp filter with constant slope"},{#1 Cos[#1 [Pi]]&, "ramp filter multiplied by cosine function"}, {(1+Cos[#1 [Pi]])/2&, "Hann filter (default)"}, {0.54` +0.46` Cos[#1 [Pi]]&, "Hamming filter"}, {Sqrt[1/(1+#^(2n))]&, Row@{"Butterworth filter of order ",n}}, {1&, "no filtering"}};
TableForm@Transpose[{Last@#,ImageAdjust@InverseRadon[i,{300,300},Method->{First@#, "CutoffFrequency"->1}]}&/@(filter/.n->2)]