*3.1. Filter Shape*

Six different Fourier transformed and band-limited filters designed in the spatial domain with regard to the frequency response are depicted in Figure 5. Because the Fourier transformed sinograms were forced to be band limited with a band width of 0.5, the signals outside of the band frequency range went to zero, as shown in Figure 5. Similarly, each window function was also band limited and multiplied by the band-limited ramp filter. The magnitude of the filter at high frequencies was rejected when going from scheme (a) to (f) in Table 4, which is generally interpreted as noise suppression. Unlike other filters, some of the value of the flat-top window are negative.

**Figure 5.** Different band-limited filter shapes as a function of frequency response.
