Now we present our second comment about (21). This equation may also
be written as
Qe(t) = Γ j2nwS
e
(xv) -t sgn(w)
J-oo |_
2π
e
j2nwt
dw
where
sgn(w) = 1 for w > 0
=
— 1
for w < 0
(33)
(34)
By using the standard convolution theorem the above may be expressed
as
Qe(t) = {IFT ofj2nwS
e
(w)} * <IFT of-^-sgn(w)
' 2n
(35)
8.3
The Filtered-Backprojection Algorithm
375
where the symbol * denotes convolution and the abbreviation IFT stands
for inverse Fourier transform. The IFT o ...
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