
8.3 The Filtered-Backprojection Algorithm
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radial lines such as in Fig. 10. In order to be able to use (18) one must then
interpolate from these radial points to the points on a square grid. Theo-
retically, one can exactly determine the N
2
coefficients required in (18)
provided as many values of the function F(u, v) are known on some radial
lines [15]. This calculation involves solving a large set of simultaneous
equations, often leading to unstable solutions. It is more common to de-
termine the values on the square grid by some kind of nearest-neighbor
or linear interpolation from the radial points. Since the density of the radial
point ...