where τ is the sampling interval for the projection data. This result says that
the variance of noise at the origin is proportional to the area under the square
of the filter function used for reconstruction. This does not imply that this
area can be made arbitrarily small since any major departure from the
I
w
I
function will introduce spatial distortion in the image even though it
may be less noisy. None of the equations above should be construed to imply
that the variance approaches zero as τ is made arbitrarily small. Note from
Fig. 6 that τ is also the width of the measurement beam. In any practica ...
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