of each view can also be done in the transform domain by a suitable approximation of differentiation with the available views as stated earlier if the attenuation data are assumed to vary at most quadratically over the distance 2z a second order series may be assumed to obtain the line integrals on the reference plane the following equation derived from equations 8 and 9 is used u222b u03bc r p sub k e sub 1 u03bb 39 e sub 2 0e sub 3 d u03bb 39 cos u03c6 f sub ikl tan u03c6 u222b u03bb 39 a r p sub k e sub 1 u03bb 39 e sub 2 0e sub 3 d u03bb 39 tan u03c6 sup 2 u222b u03bb 39 sup 2 b r p sub k e sub 1 u03bb 39 e sub 2 0e sub 3 d u03bb 39 14 if the second order series is required for correction three scans as shown in fig3 d indicated by i 1 i d and i 1 are obtained indexing each scan by i m the equation 14 for each scan can be written equ4 equation 17 can be used to obtain line integrals for b next u222b u03bb 39 b can be obtained in the spatial or transform domain by techniques discussed above with respect to two scan first order correction once u222b u03bb 39 b is available equation 16 can be used to obtain the line integrals for a finally equation 14.