The computational form of radiographic signal analysis using linear systems theory is such that optimization calculations would involve a large computational effort. An analytic approximation for angiography is described. Series expansions are used to include effects of film response, secondary and off-focus radiation, x-ray attenuation and blood vessel diameter. The degradated image profile is determined using a gaussian approximation with a Tchebycheff expansion correction term. It is found that this approach is accurate to within about 10% for blood vessels smaller than 1 mm in diameter.