Effect of asymmetric focal spots in angiography

The effect of asymmetric focal spots in blood vessel imaging is investigated by computer simulation. Phase distortion effects are studied in isolation from MTF effects. Calculations are done for a number of symmetric and asymmetric foci with identical standard deviations. It is concluded that blood vessel image degradation due to focus asymmetry per se is small and that the LSF standard deviation is a useful size parameter for both symmetric and asymmetric foci.