EVALUATION OF FOCAL SPOTS OF X-RAY TUBES BY MOMENT VALUES

Abstract

The performance of an X-ray focal spot was evaluated by three moment values of the normalized X-ray intensity distribution ; i.e., the square root of the second moment about the mean (RMS), and the third and the fourth order moments normalized by RMS. These three numbers provide especially important imaging properties of focal spot. RMS correlates well with the low-frequency performance of MTF. High-frequency performance of MTF which cannot be estimated by RMS is evaluated by the fourth order normalized moment. The symmetry of the distribution can be evaluated by the third order normalized moment.