Evaluation of physical image characteristics of phase contrast mammography

Recently, the system called PCM (phase contrast mammography) came to be applied to clinical examinations. The PCM images are acquired as 1.75x-magnified images using small focal spot, then reduced to real object's size by image processing. The PCM images had the feature that edges of objects were enhanced. It was reported that the edges were enhanced because of refraction of X rays. We measured physical image characteristics of the PCM, to compare image characteristics of the PCM with those of a conventional mammography. Specifically, response characteristics to objects and noise characteristics in the spatial frequency domain were measured. As the results, compared with the conventional mammography, response characteristics of the PCM were high. If the placement conditions of objects were changed, response characteristics were also changed. And if the shape of objects was changed, response characteristics also were changed. Noise characteristics of the PCM were better than those of the conventional mammography. Furthermore, in order to investigate why edges of objects in the PCM images were enhanced, we simulated image profiles which would be obtained if X rays were refracted. And, we found the possibility that edge enhancements of the PCM images were based on refraction of X rays.