Recently, detective quantum efficiency (DQE) arising from the concept of signal-to-noise ratio (SNR) has been used for assessing digital x-ray imaging systems. Using a phase-shift of x-rays that occurs when passing through an object, digital phase contrast imaging (herein referred to as “phase imaging”), which involves magnification, can produce images different from those of standard contact imaging (herein referred to as “regular imaging”). For this reason, assessment of the image quality based on DQE which does not include the object information may not be appropriate to compare image quality between the phase images and the regular images. As an alternative method, we proposed a new image quality assessment method based on radial direction distribution function (RDDF) and signal intensity distribution function (SIDF) in two-dimensional power spectra of images that contain information of an object. To evaluate the usefulness of our method based on RDDF and SIDF, we assessed ...