Fig. 5From: Acquisition of a single grid-based phase-contrast X-ray image using instantaneous frequency and noise filteringImage filtering of the areas indicated by the blue boxes in Fig. 4a, c (i.e., RT1 and 3) using an adaptive Gaussian notch filter (Step 1: a to c) and the corresponding spectral images. b, d The spectral images of a and c, respectively. RT: rectangleBack to article page