Figure 4. Instances of the medical image visualization tool used. (a) The original region of interest (ROI) is positioned at the mammary gland, while the reference ROI for noise estimation is positioned at the background of the mammogram. (b) Gradient magnitude images corresponding to the first two scales of the original and reference ROI. (c,d) Histogram plots and statistical information for the gradient magnitude images including the contrast indicator (ROI mean value) at the second scale (c) and the noise indicator (ROI noise level) measured at the first scale (d).