Fig. 6

The contrast-to-noise ratio (CNR), spatial resolution (SR, given in pixels) and image quality (Q) values for each energy (50, 60, 70 and 80 keV) and each propagation distance (0, 1, 3, 5, and 7 m). The values and colour gradient indicate the image quality at each energy and distance. The higher the number or the darker the colour green indicates a higher image quality, and the lower the value or the more red, the poorer the image quality.