Figure 1. (a–c) Longitudinal power Doppler images of renal allografts using a dark violet noise floor background colour. Arrows mark the limits of the renal cortex between the corticomedullary junction and the outer border of the kidney in all three images. (a) Power Doppler (PD) score=3. Note the "blush" of flow uniformly filling the renal cortex. (b) PD=2. Rather than a blush of colour, individual vessels and spaces between vessels are easily visible. (c) PD=1. Complete absence of cortical flow is shown in this graft.