Weak reflection of ultrasound by elements arranged in the steps of a one-dimensional random walk, with reference to backscatter by blood.

Blood backscatters ultrasound primarily because the erythrocytes (red blood corpuscles) have a specific acoustic impedance slightly different from that of the surrounding plasma. In an attempt to explain some of the main results concerning such scatter, a one-dimensional model is set up and analysed. The results computed from it are in qualitative agreement with, and contribute a partial explanation of, the variation of reflection coefficient with erythrocyte concentration and the noise in the backscattered signal.