Ultrasound speckle and equivalent scatterers.

B-mode ultrasound images are characterised by the speckle artefact, which introduces fine-false structures whose apparent resolution is beyond the imaging system capabilities. Speckle presence is due to interference effects between overlapping echoes and its occurrence is related to a great number of randomly distributed structure scatterers within a resolution cell. Basing our analysis on linear system theory, we show that a dense random set of scatterers can be substituted by an equivalent one with a much smaller number of periodic scatterers.