Rapid measurement of the spatial resolution of colour flow scanners

An acoustic grid for rapid measurement of the spatial resolution of colour velocity images is described. The grid is composed of alternate widths of acoustic window and acoustic attenuator. Attenuation is provided by the use of a layer of waterproof paper, which is wrapped in close contact with a tube of a flow phantom. The colour image consists of several closely spaced lines. When the grid line spacing is less than the spatial resolution, the colour lines cannot be separately visualised. The use of several grids of different spacing provides a measure of the spatial resolution. It is shown that the spatial resolution is dependent on the position of the focal zone.