An acoustic grid for rapid measurement of the spatial resolution of co
lour velocity images is described, The grid is composed of alternate w
idths of acoustic window and acoustic attenuator, Attenuation is provi
ded by the use of a layer of waterproof paper, which is wrapped in clo
se contact with a tube of a how 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 visualis
ed, The use of several grids of different spacing provides a measure o
f the spatial resolution, It is shown that the spatial resolution is d
ependent on the position of the focal zone, (C) 1997 World Federation
for Ultrasound in Medicine & Biology.