High resolution ultrasonic imaging by controlled averaging of backscattered signals

A new synthetic aperture technique for obtaining ultrasonic images with a high resolution is described. The attained resolution is in the order of the ultrasonic wavelength and, when using a 5 MHz unfocussed beam, amounts to 0.3 +/- 0.1 mm, i.e. it is much smaller than the diameter of the sound beam. Measurements have been performed on a model specimen consisting of a two-dimensional array of threads. The distance between the threads were chosen to approximate to the macroscopic fibre spacing of 1.5 mm +/- 0.3 mm in human muscle.