<title>Two-dimensional transducer arrays for medical ultrasound: beamforming and imaging (Invited Paper)</title>

Abstract

Two-dimensional (2-D) transducer arrays offer the potential for improving medical ultrasound imaging by producing symmetrically focused ultrasound beams which can be steered throughout a three-dimensional volume. Theoretical investigations of the beamforming properties of 2-D arrays have characterized the array parameters required to steer the beam up to 45 degree(s) off-axis. These investigations have also shown that the number of elements in a steered 2-D array can be dramatically reduced using a sparse set of elements, randomly distributed throughout the transducer aperture. The penalty paid for the use of a sparse array is the development of a `pedestal' sidelobe in the beam profile, the amplitude of which increases as the number of elements in the array decreases. The potential of 2-D arrays for medical imaging has been assessed by simulating images of spherical lesions embedded in a random scattering medium. Similar contrast characteristics over a range of cyst sizes are demonstrated for a dense 2-D array and a sparse array with 1/8th the number of elements, both operating at 5 MHz. A 32nd order sparse array was found to perform at a reduced level, producing unacceptable artifactual echoes within images of cysts. Experimental results are described which verify some of the theoretical predictions.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.