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

摘要

Abstract: Two-dimensional (2D) transducer arrays offer the potential for improving medical ultrasound imaging by producing symmetrically focused ultrasound beams which can be steered throughout a 3D volume. Theoretical investigations of the beamforming properties of 2D arrays have characterized the array parameters required to steer the beam up to 45 degrees off-axis. These investigations have also shown that the number of elements in a steered 2D 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 2D 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 2D 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. !22