title: Simulation of B-scan images from two-dimensional transducer arrays: Part I--Methods and quantitative contrast measurements.
abstract: Recently, theoretical investigations of the beamforming capability of two-dimensional (2-D) transducer arrays have characterized the array parameters required to steer a symmetrically focused ultrasound beam up to 45 degrees off-axis. These investigations have also shown that the number of elements in a steered 2-D array can be dramatically reduced by using a sparse set of elements, randomly distributed throughout the aperture of the transducer. 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. In this paper the potential of 2-D arrays for medical imaging is assessed by simulating B-scan images of spherical lesions, both cystic and scattering, embedded in a large random scattering volume. 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 is shown to perform at a reduced level, producing unacceptable artifactual echoes within images of cysts. The 8th order sparse array pattern has been fabricated on a fixed-focus poly(vinylidene difluoride) transducer using photolithographic techniques. Experimental images from this transducer are used to verify some of the theoretical predictions made in this paper. Comparisons between simulated B-scan images from linear and 2-D phased arrays are presented in a companion paper.
authors.affiliation: Department of Medical Biophysics, University of Toronto, Ontario, Canada.
authors.forename: D H
authors.initials: DH
authors.lastname: Turnbull
authors.forename: P K
authors.initials: PK
authors.lastname: Lum
authors.forename: A T
authors.initials: AT
authors.lastname: Kerr
authors.forename: F S
authors.initials: FS
authors.lastname: Foster
mesh_terms: D016477:Artifacts; D003560:Cysts / Q000000981:diagnostic imaging; D006801:Humans; D007089:Image Enhancement; D008961:Models, Structural; D013679:Technology, Radiologic; D014159:Transducers; D014463:Ultrasonography / Q000379:methods*