Simulation of B-scan images from two-dimensional transducer arrays: Part II--Comparisons between linear and two-dimensional phased arrays.
Two-dimensional (2-D) arrays have been proposed as a solution to the degradation in medical ultrasound image quality occurring as a result of asymmetric focusing properties of linear phased array transducers. The 2-D phased transducer array is also capable of electronically steering the symmetrically focused ultrasound beam throughout a three-dimensional volume. In a companion paper the potential of 2-D transducer arrays for medical imaging has been investigated using simulated B-scan images. In this paper, the advantages of 2-D over linear transducer arrays is demonstrated by simulating images of spherical cysts embedded in a large scattering volume. The large elevation beamwidth in the nearfield of a 5 MHz linear phased transducer array results in a severe reduction in the image contrast measured between a 4 mm diameter cyst and the surrounding scattering media. By employing a 2-D array with symmetric focusing, the contrast between the cyst and surrounding scatterers is significantly improved. The use of additional elements in the elevation direction of a linear array is also investigated. In this case the additional elements are included only to focus, but not to steer the ultrasound beam. Using the contrast characteristics of a 4 mm diameter cyst, it is shown that relatively few elevation elements are required to significantly improve the nearfield imaging capability of the linear array.
Turnbull
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DH
Department of Medical Biophysics, University of Toronto, Ontario, Canada.
Foster
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FS
D016477:Artifacts; D003560:Cysts / Q000000981:diagnostic imaging; D006801:Humans; D007089:Image Enhancement; D008961:Models, Structural; D013679:Technology, Radiologic; D014159:Transducers; D014463:Ultrasonography / Q000379:methods*