Spatial resolution performance of a one-dimensional linear amplitude-steered array in an attenuating medium

Abstract

The amplitude-steered array concept [J. Acoust. Soc. Am. 59, 1040 (1976)] introduced the idea of steering the maximum response of a linear array by amplitude weighting the output signals of the elements. Recently, an evaluation of the linear amplitude-steered array assessed its performance such as lateral and axial resolution in a lossless medium [Frazier, Hughes, and O’Brien, J. Acoust. Soc. Am. 107, 2430 (2000)]. In the present work, the array’s performance is evaluated in an attenuating medium similar to biological tissue (1 dB/cm<th>MHz). Similar to the array’s performance in a lossless medium, the length of the array limits the axial and lateral resolution in the attenuating medium. As the steering direction is decreased, which corresponds to increasing frequency, the array’s performance with attenuation has a worse resolution when compared with its performance without attenuation. For example, using a 10-cm-length array and a 6-deg steering direction (4.6 MHz), the axial resolution (−3-dB point spread function width) with attenuation was 7.9 mm, compared with 6.4 mm without attenuation. When the steering direction was increased to 12 deg (2.3 MHz), the axial resolution with attenuation was 12.8 mm compared with 11.5 mm without attenuation. In the attenuating medium there is increased importance on the steering direction or frequency. [Work supported by NIH CA09067.]