Adaptive imaging using an optimal receive aperture size
Journal
Ultrasonic Imaging
Journal Volume
27
Journal Issue
2
Pages
111-127
Date Issued
2005-04
Author(s)
Abstract
Sidelobe contribution from off-axis targets degrades image quality in a coherent array imaging system. In ultrasound imaging, focusing errors resulting from sound-velocity inhomogeneities in human tissue - also known as phase aberrations - reduce the coherence of the received signals and elevate the sidelobe level. This paper proposes an adaptive receive-aperture technique based on thresholding of the coherence factor (CF). The CF describes the coherence of the received array signals and can be used as an index of focusing quality. This paper demonstrates that thresholding of the CF allows the mainlobe-dominated signals to be distinguished from the sidelobe-dominated signals, after which the receive-aperture size at each imaging position can be optimally determined so as to enhance the mainlobe-dominated signals and suppress the sidelobe-dominated signals. Thus, image quality degradation resulting from sound-velocity inhomogeneities can be reduced. Simulations and measured ultrasound data are used to evaluate the efficacy of the proposed technique. The characteristics of the proposed technique including the effects of the signal-to-noise ratio (SNR) and the transmit focal depth, and speckle reduction are discussed. The proposed technique is also compared with the parallel adaptive receive compensation algorithm and shown to produce a better improvement in image quality. Copyright 2005 by Dynamedia, Inc. All rights of reproduction in any form reserved.
Subjects
Adaptive imaging; Aperture function; Coherence factor; Sidelobe reduction; Sound velocity inhomogeneities
Other Subjects
Acoustic wave velocity; Image enhancement; Image quality; Ultrasonic imaging; Adaptive imaging; Aperture function; Coherence factors; Inhomogeneities; Side-lobe reduction; Signal to noise ratio; adaptive imaging; algorithm; article; calculation; coherence factor; echography; energy; error; evaluation; image analysis; image quality; imaging system; mathematical analysis; mechanical probe; radiation beam; signal detection; signal noise ratio; simulation; sound; velocity
Type
journal article