Coded excitation methods for ultrasound harmonic imaging

Authors

  • Roozbeh Arshadi Institute of Biomaterials and Biomedical Engineering, University of Toronto, 163 College Street, Toronto, Ont. M5S 3G9, Canada
  • Alfred C. H. Yu Institute of Biomaterials and Biomedical Engineering, University of Toronto, 163 College Street, Toronto, Ont. M5S 3G9, Canada
  • Richard S. C. Cobbold Institute of Biomaterials and Biomedical Engineering, University of Toronto, 163 College Street, Toronto, Ont. M5S 3G9, Canada

Keywords:

Computer simulation, Harmonic analysis, Harmonic generation, Problem solving, Signal to noise ratio, Waveform analysis, Coded excitation methods, Nonlinear echoes, Sacrificing resolution

Abstract

Coded excitation methods offer the potential for improving the SNR without increasing the peak transmitted power and without sacrificing resolution. Our study examines the potential application of coded waveforms, specifically FM chirps, in harmonic imaging. Such a system, in which nonlinear echoes from tissue are used to form the image, requires the extraction and compression of the second harmonic portion of the echo signal. Our objective is to obtain the second harmonic using just one transmission, thereby avoiding problems of frame rate reduction and movement artifacts associated with multiple transmission schemes. With the help of an efficient method for predicting the transient nonlinear field from a focused transducer, design issues such as waveform and bandwidth selection, as well as filters for second harmonic extraction and compression are examined. Simulations reveal the presence of axial sidelobes in the compressed echo waveform as the bandwidth of the transmitted chirp is increased. These sidelobes, resulting from the overlap of the fundamental and third harmonic bands with the second harmonic, cannot be removed using conventional Fourier filtering. Alternative filtering techniques which utilize the separation of the harmonic bands of a backscattered chirp in the joint time-frequency domain are suggested.

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Published

2007-06-01

How to Cite

1.
Arshadi R, Yu ACH, Cobbold RSC. Coded excitation methods for ultrasound harmonic imaging. Canadian Acoustics [Internet]. 2007 Jun. 1 [cited 2021 Dec. 5];35(2):35-46. Available from: https://jcaa.caa-aca.ca/index.php/jcaa/article/view/1876

Issue

Vol. 35 No. 2 (2007)

Section

Technical Articles

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