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IMPROVED CONTRAST IN ULTRASOUND IMAGING USING DUAL
APODIZATION WITH CROSS-CORRELATION
by
Chi Hyung Seo
A Dissertation Presented to the
FACULTY OF THE VITERBI SCHOOL OF ENGINEERING
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(BIOMEDICAL ENGINEERING)
December 2008
Copyright 2008 Chi Hyung Seo
Object Description
| Title | Improved contrast in ultrasound imaging using dual apodization with cross-correlation |
| Author | Seo, Chi Hyung |
| Author email | chiseo@usc.edu; chiseo@gmail.com |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Biomedical Engineering |
| School | Viterbi School of Engineering |
| Date defended/completed | 2008-10-20 |
| Date submitted | 2008 |
| Restricted until | Unrestricted |
| Date published | 2008-12-02 |
| Advisor (committee chair) | Yen, Jesse T. |
| Advisor (committee member) |
Kim, Eun Sok Shung, Kirk Liu, Brent Cannata, Jon |
| Abstract | This dissertation work introduces a novel sidelobe and clutter suppression method in ultrasound imaging called Dual Apodization with Cross-correlation or DAX. DAX dramatically improves the contrast-to-noise ratio (CNR) allowing for easier visualization of anechoic cysts and blood vessels. This technique uses dual apodization or weighting strategies that are effective in removing or minimizing clutter and efficient in terms of computational load and hardware/software needs. This dual apodization allows us to determine the amount of mainlobe versus clutter contribution in a signal by crosscorrelating RF data acquired from two apodization functions. Simulation results using a 128 element 5 MHz linear array show an improvement in CNR of 139 % compared to standard beamformed data with uniform apodization in a 3 mm diameter anechoic cylindrical cyst. Experimental CNR using a tissue-mimicking phantom with the same sized cyst shows an improvement of 123 % in a DAX processed image.; However, due to the random nature of speckle, artifactual black spots may arise with DAX-processed images. I present several methods to optimize the DAX algorithm. I evaluate the robustness of the optimized DAX in the presence of phase aberration and noise. Simulation results using a 5 MHz 128 element linear array are presented using optimized DAX with aberrator strengths ranging from 25 ns RMS to 45 ns RMS with correlation lengths of 3 and 5 mm. When simulating a 3 mm diameter anechoic cyst, at least 100 % improvement in CNR compared to standard beamforming is seen using optimized DAX except in the most severe case. Aberrating layers of pig skin, fat, and muscle were used experimentally. Simulation and experimental results are also presented using optimized DAX in the presence of noise. With a system signal-to-noise ratio (SNR) of at least 15 dB, we have a CNR improvement of over 100 % compared to standard beamforming. An uncut whole sheep heart was imaged to assess the optimized DAX performance with excised animal tissues. The experimental result shows that the optimized DAX improves the visibility of a target with a CNR improvement of at least 56 %. DAX was also able to improve contrast limited applications such as 3-D ultrasound using 2-D array with Row-column addressing. These types of arrays have 1-way focusing thus increasing side lobe level compared to conventional linear arrays with 2-way focusing. Therefore other post processing and filtering techniques in addition to beam steering and beam focusing are needed for image improvement. The CNR improvement utsing the DAX algorithm was at least 55 %. This work shows that optimized DAX is able to reliably improve contrast-to-noise ratio. |
| Keyword | ultrasound imaging; cross-correlation; contrast improvement; 3-D ultrasound |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m1851 |
| Rights | Seo, Chi Hyung |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | http://www.usc.edu/isd/libraries/services/ask_a_librarian/email/ |
| Filename | etd-Seo-2520 |
| Archival file | uscthesesreloadpub_Volume29/etd-Seo-2520.pdf |
Description
| Title | Page 1 |
| Full text | IMPROVED CONTRAST IN ULTRASOUND IMAGING USING DUAL APODIZATION WITH CROSS-CORRELATION by Chi Hyung Seo A Dissertation Presented to the FACULTY OF THE VITERBI SCHOOL OF ENGINEERING UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (BIOMEDICAL ENGINEERING) December 2008 Copyright 2008 Chi Hyung Seo |
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