Performance Analysis of the Adaptive Pulse Compression Filter Based on Statistical Properties of Ultrasound Contrast Harmonic
Date Issued
2015
Date
2015
Author(s)
Lin, Zong-Min
Abstract
Ultrasound contrast agents are shelled air bubbles whose diameter is less than 7 micrometer. After being reconstituted, ultrasound contrast agents form a population suspending in the medium, and concentration as well as size distribution of the population are always changing so that echoes from the population changing, too. Coded excitation-pulse compression system is a technique to increase CTR. In this study, linear chirp is chosen to be the signal of coded excitation for transmitting, and, considering the nonlinear response of ultrasound contrast agents, a specific pulse compression filter should be designed at receiving end. In previous research, based on the concept of harmonic imaging, a kind of pulse compression filter, called SQLPCF, had been published. SQLPCF, however, failed to adapt to the fact that size distribution is changing all the time. In this study, based on the concept of harmonic imaging and statistical properties of echo signal, an adaptive pulse compression filter, APCF, has been proposed. The parameters of APCF are determined from the estimated Power Spectral Density of echoes, which are modeled as a random process. Due to estimated Power Spectral Density, parameters of APCF have the information of size distribution of UCAs so that APCF is able to adapt to all circumstances. The results of performance analysis show that APCF works better when the size distribution is narrow, but, however, when the size distribution is Rayleigh-like, performance of APCF, comparing with that of SQLPCF, improves slightly. Besides, frequency and bandwidth of transmitting signal also dominate the performance of APCF. Thus, performance of APCF will improve significantly only under some specific circumstances.
Subjects
Ultrasound contrast agent
Pulse compression
Harmonic imaging
Adaptive filter
Spectrum estimation
Type
thesis
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