Broadband ultrasound signals will produce distortion in viscoacoustic medium, which may influence the accuracy of time-of-flight (TOF) measurement. Under the condition of single-frequency acoustic source, the wave propagation process in viscoacoustic medium was analyzed and an approximate solution of the wave propagation was given. Instances of broadband ultrasound were analyzed and simulated based on the single-frequency results. A single-frequency matching pursuits (SFMP) algorithm was then introduced to solve the waveform distortion problem. Time-frequency decomposition was applied to extracting the single-frequency compositions from broadband ultrasound signals, and then these compositions were sent to the matching pursuits (MP) algorithm for calculating the TOF parameters. Compared with the broadband signals, the shapes of extracted single-frequency signals change more slightly as distance and attenuation coefficient increase. The residuals of SFMP were far less than those of MP algorithm. Experimental results show that the SFMP algorithm is able to eliminate waveform distortion of broadband ultrasound in viscoacoustic medium, which helps improve the accuracy of TOF measurement.
A high-performance measurement method for the artery intima-media thickness(IMT) in medical ultrasound images is proposed.The scheme mainly consists of two parts.The first part is the detection process,including adaptive gray stretching for image enhancing,gradient transforming to restrain the over-segmentation,and the watershed algorithm for edge extraction.The intima can be detected automatically and exactly.The second part,combined with regional positioning and boundary fitting stages,is used to measure the IMT.Experimental results show that the proposed scheme can yield a good measurement result,and the calculation time can satisfy the practical requirement.
