In vitro estimation of mean sound speed based on minimum average phase variance in medical ultrasound imaging |
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Authors: | Yoon Changhan Lee Yuhwa Chang Jin Ho Song Tai-Kyong Yoo Yangmo |
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Affiliation: | a Department of Electronic Engineering, Sogang University, Seoul, Republic of Korea b Sogang Institutes of Advanced Technology, Sogang University, Seoul, Republic of Korea c Interdisciplinary Program of Integrated Biotechnology, Sogang University, Seoul, Republic of Korea |
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Abstract: | Effective receive beamforming in medical ultrasound imaging is important for enhancing spatial and contrast resolution. In current ultrasound receive beamforming, a constant sound speed (e.g., 1540 m/s) is assumed. However, the variations of sound speed in soft tissues could introduce phase distortions, leading to degradation in spatial and contrast resolution. This degradation becomes even more severe in imaging fatty tissues (e.g., breast) and with obese patients. In this paper, a mean sound speed estimation method where phase variance of radio-frequency channel data in the region of interest is evaluated is presented for improving spatial and contrast resolution. The proposed estimation method was validated by the Field II simulation and the tissue mimicking phantom experiments. In the simulation, the sound speed of the medium was set to 1450 m/s and the proposed method was capable of capturing this value correctly. From the phantom experiments, the −18-dB lateral resolution of the point target at 50 mm obtained with the estimated mean sound speed was improved by a factor of 1.3, i.e., from 3.9 mm to 2.9 mm. The proposed estimation method also provides an improvement of 0.4 in the contrast-to-noise ratio, i.e., from 2.4 to 2.8. These results indicate that the proposed mean sound speed estimation method could enhance the spatial and contrast resolution in the medical ultrasound imaging systems. |
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Keywords: | Receive beamforming Sound speed estimation Phase variance Contrast resolution Spatial resolution |
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