Optimization of ultrasonic elastography by coded excitation and transmit-side multi-frequency compounding

Abstract

To improve the quality of ultrasonic elastography, by taking the advantage of code excitation and frequency compounding, a transmitting-side multi-frequency with coded excitation for elastography (TFCCE) was proposed. TFCCE adopts the chirp signal excitation scheme and strikes a balance in the selection of sub-signal bandwidth, the bandwidth overlap and the number of sub-strain image based on theoretical derivation, so as to further improve the quality of elastic image. Experiments have proved that, compared with the other optimizing methods, the elastographyic signal-to-niose ratio(R e-SN) and contrast-to-noise ratio(R e-CN) are improved significantly with different echo signal-to-noise ratios (R eSN) and attenuation coefficients. When R eSN is 50 dB, compared with short pulse, R e-SN and R e-CN obtained by TFCCE increase by 53% and 143%, respectively. Moreover, in a deeper investigation (85–95 mm), the image has lower strain noise and clear details. When the attenuation coefficient is in the range of 0-1 dB/(cm·MHz), R e-SN and R e-CN obtained by TFCCE can be kept in moderate ranges of 5<R e-SN<6.8 and 11.4<R e-CN<15.2, respectively. In particular, for higher tissue attenuation, the basic image quality cannot be ensured with short pulse excitation, while mediocre quality strain figure can be obtained by TFCCE. Therefore, the TFCCE technology can effectively improve the elastography quality and can be applied to ultrasonic clinical trials.