Breast Cancer Imaging by Color Doppler Shear Wave Elastography

Abstract

In shear wave elastography, complicated shear wave wave-front caused by the reflection, refraction, and diffraction at the tissue boundary degrades the accuracy of velocity measurement. If the shear wave wave-front is visualized in real-time, the accuracy increases because the velocity is estimated along the shear wave propagation direction. Moreover, observed wave-front pattern provides valuable information about tissue structure, which makes the detection of the stiff part easier. We have proposed a novel shear wave elastography (Color Doppler Shear Wave Imaging: CD SWI) [Y.Yamakoshi, et al. IEEE tans on UFFC. 64, 340 (2017)]. Continuous shear wave of a frequency that is n/4 (n being an odd number) times the PRF is introduced from the tissue surface. Then, the shear wave wave-front appears simultaneously as a stripe pattern on conventional ultrasound color Doppler image. This cost-effective shear wave elastography is implemented on ACUSON S3000 (Siemens). The shear wave frequency is 235.3Hz. Shear wave velocity measured by CD SWI was compared with that by ARFI for breast phantom. Shear wave velocities by two methods showed good correlation, but the standard deviation of CD SWI was 42% of that of ARFI. Malignant lesions were imaged by CD SWI as an area with high shear wave velocity. Inherent shear wave propagation around a malignant lesion was also observed. It is suggested that a combination of shear wave image of CD SWI and B-mode image improves the sensitivity in detection of malignant lesions in breast tissue.