서강대학교

초록/요약

Ultrafast ultrasound imaging based on coherent compounding using multiple plane or diverging waves has enabled a number of applications requiring high frame rate such as shear wave elastography and ultrafast Doppler imaging. However, it generally suffers from low contrast resolution due to side-lobe, grating-lobe, and axial-lobe artifacts since a limited number of steering angles can be used for compounding to attain high frame rates. Although several nonlinear beamforming methods such as the minimum variance approach have been presented for high quality ultrasound imaging at the expense of computational cost, those may perform poorly in the high-interference and low-signal-to-noise-ratio condition resulting from lack of transmit focusing. In this paper, we present a nonlinear compounding method for high-contrast ultrafast imaging based on the delay multiply and sum (DMAS) algorithm. In the proposed method, frames reconstructed using the conventional delay and sum (DAS) algorithm are coupled in pairs and multiplied in advance of summation. To evaluate the performance of the proposed method, we conducted Field II simulation, tissue-mimicking phantom, and in vivo B-mode imaging studies based on three different methods (i.e., conventional coherent compounding, compounding with DMAS beamforming, and proposed DMAS compounding). The results show that the proposed method can achieve much higher contrast ratio compared to coherent compounding (e.g., 37.6 dB vs. 27.0 dB, respectively with 20 steering angles) while inducing much less black regions compared to DMAS beamforming. These results indicate that the proposed method can effectively improve contrast of ultrafast B-mode images.