서강대학교

초록 (요약문)

Receive beamforming (RBF) based on delay-and-sum (DAS) has been widely for improving signal-to-noise ratio (SNR) and spatial resolution in medical ultrasound imaging systems. However, the DAS only shows improved image quality close to transmit focal depth. To overcome the limitation in DAS, synthetic aperture focusing (SAF) method has been proposed. In addition, coherence factor weighting (CFW) beamforming methods were recently proposed to further enhance contrast resolution by reducing interference noise in medical ultrasound imaging systems. Combining SAF and CFW methods can provide a high-resolution image with improved contrast and spatial resolution. However, conventional SAF methods based on a virtual point source (SAF-PS) yield severe degradation in SNR and gain near transmit focal depth. In this study, a new SAF method using a virtual ellipse model (SAF-VE) is presented to solve the issues associated with the degradation in gain and SNR. In addition, the proposed SAF-VE method can be combined with different types of CFW methods, such as coherence factor (CF), generalized CF (GCF), and spatially smoothed CF (SSCF). To evaluate the performance of the proposed methods, the Field-II simulation was performed, and the SNR was measured by using the ultrasound research system(Vantage 128, Verasonics Inc, Kirkland, WA) with a L7-4 linear probe. In addition, the in-vivo breast study was performed with a commercial ultrasound system equipped with a research package (SonixTouch, SonicDAQ, Ultrasonix Corp., Canada) using a 10-MHz linear probe. The Field-II and in vivo study results show that the proposed SAF-VE method successfully resolves the degradation in gain and SNR at transmit focal depth while providing improved contrast resolution when combining with CF. Moreover, the increase in computational complexity from the proposed SAF-VE with CF was negligible since the CF weighting is performed after superpositions.