Real-time high-framerate in vivo cardiac SLSC imaging with a GPU-based beamformer

Echocardiography is widely used to evaluate cardiovascular function in real-time; however, endocardial borders are often inadequately visualized due to clutter. Contrast agents, while effective, increase cost and examination time. SLSC imaging is a coherence-based beamforming technique that has demonstrated clutter reducing capabilities in a variety of applications. Previously, real-time SLSC imaging of a large field of view was achieved at up to 6 fps, inadequate for visualizing a quickly moving target such as the heart. In our previous work, we developed efficient modifications to the SLSC algorithm to obtain fast and precise measurements of spatial coherence. In this work, these techniques were implemented on a GPU-based software beamformer to develop a real-time SLSC imaging system suitable for echocardiography. The system was then used in a clinical study to image 15 patients with poor image quality, as determined by trained sonographers. Real-time display of side-by-side B-mode and SLSC images were obtained at frame rates ranging from 21 to 31 fps. B-mode and SLSC video clips were given in shuffled order to a cardiologist, who rated the visibility s of each of 12 LV segments as 0=invisible, 1=poorly visualized, or 2=well visualized. Scores of 0 and 1 indicated a need for contrast agent. A two-tailed paired t-test showed that SLSC imaging demonstrated a statistically significant increase in the number of visualized segments (s > 0, p = 0.0032) and in the number of segments that were well visualized (s = 2, p = 0.0061).