Ultrasound clutter and noise improvements applied to echocardiographic left atrial appendage visualization

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Summary Ultrasonic imaging is the most widely used advanced imaging modality in the United States, and excluding planar radiography, it represents 44% of all imaging studies. Unfortunately, ultrasound images are often subopti- mal, and some echocardiography studies show degradation in up to 98% of patients. This rate of degradation and the freehand nature of clinical ultrasound means that image quality is more dependent on operator skill than other advanced modalities, but even with the most skilled practitioners, ultrasound completely fails in 11-64% of clinical tasks. Our overall goal for this application is to fundamentally decrease ultrasound failure rates. Low-quality ultrasound is particularly problematic in echocardiography because of its role as a first-line tool for diagnosing and monitoring cardiac disease. When transthoracic echo is inadequate more costly and time-consuming exams like transesophageal echo or MRI are required. To (1) facilitate the high volumes of transthoracic echo, (2) im- prove patient comfort and safety (i.e. reduce transesophageal echo), (3) reduce cost and procedure time, and (4) maximize physician efficiency, it is crucial to have consistently high quality transthoracic echo. To provide this, we introduce new acquisition and reconstruction solutions for ultrasound imaging. Echocardiographic imaging of the left atrial appendage is growing in importance in lockstep with the rising incidence of atrial fibrillation, which currently effects as many as 2-6 million Americans and is expected to grow to 6-12 million by 2050. In patients with atrial fibrillation, thrombus may appear in as many as 12-26% of left atria with most appearing in the appendage. Therefore, in patients with current atrial fibrillation the left atrial appendage must be screened with echocardiography for thrombus before cardioversion can be performed to return the heart to sinus rhythm. Further, patients receiving a left atrial appendage closure device due to chronic atrial fibrillation require annual transesophageal echo follow ups to monitor the device. For both cases, the gold- standard and standard-of-care is transesophageal echocardiography, and while the left atrial appendage can be visualized transthoracically, is is rarely used because the image quality is considered too unreliable. Ultrasound image quality is degraded by both clutter and thermal noise, so to make clinically transforma- tional improvements to ultrasound–and echocardiography specifically–it is necessary to address both the clutter problem and the noise problem. Addressing both of these issues is becoming increasingly important because recent developments in beamforming have focused on non-linear algorithms (including deep networks), and the performance of these methods are more strongly linked to the noise level compared to conventional beamforming methods. To this end, we introduce both a solution enhancing signal-to-noise ratio using coded excitation and a comprehensive solution for clutter reduction using deep network beamforming.