PROJECT SUMMARY/ABSTRACT 4D transthoracic echocardiography (TTE) offers an excellent means to study complex heart anatomy and measure cardiac dynamics via myocardial strain imaging. While TTE-based 4D strain imaging overcomes many shortcomings of traditional strain analysis, and modern speckle-tracking algorithms enhanced reproducibility, 4D echocardiography currently lacks the necessary spatial and temporal resolution for comprehensive flow analysis. Likewise, modern systems do not still allow the user to adjust the number and location of the acquired planes, which is crucial for assessing heart valves and cardiac fluid dynamics enabled by echocardiographic particle image velocimetry (Echo-PIV). There is an unmet clinical need to study 4D flow fields in heart chambers, especially in the right ventricle (RV) via echocardiography, which is ubiquitous, real-time, and less expensive than cardiac MRI (CMR). The significance of 4D flow information in the RV and how it alters clinical diagnosis and therapy has been recently illuminated. To date, no breakthrough in transducer technology has yet evolved to offer selective control over 3D spatial information acquired about tissue strain and complex flow. Our team’s multidisciplinary expertise in hardware, software, and clinical ultrasound supports our overarching goal to develop a novel generation of broadband echocardiography transducers, which uniquely utilize only the elements around a matrix array periphery. Combined with multi-line transmit focusing and coherence-based receive beamforming methods, they will provide volume rates substantially higher than existing systems. Not available on commercial systems, the combined advantages of broadband capability, high-speed volume acquisition, and user-adjustable multiplanar acquisition will enable rapid 4D strain imaging and enhance detection, tracking, and visualization of microbubbles for 4D flow measurements. Combining both labs’ complementary expertise will devise a novel generation of 4D TTE ultrasound systems using matrix arrays with a beamformer to enable operator-controlled multiplanar acquisition at high volume-rates. SPECIFIC AIM 1. Develop a novel generation of 4D TTE probes with broadband multi-row/multi-column boundary array that will enable high-speed adjustable multi-planar acquisition. SPECIFIC AIM 2. Devise multi-line transmit-focusing and coherence-based receive beamforming methods. SPECIFIC AIM 3. Validate 4D TTE system in vitro and clinically by enabling MP-Echo-PIV and multiplanar strain imaging.