Wearable Electrostrictive Row-Column Ultrasound Arrays for Longitudinal Echocardiography - Project Summary / Abstract In patients admitted to intensive care units (ICUs) with shock (low blood pressure) that results in both clinical and biochemical evidence of tissue hypoperfusion due to inadequate cardiac output, clinicians commonly seek to assess and monitor cardiac function, but all available invasive and non-invasive methodologies have significant limitations and/or risk. The gold standard method to assess cardiac output and shock states is a pulmonary arterial catheter (PAC) which is inserted through a venous canula and passes through the right side of the heart into the pulmonary artery. The advantages of this modality are that it provides information on right and left heart pressures, and allows for the calculation of cardiac output via thermodilution techniques. Its disadvantages include the invasive nature resulting the potential risk of vascular injury. Moreover, cardiac outputs are inaccurate in common cardiac arrhythmias (ex atrial fibrillation) and valvular lesions (ex tricuspid regurgitation), and only provides information on overall cardiac function without direct information on left and right heart function. Non-invasive cardiac output monitors (NICOMs) use proprietary bio-impedance or arterial line area under the curve algorithms to estimate cardiac output. While these are minimally invasive, they have not been well validated in patients in cardiogenic shock and provide no information on left and right heart function. Finally, point of care ultrasound (POCUS) allows echocardiographic evaluation of left and right heart function, but it is not well suited for evaluation of continuous or temporal trends in cardiac function given it requires a clinician to acquire images at the bedside. A wearable ultrasound probe that would enable hands-free longitudinal imaging of patients would prove to be of considerable value in the ICU environment. In this proposal we introduce a radically new wearable ultrasound technology, bias-sensitive electrostrictive top- orthogonal-to-bottom electrode (TOBE) arrays. These TOBE arrays offer readout from every element of a 2D array through biasing control and transmit-receive control of only rows and columns, rather than require wiring from every element. With novel readout approaches, these arrays will be demonstrated to achieve image quality comparable to a linear array, but with full electronic 3D scanning capabilities. Unlike MATRIX probes that rely on complicated micro-beamformers, our approach is simpler, yet allows for advanced imaging modes such as ultrafast imaging at thousands of frames per second. We propose the development of such ultrafast imaging modes with wearable TOBE probes for angle-agnostic flow estimation and longitudinal electronic tracking of right and left heart function. The angle-agnostic flow estimation avoids errors due to unknown Doppler angles and mitigates the need for manual probe positioning. In this proposal, we aim to further develop the transducer technology, interfacing electronics, and imaging methods to enable angle-agnostic flow imaging in phantoms, then with first-in-human imaging. We aim to establish feasibility data for future research into advanced longitudinal monitoring of cardiac output, ejection fractions, pulmonary artery pressure, etc.
