Optimization of Microbubble Concentration and Acoustic Pressure for Left Ventricular High Frame Rate EchoPIV in Patients.

High frame rate (HFR) echo-particle image velocimetry (echoPIV) is a promising tool for measuring intracardiac blood flow dynamics. In this study we investigate the optimal ultrasound contrast agent (UCA: SonoVue®) infusion rate and acoustic output to use for HFR echoPIV (PRF = 4900 Hz) in the left ventricle (LV) of patients. Three infusion rates (0.3, 0.6 and 1.2 ml/min) and five acoustic output amplitudes (by varying transmit voltage: 5V, 10V, 15V, 20V and 30V - corresponding to Mechanical Indices of 0.01, 0.02, 0.03, 0.04 and 0.06 at 60 mm depth) were tested in 20 patients admitted for symptoms of heart failure. We assess the accuracy of HFR echoPIV against pulsed wave Doppler acquisitions obtained for mitral inflow and aortic outflow. In terms of image quality, the 1.2 ml/min infusion rate provided the highest contrast-to-background (CBR) ratio (3 dB improvement over 0.3 ml/min). The highest acoustic output tested resulted in the lowest CBR. Increased acoustic output also resulted in increased microbubble disruption. For the echoPIV results, the 1.2 ml/min infusion rate provided the best vector quality and accuracy; and mid-range acoustic outputs (corresponding to 15V-20V transmit voltages) provided the best agreement with the pulsed wave Doppler. Overall, the highest infusion rate (1.2 ml/min) and mid-range acoustic output amplitudes provided the best image quality and echoPIV results.