High Frequency Doppler Flow Triggering for 75 MHz Ultra-High Frame Rate 3D Ultrasonic Zebrafish Echocardiography

The ultra-high frame rate 3D high frequency ultrasound zebrafish heart image was reconstructed by using the Doppler triggering method in this study. The detailed changes of zebrafish cardiac volume were monitored during the cardiac cycle. A 40 MHz pulsed wave Doppler flowmeter was built for measuring the Doppler spectrogram from zebrafish artery, and the timing of peak flow velocity was selected by analog circuits as a trigger signal to synchronize the 3D 75 MHz high frequency ultrasound imaging system. The high frame rate 2D and 3D echocardiographs were reconstructed by acquired A-line signals at different cardiac positions with high pulse repetition frequency (PRF). The imaging frame rate was independent from the speed of scan motor. However, it was determined by the PRF of ultrasonic pulser. The boundary between heart and other tissues was detected using a matching similarity processing which used the correlation algorithm to calculate the shift at each pixel window for 3D dynamic image reconstruction. A median filter was applied to move the noise before the image reconstruction. The adult zebrafish experimental results showed that the volume size of heart was changed approximately 12-14% between diastole and systole. Even though the single element transducer was used for scanning the zebrafish heart, this technology still can be applied to array system for high frame dynamic 3D imaging.