Dual gate pulsed wave Doppler imaging for investigating cardiovascular dysfunctions

Ultrasound Doppler imaging is frequently performed in a clinical and research environment to assess cardiovascular functions. Blood flow and tissue motion velocities can be measured employing pulsed-wave flow and tissue Doppler imaging respectively. Conventionally, flow and tissue Doppler are acquired separately in different cardiac cycles and synchronized using an electrocardiogram signal as a reference. Dual gate pulsed wave Doppler imaging, which utilizes two separate gates for flow and tissue Doppler, has been implemented by interleaving tissue Doppler to flow Doppler imaging sequences to measure the velocity of flow and tissue motions simultaneously. The proposed approach was implemented on the high-frequency ultrasound imaging system operating a 28 MHz 256-element linear array transducer. Micro-flow phantom having a polyimide tube with a diameter of 510µm was fabricated. The array-based Doppler system was evaluated by measuring constant flow velocities (30, 40, 50 and 80 mm/s) in the micro-flow phantom using a single-gate Doppler, and then dual-gate Doppler was evaluated by measuring the velocity of flow and wall motions. In the micro-flow phantom experiment using dual-gate Doppler imaging, while flow velocity in the tube is changing from 0 to 70 mm/s, the wall motions of either contraction or relaxation could be identified in tissue Doppler imaging.