Maximum Velocity Estimation in Coronary Arteries Using 3-D Tracking Doppler

Several challenges currently prevent the use of Doppler echocardiography to assess blood flow in the coronary arteries. Due to the anatomy of the coronary tree, out-of-plane flow and high beam-to-flow angles easily occur. Transit-time broadening in regions with high velocities leads to overestimation of the maximum velocity envelope, which is a standard clinical parameter for flow quantification. In this paper, a commercial ultrasound system was locally modified to perform trans-thoracic, 3-D high frame-rate imaging of the coronary arteries. The imaging sequence was then combined with 3-D tracking Doppler for retrospective estimation of maximum velocities. Results from simulations showed that 3-D tracking Doppler delivers sonograms with better velocity resolution and spectral SNR compared to conventional pulsed wave (PW) Doppler. Results were confirmed using in vitro recordings. Further simulations based on realistic coronary flow data showed that 3-D tracking Doppler can provide improved performance compared to PW Doppler, suggesting a potential benefit to patients. In vivo feasibility of the method was also shown in a healthy volunteer.