Flow Angle Determination for a Heart Phantom using Transverse Oscillation

A common challenge in modern echocardiography is measuring blood flow velocities in directions that are not parallel to the ultrasound beam. This becomes even worse in cardiac ultrasound because of the heart’s complex movement and flow patterns. Transverse oscillation ultrasound imaging can be used to determine the axial and lateral components of the velocity regardless of the angle between the beam and the flow. In this study, it is hypothesized that by using this method it is possible to estimate the beam to flow angle even in complex flow structures. The measurements were performed on a calibrated flow rig and a Shelley heart phantom with blood mimicking fluid circulating through them with constant flow. The transducer used for the data acquisition was a GE M5Sc-D, 2.85 MHz phased array transducer attached on a Verasonics 256 Vantage scanner. An interleaved synthetic aperture imaging sequence with 2×12 emissions and 1 kHz pulse repetition frequency was used. The flow rate in the flow rig was 24 L/h and for the heart phantom the flow rate was 14 L/h. The transverse oscillation method was then used on the acquired data in order to estimate both the axial and the lateral component of the velocity and consequently estimate the beam to flow angle. The angle at the flow rig was calculated to be equal 60.89 ± 0.82 degrees (2.97% standard deviation) and it was also possible to estimate and illustrate how the flow follows the phantom’s walls with a RMSE=4.03 degrees.