OBJECTIVES: Visualisation of flow fields using a 2D colour Doppler technique is developed and assessed, with particular emphasis on the visualisation of secondary flow motions in arteries.
METHODS: Colour Doppler images were acquired from two directions. The images were averaged and compounded to give images of the velocity magnitude, velocity angle, and a scan-plane vector map. The accuracy of the vector technique was assessed using a rotating phantom with a circular cylinder of 1.55 cm diameter and a rotational speed of 250 rev./min. The ability of the vector technique to visualise a known flow field was tested in the laboratory using a flow phantom with a Y-shaped bifurcation, with acquisition of colour images in the plane perpendicular to the vessel axis. An initial study was performed on secondary flow motions in the lower limb arteries of young healthy volunteers.
RESULTS: The calculated velocity magnitude and angle had no significant bias. The estimated precision is 9.6% for the velocity magnitude and 7.0° for the angle. Double spiral patterns were seen in the arms of the Y-shaped junction; this is the expected flow pattern. Initial studies on normal volunteers suggests that spiral flow patterns are present in lower limb arteries.
CONCLUSIONS: The scan-plane vector technique works well and should be applicable to all commercially available colour flow systems in which colour images can be acquired from different beam directions. The velocity vector angle and vector magnitude are calculated with low errors provided that alignment of the colour Doppler images from the left and right beam directions can be achieved. The flow phantom studies have shown that in a known geometry, secondary flow motions can be demonstrated with the predicted characteristics. Initial studies on normal volunteers have shown that secondary flow motions are present in lower limb arteries
