Vector doppler imaging and secondary flow patterns in vascular prostheses

Flow patterns created by vascular prostheses designed to induce spiral flow, were compared against standard plain grafts using an in-house ultrasound flow phantom. Color Doppler and vector Doppler imaging were applied to visualize and quantify secondary flow motions distally to the grafts outflow. The flow phantom incorporates a piston pump, blood mimic fluid, vessel mimicking tubing consisting of polyvinyl alcohol, in 9% glycerol solution. Spiral Laminar Flow^TM Peripheral Vascular (PV) and Access Vascular (AV) grafts (Vascular Flow Technologies, Dundee, UK) were compared with standard control PV and AV grafts. Steady flow rates up to 720 ml min^-1 were applied. Color Doppler cine loops were acquired from the left (8 = 20) and right (8 = -20) projection, with the transducer positioned transverse to the flow direction. The velocity data was subjected to triangulation in order to generate in-plane velocity magnitude and direction maps. Complicated rotational patterns were detected in the connection between the graft and the vessel mimic, with a prevalent single helix for the spiral prostheses and a prevalent double helix for the control devices. A clear single spiral pattern was found distally of the spiral grafts and a double distally of the standard devices. The magnitude of the radial component velocity distally from the PV spiral graft, was found to be significantly higher (p <; 0.05) compared to the control device. This study compared different vascular graft designs in terms of their outflow patterns, using a dual-beam color Doppler mapping.