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™ 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 were applied. Color Doppler cine loops were acquired from the left (? = 20) and right (? =-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.