Ultrasonic intensity and Doppler power measurements with uniform and nonuniform polyethylene tubes

The vessel wall may affect the spatial distribution of ultrasound (US) over the lumen of a vessel, leading to artefacts or errors in derived data. We conducted experiments to directly examine the ultrasound intensity distribution within a vessel with a thick wall of known acoustic properties. We utilised two custom made tubes of low density polyethylene, one where the vessel wall thickness is uniform and another where the vessel wall thickness varies with angular position around the lumen. Hydrophone measurements were made under half sections of the tubes, obtained by cutting lengthwise along the tube axis. The results of these measurements were compared to simulation data. Experiments were conducted using the tubes in a flow phantom. The Doppler power distribution along a scan line was analysed with a multigate instrument for the uniform tube, and for the non-uniform tube in different rotational positions. The hydrophone data reveals an uneven US intensity distribution within the tube, with additional asymmetry for the non-uniform tube, according to the simulation predictions. The Doppler power increases with depth, again in agreement with simulation data, and asymmetrical distributions are shown for the non-uniform tube.