Intraluminal ultrasound intensity distribution and backscattered Doppler power.
Ultrasound (US) incident obliquely on a cylindrical vessel is redistributed in space when the propagation path includes walls with acoustic impedance different from that of the surrounding media. We investigated this using low-density polyethylene (PE) as the vessel wall material. Both simulations and experiments were carried out. Direct hydrophone measurements of the acoustic field were made within a half section of the PE tube, and the distribution of backscattered Doppler power along a scan line was obtained using a range-Doppler instrument. Both simulation and hydrophone results demonstrate lateral shadow regions within the lumen. In every one of various Doppler flow experiments conducted, the backscattered Doppler power, compensated for on-axis transducer behaviour, increased with depth. Simulation results for an incident continuous-wave (CW) plane wave show that it tends to be focused by the curvature of the PE tube walls. The wall interactions are, however, angle-dependent and so the behaviour of a focused US beam depends on the beam as well as the walls. This study demonstrates alterations in the spatial distribution of US within a cylindrical vessel as a result of known vessel wall properties. It also provides evidence that local intensity variations within the lumen affect the relative Doppler power backscattered from small sample volumes.
Thompson
Rosemary S
RS
School of Mathematics and Statistics, University of Sydney, Sydney, NSW 2006, Australia. roset@maths.usyd.du.au
Bambi
Giacomo
G
Steel
Robin
R
Tortoli
Piero
P
D001808:Blood Vessels / Q000502:physiology; D003198:Computer Simulation; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D019047:Phantoms, Imaging; D020959:Polyethylene; D014465:Ultrasonics; D018608:Ultrasonography, Doppler / Q000379:methods*
D020959:Polyethylene