Nonlinear scattering of crossed ultrasonic beams in a constricted flow for the detection of a simulated deep vein thrombosis: Part II

Abstract

Experiments show that the turbulence generated by a thrombosis (ping pong ball) lodged into a polyethylene cylindrical tube (leg vein) can be detected by the nonlinear scattering at the combination (3.8 MHz sum frequency) from two mutually perpendicular primary wave components (f1=1.8 MHz and f2 = 2.0 MHz). In study (1) the nonlinear scattering at the sum frequency is measured vs. angle from turbulence generated by a submerged water jet. In (2) the thrombosis model vein is submerged in the turbulent flow field, while in (3) the vein remains in place but the thrombosis is removed. Nonlinear scattering at the combination frequency in (1) shows significant Doppler shift and frequency broadening vs. angle. In (2) nonlinear scattering exists but is diminished in amplitude, Doppler shift and spectral broadening, as was expected. In case (3), there is virtually no scattering at the sum frequency, since the vein mitigates the turbulent flow. Results are presented at fine angular increments, and improved alignments to measure mean Doppler shift, standard deviation, skewness and kurtosis vs. scattering angle and thus characterize certain aspects of the turbulence behind the clot. Results extend the original work of Sean M. Mock [J. Acoust. Soc. Am., 129, 2410 (2011)].