Distortion of Doppler ultrasound beam patterns caused by acoustic impedance mismatch at vessel interfaces

It has been noted previously that Doppler ultrasound measurements from a coronary guidewire in a circular tube exhibited spectral peaks which were not directly related to hemodynamic phenomena. These peaks were more pronounced with an increase in the acoustic impedance mismatch between the tube walls and the fluid. To determine whether these peaks could be explained by mismatch-induced beam-pattern distortion, the beam pattern of an ultrasound probe inside a circular tube was measured and was used to simulate the Doppler spectrum which would result from Poiseuille flow. The resulting spectra had peaks similar in size to those from guidewire measurements in Poiseuille flow