Bilateral Axisymmetric Narrow Vascular Ultrasound Doppler Signal Resolution Simulation Model

The stenosis, the plaque developed to the point where it significantly narrows the vessels, is one of the most serious forms of arterial disease. The clinical studies suggest that the stenosis is usually found in the highly curved arterial segment, vascular bifurcation, and the confluence of medium and large arteries. Once a stenosis is formed, it may disrupt the normal blood flow to the extent depending upon the degree of the deposition of substances in the arterial lumen, even lead to total vessel blockage in some instances and further influence the development of the disease and arterial deformity. The results from recent studies show that it plays an important role to cure and prophylactic the artery stenosis through the detection of unusual slow blood flow close to the vessel wall.Doppler ultrasound is an important diagnosis technique to acquire the blood flow dynamic information of the cardiac and cerebric vascular systems. The diagnosis accuracy of the arterial stenosis by using an ultrasonic instrument dependent not only on the properties of the device, but also on the signal analysis technique and feature extraction algorithm employed. As a commonly used experimental method for evaluating and comparing the performance of signal analysis technique and feature extraction algorithm, simulation experiments are performed based on the data obtained from computer simulation models.Firstly, this study presents a novel computer simulation model based on an analytic flow velocity distribution to generate Doppler ultrasound signals from non-stationary blood flow in double sides symmetric stenosis with various degrees. Secondly, the velocity distribution of the blood flow near the vessel wall in the mildly-stenosed vessels is extract to determine the characteristics being sensitive to the arterial stenosis at an early stage. The model takes into account velocity field from pulsatile blood flow in the stenosed vessels, sample volume shape and acoustic factors that affect the Doppler signals. By analytically solving the Navier-Stokes equations, the velocity distributions of pulsatile blood flow in the vessels with various stenosis degrees are firstly calculated according to the velocity at the axis of the circular tube. Secondly, power spectral density (PSD) of the Doppler signals is estimated by summing the contribution of all scatterers passing through the sample volume grouped into elemental volumes. Thirdly, Doppler signals are generated using cosine-superposed components that are modulated by a PSD function that varies over the cardiac cycle. The model generates Doppler blood flow signals with the characteristics similar to those found in practice. Finally, the velocity distribution of the blood flow near the vessel wall in the mildly-stenosed vessels is extract to obtain its'characteristics.The results show that the proposed approach is useful for simulating Doppler ultrasound signals from non-stationary blood flow in double sides symmetric stenosis with various degrees. The results also show that Doppler ultrasound spectrogram characteristics of the blood flow near the vessel wall in the mildly-stenosed vessels, such as:increased spectral broadening index and obvious reserved blood flow (components with negative frequencies), are observed and could be used as the indications that identify the mild narrowing of arteries.