Feasibility of dual probe pulse wave imaging of the abdominal aorta

Pulse wave velocity (PWV) is an indirect measure of vessel stiffness, that has the potential to serve as a meaningful parameter for risk stratification of vascular diseases, such as abdominal aortic aneurysms (AAAs). However, assessing the PWV and pulse wave patterns in the complete abdominal aorta using ultrasound-based pulse wave imaging (PWI) is challenging due to the limited field of view (FOV) and contrast of a single ultrasound (US) probe. Hence, an approach is required that can capture distension of aortas with different levels of stiffness accurately in a large FOV. Therefore, we propose PWI based on dual probe, bistatic US. Single and dual probe ultrasound simulations were performed using finite element models of pressure waves propagating in aortas with different stiffness levels. Next, the approach was tested on an aorta and AAA mimicking phantom in a mock circulation setup. The simulation results show that the FOV, image quality, and PWV-estimation accuracy improve when using the dual probe approach (accuracy range: 94.9 - 99.8 $\%$; R$^{2}$ range: 0.92 - 0.98) compared to conventional US (accuracy range: 12.6 - 93.9 $\%$; R$^{2}$ range: 0.52 - 0.91). The approach was successfully expanded to the phantom study, which demonstrated expected wave patterns within a larger FOV. With dual probe PWI of the non-dilated phantom, the R$^{2}$-value improves (monostatic: 0.95; bistatic: 0.96) compared to use of single probe PWI (0.85). The proposed method shows to be promising for PWV-estimations in less compliant vessels with high wave speeds.