Application of a meta-analysis of aortic geometry to the generation of a compliant phantom for use in particle image velocimetry experimentation

Abstract

The evolution of pressure-flow geometry in the aortic arch is increasingly understood as a key element in the treatment of hemodynamic dysfunction in patients. However, little is known about the properties of the flow across the aortic geometry and thus the sensitivity of sensor placement is also unknown. Compliant models of the aortic path can be built to allow techniques such as particle image velocimetry to measure the velocity fields. This paper presents the justification and production methodology used to generate a compliant model of the aortic arch that represents the geometry and compliance of typical hemodynamics patients. The information from twenty papers was synthesized to generate a single model of the aortic arch. The model incorporates the three branching arteries at an apex of a tapering aortic path experimental that has been manufactured as a flexible thin-walled silicon model. Calculations were undertaken to ensure that the model matches the in vivo compliance of the arteries.The experimental setup uses the compliant silicone model of the aorta with variable flow pump to mimic the cardiac cycle, and a variable extramural pressure to mimic changes in intrathoracic pressure. This research was necessary for the development of an accurate experimental setup that would enable results that are immediately applicable to the research of cardiovascular therapy optimization.

A Novel Fabrication Method for Compliant Silicone Phantoms of Arterial Geometry for Use in Particle Image Velocimetry of Haemodynamics

“…The dimensions of the phantoms in this study were obtained from a meta-analysis of healthy aortic geometry reported by Huetter et al [37]. Figure 1 shows the phantom dimensions.…”

“…where A is the area, P is the pressure, r is the radius, A min is the cross-sectional area of the lumen at zero transmural pressure, E is the modulus of elasticity, and h is the wall thickness of the phantom. Typical aorta structures have a radius of 0.011 m, a Young's modulus of 0.526 × 10 6 Pa and a wall thickness of 0.00132 m, leading to a compliance of 31.25 × 10 −6 Pa −1 [37]. The phantom has a radius of 0.0206 m, a Young's modulus of 1.32 × 106 Pa and a wall thickness of 0.001 m, leading to a compliance of 31.25 × 10 -6 Pa -1 .…”

“…They reported a 2 mm uniform wall thickness but no declaration of wall thickness variation. However, this wall thickness is also potentially larger than appropriate [37]. Marconi et al [38] used 3D printed moulds to fabricate an aortic compliant phantom.…”

Influence of the aortic morphological changes in aging on aortic flow

“…In the first geometry, the 50 percentile of the range of geometry data was used from literature, in the second, the minimal values of the geometry data were used. In the third model, the different curvature differ as simulated by an ellipsoid as described in the article (Huetter et al 2015).…”

Experimental investigation into the effect of compliance of a mock aorta on cardiac performance

“…In addition to analytical solutions for the pulsatile flows obtained after applying simplifying assumptions, there have been many numerical and experimental investigations into pulsatile flows through rigid tubes [ 34 – 37 ], but these are ultimately limited in their physiological relevance because in-vivo , blood interacts with compliant arteries. This compliant response is particularly pronounced in the aorta which converts some of the ejection energy into elastic energy through expanding its size by 20–60% during systole [ 38 ] and storing up to 50% of the ejected stroke volume [ 39 ]. The amount of expansion is determined by the intrinsic and operative distensibility of the tissue [ 40 ] as well as the difference between the pulse pressure generated by the left ventricle and the pressure surrounding the aorta, the transmural pressure.…”