Fabrication, characterization and numerical validation of a novel thin-wall hydrogel vessel model for cardiovascular research based on a patient-specific stenotic carotid artery bifurcation

Abstract

In vitro vascular models, primarily made of silicone, have been utilized for decades for studying hemodynamics and supporting the development of implants for catheter-based treatments of diseases such as stenoses and aneurysms. Hydrogels have emerged as prominent materials in tissue-engineering applications, offering distinct advantages over silicone models for fabricating vascular models owing to their viscoelasticity, low friction, and tunable mechanical properties. Our study evaluated the feasibility of fabricating thin-wall, anatomical vessel models made of polyvinyl alcohol hydrogel (PVA-H) based on a patient-specific carotid artery bifurcation using a combination of 3D printing and molding technologies. The model's geometry, elastic modulus, volumetric compliance, and diameter distensibility were characterized experimentally and numerically simulated. Moreover, a comparison with silicone models with the same anatomy was performed. A PVA-H vessel model was integrated into a mock circulatory loop for a preliminary ultrasound-based assessment of fluid dynamics. The vascular model's geometry was successfully replicated, and the elastic moduli amounted to 0.31 ± 0.007 MPa and 0.29 ± 0.007 MPa for PVA-H and silicone, respectively. Both materials exhibited nearly identical volumetric compliance (0.346 and 0.342% mmHg^-1), which was higher compared to numerical simulation (0.248 and 0.290% mmHg^-1). The diameter distensibility ranged from 0.09 to 0.20% mmHg^-1 in the experiments and between 0.10 and 0.18% mmHg^-1 in the numerical model at different positions along the vessel model, highlighting the influence of vessel geometry on local deformation. In conclusion, our study presents a method and provides insights into the manufacturing and mechanical characterization of hydrogel-based thin-wall vessel models, potentially allowing for a combination of fluid dynamics and tissue engineering studies in future cardio- and neurovascular research.

Keywords: Cardiovascular engineering; Fluid dynamics; Fluid–structure interaction (FSI); Hydrogel; In vitro; Numerical simulation; Ultrasound; Vessel compliance; Vessel model.

Figure 1

CTA slices with 3D projection of reconstructed carotid artery bifurcation: lumen and outer wall at CCA (a), bright spot showing calcified plaque at ICAs region (b), soft plaque seen between the calcified plaque and lumen (c).

Figure 2

2D image cut (a) and projection (b) of the reconstructed carotid artery bifurcation on CTA sagittal slice of patient. 3D model depicting material injection into the core–shell mold of the carotid vessel (c).

Figure 3

Schematic view section of the carotid artery bifurcation with equally-spaced slices at a distance of 1 mm (a) and eight circumferentially-spaced measurement positions (P1–P8) (b) for the measurement of wall thickness at the corresponding position.

Figure 4

Schematic illustration of the compliance measurement setup filled with water: pump dispenser (a), vessel model (b), pressure transducer (c), and valve (d).

Figure 5

Experimental model with markers at four positions (CCA, ECA, ICA, and ICAs) for the measurement of diameter distensibility (a); strain distribution in the numerical model in the initial state (b) and at 140 mmHg (c).

Figure 6

Pulsatile pump set-up (a): linear motor (A), syringe (B), pump chamber (C), reservoir (D), compliance chamber (E), pressure transducers (F), resistance (G), vessel model (H), ultrasound probe (I), ultrasound probe stabilizer (J); Pulse pressure (74–130 mmHg) waveform measured at the outlet of PVA-H model (b).

Figure 7

Effective diameter of the vessel lumen in four sections (CCA, ECA, ICA, ICAs) in imaging data compared to the average effective diameter of silicone and PVA-H models at corresponding marked positions (n = 5; ^∗p ≤ 0.05).

Figure 8

Stress–strain relationship of silicone and PVA-H averaged among the samples (a) and elastic modulus of silicone and PVA-H at different strain values (b).

Figure 9

Experimental and numerical pressure–volume relationships of the silicone (a) and PVA-H (b) vessel models with error bars indicating the SDs of the experimental measurements. The numerical P–V curves are represented for both $\text{E (}{\epsilon }_{\text{m}}\text{)}$ and E_const.

Figure 10

Experimental and numerical diameter-pressure relationship at ICA site in five silicone (a) and four PVA-H samples (b); experimental and numerical diameter distensibilities at different vessel sites (CCA, ECA, ICA, and ICAs).

Figure 11

Vector velocities measured by VFM at peak systolic pressure (a), diastole (b), and end of diastole (c) with arrows showing the recirculation zones. WSS values are depicted on the walls (color bar ranging 0–0.6 Pa).