Anatomical Phantom Model with Pulsatile Flow

• The paper demonstrates that anatomical phantom models replicate realistic blood flow waveforms using patient-specific imaging and advanced fabrication techniques for validating computational models and device navigation.
• The methodology employs 3D printing with compliant photopolymers, programmable pulsatile pumps, and multimodal MRI to simulate and measure vascular hemodynamics accurately.
• Key findings indicate that integrating dynamic imaging and inline pressure-flow sensors in phantom models improves device testing and offers robust frameworks for in vitro and in silico validations.

An anatomical phantom model with pulsatile flow is an engineered physical construct that replicates human or animal vascular anatomy and hemodynamics, designed to simulate physiologic blood flow waveforms through anatomically accurate conduit geometries. These phantoms serve as controlled, repeatable platforms for the validation of image-based computational models, the assessment of robotic and interventional devices, and the study of hemodynamics under clinically relevant flow conditions.

1. Anatomy and Fabrication of Vascular Phantoms

Phantom geometry is derived from either generalized vascular templates or patient-specific imaging data. For example, phantoms can incorporate aortic bifurcation models featuring the infrarenal aorta, bilateral common iliac arteries, renal and mesenteric branches, and detailed branching patterns, as was implemented in the aortic-abdominal model evaluated by navigation experiments (Brumfiel et al., 15 Dec 2025). Advanced designs utilize segmentation pipelines (e.g., SimVascular) operating on contrast-free 4D-flow MRI to obtain subject-specific luminal geometries inclusive of inlets and multiple major outlet branches (brachiocephalic, left common carotid, left subclavian, etc.) (Lan et al., 2022).

Fabrication methods include 3D printing using photopolymers such as Agilus30 and VeroClear to provide compliance closely matching physiological tissue (Lan et al., 2022). Wall thickness, mechanical compliance, and prestressing strategies ensure appropriate deformation under pulsatile load. Inlet and outlet interfaces are commonly extended or adapted with barbed connectors to enable seamless integration into hydraulic circuits (Brumfiel et al., 15 Dec 2025), but precise fabrication and connection parameters are frequently vendor-specific or omitted from published descriptions.

Aspect	(Brumfiel et al., 15 Dec 2025)	(Lan et al., 2022)
Anatomy	Aortic bifurcation + major branches	Patient-specific thoracic aorta with 4 outlets
Fabrication detail	Not specified (Vivitro Lab model)	3D-printed photopolymer with tested compliance
Connector interfaces	Barbed, unspecified	2-cm extensions for tubing

2. Simulation of Pulsatile Hemodynamics

Pulsatile flow in phantom models is typically achieved using programmable piston or linear actuating pumps equipped with compliance (capacitance) and resistance elements to generate physiologically relevant pressure and flow waveforms (Brumfiel et al., 15 Dec 2025, Lan et al., 2022). These circuits may utilize internal modules for viscoelastic impedance adjustment, mimicking systemic arterial pressures (approximately 120/80 mmHg) and cardiac output (mean ~5 L/min), though exact settings are infrequently stated explicitly and may rely on standard vendor protocols.

Working fluids approximate the density and viscosity of blood; one implementation utilized a 40/60 glycerol–water mixture (ρ = 1.06 g/cm³, μ = 0.04 P) (Lan et al., 2022). Downstream pinch valves and air-chamber-based capacitance elements fulfill Windkessel-like dynamic properties. Flow and pressure splits at major branches are matched to physiological distributions through hydraulic circuit adjustment and verified using pressure transducers and flow probes during circuit tuning.

3. Measurement and Validation Techniques

In comprehensive setups, high-resolution measurement of flow, pressure, anatomical deformation, and velocity fields is enabled via multi-modal MRI (3D SPGR for geometry, 2D cine-GRE for area, 2D cine PC-MRI for velocity profiles, and volumetric 4D-flow MRI for full vector fields) (Lan et al., 2022). Contours from cine-GRE enable tracking of area pulsatility, while area-integrated velocity maps yield flow waveforms at designated cross-sections.

Experimental protocols may include inline pressure and flow transducers (e.g., Millar pressure microsensors, ultrasonic flow probes) at circuit inlets and outlets to validate simulated conditions. For device navigation studies, fluoroscopy is used for real-time visual guidance, but quantitative hemodynamic measurement may be omitted, with experimental focus placed on mechanical navigation outcomes rather than flow characterization (Brumfiel et al., 15 Dec 2025).

Measurement Modality	(Brumfiel et al., 15 Dec 2025)	(Lan et al., 2022)
Pressure/Flow Sensing	Not reported	Transducers and flow probes
Imaging	Fluoroscopy	3D/2D MRI, 4D-flow MRI

4. Mathematical and Physical Hemodynamic Modeling

Detailed mathematical models underpin both computational and experimental analyses of pulsatile flow in phantoms. The governing equations for blood flow are the incompressible Navier–Stokes equations for the intraluminal fluid:

$$\rho_f \left(\frac{\partial \mathbf{v}_f}{\partial t} + \mathbf{v}_f \cdot \nabla \mathbf{v}_f \right) = -\nabla p_f + \mu_f \Delta \mathbf{v}_f + \rho_f \mathbf{b}_f$$

and $\nabla \cdot \mathbf{v}_f = 0$, where the velocity $\mathbf{v}_f$, pressure $p_f$, density $\rho_f$, and viscosity $\mu_f$ are defined for the working fluid.

The vessel wall is represented by the linear elasticity equations for infinitesimal strain:

$$\rho_s \frac{\partial \mathbf{v}_s}{\partial t} = \nabla \cdot \sigma_s + \rho_s \mathbf{b}_s, \quad \sigma_s = \mathcal{C} : \epsilon(\mathbf{u}_s)$$

with strains $\epsilon$ and displacements $\mathbf{u}_s$. Fluid-structure interface conditions enforce matching velocities and boundary tractions. Advanced formulations, such as the Reduced Unified Continuum (RUC), leverage membrane and thin-wall assumptions to derive monolithic Eulerian FSI systems with strong kinematic and weak dynamic coupling, validated against deformable wall theory (e.g., Womersley) and yielding computational costs only marginally above rigid-wall CFD (Lan et al., 2022).

Boundary conditions are based on experimental or image-derived velocity, flow, and pressure profiles. Simulation parameters are tuned for quantitative agreement with measured pulse-wave velocities, area pulsatility, and complex vortical flow structures under dynamic load.

5. Integration with Device Testing and Robotic Platforms

Anatomical phantoms with physiologic pulsatile flow provide a critical testbed for preclinical evaluation of endovascular devices and robotic systems. In navigation studies, steerable guidewires such as the COaxially Aligned STeerable (COAST) robot are advanced through tortuous phantom vasculature under clinical imaging modalities. The flow circuit’s back-pressure and geometrical constraints can elicit phenomena such as guidewire buckling, necessitating manual intervention or future modifications to inlet design and tubing lubricity (Brumfiel et al., 15 Dec 2025).

This suggests that integration of compliance-matched phantoms and flow circuits can expose device limitations not apparent in static or non-pulsatile models, informing requirements for robust teleoperation, actuation, and hardware durability. Detailed flow and compliance metrics support computational–experimental synergy for both device validation and model calibration.

6. Limitations, Reporting Gaps, and Research Directions

Significant heterogeneity remains in the reporting of phantom dimensions, material properties, compliance, waveform profiles, and measurement instrumentation. In some studies using commercial or vendor-supplied phantoms, details such as vessel diameters, lengths, branching angles, and wall mechanics are unspecified (Brumfiel et al., 15 Dec 2025), preventing full reproducibility or quantitative model–experiment comparison. By contrast, patient-specific phantoms constructed via 3D printing with validated mechanical properties and explicit prestressing strategies enable rigorous FSI model validation (Lan et al., 2022).

Routine inclusion of inline pressure and flow measurements, thorough calibration, and public dissemination of phantom cad models and specifications would increase transparency and facilitate cross-study comparisons. Integration of advanced MRI or computational monitoring of flow, pressure, deformation, and vortex dynamics provides a framework for simultaneous mechanical and hemodynamic evaluation.

Advances in compliant phantom manufacturing, programmable physiologic waveform generation, and multi-modal imaging will continue to refine the fidelity and utility of anatomical phantom models with pulsatile flow for both device testing and in vitro–in silico validation paradigms.