Benchtop model for in vitro verification and validation of blood velocity monitoring devices

Objective: Emerging wearable and implantable blood flow monitoring technologies offer a promising alternative to traditional Doppler ultrasound surveillance following peripheral bypass surgery. However, these novel tools require rigorous, physiologically relevant preclinical validation. This study aimed to develop a reproducible, anatomically accurate benchtop model capable of simulating peripheral vascular hemodynamics and supporting in vitro testing of blood velocity monitoring devices. Methods: Four three-dimensional-printed vascular phantoms with 0%, 40%, 65%, and 75% axisymmetric stenoses were designed in SolidWorks and fabricated using carbon fiber-filled nylon. Each phantom replicated a lower limb bypass graft configuration and was embedded in gelatin to allow ultrasound coupling. Phantoms were incorporated into a closed-loop circuit perfused with Doppler-compatible blood-mimicking fluid. Flow was generated by a peristaltic pump (range, 20-250 mL/min). Real-time hemodynamic parameters, including proximal and distal pressures, were measured using solid-state pressure catheters, and volumetric flow was recorded using a calibrated clamp-on flow probe. Imaging assessments included computed tomography, digital subtraction angiography, and Doppler ultrasound. Doppler-derived velocities were compared against flow-probe-based pressure gradients at varying degrees of stenosis and flow rates. Results: All four phantom models were successfully printed and embedded without structural distortion. Computed tomography and digital subtraction angiography confirmed anatomic accuracy and patency of all phantoms. The blood-mimicking fluid demonstrated stable acoustic properties, and gelatin embedding allowed high-resolution Doppler signal acquisition. Pressure and flow data showed increasing resistance and pressure gradients with escalating stenosis severity, validating the physiological behavior of the system. Specifically, average resistance increased from 0.07 mmHg·min/L in the 0% stenosis model to 3.97 mmHg·min/L in the 75% stenosis model. Doppler ultrasound imaging yielded consistent and reproducible velocity measurements across flow conditions. However, Doppler-derived velocities systematically underestimated probe-derived values by approximately 20% (±9%). Despite this, Doppler trends correlated well with pressure-based estimates, particularly in models with lower degrees of stenosis. Conclusions: We developed a robust, cost-effective benchtop platform integrating three-dimensional-printed vascular phantoms, blood-mimicking fluid, and multimodal imaging, capable of replicating peripheral hemodynamic conditions. The model allows quantifiable assessment of blood velocity and pressure gradients across various stenosis severities. Its anatomical fidelity, compatibility with standard ultrasound imaging, and tunable flow conditions make it well-suited for early-stage testing and validation of novel blood flow monitoring devices. This system may also serve as a research and training tool, bridging the gap between device development and in vivo evaluation in vascular surgery.