Development and Evaluation of an MRI-Compatible Positive Displacement Pump for Cardiovascular Flow Simulation in a Mock Circulatory Loop

Sammanfattning

This project presents the development and evaluation of a magnetic resonance imaging (MRI)-compatible positive displacement pump designed to replicate aortic flow conditions within a Mock Circulatory Loop (MCL) for future evaluation of mechanical circulatory support (MCS) devices in 4D flow MRI environments. The pump employs a pneumatically actuated membrane mechanism to ensure both physiological pulsatility and MRI compatibility. Pump housing components were manufactured using fused deposition modeling(FDM) 3D printing, while membranes were fabricated via vacuum forming. Three membrane geometries, a hemispherical, a hemiellipsoidal and aparaboloid, were tested under fixed preload (10 mmHg) and increasing afterload pressures (90 – 180 mmHg) at 60 bpm and 14 psi using a hydrostatic setup to determine their relative flow performance. Following geometry selection, a Hybrid MCL (HMCL) was used to evaluate pump performance under varying pneumatic actuation pressures (5, 9, and 14 psi) and heart rates (HRs) (60 and 120 bpm). Flow and pressure signals were recorded and stroke volume (SV)and cardiac output (CO) were calculated. The hemispherical membrane consistently outperformed the others, achieving the highest flow rates, with statistical tests confirming significant differences. At 60 bpm and 9 psi, the pump reached an SV of 94.1 mL/beat and a CO of 5.64L/min, meeting resting physiological targets, with a maximum CO of 6 L/min at 14 psi. At 120 bpm, performance was reduced with a maximum SV of 46.8 mL/beat and a CO of 5.61 L/min. SV measurements across all tests showed low standard deviations. Although the 3D-printed housing enabled rapid prototyping, surface roughness introduced sealing challenges. Vacuum-formed membranes matched the design models and demonstrated sufficient durability. Limitations at higher HRs were attributed to reduced diastolic filling time. Pressure instability in the control system affected SV consistency and prevented continuous operation testing. Nonetheless, the pump successfully generated pulsatile flow under physiological afterload conditions. With improved pressure regulation, refined sealing and design details, and long-term runtime evaluation, this prototype shows strong potential for integration into MRI-compatible platforms for studying cardiovascular flow dynamics.