Ghost cells as a two-phase blood analog fluid – optical thrombus growth detection using particle image velocimetry

In-vitro thrombosis tests for mechanical circulatory support systems lack standardized ISO guidelines. A major limitation of current approaches is the absence of continuous thrombus monitoring, as terminated experiments at a single time point fail to capture the dynamic nature of thrombus formation. However, spatially resolved thrombus formation and its underlying dynamics are crucial for the optimization of mechanical circulatory support systems. In this study, we present a high-resolution thrombus monitoring approach using particle image velocimetry with a thrombogenic, two-phase blood analog fluid, designated as "ghost blood". Ghost blood consists of plasma and ghost cells, which are hemoglobin-depleted erythrocytes. We validate and quantify the particle image velocimetry with ghost blood and used this combination to monitor thrombus growth. The validation demonstrated velocity fields in the FDA-pump are consistent with existing literature, confirming the usability of ghost blood in particle image velocimetry. The use range of ghost blood is quantified as a formula to determine the maximum possible optical penetration depth. Finally, thrombus growth was successfully monitored in the FDA-pump. In this proof of principle study, we grew a thrombus in the FDA-pump and were able to monitor its growth from a first thrombus thread to a complete obstruction of the flow. This approach enabling both the localization and the temporal growth of the thrombus to be visualized and thereby provides a foundation for future advancements in thrombosis assessment and the optimization of mechanical circulatory support systems.