Development of experimental and numerical models of platelet deposition

• Applicant: Dr.-Ing. Ulrich Kertzscher
• Subject Area: Fluid Mechanics ; Medical Physics, Biomedical Technology
• Term: from 2014 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 257850537

The objective of this project is a better understanding of the role of platelet deposition as the beginning of thrombus formation. The formation of thrombi poses a great problem in cardiovascular diseases. The formation of thrombi does not only occur in naturally existing blood vessels but also in implants such as vascular implants, stents, heart valves, and cardiac support devices. This threatens the health of the corresponding patient. Two model flows will be used for the experimental investigation of the platelet deposition; the plane Couette flow and the stagnation point flow. Corresponding numerical models will be developed. The following objective shall be achieved: the development of a numerical model that is based on experimental data which can be used by an engineer to estimate the thrombogenicity of an implant allowing for an optimization in this regard. Recent publications in international literature demonstrate that the fluid flow itself is considered current and important for the platelet deposition and formation of thrombi. Numerical models are presented but there is a lack of experimental results. The hypothesis states, that the numerical model can closely simulate the results of the experimental models of complex flows. The applied numerical model is based on a Monte Carlo method. It includes a CFD-generated velocity field with a superimposed diffusion motion of the platelets. Therefore, problems with convergence as found in continuum models can be avoided and the amount of model parameters is limited. This can be experimentally validated. The problem shall be investigated based on Virchow's triad. According to Virchow, three parameters such as blood properties, wall properties, and fluid flow define the formation of a thrombus, which begins with the deposition of platelets. The experimental models are chosen such that blood properties, wall properties, and fluid flow can be separately investigated with regards to thrombogenicity. Fluorescence microscopy is used to measure the motion and deposition of platelets from human whole blood for the experimental models. The generated series of images can be evaluated with current methods of image processing. The numerical model simulates transport processes that move the platelets towards the artificial surface with which they can interact. The interaction between platelet and wall - the deposition - is considered a stochastic process, which is based on individual probabilities that result in a deposition likelihood if multiplied with each other. The latter ones are similar to the commonly used reaction rate. The likelihood of deposition is a quantifiable measure and can be experimentally estimated, dependent on platelet activation, wall property, and fluid flow.

• DFG Programme: Research Grants
• Participating Persons: Professor Dr.-Ing. Klaus Affeld (†); Privatdozent Dr. Christoph Sucker