Analysis and design of a thrombectomy device by using simulation techniques

Purpose: In this work, we present the analysis, design and optimization of one experimental device recently developed in the UK, called the 'GP' Thrombus Aspiration Device (GPTAD). This device has been designed to remove blood clots without the need to make contact with the clot itself thereby potentially reducing the risk of problems such as downstream embolisation. Method: To obtain the minimum pressure necessary to extract the clot and to optimize the device, we have simulated the performance of the GPTAD analysing the resistances, compliances and inertances effects. We model a range of diameters for the GPTAD considering different forces of adhesion of the blood clot to the artery wall, and different lengths of blood clot. In each case we determine the optimum pressure required to extract the blood clot from the artery using the GPTAD, which is attached at its proximal end to a suction pump. Result: We then compare the results of our mathematical modelling to measurements made in laboratory using plastic tube models of arteries of comparable diameter. We use abattoir porcine blood clots that are extracted using the GPTAD. The suction pressures required for such clot extraction in the plastic tube models compare favourably with those predicted by the mathematical modelling. Discussion & Conclusion: We conclude therefore that the mathematical modelling is a useful technique in predicting the performance of the GPTAD and may potentially be used in optimising the design of the device

Analysis and simulation of the adhesion forces between clot and the artery wall for a novel thrombectomy device applied to the Middle Cerebral Artery

A number of Thrombectomy devices using a variety of methods have now been developed to facilitate clot removal. We present research involving one such experimental device recently developed in the UK, called a 'GP' Thrombus Aspiration Device (TAD). This device has the potential to improve the process of extracting thrombosis clots in the cerebral arteries. The development of a simulation model for this device is shown using Bond-Graph formalism applied to modeling and simulating the adhesion forces between the clot and the artery wall. Bond-Graph technique is a visual methodology that adds more transparency to the processes and it has turned out to be remarkably useful as it is a simple, effective method that can be applied to any physical system where there is a power exchange. Such modelling appears to be able to simulate the device under a variety of conditions which may assist in the optimisation of the `GP' TAD device if the novel design features of the device can be effectively incorporated into the model

An investigation of the performance of a new Mechanical thrombectomy device using Bond Graph modelling: application to the extraction of blood clots in the middle cerebral artery

A number of thrombectomy devices using a variety of methods have now been developed to facilitate clot removal. We present research involving one such experimental device recently developed in the UK, called a ‘GP’ Thrombus Aspiration Device (GPTAD). This device has the potential to bring about the extraction of a thrombus. Although the device is at a relatively early stage of development, the results look encouraging. In this work, we present an analysis and modeling of the GPTAD by means of the bond graph technique; it seems to be a highly effective method of simulating the device under a variety of conditions. Such modeling is useful in optimizing the GPTAD and predicting the result of clot extraction. The aim of this simulation model is to obtain the minimum pressure necessary to extract the clot and to verify that both the pressure and the time required to complete the clot extraction are realistic for use in clinical situations, and are consistent with any experimentally obtained data. We therefore consider aspects of rheology and mechanics in our modeling

Thrombectomy aspiration device geometry optimization for removal of blood clots in cerebral vessels

A study involving the removal of blood clots in cerebral vessels by aspiration thrombectomy is presented. A robust design for the distal end geometry of a catheter is obtained that, together with adequate suction conditions, could avoid potential damage in the artery or fragmentation the thrombus. The optimization process of the parameters is undertaken by a Design of Experiments (DOE) that has been prepared based on Robust Design theories. In particular, 27 experiments are run for one factor at 9 levels (catheter geometry) and up to 9 factors at 3 levels. The experiments are formulated with virtual models that are solved with computing tools. Co-simulation between Computer Fluid Dynamics (CFD) and Finite Elements Method (FEM) structural analysis was used to obtain the suction conditions and the behavior of the blood clot during the intervention process. By comparing the results of the 27 experiments, the highest values of the suctioning force are obtained for a hole pattern based catheter design, that also gives the lowest risk for clot damage (based on the stress value obtained). Direct aspiration and designs based on conical catheter distal ends, give less robust solutions (results are not stable when the conditions of the environment change). Our study investigated the distance between the catheter and the clot, and it was noted that if the catheter was far from the clot, the suction generated a vessel narrowing and consequent potential damage. Up to 90 kPa could be applied when suctioning at a maximum distance equal to the diameter of the vessel between the distal end of the catheter and the proximal end of the clot. A maximum suctioning force of 0,514N was achieved without damage to the artery or the clot. This research enables us to determine and use the most representative parameters and geometries to be tested in in-vitro and in-vivo experiments. In this virtual study, hypothesizes are assumed with regard to the material properties, but the robustness of the design process allows to expect similar results in future in-vitro and in-vivo tests

Computational Fluid Dynamics (CFD) Simulation for the Extraction of Blood Clot in Middle Cerebral Artery using ‘GP’ 2 Device

Stroke has become the number three killer disease in Malaysia following heart disease and cancer; with 110 of people dying from it every day. The effects of stroke often lead to life-changing, permanent impairment to the patients such as paralysis, speech and logic sequencing. Hence, recent studies are looking into stroke treatments with minimal after surgical effect to patients. One of the alternatives is using mechanical thrombectomy devices. In this project, the simulation for ‘GP’ 2 device which functions to extract the blood clot in the artery without damaging the arterial wall and causing downstream embolism is presented. The simulation will be carried out using computational fluid dynamics; applying the Volume of Fluid (VOF) model. In grid size selection, it is clear that finer grids results in higher accuracy calculations i.e. better results. However, this is achieved at the cost of prolonged computational time. From grid sensitivity study in identifying the optimum grid size that is fine enough to generate accurate calculations but large enough to avoid extra computational time; the grid size of 0.2mm is used. The design for ‘GP’ 2 Device has to be characterised to identify which of the two proposed designs is efficient for the suction of blood clot for 100% occlusion in the Middle Cerebral Artery. Design for ‘GP’ 2 Model 1 device is better at clot extraction than the Model 2 device because increase in surface area for suction favours same-suction principle rather than vortex creation to break the clot. Theoretically, higher pressure results in faster clot extraction. However, the value of pressure applied shall be observed closely so that no arterial damage is done and it can be applied for clinical tests. For both models, it can be shown that higher pressure extracts blood clot at lower time whereby the fastest clot extraction occurs at time 0.00498s for Model 1, and 0.01211s for Model 2 both at 60 kPa

Modeling of blood clot removal with aspiration Thrombectomy devices

Thrombectomy by aspiration is a highly effective method of accomplishing vessel recanalization. This study aims to obtain a mathematical model that allows the prediction of the dynamic response of a thrombus in response to different suction conditions, in order to avoid potential damage or the breakage of the clot during the interventional procedure. Virtual computing models have been created using Bond-Graph data and mass-spring Multi-Degree of Freedom equations. The model allows the use of tensile and torsion loads that could potentially be generated by the suction pressure together with different catheter geometries. The stress generated in the clot depends on its length and on its stiffness. The results obtained with the mathematical model are validated with a Finite Element Method (FEM) model, shows good agreement in terms of stress and elongation values. The results are consistent with previous Bond Graph models which indicated that the forces needed to extract a blood clot from an artery in in-vitro experiments are within the range used experimentally (~40-90 kPa). Qualitative experiments are undertaken with 3D printed scale prototypes and gelatin. The results are consistent with Computer Fluid Dynamic (CFD) simulations

Blood Clot Simulation Model by Using the Bond-Graph Technique

The World Health Organization estimates that 17 million people die of cardiovascular disease, particularly heart attacks and strokes, every year. Most strokes are caused by a blood clot that occludes an artery in the cerebral circulation and the process concerning the removal of this obstruction involves catheterisation. The fundamental object of the presented study consists in determining and optimizing the necessary simulation model corresponding with the blood clot zone to be implemented jointly with other Mechanical Thrombectomy Device simulation models, which have become more widely used during the last decade. To do so, a multidomain technique is used to better explain the different aspects of the attachment to the artery wall and between the existing platelets, it being possible to obtain the mathematical equations that define the full model. For a better understanding, a consecutive approximation to the definitive model will be presented, analyzing the different problems found during the study. The final presented model considers an elastic characterization of the blood clot composition and the possibility of obtaining a consecutive detachment process from the artery wall. In conclusion, the presented model contains the necessary behaviour laws to be implemented in future blood clot simulation models

Performance of a thrombectomy device for aspiration of thrombus with various sizes based on a computational fluid dynamic modelling

It is important to thoroughly remove the thrombus within the course of aspiration thrombectomy; otherwise, it may lead to further embolization. The performance of the aspiration thrombectomy device with a generic geometry is studied through the computational approach. In order to model the thrombus aspiration, a real left coronary artery is chosen while thrombi with various sizes are located at the bifurcation area of the coronary artery and, depending on the size of the thrombus, it is stretched toward the side branches. The thrombus occupies the artery resembling the blood current obstruction in the coronary vessel similar to the situation that leads to heart attack. It is concluded that the aspiration ability of the thrombectomy device is not linked to the thrombus size; it is rather linked to the aspiration pressure and thrombus age (organized versus fresh thrombus). However, the aspiration time period correlates to the thrombus size. The minimum applicable aspiration pressure is also investigated in this study

Computational Design of Thrombectomy Device for Blood Clot Removal: A Study on Suction Pressure and Clot Hardness

According to World Health Organization (WHO), in 2008, an estimated 17.3million people died from Cardiovascular Disease, representing 30% of all global death. About 6.2 million of it was due to stroke. In Malaysia, stroke becomes the third killer after heart disease and cancer with an average 110 people dying of it every day. Stroke occurs because of the interruption of blood supply to the brain due to the blood clot formation in blood vessel and to be specific, the artery in the crane. There are several techniques that have been developed to overcome the problem and one of the techniques developed was "GP" Mechanical Thrombectomy Device(GPMTD).The concept used by the device is to remove the blood clot from the artery. This device was mechanically proven suitable for soft clot while in acute cerebrovascular stroke, the whole blood clot is firm and hard. This shows that the clot is formed at di:ffi:rent hardness. Besides, from the literature review, the clot can be removed by applying suction pressure within the range of 40kPa to 60kPa. Therefore; Navier Stokes equation will be used in ANSYS FLUENT simulation software which is Fluent 6.3.26 to simulate the blood clot extraction from the blood artery with different hardness of blood clot and under different suction pressure. By performing the simulation, the e:ffi:ct of suction pressure and clot hardness on blood clot removal process can be studied. By this understanding, it will help to increase the effectiveness of the blood clot removal system

Computational Fluid Dynamics (CFD) Simulation for the Extraction of Blood Clot in Middle Cerebral Artery using ‘GP’ 2 Device

Stroke has become the number three killer disease in Malaysia following heart disease and cancer; with 110 of people dying from it every day. The effects of stroke often lead to life-changing, permanent impairment to the patients such as paralysis, speech and logic sequencing. Hence, recent studies are looking into stroke treatments with minimal after surgical effect to patients. One of the alternatives is using mechanical thrombectomy devices. In this project, the simulation for ‘GP’ 2 device which functions to extract the blood clot in the artery without damaging the arterial wall and causing downstream embolism is presented. The simulation will be carried out using computational fluid dynamics; applying the Volume of Fluid (VOF) model. In grid size selection, it is clear that finer grids results in higher accuracy calculations i.e. better results. However, this is achieved at the cost of prolonged computational time. From grid sensitivity study in identifying the optimum grid size that is fine enough to generate accurate calculations but large enough to avoid extra computational time; the grid size of 0.2mm is used. The design for ‘GP’ 2 Device has to be characterised to identify which of the two proposed designs is efficient for the suction of blood clot for 100% occlusion in the Middle Cerebral Artery. Design for ‘GP’ 2 Model 1 device is better at clot extraction than the Model 2 device because increase in surface area for suction favours same-suction principle rather than vortex creation to break the clot. Theoretically, higher pressure results in faster clot extraction. However, the value of pressure applied shall be observed closely so that no arterial damage is done and it can be applied for clinical tests. For both models, it can be shown that higher pressure extracts blood clot at lower time whereby the fastest clot extraction occurs at time 0.00498s for Model 1, and 0.01211s for Model 2 both at 60 kPa