Thanapong Chaichana

Computation of hemodynamics in the left coronary artery with variable angulations

The purpose of this study was to investigate the hemodynamic effect of variations in the angulations of the left coronary artery, based on simulated and realistic coronary artery models. Twelve models consisting of four realistic and eight simulated coronary artery geometries were generated with the inclusion of left main stem, left anterior descending and left circumflex branches. The simulated models included various coronary artery angulations, namely, 15°, 30°, 45°, 60°, 75°, 90°, 105° and 120°. The realistic coronary angulations were based on selected patients data with angles ranging from narrow angles of 58° and 73° to wide angles of 110° and 120°. Computational fluid dynamics analysis was performed to simulate realistic physiological conditions that reflect the in vivo cardiac hemodynamics. The wall shear stress, wall shear stress gradient, velocity flow patterns and wall pressure were measured in simulated and realistic models during the cardiac cycle. Our results showed that a disturbed flow pattern was observed in models with wider angulations, and wall pressure was found to reduce when the flow changed from the left main stem to the bifurcated regions, based on simulated and realistic models. A low wall shear stress gradient was demonstrated at left bifurcations with wide angles. There is a direct correlation between coronary angulations and subsequent hemodynamic changes, based on realistic and simulated models. Further studies based on patients with different severities of coronary artery disease are required to verify our results.

Computational fluid dynamics analysis of the effect of plaques in the left coronary artery

This study was to investigate the hemodynamic effect of simulated plaques in left coronary artery models, which were generated from a sample patients data. Plaques were simulated and placed at the left main stem and the left anterior descending (LAD) to produce at least 60% coronary stenosis. Computational fluid dynamics analysis was performed to simulate realistic physiological conditions that reflect the in vivo cardiac hemodynamics, and comparison of wall shear stress (WSS) between Newtonian and non-Newtonian fluid models was performed. The pressure gradient (PSG) and flow velocities in the left coronary artery were measured and compared in the left coronary models with and without presence of plaques during cardiac cycle. Our results showed that the highest PSG was observed in stenotic regions caused by the plaques. Low flow velocity areas were found at postplaque locations in the left circumflex, LAD, and bifurcation. WSS at the stenotic locations was similar between the non-Newtonian and Newtonian models although some more details were observed with non-Newtonian model. There is a direct correlation between coronary plaques and subsequent hemodynamic changes, based on the simulation of plaques in the realistic coronary models.

Impact of plaques in the left coronary artery on wall shear stress and pressure gradient in coronary side branches

In this study, we investigate plaques located at the left coronary bifurcation. We focus on the effect that the resulting changes in wall shear stress (WSS) and wall pressure stress gradient (WPSG) have on atherosclerotic progress in coronary artery disease. Coronary plaques were simulated and placed at the left main stem and the left anterior descending to produce >50% narrowing of the coronary lumen. Computational fluid dynamics analysis was carried out, simulating realistic physiological conditions that show the in vivo cardiac haemodynamic. WSS and WPSG in the left coronary artery were calculated and compared in the left coronary models, with and without the presence of plaques during cardiac cycles. Our results showed that WSS decreased while WPSG was increased in coronary side branches due to the presence of plaques. There is a direct correlation between coronary plaques and subsequent WSS and WPSG variations based on the bifurcation plaques simulated in the realistic coronary models.

Haemodynamic analysis of the effect of different types of plaques in the left coronary artery

PURPOSE Coronary plaque has been shown to directly affect the blood parameters, however, haemodynamic variations based on the plaque configuration has not been studied. In this study we investigate the haemodynamic effects of various types of plaques in the left coronary bifurcation. METHODS Eight types of plaque configurations were simulated and located in various positions in the left main stem, the left anterior descending and left circumflex to produce a >50% narrowing of the coronary lumen. We analyse and characterise haemodynamic effects caused by each type of plaque. Computational fluid dynamics was performed to simulate realistic physiological conditions that reveal the in vivo cardiac haemodynamics. Velocity, wall shear stress (WSS) and pressure gradient (PSG) in the left coronary artery were calculated and compared in all plaque configurations during cardiac cycles. RESULTS Our results showed that the highest velocity and PSG were found in the type of plaque configuration which involved all of the three left coronary branches. Plaques located in the left circumflex branch resulted in highly significant changes of the velocity, WSS and PSG (p<0.001) when compared to the other types of plaque configurations. CONCLUSION Our analysis provides an insight into the distribution of plaque at the left bifurcation, and corresponding haemodynamic effects, thus, improving our understanding of atherosclerosis.

Analysis on intra-aneurysmal flow influence by stenting

This Using numerical simulation, the evolution of vortices in an aneurysm can be tracked. We examined large-scale swirling of blood within a significantly dilated aneurysm and quantified the pressure gradient and shear strain rate. Based on these fluid mechanical parameters, we are able to identify the difference in flow effects between the untreated and stented aneurysmal arteries. This study demosntrates that the large-scale vortex, pressure gradient and blood shear strain rate within an aneurysm sac reduces after stenting.

Acclerate a Dlt Motion Capture System With Quad-Tree Searching Scheme

This paper describes a 3D motion capture system to generate a skeleton model representing the human body. The system consists of a number of digital cameras placed at arbitrary position around the subject. The subjects joints to be measured are attached with illuminated landmarks. The 3D dynamic information of these landmarks is then detected using the direct linear transform (DLT) technique. In order to establish corresponding point of the landmarks across individual camera as required in the DLT procedure, the quad-tree searching scheme has been adopted which can speed up the dynamic 3D modelling process of up to 70 percent. The 3D motion capture system has been performed to visualize the motion of various subjects. The result is very promising

Plaque Formation at the Left Coronary Artery: Analysis of the Relationship Between Arterial Angulations and Hemodynamics

We investigate the relationship between coronary angulations and their hemodynamic effect. Six left coronary models were generated based on the anatomical details of patient specific data. Varying angles at 90°, 75°, 60°, 45°, 30° and 15° between the left anterior descending and the left circumflex branches are simulated. Numerical simulation is used to analyse flow velocity, wall pressure and wall shear stress under normal physiological conditions of human body in different cardiac cycles. Our results showed that the wall shear stress was significantly decreased in models of higher angulations. In contrast, high wall pressure occurred at coronary bifurcation regions with those models. Our preliminary study demonstrates that there is direct relationship between angulations at the left coronary artery and development of atherosclerosis.