Development of a Method to Construct Three-Dimensional Finite Element Models of Thoracic Aortic Aneurysms from MRI Images
Graduate Sch. of Eng., Tohoku Univ., Sendai
DOI: 10.1109/MIAR.2001.930275 Conference: Medical Imaging and Augmented Reality: First International Workshop, MIAR 2001, Hong Kong, China, June 10-12, 2001. Proceedings
Most patients die when thoracic aortic aneurysms rupture. In order
to avoid the ruptures, the aneurysms are replaced with aortic prostheses
when their maximum diameter exceeds 5 cm. Because this criterion is
based on the experiences, some aneurysms rupture even if the diameters
are smaller than this criterion. To treat the aneurysm properly, it is
necessary to find out the new criterion. The rupture is thought to have
a close relationship with the stress in the wall. Hence, there is much
research about the stress, but this research uses the straight tube
model. The model shape does not seem appropriate to a thoracic aorta
shape. Hence, we developed the method to construct three-dimensional
finite element models of thoracic aortic aneurysms from MRI images
Available from: Alessandro Borghi
- "The reconstruction of arterial structures involves the use of sets of clinical data (MRI or CT, in general) that are processed to extract the vessel morphology. While the segmentation of the arterial lumen is a well established technique and has been performed with different modalities in living subjects [7-10], the segmentation of the wall and its connective components is still a challenge due to the low contrast between the wall and the surrounding tissues . The extraction of wall information has been attempted for the carotid and coronary arteries, using ex vivo imaging data [12-15]. "
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ABSTRACT: The thoracic aortic aneurysm (TAA) is a pathology that involves an expansion of the aortic diameter in the thoracic aorta, leading to risk of rupture. Recent studies have suggested that internal wall stress, which is affected by TAA geometry and the presence or absence of thrombus, is a more reliable predictor of rupture than the maximum diameter, the current clinical criterion. Accurate reconstruction of TAA geometry is a crucial step in patient-specific stress calculations.
In this work, a novel methodology was developed, which combines data from several sets of magnetic resonance (MR) images with different levels of detail and different resolutions. Two sets of images were employed to create the final model, which has the highest level of detail for each component of the aneurysm (lumen, thrombus, and wall). A reference model was built by using a single set of images for comparison. This approach was applied to two patient-specific TAAs in the descending thoracic aorta.
The results of finite element simulations showed differences in stress pattern between the coarse and fine models: higher stress values were found with the coarse model and the differences in predicted maximum wall stress were 30% for patient A and 11% for patient B.
This paper presents a new approach to the reconstruction of an aneurysm model based on the use of several sets of MR images. This enables more accurate representation of not only the lumen but also the wall surface of a TAA taking account of intraluminal thrombus.
BioMedical Engineering OnLine 02/2006; 5(1):59. DOI:10.1186/1475-925X-5-59 · 1.43 Impact Factor
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ABSTRACT: In this study, a newly developed two-equation transitional model was employed for the prediction of blood flow patterns in a thoracic aortic aneurysm (TAA) where the growth and progression are closely linked to low and oscillating wall shear stresses. Laminar–turbulent transition in the dilated vessel can alter the flow structure, shear stress and pressure distribution within the aneurysm. A patient-specific TAA model was reconstructed from magnetic-resonance (MR) images and measured velocity waveform was used as the inflow condition. Laminar flow and a correlation-based transitional version of Menter’s hybrid k − ϵ/k − ω Shear Stress Transport (SST Tran) model were implemented in pulsatile simulations from which WSS distribution was obtained throughout a cardiac cycle and velocity profiles were compared with MR measurements. The correlation-based transitional model was found to produce results in closer agreement with the MR data than the laminar flow simulation.
Computers & Structures 06/2009; 87(11-12-87):680-690. DOI:10.1016/j.compstruc.2008.09.007 · 2.13 Impact Factor
Available from: Jonathan Pieter Vande Geest
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ABSTRACT: An aneurysm is a gradual and progressive ballooning of a blood vessel due to wall degeneration. Rupture of abdominal aortic aneurysm (AAA) constitutes a significant portion of deaths in the US. In this study, we describe a technique to reconstruct AAA geometry from CT images in an inexpensive and streamlined fashion. A 3D reconstruction technique was implemented with a GUI interface in MATLAB using the active contours technique. The lumen and the thrombus of the AAA were segmented individually in two separate protocols and were then joined together into a hybrid surface. This surface was then used to obtain the aortic wall. This method can deal with very poor contrast images where the aortic wall is indistinguishable from the surrounding features. Data obtained from the segmentation of image sets were smoothed in 3D using a Support Vector Machine technique. The segmentation method presented in this paper is inexpensive and has minimal user-dependency in reconstructing AAA geometry (lumen and wall) from patient image sets. The AAA model generated using this segmentation algorithm can be used to study a variety of biomechanical issues remaining in AAA biomechanics including stress estimation, endovascular stent-graft performance, and local drug delivery studies.
Annals of Biomedical Engineering 11/2009; 38(1):164-76. DOI:10.1007/s10439-009-9833-8 · 3.23 Impact Factor
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