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ABSTRACT: Some totally occluded intracranial aneurysms may recur. The role of hemodynamic mechanisms in this process remains to be elucidated. The authors used computational fluid dynamic analysis and investigated the local hemodynamic characteristics at the aneurysm neck before and after total embolization, attempting to identify hemodynamic risk factors leading to recurrence of totally embolized aneurysms.
Between May 2008 and June 2010, the authors recruited 17 consecutive patients with totally occluded intracranial aneurysms (7 recanalized and 10 stable lesions). Using patient-specific 3D digital subtraction angiography data, the hemodynamic features before and after embolization were retrospectively characterized.
The overall preembolization blood flow patterns were nearly the same in the recanalized and stable groups, with no significant difference in either the maximum wall shear stress (WSS) (p = 0.914) or the spatially averaged WSS (p = 0.322) at peak systole at the aneurysm neck. After occlusion, the overall flow pattern changed, and the WSS distribution at the treated aneurysm neck differed in the 2 groups. In all of the 7 recanalized cases, both the maximum WSS and spatially averaged WSS at peak systole at the treated aneurysm neck were higher than those at the aneurysm neck before embolization. In contrast, both parameters were decreased in 70%-80% of the stable cases. After embolization, both the maximum WSS (p = 0.021) and spatially averaged WSS (p = 0.041) at peak systole at the treated aneurysm neck were higher in the recanalized group than in the stable group.
Higher WSS at the treated aneurysm neck after total embolization can be an important hemodynamic factor that contributes to aneurysm recurrence after endovascular treatment.
Journal of Neurosurgery 06/2012; 117(2):276-83. · 2.96 Impact Factor
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ABSTRACT: Hemodynamic factors such as the wall shear stress play an important role in the pathogenesis and treatment of cerebral aneurysms.
In present study, we apply computational fluid–structure interaction analyses on cerebral aneurysms with two different constitutive
relations for aneurismal wall in order to investigate the effect of the aneurismal wall mechanical properties on the simulation
results. We carry out these analyses by using two patient-specific models of cerebral aneurysms of different sizes located
in different branches of the circle of Willis. The models are constructed from 3D rotational angiography image data and blood
flow dynamics is studied under physiologically representative waveform of inflow. From the patient models analyzed in this
investigation, we find that the deformations of cerebral aneurysms are very small. But due to the nonlinear character of the
Navier–Stokes equations, these small deformations could have significant influences on the flow characteristics. In addition,
we find that the aneurismal-wall mechanical properties have great effects on the deformation distribution of the aneurysm,
which also affects the wall shear stress distribution and flow patterns. Therefore, how to define a proper constitutive relation
for aneurismal wall should be considered carefully in the hemodynamic simulation.
Acta Mechanica Sinica 04/2012; 25(5):677-688. · 0.86 Impact Factor
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ABSTRACT: Intracranial aneurysms with daughter blebs appear to have a higher risk of rupture. Whether hemodynamic factors are involved in this phenomenon is not clear.
54 patient-specific aneurysms harboring 69 daughter blebs were divided into ruptured and unruptured groups based on their clinical history. Realistic models were retrospectively constructed and analyzed by a computational fluid dynamic method.
There were no differences in the aspect ratio and morphology type of the aneurysms, the size of blebs or other common risk factors between the two groups. The wall shear stress (WSS) was significantly lower while the oscillatory shear index (OSI) was higher in the daughter blebs than in the primary aneurysms. Bleb-bearing aneurysms with a rupture history displayed significantly lower WSS in the daughter bleb. Of the daughter blebs, 73.9% were localized to the impingement region of the inflow jet.
These observations indicate that low WSS and high OSI in the daughter blebs might be involved in increasing the risk of rupture. The localized striking force caused by inflow jets may contribute to the development of daughter blebs. However, a precise role of hemodynamics in predicting the future rupture of daughter blebs needs further study.
European Neurology 11/2011; 66(6):359-67. · 1.81 Impact Factor
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Bin Luo,
Xinjian Yang,
Shengzhang Wang, Haiyun Li,
Jialiang Chen,
Hongyu Yu,
Ying Zhang,
Yisen Zhang,
Shiqing Mu,
Zhicheng Liu,
Guanghong Ding
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ABSTRACT: Hemodynamic factors are thought to play an important role in the initiation, growth, and rupture of cerebral aneurysms. However, the hemodynamic features in the residual neck of the partially embolized aneurysms and their influences on recanalization are rarely reported. In this study, we characterized the hemodynamics of partially occluded aneurysms, which were proven to undergo recanalization during follow-up using computational fluid dynamic analysis.
From May 2007 to June 2009, we identified 11 partial aneurysms during follow-up, including 5 recanalized cases and 6 stable cases with 3-dimensional digital subtraction angiography. We retrospectively characterized the hemodynamic features around the residual aneurysmal pouch using the available postprocedural digital subtraction angiography image data. The occluded part of the aneurysm was regarded as completely separated from the circulation.
The overall blood flow patterns before embolization were almost the same in the recanalized and stable groups. After occlusion, the flow pattern changes, wall shear stress (WSS), and velocity at the remnant neck demonstrated different changes between the 2 groups. Specifically, in the recanalized group, high WSS regions were found near the neck in all 5 cases, with 4 of them being even higher than those before occlusion. Interestingly, in all cases, the high WSS area of the remnant neck coincided with the location where the aneurysm recanalization occurred. In the stable group, 5 out of 6 cases demonstrated lower WSS and velocity at the remnant neck after occlusion.
High WSS and blood flow velocity were consistently observed near the remnant neck of partially embolized aneurysms prone to future recanalization, suggesting that hemodynamic factors may have an important role in aneurysmal recurrence after endovascular treatment. The difference in flow pattern could be caused by the incomplete occlusion of the aneurysms.
Stroke 03/2011; 42(3):745-53. · 5.73 Impact Factor
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ABSTRACT: This paper presents a new functional image fusion algorithm which is the combination of SPM and ICA using multi-resolution decomposition. Firstly, we designed the fMRI experiments and obtained the fMRI image data from different experimental conditions. The brain activated regions were extracted by the SPM and ICA methods respectively. Secondly, by constructing the Laplacian pyramids of the source image, a new fusion rule based on the salience and matching measure is proposed in various resolutions. Finally, the fused functional images are reconstructed by the inverse Laplacian pyramid transformation. The results show that the algorithm can retain the details of the source images and pinpoint exactly the brain functional area associated with the hand action, thus outperforming SPM or ICA for functional regions extraction.
Neuroscience Letters 10/2010; 487(1):73-7. · 2.11 Impact Factor
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ABSTRACT: In this paper, a new algorithm based on the active contour model for medical segmentation is presented. The deformable contour in the object is optimized by a different method of minimizing the energy function based on the greedy algorithm, a novel initialization algorithm to locate the initial contour has been developed. A new term for the internal energy and another one for external energy which solve common problems associated with classical active contour model in this type of images have been introduced. The internal energy of the model depends on local behavior of the contour, while the external energy is derived from image wavelet transform modulus maxima features. The algorithm is able to detect convex and concave object, Examples are presented to demonstrate the efficiency of the approach on spinal CT/MRI images and the results are encouraging.
Complex Medical Engineering, 2007. CME 2007. IEEE/ICME International Conference on; 06/2007
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ABSTRACT: We aim to develop a finite element model of human spine of surgical training and planning. A precise three-dimensional geometric model of the intervertebral disc has been first created by segmenting and reconstructing the contour of intervertebral disc in spine CT Images; Then three-dimensional finite element model (FEM) of vertebrae has been established based on the geometric model by setting the parameters of mechanical characteristic and defining the boundary condition; Finally, the stress and strain distribution of lumbar disc segment under different axial compressive loads has been calculated and evaluated. The accuracy of the finite element method model is good based on visual comparison and would be available for analysis to facilitate preoperative planning.
Complex Medical Engineering, 2007. CME 2007. IEEE/ICME International Conference on; 06/2007
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ABSTRACT: In this paper, a biomechanical analysis method for percutaneous vertebroplasty has been presented. Integrating the anatomical structure from the spine CT images of a patient, a novel three-dimensional geometric model of lumbar functional spinal units (FSUs) has been built. Based on the geometric model, two kinds of three-dimensional finite element models (FEM) of L1-L2 segments for preoperative and postoperative vertebrae are created. A numerical calculation method on FEM for biomechanical analysis has been developed, while a boundary condition describing the relative L1-L2 displacement is imposed on the FEM to account for three-dimensional physiological states. The simulating calculation can reveal the stress and strain distribution and deformation of the preoperative and postoperative vertebrae. Our method attempts to provide new biomechanical evidence and a fresh perspective into how the procedure can be implemented more effectively toward the goal of preventing osteoporosis-related fractures. The FEM will provide a promising tool in clinical diagnosis and optimizing individual therapy in osteoporosis-related fractures. It is proved that the method is valid for the consistency of the patient's clinical observation after vertebroplasty with the FEM results in our research.
Complex Medical Engineering, 2007. CME 2007. IEEE/ICME International Conference on; 06/2007
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ABSTRACT: This paper provides a new medical image segmentation algorithm using a deformable contour model, which integrates Fuzzy C-Means(FCM) Clustering technique and deformable contour model. An external fuzzy constrain is defined from the membership function value of FCM, which joins the external constrain of the deformable model and drives the deformable model towards the contour ideal edge of the object. Examples are presented to demonstrate the efficiency and feasibility of the approach on spinal MRI images and the results are encouraging.
Sheng wu yi xue gong cheng xue za zhi = Journal of biomedical engineering = Shengwu yixue gongchengxue zazhi 09/2006; 23(4):717-21.
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ABSTRACT: In order to study the biomechanical mechanism properties of intervertebral disc herniation, combining the CT and MRI data-based anatomical structure of spine. A three-dimensional geometric model of the lumber disk was constructed. Based on the geometric model, a three-dimensional finite element modeling (FEM) for biomechanical analysis has been created. The FEM will represents a promising tool in clinical diagnosis and optimizing individual therapy in the intervertibral disc herniation
Engineering in Medicine and Biology Society, 2005. IEEE-EMBS 2005. 27th Annual International Conference of the; 02/2006
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ABSTRACT: A seepage flow model for medical image segmentation has been presented, which linked to the natural phenomenon of "water seeks its own level". The seepage flow to form the segmented pixel set by submerging all the pixels that are r-connected to the initial spring head pixels and also fall within the submerging threshold limits, the moving water fronts keep adding to the segmented pixel set all the pixels until no more pixels fall within the submerging criterion. Based on Mumford-Shah function. A new merit function for criterion has been produced which possess two main kind of measurement reflecting the characteristic of region and contour respectively. Examples are presented to demonstrate the efficiency the model on clinical images segmentation.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2005; 6:6364-7.
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ABSTRACT: In order to study the biomechanical mechanism properties of intervertebral disc herniation, combining the CT and MRI data-based anatomical structure of spine. A three-dimensional geometric model of the lumber disk was constructed. Based on the geometric model, a three-dimensional finite element modeling (FEM) for biomechanical analysis has been created. The FEM will represents a promising tool in clinical diagnosis and optimizing individual therapy in the intervertibral disc herniation.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2005; 3:3202-5.
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ABSTRACT: In this paper, a 3D geometric model of the intervertebral and lumbar disks has been presented, which integrated the spine CT and MRI data-based anatomical structure. Based on the geometric model, a 3D finite element model of an L1-L2 segment was created. Loads, which simulate the pressure from above were applied to the FEM, while a boundary condition describing the relative L1-L2 displacement is imposed on the FEM to account for 3D physiological states. The simulation calculation illustrates the stress and strain distribution and deformation of the spine. The method has two characteristics compared to previous studies: first, the finite element model of the lumbar are based on the data directly derived from medical images such as CTs and MRIs. Second, the result of analysis will be more accurate than using the data of geometric parameters. The FEM provides a promising tool in clinical diagnosis and for optimizing individual therapy in the intervertebral disc herniation.
Computerized Medical Imaging and Graphics 30(6-7):363-70. · 1.47 Impact Factor
