| 1. |
- Dabbaghchian, Saeed, et al.
(författare)
-
Reconstruction of vocal tract geometries from biomechanical simulations
- 2018
-
Ingår i: International Journal for Numerical Methods in Biomedical Engineering. - : John Wiley & Sons. - 2040-7939 .- 2040-7947.
-
Tidskriftsartikel (refereegranskat)abstract
- Medical imaging techniques are usually utilized to acquire the vocal tract geometry in 3D, which may then be used, eg, for acoustic/fluid simulation. As an alternative, such a geometry may also be acquired from a biomechanical simulation, which allows to alter the anatomy and/or articulation to study a variety of configurations. In a biomechanical model, each physical structure is described by its geometry and its properties (such as mass, stiffness, and muscles). In such a model, the vocal tract itself does not have an explicit representation, since it is a cavity rather than a physical structure. Instead, its geometry is defined implicitly by all the structures surrounding the cavity, and such an implicit representation may not be suitable for visualization or for acoustic/fluid simulation. In this work, we propose a method to reconstruct the vocal tract geometry at each time step during the biomechanical simulation. Complexity of the problem, which arises from model alignment artifacts, is addressed by the proposed method. In addition to the main cavity, other small cavities, including the piriform fossa, the sublingual cavity, and the interdental space, can be reconstructed. These cavities may appear or disappear by the position of the larynx, the mandible, and the tongue. To illustrate our method, various static and temporal geometries of the vocal tract are reconstructed and visualized. As a proof of concept, the reconstructed geometries of three cardinal vowels are further used in an acoustic simulation, and the corresponding transfer functions are derived.
|
|
| 2. |
- Funke, Simon Wolfgang, et al.
(författare)
-
Variational data assimilation for transient blood flow simulations: Cerebral aneurysms as an illustrative example
- 2019
-
Ingår i: International Journal for Numerical Methods in Biomedical Engineering. - : Wiley. - 2040-7939 .- 2040-7947. ; 35:1
-
Tidskriftsartikel (refereegranskat)abstract
- Several cardiovascular diseases are caused from localised abnormal blood flow such as in the case of stenosis or aneurysms. Prevailing theories propose that the development is caused by abnormal wall shear stress in focused areas. Computational fluid mechanics have arisen as a promising tool for a more precise and quantitative analysis, in particular because the anatomy is often readily available even by standard imaging techniques such as magnetic resonance and computed tomography angiography. However, computational fluid mechanics rely on accurate initial and boundary conditions, which are difficult to obtain. In this paper, we address the problem of recovering high-resolution information from noisy and low-resolution physical measurements of blood flow (for example, from phase-contrast magnetic resonance imaging [PC-MRI]) using variational data assimilation based on a transient Navier-Stokes model. Numerical experiments are performed in both 3D (2D space and time) and 4D (3D space and time) and with pulsatile flow relevant for physiological flow in cerebral aneurysms. The results demonstrate that, with suitable regularisation, the model accurately reconstructs flow, even in the presence of significant noise.
|
|
| 3. |
- Jansson, Johan, et al.
(författare)
-
Adaptive unified continuum FEM modeling of a 3D FSI benchmark problem
- 2017
-
Ingår i: International Journal for Numerical Methods in Biomedical Engineering. - : Wiley-Blackwell. - 2040-7939 .- 2040-7947. ; 33:9
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we address a 3D fluid-structure interaction benchmark problem that represents important characteristics of biomedical modeling. We present a goal-oriented adaptive finite element methodology for incompressible fluid-structure interaction based on a streamline diffusion–type stabilization of the balance equations for mass and momentum for the entire continuum in the domain, which is implemented in the Unicorn/FEniCS software framework. A phase marker function and its corresponding transport equation are introduced to select the constitutive law, where the mesh tracks the discontinuous fluid-structure interface. This results in a unified simulation method for fluids and structures. We present detailed results for the benchmark problem compared with experiments, together with a mesh convergence study.
|
|
| 4. |
- Petras, Argyrios, et al.
(författare)
-
A computational model of open-irrigated radiofrequency catheter ablation accounting for mechanical properties of the cardiac tissue
- 2019
-
Ingår i: International Journal for Numerical Methods in Biomedical Engineering. - : Wiley. - 2040-7939 .- 2040-7947. ; 35:11
-
Tidskriftsartikel (refereegranskat)abstract
- Radiofrequency catheter ablation (RFCA) is an effective treatment for cardiac arrhythmias. Although generally safe, it is not completely exempt from the risk of complications. The great flexibility of computational models can be a major asset in optimizing interventional strategies if they can produce sufficiently precise estimations of the generated lesion for a given ablation protocol. This requires an accurate description of the catheter tip and the cardiac tissue. In particular, the deformation of the tissue under the catheter pressure during the ablation is an important aspect that is overlooked in the existing literature, which resorts to a sharp insertion of the catheter into an undeformed geometry. As the lesion size depends on the power dissipated in the tissue and the latter depends on the percentage of the electrode surface in contact with the tissue itself, the sharp insertion geometry has the tendency to overestimate the lesion obtained, which is a consequence of the tissue temperature rise overestimation. In this paper, we introduce a full 3D computational model that takes into account the tissue elasticity and is able to capture tissue deformation and realistic power dissipation in the tissue. Numerical results in FEniCS-HPC are provided to validate the model against experimental data and to compare the lesions obtained with the new model and with the classical ones featuring a sharp electrode insertion in the tissue.
|
|
| 5. |
- Sharifimajd, Babak, et al.
(författare)
-
Identification of the mechanical parameters for the human uterus in vivo using intrauterine pressure measurements
- 2017
-
Ingår i: International Journal for Numerical Methods in Biomedical Engineering. - : John Wiley & Sons. - 2040-7939 .- 2040-7947. ; 33:1, s. 1-11
-
Tidskriftsartikel (refereegranskat)abstract
- There are limited experimental data to characterize the mechanical response of human myometrium. A method is presented in this work to identify mechanical parameters describing the active response of human myometrium from the in vivo intrauterine pressure measurements. A finite element model is developed to compute the intrauterine pressure during labor in response to an increase in the intracellular calcium ion concentration within myometrial smooth muscle cells. The finite element model provides the opportunity to tune mechanical parameters in order to fit the computed intrauterine pressure to in vivo measurements. Since the model is computationally expensive, a cheaper meta-model is generated to approximate the model response. By fitting the meta-model response to the in vivo measurements, the parameters used to determine the active response of human myometrial smooth muscle are identified.
|
|
