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Modeling Airflow Using Subject-Specific 4DCT-Based Deformable Volumetric Lung Models.

Ilegbusi OJ, Li Z, Seyfi B, Min Y, Meeks S, Kupelian P, Santhanam AP - Int J Biomed Imaging (2012)

Bottom Line: A flow-structure interaction technique is employed that simultaneously models airflow and lung deformation.The results include the 3D anisotropic lung deformation for known airflow pattern inside the lungs.The effects of anisotropy are also presented on both the spatiotemporal volumetric lung displacement and the regional lung hysteresis.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Materials and Aerospace Engineering, University of Central Florida, Orlando, FL 32816, USA.

ABSTRACT
Lung radiotherapy is greatly benefitted when the tumor motion caused by breathing can be modeled. The aim of this paper is to present the importance of using anisotropic and subject-specific tissue elasticity for simulating the airflow inside the lungs. A computational-fluid-dynamics (CFD) based approach is presented to simulate airflow inside a subject-specific deformable lung for modeling lung tumor motion and the motion of the surrounding tissues during radiotherapy. A flow-structure interaction technique is employed that simultaneously models airflow and lung deformation. The lung is modeled as a poroelastic medium with subject-specific anisotropic poroelastic properties on a geometry, which was reconstructed from four-dimensional computed tomography (4DCT) scan datasets of humans with lung cancer. The results include the 3D anisotropic lung deformation for known airflow pattern inside the lungs. The effects of anisotropy are also presented on both the spatiotemporal volumetric lung displacement and the regional lung hysteresis.

No MeSH data available.


Related in: MedlinePlus

Volume mesh for the multilayer structure.
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Related In: Results  -  Collection


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fig4: Volume mesh for the multilayer structure.

Mentions: The lung airway is like a multilevel branching tree as shown in Figure 2 [11]. Based on this airway structure of the lung, the permeability (K = φR2/8, in which R is the branch radius) should decrease significantly from the main central branches to the tip branches as the branch diameter progressively decreases. Correspondingly, the airflow velocity in the primary central branches is significantly higher than that in the peripheral branches. A relatively fine volume numerical mesh size will therefore be required in the core region to reflect the relatively higher pressure, velocity, and stress gradient there compared to the outer layers. Since proper representation of the grid structure is critical to numerical stability, the multibranching lung structure is approximated within the context of the poroelastic model used here, as a multizone structure shown in Figure 3, that permits application of different grids and, if needed, different property values. It can be seen that the multizone geometry representation is similar to the hyperspherical formulation used for representing the YM values of lung substructures. For instance, a normalized airway branch radius can be converted to permeability values associated with each voxel. This permeability is then allowed to vary from the core (inner shell) to the peripheral layers (outer shell) using the same hyperspherical parameterization. The sectional view of the volume mesh generated is shown in Figure 4. It should be noted that both Figures 3 and 4 represent cut-out views of the lobe in order to visualize the multi zone structure and the numerical grid employed.


Modeling Airflow Using Subject-Specific 4DCT-Based Deformable Volumetric Lung Models.

Ilegbusi OJ, Li Z, Seyfi B, Min Y, Meeks S, Kupelian P, Santhanam AP - Int J Biomed Imaging (2012)

Volume mesh for the multilayer structure.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3539421&req=5

fig4: Volume mesh for the multilayer structure.
Mentions: The lung airway is like a multilevel branching tree as shown in Figure 2 [11]. Based on this airway structure of the lung, the permeability (K = φR2/8, in which R is the branch radius) should decrease significantly from the main central branches to the tip branches as the branch diameter progressively decreases. Correspondingly, the airflow velocity in the primary central branches is significantly higher than that in the peripheral branches. A relatively fine volume numerical mesh size will therefore be required in the core region to reflect the relatively higher pressure, velocity, and stress gradient there compared to the outer layers. Since proper representation of the grid structure is critical to numerical stability, the multibranching lung structure is approximated within the context of the poroelastic model used here, as a multizone structure shown in Figure 3, that permits application of different grids and, if needed, different property values. It can be seen that the multizone geometry representation is similar to the hyperspherical formulation used for representing the YM values of lung substructures. For instance, a normalized airway branch radius can be converted to permeability values associated with each voxel. This permeability is then allowed to vary from the core (inner shell) to the peripheral layers (outer shell) using the same hyperspherical parameterization. The sectional view of the volume mesh generated is shown in Figure 4. It should be noted that both Figures 3 and 4 represent cut-out views of the lobe in order to visualize the multi zone structure and the numerical grid employed.

Bottom Line: A flow-structure interaction technique is employed that simultaneously models airflow and lung deformation.The results include the 3D anisotropic lung deformation for known airflow pattern inside the lungs.The effects of anisotropy are also presented on both the spatiotemporal volumetric lung displacement and the regional lung hysteresis.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Materials and Aerospace Engineering, University of Central Florida, Orlando, FL 32816, USA.

ABSTRACT
Lung radiotherapy is greatly benefitted when the tumor motion caused by breathing can be modeled. The aim of this paper is to present the importance of using anisotropic and subject-specific tissue elasticity for simulating the airflow inside the lungs. A computational-fluid-dynamics (CFD) based approach is presented to simulate airflow inside a subject-specific deformable lung for modeling lung tumor motion and the motion of the surrounding tissues during radiotherapy. A flow-structure interaction technique is employed that simultaneously models airflow and lung deformation. The lung is modeled as a poroelastic medium with subject-specific anisotropic poroelastic properties on a geometry, which was reconstructed from four-dimensional computed tomography (4DCT) scan datasets of humans with lung cancer. The results include the 3D anisotropic lung deformation for known airflow pattern inside the lungs. The effects of anisotropy are also presented on both the spatiotemporal volumetric lung displacement and the regional lung hysteresis.

No MeSH data available.


Related in: MedlinePlus