Computational Modeling with Fluid-Structure Interaction of the Severe M1 Stenosis Before and After Stenting / 신경중재치료의학

PURPOSE: Image-based computational models with fluid-structure interaction (FSI) can be used to perform plaque mechanical analysis in intracranial artery stenosis. We described a process in FSI study applied to symptomatic severe intracranial (M1) stenosis before and after stenting. MATERIALS AND METHODS: Reconstructed 3D angiography in STL format was transferred to Magics for smoothing of vessel surface and trimming of branch vessels and to HyperMesh for generating tetra volume mesh from triangular surface-meshed 3D angiogram. Computational analysis of blood flow in the blood vessels was performed using the commercial finite element software ADINA Ver 8.5. The distribution of wall shear stress (WSS), peak velocity and pressure was analyzed before and after intracranial stenting. RESULTS: The wall shear stress distributions from Computational fluid dynamics (CFD) simulation with rigid wall assumption as well as FSI simulation before and after stenting could be compared. The difference of WSS between rigid wall and compliant wall model both in pre- and post-stent case is only minor except at the stenosis region. These WSS values were greatly reduced after stenting to 15~20 Pa at systole and 3~5 Pa at end-diastole in CFD simulation, which are similar in FSI simulations. CONCLUSION: Our study revealed that FSI simulation before and after intracranial stenting was feasible despite of limited vessel wall dimension and could reveal change of WSS as well as flow velocity and wall pressure.

Computational Fluid Dynamics of Intracranial and Extracranal Arteries using 3-Dimensional Angiography: Technical Considerations with Physician's Point of View / 신경중재치료의학

We investigate the potentials and limitations of computational fluid dynamics (CFD) analysis of patient specific models from 3D angiographies. There are many technical problems in acquisition of proper vascular models, in pre-processing for making 2D surface and 3D volume meshes and also in post-processing steps for display the CFD analysis. We hope that our study could serves as a technical reference to validating other tools and CFD results.

Computational Flow Dynamics of the Severe M1 Stenosis Before and After Stenting / 신경중재치료의학

PURPOSE: Computational flow dynamic (CFD) study has not been widely applied in intracranial artery stenosis due to requirement of high resolution in identifying the small intracranial artery. We described a process in CFD study applied to symptomatic severe intracranial (M1) stenosis before and after stenting. MATERIALS AND METHODS: Reconstructed 3D angiography in STL format was transferred to Magics (Materialise NV, Leuven, Belgium) for smoothing of vessel surface and trimming of branch vessels and to HyperMesh (Altair Engineering Inc., Auckland, New Zealand) for generating tetra volume mesh from triangular surface-meshed 3D angiogram. Computational analysis of blood flow in the blood vessels was performed using the commercial finite element software ADINA Ver 8.5 (ADINA R & D, Inc., Lebanon, MA). The distribution of wall shear stress (WSS), peak velocity and pressure in a patient was analyzed before and after intracranial stenting. RESULTS: Computer simulation of wall shear stress, flow velocity and wall pressure before and after stenting could be demonstrated three dimensionally by video mode according to flow vs. time dimension. Such flow model was well correlated with angiographic finding related to maximum degree of stenosis. Change of WSS, peak velocity and pressure at the severe stenosis was demonstrated before and after stenting. There was no WSS after stenting in case without residual stenosis. CONCLUSION: Our study revealed that CFD analysis before and after intracranial stenting was feasible despite of limited vessel wall dimension and could reveal change of WSS as well as flow velocity and wall pressure.

High Shear Stress at the Surface of Enhancing Plaque in the Systolic Phase is Related to the Symptom Presentation of Severe M1 Stenosis

The computational fluid dynamics methods for the limited flow rate and the small dimensions of an intracranial artery stenosis may help demonstrate the stroke mechanism in intracranial atherosclerosis. We have modeled the high wall shear stress (WSS) in a severe M1 stenosis. The high WSS in the systolic phase of the cardiac cycle was well-correlated with a thick fibrous cap atheroma with enhancement, as was determined using high-resolution plaque imaging techniques in a severe stenosis of the middle cerebral artery.

Computational Flow Dynamics Study in Severe Carotid Bulb Stenosis with Ulceration / 신경중재치료의학

PURPOSE: Computational fluid dynamics (CFD) applications for atherosclerotic carotid stenosis have not been widely used due to limited resolution in the severely stenotic lumen as well as small flow dimension in the stenotic channel. MATERIALS AND METHODS: CT data in DICOM format was transformed into 3 dimensional (3D) CFD model of carotid bifurcation. For computational analysis of blood flow in stenosis, commercial finite element software (ADINA Ver. 8.5) was used. The blood flow was assumed to be laminar, viscous, Newtonian, and incompressible. The distribution of wall shear stress (WSS), peak velocity and pressure across the average systolic and diastolic blood pressures permitted construction of a contour map of the velocity in each cardiac cycle. RESULTS: Computer simulation of WSS, flow velocity and wall pressure could be demonstrated three dimensionally according to flow vs. time dimension. Such flow model was correlated with angiographic finding related to maximum degree of stenosis associated with ulceration. Combination of WSS map and catheter angiogram indicated that the highest WSS corresponded to the most severely stenotic segment at systolic phase, whereas ulceration, which is the weakest point of the plaque, appeared at the downstream side of the carotid bulb stenosis. CONCLUSION: Our preliminary study revealed that 3D CFD analysis in carotid stenosis was feasible from CT angiography source image and could reveal WSS, flow velocity and wall pressure in the severe carotid bulb stenosis with ulceration. Further CFD analysis is warranted to apply such hemodynamic information to the atherosclerotic lesion in the more practical way.