Hemodynamic Analysis of an Adult Vein of Galen Aneurysm Malformation by Use of 3D Image-Based Computational Fluid Dynamics
Tamer Hassana,
Eugene V. Timofeevc,e,
Masayuki Ezuraa,b,
Tsutomu Saitoc,
Akira Takahashia,
Kazuyoshi Takayamac and
Takashi Yoshimotod
a Department of Neuroendovascular Therapy, Tohoku University Graduate School of Medicine
b Khonan Hospital, Institute of Fluid Science
c Shock Wave Research Center, Institute of Fluid Science
d Department of Neurosurgery, Tohoku University, Sendai, Japan
e Ioffe Physico-Technical Institute, Russian Academy of Sciences, St. Petersburg, Russia
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FIG 1. Left vertebral angiography (arterial phase, lateral view) showing VGAM supplied from medial posterior choroidal artery and drained to an old embryonic falcine sinus (A). Panel B (internal carotid angiogram [venous phase, lateral view]) shows the venous drainage pattern of the patient after endovascular aneurysm embolization. Normal drainage of the internal cerebral vein (black arrow) to the median prosencephalic vein and then into the accessory embryonic falcine sinus (white arrow) is evident. Rotational 3D digital subtraction angiography with volume rendering, anteroposterior (C) and lateral (D) views, show the feeding artery from MPChA, MPChA aneurysm, and preaneurysmal stenosis. Greatly dilated old embryonic median prosencephalic vein and an associated hypoplastic left posterior cerebral artery are also clearly seen.
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FIG 2. Detailed procedure of image reconstruction.
A, Reformatting protocol of the angiographic image into 460 secondary DICOM sections in 10-cm DFOV.
B, Examples of the sequential secondary DICOM sections including sections of the two aneurysms and most distal part of MPChA.
C, Raster gray scale 3D binary image output by (X) MedCon to AVS/Express. Note that the columns around the image are the patient’s data and image parameters. Under AVS/Express, image manipulation and cutting out of the region of interest is done as shown in panel D. The figure in panel D is the STL file output from AVS/Express to ICEM CFD. Panel E demonstrates the STL file in its mesh form in ICEM CFD. Finally, mesh reconstruction, smoothing, and closure of the inlet and outlet are done by using the mesh generator ICEM CFD before volume mesh generation and CFD calculation with Fluent on the tetrahedral mesh illustrated in panel F.
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FIG 3. A, Left vertebral angiography (left oblique view; arterial phase), revealing the linear contrast stream through the hole between the two aneurysms. B, Computational grid representing the VGAM provides an endoscopic view (the front wall of the arterial aneurysm is removed) demonstrating the hole between the two aneurysms. C, One movie frame of typical instant streamlines colored according to the velocity values (in m/s). Compare the linear stream entering the venous aneurysm with its angiographic representation in the upper image.
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FIG 4. Relative surface pressure maps (left images; in mm Hg) for both aneurysms and MPChA at different time moments of one cardiac cycle show marked pressure variations in the arterial aneurysm caused by the jet coming from the parent artery stenosis. High-pressure areas all over the cardiac cycle are seen opposite of the stenotic artery entry hole. Central and right images demonstrate the blood velocity (magnitude; in m/s) maps in two cross sections and outflow boundary.
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