Unsteady Hemodynamics in Intracranial Aneurysms With Varying Dome Orientations

2021 ◽  
Vol 143 (6) ◽  
Author(s):  
Abdullah Y. Usmani ◽  
K. Muralidhar
Keyword(s):  
Intracranial Aneurysm ◽  
Three Dimensional ◽  
Parent Artery ◽  
Fluid Loading ◽  
Image Velocimetry ◽  
Flow Reynolds Number ◽  
Fatal Hemorrhage ◽  
Wall Loading ◽  
Spatio Temporal ◽  
Finite Volume Simulation

Abstract Fluid loading within an intracranial aneurysm is difficult to measure but can be related to the shape of the flow passage. The outcome of excessive loading is a fatal hemorrhage, making it necessary for early diagnosis. However, arterial diseases are asymptomatic and clinical assessment is a challenge. A realistic approach to examining the severity of wall loading is from the morphology of the aneurysm itself. Accordingly, this study compares pulsatile flow (Reynolds number Re = 426, Womersley number Wo = 4.7) in three different intracranial aneurysm geometries. Specifically, the spatio-temporal movement of vortices is followed in high aspect ratio aneurysm models whose domes are inclined along with angles of 0, 45, and 90 deg relative to the plane of the parent artery. The study is based on finite volume simulation of unsteady three-dimensional flow while a limited set of particle image velocimetry experiments have been carried out. Within a pulsatile cycle, an increase in inclination (0–90 deg) is seen to shift the point of impingement from the distal end toward the aneurysmal apex. This change in flow pattern strengthens helicity, drifts vortex cores, enhances spatial displacement of the vortex, and generates skewed Dean's vortices on transverse planes. Patches of wall shear stress and wall pressure shift spatially from the distal end in models of low inclination (0–45 deg) and circumscribe the aneurysmal wall for an inclination angle of 90 deg. Accordingly, it is concluded that high angles of inclination increase rupture risks while lower inclinations are comparatively safe.

scholarly journals Tomographic particle image velocimetry of desert locust wakes: instantaneous volumes combine to reveal hidden vortex elements and rapid wake deformation

2012 ◽  
Vol 9 (77) ◽  
pp. 3378-3386 ◽  
Author(s):  
Richard J. Bomphrey ◽  
Per Henningsson ◽  
Dirk Michaelis ◽  
David Hollis
Keyword(s):  
Particle Image Velocimetry ◽  
High Speed ◽  
Particle Image ◽  
Aerodynamic Force ◽  
Three Dimensional ◽  
Flow Fields ◽  
Diagnostic Methods ◽  
Tomographic Particle Image Velocimetry ◽  
Image Velocimetry ◽  
Spatio Temporal

Aerodynamic structures generated by animals in flight are unstable and complex. Recent progress in quantitative flow visualization has advanced our understanding of animal aerodynamics, but measurements have hitherto been limited to flow velocities at a plane through the wake. We applied an emergent, high-speed, volumetric fluid imaging technique (tomographic particle image velocimetry) to examine segments of the wake of desert locusts, capturing fully three-dimensional instantaneous flow fields. We used those flow fields to characterize the aerodynamic footprint in unprecedented detail and revealed previously unseen wake elements that would have gone undetected by two-dimensional or stereo-imaging technology. Vortex iso-surface topographies show the spatio-temporal signature of aerodynamic force generation manifest in the wake of locusts, and expose the extent to which animal wakes can deform, potentially leading to unreliable calculations of lift and thrust when using conventional diagnostic methods. We discuss implications for experimental design and analysis as volumetric flow imaging becomes more widespread.

scholarly journals Value of Three-Dimensional Digital Subtraction Angiography for Detection and Classification of Intracranial Aneurysm Remnants After Clipping

2021 ◽  
Author(s):  
Serge Marbacher ◽  
Matthias Halter ◽  
Deborah R Vogt ◽  
Jenny C Kienzler ◽  
Christian T J Magyar ◽  
...  
Keyword(s):  
Intracranial Aneurysm ◽  
Digital Subtraction Angiography ◽  
Diagnostic Yield ◽  
Three Dimensional ◽  
P Value ◽  
Digital Subtraction ◽  
Patient Demographics ◽  
Included Patient ◽  
2D And 3D

Abstract BACKGROUND The current gold standard for evaluation of the surgical result after intracranial aneurysm (IA) clipping is two-dimensional (2D) digital subtraction angiography (DSA). While there is growing evidence that postoperative 3D-DSA is superior to 2D-DSA, there is a lack of data on intraoperative comparison. OBJECTIVE To compare the diagnostic yield of detection of IA remnants in intra- and postoperative 3D-DSA, categorize the remnants based on 3D-DSA findings, and examine associations between missed 2D-DSA remnants and IA characteristics. METHODS We evaluated 232 clipped IAs that were examined with intraoperative or postoperative 3D-DSA. Variables analyzed included patient demographics, IA and remnant distinguishing characteristics, and 2D- and 3D-DSA findings. Maximal IA remnant size detected by 3D-DSA was measured using a 3-point scale of 2-mm increments. RESULTS Although 3D-DSA detected all clipped IA remnants, 2D-DSA missed 30.4% (7 of 23) and 38.9% (14 of 36) clipped IA remnants in intraoperative and postoperative imaging, respectively (95% CI: 30 [ 12, 49] %; P-value .023 and 39 [23, 55] %; P-value = <.001), and more often missed grade 1 (< 2 mm) clipped remnants (odds ratio [95% CI]: 4.3 [1.6, 12.7], P-value .005). CONCLUSION Compared with 2D-DSA, 3D-DSA achieves a better diagnostic yield in the evaluation of clipped IA. Our proposed method to grade 3D-DSA remnants proved to be simple and practical. Especially small IA remnants have a high risk to be missed in 2D-DSA. We advocate routine use of either intraoperative or postoperative 3D-DSA as a baseline for lifelong follow-up of clipped IA.

scholarly journals Fish larvae exploit edge vortices along their dorsal and ventral fin folds to propel themselves

2016 ◽  
Vol 13 (116) ◽  
pp. 20160068 ◽  
Author(s):  
Gen Li ◽  
Ulrike K. Müller ◽  
Johan L. van Leeuwen ◽  
Hao Liu
Keyword(s):  
Larval Fish ◽  
Fish Larvae ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Bony Fish ◽  
The Body ◽  
Functional Explanation ◽  
Image Velocimetry ◽  
Median Fins

Larvae of bony fish swim in the intermediate Reynolds number ( Re ) regime, using body- and caudal-fin undulation to propel themselves. They share a median fin fold that transforms into separate median fins as they grow into juveniles. The fin fold was suggested to be an adaption for locomotion in the intermediate Reynolds regime, but its fluid-dynamic role is still enigmatic. Using three-dimensional fluid-dynamic computations, we quantified the swimming trajectory from body-shape changes during cyclic swimming of larval fish. We predicted unsteady vortices around the upper and lower edges of the fin fold, and identified similar vortices around real larvae with particle image velocimetry. We show that thrust contributions on the body peak adjacent to the upper and lower edges of the fin fold where large left–right pressure differences occur in concert with the periodical generation and shedding of edge vortices. The fin fold enhances effective flow separation and drag-based thrust. Along the body, net thrust is generated in multiple zones posterior to the centre of mass. Counterfactual simulations exploring the effect of having a fin fold across a range of Reynolds numbers show that the fin fold helps larvae achieve high swimming speeds, yet requires high power. We conclude that propulsion in larval fish partly relies on unsteady high-intensity vortices along the upper and lower edges of the fin fold, providing a functional explanation for the omnipresence of the fin fold in bony-fish larvae.

Experimental investigation on the momentumless wake using trailing edge blowing

2008 ◽  
Vol 222 (8) ◽  
pp. 1477-1486 ◽  
Author(s):  
Y Wu ◽  
X Zhu ◽  
Z Du
Keyword(s):  
Three Dimensional ◽  
Velocity Profiles ◽  
Axial Fan ◽  
Trailing Edge ◽  
Mean Velocity ◽  
Piv Measurement ◽  
Image Velocimetry ◽  
Velocity Spectra ◽  
Momentumless Wake ◽  
Wake Characteristics

A developed plate stator model with and without trailing edge blowing (TEB) is studied using experimental methods. Wake characteristics of flow over the stator in the three-dimensional wake regimes are studied using hot-wire anemometry (HWA) and particle image velocimetry (PIV) techniques. First, the mean velocity profiles have been measured in the wake of the stator using HWA. Four wake characteristics have been obtained through momentum thickness judgments: pure wake, weak wake, momentumless wake, and jet. These velocity profiles show some differences in momentum deficit for the four cases. Then, the velocity spectra of the pure wake and momentumless wake obtained through the HWA measurements showed that TEB can eliminate the shedding vortex of the stator. Characteristic length scales based on the wake turbulent intensity profiles showed that the momentumless wake can reduce the wake width and depth. PIV measurement is carried out to measure the flow field of the four wakes. Finally, the application of TEB approaching momentumless wake status is used on an industrial ventilation low-pressure axial fan to assess noise reduction. The results show that TEB can make the outlet of the stator uniform, reduce velocity fluctuation, destroy the vorticity structure downstream of the stator, and reduce interaction noise level of the stator and rotor.

Completely Thrombosed Giant Intracranial Aneurysm with Spontaneous Thrombosis of the Parent Artery: Is It Nature's Divine Intervention and a Self-Cure?

2018 ◽  
Vol 118 ◽  
pp. 132-138 ◽  
Author(s):  
Kuntal Kanti Das ◽  
Gagandeep Singh ◽  
Satyadeo Pandey ◽  
Kamlesh Singh Bhaisora ◽  
Awadhesh Jaiswal ◽  
...  
Keyword(s):  
Intracranial Aneurysm ◽  
Parent Artery ◽  
Spontaneous Thrombosis ◽  
Divine Intervention ◽  
Giant Intracranial Aneurysm

A Method for Measuring Deformation Rates in Hydrogel Structures: Multi-Plane Imaging and Measurement Limitations

2000 ◽  
Author(s):  
Joseph M. Bauer ◽  
David J. Beebe
Keyword(s):  
Cross Sections ◽  
Particle Image ◽  
Three Dimensional ◽  
Local Deformation ◽  
Dimensional Representation ◽  
Volume Changes ◽  
Mechanical Constraints ◽  
Seed Particles ◽  
Three Dimensional Representation ◽  
Image Velocimetry

Abstract A technique for determining the three dimensional motions of hydrogel structures in microchannels is introduced. In developing this technique, we have adapted microscopic particle image velocimetry (μPIV), a method for measuring velocity fields in microfluidic devices. The motions of 1 μm fluorescent seed particles that are incorporated into a hydrogel microstructure (200 μm tall × 400 μm diameter) are tracked over several expansion cycles using microscopy. Combining measurements taken in different planes produces a three-dimensional representation of the motions present during volume changes can be reconstructed. By providing cross sections of the local deformation rates in hydrogel microstructures, this technique allows for the optimization of device designs as well as providing a better understanding of the processes by which hydrogels change volume under mechanical constraints.

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