Determining the Presence of Thin-Walled Regions at High-Pressure Areas in Unruptured Cerebral Aneurysms by Using Computational Fluid Dynamics

Neurosurgery ◽  
2016 ◽  
Vol 79 (4) ◽  
pp. 589-595 ◽  
Author(s):  
Tomoaki Suzuki ◽  
Hiroyuki Takao ◽  
Takashi Suzuki ◽  
Yukinao Kambayashi ◽  
Mitsuyoshi Watanabe ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Pressure ◽  
Dynamic Pressure ◽  
Cerebral Aneurysms ◽  
Maximum Pressure ◽  
Pressure Elevation ◽  
Risk Of Rupture ◽  
Thin Walled ◽  
Unruptured Cerebral Aneurysms

Abstract BACKGROUND Thin-walled regions (TWRs) of cerebral aneurysms are at high risk of rupture, and careful attention should be paid during surgical procedures. Despite this, an optimal imaging technique to estimate TWRs has not been established. Previously, pressure elevation at TWRs was reported with computational fluid dynamics (CFD) but not fully evaluated. OBJECTIVE To investigate the possibility of predicting aneurysmal TWRs at high-pressure areas with CFD. METHODS Fifty unruptured middle cerebral artery aneurysms were analyzed. Spatial and temporal maximum pressure (Pmax) areas were determined with a fluid-flow formula under pulsatile blood flow conditions. Intraoperatively, TWRs of aneurysm domes were identified as reddish areas relative to the healthy normal middle cerebral arteries; 5 neurosurgeons evaluated and divided these regions according to Pmax area and TWR correspondence. Pressure difference (PD) was defined as the degree of pressure elevation on the aneurysmal wall at Pmax and was calculated by subtracting the average pressure from the Pmax and dividing by the dynamic pressure at the aneurysm inlet side for normalization. RESULTS In 41 of the 50 cases (82.0%), the Pmax areas and TWRs corresponded. PD values were significantly higher in the correspondence group than in the noncorrespondence group (P = .008). A receiver-operating characteristic curve demonstrated that PD accurately predicted TWRs at Pmax areas (area under the curve, 0.764; 95% confidence interval, 0.574-0.955; cutoff value, 0.607; sensitivity, 66.7%; specificity, 82.9%). CONCLUSION A high PD may be a key parameter for predicting TWRs in unruptured cerebral aneurysms.

scholarly journals Clear Detection of Thin-Walled Regions in Unruptured Cerebral Aneurysms by Using Computational Fluid Dynamics

2019 ◽  
Vol 121 ◽  
pp. e287-e295 ◽  
Author(s):  
Hidehito Kimura ◽  
Masaaki Taniguchi ◽  
Kosuke Hayashi ◽  
Yosuke Fujimoto ◽  
Youichi Fujita ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Cerebral Aneurysms ◽  
Thin Walled ◽  
Unruptured Cerebral Aneurysms

scholarly journals Prediction of Thin-Walled Areas of Unruptured Cerebral Aneurysms through Comparison of Normalized Hemodynamic Parameters and Intraoperative Images

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Kwang-Chun Cho ◽  
Ji Hun Choi ◽  
Je Hoon Oh ◽  
Yong Bae Kim
Keyword(s):  
Interaction Analysis ◽  
Cerebral Aneurysms ◽  
Weighted Average ◽  
Weighting Factor ◽  
Hemodynamic Parameters ◽  
Color Analysis ◽  
Risk Of Rupture ◽  
Thin Walled ◽  
Unruptured Cerebral Aneurysms ◽  
Normalization Scheme

Object. Rupture of a cerebral aneurysm occurs mainly in a thin-walled area (TWA). Prediction of TWAs would help to assess the risk of rupture and select appropriate treatment strategy. There are several limitations of current prediction techniques for TWAs. To predict TWAs more accurately, HP should be normalized to minimize the influence of analysis conditions, and the effectiveness of normalized, combined hemodynamic parameters (CHPs) should be investigated with help of the quantitative color analysis of intraoperative images. Methods. A total of 21 unruptured cerebral aneurysms in 19 patients were analyzed. A normalized CHP was newly suggested as a weighted average of normalized wall shear stress (WSS) and normalized oscillatory shear index (OSI). Delta E from International Commission on Illumination was used to more objectively quantify color differences in intraoperative images. Results. CFD analysis results indicated that WSS and OSI were more predictive of TWAs than pressure (P<.001, P=.187, P=.970, respectively); these two parameters were selected to define the normalized CHP. The normalized CHP became more statistically significant (P<.001) as the weighting factor of normalized WSS increased and that of normalized OSI decreased. Locations with high CHP values corresponded well to those with high Delta E values (P<.001). Predicted TWAs based on the normalized CHP showed a relatively good agreement with intraoperative images (17 in 21 cases, 81.0%). Conclusion. 100% weighting on the normalized WSS produced the most statistically significant result. The normalization scheme for WSS and OSI suggested in this work was validated using quantitative color analyses, rather than subjective judgments, of intraoperative images, and it might be clinically useful for predicting TWAs of unruptured cerebral aneurysms. The normalization scheme would also be integrated into further fluid-structure interaction analysis for more reliable estimation of the risk of aneurysm rupture.

Investigation of the Circumferential Static Pressure Non-Uniformity Caused by a Centrifugal Compressor Discharge Volute

1998 ◽  
Author(s):  
James M. Sorokes ◽  
Cyril J. Borer ◽  
Jay M. Koch
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Pressure ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
Dynamic Pressure ◽  
Pressure Profile ◽  
Mechanical Vibrations ◽  
Flow Rates ◽  
Dynamics Analyses

The paper describes experimental and computational fluid dynamics analyses of the non-uniform static pressure distortion caused by the discharge volute in a high pressure, centrifugal compressor. The experiments described in this paper were done using a heavily instrumented gas re-injection compressor operating at over 6000 psia discharge. Instrumentation was installed to measure static, total, and dynamic pressure as well as impeller strain and mechanical vibrations. A brief description of the compressor and instrumentation are provided. Concurrent with the experimental work, CFD runs were completed to study the reasons for the pressure non-uniformity. The CFD pressure profile trends agreed well with the experimental results and provided analytical corroboration for the conclusions drawn from the test data. Conclusions are drawn regarding: a) the response of the non-uniformity to changing flow rates; b) the extent to which the non-uniformity can be detected upstream of the impeller; and c) the mechanical influences of the non-uniformity on the impellers.

scholarly journals Morphological and Hemodynamic Changes during Cerebral Aneurysm Growth

2021 ◽  
Vol 11 (4) ◽  
pp. 520
Author(s):  
Emily R. Nordahl ◽  
Susheil Uthamaraj ◽  
Kendall D. Dennis ◽  
Alena Sejkorová ◽  
Aleš Hejčl ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Kinetic Energy ◽  
Swirling Flow ◽  
Morphological Changes ◽  
Cerebral Aneurysms ◽  
Patient Specific ◽  
Aneurysm Wall ◽  
Aneurysm Growth ◽  
Computational Fluid Dynamics Cfd

Computational fluid dynamics (CFD) has grown as a tool to help understand the hemodynamic properties related to the rupture of cerebral aneurysms. Few of these studies deal specifically with aneurysm growth and most only use a single time instance within the aneurysm growth history. The present retrospective study investigated four patient-specific aneurysms, once at initial diagnosis and then at follow-up, to analyze hemodynamic and morphological changes. Aneurysm geometries were segmented via the medical image processing software Mimics. The geometries were meshed and a computational fluid dynamics (CFD) analysis was performed using ANSYS. Results showed that major geometry bulk growth occurred in areas of low wall shear stress (WSS). Wall shape remodeling near neck impingement regions occurred in areas with large gradients of WSS and oscillatory shear index. This study found that growth occurred in areas where low WSS was accompanied by high velocity gradients between the aneurysm wall and large swirling flow structures. A new finding was that all cases showed an increase in kinetic energy from the first time point to the second, and this change in kinetic energy seems correlated to the change in aneurysm volume.

Abstract TMP29: Prediction of Wall-thinning Area in Unruptured Intracerebral Aneurysms by Computational Fluid Dynamics

Stroke ◽  
2013 ◽  
Vol 44 (suppl_1) ◽  
Author(s):  
Yoshifumi Hayashi ◽  
Takanobu Yagi ◽  
Yasutaka Tobe ◽  
Yuki Iwabuchi ◽  
Momoko Yamanashi ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wall Pressure ◽  
Patient Specific ◽  
Unruptured Aneurysms ◽  
Divergent Flow ◽  
Wall Thinning ◽  
Risk Of Rupture ◽  
Angiographic Data ◽  
Intracerebral Aneurysm

[Background and purpose] During a clipping surgery, an unruptured intracerebral aneurysm often presented a spatially-localized red-colored "wall-thinning" area. The wall thinning was believed to be related with the risk of rupture. The present aim is given to investigate the predictability of a wall thinning area using computational fluid dynamics (CFD). [Method] We chose 16 unruptured aneurysms (12 MCA, 4 ICA) with clipping surgery and 24 wall-thinning areas were detected from the operation video. CFD study was carried out using patient-specific angiographic data. The wall shear stress (WSS) and the wall pressure were evaluated. [Results] The WSS magnitude was found to be uncorrelated with wall thinning. On the other hand, 20 wall-thinning areas (83%) exhibited a presence of “flow impingement”, which was defined to give the spatial variation of the WSS vector to be divergent with the local elevation of the wall pressure. From CFD, 27 flow impingements were detected and classified according to the degree of divergence. Seven impingements are full-divergent and all of them (100%) are located in the wall thinning areas. The remaining 20 impingements were partial-divergent and 13 impingements of them (65%) were located in the wall thinning areas. A classification of full-/partial-divergent flow impingement was statistically significant for the prediction of wall-thinning areas (P<0.01). [Conclusions] The full-divergent flow impingement was found to be a reliable predictor of the wall thinning area in unruptured intracerebral aneurysms. The present results demonstrated the malignant nature of flow impingement for promoting the thinning of aneurysmal walls.

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