Abstract WMP34: Multimodal Evaluation of Unruptured Intracranial Aneurysm Wall

Stroke ◽  
2020 ◽  
Vol 51 (Suppl_1) ◽  
Author(s):  
Yukishige Hashimoto ◽  
Kazuhiro Furukawa ◽  
Koji Shimonaga ◽  
Hiroki Takahashi ◽  
Chiaki Ono ◽  
...  
Keyword(s):  
Histopathological Examination ◽  
Three Dimensional ◽  
Fast Spin Echo ◽  
Maximum Diameter ◽  
Patient Specific ◽  
Wall Thickening ◽  
Hemodynamic Parameters ◽  
Aneurysm Wall ◽  
Unruptured Intracranial Aneurysms ◽  
Morphological Variables

Background and Purpose: Recent studies have suggested that MR-vessel wall imaging (VWI) or computational fluid dynamics (CFD) could evaluate aneurysm wall features in unruptured intracranial aneurysms (UIAs). The combination of these modalities might be comprehensive and help better understanding of the pathophysiology of aneurysm wall. This study was performed to disclose the relationship between VWI and hemodynamic characteristics evaluated by CFD. Methods: From April 2017 through May 2019, a total of 36 microsurgically-treated UIAs preoperatively underwent VWI and CFD were reviewed. Three-dimensional T1-weighted fast spin-echo sequences were obtained before and after injection of contrast medium, and aneurysm wall enhancement (AWE) was evaluated. CFD was carried out using patient specific geometry models from three-dimensional CT angiography. Morphological variables, intraoperative inspection and hemodynamic parameters were statistically analyzed between enhanced and nonenhanced wall of UIAs. Fourteen UIAs were available for histopathological examination. Results: In morphological variables, maximum diameter and irregularity were associated with AWE (p=0.02, respectively). AWE lesions corresponded to intraoperatively inspected atherosclerotic lesions of UIAs (sensitivity, 0.90; specificity, 0.79). Among hemodynamic parameters, oscillatory velocity index that suggests the directional changes of the flow velocity was significantly higher in UIAs with AWE (p=0.02). Histopathologic studies revealed that wall thickening accompanied by atherosclerosis, neovascularization, and macrophage infiltration corresponded to AWE lesions, while UIAs without AWE demonstrated various histopathological findings such as myointimal hyperplasia or thinning wall with loss of mural cells and wall degeneration. Conclusions: Pathophysiology of AWE could be explained as atherosclerotic changes with inflammation presumably associated with aberrant flow conditions in irregular UIAs. VWI and CFD are complementarily valuable imaging techniques to understand an aneurysm wall pathophysiology.

Hemodynamic Metrics Correlate With Intracranial Aneurysm Rupture Status Better Than Morphologic Metrics

2010 ◽  
Author(s):  
Jianping Xiang ◽  
Sabareesh K. Natarajan ◽  
Markus Tremmel ◽  
Ding Ma ◽  
J. Mocco ◽  
...  
Keyword(s):  
Prophylactic Treatment ◽  
Aneurysm Rupture ◽  
Patient Specific ◽  
Hemodynamic Parameters ◽  
Unruptured Aneurysms ◽  
3D Angiography ◽  
Unruptured Intracranial Aneurysms ◽  
Complex Shapes ◽  
Computational Fluid Dynamics Cfd ◽  
Better Than

Given the considerable risk of treating unruptured intracranial aneurysms (IAs), as well as the known severe morbidity of aneurysm rupture, elucidating those aneurysms that require prophylactic treatment can be a quandary. Traditionally, decision-making to treat an unruptured aneurysm was largely based on the Size of the aneurysm, but recent studies have failed to show significant correlation of Size with IA rupture, and a large number of ruptured aneurysms are small in Size.[1] Consequently, shape-based morphologic metrics have been explored in current investigations, and complex shapes have been correlated with rupture.[1] With the advancement of 3D angiography, and computational fluid dynamics (CFD) technology, patient-specific hemodynamics analysis has become feasible. Intra-aneurysmal hemodynamic factors, including wall shear stress (WSS), impingement regions, and oscillatory shear index (OSI), have been proposed as indicators for IA rupture risk.[2, 3] No study has rigorously examined both morphology-based and hemodynamics-based parameters from a uniform cohort to compare their relative importance. Our aim, therefore, was to identify significant morphologic and hemodynamic parameters that correlate with an aneurysm’s rupture status and examine whether hemodynamic parameters can separate ruptured and unruptured aneurysms better than morphologic parameters.

scholarly journals A longitudinal comparison of hemodynamics and intraluminal thrombus deposition in abdominal aortic aneurysms

2014 ◽  
Vol 307 (12) ◽  
pp. H1786-H1795 ◽  
Author(s):  
Amirhossein Arzani ◽  
Ga-Young Suh ◽  
Ronald L. Dalman ◽  
Shawn C. Shadden
Keyword(s):  
Spin Echo ◽  
Aortic Aneurysms ◽  
Fast Spin Echo ◽  
Patient Specific ◽  
Black Blood ◽  
Hemodynamic Parameters ◽  
Dynamics Modeling ◽  
Spatially Resolved ◽  
Abdominal Aortic ◽  
Risk Of Rupture

Abdominal aortic aneurysm (AAA) is often accompanied by in traluminal thrombus (ILT), which complicates AAA progression and risk of rupture. Patient-specific computational fluid dynamics modeling of 10 small human AAA was performed to investigate relations between hemodynamics and ILT progression. The patients were imaged using magnetic resonance twice in a 2- to 3-yr interval. Wall content data were obtained by a planar T1-weighted fast spin echo black-blood scan, which enabled quantification of thrombus thickness at midaneurysm location during baseline and followup. Computational simulations with patient-specific geometry and boundary conditions were performed to quantify the hemodynamic parameters of time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and mean exposure time at baseline. Spatially resolved quantifications of the change in ILT thickness were compared with the different hemodynamic parameters. Regions of low OSI had the strongest correlation with ILT growth and demonstrated a statistically significant correlation coefficient. Prominent regions of high OSI (>0.4) and low TAWSS (<1 dyn/cm2) did not appear to coincide with locations of thrombus deposition.

scholarly journals Stagnation and complex flow in ruptured cerebral aneurysms: a possible association with hemostatic pattern

2017 ◽  
Vol 126 (5) ◽  
pp. 1566-1572 ◽  
Author(s):  
Masanori Tsuji ◽  
Tatsuya Ishikawa ◽  
Fujimaro Ishida ◽  
Kazuhiro Furukawa ◽  
Yoichi Miura ◽  
...  
Keyword(s):  
Histopathological Examination ◽  
Cerebral Aneurysms ◽  
Hemodynamic Parameters ◽  
Complex Flow ◽  
Aneurysm Wall ◽  
Flow Stagnation ◽  
3D Ct Angiography ◽  
Computational Fluid Dynamics Cfd ◽  
Hematoxylin And Eosin ◽  
Middle Cerebral Artery Aneurysms

OBJECTHistopathological examination has revealed that ruptured cerebral aneurysms have different hemostatic patterns depending on the location of the clot formation. In this study, the authors investigated whether the hemostatic patterns had specific hemodynamic features using computational fluid dynamics (CFD) analysis.METHODSTwenty-six ruptured middle cerebral artery aneurysms were evaluated by 3D CT angiography and harvested at the time of clipping. The hemostatic patterns at the rupture points were assessed by means of histopathological examination, and morphological parameters were obtained. Transient analysis was performed, and wall shear stress–related hemodynamic parameters and invariant Q (vortex core region) were calculated. The morphological and hemodynamic parameters were compared among the hemostatic patterns.RESULTSHematoxylin and eosin staining of the aneurysm wall showed 13 inside-pattern, 9 outside-pattern, and 4 other-pattern aneurysms. Three of the 26 aneurysms were excluded from further analysis, because their geometry models could not be generated due to low vascular CT values. Mann-Whitney U-tests showed that lower dome volume (0.04 cm3 vs 0.12 cm3, p = 0.014), gradient oscillatory number (0.0234 vs 0.0289, p = 0.023), invariant Q (−0.801 10−2/sec2 vs −0.124 10−2/sec2, p = 0.045) and higher aneurysm formation indicator (0.986 vs 0.963, p = 0.041) were significantly related to inside-pattern aneurysms when compared with outside-pattern aneurysms.CONCLUSIONSInside-pattern aneurysms may have simpler flow patterns and less flow stagnation than outside-pattern aneurysms. CFD may be useful to characterize the hemostatic pattern of ruptured cerebral aneurysms.

Segmentation of aneurysm wall enhancement in evolving unruptured intracranial aneurysms

2021 ◽  
pp. 1-7
Author(s):  
Yukishige Hashimoto ◽  
Toshinori Matsushige ◽  
Reo Kawano ◽  
Koji Shimonaga ◽  
Michitsura Yoshiyama ◽  
...  
Keyword(s):  
Intracranial Aneurysms ◽  
Morphological Changes ◽  
Growth Patterns ◽  
Maximum Diameter ◽  
Aneurysm Formation ◽  
Aneurysm Wall ◽  
Unruptured Intracranial Aneurysms ◽  
Aneurysm Growth ◽  
Wall Imaging

OBJECTIVE Morphological changes in unruptured intracranial aneurysms (UIAs) are an imaging marker of aneurysm instability. Recent studies have indicated the ability of MR vessel wall imaging (VWI) to stratify unstable UIAs based on a correlation with histopathological aneurysm wall inflammation. In the present study the authors investigated the relationships between aneurysm growth patterns and the segmentation of aneurysm wall enhancement (AWE) in VWI. METHODS A total of 120 aneurysms with serial angiography from a follow-up period of at least 2 years (mean 65 months, range 24–215 months) were assessed by VWI. Two readers independently evaluated the patterns of morphological changes (stable, whole sac expansion, and secondary aneurysm formation) and the segmentation of AWE (no, focal, and circumferential AWE). The contrast enhancement ratio of the aneurysm wall versus the pituitary stalk (CRstalk) was calculated for the quantitative assessment of AWE. Statistical analyses were performed to investigate the relationships between AWE patterns and patient baseline profiles, aneurysm characteristics, and morphological modifications. RESULTS Forty-one of 120 UIAs (34%) exhibited aneurysm growth (whole sac expansion in 19 and secondary aneurysm formation in 22). AWE was detected in 35 of 120 UIAs (focal AWE in 25 and circumferential AWE in 10). The maximum diameter of, irregularities in, and morphological modifications in aneurysms were associated with the segmentation of AWE. Focal AWE correlated with secondary aneurysm formation, and circumferential AWE correlated with whole sac expansion. In focal AWE, CRstalk was significantly higher in secondary aneurysm formation than in stable UIAs. UIAs without AWE (categorized as no AWE) correlated with aneurysm stability. CONCLUSIONS The segmentation of AWE was associated with aneurysm growth scenarios and may provide a novel insight into the evaluation of unstable UIAs.

scholarly journals Validation of CFD Simulations of Cerebral Aneurysms With Implication of Geometric Variations

2006 ◽  
Vol 128 (6) ◽  
pp. 844-851 ◽  
Author(s):  
Yiemeng Hoi ◽  
Scott H. Woodward ◽  
Minsuok Kim ◽  
Dale B. Taulbee ◽  
Hui Meng
Keyword(s):  
Flow Field ◽  
Cfd Simulation ◽  
Three Dimensional ◽  
Cerebral Aneurysms ◽  
Patient Specific ◽  
Hemodynamic Parameters ◽  
Cfd Simulations ◽  
Piv Measurements ◽  
Cfd Method ◽  
Aneurysm Model

Background. Computational fluid dynamics (CFD) simulations using medical-image-based anatomical vascular geometry are now gaining clinical relevance. This study aimed at validating the CFD methodology for studying cerebral aneurysms by using particle image velocimetry (PIV) measurements, with a focus on the effects of small geometric variations in aneurysm models on the flow dynamics obtained with CFD. Method of Approach. An experimental phantom was fabricated out of silicone elastomer to best mimic a spherical aneurysm model. PIV measurements were obtained from the phantom and compared with the CFD results from an ideal spherical aneurysm model (S1). These measurements were also compared with CFD results, based on the geometry reconstructed from three-dimensional images of the experimental phantom. We further performed CFD analysis on two geometric variations, S2 and S3, of the phantom to investigate the effects of small geometric variations on the aneurysmal flow field. Results. We found poor agreement between the CFD results from the ideal spherical aneurysm model and the PIV measurements from the phantom, including inconsistent secondary flow patterns. The CFD results based on the actual phantom geometry, however, matched well with the PIV measurements. CFD of models S2 and S3 produced qualitatively similar flow fields to that of the phantom but quantitatively significant changes in key hemodynamic parameters such as vorticity, positive circulation, and wall shear stress. Conclusion. CFD simulation results can closely match experimental measurements as long as both are performed on the same model geometry. Small geometric variations on the aneurysm model can significantly alter the flow-field and key hemodynamic parameters. Since medical images are subjected to geometric uncertainties, image-based patient-specific CFD results must be carefully scrutinized before providing clinical feedback.

Three-Dimensional Geometrical Characterization of Abdominal Aortic Aneurysms: Image-Based Wall Thickness Distribution

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Giampaolo Martufi ◽  
Elena S. Di Martino ◽  
Cristina H. Amon ◽  
Satish C. Muluk ◽  
Ender A. Finol
Keyword(s):  
Wall Thickness ◽  
Three Dimensional ◽  
Aortic Aneurysms ◽  
Maximum Diameter ◽  
Patient Specific ◽  
Future Research ◽  
Geometrical Shape ◽  
Rupture Risk ◽  
Abdominal Aortic ◽  
Elective Repair

The clinical assessment of abdominal aortic aneurysm (AAA) rupture risk is based on the quantification of AAA size by measuring its maximum diameter from computed tomography (CT) images and estimating the expansion rate of the aneurysm sac over time. Recent findings have shown that geometrical shape and size, as well as local wall thickness may be related to this risk; thus, reliable noninvasive image-based methods to evaluate AAA geometry have a potential to become valuable clinical tools. Utilizing existing CT data, the three-dimensional geometry of nine unruptured human AAAs was reconstructed and characterized quantitatively. We propose and evaluate a series of 1D size, 2D shape, 3D size, 3D shape, and second-order curvature-based indices to quantify AAA geometry, as well as the geometry of a size-matched idealized fusiform aneurysm and a patient-specific normal abdominal aorta used as controls. The wall thickness estimation algorithm, validated in our previous work, is tested against discrete point measurements taken from a cadaver tissue model, yielding an average relative difference in AAA wall thickness of 7.8%. It is unlikely that any one of the proposed geometrical indices alone would be a reliable index of rupture risk or a threshold for elective repair. Rather, the complete geometry and a positive correlation of a set of indices should be considered to assess the potential for rupture. With this quantitative parameter assessment, future research can be directed toward statistical analyses correlating the numerical values of these parameters with the risk of aneurysm rupture or intervention (surgical or endovascular). While this work does not provide direct insight into the possible clinical use of the geometric parameters, we believe it provides the foundation necessary for future efforts in that direction.

Analysis of Post-Operative Abdominal Aortic Aneurysm Repair: A Multi Patient-Specific Study

2009 ◽  
Author(s):  
David Molony ◽  
Michael Walsh ◽  
Tim McGloughlin
Keyword(s):  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Abdominal Aortic Aneurysm Repair ◽  
Maximum Diameter ◽  
Patient Specific ◽  
Invasive Technique ◽  
Infrarenal Aorta ◽  
Aneurysm Wall ◽  
Abdominal Aortic ◽  
Aneurysm Repair

Abdominal aortic aneurysm is an irreversible dilation of the infrarenal aorta, which if left untreated may rupture. Surgical intervention is usually necessary to prevent this outcome. The decision to operate is based on the maximum diameter of the aneurysm. Two types of treatment exist; these are open repair and endovascular repair (EVAR). Of concern here is EVAR, which is the minimally invasive technique of inserting a stent-graft into the site of the aneurysm in order to shield the aneurysm wall from the stresses of blood pressure.

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.

scholarly journals Numerical computation of blood flow for a patient-specific hemodialysis shunt model

2021 ◽  
Author(s):  
Surabhi Rathore ◽  
Tomoki Uda ◽  
Viet Q. H. Huynh ◽  
Hiroshi Suito ◽  
Toshitaka Watanabe ◽  
...  
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Arteriovenous Shunt ◽  
Navier Stokes ◽  
Patient Specific ◽  
Stabilized Finite Element ◽  
Computed Tomography Scanning ◽  
Outflow Boundary ◽  
Stage Renal Disease ◽  
End Stage

AbstractHemodialysis procedure is usually advisable for end-stage renal disease patients. This study is aimed at computational investigation of hemodynamical characteristics in three-dimensional arteriovenous shunt for hemodialysis, for which computed tomography scanning and phase-contrast magnetic resonance imaging are used. Several hemodynamical characteristics are presented and discussed depending on the patient-specific morphology and flow conditions including regurgitating flow from the distal artery caused by the construction of the arteriovenous shunt. A simple backflow prevention technique at an outflow boundary is presented, with stabilized finite element approaches for incompressible Navier–Stokes equations.

scholarly journals Application of subject-specific adaptive mechanical loading for bone healing in a mouse tail vertebral defect

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Angad Malhotra ◽  
Matthias Walle ◽  
Graeme R. Paul ◽  
Gisela A. Kuhn ◽  
Ralph Müller
Keyword(s):  
Mechanical Loading ◽  
Bone Defect ◽  
Bone Healing ◽  
Three Dimensional ◽  
Patient Specific ◽  
Dependent Manner ◽  
Micro Computed Tomography ◽  
Computed Tomography Images ◽  
Bone Defect Healing ◽  
Subject Specific

AbstractMethods to repair bone defects arising from trauma, resection, or disease, continue to be sought after. Cyclic mechanical loading is well established to influence bone (re)modelling activity, in which bone formation and resorption are correlated to micro-scale strain. Based on this, the application of mechanical stimulation across a bone defect could improve healing. However, if ignoring the mechanical integrity of defected bone, loading regimes have a high potential to either cause damage or be ineffective. This study explores real-time finite element (rtFE) methods that use three-dimensional structural analyses from micro-computed tomography images to estimate effective peak cyclic loads in a subject-specific and time-dependent manner. It demonstrates the concept in a cyclically loaded mouse caudal vertebral bone defect model. Using rtFE analysis combined with adaptive mechanical loading, mouse bone healing was significantly improved over non-loaded controls, with no incidence of vertebral fractures. Such rtFE-driven adaptive loading regimes demonstrated here could be relevant to clinical bone defect healing scenarios, where mechanical loading can become patient-specific and more efficacious. This is achieved by accounting for initial bone defect conditions and spatio-temporal healing, both being factors that are always unique to the patient.

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