Aneurysm Flow Research Articles

Longitudinal Changes in Size of Conservatively Managed Flow-Related Aneurysms Associated with Brain Arteriovenous Malformations

Flow aneurysms (FAs) associated with brain arteriovenous malformations (AVMs) are thought to arise from increased hemodynamic stress due to high-flow shunting. This study aims to describe the changes in conservatively managed FAs after successful AVM treatment. Patients with symptomatic AVMs and associated FAs who underwent successful treatment of the AVM between 2008 and 2017 were included. FA dimensions were measured on surveillance angiography to assess longitudinal changes. Thirty-two patients were identified with 48 FAs. Sixteen (33%) FAs were treated endovascularly; 18 (38%) FAs were treated surgically; and 14 (29%) FAs (11 patients) were monitored. FAs demonstrated a decrease in size from 5.0 mm to 3.8 mm (24%; P= 0.016) and 4.9 mm to 3.6 mm (27%; P= 0.013) in height and width, respectively, over a median 35 months. However, on subgroup analysis, only class IIb aneurysms demonstrated a significant decrease in size (51% reduction in largest diameter, P= 0.046) and only 3 FAs (21%) resolved. There were no hemorrhages observed during follow-up. While conservatively managed FAs demonstrated a reduction in size after the culprit AVM was treated, this was only significant in FAs located close to an AVM nidus (class IIb). There were no hemorrhages during the median 35 months' follow-up; however, long-term data are lacking. Our data support close observation of all conservatively managed aneurysms and a tailored approach based on the proximity to the nidus and observed changes in size.

Numerical simulation of blood flow in Cerebral aneurysms using two-phase model

ABSTRACT: Computational fluid dynamic (CFD) simulation techniques have played an essential role in simulating and understanding the initiation, growth, and rupture of cerebral aneurysms. Hemodynamic parameters are mainly used to examine the rupture risk status of cerebral aneurysms using blood flow CFD simulation. Blood was considered as single-phase flow model with both Newtonian and non-Newtonian to predict the rupture risk analysis. However, to better understand predicting the risk of cerebral aneurysm rupture, blood requires two-phase, such as plasma and red blood cells (RBCs), also known as erythrocytes. In this study, the two-phase blood flow model was solved by the discrete phase model (DPM) with Lagrangian approach, in which blood was modeled two-phase fluid as a continuous phase plasma and particulate phase RBCs. Three patient-specific aneurysm geometries have been selected to determine wall shear stress (WSS), oscillatory shear index (OSI), and relative residence time (RRT) with two-phase blood flow simulation. To analyze the velocity distribution inside the aneurysms, velocity streamlines and surface velocities were reported. The pulsatile blood flow simulation was performed for aneurysm geometries, where the mean inlet Reynolds number was calculated between 490 and 1370. The value of WSS, OSI, and RRT was quantified based on the Reynolds number. Reynolds number's minimum value indicates the low WSS, low OSI, and short RRT, and the maximum value of Reynolds number shows the high WSS, high OSI, and long RRT. The high WSS, high OSI, and long RRT, velocity streamlines distribution, surface velocity changes were determined with two-phase blood in aneurysm geometries, aneurysm geometry one and three are the medium and giant size saccular aneurysm may have a higher risk of rupture while aneurysm geometry two is medium size fusiform aneurysm has a lower risk of rupture. The two-phase blood flow model presents reasonable hemodynamic parameters that correlate with aneurysms rupture risk prediction.

Real-Time Simulation of Parameter-Dependent Fluid Flows through Deep Learning-Based Reduced Order Models

Simulating fluid flows in different virtual scenarios is of key importance in engineering applications. However, high-fidelity, full-order models relying, e.g., on the finite element method, are unaffordable whenever fluid flows must be simulated in almost real-time. Reduced order models (ROMs) relying, e.g., on proper orthogonal decomposition (POD) provide reliable approximations to parameter-dependent fluid dynamics problems in rapid times. However, they might require expensive hyper-reduction strategies for handling parameterized nonlinear terms, and enriched reduced spaces (or Petrov–Galerkin projections) if a mixed velocity–pressure formulation is considered, possibly hampering the evaluation of reliable solutions in real-time. Dealing with fluid–structure interactions entails even greater difficulties. The proposed deep learning (DL)-based ROMs overcome all these limitations by learning, in a nonintrusive way, both the nonlinear trial manifold and the reduced dynamics. To do so, they rely on deep neural networks, after performing a former dimensionality reduction through POD, enhancing their training times substantially. The resulting POD-DL-ROMs are shown to provide accurate results in almost real-time for the flow around a cylinder benchmark, the fluid–structure interaction between an elastic beam attached to a fixed, rigid block and a laminar incompressible flow, and the blood flow in a cerebral aneurysm.

Bifurcation in a New Fractional Model of Cerebral Aneurysm at the Circle of Willis

A fractional-order model is proposed to describe the dynamic behaviors of the velocity of blood flow in cerebral aneurysm at the circle of Willis. The fractional-order derivative is used to model the blood flow damping term that features the viscoelasticity of the blood flow behaving between viscosity and elasticity, unlike the existing fractional models that use fractional-order derivatives to replace the integer-order derivatives as mathematical/logical generalization. A numerical analysis of the nonlinear dynamic behaviors of the model is carried out, and the influence of the damping term and the external power supply on the nonlinear dynamics of the model is investigated. It shows that not only chaos via period-doubling bifurcation is observed, but also two additional small period-doubling-bifurcation-like diagrams isolated from the big one are observed, a phenomenon that needs further investigation.

Incomplete stent expansion in flow-diversion treatment affects aneurysmal haemodynamics: a quantitative comparison of treatments affected by different severities of malapposition occurring in different segments of the parent artery.

Incomplete stent expansion (IncSE) is occasionally seen in flow-diversion (FD) treatment of intracranial aneurysms; however, its haemodynamic consequences remain inconclusive. Through a parametric study, we quantify the aneurysmal haemodynamics subject to different severities of IncSE occurring in different portions of the stent. Two patient cases with IncSE confirmed in vivo were studied. To investigate a wider variety of IncSE scenarios, we modelled IncSE at two severity levels respectively located in the proximal, central, or distal segment of a stent, yielding a total of 14 treatment scenarios (including the ideal deployment). We examined stent wire configurations in 14 scenarios and resolved aneurysm haemodynamics through computational fluid dynamics (CFD). A considerable degradation of aneurysm flow-reduction performance was observed when central or distal IncSE occurred, with the maximal elevations of the inflow rate (IR) and energy loss (EL) being 10% and 15%. The underlying mechanism might be the increased resistance for flow to remain within the FD stent, which forces more blood to leak into the aneurysm sac. Counter-intuitively, a slight reduction of aneurysm inflow was associated with proximal IncSE, with the maximal further reduction of the IR and EL being 5% and 8%. This may be due to the disruption of the predominant parent-artery flow by the collapsed wires, which decreased the strength and altered the direction of aneurysmal inflow. The effects of IncSE vary greatly with the location of occurrence, revealing the importance of performing individualised, patient-specific risk assessment before treatment.

Association Between Aneurysmal Haemodynamics and Device Microstructural Characteristics After Flow-Diversion Treatments With Dual Stents of Different Sizes: A Numerical Study.

ObjectivesTreating intracranial aneurysms with flow-diverting stents sometimes requires deployment of a second device. Herein we quantify the sizing effects of devices in dual-stent treatments upon the final stent microstructure and the post-treatment aneurysmal haemodynamics.MethodsFifteen sidewall ICA aneurysm geometries were included. Using a virtual stenting technique, we implanted either one or two stents for each aneurysm treatment considered, with each stent specified as one of two different sizes, yielding a total of two single-stent and fouir dual-stent treatment scenarios for each aneurysm. Three stent microstructural parameters and nine aneurysmal haemodynamic parameters were quantified and systematically compared across the 90 treatment scenarios.ResultsDeployment of a second stent further reduced the aneurysmal inflow rate (IR) and energy loss (EL) by, respectively, 14 ± 11% (p = 0.001) and 9 ± 12% (p = 0.056), relative to the untreated condition. Sizing effects of the earlier-deployed stent led to largest differences of 6.9% for the final IR reduction and 11.1% for the EL, whereas sizing effects from the later-deployed stent were minor (≤2.1%). The change in stent pore size was the only microstructural parameter demonstrating a strong correlation with the reduction in the post-treatment aneurysmal haemodynamics, in terms of the IR (r = 0.50, p < 0.001) and pressure drop (r = 0.63, p < 0.001).ConclusionSize of the earlier-deployed stent has substantial effects on the final haemodynamic outcomes after dual-stent treatment. The average pore size of stent wires at the aneurysm orifice shows promise as a potential index for predicting the efficacy of flow-diversion treatments.

Assessment and visualization of hemodynamic loading in aneurysm sac and neck: Effect of foam insertion.

Shape memory polymer (SMP) foam is often proposed as the future alternative of coils in aneurysm treatment devices. Present work numerically investigates the unsteady, three-dimensional simulation of blood flow in a cerebral aneurysm filled with SMP foam. Simulations are conducted on patient-specific geometries with realistic blood velocity waveform imposed at the inlet while SMP foam is treated as a porous medium. The present study introduces a "loading risk map" that helps to visualize the hemodynamic effect of foam insertion on the aneurysm sac and neck. The loading risk maps suggest that while the SMP foam subdues the flow and wall shear pulsations in the aneurysm sac, the pressure distribution is minimally affected. The maps suggest that while the downstream lip is the most risk-prone site for both geometries, downstream vascular anatomy significantly influences foam efficiency in reducing pressure and wall shear stress loading.

Guidewires as Embolic Agents? Embolotherapy of Large Splenic Artery Aneurysms

AbstractSplenic artery aneurysms are among the more frequently diagnosed intra-abdominal aneurysms and are not infrequent in patients with raised portal venous pressure often requiring endovascular or surgical therapy. A 36-year-old female patient with Non-cirrhotic portal fibrosis and portal hypertension was diagnosed with multiple large splenic artery aneurysms for which she was initially operated which resulted in substantial blood loss during dissection that required embolotherapy. Initial attempts at coil embolization proved unsuccessful due to the wide aneurysmal neck and flow characteristics. Following which the aneurysmal sac was packed with multiple guidewires to act as a scaffold for further coil embolization. Subsequently, hemostasis was achieved and the patient underwent splenectomy later thereby demonstrating that embolization of large aneurysms can be accomplished with reasonable efficacy using guidewires.

The association between hemodynamics and wall characteristics in human intracranial aneurysms: a review.

Hemodynamics plays a key role in the natural history of intracranial aneurysms (IAs). However, studies exploring the association between aneurysmal hemodynamics and the biological and mechanical characteristics of the IA wall in humans are sparse. In this review, we survey the current body of literature, summarize the studies' methodologies and findings, and assess the degree of consensus among them. We used PubMed to perform a systematic review of studies that explored the association between hemodynamics and human IA wall features using different sources. We identified 28 publications characterizing aneurysmal flow and the IA wall: 4 using resected tissues, 17 using intraoperative images, and 7 using vessel wall magnetic resonance imaging (MRI). Based on correlation to IA tissue, higher flow conditions, such as high wall shear stress (WSS) with complex pattern and elevated pressure, were associated with degenerated walls and collagens with unphysiological orientation and faster synthesis. MRI studies strongly supported that low flow, characterized by low WSS and high blood residence time, was associated with thicker walls and post-contrast enhancement. While significant discrepancies were found among those utilized intraoperative images, they generally supported that thicker walls coexist at regions with prolonged residence time and that thinner regions are mainly exposed to higher pressure with complex WSS patterns. The current body of literature supports a theory of two general hemodynamic-biologic mechanisms for IA development. One, where low flow conditions are associated with thickening and atherosclerotic-like remodeling, and the other where high and impinging flow conditions are related to wall degeneration, thinning, and collagen remodeling.

3D Modeling of Blood Flow in Simulated Abdominal Aortic Aneurysm.

Besides biological factors, abdominal aortic aneurysm rupture is also caused by mechanical parameters, which are constantly affecting the wall's tissue due to their abnormal values. The ability to evaluate these parameters could vastly improve the clinical treatment of patients with abdominal aortic aneurysms. The objective of this study was to develop and demonstrate a methodology to analyze the fluid dynamics that cause the wall stress distribution in abdominal aortic aneurysms, using accurate 3D geometry and a realistic, nonlinear, elastic biomechanical model using a computer-aided software. The geometry of the abdominal aortic aneurysm; was constructed on a 3D scale using computer-aided software SolidWorks (Dassault Systems SolidWorksCorp., Waltham MA). Due to the complex nature of the abdominal aortic aneurysm geometry, the physiological forces and constraints acting on the abdominal aortic aneurysm wall were measured by using a simulation setup using boundary conditions and initial conditions for different studies such as finite element analysis or computational fluid dynamics. The flow pattern showed an increase velocity at the angular neck, followed by a stagnated flow inside the aneurysm sack. Furthermore, the wall shear stress analysis showed to focalized points of higher stress, the top and bottom of the aneurysm sack, where the flow collides against the wall. An increase of the viscosity showed no significant velocity changed but results in a slight increase in overall pressure and wall shear stress. Conducting computational fluid dynamics modeling of the abdominal aortic aneurysm using computer-aided software SolidWorks (Dassault Systems SolidWorksCorp., Waltham MA) proves to be an insightful approach for the clinical setting. The careful consideration of the biomechanics of the abdominal aortic aneurysm may lead to an improved, case-specific prediction of the abdominal aortic aneurysm rupture potential, which could significantly improve the clinical management of these patients.

Experimental Analysis of Pressure and Flow Alterations During and After Insertion of a Multilayer Flow Modulator into an AAA Model with Incorporated Branch.

The multilayer flow modulator (MFM) device has been used for the treatment of abdominal aortic aneurysm (AAA) for over a decade. Although several clinical studies have been published, criticism and concern over the device efficacy remain, as no quantitative analysis that describes its mechanism has been performed yet. The aim of this study was to experimentally evaluate the effect of MFM device deployment on aneurysmal pressure and branch perfusion. An experimental flow and pressure monitoring system was developed to analyze the MFM deployment procedure performed by a qualified radiologist in AAA geometries with and without side branch. Particle image velocimetry experiments were then conducted on models with and without MFM device to evaluate and compare flow patterns and local flow velocity and vorticity in the aneurysm. The experiments revealed no significant change in pressure and flow rate during and after deployment of the MFM device. The flow rate of the incorporated branch was fully preserved. On both models, the aneurysmal flow velocity was significantly reduced. In addition, the device modified local flow patterns, reducing vorticity and better feeding the incorporated branch. This experimental study provides the basis for a better understanding of the mechanism of the MFM device, which allows intra-aneurysmal flow to decrease while preserving incorporated branch flow and reducing the risk of type II endoleak. The experimental system developed for this study was effective in simulating an endovascular procedure and studying the safety and effectiveness of endovascular devices.

Non-Newtonian Blood Modeling in Intracranial Aneurysm Hemodynamics: Impact on the Wall Shear Stress and Oscillatory Shear Index Metrics for Ruptured and Unruptured Cases.

When simulating blood flow in intracranial aneurysms (IAs), the Newtonian model seems to be ubiquitous. However, analyzing the results from the few studies on this subject, the doubt remains on whether it is necessary to use non-Newtonian models in computational fluid dynamics (CFD) simulations of cerebral vascular flows. The objective of this study is to investigate whether different rheology models would influence the hemodynamic parameters related to the wall shear stress (WSS) for ruptured and unruptured IA cases, especially because ruptured aneurysms normally have morphological features, such as lobular regions and blebs, that could trigger non-Newtonian phenomena in the blood flow due to low shear rates. Using CFD in an open-source framework, we simulated four ruptured and four unruptured patient-specific aneurysms to assess the influence of the blood modeling on the main hemodynamic variables associated with aneurysm formation, growth, and rupture. Results for WSS and oscillatory shear index (OSI) and their metrics were obtained using Casson and Carreau-Yasuda non-Newtonian models and were compared with those obtained using the Newtonian model. We found that all differences between non-Newtonian and the Newtonian models were consistent among all cases irrespective of their rupture status. We further found that the WSS at peak systole is overestimated by more than 50% by using the non-Newtonian models, but its metrics based on time and surface averaged values are less affected-the maximum relative difference among the cases is 7% for the Casson model. On the other hand, the surface-averaged OSI is underestimated by more than 30% by the non-Newtonian models. These results suggest that it is recommended to investigate different blood rheology models in IAs simulations when specific parameters to characterize the flow are needed, such as peak-systole WSS and OSI.

The effect of Dean, Reynolds, and Womersley number on the flow in a spherical cavity on a curved round pipe. Part 1. Fluid mechanics in the cavity as a canonical flow representing intracranial aneurysms.

Flow in side-wall cerebral aneurysms can be ideally modelled as the combination of flow over a spherical cavity and flow in a curved circular pipe, two canonical flows. Flow in a curved pipe is known to depend on the Dean number De, combining the effects of Reynolds number, Re, and of the curvature along the pipe centreline, κ. Pulsatility in the flow introduces a dependency on the Womersley number Wo. Using stereo PIV measurements, this study investigated the effect of these three key non-dimensional parameters, by modifying pipe curvature (De), flow-rate (Re), and pulsatility frequency (Wo), on the flow patterns in a spherical cavity. A single counter-rotating vortex was observed in the cavity for all values of pipe curvature κ and Re, for both steady and pulsatile inflow conditions. Increasing the pipe curvature impacted both the flow patterns in the pipe and the cavity, by shifting the velocity profile towards the cavity opening and increasing the flow rate into the cavity. The circulation in the cavity was found to collapse well with only the Dean number, for both steady and pulsatile inflows. For pulsatile inflow, the counter-rotating vortex was unstable and the location of its centre over time was impacted by the curvature of the pipe, as well as the Re and the Wo in the freestream. The circulation in the cavity was higher for steady inflow than for the equivalent average Reynolds and Dean number pulsatile inflow, with very limited impact of the Womersley in the range studied.

One way to get there

People have mused that fusion as a source of energy is ‘30 years away and always will be’. Similarly, the application of computational fluid dynamics (CFD) to solve problems in...

Teleproctoring for Neurovascular Procedures: Demonstration of Concept Using Optical See-Through Head-Mounted Display, Interactive Mixed Reality, and Virtual Space Sharing-A Critical Need Highlighted by the COVID-19 Pandemic.

Physician training and onsite proctoring are critical for safely introducing new biomedical devices, a process that has been disrupted by the pandemic. A teleproctoring concept using optical see-through head-mounted displays with a proctor's ability to see and, more important, virtually interact in the operator's visual field is presented. Test conditions were created for simulated proctoring using a bifurcation aneurysm flow model for WEB device deployment. The operator in the angiography suite wore a Magic Leap-1 optical see-through head-mounted display to livestream his or her FOV to a proctor's computer in an adjacent building. A Web-based application (Spatial) was used for the proctor to virtually interact in the operator's visual space. Tested elements included the quality of the livestream, communication, and the proctor's ability to interact in the operator's environment using mixed reality. A hotspot and a Wi-Fi-based network were tested. The operator successfully livestreamed the angiography room environment and his FOV of the monitor to the remotely located proctor. The proctor communicated and guided the operator through the procedure over the optical see-through head-mounted displays, a process that was repeated several times. The proctor used mixed reality and virtual space sharing to successfully project images, annotations, and data in the operator's FOV for highlighting any device or procedural aspects. The livestream latency was 0.71 (SD, 0.03) seconds for Wi-Fi and 0.86 (SD, 0.3) seconds for the hotspot (P = .02). The livestream quality was subjectively better over the Wi-Fi. New technologies using head-mounted displays and virtual space sharing could offer solutions applicable to remote proctoring in the neurointerventional space.

Pseudo-Enhancement in Intracranial Aneurysms on Black-Blood MRI: Effects of Flow Rate, Spatial Resolution, and Additional Flow Suppression.

Vessel-wall enhancement (VWE) on black-blood MRI (BB MRI) has been proposed as an imaging marker for a higher risk of rupture and associated with wall inflammation. Whether VWE is causally linked to inflammation or rather induced by flow phenomena has been a subject of debate. To study the effects of slow flow, spatial resolution, and motion-sensitized driven equilibrium (MSDE) preparation on signal intensities in BB MRI of patient-specific aneurysm flow models. Prospective. Aneurysm flow models based on 3D rotational angiography datasets of three patients with intracranial aneurysms were 3D printed and perfused at two different flow rates, with and without Gd-containing contrast agent. Variable refocusing flip angle 3D fast-spin echo sequence at 3 T with and without MSDE with three voxel sizes ((0.5 mm)3 , (0.7 mm)3 , and (0.9 mm)3 ); time-resolved with phase-contrast velocity-encoding 3D spoiled gradient echo sequence (4D flow MRI). Three independent observers performed a qualitative visual assessment of flow patterns and signal enhancement. Quantitative analysis included voxel-wise evaluation of signal intensities and magnitude velocity distributions in the aneurysm. Kruskal-Wallis test, potential regressions. A hyperintense signal in the lumen and adjacent to the aneurysm walls on BB MRI was colocalized with slow flow. Signal intensities increased by a factor of 2.56 ± 0.68 (P < 0.01) after administering Gd contrast. After Gd contrast administration, the signal was suppressed most in conjunction with high flows and with MSDE (2.41 ± 2.07 for slow flow without MSDE, and 0.87 ± 0.99 for high flow with MSDE). A clear result was not achieved by modifying the spatial resolution . Slow-flow phenomena contribute substantially to aneurysm enhancement and vary with MRI parameters. This should be considered in the clinical setting when assessing VWE in patients with an unruptured aneurysm. 2 TECHNICAL EFFICACY: Stage 2.

Hemodynamic effects of intracranial aneurysms from stent-induced straightening of parent vessels by stent-assisted coiling embolization.

Straightening of parent vessels happens for stent-assisted coiling embolization (SACE) treatment of intracranial aneurysms. This study aims to investigate aneurysmal hemodynamic modifications caused by stent-induced vessel straightening. Stent and coil deployments of a SACE-treated distal bifurcation aneurysm by finite element method were performed first with the preoperative (not straightened, NS) and postoperative (straightened, S) vessel models respectively. Computational fluid dynamics were then performed for eight models, including (I) NS only model, (II) NS+stent model, (III) NS+coils model, (IV) NS+stent+coils model, (V) S only model, (VI) S+stent model, (VII) S+coils model, and (VIII) S+stent+coils model. Finally, changes in aneurysmal flow velocity, isovelocity surface and wall shear stress (WSS) were analyzed qualitatively and quantitatively. The flow was less in the S models than that in the corresponding NS models. Coils blocked most of the flow into the aneurysm sac in both NS models and S models and vessel straightening had more profound effect on the high aneurysmal flow volume reduction than coiling, while stenting generated adverse effect on flow reduction. Taking the NS only model as baseline (100%), the sac-averaged velocities of models II to VIII were 112%, 36%, 42%, 45%, 39%, 12%, 13%, and high flow volumes were 119%, 21%, 30%, 10%, 8%, 3%, 3%, while the sac-averaged WSSs were 106%, 37%, 44%, 41%, 35%, 17% and 24%, respectively. Stent-induced vessel straightening combined coil embolization has the best performance in hemodynamic modifications and may reduce the recurrence rate, whereas stenting may generate adverse effect on hemodynamic alterations.

A longitudinal study of a lateral intracranial aneurysm: identifying the hemodynamic parameters behind its inception and growth using computational fluid dynamics

In the last two decades, the application of $$\hbox {computational fluid dynamics (CFD)}$$ to study the blood flow in intracranial aneurysms has gained popularity since hemodynamics plays a key role in the inception, growth, and rupture of these aneurysms. Although the rupture event has been the main focus of these studies, other researches have shown the importance of hemodynamics also on the initiation and growth of intracranial aneurysms. However, due to the lack of follow up examinations of a single aneurysm case, these studies are scarcer. In this work, two consecutive examinations of an unruptured lateral aneurysm followed up for 5 years were used to investigate the growth of the aneurysm by using $$\hbox {CFD}$$ . By simulating the flow in these two geometries and in the virtually reconstructed hypothetical healthy vasculature, correlations between hemodynamic parameters and the growth of the aneurysm were evaluated. The results showed that the inception of the aneurysm correlated positively with high $$\hbox {wall shear stress (WSS)}$$ and high positive $$\hbox {WSS}$$ spatial gradient, as other studies also suggest. Furthermore, and most importantly, as different biological pathways may explain the influence of hemodynamics on the growth process, the results also pointed out that the hemodynamic effects that drove the subsequent growth of the aneurysm have changed to a combination of low $$\hbox {WSS}$$ and high $$\hbox {oscillatory shear index (OSI)}$$ . Thus, even though the driving mechanisms observed during each period are distinct, they strongly agree with two main theories that currently explain aneurysm inception and growth.

Computational Fluid Dynamics for Cerebral Aneurysms in Clinical Settings.

Hemodynamics is thought to play an important role in the pathogenesis of cerebral aneurysms and recent development of computer technology makes it possible to simulate blood flow using high-resolution 3D images within several hours. A lot of studies of computational fluid dynamics (CFD) for cerebral aneurysms were reported; therefore, application of CFD for cerebral aneurysms in clinical settings is reviewed in this article.CFD for cerebral aneurysms using a patient-specific geometry model was first reported in 2003 and it has been revealing that hemodynamics brings a certain contribution to understanding aneurysm pathology, including initiation, growth and rupture. Based on the knowledge of the state-of-the-art techniques, this review treats the decision-making process for using CFD in several clinical settings. We introduce our CFD procedure using digital imaging and communication in medicine (DICOM) datasets of 3D CT angiography or 3D rotational angiography. In addition, we review rupture status, hyperplastic remodeling of aneurysm wall, and recurrence of coiled aneurysms using the hemodynamic parameters such as wall shear stress (WSS), oscillatory shear index (OSI), aneurysmal inflow rate coefficient (AIRC), and residual flow volume (RFV).

Prevention of complication in cerebral aneurysm microsurgery, associated with their non-radical clipping

Objective ‒ to analyze the effectiveness of intraoperative contact Doppler, repositioning the clip on the aneurysm and pilot clipping of the cervical aneurysm as the main methods of prevention of inadequate clipping of the cervical aneurysm in patients with intraoperative rupture of aneurysms. Materials and methods. Due to the use of intraoperative contact ultrasound Doppler control it was possible to avoid inadequate clipping of cerebral aneurysms in 16 cases, of which in 12 (75.00 %) cases ‒ incomplete clipping of cerebral aneurysms, in 3 (18.75 %) cases ‒ compression of the aneurysm’s artery-carrier, in 1 (6.25 %) case ‒ slipping of the clip with cerebral aneurysm. Perioperative examination of patients, in addition to intraoperative contact ultrasound Doppler control of radical clipping cerebral aneurysms, included clinical and neurological examination, computed tomography of the brain, cerebral angiography, ultrasound duplex scanning of the main vessels of the head and neck. In the analysis of observations of inadequate clipping of cerebral aneurysms (according to contact intraoperative Doppler), the following parameters were considered: size, location of cerebral aneurysm, timing of surgery after subarachnoid hemorrhage, anatomical forms of intracranial hemorrhage. Results. The purpose of the operations was to devascularize saccular aneurysm to prevent its re-rupture, to reduce the mass effect caused by intracerebral hematoma; reduction of intracranial pressure, rehabilitation of basal cisterns of the brain., But in the postoperative period there was a tendency to worsen the results of treatment, the appearance of focal neurological symptoms on the background of cerebral vasospasm with subsequent development of ischemic complications in patients with III‒V degree according to the Hunt‒Hess Scale on admission, in patients with prolonged temporary clipping of the cerebral aneurysm-artery and prolonged mechanical manipulation of the cerebral arteries and cerebral aneurysm. It should be noted that all patients in our sample, with complicated clipping of cerebral saccular aneurysms, had an intraoperative rupture of the MA, which complicated the process of clipping the saccular aneurysm and prolonged the time of surgery and was one of the inducers of postoperative aggravating consequences. There was a tendency to worsen the results of treatment in patients with III–IV degree according to the Hunt‒Hess Scale. Thus, patients with 1 point according to the Glasgow Outcome Scale, there were 2 patients who had II and III degrees according to Hunt–Hess Scale at hospitalization; among discharged patients with 3 point according to Glasgow Outcome Scale was dominated by patients from the second century according to Hunt‒Hess Scale at hospitalization, among patients with 5 point according to Glasgow Outcome Scale dominated patients who had I degree according to the Hunt‒Hess Scale at hospitalization. Conclusions. Inadequate clipping of the cervix cerebral aneurysm is the main type of non-hemorrhagic complications in the surgery of cerebral aneurysms. The Inadequate clipping of the cervix of the cerebral aneurysm includes the presence of residual blood flow in the cerebral aneurysm after its clipping, stenosis/compression of the main and perforating cerebral arteries with a clip, slipping of the clip from the aneurysm. Among the factors influencing the radical and adequate clipping of the cervix cerebral aneurysm are the size, location of the aneurysm, atherosclerotic lesions of the walls of the arteries and neck of the aneurysm and transferred subarachnoid hemorrhage. Reliable methods of prevention of inadequate clipping of saccular aneurysm are the use of intraoperative Doppler blood flow control, pilot clipping of complex aneurysms, optimization and individualization of surgical access. Aggravating factors that lead to unsatisfactory results of treatment of patients and negative clinical dynamics after the operation of clipping cerebral saccular aneurysm are: severe condition of the patient before surgery (III‒V gr. according to the Hunt‒Hess Scale), severe cerebral edema, intraoperative rupture of saccular aneurysm, long-term mechanical manipulations on cerebral arteries (long-term temporary clipping of saccular aneurysm, isolation of saccular aneurysm and «neighboring» cerebral arteries from arachnoid adhesions, frequent repositioning of the clip).