Larger Size Ratio Research Articles

Diverse morphology and motility induced emergent order in bacterial collectives.

Microbial communities exhibit complex behaviors driven by species interactions and individual characteristics. In this study, we delve into the dynamics of a mixed bacterial population comprising two distinct species with different morphology and motility aspects. Employing agent-based modeling and computer simulations, we analyze the impacts of size ratios and packing fractions on dispersal patterns, aggregate formation, clustering, and spatial ordering. Notably, we find that motility and anisotropy of elongated bacteria significantly influence the distribution and spatial organization of nonmotile spherical species. Passive spherical cells display a superdiffusive behavior, particularly at larger size ratios in the ballistic regime. As the size ratio increases, clustering of passive cells is observed, accompanied by enhanced alignment and closer packing of active cells in the presence of higher passive cell area fractions. In addition, we identify the pivotal role of passive cell area fraction in influencing the response of active cells toward nematicity, with its dependence on size ratio. These findings shed light on the significance of morphology and motility in shaping the collective behavior of microbial communities, providing valuable insights into complex microbial behaviors with implications for ecology, biotechnology, and bioengineering.

Investigation of particle size impact on dense particulate flows in a vertical pipe

In this work, a semi-resolved computational fluid dynamics-discrete element method is employed to study the effects of fluid–particle and particle–particle/wall interactions on particle mixing and segregation behaviors and particle dynamics with different particle sizes in a vertical pipe. There are two species of particles with the same density in the vertical pipe: d1 = 10 (species 1) and d2 = 2–7 mm (species 2), and species 2 contains both fine and coarse particles. The Stokes number Stp is introduced to characterize the effects of different particle sizes on particle dynamics. First, the particle mixing and segregation behaviors with different size ratios are qualitatively analyzed. By comparing with smaller size ratios, obvious granular plugs and stronger contact force networks occur at larger size ratios. Second, after the segregation of species 1 and 2, the differences in dynamic characteristics between fine and coarse particles are explored. The normalized autocorrelation length scale, which is the ratio of propagation length of particle velocity fluctuations and particle diameter, is significantly different from fine to coarse particles. One notable feature is that two different flow regimes are found through the radial distribution function. Furthermore, the hydrodynamic stress and collision stress are defined to study the mechanism for the differences between fine and coarse particles. The results imply that the reason for the differences is that the collision effects go beyond the hydrodynamic effects with the increase in the Stokes number.

Coalescence preference dynamics for droplet growth during single-component fluid phase separation

When two unequal sized droplets coalesce to form a final product drop, the product forms closer to the larger of its two parents—a phenomenon known as the coalescence-preference dynamics. In this paper, using the state-of-the-art molecular dynamics simulations, we study the time-dependent properties of coalescence preference for phase segregating single-component fluids, over a broad range of fluid density and temperature. Hydrodynamics is fully taken into account. Coalescence time is observed to be shorter for parents with larger size ratio. Our simulation data also points towards an interesting power-law dependence of the coalescence time on the droplet size ratio, which is universal for both droplets and microbubbles.

Irregular Pulsation of Intracranial Aneurysm Detected by Four-Dimensional CT Angiography and Associated With Small Aneurysm Rupture: A Single-Center Prospective Analysis.

ObjectivesPredicting the risk of rupture of small intracranial aneurysms remains challenging. The irregular pulsation of aneurysms detected by four-dimensional CT angiography (4D-CTA) could be an imaging marker of aneurysm vulnerability. We aimed to investigate the association of irregular pulsation with small aneurysm rupture.Materials and MethodsThis was a prospective study on intracranial aneurysms detected by 4D-CTA from October 2017 to January 2020. A total of 242 consecutive patients with 316 aneurysms were enrolled. Irregular pulsation was defined as a temporary focal protuberance on more than 3 consecutive frames of the 20 phases in the RR interval. Small aneurysms were defined as those <7 mm. Univariate and multivariate analyses were performed to determine the independent predictors of small aneurysm rupture.ResultsA total of 169 patients with 217 small intracranial aneurysms were included. Fourteen (6.5%) of the aneurysms had ruptured, and 77 (35.5%) had irregular pulsation. There were no significant differences in age, sex, hypertension, smoking, diabetes, drinking, or hyperlipidemia between the ruptured and unruptured aneurysm groups. The univariate analysis showed that smaller vessel size (p = 0.008), larger size ratio (p = 0.003), larger aspect ratio (p = 0.006), larger flow angle (p = 0.001), large vessel angle (p = 0.004), middle cerebral artery aneurysms (p = 0.046), anterior cerebral artery/posterior communicating artery/posterior circulation aneurysm (p = 0.006), irregular aneurysm (p = 0.001), and t presence of irregular pulsation (p = 0.001) were associated with small aneurysm rupture. The multivariate analysis showed that the presence of irregular pulsation (p = 0.003), anterior cerebral artery/posterior communicating artery/posterior circulation aneurysms (p = 0.014), and larger flow angle (p = 0.006) was independently associated with aneurysm rupture. Multivariate analysis of predictors of the irregular pulsation of small aneurysms showed that the aneurysm rupture (p = 0.022), irregular aneurysm (p < 0.001), and large size ratio (p = 0.005) were independently associated with the presence of irregular pulsation.ConclusionsThe ruptured small aneurysms more often had irregular pulsation. The irregular pulsation was independently associated with aneurysm rupture and may help evaluate the risk of rupture of small intracranial aneurysms.

Gravitational collision efficiencies of small viscous drops at finite Stokes numbers and low Reynolds numbers

Collision efficiencies are calculated for two sedimenting spherical drops of different radii with internal circulation under conditions such that drop inertia can be significant while the surrounding fluid inertia remains negligible. A trajectory analysis is employed with exact methods for determining the hydrodynamic forces. When the Reynolds number is small, fluid inertia is negligible, and the hydrodynamic forces are linear functions of the velocities of the drops. However, at nonzero Stokes numbers, drop inertia must be taken into account, and the hydrodynamic forces do not balance the applied forces. For drops in close approach, lubrication forces, slip and attractive molecular forces are considered. Comparison is made between the effects of unretarded and retarded van der Waals forces and Maxwell slip on collision efficiencies. Slip is calculated exactly for viscous drops using bispherical coordinates for motion along the drops’ line of centers. For water droplets in air, at drop radii between 10 and 30μm, drop inertia is important while the Reynolds based on the surrounding air is still small. The collision efficiency goes through a minimum and then approaches the Smoluchowski limit of no hydrodynamic interactions as the drop size and Stokes number become increasingly large. Viscous effects are most important at drop radii of about 15μm. For drops with a radius less than 10μm, the most significant factors are unretarded van der Waals forces, Maxwell slip, and retarded van der Waals forces, respectively. When van der Waals forces and slip are combined, the collision efficiencies for drops with radii of 10μm are significantly greater than the results of previous researchers. At an intermediate drop radius of 20μm, surrounding fluid inertia, as considered in earlier work, appears to lead to greater collision efficiencies at intermediate size ratios, while van der Waals forces, incorporated in the present study, cause larger values at smaller and larger size ratios. At a drop radius of 30μm, drop inertia dominates interactions, and similar results occur for both the current and prior investigations. Since temperature affects both density and viscosity, collision efficiencies can differ by a factor of two or more between 0 °C and 100 °C at certain drop radii. Change in the viscosity ratio itself leads to about a 7% difference in the collision efficiency between drops with internal circulation and solid spheres at room temperature.

The Analysis of Morphoradiological Parameters in Predicting Risk of Basilar Artery Tip Aneurysm Rupture: A Retrospective Cohort Study.

PurposeBasilar artery tip aneurysms can have fatal consequences and poor prognostic outcomes in case of rupture. We investigated the standard parameters used to evaluate aneurysmal morphology to predict aneurysm rupture.Patients and MethodsWe measured the differences between ruptured and unruptured basilar bifurcation aneurysms in terms of morphological features, including aneurysm size, size ratio, aneurysm height, perpendicular height, aneurysm width, bottleneck ratio, aspect ratio, and present daughter domes, using 3D angiography.ResultsAmong 34 patients, 21 (61.8%) and 13 (38.2%) had ruptured and unruptured basilar tip aneurysms, respectively. In the ruptured group, the mean aneurysm size, and aspect, size, and bottleneck ratios were 6.8 ± 1.9 mm, 3.2 ± 1.0, 2.3 ± 0.5, and 2.2 ± 0.4, respectively, compared to 4.5 ± 1.5 mm, 4.4 ± 2.0, 1.6 ± 0.4, and 2.7 ± 0.7, respectively, in the non-ruptured group. Univariate analysis showed a larger aneurysmal cross-sectional diameter (odds ratio [OR], 0.50; 95% confidence interval [CI], 0.5–5.392; p < 0.05), a larger size ratio (OR, 21.375; 95% CI, 3.283–139.177; p < 0.05), and presence of a daughter dome (OR, 72.0; 95% CI, 6.7–776.5; p < 0.05) with ruptured basilar artery tip aneurysms.ConclusionA larger aneurysm size and size ratio, and the presence of a daughter dome were significantly associated with increased rupture risk in basilar tip aneurysms.

Predictors of Poor-Grade Aneurysmal Subarachnoid Hemorrhage Caused by Anterior Communicating Artery Aneurysm

Patients with poor-grade aneurysmal subarachnoid hemorrhage (aSAH) are considered to have a poor prognosis. However, the underlying reason for the association between the aneurysmal characteristics and poor-grade aSAH is still unclear. In the present study, we retrospectively evaluated the independent risk factors for patients with anterior communicating artery (ACoA) aneurysms with poor-grade aSAH. From January 2009 to January 2016, 477 consecutive patients with ruptured ACoA aneurysms were included in the present study. Poor-grade aSAH was defined as a World Federation of Neurosurgical Society grade of IV or V, and good-grade aSAH was defined as a grade of I-III. Univariate and multivariable regression analyses were used to investigate the differences in aneurysm morphology and clinical characteristics between the 2 groups. On univariate analysis, older patients (P= 0.038), larger aneurysm size (P= 0.013), larger size ratio (P= 0.007), larger aspect ratio (P= 0.009), positive history of stroke (P= 0.001), and posterior projection aneurysms (P= 0.001) were associated with poor-grade aSAH. Multivariate analyses revealed that older patients (odds ratio [OR], 1.654; 95% confidence interval [CI], 1.004-2.728; P=0.048), larger size ratio (OR, 1.280; 95% CI, 1.111-1.475; P= 0.001), positive history of stroke (OR, 6.051; 95% CI, 1.712-21.381; P= 0.005), and posterior projection aneurysms (OR, 2.718; 95% CI, 1.607-4.598; P < 0.001) were independently associated with poor-grade aSAH. Poor-grade aSAH was independently associated with older patients, a larger size ratio, a positive history of stroke, and posterior projection aneurysms in patients with a ruptured ACoA aneurysm. These parameters could contribute to screening for patients with the potential for poor-grade aSAH.

Vibration induced segregation of single large particles

The vibration-induced segregation (e.g., rising of one large intruder - so called Brazil Nut Effect (BNE)) is studied by discrete element method. Vibration frequency and amplitude are two dominating factors in the occurrence of BNE and a phase diagram is constructed. For fixed vibration amplitude, segregation only occurs when vibration frequency is within a certain range. Larger vibration amplitude can expand the range of vibration frequency for BNE. Size ratio and the intruder shape are studied under certain vibration conditions. Larger size ratio can enlarge the segregation intensity. The shape of the intruder influences the segregation process by the intruder′s orientation. Standing-like initial orientation can increase the time required for the intruder to reach the top while lying-like initial orientation cannot significantly affect the vertical segregation.

CFD-DEM modelling of the migration of fines in suspension flow through a solid packed bed

In this work, based on the unresolved CFD-DEM framework, a smoothed volume distribution model (SVDM) is developed to simulate the migration of fines in suspension flow through a solid packed bed. In this model, the porosity of coarse solids is calculated by a smoothed particle volume distribution. The model is validated using two solid-liquid systems. Compared with divided particle volume method (DPVM) with a low-resolution mesh, the SVDM method allows a high-resolution mesh and can achieve a high efficiency and applicability. Moreover, the effects of inlet fine concentration and solid/fine size ratio on fines migration behaviour are studied. The results indicate that more holdup of fine powders especially in the upper zone can be captured, when a higher concentration fine phase or a larger size ratio is used. Based on the local holdup information, four powder migration mechanisms are proposed, i.e., size exclusion, powder bridging, powder deposition and powder locking.

Morphological predictors of middle cerebral artery bifurcation aneurysm rupture

ObjectiveMiddle cerebral artery (MCA) bifurcation aneurysms are more likely to be associated with severe hemorrhage or hematoma in a clinical setting. We aimed to investigate the morphological predictors of MCA bifurcation aneurysm rupture. Patients and MethodsWe conducted a retrospective analysis of 317 patients with MCA aneurysms between January 2009 and October 2016. Aneurysm status was grouped into ruptured and unruptured groups. The MCA bifurcation was defined as the bifurcation of the main trunk (the origin of the M2 trunks). Aneurysm morphologies were determined using CT angiography. We performed univariate and multivariable regression analyses to investigate the association of morphological characteristics with ruptured MCA bifurcation aneurysms. ResultsA total of 268 (84.5 %) patients with 280 MCA bifurcation aneurysms were included. 207 (73.9 %) aneurysms had ruptured. In the univariate analysis, a larger aneurysm (p = 0.042), a larger size ratio (p = 0.001), a larger aspect ratio (p = 0.017), a greater bottleneck ratio (p = 0.047), an irregular aneurysm (p = 0.004) and the presence of a daughter dome (p = 0.002) were associated with aneurysm rupture. The multivariate analysis showed that a larger size ratio (OR 1.324, 95 % CI, 1.062–1.651; p = 0.013) and the presence of daughter dome (OR 2.462, 95 % CI, 1.123–5.398; p = 0.024) were independently associated with ruptured aneurysms. The threshold of the size ratio for discriminating ruptured and unruptured aneurysms was 2.53 (p < 0.001). ConclusionsThe size ratio and the presence of a daughter dome were independent predictors of the rupture of MCA bifurcation aneurysms. These parameters may contribute to the evaluation of the risk of rupture of aneurysms.

Morphological and Hemodynamic Factors Associated with Ruptured Middle Cerebral Artery Mirror Aneurysms: A Retrospective Study

Mirror intracranial aneurysms with different rupture status is a useful model to investigate features associated with aneurysm rupture. Morphological and hemodynamic analyses of ruptured middle cerebral artery (MCA) mirror aneurysms are rarely reported. The purpose of this study was to determine the morphological or hemodynamic characteristics associated with ruptured MCA mirror aneurysms. We performed a retrospective analysis of consecutive 317 patients with MCA aneurysms. Ruptured MCA mirror aneurysms (1 ruptured and mirror unruptured aneurysm) were included. In the matched pairs of ruptured and unruptured mirror aneurysms, 13 morphological parameters were measured using 3-dimensional computed tomography angiography and 6 hemodynamic parameters were evaluated using high-resolution computational fluid dynamic simulations. The association of morphological and hemodynamic characteristics with the rupture of MCA mirror aneurysms was determined. A total of 20 (6.31%) patients with 40 MCA mirror aneurysms were included in this study. There were significant differences in morphological and hemodynamic parameters between the ruptured and unruptured mirror aneurysms. Irregular aneurysms were 3 times more common in the ruptured aneurysms than in the unruptured aneurysms. A larger aneurysm (P= 0.025), a higher aneurysm (P= 0.020), a larger size ratio (P= 0.009), a higher bottleneck ratio (P= 0.033), an irregular aneurysm (P= 0.022), a higher maximum intra-aneurysmal wall shear stress (WSS; P= 0.020), and a lower normalized average WSS (P= 0.008) were associated with MCA mirror aneurysm rupture. Larger aneurysms, a larger size ratio, irregular aneurysms, a lower spatial average WSS, and a higher maximum WSS may contribute to evaluating the risk of rupture of MCA aneurysms independent of patient characteristics.

Effects of inclusion of granulated rubber tires on the mechanical behaviour of a compressive sand

Drained triaxial shearing tests were performed on a well-graded compressive sand (completely decomposed granite, CDG) and its mixtures with granulated rubber tires to investigate the effects of rubber size and content on their mechanical behaviour. Three sizes of rubber particles, GR1, GR2, and GR3, were used with size ratios to CDG (D50,rubber : D50,CDG) of 0.9, 3.5, and 7.2, respectively, and the rubber content ranged from 0% to 30%. The results show that for CDG–GR1 mixtures, the strength decreases with increasing rubber content, while for CDG–GR2 and CDG–GR3 mixtures, the strength decreases only at 10% rubber content and then increases markedly with increasing rubber content. The increase of strength is mainly because the inclusion of large rubber particles widens the particle size distributions of the mixtures, resulting in denser packings. The denser packings also lead to a decrease in compressibility. At larger size ratio and higher rubber content, the CDG–rubber mixtures show higher shear strength and lower compressibility than pure CDG, which indicates the CDG–rubber mixtures are very suitable to be used as filling materials.

A retrospective comparison of sac and lobe morphology between ruptured and unruptured intracranial aneurysms

There are few reliable morphologic indices to aid in the determination of an intracranial aneurysm’s rupture risk. We sought to characterize morphological characteristics of aneurysm sacs and their lobes that are associated with ruptured status at time of initial evaluation with diagnostic angiography. These factors could be associated with an aneurysm’s risk of rupturing. We retrospectively reviewed all aneurysms imaged with digital subtraction angiography (DSA) at a single institution over five years. Patients presenting with aneurysmal subarachnoid hemorrhage (aSAH) were assigned to the ruptured group, and those presenting without aSAH were assigned to the unruptured group. Angiograms were evaluated for the presence of various morphological parameters. Binary logistic regression was used to assess their associations between groups. A total of 331 aneurysms among 241 patients were included in the analysis. Posterior circulation, larger size ratio, and the presence of two or more lobes were associated with aneurysm rupture (p < 0.001 for each). Aneurysms containing a lobe with a greater height than width were observed more frequently in the ruptured group (OR 5.26, 95% CI 2.66–10.41). In the receiver operating characteristic (ROC) curves, mean diameter had an AUC of 0.72 and an optimum threshold of 2.85 mm. For size ratio, the AUC was 0.70 and the optimum threshold was 2.02. A larger SR was observed in ruptured aneurysms. The presence of multiple lobes and greater lobe height than width were associated with rupture status as well. These factors merit investigation in a prospective study.

Surgical Treatment of Middle Cerebral Artery Aneurysms: Aneurysm Location and Size Ratio as Risk Factors for Neurologic Worsening and Ischemic Complications

Regardless of acceptable surgical results of middle cerebral artery aneurysms (MCAs), MCA territory infarction (MCATI) remains a major obstacle to achieving a good outcome. We investigated the MCATI in patients with surgically treated MCA aneurysms. The data of 286 consecutive patients with 322 MCA aneurysms were evaluated retrospectively. The aneurysm location was classified as early frontal cortical branch (EFCB), early temporal cortical branch (ETCB), bifurcation or trifurcation (M1-2), and distal aneurysms on the insular, opercular, or cortical segments of the MCA (distal MCA). Neurologic worsening was defined as an increase in 1 or more modified Rankin Scale (mRS) scores. Multivariate analysis identified EFCB location as the sole risk factor for MCATI (odds ratio [OR], 3.8; 95% confidence interval [CI], 1.2-12; P= 0.021) and MCATI (OR, 18; 95% CI, 2.8-117; P= 0.002) and a larger size ratio (OR, 1.4; 95% CI, 1.1-1.8; P= 0.019) were related to 12-month neurologic worsening (n= 6; 1.9%). During follow-up (median, 885 days; interquartile range, 485-1229 days), posttreatment rupture and aneurysm recurrence were not observed. In the present study, compared with M1-2 aneurysms, MCATIs were observed more frequently in EFCB aneurysms, and the presence of MCATI and a larger size ratio were related to 12-month neurologic worsening in patients with surgically treated MCA aneurysms.

Enhanced gel formation in binary mixtures of nanocolloids with short-range attraction.

Colloidal suspensions transform between fluid and disordered solid states as parameters such as the colloid volume fraction and the strength and nature of the colloidal interactions are varied. Seemingly subtle changes in the characteristics of the colloids can markedly alter the mechanical rigidity and flow behavior of these soft composite materials. This sensitivity creates both a scientific challenge and an opportunity for designing suspensions for specific applications. In this paper, we report a novel mechanism of gel formation in mixtures of weakly attractive nanocolloids with modest size ratio. Employing a combination of x-ray photon correlation spectroscopy, rheometry, and molecular dynamics simulations, we find that gels are stable at remarkably weaker attraction in mixtures with size ratio near two than in the corresponding monodisperse suspensions. In contrast with depletion-driven gelation at larger size ratio, gel formation in the mixtures is triggered by microphase demixing of the species into dense regions of immobile smaller colloids surrounded by clusters of mobile larger colloids that is not predicted by mean-field thermodynamic considerations. These results point to a new route for tailoring nanostructured colloidal solids through judicious combination of interparticle interaction and size distribution.

Granular fingering as a mechanism for ridge formation in debris avalanche deposits: Laboratory experiments and implications for Tutupaca volcano, Peru

The origin of subparallel, regularly-spaced longitudinal ridges often observed at the surface of volcanic and other rock avalanche deposits remains unclear. We addressed this issue through analogue laboratory experiments on flows of bi-disperse granular mixtures, because this type of flow is known to exhibit granular fingering that causes elongated structures resembling the ridges observed in nature. We considered four different mixtures of fine (300–400μm) glass beads and coarse (600–710μm to 900–1000μm) angular crushed fruit stones, with particle size ratios of 1.9–2.7 and mass fractions of the coarse component of 5–50wt%. The coarse particles segregated at the flow surface and accumulated at the front where flow instabilities with a well-defined wavelength grew. These formed granular fingers made of coarse-rich static margins delimiting fines-rich central channels. Coalescence of adjacent finger margins created regular spaced longitudinal ridges, which became topographic highs as finger channels drained at final emplacement stages. Three distinct deposit morphologies were observed: 1) Joined fingers with ridges were formed at low (≤1.9) size ratio and moderate (10–20wt%) coarse fraction whereas 2) separate fingers or 3) poorly developed fingers, forming series of frontal lobes, were created at larger size ratios and/or higher coarse contents. Similar ridges and lobes are observed at the debris avalanche deposits of Tutupaca volcano, Peru, suggesting that the processes operating in the experiments can also occur in nature. This implies that volcanic (and non-volcanic) debris avalanches can behave as granular flows, which has important implications for interpretation of deposits and for modeling. Such behaviour may be acquired as the collapsing material disaggregates and forms a granular mixture composed by a right grain size distribution in which particle segregation can occur. Limited fragmentation and block sliding, or grain size distributions inappropriate for promoting granular fingering can explain why ridges are absent in many deposits.

Sex differences in aneurysm morphologies and clinical outcomes in ruptured anterior communicating artery aneurysms: a retrospective study

ObjectivesRuptured anterior communicating artery (ACoA) aneurysms occur more frequently in men. The purpose of the study was to investigate sex difference in aneurysm morphologies and clinical outcomes in patients with...

Larger size ratio associated with the rupture of very small (≤3 mm) anterior communicating artery aneurysms

BackgroundAnterior communicating artery (AcoA) aneurysms have a high rupture risk, and ruptured AcoA aneurysms tend to be smaller than other intracranial aneurysms. We aimed to determine the incidence and morphologic...

The effect of anterior projection of aneurysm dome on the rupture of anterior communicating artery aneurysms compared with posterior projection

ObjectiveRecent studies have shown that anterior projection aneurysms are associated with increased risk of rupture of anterior communicating artery (ACoA) aneurysms. We aimed to determine differences in patient characteristics and aneurysm morphologies between the anterior projection and posterior projection aneurysm groups and to determine morphological predictors of rupture of the anterior projection aneurysms. Materials and methodsDecember 2007 to February 2015, 503 consecutive patients with single ACoA aneurysms were included in this report. The ACoA aneurysms were dichotomized as the anterior and posterior projection groups. Multivariate regression models were used to determine differences in patient and aneurysm characteristics between the 2 groups and to determine predictors of rupture in the anterior projection aneurysms. Results363 (72.2%) patients had anterior projection aneurysms and 140 (27.8%) had posterior projection aneurysms. In univariate analysis, the anterior projection aneurysms were associated with a larger aneurysm size, a higher aneurysm height, a higher perpendicular height, a larger aspect ratio, and a larger size ratio. The multivariate analysis showed that the anterior projection aneurysms were independently associated with a larger size ratio compared with the posterior projection aneurysms. A larger size ratio and a smaller vessel size were independently associated with rupture status in the anterior projection aneurysms. ConclusionsCompared with posterior projection aneurysms, the anterior projection aneurysms have a higher risk of rupture probably because of significant differences in aneurysm morphologies. A larger size ratio and a smaller vessel size may be helpful to predict the risk of rupture in the anterior projection aneurysms.

Smoking and Intracranial Aneurysm Morphology.

Smoking is a well-known independent risk factor for both aneurysm formation and rupture. There is mounting evidence that aneurysm morphology beyond size can have a significant role in aneurysm formation and rupture risk by its effects on aneurysmal hemodynamics. To study the variation in aneurysm morphology between smokers and nonsmokers and delineate how changes in these factors might affect aneurysm formation and rupture. We generated 3-dimensional models of aneurysms and their surrounding vasculature by analyzing preoperative computed tomography angiograms with Slicer software. We then examined the association between smoking status and intrinsic, transitional, and extrinsic aspects of aneurysm morphology in both univariate and multivariate statistical analyses. From 2005 to 2013, 199 cerebral aneurysms in never smokers and current smokers were evaluated/treated at a single institution with available computed tomography angiograms (102 in never smokers and 97 in current smokers). Multivariate analysis of current smokers vs never smokers demonstrated that aneurysms in current smokers were significantly associated with multiple aneurysms (odds ratio [OR]: 2.15, P = .03), larger daughter vessel diameters (OR: 3.13, P = .01), larger size ratio (OR: 1.78, P = .01), and location at the basilar apex (OR: 6.26, P = .02). The differences in aneurysm morphology between smoking and nonsmoking patient populations may elucidate the effects of smoking on aneurysm formation and eventual rupture. We identified several aspects of aneurysm morphology significantly associated with smoking status that may provide the morphological basis for how smoking leads to increased aneurysm rupture.