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Morphological and hemodynamic analysis of posterior communicating artery aneurysms prone to rupture: a matched case–control study

Objectives We evaluated the correlation between posterior communicating artery (PcomA) aneurysm rupture and morphological and hemodynamic parameters to assess related rupture risk indices. Methods Six patients with PcomA aneurysms that ultimately ruptured (cases) were studied after initially being included in a prospective database including their three-dimensional (3D) imaging before rupture. For each case, four incidental stable unruptured aneurysms (controls) were randomly selected and matched based on clinical factors. The 3D images from all patients were reconstructed to establish the patient-specific model. Six morphologic parameters and three hemodynamic parameters were measured and calculated. A conditional logistic regression analysis was used to assess the individual risk of rupture. Results The analysis demonstrated a larger aneurysm size (p=0.001), higher aspect ratio (p=0.018), ellipticity index (p<0.001), undulation index (p=0.005), percentage of low wall shear stress (WSS) area (LSA%) (p=0.010), and a lower normalized WSS (p=0.005) in the case group. The multivariate conditional logistic regression analysis demonstrated that only normalized WSS was significantly associated with the rupture of PcomA aneurysms (OR 0.151; 95% CI 0.025 to 0.914; p=0.040). Conclusions Hemodynamics and morphology are closely associated with aneurysm rupture, and WSS may be a more reliable parameter characterizing the rupture status of PcomA aneurysms.

Morphological and Hemodynamic Discriminators for Rupture Status in Posterior Communicating Artery Aneurysms

Background and Purpose The conflicting findings of previous morphological and hemodynamic studies on intracranial aneurysm rupture may be caused by the relatively small sample sizes and the variation in location of the patient-specific aneurysm models. We aimed to determine the discriminators for aneurysm rupture status by focusing on only posterior communicating artery (PCoA) aneurysms. Materials and Methods In 129 PCoA aneurysms (85 ruptured, 44 unruptured), clinical, morphological and hemodynamic characteristics were compared between the ruptured and unruptured cases. Multivariate logistic regression analysis was performed to determine the discriminators for rupture status of PCoA aneurysms. Results While univariate analyses showed that the size of aneurysm dome, aspect ratio (AR), size ratio (SR), dome-to-neck ratio (DN), inflow angle (IA), normalized wall shear stress (NWSS) and percentage of low wall shear stress area (LSA) were significantly associated with PCoA aneurysm rupture status. With multivariate analyses, significance was only retained for higher IA (OR = 1.539, p < 0.001) and LSA (OR = 1.393, p = 0.041). Conclusions Hemodynamics and morphology were related to rupture status of intracranial aneurysms. Higher IA and LSA were identified as discriminators for rupture status of PCoA aneurysms.

Validation of computational fluid dynamics methods with anatomically exact, 3D printed MRI phantoms and 4D pcMRI

A new concept of rapid 3D prototyping was implemented using cost-effective 3D printing for creating anatomically correct replica of cerebral aneurysms. With a dedicated flow loop set-up in a full body human MRI scanner, flow measurements were performed using 4D phase contrast magnetic resonance imaging to visualize and quantify intra-aneurysmal flow patterns. Ultrashort TE sequences were employed to obtain high-resolution 3D image data to visualize the lumen inside the plastic replica. In-vitro results were compared with retrospectively obtained in-vivo data and results from computational fluid dynamics simulations (CFD). Rapid prototyping of anatomically realistic 3D models may have future impact in treatment planning, design of image acquisition methods for MRI and angiographic systems and for the design and testing of advanced image post-processing technologies.

Morphological Risk Factors for Rupture of Small (<7 mm) Posterior Communicating Artery Aneurysms

BACKGROUND The management of small, unruptured intracranial aneurysms is still controversial. Given the distinctive natural history of aneurysm at different locations, location-specific analysis might be a reasonable approach. This study aimed to investigate morphological discriminators for rupture status by focusing on only posterior communicating artery (PcomA) aneurysms smaller than 7 mm. METHODS In 108 small PcomA aneurysms (68 ruptured, 40 unruptured), clinical and morphological characteristics were compared between the ruptured and unruptured groups. Multivariate logistic regression analysis was performed to determine the independent predictors for the rupture status of small PcomA aneurysms. RESULTS None of the clinical characteristics were significantly different between the ruptured and unruptured groups (P > 0.05). The ruptured group revealed a significantly larger size (P = 0.009), aspect ratio (P = 0.009), size ratio (P = 0.002), dome-to-neck ratio (P = 0.002), inflow angle (P < 0.001), and proportion of bleb formation (P = 0.039). Bottleneck factor (P = 0.154), diameter of PcomA (P = 0.302), and fetal-type PcomA (P = 0.832) showed no significance. With multivariate analyses, size ratio (P = 0.012) and inflow angle (P = 0.001) were shown to be independently associated with the rupture status of small PcomA aneurysms. CONCLUSIONS Morphological characteristics were closely related with the rupture status of small PcomA aneurysms. Size ratio and inflow angle were independent risk factors for rupture and might be useful in clinical risk stratification of small PcomA aneurysms.

Quantitative comparison of hemodynamic parameters from steady and transient CFD simulations in cerebral aneurysms with focus on the aneurysm ostium

Objective To quantitatively compare hemodynamics simulated with steady-state and transient computational fluid dynamics (CFD) simulations in cerebral aneurysms with single inflow, with focus at the aneurysm ostium. Methods Transient and steady-state CFD simulations were performed in 10 cerebral aneurysms. Distributions and average values for pressure, helicity, vorticity, and velocity were qualitatively compared at proximal and distal parent artery locations, at the ostium plane, and in the aneurysm, and scaling factors between the two kinds of simulations were determined. Relative inflow and outflow areas at the ostium were compared, as were average inflow and outflow velocities. In addition, values for the pressure-loss coefficient (PLC), a recently introduced parameter to assess aneurysm rupture risk, were compared for both kinds of simulation. Results Distributions of hemodynamic parameters had a similar shape but were lower for transient than for steady-state simulations. Averaged scaling factors over cases and anatomical locations showed differences for hemodynamic parameters (0.485±0.01 for pressure, 0.33±0.02 for helicity, 0.58±0.06 for vorticity and 0.56±0.04 for velocity). Good agreement between ratios of inflow and outflow areas at the aneurysm ostium was obtained (Pearson correlation coefficient >0.97, p<0.001) and for the PLC (linear regression slope 0.73±0.14, R2=0.75). Conclusions Steady-state simulations are a quick alternative to transient simulation for visualizing and quantifying inflow and outflow areas at the aneurysm ostium, potentially of value when planning flow diverter treatment and for quantifying the PLC, a potential indicator of aneurysm rupture.

Hemodynamic and morphological characteristics of unruptured posterior communicating artery aneurysms with oculomotor nerve palsy

OBJECT Unruptured posterior communicating artery (PCoA) aneurysms with oculomotor nerve palsy (ONP) have a very high risk of rupture. This study investigated the hemodynamic and morphological characteristics of intracranial aneurysms with high rupture risk by analyzing PCoA aneurysms with ONP. METHODS Fourteen unruptured PCoA aneurysms with ONP, 33 ruptured PCoA aneurysms, and 21 asymptomatic unruptured PCoA aneurysms were included in this study. The clinical, morphological, and hemodynamic characteristics were compared among the different groups. RESULTS The clinical characteristics did not differ among the 3 groups (p > 0.05), whereas the morphological and hemodynamic analyses showed that size, aspect ratio, size ratio, undulation index, nonsphericity index, ellipticity index, normalized wall shear stress (WSS), and percentage of low WSS area differed significantly (p < 0.05) among the 3 groups. Furthermore, multiple comparisons revealed that these parameters differed significantly between the ONP group and the asymptomatic unruptured group and between the ruptured group and the asymptomatic unruptured group, except for size, which differed significantly only between the ONP group and the asymptomatic unruptured group (p = 0.0005). No morphological or hemodynamic parameters differed between the ONP group and the ruptured group. CONCLUSIONS Unruptured PCoA aneurysms with ONP demonstrated a distinctive morphological-hemodynamic pattern that was significantly different compared with asymptomatic unruptured PCoA aneurysms and was similar to ruptured PCoA aneurysms. The larger size, more irregular shape, and lower WSS might be related to the high rupture risk of PCoA aneurysms.

Endovascular management of ruptured basilar artery dissection with two overlapping Low-profile Visualized Intraluminal Support stents.

The optimal endovascular treatment method of ruptured basilar artery dissection still remains controversial. We reported a case with ruptured basilar artery dissection involving the left anterior inferior cerebellar artery. The dissecting aneurysm was successfully treated with two overlapping Low-profile Visualized Intraluminal Support stents and the preservation of antegrade blood flow of the anterior inferior cerebellar artery was achieved. Three-month and six-month follow-ups revealed good clinical and angiographic results, although controversies regarding long-term stability remained to be addressed.

Combined effects of flow diverting strategies and parent artery curvature on aneurysmal hemodynamics: A CFD study

Purpose Flow diverters (FD) are increasingly being considered for treating large or giant wide-neck aneurysms. Clinical outcome is highly variable and depends on the type of aneurysm, the flow diverting device and treatment strategies. The objective of this study was to analyze the effect of different flow diverting strategies together with parent artery curvature variations on altering intra-aneurysmal hemodynamics. Methods Four ideal intracranial aneurysm models with different parent artery curvature were constructed. Computational fluid dynamics (CFD) simulations of the hemodynamics before and after applying five types of flow diverting strategies (single FD, single FD with 5% and 10% packing density of coils, two FDs with 25% and 50% overlapping rate) were performed. Changes in pressure, wall shear stress (WSS), relative residence time (RRT), inflow velocity and inflow volume rate were calculated and compared. Results Each flow diverting strategy resulted in enhancement of RRT and reduction of normalized mean WSS, inflow volume rate and inflow velocity in various levels. Among them, 50% overlapped FD induced most effective hemodynamic changes in RRT and inflow volume rate. The mean pressure only slightly decreased after treatment. Regardless of the kind of implantation of FD, the mean pressure, inflow volume rate and inflow velocity increased and the RRT decreased as the curvature of the parent artery increased. Conclusions Of all flow diverting strategies, overlapping FDs induced most favorable hemodynamic changes. Hemodynamics alterations post treatment were substantially influenced by parent artery curvature. Our results indicate the need of an individualized flow diverting strategy that is tailored for a specific aneurysm.

Intra-aneurysmal microcatheter looping technique for stent-assisted embolization of complex intracranial aneurysms

The endovascular treatment of wide-necked, large and giant aneurysms remains challenging. This retrospective study investigated the feasibility and safety of an intra-aneurysmal microcatheter looping technique for stent-assisted embolization of complicated intracranial aneurysms. This technique was used for 31 patients with complicated cerebral aneurysms from January 2007 to November 2013. The clinical and angiographic results were retrospectively evaluated. The target aneurysms were successfully treated in all cases (100%). A flow diverter was used in seven procedures. There were no aneurysmal perforations or ischemic complications, except for a microguidewire perforation of the distal vessel in one case. Among the 24 cases with conventional stent-assisted embolization, complete embolization or neck residual was obtained in 21 cases. Partial occlusion occurred in three cases. In conclusion, the intra-aneurysmal microcatheter looping technique is a safe and feasible alternative treatment of complicated intracranial aneurysms. This approach is a reasonable choice for patients and leads to successful outcomes.

Whole-Transcriptome Selection and Evaluation of Internal Reference Genes for Expression Analysis in Protocorm Development of Dendrobium officinale Kimura et Migo.

Dendrobium officinale Kimu et Migo has increased many researchers’ interest for its high medical and horticultural values and the molecular mechanism of its protocorm development remains unclear. In this study, 19 genes from 26 most stably expressed genes in whole transcriptome of protocorms and 5 housekeeping genes were used as candidate reference genes and screened with 4 application softwares (geNorm, NormFinder, BestKeeper and RefFinder). The results showed that a few reference genes could effectively normalize expression level of specific genes in protocorm development and the optimal top 2 reference genes were ASS and APH1L. Meanwhile, validation of GNOM, AP2 and temperature induced gene (TIL) for normalization demonstrates the usefulness of the validated candidate reference genes. The expression profiles of these genes varied under protocorms and temperature stress according to the stablest and unstablest reference genes, which proved the importance of the choice of appropriate reference genes. The first systematic evaluation of stably expressed genes will be very useful in the future analysis of specific genes expression in D. officinale.