Bifurcation Angle Research Articles

Experimental investigation of the thermal back-layering length in a branched tunnel fire under longitudinal ventilation

The smoke propagation in branched tunnel is more complicated because of the special bifurcation structure that has not been clarified, despite the fact that the scenario exists in practice. In this paper, the thermal smoke movement behavior in branched tunnel fire were experimentally investigated under the combined effect of bifurcation angle and ventilation velocity. The theoretical analysis was conducted to develop the smoke back-layering length equation based on the applied force of smoke propagation upstream of the fire source, and the smoke back-layering length under various longitudinal ventilation velocities was quantified. The results indicate that the smoke back-layering length decreases with the increasing of longitudinal ventilation velocity for a given heat release rate. The stronger heat release rate results in the longer smoke backflow distance under same ventilation velocity. The smoke back-layering length varied with bifurcation angle due to the bifurcation structure weakens the inertial force of longitudinal ventilation, but the affected degree varies with bifurcation angle. The experimental smoke back-layering length can be well correlated using the deduced logarithmic function. The empirical model taking the bifurcation angle into consideration is proposed to predict the smoke back-layering length in branched tunnel fire. Finally, the correlation for critical ventilation velocity of branched tunnel fire under varied bifurcation angles was also proposed based on the boundary condition of none smoke back-layering.

Presence of ramus intermedius increases the risk of atherosclerotic plaque formation at the left main bifurcation's region: A retrospective study from CT coronary angiography in UMMC

<h2>Background</h2> Ramus intermedius (RI) is a variant vessel arising from the left main bifurcation angle (LMBA). Haemodynamically, its presence increases coronary turbulence flow and reduces the endothelial shear stress. In theory, this haemodynamic effect promotes atherosclerotic plaque formation, especially around the bifurcation region. <h3>Objectives</h3> This study aims to identify RI as a risk factor for atherosclerosis at the left main coronary artery (LMCA), proximal left anterior descending (LAD) and proximal left circumflex (LCx) using coronary computed tomography angiography (CCTA). <h3>Methodology</h3> A retrospective review was carried out on 374 CCTA cases in University Malaya Medical Centre (UMMC) between January 2017 and December 2018. The atherosclerotic plaque at the LMCA, proximal LAD and proximal LCx arteries were analysed in the presence or absence of RI. Statistical analysis was done using the chi-square test and binary logistic regression. <h3>Results</h3> RI was identified in 32.4% (<i>n</i> = 121) of patients. Age > 65 years old, male gender, diabetes, hypertension and RI were identified as significant risk factors for atherosclerosis. The presence of RI increases plaque formation by 8.5-fold for proximal and distal LMCA compared to those without RI (aOR: 8.5, 95% CI: 1.7, 43.0, <i>p</i> > 0.001). Meanwhile, at the proximal LAD, RI increases the risk for plaque formation by 3.7 folds (aOR: 3.7, 95% CI: 1.5, 9.4 <i>p</i> = 0.006) at the lateral wall and by 4.9 folds (aOR: 4.9, 95% CI: 1.7, 14.2, <i>p</i> = 0.003) for both lateral and medial wall. RI also independently increases the risk for atherosclerosis by 3 folds at the lateral and medial wall of proximal LCx (aOR: 3.7, 95% CI: 1.2, 11.4, <i>p</i> = 0.020). Lastly, RI increases the risk of obstructive stenosis in the LMCA, LAD and LCx by 3.9 folds (aOR: 3.9, 95% CI: 1.4, 10.5, <i>p</i> < 0.001). <h3>Conclusion</h3> Our findings suggest that the presence of RI independently increases the risk for atherosclerotic plaque formation in the left main stem and its proximity. RI in situ is believed to exert altered haemodynamic effect promoting atherosclerotic plaque formation.

Quantitative Biomarkers for Cancer Detection Using Contrast-Free Ultrasound High-Definition Microvessel Imaging: Fractal Dimension, Murray's Deviation, Bifurcation Angle & Spatial Vascularity Pattern.

A growing body of evidence indicates that there is a strong correlation between microvascular morphological features and malignant tumors. Therefore, quantification of these features might allow more accurate differentiation of benign and malignant tumors. The main objective of this research project is to improve the quantification of microvascular networks depicted in contrast-free ultrasound microvessel images. To achieve this goal, a new series of quantitative microvessel morphological parameters are introduced for differentiation of breast masses using contrast-free ultrasound-based high-definition microvessel imaging (HDMI). Using HDMI, we quantified and analyzed four new parameters: 1) microvessel fractal dimension (mvFD), a marker of tumor microvascularcomplexity; 2) Murray’sdeviation(MD), the diameter mismatch, defined as the deviation from Murray’s law; 3) bifurcation angle (BA), abnormally decreased angle; and 4) spatial vascular pattern (SVP), indicating tumor vascular distribution pattern, either intratumoral or peritumoral. The new biomarkers have been tested on 60 patients with breast masses. Validation of the feature’s extraction algorithm was performed using a synthetic data set. All the proposed parameters had the power to discriminate the breast lesion malignancy (p < 0.05), displaying BA as the most sensitive test, with a sensitivity of 90.6%, and mvFD as the most specifictest, with a specificityof 92%. The results of all four new biomarkers showed an AUC = 0.889, sensitivity of 80% and specificity of 91.4% In conclusion, the added value of the proposed quantitative morphological parameters, as new biomarkers of angiogenesis within breast masses, paves the way for more accurate breast cancer detection with higher specificity.

Pattern formation of vascular network in a mathematical model of angiogenesis

We discuss the characteristics of the patterns of the vascular networks in a mathematical model for angiogenesis. Based on recent in vitro experiments, this mathematical model assumes that the elongation and bifurcation of blood vessels during angiogenesis are determined by the density of endothelial cells at the tip of the vascular network, and describes the dynamical changes in vascular network formation using a system of simultaneous ordinary differential equations. The pattern of formation strongly depends on the supply rate of endothelial cells by cell division, the branching angle, and also on the connectivity of vessels. By introducing reconnection of blood vessels, the statistical distribution of the size of islands in the network is discussed with respect to bifurcation angles and elongation factor distributions. The characteristics of the obtained patterns are analysed using multifractal dimension and other techniques.

Carotid Geometry and Wall Shear Stress Independently Predict Increased Wall Thickness-A Longitudinal 3D MRI Study in High-Risk Patients.

Introduction: Carotid geometry and wall shear stress (WSS) have been proposed as independent risk factors for the progression of carotid atherosclerosis, but this has not yet been demonstrated in larger longitudinal studies. Therefore, we investigated the impact of these biomarkers on carotid wall thickness in patients with high cardiovascular risk.Methods: Ninety-seven consecutive patients with hypertension, at least one additional cardiovascular risk factor and internal carotid artery (ICA) plaques (wall thickness ≥ 1.5 mm and degree of stenosis ≤ 50%) were prospectively included. They underwent high-resolution 3D multi-contrast and 4D flow MRI at 3 Tesla both at baseline and follow-up. Geometry (ICA/common carotid artery (CCA)-diameter ratio, bifurcation angle, tortuosity and wall thickness) and hemodynamics [WSS, oscillatory shear index (OSI)] of both carotid bifurcations were measured at baseline. Their predictive value for changes of wall thickness 12 months later was calculated using linear regression analysis for the entire study cohort (group 1, 97 patients) and after excluding patients with ICA stenosis ≥10% to rule out relevant inward remodeling (group 2, 61 patients).Results: In group 1, only tortuosity at baseline was independently associated with carotid wall thickness at follow-up (regression coefficient = −0.52, p < 0.001). However, after excluding patients with ICA stenosis ≥10% in group 2, both ICA/CCA-ratio (0.49, p < 0.001), bifurcation angle (0.04, p = 0.001), tortuosity (−0.30, p = 0.040), and WSS (−0.03, p = 0.010) at baseline were independently associated with changes of carotid wall thickness at follow-up.Conclusions: A large ICA bulb and bifurcation angle and low WSS seem to be independent risk factors for the progression of carotid atherosclerosis in the absence of ICA stenosis. By contrast, a high carotid tortuosity seems to be protective both in patients without and with ICA stenosis. These biomarkers may be helpful for the identification of patients who are at particular risk of wall thickness progression and who may benefit from intensified monitoring and treatment.

Discharging process and thermal evaluation in the thermal energy storage system with fractal tree-like fins

Under microgravity environment for spacecraft operation, the melting rate of phase change material is restricted by its low heat transfer performance and disappearance of natural convection. To accelerate the melting under microgravity, the insertion of fractal tree-like fins into a latent heat thermal energy storage unit is proposed. The dynamic melting behavior and heat transfer performance in cavities with fractal tree-like fins having bifurcation angle of 30°, 60° and 90° are investigated through a transient model based on the enthalpy-porosity method. The relationship between the effects of tree-like fins and thermocapillary convection on melting is disclosed. The results show that during melting driven by combined heat conduction and thermocapillary convection, the presence of tree-like fins significantly accelerates melting, and the increment degree of melting rate increases with the increase of bifurcation angle. Compared with cavity without fin, 30°, 60° and 90° fins reduce melting time by 47.7%, 57.2% and 64.3%, respectively. The fractal tree-like fins also enhance the increment speed of energy storage capacity, while enhancing and slightly deteriorating heat transfer at the beginning and end of melting, respectively. The thermocapillary convection accelerates the melting under microgravity, and the acceleration effect degree increases with the increase of bifurcation angle. With the presence of natural convection, compared with the cavity without fin, 30°, 60° and 90° fins reduce the melting time by 57.8%, 60.6% and 65.3%, respectively; the acceleration effect of fins on melting is enhanced, and the effect of bifurcation angle on melting becomes weaker. The present design innovatively introduces tree-like fins into thermal energy storage under microgravity condition, and can be used for temperature control of spacecraft electronic devices.

CFD Analysis on Effect of Angulation in A Healthy Abdominal Aorta-Renal Artery Junction

The recent developments in computational fluid dynamics (CFD) can be useful in observing the detailed haemodynamics in renal artery bifurcation for clinical evaluation and treatment. The present study focuses on haemodynamic behaviour of blood as it flows through the abdominal aorta-renal artery junction in an idealistic healthy artery with varying bifurcation angles to the abdominal aorta, i.e. from 30° to 90° with increments of 15°. This is to examine the effect of angulation on the junction and to determine whether arterial geometry plays a role in the prediction of atherosclerotic lesions. The three-dimensional models used in this study were generated using ANSYS WORKBENCH 19.0, and numerical simulation was done using FLUENT 19.0 solver. The blood flow is assumed to be Newtonian, incompressible and laminar. Haemodynamic parameters such as velocity, wall pressure and wall shear stress along with flow variation are compared among the different models. As the angulation increased, velocity and wall shear stress at the ostial region decreased by 14% and 52% respectively. Wall pressure at the same region saw an increase by 3%. Therefore, renal arteries with higher bifurcating angles to the abdominal aorta were observed to be more prone to the formation of atherosclerotic lesions. The present study is a precursor for future studies on renal artery with stenosis.

A Deep Learning Approach for Retinal Image Feature Extraction

Retinal image analysis is crucially important to detect the different kinds of life-threatening cardiovascular and ophthalmic diseases as human retinal microvasculature exhibits remarkable abnormalities responding to these disorders. The high dimensionality and random accumulation of retinal images enlarge the data size, that creating complexity in managing and understating the retinal image data. Deep Learning (DL) has been introduced to deal with this big data challenge by developing intelligent tools. Convolutional Neural Network (CNN), a DL approach, has been designed to extract hierarchical image features with more abstraction. To assist the ophthalmologist in eye screening and ophthalmic disease diagnosis, CNN is being explored to create automatic systems for microvascular pattern analysis, feature extraction, and quantification of retinal images. Extraction of the true vessel of retinal microvasculature is significant for further analysis, such as vessel diameter and bifurcation angle quantification. This study proposes a retinal image feature, true vessel segments extraction approach exploiting the Faster RCNN. The fundamental Image Processing principles have been employed for pre-processing the retinal image data. A combined database assembling image data from different publicly available databases have been used to train, test, and evaluate this proposed method. This proposed method has obtained 92.81% sensitivity and 63.34 positive predictive value in extracting true vessel segments from the top first tier of colour retinal images. It is expected to integrate this method into ophthalmic diagnostic tools with further evaluation and validation by analysing the performance.

Secondary flow in bifurcations – Important effects of curvature, bifurcation angle and stents

Coronary bifurcations have complex flow patterns including secondary flow zones and helical flow, which directly affect pathophysiological mechanisms such as the development of atherosclerosis. The objective of this study was to generate insights into the effects of curvature, bifurcation angle and the presence of stents on flow patterns and resulting haemodynamics in coronary left main bifurcations. The blood flow and associated metrics were modelled in both idealised and patient-specific bifurcations with varying curvature and bifurcation angles with and without stents, resulting in a total of 128 geometries considered. The results showed that larger curvature of bifurcating vessels has a significant influence on secondary flow, especially with distance to the bifurcation region, causing a skew, spin and asymmetry of Dean vortices, an increase in helical flow intensity with symmetry loss, and a decrease in adversely low time-average wall shear stress (TAWSS). Generally, asymmetric flow patterns coincided with adversely low TAWSS regions. In identical stented geometries, the presence of the stents induced local recirculation immediately adjacent to the stent struts, thus generating adversely low TAWSS in these areas, with some effect on the overall secondary flow. Overall, the effect of stents outweighed the effect of curvature and BA. This new knowledge contributes to a better understanding of the joint effects of curvature, bifurcation angle, and stents on flow patterns and haemodynamics in coronary bifurcations.

Is the middle cerebral artery bifurcation aneurysm affected by morphological parameters of bifurcation?

Aneurysm formation is a multifactorial process involving genetic, anatomical and environmental risk factors. A research focusing on the relationship between the presence of aneurysm and the morphology of the arteries will help in the pathogenesis and prediction of intracranial aneurysms. In this study, the relationship between the presence of aneurysm and various morphological parameters of aneurysm-related arteries was evaluated in patients with saccular middle cerebral artery (MCA) bifurcation aneurysm. The archival images of 74 patients (62.2% women) were evaluated retrospectively. In this study, the angle between the ipsilateral MCA M1 segment and the dominant truncus (Φ1), the angle between the M1 segment and the recessive truncus (Φ2), and the bifurcation angle (Φ1 + Φ2) were compared. Bilateral internal carotid artery (ICA), MCA M1 segment, dominant and recessive truncus diameters and these diameters ratios were compared with the aneurysmal side and the contralateral side without aneurysm. When the dominant truncus, recessive truncus angles and bifurcation angle were compared, a significant difference was found on the aneurysmal side (p < 0.0001). In the receiver operating characteristic analysis, when the bifurcation angle of 147.5° was accepted as the limit value, 78.4% sensitivity, 79.7% specificity, 79.5% positive predictive value and 78.7% negative predictive value were determined (area under the curve: 0.85). Our study of the morphological features of arteries associated with MCA bifurcation aneurysms showed that the presence of MCA aneurysms was significantly associated with large bifurcation angles.

Nano-crush technique in narrow-angle (

Bifurcation stenting techniques are still refining and under testing. Nano-crush is a novel technique which allow minimum protrusion of side branch struts at the ostium. To demonstrate the efficacy of Nano-crush technique in narrow-angle bifurcation (<70°) using bench test model, 3D reconstruction of the stent structure, computational fluid dynamics study and a clinical follow-up. This was a retrospective observational single-center study which included 40 patients who underwent angioplasty using Nano-crush technique for de-novo complex coronary bifurcation lesions with narrow bifurcation angle (<70°) between April-2016 to March-2019. The in-vitro bench test and computational fluid dynamics analysis were performed using a bifurcation model designed. The clinical primary endpoint was major adverse cardiac events (MACE), defined as a composite of cardiac death, myocardial infarction, and target lesion revascularization (TLR) at one-year angiographic follow-up. The reconstructed results of in-vitro bench test showed minimum length of stent struts moving away from the rounded side branch ostium. The mean age of patients was 62.8±7.98 years (32 male) and presented 100% procedural success. The mean bifurcation angle was 47.3±9.2°. The MACE was reported in four (10%) patients which included one (2.5%) death and three (7.5%) TLR at the mean follow-up of 35.54±12.31 months. No significant correlation between occurrence of MACE and gender, age, comorbidities and bifurcation angle was reported. The Nano-crush technique demonstrated least metal load around carina and abnormal flow dynamics in narrow angle (<70°) bifurcation lesions and also reported favorable long-term clinical outcomes.

Evaluation of Plaque Vulnerability via Combination of Hemodynamic Analysis and Simultaneous Non-Contrast Angiography and Intraplaque Hemorrhage (SNAP) Sequence for Carotid Intraplaque Hemorrhage.

The purpose of this study was to assess the vulnerability of plaque using a combination of simultaneous non-contrast angiography, intraplaque hemorrhage (SNAP) sequence, and local hemodynamic analysis in an intraplaque hemorrhage (IPH), and to evaluate the association between morphological and hemodynamic factors and IPH by comparing the IPH (presence of IPH) and non-IPH (plaque with absence of IPH) groups. In total, 27 IPH patients and 27 non-IPH patients were involved in this study, and baseline characteristics were collected. For morphological factors, diameters, and areas of the internal carotid artery (ICA), external carotid artery, and common carotid artery were measured, and bifurcation angle (α) and ICA angle (β) were also measured for comparison between the IPH group and non-IPH group. For hemodynamic factors, time-averaged wall shear stress (WSS), minimum WSS, maximum WSS, and oscillatory shear index were calculated using computational fluid dynamics (CFD) simulations. For the qualitative analysis, cross-sectional images with analyzed WSS and SNAP sequences were combined to precisely assess local hemodynamics. Bifurcation angle (α) was significantly different between the IPH and non-IPH groups (39.47 degrees vs. 47.60 degrees, p = 0.041). Significantly higher time-averaged WSS, minimum WSS, and maximum WSS were observed in the IPH group compared to the non-IPH group. In the IPH group, when using the combined analysis with SNAP sequences and WSS, the WSS of the region with IPH was significantly higher than the region without IPH (2.32 vs. 1.21 Pa, p = 0.005). A smaller bifurcation angle (α) and higher time-averaged WSS, minimum WSS, and maximum WSS were associated with IPH. The combined analysis of SNAP sequences and WSS might help to evaluate the risk of carotid IPH.

Prenatal features of ductus arteriosus-related branch pulmonary stenosis in fetal pulmonary atresia.

Ductus arteriosus (DA)-related branch pulmonary stenosis (PS), due to ductal tissue migration into the proximal pulmonary artery (PA) ipsilateral to the DA, is common in newborns with pulmonary atresia (PAtr) and contributes significantly to their mortality and morbidity. We sought to define fetal echocardiographic predictors of DA-PS in PAtr. This was a study of all neonates diagnosed prenatally with PAtr and a DA-dependent pulmonary circulation, with a DA that joined the underbelly of the arch, who had undergone surgical or catheter intervention in our hospital between 2009 and 2018. The postnatal echocardiograms and clinical records were reviewed to confirm the presence or absence of DA-PS based on the need for angioplasty at initial intervention and/or development of proximal PA stenosis post intervention. Fetal echocardiograms were examined for the features of DA-PS. Of 53 fetuses with PAtr, 34 (64%) had analyzable images, including 20/34 (59%) with and 14/34 (41%) without DA-PS. An inability to visualize the branch PAs in the same plane, largely associated with abnormal DA insertion into the ipsilateral PA (85% of cases), had sensitivity, specificity and positive (PPV) and negative (NPV) predictive values of 75%, 100%, 100% and 74%, respectively, for the prediction of postnatal DA-PS. The mean branch PA posterior bifurcation angle was more obtuse in cases with DA-PS compared to cases without DA-PS (117° ± 17° vs 79° ± 17°, P < 0.001), and an angle of > 100°, the preoperative cut-off observed previously in affected newborns, had a sensitivity, specificity, PPV and NPV of 88%, 79%, 82% and 85%, respectively. The receiver-operating-characteristics curve revealed an angle of ≥ 105° to have a sensitivity and specificity of 88% and 93%, respectively, for prenatal prediction of DA-PS. The presence of one or both features (inability to image in the same plane and the posterior bifurcation angle of ≥ 105°) had a sensitivity, specificity, PPV and NPV of 100%, 93%, 95% and 100%, respectively. An inability to visualize the branch PAs in the same plane, associated with abnormal insertion of the DA in most cases, and/or the presence of a posterior PA bifurcation angle of ≥ 105° are predictive features of postnatal DA-PS in fetuses with PAtr. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Simulation of imbibition in porous media with a tree-shaped fracture following the level-set method

Imbibition is an important mechanism for enhancing oil recovery in low-permeability reservoirs, such as shale and tight sandstone, and a tree-shaped network has been successfully used to characterize fracturing fracture. Therefore, understanding the imbibition mechanism in porous media with a tree-shaped fracture (TFPM) is important for developing low-permeability reservoirs. In this study, a simulation model for imbibition in TFPM was established based on the level-set method, and the model was verified by comparing it with an analytical solution. The influences of the fracture width, bifurcation angle, tortuosity, and water flow rate on imbibition in TFPM were then discussed. Based on the results, the following points have been established: (1) During the early stage, the imbibition in TFPM included countercurrent and a combined imbibition, and only countercurrent imbibition occurred during the later stage. (2) At a constant fracture width ratio, increasing the primary fracture width could reduce the residual oil in the TFPM, thereby improving the oil recovery factor. (3) At a fracture bifurcation angle ranging from 0° to 45°, the oil recovery factor increased as the bifurcation angle increased. (4) At a fracture tortuosity of 1.0 to 1.24, changes in tortuosity had little effect on the oil recovery factor during the early stage of imbibition, while it significantly affected the distribution of the residual oil. (5) At a water flow rate of 5 mm/s, the simulated oil recovery factor in the TFPM was highest. This investigation can provide a reference for the development of low-permeability reservoirs.

Correlation of coronary artery geometry with the complexity and severity of coronary atherosclerosis: rationale and design of the GEOMETRY-CTA study

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): This research is co-financed by Greece and the European Union (European Social Fund-ESF) through the Operational Programme «Human Resources Development, Education and Lifelong Learning 2014-2020» in the context of the project “Correlation of coronary artery tree geometry and clinical parameters with the distribution, complexity and severity of coronary artery disease: a pilot study using multislice CT coronary angiography” (MIS 5047882) Background Development and progression of coronary atherosclerosis is complex and not yet fully understood. Accumulative evidence supports the notion that coronary artery disease (CAD) results from an interaction of systemic factors, such as dyslipidemia, with local hemodynamic factors that regulate the site-specific predilection of atherosclerosis, particularly low endothelial shear stress (ESS). Since low ESS develops in geometrically irregular regions of the coronary tree for a given arterial blood flow, geometrical factors affect atherosclerotic plaque distribution and vulnerability. However, the correlation of coronary geometric features with the complexity and severity of CAD has not been fully elucidated. Purpose GEOMETRY-CTA is a prospective, non-randomized, observational study that aims to investigate the correlation of coronary artery geometrical features with the complexity and severity of CAD using Coronary Computed Tomography Angiography (CCTA). The prognostic value of a CCTA-derived geometric risk score will also be assessed. Methods The study aims to recruit 100 consecutive patients with suspected CAD and low/intermediate pre-test probability. Coronary geometrical characteristics such as angulation of coronary bifurcations, tortuosity, coronary artery volume index (CAVi) and vessel-length will be assessed with multi-planar reformation and volume rendering techniques, and integrated into a single geometric risk score. The extent and vulnerability of plaque burden will be calculated using several anatomical scoring systems such as the Leiden CTA risk score, CT-SYNTAX score, and CT-adapted Gensini score. Patients will be prospectively followed for 12 months after enrollment. Results The primary objective of the study is to evaluate the correlation of the geometric risk score with CAD severity and plaque vulnerability. We also hypothesize that wider bifurcation angles and lower CAVi augmenting the atherosclerosis-prone environment and predict higher CAD extent and complexity. Conclusion The present study aims to introduce a quantitative, non-invasive imaging biomarker expressing CAD severity and investigate its prognostic value in regards to adverse cardiovascular events. The derived index will be available for incorporation in larger national prospective studies for further cardiovascular risk stratification.

Experimental study on the temperature longitudinal distribution induced by a branched tunnel fire

Temperature rise induced by tunnel fire is a key factor injuring persons and destroying the tunnel lining structure as well as the facilities. In order to better comprehend the temperature distribution induced by fire in branched tunnel, a series of reduced scale experiments with different longitudinal ventilation velocity and bifurcation angles were conducted to investigate the temperature longitudinal decay in mainline tunnel and ramp in this paper. The heat release rate varied from 1.72 kW to 6.04 kW corresponding to 3.07 MW–10.8 MW in full scale. Three bifurcation angles of 5°, 10°, and 15° were considered to investigate the effect of bifurcation angle on temperature longitudinal distribution in branched tunnel. Results show that the bifurcation angle influences temperature distribution between fire source two sides due to the asymmetric air entrainment. The increasing of heat release rate results in the higher temperature under natural ventilation. The ventilation velocity had a greater enhancing effect on the temperature rise in mainline tunnel due to smoke accumulation effect at downstream of fire source. The exponential correlation is proposed to predict the longitudinal temperature beneath the tunnel ceiling not only in mainline tunnel but also in ramp by taking the bifurcation angle into consideration.

Atraumatic Endoluminal Microincisions Enhance Balloon-Based Drug Delivery in Complex Porcine Restenotic Lesions

Coronary bifurcations have complex flow patterns including secondary flow zones and helical flow, which directly affect pathophysiological mechanisms such as the development of atherosclerosis. The objective of this study was to generate insights into the effects of curvature, bifurcation angle and the presence of stents on flow patterns and resulting haemodynamics in coronary left main bifurcations. The blood flow and associated metrics were modelled in both idealised and patient-specific bifurcations with varying curvature and bifurcation angles with and without stents, resulting in a total of 128 geometries considered. The results showed that larger curvature of bifurcating vessels has a significant influence on secondary flow, especially with distance to the bifurcation region, causing a skew, spin and asymmetry of Dean vortices, an increase in helical flow intensity with symmetry loss, and a decrease in adversely low time-average wall shear stress (TAWSS). Generally, asymmetric flow patterns coincided with adversely low TAWSS regions. In identical stented geometries, the presence of the stents induced local recirculation immediately adjacent to the stent struts, thus generating adversely low TAWSS in these areas, with some effect on the overall secondary flow. Overall, the effect of stents outweighed the effect of curvature and BA. This new knowledge contributes to a better understanding of the joint effects of curvature, bifurcation angle, and stents on flow patterns and haemodynamics in coronary bifurcations.

Anterior communicating artery aneurysms: Nonmodifiable morphological parameters associated with rupture risk.

The aim of this study was to investigate the relationship between arterial morphological parameters and the rupture risk of anterior communicating artery (AComA) aneurysms. A hospital database was retrospectively reviewed to identify patients with AComA aneurysms. Morphologic parameters were evaluated on the 3-dimensional computed tomography angiograms. The patients were divided into two groups as ruptured and unruptured. Patient age, sex, morphological parameters such as aneurysm height and weight, neck diameter, aspect ratio (AR), size ratio (SR), bifurcation angle, aneurysm shape, and diameters of the artery were statistically compared between two groups. Ninety-five AComA aneurysms were analyzed in this study (60 ruptured and 35 unruptured). The aneurysm neck size (p = .005) and the diameter of the A1 segment of the ipsilateral anterior cerebral artery (i-A1) were smaller in the ruptured group than in the unruptured group (p = .001), but AR (p = .001) was higher. The number of patients with irregular shape aneurysm were higher in the ruptured group (p = .006). There was no significant difference between the two groups in terms of age, sex, aneurysm height and weight, bifurcation angle, and SR. Univariate logistic regression analysis showed that i-A1 segment diameter (odds ratio [OR]: -2.070, confidence interval [CI]: 0.030-0.531, p = .005), aneurysm neck diameter (OR: -0.409, CI: 0.491-0.899, p = .008), irregular shape (OR: 1.197, CI: 1.382-7.929, p = .007), and AR (OR: 0.880, CI: 1.315-4.417, p = .004) were significantly correlated with ruptured status. Multivariate regression analysis demonstrated that aneurysm neck diameter (OR: -0.457, CI: 0.410-0.977, p = .039) was the only independent variable for rupture. AComA aneurysm ruptureis more likely to occur inaneurysmswith smaller i-A1 segment diameter, smaller aneurysm neck diameter, irregular aneurysm shape, and higher AR. Aneurysm neck diameter may be a more important determinant for rupture prediction.

Histology-driven model of the macaque motor hyperdirect pathway.

Emerging appreciation for the hyperdirect pathway (HDP) as an important cortical glutamatergic input to the subthalamic nucleus (STN) has motivated a wide range of recent investigations on its role in motor control, as well as the mechanisms of subthalamic deep brain stimulation (DBS). However, the pathway anatomy and terminal arbor morphometry by which the HDP links cortical and subthalamic activity are incompletely understood. One critical hindrance to advancing understanding is the lack of anatomically detailed population models which can help explain how HDP pathway anatomy and neuronal biophysics give rise to spatiotemporal patterns of stimulus-response activity observed in vivo. Therefore, the goal of this study was to establish a population model of motor HDP axons through application of generative algorithms constrained by recent histology and imaging data. The products of this effort include a de novo macaque brain atlas, detailed statistical analysis of histological reconstructions of macaque motor HDP axons, and the generation of 10,000 morphometrically constrained synthetic motor HDP axons. The synthetic HDP axons exhibited a 3.8% mean error with respect to parametric distributions of the fiber target volume, total length, number of bifurcations, bifurcation angles, meander angles, and segment lengths measured in BDA-labeled HDP axon reconstructions. As such, this large population of synthetic motor HDP axons represents an anatomically based foundation for biophysical simulations that can be coupled to electrophysiological and/or behavioral measurements, with the goal of better understanding the role of the HDP in motor system activity.

Coronary Artery Bifurcation Angle Degree; Bifurcation Lesion Development and the Prognostic Impact

Abstract Background: Coronary artery bifurcation lesion is one of the challenges in coronary arteries revascularization. Hemo-dynamic factors, as bifurcation angle is widely recognized for its involvement in atherosclerotic plaque formation. Aim of Work: Our aim of this study was to detect the effect of coronary artery bifurcation angle degree on the development of bifurcation atherosclerosis using Computed Tomography Coronary Angiography [CTCA] and its prognos-tic impact. Patients and Methods: The study was included 221 patients having low and intermediate pretest probability for Coronary Artery Disease [CAD]. Coronary arteries were investigated with CTCA for detection of bifurcation lesions, assessment of bifurcation angle and bifurcation lesion type, then 1 year follow-up period for Acute Coronary Syndrome (ACS). Results: 138 patients were males (62%) and 83 were females (38%). The meanage group was 55.7±9.8 years old. Bifurcation lesions were higher at LAD-LCx (125 patients, 56.5%) than at LAD-major diagonal (104 patients, 47%), than at LCx-OM (56 patients, 25%) (p-value <0.0001). At LAD-LCx sites there were higher bifurcation angles in patients with atherosclerotic bifurcation lesions than patients without bifurcation lesions (77.32o±18.1o vs. 62.24o±18.2o, p-value 0.001), while there was no statistically significant difference as regard bifurcation angels at LAD-diagonal and LCx-OM bifurcation sites. There was no relation between bifurcation angle and type of atherosclerotic plaque at the three studied bifurcation sites. Patients with wider bifurcation angels regardless lesions severity or management protocol had higher rates of ACS. Conclusion: A strong relation between LM bifurcation angel and the development of atherosclerotic lesions was noted, where wider bifurcation angles are more prone for atherosclerotic lesions, and more prone to develop ACS.