Arterial Network Research Articles

The role of vascular complexity on optimal junction exponents

We examine the role of complexity on arterial tree structures, determining globally optimal vessel arrangements using the Simulated AnneaLing Vascular Optimization algorithm, a computational method which we have previously used to reproduce features of cardiac and cerebral vasculatures. In order to progress computational methods for growing arterial networks, deeper understanding of the stability of computational arterial growth algorithms to complexity, variations in physiological parameters (such as metabolic costs for maintaining and pumping blood), and underlying assumptions regarding the value of junction exponents is needed. We determine the globally optimal structure of two-dimensional arterial trees; analysing how physiological parameters affect tree morphology and optimal bifurcation exponent. We find that considering the full complexity of arterial trees is essential for determining the fundamental properties of vasculatures. We conclude that optimisation-based arterial growth algorithms are stable against uncertainties in physiological parameters, while optimal bifurcation exponents (a key parameter for many arterial growth algorithms) are affected by the complexity of vascular networks and the boundary conditions dictated by organs.

Synchrotron phase-contrast imaging applied to the anatomical study of the hand and its vascularization.

Microscopic anatomical study of the hand requires difficult or destructive dissection techniques for each anatomical structure. Synchrotron phase-contrast imaging (sPCI) allows us to study precisely, at a microscopic resolution and in a nondestructive approach, the soft tissues and bone structures within a single 3D image. Therefore, we aimed to assess the capacity of sPCI to study the arterial anatomy of the hand and digits in human cadavers for anatomical purposes. A non-injected hand from an embalmed body was imaged using sPCI at 21-µm pixel size. The vascularization and innervation of the hands were virtually reconstructed at 84-µm resolution, and the medial neurovascular bundle of the third digit at 21µm. The thinner-most distal structures were observed and reported. The diameter and thickness of the vascular and neural structures were defined on 2D computed tomographic axial projections, and using a granulometry method coupled to the 3D reconstructions. The vascularization of the hand was visible from the radial and ulnar arteries to the distal digital transverse anastomoses. The thinnest structure observed was the anastomotic arterial network around the proper palmar digital nerve. The latter emerged from the proper palmar digital artery and vascularized the nerve around its whole length and circumference. The perineural arterioles individualizable at this resolution had a diameter of 66-309µm. In conclusion, sPCI allows both the arterial and neural anatomy of the hand to be studied at the same time, as well as the anatomical interactions between both networks. It facilitates the study of structures that have different sizes, diameters, thickness, and histological origin with great precision, in a noninvasive way, and using a single technique.

Ferumoxytol-enhanced ultrashort TE MRA and quantitative morphometry of the human kidney vasculature

To evaluate the feasibility of Quantitative Ultrashort-Time-to-Echo Contrast-Enhanced (QUTE-CE) MRA using ferumoxytol as a contrast agent for abdominal angiography in the kidney. Four subjects underwent ferumoxytol-enhanced MRA with the 3D UTE Spiral VIBE WIP sequence at 3T. Image quality metrics were quantified, specifically the blood Signal-to-Noise Ratio (SNR), blood-tissue Contrast-to-Noise Ratio (CNR) and Intraluminal Signal Heterogeneity (ISH) from both the aorta and inferior vena cava (IVC). Morphometric analysis of the vessels was performed using manual approach and semi-automatic approach using Vascular Modeling ToolKit (VMTK). Image quality and branching order were compared between QUTE-CE MRA and the Gadolinium (Gd) CEMRA reference image. QUTE-CE MRA provides a bright blood snapshot that delineates arteries and veins equally in the same scan. The maximum SNR and CNR values were 3,282 ± 1,218 and 1,295 ± 580, respectively - significantly higher than available literature values using other CEMRA techniques. QUTE-CE MRA had lower ISH and depicted higher vessel branching order (7th vs 3rd) within the kidney compared to a standard dynamic clinical Gd CEMRA scan. Morphometric analysis yielded quantitative results for the total kidney volume, total cyst volume and for diameters of the branching arterial network down to the 7th branch. Vessel curvature was significantly increased (p < 0.001) in the presence of a renal cyst compared to equivalent vessels in normal kidney regions. QUTE-CE MRA is feasible for kidney angiography, providing greater detail of kidney vasculature, enabling quantitative morphometric analysis of the abdominal and intra-renal vessels and yielding metrics relevant to vascular diseases while using a contrast agent ferumoxytol that is safe for CKD patients.

Exploring the Spatial Distribution Characteristics and Correlation Factors of Wayfinding Performance on City-Scale Road Networks Based on Massive Trajectory Data

Understanding how urban residents process road network information and conduct wayfinding is important for both individual travel and intelligent transportation. However, most existing research is limited to the heterogeneity of individuals’ expression and perception abilities, and the results based on small samples are weakly representative. This paper proposes a quantitative and population-based evaluation method of wayfinding performance on city-scale road networks based on massive trajectory data. It can accurately compute and visualize the magnitude and spatial distribution differences of drivers’ wayfinding performance levels, which is not achieved by conventional methods based on small samples. In addition, a systematic index set of road network features are constructed for correlation analysis. This is an improvement on the current research, which focuses on the influence of single factors. Finally, taking 20,000 taxi drivers in Beijing as a case study, experimental results show the following: (1) Taxi drivers’ wayfinding performances show a spatial pattern of a high level on arterial road networks and a low level on secondary networks, and they are spatially autocorrelated. (2) The correlation factors of taxi drivers’ wayfinding performances mainly include anchor point, road grade, road importance, road complexity, origin-destination length, and complexity, and each factor has a different influence. (3) The path complexity has a higher correlation with the wayfinding performance level than with the path distance. (4) There is a critical point in the taxi drivers’ wayfinding performances in terms of path distance. When the critical value is exceeded, it is difficult for a driver to find a good route based on personal cognition. This research can provide theoretical and technical support for intelligent driving and wayfinding research.

Transcranial ultrafast ultrasound localization microscopy of brain vasculature in patients.

Changes in cerebral blood flow are associated with stroke, aneurysms, vascular cognitive impairment, neurodegenerative diseases and other pathologies. Brain angiograms, typically performed via computed tomography or magnetic resonance imaging, are limited to millimetre-scale resolution and are insensitive to blood-flow dynamics. Here, we show that ultrafast ultrasound localization microscopy of intravenously injected microbubbles enables transcranial imaging of deep vasculature in the adult human brain at microscopic resolution and the quantification of haemodynamic parameters. Adaptive speckle tracking to correct for micrometric brain-motion artefacts and for ultrasonic-wave aberrations induced during transcranial propagation allowed us to map the vascular network of tangled arteries, to functionally characterize blood-flow dynamics at a resolution of up to 25 μm, and to detect blood vortices in a small deep-seated aneurysm in a patient. Ultrafast ultrasound localization microscopy may facilitate the understanding of brain haemodynamics and of how vascular abnormalities in the brain are related to neurological pathologies.

Investigating the Upstream and Downstream Hemodynamic Boundary Conditions of Healthy and Growth-Restricted Rat Feto-Placental Arterial Networks.

The placenta uniquely develops to orchestrate maternal adaptations and support fetal growth and development. The expansion of the feto-placental vascular network, in part, underpins function. However it is unclear how vascular development is synergistically influenced by hemodynamics and how impairment may lead to fetal growth restriction (FGR). Here, we present a robust framework consisting of ex vivo placental casting, imaging and computational fluid dynamics of rat feto-placental networks where we investigate inlet (steady and transient) and outlet (zero-pressure, Murray's Law, asymmetric fractal trees and porous blocks) boundary conditions in a model of growth-restriction. We show that the Murray's Law flow-split boundary condition is not always appropriate and that mean steady-state inlet conditions produce comparable results to transient flow. However, we conclude that transient simulations should be adopted as they provide a larger amount of valuable data, a necessity to bridge the current knowledge gap in placental biomechanics. We also show preliminary data on changes in flow, shear stress, and flow deceleration between control and growth-restricted feto-placental networks. Our proposed framework provides a standardized approach for structural and hemodynamic analysis of feto-placental vasculature and has the potential to enhance our understanding of placental function.

Microvascular Dysfunction in Peripheral Artery Disease: Is Heat Therapy a Viable Treatment?

Peripheral artery disease (PAD) is characterized by the development of atherosclerotic plaques in the lower-body conduit arteries. PAD is commonly accompanied by microvascular disease, which may result in poor wound healing, plantar ulcer development, and subsequent limb amputation. Understanding the mechanisms underlying the development of plantar ulcers is a critical step in the development of adequate treatment options for patients with PAD. Skin is classified into two major components: glabrous and non-glabrous. These skin types have unique microcirculation characteristics, making it important to differentiate between the two when investigating mechanisms for plantar ulcer development in PAD. There is evidence for a microcirculation compensatory mechanism in PAD. This is evident by the maintenance of basal microcirculation perfusion and capillary filling pressure despite a reduced pressure differential beyond an occlusion in non-critical limb ischemia PAD. The major mechanism for this compensatory system seems to be progressive vasodilation of the arterial network below an occlusion. Recently, heat therapies have emerged as novel treatment options for attenuating the progression of PAD. Heat therapies are capable of stimulating the cardiovascular system, which may lead to beneficial adaptations that may ultimately reduce fatigue during walking in PAD. Early work in this area has shown that full-body heating is capable of generating an acute cardiovascular response, similar to exercise, which has been suggested as the most efficient treatment modality and may generate adaptations with chronic exposure. Heat therapies may emerge as a conservative treatment option capable of attenuating the progression of PAD and ultimately impeding the development of plantar ulcers.

Three-Dimensional Computed Tomography Scanning of Temporal Vessels to Assess the Safety of Filler Injections.

Temple filler injection is one of the most common minimally invasive cosmetic procedures involving the face; however, vascular complications are not uncommon. This study aimed to investigate the anatomy of the temporal vessels and provide a more accurate protocol for temple filler injection. Computed tomography (CT) scans of 56 cadaveric heads injected with lead oxide were obtained. We then used Mimics software to construct 3-dimensional (3D) images of the temporal vessels described by a coordinate system based on the bilateral tragus and right lateral canthus. In the XOY plane, the superficial temporal artery (STA), middle temporal artery (MTA), zygomatico-orbital artery (ZOA), posterior branch of the deep temporal artery (PDTA), and lateral margin of the orbital rim divide the temple into 4 parts (A, B, C, and D). The probabilities of the STA, MTA, ZOA, and PDTA appearing in parts A, B, C, and D were 30.73%, 37.06%, 39.48%, and 77.18%, respectively. In 3D images, these vessels together compose an arterial network that is anastomosed with other vessels, such as the external carotid, facial, and ocular arteries. 3D CT images can digitally elucidate the exact positions of temporal vessels in a coordinate system, improving the safety of temple filler injections in a clinical setting.

A study on the transport and interaction between blood flow and low-density-lipoprotein in near-wall regions of blood vessels

Differences in the dynamics and transport of blood make certain regions of the arterial network the preferred sites for initiation and formation of arterial diseases like stenosis and aneurysms. Understanding of such arterial diseases is directly linked to critical hemodynamic parameters such as the wall shear stress (WSS). The present work generalises the influence of WSS on the concentration of LDL that was observed in an earlier study. To this end, a wide variety of simplified flow domain, inspired by the near-wall regions of aneurysms and stenosis, are constructed and analyzed. The effects of pulsatile inflow condition, rheology of blood and curvature of the wall on the correlation between WSS and LDL concentration are investigated. It is demonstrated that the time-scale of variation of lumen-surface-concentration (LSC) of LDL is larger than a single cardiac cycle. As a consequence, the time-average values of WSS are sufficient to locate the regions of higher LSC. This idea is strengthened by making use of simplified flow domain that generates moving stagnation point. Further, it was observed that the rheology of the blood and curvature of the wall does not affect the observed correlation between the WSS and LDL concentration.

Stenosis diagnosis based on peripheral arterial and artificial neural network

The current diagnosis methods of arterial stenosis need to rely on large-scale equipment, which cannot provide early warning for patients with arterial stenosis and make them miss the best treatment opportunity. Therefore, we present an algorithm for the diagnosis of arterial stenosis, which is based on neural network. The input of neural network is peripheral pulse wave signal, and the output is the degree and location of arterial stenosis. The acquisition of peripheral pulse wave signal is convenient, and patients can detect it at home. In this paper, we extend firstly the existing human arterial transmission line model to include cerebral vessels, so that we can study cerebral artery stenosis. Then, we use the extended transmission line model to verify the effect of arterial stenosis (including carotid stenosis, renal artery stenosis, middle cerebral artery stenosis) on peripheral pulse wave signal. Finally, a database of peripheral pulse wave was established to simulate the actual conditions of artery stenosis based on the transmission line model. In addition, a diagnosis model of artery stenosis was constructed by using artificial neural network (ANN). The diagnostic results showed that when the degree of stenosis varied from 10 to 90%, the diagnostic accuracy was 88.7%. For moderate (50%) and severe (90%) degrees of stenosis, the diagnostic accuracy was 90.5% and 98.7%, respectively. Moreover, when the degree of stenosis was greater than 50%, the diagnostic accuracy of narrow positioning is greater than 95%. In general, the proposed algorithm does not rely on large equipment and has high accuracy, which can provide patients with early warning of arterial stenosis.

Well-Formed Segmental Cerebral Arteries Dampen the Peak Systolic Pressure Lowering the Chances of Aneurysms

Background: The segments of cerebral basal arterial network (CBAN) dampen the peak systolic pressure in blood flowing through these arteries. The number of aneurysms occurring in segments of CBAN will vary with the ability of each arterial segment to dampen the peak systolic pressure. Materials and Methods: Diameters of segments of CBAN were measured in cerebral computed tomography angiography images of 145 patients and the relative size of each vessel was calculated to standardise for differences in overall arterial sizes among patients. Relationships among sizes of CBAN components were statistically analysed. Presence of aneurysms in parts of internal carotid artery (ICA), middle cerebral artery (MCA), anterior cerebral artery (ACA), posterior cerebral artery (PCA), and vertebrobasilar (VB) arteries was recorded. Results: Forty-six aneurysms in right ICA and MCA and 32 aneurysms in left ICA and MCA segments were noted in 42 and 30 patients, respectively. Aneurysms in anterior communicating artery complex (AcomAC) and VB arterial segments were seen in 27 and 8 patients respectively, while they were not detected in parts of PCA. The significant (p<0·0001) inverse relationships between sizes of posterior communicating artery (PcomA) and the first segment of PCA on both sides indicated that blood inputs to the second part of PCA were similar. This smoothens vessels haemodynamics. Differences in means of the index of arterial size variation for people with aneurysms (0·96) and without aneurysms (0·86) was significant (p≤0·015). Aneurysms in ACA, PCA and VB arteries were less and was proposed that it is due to dampening of peak systolic blood pressures. The development of aneurysms occurring in CBAN depended on the degree of variation and asymmetry in its segments. Conclusion: Variation in segments of CBAN has been quantified. The peak pressure dampening mechanism in such arterial segments reduces the chances of development of aneurysms. Funding: None to declare Declaration of Interest: There is no conflict of interest with any of the authors. Ethical Approval: Randomly selected CCTA images of 145 patients archived in the Carestream data registry system at Royal Adelaide Hospital (RAH), South Australia between January 2011 and December 2019, were used in the study (male = 67, female = 78, mean age = 60·9 years) (Supplementary file 1). Human Research Ethics Board granted permission (approval number: H2014 -176) to access and use data from the Carestream data registry system (Vue RIS version 11·0·14·35).

Numerical Simulation of Blood Flows in Patient-specific Abdominal Aorta with Primary Organs.

The abdominal aorta is the largest artery in the abdominal cavity that supplies blood flows to vital organs through the complex visceral arterial branches, including the celiac trunk (the liver, stomach, spleen, etc.), the renal arteries (the kidneys) and the superior and inferior mesenteric arteries (the small and large intestine, pancreas, etc.). An accurate simulation of blood flows in this network of arteries is important for the understanding of the hemodynamics in various organs of healthy and diseased patients, but the computational cost is very high. As a result, most researchers choose to focus on a portion of the artery or use a low-dimensional approximation of the artery. In the present work, we introduce a parallel algorithm for the modeling of pulsatile flows in the abdominal aorta with branches to the primary organs, and an organ-based two-level method for calculating the resistances for the outflow boundary conditions. With this highly parallel approach, the simulation of the blood flow for a cardiac cycle of the anatomically detailed aorta can be obtained within a few hours, and the blood distribution to organs including liver, spleen and kidneys are also computed with certain accuracy. Moreover, we discuss the significant hemodynamic differences resulted from the influence of the peripheral branches. In addition, we examine the accuracy of the results with respect to the mesh size and time-step size and show the high parallel scalability of the proposed algorithm with up to 3000 processor cores.

In vivo tumour imaging employing regional delivery of novel gallium radiolabelled polymer composites

BackgroundUnderstanding the regional vascular delivery of particles to tumour sites is a prerequisite for developing new diagnostic and therapeutic composites for treatment of oncology patients. We describe a novel imageable 67Ga-radiolabelled polymer composite that is biocompatible in an animal tumour model and can be used for preclinical imaging investigations of the transit of different sized particles through arterial networks of normal and tumour-bearing organs.ResultsRadiolabelling of polymer microspheres with 67Ga was achieved using a simple mix and wash method, with tannic acid as an immobilising agent. Final in vitro binding yields after autoclaving averaged 94.7%. In vivo stability of the composite was demonstrated in New Zealand white rabbits by intravenous administration, and intrahepatic artery instillations were made in normal and VX2 tumour implanted rabbit livers. Stability of radiolabel was sufficient for rabbit lung and liver imaging over at least 3 hours and 1 hour respectively, with lung retention of radiolabel over 91%, and retention in both normal and VX2 implanted livers of over 95%. SPECT-CT imaging of anaesthetised animals and planar imaging of excised livers showed visible accumulation of radiolabel in tumours. Importantly, microsphere administration and complete liver dispersal was more easily achieved with 8 μm diameter MS than with 30 μm MS, and the smaller microspheres provided more distinct and localised tumour imaging.ConclusionThis method of producing 67Ga-radiolabelled polymer microspheres is suitable for SPECT-CT imaging of the regional vascular delivery of microspheres to tumour sites in animal models. Sharper distinction of model tumours from normal liver was obtained with smaller MS, and tumour resolution may be further improved by the use of 68Ga instead of 67Ga, to enable PET imaging.

Cerebral Vessels: An Overview of Anatomy, Physiology, and Role in the Drainage of Fluids and Solutes.

The cerebral vasculature is made up of highly specialized structures that assure constant brain perfusion necessary to meet the very high demand for oxygen and glucose by neurons and glial cells. A dense, redundant network of arteries is spread over the entire pial surface from which penetrating arteries dive into the cortex to reach the neurovascular units. Besides providing blood to the brain parenchyma, cerebral arteries are key in the drainage of interstitial fluid (ISF) and solutes such as amyloid-beta. This occurs along the basement membranes surrounding vascular smooth muscle cells, toward leptomeningeal arteries and deep cervical lymph nodes. The dense microvasculature is made up of fine capillaries. Capillary walls contain pericytes that have contractile properties and are lined by a highly specialized blood–brain barrier that regulates the entry of solutes and ions and maintains the integrity of the composition of ISF. They are also important for the production of ISF. Capillaries drain into venules that course centrifugally toward the cortex to reach cortical veins and empty into dural venous sinuses. The walls of the venous sinuses are also home to meningeal lymphatic vessels that support the drainage of cerebrospinal fluid, although such pathways are still poorly understood. Damage to macro- and microvasculature will compromise cerebral perfusion, hamper the highly synchronized movement of neurofluids, and affect the drainage of waste products leading to neuronal and glial degeneration. This review will present vascular anatomy, their role in fluid dynamics, and a summary of how their dysfunction can lead to neurodegeneration.

Particle swarm optimizer for arterial blood flow models

Background and objective: Mathematical modeling and computational simulations of arterial blood flow network can offer an insilico platform for both diagnostics and therapeutic phases of patients that suffer from cardiac diseases. These models are normally complex and involve many unknown parameters. For physiological relevance, these parameters should be optimized using in-vivo human/animal data sets. The main goal of this work is to develop an efficient, yet an accurate optimization algorithm to compute parameters in the arterial blood flow models.Methods: The particle swarm optimization (PSO) method is proposed herein for the first time, as an accurate algorithm that applies to computing parameters in the Windkessel type model of blood flow in the arterial system. We begin by defining a 6-element Windkessel (WK6) arterial flow model, which is then implemented and validated using multiple flow rate and aortic pressure measurements obtained from different subjects including dogs, pigs and humans. The parameters in the model are obtained using the PSO technique which minimizes the pressure root mean square (P-RMS) error between the computed and the measured aortic pressure waveform.Results: Model parameters obtained using the proposed PSO method were able to recover the pressure waveform in the aorta during the cardiac cycle for both healthy and diseased species (animals/humans). The PSO method provides an accurate approach to solve this challenging multi-dimensional parameter identification problem. The results obtained by PSO algorithm was compared with the classical gradient-based, namely the non-linear square fit (NLSF) algorithm.Conclusions: The results indicate that the PSO method offers alternative and accurate method to find optimal physiological parameters involved in the Windkessel model for the study of arterial blood flow network. The PSO method has performed better than the NLSF approach as depicted from the P-RMS calculations. Finally, we believe that the PSO method offers a great potential and could be used for many other biomedicine optimization problems.

Artificial Intelligence-Based Protocol for Macroscopic Traffic Simulation Model Development

This study proposes a machine learning-based protocol for developing a TRANSYT-7F model for an urban arterial network. The developed artificial neural network (ANN) method models the queue lengths of TRANSYT-7F using saturation flow, start-up lost time, and platoon dispersion as inputs. The queue lengths of the selected approaches of the study network can be obtained using the ANN model without running the TRANSYT-7F model. The optimum values of the selected parameters (i.e., saturation flow, start-up lost time, and platoon dispersion) were obtained using the genetic algorithm, which ensures minimum difference between the measured queue length and the ANN output (i.e., queue length). Finally, the comparison of the measured queue length and the simulated queue length with the calibrated TRANSYT-7F model revealed that the mean absolute percentage error was less than 2.5% for all approaches of the study network.

Realizing the roads of the future

Researchers are seeking simple ways to make asphalt pavements safer, quieter, and more eco-friendly . Roads encircle the globe in arterial networks that seem more pervasive each year. To some, they are a sign of progress; to others, they are a growing scar on the landscape. The United States alone hosts millions of miles of asphalt pavements, materials that aren’t particularly sustainable or good for surrounding ecosystems. Yet the United States and many other nations keep building and replacing the same sorts of roads year after year, using the same basic design that’s been around for centuries. We keep building and replacing the same sorts of roads year after year, using the same basic design that’s been around for centuries. But researchers and engineers have designs on some much safer, more sustainable pavements. Image credit: Shutterstock/Keith Homan. Despite humanity’s road-making rut, asphalt pavement upgrades are certainly possible. In recent years, researchers have started to work on a range of refinements that could make highways safer, quieter, and more sustainable. Modifications could include changing the aggregates and binders in the pavement or adding recycled materials into the mix. Even altering the pavement’s stiffness could improve the efficiency of vehicles using the road. Some of these changes could offer substantial reductions in the emissions of planet-warming CO2 and other pollutants. “There are all sorts of things that can be changed,” says Jeremy Gregory, a sustainability researcher at the Massachusetts Institute of Technology (MIT) in Cambridge. “We’re constantly looking for improvements.” Road design today is fundamentally the same as that used by the Romans. In general, a surface layer of pavement is laid atop thick layers of compacted granular materials that help transmit traffic loads to the underlying soil or bedrock. Modern pavement is typically made from either concrete, a mixture of …

Is the dorsal vascular system sufficient to vascularize the entire teguments of the thumb?

Simultaneous lesions of both proper digital arteries of the thumb are common in hand trauma surgery. The purpose of this anatomical study was to determine if the dorsal arterial network could be sufficient to ensure the vascularization of the thumb skin sheath. We carried out a cadaveric study on 22 hands. The ulnar and radial proper digital arteries of the thumb were ligated at the base of the first phalanx. Red dye was injected into the radial artery and blue dye into the ulnar artery at the wrist level. Visual evaluation of skin staining and systematic photographs was done at 1, 3 and 10min after injection of dyes. Staining of the thumb sheath was obtained in 100% of the dissections and complete in 91.91% of cases. Staining originated from mixed radial and ulnar artery origins in 81.82% of cases. It was incomplete in 9.09% of cases with a missing on the dorsoradial edge of the proximal phalanx. In one dissection, the whole hand skin was only stained red, and in another dissection only stained blue. The dorsal vascular network ensures the substitution of the skin vascularization in more than 90% of cases when ligating the proper digital arteries of the thumb. A clinical impression of good skin vascularization after injury of both proper digital arteries might lead the surgeon not to perform systematic revascularization, but the risk of variable damages of adjacent tissues due to an interruption of one major arterial system requires a palmar arterial anastomosis whenever possible.

TrafficGAN: Network-Scale Deep Traffic Prediction With Generative Adversarial Nets

Traffic flow prediction has received rising research interest recently since it is a key step to prevent and relieve traffic congestion in urban areas. Existing methods mostly focus on road-level or region-level traffic prediction, and fail to deeply capture the high-order spatial-temporal correlations among the road links to perform a road network-level prediction. In this paper, we propose a network-scale deep traffic prediction model called TrafficGAN, in which Generative Adversarial Nets (GAN) is utilized to predict traffic flows under an adversarial learning framework. To capture the spatial-temporal correlations among the road links of a road network, both Convolutional Neural Nets (CNN) and Long-Short Term Memory (LSTM) models are embedded into TrafficGAN. In addition, we also design a deformable convolution kernel for CNN to make it better handle the input road network data. We extensively evaluate our proposal over two large GPS probe datasets in the arterial road network of downtown Chicago and Bay Area of California. The results show that TrafficGAN significantly outperforms both traditional statistical models and state-of-the-art deep learning models in network-scale short-term traffic flow prediction.

Differences in road-traffic crash rates during construction and non-construction times on arterial streets: a comparative statistical analysis

Different studies over the past 30 years have shown an increase in the rates of crash frequencies during road construction time, but this trend is not reported as valid for all cities. A question is raised whether higher rates are observed in arterial roads in Bogotá, Colombia. It is possible to apply descriptive statistics and hypothesis tests to prove them and identify the variables that affect the accident rate during road construction. Our research aims to verify the incidence of high impact construction zones, in the crash rate at the arterial road network of Bogotá. We use descriptive statistics and inferential statistical tests to analyze whether crash rates are statistically higher during construction time than during non-construction time at the same highway sections considering different crash severities (damages-only, injuries, and fatalities). Our database considered 871 road links that make up 68 artery corridors for the city of Bogota, and 5.450 road construction zones, from 2015 to 2019. An analysis by corridor was performed, in which we identified seven patterns in the behavior of accident rates influenced by the presence of a road intervention in the corridor. Within the patterns, it was evident that some corridors reported an increase in the accident rate during the time of construction, while others showed a decrease in the same comparison. We used the Wilcoxon test to establish the statistical significance of our conclusions, with a significance level of 10%. We also found that those construction interventions that do not require excavation of more than half a meter there was a decrease in the accident severity, as damages-only crashes, diminished during the construction time, while for those interventions that include excavation greater than half a meter there was an increase in overall accident rates during construction time.