Understanding and simulating the dynamic response of quasi-brittle materials still remains as one of the most challenging issues in structural engineering. This paper presents the damage propagation material model (DAMP) developed in order to obtain reliable results for use in structural engineering practice. A brief overview focuses on the differences between fracture mechanics studies, and engineering material modelling is presented to highlight possible guideline improvements. An experimental dynamic test performed on ultra-high-performance concrete specimens was used to obtain evidence of the physical behaviour of brittle materials with respect to specimen size variations and, consequently, to verify the reliability of the material equations proposed. Two widely used material models (RHT and M72R3), as representatives of the classical brittle material models for structural purposes, and the proposed material model are compared. Here, we show how: (i) the multiple structural strength of brittle materials arises from the damage propagation process, (ii) there is no contradiction between fracture mechanics and the engineering approach once the velocity of damage propagation is chosen as fundamental material property and (iii) classical dynamic material models are intrinsically not objective with related loss of predictive capability. Finally, the original material model equation and the experimental strategy, dedicated to its extended verification, will be shown in order to increase the design predictiveness in the dynamic range considering structure and specimen size variations. The dynamic stress increasing factor (DIF), experimentally observed and widely recognised in literature as a fundamental concept for quasi-brittle material modelling, has been reviewed and decomposed in its geometrical and material dependencies. The new material model defines its DIF starting from the physical quantities of the damage propagation velocity applied to the test case boundary conditions. The resultant material model predictiveness results improved greatly, demonstrating its ability to model several dynamic events considering size and dynamic load variations with a unique material property set without showing contradictions between numerical and experimental approaches. Currently, in the design and construction of critical infrastructures , there is a great and renewed interest in understanding the mechanical response of quasi-brittle material and structural components subjected to high dynamic loading including earthquakes, man-made or natural hazards, oil perforations, etc. Current structural design is principally based on the knowledge of the material failure limits and on the capability of the material model to represent the actual behaviour of both material and structure. Despite the extensive experimental and theoretical investigations developed in the last several decades, structural design applied to quasi-brittle materials has brought about several open questions regarding the reliability and the predictive capability of the material models used. Better integration between the material model equations and the real physical behaviour of materials in a wider strain rate range is expected.The quasi-brittle material failure is characterised by a crack propagation process in which the final reduction of the structural element resistance is determined by the loss of its integrity. The process of brittle fracture has been investigated in different ways based on researchers’ scientific fields and practical interests. It is possible to distinguish different approaches, e.g., based on: (i) fracture mechanics which develops theoretical models to describe crack propagation; (ii) structural engineering use ; (iii) experimental dynamic with the goal of collecting raw data representative of the material behaviour. The first two approaches use different equations and theories to treat experimental data.The basic idea of fracture mechanics highlights how the presence of a dominant crack into a continuum body creates a perturbation into the stress field, leading to the stability or instability of the original crack eventually evolving then to structure failure. In the case of ideal elastic material relation, the crack geometry acts as the dominant parameter governing the fracture stability and then severely conditioning the admissible loads. Within this framework, the stress intensity factor is the parameter allowing to compute the new resistance limit of a cracked body. The stress intensity factor is highly geometry-dependent  and it iThe original Griffith’s idea described above was upgraded and current fracture dynamics considers the effect of a wide spread of interacting crack flaws , lately The DAMP model has been developed in the frame of a research project aiming to investigate the dynamic response of retrofitting slabs combining different layers of reinforced concrete and UHP(FR)C. The project was organised in different phases: first, experimental blasting tests on slabs with different contact and stand-off charges were performed, followed by experimental dynamic tests over specimens, varying their size, notch geometries, dynamic loading conditions and failure mode. Finally, data analysis, material modelling, simulation of experimental tests and structural assessment were developed.A large set of dynamic experimental test data was collected and a general approach to the dynamic structural analysis based on a new material constitutive equation was implemented. Structural calculation reliability was put in relation with material constitutive equations showing how the numerically calculated structural failure loads can be strongly different from the experimental one when a single dynamic test is accurately reconstructed. More than 400 dynamic tests were performed considering several stress states and using special shaped specimens and results were used to validate the new material model.By focusing mainly on material models, we wish to answer in this paper the basic question of whether the classical material model equations are suitable to represent the quasi-brittle material model response, or whether the DIF  concept should be reconsidered as a structural evidence rather than a material fundamental property. To do that, a benchmark was considered, and the response obtained by a classical material model represented here was compared. It is evident how a greater applicability and accuracy were reached by modifying the constitutive equation.During a blast event, a structure is subjected to high variations in loading. At each point, the local stress intensity and load duration can vary by several order of magnitudes with respect to those at another point. Variations are due to the wave propagation inside the structure, to the type of loading wave and to the geometrical position considered. In order to be reliable, the material model equation used to calculate the structural response should be able to reproduce the real material behaviour in a wide range of dynamic pulses; otherwise, the material model reliability will be insufficient. Indeed, the material model parameters should be the same ones identified by different dynamic tests. A two-sided perspective, known as the principle of material objectivity , should Many material models were created for structural engineering purposes. For the sake of brevity, we introduce only the two most commonly used models: the M72R3 and the RHT, which is widely used in dynamic applications dedicated to blast, perforation and damage calculation ,9,10. Thu to the material strain tensor D Equation  the material homogenisation at the characteristic scale and (ii) the representativeness of the test conditions with respect to the final event. These hypotheses allow to apply to concrete both of the dynamic equations developed for homogeneous materials and the continuity Equation , which lEquation , obtaineEquation  is used Equation  allows tEquation . The plaEquation , which iEquation . The damEquation :(1)ϵ_=f(The set of equations (Equations –7)) rep) rep7)) Up to now, the vast majority of the experimental efforts addressed to properly understand the quasi-brittle materials’ dynamic responses  highlighted the existence of an increase of the material failure limit. For example, for concrete, several expressions of DIF were proposed, e.g., in fib Model Code . This meThe extensive experimental program was performed by means of the modified Hopkinson bar apparatus (MHB) based over the original idea of Albertini and Montagnani . More inA specimen can be considered as the most simple structure to study the material response; it gives a measure of the material strength which is at the base of every structural calculation, design and evaluation approach. The overall description of the specimen is experimentally captured by average response. The specimen size represents a spatial and geometrical limit beyond which the engineer rarely investigates. M72R3 and RHT material models take the average stress as a model input parameter, neglecting the material–specimen interactions which originates the apparent specimen strength. This clearly represents a limitation to be overcome. In the quasi-static regime, the material–specimen interactions are due to the stress intensity factor for heterogeneous and pre-cracked materials. Instead, in the fast dynamic, there are other phenomena acting inside the specimen volume which create stress and strength dependency to the specimen geometry. The first one is the time- and geometry-dependent propagation of the material modifications under loading (damage and fracture). Those include the shear band propagation velocity for plastic materials and the damage propagation or crack propagation speed for quasi-brittle materials . Crack oThe presence of a progressive fracture propagating with finite speed has been experimentally highlighted by several works ,38. By aThose last physical observations trigger the idea to describe the material dynamic response by means of the damage propagation speed instead of DIF or other stress characteristics. Based on that, the new material model named DAMP  will be here presented.The case of an SHB apparatus loading a quasi-brittle specimen with a dynamic tensile stress wave is used to describe the DAMP material model idea . The inpreleased .As long as the input wave travels into the input bar, the stress remains into the elastic regime for the bar material. Then, the input wave is transmitted from the input bar to the specimen where it progressively increases the stress over the specimen fracture limit The crack and the process zone surrounding the crack tip start to propagate through the specimen cross-section b until tThe instantaneously damaged specimen area Equation  allows tEquation  and 10)Ad is calThe explicit solution of the whole equation set allows to obtain the specimen fracture time, the output stress wave intensity and amplitude transmitted to the SHB output bar and the reflected pulse. The complete specimen–bar interaction is calculated, resulting in time-, specimen-, material- and input-wave-coupled equations modelling the physical interactions occurring into the quasi-brittle specimen.Unlike the classical material model, the specimen geometry takes an explicit role in shaping the emerging stress pulse. In the DAMP model, the corresponding stress requires a time integration to be solved while respecting geometrical boundary conditions. This has been achieved by implementing the whole SHB test simulation in MATLAB, and in LsDyna finite element code.t is the time (s) at which the pulse reaches the notched cross section of the specimen. The initialisation of damage occurs at the activated defects From the DAMP equation set, the material model analytic response has been developed in the case of constant velocity of damage propagation and loading with a constant loading rate. The material is loaded with a linear stress in time according to the following equation:In the simplest case, the material model presents one activation once the true critical stress Until this condition is reached, the stress rises with a linear ramp. After The apparent material strength The damaged area is calculated with a kinematic propagation scheme. In the case of damage propagation starting from the notched side of the specimen, the damaged area is calculated as follow:The combination of the previous formula leads to a dynamic stress which is a function of time and material/specimen constants:t.That is a cubic function of time In the previous equation, the maximum of the dynamic stress is reached at time The specimen maximum apparent strength or dynamic strength in the SHB tensile case is given by:The dependence of the maximum dynamic strength on the test conditions and on the material properties is evident.F, stiffness matrix K, nodal displacement U, mass matrix M, nodal acceleration U″, damp matrix R and velocities U′. By the continuity equations, the strain is calculated starting from the displacements. For an intact elastic material, the stress x, y, z) at each time t.Classical material model calibration as well as its structural use requires the solution of the specimen/structure equilibrium equations. In the following, a symbolic flow allowing to obtain the structural MHB test response starting from the input loads and the constitutive material equations is presented. This is valid for a generic structure by applying the finite element method which automatically provides dynamic equilibrium equations having as input the material, geometry and loads. This general result is resumed in In case of classical material model, using the previous commented equation set, the final solution of the transmitted and reflected MHB pulse The structural solution procedure obtained with DAMP and the classical model is presented here. The procedure can be applied to any structural case. When the input stress wave invests the specimen, this is generally unloaded or subject to elastic deformations. The dynamic equilibrium equations are applied and solved up to the point at which the failure limit is reached. The use of the fracture initialisation criteria of the DAMP model allows to verify if the material undergoes fracture. Once the failure starts, the material changes its characteristics. The classical model requires computation of a new equation, including the material nonlinearity based on the damage computation. The new equation is written considering the entire specimen volume which undergoes plasticity instantaneously (MHB test case). The main difference between the DAMP model and the classical one consists into the calculation of the instantaneous damage propagation volume, activated by the velocity of damage propagation. By the actual damaged cross section, the equilibrium equation is written considering the undamaged specimen part which responds according to the undamaged material model. Equilibrium allows to obtain the transmitted and reflected MHB pulse stresses Now, having at disposal the gauge test data, the reverse simulation of the test is performed using the chosen constitutive equation. The output pulse is tuned to the experimental output pulse by modifying the material parameters at the best. The simulation obtained by using RHT, M72R3 and DAMP material model are compared.Once the material constitutive equation is defined, the material models ability to interpolate simultaneously multiple dynamic tests see  will be The material models based on the DIF function are not able to interpolate multiple tests. A conflict in amplitude and duration occurs: the more tests are added, the more interpolation constraints emerge . The impThe structural outputs calculated by the use of different material models are now parametrised to specimen size variations and loading-rate. This approach generalises the results observed reconstructing the experimental data. By adopting RHT and M72R3 material models, or any other material model based on stress–strain relation and DIF dynamic characterisation, any specimen dynamic strength output is represented by the DIF itself. That is by imposing the same loading rate to specimens of increasing size, an identical dynamic strength is obtained. Within the DAMP material model, the specimen size plays a direct role into the constitutive equations by means of the damage propagation. The DAMP interaction equations are analytically solved in case of loads increasing with time according to the loading rate quations –20) pro prop˙. Cquations ) 34]:(2:(2p˙. Couations (σd(t)=p˙·The DAMP dynamic strength calculated with diameter 10 or 40 mm specimens represents a single pseudo-plastic material model set belonging to the classical theory, as each curve can be obtained with a classical material model using a different DIF curve. In general, each time the specimen changes size, a modification into the DIF is obtained as the specimen dynamic strength changes.Because the output pulse depends on geometrical parameters, a brittle material can generate a family of different output pulse depending on the test boundary, geometrical and loading conditions. This phenomenon is here named multiple pseudo-plastic appearance of brittle materials. The identification of the output pulse in material stress–strain properties incorporates geometrical properties into the DIF, leading to material models intrinsically not objective and not suitable to be applied to different type of structures.By the DAMP formulation, the use of DIF can be avoided and the dynamic strength is a structural result obtained by the material application to the structure. This material model has proved to be closer to the material model objectivity principle increasing then the calculation accuracy in the framework presented data and, more in general, providing a promising approach to the analysis of structures subject to blast tests in the frame of the activities developed in cooperation with armasuisse S+T .Structural engineers need in everyday practice reliable material models and properties to develop widely and trustworthy structural assessment. The robustness of the structural calculation is the main attribute to save money in real scale tests and to ensure the safety requirements. The need to improve the structural reliability lead to reconsider material model equations. This has been achieved using an experimental parametric approach and numerical reconstruction of the results using different material models. Considering the fracture mechanic results, the new material model DAMP has been proposed. Relevant differences with respect to classical models in the ability to interpolate multiple dynamic tests were demonstrated. The classical choice of the material properties is based on stress and strains and dynamic strength. This choice simply fits the engineering needs but creates material models not objectives. The mathematical upgrade of material models does not solve the objectivity problems present, leading to a lack of reliability in a wide range of applications. Those material models can interpolate few dynamic tests at a time, while they prove to be inaccurate when considering more tests, showing strong limitations in case of specimen or structure size variations.Using the damage propagation as the primary material model variable into the DAMP material model, a wide range of dynamic tests were accurately reconstructed including specimen size variations. It has been shown how the real process of quasi-brittle fracture is closer to the DAMP equation set than to the classical model and that, because of the stress wave–fracture interaction, the dynamic strength is a quantity sensitive to specimen size. This interaction has been neglected in classical material models and is the primary source of their inaccuracy. Through a parametric approach, it has been shown how the fracture process or a single DAMP parameter generates a multitude of DIF curves corresponding to several material models set in a classical overlook. The multiple pseudo-plastic appearance has been defined as the emerging of multiple classical material model parameters by an identical constructive material because of its brittle fracture nature. This effect causes important restrictions in predictiveness capability of classical brittle material models.


In brain tumor surgery, an appropriate and careful surgical planning process is crucial for surgeons and can determine the success or failure of the surgery. A deep comprehension of spatial relationships between tumor borders and surrounding healthy tissues enables accurate surgical planning that leads to the identification of the optimal and patient-specific surgical strategy. A physical replica of the region of interest is a valuable aid for preoperative planning and simulation, allowing the physician to directly handle the patient’s anatomy and easily study the volumes involved in the surgery. In the literature, different anatomical models, produced with 3D technologies, are reported and several methodologies were proposed. Many of them share the idea that the employment of 3D printing technologies to produce anatomical models can be introduced into standard clinical practice since 3D printing is now considered to be a mature technology. Therefore, the main aim of the paper is to take into account the literature best practices and to describe the current workflow and methodology used to standardize the pre-operative virtual and physical simulation in neurosurgery. The main aim is also to introduce these practices and standards to neurosurgeons and clinical engineers interested in learning and implementing cost-effective in-house preoperative surgical planning processes. To assess the validity of the proposed scheme, four clinical cases of preoperative planning of brain cancer surgery are reported and discussed. Our preliminary results showed that the proposed methodology can be applied effectively in the neurosurgical clinical practice both in terms of affordability and in terms of simulation realism and efficacy. A brain tumor’s severity is mainly assessed by considering its grade and the originating tissue. Such an assessment is needed to provide the care team with an understanding of the tumor’s growth and how to match optimal treatments towards each individual . SurgeryAccordingly, the goal of this paper is to provide a methodology for applying 3D-based technology simulators  for aiding surgical planning of brain tumor interventions through an optimized repeatable process. In particular, we provide the reader with different fabrication approaches  using relatively inexpensive materials, commercial-grade printers, and open-source and freeware software with the aim of optimizing the costs and effectiveness of manufacturing. The fabrication strategy is determined based on the patient’s specific anatomy and the pre-surgical simulation goal. To explore the realism of the proposed methodology and evaluate its usefulness, we report four clinical cases that underwent neurosurgical treatment with the neurosurgery team of the Meyer Children’s Hospital in Florence. Our preliminary results showed that the proposed methodology can be employed efficiently in a neurosurgical clinical practice, ensuring increased affordability and simulation realism which in some cases enables surgeons to identify an alternative and minimally invasive surgical approach compared to the traditional one.As stated in the introductory section, brain cancer surgery is a complex procedure that is not risk-free, and possible complications can arise and even cause irreversible neurological deficits for the patient . The entBefore surgery, the time the surgeons devote a preoperative plan is essential and often determines the level of confidence they have during the intervention. During this step, the surgeon defines the surgical problem, first to fully identify all the anatomical and technical aspects of the procedure, and then to plan the approach. The first aim of the planning is to establish a correct diagnosis that starts from the visualization of multimodal data obtained from various imaging modalities. Such imaging modalities can be functional or structural such as magnetic resonance imaging (MRI), computed tomography (CT), functional magnetic resonance imaging (MRI) , computePreoperative planning is traditionally based on the identification of relevant anatomical reference points on tomographic data, on the measurement of the distance and angles between them, on the calculation of anatomical areas and volumes, and on the sketch of the possible trajectories for obtaining access to the tumor site. This process helps the surgeon to develop a correct 3D image of the problem in order to get a proprioceptive feel for the dynamics and complexity of the intervention to perform. Information on a surgical plan will ensure that the operating room staff has time to prepare for their patient and to identify and remedy potential difficulties . The surAn accurate and a high-resolution 3D reconstruction of the patient’s specific anatomy represents a major asset to the preoperative planning process. In neurosurgery, the development of virtual (VS) and physical simulators (PS) has allowed us to overcome some limitations of the traditional preoperative planning method (“in the mind” of the surgeon) . VirtualIn contrast, physical simulators can be directly palpated, easily modified according to the physician’s request, incised by real surgical instruments, and manipulated.Therefore, by using both physical and virtual simulators, it is possible to overcome the limits of traditional surgical planning, allowing the surgeon to understand the spatial relationships between vital structures and surgical targets. This in turn enables the surgeon to simulate different scenarios. In fact, the combination of virtual and physical simulation enables the identification of a set of promising surgical procedures that can be objectively compared to find the best intervention strategy. In addition, it makes the necessary clinical practices easier and safer for the treatment of patients, with the possibility for the clinicians to try procedures several times. In the state of the art research, there are some works dealing with the combination of virtual and physical simulators into a single mixed reality system, linking benefits coming from having a physical scenario to interact with and the potentialities offered by virtual reality . More spsimulation process developed in this work consists of the following phases (see (1)3D reconstruction of the patient’s anatomy;(2)Surgery virtual planning;(3)Fabrication of the bio-model;(4)Surgery simulation (the surgeon uses a hands-on bio-model to simulate the surgery).As mentioned in the introductory section, the present work provides a method for applying 3D technology for realistic surgical simulator fabrications for brain tumor treatment which integrate virtual and physical simulations. In particular, the ases see :(1)3D reWhile the 3D reconstruction is widely known, we focus on phases 2 and 3 in order to define a strategy which make the surgical procedure less invasive and provides a more realistic physical simulation.The remainder of the paper is as follows: in In the following subsections, the various phases of the simulation process are described in detail.The complete simulator manufacturing process includes some key steps represented in ®, Amira®, etc.), which has a price range of 4000 € to 6000 €, and with open source software . Within these software packages, once the segmentation of the anatomical element has been performed, the volume of the anatomical element is automatically obtained through embedded procedures, resulting in a three-dimensional configuration that can be stored in a 3D mesh file .An effective simulator for preoperative planning and simulation requires an exact patient specific geometry 3D reconstruction. The first step consists of the acquisition of patient medical images ) that provide anatomical information. More specifically, MRI better represents many soft tissues, thus enabling an accurate segmentation and 3D reconstruction of tissues such as the brain and blood vessels. Instead, the reconstruction of bones is performed from the segmentation of a CT scan, which provides a clear variation between calcium-based tissues and other types of tissues in gray values. Since information gained from different images acquired in the clinical track of events is usually of a complementary nature, a proper integration is often needed. The first step of the integration process is to find the spatial transformation that best aligns different datasets, a procedure referred to as registration . Such re®, Geomagic Design XTM, Geomagic Freeform, Materialise 3-Matic, etc., whose prices range from 12,000 € to 18,000 €) or open source . Such a process is needed to focus the simulation on a specific anatomical region, but could also be repeated to define the surgical lines needed to simulate the cranial resection process, thus leading the design to a partially operated simulator. In order to contain costs and to focus the simulator on an optimized head replica, a region of interest (ROI) can be first defined to specify the surgical interest 3D boundaries. Such an operation can be performed, using the surgeon’s instructions in a commercial 3D modeling software environment . In other words, the surgeon has to decide the position and orientation of a series of cutting planes to remove the bone and to easily reach the intervention area. The virtual simulation is carried out thanks to minimal cooperation between the surgeon and the CAD engineer.®, a mobile-based polygonal modeler running with an iOS operative system, demonstrated its effectiveness in dealing with virtual surgical planning [In detail, by using an information-sharing platform, the surgeon can autonomously manipulate 3D models and provide engineers with all the design constraints needed for the resection planes. In particular, the 3D modeler Forgerplanning . With an intuitive touch screen interface, the surgeon can quickly pan, zoom, and rotate the 3D models and can easily add resection planes to the virtual model. Once the planes are correctly positioned on the model, it is possible to simulate the surgery by cutting the bone and soft tissues defined by the planes themselves . More different surgical strategies can be simulated using such a tool, to define the best approach  to be further tested with the physical simulator. Moreover, the availability of the virtual model before and after the surgical simulation, allows us to manufacture the replica with and/or without the removed bone flap.A rigid simulator part is certainly appropriate to reproduce the bone tissue but also, when needed, to reproduce a rigid replica of the soft tissues. The latter is preferred when neurosurgeon does not need to interact with the simulator through real surgical instruments, but instead needs to simply train the proprioception and observe the spatial relationships between the anatomical elements. When the simulation requires distinguishing soft tissues from rigid tissues, the soft parts are fabricated by casting silicon materials in rigid shell molds, thus following the same fabrication process of other rigid parts.Once the virtual simulation has been carried out and the region of interest has been defined, the physical replica can be manufactured. This phase is divided into two different steps: rigid part fabrication and soft tissues fabrication.The manufacturing process of rigid parts can effectively be performed with low cost 3D printer (available starting from about 300 €). Materials like PLA (Polylactic Acid) or ABS (Acrylonitrile Butadiene Styrene)  are commFollowing negative feedback from some surgeons, wood-loaded PLA  was also tested to manufacture skull replicas. When PLA and ABS interact with the surgical drill, swarfs can be created adhering to the surface of the instrument, kneading it, and not allowing a correct and effective simulation of the cut. Wood-loaded PLA may represent a good choice to overcome this limit. In this case, the chip appears to be easily removable from the area of the tool, allowing us to easily perform the entire cutting procedure of the simulator.The separated structures need to be equipped by fixture joints to be assembled with accuracy after printing. CAD tools are employed to insert the anchoring systems between the various anatomical elements present in the ROI through the insertion of pins or other engineering/mechanical solutions. The 3D model of the parts prior to being printed, must be first processed and optimized by setting some printing parameters , which cThe last step of the bio-model fabrication consists of the post-processing of the 3D printing output. When the prototype presents a poor surface finish, high porosity, the presence of appendices, supporting materials, and unfinished surfaces, an improvement can be obtained through a sandblasting process. The next step can involve the application of a resin coating to finish the surface of the final product. The resin is brushed on the object to fill all the model’s cavities or indentations and to improve surface quality, thereby smoothing the roughness and reducing the stair stepping effect typical of a 3D printed object ,30.The low-cost soft tissues fabrication process combines 3D printing and some tissue-mimicking material casting. Soft tissue structures can be obtained by casting silicone rubbers in 3D printed molds. Indeed, the ultra-soft nature of some human tissues, such as the brain, can be replicated thanks to silicone rubber with different hardness ranging from the ultra-soft scale  to the soft scale . Other materials such as alginate, agarose, poly  (PVA), phytagel (PHY), Poly (ethylene glycol) (PEG), and polyurethanes are widely used in the literature , as theiDuring this work, four case studies were carried out, which involved the fabrication of preoperative simulators for neurosurgical interventions involving the resection of meningioma. Written informed consent was obtained from the four patients, including for publication of both subjects’ data and all accompanying images. All methods were carried out in accordance with the guidelines laid down in the Declaration of Helsinki.The first clinical case involved a sixteen-year-old girl suffering from a benign tumor at the base of the skull. The tumor was slightly compressing the optic nerve, thus making to accessing the tumor intracerebrally a hazardous process. The simulation objective was the identification of an alternative optimal surgical access option to preserve the optic nerve integrity. CT images  and MRI images  were acquired and saved in a DICOM  format. After obtaining the 3D reconstruction with Materialise Mimics, using first phase of the pipeline shown in In similar clinical cases, the pterional craniotomy is the traditional approach for accessing the tumor through the brain by opening the dura mater. Thanks to careful preoperative planning, a neurosurgeon has been able to identify a transorbital route for the resection of the tumor that enabled the removal of the bone of the orbit and provided access to the tumor, making the surgery minimally invasive and providing a low risk of brain damage.This case study focused on the fabrication of a simulator for the intervention of a 67 years old patient with a meningioma at the tentorium level. The position of the tumor required an accurate study of the geometry and spatial location of the meningioma placed near a venous sinus. The anatomical parts involved in the construction of the simulator were the skull, the tumor, the brain, the tentorium, and the falx. CT images  and MRI images  were acquired and saved in a DICOM format. Starting from the reconstructed digital 3D model obtained from CT segmentation with Materialise Mimics, the physician indicated that a cut on the skull was needed to access the tumor area. The models have been studied with the neurosurgical microscope to simulate the surgical approach with the aim of understanding the volumes, depth and spatial relationships between the tumor, brain, and tentorium in detail . Thanks The third simulator involved planning the removal of a meningioma during the clinoid process in a 55 years old patient. The simulator’s aim was to increase the neurosurgeon awareness of the spatial relationships between the patient’s brain, the cancer, and the big intracranial vessels. CT images  and MRI images  were saved in a DICOM format. A different view of the simulator is shown in This case study concerned the manufacturing of a simulator used in the case of a 76 years old patient with a meningioma located in the temporal lobe closely related to the meninges. The surgical operation involved separating the meninges from the tumor mass without affecting any tissue involved in the operation. In this case, therefore, the simulator consisted of four parts: a skull printed in PLA loaded with wood fiber, a brain, a meningioma made with different silicones as tissues with different hardness levels (the first with Eco-flex 00-50 and the second with Dragonskin 10), and meninges reproduced with a thin rubber sheet. In this case, the cut was made physically on the simulator by the surgeon, using real surgical instruments. The simulator allows resident physicians to practice craniotomy centered on the lesion and therefore primarily has an educational purpose. In the present section, an assessment of production times and costs is reported for applying the proposed method. Overall, the simulation process with the five phases described above requires about one week from the acquisition of diagnostic images to the actual surgery. The duration of each phase is closely linked to the simulator produced  and to the complexity of the surgery. Therefore, it is not possible to define a precise time for each phase, but an average time range could be evaluated based on our experience. The production costs of 3D printed parts can be evaluated according to the following equation :(1)Cp=Ced labor. When the simulators are composed of both soft and rigid parts, the material costs of the silicone rubbers and additives must be added (see Equation (2), Preoperative planning is a crucial step for any entire surgical procedure. A deep knowledge of the anatomical geometry of the patient is necessary to plan the best surgical strategy and to reduce the risk of surgical errors. Within this context, it is clear how important it is to use surgical simulators that allow the physician to simulate the operation before entering the surgical room, improving self-confidence and reducing stress during actual surgery . Specifi


Driving environment perception for automated vehicles is typically achieved by the use of automotive remote sensors such as radars and cameras. A vehicular wireless communication system can be viewed as a new type of remote sensor that plays a central role in connected and automated vehicles (CAVs), which are capable of sharing information with each other and also with the surrounding infrastructure. In this paper, we present the design and implementation of driving environment perception based on the fusion of vehicular wireless communications and automotive remote sensors. A track-to-track fusion of high-level sensor data and vehicular wireless communication data was performed to accurately and reliably locate the remote target in the vehicle surroundings and predict the future trajectory. The proposed approach was implemented and evaluated in vehicle tests conducted at a proving ground. The experimental results demonstrate that using vehicular wireless communications in conjunction with the on-board sensors enables improved perception of the surrounding vehicle located at varying longitudinal and lateral distances. The results also indicate that vehicle future trajectory and potential crash involvement can be reliably predicted with the proposed system in different cut-in driving scenarios. Automated driving has generated increasing interest in recent decades due to its potential to address some of the most challenging issues faced by people and communities across the world. Road traffic crashes account for 1.35 million deaths a year worldwide, and they are the leading cause of death among children and young adults aged 5 to 29 years .SAE International proposed different levels for driving automation, which include six levels ranging from no driving automation (level 0) to full driving automation level 5) [ [5]. In Despite the considerable interest and effort devoted to automated driving in the past decades, most experts agree that level 5 systems are still decades away from becoming a reality on public roads . At the There has been increasing interest in connected and automated vehicles (CAVs) in recent years due to its potential to improve road safety, convenience, and energy efficiency ,21,22. TThe majority of recent studies on CAVs focus on cooperative adaptive cruise control, cooperative intersection control, and cooperative perception . AlthougIn this paper, we present the design and implementation of cooperative environment perception based on the fusion of V2X communications and automotive remote sensors. In continuation of our previous work , the KalThe rest of the paper is organized as follows. In The overall design of the proposed cooperative environment perception approach based on on-board sensors and vehicular wireless communications is illustrated in For cooperative relative positioning, and particularly for the fusion of the on-board sensors and V2X communications, it is necessary to transform the GNSS positioning information  of the host vehicle and the remote targets from the World Geodetic System 1984 (WGS 84) reference frame to the host vehicle reference frame. For this, WGS-84 coordinates are converted to earth-centered, earth-fixed (ECEF) coordinates and then to east-north-up (ENU) coordinates. The GNSS course heading of the host vehicle is utilized to finally rotate the remote target positions and find their relative positions in the host vehicle reference frame. The relative positions and other dynamic information on remote targets acquired from V2X communications can be used in conjunction with the measurements from on-board sensors for more accurate and reliable target state estimation, classification, and trajectory prediction. Some of the safety applications that can be offered with this cooperative approach are shown in the safety applications block in The types of sensors used for driving environment perception and object tracking in recent years include radars, cameras, and lidars. These sensors perform detection of objects in the vehicle surroundings and provide information on the object state  and object classification. Some of the most common advanced driver assistance system (ADAS) applications enabled by the environment perception technology include forward collision warning (FCW), automatic emergency braking (AEB), adaptive cruise control (ACC), lane departure warning (LDW), and lane keeping assist system (LKAS). For this study, we equipped our test vehicle with radar and camera sensors that have already been incorporated into production vehicles.Automotive radar, which is an active ranging sensor designed for detecting and tracking remote targets in the surrounding environment, is one of the most used ranging sensors for ADAS functions these days. Automotive radars are capable of providing the relative position and speed information about the objects located within the sensor FOV, and they operate even in adverse weather conditions such as rain, fog, and snow. Two frequency bands, 24 GHz and 77 GHz, have been predominantly exploited for automotive radars ,31,32. TComputer vision techniques are increasingly utilized for automotive safety applications. Camera systems with computer vision methods perform detection and localization of the objects that have been captured in the camera images. It is also possible to extract valuable information on the driving environment, such as lane marking positions and road curvature, from the images obtained with the cameras on board the vehicle. A comprehensive review on computer vision techniques for vehicle detection, tracking, and behavior characterization is presented in . The mosLidar stands for light detection and ranging, and as the name suggests, it measures the relative distance and angle to a target within its FOV by transmitting laser light and measuring reflected light. Near-infrared light with a wavelength of 905 nm is typically used for automotive lidars, and they are capable of higher localization performance compared with other automotive ranging sensors. Lidar sensors attracted much attention of the automated driving research community since they were used by many groups who participated in the DARPA Grand Challenges ,40,41. DThere exists a range of wireless communication technologies that can be employed for CAV systems and intelligent transportation system (ITS) applications  ,46. The The vehicle state information is broadcast and shared among the vehicles equipped with DSRC devices by exchanging the BSM, which is defined in the SAE J2735 message set dictionary . The BSMA Kalman-filter-based fusion approach that was previously described in  is emploKalman filtering ,51 is a The random variable The relative positions and the motion equations of the remote targets in the vehicle surroundings are typically given in Cartesian coordinates, and it is necessary to perform a polar-to-Cartesian transformation when the ranging measurements obtained from remote sensors  are in polar coordinates. An extended Kalman filter (EKF) is often utilized to handle such nonlinear systems; however, the linear approximation of a nonlinear system may result in highly unstable performance, and the derivation of the Jacobian matrices is often nontrivial in many applications . More adThe operation of the unbiased converted measurement Kalman filter is described in The computation of the unbiased converted measurements as well as the associated covariance requires the compensation factors The rest of the steps for obtaining the covariance of the unbiased conversion are as shown in A track-to-track fusion approach is employed in this study for combining high-level data from multiple sources. The data processing for each sensor system is performed individually at the sensor level in a high-level fusion system. Each sensor system outputs one or more tracks based on the sensor measurements, and the state estimates from multiple sensor tracks are associated and combined with a track-to-track fusion algorithm. A high-level fusion of multiple sensors has been successfully implemented in many studies dealing with automotive applications ,60,61,62One of the most widely used algorithms for track-to-track fusion is the convex combination algorithm ,66,67,68The future trajectory of the remote target in the vehicle surroundings is estimated with a CTRV model. The state space at time step For the purpose of risk assessment, the circle model described in  is emploThe detection of a possible collision leads to the generation of a collision warning to the host vehicle. Based on the time-to-collision (TTC) estimate, four different collision warning messages are provided. Following the collision warning stages discussed in , the warThe proposed system for cooperative driving environment perception was evaluated experimentally in test-track environments. Two test vehicles were utilized for the experiments where both vehicles were equipped with V2X communication devices such that the exchange of the BSM between the two test vehicles was enabled. In order to evaluate the benefits of introducing V2X communications to the currently available environment perception systems, the host vehicle in this work was additionally equipped with radar and camera systems that have already been adopted in production vehicles.Two Kia Soul cars, one in white and the other in yellow as shown in For real-time data acquisition and processing, the host vehicle was equipped with a dSPACE SCALEXIO AutoBox, which is an in-vehicle prototyping system with a real-time processor and interfaces for CAN and Ethernet communications. The signals transmitted from the radar and camera systems as well as the in-vehicle ECUs were acquired via CAN interfaces, and the signals transmitted from the DSRC OBU were acquired via Ethernet interfaces. RTCM corrections were acquired with an NTRIP client running on a smartphone and streamed via a Bluetooth connection to the u-blox C099-F9P application board. In order to obtain ground truth positions for the test vehicles, both vehicles were equipped with an Ascen AKT980R, which is a highly accurate GNSS receiver that provides GNSS carrier phase measurements with a horizontal positioning accuracy of 0.008 m and a heading accuracy of 0.09 deg with a 2-m baseline. The overview of the hardware interface for the proposed system is presented in In order to obtain relative position estimates of the remote vehicle from the radar and camera and also from V2X communications, driving experiments were conducted under the scenarios where the remote vehicle is driven ahead the host vehicle. For the performance evaluation of the proposed data fusion approach for different relative target locations, the relative distance between the two test vehicles was gradually increased. As shown in As presented in The results obtained when the target vehicle is at a relative longitudinal distance of 70 m or longer are not used for this performance evaluation, considering that the lateral position accuracy of the GNSS system used for ground truth degrades at such long distances due to the limited heading accuracy such that it may not be appropriate to be utilized as a reference system. In addition, the Mobileye camera used in this work appears to suffer from significant degradation in longitudinal accuracy for remote targets located at such distances.The ground truth distance to the remote vehicle during the driving scenario where the remote vehicle is in the adjacent lane is shown in The performance of the individual remote sensing systems and the proposed cooperative environment perception approach is evaluated by computing the RMSE and the standard deviation of the error at different relative distances as shown in The performance of the proposed cooperative environment perception approach was also evaluated in cut-in driving scenarios where the remote vehicle performs a lane-change maneuver in front of the host vehicle. Three different cut-in scenarios were considered in this work as described in The ground truth relative position of the remote vehicle and the absolute error for the relative position during the cut-in driving scenario 1 are shown in In this paper, we presented the experimental design and performance evaluation of the driving environment perception system based on the fusion of multiple on-board sensors and V2X communications. The two test vehicles used for the driving experiments were each equipped with DSRC equipment and a low-cost GNSS receiver for the exchange of BSM data. The host vehicle was additionally equipped with radar and camera sensors that have already been adopted in production vehicles. The performance of the proposed fusion approach in terms of relative positioning accuracy was evaluated at varying longitudinal and lateral distances between the two test vehicles. In the longitudinal direction, the total RMSE of the relative position estimated with the proposed fusion approach was 0.27 m, whereas those estimated with the camera and radar sensors were 1.91 m and 0.57 m, respectively, which correspond to an improvement of 86% and 52%. In the lateral direction, the total RMSE of the relative position estimated with the proposed method was 0.12 m, while those estimated with the camera and radar were 0.16 m and 0.26 m, respectively, corresponding to an improvement of 27% and 56%. The performance of the trajectory prediction and risk assessment was evaluated in different cut-in driving scenarios where the remote vehicle performs a lane-change maneuver in front of the host vehicle. The test results showed that the proposed method provides accurate target localization and facilitates reliable target trajectory prediction and detection of potential collision during the events when a remote vehicle driving in an adjacent lane cuts in front of the host vehicle.Although the proposed cooperative approach for driving environment perception proved to be successful in the driving scenarios considered in this study, there still exists a number of challenges to be addressed. The scope of this paper has been limited to driving scenarios where a single remote target is present in the surroundings of the host vehicle. As part of future work, the benefits of the cooperative environment perception approach will be further investigated in scenarios that involve multiple surrounding objects for more diverse use cases. In addition, various factors that could adversely affect the accuracy and reliability of on-board sensors  and V2X communications  will be examined so that the data quality levels that can be expected for each sensor track and for V2X communications can be more accurately determined in continuously changing driving conditions. It is also important to note that the trajectory prediction performed in the scope of this study was based on the physics-based motion model, which performs well for short-term prediction but degrades in its performance when the prediction horizon is extended. Furthermore, this trajectory prediction approach cannot anticipate the state changes caused by varying road curvature, traffic signals, or future driving maneuver execution. Therefore, future work should investigate interaction-aware motion models and also incorporate the map data and the signal phase and timing message, which can be acquired via V2X communications, for accurate and reliable longer-term trajectory prediction that takes into account inter-vehicle interaction, road configuration, and traffic signal dependencies.


To endow robots with the flexibility to perform a wide range of tasks in diverse and complex environments, learning their controller from experience data is a promising approach. In particular, some recent meta-learning methods are shown to solve novel tasks by leveraging their experience of performing other tasks during training. Although studies around meta-learning of robot control have worked on improving the performance, the safety issue has not been fully explored, which is also an important consideration in the deployment. In this paper, we firstly relate uncertainty on task inference with the safety in meta-learning of visual imitation, and then propose a novel framework for estimating the task uncertainty through probabilistic inference in the task-embedding space, called PETNet. We validate PETNet with a manipulation task with a simulated robot arm in terms of the task performance and uncertainty evaluation on task inference. Following the standard benchmark procedure in meta-imitation learning, we show PETNet can achieve the same or higher level of performance (success rate of novel tasks at meta-test time) as previous methods. In addition, by testing PETNet with semantically inappropriate or synthesized out-of-distribution demonstrations, PETNet shows the ability to capture the uncertainty about the tasks inherent in the given demonstrations, which allows the robot to identify situations where the controller might not perform properly. These results illustrate our proposal takes a significant step forward to the safe deployment of robot learning systems into diverse tasks and environments. The development of generalist robots remains a key challenge in robotics. These robots are expected to perform a wide range of tasks in diverse environments, for instance, automation of household chores or operations in retail stores. As hand-engineering specific skills for every task and environment is clearly infeasible, many studies focus on data-driven approaches, which learn desired skills from experiences. For example, reinforcement learning is a popular choice, where robots learn their control policies from the interaction with the environment , which embeds task information for adapting the controller as a distribution. This algorithm is intended to measure task uncertainty while deploying a meta-imitation learning algorithm. PETNet is designed around the notion that as a demonstration can sometimes be ambiguous, task embedding should be modeled in a probabilistic manner. This probabilistic inference on the task variable allows us to quantify how certain the model is about the task from the demonstrations at hand. As for the implementation, the model simultaneously learns the task embedding network that infers explicit task variables along with the control policy conditioned on those task variables. The task embedding network outputs a distribution on the task embedding space from few-shot demonstrations and we use the variance of the distribution as the measure of task uncertainty in these demonstrations.We tested PETNet with the simulated manipulation environment presented in Finn et al.  and confTo summarize, key contributions of this paper are (1) proposing a framework for leveraging uncertainty of task indicated with demonstrations for realizing the safety of robot under various tasks in meta-imitation learning and (2) with the simple implementation with probabilistic inference on task embedding space, this approach can capture the task uncertainty, leading to identify demonstrations with which the model would not perform properly.Most studies aiming at generalist robots have focused on improving the sample efficiency of the learning algorithm. As in other domains in machine learning, such as image  takes the task variable zi and the visual observation o as inputs.The controller π for each timestep t. The variance from the task-embedding network is the measurement of the uncertainty about inference from the cue to the task. Algorithm 2 describes the procedure used in meta-testing.During meta-testing, when the robot faces with the new task The cue is not restricted, in principle, to videos of demonstrations performed by the same robot. The cue could be any demonstration, like a video of a human performing an action, as long as the task information is preserved. We will discuss the generalizability of the approach further in the section 5.In this section, we explain the experimental tests and our analysis of the characteristics of the PETNet algorithm. These tests address the following questions:Can PETNet attain performance comparable to that of previous methods in meta-testing?Does PETNet can capture the uncertainty of the task embedding inferred from the cue?Is the uncertainty estimated by PETNet useful for improving the safety of the controller?We evaluate PETNet with a simulated pushing task of MIL sim-push dataset using the MuJoCo physics simulator . The network architecture is almost the same as TecNets for fair comparison. Both task embedding network and the controller have four convolutional layers (CNN) followed by three fully-connected layers. Each convolutional layer has 5 × 5 filters of 16 channels with 4 strides and ReLU activation function  is the variant without the cosine embedding loss during the learning and its performance is worse than the other variants (58.56%), which shows the loss term is necessary to group embeddings of the same task in TecNets. However, while PETNet does not have such explicit embedding loss term, the performance is almost the same as TecNets, which implies that the probabilistic inference-based method of PETNet can contribute appropriate task representation in the embedding space. As shown in the experiment above, the proposed method for estimating task uncertainty has no negative impact on the final performance of meta-imitation.We compared the performance of PETNet with that of two previous methods, namely MIL . Here, we can hypothesize that we can prevent such failures if the inappropriate cues are detected by monitoring the variance.Therefore, we examined the relationship between the task uncertainty of the demonstrations and performance during meta-testing. We employ anomaly detection on the estimated variances to detect the anomalous demonstrations that may cause failure, using a one-class support vector machine (OCSVM) with a linear kernel  is the ongoing work in the robot learning community (Yu et al., As the extensions of our work, the approach of measuring task uncertainty on the task-embedding space can be generalizable to other learning algorithms like reinforcement learning or inverse reinforcement learning. Our results open the door for using demonstrations in other modalities like language instructions, human demonstrators (Yu et al., https://rail.eecs.berkeley.edu/datasets/mil_data.zip.Publicly available datasets were analyzed in this study. This data can be found at: TM designed the study, developed the method, and wrote the initial draft of the manuscript. NK contributed to the implementation of the code, analysis of data, and assisted in the preparation of the manuscript. YI contributed to the experimental design and has critically reviewed the manuscript. KN and YM contributed to the design of the study and preparation of the manuscript. All authors contributed to the article and approved the submitted version.KN was employed by the company DeepX Inc. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Dural arteriovenous fistulas involving the cavernous sinus can lead to orbital pain, vision loss and, in the setting of associated cortical venous reflux, intracranial hemorrhage. The treatment of dural arteriovenous fistulas has primarily become the role of the endovascular surgeon. The venous anatomy surrounding the cavernous sinus and venous sinus thrombosis that is often associated with these fistulas contributes to the complexity of these interventions. The current report gives a detailed description of the alternate endovascular routes to the cavernous sinus based on a single center’s experience as well as a literature review supporting each approach. A comprehensive understanding of the anatomy and approaches to the cavernous sinus available to the endovascular surgeon is vital to the successful treatment of this condition. The cavernous sinuses (CS) are dural venous channels located on either side of the body of the sphenoid bone. The CS has four walls, three of which consist of two layers of dura . The medial wall, the only with a single layer of dura, makes up the lateral limit of the sella. The lateral wall contains cranial nerves (CN) III, IV, and V and lies just medial to the temporal pole. The superior wall, or roof of the CS, stretches from the diaphragma sellae medially to the anterior clinoid process laterally. The posterior wall contributes to the dura of the clivus . The cavThe major tributaries to the CS are the superior ophthalmic vein (SOV), inferior ophthalmic vein, superficial middle cerebral vein (SMCV), sphenoparietal  sinus, and the contralateral sinus through the intercavernous (circular) sinus. The major egress of the CS includes the superior petrosal sinus (SPS), inferior petrosal sinus (IPS), emissary veins to the pterygoid plexus, clival plexus to the posterior fossa and paraspinal venous plexus, and the contralateral sinus through the intercavernous sinus.In 1985, Barrow et al. classified carotid cavernous fistulas (CCF) into direct (Type A) or indirect  fistulas . A direcThe presentation, work up, and management options for CCFs are well published ,4,5. IndThe current report focuses on dural CCFs and the multiple transvenous routes to the CS available to the endovascular surgeon.The inferior petrosal sinus is a common route to the CS in the setting of dural CCFs ,4,7,8. TIn general, the authors most commonly use a standard 0.010” or 0.014” microwire with a compatible microcatheter. A softer, more torqueable microwire is usually chosen first, followed by stiffer wires as needed. Microwires larger than 0.014” are rarely necessary. In longer approaches, such as with the middle temporal vein or angular vein to the SOV, a longer and softer microcatheter is selected such as the MicroVention Headway Duo 167 cm  or the Medtronic Marathon 165 cm . When torqueability and support are needed in these longer approaches, usually a 0.010 wire is used. When the anatomy is particularly tortuous a softer wire is usually chosen such as the Medtronic Mirage 0.008”  or the Balt Hybrid 0.007”/0.012” .When it is present and patent, the IPS provides a direct route to the CS. However, when this route is not available, alternatives do exist.Another common route to the CS is through the SOV, which is often dilated in dural CCFs. Transfemoral access to the SOV can be achieved by catheterization of the angular vein, which communicates with the SOV via the nasofrontal vein. The frontal and supraorbital veins join to form the angular vein which runs inferiorly in an oblique fashion, lateral to the root of the nose, down to the inferior margin of the orbit where it continues as the anterior facial vein. The anterior facial vein runs deep to the facial artery, superficial to the masseter muscle and joins the retromandibular vein to form the common facial vein, which drains directly into the IJV. The common facial vein can be selected with the curved tip of a micro- or guidewire directed anteriorly at approximately the midcervical segment of the IJV (near the angle of the mandible) . In someAnother technique to keep in mind when using this approach is the ability to “milk” the microcatheter in these superficial subcutaneous facial veins. With one finger, gentle pressure can be applied to the skin directly over the microcatheter in a sweeping fashion towards the eye. Alternatively, physically manipulating the skin and tissue can change the angle of the vein and allow the microcatheter to advance or even direct the catheter into a desired branch. This technique can be useful when attempting to navigate a difficult angle or gain more support by removing the slack in the system.Yu et al. reported endovascular embolization of 74 CCFs in 71 patients using a transvenous approach, with an overall success rate of 86.5% . The IPSThe angular vein/SOV approach is not only useful in cases of IPS thrombosis but also when the fistula site is located within the anterior CS and does not communicate with the posterior CS. This is a common occurrence secondary to compartmentalization of the CS. The IPS approach may only provide access to the posterior CS, while the SOV allows the operator to gain access to an anteriorly located fistula site.As described in the study by Yu et al., the SOV can also be accessed via the middle temporal vein . To reacIn 2002, Mounayer, et al. described the endovascular treatment of a dural CCF utilizing the SPS for access to the CS . In theiAs one of the major egresses of the CS, the pterygoid plexus can be used as an access route in the setting of dural CCFs. In 1998, Jahan et al. described the endovascular treatment of a right-sided dural CCF via the contralateral pterygoid plexus . The venKurata et al. described an alternative endovascular approach to the CS via the inferior petrooccipital vein (IPOV) . The IPOThe intercavernous sinus (aka circular sinus) is both a major egress as well as a major tributary to the CS. This venous pathway has an anterior limb, which runs in front of the pituitary stalk, and a posterior limb, running behind the pituitary stalk. The anterior limb is generally larger than the posterior limb, and together with the two CSs, they form the circular sinus. Depending on the venous anatomy, the anterior limb, posterior limb, or both may be absent.The clival plexus (aka basilar plexus) is a network of veins located between the two layers of the clival dura and drains into the anterior vertebral venous plexus. While the clival plexus primarily serves as an egress of the CS, because of its multiple interconnections, it also provides a pathway between the left and right CS.In the setting of CCFs, the venous drainage may be primarily through contralateral pathways. Therefore, the best endovascular approach to a left sided CCF may be through the right IPS. Once the contralateral CS has been accessed, the ipsilateral CS can be accessed by crossing the intercavernous sinus, or more commonly through the clival plexus. The intercavernous connection is selected with a curved microwire directed either anteriorly or posteriorly. The microwire is then traversed across the intercavernous connection and, if necessary, looped within the opposite CS to provide support for the microcatheter to follow . This apWhen transfemoral access to the fistula site is not possible, direct percutaneous transorbital puncture of the CS, SOV, or IOV can be an effective alternative. Kurata et al. described direct percutaneous puncture of the extraconal portion of the SOV in three patients with traumatic CCFs in which transarterial and IPS approaches failed . In theiAn alternative that should be considered for anteriorly located dural CCFs with venous drainage through dilated ophthalmic veins is surgical exposure of the SOV or IOV. Surgical exposure of the SOV and the IOV have been previously described ,22,23,24Despite the multiple routes to the CS available to the endovascular surgeon, in some cases, the venous anatomy and location of the fistula site make treatment with endovascular techniques alone inadequate. In these cases, open microsurgical exposure of the CS combined with endovascular embolization may be an option. Staged microsurgical obliteration of residual DAVFs after incomplete endovascular embolization is well published ,25,26. HIn the setting of direct CCFs, the tear in the cavernous segment of the ICA provides an endovascular route to the CS. A primary transarterial approach can often be used to embolize these fistulas. Prior to attempting a primary embolization of the fistula, a complete angiogram should be completed, and if adequate cross-filling is identified, a balloon test occlusion (BTO) is recommended. If the patient remains neurologically unchanged, the most effective treatment is often complete ICA occlusion. It is important to remember that the carotid occlusion should extend across the fistula site both proximally and distally to prevent retrograde filling of the fistula from collateral circulation. In the case of failed BTO, the fistula must be treated while maintaining patency of the ICA. In this case, the authors often use a two-catheter system with a microcatheter in the cavernous sinus for embolization and a Scepter balloon catheter  to protect the ICA. Using roadmapping technique, a microsystem is then navigated through the tear in the cavernous ICA into the affected CS. An occlusion balloon, or a stent, is placed within the cavernous ICA across the fistula site to protect the ICA during embolization. Coils, Onyx , or a combination of both are then used to obliterate the fistula. Alternatively, in some cases of direct CCF, a combined transarterial and transvenous approach is the safest and most effective way to embolize the fistula. For dural CCFs, a transarterial approach with embolization of the dural ICA or ECA feeders can be an effective treatment strategy. However, navigating multiple small arterial feeders can be difficult and time consuming. Furthermore, given the added risk of cranial nerve deficit with occlusion of mengingeal arteries, the authors prefer the transvenous approach for most dural CCFs and use the transarterial approach sparingly.The key to approach selection lies in careful study of initial diagnostic angiography. In particular the venous phase is reviewed looking at the connections of the internal and external jugular veins and their respective venous outlet anatomy. Characterization of the connections of the SOV to the facial venous system is of critical importance. The absence of any viable endovascular route may require more direct access to the cavernous sinus.While this work represents a detailed review of the commonly used endovascular approaches to the CS, it is not intended to be comprehensive. Other, approaches have been described including direct transovale access to the CS. Gil et al. described percutaneous puncture of a CCF that was refractory to standard approaches through the foramen ovale in order to completely obliterate the fistula . Ghosh eThe transvenous approach to the CS is an effective management strategy for the treatment of dural CCFs. The venous anatomy associated with the cavernous sinus can be complex and highly variable, with hypoplasia and venous thrombosis commonly seen ,33. CCF Many benign dural CCFs will resolve spontaneously with time, and conservative management should be discussed as a treatment option in the absence of worsening vision, increasing intraocular pressure, or CVR . HoweverOnce the decision to intervene has been made, it is important to keep in mind the goals of therapy, as well as the priority of each goal. The highest risk of death or major disability in a patient with a CCF is intracranial hemorrhage secondary to venous hypertension. For this reason, the authors prefer to disconnect the site of CVR first before addressing orbital symptoms. For example, in a CCF with reflux into both the SMCV and SOV, the authors will first block the venous outlet into the SMCV in the posterior CS  and then reposition the microcather into the anterior CS to block the reflux into the SOV. Remember that all injections should be done gently especially within orbital veins or the CS itself in order to avoid over pressurizing an abnormally high-pressure system, which can lead to vessel rupture with intraorbital and/or intracranial hemorrhage. Above all, the fistula site itself must be completely obliterated to avoid redirecting venous outflow into alternate pathways, which can turn a symptomatic CCF with reflux only into the SOV into a life-threatening fistula with reflux into cortical veins.The evaluation and management of patients with a CCF has largely become the responsibility of the endovascular surgeon. When intervention is indicated in a patient with a dural CCF, a transvenous approach through the IPS is commonly used. However, in the absence of a patent IPS multiple alternative routes do exist, and an understanding of and experience with each approach can greatly enhance the technical success of these procedures.


Fatigue influences some kinematic parameters and accuracy of passing. The findings of this study suggest that coaches conduct as many drills as possible in situational conditions that are similar to the conditions during the basketball game itself.Kinematic analysis is an objective method for examining basketball technique. However, there are just a few studies featuring a kinematic analysis of passing. The purpose of this study was to determine whether the kinematic parameters and accuracy of passing changed when players were under the influence of fatigue. Eleven Croatian basketball players who are members of the youth national program  participated in fatigue and non-fatigue repetitive tests. A Xsens suit was used to analyze the kinematic parameters of push passing; a radar gun was used to determine ball speed; heart rate and blood lactate were used to identify fatigue and non-fatigue state. There was a significant difference in angular velocities of shoulder ( The fundamental skills are the foundation for success at all levels of basketball, and all players must learn to execute them properly and quickly in order to be successful ,2. In baTherefore, given the importance of passing in basketball skills, coaches should be persistent in developing passing skill.2 max of the players during a competitive game were close to their maximal values [From a physiological point of view, basketball is an intermittent sport that involves both intensive brief movements  and less intensive long-lasting activities . Thus, the players’ physiological demands of a basketball game, which require both aerobic and anaerobic energy systems, are claimed to be high . Some stl values ,11,12. Fatigue becomes an unavoidable part of the game that may deteriorate performance, coordination, and the players’ technique . Some plOn the other hand, there are only a few studies that investigated the change of passing accuracy under fatigue ,18. HoweThe kinematic analysis represents an objective method to observe basketball players’ passing skills , which cThe sample consisted of 11 Croatian basketball players  who are members of the Croatian youth national program. Players had no health nor injury issues. In order to avoid the interference of fatigue on testing, players were asked to restrain from training sessions one day before testing. All participants were provided with a detailed explanation of the study procedures and gave written informed consent prior to the measuring procedure. The Faculty of Kinesiology, University of Zagreb (Croatia) Ethics Committee approved the study, which was performed following the ethical standards of the Declaration of Helsinki. Each player was tested in one day, but the overall testing was conducted during three days in the following manner: three players were tested on the first day, and the other eight participants were tested on the following two days . All players underwent the same protocol: before testing, they had one day of rest, while the testing performed the next day consisted of warm up, non-fatigue passing testing, fatigue protocol, and fatigue passing testing. Basic anthropometric characteristics were measured on each day of the testing and used for system calibration performed according to the instruction of the manufacturer . In order to identify the level of players’ fatigue, their Heart Rate (HR) and Blood Lactate (BL) were measured by heart rate sensors  and a portable lactate analyzer  respectively before starting the test. In addition, the participants’ HR and BL were measured once more immediately after conducting the fatigue protocol. Then, the same passing test was conducted again in order to observe the change of passing accuracy and kinematic parameters under the influence of fatigue. axis) (m/s); pelvis velocity in Y-axis from the point the player caught the ball until release (PELVIS_Yaxis) (m/s); maximum angular velocities in shoulder from the point the player started to pass the ball until release (SHOULDER_AVmax) (°/s), maximum angular velocities in elbow from the point the player started to pass the ball until release (ELBOW_AVmax) (°/s), and maximum angular velocities in wrist from the point the player started to pass the ball until release (WRIST_AVmax) (°/s); the speed of ball approaching the target (BALL_S) (km/h); and the passing accuracy (ACCURACY) (points).The following variables were observed: pelvis position from the point the player caught the ball until release (PELVIS_P) (cm); pelvis velocity in X-axis from the point the player caught the ball until release . Previous study has confirmed the reliability and validity of Xsens kinematic suit for analyzing angular velocity and other kinematic parameters in different basketball techniques . In addiAs shown in Eight points were awarded for each pass that hit the target without touching the hoop.Six points were awarded for each pass that hit the target but touched the hoop once.Four points were awarded for each pass that hit the target but touched the hoop more than once.Two points were awarded for each pass that did not hit the target but touched the hoop.No points were awarded if the ball did not hit the target nor touch the hoop, or if a pass other than a push pass was used.2 with the change of direction of 180°) was used as fatigue protocol due to similarities with game situations in which a player runs forward and backwards consecutively. The reliability of this fatigue protocol was previously verified [The 300-meter shuttle run  was used for the statistical analysis. Basic descriptive parameters were calculated for all measured variables. The normality of the data distribution was evaluated using Kolmogorov–Smirnov test. To verify the differences of the kinematic parameters between fatigue and non-fatigue, analysis of variance (ANOVA) for repeated measures was applied. With the use of the G*power program, the sample size (number of passes) was calculated (n = 98) that was needed for measurement procedure with statistical significance max) , elbow (ELBOW_AVmax) , and wrist joint (WRIST_AVmax) . The mean value of maximum angular velocity in wrist joint (WRIST_AVmax) was obviously higher than in elbow (ELBOW_AVmax) and shoulder (SHOULDER_AVmax) both in fatigue and non-fatigue conditions (axis) and Y-axis (PELVIS_Yaxis) when players were under fatigue was lower than in non-fatigue condition; the ball speed (BALL_S) when players were under fatigue was decreased compared to non-fatigue condition .As shown in nditions ; the meamax; p = 0.01), elbow  and wrist . In addition, there were significant differences in passing accuracy  and ball speed  between fatigue and non-fatigue conditions; there were significant differences in the pelvis position  and the pelvis velocity X-axis  between fatigue and non-fatigue conditions. However, there was no significant difference in the pelvis Y-axis .In addition, the results in As presented in p = 0.00).There were few studies observing the change of kinematic parameters and accuracy of basketball passing under physiological load. The present study aimed to identify whether some kinematic parameters of push passing changed when players were under the influence of fatigue and to examine if fatigue affected the passing accuracy. The main findings from this study showed that there were significant differences between non-fatigue and fatigue conditions in kinematic parameters and passing accuracy, which is in line with our previously formulated hypotheses.Physiological variables such as HR and BL can be measured not only in sterile laboratory conditions but also on field and in more authentic conditions . HR and The results from this study showed that there were significant differences between non-fatigue and fatigue conditions in kinematic parameters. Slawinski et al.  investigThere was also a significant difference in passing accuracy and the speed of the ball approaching the target. A few studies investigated the change of passing accuracy related to fatigue. There were two studies investigating the impact of fatigue on the accuracy of basketball chest passing, and their results showed that there was a significant difference in passing accuracy when players were under the influence of fatigue ,18. The In this study, the PELVIS_P in fatigue condition was significantly higher than in non-fatigue condition. Some previous studies have stated that decreases of lower limb muscle activation due to fatigue could result in changes in PELVIS_P, and the reduction of strength tended to increase the player’s center of mass ,33. LafoFatigue can cause the reduction in the capacity of the muscle to generate force, which results in a player who is unable to continue moving at the same level of performance ,36,37. Imax was higher than ELBOW_AVmax, and that of ELBOW_AVmax was higher than SHOULDER_AVmax both in fatigue and non-fatigue conditions  between fatigue and non-fatigue conditions. It is very important to perform crossover with a quick first step after receiving the ball so that the offensive player can take an advantage over the defensive player. In that situation, another defensive player on the helping side tries to stop the player’s drive to the basket. That movement creates a situation for passing to an open offensive player who stays at the corner and waits for the pass and open shot or drive. In this study, the PELVIS_Xaxis was decreased after fatigue protocol, which means that the player did not have enough velocity to pass by the defender to the basket and probably would not attract the help of the defender. As a result of that, the offensive player who stayed at the corner lost the opportunity to catch the ball and shoot.The PELVIS_Xe basket . Thus, tThe presented study focused on the technique of push passing, but different kinds of passing can be used in a game as well. Thus, it is worth exploring the change of kinematic parameters on other passing techniques such as chest or overhead passing. In addition, the limitation of this study was the situation that the testing was performed without defensive players who can be included in some future research. Therefore, these factors are worth analyzing in the future studies related to passing technique.There were significant differences in maximum angular velocity of shoulder, elbow, and wrist between fatigue and non-fatigue. The passing accuracy and ball speed when players were under the influence of fatigue were significantly decreased compared to non-fatigue condition. The players’ pelvis position was obviously increased when they were under fatigue. There was a significant difference in pelvis velocity related to X-axis between fatigue and non-fatigue; however, there was no significant difference in Y-axis. The findings of this study could also help coaches better understand the pattern of movement of push passing and correct players’ technique.It is extremely important that players adopt the correct motor structure of passing to create an automatism during the training process of learning, which will ultimately not change even under the influence of fatigue. Only this can ensure the situational efficiency of the player, because any deviation from the ideal biomechanical structure also affects the occurrence of a larger number of motor errors, and consequently reduced efficiency. From the aspect of cooperation between two players in offense, in addition to the correctly adopted movement structure, it is also necessary to perfect spatial–temporal relations in passing and catching the ball, which is possible if the conditions of the players’ training process are similar to the conditions of the game.


Philantomba monticola) in the Lomako wildlife reserve, Democratic Republic of the Congo, to investigate the use of transect-based distance sampling to monitor bushmeat stocks. The comparison of dung piles and direct observations of duikers evidenced that animals avoided both the transects in the absence of observers, and the observers themselves. This type of behavioural response appeared common in a literature survey. It causes a negative bias in the estimates of population densities from the standard distance sampling methodology. This negative bias would lead to over-pessimistic predictions of population viability, especially if the behavioural response is more intense in the locations where the animals are hunted. In turn, this would lead to excessively conservative management recommendations. To correct for the effect of the behavioural response of the animals to either the transects or the observers, we recommend recording both the forward and perpendicular distances to the observers (2D distance sampling), not just the perpendicular distance. We also recommend multiple-observer protocols. As a cautionary note, we also demonstrate a scenario where the intensity of the behavioural response is too high to reliably estimate the abundance of the population. As a perspective, we outline the general principles of a local stakeholder-based program combining distance sampling with less intensive types of ecological indicators to monitor wildlife populations.Bushmeat is a major source of protein and income in tropical regions but is often over-harvested. A better monitoring of bushmeat stocks could help achieve sustainability. We used a combination of simulations and transect survey data collected from blue duikers ( Over-harvesting jeopardizes the food safety, livelihood, and cultural identity of people who consume bushmeat, i.e., meat from wild mammals, birds, and reptiles, typically in tropical, forested environments –4. Locali.e. the fact that a fraction of the animals is missed by the observers during the surveys [The main objective is to account for the imperfect detection of individuals during surveys in the field,  surveys . That fr surveys , 18. The surveys , 20. In  surveys . The sec surveys .Applying distance sampling in forested environments remains challenging because of the low visibility, meaning that the rate at which detection probability decline with distance is much faster than in open environments. In addition, the animals may avoid the transects from which they are surveyed. They may respond to the change in vegetation around the transects, meaning that they always avoid the transect even in the absence of observers. Or they may respond to the presence of an observer, who they usually perceive as a threat especially in hunted areas –25. TheyCephalophus and Monticola sp.) varies by an order of magnitude depending on the survey method used to estimate it . Tapirsin years  (but in in years ).Borchers and Cox  recentlyPhilantomba monticola) in the Democratic Republic of the Congo. Duikers are an African lineage of small to medium-sized forest antelopes that represent a major source of bushmeat to many people throughout their distribution [Our study is motivated by surveys of blue duiker , therebrs & Cox . ImportaIn the above-described particular parameterization of the 2D distance sampling model, it is not possible to record a perpendicular distance of zero . This mastricto sensu. To compare our results to those from the 1D framework, we used the Distance package for R [The parameters of the two functions  were simultaneously estimated by fitting the model to the recorded distance data using a maximum-likelihood approach. We hereafter use the established phrases “effective strip half-width” for the average detection distance should the animals not exhibit any behavioural response, and “average detection probability” for the average probability of being both available for detection and detected. The average detection probability therefore combines the behavioural response and the detection probability ge for R , more prWe surveyed duikers from 5 transects totalling 31km in the Lomako Yokokala Wildlife Reserve . The five transects were parallel and separated by 1 km. We walked each transect twice in March-April 2012 and twice in November 2013, performing one of the surveys by day for dung piles and the other survey by night with a powerful spotlight for direct observations. We followed the established distance sampling protocol, i.e., we did not record the forward distance. Upon detection of a duiker or dung pile, we immediately walked to the nearest point on the transect, and recorded the time, GPS coordinates, and perpendicular distance of the initial location of the duiker, or of the dung pile, to the transect. When sampling dung piles, we ignored the piles that were considered older than a day old by experienced trackers upon visual examination. A preliminary investigation of the recorded perpendicular distance distribution suggested that the blue duikers avoided the transects or the observers or both .Because we did not record the forward distances in the field, and in order to illustrate our points about 2D distance sampling, we generated artificial forward distances associated to each Lomako record, following three scenarios :A pessimistic but likely scenario. We simulated the forward distances to be on average the same as the observed perpendicular distances. We added to the recorded perpendicular distance a random Gaussian noise with a mean of 0 and a standard deviation of 1 meter in order to generate some variability between replicates of the simulation. Any negative distance value resulting from an excessive negative noise we reset to zero meter.a set to half the maximum recorded perpendicular distance. We added onto that expected distance a random Gaussian noise with a mean of zero and a standard deviation of 1 meter. Any negative distance value resulting from an excessive negative noise we reset to zero meter.A somewhat less pessimistic scenario. In this scenario there is a negative correlation between the forward and perpendicular distances. In other words, when the duiker is on the transect, it is easier to detect and is spotted from a greater forward distance than when the duiker is further from the transect. We used an inverse exponential relationship  with theAn optimistic (but unlikely) scenario. The forward distances were relatively large in this scenario, meaning easy detection, and they were independent from the perpendicular distance. We simulated this scenario using a half-normal distribution function with half-detection distance set to 5 meters.b vector that controls the shape of the detection function  could bIn Lomako, there was almost no direct detection less than 2 meters from the transect and a peak in sightings occurred at 5 meters from the transect . These pIn all three scenarios, the fitted model indicated a behavioural response both in the dung pile data and in the direct observation data . The behIn the artificial datasets that did not use the Lomako data, the 1D framework over-estimated the detection rate  and direct observations (by night), we could estimate the conversion rate of dung pile density to population density. The estimate of this conversion rate was sensitive to the behavioural response, meaning that the 2D framework should be very useful for this purpose too. Previous authors derived the conversion rate indirectly using the defecation rate of animals, as recorded in captivity or during short periods in the wild, and/or the decay rate of dung piles until they disappeared in controlled conditions –47. HoweAs a side note, the small size of the dung pellets of blue duikers is what makes it possible to assign the dung piles to that species; similar assignments are more difficult in larger species of duikers. Our field protocol also entailed a somewhat subjective assessment of the freshness of the dung piles in order to record the most recent dung piles only. Instead, one may record all the dung piles along with a qualitative score of their state, and apply the principles described in the rich literature about how to account for the variation in dung pile age, the rate at which dung piles decay, and the number of defecation events per day –50.What our study clearly demonstrates is that the bias caused by the improper treatment of the behavioural response of the animals to the transects or the observers may cause the estimates of population density to artificially vary by a factor 2 to 3. This can severely flaw the comparison of duiker abundance from one site to another, or from hunted locations to hunting-free areas.Many bushmeat species have been observed to persist much longer than expected from theoretical models (reviewed by ). This mAnother potentially important implication of our findings is that estimating the behavioural response to the transects would also document the surface of habitat effectively lost by duikers due to the presence of hunting trails. This information could be incorporated into models of habitat availability and human footprint. One could maybe use the response to the observers to represent the effect of heavily used tracks, and the response to the transects to represent the effect of smaller paths. In our case, we estimated that the effect of the transect was mostly non-existent beyond 5–8 meters from the transects, but that within that strip duikers were c.30% less abundant. We could theoretically use a map of all the transects and trails in the Lomako reserve to extrapolate the overall loss in duiker habitat. As a side note, some species might be attracted, not repelled, by the transects, because the transects represent an ecotone and a change in vegetation structure , 29, 51.Now that we have discussed the benefits but also the challenges of distance sampling for duikers in the rainforest, we are providing a brief overview of the alternative methodologies that could be used instead of transect-based distance sampling, for the same objective of monitoring duiker abundance. This should serve as an argument as to why we are advocating the 2D distance sampling methodology. Namely, the alternatives are in our opinion unlikely to perform better.The N-mixture model  is a claThe frequency of animal pictures taken by automatic “camera traps” has also been proposed as an index of abundance , includiAnother alternative is to quantify the home range size and home range overlaps using movement data, and in a second step compute the population density as the number of home ranges per unit of space , 58. HowWe strongly recommend recording both the forward and perpendicular distances, or alternatively the radial distance and the observation angle. Currently, in studies of rainforest mammals, researchers record only the perpendicular distance, or only the radial distance , 56, 57.We recommend a close inspection of perpendicular distance sampling data collected from forest mammals to assess whether the patterns that we describe in Wherever possible, we also recommend having two observers perform the same protocol, keep separate logs, and then compare observations within a formal algorithm , 60, 61.i.e. surveying the same transects multiple times per season. These last two recommendations aim at allowing a switch to index-based approaches instead of distance analysis (see below for more discussion of index-based approaches).For the most challenging cases, when the behavioural response is extreme, we further recommend a replicated sampling approach, When the populations of large herbivores such as duikers fluctuate around the carrying capacity, which itself may vary through time, various density-dependent processes are triggered or suppressed . TypicalS1 Appendix(ZIP)Click here for additional data file.