There are various manufacturing techniques commonly used to fabricate TE scaffolds. However, in most cases, they do not provide materials with a highly interconnected pore design. Thus, emulsion templating is a promising and convenient route for the fabrication of matrices with up to 99% porosity and high interconnectivity. These matrices have been used for various application areas for decades. Although this polymer structuring technique is older than TE itself, the use of polymerised internal phase emulsions (PolyHIPEs) in TE is relatively new compared to other scaffold manufacturing techniques. It is likely because it requires a multidisciplinary background including materials science, chemistry and TE although producing emulsion templated scaffolds is practically simple. To date, a number of excellent reviews on emulsion templating have been published by the pioneers in this field in order to explain the chemistry behind this technique and potential areas of use of the emulsion templated structures. This particular review focusses on the key points of how emulsion templated scaffolds can be fabricated for different TE applications. Accordingly, we first explain the basics of emulsion templating and characteristics of PolyHIPE scaffolds. Then, we discuss the role of each ingredient in the emulsion and the impact of the compositional changes and process conditions on the characteristics of PolyHIPEs. Afterward, current fabrication methods of biocompatible PolyHIPE scaffolds and polymerisation routes are detailed, and the functionalisation strategies that can be used to improve the biological activity of PolyHIPE scaffolds are discussed. Finally, the applications of PolyHIPEs on soft and hard TE as well as  In this process, droplets of dispersed phase behave like templates, and they are removed following solidification to obtain porous matrices . These bAlthough emulsion templating has been mentioned as a relatively new scaffold manufacturing route in recent publications, the birth of the term of emulsion templating in the literature is older than TE itself ; it dateStudies on the use of emulsion templating for the manufacturing of 3D substrates for cell culture applications is relatively new; it dates back to the early 1990s . That isDevelopment of the emulsion templated scaffolds requires a multidisciplinary approach that combines knowledge and experience from chemistry, materials science, and TE. To date, there has been a number of significant reviews from the pioneers in the field of emulsion templating in the literature . These rOne of the most favourable features of emulsion templated scaffolds is the tunability of their porosity by simply increasing the internal phase volume. In the literature, emulsions that have at least 74.048% internal phase volume are defined as High Internal Phase Emulsions (HIPEs). The value of 0.74048 (π/√18) is the densest possible monodispersed sphere packing density, according to Kepler Conjecture . Also, aThis situation applies in monodispersed spheres, and already in 1907 Spencer Pickering questioned the validity of this value for liquid spheres as liquid droplets in emulsion are in reality not uniform but are polydisperse . AdditioAlthough emulsion polymerisation has previously been described in the literature , the terIn terminology, it is important to comprehend the difference between HIPEs and PolyHIPEs. HIPEs can be further processed until the gelation point to change their droplet size and viscosity, but PolyHIPEs are the solid matrices that are made of solely the continuous phase, and they are obtained by the polymerisation of HIPEs. The cavities formed after removal of the internal phase being defined as “pores,” “cells,” or “voids.” The throats connect the adjacent pores to each other are defined as “interconnects” or “windows” . The forEmulsion templating combines two main research areas that are emulsion science and porous polymer fabrication. Emulsions have been widely used for various industries, such as food, petroleum, paint, pharmaceutical, and cosmetic, for centuries . Also, pInternal phase volume is the main factor determining the porosity of emulsion templated scaffolds. However, the volume of the internal phase does not always correspond to the porosity of PolyHIPE scaffolds. In our recent study, the porosity of polycaprolactone (PCL) PolyHIPEs prepared using 82% internal phase volume was measured around 70%. This is likely because of 15–20% shrinkage of these scaffolds in each dimension during crosslinking and drying . This isPolyHIPE is the PolyHIPE density and ρwall is the density of PolyHIPE wall. The measured density of the bulk polymer is used for the density of the wall.Thus, the porosities of the PolyHIPEs can be calculated using Eq. 1 , where ρIt has been reported that emulsion templated scaffolds may shrink in a dry state depending on their chemical compositions . On the h) from the centre (r) rather than the exact pore radius (R), a statistical correction factor should be applied to the measured average pore size    however,d/D) .3  can be obtained using the hyper-crosslinking approach  devThere are at least three essential ingredients that need to be used to make HIPEs; (i) a continuous phase (polymer phase), (ii) an internal phase, and (iii) a stabiliser [although there is a limited number of studies on the development of stabiliser-free HIPEs ]. In addThe selection of the monomeric or oligomeric pre-polymer for the continuous phase of the PolyHIPEs is the fundamental basis to formulating emulsion templated structures with pre-determined properties and will be discussed in section “Monomers/Macromers.” The pre-polymer is typically formulated with a number of additives  to form the continuous phase, which will be discussed in this section.Pre-polymers used in the emulsification process may be in solid-state or in liquid phase with high viscosity. During the mixing of the two immiscible phases, although the high viscosity of the continuous phase increases the kinetic stability of the emulsion, it needs to be low enough to enable efficient mixing of the two phases . In ordeDiluent type  and voluRecently, we have shown the impact of absence/presence, volume and the type of diluting solvents on the stability of PCL HIPEs and the morphology of PCL PolyHIPEs . IncreasWhile the internal phase of w/o emulsions is most dominantly composed of water, in reversed emulsions (o/w), more apolar liquids, often toluene  form the2SO4), calcium chloride (CaCl2), sodium chloride (NaCl)  was also reported to increase the rigidity of the interface between the two phases  , and pote (NaCl) . Opawalee (NaCl) . Howevere (NaCl) . CaCl2 wripening . Similaro phases .4) has been reported to reduce the surfactant adsorption and increases the droplet size within the emulsion  classification described by Griffing, gives an insight for the initial surfactant choice , 1954. TThe HLB value of a surfactant is not always a sole determining factor for emulsion stability, which depends on various parameters such as the selection of the monomer and solvent, emulsification temperature, and absence/presence of the electrolyte . Indeed,W/o emulsions are mostly stabilised using oil-soluble non-ionic surfactants . Span 80Surfactants are commonly intended not to react with the monomer, and they are removed from the PolyHIPE composition following polymerisation. However, the use of reactive block copolymer surfactants in HIPE composition is also reported . As theyThe emulsion also can be stabilised using solid particles (micro or nanoparticles), and these surfactant-free emulsions are defined as Pickering emulsions . As in sThe principle behind the stabilisation mechanism of Pickering emulsions is based on the wettability of the particles by oil and the water phases  . These pHydroxyapatite (HA) is one of the most widely used particles for stabilisation of Pickering HIPEs. Interestingly it is reported to be used both o/w  and w/o Initiators are chemical compounds that react with the monomers. They form intermediate compounds that can be linked with other monomers and propagate to form the polymer chains. Initiators can be included either into the inner or continuous phase of the emulsions, and the locus of initiation has been shown to have a significant effect on porous structures .Ammonium persulphate (APS)  and potaBenzoyl peroxide (BPO) is an oil-soluble redox initiator also used for polymerisation of PPF HIPEs. Photoinitiators are the molecules that create reactive species when exposed to light, and they are included in the composition of the HIPEs that will be polymerised via photo-initiation. In the photoinitiator selection process, the critical parameter is that the absorption band of the photoinitiator should overlap with the emission spectrum of the light source . 2,4,6-TCrosslinkers are the precursors with at least two reactive ends to connect primary polymer chains by forming intermolecular linkages . Using an is the viscosity of the polymer, T is the temperature, A and B are material constants;The most dramatic effect of the temperature is on the viscosity of the oil phase which also affects the viscosity and the stability of the emulsion. The viscosity of the polymer and the temperature are inversely related to each other as shown in Eq. 4 where v) are inversely proportional , the viscosity of the polymer and the velocity of the droplet  directly affects the mixing efficiency of the emulsion and will have an impact on the final morphology. Keeping these parameters constant between batches helps the consistency and reproducibility of the PolyHIPEs.PolyHIPEs based on many popular polymers, such as; acrylates, methacrylates, and styrenes are synthesised using free-radical polymerisation (FRP) . The typThe earliest examples of the PolyHIPEs (during the 1980s) were based on thermal polymerisation . In thisIn photo-initiated polymerisation, emulsions are prepared using photosensitive materials as a continuous phase and photoinitiators are exposed to light to be able to generate free-radicals and initiate the polymerisation. This method has many advantages over thermal-induced polymerisation; polymerisation takes places at room temperature (RT) just in seconds to minutes depending on the sample size. Photopolymerisation is an efficient polymerisation route, especially in relatively small samples, as ultraviolet (UV) penetration depth can be limited in a larger volume of emulsions. Photo-initiated polymerisation of the emulsions, specifically HIPEs, were described in patents in 1986  and 19992). The bubbles of generated CO2 created additional porosity into PolyHIPE structure.Integration of step-growth polymerisation into emulsion templating process has been successfully implemented in polyurethane PolyHIPEs . It is sL-lactide are the most widely used monomers in this approach (Development of PolyHIPEs by ring-opening polymerisation (ROP) of cyclic monomers is a relatively new route of polymerisation HIPEs. ε-caprolactone and approach . One of Although the term PolyHIPE refers to polymerised emulsions, recently polylactic acid (PLA), PCL, polylactic-co-glycolic acid (PLGA) PolyHIPEs solidified without polymerisation have been reported . This prCrosslinking of PolyHIPEs as a solidification approach can be either ionic, thermal or enzymatic. Alginate PolyHIPEs has been synthesised using calcium ions . This reThe earliest examples of PolyHIPE scaffolds were fabricated using the casting technique . This teIn order to avoid the closed-pores on the surface of the PolyHIPEs, the moulded PolyHIPE blocks are typically sectioned using various methods and benefit from the open porous cross-sectional surface. Vibratomes  and micrCasting enables the manufacturing of scaffolds in a wide range of shapes and sizes, depending on the mould design . RecentlFabrication of TE scaffolds using AM techniques gained huge attention in the last decades due to various advantages of the AM such as enabling the manufacture of complex shapes using a broad range of materials, high reproducibility and providing control on the exterior architecture of the scaffolds. However, manufacturing of pores less than 20 μm using the current AM techniques remains a challenge . Alternaz-axis  (PNIPAM) grafted gelatin PolyHIPEs.PPF HIPEs, discussed in detail in section “Monomers/Macromers,” have a suitable viscosity for injection from a syringe, and they can solidify at body temperature in 15 min. They have been shown to be stable for storage up to 6 months and to integrate into the host tissue successfully . Moglia Electrospinning is a versatile route for the fabrication of the fibres with varying diameters from nanometres to micrometres scale using a wide range of materials . There aMicroporous PolyHIPE particles can be applied to the defect site by injecting and used as substrates for controlled drug delivery . They caThe earliest studies on the development of emulsion templated substrates used styrene as a monomer . In 1992The blend of acrylate based-monomers; EHA:IBOA is another commonly reported non-degradable material that is mostly solidified using photo-initiated polymerisation . Owen etAs TE scaffolds are desired to be made of biodegradable materials, the development of biodegradable PolyHIPEs is important to satisfy the need of implantable TE constructs . PCL is The earliest reported PolyHIPE made from PCL was created by copolymerisation of PCL diacrylate with non-degradable monomers . VariousPLA and its copolymer PLGA are widely used biomaterials for fabrication of TE scaffolds. in situ crosslinking in the defect site  chemistry [also classified as click chemistry ] is the In 1997, Naotaka Kitagawa described the development of hydrophilic PolyHIPEs . Since tN-isopropylacrylamide) (PNIPAM). Due to the amphiphilic nature of gelatin-graft-PNIPAM as a continuous phase, they managed to incorporate an internal phase of up to 90% without the use of any surfactants. Recently Gelatin is one of the most commonly used natural biopolymers for the fabrication of TE scaffolds. As it is derived from collagen of skin, bone or tendon of animals, it is highly abundant and cost-effective . In 2005in vitro generated ECM  incorporated DVB/styrene PolyHIPE increased the viability of cells, cell penetration into the scaffolds, and osteoblast differentiation in vitro . Wang etIncorporation of the biomolecules into the composition of PolyHIPE scaffolds requires moderate operation conditions in terms of temperature and solvents. Biomolecules such as peptides and ECM proteins can be either covalently attached to the surfaces or physically absorbed/coated to the PolyHIPEs.D-lysine and laminin coating on DVB/styrene PolyHIPEs and showed the advantages of Poly-D-lysine and laminin coating over only Poly-D-lysine coating in terms of increasing the mean neurite length  activity have been shown to be increased in comparison with the control . Hayman e length , 2005. EN-sulfosuccinimidyl-6-(4′-azido-2′-nitrophenylamino hexanoate (sulfo-SANPAH)), which is a photo-linker compound that enables conjugation of biomolecules to the surfaces, and then they further functionalised the surface by covalent attachment of fibronectin to sulfo-SANPAH molecule. An improved cell attachment and infiltration of human endometrial stromal cells have been found when compared to unmodified, just sulfo-SANPAH functionalised, and fibronectin-absorbed  PolyHIPEs  peptide by benefiting from the reaction between the unreacted thiols in PolyHIPE and the maleimide. While non-functionalised scaffolds did not support attachment and proliferation of human embryonic stem cells, PolyHIPEs functionalised with RGD showed significantly higher proliferation and infiltration rate .Hayward et al. incorporated pentafluorophenyl acrylate (PFPA) into the oil phase of the styrene HIPE to be able to conduct a coupling reaction between ester groups of PFPA and galactose afterward, as hepatocytes are known to have specific receptors that bind to galactose. Hepatocytes have been shown to proliferate on the functionalised scaffold, and they showed significantly higher activity on galactose functionalised PolyHIPEs in terms of albumin synthesis compared to cells cultured on unmodified PolyHIPEs .in vitro cell generated bone ECM rather than a single biologically active agent  and resazurin reduction. The washing process can be conducted by either series of manual soakings in selected solvents or using Soxhlet extractor.The solubilities of the materials that need to be removed should be considered for the selection of the washing solvent. Acetone is one of the commonly used solvents for washing of PolyHIPEs due to the high solubility of a wide range of polymers in acetone . In our A limited number of studies have reported the effect of the washing method, duration and the choice of solvent on the features of PolyHIPE. Pakeyangkoon et al. showed that duration of solvent extraction has an impact on the surface area and mechanical properties of the PolyHIPEs . While ain vitro and in vivo tests and also for implantation to the human body. There are various methods used for this purpose, such as treatments with heat  are known not to be a good representative of the  in vivo .in vitro test platforms due to their tunability in the physical and mechanical properties for different applications, ease of fabrication, reproducibility, and stability for long term experiments . Costello et al. developed a multi-layered skin equivalent on these scaffolds and suggested its use for disease modelling and testing of cosmetics’ active compounds  all over the scaffold. HMSCs on scaffolds were mineralised and showed higher ALP activity compared to hMSCs on TCP.Moglia et al. developed injectable PFDMA PolyHIPEs with an average compressive modulus and strength of 33 and 5 MPa and showed up to 95% initial cytocompatibility of fibroblasts after 24 h . WhitelyThe two main components of soft tissues, such as skin, nerve, fascia, and blood vessels, are elastin and collagen, which both of them have very high water content . Thus, hBarbetta et al. reported that dextran PolyHIPEs supports penetration and colonisation of the neurons into the inner cavities of the scaffold . Murphy Luo et al. developed surfactant-free and solvent-free PolyHIPEs and showed the proliferation of fibroblasts and cardiac muscle cells on PVA PolyHIPE hydrogels . RecentlMoglia et al. developed injectable PCL PolyMIPEs with 20–200 KPa and 4–60 KPa compressive moduli and strengths, respectively. They suggested their use for soft tissue regeneration and showed the initial cytocompatibility of PolyHIPEs with the activity of hMSC higher than 95% after 72 h .Controlled release of drugs and bioactive molecules is desired for accelerating tissue regeneration, controlling biological responses or inhibiting pathology. PolyHIPEs are good candidates to elute drugs in a controlled manner as the surface area of these matrices can be precisely engineered. However, there is only a limited number of studies reported the PolyHIPE matrices as drug delivery tools.All of these studies suggested promising results for the use of PolyHIPEs in drug delivery applications. The common characteristics of all the studies mentioned above were the inclusion of the drugs in the emulsion composition before emulsification, and the use of toxic solvents in the emulsion composition to dissolve the polymers. Although scaffolds were left under vacuum to remove the solvent after solidification, they did not include any washing step for the removal of any leftover uncured materials or solvent as this step may also cause washout of the high amount of drugs from the scaffolds.Moglia et al. developed bone morphogenetic protein 2 (BMP-2) releasing solvent-free ethylene glycol dimethacrylate PolyHIPE microspheres using w/o/w double emulsion system . They rein vitro. It is beyond doubt that we have gained a greater understanding of this formulation technique over the last decade. In addition to producing favourable 3D porosity, the development of surface functionalisation methods have further improved cell-material interaction of the emulsion templated matrices and increased the potential of PolyHIPEs to be used in the medical industry.To date, PolyHIPEs based on a wide variety of synthetic and natural materials have been developed, characterised, and tested in vitro growth of various cell types  assay which is a rapid and inexpensive in vivo platform to investigate initial tissue response to biomaterials and angiogenic agents  that come into force on May 2020 is that the human originated cells and tissues or their derivatives  will also be considered as a high-risk medical device (Class III) . Due to Emulsion templating is a favourable scaffold fabrication technique with various advantages, such as enabling high porosity, providing high interconnectivity, having high tunability of the architecture, mechanical properties and functionality, being suitable to be fabricated in various forms using a wide range of materials. Important to note is that emulsion templating can be used as a reliable fabrication method, but the production is dependent on a large number of process variables, and the fabrication setup is extremely sensitive to changes in the composition and condition of the process. Thus, to be able to have control over the morphology and the mechanical properties of the scaffolds, it is important to know the effect of individual parameters on the PolyHIPE properties. We devised this review as an update on the state-of-the-art of emulsion templating in TE and as a guide text for the use of emulsion templating as a TE scaffold fabrication route by summarising the key points that should be considered during the fabrication process of PolyHIPEs.The main challenge of emulsion templating is to remove the toxic organic solvents used in emulsion composition and other impurities such as unreacted monomers and residual surfactant. Thus, especially solvent-free and surfactant-free HIPE compositions are considered as promising and cost-effective as they eliminate the solvent and impurity removal steps.in vivo would aid to establish a greater degree of understanding on the potential of emulsion templated matrices to be used in the clinic.For improved scaffold-biological tissue interaction, more studies focusing on the development of o/w PolyHIPEs with enhanced mechanical properties and development functionalised w/o PolyHIPEs is needed. We are confident that emulsion templating will become an increasingly popular scaffold manufacturing technique in the next decade by considering the increasing number of publications on emulsions templating in TE. Also, future studies that concentrate on the investigation of long term behaviour of PolyHIPE matrices BA performed the review and wrote the manuscript. FC provided feedback and edited the manuscript. Both authors contributed to the article and approved the submitted version.The 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.


The trend of quick evolution and increased digital data in today’s operating rooms (ORs) has led to the construction of hybrid ORs. There is often a main control room with monitors for integrating intraoperative data from multiple devices in the hybrid OR. However, there is no adequate solution for communicating the data with people outside the OR.The objective of this study was to design an intelligent operating room (iOR) system, augmented onto the existing information technology (IT) infrastructure of hybrid ORs, to stream surgery performance and intraoperative imaging data.In this study, an all-in-one device with synergetic encoder and decoder was used. The device was able to stream multiple sources to one display. The lossless video and images from specific surgical workflows were streamed outside the hybrid OR through network protocols and were further managed by a streaming server and wireless control system. The steps of this study included the following: (1) defining the requirements and feasibility of an iOR system in the hybrid OR, (2) connecting multiple sources, (3) setting up equipment across the hybrid OR and a conference room, (4) designing a video management system, and (5) real-time streaming under specific surgical workflows.The wired streamed video was shown simultaneously on the display in the hybrid OR and the display in the conference room with near-zero latency. Additionally, an interactive video between the hybrid OR and the conference room was achieved through the bidirectional wireless control system. The functions of recording, archiving, and playback were successfully provided by the streaming server. The readily available hardware components and open-access programming reduced the cost required to construct this streaming system.This flexible and cost-effective iOR system not only provided educational benefits, but also contributed to surgical telementoring. Health information management is crucial for hospitals. In surgical departments, today’s operating rooms are evolving quickly, and large amounts of digital data, including images and videos, are produced every day. The hybrid operating room (OR) is defined as being equipped with advanced medical devices such as fixed C-arm fluoroscopy, cameras, a computed tomography (CT) scanner, or a magnetic resonance imaging (MRI) scanner . In addiCurrently, manufacturers build integrated OR infrastructures that provide video acquisition, storage and routing of continuous video data within the OR, although most of them are not based on existing OR information technology (IT) infrastructure . Other dWith regard to streaming surgery performance outside the OR, previously published studies discussed a system that could integrate data from ceiling cameras and a vital sign monitor . HoweverWe aimed to establish a framework based on the IT infrastructure of the hybrid OR, and to stream data through Ethernet methods between the hybrid OR and the conference room. The augmented system was named the intelligent OR (iOR) system. There were two streaming object categories: surgery performance and intraoperative imaging data. Furthermore, we aimed to establish a video management system (VMS) for the iOR system, with two kinds of control methods: (1) a wired server named the iOR box and (2) a bidirectional tablet controlled through a wireless connection.The workable, highly flexible, and bidirectional iOR system enables collaboration across the hybrid OR and conference room by making it easier to stream high-definition and near-zero latency data of surgery performance and relative imaging data. The system may significantly lower the costs involved compared to dedicated streaming systems by commercial brands.The iOR system was installed in the hybrid OR in the Yuanlin Christian Hospital, Yuanlin City, Changhua County, Taiwan. The installation of research equipment was approved by the hospital’s administration prior to the commencement of the project.To understand the surgical workflow, we carried out a survey of the equipment in the hybrid OR, including existing hardware and software, the demand for infrastructure for streaming open surgeries and endoscopy surgeries, and communication between the vendors and surgeons. The main system in this hybrid OR received image or video data from various sources, including videos from cameras and the endoscopy system, digital data from vital sign monitors, imaging data from portable fluoroscopy, and the picture archiving and communication system (PACS) connected to the Department of Radiology. These devices contributed to two categories of streaming data: real-time surgery performance and intraoperative imaging data. A suitable way of connecting an equipment interface and transporting line between the hybrid OR devices and the iOR system should be arranged. The ideal control systems would have both wired and wireless control systems. All materials in this study, including hardware and software, should be compared with existing products available from commercial brands.When researching how to integrate multiple data sources in the hybrid OR, the key to achieving streaming effectiveness was to use an all-in-one device with synergetic encoder and decoder. This device was named NDcoder to indicate it is an encoder and decoder in one single product. We proposed the resolution of streaming all data out of the hybrid OR by using the principle of “one NDcoder connecting one data source”. These devices are available commercially. Multiple NDcoders  were used to connect different sources from multiple devices in the hybrid OR and simultaneously transport data over an Ethernet connection. All devices in the hybrid OR could be directly or indirectly connected to an NDcoder through a digital video interface (DVI). The adapter cable was selective.One SigmaXG in the hybrid OR shared streaming data to an external NDcoder by indirectly bridging these two devices through Ethernet fibers connected with a 10 GB switch . These devices together formed the basic structure of the iOR system that bridged the hybrid OR and a conference room .The video management system (VMS) included wired and wireless control systems. The main component of the wired control system was the iOR box, which had one video capture card and a connected monitor. Conversely, the wireless control system included three components shown in : a streaOne DVI splitter was connected to the SigmaXG in the conference room through a DVI cable, enabling data to be transported via DVI cables from the SigmaXG to the iOR box (with monitor). The iOR box with monitor represented the streaming server. The Intel NUC (without monitor) and the WAP in the wireless control system were directly connected to the 10 GB switch through Ethernet cables. Additionally, the wireless panel controlled the Intel NUC through the WAP. This wireless control system served as a communicator between the two SigmaXGs in the iOR system .One medical grade display was connected to another output interface through the DVI cable. In addition to the data streamed directly from the hybrid OR, the display was able to receive videos or images controlled by the MIT-W101. To allow bidirectional communication, the iOR system had recording (microphones) and playback devices in both the hybrid OR and the conference room .In the hybrid OR, in addition to the devices connected to the NDcoders, there was a display connected to the NDcoder’s output interface with a DVI cable. Thus, the medical staff in the OR were able to see the streaming results on the display. One temporary shelf  was builFor the real-time test, the authors chose a case involving arthroscopically assisted reconstruction of the anterior cruciate ligament. The patient’s privacy was protected, and associated information was delinked according to the ethical review committee guidelines. During the surgery, three steps were defined by the imaging devices of the hybrid OR: (1) preparing, filmed by the fixed camera with 360° angle; (2) surgical approaches, filmed by the camera over the shadowless lamp; and (3) inside the knee joint, filmed by the endoscope of the arthroscopy system. The data streamed from the cameras and the arthroscopy machine were transported via the methods detailed above.In this study, data sources included the following: (1) vital sign monitors, (2) ceiling cameras, (3) cameras on the shadowless lamp, (4) system of endoscopy surgery, (5) portable C-arm fluoroscopy, (6) CT scanner, and (7) PACS from the Department of Radiology, showing preoperative image data, and receiving real time uploaded data from the C-arm or CT scanner in the hybrid OR. All of these devices had DVIs, which were able to transport uncompressed imaging data.When searching for a commercially available streaming system designed for the hybrid OR, we found that the price of one medical grade monitor was higher than the cost of all the equipment used in the iOR system. This could be due to the costs associated with importing the products of an international brand. Furthermore, in the commercial system, the hardware components and the IT infrastructure were supplied by two different companies. The relevant application programming interface (API) was not open access, which also increased the cost of modifying console applications.The NDcoder, SigmaXG, was able to distribute lossless video without compression. Through the API and software development kit (SDK), it was possible to change the resolution and the frame rate to limit bandwidth, and multiple imaging sources could be shown on one display synchronously. The API for the SigmaXG is open access and documentation can be downloaded from the manufacturer’s website. For the iOR box and the Intel NUC, the SDK programs and relevant console applications were written by software engineers. This device offered seamless switching. Moreover, there was no black frame displayed on the remote display when one input data was streamed outside the hybrid OR. This was because the NDcoder used a frame buffer in the output channels. In direct display mode, the output frame buffer was bypassed, and video input and output were synchronized with a latency of a few video lines.The wired streamed video was shown simultaneously on the display in the hybrid OR and on the medical grade display in the conference room. Two different video sources (the camera attached to the shadowless lamp and the endoscope camera) were shown on one display in real time. This streamed data was also captured by the iOR box. The iOR box is able to record, archive, and play back the streamed data .The wired streamed video had near-zero latency (60 frames per second with a resolution of 1920×1080 pixels), and the real-time iOR box control system was the data server. Furthermore, an interactive video between the hybrid OR and the conference room could be achieved through the bidirectional wireless control system by using the MIT-W101 control panel and Intel NUC. The wireless streaming console, Intel NUC, was also the server for the wireless system. The software in this wireless control system enabled the MIT-W101 control panel to distribute and split the live or playback screens to the display in the hybrid OR as well as the one in the conference room . HoweverOperating rooms are evolving quickly. New medical technologies and minimally invasive procedures have changed the OR environment and how surgeries are performed. Constant changes, increased complexity, and demands for increased productivity mean the surgical suite needs to be more efficient and flexible than ever. Despite lacking data analysis, this study is a proof of concept of the use of a real-time streaming system in a surgical context. The iOR system was intended to have the flexibility of expansion, especially the software functions. This new system includes a bidirectional control system, synergistically wired and wireless systems, and open access API and offers the potential to develop more intelligent applications capable of automatic identification or learning.Some challenges were encountered in this study. At the beginning, there were many meetings between the technicians and surgeons. Live streaming of multifocal image or video data is typically used for telementoring. Thus, the streamed data needed be collected from different sources and displayed simultaneously in an external location (the conference room). The surgeon was also the director during live streaming. Furthermore, the surgeon had to understand and use both the infrastructure of the hybrid OR and the new iOR system. Additionally, the vendor should have an understanding of how surgeries are performed, as well as the needs of telementoring.As for streaming itself, streaming surgery performance and intraoperative imaging data is different from streaming for entertainment. Good image quality and a high frame rate are required for some surgeries, such as heart surgery, due to the dynamics of the moving heart. If the streamed data are compressed and encoded, information would be lost in the decoding process. Therefore, the choice of an NDcoder for adequate streaming quality is a very important step when setting up the iOR system, as is the consideration of how to transfer the streamed data.Internet-based communication solutions rely on high-performance network infrastructure . GigabytThe iOR system streamed data from the surgical workflow. Since then, the system has promoted the real-time education of training surgeons and has enabled remote supervision. The recorded video in the streaming server (iOR box) could be further designed with an augmented reality (AR) system. Additionally, the wireless system served as the remote control for both live and playback screens. Adding more applications to the iOR system would be flexible and cost-effective .Streaming data outside the OR is a crucial component of surgical telementoring . SurgicaThe iOR system can support the trend of real-world evidence (RWE), especially in studies involving surgical procedures. The concept of RWE refers to health care data derived from sources outside typical clinical trial settings, including electronic health records . In tradThe aim of this study was to enable departments with hybrid ORs to stream data outside the OR with easily accessible equipment. Based on the existing IT infrastructure, the cost-effective iOR system described in this study is able to integrate surgery performance with imaging data from high-tech machines.Although this study was successful as a proof of concept, one limitation is that there was no control group. This study was designed to investigate the feasibility of clinical applications such as live surgeries or live webinars. The results of the study were practical, but there was no comparison to other methods nor quantitative results.The real-time iOR system was able to integrate and stream surgery performance and imaging data from existing equipment in the hybrid OR. When using the wired iOR box as the streaming server, the iOR system was able to record, archive, and play back video. Furthermore, the wireless control system manipulated the live or playback screens and further supported collaboration for surgical telementoring, educational conferences, and remote consultations. In the future, a modular prototype will be developed based on the iOR system.


Commercial interests in indoor localization have been increasing in the past decade. The success of many applications relies at least partially on indoor localization that is expected to provide reliable indoor position information. Wi-Fi received signal strength (RSS)-based indoor localization techniques have attracted extensive attentions because Wi-Fi access points (APs) are widely deployed and we can obtain the Wi-Fi RSS measurements without extra hardware cost. In this paper, we propose a hierarchical classification-based method as a new solution to the indoor localization problem. Within the developed approach, we first adopt an improved K-Means clustering algorithm to divide the area of interest into several zones and they are allowed to overlap with one another to improve the generalization capability of the following indoor positioning process. To find the localization result, the K-Nearest Neighbor (KNN) algorithm and support vector machine (SVM) with the one-versus-one strategy are employed. The proposed method is implemented on a tablet, and its performance is evaluated in real-world environments. Experiment results reveal that the proposed method offers an improvement of 1.4% to 3.2% in terms of position classification accuracy and a reduction of 10% to 22% in terms of average positioning error compared with several benchmark methods. Indoor localization refers to determining the position of an object in an indoor environment. It is an essential problem in many applications including search, rescue, and navigation in the indoor environments, monitoring and surveillance for security and defense purposes and Internet of Things (IoT) . Unlike Received signal strength (RSS)-based methods are common alternatives for indoor localization without requiring additional sensor modules. There have been a variety of techniques proposed for indoor positioning using RSS measurements from Wi-Fi , RFID 1, BLE 1111, and mIn this work, we shall take a different approach and consider the fingerprint-based indoor localization method. This is because for many practical applications, it would be sufficient if we can determine which area the object belongs to. Furthermore, the fingerprint-based approach does not require the simultaneous detection of at least three APs or knowing the precise locations of APs. Generally speaking, the deployment of a RSS fingerprinting localization system has two phases, namely the offline phase and online phase. During the offline phase, Wi-Fi RSS data at various object positions, also referred to as the reference points (RPs), are collected to build a database. Using RSS measurements as fingerprints, the object location can be estimated during the online phase. The fingerprint-based localization is essentially a pattern classification problem. Specifically, the RSS database regards the RSS measurements of the RPs as their patterns. The newly received RSS measurements are matched against these patterns to find the position estimates.In this paper, we focus on indoor localization of an object using sparsely deployed Wi-Fi APs. This work presents a novel framework that first uses an improved K-Means clustering algorithm to partition the environment into possibly partially overlapping zones. This greatly simplifies the (offline) training and (online) localization phases at the cost of increasing the number of required classifiers. When performing the object position estimation, we use the 1NN algorithm  to deterThe proposed localization technique is different from existing hierarchical classification-based approaches mainly in the sense that the indoor environment of interest is automatically partitioned into possibly overlapping zones see . This leThe rest of the paper is organized as follows. The fundamental assumption underlying the RSS-based indoor localization is that the RSSs at different RPs exhibit distinguishable patterns, so the fingerprint-based position determination can be achieved via classification. In this section, two main types of classification frameworks are discussed and then, we survey existing hierarchical localization approaches.The flat classification here refers to the standard binary or multi-class classification . This ap’s RADAR  and Pehl’s RADAR  both use’s RADAR  and neur’s RADAR  were als’s RADAR  observedHierarchical classification refers to that the RPs are successively classified at various levels of a defined dendrogram . Figure The central problem of the hierarchical classification for indoor localization is how to form zones. The most common approach is to cluster the RPs. Bai  and AltiIn the aforementioned studies, only a single attribute was employed to characterize a RP . During the establishment of the fingerprint database, usually multiple RSSs are collected at a RP. Due to the co-channel interference, multi-path effect and the absorption of wireless signals due to, e.g., walls and pedestrians, the RSS samples at a RP can fluctuate greatly and may not follow a Gaussian distribution. Therefore, exploring only the RSS mean value to characterize each RP will lose high-order statistical information in the raw data, and thus the results obtained may not be reliable. In this section, we present a new hierarchical classification framework for Wi-Fi RSS-based indoor positioning, which again contains the offline training phase and online localization phase. The block diagram of the entire system is shown in Within the conventional hierarchical classification structure, as shown in In the proposed hierarchical classification structure, zones are allowed to overlap. For illustration purpose, an example is shown in The offline phase accomplishes three tasks: clustering RPs, training the zone classifiers and training the position classifiers. In the developed system, we use the improved K-Means algorithm to cluster RPs, 1NN algorithm as the zone classifier, and SVM as the position classifier.The area of interest is automatically divided into zones using an improved K-Means clustering algorithm. Suppose there are Clearly, Algorithm 1: Improved K-Means clustering algorithmOutput: RP’s cluster labels Input: RSS database in (2), threshold Initialize Calculate the Euclidean distance between the RSS measurements and cluster centroids using Assign the RSS measurements to the cluster whose centroid is the closestWhen all RSS measurements are assigned, re-calculate the cluster centroidsIterate step 2, 3 and 4 until convergenceOutput the cluster centers Compute If When all RPs are assigned, terminate.The improved K-Means clustering algorithm achieves the purpose of clustering RPs by exploiting the available RSS measurements from all RPs. Specifically, this method first uses the standard K-Means algorithm to assign the RSS measurements to This clustering method uses all the RSS measurements for clustering and the final clustering results are expressed in terms of each RP belonging to at least one clusters, which accomplishes the area partition. It is worth mentioning that the value of The justification for the lower limit of In order to ensure that the RP would be clustered into at least one zone, it is required thatTherefore, for all Because The solution can be found to beThe upper limit for In the developed indoor localization system, we use the 1NN algorithm, a special case of the KNN method with  systems . We use We use the RSS measurement cluster centers as the first level database and use the 1NN to classify the zones. When a new set of RSS measurements are obtained, we calculate the Euclidean distance between these measurements and each cluster center We proceed to train position classifiers for each zone for position determination. The SVM is used as the position classifier to distinguish RPs in a zone through exploiting all the RSS measurements. The basic form of SVM is implemented for binary classification problem for linearly separable datasets. For the nonlinear case, the kernel trick maps the feature space to make the data linearly separable in the high-dimensional space, enabling the SVM to handle nonlinear classification problems. For multi-class classification, a number of SVM-based binary classifiers are required to distinguish multiple classes. The one-versus-all  method aIn the online localization phase, we cascade the trained zone and position classifiers, forming a complete hierarchical localization system. When new RSS measurements are input into the system for position determination, the system first uses the 1NN zone classifier to determine the zone where the target is located. After determining the zone, the system inputs the RSS measurements into the SVM position classifier corresponding to the particular zone to obtain the estimated position of the target.In order to evaluate the proposed hierarchical classification scheme in a real-world environment, we conducted a measurement campaign in a hospital in Wenling, Zhejiang, China. Since the patients in this hospital are most elderly, the accuracy in both zone classification and position determination plays a vital role in emergency handling. As shown in In our offline training phase, the RSS database was divided into two parts, with 50 percent of the measurements put into the training dataset and the remaining data being in the test dataset. The performance of our method is compared with several baseline algorithms, including SVM, KNN, multilayer neural network (NN), K-Means , VisibilFor the benchmark methods and the proposed algorithm, four performance metrics are considered for comparison. They include the zone classification error rate, position classification accuracy, average positioning error and running time. The zone classification error rate is the percentage of the number of test RSS measurements assigned to zones that do not contain their true RPs. The position classification accuracy gives the percentage of test RSS measurements assigned to the correct RPs. The average positioning error is the average distance between the selected RPs for the test RSS measurements and their true RPs.Since the experimental environment is a rectangle and 4 Wi-Fi APs have been installed priorly, it can be naturally divided into 4 parts, which makes our choice of The step that evaluates In An error in the zone classification stage will be propagated to and even amplified at a later stage under the hierarchical classification structure, which makes the accuracy of zone classification a very important performance indicator. We use 1NN as the zone classifier to compare the zone classification error rates of four hierarchical classification methods in consideration and the results are shown in With the hierarchical classification with overlap, the accuracy of zone classification improves with the increase in the overlap regions. When the overlap region is large as the test environment, the number of zones reduces to one and the zone classification error rate will become zero, which renders the hierarchical classification meaningless. Actually, when the overlap regions are too large, the efficiency of the hierarchical classification will dramatically decrease as well see . In FCM,In our experiment, the direct use of KNN, multilayer NN and SVM for flat classification-based object position estimation are selected as the benchmarks for performance evaluation. Specifically, the multilayer NN has 8 fully-connected hidden layers with 10, 18, 27, 35, 22, 16, 15 and 22 neurons, respectively, and they adopt the tanh activation function. The cross-entropy loss is employed in the training process, where 85% of the training data is used for optimizing the connection weights while the remaining 15% is applied for cross validation to avoid overfitting. In addition, we simulate three hierarchical localization methods, namely K-Means  and FCM The averaged positioning performance results of the methods in consideration are summarized in Another observation is that the performance of the multiplayer NN is inferior to those of the proposed method and even SVM. The underlying reasons could be as follows. (1) The amount of RSS measurements collected for the experiment may not be sufficient for the training of the multilayer NN to converge to a local optimum with good generalization capability. (2). The hierarchical nature of the indoor localization problem is not explored by the multilayer NN but it is explicitly accounted for in the development of the proposed method. Increasing the volume of the training dataset could be useful to obtain a multilayer NN with significantly enhanced performance and this would be subject to future measurement campaign and experiments.It is worth mentioning that the zone classification error rate of the FCM-based method is the lowest among the considered techniques see , but itsIn The running time is a key performance metric for an online system. We evaluate the running time of all the considered algorithms in the previous subsection. The obtained results are shown in In this paper, we presented a novel framework for the Wi-Fi RSS-based indoor localization based on hierarchical classification. Different from existing methods, we proposed to avoid disjoint partitioning and split the indoor environment into zones with possible overlap. In order to construct the category hierarchy, we proposed an improved algorithm based on the K-Means algorithm, which automatically divided the indoor region into overlapped zones according to the clustered RSS measurements. The 1NN and SVM were adopted to realize the zone and position classifications to establish the whole indoor localization procedure. The proposed method has been implemented on a tablet and evaluated in a real-world hospital under practical conditions with people moving around and simultaneous operations of electrical devices. The experimental results reveal that compared with the existing flat classification methods and hierarchical classification methods, our method has greatly reduced computation load and improved localization accuracy.


Percutaneous interventions via minimally invasive surgical systems can provide patients with better outcomes and faster recovery times than open surgeries. Accurate needle insertions are vital for successful procedures, and actively steered needles can increase system precision. Here, we describe how biology inspired the design of a novel Programmable Bevel-Tip Needle (PBN), mimicking the mechanics and control methods of certain insects ovipositors. Following an overview of our unique research and development journey, this paper explores our latest, biomimetic control of PBNs and its application to neurosurgery, which we validate within a simulated environment. Three modalities are presented, namely a Direct Push Controller, a Cyclic Actuation Controller, and a newly developed Hybrid Controller, which have been integrated into a surgical visual interface. The results of open loop, expert human-in-the-loop and a non-expert user study show that the Hybrid Controller is the best choice when considering system performance and the ability to lesson strain on the surrounding tissue which we hypothesis will result in less damage along the insertion tract. Over representative trajectories for neurosurgery using a Hybrid Controller, an expert user could reach a target along a 3D path with an accuracy of  The optimal low level control of needles for the application of percutaneous interventions  for MiniThe first, and earliest, category of steerable needles, consists of the base manipulation of straight, flexible needles through solid tissue, whereby the base manipulation of the robot, and the needle–tissue reaction forces, are used to move the needle along a curved path. Often, these needles have bevelled and/or precurved needle tips ,4,5, to A second category includes needles with straight, stiff shafts or flexible shafts equipped with an articulated tip-mounted tool. Articulation of the tip is provided either by pivoting the straight shaft about a fulcrum located at the insertion point into the patient, introducing further tissue deformation, or by transferring the applied force to the tip with a transmission mechanism . An examTo minimise tissue trauma, and allow for more complicated path following, a third category of needles is developing, broadly focusing on steerable, elongated and active devices. An example of a needle design in each of the third categories is shown in Commonly, designs in this category employ bevel-tip needles. These can be actively steered by using duty-cycling control techniques, whereby the rotation of the needle along its longitudinal axis allows the needle to be steered in the desired direction ,23. SuchDiachasmimorpha longicaudata (Braconidae) three-valve ovipositor. They saw that the insect could steer their ovipositors in any direction relative to the body axis-with direct pushing motions in soft substrates and via reciprocal motions in stiffer substrates. This reciprocal, or cyclic, motion can reduce the net force of the ovipositor on the surrounding substrate, lowering the risk of buckling. This control motion has inspired the control of PBNs with cyclic motion, in order to reduce the deformation and strain on the surrounding tissue, with a likely reduction in damage along the needle insertion track.Our bio-inspired Programmable Bevel-tip Needle (PBN) is in the third category. PBNs are inspired by insects that are able to use their slender ovipositors or mouthparts to both drill and steer through harder substrates, such as wood and bodies of other insects . In 26]26], the PBN designs consist of at least three interlocking, bevel-tipped segments which axially slide relative to one another to achieve 3D steering. The relative offset of the segments formed at the tip creates a bending moment when inserted into soft tissue, and is related to the resulting curvature of the needle. The multi-segment design of this needle is advantageous over other single segment needles as it can lend itself to more advanced actuation methods, hence different motion profiles, and does not suffer from the constraint of following helical paths as standard bevel-tip flexible needles do. Motion profiles can be optimised towards specific parameters, e.g., to minimise tissue deformation. Such needles can be formed by collections of nitinol wires as in , or via This paper presents research on the underlying motion profiles for PBNs that can be controlled in order to reduce the strain on the surrounding tissue, which could reduce the subsequent tissue damage that occurs along the needle tract—our clinical goal for this specific research. This can be achieved by employing cyclic motion, where each segment moves forward and backwards during a profile, in a similar manner to how some wasps can drill and steer their ovipositors through a harder substrate, such as bark, without buckling. A novel Hybrid Controller is presented and compared against a Direct Push controller and a fully Cyclic Controller. All three control methods have been integrated into the visual interface the surgeon would use to perform neurosurgery, where the navigation commands are measured by a control joystick. This is the first time the Cyclic and Hybrid Controllers have been tested using the surgical interface.PBNs have evolved over a 13-year journey that found its roots in a blue-sky collaboration with Bath university and Prof Julian Vincent, a world leading biomimeticist and the source of inspiration of this unique design. Thanks to national and international funding, the concept matured from early proof-of-concept to a medical-grade, pre-production prototype suitable for live use, which is currently at the centre of a large-scale European consortium effort on precision neurosurgery.z axis. The resulting curvature can be determined by measuring the radius of curvature, R.The Enhanced Delivery Ecosystem for Neurosurgery (EDEN2020) project is a European Union Horizon 2020 Research and Innovation Action (RIA) involving six universities and two companies, which aims to develop the gold standard for one-stop diagnosis and minimally invasive treatment in neurosurgery. Imperial College has predominately been in charge of developing the needle and robotic platform, with specialist manufacturing support provided by Xograph Technologies Ltd. . The PBN design consists of four interlocking, bevel-tipped segments that axially slide relative to one another, as shown in In , Ko et aThis control method was limited in regards to the magnitude of the control gains and a large initial position perturbation, which caused instability due to a number of control input constraints. In the work presented in  a Model Further design work focused on minimising the outer diameter of the PBN, to make it closer to clinically viable and to see the effects of smaller diameter needles on the system performance. Open loop 3D steering of the needle with an outside diameter of 8 mm was presented by Burrows et al. . ResultsHowever, the path planner in  was compIn , furtherTo better understand the deformation caused by the needle on surrounding tissue, Oldfield et al.  demonstrAfter five years of research and development, the PBN design was well understood and tested in 2D. Via extrusion of a medical-grade polymer, a clinically viable sized needle with a 2.5 mm outer diameter, as shown in The inverse model—determining the required offset to generate a desired curvature—was the subject of work presented in . This usRecent work of a path planner has used these models for the 2.5 mm outer diameter needle in order to create 3D paths that are optimised for the needle kinematics and the start and end pose constraints of the neuro anatomy. This is important, as the effectiveness on drugs  has been linked to the precision of the infusions of the drug at the tumour site . To dateThere are two main methods to control and move the catheter segments; the first is via a cyclic motion, whereby each segment is extended forward and then backward for each period of motion control. This controller is bioinspired from how wasps can drill into bark using their ovipositors. The second method is direct motion, whereby each segment is extended forward only. These modes are further described in Previous work presented in  demonstrthe human operator can correct the performance in real-time and keep the open loop cyclic controller design as is; anduse a combination of direct and cyclic motion profiles according to the magnitude of offset configuration change to benefit from the timely response of the direct controller and cyclic profiles from the cyclic controller.The cyclic controller was extended in  to handlThis work seeks to validate and optimise a controller via a full system simulation in C++ of a four-segment PBN with outer diameter of 2.5 mm, which is modelled according to Watts et al. , that doExperiments were undertaken for open loop curvilinear trajectories in 3D to evaluate the path following and target reaching performance of each of the control modalities, followed by a closed, human-in-the loop, single expert user study to evaluate the same metrics. Finally, a small human user trial was performed to understand if the control modality affected the user when using the neurosurgical human machine interface. The following hypotheses are made:Hypothesis 1.The CAC will achieve significantly less performance compared to the DPC.Hypothesis 2.There exists a HC that achieves the same performance metrics of the DPC while still using CAC profiles more than 75% of the insertion timeHypothesis 3.Users will not notice the difference in the choice of underlying control modality when using the system’s visual interface.Controlling the catheter requires continuous adjustment of the relative offsets between the segments. A direct push controller (DPC), first described in , createsThe cyclic actuation controller (CAC), first described in , moves tThe main equations governing the motion of the CAC are as follows. The velocity profile of one segment consists of a period of the segment extending at  seconds:VSegCAC project has developed a mechatronics driver for a four-segment PBN , where eActuation: The physical system uses Maxon high-precision DC brushed motors (DC16XS) with a planetary gearhead with reduction of 35:1, each equipped with a rotary magnetic encoder (1024 pulses/revolution). Each motor has a mechanical time constant of 8.57 ms, meaning it reaches 63.2% of its maximum no load speed of 10,000 rpm in 8.57 ms. The motors are connected to 1 mm pitch linear stages, and, taking into account the gearing, this means it takes 8.57 ms to reach a linear speed of 3 mm/s. The DPC has a control frequency of 5 Hz, and the CAC has a control frequency of 20 Hz. For each the net speed of the catheter is 1 mm/s, and the maximum speed of any segment when moving to create an offset is 5 mm/s for the DPC and 5.5 mm/s for the CAC; thus, the response time of the motor can be considered to be very high. In simulation, each motor velocity profile has been modelled with instantaneous acceleration, and the motor position is determined via trapezoidal numerical integration of the velocity values, with a time step of Sensing: Pose measurements of the catheter are calculated on the physical system via either embedded electromagnetic (EM) or fibre Bragg grating (FBG) optical sensors. In simulation, the pose of the catheter is calculated using the forward mechanics-based model of the catheter as detailed in . This moUser Input: The user steers the catheter using a foot pedal for on/off motion, and a 2DOF joystick to control the curvature left/right and up/down, as shown in TM (Renishaw plc). The standard release of the software provides three orthogonal views of the brain—a new fourth window that visualises the 3D navigation view has now been added. In this view, the user sees a visual interface showing the preoperative MRI and CT scans of the patient, as well as a navigational “First Person View” of the catheter position in the surrounding anatomy in order to steer the catheter along the desired path. In this window, the user can also choose to see a third person “Overview View” of the environment. They are shown visual cues to help this process: the desired path; way-points as rings that they should steer through, the colour of which reflects the Euclidean error in position from the path; the expected curvature of the future catheter track as commanded by the joystick (green overlay); and the actual curvature of the future catheter track as predicted by the forward model (blue overlay). Further details of the interface are published in [Visual Interface: This interface has been integrated into the commercial neurosurgical planning and intraoperative software neurosinpireished in  and an iThree experiments were setup to test the different control modalities when moving the catheter along a desired path. Ethical approval for the experiments was given by the Imperial College London Joint Research Compliance Office (ICREC 18IC4564). The paths were created using the path planner presented in . Based or) mm for the single curve trajectory wereTwo trajectories were generated: a single curve planar trajectory at maximum curvature, and a double curve 3D trajectory at maximum curvature. The maximum curvature was Results from  show thaIn the author’s experience, planned trajectories through real neuro-anatomy generally only require one or two shallow curves to reach the target from the entry point, and so the per cent of time the CAC is activated for these trajectories is representative of a realistic scenario. The large control inputs requiring offset configuration changes above the threshold value normally occur when the user needs to fully change direction—which would happen at the beginning of each path and at the junction of the double bend curve. At other times, only small adjustments are necessary, meaning a HC is attractive to use as the CAC can be active for the majority of time, and the DPC can be activated only when a large offset is requested.In Three paths were generated by the path planner in order to provide trajectories the catheter could reasonably be expected to follow during a neurosurgical procedure, each with a different target and initial insertion point into the skull, corresponding to paths approximately 60 mm in length—Path 2 in overview mode is shown in The user made five insertions for each of the controller modalities over each path. The underlying low level control modality was changed unknowingly to the user following a Latin squares assignment. The user was asked to achieve the following objectives in decreasing order of priority.Obj 1: Reach the target pose with the catheter tipObj 2: Follow the desired pathResults from  show thaAn expert user undertook five insertions for each path using the DPC, HC with threshold of After testing for normal distributions, a one-way between modalities ANOVA was conducted for each of the performance metrics: path following position and orientation errors and target reaching position and orientation errors. There was a significant difference for the path position error To validate the real-time performance of the visual interface and teleoperated joystick for the PBN navigation system when using different low level controller modalities, a human study  over the three paths based on a Latin square assignment—giving nine insertion performance results per modality per user, or a total of 45 trials per modality. The hybrid controller threshold parameter was set to be The results from the user trial of non experts .The results of Experiment 1 highlight the trade off among under-steering, hence performance, and per cent of time the CAC is active. As the CAC can reduce tissue deformation, which is hypothesised to reduce tissue damage, it will be necessary to quantify the magnitude of this effect during in vivo trials via functional analysis of the tissue tract after the surgery. In this way, the final choice of optimal HC threshold value can be chosen.The results of Experiments 2 and 3 indicate that the CAC has significantly lower performance than the DPC . Here, performance is measured by our metrics of the error measurements of the needle tip to the target position and orientation and path position and orientation. The CAC had significantly higher error in path position for the expert user and in target and path position for the non-expert users. However, it should be noted that the results from Experiment 2 are only from one user, and it may be too early to draw this conclusion for expert users. In Experiment 2, the result of the CAC having significantly higher error only in the path following position when compared to the DPC or the HC was surprising. It highlights that the expert user was able to mitigate the error introduced by the under steering of the CAC to achieve the target pose as per the first objective, but possibly at the expense of the path following metric which was the second objective. The user trial in Experiment 3 shows that less expert users are not able to compensate for the CAC error in target reaching performance, hence an HC could also be attractive as less training may be required from the users to achieve expert results. We found an HC with no significant performance differences compared to the DPC when used by both an expert and a group of non-experts, with All modes show orientation errors, with the CAC showing the worst case of target orientation/heading error of Following a 10-year research and development journey, this paper summarises the main milestones associated with a novel, biologically inspired needle steering system, followed by our latest control approaches, validated in silico. These experiments highlight how cyclic motion control, which is also biologically inspired, can be delivered optimally though a blended approach, where the HC threshold value must be optimised under appropriate surgical conditions. This will be the focus of future research work for the low level control of the PBN, as well as further developing the Human–Robot Interface, both of which must be evaluated by clinicians.The EDEN2020 system is currently being used for in vivo clinical trials with an animal (ovine) model, expected to be completed in Q1 of 2021. The trial will evaluate the safety of the system, as only a gadolinium contrast solution is being injected into healthy tissue. It will also evaluate the accuracy of path following and target reaching performance based on intraoperative sensing  and from pre- and postoperative CT and MRI imaging comparisons. Upon completion, a pre-commercial prototype of the EDEN2020 platform will have been fully developed under a quality management system, and the safety data from the trial will help drive the commercialisation of the project and inform future efficacy trials.


Local water governance is challenging given the significance to public health and the difficulties to manage it in a fragmented administrative system. A collaboration network is a popular governance tool in local governance to cope with functional fragmentation problems and institutional collective action (ICA) dilemmas. Empirical works are needed to examine the outcomes of such governance networks, especially in the context of environmental governance. With fuzzy-set qualitative comparative analysis (fsQCA), this article seeks to evaluate the outcomes of collaboration networks by investigating the influence of network structures on local water governance performance in China. Based on empirical analyses on a dataset of twenty local water governance networks implementing the Water Ecological Civilization Pilot Project in China, the findings suggest that a high overall bridging and bonding of social capital and a low network density are important determinants of effective collaboration networks. This study has policy implications for the design of local collaboration networks in facilitating effective environmental governance. Fragmentation among government units and across jurisdictions poses serious challenges to local governments in their collective efforts to promote effective regional governance . Such chPerformance evaluation has always been a focal question in the literature of public policy and management ,4,5. In We examine what factors motivate better network outcomes in the context of water governance collaboration networks in China. Water management always poses multi-dimensional challenges to governance ,14. The The rest of the paper is structured as follows. The following section presents the theoretical framework based on which we evaluate the performance of collaboration networks, linking social capital theory with network structures and network performance. We then introduce the background of the local water governance system in China, with details of the Water Ecological Civilization Pilot Project. Hypotheses are then proposed based on social capital theories and network governance research. With twenty prefecture-level water governance networks in China, fsQCA is utilized to test the hypotheses. The results of the fsQCA are then summarized and discussed. The article concludes with theoretical and practical implications, as well as its limitations.Provan and Milward  proposedMethodologically, extant literature evaluates network performance mainly with case studies ,16. SomeVarious forms of a network exist in the practice of network governance. Depending on who manages the whole network, the network could be jointly governed, governed by a central organization, or by an external actor ,23,24. ANetworks are a collection of social relations, which can be best understood with social capital theory. The notion of social capital indicates access to the connections and resources embedded in the network ,30. SociAs for the structural variables of networks, Salancik  emphasizBuilding upon these efforts, we further test the influence of social capital and network structures on network performance with two unique contributions. First, we examine the performance of designed networks, for which few studies have looked into the influence of social capital on network performance. Second, the networks under study are embedded in the context of China, where very few network studies have been conducted thus far.Solving water-related challenges through effective water governance is always one of the priorities on China’s policy agenda. The water system was governed by a fragmented system of multiple agencies, lacking effective coordination among them. To address the fragmentation of authorities, local governments in China have started experimentation with reforms from fragmented systems to integrative water governance institutions . In addiThe National Water Ecological Civilization Pilot Project aims to address policy issues surrounding water supply, flooding and ecological conservation. Selected pilot cities were empowered to develop their own implementation plans considering their local conditions. However, the fundamental concepts of the experimental programs and the selection of the pilot cities are determined by the central government, rather than through a bottom-up process. The Chinese central government takes the responsibility to review local pilot program plans and conduct evaluations of the selected cities after the implementation. Key policy measures of the local pilot plans include water security, water ecology, water environment, water saving, water management and water culture. The first batch of the Water Ecological Civilization Pilot Project was launched in 2013 with the following objectives: to implement strict water management; optimize water configuration; strengthen the management of water saving; reinforce water conservation; promote protection and restoration of the ecosystem; and enhance awareness. Seventy-seven of 287 prefecture-level cities in China were selected as the 1st batch and the 2nd batch pilot cities in 2013 and 2014 to implement this innovative water governance program. Similar to urban housing reform in China, policymakers did not wait until a satisfactory performance was observed to extend the program to a broader scale . TherefoDifferent from other projects, the Water Ecological Civilization Pilot Project mandated that departments to work together to address water-related challenges, which is an issue-focused collaboration network. Even though some cities have already passed the evaluation conducted by the central government, the evaluation of the overall performance of these collaboration networks should be conducted in a systematic way. Both the institutional collective action framework (ICA) and the ecology of games framework (EGF) emphasized the influence of social capital on collective outcomes in fragmented policy arenas ,41. SociBonding social capital indicated by a close-knit configuration in the network could be captured with the average clustering coefficient . It is bBonding Social Capital Hypothesis (H1): High bonding capital measured by the average clustering coefficient of the overall water governance network is one of the causal conditions of desirable water governance performance.Bridging social capital is generated when actors in a group create connections beyond a smaller circle of acquaintances and extend the scale of the network by reaching out to other unfamiliar groups . Well coThe term average degree is the mean of the connections that each node shares with others . The aveBridging Social Capital Hypothesis (H2): High bridging social capital measured by the average degree centrality of the overall water governance network is one of the causal conditions of desirable water governance performance.Besides the average degree centrality and clustering coefficient, density is also an important indicator of network closure according to social capital theory. Density, one of the properties of the network, reflects a general level of linkages in the whole network. It is calculated by dividing the actual connections within a network over the maximum number of potential connections ,47. A deHowever, mixed findings have been reported on the effect of density on network performance. Based on Coleman’s arguments on closure, Burt  contendeOur theoretical expectation on density takes both the theoretical background and the reality of the water governance system in China into account. Local water governance in China, historically, has been fragmented across multiple departments governing water-related functions. Through implementing the Water Ecological Civilization Pilot Project, local agencies started to form collaboration networks within their city boundaries. When the city government designs the network in a way that features multiple functions, and when many actors are involved in the same function, a high density is then observed. Therefore, if the network density is too high, it might signal functional fragmentation and oversubscription of responsibilities on agencies. Therefore, we expect low density to be related to better governance performance, as the sub-projects and responsibilities are jointly managed by a reasonable number of organizations in the governance network.Network Density Hypothesis (H3): Low density of the overall water governance network is one of the causal conditions of desirable water governance performance.QCA is a comparative case-oriented research approach and a collection of techniques based on set theory and Boolean algebra ,49. AccoQCA has been successfully applied to management and other social science subjects ,56,57. IFollowing the abovementioned concepts of QCA, it is appropriate for this article to detect the driving forces of local water governance performance with the acknowledgment of set relations. Local water governance is always complicated, which cannot be explained by simple correlations. Set relations combining different conditions allow for comprehensive and intuitive analysis of the complex problem. It is a more direct and easy way for configuration determination. Moreover, it is difficult to collect large samples of non-public policy implementation plans of local governments. Due to the relatively small but the best available dataset, QCA is a good practice for small-N research, providing a deep understanding of cases beyond simple correlation. More importantly, the set membership scores, in this case, should not be crudely calibrated by “0′s” and “1′s”, as the structural components of networks are diversified to varying degrees. Therefore, this study applied fsQCA with the software fsqca3.0 for empirical analyses .All possible combinations of causal conditions are collected in a truth table, and the QCA solutions are presented after manual editing based on the truth table. In our study, logical remainders are kept if they have raw consistency scores over 0.85, otherwise they are deleted ,60. In tThis study examined the performance of water governance pilot project by analyzing twenty collaboration networks that implemented the Water Ecological Civilization Pilot Project at the local level in China. In order to better understand the roles played and tasks undertaken by local governments in the implementation process, we collected implementation plans of the pilot project from twenty cities in China. Due to the difficulty in collecting such non-mandatory policy documents, we were only able to obtain a sample of twenty implementation plans. These twenty cities across thirteen different provinces are representative of the seventy-seven pilot cities because they are reasonably distributed in various areas in China and in two time points of implementing the Water Ecological Civilization Pilot Project. In addition, the twenty cities represent the complexity and diversity of local water governance in different degrees. Among the twenty cities, some of them are traditionally regarded as high-class ecological cities while some were recently reported as poorly or moderately performing cities regarding environmental governance. For example, Nanning in Guangxi province faced severe water governance challenges, especially in the governance of Nakao River. In the worst case, there are more than forty sewage outlets discharging sewage to the river. More seriously, garbage and construction spoil piled up to occupy the river, which brought extensive governance pressures to local governance . HoweverSome of the implementation plans were directly downloaded from the official website of city governments and the website of the Water Affairs Bureau; the rest were collected by reaching out to local officials via social media (WeChat) or emails. After we received implementation plans from the twenty cities, we manually coded the functions and agencies according to the division of duties in the implementation plans. Through cleaning the information of the responsible departments, we obtained a two-mode network of functions and agencies. Functions may include wastewater treatment, water quality, water recycled and reused, water culture publicity and water-related education etc. The corresponding agencies are Water Affairs Bureau, Urban Management Bureau, Organization Department, and Education Bureau, etc. Then we transformed the two-mode network data into a one-mode network to capture the collaboration network among agencies with UCINET. The transformation from a two-mode collaboration network to a one-mode collaboration network enables us to observe a direct relationship between the involved departments. The collaboration network in Yantai represents one of the twenty collaboration networks that we analyzed. Although the number of actors in these networks are not exactly the same, the collaboration network presented in To evaluate the Water Ecological Civilization Pilot Project, the outcome of the water governance network can be assessed by evaluating the accomplishment of the project objective. Through analyzing local implementation plans collected by the authors, wastewater treatment is one of the most crucial tasks of the Water Ecological Civilization Pilot Project. Although this project has multiple objectives, wastewater treatment is considered as the top priority among numerous tasks from the analysis of the financial budget allocated to each item, including wastewater treatment, flood control, water culture, water management and water safety. It is understandable because wastewater treatment is closely related to water pollution problems that have reached a record level in China. The capacity of wastewater treatment could efficiently alleviate environmental pressure resulting from water pollution and water scarcity .Based on the practical and theoretical background, this article measured the performance of the water governance network using wastewater treatment capacity collected from the China City Construction Yearbook in 2015, the latest data available. Referring to the direct calibration method, we chose three important anchors: threshold for full membership, the crossover point and the threshold for full non-membership. For the water governance outcome, it was calibrated to the 30th percentile, 50th percentile and 70th percentile, respectively. Following our hypotheses, we calculated the average degree centrality, average clustering coefficient and density score of the water governance networks with UCINET, and then calibrated the raw data from zero to one, which was then analyzed in fsQCA software. The network-related variables were calibrated based on our substantive knowledge of network variables. For example, a network with a density score over 0.7 could be regarded as a dense network, where 0.7 is the threshold for full membership in a set.Besides the structural variables of collaboration networks, we also included variables related to water governance, namely the percentage of secondary industry in a city, investment on fixed assets and the quantity of wastewater discharged. Those variables could capture the local conditions related to water governance. The percentage of secondary industry in a city measures the city’s level of industrialization while investment in fixed assets tells about local attention on infrastructure construction. The quantity of wastewater discharged directly reflects the cities’ treatment pressure. All these variables were calibrated to the 30th percentile, 50th percentile and 70th percentile. The data on network performance, attributes of the city and water-relevant data were all collected from the China City Statistical Yearbook and China City Construction Statistical Yearbook in 2015. Consistency and coverage are two critical components of the QCA results. “Consistency gauges the degree to which the cases sharing a given combination of conditions agree in displaying the outcome in question when coverage indicates how closely a perfect subset relation is approximated”  (p. 44).The first causal path was the combination of low membership in the sets of density and high membership in the sets of the quantity of wastewater discharged. This suggests that water governance networks with a low density, together with a high quantity of wastewater discharged, are very likely to be effective in treating wastewater. Other conditions in the first causal path were irrelevant. Hence, when local policy practitioners form a less dense collaboration network to implement the Water Ecological Civilization Pilot Framework under heavy treatment pressure, the established collaboration network is more likely to obtain higher performance. Seven cases were covered by this causal path, as reported in The second causal path was the combination of high membership in the sets of the average degree centrality, investment in fixed assets, the quantity of wastewater discharged and low membership in the sets of the percentage of the secondary industry. This causal path supported our second hypothesis related to bridging social capital. It suggests that cities with high bridging capital, high investment and treatment pressure, as well as a low secondary industry share, are more likely to achieve desirable water governance performance. Five cases are consistent with this configuration. The third causal path was the combination of high membership in the sets of the average degree centrality, clustering coefficient, the quantity of wastewater discharged and investment in fixed assets. In other words, a city is very likely to achieve a high wastewater treatment capacity if the city has a water collaboration network with high bridging and bonding social capital and has a large quantity of wastewater discharged and heavy investment in fixed assets, which supported our first and second hypotheses. Five cases demonstrated this configuration. Robustness checks using different consistency cutoffs and crossover points are introduced in detail in The fsQCA analysis identified three different causal paths for the presence of wastewater treatment capacity. To better understand the results, we should keep in mind that Boolean methods behind QCA represents each case with a combination of causal and outcome conditions . The firThe second and the third causal paths identified by fsQCA confirmed our hypotheses on social capital. Bridging social capital measured by the average degree centrality, along with three other environmental factors, including the quantity of wastewater discharged, investment on fixed assets, and the low percentage of the secondary industry to local GDP, leads to effective water governance. The second causal path indicates that collaborative networks with high bridging social capital with heavy treatment pressure and sufficient investment in infrastructure in less-industrial cities facilitate the desirable water governance performance. It suggests that the structure of the collaboration networks and the local conditions of the industrial structure and water environment affect governance performance. High bridging capital embedded in the collaboration networks could resolve the cooperation dilemmas through brokers. Communication channels established through bridging capital in the networks could greatly help improve effectiveness. Along with sufficient attention and industrial structure, the network should perform reasonably well.Bonding capital, indicated by the average clustering coefficient, together with high bridging capital and high memberships in two other environmental factors, leads to high performance in water governance. The last causal path further points out the combining effect of the components of collaboration networks and the variables of local conditions. High bonding and bridging capital, along with heavy treatment pressure and sufficient relevant investment, can advance water governance performance. High bonding capital can bring participants closer and simulate trust, and therefore reduce the cooperation risks and facilitate the positive outcomes. The effect of bonding capital becomes even stronger when it appears together with bridging capital and sufficient local governance attention and pressure. Local conditions are very important for the achievement of governance performance; but, if the city could formulate the collaboration network with adequate bridging and bonding capital, ensuring effective information flow and low cooperation risk, the city is still able to achieve positive governance outcomes. The major causal conditions, namely density, bridging capital and bonding capital, do not necessarily occur in each causal path, but their occurrence suggests the significance of the structural components of collaboration networks in shaping performance. The condition of the amount of wastewater discharged appeared in all three causal paths, which is a key causal condition. It is not difficult to understand that a high treatment pressure with a large amount of investment could facilitate decent treatment capacity. The presence of the average clustering coefficient and average degree centrality together further confirmed the importance of social capital and its significance in explaining network effectiveness.Drawing on social capital theory and network performance research, this study aims to evaluate the network-level performance of local water governance in China. With the implementation of the Water Ecological Civilization Pilot Project in China and twenty cases of pilot cities, we are able to test the influence of bonding and bridging social capital on network performance with fsQCA. The fsQCA results revealed that high membership in the sets of the average degree centrality and clustering coefficient lead to high performance in water governance networks, indicating the significance of social capital in network governance. Network actors should pay attention to social capital embedded in their networks in order to achieve common goals and enhance overall performance. This study confirms the findings from social capital literature and network effectiveness literature on the positive influence of bonding and bridging social capital. At the same time, this study also finds that the impact of low network density is related to effective networks, motivating scholars to reconsider the effect of the structural variables of the network in a broader picture in terms of network design, cooperation and division of labor. More importantly, the results suggest that there are no simple prescriptions for achieving positive network outcomes, based on the fact that we find complex causal relationships behind the desirable performance.We made a connection between network analysis and social capital theory in the context of China, which traditionally features a fragmented water governance system. Scholars are struggling with the difficulty in obtaining high-quality data for examining network effectiveness. The inspiration from small-N studies and complex causal configurations allows us to examine network effectiveness that is otherwise impossible to do. This study also provides public managers with practical insights on network design and collaboration process. Practitioners should recognize the influence and power of central actors in the network in coordinating with other network participants, as well as the significance of bonding structure in building trust and reducing cooperation risks. This article has several limitations that we need to acknowledge. First, due to data availability, this research only adopts one outcome variable, although it is one of the most important indicators of the project. Future studies could utilize more outcome variables, should they become available, to confirm the results. Moreover, the dynamic evaluation of the effectiveness might present a more comprehensive picture of the network performance. We also acknowledged that the samples in this study include both first-round and second-round pilot cities, which could potentially ignore the learning effect in the analysis of policy outcomes. Further studies could conduct a comparative analysis to account for the effect. Meanwhile, including more cases that are not self-motivated to apply for the pilot scheme can greatly enhance the generalizability of the results, which can also be the direction of future studies.