Pedestrian Crowd Management Experiments: A Data Guidance Paper

Understanding pedestrian dynamics and the interaction of pedestrians with their environment is crucial to the safe and comfortable design of pedestrian facilities. Experiments offer the opportunity to explore the influence of individual factors. In the context of the project CroMa (Crowd Management in transport infrastructures), experiments were conducted with about 1000 participants to test various physical and social psychological hypotheses focusing on people's behaviour at railway stations and crowd management measures. The following experiments were performed: i) Train Platform Experiment, ii) Crowd Management Experiment, iii) Single-File Experiment, iv) Personal Space Experiment, v) Boarding and Alighting Experiment, vi) Bottleneck Experiment and vii) Tiny Box Experiment. This paper describes the basic planning and implementation steps, outlines all experiments with parameters, geometries, applied sensor technologies and pre- and post-processing steps. All data can be found in the pedestrian dynamics data archive.Comment: 58 pages, 19 figures, under review Collective Dynamic

Experimental determination of the emissivity of bone

Cutting and drilling operations in bone are involved in many orthopedic and otolaryngological surgeries. The temperature elevation of these procedures is potentially harmful to bone and soft tissue cells. The research on this topic aims therefore at minimizing temperature elevation and finding optimal process parameters. Experimental studies are mostly carried out on ex vivo setups using bovine bone material. For temperature measurements, either thermocouples or infrared cameras are used. Infrared cameras have potential advantages, but the emissivity value of the material has to be known. Literature values are scattered and vary within a wide range. An experimental study was carried out to quantify the emissivity using freshly frozen bovine and human bone, as well as human bone samples which were either fixed with Formalin or Thiel solution. Additionally, different surface finishes were used and emissivity was evaluated at different temperatures. The mean emissivity of bone was determined to be ɛ=0.96±0.01 for temperature elevations up to 60 °C. A slightly higher value of ɛ=0.97±0.01 was found for temperatures around 80 °C. No significant differences for human or bovine bone samples, preparation or fixation techniques were found

Reducing temperature elevation of robotic bone drilling

This research work aims at reducing temperature elevation of bone drilling. An extensive experimental study was conducted which focused on the investigation of three main measures to reduce the temperature elevation as used in industry: irrigation, interval drilling and drill bit designs. Different external irrigation rates (0 ml/min, 15 ml/min, 30 ml/min), continuously drilled interval lengths (2 mm, 1 mm, 0.5 mm) as well as two drill bit designs were tested. A custom single flute drill bit was designed with a higher rake angle and smaller chisel edge to generate less heat compared to a standard surgical drill bit. A new experimental setup was developed to measure drilling forces and torques as well as the 2D temperature field at any depth using a high resolution thermal camera. The results show that external irrigation is a main factor to reduce temperature elevation due not primarily to its effect on cooling but rather due to the prevention of drill bit clogging. During drilling, the build up of bone material in the drill bit flutes result in excessive temperatures due to an increase in thrust forces and torques. Drilling in intervals allows the removal of bone chips and cleaning of flutes when the drill bit is extracted as well as cooling of the bone in-between intervals which limits the accumulation of heat. However, reducing the length of the drilled interval was found only to be beneficial for temperature reduction using the newly designed drill bit due to the improved cutting geometry. To evaluate possible tissue damage caused by the generated heat increase, cumulative equivalent minutes (CEM43) were calculated and it was found that the combination of small interval length (0.5 mm), high irrigation rate (30 ml/min) and the newly designed drill bit was the only parameter combination which allowed drilling below the time-thermal threshold for tissue damage. In conclusion, an optimized drilling method has been found which might also enable drilling in more delicate procedures such as that performed during minimally invasive robotic cochlear implantation

The thermal conductivity of cortical and cancellous bone

Surgical interventions close to vulnerable structures, such as nerves, require precise handling of surgical instruments and tools. These tools not only pose the risk of mechanical damage to soft tissues, but they also generate heat, which can lead to thermal necrosis of bone or soft tissues. Researchers and engineers are trying to improve those tools through experimentation and simulations. To simulate temperature distributions in anatomical structures, reliable material constants are needed. Therefore, this study aimed at investigating the thermal conductivity of cortical and cancellous bone. Accordingly, a custom-made steady-state experimental setup was designed and validated. 6 bovine and 3 human cortical bone samples, as well as 32 bovine cancellous bone samples, with variable bone volume fraction were tested. The cancellous bone samples were scanned by micro-computed tomography (µCT) and micro-finite element (µFE) voxel models were created to calculate iteratively the thermal conductivity of the bone marrow. The experimental results provided 0.64 ± 0.04 W/mK for bovine cortical bone and 0.68 ± 0.01 W/mK for human cortical bone. A linear dependency of thermal conductivity on bone volume fraction was found for cancellous bone [R-square (R2) = 0.8096, standard error of the estimates (SEE) = 0.0355 W/mK]. The thermal conductivity of the bone marrow was estimated to be 0.42 ± 0.05 W/mK. These results will help to improve thermal finite element simulations of the human skeleton and aid the development of new surgical tools or procedures

Temperature Prediction Model for Bone Drilling Based on Density Distribution and In Vivo Experiments for Minimally Invasive Robotic Cochlear Implantation

Surgical robots have been proposed ex vivo to drill precise holes in the temporal bone for minimally invasive cochlear implantation. The main risk of the procedure is damage of the facial nerve due to mechanical interaction or due to temperature elevation during the drilling process. To evaluate the thermal risk of the drilling process, a simplified model is proposed which aims to enable an assessment of risk posed to the facial nerve for a given set of constant process parameters for different mastoid bone densities. The model uses the bone density distribution along the drilling trajectory in the mastoid bone to calculate a time dependent heat production function at the tip of the drill bit. Using a time dependent moving point source Green's function, the heat equation can be solved at a certain point in space so that the resulting temperatures can be calculated over time. The model was calibrated and initially verified with in vivo temperature data. The data was collected in minimally invasive robotic drilling of 12 holes in four different sheep. The sheep were anesthetized and the temperature elevations were measured with a thermocouple which was inserted in a previously drilled hole next to the planned drilling trajectory. Bone density distributions were extracted from pre-operative CT data by averaging Hounsfield values over the drill bit diameter. Post-operative [Formula: see text]CT data was used to verify the drilling accuracy of the trajectories. The comparison of measured and calculated temperatures shows a very good match for both heating and cooling phases. The average prediction error of the maximum temperature was less than 0.7 °C and the average root mean square error was approximately 0.5 °C. To analyze potential thermal damage, the model was used to calculate temperature profiles and cumulative equivalent minutes at 43 °C at a minimal distance to the facial nerve. For the selected drilling parameters, temperature elevation profiles and cumulative equivalent minutes suggest that thermal elevation of this minimally invasive cochlear implantation surgery may pose a risk to the facial nerve, especially in sclerotic or high density mastoid bones. Optimized drilling parameters need to be evaluated and the model could be used for future risk evaluation

L'implantation cochléaire robot-assistée

Im Sommer 2016 wurde in der Schweiz doppelt Tunnelbohrgeschichte geschrieben. Neben der feierlichen Eröffnung des Gotthard-Basistunnels konnte in Bern in gänzlich anderen Grössenordnungen eine weitere Weltpremiere gefeiert werden: Die erste roboterassistierte Cochlea-Implantation am Patienten.Durant l’été 2016, l’histoire du forage de canal a été doublement marquée en Suisse. Outre l’ouverture solennelle du tunnel de base du Saint-Gothard, une autre première mondiale d’un tout autre ordre de grandeur a été célébrée à Berne: la première implantation cochléaire robot-assistée chez un patient

Instrument flight to the inner ear

Surgical robot systems can work beyond the limits of human perception, dexterity, and scale, making them inherently suitable for use in microsurgical procedures. However, despite extensive research, image-guided robotics applications for microsurgery have seen limited introduction into clinical care to date. Among others, challenges are geometric scale and haptic resolution at which the surgeon cannot sufficiently control a device outside the range of human faculties. Mechanisms are required to ascertain redundant control on process variables that ensure safety of the device, much like instrument flight in avionics. Cochlear implantation surgery is a microsurgical procedure, in which specific tasks are at submillimetric scale and exceed reliable visuo-tactile feedback. Cochlear implantation is subject to intra- and interoperative variations, leading to potentially inconsistent clinical and audiological outcomes for patients. The concept of robotic cochlear implantation aims to increase consistency of surgical outcomes, such as preservation of residual hearing, and to reduce invasiveness of the procedure. We report successful image-guided, robotic cochlear implantation in human. The robotic treatment model encompasses computer-assisted surgery planning, precision stereotactic image guidance, in situ assessment of tissue properties, and multipolar neuromonitoring, all based on in vitro, in vivo, and pilot data. The model is expandable to integrate additional robotic functionalities such as cochlear access and electrode insertion. Our results demonstrate the feasibility and possibilities of using robotic technology for microsurgery on the lateral skull base. It has the potential for benefit in other microsurgical domains for which there is no task-oriented robotic technology available at present

Instrument flight to the inner ear

Surgical robot systems can work beyond the limits of human perception, dexterity, and scale, making them inherently suitable for use in microsurgical procedures. However, despite extensive research, image-guided robotics applications for microsurgery have seen limited introduction into clinical care to date. Among others, challenges are geometric scale and haptic resolution at which the surgeon cannot sufficiently control a device outside the range of human faculties. Mechanisms are required to ascertain redundant control on process variables that ensure safety of the device, much like instrument flight in avionics. Cochlear implantation surgery is a microsurgical procedure, in which specific tasks are at submillimetric scale and exceed reliable visuo-tactile feedback. Cochlear implantation is subject to intra- and interoperative variations, leading to potentially inconsistent clinical and audiological outcomes for patients. The concept of robotic cochlear implantation aims to increase consistency of surgical outcomes, such as preservation of residual hearing, and to reduce invasiveness of the procedure. We report successful image-guided, robotic cochlear implantation in human. The robotic treatment model encompasses computer-assisted surgery planning, precision stereotactic image guidance, in situ assessment of tissue properties, and multipolar neuromonitoring, all based on in vitro, in vivo, and pilot data. The model is expandable to integrate additional robotic functionalities such as cochlear access and electrode insertion. Our results demonstrate the feasibility and possibilities of using robotic technology for microsurgery on the lateral skull base. It has the potential for benefit in other microsurgical domains for which there is no task-oriented robotic technology available at present