bluuebunny/crossref_metadata_2025_split huggingface dataset:
MRV-validated numerical flow analysis of thrombotic potential of coronary stent designs
Authors: Oldenburg Jan , Borowski Finja , Schmitz Klaus-Peter , Stiehm Michael , Öner Alper Ö , Quirin Lukas , John Kristine , Bruschewski Martin , Grundmann Sven 
Published: September 2019

Abstract
The formation of a thrombus is associated with dramatic consequences for the patient, such as increased risks of neurologic events and myocardial infarction or even death. A pathologically altered blood flow is associated with these complications. Consequently, a consistent fluid-mechanical analysis of implants, such as coronary stents, must be carried out. Computational fluid dynamics (CFD) is an important in silico tool for the analysis of different stent designs. Using three different generic stent designs (closed-cell, open-cell and helical), CFD could be performed with the OpenFOAM software package. The stents were implemented in a vascular model having a fully developed Hagen-Poiseuille velocity profile (umean = 0.6 m/s) as inlet condition. In combination with the dynamic viscosity of the Newtonian test fluid of 6.04·10-5m2/s, Reynolds numbers up to 460 were achieved. Spatially high-resolved velocity fields from measurements in the magnetic resonance tomograph (magnetic resonance velocimetry, MRV) were available for validation. The velocity field was compared in selected cross sections and longitudinal sections. The difference of the main flow proximal and distal to the stent models were below 6 %. In addition, a similar flow topology could be quantified using the Q-criterion. Due to the very good agreement of the numerical results with the MRV-measurements, the numerical method has been applied to further analysis of stent designs regarding to time average wall shear stress (TAWSS) distribution on the luminal vessel surface (surface area with TAWSS < 0.4 Pa was related to overall vessel surface) under pulsatile conditions. Although all stent designs have the same square cross-section, a large influence of the stent design on WSS distribution could be observed (closedcell vs. helical = -50.2 %; open-cell vs. helical = -38.5 %). By using validated CFD it was possible to quantify the hemodynamic benefit of helical stent design in terms of thrombosis potential.
Esophageal electrode model and simulation of directed transesophageal electrical pacing of the spinal cord
Authors: Schleh Manuela , Heinke Matthias , Hörth Johannes 
Published: September 2019

Abstract
Spinal cord stimulation (SCS) is the most commonly used technique of neurostimulation. It involves the stimulation of the spinal cord and is therefore used to treat chronic pain. The existing esophageal catheters are used for temperature monitoring during an electrophysiology study with ablation and transesophageal echocardiography. The aim of the study was to model the spine and new esophageal electrodes for the transesophageal electrical pacing of the spinal cord, and to integrate them in the Offenburg heart rhythm model for the static and dynamic simulation of transesophageal neurostimulation. The modeling and simulation were both performed with the electromagnetic and thermal simulation software CST (Computer Simulation Technology, Darmstadt). Two new esophageal catheters were modelled as well as a thoracic spine based on the dimensions of a human skeleton. The simulation of directed transesophageal neurostimulation is performed using the esophageal balloon catheter with an electric pacing potential of 5 V and a trapezoidal signal. A potential of 4.33 V can be measured directly at the electrode, 3.71 V in the myocardium at a depth of 2 mm, 2.68 V in the thoracic vertebra at a depth of 10 mm, 2.1 V in the thoracic vertebra at a depth of 50 mm and 2.09 V in the spinal cord at a depth of 70 mm. The relation between the voltage delivered to the electrodes and the voltage applied to the spinal cord is linear. Virtual heart rhythm and catheter models as well as the simulation of electrical pacing fields and electrical sensing fields allow the static and dynamic simulation of directed transesophageal electrical pacing of the spinal cord. The 3D simulation of the electrical sensing and pacing fields may be used to optimize transesophageal neurostimulation.
Correlation-based spike sorting of multivariate data
Authors: Larionov Pavel , Juergens Tom , Schanze Thomas 
Published: September 2019

Abstract
Automated classification of waveforms is an important method of data processing used in various fields of science, such as neuroscience, biomedical engineering, etc. This work shows the possibility of sorting special waveforms i.e. spikes recorded with multichannel electrode arrays by using principles of correlation and data-driven reference. A new method to estimate the number of k-means clusters by using a Monte Carlo method is introduced. To demonstrate the performance of the algorithm, generated signals were used, which are created to mimic multichannel recording of the extra-cellular neuronal signals.
Learning by Researching – Students enhance perfusionist’s workplace with data glasses in internships
Authors: Pawelzik Leonard , Ibenthal Elisabeth , Backhaus Claus 
Published: September 2019

Abstract
A new internship for the module human factors engineering of the study course biomedical engineering was developed on the concept of learning by researching combining the transfer of knowledge with gathering new and publishable findings. Students pass the research cycle, investigating whether perfusionists strain can be reduced by utilizing data glasses. Corresponding to the concept of cooperative learning, students (n = 40) are divided into teams of five, giving each member a predefined expert role. Each expert is responsible either for physiological measurements, the perfusionists workspace, planning of usability tests, data glasses applications or team leading. Following the research cycle, milestones are set at which the teams present partial results to the entire group. Initially, students immerse in the field of research by reviewing literature. They prepare and present research hypotheses and select one for their investigation. Proximately, each team develops and introduces their research design. Teams organize themselves with planning test days and inviting subjects (n ≥ 10 each team). Finally, results are presented in group and collated by each team in a scientific paper. Every team reviews a scientific paper from another team and returns it before they are send in for grading. Evaluation shows higher workloads for students, but also relevant and interesting input. Two groups publish their papers in scientific journals.
An actuated larynx phantom for pre-clinical evaluation of droplet-based reflex-stimulating laryngoscopes
Authors: Friedemann Fast Jacob , He Jiazhen , Ortmaier Tobias , Jungheim Michael , Ptok Martin , Kahrs Lüder Alexander 
Published: September 2019

Abstract
The laryngeal adductor reflex (LAR) is an important protective function of the larynx to prevent aspiration and potentially fatal aspiration pneumonia by rapidly closing the glottis. Recently, a novel method for targeted stimulation and evaluation of the LAR has been proposed to enable non-invasive and reproducible LAR performance grading and to extend the understanding of this reflexive mechanism. The method relies on the laryngoscopically controlled application of accelerated water droplets in association with a high-speed camera system for LAR stimulation site and reflex onset latency identification. Prototype laryngoscopes destined for this method require validation prior to extensive clinical trials. Furthermore, demonstrations using a realistic phantom could increase patient compliance in future clinical settings. For these purposes, a model of the human larynx including vocal fold actuation for LAR simulation was developed in this work. The combination of image processing based on a custom algorithm and individual motorization of each vocal fold enables spatio-temporal droplet impact detection and controlled vocal fold adduction. To simulate different LAR pathologies, the current implementation allows to individually adjust the reflex onset latency of the ipsi- and contralateral vocal fold with respect to the automatically detected impact location of the droplet as well as the maximum adduction angle of each vocal fold. An experimental study of the temporal offset between desired and observed LAR onset latency due to image processing was performed for three average droplet masses based on highspeed recordings of the phantom. Median offsets of 100, 120 and 128 ms were found (n=16). This offset most likely has a multifactorial cause (image processing delay, inertia of the mechanical components, droplet motion). The observed offset increased with increasing droplet mass, as fluid oscillations after impact may have been detected as motion. In future work, alternative methods for droplet impact detection could be explored and the observed offset could be used for compensation of this undesirable delay.
Computer Assisted Auscultation System for Phonoangiography of the Carotid Artery
Authors: Sühn Thomas , Mahmoodian Naghmeh , Sreenivas Arathi , Maldonado Iván , Spiller Moritz , Boese Axel , Illanes Alfredo , Friebe Michael , Bloxton Michael 
Published: September 2019

Abstract
Cerebrovascular diseases such as stenosis, atherosclerosis or distention of the carotid artery are accountable for about 1 million death per year across Europe. Diagnostic tools like ultrasound imaging, angiography or magnetic resonance-based imaging require specific hardware and highly depend on the experience of the examining clinician. In contrast auscultation with a stethoscope can be used to screen for carotid bruits - audible vascular sounds associated with turbulent blood flow - a method called phonoangiography. A reliable auscultation setup is prerequisite to ensure high signal quality, adequate processing and the objective evaluation of this audible signal. We propose a computer assisted auscultation system for the acquisition of vascular sounds of the carotid. The system comprises of an auscultation device, a smartphone-based control application and cloud-based signal analysis and storage. It is designed to facilitate the objective assessment, screening and monitoring of long-term changes in the vessel condition based on auscultation of the carotid artery.
Reconstruction accuracy of an automated serial cross-sectional preparation technique for morphological human temporal bone imaging
Authors: Hügl Silke , Erfurt Peter , Lenarz Thomas , Majdani Omid , Rau Thomas S. 
Published: September 2019

Abstract
Detailed knowledge about the three-dimensional morphology of the human cochlea and its intra-cochlear bony and soft-tissue structures is essential for development of new cochlear implant electrode carriers. A manual cross-sectional preparation and imaging technique, hereinafter referred to as “microgrinding”, uses human temporal bone samples embedded in epoxy resin. This process was automated to shorten the time needed for preparation and to increase reproducibility. In this study, reconstruction accuracy of the automated microgrinding technique was determined. Four assemblies of LEGO® bricks were used as artificial samples to analyze the resulting reconstruction accuracy of the whole procedure including embedding, preparation and image registration. The outer surfaces of the samples were measured using a portable coordinate measuring machine by manually choosing points on each surface. After embedding the samples in epoxy resin, following the protocol for human temporal bone samples, preparation using the automated microgrinding was performed with a slice thickness of 50μm. Pixel-spacing within an image was 11.5μm/px. The samples were identified within the dataset using threshold segmentation. Subsequently, points were manually chosen on each surface of the segmented samples. Planes, angles between planes and distances between corners were calculated for the physical and the digital samples. Deviation of the digitally derived measures compared to the physically derived ones describe the reconstruction accuracy of the automated microgrinding process. Parallel planes had a deviation of 0.5° ± 0.5° (range: 0 - 2.9°). Orthogonal planes, whose line of intersection is parallel to the direction of milled abrasion, had a deviation of 0.8 ° ± 0.5 ° (range: 0 - 2.1°), whereas such orthogonal planes whose line of intersection is parallel to the documented sample surface had a deviation of 0.4° ± 0.3 ° (range: 0 - 1.7 °). Distances between corners had an absolute deviation of 0.1 mm ± 0.1mm (range: 0 - 0.6mm), which corresponds to a relative deviation of 1% ± 1% (range: 0 - 6.5%). This study shows a highly accurate sample preparation using an automated microgrinding technique as an essential prerequisite for three-dimensional morphological imaging.
Preliminary Study on 3D printing of PEGDA Hydrogels for Frontal Sinus Implants using Digital Light Processing (DLP)
Authors: Mau Robert , Nazir Jamal , John Samuel , Seitz Hermann 
Published: September 2019

Abstract
Digital Light Processing (DLP) enables high precision 3D-printing of photopolymers and holds promising potential for patient-specific implant solutions. On the material side, Poly(ethylene glycol) diacrylate (PEGDA) has emerged as an interesting material for use in biomedical applications. For adequate photopolymerization, a photoinitiator and a light absorber are necessary, using welldefined concentrations. This study shows preliminary results of DLP 3D-printing of different PEGDA hydrogel compositions with varying water content (90; 70; 50; 30; 10; 0 % w/w) as well as varying concentrations of a photoinitiator and a light absorber. Printing performance and accuracy are investigated by printing rectangular test samples as well as an anatomically customised tubular frontal sinus implant prototype. For basic mechanical characterisation, the hardness of the printed hydrogels is investigated using a Shore A durometer. The results show a decrease in printing accuracy and hardness with an increasing water content of the composition. There is a need to use a light absorber to reach high printing accuracy. This leads to a need for increasing photoinitiator concentration and prolonged light exposure to achieve proper printing performance.
Superparamagnetic Iron Oxide Nanoparticles
Authors: Lüdtke-Buzug Kerstin , Penxová Zuzana 
Published: September 2019

Abstract
The direct detection of the spatial distribution of Superparamagnetic Iron Oxide Nanoparticles (SPIONs) as a tracer for Magnetic Particle Imaging (MPI) enables threedimensional functional images with high spatial and temporal resolution. The commercially available tracers have not been developed primarily for MPI. Therefore, they do not sufficiently contribute to the desired image quality. Hence, optimizing the SPIONs during the production process is of interest. A peculiarity of the here presented synthesis method - the alkaline coprecipitation - is that this process takes place under ultrasonic control. The use of ultrasound creates extraordinary reaction conditions through sonochemical phenomena, such as formation, growth and implosive collapse of cavitation bubbles within a liquid. In addition, the ultrasonic waves and the oscillation of the medium improve the mixing process and thus ensure the homogenization during the synthesis. The objective of this study is the variation of ultrasonic frequencies and the type of used dextran as coating material, to provide SPIONs with better performance for MPI and more suitable properties for in vivo application. The focus of the optimization is to increase the magnetite core size while simultaneously reducing the hydrodynamic size. The experiments have shown that both, the ultrasound frequency and the molecular weight of used dextran, influence the properties of the SPIONs.
Covalent coupling of polymers as drug coatings on silicone surfaces for future applications
Authors: Wulf Katharina , Teske Michael , Arbeiter Daniela , Eickner Thomas , Grabow Niels , Paasche Gerrit , Lenarz Thomas 
Published: September 2019

Abstract
Insertion of a cochlear implant (CI) into the scala tympani evokes electrode insertion trauma that can result in mechanical damage of the lateral and medial wall and causes ingrowth of fibrous tissue on the implant surface. In consequence, it is of great clinical interest to modify the silicone surface of CI electrodes in order to inhibit and minimize the overgrowth by connective tissue. In this case, the covalent coupling of bifunctional polymers on common CI silicone surfaces is a versatile method to influence the implant cell interaction, but is still a challenge due to the chemically unreactive properties of silicone. We present a sophisticated method to apply a biodegradable polymer coating, such as polylactide or polyhydroxybutyrate, on silicone surfaces to generate a drug delivery system using a covalently bound intermediate layer. The adhesive coatings were applied via spincoating processes with different adherence to the intermediate layer. Changes in surface morphology were investigated by comparison of pure silicone and coated silicone. Specific polymer bands of the infrared spectra were detected by IR spectroscopy. Results indicate a complete coating with polylactide or polyhydroxybutyrate. The presented method is a versatile tool for the coating of silicone CI electrodes with degradable polymer layers.
Formation and characterisation of hydrogel diffusion channels for directed drug delivery
Authors: Eickner Thomas , Kohse Stefanie , Illner Sabine , Oschatz Stefan , Teske Michael , Rekowska Natalia , Senz Volkmar , Schmitz Klaus-Peter , Grabow Niels 
Published: September 2019

Abstract
Drug Delivery Systems (DDS) are frequently operating in a surrounding liquid environment, such as blood in the case of drug-eluting stents or perilymph in the case of cochlear implants. However, there is also a demand for systems with sustained drug release in predominantly dry environments, mostly consisting of ambient air. Examples are the treatment of diseases located in the middle ear or the paranasal sinuses. On the one hand, due to the lack of transportation media, the functionality of a polymer/drug combination for delayed release would be limited in such environments. On the other hand, these environments are generally equipped with mucus membranes. Hence, a somewhat humid surrounding is ensured. In this study, a concept of a hydrogel equipped DDS for drug delivery through the round window membrane is presented, addressing two objectives. First objective is to ensure the drug transport by serving as a diffusion channel. For instance the route to the drug target destination, the round window membrane, can be provided by a hydrogel. The second objective is to ensure the adhesion to the membrane. Two promising approaches are presented in this study: The photo induced immobilisation of PEGDA700, as well as the immobilisation of chitosan on poly(l-lactid) (PLLA). For both approaches PLLA specimen had to be modified with oxygen plasma followed by activation for crosslinking with subsequent immobilisation of the hydrogel. With these methods a layer thickness of at least 5 μm was achieved. All steps were characterized with contact angle measurements. After the immobilization of the hydrogel, the swelling factor, as well as the layer thickness was examined.
Post-processed chemical treatment of polyimide electrospun nonwovens with ethylenediamine for biomedical applications
Authors: Oschatz Stefan , Arbeiter Daniela , Eickner Thomas , Grabow Niels , Illner Sabine 
Published: September 2019

Abstract
The generation of electrospun nonwovens from polyimide (PI) is challenging as the fibers are prone to distinct delamination. In consequence, the resulting nonwoven material has particularly low structural integrity and loose fibre interlocking, demanding for a follow-up treatment, such as high temperature thermal treatment. In this work, a facile method for a post-processed treatment of PI nonwoven is presented in order to obtain a mechanically stable material while maintaining the characteristics of the electrospun nonwoven. The procedure was performed using a solution of EDA in methanol at 37 °C and ambient pressure to achieve a modified fiber interaction. Overall, the developed protocol opens new possibilities in the processing of PI into delamination-free nonwovens. Potential adverse effects of a high temperature thermal treatment are being avoided, and new applications in the field of medical devices may become accessible.
Investigation of mechanical and magnetophoretic focusing for magnetic flow cytometry
Authors: Liu Jan , Reisbeck Mathias , Hayden Oliver 
Published: September 2019

Abstract
As an alternative to optical flow cytometry, magnetic flow cytometry has emerged in recent years for single cell analysis with sheath-less flow conditions. Instead of measuring scattered light, magnetic fields of magneticallylabeled cells are recorded and analyzed. To determine microfluidic opportunities to manipulate cell trajectories for in-situ cell focusing we use mechanical guiding structures and magnetophoretic forces. A 3D-microfluidic particle simulation has been implemented that revealed parameters ensuring the crucial balance between hydrodynamic drag and magnetophoretic forces. Experimental measurements verified the 3D particle tracking simulation.
Removal of ECG artifacts from EMG signals with different artifact magnitudes by template subtraction
Authors: Kahl Lorenz , Hofmann Ulrich G. 
Published: September 2019

AbstractThis work investigates the performance of eventsynchronous noise cancelling algorithms to separate ECG artifacts from thoracic EMG recordings. In focus are the precise detection of heart beats, the exact time alignment of the QRS segments and the construction of a template QRS signal. Among the utilized methods is a modified structural intensity (SI) approach based on the observation of extrema in low pass filtered versions of the second derivative as a detector. An adoption of this approach is also used to obtain the exact time alignment of QRS segments. Artificial test signals are constructed based on addition of ECG and sEMG with different magnitudes. We show that approaches based on the observation of extrema in different scales yield superior results.
Evaluation of inertial Sensors and optical measurement methods for head and shoulder angle motion analysis
Authors: Mayr Oliver , Tadayon Puian , Felderhoff Thomas 
Published: September 2019

Abstract
This paper describes the advantages and disadvantages of inertial sensors and stationary camera-based measuring methods for the application of detecting head and shoulder angles. For this purpose three inertial sensor modules from Shimmer Sensing and a Kinect 2 camera system are used. The recorded data of both systems are converted into a comparable form. Based on an evaluation of the recorded measurement data, the inertial sensor and the camera-based methods are compared with regard to their suitability for detecting movements in the head and shoulder area.