bluuebunny/crossref_metadata_2025 huggingface dataset:
Tinnitus suppression using electrical stimulation
Authors: Olze Heidi , Szczepek Agnieszka J. , Reich Uta , Gräbel Stefan , Uecker Florian
Published: September 2018

Tinnitus is a phantom sound perceived only by the affected person. Although the causes for tinnitus may be very diverse (e.g. hearing loss, cardiovascular diseases, diabetes, Meniere’s disease, otosclerosis), they all lead to pathological activation of the auditory pathway. Cochlear implants are electronic inner ear prostheses used to restore the hearing abilities of hard of hearing people. It has been noticed that the cochlear implants not only enable hearing but also reduce tinnitus that usually accompanies deafness and hearing loss. One of the likely mechanisms behind the latter phenomena is thought to be the unknown properties of electrical stimulus. This project was designed as a proof of concept for a device, which would be sending the tinnitus-suppressing electrical signal. To achieve this, the project was split into a preclinical part using experimental animals (guinea pigs) and a clinical trial part with tinnitus patients. In the preclinical part, together with Inomed Medizintechnik GmbH, we are testing the physical design and biocompatibility of anti-tinnitus implant. In the clinical part of the project, we use an electrical stimulation in the ear canal, through the eardrum (tinnitus patients), or via cochlear implant in a sample of cochlear implant patients (pre- and post-implantation). We ask the patients to mark the loudness of their tinnitus on a visual scale from 1 to 10 before, during and after routine electrical stimulation and quality of the tinnitus The results obtained during our preclinical and clinical testing as well as future plans will be presented and discussed.
Comparison of Different Training Algorithms for the Leg Extension Training with an Industrial Robot
Authors: Ketelhut Maike , Göll Fabian , Braunstein Björn , Albracht Kirsten , Abel Dirk
Published: September 2018

In the past, different training scenarios have been developed and implemented on robotic research platforms, but no systematic analysis and comparison have been done so far. This paper deals with the comparison of an isokinematic (motion with constant velocity) and an isotonic (motion against constant weight) training algorithm. Both algorithms are designed for a robotic research platform consisting of a 3D force plate and a high payload industrial robot, which allows leg extension training with arbitrary six-dimensional motion trajectories. In the isokinematic as well as the isotonic training algorithm, individual paths are defined i n C artesian s pace by sufficient s upport p oses. I n t he i sotonic t raining s cenario, the trajectory is adapted to the measured force as the robot should only move along the trajectory as long as the force applied by the user exceeds a minimum threshold. In the isotonic training scenario however, the robot’s acceleration is a function of the force applied by the user. To validate these findings, a simulative experiment with a simple linear trajectory is performed. For this purpose, the same force path is applied in both training scenarios. The results illustrate that the algorithms differ in the force dependent trajectory adaption.
Bi - Domain Intraoperative Registration of Vessels
Authors: Naber Ady , Nahm Werner
Published: September 2018

The segmentation and registration of structures are gaining importance due to the increasing demand of automated image enhancement and understanding. Especially in medicine and life science, assistance systems could have a large impact on diagnosis, treatment and quality control. Dye driven procedures, such as fluorescence imaging with Indocyanine green (ICG), are nowadays indispensable because they enhance contrast, reveal structures and deliver the operator with important information. The contact free ICG angiography is providing the surgeon spatial and temporal information on blood flow within a vessel. The processing of those information is done manually or semi automated but is very helpful for the surgeon. Extending the degree of automatism, the amount of information processed and even augment or transfer it into another domain could deliver the operator useful support and improve surgical work flow. Using, analyzing and transferring those information from ICG-IR domain into the RGB domain is the focus of this project. We are introducing a vessel registration method in the RGB domain driven by the spatial fluorescence behavior of the vessel in the ICG-IR domain. The method includes Superpixel based segmentation of the vessel in the ICG-IR domain, the spatial gradient based transfer and registration in the RGB domain and the continuous segmentation of the vessel in a RGB video. This paper show a proof of concept of the method. The results show an successful inter domain information transfer and registration of the vessel. Further tracking of the vessel over all frames is possible. Nevertheless limitations are revealed and discussed.
Mock loop for bubble generation in a centrifugal blood pump for fault simulation
Authors: Stollenwerk André , Buglowski Mateusz , Kühn Jan
Published: September 2018

In extracorporeal blood circulation intensive care treatments, the occurrence of gas within the circulation is one known major hazard. This gas volume can cause severe harm to the patient like infarctions. Consequently, within risk assessment for these treatments gas bubbles are usually addressed by either constructive or signal based approaches. All signal-based approaches do have in common that they need a sufficient amount of data to be parameterized. These data can only be acquired in animal trials or laboratory experiments, as they could result in harm to patients. Hence, we designed a mock loop, which is automatically able to create annotated data of gas bubbles injected into an extracorporeal circulation. We were able to run this setup with a periodicity of 15 seconds, which results in 240 annotated measurements per hour. For the evaluation, we created 1095 bubbles of varying sizes (0.3 to 0.5 ml). The elaborated setup enables us to produce a great amount of annotated data, which is shown to be comparable to manually generated data in a convenient and fully automated manner.
Low-cost physiological simulation system for endovascular treatment of aneurysms
Authors: Pfau Oskar , Kemmling André , Rostalski Philipp
Published: September 2018

Minimally invasive procedures are more and more becoming the standard treatment for many surgical procedures such as the treatment of cerebral aneurysms. In an endovascular procedure the aneurysm is filled with flexible platinum coils leading to embolization and blocking the blood flow in the aneurysm. This established treatment needs high skills and experience on the surgeon. In order to practice and plan a specific procedure or test a new device, a realistic simulation environment is needed. Modern 3D printing technology allows the fabrication of patient specific models incorporating the exact geometry of the pathological anatomy. This article describes the development of a low-cost physiological simulation system for the training of the endovascular treatment of aneurysms. In order to practice the procedure in a realistic scenario, a 3D printed model of the aneurysm is embedded in a fluidic simulation s ystem. In addition to the patient-specific anatomy of the aneurysm a pulsatile water flow is generated, which emulates the influence of blood flow on the behaviour of catheters and coils during deployment. The system consist of a controllable pump circuit generating a pulsatile flow which can be regulated automatically and additionally controlled externally by the user. For a suitable representation, a display which graphically represents the sensor data and settings is employed. The components were compactly integrated in a small case allowing for easy deployment in training workshops. The simulation setup was successfully tested in prospective patient specific treatment planning and workshops for students.
A drive mechanism for a blood pump integrated in an oxygenator
Authors: Aghababaei Amin , Kashefi Ali , Hexamer Martin
Published: September 2018

The achievement of a low priming volume of the components in an extracorporeal perfusion system for neonatal and pediatric patients is an open research question. This paper presents a concept of a pump-oxygenator in which an oxygenator and a pulsatile blood pump are combined in one housing. For operation of the pump-oxygenator, a special actuating system for the pump process was designed. It consists of a piston pump which is directly coupled with a voice coil actuator (VCA). A servo positioning system was developed to assure the piston motion according to predefined reference trajectories. First experimental results indicate the feasibility of driving this blood pump with a VCA. In an in-vitro study, the pump produced mean flow rates of 60-900 mL/min with stroke frequencies in the range of 60-240 beats per minute.
Proximally placed signal acquisition sensoric for robotic tissue tool interactions
Authors: Chen Chien-Hsi , Sühn Thomas , Illanes Alfredo , Maldonado Ivan , Ahmad Hesham , Wex Cora , Croner Roland , Boese Axel , Friebe Michael
Published: September 2018

Robotic surgeries are still limited with respect to the surgeon’s natural senses. The tactile sense is exceptional important in conventional clinical procedures. To identify critical structures inside the tissue, palpation is a commonly used technique in conventional open surgeries. The underlying organ or pathological structures conditions (healthy, abnormally hard or soft) can for example be localized and assessed through this process. Palpation needs a tactile sense; however, that is commonly not available or limited in robotic surgeries. The palpation need was already addressed by several research groups that integrated complex sensor-feedback-systems into prototype surgical instruments for robotic systems. We propose a new technique to acquire data of the tissue tool interaction of the surgical instruments. The structure borne transmission path is used to measure acoustic emission (AE) at the outpatient (proximal) end of the instruments with the help of different sensors attached to the surface of the surgical tool. Initial tests were performed using a microphone in combination with a stethoscope. This setup showed promising results and a more integrated prototype was subsequently designed. A piezoelectric charge accelerometer was used as vibration sensor and compared to a MEMS microphone. A signal acquisition system was developed to acquire signals from both sensors in parallel. The sensors were then attached onto the shaft of a daVinci Prograsp Forceps instrument. According to the surgery observation, a series of simulated experiments was conducted. The tip of the grasper was swiped manually over a human subject’s dorsal and palmar hand side, lateral side of neck and over the carotid artery. Additionally, contact with soft tissue and other instruments were evaluated since these are events of interest during surgery. Advanced signal processing techniques allowed the identification and characterization of significant events such as palpation dynamics, contact and pulsation. Signals acquired by the MEMS microphone showed the most promising results. This approach will now be used to build a prototype for further evaluation in a clinical setup. The paper presents the first results that show that this novel technique can provide valuable information about the tool-tissue interaction in robotic surgery that typically can only be obtained through advanced distal sensor systems or actual human touch.
Deep transfer learning for aortic root dilation identification in 3D ultrasound images
Authors: Hagenah Jannis , Heinrich Mattias , Ernst Floris
Published: September 2018

Pre-operative planning of valve-sparing aortic root reconstruction relies on the automatic discrimination of healthy and pathologically dilated aortic roots. The basis of this classification are features extracted from 3D ultrasound images. In previously published approaches, handcrafted features showed a limited classification accuracy. However, feature learning is insufficient due to the small data sets available for this specific problem. In this work, we propose transfer learning to use deep learning on these small data sets. For this purpose, we used the convolutional layers of the pretrained deep neural network VGG16 as a feature extractor. To simplify the problem, we only took two prominent horizontal slices throgh the aortic root, the coaptation plane and the commissure plane, into account by stitching the features of both images together and training a Random Forest classifier on the resulting feature vectors. We evaluated this method on a data set of 48 images (24 healthy, 24 dilated) using 10-fold cross validation. Using the deep learned features we could reach a classification accuracy of 84 %, which clearly outperformed the handcrafted features (71 % accuracy). Even though the VGG16 network was trained on RGB photos and for different classification tasks, the learned features are still relevant for ultrasound image analysis of aortic root pathology identification. Hence, transfer learning makes deep learning possible even on very small ultrasound data sets.
Optimization of stent designs regarding the thrombosis risk using computational fluid dynamics
Authors: Wüstenhagen Carolin , Pfensig Sylvia , Siewert Stefan , Kaule Sebastian , Grabow Niels , Schmitz Klaus-Peter , Stiehm Michael
Published: September 2018

In-stent thrombosis is a major complication of stent implantations. Unlike pathological occurrences as in-stent restenosis for instance, thrombosis represents an acute event associated with high mortality rates. Experiments show that low wall shear stress promotes undirected endothelial cell coverage of the vessel wall and therefore increases the risk of thrombus formation. Stent design represents a crucial factor influencing the surface areas of low wall shear stress and thus the incidence of acute in-stent thrombosis. In this study, we present an optimization method for stent designs with minimized thrombosis risk. A generic stent design was developed, based on five different stent design parameters. Optimization was conducted based on computational fluid dynamics analysis and the gradient-free Nelder-Mead approach. For each optimization step, a numerical fluid simulation was performed in a vessel with a reference vessel diameter of 2.70 mm with stent-overexpansion ratio of 1.0:1.1. For each numerical fluid simulation a physiological Reynolds number of 250, resulting in a mean velocity of 0.331 m/s at the inlet and a laminar flow as well as stiff vessel walls were assumed. The impact of different stent designs was analyzed based on the wall shear stress distribution. As a basis for the comparison of different stent designs, a dimensionless thrombosis risk number was calculated from the area of low wall shear stress and the overall stented area. The first two optimization steps already provide a decrease of thrombosis risk of approximately 83%. In conclusion, computational fluid dynamic analyses and optimization methods usind the Nelder-Mead approach represent a useful tool for the development of hemodynamically optimized stent designs with minimized thrombosis risk.
Heart phantom with electrical properties of heart muscle tissue
Authors: Korn Leonie , Lyra Simon , Rüschen Daniel , Pugovkin Alexander , Telyshev Dmitry , Leonhardt Steffen , Walter Marian
Published: September 2018

The weakened heart is supported by a left ventricular assist device (LVAD) to supply the heart muscle with oxygenated blood. In case the heart muscle recovers during LVAD therapy, the patient has to be weaned from the device. To date, there is no adequate method to detect heart muscle recovery in LVAD therapy. In order to establish a novel method based on the measurement of electric conductivity, this study presents a silicone model of a ventricle mock-up to simulate the electrical properties of cardiac muscle tissue. Previously, it has been shown that the electrical properties of myocardial tissue change during ischemia, so that these changes are a possible estimate for measuring the condition of myocardial tissue. To this purpose, this study presents a casting process for a ventricle model and describes the materials used to imitate the electrical properties of the heart muscle to obtain conductive material. Initial results showed that the higher the carbon concentration in the silicone, the higher the conductivity of the silicone samples. The measurements were performed at different frequencies and the samples were analyzed for homogenization.
Effects of local activation times on the tension development of human cardiomyocytes in a computational model
Authors: Müller Armin , Kovacheva Ekaterina , Schuler Steffen , Dössel Olaf , Baron Lukas
Published: September 2018

The human heart is an organ of high complexity and hence, very challenging to simulate. To calculate the force developed by the human heart and therefore the tension of the muscle fibers, accurate models are necessary. The force generated by the cardiac muscle has physiologically imposed limits and depends on various characteristics such as the length, strain and the contraction velocity of the cardiomyocytes. Another characteristic is the activation time of each cardiomyocyte, which is a wave and not a static value for all cardiomyocytes. To simulate a physiologically correct excitation, the functionality of the cardiac simulation framework CardioMechanics was extended to incorporate inhomogeneous activation times. The functionality was then used to evaluate the effects of local activation times with two different tension models. The active stress generated by the cardiomyocytes was calculated by (i) an explicit function and (ii) an ode-based model. The results of the simulations showed that the maximum pressure in the left ventricle dropped by 2.3% for the DoubleHill model and by 5.3% for the Lumens model. In the right ventricle the simulations showed similar results. The maximum pressure in both the left and the right atrium increased using both models. Given that the simulation of the inhomogeneously activated cardiomyocytes increases the simulation time when used with the more precise Lumens model, the small drop in maximum pressure seems to be negligible in favor of a simpler simulation model.
Context-aware medical technologies - relief or burden for clinical users?
Authors: Neumuth Thomas , Rockstroh Max , Franke Stefan
Published: September 2018

The open, cross-vendor interoperability of medical devices is an enabling technology for the implementation of context-aware biomedical systems in daily clinical routine. The surgical working environment is both a valuable field of application and a particular challenge. A design of context-aware medical technologies that shows intelligent behaviour and ensures safe operation is demanding; thus implementations are yet limited to prototypes and specific surgical use cases. Many open research questions need to be addressed to empower context-aware medical systems to be a relief and not a burden for the clinical user.
Novel 3D printing concept for the fabrication of time-controlled drug delivery systems
Authors: Konasch Jan , Riess Alexander , Teske Michael , Rekowska Natalia , Rekowska Natalia , Mau Robert , Eickner Thomas , Grabow Niels , Seitz Hermann
Published: September 2018

Three-dimensional (3D) printing has become a popular technique in many areas. One emerging field is the use of 3D printing for the development of 3D drug delivery systems (DDS) and drug-loaded medical devices. This article describes a novel concept for the fabrication of timecontrolled drug delivery systems based on stereolithography combined with inkjet printing. An inkjet printhead and an UV-LED light source have been integrated into an existing stereolithography system. Inkjet printing is used to selectively incorporate active pharmaceutical ingredients (API) during a stereolithographic 3D printing process. In an initial experimental study, poly (ethylene glycol) diacrylate (PEGDA) was used as polymer whereas 2-Hydroxy-4´-(2- hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959) and Lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) were used as photoinitiators. Basic structures could be manufactured successfully by the new hybrid 3D printing system.
Assessment of Natural User Interactions for Robot-Assisted Interventions
Authors: Berger Johann , Unger Michael , Landgraf Lisa , Bieck Richard , Neumuth Thomas , Melzer Andreas
Published: September 2018

Robotic assistance in clinical interventions provides high precision and performance. However, the acceptance of such systems is still very low. The idea of collaborative robotics promises practical solutions for this problem. To further promote these ideas in the medical domain, novel concepts for user interactions are needed. This work presents a preliminary study on the recognition accuracy of touch gesture interaction with a KUKA LBR iiwa robotic arm. A recognition application utilising a set of 4 different touch gestures was implemented and evaluated by eight participants. The overall recognition accuracy of the system is 89.8%.
Optical strain measurement for the modeling of surgical meshes and their porosity
Authors: Horbach Andreas J. , Staat Manfred
Published: September 2018

The porosity of surgical meshes makes them flexible for large elastic deformation and establishes the healing conditions of good tissue in growth. The biomechanic modeling of orthotropic and compressible materials requires new materials models and simulstaneoaus fit of deformation in the load direction as well as trannsversely to to load. This nonlinear modeling can be achieved by an optical deformation measurement. At the same time the full field deformation measurement allows the dermination of the change of porosity with deformation. Also the socalled effective porosity, which has been defined to asses the tisssue interatcion with the mesh implants, can be determined from the global deformation of the surgical meshes.
Biomechanics of a novel extra-articular implant for younger patients with knee osteoarthritis
Authors: Saeidi Mehdi , Ramezani Maziar , Kelly Piaras , Hussin Mohd Sabri , Neitzert Thomas
Published: September 2018

This research aimed to study the efficacy of a novel implant for osteoarthritic knees. This implant is designed to eliminate excessive loads through the knee and to provide suitable conditions for possible tibiofemoral cartilage regeneration. The implant was designed for the medial side of the knee joint. Finite Element Analysis (FEA) was performed for an extended knee position of the knee joint. Contact pressure distributions on the medial and lateral compartments were investigated as well as stress distributions throughout the implant’s plates. Results with and without the implant were compared, and it was seen that the contact pressures on the surface of the distal femur were reduced by more than 90% after the introduction of the implant.
Polymer drug release system for biofilm inhibition in medical application
Authors: Wulf Katharina , Arbeiter Daniela , Eickner Thomas , Riedel Katharina , Schmitz Klaus-Peter , Grabow Niels , Kohse Stefanie
Published: September 2018

Bacterial biofilm formation on surfaces is still a critical challenge regarding the application of implants. Generally, in order to avoid this, an additional systemic administration of antibiotics is given, which can lead to side effects, such as the reduction of the intestinal flora. Continuous treatment may lead to antibiotics resistance. Within this study we investigated the local drug delivery of N-acetyl-L-cysteine (NAC) from a Poly-L-lactide (PLLA) coating, an ished biodegradable polymer and a polyetherurethane (PEU) coating, a promising representative non-degradable polymer for cardiovascular applications as alternative to the administration of antibiotics. The incorporation of NAC influenced the surface properties of PEU in contrast to that of PLLA. The in vitro NAC release is almost completed after 24 h for PEU. For PLLA only small amounts of incorporated NAC, depending on the NAC loading, is released after a short time. Both systems are rather useful as local NAC delivery system directly after implantation.
Polyelectrolyte Coatings for Surface Modification of Medical Implants
Authors: Krastev Rumen , Rudt Alexander , Xiong Xin , Hartmann Hanna
Published: September 2018

Polyelectrolyte multi-layer (PEM) coatings are prepared by alternative deposition of single polyelectrolyte monolayers on charged surfaces using the Layer-by-Layer (LbL) dip coating procedure. These are nanometre scaled coatings which allow fulfilling of different technical or biological requirements. The build-up process is based on selfassembly and self-organization of polycations and polyanions on different substrates including complex geometrical structures and even closed volumes, forming homogeneous layer without defects. Depending on the proper selection of the applied polyelectrolytes, coatings with different stabilities can be prepared. Some of the coatings are stable and cannot be removed from the surface. Others are degradable and can be used as systems for controlled local drug delivery. Here we summarise the results of our experience in preparation of PEM coatings with different functionalities. PEM coatings can be used as controllable delivery system for siRNA polyplexes. They can be used to control the adhesion of different cell types on the surfaces and support e.g. the endothelialisation process on cardio-vascular medical devices as e.g. stents or reduce the immunological response of the tissue after implantation. We summarise results from physical characterisation of the coatings (e.g. film thickness, roughness, electrical charge and hydrophilicity) combined with in-vitro biological studies on adhesion of HUVEC cells.
Accelerated in vitro-calcification of potential urethane based heart valve replacement materials
Authors: Oschatz Stefan , Kohse Stefanie , Senz Volkmar , Eickner Thomas , Schmitz Klaus-Peter , Grabow Niels
Published: September 2018

Polycarbonate urethane and polyether urethane nonwovens as promising representatives of novel polymer heart valve materials were analysed regarding the susceptibility to calcification in comparison to porcine pericardium and polyamide 6. The applied method represents an accelerated calcification out of a metastable solution in short time with significant precipitates on the reference material. As our results show, urethane based nonwoven structures exhibit considerably lower susceptibility to calcification compared to pericardium as widely established material for leaflet design.
Effects of local activation times on the tension development of human cardiomyocytes in a computational model
Authors: Müller Armin , Kovacheva Ekaterina , Schuler Steffen , Dössel Olaf , Baron Lukas
Published: September 2018

The human heart is an organ of high complexity and hence, very challenging to simulate. To calculate the force developed by the human heart and therefore the tension of the muscle fibers, accurate models are necessary. The force generated by the cardiac muscle has physiologically imposed limits and depends on various characteristics such as the length, strain and the contraction velocity of the cardiomyocytes. Another characteristic is the activation time of each cardiomyocyte, which is a wave and not a static value for all cardiomyocytes. To simulate a physiologically correct excitation, the functionality of the cardiac simulation framework CardioMechanics was extended to incorporate inhomogeneous activation times. The functionality was then used to evaluate the effects of local activation times with two different tension models. The active stress generated by the cardiomyocytes was calculated by (i) an explicit function and (ii) an ode-based model. The results of the simulations showed that the maximum pressure in the left ventricle dropped by 2.3% for the DoubleHill model and by 5.3% for the Lumens model. In the right ventricle the simulations showed similar results. The maximum pressure in both the left and the right atrium increased using both models. Given that the simulation of the inhomogeneously activated cardiomyocytes increases the simulation time when used with the more precise Lumens model, the small drop in maximum pressure seems to be negligible in favor of a simpler simulation model
Fluid-structure interaction of heart valve dynamics in comparison to finite-element analysis
Authors: Borowski Finja , Sämann Michael , Pfensig Sylvia , Wüstenhagen Carolin , Ott Robert , Kaule Sebastian , Siewert Stefan , Grabow Niels , Schmitz Klaus-Peter , Stiehm Michael
Published: September 2018

An established therapy for aortic valve stenosis and insufficiency is the transcatheter aortic valve replacement. By means of numerical simulation the valve dynamics can be investigated to improve the valve prostheses performance. This study examines the influence of the hemodynamic properties on the valve dynamics utilizing fluidstructure interaction (FSI) compared with results of finiteelement analysis (FEA). FEA and FSI were conducted using a previously published aortic valve model combined with a new developed model of the aortic root. Boundary conditions for a physiological pressurization were based on measurements of ventricular and aortic pressure from in vitro hydrodynamic studies of a commercially available heart valve prosthesis using a pulse duplicator system. A linear elastic behavior was assumed for leaflet material properties and blood was specified as a homogeneous, Newtonian incompressible fluid. The type of fluid domain discretization can be described with an arbitrary Lagrangian-Eulerian formulation. Comparison of significant points of time and the leaflet opening area were used to investigate the valve opening behavior of both analyses. Numerical results show that total valve opening modelled by FEA is faster compared to FSI by a factor of 5. In conclusion the inertia of the fluid, which surrounds the valve leaflets, has an important influence on leaflet deformation. Therefore, fluid dynamics should not be neglected in numerical analysis of heart valve prostheses.
In vivo myocardial tissue characterization of all four chambers using high-resolution quantitative MRI
Authors: Becker Kirsten M. , Schulz-Menger Jeanette , Schaeffter Tobias , Kolbitsch Christoph
Published: September 2018

Quantitative native T1 Mapping of the myocardium without the application of contrast agents can be used to detect fibrosis in the left ventricle. Spatial resolution of standard native T1 mapping is limited by cardiac motion and hence is not sufficient to resolve small myocardial structures, such as the right ventricle and the atria. Here, we present a novel MR approach which provides cardiac motion information and native T1 maps from the same data. Motion information is utilized to optimize data selection for T1 mapping and a model-based iterative reconstruction scheme ensures high-resolution T1 maps for the entire heart. Feasibility of the approach was demonstrated in three healthy volunteers. In the T1 maps, the myocardium of all four chambers can be visualized and T1 values of the left atrium and right chambers were comparable to left ventricular T1 values.
Monte-Carlo Simulation of Light Tissue Interaction in Medical Hyperspectral Imaging Applications
Authors: Herrmann Bert. H. , Hornberger Christoph
Published: September 2018

In Hyperspectral imaging (HSI) applications in medicine a uniform illumination is used and the illuminated surface is recorded with a camera with spectral resolution. Unlike in tissue reflectance spectroscopy with fixed light source - detector distances, in HSI the contribution of the influence of different tissue layers to the absorption signal is poorly understood. In this work a Monte-Carlo simulation is implemented which simulates the specific HSI illumination and detector geometry. A four-layer tissue model with variable blood volume fraction and oxygen saturation is used. With 5 % blood volume fraction and 75 % oxygen saturation, SaO2, of surrounding tissue, saturation changes in 1 mm and 2 mm deep layers lead to a change in remission of up to 3 % and up to 1 % respectively. Changes in deeper layers are hardly detectable. Further simulations will be focused on different tissue models as the depth resolution is expected to vary with tissue parameters like blood volume fraction.
A demonstrator for a flexible active microelectrode array with high electrode number
Authors: Heid Andreas , Bleck Lena , Metzen Rene von , Bucher Volker
Published: September 2018

The integration of dies is a possibility to reduce the number of conducting tracks within electrical active implants. For passive microelectrode arrays the number of conducting tracks limits the number of electrodes. By embedding an array of small dies (250 μm edge length) employed to amplify and multiplex the signals of 25 electrodes each into a flexible foil we create a flexible active microelectrode array with more than 1000 electrodes. A fabrication process was developed containing a transfer process for the dies as well as an embedding procedure. Here a non-functional Dummy-System is presented as a demonstrator proving the feasibility of the proposed microelectrode array.
Development of a Stair Climbing Mechanism for a Novel Mechatronic Transport Aid: Preliminary Results
Authors: Schleer Philipp , Kinzius Max , Verjans Mark , Kähler Ferdinand , Radermacher Klaus
Published: September 2018

Emergency medical service (EMS) is an essential part of health care with the main task to transport and monitor patients. However, this duty often becomes a challenge due to obstacles - especially stairs - on the way. Associated lifting and carrying of patients regularly imposes high loads in unergonomic working postures on paramedics, leading to the highest work induced injury rates among all industries also due to a deficient usability of existing transport aids. Therefore our goal is the development of a stair climbing mechanism for a novel mechatronic transport aid characterized by high mobility and a small footprint, whereby particular attention has to be paid to application specific requirements. This paper presents the general approach accompanied by results of a functional model from an initial concept study. Acceleration and jerk measurements showed promising results, while most predefined velocities on the model test parkour rise could be reached.
A New Method of Measuring Stimulation Threshold
Authors: Irnich Werner
Published: September 2018

Louis Lapicque introduced the hyperbolic stimulation law with the key parameters “rheobase” and “chronaxie” that were obtained with rectangular current pulses. With rectangular pulses rheobase cannot be measured. It was found recently that hyperbolic stimulation rules are also valid for non-rectangular pulses and that their rheobase or chronaxie values are identical with that of their rectangular counterparts. Threshold measuring with exponential pulses allow for determining rheobase directly and chronaxie by calculation with only two measurements. The measuring procedure is described in detail.
Residual U-Net Convolutional Neural Network Architecture for Low-Dose CT Denoising
Authors: Heinrich Mattias P. , Stille Maik , Buzug Thorsten M.
Published: September 2018

Low-dose CT has received increasing attention in the recent years and is considered a promising method to reduce the risk of cancer in patients. However, the reduction of the dosage leads to quantum noise in the raw data, which is carried on in the reconstructed images. Two different multilayer convolutional neural network (CNN) architectures for the denoising of CT images are investigated. ResFCN is based on a fully-convolutional network that consists of three blocks of 5×5 convolutions filters and a ResUNet that is trained with 10 convolutional blocks that are arranged in a multi-scale fashion. Both architectures feature a residual connection of the input image to ease learning. Training images are based on realistic simulations by using the XCAT phantom. The ResUNet approach shows the most promising results with a peak signal to noise ratio of 44.00 compared to ResFCN with 41.79.
Method Comparison of In Vitro Wound Area Measurements
Authors: Gdoura Ahmed , Parente Jacquelyn D. , Hensler Sabine , Krüger-Ziolek Sabine , Kuehlbach Claudia , Mueller Margareta M. , Möller Knut
Published: September 2018

Wound area is a primary outcome measure in wound healing studies. This method comparison study evaluates differences of wound area measurements of a newly developed image analysis method based on wound edge contour to an existing method based on contrast tolerance. Digital images of 64 wounds were taken immediately after wounding matured in vitro 3D organotypic tissues with a biopsy punch. Wound area measurements were calculated using each image analysis method and then normalized. The method comparison study evaluates the difference of each paired measurements for all 64 wound areas. Measurement differences are demonstrated and evaluated in normalized data boxplots, scatter plots with a line of equality, data histogram and Normal probability plots, and a Bland-Altman plot of paired measure difference against mean. The measured wound areas using the tolerance method have large variability in comparison to the contour method measures. The tolerance method measures often underestimate and overestimate what is assumed to be an approximately repeatable initial wound size. Skewness in comparison plots are due to the ‘fat tails’ introduced by the variability of measurements of the tolerance method. In contrast, the contour method results in larger wound area measurements on average at a statistically significant level of difference. The relatively less variable range of contour method measurements suggest this method has more potential to agree with the ‘true’ wound area. Future work to improve the method are proposed for application of image analysis methods to distinguish true wound area and measurement error in time for wound healing treatment-control experiments.
Reflection on boon and bane of Water Absorbing Components in Active Implants during Package Testing and Operation
Authors: Koker Liane , Gengenbach Ulrich , Bretthauer Georg
Published: September 2018

For package testing of active implants internal humidity measurements are performed. Thereby, the water absorbency of the measurement components can affect the measurement result, leading to an erroneously prolonged predicted lifetime. Here, the influence of internal components is discussed using an exemplary setup. It is described how to model and consider the components’ absorbencies for lifetime estimation and how beneficial they are during implant operation.
Volumetric 3D stitching of optical coherence tomography volumes
Authors: Laves Max-Heinrich , Kahrs Lüder A. , Ortmaier Tobias
Published: September 2018

Optical coherence tomography (OCT) is a noninvasive medical imaging modality, which provides highresolution transectional images of biological tissue. However, its potential is limited due to a relatively small field of view. To overcome this drawback, we describe a scheme for fully automated stitching of multiple 3D OCT volumes for panoramic imaging. The voxel displacements between two adjacent images are calculated by extending the Lucas-Kanade optical flow a lgorithm to dense volumetric images. A RANSAC robust estimator is used to obtain rigid transformations out of the resulting flow v ectors. T he i mages a re t ransformed into the same coordinate frame and overlapping areas are blended. The accuracy of the proposed stitching scheme is evaluated on two datasets of 7 and 4 OCT volumes, respectively. By placing the specimens on a high-accuracy motorized translational stage, ground truth transformations are available. This results in a mean translational error between two adjacent volumes of 16.6 ± 0.8 μm (2.8 ± 0.13 voxels). To the author’s knowledge, this is the first reported stitching of multiple 3D OCT volumes by using dense voxel information in the registration process. The achieved results are sufficient for providing high accuracy OCT panoramic images. Combined with a recently available high-speed 4D OCT, our method enables interactive stitching of hand-guided acquisitions.
Development of a compact stand-alone esophageal pressure measurement device
Authors: Richter Andre J. , Schnabel Christian , Spieth Peter , Koch Emdund
Published: September 2018

Mechanical ventilation requires optimal parameter setting for every single patient. For instance sufficient positive end-expiratory pressure (PEEP) may ensure oxygenation and prevent overdistension of lungs or alveolar collapse. To find optimal PEEP, transpulmonary pressure (airway pressure minus pleural pressure) guides as an indicator for both, chest wall mechanics and lung characteristic. Since measurement of pleural pressure is impractical in clinical routine, esophageal pressure can be used to estimate pleural pressure and may help to assure protective mechanical ventilation. We developed a PESO (derived from PESO = esophageal pressure) measurement system, which provides a compact stand-alone device to measure the esophageal pressure during mechanical ventilation of patients. In addition to the esophageal pressure, air way pressure is also measured to provide the synchronized data independent of the ventilator manufacturer. The device works with two commercial pressure transducers, whose signals are conditioned and digitized with an Arduino Nano microcontroller, which samples data with 62 kHz and transmits averaged data with 100 Hz to a mobile tablet PC, which acts as process, display and record unit. The compact system provides a working time of 5 hours. Therefore, the system supports the progress for mechanical ventilation research. This paper describes technical details as well as functionality.
An HMM-based averaging approach for creating mean motion data from a full-body Motion Capture system to support the development of a biomechanical model
Authors: Kitzig Andreas , Demmer Julia , Bolten Tobias , Naroska Edwin , Stockmanns Gudrun , Viga Reinhard , Grabmaier Anton
Published: September 2018

Motion capture systems or MoCap systems are used for game development and in the field of sports for the assessment and digitalization of human movement. Furthermore, MoCap systems are also used in the medical and therapeutic field for the analysis of human movement patterns. As examples gait analysis or examination of the musculoskeletal system and its function should be mentioned. Most application relate to a specific person and their movement or to the comparison of movements of different people. Within the scope of this paper an averaged motion sequence is supposed to be generated from MoCap data in order to be able to use it in the field of biomechanical modeling and simulation. For the averaging of individual movement sequences of different persons a Hidden Markov Model (HMM) based approach is presented.
Experimental and numerical investigations of fluid flow in bioreactors for optimized in vitro stem cell loading in xenografts
Authors: Ott Robert , Wüstenhagen Carolin , Stiehm Michael , Schmitz Klaus-Peter , Siewert Stefan , Schmidt Wolfram , Martin Heiner , Grabow Niels , Kasten Annika , Liese Jan , Fechner Carsten , Frerich Bernhard , Einnolf Nadia
Published: September 2018

In tissue engineering and regenerative medicine mesenchymal stem cells (MSC) are widely used to replace and restore the function of dysfunctional or missing tissue. Recent studies have shown significant enhancements of the in vivo healing process following dentofacial bone augmentation procedures employing stem cell-loaded xenografts. We conducted experimental and numerical investigations in perfusion flow bioreactor-xenograft-systems to identify flow conditions as well as bioreactor design features that allow for homogeneous MSC-distribution in Geistlich Bio- Oss Block xenografts. Pressure gradient - velocity characteristics and flow distributions were investigated experimentally and numerically for two bioreactor designs at steady-state flow conditions with Reynolds numbers (Re) ranging from 0.01 ≤ Re ≤ 0.32. Distilled water at 20°C with a dynamic viscosity of 1.002 mPa∙s and a density of 998 kg/m3 was used. The geometry of the xenograft utilized in three-dimensional computational fluid dynamics (CFD) simulation was obtained by means of micro-computed tomography (μCT) at an isotropic spatial resolution of 9.5 μm. The permeability values calculated from the experimental data are in good accordance with the numerical results. The investigations showed that the increase of the inflow- and outflow-area diameter, as well as the decrease of the volumetric flow rate, result in a decreasing heterogeneity of the flow distribution within the xenograft. The calculated wall shear stress rates in the three-dimensional (3D) scaffold range from 1∙10-12Pa ≤ τ ≤ 0.2 Pa. Experimentally validated CFD simulations introduced in this study provide an applicable tool to assess optimal flow conditions for homogeneous MSC distribution in bioreactor-xenograft-systems.
Synchronized Sensor Insoles for Clinical Gait Analysis in Home-Monitoring Applications
Authors: Roth Nils , Martindale Christine F. , Eskofier Bjoern M. , Gaßner Heiko , Kohl Zacharias , Klucken Jochen
Published: September 2018

Wearable sensor systems are of increasing interest in clinical gait analysis. However, little information about gait dynamics of patients under free living conditions is available, due to the challenges of integrating such systems unobtrusively into a patient’s everyday live. To address this limitation, new, fully integrated low power sensor insoles are proposed, to target applications particularly in home-monitoring scenarios. The insoles combine inertial as well as pressure sensors and feature wireless synchronization to acquire biomechanical data of both feet with a mean timing offset of 15.0 μs. The proposed system was evaluated on 15 patients with mild to severe gait disorders against the GAITRite® system as reference. Gait events based on the insoles’ pressure sensors were manually extracted to calculate temporal gait features such as double support time and double support. Compared to the reference system a mean error of 0.06 s ±0.06 s and 3.89 % ±2.61 % was achieved, respectively. The proposed insoles proved their ability to acquire synchronized gait parameters and address the requirements for home-monitoring scenarios, pushing the boundaries of clinical gait analysis.
Detecting Lamellipodia in Epithelial Cell Clusters Using a Fully Convolutional Neural Network for Phase Contrast Microscopy Images
Authors: Grützmacher Simon , Kemkemer Ralf , Thies Christian , Curio Cristóbal
Published: September 2018

We present an approach for segmenting individual cells and lamellipodia in epithelial cell clusters using fully convolutional neural networks. The method will set the basis for measuring cell cluster dynamics and expansion to improve the investigation of collective cell migration phenomena. The fully learning-based front-end avoids classical feature engineering, yet the network architecture needs to be designed carefully. Our network predicts how likely each pixel belongs to one of the classes and, thus, is able to segment the image. Besides characterizing segmentation performance, we discuss how the network will be further employed.