bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of different test gases in a non-destructive 100% quality control system for medical devices
Authors: Pollack Thomas , Seitz Hermann 
Published: December 2016

Abstract
The purpose of this research is to evaluate the detectability of defect membranes in intravenous (IV) infusion filter systems. The device under test (DUT) protects critical ill patients and has a high priority for the risk management of intensive care units. The developed quality control system stands out from other filter integrity methods because no method located on this topic represents such a simple, reliable, fast and non-destructive technique, examined without liquid. The invented method works as a pressure driven test and uses gas to identify defects. Previous studies have demonstrated the capability of detecting various types of errors. In this paper the influence of different test gases on the detectability of smallest defects is presented.
Effect of left atrial hypertrophy on P-wave morphology in a computational model
Authors: Andlauer Robin , Loewe Axel , Dössel Olaf , Seemann Gunnar 
Published: December 2016

Abstract
P-wave assessment is frequently used in clinical practice to recognize atrial abnormalities. However, the use of P-wave criteria to diagnose specific atrial abnormalities such as left atrial enlargement has shown to be of limited use since these abnormalities can be difficult to distinguish using P-wave criteria to date. Hence, a mechanistic understanding how specific atrial abnormalities affect the P-wave is desirable. In this study, we investigated the effect of left atrial hypertrophy on P-wave morphology using an in silico approach. In a cohort of four realistic patient models, we homogeneously increased left atrial wall thickness in up to seven degrees of left atrial hypertrophy. Excitation conduction was simulated using a monodomain finite element approach. Then, the resulting transmembrane voltage distribution was used to calculate the corresponding extracellular potential distribution on the torso by solving the forward problem of electrocardiography. In our simulation setup, left atrial wall thickening strongly correlated with an increased absolute value of the P-wave terminal force (PTF) in Wilson lead V1 due to an increased negative amplitude while P-wave duration was unaffected. Remarkably, an increased PTF-V1 has often been associated with left atrial enlargement which is defined as a rather increased left atrial volume than a solely thickened left atrium. Hence, the observed contribution of left atrial wall thickness changes to PTF-V1 might explain the poor empirical correlation of left atrial enlargement with PTF-V1.
Simulation of intracardiac electrograms around acute ablation lesions
Authors: Greiner Joachim , Pollnow Stefan , Schuler Steffen , Lenis Gustavo , Seemann Gunnar , Dössel Olaf 
Published: December 2016

Abstract
Radiofrequency ablation (RFA) is a widely used clinical treatment for many types of cardiac arrhythmias. However, nontransmural lesions and gaps between linear lesions often lead to recurrence of the arrhythmia. Intracardiac electrograms (IEGMs) provide real-time information regarding the state of the cardiac tissue surrounding the catheter tip. Nevertheless, the formation and interpretation of IEGMs during the RFA procedure is complex and yet not fully understood. In this in-silico study, we propose a computational model for acute ablation lesions. Our model consists of a necrotic scar core and a border zone, describing irreversible and reversible temperature induced electrophysiological phenomena. These phenomena are modeled by varying the intra- and extracellular conductivity of the tissue as well as a regulating zone factor. The computational model is evaluated regarding its feasibility and validity. Therefore, this model was compared to an existing one and to clinical measurements of five patients undergoing RFA. The results show that the model can indeed be used to recreate IEGMs. We computed IEGMs arising from complex ablation scars, such as scars with gaps or two overlapping ellipsoid scars. For orthogonal catheter orientation, the presence of a second necrotic core in the near-field of a punctiform acute ablation lesion had minor impact on the resulting signal morphology. The presented model can serve as a base for further research on the formation and interpretation of IEGMs.
Parametrization of activation based cardiac electrophysiology models using bidomain model simulations
Authors: Stender Birgit 
Published: December 2016

Abstract
Eikonal models are useful to compute approximate solutions of cardiac excitation propagation in a computationally efficient way. In this work the underlying conduction velocities for different cell types were computed solving the classical bidomain model equations for planar wavefront propagation. It was further investigated how changes in the conductivity tensors within the bidomain model analytically correspond to changes in the conduction velocity. The error in the presence of local front curvature for the derived eikonal model parametrization were analyzed. The conduction velocity simulated based on the bidomain model was overestimated by a maximum of 10%.
Resistance in a non-linear autoregressive model of pulmonary mechanics
Authors: Langdon Ruby , Docherty Paul D. , Laufer Bernhard , Möller Knut 
Published: December 2016

Abstract
Respiratory system modelling can enable patient-specific mechanical ventilator settings to be found, and can thus reduce the incidence of ventilator induced lung injury in the intensive care unit. The resistance of a simple first order model (FOM) of pulmonary mechanics was compared with a flow dependent term of a non-linear autoregressive (NARX) model. Model parameters were identified for consecutive non-overlapping windows of length 20 breaths. The analysis was performed over recruitment manoeuvres for 25 sedated mechanically ventilated patients. The NARX model term, b1
, consistently decreased as positive end expiratory pressure (PEEP) increased, while the FOM resistance behaviour varied. Overall the NARX b1
behaviour is more in-line with expected trends in airway resistance as PEEP increases. This work has further verified the physiologically descriptive capability of the NARX model.
Determination of regional lung function in cystic fibrosis using electrical impedance tomography
Authors: Krueger-Ziolek Sabine , Schullcke Benjamin , Zhao Zhanqi , Gong Bo , Moeller Knut 
Published: December 2016

Abstract
Electrical impedance tomography (EIT) can be used to monitor regional lung ventilation. Due to its relatively high temporal resolution, EIT has already been applied during lung function tests in spontaneously breathing subjects with obstructive lung diseases like chronic obstructive pulmonary disease (COPD) or cystic fibrosis (CF). In our study, ratios of the maximal volume exhaled in 1 s during forced expiration and forced vital capacity (FEV1/FVC) were calculated in predefined lung regions for five CF patients and five lung healthy subjects. The degree of FEV1/FVC homogeneity was assessed by using a slightly modified version of the global inhomogeneity index (GIFEV1

/FVC). CF patients showed a higher degree of inhomogeneity in pixel FEV1/FVC than lung healthy subjects. Since EIT is able to deliver regional information to assess airway obstruction in CF patients, it might represent a promising supplement to existing methods like spirometry providing global lung parameters.
Development of parietal bone surrogates for parietal graft lift training
Authors: Hollensteiner Marianne , Fürst David , Esterer Benjamin , Hunger Stefan , Malek Michael , Augat Peter , Schrödl Falk , Stephan Daniel , Schrempf Andreas 
Published: December 2016

Abstract
Currently the surgical training of parietal bone graft techniques is performed on patients or specimens. Commercially available bone models do not deliver realistic haptic feedback. Thus customized parietal skull surrogates were developed for surgical training purposes. Two human parietal bones were used as reference. Based on the measurement of insertion forces of drilling, milling and saw procedures suitable material compositions for molding cortical and cancellous calvarial layers were found. Artificial skull caps were manufactured and tested. Additionally microtomograpy images of human and artificial parietal bones were performed to analyze outer table and diploe thicknesses. Significant differences between human and artificial skulls were not detected with the mechanical procedures tested. Highly significant differences were found for the diploe thickness values. In conclusion, an artificial bone has been created, mimicking the properties of human parietal bone thus being suitable for tabula externa graft lift training.
Numerical simulation of mechanically stimulated bone remodelling
Authors: Mauck Josephine , Wieding Jan , Kluess Daniel , Bader Rainer 
Published: December 2016

Abstract
The numerical simulation of bone remodelling provides a great opportunity to improve the choice of therapy in particular for complex bone defects. Despite this fact, its use in clinical practice is not yet expedient because of several unresolved problems. In this paper a new bone remodelling algorithm based on standard computer tomography datasets and finite element analysis is introduced.
Conversion of engineering stresses to Cauchy stresses in tensile and compression tests of thermoplastic polymers
Authors: Schümann Kerstin , Röhr Udo , Schmitz Klaus-Peter , Grabow Niels 
Published: December 2016

Abstract
Thermoplastic polymers exhibit non-isochoric behaviour during tensile and compression testing as well as particular deformations like local necking (tension) or buckling (compression). A method for the determination of Cauchy stresses from tensile and compression tests is presented, that considers the actual deformations of the test specimens. The exact geometry of the specimens in the respective present configuration is determined in photographs, which are taken continuously throughout the test. The engineering stresses at several time points are converted into Cauchy stresses using newly developed formulas in consideration of the actual specimen geometry. For validation finite element analyses of the tensile and compression tests are performed using the identified stress-strain curves. The numerical results show good agreement with the experiments for the tested polymers. Thus a method for conversion of engineering to Cauchy stresses in tensile and compression tests could be established considering the non-isochoric deformation in plasticity. With this method “true” stress-strain curves as input for finite element material models can be identified for arbitrary materials.
Numerical examinations of simplified spondylodesis models concerning energy absorption in magnetic resonance imaging
Authors: Hadert Nicole , Liu Qi , Zylka Waldemar 
Published: December 2016

Abstract
Metallic implants in magnetic resonance imaging (MRI) are a potential safety risk since the energy absorption may increase temperature of the surrounding tissue. The temperature rise is highly dependent on implant size. Numerical examinations can be used to calculate the energy absorption in terms of the specific absorption rate (SAR) induced by MRI on orthopaedic implants. This research presents the impact of titanium osteosynthesis spine implants, called spondylodesis, deduced by numerical examinations of energy absorption in simplified spondylodesis models placed in 1.5 T and 3.0 T MRI body coils. The implants are modelled along with a spine model consisting of vertebrae and disci intervertebrales thus extending previous investigations [1], [2]. Increased SAR values are observed at the ends of long implants, while at the center SAR is significantly lower. Sufficiently short implants show increased SAR along the complete length of the implant. A careful data analysis reveals that the particular anatomy, i.e. vertebrae and disci intervertebrales, has a significant effect on SAR. On top of SAR profile due to the implant length, considerable SAR variations at small scale are observed, e.g. SAR values at vertebra are higher than at disc positions.
Influence of Siluron® insertion on model drug distribution in the simulated vitreous body
Authors: Stein Sandra , Bogdahn Malte , Weitschies Werner , Seidlitz Anne 
Published: December 2016

Abstract
Biorelevant in vitro test systems may be helpful to understand the in vivo behaviour of modern intravitreal dosage forms such as implants and injections. The already presented Vitreous Model (VM) in combination with the Eye Movement System (EyeMoS) was used to simulate the situation after a vitrectomy in combination with Siluron® silicone oil (SO) insertion in vitro and to investigate the distribution of the model drug fluorescein sodium (FS) within the modified VM. The state after a vitrectomy was simulated in vitro by replacing half the volume of the gelled vitreous substitute by SO. Under consideration of simulated eye movements the position of SO towards the simulated vitreous body was examined. Furthermore, the influence of two different injection techniques was studied. On the one hand, FS was injected directly into the gel and on the other hand the injection was set through the gel in order to directly reach the SO. Independent of the injection technique, it was shown that the model drug distributed almost exclusively into the gel and not into the SO. This can be explained with the backflow of FS into the gel and the lack of solubility in the SO. Using the modified VM and EyeMoS, the in vitro characterization of drug release and distribution behaviour of intravitreal injections can be performed under consideration of a simulated vitrectomy.
Minimally spaced electrode positions for multi-functional chest sensors: ECG and respiratory signal estimation
Authors: Klum Michael , Minn Tobias , Tigges Timo , Pielmus Alexandru-Gabriel , Orglmeister Reinhold 
Published: December 2016

Abstract
Unobtrusive medical instrumentation is a key in continuous patient monitoring. To increase compliance, multi-functional sensor concepts and measurement sites different from gold-standards are used. In this work, we aim to combine both approaches. We focus on minimally spaced electrode positions with high signal correlations to gold-standards. We present twofold experimental data from six and eleven healthy volunteers and provide chest positions with individual correlations up to 0.83 ± 0.06 for ECG and 0.73 ± 0.28 for the respiratory frequency. Using a performance index, we assess positions with correlations up to 0.77 ± 0.12 for ECG and 0.65 ± 0.35 for the respiratory frequency with 24 mm electrode distance.
Automated detection of alveolar arches for nasoalveolar molding in cleft lip and palate treatment
Authors: Bauer Franz X. , Gau Dominik , Guell Florian , Eblenkamp Markus , Loeffelbein Denys J. 
Published: December 2016

Abstract
Nasoalveolar moulding (NAM) has become a widely accepted and evidence-based treatment strategy for newborns with cleft lip and palate (CLP), attempting to reduce the cleft gap and to form an appropriately shaped alveolar arch by an intraoral patient-specific NAM plate and to erect the usually flattened nostrils towards a natural nose wing occurrence. The generation of such an appropriately shaped NAM plate requires, besides 3d information of the patient’s initially cleft lip and palate, an estimated target model of the maxilla. Previous studies showed the applicability of curve-based approaches to describe the maxilla during early infancy. We have developed an automated algorithm implemented with the programming language Python, describing the alveolar arch by an approximated ellipse. Therefore, the digitalized data sets of human maxillae were aligned to a global coordinate system with a total least square method and subsequently analyzed with the curvature-based algebraic point set surfaces (APSS) algorithm. The gathered information of height ratio and curvature allows the detection of points on the alveolar segments and therewith the fit of an ellipse describing the human maxilla. In 84.5% of 193 maxilla impressions of healthy newborns the fitted ellipses described the course of the maxilla within defined margins. Applying the algorithm to 38 newborns suffering from unilateral cleft lip and palate in 76.3% the fitted ellipses bridge the CLP alveolar segments, so that a harmonic alveolar arch can be deduced. Describing the alveolar arch by one or multiple ellipses allows (i) to automatically measure the dimensions of the maxilla, (ii) to derive a growth model during early infancy, (iii) to derive a healthy harmonic arch from CLP alveolar segments and (iv) to automatically generate a basic NAM device on the basis of the virtually modified maxilla.
Interactive monitoring system for visual respiratory biofeedback
Authors: Odenbach Robert , Boese Axel , Friebe Michael 
Published: December 2016

Abstract
In almost any medical procedure respiratory motion is an issue and may result in image degradation. Most currently available devices and systems, which are intended to reduce respiratory influences do not come into operation however in clinics due to their high cost and complex operation. In our paper we evaluated an interactive breath hold control system that helps flat breathing to subsequently reduce respiratory motion during signal acquisitions or procedure treatments. With that the human subjects are enabled to regulate their own breath by following visual feedback via a specially designed display. That display shows biofeedback information about the respiratory excursion through air pressure deviations measured inside an air bellows belt. The system was assessed quantitatively in a laboratory setup and qualitatively by applications in real clinical procedures. The obtained results are very promising and can be further improved with additional developments to provide an easy to use and relatively inexpensive solution for respiratory motion related imaging problems.
A passive beating heart setup for interventional cardiology training
Authors: Granegger Marcus , Aigner Philipp , Kitzmüller Erwin , Stoiber Martin , Moscato Francesco , Michel-Behnke Ina , Schima Heinrich 
Published: December 2016

Abstract
Realistic training of cardiologic interventions in a heart catheter laboratory is hardly achievable with simple tools and requires animal experiments. Therefore, first a simple mock circuit connected to a porcine heart mimicking the natural heart motion was developed. In a second step the setup was duplicated to drive both sides of the heart independently to generate motion and physiologic pressures and flows. Using this simple setup cardiologic interventions (arterial and ventricular septal defects ASD/VSD closure) were performed successfully and allowed realistic training under the C-arm, echocardiography, placement of catheters and repair of ASD/VSD. With the second setup flows of up to 4 l/min were achieved in both sides of the heart at maximum left and right ventricular pressures of 80 mm Hg and 30 mm Hg respectively. This method is inexpensive and represents a realistic alternative to training in animal experiments.
A service for monitoring the quality of intraoperative cone beam CT images
Authors: Heckel Frank , Schlamelcher Jan , Rotermund Hanna , Rockstroh Max , Zidowitz Stephan , Neumuth Thomas 
Published: December 2016

Abstract
In recent years, operating rooms (ORs) have transformed into integrated operating rooms, where devices are able to communicate, exchange data, or even steer and control each other. However, image data processing is commonly done by dedicated workstations for specific clinical use-cases. In this paper, we propose a concept for a dynamic service component for image data processing on the example of automatic image quality assessment (AQUA) of intraoperative cone beam computed tomography (CBCT) images. The service is build using the Open Surgical Communication Protocol (OSCP) and the standard for Digital Imaging and Communications in Medicine (DICOM). We have validated the proposed concept in an integrated demonstrator OR.
Parametric Study of Obstacle Geometry Effect on Mixing Performance in a Convergent-Divergent Micromixer with Sinusoidal Walls
Authors: Heshmatnezhad Fazlollah , Aghaei Halimeh , Solaimany Nazar Ali Reza 
Published: December 2016

Abstract
This study presents a numerical simulation through computational fluid dynamics on mixing and flow structures in convergent-divergent micromixer with a triangular obstacle. The main concept in this design is to enhance the interfacial area between the two fluids by creating a transverse flow and split, and recombination of fluids flow due to the presence of obstacles. The effect of triangular obstacle size, the number of units, changing the position of an obstacle in the mixing channel and operational parameter like the Reynolds number on the mixing efficiency and pressure drop are assessed. The results indicate that at inlet Reynolds numbers below 5, the molecular diffusion is the most important mechanism of mixing, and the mixing index is almost the same for all cases. By increasing the inlet Reynolds number above 5, mixing index increases dramatically, due to the secondary flows. Based on the simulation results, due to increasing the effect of dean and separation vortices as well as more recirculation of flow in the side branches and behind the triangular obstacle, the highest mixing index is obtained at the aspect ratio of 2 for the triangular obstacle and its position at the front of the mixing unit. Also the highest value of mixing index is obtained by six unit of mixing chamber. The effect of changing the position of the obstacle in the channel and changing the aspect ratio of the obstacle is evident in high Reynolds numbers. An increase in the Reynolds number in both cases (changing the aspect ratio and position of the obstacle) leads to pressure drop increases.
Metaphors and grammar teaching
Authors: Roche Jörg , Suñer Ferran 
Published: December 2016

Abstract
Despite the need for transparency and efficiency in explaining grammatical features to learners of a foreign language only very few systematic attempts have been undertaken to demonstrate the pedagogical added value of concept-based approaches to grammar instruction. The purpose of the paper is (1) to discuss the theoretical underpinnings of such an approach, to (2) present relevant theories of multimedia learning and (3) to summarize some empirical evidence on the efficiency of such an approach to language teaching and learning. The concept-based animated grammar, developed for German, uses a broad range of cognitive linguistic principles for foreign language learning in such areas as, for example, modal verbs or the passive voice.