bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical simulation of a transcatheter aortic heart valve under application-related loading
Authors: Pfensig Sylvia , Kaule Sebastian , Ott Robert , Wüstenhagen Carolin , Stiehm Michael , Keiler Jonas , Wree Andreas , Grabow Niels , Schmitz Klaus-Peter , Siewert Stefan 
Published: September 2018

Abstract
For the treatment of severe symptomatic aortic valve stenosis, minimally invasive heart valve prostheses have more recently become the lifesaving solution for elderly patients with high operational risk and thus, are often implanted in patients with challenging aortic root configuration. A correct prosthesis deployment and stent adaption to the target region is essential to ensure optimal leaflet performance and long-term prosthesis function. The objective of this study was the development of a suitable in silico setup for structural numerical simulation of a transcatheter aortic valve (TAV) in different cases of clinical relevance. A transcatheter valve prosthesis comprising an unpressurized trileaflet heart valve and an adapted stent configuration was designed. An aortic root (AR) model was developed, based on microcomputed tomography of a native healthy specimen. Using the finite-element analysis (FEA), various loading cases including prosthesis biomechanics with valve opening and closing under physiological pressure ratios throughout a cardiac cycle, prosthesis crimping as well as crimping and release into the developed AR model were simulated. Hyperelastic constitutive law for polymeric leaflet material and superelasticity of shape memory alloys for the self-expanding Nitinol stent structure were implemented into the FEA setup. Calculated performance of the valve including the stent structure demonstrated enhanced leaflet opening and closing as a result of stent deformation and redirected loading. Crimping and subsequent release into the AR model as well as the stent adaption to the target region after expansion proved the suitability of the TAV design for percutaneous application. FEA represented a useful tool for numerical simulation of an entire minimally invasive heart valve prosthesis in relevant clinical scenarios.
Experimental setup for evaluation of cavitation effects in ESWL
Authors: Reinhardt Nina , Dietz-Laursonn Kristin , Janzen Marc , Radermacher Klaus , Bach Christian , Radermacher Klaus , Fuente Matias de la 
Published: September 2018

Abstract
Cavitation is a major fracture mechanism in extracorporeal shock wave lithotripsy (ESWL). However, it can cause tissue trauma and its effects on kidney stones and surrounding tissue are not fully understood. Therefore experimental setups enabling systematic parameter studies are crucial. We developed and evaluated a testing rig comprising three measuring methods in order to examine this mechanism. Our initial evaluation of this setup based on standard components showed promising results. Primary cavitation was displayed by high-speed photography 195 μs after the shock front had passed the focal zone. The effect of different pulse repetition rates (30, 60, 90, 120 SW/min) on the extension of the cavitation area was determined. The lifetime of secondary cavitation was analysed by B-mode ultrasound imaging. In a post processing progress the images showing bubbles were compared to a reference picture for both types of cavitation and the number of pixels that changed colour was counted. Furthermore stone comminution at different pulse repetition rates (30, 60, 90, 120 SW/min) was investigated by fixed-dose fragmentation. We observed an inverse correlation of cavitation and fragmentation. As the pulse repetition rate increases, the area of primary cavitation grows whereas the fragmentation efficiency decreases. B-mode imaging showed that secondary cavitation bubbles persisted between the shocks and can serve as nuclei. The higher the pulse repetition rate is, the more of these nuclei remain and thus facilitate formation of primary cavitation. The experimental setup provides reproducible results regarding the development of primary and secondary cavitation on the one hand and the fragmentation of phantom stones on the other hand. Therefore it can be utilized to further investigate the effect of different boundary conditions and shock wave parameters on cavitation and stone comminution. The impact of different focal sound fields is subject of ongoing research.
Effects of the medial and lateral tibial slope on knee joint kinematics in total knee arthroplasty
Authors: Asseln Malte , Berger Luisa , Verjans Mark , Radermacher Klaus 
Published: September 2018

Abstract
Implant design in total knee arthroplasty is a key factor for the recovery of function and mobility of the joint. However, there is a lack of knowledge on the complex relationship between design features and the biomechanical situation. The posterior inclination of the tibial plateau (tibial slope) has a known functional impact on knee joint kinematics. In the native knee it shows high inter-individual differences, which is inadequately considered in total knee arthroplasty. We investigated the effects of the separate and combined variation of the medial and lateral tibial slope on knee joint kinematics in an in vitro setup. Therefore, the medial and lateral inserts of a knee implant were parameterised and the initial slope was gradually varied to +4°, +2° (posterior) and -2°, -4° (anterior). The variations were manufactured by using polymer based rapid prototyping. The effects on semi-active tibiofemoral and patellofemoral kinematics were studied and quantified in terms of the Root Mean Square Error and Pearson’s Correlation coefficient. The overall largest effect was observed on tibiofemoral internal-external rotation by the variation of the lateral insert. The anterior-posterior translation was predominantly effected by the combined variation. Nevertheless, the lateral variation showed greater influence than medial. In contrast, changes in patellofemoral kinematics were small. Our findings suggest that in total knee arthroplasty the lateral tibial slope has a larger functional effect than the medial tibial slope. Thus, functional design optimization should focus on the lateral insert.
Quantification method for timolol from in vivo samples for the development of a new glaucoma drug depot
Authors: Eickner Thomas , Kopp Franziska , Brietzke Andreas , Kischkel Sabine , Oschatz Stefan , Schmitz Klaus-Peter , Guthoff Rudolf , Grabow Niels 
Published: September 2018

Abstract
Glaucoma is the second most common cause of blindness. An increased intraocular pressure is the only treatable symptom of glaucoma. Because patients often exhibit a poor therapy adherence, a drug depot consisting of ELA-NCO and hyaluronic acid with timolol was developed to ensure sustained drug release. This drug depot is formed by in situ polymerisation after injection into the subconjunctival space. To test the in vivo drug release of timolol in serum and aqueous humour, a liquid chromatography mass spectrometry (LCMS) method was developed and tested using spike- and recovery experiments, and on in vivo samples after topical application. Samples of serum and aqueous humour were taken from New Zealand White rabbits. For topical application, a commercially available formulation of timolol was used. This study presents results concerning the recovery of timolol from spiked samples. Serum and aqueous humour samples were spiked with timolol maleate to a final concentration of 50 ng/mL. Subsequently, the samples were extracted and analysed by LCMS. External calibration of the developed method showed high linearity. Recovery experiments showed no loss of timolol. Hence, the extraction method is robust and able to recover the whole amount of timolol from aqueous humour and serum.
Novel test procedure for testing antimicrobially active materials
Authors: Stich Alexander , Buhl Sebastian , Bulitta Clemens 
Published: September 2018

Abstract
Antimicrobial coatings are typically tested for their activity and effectiveness based on an artificial procedure, the standard JIS Z 2801 (or ISO 22196). The test samples are contaminated with a predetermined concentration of bacteria and covered with a sterile film. Due to the artificial structure of this process, however, there is always the question of the validity in the practical application of these surfaces and how comparable this germ-reducing effect is to currently common disinfection measures. Therefore, we developed a more realistic test procedure in our laboratory. The test samples are inoculated and incubated at standard room conditions. To compare the antimicrobial activity to standard cleaning procedures also disinfection and wipe controls were performed. The results show that the antimicrobial test patterns we use have a strong efficacy. This could be shown reproducibly both with the standard method JIS Z 2801 as well as with our new test procedure.
Inkjet printing for localized coating and functionalization of medical devices
Authors: Mau Robert , Paasche Gerrit , Lenarz Thomas , Seitz Hermann 
Published: September 2018

Abstract
Inkjet printing has become essential for pharmaceutical research as well as biomedical applications. It is a promising tool to meet future challenges in patientindividual designed pharmaceuticals and implants. In this context, the main areas of use are high-throughput screening (HTS), drug-loaded microparticles, drug formulation and oral dose development, 3D-printing/bioprinting as well as coating of implants. This study deals with the latter. In view of promising applications for localized coating and functionalization of implant surfaces this work shows preliminary results on inkjet printing of the polymer poly(2- ethyl-2-oxazoline) (PetOx), a protein repellent polymer (PRP). To deposit single droplets with small volumes (~500 pl) of aqueous PetOx solution (50 g/l), printing parameters were determined for the piezo-driven drop-ondemand inkjet printhead NanoTip J, operating in a Nanoplotter 2.1 (both from GeSiM mbH, Germany). Different printing strategies are demonstrated by varying droplet spacing and drying time while printing on hydrophilic glass substrate. Printing and stacking of almost uniform polymer lines (width ~ 200 μm) is demonstrated.
Soft tissue volume augmentation in the oral cavity with a collagen-based 3D matrix with orientated open pore structure
Authors: Damink Leon Olde , Heschel Ingo , Leemhuis Hans , Tortorici Martina , Wessing Bastian 
Published: September 2018

Abstract
In this study, characteristic features of a new regenerative 3D collagen matrix with an orientated open pore structure are studied in-vitro and in-vivo. The noncrosslinked porcine-based resorbable collagen-elastin matrix is designed to provide support during coverage procedures of localized gingival recessions and for local soft tissue augmentation around teeth and implants and is designed to provide an off-the-shelf alternative to autogenous soft tissue grafts. The in-vitro studies show that the mechanical properties (e.g. suture retention, volume recovery after cyclic compression) and the observed active cell migration into the open porous structure of the matrix fulfil essential design requirements. The in-vivo pig animal study shows that the matrix is well integrated into the surrounding tissue and replaced by newly formed autogenous soft tissue without a significant loss in tissue volume. First clinical case series are being performed to further analyse the new 3D matrix in clinical settings.
An analysis of the impact of the inclusion of expiration data on the fitting of a predictive pulmonary elastance model
Authors: Morton Sophie , Docherty Paul , Dickson Jennifer , Chase J. Geoffrey 
Published: September 2018

Abstract
Mechanical ventilation is a primary therapy for patients with respiratory failure. However, incorrect ventilator settings can cause lung damage. Optimising ventilation while minimising risk is complex in practice. A common lung protective strategy is to titrate positive end-expiratory pressure (PEEP) to the point of minimum elastance. This process can result in additional available lung volume due to alveolar recruitment but comes with the risk of subjecting the lungs to excessive pressure and lung damage. Predictive elastance models can mitigate this risk by estimating airway pressure at a higher PEEP level. Due to the increased risk of barotrauma during inspiration, many models exclude expiration data. However, this section of the breath can include useful information about lung mechanics. This research investigates the impact that including expiration data into the fitting of a validated predictive elastance model will have on its ability to predict peak inspiratory pressure. Results showed that expiration data did not improve the efficacy of the model in this case with an increase in error (median (%)) of predicting peak inspiratory pressure through an increase in PEEP of 8 cmH2O from 6% to 16%.
Smartphone-based low-cost microscope with monolithic focusing mechanism
Authors: Schäfer Max B. , Reichert David , Stewart Kent , Herkommer Alois M. , Reichert Carsten , Pott Peter P. 
Published: September 2018

Abstract
Microscopy enables fast and effective diagnostics. However, its functionality is not accessible to everyone. Smartphone-based low-cost microscopes could be a powerful tool for diagnostics and educational purposes. Current smartphone-based microscopy approaches struggle with high cost, poor image quality and/or insufficient smartphone compatibility. In this paper, a very feasible and effective lowcost microscope is presented which addresses these issues. To minimize cost, a monolithic foldable structure is designed for production by injection molding. The design has a high order of functional integration, minimizing the number of components, while still enabling a micrometer focusing accuracy.
Context-awareness for control consoles in integrated operating rooms
Authors: Franke Stefan , Rockstroh Max , Neumuth Thomas 
Published: September 2018

Abstract
In surgery, the possibilities of fully automatic assistance are limited. A valuable automated assistance can be implemented by realizing context-aware behaviour of control consoles in integrated operating rooms (ORs). We developed an intraoperative pipeline for surgical context interpretation and an integrated console. Based on that, we propose a method for the context-aware ranking of configuration profiles, which facilitate the handling of devices during endoscopic interventions. The method is evaluated with twenty-four simulated endoscopic ear-nosethroat (ENT) workflows. The results indicate that a continuous automatic ranking based on the surgical situation, can significantly reduce manual user interaction while the surgeon’s control is preserved.
Imaging of the human tympanic membrane by endoscopic optical coherence tomography
Authors: Schindler Martin , Kirsten Lars , Morgenstern Joseph , Golde Jonas , Erkkilä Mikael , Walther Julia , Kemper Max , Bornitz Matthias , Neudert Marcus , Zahnert Thomas , Koch Edmund 
Published: September 2018

Abstract
Endoscopic optical coherence tomography is a non-invasive and contactless imaging technique based on white light interferometry. It enables high-resolution three-dimensional imaging of scattering tissue up to a depth of about 2 mm. In addition, Doppler-OCT can detect sub-resolution movements. These features can be used to examine the tympanic membrane, the surrounding tissue and nearby areas of the tympanic cavity. For this purpose, we present an endoscopic OCT system, which provides access to the tympanic membrane. The design of the endoscope is based on a gradientindex (GRIN) lens system. This allows a broad field of view and a large working distance. An additional VIS beam path allows visual imaging and orientation inside the auditory canal. Therefore, illumination fibers are attached a round the GRIN-system. The resulting endoscope has a length of 55 mm and a diameter of 3.5 mm. By attaching an earphone and a probe microphone, the oscillation of the tympanic membrane can be measured under acoustic stimulation. With the endoscopic OCT system, we provide an examination tool for the diagnosis of a broad number of diseases like conductive hearing loss.
Effects of uniaxial stretching on tenocyte migration behaviour
Authors: Dursun Gözde , Tohidnezhad Mersedeh , Markert Bernd , Stoffel Marcus 
Published: September 2018

Abstract
It is widely known that tendon tissues are subjected to repeated cyclic mechanical load which influences cellular processes. The involvement of principles of mechanics in tissue engineering contributes to the investigations of the connection between mechanical and biological parameters in cellular processes and as well as to the development of new approaches for specific treatment methods. The healing process of injured tendons includes tenocyte migration which occurs from intact regions of tendon into the wound site. The aim of the present study is to investigate and enhance the migration characteristics of tenocytes under uniaxial mechanical stretching using an in-house tensile bioreactor system. Uniaxial mechanical stretching is applied to tenocyte-seeded silicone as well as collagen membranes, which possess different material properties. Tenocyte-seeded silicone membranes were investigated under three different loading conditions, including unstimulated (control), 3% and 5% strain, at frequency of 0.5 Hz. Tenocyte-seeded collagen membranes were investigated using three different frequencies, including unstimulated (control), 0.1 Hz and 0.5 Hz at strain of 4%. The main finding in this study is that uniaxially mechanical stretching at 3% strain enhances the cell migration more than 5% strain on silicone membranes.
Enhancement of Region of Interest CT Reconstructions through Multimodal Data
Authors: Schote David , Pfeiffer Tim , Rose Georg 
Published: September 2018

Abstract
Computed tomography (CT) scans are frequently used intraoperatively, for example to control the positioning of implants during intervention. Often, to provide the required information, a full field of view is unnecessary. I nstead, the region-of-interest (ROI) imaging can be performed, allowing for substantial reduction in the applied X-ray dose. However, ROI imaging leads to data inconsistencies, caused by the truncation of the projections. This lack of information severely impairs the quality of the reconstructed images. This study presents a proof-of-concept for a new approach that combines the incomplete CT data with ultrasound data and time of flight measurements in order to restore some of the lacking information. The routine is evaluated in a simulation study using the original Shepp-Logan phantom in ROI cases with different degrees of truncation. Image quality is assessed by means of normalized root mean square error. The proposed method significantly reduces truncation artifacts in the reconstructions and achieves considerable radiation exposure reductions.
Intervention assessment tool for primary tumors in the liver
Authors: Oyarzun Cristina Laura , Drechsler Klaus , Erdt Marius , Wesarg Stefan , Bale Reto 
Published: September 2018

Abstract
After a liver tumor intervention the medical doctor has to compare both pre and postoperative CT acquisitions to ensure that all carcinogenic cells are destroyed. A correct assessment of the intervention is of vital importance, since it will reduce the probability of tumor recurrence. Some methods have been proposed to support the medical doctors during the assessment process, however, all of them focus on secondary tumors. In this paper a tool is presented that enables the outcome validation for both primary and secondary tumors. Therefore, a multiphase registration (preoperative arterial and portal phases) followed by a registration between the pre and postoperative CT images is carried out. The first registration is in charge of the primary tumors that are only visible in the arterial phase. The secondary tumors will be incorporated in the second registration step. Finally, the part of the tumor that was not covered by the necrosis is quantified and visualized. The method has been tested in 9 patients, with an average registration error of 1.41 mm.
Motility analysis by means of video tracked markers
Authors: Lente Kornelius , Somerlik-Fuchs Karin H. , Schiemer Jonas Friedrich , Heimann Axel , Ruff Roman , Baumgart Jan , Hoffmann Klaus-Peter , Krüger Thilo B. , Kneist Werner 
Published: September 2018

Abstract
The motility of the gastrointestinal tract is crucial for digestive activity and dysfunction can lead to severe disease pattern. A method for analysing the motility is needed when treatment approaches shall be evaluated. Therefore markers attached to different locations on the stomach and the bowel of pigs are video tracked in this research study. The markers are designed to provide a high contrast and have an adhesive side for fixation. Above the operation field a video camera has been placed to film the markers during the procedure. To analyse the video data a special algorithm has been implemented. The algorithm requires a registration process at the beginning of each recording which allows the parallel tracking of multiple markers. After the registration the algorithm tracks the position of the marker frame by frame. Each frame is converted into a greyscale picture by adding specified colour values of each pixel. This allows emphasizing certain colours. The centre of the marker is determined by computing the horizontal and vertical centre of the marker starting at the corresponding marker position of the previous frame. After completion the data is stored as coordinates and a video with the marker position displayed for further processing. For advanced analysis the data can be synchronized with electromyography signals, for example. The marked videos show a promising tracking of the markers. However, if the algorithm loses track of a marker during a recording, it is unlikely to relocate it due to the successive processing of the frames. Nevertheless this method provides a simple and easy to use solution for movement detection of the gastrointestinal tract.
An In vitro Laboratory Investigation on Layer Thickness-Independent Prediction of the Hemoglobin Concentration
Authors: Wegerich Philipp , Gehring Hartmut 
Published: September 2018

Abstract
In the noninvasive determination of the hemoglobin concentration a main challenge is the "optical path". With sensors - fixed on human skin - the optical path cannot be exactly determined, as it is defined as the layer thickness in the Lambert Beer principle. The layer thickness is significantly involved in the optical interactions in the tissue. To circumvent this problem self-learning algorithms were evaluated which provide the hemoglobin concentration from reflection and transmission data without knowledge of the layer thickness. First various regression models were trained based on an high rate data set. To evaluate the six most promising models, a prediction dataset was measured in a prospective randomized and blinded study to guarantee integrity of the results. For both data sets, the transmission and reflection of diluted heparinized erythrocyte concentrate was determined with a double integrating sphere setup (laser diodes with 780 to 1310 nm). The evaluated hemoglobin concentrations ranged from 4 to 16 g/dl at a constant oxygen saturation above 97 %. Optical flow through cuvettes (1, 2, 3 mm) simulated different layer thicknesses of the blood. The evaluation of the predictions yielded that the layer thickness independent prediction of the hemoglobin concentration is feasible with the selected approaches. The mean absolute error (MAE) of the best regression model (GPRM - Matern 5/2) is 0.79 g/dl. In the clinically relevant tHb range of less than 8 g/dl the MAE was as low as 0.52 g/dl.