bluuebunny/crossref_metadata_2025 huggingface dataset:
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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Visualization and Parametrization of the Motion Behaviour of Subviral Particles
Authors: Kaak Michelle , Rausch Andreas , Müller Dennis , Schanze Thomas
Published: September 2018

The development of a drug against pathogens of hemorrhagic fever, like the Marburg virus, is a great challenge. Therefore, accurate knowledge of the properties of subviral particles in the host cell must be obtained. The base for subviral particle analysis is a special fluorescence microscopy technique. In order to automate and visualize the subviral particles’ motion patterns, previously a tracking algorithm was developed. In this article a new algorithm to parameterize and visualize the achieved particle tracks is introduced. A good potential for a fast data recognition is shown, with constantly respecting a high usability for pharmaceutical researchers. This algorithm was tested on both simulated and real data and provides reproducible results.
Magnetoneurograhy of an Electrically Stimulated Arm Nerve
Authors: Elzenheimer Eric , Laufs Helmut , Sander-Thömmes Tilmann , Schmidt Gerhard
Published: September 2018

For further development and optimization of novel uncooled magnetoelectric (ME) sensors, a better understanding of spectral power distribution and signal strength of nerve signals is of high interest. For obtaining information on these signal properties, Superconducting Quantum Interference Device (SQUID) measurements were performed at the Physikalisch-Technische Bundesanstalt (PTB) in Berlin. Signal amplitudes were subject-dependent and ranged from 17 fT to 60 fT in a frequency range from 100 Hz to 1 kHz. The required SQUID averaging time was in the range of minutes, while for current ME sensors significantly longer averaging times are expected to be necessary.
Measuring of calcification risk with polymer microchips
Authors: Bavendiek Julia , Sackmann Johannes , Schomburg Werner Karl , Gräber Steffen , Jahnen-Dechent Wilhelm , Pasch Andreas
Published: September 2018

It has been shown that the formation of calcium phosphate crystals can be detected in patient blood using a polymer microchip manufactured by ultrasonic processing. Ultrasonic processing is recently evolving for the fabrication of low-cost microfluidic devices from thermoplastic polymers. The formation of calcium phosphate crystals can be measured in the blood serum of a patient both optically from a change in turbidity or in electrical resistance.
Dynamic Time Warping of Pulse Wave Curves
Authors: Pielmuş Alexandru-Gabriel , Osterland Dennis , Tigges Timo , Klum Michael , Orglmeister Reinhold , Feldheiser Aarne , Hunsicker Oliver
Published: September 2018

Being able to non-obtrusively and continuously monitor arterial blood pressure is of great interest, particularly in the context of wearable sensors. A common limitation is the need for dedicated hardware, which is either obtrusive or expensive. In our current work, we investigate unimodal pulse waves from three handily accessible heterogeneous sources: photoplethysmography, bioimpedance and pulse applanation tonometry. We derive and evaluate multiple parameters regarding their correlation to reference blood pressure curves. These parameters stem from features of the warping paths resulting from dynamic and derivative dynamic time warping. The warping is performed between adjacent pulses or to a reference waveform. Spearman Rho coefficients of up to 0.98 and averaging 0.77 at highly significant p-values are recorded for single parameters. We record mean absolute deviation values of 0.08 across subjects. The results indicate there are negligible lags between reference and parameter curves. The sign of the correlation coefficients is consistent only for a small subset of parameters; the underlying cause could not yet be identified. We conclude that the warping path approach seems a promising way to go, yet still needs refinement. In particular, developing a time and amplitude warping method is paramount. Since warping quantizes all the morphological changes in the pulse wave without fiducial point detection, it could become a powerful tool for future investigations.
Using singular value decomposition for generalized linear autoregression of signals
Authors: Schanze Thomas
Published: September 2018

Autoregressive models (AR) are fundamental for analysis, representation, and prediction of signals. AR modelling uses the premise that past signal values influence current ones. This influence is causal and is modelled as a linear superposition, because a weighted addition of past values is used. The calculation of the required linear superposition parameters or weights can be done by the classical Yule-Walker approach or by least squares procedures. Here we show how to use singular value decomposition (SVD) for generalized linear autoregression (GLAR), i.e. using SVD to compute the weights of a linear combination of functions of given signal values and to check or optimize the GLAR model. The GLAR approach opens the possibility to take directly into account non-linear influences from past to current signal values. T he potential of this approach for analysis and representation is presented and demonstrated for simulated signals, i.e. pure and noisy sequences of non-linear recursions, and biomedical signals.
Monte-Carlo parameter variation study of cardiovascular pathologies to quantify parameter specific signal uncertainty
Authors: Krickl Stefan , Bernhard Stefan
Published: September 2018

Cardiovascular diseases are the leading cause of death worldwide. Early detection of abnormal vascular morphologies like aneurysms in the abdominal (abdominal aortic aneurysm, AAA) or thoracic aorta (thoracic aortic aneurysm, TAA) are essential to prevent fatal events. The aim of this study is the development of a patient-specific simulation model to obtain statistical information about ab- /normal pressure-flow conditions to improve the basic understanding and methods for the early detection of diseases. For this purpose, the numerical cardiovascular modeling tool SISCA was used, to generate a series of simulations by Monte- Carlo parameter variation. The considered variational scenario was built upon a control group of normal patients, deriving two pathological conditions for AAA and TAA with different severity and location. Therefore, the nominal diameters were enlarged between 200 % and 500 %, while the length of the aneurysms were modified within a range of 30 and 90 mm. Within each statistical set the convergence was tested by the bootstrap method ensuring that within a set of 3500 runs a 2 % deviation error of the mean value of the blood pressure was obtained compared to a set of 10000 runs.The parameter variation method allows the generation of disease specific data in the context of physiological/clinical findings and consequently the disease specific quantification of signal uncertainties and variances.
High-density Mapping Reveals Short-term Reversibility of Atrial Ablation Lesions
Authors: Huhn Oliver , Pollnow Stefan , Unger Laura , Dössel Olaf , Oesterlein Tobias , Luik Armin , Schmitt Claus
Published: September 2018

Cardiac arrhythmias such as atrial fibrillation occur frequently in industrialized countries. Radiofrequency ablation (RFA) is a standard treatment if drug therapy fails. This minimally invasive surgery aims at stabilizing the heart rhythm on a permanent basis. However, the procedure commonly needs to be repeated because of the high recurrence rate of arrhythmias. Non-transmural lesions as well as gaps within linear lesions are among the main problems during the RFA. The assessment of lesion formation is not adequate in state of the art procedures. Therefore, the aim of this study is to investigate the short-term reversibility of lesions using human electrograms recorded by a high-density mapping system during an electrophysiological study (EPS). A predefined measurement protocol was executed during the EPS in order to create three ablation points in the left atrium. Subsequently, after preprocessing the recorded signals, electrogram (EGM) paths were formed along the endocardial surface of the atrium. By analyzing changes of peak to peak amplitudes of unipolar EGMs before and after ablation, it was possible to distinguish lesion area and healthy myocardium. The peak to peak amplitudes of the EGMs decreased by 40-61% after 30 seconds of ablation. Furthermore, we analyzed the morphological changes of EGMs surrounding the lesion. High-density mapping data showed that not only the tissue, which had direct contact with the catheter tip during the RFA, but also the surrounding tissue was affected. This was demonstrated by low peak to peak amplitudes in large areas with a width of 14 mm around the center of the ablation lesion. After right pulmonary vein isolation, high-density mapping was repeated on the previous lesions. The outer region of RFA-treated tissue appears to recover as opposed to the central core of the ablation point. This observation suggests that the meaningfulness of an immediate remap after ablation during an EPS may lead the physician to false conclusions
Seizure Prediction by Multivariate Autoregressive Model Order Optimization
Authors: Mühlberg Katja , Müller Jens , Tetzlaff Ronald
Published: September 2018

For several decades, researchers are aiming for the detection of precursors of epileptic seizures. A system that is able to issue a warning about an impending seizure could dramatically improve the quality of life of affected patients. In this work, we apply multivariate autoregressive (MVAR) modeling to intracranial electroencephalography (iEEG) recordings of patients with therapy resistant epilepsy. As compared to our previous investigations, we studied the optimal model order of the autoregressive process as a feature for seizure prediction. In a statistical evaluation, we obtain significant results for 17 out of 20 patients.
Hyperspectral based discrimination of thyroid and parathyroid during surgery
Authors: Barberio Manuel , Maktabi Marianne , Gockel Ines , Rayes Nada , Jansen-Winkeln Boris , Köhler Hannes , Rabe Sebastian M. , Seidemann Lena , Takoh Jonathan P. , Diana Michele , Neumuth Thomas , Chalopin Claire
Published: September 2018

Unintended injuring of anatomical structures during endocrine neck operations can have severe consequences for patient. Especially the nerves and the parathyroid gland can be hard to identify visually. Therefore, intraoperative methods are needed to support the surgeon in this task. Hyperspectral imaging (HSI) is a new approach in the medical area which combines a camera with a spectrometer. It showed promising results for the discrimination of tissue. In this work, HSI-data of seven patients were acquired during thyroid and parathyroid operations. The mean absorbance spectra of both glands showed differences in the range between 600 and 700 nm and at 760 and 960 nm. This means that thyroid and parathyroid have different oxygenation states and different contents of deoxygenated hemoglobin and water. From these observations, it is possible to define spectral signatures to characterize both glands. We showed on one patient how spectral signatures can be used in classification algorithms to automatically identify the thyroid and parathyroid from other structures.
Minimally invasive mastoidectomy approach using a mouldable surgical targeting system
Authors: Rau Thomas S. , Witte Sina , Uhlenbusch Lea , Lexow Jakob , Hügl Silke , Majdani Omid , Lenarz Thomas
Published: September 2018

Hearing restoration using a cochlear implant requires a surgical access to the inner ear. In order to enhance patient safety, reduce trauma, and shorten the patient’s time under anaesthesia current research focusses on minimally invasive cochlear implantation surgery by drilling only a single bore hole. This demands a highly accurate surgical assistance device to guide the drill along a predetermined trajectory planned in patient’s image data. In this study a recently developed surgical targeting system was evaluated for the first time in a human cadaver trial. After screwing a reference frame on a temporal bone specimen and imaging of both, a trajectory through the facial recess was planned in order to reach the middle ear. Based on this plan a patient specific surgical template including a linear guide for the surgical drill was composed utilizing bone cement. After the hardening of the bone cement the surgical template was mounted on top of the reference frame. The drilling could be performed as previously planned without harming facial nerve and chorda tympani. The deviation of the actual drill hole to the planned trajectory was 0.17 mm at the level of the facial recess. The minimal distance of the drill hole to the facial nerve was 0.59 mm. This proof-of-concept study demonstrates the feasibility of performing the access to the middle ear in a minimally invasive manner using the mouldable surgical targeting system. The presented process allows the patient specific individualization of a drill guide under sterile conditions. This might facilitate its integration into clinical routine.
Modular design of versatile surgical mini-robots
Authors: Theisgen Lukas , de la Fuente Matías , Radermacher Klaus
Published: September 2018

Surgical robots have been introduced in the field of Computer Assisted Surgery (CAS) to assist the surgeon by providing an accurate link between the computer-based plan and the exact (a) positioning or (b) dynamic path control of an instrument on the operating site respectively. Whereas initial systems mostly have been based on an active supervisory control scheme of industrial robots with large universal workspaces, later on specialized miniaturized kinematics have been proposed, with restricted workspaces adapted to specific applications in order to ease handling and provide inherent safety properties. However, this specialization resulted in even narrower fields of application, low quantities and higher costs. Modularization seems to be a key factor to combine the benefits of both approaches. In this paper two modular robotic solutions, validated in the context of their purpose, are analysed regarding their modular design. Based on this, the potential of modularity for instrument guiding tasks in surgery is discussed.
Evaluating Convolutional Neural Network and Hidden Markov Model for Recognising Surgical Phases in Sigmoid Resection
Authors: Jalal Nour Aldeen , Abdulnaki Alshirbaji Tamer , Möller Knut
Published: September 2018

Surgical workflow analysis in laparoscopic surgeries has been studied widely during last years because of its various applications. For example, optimising the schedule of operating rooms (OR) and developing a context-aware system that supports surgical team during the intervention. Surgical phase recognition has been applied to various kinds of laparoscopic procedures, mainly of type cholecystectomy. Sigmoid resection procedures are considered more complex than cholecystectomy, and they have not been extensively studied. Therefore, the focus of this work is to study phase recognition in sigmoid resection. In this paper, a convolutional neural network (CNN) architecture and Hidden Markov Model (HMM) were evaluated for performing phase recognition in sigmoid resection videos. The CNN is an extension of a pretrained model, and it was fine-tuned to perform the recognition. To consider the temporal aspect of the phase sequences, confidences obtained by the CNN were then provided into a HMM to release final classification. Experimental results show a low performance of the proposed method to recognise surgical phases in such complex procedures. Therefore, the dataset used for the evaluation was also reviewed, and statistics of each phase were generated.
Detecting Signatures in Hyperspectral Image Data of Wounds: A Compound Model of Self- Organizing Map and Least Square Fitting
Authors: Mohammed Redwan Abdo A. , Schäle Daniel , Hornberger Christoph , Emmert Steffen
Published: September 2018

The purpose of this study is to develop a method to discriminate spectral signatures in wound tissue. We have collected a training set of the intensity of the remitted light for different types of wound tissue from different patients using a TIVITA™ tissue camera. We used a neural network technique (self-organizing map) to group areas with the same spectral properties together. The results of this work indicates that neural network models are capable of finding clusters of closely related hyperspectral signatures in wound tissue, and thus can be used as a powerful tool to reach the anticipated classification. Moreover, we used a least square method to fit literature spectra (i.e. oxygenated haemoglobin (O2Hb), deoxygenated haemoglobin (HHb), water and fat) to the learned spectral classes. This procedure enables us to label each spectral class with the corresponding absorbance properties for the different absorbance of interest (i.e. O2Hb, HHb, water and fat). The calculated parameters of a testing set were consistent with the expected behaviour and show a good agreement with the results of a second algorithm which is used in the TIVITA™ tissue camera.
Hierarchical Analysis of Thorax Models to Measure Tidal Volume
Authors: Laufer Bernhard , Krueger-Ziolek Sabine , Moeller Knut , Docherty Paul David , Hoeflinger Fabian , Reindl Leonhard
Published: September 2018

Motion tracking of thorax kinematics can be used to determine respiration. However, determining a minimal sensor configuration from 64 candidate sensor locations is associated with high computational costs. Hence, a hierarchical optimization method was proposed to determine the optimal combination of sensors. The hierarchical method was assessed by its ability to quickly determine the sensor combination that will yield optimal modelled tidal volume compared to body plethysmograph measurements. This method was able to find the optimal sensor combinations, in approximately 2% of the estimated time required by an exhaustive search.
CurvChip - chip platform for investigating cell responses to curved surface features
Authors: Kemkemer Ralf , Frey Kerstin , Fischer Alena , Krastev Rumen
Published: September 2018

Surface topographies are often discussed as an important parameter influencing basic cell behavior. Whereas most in-vitro studies deal with microstructures with sharp edges, smooth, curved microscale topographies might be more relevant concerning in-vivo situations. Addressing the lack of highly defined surfaces with varying curvature, we present a topography chip system with 3D curved features of varying spacing, curvature radii as well as varying overall dimensions of curved surfaces. The CurvChip is produced by low-cost photolithography with thermal reflow, subsequent (repetitive) PDMS molding and hot embossing. The platform facilitates the systematic invitro investigation of the impact of substrate curvature on cell types like epithelial, endothelial, smooth muscle cells, or stem cells. Such investigations will not only help to further understand the mechanism of curvature sensation but may also contribute to optimize cellmaterial interactions in the field of regenerative medicine.
Sonographic Detection of Iron Oxide Nanoparticles Employing Shear Waves
Authors: Fink Michael , Lyer Stefan , Alexiou Christoph , Ermert Helmut
Published: September 2018

Research in biomedical nanotechnology led already to a variety of applications of nanoparticles in diagnosis as well as in therapy. One of these medical applications is Magnetic Drug Targeting, a promising cancer treatment technique. The aim of this medical attendance is a local chemotherapeutic treatment of the cancerous tissue. For this purpose, chemotherapeutic drugs are bound to magnetic nanoparticles and accumulated in the tumor area by means of an external static magnetic field. Hereby, a well-defined particle concentration in the cancerous tissue requires monitoring of the particle accumulation. Therefore, we present an ultrasound imaging technique that is capable of detecting quantitatively the concentration of iron oxide nanoparticles in biological tissue. The evaluation is based on the variation of the speed of sound of an induced shear wave with respect to the particle concentration.
Vascular response towards biodegradable sirolimus-eluting polymeric scaffolds in the porcine model
Authors: Kischkel Sabine , Bünger Carsten M. , Püschel Anja , Schareck Wolfgang , Schmitz Klaus-Peter , Grabow Niels
Published: September 2018

In this study, PLLA-based sirolimus-eluting polymer scaffolds and permanent bare-metal stents (316L) were implanted interventionally into both common carotid arteries (CCA) of 6 female pigs via the left common iliac artery (8F-sheath). The pigs were administered dual antiplatelet drugs peroral starting 3 days before the procedure until the end of the study. Stented CCA segments were explanted after 12 weeks, and processed for quantitative histomorphometry, and estimation of vascular inflammation and injury scores. SIR/polymer scaffolds showed a decreased residual lumen area and higher restenosis after 12 weeks (4.45 ± 2.23 mm² and 61.68 ± 22.39%) as compared to the 316L reference stent (16.53 ± 1.23 mm² and 6.65 ± 1.30%). After 12 weeks, inflammation score and vascular injury score were higher in the SIR/polymer group (1.90 ± 1.15 and 1.26 ± 0.87) compared to the 316L group (0.57 ± 0.37 and 0.83 ± 0.34).
Development of a graphical user interface and cross manufacturer adaptation of a program for determining the pulse wave velocity in the aorta from phase-contrast magnetic resonance images
Authors: Schareck Constantin , Oechtering Thekla , Frydrychowicz Alex , Koch Martin
Published: September 2018

Due to the periodic contraction of the heart, a pulse-shaped course of the blood velocity is caused in the aortic system. The speed at which this pulse wave moves is called pulse wave velocity (PWV). Since it depends, among other parameters, on the elasticity of the vascular wall, it can be used clinically as an indicator of atherosclerotic changes and, above all, as a measure of the risk of stroke for hypertensive patients. PWV can be determined non-invasively if the blood flow in the aorta is measured via flow-sensitive MRI. Within the scope of this work, existing phase-contrast (PC) image analysis algorithms, resulting in the PWV, were embedded in a graphical user interface (GUI). These algorithms were only able to evaluate PC images which were acquired on a Philips tomograph. Therefore they have been extended for the analysis of PC images acquired on a Siemens tomograph.
Biphasic parameter identification of equine articular cartilage from creep indentation data using an optimized 3D FE-based method
Authors: Reuter Thomas , Hurschler Christof
Published: September 2018

Mechanical parameters of hard and soft tissues are explicit markers for quantitative tissue characterization. In this study, we present a biphasic 3D-FE-based method to determine the biomechanical properties of equine articular cartilage from creep indentation tests (F = 0.1 N, t = 1000 s). The FE-model computation was optimized by exploiting the axial symmetry and mesh resolution. Parameter identification was executed with the Levenberg-Marquardt-algorithm. Additionally, sensitivity analyses of the calculated biomechanical parameters were performed. Results show that the Young’s modulus has the largest influence and the Poisson’s ratio of ν ≤ 0.1 is rather insensitive. The R² of the fit results varies between 0.882 and 0.974. The determined values for the Young’s modulus were 0.806 ± 0.093 MPa, the Poisson’s ratio 0.03 ± 0.06 and the permeability 0.012 ± 0.002 mm4/Ns. Future work will deal with mathematical extensions of the biphasic 3D-FE-model.
Comparison of biphasic material properties of equine articular cartilage from stress relaxation indentation tests with and without tension-compression nonlinearity
Authors: Reuter Thomas , Hurschler Christof
Published: September 2018

The mechanical parameters of articular cartilage estimated from indentation tests depend on the constitutive model adopted to analyze the data. In this study, we present a 3D-FE-based method to determine the biomechanical properties of equine articular cartilage from stress relaxation indentation tests (ε = 6 %, t = 1000 s) whereby articular cartilage is modeled as a biphasic material without (BM) and with tension-compression nonlinearity (BMTCN). The FEmodel computation was optimized by exploiting the axial symmetry and mesh resolution. Parameter identification was executed with the Levenberg-Marquardt-algorithm. The R² of the fit results varies between 0.695 and 0.930 for the BMmodel and between 0.877 and 0.958 for the BMTCN-model. The differences of the R² occur from the more exact description of the initial stress relaxation behaviour by the fiber modulus from the BMTCN-model. The fiber modulus defines the collagen matrix of cartilage. Furthermore, for both models the determined values of Young’s modulus and permeability were in the same order of magnitude.
Molecular processes of corneal collagen cross-linking in keratoconus therapy
Authors: Melcher Steven , Spörl Eberhard , Koch Edmund , Steiner Gerald
Published: September 2018

Corneal collagen cross-linking (CXL) with riboflavin and UVA light is a therapeutic procedure to restore the mechanical stability of corneal tissue. The treatment method applies to pathological tissue changes, such as keratoconus. It induces the photochemical formation of new collagen cross-links. Although therapeutic effects are indisputable, the exact molecular process of CXL and how cross-links are formed is still unclear. In this work, Fouriertransform infrared (FT-IR) spectroscopy is used to investigate the cross-linking process. For that purpose, in-situ experiments with porcine corneas are carried out using attenuated total reflection (ATR) spectroscopy. Furthermore, IR micro-spectroscopic imaging in transmission mode is used to investigate thin tissue sections of the cornea and initial approaches for the distinction of cross-linked and untreated tissue by IR microspectroscopic imaging were performed. Multivariate methods are applied to access changes that occur as a result of CXL. It is shown that spectral changes after cross-linking are caused predominantly by an increase of methyl- and methylene groups as well as primary and secondary amines. In addition, a decrease of carbonyl groups could be observed.
Influence of additives on physico-chemical properties of electrospun poly(L-lactide)
Authors: Arbeiter Daniela , Kohse Stefanie , Eickner Thomas , Grabow Nils , Schmitz Klaus-Peter
Published: September 2018

Electrospun poly(L-lactide) (PLLA) nonwoven represent potential options for biodegradable medical implants. They can be manufactured with high reproducibility and do offer the potential for chemical modification to alter matrix properties. In our study, we investigate the mechanical, thermal and morphological properties of PLLA fiber matrices. Fibrous nonwovens were fabricated from polymer solution by needle electrospinning. The polymer solutions were loaded with Triton X-100 (TX- 100), formic acid and tetraethyl ammonium chloride (TEAC) with respect to polymer weight. Morphology of the PLLA nonwoven scaffolds was examined with SEM. We performed uniaxial tensile tests and differential scanning calorimetry (DSC). Different concentrations of the additives TEAC, formic acid and Triton X-100 lead to strong changes regarding mechanical and thermal properties of the electrospun PLLA fiber matrices. In comparison with mechanical properties of established biological tissue materials, the results indicate the suitability for medical applications.
Development of biodegradable stents for the treatment of Eustachian tube dysfunction
Authors: Schümann Kerstin , Wilfling Tamara , Paasche Gerrit , Schuon Robert , Robert Schuon , Lenarz Thomas , Schmidt Wolfram , Grabow Niels , Müller Heinz , Momma Carsten , Schmitz Klaus-Peter
Published: September 2018

To provide an effective and safe therapy for chronic Eustachian tube dysfunction (ETD), biodegradable stents should be developed to restore important functions, e.g. middle ear ventilation and drainage. After defining general requirements specifications, stent designs of cardiovascular polymeric stents were modified according to dimensions and conditions of the Eustachian tube. Finite element simulations demonstrated the crimping capacity of the developed stent design and the ability of expansion in the specific geometry of the target location. Subsequent in vitro tests of stent prototypes showed satisfying properties concerning crimpability, expansion behavior and elastic recoil to demonstrate general feasibility. Further developments and additional testing will advance the implementation of a new treatment option of ETD.