bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of microsleep events in a car driving simulation study using electrocardiographic features
Authors: Lenis Gustavo , Reichensperger Patrick , Sommer David , Heinze Christian , Golz Martin , Dössel Olaf
Published: December 2016

Microsleep events (MSE) are short intrusions of sleep under the demand of sustained attention. They can impose a major threat to safety while driving a car and are considered one of the most significant causes of traffic accidents. Driver’s fatigue and MSE account for up to 20% of all car crashes in Europe and at least 100,000 accidents in the US every year. Unfortunately, there is not a standardized test developed to quantify the degree of vigilance of a driver. To account for this problem, different approaches based on biosignal analysis have been studied in the past. In this paper, we investigate an electrocardiographic-based detection of MSE using morphological and rhythmical features. 14 records from a car driving simulation study with a high incidence of MSE were analyzed and the behavior of the ECG features before and after an MSE in relation to reference baseline values (without drowsiness) were investigated. The results show that MSE cannot be detected (or predicted) using only the ECG. However, in the presence of MSE, the rhythmical and morphological features were observed to be significantly different than the ones calculated for the reference signal without sleepiness. In particular, when MSE were present, the heart rate diminished while the heart rate variability increased. Time distances between P wave and R peak, and R peak and T wave and their dispersion increased also. This demonstrates a noticeable change of the autonomous regulation of the heart. In future, the ECG parameter could be used as a surrogate measure of fatigue.
Automation of a test bench for accessing the bendability of electrospun vascular grafts
Authors: Bensch Martin , Müller Marc , Bode Michael , Glasmacher Birgit
Published: December 2016

One of the greatest challenges in cardiovascular tissue engineering is to develop vascular grafts with properties similar to autologous vessels. A promising approach is the fabrication of scaffolds from biodegradable polymers by electrospinning. Unstructured vascular subs possess a weak dimensional stability resulting in lumen collapse when subjected to bending stress. In order to examine different structured grafts, a standardised test method is required. A manual test method, designed in a former study, was adopted in terms of standardisation and automation. Therefore, a control system was programmed to regulate the required electronics. The electronic circuit was then developed and put into service. To fix samples into the test bench a new sample holder and a new collector for electrospinning were designed. Subsequently, a validation showed the new systems’ improved functionality compared to the former test bench. The samples were manufactured with the new collector. They could be fixed to the sample holder with high repeatability. The demand for vascular grafts with biological and mechanical properties similar to autologous vessels requires a standardised test method to examine bendability. The new test system enables the scaffolds to be examined regarding bendability with low personal expense and a simultaneously high degree of reproducibility. In addition, the new collector geometry can be easily adapted to higher or lower inner diameters. Hence, a new sample geometry was developed within this work.
Influence of storage conditions on the release of growth factors in platelet-rich blood derivatives
Authors: Düregger Katharina , Peng Anqi , Eblenkamp Markus
Published: December 2016

Thrombocytes can be concentrated in blood derivatives and used as autologous transplants e.g. for wound treatment due to the release of growth factors such as platelet derived growth factor (PDGF). Conditions for processing and storage of these platelet-rich blood derivatives influence the release of PDGF from the platelet-bound α-granules into the plasma. In this study Platelet rich plasma (PRP) and Platelet concentrate (PC) were produced with a fully automated centrifugation system. Storage of PRP and PC for 1 h up to 4 months at temperatures between −20°C and +37°C was applied with the aim of evaluating the influence on the amount of released PDGF. Storage at −20°C resulted in the highest release of PDGF in PRP and a time dependency was determined: prolonged storage up to 1 month in PRP and 10 days in PC increased the release of PDGF. Regardless of the storage conditions, the release of PDGF per platelet was higher in PC than in PRP.
Cryopreservation of cells using defined serum-free cryoprotective agents
Authors: Volbers Jan-Cedric , Lauterböck Lothar , Hofmann Nicola , Glasmacher Birgit
Published: December 2016

For regenerative purposes, there is a high demand for viable and active cells. A big issue is to have enough viable cells available at any given time. One solution is cryopreservation. In this context, DMSO is used as cryoprotective agent (CPA) along with fetal bovine serum for nutrient supply and stress shielding effects. To use these cells for human clinical studies, it is important to eliminate the serum to prevent foreign immune reactions and virus transmittance and DMSO for its toxic effect. In this study a serum free cryopreservation solution and protocol has been established. The combination of methylcellulose and poloxamer 188 provide the basis for the new CPA. Other additves are α-tocopherol, ectoine, prolin and ascorbic acid. The CPAs were examined with 3T3-cells and multipotent stromal cells from the common marmoset monkey (Callithrix jacchus). The cells were preserved with various CPA concentrations, incubation times and different cooling rates. To enable a higher throughput of encouraging conditions a fluorescence microscopy analysis was used. The use of methylcellulose, poloxamer 188 and α-tocopherol enables the reduction of DMSO [up to 2.5% (v/v)] and the elimination of serum without viability losses compared to control.
New bioreactor vessel for tissue engineering of human nasal septal chondrocytes
Authors: Princz Sascha , Wenzel Ulla , Schwarz Silke , Rotter Nicole , Hessling Martin
Published: December 2016

Cultivation of human nasal septal chondrocytes in a self-established automated bioreactor system with a new designed reactor glass vessel and the results of a computational fluid dynamics model are presented. The first results show the effect of a homogeneous fluidic condition of the continuous medium flow and the resulting stresses on the scaffolds’ surface and their influence on the migration of the cells into the scaffold matrix under these conditions. For this purpose computational models, generated with the computational fluid dynamics software STAR-CCM+, and the results of alcian blue staining for newly synthesized sulphated glycosaminoglycans have been compared during cultivation in the new and a first version of the glass reactor vessel with inhomogeneous fluidic conditions, with the same automated bioreactor system and under similar cultivation conditions.
Climate retainment in carbon dioxide incubators
Authors: Schuh Matthias B. , Kirsch Michael , Dillmann David , Breuer Franziska , Eblenkamp Markus
Published: December 2016

Ensuring optimal climate conditions during cultivation is essential for successful and reproducible cell culture based investigation. Being the gold standard, carbon dioxide incubators fulfill this demand in various geometries and sizes to suit diverse cultivation applications. A door opening results in a climate breakdown followed by a restoration period during which optimal conditions cannot be guaranteed. The following paper investigates the influence of incubator door design to optimize climate retainment during the above mentioned event.
Multiple factors influencing OR ventilation system effectiveness
Authors: Buhl Sebastian , Eschenbecher Nicole , Hentschel Sabine , Bulitta Clemens
Published: December 2016

The issue of surgical site infections has become more critical during the last years. The number of airborne microbes depends on the number released by the staff in the room or supplied from neighbouring rooms. In order to minimize the risk of nosocomial infections during surgical procedures technical developments like ventilation systems were introduced in the operating room (OR). In this study several factors like clothing and types of ventilation systems have been investigated and their impact on the effectiveness for reducing microbial burden in the OR has been assessed. In case of OR-gowns we found a benefit for a disposable Swedish clothing concept regarding microbiological contamination in comparison with the German standard multiuse clothing. Moreover our study shows that there is comparable effectiveness of a fairly novel temperature controlled airflow ventilation system (TAF) compared to standard low turbulent uni-directional airflow (TAV).
Evaluation of an app-based stress protocol
Authors: Noeh Claudius , Fonseca Carlos , Mollenhauer Johannes , Hofmann Simon , Steinbrecher Llisa , Haller Andreas , Scholtes Michael , Schudt Florian , Sohrabi Keywan , Gross Volker
Published: December 2016

Stress is a major influence on the quality of life in our fast-moving society. This paper describes a standardized and contemporary protocol that is capable of inducing moderate psychological stress in a laboratory setting. Furthermore, it evaluates its effects on physiological biomarkers. The protocol called “THM-Stresstest” mainly consists of a rest period (30 min), an app-based stress test under the surveillance of an audience (4 min) and a regeneration period (32 min). We investigated 12 subjects to evaluate the developed protocol. We could show significant changes in heart rate variability, electromyography, electro dermal activity and salivary cortisol and α-amylase. From this data we conclude that the THM-Stresstest can serve as a psychobiological tool for provoking responses in the cardiovascular-, the endocrine and exocrine system as well as the sympathetic part of the central nervous system.
Surgical navigation with QR codes
Authors: Katanacho Manuel , De la Cadena Wladimir , Engel Sebastian
Published: December 2016

The presented work is an alternative to established measurement systems in surgical navigation. The system is based on camera based tracking of QR code markers. The application uses a single video camera, integrated in a surgical lamp, that captures the QR markers attached to surgical instruments and to the patient.
Investigation of the pressure gradient of embolic protection devices
Authors: Kurzhals Anja , Matthies Jörn-Bo , Andresen Reimer , Grabow Niels , Schmitz Klaus-Peter , Schmidt Wolfram
Published: December 2016

To avoid debris coming to the cerebral vessels during carotid artery stenting, embolic protection devices (EPD) are placed in front of the lesion. To evaluate their influence on the antegrade blood flow a test setup with a silicone tube simulating the internal carotid artery is realized. The pressure gradient of five different EPD was measured while particles were brought into the circuit and were caught by the systems. Additionally the microscopic structure of the systems was observed to correlate the morphology and the pressure gradient. The FiberNet device had the lowest pressure gradient. It was the only system that consists of fibers contrary to the systems RX Accunet, Angioguard RX, FilterWireEZ and EmboshieldNAV that contain porous membranes.
Computer assistance in femoral derotation osteotomy: a bottom-up approach
Authors: Auer Christoph , Kallus Sebastian , Geisbüsch Andreas , Dreher Thomas , Dickhaus Hartmut
Published: December 2016

Severe gait abnormalities in patients with cerebral palsy are often treated by correction osteotomy. The established procedure of femoral derotation osteotomy (FDO) has proven effective to realign femur anteversion. Nevertheless, studies have revealed that therapy outcome is subject to substantial inter-patient variability and systematic loss of correction. Our previous work suggests that practical limitations in FDO may significantly contribute to this effect. In this work, we propose a novel computer assisted measurement system to support FDO with objective measurement (desired accuracy: ∼ ± 3°) and continuous monitoring of derotation. A prototype system based on the clinically emerging electromagnetic tracking technology is demonstrated which incorporates technical and operational considerations to enable continuous measurement in OR conditions while preserving the conventional workflow without disruptions. In phantom studies, the achieved measurement accuracy (standard error

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proved high potential and may hugely benefit the quality of surgical execution. Currently, the prototype system is assessed under OR conditions in an in-vivo study with CP patients. Early experience shows high appreciation among surgeons and good potential for future application.
Resectoscope with an easy to use twist mechanism for improved handling
Authors: Fritzsche Holger , Boese Axel , Schostak Martin , Friebe Michael
Published: December 2016

One of the oldest methods used in minimally invasive surgeries is the transurethral resection. This is an operation technique in which diseased tissue from the bladder or the prostate is removed using a resectoscope through the urethra [Schostak M, Blana A, Hrsg. Alternative operative Therapien in der Uroonkologie. Berlin, Heidelberg, Springer Berlin Heidelberg; 2016]. A resectoscope has a channel for the view of the surgeon, a liquid supply, a working channel and a hand piece which could rotate up to 360 degrees. A RF- electrode on the tip of the resectoscope is used to cut out pathological growths. For diseased tissue which is located in the bladder on the ventral side, a rotation of the resectoscope up to 180 degrees is necessary. This means on the one side tiring of the hands, wrist pain and a change of the position of the operating surgeon. On the other side a reorganization of the connected tubes and cables is necessary. To avoid these problems and integrate additional features a standard resectoscope was adapted with an easy to use twist mechanism. After discussion with experienced urological surgeons a complete new design of the resectoscope with a twist mechanism in combination with a gyro sensor and a reference display was realized.
In vitro simulation of distribution processes following intramuscular injection
Authors: Probst Mareike , Schmidt Martin , Weitschies Werner , Seidlitz Anne
Published: December 2016

There is an urgent need for in vitro dissolution test setups for intramuscularly applied dosage forms. Especially biorelevant methods are needed to predict the in vivo behavior of newly developed dosage forms in a realistic way. There is a lack of knowledge regarding critical in vivo parameters influencing the release and absorption behavior of an intramuscularly applied drug. In the presented work the focus was set on the simulation of blood perfusion and muscle tissue. A solid agarose gel, being incorporated in an open-pored foam, was used to mimic the gel phase of muscle tissue and implemented in a flow through cell. An aqueous solution of fluorescein sodium was injected. Compared to recently obtained in vivo results the distribution of the model substance was very slow. Furthermore an agarose gel of lower viscosity an open-pored foam and phosphate buffer saline pH 7.4 were implemented in a multi-channel-ceramic membrane serving as a holder for the muscle imitating material. Blood simulating release medium was perfused through the ceramic membrane including filling materials. Transport of the dissolved fluorescein sodium was, in case of the gel, not only determined by diffusion but also by convective transport processes. The more realistic the muscle simulating materials were constituted the less reproducible results were obtained with the designed test setups.
Adjusting inkjet printhead parameters to deposit drugs into micro-sized reservoirs
Authors: Mau Robert , Oldorf Paul , Peters Rigo , Seitz Hermann
Published: December 2016

Drug delivery systems (DDS) ensure that therapeutically effective drug concentrations are delivered locally to the target site. For that reason, it is common to coat implants with a degradable polymer which contains drugs. However, the use of polymers as a drug carrier has been associated with adverse side effects. For that reason, several technologies have been developed to design polymer-free DDS. In literature it has been shown that micro-sized reservoirs can be applied as drug reservoirs. Inkjet techniques are capable of depositing drugs into these reservoirs. In this study, two different geometries of micro-sized reservoirs have been laden with a drug (ASA) using a drop-on-demand inkjet printhead. Correlations between the characteristics of the drug solution, the operating parameters of the printhead and the geometric parameters of the reservoir are shown. It is indicated that wettability of the surface play a key role for drug deposition into micro-sized reservoirs.
A flexible standalone system with integrated sensor feedback for multi-pad electrode FES of the hand
Authors: Loitz Jan C. , Reinert Aljoscha , Neumann Ann-Kristin , Quandt Fanny , Schroeder Dietmar , Krautschneider Wolfgang H.
Published: December 2016

Functional electrical stimulation aims to help patients suffering from stroke or spinal cord injury to supplement lost motor function. Effective functional electrical stimulation requires precise placement of the stimulation electrode. Finding the correct placement, however, can be difficult and time consuming. Another common problem with functional electrical stimulation is early occurrence of muscle fatigue upon repetitive stimulation, limiting treatment efficiency. Both, precise electrode placement as well as the reduction of muscle fatigue can be achieved using multi-pad electrodes. Here we present a new standalone device for multi-pad functional electrical stimulation. The device is easy to use and designed to help patients recovering from stroke to train and perform opening of the hand.
Smart control for functional electrical stimulation with optimal pulse intensity
Authors: Reinert Aljoscha , Loitz Jan C. , Quandt Fanny , Schroeder Dietmar , Krautschneider Wolfgang H.
Published: December 2016

Transcutaneous electrical stimulation is a common treatment option for patients suffering from spinal cord injury or stroke. Two major difficulties arise when employing electrical stimulation in patients: Accurate stimulation electrode placement and configuration of optimal stimulation parameters. Optimizing the stimulation parameters has the advantage to reduce muscle fatigue after repetitive stimulation. Here we present a newly developed system which is able to automatically find the optimal individual stimulation intensity by varying the pulse length. The effectiveness is measured with flex sensors. By adapting the stimulation parameters, the effect of muscle fatigue can be compensated, allowing for a more stable movement upon stimulation over time.
Tactile display on the remaining hand for unilateral hand amputees
Authors: Li Tao , Huang Huaiqi , Antfolk Christian , Justiz Jörn , Koch Volker M.
Published: December 2016

Human rely profoundly on tactile feedback from fingertips to interact with the environment, whereas most hand prostheses used in clinics provide no tactile feedback. In this study we demonstrate the feasibility to use a tactile display glove that can be worn by a unilateral hand amputee on the remaining healthy hand to display tactile feedback from a hand prosthesis. The main benefit is that users could easily distinguish the feedback for each finger, even without training. The claimed advantage is supported by preliminary tests with healthy subjects. This approach may lead to the development of effective and affordable tactile display devices that provide tactile feedback for individual fingertip of hand prostheses.
Effects of sustained electrical stimulation on spasticity assessed by the pendulum test
Authors: Vargas Luna José L. , Guðfinnsdóttir Halla K. , Magnúsdóttir Gígja , Guðmundsdóttir Vilborg , Krenn Matthias , Mayr Winfried , Ludvigsdóttir Guðbjörg K. , Helgason Thordur
Published: December 2016

Neuromodulation using electrical stimulation is able to enhance motor control of individuals suffering an upper motor neuron disorder. This work examined the effect of sustained electrical stimulation to modify spasticity in the leg muscles. We applied transcutaneous spinal cord stimulation with a pulse rate of 50 Hz for 30 min. The subjects were assessed before and after the intervention using in a pendulum test setup. The motion of the free swinging leg was acquired through video tracking and goniometer measurements. The quantification was done through the R2n index which shows consistency identifying the spasticity levels. In all incomplete SCI subjects having severe spasticity, the results show that electrical stimulation is effective to modify the increased muscle tone.
An improved tracking framework for ultrasound probe localization in image-guided radiosurgery
Authors: Ipsen Svenja , Bruder Ralf , Jauer Philipp , Ernst Floris , Blanck Oliver , Schweikard Achim
Published: December 2016

Real-time target localization with ultrasound holds high potential for image guidance and motion compensation in radiosurgery due to its non-invasive image acquisition free from ionizing radiation. However, a two-step localization has to be performed when integrating ultrasound into the existing radiosurgery workflow. In addition to target localization inside the ultrasound volume, the probe itself has to be localized in order to transform the target position into treatment room coordinates. By adapting existing camera calibration tools, we have developed a method to extend the stereoscopic X-ray tracking system of a radiosurgery platform in order to locate objects such as marker geometries with six degrees of freedom. The calibration was performed with 0.1 mm reprojection error. By using the full area of the flat-panel detectors without pre-processing the extended software increased the tracking volume and resolution by up to 80%, substantially improving patient localization and marker detectability. Furthermore, marker-tracking showed sub-millimeter accuracy and rotational errors below 0.1°. This demonstrates that the developed extension framework can accurately localize marker geometries using an integrated X-ray system, establishing the link for the integration of real-time ultrasound image guidance into the existing system.
Learning discriminative classification models for grading anal intraepithelial neoplasia
Authors: Kainz Philipp , Mayrhofer-Reinhartshuber Michael , Sedivy Roland , Ahammer Helmut
Published: December 2016

Grading intraepithelial neoplasia is crucial to derive an accurate estimate of pre-cancerous stages and is currently performed by pathologists assessing histopathological images. Inter- and intra-observer variability can significantly be reduced, when reliable, quantitative image analysis is introduced into diagnostic processes. On a challenging dataset, we evaluated the potential of learning a classifier to grade anal intraepitelial neoplasia. Support vector machines were trained on images represented by fractal and statistical features. We show that pursuing a learning-based grading strategy yields highly reliable results. Compared to existing methods, the proposed method outperformed them by a significant margin.
Regularization of EIT reconstruction based on multi-scales wavelet transforms
Authors: Gong Bo , Schullcke Benjamin , Krueger-Ziolek Sabine , Moeller Knut
Published: December 2016

Electrical Impedance Tomography (EIT) intends to obtain the conductivity distribution of a domain from the electrical boundary conditions. This is an ill-posed inverse problem usually solved on finite element meshes. Wavelet transforms are widely used for medical image reconstruction. However, because of the irregular form of the finite element meshes, the canonical wavelet transforms is impossible to perform on meshes. In this article, we present a framework that combines multi-scales wavelet transforms and finite element meshes by viewing meshes as undirected graphs and applying spectral graph wavelet transform on the meshes.
Assessing MRI susceptibility artefact through an indicator of image distortion
Authors: Illanes Alfredo , Krug Johannes W. , Friebe Michael
Published: December 2016

Susceptibility artefacts in magnetic resonance imaging (MRI) caused by medical devices can result in a severe degradation of the MR image quality. The quantification of susceptibility artefacts is regulated by the ASTM standard which defines a manual method to assess the size of an artefact. This means that the estimated artefact size can be user dependent. To cope with this problem, we propose an algorithm to automatically quantify the size of such susceptibility artefacts. The algorithm is based on the analysis of a 3D surface generated from the 2D MR images. The results obtained by the automatic algorithm were compared to the manual measurements performed by study participants. The results show that the automatic and manual measurements follow the same trend. The clear advantage of the automated algorithm is the absence of the inter- and intra-observer variability. In addition, the algorithm also detects the slice containing the largest artefact which was not the case for the manual measurements.
A framework for feedback-based segmentation of 3D image stacks
Authors: Stegmaier Johannes , Peter Nico , Portl Julia , Mang Ira V. , Schröder Rasmus , Leitte Heike , Mikut Ralf , Reischl Markus
Published: December 2016

3D segmentation has become a widely used technique. However, automatic segmentation does not deliver high accuracy in optically dense images and manual segmentation lowers the throughput drastically. Therefore, we present a workflow for 3D segmentation being able to forecast segments based on a user-given ground truth. We provide the possibility to correct wrong forecasts and to repeatedly insert ground truth in the process. Our aim is to combine automated and manual segmentation and therefore to improve accuracy by a tunable amount of manual input.
Doppler optical coherence tomography as a promising tool for detecting fluid in the human middle ear
Authors: Kirsten Lars , Baumgärtner Simon , Erkkilä Mikael Timo , Golde Jonas , Kemper Max , Stoppe Thomas , Bornitz Matthias , Neudert Marcus , Zahnert Thomas , Koch Edmund
Published: December 2016

The treatment of otitis media requires classifying the effusion in the tympanic cavity for choosing appropriate therapeutic strategies. Otoscopic examination of the middle ear depends on the expertise of the physician and is often hampered in case of inflammatory alterations of the tympanic membrane. In otologic research, optical coherence tomography is an innovative non-invasive imaging technique utilized for visualizing the tympanic membrane. This ex vivo study presents the possibility of OCT and Doppler-OCT for the detection of effusions in the tympanic cavity. Structural OCT imaging allows the direct visualization of scattering fluids behind the tympanic membrane. In addition, the measurement of the reduced oscillation amplitude by means of Doppler-OCT permits the indirect detection of scattering and transparent fluids.
3D Local in vivo Environment (LivE) imaging for single cell protein analysis of bone tissue
Authors: Taylor Carly , Scheuren Ariane , Trüssel Andreas , Müller Ralph
Published: December 2016

The molecular processes behind pathological bone remodelling seen in diseases such as osteoporosis are unclear. However, a recently developed methodological platform known as Local in vivo Environment (LivE) imaging has been used to link cellular expression data to the local remodelling and mechanical environment in 2D sections of bone tissue. The method therefore can be used to give insight into which proteins are important for pathological bone remodelling. However, the cells within bone tissue exist as a 3D network. Therefore extension of LivE to accommodate 3D data may provide additional physiologically relevant information that is not possible to determine using 2D analysis alone. This will have implications for the further understanding of the cellular basis that underlies bone diseases such as osteoporosis. Here the LivE imaging technique is expanded to incorporate data from cells in a three dimensional manner via a serial sectioning technique. The methodological steps involved in the LivE imaging approach are defined and the optimisation steps performed are explained in detail.
Inside-Out access strategy using new trans-vascular catheter approach
Authors: Boese Axel , Foerstenberg Dirk , Wu Tong , Friebe Michael
Published: December 2016

Image guided minimal invasive treatment can have large benefits for patient recovery and is lowering hospitalisation costs. But an access path, minimizing patient’s risk, is needed to reach the target structure inside of the body. Beside the use of natural orifices like oral, vaginal or anal cavities, a percutaneous puncture is common to enter the body. Also an interstitial path can be selected but if the pathological structure is situated in the deep, a long accesses path is required. Thereby the risk of additional damage and affecting organ functionality is increased. A possible option to come closer to the target structure with less organ damage is by using the vascular system. Entering the vessel from an uncritical point, the vasculature can be used as “highway” to the target structures. For the treatment of these nearby structures, the vessel has to be punctured and occluded afterwards by a save procedure. We propose an Inside-Out access strategy using a new trans-vascular catheter approach.
Impact of different registration methods in MEG source analysis
Authors: Theiß Marie , Wollbrink Andreas , Wolters Carsten H. , Brinck Heinrich
Published: December 2016

For this study the impact of different co-registration procedures on MEG source localization of somatosensory evoked fields was evaluated. Two different co-registration procedures were used to calculate the transformation matrix which specifies how to align the MRI data to the MEG head coordinate system. In order to depict the differences, caused by the method, the Euclidian distance between the reconstructed sources was noted. It was shown that, erroneous MRI and MEG data co- registration effects source localization results. Most dipoles are located more posterior and superior when the more advanced registration procedure was applied. In conclusion the results show, that an iterative matching procedure allows an accurate knowledge of the MEG gradiometer sensor position relative to the head which is crucial to correctly reconstruct neuronal activity derived from MEG measurements.
Designing a compact MRI motion phantom
Authors: Schmiedel Max , Moeller Anita , Koch Martin A. , Mertins Alfred
Published: December 2016

Even today, dealing with motion artifacts in magnetic resonance imaging (MRI) is a challenging task. Image corruption due to spontaneous body motion complicates diagnosis. In this work, an MRI phantom for rigid motion is presented. It is used to generate motion-corrupted data, which can serve for evaluation of blind motion compensation algorithms. In contrast to commercially available MRI motion phantoms, the presented setup works on small animal MRI systems. Furthermore, retrospective gating is performed on the data, which can be used as a reference for novel motion compensation approaches. The motion of the signal source can be reconstructed using motor trigger signals and be utilized as the ground truth for motion estimation. The proposed setup results in motion corrected images. Moreover, the importance of preprocessing the MRI raw data, e.g. phase-drift correction, is demonstrated. The gained knowledge can be used to design an MRI phantom for elastic motion.
Cerebral cortex classification by conditional random fields applied to intraoperative thermal imaging
Authors: Hoffmann Nico , Koch Edmund , Petersohn Uwe , Kirsch Matthias , Steiner Gerald
Published: December 2016

Intraoperative thermal neuroimaging is a novel intraoperative imaging technique for the characterization of perfusion disorders, neural activity and other pathological changes of the brain. It bases on the correlation of (sub-)cortical metabolism and perfusion with the emitted heat of the cortical surface. In order to minimize required computational resources and prevent unwanted artefacts in subsequent data analysis workflows foreground detection is a important preprocessing technique to differentiate pixels representing the cerebral cortex from background objects. We propose an efficient classification framework that integrates characteristic dynamic thermal behaviour into this classification task to include additional discriminative features. The first stage of our framework consists of learning this representation of characteristic thermal time-frequency behaviour. This representation models latent interconnections in the time-frequency domain that cover specific, yet a priori unknown, thermal properties of the cortex. In a second stage these features are then used to classify each pixel’s state with conditional random fields. We quantitatively evaluate several approaches to learning high-level features and their impact to the overall prediction accuracy. The introduction of high-level features leads to a significant accuracy improvement compared to a baseline classifier.
Analysis of muscle fatigue conditions using time-frequency images and GLCM features
Authors: Karthick P.A. , Navaneethakrishna M. , Punitha N. , Fredo A.R. Jac , Ramakrishnan S.
Published: December 2016

In this work, an attempt has been made to differentiate muscle non-fatigue and fatigue conditions using sEMG signals and texture representation of the time-frequency images. The sEMG signals are recorded from the biceps brachii muscle of 25 healthy adult volunteers during dynamic fatiguing contraction. The first and last curls of these signals are considered as the non-fatigue and fatigue zones, respectively. These signals are preprocessed and the time-frequency spectrum is computed using short time fourier transform (STFT). Gray-Level Co-occurrence Matrix (GLCM) is extracted from low (15–45 Hz), medium (46–95 Hz) and high (96–150 Hz) frequency bands of the time-frequency images. Further, the features such as contrast, correlation, energy and homogeneity are calculated from the resultant matrices. The results show that the high frequency band based features are able to differentiate non-fatigue and fatigue conditions. The features such as correlation, contrast and homogeneity extracted at angles 0°, 45°, 90°, and 135° are found to be distinct with high statistical significance (p < 0.0001). Hence, this framework can be used for analysis of neuromuscular disorders.
Numerical evaluation of image parameters of ETR-1
Authors: Ahmed Shamim , Krüger Marian , Willomitzer Christian , Zakaria Golam A.
Published: December 2016

In this work, we developed a method to handle the image quality test-tool precisely. This test-tool is important to evaluate the quality of the medical images for pre-treatment planning phase. But the achieved images are estimated by naked eyes, which does not provide the precise result. Our main goal is to get the desired image parameters numerically. This numerical estimation overcomes the limitation of naked eye observation. Hence, it enhances the pre-treatment planning. The ETR-1 test-tool is considered here. The contrast, the low contrast details and line-pairs (lp/mm) were estimated.
Hardware dependencies of GPU-accelerated beamformer performances for microwave breast cancer detection
Authors: Salomon Christoph J. , Ley Sebastian , Helbig Marko
Published: December 2016

UWB microwave imaging has proven to be a promising technique for early-stage breast cancer detection. The extensive image reconstruction time can be accelerated by parallelizing the execution of the underlying beamforming algorithms. However, the efficiency of the parallelization will most likely depend on the grade of parallelism of the imaging algorithm and of the utilized hardware. This paper investigates the dependencies of two different beamforming algorithms on multiple hardware specification of several graphics boards. The parallel implementation is realized by using NVIDIA’s CUDA. Three conclusions are drawn about the behavior of the parallel implementation and how to efficiently use the accessible hardware.
Evaluation of reconstruction parameters of electrical impedance tomography on aorta detection during saline bolus injection
Authors: Thürk Florian , Waldmann Andreas D. , Wodack Karin H. , Trepte Constantin J. , Reuter Daniel , Kampusch Stefan , Kaniusas Eugenijus
Published: December 2016

An accurate detection of anatomical structures in electrical impedance tomography (EIT) is still at an early stage. Aorta detection in EIT is of special interest, since it would favor non-invasive assessment of hemodynamic processes in the body. Here, diverse EIT reconstruction parameters of the GREIT algorithm were systematically evaluated to detect the aorta after saline bolus injection in apnea. True aorta position and size were taken from computed tomography (CT). A comparison with CT showed that the smallest error for aorta displacement was attained for noise figure nf = 0.7, weighting radius rw = 0.15, and target size ts = 0.01. The spatial extension of the aorta was most precise for nf = 0.7, rw = 0.25, and ts = 0.07. Detection accuracy (F1-score) was highest with nf = 0.6, rw = 0.15, and ts = 0.04. This work provides algorithm-related evidence for potentially accurate aorta detection in EIT after injection of a saline bolus.
Automatic determination of lung features of CF patients in CT scans
Authors: Chaudhuri Tanusree , Gong Bo , Krueger-Ziolek Sabine , Schullcke Benjamin , Moeller Knut
Published: December 2016

This paper describes a prototype of an automatic system for the detection and evaluation of Cystic fibrosis features (CF) in High resolution computed tomography (HRCT) Scans. The aim of this study lies in presenting this system as a decision support tool for radiologists in future. The CF features that have been detected and evaluated are Bronchiectasis and Mucus Plugging. This system recognizes Bronchiectasis as the presence of enlarged airways in pulmonary CF-CT slices whereas, Mucus Plugging has been recognized as clusters of high attenuation pixels. The dataset of this study consists of HRCT Scans of five CF patients of varying disease stages. Mean percentages of these CF features that were computed for each intercostal space, starting from the first to the fifth, fairly accurately match the different stages of the disease.
Image analysis of self-organized multicellular patterns
Authors: Thies Christian , Khachaturyan Galina , Zemel Assaf , Kemkemer Ralf
Published: December 2016

Analysis of multicellular patterns is required to understand tissue organizational processes. By using a multi-scale object oriented image processing method, the spatial information of cells can be extracted automatically. Instead of manual segmentation or indirect measurements, such as general distribution of contrast or flow, the orientation and distribution of individual cells is extracted for quantitative analysis. Relevant objects are identified by feature queries and no low-level knowledge of image processing is required.
Effect of key parameters on synthesis of superparamagnetic nanoparticles (SPIONs)
Authors: Malhotra Ankit , Spieß Felix , Stegelmeier Corinna , Debbeler Christina , Lüdtke-Buzug Kerstin
Published: December 2016

There are various methods to synthesize superparamagnetic nanoparticles (SPIONs) useful for MPI (magnetic particle imaging) and in therapy (Hypothermia) such as co-precipitation, hydrothermal reactions etc. In this research, the focus is to analyse the effects of crucial parameters such as effect of molecular mass of dextran and temperature of the co-precipitation. These parameters play a crucial role in the inherent magnetic properties of the resulting SPIONs. The amplitude spectrum and hysteresis curve of the SPIONs is analysed with MPS (magnetic particle spectrometer). PCCS (photon cross-correlation spectroscopy) measurements are done to analyse the size distribution of hydrodynamic diameter the resulting SPIONs.
Development of a desiccant based dielectric for monitoring humidity conditions in miniaturized hermetic implantable packages
Authors: Langenmair Michael , Rudmann Linda , Ordonez Juan , Stieglitz Thomas
Published: December 2016

Lifetime estimation of implanted electronics in hermetic packages requires the prediction of the humidity induced lifetime. Classical approaches are limited in applications where miniaturized packages and a buffered humidity at low values are being utilized. An approach to overcome these limitations is described and investigations on suitable materials and measurement setups are presented. The findings support the usability of a Zeolite-silicone based desiccant system as a dielectric for a new type of online sensor. The future exploitation of this new sensing principle can allow the monitoring and prediction of humidity conditions inside of highly reliable miniaturized hermetic implantable packages.
Development of an artifact-free aneurysm clip
Authors: Brack Alexander , Senger Sebastian , Fischer Gerrit , Janssen Henning , Oertel Joachim , Brecher Christian
Published: December 2016

For the treatment of intracranial aneurysms with aneurysm clips, usually a follow-up inspection in MRI is required. To avoid any artifacts, which can make a proper diagnosis difficult, a new approach for the manufacturing of an aneurysm clip entirely made from fiber-reinforced plastics has been developed. In this paper the concept for the design of the clip, the development of a new manufacturing technology for the fiber-reinforced components as well as first results from the examination of the components in phantom MRI testing is shown.
Enhancing the regeneration of bone defects by alkalizing the peri-implant zone – anin vitroapproach
Authors: Galow Anne-Marie , Wysotzki Philipp , Baumann Werner , Gimsa Jan
Published: December 2016

The effects of alkaline pH on the initial adhesion of osteoblasts to titanium surfaces was analyzed by single cell force microscopy (SCFM). In the SCFM measurements, the same cells were used to compare their unspecific adhesion to uncoated titanium with their specific adhesion to collagen coated titanium. When the maximum detachment forces (MDFs) were compared at pH 7.4 and 8.0, only slight differences were found on pure titanium, while the MDFs were significantly increased at collagen coated surfaces at pH 8.0. Effects on the subsequent proliferation and gene expression were investigated in anin vitromodel system consisting of an alkalizing polyvinyl alcohol (PVA) matrix and a perforated titanium disc. The sodium hydroxide releasing matrix maintained the medium pH between pH 7.6 and pH 8.4 during the entire experiment. Under these conditions, cell counts were significantly increased with respect to the control system after 7 days in culture. These results were supported by gene expression analyses, which showed an upregulation of proliferation-controlling genes of the EGFR1 and PI3K/AKT pathways after 14 days in culture. The SCFM data were complemented by findings of an intensive regulation of genes known to be associated with focal adhesion such as Itga8 and Tnn.
Advanced wettability analysis of implant surfaces
Authors: Jennissen Herbert P.
Published: December 2016

New methodologies are a major driving force of scientific progress. In this case the finding that contact angles can be expressed as complex numbers offers the possibility of a much refined analysis beyond zero degrees of rough ultra-/superhydrophilic, (now called hyperhydrophilic), metal surfaces, which play a distinct role in dental and orthopedic implantology. The approaches, a short theoretical introduction and examples from medical applications are given.
Influence of different test gases in a non-destructive 100% quality control system for medical devices
Authors: Pollack Thomas , Seitz Hermann
Published: December 2016

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

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.