bluuebunny/crossref_metadata_2025_split huggingface dataset:
Towards Dual-Use Training Simulator in Interventional Neuroradiology
Authors: Paulsen Benjamin Alexander , Schwenke Hannes , Schramm Peter , Männel Georg , Rostalski Philipp 
Published: September 2023

Abstract
Cerebral aneurysms are common lesions in the general population and are increasingly treated by endovascular procedures. Training of these methods not only improves the learning period of physicians but also increases patient safety. However, the use of traditional medical training methods such as training in living animal models is decreasing due to high costs and ethical issues, so computer simulations and 3D-printed phantoms are being used instead. A more realistic simulation requires pulsatile blood flow that can be customized and has body temperature. Current simulators that use 3D-printed phantoms are mainly used under X-Ray in an angiography intervention room, therefore a dual-use simulator that is easy to transport and can be used also without X-Ray is desirable. Either it could be used traditionally in an angiography intervention room or externally in any regular room with an image simulation according to rotational angiography. In this work, a prototype for blood flow simulation is presented as a first step towards such simulator and its application is demonstrated through different investigations. The fluid system is capable of simulating a given blood flow profile and the heating system can generate an accurate body temperature. The case can be easily integrated into a modular phantom system and is convenient to transport, although the weight could be further reduced.
Manufacture and extraction of PLLA films with incorporated metal ions
Authors: Eickner Thomas , Illner Sabine , Hahn Olga , Müller-Hilke Brigitte , Jonitz-Heincke Anika , Bader Rainer , Fiedler Tomas , Peters Kirsten , Grabow Niels 
Published: September 2023

Abstract
For the in vitro examination of the effects on cells and tissues of metal ions derived from implants by wear and corrosion, a system is needed to release metal ions in a controlled and sustained manner. As small concentrations may have an impact on biological systems, a corresponding slow release over a defined period of time is necessary. Here, a manufacturing method of polymeric Poly(L-lactic acid) (PLLA) films with incorporated cobalt ions via dip coating is reported. The establishment of two analytical methods for the detection and quantification of cobalt ions is shown. High performance liquid chromatography enables cobalt quantification over a concentration range of 0.33 μg/mL up to 33 μg/mL in sample solutions. Extraction and detection of cobalt ions from solvent cast PLLA-cobalt-films shows the feasibility of the manufacturing method. Initial biocompatibility tests with manufactured PLLA-cobaltfilms showed no effects on adipose derived primary mesenchymal stem cells (adMSCs).
Designing and Validating Magnetic Motion Sensing Approaches with a Real-time Simulation Pipeline
Authors: Hoffmann Johannes , Bald Christin , Schmidt Tobias , Boueke Moritz , Engelhardt Erik , Krüger Karolin , Elzenheimer Eric , Hansen Clint , Maetzler Walter , Schmidt Gerhard 
Published: September 2023

Abstract
Magnetic motion sensing enables non-contact tracking of relative position and orientation in 3D space. With recent advances in sensor and actuator devices, applications in human movement analysis seem feasible. However, establishing a setup from scratch in terms of hardware and software is challenging. Therefore, we introduce a comprehensive simulation pipeline based on a digital twin concept that enables the design and validation of new approaches based on kinematics, magnetics, and digital real-time signal processing. We also elaborate on related applications.
Strain-rate dependence of mechanical characteristics of PLLA with different MW
Authors: Fiedler Nicklas , Oschatz Stefan , Grabow Niels , Lebahn Kerstin 
Published: September 2023

Abstract
Dynamic mechanical properties of polymers for biomedical applications are crucial parameters for development and engineering of new medical devices. Here, the time-dependent material behavior is a key factor for durability. Varying the strain rate is a convenient implementation of time-dependency for uniaxial testing. This study investigates time-dependence of Poly(L-Lactide) (PLLA) through uniaxial testing with different strain rates and PLLA with different molecular weight. The results show strain dependence for elongation at break and yield stress, Young’s modulus however is not rate dependent. An increase in elongation at break is also seen with increasing molecular weight of PLLA. Plastic strain increases significantly only for PLLA with an intermediate inherent viscosity. Results show distinct time dependencies regarding strain rate for PLLA with slightly different inherent viscosities. For stent-related mechanical material characteristics, higher molecular weight PLLA seems to be advantageous. This study only considers base materials, although appropriate thermal, mechanical as well as chemical post processing approaches for further adjustment of different properties have already been shown. A combination of the best possible base material and a suitable post-processing should be targeted.
In silico model to assess thrombosis risk of TAVR with hemodynamic predictors using fluid structure interaction
Authors: Borowski Finja , Kaule Sebastian , Oldenburg Jan , Öner Alper , Schmitz Klaus-Peter , Stiehm Michael 
Published: September 2023

Abstract
The promising results of transcatheter aortic valve replacement (TAVR) over the past two decades indicate an expansion of the patient cohort toward patients with intermediate or low surgical risk. Since some complications of TAVR have already been minimized, subclinical leaflet thrombosis (SLT) has gained importance in recent years. SLT is manifested by a thrombotic layer on the prosthetic leaflets that gradually reduces leaflet motion. The resulting decrease in functionality of the TAVR causes a need for re-intervention. The origin of SLT and approaches to prevent SLT are still unexplored. For this reason, we have developed an in silicomodel that can be used during the design development process of TAVR devices to estimate the thrombosis risk of the implant. Based on passive scalar transport, hemodynamic metrics are used to quantify platelet activation and aggregation which are associated with the formation of thrombosis. In conjunction with a numerical simulation model considering the fluid-structure interaction between the blood mimicking fluid and the TAVR implanted in an aortic root, the thrombosis risk can be modeled. The simulation model can be used to calculate the three-dimensional flow structures within the native sinus and neo-sinus and also provides the ability to derive metrics to assess the risk of thrombosis. We demonstrated that this in silicomodel is a time-effective tool to assess thrombosis risk in TAVR product development.
Augmentation of experimentally obtained flow fields by means of Physics Informed Neural Networks (PINN) demonstrated on aneurysm flow
Authors: Oldenburg Jan , Borowski Finja , Wollenberg Wiebke , Öner Alper , Schmitz Klaus-Peter , Stiehm Michael 
Published: September 2023

Abstract
Biofluid mechanics play an important role in the study of the mechanism of cardiovascular diseases and in the development of new implants. For the assessment of hydrodynamic parameters, experimental methods as well as in-silico approaches can be used, such as particle image velocimetry (PIV) and Deep Learning, respectively. Challenges for PIV are the optical access to the region of interest, and time consumption for measuring and post-processing analysis in particular for three dimensional flow. To overcome these limitations state-of-the-art deep learning algorithms could be utilized to augment spatially coarse resolved flow fields. In this study, we demonstrate the use of Physics Informed Neural Networks (PINN) to augment PIV measurement data. To demonstrate a combined workflow, we investigate the flow of a Newtonian fluid through a simplified aneurysm under laminar conditions. Generation of synthetic PIV particle images of a single measurement plane and the corresponding PIV vector calculations were performed as the basis for the PINN algorithm. Based on the Navier-Stokes equations the PINN reconstructs the entire 3D flow field and pressure distribution inside the aneurysm. We observed qualitative agreements between ground through data and PINN predictions. Nevertheless, there are substantial differences in the quantitative, locally resolved comparison of the flow metrics, despite the generally tendency for the PINN algorithm to correctly augment the flow field.
Biomechanical Test Setup for the Investigation of Forehead Suture Techniques
Authors: Micheler Carina M. , Lang Jan J. , Bäumlisberger Anja , Wachtel Nikolaus , Wilhelm Nikolas J. , Schaack Victor G. , Eisenhart-Rothe Rüdiger von , Burgkart Rainer H. H. 
Published: September 2023

Abstract
Wound healing can be delayed if the biomechanical stability of the wound closure is inadequate. Therefore, it is necessary to investigate different suturing techniques for their biomechanical stability. In this study, suturing techniques suitable for the forehead area were investigated. For this application, a special test setup was developed to simulate the curvature of the forehead and the corresponding physiological configuration. The average forehead curvature is 62.24 ± 4.11 mm in radius. To simulate this curvature, the skin specimens are subjected to tensile stress over the spherical surface using a standard uniaxial testing machine. For the evaluation, an automated evaluation tool for MATLAB was also developed. Three different suturing techniques (Straight, Lazy-S, Zigzag) were investigated and tested for their biomechanical stability. Of the three suturing techniques, the Zigzag suture proved to be the most stable with the highest stiffness of 44.23 ± 8.18 % and the highest final failure of 32.60 ± 4.95 % (relative to the control sample without incision). The study has shown that the test setup can be used to investigate different forehead suture techniques.
On the thermographic measurement of the respiratory rate
Authors: Vianden Maurice , Gräf Stefan , Schanze Thomas 
Published: September 2023

Abstract
Respiration is a vital process for normal function at every level of organization of living beings. A simple and noncontact measurement of the respiratory rate certainly offers advantages in many situations compared to classical measurements, e.g., with a respiratory measurement belt. Thus, we started a study for thermographic detection of breathing rate. For this purpose, several subjects were filmed with an infrared (IR) camera and the recordings were subjected to pixel value analysis using MATLAB. By using different regions of interest (ROIs), the pixel values were averaged and mapped graphically. The resulting graphs generally show a periodic breathing process based on the temperature changes within the selected ROIs. To put this pixel value analysis into perspective, control measurements were taken with a BIOPAC-system using a respiratory measurement belt to measure abdominal/thoracic respiration. The two sets of measurements were compared by cross correlation and a moderately strong anti-correlation was demonstrated.
Evaluation of loading behavior of a selfexpanding polymeric microstent for the treatment of Fallopian tube occlusions
Authors: Dierke Ariane , Supp Laura , Paetow Hagen , Rosam Paula , Knorre Luise , Stahnke Thomas , Stiehm Michael , Bock Andrea , Zygmunt Marek , Schmitz Klaus-Peter , Siewert Stefan 
Published: September 2023

Abstract
Female sterility is caused by Fallopian tube occlusions in one of three cases. Current treatment methods achieve unsatisfying pregnancy rates and are associated with high costs or significant psychological and physiological stress. Our previously described microstent technology opens up new therapeutic possibilities to restore the lumen of the Fallopian tube without surgery. In this work, a Finite Element Analysis model of a physiologically relevant loading of the device is presented. Therefore, microstent radial force was analysed as a function of the device diameter up to a minimum diameter of 1.4 mm, which was found after microstent implantation ex vivo. A bilinear constitutive material model considering isotropic hardening was used for modeling of the microstent. The Finite Element Analysis results were validated using corresponding results of experimental investigations. In this context, a maximum deviation of 15% between experimental radial force and the corresopnding simulation results (1.33 N vs. 1.13 N) was found. Maximum von Mises stresses of approximately 88 MPa were determined. A good agreement between simulation and experiments was found. Therefore, future simulations will be carried out as a basis for microstent design optimisation.
3D Hyperspectral Light-Field Imaging: a first intraoperative implementation
Authors: Wisotzky Eric L. , Hilsmann Anna , Eisert Peter 
Published: September 2023

Abstract
Hyperspectral imaging is an emerging technology that has gained significant attention in the medical field due to its ability to provide precise and accurate imaging of biological tissues. The current methods of hyperspectral imaging, such as filter-wheel, snapshot, line-scanning, and push-broom cameras have limitations such as low spatial and spectral resolution, slow acquisition time. New developments on the field of light field cameras show the potential to overcome these limitations. In this paper, we use a novel hyperspectral lightfield camera and try to combine the capability of hyperspectral and 3D analysis. For this purpose we calibrate our system and test it during two ENT-surgeries to show its potential for improving surgical outcomes. The micro-lenses of the camera map 66 spectral sub-images onto the sensor allowing to reconstruct the spectral behavior of the captured scene in the spectral range of 350-1000nm. In addition, we use the sensor data to apply a 3D camera calibration pipeline to allow 3D surface reconstruction. We captured 26 calibration images and achieved calibration results in accordance to stated company data. The best calibration showed a re-projection error of 0.55 px. Further, we tested the camera during a parotidectomy and a neck-dissection. The extracted reflectance spectra of the selected venal and arterial regions correspond perfectly to the spectrum of oxygenated and deoxygenated hemoglobin. For the first time, up to our knowledge, a hyperspectral lightfield camera has been used during a surgery. We were able to continuously capture images and analyze the reconstructed spectra of specific tissue types. Further, we are able to use the sensor data of the micro-lens projections to calibrate the multilens camera system for later intraoperative measurement tasks.
Automatic Registration of Anatomical Structures of Stereo-Endoscopic Point Clouds
Authors: Beckmann Sophie , Rosenthal Jean-Claude , Wisotzky Eric L. , Hilsmann Anna , Eisert Peter 
Published: September 2023

Abstract
In image-guided surgery, imaging systems such as (stereo-)endoscopes allow intra-operative 3D reconstructions in form of point clouds. However, endoscopes provide only a narrow field of view, resulting in a confined point cloud. In this paper, we present an analysis and registration pipeline for confined point clouds acquired by stereo endoscopes into a fused representation. For a coarse registration, TEASER is applied, while a refinement is conducted utilizing point-to-plane ICP. The pipeline is tested on two datasets: acquired point clouds of a head phantom using a EinsteinVision® 3.0 endoscope and point clouds from the Stereo Correspondence And Reconstruction of Endoscopic Data challenge. The results for both datasets show that 3D reconstructions of anatomical structures by utilizing stereo-endoscopes and point cloud registration is a promising contactless and radiation-free method. However, non-rigid deformations are not yet incorporated and evaluation of the method compared to reference data is challenging.
Towards the Application of Hearables for Near-Fall Detection
Authors: Feld Lea , Hellmers Sandra , Schell-Majoor Lena , Koschate Jessica , Zieschang Tania , Kollmeier Birger , Hein Andreas 
Published: September 2023

Abstract
Introduction: Falls and gait disorders often result in hospitalization and immobilization. Near-falls may be one of the earliest signs of increased fall risk. In the literature, several sensor positions are used for fall detection, but few studies include the head as a sensor position. Hearables and hearing aids are increasingly equipped with inertial measurement units (IMUs) and are therefore of particular interest for measuring the risk of falling in everyday life. Methods: Therefore, we investigate the suitability of the ear as a sensor position for near-fall detection in comparison to the standard sensor positions. The motion data of one study participant (female, 63 years) was exemplary analyzed. The participant walked at her individually preferred gait speed on a perturbation treadmill while nine different perturbations (anterior-posterior, medio-lateral and pitch) were applied with a time interval of 20-30 seconds. We used seven IMUs during the measurement at the positions ear, sternum, lumbar, wrist (left/right), foot (left/right). Results: The absolute acceleration signals at the seven different positions show the periodicity of the normal gait before the perturbation. During and after the perturbation changes in the motion pattern can be seen, whereby the response to the perturbation occurs with a slight time lag. The Pearson correlations show that the sensor positions sternum, lumbar and ear correlate well with each other and thus show similar signal characteristics in the reaction to this perturbation. Conclusion: This provides evidence that the ear sensor position is at least comparable to the preferred sensor positions in the literature on the torso. However, these results were obtained under laboratory conditions. Further research is needed to investigate the sensor position at the ear in everyday life.
A CNN-BiLSTM Deep Learning Model for Automatic Scoring of EEG Signals
Authors: ElMoaqet Hisham , Eid Mohammad , Ryalat Mutaz , Penzel Thomas 
Published: September 2023

Abstract
Recently, several automatic sleep stage classification methods have been proposed based on deep learning using convolutional (CNN) and recurrent (RNN) neural networks. However, the state of the art CNN methods are still complex which usually require significant time and considerable computational resources in order to set up and sufficiently train a deep CNN from scratch. This study eliminates the need to establish and train a deep CNN from scratch by leveraging a pre-trained deep architecture that has been previously trained from sufficient labeled data in a different context. A convolutional neural network (CNN) and a Bidrectional long short term memory network (BiLSTM) are integrated for automatic feature extraction and sleep stage scoring using only a singlechannel EEG signal. To demonstrate the generalizability of our results, the proposed model was evaluated using PSG records of 81 patients that were collected in different environments, through different recording hardware, and annotated with different sleep experts. The use of a single EEG source and a one-to-one classification scheme in the proposed model can allow further development towards wearable systems and online in home monitoring applications.
High-Speed Laser Drilling for Dental Implantation: Ablation Process and Applicator Technology
Authors: Giesen Christina , Bochvarov Lazar , Yo Yong-Min , Bogdoll Marcel , Vervoort Simon , Lenenbach Achim 
Published: September 2023

Abstract
Conventional mechanical drilling for implant placement is limited to specific geometry and orientation, resulting in incorrect positioning and inadequate anchoring in thin or porous bone. This study presents the development of a laser-based ablation process and an applicator technology for precise and fast laser drilling in the oral cavity. For the process development, a CO2 laser with a wavelength of 10.6 μm was used. Pulse durations between 10 μs and 400 μs were investigated for fast laser drilling with low thermal impact. For efficient ablation and cooling of the bone tissue, we applied a fine water spray. The laser applicator is designed with an integrated scanning module, focusing optics and a compact water spray system with three spray nozzles in the applicator tip. The geometry of the cavities was analyzed using digital microscopy and scanning electron microscopy, allowing to measure the ablated volume and depth as well as investigating the bone microstructure. This study demonstrates a laser ablation process capable to generate cavities with an ablation rate of 1.75mm3/s which is about 80% higher than previously reported. At this ablation rate the melted zones were smaller than 30 μm. This paper demonstrates a concept for a dental laser drilling system with a fast ablation process and a highlyintegrated applicator for treatment in the oral cavity.
Mechanical Adaptive Silicone Composites for UV-triggered Facilitated Cochlear-Implant Removal
Authors: Klodwig Florian , Herrmann Timo , Menzel Henning , Ehlert Nina 
Published: September 2023

Abstract
The removal of the cochlear implant (CI), which in some cases is without alternative, is still an act of simple pulling, not only causing harm for the patient by damaging tissue but also making reimplantation more difficult. For that reason, it is necessary to develop mechanisms to make an explantation easier. To overcome this problem adaption of the mechanical properties by light-degradable periodic mesoporous organosilica (PMO) can be one solution. By introducing PMO nanoparticles into the CI’s silicone matrix, the particles act as a stiffening agent, which can be degraded by irradiation with UV light. Using this mechanism, the silicone becomes softer, thus making explantation easier and safer for patients. Here first results, concerning the creation of a silicone composite material with light-sensitive adaptive mechanical properties are reported.
Enhancing virtual monoenergetic images for non-congruent dual-energy CT projection data
Authors: Hellwege Laura , Schaar Moritz , Buzug Thorsten M. , Stille Maik 
Published: September 2023

Abstract
This study investigates the application of joint bilateral filtering for noise reduction in fast kVp switching dualenergy computed tomography (DECT). A high resolution image is calculated from non-congruent data of two scans with different energy spectra. This image guides the denoising process of the material decomposition that are used to obtain virtual monoenergetic images (VMIs). The performance of the filter was evaluated in terms of standard deviations on measured data. The proposed filter significantly reduces noise in the VMIs and preserves edges. Furthermore, the simple implementation of the filter can be used for various scanning protocols.
Optimization and evaluation of a mobile IMU-based ballistocardiography system
Authors: Klauth Lucas , Mühlen Andreas , Kitzig Andreas , Naroska Edwin , Stockmanns Gudrun 
Published: September 2023

Abstract
In recent decades ballistocardiography (BCG) has regained popularity as a way to measure the mechanical activ- ity of the heart. In this paper we present and evaluate a new iteration of our mobile BCG measurement system. The pro- posed system uses an inertial measurement unit (IMU) placed on the carotid artery to derive the BCG. We conducted a mea- surement series to evaluate the system and to do an initial in- vestigation into whether more complex heart parameters can be derived from BCG data. The evaluation shows that heart rate (HR) and heart rate variability (HRV) calculated using BCG data, agrees well with the reference measurement and amplitudes calculated are mostly comparable in range to other papers. In conclusion, the system can reliably derive features from BCG data that can be used in further research.