bluuebunny/crossref_metadata_2025 huggingface dataset:
Supervised Skeleton-Based Reference Movement Adjustment
Authors: Lehmann Lars , Seidel Roman , Hirtz Gangolf
Published: December 2021

In Medical Training Therapy (MTT) the exact execution of training exercises developed by the therapist is crucial for the success of the therapy. Currently, a therapist has to treat up to 15 patients at the same time on an outpatient basis. The aim of this paper is to provide an assistance system that can evaluate both the quantity and the quality of the movement performed using a goal-oriented model which gives the patient direct recommendations for action through automated, machine-monitored feedback. To implement the therapeutic measures in a targeted manner, it is advantageous to transfer their knowledge to the patients. This would be possible by transferring the therapist's movement into a patient's movement. Under this assumption a movement sequence of the therapist is recorded and a movement reference frame is extracted with the help of a smart sensor, which is made available to the patient as a target movement. The assistance system records the patient's movement in real time, extracts the its skeleton and compares this movement with the reference. Due to anatomical body differences, the reference skeleton must be adapted to the current patient skeleton, otherwise no movement evaluation can take place. By adjusting the bone lengths and angles in the individual frames of the patient's movement the selected sequence can be compared and any movement deviations that occur can be projected in directly in real time onto the patient's 3D avatar as an error image. The patient tries to reduce the errors and in doing so comes closer and closer to the ideal movement of the therapist which guarantees the best possible therapy success.
Cell colonization potential of thermoplastic silicone-based polyurethane nonwovens for novel heart valve prosthesis
Authors: Ratna Tuladhar Sugat , Teske Michael , Oschatz Stefan , Illner Sabine , Schilling Tobias , Schmidt Wolfram , Grabow Niels , Haverich Axel , Schmitz Klaus-Peter
Published: December 2021

Heart valve tissue engineering aims at creating living valves through colonization of scaffolds with patient’s own cells. Various cell sources have been explored focusing mainly on endothelialization of the scaffold surface. Endothelial like cells, such as endothelial progenitor cells (EPCs), which can be isolated from peripheral blood or bone marrow could be a suitable option. In this study we investigated cell colonization potential of ovine EPCs (OEPCs) on thermoplastic silicone-based polyurethane (TSPU) polymer scaffolds. TSPU nonwovens with and without vascular endothelial growth factor (VEGF) functionalization were used. SEM images showed that by day 3 the cells were growing as patches on the surface of both polymer groups. The cell patches continued growing and started covering more of the nonwoven surface. On day 7 the cells had almost covered the scaffold surface. The cells were more uniformly distributed as monolayer on the functionalized TSPU compared to the non-functionalized nonwovens. Live/Dead staining provided bright green fluorescence on the samples, indicating metabolically active alive cells. These static cell seeding experiments demonstrated that functionalized TPSU nonwovens support endothelialization. The feasibility of TPSU nonwovens as heart valve prosthesis scaffold could be further explored with animal studies in an ovine model.
Towards an intraoperative feedback system for laparoscopic access with the Veress needle
Authors: Spiller Moritz , Esmaeili Nazila , Sühn Thomas , Boese Axel , Turial Salmai , Friebe Michael , Illanes Alfredo
Published: December 2021

About 50 % of complications during laparoscopy occur when surgical access is created. The Veress needle and proposed technical alternatives do not provide reliable information to support the surgeons in guiding the needle, or the feedback is not clearly perceivable. Based on acoustic emissions, Surgical Audio Guidance (SURAG) proposes a non-invasive and efficient way to enhance the perception of guidance information through acoustic and visual feedback displayed in real-time. This article demonstrates that the developed feedback matches the information about tissue layer crossings provided by force measurements. This indicates that SURAG can provide an effective means to make laparoscopic access more precise and safe, especially in pediatric surgery, where space for placing the needle is minimal.
Multispectral single chip reconstruction using DNNs with application to open neurosurgery
Authors: Göb Stephan , Götz Theresa Ida , Wittenberg Thomas
Published: December 2021

Multispectral imaging devices incorporating up to 256 different spectral channels have recently become available for various healthcare applications, as e.g. laparoscopy, gastroscopy, dermatology or perfusion imaging for wound analysis. Currently, the use of such devices is limited due to very high investment costs and slow capture times. To compensate these shortcomings, single sensors with spectral masking on the pixel level have been proposed. Hence, adequate spectral reconstruction methods are needed. Within this work, two deep convolutional neural networks (DCNN) architectures for spectral image reconstruction from single sensors are compared with each other. Training of the networks is based on a huge collection of different MSI imagestacks, which have been subsampled, simulating 16-channel single sensors with spectral masking. We define a training, validation and test set (‘HITgoC’) resulting in 351 training (631.128 sub-images), 99 validation (163.272 sub-images) and 51 test images. For the application in the field of neurosurgery an additional testing set of 36 image stacks from the Nimbus data collection is used, depicting MSI brain data during open surgery. Two DCNN architectures were compared to bilinear interpolation (BI) and an intensity difference (ID) algorithm. The DCNNs (ResNet-Shinoda) were trained on HITgoC and consist of a preprocessing step using BI or ID and a refinement part using a ResNet structure. Similarity measures used were PSNR, SSIM and MSE between predicted and reference images. We calculated the similarity measures for HitgoC and Nimbus data and determined differences of the mean similarity measure values achieved with the ResNet-ID and baseline algorithms such as BI algorithm and ResNet-Shinoda. The proposed method achieved better results against BI in SSIM (.0644 vs. .0252), PSNR (15.3 dB vs. 9.1 dB) and 1-MSE*100 (.0855 vs. .0273) and compared to ResNet-Shinoda in SSIM (.0103 vs. .0074), PSNR (3.8 dB vs. 3.6 dB) and 1-MSE*100 (.0075 vs. .0047) for HITgoC/Nimbus. In this study, significantly better results for spectral reconstruction in MSI images of open neurosurgery was achieved using a combination of ID-interpolation and ResNet structure compared to standard methods.
To improve patients’ empowerment by selfconnection in home parenteral nutrition
Authors: Völz Diana , Eisele Joshua , Benderoth Günther , Schulze Ulrike
Published: December 2021

One promising approach for patients who need parenteral nutrition to live an almost normal life, is to provide extra-hospital therapy. This therapy is supported by an ambulatory care service whose staff connects and disconnects the nutritional fluid day by day. The nutrition therapy takes a long time every day and studies show that this therapy significantly disturbs patients’ daily life. Although home parenteral nutrition is part of the range of services provided by the statutory health insurance (German GKV), it is also expensive in the long run. Therefore, the cost-effectiveness of this form of therapy is constantly reviewed on an individual basis. Aim of this project is to enable a more autonomous life for patients by self-determined in between disconnection and connection of the therapy independently of the ambulatory care service. It has to be taken into account that any interruption of the nutrition process poses health risks to the patient, e.g. if air bubbles or bio contaminants enter the tube system. Flushing with saline solution before and after connecting is therefore an elementary component of the nutrition process. The redesigning of the connecting/disconnecting system and the subsequent development of an automated port flushing system integrated into a mobile feeding pump to realize a safe interruption of the therapy is the overall goal of the project. This paper deals with redesigning the connecting system. After having analysed group discussions, detected impact factors are used as basis of an experimental setup to get the final requirements for redesigning the connector system. The experimental study is done according to the rules of Design of Experimental (DoE). DoE is a statistical method to determine the optimal number of tests by using a complete factorial design. Two repetitions of the tests were carried out to analyse the significance of the impact factors by ANOVA (Analysis of Variance).
Reliability of start and stop control of hydraulic actuation for the insertion of electrode arrays
Authors: Zuniga M. Geraldine , Schell Viktor , Cramer Jakob , Lenarz Thomas , Rau Thomas S.
Published: December 2021

Atraumatic insertions of electrode arrays (EA) into the cochlea aim to preserve natural structures and residual hearing. However, there is a limit as to how smooth and slow a surgeon can insert an EA. As a potential solution, we recently presented a tool (cochlea hydro drive, CHD) that makes use of an infusion pump to prompt and control the desired, continuous and very slow (< 1 mm/s) forward movement for such insertions. The present work further describes the onset, delay and cessation of the hydraulic actuation in response to different start and stop mechanisms, to better understand the safety of its application for cochlear implant surgery. Methods: Our previously designed tool was used to perform insertions of an EA into an artificial scala tympani model. The prototype is designed to hold an EA, which is then actuated by a standard infusion pump programmed to operate at 0.4 mm/ and 0.1 mm/s. A tubing system between the CHD and the pump includes a three-way valve. Ten insertions were operated using the functions of the pump and ten using the valve. Results: From the programmed start to the actual movement, we observed a larger average delay using the pump’s start function (5 s at 0.4 mm/s; 17 s at 0.1 mm/s) vs. opening the valve (< 0.7 s for both velocities). Moreover, the average cessation of movement with the valve closure was almost immediate (0.7 s for both velocities; this corresponds to < 0.1 mm with the slower tested velocity), as opposed to 60- 80 s delay when using the pump’s stop function. Conclusion: The use of a 3-way valve facilitates motion cessation to the high accuracy level required for cochlear implant surgery. These promising findings support future clinical translation of our tool.
Smart surgical template models for customized knee joint replacements
Authors: Sembdner Philipp , Bust Bernhard , Dornheim Lars , Holtzhausen Stefan , Stelzer Ralph
Published: December 2021

The paper introduces a method for the automated generation of patient-specific instruments (PSI), here in particular templates, for the implantation of customized implants. The basis is the derivation of data from the morphology of the bony situation and the medical planning. A developed methodological approach based on an Active Shape Model (ASM) is used for the morphological measurement. Determined geometric dimensions are placed on this ASM and automatically adjusted in each case. In addition, specially developed software tools for the planning and design of medical devices will be presented. This includes, among other things, the intuitive control of template parameters by the user when manual adjustments are necessary. The determined data is bundled and applied to previously methodically thought-out and categorized master CAD (Computer Aided Design) models of surgical templates. These master models are fully configurable and designed to be adjusted within defined ranges of values. The templates are printed from the biocompatible material PA12 using selective laser sintering (SLS).
Techniques of Recording Photoplethysmographic Signals
Authors: Herrmann Hans , Ewald Hartmut
Published: December 2021

The photoplethysmography optically measures blood volume changes within micro vascular tissue. Furthermore, photoplethysmographic signals are used within pulse oximeters in order to calculate the oxygen saturation of the blood. This standard measurement technique is performed as a non-invasive spot check method for human health conditions in hospitals or other health care facilities. Usually at least two light sources are used alternating in order to measure photoplethysmograms at different wavelengths. In this paper we will investigate different methods of optically recording photoplethysmographic signals.
A Robust Multi-Channel EMG System for Lower Back and Abdominal Muscles Training
Authors: Kusche Roman , Graßhoff Jan , Oltmann Andra , Boudnik Lukas , Rostalski Philipp
Published: December 2021

EMG is an established method to acquire the action potentials of contracted muscles. Although commercial EMG systems are available and it is one of the most researched biosignals, it has never become widely used in rehabilitation or fitness training monitoring. The reasons are technical challenges of wearable EMG systems regarding electrode placement, motion artefacts and the complex connectivity of multi-channel EMG measurements. We address this problem for the lower back and abdominal musculature, through a novel dry electrodes belt, multi-channel high density EMG circuitry and problem-specific signal processing. The subject can easily strap the dry electrodes belt around himself which provides 16 EMG channels. Interferences from the ECG and motion artefacts are reduced by a stationary wavelet decomposition. Afterwards, an inter-channel filter is applied to increase the robustness of the signals. Subject measurements during different kinds of typical abdominal and lower back training exercises were performed wearing the novel dry electrodes belt. The results show the possibility of robust EMG measurements from the lower back and abdominal muscles by utilizing the gathered redundancy, appropriately. The additional information obtained via the multi-channel EMG circuitry and spatial oversampling can be used to address current problems of EMG applications. It combines the advantages of robustness and the capability of using comfortable dry electrodes. Therefore, the proposed measurement method for acquiring spatial information about the muscle contractions from the lower trunk can be used for rehabilitation or fitness training monitoring.
Gesture-controlled image system positioning for minimally invasive interventions
Authors: Fritsch Benjamin , Hoffmann Thomas , Mewes André , Rose Georg
Published: December 2021

This work examines how a touchless interaction concept contributes to an efficient, direct, and sterile interaction workflow during CT-guided interventions. Two hand gesture sets were designed specifically under consideration of the clinical workflow and the hardware capabilities. These were used to change the position of an X-Ray tube and detector of a CT scanner without breaking sterility and are compared regarding usability and performance in a user study with 10 users. The user study revealed that it is possible to change the angle of the gantry within 10 seconds average in an experimental setup. A straight hand gesture showed higher acceptance than a pistol motivated gesture. Furthermore, the sequences were not optimal and confused the users. It turned out that it feels more natural to activate and confirm the system with the same gesture.
Effect of volume flows on the viability of MSCs during injection through a cannula
Authors: Nießen Lina , Facchinetti Giulia , Elsner Till , Wendlandt Robert , Gemoll Timo , Habermann Jens K. , Schulz Arndt-Peter
Published: December 2021

Introduction: Clinical trials currently evaluate the use of mesenchymal stem cells (MSCs) for the treatment of non-union bone fractures. The stem cells are injected directly into the non-union area of a bone via a cannula. During this injection process, pressure and shear forces affect the MSCs which could influence the viability of the cells. One parameter that influences the level of the shear forces is the volume flow. The aim of this study is to show whether the injection process with two different volume flows influences the cell viability. Methods: MSCs were isolated from bone tissue, harvested during arthroplasty. Afterwards, they were diluted to a concentration of 1 million cells/mL and 1 mL of this suspension was injected through a cannula with 200 mm length and 2 mm diameter (14 G) with volume flows of 38 and 100 mL/min. The evaluation was performed by detecting living, apoptotic, and dead cells using flow cytometry. The statistical analysis was performed with a Kruskal-Wallis-test to identify significant differences and with a TOST procedure for significant equivalence. The significance level was set to 5 % and the equivalence margin to 20 %. Results: The cell population of healthy cells was in the control group 85.88±2.98 %. After an injection with 38 mL/min the population of healthy cells was 86.04±2.53 % and with 100 ml/min 85.48±1.64 %. The statistical analysis revealed no significant difference between these groups (p = 0.99), but a significant equivalence between the control group and the two volume flows (38 mL/min: p = 0.002, 100 mL/min: p = 0.001). In addition the results show no increase of apoptotic and dead cells in the population after injection. Conclusion: The results indicate that the injection process through the cannula with these volume flows has no effect on the viability of the MSCs.
Exploitation of Kronecker Structure in Gaussian Process Regression for Efficient Biomedical Signal Processing
Authors: Prüßmann Jannik , Graßhoff Jan , Rostalski Philipp
Published: December 2021

Gaussian processes are a versatile tool for data processing. Unfortunately, due to storage and runtime requirements, standard Gaussian process (GP) methods are limited to a few thousand data points. Thus, they are infeasible in most biomedical, spatio-temporal problems. The methods treated in this work cover GP inference and hyperparameter optimization, exploiting the Kronecker structure of covariance matrices. To solve regression and source separation problems, two different approaches are presented. The first approach uses efficient matrix-vector-products, whilst the second approach is based on efficient solutions to the eigendecomposition. The latter also enables efficient hyperparameter optimization. In comparison to standard GP methods, the proposed methods can be applied to very large biomedical datasets without any further performance loss and perform substantially faster. The performance is demonstrated on esophageal manometry data, where the cardiac and respiratory signal components are to be inferred by source separation.
Preadaptation of cell numbers for wound healing assays
Authors: Markhoff Jana , Brietzke Andreas , Grabow Niels
Published: December 2021

In vitro wound healing assays are a suitable application to verify the efficiency of pharmaceuticals or growth factors that will be incorporated in or immobilized to e.g. electrospun biomaterials for wound dressings or other biological devices in advance. Thereby, various factors like culture conditions or cell density influence the specific cell proliferation. Hence, to establish a wound healing assay for various cell types, a stepwise adaptation of cell numbers was done for better estimation and comparison of cell density for the validation of the influence of drugs on the wound healing process. Cell proliferation of different tissue relevant cell types was evaluated by impedance measurements and live cell imaging. Cell numbers could be successfully adapted for assay specific cell densities. In general, a universal comparison of biological or chemical materials and agents in vitro may require the creation of appropriate ISO or OECD standards for a consistent and cell specific adaptation or demand of initial cell density.
Development of an app-controlled simple, wearable teeth grinding sensing device
Authors: Eisenhardt Laura E. , Mayer Juliane , Pott Peter P.
Published: December 2021

Teeth grinding is, due to its various impacts on the human body, a highly discussed issue in dentistry. It can damage the tooth structure or cause pain due to muscle tension. At the moment, there is neither a satisfactory diagnostic nor a comprehensive treatment option. This paper deals with the development of an app-controlled, small, portable sensor unit that can be used by patients to monitor their teeth grinding in everyday life. It also offers a treatment option due to an implemented biofeedback option. To achieve the most cost-effective device possible, only off-the-shelf electronics and no proprietary software were used. In initial tests, the measuring device showed high level of measurement accuracy when performing measurements without feedback at rest (f_score=-0.025...0).
Dependence of SpO2 signal noise on the pulse oximeter averaging time
Authors: Rafl-Huttova Veronika , Hlavac Vit , Rafl Jakub , Rozanek Martin
Published: December 2021

A model of the pulse oximeter, which consists of a transfer function between arterial and peripheral blood oxygen saturation (SpO2) and the noise typical for SpO2 records, is an important part of a mathematical model of oxygenation in neonates that is designed to test and compare different algorithms of oxygen control. The noise level in the SpO2 signal is affected by the averaging time setting of the pulse oximeter. This study aimed to characterize the noise level in the SpO2 signal at the set pulse oximeter averaging times of 2- 4, 8, and 16 seconds. We evaluated SpO2 records of 17 healthy volunteers who underwent a laboratory experiment in which they evoked different types of artifacts. The noise level in the SpO2 signal was characterized by two parameters, the deviation of SpO2 from the true value and the SpO2 time stability, defined as the interval during which the measured SpO2 value remained unchanged. Statistical properties of the noise level for the three averaging times were represented by normalized histograms of both the parameters and varied according to the type of artifact. With motion artifacts, the SpO2 readings deviated from the true value by more than ±2% SpO2 in 10%, 7%, or 5% of the measurements when the set averaging time was 2-4 s, 8 s, or 16 s. The length of the interval over which the SpO2 value remained unchanged was most frequently 2 seconds for all set averaging times. Implementation of the noise characteristics into the computer model of oxygenation in neonates will allow more faithful simulations of the output SpO2 signal that better match clinical observations.
An interactive system for muscle and fat tissue identification of the lumbar spine using semantic segmentation
Authors: Bieck Richard , Baur David , Berger Johann , Stelzner Tim , Völker Anna , Neumann Juliane , Heyde Christoph-E. , Neumuth Thomas
Published: December 2021

We introduce a system that allows the immediate identification and inspection of fat and muscle structures around the lumbar spine as a means of orthopaedic diagnostics before surgical treatment. The system comprises a backend component that accepts MRI data from a web-based interactive frontend as REST requests. The MRI data is passed through a U-net model, fine-tuned on lumbar MRI images, to generate segmentation masks of fat and muscle areas. The result is sent back to the frontend that functions as an inspection tool. For the model training, 4000 MRI images from 108 patients were used in a k-fold cross-validation study with k = 10. The model training was performed over 25-30 epochs. We applied shift, scale, and rotation operations as well as elastic deformation and distortion functions for image augmentation and a combined objective function using Dice and Focal loss. The trained models reached a mean dice score of 0.83 and 0.52 and a mean area error tissue of 0.1 and 0.3 for muscle and fat tissue, respectively. The interactive webbased frontend as an inspection tool was evaluated by clinicians to be suitable for the exploration of patient data as well as the assessment of segmentation results. We developed a system that uses semantic segmentation to identify fat and muscle tissue areas in MRI images of the lumbar spine. Further improvements should focus on the segmentation accuracy of fat tissue, as it is a determining factor in surgical decisionmaking. To our knowledge, this is the first system that automatically provides semantic information of the respective lumbar tissues.
Hybrid test bench for high repetition rate radial shock wave measurement
Authors: Reinhardt Nina , Dick Theresa , Lang Laura , Radermacher Klaus , Fuente Matías de la
Published: December 2021

Radial shock wave therapy is used for different therapeutic indications. In order to assess the effect on the treated tissue, it is important to know the sound field parameters. However, it is challenging to measure the pressure curves of ballistic devices, especially at high pulse repetition rates. In the new standard IEC 63045:2020 two possibilities for sound field measurements of non-focusing devices are described, a wet and a dry test bench. The whole sound field can be characterised using a wet test bench, but the process is cumbersome and cavitation is likely to occur at high pulse repetition rates. This effect is avoided using a dry test bench where the measurement position is limited to a single spot. Therefore, a hybrid test bench was developed combining the dry bench’s device mounting and coupling with a small water basin. The ballistic device was coupled to the basin filled with degassed ultrapure water using a latex membrane covered with ultrasound gel and the contact pressure was applied with a spring. A fibre optic probe hydrophone was used for the sound field measurements. The pressure curves of every 10th shot were measured on the beam axis in a distance of 1mm to the membrane. The device was analysed at 3.5 bar with different pulse repetition rates (1 Hz, 10 Hz, 20 Hz). The test setup enables an easy handling and reproducible results at all pulse repetition rates. The ballistic device provides constant peak pressures over different frequencies. The small water basin has the advantage that the water quality is easy to control and the measuring process is fast and uncomplicated. Cavitation suppression requires a clean water basin filled with degassed ultrapure water kept at a constant, low temperature. The hybrid test bench can be used to easily study shock wave parameters of ballistic devices at high repetition rates.
TeleSDC
Authors: Pabst Tobias , Stegemann Dominik , Georgi Christoph , Kasparick Martin , Suleder Julian , Neumuth Thomas , Rockstroh Max
Published: December 2021

Telemedicine promises to increase the quality of emergency treatments. Besides the transfer of speech and video data, medical device and patient data will add additional value to the tele-guided emergency personnel. In this paper, we develop a concept for transmitting device and patient data via the open communication standards SDC in a telemedical context, including data transmission over mobile radio networks while considering the limitations of public networks, and opening new usage scenarios for telemedicine.
Field test of innovative digital technical assistance systems in the outpatient and inpatient care
Authors: Fischer Ulrich H. P. , Just Jens-Uwe , Haupt Matthias
Published: December 2021

The tecLA project developed a modular system for the area of Ambient Assisted Living (AAL) that enables older people to have simple, intuitive access to medical and technical assistance systems. A commercially available AAL application portal has been subjected to acceptance tests and optimizations and has proven itself in field tests. Furthermore, when comparing the self-assessment values to cognitive measures before and after the intervention, a clear trend towards more positive values in the post-test was recorded. It was also shown that the use of the system has very positive effects on communication behavior and cognitive selfassessment. The nurses and doctors can follow the vital signs online in the patient's file and evaluate them immediately.
Collaborative robot assisted smart needle placement
Authors: Neidhardt Maximilian , Gerlach Stefan , Laves Max-Heinrich , Latus Sarah , Stapper Carolin , Gromniak Martin , Schlaefer Alexander
Published: December 2021

Needles are key tools to realize minimally invasive interventions. Physicians commonly rely on subjectively perceived insertion forces at the distal end of the needle when advancing the needle tip to the desired target. However, detecting tissue transitions at the distal end of the needle is difficult since the sensed forces are dominated by shaft forces. Disentangling insertion forces has the potential to substantially improve needle placement accuracy.We propose a collaborative system for robotic needle insertion, relaying haptic information sensed directly at the needle tip to the physician by haptic feedback through a light weight robot. We integrate optical fibers into medical needles and use optical coherence tomography to image a moving surface at the tip of the needle. Using a convolutional neural network, we estimate forces acting on the needle tip from the optical coherence tomography data. We feed back forces estimated at the needle tip for real time haptic feedback and robot control. When inserting the needle at constant velocity, the force change estimated at the tip when penetrating tissue layers is up to 94% between deep tissue layers compared to the force change at the needle handle of 2.36 %. Collaborative needle insertion results in more sensible force change at tissue transitions with haptic feedback from the tip (49.79 ± 25.51)% compared to the conventional shaft feedback (15.17 ± 15.92) %. Tissue transitions are more prominent when utilizing forces estimated at the needle tip compared to the forces at the needle shaft, indicating that a more informed advancement of the needle is possible with our system.
Analysis of expansion within a pressure inflated section of an urethral stricture model
Authors: Bhave Ashish , Möller Knut
Published: December 2021

The Urethra is a long tubular structure in the genitourinary tract and serves important functions. Researchers have experimented with some approaches to model the urethra and to analyse its biomechanical properties. However, experiments to model the in-vivo behaviour of urethra with strictures is not thoroughly explored. To analyse the in-vivo urethral properties and specifically for supporting treatment of strictures, a new inflatable sensor-actuator system is being developed. The capabilities of this sensor shall be evaluated in simulations which require appropriate modelling of the human male urethra with strictures. This forms a part of the identification procedure for a variety of urethra conditions and geometries, which in turn forms a basis for inverse modelling. As an initial simplified approach, an axisymmetric Finite Element model was generated that resembled the urethra incorporating a stricture region. An ideal actuator with sensor elements exerting a pressure on inner wall of this urethra was simulated. Three circumference measurement zones within the sensor height (top surface, centre and bottom surface) were implemented. The resulting pressure-extension (circumferential) responses were determined at these measurement zones. The sensor was placed at different lengths within this urethral tube and inflated and the pressure-extension responses were noted. It was found that depending on the position of the sensor-actuator, the extension of tissue can vary. The possible factors for this variation were the finite length of the actuator as well as the influence of tissue properties around the measurement zones. This is important information for the interpretation of sensor data to be gained by the current development. It was possible to generate datasets based on an ideal sensor model, that proved helpful in the evaluation of biomechanical tissue properties in healthy and stricture conditions. This indicates simulations are a versatile and prospective way to test new sensors prior to real experiments.
Classification of Bundle Branch Blocks with QRS Templates Extracted from 12-lead ECGs
Authors: Welle Hannes , Nagel Claudia , Loewe Axel , Mikut Ralf , Dössel Olaf
Published: December 2021

Being non-invasive, cheap and widely available, the 12-lead electrocardiogram (ECG) is a standard method to assess cardiac function. Still, its reliable interpretation requires specialized knowledge and experience, rendering a second opinion valuable. We evaluated the performance of machine learning based classification of 11,705 healthy and bundle branch block 12-lead ECGs from 3 open databases. For each lead of the ECG signal, a representative QRS-complex template was extracted automatically. Principal component analysis (PCA) was applied to the concatenated, normalized and rescaled QRS signals to reduce their dimensionality. Multilayer perceptron and support-vector machine classifiers were trained using the principal components of weighted and non-weighted QRS template signals as input data. Classifiers achieved F1 scores between 0.92 and 0.96 on the test set for different input configurations. Anomaly based weighting slightly improved the performance of the classifiers. Neither class-wise PCA for feature extraction nor adding information on sex, gender and electrical heart axis to the input data yielded considerable improvement of the F1 scores. The achieved classification accuracy is similar to deep learning classifier performances and should generalize robustly to other ECG datasets. Our results suggest that this simple and well interpretable approach based on morphological signal characteristics is suitable for automatically and non-invasively identifying bundle branch block pathologies in clinical or smart electronics contexts.
In vitro biocompatibility testing of polymeric nanofiber scaffolds: fine-tuning for a better prediction of the in vivo behaviour
Authors: Khaimov Valeria , Klußmann-Fricke Bastian-Jesper , Illner Sabine , Siewert Stefan , Schmitz Klaus-Peter
Published: December 2021

Biomaterial research efforts focus on the development of biomaterials that mimic the natural extracellular environment. In addition, different strategies are applied to render materials for blood-contacting devices nonthrombogenic through surface modifications that would suppress activation of platelets, coagulation and the complement system. A confluent thin layer of endothelial cells lines all blood vessels and produces factors responsible for inhibition of coagulation, thrombosis and neointimal hyperplasia. Thus, the ability to rapidly form a healthy endothelium upon implantation represents a desired property of biomaterials used for cardiovascular devices. In this study we used advanced in vitro methods to investigate the biocompatibility of a biodegradable and a permanent electrospun nanofiber fabric, poly-L-lactic acid and polycarbonate-based silicone elastomer respectively, with the focus on endothelialization and hemocompatibility.
Universal single-board computer based control unit for biomedical test benches
Authors: Rhinow Grit , Tautorat Carsten , Grossmann Swen , Grabow Niels , Siewert Stefan , Schmitz Klaus-Peter , Schmidt Wolfram
Published: December 2021

Continuous adaptation of international standards for medical devices requires recurrent modification of test benches. A universal control unit using an open software environment is presented to simplify the maintenance of various test benches. Our developed control unit is equipped with a Raspberry Pi 4, with standard communication interfaces and application-specific electronic assemblies. The software is based on Node-RED, a browser-based editor. A measuring setup was adapted for a flow perfusion system. Our control unit simplifies the handling of the flow perfusion system by controlling a hydraulic pump and all required valves. A software programmed PID algorithm adapts the speed of the pump to adjust the pressure automatically. Actuators like proportional pinch valves are handled to control volumetric flow and pressure within the circulation. Consequently, the user directly observes changes inside the system. The measured data are stored and are available for documentation.
Quantitative evaluation of cell morphology and material interactions on opaque biomaterials
Authors: Klußmann-Fricke Bastian-J. , Reske Thomas , Schmitz Klaus-Peter , Siewert Stefan , Khaimov Valeria
Published: December 2021

One of the key aspects in the development of novel implants is to find suitable materials and understand the mechanisms that occur when a material is exposed to the tissues of the human body. These mechanisms are commonly referred to as the biocompatibility of the material. A better understanding of the tissue-material interactions becomes more urgent as biomaterials are used in wide-ranging applications like modern medical devices. However, most biomaterials used for implants are opaque, resulting in difficulties for the microscopical evaluation during in vitro biocompatibility testing. Particularly, cell morphology and adhesion capabilities of cells can provide insights in the interactions between implant materials and tissues at the implant site. To improve our capabilities in biocompatibility testing of novel biomaterials we applied a new method to quantitatively assess cellular parameters on opaque samples using fluorescence microscopy and bio-image analysis.
Definition of test parameters for dynamic mechanical testing of polymeric implant materials
Authors: Fiedler Nicklas , Arbeiter Daniela , Oschatz Stefan , Grabow Niels , Lebahn Kerstin
Published: December 2021

The selection of appropriate test conditions is of critical importance in mechanical testing of biomaterials. In particular the definition of dynamic test conditions is requiring high efforts. In this work, a thermoplastic semicrystalline polymer was characterized regarding mechanical properties by dynamic mechanical analysis (DMA). Timetemperature- superposition (TTS) of dynamic mechanical data provides an efficient method for the experimental design of follow-up studies. Our focus was to provide test conditions for cyclic tests, which correspond to viscoelastic materials. The results show, that the test temperature for dynamic mechanical fatigue tests, as an indicator of mechanical modification for viscoelastic materials, should necessarily remain below the onset temperatures of storage modulus and loss modulus. Moreover, changes in material characteristics due to varying frequencies should be considered when constructing a master curve for the evaluation of test frequencies. Therefore, TTS is particularly beneficial for the rapid determination of test parameters for accelerated material examination.
Electrospun coaxial hyaluronan-based fiber networks for ophthalmic drug release
Authors: Walter Torsten , Wyrwa Ralf , Altmann Cindy , Schnabelrauch Matthias
Published: December 2021

A micro-sized core-shell drug release device has been prepared by coaxial electrospinning based on a polylactide shell and the inner core phase made of high molecular weight hyaluronan or a cross-linked hyaluronan network. Timolol, which was inserted into the core phase, is widely used as drug for glaucoma treatment to depress the intraocular eye pressure and should be released over a longer time period from this fiber networks. Release studies of drug loaded fiber devices showed an only moderate burst release of timolol in the first days followed by a continuous longlasting drug release period over several weeks. With these findings, coaxial electrospinning represents a promising approach for the development of drug release systems with long-lasting, relatively constant drug delivery.
Functional Safety Concept EGAS for Medical Devices
Authors: Paulsen Benjamin Alexander , Henn Sandra , Männel Georg , Rostalski Philipp
Published: December 2021

For patient safety, it is important that a medical device can safely and reliably perform its intended purpose. The challenge in medical technology is that medical devices are heterogeneous systems and thus no widely applicable standard concepts for functional safety exist in medical technology. This is also reflected in the regulatory landscape, with its rather generally applicable standards. Patient safety is currently achieved by performing continuous risk management with an acceptable level of residual risk. Functional safety and its design concepts, as applied in other industries, have so far found little application in the field of medical technology. In this paper, the automotive safety concept "EGAS" is analyzed with regard to its applicability for medical devices. Based on the investigated example of a medical ventilator, important parallels were found between the automotive and the medical device sector, indicating the possibility of successfully applying the EGAS safety concept to medical devices.
Influence of pedicle screw thread width and recovery time after surgery on fixation strength
Authors: Makaram Harikrishna , Swaminathan Ramakrishnan
Published: December 2021

Introduction: Pedicle screw fixation systems are widely used for treatment of various spinal pathologies, including spinal stenosis, scoliosis, spinal deformities and fractures. Stress shielding is considered to be a major factor contributing to insufficient fixation strength, leading to screw loosening. In this study, the influence of pedicle screw thread width on the displacement of pedicle screw and stress transfer is analyzed using 2-Dimensional axisymmetric finite element (FE) model. Methods: FE model consisting of cancellous and cortical bone, along with pedicle screw is developed for this study. The pedicle screw thread width is varied between 0.1 mm and 0.6 mm in steps of 0.1 mm, while the other geometric parameters, including screw half-angle, pitch, diameter, and length are kept constant. Three different contact conditions between screw and bone, such as frictionless, frictional, and bonded are considered to simulate hours, days, and months after surgery, respectively. The material properties and boundary conditions are applied based on previous studies. An axial force of 80 N is applied on the screw head to simulate axial pull-out test. Results: Similar patterns of stress distribution are observed for all screw models, with high stress concentration above the first thread. The highest displacement in screw is observed shortly after surgery, while the highest displacement in cancellous and cortical bone is observed few days and months after the surgery, respectively. The average von Mises stress in screw decreases with increase in thread width for all contact conditions. In few hours/days after the surgery, stress transfer parameter increases with increase in thread width, up to a thread width of 0.5 mm and then decreases. The changes in stress transfer parameter are negligible few months after the surgery.

Conclusion: This study highlights the influence of thread width on displacement and stress transferred to the bone, at different durations after the surgery. It is observed that a thread width of 0.5 mm exhibits the highest stress transfer, leading to reduced stress shielding and improved bone remodeling. It appears that this study might aid in developing better pedicle screws for the treatment of various spinal pathologies.
Classification of Alzheimer Condition using MR Brain Images and Inception-Residual Network Model
Authors: Shaji Sreelakshmi , Ganapathy Nagarajan , Swaminathan Ramakrishnan
Published: December 2021

Alzheimer’s Disease (AD) is an irreversible progressive neurodegenerative disorder. Magnetic Resonance (MR) imaging based deep learning models with visualization capabilities are essential for the precise diagnosis of AD. In this study, an attempt has been made to categorize AD and Healthy Controls (HC) using structural MR images and an Inception-Residual Network (ResNet) model. For this, T1- weighted MR brain images are acquired from a public database. These images are pre-processed and are applied to a two-layer Inception-ResNet-A model. Additionally, Gradient weighted Class Activation Mapping (Grad-CAM) is employed to visualize the significant regions in MR images identified by the model for AD classification. The network performance is validated using standard evaluation metrics. Results demonstrate that the proposed Inception-ResNet model differentiates AD from HC using MR brain images. The model achieves an average recall and precision of 69%. The Grad- CAM visualization identified lateral ventricles in the mid-axial slice as the most discriminative brain regions for AD classification. Thus, the computer aided diagnosis study could be useful in the visualization and automated analysis of AD diagnosis with minimal medical expertise.
Tracking blood pressure changes by means of non-invasive intermittent blood pressure measurements in clinical application
Authors: Huhle Robert , Richter Thorsten , Gama de Abreu Marcelo
Published: December 2021

Considering accuracy/precision cut-offs of 5 ± 8 mmHg and cut-off values for inter-class correlation coefficients (ICC=0.37...1, from DIN EN ISO 81060-2), absolute and relative errors in time independent measurement of blood pressure changes with non-invasive intermittent devices (NiBP) are derived mathematically for mean arterial blood pressure range of 40-180 mmHg. As a clinically relevant value for change of arterial blood pressure 20% of the baseline blood pressure is considered. The mean ratio between the change of BP measured by the NiBP and measured by the invasive reference device (TE%) were proposed as quality measure for the evaluation of NiBP device tracking capability. The proposed measure TE%is theoretically independent of absolute accuracy but depends on precision and ICC of a device. NiBP devices show considerable maximum TE% of 41% in tracking mean blood pressure changes respectively. In 10% of the measurements in the low blood pressure range TE% exceeding 100%. The mean 50th/90th TE% percentile over the whole blood pressure range were 25/61%, respectively. Furthermore, TE% was relatively insensitive to assumed blood

pressure range but sensitive to ICC. NiBP devices have high relative error in tracking blood

pressure changes that make those devices not well-suited for tracking blood pressure changes. The proposed tracking error allows the definition of reasonable accuracy/precision requirements of NBP devices.
Hemodynamics of anterior communicating artery aneurysms using combined imaging of the anterior circulation
Authors: Saalfeld Sylvia , Behme Daniel , Almizel Mahmoud , Berg Philipp
Published: December 2021

Intracranial aneurysms at the anterior communicating artery (AcomA) are associated with a higher rupture risk and a more challenging therapy since they are supplied with blood from both sides of the anterior vasculature. Since the standard imaging modality, i.e. digital subtraction angiography, involves the contrast agent injection into a single cerebral artery, this relationship cannot be satisfactorily considered in subsequent blood flow analysis based on the single-sided segmentation. In this study, we analysed five patients harbouring multiple intracranial aneurysms including those located at the AcomA. We virtually combined the segmentations from both sides into a single model and examined the influence on blood flow simulations based on different inlets: (1) only the left internal carotid artery, (2) only the right internal carotid artery and (3) both internal carotid arteries. Our results indicate a strong influence of the blood flow simulation for AcomA aneurysms as well as large differences between left and right side of the patient’s vasculature