Biomedical Engineering / Biomedizinische Technik

Published by De Gruyter

Volume 64 Issue 4

Issue of Biomedical Engineering / Biomedizinische Technik

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Contents
Journal Overview

Publicly Available August 2, 2019

Frontmatter

Page range: i-iii

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Research articles

September 6, 2018

Wireless video transmission into the MRI magnet room: implementation and evaluation at 1.5T, 3T and 7T

Bennet Hensen, Urte Kägebein, Marcel Gutberlet, Kristina I. Ringe, Van Dai Vo-Chieu, Daniel Stucht, Oliver Speck, Ralf Vick, Frank Wacker, Enrico Pannicke

Page range: 373-382

Abstract

Purpose To analyze the interference between a wireless high definition multimedia interface (WHDMI) and magnetic resonance imaging (MRI) image quality at 1.5T, 3T and 7T. Materials and methods A wireless video transmission system (WVTS) consisting of a WHDMI and a projector was used to transmit and display a video stream into the magnet room. MR image quality was analyzed at 1.5T, 3T and 7T. Signal-to-noise-ratio (SNR¯)$(\overline {{\rm{SNR}}} )$ and radio frequency (RF)-noise spectrum were measured at three transmitter positions (A: inside the cabin, B: in front of the waveguide and C: in the control room). WVTS system functionality tests included measurements of reliability, delay and image quality. Results With the WVTS mean SNR¯$\overline {{\rm{SNR}}} $ values significantly decreased in comparison to the reference for all positions and fieldstrenghts, while the spectra’s baseline is elevated at 1.5T and 3T. Peaks related to continuous wave interferences are apparent at all field strenghts. For WHDMI alone mean SNR¯$\overline {{\rm{SNR}}} $ values were stable without significant differences to the reference. No elevation of the spectra’s baseline could be observed. Functionality measurements confirmed high connection reliability with stable image quality and no delays for all field strengths. Conclusion We conclude that wireless transmission of video streams into the MRI magnet room is feasible at all field strengths without hampering image quality.

September 3, 2018

Biomimetic multilayer coatings deliver gentamicin and reduce implant-related osteomyelitis in rats

Steffi Grohmann, Manuela Menne, Diana Hesse, Sabine Bischoff, René Schiffner, Michael Diefenbeck, Klaus Liefeith

Page range: 383-395

Abstract

Implant-related infections like periprosthetic joint infections (PJI) are still a challenging issue in orthopedic surgery. In this study, we present a prophylactic anti-infective approach based on a local delivery of the antibiotic gentamicin. The local delivery is achieved via a nanoscale polyelectrolyte multilayer (PEM) coating that leaves the bulk material properties of the implant unaffected while tuning the surface properties. The main components of the coating, i.e. polypeptides and sulfated glycosaminoglycans (sGAG) render this coating both biomimetic (matrix mimetic) and biodegradable. We show how adaptions in the conditions of the multilayer assembly process and the antibiotic loading process affect the amount of delivered gentamicin. The highest concentration of gentamicin could be loaded into films composed of polypeptide poly-glutamic acid when the pH of the loading solution was acidic. The concentration of gentamicin on the surface could be tailored with the number of deposited PEM layers. The resulting coatings reveal a bacteriotoxic effect on Staphylococcus cells but show no signs of cytotoxic effects on MC3T3-E1 osteoblasts. Moreover, when multilayer-coated titanium rods were implanted into contaminated medullae of rat tibiae, a reduction in the development of implant-related osteomyelitis was observed. This reduction was more pronounced for the multifunctional, matrix-mimetic heparin-based coatings that only deliver lower amounts of gentamicin.

September 18, 2018

A versatile perfusion bioreactor and endothelializable photo cross-linked tubes of gelatin methacryloyl as promising tools in tissue engineering

Birgit Huber, Eva Hoch, Iván Calderon, Kirsten Borchers, Petra J. Kluger

Page range: 397-406

Abstract

Size and function of bioartificial tissue models are still limited due to the lack of blood vessels and dynamic perfusion for nutrient supply. In this study, we evaluated the use of cytocompatible methacryl-modified gelatin for the fabrication of a hydrogel-based tube by dip-coating and subsequent photo-initiated cross-linking. The wall thickness of the tubes and the diameter were tuned by the degree of gelatin methacryl-modification and the number of dipping cycles. The dipping temperature of the gelatin solution was adjusted to achieve low viscous fluids of approximately 0.1 Pa s and was different for gelatin derivatives with different modification degrees. A versatile perfusion bioreactor for the supply of surrounding tissue models was developed, which can be adapted to several geometries and sizes of blood-vessel mimicking tubes. The manufactured bendable gelatin tubes were permeable for water and dissolved substances, like Nile Blue and serum albumin. As a proof of concept, human fibroblasts in a three-dimensional collagen tissue model were successfully supplied with nutrients via the central gelatin tube under dynamic conditions for 2 days. Moreover, the tubes could be used as scaffolds to build-up a functional and viable endothelial layer. Hence, the presented tools can contribute to solving current challenges in tissue engineering.

Open Access December 12, 2018

Comparative biomechanical evaluation of two technologically different microprocessor-controlled prosthetic knee joints in safety-relevant daily-life situations

Malte Bellmann, Thomas Maximilian Köhler, Thomas Schmalz

Page range: 407-420

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Abstract

Safety-relevant gait situations (walking on stairs and slopes, walking backwards, walking with small steps, simulated perturbations of swing phase extension) were investigated in a motion analysis laboratory with six unilateral transfemoral amputees using two different microprocessor-controlled prosthetic knee joints (Rheo Knee XC, C-Leg). A randomized crossover design was chosen. The study results imply that the performance and safety potential of a microprocessor-controlled knee joint can be associated with the individual control algorithms and the technological concepts that are implemented to generate motion resistances for controlling flexion and extension movements. When walking with small steps, advantages of the “default swing” concept used in the Rheo Knee XC were identified due to a highly reproducible swing phase release. However, when walking backwards, this concept may lead to an uncontrolled knee flexion which partly resulted in falls. When walking down stairs, walking on slopes or while recovering from a stumble after perturbations of the swing phase extension, the C-Leg demonstrated a reliable prosthetic side load-bearing capacity resulting in reduced loading on the residual body. In contrast, the Rheo Knee XC required increased compensatory movements of the remaining locomotor system in order to compensate for reduced load-bearing and safety reserves.

October 6, 2018

Non-invasive improved technique for lumbar discus hernia classification based on fuzzy logic

Aleksandar Peulić, Tijana Šušteršič, Miodrag Peulić

Page range: 421-428

Abstract

This paper presents the improved technique for classification of the type of lumbar discus hernia based on fuzzy logic. The reduced mobility of the foot is one of the symptoms of the disease that occurs because of the displaced discs in the space of two vertebrae. This fact was used for non-invasive discus hernia diagnosis by measuring force values from four sensors placed on both feet (first, second and fourth metatarsal head as well as the heel). Hardware and software systems were constructed for the doctor to perform the measurements and have a graphical representation during the measuring procedure. The procedure included measuring force values of 18 subjects during normal standing, standing on forefeet and heels. All subjects were diagnosed by a specialist with either L4/L5 or L5/S1 discus hernia. Filtering and further preprocessing of acquired values included separation of forefeet and heel segments that were used as inputs to fuzzy system. The results showed that the accuracy of such a fuzzy system was around 72%, and the proposed system correctly recognizes healthy individuals. Obtained information about forces on characteristic points on the foot represents useful data in diagnosis which further can be processed in order to be a supportive tool to doctors.

September 19, 2018

Development of a wheeled walker braking device using the four-bar mechanism

ChangMin Choi, Se-Han Lee, DongGeon Lee, SoungKyun Hong, SeungHyeon Pyo, SuHo Park, Kyeongbong Lee, GyuChang Lee

Page range: 429-437

Abstract

The elderly population in many countries has been rising rapidly, and falls are a serious event many elderly people experience. Assistive equipment is actively used to reduce falls among elderly people. Popular types of assistive equipment include canes, electric wheelchairs, and wheeled walkers. Wheeled walkers support the body of elderly people, making their gait comfortable as they age or recover from injuries. Wheeled walkers may be equipped with hand brakes; however, frail older people may experience difficulty using such hand brakes, as they require force to operate. Thus, in the present study, a braking method using a wire connected to a user’s belt or clothes was designed and implemented; if the tension of the wire connecting the safety device and the user exceeds a critical value, the wheeled walker brakes, which can prevent the rapid motion of walkers. Two feasibility tests of the wheeled walker with the braking device were conducted: one with 10 healthy adults in their 20s and the other with 10 elderly people over 65 years of age; the tests measured the braking time and speed control using a speed measuring device. The results of the first and second feasibility tests demonstrated that the average braking time of participants was 50.3 ms and 50.7 ms, respectively. All participants in the feasibility tests succeeded in the speed control test. Thus, based on the results, the braking device on the wheeled walker worked properly.

September 19, 2018

Electrically evoked wrist extensor muscle fatigue throughout repetitive motion as measured by mechanomyography and near-infrared spectroscopy

Nurul Salwani Mohamad Saadon, Nur Azah Hamzaid, Nazirah Hasnan, Muhammad Afiq Dzulkifli, Glen M. Davis

Page range: 439-448

Abstract

Repetitive electrically-evoked muscle contraction leads to accelerated muscle fatigue. This study assessed electrically-evoked fatiguing muscle with changes to mechanomyography root mean square percentage (%RMS-MMG) and tissue saturation index (%TSI) in extensor carpi radialis. Forty healthy volunteers (n=40) performed repetitive electrical-evoked wrist extension to fatigue and results were analyzed pre- and post-fatigue, i.e. 50% power output (%PO) drop. Responses of %PO, %TSI and %RMS-MMG were correlated while the relationships between %RMS-MMG and %TSI were investigated using linear regression. The %TSI for both groups were negatively correlated with declining %PO as the ability of the muscle to take up oxygen became limited due to fatigued muscle. The %RMS-MMG behaved in two different patterns post-fatigue against declining %PO whereby; (i) group A showed positive correlation (%RMS-MMG decreased) throughout the session and (ii) group B demonstrated negative correlation (%RMS-MMG increased) with declining %PO until the end of the session. Regression analysis showed %TSI was inversely proportional to %RMS-MMG during post-fatigue in group A. Small gradients in both groups suggested that %TSI was not sensitive to the changes in %RMS-MMG and they were mutually exclusive. Most correlation and regression changed significantly post-fatigue indicating that after fatigue, the condition of muscle had changed mechanically and physiologically.

September 22, 2018

A thermometry software tool for monitoring laser-induced interstitial thermotherapy

Babak Bazrafshan, Ahmad Koujan, Frank Hübner, Christian Leithäuser, Norbert Siedow, Thomas J. Vogl

Page range: 449-457

Abstract

The purpose of this study was to develop a thermometry software tool for temperature monitoring during laser-induced interstitial thermotherapy (LITT). C++ programming language and several libraries including DICOM Toolkit, Grassroots DICOM library, Insight Segmentation and Registration Toolkit, Visualization Toolkit and Quasar Toolkit were used. The software’s graphical user interface creates windows displaying the temperature map and the coagulation extent in the tissue, determined by the magnetic resonance imaging (MRI) thermometry with the echo planar imaging sequence and a numerical simulation based on the radiation and heat transfer in biological tissues, respectively. The software was evaluated applying the MRI-guided LITT to ex vivo pig liver and simultaneously measuring the temperature through a fiber-optic thermometer as reference. Using the software, the temperature distribution determined by the MRI method was compared with the coagulation extent simulation. An agreement was shown between the MRI temperature map and the simulated coagulation extent. Furthermore, the MRI-based and simulated temperatures agreed with the measured one – a correlation coefficient of 0.9993 and 0.9996 was obtained, respectively. The precision of the MRI temperature amounted to 2.4°C. In conclusion, the software tool developed in the present study can be applied for monitoring and controlling the LITT procedure in ex vivo tissues.

September 21, 2018

Dual frequency bioelectrical impedance analysis to estimate hematocrit for prognosis of dengue fever in Indian children

Neelamegam Devarasu, Gnanou Florence Sudha

Page range: 459-469

Abstract

A noninvasive investigation to ascertain the hematocrit (HCT) or packed cell volume (PCV) was conducted on 44 hospitalized dengue hemorrhagic fever (DHF) subjects, male and female aged between 3 and 14 years using bioelectrical impedance analysis (BIA). Among the 44 subjects, 30 subjects were confirmed to be non-structural protein-1 (NS1) positive at the time of admission, whose blood investigations such as HCT level, platelet (PLT) count, aspartate aminotransferase (AST) level and alanine aminotransferase (ALT) level were taken for the classification of risk as low risk (LR) and high risk (HR) DHF. Electrical conductivity of blood reflects a linear correlation with HCT. To provide a better and more accurate estimate of HCT, a dual frequency method is proposed to calculate the conductivities of plasma and blood cells. The resistance at 100 kHz is used to estimate the conductivity of blood cells and the impedance at 5 kHz to estimate the conductivity of plasma. Statistical analysis reveals that the HCT estimated using the proposed dual frequency method shows a significant difference with a single frequency (50 kHz) estimate of HCT and also shows a good correlation with the blood investigation results. In addition, statistical analysis of the proposed method on different fever subjects indicates a significant difference with DHF.

September 19, 2018

Optical measurement of the corneal oscillation for the determination of the intraocular pressure

Jan Osmers, Michael Sorg, Andreas Fischer

Page range: 471-480

Abstract

Motivation Glaucoma is currently the most common irreversible cause of blindness worldwide. A significant risk factor is an individually increased intraocular pressure (IOP). A precise measurement method is needed to determine the IOP in order to support the diagnosis of the disease and to monitor the outcome of the IOP reduction as a medical intervention. A handheld device is under development with which the patient can perform self-measurements outside the clinical environment. Method For the measurement principle of the self-tonometer the eye is acoustically excited to oscillate, which is analyzed and attributed to the present IOP. In order to detect the corneal oscillation, an optical sensor is required which meets the demands of a compact, battery driven self-tonometer. A combination of an infrared diode and a phototransistor provides a high-resolution measurement of the corneal oscillation in the range of 10 μm–150 μm, which is compared to a reference sensor in the context of this study. By means of an angular arrangement of the emitter and the detector, the degree of reflected radiation of the cornea can be increased, allowing a measurement with a high signal-to-noise ratio. Results By adjusting the angle of incidence between the detector and the emitter, the signal-to-noise ratio was improved by 40 dB which now allows reasonable measurements of the corneal oscillation. For low amplitudes (10 μm) the signal-to-noise ratio is 10% higher than that of the commercial reference sensor. On the basis of amplitude variations at different IOP levels, the estimated standard uncertainty amounts to <0.5 mm Hg in the physiological pressure range with the proposed measuring approach. Conclusion With a compact and cost-effective approach, that suits the requirements for a handheld self-tonometer, the corneal oscillation can be detected with high temporal resolution. The cross-sensitivity of the sensor concept concerning a distance variation can be reduced by adding a distance sensor. Existing systematic influences of corneal biomechanics will be integrated in the sensor concept as a consecutive step.

Open Access January 18, 2019

Does airborne ultrasound lead to activation of the auditory cortex?

Robert Kühler, Markus Weichenberger, Martin Bauer, Johannes Hensel, Rüdiger Brühl, Albrecht Ihlenfeld, Bernd Ittermann, Tilmann Sander, Simone Kühn, Christian Koch

Page range: 481-493

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Abstract

As airborne ultrasound can be found in many technical applications and everyday situations, the question as to whether sounds at these frequencies can be heard by human beings or whether they present a risk to their hearing system is of great practical relevance. To objectively study these issues, the monaural hearing threshold in the frequency range from 14 to 24 kHz was determined for 26 test subjects between 19 and 33 years of age using pure tone audiometry. The hearing threshold values increased strongly with increasing frequency up to around 21 kHz, followed by a range with a smaller slope toward 24 kHz. The number of subjects who could respond positively to the threshold measurements decreased dramatically above 21 kHz. Brain activation was then measured by means of magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) and with acoustic stimuli at the same frequencies, with sound pressure levels (SPLs) above and below the individual threshold. No auditory cortex activation was found for levels below the threshold. Although test subjects reported audible sounds above the threshold, no brain activity was identified in the above-threshold case under current experimental conditions except at the highest sensation level, which was presented at the lowest test frequency.

About this journal

Objective
Biomedical Engineering / Biomedizinische Technik (BMT) is a high-quality forum for the exchange of knowledge in the fields of biomedical engineering, medical information technology and biotechnology/bioengineering. As an established journal with a tradition of more than 60 years, BMT addresses engineers, natural scientists, and clinicians working in research, industry, or clinical practice. All articles are peer-reviewed. All manuscripts must be submitted in English.

Topics

diagnostic imaging
image processing
biosignal processing
modelling and simulation
biomechanics
information and communication in medicine
telemedicine and e-health
surgery
minimum invasive interventions
endoscopy and image-guided therapy
diagnostic and therapeutic instrumentation
clinical engineering
micro- and nanosystems in medicine
active implants
biosensors
neuro-engineering
neural systems
rehabilitation and prosthetics
biomaterials
cellular and tissue engineering
artificial organs
biomedical engineering for audiology, ophthalmology, emergency and dental medicine
general subjects (e.g., education and training, health technology assessment)
special topics (e.g., linking proteomics and genomics with biomedical engineering, emergency medicine)

Article formats
Reviews, Research Articles, Short Communications