Current Directions in Biomedical Engineering

Open Access Published by De Gruyter

Volume 5 Issue 1 - Proceedings of the 2019 Annual Meeting of the German Society of Biomedical Engineering (25–26 September 2019, Frankfurt am Main)

Issue of Current Directions in Biomedical Engineering

Contents
Journal Overview

Automated classification of waveforms is an important method of data processing used in various fields of science, such as neuroscience, biomedical engineering, etc. This work shows the possibility of sorting special waveforms i.e. spikes recorded with multichannel electrode arrays by using principles of correlation and data-driven reference. A new method to estimate the number of k-means clusters by using a Monte Carlo method is introduced. To demonstrate the performance of the algorithm, generated signals were used, which are created to mimic multichannel recording of the extra-cellular neuronal signals.

Cerebrovascular diseases such as stenosis, atherosclerosis or distention of the carotid artery are accountable for about 1 million death per year across Europe. Diagnostic tools like ultrasound imaging, angiography or magnetic resonance-based imaging require specific hardware and highly depend on the experience of the examining clinician. In contrast auscultation with a stethoscope can be used to screen for carotid bruits - audible vascular sounds associated with turbulent blood flow - a method called phonoangiography. A reliable auscultation setup is prerequisite to ensure high signal quality, adequate processing and the objective evaluation of this audible signal. We propose a computer assisted auscultation system for the acquisition of vascular sounds of the carotid. The system comprises of an auscultation device, a smartphone-based control application and cloud-based signal analysis and storage. It is designed to facilitate the objective assessment, screening and monitoring of long-term changes in the vessel condition based on auscultation of the carotid artery.

A piezoelectric FPW-sensor has been developed for a point of care device in this work. The Bio- MEMS FPW-sensor consists of an electrode configuration termed as an interdigital transducer (IDT) placed on a membrane. An input IDT excites and an output IDT detects the propagating acoustic waves through a PZT layer. Design optimizations and fabrication improvements of the FPW-sensor led to significantly reduced attenuation of the wave signal and the damping of the propagating waves between the IDTs. The working principle of mass loading is shown using different low-viscous liquids. A densitydependent sensitivity of -0.39 MHz/g/cm³ was evaluated. After the membrane was functionalized, the Bio-MEMS FPW-sensor was used to measure a specific chemokine in complex solution. By design improvements, the resolution was significantly increased from 0.7 Hz/nM to 14 Hz/nM.

Immobilizing a single growth factor such as rhBMP-2 on Implant materials can significantly increase the integration of implants into bone in animals. Paradoxically the effective osteoinductive dose of rhBMP-2 in humans is ca. 100-1000-fold higher than in animals and may induce serious side effects in spine fusion surgery. In physiological bone healing at least 10 separate growth and differentiation factors are sequentially involved in the first two healing phases leading to a callus and/or woven bone. It is therefore hypothesized that a significant dose reduction for rhBMP-2 applications in humans may be achieved by a combination of rhBMP-2 with other growth factors in a biomimetically oriented manner. Some aspects involved in multimodal bioactive hybrid carriers with spatio-temporal release kinetics and a new phenomenon ("protein interference") are presented.

The bend and free recovery (BFR) test according to ASTM F2082 is a standard method to determine the transition temperatures of Nitinol shape memory alloys (SMAs). Unfortunately, this standard method is limited to SMA wires which are straight in its trained shape. Thus, the standard BFR test is not suitable for thermomechanical characterization of curved Nitinol SMA wires which should serve as actuators in cochlear implants in future. We developed a modified BFR measurement setup to determine the active austenite finish (AF) temperature of these very thin wires (Ø100 μm). The active AF temperature specifies the completion of the shape recovery upon heating. A parametric study of the measurement setup was carried out to investigate the influence of the heating rate on the observed active AF temperature and to verify the repeatability of the measurement setup. First, the curved wire was straightened in a cold water bath before inserting it into a water bath that is gradually heated from 5 °C to 45 °C. The shape change of the previously straightened wire was then recorded throughout the experiment using a digital microscope. Five different heating rates were employed: 0.25 K/min, 0.33 K/min, 0.5 K/min, 1 K/min as well as an unregulated maximum heating rate achievable of approximately 1.5 K/min. Furthermore, an investigation on the test-retest reliability was performed with three wires by repeating the experiment ten times with each wire. The results of this study revealed no influence of the heating rate on the thermomechanical response of the wires. Based on data from this study, a regulated heating rate of 1 K/min is suggested for future investigations, as this reduces the duration of the measurement from four hours to less than an hour. The values obtained from each wire through the test-retest reliability investigation showed a standard deviation of 1.9 K, 1.1 K and 2.1 K respectively. Our developed measurement setup demonstrates appropriate repeatability of the measurements.

Along with increasing enthusiasm for sports comes an increase of sport related injuries. One of the most common injuries in the human knee is the tear of the anterior cruciate ligament (ACL). The selection of a graft fixation device is an important factor that determines the outcome of an anterior cruciate ligament reconstruction. Before the healing process is completed, the graft is dependent on tibial and femoral fixation devices to maintain normal ACL graft tension. Among various devices, the use of an adjustable loop suspensory fixation device (ALD) in soft-tissue graft reconstruction attracts current interest. An advantage of the ALD is the ability to draw the graft to the depth of the bone tunnel to achieve adequate graft tension while minimizing the empty space in the tunnel. In this study a comprehensive controlled laboratory investigation is performed to examine the biomechanical properties of commonly used cortical fixation devices, with the aim of implementing a standard testing procedure for adjustable loop devices. The procedure consists of three test series, a loop shortening test and two different stability test series (singe device and tendon device test). Those test series are used to compare the performance of a new ALD from Arthrex (Naples, USA) with five competitor devices already on the market. In order to obtain representative results eight samples of each device are tested. In comparison to the previously performed studies, a complete unloading is applied in the stability tests, which allows for a detailed examination of the ALDs locking mechanisms in dynamically loaded test situations. Furthermore, the performed loop shortening tests reveal important aspects, such as the shortening accuracy and settling effects of the loops, that are not found in previous studies. Therefore, the used test protocol can be recommended for further testing.

In Medical Training Therapy (MTT), the precise execution of the training exercises is of decisive importance for the success of the therapy. Currently, a therapist has to treat up to 15 patients simultaneously on an outpatient basis. We propose, an assistance system, can evaluate both quantity and quality of the movement performed using a target-oriented model and give recommendations for action directly to the patient by means of feedback. An avatar in traffic light colours signals in which body region an error has occurred. The individualisation of the underlying three-dimensional avatar increases the willingness of the patients to participate in the exercises without the supervision of therapist. The monitored error frequency was decreased by 50% by the assistance system.

About this journal

Objective
Current Directions in Biomedical Engineering (CDBME) is an open access journal and closely related to the journal Biomedical Engineering - Biomedizinische Technik (BME-BMT) that is well established and of high quality for more than 50 years. CDBME is as BME-BMT a forum for the exchange of knowledge in the fields of biomedical engineering, medical information technology and biotechnology/bioengineering for medicine and addresses engineers, natural scientists, and clinicians working in research, industry, or clinical practice.

Topics

Diagnostic Imaging
Biosignal Processing, Biomechanics, Image Processing, Modelling and Simulation
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
Neuroengineering, Neural Systems, Rehabilitation and Prosthetics
Biomaterials, Cellular and Tissue Engineering, Artificial Organs
Biomedical Engineering for Audiology, Ophthalmology, Emergency and Dental Medicine

Article formats
Conference Proceedings