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At least 703 records · Page 39Linked to original sources
PubMed2002

Smoothing of pixelated finite element models of cancellous bone structures and the effect on the predicted structural properties of the bone.

Many areas of biomedical engineering involve the modelling of biological systems, often using data from medical scanning techniques such as computed microtomography (microCT), and the prediction of the mechanical properties of these systems via finite element models. These models, and also those produced from remodelling simulations on idealized bone structures, are inherently highly pixelated and therefore have a high degree of surface roughness. The purpose of this paper is to demonstrate that this surface roughness need not necessarily have an influence on the predicted properties of the object under examination. To demonstrate this, two-dimensional idealized models of cancellous bone structures were used that were initially depleted and then rebuilt stochastically. A hysteresis effect was observed such that a significant amount of rebuilding beyond the original density was required to regain the initial intact stiffness. To ensure that this effect was not an artefact of the high degree of surface roughness of the rebuilt structures, a two-stage smoothing procedure was applied to assess if this had any effect on the stiffness of the structures. The superpixelation of the structures appeared to have a more profound effect than the smoothing procedures, although the smoothed structures still had stiffness and density values similar to those of the original structures, with a hysteresis effect still evident. This proves that the pixelization of the structures does not have a significant effect on the predicted mechanical properties of the structures. This work has important implications for other models that exhibit a high degree of surface roughness.

Artifacts↗
PubMed1992

The CADCAM contribution to customized orthopaedic implants.

CADCAM (computer aided design/manufacture) production methods are often associated with mass production; working in the medical field at the Department of Biomedical Engineering, the requirement is for one-off, individualized implants. Using a knowledge-based system, implant designs are produced from X-ray data. Assembly from modular components has greatly reduced the production time of implants for bone tumour cases. CADCAM techniques are also used in the production of custom-made hip replacements using digitized data gathered from radiographs. Femoral canal shape is calculated and the optimal implant designed and manufactured from titanium alloy on the Department's CNC (computer numerically controlled) machines.

Computer-Aided Design↗
PubMed2005

Molecularly imprinted polymers for biomolecular recognition.

Molecular imprinting of polymers is a concept for the synthetic formation of structurally organized materials providing binding sites with molecular selectivity. Compared to biological receptors, these polymeric recognition systems have the advantage of superior chemical and mechanical stability with potential applications in areas such as biomimetic catalysis and engineering, biomedical analysis, sensor technology, or the food industry. In particular, molecularly imprinted polymers (MIPs) providing selectivity for biorelated molecules are gaining substantial importance. In this context, a self-assembly approach for the synthesis of imprinted polymers against the flavonol quercetin is presented, which is exemplary for the biologically relevant group of flavonoid compounds. The creation of synthetic selective recognition sites for this biomolecule is demonstrated by comparing the separation capabilities of imprinted and nonimprinted polymer particles for several structurally related molecules via high-performance liquid chromatography experiments. The developed quercetin-MIP enables selective extraction of quercetin even from complex mixtures, demonstrating the potential for designing biomimetic recognition materials with improved selectivity for biomolecules with tunable functionality at a nanoscale.

Chemistry Techniques, Analytical↗
PubMed2002

Imaging characteristics of different multichannel magnetocardiographic systems.

In this study a comparison of multichannel magnetocardiographic systems is performed with respect to the "detectable" information content. We investigate the lead-field matrices, the slope of the singular values and the source spaces of three different devices: the VectorView (Neuromag: magnetometer-gradiometer mixed device) of the BioMag Laboratory, Helsinki University Central Hospital (HUCH), the arrangement of electronically coupled magnetometers of the Physikalisch-Technische Bundesanstalt Berlin (PTB) and a virtual sensor geometry which was optimized for an improved slope of the singular values at the Institute of Biomedical Engineering, Karlsruhe.

Adult↗
PubMed2002

[Development of a laser-optical tomograph for demonstration of CT imaging without ionizing radiation].

Computed X-ray tomography (CT) is one of the most powerful diagnostic procedures in medicine. In this study, we developed a laser-optical CT scanner for the use by students as part of their curriculum in biomedical engineering. Our CT set-up employs a linear-scan technique where the measurement objects (light absorbing phantoms embedded in immersion oil), the light emitter (modulated laserdiode), and the detector (photodiode) are moved by linear-step motors. The spatial resolution is limited by the width of the laser beam (2 mm) and the smallest achievable raster step size (0.02 mm). Optical tomographic images of various objects can be measured within a few minutes and allow the demonstration of imaging principles like extinction, scanning, projection, and reconstruction techniques.

Equipment Design↗
PubMed2002

["Saar Stroke Teleservice--pilot study for stroke after care with a home care platform].

In the German region Saarland a pilot trial has been conducted for the post-clinical telecare and rehabilitation of stroke patients in there homes by a cooperative network of local healthcare providers. For that purpose an e-home care platform has been developed by a combine of Fraunhofer institutes under the leadership of the Fraunhofer Institute for Biomedical Engineering. A network formed by a clinic, 2 general practitioners and an advice centre cared for 18 patients using the so-called PHS Homecare Platform for telemonitoring and virtual visits by videophone. (PHS: Personal Health Service--A research initiative of the Fraunhofer Society in the years 1996-2001). In the underlying feasibility study the telecare of stroke patients in the context of the German healthcare system has been tested and the e-home care platform has been evaluated.

Computer Communication Networks↗
PubMed2002

Clinical treatment regimens for chronic heart failure: a review.

Chronic heart failure (CHF) is increasing in prevalence worldwide, particularly in the elderly. Accordingly, this epidemic is likely to translate into a major increase in healthcare costs. Systolic heart failure is the most common cause of CHF presentations. Although the causes vary, the most common single aetiological factor is ischaemic heart disease, which accounts for approximately 50% of heart failure presentations. Research into CHF pharmacotherapy has been copious, with the focus principally centred on systolic heart failure. The evidence base for pharmacotherapy in CHF is amongst the largest currently in clinical medicine. There have been multiple trials establishing the mortality and morbidity benefits of pharmacotherapy. Amongst these, large scale trials of angiotensin-converting enzyme inhibitors, beta-blockers and spironolactone have provided a sound basis for evidence-based treatment approaches to the CHF patient. Recently research interest has increased in biomedical engineering with studies being performed in biventricular pacing and mechanical hearts. Early data with biventricular pacing or cardiac resynchronisation therapy is encouraging. Diastolic heart failure alone accounts for at least 20 - 40% of CHF presentations and whilst it may occur in isolation, is most commonly seen in association with systolic heart failure. In this study, we present a broad overview of the current therapeutic modalities for the management of CHF, with particular emphasis on pharmacotherapy.

Adrenergic beta-Antagonists↗
PubMed1995

Acoustic emission and nondestructive evaluation of biomaterials and tissues.

Acoustic emission (AE) is an acoustic wave generated by the release of energy from localized sources in a material subjected to an externally applied stimulus. This technique may be used nondestructively to analyze tissues, materials, and biomaterial/tissue interfaces. Applications of AE include use as an early warning tool for detecting tissue and material defects and incipient failure, monitoring damage progression, predicting failure, characterizing failure mechanisms, and serving as a tool to aid in understanding material properties and structure-function relations. All these applications may be performed in real time. This review discusses general principles of AE monitoring and the use of the technique in 3 areas of importance to biomedical engineering: (1) analysis of biomaterials, (2) analysis of tissues, and (3) analysis of tissue/biomaterial interfaces. Focus in these areas is on detection sensitivity, methods of signal analysis in both the time and frequency domains, the relationship between acoustic signals and microstructural phenomena, and the uses of the technique in establishing a relationship between signals and failure mechanisms.

Acoustics↗
PubMed1997

Biomechanics of penetrating trauma.

It is well known that injuries and deaths due to penetrating projectiles have become a national and an international epidemic in Western society. The application of biomedical engineering to solve day-to-day problems has produced considerable advances in safety and mitigation/prevention of trauma. The study of penetrating trauma has been largely in the military domain where war-time specific applications were advanced with the use of high-velocity weapons. With the velocity and weapon caliber in the civilian population at half or less compared with the military counterpart, wound ballistics is a largely different problem in today's trauma centers. The principal goal of the study of penetrating injuries in the civilian population is secondary prevention and optimized emergency care after occurrence. A thorough understanding of the dynamic biomechanics of penetrating injuries quantifies missile type, caliber, and velocity to hard and soft tissue damage. Such information leads to a comprehensive assessment of the acute and long-term treatment of patients with penetrating injuries. A review of the relevant military research applied to the civilian domain and presentation of new technology in the biomechanical study of these injuries offer foundation to this field. Relevant issues addressed in this review article include introduction of the military literature, the need for secondary prevention, environmental factors including projectile velocity and design, experimental studies with biological tissues and physical models, and mathematical simulations and analyses. Areas of advancement are identified that enables the pursuit of biomechanics research in order to arrive at better secondary prevention strategies.

Animals↗
PubMed1998

Biomedical concerns in wireless communications.

The last decade witnessed rapid development of new communication technologies and their broad acceptance at large. Digital wireless telephones are the most popular example of these technologies. There are two aspects of these technologies that are related to human health and therefore biomedical engineering. First, antennas of some devices are in close proximity to the user's head, thus possibly producing locally excessive energy deposition. Second, radiofrequency (RF) signals emitted are amplitude modulated at extremely low frequencies, potentially eliciting different biological effects from those of unmodulated RF radiation. Recent progress in addressing these two issues is reviewed in this article. Another area of research and concern not covered here is electromagnetic interference (EMI) with medical devices. Considerable research has been conducted on the development of a new method for numerical and experimental evaluation of the spatial distribution of the power deposition in tissue. Improved implantable electric field probes and automated scanning systems are presently available. With respect to numerical evaluation of electric fields in tissue, the finite difference time domain (FDTD) technique has proven to be a useful and accurate tool. These developments also are critical in view of the regulatory requirements now imposed on mobile/portable transmitters. Similarly, significant research effort on biological effects of modulated fields has been undertaken. Most of the studies are still in progress, and further research agendas have been proposed.

Electromagnetic Fields↗
PubMed2002

Biomedical signal processing and modeling in cardiovascular systems.

This article revisits the subject of short-term heart-rate and arterial-pressure variability from the perspective of model structures that can be useful in defining signal processing algorithms. We draw a general scheme of the oscillation sources and interactions that contribute to cardiovascular control mechanisms and highlight the elements that were considered in different modeling works. The origin, superposition, and interaction of respiratory high-frequency (HF) and vasomotor low-frequency (LF) rhythms is presented as the integration of supraspinal and spinal circuits, vasomotor activity, and pressure control loops. We analyze in detail the necessity of considering all relevant interactions for the algorithms designed to estimate the baroreflex sensitivity. We also pinpoint the components of cardiorespiratory coupling in relation to the analysis of data from the acoustic quantification of the left ventricular volume. Finally, we analyze the tendency to produce complex behaviors even in extremely simplified systems involving interactions between oscillatory mechanisms.

Animals↗
PubMed2003

Health risks of electromagnetic fields. Part III: Risk analysis.

The management of potential health risks from electromagnetic (EM) fields presents both scientific and nonscientific challenges. When the scientific evidence is ambiguous, as is the case with EM fields, expert judgment of this evidence becomes particularly important. This article provides biomedical researchers with a comprehensive assessment of the status of EM health risk based on our two previous articles [Parts I and II, Critical Reviews in Biomedical Engineering, Volume 31, Issue 3]. Ambiguous evidence also necessitates rigorous public debate. This article also discusses effective risk communication approaches that play a key role in the EM risk issue. Because of uncertainty about health risks associated with EMF exposure, the public is more likely to experience difficulty in evaluating the available information and rely more on perceptions than facts when drawing conclusions. Even the most effective risk communication approaches are not likely to clarify all of the subtleties surrounding EM fields as a population health issue. Thus it is essential that all stakeholders involved in this issue participate in developing consensus solutions.

Attitude to Health↗
PubMed2003

Heart rate variability in athletes.

This review examines the influence on heart rate variability (HRV) indices in athletes from training status, different types of exercise training, sex and ageing, presented from both cross-sectional and longitudinal studies. The predictability of HRV in over-training, athletic condition and athletic performance is also included. Finally, some recommendations concerning the application of HRV methods in athletes are made.The cardiovascular system is mostly controlled by autonomic regulation through the activity of sympathetic and parasympathetic pathways of the autonomic nervous system. Analysis of HRV permits insight in this control mechanism. It can easily be determined from ECG recordings, resulting in time series (RR-intervals) that are usually analysed in time and frequency domains. As a first approach, it can be assumed that power in different frequency bands corresponds to activity of sympathetic (0.04-0.15 Hz) and parasympathetic (0.15-0.4 Hz) nerves. However, other mechanisms (and feedback loops) are also at work, especially in the low frequency band. During dynamic exercise, it is generally assumed that heart rate increases due to both a parasympathetic withdrawal and an augmented sympathetic activity. However, because some authors disagree with the former statement and the fact that during exercise there is also a technical problem related to the non-stationary signals, a critical look at interpretation of results is needed. It is strongly suggested that, when presenting reports on HRV studies related to exercise physiology in general or concerned with athletes, a detailed description should be provided on analysis methods, as well as concerning population, and training schedule, intensity and duration. Most studies concern relatively small numbers of study participants, diminishing the power of statistics. Therefore, multicentre studies would be preferable. In order to further develop this fascinating research field, we advocate prospective, randomised, controlled, long-term studies using validated measurement methods. Finally, there is a strong need for basic research on the nature of the control and regulating mechanism exerted by the autonomic nervous system on cardiovascular function in athletes, preferably with a multidisciplinary approach between cardiologists, exercise physiologists, pulmonary physiologists, coaches and biomedical engineers.

Autonomic Nervous System↗
PubMedDate not supplied

Vibrotactile stimulation system to treat apnea of prematurity.

We modified a system that uses vibrotactile stimulation (VTS) to treat apnea (a cessation of respiration) in neonates in order to make the system more portable and easier to use by clinicians and nurses. The biomedical engineering department at Hartford Hospital (Hartford, CT) together with the Neonatology Division at the Connecticut Children's Medical Center (CCMC) (Hartford, CT) has been involved in developing the VTS system. Clinical trails were conducted in the neonatal intensive care unit of CCMC, and further preliminary data were collected. The main components of the system are a Tacaid vibrotactile stimulator (Audiological Engineering, Somerville, MA), a neonatal physiological monitor (Model 511; CAS Medical Inc, Branford, CT), a laptop computer running Windows 95 by Microsoft, National Instruments' data acquisition cards DAQCard-1200 and DAQCard-5102, and a software application developed by Premise Development Corporation, Hartford, CT. Heart rate, oxygen saturation, pulse, thoracic impedance, nasal airflow, and electrocardiogram are recorded from the monitor to the laptop. Whenever an apneic spell is detected, the nurse has the option of triggering a 3-second, 10-V, 250-Hz square-wave pulse to the transducer. The vibrotactile transducer is placed noninvasively with tape on the infant's thorax. This stimulus should arouse the infant and end the apneic event. To facilitate clinical study, the system provides voice and visual prompts for the clinician and nurses. Preliminary data continue to support both the safety and efficacy of the VTS.

Apnea↗