Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Biomedical Engineering”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 577 records · Page 32Linked to original sources
PubMed2002

The importance of biomechanics.

When neuroscientists gather to discuss "Movement and Sensation", they tend to discuss neurons rather than muscles and bones. Neurons may be more interesting, but their roles in motor control depend on the mechanical properties of the system to be controlled. Understanding of those properties has been surprisingly elusive, despite the well-developed disciplines of biomechanics and muscle physiology. Each experimental field has its favorite, often unique preparation. Mathematical models range in scale from individual cross-bridges to articulated limbs, usually written in different computer languages. The shortcomings of such fragmented knowledge become particularly apparent when biomedical engineers must design safe and effective control systems for real limbs, such as for functional electrical stimulation (FES) of reach and grasp in quadriplegic patients. We are addressing the question of how to model neuromusculoskeletal systems so that they are sufficiently complete, valid and accessible to be useful in both basic and applied sensorimotor research.

Biomechanical Phenomena↗
PubMed1978

High volume intraperitoneal chemotherapy ("belly bath") for ovarian cancer. Pharmacologic basis and early results.

The currently accepted therapies for ovarian cancer have produced only limited numbers of extended complete remissions in advanced-stage disease. Studies of high-volume intraperitoneal chemotherapy have been initiated to define the toxicology, pharmacokinetics, and the therapeutic effectiveness of this treatment modality. This technique has been virtually ignored until recently, because little success has been achieved with it except in one study (Rutledge, 1966), in which large intraperitoneal fluid volumes were used. The general lack of success probably reflects inadequate attention to physiologic and pharmacologic principles of drug distribution and absorption in a space as large as the peritoneal cavity. Biomedical engineers, pharmacologists, and clinicians at the NCI have cooperated in the development of a rational chemotherapy for ovarian cancer. Following mathematical pharmacokinetic modeling and toxicologic studies in rat, a Phase I clinical trial of intraperitoneal methotrexate administered in large volumes of dialysis fluid was initiated. Results in three patients confirm the practicality of this approach, and further investigation is warranted.

Animals↗
PubMed1989

The initial clinical evaluation of a transesophageal system with pulsed Doppler, continuous wave Doppler, and color flow imaging based on an annular array technology.

The application of transesophageal echocardiography (TEE) offers access to a great deal of important clinical information regarding cardiovascular anatomy and physiology. Two applications which have not been reported and would appear to be of interest are continuous wave Doppler capabilities and the implementation of higher frequency transducers. A TEE system designed at the Institute of Biomedical Engineering in Trondheim, which is based on an annular array technology, offers these capabilities. We evaluated this instrument in the clinical setting in a series of 30 patients to test the probe function in terms of the tissue and flow imaging quality with a 7.5 MHz carrier frequency, and to report on the implementation of a continuous wave Doppler modality in a TEE probe. We found that the annular array method permitted the use of high frequency probes for tissue and flow imaging which resulted in excellent image resolution, and that shifting the carrier frequency of the transducer to a lower frequency permitted the optimization of the Doppler sensitivity. The continuous wave Doppler was used to measure abnormal blood flow velocities in excess of 5.0 m/s, and was particularly useful in the operating room as velocity measurements could be obtained without compromising the sterile field. The results of our evaluation indicate that high imaging frequencies and continuous wave Doppler can be applied by an annular array TEE transducer.

Adolescent↗
PubMedDate not supplied

Noninvasive acceleration measurements to characterize knee arthritis and chondromalacia.

Devising techniques and instrumentation for early detection of knee arthritis and chondromalacia presents a challenge in the domain of biomedical engineering. The purpose of the present investigation was to characterize normal knees and knees affected by osteoarthritis, rheumatoid arthritis, and chondromalacia using a set of noninvasive acceleration measurements. Ultraminiature accelerometers were placed on the skin over the patella in four groups of subjects, and acceleration measurements were obtained during leg rotation. Acceleration measurements were significantly different in the four groups of subjects in the time and frequency domains. Power spectral analysis revealed that the average power was significantly different for these groups over a 100-500 Hz range. Noninvasive acceleration measurements can characterize the normal, arthritis, and chondromalacia knees. However, a study on a larger group of subjects is indicated.

Acceleration↗
PubMed1992

Cardiac mechanics: basic and clinical contemporary research.

This survey of cardiac hemodynamics updates evolving concepts of myocardial and ventricular systolic and diastolic loading and function. The pumping action of the heart and its interactions with arterial and venous systems in health and disease provide an extremely rich and challenging field of research, viewed from a fluid dynamic perspective. Many of the more important problems in this field, even if the fluid dynamics in them are considered in isolation, are found to raise questions which have not been asked in the history of fluid dynamics research. Biomedical engineering will increasingly contribute to their solution.

Animals↗
PubMed1999

Computer modelling of the adsorption of proteins on solid surfaces under the influence of double layer and van der Waals energy.

The study of protein interactions with surfaces is important in many branches of biomedical engineering. A computer model has been set up in order to aid the understanding and prediction of the likelihood of protein adsorption at a surface and of coagulation between two proteins. In this model, a protein is represented as a hard sphere, neglecting conformation changes which may occur during the adsorption process. The sphere is assumed to be in a medium whose properties are described by the ionic strength, the pH and the dielectric permittivity. It is considered to interact both with an infinite plane, representing the surface, and with another sphere, representing another protein. The model focuses on the total interaction energy between a protein and a surface and between two proteins. The energy is expressed according to the DLVO theory of colloidal stability, which assumes that the adsorption behaviour of proteins at a surface depends, first, on the van der Waals interactions energy and, second, on the electrostatic double layer interaction energy. The conditions under which adhesion is prevented correspond to the presence of local extremes of the energy function, whereas the conditions under which adhesion is likely to take place correspond to absence of local extremes.

Adsorption↗
PubMed1999

Colonoscopy aided by magnetic 3D imaging: is the technique sufficiently sensitive to detect differences between men and women?

Colonoscopy tends to be more difficult to perform in women. Women also experience more pain during flexible sigmoidoscopy, and the mean insertion distance of the instrument is less than in men. The 'Bladen system', first described in 1993, is a non-radiological method of continuously visualising the path of the endoscope using magnetic drive coils under the patient and a chain of sensors up the biopsy channel of the instrument. In 1998, results were published that used a novel computer graphics system (the 'RMR system'), in which a much more realistic endoscope could be produced using the stored positional data from the Bladen system. The RMR computer graphics system has been further refined to enable measurement of the anatomical lengths of different parts of the large intestine to an accuracy of greater than 5 mm. The system is used to analyse the results obtained in 232 patients undergoing a total colonoscopy. In women, the colonoscope tends to form loops in the sigmoid colon more readily than in men (p < 0.05). When the first 50 cm of the endoscope are inserted for the first time, the tip passes either up to or beyond the splenic flexure in 40/116, or 34.5%, of males, compared with 24/117, or 20.5%, of females (p = 0.0137). It is demonstrated that women have longer transverse colons than men, and the differences are especially apparent when a stiffening tube is used to splint the left side of the colon (p < 0.0001). The possible relevance of these observations to biomedical engineers and those manufacturing and assessing prototype endoscopes is discussed.

Adult↗
PubMedDate not supplied

Electrical signal transmission and gap junction regulation in a bone cell network: a cable model for an osteon.

A cable model is formulated to estimate the spatial distribution of intracellular electric potential and current, from the cement line to the lumen of an osteon, as the frequency of the loading and the conductance of the gap junction are altered. The model predicts that the characteristic diffusion time for the spread of current along the membrane of the osteocytic processes, 0.03 sec, is nearly the same as the predicted pore pressure relaxation time in Zeng et al. (Annals of Biomedical Engineering. 1994) for the draining of the bone fluid into the osteonal canal. This approximate equality of characteristic times causes the cable to behave as a high-pass, low-pass filter cascade with a maximum in the spectral response for the intracellular potential at approximately 30 Hz. This behavior could be related to the experiments of Rubin and McLeod (Osteoporosis, Academic Press, 1996) which show that live bone appears to be selectively responsive to mechanical loading in a specific frequency range (15-30 Hz) for several species.

Action Potentials↗
PubMed2000

Computers in imaging and health care: now and in the future.

Early picture archiving and communication systems (PACS) were characterized by the use of very expensive hardware devices, cumbersome display stations, duplication of database content, lack of interfaces to other clinical information systems, and immaturity in their understanding of the folder manager concepts and workflow reengineering. They were implemented historically at large academic medical centers by biomedical engineers and imaging informaticists. PACS were nonstandard, home-grown projects with mixed clinical acceptance. However, they clearly showed the great potential for PACS and filmless medical imaging. Filmless radiology is a reality today. The advent of efficient softcopy display of images provides a means for dealing with the ever-increasing number of studies and number of images per study. Computer power has increased, and archival storage cost has decreased to the extent that the economics of PACS is justifiable with respect to film. Network bandwidths have increased to allow large studies of many megabytes to arrive at display stations within seconds of examination completion. PACS vendors have recognized the need for efficient workflow and have built systems with intelligence in the management of patient data. Close integration with the hospital information system (HIS)-radiology information system (RIS) is critical for system functionality. Successful implementation of PACS requires integration or interoperation with hospital and radiology information systems. Besides the economic advantages, secure rapid access to all clinical information on patients, including imaging studies, anytime and anywhere, enhances the quality of patient care, although it is difficult to quantify. Medical image management systems are maturing, providing access outside of the radiology department to images and clinical information throughout the hospital or the enterprise via the Internet. Small and medium-sized community hospitals, private practices, and outpatient centers in rural areas will begin realizing the benefits of PACS already realized by the large tertiary care academic medical centers and research institutions. Hand-held devices and the Worldwide Web are going to change the way people communicate and do business. The impact on health care will be huge, including radiology. Computer-aided diagnosis, decision support tools, virtual imaging, and guidance systems will transform our practice as value-added applications utilizing the technologies pushed by PACS development efforts. Outcomes data and the electronic medical record (EMR) will drive our interactions with referring physicians and we expect the radiologist to become the informaticist, a new version of the medical management consultant.

Computers↗
PubMed2007

Biomimetics and the case of the remarkable ragworms.

Biomimetics is a rapidly growing field both as an academic and as an applied discipline. This paper gives a short introduction to the current status of the discipline before it describes three approaches to biomimetics: the mechanism-driven, which is based on the study of a specific mechanism; the focused organism-driven, which is based on the study of one function in a model organism; and the integrative organism-driven approach, where multiple functions of a model organism provide inspiration. The first two are established approaches and include many modern studies and the famous biomimetic discoveries of Velcro and the Lotus-Effect, whereas the last approach is not yet well recognized. The advantages of the integrative organism-driven approach are discussed using the ragworms as a case study. A morphological and locomotory study of these marine polychaetes reveals their biomimetic potential, which includes using their ability to move in slippery substrates as inspiration for novel endoscopes, using their compound setae as models for passive friction structures and using their three gaits, slow crawling, fast crawling, and swimming as well as their rapid burrowing technique to provide inspiration for the design of displacement pumps and multifunctional robots.

Animals↗
PubMed1998

Comparison and cross-calibration of DXA systems: ODX-240 and Sophos L-XRA versus Hologic QDR-4500, for spinal bone mineral measurement. Translation of a reference database.

Replacement of dual-energy X-ray densitometry equipment may be necessary in time as a result of upgrading systems or new equipment. The lack of standardization in bone mineral density (BMD) measurements is known. Standardization efforts have been made for several years by the European Union under its organization COMAC-BME (Comité d'Actions Concertés-BioMedical Engineering) and by the International Committee for Standards in Bone Measurement. Cross-calibration is generally considered to be the result of linear regression between the measurements obtained with two densitometers. A major disadvantage of the regression method is the noncompatibility of the two formulae of calibration (Y versus X and X versus Y). In this study we considered cross-calibration in terms of a structural model that produced circular equations when, for example, three systems were cross-calibrated. Cross-calibration in this study was calculated from the measurement of the lumbar BMD of a population of 204 patients, with Hologic QDR-4500, ODX-240 and Sophos L-XRA systems. In vitro accuracy and short-term reproducibility of the three systems were studied. Using the structural calibration equation we transformed a reference database for L2-4 BMD obtained from a population of 983 French females, aged 11-47 years, on an ODX-240 to a reference database for a Hologic QDR-4500. A new young adult reference was obtained and consequently a new evaluation of the T-score for the Hologic QDR-4500.

Absorptiometry, Photon↗
PubMed2005

Julius Bernstein (1839-1917): pioneer neurobiologist and biophysicist.

Julius Bernstein belonged to the Berlin school of "organic physicists" who played a prominent role in creating modern physiology and biophysics during the second half of the nineteenth century. He trained under du Bois-Reymond in Berlin, worked with von Helmholtz in Heidelberg, and finally became Professor of Physiology at the University of Halle. Nowadays his name is primarily associated with two discoveries: (1) The first accurate description of the action potential in 1868. He developed a new instrument, a differential rheotome (= current slicer) that allowed him to resolve the exact time course of electrical activity in nerve and muscle and to measure its conduction velocity. (2) His 'Membrane Theory of Electrical Potentials' in biological cells and tissues. This theory, published by Bernstein in 1902, provided the first plausible physico-chemical model of bioelectric events; its fundamental concepts remain valid to this day. Bernstein pursued an intense and long-range program of research in which he achieved a new level of precision and refinement by formulating quantitative theories supported by exact measurements. The innovative design and application of his electromechanical instruments were milestones in the development of biomedical engineering techniques. His seminal work prepared the ground for hypotheses and experiments on the conduction of the nervous impulse and ultimately the transmission of information in the nervous system. Shortly after his retirement, Bernstein (1912) summarized his electrophysiological work and extended his theoretical concepts in a book Elektrobiologie that became a classic in its field. The Bernstein Centers for Computational Neuroscience recently established at several universities in Germany were named to honor the person and his work.

Animals↗
PubMed2005

Role of facet curvature for accurate vertebral facet load analysis.

The curvature of vertebral facet joints may play an important role in the study of load-bearing characteristics and clinical interventions such as graded facetectomy. In previously-published finite element simulations of this procedure, the curvature was either neglected or approximated with a varying degree of accuracy. Here we study the effect of the curvature in three different load situations by using a numerical model which is able to represent the actual curvature without any loss of accuracy. The results show that previously-used approximations of the curvature lead to good results in the analysis of sagittal moment/rotation. However, for sagittal shear-force/displacement and for the contact stress distribution, previous results deviate significantly from our results. These findings are supported through related convergence studies. Hence we can conclude that in order to obtain reliable results for the analysis of sagittal shear-force/displacement and the contact stress distribution in the facet joint, the curvature must not be neglected. This is of particular importance for the numerical simulation of the spine, which may lead to improved diagnostics, effective surgical planning and intervention. The proposed method may represent a more reliable basis for optimizing the biomedical engineering design for tissue engineering or, for example, for spinal implants.

Biomechanical Phenomena↗
PubMed2005

Flow in prosthetic heart valves: state-of-the-art and future directions.

Since the first successful implantation of a prosthetic heart valve four decades ago, over 50 different designs have been developed including both mechanical and bioprosthetic valves. Today, the most widely implanted design is the mechanical bileaflet, with over 170,000 implants worldwide each year. Several different mechanical valves are currently available and many of them have good bulk forward flow hemodynamics, with lower transvalvular pressure drops, larger effective orifice areas, and fewer regions of forward flow stasis than their earlier-generation counterparts such as the ball-and-cage and tilting-disc valves. However, mechanical valve implants suffer from complications resulting from thrombus deposition and patients implanted with these valves need to be under long-term anti-coagulant therapy. In general, blood thinners are not needed with bioprosthetic implants, but tissue valves suffer from structural failure with, an average life-time of 10-12 years, before replacement is needed. Flow-induced stresses on the formed elements in blood have been implicated in thrombus initiation within the mechanical valve prostheses. Regions of stress concentration on the leaflets during the complex motion of the leaflets have been implicated with structural failure of the leaflets with bioprosthetic valves. In vivo and in vitro experimental studies have yielded valuable information on the relationship between hemodynamic stresses and the problems associated with the implants. More recently, Computational Fluid Dynamics (CFD) has emerged as a promising tool, which, alongside experimentation, can yield insights of unprecedented detail into the hemodynamics of prosthetic heart valves. For CFD to realize its full potential, however, it must rely on numerical techniques that can handle the enormous geometrical complexities of prosthetic devices with spatial and temporal resolution sufficiently high to accurately capture all hemodynamically relevant scales of motion. Such algorithms do not exist today and their development should be a major research priority. For CFD to further gain the confidence of valve designers and medical practitioners it must also undergo comprehensive validation with experimental data. Such validation requires the use of high-resolution flow measuring tools and techniques and the integration of experimental studies with CFD modeling.

Animals↗
PubMed2006

Design and control optimization of microclimate liquid cooling systems underneath protective clothing.

The use of protective clothing, whether in space suits, hazardous waste disposal, or sporting equipment, generally increases the risk of heat stress and hyperthermia by impairing the capacity for evaporative heat exchange from the body to the environment. To date the most efficient method of microclimate cooling underneath protective clothing has been via conductive heat exchange from circulating cooling fluid next to the skin. In order to make the use of liquid microclimate cooling systems ((LQ)MCSs) as portable and practical as possible, the physiological and biomedical engineering design goals should be towards maximizing the efficiency of cooling to maintain thermal comfort/neutrality with the least cooling possible to minimize coolant and power requirements. Meeting these conditions is an extremely complex task that requires designing for a plethora of different factors. The optimal fitting of the (LQ)MCSs, along with placement and design of tubing and control of cooling, appear to be key avenues towards maximizing efficiency of heat exchange. We review the history and major design constraints of (LQ)MCSs, the basic principles of human thermoregulation underneath protective clothing, and explore potential areas of research into tubing/fabric technology, coolant distribution, and control optimization that may enhance the efficiency of (LQ)MCSs.

Cold Temperature↗
PubMed2006

A modeling study of notch noise responses of type III units in the gerbil dorsal cochlear nucleus.

A computational model of the neural circuitry of the gerbil dorsal cochlear nucleus (DCN), based on the MacGregor's neuromime model, was used to simulate type III unit (P-cell) responses to notch noise stimuli. The DCN patch model is based on a previous computational model of the cat DCN [Hancock, K. E., and H. F. Voigt. Ann. Biomed. Eng. 27:73-87, 1999]. According to the experimental study of Parsons et al. [Ann. Biomed. Eng. 29:887-896, 2001], the responses of gerbil DCN type III units to notch noise stimuli are similar to those of cat DCN type IV units, which are thought to be spectral notch detectors. This suggests that type III units in the gerbil DCN may serve as spectral notch detectors. In this modeling study, a simplified notch noise response plot-spike discharge rate vs. notch cutoff frequency plot-was used to compare model responses to the experimental results. Parameter estimation and sensitivity analysis of three connection parameters within the DCN patch have been studied and shows the model is robust, providing reasonable fits to the experimental data from 14 of 15 type III units examined [work supported by a grant from NIDCD, Boston University's Biomedical Engineering department and Hearing Research Center].

Animals↗
PubMed2006

Wound healing effect of silk fibroin/alginate-blended sponge in full thickness skin defect of rat.

Silk fibroin (SF) and alginate (AA) have been proved to be invaluable natural materials in the field of biomedical engineering. This study was designed to compare the wound healing effect of SF, AA and SF/AA-blended sponge (SF/AA) with clinically used Nu Gauze(TM) (CONT) in a rat full thickness wound model. Two circular skin wounds on the back of rat were covered with either of CONT, SF, AA or SF/AA. On the postoperative days of 3, 7, 10 and 14, residual wound area was calculated, and skin wound tissues were biopsied to measure the area of regenerated epithelium and collagen deposition as well as the number of proliferating cell nuclear antigen (PCNA)-immunoreactive cells. Half healing time (HT(50)) of SF/AA was dramatically reduced as compared with that of SF, AA or CONT. Furthermore, SF/AA significantly increased the size of re-epithelialization and the number of PCNA positive cells, whereas the effect of SF/AA on collagen deposition was not significantly different as compared with that of SF or AA. These results demonstrate that the wound healing effect of SF/AA is the best among other treatments including SF and AA, and this synergic effect is mediated by re-epithelialization via rapid proliferation of epithelial cell.

Alginates↗
PubMed2006

Tutorial on univariate autoregressive spectral analysis.

In the present paper, the theoretical basis of autoregressive (AR) modelling in spectral analysis is explained in simple terms. Spectral analysis gives information about the frequency content and sources of variation in a time series. The AR method is an alternative to discrete Fourier transform, and the method of choice for high-resolution spectral estimation of a short time series. In biomedical engineering, AR modelling is used especially in the spectral analysis of heart rate variability and electroencephalogram tracings. In AR modelling, each value of a time series is regressed on its past values. The number of past values used is called the model order. An AR model or process may be used in either process synthesis or process analysis, each of which can be regarded as a filter. The AR analysis filter divides the time series into two additive components, the predictable time series and the prediction error sequence. When the prediction error sequence has been separated from the modelled time series, the AR model can be inverted, and the prediction error sequence can be regarded as an input and the measured time series as an output to the AR synthesis filter. When a time series passes through a filter, its amplitudes of frequencies are rescaled. The properties of the AR synthesis filter are used to determine the amplitude and frequency of the different components of a time series. Heart rate variability data are here used to illustrate the method of AR spectral analysis. Some basic definitions of discrete-time signals, necessary for understanding of the content of the paper, are also presented.

Heart Rate↗