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 613 records · Page 34Linked to original sources
PubMed2004

A combined dielectrophoresis, traveling wave dielectrophoresis and electrorotation microchip for the manipulation and characterization of human malignant cells.

The study of the dielectric properties of micrometer- or nanometer-scale particles is of particular interest in present-day applications of biomedical engineering. Electrokinetics utilises electrically energised microelectrode structures within microfluidic chambers to noninvasively probe the physiological structure of live cancer cells. A system is described that combines the three complementary techniques of dielectrophoresis (DEP), travelling wave dielectrophoresis (TWD) and electrorotation (ROT) for the first time on a single, integrated chip (3 x 6 mm). The chip employs planar microelectrode arrays fabricated on a silicon substrate to facilitate the synthesis of the various nonuniform electric fields required for the controlled manipulation, measurement and characterization of mammalian cells. A study of the dielectric properties of human malignant cells (Daudi and NCI-H929) was performed to demonstrate the potential and the versatility of the system in providing a fully programmable microsystem.

Burkitt Lymphoma↗
PubMed2005

Biologic approaches to articular cartilage surgery: future trends.

The treatment of unicompartmental osteoarthritis and focal chondral pathologic conditions in the knee in active aging athletes has captured the interest of patients, clinicians, basic scientists, and medical industry researchers. Most would agree that a biologic solution to treating hyaline cartilage injuries and degeneration would be optimal over prosthetic joint arthroplasty. Articular cartilage resurfacing techniques and biologic surgical methods continue to evolve and have gained more acceptance in orthopedic practice. A consensus exists for the ultimate goal of achieving a more predictable and durable result after surgical tissue repair or regeneration. Numerous promising approaches are now on the horizon and although the final word is far from in, the integration of many of the anticipated advances in molecular medicine, biomedical engineering, polymer chemistry, cell biology, and clinical orthopedics contributes to an exciting and rapidly evolving field. This article reviews the current concepts of the biologic approach to articular cartilage pathologic conditions and discusses future trends and novel technologies.

Arthroplasty↗
PubMed1998

ORBIS--training nurses worldwide in ophthalmic care.

The unique nature of the ORBIS teaching mission is reflected in many arenas. The ORBIS organization recognizes that the nurse's role is critical to achieving their mission of preventing blindness through education, hence the emphasis on nurse education. The roles of the head nurse, nurse educator, staff nurses, and the biomedical engineering department are discussed briefly with emphasis on the needs assessment and the different programs offered to meet the identified needs.

Aircraft↗
PubMed1996

Stimulus artifact reduction in evoked potential measurements.

OBJECTIVE: To investigate the main coupling mechanisms involved in stimulus artifact contamination of evoked potential recordings and to suggest techniques that minimize this interference. DESIGN: A before-after trial of a single subject. SETTING: Measurements were obtained at a university biomedical engineering laboratory. PARTICIPANTS: Data were obtained from one volunteer subject. INTERVENTION: An electrical stimulus was used to depolarize the posterior tibial nerve at the ankle. Various recording electrode configurations were used to demonstrate stimulus artifact recordings. RESULTS: Three mechanisms are defined as contributing significantly to stimulus artifact contamination of evoked potential data. These are: the volume conducted component, the displacement current component, and the electromagnetic coupling component. When each component is maximally controlled, the problem of stimulus artifact is greatly reduced. CONCLUSION: Three major factors that contribute to stimulus artifact contamination of the evoked potential waveform can be identified and minimized by relatively simple clinical techniques.

Artifacts↗
PubMed1999

Functional correlates with left-right asymmetry of visual evoked potentials in stroke patients: modeling and experimental results.

OBJECTIVE: To determine the correlation between a clinical measure of function in patients after first stroke and left-right scalp amplitude of visual evoked potentials using a theoretical model of the head. DESIGN: A random sample of first-stroke patients underwent routine function measurement and investigation of left-right scalp potential asymmetry. Results of the encephalographic tests were compared with those of a healthy subject. To examine the effect of the conductivity in the damaged area on the potential asymmetry, numerical calculations were performed on a model, with four concentric circular compartments representing the brain, cerebrospinal fluid layer, skull, and scalp. The damaged region was modeled as a circular section. SETTING: Neurologic rehabilitation ward of a major rehabilitation hospital and university-affiliated biomedical engineering laboratory. PATIENTS: Four men aged 58 to 71 years, 3 with brain thrombosis and 1 with hemorrhagic stroke. The patients were admitted for rehabilitation an average of 3 weeks after the stroke and stayed for an average of 137 days. Damage was confined to the right brain in all cases; three of the patients had neglect syndrome and/or sensory disturbances. A healthy subject without stroke was also examined. MEASURES: Function was measured with the Functional Independence Measure (FIM) at 48 to 72 hours from admission and during the last week before discharge. Functional gain was calculated by subtracting the FIM admission score from the discharge score. Left-right scalp visual evoked potential amplitude was studied with flash stimuli according to the 10-20 international system and a theoretical model of the head based on two-dimensional computed tomography images; the volume conductor equation was solved numerically using the finite volume method. Left-right potential asymmetry and the damaged-region-to-brain-area ratio were calculated and correlated with the FIM values by linear regression analysis. Negative asymmetry indicates that the activity in the right damaged hemisphere is lower than in the undamaged one. RESULTS: A negative correlation was noted between the FIM score on admission and the left-right scalp potential amplitude asymmetry, and between the FIM gain and the damaged-region-to-brain-area ratio obtained from the computed tomography image. Asymmetry was negative in the thrombotic patients and positive in the hemorrhagic one. The healthy subject showed nonsignificant asymmetry. CONCLUSION: A relationship might exist between the left-right asymmetry of the scalp visual evoked potential and both the damaged-region-to-brain-area ratio and the functional outcome of rehabilitation in poststroke patients. The modeling study shows that the left-right asymmetry is most likely the result of changes in the conductivity at the damaged area, which, in turn, are probably associated with patient functional status and evolution. Further validation in larger groups of patients and normal subjects is needed before these parameters can serve as useful indices for clinical purposes.

Aged↗
PubMed1999

Clinical use of the Odstock dropped foot stimulator: its effect on the speed and effort of walking.

OBJECTIVE: To assess the clinical effectiveness of the Odstock dropped foot stimulator by analysis of its effect on physiological cost index (PCI) and speed of walking. This functional electrical stimulation (FES) device stimulates the common peroneal nerve during the swing phase of gait. DESIGN: A retrospective study of patients who had used the device for 4 1/2 months. SUBJECTS: One hundred fifty-one patients with a dropped foot resulting from an upper motor neuron lesion. SETTING: A medical physics and biomedical engineering department of a district general hospital specializing in the clinical application of FES and a neurophysiotherapy department at a separate hospital. MAIN OUTCOME MEASURES: Changes in walking speed and effort of walking, as measured by PCI over a 10-meter course. RESULTS: There was a 92.7% compliance with treatment. Stroke patients showed a mean increase in walking speed of 27% (p<.01) and reduction in PCI of 31% (p<.01) with stimulation, and changes of 14% (p<.01) and 19% (p<.01), respectively, while not using the stimulator. Multiple sclerosis patients gained similar orthotic benefit but no "carry-over." CONCLUSIONS: The measured differences in walking with and without stimulation were statistically significant in the stroke and multiple sclerosis groups. In this study use of the stimulator improved walking. Those with stroke demonstrated a short-term "carry-over" effect.

Adult↗
PubMed2003

Concentration effect on the aggregation of a self-assembling oligopeptide.

Concentration is a key parameter in controlling the aggregation of self-assembling oligopeptides. By investigating the concentration effects, an aggregation mechanism of EAK16-II is proposed. Depending on the critical aggregation concentration (CAC) of EAK16-II, the oligopeptide aggregates into protofibrils through seeding and/or a nucleation process. Protofibrils then associate with each other to form fibrils. The CAC was found to be approximately 0.1 mg/ml by surface tension measurements. The nanostructures of aggregates were imaged and analyzed by atomic force microscopy. Globular and fibrillar aggregates were observed, and their dimensions were further quantified. To ensure that the aggregates were formed in bulk solution, light scattering (LS) measurements were conducted to monitor the fibril formation with time. The LS profile showed two different rates of aggregation depending on whether the peptide concentration was above or below the CAC. At high concentrations, the LS intensity increased strongly at early times. At low concentrations, the LS intensity increased only slightly. Our study provides information about the nature of the oligopeptide self-assembly, which is important to the understanding of the fibrillogenesis occurring in conformational diseases and to many biomedical engineering applications.

Binding Sites↗
PubMed2001

An analysis of the effects of depth-dependent aggregate modulus on articular cartilage stress-relaxation behavior in compression.

An accurate description of the mechanical environment around chondrocytes embedded within their dense extracellular matrix (ECM) is essential for the study of mechano-signal transduction mechanism(s) in explant experiments. New methods have been developed to determine the inhomogeneous strain distribution throughout the depth of the ECM during compression (Schinagl et al., 1996, Annals of Biomedical Engineering 24, 500-512; Schinagl et al 1997. Journal of Orthopaedics Research 15, 499-506) and the corresponding depth-dependent aggregate modulus distribution (Wang and Mow, 1998. Transactions of the Orthopaedics Research Society 23, 484; Chen and Sah, 1999. Transactions of the Orthopaedics Research Society 24, 635). These results provide the motivation for the current investigation to assess the influence of tissue inhomogeneity on the chondrocyte milieu in situ, e.g. stress, strain, fluid velocity and pressure fields within articular cartilage. To describe this inhomogeneity, we adopted the finite deformation biphasic constitutive law developed by Holmes and Mow (1990 Journal of Biomechanics 23, 1145-1156). Our calculations show that the mechanical environment inside an inhomogeneous tissue differs significantly from that inside a homogeneous tissue. Furthermore, our results indicate that the need to incorporate an inhomogeneous aggregate modulus. or an anisotropy, into the biphasic theory to describe articular cartilage depends largely on the motivation for the study.

Cartilage, Articular↗
PubMed2001

Application of an anisotropic bone-remodelling model based on a damage-repair theory to the analysis of the proximal femur before and after total hip replacement.

In this work, a new model for internal anisotropic bone remodelling is applied to the study of the remodelling behaviour of the proximal femur before and after total hip replacement (THR). This model considers bone remodelling under the scope of a general damage-repair theory following the principles of continuum damage mechanics. A "damage-repair" tensor is defined in terms of the apparent density and Cowin's "fabric tensor", respectively, associated with porosity and directionality of the trabeculae. The different elements of a thermodynamically consistent damage theory are established, including resorption and apposition criteria, evolution law and rate of remodelling. All of these elements were introduced and discussed in detail in a previous paper (García, J. M., Martinez, M. A., Doblaré, M., 2001. An anisotrophic internal-external bone adaptation model based on a combination of CAO and continuum damage mechanics technologies. Computer Methods in Biomechanics and Biomedical Engineering 4(4), 355-378.), including the definition of the proposed mechanical stimulus and the qualitative properties of the model. In this paper, the fundamentals of the proposed model are briefly reviewed and the computational aspects of its implementation are discussed. This model is then applied to the analysis of the remodelling behaviour of the intact femur obtaining densities and mass principal values and directions very close to the experimental data. The second application involved the proximal femoral extremity after THR and the inclusion of an Exeter prosthesis. As a result of the simulation process, some well-known features previously detected in medical clinics were recovered, such as the stress yielding effect in the proximal part of the implant or the enlargement of the cortical layer at the distal part of the implant. With respect to the anisotropic properties, bone microstructure and local stiffness are known to tend to align with the stress principal directions. This experimental fact is mathematically proved in the framework of this remodelling model and clearly shown in the results corresponding to the intact femur. After THR the degree of anisotropy decreases tending, specifically in the proximal femur, to a more isotropic behaviour.

Anisotropy↗
PubMed2002

An alternative ultrasonic method for measuring the elastic properties of cortical bone.

We studied the elastic properties of bone to analyze its mechanical behavior. The basic principles of ultrasonic methods are now well established for varying isotropic media, particularly in the field of biomedical engineering. However, little progress has been made in its application to anisotropic materials. This is largely due to the complex nature of wave propagation in these media. In the present study, the theory of elastic waves is essential because it relates the elastic moduli of a material to the velocity of propagation of these waves along arbitrary directions in a solid. Transducers are generally placed in contact with the samples which are often cubes with parallel faces that are difficult to prepare. The ultrasonic method used here is original, a rough preparation of the bone is sufficient and the sample is rotated. Moreover, to analyze heterogeneity of the structure we measure velocities in different points on the sample. The aim of the present study was to determine in vitro the anisotropic elastic properties of cortical bones. For this purpose, our method allowed measurement of longitudinal and transverse velocities (C(L) and C(T)) in longitudinal (fiber direction) and the radial directions (orthogonal to the fiber direction) of compact bones. Young's modulus E and Poisson's ratio nu, were then deduced from the velocities measured considering the compact bone as transversely isotropic or orthotropic. The results are in line with those of other methods.

Animals↗
PubMed1976

Neurology of micturition.

The understanding, diagnosis and management of neurologic dysfunction of the bladder have undergone considerable changes during the last 2 decades. These changes were the result of animal experimentation into physiology and pharmacology and the accelerated use of biomedical engineering technology. The implementation of these advances will require physician re-education in the neurology of micturition.

Electric Stimulation↗
PubMed1985

When organs match and health beliefs don't. Bioethical challenges.

This paper addresses the problems that psychologically unprepared individuals may experience when the socioethnic aspects of their health belief systems are not addressed in the decision-making process for renal transplantation. Case studies of two Hispanic adolescents are presented. A cognitive behavioral therapeutic approach that specifically concentrates on changing health beliefs related to organ transplant is recommended to help maximize the probability of a successful transplant. Past assumptions by psychosocial transplant teams that make self-esteem the primary basis on which to predict transplant or therapeutic outcome are challenged. The exchange of scientific cognition modifying strategies to address health beliefs that are deleterious to biologic and psychologic survival are recommended as a critical part of biomedical engineering practice for the next decade.

Adolescent↗
PubMed2003

Equipment and water treatment considerations for the provision of quotidian home hemodialysis.

BACKGROUND: Whereas clinical benefits of more frequent hemodialysis (HD) treatment are well documented, little information is available about technical aspects involved in setting up a patient's home for home HD. Technical considerations include the home infrastructure, as well as required plumbing modifications and electrical hook-ups. METHODS: Twenty home HD installations were supported for the London Daily/Nocturnal Hemodialysis Study. The Fresenius 2008H (Fresenius Medical Care, North America, Lexington, MA) HD machine was used for all home HD installations in conjunction with a Service Deionization Tank (SDI) water treatment system composed of pretreatment, purification, and posttreatment components. To ensure that SDI systems provided high-quality water and dialysate, standard bacteriological testing was performed throughout the study, and patient serum C-reactive protein (CRP) levels were tracked as an indicator of nonspecific inflammation. RESULTS: The annual number of hours of work required for each home HD installation and service/maintenance was approximately 75 and 58 hours, respectively. Water quality proved high because there were only 4 occurrences of failed endotoxin and bacterial tests; all were subsequently retested and provided satisfactory results. Serum CRP levels showed no significant difference comparing home HD patients with conventional in-center HD control patients. CONCLUSION: Although support of 20 home HD installations was economically feasible within the constraints of the London Health Sciences Centre Department of Biomedical Engineering, resources were strained by the final year of the study. This suggests that any sustained growth beyond the current study design may require a review of staffing, resources, and model of service delivery needs.

Adult↗
PubMed2001

Noninvasive Raman spectroscopic identification of intraocular lens material in the living human eye.

PURPOSE: To develop a safe noninvasive technique for identifying the material of intraocular lenses (IOLs) implanted in patients. SETTING: Center for Biomedical Engineering and the Department of Ophthalmology and Visual Sciences, University of Texas Medical Branch, Galveston, Texas, USA. METHODS: Raman spectroscopy was used to noninvasively identify the type of IOL implanted after previous cataract surgery in 9 eyes of 6 patients who were legally blind as a result of eye disease. Three IOLs were characterized: poly(methyl methacrylate) (PMMA) (n = 5), acrylic (n = 3), and silicone (n = 1). Confocal Raman spectroscopy was used with a laser power of 95 microW and exposure time of 1 second. RESULTS: Distinct spectral peaks associated with each type of IOL were obtained. These included spectra peaks at 2840 cm(-1), 2946 cm(-1), and 3000 cm(-1) for PMMA; 2917 cm(-1), 2939 cm(-1), and 3055 cm(-1) for acrylic; and 2900 cm(-1), 2961 cm(-1), and 3048 cm(-1) for silicone. The procedure was well accepted by patients, and there were no complications. CONCLUSIONS: The specific Raman spectra of the IOLs allowed for noninvasive determination of IOL material with the use of a safe light dose and an exposure time of 1 second.

Acrylic Resins↗
PubMed1999

Identification of intraocular lens materials using confocal Raman spectroscopy.

PURPOSE: To develop and test a noninvasive method to identify intraocular lens (IOL) materials in vitro. SETTING: Center for Biomedical Engineering and the Department of Ophthalmology, University of Texas Medical Branch, Galveston, Texas, USA. METHODS: A laser confocal Raman spectroscopy system (Conforam) was used for the noninvasive assessment of Raman spectra in the lower and the higher spectral regions (299.1 to 1833.7 cm-1 and 2633.8 to 3819.6 cm-1, respectively) of 4 IOL materials: silicone, poly(methyl methacrylate) (PMMA), acrylic, and hydrogel. RESULTS: Each lens material showed a distinctive spectrum in both the higher and the lower spectral regions. Most materials had unique peaks and a distinct profile using 1 mW of laser power and a 1 second exposure time. All materials still had a unique spectrum in both the higher and the lower region that allowed 1 material to be distinguished from the others. CONCLUSIONS: A Conforam differentiated silicone, PMMA, acrylic, and hydrogel lenses in vitro. Raman spectroscopy using the Conforam may provide a fast, safe, and reliable noninvasive method to gain information about the material of an implanted IOL and the stability of lens materials and their coatings.

Acrylates↗
PubMedDate not supplied

Clinical assessment, objectivity, and the ubiquitous laws of instrumentation.

With the Carville approach to interdisciplinary rehabilitation, special emphasis is placed on improved objective measurement of human function. This article defines essential elements for objective measurement, based on the experiences of a biomedical engineer on the rehabilitation team. Applied to manmade system, these elements are straightforward. Applied to living systems, these elements present difficulties, and special consideration must be given to the methods of measurement applied in the clinical setting. The rules for successful instrumentation and measurement are discussed with respect to the hand therapist's continuing challenge to measure the threshold to tactile sensation.

Humans↗
PubMed1997

Design and validation of an intelligent patient monitoring and alarm system based on a fuzzy logic process model.

The process of patient care performed by an anaesthesiologist during high invasive surgery requires fundamental knowledge of the physiologic processes and a long standing experience in patient management to cope with the inter-individual variability of the patients. Biomedical engineering research improves the patient monitoring task by providing technical devices to measure a large number of a patient's vital parameters. These measurements improve the safety of the patient during the surgical procedure, because pathological states can be recognised earlier, but may also lead to an increased cognitive load of the physician. In order to reduce cognitive strain and to support intra-operative monitoring for the anaesthesiologist an intelligent patient monitoring and alarm system has been proposed and implemented which evaluates a patient's haemodynamic state on the basis of a current vital parameter constellation with a knowledge-based approach. In this paper general design aspects and evaluation of the intelligent patient monitoring and alarm system in the operating theatre are described. The validation of the inference engine of the intelligent patient monitoring and alarm system was performed in two steps. Firstly, the knowledge base was validated with real patient data which was acquired online in the operating theatre. Secondly, a research prototype of the whole system was implemented in the operating theatre. In the first step, the anaesthetists were asked to enter a state variable evaluation before a drug application or any other intervention on the patient into a recording system. These state variable evaluations were compared to those generated by the intelligent alarm system on the same vital parameter constellations. Altogether 641 state variable evaluations were entered by six different physicians. In total, the sensitivity of alarm recognition is 99.3%, the specificity is 66% and the predictability is 45%. The second step was performed using a research prototype of the system in anaesthesiological routine. The evaluation of 684 events yielded a sensitivity, specificity and predictability of the alarm recognition of more than 99%.

Anesthesiology↗