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  Subjects -> BIOLOGY (Total: 2541 journals)
    - BIOCHEMISTRY (188 journals)
    - BIOENGINEERING (55 journals)
    - BIOLOGY (1298 journals)
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BIOLOGY (1298 journals)            First | 4 5 6 7 8 9 10 11 | Last

Journal of Biosocial Science     Hybrid Journal   (4 followers)
Journal of Biotechnology and Biodiversity     Open Access  
Journal of Bryology     Hybrid Journal   (1 follower)
Journal of Cell and Plant Sciences     Open Access   (3 followers)
Journal of Cell Communication and Signaling     Hybrid Journal  
Journal of Cell Death     Open Access   (1 follower)
Journal of Cell Science     Full-text available via subscription   (9 followers)
Journal of Cellular Biochemistry     Hybrid Journal   (3 followers)
Journal of Cellular Physiology     Hybrid Journal   (2 followers)
Journal of Cerebral Blood Flow & Metabolism     Hybrid Journal   (1 follower)
Journal of Chromatography B     Hybrid Journal   (15 followers)
Journal of Clinical Bioinformatics     Open Access   (5 followers)
Journal of Communications Technology and Electronics     Hybrid Journal   (2 followers)
Journal of Contemporary Physics (Armenian Academy of Sciences)     Hybrid Journal   (1 follower)
Journal of Contradicting Results in Science     Open Access   (1 follower)
Journal of Crustacean Biology     Full-text available via subscription   (2 followers)
Journal of Developmental Biology     Open Access   (2 followers)
Journal of Ecosystems     Open Access   (4 followers)
Journal of Electrical Bioimpedance     Full-text available via subscription   (2 followers)
Journal of Electromyography and Kinesiology     Hybrid Journal   (3 followers)
Journal of Environment and Ecology     Open Access   (9 followers)
Journal of Environmental Radioactivity     Hybrid Journal   (2 followers)
Journal of Environmental Science and Natural Resources     Open Access   (2 followers)
Journal of Ethnobiology     Full-text available via subscription   (4 followers)
Journal of Ethnobiology and Ethnomedicine     Open Access  
Journal of Ethology     Hybrid Journal   (1 follower)
Journal of Evolutionary Biology     Hybrid Journal   (17 followers)
Journal of Experimental and Clinical Anatomy     Full-text available via subscription  
Journal of Experimental Marine Biology and Ecology     Hybrid Journal   (22 followers)
Journal of Fish Biology     Hybrid Journal   (22 followers)
Journal of Functional Biomaterials     Open Access   (1 follower)
Journal of Great Lakes Research     Hybrid Journal   (7 followers)
Journal of Health and Biological Sciences     Open Access  
Journal of Health Sciences     Open Access   (5 followers)
Journal of Heredity     Hybrid Journal   (2 followers)
Journal of Herpetology     Full-text available via subscription   (2 followers)
Journal of Huazhong University of Science and Technology [Medical Sciences]     Hybrid Journal  
Journal of Human Evolution     Hybrid Journal   (9 followers)
Journal of Hymenoptera Research     Open Access   (2 followers)
Journal of Ichthyology     Hybrid Journal   (3 followers)
Journal of Insect Behavior     Hybrid Journal   (6 followers)
Journal of Insect Biodiversity     Open Access   (1 follower)
Journal of Insect Conservation     Hybrid Journal   (5 followers)
Journal of Integrated OMICS     Open Access  
Journal of Integrated Pest Management     Open Access   (2 followers)
Journal of Integrative Environmental Sciences     Hybrid Journal   (3 followers)
Journal of Intelligent Transportation Systems: Technology, Planning, and Operations     Hybrid Journal   (5 followers)
Journal of Invertebrate Pathology     Hybrid Journal   (3 followers)
Journal of Landscape Ecology     Open Access   (4 followers)
Journal of Law and the Biosciences     Open Access  
Journal of Leukocyte Biology     Open Access   (5 followers)
Journal of Life and Earth Science     Open Access  
Journal of Lipid Research     Full-text available via subscription   (4 followers)
Journal of Lipids     Open Access   (1 follower)
Journal of Luminescence     Hybrid Journal   (2 followers)
Journal of Mammalian Evolution     Hybrid Journal   (4 followers)
Journal of Mammalian Ova Research     Full-text available via subscription  
Journal of Mammalogy     Full-text available via subscription   (5 followers)
Journal of Mammary Gland Biology and Neoplasia     Hybrid Journal  
Journal of Marine Biology     Open Access   (13 followers)
Journal of Mathematical Biology     Hybrid Journal   (11 followers)
Journal of Mechanics in Medicine and Biology     Hybrid Journal  
Journal of Medical Primatology     Hybrid Journal   (1 follower)
Journal of Medical Toxicology     Hybrid Journal   (4 followers)
Journal of Medicine and Philosophy     Hybrid Journal   (6 followers)
Journal of Membrane Biology     Hybrid Journal   (2 followers)
Journal of Membrane Science     Hybrid Journal   (8 followers)
Journal of Molecular Biology     Hybrid Journal   (27 followers)
Journal of Molecular Biology Research     Open Access   (1 follower)
Journal of Molecular Catalysis B: Enzymatic     Hybrid Journal  
Journal of Molecular Cell Biology     Hybrid Journal   (7 followers)
Journal of Molecular Evolution     Hybrid Journal   (8 followers)
Journal of Molecular Signaling     Open Access  
Journal of Molecular Structure     Hybrid Journal   (3 followers)
Journal of Molluscan Studies     Hybrid Journal   (2 followers)
Journal of Muscle Research and Cell Motility     Hybrid Journal   (1 follower)
Journal of Nanoparticle Research     Hybrid Journal   (3 followers)
Journal of Natural History     Hybrid Journal   (4 followers)
Journal of Natural Products     Full-text available via subscription   (8 followers)
Journal of Natural Science, Biology and Medicine     Open Access   (2 followers)
Journal of Natural Sciences Research     Open Access   (3 followers)
Journal of Negative Results in BioMedicine     Open Access   (2 followers)
Journal of Nematology     Open Access   (2 followers)
Journal of Neuroscience and Behavioral Health     Open Access  
Journal of New Seeds     Hybrid Journal  
Journal of Nucleic Acids     Open Access   (2 followers)
Journal of Parasitology     Full-text available via subscription   (9 followers)
Journal of Parasitology and Vector Biology     Open Access  
Journal of Pharmacological and Toxicological Methods     Hybrid Journal   (3 followers)
Journal of Phycology     Hybrid Journal   (5 followers)
Journal of Physics D : Applied Physics     Partially Free   (12 followers)
Journal of Physics: Condensed Matter     Partially Free   (7 followers)
Journal of Physics: Conference Series     Open Access   (3 followers)
Journal of Phytopathology     Hybrid Journal   (2 followers)
Journal of Plankton Research     Hybrid Journal   (4 followers)
Journal of Plant Ecology     Hybrid Journal   (11 followers)
Journal of Plasma Physics     Hybrid Journal   (4 followers)
Journal of Porphyrins and Phthalocyanines     Hybrid Journal   (2 followers)
Journal of Proteome Research     Full-text available via subscription   (5 followers)
Journal of Proteomics     Hybrid Journal   (4 followers)

  First | 4 5 6 7 8 9 10 11 | Last

Medical Engineering & Physics    [11 followers]  Follow    
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 1350-4533
     Published by Elsevier Homepage  [2556 journals]   [SJR: 0.722]   [H-I: 57]
  • Transfer function analysis for the assessment of cerebral autoregulation
           using spontaneous oscillations in blood pressure and cerebral blood flow
    • Abstract: Publication date: Available online 12 April 2014
      Source:Medical Engineering & Physics
      Author(s): Aisha S.S. Meel-van den Abeelen , Arenda H.E.A. van Beek , Cornelis H. Slump , Ronney B. Panerai , Jurgen A.H.R. Claassen
      Cerebral autoregulation (CA) is a key mechanism to protect the brain against excessive fluctuations in blood pressure (BP) and maintain cerebral blood flow. Analyzing the relationship between spontaneous BP and cerebral blood flow velocity (CBFV) using transfer function analysis is a widely used technique to quantify CA in a non-invasive way. The objective of this review was to provide an overview of transfer function techniques used in the assessment of CA. 113 publications were included. This literature showed that there is no gold standard for the execution and implementation of the transfer function. There is a high diversity in settings and criteria used for transfer function analysis. Notable is also the high number of studies which report little on the settings. This disparity makes it difficult to replicate or compare the results of the different studies and further hinders the opportunity to make a distinction between intact and impaired CA in different patient groups. More research on the effects of different implementation techniques on CA results and optimization of the transfer function analysis is urgently needed. Furthermore, international guidelines should be created to inform the minimal description of the applied technique and the interpretation of transfer function outcomes in scientific research.


      PubDate: 2014-04-13T04:46:32Z
       
  • Fatigue behaviour of Nitinol peripheral stents: The role of plaque shape
           studied with computational structural analyses
    • Abstract: Publication date: Available online 12 April 2014
      Source:Medical Engineering & Physics
      Author(s): Elena Dordoni , Alessio Meoli , Wei Wu , Gabriele Dubini , Francesco Migliavacca , Giancarlo Pennati , Lorenza Petrini
      Fatigue resistance of Nitinol stents implanted into femoro-popliteal arteries is a critical issue for the particular biomechanical environment of this district. Hip and knee joint movements due to the cyclic daily activity expose the superficial femoral artery (SFA), and therefore the implanted stents, to quite large and cyclic deformations influencing stent fatigue resistance. Objective of this work is to provide a tool based on finite element analysis able to evaluate the biomechanical effect of SFA on stent fatigue resistance. Computer simulations of the treatment of stenotic vessel by angioplasty and stenting and of the subsequent in vivo loading conditions (axial compression and bending) were carried out. Three different stenotic vessel models were defined, by keeping a constant stenosis rate and changing the plaque sharpness and number of stenoses. The fatigue behaviour was analysed comparing the amplitude and mean value distribution of the first principal strain in the whole stent for the different simulated conditions. Results showed that the maximum mean strain is similar in all the models, while the alternating strain is related to both plaque shape and loading conditions. In conclusion, this study confirms the requisite of replicating in vivo loading conditions. It also reveals the importance of taking into account the thickness variation of the vessel in the stenotic zone in the assessment of the stent fatigue resistance.


      PubDate: 2014-04-13T04:46:32Z
       
  • Biomechanical responses due to discitis infection of a juvenile
           thoracolumbar spine using finite element modeling
    • Abstract: Publication date: Available online 3 April 2014
      Source:Medical Engineering & Physics
      Author(s): D. Davidson Jebaseelan , C. Jebaraj , N. Yoganandan , S. Rajasekaran , J. Yerramshetty
      Growth modulation changes occur in pediatric spines and lead to kyphotic deformity during discitis infection from mechanical forces. The present study was done to understand the consequences of discitis by simulating inflammatory puss at the T12/L1 disc space using a validated eight-year-old thoracolumbar spine finite element model. Changes in the biomechanical responses of the bone, disc and ligaments were determined under physiological compression and flexion loads in the intact and discitis models. During flexion, the angular-displacement increased by 3.33 times the intact spine and localized at the infected junction (IJ). The IJ became a virtual hinge. During compression loading, higher stresses occurred in the growth plate superior to the IJ. The components of the principal stresses in the growth plates at the T12/L1 junction indicated differential stresses. The strain increased by 143% during flexion loading in the posterior ligaments. The study indicates that the flexible pediatric spine increases the motion of the infected spine during physiological loadings. Understanding intrinsic responses around growth plates is important within the context of growth modulation in children. These results are clinically relevant as it might help surgeons to come up with better decisions while developing treatment protocols or performing surgeries.


      PubDate: 2014-04-08T10:25:54Z
       
  • Hemodynamics in the cephalic arch of a brachiocephalic fistula
    • Abstract: Publication date: Available online 30 March 2014
      Source:Medical Engineering & Physics
      Author(s): M. Boghosian , K. Cassel , M. Hammes , B. Funaki , S. Kim , X. Qian , X. Wang , P. Dhar , J. Hines
      The care and outcome of patients with end stage renal disease (ESRD) on chronic hemodialysis is directly dependent on their hemodialysis access. A brachiocephalic fistula (BCF) is commonly placed in the elderly and in patients with a failed lower-arm, or radiocephalic, fistula. However, there are numerous complications such that the BCF has an average patency of only 3.6 years. A leading cause of BCF dysfunction and failure is stenosis in the arch of the cephalic vein near its junction with the axillary vein, which is called cephalic arch stenosis (CAS). Using a combined clinical and computational investigation, we seek to improve our understanding of the cause of CAS, and to develop a means of predicting CAS risk in patients with a planned BCF access. This paper details the methodology used to determine the hemodynamic consequences of the post-fistula environment and illustrates detailed results for a representative sample of patient-specific anatomies, including a single, bifurcated, and trifurcated arch. It is found that the high flows present due to fistula creation lead to secondary flows in the arch owing to its curvature with corresponding low wall shear stresses. The abnormally low wall shear stress locations correlate with the development of stenosis in the singular case that is tracked in time for a period of one year.


      PubDate: 2014-04-03T06:18:08Z
       
  • Model-based physiomarkers of cerebral hemodynamics in patients with mild
           cognitive impairment
    • Abstract: Publication date: Available online 31 March 2014
      Source:Medical Engineering & Physics
      Author(s): V.Z. Marmarelis , D.C. Shin , M.E. Orme , R. Zhang
      In our previous studies, we have introduced model-based “functional biomarkers” or “physiomarkers” of cerebral hemodynamics that hold promise for improved diagnosis of early-stage Alzheimer's disease (AD). The advocated methodology utilizes subject-specific data-based dynamic nonlinear models of cerebral hemodynamics to compute indices (serving as possible diagnostic physiomarkers) that quantify the state of cerebral blood flow autoregulation to pressure-changes (CFAP) and cerebral CO2 vasomotor reactivity (CVMR) in each subject. The model is estimated from beat-to-beat measurements of mean arterial blood pressure, mean cerebral blood flow velocity and end-tidal CO2, which can be made reliably and non-invasively under resting conditions. In a previous study, it was found that a CVMR index quantifying the impairment in CO2 vasomotor reactivity correlates with clinical indications of early AD, offering the prospect of a potentially useful diagnostic tool. In this paper, we explore the use of the same model-based indices for patients with amnestic Mild Cognitive Impairment (MCI), a preclinical stage of AD, relative to a control subjects and clinical cognitive assessments. It was found that the model-based CVMR values were lower for MCI patients relative to the control subjects.


      PubDate: 2014-04-03T06:18:08Z
       
  • Continuous time-domain monitoring of cerebral autoregulation in
           neurocritical care
    • Abstract: Publication date: Available online 1 April 2014
      Source:Medical Engineering & Physics
      Author(s): Christian Zweifel , Celeste Dias , Peter Smielewski , Marek Czosnyka
      Integration of various brain signals can be used to determine cerebral autoregulation in neurocritical care patients to guide clinical management and to predict outcome. In this review, we will discuss current methodology of multimodal brain monitoring focusing on secondary ‘reactivity indices’ derived from various brain signals which are based on a ‘moving correlation coefficient’. This algorithm was developed in order to analyze in a time dependent manner the degree of correlation between two factors within a time series where the number of paired observations is large. Of the various primary neuromonitoring sources which can be used to calculate reactivity indices, we will focus in this review on indices based on transcranial Doppler (TCD), intracranial pressure (ICP), brain tissue oxygenation (PbtO2) and near infrared spectroscopy (NIRS). Furthermore, we will demonstrate how reactivity indices can show transient changes of cerebral autoregulation and can be used to optimize management of arterial blood pressure (ABP) and cerebral perfusion pressure (CPP).


      PubDate: 2014-04-03T06:18:08Z
       
  • MR-compatible pedal ergometer for reproducible exercising of the human
           calf muscle
    • Abstract: Publication date: Available online 2 April 2014
      Source:Medical Engineering & Physics
      Author(s): Kevin Tschiesche , Markus Rothamel , Reinhard Rzanny , Alexander Gussew , Patrick Hiepe , Jürgen R. Reichenbach
      A pneumatic MR-compatible pedal ergometer was designed to perform dynamic contraction exercises of the human calf muscle in a whole-body 3T MR scanner. The set-up includes sensors for monitoring mechanical parameters, such as pedal angle, cadence as well as applied force and power. Actual parameter values during the exercise were presented to the volunteer as a visual feedback to enable real-time self-adjustment of pedal deflection and cadence to the target reference value. Time-resolved dynamic 31P-MR spectroscopic measurements of phosphocreatine (PCr), inorganic phosphate (Pi) and pH were performed in a pilot experiment before, during, and after the exercise by a single volunteer. Two different load strengths were applied in these experiments (15% and 25% of the maximum voluntary contraction, MVC). As expected, mechanical and metabolic parameters differed for the two load levels. Small variations of the cadence, power and metabolic changes (time constants of PCr depletion and Pi accumulation) during the experiments demonstrate a highly reproducible mechanical output by the volunteer mediated by the ergometer.


      PubDate: 2014-04-03T06:18:08Z
       
  • Automatic distinction of upper body motions in the main anatomical planes
    • Abstract: Publication date: April 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 4
      Author(s): Tobias Consmüller , Antonius Rohlmann , Daniel Weinland , Hendrik Schmidt , Timo Zippelius , Georg N. Duda , William R. Taylor
      The assessment of spinal mobility and function is gaining clinical importance for the diagnosis and monitoring of low back pain, but its measurement and evaluation remains difficult. As a critical step towards non-supervised assessment of spinal functional, the aim of this study was to assess the efficacy of symmetrical sensors fixed to the sides of the spinal column to distinguish between different upper body movements in the main anatomical planes. 429 healthy volunteers underwent a defined choreography including repeated upper body flexion, extension, lateral bending and axial rotation exercises. The movements were assessed using the Epionics SPINE sensor system. Two pattern recognition models were developed and applied to distinguish between the different movements in a frame-by-frame manner, as well as for whole motion sequences. On average, it was possible to differentiate between different upper body movements with a sensitivity of over 96% for both modelling approaches. The largest type II error was the incorrect identification of extension, possibly due to deviations from the reference standing posture during measurements and small changes in the lordotic angle during extension. The use of two sagittal sensors attached symmetrically to the back therefore seems to allow the distinction of upper body movements in a robust manner, and therefore opens perspectives for the unsupervised recognition of movements and functional activity over extended periods.


      PubDate: 2014-03-29T03:14:20Z
       
  • ISO 16840-2:2007 load deflection and hysteresis measurements for a sample
           of wheelchair seating cushions
    • Abstract: Publication date: April 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 4
      Author(s): James Hollington , Susan J. Hillman , Carmen Torres-Sánchez , Jens Boeckx , Neil Crossan
      Load deflection and hysteresis measurements were made on 37 wheelchair seating cushions according to ISO 16840-2:2007. Load deflection plots for all 37 cushions are reported and fundamental aspects of graph interpretation discussed. ISO hysteresis data are also reported and interpretation discussed.


      PubDate: 2014-03-29T03:14:20Z
       
  • Gait event detection for use in FES rehabilitation by radial and
           tangential foot accelerations
    • Abstract: Publication date: April 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 4
      Author(s): Jan Rueterbories , Erika G. Spaich , Ole K. Andersen
      Gait rehabilitation by Functional Electrical Stimulations (FESs) requires a reliable trigger signal to start the stimulations. This could be obtained by a simple switch under the heel or by means of an inertial sensor system. This study provides an algorithm to detect gait events in differential acceleration signals of the foot. The key feature of differential measurements is that they compensate the impact of gravity. The real time detection capability of a rule based algorithm in healthy and hemiparetic individuals was investigated. Detection accuracy and precision compared to signals from foot switches were evaluated. The algorithm detected curve features of the vectorial sum of radial and tangential accelerations and mapped those to discrete gait states. The results showed detection rates for healthy and hemiparetic gait ranging form 84.2% to 108.5%. The sensitivity was between 0.81 and 1, and the specificity between 0.85 and 1, depending on gait phase and group of subjects. The algorithm detected gait phase changes earlier than the reference. Differential acceleration signals combined with the proposed algorithm have the potential to be implemented in a future FES system.


      PubDate: 2014-03-29T03:14:20Z
       
  • Pneumatic cell stretching system for cardiac differentiation and culture
    • Abstract: Publication date: April 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 4
      Author(s): Joose Kreutzer , Liisa Ikonen , Juha Hirvonen , Mari Pekkanen-Mattila , Katriina Aalto-Setälä , Pasi Kallio
      This paper introduces a compact mechanical stimulation device suitable for applications to study cellular mechanobiology. The pneumatically controlled device provides equiaxial strain for cells on a coated polydimethylsiloxane (PDMS) membrane and enables real time observation of cells with an inverted microscope. This study presents the implementation and operation principles of the device and characterizes membrane stretching. Different coating materials are also analyzed on an unstretched membrane to optimize the cell attachment on PDMS. As a result, gelatin coating was selected for further experiments to demonstrate the function of the device and evaluate the effect of long-term cyclic equiaxial stretching on human pluripotent stem cells (hPSCs). Cardiac differentiation was induced with mouse visceral endoderm-like (END-2) cells, either on an unstretched membrane or with mechanical stretching. In conclusion, hPSCs grew well on the stretching platform and cardiac differentiation was induced. Thus, the platform provides a new possibility to study the effect of stretching on cellular properties including differentiation and stress induced cardiac diseases.


      PubDate: 2014-03-29T03:14:20Z
       
  • Development and evaluation of a new instrument to measure visual
           exploration behavior
    • Abstract: Publication date: April 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 4
      Author(s): T. Nef , N. Gruber , G.A. Zito , T. Nyffeler , R. Müri , U.P. Mosimann
      Effective visual exploration is required for many activities of daily living and instruments to assess visual exploration are important for the evaluation of the visual and the oculomotor system. In this article, the development of a new instrument to measure central and peripheral target recognition is described. The measurement setup consists of a hemispherical projection which allows presenting images over a large area of ±90° horizontal and vertical angle. In a feasibility study with 14 younger (21–49years) and 12 older (50–78years) test persons, 132 targets and 24 distractors were presented within naturalistic color photographs of everyday scenes at 10°, 30°, and 50° eccentricity. After the experiment, both younger and older participants reported in a questionnaire that the task is easy to understand, fun and that it measures a competence that is relevant for activities of daily living. A main result of the pilot study was that younger participants recognized more targets with smaller reaction times than older participants. The group differences were most pronounced for peripheral target detection. This test is feasible and appropriate to assess the functional field of view in younger and older adults.


      PubDate: 2014-03-29T03:14:20Z
       
  • Comparison of the pedalling performance induced by magnetic and electrical
           stimulation cycle ergometry in able-bodied subjects
    • Abstract: Publication date: April 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 4
      Author(s): J. Szecsi , A. Straube , C. Fornusek
      The purpose of the study was to compare the mechanical power and work generated by able-bodied subjects during functional magnetic stimulation (FMS) vs. functional electrical stimulation (FES) induced ergometer training conditions. Both stimulation methods were applied at a 30Hz frequency to the quadriceps muscles of 22 healthy able-bodied subjects to induce cycling for 4× four minutes or until exhaustion. FMS was performed via large surface, cooled coils, while FES was applied with a typical stimulation setup used for cycling. Significantly more (p <10−3) muscular power was generated by FMS (23.8±9.1W [mean±SD]) than by FES (11.3±11.3W). Additionally, significantly more (p <10−6) work was produced by FMS than by FES (4.413±2.209kJ vs. 0.974±1.269kJ). The increase in the work was paralleled by a significant prolongation of time to cycling failure (181.8±33.4s vs. 87.0±54.0s, respectively, p <10−5). Compared to FES, FMS can produce more intense and longer cycling exercise in able-bodied subjects. The differing dynamic behaviour of FMS and FES in the presented measurement setup might be related to stimulation induced pain and fatigue mechanisms of the neuromuscular system.


      PubDate: 2014-03-29T03:14:20Z
       
  • A numerical investigation into the influence of the properties of cobalt
           chrome cellular structures on the load transfer to the periprosthetic
           femur following total hip arthroplasty
    • Abstract: Publication date: April 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 4
      Author(s): Kevin Brian Hazlehurst , Chang Jiang Wang , Mark Stanford
      Stress shielding of the periprosthetic femur following total hip arthroplasty is a problem that can promote the premature loosening of femoral stems. In order to reduce the need for revision surgery it is thought that more flexible implant designs need to be considered. In this work, the mechanical properties of laser melted square pore cobalt chrome molybdenum cellular structures have been incorporated into the design of a traditional monoblock femoral stem. The influence of incorporating the properties of cellular structures on the load transfer to the periprosthetic femur was investigated using a three dimensional finite element model. Eleven different stiffness configurations were investigated by using fully porous and functionally graded approaches. This investigation confirms that the periprosthetic stress values depend on the stiffness configuration of the stem. The numerical results showed that stress shielding is reduced in the periprosthetic Gruen zones when the mechanical properties of cobalt chrome molybdenum cellular structures are used. This work identifies that monoblock femoral stems manufactured using a laser melting process, which are designed for reduced stiffness, have the potential to contribute towards reducing stress shielding.


      PubDate: 2014-03-29T03:14:20Z
       
  • Contact mechanics studies of an ellipsoidal contact bearing surface of
           metal-on-metal hip prostheses under micro-lateralization
    • Abstract: Publication date: April 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 4
      Author(s): Ling Wang , Xiaohua Liu , Dichen Li , Feng Liu , Zhongmin Jin
      The morphology of the contact bearing surfaces plays an important role in the contact mechanics and potential wear of metal-on-metal (MOM) hip prostheses. An ellipsoidal bearing surface was proposed for MOM hip implants and the corresponding contact mechanics were studied by using the finite element method (FEM) under both standard and micro-lateralization conditions. When under micro-lateralization, the maximum contact pressure decreased from 927.3MPa to 203.0MPa, with increased ellipticity ratio medial-laterally. And the contact region was found to shift from the rim of the cup to the inner region compared to the spherical design. Under standard conditions, an increasing trend of the maximum contact pressure for the acetabular component was predicted as the major radius of the ellipsoidal bearing surface was increased. Nevertheless, the maximum contact pressure reached an asymptotic value when the ellipticity ratio was increased to 1.04. Therefore it is critical to optimize the ellipticity ratio in order to reduce the contact pressure under micro-lateralization condition and yet not to cause a markedly increased contact pressure under normal condition. Additionally, the maximum contact pressure in the ellipsoidal bearing surface remained relatively constant with the increased micro-lateralization. It is concluded that an ellipsoidal bearing surface morphology may be a promising alternative by offering better contact mechanisms when micro-lateralization should occur and attributing to minimized wear.


      PubDate: 2014-03-29T03:14:20Z
       
  • Editorial Board
    • Abstract: Publication date: April 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 4




      PubDate: 2014-03-29T03:14:20Z
       
  • Cardiopulmonary responses to robotic end-effector-based walking and stair
           climbing
    • Abstract: Publication date: April 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 4
      Author(s): Oliver Stoller , Matthias Schindelholz , Lukas Bichsel , Kenneth J. Hunt
      Background A recently developed robotic end-effector device (G-EO system, Reha Technology AG) can simulate walking and stair climbing. This approach has the potential to promote cardiovascular exercise training during rehabilitation. The aim of this study was to characterise cardiopulmonary responses of end-effector-based exercise in able-bodied subjects and to evaluate the feasibility of intensity-guided exercise testing. Methods Five healthy subjects aged 33.7±8.8 years (mean±SD) performed a constant load test and an intensity-guided incremental exercise test. The outcome measures were steady-state and peak cardiopulmonary performance parameters including oxygen uptake (VO2) and heart rate (HR). Results Passive end-effector-based stair climbing (VO2 =13.6±4.5mL/min/kg, HR=95±23beats/min) showed considerably lower cardiopulmonary responses compared to reference data (VO2 =33.5±4.8mL/min/kg, HR=159±15beats/min). Peak performance parameters during intensity-guided incremental exercise testing were: VO2 =35.8±5.1mL/min/kg and HR=161±27 beats/min, corresponding to a relative VO2 =76.0±18.7% of predicted aerobic capacity and a relative HR=87.3±14.5% of age-predicted HR maximum. Conclusion End-effector-based exercise is a promising method for the implementation of cardiovascular exercise. Although end-effector-based stair climbing evoked lower cardiopulmonary responses than conventional stair climbing, active contribution during exercise elicited substantial cardiopulmonary responses within recommended ranges for aerobic training.


      PubDate: 2014-03-29T03:14:20Z
       
  • Atrial fibrillation subtypes classification using the General
           Fourier-family Transform
    • Abstract: Publication date: April 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 4
      Author(s): Nuria Ortigosa , Óscar Cano , Guillermo Ayala , Antonio Galbis , Carmen Fernández
      Atrial fibrillation patients can be classified into paroxysmal, persistent and permanent attending to the temporal pattern of this arrhythmia. The surface electrocardiogram hides this differentiation. A classification method to discriminate between the different subtypes of atrial fibrillation by using short segments of electrocardiograms recordings is presented. We will process the electrocardiograms (ECGs) using time–frequency techniques with a global accuracy of 80%. Real cases are evaluated showing promising results for an implementation in a semiautomated diagnostic system.


      PubDate: 2014-03-29T03:14:20Z
       
  • A novel vacuum assisted closure therapy model for use with percutaneous
           devices
    • Abstract: Publication date: Available online 27 March 2014
      Source:Medical Engineering & Physics
      Author(s): Saranne J. Cook , Francesca R. Nichols , Lucille B. Brunker , Kent N. Bachus
      Long-term maintenance of a dermal barrier around a percutaneous prosthetic device remains a common clinical problem. A technique known as Negative Pressure Wound Therapy (NPWT) uses negative pressure to facilitate healing of impaired and complex soft tissue wounds. However, the combination of using negative pressure with percutaneous prosthetic devices has not been investigated. The goal of this study was to develop a methodology to apply negative pressure to the tissues surrounding a percutaneous device in an animal model; no tissue healing outcomes are presented. Specifically, four hairless rats received percutaneous porous coated titanium devices implanted on the dorsum and were bandaged with a semi occlusive film dressing. Two of these animals received NPWT; two animals received no NPWT and served as baseline controls. Over a 28-day period, both the number of dressing changes required between the two groups as well as the pressures were monitored. Negative pressures were successfully applied to the periprosthetic tissues in a clinically relevant range with a manageable number of dressing changes. This study provides a method for establishing, maintaining, and quantifying controlled negative pressures to the tissues surrounding percutaneous devices using a small animal model.


      PubDate: 2014-03-29T03:14:20Z
       
  • Filtering and thresholding the analytic signal envelope in order to
           improve peak and spike noise reduction in EEG signals
    • Abstract: Publication date: April 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 4
      Author(s): Umberto Melia , Francesc Clariá , Montserrat Vallverdú , Pere Caminal
      To remove peak and spike artifacts in biological time series has represented a hard challenge in the last decades. Several methods have been implemented mainly based on adaptive filtering in order to solve this problem. This work presents an algorithm for removing peak and spike artifacts based on a threshold built on the analytic signal envelope. The algorithm was tested on simulated and real EEG signals that contain peak and spike artifacts with random amplitude and frequency occurrence. The performance of the filter was compared with commonly used adaptive filters. Three indexes were used for testing the performance of the filters: Correlation coefficient (ρ), mean of coherence function (C), and rate of absolute error (RAE). All these indexes were calculated between filtered signal and original signal without noise. It was found that the new proposed filter was able to reduce the amplitude of peak and spike artifacts with ρ >0.85, C >0.8, and RAE <0.5. These values were significantly better than the performance of LMS adaptive filter (ρ <0.85, C <0.6, and RAE >1).


      PubDate: 2014-03-29T03:14:20Z
       
  • Development and validation of a low-cost, portable and wireless gait
           assessment tool
    • Abstract: Publication date: April 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 4
      Author(s): Catherine A. Macleod , Bernard A. Conway , David B. Allan , Sujay S. Galen
      Background Performing gait analysis in a clinical setting can often be challenging due to time, cost and the availability of sophisticated three-dimensional (3D) gait analysis systems. This study has developed and tested a portable wireless gait assessment tool (wi-GAT) to address these challenges. Aim To investigate the concurrent validity of the wi-GAT in measuring spatio-temporal gait parameters such as stride length, stride duration, cadence, double support time (DST), stance and swing time compared to a 3D Vicon motion analysis system. Methods Ten healthy volunteers participated in the study (age range 23–30 years). Spatio-temporal gait parameters were recorded simultaneously by the Vicon and the wi-GAT systems as each subject walked at their self-selected speed. Results The stride length and duration, cadence, stance duration and walking speed recorded using the wi-GAT showed strong agreement with those same parameters recorded by the Vicon (ICC of 0.94–0.996). A difference between the systems in registering “toe off” resulted in less agreement (ICC of 0.299–0.847) in gait parameters such as %stance and %swing and DST. Discussion and conclusion The study demonstrated good concurrent validity for the wi-GAT system. The wi-GAT has the potential to be a useful assessment tool for clinicians.


      PubDate: 2014-03-29T03:14:20Z
       
  • Quantification of photocatalytic oxygenation of human blood
    • Abstract: Publication date: April 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 4
      Author(s): Aryasomayajula Subrahmanyam , Paul R. Thangaraj , Chandrasekhar Kanuru , Albert Jayakumar , Jayashree Gopal
      Photocatalytic oxygenation of human blood is an emerging concept based on the principle of photocatalytic splitting of water into oxygen and hydrogen. This communication reports: (i) a design of a photocatalytic cell (PC) that separates the blood from UV (incident) radiation source, (ii) a pH, temperature and flow controlled circuit designed for quantifying the oxygenation of human blood by photocatalysis and (iii) measuring the current efficacy of ITO/TiO2 nano thin films in oxygenating human blood in a dynamic circuit in real time. The average increase in oxygen saturation was around 5% above baseline compared to control (p <0.0005). We believe this is one of the first attempts to quantify photocatalytic oxygenation of human blood under controlled conditions.


      PubDate: 2014-03-29T03:14:20Z
       
  • Design and validation of an in vitro loading system for the combined
           application of cyclic compression and shear to 3D chondrocytes-seeded
           agarose constructs
    • Abstract: Publication date: April 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 4
      Author(s): Erica Di Federico , Dan L. Bader , Julia C. Shelton
      Physiological loading is essential for the maintenance of articular cartilage by regulating tissue remodelling, in the form of both catabolic and anabolic processes. To promote the development of tissue engineered cartilage which closely matches the long term functionality of native tissue, bioreactors have been developed to provide a combination of loading modalities, which reflect the nature of normal physiological loads. This study describes the design and validation of an in vitro mechanical system for the controlled application of bi-axial loading regimes to chondrocyte-seeded agarose constructs. The computer-controlled system incorporates a robust gripping system, which ensures the delivery of precise values of cyclic compressive and shear strain to 3D cell-seeded constructs. Sample prototypes were designed, optimised using finite element analysis and validated performing compressive and shear fatigue mechanical tests. The horizontal and vertical displacements within the bioreactor are precisely controlled by a dedicated programme that can be easily implemented. The synchronisation of the orthogonal displacements was shown to be accurate and reproducible. Constructs were successfully loaded with a combined compressive and shear loading regimen at 1Hz for up to 48h with no appreciable loss of cell viability or mechanical integrity. These features along with the demonstrated high consistency make the system ideally suitable for a systematic investigation of the response of chondrocytes to a complex physiologically relevant deformation profile.


      PubDate: 2014-03-29T03:14:20Z
       
  • Neonatal phototherapy radiometers: Current performance characteristics and
           future requirements
    • Abstract: Publication date: April 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 4
      Author(s): Douglas McG. Clarkson , Ruth Nicol , Phillip Chapman
      Hand held radiometers provide a convenient means of monitoring the output of neonatal phototherapy treatment devices as part of planned programs of device maintenance and output monitoring. It was considered appropriate to determine the wavelength and angular response of a selection of such meters and compare their indicated values with that derived from spectral analysis of phototherapy light sources. This was undertaken using a Bentham DMc150 double grating spectroradiometer and a series of 10nm band pass optical filters in the range 400–640nm used in conjunction with a fiber optic light source. Specific meters investigated included a GE Biliblanket Light Meter II, a NeoBLUE radiometer and a Bio-TEK radiometer 74345 device. Comparisons were made of measurements made using the hand held meters and the Bentham DMc 150 system for a range of neonatal phototherapy treatment devices. The use of such meters is discussed in relation to applicable equipment standards and recommendations of intensive phototherapy from clinical groups such as the American Academy of Pediatrics and a specification for a spectroradiometer based measurement system is proposed.


      PubDate: 2014-03-29T03:14:20Z
       
  • Optical tracking of local surface wave for skin viscoelasticity
    • Abstract: Publication date: Available online 24 March 2014
      Source:Medical Engineering & Physics
      Author(s): Yubo Guan , Mingzhu Lu , Zhilong Shen , Mingxi Wan
      Rapid and effective determination of biomechanical properties is important in examining and diagnosing skin thermal injury. Among the methods used, viscoelasticity quantification is one of the most effective methods in determining such properties. This study aims to rapidly determine skin viscoelasticity by optically tracking the local surface wave. New elastic and viscous coefficients were proposed to indicate skin viscoelasticity based on a single impulse response of the skin. Experiments were performed using fresh porcine skin samples. Surface wave was generated in a single impulse using a vibrator with a ball-tipped device and was detected using a laser Doppler vibrometer. The motions along the depth direction were monitored using an ultrasound system. The ultrasound monitoring results indicated the multi-layered viscoelasticity of the epidermis and dermis. The viscoelastic coefficients from four healthy samples show a potential viscoelasticity variation of porcine skin. In one sample, the two coefficients were evidently higher than those in a healthy area if the skin was slightly burned. These results indicate that the proposed method is sensitive, effective, and quick in determining skin viscoelasticity.


      PubDate: 2014-03-25T22:36:59Z
       
  • Development of a novel pulse wave velocity measurement system: Using dual
           piezoelectric elements
    • Abstract: Publication date: Available online 25 March 2014
      Source:Medical Engineering & Physics
      Author(s): Kei-ichiro Kitamura , Ryuya Takeuchi , Kazuhiro Ogai , Zhu Xin , Wenxi Chen , Tetsu Nemoto
      The aim of this study is to develop a painless system of measuring the brachial-ankle arterial pulse wave velocity (baPWV) without compression cuffs. The PWV reflects the compliance of the artery and is measured for the early diagnosis of arteriosclerotic vascular diseases. However, the conventional baPWV system, which measures four cuff pressures simultaneously, easily causes circulation block and tightening pain at the extremities. In addition, approximately 15min are required to stabilise the blood pressure for re-examination. Therefore, we developed a novel baPWV measurement system using dual piezoelectric sensor elements. The principle of this high-sensitivity pressure pulse detection system is based on adding the two in-phase outputs from the coaxially arranged dual piezoelectric sensor. As our system facilitates the measurement of the baPWV by detecting the pulsation of an artery using sensors fixed on the skin where the pulse is palpable, it does not cause pain and reduces examination time. The coefficients of correlation between the baPWV values obtained from the conventional and present methods were 0.93 (right side) and 0.90 (left side). The results suggest that our system can be used to measure the baPWV without pressure cuffs as accurately as the conventional method.


      PubDate: 2014-03-25T22:36:59Z
       
  • Validity of using tri-axial accelerometers to measure human movement
           – Part II: Step counts at a wide range of gait velocities
    • Abstract: Publication date: Available online 20 March 2014
      Source:Medical Engineering & Physics
      Author(s): Emma Fortune , Vipul Lugade , Melissa Morrow , Kenton Kaufman
      A subject-specific step counting method with a high accuracy level at all walking speeds is needed to assess the functional level of impaired patients. The study aim was to validate step counts and cadence calculations from acceleration data by comparison to video data during dynamic activity. Custom-built activity monitors, each containing one tri-axial accelerometer, were placed on the ankles, thigh, and waist of 11 healthy adults. ICC values were greater than 0.98 for video inter-rater reliability of all step counts. The activity monitoring system (AMS) algorithm demonstrated a median (interquartile range; IQR) agreement of 92% (8%) with visual observations during walking/jogging trials at gait velocities ranging from 0.1 to 4.8m/s, while FitBits (ankle and waist), and a Nike Fuelband (wrist) demonstrated agreements of 92% (36%), 93% (22%), and 33% (35%), respectively. The algorithm results demonstrated high median (IQR) step detection sensitivity (95% (2%)), positive predictive value (PPV) (99% (1%)), and agreement (97% (3%)) during a laboratory-based simulated free-living protocol. The algorithm also showed high median (IQR) sensitivity, PPV, and agreement identifying walking steps (91% (5%), 98% (4%), and 96% (5%)), jogging steps (97% (6%), 100% (1%), and 95% (6%)), and less than 3% mean error in cadence calculations.


      PubDate: 2014-03-21T04:24:41Z
       
  • Flow transport and gas mixing during invasive high frequency oscillatory
           ventilation
    • Abstract: Publication date: Available online 18 March 2014
      Source:Medical Engineering & Physics
      Author(s): Mohammed Alzahrany , Arindam Banerjee , Gary Salzman
      A large Eddy simulation (LES) based computational fluid dynamics study was performed to investigate gas transport and mixing in patient specific human lung models during high frequency oscillatory ventilation. Different pressure-controlled waveforms (sinusoidal, exponential and square) and ventilator frequencies (15, 10 and 6Hz) were used (tidal volume=50mL). The waveforms were created by solving the equation of motion subjected to constant lung wall compliance and flow resistance. Simulations were conducted with and without endotracheal tube to understand the effect of invasive management device. Variation of pressure-controlled waveform and frequency exhibits significant differences on counter flow pattern, which could lead to a significant impact on the gas mixing efficiency. Pendelluft-like flow was present for the sinusoidal waveform at all frequencies but occurred only at early inspiration for the square waveform at highest frequency. The square waveform was most efficient for gas mixing, resulting in the least wall shear stress on the lung epithelium layer thereby reducing the risk of barotrauma to both airways and the alveoli for patients undergoing therapy.


      PubDate: 2014-03-21T04:24:41Z
       
  • Objective diagnosis of ADHD using IMUs
    • Abstract: Publication date: Available online 20 March 2014
      Source:Medical Engineering & Physics
      Author(s): Niamh O’Mahony , Blanca Florentino-Liano , Juan J. Carballo , Enrique Baca-García , Antonio Artés Rodríguez
      This work proposes the use of miniature wireless inertial sensors as an objective tool for the diagnosis of ADHD. The sensors, consisting of both accelerometers and gyroscopes to measure linear and rotational movement, respectively, are used to characterize the motion of subjects in the setting of a psychiatric consultancy. A support vector machine is used to classify a group of subjects as either ADHD or non-ADHD and a classification accuracy of greater than 95% has been achieved. Separate analyses of the motion data recorded during various activities throughout the visit to the psychiatric consultancy show that motion recorded during a continuous performance test (a forced concentration task) provides a better classification performance than that recorded during “free time”.


      PubDate: 2014-03-21T04:24:41Z
       
  • Application of an asymmetric finite element model of the C2-T1 cervical
           spine for evaluating the role of soft tissues in stability
    • Abstract: Publication date: Available online 15 March 2014
      Source:Medical Engineering & Physics
      Author(s): D.U. Erbulut , I. Zafarparandeh , I. Lazoglu , A.F. Ozer
      Different finite element models of the cervical spine have been suggested for evaluating the roles of ligaments, facet joints, and disks in the stability of cervical spine under sagittal moments. However, no comprehensive study on the response of the full cervical spine that has used a detailed finite element (FE) model (C2-T1) that considers the asymmetry about the mid-sagittal plane has been reported. The aims of this study were to consider asymmetry in a FE model of the full cervical spine and to investigate the influences of ligaments, facet joints, and disk nucleus on the stability of the asymmetric model during flexion and extension. The model was validated against various published in vitro studies and FE studies for the three main loading planes. Next, the C4-C5 level was modified to simulate different cases to investigate the role of the soft tissues in segmental stability. The FE model predicted that excluding the interspinous ligament (ISL) from the index level would cause excessive instability during flexion and that excluding the posterior longitudinal ligament (PLL) or the ligamentum flavum (LF) would not affect segmental rotation. During extension, motion increased when the facet joints were excluded. The model without disk nucleus was unstable compared to the intact model at lower loads and exhibited a similar rotation response at higher loads.


      PubDate: 2014-03-17T03:32:24Z
       
  • Response to “Letter to Editor”, submitted by Chris Ramsey et
           al. (MEP-D-13-00511), regarding to the algebraic error in our technical
           note, entitled “Determination of body segment masses and centers of
           mass using a force plate method in individuals of different
           morphology” [Med. Eng. Phys. 31 (2009) 1187–1194]
    • Abstract: Publication date: Available online 14 March 2014
      Source:Medical Engineering & Physics
      Author(s): Mohsen Damavandi , Nader Farahpour , Paul Allard



      PubDate: 2014-03-17T03:32:24Z
       
  • Special Issue on Cerebral Autoregulation: Measurement and modelling
    • Abstract: Publication date: Available online 15 March 2014
      Source:Medical Engineering & Physics
      Author(s): Georgios D. Mitsis , David M. Simpson



      PubDate: 2014-03-17T03:32:24Z
       
  • Activity recognition with smartphone support
    • Abstract: Publication date: Available online 15 March 2014
      Source:Medical Engineering & Physics
      Author(s): John J. Guiry , Pepijn van de Ven , John Nelson , Lisanne Warmerdam , Heleen Riper
      In this paper, the authors describe a method of accurately detecting human activity using a smartphone accelerometer paired with a dedicated chest sensor. The design, implementation, testing and validation of a custom mobility classifier are also presented. Offline analysis was carried out to compare this custom classifier to de-facto machine learning algorithms, including C4.5, CART, SVM, Multi-Layer Perceptrons, and Naïve Bayes. A series of trials were carried out in Ireland, initially involving N =6 individuals to test the feasibility of the system, before a final trial with N =24 subjects took place in the Netherlands. The protocol used and analysis of 1165min of recorded activities from these trials are described in detail in this paper. Analysis of collected data indicate that accelerometers placed in these locations, are capable of recognizing activities including sitting, standing, lying, walking, running and cycling with accuracies as high as 98%.


      PubDate: 2014-03-17T03:32:24Z
       
  • Optimization of scaffold design for bone tissue engineering: A
           computational and experimental study
    • Abstract: Publication date: Available online 11 March 2014
      Source:Medical Engineering & Physics
      Author(s): Marta R. Dias , José M. Guedes , Colleen L. Flanagan , Scott J. Hollister , Paulo R. Fernandes
      In bone tissue engineering, the scaffold has not only to allow the diffusion of cells, nutrients and oxygen but also provide adequate mechanical support. One way to ensure the scaffold has the right properties is to use computational tools to design such a scaffold coupled with additive manufacturing to build the scaffolds to the resulting optimized design specifications. In this study a topology optimization algorithm is proposed as a technique to design scaffolds that meet specific requirements for mass transport and mechanical load bearing. Several micro-structures obtained computationally are presented. Designed scaffolds were then built using selective laser sintering and the actual features of the fabricated scaffolds were measured and compared to the designed values. It was possible to obtain scaffolds with an internal geometry that reasonably matched the computational design (within 14% of porosity target, 40% for strut size and 55% for throat size in the building direction and 15% for strut size and 17% for throat size perpendicular to the building direction). These results support the use of these kind of computational algorithms to design optimized scaffolds with specific target properties and confirm the value of these techniques for bone tissue engineering.


      PubDate: 2014-03-13T00:03:27Z
       
  • A micro-optical system for endoscopy based on mechanical compensation
           paradigm using miniature piezo-actuation
    • Abstract: Publication date: Available online 12 March 2014
      Source:Medical Engineering & Physics
      Author(s): Pietro Cerveri , Cynthia Corinna Zazzarini , Paolo Patete , Guido Baroni
      The goal of the study was to investigate the feasibility of a novel miniaturized optical system for endoscopy. Fostering the mechanical compensation paradigm, the modeled optical system, composed by 14 lenses, separated in 4 different sets, had a total length of 15.55mm, an effective focal length ranging from 1.5 to 4.5mm with a zoom factor of about 2.8×, and an angular field of view up to 56°. Predicted maximum lens travel was less than 3.5mm. The consistency of the image plane height across the magnification range testified the zoom capability. The maximum predicted achromatic astigmatism, transverse spherical aberration, longitudinal spherical aberration and relative distortion were less than or equal to 25μm, 15μm, 35μm and 12%, respectively. Tests on tolerances showed that the manufacturing and opto-mechanics mounting are critical as little deviations from design dramatically decrease the optical performances. However, recent micro-fabrication technology can guarantee tolerances close to nominal design. A closed-loop actuation unit, devoted to move the zoom and the focus lens sets, was implemented adopting miniaturized squiggle piezo-motors and magnetic position encoders based on Hall effect. Performance results, using a prototypical test board, showed a positioning accuracy of less than 5μm along a lens travel path of 4.0mm, which was in agreement with the lens set motion features predicted by the analysis. In conclusion, this study demonstrated the feasibility of the optical design and the viability of the actuation approach while tolerances must be carefully taken into account.


      PubDate: 2014-03-13T00:03:27Z
       
  • Evaluation of accelerometer based multi-sensor versus single-sensor
           activity recognition systems
    • Abstract: Publication date: Available online 11 March 2014
      Source:Medical Engineering & Physics
      Author(s): Lei Gao , A.K. Bourke , John Nelson
      Physical activity has a positive impact on people's well-being and it had been shown to decrease the occurrence of chronic diseases in the older adult population. To date, a substantial amount of research studies exist, which focus on activity recognition using inertial sensors. Many of these studies adopt a single sensor approach and focus on proposing novel features combined with complex classifiers to improve the overall recognition accuracy. In addition, the implementation of the advanced feature extraction algorithms and the complex classifiers exceed the computing ability of most current wearable sensor platforms. This paper proposes a method to adopt multiple sensors on distributed body locations to overcome this problem. The objective of the proposed system is to achieve higher recognition accuracy with “light-weight” signal processing algorithms, which run on a distributed computing based sensor system comprised of computationally efficient nodes. For analysing and evaluating the multi-sensor system, eight subjects were recruited to perform eight normal scripted activities in different life scenarios, each repeated three times. Thus a total of 192 activities were recorded resulting in 864 separate annotated activity states. The methods for designing such a multi-sensor system required consideration of the following: signal pre-processing algorithms, sampling rate, feature selection and classifier selection. Each has been investigated and the most appropriate approach is selected to achieve a trade-off between recognition accuracy and computing execution time. A comparison of six different systems, which employ single or multiple sensors, is presented. The experimental results illustrate that the proposed multi-sensor system can achieve an overall recognition accuracy of 96.4% by adopting the mean and variance features, using the Decision Tree classifier. The results demonstrate that elaborate classifiers and feature sets are not required to achieve high recognition accuracies on a multi-sensor system.


      PubDate: 2014-03-13T00:03:27Z
       
  • A study of the metabolism of transplanted tumor in the lung by micro
           PET/CT in mice
    • Abstract: Publication date: March 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 3
      Author(s): Huiting Qiao , Jun Li , Yingmao Chen , Daifa Wang , Jintao Han , Mengqi Mei , Deyu Li
      The difference of tumor metabolism from that of normal tissue is an important factor for diagnosis through functional imaging such as positron emission tomography (PET). A quantitative description of the metabolic process will help to improve the diagnosis methods. In this study, the metabolism of tumor in lung was quantitatively described in mice. The melanoma was transplanted into the lung of mice, and the metabolism of the transplanted tumor was detected by micro PET/CT with [18F]fluoro-2-deoxy-d-glucose (FDG). Nine mice were transplanted with B16 melanoma cells through their tail vein. Lung tumor was detected by pathological method. The lesions smaller than 1mm could hardly be directly detected directly by micro PET/CT, while the tumor with a 1–4mm diameter could be detected by micro PET/CT. A metabolic model with three compartments was separately established for lung tumors and normal lung tissues. In this model, the lung cancer had a significantly higher metabolic rate constant as compared to that of the normal lung tissue (p =0.01). The outputs of the model fit well with the original curve from the dynamic images. It is also found that difference of tissue activity between tumors and normal lung tissues varied along scan time. Through this comparison, it was suggested that the difference in metabolism between the lung tissue and the tumor might contribute to the tumor diagnosis.


      PubDate: 2014-03-13T00:03:27Z
       
  • Load-transfer analysis after insertion of cementless anatomical femoral
           stem using pre- and post-operative CT images based patient-specific finite
           element analysis
    • Abstract: Publication date: Available online 12 March 2014
      Source:Medical Engineering & Physics
      Author(s): Go Yamako , Etsuo Chosa , Xin Zhao , Koji Totoribe , Shinji Watanabe , Takero Sakamoto , Nobutake Nakane
      Periprosthetic bone remodeling is commonly seen after total hip arthroplasty, but the remodeling pattern differs among patients even in those implanted with the same stem. Remodeling occurs mainly because of the difference in load transmitted from the stem to the femur. In this study, we evaluated the load-transfer pattern in eight female patients implanted with an anatomical stem on an individual basis by patient-specific finite element analysis that is based on pre- and postoperative computed tomography images. Load transfer was evaluated using interface stress between the stem and bone. One of eight patients demonstrated proximal dominant load transfer, while the other patients demonstrated a distal dominant pattern. The results of our biomechanical simulations reveal the differences in load-transfer pattern after surgery among patients with the same anatomical stem.


      PubDate: 2014-03-13T00:03:27Z
       
  • A model to predict deflection of bevel-tipped active needle advancing in
           soft tissue
    • Abstract: Publication date: March 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 3
      Author(s): Naresh V. Datla , Bardia Konh , Mohammad Honarvar , Tarun K. Podder , Adam P. Dicker , Yan Yu , Parsaoran Hutapea
      Active needles are recently being developed to improve steerability and placement accuracy for various medical applications. These active needles can bend during insertion by actuators attached to their bodies. The bending of active needles enables them to be steered away from the critical organs on the way to target and accurately reach target locations previously unachievable with conventional rigid needles. These active needles combined with an asymmetric bevel-tip can further improve their steerability. To optimize the design and to develop accurate path planning and control algorithms, there is a need to develop a tissue–needle interaction model. This work presents an energy-based model that predicts needle deflection of active bevel-tipped needles when inserted into the tissue. This current model was based on an existing energy-based model for bevel-tipped needles, to which work of actuation was included in calculating the system energy. The developed model was validated with needle insertion experiments with a phantom material. The model predicts needle deflection reasonably for higher diameter needles (11.6% error), whereas largest error was observed for the smallest needle diameter (24.7% error).


      PubDate: 2014-03-13T00:03:27Z
       
  • Development of a patient-specific simulation tool to analyse aortic
           dissections: Assessment of mixed patient-specific flow and pressure
           boundary conditions
    • Abstract: Publication date: March 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 3
      Author(s): Mona Alimohammadi , Obiekezie Agu , Stavroula Balabani , Vanessa Díaz-Zuccarini
      Aortic dissection has high morbidity and mortality rates and guidelines regarding surgical intervention are not clearly defined. The treatment of aortic dissection varies with each patient and detailed knowledge of haemodynamic and mechanical forces would be advantageous in the process of choosing a course of treatment. In this study, a patient-specific dissected aorta geometry is constructed from computed tomography scans. Dynamic boundary conditions are implemented by coupling a three element Windkessel model to the 3D domain at each outlet, in order to capture the essential behaviour of the downstream vasculature. The Windkessel model parameters are defined based on clinical data. The predicted minimum and maximum pressures are close to those measured invasively. Malperfusion is indicated and complex flow patterns are observed. Pressure, flow and wall shear stress distributions are analysed. The methodology presented here provides insight into the haemodynamics in a patient-specific dissected aorta and represents a development towards the use of CFD simulations as a diagnostic tool for aortic dissection.


      PubDate: 2014-03-13T00:03:27Z
       
  • Editorial Board
    • Abstract: Publication date: March 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 3




      PubDate: 2014-03-13T00:03:27Z
       
  • Development of a balanced experimental–computational approach to
           understanding the mechanics of proximal femur fractures
    • Abstract: Publication date: Available online 12 March 2014
      Source:Medical Engineering & Physics
      Author(s): B. Helgason , S.Gilchrist , O. Ariza , J.D. Chak , G. Zheng , R.P. Widmer , S.J. Ferguson , P. Guy , P.A. Cripton
      The majority of people who sustain hip fractures after a fall to the side would not have been identified using current screening techniques such as areal bone mineral density. Identifying them, however, is essential so that appropriate pharmacological or lifestyle interventions can be implemented. A protocol, demonstrated on a single specimen, is introduced, comprising the following components; in vitro biofidelic drop tower testing of a proximal femur; high-speed image analysis through digital image correlation; detailed accounting of the energy present during the drop tower test; organ level finite element simulations of the drop tower test; micro level finite element simulations of critical volumes of interest in the trabecular bone. Fracture in the femoral specimen initiated in the superior part of the neck. Measured fracture load was 3760N, compared to 4871N predicted based on the finite element analysis. Digital image correlation showed compressive surface strains as high as 7.1% prior to fracture. Voxel level results were consistent with high-speed video data and helped identify hidden local structural weaknesses. We found using a drop tower test protocol that a femoral neck fracture can be created with a fall velocity and energy representative of a sideways fall from standing. Additionally, we found that the nested explicit finite element method used allowed us to identify local structural weaknesses associated with femur fracture initiation.


      PubDate: 2014-03-13T00:03:27Z
       
  • Generating finite element models of the knee: How accurately can we
           determine ligament attachment sites from MRI scans'
    • Abstract: Publication date: Available online 12 March 2014
      Source:Medical Engineering & Physics
      Author(s): H.H. Rachmat , D. Janssen , W.J. Zevenbergen , G.J. Verkerke , R.L. Diercks , N. Verdonschot
      In this study, we evaluated the intra- and inter-observer variability when determining the insertion and origin sites of knee ligaments on MRI scan images. We collected data of five observers with different backgrounds, who determined the ligament attachment sites in an MRI scan of a right knee of a 66-year-old male cadaver donor. We evaluated the intra- and inter-observer differences between the ligament attachment center points, and also determined the differences relative to a physical measurement performed on the same cadaver. The largest mean intra- and inter-observer differences were 4.30mm (ACL origin) and 16.81mm (superficial MCL insertion), respectively. Relative to the physical measurement, the largest intra- and inter-observer differences were 31.84mm (superficial MCL insertion) and 23.39mm (deep MCL insertion), respectively. The results indicate that, dependent on the location, a significant variation can occur when identifying the attachment site of the knee ligaments. This finding is of particular importance when creating computational models based on MRI data, as the variations in attachment sites may have a considerable effect on the biomechanical behavior of the human knee joint.


      PubDate: 2014-03-13T00:03:27Z
       
  • A low-pass differentiation filter based on the 2nd-order B-spline wavelet
           for calculating augmentation index
    • Abstract: Publication date: Available online 7 March 2014
      Source:Medical Engineering & Physics
      Author(s): Zijun He , Yongliang Zhang , Zuchang Ma , Fusong Hu , Yining Sun
      The key point to calculate augmentation index (AIx) related to cardiovascular diseases is the precise identification of the shoulder point. The commonly used method for extracting the shoulder point is to calculate the fourth derivative of the pulse waveform by numerical differentiation. However, this method has a poor anti-noise capability and is computationally intensive. The aims of this study were to develop a new method based on the 2nd-order B-spline wavelet for calculating AIx, and to compare it with numerical differentiation and Savitzky–Golay digital differentiator (SGDD). All the three methods were applied to pulse waveforms derived from 60 healthy subjects. There was a significantly high correlation between the proposed method and numerical differentiation (r =0.998 for carotid pulses, and r =0.997 for radial pulses), as well as between the proposed method and the SGDD (r =0.995 for carotid pulses, and r =0.993 for radial pulses). In addition, the anti-noise capability of the proposed method was evaluated by adding simulated noise (>10Hz) on pulse waveforms. The results showed that the proposed method was advantageous in noise tolerance than the other two methods. These findings indicate that the proposed method can quickly and accurately calculate AIx with a good anti-noise capability.


      PubDate: 2014-03-09T22:25:11Z
       
  • New experimental protocols for tensile testing of abdominal aortic
           analogues
    • Abstract: Publication date: Available online 5 March 2014
      Source:Medical Engineering & Physics
      Author(s): L. Bailly , V. Deplano , A. Lemercier , O. Boiron , C. Meyer
      This work proposes an in vitro tensile testing protocol that is able to characterize abdominal aortic (AA) analogues under physiologically inspired mechanical loadings. Kinematic parameters are defined in agreement with in vivo measurements of aortic dynamics. A specific focus is given to the choice of the applied loading rates, deriving from the knowledge of aortic Peterson modulus and blood pressure variations from diastolic to systolic instants. The influence of physiological elongation rates has been tested on both porcine AAs and a thermoplastic polyurethane (TPU) material used to elaborate AA analogues. The diastolic and systolic elongation rates estimates vary between orders of magnitude O ( 10 − 2 ) and O ( 10 − 1 ) s − 1 . Negligible differences are obtained when comparing stress–elongation responses between both physiological elongation rates. In contrast, a noticeable stiffening of the TPU mechanical response is observed compared to that obtained under the common low traction rate of O ( 10 − 3 ) s − 1 . This work shows how relevant physiological elongation rates can be evaluated as a function of age, gender and pathological context.


      PubDate: 2014-03-09T22:25:11Z
       
  • Detection of systolic ejection click using time growing neural network
    • Abstract: Publication date: Available online 7 March 2014
      Source:Medical Engineering & Physics
      Author(s): Arash Gharehbaghi , Thierry Dutoit , Per Ask , Leif Sörnmo
      In this paper, we present a novel neural network for classification of short-duration heart sounds: the time growing neural network (TGNN). The input to the network is the spectral power in adjacent frequency bands as computed in time windows of growing length. Children with heart systolic ejection click (SEC) and normal children are the two groups subjected to analysis. The performance of the TGNN is compared to that of a time delay neural network (TDNN) and a multi-layer perceptron (MLP), using training and test datasets of similar sizes with a total of 614 normal and abnormal cardiac cycles. From the test dataset, the classification rate/sensitivity is found to be 97.0%/98.1% for the TGNN, 85.1%/76.4% for the TDNN, and 92.7%/85.7% for the MLP. The results show that the TGNN performs better than do TDNN and MLP when frequency band power is used as classifier input. The performance of TGNN is also found to exhibit better immunity to noise.


      PubDate: 2014-03-09T22:25:11Z
       
  • Simulation of longitudinal stent deformation in a patient-specific
           coronary artery
    • Abstract: Publication date: Available online 7 March 2014
      Source:Medical Engineering & Physics
      Author(s): Georgios E. Ragkousis , Nick Curzen , Neil W. Bressloff
      In percutaneous coronary intervention (PCI), stent malapposition is a common complication often leading to stent thrombosis (ST). More recently, it has also been associated with longitudinal stent deformation (LSD) normally occurring through contact of a post balloon catheter tip and the protruding malapposed stent struts. The aim of this study was to assess the longitudinal integrity of first and second generation drug eluting stents in a patient specific coronary artery segment and to compare the range of variation of applied loads with those reported elsewhere. We successfully validated computational models of three drug-eluting stent designs when assessed for longitudinal deformation. We then reconstructed a patient specific stenosed right coronary artery segment by fusing angiographic and intravascular ultrasound (IVUS) images from a real case. Within this model the mechanical behaviour of the same stents along with a modified device was compared. Specifically, after the deployment of each device, a compressive point load of 0.3N was applied on the most malapposed strut proximally to the models. Results indicate that predicted stent longitudinal strength (i) is significantly different between the stent platforms in a manner consistent with physical testing in a laboratory environment, (ii) shows a smaller range of variation for simulations of in vivo performance relative to models of in vitro experiments, and (iii) the modified stent design demonstrated considerably higher longitudinal integrity. Interestingly, stent longitudinal stability may differ drastically after a localised in vivo force compared to a distributed in vitro force.


      PubDate: 2014-03-09T22:25:11Z
       
  • Comparison of in vitro techniques to controllably decrease bone mineral
           density of cancellous bone for biomechanical compressive testing
    • Abstract: Publication date: Available online 4 March 2014
      Source:Medical Engineering & Physics
      Author(s): Francesca R. Nichols , Kent N. Bachus
      It is not surprising that an orthopedic device used with poorly mineralized bone can have lower mechanical fixation strength than the same device with well-mineralized bone. As new devices are being designed and tested, it is important to develop a controllable technique to decrease the bone mineral density of bone in vitro, so the fixation strength of the devices can be better modeled. Several different bone demineralization techniques have been established, but some use caustic chemicals and comparisons of their rates of demineralization have not been performed. In this study, a total of 120 cancellous bone cores were excised from ovine vertebra, scanned using a pico dual energy X-ray absorptiometry system to determine bone mineral density, then placed into one of five solutions (0.9% saline, 0.5M hydrochloric acid, 0.5M ethylenediaminetetraacetic acid, 0.5M formic acid, and 5% acetic acid). For each solution, 12 time periods ranging from 0 to 144h were investigated. After demineralization, all cores were rescanned and biomechanically loaded in compression to failure. Based on the rate of demineralization, the ease of use, the availability, and the correlation with the compressive bone strength, it was determined that the 5% acetic acid was the optimal demineralization solution to controllably decrease the bone mineral density of cancellous bone.


      PubDate: 2014-03-05T08:42:33Z
       
  • Can a 15m-overground wheelchair sprint be used to assess
           wheelchair-specific anaerobic work capacity'
    • Abstract: Publication date: Available online 14 February 2014
      Source:Medical Engineering & Physics
      Author(s): Jan W. van der Scheer , Sonja de Groot , Riemer J.K. Vegter , DirkJan (H.E.J.) Veeger , Lucas H.V. van der Woude
      Objective To evaluate whether outcomes based on stopwatch time and power output (PO) over a 15m-overground wheelchair sprint test can be used to assess wheelchair-specific anaerobic work capacity, by studying their relationship with outcomes on a Wingate-based 30s-wheelchair ergometer sprint (WAnT). Methods Able-bodied persons (N =19, 10 men, aged 18–26y) performed a 15m overground sprint test in an instrumented wheelchair and a WAnT. 15m-outcomes were based on stopwatch time (time and mean velocity over 15m) and on PO (primary outcome: highest mean unilateral PO over successive 5s-intervals (P5-15m)). WAnT-outcomes were mean unilateral PO over 30s and the highest mean unilateral PO over successive 5s-intervals. Correlation coefficients (Pearson's r) and coefficients of determination (R 2) were calculated between 15m-sprint outcomes and WAnT-outcomes. Results Time over 15m (7.2s (±1.0)) was weakly related to WAnT-outcomes (r =−0.61 and −0.60, R 2 =0.38 and 0.36, p <0.01), similar to mean velocity over 15m (2.1m·s−1 (±0.3), R 2 =0.43 and 0.39, p <0.01). P5-15m (38.1W (±14.0)) showed a moderate relationship to WAnT-outcomes (r =0.77 and 0.75, R 2 =0.59 and 0.56, p <0.001). Conclusions It seems that outcomes based on stopwatch time over a 15m-overground sprint cannot be used to assess wheelchair-specific anaerobic work capacity, in contrast to an outcome based on PO (P5-15m). The 15m-sprint with an instrumented wheel can be implemented in rehabilitation practice and research settings when WAnT equipment is not available, although care is needed when interpreting P5-15m as an outcome of anaerobic work capacity given that it seems more skill-dependent than the WAnT.


      PubDate: 2014-02-16T07:16:49Z
       
  • Comparison of stress on knee cartilage during kneeling and standing using
           finite element models
    • Abstract: Publication date: Available online 5 February 2014
      Source:Medical Engineering & Physics
      Author(s): Yuxing Wang , Yubo Fan , Ming Zhang
      Kneeling is a common activity required for both occupational and cultural reasons and has been shown to be associated with an increased risk of knee disorders. While excessive contact pressure is considered to be a possible aggressor, it is not clear whether and to what extent stress on the cartilage during kneeling is different from that while standing. In this study, finite element models of the knee joint for both kneeling and standing positions were constructed. The results indicated differences in high-stress regions between kneeling and standing. And both the peak von-Mises stress and contact pressure on the cartilage were larger in kneeling. During kneeling, the contact pressure reached 4.25MPa under a 300N compressive load. It then increased to 4.66MPa at 600N and 5.15MPa at 1000N. Changing the Poisson's ratio of the cartilage, which represents changes in compressibility caused by different loading rates, was found to have an influence on the magnitude of stress.


      PubDate: 2014-02-06T22:22:27Z
       
 
 
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