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  Subjects -> BIOLOGY (Total: 2799 journals)
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BIOLOGY (1369 journals)            First | 4 5 6 7 8 9 10 11 | Last

Journal of Avian Biology     Hybrid Journal   (Followers: 17)
Journal of Bacteriology     Full-text available via subscription   (Followers: 16)
Journal of Basic Microbiology     Hybrid Journal   (Followers: 3)
Journal of Bio-Science     Open Access   (Followers: 1)
Journal of Biobased Materials and Bioenergy     Full-text available via subscription  
Journal of Biodiversity & Endangered Species     Open Access  
Journal of Biodiversity Management & Forestry     Hybrid Journal  
Journal of Bioenergetics and Biomembranes     Hybrid Journal  
Journal of Biogeography     Hybrid Journal   (Followers: 20)
Journal of Bioinformatics and Computational Biology     Hybrid Journal   (Followers: 13)
Journal of Bioinformatics and Intelligent Control     Full-text available via subscription  
Journal of Biological and Information Sciences     Open Access   (Followers: 2)
Journal of Biological Dynamics     Open Access   (Followers: 1)
Journal of Biological Education     Hybrid Journal   (Followers: 1)
Journal of Biological Engineering     Open Access   (Followers: 5)
Journal of Biological Methods     Open Access  
Journal of Biological Physics     Hybrid Journal  
Journal of Biological Research - Thessaloniki     Open Access  
Journal of Biological Sciences     Open Access   (Followers: 4)
Journal of Biological Systems     Hybrid Journal   (Followers: 2)
Journal of Biology and Earth Sciences     Open Access   (Followers: 1)
Journal of Biology and Life Science     Open Access   (Followers: 2)
Journal of Biology, Agriculture and Healthcare     Open Access   (Followers: 4)
Journal of Biomarkers     Open Access  
Journal of Biomechanics     Hybrid Journal   (Followers: 26)
Journal of Biomedical Discovery and Collaboration     Open Access   (Followers: 1)
Journal of Biomedical Education     Open Access   (Followers: 1)
Journal of Biomedical Informatics     Partially Free   (Followers: 13)
Journal of Biomedical Materials Research Part A     Hybrid Journal   (Followers: 1)
Journal of Biomedical Materials Research Part B : Applied Biomaterials     Hybrid Journal   (Followers: 1)
Journal of Biomedical Nanotechnology     Full-text available via subscription   (Followers: 6)
Journal of Biomedical Physics and Engineering     Open Access  
Journal of Biomedical Science and Engineering     Open Access   (Followers: 2)
Journal of Biomedical Sciences     Open Access   (Followers: 2)
Journal of Biomolecular Screening     Hybrid Journal   (Followers: 4)
Journal of Bionic Engineering     Full-text available via subscription  
Journal of Biorheology     Hybrid Journal  
Journal of Bioscience and Bioengineering     Full-text available via subscription   (Followers: 17)
Journal of Biosciences and Medicines     Open Access  
Journal of Biosocial Science     Hybrid Journal   (Followers: 4)
Journal of Biotechnology and Biodiversity     Open Access   (Followers: 1)
Journal of Bryology     Hybrid Journal   (Followers: 1)
Journal of Cell and Plant Sciences     Open Access   (Followers: 3)
Journal of Cell Communication and Signaling     Hybrid Journal  
Journal of Cell Death     Open Access   (Followers: 1)
Journal of Cell Science     Full-text available via subscription   (Followers: 11)
Journal of Cellular Biochemistry     Hybrid Journal   (Followers: 3)
Journal of Cellular Physiology     Hybrid Journal   (Followers: 2)
Journal of Cerebral Blood Flow & Metabolism     Hybrid Journal   (Followers: 2)
Journal of Chromatography B     Hybrid Journal   (Followers: 20)
Journal of Clinical Bioinformatics     Open Access   (Followers: 5)
Journal of Clinical Toxicology     Open Access  
Journal of Communications Technology and Electronics     Hybrid Journal   (Followers: 1)
Journal of Contemporary Physics (Armenian Academy of Sciences)     Hybrid Journal   (Followers: 1)
Journal of Contradicting Results in Science     Open Access   (Followers: 2)
Journal of Crustacean Biology     Full-text available via subscription   (Followers: 2)
Journal of Developmental Biology     Open Access   (Followers: 2)
Journal of Ecosystems     Open Access   (Followers: 4)
Journal of Education, Health and Sport     Open Access   (Followers: 5)
Journal of Electrical Bioimpedance     Full-text available via subscription   (Followers: 2)
Journal of Electromyography and Kinesiology     Hybrid Journal   (Followers: 3)
Journal of Environment and Ecology     Open Access   (Followers: 11)
Journal of Environmental Radioactivity     Hybrid Journal   (Followers: 2)
Journal of Environmental Science and Natural Resources     Open Access   (Followers: 2)
Journal of Ethnobiology     Full-text available via subscription   (Followers: 5)
Journal of Ethnobiology and Ethnomedicine     Open Access  
Journal of Ethology     Hybrid Journal   (Followers: 1)
Journal of Evolutionary Biology     Hybrid Journal   (Followers: 22)
Journal of Experimental and Clinical Anatomy     Full-text available via subscription  
Journal of Experimental Marine Biology and Ecology     Hybrid Journal   (Followers: 26)
Journal of Fish Biology     Hybrid Journal   (Followers: 25)
Journal of Functional Biomaterials     Open Access   (Followers: 1)
Journal of Fungi     Open Access  
Journal of Genomes and Exomes     Open Access  
Journal of Great Lakes Research     Hybrid Journal   (Followers: 7)
Journal of Green Science and Technology     Full-text available via subscription  
Journal of Health and Biological Sciences     Open Access  
Journal of Heredity     Hybrid Journal   (Followers: 2)
Journal of Herpetology     Full-text available via subscription   (Followers: 4)
Journal of Histology & Histopathology     Open Access  
Journal of Huazhong University of Science and Technology [Medical Sciences]     Hybrid Journal  
Journal of Human Evolution     Hybrid Journal   (Followers: 12)
Journal of Hymenoptera Research     Open Access   (Followers: 2)
Journal of Ichthyology     Hybrid Journal   (Followers: 3)
Journal of Insect Behavior     Hybrid Journal   (Followers: 6)
Journal of Insect Biodiversity     Open Access   (Followers: 2)
Journal of Insect Conservation     Hybrid Journal   (Followers: 5)
Journal of Integrated OMICS     Open Access  
Journal of Integrated Pest Management     Open Access   (Followers: 2)
Journal of Integrative Environmental Sciences     Hybrid Journal   (Followers: 4)
Journal of Intelligent Transportation Systems: Technology, Planning, and Operations     Hybrid Journal   (Followers: 5)
Journal of Invertebrate Pathology     Hybrid Journal   (Followers: 3)
Journal of Landscape Ecology     Open Access   (Followers: 7)
Journal of Law and the Biosciences     Open Access   (Followers: 1)
Journal of Leukocyte Biology     Open Access   (Followers: 4)
Journal of Life and Earth Science     Open Access  
Journal of Lipid Research     Full-text available via subscription   (Followers: 3)
Journal of Lipids     Open Access   (Followers: 1)
Journal of Luminescence     Hybrid Journal   (Followers: 2)
Journal of Mammalian Evolution     Hybrid Journal   (Followers: 6)

  First | 4 5 6 7 8 9 10 11 | Last

Journal Cover   Medical Engineering & Physics
  [SJR: 0.871]   [H-I: 64]   [11 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1350-4533
   Published by Elsevier Homepage  [2586 journals]
  • MEG analysis of neural dynamics in attention-deficit/hyperactivity
           disorder with fuzzy entropy
    • Abstract: Publication date: April 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 4
      Author(s): Jesús Monge , Carlos Gómez , Jesús Poza , Alberto Fernández , Javier Quintero , Roberto Hornero
      The aim of this study was to analyze the neural dynamics in attention-deficit/hyperactivity disorder (ADHD). For this purpose, magnetoencephalographic (MEG) background activity was analyzed using fuzzy entropy (FuzzyEn), an entropy measure that quantifies signal irregularity, in 13 ADHD patients and 14 control children. Additionally, relative power (RP) was computed in conventional frequency bands (delta, theta, alpha, beta and gamma). FuzzyEn results showed that MEG activity was more regular in ADHD patients than in controls. Moreover, we found an increase of power in delta band and a decrease in the remaining frequency bands. Statistically significant differences (p-values <0.05; nonparametric permutation test for multiple comparisons) were detected for FuzzyEn in the posterior and left temporal regions, and for RP in the posterior, anterior and left temporal regions. Our results support the hypothesis that ADHD involves widespread functional brain abnormalities, affecting more areas than fronto-striatal circuits, such as the left temporal and posterior regions.


      PubDate: 2015-04-25T00:37:37Z
       
  • Adaptive myoelectric pattern recognition toward improved multifunctional
           prosthesis control
    • Abstract: Publication date: April 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 4
      Author(s): Jie Liu
      The non-stationary property of electromyography (EMG) signals in real life settings usually hinders the clinical application of the myoelectric pattern recognition for prosthesis control. The classical EMG pattern recognition approach consists of two separate steps: training and testing, without considering the changes between training and testing data induced by electrode shift, fatigue, impedance changes and psychological factors, and often results in performance degradation. The aim of this study was to develop an adaptive myoelectric pattern recognition system, aiming to retrain the classifier online with the testing data without supervision, providing a self-correction mechanism for suppressing misclassifications. This paper presents an adaptive unsupervised classifier based on support vector machine (SVM) to improve the classification performance. Experimental data from 15 healthy subjects were used to evaluate performance. Preliminary study on intra-session and inter-session EMG data was conducted to verify the performance of the unsupervised adaptive SVM classifier. The unsupervised adaptive SVM classifier outperformed the conventional SVM by 3.3% and 8.0% for the combination of time-domain and autoregressive features in the intra-session and inter-session tests, respectively. The proposed approach is capable of incorporating the useful information in testing data to the classification model by taking into account the overtime changes in the testing data with respect to the training data to retrain the original classifier, therefore providing a self-correction mechanism for suppressing misclassifications.


      PubDate: 2015-04-25T00:37:37Z
       
  • Mechanical properties of different airway stents
    • Abstract: Publication date: April 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 4
      Author(s): Anat Ratnovsky , Noa Regev , Shaily Wald , Mordechai Kramer , Sara Naftali
      Airway stents improve pulmonary function and quality of life in patients suffering from airway obstruction. The aim of this study was to compare main types of stents (silicone, balloon-dilated metal, self-expanding metal, and covered self-expanding metal) in terms of their mechanical properties and the radial forces they exert on the trachea. Mechanical measurements were carried out using a force gauge and specially designed adaptors fabricated in our lab. Numerical simulations were performed for eight different stent geometries, inserted into trachea models. The results show a clear correlation between stent diameter (oversizing) and the levels of stress it exerts on the trachea. Compared with uncovered metal stents, metal stents that are covered with less stiff material exert significantly less stress on the trachea while still maintaining strong contact with it. The use of such stents may reduce formation of mucosa necrosis and fistulas while still preventing stent migration. Silicone stents produce the lowest levels of stress, which may be due to weak contact between the stent and the trachea and can explain their propensity for migration. Unexpectedly, stents made of the same materials exerted different stresses due to differences in their structure. Stenosis significantly increases stress levels in all stents.


      PubDate: 2015-04-25T00:37:37Z
       
  • Influence of wheel configuration on wheelchair basketball performance:
           Wheel stiffness, tyre type and tyre orientation
    • Abstract: Publication date: April 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 4
      Author(s): B.S. Mason , M. Lemstra , L.H.V. van der Woude , R. Vegter , V.L. Goosey-Tolfrey
      The aim of the current investigation was to explore the lateral stiffness of different sports wheelchair wheels available to athletes in ‘new’ and ‘used’ conditions and to determine the effect of (a) stiffness, (b) tyre type (clincher vs. tubular) and (c) tyre orientation on the physiological and biomechanical responses to submaximal and maximal effort propulsion specific to wheelchair basketball. Eight able-bodied individuals participated in the laboratory-based testing, which took place on a wheelchair ergometer at two fixed speeds (1.1 and 2.2 m s−1). Outcome measures were power output and physiological demand (oxygen uptake and heart rate). Three participants with experience of over-ground sports wheelchair propulsion also performed 2 × 20 m sprints in each wheel configuration. Results revealed that wheels differed significantly in lateral stiffness with the ‘new’ Spinergy wheel shown to be the stiffest (678.2 ± 102.1 N mm−1). However the effects of stiffness on physiological demand were minimal compared to tyre type whereby tubular tyres significantly reduced the rolling resistance and power output in relation to clincher tyres. Therefore tyre type (and subsequently inflation pressure) remains the most important aspect of wheel specification for athletes to consider and monitor when configuring a sports wheelchair.


      PubDate: 2015-04-25T00:37:37Z
       
  • Optimization of dual slot antenna using floating metallic sleeve for
           microwave ablation
    • Abstract: Publication date: April 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 4
      Author(s): Z.A. Ibitoye , E.O. Nwoye , M.A. Aweda , A.A. Oremosu , C.C. Annunobi , O.N. Akanmu
      Backward heating reduction is vital in power distribution optimization in microwave thermal ablation. In this study, we optimized dual slot antenna to yield reduction in backward heating pattern along the antenna shaft with the application of floating metallic sleeve. Finite element methods were used to generate the electromagnetic (EM) field and thermal distribution in liver tissue. The position of the sleeve from the tip of the probe (z = 0 mm) was varied within the range 14 ≤ z ≤ 22 mm while sleeve length was varied within 16 ≤ z ≤ 48 mm at 2 mm interval using operating frequency of 2.45 GHz. The best optimized design has reflection coefficient of −20.87 dB and axial ratio of 0.41 when the sleeve position was at 17 mm and sleeve length was 18 mm. Experimental validation shows that inclusion of a floating metallic sleeve on dual slot antenna for hepatic microwave ablation averagely increased ablation diameter and aspect ratio by 17.8% and 33.9% respectively and decreased ablation length by 11.2%. Reduction in backward heating and increase in power deposition into liver tissue could be achieved by using this antenna to provide greater efficiency and localization of specific absorption rate in delivering microwave energy for hepatic ablation.


      PubDate: 2015-04-25T00:37:37Z
       
  • 3D surface imaging of the human female torso in upright to supine
           positions
    • Abstract: Publication date: April 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 4
      Author(s): Gregory P. Reece , Fatima Merchant , Johnny Andon , Hamed Khatam , K. Ravi-Chandar , June Weston , Michelle C. Fingeret , Chris Lane , Kelly Duncan , Mia K. Markey
      Three-dimensional (3D) surface imaging of breasts is usually done with the patient in an upright position, which does not permit comparison of changes in breast morphology with changes in position of the torso. In theory, these limitations may be eliminated if the 3D camera system could remain fixed relative to the woman's torso as she is tilted from 0 to 90°. We mounted a 3dMDtorso imaging system onto a bariatric tilt table to image breasts at different tilt angles. The images were validated using a rigid plastic mannequin and the metrics compared to breast metrics obtained from five subjects with diverse morphology. The differences between distances between the same fiducial marks differed between the supine and upright positions by less than 1% for the mannequin, whereas the differences for distances between the same fiducial marks on the breasts of the five subjects differed significantly and could be correlated with body mass index and brassiere cup size for each position change. We show that a tilt table–3D imaging system can be used to determine quantitative changes in the morphology of ptotic breasts when the subject is tilted to various angles.


      PubDate: 2015-04-25T00:37:37Z
       
  • Is there a bone-nail specific entry point' Automated fit
           quantification of tibial nail designs during the insertion for six
           different nail entry points
    • Abstract: Publication date: April 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 4
      Author(s): J.P. Amarathunga , M.A. Schuetz , K.V.D. Yarlagadda , B. Schmutz
      Intramedullary nailing is the standard fixation method for displaced diaphyseal fractures of tibia. Selection of the correct nail insertion point is important for axial alignment of bone fragments and to avoid iatrogenic fractures. However, the standard entry point (SEP) may not always optimise the bone-nail fit due to geometric variations of bones. This study aimed to investigate the optimal entry for a given bone-nail pair using the fit quantification software tool previously developed by the authors. The misfit was quantified for 20 bones with two nail designs (ETN and ETN-Proximal Bend) related to the SEP and 5 entry points which were 5 mm and 10 mm away from the SEP. The SEP was the optimal entry point for 50% of the bones used. For the remaining bones, the optimal entry point was located 5 mm away from the SEP, which improved the overall fit by 40% on average. However, entry points 10 mm away from the SEP doubled the misfit. The optimised bone-nail fit can be achieved through the SEP and within the range of a 5 mm radius, except posteriorly. The study results suggest that the optimal entry point should be selected by considering the fit during insertion and not only at the final position.


      PubDate: 2015-04-25T00:37:37Z
       
  • Editorial Board
    • Abstract: Publication date: April 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 4




      PubDate: 2015-04-25T00:37:37Z
       
  • A mathematical model approach quantifying patients’ response to
           changes in mechanical ventilation: Evaluation in volume support
    • Abstract: Publication date: April 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 4
      Author(s): S. Larraza , N. Dey , D.S. Karbing , J.B. Jensen , M. Nygaard , R. Winding , S.E. Rees
      This paper presents a mathematical model-approach to describe and quantify patient-response to changes in ventilator support. The approach accounts for changes in metabolism ( V ˙ O2, V ˙ CO2) and serial dead space (VD), and integrates six physiological models of: pulmonary gas-exchange; acid–base chemistry of blood, and cerebrospinal fluid; chemoreflex respiratory-drive; ventilation; and degree of patients’ respiratory muscle-response. The approach was evaluated with data from 12 patients on volume support ventilation mode. The models were tuned to baseline measurements of respiratory gases, ventilation, arterial acid–base status, and metabolism. Clinical measurements and model simulated values were compared at five ventilator support levels. The models were shown to adequately describe data in all patients (χ 2, p > 0.2) accounting for changes in V ˙ CO2, VD and inadequate respiratory muscle-response. F-ratio tests showed that this approach provides a significantly better (p < 0.001) description of measured data than: (a) a similar model omitting the degree of respiratory muscle-response; and (b) a model of constant alveolar ventilation. The approach may help predict patients’ response to changes in ventilator support at the bedside.


      PubDate: 2015-04-25T00:37:37Z
       
  • A numerical performance assessment of a commercial cardiopulmonary by-pass
           blood heat exchanger
    • Abstract: Publication date: Available online 15 April 2015
      Source:Medical Engineering & Physics
      Author(s): Filippo Consolo , Gianfranco B. Fiore , Alessandra Pelosi , Stefano Reggiani , Alberto Redaelli
      We developed a numerical model, based on multi-physics computational fluid dynamics (CFD) simulations, to assist the design process of a plastic hollow-fiber bundle blood heat exchanger (BHE) integrated within the INSPIRETM, a blood oxygenator (OXY) for cardiopulmonary by-pass procedures, recently released by Sorin Group Italia. In a comparative study, we analyzed five different geometrical design solutions of the BHE module. Quantitative geometrical-dependent parameters providing a comprehensive evaluation of both the hemo- and thermo-dynamics performance of the device were extracted to identify the best-performing prototypical solution. A convenient design configuration was identified, characterized by (i) a uniform blood flow pattern within the fiber bundle, preventing blood flow shunting and the onset of stagnation/recirculation areas and/or high velocity pathways, (ii) an enhanced blood heating efficiency, and (iii) a reduced blood pressure drop. The selected design configuration was then prototyped and tested to experimentally characterize the device performance. Experimental results confirmed numerical predictions, proving the effectiveness of CFD modeling as a reliable tool for in silico identification of suitable working conditions of blood handling medical devices. Notably, the numerical approach limited the need for extensive prototyping, thus reducing the corresponding machinery costs and time-to-market.


      PubDate: 2015-04-25T00:37:37Z
       
  • Incorporating in vivo fall assessments in the simulation of femoral
           fractures with finite element models
    • Abstract: Publication date: Available online 16 April 2015
      Source:Medical Engineering & Physics
      Author(s): A.M. van der Zijden , D. Janssen , N. Verdonschot , B.E. Groen , B. Nienhuis , V. Weerdesteyn , E. Tanck
      Femoral fractures are a major health issue. Most experimental and finite element (FE) fracture studies use polymethylmethacrylate cups on the greater trochanter (GT) to simulate fall impact loads. However, in vivo fall studies showed that the femur is loaded distally from the GT. Our objective was to incorporate in vivo fall data in FE models to determine the effects of loading position and direction, and size of simulated impact site on the fracture load and fracture type for a healthy and an osteoporotic femur. Twelve sets of loading position and angles were applied through ‘near point loads’ on the models. Additional simulations were performed with ‘cup loads’ on the GT, similar to the literature. The results showed no significant difference between fracture loads from simulations with near point loads distally from the GT and those with cup loads on the GT. However, simulated fracture types differed, as near point loads distally from the GT generally resulted in various neck fractures, whilst cup load simulations predicted superior neck and trochanteric fractures only. This study showed that incorporating in vivo fall assessments in FE models by loading the models distally from the GT results in prediction of realistic fracture loads and fracture types.


      PubDate: 2015-04-25T00:37:37Z
       
  • The influence of stem taper re-use upon the failure load of ceramic heads
    • Abstract: Publication date: Available online 20 April 2015
      Source:Medical Engineering & Physics
      Author(s): Julian Gührs , Annika Krull , Florian Witt , Michael M. Morlock
      Ceramic components are frequently used in total hip replacement due to their good tribological properties. In revision of broken ceramic heads clinical uncertainties arise, whether the taper of the stem can be re-used with a new ceramic head, especially if the stem is well fixed. Ceramic is a brittle material. Even small damage on the male stem taper can lead to stress concentrations causing premature failure of a new ceramic head. As a consequence, manufactures strictly prohibit stem taper re-use for ceramic heads. The aim of this study was to determine the fracture strength of ceramic heads assembled to re-used male stem tapers, which were subjected to prior head fracture. Five 12/14 Ti6Al4V male tapers and 15 Al2O3 ceramic heads (BIOLOX forte®; ∅ 28 mm, L) were used for three consecutive fracture tests. Before and after every fracture test, all components were inspected visually and the surface geometry was analyzed. Mean fracture force (52.5 kN) did not decrease with the number of taper re-uses (p ≥ 0.77) but the range increased significantly from initially 4.1 kN to 31.8 kN for the first and 52.6 kN for the second re-use due to some components failing at very low loads. Visual inspection was not sufficient to predict the reduced failure loads. Ceramic heads should therefore not be put on used male tapers without metal adapter sleeves.


      PubDate: 2015-04-25T00:37:37Z
       
  • Design of an actively controlled steerable needle with tendon actuation
           and FBG-based shape sensing
    • Abstract: Publication date: Available online 23 April 2015
      Source:Medical Engineering & Physics
      Author(s): Nick J. van de Berg , Jenny Dankelman , John J. van den Dobbelsteen
      This work presents a new steerable needle to facilitate active steering toward predefined target locations. It focuses on mechanical aspects and design choices in relation to the observed response in a tissue phantom. Tip steering with two rotational degrees of freedom was achieved by a tendon actuated ball joint mechanism. During insertion, the flexible cannula bends as a result of asymmetric tip–tissue interaction forces. The stylet was equipped with fiber Bragg gratings to measure the needle shape and tip position during use. A PI-controller was implemented to facilitate steering to predefined targets. During the validation study, nine targets were defined at a depth of 100 mm below the gelatin surface. One was located below the insertion point, the others at a radial offset of 30 mm in each of the eight principle steering directions. Per location, six repetitions were performed. The targeting accuracy was 6.2 ± 1.4 mm (mean ± std). The steering precision was 2.6 ± 1.1 mm. The ability to steer with this new needle steering approach is presented and the mechanical characteristics are discussed for this representative subset of steering directions.


      PubDate: 2015-04-25T00:37:37Z
       
  • Precision of image-based registration for intraoperative navigation in the
           presence of metal artifacts: Application to corrective osteotomy surgery
    • Abstract: Publication date: Available online 20 April 2015
      Source:Medical Engineering & Physics
      Author(s): J.G.G. Dobbe , F. Curnier , X. Rondeau , G.J. Streekstra
      Navigation for corrective osteotomy surgery requires patient-to-image registration. When registration is based on intraoperative 3-D cone-beam CT (CBCT) imaging, metal landmarks may be used that deteriorate image quality. This study investigates whether metal artifacts influence the precision of image-to-patient registration, either with or without intermediate user intervention during the registration procedure, in an application for corrective osteotomy of the distal radius. A series of 3-D CBCT scans is made of a cadaver arm with and without metal landmarks. Metal artifact reduction (MAR) based on inpainting techniques is used to improve 3-D CBCT images hampered by metal artifacts. This provides three sets of images (with metal, with MAR, and without metal), which enable investigating the differences in precision of intraoperative registration. Gray-level based point-to-image registration showed a better correlation coefficient if intraoperative images with MAR are used, indicating a better image similarity. The precision of registration without intermediate user intervention during the registration procedure, expressed as the residual angulation and displacement error after repetitive registration was very low and showed no improvement when MAR was used. By adding intermediate user intervention to the registration procedure however, precision was very high but was not affected by the presence of metal artifacts in the specific application.


      PubDate: 2015-04-25T00:37:37Z
       
  • Envelopment filter and K-means for the detection of QRS waveforms in
           electrocardiogram
    • Abstract: Publication date: Available online 23 April 2015
      Source:Medical Engineering & Physics
      Author(s): Manuel Merino , Isabel María Gómez , Alberto J. Molina
      The electrocardiogram (ECG) is a well-established technique for determining the electrical activity of the heart and studying its diseases. One of the most common pieces of information that can be read from the ECG is the heart rate (HR) through the detection of its most prominent feature: the QRS complex. This paper describes an offline version and a real-time implementation of a new algorithm to determine QRS localization in the ECG signal based on its envelopment and K-means clustering algorithm. The envelopment is used to obtain a signal with only QRS complexes, deleting P, T, and U waves and baseline wander. Two moving average filters are applied to smooth data. The K-means algorithm classifies data into QRS and non-QRS. The technique is validated using 22 h of ECG data from five Physionet databases. These databases were arbitrarily selected to analyze different morphologies of QRS complexes: three stored data with cardiac pathologies, and two had data with normal heartbeats. The algorithm has a low computational load, with no decision thresholds. Furthermore, it does not require any additional parameter. Sensitivity, positive prediction and accuracy from results are over 99.7%.


      PubDate: 2015-04-25T00:37:37Z
       
  • Drill wear monitoring in cortical bone drilling
    • Abstract: Publication date: Available online 23 April 2015
      Source:Medical Engineering & Physics
      Author(s): Tomislav Staroveski , Danko Brezak , Toma Udiljak
      Medical drills are subject to intensive wear due to mechanical factors which occur during the bone drilling process, and potential thermal and chemical factors related to the sterilisation process. Intensive wear increases friction between the drill and the surrounding bone tissue, resulting in higher drilling temperatures and cutting forces. Therefore, the goal of this experimental research was to develop a drill wear classification model based on multi-sensor approach and artificial neural network algorithm. A required set of tool wear features were extracted from the following three types of signals: cutting forces, servomotor drive currents and acoustic emission. Their capacity to classify precisely one of three predefined drill wear levels has been established using a pattern recognition type of the Radial Basis Function Neural Network algorithm. Experiments were performed on a custom-made test bed system using fresh bovine bones and standard medical drills. Results have shown high classification success rate, together with the model robustness and insensitivity to variations of bone mechanical properties. Features extracted from acoustic emission and servomotor drive signals achieved the highest precision in drill wear level classification (92.8%), thus indicating their potential in the design of a new type of medical drilling machine with process monitoring capabilities.


      PubDate: 2015-04-25T00:37:37Z
       
  • Finite element analysis predicts experimental failure patterns in
           vertebral bodies loaded via intervertebral discs up to large deformation
    • Abstract: Publication date: Available online 23 April 2015
      Source:Medical Engineering & Physics
      Author(s): Allison L. Clouthier , Hadi S. Hosseini , Ghislain Maquer , Philippe K. Zysset
      Vertebral compression fractures are becoming increasingly common. Patient-specific nonlinear finite element (FE) models have shown promise in predicting yield strength and damage pattern but have not been experimentally validated for clinically relevant vertebral fractures, which involve loading through intervertebral discs with varying degrees of degeneration up to large compressive strains. Therefore, stepwise axial compression was applied in vitro on segments and performed in silico on their FE equivalents using a nonlocal damage-plastic model including densification at large compression for bone and a time-independent hyperelastic model for the disc. The ability of the nonlinear FE models to predict the failure pattern in large compression was evaluated for three boundary conditions: healthy and degenerated intervertebral discs and embedded endplates. Bone compaction and fracture patterns were predicted using the local volume change as an indicator and the best correspondence was obtained for the healthy intervertebral discs. These preliminary results show that nonlinear finite element models enable prediction of bone localisation and compaction. To the best of our knowledge, this is the first study to predict the collapse of osteoporotic vertebral bodies up to large compression using realistic loading via the intervertebral discs.
      Graphical abstract image

      PubDate: 2015-04-25T00:37:37Z
       
  • A dual mode breath sampler for the collection of the end-tidal and dead
           space fractions
    • Abstract: Publication date: Available online 24 April 2015
      Source:Medical Engineering & Physics
      Author(s): P. Salvo , C. Ferrari , R. Persia , S. Ghimenti , T. Lomonaco , F. Bellagambi , F. Di Francesco
      This work presents a breath sampler prototype automatically collecting end-tidal (single and multiple breaths) or dead space air fractions (multiple breaths). This result is achieved by real time measurements of the CO2 partial pressure and airflow during the expiratory and inspiratory phases. Suitable algorithms, used to control a solenoid valve, guarantee that a Nalophan® bag is filled with the selected breath fraction even if the subject under test hyperventilates. The breath sampler has low pressure drop (<0.5 kPa) and uses inert or disposable components to avoid bacteriological risk for the patients and contamination of the breath samples. A fully customisable software interface allows a real time control of the hardware and software status. The performances of the breath sampler were evaluated by comparing (a) the CO2 partial pressure calculated during the sampling with the CO2 pressure measured off-line within the Nalophan® bag; (b) the concentrations of four selected volatile organic compounds in dead space, end-tidal and mixed breath fractions. Results showed negligible deviations between calculated and off-line CO2 pressure values and the distributions of the selected compounds into dead space, end-tidal and mixed breath fractions were in agreement with their chemical–physical properties.


      PubDate: 2015-04-25T00:37:37Z
       
  • Individual variability analysis of fluorescence parameters measured in
           skin with different levels of nutritive blood flow
    • Abstract: Publication date: Available online 24 April 2015
      Source:Medical Engineering & Physics
      Author(s): Andrey V. Dunaev , Victor V. Dremin , Evgeny A. Zherebtsov , Ilya E. Rafailov , Karina S. Litvinova , Scott G. Palmer , Neil A. Stewart , Sergei G. Sokolovski , Edik U. Rafailov
      Fluorescence spectroscopy has recently become more common in clinical medicine. However, there are still many unresolved issues related to the methodology and implementation of instruments with this technology. In this study, we aimed to assess individual variability of fluorescence parameters of endogenous markers (NADH, FAD, etc.) measured by fluorescent spectroscopy (FS) in situ and to analyse the factors that lead to a significant scatter of results. Most studied fluorophores have an acceptable scatter of values (mostly up to 30%) for diagnostic purposes. Here we provide evidence that the level of blood volume in tissue impacts FS data with a significant inverse correlation. The distribution function of the fluorescence intensity and the fluorescent contrast coefficient values are a function of the normal distribution for most of the studied fluorophores and the redox ratio. The effects of various physiological (different content of skin melanin) and technical (characteristics of optical filters) factors on the measurement results were additionally studied. The data on the variability of the measurement results in FS should be considered when interpreting the diagnostic parameters, as well as when developing new algorithms for data processing and FS devices.


      PubDate: 2015-04-25T00:37:37Z
       
  • High energy spectrogram with integrated prior knowledge for EMG-based
           locomotion classification
    • Abstract: Publication date: May 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 5
      Author(s): Deepak Joshi , Bryson H. Nakamura , Michael E. Hahn
      Electromyogram (EMG) signal representation is crucial in classification applications specific to locomotion and transitions. For a given signal, classification can be performed using discriminant functions or if-else rule sets, using learning algorithms derived from training examples. In the present work, a spectrogram based approach was developed to classify (EMG) signals for locomotion mode. Spectrograms for each muscle were calculated and summed to develop a histogram. If-else rules were used to classify test data based on a matching score. Prior knowledge of locomotion type reduced class space to exclusive locomotion modes. The EMG data were collected from seven leg muscles in a sample of able-bodied subjects while walking over ground (W), ascending stairs (SA) and the transition between (W-SA). Three muscles with least discriminating power were removed from the original data set to examine the effect on classification accuracy. Initial classification error was <20% across all modes, using leave one out cross validation. Use of prior knowledge reduced the average classification error to <11%. Removing three EMG channels decreased the classification accuracy by 10.8%, 24.3%, and 8.1% for W, W-SA, and SA respectively, and reduced computation time by 42.8%. This approach may be useful in the control of multi-mode assistive devices.


      PubDate: 2015-04-25T00:37:37Z
       
  • Full-surface deformation measurement of anisotropic tissues under
           indentation
    • Abstract: Publication date: May 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 5
      Author(s): Katia Genovese , Areli Montes , Amalia Martínez , Sam L. Evans
      Inverse finite element-based analysis of soft biological tissues is an important tool to investigate their complex mechanical behavior and to develop physical models for medical simulations. Although there have recently been advances in dealing with the computational complexities of modeling biological materials, the collection of a sufficiently dense set of experimental data to properly capture their typically regionally varying properties still remains a critical issue. The aim of this work was to develop and test an optical system that combines 2D-Digital Image Correlation (DIC) and a novel Fringe Projection method with radial sensitivity (RFP) to test soft biological tissues under in vitro indentation. This system has the distinctive capability of using a single camera to retrieve the shape and 3D deformation of the whole upper surface of the indented sample without any blind measurement areas (with exception of the area under the indenter), with nominal depth and in-plane resolution of 0.05 mm and 0.004 mm, respectively. To test and illustrate the capabilities of the developed DIC/RFP system, the in vitro response to indentation of a homogeneous and isotropic latex foam is presented against the response of a slab of porcine ventricular myocardium, a highly in-homogeneous and anisotropic tissue. Our results illustrate the enhanced capabilities of the developed method to capture asymmetry in deformation with respect to standard indentation tests. This feature, together with the possibility of miniaturizing the system into a hand-held probe, makes this method potentially extendable to in vivo settings, alone or in combination with ultrasound measurements.


      PubDate: 2015-04-25T00:37:37Z
       
  • A novel passive left heart platform for device testing and research
    • Abstract: Publication date: April 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 4
      Author(s): A.M. Leopaldi , R. Vismara , S. van Tuijl , A. Redaelli , F.N. van de Vosse , G.B. Fiore , M.C.M. Rutten
      Integration of biological samples into in vitro mock loops is fundamental to simulate real device's operating conditions. We developed an in vitro platform capable of simulating the pumping function of the heart through the external pressurization of the ventricle. The system consists of a fluid-filled chamber, in which the ventricles are housed and sealed to exclude the atria from external loads. The chamber is connected to a pump that drives the motion of the ventricular walls. The aorta is connected to a systemic impedance simulator, and the left atrium to an adjustable preload. The platform reproduced physiologic hemodynamics, i.e. aortic pressures of 120/80 mmHg with 5 L/min of cardiac output, and allowed for intracardiac endoscopy. A pilot study with a left ventricular assist device (LVAD) was also performed. The LVAD was connected to the heart to investigate aortic valve functioning at different levels of support. Results were consistent with the literature, and high speed video recordings of the aortic valve allowed for the visualization of the transition between a fully opening valve and a permanently closed configuration. In conclusion, the system showed to be an effective tool for the hemodynamic assessment of devices, the simulation of surgical or transcatheter procedures and for visualization studies.


      PubDate: 2015-04-25T00:37:37Z
       
  • Posterior stabilized versus cruciate retaining total knee arthroplasty
           designs: Conformity affects the performance reliability of the design over
           the patient population
    • Abstract: Publication date: April 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 4
      Author(s): Marzieh M. Ardestani , Mehran Moazen , Ehsan Maniei , Zhongmin Jin
      Commercially available fixed bearing knee prostheses are mainly divided into two groups: posterior stabilized (PS) versus cruciate retaining (CR). Despite the widespread comparative studies, the debate continues regarding the superiority of one type over the other. This study used a combined finite element (FE) simulation and principal component analysis (PCA) to evaluate "reliability" and "sensitivity" of two PS designs versus two CR designs over a patient population. Four fixed bearing implants were chosen: PFC (DePuy), PFC Sigma (DePuy), NexGen (Zimmer) and Genesis II (Smith & Nephew). Using PCA, a large probabilistic knee joint motion and loading database was generated based on the available experimental data from literature. The probabilistic knee joint data were applied to each implant in a FE simulation to calculate the potential envelopes of kinematics (i.e. anterior–posterior [AP] displacement and internal–external [IE] rotation) and contact mechanics. The performance envelopes were considered as an indicator of performance reliability. For each implant, PCA was used to highlight how much the implant performance was influenced by changes in each input parameter (sensitivity). Results showed that (1) conformity directly affected the reliability of the knee implant over a patient population such that lesser conformity designs (PS or CR), had higher kinematic variability and were more influenced by AP force and IE torque, (2) contact reliability did not differ noticeably among different designs and (3) CR or PS designs affected the relative rank of critical factors that influenced the reliability of each design. Such investigations enlighten the underlying biomechanics of various implant designs and can be utilized to estimate the potential performance of an implant design over a patient population.


      PubDate: 2015-04-25T00:37:37Z
       
  • Numerical and experimental investigation of the structural behavior of a
           carbon fiber reinforced ankle-foot orthosis
    • Abstract: Publication date: May 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 5
      Author(s): Bertram Stier , Jaan-Willem Simon , Stefanie Reese
      Ankle-foot orthoses (AFOs) are designed to enhance the gait function of individuals with motor impairments. Recent AFOs are often made of laminated composites due to their high stiffness and low density. Since the performance of AFO is primarily influenced by their structural stiffness, the investigation of the mechanical response is very important for the design. The aim of this paper is to present a three dimensional multi-scale structural analysis methodology to speed up the design process of AFO. The multi-scale modeling procedure was applied such that the intrinsic micro-structure of the fiber reinforced laminates could be taken into account. In particular, representative volume elements were used on the micro-scale, where fiber and matrix were treated separately, and on the textile scale of the woven structure. For the validation of this methodology, experimental data were generated using digital image correlation (DIC) measurements. Finally, the structural behavior of the whole AFO was predicted numerically for a specific loading scenario and compared with experimental results. It was shown that the proposed numerical multi-scale scheme is well suited for the prediction of the structural behavior of AFOs, validated by the comparison of local strain fields as well as the global force-displacement curves.


      PubDate: 2015-04-25T00:37:37Z
       
  • ECG-derived respiration methods: Adapted ICA and PCA
    • Abstract: Publication date: May 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 5
      Author(s): Suvi Tiinanen , Kai Noponen , Mikko Tulppo , Antti Kiviniemi , Tapio Seppänen
      Respiration is an important signal in early diagnostics, prediction, and treatment of several diseases. Moreover, a growing trend toward ambulatory measurements outside laboratory environments encourages developing indirect measurement methods such as ECG derived respiration (EDR). Recently, decomposition techniques like principal component analysis (PCA), and its nonlinear version, kernel PCA (KPCA), have been used to derive a surrogate respiration signal from single-channel ECG. In this paper, we propose an adapted independent component analysis (AICA) algorithm to obtain EDR signal, and extend the normal linear PCA technique based on the best principal component (PC) selection (APCA, adapted PCA) to improve its performance further. We also demonstrate that the usage of smoothing spline resampling and bandpass-filtering improve the performance of all EDR methods. Compared with other recent EDR methods using correlation coefficient and magnitude squared coherence, the proposed AICA and APCA yield a statistically significant improvement with correlations 0.84, 0.82, 0.76 and coherences 0.90, 0.91, 0.85 between reference respiration and AICA, APCA and KPCA, respectively.


      PubDate: 2015-04-25T00:37:37Z
       
  • Unobtrusive monitoring and identification of fall accidents
    • Abstract: Publication date: May 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 5
      Author(s): Pepijn van de Ven , Hugh O'Brien , John Nelson , Amanda Clifford
      Falls are a societal and economic problem of great concern with large parts of the population, in particular older citizens, at significant risk and the result of a fall often being grave. It has long been established that it is of importance to provide help to a faller soon after the event to prevent complications and this can be achieved with a fall monitor. Yet, the practical use of currently available fall monitoring solutions is limited due to accuracy, usability, cost, and, not in the least, the stigmatising effect of many solutions. This paper proposes a fall sensor concept that can be embedded in the user's footwear and discusses algorithms, software and hardware developed. Sensor performance is illustrated using results of a series of functional tests. These show that the developed sensor can be used for the accurate measurement of various mobility and gait parameters and that falls are detected accurately.


      PubDate: 2015-04-25T00:37:37Z
       
  • Comparing passive angle–torque curves recorded simultaneously with a
           load cell versus an isokinetic dynamometer during dorsiflexion stretch
           tolerance assessments
    • Abstract: Publication date: May 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 5
      Author(s): Samuel L. Buckner , Nathaniel D.M. Jenkins , Pablo B. Costa , Eric D. Ryan , Trent J. Herda , Joel T. Cramer
      The purpose of the present study was to compare the passive angle–torque curves and the passive stiffness (PS, N m °− 1) values recorded simultaneously from a load cell versus an isokinetic dynamometer during dorsiflexion stretch tolerance assessments in vivo. Nine healthy men (mean ± SD age = 21.4 ± 1.6 years) completed stretch tolerance assessments on a custom-built apparatus where passive torque was measured simultaneously from an isokinetic dynamometer and a load cell. Passive torque values that corresponded with the last 10° of dorsiflexion, verified by surface electromyographic amplitude, were analyzed for each device (θ1, θ2, θ3, …, θ10). Passive torque values measured with the load cell were greater (p ≤ 0.05) than the dynamometer torque values for θ4 through θ10. There were more statistical differentiations among joint angles for passive torque measured by the load cell, and the load cell measured a greater (p ≤ 0.01) increase in passive torque and PS than the isokinetic dynamometer. These findings suggested that when examining the angle–torque curves from passive dorsiflexion stretch tolerance tests, a load cell placed under the distal end of the foot may be more sensitive than the torque recorded from an isokinetic dynamometer.


      PubDate: 2015-04-25T00:37:37Z
       
  • Effects of particle uptake, encapsulation, and localization in cancer
           cells on intracellular applications
    • Abstract: Publication date: May 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 5
      Author(s): N. Gal , S. Massalha , O. Samuelly-Nafta , D. Weihs
      Endocytosis is a normal process in living cells, often used to internalize drug-containing particles and probes for intracellular mechanics. The cell type, and especially malignancy, may affect particle internalization and transport. Specifically, membrane-encapsulation following internalization can affect particle interaction with the cell interior. Hence, particle-tracking measurements that reveal intracellular mechanics and dynamics require determination of effects of encapsulation. Here, we compare closely related, breast-cancer cell lines with high- and low-metastatic potential (MP) and benign, control cells. We evaluate time-dependent particle internalization, localization with endocytotic-pathway organelles, and membrane encapsulation at 2, 6, 24, and 48 h after initial cell exposure to particles. High MP cells internalize particles more rapidly and in larger amounts than low MP and benign cells. Moreover, while only cells at the edge of two-dimensional colonies of benign cells internalized particles, all cancer cells uniformly internalize particles. Particles mostly colocalize with late endosomes (>80%), yet surprisingly, overall membrane encapsulation decreases with time, indicating release into the cytoplasm; encapsulation at 48 h is <35% in all three cell types. We discuss implications to drug delivery and show that encapsulation does not significantly affect intracellular particle-tracking experiments, showing the applicability of endocytosis.


      PubDate: 2015-04-25T00:37:37Z
       
  • Design optimization study of a shape memory alloy active needle for
           biomedical applications
    • Abstract: Publication date: May 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 5
      Author(s): Bardia Konh , Mohammad Honarvar , Parsaoran Hutapea
      Majority of cancer interventions today are performed percutaneously using needle-based procedures, i.e. through the skin and soft tissue. The difficulty in most of these procedures is to attain a precise navigation through tissue reaching target locations. To overcome this challenge, active needles have been proposed recently where actuation forces from shape memory alloys (SMAs) are utilized to assist the maneuverability and accuracy of surgical needles. In the first part of this study, actuation capability of SMA wires was studied. The complex response of SMAs was investigated via a MATLAB implementation of the Brinson model and verified via experimental tests. The isothermal stress–strain curves of SMAs were simulated and defined as a material model in finite element analysis (FEA). The FEA was validated experimentally with developed prototypes. In the second part of this study, the active needle design was optimized using genetic algorithm aiming its maximum flexibility. Design parameters influencing the steerability include the needle's diameter, wire diameter, pre-strain and its offset from the needle. A simplified model was presented to decrease the computation time in iterative analyses. Integration of the SMA characteristics with the automated optimization schemes described in this study led to an improved design of the active needle.


      PubDate: 2015-04-25T00:37:37Z
       
  • Mechanical characterization of bone anchors used with a bone-attached,
           parallel robot for skull surgery
    • Abstract: Publication date: May 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 5
      Author(s): Jan-Philipp Kobler , Lenka Prielozny , G.Jakob Lexow , Thomas S. Rau , Omid Majdani , Tobias Ortmaier
      Bone-attached robots and microstereotactic frames, intended for deep brain stimulation and minimally invasive cochlear implantation, typically attach to a patient’s skull via bone anchors. A rigid and reliable link between such devices and the skull is mandatory in order to fulfill the high accuracy demands of minimally invasive procedures while maintaining patient safety. In this paper, a method is presented to experimentally characterize the mechanical properties of the anchor–bone linkage. A custom-built universal testing machine is used to measure the pullout strength as well as the spring constants of bone anchors seated in four different bone substitutes as well as in human cranial bone. Furthermore, the angles at which forces act on the bone anchors are varied to simulate realistic conditions. Based on the experimental results, a substitute material that has mechanical properties similar to those of cranial bone is identified. The results further reveal that the pullout strength of the investigated anchor design is sufficient with respect to the proposed application. However, both the measured load capacity as well as the spring constants vary depending on the load angles. Based on these findings, an alternative bone anchor design is presented and experimentally validated. Furthermore, the results serve as a basis for stiffness simulation and optimization of bone-attached microstereotactic frames.


      PubDate: 2015-04-25T00:37:37Z
       
  • Monitoring brain damage using bioimpedance technique in a 3D numerical
           model of the head
    • Abstract: Publication date: May 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 5
      Author(s): Rotem Cohen , Shimon Abboud , Marina Arad
      Disturbance in the blood supply to the brain causes a stroke or cerebrovascular accident. This can be due to ischemia caused by blockage (thrombosis, arterial embolism) or a hemorrhage. In this study, the feasibility of basic electrical impedance technique for monitoring such damage was analyzed using a computerized model. Simulations were conducted on a realistic 3D numerical model of the head. Tissues were assumed to act as linear isotropic volume conductors, and the quasi-static approximation was applied. Electrical potentials were calculated by solving Poisson's equation, using the finite volume method and the successive over relaxation method. Left–right asymmetry was calculated for several conductivities and volumes of the damaged region. The results were compared with the left–right asymmetry in a head model with normal brain. A negative asymmetry was revealed for blockage (i.e. the potential amplitude over the ischemic hemisphere was greater than that over the intact hemisphere). In case of hemorrhage, a positive asymmetry was found. Furthermore, correlation was found between the location of the damaged region and the electrodes with significant asymmetry. The 3D numerical simulations revealed that the electrical conductivity and the size of the damaged tissue have an effect on the left–right asymmetry of the surface potential.


      PubDate: 2015-04-25T00:37:37Z
       
  • Editorial Board
    • Abstract: Publication date: May 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 5




      PubDate: 2015-04-25T00:37:37Z
       
  • Cement applicator use for hip resurfacing arthroplasty
    • Abstract: Publication date: May 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 5
      Author(s): Sebastian Jaeger , Johannes S. Rieger , Beate Obermeyer , Matthias C. Klotz , J. Philippe Kretzer , Rudi G. Bitsch
      We compared the manufacturer recommended cementing technique for a femoral hip resurfacing implant (BHR, S&N) to a newly designed cement applicator on 20 porous carbon foam specimens. Substantial design changes and improvements of the cement applicator were necessary: The diameter and number of the cement escaping holes at the top of the applicator were optimized for medium viscosity cement. It was necessary to add four separate air inlet holes with large diameters. The inner shape of the applicator had to be adapted to the BHR design with a circular extending chamfer in the proximal region, a parallel inner wall and a second chamfer distally. The interface temperatures showed no risk for heat necrosis using both techniques. The cement penetration depth was more uniform and significantly reduced for the applicator cementing technique (4.34 ± 1.42 mm, 6.42 ± 0.43 mm, p = 0.001). The cement-applicator showed no cement defects compared to a large defect length (0.0 ± 0.0 mm, 10.36 ± 1.10 mm, p < 0.001) with the manufacturer recommended cementing technique. The cement applicator technique appears to be effective for a homogenous cement distribution without cement defects and safe with a lower risk of polar over-penetration.


      PubDate: 2015-04-25T00:37:37Z
       
  • Number and localization of the implants for the fixed prosthetic
           reconstructions: On the strain in the anterior maxillary region
    • Abstract: Publication date: April 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 4
      Author(s): Nilüfer Bölükbaşı , Sinem Yeniyol
      Resorption following tooth loss and poor bone quality affect the success of implants in the anterior maxilla. Inappropriate planning can cause implant loss and aesthetics problems that are difficult to resolve. There is a limited literature on the optimum number and location of implants in anterior maxilla for fabricating fixed prosthesis in biomechanical terms. This study investigated the effect of dental implant localizations in anterior maxilla on the strain values around implants using a three dimensional finite elements analysis method. Obtained strain values were compared to the data in Frost's mechanostat theory. The entire totally edentulous maxilla was modeled using computer tomography images and five models were prepared representing different implant localizations. The distribution of implants in the models was as follows: two canines in the first model, two canines and one central incisor in the second model, two canines and central incisor in the third model, two canines and one lateral incisor in the fourth model and two canines and two lateral incisors in the fifth model. Anatomic abutments with a gingival height of 2 mm and angle of 15° were used as the abutments to fabricate one piece cemented metal fused to porcelain restoration. A chewing strength of 100 N was applied to the cingulum of all crowns at a 45° angle. Maximum strain values in all models were measured in cortical bone in implant necks. The highest strain value was measured in the first model at the cortical bone area (3037 microstrain). Except the first model, all models showed micro strain values within 1000–3000 microstrain. The fifth model was the least risky method in biomechanical terms. The results of this study should be compared with different clinical scenarios (for example different implant designs and sizes). Due to the limitations of three-dimensional finite elements analysis studies, the findings of the study need to be supported by clinical studies.


      PubDate: 2015-04-25T00:37:37Z
       
  • Editorial Board
    • Abstract: Publication date: March 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 3




      PubDate: 2015-04-25T00:37:37Z
       
  • Flow measurement in mechanical ventilation: A review
    • Abstract: Publication date: March 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 3
      Author(s): Emiliano Schena , Carlo Massaroni , Paola Saccomandi , Stefano Cecchini
      Accurate monitoring of flow rate and volume exchanges is essential to minimize ventilator-induced lung injury. Mechanical ventilators employ flowmeters to estimate the amount of gases delivered to patients and use the flow signal as a feedback to adjust the desired amount of gas to be delivered. Since flowmeters play a crucial role in this field, they are required to fulfill strict criteria in terms of dynamic and static characteristics. Therefore, mechanical ventilators are equipped with only the following kinds of flowmeters: linear pneumotachographs, fixed and variable orifice meters, hot wire anemometers, and ultrasonic flowmeters. This paper provides an overview of these sensors. Their working principles are described together with their relevant advantages and disadvantages. Furthermore, the most promising emerging approaches for flowmeters design (i.e., fiber optic technology and three dimensional micro-fabrication) are briefly reviewed showing their potential for this application.


      PubDate: 2015-04-25T00:37:37Z
       
  • Is aortic wall shear stress affected by aging' An image-based
           numerical study with two age groups
    • Abstract: Publication date: March 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 3
      Author(s): Jonas Lantz , Johan Renner , Toste Länne , Matts Karlsson
      The size of the larger arteries increases during the entire life, but not much is known about how the change in size affects the blood flow. This study compares the flow field in a group of young males (N = 10, age = 23.5 ± 1.4), with a group of older males (N = 8, age = 58.0 ± 2.8). Aortic geometries were obtained by magnetic resonance imaging, and the aortic blood flow field was computed using computational fluid dynamics. The aortic wall shear stress was obtained from the computations, and it was concluded that time-averaged wall shear stress decreased with increased age, probably as a consequence of increased aortic diameter and decreased stroke volume, which in turn reduces the shear rates in the aorta. However, the oscillatory shear index, which is a measure of the oscillatory nature of the wall shear stress vector, seemed to be unaffected by aging.


      PubDate: 2015-04-25T00:37:37Z
       
  • Beneficial fluid-dynamic features of pulsatile swirling flow in 45°
           end-to-side anastomosis
    • Abstract: Publication date: March 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 3
      Author(s): Hojin Ha , Woorak Choi , Sang Joon Lee
      Although a large number of vascular grafts are surgically implanted annually, approximately 10–15% of these grafts fail in the first year after operation and about 50% are only effective for five to ten years. Surgical implantation of a vascular graft modifies the inherent hemodynamic environment in blood vessels; hence, fluid dynamic characteristics of pathological blood flow are highly related to the performance of the vascular graft. In this study, pathological fluid-dynamic characteristics in a 45° end-to-side anastomosis were experimentally investigated using a particle image velocimetry technique. In particular, the effect of the pulsatile swirling inlet flow in the vascular graft on the improvement of pathological hemodynamic features was systematically investigated. Introducing the pulsatile swirling flow equalizes the asymmetric distribution of wall shear stress and reduces oscillatory shear index and the size of flow separation because the flow disturbs the formation of Dean-type vortices and suppresses secondary flow collision. The fluid dynamic features of the pulsatile swirling flow are expected to be beneficial in designing vascular grafts that can suppress pathological hemodynamic characteristics in the recipient host vessel.


      PubDate: 2015-04-25T00:37:37Z
       
  • NIRS-based classification of clench force and speed motor imagery with the
           use of empirical mode decomposition for BCI
    • Abstract: Publication date: March 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 3
      Author(s): Xuxian Yin , Baolei Xu , Changhao Jiang , Yunfa Fu , Zhidong Wang , Hongyi Li , Gang Shi
      Near-infrared spectroscopy (NIRS) is a non-invasive optical technique used for brain–computer interface (BCI). This study aims to investigate the brain hemodynamic responses of clench force and speed motor imagery and extract task-relevant features to obtain better classification performance. Given the non-stationary characteristics of real hemodynamic measurements, empirical mode decomposition (EMD) was applied to reduce the physiological noise overwhelmed in the task-relevant NIRS signals. Compared with continuous wavelet decomposition, EMD does not require a pre-determined basis function. EMD decomposes the original signals into a set of intrinsic mode functions (IMFs). In this study, joint mutual information was applied to select the optimal features, and support vector machine was used as a classifier. Offline and pseudo-online analyses showed that the most feasible classification accuracy can be obtained using IMFs as input features. Accordingly, an alternative feature is provided to develop the NIRS–BCI system.


      PubDate: 2015-04-25T00:37:37Z
       
  • Bioresorbable scaffolds for bone tissue engineering: Optimal design,
           fabrication, mechanical testing and scale-size effects analysis
    • Abstract: Publication date: March 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 3
      Author(s): Pedro G. Coelho , Scott J. Hollister , Colleen L. Flanagan , Paulo R. Fernandes
      Bone scaffolds for tissue regeneration require an optimal trade-off between biological and mechanical criteria. Optimal designs may be obtained using topology optimization (homogenization approach) and prototypes produced using additive manufacturing techniques. However, the process from design to manufacture remains a research challenge and will be a requirement of FDA design controls to engineering scaffolds. This work investigates how the design to manufacture chain affects the reproducibility of complex optimized design characteristics in the manufactured product. The design and prototypes are analyzed taking into account the computational assumptions and the final mechanical properties determined through mechanical tests. The scaffold is an assembly of unit-cells, and thus scale size effects on the mechanical response considering finite periodicity are investigated and compared with the predictions from the homogenization method which assumes in the limit infinitely repeated unit cells. Results show that a limited number of unit-cells (3–5 repeated on a side) introduce some scale-effects but the discrepancies are below 10%. Higher discrepancies are found when comparing the experimental data to numerical simulations due to differences between the manufactured and designed scaffold feature shapes and sizes as well as micro-porosities introduced by the manufacturing process. However good regression correlations (R 2 > 0.85) were found between numerical and experimental values, with slopes close to 1 for 2 out of 3 designs.


      PubDate: 2015-04-25T00:37:37Z
       
  • Mutual information measures applied to EEG signals for sleepiness
           characterization
    • Abstract: Publication date: March 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 3
      Author(s): Umberto Melia , Marc Guaita , Montserrat Vallverdú , Cristina Embid , Isabel Vilaseca , Manel Salamero , Joan Santamaria
      Excessive daytime sleepiness (EDS) is one of the main symptoms of several sleep related disorders with a great impact on the patient lives. While many studies have been carried out in order to assess daytime sleepiness, the automatic EDS detection still remains an open problem. In this work, a novel approach to this issue based on non-linear dynamical analysis of EEG signal was proposed. Multichannel EEG signals were recorded during five maintenance of wakefulness (MWT) and multiple sleep latency (MSLT) tests alternated throughout the day from patients suffering from sleep disordered breathing. A group of 20 patients with excessive daytime sleepiness (EDS) was compared with a group of 20 patients without daytime sleepiness (WDS), by analyzing 60-s EEG windows in waking state. Measures obtained from cross-mutual information function (CMIF) and auto-mutual-information function (AMIF) were calculated in the EEG. These functions permitted a quantification of the complexity properties of the EEG signal and the non-linear couplings between different zones of the scalp. Statistical differences between EDS and WDS groups were found in β band during MSLT events (p-value < 0.0001). WDS group presented more complexity than EDS in the occipital zone, while a stronger nonlinear coupling between occipital and frontal zones was detected in EDS patients than in WDS. The AMIF and CMIF measures yielded sensitivity and specificity above 80% and AUC of ROC above 0.85 in classifying EDS and WDS patients.


      PubDate: 2015-04-25T00:37:37Z
       
  • Denoising preterm EEG by signal decomposition and adaptive filtering: A
           comparative study
    • Abstract: Publication date: March 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 3
      Author(s): X. Navarro , F. Porée , A. Beuchée , G. Carrault
      Electroencephalography (EEG) from preterm infant monitoring systems is usually contaminated by several sources of noise that have to be removed in order to correctly interpret signals and perform automated analysis reliably. Band-pass and adaptive filters (AF) continue to be systematically applied, but their efficacy may be decreased facing preterm EEG patterns such as the tracé alternant and slow delta-waves. In this paper, we propose the combination of EEG decomposition with AF to improve the overall denoising process. Using artificially contaminated signals from real EEGs, we compared the quality of filtered signals applying different decomposition techniques: the discrete wavelet transform, the empirical mode decomposition (EMD) and a recent improved version, the complete ensemble EMD with adaptive noise. Simulations demonstrate that introducing EMD-based techniques prior to AF can reduce up to 30% the root mean squared errors in denoised EEGs.


      PubDate: 2015-04-25T00:37:37Z
       
  • Non-invasive determination of transcatheter pressure gradient in stenotic
           aortic valves: An analytical model
    • Abstract: Publication date: March 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 3
      Author(s): Zahra Keshavarz-Motamed , Pouyan K. Motamed , Nima Maftoon
      Aortic stenosis (AS), in which the opening of the aortic valve is narrowed, is the most common valvular heart disease. Cardiac catheterization is considered the reference standard for definitive evaluation of AS severity, based on instantaneous systolic value of transvalvular pressure gradient (TPG). However, using invasive cardiac catheterization might carry high risks knowing that undergoing multiple cardiac catheterizations for follow-up in patients with AS is common. The objective of this study was to suggest an analytical description of the AS that estimates TPG without a need for high risk invasive data collection. For this purpose, Navier–Stokes equation coupled with the elastic-deformation equation was solved analytically. The estimated TPG resulted from the suggested analytical description was validated against published in vivo and in vitro measurement data. Very good concordances were found between TPG obtained from the analytical formulation and in vivo (maximum root mean square error: 3.8 mmHg) and in vitro (maximum root mean square error: 9.4 mmHg). The analytical description can be integrated to non-invasive imaging modalities to estimate AS severity as an alternative to cardiac catheterization to help preventing its risks in patients with AS.


      PubDate: 2015-04-25T00:37:37Z
       
  • Sensitivity analysis of geometric errors in additive manufacturing medical
           models
    • Abstract: Publication date: March 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 3
      Author(s): Jose Miguel Pinto , Cristobal Arrieta , Marcelo E. Andia , Sergio Uribe , Jorge Ramos-Grez , Alex Vargas , Pablo Irarrazaval , Cristian Tejos
      Additive manufacturing (AM) models are used in medical applications for surgical planning, prosthesis design and teaching. For these applications, the accuracy of the AM models is essential. Unfortunately, this accuracy is compromised due to errors introduced by each of the building steps: image acquisition, segmentation, triangulation, printing and infiltration. However, the contribution of each step to the final error remains unclear. We performed a sensitivity analysis comparing errors obtained from a reference with those obtained modifying parameters of each building step. Our analysis considered global indexes to evaluate the overall error, and local indexes to show how this error is distributed along the surface of the AM models. Our results show that the standard building process tends to overestimate the AM models, i.e. models are larger than the original structures. They also show that the triangulation resolution and the segmentation threshold are critical factors, and that the errors are concentrated at regions with high curvatures. Errors could be reduced choosing better triangulation and printing resolutions, but there is an important need for modifying some of the standard building processes, particularly the segmentation algorithms.


      PubDate: 2015-04-25T00:37:37Z
       
  • Acoustic power measurement of high-intensity focused ultrasound transducer
           using a pressure sensor
    • Abstract: Publication date: March 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 3
      Author(s): Yufeng Zhou
      The acoustic power of high-intensity focused ultrasound (HIFU) is an important parameter that should be measured prior to each treatment to guarantee effective and safe outcomes. A new calibration technique was developed that involves estimating the pressure distribution, calculating the acoustic power using an underwater pressure blast sensor, and compensating the contribution of harmonics to the acoustic power. The output of a clinical extracorporeal HIFU system (center frequency of ~1 MHz, p+ = 2.5–57.2 MPa, p−  = −1.8 to −13.9 MPa, I SPPA = 513–22,940 W/cm2, −6 dB size of 1.6 × 10 mm: lateral × axial) was measured using this approach and then compared with that obtained using a radiation force balance. Similarities were found between each method at acoustic power ranging from 18.2 W to 912 W with an electrical-to-acoustic conversion efficiency of ~42%. The proposed method has advantages of low weight, smaller size, high sensitivity, quick response, high signal-to-noise ratio (especially at low power output), robust performance, and easy operation of HIFU exposimetry measurement.


      PubDate: 2015-04-25T00:37:37Z
       
  • Editorial Board
    • Abstract: Publication date: February 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 2




      PubDate: 2015-04-25T00:37:37Z
       
  • Loosening detection of the femoral component of hip prostheses with
           extracorporeal shockwaves: A pilot study
    • Abstract: Publication date: February 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 2
      Author(s): Johannes S. Rieger , Sebastian Jaeger , Jan Philippe Kretzer , Rüdiger Rupp , Rudi G. Bitsch
      The diagnosis of aseptic loosening of hip implants is often challenging. A vibrational analysis of the bone-implant interface could be an alternative method to analyze the fixation of endoprostheses. We assessed an innovative and new approach for excitation by using extracorporeal shockwaves in this study. In three cadaver specimens total hip arthroplasty was performed bilaterally. Four different states of implant loosening were simulated. Three accelerometers were fixed at the medial condyle, the greater trochanter, and the crest of the ilium. The bone-implant compound was excited with highly standardized extracorporeal shock waves. Resonance spectra between 100 Hz and 5000 Hz were recorded. This technique permitted a good adaptation to varying soft tissue conditions. The main resonance frequency of the hip joints occurred at about 2000 Hz. The analysis of the measured spectra showed an interrelation between the state of loosening and the frequency values of the resonances. In case of a stem loosening, there were significant shifts of the resonance into the lower frequency area between 386 Hz and 847 Hz. With this novel technique the degree of stem loosening could be assessed in a soft tissue considering configuration. This study forms a first step for future establishment of a non-invasive, non-radiological and fast applicable diagnostic procedure for early detection of endoprostheses loosening before manifest presence of clinical signs.


      PubDate: 2015-04-25T00:37:37Z
       
  • Sensitivity analysis of human lower extremity joint moments due to changes
           in joint kinematics
    • Abstract: Publication date: February 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 2
      Author(s): Marzieh M. Ardestani , Mehran Moazen , Zhongmin Jin
      Despite the widespread applications of human gait analysis, causal interactions between joint kinematics and joint moments have not been well documented. Typical gait studies are often limited to pure multi-body dynamics analysis of a few subjects which do not reveal the relative contributions of joint kinematics to joint moments. This study presented a computational approach to evaluate the sensitivity of joint moments due to variations of joint kinematics. A large data set of probabilistic joint kinematics and associated ground reaction forces were generated based on experimental data from literature. Multi-body dynamics analysis was then used to calculate joint moments with respect to the probabilistic gait cycles. Employing the principal component analysis (PCA), the relative contributions of individual joint kinematics to joint moments were computed in terms of sensitivity indices (SI). Results highlighted high sensitivity of (1) hip abduction moment due to changes in pelvis rotation (SI = 0.38) and hip abduction (SI = 0.4), (2) hip flexion moment due to changes in hip flexion (SI = 0.35) and knee flexion (SI = 0.26), (3) hip rotation moment due to changes in pelvis obliquity (SI = 0.28) and hip rotation (SI = 0.4), (4) knee adduction moment due to changes in pelvis rotation (SI = 0.35), hip abduction (SI = 0.32) and knee flexion (SI = 0.34), (5) knee flexion moment due to changes in pelvis rotation (SI = 0.29), hip flexion (SI = 0.28) and knee flexion (SI = 0.31), and (6) knee rotation moment due to changes in hip abduction (SI = 0.32), hip flexion and knee flexion (SI = 0.31). Highlighting the “cause-and-effect” relationships between joint kinematics and the resultant joint moments provides a fundamental understanding of human gait and can lead to design and optimization of current gait rehabilitation treatments.


      PubDate: 2015-04-25T00:37:37Z
       
  • Instrumenting gait with an accelerometer: A system and algorithm
           examination
    • Abstract: Publication date: Available online 4 March 2015
      Source:Medical Engineering & Physics
      Author(s): A. Godfrey , S. Del Din , G. Barry , J.C. Mathers , L. Rochester
      Gait is an important clinical assessment tool since changes in gait may reflect changes in general health. Measurement of gait is a complex process which has been restricted to the laboratory until relatively recently. The application of an inexpensive body worn sensor with appropriate gait algorithms (BWM) is an attractive alternative and offers the potential to assess gait in any setting. In this study we investigated the use of a low-cost BWM, compared to laboratory reference using a robust testing protocol in both younger and older adults. We observed that the BWM is a valid tool for estimating total step count and mean spatio-temporal gait characteristics however agreement for variability and asymmetry results was poor. We conducted a detailed investigation to explain the poor agreement between systems and determined it was due to inherent differences between the systems rather than inability of the sensor to measure the gait characteristics. The results highlight caution in the choice of reference system for validation studies. The BWM used in this study has the potential to gather longitudinal (real-world) spatio-temporal gait data that could be readily used in large lifestyle-based intervention studies, but further refinement of the algorithm(s) is required.


      PubDate: 2015-03-05T09:31:40Z
       
  • Colourimetric image analysis as a diagnostic tool in female genital
           schistosomiasis
    • Abstract: Publication date: Available online 24 January 2015
      Source:Medical Engineering & Physics
      Author(s): Sigve Dhondup Holmen , Eyrun Floerecke Kjetland , Myra Taylor , Elisabeth Kleppa , Kristine Lillebø , Svein Gunnar Gundersen , Mathias Onsrud , Fritz Albregtsen
      Female genital schistosomiasis (FGS) is a highly prevalent waterborne disease in some of the poorest areas of sub-Saharan Africa. Reliable and affordable diagnostics are unavailable. We explored colourimetric image analysis to identify the characteristic, yellow lesions caused by FGS. We found that the method may yield a sensitivity of 83% and a specificity of 73% in colposcopic images. The accuracy was also explored in images of simulated inferior quality, to assess the possibility of implementing such a method in simple, electronic devices. This represents the first step towards developing a safe and affordable aid in clinical diagnosis, allowing for a point-of-care approach.


      PubDate: 2015-01-28T10:09:18Z
       
 
 
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