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BIOLOGY (1378 journals)            First | 4 5 6 7 8 9 10 11 | Last

Journal of Aquatic Sciences     Full-text available via subscription  
Journal of Arachnology     Full-text available via subscription  
Journal of Asia-Pacific Biodiversity     Open Access  
Journal of Astrobiology & Outreach     Open Access  
Journal of Avian Biology     Hybrid Journal   (Followers: 19)
Journal of Bacteriology     Full-text available via subscription   (Followers: 17)
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   (Followers: 1)
Journal of Bioenergetics and Biomembranes     Hybrid Journal  
Journal of Biogeography     Hybrid Journal   (Followers: 21)
Journal of Bioinformatics and Computational Biology     Hybrid Journal   (Followers: 12)
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: 4)
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: 28)
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 Biomolecular Screening     Hybrid Journal   (Followers: 5)
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: 4)
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: 3)
Journal of Cerebral Blood Flow & Metabolism     Hybrid Journal   (Followers: 2)
Journal of Chromatography B     Hybrid Journal   (Followers: 22)
Journal of Clinical Bioinformatics     Open Access   (Followers: 5)
Journal of Clinical Toxicology     Open Access   (Followers: 1)
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     Hybrid Journal   (Followers: 2)
Journal of Developmental Biology     Open Access   (Followers: 3)
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: 4)
Journal of Environment and Ecology     Open Access   (Followers: 12)
Journal of Environmental Radioactivity     Hybrid Journal   (Followers: 3)
Journal of Environmental Science and Natural Resources     Open Access   (Followers: 3)
Journal of Ethnobiology     Full-text available via subscription   (Followers: 5)
Journal of Ethnobiology and Ethnomedicine     Open Access  
Journal of Ethology     Hybrid Journal   (Followers: 2)
Journal of Evolutionary Biology     Hybrid Journal   (Followers: 23)
Journal of Experimental and Clinical Anatomy     Open Access   (Followers: 1)
Journal of Experimental Marine Biology and Ecology     Hybrid Journal   (Followers: 27)
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: 3)
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: 1)
Journal of Ichthyology     Hybrid Journal   (Followers: 4)
Journal of Insect Behavior     Hybrid Journal   (Followers: 6)
Journal of Insect Biodiversity     Open Access   (Followers: 3)
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: 4)
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: 2)
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: 4)

  First | 4 5 6 7 8 9 10 11 | Last

Journal Cover   Medical Engineering & Physics
  [SJR: 0.871]   [H-I: 64]   [9 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1350-4533
   Published by Elsevier Homepage  [2800 journals]
  • A review of the functionalities of smart walkers
    • Abstract: Publication date: Available online 22 August 2015
      Source:Medical Engineering & Physics
      Author(s): Maria Martins, Cristina Santos, Anselmo Frizera, Ramón Ceres
      There is a need to conceptualize and improve the investigation and developments in assistive devices, focusing on the design and effectiveness of walkers in the user's rehabilitation process and functional compensation. This review surveys the importance of smart walkers in maintaining mobility and discusses their potential in rehabilitation and their demands as assistive devices. It also presents related research in addressing and quantifying the smart walker's efficiency and influence on gait. Besides, it discusses smart walkers focusing on studies related to the concept of autonomous and shared-control and manual guidance, the use of smart walkers as personal helpers to sit-to-stand and diagnostic tools for patients' rehabilitation through the evaluation of their gait.

      PubDate: 2015-08-26T06:59:30Z
  • Effect of power-assisted hand-rim wheelchair propulsion on shoulder load
           in experienced wheelchair users: A pilot study with an instrumented
    • Abstract: Publication date: Available online 22 August 2015
      Source:Medical Engineering & Physics
      Author(s): Marieke G.M. Kloosterman, Jaap H. Buurke, Wiebe de Vries, Lucas H.V. Van der Woude, Johan S. Rietman
      This study aims to compare hand-rim and power-assisted hand-rim propulsion on potential risk factors for shoulder overuse injuries: intensity and repetition of shoulder loading and force generation in the extremes of shoulder motion. Eleven experienced hand-rim wheelchair users propelled an instrumented wheelchair on a treadmill while upper-extremity kinematic, kinetic and surface electromyographical data was collected during propulsion with and without power-assist. As a result during power-assisted propulsion the peak resultant force exerted at the hand-rim decreased and was performed with significantly less abduction and internal rotation at the shoulder. At shoulder level the anterior directed force and internal rotation and flexion moments decreased significantly. In addition, posterior and the minimal inferior directed forces and the external rotation moment significantly increased. The stroke angle decreased significantly, as did maximum shoulder flexion, extension, abduction and internal rotation. Stroke-frequency significantly increased. Muscle activation in the anterior deltoid and pectoralis major also decreased significantly. In conclusion, compared to hand-rim propulsion power-assisted propulsion seems effective in reducing potential risk factors of overuse injuries with the highest gain on decreased range of motion of the shoulder joint, lower peak propulsion force on the rim and reduced muscle activity.

      PubDate: 2015-08-26T06:59:30Z
  • Response of single cell with acute angle exposed to an external electric
    • Abstract: Publication date: Available online 22 August 2015
      Source:Medical Engineering & Physics
      Author(s): Saber Sarbazvatan, Dariush Sardari, Nahid Taheri, Kamran Sepanloo
      It is known that the electric field incurs effects on the living cells. Predicting the response of single cell or multilayer cells to induced alternative or static eclectic field has permanently been a challenge. In the present study a first order single cell with acute angle under the influence of external electric field is considered. The cell division stage or the special condition of reshaping is modelled with a cone being connected. In the case of cell divisions, anaphase, it can be considered with two cones that connected nose-to-nose. Each cone consists of two regions. The first is the membrane modelled with a superficial layer, and the second is cytoplasm at the core. A Laplace equation is written for this model and the distribution of its electric field is a sharp point in the single cell for which an acute angle model is calculated.

      PubDate: 2015-08-26T06:59:30Z
  • A time-dependent model for improved biogalvanic tissue characterisation
    • Abstract: Publication date: Available online 19 August 2015
      Source:Medical Engineering & Physics
      Author(s): J.H. Chandler, P.R. Culmer, D.G. Jayne, A. Neville
      Measurement of the passive electrical resistance of biological tissues through biogalvanic characterisation has been proposed as a simple means of distinguishing healthy from diseased tissue. This method has the potential to provide valuable real-time information when integrated into surgical tools. Characterised tissue resistance values have been shown to be particularly sensitive to external load switching direction and rate, bringing into question the stability and efficacy of the technique. These errors are due to transient variations observed in measurement data that are not accounted for in current electrical models. The presented research proposes the addition of a time-dependent element to the characterisation model to account for losses associated with this transient behaviour. Influence of switching rate has been examined, with the inclusion of transient elements improving the repeatability of the characterised tissue resistance. Application of this model to repeat biogalvanic measurements on a single ex vivo human colon tissue sample with healthy and cancerous (adenocarcinoma) regions showed a statistically significant difference (p < 0.05) between tissue types. In contrast, an insignificant difference (p > 0.05) between tissue types was found when measurements were subjected to the current model, suggesting that the proposed model may allow for improved biogalvanic tissue characterisation.

      PubDate: 2015-08-22T06:19:53Z
  • Validation of a method for combining biplanar radiography and magnetic
           resonance imaging to estimate knee cartilage contact
    • Abstract: Publication date: Available online 21 August 2015
      Source:Medical Engineering & Physics
      Author(s): Eric Thorhauer, Scott Tashman
      Combining accurate bone kinematics data from biplane radiography with cartilage models from magnetic resonance imaging, it is possible to estimate tibiofemoral cartilage contact area and centroid location. Proper validation of such estimates, however, has not been performed under loading conditions approximating functional tasks, such as gait, squatting, and stair descent. The goal of this study was to perform an in vitro validation to resolve the accuracy of cartilage contact estimations in comparison to a laser scanning gold standard. Results demonstrated acceptable reliability and accuracy for both contact area and centroid location estimates. Root mean square errors in contact area averaged 8.4% and 4.4% of the medial and lateral compartmental areas, respectively. Modified Sorensen-Dice agreement scores of contact regions averaged 0.81 ± 0.07 for medial and 0.83 ± 0.07 for lateral compartments. These validated methods have applications for in vivo assessment of a variety of patient populations and physical activities, and may lead to greater understanding of the relationships between knee cartilage function, effects of joint injury and treatment, and the development of osteoarthritis.

      PubDate: 2015-08-22T06:19:53Z
  • Influence of contextual task constraints on preferred stride parameters
           and their variabilities during human walking
    • Abstract: Publication date: Available online 4 August 2015
      Source:Medical Engineering & Physics
      Author(s): Lauro V. Ojeda, John R. Rebula, Arthur D. Kuo, Peter G. Adamczyk
      Walking is not always a free and unencumbered task. Everyday activities such as walking in pairs, in groups, or on structured walkways can limit the acceptable gait patterns, leading to motor behavior that differs from that observed in more self-selected gait. Such different contexts may lead to gait performance different than observed in typical laboratory experiments, for example, during treadmill walking. We sought to systematically measure the impact of such task constraints by comparing gait parameters and their variability during walking in different conditions over-ground, and on a treadmill. We reconstructed foot motion from foot-mounted inertial sensors, and characterized forward, lateral and angular foot placement while subjects walked over-ground in a straight hallway and on a treadmill. Over-ground walking was performed in three variations: with no constraints (self-selected, SS); while deliberately varying walking speed (self-varied, SV); and while following a toy pace car programmed to vary speed (externally-varied, EV). We expected that these conditions would exhibit a statistically similar relationship between stride length and speed, and between stride length and stride period. We also expected treadmill walking (TM) would differ in two ways: first, that variability in stride length and stride period would conform to a constant-speed constraint opposite in slope from the normal relationship; and second, that stride length would decrease, leading to combinations of stride length and speed not observed in over-ground conditions. Results showed that all over-ground conditions used similar stride length-speed relationships, and that variability in treadmill walking conformed to a constant-speed constraint line, as expected. Decreased stride length was observed in both TM and EV conditions, suggesting adaptations due to heightened awareness or to prepare for unexpected changes or problems. We also evaluated stride variability in constrained and unconstrained tasks. We observed that in treadmill walking, lateral variability decreased while forward variability increased, and the normally-observed correlation between wider foot placement and external foot rotation was eliminated. Preferred stride parameters and their variability appear significantly influenced by the context and constraints of the walking task.

      PubDate: 2015-08-06T03:53:11Z
  • A comparison of public datasets for acceleration-based fall detection
    • Abstract: Publication date: Available online 29 July 2015
      Source:Medical Engineering & Physics
      Author(s): Raul Igual, Carlos Medrano, Inmaculada Plaza
      Falls are one of the leading causes of mortality among the older population, being the rapid detection of a fall a key factor to mitigate its main adverse health consequences. In this context, several authors have conducted studies on acceleration-based fall detection using external accelerometers or smartphones. The published detection rates are diverse, sometimes close to a perfect detector. This divergence may be explained by the difficulties in comparing different fall detection studies in a fair play since each study uses its own dataset obtained under different conditions. In this regard, several datasets have been made publicly available recently. This paper presents a comparison, to the best of our knowledge for the first time, of these public fall detection datasets in order to determine whether they have an influence on the declared performances. Using two different detection algorithms, the study shows that the performances of the fall detection techniques are affected, to a greater or lesser extent, by the specific datasets used to validate them. We have also found large differences in the generalization capability of a fall detector depending on the dataset used for training. In fact, the performance decreases dramatically when the algorithms are tested on a dataset different from the one used for training. Other characteristics of the datasets like the number of training samples also have an influence on the performance while algorithms seem less sensitive to the sampling frequency or the acceleration range.
      Graphical abstract image

      PubDate: 2015-08-02T03:33:52Z
  • Failure location prediction by finite element analysis for an additive
           manufactured mandible implant
    • Abstract: Publication date: Available online 27 July 2015
      Source:Medical Engineering & Physics
      Author(s): Jinxing Huo, Per Dérand, Lars-Erik Rännar, Jan-Michaél Hirsch, E. Kristofer Gamstedt
      In order to reconstruct a patient with a bone defect in the mandible, a porous scaffold attached to a plate, both in a titanium alloy, was designed and manufactured using additive manufacturing. Regrettably, the implant fractured in vivo several months after surgery. The aim of this study was to investigate the failure of the implant and show a way of predicting the mechanical properties of the implant before surgery. All computed tomography data of the patient were preprocessed to remove metallic artefacts with metal deletion technique before mandible geometry reconstruction. The three-dimensional geometry of the patient's mandible was also reconstructed, and the implant was fixed to the bone model with screws in Mimics medical imaging software. A finite element model was established from the assembly of the mandible and the implant to study stresses developed during mastication. The stress distribution in the load-bearing plate was computed, and the location of main stress concentration in the plate was determined. Comparison between the fracture region and the location of the stress concentration shows that finite element analysis could serve as a tool for optimizing the design of mandible implants.

      PubDate: 2015-07-28T20:58:54Z
  • Tailoring the hybrid palliation for hypoplastic left heart syndrome: A
           simulation study using a lumped parameter model
    • Abstract: Publication date: Available online 26 July 2015
      Source:Medical Engineering & Physics
      Author(s): A. Di Molfetta, M. Pilati, M.G. Gagliardi, L. Fresiello, A. Amodeo, A. Cristofaletti, G. Pongiglione, G. Ferrari
      The results of Hybrid procedure (HP) for the hypoplastic left heart syndrome (HLHS) depend on several variables: pulmonary artery banding tightness (PAB), atrial septal defect size (ASD) and patent ductus arteriosus stent size (PDA). A HP complication could be the aortic coarctaction (CoAo). The reverse Blalock–Taussig shunt (RevBT) placement was proposed to avoid CoAo effects. This work aims at developing a lumped parameter model (LPM) to investigate the effects of the different variables on HP haemodynamics. A preliminary verification was performed collecting measurements on a newborn HLHS patient to calculate LPM input parameters to reproduce patient's baseline. Results suggest that haemodynamics is affected by ASD (ASD: 0.15–0.55 cm, pulmonary to systemic flow ratio Q p/Q s: 0.73–1, cardiac output (CO): 1–1.5 l/min and ventricular stroke work SW: 336–577 ml mmHg) and by the PAB diameter (PAB: 0.07–0.2 cm, Q p/Q s: 0.46–2.1, CO: 1.3–1.6 l/min and SW: 591–535 ml mmHg). Haemodynamics was neither affected by RevBT diameter nor by PDA diameter higher than 0.2 cm. RevBT implantation does not change the HP haemodynamics, but it can make the CoAo effect negligible. LPM could be useful to support clinical decision in complex physiopathology and to calibrate and personalise the parameters that play a role on flow distribution.

      PubDate: 2015-07-28T20:58:54Z
  • Surrogate modeling of deformable joint contact using artificial neural
    • Abstract: Publication date: Available online 26 July 2015
      Source:Medical Engineering & Physics
      Author(s): Ilan Eskinazi, Benjamin J. Fregly
      Deformable joint contact models can be used to estimate loading conditions for cartilage–cartilage, implant–implant, human–orthotic, and foot–ground interactions. However, contact evaluations are often so expensive computationally that they can be prohibitive for simulations or optimizations requiring thousands or even millions of contact evaluations. To overcome this limitation, we developed a novel surrogate contact modeling method based on artificial neural networks (ANNs). The method uses special sampling techniques to gather input–output data points from an original (slow) contact model in multiple domains of input space, where each domain represents a different physical situation likely to be encountered. For each contact force and torque output by the original contact model, a multi-layer feed-forward ANN is defined, trained, and incorporated into a surrogate contact model. As an evaluation problem, we created an ANN-based surrogate contact model of an artificial tibiofemoral joint using over 75,000 evaluations of a fine-grid elastic foundation (EF) contact model. The surrogate contact model computed contact forces and torques about 1000 times faster than a less accurate coarse grid EF contact model. Furthermore, the surrogate contact model was seven times more accurate than the coarse grid EF contact model within the input domain of a walking motion. For larger input domains, the surrogate contact model showed the expected trend of increasing error with increasing domain size. In addition, the surrogate contact model was able to identify out-of-contact situations with high accuracy. Computational contact models created using our proposed ANN approach may remove an important computational bottleneck from musculoskeletal simulations or optimizations incorporating deformable joint contact models.

      PubDate: 2015-07-28T20:58:54Z
  • An integrated CAD/CAM/robotic milling method for custom cementless femoral
    • Abstract: Publication date: Available online 22 July 2015
      Source:Medical Engineering & Physics
      Author(s): Xi Wen-ming, Wang Ai-min, Wu Qi, Liu Chang-Hua, Zhu Jian-fei, Xia Fang-fang
      Aseptic loosening is the primary cause of cementless femoral prosthesis failure and is related to the primary stability of the cementless femoral prosthesis in the femoral cavity. The primary stability affects both the osseointegration and the long-term stability of cementless femoral prostheses. A custom cementless femoral prosthesis can improve the fit and fill of the prosthesis in the femoral cavity and decrease the micromotion of the proximal prosthesis such that the primary stability of the custom prosthesis can be improved, and osseointegration of the proximal prosthesis is achieved. These results will help to achieve long-term stability in total hip arthroplasty (THA). In this paper, we introduce an integrated CAD/CAM/robotic method of milling custom cementless femoral prostheses. The 3D reconstruction model uses femoral CT images and 3D design software to design a CAD model of the custom prosthesis. After the transformation matrices between two units of the robotic system are calibrated, consistency between the CAM software and the robotic system can be achieved, and errors in the robotic milling can be limited. According to the CAD model of the custom prosthesis, the positions of the robotic tool points are produced by the CAM software of the CNC machine. The normal vector of the three adjacent robotic tool point positions determines the pose of the robotic tool point. In conclusion, the fit rate of custom pig femur stems in the femoral cavities was 90.84%. After custom femoral prostheses were inserted into the femoral cavities, the maximum gaps between the prostheses and the cavities measured less than 1 mm at the diaphysis and 1.3 mm at the metaphysis.

      PubDate: 2015-07-24T10:56:39Z
  • Comparison of the bending performance of solid and cannulated spinal
           pedicle screws using finite element analyses and biomechanical tests
    • Abstract: Publication date: Available online 21 July 2015
      Source:Medical Engineering & Physics
      Author(s): Kao-Shang Shih, Ching-Chi Hsu, Sheng-Mou Hou, Shan-Chuen Yu, Chen-Kun Liaw
      Spinal pedicle screw fixations have been used extensively to treat fracture, tumor, infection, or degeneration of the spine. Cannulated spinal pedicle screws with bone cement augmentation might be a useful method to ameliorate screw loosening. However, cannulated spinal pedicle screws might also increase the risk of screw breakage. Thus, the purpose of this study was to investigate the bending performance of different spinal pedicle screws with either solid design or cannulated design. Three-dimensional finite element models, which consisted of the spinal pedicle screw and the screw's hosting material, were first constructed. Next, monotonic and cyclic cantilever bending tests were both applied to validate the results of the finite element analyses. Finally, both the numerical and experimental approaches were evaluated and compared. The results indicated that the cylindrical spinal pedicle screws with a cannulated design had significantly poorer bending performance. In addition, conical spinal pedicle screws maintained the original bending performance, whether they were solid or of cannulated design. This study may provide useful recommendations to orthopedic surgeons before surgery, and it may also provide design rationales to biomechanical engineers during the development of spinal pedicle screws.

      PubDate: 2015-07-24T10:56:39Z
  • Re: Chung et al.’s Letter to the Editor in response to: Early
           detection of abnormal left ventricular relaxation in acute myocardial
           ischemia with a quadratic model. Med Eng Phys 2014;36(September
           (9)):1101–5 by Morimont et al.
    • Abstract: Publication date: August 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 8
      Author(s): Philippe Morimont, Antoine Pironet, Thomas Desaive, Geoffrey Chase, Bernard Lambermont

      PubDate: 2015-07-24T10:56:39Z
  • Call for Papers: The mechanobiology and biomechanics of chronic wounds:
           aetiology, prevention and treatment
    • Abstract: Publication date: August 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 8

      PubDate: 2015-07-24T10:56:39Z
  • Detection of central fixation using short-time autoregressive spectral
           estimation during retinal birefringence scanning
    • Abstract: Publication date: Available online 23 July 2015
      Source:Medical Engineering & Physics
      Author(s): Boris I. Gramatikov
      The manuscript reports on the implementation of autoregressive spectral estimation aimed at improving the accuracy of detecting short-lasting events in signals acquired by a retinal birefringence scanning device that was reported earlier. A signal consisting of two frequency components is generated, where each frequency is a multiple of the scanning frequency. One frequency is produced during central fixation, while another one prevails during off-central fixation. These components may be of a very short duration, presenting a challenge for the FFT to identify them with sufficient time- and frequency resolution. Autoregressive spectral estimation using the Burg algorithm provided a satisfactory solution, capable of reliably differentiating between the two frequency components (96 and 192 Hz) on signal segments of duration as short as 5 ms. The device and the signal analysis methods were developed originally with the purpose of checking for eye alignment and strabismus – a major risk factor for amblyopia. The method enables the technology to work with less-cooperative patients, such as young children. Other medical and non-medical applications are possible.

      PubDate: 2015-07-24T10:56:39Z
  • Accuracy assessment of 3D bone reconstructions using CT: an intro
    • Abstract: Publication date: August 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 8
      Author(s): Emily A. Lalone, Ryan T. Willing, Hannah L. Shannon, Graham J.W. King, James A. Johnson
      Computed tomography provides high contrast imaging of the joint anatomy and is used routinely to reconstruct 3D models of the osseous and cartilage geometry (CT arthrography) for use in the design of orthopedic implants, for computer assisted surgeries and computational dynamic and structural analysis. The objective of this study was to assess the accuracy of bone and cartilage surface model reconstructions by comparing reconstructed geometries with bone digitizations obtained using an optical tracking system. Bone surface digitizations obtained in this study determined the ground truth measure for the underlying geometry. We evaluated the use of a commercially available reconstruction technique using clinical CT scanning protocols using the elbow joint as an example of a surface with complex geometry. To assess the accuracies of the reconstructed models (8 fresh frozen cadaveric specimens) against the ground truth bony digitization—as defined by this study—proximity mapping was used to calculate residual error. The overall mean error was less than 0.4 mm in the cortical region and 0.3 mm in the subchondral region of the bone. Similarly creating 3D cartilage surface models from CT scans using air contrast had a mean error of less than 0.3 mm. Results from this study indicate that clinical CT scanning protocols and commonly used and commercially available reconstruction algorithms can create models which accurately represent the true geometry.

      PubDate: 2015-07-24T10:56:39Z
  • Editorial Board
    • Abstract: Publication date: August 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 8

      PubDate: 2015-07-24T10:56:39Z
  • Numerical evaluation of sequential bone drilling strategies based on
           thermal damage
    • Abstract: Publication date: Available online 7 July 2015
      Source:Medical Engineering & Physics
      Author(s): Bruce L. Tai , Andrew C. Palmisano , Barry Belmont , Todd A Irwin , James Holmes , Albert J. Shih
      Sequentially drilling multiple holes in bone is used clinically for surface preparation to aid in fusion of a joint, typically under non-irrigated conditions. Drilling induces a significant amount of heat and accumulates after multiple passes, which can result in thermal osteonecrosis and various complications. To understand the heat propagation over time, a 3D finite element model was developed to simulate sequential bone drilling. By incorporating proper material properties and a modified bone necrosis criteria, this model can visualize the propagation of damaged areas. For this study, comparisons between a 2.0 mm Kirschner wire and 2.0 mm twist drill were conducted with their heat sources determined using an inverse method and experimentally measured bone temperatures. Three clinically viable solutions to reduce thermally-induced bone damage were evaluated using finite element analysis, including tool selection, time interval between passes, and different drilling sequences. Results show that the ideal solution would be using twist drills rather than Kirschner wires if the situation allows. A shorter time interval between passes was also found to be beneficial as it reduces the total heat exposure time. Lastly, optimizing the drilling sequence reduced the thermal damage of bone, but the effect may be limited. This study demonstrates the feasibility of using the proposed model to study clinical issues and find potential solutions prior to clinical trials.

      PubDate: 2015-07-12T10:07:23Z
  • Breakdown of deterministic lateral displacement efficiency for non-dilute
           suspensions: A numerical study
    • Abstract: Publication date: Available online 2 July 2015
      Source:Medical Engineering & Physics
      Author(s): R. Vernekar , T. Krüger
      We investigate the effect of particle volume fraction on the efficiency of deterministic lateral displacement (DLD) devices. DLD is a popular passive sorting technique for microfluidic applications. Yet, it has been designed for treating dilute suspensions, and its efficiency for denser samples is not well known. We perform 3D simulations based on the immersed-boundary, lattice-Boltzmann and finite-element methods to model the flow of red blood cells (RBCs) in different DLD devices. We quantify the DLD efficiency in terms of appropriate “failure” probabilities and RBC counts in designated device outlets. Our main result is that the displacement mode breaks down upon an increase of RBC volume fraction, while the zigzag mode remains relatively robust. This suggests that the separation of larger particles (such as white blood cells) from a dense RBC background is simpler than separating smaller particles (such as platelets) from the same background. The observed breakdown stems from non-deterministic particle collisions interfering with the designed deterministic nature of DLD devices. Therefore, we postulate that dense suspension effects generally hamper efficient particle separation in devices based on deterministic principles.

      PubDate: 2015-07-07T15:00:04Z
  • Design and testing of a high-speed treadmill to measure ground reaction
           forces at the limit of human gait
    • Abstract: Publication date: Available online 2 July 2015
      Source:Medical Engineering & Physics
      Author(s): Matthew W. Bundle , Michael O. Powell , Laurence J. Ryan
      Investigations focused on the gait and physiological limits of human speed have been on-going for more than a century. However, due to measurement limitation a kinetic understanding of the foot-ground collision and how these dynamics differ between individuals to confer speed and limit gait has only recently begun to come forth. Therefore, we designed and tested an instrumented high-speed force treadmill to measure the forces occurring at the limits of human performance. The treadmill was designed to maximize flexural stiffness and natural frequency by using a honeycomb sandwich panel as the bed surface and a flexible drive shaft between the drive roller and servo motor to reduce the mass of the supported elements which contribute to the system's response frequency. The functional performance of the force treadmill met or exceeded the measurement criteria established for ideal force plates: high natural frequency (z-axis = 113 Hz), low crosstalk between components of the force (Fx /Fz = 0.0020[SD = 0.0010]; Fy /Fz = 0.0016[SD = 0.0003]), a linear response (R 2 > 0.999) for loading with known weights (range: 44–3857 N), and an accuracy of 2.5[SD = 1.7] mm and 2.8[SD = 1.5] mm in the x and y-axes, respectively, for the point of force application. In dynamic testing at running speeds up to 10 m s−1, the measured durations and magnitudes of force application were similar between the treadmill and over-ground running using a force platform. This design provides a precise instrumented treadmill capable of recording multi-axis ground reaction forces applied during the foot ground contacts of the fastest men and animals known to science.

      PubDate: 2015-07-07T15:00:04Z
  • Influence of proximal drug eluting stent (DES) on distal bare metal stent
           (BMS) in multi-stent implantation strategies in coronary arteries
    • Abstract: Publication date: Available online 3 July 2015
      Source:Medical Engineering & Physics
      Author(s): Anqiang Sun , Zhenze Wang , Zhenmin Fan , Xiaopeng Tian , Fan Zhan , Xiaoyan Deng , Xiao Liu
      The aim of this study was to investigate the drug distribution in arteries treated with DES-BMS stenting strategy and to analyze the influence of proximal DES on distal segments of BMS. A straight artery model (Straight Model) and a branching artery model (Branching Model) were constructed in this study. In each model, the DES was implanted at the proximal position and the BMS was implanted distally. Hemodynamic environments, drug delivery and distribution features were simulated and analyzed in each model. The results showed that blood flow would contribute to non-uniform drug distribution in arteries. In the Straight Model the proximal DES would cause drug concentration in BMS segments. While in the Branching Model the DES in the main artery has slight influence on the BMS segments in the branch artery. In conclusion, due to the blood flow washing effect the uniformly released drug from DES would distribute focally and distally. The proximal DES would have greater influence on the distal BMS in straight artery than that in branching artery. This preliminary study would provide good reference for atherosclerosis treatment, especially for some complex cases, like coronary branching stenting.

      PubDate: 2015-07-07T15:00:04Z
  • Realistic glottal motion and airflow rate during human breathing
    • Abstract: Publication date: Available online 7 July 2015
      Source:Medical Engineering & Physics
      Author(s): Adam Scheinherr , Lucie Bailly , Olivier Boiron , Aude Lagier , Thierry Legou , Marine Pichelin , Georges Caillibotte , Antoine Giovanni
      The glottal geometry is a key factor in the aerosol delivery efficiency for treatment of lung diseases. However, while glottal vibrations were extensively studied during human phonation, the realistic glottal motion during breathing is poorly understood. Therefore, most current studies assume an idealized steady glottis in the context of respiratory dynamics, and thus neglect the flow unsteadiness related to this motion. This is particularly important to assess the aerosol transport mechanisms in upper airways. This article presents a clinical study conducted on 20 volunteers, to examine the realistic glottal motion during several breathing tasks. Nasofibroscopy was used to investigate the glottal geometrical variations simultaneously with accurate airflow rate measurements. In total, 144 breathing sequences of 30s were recorded. Regarding the whole database, two cases of glottal time-variations were found: “static” or “dynamic” ones. Typically, the peak value of glottal area during slow breathing narrowed from 217 ± 54 mm2 (mean ± STD) during inspiration, to 178 ± 35 mm2 during expiration. Considering flow unsteadiness, it is shown that the harmonic approximation of the airflow rate underevaluates the inertial effects as compared to realistic patterns, especially at the onset of the breathing cycle. These measurements provide input data to conduct realistic numerical simulations of laryngeal airflow and particle deposition.

      PubDate: 2015-07-07T15:00:04Z
  • Individual and combined effects of OA-related subchondral bone alterations
           on proximal tibial surface stiffness: a parametric finite element modeling
    • Abstract: Publication date: Available online 12 June 2015
      Source:Medical Engineering & Physics
      Author(s): Morteza Amini , S. Majid Nazemi , Joel L. Lanovaz , Saija Kontulainen , Bassam A. Masri , David R. Wilson , Walerian Szyszkowski , James D. Johnston
      The role of subchondral bone in OA pathogenesis is unclear. While some OA-related changes to morphology and material properties in different bone regions have been described, the effect of these alterations on subchondral bone surface stiffness has not been investigated. The objectives of this study were to characterize the individual (Objective 1) and combined (Objective 2) effects of OA-related morphological and mechanical alterations to subchondral and epiphyseal bone on surface stiffness of the proximal tibia. We developed and validated a parametric FE model of the proximal tibia using quantitative CT images of 10 fresh-frozen cadaveric specimens and in situ macro-indentation testing. Using this validated FE model, we estimated the individual and combined roles of OA-related alterations in subchondral cortical thickness and elastic modulus, and subchondral trabecular and epiphyseal trabecular elastic moduli on local surface stiffness. A 20% increase in subchondral cortical or subchondral trabecular elastic moduli resulted in little change in stiffness (1% increase). A 20% reduction in epiphyseal trabecular elastic modulus, however, resulted in an 11% reduction in stiffness. Our parametric analysis suggests that subchondral bone stiffness is affected primarily by epiphyseal trabecular bone elastic modulus rather than subchondral cortical and trabecular morphology or mechanical properties. Our results suggest that observed OA-related alterations to epiphyseal trabecular bone (e.g., lower mineralization, bone volume fraction, density and elastic modulus) may contribute to OA proximal tibiae being less stiff than normal.

      PubDate: 2015-06-28T14:01:24Z
  • Comparison of trunk muscle forces, spinal loads and stability estimated by
           one stability- and three EMG-assisted optimization approaches
    • Abstract: Publication date: Available online 25 June 2015
      Source:Medical Engineering & Physics
      Author(s): Yousef Mohammadi , Navid Arjmand , Aboulfazl Shirazi-Adl
      Various hybrid EMG-assisted optimization (EMGAO) approaches are commonly used to estimate muscle forces and joint loads of human musculoskeletal systems. Use of EMG data and optimization enables the EMGAO models to account for inter- and intra-individual variations in muscle recruitments while satisfying equilibrium requirements. Due to implications in ergonomics/prevention and rehabilitation/treatment managements of low-back disorders, there is a need to evaluate existing approaches. The present study aimed to compare predictions of three different EMGAO and one stability-based optimization (OPT) approaches for trunk muscle forces, spinal loads, and stability. Identical measured kinematics/EMG data and anatomical model were used in all approaches when simulating several sagittally symmetric static activities. Results indicated substantial inter-model differences in predicted muscle forces (up to 123% and 90% for total muscle forces in tasks with upright and flexed postures, respectively) and spinal loads (up to 74% and 78% for compression loads in upright and flexed postures, respectively). Results of EMGAO models markedly varied depending on the manner in which correction (gain) factors were introduced. Large range of gain values (from ∼0.47 to 41) was estimated in each model. While EMGAO methods predicted an unstable spine for some tasks, OPT predicted, as intended, either a meta-stable or stable states in all simulated tasks. An unrealistic unstable state of the spine predicted by EMGAO methods for some of the simulated tasks (which are in reality stable) could be an indication of the shortcoming of these models in proper prediction of muscle forces.

      PubDate: 2015-06-28T14:01:24Z
  • From mechanical stimulus to bone formation: A review
    • Abstract: Publication date: Available online 25 June 2015
      Source:Medical Engineering & Physics
      Author(s): Natacha Rosa , Ricardo Simoes , Fernão D. Magalhães , Antonio Torres Marques
      Bone is a remarkable tissue that can respond to external stimuli. The importance of mechanical forces on the mass and structural development of bone has long been accepted. This adaptation behaviour is very complex and involves multidisciplinary concepts, and significant progress has recently been made in understanding this process. In this review, we describe the state of the art studies in this area and highlight current insights while simultaneously clarifying some basic yet essential topics related to the origin of mechanical stimulus in bone, the biomechanisms associated with mechanotransduction, the nature of physiological bone stimuli and the test systems most commonly used to study the mechanical stimulation of bone.

      PubDate: 2015-06-28T14:01:24Z
  • Magnetic resonance-based thermometry during laser ablation on ex-vivo
           swine pancreas and liver
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): G. Allegretti , P. Saccomandi , F. Giurazza , M.A. Caponero , G. Frauenfelder , F.M. Di Matteo , B. Beomonte Zobel , S. Silvestri , E. Schena
      Laser Ablation (LA) is a minimally-invasive procedure for tumor treatment. LA outcomes depend on the heat distribution inside tissues and require accurate temperature measurement during the procedure. Magnetic resonance imaging (MRI) allows a non-invasive and three-dimensional thermometry of the organ undergoing LA. In this study, the temperature distribution within two swine pancreases and three swine livers undergoing LA (Nd:YAG, power: 2 W, treatment time: 4 min) was monitored by a 1.5-T MR scanner, utilizing two T 1-weighted sequences (IRTF and SRTF). The signal intensity in four regions of interest, placed at different distances from the laser applicator, was related to temperature variations monitored in the same regions by twelve fiber Bragg grating sensors. The relationship between the signal intensity and temperature increase was calculated to obtain the calibration curve and to evaluate accuracy, sensibility and precision of each sequence. This is the first study of MR-based thermometry during LA on pancreas. More specifically, the IRTF sequence provides the highest temperature sensitivity in both liver (1.8 ± 0.2 °C−1) and pancreas (1.8 ± 0.5 °C−1) and the lowest precision and accuracy. SRTF sequence on pancreas presents the highest accuracy and precision (MODSFRT = −0.1 °C and LOASFRT = [−2.3; 2.1] °C).

      PubDate: 2015-06-28T14:01:24Z
  • Trade-off between stress shielding and initial stability on an anatomical
           cementless stem shortening: in-vitro biomechanical study
    • Abstract: Publication date: Available online 25 June 2015
      Source:Medical Engineering & Physics
      Author(s): Go Yamako , Etsuo Chosa , Koji Totoribe , Shinji Watanabe , Takero Sakamoto
      Shortened cementless femoral stems have become popular with the advent of minimally invasive total hip arthroplasty (THA). Successful THA requires initial stem stability and prevention of stress shielding-mediated bone loss, although the effect of stem shortening is controversial. Here we experimentally examined whether stem shortening affects stress shielding and initial stability. Anatomical stems (length, 120 mm) were cut to an 80 mm or 50 mm length. Ten tri-axial strain gauges measured the cortical strain on each stem-implanted femur to evaluate stress shielding. Two transducers measured axial relative displacement and rotation under single-leg stance loading. The 50 mm stem increased the equivalent strains with respect to the original stem in the proximal calcar region (31.0% relative to intact strain), proximal medial region (63.1%), and proximal lateral region (53.9%). In contrast, axial displacement and rotation increased with a decreasing stem length. However, the axial displacement of the 50 mm stem was below a critical value of 150 µm for bone ingrowth. Our findings indicate that, with regard to a reduction in stem length, there is a tradeoff between stress shielding and initial stability. Shortening the stem up to 50 mm can promote proximal load transfer, but bone loss would be inevitable, even with sufficient initial stability for long-term fixation.

      PubDate: 2015-06-28T14:01:24Z
  • Alteration of the P-wave non-linear dynamics near the onset of paroxysmal
           atrial fibrillation
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): Arturo Martínez , Daniel Abásolo , Raúl Alcaraz , José J. Rieta
      The analysis of P-wave variability from the electrocardiogram (ECG) has been suggested as an early predictor of the onset of paroxysmal atrial fibrillation (PAF). Hence, a preventive treatment could be used to avoid the loss of normal sinus rhythm, thus minimising health risks and improving the patient’s quality of life. In these previous studies the variability of different temporal and morphological P-wave features has been only analysed in a linear fashion. However, the electrophysiological alteration occurring in the atria before the onset of PAF has to be considered as an inherently complex, chaotic and non-stationary process. This work analyses the presence of non-linear dynamics in the P-wave progression before the onset of PAF through the application of the central tendency measure (CTM), which is a non-linear metric summarising the degree of variability in a time series. Two hour-length ECG intervals just before the arrhythmia onset belonging to 46 different PAF patients were analysed. In agreement with the invasively observed inhomogeneous atrial conduction preceding the onset of PAF, CTM for all the considered P-wave features showed higher variability when the arrhythmia was closer to its onset. A diagnostic accuracy around 80% to discern between ECG segments far from PAF and close to PAF was obtained with the CTM of the metrics considered. This result was similar to previous P-wave variability methods based on linear approaches. However, the combination of linear and non-linear methods with a decision tree improved considerably their discriminant ability up to 90%, thus suggesting that both dynamics could coexist at the same time in the fragmented depolarisation of the atria preceding the arrhythmia.

      PubDate: 2015-06-28T14:01:24Z
  • On growth measurements of abdominal aortic aneurysms using maximally
           inscribed spheres
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): H. Gharahi , B.A. Zambrano , C. Lim , J. Choi , W. Lee , S. Baek
      The maximum diameter, total volume of the abdominal aorta, and its growth rate are usually regarded as key factors for making a decision on the therapeutic operation time for an abdominal aortic aneurysm (AAA) patient. There is, however, a debate on what is the best standard method to measure the diameter. Currently, two dominant methods for measuring the maximum diameter are used. One is measured on the planes perpendicular to the aneurism's central line (orthogonal diameter) and the other one is measured on the axial planes (axial diameter). In this paper, another method called ‘inscribed-spherical diameter’ is proposed to measure the diameter. The main idea is to find the diameter of the largest sphere that fits within the aorta. An algorithm is employed to establish a centerline for the AAA geometries obtained from a set of longitudinal scans obtained from South Korea. This centerline, besides being the base of the inscribed spherical method, is used for the determination of orthogonal and axial diameter. The growth rate parameters are calculated in different diameters and the total volume and the correlations between them are studied. Furthermore, an exponential growth pattern is sought for the maximum diameters over time to examine a nonlinear growth pattern of AAA expansion both globally and locally. The results present the similarities and discrepancies of these three methods. We report the shortcomings and the advantages of each method and its performance in the quantification of expansion rates. While the orthogonal diameter measurement has an ability of capturing a realistic diameter, it fluctuated. On the other hand, the inscribed sphere diameter method tends to underestimate the diameter measurement but the growth rate can be bounded in a narrow region for aiding prediction capability. Moreover, expansion rate parameters derived from this measurement exhibit good correlation with each other and with growth rate of volume. In conclusion, although the orthogonal method remains the main method of measuring the diameter of an abdominal aorta, employing the idea of maximally inscribed spheres provides both a tool for generation of the centerline, and an additional parameter for quantification of aneurysmal growth rates.

      PubDate: 2015-06-28T14:01:24Z
  • A novel method for discrimination between innocent and pathological heart
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): Arash Gharehbaghi , Magnus Borga , Birgitta Janerot Sjöberg , Per Ask
      This paper presents a novel method for discrimination between innocent and pathological murmurs using the growing time support vector machine (GTSVM). The proposed method is tailored for characterizing innocent murmurs (IM) by putting more emphasis on the early parts of the signal as IMs are often heard in early systolic phase. Individuals with mild to severe aortic stenosis (AS) and IM are the two groups subjected to analysis, taking the normal individuals with no murmur (NM) as the control group. The AS is selected due to the similarity of its murmur to IM, particularly in mild cases. To investigate the effect of the growing time windows, the performance of the GTSVM is compared to that of a conventional support vector machine (SVM), using repeated random sub-sampling method. The mean value of the classification rate/sensitivity is found to be 88%/86% for the GTSVM and 84%/83% for the SVM. The statistical evaluations show that the GTSVM significantly improves performance of the classification as compared to the SVM.

      PubDate: 2015-06-28T14:01:24Z
  • Swallowing accelerometry signal feature variations with sensor
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): Khondaker A. Mamun , Catriona M. Steele , Tom Chau
      Dual-axis accelerometry has recently shown promise as a non-invasive method for detecting swallowing impairment using signal processing and pattern classification algorithms. However, it is unknown whether variations in sensor placement alter signal characteristics, threatening the accuracy of signal processing classifiers for aspiration detection. To address this question, water swallows were recorded in 14 healthy adults using a dual-axis accelerometer in 13 different positions (baseline, and 2, 4, 6 and 8 mm above, below and to the right of baseline). The baseline position was midline, immediately below the thyroid cartilage during quiet breathing. After segmentation and pre-processing, signal features were extracted in multiple domains (time, frequency, time-frequency). The effect of sensor position on signal feature distributions was examined with non-parametric statistical analysis. The analysis showed that the sensor could be displaced by as much as 4 mm inferior and lateral to the baseline position and by up to 6 mm above the baseline location without significantly altering time-frequency features. In other words, when considering the baseline position as the origin, the admissible region for sensor placement spans 10 mm in the superior-inferior axis and 8 mm in the medial-lateral direction. Results of this study suggest that time-frequency representations of accelerometry signals are most robust to sensor placement variations around the baseline position. The implication of this finding is that a swallowing accelerometry classifier based on time-frequency features can likely tolerate small variations in sensor location without degradation in classification performance.

      PubDate: 2015-06-28T14:01:24Z
  • Evaluation of delamination in drilling of bone
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): Rupesh Kumar Pandey , Sudhansu Sekhar Panda
      In this paper, delamination of bone associated with drilling is investigated using design of experiments. Experiments have been planned based on L25 design of the orthogonal arrays with different conditions of drill bit, spindle speed and feed rate. Regression analysis is used to develop a mathematical model of delamination as a function of bone drilling process parameters. Analysis of variance (ANOVA) is carried out to find the significance of the developed model along with the percentage contribution of each factor on delamination. Optimum setting of bone drilling parameters for minimum delamination is determined using Taguchi optimization methodology. Finally, the results obtained are validated by conducting confirmation experiments.

      PubDate: 2015-06-28T14:01:24Z
  • Sensitivities of biomechanical assessment methods for fracture healing of
           long bones
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): G. Chen , F.Y. Wu , J.Q. Zhang , G.Q. Zhong , F. Liu
      There is a controversy as to whether the biomechanical methods are feasible to assess fracture healing of long bones. This paper investigated the sensitivities of two biomechanical methods, torsion and bending, for assessing fracture healing of long bones; both a simplified beam model and finite element model of an artificial femur were employed. The results demonstrated that, in the initial healing stage, the whole-bone stiffness of the fractured bone is extremely sensitive to the variation of the callus stiffness at the fracture site; when the shear (or Young's) modulus of the callus reaches 15% that of the intact bone, the whole-bone stiffness rises up to 90% that of the intact bone. After that, the whole-bone torsional (or bending) stiffness increases slowly; it becomes less sensitive to the variation of the callus stiffness. These results imply that the whole-bone stiffness is of limited reliability to assess the healing quality particular at late stages of the healing process. The simplified model in this paper provided a theoretical framework to explain why the whole-bone stiffness is insensitive to the healing process of fractured long bones in the late stage of healing. The conclusions obtained from the simplified model were verified with the finite element simulations of the artificial femur.

      PubDate: 2015-06-28T14:01:24Z
  • A whole body vibration perception map and associated acceleration loads at
           the lower leg, hip and head
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): Anelise Sonza , Nina Völkel , Milton A. Zaro , Matilde Achaval , Ewald M. Hennig
      Whole-body vibration (WBV) training has become popular in recent years. However, WBV may be harmful to the human body. The goal of this study was to determine the acceleration magnitudes at different body segments for different frequencies of WBV. Additionally, vibration sensation ratings by subjects served to create perception vibration magnitude and discomfort maps of the human body. In the first of two experiments, 65 young adults mean (± SD) age range of 23 (± 3.0) years, participated in WBV severity perception ratings, based on a Borg scale. Measurements were performed at 12 different frequencies, two intensities (3 and 5 mm amplitudes) of rotational mode WBV. On a separate day, a second experiment (n = 40) included vertical accelerometry of the head, hip and lower leg with the same WBV settings. The highest lower limb vibration magnitude perception based on the Borg scale was extremely intense for the frequencies between 21 and 25 Hz; somewhat hard for the trunk region (11–25 Hz) and fairly light for the head (13–25 Hz). The highest vertical accelerations were found at a frequency of 23 Hz at the tibia, 9 Hz at the hip and 13 Hz at the head. At 5 mm amplitude, 61.5% of the subjects reported discomfort in the foot region (21–25 Hz), 46.2% for the lower back (17, 19 and 21 Hz) and 23% for the abdominal region (9–13 Hz). The range of 3–7 Hz represents the safest frequency range with magnitudes less than 1 g*sec for all studied regions.

      PubDate: 2015-06-28T14:01:24Z
  • Corrigendum to “Biomechanical analysis of different types of pedicle
           screw augmentation: a cadaveric and synthetic bone sample study of
           instrumented vertebral specimens” [Med. Eng. Phys. 35/10 (2013)
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): Kuo-Hua Chao , Yu-Shu Lai , Wen-Chuan Chen , Chia-Ming Chang , Colin J. McClean , Chang-Yuan Fan , Chia-Hao Chang , Leou-Chyr Lin , Cheng-Kung Cheng

      PubDate: 2015-06-28T14:01:24Z
  • Carotid plaque elasticity estimation using ultrasound elastography, MRI,
           and inverse FEA – A numerical feasibility study
    • Abstract: Publication date: Available online 27 June 2015
      Source:Medical Engineering & Physics
      Author(s): H.A. Nieuwstadt , S. Fekkes , H.H.G. Hansen , C.L. de Korte , A. van der Lugt , J.J. Wentzel , A.F.W. van der Steen , F.J.H. Gijsen
      The material properties of atherosclerotic plaques govern the biomechanical environment, which is associated with rupture-risk. We investigated the feasibility of noninvasively estimating carotid plaque component material properties through simulating ultrasound (US) elastography and in vivo magnetic resonance imaging (MRI), and solving the inverse problem with finite element analysis. 2D plaque models were derived from endarterectomy specimens of nine patients. Nonlinear neo-Hookean models (tissue elasticity C 1) were assigned to fibrous intima, wall (i.e., media/adventitia), and lipid-rich necrotic core. Finite element analysis was used to simulate clinical cross-sectional US strain imaging. Computer-simulated, single-slice in vivo MR images were segmented by two MR readers. We investigated multiple scenarios for plaque model elasticity, and consistently found clear separations between estimated tissue elasticity values. The intima C 1 (160 kPa scenario) was estimated as 125.8 ± 19.4 kPa (reader 1) and 128.9 ± 24.8 kPa (reader 2). The lipid-rich necrotic core C 1 (5 kPa) was estimated as 5.6 ± 2.0 kPa (reader 1) and 8.5 ± 4.5 kPa (reader 2). A scenario with a stiffer wall yielded similar results, while realistic US strain noise and rotating the models had little influence, thus demonstrating robustness of the procedure. The promising findings of this computer-simulation study stimulate applying the proposed methodology in a clinical setting.

      PubDate: 2015-06-28T14:01:24Z
  • Varying behavior of different window sizes on the classification of static
           and dynamic physical activities from a single accelerometer
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): Benish Fida , Ivan Bernabucci , Daniele Bibbo , Silvia Conforto , Maurizio Schmid
      Accuracy of systems able to recognize in real time daily living activities heavily depends on the processing step for signal segmentation. So far, windowing approaches are used to segment data and the window size is usually chosen based on previous studies. However, literature is vague on the investigation of its effect on the obtained activity recognition accuracy, if both short and long duration activities are considered. In this work, we present the impact of window size on the recognition of daily living activities, where transitions between different activities are also taken into account. The study was conducted on nine participants who wore a tri-axial accelerometer on their waist and performed some short (sitting, standing, and transitions between activities) and long (walking, stair descending and stair ascending) duration activities. Five different classifiers were tested, and among the different window sizes, it was found that 1.5 s window size represents the best trade-off in recognition among activities, with an obtained accuracy well above 90%. Differences in recognition accuracy for each activity highlight the utility of developing adaptive segmentation criteria, based on the duration of the activities.

      PubDate: 2015-06-28T14:01:24Z
  • Achilles tendon displacement patterns during passive stretch and eccentric
           loading are altered in middle-aged adults
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): Laura Chernak Slane , Darryl G. Thelen
      The purpose of this study was to investigate middle-age effects on Achilles displacement patterns under passive stretch and eccentric loading. Healthy young (24.1 ± 1.4 years, n = 9) and middle-aged (49.0 ± 3.1 years, n = 9) adults were positioned prone and the ankle was cyclically dorsiflexed (0.5 Hz, 25° range) during passive stretch and active lengthening. Achilles displacements were tracked in cine ultrasound using 2D speckle tracking. Displacements were found to be non-uniform, with mid and deep portions of the tendon displacing more than superficial portions. However, the degree of non-uniformity was significantly reduced in middle-aged adults, suggesting a potential age-related reduction in inter-fascicle sliding or a shift in loading sharing between plantarflexors. Eccentric loading reduced displacement magnitudes, likely reflecting distal tendon stretch induced via active muscle contractions. Changes in tendon displacement with active loading were greater in middle-aged adults, which could reflect greater tendon compliance. The observed age-related changes in Achilles tendon behavior may have implications for both plantarflexor performance and injury risk.

      PubDate: 2015-06-28T14:01:24Z
  • Editorial Board
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7

      PubDate: 2015-06-28T14:01:24Z
  • Multi-selective catheter for MR-guided endovascular interventions
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): Helene C.M. Clogenson , Joris Y. van Lith , Jenny Dankelman , Andreas Melzer , John J. van den Dobbelsteen
      Selective catheters have predefined distal shapes and need to be exchanged to change tip geometry to facilitate selective catheterization of vascular side branches. These repeated insertions increase the risk of endovascular injury and radiation dose in conventional catheterization laboratories. The aim of this study is to develop a multi-selective catheter that can replace three conventional selective catheters that are commonly used sequentially in a single procedure. By integrating the different shapes in one instrument, it is possible to avoid the required time-consuming exchange. This new instrument is also made compatible with magnetic resonance imaging (MRI) guidance, which, unlike X-ray, presents variable soft tissue contrast without the use of ionizing radiation. A 1.2 m long and 2.15 mm diameter deflectable polymer-based catheter was assembled and three widely used selective catheters could be mimicked. The instrument was visible on the images without producing unwanted artifacts in an abdominal model and in an animal under real-time MRI guidance. Simple navigation tasks were performed together with a 0.035 in. MRI-safe guidewire. In these tasks, the iliac, renal, brachiocephalic, and left subclavian arteries were cannulated only by using the shape setting and without exchange of the instruments.

      PubDate: 2015-06-28T14:01:24Z
  • Anatomical calibration for wearable motion capture systems: Video
           calibrated anatomical system technique
    • Abstract: Publication date: Available online 12 June 2015
      Source:Medical Engineering & Physics
      Author(s): Maria Cristina Bisi , Rita Stagni , Alessio Caroselli , Angelo Cappello
      Inertial sensors are becoming widely used for the assessment of human movement in both clinical and research applications, thanks to their usability out of the laboratory. This work aims to propose a method for calibrating anatomical landmark position in the wearable sensor reference frame with an ease to use, portable and low cost device. An off-the-shelf camera, a stick and a pattern, attached to the inertial sensor, compose the device. The proposed technique is referred to as video Calibrated Anatomical System Technique (vCAST). The absolute orientation of a synthetic femur was tracked both using the vCAST together with an inertial sensor and using stereo-photogrammetry as reference. Anatomical landmark calibration showed mean absolute error of 0.6±0.5 mm: these errors are smaller than those affecting the in-vivo identification of anatomical landmarks. The roll, pitch and yaw anatomical frame orientations showed root mean square errors close to the accuracy limit of the wearable sensor used (1°), highlighting the reliability of the proposed technique. In conclusion, the present paper proposes and preliminarily verifies the performance of a method (vCAST) for calibrating anatomical landmark position in the wearable sensor reference frame: the technique is low time consuming, highly portable, easy to implement and usable outside laboratory.

      PubDate: 2015-06-28T14:01:24Z
  • Low-intensity functional electrical stimulation can increase
           multidirectional trunk stiffness in able-bodied individuals during sitting
    • Abstract: Publication date: Available online 10 June 2015
      Source:Medical Engineering & Physics
      Author(s): Albert H. Vette , Noel Wu , Kei Masani , Milos R. Popovic
      The inability to voluntarily control the trunk musculature is a major problem following spinal cord injury as it can compromise functional independence and produce unwanted secondary complications. Recent developments suggest that neuroprostheses utilizing functional electrical stimulation (FES) may be able to facilitate or restore trunk control during sitting, standing, and other tasks involving postural control. In spite of these efforts, no study to date has used low-intensity FES to increase multidirectional trunk stiffness and damping in an attempt to bolster stability while minimizing muscle fatigue. Therefore, we set out to investigate how multidirectional trunk stiffness changes in response to low-intensity FES of a few selected trunk muscles. Fifteen healthy participants sitting naturally were randomly perturbed in eight horizontal directions. Trunk stiffness and damping during natural and FES-supported sitting conditions were quantified using force and trunk kinematics in combination with two models of a mass-spring-damper system. Our results indicate that low-intensity FES can increase trunk stiffness in healthy individuals, and this specifically for directions associated with the stimulated muscles. In contrast, trunk damping was not found to be altered during FES. The presented results suggest that low-intensity FES is a simple and effective method for increasing trunk stiffness on demand.

      PubDate: 2015-06-28T14:01:24Z
  • Development of a non-invasive diagnostic technique for acetabular
           component loosening in total hip replacements
    • Abstract: Publication date: Available online 6 June 2015
      Source:Medical Engineering & Physics
      Author(s): Abdullah A. Alshuhri , Timothy P. Holsgrove , Anthony W. Miles , James L. Cunningham
      Current techniques for diagnosing early loosening of a total hip replacement (THR) are ineffective, especially for the acetabular component. Accordingly, new, accurate, and quantifiable methods are required. The aim of this study was to investigate the viability of vibrational analysis for accurately detecting acetabular component loosening. A simplified acetabular model was constructed using a Sawbones® foam block. By placing a thin silicone layer between the acetabular component and the Sawbones block, 2- and 4-mm soft tissue membranes were simulated representing different loosening scenarios. A constant amplitude sinusoidal excitation with a sweep range of 100–1500 Hz was used. Output vibration from the model was measured using an accelerometer and an ultrasound probe. Loosening was determined from output signal features such as the number and relative strength of observed harmonic frequencies. Both measurement methods were sufficient to measure the output vibration. Vibrational analysis reliably detected loosening corresponding to both 2 and 4 mm tissue membranes at driving frequencies between 100 and 1000 Hz (p < 0.01) using the accelerometer. In contrast, ultrasound detected 2-mm loosening at a frequency range of 850–1050 Hz (p < 0.01) and 4-mm loosening at 500–950 Hz (p < 0.01).

      PubDate: 2015-06-28T14:01:24Z
  • Effect of different radial hole designs on pullout and structural strength
           of cannulated pedicle screws
    • Abstract: Publication date: Available online 6 June 2015
      Source:Medical Engineering & Physics
      Author(s): Hsin-Chang Chen , Yu-Shu Lai , Wen-Chuan Chen , Jou-Wen Chen , Chia-Ming Chang , Yi-Long Chen , Shih-Tien Wang , Cheng-Kung Cheng
      Cannulated pedicle screws are designed for bone cement injection to enhance fixation strength in severely osteoporotic spines. However, the screws commonly fracture during insertion. This study aims to evaluate how different positions/designs of radial holes may affect the pullout and structural strength of cannulated pedicle screws using finite element analysis. Three different screw hole designs were evaluated under torsion and bending conditions. The pullout strength for each screw was determined by axial pullout failure testing. The results showed that when the Von Mises stress reached the yield stress of titanium alloy the screw with four radial holes required a greater torque or bending moment than the nine and twelve hole screws. In the pullout test, the strength and stiffness of each screw with cement augmentation showed no significant differences, but the screw with four radial holes had a greater average pullout strength, which probably resulted from the significantly greater mean maximum lengths of cement augmentation. Superior biomechanical responses, with lower stress around the radial holes and greater pullout strength, represented by cannulated pedicle screw with four radial holes may worth recommending for clinical application.

      PubDate: 2015-06-28T14:01:24Z
  • Biomechanical properties of the Marfan's aortic root and ascending aorta
           before and after personalised external aortic root support surgery
    • Abstract: Publication date: Available online 6 June 2015
      Source:Medical Engineering & Physics
      Author(s): S.D. Singh , X.Y. Xu , J.R. Pepper , T. Treasure , R.H. Mohiaddin
      Marfan syndrome is an inherited systemic connective tissue disease which may lead to aortic root disease causing dilatation, dissection and rupture of the aorta. The standard treatment is a major operation involving either an artificial valve and aorta or a complex valve repair. More recently, a personalised external aortic root support (PEARS) has been used to strengthen the aorta at an earlier stage of the disease avoiding risk of both rupture and major surgery. The aim of this study was to compare the stress and strain fields of the Marfan aortic root and ascending aorta before and after insertion of PEARS in order to understand its biomechanical implications. Finite element (FE) models were developed using patient-specific aortic geometries reconstructed from pre and post-PEARS magnetic resonance images in three Marfan patients. For the post-PEARS model, two scenarios were investigated—a bilayer model where PEARS and the aortic wall were treated as separate layers, and a single-layer model where PEARS was incorporated into the aortic wall. The wall and PEARS materials were assumed to be isotropic, incompressible and linearly elastic. A static load on the inner wall corresponding to the patients’ pulse pressure was applied. Results from our FE models with patient-specific geometries show that peak aortic stresses and displacements before PEARS were located at the sinuses of Valsalva but following PEARS surgery, these peak values were shifted to the aortic arch, particularly at the interface between the supported and unsupported aorta. Further studies are required to assess the statistical significance of these findings and how PEARS compares with the standard treatment.

      PubDate: 2015-06-28T14:01:24Z
  • Evaluating the effect of increasing ceramic content on the mechanical
           properties, material microstructure and degradation of selective laser
           sintered polycaprolactone/β-tricalcium phosphate materials
    • Abstract: Publication date: Available online 6 June 2015
      Source:Medical Engineering & Physics
      Author(s): Heather Doyle , Stefan Lohfeld , Peter McHugh
      Orthopaedic scaffold materials were fabricated from polycaprolactone (PCL) and composite PCL–β-tricalcium phosphate (PCL/β-TCP) powders using selective laser sintering (SLS). Incorporating β-TCP particles is desirable to promote osteogenesis. The effects of increasing β-TCP content on the material's mechanical properties and microstructure were evaluated. The wt% of β-TCP and PCL particle sizes were found to influence material microstructure and mechanical properties, with increasing ceramic content causing a small but significant increase in stiffness but significant reductions in strength. Degradation of materials was achieved using accelerated ageing methods. The influence of β-TCP content on degradation at 7 weeks was evaluated through changes in mechanical properties and microstructure, and the ceramic particles were found to reduce elastic modulus and increase strength. The results of this study highlight the influence of ceramic content on mechanical properties and degradation behaviour of PCL/β-TCP SLS materials, and indicate that these changes must be considered in the design of scaffolds for critical-sized defects.

      PubDate: 2015-06-28T14:01:24Z
  • Comparisons of node-based and element-based approaches of assigning bone
           material properties onto subject-specific finite element models
    • Abstract: Publication date: Available online 6 June 2015
      Source:Medical Engineering & Physics
      Author(s): G. Chen , F.Y. Wu , Z.C. Liu , K. Yang , F. Cui
      Subject-specific finite element (FE) models can be generated from computed tomography (CT) datasets of a bone. A key step is assigning material properties automatically onto finite element models, which remains a great challenge. This paper proposes a node-based assignment approach and also compares it with the element-based approach in the literature. Both approaches were implemented using ABAQUS. The assignment procedure is divided into two steps: generating the data file of the image intensity of a bone in a MATLAB program and reading the data file into ABAQUS via user subroutines. The node-based approach assigns the material properties to each node of the finite element mesh, while the element-based approach assigns the material properties directly to each integration point of an element. Both approaches are independent from the type of elements. A number of FE meshes are tested and both give accurate solutions; comparatively the node-based approach involves less programming effort. The node-based approach is also independent from the type of analyses; it has been tested on the nonlinear analysis of a Sawbone femur. The node-based approach substantially improves the level of automation of the assignment procedure of bone material properties. It is the simplest and most powerful approach that is applicable to many types of analyses and elements.

      PubDate: 2015-06-28T14:01:24Z
  • Early detection of abnormal left ventricular relaxation in acute
           myocardial ischemia with a quadratic model. Med Eng Phys 2014;36(September
           (9)):1101–5 by Morimont et al.
    • Abstract: Publication date: Available online 3 June 2015
      Source:Medical Engineering & Physics
      Author(s): Charles S. Chung , Leonid Shmuylovich , Sándor J. Kovács

      PubDate: 2015-06-28T14:01:24Z
  • A model of lung parenchyma stress relaxation using fractional
    • Abstract: Publication date: Available online 3 June 2015
      Source:Medical Engineering & Physics
      Author(s): Zoujun Dai , Ying Peng , Hansen A. Mansy , Richard H. Sandler , Thomas J. Royston
      Some pulmonary diseases and injuries are believed to correlate with lung viscoelasticity changes. Hence, a better understanding of lung viscoelastic models could provide new perspectives on the progression of lung pathology and trauma. In the presented study, stress relaxation measurements were performed to quantify relaxation behavior of pig lungs. Results have uncovered certain trends, including an initial steep decay followed by a slow asymptotic relaxation, which would be better described by a power law than exponential decay. The fractional standard linear solid (FSLS) and two integer order viscoelastic models – standard linear solid (SLS) and generalized Maxwell (GM) – were used to fit the stress relaxation curves; the FSLS was found to be a better fit. It is suggested that fractional order viscoelastic models, which have nonlocal, multi-scale attributes and exhibit power law behavior, better capture the lung parenchyma viscoelastic behavior.

      PubDate: 2015-06-28T14:01:24Z
  • Use of wearable technology for performance assessment: A validation study
    • Abstract: Publication date: Available online 30 April 2015
      Source:Medical Engineering & Physics
      Author(s): Enrica Papi , Denise Osei-Kuffour , Yen-Ming A Chen , Alison H McGregor
      The prevalence of osteoarthritis is increasing globally but current compliance with rehabilitation remains poor. This study explores whether wearable sensors can be used to provide objective measures of performance with a view to using them as motivators to aid compliance to osteoarthritis rehabilitation. More specifically, the use of a novel attachable wearable sensor integrated into clothing and inertial measurement units located in two different positions, at the waist and thigh pocket, was investigated. Fourteen healthy volunteers were asked to complete exercises adapted from a knee osteoarthritis rehabilitation programme whilst wearing the three sensors including five times sit-to-stand test, treadmill walking at slow, preferred and fast speeds. The performances of the three sensors were validated against a motion capture system and an instrumented treadmill. The systems showed a high correlation (r 2 > 0.7) and agreement (mean difference range: −0.02–0.03 m, 0.005–0.68 s) with gold standards. The novel attachable wearable sensor was able to monitor exercise tasks as well as the inertial measurement units (ICC > 0.95). Results also suggested that a functional placement (e.g., situated in a pocket) is a valid position for performance monitoring. This study shows the potential use of wearable technologies for assessing subject performance during exercise and suggests functional solutions to enhance acceptance.

      PubDate: 2015-05-03T02:17:52Z
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