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  Subjects -> BIOLOGY (Total: 2598 journals)
    - BIOCHEMISTRY (192 journals)
    - BIOENGINEERING (63 journals)
    - BIOLOGY (1320 journals)
    - BIOPHYSICS (42 journals)
    - BIOTECHNOLOGY (145 journals)
    - BOTANY (194 journals)
    - CYTOLOGY AND HISTOLOGY (24 journals)
    - ENTOMOLOGY (54 journals)
    - GENETICS (136 journals)
    - MICROBIOLOGY (210 journals)
    - MICROSCOPY (9 journals)
    - ORNITHOLOGY (23 journals)
    - PHYSIOLOGY (66 journals)
    - ZOOLOGY (120 journals)

BIOLOGY (1320 journals)            First | 4 5 6 7 8 9 10 11 | Last

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: 3)
Journal of Biomarkers     Open Access  
Journal of Biomechanics     Hybrid Journal   (Followers: 16)
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: 5)
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: 15)
Journal of Biosocial Science     Hybrid Journal   (Followers: 4)
Journal of Biotechnology and Biodiversity     Open Access  
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: 10)
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: 1)
Journal of Chromatography B     Hybrid Journal   (Followers: 16)
Journal of Clinical Bioinformatics     Open Access   (Followers: 5)
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 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: 9)
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: 4)
Journal of Ethnobiology and Ethnomedicine     Open Access  
Journal of Ethology     Hybrid Journal   (Followers: 1)
Journal of Evolutionary Biology     Hybrid Journal   (Followers: 18)
Journal of Experimental and Clinical Anatomy     Full-text available via subscription  
Journal of Experimental Marine Biology and Ecology     Hybrid Journal   (Followers: 23)
Journal of Fish Biology     Hybrid Journal   (Followers: 23)
Journal of Functional Biomaterials     Open Access   (Followers: 1)
Journal of Great Lakes Research     Hybrid Journal   (Followers: 7)
Journal of Health and Biological Sciences     Open Access  
Journal of Health Sciences     Open Access   (Followers: 5)
Journal of Heredity     Hybrid Journal   (Followers: 2)
Journal of Herpetology     Full-text available via subscription   (Followers: 3)
Journal of Huazhong University of Science and Technology [Medical Sciences]     Hybrid Journal  
Journal of Human Evolution     Hybrid Journal   (Followers: 9)
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: 1)
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: 3)
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: 5)
Journal of Law and the Biosciences     Open Access  
Journal of Leukocyte Biology     Open Access   (Followers: 5)
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: 5)
Journal of Mammalian Ova Research     Full-text available via subscription  
Journal of Mammalogy     Full-text available via subscription   (Followers: 5)
Journal of Mammary Gland Biology and Neoplasia     Hybrid Journal  
Journal of Marine Biology     Open Access   (Followers: 13)
Journal of Mathematical Biology     Hybrid Journal   (Followers: 12)
Journal of Mechanics in Medicine and Biology     Hybrid Journal  
Journal of Medical Primatology     Hybrid Journal   (Followers: 1)
Journal of Medical Toxicology     Hybrid Journal   (Followers: 4)
Journal of Medicine and Philosophy     Hybrid Journal   (Followers: 6)
Journal of Membrane Biology     Hybrid Journal   (Followers: 2)
Journal of Membrane Science     Hybrid Journal   (Followers: 9)
Journal of Molecular Biology     Hybrid Journal   (Followers: 27)
Journal of Molecular Biology Research     Open Access   (Followers: 1)
Journal of Molecular Catalysis B: Enzymatic     Hybrid Journal  
Journal of Molecular Cell Biology     Hybrid Journal   (Followers: 8)
Journal of Molecular Evolution     Hybrid Journal   (Followers: 8)
Journal of Molecular Signaling     Open Access  
Journal of Molecular Structure     Hybrid Journal   (Followers: 3)
Journal of Molluscan Studies     Hybrid Journal   (Followers: 2)
Journal of Muscle Research and Cell Motility     Hybrid Journal   (Followers: 1)
Journal of Nanoparticle Research     Hybrid Journal   (Followers: 3)
Journal of Nanoparticles     Open Access  
Journal of Natural History     Hybrid Journal   (Followers: 4)
Journal of Natural Products     Full-text available via subscription   (Followers: 8)
Journal of Natural Science, Biology and Medicine     Open Access   (Followers: 2)
Journal of Natural Sciences Research     Open Access   (Followers: 3)

  First | 4 5 6 7 8 9 10 11 | Last

Journal Cover Medical Engineering & Physics
   [11 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 1350-4533
     Published by Elsevier Homepage  [2563 journals]   [SJR: 0.722]   [H-I: 57]
  • Comprehensive evaluation of PCA-based finite element modelling of the
           human femur
    • Abstract: Publication date: Available online 14 August 2014
      Source:Medical Engineering & Physics
      Author(s): Lorenzo Grassi , Enrico Schileo , Christelle Boichon , Marco Viceconti , Fulvia Taddei
      Computed tomography (CT)-based finite element (FE) reconstructions describe shape and density distribution of bones. Both shape and density distribution, however, can vary a lot between individuals. Shape/density indexation (usually achieved by principal component analysis—PCA) can be used to synthesize realistic models, thus overcoming the shortage of CT-based models, and helping e.g. to study fracture determinants, or steer prostheses design. The aim of this study was to describe a PCA-based statistical modelling algorithm, and test it on a large CT-based population of femora, to see if it can accurately describe and reproduce bone shape, density distribution, and biomechanics. To this aim, 115 CT-datasets showing normal femoral anatomy were collected and characterized. Isotopological FE meshes were built. Shape and density indexation procedures were performed on the mesh database. The completeness of the database was evaluated through a convergence study. The accuracy in reconstructing bones not belonging to the indexation database was evaluated through (i) leave-one-out tests (ii) comparison of calculated vs. in-vitro measured strains. Fifty indexation modes for shape and 40 for density were necessary to achieve reconstruction errors below pixel size for shape, and below 10% for density. Similar errors for density, and slightly higher errors for shape were obtained when reconstructing bones not belonging to the database. The in-vitro strain prediction accuracy of the reconstructed FE models was comparable to state-of-the-art studies. In summary, the results indicate that the proposed statistical modelling tools are able to accurately describe a population of femora through finite element models.


      PubDate: 2014-08-17T03:03:44Z
       
  • Subject-specific evaluation of patellofemoral joint biomechanics during
           functional activity
    • Abstract: Publication date: September 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 9
      Author(s): Massoud Akbarshahi , Justin W. Fernandez , Anthony G. Schache , Marcus G. Pandy
      Patellofemoral joint pain is a common problem experienced by active adults. However, relatively little is known about patellofemoral joint load and its distribution across the medial and lateral facets of the patella. In this study, biomechanical experiments and computational modeling were used to study patellofemoral contact mechanics in four healthy adults during stair ambulation. Subject-specific anatomical and gait data were recorded using magnetic resonance imaging, dynamic X-ray fluoroscopy, video motion capture, and multiple force platforms. From these data, in vivo tibiofemoral joint kinematics and knee muscle forces were computed and then applied to a deformable finite-element model of the patellofemoral joint. The contact force acting on the lateral facet of the patella was 4–6 times higher than that acting on the medial facet. The peak average patellofemoral contact stresses were 8.2±1.0MPa and 5.9±1.3MPa for the lateral and medial patellar facets, respectively. Peak normal compressive stress and peak octahedral shear stress occurred near toe-off of the contralateral leg and were higher on the lateral facet than the medial facet; furthermore, the peak compressive stress (11.5±3.0MPa) was higher than the peak octahedral shear stress (5.2±0.9MPa). The dominant stress pattern on the lateral patellar facet corresponded well to the location of maximum cartilage thickness. Higher loading of the lateral facet is also consistent with the clinical observation that the lateral compartment of the patellofemoral joint is more prone to osteoarthritis than the medial compartment. Predicted cartilage contact stress maps near contralateral toe-off showed three distinctly different patterns: peak stresses located on the lateral patellar facet; peak stresses located centrally between the medial and lateral patellar facets; and peak stresses located superiorly on both the medial and lateral patellar facets.


      PubDate: 2014-08-17T03:03:44Z
       
  • Comparative study of corneal tangent elastic modulus measurement using
           corneal indentation device
    • Abstract: Publication date: September 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 9
      Author(s): Match W.L. Ko , Leo K.K. Leung , David C.C. Lam
      The aim of this study is to examine the corneal tangent modulus measurement repeatability and performance of the corneal indentation device (CID). Twenty enucleated porcine eyes were measured and the eyes were pressurized using saline solution-filled manometer to 15 and 30mmHg. Corneal tangent moduli measured using the CID were compared with those measured using high precision universal testing machine (UTM). The within-subject standard deviation (Sw), repeatability (2.77×Sw), coefficient of variation (CV) (Sw/overall mean), and intraclass correlation coefficient (ICC) were determined. The mean corneal tangent moduli measured using UTM and CID were 0.094±0.030 and 0.094±0.028MPa at 15mmHg, and 0.207±0.056 and 0.207±0.055MPa at 30mmHg, respectively, with a difference less than 0.13%. The 95% limit of agreement was between −0.009 and 0.009MPa. The Sw, repeatability, CV and ICC of corneal tangent moduli measured by the CID were 0.006MPa, 0.015MPa, 4.3% and 0.993, respectively. The results showed that the corneal tangent moduli measured by the CID are repeatable and are in good agreement with the results measured by the high precision UTM.


      PubDate: 2014-08-17T03:03:44Z
       
  • Effect of pulsatile swirling flow on stenosed arterial blood flow
    • Abstract: Publication date: September 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 9
      Author(s): Hojin Ha , Sang Joon Lee
      The existence of swirling flow phenomena is frequently observed in arterial vessels, but information on the fluid-dynamic roles of swirling flow is still lacking. In this study, the effects of pulsatile swirling inlet flows with various swirling intensities on the flow field in a stenosis model are experimentally investigated using a particle image velocimetry velocity field measurement technique. A pulsatile pump provides cyclic pulsating inlet flow and spiral inserts with two different helical pitches (10D and 10/3D) induce swirling flow in the stenosed channel. Results show that the pulsatile swirling flow has various beneficial effects by reducing the negative wall shear stress, the oscillatory shear index, and the flow reverse coefficient at the post-stenosis channel. Temporal variations of vorticity fields show that the short propagation length of the jet flow and the early breakout of turbulent flow are initiated as the swirling flow disturbs the symmetric development of the shear layer. In addition, the overall energy dissipation rate of the flow is suppressed by the swirling component of the flow. The results will be helpful for elucidating the hemodynamic characteristics of atherosclerosis and discovering better diagnostic procedures and clinical treatments.


      PubDate: 2014-08-17T03:03:44Z
       
  • Editorial Board
    • Abstract: Publication date: September 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 9




      PubDate: 2014-08-17T03:03:44Z
       
  • Optimal needle design for minimal insertion force and bevel length
    • Abstract: Publication date: September 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 9
      Author(s): Yancheng Wang , Roland K. Chen , Bruce L. Tai , Patrick W. McLaughlin , Albert J. Shih
      This research presents a methodology for optimal design of the needle geometry to minimize the insertion force and bevel length based on mathematical models of cutting edge inclination and rake angles and the insertion force. In brachytherapy, the needle with lower insertion force typically is easier for guidance and has less deflection. In this study, the needle with lancet point (denoted as lancet needle) is applied to demonstrate the model-based optimization for needle design. Mathematical models to calculate the bevel length and inclination and rake angles for lancet needle are presented. A needle insertion force model is developed to predict the insertion force for lancet needle. The genetic algorithm is utilized to optimize the needle geometry for two cases. One is to minimize the needle insertion force. Using the geometry of a commercial lancet needle as the baseline, the optimized needle has 11% lower insertion force with the same bevel length. The other case is to minimize the bevel length under the same needle insertion force. The optimized design can reduce the bevel length by 46%. Both optimized needle designs were validated experimentally in ex vivo porcine liver needle insertion tests and demonstrated the methodology of the model-based optimal needle design.


      PubDate: 2014-08-17T03:03:44Z
       
  • Characterization of robotic system passive path repeatability during
           specimen removal and reinstallation for in vitro knee joint testing
    • Abstract: Publication date: Available online 12 August 2014
      Source:Medical Engineering & Physics
      Author(s): Mary T. Goldsmith , Sean D. Smith , Kyle S. Jansson , Robert F. LaPrade , Coen A. Wijdicks
      Robotic testing systems are commonly utilized for the study of orthopaedic biomechanics. Quantification of system error is essential for reliable use of robotic systems. Therefore, the purpose of this study was to quantify a 6-DOF robotic system's repeatability during knee biomechanical testing and characterize the error induced in passive path repeatability by removing and reinstalling the knee. We hypothesized removing and reinstalling the knee would substantially alter passive path repeatability. Testing was performed on four fresh-frozen cadaver knees. To determine repeatability and reproducibility, the passive path was collected three times per knee following the initial setup (intra-setup), and a single time following two subsequent re-setups (inter-setup). Repeatability was calculated as root mean square error. The intra-setup passive path had a position repeatability of 0.23mm. In contrast, inter-setup passive paths had a position repeatability of 0.89mm. When a previously collected passive path was replayed following re-setup of the knee, resultant total force repeatability across the passive path increased to 28.2N (6.4N medial–lateral, 25.4N proximal–distal, and 10.5N anterior–posterior). This study demonstrated that removal and re-setup of a knee can have substantial, clinically significant changes on our system's repeatability and ultimately, accuracy of the reported results.


      PubDate: 2014-08-14T02:43:52Z
       
  • Monolithic superelastic rods with variable flexural stiffness for spinal
           fusion: Modeling of the processing–properties relationship
    • Abstract: Publication date: Available online 12 August 2014
      Source:Medical Engineering & Physics
      Author(s): Yann Facchinello , Vladimir Brailovski , Yvan Petit , Jean-Marc Mac-Thiong
      The concept of a monolithic Ti–Ni spinal rod with variable flexural stiffness is proposed to reduce the risks associated with spinal fusion. The variable stiffness is conferred to the rod using the Joule-heating local annealing technique. The annealing temperature and the mechanical properties’ distributions resulted from this thermal treatment are numerically modeled and experimentally measured. To illustrate the possible applications of such a modeling approach, two case studies are presented: (a) optimization of the Joule-heating strategy to reduce annealing time, and (b) modulation of the rod's overall flexural stiffness using partial annealing. A numerical model of a human spine coupled with the model of the variable flexural stiffness spinal rod developed in this work can ultimately be used to maximize the stabilization capability of spinal instrumentation, while simultaneously decreasing the risks associated with spinal fusion.


      PubDate: 2014-08-14T02:43:52Z
       
  • First in vivo application and evaluation of a novel method for
           non-invasive estimation of cardiac output
    • Abstract: Publication date: Available online 6 August 2014
      Source:Medical Engineering & Physics
      Author(s): Theodore G. Papaioannou , Dimitrios Soulis , Orestis Vardoulis , Athanase Protogerou , Petros P. Sfikakis , Nikolaos Stergiopulos , Christodoulos Stefanadis
      Surgical or critically ill patients often require continuous assessment of cardiac output (CO) for diagnostic purposes or for guiding therapeutic interventions. A new method of non-invasive CO estimation has been recently developed, which is based on pressure wave analysis. However, its validity has been examined only in silico. Aim of this study was to evaluate in vivo the reproducibility and accuracy of the “systolic volume balance” method (SVB). Twenty two subjects underwent 2-D transthoracic echocardiography for CO measurement (reference value of CO). The application of SVB method required aortic pressure wave analysis and estimation of total arterial compliance. Aortic pulses were derived by mathematical transformation of radial pressure waves recorded by applanation tonometry. Total compliance was estimated by the “pulse pressure” method. The agreement, association, variability, bias and precision between Doppler and SVB measures of CO were evaluated by intraclass correlation coefficient (ICC), mean difference, SD of differences, percentage error (PR) and Bland–Altman analysis. SVB yielded very reproducible CO estimates (ICC=0.84, mean difference 0.27±0.73L/min, PR=16.7%). SVB-derived CO was comparable with Doppler measurements, indicating a good agreement and accuracy (ICC=0.74, mean difference=−0.22±0.364L/min, PR≈15). The basic mathematical and physical principles of the SVB method provide highly reproducible and accurate estimates of CO compared with echocardiography.


      PubDate: 2014-08-09T02:28:26Z
       
  • Finite element analysis of three commonly used external fixation devices
           for treating Type III pilon fractures
    • Abstract: Publication date: Available online 7 August 2014
      Source:Medical Engineering & Physics
      Author(s): Muhammad Hanif Ramlee , Mohammed Rafiq Abdul Kadir , Malliga Raman Murali , Tunku Kamarul
      Pilon fractures are commonly caused by high energy trauma and can result in long-term immobilization of patients. The use of an external fixator i.e. the (1) Delta, (2) Mitkovic or (3) Unilateral frame for treating type III pilon fractures is generally recommended by many experts owing to the stability provided by these constructs. This allows this type of fracture to heal quickly whilst permitting early mobilization. However, the stability of one fixator over the other has not been previously demonstrated. This study was conducted to determine the biomechanical stability of these external fixators in type III pilon fractures using finite element modelling. Three-dimensional models of the tibia, fibula, talus, calcaneus, navicular, cuboid, three cuneiforms and five metatarsal bones were reconstructed from previously obtained CT datasets. Bones were assigned with isotropic material properties, while the cartilage was assigned as hyperelastic springs with Mooney–Rivlin properties. Axial loads of 350N and 70N were applied at the tibia to simulate the stance and the swing phase of a gait cycle. To prevent rigid body motion, the calcaneus and metatarsals were fixed distally in all degrees of freedom. The results indicate that the model with the Delta frame produced the lowest relative micromovement (0.03mm) compared to the Mitkovic (0.05mm) and Unilateral (0.42mm) fixators during the stance phase. The highest stress concentrations were found at the pin of the Unilateral external fixator (509.2MPa) compared to the Mitkovic (286.0MPa) and the Delta (266.7MPa) frames. In conclusion, the Delta external fixator was found to be the most stable external fixator for treating type III pilon fractures.


      PubDate: 2014-08-09T02:28:26Z
       
  • In vitro measurements of velocity and wall shear stress in a novel
           
    • Abstract: Publication date: Available online 4 August 2014
      Source:Medical Engineering & Physics
      Author(s): Foad Kabinejadian , Dhanjoo N. Ghista , Boyang Su , Mercedeh Kaabi Nezhadiana , Leok Poh Chua , Joon Hock Yeo , Hwa Liang Leo
      This study documents the superior hemodynamics of a novel coupled sequential anastomoses (SQA) graft design in comparison with the routine conventional end-to-side (ETS) anastomoses in coronary artery bypass grafts (CABG). The flow fields inside three polydimethylsiloxane (PDMS) models of coronary artery bypass grafts, including the coupled SQA graft design, a conventional ETS anastomosis, and a parallel side-to-side (STS) anastomosis, are investigated under pulsatile flow conditions using particle image velocimetry (PIV). The velocity field and distributions of wall shear stress (WSS) in the models are studied and compared with each other. The measurement results and WSS distributions, computed from the near wall velocity gradients reveal that the novel coupled SQA design provides: (i) a uniform and smooth flow at its ETS anastomosis, without any stagnation point on the artery bed and vortex formation in the heel region of the ETS anastomosis within the coronary artery; (ii) more favorable WSS distribution; and (iii) a spare route for the blood flow to the coronary artery, to avoid re-operation in case of re-stenosis in either of the anastomoses. This in vitro investigation complements the previous computational studies of blood flow in this coupled SQA design, and is another necessary step taken toward the clinical application of this novel design. At this point and prior to the clinical adoption of this novel design, in vivo animal trials are warranted, in order to investigate the biological effects and overall performance of this anastomotic configuration in vivo.


      PubDate: 2014-08-06T02:06:05Z
       
  • Biomechanical evaluation of two commonly used external fixators in the
           treatment of open subtalar dislocation—A finite element analysis
    • Abstract: Publication date: Available online 2 August 2014
      Source:Medical Engineering & Physics
      Author(s): Muhammad Hanif Ramlee , Mohammed Rafiq Abdul Kadir , Malliga Raman Murali , Tunku Kamarul
      Subtalar dislocation is a rare injury caused by high-energy trauma. Current treatment strategies include leg casts, internal fixation and external fixation. Among these, external fixators are the most commonly used as this method is believed to provide better stabilization. However, the biomechanical stability provided by these fixators has not been demonstrated. This biomechanical study compares two commonly used external fixators, i.e. Mitkovic and Delta. CT imaging data were used to reconstruct three-dimensional models of the tibia, fibula, talus, calcaneus, navicular, cuboid, three cuneiforms and five metatarsal bones. The 3D models of the bones and cartilages were then converted into four-noded linear tetrahedral elements, whilst the ligaments were modelled with linear spring elements. Bones and cartilage were idealized as homogeneous, isotropic and linear. To simulate loading during walking, axial loading (70N during the swing and 350N during the stance phase) was applied at the end of diaphyseal tibia. The results demonstrate that the Mitkovic fixator produced greater displacement (peak 3.0mm and 15.6mm) compared to the Delta fixator (peak 0.8mm and 3.9mm), in both the swing and stance phase, respectively. This study demonstrates that the Delta external fixator provides superior stability over the Mitkovic fixator. The Delta fixator may be more effective in treating subtalar dislocation.


      PubDate: 2014-08-06T02:06:05Z
       
  • Representation of fluctuation features in pathological knee joint
           vibroarthrographic signals using kernel density modeling method
    • Abstract: Publication date: Available online 3 August 2014
      Source:Medical Engineering & Physics
      Author(s): Shanshan Yang , Suxian Cai , Fang Zheng , Yunfeng Wu , Kaizhi Liu , Meihong Wu , Quan Zou , Jian Chen
      This article applies advanced signal processing and computational methods to study the subtle fluctuations in knee joint vibroarthrographic (VAG) signals. Two new features are extracted to characterize the fluctuations of VAG signals. The fractal scaling index parameter is computed using the detrended fluctuation analysis algorithm to describe the fluctuations associated with intrinsic correlations in the VAG signal. The averaged envelope amplitude feature measures the difference between the upper and lower envelopes averaged over an entire VAG signal. Statistical analysis with the Kolmogorov–Smirnov test indicates that both of the fractal scaling index (p =0.0001) and averaged envelope amplitude (p =0.0001) features are significantly different between the normal and pathological signal groups. The bivariate Gaussian kernels are utilized for modeling the densities of normal and pathological signals in the two-dimensional feature space. Based on the feature densities estimated, the Bayesian decision rule makes better signal classifications than the least-squares support vector machine, with the overall classification accuracy of 88% and the area of 0.957 under the receiver operating characteristic (ROC) curve. Such VAG signal classification results are better than those reported in the state-of-the-art literature. The fluctuation features of VAG signals developed in the present study can provide useful information on the pathological conditions of degenerative knee joints. Classification results demonstrate the effectiveness of the kernel feature density modeling method for computer-aided VAG signal analysis.


      PubDate: 2014-08-06T02:06:05Z
       
  • Simulation of carbon dioxide insufflation via a diffuser in an open
           surgical wound model
    • Abstract: Publication date: Available online 5 August 2014
      Source:Medical Engineering & Physics
      Author(s): John E. Cater , Jan van der Linden
      Flow within a model surgical opening during insufflation with heated carbon dioxide was studied using computational fluid dynamics. A volume of fluid method was used to simulate the mixture of ambient air and carbon dioxide gas. The negative buoyancy of the carbon dioxide caused it to fill the wound and form a protective layer on the internal surfaces for a range of flow rates, temperatures, and angles of patient inclination. It was observed that the flow remained attached to the surface of the model due to the action of the Coanda effect. A flow rate of 10L/min was sufficient to maintain a warm carbon dioxide barrier for a moderately sized surgical incision for all likely angles of inclination.


      PubDate: 2014-08-06T02:06:05Z
       
  • In vitro dermal and epidermal cellular response to titanium alloy implants
           fabricated with electron beam melting
    • Abstract: Publication date: Available online 28 July 2014
      Source:Medical Engineering & Physics
      Author(s): Jessica Collins Springer , Ola L.A. Harrysson , Denis J. Marcellin-Little , Susan H. Bernacki
      Transdermal osseointegrated prostheses (TOPs) are emerging as an alternative to socket prostheses. Electron beam melting (EBM) is a promising additive manufacturing technology for manufacture of custom, freeform titanium alloy (Ti6Al4V) implants. Skin ongrowth for infection resistance and mechanical stability are critically important to the success of TOP, which can be influenced by material composition and surface characteristics. We assessed viability and proliferation of normal human epidermal keratinocytes (NHEK) and normal human dermal fibroblasts (NHDF) on several Ti6Al4V surfaces: solid polished commercial, solid polished EBM, solid unpolished EBM and porous unpolished EBM. Cell proliferation was evaluated at days 2 and 7 using alamarBlue® and cell viability was analyzed with a fluorescence-based live–dead assay after 1 week. NHDF and NHEK were viable and proliferated on all Ti6Al4V surfaces. NHDF proliferation was highest on commercial and EBM polished surfaces. NHEK was highest on commercial polished surfaces. All EBM Ti6Al4V discs exhibited an acceptable biocompatibility profile compared to solid Ti6Al4V discs from a commercial source for dermal and epidermal cells. EBM may be considered as an option for fabrication of custom transdermal implants.


      PubDate: 2014-08-02T01:52:58Z
       
  • Design and validation of a cadaveric knee joint loading device compatible
           with magnetic resonance imaging and computed tomography
    • Abstract: Publication date: Available online 28 July 2014
      Source:Medical Engineering & Physics
      Author(s): Larry Chen , Karen Gordon , Mark Hurtig
      Purpose Design and validation of a magnetic resonance and computed tomography compatible device capable of applying physiologically relevant muscle forces to cadaveric knee joints with high levels of repeatability and reproducibility. Methods Repeatability and reproducibility were assessed with two porcine stifle joints. Load was applied to joints at full extension, five and 15 degrees of flexion through two cables simulating the lines of action of the quadriceps and hamstrings muscles. Five repeatability and five reproducibility trials were performed at each flexion angle. Standard deviations (SDs) of joint angle and load were recorded. Results For repeatability, the maximum SDs for joint angle were 1.26° (flexion), 1.54° (ab/adduction) and 0.90° (in/external rotation). The maximum SDs for joint load were 4.60N (anterior/posterior), 7.36N (medial/lateral), and 42.6N (axial). For reproducibility, the maximum SDs for joint angle were 0.84° (flexion), 0.66° (ab/adduction) and 0.92° (in/external rotation). The maximum SDs for joint load were 6.40N (anterior/posterior), 11.7N (medial/lateral), and 39.7N (axial). Conclusions This level of repeatability and reproducibility is within intra-subject variability of measured gait kinematics. Therefore, this device is considered to be an effective tool for in vitro testing of knee soft tissue repair.


      PubDate: 2014-08-02T01:52:58Z
       
  • 3D printing of MRI compatible components: Why every MRI research group
           should have a low-budget 3D printer
    • Abstract: Publication date: Available online 1 August 2014
      Source:Medical Engineering & Physics
      Author(s): Karl-Heinz Herrmann , Clemens Gärtner , Daniel Güllmar , Martin Krämer , Jürgen R. Reichenbach
      Purpose To evaluate low budget 3D printing technology to create MRI compatible components. Material and methods A 3D printer is used to create customized MRI compatible components, a loop-coil platform and a multipart mouse fixation. The mouse fixation is custom fit for a dedicated coil and facilitates head fixation with bite bar, anesthetic gas supply and biomonitoring sensors. The mouse fixation was tested in a clinical 3T scanner. Results All parts were successfully printed and proved MR compatible. Both design and printing were accomplished within a few days and the final print results were functional with well defined details and accurate dimensions (Δ < 0.4mm). MR images of the mouse head clearly showed reduced motion artifacts, ghosting and signal loss when using the fixation. Conclusions We have demonstrated that a low budget 3D printer can be used to quickly progress from a concept to a functional device at very low production cost. While 3D printing technology does impose some restrictions on model geometry, additive printing technology can create objects with complex internal structures that can otherwise not be created by using lathe technology. Thus, we consider a 3D printer a valuable asset for MRI research groups.


      PubDate: 2014-08-02T01:52:58Z
       
  • Robust heart sound detection in respiratory sound using LRT with maximum a
           posteriori based online parameter adaptation
    • Abstract: Publication date: Available online 28 July 2014
      Source:Medical Engineering & Physics
      Author(s): Hamed Shamsi , I. Yucel Ozbek
      This paper investigates the utility of a likelihood ratio test (LRT) combined with an efficient adaptation procedure for the purpose of detecting the heart sound (HS) with lung sound and the lung sound only (non-HS) segments in a respiratory signal. The proposed detection method has four main stages: feature extraction, training of the models, detection, and adaptation of the model parameter. In the first stage, the logarithmic energy features are extracted for each frame of respiratory sound. In the second stage, the probabilistic models for HS and non-HS segments are constructed by training Gaussian mixture models (GMMs) with an expectation maximization algorithm in a subject-independent manner, and then the HS and non-HS segments are detected by the results of the LRT based on the GMMs. In the adaptation stage, the subject-independent trained model parameter is modified online using the observed test data to fit the model parameter of the target subject. Experiments were performed on the database from 24 healthy subjects. The experimental results indicate that the proposed heart sound detection algorithm outperforms two well-known heart sound detection methods in terms of the values of the normalized area under the detection error trade-off curve (NAUC), the false negative rate (FNR), and the false positive rate (FPR).


      PubDate: 2014-08-02T01:52:58Z
       
  • Does surface roughness influence the primary stability of acetabular
           cups' A numerical and experimental biomechanical evaluation
    • Abstract: Publication date: Available online 28 July 2014
      Source:Medical Engineering & Physics
      Author(s): Sophie Le Cann , Alexandre Galland , Benoît Rosa , Thomas Le Corroller , Martine Pithioux , Jean-Noël Argenson , Patrick Chabrand , Sébastien Parratte
      Most acetabular cups implanted today are press-fit impacted cementless. Anchorage begins with the primary stability given by insertion of a slightly oversized cup. This primary stability is key to obtaining bone ingrowth and secondary stability. We tested the hypothesis that primary stability of the cup is related to surface roughness of the implant, using both an experimental and a numerical models to analyze how three levels of surface roughness (micro, macro and combined) affect the primary stability of the cup. We also investigated the effect of differences in diameter between the cup and its substrate, and of insertion force, on the cups’ primary stability. The results of our study show that primary stability depends on the surface roughness of the cup. The presence of macro-roughness on the peripheral ring is found to decrease primary stability; there was excessive abrasion of the substrate, damaging it and leading to poor primary stability. Numerical modeling indicates that oversizing the cup compared to its substrate has an impact on primary stability, as has insertion force.


      PubDate: 2014-08-02T01:52:58Z
       
  • Effect of fixation on neovascularization during bone healing
    • Abstract: Publication date: Available online 28 July 2014
      Source:Medical Engineering & Physics
      Author(s): Feng Zhao , Zhilun Zhou , Yang Yan , Zhen Yuan , Guanzhong Yang , Hao Yu , Hao Su , Tao Zhang , Yubo Fan
      Fixation and vascularity after bone fracture are two critical factors for successful healing, and their influences on bone healing have been studied by many researchers. This research aims to obtain three-dimensional (3D) reconstruction images of neovascularization of the soft tissues surrounding the fracture with vascular perfusion and micro-computer tomography (micro-CT) imaging, and to investigate the effect of stable fixation on neovascularization and the pattern of vascularity during the process of bone healing. To accomplish this, 36 Sprague-Dawley (SD) rats underwent mid-shaft transverse osteotomy of the right tibia. Half of them received stable fixation with a newly custom-designed external fixator (FSF, the group of fracture with stable fixation), while the rest received no fixation (FNF, the group of fracture with no fixation). The results indicated that FNF samples had more transversal vascular distribution than FSF samples; FSF samples had more longitudinal vascular distribution than FNF samples; and the spatio-temporal pattern of vascularity in FSF samples was more similar to that in the control group (CON, the group without fracture) than that in FNF samples. At the time of 2 and 4 weeks postoperatively, FNF samples had significantly higher vessel volume ratio (VV/TV), larger vessel number (VN) and higher vessel surface density (VS/TV) than CON samples. At all sacrifice times, FSF samples contained significantly higher VV/TV, VN and VS/TV values compared with FNF samples. In summary, neovascularization and its pattern are obviously influenced by the mechanical fixation. Stable fixation can promote longitudinal vascularity pattern formation, which tends to be similar to the natural vascularity pattern, and this benefits the inter-fragmentary blood fluid connectivity during bone healing process.


      PubDate: 2014-08-02T01:52:58Z
       
  • Markerless motion capture can provide reliable 3D gait kinematics in the
           sagittal and frontal plane
    • Abstract: Publication date: Available online 30 July 2014
      Source:Medical Engineering & Physics
      Author(s): Martin Sandau , Henrik Koblauch , Thomas B. Moeslund , Henrik Aanæs , Tine Alkjær , Erik B. Simonsen
      Estimating 3D joint rotations in the lower extremities accurately and reliably remains unresolved in markerless motion capture, despite extensive studies in the past decades. The main problems have been ascribed to the limited accuracy of the 3D reconstructions. Accordingly, the purpose of the present study was to develop a new approach based on highly detailed 3D reconstructions in combination with a translational and rotational unconstrained articulated model. The highly detailed 3D reconstructions were synthesized from an eight camera setup using a stereo vision approach. The subject specific articulated model was generated with three rotational and three translational degrees of freedom for each limb segment and without any constraints to the range of motion. This approach was tested on 3D gait analysis and compared to a marker based method. The experiment included ten healthy subjects in whom hip, knee and ankle joint were analysed. Flexion/extension angles as well as hip abduction/adduction closely resembled those obtained from the marker based system. However, the internal/external rotations, knee abduction/adduction and ankle inversion/eversion were less reliable.


      PubDate: 2014-08-02T01:52:58Z
       
  • Effect of an exclusion range of jaw movement data from the intercuspal
           positionon the estimation of the kinematic axis point
    • Abstract: Publication date: Available online 19 July 2014
      Source:Medical Engineering & Physics
      Author(s): Shuji Shigemoto , Nobuyuki Bando , Keisuke Nishigawa , Yoshitaka Suzuki , Toyoko Tajima , Kazuo Okura , Yoshizo Matsuka
      In patients who have lost natural occlusal contacts, the centric relation is usually estimated based on several anatomical factors such as the temporomandibular joint and masticatory muscles except dental arch. The clinical procedure to record the centric relation often depends on the clinician's expertise and technique; an objective method to determine proper occlusal position is desirable. The kinematic axis point (KAP) is kinematically estimated from sagittal movements and is an ideal posterior reference point that is used in dental articulators for reproducing jaw movement. Occlusal registration using the KAP may serve as a definite objective technique. The aim of this study is to investigate the effect of the exclusion range of sagittal jaw movement data from the intercuspal position (ICP) on the estimation of the KAP. The complete and incomplete sagittal border movement data of dentate subjects were used to estimate the KAPs. The locations of the estimated KAPs were compared. The results indicate that the incomplete sagittal border jaw movement data set does not include data points inside a 7mm distance from the ICP can be used for estimation of the KAP. In conclusion, the sagittal border jaw movement data around the ICP is not indispensable in the valid identification of the KAP.


      PubDate: 2014-07-28T01:17:01Z
       
  • Biomechanical evaluation of bending strength of spinal pedicle screws,
           including cylindrical, conical, dual core and double dual core designs
           using numerical simulations and mechanical tests
    • Abstract: Publication date: Available online 21 July 2014
      Source:Medical Engineering & Physics
      Author(s): Yongyut Amaritsakul , Ching-Kong Chao , Jinn Lin
      Pedicle screws are used for treating several types of spinal injuries. Although several commercial versions are presently available, they are mostly either fully cylindrical or fully conical. In this study, the bending strengths of seven types of commercial pedicle screws and a newly designed double dual core screw were evaluated by finite element analyses and biomechanical tests. All the screws had an outer diameter of 7mm, and the biomechanical test consisted of a cantilever bending test in which a vertical point load was applied using a level arm of 45mm. The boundary and loading conditions of the biomechanical tests were applied to the model used for the finite element analyses. The results showed that only the conical screws with fixed outer diameter and the new double dual core screw could withstand 1,000,000 cycles of a 50–500N cyclic load. The new screw, however, exhibited lower stiffness than the conical screw, indicating that it could afford patients more flexible movements. Moreover, the new screw produced a level of stability comparable to that of the conical screw, and it was also significantly stronger than the other screws. The finite element analysis further revealed that the point of maximum tensile stress in the screw model was comparable to the point at which fracture occurred during the fatigue test.


      PubDate: 2014-07-28T01:17:01Z
       
  • Predicting flow in aortic dissection: Comparison of computational model
           with PC-MRI velocity measurements
    • Abstract: Publication date: Available online 26 July 2014
      Source:Medical Engineering & Physics
      Author(s): Z. Cheng , C. Juli , N.B. Wood , R.G.J. Gibbs , X.Y. Xu
      Aortic dissection is a life-threatening process in which the weakened wall develops a tear, causing separation of wall layers. The dissected layers separate the original true aortic lumen and a newly created false lumen. If untreated, the condition can be fatal. Flow rate in the false lumen is a key feature for false lumen patency, which has been regarded as one of the most important predictors of adverse early and later outcomes. Detailed flow analysis in the dissected aorta may assist vascular surgeons in making treatment decisions, but computational models to simulate flow in aortic dissections often involve several assumptions. The purpose of this study is to assess the computational models adopted in previous studies by comparison with in vivo velocity data obtained by means of phase-contrast magnetic resonance imaging (PC-MRI). Aortic dissection geometry was reconstructed from computed tomography (CT) images, while PC-MRI velocity data were used to define inflow conditions and to provide distal velocity components for comparison with the simulation results. The computational fluid dynamics (CFD) simulation incorporated a laminar–turbulent transition model, which is necessary for adequate flow simulation in aortic conditions. Velocity contours from PC-MRI and CFD in the two lumens at the distal plane were compared at four representative time points in the pulse cycle. The computational model successfully captured the complex regions of flow reversal and recirculation qualitatively, although quantitative differences exist. With a rigid wall assumption and exclusion of arch branches, the CFD model over-predicted the false lumen flow rate by 25% at peak systole. Nevertheless, an overall good agreement was achieved, confirming the physiological relevance and validity of the computational model for type B aortic dissection with a relatively stiff dissection flap.


      PubDate: 2014-07-28T01:17:01Z
       
  • An in vitro investigation of the influence of stenosis severity on the
           flow in the ascending aorta
    • Abstract: Publication date: Available online 25 July 2014
      Source:Medical Engineering & Physics
      Author(s): Utku Gülan , Beat Lüthi , Markus Holzner , Alex Liberzon , Arkady Tsinober , Wolfgang Kinzelbach
      Cardiovascular diseases can lead to abnormal blood flows, some of which are linked to hemolysis and thrombus formation. Abnormal turbulent flows of blood in the vessels with stenosis create strong shear stresses on blood elements and may cause blood cell destruction or platelet activation. We implemented a Lagrangian (following the fluid elements) measurement technique of three dimensional particle tracking velocimetry that provides insight on the evolution of viscous and turbulent stresses along blood element trajectories. We apply this method to study a pulsatile flow in a compliant phantom of an aorta and compare the results in three cases: the reference case (called “healthy” case), and two cases of abnormal flows due to mild and severe stenosis, respectively. The chosen conditions can mimic a clinical application of an abnormal flow due to a calcific valve. We estimate the effect of aortic stenosis on the kinetic energy of the mean flow and the turbulent kinetic energy, which increases about two orders of magnitude as compared with the healthy flow case. Measuring the total flow stress acting on a moving fluid element that incorporates viscous stresses and the apparent turbulent-induced stresses (the so-called Reynolds stresses) we find out similar increase of the stresses with the increased severity of the stenosis. Furthermore, these unique Lagrangian measurements provide full acceleration and, consequently, the forces acting on the blood elements that are estimated to reach the level that can considerably deform red blood cells. These forces are strong and abrupt due to the contribution of the turbulent fluctuations which is much stronger than the typically measured phase-averaged values.


      PubDate: 2014-07-28T01:17:01Z
       
  • Changes in dissipated energy and contact pressure after osteochondral
           graft transplantation
    • Abstract: Publication date: Available online 25 July 2014
      Source:Medical Engineering & Physics
      Author(s): Evgenij Bobrowitsch , Andrea Lorenz , Johanna Jörg , Ulf G. Leichtle , Nikolaus Wülker , Christian Walter
      Osteochondral autologous transplantation is frequently used to repair small cartilage defects. Incongruence between the osteochondral graft surface and the adjacent cartilage leads to changed friction and contact pressure. The present study wanted to analyze the differences between intact and surgically treated cartilage surface in respect to contact pressure and frictional characteristic (dissipated energy). Six ovine carpometacarpal joints were used in the present study. Dissipated energy during instrumentally controlled joint movement as well as static contact pressure were measured in different cartilage states (intact, defect, deep-, flush-, high-implanted osteochondral graft and cartilage failure simulation on a high-implanted graft). The best contact area restoration was observed after the flush implantation. However, the dissipated energy measurements did not reveal an advantage of the flush implantation compared to the defect and deep-implanted graft states. The high-implanted graft was associated with a significant increase of the mean contact pressure and decrease of the contact area but the dissipated energy was on the level of intact cartilage in contrast to other treatments where the dissipated energy was significantly higher as in the intact state. However the cartilage failure simulation on the high-implanted graft showed the highest increase of the dissipated energy.


      PubDate: 2014-07-28T01:17:01Z
       
  • Baseline drift removal and denoising of MCG data using EEMD: Role of noise
           amplitude and the thresholding effect
    • Abstract: Publication date: Available online 26 July 2014
      Source:Medical Engineering & Physics
      Author(s): N. Mariyappa , S. Sengottuvel , C. Parasakthi , K. Gireesan , M.P. Janawadkar , T.S. Radhakrishnan , C.S. Sundar
      We adopt the Ensemble Empirical Mode Decomposition (EEMD) method, with an appropriate thresholding on the Intrinsic Mode Functions (IMFs), to denoise the magnetocardiography (MCG) signal. To this end, we discuss the two associated problems that relate to: (i) the amplitude of noise added to the observed signal in the EEMD method with a view to prevent mode mixing and (ii) the effect of direct thresholding that causes discontinuities in the reconstructed denoised signal. We then denoise the MCG signals, having various signal-to-noise ratios, by using this method and compare the results with those obtained by the standard wavelet based denoising method. We also address the problem of eliminating the high frequency baseline drift such as the sudden and discontinuous changes in the baseline of the experimentally measured MCG signal using the EEMD based method. We show that the EEMD method used for denoising and the elimination of baseline drift is superior in performance to other standard methods such as wavelet based techniques and Independent Component Analysis (ICA).


      PubDate: 2014-07-28T01:17:01Z
       
  • Screening of obstructive sleep apnea with empirical mode decomposition of
           pulse oximetry
    • Abstract: Publication date: August 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 8
      Author(s): Gastón Schlotthauer , Leandro E. Di Persia , Luis D. Larrateguy , Diego H. Milone
      Detection of desaturations on the pulse oximetry signal is of great importance for the diagnosis of sleep apneas. Using the counting of desaturations, an index can be built to help in the diagnosis of severe cases of obstructive sleep apnea–hypopnea syndrome. It is important to have automatic detection methods that allows the screening for this syndrome, reducing the need of the expensive polysomnography based studies. In this paper a novel recognition method based on the empirical mode decomposition of the pulse oximetry signal is proposed. The desaturations produce a very specific wave pattern that is extracted in the modes of the decomposition. Using this information, a detector based on properly selected thresholds and a set of simple rules is built. The oxygen desaturation index constructed from these detections produces a detector for obstructive sleep apnea–hypopnea syndrome with high sensitivity (0.838) and specificity (0.855) and yields better results than standard desaturation detection approaches.


      PubDate: 2014-07-28T01:17:01Z
       
  • Computational fluid dynamics analysis of balloon-expandable coronary
           stents: Influence of stent and vessel deformation
    • Abstract: Publication date: August 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 8
      Author(s): David M. Martin , Eoin A. Murphy , Fergal J. Boyle
      In many computational fluid dynamics (CFD) studies of stented vessel haemodynamics, the geometry of the stented vessel is described using non-deformed (NDF) geometrical models. These NDF models neglect complex physical features, such as stent and vessel deformation, which may have a major impact on the haemodynamic environment in stented coronary arteries. In this study, CFD analyses were carried out to simulate pulsatile flow conditions in both NDF and realistically-deformed (RDF) models of three stented coronary arteries. While the NDF models were completely idealised, the RDF models were obtained from nonlinear structural analyses and accounted for both stent and vessel deformation. Following the completion of the CFD analyses, major differences were observed in the time-averaged wall shear stress (TAWSS), time-averaged wall shear stress gradient (TAWSSG) and oscillatory shear index (OSI) distributions predicted on the luminal surface of the artery for the NDF and RDF models. Specifically, the inclusion of stent and vessel deformation in the CFD analyses resulted in a 32%, 30% and 31% increase in the area-weighted mean TAWSS, a 3%, 7% and 16% increase in the area-weighted mean TAWSSG and a 21%, 13% and 21% decrease in the area-weighted mean OSI for Stents A, B and C, respectively. These results suggest that stent and vessel deformation are likely to have a major impact on the haemodynamic environment in stented coronary arteries. In light of this observation, it is recommended that these features are considered in future CFD studies of stented vessel haemodynamics.


      PubDate: 2014-07-28T01:17:01Z
       
  • Characterization of a CMOS sensing core for ultra-miniature wireless
           implantable temperature sensors with application to cryomedicine
    • Abstract: Publication date: Available online 4 July 2014
      Source:Medical Engineering & Physics
      Author(s): Ahmad Khairi , Chandrajit Thaokar , Gary Fedder , Jeyanandh Paramesh , Yoed Rabin
      In effort to improve thermal control in minimally invasive cryosurgery, the concept of a miniature, wireless, implantable sensing unit has been developed recently. The sensing unit integrates a wireless power delivery mechanism, wireless communication means, and a sensing core—the subject matter of the current study. The current study presents a CMOS ultra-miniature PTAT temperature sensing core and focuses on design principles, fabrication of a proof-of-concept, and characterization in a cryogenic environment. For this purpose, a 100μm×400μm sensing core prototype has been fabricated using a 130nm CMOS process. The senor has shown to operate between −180°C and room temperature, to consume power of less than 1μW, and to have an uncertainty range of 1.4°C and non-linearity of 1.1%. Results of this study suggest that the sensing core is ready to be integrated in the sensing unit, where system integration is the subject matter of a parallel effort.


      PubDate: 2014-07-28T01:17:01Z
       
  • An MRI compatible loading device for the reconstruction of clinically
           relevant plantar pressure distributions and loading scenarios of the
           forefoot
    • Abstract: Publication date: Available online 7 July 2014
      Source:Medical Engineering & Physics
      Author(s): Panagiotis E. Chatzistergos , Roozbeh Naemi , Nachiappan Chockalingam
      The purpose of this study is to demonstrate a new MRI compatible loading device capable of reconstructing realistic loading scenarios of the human foot for research in the field of foot biomechanics. This device has two different configurations: one used to compress the forefoot and one to bend the metatarsophalangeal joints. Required plantar pressure distribution under the metatarsal heads can be achieved by modifying the distribution of the dorsally applied forces. To validate the device, subject-specific plantar pressures were measured and then reconstructed using the device. For quiet stance the peak pressure reconstruction error was 3% while for mid-stance phase of gait it was 8%. The device was also used to measure the passive bending stiffness of the metatarsophalangeal joints of one subject with low intra-subject variability. A series of preliminary MRI scans confirmed that the loading device can be used to produce static weight-bearing images of the foot (voxel size: 0.23mm×0.23mm×1.00mm). The results indicate that the device presented here can accurately reconstruct subject specific plantar pressure distributions and measure the foot's metatarsophalangeal passive stiffness. Possible future applications include the validation of finite element models, the investigation of the relationship between plantar pressure and internal stresses/strains and the study of the foot's inter-segmental passive stiffness.


      PubDate: 2014-07-28T01:17:01Z
       
  • Fast computation of voxel-level brain connectivity maps from resting-state
           functional MRI using l1-norm as approximation of Pearson's temporal
           correlation: Proof-of-concept and example vector hardware implementation
    • Abstract: Publication date: Available online 8 July 2014
      Source:Medical Engineering & Physics
      Author(s): Ludovico Minati , Domenico Zacà , Ludovico D’Incerti , Jorge Jovicich
      An outstanding issue in graph-based analysis of resting-state functional MRI is choice of network nodes. Individual consideration of entire brain voxels may represent a less biased approach than parcellating the cortex according to pre-determined atlases, but entails establishing connectedness for 19–111 links, with often prohibitive computational cost. Using a representative Human Connectome Project dataset, we show that, following appropriate time-series normalization, it may be possible to accelerate connectivity determination replacing Pearson correlation with l1-norm. Even though the adjacency matrices derived from correlation coefficients and l1-norms are not identical, their similarity is high. Further, we describe and provide in full an example vector hardware implementation of l1-norm on an array of 4096 zero instruction-set processors. Calculation times <1000s are attainable, removing the major deterrent to voxel-based resting-sate network mapping and revealing fine-grained node degree heterogeneity. L1-norm should be given consideration as a substitute for correlation in very high-density resting-state functional connectivity analyses.


      PubDate: 2014-07-28T01:17:01Z
       
  • A tissue stabilization device for MRI-guided breast biopsy
    • Abstract: Publication date: Available online 8 July 2014
      Source:Medical Engineering & Physics
      Author(s): Alexandru Patriciu , Maggie Chen , Behzad Iranpanah , Shahin Sirouspour
      We present a breast tissue stabilization device that can be used in magnetic resonance imaging-guided biopsy. The device employs adjustable support plates with an optimized geometry to minimize the biopsy target displacement using smaller compression than the conventional parallel plates approach. It is expected that the reduced compression will cause less patient discomfort and improve image quality by enhancing the contrast intake. Precomputed optimal positions of the stabilization plates for a given biopsy target location are provided in a look-up table. The results of several experiments with a prototype of the device carried out on chicken breast tissue demonstrate the effectiveness of the new design when compared with conventional stabilization methods. The proposed stabilization mechanism provides excellent flexibility in selecting the needle insertion point and can be used in manual as well as robot-assisted biopsy procedures.


      PubDate: 2014-07-28T01:17:01Z
       
  • Soft wearable contact lens sensor for continuous intraocular pressure
           monitoring
    • Abstract: Publication date: Available online 14 July 2014
      Source:Medical Engineering & Physics
      Author(s): Guo-Zhen Chen , Ion-Seng Chan , Leo K.K. Leung , David C.C. Lam
      Intraocular pressure (IOP) is a primary indicator of glaucoma, but measurements from a single visit to the clinic miss the peak IOP that may occur at night during sleep. A soft chipless contact lens sensor that allows the IOP to be monitored throughout the day and at night is developed in this study. A resonance circuit composed of a thin film capacitor coupled with a sensing coil that can sense corneal curvature deformation is designed, fabricated and embedded into a soft contact lens. The resonance frequency of the sensor is designed to vary with the lens curvature as it changes with the IOP. The frequency responses and the ability of the sensor to track IOP cycles were tested using a silicone rubber model eye. The results showed that the sensor has excellent linearity with a frequency response of ∼8kHz/mmHg, and the sensor can accurately track fluctuating IOP. These results showed that the chipless contact lens sensor can potentially be used to monitor IOP to improve diagnosis accuracy and treatment of glaucoma.


      PubDate: 2014-07-28T01:17:01Z
       
  • Design of tissue engineering scaffolds based on hyperbolic surfaces:
           Structural numerical evaluation
    • Abstract: Publication date: August 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 8
      Author(s): Henrique A. Almeida , Paulo J. Bártolo
      Tissue engineering represents a new field aiming at developing biological substitutes to restore, maintain, or improve tissue functions. In this approach, scaffolds provide a temporary mechanical and vascular support for tissue regeneration while tissue in-growth is being formed. These scaffolds must be biocompatible, biodegradable, with appropriate porosity, pore structure and distribution, and optimal vascularization with both surface and structural compatibility. The challenge is to establish a proper balance between porosity and mechanical performance of scaffolds. This work investigates the use of two different types of triple periodic minimal surfaces, Schwarz and Schoen, in order to design better biomimetic scaffolds with high surface-to-volume ratio, high porosity and good mechanical properties. The mechanical behaviour of these structures is assessed through the finite element method software Abaqus. The effect of two parametric parameters (thickness and surface radius) is also evaluated regarding its porosity and mechanical behaviour.


      PubDate: 2014-07-28T01:17:01Z
       
  • Early detection of abnormal left ventricular relaxation in acute
           myocardial ischemia with a quadratic model
    • Abstract: Publication date: Available online 16 July 2014
      Source:Medical Engineering & Physics
      Author(s): Philippe Morimont , Antoine Pironet , Thomas Desaive , Geoffrey Chase , Bernard Lambermont
      Aims The time constant of left ventricular (LV) relaxation derived from a monoexponential model is widely used as an index of LV relaxation rate, although this model does not reflect the non-uniformity of ventricular relaxation. This study investigates whether the relaxation curve can be better fitted with a “quadratic” model than with the “conventional” monoexponential model and if changes in the LV relaxation waveform due to acute myocardial ischemia could be better detected with the quadratic model. Methods and results Isovolumic relaxation was assessed with quadratic and conventional models during acute myocardial ischemia performed in 6 anesthetized pigs. Mathematical development indicates that one parameter (Tq) of the quadratic model reflects the rate of LV relaxation, while the second parameter (K) modifies the shape of the relaxation curve. Analysis of experimental data obtained in anesthetized pigs showed that the shape of LV relaxation consistently deviates from the conventional monoexponential decay. During the early phase of acute myocardial ischemia, the rate and non-uniformity of LV relaxation, assessed with the quadratic function, were significantly enhanced. Tq increased by 16% (p <0.001) and K increased by 12% (p <0.001) within 30 and 60min, respectively, after left anterior descending (LAD) coronary artery occlusion. However, no significant changes were observed with the conventional monoexponential decay within 60min of ischemia. Conclusions The quadratic model better fits LV isovolumic relaxation than the monoexponential model and can detect early changes in relaxation due to acute myocardial ischemia that are not detectable with conventional methods.


      PubDate: 2014-07-28T01:17:01Z
       
  • Low torque levels can initiate a removal of the passivation layer and
           cause fretting in modular hip stems
    • Abstract: Publication date: Available online 19 July 2014
      Source:Medical Engineering & Physics
      Author(s): S.Y. Jauch , L.G. Coles , L.V. Ng , A.W. Miles , H.S. Gill
      Taper connections of modular hip prostheses are at risk of fretting and corrosion, which can result in reduced implant survival. The purpose of this study was to identify the minimum torque required to initiate a removal of the passivation layer at the taper interface as a function of assembly force and axial load. Titanium stems and cobalt–chromium heads were assembled with peak impaction forces of 4.5kN or 6.0kN and then mounted on a materials testing machine whilst immersed in Ringer's solution. The stems were subjected to a static axial load (1kN or 3kN) along the taper axis. After a period of equilibration, a torque ramp from 0 to 15Nm was manually applied and the galvanic potential was continuously recorded. Prostheses assembled with a force of 6kN required a significantly higher torque to start a removal of the passivation layer compared to those assembled with 4.5kN (7.23±0.55Nm vs. 3.92±0.97Nm, p =0.029). No influence of the axial load on the fretting behaviour was found (p =0.486). The torque levels, which were demonstrated to initiate surface damage under either assembly force, can be readily reached during activities of daily living. The damage will be intensified in situations of large weight and high activity of the patient or malpositioning of the prosthesis.


      PubDate: 2014-07-28T01:17:01Z
       
  • Editorial Board
    • Abstract: Publication date: August 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 8




      PubDate: 2014-07-28T01:17:01Z
       
  • The effects of implant angulation on the resonance frequency of a dental
           implant
    • Abstract: Publication date: August 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 8
      Author(s): R. Harirforoush , S. Arzanpour , B. Chehroudi
      Dental implants are ideally placed in an orientation that allows vertical transfer of occlusal forces along their long axis. Nevertheless, optimal situations for implant placement are seldom encountered resulting in implants placement in angulated positions, which may affect their long-term success. The resonance frequency (RF) is an objective tool used to monitor stability of the implant tissue integration; however, little is known of the effect of the implant orientation in bone on the RF and its potential significance. The purpose of this research was to determine the relation between the dental implant orientation and the corresponding RF of implant. Three-dimensional (3D) modelling software was used to construct a 3D model of a pig mandible from computed tomography (CT) images. The RF of the implant was analysed using finite element (FE) modal analysis in software ANSYS (v.12). In addition, a cubical model was also developed in MIMICS to investigate the parameters affecting the relationship between RF and implant orientation in a simplified environment. The orientation angle was increased from 0 to 10 degrees in 1 degree increments and the resulting RF was analysed using correlation analysis and one-way ANOVA. Our analysis illustrated that the RF fluctuation following altering implant orientation was strongly correlated (r =0.97) with the contacting cortical to cancellous bone ratio (CCBR) at the implant interface. The most extreme RF change (from 9.81kHz to 10.07kHz) occurred when the implant was moved 0.5mm in positive z-direction, which resulted in the maximum change of CCBR from 52.9 to 54.8.


      PubDate: 2014-07-28T01:17:01Z
       
  • Prediction of structural failure of tibial bone models under physiological
           loads: Effect of CT density–modulus relationships
    • Abstract: Publication date: Available online 3 June 2014
      Source:Medical Engineering & Physics
      Author(s): Mahmut Tuncer , Ulrich N. Hansen , Andrew A. Amis
      Although finite element (FE) models can provide distinct benefits in understanding knee biomechanics, in particular the response of the knee to implants, their usefulness is limited by the modelling assumptions and input parameters. This study highlights the uncertainty of material input parameters derived from the literature and its limitation on the accuracy and usefulness of FE models of the tibia. An FE model of the intact human knee and a database of knee forces (muscles, ligaments and medial and lateral tibio-femoral contacts) were developed for walking and stair-descent activities. Ten models were constructed from ten different combinations of apparent bone density to elastic modulus material property relationships, published in the literature. Some of the published material property relationships led to predictions of bone strains in the proximal tibia which exceeded published failure criteria under loads imposed by normal activities. These relationships appear not to be applicable for the human tibia. There is a large discrepancy in proposed relationships that cover the cancellous bone density range. For FE models of the human tibia, the material relationship proposed by Morgan et al., which assumed species and anatomic site dependence, produced the most believable results for cancellous bone. In addition to casting doubt on the use of some of the published density–modulus relationships for analysis of the human proximal tibia, this study highlights the need for further experimental work to characterise the behaviour of bone with intermediate densities.


      PubDate: 2014-06-10T18:38:57Z
       
  • Evaluation of a CT-based technique to measure the transfer accuracy of a
           virtually planned osteotomy
    • Abstract: Publication date: Available online 6 June 2014
      Source:Medical Engineering & Physics
      Author(s): J.G.G. Dobbe , A.J. Kievit , M.U. Schafroth , L. Blankevoort , G.J. Streekstra
      Accurate transfer of a preoperatively planned osteotomy plane to the bone is of significance for corrective surgery, tumor resection, implant positioning and evaluation of new osteotomy techniques. Methods for comparing a preoperatively planned osteotomy plane with a surgical cut exist but the accuracy of these techniques are either limited or unknown. This paper proposes and evaluates a CT-based technique that enables comparing virtual with actual osteotomy planes. The methodological accuracy and reproducibility of the technique is evaluated using CT-derived volume data of a cadaver limb, which serves to plan TKA osteotomies in 3-D space and to simulate perfect osteotomies not hampered by surgical errors. The methodological variability of the technique is further investigated with repeated CT scans after actual osteotomy surgery of the same cadaver specimen. Plane displacement (d err ) and angulation errors in the sagittal and coronal plane (β err , γ err ) are measured with high accuracy and reproducibility (d err =−0.11±0.06mm; β err =0.08±0.04°, γ err =−0.03±0.03°). The proposed method for evaluating an osteotomy plane position and orientation has a high intrinsic accuracy and reproducibility. The method can be of great value for measuring the transfer accuracy of new techniques for positioning and orienting a surgical cut in 3-D space.


      PubDate: 2014-06-10T18:38:57Z
       
  • A viscoelastic poromechanical model of the knee joint in large compression
    • Abstract: Publication date: Available online 2 June 2014
      Source:Medical Engineering & Physics
      Author(s): M. Kazemi , L.P. Li
      The elastic response of the knee joint in various loading and pathological conditions has been investigated using anatomically accurate geometry. However, it is still challenging to predict the poromechanical response of the knee in realistic loading conditions. In the present study, a viscoelastic, poromechanical model of the knee joint was developed for soft tissues undergoing large deformation. Cartilages and menisci were modeled as fibril-reinforced porous materials and ligaments were considered as fibril-reinforced hyperelastic solids. Quasi-linear viscoelasticty was formulated for the collagen network of these tissues and nearly incompressible Neo-Hookean hyperelasticity was used for the non-fibrillar matrix. The constitutive model was coded with a user defined FORTRAN subroutine, in order to use ABAQUS for the finite element analysis. Creep and stress relaxation were investigated with large compression of the knee in full extension. The contact pressure distributions were found similar in creep and stress relaxation. However, the load transfer in the joint was completely different in these two loading scenarios. During creep, the contact pressure between cartilages decreased but the pressure between cartilage and meniscus increased with time. This led to a gradual transfer of some loading from the central part of cartilages to menisci. During stress relaxation, however, both contact pressures decreased monotonically.


      PubDate: 2014-06-10T18:38:57Z
       
  • In vivo application of an optical segment tracking approach for bone
           loading regimes recording in humans: A reliability study
    • Abstract: Publication date: Available online 3 June 2014
      Source:Medical Engineering & Physics
      Author(s): Peng-Fei Yang , Maximilian Sanno , Bergita Ganse , Timmo Koy , Gert-Peter Brüggemann , Lars Peter Müller , Jörn Rittweger
      This paper demonstrates an optical segment tracking (OST) approach for assessing the in vivo bone loading regimes in humans. The relative movement between retro-reflective marker clusters affixed to the tibia cortex by bone screws was tracked and expressed as tibia loading regimes in terms of segment deformation. Stable in vivo fixation of bone screws was tested by assessing the resonance frequency of the screw-marker structure and the relative marker position changes after hopping and jumping. Tibia deformation was recorded during squatting exercises to demonstrate the reliability of the OST approach. Results indicated that the resonance frequencies remain unchanged prior to and after all exercises. The changes of Cardan angle between marker clusters induced by the exercises were rather minor, maximally 0.06°. The reproducibility of the deformation angles during squatting remained small (0.04°/m–0.65°/m). Most importantly, all surgical and testing procedures were well tolerated. The OST method promises to bring more insights of the mechanical loading acting on bone than in the past.


      PubDate: 2014-06-10T18:38:57Z
       
  • Validation of a numerical FSI simulation of an aortic BMHV by in vitro PIV
           experiments
    • Abstract: Publication date: Available online 10 June 2014
      Source:Medical Engineering & Physics
      Author(s): S. Annerel , T. Claessens , J. Degroote , P. Segers , J. Vierendeels
      In this paper, a validation of a recently developed fluid–structure interaction (FSI) coupling algorithm to simulate numerically the dynamics of an aortic bileaflet mechanical heart valve (BMHV) is performed. This validation is done by comparing the numerical simulation results with in vitro experiments. For the in vitro experiments, the leaflet kinematics and flow fields are obtained via the particle image velocimetry (PIV) technique. Subsequently, the same case is numerically simulated by the coupling algorithm and the resulting leaflet kinematics and flow fields are obtained. Finally, the results are compared, revealing great similarity in leaflet motion and flow fields between the numerical simulation and the experimental test. Therefore, it is concluded that the developed algorithm is able to capture very accurately all the major leaflet kinematics and dynamics and can be used to study and optimize the design of BMHVs.


      PubDate: 2014-06-10T18:38:57Z
       
  • Automation of a portable extracorporeal circulatory support system with
           adaptive fuzzy controllers
    • Abstract: Publication date: Available online 2 June 2014
      Source:Medical Engineering & Physics
      Author(s): A. Mendoza García , M. Krane , B. Baumgartner , N. Sprunk , U. Schreiber , S. Eichhorn , R. Lange , A. Knoll
      The presented work relates to the procedure followed for the automation of a portable extracorporeal circulatory support system. Such a device may help increase the chances of survival after suffering from cardiogenic shock outside the hospital, additionally a controller can provide of optimal organ perfusion, while reducing the workload of the operator. Animal experiments were carried out for the acquisition of haemodynamic behaviour of the body under extracorporeal circulation. A mathematical model was constructed based on the experimental data, including a cardiovascular model, gas exchange and the administration of medication. As the base of the controller fuzzy logic was used allowing the easy integration of knowledge from trained perfusionists, an adaptive mechanism was included to adapt to the patient's individual response. Initial simulations show the effectiveness of the controller and the improvements of perfusion after adaptation.


      PubDate: 2014-06-03T12:08:17Z
       
  • Bioelectric signal detrending using smoothness prior approach
    • Abstract: Publication date: Available online 2 June 2014
      Source:Medical Engineering & Physics
      Author(s): Fan Zhang , Shixiong Chen , Haoshi Zhang , Xiufeng Zhang , Guanglin Li
      Bioelectric signals such as electromyogram (EMG) and electrocardiogram (ECG) are often affected by various low-frequency trending interferences. It is critical to remove these interferences from the recordings so that the critical features of the bioelectric signals could be clearly observed. In this study, an advanced method based on smoothness prior approach (SPA) was proposed to solve this problem. EMG and ECG signals from both the MIT-BIH database and the experiments were employed to evaluate the detrending performance of the proposed method. For comparison purposes, a conventional high-pass Butterworth filter was also used for the detrending of the EMG and ECG signals. Two numerical measures, the correlation coefficient (CC) and root mean square error (RMSE) between the clean data and the detrended data, were calculated to evaluate the detrending performance. The results showed that the proposed SPA method outperformed the high-pass filtering method in reducing various kinds of trending interferences and preserving the desired frequency contents of the EMG and ECG signals. The study suggested that the SPA method might be a promising approach in detrending bioelectric signals.


      PubDate: 2014-06-03T12:08:17Z
       
  • A new paradigm of electrical stimulation to enhance sensory neural
           function
    • Abstract: Publication date: Available online 2 June 2014
      Source:Medical Engineering & Physics
      Author(s): Paul P. Breen , Gearóid ÓLaighin , Caroline McIntosh , Sean F. Dinneen , Leo R. Quinlan , Jorge M. Serrador
      The ability to improve peripheral neural transmission would have significant therapeutic potential in medicine. A technology of this kind could be used to restore and/or enhance sensory function in individuals with depressed sensory function, such as older adults or patients with peripheral neuropathies. The goal of this study was to investigate if a new paradigm of subsensory electrical noise stimulation enhances somatosensory function. Vibration (50Hz) was applied with a Neurothesiometer to the plantar aspect of the foot in the presence or absence of subsensory electrical noise (1/f type). The noise was applied at a proximal site, on a defined region of the tibial nerve path above the ankle. Vibration perception thresholds (VPT) of younger adults were measured in control and experimental conditions, in the absence or presence of noise respectively. An improvement of ∼16% in VPT was found in the presence of noise. These are the first data to demonstrate that modulation of axonal transmission with externally applied electrical noise improves perception of tactile stimuli in humans.


      PubDate: 2014-06-03T12:08:17Z
       
  • Non-intrusive real-time breathing pattern detection and classification for
           automatic abdominal functional electrical stimulation
    • Abstract: Publication date: Available online 2 June 2014
      Source:Medical Engineering & Physics
      Author(s): E.J. McCaughey , A.J. McLachlan , H. Gollee
      Abdominal Functional Electrical Stimulation (AFES) has been shown to improve the respiratory function of people with tetraplegia. The effectiveness of AFES can be enhanced by using different stimulation parameters for quiet breathing and coughing. The signal from a spirometer, coupled with a facemask, has previously been used to differentiate between these breath types. In this study, the suitability of less intrusive sensors was investigated with able-bodied volunteers. Signals from two respiratory effort belts, positioned around the chest and the abdomen, were used with a Support Vector Machine (SVM) algorithm, trained on a participant by participant basis, to classify, in real-time, respiratory activity as either quiet breathing or coughing. This was compared with the classification accuracy achieved using a spirometer signal and an SVM. The signal from the belt positioned around the chest provided an acceptable classification performance compared to the signal from a spirometer (mean cough (c) and quiet breath (q) sensitivity (Se) of Se c =92.9% and Se q =96.1% vs. Se c =90.7% and Se q =98.9%). The abdominal belt and a combination of both belt signals resulted in lower classification accuracy. We suggest that this novel SVM classification algorithm, combined with a respiratory effort belt, could be incorporated into an automatic AFES device, designed to improve the respiratory function of the tetraplegic population.


      PubDate: 2014-06-03T12:08:17Z
       
  • Influence of 3D QCT scan protocol on the QCT-based finite element models
           of human vertebral cancellous bone
    • Abstract: Publication date: Available online 2 June 2014
      Source:Medical Engineering & Physics
      Author(s): Yongtao Lu , Klaus Engelke , Klaus Püschel , Michael M. Morlock , Gerd Huber
      Quantitative computed tomography (QCT)-based finite element (FE) models provide a better prediction of vertebral strength than dual-energy X-ray absorptiometry. However, FE models are often created from datasets acquired at different CT scan protocols and it is unclear whether this influences the FE results. The aim of this paper was to investigate whether there was an effect of the CT scan protocol on the FE models. 12 human thoracolumbar vertebrae were scanned on top of a calcium hydroxyapatite calibration phantom using a standard QCT scan protocol – 120kV, 100mAs (PA); and a low dose protocol – 90kV, 150mAs (PB). FE cancellous models with cuboid volume of interest and inhomogeneous nonlinear bone properties were created. Axial compression was simulated. The apparent BMD, modulus and yield strength showed significant differences between the two scan protocols. The apparent BMD, the modulus and yield strength between the two groups were highly linearly correlated. This paper indicated that the FE models created from image datasets acquired at different X-ray tube voltage settings would give significantly different results and this effect could be possibly corrected using a linear correction approach.


      PubDate: 2014-06-03T12:08:17Z
       
  • Uncertainty assessment of imaging techniques for the 3D reconstruction of
           stent geometry
    • Abstract: Publication date: Available online 2 June 2014
      Source:Medical Engineering & Physics
      Author(s): Daria Cosentino , Iwona Zwierzak , Silvia Schievano , Vanessa Díaz-Zuccarini , John W. Fenner , Andrew J. Narracott
      This paper presents a quantitative assessment of uncertainty for the 3D reconstruction of stents. This study investigates a CP stent (Numed, USA) used in congenital heart disease applications with a focus on the variance in measurements of stent geometry. The stent was mounted on a model of patient implantation site geometry, reconstructed from magnetic resonance images, and imaged using micro-computed tomography (CT), conventional CT, biplane fluoroscopy and optical stereo-photogrammetry. Image data were post-processed to retrieve the 3D stent geometry. Stent strut length, separation angle and cell asymmetry were derived and repeatability was assessed for each technique along with variation in relation to μCT data, assumed to represent the gold standard. The results demonstrate the performance of biplanar reconstruction methods is comparable with volumetric CT scans in evaluating 3D stent geometry. Uncertainty on the evaluation of strut length, separation angle and cell asymmetry using biplanar fluoroscopy is of the order ±0.2mm, 3° and 0.03, respectively. These results support the use of biplanar fluoroscopy for in vivo measurement of 3D stent geometry and provide quantitative assessment of uncertainty in the measurement of geometric parameters.


      PubDate: 2014-06-03T12:08:17Z
       
 
 
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