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  Subjects -> BIOLOGY (Total: 2603 journals)
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BIOLOGY (1322 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: 6)
Journal of Biomedical Physics and Engineering     Open Access  
Journal of Biomedical Science and Engineering     Open Access   (Followers: 2)
Journal of Biomedical Sciences     Open Access   (Followers: 2)
Journal of Biomolecular Screening     Hybrid Journal   (Followers: 4)
Journal of Bionic Engineering     Full-text available via subscription  
Journal of Biorheology     Hybrid Journal  
Journal of Bioscience and Bioengineering     Full-text available via subscription   (Followers: 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: 11)
Journal of Cellular Biochemistry     Hybrid Journal   (Followers: 3)
Journal of Cellular Physiology     Hybrid Journal   (Followers: 2)
Journal of Cerebral Blood Flow & Metabolism     Hybrid Journal   (Followers: 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: 25)
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: 8)
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: 6)
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   (Followers: 1)
Journal of Marine Biology     Open Access   (Followers: 14)
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
   Journal TOC RSS feeds Export to Zotero [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]
  • Control strategies for effective robot assisted gait rehabilitation: The
           state of art and future prospects
    • Abstract: Publication date: Available online 7 September 2014
      Source:Medical Engineering & Physics
      Author(s): Jinghui Cao , Sheng Quan Xie , Raj Das , Guo L. Zhu
      A large number of gait rehabilitation robots, together with a variety of control strategies, have been developed and evaluated during the last decade. Initially, control strategies applied to rehabilitation robots were adapted from those applied to traditional industrial robots. However, these strategies cannot optimise effectiveness of gait rehabilitation. As a result, researchers have been investigating control strategies tailored for the needs of rehabilitation. Among these control strategies, assisted-as-needed (AAN) control is one of the most popular research topics in this field. AAN training strategies have gained the theoretical and practical evidence based backup from motor learning principles and clinical studies. Various approaches to AAN training have been proposed and investigated by research groups all around the world. This article presents a review on control algorithms of gait rehabilitation robots to summarise related knowledge and investigate potential trends of development. There are existing review papers on control strategies of rehabilitation robots. The review by Marchal-Crespo and Reinkensmeyer (2009) had a broad cover of control strategies of all kinds of rehabilitation robots. Hussain et al. (2011) had specifically focused on treadmill gait training robots and covered a limited number of control implementations on them. This review article encompasses more detailed information on control strategies for robot assisted gait rehabilitation, but is not limited to treadmill based training. It also investigates the potential to further develop assist-as-needed gait training based on assessments of patients’ ability. In this paper, control strategies are generally divided into the trajectory tracking control and AAN control. The review covers these two basic categories, as well as other control algorithm and technologies derived from them, such as biofeedback control. Assessments on human gait ability are also included to investigate how to further develop implementations based on assist-as-needed concept. For the consideration of effectiveness, clinical studies on robotic gait rehabilitation are reviewed and analysed from the viewpoint of control algorithm.


      PubDate: 2014-09-11T05:24:38Z
       
  • Static autoregulation in humans: a review and reanalysis
    • Abstract: Publication date: Available online 7 September 2014
      Source:Medical Engineering & Physics
      Author(s): Tianne Numan , Anthony R. Bain , Ryan L. Hoiland , Jonathan D. Smirl , Nia C. Lewis , Philip N. Ainslie
      Introduction Cerebral autoregulation (CA) is a theoretical construct characterized by the relationship between mean arterial pressure (MAP) and cerebral blood flow (CBF). We performed a comprehensive literature search to provide an up-to-date review on the static relationship between MAP and CBF. Methods The results are based on 40 studies (49 individual experimental protocols) in healthy subjects between 18 and 65 years. Exclusion criteria were: a ΔMAP <5%, hypoxia/hyperoxia or hypo/hypercapnia, and unstable levels (<2min stages). The partial pressure of arterial CO2 (PaCO2) was measured in a subset of the included studies (n =28); therefore, CBF was also adjusted to account for small changes in PaCO2. Results The linear regression coefficient between MAP and CBF (or velocity) of 0.82±0.77%ΔCBF/%ΔMAP during decreases in MAP (n =23 experiments) was significantly different than the relationship of 0.21±0.47%ΔCBF/%ΔMAP during increases (n =26 experiments; p <0.001). After correction for increases/decreases in PaCO2, the slopes were not significantly different: 0.64±1.16%ΔCBF/%ΔMAP (n =16) and 0.39±0.30%ΔCBF/%ΔMAP (n =12) for increased vs. decreased MAP changes, respectively (p =0.60). Conclusion The autoregulatory ability of the cerebral circulation appears to be more active in buffering increases in MAP as compared to reductions in MAP. However, the statistical finding of hysteresis is lost following an attempt to correct for PaCO2.


      PubDate: 2014-09-11T05:24:38Z
       
  • What if you stretch the IFU' A mechanical insight into stent graft
           instructions for use in angulated proximal aneurysm necks
    • Abstract: Publication date: Available online 10 September 2014
      Source:Medical Engineering & Physics
      Author(s): S. De Bock , F. Iannaccone , M. De Beule , F. Vermassen , P. Segers , B. Verhegghe
      Endovascular treatment for patients with a proximal neck anatomy outside instructions for use is an ongoing topic of debate in endovascular aneurysm repair. This paper employs the finite element method to offer insight into possible adverse effects of deploying a stent graft into an angulated geometry. The effect of angulation, straight neck length and device oversize was investigated in a full factorial parametric analysis. Stent apposition, area reduction of the graft, asymmetry of contact forces and the ability to find a good seal were investigated. Most adverse effects are expected for combinations of high angulation and short straight landing zones. Higher oversize has a beneficiary effect, but not enough to compensate the adverse effects of (very) short and angulated angles. Our analysis shows that for an angle between the suprarenal aorta and proximal neck above 60°, proximal kinking of the device can occur. The method used offers a engineering view on the morphological limits of EVAR for a clinically used device.


      PubDate: 2014-09-11T05:24:38Z
       
  • Walking speed estimation using foot-mounted inertial sensors: Comparing
           machine learning and strap-down integration methods
    • Abstract: Publication date: Available online 5 September 2014
      Source:Medical Engineering & Physics
      Author(s): Andrea Mannini , Angelo Maria Sabatini
      In this paper we implemented machine learning (ML) and strap-down integration (SDI) methods and analyzed them for their capability of estimating stride-by-stride walking speed. Walking speed was computed by dividing estimated stride length by stride time using data from a foot mounted inertial measurement unit. In SDI methods stride-by-stride walking speed estimation was driven by detecting gait events using a hidden Markov model (HMM) based method (HMM-based SDI); alternatively, a threshold-based gait event detector was investigated (threshold-based SDI). In the ML method a linear regression model was developed for stride length estimation. Whereas the gait event detectors were a priori fixed without training, the regression model was validated with leave-one-subject-out cross-validation. A subject-specific regression model calibration was also implemented to personalize the ML method. Healthy adults performed over-ground walking trials at natural, slower-than-natural and faster-than-natural speeds. The ML method achieved a root mean square estimation error of 2.0% and 4.2%, with and without personalization, against 2.0% and 3.1% by HMM-based SDI and threshold-based SDI. In spite that the results achieved by the two approaches were similar, the ML method, as compared with SDI methods, presented lower intra-subject variability and higher inter-subject variability, which was reduced by personalization.


      PubDate: 2014-09-06T04:51:13Z
       
  • Nonlinear properties of cardiac rhythm and respiratory signal under paced
           breathing in young and middle-aged healthy subjects
    • Abstract: Publication date: Available online 4 September 2014
      Source:Medical Engineering & Physics
      Author(s): Ana Kapidžić , Mirjana M Platiša , Tijana Bojić , Aleksandar Kalauzi
      We examined the effects of gender and age in young and middle-aged subjects on the level of cardio-respiratory interaction by analyzing properties of cardiac, respiratory and cardiac-respiratory regulatory mechanisms under paced breathing. In 56 healthy subjects, ECG (RR interval) and respiratory signal were simultaneously acquired in supine position at paced (0.1–0.45Hz, steps of 0.05Hz) and spontaneous breathing. The participants were divided into gender matched group of young adults (19–25 years old) and middle-aged adults (35–44 years old). Power spectral analysis was applied on RR interval time series and spectral components in very low frequency (VLF), low frequency (LF) and high frequency (HF) ranges were computed. We also calculated sample entropy of RR interval series (SampEnRR), respiratory series (SampEnResp), and their cross-sample entropy (cross-SampEn). Under paced breathing, reduction of all spectral powers with age (p <0.05) is not gender dependent but reduction of some entropy measures is; SampEnRR and SampEnResp were lower only in men (p <0.05). In the middle-aged subjects, effect of gender on spectral measures is significant; males had lower HF (p <0.05). Pattern of dependencies of SampEn and cross-SampEn on paced breathing frequency were significantly different in men (young vs. middle-aged, p =0.001 and p =0.037) and in middle-aged subjects (females vs. males, p =0.011 and p =0.008). In middle-aged males, lower entropy measures indicated reduced and less complex partial cardiac and respiratory control, and central cardio-respiratory control. In conclusion, in healthy middle-aged subjects changes in cardio-respiratory coupling are detectable only in males.


      PubDate: 2014-09-06T04:51:13Z
       
  • Computer-aided surgical planner for a new bone deformity correction device
           using axis-angle representation
    • Abstract: Publication date: Available online 4 September 2014
      Source:Medical Engineering & Physics
      Author(s): Ying Ying Wu , Anton Plakseychuk , Kenji Shimada
      Current external fixators for distraction osteogenesis (DO) are unable to correct all types of deformities in the lower limb and are difficult to use because of the lack of a pre-surgical planning system. We propose a DO system that consists of a surgical planner and a new, easy-to-setup unilateral fixator that not only corrects all lower limb deformity, but also generates the contralateral/predefined bone shape. Conventionally, bulky constructs with six or more joints (six degrees of freedom, 6DOF) are needed to correct a 3D deformity. By applying the axis-angle representation, we can achieve that with a compact construct with only two joints (2DOF). The proposed system makes use of computer-aided design software and computational methods to plan and simulate the planned procedure. Results of our stress analysis suggest that the stiffness of our proposed fixator is comparable to that of the Orthofix unilateral external fixator. We tested the surgical system on a model of an adult deformed tibia and the resulting bone trajectory deviates from the target bone trajectory by 1.8mm, which is below our defined threshold error of 2mm. We also extracted the transformation matrix that defines the deformity from the bone model and simulated the planned procedure.


      PubDate: 2014-09-06T04:51:13Z
       
  • Intraluminal magnetisation of bowel by ferromagnetic particles for
           retraction and manipulation by magnetic probes
    • Abstract: Publication date: Available online 26 August 2014
      Source:Medical Engineering & Physics
      Author(s): Z. Wang , P. André , D. McLean , S.I. Brown , G.J. Florence , A. Cuschieri
      Feasibility studies are needed to demonstrate that safe and effective manipulation of bowel during Minimal Access Surgery (MAS) can be obtained by use of magnetic force. This paper characterises two classes of magnetic particles: stainless steel microparticles (SS-μPs) and iron oxide nanoparticles (IO-nPs) in terms of their magnetisation, chemical composition, crystallinity, morphology and size distribution. Both magnetic particles were dispersed in a high viscosity biological liquid for intraluminal injection of bowel. Ex vivo porcine bowel segments were then retracted by permanent magnetic probes of 5.0 and 10mm diameter. Strong retraction forces reaching 6N maximum were obtained by magnetic fluid based on dispersion of SS-μPs. In contrast, the IO-nP-based magnetic liquid generated less attraction force, due to both lower magnetic and solution properties of the IO-nPs. The comparison of the two particles allowed the identification of the rules to engineer the next generation of particles. The results with SS-μPs provide proof on concept that intraluminal injection of magnetic fluid can generate sufficient force for efficient bowel retraction. Thereafter we shall carry out in vivo animal studies for efficacy and safety of both types of ferrofluids.


      PubDate: 2014-09-02T04:03:36Z
       
  • Is the callus shape an optimal response to a mechanobiological
           stimulus'
    • Abstract: Publication date: Available online 27 August 2014
      Source:Medical Engineering & Physics
      Author(s): Frederico O. Ribeiro , João Folgado , José Manuel Garcia-Aznar , María José Gómez-Benito , Paulo R. Fernandes
      After bone trauma, the natural response to restore bone function is the formation of a callus around the fracture. Although several bone healing models have been developed, none have effectively perceived early callus formation and shape as the result of an optimal response to a mechanobiological stimulus. In this paper, we investigate which stimulus regulates early callus formation. An optimal design problem is formulated, and several objective functions are defined, each using a different mechanobiological stimulus. The following stimuli were analysed: the interfragmentary strain, the second invariant of the deviatoric strain tensor and a generic inflammatory factor. Different regions for callus formation were also evaluated, such as the gap region, the periosteum and the periosteum border. Each stimulus was computed using the finite element method, and the callus shape was optimised using the steepest descent method. The results demonstrated that the inflammatory factor approach, the interfragmentary strain and the second invariant of the deviatoric strain tensor over the inner gap provided the best results when compared with histological callus shapes. Therefore, this work suggests that callus growth can be an optimal mechanobiological response to either local mechanical instability and/or local inflammatory reaction.


      PubDate: 2014-09-02T04:03:36Z
       
  • A novel device for the clearance and prevention of blockages within
           biomedical catheters
    • Abstract: Publication date: Available online 28 August 2014
      Source:Medical Engineering & Physics
      Author(s): Richard Fox , Jonathan Norton
      Biomedical catheters are commonly used to move fluids from one part of the body to another, or remove them from the body completely. In some instances, these catheters become occluded due to blood or other debris. Such occlusions may prove fatal or require re-operation with enormous costs and effects on the health-care system and the individual. We developed a model of occlusion in both a ventriculo-peritoneal shut system and en external ventricular drain. Having demonstrated that occlusions can be reliably generated in a manner that resembles the clinical situation we show that vibration can clear the blockages. Vibration in the 50–60Hz range was able to maintain patency in the catheters or to clear the blockage when the catheter was completely occluded. In high concentrations of blood, 150s of vibration applied every 30min was able to maintain the patency of the catheter. Clinically, as the level of blood in the fluid decreases, the time intervals between vibration applications could be increased. We believe that vibration offers a safe, non-invasive method to maintain the patency of biomedical catheters.


      PubDate: 2014-09-02T04:03:36Z
       
  • Development of a closed-loop J–T cryoablation device with a long
           cooling area and multiple expansion parts
    • Abstract: Publication date: Available online 20 August 2014
      Source:Medical Engineering & Physics
      Author(s): Cheonkyu Lee , Seungwhan Baek , Jisung Lee , Gyuwan Hwang , Sangkwon Jeong , Sang Woo Park
      Cryoablation is a surgical procedure used to freeze defective cells by inserting a low temperature probe into a human body to destroy malignant tissues. Miniaturized Joule–Thomson (J–T) refrigerators are often used to minimize the volume of the cooling device and reduce the destruction zone of normal tissue. The cooling effects of the existing probes are not uniformly generated along the longitudinal direction of the probe, which makes their applications less effective in surgeries of incompetent great saphenous veins (GSVs), where the target cells are distributed over a broad range. Long uniform refrigeration is required across the entire area of the probe to apply the same cooling effects. In this paper, a closed-loop J–T cryoablation probe was designed and fabricated to provide uniform refrigeration over a large area, with multiple expansion parts. Using flow boiling heat transfer, uniform cooling of a 200mm-long and 0.3mm thickness piece of target tissue was possible and simulated in a gelatin solution. The developed probe produced a greater than 53Kmin−1 cooling rate and the cooling temperature was below 253K to satisfy the required cell death conditions.


      PubDate: 2014-09-02T04:03:36Z
       
  • Measurement of compliance of infusion device consumable elements using an
           analytical weighing balance
    • Abstract: Publication date: Available online 20 August 2014
      Source:Medical Engineering & Physics
      Author(s): Douglas McG. Clarkson , Romain Barbosa
      The value of compliance of disposable elements such as infusion lines and syringes can significantly affect the performance characteristics of infusion devices. In a technique used to determine the compliance of infusion lines, the item under test is placed in a semi sealed water filled enclosure and the volume of fluid displaced is measured on an analytical weighing balance as set pressures are applied to the test item. Thermal drift of the measurement chamber was minimised by inclusion of discs of Invar alloy. Measurements were also made to determine the compliance of syringes used with syringe drivers where the volume of fluid displaced upon release of established pressure levels within a syringe was measured using a separate measurement configuration using again an analytical weighing balance. These techniques were used to determine the relative contributions to compliance of infusion lines and syringes to the dynamics of operation of syringe drivers. This indicated that contributions to compliance from syringes were significantly greater than that of connected infusion lines. Values of time to occlude, occlusion bolus and effects of height elevation for infusion devices with elements of varying compliance and line configuration are discussed.


      PubDate: 2014-09-02T04:03:36Z
       
  • Pulse pressure waveform estimation using distension profiling with
           contactless optical probe
    • Abstract: Publication date: Available online 29 August 2014
      Source:Medical Engineering & Physics
      Author(s): Tânia Pereira , Inês Santos , Tatiana Oliveira , Pedro Vaz , Telmo Pereira , Helder Santos , Helena Pereira , Carlos Correia , João Cardoso
      The pulse pressure waveform has, for long, been known as a fundamental biomedical signal and its analysis is recognized as a non-invasive, simple, and resourceful technique for the assessment of arterial vessels condition observed in several diseases. In the current paper, waveforms from non-invasive optical probe that measures carotid artery distension profiles are compared with the waveforms of the pulse pressure acquired by intra-arterial catheter invasive measurement in the ascending aorta. Measurements were performed in a study population of 16 patients who had undergone cardiac catheterization. The hemodynamic parameters: area under the curve (AUC), the area during systole (AS) and the area during diastole (AD), their ratio (AD/AS) and the ejection time index (ETI), from invasive and non-invasive measurements were compared. The results show that the pressure waveforms obtained by the two methods are similar, with 13% of mean value of the root mean square error (RMSE). Moreover, the correlation coefficient demonstrates the strong correlation. The comparison between the AUCs allows the assessment of the differences between the phases of the cardiac cycle. In the systolic period the waveforms are almost equal, evidencing greatest clinical relevance during this period. Slight differences are found in diastole, probably due to the structural arterial differences. The optical probe has lower variability than the invasive system (13% vs 16%). This study validates the capability of acquiring the arterial pulse waveform with a non-invasive method, using a non-contact optical probe at the carotid site with residual differences from the aortic invasive measurements.


      PubDate: 2014-09-02T04:03:36Z
       
  • Construction of a conductive distortion reduced electromagnetic tracking
           system for computer assisted image-guided interventions
    • Abstract: Publication date: Available online 22 August 2014
      Source:Medical Engineering & Physics
      Author(s): Mengfei Li , Tomasz Bien , Georg Rose
      Alternating current electromagnetic tracking system (EMTS) is widely used in computer-assisted image-guided interventions. However, EMTS suffers from distortions caused by electrically conductive objects in close proximity to tracker tools. Eddy currents in conductive distorters generate secondary magnetic fields that disrupt the measured position and orientation (P&O) of the tracker. This paper proposes a LabVIEW field programmable gate array (FPGA) based EMTS to reduce the interference caused by nearby conductive, but non-ferromagnetic objects upon the method developed in the authors’ previous studies. The system's performance was tested in the presence of single/multiple nearby conductive distorters. The results illustrated that the constructed EMTS worked accurately and stably despite nearby static or mobile conductive objects. The technology will allow surgeons to perform image-guided interventions with EMTS even when there are conductive objects close by the tracker tool.


      PubDate: 2014-09-02T04:03:36Z
       
  • A new measure of the CoP trajectory in postural sway: Dynamics of heading
           change
    • Abstract: Publication date: Available online 1 September 2014
      Source:Medical Engineering & Physics
      Author(s): Christopher K. Rhea , Adam W. Kiefer , F.J. Haran , Stephen M. Glass , William H. Warren
      The maintenance of upright stance requires the simultaneous control of posture in both the anterior–posterior (AP) and medial–lateral (ML) dimensions. Postural sway is typically measured by quantifying the movement of the center of pressure (CoP) in the AP and ML dimensions independently. Metrics such as path length and 95% ellipse area have been developed to take into account movement in both the AP and ML directions, but these metrics only quantify the magnitude of the CoP movement. The movement of the CoP is technically a vector quantity with both magnitude and direction characteristics. The direction of displacement, or heading, of the CoP may provide further insight into the control of posture. Accordingly, we present a novel variable that describes the rate of change in direction of CoP displacement in two dimensions, the heading change (Δϕ), which is derived from the CoP heading (ϕ). We then compared the standard deviation (SD) and the dynamic structure characterized by sample entropy (SampEn) of the heading change time series to previously examined metrics presented in the literature (SD and SampEn of the AP and ML time series, path length, SD and SampEn of the CoP resultant magnitude time series) during a 60s single-leg stance performed by healthy participants and patients with a ruptured anterior cruciate ligament (ACL) prior to surgical intervention. Patients with an ACL rupture exhibited a different dynamic structure in Δϕ compared to healthy controls, t(14)=2.44, p =0.029, whereas none of the other metrics differed between groups (all p >0.05). The novelty and utility of Δϕ is that it characterizes directional changes of the CoP, whereas previously documented postural control analyses describe only changes in magnitude.


      PubDate: 2014-09-02T04:03:36Z
       
  • Experimental analysis of the minimally invasive plate osteosynthesis
           technique applied with non-locking screws and screw locking elements
    • Abstract: Publication date: Available online 30 August 2014
      Source:Medical Engineering & Physics
      Author(s): A. Yánez , A. Cuadrado , P.J. Cabrera , O. Martel , G. Garcés
      Minimally invasive plate osteosynthesis (MIPO) is an effective surgical technique in the repair of humeral and tibial shaft fractures. There is some controversy as to the minimum number of screws required to ensure correct stability to promote healing, especially when dealing with low quality bones. This work compared different systems assembled on synthetic models simulating a comminuted fracture. Group 1 comprised a locking compression plate with four non-locking screws placed at the holes furthest from the fracture. Group 2 differed from group 1 only in the additional use of two screw locking elements (SLE). Group 3 had four rather than two SLE and, finally, Group 4 used 4 locking screws. The compression and torsion tests with static and cyclic loads showed that, in MIPO, two locking screws or two non-locking screws with SLE could be used per segment without any significant loss in stiffness after 1000 cycles, with system stability guaranteed in both cases. However, lower strength and significant loss of stiffness were observed when non-locking screws were used alone.


      PubDate: 2014-09-02T04:03:36Z
       
  • The effect of stent graft oversizing on radial forces considering nitinol
           wire behavior and vessel characteristics
    • Abstract: Publication date: Available online 30 August 2014
      Source:Medical Engineering & Physics
      Author(s): B. Senf , S. von Sachsen , R. Neugebauer , W.-G. Drossel , H.-J. Florek , F.W. Mohr , C.D. Etz
      Stent graft fixation in the vessel affects the success of endovascular aneurysm repair. Thereby the radial forces of the stent, which are dependent on several factors, play a significant role. In the presented work, a finite element sensitivity study was performed. The radial forces are 29% lower when using the hyperelastic approach for the vessel compared with linear elastic assumptions. Without the linear elastic modeled plaque, the difference increases to 35%. Modeling plaque with linear elastic material approach results in 8% higher forces than with a hyperelastic characteristic. The significant differences resulting from the investigated simplifications of the material lead to the conclusion that it is important to apply an anisotropic nonlinear approach for the vessel. The oversizing study shows that radial forces increase by 64% (0.54N) when raising the oversize from 10 to 22%, and no further increase in force can be observed beyond these values (vessel diameter D =12mm). Starting from an oversize of 24%, the radial force steadily decreases. The findings of the investigation show that besides the oversizing the material properties, the ring design and the vessel characteristics have an influence on radial forces.


      PubDate: 2014-09-02T04:03:36Z
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
 
 
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