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  Subjects -> BIOLOGY (Total: 2912 journals)
    - BIOCHEMISTRY (217 journals)
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    - BIOLOGY (1408 journals)
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BIOLOGY (1408 journals)            First | 4 5 6 7 8 9 10 11 | Last

JCP : BioChemical Physics     Hybrid Journal   (Followers: 2)
JETP Letters     Hybrid Journal   (Followers: 2)
Journal of Bacteriology & Parasitology     Open Access   (Followers: 3)
Journal of Bioanalysis & Biomedicine     Open Access   (Followers: 1)
Journal of Bioequivalence & Bioavailability     Open Access  
Journal of Bioremediation & Biodegradation     Open Access   (Followers: 3)
Journal of Computer Science & Systems Biology     Open Access   (Followers: 2)
Journal of Proteomics & Bioinformatics     Open Access   (Followers: 7)
Journal of Advance Researches In Biological Sciences     Open Access   (Followers: 3)
Journal of Advances in Biology     Open Access   (Followers: 3)
Journal of Agricultural, Biological & Environmental Statistics     Hybrid Journal   (Followers: 9)
Journal of Amino Acids     Open Access   (Followers: 2)
Journal of AOAC International     Full-text available via subscription   (Followers: 9)
Journal of Applied Biobehavioral Research     Hybrid Journal  
Journal of Applied Bioinformatics & Computational Biology     Hybrid Journal   (Followers: 2)
Journal of Applied Biosciences     Open Access  
Journal of Applied Ichthyology     Hybrid Journal   (Followers: 6)
Journal of Applied Phycology     Hybrid Journal   (Followers: 10)
Journal of Applied Virology     Open Access   (Followers: 8)
Journal of Aquatic Sciences     Full-text available via subscription   (Followers: 3)
Journal of Arachnology     Full-text available via subscription  
Journal of Asia-Pacific Biodiversity     Open Access  
Journal of Astrobiology & Outreach     Open Access  
Journal of Avian Biology     Hybrid Journal   (Followers: 22)
Journal of Bacteriology     Full-text available via subscription   (Followers: 20)
Journal of Basic Microbiology     Hybrid Journal   (Followers: 3)
Journal of Bio-Science     Open Access   (Followers: 1)
Journal of Biobased Materials and Bioenergy     Full-text available via subscription  
Journal of Biodiversity & Endangered Species     Open Access  
Journal of Biodiversity Management & Forestry     Hybrid Journal   (Followers: 1)
Journal of Bioenergetics and Biomembranes     Hybrid Journal   (Followers: 1)
Journal of Biogeography     Hybrid Journal   (Followers: 29)
Journal of Bioinformatics and Computational Biology     Hybrid Journal   (Followers: 14)
Journal of Bioinformatics and Intelligent Control     Full-text available via subscription  
Journal of Biological and Information Sciences     Open Access   (Followers: 2)
Journal of Biological Dynamics     Open Access   (Followers: 1)
Journal of Biological Education     Hybrid Journal   (Followers: 1)
Journal of Biological Engineering     Open Access   (Followers: 4)
Journal of Biological Methods     Open Access  
Journal of Biological Physics     Hybrid Journal  
Journal of Biological Research - Thessaloniki     Open Access  
Journal of Biological Sciences     Open Access   (Followers: 4)
Journal of Biological Systems     Hybrid Journal   (Followers: 2)
Journal of Biology and Earth Sciences     Open Access   (Followers: 3)
Journal of Biology and Life Science     Open Access   (Followers: 2)
Journal of Biology, Agriculture and Healthcare     Open Access   (Followers: 5)
Journal of Biomarkers     Open Access  
Journal of Biomechanics     Hybrid Journal   (Followers: 29)
Journal of Biomedical Discovery and Collaboration     Open Access   (Followers: 1)
Journal of Biomedical Education     Open Access   (Followers: 2)
Journal of Biomedical Informatics     Partially Free   (Followers: 14)
Journal of Biomedical Materials Research Part A     Hybrid Journal   (Followers: 2)
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   (Followers: 1)
Journal of Biomedical Science and Engineering     Open Access   (Followers: 3)
Journal of Biomolecular Screening     Hybrid Journal   (Followers: 6)
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: 16)
Journal of Biosciences and Medicines     Open Access  
Journal of Biosocial Science     Hybrid Journal   (Followers: 4)
Journal of Biotechnology and Biodiversity     Open Access   (Followers: 1)
Journal of Bryology     Hybrid Journal   (Followers: 6)
Journal of Cell and Plant Sciences     Open Access   (Followers: 5)
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: 13)
Journal of Cellular Biochemistry     Hybrid Journal   (Followers: 4)
Journal of Cellular Physiology     Hybrid Journal   (Followers: 4)
Journal of Cerebral Blood Flow & Metabolism     Hybrid Journal   (Followers: 1)
Journal of Chromatography B     Hybrid Journal   (Followers: 25)
Journal of Clinical Bioinformatics     Open Access   (Followers: 6)
Journal of Clinical Toxicology     Open Access   (Followers: 2)
Journal of Communications Technology and Electronics     Hybrid Journal   (Followers: 1)
Journal of Contemporary Physics (Armenian Academy of Sciences)     Hybrid Journal   (Followers: 1)
Journal of Contradicting Results in Science     Open Access   (Followers: 2)
Journal of Crustacean Biology     Hybrid Journal   (Followers: 3)
Journal of Developmental Biology     Open Access   (Followers: 2)
Journal of Ecosystems     Open Access   (Followers: 4)
Journal of Education, Health and Sport     Open Access   (Followers: 5)
Journal of Electrical Bioimpedance     Full-text available via subscription   (Followers: 2)
Journal of Electromyography and Kinesiology     Hybrid Journal   (Followers: 4)
Journal of Environment and Ecology     Open Access   (Followers: 13)
Journal of Environmental Radioactivity     Hybrid Journal   (Followers: 3)
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: 2)
Journal of Evolutionary Biology     Hybrid Journal   (Followers: 25)
Journal of Experimental and Clinical Anatomy     Open Access   (Followers: 2)
Journal of Experimental Marine Biology and Ecology     Hybrid Journal   (Followers: 38)
Journal of Fish Biology     Hybrid Journal   (Followers: 33)
Journal of Functional Biomaterials     Open Access   (Followers: 1)
Journal of Fungi     Open Access  
Journal of Genomes and Exomes     Open Access  
Journal of Great Lakes Research     Hybrid Journal   (Followers: 7)
Journal of Green Science and Technology     Full-text available via subscription   (Followers: 1)
Journal of Health and Biological Sciences     Open Access  
Journal of Heredity     Hybrid Journal   (Followers: 4)

  First | 4 5 6 7 8 9 10 11 | Last

Journal Cover Medical Engineering & Physics
  [SJR: 0.871]   [H-I: 64]   [10 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1350-4533
   Published by Elsevier Homepage  [2801 journals]
  • Microconfined flow behavior of red blood cells
    • Abstract: Publication date: January 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 1
      Author(s): Giovanna Tomaiuolo, Luca Lanotte, Rosa D'Apolito, Antonio Cassinese, Stefano Guido
      Red blood cells (RBCs) perform essential functions in human body, such as gas exchange between blood and tissues, thanks to their ability to deform and flow in the microvascular network. The high RBC deformability is mainly due to the viscoelastic properties of the cell membrane. Since an impaired RBC deformability could be found in some diseases, such as malaria, sickle cell anemia, diabetes and hereditary disorders, there is the need to provide further insight into measurement of RBC deformability in a physiologically relevant flow field. Here, RBCs deformability has been studied in terms of the minimum apparent plasma-layer thickness by using high-speed video microscopy of RBCs flowing in cylindrical glass capillaries. An in vitro systematic microfluidic investigation of RBCs in micro-confined conditions has been performed, resulting in the determination of the RBCs time recovery constant, RBC volume and surface area and RBC membrane shear elastic modulus and surface viscosity. It has been noticed that the deformability of RBCs induces cells aggregation during flow in microcapillaries, allowing the formation of clusters of cells. Overall, our results provide a novel technique to estimate RBC deformability and also RBCs collective behavior, which can be used for the analysis of pathological RBCs, for which reliable quantitative methods are still lacking.


      PubDate: 2016-02-08T20:22:50Z
       
  • Editorial Board
    • Abstract: Publication date: January 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 1




      PubDate: 2016-02-08T20:22:50Z
       
  • Understanding particle margination in blood flow – A step toward
           optimized drug delivery systems
    • Abstract: Publication date: January 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 1
      Author(s): Kathrin Müller, Dmitry A. Fedosov, Gerhard Gompper
      Targeted delivery of drugs and imaging agents is very promising to develop new strategies for the treatment of various diseases such as cancer. For an efficient targeted adhesion, the particles have to migrate toward the walls in blood flow – a process referred to as margination. Due to a huge diversity of available carriers, a good understanding of their margination properties in blood flow depending on various flow conditions and particle properties is required. We employ a particle-based mesoscopic hydrodynamic simulation approach to investigate the margination of different carriers for a wide range of hematocrits (volume fraction of red blood cells) and flow rates. Our results show that margination strongly depends on the thickness of the available free space close to the wall, the so-called red blood cell-free layer (RBC-FL), in comparison to the carrier size. The carriers with a few micrometers in size are comparable with the RBC-FL thickness and marginate better than their sub-micrometer counterparts. Deformable carriers, in general, show worse margination properties than rigid particles. Particle margination is also found to be most pronounced in small channels with a characteristic size comparable to blood capillaries. Finally, different margination mechanisms are discussed.


      PubDate: 2016-02-08T20:22:50Z
       
  • Modelling the effects of cerebral microvasculature morphology on oxygen
           transport
    • Abstract: Publication date: January 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 1
      Author(s): Chang Sub Park, Stephen J. Payne
      The cerebral microvasculature plays a vital role in adequately supplying blood to the brain. Determining the health of the cerebral microvasculature is important during pathological conditions, such as stroke and dementia. Recent studies have shown the complex relationship between cerebral metabolic rate and transit time distribution, the transit times of all the possible pathways available dependent on network topology. In this paper, we extend a recently developed technique to solve for residue function, the amount of tracer left in the vasculature at any time, and transit time distribution in an existing model of the cerebral microvasculature to calculate cerebral metabolism. We present the mathematical theory needed to solve for oxygen concentration followed by results of the simulations. It is found that oxygen extraction fraction, the fraction of oxygen removed from the blood in the capillary network by the tissue, and cerebral metabolic rate are dependent on both mean and heterogeneity of the transit time distribution. For changes in cerebral blood flow, a positive correlation can be observed between mean transit time and oxygen extraction fraction, and a negative correlation between mean transit time and metabolic rate of oxygen. A negative correlation can also be observed between transit time heterogeneity and the metabolic rate of oxygen for a constant cerebral blood flow. A sensitivity analysis on the mean and heterogeneity of the transit time distribution was able to quantify their respective contributions to oxygen extraction fraction and metabolic rate of oxygen. Mean transit time has a greater contribution than the heterogeneity for oxygen extraction fraction. This is found to be opposite for metabolic rate of oxygen. These results provide information on the role of the cerebral microvasculature and its effects on flow and metabolism. They thus open up the possibility of obtaining additional valuable clinical information for diagnosing and treating cerebrovascular diseases.


      PubDate: 2016-02-08T20:22:50Z
       
  • Analysis and measurement of dielectrophoretic manipulation of particles
           and lymphocytes using rail-type electrodes
    • Abstract: Publication date: January 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 1
      Author(s): K. Tatsumi, K. Kawano, H. Okui, H. Shintani, K. Nakabe
      A particle manipulation and sorting device using the dielectrophoretic (DEP) force is described in this study. The device consists of “ladder-type”, “flip-type” and “oblique rail-type” electrode regions. The ladder-type and rail-type electrodes can generate a DEP force distribution that captures the particles, the DEP force of which is negative, in the area located at the center of the electrodes. The ladder-type electrode can align the particles with equal spacing in the streamwise direction. Using the flip-type electrode, which pushes the particles away, in combination with these electrodes, the direction of the particle and timing can be selected with high accuracy, reliability, and response. In the first half of this study, a numerical simulation is carried out to calculate the particle motion and evaluate the performance of the ladder-type electrode. Several models are used to investigate the influences of the non-uniformity of the electric field and the electric interaction of the surface charges and polarizations. Experiments are then carried out to demonstrate the motions of the particles and the sorting reliability. The trajectories and the probability density functions of the particles at the inlet and outlet of the electrode region showed that by using these electrodes the particles can be aligned, sorted, and guided accurately.


      PubDate: 2016-02-08T20:22:50Z
       
  • Design and evaluation of an actuated knee implant for postoperative
           ligament imbalance correction
    • Abstract: Publication date: Available online 29 January 2016
      Source:Medical Engineering & Physics
      Author(s): A. Collo, S. Almouahed, P. Poignet, C. Hamitouche, E. Stindel
      In Total Knee Arthroplasty (TKA), the collateral ligament tensioning stage cannot be standardised for all patients and relies heavily on the surgeon’s experience and perception. Intraoperative inaccuracies are practically unavoidable and may give rise to severe postoperative complications, leading to the need for revision surgery already a few years after primary TKA. This work proposes a novel instrumented tibial component able to detect collateral ligament laxity conditions right after primary TKA and, if needed, to compensate for them in the postoperative period. A miniaturised actuation system, designed to be embedded in the tibial baseplate, was initially evaluated by means of 3D simulations and then fabricated as a full-scale prototype. Stability and force sensors tests carried out on a knee simulator allowed to assess the effectiveness of the proposed design under normal working conditions and provided valuable insights for future work and improvements.


      PubDate: 2016-02-08T20:22:50Z
       
  • Prediction of elbow joint contact mechanics in the multibody framework
    • Abstract: Publication date: Available online 29 January 2016
      Source:Medical Engineering & Physics
      Author(s): Munsur Rahman, Akin Cil, Antonis P. Stylianou
      Computational multibody musculoskeletal models of the elbow joint that are capable of simultaneous and accurate predictions of muscle and ligament forces, along with cartilage contact mechanics can be immensely useful in clinical practice. As a step towards producing a musculoskeletal model that includes the interaction between cartilage and muscle loading, the goal of this study was to develop subject-specific multibody models of the elbow joint with discretized humerus cartilage representation interacting with the radius and ulna cartilages through deformable contacts. The contact parameters for the compliant contact law were derived using simplified elastic foundation contact theory. The models were then validated by placing the model in a virtual mechanical tester for flexion-extension motion similar to a cadaver experiment, and the resulting kinematics were compared. Two cadaveric upper limbs were used in this study. The humeral heads were subjected to axial motion in a mechanical tester and the resulting kinematics from three bones were recorded for model validation. The maximum RMS error between the predicted and measured kinematics during the complete testing cycle was 2.7mm medial-lateral translation and 9.7° varus–valgus rotation of radius relative to humerus (for elbow 2). After model validation, a lateral ulnar collateral ligament (LUCL) deficient condition was simulated and, contact pressures and kinematics were compared to the intact elbow model. A noticeable difference in kinematics, contact area, and contact pressure were observed for LUCL deficient condition. LUCL deficiency induced higher internal rotations for both the radius and ulna during flexion and an associated medial shift of the articular contact area.


      PubDate: 2016-02-08T20:22:50Z
       
  • The influence of a polymer damper on swing-through crutch gait
           biomechanics
    • Abstract: Publication date: Available online 3 February 2016
      Source:Medical Engineering & Physics
      Author(s): Megan K. MacGillivray, Ranita H.K. Manocha, Bonita Sawatzky
      Forearm crutch technology has evolved slowly compared to other assistive mobility devices, despite the highly repetitive nature of forearm crutch gait and the high incidence of overuse injuries. Using 13 able-bodied volunteers between the ages of 19 and 27, we compared the ground reaction forces of a novel crutch design featuring an elastomeric polymer situated below the handle to an identical design without a damper system and to a commercially available generic rigid forearm crutch model. There were no differences in peak vertical force or impulse between crutches. The crutch with the damper system demonstrated a significantly smaller peak braking force and impulse compared to the generic forearm crutch model. However, the crutch with the damper system demonstrated a significantly larger peak propulsive force and impulse compared to both crutch models. This finding indicates that a forearm crutch with a damper system may help to propel the crutch forward when walking on level surfaces, which could impact forward momentum.


      PubDate: 2016-02-08T20:22:50Z
       
  • Penetration of an artificial arterial thromboembolism in a live animal
           using an intravascular therapeutic microrobot system
    • Abstract: Publication date: Available online 5 February 2016
      Source:Medical Engineering & Physics
      Author(s): Semi Jeong, Hyunchul Choi, Gwangjun Go, Cheong Lee, Kyung Seob Lim, Doo Sun Sim, Myung Ho Jeong, Seong Young Ko, Jong-Oh Park, Sukho Park
      The biomedical applications of wireless robots are an active area of study. In addition to moving to a target lesion, wireless locomotive robots can deliver a therapeutic drug for a specific disease. Thus, they hold great potential as therapeutic devices in blood vessel diseases, such as thrombi and occlusions, and in other diseases, such as cancer and inflammation. During a percutaneous coronary intervention (PCI), surgeons wear a heavy shielding cloth. However, they cannot escape severe radiation exposure owing to unstable shielding. They may also suffer from joint pains because of the weight of the shielding cloth. In addition, the catheters in PCIs are controlled by the surgeon's hand. Thus, they lack steering ability. A new intravascular therapeutic system is needed to address these problems in conventional PCIs. We developed an intravascular therapeutic microrobot system (ITMS) using an electromagnetic actuation (EMA) system with bi-plane X-ray devices that can remotely control a robot in blood vessels. Using this proposed ITMS, we demonstrated the locomotion of the robot in abdominal and iliac arteries of a live pig by the master-slave method. After producing an arterial thromboembolism in a live pig in a partial iliac artery, the robot moved to the target lesion and penetrated by specific motions (twisting and hammering) of the robot using the proposed ITMS. The results reveal that the proposed ITMS can realize stable locomotion (alignment and propulsion) of a robot in abdominal and iliac arteries of a live pig. This can be considered the first preclinical trial of the treatment of an artificial arterial thromboembolism by penetration of a blood clot.


      PubDate: 2016-02-08T20:22:50Z
       
  • Sensorized pacifier to evaluate non-nutritive sucking in newborns
    • Abstract: Publication date: Available online 29 January 2016
      Source:Medical Engineering & Physics
      Author(s): Angela Grassi, Francesca Cecchi, Giada Sgherri, Andrea Guzzetta, Luigi Gagliardi, Cecilia Laschi
      We developed a device for an objective measurement of non-nutritive sucking (NNS). NNS is newborns’ spontaneous action that is a predictor of their neural system development and can be adopted as an intervention to train oral feeding skills in preterms. Two miniaturized digital pressure sensors were embedded into a commercial pacifier and the two signals were simultaneously acquired using the Inter-Integrated circuit (I²C) interface. This solution traced a complete pressures profile of the sucking pattern in order to better understand the functional aspects of the two NNS phases, the suction and the expression. Experimental tests with nine newborns confirmed that the sensorized pacifier is an adequate tool for measuring NNS burst-pause patterns. The identified parameters related to the suction/expression rhythmicity could be used as indicators of the NNS ability. This device might be used both for exploring the possible diagnostic data contained in NNS pattern and for monitoring the sucking skills of premature infants.


      PubDate: 2016-01-29T09:17:01Z
       
  • Development of a sliding mode control model for quiet upright stance
    • Abstract: Publication date: Available online 19 January 2016
      Source:Medical Engineering & Physics
      Author(s): Hongbo Zhang, Maury A. Nussbaum, Michael J. Agnew
      Human upright stance appears maintained or controlled intermittently, through some combination of passive and active ankle torques, respectively representing intrinsic and contractile contributions of the ankle musculature. Several intermittent postural control models have been proposed, though it has been challenging to accurately represent actual kinematics and kinetics and to separately estimate passive and active ankle torque components. Here, a simplified single-segment, 2D (sagittal plane) sliding mode control model was developed for application to track kinematics and kinetics during upright stance. The model was implemented and evaluated using previous experimental data consisting of whole body angular kinematics and ankle torques. Tracking errors for the whole-body center-of-mass (COM) angle and angular velocity, as well as ankle torque, were all within ∼10% of experimental values, though tracking performance for COM angular acceleration was substantially poorer. The model also enabled separate estimates of the contributions of passive and active ankle torques, with overall contributions estimated here to be 96% and 4% of the total ankle torque, respectively. Such a model may have future utility in understanding human postural control, though additional work is needed, such as expanding the model to multiple segments and to three dimensions.


      PubDate: 2016-01-23T08:43:08Z
       
  • Up-Down Chair: A novel mechatronic device to assess otolith function in
           patients with vestibular disorders
    • Abstract: Publication date: Available online 21 January 2016
      Source:Medical Engineering & Physics
      Author(s): Lorenzo Bassi Luciani, Dario Martelli, Vito Monaco, Vincenzo Genovese, Silvestro Micera
      This paper describes a novel mechatronic platform, named “Up-Down Chair” (UDC), aimed at investigating otolith function in patients with vestibular disorders. The UDC was designed to provide a wide range of repeatable and controllable vertical oscillations of the head whose kinematic features match those encountered during daily activities. The following parameters were assessed to characterize the performance of the UDC: accordance between expected and measured kinematics in both loaded and unloaded conditions; Dynamic Visual Acuity (DVA) of a group of 15 healthy subjects who were asked to identify a set of Snellen optotypes while being repeatedly moved at different perturbation intensities. Results revealed a good agreement between expected and measured kinematic patterns, and excellent reliability of DVA assessed across enrolled participants. In addition, we observed that the proposed paradigm was effective in inducing oscillopsia in enrolled subjects and that the frequency of the oscillation significantly induced blurred vision during the experimental tests. The UDC appears to be usable as a complementary vestibular clinical test to investigate the effects of therapeutic treatments while applying a wide range of physiological stimuli compatible with those encountered during daily activities.


      PubDate: 2016-01-23T08:43:08Z
       
  • Accuracy and re-test reliability of mobile eye-tracking in Parkinson's
           disease and older adults
    • Abstract: Publication date: Available online 16 January 2016
      Source:Medical Engineering & Physics
      Author(s): S. Stuart, L. Alcock, A. Godfrey, S. Lord, L. Rochester, B. Galna
      Mobile eye-tracking is important for understanding the role of vision during real-world tasks in older adults (OA) and people with Parkinson's disease (PD). However, accuracy and reliability of such devices have not been established in these populations. We used a novel protocol to quantify accuracy and reliability of a mobile eye-tracker in OA and PD. A mobile eye-tracker (Dikablis) measured the saccade amplitudes of 20 OA and 14 PD on two occasions. Participants made saccades between targets placed 5°, 10° and 15° apart. Impact of visual correction (glasses) on saccadic amplitude measurement was also investigated in 10 OA. Saccade amplitude accuracy (median bias) was −1.21° but a wide range of bias (−7.73° to 5.81°) was seen in OA and PD, with large vertical saccades (15°) being least accurate. Reliability assessment showed a median difference between sessions of <1° for both groups, with poor to good relative agreement (Spearman rho: 0.14 to 0.85). Greater accuracy and reliability was observed in people without visual correction. Saccade amplitude can be measured with variable accuracy and reliability using a mobile eye-tracker in OA and PD. Human, technological and study-specific protocol factors may introduce error and are discussed along with methodological recommendations.


      PubDate: 2016-01-19T08:22:17Z
       
  • Development of a small wireless device for perspiration monitoring
    • Abstract: Publication date: Available online 15 January 2016
      Source:Medical Engineering & Physics
      Author(s): Kazuhiro Ogai, Masakazu Fukuoka, Kei-ichiro Kitamura, Kiyoshi Uchide, Tetsu Nemoto
      A small and wireless device that can capture the temporal pattern of perspiration by a novel structure of water vapor collection combined with reusable desiccant has been developed. The novel device consists of a small cylindrical case with a temperature/relative humidity sensor, battery-driven data logger, and silica gel (desiccant). Water vapor of perspiration was detected by the change in relative humidity and then adsorbed by silica gel, allowing continuous recording of perspiration within a closed and wireless chamber, which has not been previously achieved. By comparative experiments using the commercially-available perspiration monitoring device, the developed device could measure perspiration as efficiently as the conventional one, with a normalized cross coefficient of 0.738 with 6 s delay and the interclass correlation coefficient [ICC(2, 1)] of 0.84. These results imply a good agreement between the conventional and developed devices, and thus suggest the applicability of the developed device for perspiration monitoring.


      PubDate: 2016-01-19T08:22:17Z
       
  • A simple and reproducible capacitive electrode
    • Abstract: Publication date: Available online 11 January 2016
      Source:Medical Engineering & Physics
      Author(s): Enrique Spinelli, Federico Guerrero, Pablo García, Marcelo Haberman
      Capacitive Electrodes (CE) allow the acquisition of biopotentials through a dielectric layer, without the use of electrolytes, just by placing them on skin or clothing, but demands front-ends with ultra-high input impedances. This must be achieved while providing a path for bias currents, calling for ultra-high value resistors and special components and construction techniques. A simple CE that uses bootstrap techniques to avoid ultra-high value components and special materials is proposed. When electrodes are placed on the skin; that is, with coupling capacitances C S of around 100 pF, they present a noise level of 3.3 µVRMS in a 0.5–100 Hz bandwidth, which is appropriate for electrocardiography (ECG) measurements. Construction details of the CE and the complete circuit, including a fast recovery feature, are presented.


      PubDate: 2016-01-15T08:00:52Z
       
  • Wavelet-based unsupervised learning method for electrocardiogram
           suppression in surface electromyograms
    • Abstract: Publication date: Available online 13 January 2016
      Source:Medical Engineering & Physics
      Author(s): Maciej Niegowski, Miroslav Zivanovic
      We present a novel approach aimed at removing electrocardiogram (ECG) perturbation from single-channel surface electromyogram (EMG) recordings by means of unsupervised learning of wavelet-based intensity images. The general idea is to combine the suitability of certain wavelet decomposition bases which provide sparse electrocardiogram time-frequency representations, with the capacity of non-negative matrix factorization (NMF) for extracting patterns from images. In order to overcome convergence problems which often arise in NMF-related applications, we design a novel robust initialization strategy which ensures proper signal decomposition in a wide range of ECG contamination levels. Moreover, the method can be readily used because no a priori knowledge or parameter adjustment is needed. The proposed method was evaluated on real surface EMG signals against two state-of-the-art unsupervised learning algorithms and a singular spectrum analysis based method. The results, expressed in terms of high-to-low energy ratio, normalized median frequency, spectral power difference and normalized average rectified value, suggest that the proposed method enables better ECG–EMG separation quality than the reference methods.


      PubDate: 2016-01-15T08:00:52Z
       
  • Design and evaluation of a seat orientation controller during uneven
           terrain driving
    • Abstract: Publication date: Available online 13 January 2016
      Source:Medical Engineering & Physics
      Author(s): Jorge Candiotti, Hongwu Wang, Cheng-Shiu Chung, Deepan C Kamaraj, Garrett G Grindle, Motoki Shino, Rory A Cooper
      Electric powered wheelchairs (EPWs) are essential devices for people with disabilities as aids for mobility and quality of life improvement. However, the design of currently available common EPWs is still limited and makes it challenging for the users to drive in both indoor and outdoor environments such as uneven surfaces, steep hills, or cross slopes, making EPWs susceptible to loss of stability and at risk for falls. An alternative wheel-legged robotic wheelchair, “MEBot”, was designed to improve the safety and mobility of EPW users in both indoor and outdoor environments. MEBot is able to elevate its six wheels using pneumatic actuators, as well to detect changes in the seat angle using a gyroscope and accelerometer. This capability enables MEBot to provide sensing for a dynamic self-leveling seat application that can maintain the center of mass within the boundaries of the wheelchair, thereby, improving EPW safety. To verify the effectiveness of the application, MEBot was tested on a motion platform with six degrees of freedom to simulate different slopes that could be experienced by the EPW in outdoor environments. The results demonstrate the robustness of the application to maintain the wheelchair seat in a horizontal reference against changes in the ground angle.


      PubDate: 2016-01-15T08:00:52Z
       
  • The biomechanical effect of anteversion and modular neck offset on stress
           shielding for short-stem versus conventional long-stem hip implants
    • Abstract: Publication date: Available online 7 January 2016
      Source:Medical Engineering & Physics
      Author(s): Peter Goshulak, Saeid Samiezadeh, Mina S.R. Aziz, Habiba Bougherara, Radovan Zdero, Emil H. Schemitsch
      Short-stem hip implants are increasingly common since they preserve host bone stock and presumably reduce stress shielding by improving load distribution in the proximal femur. Stress shielding may lead to decreased bone density, implant loosening, and fracture. However, few biomechanical studies have examined short-stem hip implants. The purpose of this study was to compare short-stem vs. standard length stemmed implants for stress shielding effects due to anteversion–retroversion, anterior–posterior position, and modular neck offset. Twelve artificial femurs were implanted with either a short-stem modular-neck implant or a conventional length monolithic implant in 0° or 15° of anteversion. Three modular neck options were tested in the short-stem implants. Three control femurs remained intact. Femurs were mounted in adduction and subjected to axial loading. Strain gauge values were collected to validate a Finite Element (FE) model, which was used to simulate the full range of physiologically possible anteversion and anterior–posterior combinations (n = 25 combinations per implant). Calcar stress was compared between implants and across each implant's range of anteversion using one and two-way ANOVA. Stress shielding was defined as the overall change in stress compared to an intact femur. The FE model compared well with experimental strains (intact: slope = 0.898, R = 0.943; short-stem: slope = 0.731, R = 0.948; standard-stem: slope = 0.743, R = 0.859); correction factors were used to adjust slopes to unity. No implant anteversion showed significant reduction in stress shielding (α = 0.05, p > 0.05). Stress shielding was significantly higher in the standard-stem implant (63% change from intact femur, p < 0.001) than in short-stem implants (29–39% change, p < 0.001). Short-stem implants reduce stress shielding compared to standard length stemmed implants, while implant anteversion and anterior–posterior position had no effect. Therefore, short-stem implants have a greater likelihood of maintaining calcar bone strength in the long term.


      PubDate: 2016-01-11T07:48:46Z
       
  • Determining in vivo sternoclavicular, acromioclavicular and glenohumeral
           joint centre locations from skin markers, CT-scans and intracortical pins:
           A comparison study
    • Abstract: Publication date: Available online 7 January 2016
      Source:Medical Engineering & Physics
      Author(s): B. Michaud, M. Jackson, A. Arndt, A. Lundberg, M. Begon
      To describe shoulder motion the sternoclavicular, acromioclavicular and glenohumeral joint centres must be accurately located. Within the literature various methods to estimate joint centres of rotation location are proposed, with no agreement of the method best suited to the shoulder. The objective of this study was to determine the most reliable non-invasive method for locating joint centre locations of the shoulder complex. Functional methods using pin mounted markers were compared to anatomical methods, functional methods using skin mounted markers, imaging-based methods using CT-scan data, and regression equations. Three participants took part in the study, that involved insertion of intracortical pins into the clavicle, scapula and humerus, a CT-scan of the shoulder, and finally data collection using a motion analysis system. The various methods to estimate joint centre location did not all agree, however suggestions about the most reliable non-invasive methods could be made. For the sternoclavicular joint, the authors suggest the anatomical method using the most ventral landmark on the sternoclavicular joint, as recommended by the International Society of Biomechanics. For the acromioclavicular joint, the authors suggest the anatomical method using the landmark defined as the most dorsal point on the acromioclavicular joint, as proposed by van der Helm. For the glenohumeral joint, the simple regression equation of Rab is recommended.


      PubDate: 2016-01-11T07:48:46Z
       
  • Sensitivity analysis of the position of the intervertebral centres of
           reaction in upright standing – a musculoskeletal model investigation
           of the lumbar spine
    • Abstract: Publication date: Available online 7 January 2016
      Source:Medical Engineering & Physics
      Author(s): Thomas Zander, Marcel Dreischarf, Hendrik Schmidt
      The loads between adjacent vertebrae can be generalised as a single spatial force acting at the intervertebral centre of reaction. The exact position in vivo is unknown. However, in rigid body musculoskeletal models that simulate upright standing, the position is generally assumed to be located at the discs’ centres of rotation. The influence of the antero-posterior position of the centre of reaction on muscle activity and joint loads remains unknown. Thus, by using an inverse dynamic model, we varied the position of the centre of reaction at L4/L5 (i), simultaneously at all lumbar levels (ii), and by optimisation at all lumbar levels (iii). Variation of the centres of reaction can considerably influence the activities of lumbar muscles and the joint forces between vertebrae. The optimisation of the position of the centre of reaction reduced the maximum lumbar muscle activity and axial joint forces at L4/L5 from 17.5% to 1.5% of the muscle strength and from 490 N to 390 N, respectively. Thus, when studying individual postures, such as for therapeutic or preventive evaluations, potential differences between the centre of reaction and the centre of rotation might influence the study results. These differences could be taken into account by sensitivity analyses.


      PubDate: 2016-01-11T07:48:46Z
       
  • Pedicle screw cement augmentation. A mechanical pullout study on different
           cement augmentation techniques
    • Abstract: Publication date: Available online 4 January 2016
      Source:Medical Engineering & Physics
      Author(s): Francesco Costa, Alessandro Ortolina, Fabio Galbusera, Andrea Cardia, Giuseppe Sala, Franco Ronchi, Carlo Uccelli, Rossella Grosso, Maurizio Fornari
      Pedicle screws with polymethyl methacrylate (PMMA) cement augmentation have been shown to significantly improve the fixation strength in a severely osteoporotic spine. However, the efficacy of screw fixation for different cement augmentation techniques remains unknown. This study aimed to determine the difference in pullout strength between different cement augmentation techniques. Uniform synthetic bones simulating severe osteoporosis were used to provide a platform for each augmentation technique. In all cases a polyaxial screw and acrylic cement (PMMA) at medium viscosity were used. Five groups were analyzed: I) only screw without PMMA (control group); II) retrograde cement pre-filling of the tapped area; III) cannulated and fenestrate screw with cement injection through perforation; IV) injection using a standard trocar of PMMA (vertebroplasty) and retrograde pre-filling of the tapped area; V) injection through a fenestrated trocar and retrograde pre-filling of the tapped area. Standard X-rays were taken in order to visualize cement distribution in each group. Pedicle screws at full insertion were then tested for axial pullout failure using a mechanical testing machine. A total of 30 screws were tested. The results of pullout analysis revealed better results of all groups with respect to the control group. In particular the statistical analysis showed a difference of Group V (p = 0.001) with respect to all other groups. These results confirm that the cement augmentation grants better results in pullout axial forces. Moreover they suggest better load resistance to axial forces when the distribution of the PMMA is along all the screw combining fenestration and pre-filling augmentation technique.


      PubDate: 2016-01-07T07:29:16Z
       
  • Quantitative assessment of colorectal morphology: Implications for robotic
           colonoscopy
    • Abstract: Publication date: Available online 4 January 2016
      Source:Medical Engineering & Physics
      Author(s): A. Alazmani, A. Hood, D. Jayne, A. Neville, P. Culmer
      This paper presents a method of characterizing the distribution of colorectal morphometrics. It uses three-dimensional region growing and topological thinning algorithms to determine and visualize the luminal volume and centreline of the colon, respectively. Total and segmental lengths, diameters, volumes, and tortuosity angles were then quantified. The effects of body orientations on these parameters were also examined. Variations in total length were predominately due to differences in the transverse colon and sigmoid segments, and did not significantly differ between body orientations. The diameter of the proximal colon was significantly larger than the distal colon, with the largest value at the ascending and cecum segments. The volume of the transverse colon was significantly the largest, while those of the descending colon and rectum were the smallest. The prone position showed a higher frequency of high angles and consequently found to be more torturous than the supine position. This study yielded a method for complete segmental measurements of healthy colorectal anatomy and its tortuosity. The transverse and sigmoid colons were the major determinant in tortuosity and morphometrics between body orientations. Quantitative understanding of these parameters may potentially help to facilitate colonoscopy techniques, accuracy of polyp spatial distribution detection, and design of novel endoscopic devices.


      PubDate: 2016-01-07T07:29:16Z
       
  • Femoral neck anteversion measurement using linear slot scanning
           radiography
    • Abstract: Publication date: Available online 6 January 2016
      Source:Medical Engineering & Physics
      Author(s): Chipo Chimhundu, Sudesh Sivarasu, Stefan Steiner, Julian Smit, Tania S. Douglas
      Measurements between anatomical landmarks on radiographs are useful for diagnosis and treatment planning in the orthopedic field. Direct measurement on single radiographic images, however, does not truly reflect spatial relationships, as depth information is lost. We used stereo images from a slot scanning X-ray machine to estimate coordinates of three-dimensional (3D) bony landmarks for femoral neck anteversion (FNA) measurement. A set of 7 landmarks consisting of the centre of the femoral head; the centre of the base of the femoral neck; the medial and lateral condyles; the medial and lateral posterior condyles; and finally the centre of the knee; were found to be identifiable and suitable for radiographic measurement. The reconstructed 3D coordinates were then used to define the 3D geometry of the anatomical axes required to estimate FNA. Stereophotogrammetric measurements on a sample of 30 dry right adult femurs were compared to reference values obtained using the Kingsley Olmstead method applied to photographic images. A strong positive correlation (0.998) was found and the mean ± standard deviation of the stereophotogrammetric approach (13.08 ± 6.87)° was comparable to that of the Kingsley Olmstead method (13.14 ± 6.88)°. Intra- and inter-observer reliability were high, with the lower bound of the 95% confidence interval above 0.98 for the intra-class correlation coefficient. The results merit further validation against three dimensional imaging technology such as computed tomography, to confirm stereophotogrammetry as a suitable alternative for FNA measurement.


      PubDate: 2016-01-07T07:29:16Z
       
  • Effect of embedded optical fibres on the mechanical properties of cochlear
           electrode arrays
    • Abstract: Publication date: Available online 6 January 2016
      Source:Medical Engineering & Physics
      Author(s): Emma M. Carland, Paul R. Stoddart, Peter J. Cadusch, James B. Fallon, Scott A. Wade
      Incorporating optical fibres in cochlear electrode arrays has been proposed to provide sensors to help minimise insertion trauma and also for the delivery of light in optical nerve stimulation applications. However, embedding an optical fibre into an electrode array may change its stiffness properties, which can affect the level of trauma during insertion. This report uses measurements of buckling and deflection force to compare the stiffness properties of a range of cochlear electrode arrays (Nucleus straight array, rat array, cat array and guinea pig array) with custom arrays containing an embedded optical fibre. The cladding diameters of the optical fibres tested were 125 µm, 80 µm and 50 µm. The results show that the stiffness of the optical-fibre-embedded arrays is related to the diameter of the optical fibre. Comparison with wired arrays suggests optical fibres with a diameter of 50 µm could be embedded into an electrode array without significantly changing the stiffness properties of the array.


      PubDate: 2016-01-07T07:29:16Z
       
  • Investigating cerebral oedema using poroelasticity
    • Abstract: Publication date: Available online 31 December 2015
      Source:Medical Engineering & Physics
      Author(s): John C. Vardakis, Dean Chou, Brett J. Tully, Chang C. Hung, Tsong H. Lee, Po-Hsiang Tsui, Yiannis Ventikos
      Cerebral oedema can be classified as the tangible swelling produced by expansion of the interstitial fluid volume. Hydrocephalus can be succinctly described as the abnormal accumulation of cerebrospinal fluid (CSF) within the brain which ultimately leads to oedema within specific sites of parenchymal tissue. Using hydrocephalus as a test bed, one is able to account for the necessary mechanisms involved in the interaction between oedema formation and cerebral fluid production, transport and drainage. The current state of knowledge about integrative cerebral dynamics and transport phenomena indicates that poroelastic theory may provide a suitable framework to better understand various diseases. In this work, Multiple-Network Poroelastic Theory (MPET) is used to develop a novel spatio-temporal model of fluid regulation and tissue displacement within the various scales of the cerebral environment. The model is applied through two formats, a one-dimensional finite difference – Computational Fluid Dynamics (CFD) coupling framework, as well as a two-dimensional Finite Element Method (FEM) formulation. These are used to investigate the role of endoscopic fourth ventriculostomy in alleviating oedema formation due to fourth ventricle outlet obstruction (1D coupled model) in addition to observing the capability of the FEM template in capturing important characteristics allied to oedema formation, like for instance in the periventricular region (2D model).


      PubDate: 2016-01-03T05:32:51Z
       
  • Can we safely deform a plate to fit every bone' Population-based fit
           assessment and finite element deformation of a distal tibial plate
    • Abstract: Publication date: Available online 28 December 2015
      Source:Medical Engineering & Physics
      Author(s): Hazreen Harith, Beat Schmutz, Javad Malekani, Michael A. Schuetz, Prasad K. Yarlagadda
      Anatomically precontoured plates are commonly used to treat periarticular fractures. A well-fitting plate can be used as a tool for anatomical reduction of the fractured bone. Recent studies highlighted that some plates fit poorly for many patients due to considerable shape variations between bones of the same anatomical site. While it is impossible to design one shape that fits all, it is also burdensome for the manufacturers and hospitals to produce, store and manage multiple plate shapes without the certainty of utilization by a patient population. In this study, we investigated the number of shapes required for maximum fit within a given dataset, and if they could be obtained by manually deforming the original plate. A distal medial tibial plate was automatically positioned on 45 individual tibiae, and the optimal deformation was determined iteratively using finite element analysis simulation. Within the studied dataset, we found that: (i) 89% fit could be achieved with four shapes, (ii) 100% fit was impossible through mechanical deformation, and (iii) the deformations required to obtain the four plate shapes were safe for the stainless steel plate for further clinical use. The proposed framework is easily transferable to other orthopaedic plates.


      PubDate: 2015-12-30T04:31:07Z
       
  • Long-term response of femoral density to hip implant and bone fracture
           plate: Computational study using a mechano-biochemical model
    • Abstract: Publication date: Available online 29 December 2015
      Source:Medical Engineering & Physics
      Author(s): Pouria Tavakkoli Avval, Saeid Samiezadeh, Habiba Bougherara
      Although bone fracture plates can provide appropriate stability at the fracture site and lead to early patient mobilization, they significantly change the loading pattern in the bone after union (Stress shielding). This phenomenon results in a bone density decrease, which may cause premature failure of the implant. This paper presents the first study that quantifies the long-term response of femoral density to hip implantation and plating (lateral and anterior plating) using a mechano-biochemical model which considers the coupling effect between mechanical loading and biochemical affinities as stimuli for bone remodeling. The results showed that the regions directly beneath the plate experienced severe bone loss (i.e. up to ∼ –70%). However, some level of bone formation was observed in the vicinity of the most proximal and distal screw holes in both lateral and anterior plated femurs (i.e. up to ∼ +110%). The bone under the plate was divided into six zones. With respect to bone remodeling response, the findings revealed that anterior plating was not superior to lateral plating since the maximum and average bone losses among the zones in the anterior plated femur (i.e. –36% and –24%, respectively) were approximately the same as their corresponding values in the lateral plated femur (i.e. –38% and –24%, respectively).


      PubDate: 2015-12-30T04:31:07Z
       
  • Measurement of wheelchair contact force with a low cost bench test
    • Abstract: Publication date: Available online 28 December 2015
      Source:Medical Engineering & Physics
      Author(s): L.C.A. Silva, F.G. Dedini, F.C. Corrêa, J.J. Eckert, M. Becker
      In mechanical engineering, it is well established that contact between the tire and the ground is a key parameter in characterizing the dynamic behavior of vehicles and an important factor in design control. Therefore, it is an important part of dynamic simulation models for vehicles, including wheelchairs. This work presents a bench test designed to experimentally monitor and measure the forces transmitted to the ground by a moving wheel. The test bench is composed of a table and a track with a fixed wheel structure and powertrain system. The table is an integrated structure that measures the longitudinal and lateral forces produced by tire contact. This table allows characterization of the tire and tests the tire under varying loads at different slip and camber angles. Additionally, the test bench can also be used to evaluate other tires, such as caster tires. The performances of the new device are illustrated, and the results show the differences between tires, which are related to the dynamic behaviors of wheelchair model. Finally, preliminary experiments performed using the test bench have shown that it is able to monitor and measure the forces generated by the contact between the tire and the ground.


      PubDate: 2015-12-30T04:31:07Z
       
  • A review of virtual reality based training simulators for orthopaedic
           surgery
    • Abstract: Publication date: Available online 29 December 2015
      Source:Medical Engineering & Physics
      Author(s): Neil Vaughan, Venketesh N. Dubey, Thomas W. Wainwright, Robert G. Middleton
      This review presents current virtual reality based training simulators for hip, knee and other orthopaedic surgery, including elective and trauma surgical procedures. There have not been any reviews focussing on hip and knee orthopaedic simulators. A comparison of existing simulator features is provided to identify what is missing and what is required to improve upon current simulators. In total 11 hip replacements pre-operative planning tools were analysed, plus 9 hip trauma fracture training simulators. Additionally 9 knee arthroscopy simulators and 8 other orthopaedic simulators were included for comparison. The findings are that for orthopaedic surgery simulators in general, there is increasing use of patient-specific virtual models which reduce the learning curve. Modelling is also being used for patient-specific implant design and manufacture. Simulators are being increasingly validated for assessment as well as training. There are very few training simulators available for hip replacement, yet more advanced virtual reality is being used for other procedures such as hip trauma and drilling. Training simulators for hip replacement and orthopaedic surgery in general lag behind other surgical procedures for which virtual reality has become more common. Further developments are required to bring hip replacement training simulation up to date with other procedures. This suggests there is a gap in the market for a new high fidelity hip replacement and resurfacing training simulator.


      PubDate: 2015-12-30T04:31:07Z
       
  • In-situ mechanical behavior and slackness of the anterior cruciate
           ligament at multiple knee flexion angles
    • Abstract: Publication date: Available online 22 December 2015
      Source:Medical Engineering & Physics
      Author(s): H.H. Rachmat, D. Janssen, G.J. Verkerke, R.L. Diercks, N. Verdonschot
      In this study the in-situ tensile behavior and slackness of the anterior cruciate ligament (ACL) was evaluated at various knee flexion angles. In four cadaveric knees the ACL was released at the tibial insertion, after which it was re-connected to a tensiometer. After pre-tensioning (10 N) the ACL in full-extension, the knee was flexed from 0° to 150° at 15° increments, during which the ACL tension was measured. At each angle the ACL was subsequently elongated and shortened under displacement control, while measuring the ACL tension. In this manner, the pre-tension or the slackness, and the mechanical response of the ACL were measured. All ACL's displayed a higher tension at low (0°–60°) and high (120°–150°) flexion angles. The ACL slackness depended on flexion angle, with the highest slackness found at 75°–90°. Additionally, the ACL stiffness also varied with flexion angle, with the ACL behaving stiffer at low and high flexion angels. In general, the ACL was stiffest at 150°, and most compliant at 90°. The results of this study contribute to understanding the mechanical behavior of the ACL in-situ, and may help tuning and validating computational knee models studying ACL function.


      PubDate: 2015-12-26T03:55:56Z
       
  • High intensity focused ultrasound as a tool for tissue engineering:
           Application to cartilage
    • Abstract: Publication date: Available online 24 December 2015
      Source:Medical Engineering & Physics
      Author(s): Adam B. Nover, Gary Y. Hou, Yang Han, Shutao Wang, Grace D. O'Connell, Gerard A. Ateshian, Elisa E. Konofagou, Clark T. Hung
      This article promotes the use of High Intensity Focused Ultrasound (HIFU) as a tool for affecting the local properties of tissue engineered constructs in vitro. HIFU is a low cost, non-invasive technique used for eliciting focal thermal elevations at variable depths within tissues. HIFU can be used to denature proteins within constructs, leading to decreased permeability and potentially increased local stiffness. Adverse cell viability effects remain restricted to the affected area. The methods described in this article are explored through the scope of articular cartilage tissue engineering and the fabrication of osteochondral constructs, but may be applied to the engineering of a variety of different tissues.
      Graphical abstract image

      PubDate: 2015-12-26T03:55:56Z
       
  • Automated pressure map segmentation for quantifying phalangeal kinetics
           during cylindrical gripping
    • Abstract: Publication date: Available online 18 December 2015
      Source:Medical Engineering & Physics
      Author(s): Erik W. Sinsel, Daniel S. Gloekler, Bryan M. Wimer, Christopher M. Warren, John Z. Wu, Frank L. Buczek
      Inverse dynamics models used to investigate musculoskeletal disorders associated with handle gripping require accurate phalangeal kinetics. Cylindrical handles wrapped with pressure film grids have been used in studies of gripping kinetics. We present a method fusing six degree-of-freedom hand kinematics and a kinematic calibration of a cylinder-wrapped pressure film. Phalanges are modeled as conic frusta and projected onto the pressure grid, automatically segmenting the pressure map into regions of interest (ROIs). To demonstrate the method, segmented pressure maps are presented from two subjects with substantially different hand length and body mass, gripping cylinders 50 and 70 mm in diameter. For each ROI, surface-normal force vectors were summed to create a reaction force vector and center of pressure location. Phalangeal force magnitudes for a data sample were similar to that reported in previous studies. To evaluate our method, a surrogate was designed for each handle such that when modeled as a phalanx it would generate a ROI around the cells under its supports; the classification F-score was above 0.95 for both handles. Both the human subject results and the surrogate evaluation suggest that the approach can be used to automatically segment the pressure map for quantifying phalangeal kinetics of the fingers during cylindrical gripping.


      PubDate: 2015-12-22T03:22:08Z
       
  • Validity of an inertial measurement unit to assess pelvic orientation
           angles during gait, sit–stand transfers and step-up transfers:
           Comparison with an optoelectronic motion capture system*
    • Abstract: Publication date: Available online 19 December 2015
      Source:Medical Engineering & Physics
      Author(s): S.A.A.N. Bolink, H. Naisas, R. Senden, H. Essers, I.C. Heyligers, K. Meijer, B. Grimm
      An inertial measurement unit (IMU) allows kinematic evaluation of human motion with fewer operational constraints than a gold standard optoelectronic motion capture (MOCAP) system. The study's aim was to compare IMU and MOCAP measurements of dynamic pelvic orientation angles during different activities of daily life (ADL): gait, sit-to-stand (STS) transfers and block step-up (BS) transfers. A single IMU was attached onto the lower back in seventeen healthy participants (8F/9 M, age 19–31 years; BMI < 25) and optical skin markers were attached onto anatomical pelvic landmarks for MOCAP measurements. Comparisons between IMU and MOCAP by Bland–Altman plots demonstrated that measurements were between 2SD of the absolute difference and Pearson's correlation coefficients were between 0.85 and 0.94. Frontal plane pelvic angle estimations achieved a RMSE in the range of [2.7°–4.5°] and sagittal plane measurements achieved a RMSE in the range of [2.7°–8.9°] which were both lowest in gait. Waveform peak detection times demonstrated ICCs between 0.96 and 1.00. These results are in accordance to other studies comparing IMU and MOCAP measurements with different applications and suggest that an IMU is a valid tool to measure dynamic pelvic angles during various activities of daily life which could be applied to monitor rehabilitation in a wide variety of musculoskeletal disorders.


      PubDate: 2015-12-22T03:22:08Z
       
  • Regularity analysis of nocturnal oximetry recordings to assist in the
           diagnosis of sleep apnoea syndrome
    • Abstract: Publication date: Available online 21 December 2015
      Source:Medical Engineering & Physics
      Author(s): J. Víctor Marcos, Roberto Hornero, Ian T. Nabney, Daniel Álvarez, Gonzalo C. Gutiérrez-Tobal, Félix del Campo
      The relationship between sleep apnoea–hypopnoea syndrome (SAHS) severity and the regularity of nocturnal oxygen saturation (SaO2) recordings was analysed. Three different methods were proposed to quantify regularity: approximate entropy (AEn), sample entropy (SEn) and kernel entropy (KEn). A total of 240 subjects suspected of suffering from SAHS took part in the study. They were randomly divided into a training set (96 subjects) and a test set (144 subjects) for the adjustment and assessment of the proposed methods, respectively. According to the measurements provided by AEn, SEn and KEn, higher irregularity of oximetry signals is associated with SAHS-positive patients. Receiver operating characteristic (ROC) and Pearson correlation analyses showed that KEn was the most reliable predictor of SAHS. It provided an area under the ROC curve of 0.91 in two-class classification of subjects as SAHS-negative or SAHS-positive. Moreover, KEn measurements from oximetry data exhibited a linear dependence on the apnoea–hypopnoea index, as shown by a correlation coefficient of 0.87. Therefore, these measurements could be used for the development of simplified diagnostic techniques in order to reduce the demand for polysomnographies. Furthermore, KEn represents a convincing alternative to AEn and SEn for the diagnostic analysis of noisy biomedical signals.


      PubDate: 2015-12-22T03:22:08Z
       
  • Composite time-lapse computed tomography and micro finite element
           simulations: A new imaging approach for characterizing cement flows and
           mechanical benefits of vertebroplasty
    • Abstract: Publication date: Available online 10 December 2015
      Source:Medical Engineering & Physics
      Author(s): Vincent A Stadelmann, Ivan Zderic, Annick Baur, Cynthia Unholz, Ursula Eberli, Boyko Gueorguiev
      Vertebroplasty has been shown to reinforce weak vertebral bodies and reduce fracture risks, yet cement leakage is a major problem that can cause severe complications. Since cement flow is nearly impossible to control during surgery, small volumes of cement are injected, but then mechanical benefits might be limited. A better understanding of cement flows within bone structure is required to further optimize vertebroplasty and bone augmentation in general. We developed a novel imaging method, composite time-lapse CT, to characterize cement flow during injection. In brief, composite-resolution time-lapse CT exploits the qualities of microCT and clinical CT. The method consists in overlaying low-resolution time-lapse CT scans acquired during injection onto pre-operative high-resolution microCT scans, generating composite-resolution time-lapse CT series of cement flow within bone. In this in vitro study, composite-resolution time-lapse CT was applied to eight intact and five artificially fractured cadaveric vertebrae during vertebroplasty. The time-lapse scans were acquired at one-milliliter cement injection steps until a total of 10 ml cement was injected. The composite-resolution series were then converted into micro finite element models to compute strains distribution under virtual axial loading. Relocation of strain energy density within bone structure was observed throughout the progression of the procedure. Interestingly, the normalized effect of cement injection on the overall stiffness of the vertebrae was similar between intact and fractured specimens, although at different orders of magnitude. In conclusion, composite time-lapse CT can picture cement flows during bone augmentation. The composite images can also be easily converted into finite element models to compute virtual strain distributions under loading at every step of an injection, providing deeper understanding on the biomechanics of vertebroplasty.


      PubDate: 2015-12-14T01:43:27Z
       
  • Special Issue “Micro and Nano Flows 2014 (MNF2014) –
           Biomedical Stream”
    • Abstract: Publication date: Available online 11 December 2015
      Source:Medical Engineering & Physics
      Author(s): Guest Editor Carola S. König, Guest Editor Stavroula Balabani



      PubDate: 2015-12-14T01:43:27Z
       
  • Electromagnetic interference in intraoperative monitoring of motor evoked
           potentials and a wireless solution
    • Abstract: Publication date: Available online 8 December 2015
      Source:Medical Engineering & Physics
      Author(s): Aydin Farajidavar, Jennifer L. Seifert, Mauricio R. Delgado, Steven Sparagana, Mario I. Romero-Ortega, J.-C. Chiao
      Intraoperative neurophysiological monitoring (IONM) is utilized to minimize neurological morbidity during spine surgery. Transcranial motor evoked potentials (TcMEPs) are principal IONM signals in which the motor cortex of the subject is stimulated with electrical pulses and the evoked potentials are recorded from the muscles of interest. Currently available monitoring systems require the connection of 40–60 lengthy lead wires to the patient. These wires contribute to a crowded and cluttered surgical environment, and limit the maneuverability of the surgical team. In this work, it was demonstrated that the cumbersome wired system is vulnerable to electromagnetic interference (EMI) produced by operating room (OR) equipment. It was hypothesized that eliminating the lengthy recording wires can remove the EMI induced in the IONM signals. Hence, a wireless system to acquire TcMEPs was developed and validated through bench-top and animal experiments. Side-by-side TcMEPs acquisition from the wired and wireless systems in animal experiments under controlled conditions (absence of EMI from OR equipment) showed comparable magnitudes and waveforms, thus demonstrating the fidelity in the signal acquisition of the wireless solution. The robustness of the wireless system to minimize EMI was compared with a wired-system under identical conditions. Unlike the wired-system, the wireless system was not influenced by the electromagnetic waves from the C-Arm X-ray machine and temperature management system in the OR.


      PubDate: 2015-12-10T01:01:07Z
       
  • Constitutive modeling of ascending thoracic aortic aneurysms using
           microstructural parameters
    • Abstract: Publication date: Available online 6 December 2015
      Source:Medical Engineering & Physics
      Author(s): Salvatore Pasta, Julie A. Phillippi, Alkiviadis Tsamis, Antonio D'Amore, Giuseppe M. Raffa, Michele Pilato, Cesare Scardulla, Simon C. Watkins, William R. Wagner, Thomas G. Gleason, David A. Vorp
      Ascending thoracic aortic aneurysm (ATAA) has been associated with diminished biomechanical strength and disruption in the collagen fiber microarchitecture. Additionally, the congenital bicuspid aortic valve (BAV) leads to a distinct extracellular matrix structure that may be related to ATAA development at an earlier age than degenerative aneurysms arising in patients with the morphological normal tricuspid aortic valve (TAV). The purpose of this study was to model the fiber-reinforced mechanical response of ATAA specimens from patients with either BAV or TAV. This was achieved by combining image-analysis derived parameters of collagen fiber dispersion and alignment with tensile testing data. Then, numerical simulations were performed to assess the role of anisotropic constitutive formulation on the wall stress distribution of aneurysmal aorta. Results indicate that both BAV ATAA and TAV ATAA have altered collagen fiber architecture in the medial plane of experimentally-dissected aortic tissues when compared to normal ascending aortic specimens. The study findings highlight that differences in the collagen fiber distribution mostly influences the resulting wall stress distribution rather than the peak stress. We conclude that fiber-reinforced constitutive modeling that takes into account the collagen fiber defect inherent to the aneurysmal ascending aorta is paramount for accurate finite element predictions and ultimately for biomechanical-based indicators to reliably distinguish the more from the less ‘malignant’ ATAAs.
      Graphical abstract image

      PubDate: 2015-12-10T01:01:07Z
       
  • Editorial Board
    • Abstract: Publication date: December 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 12




      PubDate: 2015-12-06T00:50:03Z
       
  • Microfluidic interactions between red blood cells and drug carriers by
           image analysis techniques
    • Abstract: Publication date: Available online 2 December 2015
      Source:Medical Engineering & Physics
      Author(s): Rosa D'Apolito, Francesca Taraballi, Silvia Minardi, Xuewu Liu, Sergio Caserta, Armando Cevenini, Ennio Tasciotti, Giovanna Tomaiuolo, Stefano Guido
      Blood is a complex biological fluid composed of deformable cells and platelets suspended in plasma, a protein-rich liquid. The peculiar nature of blood needs to be considered when designing a drug delivery strategy based on systemically administered carriers. Here, we report on an in vitro fluid dynamic investigation of the influence of the microcapillary flow of red blood cells (RBCs) on micron-sized carriers by high-speed imaging methods. The experiments were carried out in a 50 µm diameter glass capillary that mimicked the hydrodynamic conditions of human microcirculation. Spherical μ-particles (μ-Ps), with sizes ranging between 0.5 and 3 µm, were tested. Images of the flowing RBCs and μ-Ps were acquired by a high- speed/high-magnification microscopy. The transport and distribution of rigid particles in a suspension of RBCs under shear flow were investigated by analyzing: (i) the velocity profile of both μ-Ps and RBCs in the capillary; (ii) the radial distribution of μ-Ps in the presence of RBCs; (iii) the migration of μ-Ps towards the vessel wall due to their hydrodynamic interactions with RBCs. This study suggests that the therapeutic efficacy of μ-Ps could be ultimately affected by their interactions with the flowing RBCs in the vasculature.


      PubDate: 2015-12-06T00:50:03Z
       
  • The performance characteristics of a piezoelectric ultrasonic dental
           scaler
    • Abstract: Publication date: Available online 2 December 2015
      Source:Medical Engineering & Physics
      Author(s): E. Pecheva, R.L. Sammons, A.D. Walmsley
      The objective of this work was to investigate the performance characteristics of a piezoelectric ultrasonic dental scaler using scanning laser vibrometry. The vibration characteristics of three standard piezoelectric tips were assessed with scanning laser vibrometry under various conditions: unconstrained, under a stream of flowing water, in a water tank, as well as subjected to loads to simulate clinical conditions. Subsequently, the tips were used to disrupt an in-vitro biofilm model of dental plaque, developed using a non-pathogenic Gram-negative species of Serratia (NCIMB40259). The laser vibrometry data showed that the oscillation pattern of the ultrasonic tip depends primarily on its shape and design, as well as on the generator power. Thin tips and high power settings induce the highest vibrations. Water irrigation of the tip and loads influence the tip performance by diminishing its vibration, while water volume increases it. Serratia biofilm was disrupted by the cavitation bubbles occurring around the scaler tip. The most effective biofilm removal occurred with the thinner tip. Understanding how the ultrasonic tip oscillates when in use and how it removes dental plaque is essential for gaining more knowledge regarding the cleaning mechanisms of the ultrasonic system. Cavitation may be used to remove plaque and calculus without a mechanical contact between the dental tip and the teeth. Better knowledge would enable dental specialists to understand and improve their techniques during routine cleaning of teeth. It will also lead to improving tip design and to the production of more effective instruments for clinical use.


      PubDate: 2015-12-06T00:50:03Z
       
  • Design of a microfluidic strategy for trapping and screening single cells
    • Abstract: Publication date: Available online 2 December 2015
      Source:Medical Engineering & Physics
      Author(s): Paola Occhetta, Mara Licini, Alberto Redaelli, Marco Rasponi
      Traditionally, in vitro investigations on biology and physiology of cells rely on averaging the responses eliciting from heterogeneous cell populations, thus being unsuitable for assessing individual cell behaviors in response to external stimulations. In the last years, great interest has thus been focused on single cell analysis and screening, which represents a promising tool aiming at pursuing the direct and deterministic control over cause-effect relationships guiding cell behavior. In this regard, a high-throughput microfluidic platform for trapping and culturing adherent single cells was presented. A single cell trapping mechanism was implemented based on dynamic variation of fluidic resistances. A round-shaped culture chamber (Φ  =  250 µm, h  =  25 µm) was conceived presenting two connections with a main fluidic path: (i) an upper wide opening, and (ii) a bottom trapping junction which modulates the hydraulic resistance. Starting from eight different layouts, the chamber geometry was computationally optimized for maximizing the single cell trapping efficacy and then integrated in a polydimethylsiloxane (PDMS) microfluidic device. The final platform consists in (i) 288 chambers for trapping single cells organized in six culture units, independently addressable through the lines of (ii) a chaotic-mixer based serial dilution generator (SDG), designed for creating spatio-temporally controlled patterns of both soluble factors and non-diffusive particles. The device was experimentally validated by trapping polystyrene microspheres, featuring diameters comparable to cell size (Φ  =  10 µm).


      PubDate: 2015-12-06T00:50:03Z
       
  • A finite element analysis of two novel screw designs for scaphoid waist
           fractures
    • Abstract: Publication date: Available online 2 December 2015
      Source:Medical Engineering & Physics
      Author(s): Peter Varga, Philippe K. Zysset, Philip Schefzig, Ewald Unger, Winfried Mayr, Jochen Erhart
      The scaphoid is the most often fractured carpal bone. Scaphoid fracture repair with a headless compression screw allows for early functional recovery. The rotational stability of a single screw may be limited, having a potential negative impact on the healing process. Two novel screws have been designed to provide improved rotational stability compared to the existing ones. Using a computational finite element model of a scaphoid osteotomy, we compared the efficacy of one simple screw and the two new screws in restricting inter-fragmentary motion (IFM) in three functional positions of the wrist and as a function of inter-fragmentary compression force. The in-plane IFM was primary rotational and was better restricted by the new screws compared to the conventional one when the inter-fragmentary compression force was below 15–20 N, but provided no clear benefit in total flexion independently of the compression force. To better understand the differences in the non-compressed case, we analyzed the acting moments and investigated the effects of the bending and torsional screw stiffness on IFM. By efficiently restricting the inter-fragmentary shear, the new screws may be clinically advantageous when the inter-fragmentary compression force is partially or completely lost and may provide further benefits toward earlier and better healing of transverse waist fractures of the scaphoid.


      PubDate: 2015-12-06T00:50:03Z
       
  • Mesh management methods in finite element simulations of orthodontic tooth
           movement
    • Abstract: Publication date: Available online 3 December 2015
      Source:Medical Engineering & Physics
      Author(s): M. Mengoni, J.-P. Ponthot, R. Boman
      In finite element simulations of orthodontic tooth movement, one of the challenges is to represent long term tooth movement. Large deformation of the periodontal ligament and large tooth displacement due to bone remodelling lead to large distortions of the finite element mesh when a Lagrangian formalism is used. We propose in this work to use an Arbitrary Lagrangian Eulerian (ALE) formalism to delay remeshing operations. A large tooth displacement is obtained including effect of remodelling without the need of remeshing steps but keeping a good-quality mesh. Very large deformations in soft tissues such as the periodontal ligament is obtained using a combination of the ALE formalism used continuously and a remeshing algorithm used when needed. This work demonstrates that the ALE formalism is a very efficient way to delay remeshing operations.


      PubDate: 2015-12-06T00:50:03Z
       
  • Ex vivo estimation of cementless acetabular cup stability using an impact
           hammer
    • Abstract: Publication date: Available online 3 December 2015
      Source:Medical Engineering & Physics
      Author(s): Adrien Michel, Romain Bosc, Frédéric Sailhan, Romain Vayron, Guillaume Haiat
      Obtaining primary stability of acetabular cup (AC) implants is one of the main objectives of press-fit procedures used for cementless hip arthroplasty. The aim of this study is to investigate whether the AC implant primary stability can be evaluated using the signals obtained with an impact hammer. A hammer equipped with a force sensor was used to impact the AC implant in 20 bovine bone samples. For each sample, different stability conditions were obtained by changing the cavity diameter. For each configuration, the inserted AC implant was impacted four times with a maximum force comprised between 2500 and 4500 N. An indicator I was determined based on the partial impulse estimation and the pull-out force was measured. The implant stability and the value of the indicator I reached a maximum value for an interference fit equal to 1 mm for 18 out of 20 samples. When pooling all samples and all configurations, the implant stability and I were significantly correlated (R2 = 0.83). The AC implant primary stability can be assessed through the analysis of the impact force signals obtained using an impact hammer. Based on these ex vivo results, a medical device could be developed to provide a decision support system to the orthopedic surgeons.


      PubDate: 2015-12-06T00:50:03Z
       
  • Increased minimum toe clearance variability in patients with peripheral
           arterial disease
    • Abstract: Publication date: Available online 24 October 2015
      Source:Medical Engineering & Physics
      Author(s): Troy J. Rand, Shane R. Wurdeman, Jason M. Johanning, Iraklis I. Pipinos, Sara A. Myers
      Individuals with peripheral arterial disease (PAD) report difficulty walking and experience 73% more falls than their healthy counterparts, but no studies have investigated functional mechanisms contributing to increased falls. Minimum toe clearance (MTC) is the minimum vertical distance between the toe of the swinging leg and the walking surface when the leg is swinging, and decreased values are associated with an increased risk for falls. This study is the first such analysis in patients with PAD. Eighteen individuals with PAD and eighteen healthy controls walked on a treadmill before and after the onset of claudication pain. Mean MTC and the standard deviation of MTC values across the trial were calculated. Mean MTC was not different between groups in the pain-free (P = 0.244) or pain conditions (P = 0.565). MTC variability was increased for patients with PAD in pain-free (P = 0.048) and pain conditions (P = 0.019). No significant differences existed between conditions for MTC mean (P = 0.134) or MTC variability (P = 0.123). Increased MTC variability is present before and after the onset of claudication pain, and may be a useful assessment for treatment and rehabilitation efficacy in these patients.


      PubDate: 2015-10-27T02:54:27Z
       
  • Towards the assessment of local dynamic stability of level-grounded
           walking in an older population
    • Abstract: Publication date: Available online 16 October 2015
      Source:Medical Engineering & Physics
      Author(s): Dennis Hamacher, Daniel Hamacher, Navrag B. Singh, William R. Taylor, Lutz Schega
      Local dynamic stability is a critical aspect of stable gait but its assessment for use in clinical settings has not yet been sufficiently evaluated, particularly with respect to inertial sensors applied on the feet and/or trunk. Furthermore, key questions remain as to which state-space reconstruction is most reliable and valid. In this study, we evaluated the reliability as well as the ability of different sensor placement and state-spaces to distinguish between local dynamic stability in young and older adults. Gait data of 19 older and 20 young subjects were captured with inertial sensors twice within the first day as well as after seven days. 21 different signals (and combinations of signals) were used to span the system's state-space to calculate different measures of local dynamic stability. Our data revealed moderate or high effect sizes in 12 of the 21 old vs. young comparisons. We also observed considerable differences in the reliability of these 12 results, with intra-class correlation coefficients ranging from 0.09 to 0.81. Our results demonstrate that in order to obtain reliable and valid estimates of gait stability λ of walking time series is best evaluated using trunk data or 1-dimensional data from foot sensors.


      PubDate: 2015-10-27T02:54:27Z
       
  • The formation and function of the sclerosis rim in the femoral head: A
           biomechanical point of view
    • Abstract: Publication date: Available online 20 October 2015
      Source:Medical Engineering & Physics
      Author(s): ZhiPing Chen, Yong Xu, ZhenXi Qi, JinShui Zho
      Sclerosis rim surrounding the necrotic area is commonly found in necrotic femoral head, but the biomechanical function of sclerosis rim has received relatively little attention. Little is known about the formation and natural history of sclerosis rim. In the present work, we assume that the necrotic change may trigger bone remodeling process in the femoral head, which took place according to Huiskes' bone remodeling model incorporated with the FE simulations as described earlier. We then investigate the function of sclerosis rim as a mechanical supporter in delaying further collapse of the femoral head based on our sclerotic rim model. The main tasks of this study are: (1) simulation of the density distribution in the necrotic femoral head after bone remodeling; (2) calculation of maximal von Mises stress in the subchondral bone of the weight-bearing area of the femoral head over the necrotic area before and after bone remodeling. Results show that the sclerotic rim is, from the biomechanical point of view, an adaptive response to the decrease in elastic modulus of the femoral head, and that the sclerotic rim that acts as a compensatory structural reinforcement can usually significantly reduce the maximal stress in the subchondral bone when the lesion is small, but not when the lesion is large.


      PubDate: 2015-10-27T02:54:27Z
       
  • Gas transfer model to design a ventilator for neonatal total liquid
           ventilation
    • Abstract: Publication date: Available online 23 October 2015
      Source:Medical Engineering & Physics
      Author(s): Mirko Bonfanti, Antonio Cammi, Paola Bagnoli
      The study was aimed to optimize the gas transfer in an innovative ventilator for neonatal Total Liquid Ventilation (TLV) that integrates the pumping and oxygenation functions in a non-volumetric pulsatile device made of parallel flat silicone membranes. A computational approach was adopted to evaluate oxygen (O2) and carbon dioxide (CO2) exchanges between the liquid perfluorocarbon (PFC) and the oxygenating gas, as a function of the geometrical parameter of the device. A 2D semi-empirical model was implemented to this purpose using Comsol Multiphysics to study both the fluid dynamics and the gas exchange in the ventilator. Experimental gas exchanges measured with a preliminary prototype were compared to the simulation outcomes to prove the model reliability. Different device configurations were modeled to identify the optimal design able to guarantee the desired gas transfer. Good agreement between experimental and simulation outcomes was obtained, validating the model. The optimal configuration, able to achieve the desired gas exchange (ΔpCO2 = 16.5 mmHg and ΔpO2 = 69 mmHg), is a device comprising 40 modules, 300 mm in length (total exchange area = 2.28 m2). With this configuration gas transfer performance is satisfactory for all the simulated settings, proving good adaptability of the device.


      PubDate: 2015-10-27T02:54:27Z
       
  • Estimation of heart rate variability using a compact radiofrequency motion
           sensor
    • Abstract: Publication date: Available online 24 October 2015
      Source:Medical Engineering & Physics
      Author(s): Norihiro Sugita, Narumi Matsuoka, Makoto Yoshizawa, Makoto Abe, Noriyasu Homma, Hideharu Otake, Junghyun Kim, Yukio Ohtaki
      Physiological indices that reflect autonomic nervous activity are considered useful for monitoring peoples’ health on a daily basis. A number of such indices are derived from heart rate variability, which is obtained by a radiofrequency (RF) motion sensor without making physical contact with the user's body. However, the bulkiness of RF motion sensors used in previous studies makes them unsuitable for home use. In this study, a new method to measure heart rate variability using a compact RF motion sensor that is sufficiently small to fit in a user's shirt pocket is proposed. To extract a heart rate related component from the sensor signal, an algorithm that optimizes a digital filter based on the power spectral density of the signal is proposed. The signals of the RF motion sensor were measured for 29 subjects during the resting state and their heart rate variability was estimated from the measured signals using the proposed method and a conventional method. A correlation coefficient between true heart rate and heart rate estimated from the proposed method was 0.69. Further, the experimental results showed the viability of the RF sensor for monitoring autonomic nervous activity. However, some improvements such as controlling the direction of sensing were necessary for stable measurement.


      PubDate: 2015-10-27T02:54:27Z
       
 
 
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