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Showing 1401 - 1600 of 1720 Journals sorted alphabetically
Walailak Journal of Science and Technology     Open Access  
Web Ecology     Open Access   (Followers: 6)
Weed Science     Full-text available via subscription   (Followers: 7)
Weed Technology     Full-text available via subscription   (Followers: 2)
West African Journal of Applied Ecology     Open Access  
Western Undergraduate Research Journal : Health and Natural Sciences     Open Access  
Wetlands     Hybrid Journal   (Followers: 25)
Wildlife Biology     Open Access   (Followers: 14)
Wildlife Research     Hybrid Journal   (Followers: 15)
Wiley Interdisciplinary Reviews - System Biology and Medicine     Hybrid Journal   (Followers: 5)
Wiley Interdisciplinary Reviews : Developmental Biology     Hybrid Journal   (Followers: 3)
Wiley Interdisciplinary Reviews : Membrane Transport and Signaling     Hybrid Journal  
Wiley Interdisciplinary Reviews : RNA     Hybrid Journal   (Followers: 3)
World Crop Pests     Full-text available via subscription   (Followers: 1)
World Mycotoxin Journal     Full-text available via subscription   (Followers: 6)
Xenobiotica     Hybrid Journal   (Followers: 10)
Yeast     Hybrid Journal   (Followers: 10)
Zebrafish     Hybrid Journal   (Followers: 1)
Zeitschrift für Evidenz, Fortbildung und Qualität im Gesundheitswesen     Full-text available via subscription   (Followers: 6)
Zeitschrift für Naturforschung C : A Journal of Biosciences     Open Access   (Followers: 2)
Биологический вестник МГПУ имени Богдана Хмельницкого     Open Access   (Followers: 1)

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Journal Cover Medical Engineering & Physics
  [SJR: 0.784]   [H-I: 76]   [9 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1350-4533
   Published by Elsevier Homepage  [3039 journals]
  • Model-dependent and model-independent approaches for evaluating hepatic
           fibrosis in rat liver using shearwave dispersion ultrasound vibrometry
    • Authors: Haoming Lin; Xinyu Zhang; Yuanyuan Shen; Yi Zheng; Yanrong Guo; Ying Zhu; Xianfen Diao; Tianfu Wang; Siping Chen; Xin Chen
      Pages: 66 - 72
      Abstract: Publication date: January 2017
      Source:Medical Engineering & Physics, Volume 39
      Author(s): Haoming Lin, Xinyu Zhang, Yuanyuan Shen, Yi Zheng, Yanrong Guo, Ying Zhu, Xianfen Diao, Tianfu Wang, Siping Chen, Xin Chen
      This study assesses gradations of hepatic fibrosis in rat livers using both model-dependent and model-independent approaches. Liver fibrosis was induced in 37 rats using carbon tetrachloride (CCl4); 6 rats served as the controls. Shear wave velocity as a function of frequency, referred to as velocity dispersion, was measured in vitro by an ultrasound elastography method called shearwave dispersion ultrasound vibrometry (SDUV). For the model-dependent approach, the velocity dispersion data were fit to the Voigt model to solve the viscoelastic modulus. For the model-independent approach, the pattern of the velocity dispersion data was analyzed by linear regression to extract the slope and intercept features. The parameters obtained by both approaches were evaluated separately using a receiver operating characteristic (ROC) curve analysis. The results show that, of all the parameters for differentiating between grade F0–F1 and grade F2–F4 fibrosis, the intercept had the greatest value for the area under the ROC curve. This finding suggests that the model-independent approach may provide an alternative method to the model-dependent approach for staging liver fibrosis.

      PubDate: 2017-01-17T21:19:32Z
      DOI: 10.1016/j.medengphy.2016.10.007
      Issue No: Vol. 39 (2017)
       
  • Multiobjective optimization of cartilage stress for non-invasive,
           patient-specific recommendations of high tibial osteotomy correction angle
           – a novel method to investigate alignment correction
    • Abstract: Publication date: Available online 13 February 2017
      Source:Medical Engineering & Physics
      Author(s): Keke Zheng, Corey J Scholes, Junning Chen, David Parker, Qing Li
      Medial opening wedge high tibial osteotomy (MOWHTO) is a surgical procedure to treat knee osteoarthritis associated with varus deformity. However, the ideal final alignment of the Hip-Knee-Ankle (HKA) angle in the frontal plane, that maximizes procedural success and post-operative knee function, remains controversial. Therefore, the purpose of this study was to introduce a subject-specific modeling procedure in determining the biomechanical effects of MOWHTO alignment on tibiofemoral cartilage stress distribution. A 3D finite element knee model derived from magnetic resonance imaging of a healthy participant was manipulated in-silico to simulate a range of final HKA angles (i.e. 0.2°, 2.7°, 3.9° and 6.6° valgus). Loading and boundary conditions were assigned based on subject-specific kinematic and kinetic data from gait analysis. Multiobjective optimization was used to identify the final alignment that balanced compressive and shear forces between medial and lateral knee compartments. Peak stresses decreased in the medial and increased in the lateral compartment as the HKA was shifted into valgus, with balanced loading occurring at angles of 4.3° and 2.9° valgus for the femoral and tibial cartilage respectively. The concept introduced here provides a platform for non-invasive, patient-specific preoperative planning of the osteotomy for medial compartment knee osteoarthritis.

      PubDate: 2017-02-14T13:13:10Z
       
  • Simulation of fetal heart rate variability with a mathematical model
    • Abstract: Publication date: Available online 11 February 2017
      Source:Medical Engineering & Physics
      Author(s): Germaine J.L.M. Jongen, M. Beatrijs van der Hout-van der Jagt, S. Guid Oei, Frans N. van de Vosse, Peter H.M. Bovendeerd
      In the clinic, the cardiotocogram (CTG), the combined registration of fetal heart rate (FHR) and uterine contractions, is used to predict fetal well-being. Amongst others, fetal heart rate variability (FHRV) is an important indicator of fetal distress. In this study we add FHRV to our previously developed CTG simulation model, in order to improve its use as a research and educational tool. We implemented three sources of variability by applying either 1/f or white noise to the peripheral vascular resistance, baroreceptor output, or efferent vagal signal. Simulated FHR tracings were evaluated by visual inspection and spectral analysis. All power spectra showed a 1/f character, irrespective of noise type and source. The clinically observed peak near 0.1 Hz was only obtained by applying white noise to the different sources of variability. Similar power spectra were found when peripheral vascular resistance or baroreceptor output was used as source of variability. Sympathetic control predominantly influenced the low frequency power, while vagal control influenced both low and high frequency power. In contrast to clinical data, model results did not show an increase of FHRV during FHR decelerations. Still, addition of FHRV improves the applicability of the model as an educational and research tool.

      PubDate: 2017-02-14T13:13:10Z
       
  • Optimised analytical models of the dielectric properties of biological
           tissue
    • Abstract: Publication date: Available online 9 February 2017
      Source:Medical Engineering & Physics
      Author(s): Saqib Salahuddin, Emily Porter, Finn Krewer, Martin O’ Halloran
      The interaction of electromagnetic fields with the human body is quantified by the dielectric properties of biological tissues. These properties are incorporated into complex numerical simulations using parametric models such as Debye and Cole-Cole, for the computational investigation of electromagnetic wave propagation within the body. These parameters can be acquired through a variety of optimisation algorithms to achieve an accurate fit to measured data sets. A number of different optimisation techniques have been proposed, but these are often limited by the requirement for initial value estimations or by the large overall error (often up to several percentage points). In this work, a novel two-stage genetic algorithm proposed by the authors is applied to optimise the multi-pole Debye parameters for 54 types of human tissues. The performance of the two-stage genetic algorithm has been examined through a comparison with five other existing algorithms. The experimental results demonstrate that the two-stage genetic algorithm produces an accurate fit to a range of experimental data and efficiently out-performs all other optimisation algorithms under consideration. Accurate values of the three-pole Debye models for 54 types of human tissues, over 500 MHz to 20 GHz, are also presented for reference.

      PubDate: 2017-02-14T13:13:10Z
       
  • The effects of tibia profile, distraction angle, and knee load on wedge
           instability and hinge fracture: A finite element study
    • Abstract: Publication date: Available online 5 February 2017
      Source:Medical Engineering & Physics
      Author(s): Pei-Wei Weng, Chia-Hsien Chen, Chu-An Luo, Jui-Sheng Sun, Yang-Hwei Tsuang, Cheng-Kung Cheng, Shang-Chih Lin
      Several plate systems for high tibial osteotomy (HTO) have been developed to stabilize the opening wedge of an osteotomized tibia. Among them, the TomoFix system, having a quasi-straight and T-shaped design, has been widely adopted in the literature. However, this system is implemented by inserting a lag (i.e., cortical) screw through the proximal combi-hole, to deform the plate and pull the distal tibia toward the plate. This process potentially induces plate springback and creates an elastic preload on the osteotomized tibia, especially at the lateral hinge of the distracted wedge. Using the finite-element method, this study aims to investigate the contoured effect of lag-screw application on the biomechanical behavior of the tibia-plate construct. Two tibial profiles (normal and more concave), three distraction angles (6°, 9°, and 12°), and three knee loads (intraoperative: contouring plate; postoperative: weight and nonweight bearing) are systematically varied in this study. The wedge instability and fracture risk at the lateral hinge are chosen as the comparison indices. The results show the necessity of preoperative planning for a precontoured procedure, rather than elastic deformation using a lag screw. Within the intraoperative period, a more concave tibial profile and/or reduced distraction angle (i.e., 6° or 9°) necessitate a higher compressive load to elastically deform the plate, thereby deteriorating the lateral-hinge fracture risk. A precontoured plate is recommended in the case that the proximal tibia is highly concave and the distraction angle is insufficient to stretch the tibial profile.

      PubDate: 2017-02-07T12:36:51Z
       
  • Assessing the immediate impact of botulinum toxin injection on impedance
           of spastic muscle
    • Abstract: Publication date: Available online 4 February 2017
      Source:Medical Engineering & Physics
      Author(s): Xiaoyan Li, Henry Shin, Le Li, Elaine Magat, Sheng Li, Ping Zhou
      This study aimed to investigate the immediate impacts of Botulinum Toxin A (BoNT-A) injections on the inherent electrical properties of spastic muscles using a newly developed electrical impedance myography (EIM) technique. Impedance measures were performed before and after a BoNT-A injection in biceps brachii muscles of 14 subjects with spasticity. Three major impedance variables, resistance (R), reactance (X) and phase angle (θ) were obtained from three different configurations, and were evaluated using the conventional EIM frequency at 50kHz as well as multiple frequency analysis. Statistical analysis demonstrated a significant decrease of resistance in the injected muscles (Multiple-frequency: Rpre =25.17±1.94Ohm, Rpost =23.65±1.63Ohm, p<0.05; 50kHz: Rpre =29.06±2.16Ohm, Rpost =27.7±1.89Ohm, p<0.05). Despite this decrease, there were no substantial changes in the reactance, phase angle, or anisotropy features after a BoNT-A injection. The significant changes of muscle resistance were most likely associated with the liquid injection of the BoNT-A-saline solution rather than the immediate toxin effects on the muscle. This study demonstrated high sensitivity of the EIM technique in the detection of alterations to muscle composition.

      PubDate: 2017-02-07T12:36:51Z
       
  • Editorial Board of Medical Engineering &amp; Physics
    • Abstract: Publication date: February 2017
      Source:Medical Engineering & Physics, Volume 40
      Author(s): Richard A. Black (PhD CSci CEng FIMechE FIPEM)


      PubDate: 2017-02-07T12:36:51Z
       
  • Estimating the material properties of heel pad sub-layers using inverse
           Finite Element Analysis
    • Abstract: Publication date: February 2017
      Source:Medical Engineering & Physics, Volume 40
      Author(s): Nafiseh Ahanchian, Christopher J. Nester, David Howard, Lei Ren, Daniel Parker
      Detailed information about the biomechanical behaviour of plantar heel pad tissue contributes to our understanding of load transfer when the foot impacts the ground. The objective of this work was to obtain the hyperelastic and viscoelastic material properties of heel pad sub-layers (skin, micro-chamber and macro-chamber layers) in-vivo. An anatomically detailed 3D Finite Element model of the human heel was used to derive the sub-layer material properties. A combined ultrasound imaging and motorised platform system was used to compress heel pad and to create input data for the Finite Element model. The force–strain responses of the heel pad and its sub-layers under slow compression (5mm/s) and rapid loading-hold-unloading cycles (225mm/s), were measured and hyperelastic and viscoelastic properties of the three heel pad sub-layers were estimated by the model. The loaded (under ∼315N) thickness of the heel pad was measured from MR images and used for hyperelastic model validation. The capability of the model to predict peak plantar pressure was used for further validation. Experimental responses of the heel pad under different dynamic loading scenarios (loading-hold-unloading cycles at 141mm/s and sinusoidal loading with maximum velocity of 300mm/s) were used to validate the viscoelastic model. Good agreement was achieved between the predicted and experimental results for both hyperelastic (<6.4% unloaded thickness, 4.4% maximum peak plantar pressure) and viscoelastic (Root Mean Square errors for loading and unloading periods <14.7%, 5.8% maximum force) simulations. This paper provides the first definition of material properties for heel pad sub-layers by using in-vivo experimental force–strain data and an anatomically detailed 3D Finite Element model of the heel.

      PubDate: 2017-02-07T12:36:51Z
       
  • Dynamic assessment of center of pressure measurements from an instrumented
           AMTI treadmill with controlled precision
    • Abstract: Publication date: Available online 1 February 2017
      Source:Medical Engineering & Physics
      Author(s): Emma Fortune, Jeremy Crenshaw, Vipul Lugade, Kenton R. Kaufman
      With the increasing use of instrumented force treadmills in biomechanical research, it is imperative that the validity of center of pressure (COP) measurements is established. The study aims were to compare an instrumented treadmill's static-belt COP accuracy to that of a floor-embedded platform, develop a novel method to quantify dynamic-belt COP accuracy with controlled precision and perform an initial investigation of how dynamic COP accuracy changes with weight and velocity. Static COP accuracy was assessed by applying a force while moving a rigid rod in a circular clockwise motion at nine positions of interest on the two treadmill and two ground-embedded force plates. Dynamic COP accuracy was assessed for weights (68.0, 102.1, and 136.1kg), applied through a ball bearing of 2.54cm circumference, with peak treadmill belt speeds of 0.5, 0.75, and 1.0m/s. COP accuracy was assessed relative to motion capture marker trajectories. Statically, treadmill COP error was similar to that of the ground-embedded force plates and that reported for other treadmills. Dynamically, COP error appeared to vary systematically with weight and velocity and in the case of anteroposterior COP error, shear force, although testing with a larger number of weights and velocities is needed to fully define the relationship. This novel method can be used to assess any instrumented treadmill's dynamic COP accuracy with controlled precision.

      PubDate: 2017-02-07T12:36:51Z
       
  • Exploration of Force Myography and surface Electromyography in hand
           gesture classification
    • Abstract: Publication date: Available online 1 February 2017
      Source:Medical Engineering & Physics
      Author(s): Xianta Jiang, Lukas-Karim Merhi, Zhen Gang Xiao, Carlo Menon
      Whereas pressure sensors increasingly have received attention as a non-invasive interface for hand gesture recognition, their performance has not been comprehensively evaluated. This work examined the performance of hand gesture classification using Force Myography (FMG) and surface Electromyography (sEMG) technologies by performing 3 sets of 48 hand gestures using a prototyped FMG band and an array of commercial sEMG sensors worn both on the wrist and forearm simultaneously. The results show that the FMG band achieved classification accuracies as good as the high quality, commercially available, sEMG system on both wrist and forearm positions; specifically, by only using 8 Force Sensitive Resisters (FSRs), the FMG band achieved accuracies of 91.2% and 83.5% in classifying the 48 hand gestures in cross-validation and cross-trial evaluations, which were higher than those of sEMG (84.6% and 79.1%). By using all 16 FSRs on the band, our device achieved high accuracies of 96.7% and 89.4% in cross-validation and cross-trial evaluations.

      PubDate: 2017-02-07T12:36:51Z
       
  • Medical Device Guidebook: A browser information resource for medical
           device users
    • Abstract: Publication date: Available online 31 January 2017
      Source:Medical Engineering & Physics
      Author(s): Douglas M. Clarkson
      A web based information resource – the ‘Medical Device Guidebook’ – for the enabling of safe use of medical devices is described. Medical devices are described within a ‘catalogue’ of specific models and information on a specific model is provided within a consistent set of information ‘keys’. These include ‘user manuals’, ‘points of caution’, ‘clinical use framework’, ‘training/assessment material’, ‘frequently asked questions’, ‘authorised user comments’ and ‘consumables’. The system allows identification of known risk/hazards associated with specific devices, triggered, for example, by national alerts or locally raised safety observations. This provides a mechanism for more effective briefing of equipment users on the associated hazards of equipment. A feature of the system is the inclusion of a specific ‘Operational Procedure’ for each device, where the lack of this focus is shown in the literature to often be a key factor in equipment misuse and associated patient injury. The 'Guidebook' provides a mechanism for the development of an information resource developed within local clinical networks and encourages a consistent approach to medical device use.

      PubDate: 2017-02-07T12:36:51Z
       
  • Laser fabrication of electrical feedthroughs in polymer encapsulations for
           active implantable medical devices
    • Abstract: Publication date: Available online 31 January 2017
      Source:Medical Engineering & Physics
      Author(s): Zara Gough, Cedric Chaminade, Philip Barclay-Monteith, Annukka Kallinen, Wenwen Lei, Rajesh Ganesan, John Grace, David R. McKenzie
      Hermetic electrical feedthroughs are essential for safe and functional active implantable biomedical devices and for a wide range of other applications such as batteries, supercapacitors, OLEDs and solar cells. Ceramics and metals have previously been the materials of choice for encapsulations, while polymers have advantages of ease of mass production and end user compatibility. We demonstrate a laser sealing technology that gives hermetic, mechanically strong feedthroughs with low electrical resistance in a polyetheretherketone (PEEK) encapsulation. The conductive pathways are wires and sputtered thin films. The water vapor transmission rate through the fabricated encapsulations is comparable to that of PEEK itself.

      PubDate: 2017-02-07T12:36:51Z
       
  • Characterization of micro-resonator based on enhanced metal insulator
           semiconductor capacitor for glucose recognition
    • Abstract: Publication date: Available online 31 January 2017
      Source:Medical Engineering & Physics
      Author(s): Rajendra Dhakal, E.S. Kim, Yong-Hwa Jo, Sung-Soo Kim, Nam-Young Kim
      We present a concept for the characterization of micro-fabricated based resonator incorporating air-bridge metal-insulator-semiconductor (MIS) capacitor to continuously monitor an individual's state of glucose levels based on frequency variation. The investigation revealed that, the micro-resonator based on MIS capacitor holds considerable promise for implementation and recognition as a glucose sensor for human serum. The discrepancy in complex permittivity as a result of enhanced capacitor was achieved for the detection and determination of random glucose concentration levels using a unique variation of capacitor that indeed results in an adequate variation of the resonance frequency. Moreover, the design and development of micro-resonator with enhanced MIS capacitor generate a resolution of 112.38 × 10−3 pF/mg/dl, minimum detectable glucose level of 7.45mg/dl, and a limit of quantification of 22.58mg/dl. Additionally, this unique approach offers long-term reliability for mediator-free glucose sensing with a relative standard deviation of less than 0.5%.

      PubDate: 2017-02-07T12:36:51Z
       
  • A surface wave elastography technique for measuring tissue viscoelastic
           properties
    • Abstract: Publication date: Available online 31 January 2017
      Source:Medical Engineering & Physics
      Author(s): Xiaoming Zhang
      A surface wave elastography method is proposed to study the viscoelastic properties of skin by measuring the surface wave speed and attenuation on the skin. Experiments were carried out on porcine skin tissues. The surface wave speed is measured by the change of phase with distance. The wave attenuation is measured by the decay of wave amplitude with distance. The change of viscoelastic properties with temperature was studied at room and body temperatures. The wave speed was 1.83m/s at 22°C but reduced to 1.52m/s at 33°C. The viscoelastic ratio was almost constant from 22°C to 33°C. Fresh and decayed tissues were studied. The wave speed of the decayed tissue increased from 1.83m/s of fresh state to 2.73m/s. The viscoelastic ratio was 0.412/mm at the decayed state compared to 0.215/mm at the fresh state. More tissue samples are needed to study these viscoelastic parameters according to specific applications.

      PubDate: 2017-02-07T12:36:51Z
       
  • Interfragmentary compression and pull-out properties of 6.5-mm AO
           cancellous lag screws in a uniform synthetic material during tightening
           procedures
    • Abstract: Publication date: Available online 31 January 2017
      Source:Medical Engineering & Physics
      Author(s): Peidong Sun, Daqiang Xu, Weidong Zhao, Peifeng Jiao, Zeyu Li, Chang Liu, Jun Ouyang
      AO lag screws are widely used in surgical intra-articular fracture treatment for anatomical reduction and rigid fixation. Interfragmentary compressive force (IFCF) and pull-out strength (POS) are two critical parameters generated by AO lag screws during tightening, and both of these parameters could be used to estimate screw insert conditions to prevent screw stripping. The aim of this study is to evaluate the IFCF and POS of AO cancellous screws inserted into uniform synthetic cancellous bone during tightening procedures. Seven synthetic cancellous bone blocks were used for this research. Each test contained two continuous portions as follows: the rotation test portion and the pull-out test portion. IFCF and POS were captured by the pressure transducer and the sensor of the test machine. The properties of IFCF and POS based on tightening degrees were obtained in this study. The ideal balance between POS and IFCF during screw tightening exists, and the peak values of these parameters cannot be simultaneously achieved. Moreover, rotation angles of 100–150° appear to serve as the optimum balance between IFCF and POS in the present study.

      PubDate: 2017-02-07T12:36:51Z
       
  • Respiratory effort from the photoplethysmogram
    • Abstract: Publication date: Available online 23 January 2017
      Source:Medical Engineering & Physics
      Author(s): Paul S. Addison
      The potential for a simple, non-invasive measure of respiratory effort based on the pulse oximeter signal - the photoplethysmogram or ‘pleth’ – was investigated in a pilot study. Several parameters were developed based on a variety of manifestations of respiratory effort in the signal, including modulation changes in amplitude, baseline, frequency and pulse transit times, as well as distinct baseline signal shifts. Thirteen candidate parameters were investigated using data from healthy volunteers. Each volunteer underwent a series of controlled respiratory effort maneuvers at various set flow resistances and respiratory rates. Six oximeter probes were tested at various body sites. In all, over three thousand pleth-based effort–airway pressure (EP) curves were generated across the various airway constrictions, respiratory efforts, respiratory rates, subjects, probe sites, and the candidate parameters considered. Regression analysis was performed to determine the existence of positive monotonic relationships between the respiratory effort parameters and resulting airway pressures. Six of the candidate parameters investigated exhibited a distinct positive relationship (p <0.001 across all probes tested) with increasing upper airway pressure repeatable across the range of respiratory rates and flow constrictions studied. These were: the three fundamental modulations in amplitude (AM-Effort), baseline (BM-Effort) and respiratory sinus arrhythmia (RSA-Effort); two pulse transit time modulations - one using a pulse oximeter probe and an ECG (P2E-Effort) and the other using two pulse oximeter probes placed at different peripheral body sites (P2-Effort); and baseline shifts in heart rate, (BL-HR-Effort). In conclusion, a clear monotonic relationship was found between several pleth-based parameters and imposed respiratory loadings at the mouth across a range of respiratory rates and flow constrictions. The results suggest that the pleth may provide a measure of changing upper airway dynamics indicative of the effort to breathe.

      PubDate: 2017-01-24T22:13:33Z
       
  • Three-dimensional intervertebral range of motion in the cervical spine:
           Does the method of calculation matter'
    • Abstract: Publication date: Available online 23 January 2017
      Source:Medical Engineering & Physics
      Author(s): William J Anderst, Yashar Aucie
      Intervertebral range of motion (ROM) is commonly calculated using ordered rotations or projection angles. Ordered rotations are sequence-dependent, and projection angles are dependent upon on which orientation vectors are projected. This study assessed the effect of calculation method on intervertebral ROM in the subaxial cervical spine (C3–C7) during in vivo dynamic, three-dimensional, functional movement. Biplane radiographs were collected at 30 images per second while 29 participants performed full ROM flexion/extension, axial rotation and lateral bending movements of their cervical spine. In vivo bone motion was tracked with sub-millimeter accuracy using a validated volumetric model-based tracking technique. Intervertebral rotations were calculated using six Cardan angle sequences and two projection angle combinations. Within-subject comparisons revealed significant differences in intervertebral ROM among calculation methods (all p <0.002). Group mean ROM differences were small, but significantly different among calculation methods (p <0.001). A resampling technique demonstrated that as group size increases, the differences between calculation methods decreases substantially. It is concluded that the method used to calculate intervertebral rotations of the sub-axial cervical spine can significantly affect within-subject and between group comparisons of intervertebral ROM.

      PubDate: 2017-01-24T22:13:33Z
       
  • A novel fully automatic measurement of apparent breast volume from trunk
           surface mesh
    • Abstract: Publication date: Available online 23 January 2017
      Source:Medical Engineering & Physics
      Author(s): Lama Seoud, Joyce Ramsay, Stefan Parent, Farida Cheriet
      This paper presents a novel method for assessing apparent breast volume from trunk surface mesh without any manual intervention. The proposed method requires a closed and smooth triangular mesh of the trunk. It comprises four main steps: automatic nipple localization, automatic breasts delineation, chest-wall interpolation and volume computation. The mean curvature is computed for each vertex using a quadratic fitting approach and used as an indicator to determine the convex fold of the breasts. The delineation is modeled as an ellipse in the frontal plane and all the vertices inside it are removed. The remaining ones are used to interpolate the chest wall with radial basis functions. The voxels inside the resulting mesh without breasts are then subtracted from the original voxelized volume to generate the breasts volume. The validation is conducted on 30 adolescent female for each of which an MRI and a trunk surface (TS) acquisitions were available. Three breast volumes are considered: the anatomical volumes (AV) manually segmented on the MRI, the external volumes computed with the proposed method first in prone position (EVP) using the trunk mesh extracted from the MRI, and second, in standing position (EVS) using the TS’s mesh. Significant correlations (R> 0.77) are found between each two of the three volumes. AVs are much larger than both EVS and EPS. In fact, the manual segmentation using MRI slices allows for a direct visualization of the breast posterior delineation. Computed automatically, EVS and EPS are highly similar, indicating that the proposed method is robust to changes from prone to standing position. No significant difference between the regressions on the left and right breasts is noted. Fully-automatic 3D breast volumetry from trunk surface mesh is feasible and provides measurements that are highly correlated to manual MRI volumetry and robust to changes in posture.

      PubDate: 2017-01-24T22:13:33Z
       
  • Determining 3D scapular orientation with scapula models and biplane 2D
           images
    • Abstract: Publication date: Available online 23 January 2017
      Source:Medical Engineering & Physics
      Author(s): Kristen F Nicholson, R Tyler Richardson, Freeman Miller, James G Richards
      This study evaluated a strategy for identifying 3D scapulothoracic orientation using bilateral X-ray scans and 3D scapula models. Both subject-specific scapula models and a scaled general model were utilized. 3D scapulothoracic orientations obtained from X-rays were compared to motion capture data. “Subjects” consisted of a skeletal model of a human torso and ten real bone scapulae. Retroreflective markers were placed on the scapulae and a three-marker triad was placed on the trunk. Marker positions were recorded using an eight camera motion capture system. A biplane X-ray system from EOS Imaging was used to collect two orthogonal 2D images of the skeleton and markers. Custom software was created for the 3D to 2D matching process. The results indicated that the matched orientations compared favorably to motion capture orientations, with RMSE errors ranging from 3.1° to 5.5° and a mean error of 3.9° The proposed strategy was shown to be accurate for both subject-specific models and a scaled general model.

      PubDate: 2017-01-24T22:13:33Z
       
  • Mechanical characterization and comparison of energy storage and return
           prostheses
    • Abstract: Publication date: Available online 20 January 2017
      Source:Medical Engineering & Physics
      Author(s): Stacey M. Rigney, Anne Simmons, Lauren Kark
      The suitability of finite element analysis (FEA) for standardizing the mechanical characterization of energy storage and return (ESAR) prostheses was investigated. A methodology consisting of both experimental and numerical analysis was proposed and trialed for the Vari-flex® ModularTM, Flex-foot Cheetah and Cheetah Xtreme by Össur® and a 1E90 Sprinter by Ottobock®. Gait analysis was conducted to determine suitable orientation angles for non-destructive testing (NDT) of the ESAR prostheses followed by a quasi-static inverse FEA procedure within COMSOL Multiphysics®, where the NDT conditions were replicated to determine the homogenized material properties of the prostheses. The prostheses’ loading response under bodyweight for an 80kg person was then simulated, using both Eigenfrequency and time-dependent analysis. The apparent stiffness under bodyweight was determined to be 94.7, 48.6, 57.4 and 65.0Nmm−1 for the Vari-flex® ModularTM, Flex-foot Cheetah, Cheetah Xtreme and 1E90 Sprinter, respectively. Both the energy stored and returned by the prostheses varied negatively with stiffness, yet the overall efficiency of the prostheses were similar, at 52.7, 52.0, 51.7 and 52.4% for the abovementioned prostheses. The proposed methodology allows the standardized assessment and comparison of ESAR prostheses without the confounding influences of subject-specific gait characteristics.
      Graphical abstract image

      PubDate: 2017-01-24T22:13:33Z
       
  • Development of a surgical navigation system based on 3D Slicer for
           intraoperative implant placement surgery
    • Abstract: Publication date: Available online 18 January 2017
      Source:Medical Engineering & Physics
      Author(s): Xiaojun Chen, Lu Xu, Huixiang Wang, Fang Wang, Qiugen Wang, Ron Kikinis
      Implant placement has been widely used in various kinds of surgery. However, accurate intraoperative drilling performance is essential to avoid injury to adjacent structures. Although some commercially-available surgical navigation systems have been approved for clinical applications, these systems are expensive and the source code is not available to researchers. 3D Slicer is a free, open source software platform for the research community of computer-aided surgery. In this study, a loadable module based on Slicer has been developed and validated to support surgical navigation. This research module allows reliable calibration of the surgical drill, point-based registration and surface matching registration, so that the position and orientation of the surgical drill can be tracked and displayed on the computer screen in real time, aiming at reducing risks. In accuracy verification experiments, the mean target registration error (TRE) for point-based and surface-based registration were 0.31±0.06mm and 1.01±0.06mm respectively, which should meet clinical requirements. Both phantom and cadaver experiments demonstrated the feasibility of our surgical navigation software module.
      Graphical abstract image

      PubDate: 2017-01-24T22:13:33Z
       
  • Musical Stairs: A motivational therapy tool for children with disabilities
           featuring automated detection of stair-climbing gait events via inertial
           sensors
    • Authors: Ajmal Khan; Elaine Biddiss
      Abstract: Publication date: Available online 16 January 2017
      Source:Medical Engineering & Physics
      Author(s): Ajmal Khan, Elaine Biddiss
      Stair-climbing is a key component of rehabilitation therapies for children with physical disabilities. This paper reports on the design of a system, Musical Stairs, to provide auditory feedback during stair-climbing therapies. Musical Stairs is composed of two foot-mounted inertial sensors, a step detection algorithm, and an auditory feedback response. In Phase 1, we establish its clinical feasibility via a Wizard-of-Oz AB/BA cross-over design with 17 children, aged 4–6 years, having diverse diagnoses and gait abilities. Self-, therapist- and blinded-observer reports indicated increased motivation with auditory feedback. Phase 2 describes the construction of a database comprised of synchronized video and inertial data associated with 1568 steps up and down stairs completed by 26 children aged 4–6 years with diverse diagnoses and gait. Lastly, in Phase 3, data from 18 children in the database were used to train a rule-based step detection algorithm based on local minima in the acceleration profile and the foot's swing angle. A step detection rate of 96% [SD=3%] and false positive rate of 6% [SD=5%] were achieved with an independent test set (n =8). Recommendations for future development and evaluation are discussed.

      PubDate: 2017-01-17T21:19:32Z
      DOI: 10.1016/j.medengphy.2016.12.009
       
  • Dynamic Hilbert warping, a new measure of RR-interval signals evaluated in
           the cognitive load estimation
    • Authors: Peyvand Ghaderyan; Ataollah Abbasi
      Abstract: Publication date: Available online 16 January 2017
      Source:Medical Engineering & Physics
      Author(s): Peyvand Ghaderyan, Ataollah Abbasi
      RR interval (RRI) signals represent the time intervals between successive heart R-waves. These signals are influenced by many cognitive and psychological processes. In this study, a new technique based on the combination of empirical mode decomposition and dynamic Hilbert warping (DHW) was proposed to inference cognitive states from measured RRI signals. Moreover, a set of entropic and statistical measures was extracted to characterize the regularity and temporal distribution in the phase spectra and amplitude envelope of the analytic signals. The discriminating capability of the proposed method was studied in 45 healthy subjects. They performed an arithmetic task with five levels of difficulty. The study indicated the importance of phase information in cognitive load estimation (CLE). The new phase characteristics were able to extract hidden information from the RRI signals. The results revealed a striking decrease in DHW value with increasing load level. The entropic measures of analytic signal also showed an increasing trend as the mental load increased. Although, phase information had an ability to discriminate between more distinct levels as well as between more similar ones, amplitude information was effective only in discriminating between more distinct levels.

      PubDate: 2017-01-17T21:19:32Z
      DOI: 10.1016/j.medengphy.2016.12.008
       
  • Modeling of path planning and needle steering with path tracking in
           anatomical soft tissues for minimally invasive surgery
    • Authors: Pan Li; Shan Jiang; Dong Liang; Zhiyong Yang; Yan Yu; Wei Wang
      Abstract: Publication date: Available online 16 January 2017
      Source:Medical Engineering & Physics
      Author(s): Pan Li, Shan Jiang, Dong Liang, Zhiyong Yang, Yan Yu, Wei Wang
      Steerable needles can potentially improve the effectiveness of diagnostic and therapeutic procedures, such as biopsy and cancer treatment, by increasing the targeting accuracy and reaching previously inaccessible targets. A discrete potential field algorithm based on three dimensional (3D) anatomical structures is proposed in this paper to plan the needle path in minimally invasive surgery. A 3D kinematic model of needle steering is formulated using Lie group theory. Model parameters are fitted using experimental data acquired via a 2-degree of freedom robotic device and an ultrasound imaging device. To execute the paths with variable curvatures, the model is incorporated with duty cycled spinning. Empirical formula between needle curvature and duty cycled factor is obtained through insertion experiments. To improve the targeting accuracy, a path tracking algorithm is developed by correcting for the heading error and cross-track error of the needle tip. The targeting error of the simulation is 0.29 mm. We experimentally evaluate the path tracking model and it achieves an average targeting error of 1.15 ± 0.56 mm in 3D environments with anatomical obstacles. The results of simulation are in agreement with steering experiments, showing that the discrete potential field algorithm and path tracking model have the potential to improve targeting accuracy and advance the therapeutic and diagnostic procedures.

      PubDate: 2017-01-17T21:19:32Z
      DOI: 10.1016/j.medengphy.2017.01.006
       
  • Loading of the medial meniscus in the ACL deficient knee: A multibody
           computational study
    • Authors: Trent M. Guess; Swithin Razu
      Abstract: Publication date: Available online 11 January 2017
      Source:Medical Engineering & Physics
      Author(s): Trent M. Guess, Swithin Razu
      The menisci of the knee reduce tibiofemoral contact pressures and aid in knee lubrication and nourishment. Meniscal injury occurs in half of knees sustaining anterior cruciate ligament injury and the vast majority of tears in the medial meniscus transpire in the posterior horn region. In this study, computational multibody models of the knee were derived from medical images and passive leg motion for two female subjects. The models were validated against experimental measures available in the literature and then used to evaluate medial meniscus contact force and internal hoop tension. The models predicted that the loss of anterior cruciate ligament (ACL) constraint increased contact and hoop forces in the medial menisci by a factor of 4 when a 100N anterior tibial force was applied. Contact forces were concentrated in the posterior horn and hoop forces were also greater in this region. No differences were found in contact or hoop tension between the intact and ACL deficient (ACLd) knees when only a 5Nm external tibial torque was applied about the long axis of the tibia. Combining a 100N anterior tibial force and a 5Nm external tibial torque increased posterior horn contact and hoop forces, even in the intact knee. The results of this study show that the posterior horn region of the medial meniscus experiences higher contact forces and hoop tension, making this region more susceptible to injury, especially with the loss of anterior tibia motion constraint provided by the ACL. The contribution of the dMCL in constraining posterior medial meniscus motion, at the cost of higher posterior horn hoop tension, is also demonstrated.

      PubDate: 2017-01-17T21:19:32Z
      DOI: 10.1016/j.medengphy.2016.12.006
       
  • The effect of bone growth onto massive prostheses collars in protecting
           the implant from fracture
    • Authors: Paul Fromme; Gordon W. Blunn; William J. Aston; Tasneem Abdoola; Jacob Koris; Melanie J. Coathup
      Abstract: Publication date: Available online 10 January 2017
      Source:Medical Engineering & Physics
      Author(s): Paul Fromme, Gordon W. Blunn, William J. Aston, Tasneem Abdoola, Jacob Koris, Melanie J. Coathup
      Limb-sparing distal femoral endoprotheses used in cancer patients have a high risk of aseptic loosening. It had been reported that young adolescent patients have a higher rate of loosening and fatigue fracture of intramedullary stems because the implant becomes undersized as patients grow. Extracortical bone growth into the grooved hydroxyapatite-coated collar had been shown to reduce failure rates. The stresses in the implant and femur have been calculated from Finite Element models for different stages of bone growth onto the collar. For a small diameter stem without any bone growth, a large stress concentration at the implant shoulder was found, leading to a significant fracture risk under normal walking loads. Bone growth and osseointergration onto the implant collar reduced the stress level in the implant to safe levels. For small bone bridges a risk of bone fracture was observed.

      PubDate: 2017-01-17T21:19:32Z
      DOI: 10.1016/j.medengphy.2016.12.007
       
  • Influence of mouth opening on oropharyngeal humidification and temperature
           in a bench model of neonatal continuous positive airway pressure
    • Authors: Hendrik S. Fischer; Tim L. Ullrich; Christoph Bührer; Christoph Czernik; Gerd Schmalisch
      Abstract: Publication date: Available online 30 December 2016
      Source:Medical Engineering & Physics
      Author(s): Hendrik S. Fischer, Tim L. Ullrich, Christoph Bührer, Christoph Czernik, Gerd Schmalisch
      Clinical studies show that non-invasive respiratory support by continuous positive airway pressure (CPAP) affects gas conditioning in the upper airways, especially in the presence of mouth leaks. Using a new bench model of neonatal CPAP, we investigated the influence of mouth opening on oropharyngeal temperature and humidity. The model features the insertion of a heated humidifier between an active model lung and an oropharyngeal head model to simulate the recurrent expiration of heated, humidified air. During unsupported breathing, physiological temperature and humidity were attained inside the model oropharynx, and mouth opening had no significant effect on oropharyngeal temperature and humidity. During binasal CPAP, the impact of mouth opening was investigated using three different scenarios: no conditioning in the CPAP circuit, heating only, and heated humidification. Mouth opening had a strong negative impact on oropharyngeal humidification in all tested scenarios, but heated humidification in the CPAP circuit maintained clinically acceptable humidity levels regardless of closed or open mouths. The model can be used to test new equipment for use with CPAP, and to investigate the effects of other methods of non-invasive respiratory support on gas conditioning in the presence of leaks.

      PubDate: 2017-01-17T21:19:32Z
      DOI: 10.1016/j.medengphy.2016.12.005
       
  • In-vitro investigation of the hemodynamic responses of the cerebral,
           coronary and renal circulations with a rotary blood pump installed in the
           descending aorta
    • Authors: M.A. Rezaienia; G. Paul; E.J. Avital; S. Mozafari; M. Rothman; T. Korakianitis
      Abstract: Publication date: Available online 28 December 2016
      Source:Medical Engineering & Physics
      Author(s): M.A. Rezaienia, G. Paul, E.J. Avital, S. Mozafari, M. Rothman, T. Korakianitis
      This study investigates the hemodynamic responses of the cardiovascular system when a rotary blood pump is operating in the descending aorta, with a focus on the cerebral, coronary and renal autoregulation, using our in-house cardiovascular emulator. Several improvements have been made from our previous studies. A novel coronary system was developed to replicate the native coronary perfusion. Three pinch valves actuated by stepper motors were used to simulate the regional autoregulation systems of the native cerebral, coronary and renal circulations. A rotary pump was installed in the descending aorta, in series with the heart, and the hemodynamic responses of the cardiovascular system were investigated with a focus on cerebral, coronary and renal circulation over a wide range of pump rotor speeds. Experiments were performed twice, once with the autoregulation systems active and once with the autoregulation systems inactive, to reflect that there will be some impairment of autoregulatory systems in a patient with heart failure. It was shown that by increasing the rotor speed to 3000 rpm, the cardiac output was improved from 2.9 to 4.1 L/min as a result of an afterload reduction induced by the pressure drop upstream of the pump. The magnitudes of changes in perfusion in the cerebral, coronary and renal circulations were recorded with regional autoregulation systems active and inactive.

      PubDate: 2017-01-17T21:19:32Z
      DOI: 10.1016/j.medengphy.2016.11.006
       
  • A novel method for extraction of neural response from single channel
           cochlear implant auditory evoked potentials
    • Authors: Daniel Sinkiewicz; Lendra Friesen; Behnaz Ghoraani
      Abstract: Publication date: Available online 20 December 2016
      Source:Medical Engineering & Physics
      Author(s): Daniel Sinkiewicz, Lendra Friesen, Behnaz Ghoraani
      Cortical auditory evoked potentials (CAEP) are used to evaluate cochlear implant (CI) patient auditory pathways, but the CI device produces an electrical artifact, which obscures the relevant information in the neural response. Currently there are multiple methods, which attempt to recover the neural response from the contaminated CAEP, but there is no gold standard, which can quantitatively confirm the effectiveness of these methods. To address this crucial shortcoming, we develop a wavelet-based method to quantify the amount of artifact energy in the neural response. In addition, a novel technique for extracting the neural response from single channel CAEPs is proposed. The new method uses matching pursuit (MP) based feature extraction to represent the contaminated CAEP in a feature space, and support vector machines (SVM) to classify the components as normal hearing (NH) or artifact. The NH components are combined to recover the neural response without artifact energy, as verified using the evaluation tool. Although it needs some further evaluation, this approach is a promising method of electrical artifact removal from CAEPs.

      PubDate: 2017-01-17T21:19:32Z
      DOI: 10.1016/j.medengphy.2016.11.009
       
  • Evaluation of predicted knee function for component malrotation in total
           knee arthroplasty
    • Authors: Valentine Vanheule; Hendrik Pieter Delport Michael Skipper Andersen Lennart Scheys
      Abstract: Publication date: Available online 15 December 2016
      Source:Medical Engineering & Physics
      Author(s): Valentine Vanheule, Hendrik Pieter Delport, Michael Skipper Andersen, Lennart Scheys, Roel Wirix-Speetjens, Ilse Jonkers, Jan Victor, Jos Vander Sloten
      Soft-tissue balancing for total knee arthroplasty (TKA) remains subjective and highly dependent on surgical expertise. Pre-operative planning may support the clinician in taking decisions by integrating subject-specific computer models that predict functional outcome. However, validation of these models is essential before they can be applied in clinical practice. The aim of this study was to evaluate a knee modelling workflow by comparing experimental cadaveric measures to model-based kinematics and ligament length changes. Subject-specific models for three cadaveric knees were constructed from medical images. The implanted knees were mounted onto a mechanical rig to perform squatting, measuring kinematics and ligament length changes with optical markers and extensometers. Coronal malrotation was introduced using tibial inserts with a built-in slope. The model output agreed well with the experiment in all alignment conditions. Kinematic behaviour showed an average RMSE of less than 2.7mm and 2.3° for translations and rotations. The average RMSE was below 2.5% for all ligaments. These results show that the presented model can quantitatively predict subject-specific knee behaviour following TKA, allowing evaluation of implant alignment in terms of kinematics and ligament length changes. In future work, the model will be used to evaluate subject-specific implant position based on ligament behaviour.

      PubDate: 2016-12-16T14:40:05Z
       
  • Dynamic property changes in stapedial annular ligament associated with
           acute otitis media in the chinchilla
    • Authors: Brooke Hitt; Xuelin Wang Rong Gan
      Abstract: Publication date: Available online 15 December 2016
      Source:Medical Engineering & Physics
      Author(s): Brooke M. Hitt, Xuelin Wang, Rong Z. Gan
      Located at the end of the ossicular chain, the stapedial annular ligament (SAL) serves as a closed yet mobile boundary between the cochlear fluid and stapes footplate. It is unclear how SAL properties change with acute otitis media (AOM). This paper reports the measurements of SAL dynamic properties in chinchilla AOM model using dynamic mechanical analyzer (DMA) and frequency-temperature superposition (FTS) principle. AOM was analyzed in two infection groups: 4 days (4D) and 8 days (8D) post induction. SAL specimens were measured using DMA at three temperatures: 5, 25, and 37°C. To extend the testing frequencies to higher levels, FTS principle was employed. Then generalized Maxwell model was utilized to define the constitutive equations of the SAL. The complex shear moduli were obtained from seven samples of control, 4D, and 8D groups. Results show that the storage and loss shear moduli of SALs decreased due to AOM. The storage moduli for 4D and 8D ears were similar below 100Hz, and the loss modulus for 4D was significantly larger than 8D across the entire frequency range. This study reports data that contributes to ear biomechanics and improves understanding on the effects of AOM in middle ear tissues.

      PubDate: 2016-12-16T14:40:05Z
       
  • Wheelchair pushrim kinetics measurement: A method to cancel inaccuracies
           due to pushrim weight and wheel camber
    • Authors: Félix Chénier; Rachid Aissaoui; Cindy Gauthier; Dany H. Gagnon
      Abstract: Publication date: Available online 14 December 2016
      Source:Medical Engineering & Physics
      Author(s): Félix Chénier, Rachid Aissaoui, Cindy Gauthier, Dany H. Gagnon
      The commercially available SmartWheelTM is largely used in research and increasingly used in clinical practice to measure the forces and moments applied on the wheelchair pushrims by the user. However, in some situations (i.e. cambered wheels or increased pushrim weight), the recorded kinetics may include dynamic offsets that affect the accuracy of the measurements. In this work, an automatic method to identify and cancel these offsets is proposed and tested. First, the method was tested on an experimental bench with different cambers and pushrim weights. Then, the method was generalized to wheelchair propulsion. Nine experienced wheelchair users propelled their own wheelchairs instrumented with two SmartWheels with anti-slip pushrim covers. The dynamic offsets were correctly identified using the propulsion acquisition, without needing a separate baseline acquisition. A kinetic analysis was performed with and without dynamic offset cancellation using the proposed method. The most altered kinetic variables during propulsion were the vertical and total forces, with errors of up to 9N (p <0.001, large effect size of 5). This method is simple to implement, fully automatic and requires no further acquisitions. Therefore, we advise to use it systematically to enhance the accuracy of existing and future kinetic measurements.

      PubDate: 2016-12-16T14:40:05Z
      DOI: 10.1016/j.medengphy.2016.12.002
       
  • Evaluation of the magnitude of hip joint deformation in subjects with
           avascular necrosis of the hip joint during walking with and without
           Scottish Rite orthosis
    • Authors: Mohammad Taghi Karimi; Ali Mohammadi; Mohammad Hossein Ebrahimi; Anthony McGarry
      Abstract: Publication date: Available online 13 December 2016
      Source:Medical Engineering & Physics
      Author(s): Mohammad Taghi Karimi, Ali Mohammadi, Mohammad Hossein Ebrahimi, Anthony McGarry
      The femoral head in subjects with leg calve perthes disease (LCPD) is generally considerably deformed. It is debatable whether this deformation is due to an increase in applied loads, a decrease in bone mineral density or a change in containment of articular surfaces. The aim of this study was to determine the influence of these factors on deformation of the femoral head. Two subjects with LCPD participated in this study. Subject motion and the forces applied on the affected leg were recorded using a motion analysis system (QualsisTM ) and a Kistler force plate. OpenSim software was used to determine joint contact force of the hip joint whilst walking with and without a Scottish Rite orthosis. 3D Models of hip joints of both subjects were produced by Mimics software. The deformation of femoral bone was determined by Abaqus. Mean values of the force applied on the leg increased while walking with the orthosis. There was no difference between bone mineral density (BMD) of the femoral bone of normal and LCPD sides (p-value>0.05) and no difference between hip joint contact force of normal and LCPD sides. Hip joint containment appeared to decrease follow the use of the orthosis. It can be concluded that the deformation of femoral head in LCPD may not be due to change in BMD or applied load. Although the Scottish Rite orthosis is used mostly to increase hip joint containment, it appears to reduce hip joint contact area. It is recommended that a similar study is conducted using a higher number of subjects.

      PubDate: 2016-12-16T14:40:05Z
      DOI: 10.1016/j.medengphy.2016.10.015
       
  • Prediction of the drilling path to surgically pin the femoral neck from
           the spatial location of pelvic and femoral anatomical landmarks: A cadaver
           validation study
    • Authors: V. Sholukha; J. Panda; P. Salvia; B. Beyer; M. Rooze; S. Van Sint Jan
      Abstract: Publication date: Available online 10 December 2016
      Source:Medical Engineering & Physics
      Author(s): V. Sholukha, J. Panda, P. Salvia, B. Beyer, M. Rooze, S. Van Sint Jan
      Several clinical applications rely on accurate guiding information when drilling along the femoral neck (e.g., pin insertion in case of neck fracture). Currently, applications rely on real-time X-ray imaging, which results in irradiation issues for the surgeon conducting the operation. The goal of this paper was to develop an X-ray-free method that would allow for a pathway to be drilled between the lateral aspect of the femoral diaphysis (the so-called piercing point), the femoral neck and the head centres. The method is based on on-the-fly computational predictions relying on a biomechanical database that includes morphological data related to the femoral neck and head and various palpable anatomical landmarks located on the pelvis and the femoral bone. From the spatial location of the anatomical landmarks, scalable multiple regressions allow for the prediction of the most optimal drilling pathway. The method has been entirely validated using in vitro experiments that reproduce surgical conditions. Further, a surgical ancillary prototype that integrates the method of guiding the pin drilling has been developed and used during in vitro and in situ validation using nine hip joints. Pin insertion was controlled after drilling using medical imaging and show successful result for each of the nine trials. The mean accuracy of the estimated hip joint centre and neck orientation was 6.0 ± 2.8mm and 7.1 ± 3.8°, respectively.

      PubDate: 2016-12-16T14:40:05Z
      DOI: 10.1016/j.medengphy.2016.11.008
       
  • Characterizing the reduction of stimulation artifact noise in a tripolar
           nerve cuff electrode by application of a conductive shield layer
    • Authors: Parisa Sabetian; Bita Sadeghlo; Chengran Harvey Zhang; Paul B Yoo
      Abstract: Publication date: Available online 10 December 2016
      Source:Medical Engineering & Physics
      Author(s): Parisa Sabetian, Bita Sadeghlo, Chengran Harvey Zhang, Paul B Yoo
      Tripolar nerve cuff electrodes have been widely used for measuring peripheral nerve activity. However, despite the high signal-to-noise ratio levels that can be achieved with this recording configuration, the clinical use of cuff electrodes in closed-loop controlled neuroprostheses remains limited. This is largely attributed to artifact noise signals that contaminate the recorded neural activity. In this study, we investigated the use of a conductive shield layer (CSL) as a means of reducing the artifact noise recorded by nerve cuff electrodes. Using both computational simulations and in vivo experiments, we found that the CSL can result in up to an 85% decrease in the recorded artifact signal. Both the electrical conductivity and the surface area of the CSL were identified as important design criteria. Although this study shows that the CSL can significantly reduce artifact noise in tripolar nerve cuff electrodes, long-term implant studies are needed to validate our findings.

      PubDate: 2016-12-16T14:40:05Z
      DOI: 10.1016/j.medengphy.2016.11.010
       
  • Effect of various factors on pull out strength of pedicle screw in normal
           and osteoporotic cancellous bone models
    • Authors: Vicky Varghese; Gurunathan Saravana Kumar; Venkatesh Krishnan
      Abstract: Publication date: Available online 9 December 2016
      Source:Medical Engineering & Physics
      Author(s): Vicky Varghese, Gurunathan Saravana Kumar, Venkatesh Krishnan
      Pedicle screws are widely used for the treatment of spinal instability by spine fusion. Screw loosening is a major problem of spine fusion, contributing to delayed patient recovery. The present study aimed to understand the factor and interaction effects of density, insertion depth and insertion angle on pedicle screw pull out strength and insertion torque. A pull out study was carried out on rigid polyurethane foam blocks representing osteoporotic to normal bone densities according to the ASTM-1839 standard. It was found that density contributes most to pullout strength and insertion torque. The interaction effect is significant (p < 0.05) and contributes 8% to pull out strength. Axial pullout strength was 34% lower than angled pull out strength in the osteoporotic bone model. Insertion angle had no significant effect (p > 0.05) on insertion torque. Pullout strength and insertion torque had no significant correlation (p > 0.05) in the case of the extremely osteoporotic bone model.

      PubDate: 2016-12-09T21:38:53Z
      DOI: 10.1016/j.medengphy.2016.11.012
       
  • Biomechanical properties of human T cells in the process of activation
           based on diametric compression by micromanipulation
    • Authors: Mingming Du; Neena Kalia; Guido Frumento; Frederick Chen; Zhibing Zhang
      Abstract: Publication date: Available online 9 December 2016
      Source:Medical Engineering & Physics
      Author(s): Mingming Du, Neena Kalia, Guido Frumento, Frederick Chen, Zhibing Zhang
      A crucial step in enabling adoptive T cell therapy is the isolation of antigen (Ag)-specific CD8+ T lymphocytes. Mechanical changes that accompany CD8+ T lymphocyte activation and migration from circulating blood across endothelial cells into target tissue, may be used as parameters for microfluidic sorting of activated CD8+ T cells. CD8+ T cells were activated in vitro using anti-CD3 for a total of 4 days, and samples of cells were mechanically tested on day 0 prior to activation and on day 2 and 4 post-activation using a micromanipulation technique. The diameter of activated CD8+ T cells was significantly larger than resting cells suggesting that activation was accompanied by an increase in cell volume. While the Young's modulus value as determined by the force versus displacement data up to a nominal deformation of 10% decreased after activation, this may be due to the activation causing a weakening of the cell membrane and cytoskeleton. However, nominal rupture tension determined by compressing single cells to large deformations until rupture, decreased from day 0 to day 2, and then recovered on day 4 post-activation. This may be related to the mechanical properties of the cell nucleus. These novel data show unique biomechanical changes of activated CD8+ T cells which may be further exploited for the development of new microfluidic cell separation systems.

      PubDate: 2016-12-09T21:38:53Z
      DOI: 10.1016/j.medengphy.2016.11.011
       
  • Effect of trunnion roughness and length on the modular taper junction
           strength under typical intraoperative assembly forces
    • Authors: S.Y. Jauch-Matt; A.W. Miles; H.S. Gill
      Abstract: Publication date: Available online 29 November 2016
      Source:Medical Engineering & Physics
      Author(s): S.Y. Jauch-Matt, A.W. Miles, H.S. Gill
      Modular hip implants are at risk of fretting-induced postoperative complications most likely initiated by micromotion between adjacent implant components. A stable fixation between ball head and stem-neck taper is critical to avoid excessive interface motions. Therefore, the aim of this study was to identify the effect of trunnion roughness and length on the modular taper strength under typical intraoperative assembly forces. Custom-made Titanium trunnions (standard/mini taper, smooth/grooved surface finish) were assembled with modular Cobalt-chromium heads by impaction with peak forces ranging from 2kN to 6kN. After each assembly process these were disassembled with a materials testing machine to detect the pull-off force as a measure for the taper strength. As expected, the pull-off forces increased with rising peak assembly force (p < 0.001). For low and moderate assembly forces, smooth standard tapers offered higher pull-off forces compared to grooved tapers (p < 0.038). In the case of an assembly force of 2kN, mini tapers showed a higher taper strength than standard ones (p =0.037). The results of this study showed that smooth tapers provided a higher strength for taper junctions. This higher taper strength may reduce the risk of fretting-related complications especially in the most common range of intraoperative assembly forces.

      PubDate: 2016-12-09T21:38:53Z
      DOI: 10.1016/j.medengphy.2016.11.001
       
  • Review of fall detection techniques: A data availability perspective
    • Authors: Shehroz Khan; Jesse Hoey
      Abstract: Publication date: Available online 23 November 2016
      Source:Medical Engineering & Physics
      Author(s): Shehroz S. Khan, Jesse Hoey
      A fall is an abnormal activity that occurs rarely; however, missing to identify falls can have serious health and safety implications on an individual. Due to the rarity of occurrence of falls, there may be insufficient or no training data available for them. Therefore, standard supervised machine learning methods may not be directly applied to handle this problem. In this paper, we present a taxonomy for the study of fall detection from the perspective of availability of fall data. The proposed taxonomy is independent of the type of sensors used and specific feature extraction/selection methods. The taxonomy identifies different categories of classification methods for the study of fall detection based on the availability of their data during training the classifiers. Then, we present a comprehensive literature review within those categories and identify the approach of treating a fall as an abnormal activity to be a plausible research direction. We conclude our paper by discussing several open research problems in the field and pointers for future research.

      PubDate: 2016-12-09T21:38:53Z
       
  • Importance of trabecular anisotropy in finite element predictions of
           patellar strain after Total Knee Arthroplasty
    • Authors: A. Latypova; D.P. Pioletti; A. Terrier
      Abstract: Publication date: Available online 18 November 2016
      Source:Medical Engineering & Physics
      Author(s): A. Latypova, D.P. Pioletti, A. Terrier
      Patellar fracture and anterior knee pain remain major complications after Total Knee Arthroplasty (TKA). Patient-specific finite element (FE) models should help improve understanding of these complications through estimation of joint and bone mechanics. However, sensitivity of predictions on modeling techniques and approaches is not fully investigated. In particular, the importance of patellar bone anisotropy, usually omitted in FE models, on strain prediction is still unknown. The objective of this study was thus to estimate the influence of modeling patellar trabecular anisotropy on prediction of patellar strain in TKA models. We compared FE-derived strain predictions with isotopic and anisotropic material properties using 17 validated FE models of the patella after TKA. We considered both non-resurfaced and resurfaced patellae, in a load-bearing TKA joint. We evaluated and compared the bone volume above a strain threshold and, in addition, estimated if the difference in isotopic and anisotropic predictions was consistent between patellae of different average bone volume fraction. Compared to the anisotropic reference, the isotropic prediction of strained volume was 3.7±1.8 times higher for non-resurfaced patellae and 1.5±0.4 times for resurfaced patellae. This difference was higher for patellae with lower average bone volume fraction. This study indicates that strain predictions acquired via isotropic patellar FE models should be interpreted with caution, especially when patellae of different average bone volume fraction are compared.

      PubDate: 2016-12-09T21:38:53Z
      DOI: 10.1016/j.medengphy.2016.10.003
       
  • Finite element modelling of the foot for clinical application: A
           systematic review
    • Authors: Sara Behforootan; Panagiotis Chatzistergos; Roozbeh Naemi; Nachiappan Chockalingam
      Abstract: Publication date: Available online 15 November 2016
      Source:Medical Engineering & Physics
      Author(s): Sara Behforootan, Panagiotis Chatzistergos, Roozbeh Naemi, Nachiappan Chockalingam
      Over the last two decades finite element modelling has been widely used to give new insight on foot and footwear biomechanics. However its actual contribution for the improvement of the therapeutic outcome of different pathological conditions of the foot, such as the diabetic foot, remains relatively limited. This is mainly because finite element modelling has only been used within the research domain. Clinically applicable finite element modelling can open the way for novel diagnostic techniques and novel methods for treatment planning/optimisation which would significantly enhance clinical practice. In this context this review aims to provide an overview of modelling techniques in the field of foot and footwear biomechanics and to investigate their applicability in a clinical setting. Even though no integrated modelling system exists that could be directly used in the clinic and considerable progress is still required, current literature includes a comprehensive toolbox for future work towards clinically applicable finite element modelling. The key challenges include collecting the information that is needed for geometry design, the assignment of material properties and loading on a patient-specific basis and in a cost-effective and non-invasive way. The ultimate challenge for the implementation of any computational system into clinical practice is to ensure that it can produce reliable results for any person that belongs in the population for which it was developed. Consequently this highlights the need for thorough and extensive validation of each individual step of the modelling process as well as for the overall validation of the final integrated system.

      PubDate: 2016-12-09T21:38:53Z
      DOI: 10.1016/j.medengphy.2016.10.011
       
  • Gabor frames for classification of paroxysmal and persistent atrial
           fibrillation episodes
    • Authors: Nuria Ortigosa; Antonio Galbis; Carmen Fernández; Óscar Cano
      Abstract: Publication date: Available online 15 November 2016
      Source:Medical Engineering & Physics
      Author(s): Nuria Ortigosa, Antonio Galbis, Carmen Fernández, Óscar Cano
      In this study, we propose a new classification method for early differentiation of paroxysmal and persistent atrial fibrillation episodes, i.e. those which spontaneously or with external intervention will return to sinus rhythm within 7 days of onset from the ones where the arrhythmia is sustained for more than 7 days. Today, clinicians provide patients classification once the course of the arrhythmia has been disclosed. This classification problem is dealt with in this study. We study a sparse representation of surface electrocardiogram signals by means of Gabor frames and afterwards we apply a linear discriminant analysis. Thus, we provide an early discrimination, obtaining promising performances on a heterogeneous cohort of patients in terms of pharmacological treatment and state of progression of the arrhythmia: 95% sensitivity, 82% specificity, 89% accuracy. In this manner, the proposed method can help clinicians to choose the most appropriate treatment using the electrocardiogram, which is a widely available and non-invasive technique. This early differentiation is clinically highly significant in order to choose optimal patients who may undergo catheter ablation with higher success rates.

      PubDate: 2016-12-09T21:38:53Z
      DOI: 10.1016/j.medengphy.2016.10.013
       
  • Energy flow analysis of amputee walking shows a proximally-directed
           transfer of energy in intact limbs, compared to a distally-directed
           transfer in prosthetic limbs at push-off
    • Authors: R.A. Weinert-Aplin; D. Howard; M. Twiste; H.L. Jarvis; A.N. Bennett; R.J. Baker
      Abstract: Publication date: Available online 8 November 2016
      Source:Medical Engineering & Physics
      Author(s): R.A. Weinert-Aplin, D. Howard, M. Twiste, H.L. Jarvis, A.N. Bennett, R.J. Baker
      Reduced capacity and increased metabolic cost of walking occurs in amputees, despite advances in prosthetic componentry. Joint powers can quantify deficiencies in prosthetic gait, but do not reveal how energy is exchanged between limb segments. This study aimed to quantify these energy exchanges during amputee walking. Optical motion and forceplate data collected during walking at a self-selected speed for cohorts of 10 controls, 10 unilateral trans-tibial, 10 unilateral trans-femoral and 10 bilateral trans-femoral amputees were used to determine the energy exchanges between lower limb segments. At push-off, consistent thigh and shank segment powers were observed between amputee groups (1.12W/kg vs. 1.05W/kg for intact limbs and 0.97W/kg vs. 0.99W/kg for prosthetic limbs), and reduced prosthetic ankle power, particularly in trans-femoral amputees (3.12W/kg vs. 0.87W/kg). Proximally-directed energy exchange was observed in the intact limbs of amputees and controls, while prosthetic limbs displayed distally-directed energy exchanges at the knee and hip. This study used energy flow analysis to show a reversal in the direction in which energy is exchanged between prosthetic limb segments at push-off. This reversal was required to provide sufficient energy to propel the limb segments and is likely a direct result of the lack of push-off power at the prosthetic ankle, particularly in trans-femoral amputees, and leads to their increased metabolic cost of walking.

      PubDate: 2016-11-11T17:14:03Z
      DOI: 10.1016/j.medengphy.2016.10.005
       
  • Biomechanical analysis of combining head-down tilt traction with vibration
           for different grades of degeneration of the lumbar spine
    • Authors: Sicong Wang; Lizhen Wang; Yawei Wang; Chengfei Du; Ming Zhang; Yubo Fan
      Abstract: Publication date: Available online 3 November 2016
      Source:Medical Engineering & Physics
      Author(s): Sicong Wang, Lizhen Wang, Yawei Wang, Chengfei Du, Ming Zhang, Yubo Fan
      In recent years, a combination of traction and vibration therapy is usually used to alleviate low back pain (LBP) in clinical settings. Combining head-down tilt (HDT) traction with vibration was demonstrated to be efficacious for LBP patients in our previous study. However, the biomechanics of the lumbar spine during this combined treatment is not well known and need quantitative analysis. In addition, LBP patients have different grades of degeneration of the lumbar spinal structure, which are often age related. Selecting a suitable rehabilitation therapy for different age groups of patients has been challenging. Therefore, a finite element (FE) model of the L1–L5 lumbar spine and a vibration dynamic model are developed in this study in order to investigate the biomechanical effects of the combination of HDT traction and vibration therapy on the age-related degeneration of the lumbar spine. The decrease of intradiscal pressure is more effective when vibration is combined with traction therapy. Moreover, the stresses on the discs are lower in the “traction+vibration” mode than the “traction-only” mode. The stress concentration at the posterior part of nucleus is mitigated after the vibration is combined. The disc deformations especially posterior disc radial retraction is improved in the “traction+vibration” mode. These beneficial effects of this therapy could help decompress the discs and spinal nerves and therefore relieve LBP. Simultaneously, patients with grade 1 degeneration (approximately 41–50 years old) are able to achieve better results compared with other age groups. This study could be used to provide a more effective LBP rehabilitation therapy.

      PubDate: 2016-11-05T16:20:44Z
      DOI: 10.1016/j.medengphy.2016.10.004
       
  • Studying the magnetic stimulation of nervous tissues: A calculation
           framework to investigate stimulation areas
    • Authors: Simona Valentini; Iacopo Portaccio; Dino Accoto
      Abstract: Publication date: Available online 3 November 2016
      Source:Medical Engineering & Physics
      Author(s): Simona Valentini, Iacopo Portaccio, Dino Accoto
      The electromagnetic stimulation of nervous tissue has represented an alternative to electrical stimulation since the 1980s. The growing number of potential applications has led to an increasing interest in the development of modeling tools that can help the design of novel electromagnetic stimulators. In this context, the aim of this paper is to provide a versatile calculation framework to investigate the properties of the electric field generated by a plurality of miniature coils, arranged in cuff configuration. Furthermore, the capability of the miniature coils to elicit a neuronal response in specific portions of the (peripheral) nerve will be investigated. Starting from Jefimenko’s equations, a model was implemented in MATLAB. It calculates the electromagnetic field induced by coils, with arbitrary shape and spatial orientation, and the activating function around the coils through simple numerical integration. By studying the activating functions, it is possible to determine where the neurons can be excited. The model was validated by comparison with FEM simulations. A dimensional analysis was conducted to compare in terms of shape and depth of the stimulation volumes different coil geometries, regardless of design parameters such as current, number of turns and coil sizes.The dimensionless groups identified according to Buckingham’s theorem provide a direct estimate of the stimulation depth reached within the nerve.The calculation tools developed in this paper can be used in the design of coils to quickly compare different geometries and spatial distribution of coils in order to identify the optimal configurations for the specific application addressed by the designer.

      PubDate: 2016-11-05T16:20:44Z
      DOI: 10.1016/j.medengphy.2016.10.012
       
  • An active simulator for neonatal intubation: Design, development and
           assessment
    • Authors: Ilaria Baldoli; Selene Tognarelli; Ferdinando Vangi; Davide Panizza; Rosa T. Scaramuzzo; Armando Cuttano; Cecilia Laschi; Arianna Menciassi
      Abstract: Publication date: Available online 3 November 2016
      Source:Medical Engineering & Physics
      Author(s): Ilaria Baldoli, Selene Tognarelli, Ferdinando Vangi, Davide Panizza, Rosa T. Scaramuzzo, Armando Cuttano, Cecilia Laschi, Arianna Menciassi
      This study describes the technical realization and the pre-clinical validation of a instrumented neonatal intubation skill trainer able to provide objective feedback for the improvement of clinical competences required for such a delicate procedure. The Laerdal® Neonatal Intubation Trainer was modified by applying pressure sensors on areas that are mainly subject to stress and potential injuries. Punctual Force Sensing Resistors (FSRs) were characterized and fixed on the external side of the airway structure on the dental arches and epiglottis. A custom silicone tongue was designed and developed to integrate a matrix textile sensor for mapping the pressure applied on its whole surface. The assessment of the developed tool was performed by nine clinical experts who were asked to practice three intubation procedures apiece. Median and maximum forces, over threshold events (i.e. 2N for gingival arch sensors and 7N for epiglottis and tongue sensors respectively) and execution time were measured for each trainee. Data analysis from training sessions revealed that the epiglottis is the point mainly stressed during an intubation procedure (maximum value: 16.69N, median value: 3.11N), while the analysis carried out on the pressure distribution on the instrumented tongue provided information on both force values and distribution, according to clinicians' performance. The debriefing phase was used to enhance the clinicians’ awareness of applied force and gestures performed, confirming that the present study is an adequate starting point for achieving and optimizing neonatal intubation skills for both residents and expert clinicians.

      PubDate: 2016-11-05T16:20:44Z
      DOI: 10.1016/j.medengphy.2016.10.008
       
  • Biomechanical optimization of the angle and position for surgical
           implantation of a straight short stem hip implant
    • Authors: Gillian E. Cook; Saeid Samiezadeh; Zachary Morison; Mina S.R. Aziz; Habiba Bougherara; Radovan Zdero; Emil H. Schemitsch
      Abstract: Publication date: Available online 2 November 2016
      Source:Medical Engineering & Physics
      Author(s): Gillian E. Cook, Saeid Samiezadeh, Zachary Morison, Mina S.R. Aziz, Habiba Bougherara, Radovan Zdero, Emil H. Schemitsch
      Conservative hip implants preserve healthy bone for revision surgeries and improve physiological loading; however, they have little supporting biomechanical data with respect to their 3D orientation during implantation. This study endeavored to determine the optimal 3D orientation of a straight short stem hip implant within the proximal femur that would yield a stress distribution most similar to an intact femur. Synthetic femurs were implanted with a stem in one of seven maximum angles or positions and axially loaded, with resultant strain values used to validate a finite element model. Design of experiments was used to analyze the range of potential implant orientations under three gait cycle loading conditions. A global optimal orientation of 9.14° valgus, 2.49° anteversion, 0.48mm posterior position, and 0.23mm inferior position was found to yield stress distributions most similar to the intact femur across the gait cycle range. In general, it was determined that the valgus orientation was optimal throughout the gait cycle, consistently exhibiting a stress distribution more similar to that of the intact femur. Minimal levels of anterior/posterior and inferior positioning were seen to be beneficial in achieving more physiological stresses in specific regions of interest within the proximal femur, while the anteverted orientation was only beneficial in loading under flexion. Overall, orthopaedic surgeons should aim to implant straight short stem hip implants in valgus up to 10°, with an otherwise neutral position and version, unless some degree of deviation would be beneficial for a patient-specific reason. This work has implications for the best surgical placement of straight short stem hip implants to yield maximal biomechanical stability.

      PubDate: 2016-11-05T16:20:44Z
      DOI: 10.1016/j.medengphy.2016.10.002
       
  • The coupling between peripheral microcirculation and slow breathing
    • Authors: Zehava Ovadia-Blechman; Benjamin Gavish; Danit Levy-Aharoni; David Shashar; Vered Aharonson
      Abstract: Publication date: Available online 2 November 2016
      Source:Medical Engineering & Physics
      Author(s): Zehava Ovadia-Blechman, Benjamin Gavish, Danit Levy-Aharoni, David Shashar, Vered Aharonson
      Vasomotion (rhythmic changes in arteriolar diameter) is believed to enhance tissue perfusion at low oxygenation levels. We hypothesized that slow breathing and vasomotion may correlate temporally (“coupling”), especially at low oxygenation levels. We paced down spontaneous breathing to about 5 or 6breaths/min in 14 healthy subjects using device-guided breathing (DGB), and continuously monitored respiration, transcutaneous oxygen pressure (“oxygenation”), and skin capillary blood flow ("microflow”) using a laser Doppler flowmeter. The coupling was expressed by cross-correlation calculated in 1-min time windows. Our main results illustrated that: (1) coupling increased gradually upon slowing breathing down in a subgroup, in which initial oxygenation was lower than a threshold of 30mmHg (0.3±0.2 vs. 0.07±0.2, P <10−6); (2) during DGB changes in oxygenation elicited opposite (relative) changes in microflow, with 4-fold higher sensitivity for low initial oxygenation relative to high (regression slope −0.094±0.010mmHg−1 vs. −0.020±0.002mmHg−1, P <10−6); (3) at low initial oxygenation, we observed larger coupling and (relative) microflow changes in younger subjects, and greater oxygenation changes in females (P <10−6 for all); (4) pulse pressure changes from before to after DGB were reduced by increased oxygenation changes during DGB (−5.5±7.4mmHg, r =−0.73, P <0.001). In conclusion, the present methodology can provide the variation trend of respiration–vasomotion coupling during DGB that may characterize microcirculation behavior at tissue oxygenation below a measurable threshold. The potential association of these trends and thresholds with pathologies or specific conditions of the cardiopulmonary system, and the possible role played by the neural sympathetic activity in that coupling, deserve further studies.

      PubDate: 2016-11-05T16:20:44Z
      DOI: 10.1016/j.medengphy.2016.10.009
       
 
 
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