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Showing 1401 - 1600 of 1720 Journals sorted alphabetically
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)
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Yeast     Hybrid Journal   (Followers: 10)
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Zeitschrift für Evidenz, Fortbildung und Qualität im Gesundheitswesen     Full-text available via subscription   (Followers: 5)
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  [3043 journals]
  • Rotary ultrasonic bone drilling: Improved pullout strength and reduced
    • Authors: Vishal Gupta; Pulak M. Pandey; Vadim V. Silberschmidt
      Pages: 1 - 8
      Abstract: Publication date: March 2017
      Source:Medical Engineering & Physics, Volume 41
      Author(s): Vishal Gupta, Pulak M. Pandey, Vadim V. Silberschmidt
      Bone drilling is one of the most common operations used to repair fractured parts of bones. During a bone drilling process, microcracks are generated on the inner surface of the drilled holes that can detrimentally affect osteosynthesis and healing. This study focuses on the investigation of microcracks and pullout strength of cortical-bone screws in drilled holes. It compares conventional surgical bone drilling (CSBD) with rotary ultrasonic bone drilling (RUBD), a novel approach employing ultrasonic vibration with a diamond-coated hollow tool. Both techniques were used to drill holes in porcine bones in an in-vitro study. Scanning electron microscopy was used to observe microcracks and surface morphology. The results obtained showed a significant decrease in the number and dimensions of microcracks generated on the inner surface of drilled holes with the RUBD process in comparison to CSBD. It was also observed that a higher rotational speed and a lower feed rate resulted in lower damage, i.e. fewer microcracks. Biomechanical axial pullout strength of a cortical bone screw inserted into a hole drilled with RUBD was found to be much higher (55–385%) than that for CSBD.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2016.11.004
      Issue No: Vol. 41 (2017)
  • Respiratory effort from the photoplethysmogram
    • Authors: Paul S. Addison
      Pages: 9 - 18
      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
      DOI: 10.1016/j.medengphy.2016.12.010
      Issue No: Vol. 41 (2017)
  • A novel fully automatic measurement of apparent breast volume from trunk
           surface mesh
    • Authors: Lama Seoud; Joyce Ramsay; Stefan Parent; Farida Cheriet
      Pages: 46 - 54
      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
      DOI: 10.1016/j.medengphy.2017.01.004
      Issue No: Vol. 41 (2017)
  • Characterization of micro-resonator based on enhanced metal insulator
           semiconductor capacitor for glucose recognition
    • Authors: Rajendra Dhakal; E.S. Kim; Yong-Hwa Jo; Sung-Soo Kim; Nam-Young Kim
      Pages: 55 - 62
      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
      DOI: 10.1016/j.medengphy.2017.01.008
      Issue No: Vol. 41 (2017)
  • Exploration of Force Myography and surface Electromyography in hand
           gesture classification
    • Authors: Xianta Jiang; Lukas-Karim Merhi; Zhen Gang Xiao; Carlo Menon
      Pages: 63 - 73
      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
      DOI: 10.1016/j.medengphy.2017.01.015
      Issue No: Vol. 41 (2017)
  • The application of physiological loading using a dynamic, multi-axis spine
    • Authors: Timothy Patrick Holsgrove; Anthony W Miles; Sabina Gheduzzi
      Pages: 74 - 80
      Abstract: Publication date: March 2017
      Source:Medical Engineering & Physics, Volume 41
      Author(s): Timothy Patrick Holsgrove, Anthony W Miles, Sabina Gheduzzi
      In-vitro testing protocols used for spine studies should replicate the in-vivo load environment as closely as possible. Unconstrained moments are regularly employed to test spinal specimens in-vitro, but applying such loads dynamically using an active six-axis testing system remains a challenge. The aim of this study was to assess the capability of a custom-developed spine simulator to apply dynamic unconstrained moments with an axial preload. Flexion–extension, lateral bending, and axial rotation were applied to an L5/L6 porcine specimen at 0.1 and 0.3Hz. Non-principal moments and shear forces were minimized using load control. A 500N axial load was applied prior to tests, and held stationary during testing to assess the effect of rotational motion on axial load. Non-principal loads were minimized to within the load cell noise-floor at 0.1Hz, and within two-times the load-cell noise-floor in all but two cases at 0.3Hz. The adoption of position control in axial compression–extension resulted in axial loads with qualitative similarities to in-vivo data. This study successfully applied dynamic, unconstrained moments with a physiological preload using a six-axis control system. Future studies will investigate the application of dynamic load vectors, multi-segment specimens, and assess the effect of injury and degeneration.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2016.12.004
      Issue No: Vol. 41 (2017)
  • Development of a surgical navigation system based on 3D Slicer for
           intraoperative implant placement surgery
    • Authors: Xiaojun Chen; Lu Xu; Huixiang Wang; Fang Wang; Qiugen Wang; Ron Kikinis
      Pages: 81 - 89
      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
      DOI: 10.1016/j.medengphy.2017.01.005
      Issue No: Vol. 41 (2017)
  • Mechanical characterization and comparison of energy storage and return
    • Authors: Stacey M. Rigney; Anne Simmons; Lauren Kark
      Pages: 90 - 96
      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
      DOI: 10.1016/j.medengphy.2017.01.003
      Issue No: Vol. 41 (2017)
  • Medical Device Guidebook: A browser information resource for medical
           device users
    • Authors: Douglas M. Clarkson
      Pages: 97 - 102
      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
      DOI: 10.1016/j.medengphy.2017.01.013
      Issue No: Vol. 41 (2017)
  • Determining 3D scapular orientation with scapula models and biplane 2D
    • Authors: Kristen F Nicholson; R Tyler Richardson; Freeman Miller; James G Richards
      Pages: 103 - 108
      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
      DOI: 10.1016/j.medengphy.2017.01.012
      Issue No: Vol. 41 (2017)
  • Three-dimensional intervertebral range of motion in the cervical spine:
           Does the method of calculation matter'
    • Authors: William J Anderst; Yashar Aucie
      Pages: 109 - 115
      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
      DOI: 10.1016/j.medengphy.2017.01.009
      Issue No: Vol. 41 (2017)
  • Editorial Board of Medical Engineering &amp; Physics
    • Authors: Richard A. Black (PhD; CSci; CEng; FIMechE; FIPEM)
      First page: 1
      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
      DOI: 10.1016/j.medengphy.2017.01.019
      Issue No: Vol. 40 (2017)
  • Estimating the material properties of heel pad sub-layers using inverse
           Finite Element Analysis
    • Authors: Nafiseh Ahanchian; Christopher J. Nester; David Howard; Lei Ren; Daniel Parker
      Pages: 11 - 19
      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
      DOI: 10.1016/j.medengphy.2016.11.003
      Issue No: Vol. 40 (2017)
  • A one-dimensional arterial network model for bypass graft assessment
    • Authors: A.R. Ghigo; S. Abou Taam; X. Wang; P-Y Lagrée; J-M Fullana
      Abstract: Publication date: Available online 11 March 2017
      Source:Medical Engineering & Physics
      Author(s): A.R. Ghigo, S. Abou Taam, X. Wang, P-Y Lagrée, J-M Fullana
      We propose an arterial network model based on one-dimensional hemodynamic equations to study the behavior of different vascular surgical bypass grafts in the case of an arterial occlusive pathology: a stenosis of the Right Iliac artery. We investigate the performances of three different bypass grafts (Aorto-Femoral, Axillo-Femoral and cross-over Femoral) depending on the degree of obstruction of the stenosis. Numerical simulations show that all bypass grafts are efficient since we retrieve in each case the healthy hemodynamics downstream of the stenosed region while ensuring at the same time a global healthy circulation. We analyze in detail the behavior of the Axillo-Femoral bypass graft by performing hundreds of simulations where we vary the values of its Young’s modulus [0.1–50 MPa] and radius [0.01–5 cm]. Our analysis shows that Young’s modulus and radius of commercial bypass grafts are optimal in terms of hemodynamic considerations. Our numerical findings prove that this model approach can be used to optimize or plan patient-specific surgeries, to numerically assess the viability of bypass grafts and to perform parametric analysis and error propagation evaluations by running extensive simulations.

      PubDate: 2017-03-12T21:53:44Z
      DOI: 10.1016/j.medengphy.2017.02.002
  • In silico investigation of cornea deformation during irrigation/aspiration
           in phacoemulsification in cataract surgery
    • Authors: Dariush Bayatpour; Omid Abouali; Alireza Ghaffarieh; Goodarz Ahmadi
      Abstract: Publication date: Available online 10 March 2017
      Source:Medical Engineering & Physics
      Author(s): Dariush Bayatpour, Omid Abouali, Alireza Ghaffarieh, Goodarz Ahmadi
      To analyze the stress, strain and displacement of the human cornea under the action of negative intraocular pressure, which occurs during phacoemulsification in cataract surgery, a multidisciplinary approach including biomedical engineering, solid mechanics, numerical analysis, and fluid dynamics was used. Fluid-structure interaction method was implemented using 3-dimensional nonlinear finite element analysis of cornea tissue in conjunction with CFD analysis of anterior chamber fluid flow to study the deformation of the cornea under negative gage pressure during irrigation and aspiration (I/A). The computational model of the eye includes both cornea and sclera. To increase the accuracy of the computational model, both cornea hyperelasticity and thickness variation were included in the analysis. The simulation was performed for both coaxial and bimanual I/A systems with different flow rates. The cornea deformations for various flow rates were evaluated, and the possibility of an unstable anterior chamber was assessed. The results show that the critical pressure in the anterior chamber, which may lead to the surge condition due to buckling of the cornea, is sub-ambient (below zero gauge pressure). Anterior chamber instability occurs at higher volume flow rates for coaxial I/A system compared with that for bimanual system, but the deformation of the cornea is more intense for the bimanual system.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2017.02.010
  • An articulated ankle–foot orthosis with adjustable plantarflexion
           resistance, dorsiflexion resistance and alignment: A pilot study on
           mechanical properties and effects on stroke hemiparetic gait
    • Authors: Toshiki Kobayashi; Michael S. Orendurff; Grace Hunt; Lucas S. Lincoln; Fan Gao; Nicholas LeCursi; K. Bo Foreman
      Abstract: Publication date: Available online 9 March 2017
      Source:Medical Engineering & Physics
      Author(s): Toshiki Kobayashi, Michael S. Orendurff, Grace Hunt, Lucas S. Lincoln, Fan Gao, Nicholas LeCursi, K. Bo Foreman
      Mechanical properties of an articulated ankle–foot orthosis (AFO) are closely related to gait performance in individuals post-stroke. This paper presents a pilot study on the mechanical properties of a novel articulated AFO with adjustable plantarflexion resistance, dorsiflexion resistance and alignment, and its effect on ankle and knee joint kinematics and kinetics in an individual post-stroke during gait. The mechanical properties of the AFO were quantified. Gait analysis was performed using a 3D motion capture system with a split-belt instrumented treadmill under 12 different settings of the mechanical properties of the AFO [i.e. 4 plantarflexion resistances (P1<P4), 4 dorsiflexion resistances (D1<D4), 4 initial alignments (A1<A4)]. The AFO demonstrated systematic changes in moment–angle relationship in response to changes in AFO joint settings. The gait analysis demonstrated that the ankle and knee angle and moment were responsive to changes in the AFO joint settings. Mean ankle angle at initial contact changed from −0.86° (P1) to 0.91° (P4) and from −1.48° (A1) to 4.45° (A4), while mean peak dorsiflexion angle changed from 12.01° (D1) to 6.40° (D4) at mid-stance. The novel articulated AFO appeared effective in influencing lower-limb joint kinematics and kinetics of gait in the individual post-stroke.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2017.02.012
  • Dynamic mechanical analysis to assess viscoelasticity of liver tissue in a
           rat model of nonalcoholic fatty liver disease
    • Authors: Xinyu Zhang; Xuehua Gao; Pengpeng Zhang; Yanrong Guo; Haoming Lin; Xianfen Diao; Yingxia Liu; Changfeng Dong; Yaxin Hu; Siping Chen; Xin Chen
      Abstract: Publication date: Available online 9 March 2017
      Source:Medical Engineering & Physics
      Author(s): Xinyu Zhang, Xuehua Gao, Pengpeng Zhang, Yanrong Guo, Haoming Lin, Xianfen Diao, Yingxia Liu, Changfeng Dong, Yaxin Hu, Siping Chen, Xin Chen
      Nonalcoholic fatty liver disease (NAFLD) is the most common liver disorder in both developed and developing countries. A noninvasive method of detecting early stage NAFLD and distinguishing non-alcoholic steatohepatitis (NASH) from simple steatosis (SS) would be useful. The over-accumulation of fat in hepatocytes alters the physical microstructure and chemical contents of the liver tissue. This study included dynamic mechanical analysis (DMA) testing on liver samples from a rat model of NAFLD to determine whether the tissue shows any significant changes in viscoelasticity due to the histological changes. Liver steatosis was induced in 57 rats by gavage feeding of a high fat emulsion; 12 rats received a standard diet only and served as controls. Each rat provided 2 or 3 samples for DMA tests. The shear modulus and loss modulus were measured at 9 frequency points evenly-spaced in the range from 1Hz to 41Hz. The phase velocity of shear wave was calculated from the measured modulus. Multivariate T 2 test was used to assess the significance of intra-group difference. The results showed significant changes (p < 0.05) in storage modulus in livers with moderate to severe (S2 to S4) steatosis in comparison with livers without steatosis (S0), while the loss modulus demonstrated significant changes earlier in stage S1, indicating that fat accumulation affects the mechanical properties of liver, particularly viscosity. However, no significant differences were observed between the steatosis grades. These results also suggest that mild inflammation may affect the mechanical properties, which requires further verification. These findings provide new information about the mechanical properties of livers with NAFLD in low frequency range and suggest that it is possible to distinguish normal livers from livers with NAFLD.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2017.02.014
  • Finite element analysis of the amputated lower limb: A systematic review
           and recommendations
    • Authors: A.S. Dickinson; J.W. Steer; P.R. Worsley
      Abstract: Publication date: Available online 9 March 2017
      Source:Medical Engineering & Physics
      Author(s): A.S. Dickinson, J.W. Steer, P.R. Worsley
      The care and rehabilitation of individuals after lower limb amputation presents a substantial and growing socioeconomic challenge. Clinical outcome is closely linked to successful functional rehabilitation with a prosthetic limb, which depends upon comfortable prosthetic limb – residual limb load transfer. Despite early interest in the 1980s, the amputated limb has received considerably less attention in computational biomechanical analysis than other subjects, such as arthroplasty. This systematic literature review investigates the state of the art in residual limb finite element analysis published since 2000. The identified studies were grouped into the following categories: (1) residuum-prosthesis interface mechanics; (2) residuum soft tissue internal mechanics; (3) identification of residuum tissue characteristics; (4) proposals for incorporating FEA into the prosthesis fitting process; (5) analysis of the influence of prosthetic componentry concepts to improve load transfer to the residuum, such as the monolimb and structural socket compliance; and (6) analysis of osseointegrated (OI) prostheses. The state of the art is critically appraised in order to form recommendations for future modeling studies in terms of geometry, material properties, boundary conditions, interface models, and relevant but un-investigated issues. Finally, the practical implementation of these approaches is discussed.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2017.02.008
  • Biplane fluoroscopy for hindfoot motion analysis during gait: A
           model-based evaluation
    • Authors: Janelle A. Cross; Benjamin D. McHenry; Robert Molthen; Emily Exten; Taly Gilat Schmidt; Gerald F. Harris
      Abstract: Publication date: Available online 1 March 2017
      Source:Medical Engineering & Physics
      Author(s): Janelle A. Cross, Benjamin D. McHenry, Robert Molthen, Emily Exten, Taly Gilat Schmidt, Gerald F. Harris
      The purpose of this study was to quantify the accuracy and precision of a biplane fluoroscopy system for model-based tracking of in vivo hindfoot motion during over-ground gait. Gait was simulated by manually manipulating a cadaver foot specimen through a biplane fluoroscopy system attached to a walkway. Three 1.6-mm diameter steel beads were implanted into the specimen to provide marker-based tracking measurements for comparison to model-based tracking. A CT scan was acquired to define a gold standard of implanted bead positions and to create 3D models for model-based tracking. Static and dynamic trials manipulating the specimen through the capture volume were performed. Marker-based tracking error was calculated relative to the gold standard implanted bead positions. The bias, precision, and root-mean-squared (RMS) error of model-based tracking was calculated relative to the marker-based measurements. The overall RMS error of the model-based tracking method averaged 0.43 ± 0.22mm and 0.66 ± 0.43° for static and 0.59 ± 0.10mm and 0.71 ± 0.12° for dynamic trials. The model-based tracking approach represents a non-invasive technique for accurately measuring dynamic hindfoot joint motion during in vivo, weight bearing conditions. The model-based tracking method is recommended for application on the basis of the study results.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2017.02.009
  • Above-knee prosthesis design based on fatigue life using finite element
           method and design of experiment
    • Authors: Suwattanarwong Phanphet; Surangsee Dechjarern; Sermkiat Jomjanyong
      Abstract: Publication date: Available online 1 March 2017
      Source:Medical Engineering & Physics
      Author(s): Suwattanarwong Phanphet, Surangsee Dechjarern, Sermkiat Jomjanyong
      The main objective of this work is to improve the standard of the existing design of knee prosthesis developed by Thailand's Prostheses Foundation of Her Royal Highness The Princess Mother. The experimental structural tests, based on the ISO 10328, of the existing design showed that a few components failed due to fatigue under normal cyclic loading below the required number of cycles. The finite element (FE) simulations of structural tests on the knee prosthesis were carried out. Fatigue life predictions of knee component materials were modeled based on the Morrow's approach. The fatigue life prediction based on the FE model result was validated with the corresponding structural test and the results agreed well. The new designs of the failed components were studied using the design of experimental approach and finite element analysis of the ISO 10328 structural test of knee prostheses under two separated loading cases. Under ultimate loading, knee prosthesis peak von Mises stress must be less than the yield strength of knee component's material and the total knee deflection must be lower than 2.5mm. The fatigue life prediction of all knee components must be higher than 3,000,000 cycles under normal cyclic loading. The design parameters are the thickness of joint bars, the diameter of lower connector and the thickness of absorber-stopper. The optimized knee prosthesis design meeting all the requirements was recommended. Experimental ISO 10328 structural test of the fabricated knee prosthesis based on the optimized design confirmed the finite element prediction.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2017.01.001
  • Effect of vibration frequency on biopsy needle insertion force
    • Authors: Lei Tan; Xuemei Qin; Qinhe Zhang; Hongcai Zhang; Hongjian Dong; Tuodang Guo; Guowei Liu
      Abstract: Publication date: Available online 1 March 2017
      Source:Medical Engineering & Physics
      Author(s): Lei Tan, Xuemei Qin, Qinhe Zhang, Hongcai Zhang, Hongjian Dong, Tuodang Guo, Guowei Liu
      Needle insertion is critical in many clinical medicine procedures, such as biopsy, brachytherapy, and injection therapy. A platform with two degrees of freedom was set up to study the effect of vibration frequency on needle insertion force. The gel phantom deformation at the needle cutting edge and the Voigt model are utilized to develop a dynamic model to explain the relationship between the insertion force and needle-tip velocity. The accuracy of this model was verified by performing needle insertions into phantom gel. The effect of vibration on insertion force can be explained as the vibration increasing the needle-tip velocity and subsequently increasing the insertion force. In a series of needle insertion experiments with different vibration frequencies, the peak forces were selected for comparison to explore the effect of vibration frequency on needle insertion force. The experimental results indicate that the insertion force at 500Hz increases up to 17.9% compared with the force at 50Hz.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2017.02.011
  • The effect of boundary constraints on finite element modelling of the
           human pelvis
    • Authors: Peter J. Watson; Ali Dostanpor; Michael J. Fagan; Catherine A. Dobson
      Abstract: Publication date: Available online 1 March 2017
      Source:Medical Engineering & Physics
      Author(s): Peter J. Watson, Ali Dostanpor, Michael J. Fagan, Catherine A. Dobson
      The use of finite element analysis (FEA) to investigate the biomechanics of anatomical systems critically relies on the specification of physiologically representative boundary conditions. The biomechanics of the pelvis has been the specific focus of a number of FEA studies previously, but it is also a key aspect in other investigations of, for example, the hip joint or new design of hip prostheses. In those studies, the pelvis has been modelled in a number of ways with a variety of boundary conditions, ranging from a model of the whole pelvic girdle including soft tissue attachments to a model of an isolated hemi-pelvis. The current study constructed a series of FEA models of the same human pelvis to investigate the sensitivity of the predicted stress distributions to the type of boundary conditions applied, in particular to represent the sacro-iliac joint and pubic symphysis. Varying the method of modelling the sacro-iliac joint did not produce significant variations in the stress distribution, however changes to the modelling of the pubic symphysis were observed to have a greater effect on the results. Over-constraint of the symphysis prevented the bending of the pelvis about the greater sciatic notch, and underestimated high stresses within the ilium. However, permitting medio-lateral translation to mimic widening of the pelvis addressed this problem. These findings underline the importance of applying the appropriate boundary conditions to FEA models, and provide guidance on suitable methods of constraining the pelvis when, for example, scan data has not captured the full pelvic girdle. The results also suggest a valid method for performing hemi-pelvic modelling of cadaveric or archaeological remains which are either damaged or incomplete.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2017.02.001
  • The relationship between RMS electromyography and thickness change in the
           skeletal muscles
    • Authors: Sharareh Kian-Bostanabad; Mahmood-Reza Azghani
      Abstract: Publication date: Available online 28 February 2017
      Source:Medical Engineering & Physics
      Author(s): Sharareh Kian-Bostanabad, Mahmood-Reza Azghani
      The knowledge of muscle function may affect prescribing medications and physical treatments. Recently, ultrasound and electromyography (EMG) have been used to assess the skeletal muscles activity. The relationship between these methods has been reported in numerous articles qualitatively. In this paper, the relationship between EMG root-mean-square (RMS) and ultrasound data of muscle thickness has been investigated using Response Surface Methodology in the muscles separately and together and predictive models reported. Results show that to assess the relationship between the changes of thickness and activity (EMG) in muscles, we can use quadratic model for the rectus femoris, tibialis anterior, transverse abdominal, biceps brachii and brachialis muscles (R 2 =0.624–0.891) and linear model for the internal and external oblique abdominal, lumbar multifidus and deep cervical flexor muscles (R 2 =0.348–0.767). Due to the high correlation coefficient for the equations in the bulky muscles, it seems that the correlation between EMG RMS and ultrasound data of muscle thickness on the bulky muscles is higher than the flat muscles. This relationship may depend more on the type of activity than the type of muscle.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2017.01.020
  • Detecting knee osteoarthritis and its discriminating parameters using
           random forests
    • Authors: Margarita Kotti; Lynsey D. Duffell; Aldo A. Faisal; Alison H. McGregor
      Abstract: Publication date: Available online 24 February 2017
      Source:Medical Engineering & Physics
      Author(s): Margarita Kotti, Lynsey D. Duffell, Aldo A. Faisal, Alison H. McGregor
      This paper tackles the problem of automatic detection of knee osteoarthritis. A computer system is built that takes as input the body kinetics and produces as output not only an estimation of presence of the knee osteoarthritis, as previously done in the literature, but also the most discriminating parameters along with a set of rules on how this decision was reached. This fills the gap of interpretability between the medical and the engineering approaches. We collected locomotion data from 47 subjects with knee osteoarthritis and 47 healthy subjects. Osteoarthritis subjects were recruited from hospital clinics and GP surgeries, and age and sex matched healthy subjects from the local community. Subjects walked on a walkway equipped with two force plates with piezoelectric 3-component force sensors. Parameters of the vertical, anterior–posterior, and medio-lateral ground reaction forces, such as mean value, push-off time, and slope, were extracted. Then random forest regressors map those parameters via rule induction to the degree of knee osteoarthritis. To boost generalisation ability, a subject-independent protocol is employed. The 5-fold cross-validated accuracy is 72.61%±4.24%. We show that with 3 steps or less a reliable clinical measure can be extracted in a rule-based approach when the dataset is analysed appropriately.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2017.02.004
  • Development and validation of an improved mechanical thorax for simulating
           cardiopulmonary resuscitation with adjustable chest stiffness and
           simulated blood flow
    • Authors: Stefan Eichhorn; Johannes Spindler; Marcin Polski; Alejandro Mendoza; Ulrich Schreiber; Michael Heller; Marcus Andre Deutsch; Christian Braun; Rüdiger Lange; Markus Krane
      Abstract: Publication date: Available online 24 February 2017
      Source:Medical Engineering & Physics
      Author(s): Stefan Eichhorn, Johannes Spindler, Marcin Polski, Alejandro Mendoza, Ulrich Schreiber, Michael Heller, Marcus Andre Deutsch, Christian Braun, Rüdiger Lange, Markus Krane
      Investigations of compressive frequency, duty cycle, or waveform during CPR are typically rooted in animal research or computer simulations. Our goal was to generate a mechanical model incorporating alternate stiffness settings and an integrated blood flow system, enabling defined, reproducible comparisons of CPR efficacy. Based on thoracic stiffness data measured in human cadavers, such a model was constructed using valve-controlled pneumatic pistons and an artificial heart. This model offers two realistic levels of chest elasticity, with a blood flow apparatus that reflects compressive depth and waveform changes. We conducted CPR at opposing levels of physiologic stiffness, using a LUCAS device, a motor-driven plunger, and a group of volunteers. In high-stiffness mode, blood flow generated by volunteers was significantly less after just 2min of CPR, whereas flow generated by LUCAS device was superior by comparison. Optimal blood flow was obtained via motor-driven plunger, with trapezoidal waveform.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2017.02.005
  • Application of data fusion techniques and technologies for wearable health
    • Authors: Rachel C. King; Emma Villeneuve; Ruth J. White; R. Simon Sherratt; William Holderbaum; William S. Harwin
      Abstract: Publication date: Available online 23 February 2017
      Source:Medical Engineering & Physics
      Author(s): Rachel C. King, Emma Villeneuve, Ruth J. White, R. Simon Sherratt, William Holderbaum, William S. Harwin
      Technological advances in sensors and communications have enabled discrete integration into everyday objects, both in the home and about the person. Information gathered by monitoring physiological, behavioural, and social aspects of our lives, can be used to achieve a positive impact on quality of life, health, and well-being. Wearable sensors are at the cusp of becoming truly pervasive, and could be woven into the clothes and accessories that we wear such that they become ubiquitous and transparent. To interpret the complex multidimensional information provided by these sensors, data fusion techniques are employed to provide a meaningful representation of the sensor outputs. This paper is intended to provide a short overview of data fusion techniques and algorithms that can be used to interpret wearable sensor data in the context of health monitoring applications. The application of these techniques are then described in the context of healthcare including activity and ambulatory monitoring, gait analysis, fall detection, and biometric monitoring. A snap-shot of current commercially available sensors is also provided, focusing on their sensing capability, and a commentary on the gaps that need to be bridged to bring research to market.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2016.12.011
  • Computational modelling of bone fracture healing under partial
           weight-bearing exercise
    • Authors: Lihai Zhang; Saeed Miramini; Martin Richardson; Peter Ebeling; David Little; Yi Yang; Zhiyong Huang
      Abstract: Publication date: Available online 22 February 2017
      Source:Medical Engineering & Physics
      Author(s): Lihai Zhang, Saeed Miramini, Martin Richardson, Peter Ebeling, David Little, Yi Yang, Zhiyong Huang
      A great deal of evidence suggests that partial weight-bearing exercise plays an important role in bone fracture healing. However, current physiotherapy program tends to follow the “Let's try it and see” strategy due to the lack of a fundamental understanding of in vivo mechanical environment required for the better healing outcomes. The purpose of present study is to develop an innovative framework to predict the healing outcomes as a result of post-surgical physical therapy. The raw acceleration data corresponding to a series of walking tests is firstly captured by ActiGraph accelerometers, and then used as input to theoretically estimate the peak ground reaction force (PGRF) and peak loading rate (PLR). Finally, the healing outcomes as a result of different walking speeds are predicated based on the interfragmentary movement (IFM) measured by using mechanical testing. The results show that PGRF and PLR are important factors for the callus tissue differentiation at the early stage of healing. The developed model could potentially allow the design of effective patient specific post-surgical physical therapy.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2017.01.025
  • Consistency of cutaneous electrical activity of the human colon with
           respect to serosal slow waves: A simulation study
    • Authors: Nicola Mirizzi; Giuseppe Riezzo
      Abstract: Publication date: Available online 22 February 2017
      Source:Medical Engineering & Physics
      Author(s): Nicola Mirizzi, Giuseppe Riezzo
      The serosal slow waves in the human colon are complex, since their amplitude and frequency vary over time. Therefore, this study employed a simulation to investigate the consistency between serosal slow waves and cutaneous electrical activity by evaluating whether changes of the cutaneous waveform features due to anatomical and physiological parameters are detectable in the cutaneous electrical activity. The simulation results indicated that (a) changes in the dipole moment involve detectable changes in the amplitude of the cutaneous electrical activity; (b) changes in the annular band velocity induce modifications in the cutaneous signal frequency; and (c) changes in the anatomical factors affect both the amplitude and the frequency of the cutaneous signal. Therefore, we observed that there is consistency between serosal slow waves and cutaneous electrical activity. On these bases, we think that modifications in the cutaneous electrical activity observed in our study could represent the marker of specific physiological motor activity of the colon, and such information can improve the recording of the experimental measurements of the cutaneous electrical activity of the colon in humans.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2017.02.006
  • Ex vivo study of prostate cancer localization using rolling mechanical
           imaging towards minimally invasive surgery
    • Authors: Jichun Li; Hongbin Liu; Matthew Brown; Pardeep Kumar; Benjamin J Challacombe; Ashish Chandra; Giles Rottenberg; Lakmal D Seneviratne; Kaspar Althoefer; Prokar Dasgupta
      Abstract: Publication date: Available online 21 February 2017
      Source:Medical Engineering & Physics
      Author(s): Jichun Li, Hongbin Liu, Matthew Brown, Pardeep Kumar, Benjamin J Challacombe, Ashish Chandra, Giles Rottenberg, Lakmal D Seneviratne, Kaspar Althoefer, Prokar Dasgupta
      Rolling mechanical imaging (RMI) is a novel technique towards the detection and quantification of malignant tissue in locations that are inaccessible to palpation during robotic minimally invasive surgery (MIS); the approach is shown to achieve results of higher precision than is possible using the human hand. Using a passive robotic manipulator, a lightweight and force sensitive wheeled probe is driven across the surface of tissue samples to collect continuous measurements of wheel-tissue dynamics. A color-coded map is then generated to visualize the stiffness distribution within the internal tissue structure. Having developed the RMI device in-house, we aim to compare the accuracy of this technique to commonly used methods of localizing prostate cancer in current practice: digital rectal exam (DRE), magnetic resonance imaging (MRI) and transrectal ultrasound (TRUS) biopsy. Final histology is the gold standard used for comparison. A total of 126 sites from 21 robotic-assisted radical prostatectomy specimens were examined. Analysis was performed for sensitivity, specificity, accuracy, and predictive value across all patient risk profiles (defined by PSA, Gleason score and pathological score). Of all techniques, pre-operative biopsy had the highest sensitivity (76.2%) and accuracy (64.3%) in the localization of tumor in the final specimen. However, RMI had a higher sensitivity (44.4%) and accuracy (57.9%) than both DRE (38.1% and 52.4%, respectively) and MRI (33.3% and 57.9%, respectively). These findings suggest a role for RMI towards MIS, where haptic feedback is lacking. While our approach has focused on urological tumors, RMI has potential applicability to other extirpative oncological procedures and to diagnostics (e.g., breast cancer screening).

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2017.01.021
  • Total ankle replacement design and positioning affect implant-bone
           micromotion and bone strains
    • Authors: Ran S. Sopher; Andrew A. Amis; James D. Calder; Jonathan R.T. Jeffers
      Abstract: Publication date: Available online 21 February 2017
      Source:Medical Engineering & Physics
      Author(s): Ran S. Sopher, Andrew A. Amis, James D. Calder, Jonathan R.T. Jeffers
      Implant loosening – commonly linked with elevated initial micromotion – is the primary indication for total ankle replacement (TAR) revision. Finite element modelling has not been used to assess micromotion of TAR implants; additionally, the biomechanical consequences of TAR malpositioning – previously linked with higher failure rates – remain unexplored. The aim of this study was to estimate implant-bone micromotion and peri-implant bone strains for optimally positioned and malpositioned TAR prostheses, and thereby identify fixation features and malpositioning scenarios increasing the risk of loosening. Finite element models simulating three of the most commonly used TAR devices (BOX®, Mobility® and Salto®) implanted into the tibia/talus and subjected to physiological loads were developed. Mobility and Salto demonstrated the largest micromotion of all tibial and talar components, respectively. Any malpositioning of the implant creating a gap between it and the bone resulted in a considerable increase in micromotion and bone strains. It was concluded that better primary stability can be achieved through fixation nearer to the joint line and/or while relying on more than a single peg. Incomplete seating on the bone may result in considerably elevated implant-bone micromotion and bone strains, thereby increasing the risk for TAR failure.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2017.01.022
  • Non-invasive aortic systolic pressure and pulse wave velocity estimation
           in a primary care setting: An in silico study
    • Authors: Andrea Guala; Carlo Camporeale; Luca Ridolfi; Luca Mesin
      Abstract: Publication date: Available online 21 February 2017
      Source:Medical Engineering & Physics
      Author(s): Andrea Guala, Carlo Camporeale, Luca Ridolfi, Luca Mesin
      Everyday clinical cardiovascular evaluation is still largely based on brachial systolic and diastolic pressures. However, several clinical studies have demonstrated the higher diagnostic capacities of the aortic pressure, as well as the need to assess the aortic mechanical properties (e.g., by measuring the aortic pulse wave velocity). In order to fill this gap, we propose to exploit a set of easy-to-obtain physical characteristics to estimate the aortic pressure and pulse wave velocity. To this aim, a large population of virtual subjects is created by a validated mathematical model of the cardiovascular system. Quadratic regressive models are then fitted and statistically selected in order to obtain reliable estimations of the aortic pressure and pulse wave velocity starting from the knowledge of the subject age, height, weight, brachial pressure, photoplethysmographic measures and either electrocardiogram or phonocardiogram. The results are very encouraging and foster clinical studies aiming to apply a similar technique to a real population.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2017.02.007
  • Electric field estimation of deep transcranial magnetic stimulation
           clinically used for the treatment of neuropsychiatric disorders in
           anatomical head models
    • Authors: Marta Parazzini; Serena Fiocchi; Emma Chiaramello; Yiftach Roth; Abraham Zangen; Paolo Ravazzani
      Abstract: Publication date: Available online 21 February 2017
      Source:Medical Engineering & Physics
      Author(s): Marta Parazzini, Serena Fiocchi, Emma Chiaramello, Yiftach Roth, Abraham Zangen, Paolo Ravazzani
      Literature studies showed the ability to treat neuropsychiatric disorders using H1 coil, developed for the deep Transcranial Magnetic Stimulation (dTMS). Despite the positive results of the clinical studies, the electric field (E) distributions inside the brain induced by this coil when it is positioned on the scalp according to the clinical studies themselves are not yet precisely estimated. This study aims to characterize the E distributions due to the H1 coil in the brain of two realistic human models by computational electromagnetic techniques and to compare them with the ones due to the figure-of-8 coil, traditionally used in TMS and positioned as such to simulate the clinical experiments. Despite inter-individual differences, our results show that the dorsolateral prefrontal cortex is the region preferentially stimulated by both H1 and figure-of-8 coil when they are placed in the position on the scalp according to the clinical studies, with a more broad and non-focal distribution in the case of H1 coil. Moreover, the H1 coil spreads more than the figure-of-8 coil both in the prefrontal cortex and medial prefrontal cortex and towards some deeper brain structures and it is characterized by a higher penetration depth in the frontal lobe. This work highlights the importance of the knowledge of the electric field distribution in the brain tissues to interpret the outcomes of the experimental studies and to optimize the treatments.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2017.02.003
  • 3D measurements in conventional X-ray imaging with RGB-D sensors
    • Authors: Francisco Albiol; Alberto Corbi; Alberto Albiol
      Abstract: Publication date: Available online 17 February 2017
      Source:Medical Engineering & Physics
      Author(s): Francisco Albiol, Alberto Corbi, Alberto Albiol
      A method for deriving 3D internal information in conventional X-ray settings is presented. It is based on the combination of a pair of radiographs from a patient and it avoids the use of X-ray-opaque fiducials and external reference structures. To achieve this goal, we augment an ordinary X-ray device with a consumer RGB-D camera. The patient’ s rotation around the craniocaudal axis is tracked relative to this camera thanks to the depth information provided and the application of a modern surface-mapping algorithm. The measured spatial information is then translated to the reference frame of the X-ray imaging system. By using the intrinsic parameters of the diagnostic equipment, epipolar geometry, and X-ray images of the patient at different angles, 3D internal positions can be obtained. Both the RGB-D and X-ray instruments are first geometrically calibrated to find their joint spatial transformation. The proposed method is applied to three rotating phantoms. The first two consist of an anthropomorphic head and a torso, which are filled with spherical lead bearings at precise locations. The third one is made of simple foam and has metal needles of several known lengths embedded in it. The results show that it is possible to resolve anatomical positions and lengths with a millimetric level of precision. With the proposed approach, internal 3D reconstructed coordinates and distances can be provided to the physician. It also contributes to reducing the invasiveness of ordinary X-ray environments and can replace other types of clinical explorations that are mainly aimed at measuring or geometrically relating elements that are present inside the patient’s body.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2017.01.024
  • Restoring standing capabilities with feedback control of functional
           neuromuscular stimulation following spinal cord injury
    • Authors: Raviraj Nataraj; Musa L. Audu; Ronald J. Triolo
      Abstract: Publication date: Available online 15 February 2017
      Source:Medical Engineering & Physics
      Author(s): Raviraj Nataraj, Musa L. Audu, Ronald J. Triolo
      This paper reviews the field of feedback control for neuroprosthesis systems that restore advanced standing function to individuals with spinal cord injury. Investigations into closed-loop control of standing by functional neuromuscular stimulation (FNS) have spanned three decades. The ultimate goal for FNS standing control systems is to facilitate hands free standing and enabling the user to perform manual functions at self-selected leaning positions. However, most clinical systems for home usage currently only provide basic upright standing using preprogrammed stimulation patterns. To date, online modulation of stimulation to produce advanced standing functions such as balance against postural disturbances or the ability to assume leaning postures have been limited to simulation and laboratory investigations. While great technological advances have been made in biomechanical sensing and interfaces for neuromuscular stimulation, further progress is still required for finer motor control by FNS. Another major challenge is the development of sophisticated control schemes that produce the necessary postural adjustments, adapt against accelerating muscle fatigue, and consider volitional actions of the intact upper-body of the user. Model-based development for novel control schemes are proven and sensible approaches to prototype and test the basic operating efficacy of potentially complex and multi-faceted control systems. The major considerations for further innovation of such systems are summarized in this paper prior to describing the evolution of closed-loop FNS control of standing from previous works. Finally, necessary emerging technologies to for implementing FNS feedback control systems for standing are identified. These technological advancements include novel electrodes that more completely and selectively activate paralyzed musculature and implantable sensors and stimulation modules for flexible neuroprosthesis system deployment.

      PubDate: 2017-03-11T12:45:00Z
      DOI: 10.1016/j.medengphy.2017.01.023
  • Multiobjective optimization of cartilage stress for non-invasive,
           patient-specific recommendations of high tibial osteotomy correction angle
           – a novel method to investigate alignment correction
    • Authors: Keke Zheng; Corey J Scholes; Junning Chen; David Parker; Qing Li
      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
      DOI: 10.1016/j.medengphy.2016.11.013
  • Simulation of fetal heart rate variability with a mathematical model
    • Authors: 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
      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
      DOI: 10.1016/j.medengphy.2017.01.016
  • Optimised analytical models of the dielectric properties of biological
    • Authors: Saqib Salahuddin; Emily Porter; Finn Krewer; Martin O’ Halloran
      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
      DOI: 10.1016/j.medengphy.2017.01.017
  • The effects of tibia profile, distraction angle, and knee load on wedge
           instability and hinge fracture: A finite element study
    • Authors: Pei-Wei Weng; Chia-Hsien Chen; Chu-An Luo; Jui-Sheng Sun; Yang-Hwei Tsuang; Cheng-Kung Cheng; Shang-Chih Lin
      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
      DOI: 10.1016/j.medengphy.2017.01.007
  • Assessing the immediate impact of botulinum toxin injection on impedance
           of spastic muscle
    • Authors: Xiaoyan Li; Henry Shin; Le Li; Elaine Magat; Sheng Li; Ping Zhou
      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
      DOI: 10.1016/j.medengphy.2017.01.018
  • 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
  • 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
  • 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
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