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Showing 1401 - 1600 of 1720 Journals sorted alphabetically
Visnyk of Dnipropetrovsk University. Biology, ecology     Open Access   (Followers: 2)
Visnyk of Dnipropetrovsk University. Biology, medicine     Open Access  
Walailak Journal of Science and Technology     Open Access  
Web Ecology     Open Access   (Followers: 5)
Weed Science     Full-text available via subscription   (Followers: 6)
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: 24)
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: 9)
Yeast     Hybrid Journal   (Followers: 9)
Zebrafish     Hybrid Journal   (Followers: 1)
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)

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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  [3034 journals]
  • 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
      Pages: 79 - 86
      Abstract: Publication date: June 2017
      Source:Medical Engineering & Physics, Volume 44
      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: 2017-05-05T15:15:41Z
      DOI: 10.1016/j.medengphy.2017.02.014
      Issue No: Vol. 44 (2017)
       
  • 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
      Pages: 94 - 101
      Abstract: Publication date: June 2017
      Source:Medical Engineering & Physics, Volume 44
      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: 2017-05-05T15:15:41Z
      DOI: 10.1016/j.medengphy.2017.02.012
      Issue No: Vol. 44 (2017)
       
  • A custom-made temporomandibular joint prosthesis for fabrication by
           selective laser melting: Finite element analysis
    • Authors: Xiangliang Xu; Danmei Luo; Chuanbin Guo; Qiguo Rong
      Abstract: Publication date: Available online 17 June 2017
      Source:Medical Engineering & Physics
      Author(s): Xiangliang Xu, Danmei Luo, Chuanbin Guo, Qiguo Rong
      A novel and custom-made selective laser melting (SLM) 3D-printed alloplastic temporomandibular joint (TMJ) prosthesis is proposed. The titanium-6aluminium-4vanadium (Ti-6Al-4V) condyle component and ultra-high molecular weight polyethylene (UHMWPE) fossa component comprised the total alloplastic TMJ replacement prosthesis. For the condyle component, an optimized tetrahedral open-porous scaffold with combined connection structures, i.e. an inlay rod and an onlay plate, between the prosthesis and remaining mandible was designed. The trajectory of movement of the intact condyle was assessed via kinematic analysis to facilitate the design of the fossa component. The behaviours of the intact mandible and mandible with the prosthesis were compared. The biomechanical behaviour was analysed by assessing the stress distribution on the prosthesis and strain distribution on the mandible. After muscle force was applied, the magnitude of the compressive strain on the condyle neck of the mandible with the prosthesis was lower than that on the condyle neck of the intact mandible, with the exception of the area about the screws; additionally, the magnitude of the strain at the scaffold–bone interface was relatively high.

      PubDate: 2017-06-20T03:14:02Z
      DOI: 10.1016/j.medengphy.2017.04.012
       
  • Biomechanical evaluation of a novel pedicle screw-based interspinous
           spacer: A finite element analysis
    • Authors: Hsin-Chang Chen; Jia-Lin Wu; Shou-Chieh Huang; Zheng-Cheng Zhong; Shiu-Ling Chiu; Yu-Shu Lai; Cheng-Kung Cheng
      Abstract: Publication date: Available online 15 June 2017
      Source:Medical Engineering & Physics
      Author(s): Hsin-Chang Chen, Jia-Lin Wu, Shou-Chieh Huang, Zheng-Cheng Zhong, Shiu-Ling Chiu, Yu-Shu Lai, Cheng-Kung Cheng
      Interspinous spacers have been designed to provide a minimally invasive surgical technique for patients with lumbar spinal stenosis or foraminal stenosis. A novel pedicle screw-based interspinous spacer has been developed in this study, and the aim of this finite element experiment was to investigate the biomechanical differences between the pedicle screw-based interspinous spacer (M-rod system) and the typical interspinous spacer (Coflex-F™). A validated finite element model of an intact lumbar spine was used to analyze the insertions of the Coflex-F™, titanium alloy M-rod (M-Ti), and polyetheretherketone M-rod (M-PEEK), independently. The range of motion (ROM) between each vertebrae, stiffness of the implanted level, the peak stress at the intervertebral discs, and the contact forces on spinous process were analyzed. Of all three devices, the Coflex-F™ provided the largest restrictions in extension, flexion and lateral bending. For intervertebral disc, the peak stress at the implanted segment decreased by 81% in the Coflex-F™, 60.2% in the M-Ti and 46.7% in the M-PEEK when compared to the intact model. For the adjacent segments, while the Coflex-F™ caused considerable increases in the ROM and disc stress, the M-PEEK only had small changes.

      PubDate: 2017-06-20T03:14:02Z
      DOI: 10.1016/j.medengphy.2017.05.004
       
  • On the halt of spontaneous capillary flows in diverging open channels
    • Authors: J. Berthier; K.A. Brakke; D. Gosselin; F. Navarro; N. Belgacem; D. Chaussy; E. Berthier
      Abstract: Publication date: Available online 13 June 2017
      Source:Medical Engineering & Physics
      Author(s): J. Berthier, K.A. Brakke, D. Gosselin, F. Navarro, N. Belgacem, D. Chaussy, E. Berthier
      Due to their compactness and independence of exterior energy sources, capillary microsystems are increasingly used in many different scientific domains, from biotechnology to medicine and biology, chemistry, energy and space. Obtaining a capillary flow depends on channel geometry and contact angle. A general condition for the establishment of a spontaneous capillary flow in a uniform cross section channel has already been derived from Gibbs free energy. In this work, we consider spontaneous capillary flows (SCF) in diverging open rectangular channels and suspended channels, and we show that they do not flow indefinitely but stop at some location in the channel. In the case of linearly diverging open channels, we derive the expression that determines the location where the flow stops. The theoretical approach is verified by using the Surface Evolver numerical program and is checked by experiments. The approach is extended to sudden enlargements, and it is shown that the enlargements can act as stop and trigger valves.

      PubDate: 2017-06-15T02:27:05Z
      DOI: 10.1016/j.medengphy.2017.05.005
       
  • Characterisation of medical microfluidic systems regarding fast changing
           flow rates using optical front tracking methods
    • Authors: Joerg Schroeter; Lino del Bianco; Christian Damiani; Stephan Klein; Bodo Nestler
      Abstract: Publication date: Available online 12 June 2017
      Source:Medical Engineering & Physics
      Author(s): Joerg Schroeter, Lino del Bianco, Christian Damiani, Stephan Klein, Bodo Nestler
      The presented optical flow metering methods are appropriate to characterise the dynamic properties of microfluidic systems. The dynamic behaviour of clinical or medical devices, micro pumps and flow sensors based on thermal methods were investigated. The Camera-System covers a flow range from 50nl/min to 500µl/min. The uncertainty is less than 4%, sample rates up to 5kS/s. The Displacement-Sensor-System covers a flow range between 100µl/min and 50ml/min. The uncertainty is less than 3% at sample rates up to 49kS/s. It was shown that measuring pulsating flow rates with thermal flow sensors is possible, but the signal is low pass filtered. The low pass behaviour is determined by the thermal properties, thermal resistance and heat capacity, of the flow channel. But the mean flow rate was always measured properly. The fluidic properties of two different types of micro pumps were examined and characterised exemplary.

      PubDate: 2017-06-15T02:27:05Z
      DOI: 10.1016/j.medengphy.2017.05.001
       
  • Precision and accuracy of consumer-grade motion tracking system for
           pedicle screw placement in pediatric spinal fusion surgery
    • Authors: Andrew Chan; Janelle Aguillon; Doug Hill; Edmond Lou
      Abstract: Publication date: Available online 9 June 2017
      Source:Medical Engineering & Physics
      Author(s): Andrew Chan, Janelle Aguillon, Doug Hill, Edmond Lou
      Adolescent idiopathic scoliosis (AIS) is a 3-dimensional spinal deformity involving lateral curvature and axial rotation. Surgical intervention involves insertion of pedicle screws into the spine, requiring accuracies of 1mm and 5° in translation and rotation to prevent neural and vascular complications. While commercial CT-navigation is available, the significant cost, bulk and radiation dose hinders their use in AIS surgery. The objective of this study was to evaluate a commercial-grade Optitrack Prime 13W motion capture cameras to determine if they can achieve adequate accuracy for screw insertion guidance in AIS. Static precision, camera and tracked rigid body configurations, translational and rotational accuracy were investigated. A 1-h camera warm-up time was required to achieve precisions of 0.13mm and 0.10°. A three-camera system configuration with cameras at equal height but staggered depth achieved the best accuracy. A triangular rigid body with 7.9mm markers had superior accuracy. The translational accuracy for motions up to 150mm was 0.25mm while rotational accuracy was 4.9° for rotations in two directions from 0° to 70°. Required translational and rotational accuracies were achieved using this motion capture system as well as being comparable to surgical-grade navigators.

      PubDate: 2017-06-15T02:27:05Z
      DOI: 10.1016/j.medengphy.2017.05.003
       
  • A novel flexible capacitive load sensor for use in a mobile
           unicompartmental knee replacement bearing: An in vitro proof of concept
           study
    • Authors: M J A Mentink; B H Van Duren; D W Murray; H S Gill
      Abstract: Publication date: Available online 9 June 2017
      Source:Medical Engineering & Physics
      Author(s): M J A Mentink, B H Van Duren, D W Murray, H S Gill
      Instrumented knee replacements can provide in vivo data quantifying physiological loads acting on the knee. To date instrumented mobile unicompartmental knee replacements (UKR) have not been realised. Ideally instrumentation would be embedded within the polyethylene bearing. This study investigated the feasibility of an embedded flexible capacitive load sensor. A novel flexible capacitive load sensor was developed which could be incorporated into standard manufacturing of compression moulded polyethylene bearings. Dynamic experiments were performed to determine the characteristics of the sensor on a uniaxial servo-hydraulic material testing machine. The instrumented bearing was measured at sinusoidal frequencies between 0.1 and 10Hz, allowing for measurement of typical gait load magnitudes and frequencies. These correspond to frequencies of interest in physiological loading. The loads that were applied were a static load of 390N, corresponding to an equivalent body weight load for UKR, and a dynamic load of ±293N. The frequency transfer response of the sensor suggests a low pass filter response with a −3dB frequency of 10Hz. The proposed embedded capacitive load sensor was shown to be applicable for measuring in vivo loads within a polyethylene mobile UKR bearing.

      PubDate: 2017-06-10T01:10:48Z
      DOI: 10.1016/j.medengphy.2017.05.002
       
  • MicroCT-based finite element models as a tool for virtual testing of
           cortical bone
    • Authors: Masoud Ramezanzadehkoldeh; Bjørn H. Skallerud
      Abstract: Publication date: Available online 18 May 2017
      Source:Medical Engineering & Physics
      Author(s): Masoud Ramezanzadehkoldeh, Bjørn H. Skallerud
      The aim of this study was to assess a virtual biomechanics testing approach purely based on microcomputed tomography (microCT or µCT) data, providing non-invasive methods for determining the stiffness and strength of cortical bone. Mouse femurs were µCT scanned prior to three-point-bend tests. Then microCT-based finite element models were generated with spatial variation in bone elastoplastic properties and subject-specific femur geometries. Empirical relationships of density versus Young's moduli and yield stress were used in assigning elastoplastic properties to each voxel. The microCT-based finite element modeling (µFEM) results were employed to investigate the model's accuracy through comparison with experimental tests. The correspondence of elastic stiffness and strength from the µFE analyses and tests was good. The interpretation of the derived data showed a 6.1%, 1.4%, 1.5%, and 1.6% difference between the experimental test result and µFEM output on global stiffness, nominal Young's modulus, nominal yield stress, and yield force, respectively. We conclude that virtual testing outputs could be used to predict global elastic-plastic properties and may reduce the cost, time, and number of test specimens in performing physical experiments.

      PubDate: 2017-05-20T21:56:27Z
      DOI: 10.1016/j.medengphy.2017.04.011
       
  • Biomechanical study on surgical fixation methods for minimally invasive
           treatment of hallux valgus
    • Authors: Rui Mao; Junchao Guo; Chenyu Luo; Yubo Fan; Jianmin Wen; Lizhen Wang
      Abstract: Publication date: Available online 17 May 2017
      Source:Medical Engineering & Physics
      Author(s): Rui Mao, Junchao Guo, Chenyu Luo, Yubo Fan, Jianmin Wen, Lizhen Wang
      Hallux valgus (HV) was one of the most frequent female foot deformities. The aim of this study was to evaluate mechanical responses and stabilities of the Kirschner, bandage and fiberglass fixations after the distal metatarsal osteotomy in HV treatment. Surface traction of different forefoot regions in bandage fixation and the biomechanical behavior of fiberglass bandage material were measured by a pressure sensor device and a mechanical testing, respectively. A three-dimensional foot finite element (FE) model was developed to simulate the three fixation methods (Kirschner, bandage and fiberglass fixations) in weight bearing. The model included 28 bones, sesamoids, ligaments, plantar fascia, cartilages and soft tissue. The peak Von Mises stress (MS) and compression stress (CS) of the distal fragment were predicted from the three fixation methods: Kirschner fixation (MS=6.71MPa, CS=1.232MPa); Bandage fixation (MS=14.90MPa, CS=9.642MPa); Fiberglass fixation (MS=15.83MPa, CS=19.70MPa). Compared with the Kirschner and bandage fixation, the fiberglass fixation reduced the relative movement of osteotomy fragments and obtained the maximum CS. We concluded that fiberglass fixation in HV treatment was helpful to the bone healing of distal fragment. The findings were expected to guide further therapeutic planning of HV patient.

      PubDate: 2017-05-20T21:56:27Z
      DOI: 10.1016/j.medengphy.2017.04.010
       
  • Computed tomography (CT)-compatible remote center of motion needle
           steering robot: Fusing CT images and electromagnetic sensor data
    • Authors: Navid Shahriari; Wout Heerink; Tim van Katwijk; Edsko Hekman; Matthijs Oudkerk; Sarthak Misra
      Abstract: Publication date: Available online 13 May 2017
      Source:Medical Engineering & Physics
      Author(s): Navid Shahriari, Wout Heerink, Tim van Katwijk, Edsko Hekman, Matthijs Oudkerk, Sarthak Misra
      Lung cancer is the most common cause of cancer-related death, and early detection can reduce the mortality rate. Patients with lung nodules greater than 10 mm usually undergo a computed tomography (CT)-guided biopsy. However, aligning the needle with the target is difficult and the needle tends to deflect from a straight path. In this work, we present a CT-compatible robotic system, which can both position the needle at the puncture point and also insert and rotate the needle. The robot has a remote-center-of-motion arm which is achieved through a parallel mechanism. A new needle steering scheme is also developed where CT images are fused with electromagnetic (EM) sensor data using an unscented Kalman filter. The data fusion allows us to steer the needle using the real-time EM tracker data. The robot design and the steering scheme are validated using three experimental cases. Experimental Case I and II evaluate the accuracy and CT-compatibility of the robot arm, respectively. In experimental Case III, the needle is steered towards 5 real targets embedded in an anthropomorphic gelatin phantom of the thorax. The mean targeting error for the 5 experiments is 1.78 ± 0.70 mm. The proposed robotic system is shown to be CT-compatible with low targeting error. Small nodule size and large needle diameter are two risk factors that can lead to complications in lung biopsy. Our results suggest that nodules larger than 5 mm in diameter can be targeted using our method which may result in lower complication rate.

      PubDate: 2017-05-15T20:41:04Z
      DOI: 10.1016/j.medengphy.2017.04.009
       
  • Modeling of the interaction between grip force and vibration
           transmissibility of a finger
    • Authors: John Z. Wu; Daniel E. Welcome; Thomas W. McDowell; Xueyan S. Xu; Ren G. Dong
      Abstract: Publication date: Available online 9 May 2017
      Source:Medical Engineering & Physics
      Author(s): John Z. Wu, Daniel E. Welcome, Thomas W. McDowell, Xueyan S. Xu, Ren G. Dong
      It is known that the vibration characteristics of the fingers and hand and the level of grip action interacts when operating a power tool. In the current study, we developed a hybrid finger model to simulate the vibrations of the hand–finger system when gripping a vibrating handle covered with soft materials. The hybrid finger model combines the characteristics of conventional finite element (FE) models, multi-body musculoskeletal models, and lumped mass models. The distal, middle, and proximal finger segments were constructed using FE models, the finger segments were connected via three flexible joint linkages (i.e., distal interphalangeal joint (DIP), proximal interphalangeal joint (PIP), and metacarpophalangeal (MCP) joint), and the MCP joint was connected to the ground and handle via lumped parameter elements. The effects of the active muscle forces were accounted for via the joint moments. The bone, nail, and hard connective tissues were assumed to be linearly elastic whereas the soft tissues, which include the skin and subcutaneous tissues, were considered as hyperelastic and viscoelastic. The general trends of the model predictions agree well with the previous experimental measurements in that the resonant frequency increased from proximal to the middle and to the distal finger segments for the same grip force, that the resonant frequency tends to increase with increasing grip force for the same finger segment, especially for the distal segment, and that the magnitude of vibration transmissibility tends to increase with increasing grip force, especially for the proximal segment. The advantage of the proposed model over the traditional vibration models is that it can predict the local vibration behavior of the finger to a tissue level, while taking into account the effects of the active musculoskeletal force, the effects of the contact conditions on vibrations, the global vibration characteristics.

      PubDate: 2017-05-10T15:43:09Z
      DOI: 10.1016/j.medengphy.2017.04.008
       
  • Red blood cell aggregate flux in a bifurcating microchannel
    • Authors: E Kaliviotis; D. Pasias; J.M. Sherwood; S. Balabani
      Abstract: Publication date: Available online 9 May 2017
      Source:Medical Engineering & Physics
      Author(s): E Kaliviotis, D. Pasias, J.M. Sherwood, S. Balabani
      Red blood cell aggregation plays a key role in microcirculatory flows, however, little is known about the transport characteristics of red blood cell aggregates in branching geometries. This work reports on the fluxes of red blood cell aggregates of various sizes in a T-shaped microchannel, aiming to clarify the effects of different flow conditions in the outlet branches of the channel. Image analysis techniques, were utilised, and moderately aggregating human red blood cell suspensions were tested in symmetric (∼50–50%) and asymmetric flow splits through the two outlet (daughter) branches. The results revealed that the flux decreases with aggregate size in the inlet (parent) and daughter branches, mainly due to the fact that the number of larger structures is significantly smaller than that of smaller structures. However, when the flux in the daughter branches is examined relative to the aggregate size flux in the parent branch an increase with aggregate size is observed for a range of asymmetric flow splits. This increase is attributed to size distribution and local concentration changes in the daughter branches. The results show that the flow of larger aggregates is not suppressed downstream of a bifurcation, and that blood flow is maintained, for physiological levels of red blood cell aggregation.

      PubDate: 2017-05-10T15:43:09Z
      DOI: 10.1016/j.medengphy.2017.04.007
       
  • Backflow-free catheters for efficient and safe convection-enhanced
           delivery of therapeutics
    • Authors: Eric Lueshen; Kevin Tangen; Ankit I. Mehta; Andreas Linninger
      Abstract: Publication date: Available online 3 May 2017
      Source:Medical Engineering & Physics
      Author(s): Eric Lueshen, Kevin Tangen, Ankit I. Mehta, Andreas Linninger
      Convection-enhanced delivery (CED) is an invasive drug delivery technique used to target specific regions of the brain for the treatment of cancer and neurodegenerative diseases while bypassing the blood-brain barrier. In order to prevent the possibility of backflow, low volumetric flow rates are applied which limit the achievable drug distribution volumes from CED. This can render CED treatment ineffective since a small convective flow produces narrow drug distribution inside the treatment region. Novel catheter designs and CED protocols are needed to improve the drug distribution inside the treatment region. This is especially important when administering toxic chemotherapeutics which could adversely affect other organs if backflow occurred and these drugs entered the circulating blood stream. In order to help elucidate the causes of backflow and to design backflow-free catheters, we have studied the impact that microfluid flow has on deformable brain phantom gels experimentally as well as numerically. We found that fluid injections into porous media have considerable effects on local transport properties such as porosity and hydraulic conductivity. These phenomena not only alter the bulk flow velocity distribution of the microfluid flow due to the changing porosity, but significantly modify flow direction and even volumetric flow distribution due to induced local hydraulic conductivity anisotropy. These studies led us to the development of novel backflow-free catheters with safe volumetric flow rates up to 10 µL/min. The catheter designs, numerical simulations and experimental results are described throughout this article.

      PubDate: 2017-05-05T15:15:41Z
      DOI: 10.1016/j.medengphy.2017.02.018
       
  • Mathematical modelling of variable porosity coatings for controlled drug
           release
    • Authors: Sean McGinty; David King; Giuseppe Pontrelli
      Abstract: Publication date: Available online 29 April 2017
      Source:Medical Engineering & Physics
      Author(s): Sean McGinty, David King, Giuseppe Pontrelli
      In this paper we investigate the extent to which variable porosity drug-eluting coatings can provide better control over drug release than coatings where the porosity is constant throughout. In particular, we aim to establish the potential benefits of replacing a single-layer with a two-layer coating of identical total thickness and initial drug mass. In our study, what distinguishes the layers (other than their individual thickness and initial drug loading) is the underlying microstructure, and in particular the effective porosity and the tortuosity of the material. We consider the effect on the drug release profile of varying the initial distribution of drug, the relative thickness of the layers and the relative resistance to diffusion offered by each layer’s composition. Our results indicate that the contrast in properties of the two layers can be used as a means of better controlling the release, and that the quantity of drug delivered in the early stages can be modulated by varying the distribution of drug across the layers. We conclude that microstructural and loading differences between multi-layer variable porosity coatings can be used to tune the properties of the coating materials to obtain the desired drug release profile for a given application.

      PubDate: 2017-04-29T14:59:07Z
      DOI: 10.1016/j.medengphy.2017.04.006
       
  • A review of cutting mechanics and modeling techniques for biological
           materials
    • Authors: Behrouz Takabi; Bruce L. Tai
      Abstract: Publication date: Available online 28 April 2017
      Source:Medical Engineering & Physics
      Author(s): Behrouz Takabi, Bruce L. Tai
      This paper presents a comprehensive survey on the modeling of tissue cutting, including both soft tissue and bone cutting processes. In order to achieve higher accuracy in tissue cutting, as a critical process in surgical operations, the meticulous modeling of such processes is important in particular for surgical tool development and analysis. This review paper is focused on the mechanical concepts and modeling techniques utilized to simulate tissue cutting such as cutting forces and chip morphology. These models are presented in two major categories, namely soft tissue cutting and bone cutting. Fracture toughness is commonly used to describe tissue cutting while Johnson–Cook material model is often adopted for bone cutting in conjunction with finite element analysis (FEA). In each section, the most recent mathematical and computational models are summarized. The differences and similarities among these models, challenges, novel techniques, and recommendations for future work are discussed along with each section. This review is aimed to provide a broad and in-depth vision of the methods suitable for tissue and bone cutting simulations.

      PubDate: 2017-04-29T14:59:07Z
      DOI: 10.1016/j.medengphy.2017.04.004
       
  • Simulation and performance analysis of a novel high-accuracy sheathless
           microfluidic impedance cytometer with coplanar electrode layout
    • Authors: Federica Caselli; Paolo Bisegna
      Abstract: Publication date: Available online 24 April 2017
      Source:Medical Engineering & Physics
      Author(s): Federica Caselli, Paolo Bisegna
      The performance of a novel microfluidic impedance cytometer (MIC) with coplanar configuration is investigated in silico. The main feature of the device is the ability to provide accurate particle-sizing despite the well-known measurement sensitivity to particle trajectory. The working principle of the device is presented and validated by means of an original virtual laboratory providing close-to-experimental synthetic data streams. It is shown that a metric correlating with particle trajectory can be extracted from the signal traces and used to compensate the trajectory-induced error in the estimated particle size, thus reaching high-accuracy. An analysis of relevant parameters of the experimental setup is also presented.
      Graphical abstract image

      PubDate: 2017-04-29T14:59:07Z
      DOI: 10.1016/j.medengphy.2017.04.005
       
  • Characterization of human cancellous and subchondral bone with respect to
           electro physical properties and bone mineral density by means of impedance
           spectroscopy
    • Authors: Yvonne Haba; Andreas Wurm; Martin Köckerling; Christoph Schick; Wolfram Mittelmeier; Rainer Bader
      Abstract: Publication date: Available online 24 April 2017
      Source:Medical Engineering & Physics
      Author(s): Yvonne Haba, Andreas Wurm, Martin Köckerling, Christoph Schick, Wolfram Mittelmeier, Rainer Bader
      Computational simulation of electrical bone stimulation of the electrical and dielectric parameters of osteoarthritic bone tissue is useful for an exact patient-individual adaptation of the bone models. Therefore, we investigated electrical and dielectric parameters at a frequency of 20Hz of cancellous and subchondral human femoral head bone samples. Furthermore, the mechanical properties and the bone mineral density (BMD) were determined. Finally, these data were compared with the electrical and dielectric parameters. The bone samples were taken from patients with hip osteoarthritis. Electrical conductivity and dielectric permittivity of cancellous bone amounted to 0.043S/m and 8.1⋅106. BMD of the bone samples determined by dual-x-ray-absorptiometry (DXA) and ashing resulted in 193 ± 70mg/cm² and 286 ± 59mg/cm³ respectively. Structural modulus (ES ) and ultimate compression strength (σ max) were measured with 227 ± 94N/mm² and 6.5 ± 3.4N/mm². No linear correlation of the electrical and dielectric parameters compared with BMD and mechanical properties of cancellous bone samples was found. Electrical conductivity and dielectric permittivity of subchondral bone resulted in 0.029S/m and 8.97×106.

      PubDate: 2017-04-29T14:59:07Z
      DOI: 10.1016/j.medengphy.2017.04.002
       
  • Notched K-wire for low thermal damage bone drilling
    • Authors: Yao Liu; Barry Belmont; Yiwen Wang; Bruce Tai; James Holmes; Albert Shih
      Abstract: Publication date: Available online 24 April 2017
      Source:Medical Engineering & Physics
      Author(s): Yao Liu, Barry Belmont, Yiwen Wang, Bruce Tai, James Holmes, Albert Shih
      The Kirschner wire (K-wire) is a common bone drilling tool in orthopedic surgery to affix fractured bone. Significant heat is produced due to both the cutting and the friction between the K-wire and the bone debris during drilling. Such heat can result in high temperatures, leading to osteonecrosis and other secondary injuries. To reduce thermal injury and other high-temperature associated complications, a new K-wire design with three notches along the three-plane trocar tip fabricated using a thin micro-saw tool is studied. These notches evacuate bone debris and reduce the clogging and heat generation during bone drilling. A set of four K-wires, one without notches and three notched, with depths of 0.5, 0.75, and 1mm, are evaluated. Bone drilling experiments conducted on bovine cortical bone show that notched K-wires could effectively decrease the temperature, thrust force, and torque during bone drilling. K-wires with notches 1mm deep reduced the thrust force and torque by approximately 30%, reduced peak temperatures by 43%, and eliminated blackened burn marks in bone. This study demonstrates that a simple modification of the tip of K-wires can effectively reduce bone temperatures during drilling.

      PubDate: 2017-04-29T14:59:07Z
      DOI: 10.1016/j.medengphy.2017.04.001
       
  • Detecting bursts in the EEG of very and extremely premature infants using
           a multi-feature approach
    • Authors: John M. O’Toole; Geraldine B. Boylan; Rhodri O. Lloyd; Robert M. Goulding; Sampsa Vanhatalo; Nathan J. Stevenson
      Abstract: Publication date: Available online 18 April 2017
      Source:Medical Engineering & Physics
      Author(s): John M. O’Toole, Geraldine B. Boylan, Rhodri O. Lloyd, Robert M. Goulding, Sampsa Vanhatalo, Nathan J. Stevenson
      Aim: To develop a method that segments preterm EEG into bursts and inter-bursts by extracting and combining multiple EEG features. Methods: Two EEG experts annotated bursts in individual EEG channels for 36 preterm infants with gestational age < 30 weeks. The feature set included spectral, amplitude, and frequency-weighted energy features. Using a consensus annotation, feature selection removed redundant features and a support vector machine combined features. Area under the receiver operator characteristic (AUC) and Cohen’s kappa (κ) evaluated performance within a cross-validation procedure. Results: The proposed channel-independent method improves AUC by 4–5% over existing methods (p < 0.001, n = 36 ), with median (95% confidence interval) AUC of 0.989 (0.973–0.997) and sensitivity–specificity of 95.8–94.4%. Agreement rates between the detector and experts’ annotations, κ = 0.72 (0.36–0.83) and κ = 0.65 (0.32–0.81), are comparable to inter-rater agreement, κ = 0.60 (0.21–0.74). Conclusions: Automating the visual identification of bursts in preterm EEG is achievable with a high level of accuracy. Multiple features, combined using a data-driven approach, improves on existing single-feature methods.

      PubDate: 2017-04-22T13:35:07Z
      DOI: 10.1016/j.medengphy.2017.04.003
       
  • Engineering human renal epithelial cells for transplantation in
           regenerative medicine
    • Authors: Vita Manzoli; David Colter Sridevi Dhanaraj Alessia Fornoni Camillo Ricordi
      Abstract: Publication date: Available online 14 April 2017
      Source:Medical Engineering & Physics
      Author(s): Vita Manzoli, David C. Colter, Sridevi Dhanaraj, Alessia Fornoni, Camillo Ricordi, Antonello Pileggi, Alice A. Tomei
      Cellular transplantation may treat several human diseases by replacing damaged cells and/or providing a local source of trophic factors promoting regeneration. We utilized human renal epithelial cells (hRECs) isolated from cadaveric donors as a cell model. For efficacious implementation of hRECs for treatment of kidney diseases, we evaluated a novel encapsulation strategy for immunoisolation of hRECs and lentiviral transduction of the Green Fluorescent Protein (GFP) as model gene for genetic engineering of hRECs to secrete desired trophic factors. In specific, we determined whether encapsulation through conformal coating and/or GFP transduction of hRECs allowed preservation of cell viability and of their trophic factor secretion. To that end, we optimized cultures of hRECs and showed that aggregation in three-dimensional spheroids significantly preserved cell viability, proliferation, and trophic factor secretion. We also showed that both wild type and GFP-engineered hRECs could be efficiently encapsulated within conformal hydrogel coatings through our fluid dynamic platform and that this resulted in further improvement of cell viability and trophic factors secretion. Our findings may lay the groundwork for future therapeutics based on transplantation of genetically engineered human primary cells for treatment of diseases affecting kidneys and potentially other tissues.

      PubDate: 2017-04-15T13:03:44Z
       
  • Validity of the activPAL3 activity monitor in people moderately affected
           by Multiple Sclerosis
    • Authors: E.H. Coulter; L. Miller; S. McCorkell; C. McGuire; K. Algie; J. Freeman; B. Weller; P.G. Mattison; A. McConnachie; O. Wu; L. Paul
      Abstract: Publication date: Available online 10 April 2017
      Source:Medical Engineering & Physics
      Author(s): E.H. Coulter, L. Miller, S. McCorkell, C. McGuire, K. Algie, J. Freeman, B. Weller, P.G. Mattison, A. McConnachie, O. Wu, L. Paul
      Walking is the primary form of physical activity performed by people with Multiple Sclerosis (MS), therefore it is important to ensure the validity of tools employed to measure walking activity. The aim of this study was to assess the criterion validity of the activPAL3 activity monitor during overground walking in people with MS. Validity of the activPAL3 accelerometer was compared to video observation in 20 people moderately affected by MS. Participants walked 20–30m twice along a straight quiet corridor at a comfortable speed. Inter-rater reliability of video observations was excellent (all intraclass correlations >0.99). The mean difference (activPAL3- mean of raters) was −4.70±9.09, −4.55s±10.76 and 1.11s±1.11 for steps taken, walking duration and upright duration respectively. These differences represented 8.7%, 10.0% and 1.8% of the mean for each measure respectively. The activPAL3 tended to underestimate steps taken and walking duration in those who walked at cadences of ≤38 steps/min by 60% and 47%, respectively. The activPAL3 is valid for measuring walking activity in people moderately affected by MS. It is accurate for upright duration regardless of cadence. In participants with slow walking cadences, outcomes of steps taken and walking duration should be interpreted with caution.

      PubDate: 2017-04-15T13:03:44Z
      DOI: 10.1016/j.medengphy.2017.03.008
       
  • Microsoft Kinect can distinguish differences in over-ground gait between
           older persons with and without Parkinson's disease
    • Authors: Moataz Eltoukhy; Christopher Kuenze; Jeonghoon Oh; Marco Jacopetti; Savannah Wooten; Joseph Signorile
      Abstract: Publication date: Available online 10 April 2017
      Source:Medical Engineering & Physics
      Author(s): Moataz Eltoukhy, Christopher Kuenze, Jeonghoon Oh, Marco Jacopetti, Savannah Wooten, Joseph Signorile
      Gait patterns differ between healthy elders and those with Parkinson's disease (PD). A simple, low-cost clinical tool that can evaluate kinematic differences between these populations would be invaluable diagnostically; since gait analysis in a clinical setting is impractical due to cost and technical expertise. This study investigated the between group differences between the Kinect and a 3D movement analysis system (BTS) and reported validity and reliability of the Kinect v2 sensor for gait analysis. Nineteen subjects participated, eleven without (C) and eight with PD (PD). Outcome measures included spatiotemporal parameters and kinematics. Ankle range of motion for C was significantly less during ankle swing compared to PD (p =0.04) for the Kinect. Both systems showed significant differences for stride length (BTS (C 1.24±0.16, PD=1.01±0.17, p =0.009), Kinect (C=1.24±0.17, PD=1.00±0.18, p =0.009)), gait velocity (BTS (C=1.06±0.14, PD=0.83±0.15, p =0.01), Kinect (C=1.06±0.15, PD=0.83±0.16, p =0.01)), and swing velocity (BTS (C=2.50±0.27, PD=2.12±0.36, p =0.02), Kinect (C=2.32±0.25, PD=1.95±0.31, p =0.01)) between groups. Agreement (Range ICC =0.93–0.99) and consistency (Range ICC =0.94–0.99) were excellent between systems for stride length, stance duration, swing duration, gait velocity, and swing velocity. The Kinect v2 can was sensitive enough to detect between group differences and consistently produced results similar to the BTS system.

      PubDate: 2017-04-15T13:03:44Z
      DOI: 10.1016/j.medengphy.2017.03.007
       
  • Effects of socket size on metrics of socket fit in trans-tibial prosthesis
           users
    • Authors: Joan E Sanders; Robert T Youngblood; Brian J Hafner; John C Cagle; Jake B McLean; Christian B Redd; Colin R Dietrich; Marcia A Ciol; Katheryn J Allyn
      Abstract: Publication date: Available online 1 April 2017
      Source:Medical Engineering & Physics
      Author(s): Joan E Sanders, Robert T Youngblood, Brian J Hafner, John C Cagle, Jake B McLean, Christian B Redd, Colin R Dietrich, Marcia A Ciol, Katheryn J Allyn
      The purpose of this research was to conduct a preliminary effort to identify quantitative metrics to distinguish a good socket from an oversized socket in people with trans-tibial amputation. Results could be used to inform clinical practices related to socket replacement. A cross-over study was conducted on community ambulators (K-level 3 or 4) with good residual limb sensation. Participants were each provided with two sockets, a duplicate of their as-prescribed socket and a modified socket that was enlarged or reduced by 1.8mm (∼6% of the socket volume) based on the fit quality of the as-prescribed socket. The two sockets were termed a larger socket and a smaller socket. Activity was monitored while participants wore each socket for 4 weeks. Participants’ gait; self-reported satisfaction, quality of fit, and performance; socket comfort; and morning-to-afternoon limb fluid volume changes were assessed. Visual analysis of plots and estimated effect sizes (measured as mean difference divided by standard deviation) showed largest effects for step time asymmetry, step width asymmetry, anterior and anterior-distal morning-to-afternoon fluid volume change, socket comfort score, and self-reported utility. These variables may be viable metrics for early detection of deterioration in socket fit, and should be tested in a larger clinical study.

      PubDate: 2017-04-08T12:19:15Z
      DOI: 10.1016/j.medengphy.2017.03.003
       
  • Penetration of inhaled aerosols in the bronchial tree
    • Authors: Antonio F. Miguel
      Abstract: Publication date: Available online 31 March 2017
      Source:Medical Engineering & Physics
      Author(s): Antonio F. Miguel
      It has long been recognized that the pattern of particle deposition in the respiratory tree affects how far aerosols penetrate into the deeper zones of the arterial tree, and hence contribute to either their pathogenic potential or therapeutic benefit. In this paper, we introduce an anatomically-inspired model of the human respiratory tree featuring the generations 0–7 in the Weibel model of respiratory tree (i.e., the conducting zone). This model is used to study experimentally the dynamics of inhaled aerosol particles (0.5–20µm aerodynamic diameter), in terms of the penetration fraction of particles (i.e., the fraction of inflowing particles that leave the flow system) during typical breathing patterns. Our study underline important modifications in the penetration patterns for coarse particles compared to fine particles. Our experiments suggest a significant decrease of particle penetration for large-sized particles and higher respiratory frequencies. Dimensionless numbers are also introduced to further understand the particle penetration into the respiratory tree. A decline is seen in the penetration fraction with decreasing Reynolds number and increasing Stokes number. A simple conceptual framework is presented to provide additional insights into the findings obtained.

      PubDate: 2017-04-08T12:19:15Z
      DOI: 10.1016/j.medengphy.2017.03.004
       
  • Validation of a new multiscale finite element analysis approach at the
           distal radius
    • Authors: Joshua E Johnson; Karen L Troy
      Abstract: Publication date: Available online 31 March 2017
      Source:Medical Engineering & Physics
      Author(s): Joshua E Johnson, Karen L Troy
      High-resolution peripheral computed tomography is commonly used to evaluate mechanical behavior of the distal radius microstructure using micro-finite element (FE) modeling. However, only a 9mm section is considered and boundary conditions (BCs) are usually simplified (platen-compression), and may not represent physiologic loading. Regardless, these methods are increasingly being used for clinical evaluations. Our goal was to develop and validate a novel multiscale solution that allows for physiologically relevant loading simulations (such as bracing during a fall), and show that mechanical behavior in the distal radius is different under platen BCs. Our approach incorporated bone microstructure together with organ-level radius geometry, by replacing matching continuum regions with micro-FE sections in user-defined regions of interest. Multiscale model predicted strains showed a strong correlation and a significant relationship with measured strains (r =0.836, p <0.001; slope=0.881, intercept=−12.17 µε, p <0.001). Interestingly, platen BC simulated strains were almost 50% lower than measured strains (r =0.835, p <0.001), and strain distributions were clearly different. Our multiscale method demonstrated excellent potential as a computationally efficient alternative for observing true mechanical environment within distal radius microstructure under physiologically accurate loading.

      PubDate: 2017-04-08T12:19:15Z
      DOI: 10.1016/j.medengphy.2017.03.005
       
  • Prediction of damage formation in hip arthroplasties by finite element
           analysis using computed tomography images
    • Authors: Abdul Halim Abdullah; Mitsugu Todo; Yasuharu Nakashima
      Abstract: Publication date: Available online 31 March 2017
      Source:Medical Engineering & Physics
      Author(s): Abdul Halim Abdullah, Mitsugu Todo, Yasuharu Nakashima
      Femoral bone fracture is one of the main causes for the failure of hip arthroplasties (HA). Being subjected to abrupt and high impact forces in daily activities may lead to complex loading configuration such as bending and sideway falls. The objective of this study is to predict the risk of femoral bone fractures in total hip arthroplasty (THA) and resurfacing hip arthroplasty (RHA). A computed tomography (CT) based on finite element analysis was conducted to demonstrate damage formation in a three dimensional model of HAs. The inhomogeneous model of femoral bone was constructed from a 79 year old female patient with hip osteoarthritis complication. Two different femoral components were modeled with titanium alloy and cobalt chromium and inserted into the femoral bones to present THA and RHA models respectively. The analysis included six configurations, which exhibited various loading and boundary conditions, including axial compression, torsion, lateral bending, stance and two types of falling configurations. The applied hip loadings were normalized to body weight (BW) and accumulated from 1 BW to 3 BW. Predictions of damage formation in the femoral models were discussed as the resulting tensile failure as well as the compressive yielding and failure elements. The results indicate that loading directions can forecast the pattern and location of fractures at varying magnitudes of loading. Lateral bending configuration experienced the highest damage formation in both THA and RHA models. Femoral neck and trochanteric regions were in a common location in the RHA model in most configurations, while the predicted fracture locations in THA differed as per the Vancouver classification.

      PubDate: 2017-04-08T12:19:15Z
      DOI: 10.1016/j.medengphy.2017.03.006
       
  • The Combyn™ ECG: Adding haemodynamic and fluid leads for the ECG. Part
           II: Prediction of total body water (TBW), extracellular fluid (ECF), ECF
           overload, fat mass (FM) and “dry” appendicular muscle mass (AppMM)
    • Authors: Falko Skrabal; Georg P. Pichler; Mathias Penatzer; Johannes Steinbichl; Anna-Katharina Hanserl; Alfred Leis; Herbert Loibner
      Abstract: Publication date: Available online 31 March 2017
      Source:Medical Engineering & Physics
      Author(s): Falko Skrabal, Georg P. Pichler, Mathias Penatzer, Johannes Steinbichl, Anna-Katharina Hanserl, Alfred Leis, Herbert Loibner
      Simultaneous with a 12 channel ECG, body composition was analysed by segmental multi-frequency impedance analysis in 101 healthy subjects and in 118 patients with chronic heart failure (CHF, n = 40), chronic renal failure with haemodialysis (HD, n = 20), and miscellaneous internal diseases (n = 58). Whole body DXA and sodium bromide dilution were used as reference methods for total body water (TBW), extracellular fluid (ECF), appendicular muscle mass (AppMM) and fat mass (FM). Empirical prediction equations were developed in a randomized evaluation sample and then evaluated in unknowns. TBW, ECF, AppMM and FM could be predicted with regression coefficients of 0.96, 0.90, 0.95 and 0.93, respectively, all with p < 0.001. Only segmental impedances and height, but not age, sex, weight and BMI contributed to the prediction of water compartments. About half the patients with CHF and half of those on HD showed increased ECF/ICF ratio in relation to % FM at the legs but not at the thorax. The predicted AppMM was additionally corrected for increased ECF to determine “dry AppMM”, which is markedly lower than the misleading reference DXA. This methodology shows promise as a combination of routine ECG with measurement of body composition, assessment of sarcopenia and detection of overhydration.

      PubDate: 2017-04-08T12:19:15Z
      DOI: 10.1016/j.medengphy.2017.03.002
       
  • Time-scaling based sliding mode control for Neuromuscular Electrical
           Stimulation under uncertain relative degrees
    • Authors: Tiago Roux Oliveira; Luiz Rennó Costa; João Marcos Yamasaki Catunda; Alexandre Visintainer Pino; William Barbosa; Márcio Nogueira de Souza
      Abstract: Publication date: Available online 28 March 2017
      Source:Medical Engineering & Physics
      Author(s): Tiago Roux Oliveira, Luiz Rennó Costa, João Marcos Yamasaki Catunda, Alexandre Visintainer Pino, William Barbosa, Márcio Nogueira de Souza
      This paper addresses the application of the sliding mode approach to control the arm movements by artificial recruitment of muscles using Neuromuscular Electrical Stimulation (NMES). Such a technique allows the activation of motor nerves using surface electrodes. The goal of the proposed control system is to move the upper limbs of subjects through electrical stimulation to achieve a desired elbow angular displacement. Since the human neuro-motor system has individual characteristics, being time-varying, nonlinear and subject to uncertainties, the use of advanced robust control schemes may represent a better solution than classical Proportional-Integral (PI) controllers and model-based approaches, being simpler than more sophisticated strategies using fuzzy logic or neural networks usually applied in this control problem. The objective is the introduction of a new time-scaling base sliding mode control (SMC) strategy for NMES and its experimental evaluation. The main qualitative advantages of the proposed controller via time-scaling procedure are its independence of the knowledge of the plant relative degree and the design/tuning simplicity. The developed sliding mode strategy allows for chattering alleviation due to the impact of the integrator in smoothing the control signal. In addition, no differentiator is applied to construct the sliding surface. The stability analysis of the closed-loop system is also carried out by using singular perturbation methods. Experimental results are conducted with healthy volunteers as well as stroke patients. Quantitative results show a reduction of 45% in terms of root mean square (RMS) error (from 5.9° to 3 . 3 ∘ ) in comparison with PI control scheme, which is similar to that obtained in the literature.

      PubDate: 2017-04-08T12:19:15Z
      DOI: 10.1016/j.medengphy.2017.03.001
       
  • Wing-augmentation reduces femoral head cutting out of dynamic hip screw
    • Authors: Chih-Yu Chen; Shu-Wei Huang; Jui-Sheng Sun; Shin-Yiing Lin; Chih-Sheng Yu; Hsu-Pin Pan; Ping-Hung Lin; Fan-Chun Hsieh; Yang-Hwei Tsuang; Feng-Huei Lin; Rong-Sen Yang; Cheng-Kung Cheng
      Abstract: Publication date: Available online 18 March 2017
      Source:Medical Engineering & Physics
      Author(s): Chih-Yu Chen, Shu-Wei Huang, Jui-Sheng Sun, Shin-Yiing Lin, Chih-Sheng Yu, Hsu-Pin Pan, Ping-Hung Lin, Fan-Chun Hsieh, Yang-Hwei Tsuang, Feng-Huei Lin, Rong-Sen Yang, Cheng-Kung Cheng
      The dynamic hip screw (DHS) is commonly used in the treatment of femoral intertrochanteric fracture with high satisfactory results. However, post-operative failure does occur and result in poor prognosis. The most common failure is femoral head varus collapse, followed by lag screw cut-out through the femoral head. In this study, a novel-designed DHS with two supplemental horizontal blades was used to improve the fixation stability. In this study, nine convention DHS and 9 Orthopaedic Device Research Center (ODRC) DHSs were tested in this study. Each implant was fixed into cellular polyurethane rigid foam as a surrogate of osteoporotic femoral head. Under biaxial rocking motion, all constructs were loaded to failure point (12mm axial displacement) or up to 20,000 cycles of 1.45kN peak magnitude were achieved, whichever occurred first. The migration kinematics was continuously monitored and recorded. The final tip-to-apex distance, rotational angle and varus deformation were also recorded. The results showed that the ODRC DHS sustained significantly more loading cycles and exhibited less axial migration in comparison to the conventional DHS. The ODRC DHS showed a significantly smaller bending strain and larger torsional strain compared to the conventional DHS. The changes in tip-to-apex distance (TAD), post-study varus angle, post-study rotational angle of the ODRC DHS were all significantly less than that of the conventional DHS (p < 0.05). We concluded that the ODRC DHS augmented with two horizontal wings would increase the bone–implant interface contact surface, dissipate the load to the screw itself, which improves the migration resistance and increases the anti-rotational implant effect. In conclusion, the proposed ODRC DHS demonstrated significantly better migration resistance and anti-rotational effect in comparison to the conventional DHS construct.

      PubDate: 2017-04-08T12:19:15Z
      DOI: 10.1016/j.medengphy.2017.02.015
       
  • Comparative assessment of intrinsic mechanical stimuli on knee cartilage
           and compressed agarose constructs
    • Authors: A. Completo; C. Bandeiras; F. Fonseca
      Abstract: Publication date: Available online 18 March 2017
      Source:Medical Engineering & Physics
      Author(s): A. Completo, C. Bandeiras, F. Fonseca
      A well-established cue for improving the properties of tissue-engineered cartilage is mechanical stimulation. However, the explicit ranges of mechanical stimuli that correspond to favorable metabolic outcomes are elusive. Usually, these outcomes have only been associated with the applied strain and frequency, an oversimplification that can hide the fundamental relationship between the intrinsic mechanical stimuli and the metabolic outcomes. This highlights two important key issues: the firstly is related to the evaluation of the intrinsic mechanical stimuli of native cartilage; the second, assuming that the intrinsic mechanical stimuli will be important, deals with the ability to replicate them on the tissue-engineered constructs. This study quantifies and compares the volume of cartilage and agarose subjected to a given magnitude range of each intrinsic mechanical stimulus, through a numerical simulation of a patient-specific knee model coupled with experimental data of contact during the stance phase of gait, and agarose constructs under direct-dynamic compression. The results suggest that direct compression loading needs to be parameterized with time-dependence during the initial culture period in order to better reproduce each one of the intrinsic mechanical stimuli developed in the patient-specific cartilage. A loading regime which combines time periods of low compressive strain (5%) and frequency (0.5Hz), in order to approach the maximal principal strain and fluid velocity stimulus of the patient-specific cartilage, with time periods of high compressive strain (20%) and frequency (3Hz), in order to approach the pore pressure values, may be advantageous relatively to a single loading regime throughout the full culture period.

      PubDate: 2017-04-08T12:19:15Z
      DOI: 10.1016/j.medengphy.2017.02.013
       
  • N2 gas egress from patients’ airways during LN2 spray cryotherapy
    • Authors: John P. O'Connor; Brian M. Hanley; Thomas I. Mulcahey; Ellen E. Sheets; Kacey W. Shuey
      Abstract: Publication date: Available online 18 March 2017
      Source:Medical Engineering & Physics
      Author(s): John P. O'Connor, Brian M. Hanley, Thomas I. Mulcahey, Ellen E. Sheets, Kacey W. Shuey
      Spray cryotherapy using liquid nitrogen (LN2) is a general surgical tool used to ablate benign or malignant lesions. Adequate egress of the gaseous nitrogen (N2) generated during this process must be provided for safe use when LN2 is used within the body rather than topically. When delivered to either the gastrointestinal tract (requiring active venting via a suction tube) or body cavities open to room barometric pressure (such as lung airways) allowing for passive venting, the N2 gas generated from the boiling process must be evacuated. This work will examine the egress of N2 during procedures requiring passive venting from human airways undergoing liquid nitrogen spray cryotherapy. Venting characteristics for safe N2 egress will be presented and discussed based on analytical modeling using fluid mechanics simulations and experimental studies of N2 venting with laboratory and porcine models.

      PubDate: 2017-04-08T12:19:15Z
      DOI: 10.1016/j.medengphy.2017.02.017
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • Optimised analytical models of the dielectric properties of biological
           tissue
    • 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
       
  • 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
       
 
 
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