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

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Journal Cover Medical Engineering & Physics
  [SJR: 0.784]   [H-I: 76]   [9 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1350-4533
   Published by Elsevier Homepage  [3040 journals]
  • Model-dependent and model-independent approaches for evaluating hepatic
           fibrosis in rat liver using shearwave dispersion ultrasound vibrometry
    • Authors: Haoming Lin; Xinyu Zhang; Yuanyuan Shen; Yi Zheng; Yanrong Guo; Ying Zhu; Xianfen Diao; Tianfu Wang; Siping Chen; Xin Chen
      Pages: 66 - 72
      Abstract: Publication date: January 2017
      Source:Medical Engineering & Physics, Volume 39
      Author(s): Haoming Lin, Xinyu Zhang, Yuanyuan Shen, Yi Zheng, Yanrong Guo, Ying Zhu, Xianfen Diao, Tianfu Wang, Siping Chen, Xin Chen
      This study assesses gradations of hepatic fibrosis in rat livers using both model-dependent and model-independent approaches. Liver fibrosis was induced in 37 rats using carbon tetrachloride (CCl4); 6 rats served as the controls. Shear wave velocity as a function of frequency, referred to as velocity dispersion, was measured in vitro by an ultrasound elastography method called shearwave dispersion ultrasound vibrometry (SDUV). For the model-dependent approach, the velocity dispersion data were fit to the Voigt model to solve the viscoelastic modulus. For the model-independent approach, the pattern of the velocity dispersion data was analyzed by linear regression to extract the slope and intercept features. The parameters obtained by both approaches were evaluated separately using a receiver operating characteristic (ROC) curve analysis. The results show that, of all the parameters for differentiating between grade F0–F1 and grade F2–F4 fibrosis, the intercept had the greatest value for the area under the ROC curve. This finding suggests that the model-independent approach may provide an alternative method to the model-dependent approach for staging liver fibrosis.

      PubDate: 2017-01-17T21:19:32Z
      DOI: 10.1016/j.medengphy.2016.10.007
      Issue No: Vol. 39 (2017)
       
  • Modification of the Grood and Suntay Joint Coordinate System equations for
           knee joint flexion
    • Authors: Danè Dabirrahmani; Michael Hogg
      Pages: 113 - 116
      Abstract: Publication date: January 2017
      Source:Medical Engineering & Physics, Volume 39
      Author(s): Danè Dabirrahmani, Michael Hogg
      Since its introduction, the Grood and Suntay Joint Coordinate System (JCS) has been embraced by the International Society of Biomechanics (ISB) and been widely used for biomechanical reporting. There is, however, a limitation in its ability to provide correct flexion values over a wide range of clinically relevant flexion angles. This technical note addresses the limitation of the JCS equations and introduces a new set of equations to overcome this problem.

      PubDate: 2017-01-17T21:19:32Z
      DOI: 10.1016/j.medengphy.2016.10.006
      Issue No: Vol. 39 (2017)
       
  • 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
       
  • 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
       
  • Influence of mouth opening on oropharyngeal humidification and temperature
           in a bench model of neonatal continuous positive airway pressure
    • Authors: Hendrik S. Fischer; Tim L. Ullrich; Christoph Bührer; Christoph Czernik; Gerd Schmalisch
      Abstract: Publication date: Available online 30 December 2016
      Source:Medical Engineering & Physics
      Author(s): Hendrik S. Fischer, Tim L. Ullrich, Christoph Bührer, Christoph Czernik, Gerd Schmalisch
      Clinical studies show that non-invasive respiratory support by continuous positive airway pressure (CPAP) affects gas conditioning in the upper airways, especially in the presence of mouth leaks. Using a new bench model of neonatal CPAP, we investigated the influence of mouth opening on oropharyngeal temperature and humidity. The model features the insertion of a heated humidifier between an active model lung and an oropharyngeal head model to simulate the recurrent expiration of heated, humidified air. During unsupported breathing, physiological temperature and humidity were attained inside the model oropharynx, and mouth opening had no significant effect on oropharyngeal temperature and humidity. During binasal CPAP, the impact of mouth opening was investigated using three different scenarios: no conditioning in the CPAP circuit, heating only, and heated humidification. Mouth opening had a strong negative impact on oropharyngeal humidification in all tested scenarios, but heated humidification in the CPAP circuit maintained clinically acceptable humidity levels regardless of closed or open mouths. The model can be used to test new equipment for use with CPAP, and to investigate the effects of other methods of non-invasive respiratory support on gas conditioning in the presence of leaks.

      PubDate: 2017-01-17T21:19:32Z
      DOI: 10.1016/j.medengphy.2016.12.005
       
  • The application of physiological loading using a dynamic, multi-axis spine
           simulator
    • Authors: Timothy Patrick Holsgrove; Anthony W Miles; Sabina Gheduzzi
      Abstract: Publication date: Available online 30 December 2016
      Source:Medical Engineering & Physics
      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: 2017-01-17T21:19:32Z
      DOI: 10.1016/j.medengphy.2016.12.004
       
  • 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
       
  • 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
       
  • 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
       
  • Dynamic Hilbert warping, a new measure of RR-interval signals evaluated in
           the cognitive load estimation
    • Authors: Peyvand Ghaderyan; Ataollah Abbasi
      Abstract: Publication date: Available online 16 January 2017
      Source:Medical Engineering & Physics
      Author(s): Peyvand Ghaderyan, Ataollah Abbasi
      RR interval (RRI) signals represent the time intervals between successive heart R-waves. These signals are influenced by many cognitive and psychological processes. In this study, a new technique based on the combination of empirical mode decomposition and dynamic Hilbert warping (DHW) was proposed to inference cognitive states from measured RRI signals. Moreover, a set of entropic and statistical measures was extracted to characterize the regularity and temporal distribution in the phase spectra and amplitude envelope of the analytic signals. The discriminating capability of the proposed method was studied in 45 healthy subjects. They performed an arithmetic task with five levels of difficulty. The study indicated the importance of phase information in cognitive load estimation (CLE). The new phase characteristics were able to extract hidden information from the RRI signals. The results revealed a striking decrease in DHW value with increasing load level. The entropic measures of analytic signal also showed an increasing trend as the mental load increased. Although, phase information had an ability to discriminate between more distinct levels as well as between more similar ones, amplitude information was effective only in discriminating between more distinct levels.

      PubDate: 2017-01-17T21:19:32Z
      DOI: 10.1016/j.medengphy.2016.12.008
       
  • Musical Stairs: A motivational therapy tool for children with disabilities
           featuring automated detection of stair-climbing gait events via inertial
           sensors
    • Authors: Ajmal Khan; Elaine Biddiss
      Abstract: Publication date: Available online 16 January 2017
      Source:Medical Engineering & Physics
      Author(s): Ajmal Khan, Elaine Biddiss
      Stair-climbing is a key component of rehabilitation therapies for children with physical disabilities. This paper reports on the design of a system, Musical Stairs, to provide auditory feedback during stair-climbing therapies. Musical Stairs is composed of two foot-mounted inertial sensors, a step detection algorithm, and an auditory feedback response. In Phase 1, we establish its clinical feasibility via a Wizard-of-Oz AB/BA cross-over design with 17 children, aged 4–6 years, having diverse diagnoses and gait abilities. Self-, therapist- and blinded-observer reports indicated increased motivation with auditory feedback. Phase 2 describes the construction of a database comprised of synchronized video and inertial data associated with 1568 steps up and down stairs completed by 26 children aged 4–6 years with diverse diagnoses and gait. Lastly, in Phase 3, data from 18 children in the database were used to train a rule-based step detection algorithm based on local minima in the acceleration profile and the foot's swing angle. A step detection rate of 96% [SD=3%] and false positive rate of 6% [SD=5%] were achieved with an independent test set (n =8). Recommendations for future development and evaluation are discussed.

      PubDate: 2017-01-17T21:19:32Z
      DOI: 10.1016/j.medengphy.2016.12.009
       
  • Isolated effects of external bath osmolality, solute concentration, and
           electrical charge on solute transport across articular cartilage
    • Authors: Behdad Pouran; Vahid Arbabi; Amir A. Zadpoor; Harrie Weinans
      Pages: 1399 - 1407
      Abstract: Publication date: December 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 12
      Author(s): Behdad Pouran, Vahid Arbabi, Amir A. Zadpoor, Harrie Weinans
      The metabolic function of cartilage primarily depends on transport of solutes through diffusion mechanism. In the current study, we use contrast enhanced micro-computed tomography to determine equilibrium concentration of solutes through different cartilage zones and solute flux in the cartilage, using osteochondral plugs from equine femoral condyles. Diffusion experiments were performed with two solutes of different charge and approximately equal molecular weight, namely iodixanol (neutral) and ioxaglate (charge=−1) in order to isolate the effects of solute’s charge on diffusion. Furthermore, solute concentrations as well as bath osmolality were changed to isolate the effects of steric hindrance on diffusion. Bath concentration and bath osmolality only had minor effects on the diffusion of the neutral solute through cartilage at the surface, middle and deep zones, indicating that the diffusion of the neutral solute was mainly Fickian. The negatively charged solute diffused considerably slower through cartilage than the neutral solute, indicating a large non-Fickian contribution in the diffusion of charged molecules. The numerical models determined maximum solute flux in the superficial zone up to a factor of 2.5 lower for the negatively charged solutes (charge=−1) as compared to the neutral solutes confirming the importance of charge-matrix interaction in diffusion of molecules across cartilage.

      PubDate: 2016-12-09T21:38:53Z
      DOI: 10.1016/j.medengphy.2016.09.003
       
  • Study of the transdentinal diffusion of bioactive molecules
    • Authors: A.D. Passos; D. Tziafas; A.A. Mouza; S.V. Paras
      Pages: 1408 - 1415
      Abstract: Publication date: December 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 12
      Author(s): A.D. Passos, D. Tziafas, A.A. Mouza, S.V. Paras
      In this work the mass transfer characteristics in a µ-tube that simulates a simplified dentinal tubule geometry are numerically investigated. The aim is to assess the key features that affect transdentinal diffusion of substances and consequently to define the necessary quantitative and qualitative issues related to a specific bioactive agent before its potential application in clinical practice. CFD simulations were performed in an S-shaped tapered micro-tube, while the code was validated using the non-intrusive optical measuring technique Laser Induced Fluorescence (LIF). As the phenomenon is one-dimensional, diffusion dominated and strongly dependent on the molecular size, the time needed for the concentration of released molecules to attain a required value can be controlled by their initial concentration. Thus, we propose a model, which is successfully verified by experimental data using a dentinal disc and which given the type of applied molecules and their critical pulpal concentration is able to estimate the initial concentration to be imposed.
      Graphical abstract image

      PubDate: 2016-12-09T21:38:53Z
      DOI: 10.1016/j.medengphy.2016.09.005
       
  • Design and biomechanical study of a novel adjustable hemipelvic prosthesis
    • Authors: Dongxu Liu; Zikai Hua; Xinyi Yan; Zhongmin Jin
      Pages: 1416 - 1425
      Abstract: Publication date: December 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 12
      Author(s): Dongxu Liu, Zikai Hua, Xinyi Yan, Zhongmin Jin
      A pelvic endoprosthesis is commonly used in orthopedic surgeries to reconstruct the pelvis after internal hemipelvectomy. This study presents the detailed design of a novel type I+II+III adjustable hemipelvic prosthesis based on the geometrical features of massive human pelvises. Finite element analysis is conducted to estimate the biomechanical performance of the newly designed adjustable hemipelvic prosthesis. Detailed numerical models of the natural and reconstructed pelvises including related soft tissues are developed. Hip contact forces during normal walking, which is one of the most frequent dynamic activities in daily living, are imposed on the pelvis. Results show that the peak stress observed in the reconstructed pelvis model is still within a low and elastic range below the yielding strength of the cortical bone and Ti6Al4V. No significant difference of the stress transferring route, displacement distributions and principal stress vectors is observed between the reconstructed and natural pelvises. The results indicate that the load transferring function of the partially resected pelvis is able to be reliably recovered by the adjustable hemipelvic prosthesis. The principal stress vectors in both pelvis models predict that bone absorption may not apparently occur in the long run. Long-term biomechanical performance of this newly designed prosthesis may be stability.

      PubDate: 2016-12-09T21:38:53Z
      DOI: 10.1016/j.medengphy.2016.09.017
       
  • Bone cement flow analysis by stepwise injection through medical cannulas
    • Authors: Ivan Zderic; Philipp Steinmetz; Markus Windolf; R. Geoff Richards; Andreas Boger; Boyko Gueorguiev
      Pages: 1434 - 1438
      Abstract: Publication date: December 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 12
      Author(s): Ivan Zderic, Philipp Steinmetz, Markus Windolf, R. Geoff Richards, Andreas Boger, Boyko Gueorguiev
      Cement leakage is a serious adverse event potentially occurring during vertebroplasty. Pre-operative in-silico planning of the cement filling process can help reducing complication rates related to leakage. This requires a better understanding of the cement flow along the whole injection path. Therefore, the aim of the present study was to analyze bone cement flow behavior by stepwise injections through medical cannulas. Sixteen cannulas were assigned to four groups for stepwise injection of differently colored cement portions of 1ml volume. Each group differed in the amount of injected cement portions with a range of 1–4ml. After cement curing longitudinal cross-sections of the cannulas were performed and high-resolution pictures taken. Based on these pictures, quadratic polynomial interpolation was applied to the marked intersections between the last two injected cement portions to calculate the leading coefficients. Leading coefficients in the groups with three cement portions (0.287 ± 0.078), four portions (0.243 ± 0.041) and two portions (0.232 ± 0.050) were comparable and significantly higher than the group with one cement portion (0.0032 ± 0.0004), p ≤ 0.016. Based on these findings, cement flow through medical cannulas can be considered as predictable and can therefore be excluded as a source of risk for possible cement leakage complications during vertebroplasty procedures.

      PubDate: 2016-12-09T21:38:53Z
      DOI: 10.1016/j.medengphy.2016.09.015
       
  • Cone-beam micro computed tomography dedicated to the breast
    • Authors: Antonio Sarno; Giovanni Mettivier; Francesca Di Lillo; Mario Cesarelli; Paolo Bifulco; Paolo Russo
      Pages: 1449 - 1457
      Abstract: Publication date: December 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 12
      Author(s): Antonio Sarno, Giovanni Mettivier, Francesca Di Lillo, Mario Cesarelli, Paolo Bifulco, Paolo Russo
      We developed a scanner for micro computed tomography dedicated to the breast (BµCT) with a high resolution flat-panel detector and a microfocus X-ray tube. We evaluated the system spatial resolution via the 3D modulation transfer function (MTF). In addition to conventional absorption-based X-ray imaging, such a prototype showed capabilities for propagation-based phase-contrast and related edge enhancement effects in 3D imaging. The system limiting spatial resolution is 6.2mm−1 (MTF at 10%) in the vertical direction and 3.8mm−1 in the radial direction, values which compare favorably with the spatial resolution reached by mini focus breast CT scanners of other groups. The BµCT scanner was able to detect both microcalcification clusters and masses in an anthropomorphic breast phantom at a dose comparable to that of two-view mammography. The use of a breast holder is proposed in order to have 1–2min long scan times without breast motion artifacts.

      PubDate: 2016-12-09T21:38:53Z
      DOI: 10.1016/j.medengphy.2016.09.012
       
  • Pharmaceutical aerosols deposition patterns from a Dry Powder Inhaler:
           Euler Lagrangian prediction and validation
    • Authors: Ravishekar (Ravi); Kannan A.J. Przekwas Narender Singh Renishkumar Delvadia Geng
      Abstract: Publication date: Available online 16 December 2016
      Source:Medical Engineering & Physics
      Author(s): Ravishekar (Ravi) Kannan, A.J. Przekwas, Narender Singh, Renishkumar Delvadia, Geng Tian, Ross Walenga
      This study uses Computational Fluid Dynamics (CFD) to predict, analyze and validate the deposition patterns in a human lung for a Budesonide drug delivered from the Novolizer Dry Powder Inhaler device. We used a test case of known deposition patterns to validate our computational Euler Lagrangian-based deposition predictions. Two different lung models are used: (i) a basic ring-less trachea model and (ii) an advanced Human Zygote5 model. Unlike earlier attempts, the current simulations do not include the device in the computational domain. This greatly reduces the computational effort. To mimic the device, we model the inlet particle jet stream from the device as a spray entering the mouth in a conical fashion. Deposition studies in the various lung regions were performed. We were able to computationally predict and then demonstrate the enhanced deposition in the tracheal and first generation rings/ridges. The enhanced vorticity creation due to the ring structure and the geometrical design contributes to larger deposition in the Zygote5 model. These are in accord with existing data, unlike the ring-less model. Our validated results indicate the need to (i) introduce the ridges in the experimental casts and the CFD surface meshes to be anatomically consistent and obtain physiologically consistent depositions; (ii) introduce a factor to account for the recirculating lighter particles in empirical models.
      Graphical abstract image

      PubDate: 2016-12-16T14:40:05Z
       
  • Evaluation of predicted knee function for component malrotation in total
           knee arthroplasty
    • Authors: Valentine Vanheule; Hendrik Pieter Delport Michael Skipper Andersen Lennart Scheys
      Abstract: Publication date: Available online 15 December 2016
      Source:Medical Engineering & Physics
      Author(s): Valentine Vanheule, Hendrik Pieter Delport, Michael Skipper Andersen, Lennart Scheys, Roel Wirix-Speetjens, Ilse Jonkers, Jan Victor, Jos Vander Sloten
      Soft-tissue balancing for total knee arthroplasty (TKA) remains subjective and highly dependent on surgical expertise. Pre-operative planning may support the clinician in taking decisions by integrating subject-specific computer models that predict functional outcome. However, validation of these models is essential before they can be applied in clinical practice. The aim of this study was to evaluate a knee modelling workflow by comparing experimental cadaveric measures to model-based kinematics and ligament length changes. Subject-specific models for three cadaveric knees were constructed from medical images. The implanted knees were mounted onto a mechanical rig to perform squatting, measuring kinematics and ligament length changes with optical markers and extensometers. Coronal malrotation was introduced using tibial inserts with a built-in slope. The model output agreed well with the experiment in all alignment conditions. Kinematic behaviour showed an average RMSE of less than 2.7mm and 2.3° for translations and rotations. The average RMSE was below 2.5% for all ligaments. These results show that the presented model can quantitatively predict subject-specific knee behaviour following TKA, allowing evaluation of implant alignment in terms of kinematics and ligament length changes. In future work, the model will be used to evaluate subject-specific implant position based on ligament behaviour.

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

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

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

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

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

      PubDate: 2016-12-16T14:40:05Z
      DOI: 10.1016/j.medengphy.2016.11.010
       
  • Gabor frames for classification of paroxysmal and persistent atrial
           fibrillation episodes
    • Authors: Nuria Ortigosa; Antonio Galbis; Carmen Fernández; Óscar Cano
      Abstract: Publication date: Available online 15 November 2016
      Source:Medical Engineering & Physics
      Author(s): Nuria Ortigosa, Antonio Galbis, Carmen Fernández, Óscar Cano
      In this study, we propose a new classification method for early differentiation of paroxysmal and persistent atrial fibrillation episodes, i.e. those which spontaneously or with external intervention will return to sinus rhythm within 7 days of onset from the ones where the arrhythmia is sustained for more than 7 days. Today, clinicians provide patients classification once the course of the arrhythmia has been disclosed. This classification problem is dealt with in this study. We study a sparse representation of surface electrocardiogram signals by means of Gabor frames and afterwards we apply a linear discriminant analysis. Thus, we provide an early discrimination, obtaining promising performances on a heterogeneous cohort of patients in terms of pharmacological treatment and state of progression of the arrhythmia: 95% sensitivity, 82% specificity, 89% accuracy. In this manner, the proposed method can help clinicians to choose the most appropriate treatment using the electrocardiogram, which is a widely available and non-invasive technique. This early differentiation is clinically highly significant in order to choose optimal patients who may undergo catheter ablation with higher success rates.

      PubDate: 2016-12-09T21:38:53Z
      DOI: 10.1016/j.medengphy.2016.10.013
       
  • Finite element modelling of the foot for clinical application: A
           systematic review
    • Authors: Sara Behforootan; Panagiotis Chatzistergos; Roozbeh Naemi; Nachiappan Chockalingam
      Abstract: Publication date: Available online 15 November 2016
      Source:Medical Engineering & Physics
      Author(s): Sara Behforootan, Panagiotis Chatzistergos, Roozbeh Naemi, Nachiappan Chockalingam
      Over the last two decades finite element modelling has been widely used to give new insight on foot and footwear biomechanics. However its actual contribution for the improvement of the therapeutic outcome of different pathological conditions of the foot, such as the diabetic foot, remains relatively limited. This is mainly because finite element modelling has only been used within the research domain. Clinically applicable finite element modelling can open the way for novel diagnostic techniques and novel methods for treatment planning/optimisation which would significantly enhance clinical practice. In this context this review aims to provide an overview of modelling techniques in the field of foot and footwear biomechanics and to investigate their applicability in a clinical setting. Even though no integrated modelling system exists that could be directly used in the clinic and considerable progress is still required, current literature includes a comprehensive toolbox for future work towards clinically applicable finite element modelling. The key challenges include collecting the information that is needed for geometry design, the assignment of material properties and loading on a patient-specific basis and in a cost-effective and non-invasive way. The ultimate challenge for the implementation of any computational system into clinical practice is to ensure that it can produce reliable results for any person that belongs in the population for which it was developed. Consequently this highlights the need for thorough and extensive validation of each individual step of the modelling process as well as for the overall validation of the final integrated system.

      PubDate: 2016-12-09T21:38:53Z
      DOI: 10.1016/j.medengphy.2016.10.011
       
  • Importance of trabecular anisotropy in finite element predictions of
           patellar strain after Total Knee Arthroplasty
    • Authors: A. Latypova; D.P. Pioletti; A. Terrier
      Abstract: Publication date: Available online 18 November 2016
      Source:Medical Engineering & Physics
      Author(s): A. Latypova, D.P. Pioletti, A. Terrier
      Patellar fracture and anterior knee pain remain major complications after Total Knee Arthroplasty (TKA). Patient-specific finite element (FE) models should help improve understanding of these complications through estimation of joint and bone mechanics. However, sensitivity of predictions on modeling techniques and approaches is not fully investigated. In particular, the importance of patellar bone anisotropy, usually omitted in FE models, on strain prediction is still unknown. The objective of this study was thus to estimate the influence of modeling patellar trabecular anisotropy on prediction of patellar strain in TKA models. We compared FE-derived strain predictions with isotopic and anisotropic material properties using 17 validated FE models of the patella after TKA. We considered both non-resurfaced and resurfaced patellae, in a load-bearing TKA joint. We evaluated and compared the bone volume above a strain threshold and, in addition, estimated if the difference in isotopic and anisotropic predictions was consistent between patellae of different average bone volume fraction. Compared to the anisotropic reference, the isotropic prediction of strained volume was 3.7±1.8 times higher for non-resurfaced patellae and 1.5±0.4 times for resurfaced patellae. This difference was higher for patellae with lower average bone volume fraction. This study indicates that strain predictions acquired via isotropic patellar FE models should be interpreted with caution, especially when patellae of different average bone volume fraction are compared.

      PubDate: 2016-12-09T21:38:53Z
      DOI: 10.1016/j.medengphy.2016.10.003
       
  • Review of fall detection techniques: A data availability perspective
    • Authors: Shehroz Khan; Jesse Hoey
      Abstract: Publication date: Available online 23 November 2016
      Source:Medical Engineering & Physics
      Author(s): Shehroz S. Khan, Jesse Hoey
      A fall is an abnormal activity that occurs rarely; however, missing to identify falls can have serious health and safety implications on an individual. Due to the rarity of occurrence of falls, there may be insufficient or no training data available for them. Therefore, standard supervised machine learning methods may not be directly applied to handle this problem. In this paper, we present a taxonomy for the study of fall detection from the perspective of availability of fall data. The proposed taxonomy is independent of the type of sensors used and specific feature extraction/selection methods. The taxonomy identifies different categories of classification methods for the study of fall detection based on the availability of their data during training the classifiers. Then, we present a comprehensive literature review within those categories and identify the approach of treating a fall as an abnormal activity to be a plausible research direction. We conclude our paper by discussing several open research problems in the field and pointers for future research.

      PubDate: 2016-12-09T21:38:53Z
       
  • Automated CTA based measurements for planning support of minimally
           invasive aortic valve replacement surgery
    • Authors: Mustafa A. Elattar; Floortje van Kesteren; Esther M. Wiegerinck; Ed Vanbavel; Jan Baan; Riccardo Cocchieri; Bas de Mol; Nils R. Planken; Henk A. Marquering
      Abstract: Publication date: Available online 29 November 2016
      Source:Medical Engineering & Physics
      Author(s): Mustafa A. Elattar, Floortje van Kesteren, Esther M. Wiegerinck, Ed Vanbavel, Jan Baan, Riccardo Cocchieri, Bas de Mol, Nils R. Planken, Henk A. Marquering
      Minimally invasive aortic valve replacement (mini-AVR) procedures are a valuable alternative to conventional open heart surgery. Currently, planning of mini-AVR consists of selection of the intercostal space closest to the sinotubular junction on preoperative computer tomography images. We developed an automated algorithm detecting the sinotubular junction (STJ) and intercostal spaces for finding the optimal incision location. The accuracy of the STJ detection was assessed by comparison with manual delineation by measuring the Euclidean distance between the manually and automatically detected points. In all 20 patients, the intercostal spaces were accurately detected. The median distance between automated and manually detected STJ locations was 1.4 [IQR= 0.91–4.7] mm compared to the interobserver variation of 1.0 [IQR= 0.54–1.3] mm. For 60% of patients, the fourth intercostal space was the closest to the STJ. The proposed algorithm is the first automated approach for detecting optimal incision location and has the potential to be implemented in clinical practice for planning of various mini-AVR procedures.

      PubDate: 2016-12-09T21:38:53Z
      DOI: 10.1016/j.medengphy.2016.11.002
       
  • Effect of trunnion roughness and length on the modular taper junction
           strength under typical intraoperative assembly forces
    • Authors: S.Y. Jauch-Matt; A.W. Miles; H.S. Gill
      Abstract: Publication date: Available online 29 November 2016
      Source:Medical Engineering & Physics
      Author(s): S.Y. Jauch-Matt, A.W. Miles, H.S. Gill
      Modular hip implants are at risk of fretting-induced postoperative complications most likely initiated by micromotion between adjacent implant components. A stable fixation between ball head and stem-neck taper is critical to avoid excessive interface motions. Therefore, the aim of this study was to identify the effect of trunnion roughness and length on the modular taper strength under typical intraoperative assembly forces. Custom-made Titanium trunnions (standard/mini taper, smooth/grooved surface finish) were assembled with modular Cobalt-chromium heads by impaction with peak forces ranging from 2kN to 6kN. After each assembly process these were disassembled with a materials testing machine to detect the pull-off force as a measure for the taper strength. As expected, the pull-off forces increased with rising peak assembly force (p < 0.001). For low and moderate assembly forces, smooth standard tapers offered higher pull-off forces compared to grooved tapers (p < 0.038). In the case of an assembly force of 2kN, mini tapers showed a higher taper strength than standard ones (p =0.037). The results of this study showed that smooth tapers provided a higher strength for taper junctions. This higher taper strength may reduce the risk of fretting-related complications especially in the most common range of intraoperative assembly forces.

      PubDate: 2016-12-09T21:38:53Z
      DOI: 10.1016/j.medengphy.2016.11.001
       
  • High gain driven right leg circuit for dry electrode systems
    • Authors: Federico N. Guerrero; Enrique Spinelli
      Abstract: Publication date: Available online 29 November 2016
      Source:Medical Engineering & Physics
      Author(s): Federico N. Guerrero, Enrique Spinelli
      This paper presents an improved driven right leg (DRL) circuit compensation together with a practical implementation. The proposed design allows to increase common mode voltage attenuation compared with the widely used dominant pole compensation while maintaining the same proven stability margin and design criteria, and requiring only a modification of its passive feedback network. A sample implementation of the proposed DRL was obtained estimating the values of interference model parameters for a dry electrode measurement system. A dominant pole compensated DRL with the same stability margin was also implemented in order to experimentally validate the proposed design against this established alternative. Measurements were conducted under both controlled and uncontrolled interference conditions. The proposed compensation experimentally demonstrated achieving a better reduction of power line harmonics, with a peak comparative improvement of around 18  dB at 50  Hz.

      PubDate: 2016-12-09T21:38:53Z
      DOI: 10.1016/j.medengphy.2016.11.005
       
  • 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
       
  • Energy flow analysis of amputee walking shows a proximally-directed
           transfer of energy in intact limbs, compared to a distally-directed
           transfer in prosthetic limbs at push-off
    • Authors: R.A. Weinert-Aplin; D. Howard; M. Twiste; H.L. Jarvis; A.N. Bennett; R.J. Baker
      Abstract: Publication date: Available online 8 November 2016
      Source:Medical Engineering & Physics
      Author(s): R.A. Weinert-Aplin, D. Howard, M. Twiste, H.L. Jarvis, A.N. Bennett, R.J. Baker
      Reduced capacity and increased metabolic cost of walking occurs in amputees, despite advances in prosthetic componentry. Joint powers can quantify deficiencies in prosthetic gait, but do not reveal how energy is exchanged between limb segments. This study aimed to quantify these energy exchanges during amputee walking. Optical motion and forceplate data collected during walking at a self-selected speed for cohorts of 10 controls, 10 unilateral trans-tibial, 10 unilateral trans-femoral and 10 bilateral trans-femoral amputees were used to determine the energy exchanges between lower limb segments. At push-off, consistent thigh and shank segment powers were observed between amputee groups (1.12W/kg vs. 1.05W/kg for intact limbs and 0.97W/kg vs. 0.99W/kg for prosthetic limbs), and reduced prosthetic ankle power, particularly in trans-femoral amputees (3.12W/kg vs. 0.87W/kg). Proximally-directed energy exchange was observed in the intact limbs of amputees and controls, while prosthetic limbs displayed distally-directed energy exchanges at the knee and hip. This study used energy flow analysis to show a reversal in the direction in which energy is exchanged between prosthetic limb segments at push-off. This reversal was required to provide sufficient energy to propel the limb segments and is likely a direct result of the lack of push-off power at the prosthetic ankle, particularly in trans-femoral amputees, and leads to their increased metabolic cost of walking.

      PubDate: 2016-11-11T17:14:03Z
      DOI: 10.1016/j.medengphy.2016.10.005
       
  • Towards bioreactor development with physiological motion control and its
           applications
    • Authors: Marcus Stoffel; Wolfgang Willenberg; Marzieh Azarnoosh; Nadine Fuhrmann-Nelles; Bei Zhou; Bernd Markert
      Abstract: Publication date: Available online 9 November 2016
      Source:Medical Engineering & Physics
      Author(s): Marcus Stoffel, Wolfgang Willenberg, Marzieh Azarnoosh, Nadine Fuhrmann-Nelles, Bei Zhou, Bernd Markert
      In biomedical applications bioreactors are used, which are able to apply mechanical loadings under cultivation conditions on biological tissues. However, complex mechanobiological evolutions, such as the dependency between mechanical properties and cell activity, depend strongly on the applied loading conditions. This requires correct physiological movements and loadings in bioreactors. The aim of the present study is to develop bioreactors, in which native and artificial biological tissues can be cultivated under physiological conditions in knee joints and spinal motion segments. However, in such complex systems, where motions with different degrees of freedom are applied to whole body parts, it is necessary to investigate elements of joints and spinal parts separately. Consequently, two further bioreactors for investigating tendons and cartilage specimens are proposed additionally. The study is complemented by experimental and numerical examples with emphasis on medical and engineering applications, such as biomechanical properties of cartilage replacement materials, injured tendons, and intervertebral discs.

      PubDate: 2016-11-11T17:14:03Z
      DOI: 10.1016/j.medengphy.2016.10.010
       
  • The coupling between peripheral microcirculation and slow breathing
    • Authors: Zehava Ovadia-Blechman; Benjamin Gavish; Danit Levy-Aharoni; David Shashar; Vered Aharonson
      Abstract: Publication date: Available online 2 November 2016
      Source:Medical Engineering & Physics
      Author(s): Zehava Ovadia-Blechman, Benjamin Gavish, Danit Levy-Aharoni, David Shashar, Vered Aharonson
      Vasomotion (rhythmic changes in arteriolar diameter) is believed to enhance tissue perfusion at low oxygenation levels. We hypothesized that slow breathing and vasomotion may correlate temporally (“coupling”), especially at low oxygenation levels. We paced down spontaneous breathing to about 5 or 6breaths/min in 14 healthy subjects using device-guided breathing (DGB), and continuously monitored respiration, transcutaneous oxygen pressure (“oxygenation”), and skin capillary blood flow ("microflow”) using a laser Doppler flowmeter. The coupling was expressed by cross-correlation calculated in 1-min time windows. Our main results illustrated that: (1) coupling increased gradually upon slowing breathing down in a subgroup, in which initial oxygenation was lower than a threshold of 30mmHg (0.3±0.2 vs. 0.07±0.2, P <10−6); (2) during DGB changes in oxygenation elicited opposite (relative) changes in microflow, with 4-fold higher sensitivity for low initial oxygenation relative to high (regression slope −0.094±0.010mmHg−1 vs. −0.020±0.002mmHg−1, P <10−6); (3) at low initial oxygenation, we observed larger coupling and (relative) microflow changes in younger subjects, and greater oxygenation changes in females (P <10−6 for all); (4) pulse pressure changes from before to after DGB were reduced by increased oxygenation changes during DGB (−5.5±7.4mmHg, r =−0.73, P <0.001). In conclusion, the present methodology can provide the variation trend of respiration–vasomotion coupling during DGB that may characterize microcirculation behavior at tissue oxygenation below a measurable threshold. The potential association of these trends and thresholds with pathologies or specific conditions of the cardiopulmonary system, and the possible role played by the neural sympathetic activity in that coupling, deserve further studies.

      PubDate: 2016-11-05T16:20:44Z
      DOI: 10.1016/j.medengphy.2016.10.009
       
  • A computational assessment of the hemodynamic effects of crossed and
           non-crossed bifurcated stent-graft devices for the treatment of abdominal
           aortic aneurysms
    • Authors: Florian Stefanov; Tim McGloughlin; Liam Morris
      Abstract: Publication date: Available online 20 October 2016
      Source:Medical Engineering & Physics
      Author(s): Florian Stefanov, Tim McGloughlin, Liam Morris
      There are several issues attributed with abdominal aortic aneurysm endovascular repair. The positioning of bifurcated stent-grafts (SG) may affect SG hemodynamics. The hemodynamics and geometrical parameters of crossing or non-crossing graft limbs have not being totally accessed. Eight patient-specific SG devices and four pre-operative cases were computationally simulated, assessing the hemodynamic and geometrical effects for crossed (n = 4) and non-crossed (n = 4) configurations. SGs eliminated the occurrence of significant recirculations within the sac prior treatment. Dean's number predicted secondary flow locations with the greatest recirculations occurring at the outlets especially during the deceleration phase. Peak drag force varied from 3.9 to 8.7N, with greatest contribution occurring along the axial and anterior/posterior directions. Average resultant drag force was 20% smaller for the crossed configurations. Maximum drag force orientation varied from 1.4° to 51°. Drag force angle varied from 1° to 5° during one cardiac cycle. 44% to 62% of the resultant force acted along the proximal centerline where SG migration is most likely to occur. The clinician's decision for SG positioning may be a critical parameter, and should be considered prior to surgery. All crossed SG devices had an increased spiral flow effect along the distal legs with reductions in drag forces.
      Graphical abstract image

      PubDate: 2016-11-05T16:20:44Z
      DOI: 10.1016/j.medengphy.2016.09.011
       
  • Biomechanical optimization of the angle and position for surgical
           implantation of a straight short stem hip implant
    • Authors: Gillian E. Cook; Saeid Samiezadeh; Zachary Morison; Mina S.R. Aziz; Habiba Bougherara; Radovan Zdero; Emil H. Schemitsch
      Abstract: Publication date: Available online 2 November 2016
      Source:Medical Engineering & Physics
      Author(s): Gillian E. Cook, Saeid Samiezadeh, Zachary Morison, Mina S.R. Aziz, Habiba Bougherara, Radovan Zdero, Emil H. Schemitsch
      Conservative hip implants preserve healthy bone for revision surgeries and improve physiological loading; however, they have little supporting biomechanical data with respect to their 3D orientation during implantation. This study endeavored to determine the optimal 3D orientation of a straight short stem hip implant within the proximal femur that would yield a stress distribution most similar to an intact femur. Synthetic femurs were implanted with a stem in one of seven maximum angles or positions and axially loaded, with resultant strain values used to validate a finite element model. Design of experiments was used to analyze the range of potential implant orientations under three gait cycle loading conditions. A global optimal orientation of 9.14° valgus, 2.49° anteversion, 0.48mm posterior position, and 0.23mm inferior position was found to yield stress distributions most similar to the intact femur across the gait cycle range. In general, it was determined that the valgus orientation was optimal throughout the gait cycle, consistently exhibiting a stress distribution more similar to that of the intact femur. Minimal levels of anterior/posterior and inferior positioning were seen to be beneficial in achieving more physiological stresses in specific regions of interest within the proximal femur, while the anteverted orientation was only beneficial in loading under flexion. Overall, orthopaedic surgeons should aim to implant straight short stem hip implants in valgus up to 10°, with an otherwise neutral position and version, unless some degree of deviation would be beneficial for a patient-specific reason. This work has implications for the best surgical placement of straight short stem hip implants to yield maximal biomechanical stability.

      PubDate: 2016-11-05T16:20:44Z
      DOI: 10.1016/j.medengphy.2016.10.002
       
  • Progress in anterior chamber angle imaging for glaucoma risk prediction
           – A review on clinical equipment, practice and research
    • Authors: Shinoj V.K.; Xun Jie Jeesmond Hong; Murukeshan V.M.; Baskaran M.; Aung Tin
      Abstract: Publication date: Available online 24 October 2016
      Source:Medical Engineering & Physics
      Author(s): Shinoj V.K., Xun Jie Jeesmond Hong, Murukeshan V.M., Baskaran M., Aung Tin
      The visualization capabilities of various ocular imaging instruments can generally be categorized into photographic (e.g. gonioscopy, Pentacam, RetCam) and optical tomographic (e.g. optical coherence tomography (OCT), photoacoustic (PA) imaging, ultrasound biomicriscopy (UBM)) methods. These imaging instruments allow vision researchers and clinicians to visualize the iridocorneal angle, and are essential in the diagnosis and management of glaucoma. Each of these imaging modalities has particular benefits and associated drawbacks in obtaining repeatable and reliable measurement in the evaluation of the angle. This review article in this context summarized recent progresses in anterior chamber imaging techniques in glaucoma diagnosis and follow-up procedures.

      PubDate: 2016-11-05T16:20:44Z
      DOI: 10.1016/j.medengphy.2016.09.014
       
  • An active simulator for neonatal intubation: Design, development and
           assessment
    • Authors: Ilaria Baldoli; Selene Tognarelli; Ferdinando Vangi; Davide Panizza; Rosa T. Scaramuzzo; Armando Cuttano; Cecilia Laschi; Arianna Menciassi
      Abstract: Publication date: Available online 3 November 2016
      Source:Medical Engineering & Physics
      Author(s): Ilaria Baldoli, Selene Tognarelli, Ferdinando Vangi, Davide Panizza, Rosa T. Scaramuzzo, Armando Cuttano, Cecilia Laschi, Arianna Menciassi
      This study describes the technical realization and the pre-clinical validation of a instrumented neonatal intubation skill trainer able to provide objective feedback for the improvement of clinical competences required for such a delicate procedure. The Laerdal® Neonatal Intubation Trainer was modified by applying pressure sensors on areas that are mainly subject to stress and potential injuries. Punctual Force Sensing Resistors (FSRs) were characterized and fixed on the external side of the airway structure on the dental arches and epiglottis. A custom silicone tongue was designed and developed to integrate a matrix textile sensor for mapping the pressure applied on its whole surface. The assessment of the developed tool was performed by nine clinical experts who were asked to practice three intubation procedures apiece. Median and maximum forces, over threshold events (i.e. 2N for gingival arch sensors and 7N for epiglottis and tongue sensors respectively) and execution time were measured for each trainee. Data analysis from training sessions revealed that the epiglottis is the point mainly stressed during an intubation procedure (maximum value: 16.69N, median value: 3.11N), while the analysis carried out on the pressure distribution on the instrumented tongue provided information on both force values and distribution, according to clinicians' performance. The debriefing phase was used to enhance the clinicians’ awareness of applied force and gestures performed, confirming that the present study is an adequate starting point for achieving and optimizing neonatal intubation skills for both residents and expert clinicians.

      PubDate: 2016-11-05T16:20:44Z
      DOI: 10.1016/j.medengphy.2016.10.008
       
  • Studying the magnetic stimulation of nervous tissues: A calculation
           framework to investigate stimulation areas
    • Authors: Simona Valentini; Iacopo Portaccio; Dino Accoto
      Abstract: Publication date: Available online 3 November 2016
      Source:Medical Engineering & Physics
      Author(s): Simona Valentini, Iacopo Portaccio, Dino Accoto
      The electromagnetic stimulation of nervous tissue has represented an alternative to electrical stimulation since the 1980s. The growing number of potential applications has led to an increasing interest in the development of modeling tools that can help the design of novel electromagnetic stimulators. In this context, the aim of this paper is to provide a versatile calculation framework to investigate the properties of the electric field generated by a plurality of miniature coils, arranged in cuff configuration. Furthermore, the capability of the miniature coils to elicit a neuronal response in specific portions of the (peripheral) nerve will be investigated. Starting from Jefimenko’s equations, a model was implemented in MATLAB. It calculates the electromagnetic field induced by coils, with arbitrary shape and spatial orientation, and the activating function around the coils through simple numerical integration. By studying the activating functions, it is possible to determine where the neurons can be excited. The model was validated by comparison with FEM simulations. A dimensional analysis was conducted to compare in terms of shape and depth of the stimulation volumes different coil geometries, regardless of design parameters such as current, number of turns and coil sizes.The dimensionless groups identified according to Buckingham’s theorem provide a direct estimate of the stimulation depth reached within the nerve.The calculation tools developed in this paper can be used in the design of coils to quickly compare different geometries and spatial distribution of coils in order to identify the optimal configurations for the specific application addressed by the designer.

      PubDate: 2016-11-05T16:20:44Z
      DOI: 10.1016/j.medengphy.2016.10.012
       
  • Reducing temperature elevation of robotic bone drilling
    • Authors: Arne Feldmann; Jasmin Wandel; Philippe Zysset
      Abstract: Publication date: Available online 24 October 2016
      Source:Medical Engineering & Physics
      Author(s): Arne Feldmann, Jasmin Wandel, Philippe Zysset
      This research work aims at reducing temperature elevation of bone drilling. An extensive experimental study was conducted which focused on the investigation of three main measures to reduce the temperature elevation as used in industry: irrigation, interval drilling and drill bit designs. Different external irrigation rates (0 ml/min, 15 ml/min, 30 ml/min), continuously drilled interval lengths (2 mm, 1 mm, 0.5 mm) as well as two drill bit designs were tested. A custom single flute drill bit was designed with a higher rake angle and smaller chisel edge to generate less heat compared to a standard surgical drill bit. A new experimental setup was developed to measure drilling forces and torques as well as the 2D temperature field at any depth using a high resolution thermal camera. The results show that external irrigation is a main factor to reduce temperature elevation due not primarily to its effect on cooling but rather due to the prevention of drill bit clogging. During drilling, the build up of bone material in the drill bit flutes result in excessive temperatures due to an increase in thrust forces and torques. Drilling in intervals allows the removal of bone chips and cleaning of flutes when the drill bit is extracted as well as cooling of the bone in-between intervals which limits the accumulation of heat. However, reducing the length of the drilled interval was found only to be beneficial for temperature reduction using the newly designed drill bit due to the improved cutting geometry. To evaluate possible tissue damage caused by the generated heat increase, cumulative equivalent minutes (CEM43) were calculated and it was found that the combination of small interval length (0.5 mm), high irrigation rate (30 ml/min) and the newly designed drill bit was the only parameter combination which allowed drilling below the time-thermal threshold for tissue damage. In conclusion, an optimized drilling method has been found which might also enable drilling in more delicate procedures such as that performed during minimally invasive robotic cochlear implantation.

      PubDate: 2016-11-05T16:20:44Z
      DOI: 10.1016/j.medengphy.2016.10.001
       
  • Three-dimensional finite element analysis of a newly developed aliform
           internal fixation system for occipitocervical fusion
    • Authors: Sui-Xiang Liao; Jian-Hua Wang; Yong-Qiang Zheng; Guan Zheng; Ge-Jing Wei; Hong Xia; Xiao-Hua Chen
      Abstract: Publication date: Available online 28 October 2016
      Source:Medical Engineering & Physics
      Author(s): Sui-Xiang Liao, Jian-Hua Wang, Yong-Qiang Zheng, Guan Zheng, Ge-Jing Wei, Hong Xia, Xiao-Hua Chen
      For patients with occipital malformation, it is difficult to obtain reliable stability using three screws on the midline. A new aliform occipitocervical internal fixation system was designed. The occiput was fixed with 3, 7, or 11 screws, and a three-dimensional finite element model of the system was established. A compressive preload of 40N combined with a pure moment of 1.5Nm was applied to simulate normal flexion, extension, lateral bending, and axial rotation. The stress distribution across the screws on the occiput and the occipital displacement produced by the newly developed system were compared with those produced by the DePuy SUMMIT system. Compared with the SUMMIT system (control group), in the new system, the maximum stress on the occiputs fixed with 3 screws (group A) and 7 screws (group B) increased by 16.5% and 15.0%, respectively. In contrast, the maximum stress on the occiput fixed with 11 screws (group C) decreased by 15.6%. In addition, the maximum occipital displacements under extension decreased by 10.0%, 11.4%, and 11.8% in the A, B, and, C groups, respectively. Our results indicate that both group A and the control group exhibited sufficient strength and instant stability; however, group C exhibited the highest stability and the lowest maximum von Mises stress.

      PubDate: 2016-11-05T16:20:44Z
      DOI: 10.1016/j.medengphy.2016.08.011
       
  • Biomechanical analysis of combining head-down tilt traction with vibration
           for different grades of degeneration of the lumbar spine
    • Authors: Sicong Wang; Lizhen Wang; Yawei Wang; Chengfei Du; Ming Zhang; Yubo Fan
      Abstract: Publication date: Available online 3 November 2016
      Source:Medical Engineering & Physics
      Author(s): Sicong Wang, Lizhen Wang, Yawei Wang, Chengfei Du, Ming Zhang, Yubo Fan
      In recent years, a combination of traction and vibration therapy is usually used to alleviate low back pain (LBP) in clinical settings. Combining head-down tilt (HDT) traction with vibration was demonstrated to be efficacious for LBP patients in our previous study. However, the biomechanics of the lumbar spine during this combined treatment is not well known and need quantitative analysis. In addition, LBP patients have different grades of degeneration of the lumbar spinal structure, which are often age related. Selecting a suitable rehabilitation therapy for different age groups of patients has been challenging. Therefore, a finite element (FE) model of the L1–L5 lumbar spine and a vibration dynamic model are developed in this study in order to investigate the biomechanical effects of the combination of HDT traction and vibration therapy on the age-related degeneration of the lumbar spine. The decrease of intradiscal pressure is more effective when vibration is combined with traction therapy. Moreover, the stresses on the discs are lower in the “traction+vibration” mode than the “traction-only” mode. The stress concentration at the posterior part of nucleus is mitigated after the vibration is combined. The disc deformations especially posterior disc radial retraction is improved in the “traction+vibration” mode. These beneficial effects of this therapy could help decompress the discs and spinal nerves and therefore relieve LBP. Simultaneously, patients with grade 1 degeneration (approximately 41–50 years old) are able to achieve better results compared with other age groups. This study could be used to provide a more effective LBP rehabilitation therapy.

      PubDate: 2016-11-05T16:20:44Z
      DOI: 10.1016/j.medengphy.2016.10.004
       
  • A theoretical computerized study for the electrical conductivity of
           arterial pulsatile blood flow by an elastic tube model
    • Authors: Hua Shen; Yong Zhu; Kai-Rong Qin
      Abstract: Publication date: Available online 10 October 2016
      Source:Medical Engineering & Physics
      Author(s): Hua Shen, Yong Zhu, Kai-Rong Qin
      The electrical conductivity of pulsatile blood flow in arteries is an important factor for the application of the electrical impedance measurement system in clinical settings. The electrical conductivity of pulsatile blood flow depends not only on blood-flow-induced red blood cell (RBC) orientation and deformation but also on artery wall motion. Numerous studies have investigated the conductivity of pulsatile blood based on a rigid tube model, in which the effects of wall motion on blood conductivity are not considered. In this study, integrating Ling and Atabek's local flow theory and Maxwell–Fricke theory, we develop an elastic tube model to explore the effects of wall motion as well as blood flow velocity on blood conductivity. The simulation results suggest that wall motion, rather than blood flow velocity, is the primary factor that affects the conductivity of flowing blood in arteries.

      PubDate: 2016-10-15T13:02:11Z
      DOI: 10.1016/j.medengphy.2016.09.013
       
  • Stress shielding in periprosthetic bone following a total knee
           replacement: Effects of implant material, design and alignment
    • Authors: Qing-Hang Zhang; Andrew Cossey; Jie Tong
      Abstract: Publication date: Available online 10 October 2016
      Source:Medical Engineering & Physics
      Author(s): Qing-Hang Zhang, Andrew Cossey, Jie Tong
      Periprosthetic bone strain distributions in some of the typical cases of total knee replacement (TKR) were studied with regard to the selection of material, design and the alignments of tibial components to examine which conditions are more forgiving than the others to stress shielding post a TKR. Four tibial components with two implant designs (cruciate sacrificing and cruciate retaining) and material properties (metal-backed (MB) and all-polyethylene (AP)) were considered in a specimen-specific finite element tibia bone model loaded in a neutral position. The influence of tibial material and design on the periprosthetic bone strain response was investigated under the peak loads of walking and stair descending/ascending. Two of the models were also modified to examine the effect of selected implant malalignment conditions (7° posterior, 5° valgus and 5° varus) on stress shielding in the bone, where the medio-lateral load share ratios were adjusted accordingly. The predicted increases of bone density due to implantation for the selected cases studied were also presented. For the cases examined, the effect of stress shielding on the periprosthetic bone seems to be more significantly influenced by the implant material than by the implant geometry. Significant stress shielding is found in MB cases, as opposed to increase in bone density found in AP cases, particularly in the bones immediately beneath the baseplate. The effect of stress shielding is reduced somewhat for the MB components in the malaligned positions compared with the neutral case. In AP cases, the effect of stress shielding is mostly low except in the varus position, possibly due to off-loading of lateral condyle. Increases in bone density are found in both MB and AP cases for the malaligned conditions.

      PubDate: 2016-10-15T13:02:11Z
      DOI: 10.1016/j.medengphy.2016.09.018
       
  • Discrete sensors distribution for accurate plantar pressure analyses
    • Authors: Laetitia Claverie; Anne Ille; Pierre Moretto
      Abstract: Publication date: Available online 10 October 2016
      Source:Medical Engineering & Physics
      Author(s): Laetitia Claverie, Anne Ille, Pierre Moretto
      The aim of this study was to determine the distribution of discrete sensors under the footprint for accurate plantar pressure analyses. For this purpose, two different sensor layouts have been tested and compared, to determine which was the most accurate to monitor plantar pressure with wireless devices in research and/or clinical practice. Ten healthy volunteers participated in the study (age range: 23–58 years). The barycenter of pressures (BoP) determined from the plantar pressure system (W-inshoe®) was compared to the center of pressures (CoP) determined from a force platform (AMTI) in the medial-lateral (ML) and anterior-posterior (AP) directions. Then, the vertical ground reaction force (vGRF) obtained from both W-inshoe® and force platform was compared for both layouts for each subject. The BoP and vGRF determined from the plantar pressure system data showed good correlation (SCC) with those determined from the force platform data, notably for the second sensor organization (ML SCC= 0.95; AP SCC=0.99; vGRF SCC=0.91). The study demonstrates that an adjusted placement of removable sensors is key to accurate plantar pressure analyses. These results are promising for a plantar pressure recording outside clinical or laboratory settings, for long time monitoring, real time feedback or for whatever activity requiring a low-cost system.

      PubDate: 2016-10-15T13:02:11Z
      DOI: 10.1016/j.medengphy.2016.09.021
       
  • Fully automatic segmentation of femurs with medullary canal definition in
           high and in low resolution CT scans
    • Authors: Diogo F. Almeida; Rui B. Ruben; João Folgado; Paulo R. Fernandes; Emmanuel Audenaert; Benedict Verhegghe; Matthieu De Beule
      Abstract: Publication date: Available online 15 October 2016
      Source:Medical Engineering & Physics
      Author(s): Diogo F. Almeida, Rui B. Ruben, João Folgado, Paulo R. Fernandes, Emmanuel Audenaert, Benedict Verhegghe, Matthieu De Beule
      Femur segmentation can be an important tool in orthopedic surgical planning. However, in order to overcome the need of an experienced user with extensive knowledge on the techniques, segmentation should be fully automatic. In this paper a new fully automatic femur segmentation method for CT images is presented. This method is also able to define automatically the medullary canal and performs well even in low resolution CT scans. Fully automatic femoral segmentation was performed adapting a template mesh of the femoral volume to medical images. In order to achieve this, an adaptation of the active shape model (ASM) technique based on the statistical shape model (SSM) and local appearance model (LAM) of the femur with a novel initialization method was used, to drive the template mesh deformation in order to fit the in-image femoral shape in a time effective approach. With the proposed method a 98% convergence rate was achieved. For high resolution CT images group the average error is less than 1mm. For the low resolution image group the results are also accurate and the average error is less than 1.5mm. The proposed segmentation pipeline is accurate, robust and completely user free. The method is robust to patient orientation, image artifacts and poorly defined edges. The results excelled even in CT images with a significant slice thickness, i.e., above 5mm. Medullary canal segmentation increases the geometric information that can be used in orthopedic surgical planning or in finite element analysis.

      PubDate: 2016-10-15T13:02:11Z
      DOI: 10.1016/j.medengphy.2016.09.019
       
  • Rôle of contrast media viscosity in altering vessel wall shear stress and
           relation to the risk of contrast extravasations
    • Authors: Sophia Sakellariou; Wenguang Li; Manosh C Paul; Giles Roditi
      Abstract: Publication date: Available online 8 October 2016
      Source:Medical Engineering & Physics
      Author(s): Sophia Sakellariou, Wenguang Li, Manosh C Paul, Giles Roditi
      Iodinated contrast media (CM) are the most commonly used injectables in radiology today. A range of different media are commercially available, combining various physical and chemical characteristics (ionic state, osmolality, viscosity) and thus exhibiting distinct in vivo behaviour and safety profiles. In this paper, numerical simulations of blood flow with contrast media were conducted to investigate the effects of contrast viscosity on generated vessel wall shear stress and vessel wall pressure to elucidate any possible relation to extravasations. Five different types of contrast for Iodine fluxes ranging at 1.5–2.2gI/s were modelled through 18G and 20G cannulae placed in an ideal vein at two different orientation angles. Results demonstrate that the least viscous contrast media generate the least maximum wall shear stress as well as the lowest total pressure for the same flow rate. This supports the empirical clinical observations and hypothesis that more viscous contrast media are responsible for a higher percentage of contrast extravasations. In addition, results support the clinical hypothesis that a catheter tip directed obliquely to the vein wall always produces the highest maximum wall shear stress and total pressure due to impingement of the contrast jet on the vessel wall.

      PubDate: 2016-10-09T12:41:42Z
      DOI: 10.1016/j.medengphy.2016.09.016
       
 
 
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