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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: 13)
Wiley Interdisciplinary Reviews - System Biology and Medicine     Hybrid Journal   (Followers: 5)
Wiley Interdisciplinary Reviews : Developmental Biology     Hybrid Journal   (Followers: 3)
Wiley Interdisciplinary Reviews : Membrane Transport and Signaling     Hybrid Journal  
Wiley Interdisciplinary Reviews : RNA     Hybrid Journal   (Followers: 3)
World Crop Pests     Full-text available via subscription   (Followers: 1)
World Mycotoxin Journal     Full-text available via subscription   (Followers: 6)
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Yeast     Hybrid Journal   (Followers: 10)
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Zeitschrift für Evidenz, Fortbildung und Qualität im Gesundheitswesen     Full-text available via subscription   (Followers: 5)
Zeitschrift für Naturforschung C : A Journal of Biosciences     Open Access   (Followers: 2)
Zygote     Hybrid Journal  
Биологический вестник МГПУ имени Богдана Хмельницкого     Open Access   (Followers: 1)

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Journal Cover Medical Engineering & Physics
  [SJR: 0.871]   [H-I: 64]   [8 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1350-4533
   Published by Elsevier Homepage  [2970 journals]
  • Cytoskeleton and plasma-membrane damage resulting from exposure to
           sustained deformations: A review of the mechanobiology of chronic wounds
    • Abstract: Publication date: Available online 13 June 2016
      Source:Medical Engineering & Physics
      Author(s): Amit Gefen, Daphne Weihs
      The purpose of this review paper is to summarize the current knowledge on cell-scale mechanically-inflicted deformation-damage, which is at the frontier of cell mechanobiology and biomechanics science, specifically in the context of chronic wounds. The dynamics of the mechanostructure of cells and particularly, the damage occurring to the cytoskeleton and plasma-membrane when cells are chronically deformed (as in a weight-bearing static posture) is correlated to formation of the most common chronic wounds and injuries, such as pressure ulcers (injuries). The first occurrence is microscopic injury which onsets as damage in individual cells and then progresses macroscopically to the tissue-scale. Here, we specifically focus on sub-catastrophic and catastrophic damage to cells that can result from mechanical loads that are delivered statically or at physiological rates; this results in apoptosis at prolonged times or necrosis, rapidly. We start by providing a basic background of cell mechanics and dynamics, focusing on the plasma-membrane and the cytoskeleton, and discuss approaches to apply and estimate deformations in cells. We then consider the effects of different levels of mechanical loads, i.e. low, high and intermediate, and describe the expected damage in terms of time-scales of application and in terms of cell response, providing experimental examples where available. Finally, we review different theoretical and computational modeling approaches that have been used to describe cell responses to sustained deformation. We highlight the insights that those models provide to explain, for example, experimentally observed variabilities in cell damage and death under loading.
      Graphical abstract image

      PubDate: 2016-06-17T18:04:06Z
       
  • Peripheral tactile sensory perception of older adults improved using
           subsensory electrical noise stimulation
    • Abstract: Publication date: Available online 15 June 2016
      Source:Medical Engineering & Physics
      Author(s): Paul P. Breen, Jorge M. Serrador, Claire O'Tuathail, Leo R. Quinlan, Caroline McIntosh, Gearóid ÓLaighin
      Loss of tactile sensory function is common with aging and can lead to numbness and difficulty with balance and gait. In previous work we found that subsensory electrical noise stimulation (SENS) applied to the tibial nerve improved tactile perception in the soles of the feet of healthy adults. In this work we aimed to determine if SENS remained effective in an older adult population with significant levels of sensory loss. Older adult subjects (N =8, female = 4, aged 65–80) had SENS applied via surface electrodes placed proximally to the medial and lateral malleoli. Vibration perception thresholds (VPTs) were assessed in six conditions, two control conditions (no SENS) and four SENS conditions (zero mean ±15µA, 30µA, 45µA and 60µA SD). VPT was assessed at three sites on the plantar aspect of the foot. Vibration perception was significantly improved in the presence of ±30µA SENS and by 16.2±2.4% (mean ± s.e.m.) when optimised for each subject. The improvement in perception was similar across all VPT test sites.


      PubDate: 2016-06-17T18:04:06Z
       
  • Heat transfer analysis of catheters used for localized tissue cooling to
           attenuate reperfusion injury
    • Abstract: Publication date: Available online 13 June 2016
      Source:Medical Engineering & Physics
      Author(s): Thomas L. Merrill, Jennifer E. Mitchell, Denise R. Merrill
      Recent revascularization success for ischemic stroke patients using stentrievers has created a new opportunity for therapeutic hypothermia. By using short term localized tissue cooling interventional catheters can be used to reduce reperfusion injury and improve neurological outcomes. Using experimental testing and a well-established heat exchanger design approach, the ɛ-NTU method, this paper examines the cooling performance of commercially available catheters as function of four practical parameters: (1) infusion flow rate, (2) catheter location in the body, (3) catheter configuration and design, and (4) cooling approach. While saline batch cooling outperformed closed-loop autologous blood cooling at all equivalent flow rates in terms of lower delivered temperatures and cooling capacity, hemodilution, systemic and local, remains a concern. For clinicians and engineers this paper provides insights for the selection, design, and operation of commercially available catheters used for localized tissue cooling.


      PubDate: 2016-06-17T18:04:06Z
       
  • Calculation of muscle forces during normal gait under consideration of
           femoral bending moments
    • Abstract: Publication date: Available online 16 June 2016
      Source:Medical Engineering & Physics
      Author(s): Frederick Lutz, Roland Mastel, Martin Runge, Felix Stief, André Schmidt, Andrea Meurer, Hartmut Witte
      This paper introduces a new approach for computing lower extremity muscle forces by incorporating equations that consider “bone structure” and “prevention of bending by load reduction” into existing optimization algorithms. Lower extremity muscle and joint forces, during normal gait, were calculated and compared using two different optimization approaches. We added constraint equations that prevent femoral bending loads to an existing approach that considers “minimal total muscular force”. Gait parameters such as kinematics, ground reaction forces, and surface electromyographic activation patterns were examined using standardized gait analysis. A subject-specific anatomic model of the lower extremities, obtained from magnetic resonance images of a healthy male, was used for the simulations. Finite element analysis was used to calculate femoral loads. The conventional method of calculating muscle forces leads to higher rates of femoral bending and structural stress than the new approach. Adding equations with structural subject-specific parameters in our new approach resulted in reduced femoral stress patterns. These findings show that our new approach improves the accuracy of femoral stress and strain simulations. Structural overloads caused by bending can be avoided during inverse calculation of muscle forces.


      PubDate: 2016-06-17T18:04:06Z
       
  • Torque and mechanomyogram relationships during electrically-evoked
           isometric quadriceps contractions in persons with spinal cord injury
    • Abstract: Publication date: Available online 8 June 2016
      Source:Medical Engineering & Physics
      Author(s): Morufu Olusola Ibitoye, Nur Azah Hamzaid, Nazirah Hasnan, Ahmad Khairi Abdul Wahab, Md. Anamul Islam, Victor S.P. Kean, Glen M. Davis
      The interaction between muscle contractions and joint loading produces torques necessary for movements during activities of daily living. However, during neuromuscular electrical stimulation (NMES)-evoked contractions in persons with spinal cord injury (SCI), a simple and reliable proxy of torque at the muscle level has been minimally investigated. Thus, the purpose of this study was to investigate the relationships between muscle mechanomyographic (MMG) characteristics and NMES-evoked isometric quadriceps torques in persons with motor complete SCI. Six SCI participants with lesion levels below C4 [(mean (SD) age, 39.2 (7.9) year; stature, 1.71 (0.05) m; and body mass, 69.3 (12.9) kg)] performed randomly ordered NMES-evoked isometric leg muscle contractions at 30°, 60° and 90° knee flexion angles on an isokinetic dynamometer. MMG signals were detected by an accelerometer-based vibromyographic sensor placed over the belly of rectus femoris muscle. The relationship between MMG root mean square (MMG-RMS) and NMES-evoked torque revealed a very high association (R 2 =0.91 at 30°; R 2 =0.98 at 60°; and R 2 =0.97 at 90° knee angles; P <0.001). MMG peak-to-peak (MMG-PTP) and stimulation intensity were less well related (R 2 =0.63 at 30°; R 2 =0.67 at 60°; and R 2 =0.45 at 90° knee angles), although were still significantly associated (P ≤0.006). Test-retest interclass correlation coefficients (ICC) for the dependent variables ranged from 0.82 to 0.97 for NMES-evoked torque, between 0.65 and 0.79 for MMG-RMS, and from 0.67 to 0.73 for MMG-PTP. Their standard error of measurements (SEM) ranged between 10.1% and 31.6% (of mean values) for torque, MMG-RMS and MMG-PTP. The MMG peak frequency (MMG-PF) of 30Hz approximated the stimulation frequency, indicating NMES-evoked motor unit firing rate. The results demonstrated knee angle differences in the MMG-RMS versus NMES-isometric torque relationship, but a similar torque related pattern for MMG-PF. These findings suggested that MMG was well associated with torque production, reliably tracking the motor unit recruitment pattern during NMES-evoked muscle contractions. The strong positive relationship between MMG signal and NMES-evoked torque production suggested that the MMG might be deployed as a direct proxy for muscle torque or fatigue measurement during leg exercise and functional movements in the SCI population.


      PubDate: 2016-06-13T12:11:19Z
       
  • Smartphone application for emergency signal detection
    • Abstract: Publication date: Available online 2 June 2016
      Source:Medical Engineering & Physics
      Author(s): Isabel N. Figueiredo, Carlos Leal, Luís Pinto, Jason Bolito, André Lemos
      Currently, a number of studies focus on the study and design of new healthcare technologies to improve elderly health and quality of life. Taking advantage of the popularity, portability, and inherent technology of smartphones, we present an emergency application for smartphones, designated as knock-to-panic (KTP). This innovative and novel system enables users to simply hit their devices in order to send an alarm signal to an emergency service. This application is a complete and autonomous emergency system, and can provide an economic, reliable, and unobtrusive method for elderly monitoring or safety protection. Moreover, the simple and fast activation of KTP makes it a viable and potentially superior alternative to traditional ambient assisted living emergency calls. Furthermore, KTP can be further extended to the general population as well and not just be limited for elderly persons. The proposed method is a threshold-based algorithm and is designed to require a low battery power consumption. The evaluation of the performance of the algorithm in collected data indicates that both sensitivity and specificity are above 90%.


      PubDate: 2016-06-07T11:58:22Z
       
  • The influence of foreign body surface area on the outcome of chronic
           osteomyelitis
    • Abstract: Publication date: Available online 2 June 2016
      Source:Medical Engineering & Physics
      Author(s): Carmen Cristina Surdu-Bob, Cristin Coman, Florica Barbuceanu, Danut Turcu, Nicolae Bercaru, Marius Badulescu
      Reproducible animal models of osteomyelitis close to the clinical scenario are difficult to obtain as the animals either die shortly after inoculation of bacteria or the bone cures itself of infection. Additional materials used as foreign bodies offer increased chances for localized infection due to bacterial attachment and are closer to clinical pathology. Through in vivo experimentation we investigated here the influence of surface area of a series of foreign bodies on the final outcome of the animal model, in terms of reproducibility, survival rate and time necessary for onset of chronic disease. Stainless steel Kirschner wire segments, stainless steel balls and cotton meshes were employed for this purpose. The clinical, microbiological, radiological and histological results obtained were compared with the simple case where no foreign body was used. The follow-up period was 57days. The cotton meshes, which had the highest surface area, were observed to provide the best outcome, with the lowest disease onset time interval (of 1week earlier than the others), the highest survival (of 90%) and disease reproduction rate (90%). The only clinical pattern of the mesh group rabbits was short lived inflammation while the other rabbits presented also some other clinical signs such as rhinorrheas, abscesses, rush and/or dyspnea. Moreover, this model is the most suitable for further treatment studies, as the cotton meshes could be easily removed after disease onset, without any intervention on the bone. This is important, as the treatment would address the bacteria present within the bone parts (marrow, cortex, periosteum etc.) not those forming the biofilm.


      PubDate: 2016-06-07T11:58:22Z
       
  • Effect of the stiffness of bone substitutes on the biomechanical behaviour
           of femur for core decompression
    • Abstract: Publication date: Available online 6 June 2016
      Source:Medical Engineering & Physics
      Author(s): T.N. Tran, W. Kowalczyk, H.P. Hohn, M. Jäger, S. Landgraeber
      Core decompression is the most common procedure for treatment of the early stages of osteonecrosis of the femoral head. The purpose of this study was to compare the biomechanical performance of four different bone graft substitutes combined with core decompression. Subject-specific finite element models generated from computed tomography (CT) scan data were used for a comprehensive analysis. Two different contact conditions were simulated representing states of osseointegration at the interface. Our results showed that the use of a low-stiffness bone substitute did not increase the risk of femoral fracture in the early postoperative phase, but resulted in less micromotion and interfacial stresses than high-stiffness bone substitutes.


      PubDate: 2016-06-07T11:58:22Z
       
  • Epidermal electronics for electromyography: An application to swallowing
           therapy
    • Abstract: Publication date: Available online 30 May 2016
      Source:Medical Engineering & Physics
      Author(s): Gabriela Constantinescu, Jae-Woong Jeong, Xinda Li, Dylan K. Scott, Kyung-In Jang, Hyun-Joong Chung, John A. Rogers, Jana Rieger
      Head and neck cancer treatment alters the anatomy and physiology of patients. Resulting swallowing difficulties can lead to serious health concerns. Surface electromyography (sEMG) is used as an adjuvant to swallowing therapy exercises. sEMG signal collected from the area under the chin provides visual biofeedback from muscle contractions and is used to help patients perform exercises correctly. However, conventional sEMG adhesive pads are relatively thick and difficult to effectively adhere to a patient's altered chin anatomy, potentially leading to poor signal acquisition in this population. Here, the emerging technology of epidermal electronics is introduced, where ultra-thin geometry allows for close contouring of the chin. The two objectives of this study were to (1) assess the potential of epidermal electronics technology for use with swallowing therapy and (2) assess the significance of the reference electrode placement. This study showed comparative signals between the new epidermal sEMG patch and the conventional adhesive patches used by clinicians. Furthermore, an integrated reference yielded optimal signal for clinical use; this configuration was more robust to head movements than when an external reference was used. Improvements for future iterations of epidermal sEMG patches specific to day-to-day clinical use are suggested.


      PubDate: 2016-06-02T11:44:43Z
       
  • Mathematical modeling to predict the sub-bandage pressure on a conical
           limb for multi-layer bandaging
    • Abstract: Publication date: Available online 1 June 2016
      Source:Medical Engineering & Physics
      Author(s): M.P. Sikka, S. Ghosh, A. Mukhopadhyay
      The effectiveness of the compression treatment by a medical compression bandage is dependent on the pressure generated at the interface between the bandage and the skin. This pressure is called interface pressure or sub-bandage pressure. The performance of a bandage depends upon the level of interface pressure applied by the bandage and the sustenance of this pressure over time. The interface pressure exerted by the bandage depends on several other factors like limb shape or size, application technique, physical and structural properties of the bandage, physical activities taken by the patient, etc. The current understanding of how bandages apply pressure to a limb is based on the Law of Laplace, which states that tension in the walls of a container is dependent on both the pressure of the container's content and its radius. This concept was translated mathematically into equation relating pressure to tension and radius by Thomas. In addition, a modified equation was generated by multiplying the model with a constant that represents the number of bandage layers in order to use the model to estimate the pressure applied by multi-layer bandages. This simple multiplication adjustment was questioned by researchers. They had doubts about the model validity and whether it can be used to predict the sub-bandage pressure applied by pressure garments. One of the questions that were raised regarding the bandage thickness affecting the sub-bandage pressure has been recently explored by Al Khaburi where he used the thin and thick cylinder shell theory to study the effect of Multi Component Bandage's (MCB) thickness on the sub-bandage pressure. The model by Al Khaburi and the earlier models developed for pressure prediction are all based on calculations considering the cylindrical limb shapes although the human limb normally is wider at the calf and reduces in circumference towards the ankle. So in our approach, the bandage is assumed to take a conical shape during application and membrane shell theory is used for developing pressure prediction model for multi-layers of bandage. Both analytical and experimental work showed that the effect of bandage thickness and the geometry of the limb on pressure produced by multi-layers of bandage are significant. The model developed when compared to the data obtained using experimental setup confirmed the validity of the mathematical model for multi-layers of bandage based on conical geometry of the limb.


      PubDate: 2016-06-02T11:44:43Z
       
  • Corrigendum to “The contact mechanics and occurrence of edge loading
           in modular metal-on-polyethylene total hip replacement during daily
           activities.” [Medical Engineering &amp; Physics, Volume 38,
           Issue 6 (June 2016) Pages 518–525]
    • Abstract: Publication date: Available online 1 June 2016
      Source:Medical Engineering & Physics
      Author(s): Xijin Hua, Junyan Li, Zhongmin Jin, John Fisher



      PubDate: 2016-06-02T11:44:43Z
       
  • Ensemble framework based real-time respiratory motion prediction for
           adaptive radiotherapy applications
    • Abstract: Publication date: Available online 26 May 2016
      Source:Medical Engineering & Physics
      Author(s): Sivanagaraja Tatinati, Kianoush Nazarpour, Wei Tech Ang, Kalyana C. Veluvolu
      Successful treatment of tumors with motion-adaptive radiotherapy requires accurate prediction of respiratory motion, ideally with a prediction horizon larger than the latency in radiotherapy system. Accurate prediction of respiratory motion is however a non-trivial task due to the presence of irregularities and intra-trace variabilities, such as baseline drift and temporal changes in fundamental frequency pattern. In this paper, to enhance the accuracy of the respiratory motion prediction, we propose a stacked regression ensemble framework that integrates heterogeneous respiratory motion prediction algorithms. We further address two crucial issues for developing a successful ensemble framework: (1) selection of appropriate prediction methods to ensemble (level-0 methods) among the best existing prediction methods; and (2) finding a suitable generalization approach that can successfully exploit the relative advantages of the chosen level-0 methods. The efficacy of the developed ensemble framework is assessed with real respiratory motion traces acquired from 31 patients undergoing treatment. Results show that the developed ensemble framework improves the prediction performance significantly compared to the best existing methods.


      PubDate: 2016-05-29T11:39:41Z
       
  • Modular development of a prototype point of care molecular diagnostic
           platform for sexually transmitted infections
    • Abstract: Publication date: Available online 26 May 2016
      Source:Medical Engineering & Physics
      Author(s): Manoharanehru Branavan, Ruth E Mackay, Pascal Craw, Angel Naveenathayalan, Jeremy C. Ahern, Tulasi Sivanesan, Chris Hudson, Thomas Stead, Jessica Kremer, Neha Garg, Mark Baker, Syed T Sadiq, Wamadeva Balachandran
      This paper presents the design of a modular point of care test platform that integrates a proprietary sample collection device directly with a microfluidic cartridge. Cell lysis, within the cartridge, is conducted using a chemical method and nucleic acid purification is done on an activated cellulose membrane. The microfluidic device incorporates passive mixing of the lysis-binding buffers and sample using a serpentine channel. Results have shown extraction efficiencies for this new membrane of 69% and 57% compared to the commercial Qiagen extraction method of 85% and 59.4% for 0.1ng/µL and 100ng/µL salmon sperm DNA respectively spiked in phosphate buffered solution. Extraction experiments using the serpentine passive mixer cartridges incorporating lysis and nucleic acid purification showed extraction efficiency around 80% of the commercial Qiagen kit. Isothermal amplification was conducted using thermophillic helicase dependant amplification and recombinase polymerase amplification. A low cost benchtop real-time isothermal amplification platform has been developed capable of running six amplifications simultaneously. Results show that the platform is capable of detecting 1.32×106 of sample DNA through thermophillic helicase dependant amplification and 1×105 copy numbers Chlamydia trachomatis genomic DNA within 10min through recombinase polymerase nucleic acid amplification tests.


      PubDate: 2016-05-29T11:39:41Z
       
  • Monitoring contractile dermal lymphatic activity following uniaxial
           mechanical loading
    • Abstract: Publication date: Available online 27 May 2016
      Source:Medical Engineering & Physics
      Author(s): RJ Gray, PR Worsley, D Voegeli, DL Bader
      It is proposed that direct mechanical loading can impair dermal lymphatic function, contributing to the causal pathway of pressure ulcers. The present study aims to investigate the effects of loading on human dermal lymphatic vessels. Ten participants were recruited with ages ranging from 24 to 61 years. Participants had intradermal Indocyanine Green injections administrated between left finger digits. Fluorescence was imaged for 5min sequences with an infra-red camera prior to lymph vessel loading, immediately after axial loading (60mmHg) and following a recovery period. Image processing was employed to defined transient lymph packets and compare lymph function between each test phase. The results revealed that between 1-8 transient events (median=4) occurred at baseline, with a median velocity of 8.1mm/sec (range 4.1–20.1mm/sec). Immediately post-loading, there was a significant (p <0.05) reduction in velocity (median=6.4, range 2.2–13.5mm/sec), although the number of transient lymph packages varied between participants. During the recovery period the number (range 1–7) and velocity (recovery median=9.6mm/sec) of transient packets were largely restored to basal values. The present study revealed that some individuals present with impaired dermal lymphatic function immediately after uniaxial mechanical loading. More research is needed to investigate the effects of pressure and shear on lymphatic vessel patency.


      PubDate: 2016-05-29T11:39:41Z
       
  • Evaluation of a subject-specific musculoskeletal modelling framework for
           load prediction in total knee arthroplasty
    • Abstract: Publication date: Available online 27 May 2016
      Source:Medical Engineering & Physics
      Author(s): Zhenxian Chen, Zhifeng Zhang, Ling Wang, Dichen Li, Yuanzhi Zhang, Zhongmin Jin
      Musculoskeletal (MSK) multibody dynamics (MBD) models have been used to predict in vivo biomechanics in total knee arthroplasty (TKA). However, a full lower limb MSK MBD modelling approach for TKA that combines subject-specific skeletal and prosthetic knee geometry has not yet been applied and evaluated over a range of patients. This study evaluated a subject-specific MSK MBD modelling framework for TKA using force-dependent kinematics (FDK) and applied it to predict knee contact forces during gait trials for three patients implanted with instrumented prosthetic knees. The prediction accuracy was quantified in terms of the mean absolute deviation (MAD), root mean square error (RMSE), Pearson correlation coefficient (ρ), and Sprague and Geers metrics of magnitude (M), phase (P) and combined error (C). Generally good agreements were found between the predictions and the experimental measurements from all patients for the medial contact forces (150 N < MAD <178 N, 174 N < RMSE < 224 N, 0.87 < ρ < 0.95, −0.04 < M < 0.20, 0.06 < P < 0.09, 0.08 < C < 0.22) and the lateral contact force (113 N < MAD <195 N, 131 N < RMSE < 240 N, 0.41 < ρ < 0.82, −0.25 < M < 0.34, 0.08 < P < 0.22, 0.13 < C < 0.36). The results suggest that the subject-specific MSK MBD modelling framework for TKA using FDK has potential as a powerful tool for investigating the functional outcomes of knee implants.


      PubDate: 2016-05-29T11:39:41Z
       
  • Attention attraction in an ophthalmic diagnostic device using
           sound-modulated fixation targets
    • Abstract: Publication date: Available online 27 May 2016
      Source:Medical Engineering & Physics
      Author(s): Boris I. Gramatikov, Shreya Rangarajan, Kristina Irsch, David L. Guyton
      This study relates to eye fixation systems with combined optical and audio systems. Many devices for eye diagnostics and some devices for eye therapeutics require the patient to fixate on a small target for a certain period of time, during which the eyes do not move and data from substructures of one or both eyes are acquired and analyzed. With young pediatric patients, a monotonously blinking target is not sufficient to retain attention steadily. We developed a method for modulating the intensity of a point fixation target using sounds appropriate to the child's age and preference. The method was realized as a subsystem of a Pediatric Vision Screener which employs retinal birefringence scanning for detection of central fixation. Twenty-one children, age 2–18, were studied. Modulation of the fixation target using sounds ensured the eye fixated on the target, and with appropriate choice of sounds, performed significantly better than a monotonously blinking target accompanied by a plain beep. The method was particularly effective with children of ages up to 10, after which its benefit disappeared. Typical applications of target modulation would be as supplemental subsystems in pediatric ophthalmic diagnostic devices, such as scanning laser ophthalmoscopes, optical coherence tomography units, retinal birefringence scanners, fundus cameras, and perimeters.
      Graphical abstract image

      PubDate: 2016-05-29T11:39:41Z
       
  • Measuring temperature rise during orthopaedic surgical procedures
    • Abstract: Publication date: Available online 28 May 2016
      Source:Medical Engineering & Physics
      Author(s): Sarah Manoogian, Adam K. Lee, James C. Widmaier
      A reliable means for measuring temperatures generated during surgical procedures is needed to recommend best practices for inserting fixation devices and minimizing the risk of osteonecrosis. Twenty four screw tests for three surgical procedures were conducted using the four thermocouples in the bone and one thermocouple in the screw. The maximum temperature rise recorded from the thermocouple in the screw (92.7±8.9°C, 158.7±20.9°C, 204.4±35.2°C) was consistently higher than the average temperature rise recorded in the bone (31.8±9.3°C, 44.9±12.4°C, 77.3±12.7°C). The same overall trend between the temperatures that resulted from three screw insertion procedures was recorded with significant statistical analyses using either the thermocouple in the screw or the average of several in-bone thermocouples. Placing a single thermocouple in the bone was determined to have limitations in accurately comparing temperatures from different external fixation screw insertion procedures. Using the preferred measurement techniques, a standard screw with a predrilled hole was found to have the lowest maximum temperatures for the shortest duration compared to the other two insertion procedures. Future studies evaluating bone temperature increase need to use reliable temperature measurements for recommending best practices to surgeons.


      PubDate: 2016-05-29T11:39:41Z
       
  • Editorial Board
    • Abstract: Publication date: July 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 7




      PubDate: 2016-05-29T11:39:41Z
       
  • Using an inertial navigation algorithm and accelerometer to monitor chest
           compression depth during cardiopulmonary resuscitation
    • Abstract: Publication date: Available online 28 May 2016
      Source:Medical Engineering & Physics
      Author(s): Salah Boussen, Harold Ibouanga-Kipoutou, Nathalie Fournier, Yves Godio Raboutet, Maxime Llari, Nicolas Bruder, Pierre Jean Arnoux, Michel Behr
      We present an original method using a low cost accelerometer and a Kalman-filter based algorithm to monitor cardiopulmonary resuscitation chest compressions (CC) depth. A three-axis accelerometer connected to a computer was used during CC. A Kalman filter was used to retrieve speed and position from acceleration data. We first tested the algorithm for its accuracy and stability on surrogate data. The device was implemented for CC performed on a manikin. Different accelerometer locations were tested. We used a classical inertial navigation algorithm to reconstruct CPR depth and frequency. The device was found accurate enough to monitor CPR depth and its stability was checked for half an hour without any drift. Average error on displacement was ±0.5mm. We showed that depth measurement was dependent on the device location on the patient or the rescuer. The accuracy and stability of this small low-cost accelerometer coupled to a Kalman-filter based algorithm to reconstruct CC depth and frequency, was found well adapted and could be easily implemented.


      PubDate: 2016-05-29T11:39:41Z
       
  • Influence of different mechanical stimuli in a multi-scale
           mechanobiological isotropic model for bone remodelling
    • Abstract: Publication date: Available online 20 May 2016
      Source:Medical Engineering & Physics
      Author(s): E.G.F. Mercuri, A.L. Daniel, M.B. Hecke, L. Carvalho
      This work represents a study of a mathematical model that describes the biological response to different mechanical stimuli in a cellular dynamics model for bone remodelling. The biological system discussed herein consists of three specialised cellular types, responsive osteoblasts, active osteoblasts and osteoclasts, three types of signalling molecules, transforming growth factor beta (TGF-β), receptor activator of nuclear factor kappa-b ligand (RANKL) and osteoprotegerin (OPG) and the parathyroid hormone (PTH). Three proposals for mechanical stimuli were tested: strain energy density (SED), hydrostatic and deviatoric parts of SED. The model was tested in a two-dimensional geometry of a standard human femur. The spatial discretization was performed by the finite element method while the temporal evolution of the variables was calculated by the 4th order Runge–Kutta method. The obtained results represent the temporal evolution of the apparent density distribution and the mean apparent density and thickness for the cortical bone after 600 days of remodelling simulation. The main contributions of this paper are the coupling of mechanical and biological models and the exploration of how the different mechanical stimuli affect the cellular activity in different types of physical activities. The results revealed that hydrostatic SED stimulus was able to form more cortical bone than deviatoric SED and total SED stimuli. The computational model confirms how different mechanical stimuli can impact in the balance of bone homeostasis.


      PubDate: 2016-05-24T11:14:51Z
       
  • Facilitatory effect of paired-pulse stimulation by transcranial magnetic
           stimulation with biphasic wave-form
    • Abstract: Publication date: Available online 20 May 2016
      Source:Medical Engineering & Physics
      Author(s): Petro Julkunen, Gustaf Järnefelt, Petri Savolainen, Jarmo Laine, Jari Karhu
      Transcranial magnetic stimulation (TMS) is used to probe corticospinal excitability by stimulating the motor cortex. Our aim was to enhance the effects of biphasic TMS by coupling a suprathreshold test pulse and a following subthreshold priming pulse to induce short-interval intracortical facilitation (SICF), which is conventionally produced with monophasic TMS. Biphasic TMS could potentially induce the SICF effect with better energy-efficiency and with lower stimulus intensities. This would make the biphasic paired-pulses better applicable in patients with reduced cortical excitability. A prototype stimulator was built to produce biphasic paired-pulses. Resting motor thresholds (rMTs) from the right and left hand abductor pollicis brevis muscles, and the right tibialis anterior muscle of eight healthy volunteers were determined using single-pulse paradigm with neuronavigated TMS. The rMTs and MEPs were measured using single-pulses and three paired-pulse setups (interstimulus interval, ISI of 3, 7 or 15ms). The rMTs were lower and MEPs were higher with biphasic paired-pulses compared to single-pulses. The SICF effect was greatest at 3ms ISI. This suggests that the application of biphasic paired-pulses to enhance stimulation effects is possible.


      PubDate: 2016-05-24T11:14:51Z
       
  • Modeling the fluid-dynamics and oxygen consumption in a porous scaffold
           stimulated by cyclic squeeze pressure
    • Abstract: Publication date: Available online 14 May 2016
      Source:Medical Engineering & Physics
      Author(s): Marco Ferroni, Serena Giusti, Diana Nascimento, Ana Silva, Federica Boschetti, Arti Ahluwalia
      The architecture and dynamic physical environment of tissues can be recreated in-vitro by combining 3D porous scaffolds and bioreactors able to apply controlled mechanical stimuli on cells. In such systems, the entity of the stimuli and the distribution of nutrients within the engineered construct depend on the micro-structure of the scaffolds. In this work, we present a new approach for optimizing computational fluid-dynamics (CFD) models for the investigation of fluid-induced forces generated by cyclic squeeze pressure within a porous construct, coupled with oxygen consumption of cardiomyocytes. A 2D axial symmetric macro-scaled model of a squeeze pressure bioreactor chamber was used as starting point for generating time dependent pressure profiles. Subsequently the fluid movement generated by the pressure fields was coupled with a complete 3D micro-scaled model of a porous protein cryogel. Oxygen transport and consumption inside the scaffold was evaluated considering a homogeneous distribution of cardiomyocytes throughout the structure, as confirmed by preliminary cell culture experiments. The results show that a 3D description of the system, coupling a porous geometry and time dependent pressure driven flow with fluid–structure-interaction provides an accurate and meaningful description of the microenvironment in terms of shear stress and oxygen distribution than simple stationary 2D models.


      PubDate: 2016-05-19T10:32:53Z
       
  • Technical note: Computer-manufactured inserts for prosthetic sockets
    • Abstract: Publication date: Available online 17 May 2016
      Source:Medical Engineering & Physics
      Author(s): Joan E Sanders, Jake B McLean, John C Cagle, David W Gardner, Katheryn J Allyn
      The objective of this research was to use computer-aided design software and a tabletop 3-D additive manufacturing system to design and fabricate custom plastic inserts for trans-tibial prosthesis users. Shape quality of inserts was tested right after they were inserted into participant's test sockets and again after four weeks of wear. Inserts remained properly positioned and intact throughout testing. Right after insertion the inserts caused the socket to be slightly under-sized, by a mean of 0.11mm, approximately 55% of the thickness of a nylon sheath. After four weeks of wear the under-sizing was less, averaging 0.03mm, approximately 15% of the thickness of a nylon sheath. Thus the inserts settled into the sockets over time. If existing prosthetic design software packages were enhanced to conduct insert design and to automatically generate fabrication files for manufacturing, then computer manufactured inserts may offer advantages over traditional methods in terms of speed of fabrication, ease of design, modification, and record keeping.


      PubDate: 2016-05-19T10:32:53Z
       
  • Numerical and ex vivo studies of a bioprobe developed for laser-induced
           thermotherapy (LITT) in contact with liver tissue
    • Abstract: Publication date: Available online 17 May 2016
      Source:Medical Engineering & Physics
      Author(s): T. Chartier, O. Carpentier, B. Genestie, J-C. Hornez, F. Monchau
      This work is based on the production of a bioprobe that is compatible with magnetic resonance imaging (MRI) for laser-induced thermotherapy (LITT) in liver cancer laser therapy. This probe is made of an alumina tube (3-mm diameter) in which an optical fibre is centred and fixed. A shooting window (20mm) is created using a mechanical rectifier. The device is then consolidated by the injection of a transparent and heat-resistant resin. Through numerical modelling, the thermal power damping of the laser source is evaluated as well as the propagation of the heat in the ex vivo liver tissue according to different heating scenarios. These analyses allow for an estimation of the irradiated volume. Ex vivo tests were performed on bovine liver to confirm the adequacy of the bioprobe for LITT and of the irradiated volumes predicted by the numerical model. There was a difference of 8% between the simulations and ex vivo experiments. The pulsed mode heating scenario was the most effective under the experimental conditions.
      Graphical abstract image

      PubDate: 2016-05-19T10:32:53Z
       
  • Clinical workflow for personalized foot pressure ulcer prevention
    • Abstract: Publication date: Available online 17 May 2016
      Source:Medical Engineering & Physics
      Author(s): M. Bucki, V. Luboz, A. Perrier, E. Champion, B. Diot, N. Vuillerme, Y. Payan
      Foot pressure ulcers are a common complication of diabetes because of patient's lack of sensitivity due to neuropathy. Deep pressure ulcers appear internally when pressures applied on the foot create high internal strains nearby bony structures. Monitoring tissue strains in persons with diabetes is therefore important for an efficient prevention. We propose to use personalized biomechanical foot models to assess strains within the foot and to determine the risk of ulcer formation. Our workflow generates a foot model adapted to a patient's morphology by deforming an atlas model to conform it to the contours of segmented medical images of the patient's foot. Our biomechanical model is composed of rigid bodies for the bones, joined by ligaments and muscles, and a finite element mesh representing the soft tissues. Using our registration algorithm to conform three datasets, three new patient models were created. After applying a pressure load below these foot models, the Von Mises equivalent strains and “cluster volumes” (i.e. volumes of contiguous elements with strains above a given threshold) were measured within eight functionally meaningful foot regions. The results show the variability of both location and strain values among the three considered patients. This study also confirms that the anatomy of the foot has an influence on the risk of pressure ulcer.


      PubDate: 2016-05-19T10:32:53Z
       
  • The influence of the modulus–density relationship and the material
           mapping method on the simulated mechanical response of the proximal femur
           in side-ways fall loading configuration
    • Abstract: Publication date: Available online 12 May 2016
      Source:Medical Engineering & Physics
      Author(s): B. Helgason, S. Gilchrist, O. Ariza, P. Vogt, W. Enns-Bray, R.P. Widmer, T. Fitze, H. Pálsson, Y. Pauchard, P. Guy, S.J. Ferguson, P.A. Cripton
      Contributing to slow advance of finite element (FE) simulations for hip fracture risk prediction, into clinical practice, could be a lack of consensus in the biomechanics community on how to map properties to the models. Thus, the aim of the present study was first, to systematically quantify the influence of the modulus–density relationship (E–ρ) and the material mapping method (MMM) on the predicted mechanical response of the proximal femur in a side-ways fall (SWF) loading configuration and second, to perform a model-to-model comparison of the predicted mechanical response within the femoral neck for all the specimens tested in the present study, using three different modelling techniques that have yielded good validation outcome in terms of surface strain prediction and whole bone response according to the literature. We found the outcome to be highly dependent on both the E–ρ relationship and the MMM. In addition, we found that the three modelling techniques that have resulted in good validation outcome in the literature yielded different principal strain prediction both on the surface as well as internally in the femoral neck region of the specimens modelled in the present study. We conclude that there exists a need to carry out a more comprehensive validation study for the SWF loading mode to identify which combination of MMMs and E–ρ relationship leads to the best match for whole bone and local mechanical response. The MMMs tested in the present study have been made publicly available at https://simtk.org/home/mitk-gem.


      PubDate: 2016-05-14T10:10:55Z
       
  • Evaluation of suitability of a micro-processing unit of motion analysis
           for upper limb tracking
    • Abstract: Publication date: Available online 13 May 2016
      Source:Medical Engineering & Physics
      Author(s): José Antonio Barraza Madrigal, Eladio Cardiel, Pablo Rogeli, Lorenzo Leija Salas, Roberto Muñoz Guerrero
      The aim of this study is to assess the suitability of a micro-processing unit of motion analysis (MPUMA), for monitoring, reproducing, and tracking upper limb movements. The MPUMA is based on an inertial measurement unit, a 16-bit digital signal controller and a customized algorithm. To validate the performance of the system, simultaneous recordings of the angular trajectory were performed with a video-based motion analysis system. A test of the flexo-extension of the shoulder joint during the active elevation in a complete range of 120º of the upper limb was carried out in 10 healthy volunteers. Additional tests were carried out to assess MPUMA performance during upper limb tracking. The first, a 3D motion reconstruction of three movements of the shoulder joint (flexo-extension, abduction–adduction, horizontal internal–external rotation), and the second, an upper limb tracking online during the execution of three movements of the shoulder joint followed by a continuous random movement without any restrictions by using a virtual model and a mechatronic device of the shoulder joint. Experimental results demonstrated that the MPUMA measured joint angles that are close to those from a motion-capture system with orientation RMS errors less than 3º.
      Graphical abstract image

      PubDate: 2016-05-14T10:10:55Z
       
  • Editorial Board
    • Abstract: Publication date: June 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 6




      PubDate: 2016-05-14T10:10:55Z
       
  • Pump function curve shape for a model lymphatic vessel
    • Abstract: Publication date: Available online 13 May 2016
      Source:Medical Engineering & Physics
      Author(s): C.D. Bertram, C. Macaskill, J.E. Moore
      The transport capacity of a contractile segment of lymphatic vessel is defined by its pump function curve relating mean flow-rate and adverse pressure difference. Numerous system characteristics affect curve shape and the magnitude of the generated flow-rates and pressures. Some cannot be varied experimentally, but their separate and interacting effects can be systematically revealed numerically. This paper explores variations in the rate of change of active tension and the form of the relation between active tension and muscle length, factors not known from experiment to functional precision. Whether the pump function curve bends toward or away from the origin depends partly on the curvature of the passive pressure–diameter relation near zero transmural pressure, but rather more on the form of the relation between active tension and muscle length. A pump function curve bending away from the origin defines a well-performing pump by maximum steady output power. This behaviour is favoured by a length/active-tension relationship which sustains tension at smaller lengths. Such a relationship also favours high peak mechanical efficiency, defined as output power divided by the input power obtained from the lymphangion diameter changes and active-tension time-course. The results highlight the need to pin down experimentally the form of the length/active-tension relationship.


      PubDate: 2016-05-14T10:10:55Z
       
  • Experimental investigation of the abrasive crown dynamics in orbital
           atherectomy
    • Abstract: Publication date: Available online 6 May 2016
      Source:Medical Engineering & Physics
      Author(s): Yihao Zheng, Barry Belmont, Albert J. Shih
      Orbital atherectomy is a catheter-based minimally invasive procedure to modify the plaque within atherosclerotic arteries using a diamond abrasive crown. This study was designed to investigate the crown motion and its corresponding contact force with the vessel. To this end, a transparent arterial tissue-mimicking phantom made of polyvinyl chloride was developed, a high-speed camera and image processing technique were utilized to visualize and quantitatively analyze the crown motion in the vessel phantom, and a piezoelectric dynamometer measured the forces on the phantom during the procedure. Observed under typical orbital atherectomy rotational speeds of 60,000, 90,000, and 120,000rpm in a 4.8mm caliber vessel phantom, the crown motion was a combination of high-frequency rotation at 1000, 1500, and 1660.4-1866.1Hz and low-frequency orbiting at 18, 38, and 40Hz, respectively. The measured forces were also composed of these high and low frequencies, matching well with the rotation of the eccentric crown and the associated orbital motion. The average peak force ranged from 0.1 to 0.4N at different rotational speeds.
      Graphical abstract image

      PubDate: 2016-05-09T10:04:53Z
       
  • A reduction in the knee adduction moment with medial thrust gait is
           associated with a medial shift in center of plantar pressure
    • Abstract: Publication date: Available online 4 May 2016
      Source:Medical Engineering & Physics
      Author(s): Christopher Ferrigno, Markus A Wimmer, Robert M Trombley, Hannah J Lundberg, Najia Shakoor, Laura E Thorp
      The knee adduction moment (KAM) is an established marker of compartmental load distribution across the tibiofemoral joint. Research suggests a link between the magnitude of the KAM and center of plantar pressure (COP) thus alterations in the two may be related. The objective of this study was to investigate whether the COP predictably shifts when the KAM is reduced through a gait adaptation. Twenty healthy adults underwent gait analysis walking with their normal gait pattern and with medial thrust gait, a gait adaptation known to significantly reduce the KAM. Simultaneous COP and 3-D kinetics were acquired to allow for a comparison of the change in COP to the change in the KAM. The COP was quantified by determining a customized medial-lateral pressure index (MLPI) which compares the COP tracing line during the first and second halves of stance to the longitudinal axis of the foot. Linear regressions assessing the association between the changes in KAM and MLPI indicated that 48.3% (p =0.001) of the variation in MLPI during the first half of stance can be explained by the KAM during the same period. A trend was observed between the association between the KAM and MLPI during the second half of stance (R 2 =0.16, p =0.080). Backwards elimination regression analysis was used to explore whether simultaneous consideration of the KAM and other potential confounding factors such as sagittal plane knee moments and speed explained variance in the MLPI during the first half of stance. Only the KAM exhibited explanatory power (β =0.695, p =0.001). During medial thrust gait, a reduction in the KAM was associated with a medial shift in the MLPI, and an increase in the KAM was associated with a lateral shift in the MLPI, especially in the first half of the stance phase. Together, these results demonstrate an inherent link between foot pressure and the KAM during medial thrust gait, and suggest that manipulating foot pressure may be a biomechanical mechanism for an intervention designed to improve loading conditions at the knee.


      PubDate: 2016-05-05T09:58:07Z
       
  • A method to adapt thoracic impedance based on chest geometry and
           composition to assess congestion in heart failure patients
    • Abstract: Publication date: Available online 14 April 2016
      Source:Medical Engineering & Physics
      Author(s): Illapha Cuba-Gyllensten, Paloma Gastelurrutia, Alberto G. Bonomi, Jarno Riistama, Antoni Bayes-Genis, Ronald M. Aarts
      Multi-frequency trans-thoracic bioimpedance (TTI) could be used to track fluid changes and congestion of the lungs, however, patient specific characteristics may impact the measurements. We investigated the effects of thoracic geometry and composition on measurements of TTI and developed an equation to calculate a personalized fluid index. Simulations of TTI measurements for varying levels of chest circumference, fat and muscle proportion were used to derive parameters for a model predicting expected values of TTI. This model was then adapted to measurements from a control group of 36 healthy volunteers to predict TTI and lung fluids (fluid index). Twenty heart failure (HF) patients treated for acute HF were then used to compare the changes in the personalized fluid index to symptoms of HF and predicted TTI to measurements at hospital discharge. All the derived body characteristics affected the TTI measurements in healthy volunteers and together the model predicted the measured TTI with 8.9% mean absolute error. In HF patients the estimated TTI correlated well with the discharged TTI ( r = 0.73 , p <0.001) and the personalized fluid index followed changes in symptom levels during treatment. However, 37% ( n = 7 ) of the patients were discharged well below the model expected value. Accounting for chest geometry and composition might help in interpreting TTI measurements.


      PubDate: 2016-04-26T16:13:35Z
       
  • Comparison of three methods for identifying the heelstrike transient
           during walking gait
    • Abstract: Publication date: Available online 21 April 2016
      Source:Medical Engineering & Physics
      Author(s): J. Troy Blackburn, Brian G. Pietrosimone, Matt S. Harkey, Brittney A. Luc, Derek N. Pamukoff
      Impulsive, or high rate, loading contributes to cartilage degradation and is commonly identified via the heelstrike transient (HST) in the vertical ground reaction force (vGRF) during gait. Investigation of the HST may improve our understanding of knee osteoarthritis mechanical pathogenesis. However, the most appropriate method for objectively identifying the HST is unclear. Twenty-eight healthy subjects walked at a self-selected pace while vGRF data were captured. The efficacies of three HST identification methods (Radin, Hunt, and Modified Hunt) were evaluated using vGRF data lowpass filtered at three frequencies (raw/unfiltered, 75Hz, and 50Hz). Both the HST identification method and lowpass filter frequency influenced whether a HST was identified and whether a subject was classified as an “impulsive loader” (i.e. HST identified in 3 of 5 trials). The methods identified different phenomena in the vGRF, with the Radin and Modified Hunt methods identifying the HST 11-16ms following ground contact and the Hunt method identifying the HST 83–122ms following ground contact. Lowpass filtering the vGRF at 75Hz and implementing the Radin method was the most effective approach for identifying the HST. Future longitudinal observations are necessary to determine if specific HST criteria are indicative of knee osteoarthritis development and progression.


      PubDate: 2016-04-26T16:13:35Z
       
  • Segmented beat modulation method for electrocardiogram estimation from
           noisy recordings
    • Abstract: Publication date: Available online 21 April 2016
      Source:Medical Engineering & Physics
      Author(s): Angela Agostinelli, Agnese Sbrollini, Corrado Giuliani, Sandro Fioretti, Francesco Di Nardo, Laura Burattini
      Clinical utility of an electrocardiogram (ECG) affected by too high levels of noise such as baseline wanders, electrode motion artifacts, muscular artifacts and power-line interference may be jeopardized if not opportunely processed. Template-based techniques have been proposed for ECG estimation from noisy recordings, but usually they do not reproduce physiological ECG variability, which, however, provides clinically useful information on the patient's health. Thus, this study proposes the Segmented-Beat Modulation Method (SBMM) as a new template-based filtering procedure able to reproduce ECG variability, and assesses SBMM robustness to the aforementioned noises in comparison to a standard template method (STM). SBMM performs a unique ECG segmentation into QRS segment and TUP segment, and successively modulates/demodulates (by stretching or compressing) the former segments in order to adaptively adjust each estimated beat to its original morphology and duration. Consequently, SBMM estimates ECG with significantly lower estimation errors than STM when applied to recordings affected by various levels of the considered noises (SBMM: 176–232µV and 79–499µV; STM: 215–496µV and 93–1056µV, for QRS and TUP segments, respectively). Thus, SBMM is able to reproduce ECG variability and is more robust to noise than STM.


      PubDate: 2016-04-26T16:13:35Z
       
  • Bioactive glass surface for fiber reinforced composite implants via
           surface etching by Excimer laser
    • Abstract: Publication date: Available online 25 April 2016
      Source:Medical Engineering & Physics
      Author(s): Julia Kulkova, Niko Moritz, Hannu Huhtinen, Riina Mattila, Ivan Donati, Eleonora Marsich, Sergio Paoletti, Pekka K Vallittu
      Biostable fiber-reinforced composites (FRC) prepared from bisphenol-A-glycidyldimethacrylate (BisGMA)-based thermosets reinforced with E-glass fibers are promising alternatives to metallic implants due to the excellent fatigue resistance and the mechanical properties matching those of bone. Bioactive glass (BG) granules can be incorporated within the polymer matrix to improve the osteointegration of the FRC implants. However, the creation of a viable surface layer using BG granules is technically challenging. In this study, we investigated the potential of Excimer laser ablation to achieve the selective removal of the matrix to expose the surface of BG granules. A UV–vis spectroscopic study was carried out to investigate the differences in the penetration of light in the thermoset matrix and BG. Thereafter, optimal Excimer laser ablation parameters were established. The formation of a calcium phosphate (CaP) layer on the surface of the laser-ablated specimens was verified in simulated body fluid (SBF). In addition, the proliferation of MG63 cells on the surfaces of the laser-ablated specimens was investigated. For the laser-ablated specimens, the pattern of proliferation of MG63 cells was comparable to that in the positive control group (Ti6Al4V). We concluded that Excimer laser ablation has potential for the creation of a bioactive surface on FRC-implants.
      Graphical abstract image

      PubDate: 2016-04-26T16:13:35Z
       
  • A robust approach for ECG-based analysis of cardiopulmonary coupling
    • Abstract: Publication date: Available online 23 April 2016
      Source:Medical Engineering & Physics
      Author(s): Jiewen Zheng, Weidong Wang, Zhengbo Zhang, Dalei Wu, Hao Wu, Chung-kang Peng
      Deriving respiratory signal from a surface electrocardiogram (ECG) measurement has advantage of simultaneously monitoring of cardiac and respiratory activities. ECG-based cardiopulmonary coupling (CPC) analysis estimated by heart period variability and ECG-derived respiration (EDR) shows promising applications in medical field. The aim of this paper is to provide a quantitative analysis of the ECG-based CPC, and further improve its performance. Two conventional strategies were tested to obtain EDR signal: R-S wave amplitude and area of the QRS complex. An adaptive filter was utilized to extract the common component of inter-beat interval (RRI) and EDR, generating enhanced versions of EDR signal. CPC is assessed through probing the nonlinear phase interactions between RRI series and respiratory signal. Respiratory oscillations presented in both RRI series and respiratory signals were extracted by ensemble empirical mode decomposition for coupling analysis via phase synchronization index. The results demonstrated that CPC estimated from conventional EDR series exhibits constant and proportional biases, while that estimated from enhanced EDR series is more reliable. Adaptive filtering can improve the accuracy of the ECG-based CPC estimation significantly and achieve robust CPC analysis. The improved ECG-based CPC estimation may provide additional prognostic information for both sleep medicine and autonomic function analysis.


      PubDate: 2016-04-26T16:13:35Z
       
  • Shoulder pain and time dependent structure in wheelchair propulsion
           variability
    • Abstract: Publication date: Available online 25 April 2016
      Source:Medical Engineering & Physics
      Author(s): Chandrasekaran Jayaraman, Yaejin Moon, Jacob J. Sosnoff
      Manual wheelchair propulsion places considerable repetitive mechanical strain on the upper limbs leading to shoulder injury and pain. While recent research indicates that the amount of variability in wheelchair propulsion and shoulder pain may be related. There has been minimal inquiry into the fluctuation over time (i.e. time-dependent structure) in wheelchair propulsion variability. Consequently the purpose of this investigation was to examine if the time-dependent structure in the wheelchair propulsion parameters are related to shoulder pain. 27 experienced wheelchair users manually propelled their own wheelchair fitted with a SMARTWheel on a roller at 1.1m/s for 3min. Time-dependent structure of cycle-to-cycle fluctuations in contact angle and inter push time interval was quantified using sample entropy (SampEn) and compared between the groups with/without shoulder pain using non-parametric statistics. Overall findings were, (1) variability observed in contact angle fluctuations during manual wheelchair propulsion is structured (Z=3.15;p<0.05), (2) individuals with shoulder pain exhibited higher SampEn magnitude for contact angle during wheelchair propulsion than those without pain (χ2(1)=6.12;p<0.05); and (3) SampEn of contact angle correlated significantly with self-reported shoulder pain (rs (WUSPI) =0.41;rs (VAS)=0.56;p<0.05). It was concluded that the time-dependent structure in wheelchair propulsion may provide novel information for tracking and monitoring shoulder pain.


      PubDate: 2016-04-26T16:13:35Z
       
  • Assessment of accuracy and precision of 3D reconstruction of
           unicompartmental knee arthroplasty in upright position using biplanar
           radiography
    • Abstract: Publication date: Available online 23 April 2016
      Source:Medical Engineering & Physics
      Author(s): Tsung-Yuan Tsai, Dimitris Dimitriou, Ali Hosseini, Ming Han Lincoln Liow, Martin Torriani, Guoan Li, Young-Min Kwon
      This study aimed to evaluate the precision and accuracy of 3D reconstruction of UKA component position, contact location and lower limb alignment in standing position using biplanar radiograph. Two human specimens with 4 medial UKAs were implanted with beads for radiostereometric analysis (RSA). The specimens were frozen in standing position and CT-scanned to obtain relative positions between the beads, bones and UKA components. The specimens were then imaged using biplanar radiograph (EOS). The positions of the femur, tibia, UKA components and UKA contact locations were obtained using RSA- and EOS-based techniques. Intraclass correlation coefficient (ICC) was calculated for inter-observer reliability of the EOS technique. The average (standard deviation) of the differences between two techniques in translations and rotations were less than 0.18 (0.29) mm and 0.39° (0.66°) for UKA components. The root-mean-square-errors (RMSE) of contact location along the anterior/posterior and medial/lateral directions were 0.84mm and 0.30mm. The RMSEs of the knee rotations were less than 1.70°. The ICCs for the EOS-based segmental orientations between two raters were larger than 0.98. The results suggest the EOS-based 3D reconstruction technique can precisely determine component position, contact location and lower limb alignment for UKA patients in weight-bearing standing position.


      PubDate: 2016-04-26T16:13:35Z
       
  • Corrigendum to ‘Intraprosthetic screw fixation increases primary
           fixation stability in periprosthetic fractures of the femur—A
           biomechanical study.’ [Med. Eng. Phys. 36 (2014) 239–243]
    • Abstract: Publication date: Available online 23 April 2016
      Source:Medical Engineering & Physics
      Author(s): Stephan Brand, Johannes Klotz, Thomas Hassel, Maximilian Petri, Max Ettinger, Friedrich-Wilhelm Bach, Christian Krettek, Thomas Gösling



      PubDate: 2016-04-26T16:13:35Z
       
  • Evaluating the usability of a smartphone virtual seating coach application
           for powered wheelchair users
    • Abstract: Publication date: Available online 11 April 2016
      Source:Medical Engineering & Physics
      Author(s): Yu-Kuang Wu, Hsin-Yi Liu, Annmarie Kelleher, Jonathan Pearlman, Rory A. Cooper
      The aim of the smartphone virtual seating coach (SVSC) was to provide a personalized reminder/warning system to encourage powered wheelchair users to use their powered seating functions (PSFs) as clinically recommended. This study evaluated the usability of the SVSC system by gathering feedback from five powered wheelchair users and five rehabilitation professionals through questionnaires and interviews. The results indicated that clear and understandable instructions to adjust the PSFs are the most important requirement for SVSC application. The instructions must be intuitive, could benefit from animations or indications of PSFs control buttons so powered wheelchair users can adjust their PSFs immediately and appropriately.


      PubDate: 2016-04-26T16:13:35Z
       
  • Mechanical testing and modelling of the Universal 2 implant
    • Abstract: Publication date: Available online 12 April 2016
      Source:Medical Engineering & Physics
      Author(s): M.K. Gislason, E. Foster, D. Main, G. Fusiek, P. Niewczas, M. Bransby-Zachary, D.H. Nash
      Understanding the load mechanics of orthopaedic implants is important to be able to predict their behaviour in-vivo. Much research, both mechanical and clinical, has been carried out on hip and knee implants, but less has been written about the mechanics of wrist implants. In this paper, the load mechanics of the Universal 2 wrist implant have been measured using two types of measuring techniques, strain gauges and Fibre Bragg Grating measurements to measure strains. The results were compared to a finite element model of the implant. The results showed that the computational results were in good agreement with the experimental results. Better understanding of the load mechanics of wrist implants, using models and experimental results can catalyse the development of future generation implants.


      PubDate: 2016-04-26T16:13:35Z
       
  • Accuracy and repeatability of quantitative fluoroscopy for the measurement
           of sagittal plane translation and finite centre of rotation in the lumbar
           spine
    • Abstract: Publication date: Available online 26 April 2016
      Source:Medical Engineering & Physics
      Author(s): Alexander Breen, Alan Breen
      Quantitative fluoroscopy (QF) was developed to measure intervertebral mechanics in vivo and has been found to have high repeatability and accuracy for the measurement of intervertebral rotations. However, sagittal plane translation and finite centre of rotation (FCR) are potential measures of stability but have not yet been fully validated for current QF. This study investigated the repeatability and accuracy of QF for measuring these variables. Repeatability was assessed from L2-S1 in 20 human volunteers. Accuracy was investigated using 10 consecutive measurements from each of two pairs of linked and instrumented dry human vertebrae as reference; one which tilted without translation and one which translated without tilt. The results found intra- and inter-observer repeatability for translation to be 1.1mm or less (SEM) with fair to substantial reliability (ICC 0.533–0.998). Intra-observer repeatability of FCR location for inter-vertebral rotations of 5° and above ranged from 1.5mm to 1.8mm (SEM) with moderate to substantial reliability (ICC 0.626–0.988). Inter-observer repeatability for FCR ranged from 1.2mm to 5.7mm, also with moderate to substantial reliability (ICC 0.621–0.878). Reliability was substantial (ICC>0.81) for 10/16 measures for translation and 5/8 for FCR location. Accuracy for translation was 0.1mm (fixed centre) and 2.2mm (moveable centre), with an FCR error of 0.3mm(x) and 0.4mm(y) (fixed centre). This technology was found to have a high level of accuracy and with a few exceptions, moderate to substantial repeatability for the measurement of translation and FCR from fluoroscopic motion sequences.


      PubDate: 2016-04-26T16:13:35Z
       
  • Physics-driven impeller designs for a novel intravascular blood pump for
           patients with congenital heart disease
    • Abstract: Publication date: Available online 26 April 2016
      Source:Medical Engineering & Physics
      Author(s): Steven G. Chopski, Carson S. Fox, Kelli L. McKenna, Michelle L. Riddle, Dhyaa H. Kafagy, Randy M. Stevens, Amy L. Throckmorton
      Mechanical circulatory support offers an alternative therapeutic treatment for patients with dysfunctional single ventricle physiology. An intravascular axial flow pump is being developed as a cavopulmonary assist device for these patients. This study details the development of a new rotating impeller geometry. We examined the performance of 8 impeller geometries with blade stagger or twist angles varying from 100° to 800° using computational methods. A refined range of blade twist angles between 300° and 400° was then identified, and 4 additional geometries were evaluated. Generally, the impeller designs produced 4–26mmHg for flow rates of 1–4L/min for 6000–8000 RPM. A data regression analysis was completed and found the impeller with 400° of blade twist to be the superior performer. A hydraulic test was conducted on a prototype of the 400° impeller, which generated measurable pressure rises of 7–28mmHg for flow rates of 1–4L/min at 6000–8000 RPM. The findings of the numerical model and experiment were in reasonable agreement within approximately 20%. These results support the continued development of an axial-flow, mechanical cavopulmonary assist device as a new clinical therapeutic option for Fontan patients.


      PubDate: 2016-04-26T16:13:35Z
       
  • A pressure and shear sensor system for stress measurement at lower limb
           residuum/socket interface
    • Abstract: Publication date: Available online 23 April 2016
      Source:Medical Engineering & Physics
      Author(s): P. Laszczak, M. McGrath, J. Tang, J. Gao, L. Jiang, D.L. Bader, D. Moser, S. Zahedi
      A sensor system for measurement of pressure and shear at the lower limb residuum/socket interface is described. The system comprises of a flexible sensor unit and a data acquisition unit with wireless data transmission capability. Static and dynamic performance of the sensor system was characterised using a mechanical test machine. The static calibration results suggest that the developed sensor system presents high linearity (linearity error ≤ 3.8%) and resolution (0.9 kPa for pressure and 0.2 kPa for shear). Dynamic characterisation of the sensor system shows hysteresis error of approximately 15% for pressure and 8% for shear. Subsequently, a pilot amputee walking test was conducted. Three sensors were placed at the residuum/socket interface of a knee disarticulation amputee and simultaneous measurements were obtained during pilot amputee walking test. The pressure and shear peak values as well as their temporal profiles are presented and discussed. In particular, peak pressure and shear of approximately 58 kPa and 27 kPa, respectively, were recorded. Their temporal profiles also provide dynamic coupling information at this critical residuum/socket interface. These preliminary amputee test results suggest strong potential of the developed sensor system for exploitation as an assistive technology to facilitate socket design, socket fit and effective monitoring of lower limb residuum health.


      PubDate: 2016-04-26T16:13:35Z
       
  • Bilateral robots for upper-limb stroke rehabilitation: State of the art
           and future prospects
    • Abstract: Publication date: Available online 24 April 2016
      Source:Medical Engineering & Physics
      Author(s): Bo Sheng, Yanxin Zhang, Wei Meng, Chao Deng, Shengquan Xie
      Robot-assisted bilateral upper-limb training grows abundantly for stroke rehabilitation in recent years and an increasing number of devices and robots have been developed. This paper aims to provide a systematic overview and evaluation of existing bilateral upper-limb rehabilitation devices and robots based on their mechanisms and clinical-outcomes. Most of the articles studied here were searched from nine online databases and the China National Knowledge Infrastructure (CNKI) from year 1993 to 2015. Devices and robots were categorized as end-effectors, exoskeletons and industrial robots. Totally ten end-effectors, one exoskeleton and one industrial robot were evaluated in terms of their mechanical characteristics, degrees of freedom (DOF), supported control modes, clinical applicability and outcomes. Preliminary clinical results of these studies showed that all participants could gain certain improvements in terms of range of motion, strength or physical function after training. Only four studies supported that bilateral training was better than unilateral training. However, most of clinical results cannot definitely verify the effectiveness of mechanisms and clinical protocols used in robotic therapies. To explore the actual value of these robots and devices, further research on ingenious mechanisms, dose-matched clinical protocols and universal evaluation criteria should be conducted in the future.


      PubDate: 2016-04-26T16:13:35Z
       
  • The carotid artery as an alternative site for dynamic autoregulation
           measurement: an inter-observer reproducibility study
    • Abstract: Publication date: Available online 25 April 2016
      Source:Medical Engineering & Physics
      Author(s): R.C. Nogueira, N.P. Saeed, E. Bor-Seng-Shu, M.J. Teixeira, T.G. Robinson, R.B. Panerai
      The internal carotid artery (ICA) has been proposed as an alternative site to the middle cerebral artery (MCA) to measure dynamic cerebral autoregulation (dCA) using transcranial Doppler ultrasound (TCD). Our aim was to test the inter-operator reproducibility of dCA assessment in the ICA and the effect of interaction amongst different variables (artery source × operator × intra-subject variability). Two operators measured blood flow velocity using TCD at the ICA and MCA simultaneously on each side in 12 healthy volunteers. The autoregulation index (ARI) was estimated by transfer function analysis. A two-way repeated measurements ANOVA with post-hoc Tukey tested the difference between ARI by different operators and interaction effects were analysed based on the generalized linear model. In this healthy population, no significant differences between operator and no interaction effects were identified amongst the different variables. This study reinforced the validity of using the ICA as an alternative site for the assessment of dCA. Further work is needed to confirm and extend our findings, particularly to disease populations.


      PubDate: 2016-04-26T16:13:35Z
       
  • Towards the generation of a parametric foot model using principal
           component analysis: A pilot study
    • Abstract: Publication date: Available online 7 April 2016
      Source:Medical Engineering & Physics
      Author(s): Alessandra Scarton, Zimi Sawacha, Claudio Cobelli, Xinshan Li
      There have been many recent developments in patient-specific models with their potential to provide more information on the human pathophysiology and the increase in computational power. However they are not yet successfully applied in a clinical setting. One of the main challenges is the time required for mesh creation, which is difficult to automate. The development of parametric models by means of the Principle Component Analysis (PCA) represents an appealing solution. In this study PCA has been applied to the feet of a small cohort of diabetic and healthy subjects, in order to evaluate the possibility of developing parametric foot models, and to use them to identify variations and similarities between the two populations. Both the skin and the first metatarsal bones have been examined. Besides the reduced sample of subjects considered in the analysis, results demonstrated that the method adopted herein constitutes a first step towards the realization of a parametric foot models for biomechanical analysis. Furthermore the study showed that the methodology can successfully describe features in the foot, and evaluate differences in the shape of healthy and diabetic subjects.


      PubDate: 2016-04-09T05:35:45Z
       
  • Staying in dynamic balance on a prosthetic limb: A leg to stand on?
    • Abstract: Publication date: Available online 1 April 2016
      Source:Medical Engineering & Physics
      Author(s): Carolin Curtze, At L. Hof, Klaas Postema, Bert Otten
      With the loss of a lower limb, amputees lack the active muscle empowered control of the ankle that is important for balance control. We examined single-leg stance on prosthesis vs. sound limb balancing on narrow ridges in transtibial amputees. When balancing on the prosthetic limb, the lateral displacement of the center of pressure was reduced and was compensated by an increase in counter-rotation. We show that single-leg stance on a prosthetic limb can be compared to balancing on a narrow ridge. Standing on a prosthetic limb involves the same balance mechanisms as balancing on narrow ridges of 40-mm to 20-mm width. Yet, the ability to balance on a narrow ridge with the sound limb was only a weak predictor for an amputee's ability to stand on the prosthetic limb. Balancing in single-leg stance on a prosthetic limb is not a common activity. The ability to compensate with the sound limb may therefore be functionally more important than the ability to stay in dynamic balance on the prosthetic limb.


      PubDate: 2016-04-05T05:08:34Z
       
  • The contact mechanics and occurrence of edge loading in modular
           metal-on-polyethylene total hip replacement during daily activities
    • Abstract: Publication date: Available online 4 April 2016
      Source:Medical Engineering & Physics
      Author(s): Xijin Hua, Junyan Li, Zhongmin Jin, John Fisher
      The occurrence of edge loading in hip joint replacement has been associated with many factors such as prosthetic design, component malposition and activities of daily living. The present study aimed to quantify the occurrence of edge loading/contact at the articulating surface and to evaluate the effect of cup angles and edge loading on the contact mechanics of a modular metal-on-polyethylene (MoP) total hip replacement (THR) during different daily activities. A three-dimensional finite element model was developed based on a modular MoP bearing system. Different cup inclination and anteversion angles were modelled and six daily activities were considered. The results showed that edge loading was predicted during normal walking, ascending and descending stairs activities under steep cup inclination conditions (≥55°) while no edge loading was observed during standing up, sitting down and knee bending activities. The duration of edge loading increased with increased cup inclination angles and was affected by the cup anteversion angles. Edge loading caused elevated contact pressure at the articulating surface and substantially increased equivalent plastic strain of the polyethylene liner. The present study suggested that correct positioning the component to avoid edge loading that may occur during daily activities is important for MoP THR in clinical practice.


      PubDate: 2016-04-05T05:08:34Z
       
  • Patient-specific modelling of abdominal aortic aneurysms: The influence of
           wall thickness on predicted clinical outcomes
    • Abstract: Publication date: Available online 4 April 2016
      Source:Medical Engineering & Physics
      Author(s): Noel Conlisk, Arjan J. Geers, Olivia M.B. McBride, David E. Newby, Peter R. Hoskins
      Rupture of abdominal aortic aneurysms (AAAs) is linked to aneurysm morphology. This study investigates the influence of patient-specific (PS) AAA wall thickness on predicted clinical outcomes. Eight patients under surveillance for AAAs were selected from the MA3RS clinical trial based on the complete absence of intraluminal thrombus. Two finite element (FE) models per patient were constructed; the first incorporated variable wall thickness from CT (PS_wall), and the second employed a 1.9mm uniform wall (Uni_wall). Mean PS wall thickness across all patients was 1.77±0.42mm. Peak wall stress (PWS) for PS_wall and Uni_wall models was 0.6761±0.3406N/mm2 and 0.4905±0.0850N/mm2, respectively. In 4 out of 8 patients the Uni_wall underestimated stress by as much as 55%; in the remaining cases it overestimated stress by up to 40%. Rupture risk more than doubled in 3 out of 8 patients when PS_wall was considered. Wall thickness influenced the location and magnitude of PWS as well as its correlation with curvature. Furthermore, the volume of the AAA under elevated stress increased significantly in AAAs with higher rupture risk indices. This highlights the sensitivity of standard rupture risk markers to the specific wall thickness strategy employed.


      PubDate: 2016-04-05T05:08:34Z
       
 
 
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