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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: 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)
Xenobiotica     Hybrid Journal   (Followers: 10)
Yeast     Hybrid Journal   (Followers: 9)
Zebrafish     Hybrid Journal   (Followers: 1)
Zeitschrift für Evidenz, Fortbildung und Qualität im Gesundheitswesen     Full-text available via subscription   (Followers: 5)
Zeitschrift für Naturforschung C : A Journal of Biosciences     Open Access   (Followers: 2)
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  [2969 journals]
  • Feedback control of electrical stimulation electrode arrays
    • Abstract: Publication date: Available online 21 July 2016
      Source:Medical Engineering & Physics
      Author(s): C.T. Freeman, K. Yang, J. Tudor, M. Kutlu
      Electrical stimulation electrode arrays are an emerging technology that enables muscles to be artificially contracted through the activation of their associated motor neurons. A principal application of electrical stimulation is to assist human motion for orthotic or therapeutic purposes. This paper develops a framework for the design of model-based electrode array feedback controllers that balance joint angle tracking performance with the degree of disturbance and modeling mismatch that can exist in the true underlying biomechanical system. This framework is used to develop a simplified control design procedure that is suitable for application in a clinical setting. Experimental results evaluate the feasibility of the control design approach through tests on ten participants using both fabric and polycarbonate electrode arrays.


      PubDate: 2016-07-27T07:15:47Z
       
  • Comparison of adaptive neuro-fuzzy inference system (ANFIS) and Gaussian
           processes for machine learning (GPML) algorithms for the prediction of
           skin temperature in lower limb prostheses
    • Abstract: Publication date: Available online 21 July 2016
      Source:Medical Engineering & Physics
      Author(s): Neha Mathur, Ivan Glesk, Arjan Buis
      Monitoring of the interface temperature at skin level in lower-limb prosthesis is notoriously complicated. This is due to the flexible nature of the interface liners used impeding the required consistent positioning of the temperature sensors during donning and doffing. Predicting the in-socket residual limb temperature by monitoring the temperature between socket and liner rather than skin and liner could be an important step in alleviating complaints on increased temperature and perspiration in prosthetic sockets. In this work, we propose to implement an adaptive neuro fuzzy inference strategy (ANFIS) to predict the in-socket residual limb temperature. ANFIS belongs to the family of fused neuro fuzzy system in which the fuzzy system is incorporated in a framework which is adaptive in nature. The proposed method is compared to our earlier work using Gaussian processes for machine learning. By comparing the predicted and actual data, results indicate that both the modeling techniques have comparable performance metrics and can be efficiently used for non-invasive temperature monitoring.


      PubDate: 2016-07-27T07:15:47Z
       
  • On the use of a Euclidean norm function for the estimation of local
           
    • Abstract: Publication date: Available online 22 July 2016
      Source:Medical Engineering & Physics
      Author(s): Shawn M. Beaudette, Samuel J. Howarth, Ryan B. Graham, Stephen H.M. Brown
      Several different state-space reconstruction methods have been employed to assess the local dynamic stability (LDS) of a 3D kinematic system. One common method is to use a Euclidean norm ( N ) transformation of three orthogonal x, y, and z time-series’ followed by the calculation of the maximum finite-time Lyapunov exponent (λ max) from the resultant N waveform (using a time-delayed state space reconstruction technique). By essentially acting as a weighted average, N has been suggested to account for simultaneous expansion and contraction along separate degrees of freedom within a 3D system (e.g. the coupling of dynamic movements between orthogonal planes). However, when estimating LDS using N , non-linear transformations inherent within the calculation of N should be accounted for. Results demonstrate that the use of N on 3D time-series data with arbitrary magnitudes of relative bias and zero-crossings cause the introduction of error in estimates of λ max obtained through N . To develop a standard for the analysis of 3D dynamic kinematic waveforms, we suggest that all dimensions of a 3D signal be independently shifted to avoid the incidence of zero-crossings prior to the calculation of N and subsequent estimation of LDS through the use of λ max.


      PubDate: 2016-07-27T07:15:47Z
       
  • Impact of anomalous transport kinetics on the progress of wound healing
    • Abstract: Publication date: Available online 25 July 2016
      Source:Medical Engineering & Physics
      Author(s): E. Javierre
      This work focuses on the transport kinetics of chemical and cellular species during wound healing. Anomalous transport kinetics, coupling sub- and superdiffusion with chemotaxis, and fractional viscoelasticity of soft tissues are analyzed from a modeling point of view. The paper presents a generalization of well stablished mechano-chemical models of wound contraction (Murphy et al., 2012; Valero et al., 2014) to include the previously mentioned anomalous effects by means of partial differential equations of fractional order. Results show the effect that anomalous dynamics have on the contraction rate and extension and on the distribution of biological species, and indicators of fibroproliferative disorders are identified.


      PubDate: 2016-07-27T07:15:47Z
       
  • Optimal calibration of instrumented treadmills using an instrumented pole
    • Abstract: Publication date: August 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 8
      Author(s): L.H. Sloot, H. Houdijk, M.M. van der Krogt, J. Harlaar
      Calibration of instrumented treadmills is imperative for accurate measurement of ground reaction forces and center of pressure (COP). A protocol using an instrumented pole has been shown to considerably increase force and COP accuracy. This study examined how this protocol can be further optimized to maximize accuracy, by varying the measurement time and number of spots, using nonlinear approaches to calculate the calibration matrix and by correcting for potential inhomogeneity in the distribution of COP errors across the treadmill's surface. The accuracy increased with addition of spots and correction for the inhomogeneous distribution across the belt surface, decreased with reduction of measurement time, and did not improve by including nonlinear terms. Most of these methods improved the overall accuracy only to a limited extent, suggesting that the maximal accuracy is approached given the treadmill's inherent mechanical limitations. However, both correction for position dependence of the accuracy as well as its optimization within the walking area are found to be valuable additions to the standard calibration process.


      PubDate: 2016-07-18T06:41:29Z
       
  • Effects of aqueous humor hydrodynamics on human eye heat transfer under
           external heat sources
    • Abstract: Publication date: August 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 8
      Author(s): Kor L. Tiang, Ean H. Ooi
      The majority of the eye models developed in the late 90s and early 00s considers only heat conduction inside the eye. This assumption is not entirely correct, since the anterior and posterior chambers are filled aqueous humor (AH) that is constantly in motion due to thermally-induced buoyancy. In this paper, a three-dimensional model of the human eye is developed to investigate the effects AH hydrodynamics have on the human eye temperature under exposure to external heat sources. If the effects of AH flow are negligible, then future models can be developed without taking them into account, thus simplifying the modeling process. Two types of external thermal loads are considered; volumetric and surface irradiation. Results showed that heat convection due to AH flow contributes to nearly 95% of the total heat flow inside the anterior chamber. Moreover, the circulation inside the anterior chamber can cause an upward shift of the location of hotspot. This can have significant consequences to our understanding of heat-induced cataractogenesis.


      PubDate: 2016-07-18T06:41:29Z
       
  • A patient-controlled functional electrical stimulation system for arm
           weight relief
    • Abstract: Publication date: Available online 5 July 2016
      Source:Medical Engineering & Physics
      Author(s): C. Klauer, S. Ferrante, E. Ambrosini, U. Shiri, F. Dähne, I. Schmehl, A. Pedrocchi, T. Schauer
      A patient-driven control strategy for Functional Electrical Stimulation (FES), which amplifies volitionally-initiated shoulder abductions, is proposed to improve stroke patients’ rehabilitation. Based on the measured abduction angle, a FES-induced muscle recruitment is generated that yields a pre-specified percentage of this angle – yielding arm weight relief. To guarantee the correct recruitment also under fatigue and uncertain muscle activation we employ feedback control of the recruitment level determined by filtering the FES-evoked electromyogram. Filter parameters are user-optimized to obtain a linear relation between filter output and angle with a good signal-to-noise ratio. The auto-tuned recruitment controller (RC) was tested on five healthy subjects and compared to direct stimulation (DS) while muscle fatigue progressively occurred. Results showed a more linear relation between recruitment level and angle than between non-controlled stimulation intensity and angle ( R 2 = 0.93 vs. R 2 = 0.79 , angular range of 54°). After 6 min of stimulation, abduction decreased by 42% ± 14 for DS and by 0% ± 12 for RC, showing an effective compensation of fatigue. RC yielded significant smaller errors than DS in generating desired angles (0.23% ± 5.9 vs. 14.6% ± 9.7). When FES-induced arm weight support was provided, a mean reduction of the volitional effort (determined by Electromyography) of 78% was achieved compared to angular tracking without FES. First experiments with one acute stroke patient are also reported.


      PubDate: 2016-07-18T06:41:29Z
       
  • The effect of dynamic hip motion on the micromotion of press-fit
           acetabular cups in six degrees of freedom
    • Abstract: Publication date: August 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 8
      Author(s): Emilie A. Crosnier, Patrick S. Keogh, Anthony W. Miles
      The hip joint is subjected to cyclic loading and motion during activities of daily living and this can induce micromotions at the bone-implant interface of cementless total hip replacements. Initial stability has been identified as a crucial factor to achieve osseointegration and long-term survival. Whilst fixation of femoral stems achieves good clinical results, the fixation of acetabular components remains a challenge. In vitro methods assessing cup stability keep the hip joint in a fixed position, overlooking the effect of hip motion. The effect of hip motion on cup micromotion using a hip motion simulator replicating hip flexion-extension and a six degrees of freedom measurement system was investigated. The results show an increase in cup micromotion under dynamic hip motion compared to Static Flexion. This highlights the need to incorporate hip motion and measure all degrees of freedom when assessing cup micromotion. In addition, comparison of two press-fit acetabular cups with different surface coatings suggested similar stability between the two cups. This new method provides a basis for a more representative protocol for future pre-clinical evaluation of different cup designs.


      PubDate: 2016-07-18T06:41:29Z
       
  • Editorial Board
    • Abstract: Publication date: August 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 8




      PubDate: 2016-07-18T06:41:29Z
       
  • Parametric electrical impedance tomography for measuring bone mineral
           density in the pelvis using a computational model
    • Abstract: Publication date: August 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 8
      Author(s): Shani Kimel-Naor, Shimon Abboud, Marina Arad
      Osteoporosis is defined as bone microstructure deterioration resulting a decrease of bone's strength. Measured bone mineral density (BMD) constitutes the main tool for Osteoporosis diagnosis, management, and defines patient's fracture risk. In the present study, parametric electrical impedance tomography (pEIT) method was examined for monitoring BMD, using a computerized simulation model and preliminary real measurements. A numerical solver was developed to simulate surface potentials measured over a 3D computerized pelvis model. Varying cortical and cancellous BMD were simulated by changing bone conductivity and permittivity. Up to 35% and 16% change was found in the real and imaginary modules of the calculated potential, respectively, while BMD changes from 100% (normal) to 60% (Osteoporosis). Negligible BMD relative error was obtained with SNR>60 [dB]. Position changes errors indicate that for long term monitoring, measurement should be taken at the same geometrical configuration with great accuracy. The numerical simulations were compared to actual measurements that were acquired from a healthy male subject using a five electrodes belt bioimpedance device. The results suggest that pEIT may provide an inexpensive easy to use tool for frequent monitoring BMD in small clinics during pharmacological treatment, as a complementary method to DEXA test.


      PubDate: 2016-07-18T06:41:29Z
       
  • Influence of catheter insertion on the hemodynamic environment in coronary
           arteries
    • Abstract: Publication date: Available online 6 July 2016
      Source:Medical Engineering & Physics
      Author(s): Xiaopeng Tian, Anqiang Sun, Xiao Liu, Fang Pu, Xiaoyan Deng, Hongyan Kang, Yubo Fan
      Intravascular stenting is one of the most commonly used treatments to restore the vascular lumen and flow conditions, while perioperative complications such as thrombosis and restenosis are still nagging for patients. As the catheter with crimped stent and folded balloon is directly advanced through coronary artery during surgery, it is destined to cause interference as well as obstructive effect on blood flow. We wonder how the hemodynamic environment would be disturbed and weather these disturbances cause susceptible factors for those complications. Therefore, a realistic three-dimensional model of left coronary artery was reconstructed and blood flow patterns were numerically simulated at seven different stages in the catheter insertion process. The results revealed that the wall shear stress (WSS) and velocity in left anterior descending (LAD) were both significantly increased after catheter inserted into LAD. Besides, the WSS on the catheter, especially at the ending of the catheter, was also at high level. Compared with the condition before catheter inserted, the endothelial cells of LAD was exposed to high-WSS condition and the risk of platelet aggregation in blood flow was increased. These influences may make coronary arteries more vulnerable for perioperative complications.


      PubDate: 2016-07-18T06:41:29Z
       
  • The adaptive drop foot stimulator – Multivariable learning control
           of foot pitch and roll motion in paretic gait
    • Abstract: Publication date: Available online 7 July 2016
      Source:Medical Engineering & Physics
      Author(s): Thomas Seel, Cordula Werner, Thomas Schauer
      Many stroke patients suffer from the drop foot syndrome, which is characterized by a limited ability to lift (the lateral and/or medial edge of) the foot and leads to a pathological gait. In this contribution, we consider the treatment of this syndrome via functional electrical stimulation (FES) of the peroneal nerve during the swing phase of the paretic foot. A novel three-electrodes setup allows us to manipulate the recruitment of m. tibialis anterior and m. fibularis longus via two independent FES channels without violating the zero-net-current requirement of FES. We characterize the domain of admissible stimulation intensities that results from the nonlinearities in patients’ stimulation intensity tolerance. To compensate most of the cross-couplings between the FES intensities and the foot motion, we apply a nonlinear controller output mapping. Gait phase transitions as well as foot pitch and roll angles are assessed in realtime by means of an Inertial Measurement Unit (IMU). A decentralized Iterative Learning Control (ILC) scheme is used to adjust the stimulation to the current needs of the individual patient. We evaluate the effectiveness of this approach in experimental trials with drop foot patients walking on a treadmill and on level ground. Starting from conventional stimulation parameters, the controller automatically determines individual stimulation parameters and thus achieves physiological foot pitch and roll angle trajectories within at most two strides.


      PubDate: 2016-07-18T06:41:29Z
       
  • Accuracy of model-based tracking of knee kinematics and cartilage contact
           measured by dynamic volumetric MRI
    • Abstract: Publication date: Available online 4 July 2016
      Source:Medical Engineering & Physics
      Author(s): Jarred Kaiser, Arezu Monawer, Rajeev Chaudhary, Kevin M. Johnson, Oliver Wieben, Richard Kijowski, Darryl G. Thelen
      The purpose of this study was to determine the accuracy of knee kinematics and cartilage contact measured by volumetric dynamic MRI. A motor-actuated phantom drove femoral and tibial bone segments through cyclic 3D motion patterns. Volumetric images were continuously acquired using a 3D radially undersampled cine spoiled gradient echo sequence (SPGR-VIPR). Image data was binned based on position measured via a MRI-compatible rotary encoder. High-resolution static images were segmented to create bone models. Model-based tracking was performed by optimally registering the bone models to the volumetric images at each frame of the SPGR-VIPR series. 3D tibiofemoral translations and orientations were reconstructed, and compared to kinematics obtained by tracking fiducial markers. Imaging was repeated on a healthy subject who performed cyclic knee flexion-extension. Cartilage contact for the subject was assessed by measuring the overlap between articular cartilage surfaces. Model-based tracking was able to track tibiofemoral angles and translations with precisions less than 0.8° and 0.5mm. These precisions resulted in an uncertainty of less than 0.5mm in cartilage contact location. Dynamic SPGR-VIPR imaging can accurately assess in vivo knee kinematics and cartilage contact during voluntary knee motion performed in a MRI scanner. This technology could facilitate the quantitative investigation of links between joint mechanics and the development of osteoarthritis.


      PubDate: 2016-07-18T06:41:29Z
       
  • In vivo tissue interaction between the transverse carpal ligament and
           finger flexor tendons
    • Abstract: Publication date: Available online 9 July 2016
      Source:Medical Engineering & Physics
      Author(s): Joseph N. Gabra, Joshua L. Gordon, Tamara L. Marquardt, Zong-Ming Li
      The transverse carpal ligament (TCL) is a component of the flexor pulley system of the wrist, keeping the flexor tendons in place by resisting their volar displacement. The purpose of this study was to investigate the in vivo biomechanical interaction between the TCL and flexor tendons in response to tendon tensioning with the wrist at various postures. In eight healthy subjects, the flexor digitorum superficialis and profundus tendons were tensioned by isometrically applying loads (5, 10, and 15N) to the index finger while the wrist posture was at 20° extension, neutral, 20° flexion, and 40° flexion. The TCL and flexor tendons were imaged at the distal carpal tunnel cross section using ultrasound. The volar-dorsal positions of the tendons, TCL arch height, and TCL-tendon distances were calculated. With increasing wrist flexion, the flexor tendons moved volarly, the TCL arch height increased, and the TCL-tendon distances decreased, indicating that the flexor tendons contacted the TCL and pushed it volarly. The TCL-tendon interaction was amplified by the combination of finger loading and wrist flexion. This study provides in vivo evidence of the biomechanical interaction between the TCL and flexor tendons. Repetitive TCL-tendon interactions may implicate the interacting tissues and the median nerve resulting in tissue maladaptation and nerve compression.


      PubDate: 2016-07-18T06:41:29Z
       
  • Mechanical and material properties of cortical and trabecular bone from
           cannabinoid receptor-1-null (Cnr1−/−) mice
    • Abstract: Publication date: Available online 9 July 2016
      Source:Medical Engineering & Physics
      Author(s): Aysha B. Khalid, Simon R. Goodyear, Ruth A. Ross, Richard M. Aspden
      The endocannabinoid system is known for its regulatory effects on bone metabolism through the cannabinoid receptors, Cnr1 and Cnr2. In this study we analysed the mechanical and material properties of long bones from Cnr1−/− mice on a C57BL/6 background. Tibiae and femora from 5- and 12-week-old mice were subjected to three-point bending to measure bending stiffness and yield strength. Elastic modulus, density and mineral content were measured in the diaphysis. Second moment of area (MOA2), inner and outer perimeters of the cortical shaft and trabecular fractional bone volume (BV/TV) were measured using micro-CT. In Cnr1−/− males and females at both ages the bending stiffness was reduced due to a smaller MOA2. Bone from Cnr1−/− females had a greater modulus than wild-type controls, although no differences were observed in males. BV/TV of 12-week-old Cnr1−/− females was greater than controls, although no difference was seen at 5-weeks. On the contrary, Cnr1−/− males had the same BV/TV as controls at 12-weeks while they had significantly lower values at 5-weeks. This study shows that deleting Cnr1 decreases the amount of cortical bone in both males and females at 12-weeks, but increases the amount of trabecular bone only in females.
      Graphical abstract image

      PubDate: 2016-07-18T06:41:29Z
       
  • Additional double-wall roof in single-wall, closed, convective incubators:
           Impact on body heat loss from premature infants and optimal adjustment of
           the incubator air temperature
    • Abstract: Publication date: Available online 4 July 2016
      Source:Medical Engineering & Physics
      Author(s): Stéphane Delanaud, Pauline Decima, Amandine Pelletier, Jean-Pierre Libert, Erwan Stephan-Blanchard, Véronique Bach, Pierre Tourneux
      Radiant heat loss is high in low-birth-weight (LBW) neonates. Double-wall or single-wall incubators with an additional double-wall roof panel that can be removed during phototherapy are used to reduce Radiant heat loss. There are no data on how the incubators should be used when this second roof panel is removed. The aim of the study was to assess the heat exchanges in LBW neonates in a single-wall incubator with and without an additional roof panel. To determine the optimal thermoneutral incubator air temperature. Influence of the additional double-wall roof was assessed by using a thermal mannequin simulating a LBW neonate. Then, we calculated the optimal incubator air temperature from a cohort of human LBW neonate in the absence of the additional roof panel. Twenty-three LBW neonates (birth weight: 750–1800g; gestational age: 28–32 weeks) were included. With the additional roof panel, R was lower but convective and evaporative skin heat losses were greater. This difference can be overcome by increasing the incubator air temperature by 0.15–0.20°C. The benefit of an additional roof panel was cancelled out by greater body heat losses through other routes. Understanding the heat transfers between the neonate and the environment is essential for optimizing incubators.


      PubDate: 2016-07-18T06:41:29Z
       
  • Experimental determination of the emissivity of bone
    • Abstract: Publication date: Available online 4 July 2016
      Source:Medical Engineering & Physics
      Author(s): Arne Feldmann, Philippe Zysset
      Cutting and drilling operations in bone are involved in many orthopedic and otolaryngological surgeries. The temperature elevation of these procedures is potentially harmful to bone and soft tissue cells. The research on this topic aims therefore at minimizing temperature elevation and finding optimal process parameters. Experimental studies are mostly carried out on ex vivo setups using bovine bone material. For temperature measurements, either thermocouples or infrared cameras are used. Infrared cameras have potential advantages, but the emissivity value of the material has to be known. Literature values are scattered and vary within a wide range. An experimental study was carried out to quantify the emissivity using freshly frozen bovine and human bone, as well as human bone samples which were either fixed with Formalin or Thiel solution. Additionally, different surface finishes were used and emissivity was evaluated at different temperatures. The mean emissivity of bone was determined to be ɛ = 0.96 ± 0.01 for temperature elevations up to 60 °C. A slightly higher value of ɛ = 0.97 ± 0.01 was found for temperatures around 80 °C. No significant differences for human or bovine bone samples, preparation or fixation techniques were found.


      PubDate: 2016-07-18T06:41:29Z
       
  • An efficient method to capture the impact of total knee replacement on a
           variety of simulated patient types: A finite element study
    • Abstract: Publication date: Available online 4 July 2016
      Source:Medical Engineering & Physics
      Author(s): Noel Conlisk, Colin R. Howie, Pankaj Pankaj
      Osteoporosis resulting in a reduction in bone stiffness and thinning of the cortex is almost universal in older patients. In this study a novel method to generate computational models of the distal femur which incorporate the effects of ageing and endosteal trabecularisation are presented. Application of this method to pre- and post-knee arthroplasty scenarios is then considered. These computational methods are found to provide a simple yet effective tool for assessing the post-arthroplasty mechanical environment in the knee for different patient types and can help evaluate vulnerability to supracondylar periprosthetic fracture following implantation. Our results show that the stresses in the periprosthetic region increase dramatically with ageing; this is particularly true for higher flexion angles. Stresses in the anterior region of the femoral cortex were also found to increase significantly post-implantation. The most dramatic increases in stresses and strains at these locations were observed in old osteoporotic patients, explaining why this patient group in particular is at greater risk of periprosthetic fractures.


      PubDate: 2016-07-18T06:41:29Z
       
  • Dynamic material characterization of the human heel pad based on in vivo
           experimental tests and numerical analysis
    • Abstract: Publication date: Available online 4 July 2016
      Source:Medical Engineering & Physics
      Author(s): M. Kardeh, T.J. Vogl, F. Huebner, K. Nelson, F. Stief, G. Silber
      A numerical-experimental, proof-of-concept approach is described to characterize the mechanical material behavior of the human heel pad under impact conditions similar to a heel strike while running. A 3D finite-element model of the right foot of a healthy female subject was generated using magnetic resonance imaging. Based on quasi-static experimental testing of the subject's heel pad, force-displacement data was obtained. Using this experimental data as well as a numerical optimization algorithm, an inverse finite-element analysis and the 3D model, heel pad hyperelastic (long-term) material parameters were determined. Applying the same methodology, based on the dynamic experimental data from the impact test and obtained long-term parameters, linear viscoelastic parameters were established with a Prony series. Model validation was performed employing quasi-static and dynamic force-displacement data. Coefficients of determination when comparing model to experimental data during quasi-static and dynamic (initial velocity: 1480mm/s) procedure were R2 = 0.999 and R2 = 0.990, respectively. Knowledge of these heel pad material parameters enables realistic numerical analysis to evaluate internal stress and strain in the heel pad during different quasi-static or dynamic load conditions.


      PubDate: 2016-07-18T06:41:29Z
       
  • In vitro osteocytic microdamage and viability quantification using a
           microloading platform
    • Abstract: Publication date: Available online 4 July 2016
      Source:Medical Engineering & Physics
      Author(s): S.L. York, P. Sethu, M.M. Saunders
      Bone remodeling is a process in which bone is resorbed by osteoclasts and formed by osteoblasts. This is normally a paired process, although it can be disrupted by changes in mechanical load. One theory is that osteocytes play a key role in the cellular regulation of this process. Mechanotransduction studies, which investigate how cells convert mechanical stimuli into biophysical effects and cellular activity, offer one way to investigate this theory. Mechanotransduction work is commonly done by applying an isolated mechanical load to cells grown in vitro, and quantifying the response. While in vitro work does not fully replicate the natural environment, it does allow the study of isolated factors. In this study, a mechanical loading platform was designed, fabricated, and characterized for bone mechanotransduction studies. This platform was designed to tent cell-seeded substrates from below, loading using out of plane distension. This introduced a nonuniform strain profile, enabling the study of cells cultured under identical conditions and variable strains as a function of substrate location. An alphanumerically gridded polydimethylsiloxane well substrate was designed and fabricated for cellular loading experiments. Following initial characterization, a study was run to quantify the cellular activity of osteocyte-like MLO-Y4 cells as a function of strain field. The results indicated that regions with lower strains led to an increase in cellular activity while higher strains led to a reduction in cellular activity. This demonstrated that cells could be exposed to mechanically-induced microdamage using the microloading platform.


      PubDate: 2016-07-18T06:41:29Z
       
  • Erratum to ‘Realistic glottal motion and airflow rate during human
           breathing’. [Medical Engineering & Physics, Volume 37, Issue
           9, September 2015, Pages 829–839]
    • Abstract: Publication date: Available online 12 July 2016
      Source:Medical Engineering & Physics
      Author(s): Adam Scheinherr, Lucie Bailly, Olivier Boiron, Aude Lagier, Thierry Legou, Marine Pichelin, Georges Caillibotte, Antoine Giovanni



      PubDate: 2016-07-18T06:41:29Z
       
  • EEG-based BCI for the linear control of an upper-limb neuroprosthesis
    • Abstract: Publication date: Available online 12 July 2016
      Source:Medical Engineering & Physics
      Author(s): Carmen Vidaurre, Christian Klauer, Thomas Schauer, Ander Ramos-Murguialday, Klaus-Robert Müller
      Assistive technologies help patients to reacquire interacting capabilities with the environment and improve their quality of life. In this manuscript we present a feasibility study in which healthy users were able to use a non-invasive Motor Imagery (MI)-based brain computer interface (BCI) to achieve linear control of an upper-limb functional electrical stimulation (FES) controlled neuro-prosthesis. The linear control allowed the real-time computation of a continuous control signal that was used by the FES system to physically set the stimulation parameters to control the upper-limb position. Even if the nature of the task makes the operation very challenging, the participants achieved a mean selection accuracy of 82.5% in a target selection experiment. An analysis of limb kinematics as well as the positioning precision was performed, showing the viability of using a BCI–FES system to control upper-limb reaching movements. The results of this study constitute an accurate use of an online non-invasive BCI to operate a FES-neuroprosthesis setting a step toward the recovery of the control of an impaired limb with the sole use of brain activity.


      PubDate: 2016-07-18T06:41:29Z
       
  • Identifying characteristic back shapes from anatomical scans of wheelchair
           users to improve seating design
    • Abstract: Publication date: Available online 15 July 2016
      Source:Medical Engineering & Physics
      Author(s): Theresa M. Crytzer, Eun-Kyoung Hong, Brad E. Dicianno, Jon Pearlman, Mark Schmeler, Rory A. Cooper
      Spinal deformities are common in people who require the use of a wheelchair for mobility as a result of spinal cord injuries and other disabilities. Sitting positions vary between individuals with disabilities who use wheelchairs and individuals without disabilities. In individuals with spinal cord injury, spinal deformities can result in the development of back contours that deviate from the shape of standard rigid back support shells. The purpose of this study was to distinguish and classify various back contours of wheelchair users by utilizing digital anatomic scanning technology in order to inform the future development of back supports that would enhance postural support for those with spinal deformities. The three dimensional (3D) locations of bony landmarks were digitized when participants were in position, using a mechanical wand linked to the FastScantm system commonly used to measure surface contours. Raw FastScantm data were transformed according to bony landmarks. A total of 129 individuals participated in this study. A wide range of back contours were identified and categorized. Although participant characteristics (e.g., gender, diagnosis) were similar amongst the contour groups; no one characteristic explained the contours. Participants who were seated in a forward lean position had a higher amount of pelvic obliquity compared to those seated in an upright position; however, participants’ back contour was not correlated with pelvic obliquity. In conclusion, an array of different back shapes were classified in our cohort through 3D laser scanning technology. The methods and technology applied in this study could be replicated in future studies to categorize ranges of back shapes in larger populations of people with spinal cord injuries. Preliminary evidence indicates that customized postural support may be warranted to optimize positioning and posture when a standard rigid shell does not align with contours of a person's back. To optimize positioning, a range of contoured rigid backrests as well as height and angle adjustability are likely needed.


      PubDate: 2016-07-18T06:41:29Z
       
  • In vivo evaluation of a novel, wrist-mounted arterial pressure sensing
           device versus the traditional hand-held tonometer
    • Abstract: Publication date: Available online 15 July 2016
      Source:Medical Engineering & Physics
      Author(s): Orestis Vardoulis, T. Scott Saponas, Dan Morris, Nicolas Villar, Greg Smith, Shwetak Patel, Desney Tan
      Although hemodynamic parameters can be assessed non-invasively, state-of-the-art non-invasive systems generally require an expert operator and are not applicable for ambulatory measurements. These limitations have restricted our understanding of the continuous behavior of hemodynamic parameters. In this manuscript, we introduce a novel wrist-mounted device that incorporates an array of pressure sensors which can be used to extract arterial waveforms and relevant pulse wave analysis biomarkers. In vivo evaluation is performed with Bland–Altman analysis to compare the novel sensor to a gold-standard hand-held tonometer by assessing their reproducibility and agreement in peripheral augmentation index (AIx) estimation at the radial artery. Arterial waves from 28 randomly selected participants were recorded in a controlled environment. Initially we assess the reproducibility of AIx results for both devices. The intra-class correlation coefficient (ICC) and mean difference ± SD were [0.913, 0.033±0.048] and [0.859, 0.039±0.076] for the hand-held and the wrist-mounted tonometer respectively. We then show that the AIx values derived from the novel tonometer have good agreement, accuracy, and precision when compared against the AIx values derived from the reference hand-held tonometer (ICC 0.927, mean difference 0.026±0.049). In conclusion, we have presented evidence that the new wrist-mounted arterial pressure sensor records arterial waveforms that can be processed to yield AIx values that are in good agreement with its traditional hand-held counterpart.


      PubDate: 2016-07-18T06:41:29Z
       
  • Derivation of flow related risk indices for stenosed left anterior
           descending coronary arteries with the use of computer simulations
    • Abstract: Publication date: Available online 4 July 2016
      Source:Medical Engineering & Physics
      Author(s): Konstantinos P. Papadopoulos, Manolis Gavaises, Ioannis Pantos, Demosthenes G. Katritsis, Nicholas Mitroglou
      The geometry of the coronary vessel network is believed to play a decisive role in the initiation, progression and outcome of coronary artery disease (CAD) and the occurrence of acute coronary syndromes (ACS). It also determines the flow field in the coronary artery which can be linked to CAD evolution. In this work geometric 3D models of left anterior descending (LAD) coronary arteries associated with either myocardial infarction (MI) or stable (STA) CAD were constructed. Transient numerical simulations of the flow for each model showed that specific flow patterns develop in different extent in the different groups examined. Recirculation zones, present distal the stenosis in all models, had larger extent and duration in MI cases. For mild stenosis (up to 50%) areas with low time averaged wall shear stress TAWSS (<0.15Pa) as well as areas with high TAWSS (>3Pa) appeared only in MI models; in moderate and severe stenosis (>50%) these areas were present in all models but were significantly larger for MI than STA models. These differentiations were expressed via numerical indices based on TAWSS, oscillating shear index (OSI) and relative residence time (RRT). Additionally we introduced the coagulation activation index (CAI), based on the threshold behaviour of coagulation initiation, which exceeded the suggested threshold only for MI models with intermediate stenosis (up to 50%). These results show that numerical simulations of flow can produce arithmetic indices linked with the risk of CAD complications.


      PubDate: 2016-07-18T06:41:29Z
       
  • Feasibility of freehand ultrasound to measure anatomical features
           associated with deep tissue injury risk
    • Abstract: Publication date: Available online 4 July 2016
      Source:Medical Engineering & Physics
      Author(s): Jonathan S. Akins, Jaxon J. Vallely, Patricia E. Karg, Kara Kopplin, Amit Gefen, Prerna Poojary-Mazzotta, David M. Brienza
      Deep tissue injuries (DTI) are severe forms of pressure ulcers that start internally and are difficult to diagnose. Magnetic resonance imaging (MRI) is the currently preferred imaging modality to measure anatomical features associated with DTI, but is not a clinically feasible risk assessment tool. B-mode ultrasound (US) is proposed as a practical, alternative technology suitable for bedside or outpatient clinic use. The goal of this research was to confirm US as an imaging modality for acquiring measurements of anatomical features associated with DTI. Tissue thickness measurements using US were reliable (ICC=.948) and highly correlated with MRI measurements (muscle r =.988, p ≤ .001; adipose r =.894, p ≤ .001; total r =.919; p ≤ .001). US measures of muscle tissue thickness were 5.4mm (34.1%) higher than MRI, adipose tissue thickness measures were 1.6mm (11.9%) lower, and total tissue thickness measures were 3.8mm (12.8%) higher. Given the reliability and ability to identify high-risk anatomies, as well as the cost effectiveness and availability, US measurements show promise for use in future development of a patient-specific, bedside, biomechanical risk assessment tool to guide clinicians in appropriate interventions to prevent DTI.


      PubDate: 2016-07-18T06:41:29Z
       
  • Concurrent validity of the Microsoft Kinect for Windows v2 for measuring
           spatiotemporal gait parameters
    • Abstract: Publication date: Available online 4 July 2016
      Source:Medical Engineering & Physics
      Author(s): Elham Dolatabadi, Babak Taati, Alex Mihailidis
      This paper presents a study to evaluate the concurrent validity of the Microsoft Kinect for Windows v2 for measuring the spatiotemporal parameters of gait. Twenty healthy adults performed several sequences of walks across a GAITRite mat under three different conditions: usual pace, fast pace, and dual task. Each walking sequence was simultaneously captured with two Kinect for Windows v2 and the GAITRite system. An automated algorithm was employed to extract various spatiotemporal features including stance time, step length, step time and gait velocity from the recorded Kinect v2 sequences. Accuracy in terms of reliability, concurrent validity and limits of agreement was examined for each gait feature under different walking conditions. The 95% Bland–Altman limits of agreement were narrow enough for the Kinect v2 to be a valid tool for measuring all reported spatiotemporal parameters of gait in all three conditions. An excellent intraclass correlation coefficient (ICC 2, 1) ranging from 0.9 to 0.98 was observed for all gait measures across different walking conditions. The inter trial reliability of all gait parameters were shown to be strong for all walking types (ICC 3, 1 > 0.73). The results of this study suggest that the Kinect for Windows v2 has the capacity to measure selected spatiotemporal gait parameters for healthy adults.


      PubDate: 2016-07-18T06:41:29Z
       
  • A new shoulder model with a biologically inspired glenohumeral joint
    • Abstract: Publication date: Available online 2 July 2016
      Source:Medical Engineering & Physics
      Author(s): C. Quental, J. Folgado, J. Ambrósio, J. Monteiro
      Kinematically unconstrained biomechanical models of the glenohumeral (GH) joint are needed to study the GH joint function, especially the mechanisms of joint stability. The purpose of this study is to develop a large-scale multibody model of the upper limb that simulates the 6 degrees of freedom (DOF) of the GH joint and to propose a novel inverse dynamics procedure that allows the evaluation of not only the muscle and joint reaction forces of the upper limb but also the GH joint translations. The biomechanical model developed is composed of 7 rigid bodies, constrained by 6 anatomical joints, and acted upon by 21 muscles. The GH joint is described as a spherical joint with clearance. Assuming that the GH joint translates according to the muscle load distribution, the redundant muscle load sharing problem is formulated considering as design variables the 3 translational coordinates associated with the GH joint translations, the joint reaction forces associated with the remaining kinematic constraints, and the muscle activations. For the abduction motion in the frontal plane analysed, the muscle and joint reaction forces estimated by the new biomechanical model proposed are similar to those estimated by a model in which the GH joint is modeled as an ideal spherical joint. Even though this result supports the assumption of an ideal GH joint to study the muscle load sharing problem, only a 6 DOF model of the GH joint, as the one proposed here, provides information regarding the joint translations. In this study, the biomechanical model developed predicts an initial upward and posterior migration of the humeral head, followed by an inferior and anterior movement, which is in good agreement with the literature.
      Graphical abstract image

      PubDate: 2016-07-18T06:41:29Z
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • Editorial Board
    • Abstract: Publication date: July 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 7




      PubDate: 2016-05-29T11:39:41Z
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
 
 
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