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Showing 1401 - 1600 of 1720 Journals sorted alphabetically
Wiley Interdisciplinary Reviews : Membrane Transport and Signaling     Hybrid Journal  
Wiley Interdisciplinary Reviews : RNA     Hybrid Journal   (Followers: 3)
World Crop Pests     Full-text available via subscription   (Followers: 1)
World Mycotoxin Journal     Full-text available via subscription   (Followers: 6)
Xenobiotica     Hybrid Journal   (Followers: 10)
Yeast     Hybrid Journal   (Followers: 10)
Zebrafish     Hybrid Journal   (Followers: 1)
Zeitschrift für Evidenz, Fortbildung und Qualität im Gesundheitswesen     Full-text available via subscription   (Followers: 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]
  • 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
       
  • Optimal calibration of instrumented treadmills using an instrumented pole
    • Abstract: Publication date: Available online 11 May 2016
      Source:Medical Engineering & Physics
      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: 2016-05-14T10:10:55Z
       
  • 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
       
  • Parametric electrical impedance tomography for measuring bone mineral
           density in the pelvis using a computational model
    • Abstract: Publication date: Available online 13 May 2016
      Source:Medical Engineering & Physics
      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: 2016-05-14T10:10:55Z
       
  • 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
       
  • Editorial Board
    • Abstract: Publication date: May 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 5




      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
       
  • Red blood cell ghosts as promising drug carriers to target wound
           infections
    • Abstract: Publication date: Available online 6 April 2016
      Source:Medical Engineering & Physics
      Author(s): Kulzhan Berikkhanova, Rustam Omarbaev, Alexandr Gulyayev, Zarina Shulgau, Dilbar Ibrasheva, Gulsim Adilgozhina, Shynggys Sergazy, Zhaxybay Zhumadilov, Sholpan Askarova
      Autologous red blood cell ghosts (RBC ghosts) can carry cytokines to the sites of inflammation. The targeting moiety of the RBC ghosts is associated with the nature of purulent inflammation, where the erythrocytes are phagocyted and encapsulated drugs are released. In the present study we have investigated the healing potential of RBC ghosts loaded with cytokine IL-1β and antibiotic. Additionally, the pharmacokinetic properties of RBC ghosts loaded with IL-1β were studied. 35 Male Wistar rats (250–300g) were used in the pharmacokinetic study and in a wound infection model where a suspension of Staphylococcus aureus was placed into a surgical cut of the skin and subcutaneous tissue in the femoral region. In order to monitor progression of the wound repair processes, wound swabs or aspiration biopsies were taken for analyses on the 1st–6th days. Wound repair dynamics assessment was based on suppression of S. aureus growth, signs of pain, time of disappearance of pus and infiltration around the wound. Visual observations, as well as microbiological and cytological analysis of wound exudates demonstrated a significant acceleration of healing processes in a group of animals treated with a local injection of IL-1β and ceftriaxone encapsulated into RBC ghosts when compared to the animals treated either with a local or IM injection of free drugs. For the pharmacokinetic study, single IV injections of either free or encapsulated IL-1β were made and the concentration of IL-1β in serum samples and tissue homogenates were determined. Encapsulation in RBC ghosts improved pharmacokinetic profiles of IL-1β by increasing the half-life, reducing its clearance, and increasing the deposition of the drug in the liver, spleen and lungs. These data suggest that RBC ghosts are effective drug carriers for targeted delivery of cytokines to the sites of inflammation, and have a potential for improving the treatment outcomes of purulent diseases.


      PubDate: 2016-04-09T05:35:45Z
       
  • 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
       
  • An external portable device for adaptive deep brain stimulation (aDBS)
           clinical research in advanced Parkinson's Disease
    • Abstract: Publication date: Available online 27 March 2016
      Source:Medical Engineering & Physics
      Author(s): Mattia Arlotti, Lorenzo Rossi, Manuela Rosa, Sara Marceglia, Alberto Priori
      Compared to conventional deep brain stimulation (DBS) for patients with Parkinson's Disease (PD), the newer approach of adaptive DBS (aDBS), regulating stimulation on the basis of the patient's clinical state, promises to achieve better clinical outcomes, avoid adverse-effects and save time for tuning parameters. A remaining challenge before aDBS comes into practical use is to prove its feasibility and its effectiveness in larger groups of patients and in more ecological conditions. We developed an external portable aDBS system prototype designed for clinical testing in freely-moving PD patients with externalized DBS electrodes. From a single-channel bipolar artifact-free recording, it analyses local field potentials (LFPs), during ongoing DBS for tuning stimulation parameters, independent from the specific feedback algorithm implemented. We validated the aDBS system in vitro, by testing both its sensing and closed-loop stimulation capabilities, and then tested it in vivo, focusing on the sensing capabilities. By applying the aDBS system prototype in a patient with PD, we provided evidence that it can track levodopa and DBS-induced LFP spectral power changes among different patient's clinical states. Our system, intended for testing LFP-based feedback strategies for aDBS, should help understanding how and whether aDBS therapy works in PD and indicating future technical and clinical advances.


      PubDate: 2016-03-28T03:44:03Z
       
  • Radiofrequency ablation with a vibrating catheter: A new method for
           electrode cooling
    • Abstract: Publication date: Available online 21 March 2016
      Source:Medical Engineering & Physics
      Author(s): Kaihong Yu, Tetsui Yamashita, Shigeaki Shingyochi, Kazuo Matsumoto, Makoto Ohta
      A new electrode cooling system using a vibrating catheter is described for conditions of low blood flow when saline irrigation cannot be used. Vibrations of the catheter are hypothesized to disturb blood flow around the electrode, leading to increased convective cooling of the electrode. The aim of this study is to confirm the cooling effect of vibration and investigate the associated mechanisms. As methods, an in vitro system with polyvinyl alcohol-hydrogel (PVA-H) as ablated tissue and saline flow in an open channel was used to measure changes in electrode and tissue temperatures under vibration of 0–63Hz and flow velocity of 0–0.1m/s. Flow around the catheter was observed using particle image velocimetry (PIV). Results show that under conditions of no flow, electrode temperatures decreased with increasing vibration frequency, and in the absence of vibrations, electrode temperatures decreased with increasing flow velocity. In the presence of vibrations, electrode temperatures decreased under conditions of low flow velocity, but not under those of high flow velocity. PIV analyses showed disturbed flow around the vibrating catheter, and flow velocity around the catheter increased with higher-frequency vibrations. In conclusion, catheter vibration facilitated electrode cooling by increasing flow around the catheter, and cooling was proportional to vibration frequency.


      PubDate: 2016-03-24T03:09:52Z
       
  • Product limit estimation for capturing of pressure distribution dynamics
    • Abstract: Publication date: Available online 22 March 2016
      Source:Medical Engineering & Physics
      Author(s): Michael Wininger, Barbara A. Crane
      Measurement of contact pressures at the wheelchair-seating interface is a critically important approach for laboratory research and clinical application in monitoring risk for pressure ulceration. As yet, measures obtained from pressure mapping are static in nature: there is no accounting for changes in pressure distribution over time, despite the well-known interaction between time and pressure in risk estimation. Here, we introduce the first dynamic analysis for distribution of pressure data, based on the Kaplan–Meier (KM) Product Limit Estimator (PLE) a ubiquitous tool encountered in clinical trials and survival analysis. In this approach, the pressure array-over-time data set is sub-sampled two frames at a time (random pairing), and their similarity of pressure distribution is quantified via a correlation coefficient. A large number (here: 100) of these frame pairs is then sorted into descending order of correlation value, and visualized as a KM curve; we build confidence limits via a bootstrap computed over 1000 replications. PLEs and the KM have robust statistical support and extensive development: the opportunities for extended application are substantial. We propose that the KM-PLE in particular, and dynamic analysis in general, may provide key leverage on future development of seating technology, and valuable new insight into extant datasets.


      PubDate: 2016-03-24T03:09:52Z
       
  • Influence of fibrous encapsulation on electro-chemical properties of TiN
           electrodes
    • Abstract: Publication date: Available online 17 March 2016
      Source:Medical Engineering & Physics
      Author(s): Suzan Meijs, Morten Fjorback, Carina Jensen, Søren Sørensen, Kristian Rechendorff, Nico J.M. Rijkhoff
      The aim of this study was to investigate how the electrochemical properties of porous titanium nitride stimulation electrode are affected by fibrous encapsulation in vivo. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry and voltage transient (VT) measurements were performed in vivo and in phosphate buffered saline, where the encapsulation process is absent. EIS was used as a non-invasive measurement to follow the inflammation, healing and encapsulation process. EIS showed that the healing and encapsulation process lasted 3–4 weeks. The VTs increased during the first 3–4 weeks, after which they stabilized. The charge storage capacity (CSC) decreased most during the first 3–4 weeks. The increasing VTs and decreasing CSC during the first 3–4 weeks after implantation of the in vivo electrodes seem related to healing and fibrous encapsulation. It is suggested that the charge injection pathway during the encapsulation process changes, which implies that charge injection limits are underestimated with conventional methods.
      Graphical abstract image

      PubDate: 2016-03-20T02:46:24Z
       
  • Non-invasive estimation of static and pulsatile intracranial pressure from
           transcranial acoustic signals
    • Abstract: Publication date: Available online 17 March 2016
      Source:Medical Engineering & Physics
      Author(s): Alexandra Levinsky, Surik Papyan, Guy Weinberg, Trond Stadheim, Per Kristian Eide
      The aim of the present study was to examine whether a method for estimation of non-invasive ICP (nICP) from transcranial acoustic (TCA) signals mixed with head-generated sounds estimate the static and pulsatile invasive ICP (iICP). For that purpose, simultaneous iICP and mixed TCA signals were obtained from patients undergoing continuous iICP monitoring as part of clinical management. The ear probe placed in the right outer ear channel sent a TCA signal with fixed frequency (621Hz) that was picked up by the left ear probe along with acoustic signals generated by the intracranial compartment. Based on a mathematical model of the association between mixed TCA and iICP, the static and pulsatile nICP values were determined. Total 39 patients were included in the study; the total number of observations for prediction of static and pulsatile iICP were 5789 and 6791, respectively. The results demonstrated a good agreement between iICP/nICP observations, with mean difference of 0.39mmHg and 0.53mmHg for static and pulsatile ICP, respectively. In summary, in this cohort of patients, mixed TCA signals estimated the static and pulsatile iICP with rather good accuracy. Further studies are required to validate whether mixed TCA signals may become useful for measurement of nICP.


      PubDate: 2016-03-20T02:46:24Z
       
  • Objectively quantifying walking ability in degenerative spinal disorder
           patients using sensor equipped smart shoes
    • Abstract: Publication date: Available online 9 March 2016
      Source:Medical Engineering & Physics
      Author(s): Sunghoon Ivan Lee, Eunjeong Park, Alex Huang, Bobak Mortazavi, Jordan Hayward Garst, Nima Jahanforouz, Marie Espinal, Tiffany Siero, Sophie Pollack, Marwa Afridi, Meelod Daneshvar, Saif Ghias, Daniel C. Lu, Majid Sarrafzadeh
      Lumbar spinal stenosis (LSS) is a condition associated with the degeneration of spinal disks in the lower back. A significant majority of the elderly population experiences LSS, and the number is expected to grow. The primary objective of medical treatment for LSS patients has focused on improving functional outcomes (e.g., walking ability) and thus, an accurate, objective, and inexpensive method to evaluate patients’ functional levels is in great need. This paper aims to quantify the functional level of LSS patients by analyzing their clinical information and their walking ability from a 10 m self-paced walking test using a pair of sensorized shoes. Machine learning algorithms were used to estimate the Oswestry Disability Index, a clinically well-established functional outcome, from a total of 29 LSS patients. The estimated ODI scores showed a significant correlation to the reported ODI scores with a Pearson correlation coefficient (r) of 0.81 and p < 3.5 × 10 − 11 . It was further shown that the data extracted from the sensorized shoes contribute most to the reported estimation results, and that the contribution of the clinical information was minimal. This study enables new research and clinical opportunities for monitoring the functional level of LSS patients in hospital and ambulatory settings.


      PubDate: 2016-03-12T01:44:57Z
       
  • Predictive statistical models of baseline variations in 3-D femoral cortex
           morphology
    • Abstract: Publication date: Available online 10 March 2016
      Source:Medical Engineering & Physics
      Author(s): Ju Zhang, Jacqui Hislop-Jambrich, Thor F. Besier
      Quantifying human femoral cortex morphology is important for forensic science, surgical planning, prosthesis design and musculoskeletal modeling. Previous studies have been restricted by traditional zero or one dimensional morphometric measurements at discrete locations. We have used automatic image segmentation and statistical shape modeling methods to create predictive models of baseline 3-D femoral cortex morphology on a statistically significant population. A total of 204 femurs were automatically segmented and measured to obtain 3-D shape, whole-surface cortical thickness, and morphometric measurements. Principal components of shape and cortical thickness were correlated to anthropological data (age, sex, height and body mass) to produce predictive statistical models. We show that predictions of an individual's age, height, and sex can be improved by using 3-D shape and cortical thickness when compared with traditional morphometric measurements. We also show that femoral cortex geometry can be predicted from anthropological data combined with femoral measurements with less than 2.3mm root mean square error, and cortical thickness with less than 0.5mm root mean square error. The predictive models presented offer new ways to infer subject-specific 3-D femur morphology from sparse subject data for biomechanical simulations, and inversely infer subject data from femur morphology for anthropological and forensic studies.
      Graphical abstract image

      PubDate: 2016-03-12T01:44:57Z
       
  • Finite element analysis of the lumbar destabilization following pedicle
           subtraction osteotomy
    • Abstract: Publication date: Available online 8 March 2016
      Source:Medical Engineering & Physics
      Author(s): Claudia Ottardi, Fabio Galbusera, Andrea Luca, Liliana Prosdocimo, Maurizio Sasso, Marco Brayda-Bruno, Tomaso Villa
      This study aims to analyze the destabilization produced following a pedicle subtraction osteotomy (PSO), with a calibrated numerical model. A 30° resection was created on L3 and L4. Range of Motion (ROM) and the force acting on the vertebral body were calculated. Osteotomies consistently increased the ROMs. In the intact model, 87% of the compressive load was acting on the vertebral bodies whereas in the destabilized models all the load was on the fractured surface. Osteotomies at both levels induced a marked instability but the PSO at L4 seemed to have a greater influence on the ROM. Despite the significant deformity corrections which could be achieved with PSO, this technique needs further analyses.


      PubDate: 2016-03-12T01:44:57Z
       
  • Structural identifiability analysis of a cardiovascular system model
    • Abstract: Publication date: Available online 9 March 2016
      Source:Medical Engineering & Physics
      Author(s): Antoine Pironet, Pierre C. Dauby, J. Geoffrey Chase, Paul D. Docherty, James A. Revie, Thomas Desaive
      The six-chamber cardiovascular system model of Burkhoff and Tyberg has been used in several theoretical and experimental studies. However, this cardiovascular system model (and others derived from it) are not identifiable from any output set. In this work, two such cases of structural non-identifiability are first presented. These cases occur when the model output set only contains a single type of information (pressure or volume). A specific output set is thus chosen, mixing pressure and volume information and containing only a limited number of clinically available measurements. Then, by manipulating the model equations involving these outputs, it is demonstrated that the six-chamber cardiovascular system model is structurally globally identifiable. A further simplification is made, assuming known cardiac valve resistances. Because of the poor practical identifiability of these four parameters, this assumption is usual. Under this hypothesis, the six-chamber cardiovascular system model is structurally identifiable from an even smaller dataset. As a consequence, parameter values computed from limited but well-chosen datasets are theoretically unique. This means that the parameter identification procedure can safely be performed on the model from such a well-chosen dataset. Thus, the model may be considered suitable for use in diagnosis.
      Graphical abstract image

      PubDate: 2016-03-12T01:44:57Z
       
  • Editorial Board
    • Abstract: Publication date: April 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 4




      PubDate: 2016-03-12T01:44:57Z
       
  • Towards compliant and wearable robotic orthoses: A review of current and
           emerging actuator technologies
    • Abstract: Publication date: Available online 26 February 2016
      Source:Medical Engineering & Physics
      Author(s): Allan Joshua Veale, Shane Quan Xie
      Robotic orthoses, or exoskeletons, have the potential to provide effective rehabilitation while overcoming the availability and cost constraints of therapists. However, current orthosis actuation systems use components designed for industrial applications, not specifically for interacting with humans. This can limit orthoses' capabilities and, if their users’ needs are not adequately considered, contribute to their abandonment. Here, a user centered review is presented on: requirements for orthosis actuators; the electric, hydraulic, and pneumatic actuators currently used in orthoses and their advantages and limitations; the potential of new actuator technologies, including smart materials, to actuate orthoses; and the future of orthosis actuator research.


      PubDate: 2016-03-02T00:20:11Z
       
  • How measurement artifacts affect cerebral autoregulation outcomes: A
           technical note on transfer function analysis
    • Abstract: Publication date: Available online 28 February 2016
      Source:Medical Engineering & Physics
      Author(s): Aisha S.S. Meel-van den Abeelen, Daan L.K. de Jong, Joep Lagro, Ronney B. Panerai, Jurgen A.H.R. Claassen
      Cerebral autoregulation (CA) is the mechanism that aims to maintain adequate cerebral perfusion during changes in blood pressure (BP). Transfer function analysis (TFA), the most reported method in literature to quantify CA, shows large between-study variability in outcomes. The aim of this study is to investigate the role of measurement artifacts in this variation. Specifically, the role of distortion in the BP and/or CBFV measurementon TFA outcomes was investigated. The influence of three types of artifacts on TFA outcomes was studied: loss of signal, motion artifacts, and baseline drifts. TFA metrics of signals without the simulated artifacts were compared with those of signals with artifacts. TFA outcomes scattered highly when more than 10% of BP signal or over 8% of the CBFV signal was lost, or when measurements contained one or more artifacts resulting from head movement. Furthermore, baseline drift affected interpretation of TFA outcomes when the power in the BP signal was 5 times the power in the LF band. In conclusion, loss of signal in BP and loss in CBFV, affects interpretation of TFA outcomes. Therefore, it is vital to validate signal quality to the defined standards before interpreting TFA outcomes.


      PubDate: 2016-03-02T00:20:11Z
       
  • A quantitative measurement method for comparison of seated postures
    • Abstract: Publication date: Available online 23 February 2016
      Source:Medical Engineering & Physics
      Author(s): Susan J Hillman, James Hollington
      This technical note proposes a method to measure and compare seated postures. The three-dimensional locations of palpable anatomical landmarks corresponding to the anterior superior iliac spines, clavicular notch, head, shoulders and knees are measured in terms of x, y and z co-ordinates in the reference system of the measuring apparatus. These co-ordinates are then transformed onto a body-based axis system which allows comparison within-subject. The method was tested on eleven unimpaired adult participants and the resulting data used to calculate a Least Significant Difference (LSD) for the measure, which is used to determine whether two postures are significantly different from one another. The method was found to be sensitive to the four following standardised static postural perturbations: posterior pelvic tilt, pelvic obliquity, pelvic rotation, and abduction of the thighs. The resulting data could be used as an outcome measure for the postural alignment aspect of seating interventions in wheelchairs.


      PubDate: 2016-02-25T23:41:03Z
       
  • Influence of lumbar spine rhythms and intra-abdominal pressure on spinal
           loads and trunk muscle forces during upper body inclination
    • Abstract: Publication date: Available online 24 February 2016
      Source:Medical Engineering & Physics
      Author(s): Rizwan Arshad, Thomas Zander, Marcel Dreischarf, Hendrik Schmidt
      Improved knowledge on spinal loads and trunk muscle forces may clarify the mechanical causes of various spinal diseases and has the potential to improve the current treatment options. Using an inverse dynamic musculoskeletal model, this sensitivity analysis was aimed to investigate the influence of lumbar spine rhythms and intra-abdominal pressure on the compressive and shear forces in L4-L5 disc and the trunk muscle forces during upper body inclination. Based on in vivo data, three different spine rhythms (SRs) were used along with alternative settings (with/without) of intra-abdominal pressure (IAP). Compressive and shear forces in L4-L5 disc as well as trunk muscle forces were predicted by inverse static simulations from standing upright to 55° of intermediate trunk inclination. Alternate model settings of intra-abdominal pressure and different spine rhythms resulted in significant variation of compression (763N) and shear forces (195N) in the L4-L5 disc and in global (454N) and local (156N) trunk muscle forces at maximum flexed position. During upper body inclination, the compression forces at L4-L5 disc were mostly released by IAP and increased for larger intervertebral rotation in a lumbar spine rhythm. This study demonstrated that with various possible assumptions of lumbar spine rhythm and intra-abdominal pressure, variation in predicted loads and muscles forces increase with larger flexion. It is therefore, essential to adapt these model parameters for accurate prediction of spinal loads and trunk muscle forces.


      PubDate: 2016-02-25T23:41:03Z
       
  • Design and evaluation of an actuated knee implant for postoperative
           ligament imbalance correction
    • Abstract: Publication date: Available online 29 January 2016
      Source:Medical Engineering & Physics
      Author(s): A. Collo, S. Almouahed, P. Poignet, C. Hamitouche, E. Stindel
      In Total Knee Arthroplasty (TKA), the collateral ligament tensioning stage cannot be standardised for all patients and relies heavily on the surgeon’s experience and perception. Intraoperative inaccuracies are practically unavoidable and may give rise to severe postoperative complications, leading to the need for revision surgery already a few years after primary TKA. This work proposes a novel instrumented tibial component able to detect collateral ligament laxity conditions right after primary TKA and, if needed, to compensate for them in the postoperative period. A miniaturised actuation system, designed to be embedded in the tibial baseplate, was initially evaluated by means of 3D simulations and then fabricated as a full-scale prototype. Stability and force sensors tests carried out on a knee simulator allowed to assess the effectiveness of the proposed design under normal working conditions and provided valuable insights for future work and improvements.


      PubDate: 2016-02-08T20:22:50Z
       
 
 
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