for Journals by Title or ISSN
for Articles by Keywords
help
  Subjects -> BIOLOGY (Total: 2953 journals)
    - BIOCHEMISTRY (230 journals)
    - BIOENGINEERING (104 journals)
    - BIOLOGY (1413 journals)
    - BIOPHYSICS (45 journals)
    - BIOTECHNOLOGY (205 journals)
    - BOTANY (212 journals)
    - CYTOLOGY AND HISTOLOGY (26 journals)
    - ENTOMOLOGY (63 journals)
    - GENETICS (161 journals)
    - MICROBIOLOGY (255 journals)
    - MICROSCOPY (10 journals)
    - ORNITHOLOGY (26 journals)
    - PHYSIOLOGY (69 journals)
    - ZOOLOGY (134 journals)

BIOLOGY (1413 journals)            First | 1 2 3 4 5 6 7 8 | Last

Showing 1401 - 1600 of 1720 Journals sorted alphabetically
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: 6)
Zeitschrift für Naturforschung C : A Journal of Biosciences     Open Access   (Followers: 2)
Биологический вестник МГПУ имени Богдана Хмельницкого     Open Access   (Followers: 1)

  First | 1 2 3 4 5 6 7 8 | Last

Journal Cover Medical Engineering & Physics
  [SJR: 0.784]   [H-I: 76]   [9 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1350-4533
   Published by Elsevier Homepage  [3039 journals]
  • Experimental investigation and statistical modeling of temperature rise in
           rotary ultrasonic bone drilling
    • Abstract: Publication date: Available online 14 September 2016
      Source:Medical Engineering & Physics
      Author(s): Vishal Gupta, Pulak M. Pandey
      Thermal necrosis is one of the major problems associated with the bone drilling process in orthopedic/trauma surgical operations. To overcome this problem a new bone drilling method has been introduced recently. Studies have been carried out with rotary ultrasonic drilling (RUD) on pig bones using diamond coated abrasive hollow tools. In the present work, influence of process parameters (rotational speed, feed rate, drill diameter and vibrational amplitude) on change in the temperature was studied using design of experiment technique i.e., response surface methodology (RSM) and data analysis was carried out using analysis of variance (ANOVA). Temperature was recorded and measured by using embedded thermocouple technique at a distance of 0.5mm, 1.0mm, 1.5mm and 2.0mm from the drill site. Statistical model was developed to predict the maximum temperature at the drill tool and bone interface. It was observed that temperature increased with increase in the rotational speed, feed rate and drill diameter and decreased with increase in the vibrational amplitude.


      PubDate: 2016-09-17T20:56:52Z
       
  • A review of the design and clinical evaluation of the ShefStim array-based
           functional electrical stimulation system
    • Abstract: Publication date: Available online 14 September 2016
      Source:Medical Engineering & Physics
      Author(s): Laurence P. Kenney, Ben W. Heller, Anthony T. Barker, Mark L. Reeves, Jamie Healey, Timothy R. Good, Glen Cooper, Ning Sha, Sarah Prenton, Anmin Liu, David Howard
      Functional electrical stimulation has been shown to be a safe and effective means of correcting foot drop of central neurological origin. Current surface-based devices typically consist of a single channel stimulator, a sensor for determining gait phase and a cuff, within which is housed the anode and cathode. The cuff-mounted electrode design reduces the likelihood of large errors in electrode placement, but the user is still fully responsible for selecting the correct stimulation level each time the system is donned. Researchers have investigated different approaches to automating aspects of setup and/or use, including recent promising work based on iterative learning techniques. This paper reports on the design and clinical evaluation of an electrode array-based FES system for the correction of drop foot, ShefStim. The paper reviews the design process from proof of concept lab-based study, through modelling of the array geometry and interface layer to array search algorithm development. Finally, the paper summarises two clinical studies involving patients with drop foot. The results suggest that the ShefStim system with automated setup produces results which are comparable with clinician setup of conventional systems. Further, the final study demonstrated that patients can use the system without clinical supervision. When used unsupervised, setup time was 14min (9min for automated search plus 5min for donning the equipment), although this figure could be reduced significantly with relatively minor changes to the design.


      PubDate: 2016-09-17T20:56:52Z
       
  • Morphology based anisotropic finite element models of the proximal femur
           validated with experimental data
    • Abstract: Publication date: Available online 15 September 2016
      Source:Medical Engineering & Physics
      Author(s): W.S. Enns-Bray, O. Ariza, S. Gilchrist, R.P. Widmer Soyka, P.J. Vogt, H. Palsson, S.K. Boyd, P. Guy, P.A. Cripton, S.J. Ferguson, B. Helgason
      Finite element analysis (FEA) of bones scanned with Quantitative Computed Tomography (QCT) can improve early detection of osteoporosis. The accuracy of these models partially depends on the assigned material properties, but anisotropy of the trabecular bone cannot be fully captured due to insufficient resolution of QCT. The inclusion of anisotropy measured from high resolution peripheral QCT (HR-pQCT) could potentially improve QCT-based FEA of the femur, although no improvements have yet been demonstrated in previous experimental studies. This study analyzed the effects of adding anisotropy to clinical resolution femur models by constructing six sets of FE models (two isotropic and four anisotropic) for each specimen from a set of sixteen femurs that were experimentally tested in sideways fall loading with a strain gauge on the superior femoral neck. Two different modulus–density relationships were tested, both with and without anisotropy derived from mean intercept length analysis of HR-pQCT scans. Comparing iso- and anisotropic models to the experimental data resulted in nearly identical correlation and highly similar linear regressions for both whole bone stiffness and strain gauge measurements. Anisotropic models contained consistently greater principal compressive strains, approximately 14% in magnitude, in certain internal elements located in the femoral neck, greater trochanter, and femoral head. In summary, anisotropy had minimal impact on macroscopic measurements, but did alter internal strain behavior. This suggests that organ level QCT-based FE models measuring femoral stiffness have little to gain from the addition of anisotropy, but studies considering failure of internal structures should consider including anisotropy to their models.


      PubDate: 2016-09-17T20:56:52Z
       
  • Numerical prediction of peri-implant bone adaptation: Comparison of
           mechanical stimuli and sensitivity to modeling parameters
    • Abstract: Publication date: Available online 15 September 2016
      Source:Medical Engineering & Physics
      Author(s): Marco Piccinini, Joel Cugnoni, John Botsis, Patrick Ammann, Anselm Wiskott
      Long term durability of osseointegrated implants depends on bone adaptation to stress and strain occurring in proximity of the prosthesis. Mechanical overloading, as well as disuse, may reduce the stability of implants by provoking bone resorption. However, an appropriate mechanical environment can improve integration. Several studies have focused on the definition of numerical methods to predict bone peri-implant adaptation to the mechanical environment. Existing adaptation models differ notably in the type of mechanical variable adopted as stimulus but also in the bounds and shape of the adaptation rate equation. However, a general comparison of the different approaches on a common benchmark case is still missing and general guidelines to determine physically sound parameters still need to be developed. This current work addresses these themes in two steps. Firstly, the histograms of effective stress, strain and strain energy density are compared for rat tibiae in physiological (homeostatic) conditions. According to the Mechanostat, the ideal stimulus should present a clearly defined, position and tissue invariant lazy zone in homeostatic conditions. Our results highlight that only the octahedral shear strain presents this characteristic and can thus be considered the optimal choice for implementation of a continuum level bone adaptation model. Secondly, critical modeling parameters such as lazy zone bounds, type of rate equation and bone overloading response are classified depending on their influence on the numerical predictions of bone adaptation. Guidelines are proposed to establish the dominant model parameters based on experimental and simulated data.


      PubDate: 2016-09-17T20:56:52Z
       
  • Effects of implant drilling parameters for pilot and twist drills on
           temperature rise in bone analog and alveolar bones
    • Abstract: Publication date: Available online 16 September 2016
      Source:Medical Engineering & Physics
      Author(s): Yung-Chuan Chen, Chih-Kun Hsiao, Ji-Sih Ciou, Yi-Jung Tsai, Yuan-Kun Tu
      This study concerns the effects of different drilling parameters of pilot drills and twist drills on the temperature rise of alveolar bones during dental implant procedures. The drilling parameters studied here include the feed rate and rotation speed of the drill. The bone temperature distribution was analyzed through experiments and numerical simulations of the drilling process. In this study, a three dimensional (3D) elasto-plastic dynamic finite element model (DFEM) was proposed to investigate the effects of drilling parameters on the bone temperature rise. In addition, the FE model is validated with drilling experiments on artificial human bones and porcine alveolar bones. The results indicate that 3D DFEM can effectively simulate the bone temperature rise during the drilling process. During the drilling process with pilot drills or twist drills, the maximum bone temperature occurred in the region of the cancellous bones close to the cortical bones. The feed rate was one of the important factors affecting the time when the maximum bone temperature occurred. Our results also demonstrate that the elevation of bone temperature was reduced as the feed rate increased and the drill speed decreased, which also effectively reduced the risk region of osteonecrosis. These findings can serve as a reference for dentists in choosing drilling parameters for dental implant surgeries.


      PubDate: 2016-09-17T20:56:52Z
       
  • Termination of atrial spiral waves by traction into peripheral non 1:1
           conducting regions – A numerical study
    • Abstract: Publication date: Available online 7 September 2016
      Source:Medical Engineering & Physics
      Author(s): Amit Rozner, Sharon Zlochiver
      Atrial ablation has been recently utilized to treat atrial fibrillation (AF) by isolation or destruction of arrhythmia drivers. In chronic or persistent AF patients these drivers often consist of one or few rotors at unknown locations, and several ablations are commonly conducted before arrhythmia is terminated. However, the irreversible damage done to the tissue may lead to AF recurrence. We propose an alternative strategy to terminate rotor activity by its attraction into a non 1:1 conducting region. The feasibility of the method was numerically tested in 2D models of chronic AF human atrial tissue. Left-to-right gradients of either acetylcholine (ACh) or potassium conductance were employed to generate regions of 1:1 and non 1:1 conduction, characterized by their dominant frequency (DF) ratios. Spiral waves were established in the 1:1 conducting region and raster scanning was employed using a stimulating probe to attract the spiral wave tip. The probe was then linearly moved towards the boundary between the two regions. Successful attraction of spiral waves to the probe was demonstrated when the probe was <8mm from the spiral wave tip. Maximal traction velocity without loss of anchoring increased in a non-linear way with increasing values of ACh. Success rate of spiral wave termination was over 90% for regional DF ratios of as low as 1:1.2. Given that normally much higher ratios are measured in physiological atrial tissues, we envision this technique to provide a feasible, safer alternative to ablation procedures performed in persistent AF patients.


      PubDate: 2016-09-08T19:50:19Z
       
  • Comparison of calibration methods for accelerometers used in human motion
           analysis
    • Abstract: Publication date: Available online 30 August 2016
      Source:Medical Engineering & Physics
      Author(s): Alexis Nez, Laetitia Fradet, Pierre Laguillaumie, Tony Monnet, Patrick Lacouture
      In the fields of medicine and biomechanics, MEMS accelerometers are increasingly used to perform activity recognition by directly measuring acceleration; to calculate speed and position by numerical integration of the signal; or to estimate the orientation of body parts in combination with gyroscopes. For some of these applications, a highly accurate estimation of the acceleration is required. Many authors suggest improving result accuracy by updating sensor calibration parameters. Yet navigating the vast array of published calibration methods can be confusing. In this context, this paper reviews and evaluates the main measurement models and calibration methods. It also gives useful recommendations for better selection of a calibration process with regard to a specific application, which boils down to a compromise between accuracy, required installation, algorithm complexity, and time.


      PubDate: 2016-09-03T19:26:00Z
       
  • Accurate harmonic phase tracking of tagged MRI using locally-uniform
           myocardium displacement constraint
    • Abstract: Publication date: Available online 29 August 2016
      Source:Medical Engineering & Physics
      Author(s): Safaa M. ElDeeb, Ahmed S. Fahmy
      Harmonic phase (HARP) tracking is one of the most commonly used techniques for estimating the myocardium regional function from tagged cardiac Magnetic Resonance Imaging sequences. Nevertheless, tag fading and phase distortion can severely limit the tracking accuracy of the technique. In this work, we propose to modify the HARP tracking algorithm to impose a constraint of locally uniform displacement field while tracking the different myocardium points. A numerical contracting phantom and a dataset of 11 patients are used to study the performance of the proposed technique at the different cardiac phases, slices, and regions. The results show that the proposed method improves the tracking accuracy and the reliability of the conventional HARP technique.


      PubDate: 2016-08-30T18:33:10Z
       
  • Fixation strength of four headless compression screws
    • Abstract: Publication date: Available online 29 August 2016
      Source:Medical Engineering & Physics
      Author(s): Adam Hart, Edward J. Harvey, Reza Rabiei, Francois Barthelat, Paul A. Martineau
      To promote a quicker return to function, an increasing number of patients are treated with headless screws for acute displaced and even non-displaced scaphoid fractures. Therefore, it is imperative to understand and optimize the biomechanical characteristics of different implants to support the demands of early mobilization. The objective of this study was to evaluate the biomechanical fixation strength of 4 headless compression screws under distracting and bending forces. The Acutrak Standard, Acutrak Mini, Synthes 3.0, and Herbert-Whipple screws were tested using a polyurethane foam scaphoid fracture model. Implants were inserted into the foam blocks across a linear osteotomy. Custom fixtures applied pull-apart and four-point bending forces until implant failure. Pull-apart testing was performed in three different foam densities in order to simulate osteoporotic, osteopenic, and normal bone. The peak pull-apart forces varied significantly between implants and were achieved by (from greatest to least): the Acutrak Standard, Synthes 3.0, Acutrak Mini, and Herbert-Whipple screws. The fully threaded screws (Acutrak) failed at their proximal threads while the shanked screw (Synthes and Herbert Whipple) failed at their distal threads. Similarly, the screws most resistant to bending were (from greatest to least): the Acutrak Standard, Acutrak Mini, Herbert-Whipple, and Synthes. Although the amount of force required for pull-apart failure increased with each increasing simulated bone density (a doubling in density required triple the amount of pull apart force), the mode and sequence of failure was the same. Overall, the fully threaded, conical design of the Acutrak screws demonstrated superior fixation against pull-apart and bending forces than the shanked designs of the Synthes and Herbert-Whipple. We also found a strong relationship between simulated bone density and pull-apart force.


      PubDate: 2016-08-30T18:33:10Z
       
  • A comparative study of skin cell activities in collagen and fibrin
           constructs
    • Abstract: Publication date: September 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 9
      Author(s): Jia Xian Law, Faiza Musa, Bt Hj Idrus Ruszymah, Alicia J El Haj, Ying Yang
      Collagen and fibrin are widely used in tissue engineering due to their excellent biocompatibility and bioactivities that support in vivo tissue formation. These two hydrogels naturally present in different wound healing stages with different regulatory effects on cells, and both of them are mechanically weak in the reconstructed hydrogels. We conducted a comparative study by the growth of rat dermal fibroblasts or dermal fibroblasts and epidermal keratinocytes together in collagen and fibrin constructs respectively with and without the reinforcement of electrospun poly(lactic acid) nanofiber mesh. Cell proliferation, gel contraction and elastic modulus of the constructs were measured on the same gels at multiple time points during the 22 day culturing period using multiple non-destructive techniques. The results demonstrated considerably different cellular activities within the two types of constructs. Co-culturing keratinocytes with fibroblasts in the collagen constructs reduced the fibroblast proliferation, collagen contraction and mechanical strength at late culture point regardless of the presence of nanofibers. Co-culturing keratinocytes with fibroblasts in the fibrin constructs promoted fibroblast proliferation but exerted no influence on fibrin contraction and mechanical strength. The presence of nanofibers in the collagen and fibrin constructs played a favorable role on the fibroblast proliferation when keratinocytes were absent. Thus, this study exhibited new evidence of the strong cross-talk between keratinocytes and fibroblasts, which can be used to control fibroblast proliferation and construct contraction. This cross-talk activity is extracellular matrix-dependent in terms of the fibrous network morphology, density and strength.


      PubDate: 2016-08-21T17:00:20Z
       
  • Clinical workflow for personalized foot pressure ulcer prevention
    • Abstract: Publication date: September 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 9
      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: 2016-08-21T17:00:20Z
       
  • Mathematical modeling to predict the sub-bandage pressure on a conical
           limb for multi-layer bandaging
    • Abstract: Publication date: September 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 9
      Author(s): M.P. Sikka, S. Ghosh, A. Mukhopadhyay
      The effectiveness of the compression treatment by a medical compression bandage is dependent on the pressure generated at the interface between the bandage and the skin. This pressure is called interface pressure or sub-bandage pressure. The performance of a bandage depends upon the level of interface pressure applied by the bandage and the sustenance of this pressure over time. The interface pressure exerted by the bandage depends on several other factors like limb shape or size, application technique, physical and structural properties of the bandage, physical activities taken by the patient, etc. The current understanding of how bandages apply pressure to a limb is based on the Law of Laplace, which states that tension in the walls of a container is dependent on both the pressure of the container's content and its radius. This concept was translated mathematically into equation relating pressure to tension and radius by Thomas. In addition, a modified equation was generated by multiplying the model with a constant that represents the number of bandage layers in order to use the model to estimate the pressure applied by multi-layer bandages. This simple multiplication adjustment was questioned by researchers. They had doubts about the model validity and whether it can be used to predict the sub-bandage pressure applied by pressure garments. One of the questions that were raised regarding the bandage thickness affecting the sub-bandage pressure has been recently explored by Al Khaburi where he used the thin and thick cylinder shell theory to study the effect of Multi Component Bandage's (MCB) thickness on the sub-bandage pressure. The model by Al Khaburi and the earlier models developed for pressure prediction are all based on calculations considering the cylindrical limb shapes although the human limb normally is wider at the calf and reduces in circumference towards the ankle. So in our approach, the bandage is assumed to take a conical shape during application and membrane shell theory is used for developing pressure prediction model for multi-layers of bandage. Both analytical and experimental work showed that the effect of bandage thickness and the geometry of the limb on pressure produced by multi-layers of bandage are significant. The model developed when compared to the data obtained using experimental setup confirmed the validity of the mathematical model for multi-layers of bandage based on conical geometry of the limb.


      PubDate: 2016-08-21T17:00:20Z
       
  • Effect of the stiffness of bone substitutes on the biomechanical behaviour
           of femur for core decompression
    • Abstract: Publication date: September 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 9
      Author(s): T.N. Tran, W. Kowalczyk, H.P. Hohn, M. Jäger, S. Landgraeber
      Core decompression is the most common procedure for treatment of the early stages of osteonecrosis of the femoral head. The purpose of this study was to compare the biomechanical performance of four different bone graft substitutes combined with core decompression. Subject-specific finite element models generated from computed tomography (CT) scan data were used for a comprehensive analysis. Two different contact conditions were simulated representing states of osseointegration at the interface. Our results showed that the use of a low-stiffness bone substitute did not increase the risk of femoral fracture in the early postoperative phase, but resulted in less micromotion and interfacial stresses than high-stiffness bone substitutes.


      PubDate: 2016-08-21T17:00:20Z
       
  • Influence of different mechanical stimuli in a multi-scale
           mechanobiological isotropic model for bone remodelling
    • Abstract: Publication date: September 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 9
      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: 2016-08-21T17:00:20Z
       
  • Asymmetry in traction forces produced by migrating preadipocytes is
           bounded to 33%
    • Abstract: Publication date: September 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 9
      Author(s): Shada Abuhattum, Daphne Weihs
      Wound healing by gap closure is accomplished by the migratory cells within tissues. In fat tissue, the preadipocytes, stem cells committed to the adipose (fat) lineage, typically migrate into the wound area, and then differentiate into mature adipocytes to facilitate tissue repair and regeneration. While cell migration has previously been characterized, typically for fibroblasts, little is known about the dynamic, mechanical interactions of migrating cells with their microenvironment; cells crawl on a two-dimensional (2D) substrate by attaching and applying forces that allow them to extend leading edges and retract their rear. Moreover, preadipocytes, the highly migratory precursors of fat cells, have not been studied from this aspect. Here, we have evaluated the migration of preadipocytes, through their speed and directionality as well as the magnitude of the lateral forces applied during their migration on a 2D gel with Young's modulus of 2.44 kPa. We have found that the preadipocytes migrate non-directionally in the absence of chemoattractant, at an average rate of 0.27 µm/min, similar to fibroblasts. The preadipocytes exhibited a wide range of total traction forces (100–800 nN), and migrated along the long axis of their elongated morphology. Interestingly, we have observed an asymmetry in the location of force application between the lead and rear of the cells that was bounded in magnitude, where cells applied only up to 33% more force on either side; cell sides were defined relative to the minor axis of a bounding ellipse. These quantitative mechanobiological aspects of natural preadipocyte migration may shed light on the wound healing processes occurring in adipose tissue.


      PubDate: 2016-08-21T17:00:20Z
       
  • Monitoring contractile dermal lymphatic activity following uniaxial
           mechanical loading
    • Abstract: Publication date: September 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 9
      Author(s): RJ Gray, PR Worsley, D Voegeli, DL Bader
      It is proposed that direct mechanical loading can impair dermal lymphatic function, contributing to the causal pathway of pressure ulcers. The present study aims to investigate the effects of loading on human dermal lymphatic vessels. Ten participants were recruited with ages ranging from 24 to 61 years. Participants had intradermal Indocyanine Green injections administrated between left finger digits. Fluorescence was imaged for 5min sequences with an infra-red camera prior to lymph vessel loading, immediately after axial loading (60mmHg) and following a recovery period. Image processing was employed to defined transient lymph packets and compare lymph function between each test phase. The results revealed that between 1-8 transient events (median=4) occurred at baseline, with a median velocity of 8.1mm/sec (range 4.1–20.1mm/sec). Immediately post-loading, there was a significant (p <0.05) reduction in velocity (median=6.4, range 2.2–13.5mm/sec), although the number of transient lymph packages varied between participants. During the recovery period the number (range 1–7) and velocity (recovery median=9.6mm/sec) of transient packets were largely restored to basal values. The present study revealed that some individuals present with impaired dermal lymphatic function immediately after uniaxial mechanical loading. More research is needed to investigate the effects of pressure and shear on lymphatic vessel patency.


      PubDate: 2016-08-21T17:00:20Z
       
  • Red blood cell ghosts as promising drug carriers to target wound
           infections
    • Abstract: Publication date: September 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 9
      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: 2016-08-21T17:00:20Z
       
  • The influence of foreign body surface area on the outcome of chronic
           osteomyelitis
    • Abstract: Publication date: September 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 9
      Author(s): Carmen Cristina Surdu-Bob, Cristin Coman, Florica Barbuceanu, Danut Turcu, Nicolae Bercaru, Marius Badulescu
      Reproducible animal models of osteomyelitis close to the clinical scenario are difficult to obtain as the animals either die shortly after inoculation of bacteria or the bone cures itself of infection. Additional materials used as foreign bodies offer increased chances for localized infection due to bacterial attachment and are closer to clinical pathology. Through in vivo experimentation we investigated here the influence of surface area of a series of foreign bodies on the final outcome of the animal model, in terms of reproducibility, survival rate and time necessary for onset of chronic disease. Stainless steel Kirschner wire segments, stainless steel balls and cotton meshes were employed for this purpose. The clinical, microbiological, radiological and histological results obtained were compared with the simple case where no foreign body was used. The follow-up period was 57days. The cotton meshes, which had the highest surface area, were observed to provide the best outcome, with the lowest disease onset time interval (of 1week earlier than the others), the highest survival (of 90%) and disease reproduction rate (90%). The only clinical pattern of the mesh group rabbits was short lived inflammation while the other rabbits presented also some other clinical signs such as rhinorrheas, abscesses, rush and/or dyspnea. Moreover, this model is the most suitable for further treatment studies, as the cotton meshes could be easily removed after disease onset, without any intervention on the bone. This is important, as the treatment would address the bacteria present within the bone parts (marrow, cortex, periosteum etc.) not those forming the biofilm.


      PubDate: 2016-08-21T17:00:20Z
       
  • Dermis mechanical behaviour after different cell removal treatments
    • Abstract: Publication date: September 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 9
      Author(s): Mara Terzini, Cristina Bignardi, Carlotta Castagnoli, Irene Cambieri, Elisabetta M. Zanetti, Alberto L. Audenino
      Human acellular dermal matrices (HADMs) are used in reconstructive surgery as scaffolds promoting autologous tissue regeneration. Critical to the HADM ability to remodel and integrate into the host tissue is the removal of cells while maintaining an intact extracellular architecture. The objective of this work is to develop a methodology to analyse the mechanical properties of HADMs after decellularization to identify its ideal form of treatment and its duration. Two different decellularization techniques were used as a benchmark: the first is a well-established technique (incubation in NaOH for 1–7 weeks), and the second is an innovative technique developed by this research group (incubation in DMEM (Dulbecco's modified Eagle medium) for 1–7 weeks). After decellularization, the specimens underwent uniaxial tensile tests, and experimental data were represented with stress strain curves, calculating both engineering and true values. Mechanical tests have led to the identification of the optimal method (NaOH or DMEM) and duration for the decellularization treatment; differences between engineering and true values can reach 84%, but the engineering values remain useful to make comparisons, providing reliable indications with a simpler experimental set up and data processing.
      Graphical abstract image

      PubDate: 2016-08-21T17:00:20Z
       
  • The mechanobiology of wounds: The science of preventing pain and suffering
    • Abstract: Publication date: September 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 9
      Author(s): Amit Gefen



      PubDate: 2016-08-21T17:00:20Z
       
  • Cytoskeleton and plasma-membrane damage resulting from exposure to
           sustained deformations: A review of the mechanobiology of chronic wounds
    • Abstract: Publication date: September 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 9
      Author(s): Amit Gefen, Daphne Weihs
      The purpose of this review paper is to summarize the current knowledge on cell-scale mechanically-inflicted deformation-damage, which is at the frontier of cell mechanobiology and biomechanics science, specifically in the context of chronic wounds. The dynamics of the mechanostructure of cells and particularly, the damage occurring to the cytoskeleton and plasma-membrane when cells are chronically deformed (as in a weight-bearing static posture) is correlated to formation of the most common chronic wounds and injuries, such as pressure ulcers (injuries). The first occurrence is microscopic injury which onsets as damage in individual cells and then progresses macroscopically to the tissue-scale. Here, we specifically focus on sub-catastrophic and catastrophic damage to cells that can result from mechanical loads that are delivered statically or at physiological rates; this results in apoptosis at prolonged times or necrosis, rapidly. We start by providing a basic background of cell mechanics and dynamics, focusing on the plasma-membrane and the cytoskeleton, and discuss approaches to apply and estimate deformations in cells. We then consider the effects of different levels of mechanical loads, i.e. low, high and intermediate, and describe the expected damage in terms of time-scales of application and in terms of cell response, providing experimental examples where available. Finally, we review different theoretical and computational modeling approaches that have been used to describe cell responses to sustained deformation. We highlight the insights that those models provide to explain, for example, experimentally observed variabilities in cell damage and death under loading.
      Graphical abstract image

      PubDate: 2016-08-21T17:00:20Z
       
  • Editorial Board
    • Abstract: Publication date: September 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 9




      PubDate: 2016-08-21T17:00:20Z
       
  • A new shoulder model with a biologically inspired glenohumeral joint
    • Abstract: Publication date: September 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 9
      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: 2016-08-21T17:00:20Z
       
  • Quantifying trabecular bone material anisotropy and orientation using low
           resolution clinical CT images: A feasibility study
    • Abstract: Publication date: September 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 9
      Author(s): S. Majid Nazemi, David M.L. Cooper, James D. Johnston
      Accounting for spatial variation of trabecular material anisotropy and orientation can improve the accuracy of quantitative computed tomography-based finite element (FE) modeling of bone. The objective of this study was to investigate the feasibility of quantifying trabecular material anisotropy and orientation using clinical computed tomography (CT). Forty four cubic volumes of interest were obtained from micro-CT images of the human radius. Micro-FE modeling was performed on the samples to obtain orthotropic stiffness entries as well as trabecular orientation. Simulated computed tomography images (0.32, 0.37, and 0.5mm isotropic voxel sizes) were created by resampling micro-CT images with added image noise. The gray-level structure tensor was used to derive fabric eigenvalues and eigenvectors in simulated CT images. For ‘best case’ comparison purposes, Mean Intercept Length was used to define fabric from micro-CT images. Regression was used in combination with eigenvalues, imaged density and FE to inversely derive the constants used in Cowin and Zysset–Curnier fabric-elasticity equations, and for comparing image derived fabric-elasticity stiffness entries to those obtained using micro-FE. Image derived eigenvectors (which indicated trabecular orientation) were then compared to orientation derived using micro-FE. When using clinically available voxel sizes, gray-level structure tensor derived fabric combined with Cowin's equations was able to explain 94–97% of the variance in orthotropic stiffness entries while Zysset–Curnier equations explained 82–88% of the variance in stiffness. Image derived orientation deviated by 4.4–10.8° from micro-FE derived orientation. Our results indicate potential to account for spatial variation of trabecular material anisotropy and orientation in subject-specific finite element modeling of bone using clinically available CT.


      PubDate: 2016-08-21T17:00:20Z
       
  • A thermoregulation model for hypothermic treatment of neonates
    • Abstract: Publication date: September 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 9
      Author(s): Ana Beatriz C.G. Silva, Joanna Laszczyk, Luiz C. Wrobel, Fernando L.B. Ribeiro, Andrzej J. Nowak
      This paper presents a thermoregulation finite element model (FEM) to simulate hypothermia procedures for the treatment of encephalopathy hypoxic-ischemia (EHI) in neonates, a dangerous ischemic condition that can cause neurological damages and even death. Therapeutic hypothermia is the only recommended technique to reduce sequels caused by EHI in neonates; intervention with moderate cooling for neural rescue in newborns with hypoxic-ischemic brain injury is the culmination of a series of clinical research studies spanning decades. However, the direct monitoring of brain cooling is difficult and can lead to additional tissue damage. Therefore, the measurement of efficiency during clinical trials of hypothermia treatment is still challenging. The use of computational methods can aid clinicians to observe the continuous temperature of tissues and organs during cooling procedures without the need for invasive techniques, and can thus be a valuable tool to assist clinical trials simulating different cooling options that can be used for treatment. The use of low cost methods such as cooling blankets can open the possibility of using brain cooling techniques in hospitals and clinics that cannot currently afford the available expensive equipment and techniques. In this work, we developed a FEM package using isoparametric linear three-dimensional elements which is applied to the solution of the continuum bioheat Pennes equation. Blood temperature changes were considered using a blood pool approach. The results of the FEM model were compared to those obtained through the implementation of a user-defined function (UDF) in the commercial finite volume software FLUENT and validated with experimental tests. Numerical analyses were performed using a three-dimensional mesh based on a complex geometry obtained from MRI scan medical images.


      PubDate: 2016-08-21T17:00:20Z
       
  • Calculation of muscle forces during normal gait under consideration of
           femoral bending moments
    • Abstract: Publication date: September 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 9
      Author(s): Frederick Lutz, Roland Mastel, Martin Runge, Felix Stief, André Schmidt, Andrea Meurer, Hartmut Witte
      This paper introduces a new approach for computing lower extremity muscle forces by incorporating equations that consider “bone structure” and “prevention of bending by load reduction” into existing optimization algorithms. Lower extremity muscle and joint forces, during normal gait, were calculated and compared using two different optimization approaches. We added constraint equations that prevent femoral bending loads to an existing approach that considers “minimal total muscular force”. Gait parameters such as kinematics, ground reaction forces, and surface electromyographic activation patterns were examined using standardized gait analysis. A subject-specific anatomic model of the lower extremities, obtained from magnetic resonance images of a healthy male, was used for the simulations. Finite element analysis was used to calculate femoral loads. The conventional method of calculating muscle forces leads to higher rates of femoral bending and structural stress than the new approach. Adding equations with structural subject-specific parameters in our new approach resulted in reduced femoral stress patterns. These findings show that our new approach improves the accuracy of femoral stress and strain simulations. Structural overloads caused by bending can be avoided during inverse calculation of muscle forces.


      PubDate: 2016-08-21T17:00:20Z
       
  • Measuring temperature rise during orthopaedic surgical procedures
    • Abstract: Publication date: September 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 9
      Author(s): Sarah Manoogian, Adam K. Lee, James C. Widmaier
      A reliable means for measuring temperatures generated during surgical procedures is needed to recommend best practices for inserting fixation devices and minimizing the risk of osteonecrosis. Twenty four screw tests for three surgical procedures were conducted using the four thermocouples in the bone and one thermocouple in the screw. The maximum temperature rise recorded from the thermocouple in the screw (92.7±8.9°C, 158.7±20.9°C, 204.4±35.2°C) was consistently higher than the average temperature rise recorded in the bone (31.8±9.3°C, 44.9±12.4°C, 77.3±12.7°C). The same overall trend between the temperatures that resulted from three screw insertion procedures was recorded with significant statistical analyses using either the thermocouple in the screw or the average of several in-bone thermocouples. Placing a single thermocouple in the bone was determined to have limitations in accurately comparing temperatures from different external fixation screw insertion procedures. Using the preferred measurement techniques, a standard screw with a predrilled hole was found to have the lowest maximum temperatures for the shortest duration compared to the other two insertion procedures. Future studies evaluating bone temperature increase need to use reliable temperature measurements for recommending best practices to surgeons.


      PubDate: 2016-08-21T17:00:20Z
       
  • Smartphone application for emergency signal detection
    • Abstract: Publication date: September 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 9
      Author(s): Isabel N. Figueiredo, Carlos Leal, Luís Pinto, Jason Bolito, André Lemos
      Currently, a number of studies focus on the study and design of new healthcare technologies to improve elderly health and quality of life. Taking advantage of the popularity, portability, and inherent technology of smartphones, we present an emergency application for smartphones, designated as knock-to-panic (KTP). This innovative and novel system enables users to simply hit their devices in order to send an alarm signal to an emergency service. This application is a complete and autonomous emergency system, and can provide an economic, reliable, and unobtrusive method for elderly monitoring or safety protection. Moreover, the simple and fast activation of KTP makes it a viable and potentially superior alternative to traditional ambient assisted living emergency calls. Furthermore, KTP can be further extended to the general population as well and not just be limited for elderly persons. The proposed method is a threshold-based algorithm and is designed to require a low battery power consumption. The evaluation of the performance of the algorithm in collected data indicates that both sensitivity and specificity are above 90%.


      PubDate: 2016-08-21T17:00:20Z
       
  • Using an inertial navigation algorithm and accelerometer to monitor chest
           compression depth during cardiopulmonary resuscitation
    • Abstract: Publication date: September 2016
      Source:Medical Engineering & Physics, Volume 38, Issue 9
      Author(s): Salah Boussen, Harold Ibouanga-Kipoutou, Nathalie Fournier, Yves Godio Raboutet, Maxime Llari, Nicolas Bruder, Pierre Jean Arnoux, Michel Behr
      We present an original method using a low cost accelerometer and a Kalman-filter based algorithm to monitor cardiopulmonary resuscitation chest compressions (CC) depth. A three-axis accelerometer connected to a computer was used during CC. A Kalman filter was used to retrieve speed and position from acceleration data. We first tested the algorithm for its accuracy and stability on surrogate data. The device was implemented for CC performed on a manikin. Different accelerometer locations were tested. We used a classical inertial navigation algorithm to reconstruct CPR depth and frequency. The device was found accurate enough to monitor CPR depth and its stability was checked for half an hour without any drift. Average error on displacement was ±0.5mm. We showed that depth measurement was dependent on the device location on the patient or the rescuer. The accuracy and stability of this small low-cost accelerometer coupled to a Kalman-filter based algorithm to reconstruct CC depth and frequency, was found well adapted and could be easily implemented.


      PubDate: 2016-08-21T17:00:20Z
       
  • Identification of ankle plantar-flexors dynamics in response to electrical
           stimulation
    • Abstract: Publication date: Available online 17 August 2016
      Source:Medical Engineering & Physics
      Author(s): Hossein Rouhani, Milos R. Popovic, Michael Same, Ya Qi Li, Kei Masani
      Modeling the muscle response to functional electrical stimulation (FES) is an essential step in the design of closed-loop controlled neuroprostheses. This study was aimed at identifying the dynamic response of ankle plantar-flexors to FES during quiet standing. Thirteen healthy subjects stood in a standing frame that locked the knee and hip joints. The ankle plantar-flexors were stimulated bilaterally through surface electrodes and the generated ankle torque was measured. The pulse amplitude was sinusoidally modulated at five different frequencies. The pulse amplitude and the measured ankle torque fitted by a sine function were considered as input and output, respectively. First-order and critically-damped second-order linear models were fitted to the experimental data. Both models fitted similarly well to the experimental data. The coefficient of variation of the time constant among subjects was smaller in the case of the second-order model compared to the first-order model (18.1%vs. 79.9%, p <0.001). We concluded that the critically-damped second-order model more consistently described the relationship between isometric ankle torque and surface FES pulse amplitude, which was applied to the ankle plantar-flexors during quiet standing.


      PubDate: 2016-08-21T17:00:20Z
       
  • Bayesian fusion algorithm for improved oscillometric blood pressure
           estimation
    • Abstract: Publication date: Available online 16 August 2016
      Source:Medical Engineering & Physics
      Author(s): Mohamad Forouzanfar, Hilmi R. Dajani, Voicu Z. Groza, Miodrag Bolic, Sreeraman Rajan, Izmail Batkin
      A variety of oscillometric algorithms have been recently proposed in the literature for estimation of blood pressure (BP). However, these algorithms possess specific strengths and weaknesses that should be taken into account before selecting the most appropriate one. In this paper, we propose a fusion method to exploit the advantages of the oscillometric algorithms and circumvent their limitations. The proposed fusion method is based on the computation of the weighted arithmetic mean of the oscillometric algorithms estimates, and the weights are obtained using a Bayesian approach by minimizing the mean square error. The proposed approach is used to fuse four different oscillometric blood pressure estimation algorithms. The performance of the proposed method is evaluated on a pilot dataset of 150 oscillometric recordings from 10 subjects. It is found that the mean error and standard deviation of error are reduced relative to the individual estimation algorithms by up to 7 mmHg and 3 mmHg in estimation of systolic pressure, respectively, and by up to 2 mmHg and 3 mmHg in estimation of diastolic pressure, respectively.


      PubDate: 2016-08-21T17:00:20Z
       
  • Ability of electrical stimulation therapy to improve the effectiveness of
           robotic training for paretic upper limbs in patients with stroke
    • Abstract: Publication date: Available online 13 August 2016
      Source:Medical Engineering & Physics
      Author(s): Hiroyuki Miyasaka, Abbas Orand, Hitoshi Ohnishi, Genichi Tanino, Kotaro Takeda, Shigeru Sonoda
      We investigated whether untriggered neuromuscular electrical stimulation (NMES) can increase the effectiveness of shoulder and elbow robotic training in patients with hemiparesis. Thirty subacute stroke patients were randomly equally allocated to robot only (RO) and robot and electrical stimulation (RE) groups. During training, shoulder and elbow movements were trained by operating the robotic arm with the paretic arm, and the robotic device helped to move the arm. In the RE group, the anterior deltoid and triceps brachii muscles were electrically stimulated at sub-motor threshold intensity. Training was performed (approximately 1h/day, 5 days/week for 2 weeks) in addition to regular rehabilitation. Active range of motion (ROM) values of shoulder flexion and abduction, and Fugl-Meyer assessment (FMA) scores were measured before and after training. Active shoulder ROM was significantly better after than before training in the RE group; however, no such improvement was noted in the RO group. FMA scores were significantly better in both groups, and there was no significant difference between the groups. Untriggered NMES might increase the effectiveness of shoulder and elbow robotic training in patients with hemiparesis. Additionally, NMES at a sub-motor threshold during robotic training might facilitate activation of paretic muscles, resulting in paralysis improvement.


      PubDate: 2016-08-16T16:43:15Z
       
  • Vector-based forearm rotation moment arms – A sensitivity analysis
    • Abstract: Publication date: Available online 10 August 2016
      Source:Medical Engineering & Physics
      Author(s): Desney Greybe, Michael R. Boland, Kumar Mithraratne
      All existing moment arm data for muscles of the forearm derive from tendon excursion experiments. Moment arms determined this way are only valid for movement about the same generalised coordinate system as was used during the tendon excursion, which makes their implementation in more complex or realistic joint models problematic. This study used a vector-based method to calculate muscle moment arms in a three dimensional model of forearm rotation. It also evaluated the sensitivity of this method to errors in the input data. There was reasonably close agreement between the moment arms calculated in this study and those published using tendon excursion methods. Six out of eight muscles had moment arms within the range of values reported previously. However, the vector-based method was sensitive to the accuracy of the input data. This sensitivity varied between muscles and input variables. Generally, the calculations were more robust to the point of force application than the muscle lines of action and the joint's axis of rotation. A small change in these variables could produce substantial changes in the calculated moment arms. Consequently, accurate input data is important when using the vector-based method in a joint model.


      PubDate: 2016-08-13T16:33:34Z
       
  • Can a single lower trunk body-fixed sensor differentiate between
           level-walking and stair descent and ascent in older adults'
           Preliminary findings
    • Abstract: Publication date: Available online 12 August 2016
      Source:Medical Engineering & Physics
      Author(s): Aner Weiss, Marina Brozgol, Nir Giladi, Jeffrey M. Hausdorff
      Stair ascent and descent are common forms of ambulation that may be challenging to detect. Here, we propose the first step towards differentiating between stair negotiation and level-walking using a single body-fixed sensor. Seventeen healthy older adults (age: 79.3±4.2 years, 47% women) wore a body-fixed sensor on the lower-back while performing level-walking and stair negotiation. Measures derived from the 3D acceleration and angular-velocity signals included medians, ranges, step duration, step and stride regularity, filtered vertical to horizontal acceleration ratio (VAF/HAF), and wavelet-based features. Friedman's and Wilcoxon tests compared between conditions. Stepwise-binary logistic-regression evaluated classification accuracy. During level-walking, yaw range was lowest and anterior–posterior and vertical step and stride regularity were highest (p ≤0.007). Anterior–posterior step regularity (p =0.003), VAF/HAF (p =0.094), and yaw range (p =0.105) identified level-walking (92.2% accuracy). During stair ascent, roll range, median anterior–posterior acceleration and anterior–posterior wavelet-coefficient were lowest (p ≤0.006), while VAF/HAF was highest (p =0.0029). Anterior posterior wavelet coefficient (p =0.038) and VAF/HAF (p =0.018) identified stair ascent (94.3% accuracy). During stair descent, vertical and medio-lateral ranges were highest and medio-lateral stride regularity and VAF/HAF were lowest (p ≤0.006). VAF/HAF (p =0.01), medio-lateral acceleration range (p =0.069), and medio-lateral stride regularity (p =0.072) identified stair descent (90.2% accuracy). These findings suggest that a single worn body-fixed sensor can be used to differentiate between level-walking and stair negotiation.


      PubDate: 2016-08-13T16:33:34Z
       
  • Conceptual finite element study for comparison among superior, anterior,
           and spiral clavicle plate fixations for midshaft clavicle fracture
    • Abstract: Publication date: Available online 8 August 2016
      Source:Medical Engineering & Physics
      Author(s): Teng-Le Huang, Wen-Chuan Chen, Kun-Jhih Lin, Cheng-Lun Tsai, Kang-Ping Lin, Hung-Wen Wei
      Open reduction internal fixation technique has been generally accepted for treatment of midshaft clavicle fractures. Both superior and anterior clavicle plates have been reported in clinical or biomechanical researches, while presently the spiral clavicle plate design has been introduced improved biomechanical behavior over conventional designs. In order to objectively realize the multi-directional biomechanical performances among the three geometries for clavicle plate designs, a current conceptual finite element study has been conducted with identical cross-sectional features for clavicle plates. The conceptual superior, anterior, and spiral clavicle plate models were constructed for virtual reduction and fixation to an OTA 15-B1.3 midshaft transverse fracture of clavicle. Mechanical load cases including cantilever bending, axial compression, inferior bending, and axial torsion have been applied for confirming the multi-directional structural stability and implant safety in biomechanical perspective. Results revealed that the anterior clavicle plate model represented lowest plate stress under all loading cases. The superior clavicle plate model showed greater axial compressive stiffness, while the anterior clavicle plate model performed greater rigidity under cantilever bending load. Three model represented similar structural stiffness under axial torsion. Played as a transition structure between superior and anterior clavicle plate, the spiral clavicle plate model revealed comparable results with acceptable multi-directional biomechanical behavior. The concept of spiral clavicle plate design is worth considering in practical application in clinics. Implant safety should be further investigated by evidences in future mechanical tests and clinical observations.


      PubDate: 2016-08-09T16:13:49Z
       
  • FES-induced co-activation of antagonist muscles for upper limb control and
           disturbance rejection
    • Abstract: Publication date: Available online 8 August 2016
      Source:Medical Engineering & Physics
      Author(s): Antônio Padilha L. Bó, Lucas O. da Fonseca, Ana Carolina C. de Sousa
      Control systems for human movement based on Functional Electrical Stimulation (FES) have shown to provide excellent performance in different experimental setups. Nevertheless, there is still a limited number of such applications available today on worldwide markets, indicating poor performance in real settings, particularly for upper limb rehabilitation and assistance. Based on these premises, in this paper we explore the use of an alternative control strategy based on co-activation of antagonist muscles using FES. Although co-contraction may accelerate fatigue when compared to single-muscle activation, knowledge from motor control indicate it may be useful for some applications. We have performed a simulation and experimental study designed to evaluate whether controllers that integrate such features can modulate joint impedance and, by doing so, improving performance with respect to disturbance rejection. The simulation results, obtained using a novel model including proprioceptive feedback and anatomical data, indicate that both stiffness and damping components of joint impedance may be modulated by using FES-induced co-activation of antagonist muscles. Preliminary experimental trials were conducted on four healthy subjects using surface electrodes. While the simulation investigation predicted a maximum 494% increase in joint stiffness for wrist flexion/extension, experiments provided an average elbow stiffness increase of 138% using lower stimulation intensity. Closed-loop experiments in which disturbances were applied have demonstrated that improved behavior may be obtained, but increased joint stiffness and other issues related to simultaneous stimulation of antagonist muscles may indeed produce greater errors.


      PubDate: 2016-08-09T16:13:49Z
       
  • The influence of high-heeled shoes on strain and tension force of the
           anterior talofibular ligament and plantar fascia during balanced standing
           and walking
    • Abstract: Publication date: Available online 4 August 2016
      Source:Medical Engineering & Physics
      Author(s): Jia Yu, Duo Wai-Chi Wong, Hongtao Zhang, Zong-Ping Luo, Ming Zhang
      High-heeled shoes have the capability to alter the strain and tension of ligamentous structures between the foot and ankle, which may result in ankle instability. However, high-heeled shoes can also reduce the strain on plantar fascia, which may be beneficial for the treatment of plantar fasciitis. In this study, the influence of heel height on strain and tension force applied to the anterior talofibular ligament (ATL) and plantar fascia were investigated. A three-dimensional finite element model of coupled foot–ankle–shoe complex was constructed. Four heel heights were studied in balanced standing: 0 in. (0cm), 1 in. (2.54cm), 2 in. (5.08cm), and 3 in. (7.62cm). A walking analysis was performed using 2-in. (5.08cm) high-heeled shoes. During balanced standing, the tension force on the ATL increased from 14.8N to 97.0N, with a six-fold increase in strain from 0 in. to 3 in. (0–7.62cm). The tension force and the average strain on the plantar fascia decreased from 151.0N (strain: 0.74%) to 59.6N (strain: 0.28%) when the heel height increased from 0 in. to 2 in. (0–5.08cm). When heel height reached 3 in. (7.62cm), the force and average strain increased to 278.3N (strain: 1.33%). The walking simulation showed that the fascia stretched out while the ATL loading decreased during push off. The simulation outcome demonstrated the influence of heel height on ATL alteration and plantar fascia strain, which implies risks for ankle injury and suggests guidance for the treatment of plantar fasciitis.


      PubDate: 2016-08-05T15:12:13Z
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
 
 
JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
 
Home (Search)
Subjects A-Z
Publishers A-Z
Customise
APIs
Your IP address: 54.160.198.60
 
About JournalTOCs
API
Help
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-2016