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  Subjects -> BIOLOGY (Total: 2708 journals)
    - BIOCHEMISTRY (207 journals)
    - BIOENGINEERING (82 journals)
    - BIOLOGY (1344 journals)
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BIOLOGY (1344 journals)            First | 4 5 6 7 8 9 10 11 | Last

Journal of Biobased Materials and Bioenergy     Full-text available via subscription  
Journal of Biodiversity Management & Forestry     Full-text available via subscription  
Journal of Bioenergetics and Biomembranes     Hybrid Journal  
Journal of Biogeography     Hybrid Journal   (Followers: 18)
Journal of Bioinformatics and Computational Biology     Hybrid Journal   (Followers: 13)
Journal of Biological and Information Sciences     Open Access   (Followers: 2)
Journal of Biological Dynamics     Open Access   (Followers: 1)
Journal of Biological Education     Hybrid Journal   (Followers: 1)
Journal of Biological Engineering     Open Access   (Followers: 4)
Journal of Biological Methods     Open Access  
Journal of Biological Physics     Hybrid Journal  
Journal of Biological Research - Thessaloniki     Open Access  
Journal of Biological Sciences     Open Access   (Followers: 4)
Journal of Biological Systems     Hybrid Journal   (Followers: 2)
Journal of Biology and Earth Sciences     Open Access   (Followers: 1)
Journal of Biology and Life Science     Open Access   (Followers: 2)
Journal of Biology, Agriculture and Healthcare     Open Access   (Followers: 3)
Journal of Biomarkers     Open Access  
Journal of Biomechanics     Hybrid Journal   (Followers: 23)
Journal of Biomedical Discovery and Collaboration     Open Access   (Followers: 1)
Journal of Biomedical Education     Open Access   (Followers: 1)
Journal of Biomedical Informatics     Partially Free   (Followers: 13)
Journal of Biomedical Materials Research Part A     Hybrid Journal   (Followers: 1)
Journal of Biomedical Materials Research Part B : Applied Biomaterials     Hybrid Journal   (Followers: 1)
Journal of Biomedical Nanotechnology     Full-text available via subscription   (Followers: 6)
Journal of Biomedical Physics and Engineering     Open Access  
Journal of Biomedical Science and Engineering     Open Access   (Followers: 2)
Journal of Biomedical Sciences     Open Access   (Followers: 2)
Journal of Biomolecular Screening     Hybrid Journal   (Followers: 4)
Journal of Bionic Engineering     Full-text available via subscription  
Journal of Biorheology     Hybrid Journal  
Journal of Bioscience and Bioengineering     Full-text available via subscription   (Followers: 15)
Journal of Biosciences and Medicines     Open Access  
Journal of Biosocial Science     Hybrid Journal   (Followers: 4)
Journal of Biotechnology and Biodiversity     Open Access   (Followers: 1)
Journal of Cell and Plant Sciences     Open Access   (Followers: 3)
Journal of Cell Communication and Signaling     Hybrid Journal  
Journal of Cell Death     Open Access   (Followers: 1)
Journal of Cell Science     Full-text available via subscription   (Followers: 10)
Journal of Cellular Biochemistry     Hybrid Journal   (Followers: 3)
Journal of Cellular Physiology     Hybrid Journal   (Followers: 2)
Journal of Cerebral Blood Flow & Metabolism     Hybrid Journal   (Followers: 2)
Journal of Chromatography B     Hybrid Journal   (Followers: 17)
Journal of Clinical Bioinformatics     Open Access   (Followers: 5)
Journal of Communications Technology and Electronics     Hybrid Journal   (Followers: 1)
Journal of Contemporary Physics (Armenian Academy of Sciences)     Hybrid Journal   (Followers: 1)
Journal of Contradicting Results in Science     Open Access   (Followers: 2)
Journal of Crustacean Biology     Full-text available via subscription   (Followers: 2)
Journal of Developmental Biology     Open Access   (Followers: 2)
Journal of Ecosystems     Open Access   (Followers: 4)
Journal of Education, Health and Sport     Open Access   (Followers: 5)
Journal of Electrical Bioimpedance     Full-text available via subscription   (Followers: 2)
Journal of Electromyography and Kinesiology     Hybrid Journal   (Followers: 3)
Journal of Environment and Ecology     Open Access   (Followers: 10)
Journal of Environmental Radioactivity     Hybrid Journal   (Followers: 2)
Journal of Environmental Science and Natural Resources     Open Access   (Followers: 2)
Journal of Ethnobiology     Full-text available via subscription   (Followers: 5)
Journal of Ethnobiology and Ethnomedicine     Open Access  
Journal of Ethology     Hybrid Journal   (Followers: 1)
Journal of Evolutionary Biology     Hybrid Journal   (Followers: 22)
Journal of Experimental and Clinical Anatomy     Full-text available via subscription  
Journal of Experimental Marine Biology and Ecology     Hybrid Journal   (Followers: 26)
Journal of Fish Biology     Hybrid Journal   (Followers: 25)
Journal of Functional Biomaterials     Open Access   (Followers: 1)
Journal of Genomes and Exomes     Open Access  
Journal of Great Lakes Research     Hybrid Journal   (Followers: 7)
Journal of Health and Biological Sciences     Open Access  
Journal of Heredity     Hybrid Journal   (Followers: 2)
Journal of Herpetology     Full-text available via subscription   (Followers: 4)
Journal of Huazhong University of Science and Technology [Medical Sciences]     Hybrid Journal  
Journal of Human Evolution     Hybrid Journal   (Followers: 10)
Journal of Hymenoptera Research     Open Access   (Followers: 2)
Journal of Ichthyology     Hybrid Journal   (Followers: 3)
Journal of Insect Behavior     Hybrid Journal   (Followers: 6)
Journal of Insect Biodiversity     Open Access   (Followers: 2)
Journal of Insect Conservation     Hybrid Journal   (Followers: 5)
Journal of Integrated OMICS     Open Access  
Journal of Integrated Pest Management     Open Access   (Followers: 2)
Journal of Integrative Environmental Sciences     Hybrid Journal   (Followers: 4)
Journal of Intelligent Transportation Systems: Technology, Planning, and Operations     Hybrid Journal   (Followers: 5)
Journal of Invertebrate Pathology     Hybrid Journal   (Followers: 3)
Journal of Landscape Ecology     Open Access   (Followers: 7)
Journal of Law and the Biosciences     Open Access  
Journal of Leukocyte Biology     Open Access   (Followers: 5)
Journal of Life and Earth Science     Open Access  
Journal of Lipid Research     Full-text available via subscription   (Followers: 3)
Journal of Lipids     Open Access   (Followers: 1)
Journal of Luminescence     Hybrid Journal   (Followers: 2)
Journal of Mammalian Evolution     Hybrid Journal   (Followers: 6)
Journal of Mammalian Ova Research     Full-text available via subscription  
Journal of Mammalogy     Full-text available via subscription   (Followers: 6)
Journal of Mammary Gland Biology and Neoplasia     Hybrid Journal   (Followers: 1)
Journal of Marine Biology     Open Access   (Followers: 14)
Journal of Mathematical Biology     Hybrid Journal   (Followers: 14)
Journal of Mechanics in Medicine and Biology     Hybrid Journal  
Journal of Medical Primatology     Hybrid Journal   (Followers: 1)
Journal of Medical Toxicology     Hybrid Journal   (Followers: 5)
Journal of Medicine and Philosophy     Hybrid Journal   (Followers: 7)
Journal of Membrane Biology     Hybrid Journal   (Followers: 2)
Journal of Membrane Science     Hybrid Journal   (Followers: 12)

  First | 4 5 6 7 8 9 10 11 | Last

Journal Cover Medical Engineering & Physics     [SJR: 0.722]   [H-I: 57]
   [11 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1350-4533
   Published by Elsevier Homepage  [2585 journals]
  • Waterjet cutting of periprosthetic interface tissue in loosened hip
           prostheses: An in vitro feasibility study
    • Abstract: Publication date: Available online 22 January 2015
      Source:Medical Engineering & Physics
      Author(s): Gert Kraaij , Gabrielle J.M. Tuijthof , Jenny Dankelman , Rob G.H.H. Nelissen , Edward R. Valstar
      Waterjet cutting technology is considered a promising technology to be used for minimally invasive removal of interface tissue surrounding aseptically loose hip prostheses. The goal of this study was to investigate the feasibility of waterjet cutting of interface tissue membrane. Waterjets with 0.2 mm and 0.6 mm diameter, a stand-off distance of 5 mm, and a traverse speed of 0.5 mm/s were used to cut interface tissue samples in half. The water flow through the nozzle was controlled by means of a valve. By changing the flow, the resulting waterjet pressure was regulated. Tissue sample thickness and the required waterjet pressures were measured. Mean thickness of the samples tested within the 0.2 mm nozzle group was 2.3 mm (SD 0.7 mm) and within the 0.6 mm nozzle group 2.6 mm (SD 0.9 mm). The required waterjet pressure to cut samples was between 10 and 12 MPa for the 0.2 mm nozzle and between 5 and 10 MPa for the 0.6 mm nozzle. Cutting bone or bone cement requires about 3 times higher waterjet pressure (30–50 MPa, depending on used nozzle diameter) and therefore we consider waterjet cutting as a safe technique to be used for minimally invasive interface tissue removal.


      PubDate: 2015-01-28T10:09:18Z
       
  • An advanced compliance monitor for patients undergoing brace treatment for
           idiopathic scoliosis
    • Abstract: Publication date: Available online 22 January 2015
      Source:Medical Engineering & Physics
      Author(s): Eric Chalmers , Edmond Lou , Doug Hill , H. Vicky Zhao
      Adolescent idiopathic scoliosis is a spinal deformity affecting 2–3% of adolescents. Brace treatment, the most common non-surgical treatment, uses a hard plastic orthotic shell to prevent progression of the deformity. Previous studies have found association between treatment outcome and patients’ compliance with the prescribed brace-wear regimen. However, the exact relationship between compliance and treatment outcome has yet to be elucidated. Current compliance monitoring techniques may not be providing enough information about patients’ brace-wear habits. Building on previous work, we present a new compliance monitor which records both temperature and force applied to the patient's body. The combination of temperature and force readings shows both how often and how tightly the brace is worn. The new monitor is designed for minimal size and power consumption, measuring 5.2 cm × 2.5 cm × 0.8 cm, with a battery life of approximately one year. Seven patients wore the monitor in this pilot study. The temperature-based compliance estimate differed significantly from the force-based estimate in four out of seven cases. This suggests that some patients may wear their braces very loosely, and that existing temperature-only or force-only compliance monitors may not be giving a complete picture of brace-wear habits.


      PubDate: 2015-01-28T10:09:18Z
       
  • Is aortic wall shear stress affected by aging' An image-based
           numerical study with two age groups
    • Abstract: Publication date: Available online 24 January 2015
      Source:Medical Engineering & Physics
      Author(s): Jonas Lantz , Johan Renner , Toste Länne , Matts Karlsson
      The size of the larger arteries increases during the entire life, but not much is known about how the change in size affects the blood flow. This study compares the flow field in a group of young males (N = 10, age = 23.5 ± 1.4), with a group of older males (N = 8, age = 58.0 ± 2.8). Aortic geometries were obtained by magnetic resonance imaging, and the aortic blood flow field was computed using computational fluid dynamics. The aortic wall shear stress was obtained from the computations, and it was concluded that time-averaged wall shear stress decreased with increased age, probably as a consequence of increased aortic diameter and decreased stroke volume, which in turn reduces the shear rates in the aorta. However, the oscillatory shear index, which is a measure of the oscillatory nature of the wall shear stress vector, seemed to be unaffected by aging.


      PubDate: 2015-01-28T10:09:18Z
       
  • Colourimetric image analysis as a diagnostic tool in female genital
           schistosomiasis
    • Abstract: Publication date: Available online 24 January 2015
      Source:Medical Engineering & Physics
      Author(s): Sigve Dhondup Holmen , Eyrun Floerecke Kjetland , Myra Taylor , Elisabeth Kleppa , Kristine Lillebø , Svein Gunnar Gundersen , Mathias Onsrud , Fritz Albregtsen
      Female genital schistosomiasis (FGS) is a highly prevalent waterborne disease in some of the poorest areas of sub-Saharan Africa. Reliable and affordable diagnostics are unavailable. We explored colourimetric image analysis to identify the characteristic, yellow lesions caused by FGS. We found that the method may yield a sensitivity of 83% and a specificity of 73% in colposcopic images. The accuracy was also explored in images of simulated inferior quality, to assess the possibility of implementing such a method in simple, electronic devices. This represents the first step towards developing a safe and affordable aid in clinical diagnosis, allowing for a point-of-care approach.


      PubDate: 2015-01-28T10:09:18Z
       
  • Principal component analysis of atrial fibrillation: Inclusion of
           posterior ECG leads does not improve correlation with left atrial activity
           
    • Abstract: Publication date: Available online 22 January 2015
      Source:Medical Engineering & Physics
      Author(s): Daniel Raine , Philip Langley , Ewen Shepherd , Stephen Lord , Stephen Murray , Alan Murray , John P. Bourke
      Background Lead V1 is routinely analysed due to its large amplitude AF waveform. V1 correlates strongly with right atrial activity but only moderately with left atrial activity. Posterior lead V9 correlates strongest with left atrial activity. Aims (1) To establish whether surface dominant AF frequency (DAF) calculated using principal component analysis (PCA) of a modified 12-lead ECG (including posterior leads) has a stronger correlation with left atrial activity compared to the standard ECG. (2) To assess the contribution of individual ECG leads to the AF principal component in both ECG configurations. Methods Patients were assigned to modified or standard ECG groups. In the modified ECG, posterior leads V8 and V9 replaced V4 and V6. AF waveform was extracted from one-minute surface ECG recordings using PCA. Surface DAF was correlated with intracardiac DAF from the high right atrium (HRA), coronary sinus (CS) and pulmonary veins (PVs). Results 96 patients were studied. Surface DAF from the modified ECG did not have a stronger correlation with left atrial activity compared to the standard ECG. Both ECG configurations correlated strongly with HRA, CS and right PVs but only moderately with left PVs. V1 contributed most to the AF principal component in both ECG configurations.


      PubDate: 2015-01-23T09:29:00Z
       
  • A robust real-time gait event detection using wireless gyroscope and its
           application on normal and altered gaits
    • Abstract: Publication date: Available online 22 January 2015
      Source:Medical Engineering & Physics
      Author(s): Darwin Gouwanda , Alpha Agape Gopalai
      Gait events detection allows clinicians and biomechanics researchers to determine timing of gait events, to estimate duration of stance phase and swing phase and to segment gait data. It also aids biomedical engineers to improve the design of orthoses and FES (functional electrical stimulation) systems. In recent years, researchers have resorted to using gyroscopes to determine heel-strike (HS) and toe-off (TO) events in gait cycles. However, these methods are subjected to significant delays when implemented in real-time gait monitoring devices, orthoses, and FES systems. Therefore, the work presented in this paper proposes a method that addresses these delays, to ensure real-time gait event detection. The proposed algorithm combines the use of heuristics and zero-crossing method to identify HS and TO. Experiments involving: (1) normal walking; (2) walking with knee brace; and (3) walking with ankle brace for overground walking and treadmill walking were designed to verify and validate the identified HS and TO. The performance of the proposed method was compared against the established gait detection algorithms. It was observed that the proposed method produced detection rate that was comparable to earlier reported methods and recorded reduced time delays, at an average of 100 ms.


      PubDate: 2015-01-23T09:29:00Z
       
  • Development and validation of an accelerometer-based method for
           quantifying gait events
    • Abstract: Publication date: Available online 21 January 2015
      Source:Medical Engineering & Physics
      Author(s): Mohamed Boutaayamou , Cédric Schwartz , Julien Stamatakis , Vincent Denoël , Didier Maquet , Bénédicte Forthomme , Jean-Louis Croisier , Benoît Macq , Jacques G. Verly , Gaëtan Garraux , Olivier Brüls
      An original signal processing algorithm is presented to automatically extract, on a stride-by-stride basis, four consecutive fundamental events of walking, heel strike (HS), toe strike (TS), heel-off (HO), and toe-off (TO), from wireless accelerometers applied to the right and left foot. First, the signals recorded from heel and toe three-axis accelerometers are segmented providing heel and toe flat phases. Then, the four gait events are defined from these flat phases. The accelerometer-based event identification was validated in seven healthy volunteers and a total of 247 trials against reference data provided by a force plate, a kinematic 3D analysis system, and video camera. HS, TS, HO, and TO were detected with a temporal accuracy ± precision of 1.3 ms ± 7.2 ms, −4.2 ms ± 10.9 ms, −3.7 ms ± 14.5 ms, and −1.8 ms ± 11.8 ms, respectively, with the associated 95% confidence intervals ranging from −6.3 ms to 2.2 ms. It is concluded that the developed accelerometer-based method can accurately and precisely detect HS, TS, HO, and TO, and could thus be used for the ambulatory monitoring of gait features computed from these events when measured concurrently in both feet.


      PubDate: 2015-01-23T09:29:00Z
       
  • Data dependent random forest applied to screening for laryngeal disorders
           through analysis of sustained phonation: Acoustic versus contact
           microphone
    • Abstract: Publication date: Available online 22 January 2015
      Source:Medical Engineering & Physics
      Author(s): A. Verikas , A. Gelzinis , E. Vaiciukynas , M. Bacauskiene , J. Minelga , M. Hållander , V. Uloza , E. Padervinskis
      Comprehensive evaluation of results obtained using acoustic and contact microphones in screening for laryngeal disorders through analysis of sustained phonation is the main objective of this study. Aiming to obtain a versatile characterization of voice samples recorded using microphones of both types, 14 different sets of features are extracted and used to build an accurate classifier to distinguish between normal and pathological cases. We propose a new, data dependent random forests-based, way to combine information available from the different feature sets. An approach to exploring data and decisions made by a random forest is also presented. Experimental investigations using a mixed gender database of 273 subjects have shown that the perceptual linear predictive cepstral coefficients (PLPCC) was the best feature set for both microphones. However, the linear predictive coefficients (LPC) and linear predictive cosine transform coefficients (LPCTC) exhibited good performance in the acoustic microphone case only. Models designed using the acoustic microphone data significantly outperformed the ones built using data recorded by the contact microphone. The contact microphone did not bring any additional information useful for the classification. The proposed data dependent random forest significantly outperformed the traditional random forest.


      PubDate: 2015-01-23T09:29:00Z
       
  • In-vivo quantification of human breast deformation associated with the
           position change from supine to upright
    • Abstract: Publication date: January 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 1
      Author(s): Hamed Khatam , Gregory P. Reece , Michelle C. Fingeret , Mia K. Markey , Krishnaswamy Ravi-Chandar
      Stereophotographic imaging and digital image correlation are used to determine the variation of breast skin deformation as the subject orientation is altered from supine to upright. A change in subject's position from supine to upright can result in significant stretches in some parts of the breast skin. The maximum of the major principal stretch ratio of the skin is different in different subjects and varies in the range of 1.25–1.60. It is also found that the boundaries of the breast move significantly relative to the skeletal structure and other fixed points such as the sternal notch. Such measurements are crucial since they provide basic data for validation of biomechanical breast models based on finite element formulations.


      PubDate: 2015-01-15T06:23:13Z
       
  • Editorial Board
    • Abstract: Publication date: January 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 1




      PubDate: 2015-01-15T06:23:13Z
       
  • Review of 2014: Jack Perkins Prize, Journal Impact Factor, and Editorial
           Board of Medical Engineering & Physics
    • Abstract: Publication date: January 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 1
      Author(s): Richard A. Black



      PubDate: 2015-01-15T06:23:13Z
       
  • Acknowledgement to Reviewers 2014
    • Abstract: Publication date: January 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 1




      PubDate: 2015-01-15T06:23:13Z
       
  • Computational analysis of the radial mechanical performance of PLLA
           coronary artery stents
    • Abstract: Publication date: January 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 1
      Author(s): R.G. Pauck , B.D. Reddy
      Stents have been an effective tool to restore and maintain the patency of narrowed blood vessels, but they must have sufficient radial strength. Biodegradable stent materials have substantially lower mechanical properties than permanent stents. The stent geometry and material properties must be considered simultaneously when assessing stent performance. Material tests were performed to determine the mechanical characteristics of high-molecular-weight poly-l-lactic acid (PLLA). The results were used to calibrate an anisotropic elastic-plastic material model. Three distinct geometries were analysed with a range of material stiffness values in a finite element analysis to investigate their comparative effect on the radial strength, recoil, and radial stiffness. The performance of the different geometries varies substantially, with one particular geometry, with the highest material stiffness of 9GPa, exceeding the desired radial strength of 300mmHg.


      PubDate: 2015-01-15T06:23:13Z
       
  • Ultrasound-guided three-dimensional needle steering in biological tissue
           with curved surfaces
    • Abstract: Publication date: January 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 1
      Author(s): Momen Abayazid , Pedro Moreira , Navid Shahriari , Sachin Patil , Ron Alterovitz , Sarthak Misra
      In this paper, we present a system capable of automatically steering a bevel-tipped flexible needle under ultrasound guidance toward a physical target while avoiding a physical obstacle embedded in gelatin phantoms and biological tissue with curved surfaces. An ultrasound pre-operative scan is performed for three-dimensional (3D) target localization and shape reconstruction. A controller based on implicit force control is developed to align the transducer with curved surfaces to assure the maximum contact area, and thus obtain an image of sufficient quality. We experimentally investigate the effect of needle insertion system parameters such as insertion speed, needle diameter and bevel angle on target motion to adjust the parameters that minimize the target motion during insertion. A fast sampling-based path planner is used to compute and periodically update a feasible path to the target that avoids obstacles. We present experimental results for target reconstruction and needle insertion procedures in gelatin-based phantoms and biological tissue. Mean targeting errors of 1.46±0.37mm, 1.29±0.29mm and 1.82±0.58mm are obtained for phantoms with inclined, curved and combined (inclined and curved) surfaces, respectively, for insertion distance of 86–103mm. The achieved targeting errors suggest that our approach is sufficient for targeting lesions of 3mm radius that can be detected using clinical ultrasound imaging systems.


      PubDate: 2015-01-15T06:23:13Z
       
  • Characteristics of very slow stepping in healthy adults and validity of
           the activPAL3™ activity monitor in detecting these steps
    • Abstract: Publication date: January 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 1
      Author(s): Ben Stansfield , Mugdha Hajarnis , Radhika Sudarshan
      The use of activity monitors to objectively measure stepping activity allows the characterisation of free-living daily activity performance. However, they must be fully validated. The characteristics of very slow stepping were examined and the validity of an activity monitor, the activPAL3™ (PAL Technologies Ltd., Glasgow, UK) to detect these steps was assessed. 10M/10F healthy adults (36±10y) performed a treadmill walking protocol from 1.0m/s down to 0.1m/s (0.1m/s increments) whilst wearing the monitor under video observation (gold standard). Within the 800 stepping periods recorded the proportion of the steps correctly detected by the activPAL3™ was explored against speed and cadence. Below 0.4m/s walking began to be intermittent, stepping interspersed with stationary postures. At 0.1m/s almost 90% of walking periods were intermittent. The percentage of steps detected was over 90% for walking speed at or above 0.5m/s and cadence at or above 69steps/min. However, below these limits % steps detected reduced rapidly with zero steps detected at 0.1m/s and at or below 24steps/min. When examining the stepping activity of groups with limited stepping cadence the above thresholds of performance should be considered to ensure that outcomes are not misinterpreted and important very slow stepping activity missed.


      PubDate: 2015-01-15T06:23:13Z
       
  • Simulation of carbon dioxide insufflation via a diffuser in an open
           surgical wound model
    • Abstract: Publication date: January 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 1
      Author(s): John E. Cater , Jan van der Linden
      Flow within a model surgical opening during insufflation with heated carbon dioxide was studied using computational fluid dynamics. A volume of fluid method was used to simulate the mixture of ambient air and carbon dioxide gas. The negative buoyancy of the carbon dioxide caused it to fill the wound and form a protective layer on the internal surfaces for a range of flow rates, temperatures, and angles of patient inclination. It was observed that the flow remained attached to the surface of the model due to the action of the Coanda effect. A flow rate of 10L/min was sufficient to maintain a warm carbon dioxide barrier for a moderately sized surgical incision for all likely angles of inclination.


      PubDate: 2015-01-15T06:23:13Z
       
  • Development and validation of a 3D-printed interfacial stress sensor for
           prosthetic applications
    • Abstract: Publication date: January 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 1
      Author(s): P. Laszczak , L. Jiang , D.L. Bader , D. Moser , S. Zahedi
      A novel capacitance-based sensor designed for monitoring mechanical stresses at the stump–socket interface of lower-limb amputees is described. It provides practical means of measuring pressure and shear stresses simultaneously. In particular, it comprises of a flexible frame (20mm×20mm), with thickness of 4mm. By employing rapid prototyping technology in its fabrication, it offers a low-cost and versatile solution, with capability of adopting bespoke shapes of lower-limb residua. The sensor was first analysed using finite element analysis (FEA) and then evaluated using lab-based electromechanical tests. The results validate that the sensor is capable of monitoring both pressure and shear at stresses up to 350kPa and 80kPa, respectively. A post-signal processing model is developed to induce pressure and shear stresses, respectively. The effective separation of pressure and shear signals can be potentially advantageous for sensor calibration in clinical applications. The sensor also demonstrates high linearity (approx. 5–8%) and high pressure (approx. 1.3kPa) and shear (approx. 0.6kPa) stress resolution performance. Accordingly, the sensor offers the potential for exploitation as an assistive tool to both evaluate prosthetic socket fitting in clinical settings and alert amputees in home settings of excessive loading at the stump–socket interface, effectively preventing stump tissue breakdown at an early stage.


      PubDate: 2015-01-15T06:23:13Z
       
  • In vitro localisation of intracranial haematoma using electrical impedance
           tomography semi-array
    • Abstract: Publication date: January 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 1
      Author(s): S. Bentolhoda Ayati , Kaddour Bouazza-Marouf , David Kerr
      Electrical Impedance Tomography is a non-invasive and portable method that has good potential as an alternative to the conventional modalities for early detection of intracranial haematomas in high risk patients. Early diagnosis can reduce treatment delays and most significantly can impact patient outcomes. Two eight-electrode layouts, a standard ring full array (FA) and a semi-array (SA), were investigated for their ability to detect, localise and quantify simulated intracranial haematomas in vitro on ovine models for the purpose of early diagnosis. SA layout speeds up electrode application and avoids the need to move and lift the patient's head. Haematomas were simulated using gel samples with the same conductivity as blood. Both layouts, FA and SA, could detect the presence of haematomas at any location within the skull. The mean of the relative radial position error with respect to the brain radius was 7% for FA and 6% for SA, for haematomas close to the electrodes, and 11% for SA for haematomas far from the electrodes at the back of the head. Size estimation was not as good; the worst size estimation error for FA being around 30% while the best for SA was 50% for simulated haematomas close to the electrodes.


      PubDate: 2015-01-15T06:23:13Z
       
  • Morphological and stent design risk factors to prevent migration phenomena
           for a thoracic aneurysm: A numerical analysis
    • Abstract: Publication date: January 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 1
      Author(s): H.-E. Altnji , B. Bou-Saïd , H. Walter-Le Berre
      The primary mechanically related problems of endovascular aneurysm repair are migration and type Ia endoleaks. They occur when there is no effective seal between the proximal end of the stent-graft and the vessel. In this work, we have developed several deployment simulations of parameterized stents using the finite element method (FEM) to investigate the contact stiffness of a nitinol stent in a realistic Thoracic Aortic Aneurysm (TAA). Therefore, we evaluated the following factors associated with these complications: (1) Proximal Attachment Site Length (PASL), (2) stent oversizing value (O%), (3) different friction conditions of the stent/aorta contact, and (4) proximal neck angulation α. The simulation results show that PASL>18mm is a crucial factor to prevent migration at a neck angle of 60°, and the smoothest contact condition with low friction coefficient (μ =0.05). The increase in O% ranging from 10% to 20% improved the fixation strength. However, O%≥25% at 60° caused eccentric deformation and stent collapse. Higher coefficient of friction μ >0.01 considerably increased the migration risk when PASL=18mm. No migration was found in an idealized aorta model with a neck angle of 0°, PASL=18mm and μ =0.05. Our results suggest carefully considering the stent length and oversizing value in this neck morphology to strengthen the contact and prevent migration.


      PubDate: 2015-01-15T06:23:13Z
       
  • Evaluation of acceleration and deceleration cardiac processes using
           phase-rectified signal averaging in healthy and idiopathic dilated
           cardiomyopathy subjects
    • Abstract: Publication date: Available online 10 January 2015
      Source:Medical Engineering & Physics
      Author(s): Rosana Bas , Montserrat Vallverdú , Jose F. Valencia , Andreas Voss , Antonio Bayés de Luna , Pere Caminal
      The aim of the present study was to investigate the suitability of the Phase-Rectified Signal Averaging (PRSA) method for improved risk prediction in cardiac patients. Moreover, this technique, which separately evaluates acceleration and deceleration processes of cardiac rhythm, allows the effect of sympathetic and vagal modulations of beat-to-beat intervals to be characterized. Holter recordings of idiopathic dilated cardiomyopathy (IDC) patients were analyzed: high-risk (HR), who suffered sudden cardiac death (SCD) during the follow-up; and low-risk (LR), without any kind of cardiac-related death. Moreover, a control group of healthy subjects was analyzed. PRSA indexes were analyzed, for different time scales T and wavelet scales s, from RR series of 24 h-ECG recordings, awake periods and sleep periods. Also, the behavior of these indexes from simulated data was analyzed and compared with real data results. Outcomes demonstrated the PRSA capacity to significantly discriminate healthy subjects from IDC patients and HR from LR patients on a higher level than traditional temporal and spectral measures. The behavior of PRSA indexes agrees with experimental evidences related to cardiac autonomic modulations. Also, these parameters reflect more regularity of the autonomic nervous system (ANS) in HR patients.


      PubDate: 2015-01-15T06:23:13Z
       
  • Activity classification in persons with stroke based on frequency features
    • Abstract: Publication date: Available online 2 January 2015
      Source:Medical Engineering & Physics
      Author(s): Annemarie Laudanski , Brenda Brouwer , Qingguo Li
      Recent advances in the use of inertial measurement units (IMUs) for motion analysis suggest the possibility of using this technology for the monitoring of daily activities of individuals during rehabilitation post-stroke. Previous studies have utilized features extracted from accelerometer and gyroscope signals to develop classification models capable of identifying activities performed within large datasets. In this study, nine k-nearest neighbor cross-validated classifiers were developed using frequency-features derived from shank-mounted IMUs on the less-affected and affected limbs of subjects with stroke. These classifiers were evaluated for two separate datasets of post-stroke gait; the first a classification of three separate gait activities (overground walking, stair ascent, and stair descent), and the second a classification of five gait activities, overground walking, stair ascent, and descent with a distinction between stepping pattern used while negotiating stairs (step-over-step (SOS) and step-by-step (SBS)). The comparison showed the highest classification accuracy, 100% for the three-activities and 94% for the five-activities, was obtained using a classifier composed of features derived from accelerometer and gyroscope measurements from both IMUs on less-affected and affected limbs.


      PubDate: 2015-01-07T06:01:44Z
       
  • Bone geometry on the contact stress in the shoulder for evaluation of
           pressure ulcers: Finite element modeling and experimental validation
    • Abstract: Publication date: Available online 6 January 2015
      Source:Medical Engineering & Physics
      Author(s): Ying Luo , Yancheng Wang , Bruce L. Tai , Roland K. Chen , Albert J. Shih
      This research presents the finite element modeling (FEM) of human-specific computed tomography (CT) data to study the effect of bone prominences on contact stress in the shoulder for prevention of pressure ulcers. The 3D geometry of scapula, skin, and surrounding soft tissues in the shoulder was reconstructed based on the anonymous CT data of a human subject in a prone posture (without loading on the shoulder) for FEM analysis of the contact stress. FEM analysis results show that the maximum stress is located at the prominence of the scapula with sharp bone geometry. This demonstrates that stress concentration at the bone prominence is a significant factor to cause the high contact stress, which is a source for pressure ulcers. For experimental validation, a physical shoulder model manufactured by 3D printing of the bone geometry and the mold for molding of tissue-mimicking silicone was developed. Compression tests of the mattress foam and silicone were conducted to find the nonlinear stress–strain relations as inputs for FEM. Experiments of compressing the shoulder model against the foam were carried out. Three flexible force sensors were embedded inside the model to measure the contact forces and compared to the FEM predictions. Results show that the FEM predicted forces match well with the experimental measurements and demonstrate that FEM can accurately predict the stress distributions in the shoulder to study the effect of bone geometry on the inception of pressure ulcers.


      PubDate: 2015-01-07T06:01:44Z
       
  • Light protection of chemotherapy drugs for infusion
    • Abstract: Publication date: Available online 30 December 2014
      Source:Medical Engineering & Physics
      Author(s): Douglas McG. Clarkson , Roger Harvey , Dave Sheepy
      Specific chemotherapy drugs which require to be delivered by continuous infusion over time can have their effectiveness impaired by exposure to optical radiation. Mechanisms and processes of drug preparation and patient administration associated with light sensitive drugs were monitored within a Chemotherapy Unit. Levels of ambient light at locations of drug preparation/administration and levels of protection afforded by optical filter elements such as infusion lines were determined using a double grating Bentham Dmc150 spectroradiometer. Models of light exposure were developed for separate components of drug preparation and infusion delivery systems where the latter included the fluid bag with protective light cover, drip chamber and giving set line. In addition, the attenuation coefficient of Dacarbazine at the concentration typically used in patient treatments was determined using specially manufactured measurement cells. The relative contributions to light absorption of the drug bag, drip chamber and patient line were identified for specific types of giving sets, spectral content/intensity of light exposure and specific drug light absorption profiles. This indicated significant differences in the level of light protection afforded by specific giving sets and either single or double layer protection of the drug bag reservoir. It is not clear, however, if these variations could lead to significant differences of levels of drug de-activation and/or creation of undesirable photo-products such as in the case of Dacarbazine. Such techniques, however, provide a means of identifying how light exposure can be maintained at levels as low as reasonably possible as a precautionary measure.


      PubDate: 2015-01-02T05:41:42Z
       
  • Validation of 3D surface reconstruction of vertebrae and spinal column
           using 3D ultrasound data – A pilot study
    • Abstract: Publication date: Available online 27 December 2014
      Source:Medical Engineering & Physics
      Author(s): Duc V. Nguyen , Quang N. Vo , Lawrence H. Le , Edmond H.M. Lou
      Adolescent idiopathic scoliosis (AIS) is a three-dimensional deformity of spine associated with vertebra rotation. The Cobb angle and axial vertebral rotation are important parameters to assess the severity of scoliosis. However, the vertebral rotation is seldom measured from radiographs due to time consuming. Different techniques have been developed to extract 3D spinal information. Among many techniques, ultrasound imaging is a promising method. This pilot study reported an image processing method to reconstruct the posterior surface of vertebrae from 3D ultrasound data. Three cadaver vertebrae, a Sawbones spine phantom, and a spine from a child with AIS were used to validate the development. The in-vitro result showed the surface of the reconstructed image was visually similar to the original objects. The dimension measurement error was <5 mm and the Pearson correlation was >0.99. The results also showed a high accuracy in vertebral rotation with errors of 0.8 ± 0.3°, 2.8 ± 0.3° and 3.6 ± 0.5° for the rotation values of 0°, 15° and 30°, respectively. Meanwhile, the difference in the Cobb angle between the phantom and the image was 4° and the vertebral rotation at the apex was 2°. The Cobb angle measured from the in-vivo ultrasound image was 4° different from the radiograph.


      PubDate: 2014-12-29T05:37:34Z
       
  • Sensitivity analysis of human lower extremity joint moments due to changes
           in joint kinematics
    • Abstract: Publication date: Available online 29 December 2014
      Source:Medical Engineering & Physics
      Author(s): Marzieh M. Ardestani , Mehran Moazen , Zhongmin Jin
      Despite the widespread applications of human gait analysis, causal interactions between joint kinematics and joint moments have not been well documented. Typical gait studies are often limited to pure multi-body dynamics analysis of a few subjects which do not reveal the relative contributions of joint kinematics to joint moments. This study presented a computational approach to evaluate the sensitivity of joint moments due to variations of joint kinematics. A large data set of probabilistic joint kinematics and associated ground reaction forces were generated based on experimental data from literature. Multi-body dynamics analysis was then used to calculate joint moments with respect to the probabilistic gait cycles. Employing the principal component analysis (PCA), the relative contributions of individual joint kinematics to joint moments were computed in terms of sensitivity indices (SI). Results highlighted high sensitivity of (1) hip abduction moment due to changes in pelvis rotation (SI = 0.38) and hip abduction (SI = 0.4), (2) hip flexion moment due to changes in hip flexion (SI = 0.35) and knee flexion (SI = 0.26), (3) hip rotation moment due to changes in pelvis obliquity (SI = 0.28) and hip rotation (SI = 0.4), (4) knee adduction moment due to changes in pelvis rotation (SI = 0.35), hip abduction (SI = 0.32) and knee flexion (SI = 0.34), (5) knee flexion moment due to changes in pelvis rotation (SI = 0.29), hip flexion (SI = 0.28) and knee flexion (SI = 0.31), and (6) knee rotation moment due to changes in hip abduction (SI = 0.32), hip flexion and knee flexion (SI = 0.31). Highlighting the “cause-and-effect” relationships between joint kinematics and the resultant joint moments provides a fundamental understanding of human gait and can lead to design and optimization of current gait rehabilitation treatments.


      PubDate: 2014-12-29T05:37:34Z
       
  • Loosening detection of the femoral component of hip prostheses with
           extracorporeal shockwaves: A pilot study
    • Abstract: Publication date: Available online 29 December 2014
      Source:Medical Engineering & Physics
      Author(s): Johannes S. Rieger , Sebastian Jaeger , Jan Philippe Kretzer , Rüdiger Rupp , Rudi G. Bitsch
      The diagnosis of aseptic loosening of hip implants is often challenging. A vibrational analysis of the bone-implant interface could be an alternative method to analyze the fixation of endoprostheses. We assessed an innovative and new approach for excitation by using extracorporeal shockwaves in this study. In three cadaver specimens total hip arthroplasty was performed bilaterally. Four different states of implant loosening were simulated. Three accelerometers were fixed at the medial condyle, the greater trochanter, and the crest of the ilium. The bone-implant compound was excited with highly standardized extracorporeal shock waves. Resonance spectra between 100 Hz and 5000 Hz were recorded. This technique permitted a good adaptation to varying soft tissue conditions. The main resonance frequency of the hip joints occurred at about 2000 Hz. The analysis of the measured spectra showed an interrelation between the state of loosening and the frequency values of the resonances. In case of a stem loosening, there were significant shifts of the resonance into the lower frequency area between 386 Hz and 847 Hz. With this novel technique the degree of stem loosening could be assessed in a soft tissue considering configuration. This study forms a first step for future establishment of a non-invasive, non-radiological and fast applicable diagnostic procedure for early detection of endoprostheses loosening before manifest presence of clinical signs.


      PubDate: 2014-12-29T05:37:34Z
       
  • Traumatic brain injury: Increasing ICP attenuates respiratory modulations
           of cerebral blood flow velocity
    • Abstract: Publication date: Available online 29 December 2014
      Source:Medical Engineering & Physics
      Author(s): Christina Haubrich , Rolf R. Diehl , Magdalena Kasprowicz , Jennifer Diedler , Enrico Sorrentino , Piotr Smielewski , Marek Czosnyka
      In vitro experiments have suggested that respiratory oscillations (R waves) in cerebral blood flow velocity are reduced as soon as the intracranial pressure–volume reserve is exhausted. Could R waves hence, provide indication for increasing ICP after traumatic brain injury (TBI)' On days 1 to 4 after TBI, 22 sedated and ventilated patients were monitored for intracranial pressure (ICP) in brain parenchyma, Doppler flow velocity (FV) in the middle cerebral arteries (MCA), and arterial blood pressure (ABP). The analysis included the transfer function gains of R waves (respiratory rate of 9–20 cpm) between ABP and FV (GainFv) as well as between ABP and ICP (GainICP). Also, the index of the intracranial pressure–volume reserve (RAP) was calculated. The rise of ICP (day 1: 14.10 ± 6.22 mmHg; to day 4: 29.69 ± 12.35 mmHg) and increase of RAP (day 1: 0.72 ± 0.22; to day 4: 0.85 ± 0.18) were accompanied by a decrease of GainFv (right MCA; day 1: 1.78 ± 1.0; day 4: 0.84 ± 0.47; left MCA day 1: 1.74 ± 1.10; day 4: 0.86 ± 0.46; p < 0.01) but no significant change in GainICP day 1: 1.50 ± 0.77; day 4: 1.15 ± 0.47; p = 0.07). The transfer of ventilatory oscillations to the intracerebral arteries after TBI appears to be dampened by increasing ICP and exhausted intracranial pressure–volume reserves. Results warrant prospective studies of whether respiratory waves in cerebral blood flow velocity may anticipate intracranial hypertension non-invasively.


      PubDate: 2014-12-29T05:37:34Z
       
  • A non-invasive, 3D, dynamic MRI method for measuring muscle moment arms in
           vivo: Demonstration in the human ankle joint and Achilles tendon
    • Abstract: Publication date: Available online 26 November 2014
      Source:Medical Engineering & Physics
      Author(s): E.C. Clarke , J.H. Martin , A.G. d’Entremont , M.G. Pandy , D.R. Wilson , R.D. Herbert
      Muscle moment arms are used widely in biomechanical analyses. Often they are measured in 2D or at a series of static joint positions. In the present study we demonstrate a simple MRI method for measuring muscle moment arms dynamically in 3D from a single range-of-motion cycle. We demonstrate this method in the Achilles tendon for comparison with other methods, and validate the method using a custom apparatus. The method involves registration of high-resolution joint geometry from MRI scans of the stationary joint with low-resolution geometries from ultrafast MRI scans of the slowly moving joint. Tibio-talar helical axes and 3D Achilles tendon moment arms were calculated throughout passive rotation for 10 adult subjects, and compared with recently published data. A simple validation was conducted by comparing MRI measurements with direct physical measurements made on a phantom. The moment arms measured using our method and those of others were similar and there was good agreement between physical measurements (mean 41.0mm) and MRI measurements (mean 39.5mm) made on the phantom. This new method can accurately measure muscle moment arms from a single range-of-motion cycle without the need to control rotation rate or gate the scanning. Supplementary data includes custom software to assist implementation.


      PubDate: 2014-12-16T04:42:30Z
       
  • Detection of physical activities using a physical activity monitor system
           for wheelchair users
    • Abstract: Publication date: Available online 10 November 2014
      Source:Medical Engineering & Physics
      Author(s): Shivayogi V. Hiremath , Stephen S. Intille , Annmarie Kelleher , Rory A. Cooper , Dan Ding
      Availability of physical activity monitors for wheelchair users can potentially assist these individuals to track regular physical activity (PA), which in turn could lead to a healthier and more active lifestyle. Therefore, the aim of this study was to develop and validate algorithms for a physical activity monitoring system (PAMS) to detect wheelchair based activities. The PAMS consists of a gyroscope based wheel rotation monitor (G-WRM) and an accelerometer device (wocket) worn on the upper arm or on the wrist. A total of 45 persons with spinal cord injury took part in the study, which was performed in a structured university-based laboratory environment, a semi-structured environment at the National Veterans Wheelchair Games, and in the participants’ home environments. Participants performed at least ten PAs, other than resting, taken from a list of PAs. The classification performance for the best classifiers on the testing dataset for PAMS-Arm (G-WRM and wocket on upper arm) and PAMS-Wrist (G-WRM and wocket on wrist) was 89.26% and 88.47%, respectively. The outcomes of this study indicate that multi-modal information from the PAMS can help detect various types of wheelchair-based activities in structured laboratory, semi-structured organizational, and unstructured home environments.


      PubDate: 2014-12-16T04:42:30Z
       
  • Imaging and finite element analysis: A methodology for non-invasive
           characterization of aortic tissue
    • Abstract: Publication date: Available online 6 November 2014
      Source:Medical Engineering & Physics
      Author(s): Vittoria Flamini , Arthur P. Creane , Christian M. Kerskens , Caitríona Lally
      Characterization of the mechanical properties of arterial tissues usually involves an invasive procedure requiring tissue removal. In this work we propose a non-invasive method to perform a biomechanical analysis of cardiovascular aortic tissue. This method is based on combining medical imaging and finite element analysis (FEA). Magnetic resonance imaging (MRI) was chosen since it presents relatively low risks for human health. A finite element model was created from the MRI images and loaded with systolic physiological pressures. By means of an optimization routine, the structural material properties were changed until average strains matched those measured by MRI. The method outlined in this work produced an estimate of the in situ properties of cardiovascular tissue based on non-invasive image datasets and finite element analysis.


      PubDate: 2014-12-16T04:42:30Z
       
  • A novel in vivo impact device for evaluation of sudden limb loading
           response
    • Abstract: Publication date: Available online 11 November 2014
      Source:Medical Engineering & Physics
      Author(s): Erin Boutwell , Rebecca Stine , Steven Gard
      The lower limbs are subjected to large impact forces on a daily basis during gait, and ambulators rely on various mechanisms to protect the musculoskeletal system from these potentially damaging shocks. However, it is difficult to assess the efficacy of anatomical mechanisms and potential clinical interventions on impact forces because of limitations of the testing environment. The current paper describes a new in vivo measurement device (sudden loading evaluation device, or SLED) designed to address shortcomings of previous loading protocols. To establish the repeatability and validity of this testing device, reliability and human participant data were collected while the stiffnesses of simulated and prosthetic limbs were systematically varied. The peak impact forces delivered by the SLED ranged from 706±3N to 2157±32N during reliability testing and from 784±30N to 938±18N with the human participant. The relatively low standard deviations indicate good reliability within the impacts delivered by the SLED, while the magnitude of the loads experienced by the human participant (98–117% BW) were comparable to ground reaction forces during level walking. Thus, the SLED may be valuable as a research tool for investigations of lower-limb impact loading events.


      PubDate: 2014-12-16T04:42:30Z
       
  • Editorial Board
    • Abstract: Publication date: December 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 12




      PubDate: 2014-12-16T04:42:30Z
       
  • Operational challenges of retinal prostheses
    • Abstract: Publication date: December 2014
      Source:Medical Engineering & Physics, Volume 36, Issue 12
      Author(s): Erich W. Schmid , Wolfgang Fink , Robert Wilke
      Two computational models for research on retinal implants are presented. In the first model, the electric field produced by a multi-electrode array in a uniform retina is calculated. It is shown how cross talk of activated electrodes and the resulting bunching of field lines in monopole and dipole activation prevent high resolution imaging with retinal implants. Furthermore, it is demonstrated how sequential stimulation and multipolar stimulation may overcome this limitation. In the second model a target volume, i.e., a probe cylinder approximating a bipolar cell, in the retina is chosen, and the passive Heaviside cable equation is solved inside this target volume to calculate the depolarization of the cell membrane. The depolarization as a function of time indicates that shorter signals stimulate better as long as the current does not change sign during stimulation of the retina, i.e., mono-phasic stimulation. Both computational models are equally applicable to epiretinal, subretinal, and suprachoroidal vision implants.


      PubDate: 2014-12-16T04:42:30Z
       
  • Multi-frequency Rayleigh damped elastography: in silico studies
    • Abstract: Publication date: Available online 2 December 2014
      Source:Medical Engineering & Physics
      Author(s): Andrii Y. Petrov , Paul D. Docherty , Mathieu Sellier , J. Geoffrey Chase
      Rayleigh damping (RD) is commonly used to model energy attenuation for analyses of structures subjected to dynamic loads. In time-harmonic Magnetic Resonance Elastography (MRE), the RD model was shown to be non-identifiable at a single frequency data due to the ill-posed nature of the imaginary components describing energy dissipation arising from elastic and inertial forces. Thus, parametrisation or multi-frequency (MF) input data is required to overcome the fundamental identifiability issue of the model. While parametrisation allows improved accuracy of the identified parameters, simultaneous inversion using MF input data is a prerequisite for theoretical identifiably of the model. Furthermore, to establish good practical identifiability, frequencies should be separated over a wide range to produce different dynamic response. This research investigates the effects on practical identifiability of the RD model using MF data over different combinations of frequencies in noise-free heterogenous simulated geometry and compares the outcomes to reconstruction result based on single frequency input data. We tested eight frequencies in silico for a phantom type geometry comprises three independent material regions characterised by different mechanical properties. Combinations of two near or well separated frequencies are used to test the separation necessary to obtain accurate results, while the use of four or eight simultaneous frequencies is used to assess robustness. Results confirm expected non-identifiability of the RD model given single frequency input data. Practical identifiability of the RD parameters improved as more input frequencies were used for simultaneous inversion and when two frequencies were well separated. Best quality reconstruction results were achieved using full range data comprising eight available frequencies over a wide range. The main outcome is that high quality motion data over at least two frequencies over a wide range is required for establishing minimal practical identifiability of the model, while quality of the practical identifiability increases proportionally with more input frequencies used. Further simulation studies are required to determine acceptable signal-to-noise ratio (SNR) thresholds in motion data for accurate inversion of the RD parameters.


      PubDate: 2014-12-16T04:42:30Z
       
  • Permeability study of cancellous bone and its idealised structures
    • Abstract: Publication date: Available online 16 December 2014
      Source:Medical Engineering & Physics
      Author(s): Ardiyansyah Syahrom , Mohammed Rafiq Abdul Kadir , Muhamad Nor Harun , Andreas Öchsner
      Artificial bone is a suitable alternative to autografts and allografts, however their use is still limited. Though there were numerous reports on their structural properties, permeability studies of artificial bones were comparably scarce. This study focused on the development of idealised, structured models of artificial cancellous bone and compared their permeability values with bone surface area and porosity. Cancellous bones from fresh bovine femur were extracted and cleaned following an established protocol. The samples were scanned using micro-computed tomography (μCT) and three-dimensional models of the cancellous bones were reconstructed for morphology study. Seven idealised and structured cancellous bone models were then developed and fabricated via rapid prototyping technique. A test-rig was developed and permeability tests were performed on the artificial and real cancellous bones. The results showed a linear correlation between the permeability and the porosity as well as the bone surface area. The plate-like idealised structure showed a similar value of permeability to the real cancellous bones.


      PubDate: 2014-12-16T04:42:30Z
       
  • Digital tomosynthesis (DTS) for quantitative assessment of trabecular
           microstructure in human vertebral bone
    • Abstract: Publication date: Available online 8 December 2014
      Source:Medical Engineering & Physics
      Author(s): Woong Kim , Daniel Oravec , Srikant Nekkanty , Janardhan Yerramshetty , Edward A. Sander , George W. Divine , Michael J. Flynn , Yener N. Yeni
      Digital tomosynthesis (DTS) provides slice images of an object using conventional radiographic methods with high in-plane resolution. The objective of this study was to explore the potential of DTS for describing microstructural, stiffness and stress distribution properties of vertebral cancellous bone. Forty vertebrae (T6, T8, T11, and L3) from 10 cadavers (63–90 years) were scanned using microCT and DTS. Anisotropy (μCT.DA), and the specimen-average and standard deviation of trabecular bone volume fraction (BV/TV), thickness (Tb.Th), number (Tb.N) and separation (Tb.Sp) were obtained using stereology. Apparent modulus (E FEM), and the magnitude (VMExp/σ app) and variability (VMCV) of trabecular stresses were calculated using microCT-based finite element modeling. Mean intercept length, line fraction deviation and fractal parameters were obtained from coronal DTS slices, then correlated with stereological and finite element parameters using linear regression models. Twenty-one DTS parameters (out of 27) correlated to BV/TV, Tb.Th, Tb.N, Tb.Sp and/or μCT.DA (p <0.0001–p <0.05). DTS parameters increased the explained variability in E FEM and VMCV (by 9–11% and 13–19%, respectively; p <0.0001–p <0.04) over that explained by BV/TV. In conclusion, DTS has potential for quantitative assessment of cancellous bone and may be used as a modality complementary to those measuring bone mass for assessing spinal fracture risk.


      PubDate: 2014-12-16T04:42:30Z
       
  • On feature extraction and classification in prostate cancer radiotherapy
           using tensor decompositions
    • Abstract: Publication date: Available online 20 November 2014
      Source:Medical Engineering & Physics
      Author(s): Auréline Fargeas , Laurent Albera , Amar Kachenoura , Gaël Dréan , Juan-David Ospina , Julie Coloigner , Caroline Lafond , Jean-Bernard Delobel , Renaud De Crevoisier , Oscar Acosta
      External beam radiotherapy is commonly prescribed for prostate cancer. Although new radiation techniques allow high doses to be delivered to the target, the surrounding healthy organs (rectum and bladder) may suffer from irradiation, which might produce undesirable side-effects. Hence, the understanding of the complex toxicity dose–volume effect relationships is crucial to adapt the treatment, thereby decreasing the risk of toxicity. In this paper, we introduce a novel method to classify patients at risk of presenting rectal bleeding based on a Deterministic Multi-way Analysis (DMA) of three-dimensional planned dose distributions across a population. After a non-rigid spatial alignment of the anatomies applied to the dose distributions, the proposed method seeks for two bases of vectors representing bleeding and non bleeding patients by using the Canonical Polyadic (CP) decomposition of two fourth order arrays of the planned doses. A patient is then classified according to its distance to the subspaces spanned by both bases. A total of 99 patients treated for prostate cancer were used to analyze and test the performance of the proposed approach, named CP-DMA, in a leave-one-out cross validation scheme. Results were compared with supervised (linear discriminant analysis, support vector machine, K-means, K-nearest neighbor) and unsupervised (recent principal component analysis-based algorithm, and multidimensional classification method) approaches based on the registered dose distribution. Moreover, CP-DMA was also compared with the Normal Tissue Complication Probability (NTCP) model. The CP-DMA method allowed rectal bleeding patients to be classified with good specificity and sensitivity values, outperforming the classical approaches.


      PubDate: 2014-12-16T04:42:30Z
       
  • Simultaneous pressure–volume measurements using optical sensors and
           MRI for left ventricle function assessment during animal experiment
    • Abstract: Publication date: Available online 11 December 2014
      Source:Medical Engineering & Physics
      Author(s): Dima Abi-Abdallah Rodriguez , Emmanuel Durand , Ludovic de Rochefort , Younes Boudjemline , Elie Mousseaux
      Simultaneous pressure and volume measurements enable the extraction of valuable parameters for left ventricle function assessment. Cardiac MR has proven to be the most accurate method for volume estimation. Nonetheless, measuring pressure simultaneously during MRI acquisitions remains a challenge given the magnetic nature of the widely used pressure transducers. In this study we show the feasibility of simultaneous in vivo pressure–volume acquisitions with MRI using optical pressure sensors. Pressure–volume loops were calculated while inducing three inotropic states in a sheep and functional indices were extracted, using single beat loops, to characterize systolic and diastolic performance. Functional indices evolved as expected in response to positive inotropic stimuli. The end-systolic elastance, representing the contractility index, the diastolic myocardium compliance, and the cardiac work efficiency all increased when inducing inotropic state enhancement. The association of MRI and optical pressure sensors within the left ventricle successfully enabled pressure–volume loop analysis after having respective data simultaneously recorded during the experimentation without the need to move the animal between each inotropic state.


      PubDate: 2014-12-16T04:42:30Z
       
  • Modelling the heart with the atrioventricular plane as a piston unit
    • Abstract: Publication date: Available online 22 November 2014
      Source:Medical Engineering & Physics
      Author(s): Elira Maksuti , Anna Bjällmark , Michael Broomé
      Medical imaging and clinical studies have proven that the heart pumps by means of minor outer volume changes and back-and-forth longitudinal movements in the atrioventricular (AV) region. The magnitude of AV-plane displacement has also shown to be a reliable index for diagnosis of heart failure. Despite this, AV-plane displacement is usually omitted from cardiovascular modelling. We present a lumped-parameter cardiac model in which the heart is described as a displacement pump with the AV plane functioning as a piston unit (AV piston). This unit is constructed of different upper and lower areas analogous with the difference in the atrial and ventricular cross-sections. The model output reproduces normal physiology, with a left ventricular pressure in the range of 8–130mmHg, an atrial pressure of approximatly 9mmHg, and an arterial pressure change between 75mmHg and 130mmHg. In addition, the model reproduces the direction of the main systolic and diastolic movements of the AV piston with realistic velocity magnitude (∼10cm/s). Moreover, changes in the simulated systolic ventricular-contraction force influence diastolic filling, emphasizing the coupling between cardiac systolic and diastolic functions. The agreement between the simulation and normal physiology highlights the importance of myocardial longitudinal movements and of atrioventricular interactions in cardiac pumping.


      PubDate: 2014-12-16T04:42:30Z
       
  • Design optimization of a deflectable guidewire
    • Abstract: Publication date: Available online 22 November 2014
      Source:Medical Engineering & Physics
      Author(s): H.C.M. Clogenson , A. Simonetto , J.J. van den Dobbelsteen
      Over the years, the design of the tip of available catheters and guidewires has evolved into various shapes whose geometry is mostly based on common sense and experimentation. However, while the tip shape of conventional instruments can be easily modified and tested, the length of the tip of a deflectable guidewire cannot. Hence, other approaches are necessary in order to determine the proper dimensions of original instruments. In this paper, we formulate the length of the different parts of the deflectable tip of a guidewire as an optimization problem with the objective to obtain a design that is suitable for cannulating several target bifurcations of the peripheral vasculature. A direct relationship between the design of the deflectable tip and the geometry of the target bifurcations was found and the optimal dimension of the tip of the instrument was computed. Following the length specifications defined by the optimization, a new prototype was assembled, and evaluated. The deflectable guidewire could successfully cannulate most of the pre-selected branches except those bifurcations with an angle α >70°. The latter limitation could be ascribed to the mechanical properties of the instrument.


      PubDate: 2014-12-16T04:42:30Z
       
  • Rapid pressure-to-flow dynamics of cerebral autoregulation induced by
           instantaneous changes of arterial CO2
    • Abstract: Publication date: Available online 5 October 2014
      Source:Medical Engineering & Physics
      Author(s): Jia Liu , David M. Simpson , Hesam Kouchakpour , Ronney B. Panerai , Jie Chen , Shan Gao , Pandeng Zhang , Xinyu Wu
      Continuous assessment of CA is desirable in a number of clinical conditions, where cerebral hemodynamics may change within relatively short periods. In this work, we propose a novel method that can improve temporal resolution when assessing the pressure-to-flow dynamics in the presence of rapid changes in arterial CO2. A time-varying multivariate model is proposed to adaptively suppress the instantaneous effect of CO2 on CBFV by the recursive least square (RLS) method. Autoregulation is then quantified from the phase difference (PD) between arterial blood pressure (ABP) and CBFV by calculating the instantaneous PD between the signals using the Hilbert transform (HT). A Gaussian filter is used prior to HT in order to optimize the temporal and frequency resolution and show the rapid dynamics of cerebral autoregulation. In 13 healthy adult volunteers, rapid changes of arterial CO2 were induced by rebreathing expired air, while simultaneously and continuously recording ABP, CBFV and end-tidal CO2 (ETCO2). Both simulation and physiological studies show that the proposed method can reduce the transient distortion of the instantaneous phase dynamics caused by the effect of CO2 and is faster than our previous method in tracking time-varying autoregulation. The normalized mean square error (NMSE) of the predicted CBFV can be reduced significantly by 38.7% and 37.7% (p <0.001) without and with the Gaussian filter applied, respectively, when compared with the previous univariate model. These findings suggest that the proposed method is suitable to track rapid dynamics of cerebral autoregulation despite the influence of confounding covariates.


      PubDate: 2014-10-09T11:21:43Z
       
  • Assessing the bilateral geometrical differences of the tibia – Are
           they the same'
    • Abstract: Publication date: Available online 27 September 2014
      Source:Medical Engineering & Physics
      Author(s): S. Radzi , M. Uesugi , A. Baird , S. Mishra , M. Schuetz , B. Schmutz
      Contralateral bones are often used in many medical applications but it is assumed that their bilateral differences are insignificant. Previous studies used a limited number of distance measurements in quantifying the corresponding differences; therefore, little is known about their bilateral 3D surface asymmetries. The aim of the study is to develop a comprehensive method to quantify geometrical asymmetries between the left and right tibia in order to provide first results on whether the contralateral tibia can be used as an equivalent reference. In this study, 3D bone models were reconstructed from CT scans of seven tibiae pairs, and 34 variables consisting of 2D and 3D measurements were measured from various anatomical regions. All 2D measurements, and lateral plateau and distal subchondral bone surface measurements showed insignificant differences (p >0.05), but the rest of the surfaces showed significant differences (p <0.05). Our results suggest that the contralateral tibia can be used as a reference especially in surgical applications such as articular reconstructions since the bilateral differences in the subchondral bone surfaces were less than 0.3mm. The method can also be potentially transferable to other relevant studies that require the accurate quantification of bone bilateral asymmetries.


      PubDate: 2014-09-29T10:05:58Z
       
  • Automatic detection of wakefulness and rest intervals in actigraphic
           signals: A data-driven approach
    • Abstract: Publication date: Available online 26 September 2014
      Source:Medical Engineering & Physics
      Author(s): D. Martín-Martínez , P. Casaseca-de-la-Higuera , J.M. Andrés-de-Llano , J.R. Garmendia-Leiza , S. Alberola-López , C. Alberola-López
      Actigraphy is an useful tool for evaluating the activity pattern of a subject; activity registries are usually processed by first splitting the signal into its wakefulness and rest intervals and then analyzing each one in isolation. Consequently, a preprocessing stage for such a splitting is needed. Several methods have been reported to this end but they rely on parameters and thresholds which are manually set based on previous knowledge of the signals or learned from training. This compromises the general applicability of this methods. In this paper we propose a new method in which thresholds are automatically set based solely on the specific registry to be analyzed. The method consists of two stages: (1) estimation of an initial classification mask by means of the expectation maximization algorithm and (2) estimation of a final refined mask through an iterative method which re-estimates both the mask and the classifier parameters at each iteration step. Results on real data show that our methodology outperforms those so far proposed and can be more effectively used to obtain derived sleep quality parameters from actigraphy registries.


      PubDate: 2014-09-29T10:05:58Z
       
  • Image-based vs. mesh-based statistical appearance models of the human
           femur: Implications for finite element simulations
    • Abstract: Publication date: Available online 27 September 2014
      Source:Medical Engineering & Physics
      Author(s): Serena Bonaretti , Christof Seiler , Christelle Boichon , Mauricio Reyes , Philippe Büchler
      Statistical appearance models have recently been introduced in bone mechanics to investigate bone geometry and mechanical properties in population studies. The establishment of accurate anatomical correspondences is a critical aspect for the construction of reliable models. Depending on the representation of a bone as an image or a mesh, correspondences are detected using image registration or mesh morphing. The objective of this study was to compare image-based and mesh-based statistical appearance models of the femur for finite element (FE) simulations. To this aim, (i) we compared correspondence detection methods on bone surface and in bone volume; (ii) we created an image-based and a mesh-based statistical appearance models from 130 images, which we validated using compactness, representation and generalization, and we analyzed the FE results on 50 recreated bones vs. original bones; (iii) we created 1000 new instances, and we compared the quality of the FE meshes. Results showed that the image-based approach was more accurate in volume correspondence detection and quality of FE meshes, whereas the mesh-based approach was more accurate for surface correspondence detection and model compactness. Based on our results, we recommend the use of image-based statistical appearance models for FE simulations of the femur.


      PubDate: 2014-09-29T10:05:58Z
       
  • The role of coupled resistance–compliance in upper tracheobronchial
           airways under high frequency oscillatory ventilation
    • Abstract: Publication date: Available online 22 September 2014
      Source:Medical Engineering & Physics
      Author(s): Mohammed Alzahrany , Arindam Banerjee , Gary Salzman
      A large eddy simulation (LES) based computational fluid dynamics (CFD) study was conducted to investigate lung lobar ventilation and gas exchange under high frequency oscillatory ventilation conditions. Time-dependent pressure coupled with the airways resistance and compliance (R&C) were imposed as boundary conditions (BCs) in the upper tracheobronchial tree of patient-specific lung geometry. The flow distribution in the left and right lungs demonstrated significant variations compared to the case in which traditional BCs based on mass flow rate fractions was used and is in agreement with the in vivo data available in the literature. The gas transport due to the pendelluft mechanism was captured in the different lung lobes and units. The computed pendelluft elapsed time was consistent with available physiological data. In contrast to in vivo studies, our simulations were able to predict the volume associated with the pendelluft elapsed time at different frequencies. Significant differences in coaxial counter flow and flow structures were observed between different BCs. The consistency of the results with the physiological in vivo data indicates that computations with coupled R&C BCs provide a suitable alternative tool for understanding the gas transport, diagnosing lung pathway disease severity, and optimizing ventilation management techniques.


      PubDate: 2014-09-22T06:41:31Z
       
  • In vivo measurements of patellar tracking and finite helical axis using a
           static magnetic resonance based methodology
    • Abstract: Publication date: Available online 18 September 2014
      Source:Medical Engineering & Physics
      Author(s): Jie Yao , Bin Yang , Wenxin Niu , Jianwei Zhou , Yuxing Wang , He Gong , Huasong Ma , Rong Tan , Yubo Fan
      Patellofemoral (PF) maltracking is a critical factor predisposing to PF pain syndrome. Many novel techniques of measuring patellar tracking remain research tools. This study aimed to develop a method to measure the in vivo patellar tracking and finite helical axis (FHA) by using a static magnetic resonance (MR) based methodology. The geometrical models of PF joint at 0°, 45°, 60°, 90°, and 120° of knee flexion were developed from MR images. The approximate patellar tracking was derived from the discrete PF models with a spline interpolation algorithm. The patellar tracking was validated with the previous in vitro and in vivo experiments. The patellar FHA throughout knee flexion was calculated. In the present case, the FHA drew an “L-shaped” curve in the sagittal section. This methodology could advance the examination of PF kinematics in clinics, and may also provide preliminary knowledge on patellar FHA study.


      PubDate: 2014-09-19T06:16:56Z
       
  • A new protocol from real joint motion data for wear simulation in total
           knee arthroplasty: Stair climbing
    • Abstract: Publication date: Available online 18 September 2014
      Source:Medical Engineering & Physics
      Author(s): Santina Battaglia , Claudio Belvedere , Sami Abdel Jaber , Saverio Affatato , Valentina D’Angeli , Alberto Leardini
      In its normal lifespan, a knee prosthesis must bear highly demanding loading conditions, going beyond the sole activity of level walking required by ISO standard 14243. We have developed a protocol for in vitro wear simulation of stair climbing on a displacement controlled knee simulator. The flexion/extension angle, intra/extra rotation angle, and antero/posterior translation were obtained in patients by three-dimensional video-fluoroscopy. Axial load data were collected by gait analysis. Kinematics and load data revealed a good consistence across patients, in spite of the different prosthesis size. The protocol was then implemented and tested on a displacement controlled knee wear simulator, showing an accurate reproduction of stair climbing waveforms with a relative error lower than 5%.


      PubDate: 2014-09-19T06:16:56Z
       
  • Control strategies for effective robot assisted gait rehabilitation: The
           state of art and future prospects
    • Abstract: Publication date: Available online 7 September 2014
      Source:Medical Engineering & Physics
      Author(s): Jinghui Cao , Sheng Quan Xie , Raj Das , Guo L. Zhu
      A large number of gait rehabilitation robots, together with a variety of control strategies, have been developed and evaluated during the last decade. Initially, control strategies applied to rehabilitation robots were adapted from those applied to traditional industrial robots. However, these strategies cannot optimise effectiveness of gait rehabilitation. As a result, researchers have been investigating control strategies tailored for the needs of rehabilitation. Among these control strategies, assisted-as-needed (AAN) control is one of the most popular research topics in this field. AAN training strategies have gained the theoretical and practical evidence based backup from motor learning principles and clinical studies. Various approaches to AAN training have been proposed and investigated by research groups all around the world. This article presents a review on control algorithms of gait rehabilitation robots to summarise related knowledge and investigate potential trends of development. There are existing review papers on control strategies of rehabilitation robots. The review by Marchal-Crespo and Reinkensmeyer (2009) had a broad cover of control strategies of all kinds of rehabilitation robots. Hussain et al. (2011) had specifically focused on treadmill gait training robots and covered a limited number of control implementations on them. This review article encompasses more detailed information on control strategies for robot assisted gait rehabilitation, but is not limited to treadmill based training. It also investigates the potential to further develop assist-as-needed gait training based on assessments of patients’ ability. In this paper, control strategies are generally divided into the trajectory tracking control and AAN control. The review covers these two basic categories, as well as other control algorithm and technologies derived from them, such as biofeedback control. Assessments on human gait ability are also included to investigate how to further develop implementations based on assist-as-needed concept. For the consideration of effectiveness, clinical studies on robotic gait rehabilitation are reviewed and analysed from the viewpoint of control algorithm.


      PubDate: 2014-09-11T05:24:38Z
       
  • What if you stretch the IFU' A mechanical insight into stent graft
           instructions for use in angulated proximal aneurysm necks
    • Abstract: Publication date: Available online 10 September 2014
      Source:Medical Engineering & Physics
      Author(s): S. De Bock , F. Iannaccone , M. De Beule , F. Vermassen , P. Segers , B. Verhegghe
      Endovascular treatment for patients with a proximal neck anatomy outside instructions for use is an ongoing topic of debate in endovascular aneurysm repair. This paper employs the finite element method to offer insight into possible adverse effects of deploying a stent graft into an angulated geometry. The effect of angulation, straight neck length and device oversize was investigated in a full factorial parametric analysis. Stent apposition, area reduction of the graft, asymmetry of contact forces and the ability to find a good seal were investigated. Most adverse effects are expected for combinations of high angulation and short straight landing zones. Higher oversize has a beneficiary effect, but not enough to compensate the adverse effects of (very) short and angulated angles. Our analysis shows that for an angle between the suprarenal aorta and proximal neck above 60°, proximal kinking of the device can occur. The method used offers a engineering view on the morphological limits of EVAR for a clinically used device.


      PubDate: 2014-09-11T05:24:38Z
       
  • Nonlinear properties of cardiac rhythm and respiratory signal under paced
           breathing in young and middle-aged healthy subjects
    • Abstract: Publication date: Available online 4 September 2014
      Source:Medical Engineering & Physics
      Author(s): Ana Kapidžić , Mirjana M Platiša , Tijana Bojić , Aleksandar Kalauzi
      We examined the effects of gender and age in young and middle-aged subjects on the level of cardio-respiratory interaction by analyzing properties of cardiac, respiratory and cardiac-respiratory regulatory mechanisms under paced breathing. In 56 healthy subjects, ECG (RR interval) and respiratory signal were simultaneously acquired in supine position at paced (0.1–0.45Hz, steps of 0.05Hz) and spontaneous breathing. The participants were divided into gender matched group of young adults (19–25 years old) and middle-aged adults (35–44 years old). Power spectral analysis was applied on RR interval time series and spectral components in very low frequency (VLF), low frequency (LF) and high frequency (HF) ranges were computed. We also calculated sample entropy of RR interval series (SampEnRR), respiratory series (SampEnResp), and their cross-sample entropy (cross-SampEn). Under paced breathing, reduction of all spectral powers with age (p <0.05) is not gender dependent but reduction of some entropy measures is; SampEnRR and SampEnResp were lower only in men (p <0.05). In the middle-aged subjects, effect of gender on spectral measures is significant; males had lower HF (p <0.05). Pattern of dependencies of SampEn and cross-SampEn on paced breathing frequency were significantly different in men (young vs. middle-aged, p =0.001 and p =0.037) and in middle-aged subjects (females vs. males, p =0.011 and p =0.008). In middle-aged males, lower entropy measures indicated reduced and less complex partial cardiac and respiratory control, and central cardio-respiratory control. In conclusion, in healthy middle-aged subjects changes in cardio-respiratory coupling are detectable only in males.


      PubDate: 2014-09-06T04:51:13Z
       
 
 
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