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  Subjects -> BIOLOGY (Total: 2843 journals)
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BIOLOGY (1382 journals)            First | 4 5 6 7 8 9 10 11 | Last

Journal of Aquatic Sciences     Full-text available via subscription  
Journal of Arachnology     Full-text available via subscription  
Journal of Asia-Pacific Biodiversity     Open Access  
Journal of Astrobiology & Outreach     Open Access  
Journal of Avian Biology     Hybrid Journal   (Followers: 19)
Journal of Bacteriology     Full-text available via subscription   (Followers: 16)
Journal of Basic Microbiology     Hybrid Journal   (Followers: 3)
Journal of Bio-Science     Open Access   (Followers: 1)
Journal of Biobased Materials and Bioenergy     Full-text available via subscription  
Journal of Biodiversity & Endangered Species     Open Access  
Journal of Biodiversity Management & Forestry     Hybrid Journal   (Followers: 1)
Journal of Bioenergetics and Biomembranes     Hybrid Journal  
Journal of Biogeography     Hybrid Journal   (Followers: 20)
Journal of Bioinformatics and Computational Biology     Hybrid Journal   (Followers: 12)
Journal of Bioinformatics and Intelligent Control     Full-text available via subscription  
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: 4)
Journal of Biomarkers     Open Access  
Journal of Biomechanics     Hybrid Journal   (Followers: 27)
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: 5)
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: 17)
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 Bryology     Hybrid Journal   (Followers: 1)
Journal of Cell and Plant Sciences     Open Access   (Followers: 4)
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: 11)
Journal of Cellular Biochemistry     Hybrid Journal   (Followers: 3)
Journal of Cellular Physiology     Hybrid Journal   (Followers: 3)
Journal of Cerebral Blood Flow & Metabolism     Hybrid Journal   (Followers: 2)
Journal of Chromatography B     Hybrid Journal   (Followers: 21)
Journal of Clinical Bioinformatics     Open Access   (Followers: 5)
Journal of Clinical Toxicology     Open Access   (Followers: 1)
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     Hybrid Journal   (Followers: 2)
Journal of Developmental Biology     Open Access   (Followers: 3)
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: 12)
Journal of Environmental Radioactivity     Hybrid Journal   (Followers: 3)
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: 2)
Journal of Evolutionary Biology     Hybrid Journal   (Followers: 23)
Journal of Experimental and Clinical Anatomy     Open Access  
Journal of Experimental Marine Biology and Ecology     Hybrid Journal   (Followers: 27)
Journal of Fish Biology     Hybrid Journal   (Followers: 24)
Journal of Functional Biomaterials     Open Access   (Followers: 1)
Journal of Fungi     Open Access  
Journal of Genomes and Exomes     Open Access  
Journal of Great Lakes Research     Hybrid Journal   (Followers: 7)
Journal of Green Science and Technology     Full-text available via subscription  
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 Histology & Histopathology     Open Access  
Journal of Huazhong University of Science and Technology [Medical Sciences]     Hybrid Journal  
Journal of Human Evolution     Hybrid Journal   (Followers: 12)
Journal of Hymenoptera Research     Open Access   (Followers: 1)
Journal of Ichthyology     Hybrid Journal   (Followers: 3)
Journal of Insect Behavior     Hybrid Journal   (Followers: 6)
Journal of Insect Biodiversity     Open Access   (Followers: 3)
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: 4)
Journal of Invertebrate Pathology     Hybrid Journal   (Followers: 3)
Journal of Landscape Ecology     Open Access   (Followers: 7)
Journal of Law and the Biosciences     Open Access   (Followers: 2)
Journal of Leukocyte Biology     Open Access   (Followers: 4)
Journal of Life and Earth Science     Open Access  

  First | 4 5 6 7 8 9 10 11 | Last

Journal Cover   Medical Engineering & Physics
  [SJR: 0.871]   [H-I: 64]   [9 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1350-4533
   Published by Elsevier Homepage  [2812 journals]
  • Individual and combined effects of OA-related subchondral bone alterations
           on proximal tibial surface stiffness: a parametric finite element modeling
           study
    • Abstract: Publication date: Available online 12 June 2015
      Source:Medical Engineering & Physics
      Author(s): Morteza Amini , S. Majid Nazemi , Joel L. Lanovaz , Saija Kontulainen , Bassam A. Masri , David R. Wilson , Walerian Szyszkowski , James D. Johnston
      The role of subchondral bone in OA pathogenesis is unclear. While some OA-related changes to morphology and material properties in different bone regions have been described, the effect of these alterations on subchondral bone surface stiffness has not been investigated. The objectives of this study were to characterize the individual (Objective 1) and combined (Objective 2) effects of OA-related morphological and mechanical alterations to subchondral and epiphyseal bone on surface stiffness of the proximal tibia. We developed and validated a parametric FE model of the proximal tibia using quantitative CT images of 10 fresh-frozen cadaveric specimens and in situ macro-indentation testing. Using this validated FE model, we estimated the individual and combined roles of OA-related alterations in subchondral cortical thickness and elastic modulus, and subchondral trabecular and epiphyseal trabecular elastic moduli on local surface stiffness. A 20% increase in subchondral cortical or subchondral trabecular elastic moduli resulted in little change in stiffness (1% increase). A 20% reduction in epiphyseal trabecular elastic modulus, however, resulted in an 11% reduction in stiffness. Our parametric analysis suggests that subchondral bone stiffness is affected primarily by epiphyseal trabecular bone elastic modulus rather than subchondral cortical and trabecular morphology or mechanical properties. Our results suggest that observed OA-related alterations to epiphyseal trabecular bone (e.g., lower mineralization, bone volume fraction, density and elastic modulus) may contribute to OA proximal tibiae being less stiff than normal.


      PubDate: 2015-06-28T14:01:24Z
       
  • Comparison of trunk muscle forces, spinal loads and stability estimated by
           one stability- and three EMG-assisted optimization approaches
    • Abstract: Publication date: Available online 25 June 2015
      Source:Medical Engineering & Physics
      Author(s): Yousef Mohammadi , Navid Arjmand , Aboulfazl Shirazi-Adl
      Various hybrid EMG-assisted optimization (EMGAO) approaches are commonly used to estimate muscle forces and joint loads of human musculoskeletal systems. Use of EMG data and optimization enables the EMGAO models to account for inter- and intra-individual variations in muscle recruitments while satisfying equilibrium requirements. Due to implications in ergonomics/prevention and rehabilitation/treatment managements of low-back disorders, there is a need to evaluate existing approaches. The present study aimed to compare predictions of three different EMGAO and one stability-based optimization (OPT) approaches for trunk muscle forces, spinal loads, and stability. Identical measured kinematics/EMG data and anatomical model were used in all approaches when simulating several sagittally symmetric static activities. Results indicated substantial inter-model differences in predicted muscle forces (up to 123% and 90% for total muscle forces in tasks with upright and flexed postures, respectively) and spinal loads (up to 74% and 78% for compression loads in upright and flexed postures, respectively). Results of EMGAO models markedly varied depending on the manner in which correction (gain) factors were introduced. Large range of gain values (from ∼0.47 to 41) was estimated in each model. While EMGAO methods predicted an unstable spine for some tasks, OPT predicted, as intended, either a meta-stable or stable states in all simulated tasks. An unrealistic unstable state of the spine predicted by EMGAO methods for some of the simulated tasks (which are in reality stable) could be an indication of the shortcoming of these models in proper prediction of muscle forces.


      PubDate: 2015-06-28T14:01:24Z
       
  • From mechanical stimulus to bone formation: A review
    • Abstract: Publication date: Available online 25 June 2015
      Source:Medical Engineering & Physics
      Author(s): Natacha Rosa , Ricardo Simoes , Fernão D. Magalhães , Antonio Torres Marques
      Bone is a remarkable tissue that can respond to external stimuli. The importance of mechanical forces on the mass and structural development of bone has long been accepted. This adaptation behaviour is very complex and involves multidisciplinary concepts, and significant progress has recently been made in understanding this process. In this review, we describe the state of the art studies in this area and highlight current insights while simultaneously clarifying some basic yet essential topics related to the origin of mechanical stimulus in bone, the biomechanisms associated with mechanotransduction, the nature of physiological bone stimuli and the test systems most commonly used to study the mechanical stimulation of bone.


      PubDate: 2015-06-28T14:01:24Z
       
  • Magnetic resonance-based thermometry during laser ablation on ex-vivo
           swine pancreas and liver
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): G. Allegretti , P. Saccomandi , F. Giurazza , M.A. Caponero , G. Frauenfelder , F.M. Di Matteo , B. Beomonte Zobel , S. Silvestri , E. Schena
      Laser Ablation (LA) is a minimally-invasive procedure for tumor treatment. LA outcomes depend on the heat distribution inside tissues and require accurate temperature measurement during the procedure. Magnetic resonance imaging (MRI) allows a non-invasive and three-dimensional thermometry of the organ undergoing LA. In this study, the temperature distribution within two swine pancreases and three swine livers undergoing LA (Nd:YAG, power: 2 W, treatment time: 4 min) was monitored by a 1.5-T MR scanner, utilizing two T 1-weighted sequences (IRTF and SRTF). The signal intensity in four regions of interest, placed at different distances from the laser applicator, was related to temperature variations monitored in the same regions by twelve fiber Bragg grating sensors. The relationship between the signal intensity and temperature increase was calculated to obtain the calibration curve and to evaluate accuracy, sensibility and precision of each sequence. This is the first study of MR-based thermometry during LA on pancreas. More specifically, the IRTF sequence provides the highest temperature sensitivity in both liver (1.8 ± 0.2 °C−1) and pancreas (1.8 ± 0.5 °C−1) and the lowest precision and accuracy. SRTF sequence on pancreas presents the highest accuracy and precision (MODSFRT = −0.1 °C and LOASFRT = [−2.3; 2.1] °C).


      PubDate: 2015-06-28T14:01:24Z
       
  • Trade-off between stress shielding and initial stability on an anatomical
           cementless stem shortening: in-vitro biomechanical study
    • Abstract: Publication date: Available online 25 June 2015
      Source:Medical Engineering & Physics
      Author(s): Go Yamako , Etsuo Chosa , Koji Totoribe , Shinji Watanabe , Takero Sakamoto
      Shortened cementless femoral stems have become popular with the advent of minimally invasive total hip arthroplasty (THA). Successful THA requires initial stem stability and prevention of stress shielding-mediated bone loss, although the effect of stem shortening is controversial. Here we experimentally examined whether stem shortening affects stress shielding and initial stability. Anatomical stems (length, 120 mm) were cut to an 80 mm or 50 mm length. Ten tri-axial strain gauges measured the cortical strain on each stem-implanted femur to evaluate stress shielding. Two transducers measured axial relative displacement and rotation under single-leg stance loading. The 50 mm stem increased the equivalent strains with respect to the original stem in the proximal calcar region (31.0% relative to intact strain), proximal medial region (63.1%), and proximal lateral region (53.9%). In contrast, axial displacement and rotation increased with a decreasing stem length. However, the axial displacement of the 50 mm stem was below a critical value of 150 µm for bone ingrowth. Our findings indicate that, with regard to a reduction in stem length, there is a tradeoff between stress shielding and initial stability. Shortening the stem up to 50 mm can promote proximal load transfer, but bone loss would be inevitable, even with sufficient initial stability for long-term fixation.


      PubDate: 2015-06-28T14:01:24Z
       
  • Alteration of the P-wave non-linear dynamics near the onset of paroxysmal
           atrial fibrillation
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): Arturo Martínez , Daniel Abásolo , Raúl Alcaraz , José J. Rieta
      The analysis of P-wave variability from the electrocardiogram (ECG) has been suggested as an early predictor of the onset of paroxysmal atrial fibrillation (PAF). Hence, a preventive treatment could be used to avoid the loss of normal sinus rhythm, thus minimising health risks and improving the patient’s quality of life. In these previous studies the variability of different temporal and morphological P-wave features has been only analysed in a linear fashion. However, the electrophysiological alteration occurring in the atria before the onset of PAF has to be considered as an inherently complex, chaotic and non-stationary process. This work analyses the presence of non-linear dynamics in the P-wave progression before the onset of PAF through the application of the central tendency measure (CTM), which is a non-linear metric summarising the degree of variability in a time series. Two hour-length ECG intervals just before the arrhythmia onset belonging to 46 different PAF patients were analysed. In agreement with the invasively observed inhomogeneous atrial conduction preceding the onset of PAF, CTM for all the considered P-wave features showed higher variability when the arrhythmia was closer to its onset. A diagnostic accuracy around 80% to discern between ECG segments far from PAF and close to PAF was obtained with the CTM of the metrics considered. This result was similar to previous P-wave variability methods based on linear approaches. However, the combination of linear and non-linear methods with a decision tree improved considerably their discriminant ability up to 90%, thus suggesting that both dynamics could coexist at the same time in the fragmented depolarisation of the atria preceding the arrhythmia.


      PubDate: 2015-06-28T14:01:24Z
       
  • On growth measurements of abdominal aortic aneurysms using maximally
           inscribed spheres
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): H. Gharahi , B.A. Zambrano , C. Lim , J. Choi , W. Lee , S. Baek
      The maximum diameter, total volume of the abdominal aorta, and its growth rate are usually regarded as key factors for making a decision on the therapeutic operation time for an abdominal aortic aneurysm (AAA) patient. There is, however, a debate on what is the best standard method to measure the diameter. Currently, two dominant methods for measuring the maximum diameter are used. One is measured on the planes perpendicular to the aneurism's central line (orthogonal diameter) and the other one is measured on the axial planes (axial diameter). In this paper, another method called ‘inscribed-spherical diameter’ is proposed to measure the diameter. The main idea is to find the diameter of the largest sphere that fits within the aorta. An algorithm is employed to establish a centerline for the AAA geometries obtained from a set of longitudinal scans obtained from South Korea. This centerline, besides being the base of the inscribed spherical method, is used for the determination of orthogonal and axial diameter. The growth rate parameters are calculated in different diameters and the total volume and the correlations between them are studied. Furthermore, an exponential growth pattern is sought for the maximum diameters over time to examine a nonlinear growth pattern of AAA expansion both globally and locally. The results present the similarities and discrepancies of these three methods. We report the shortcomings and the advantages of each method and its performance in the quantification of expansion rates. While the orthogonal diameter measurement has an ability of capturing a realistic diameter, it fluctuated. On the other hand, the inscribed sphere diameter method tends to underestimate the diameter measurement but the growth rate can be bounded in a narrow region for aiding prediction capability. Moreover, expansion rate parameters derived from this measurement exhibit good correlation with each other and with growth rate of volume. In conclusion, although the orthogonal method remains the main method of measuring the diameter of an abdominal aorta, employing the idea of maximally inscribed spheres provides both a tool for generation of the centerline, and an additional parameter for quantification of aneurysmal growth rates.


      PubDate: 2015-06-28T14:01:24Z
       
  • A novel method for discrimination between innocent and pathological heart
           murmurs
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): Arash Gharehbaghi , Magnus Borga , Birgitta Janerot Sjöberg , Per Ask
      This paper presents a novel method for discrimination between innocent and pathological murmurs using the growing time support vector machine (GTSVM). The proposed method is tailored for characterizing innocent murmurs (IM) by putting more emphasis on the early parts of the signal as IMs are often heard in early systolic phase. Individuals with mild to severe aortic stenosis (AS) and IM are the two groups subjected to analysis, taking the normal individuals with no murmur (NM) as the control group. The AS is selected due to the similarity of its murmur to IM, particularly in mild cases. To investigate the effect of the growing time windows, the performance of the GTSVM is compared to that of a conventional support vector machine (SVM), using repeated random sub-sampling method. The mean value of the classification rate/sensitivity is found to be 88%/86% for the GTSVM and 84%/83% for the SVM. The statistical evaluations show that the GTSVM significantly improves performance of the classification as compared to the SVM.


      PubDate: 2015-06-28T14:01:24Z
       
  • Swallowing accelerometry signal feature variations with sensor
           displacement
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): Khondaker A. Mamun , Catriona M. Steele , Tom Chau
      Dual-axis accelerometry has recently shown promise as a non-invasive method for detecting swallowing impairment using signal processing and pattern classification algorithms. However, it is unknown whether variations in sensor placement alter signal characteristics, threatening the accuracy of signal processing classifiers for aspiration detection. To address this question, water swallows were recorded in 14 healthy adults using a dual-axis accelerometer in 13 different positions (baseline, and 2, 4, 6 and 8 mm above, below and to the right of baseline). The baseline position was midline, immediately below the thyroid cartilage during quiet breathing. After segmentation and pre-processing, signal features were extracted in multiple domains (time, frequency, time-frequency). The effect of sensor position on signal feature distributions was examined with non-parametric statistical analysis. The analysis showed that the sensor could be displaced by as much as 4 mm inferior and lateral to the baseline position and by up to 6 mm above the baseline location without significantly altering time-frequency features. In other words, when considering the baseline position as the origin, the admissible region for sensor placement spans 10 mm in the superior-inferior axis and 8 mm in the medial-lateral direction. Results of this study suggest that time-frequency representations of accelerometry signals are most robust to sensor placement variations around the baseline position. The implication of this finding is that a swallowing accelerometry classifier based on time-frequency features can likely tolerate small variations in sensor location without degradation in classification performance.


      PubDate: 2015-06-28T14:01:24Z
       
  • Evaluation of delamination in drilling of bone
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): Rupesh Kumar Pandey , Sudhansu Sekhar Panda
      In this paper, delamination of bone associated with drilling is investigated using design of experiments. Experiments have been planned based on L25 design of the orthogonal arrays with different conditions of drill bit, spindle speed and feed rate. Regression analysis is used to develop a mathematical model of delamination as a function of bone drilling process parameters. Analysis of variance (ANOVA) is carried out to find the significance of the developed model along with the percentage contribution of each factor on delamination. Optimum setting of bone drilling parameters for minimum delamination is determined using Taguchi optimization methodology. Finally, the results obtained are validated by conducting confirmation experiments.


      PubDate: 2015-06-28T14:01:24Z
       
  • Sensitivities of biomechanical assessment methods for fracture healing of
           long bones
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): G. Chen , F.Y. Wu , J.Q. Zhang , G.Q. Zhong , F. Liu
      There is a controversy as to whether the biomechanical methods are feasible to assess fracture healing of long bones. This paper investigated the sensitivities of two biomechanical methods, torsion and bending, for assessing fracture healing of long bones; both a simplified beam model and finite element model of an artificial femur were employed. The results demonstrated that, in the initial healing stage, the whole-bone stiffness of the fractured bone is extremely sensitive to the variation of the callus stiffness at the fracture site; when the shear (or Young's) modulus of the callus reaches 15% that of the intact bone, the whole-bone stiffness rises up to 90% that of the intact bone. After that, the whole-bone torsional (or bending) stiffness increases slowly; it becomes less sensitive to the variation of the callus stiffness. These results imply that the whole-bone stiffness is of limited reliability to assess the healing quality particular at late stages of the healing process. The simplified model in this paper provided a theoretical framework to explain why the whole-bone stiffness is insensitive to the healing process of fractured long bones in the late stage of healing. The conclusions obtained from the simplified model were verified with the finite element simulations of the artificial femur.


      PubDate: 2015-06-28T14:01:24Z
       
  • A whole body vibration perception map and associated acceleration loads at
           the lower leg, hip and head
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): Anelise Sonza , Nina Völkel , Milton A. Zaro , Matilde Achaval , Ewald M. Hennig
      Whole-body vibration (WBV) training has become popular in recent years. However, WBV may be harmful to the human body. The goal of this study was to determine the acceleration magnitudes at different body segments for different frequencies of WBV. Additionally, vibration sensation ratings by subjects served to create perception vibration magnitude and discomfort maps of the human body. In the first of two experiments, 65 young adults mean (± SD) age range of 23 (± 3.0) years, participated in WBV severity perception ratings, based on a Borg scale. Measurements were performed at 12 different frequencies, two intensities (3 and 5 mm amplitudes) of rotational mode WBV. On a separate day, a second experiment (n = 40) included vertical accelerometry of the head, hip and lower leg with the same WBV settings. The highest lower limb vibration magnitude perception based on the Borg scale was extremely intense for the frequencies between 21 and 25 Hz; somewhat hard for the trunk region (11–25 Hz) and fairly light for the head (13–25 Hz). The highest vertical accelerations were found at a frequency of 23 Hz at the tibia, 9 Hz at the hip and 13 Hz at the head. At 5 mm amplitude, 61.5% of the subjects reported discomfort in the foot region (21–25 Hz), 46.2% for the lower back (17, 19 and 21 Hz) and 23% for the abdominal region (9–13 Hz). The range of 3–7 Hz represents the safest frequency range with magnitudes less than 1 g*sec for all studied regions.


      PubDate: 2015-06-28T14:01:24Z
       
  • Corrigendum to “Biomechanical analysis of different types of pedicle
           screw augmentation: a cadaveric and synthetic bone sample study of
           instrumented vertebral specimens” [Med. Eng. Phys. 35/10 (2013)
           1506–1522]
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): Kuo-Hua Chao , Yu-Shu Lai , Wen-Chuan Chen , Chia-Ming Chang , Colin J. McClean , Chang-Yuan Fan , Chia-Hao Chang , Leou-Chyr Lin , Cheng-Kung Cheng



      PubDate: 2015-06-28T14:01:24Z
       
  • Carotid plaque elasticity estimation using ultrasound elastography, MRI,
           and inverse FEA – A numerical feasibility study
    • Abstract: Publication date: Available online 27 June 2015
      Source:Medical Engineering & Physics
      Author(s): H.A. Nieuwstadt , S. Fekkes , H.H.G. Hansen , C.L. de Korte , A. van der Lugt , J.J. Wentzel , A.F.W. van der Steen , F.J.H. Gijsen
      The material properties of atherosclerotic plaques govern the biomechanical environment, which is associated with rupture-risk. We investigated the feasibility of noninvasively estimating carotid plaque component material properties through simulating ultrasound (US) elastography and in vivo magnetic resonance imaging (MRI), and solving the inverse problem with finite element analysis. 2D plaque models were derived from endarterectomy specimens of nine patients. Nonlinear neo-Hookean models (tissue elasticity C 1) were assigned to fibrous intima, wall (i.e., media/adventitia), and lipid-rich necrotic core. Finite element analysis was used to simulate clinical cross-sectional US strain imaging. Computer-simulated, single-slice in vivo MR images were segmented by two MR readers. We investigated multiple scenarios for plaque model elasticity, and consistently found clear separations between estimated tissue elasticity values. The intima C 1 (160 kPa scenario) was estimated as 125.8 ± 19.4 kPa (reader 1) and 128.9 ± 24.8 kPa (reader 2). The lipid-rich necrotic core C 1 (5 kPa) was estimated as 5.6 ± 2.0 kPa (reader 1) and 8.5 ± 4.5 kPa (reader 2). A scenario with a stiffer wall yielded similar results, while realistic US strain noise and rotating the models had little influence, thus demonstrating robustness of the procedure. The promising findings of this computer-simulation study stimulate applying the proposed methodology in a clinical setting.


      PubDate: 2015-06-28T14:01:24Z
       
  • Varying behavior of different window sizes on the classification of static
           and dynamic physical activities from a single accelerometer
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): Benish Fida , Ivan Bernabucci , Daniele Bibbo , Silvia Conforto , Maurizio Schmid
      Accuracy of systems able to recognize in real time daily living activities heavily depends on the processing step for signal segmentation. So far, windowing approaches are used to segment data and the window size is usually chosen based on previous studies. However, literature is vague on the investigation of its effect on the obtained activity recognition accuracy, if both short and long duration activities are considered. In this work, we present the impact of window size on the recognition of daily living activities, where transitions between different activities are also taken into account. The study was conducted on nine participants who wore a tri-axial accelerometer on their waist and performed some short (sitting, standing, and transitions between activities) and long (walking, stair descending and stair ascending) duration activities. Five different classifiers were tested, and among the different window sizes, it was found that 1.5 s window size represents the best trade-off in recognition among activities, with an obtained accuracy well above 90%. Differences in recognition accuracy for each activity highlight the utility of developing adaptive segmentation criteria, based on the duration of the activities.


      PubDate: 2015-06-28T14:01:24Z
       
  • Achilles tendon displacement patterns during passive stretch and eccentric
           loading are altered in middle-aged adults
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): Laura Chernak Slane , Darryl G. Thelen
      The purpose of this study was to investigate middle-age effects on Achilles displacement patterns under passive stretch and eccentric loading. Healthy young (24.1 ± 1.4 years, n = 9) and middle-aged (49.0 ± 3.1 years, n = 9) adults were positioned prone and the ankle was cyclically dorsiflexed (0.5 Hz, 25° range) during passive stretch and active lengthening. Achilles displacements were tracked in cine ultrasound using 2D speckle tracking. Displacements were found to be non-uniform, with mid and deep portions of the tendon displacing more than superficial portions. However, the degree of non-uniformity was significantly reduced in middle-aged adults, suggesting a potential age-related reduction in inter-fascicle sliding or a shift in loading sharing between plantarflexors. Eccentric loading reduced displacement magnitudes, likely reflecting distal tendon stretch induced via active muscle contractions. Changes in tendon displacement with active loading were greater in middle-aged adults, which could reflect greater tendon compliance. The observed age-related changes in Achilles tendon behavior may have implications for both plantarflexor performance and injury risk.


      PubDate: 2015-06-28T14:01:24Z
       
  • Editorial Board
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7




      PubDate: 2015-06-28T14:01:24Z
       
  • Multi-selective catheter for MR-guided endovascular interventions
    • Abstract: Publication date: July 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 7
      Author(s): Helene C.M. Clogenson , Joris Y. van Lith , Jenny Dankelman , Andreas Melzer , John J. van den Dobbelsteen
      Selective catheters have predefined distal shapes and need to be exchanged to change tip geometry to facilitate selective catheterization of vascular side branches. These repeated insertions increase the risk of endovascular injury and radiation dose in conventional catheterization laboratories. The aim of this study is to develop a multi-selective catheter that can replace three conventional selective catheters that are commonly used sequentially in a single procedure. By integrating the different shapes in one instrument, it is possible to avoid the required time-consuming exchange. This new instrument is also made compatible with magnetic resonance imaging (MRI) guidance, which, unlike X-ray, presents variable soft tissue contrast without the use of ionizing radiation. A 1.2 m long and 2.15 mm diameter deflectable polymer-based catheter was assembled and three widely used selective catheters could be mimicked. The instrument was visible on the images without producing unwanted artifacts in an abdominal model and in an animal under real-time MRI guidance. Simple navigation tasks were performed together with a 0.035 in. MRI-safe guidewire. In these tasks, the iliac, renal, brachiocephalic, and left subclavian arteries were cannulated only by using the shape setting and without exchange of the instruments.


      PubDate: 2015-06-28T14:01:24Z
       
  • Anatomical calibration for wearable motion capture systems: Video
           calibrated anatomical system technique
    • Abstract: Publication date: Available online 12 June 2015
      Source:Medical Engineering & Physics
      Author(s): Maria Cristina Bisi , Rita Stagni , Alessio Caroselli , Angelo Cappello
      Inertial sensors are becoming widely used for the assessment of human movement in both clinical and research applications, thanks to their usability out of the laboratory. This work aims to propose a method for calibrating anatomical landmark position in the wearable sensor reference frame with an ease to use, portable and low cost device. An off-the-shelf camera, a stick and a pattern, attached to the inertial sensor, compose the device. The proposed technique is referred to as video Calibrated Anatomical System Technique (vCAST). The absolute orientation of a synthetic femur was tracked both using the vCAST together with an inertial sensor and using stereo-photogrammetry as reference. Anatomical landmark calibration showed mean absolute error of 0.6±0.5 mm: these errors are smaller than those affecting the in-vivo identification of anatomical landmarks. The roll, pitch and yaw anatomical frame orientations showed root mean square errors close to the accuracy limit of the wearable sensor used (1°), highlighting the reliability of the proposed technique. In conclusion, the present paper proposes and preliminarily verifies the performance of a method (vCAST) for calibrating anatomical landmark position in the wearable sensor reference frame: the technique is low time consuming, highly portable, easy to implement and usable outside laboratory.


      PubDate: 2015-06-28T14:01:24Z
       
  • Microconfined flow behavior of red blood cells
    • Abstract: Publication date: Available online 10 June 2015
      Source:Medical Engineering & Physics
      Author(s): Giovanna Tomaiuolo , Luca Lanotte , Rosa D'Apolito , Antonio Cassinese , Stefano Guido
      Red blood cells (RBCs) perform essential functions in human body, such as gas exchange between blood and tissues, thanks to their ability to deform and flow in the microvascular network. The high RBC deformability is mainly due to the viscoelastic properties of the cell membrane. Since an impaired RBC deformability could be found in some diseases, such as malaria, sickle cell anemia, diabetes and hereditary disorders, there is the need to provide further insight into measurement of RBC deformability in a physiologically relevant flow field. Here, RBCs deformability has been studied in terms of the minimum apparent plasma-layer thickness by using high-speed video microscopy of RBCs flowing in cylindrical glass capillaries. An in vitro systematic microfluidic investigation of RBCs in micro-confined conditions has been performed, resulting in the determination of the RBCs time recovery constant, RBC volume and surface area and RBC membrane shear elastic modulus and surface viscosity. It has been noticed that the deformability of RBCs induces cells aggregation during flow in microcapillaries, allowing the formation of clusters of cells. Overall, our results provide a novel technique to estimate RBC deformability and also RBCs collective behavior, which can be used for the analysis of pathological RBCs, for which reliable quantitative methods are still lacking.


      PubDate: 2015-06-28T14:01:24Z
       
  • Low-intensity functional electrical stimulation can increase
           multidirectional trunk stiffness in able-bodied individuals during sitting
           
    • Abstract: Publication date: Available online 10 June 2015
      Source:Medical Engineering & Physics
      Author(s): Albert H. Vette , Noel Wu , Kei Masani , Milos R. Popovic
      The inability to voluntarily control the trunk musculature is a major problem following spinal cord injury as it can compromise functional independence and produce unwanted secondary complications. Recent developments suggest that neuroprostheses utilizing functional electrical stimulation (FES) may be able to facilitate or restore trunk control during sitting, standing, and other tasks involving postural control. In spite of these efforts, no study to date has used low-intensity FES to increase multidirectional trunk stiffness and damping in an attempt to bolster stability while minimizing muscle fatigue. Therefore, we set out to investigate how multidirectional trunk stiffness changes in response to low-intensity FES of a few selected trunk muscles. Fifteen healthy participants sitting naturally were randomly perturbed in eight horizontal directions. Trunk stiffness and damping during natural and FES-supported sitting conditions were quantified using force and trunk kinematics in combination with two models of a mass-spring-damper system. Our results indicate that low-intensity FES can increase trunk stiffness in healthy individuals, and this specifically for directions associated with the stimulated muscles. In contrast, trunk damping was not found to be altered during FES. The presented results suggest that low-intensity FES is a simple and effective method for increasing trunk stiffness on demand.


      PubDate: 2015-06-28T14:01:24Z
       
  • Development of a non-invasive diagnostic technique for acetabular
           component loosening in total hip replacements
    • Abstract: Publication date: Available online 6 June 2015
      Source:Medical Engineering & Physics
      Author(s): Abdullah A. Alshuhri , Timothy P. Holsgrove , Anthony W. Miles , James L. Cunningham
      Current techniques for diagnosing early loosening of a total hip replacement (THR) are ineffective, especially for the acetabular component. Accordingly, new, accurate, and quantifiable methods are required. The aim of this study was to investigate the viability of vibrational analysis for accurately detecting acetabular component loosening. A simplified acetabular model was constructed using a Sawbones® foam block. By placing a thin silicone layer between the acetabular component and the Sawbones block, 2- and 4-mm soft tissue membranes were simulated representing different loosening scenarios. A constant amplitude sinusoidal excitation with a sweep range of 100–1500 Hz was used. Output vibration from the model was measured using an accelerometer and an ultrasound probe. Loosening was determined from output signal features such as the number and relative strength of observed harmonic frequencies. Both measurement methods were sufficient to measure the output vibration. Vibrational analysis reliably detected loosening corresponding to both 2 and 4 mm tissue membranes at driving frequencies between 100 and 1000 Hz (p < 0.01) using the accelerometer. In contrast, ultrasound detected 2-mm loosening at a frequency range of 850–1050 Hz (p < 0.01) and 4-mm loosening at 500–950 Hz (p < 0.01).


      PubDate: 2015-06-28T14:01:24Z
       
  • Effect of different radial hole designs on pullout and structural strength
           of cannulated pedicle screws
    • Abstract: Publication date: Available online 6 June 2015
      Source:Medical Engineering & Physics
      Author(s): Hsin-Chang Chen , Yu-Shu Lai , Wen-Chuan Chen , Jou-Wen Chen , Chia-Ming Chang , Yi-Long Chen , Shih-Tien Wang , Cheng-Kung Cheng
      Cannulated pedicle screws are designed for bone cement injection to enhance fixation strength in severely osteoporotic spines. However, the screws commonly fracture during insertion. This study aims to evaluate how different positions/designs of radial holes may affect the pullout and structural strength of cannulated pedicle screws using finite element analysis. Three different screw hole designs were evaluated under torsion and bending conditions. The pullout strength for each screw was determined by axial pullout failure testing. The results showed that when the Von Mises stress reached the yield stress of titanium alloy the screw with four radial holes required a greater torque or bending moment than the nine and twelve hole screws. In the pullout test, the strength and stiffness of each screw with cement augmentation showed no significant differences, but the screw with four radial holes had a greater average pullout strength, which probably resulted from the significantly greater mean maximum lengths of cement augmentation. Superior biomechanical responses, with lower stress around the radial holes and greater pullout strength, represented by cannulated pedicle screw with four radial holes may worth recommending for clinical application.


      PubDate: 2015-06-28T14:01:24Z
       
  • Biomechanical properties of the Marfan's aortic root and ascending aorta
           before and after personalised external aortic root support surgery
    • Abstract: Publication date: Available online 6 June 2015
      Source:Medical Engineering & Physics
      Author(s): S.D. Singh , X.Y. Xu , J.R. Pepper , T. Treasure , R.H. Mohiaddin
      Marfan syndrome is an inherited systemic connective tissue disease which may lead to aortic root disease causing dilatation, dissection and rupture of the aorta. The standard treatment is a major operation involving either an artificial valve and aorta or a complex valve repair. More recently, a personalised external aortic root support (PEARS) has been used to strengthen the aorta at an earlier stage of the disease avoiding risk of both rupture and major surgery. The aim of this study was to compare the stress and strain fields of the Marfan aortic root and ascending aorta before and after insertion of PEARS in order to understand its biomechanical implications. Finite element (FE) models were developed using patient-specific aortic geometries reconstructed from pre and post-PEARS magnetic resonance images in three Marfan patients. For the post-PEARS model, two scenarios were investigated—a bilayer model where PEARS and the aortic wall were treated as separate layers, and a single-layer model where PEARS was incorporated into the aortic wall. The wall and PEARS materials were assumed to be isotropic, incompressible and linearly elastic. A static load on the inner wall corresponding to the patients’ pulse pressure was applied. Results from our FE models with patient-specific geometries show that peak aortic stresses and displacements before PEARS were located at the sinuses of Valsalva but following PEARS surgery, these peak values were shifted to the aortic arch, particularly at the interface between the supported and unsupported aorta. Further studies are required to assess the statistical significance of these findings and how PEARS compares with the standard treatment.


      PubDate: 2015-06-28T14:01:24Z
       
  • Evaluating the effect of increasing ceramic content on the mechanical
           properties, material microstructure and degradation of selective laser
           sintered polycaprolactone/β-tricalcium phosphate materials
    • Abstract: Publication date: Available online 6 June 2015
      Source:Medical Engineering & Physics
      Author(s): Heather Doyle , Stefan Lohfeld , Peter McHugh
      Orthopaedic scaffold materials were fabricated from polycaprolactone (PCL) and composite PCL–β-tricalcium phosphate (PCL/β-TCP) powders using selective laser sintering (SLS). Incorporating β-TCP particles is desirable to promote osteogenesis. The effects of increasing β-TCP content on the material's mechanical properties and microstructure were evaluated. The wt% of β-TCP and PCL particle sizes were found to influence material microstructure and mechanical properties, with increasing ceramic content causing a small but significant increase in stiffness but significant reductions in strength. Degradation of materials was achieved using accelerated ageing methods. The influence of β-TCP content on degradation at 7 weeks was evaluated through changes in mechanical properties and microstructure, and the ceramic particles were found to reduce elastic modulus and increase strength. The results of this study highlight the influence of ceramic content on mechanical properties and degradation behaviour of PCL/β-TCP SLS materials, and indicate that these changes must be considered in the design of scaffolds for critical-sized defects.


      PubDate: 2015-06-28T14:01:24Z
       
  • Comparisons of node-based and element-based approaches of assigning bone
           material properties onto subject-specific finite element models
    • Abstract: Publication date: Available online 6 June 2015
      Source:Medical Engineering & Physics
      Author(s): G. Chen , F.Y. Wu , Z.C. Liu , K. Yang , F. Cui
      Subject-specific finite element (FE) models can be generated from computed tomography (CT) datasets of a bone. A key step is assigning material properties automatically onto finite element models, which remains a great challenge. This paper proposes a node-based assignment approach and also compares it with the element-based approach in the literature. Both approaches were implemented using ABAQUS. The assignment procedure is divided into two steps: generating the data file of the image intensity of a bone in a MATLAB program and reading the data file into ABAQUS via user subroutines. The node-based approach assigns the material properties to each node of the finite element mesh, while the element-based approach assigns the material properties directly to each integration point of an element. Both approaches are independent from the type of elements. A number of FE meshes are tested and both give accurate solutions; comparatively the node-based approach involves less programming effort. The node-based approach is also independent from the type of analyses; it has been tested on the nonlinear analysis of a Sawbone femur. The node-based approach substantially improves the level of automation of the assignment procedure of bone material properties. It is the simplest and most powerful approach that is applicable to many types of analyses and elements.


      PubDate: 2015-06-28T14:01:24Z
       
  • Analysis and measurement of dielectrophoretic manipulation of particles
           and lymphocytes using rail-type electrodes
    • Abstract: Publication date: Available online 6 June 2015
      Source:Medical Engineering & Physics
      Author(s): K. Tatsumi , K. Kawano , H. Okui , H. Shintani , K. Nakabe
      A particle manipulation and sorting device using the dielectrophoretic (DEP) force is described in this study. The device consists of “ladder-type”, “flip-type” and “oblique rail-type” electrode regions. The ladder-type and rail-type electrodes can generate a DEP force distribution that captures the particles, the DEP force of which is negative, in the area located at the center of the electrodes. The ladder-type electrode can align the particles with equal spacing in the streamwise direction. Using the flip-type electrode, which pushes the particles away, in combination with these electrodes, the direction of the particle and timing can be selected with high accuracy, reliability, and response. In the first half of this study, a numerical simulation is carried out to calculate the particle motion and evaluate the performance of the ladder-type electrode. Several models are used to investigate the influences of the non-uniformity of the electric field and the electric interaction of the surface charges and polarizations. Experiments are then carried out to demonstrate the motions of the particles and the sorting reliability. The trajectories and the probability density functions of the particles at the inlet and outlet of the electrode region showed that by using these electrodes the particles can be aligned, sorted, and guided accurately.


      PubDate: 2015-06-28T14:01:24Z
       
  • Early detection of abnormal left ventricular relaxation in acute
           myocardial ischemia with a quadratic model. Med Eng Phys 2014;36(September
           (9)):1101–5 by Morimont et al.
    • Abstract: Publication date: Available online 3 June 2015
      Source:Medical Engineering & Physics
      Author(s): Charles S. Chung , Leonid Shmuylovich , Sándor J. Kovács



      PubDate: 2015-06-28T14:01:24Z
       
  • A model of lung parenchyma stress relaxation using fractional
           viscoelasticity
    • Abstract: Publication date: Available online 3 June 2015
      Source:Medical Engineering & Physics
      Author(s): Zoujun Dai , Ying Peng , Hansen A. Mansy , Richard H. Sandler , Thomas J. Royston
      Some pulmonary diseases and injuries are believed to correlate with lung viscoelasticity changes. Hence, a better understanding of lung viscoelastic models could provide new perspectives on the progression of lung pathology and trauma. In the presented study, stress relaxation measurements were performed to quantify relaxation behavior of pig lungs. Results have uncovered certain trends, including an initial steep decay followed by a slow asymptotic relaxation, which would be better described by a power law than exponential decay. The fractional standard linear solid (FSLS) and two integer order viscoelastic models – standard linear solid (SLS) and generalized Maxwell (GM) – were used to fit the stress relaxation curves; the FSLS was found to be a better fit. It is suggested that fractional order viscoelastic models, which have nonlocal, multi-scale attributes and exhibit power law behavior, better capture the lung parenchyma viscoelastic behavior.


      PubDate: 2015-06-28T14:01:24Z
       
  • Editorial Board
    • Abstract: Publication date: June 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 6




      PubDate: 2015-06-28T14:01:24Z
       
  • Precision of image-based registration for intraoperative navigation in the
           presence of metal artifacts: Application to corrective osteotomy surgery
    • Abstract: Publication date: June 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 6
      Author(s): J.G.G. Dobbe , F. Curnier , X. Rondeau , G.J. Streekstra
      Navigation for corrective osteotomy surgery requires patient-to-image registration. When registration is based on intraoperative 3-D cone-beam CT (CBCT) imaging, metal landmarks may be used that deteriorate image quality. This study investigates whether metal artifacts influence the precision of image-to-patient registration, either with or without intermediate user intervention during the registration procedure, in an application for corrective osteotomy of the distal radius. A series of 3-D CBCT scans is made of a cadaver arm with and without metal landmarks. Metal artifact reduction (MAR) based on inpainting techniques is used to improve 3-D CBCT images hampered by metal artifacts. This provides three sets of images (with metal, with MAR, and without metal), which enable investigating the differences in precision of intraoperative registration. Gray-level based point-to-image registration showed a better correlation coefficient if intraoperative images with MAR are used, indicating a better image similarity. The precision of registration without intermediate user intervention during the registration procedure, expressed as the residual angulation and displacement error after repetitive registration was very low and showed no improvement when MAR was used. By adding intermediate user intervention to the registration procedure however, precision was very high but was not affected by the presence of metal artifacts in the specific application.


      PubDate: 2015-06-28T14:01:24Z
       
  • A method for subject-specific modelling and optimisation of the cushioning
           properties of insole materials used in diabetic footwear
    • Abstract: Publication date: June 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 6
      Author(s): Panagiotis E. Chatzistergos , Roozbeh Naemi , Nachiappan Chockalingam
      This study aims to develop a numerical method that can be used to investigate the cushioning properties of different insole materials on a subject-specific basis. Diabetic footwear and orthotic insoles play an important role for the reduction of plantar pressure in people with diabetes (type-2). Despite that, little information exists about their optimum cushioning properties. A new in-vivo measurement based computational procedure was developed which entails the generation of 2D subject-specific finite element models of the heel pad based on ultrasound indentation. These models are used to inverse engineer the material properties of the heel pad and simulate the contact between plantar soft tissue and a flat insole. After its validation this modelling procedure was utilised to investigate the importance of plantar soft tissue stiffness, thickness and loading for the correct selection of insole material. The results indicated that heel pad stiffness and thickness influence plantar pressure but not the optimum insole properties. On the other hand loading appears to significantly influence the optimum insole material properties. These results indicate that parameters that affect the loading of the plantar soft tissues such as body mass or a person's level of physical activity should be carefully considered during insole material selection.


      PubDate: 2015-06-28T14:01:24Z
       
  • A dual mode breath sampler for the collection of the end-tidal and dead
           space fractions
    • Abstract: Publication date: June 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 6
      Author(s): P. Salvo , C. Ferrari , R. Persia , S. Ghimenti , T. Lomonaco , F. Bellagambi , F. Di Francesco
      This work presents a breath sampler prototype automatically collecting end-tidal (single and multiple breaths) or dead space air fractions (multiple breaths). This result is achieved by real time measurements of the CO2 partial pressure and airflow during the expiratory and inspiratory phases. Suitable algorithms, used to control a solenoid valve, guarantee that a Nalophan® bag is filled with the selected breath fraction even if the subject under test hyperventilates. The breath sampler has low pressure drop (<0.5 kPa) and uses inert or disposable components to avoid bacteriological risk for the patients and contamination of the breath samples. A fully customisable software interface allows a real time control of the hardware and software status. The performances of the breath sampler were evaluated by comparing (a) the CO2 partial pressure calculated during the sampling with the CO2 pressure measured off-line within the Nalophan® bag; (b) the concentrations of four selected volatile organic compounds in dead space, end-tidal and mixed breath fractions. Results showed negligible deviations between calculated and off-line CO2 pressure values and the distributions of the selected compounds into dead space, end-tidal and mixed breath fractions were in agreement with their chemical–physical properties.


      PubDate: 2015-06-28T14:01:24Z
       
  • The influence of stem taper re-use upon the failure load of ceramic heads
    • Abstract: Publication date: June 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 6
      Author(s): Julian Gührs , Annika Krull , Florian Witt , Michael M. Morlock
      Ceramic components are frequently used in total hip replacement due to their good tribological properties. In revision of broken ceramic heads clinical uncertainties arise, whether the taper of the stem can be re-used with a new ceramic head, especially if the stem is well fixed. Ceramic is a brittle material. Even small damage on the male stem taper can lead to stress concentrations causing premature failure of a new ceramic head. As a consequence, manufactures strictly prohibit stem taper re-use for ceramic heads. The aim of this study was to determine the fracture strength of ceramic heads assembled to re-used male stem tapers, which were subjected to prior head fracture. Five 12/14 Ti6Al4V male tapers and 15 Al2O3 ceramic heads (BIOLOX forte®; ∅ 28 mm, L) were used for three consecutive fracture tests. Before and after every fracture test, all components were inspected visually and the surface geometry was analyzed. Mean fracture force (52.5 kN) did not decrease with the number of taper re-uses (p ≥ 0.77) but the range increased significantly from initially 4.1 kN to 31.8 kN for the first and 52.6 kN for the second re-use due to some components failing at very low loads. Visual inspection was not sufficient to predict the reduced failure loads. Ceramic heads should therefore not be put on used male tapers without metal adapter sleeves.


      PubDate: 2015-06-28T14:01:24Z
       
  • Processing of laser Doppler flowmetry signals from healthy subjects and
           patients with varicose veins: Information categorisation approach based on
           intrinsic mode functions and entropy computation
    • Abstract: Publication date: June 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 6
      Author(s): Anne Humeau-Heurtier , Markos Klonizakis
      The diagnosis of pathologies from signal processing approaches has shown to be of importance. This can provide noninvasive information at the earliest stage. In this work, the problem of categorising – in a quantifiable manner – information content of microvascular blood flow signals recorded in healthy participants and patients with varicose veins is addressed. For this purpose, laser Doppler flowmetry (LDF) signals – that reflect microvascular blood flow – recorded both at rest and after acetylcholine (ACh) stimulation (an endothelial-dependent vasodilator) are analyzed. Each signal is processed with the empirical mode decomposition (EMD) to obtain its intrinsic mode functions (IMFs). An entropy measure of each IMFs is then computed. The results show that IMFs of LDF signals have different complexity for different physiologic/pathological states. This is true both at rest and after ACh stimulation. Thus, the proposed framework (EMD + entropy computation) may be used to gain a noninvasive understanding of LDF signals in patients with microvascular dysfunctions.


      PubDate: 2015-06-28T14:01:24Z
       
  • Drill wear monitoring in cortical bone drilling
    • Abstract: Publication date: June 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 6
      Author(s): Tomislav Staroveski , Danko Brezak , Toma Udiljak
      Medical drills are subject to intensive wear due to mechanical factors which occur during the bone drilling process, and potential thermal and chemical factors related to the sterilisation process. Intensive wear increases friction between the drill and the surrounding bone tissue, resulting in higher drilling temperatures and cutting forces. Therefore, the goal of this experimental research was to develop a drill wear classification model based on multi-sensor approach and artificial neural network algorithm. A required set of tool wear features were extracted from the following three types of signals: cutting forces, servomotor drive currents and acoustic emission. Their capacity to classify precisely one of three predefined drill wear levels has been established using a pattern recognition type of the Radial Basis Function Neural Network algorithm. Experiments were performed on a custom-made test bed system using fresh bovine bones and standard medical drills. Results have shown high classification success rate, together with the model robustness and insensitivity to variations of bone mechanical properties. Features extracted from acoustic emission and servomotor drive signals achieved the highest precision in drill wear level classification (92.8%), thus indicating their potential in the design of a new type of medical drilling machine with process monitoring capabilities.


      PubDate: 2015-06-28T14:01:24Z
       
  • Subject specific finite element modeling of periprosthetic femoral
           fracture using element deactivation to simulate bone failure
    • Abstract: Publication date: June 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 6
      Author(s): Brad Miles , Elizabeth Kolos , William L. Walter , Richard Appleyard , Angela Shi , Qing Li , Andrew J. Ruys
      Subject-specific finite element (FE) modeling methodology could predict peri-prosthetic femoral fracture (PFF) for cementless hip arthoplasty in the early postoperative period. This study develops methodology for subject-specific finite element modeling by using the element deactivation technique to simulate bone failure and validate with experimental testing, thereby predicting peri-prosthetic femoral fracture in the early postoperative period. Material assignments for biphasic and triphasic models were undertaken. Failure modeling with the element deactivation feature available in ABAQUS 6.9 was used to simulate a crack initiation and propagation in the bony tissue based upon a threshold of fracture strain. The crack mode for the biphasic models was very similar to the experimental testing crack mode, with a similar shape and path of the crack. The fracture load is sensitive to the friction coefficient at the implant–bony interface. The development of a novel technique to simulate bone failure by element deactivation of subject-specific finite element models could aid prediction of fracture load in addition to fracture risk characterization for PFF.


      PubDate: 2015-06-28T14:01:24Z
       
  • Individual variability analysis of fluorescence parameters measured in
           skin with different levels of nutritive blood flow
    • Abstract: Publication date: June 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 6
      Author(s): Andrey V. Dunaev , Victor V. Dremin , Evgeny A. Zherebtsov , Ilya E. Rafailov , Karina S. Litvinova , Scott G. Palmer , Neil A. Stewart , Sergei G. Sokolovski , Edik U. Rafailov
      Fluorescence spectroscopy has recently become more common in clinical medicine. However, there are still many unresolved issues related to the methodology and implementation of instruments with this technology. In this study, we aimed to assess individual variability of fluorescence parameters of endogenous markers (NADH, FAD, etc.) measured by fluorescent spectroscopy (FS) in situ and to analyse the factors that lead to a significant scatter of results. Most studied fluorophores have an acceptable scatter of values (mostly up to 30%) for diagnostic purposes. Here we provide evidence that the level of blood volume in tissue impacts FS data with a significant inverse correlation. The distribution function of the fluorescence intensity and the fluorescent contrast coefficient values are a function of the normal distribution for most of the studied fluorophores and the redox ratio. The effects of various physiological (different content of skin melanin) and technical (characteristics of optical filters) factors on the measurement results were additionally studied. The data on the variability of the measurement results in FS should be considered when interpreting the diagnostic parameters, as well as when developing new algorithms for data processing and FS devices.


      PubDate: 2015-06-28T14:01:24Z
       
  • A numerical performance assessment of a commercial cardiopulmonary by-pass
           blood heat exchanger
    • Abstract: Publication date: June 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 6
      Author(s): Filippo Consolo , Gianfranco B. Fiore , Alessandra Pelosi , Stefano Reggiani , Alberto Redaelli
      We developed a numerical model, based on multi-physics computational fluid dynamics (CFD) simulations, to assist the design process of a plastic hollow-fiber bundle blood heat exchanger (BHE) integrated within the INSPIRETM, a blood oxygenator (OXY) for cardiopulmonary by-pass procedures, recently released by Sorin Group Italia. In a comparative study, we analyzed five different geometrical design solutions of the BHE module. Quantitative geometrical-dependent parameters providing a comprehensive evaluation of both the hemo- and thermo-dynamics performance of the device were extracted to identify the best-performing prototypical solution. A convenient design configuration was identified, characterized by (i) a uniform blood flow pattern within the fiber bundle, preventing blood flow shunting and the onset of stagnation/recirculation areas and/or high velocity pathways, (ii) an enhanced blood heating efficiency, and (iii) a reduced blood pressure drop. The selected design configuration was then prototyped and tested to experimentally characterize the device performance. Experimental results confirmed numerical predictions, proving the effectiveness of CFD modeling as a reliable tool for in silico identification of suitable working conditions of blood handling medical devices. Notably, the numerical approach limited the need for extensive prototyping, thus reducing the corresponding machinery costs and time-to-market.


      PubDate: 2015-06-28T14:01:24Z
       
  • Incorporating in vivo fall assessments in the simulation of femoral
           fractures with finite element models
    • Abstract: Publication date: June 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 6
      Author(s): A.M. van der Zijden , D. Janssen , N. Verdonschot , B.E. Groen , B. Nienhuis , V. Weerdesteyn , E. Tanck
      Femoral fractures are a major health issue. Most experimental and finite element (FE) fracture studies use polymethylmethacrylate cups on the greater trochanter (GT) to simulate fall impact loads. However, in vivo fall studies showed that the femur is loaded distally from the GT. Our objective was to incorporate in vivo fall data in FE models to determine the effects of loading position and direction, and size of simulated impact site on the fracture load and fracture type for a healthy and an osteoporotic femur. Twelve sets of loading position and angles were applied through ‘near point loads’ on the models. Additional simulations were performed with ‘cup loads’ on the GT, similar to the literature. The results showed no significant difference between fracture loads from simulations with near point loads distally from the GT and those with cup loads on the GT. However, simulated fracture types differed, as near point loads distally from the GT generally resulted in various neck fractures, whilst cup load simulations predicted superior neck and trochanteric fractures only. This study showed that incorporating in vivo fall assessments in FE models by loading the models distally from the GT results in prediction of realistic fracture loads and fracture types.


      PubDate: 2015-06-28T14:01:24Z
       
  • Finite element analysis predicts experimental failure patterns in
           vertebral bodies loaded via intervertebral discs up to large deformation
    • Abstract: Publication date: June 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 6
      Author(s): Allison L. Clouthier , Hadi S. Hosseini , Ghislain Maquer , Philippe K. Zysset
      Vertebral compression fractures are becoming increasingly common. Patient-specific nonlinear finite element (FE) models have shown promise in predicting yield strength and damage pattern but have not been experimentally validated for clinically relevant vertebral fractures, which involve loading through intervertebral discs with varying degrees of degeneration up to large compressive strains. Therefore, stepwise axial compression was applied in vitro on segments and performed in silico on their FE equivalents using a nonlocal damage-plastic model including densification at large compression for bone and a time-independent hyperelastic model for the disc. The ability of the nonlinear FE models to predict the failure pattern in large compression was evaluated for three boundary conditions: healthy and degenerated intervertebral discs and embedded endplates. Bone compaction and fracture patterns were predicted using the local volume change as an indicator and the best correspondence was obtained for the healthy intervertebral discs. These preliminary results show that nonlinear finite element models enable prediction of bone localisation and compaction. To the best of our knowledge, this is the first study to predict the collapse of osteoporotic vertebral bodies up to large compression using realistic loading via the intervertebral discs.
      Graphical abstract image

      PubDate: 2015-06-28T14:01:24Z
       
  • Envelopment filter and K-means for the detection of QRS waveforms in
           electrocardiogram
    • Abstract: Publication date: June 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 6
      Author(s): Manuel Merino , Isabel María Gómez , Alberto J. Molina
      The electrocardiogram (ECG) is a well-established technique for determining the electrical activity of the heart and studying its diseases. One of the most common pieces of information that can be read from the ECG is the heart rate (HR) through the detection of its most prominent feature: the QRS complex. This paper describes an offline version and a real-time implementation of a new algorithm to determine QRS localization in the ECG signal based on its envelopment and K-means clustering algorithm. The envelopment is used to obtain a signal with only QRS complexes, deleting P, T, and U waves and baseline wander. Two moving average filters are applied to smooth data. The K-means algorithm classifies data into QRS and non-QRS. The technique is validated using 22 h of ECG data from five Physionet databases. These databases were arbitrarily selected to analyze different morphologies of QRS complexes: three stored data with cardiac pathologies, and two had data with normal heartbeats. The algorithm has a low computational load, with no decision thresholds. Furthermore, it does not require any additional parameter. Sensitivity, positive prediction and accuracy from results are over 99.7%.


      PubDate: 2015-06-28T14:01:24Z
       
  • A comprehensive protocol to test instrumented treadmills
    • Abstract: Publication date: June 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 6
      Author(s): L.H. Sloot , H. Houdijk , J. Harlaar
      Instrumented treadmills are becoming more common in gait analysis. Due to their large and compliant structure, errors in force measurements are expected to be higher compared with conventional force plates. There is, however, no consistency in the literature on testing the performance of these treadmills. Therefore, we propose a standard protocol to assess and report error sources in instrumented treadmills. The first part of this protocol consists of assessment of the accuracy of forces and center of pressure (COP), including non-linearity, hysteresis and crosstalk. The second part consists of (novel) instrumented resonance testing and belt speed variability tests. The third part focuses on measurement variability over time, including drift, warming of the system and noise. The performance of two in-house instrumented treadmills with different dynamics was measured. Differences were found between the treadmills in COP accuracy (4.0 mm versus 6.5 mm), lowest eigen frequency (35 Hz versus 23 Hz) and noise level at 5 km/h (10 N versus 29 N). The loaded treadmills both showed a 3.3% belt speed variability at 5 km/h. Thus, the protocol was able to characterize strong and weak characteristics of the treadmills and allowed for a proper judgement on the validity of the instruments and their application in the domain of gait analysis. We propose to use this protocol when testing and reporting the performance of instrumented treadmills.


      PubDate: 2015-06-28T14:01:24Z
       
  • Design of an actively controlled steerable needle with tendon actuation
           and FBG-based shape sensing
    • Abstract: Publication date: June 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 6
      Author(s): Nick J. van de Berg , Jenny Dankelman , John J. van den Dobbelsteen
      This work presents a new steerable needle to facilitate active steering toward predefined target locations. It focuses on mechanical aspects and design choices in relation to the observed response in a tissue phantom. Tip steering with two rotational degrees of freedom was achieved by a tendon actuated ball joint mechanism. During insertion, the flexible cannula bends as a result of asymmetric tip–tissue interaction forces. The stylet was equipped with fiber Bragg gratings to measure the needle shape and tip position during use. A PI-controller was implemented to facilitate steering to predefined targets. During the validation study, nine targets were defined at a depth of 100 mm below the gelatin surface. One was located below the insertion point, the others at a radial offset of 30 mm in each of the eight principle steering directions. Per location, six repetitions were performed. The targeting accuracy was 6.2 ± 1.4 mm (mean ± std). The steering precision was 2.6 ± 1.1 mm. The ability to steer with this new needle steering approach is presented and the mechanical characteristics are discussed for this representative subset of steering directions.


      PubDate: 2015-06-28T14:01:24Z
       
  • Accuracy assessment of 3D bone reconstructions using CT: an intro
           comparison
    • Abstract: Publication date: Available online 30 May 2015
      Source:Medical Engineering & Physics
      Author(s): Emily A. Lalone , Ryan T. Willing , Hannah L. Shannon , Graham J.W. King , James A. Johnson
      Computed tomography provides high contrast imaging of the joint anatomy and is used routinely to reconstruct 3D models of the osseous and cartilage geometry (CT arthrography) for use in the design of orthopedic implants, for computer assisted surgeries and computational dynamic and structural analysis. The objective of this study was to assess the accuracy of bone and cartilage surface model reconstructions by comparing reconstructed geometries with bone digitizations obtained using an optical tracking system. Bone surface digitizations obtained in this study determined the ground truth measure for the underlying geometry. We evaluated the use of a commercially available reconstruction technique using clinical CT scanning protocols using the elbow joint as an example of a surface with complex geometry. To assess the accuracies of the reconstructed models (8 fresh frozen cadaveric specimens) against the ground truth bony digitization—as defined by this study—proximity mapping was used to calculate residual error. The overall mean error was less than 0.4 mm in the cortical region and 0.3 mm in the subchondral region of the bone. Similarly creating 3D cartilage surface models from CT scans using air contrast had a mean error of less than 0.3 mm. Results from this study indicate that clinical CT scanning protocols and commonly used and commercially available reconstruction algorithms can create models which accurately represent the true geometry.


      PubDate: 2015-06-28T14:01:24Z
       
  • Re: Chung et al.’s Letter to the Editor in response to: Early
           detection of abnormal left ventricular relaxation in acute myocardial
           ischemia with a quadratic model. Med Eng Phys 2014;36(September
           (9)):1101–5 by Morimont et al.
    • Abstract: Publication date: Available online 29 May 2015
      Source:Medical Engineering & Physics
      Author(s): Philippe Morimont , Antoine Pironet , Thomas Desaive , Geoffrey Chase , Bernard Lambermont



      PubDate: 2015-06-28T14:01:24Z
       
  • Editorial Board
    • Abstract: Publication date: May 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 5




      PubDate: 2015-06-28T14:01:24Z
       
  • Cement applicator use for hip resurfacing arthroplasty
    • Abstract: Publication date: May 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 5
      Author(s): Sebastian Jaeger , Johannes S. Rieger , Beate Obermeyer , Matthias C. Klotz , J. Philippe Kretzer , Rudi G. Bitsch
      We compared the manufacturer recommended cementing technique for a femoral hip resurfacing implant (BHR, S&N) to a newly designed cement applicator on 20 porous carbon foam specimens. Substantial design changes and improvements of the cement applicator were necessary: The diameter and number of the cement escaping holes at the top of the applicator were optimized for medium viscosity cement. It was necessary to add four separate air inlet holes with large diameters. The inner shape of the applicator had to be adapted to the BHR design with a circular extending chamfer in the proximal region, a parallel inner wall and a second chamfer distally. The interface temperatures showed no risk for heat necrosis using both techniques. The cement penetration depth was more uniform and significantly reduced for the applicator cementing technique (4.34 ± 1.42 mm, 6.42 ± 0.43 mm, p = 0.001). The cement-applicator showed no cement defects compared to a large defect length (0.0 ± 0.0 mm, 10.36 ± 1.10 mm, p < 0.001) with the manufacturer recommended cementing technique. The cement applicator technique appears to be effective for a homogenous cement distribution without cement defects and safe with a lower risk of polar over-penetration.


      PubDate: 2015-06-28T14:01:24Z
       
  • Monitoring brain damage using bioimpedance technique in a 3D numerical
           model of the head
    • Abstract: Publication date: May 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 5
      Author(s): Rotem Cohen , Shimon Abboud , Marina Arad
      Disturbance in the blood supply to the brain causes a stroke or cerebrovascular accident. This can be due to ischemia caused by blockage (thrombosis, arterial embolism) or a hemorrhage. In this study, the feasibility of basic electrical impedance technique for monitoring such damage was analyzed using a computerized model. Simulations were conducted on a realistic 3D numerical model of the head. Tissues were assumed to act as linear isotropic volume conductors, and the quasi-static approximation was applied. Electrical potentials were calculated by solving Poisson's equation, using the finite volume method and the successive over relaxation method. Left–right asymmetry was calculated for several conductivities and volumes of the damaged region. The results were compared with the left–right asymmetry in a head model with normal brain. A negative asymmetry was revealed for blockage (i.e. the potential amplitude over the ischemic hemisphere was greater than that over the intact hemisphere). In case of hemorrhage, a positive asymmetry was found. Furthermore, correlation was found between the location of the damaged region and the electrodes with significant asymmetry. The 3D numerical simulations revealed that the electrical conductivity and the size of the damaged tissue have an effect on the left–right asymmetry of the surface potential.


      PubDate: 2015-06-28T14:01:24Z
       
  • Use of wearable technology for performance assessment: A validation study
    • Abstract: Publication date: Available online 30 April 2015
      Source:Medical Engineering & Physics
      Author(s): Enrica Papi , Denise Osei-Kuffour , Yen-Ming A Chen , Alison H McGregor
      The prevalence of osteoarthritis is increasing globally but current compliance with rehabilitation remains poor. This study explores whether wearable sensors can be used to provide objective measures of performance with a view to using them as motivators to aid compliance to osteoarthritis rehabilitation. More specifically, the use of a novel attachable wearable sensor integrated into clothing and inertial measurement units located in two different positions, at the waist and thigh pocket, was investigated. Fourteen healthy volunteers were asked to complete exercises adapted from a knee osteoarthritis rehabilitation programme whilst wearing the three sensors including five times sit-to-stand test, treadmill walking at slow, preferred and fast speeds. The performances of the three sensors were validated against a motion capture system and an instrumented treadmill. The systems showed a high correlation (r 2 > 0.7) and agreement (mean difference range: −0.02–0.03 m, 0.005–0.68 s) with gold standards. The novel attachable wearable sensor was able to monitor exercise tasks as well as the inertial measurement units (ICC > 0.95). Results also suggested that a functional placement (e.g., situated in a pocket) is a valid position for performance monitoring. This study shows the potential use of wearable technologies for assessing subject performance during exercise and suggests functional solutions to enhance acceptance.


      PubDate: 2015-05-03T02:17:52Z
       
 
 
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