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BIOLOGY (1353 journals)            First | 4 5 6 7 8 9 10 11 | Last

Journal of Applied Virology     Open Access   (Followers: 5)
Journal of Aquatic Sciences     Full-text available via subscription  
Journal of Arachnology     Full-text available via subscription  
Journal of Avian Biology     Hybrid Journal   (Followers: 17)
Journal of Bacteriology     Full-text available via subscription   (Followers: 15)
Journal of Basic Microbiology     Hybrid Journal   (Followers: 3)
Journal of Bio-Science     Open Access  
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: 20)
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: 25)
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: 16)
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: 19)
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: 12)
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: 7)
Journal of Mammary Gland Biology and Neoplasia     Hybrid Journal   (Followers: 1)
Journal of Marine Biology     Open Access   (Followers: 14)

  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  [2589 journals]
  • Is there a bone-nail specific entry point' Automated fit
           quantification of tibial nail designs during the insertion for six
           different nail entry points
    • Abstract: Publication date: Available online 7 February 2015
      Source:Medical Engineering & Physics
      Author(s): J.P. Amarathunga , M.A. Schuetz , K.V.D. Yarlagadda , B. Schmutz
      Intramedullary nailing is the standard fixation method for displaced diaphyseal fractures of tibia. Selection of the correct nail insertion point is important for axial alignment of bone fragments and to avoid iatrogenic fractures. However, the standard entry point (SEP) may not always optimise the bone-nail fit due to geometric variations of bones. This study aimed to investigate the optimal entry for a given bone-nail pair using the fit quantification software tool previously developed by the authors. The misfit was quantified for 20 bones with two nail designs (ETN and ETN-Proximal Bend) related to the SEP and 5 entry points which were 5 mm and 10 mm away from the SEP. The SEP was the optimal entry point for 50% of the bones used. For the remaining bones, the optimal entry point was located 5 mm away from the SEP, which improved the overall fit by 40% on average. However, entry points 10 mm away from the SEP doubled the misfit. The optimised bone-nail fit can be achieved through the SEP and within the range of a 5 mm radius, except posteriorly. The study results suggest that the optimal entry point should be selected by considering the fit during insertion and not only at the final position.

      PubDate: 2015-02-13T11:34:57Z
  • A novel passive left heart platform for device testing and research
    • Abstract: Publication date: Available online 7 February 2015
      Source:Medical Engineering & Physics
      Author(s): A.M. Leopaldi , R. Vismara , S. van Tuijl , A. Redaelli , F.N. van de Vosse , G.B. Fiore , M.C.M. Rutten
      Integration of biological samples into in vitro mock loops is fundamental to simulate real device's operating conditions. We developed an in vitro platform capable of simulating the pumping function of the heart through the external pressurization of the ventricle. The system consists of a fluid-filled chamber, in which the ventricles are housed and sealed to exclude the atria from external loads. The chamber is connected to a pump that drives the motion of the ventricular walls. The aorta is connected to a systemic impedance simulator, and the left atrium to an adjustable preload. The platform reproduced physiologic hemodynamics, i.e. aortic pressures of 120/80 mmHg with 5 L/min of cardiac output, and allowed for intracardiac endoscopy. A pilot study with a left ventricular assist device (LVAD) was also performed. The LVAD was connected to the heart to investigate aortic valve functioning at different levels of support. Results were consistent with the literature, and high speed video recordings of the aortic valve allowed for the visualization of the transition between a fully opening valve and a permanently closed configuration. In conclusion, the system showed to be an effective tool for the hemodynamic assessment of devices, the simulation of surgical or transcatheter procedures and for visualization studies.

      PubDate: 2015-02-13T11:34:57Z
  • Beneficial fluid-dynamic features of pulsatile swirling flow in 45°
           end-to-side anastomosis
    • Abstract: Publication date: Available online 7 February 2015
      Source:Medical Engineering & Physics
      Author(s): Hojin Ha , Woorak Choi , Sang Joon Lee
      Although a large number of vascular grafts are surgically implanted annually, approximately 10–15% of these grafts fail in the first year after operation and about 50% are only effective for five to ten years. Surgical implantation of a vascular graft modifies the inherent hemodynamic environment in blood vessels; hence, fluid dynamic characteristics of pathological blood flow are highly related to the performance of the vascular graft. In this study, pathological fluid-dynamic characteristics in a 45° end-to-side anastomosis were experimentally investigated using a particle image velocimetry technique. In particular, the effect of the pulsatile swirling inlet flow in the vascular graft on the improvement of pathological hemodynamic features was systematically investigated. Introducing the pulsatile swirling flow equalizes the asymmetric distribution of wall shear stress and reduces oscillatory shear index and the size of flow separation because the flow disturbs the formation of Dean-type vortices and suppresses secondary flow collision. The fluid dynamic features of the pulsatile swirling flow are expected to be beneficial in designing vascular grafts that can suppress pathological hemodynamic characteristics in the recipient host vessel.

      PubDate: 2015-02-13T11:34:57Z
  • Flow measurement in mechanical ventilation: A review
    • Abstract: Publication date: Available online 7 February 2015
      Source:Medical Engineering & Physics
      Author(s): Emiliano Schena , Carlo Massaroni , Paola Saccomandi , Stefano Cecchini
      Accurate monitoring of flow rate and volume exchanges is essential to minimize ventilator-induced lung injury. Mechanical ventilators employ flowmeters to estimate the amount of gases delivered to patients and use the flow signal as a feedback to adjust the desired amount of gas to be delivered. Since flowmeters play a crucial role in this field, they are required to fulfill strict criteria in terms of dynamic and static characteristics. Therefore, mechanical ventilators are equipped with only the following kinds of flowmeters: linear pneumotachographs, fixed and variable orifice meters, hot wire anemometers, and ultrasonic flowmeters. This paper provides an overview of these sensors. Their working principles are described together with their relevant advantages and disadvantages. Furthermore, the most promising emerging approaches for flowmeters design (i.e., fiber optic technology and three dimensional micro-fabrication) are briefly reviewed showing their potential for this application.

      PubDate: 2015-02-13T11:34:57Z
  • Acoustic power measurement of high-intensity focused ultrasound transducer
           using a pressure sensor
    • Abstract: Publication date: Available online 7 February 2015
      Source:Medical Engineering & Physics
      Author(s): Yufeng Zhou
      The acoustic power of high-intensity focused ultrasound (HIFU) is an important parameter that should be measured prior to each treatment to guarantee effective and safe outcomes. A new calibration technique was developed that involves estimating the pressure distribution, calculating the acoustic power using an underwater pressure blast sensor, and compensating the contribution of harmonics to the acoustic power. The output of a clinical extracorporeal HIFU system (center frequency of ~1 MHz, p+ = 2.5–57.2 MPa, p−  = −1.8 to −13.9 MPa, I SPPA = 513–22,940 W/cm2, −6 dB size of 1.6 × 10 mm: lateral × axial) was measured using this approach and then compared with that obtained using a radiation force balance. Similarities were found between each method at acoustic power ranging from 18.2 W to 912 W with an electrical-to-acoustic conversion efficiency of ~42%. The proposed method has advantages of low weight, smaller size, high sensitivity, quick response, high signal-to-noise ratio (especially at low power output), robust performance, and easy operation of HIFU exposimetry measurement.

      PubDate: 2015-02-13T11:34:57Z
  • Denoising preterm EEG by signal decomposition and adaptive filtering: A
           comparative study
    • Abstract: Publication date: Available online 3 February 2015
      Source:Medical Engineering & Physics
      Author(s): X. Navarro , F. Porée , A. Beuchée , G. Carrault
      Electroencephalography (EEG) from preterm infant monitoring systems is usually contaminated by several sources of noise that have to be removed in order to correctly interpret signals and perform automated analysis reliably. Band-pass and adaptive filters (AF) continue to be systematically applied, but their efficacy may be decreased facing preterm EEG patterns such as the tracé alternant and slow delta-waves. In this paper, we propose the combination of EEG decomposition with AF to improve the overall denoising process. Using artificially contaminated signals from real EEGs, we compared the quality of filtered signals applying different decomposition techniques: the discrete wavelet transform, the empirical mode decomposition (EMD) and a recent improved version, the complete ensemble EMD with adaptive noise. Simulations demonstrate that introducing EMD-based techniques prior to AF can reduce up to 30% the root mean squared errors in denoised EEGs.

      PubDate: 2015-02-06T03:36:58Z
  • Bioresorbable scaffolds for bone tissue engineering: Optimal design,
           fabrication, mechanical testing and scale-size effects analysis
    • Abstract: Publication date: Available online 29 January 2015
      Source:Medical Engineering & Physics
      Author(s): Pedro G. Coelho , Scott J. Hollister , Colleen L. Flanagan , Paulo R. Fernandes
      Bone scaffolds for tissue regeneration require an optimal trade-off between biological and mechanical criteria. Optimal designs may be obtained using topology optimization (homogenization approach) and prototypes produced using additive manufacturing techniques. However, the process from design to manufacture remains a research challenge and will be a requirement of FDA design controls to engineering scaffolds. This work investigates how the design to manufacture chain affects the reproducibility of complex optimized design characteristics in the manufactured product. The design and prototypes are analyzed taking into account the computational assumptions and the final mechanical properties determined through mechanical tests. The scaffold is an assembly of unit-cells, and thus scale size effects on the mechanical response considering finite periodicity are investigated and compared with the predictions from the homogenization method which assumes in the limit infinitely repeated unit cells. Results show that a limited number of unit-cells (3–5 repeated on a side) introduce some scale-effects but the discrepancies are below 10%. Higher discrepancies are found when comparing the experimental data to numerical simulations due to differences between the manufactured and designed scaffold feature shapes and sizes as well as micro-porosities introduced by the manufacturing process. However good regression correlations (R 2 > 0.85) were found between numerical and experimental values, with slopes close to 1 for 2 out of 3 designs.

      PubDate: 2015-02-03T10:30:38Z
  • NIRS-based classification of clench force and speed motor imagery with the
           use of empirical mode decomposition for BCI
    • Abstract: Publication date: Available online 29 January 2015
      Source:Medical Engineering & Physics
      Author(s): Xuxian Yin , Baolei Xu , Changhao Jiang , Yunfa Fu , Zhidong Wang , Hongyi Li , Gang Shi
      Near-infrared spectroscopy (NIRS) is a non-invasive optical technique used for brain–computer interface (BCI). This study aims to investigate the brain hemodynamic responses of clench force and speed motor imagery and extract task-relevant features to obtain better classification performance. Given the non-stationary characteristics of real hemodynamic measurements, empirical mode decomposition (EMD) was applied to reduce the physiological noise overwhelmed in the task-relevant NIRS signals. Compared with continuous wavelet decomposition, EMD does not require a pre-determined basis function. EMD decomposes the original signals into a set of intrinsic mode functions (IMFs). In this study, joint mutual information was applied to select the optimal features, and support vector machine was used as a classifier. Offline and pseudo-online analyses showed that the most feasible classification accuracy can be obtained using IMFs as input features. Accordingly, an alternative feature is provided to develop the NIRS–BCI system.

      PubDate: 2015-02-03T10:30:38Z
  • Mutual information measures applied to EEG signals for sleepiness
    • Abstract: Publication date: Available online 29 January 2015
      Source:Medical Engineering & Physics
      Author(s): Umberto Melia , Marc Guaita , Montserrat Vallverdú , Cristina Embid , Isabel Vilaseca , Manel Salamero , Joan Santamaria
      Excessive daytime sleepiness (EDS) is one of the main symptoms of several sleep related disorders with a great impact on the patient lives. While many studies have been carried out in order to assess daytime sleepiness, the automatic EDS detection still remains an open problem. In this work, a novel approach to this issue based on non-linear dynamical analysis of EEG signal was proposed. Multichannel EEG signals were recorded during five maintenance of wakefulness (MWT) and multiple sleep latency (MSLT) tests alternated throughout the day from patients suffering from sleep disordered breathing. A group of 20 patients with excessive daytime sleepiness (EDS) was compared with a group of 20 patients without daytime sleepiness (WDS), by analyzing 60-s EEG windows in waking state. Measures obtained from cross-mutual information function (CMIF) and auto-mutual-information function (AMIF) were calculated in the EEG. These functions permitted a quantification of the complexity properties of the EEG signal and the non-linear couplings between different zones of the scalp. Statistical differences between EDS and WDS groups were found in β band during MSLT events (p-value < 0.0001). WDS group presented more complexity than EDS in the occipital zone, while a stronger nonlinear coupling between occipital and frontal zones was detected in EDS patients than in WDS. The AMIF and CMIF measures yielded sensitivity and specificity above 80% and AUC of ROC above 0.85 in classifying EDS and WDS patients.

      PubDate: 2015-02-03T10:30:38Z
  • Editorial Board
    • Abstract: Publication date: February 2015
      Source:Medical Engineering & Physics, Volume 37, Issue 2

      PubDate: 2015-02-03T10:30:38Z
  • Sensitivity analysis of geometric errors in additive manufacturing medical
    • Abstract: Publication date: Available online 31 January 2015
      Source:Medical Engineering & Physics
      Author(s): Jose Miguel Pinto , Cristobal Arrieta , Marcelo E. Andia , Sergio Uribe , Jorge Ramos-Grez , Alex Vargas , Pablo Irarrazaval , Cristian Tejos
      Additive manufacturing (AM) models are used in medical applications for surgical planning, prosthesis design and teaching. For these applications, the accuracy of the AM models is essential. Unfortunately, this accuracy is compromised due to errors introduced by each of the building steps: image acquisition, segmentation, triangulation, printing and infiltration. However, the contribution of each step to the final error remains unclear. We performed a sensitivity analysis comparing errors obtained from a reference with those obtained modifying parameters of each building step. Our analysis considered global indexes to evaluate the overall error, and local indexes to show how this error is distributed along the surface of the AM models. Our results show that the standard building process tends to overestimate the AM models, i.e. models are larger than the original structures. They also show that the triangulation resolution and the segmentation threshold are critical factors, and that the errors are concentrated at regions with high curvatures. Errors could be reduced choosing better triangulation and printing resolutions, but there is an important need for modifying some of the standard building processes, particularly the segmentation algorithms.

      PubDate: 2015-02-03T10:30:38Z
  • 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
    • 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
    • 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 &amp; 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
    • 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
  • 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
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