Displaying publications 81 - 100 of 279 in total

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  1. Tham LK, Abu Osman NA, Wan Abas WA, Lim KS
    PLoS One, 2013;8(2):e55702.
    PMID: 23409022 DOI: 10.1371/journal.pone.0055702
    The deep tendon reflex assessments that are essential to the accurate diagnosis of neurological or neuromuscular disorders are conducted subjectively in clinical neurology. Our aim was to assess deep tendon reflexes objectively with a new reflex quantification method.
    Matched MeSH terms: Motion*
  2. Dawood F, Loo CK
    PLoS One, 2016;11(3):e0152003.
    PMID: 26998923 DOI: 10.1371/journal.pone.0152003
    Mirror neurons are visuo-motor neurons found in primates and thought to be significant for imitation learning. The proposition that mirror neurons result from associative learning while the neonate observes his own actions has received noteworthy empirical support. Self-exploration is regarded as a procedure by which infants become perceptually observant to their own body and engage in a perceptual communication with themselves. We assume that crude sense of self is the prerequisite for social interaction. However, the contribution of mirror neurons in encoding the perspective from which the motor acts of others are seen have not been addressed in relation to humanoid robots. In this paper we present a computational model for development of mirror neuron system for humanoid based on the hypothesis that infants acquire MNS by sensorimotor associative learning through self-exploration capable of sustaining early imitation skills. The purpose of our proposed model is to take into account the view-dependency of neurons as a probable outcome of the associative connectivity between motor and visual information. In our experiment, a humanoid robot stands in front of a mirror (represented through self-image using camera) in order to obtain the associative relationship between his own motor generated actions and his own visual body-image. In the learning process the network first forms mapping from each motor representation onto visual representation from the self-exploratory perspective. Afterwards, the representation of the motor commands is learned to be associated with all possible visual perspectives. The complete architecture was evaluated by simulation experiments performed on DARwIn-OP humanoid robot.
    Matched MeSH terms: Motion
  3. Saif AF, Prabuwono AS, Mahayuddin ZR
    PLoS One, 2015;10(6):e0126212.
    PMID: 26030818 DOI: 10.1371/journal.pone.0126212
    Fast and computationally less complex feature extraction for moving object detection using aerial images from unmanned aerial vehicles (UAVs) remains as an elusive goal in the field of computer vision research. The types of features used in current studies concerning moving object detection are typically chosen based on improving detection rate rather than on providing fast and computationally less complex feature extraction methods. Because moving object detection using aerial images from UAVs involves motion as seen from a certain altitude, effective and fast feature extraction is a vital issue for optimum detection performance. This research proposes a two-layer bucket approach based on a new feature extraction algorithm referred to as the moment-based feature extraction algorithm (MFEA). Because a moment represents the coherent intensity of pixels and motion estimation is a motion pixel intensity measurement, this research used this relation to develop the proposed algorithm. The experimental results reveal the successful performance of the proposed MFEA algorithm and the proposed methodology.
    Matched MeSH terms: Motion*
  4. Jawarneh S, Abdullah S
    PLoS One, 2015;10(7):e0130224.
    PMID: 26132158 DOI: 10.1371/journal.pone.0130224
    This paper presents a bee colony optimisation (BCO) algorithm to tackle the vehicle routing problem with time window (VRPTW). The VRPTW involves recovering an ideal set of routes for a fleet of vehicles serving a defined number of customers. The BCO algorithm is a population-based algorithm that mimics the social communication patterns of honeybees in solving problems. The performance of the BCO algorithm is dependent on its parameters, so the online (self-adaptive) parameter tuning strategy is used to improve its effectiveness and robustness. Compared with the basic BCO, the adaptive BCO performs better. Diversification is crucial to the performance of the population-based algorithm, but the initial population in the BCO algorithm is generated using a greedy heuristic, which has insufficient diversification. Therefore the ways in which the sequential insertion heuristic (SIH) for the initial population drives the population toward improved solutions are examined. Experimental comparisons indicate that the proposed adaptive BCO-SIH algorithm works well across all instances and is able to obtain 11 best results in comparison with the best-known results in the literature when tested on Solomon's 56 VRPTW 100 customer instances. Also, a statistical test shows that there is a significant difference between the results.
    Matched MeSH terms: Motion
  5. Rasedee AFN, Abdul Sathar MH, Othman KI, Hamzah SR, Ishak N
    PLoS One, 2021;16(2):e0246904.
    PMID: 33577619 DOI: 10.1371/journal.pone.0246904
    Differential equations are commonly used to model various types of real life applications. The complexity of these models may often hinder the ability to acquire an analytical solution. To overcome this drawback, numerical methods were introduced to approximate the solutions. Initially when developing a numerical algorithm, researchers focused on the key aspect which is accuracy of the method. As numerical methods becomes more and more robust, accuracy alone is not sufficient hence begins the pursuit of efficiency which warrants the need for reducing computational cost. The current research proposes a numerical algorithm for solving initial value higher order ordinary differential equations (ODEs). The proposed algorithm is derived as a three point block multistep method, developed in an Adams type formulae (3PBCS) and will be used to solve various types of ODEs and systems of ODEs. Type of ODEs that are selected varies from linear to nonlinear, artificial and real life problems. Results will illustrate the accuracy and efficiency of the proposed three point block method. Order, stability and convergence of the method are also presented in the study.
    Matched MeSH terms: Motion
  6. Javanmardi A, Ibrahim Z, Ghaedi K, Khan NB, Benisi Ghadim H
    PLoS One, 2018;13(7):e0200482.
    PMID: 30059506 DOI: 10.1371/journal.pone.0200482
    This paper investigated the seismic retrofitting of an existing cable-stayed bridge through the use of a seismic isolation system. The bridge is situated in a high seismic zone. During the Saguenay earthquake 1988, one of the anchorage plates of the bridge supports failed. Herein, several configurations of seismic isolation system were considered to identify an appropriate solution for the seismic retrofitting of the bridge in both the longitudinal and transverse directions. A three-dimensional model of the bridge was created, and its seismic behavior studied through nonlinear dynamic time-history analysis. The comparative performance study among the five retrofitting configurations showed that the partial seismic isolation of the bridge led to an enhancement of the seismic response of the bridge in one direction only. However, the overall seismic response of the cable-stayed bridge substantially improved in the longitudinal and transverse directions in cases where the isolation systems were utilized between the supports and the deck-tower connection of the bridge.
    Matched MeSH terms: Motion
  7. Ghaleb FA, Kamat MB, Salleh M, Rohani MF, Abd Razak S
    PLoS One, 2018;13(11):e0207176.
    PMID: 30457996 DOI: 10.1371/journal.pone.0207176
    The presence of motion artefacts in ECG signals can cause misleading interpretation of cardiovascular status. Recently, reducing the motion artefact from ECG signal has gained the interest of many researchers. Due to the overlapping nature of the motion artefact with the ECG signal, it is difficult to reduce motion artefact without distorting the original ECG signal. However, the application of an adaptive noise canceler has shown that it is effective in reducing motion artefacts if the appropriate noise reference that is correlated with the noise in the ECG signal is available. Unfortunately, the noise reference is not always correlated with motion artefact. Consequently, filtering with such a noise reference may lead to contaminating the ECG signal. In this paper, a two-stage filtering motion artefact reduction algorithm is proposed. In the algorithm, two methods are proposed, each of which works in one stage. The weighted adaptive noise filtering method (WAF) is proposed for the first stage. The acceleration derivative is used as motion artefact reference and the Pearson correlation coefficient between acceleration and ECG signal is used as a weighting factor. In the second stage, a recursive Hampel filter-based estimation method (RHFBE) is proposed for estimating the ECG signal segments, based on the spatial correlation of the ECG segment component that is obtained from successive ECG signals. Real-World dataset is used to evaluate the effectiveness of the proposed methods compared to the conventional adaptive filter. The results show a promising enhancement in terms of reducing motion artefacts from the ECG signals recorded by a cost-effective single lead ECG sensor during several activities of different subjects.
    Matched MeSH terms: Motion
  8. Mat Daud NI, Viswanathan KK
    PLoS One, 2019;14(7):e0219089.
    PMID: 31269073 DOI: 10.1371/journal.pone.0219089
    Vibrational behaviour of symmetric angle-ply layered circular cylindrical shell filled with quiescent fluid is presented. The equations of motion of cylindrical shell in terms of stress and moment resultants are derived from the first order shear deformation theory. Irrotational of inviscid fluid are expressed as the wave equation. These two equations are coupled. Strain-displacement relations and stress-strain relations are adopted into the equations of motion to obtain the differential equations with displacements and rotational functions. A system of ordinary differential equation is obtained in one variable by assuming the functions in separable form. Spline of order three is applied to approximate the displacement and rotational functions, together with boundary conditions, to get a generalised eigenvalue problem. The eigenvalue problem is solved for eigen frequency parameter and associate eigenvectors of spline coefficients. The study of frequency parameters are analysed using the parameters the thickness ratio, length ratio, angle-ply, properties of material and number of layers under different boundary conditions.
    Matched MeSH terms: Motion
  9. Mat Noor NA, Shafie S, Admon MA
    PLoS One, 2021;16(5):e0250402.
    PMID: 33956793 DOI: 10.1371/journal.pone.0250402
    The heat and mass transfer on time dependent hydrodynamic squeeze flow of Jeffrey nanofluid across two plates over permeable medium in the slip condition with heat generation/absorption, thermal radiation and chemical reaction are investigated. The impacts of Brownian motion and thermophoresis is examined in the Buongiorno's nanofluid model. Conversion of the governing partial differential equations to the ordinary differential equations is conducted via similarity transformation. The dimensionless equations are solved by imposing numerical method of Keller-box. The outputs are compared with previous reported works in the journals for the validation of the present outputs and found in proper agreement. The behavior of velocity, temperature, and nanoparticles concentration profiles by varying the pertinent parameters are examined. Findings portray that the acceleration of the velocity profile and the wall shear stress is due to the squeezing of plates. Furthermore, the velocity, temperature and concentration profile decline with boost in Hartmann number and ratio of relaxation to retardation times. It is discovered that the rate of heat transfer and temperature profile increase when viscous dissipation, thermophoresis and heat source/sink rises. In contrast, the increment of thermal radiation reduces the temperature and enhances the heat transfer rate. Besides, the mass transfer rate decelerates for increasing Brownian motion in nanofluid, while it elevates when chemical reaction and thermophoresis increases.
    Matched MeSH terms: Motion
  10. Rehman MZ, Zamli KZ, Almutairi M, Chiroma H, Aamir M, Kader MA, et al.
    PLoS One, 2021;16(12):e0259786.
    PMID: 34855771 DOI: 10.1371/journal.pone.0259786
    Team formation (TF) in social networks exploits graphs (i.e., vertices = experts and edges = skills) to represent a possible collaboration between the experts. These networks lead us towards building cost-effective research teams irrespective of the geolocation of the experts and the size of the dataset. Previously, large datasets were not closely inspected for the large-scale distributions & relationships among the researchers, resulting in the algorithms failing to scale well on the data. Therefore, this paper presents a novel TF algorithm for expert team formation called SSR-TF based on two metrics; communication cost and graph reduction, that will become a basis for future TF's. In SSR-TF, communication cost finds the possibility of collaboration between researchers. The graph reduction scales the large data to only appropriate skills and the experts, resulting in real-time extraction of experts for collaboration. This approach is tested on five organic and benchmark datasets, i.e., UMP, DBLP, ACM, IMDB, and Bibsonomy. The SSR-TF algorithm is able to build cost-effective teams with the most appropriate experts-resulting in the formation of more communicative teams with high expertise levels.
    Matched MeSH terms: Motion Pictures as Topic
  11. Lim LK, Yap SL, Bradley DA
    PLoS One, 2018;13(1):e0188009.
    PMID: 29309425 DOI: 10.1371/journal.pone.0188009
    The plasma focus device discussed herein is a Z-pinch pulsed-plasma arrangement. In this, the plasma is heated and compressed into a cylindrical column, producing a typical density of > 1025 particles/m3 and a temperature of (1-3) × 107 oC. The plasma focus has been widely investigated as a radiation source, including as ion-beams, electron-beams and as a source of x-ray and neutron production, providing considerable scope for use in a variety of technological situations. Thus said, the nature of the radiation emission depends on the dynamics of the plasma pinch. In this study of the characteristics of deuteron-beam emission, in terms of energy, fluence and angular distribution were analyzed. The 2.7 kJ plasma focus discharge has been made to operate at a pressure of less than 1 mbar rather than at its more conventional operating pressure of a few mbar. Faraday cup were used to determine deuteron-beam energy and deuteron-beam fluence per shot while CR-39 solid-state nuclear track detectors were employed in studying the angular distribution of deuteron emission. Beam energy and deuteron-beam fluence per shot have been found to be pressure dependent. The largest value of average deuteron energy measured for present conditions was found to be (52 ± 7) keV, while the deuteron-beam fluence per shot was of the order of 1015 ions/m2 when operated at a pressure of 0.2 mbar. The deuteron-beam emission is in the forward direction and is observed to be highly anisotropic.
    Matched MeSH terms: Time and Motion Studies
  12. Mamat-Noorhidayah, Yazawa K, Numata K, Norma-Rashid Y
    PLoS One, 2018;13(3):e0193147.
    PMID: 29513694 DOI: 10.1371/journal.pone.0193147
    Resilin functions as an elastic spring that demonstrates extraordinary extensibility and elasticity. Here we use combined techniques, laser scanning confocal microscopy (LSCM) and scanning electron microscopy (SEM) to illuminate the structure and study the function of wing flexibility in damselflies, focusing on the genus Rhinocypha. Morphological studies using LSCM and SEM revealed that resilin patches and cuticular spikes were widespread along the longitudinal veins on both dorsal and ventral wing surfaces. Nanoindentation was performed by using atomic force microscopy (AFM), where the wing samples were divided into three sections (membrane of the wing, mobile and immobile joints). The resulting topographic images revealed the presence of various sizes of nanostructures for all sample sections. The elasticity range values were: membrane (0.04 to 0.16 GPa), mobile joint (1.1 to 2.0 GPa) and immobile joint (1.8 to 6.0 GPa). The elastomeric and glycine-rich biopolymer, resilin was shown to be an important protein responsible for the elasticity and wing flexibility.
    Matched MeSH terms: Range of Motion, Articular
  13. Badrasawi M, Hamdan M, Vanoh D, Zidan S, ALsaied T, Muhtaseb TB
    PLoS One, 2022;17(11):e0276967.
    PMID: 36395173 DOI: 10.1371/journal.pone.0276967
    INTRODUCTION: Fear of falling has serious implications for health and is an important threat to autonomy. The purpose of this cross-sectional study was to investigate risk factors for fear of falling among Palestinian older adults in Hebron district.

    METHODS: A cross-sectional study was conducted among Palestinians > 60 years living in Hebron, West Bank. The Falls Efficacy Scale-International was used to predict falls among Palestinian older adults. Moreover, socio-demographic data, medical history, lifestyle habits, body composition, nutritional status, cognitive status (using the Montreal cognitive assessment tool), and functional status (using activities of daily living and instrumental activities of daily living scale), the presence of depressive symptoms (using geriatric depression scale), and physical fitness performance (using senior fitness test) were collected through an interview-based questionnaire. Data were analyzed using univariate and multivariate approach.

    RESULTS: A total of 200 participants were included in the study; 137 (68.5%) females and 63 (31.5%) males. Mean age was 70.5 ± 5.7 years, ranged from 65 to 98 years old. Fear of falling was significantly higher among older adults with advanced aged, living in villages or camps, low educational level, and being married (p < 0.05). Functional status (ADL and IADL), physical fitness status (timed up and go), and depression symptoms were significantly related to fear of falling (p < 0.05).

    CONCLUSION: High concern of falling is significantly associated with advanced age, low education level, being married, and living in villages or camps. ADLs were among the factors that had a significant relationship with increased fear of falling. Predictors of fear of falling among Palestinian older adults were IADL scores, body fat percentage, rapid gait speed, timed up and go test. Future studies could investigate further correlates of fear of falling among older adults.

    Matched MeSH terms: Time and Motion Studies
  14. Majeed Z, Nawazish S, Baig A, Akhtar W, Iqbal A, Muhammad Khan W, et al.
    PLoS One, 2023;18(2):e0278568.
    PMID: 36848343 DOI: 10.1371/journal.pone.0278568
    Green biomass is a renewable and biodegradable material that has the potential use to trap urea to develop a high-efficiency urea fertilizer for crops' better performance. Current work examined the morphology, chemical composition, biodegradability, urea release, soil health, and plant growth effects of the SRF films subjected to changes in the thickness of 0.27, 0.54, and 1.03 mm. The morphology was examined by Scanning Electron Microscopy, chemical composition was analyzed by Infrared Spectroscopy, and biodegradability was assessed through evolved CO2 and CH4 quantified through Gas Chromatography. The chloroform fumigation technique was used for microbial growth assessment in the soil. The soil pH and redox potential were also measured using a specific probe. CHNS analyzer was used to calculate the total carbon and total nitrogen of the soil. A plant growth experiment was conducted on the Wheat plant (Triticum sativum). The thinner the films, the more they supported the growth and penetration of the soil's microorganisms mainly the species of fungus possibly due to the presence of lignin in films. The fingerprint regions of the infrared spectrum of SRF films showed all films in soil changed in their chemical composition due to biodegradation but the increase in the thickness possibly provides resistance to the films' losses. The higher thickness of the film delayed the rate and time for biodegradation and the release of methane gas in the soil. The 1.03 mm film (47% in 56 days) and 0.54 mm film (35% in 91 days) showed the slowest biodegradability as compared to the 0.27 mm film with the highest losses (60% in 35 days). The slow urea release is more affected by the increase in thickness. The Korsymer Pappas model with release exponent value of < 0.5 explained the release from the SRF films followed the quasi-fickian diffusion and also reduced the diffusion coefficient for urea. An increase in the pH and decrease in the redox potential of the soil is correlated with higher total organic content and total nitrogen in the soil in response to amending SRF films with variable thickness. Growth of the wheat plant showed the highest average plant length, leaf area index and grain per plant in response to the increase in the film's thickness. This work developed an important knowledge to enhance the efficiency of film encapsulated urea that can better slow the urea release if the thickness is optimized.
    Matched MeSH terms: Motion Pictures as Topic*
  15. AlDahas A, Devecchi V, Deane JA, Falla D
    PLoS One, 2023;18(10):e0292798.
    PMID: 37824590 DOI: 10.1371/journal.pone.0292798
    BACKGROUND: People with chronic neck pain (CNP) often present with impaired neck proprioception. The most widely used clinical test for assessing neck proprioception is cervical joint position sense which measures joint position error (JPE). This clinical test is typically performed using a laser pointer to examine the accuracy of returning to a neutral head position (NHP) or target head position (THP) following active neck movements. The aim of this study was to determine the measurement properties of JPE using a laser pointer when tested in people with and without CNP under a variety of different testing conditions (i.e., different movement directions, sitting versus standing, NHP versus THP).

    METHODS: Forty-three participants (23 asymptomatic and 20 with CNP) underwent neck proprioception testing, returning to a NHP and THP in both sitting and standing positions (six trials for each test). A laser pointer was secured on the participant's forehead and inertial measurement unit (IMU) sensors were placed beneath the laser pointer and at the level of the spinous process of the seventh cervical vertebra. Both the absolute and the constant JPE were assessed.

    FINDINGS: For the asymptomatic participants, good reliability (ICC: 0.79) was found only for right rotation of the THP task in sitting. In standing, good reliability (ICC: 0.77) was only found in flexion for the THP task. In standing, good reliability (ICC: 0.77) was only found for right rotation of the THP for the absolute JPE and left rotation (ICC: 0.85) for the constant error of the NHP task. In those with CNP, when tested in sitting, good reliability was found for flexion (ICC: 0.8) for the absolute JPE and good reliability (ICC range: 0.8-0.84) was found for flexion, extension, and right rotation for the constant JPE. In standing, good reliability (ICC range: 0.81-0.88) was found for flexion, and rotation for the absolute JPE. The constant JPE showed good reliability (ICC: 0.85) for right rotation and excellent reliability (ICC: 0.93) for flexion. Validity was weak to strong (r range: 0.26-0.83) and moderate to very strong (r range: 0.47-0.93) for absolute and constant error respectively, when tested in sitting. In standing, the validity was weak to very strong (0.38-0.96) for the absolute JPE and moderate to very strong (r range: 0.54-0.92) for the constant JPE.

    CONCLUSION: The reliability of the measure of JPE when tested in sitting and standing in both groups showed good reliability, but not for all movements. The results of the current study also showed that the laser pointer correlated well with the Noraxon IMUs, but not for all movements. The results of the current study support the use of the JPE using a laser pointer in clinical and research settings.

    Matched MeSH terms: Range of Motion, Articular
  16. Ziaee M, Hejazi F
    PLoS One, 2023;18(8):e0290248.
    PMID: 37590241 DOI: 10.1371/journal.pone.0290248
    Coulomb friction is considered as a mechanical approach to diminish the structural responses during the excitations. However, in case of severe oscillations supplementary mechanisms are employed besides the friction to mitigate the destructive effects of the vibrations in structures. Therefore, the main goal of this research is to develop a new Hybrid System (HS) which is a parallel combination of Viscous Damping (VD) and Coulomb friction for structures subjected to dynamic load. To achieve this goal, the effect of viscous damper is embedded in the equation of motion which is proposed by Den Hartog for a Single-Degree-of-Freedom (SDOF) Coulomb system, and has been extensively implemented for past few decades. In the considered numerical example in this study, implementing the proposed HDM in system resulted in decreasing the maximum displacement in the range of 1% to 98% for different amounts of force amplitude and viscous damping ratios. Also, applying the proposed HDM increased the time lag for about up to 24% for the frequency ratios greater than 1. The developed hybridized system in this study can be utilised as new generation of Tuned Mass Damper (TMD) to improve their energy dissipating efficiency under severe excitations.
    Matched MeSH terms: Motion
  17. Zhao J, Tien HY, Abdullah S, Zhang Z
    Plast Reconstr Surg, 2010 Dec;126(6):2052-2059.
    PMID: 21124145 DOI: 10.1097/PRS.0b013e3181f44994
    BACKGROUND: Second toe-to-thumb transfer is a good alternative to using the great toe for reconstruction of the thumb. It achieves excellent function and reduces morbidity to the donor foot. However, cosmesis is often poor. The second toe has three unattractive features, a narrow "neck," a bulbous tip, and a short nail.

    METHODS: The authors describe a modified second toe transfer that addresses cosmesis in six patients. These include (1) harvesting a flap from the adjacent side of the great toe and insetting it into the volar aspect of the second toe to give more bulk, (2) making skin excisions on each side of the tip to reduce the bulbous appearance, and (3) excising the eponychium to produce apparent lengthening of the nail.

    RESULTS: The mean follow-up period was 18 months (range, 6 to 36 months). The procedure resulted in good function and improved cosmesis in all six cases. Part of the great toe flap was lost in one case. The mean two-point discrimination in the transferred toes was 10.1 mm, with protective sensation present in the flaps. The range of motion of the transferred toe was 14 to 38 degrees at the metatarsophalangeal joint, 16 to 55 degrees at the proximal interphalangeal joints, and 20 to 36 degrees in the distal interphalangeal joints. All patients except one were happy with the appearance of the transferred toe.

    CONCLUSION: This novel approach will allow patients to take advantage of the lower morbidity to the donor site afforded by second toe-to-thumb transfer and provide the patients with a more aesthetic appearance of the new thumb.

    Matched MeSH terms: Range of Motion, Articular/physiology
  18. Krupa BN, Mohd Ali MA, Zahedi E
    Physiol Meas, 2009 Aug;30(8):729-43.
    PMID: 19550027 DOI: 10.1088/0967-3334/30/8/001
    Cardiotocograph (CTG) is widely used in everyday clinical practice for fetal surveillance, where it is used to record fetal heart rate (FHR) and uterine activity (UA). These two biosignals can be used for antepartum and intrapartum fetal monitoring and are, in fact, nonlinear and non-stationary. CTG recordings are often corrupted by artifacts such as missing beats in FHR, high-frequency noise in FHR and UA signals. In this paper, an empirical mode decomposition (EMD) method is applied on CTG signals. A recursive algorithm is first utilized to eliminate missing beats. High-frequency noise is reduced using EMD followed by the partial reconstruction (PAR) method, where the noise order is identified by a statistical method. The obtained signal enhancement from the proposed method is validated by comparing the resulting traces with the output obtained by applying classical signal processing methods such as Butterworth low-pass filtering, linear interpolation and a moving average filter on 12 CTG signals. Three obstetricians evaluated all 12 sets of traces and rated the proposed method, on average, 3.8 out of 5 on a scale of 1(lowest) to 5 (highest).
    Matched MeSH terms: Motion
  19. Lim PK, Ng SC, Lovell NH, Yu YP, Tan MP, McCombie D, et al.
    Physiol Meas, 2018 10 11;39(10):105005.
    PMID: 30183675 DOI: 10.1088/1361-6579/aadf1e
    OBJECTIVE: The photoplethysmography (PPG) signal, commonly used in the healthcare settings, is easily affected by movement artefact leading to errors in the extracted heart rate and SpO2 estimates. This study aims to develop an online artefact detection system based on adaptive (dynamic) template matching, suitable for continuous PPG monitoring during daily living activities or in the intensive care units (ICUs).

    APPROACH: Several master templates are initially generated by applying principal component analysis to data obtained from the PhysioNet MIMIC II database. The master template is then updated with each incoming clean PPG pulse. The correlation coefficient is used to classify the PPG pulse into either good or bad quality categories. The performance of our algorithm was evaluated using data obtained from two different sources: (i) our own data collected from 19 healthy subjects using the wearable Sotera Visi Mobile system (Sotera Wireless Inc.) as they performed various movement types; and (ii) ICU data provided by the PhysioNet MIMIC II database. The developed algorithm was evaluated against a manually annotated 'gold standard' (GS).

    MAIN RESULTS: Our algorithm achieved an overall accuracy of 91.5%  ±  2.9%, with a sensitivity of 94.1%  ±  2.7% and a specificity of 89.7%  ±  5.1%, when tested on our own data. When applying the algorithm to data from the PhysioNet MIMIC II database, it achieved an accuracy of 98.0%, with a sensitivity and specificity of 99.0% and 96.1%, respectively.

    SIGNIFICANCE: The proposed method is simple and robust against individual variations in the PPG characteristics, thus making it suitable for a diverse range of datasets. Integration of the proposed artefact detection technique into remote monitoring devices could enhance reliability of the PPG-derived physiological parameters.

    Matched MeSH terms: Motion
  20. Liew YM, McLaughlin RA, Chan BT, Abdul Aziz YF, Chee KH, Ung NM, et al.
    Phys Med Biol, 2015 Apr 7;60(7):2715-33.
    PMID: 25768708 DOI: 10.1088/0031-9155/60/7/2715
    Cine MRI is a clinical reference standard for the quantitative assessment of cardiac function, but reproducibility is confounded by motion artefacts. We explore the feasibility of a motion corrected 3D left ventricle (LV) quantification method, incorporating multislice image registration into the 3D model reconstruction, to improve reproducibility of 3D LV functional quantification. Multi-breath-hold short-axis and radial long-axis images were acquired from 10 patients and 10 healthy subjects. The proposed framework reduced misalignment between slices to subpixel accuracy (2.88 to 1.21 mm), and improved interstudy reproducibility for 5 important clinical functional measures, i.e. end-diastolic volume, end-systolic volume, ejection fraction, myocardial mass and 3D-sphericity index, as reflected in a reduction in the sample size required to detect statistically significant cardiac changes: a reduction of 21-66%. Our investigation on the optimum registration parameters, including both cardiac time frames and number of long-axis (LA) slices, suggested that a single time frame is adequate for motion correction whereas integrating more LA slices can improve registration and model reconstruction accuracy for improved functional quantification especially on datasets with severe motion artefacts.
    Matched MeSH terms: Motion
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