Search for: photoplethysmography
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    Flow mediated dilation with photoplethysmography as a substitute for ultrasonic imaging

    , Article Physiological Measurement ; Volume 36, Issue 7 , 2015 , Pages 1551-1571 ; 09673334 (ISSN) Mashayekhi, G ; Zahedi, E ; Movahedian Attar, H ; Sharifi, F ; Sharif University of Technology
    Institute of Physics Publishing  2015
    Flow mediated dilation (FMD) is a non-invasive method for endothelial function assessment providing an index extracted from ultrasonic B-mode images. Although utilized in the research community, the difficulty of its application and high cost of ultrasonic devices prevent it from being widely used in clinical settings. In this study we show that substituting the ultrasonic device with more easily handled and low cost photoplethysmography and electrocardiography is possible. We introduce new indices based on the photoplethysmogram (PPG) and electrocardiogram (ECG) and show that they are correlated with the ultrasound-based FMD Index. To this end, a conventional ultrasound FMD test was carried... 

    Low complexity heart rate measurement from wearable wrist-type photoplethysmographic sensors robust to motion artifacts

    , Article ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings, 15 April 2018 through 20 April 2018 ; Volume 2018-April , 2018 , Pages 921-924 ; 15206149 (ISSN) ; 9781538646588 (ISBN) Boloursaz Mashhadi, M ; Farhadi, M ; Essalat, M ; Marvasti, F ; Sharif University of Technology
    This paper presents a low complexity while accurate Heart Rate (HR) estimation technique from signals captured by Photoplethysmographic (PPG) sensors worn on the wrist during intensive physical exercise. Wrist-type PPG signals experience severe Motion Artifacts (MA) that hinder efficient HR estimation especially during intensive physical exercises. To suppress the motion artifacts efficiently, simultaneous 3 dimensional acceleration signals are used as reference MAs. The proposed method achieves an Average Absolute Error (AAE) of 1.19 Beats Per Minute (BPM) on the 12 benchmark PPG recordings in which subjects run at speeds of up to 15 km/h. This method also achieves an AAE of 2.17 BPM on the... 

    Modeling of photoplethysmography signal for quantitative analysis of endothelial cells during reactive hyperemia

    , Article 2012 19th Iranian Conference of Biomedical Engineering, ICBME 2012 ; 2012 , Pages 174-178 ; 9781467331302 (ISBN) Shiri, F ; Firoozabadi, B ; Saidi, M. S ; Sharif University of Technology
    In this study, at first the cardiovascular system is modeled based on the 1D method and then the simulation of the reactive hyperemia experiment has been applied on the model. In this simulation, by applying a cuff at the brachial artery, the flow downstream of the cuff is occluded. Then with releasing the cuff immediately, a large amount of shear stress, about 4 times the basal amount, is applied downstream of the cuff and consequently to the endothelial cells in a very short moment. Considering a reported experimental transfer function between shear stress and vasodilation, the increase of the artery diameter due to the sudden increase of the shear stress is obtained. Finally, the... 

    Modeling Brachial Blood Pressure by Using Finger PPG Signal

    , M.Sc. Thesis Sharif University of Technology Asadpour, Abdoreza (Author) ; Zahedi, Edmond (Supervisor)
    Nowadays, all of the devices that measure blood pressure commercially at home are using wrist or arm cuffs preventing the systolic or diastolic blood pressure from being measured continuously. Various parameters such as blood flow with some degree of correlation with blood pressure that can be measured noninvasively have been suggested. However, these parameters do not produce accurate estimates for blood pressure. Pulse Transit Time (PTT) which is defined as the interval between the R peak of ECG signal and the next PPG signal valley has shown to have over 90% correlation with systolic blood pressure in past studies. In this thesis, the relationship between the value of the systolic blood... 

    , M.Sc. Thesis Sharif University of Technology Malek Mohammadi, Mahsa (Author) ; Zahedi, Edmond (Supervisor)
    Cardiovascular (CV) system is very similar to a wireless communication system in which a common input signal from the heart is fed into different arterial channels throughout different body parts. By putting multiple sensors on different peripheral body sites effects of this circulation from the heart can be recorded and be used as inputs for different multi channel blind system identification (BSI) methods for estimation of arterial channel dynamics. This Thesis is defined in order to investigate different BSI methods capability in CV characterization. To achieve this goal photoplethysmogram signals has been used as primary sensory recorded effect of heart function at three different... 

    Sensor module for multi-channel wireless photoplethysmography system

    , Article 2007 5th Student Conference on Research and Development, SCORED, Selangor, 11 December 2007 through 12 December 2007 ; 2007 ; 1424414709 (ISBN); 9781424414703 (ISBN) Kadhim, A. Y ; Mohd Ali, M. A ; Zahedi, E ; Sharif University of Technology
    The digital sensor module is developed to sample the input signal fed from a photo-sensor probe at sampling times ranging from 400-4000 μs equivalent to sampling rates of 2500-250 sample/second (S/s), respectively. The module produces 16-bit data packets which are transmitted serially and plotted to output the photoplethysmography signal (PPG). It displays accurate sampling values (packets) similar to the calculated ones. ©2007 IEEE  

    Non-invasive techniques for assessing the endothelial dysfunction: ultrasound versus photoplethysmography

    , Article IFMBE Proceedings, 3 December 2008 through 6 December 2008 ; Volume 23 , 2009 , Pages 65-68 ; 16800737 (ISSN) ; 9783540928409 (ISBN) Zaheditochai, M ; Jaafar, R ; Zahedi, E ; Sharif University of Technology
    Endothelial dysfunction, which can be noninvasively assessed by flow mediated vasodilation (FMD), predicts an increased rate of adverse cardiovascular events. The endothelial dysfunction is considered as a leading cause of development and progression of the atherosclerotic process. The main aim of this study is to review different non-invasive methods to assess the endothelial dysfunction and to propose enhancements to a new method based on photoplethysmography (PPG). First, non-invasive techniques developed for the evaluation of peripheral endothelial function (including the Doppler ultrasound (US)) will be reviewed. Although noninvasive, US -based techniques present a few disadvantages. To... 

    Meaurement of Flow Mediated Dilation Using Photoplethysmography

    , M.Sc. Thesis Sharif University of Technology Goldoozian, Layli Sadat (Author) ; Zahedi, Edmond (Supervisor)
    Endothelial cells cover the inner surface of blood vessels. In response to different physical (such as reactive hyperemia-RH) and pharmacological stimuli, they maintain homeostasis by changing the vascular diameter (by releasing chemical agents like nitric oxide). The endothelium inability to respond to metabolic need (endothelial dysfunction) is an early marker of cardiovascular diseases such as atherosclerosis. Flow mediated dilation (FMD) measurement using ultrasound imaging (FMD-US) has been established as a standard method for assessing the endothelial function. Recently, a less skilled-operator demanding method has been proposed based on the photoplethysmographic (PPG) signal changes... 

    Prediction of Coronary Angiography Results by Flow Mediated Dilation Assessments with Photoplethysmography

    , M.Sc. Thesis Sharif University of Technology Hosseini, Zahra Sadat (Author) ; Zahedi, Edmond (Supervisor) ; Fakhrzadeh, Hossein (Supervisor)
    Cardio Vascular Diseases (CVD) is currently the most important cause of mortality in the world. Coronary artery disease (CAD-with 3 major epicardial vessels) is one of the significant CVD. Coronary angiography remains the gold standard for identifying the presence and absence of stenosis due to CAD. It is performed by inserting a catheter into the coronary artery, directly injecting radiopaque contrast material there and recording radiographic images in different view of arteries. Images of this invasive way show severity and area of stenosis.
    A sign of CAD is endothelial dysfunction (inner artery layer) in peripheral arteries like the brachial artery. Due to a significant correlation... 

    Experimental investigation of the roles of blood volume and density in finger photoplethysmography

    , Article IEEE Sensors Journal ; Volume 13, Issue 5 , 2013 , Pages 1397-1398 ; 1530437X (ISSN) Keikhosravi, A ; Zahedi, E ; Attar, H. M ; Aghajani, H ; Sharif University of Technology
    Using simultaneous photoplethysmogram (PPG) and pulse transducer signals from the same finger, a high correlation (Mean: 98.6, STD: 1) is obtained between the AC part of the PPG and estimated volume changes (after normalization). These results point to the fact that in the resting fingertip, PPG signal variations are only due to volume changes and that blood density does not change thus has no contribution  

    An age index for vascular system based on photoplethysmogram pulse contour analysis

    , Article IFMBE Proceedings ; Volume 21 IFMBE, Issue 1 , 2008 , Pages 125-128 ; 16800737 (ISSN); 9783540691389 (ISBN) Chellappan, K ; Mohd Ali, M. A ; Zahedi, E ; Sharif University of Technology
    Springer Verlag  2008
    An approach based pulse on contour analysis is proposed for the development of an aging index for the vascular system. The approach is non-invasive, using photoplethysmography (PPG), which is in wide clinical use. A probe is applied to the subject's finger-tip to provide a measure of the pulse waveform. The measured waveforms are filtered, digitized and post-processed. Individual pulses are extracted and the best pulse was selected by using the best pulse selection algorithm. Pulse contour analysis is then performed with specially formulated PPG fitness equation. Results of measurements taken from 72 subjects are reported. The age range of the subjects was from 19 to 68 years, all of them... 

    Design and implementation of a PC-based digital synchronous detection system for biological signal measurement

    , Article 2007 5th Student Conference on Research and Development, SCORED, Selangor, 11 December 2007 through 12 December 2007 ; 2007 ; 1424414709 (ISBN); 9781424414703 (ISBN) Gan, K. B ; Zahedi, E ; Mohd Ali, M. A ; Sharif University of Technology
    A PC-based digital lock-in amplifier was implemented completely in software (Labview) for photoplethysmograph (PPG) measurement. Experiments carried out to evaluate the performance of the amplifier show that the system can recover the signals up to 40 dB below the interference (ambient light). This system can be customized later to measure the trans-abdominal PPG signal of pregnant women for fetal heart rate detection. ©2007 IEEE  

    Simulating the Effect of Cuff Pressure on Brachial Artery for Calculating the Photoplethysmography(PPG) Singnal

    , M.Sc. Thesis Sharif University of Technology Shiri, Farhad (Author) ; Firoozabadi, Bahar (Supervisor) ; Saeedi, Mohammad Saeed (Supervisor)
    One of the most important reasons of death in today’s world is the diseases related to cardiovascular system. Hypercholesterolemia is one of the most common forms of these diseases. There are a lot of experiments for diagnosing this disease, which are classified into two groups: invasive and noninvasive experiments. One of the well-known noninvasive experiments in this area is the photoplethysmography in which the changes of the photoplethysmography signal can reveal some valuable information about the cardiovascular system’s health.The objective of this study is to simulate the photoplethysmography experiment considering the clinical conditions of the experiment. In this work, the obtained... 

    Analyzing the Endothelial Function by Means of Photoplethysmogram Signal Modeling

    , M.Sc. Thesis Sharif University of Technology Amiri, Mina (Author) ; Zahedi, Edmond (Supervisor) ; Behnia, Fereidoon (Supervisor)
    The endothelial (the artery inner lumen cells) function is associated with cardiovascular risk factors. Its assessment methods can be classified into the two groups of invasive and noninvasive ones. The most widely used method among the current non-invasive tests employed in research settings is flow-mediated dilation (FMD). This technique measures endothelial function by inducing reactive hyperemia via the temporary arterial occlusion and measuring the resultant relative increase in the blood vessel diameter via ultrasound. The high price and large size of the device, and being operator dependent are the limitation of this method. In this work, we propose using the photoplethysmogram (PPG)... 

    Modeling of the Cardiovascular System using Breathing Stimuli for Evaluation of the Autonomic Nervous System

    , Ph.D. Dissertation Sharif University of Technology Goldouzian, Layli Sadat (Author) ; Zahedi, Edmond (Supervisor) ; Jehed, Mehran (Supervisor) ; Zarzoso, Vicente (Supervisor)
    Autonomic nervous system (ANS) controls involuntary activities of the body, e.g. heartbeat function and blood circulation. Common tests used for evaluation of the functionality of ANS system in regulation of the cardiovascular system include heart rate variability (HRV) analysis and studying the changes in heart rate or blood pressure during deep respiration, sit-to-stand or head-up tilt table test and Valsalva maneuver. Test parameters affect the amplitude of the variations of the cardiovascular signals. Therefore, in the recent years, analysis and modeling of the interaction between the relevant signals, e.g. heart rate, blood pressure and respiration, have been widely used for the... 

    Time Delay Estimation between Two Photoplethysmography Signals under Noisy Conditions

    , M.Sc. Thesis Sharif University of Technology Teymoori, Parisa (Author) ; Zahedi, Edmond (Supervisor) ; Shamsollahi, Mohammad Bagher (Supervisor)
    In this project, a processing algorithm is approached which is resistant against environmental and motion noises to find the pulse transmission time using two photoplethysmography signals. For this purpose, a new processing framework is checked and generalized for photoplethysmography signals. Already, this processing framework had impressive results. The considered processing method is obtained by offering a dynamic model for the signal and using it in a Kalman filter structure. For the photoplethysmography signals, with modeling every beat of signal to a Gaussian three or four sum form and with adding self-returned equations for model parameters, a nonlinear signal model is obtained. Then,... 

    Blood Pressure Estimation from PPG Signal Using Dynamic Time Warping Based Methods

    , M.Sc. Thesis Sharif University of Technology Hajikazem, Helia (Author) ; Mohammadzade, Narjes alhoda (Supervisor) ; Behrozi, Hamid (Co-Supervisor)
    By continuously measuring blood pressure, we can prevent the irreversible effects of high blood pressure. With the traditional method of using a cuff, it is not possible to measure blood pressure continuously during the day, so for continuous monitoring of blood pressure, it is necessary to use a method without the need for a cuff. Based on previous studies, to estimate blood pressure, Photoplethysmogram and ECG signal features, or temporal and morphological features of Photoplethysmogram signal have been used. In methods that use ECG signals, signal recording is difficult, and methods that use both PPG and ECG signals are even more complex. Using only PPG signals also has its problems.... 

    Time Series Analysis Using Deep Neural Networks Based on DTW Kernels and its Application in Blood Pressure Estimation Using PPG Signals

    , M.Sc. Thesis Sharif University of Technology Ahmadi Mobarakeh, Mohammad (Author) ; Mohammadzadeh, Narjesolhoda (Supervisor)
    This work presents a modification of deep neural networks for time series analysis. We used kernel layer(s), as a novel approach, at the beginning of the common deep neural networks. These kernels learn based on dynamic time warping (DTW). In each kernel, DTW is calculated between the kernel value and a part of input time series or a part of last layer output (if the kernel is not in the first layer). DTW also gives an alignment path for the input series. This alignment path is used to defining a loss function with the goal of getting better alignment (lower DTW distance) between the kernel and the other input. Besides getting better accuracy on the examined datasets, the other achievement... 

    Electrical analog model of arterial compliance during reactive hyperemia

    , Article 2011 1st Middle East Conference on Biomedical Engineering, MECBME 2011, 21 February 2011 through 24 February 2011, Sharjah ; 2011 , Pages 49-53 ; 9781424470006 (ISBN) Goldoozian, L. S ; Zahedi, E ; Sharif University of Technology
    Flow mediated dilation (FMD) measurement using ultrasound imaging (FMD-US) has been established as a standard method for assessing the endothelial function. Recently, a less skilled-operator demanding method has been proposed based on the photoplethysmogram (PPG) changes during reactive hyperemia. It was shown that the amplitude of the PPG pulse (FMD-PPG) changed in a quite similar manner to that of the artery diameter in the method of the FMD-US i.e. increases following releasing the cuff and then gradually returns to baseline. In this study PPG changes following reactive hyperaemia were modelled using time-varying passive electrical elements (R, L and C). The output of the electric analog... 

    Definition and comparison of a new vascular index between young healthy and aged subjects

    , Article IECBES 2014, Conference Proceedings - 2014 IEEE Conference on Biomedical Engineering and Sciences: "Miri, Where Engineering in Medicine and Biology and Humanity Meet", 8 December 2014 through 10 December 2014 ; 2015 , Pages 911-915 ; 9781479940844 (ISBN) Jaafar, R ; Zahedi, E ; Mohd Ali, M. A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    In an effort to identify a useful noninvasive screening tool for cardiovascular diseases (CVD) screening, photoplethysmograph (PPG) signals were acquired and analyzed. These PPG signals were recorded during reactive hyperemia experiments consisting of a 4-minute blood flow blockage of the right arm (RA) brachial artery (BA) using a blood pressure cuff inflator. This procedure is usually done for the assessment of endothelial dysfunction which is a risk factor for developing CVD. In this study, signals of the infrared (IR) and red (R) LED's of the PPG sensor were analyzed. These signals were preprocessed, normalized and slow varying component of the signal (DC values) and the pulsatile...