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    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  

    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... 

    Estimation of phase signal change in neuronal current MRI for evoke response of tactile detection with realistic somatosensory laminar network model

    , Article Australasian Physical and Engineering Sciences in Medicine ; Volume 39, Issue 3 , 2016 , Pages 717-726 ; 01589938 (ISSN) BagheriMofidi, S. M ; Pouladian, M ; Jameie, S. B ; Abbaspour Tehrani Fard, A ; Sharif University of Technology
    Springer Netherlands  2016
    Magnetic field generated by neuronal activity could alter magnetic resonance imaging (MRI) signals but detection of such signal is under debate. Previous researches proposed that magnitude signal change is below current detectable level, but phase signal change (PSC) may be measurable with current MRI systems. Optimal imaging parameters like echo time, voxel size and external field direction, could increase the probability of detection of this small signal change. We simulate a voxel of cortical column to determine effect of such parameters on PSC signal. We extended a laminar network model for somatosensory cortex to find neuronal current in each segment of pyramidal neurons (PN). 60,000... 

    Surface profiling using a double-fiber optical design

    , Article Optics and Lasers in Engineering ; Volume 48, Issue 4 , April , 2010 , Pages 421-426 ; 01438166 (ISSN) Golnabi, H ; Sharif University of Technology
    In this study surface profiling is performed by using a scanning system and an opto-pair fiber design. In this method one fiber transmits the laser light to the target and the second one transmits back the light reflected off the target to a photodetector. The monitoring of the reflected light signal from a surface is accomplished by converting the photon light into an electric signal and measuring by a digital multimeter. By scanning an object mounted on a XYZ-translational stage the reflection signal profiles are obtained for plane and curved surfaces. Output reflection signal variations in the X-, Y-, and Z-directions are measured for different plane and cylindrical surfaces and compared....