Papers by DIMITRIS A . FOTIADIS
Stress has multiple effects on human health. Sensors designed to measure stress and indicate heal... more Stress has multiple effects on human health. Sensors designed to measure stress and indicate health status by recognizing illnesses or other conditions (e.g., heart problems and blood pressure) have been widely utilized to monitor and characterize this physiological phenomenon. Stress has two response mechanisms: the autonomic nervous system (ANS) and hypothalamic-pituitaryadrenal (HPA) axis. ANS can affect heart rate, breathing rate, skin conductance, blood pressure, and other hemodynamic parameters. Continuous non-invasive blood pressure (cNIBP) measurement, pulse volume, cardiac output, and other hemodynamic parameters are important for stress measurement and health indicators. There is still room for research and development of different approaches to measurement in this area. Very few sensor systems associated with cNIBP have been developed or are currently in progress. Photoplethysmography (PPG), impedance plethysmography (IPG), and ultrasound imaging were performed along with other non-invasive sensors, such as electrocardiography (ECG), cardioseismography (CSG), and ballistocardiography (BCG), to measure hemodynamic parameters. In the HPA axis, stress hormones are the most important measurement from the perspective of cortisol levels. This measurement is also important in general for the health of the subject, especially for good functioning of the axis itself (HPA axis). Sensors have been developed to detect cortisol levels for academic and research purposes. Cortisol levels can be measured in two ways: direct and indirect hormone measurements. Non-invasive direct hormone measurement uses a sensor to evaluate the cortisol levels in sweat. In contrast, indirect measurement uses an increase or decrease in cortisol levels in relation to other substances such as sodium or potassium. Therefore, in the present study, we investigated technologies, methods, and wearable sensors for continuous hemodynamic measurements at the ANS level and cortisol measurements at the HPA axis level. These sensors and measurements are crucial for improving healthcare applications.
Stress is a significant factor that affects well-being and health. Factors that trigger stress in... more Stress is a significant factor that affects well-being and health. Factors that trigger stress include work, social interactions, and economic and environmental factors. Stress may cause lower labor productivity, physical and mental health problems, and malfunctions in all social aspects of life. Psychosomatic health can be improved if proper stress detection mechanisms are present in daily life and stress reduction methods can occur. Wearable sensors are currently used in many commercial and scientific applications in a non-invasive or unobtrusive manner. These devices are used in daily routines. In this paper, a comprehensive review of the latest literature and developments in stress detection methods is presented through extensive and holistic research on stress response, both at the level of the autonomic nervous system (ANS) and hypothalamic-pituitary-adrenal axis (HPA). This review focuses on the exploitation of various methods, technologies, and data analysis systems to understand stress in a multifaceted and comprehensive manner. Various stress-related factors are presented along with biological signal measurements, and physical secretions or biomarkers are primarily used for stress detection. Furthermore, the manner in which body movement and posture measurements may be related to stress was investigated, together with speech and hand tremors. Various stress-detection technologies have been analyzed, and existing data analysis methods that can be applied to stress-detection systems have been highlighted. This review serves as a reference and guideline for exploring this area of interest, identifying research opportunities, and offering ideas, options, and suggestions for optimized solutions regarding future applications and research.
International Journal of Computing, Aug 1, 2014
Measuring the position of a medical instrument inside the human body can be performed with variou... more Measuring the position of a medical instrument inside the human body can be performed with various methods. One option is to measure the phase shift of the signal originating from a transmitter embedded into the tip of the medical instrument, determining its displacement with respect to a set of stationary receivers. The phase shift is converted into a low frequency voltage with the use of a Phased Locked Loop (PLL). This voltage can subsequently be converted into displacement, providing the position of the medical instrument in one (1D), two (2D) and three (3D) dimensions using trilateration. The instrument's displacement can be defined in either the time or frequency domain. This paper presents a novel method for constant velocity displacement of the transmitter, using either the Locally Weighted Scatter-Plot Smoothing (LOWESS) curve fitting method or a Lomb-Scargle periodogram. The Lomb-Scargle periodogram is based on the least-squares power spectrum and can be used instead of waveform smoothing and measurement into the time domain, providing more precise and accurate measurement results as compared to LOWESS curve fitting method.
i-BRAIN: A Broadband Radio Access Interactive Network, Challenging the Barriers of the Last-Mile Wireless Infrastructure Concept
ABSTRACT
i-BRAIN: A Broadband Radio Access Interactive Network, Challenging the Barriers of the Last-Mile Wireless Infrastructure Concept
ABSTRACT
IEEE journal of biomedical and health informatics, Jan 24, 2014
This paper presents a novel method for tracking the position of a medical instrument's tip. T... more This paper presents a novel method for tracking the position of a medical instrument's tip. The system is based on phase locking a high frequency signal transmitted from the medical instrument's tip to a reference signal. Displacement measurement is established having the loop open, in order to get a low frequency voltage representing the medical instrument's movement; therefore, positioning is established by means of conventional measuring techniques. The Voltage Controlled Oscillator (VCO) stage of the Phase Locked Loop (PLL), combined to an appropriate antenna comprise the associated transmitter located inside the medical instrument tip. All the other low frequency PLL components, Low Noise Amplifier (LNA) and Mixer, are located outside the human body, forming the receiver part of the system. The operating details of the proposed system were coded in Verilog-AMS. Simulation results indicate robust medical instrument tracking in one dimension (1D). Experimental evaluat...
Precise determination of the position of a medical device inside the human body, specifically the... more Precise determination of the position of a medical device inside the human body, specifically the tip of an Intravascular Ultrasound (IVUS) catheter, is a process currently relying primarily on angiography techniques. The injection of a radio-opaque contrast agent into the bloodstream and subsequent use of contrast-enhanced Xray imaging is still the most common technique used by medical staff to track the exact position of the IVUS catheter inside the human body. This position tracking methodology has numerous shortcomings and imposes unnecessary risks on the patient, as compared to a new technology and associated methodology proposed in this paper. In the first part, a position tracking technology survey is presented, followed by the details of the proposed Ultra Wideband (UWB) methodology, a discussion of its advantages and disadvantages, as well as the definition of a development roadmap.
Precise determination of the position of a medical device inside the human body, specifically the... more Precise determination of the position of a medical device inside the human body, specifically the tip of an Intravascular Ultrasound (IVUS) catheter, is a process currently relying primarily on angiography techniques. The injection of a radio-opaque contrast agent into the bloodstream and subsequent use of contrast-enhanced Xray imaging is still the most common technique used by medical staff to track the exact position of the IVUS catheter inside the human body. This position tracking methodology has numerous shortcomings and imposes unnecessary risks on the patient, as compared to a new technology and associated methodology proposed in this paper. In the first part, a position tracking technology survey is presented, followed by the details of the proposed Ultra Wideband (UWB) methodology, a discussion of its advantages and disadvantages, as well as the definition of a development roadmap.
A novel signal processing method based on the frequency modality for intra-body medical instrument tracking
2016 5th International Conference on Modern Circuits and Systems Technologies (MOCAST), 2016
The path on the way to 4G networks incorporates a number of significant trends. Moreover, future ... more The path on the way to 4G networks incorporates a number of significant trends. Moreover, future wireless infrastructures will have to compete with multiple deployed wired and wireless communication systems. The 4G “era” has to ensure really break-through technologies in order to persuade for its necessity and to gain its share in the world communication market. This paper deals with the fourth generation (4G) of wireless communication networks. In the beginning a brief review of previous generation networks (1st , 2nd, 2,5 and 3rd) is presented. We will examine 3G network’s commercial success or failure worldwide, and throughout this analysis, the necessity for 4G networks will arise. Available information will be provided, concerning the various standardization activities, currently performed on 4G standards. A short analysis of the various layer trends (physical, network, MAC, security, application, etc.) will be described. Furthermore the globalisation of 4G, not only as a mobil...
Novel position tracking method of a medical instrument
Position tracking or the ability to locate the exact position of a medical instrument inside huma... more Position tracking or the ability to locate the exact position of a medical instrument inside human body is treated with various ways. The use of X-ray imaging is the dominant method for most of the invasive medical instruments position tracking (Watson and Gorski, 2010), while other methods such as optical or electromagnetic tracking appear as new trends in invasive surgery during the last years. An alternative method for displacement tracking of a medical instrument is presented, able to provide accuracy down to millimeter level, while problems with interference, non-line of sight (LOS), physical size or power consumption are minimized.
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Papers by DIMITRIS A . FOTIADIS