Karel Hana

New methods for precise detection of systolic complexes in the signal acquired from quantitative seismocardiograph

Quantitative seismocardiography is a simple and non-invasive method of measuring compression waves generated by heart activity. It provides important information about the cardiovascular system. The first important information acquired from quantitative seismocardiogram (QSCG) is the pseudo-period rate. This paper focuses just on the detection of pseudo-periods in the QSCG signal. Two methods of detection together with a method of sophisticated data preprocessing are presented. The results of the methods are demonstrated using real data.

Evaluation of relationship between the activity of upper limb and the piloting precision

Flying an aircraft requires a significant degree of coordination of upper and lower limbs. Such movements tend to be rather uncoordinated in the case of inexperienced pilots which results in inaccurate piloting. The aim of this study is to prove or disprove the dependence of the upper limb activity in relation to the aircraft steering during various actions which are required for precise maneuvering. We also deal with the design of a method to determine the degree of correlation between the movement of the hand and the airplane. The study was conducted on 8 subjects with the same level of experience during 11 hours of flight training on the simulator of type TRD40 and aircraft of type DA40. Subjects performed 14 maneuvers in total. Between takeoff and landing a recurring cycle of four maneuvers has been carried out by the subjects. Repeated maneuvers were in the order from the straight-and-level flight, horizontal turn by 360°, ascend turn by 180°, and descent turn by 180°. Recorded data except for basic flight data (magnetic course, banked and altitude) have been variables depicting the activity of the pilots upper limb. The activity was measured using triaxial accelerometer located on the dorsal side of the distal end of the forearm. The correlation coefficient proved relationship between the upper limb movement and aircraft steering both at bank and altitude. It testifies that change of bank and altitude of aircraft is directly connected with upper limb movements. Resultant activity standard deviation relation correlation coefficient is 0.7.

FlexiGuard: Modular biotelemetry system for military applications

The article presents a FlexiGuard modular biotelemetric system for real-time monitoring of special military units. The main focus of the system is on automated monitoring of special forces via parallel monitoring of each member of the special team individually, witch includes collecting sets of physiologic (or environmental) parameters. The systems consists of a set of sensors (for monitoring temperature, heart rate, acceleration, humidity etc.) and modular sensing unit, which records the measured data and sends them to the visualization unit. The measured values (i.e. heart rate, surface temperature of the body and so on) are then visualized in the graphic user interface of the visualization unit. Testing of the functionality of the system took place in both laboratory and real environment. In the case of carrying out the measurements on 34 soldiers at series of 4 probands at the same time, the sensor networks worked without any loss of signal. During the data transfer to the visualization unit, a loss of approx 0.2% of packets occurred. The system thus can offer information to the commander, which may prove essential for the optimalization of operational strategies, taking the state of wellbeing of the team members into account.

Volume of confidence ellipsoid: a technique for quantifying trunk sway during stance

Abstract The position of the trunk can be negatively affected by many diseases. This work focuses on a noninvasive method of quantifying human postural stability and identifying defects in balance and coordination as a result of the nervous system pathology. We used a three-degree-of-freedom orientation tracker (Xsens MTx unit) placed on a patient’s trunk and measured three-dimensional (3-D) data (pitch, roll, and yaw) during quiet stance. The principal component analysis was used to analyze the data and to determine the volume of 3-D 95% confidence ellipsoid. Using this method, we were able to model the distribution of the measured 3-D data (pitch, roll, and yaw). Eight patients with degenerative cerebellar disease and eight healthy subjects in this study were measured during stance, with eyes open and eyes closed, and statistical analysis was performed. The results of the new method based on the 3-D confidence ellipsoid show that the volumes related to the patients are significantly larger than the volumes related to the healthy subjects. The concept of confidence ellipsoid volume, although known to the biomechanics community, has not been used before to study the postural balance problems. The method can also be used to study, for example, head and pelvis movements or alignments during stance.

Analysis and prediction of upper extremity movements by cyclograms

Quantification of upper extremity movement is a common objective in both research and clinical practice. Currently, methods based on angle-angle diagrams, also called cyclograms, seem to be promising. Nevertheless, compared to the study of lower limbs, the concept of angle-angle diagrams has not been systematically used to study upper limb movements during walking. The paper describes two examples of new methods based on angle-angle diagrams for application in rehabilitation and assistive robotics. The cyclograms represent information about the relationship between the angles and their changes over time. We used cyclograms as patterns for learning artificial neural networks and predicting the movement of upper-limb. Together with artificial intelligence, cyclograms offer wide scope of application in prosthesis control systems. Using bilateral cyclogram, the information about the relationship between the right and left arm joint angles is used to evaluate the symmetry of movements. The method based on the orientation of the bilateral cyclogram can be used as an additional method for determining the symmetry of movements of the upper limbs or exo-prosthesis.

Wearable systems for monitoring the health condition of soldiers: Review and application

From the second half of the 1990s, thanks to more affordable and more powerful technology and systems for recording based on miniaturized sensors, we can observe a more intensive development of a system that monitors the physical and psychological conditions of soldiers. Systems for measuring of physical and medical data for the diagnostics of physical and psychological state has significantly spread. This study, however, examines the current technologies and usage of the wearable monitoring systems in military. The article can serve as a guide for choosing suitable and affordable systems of quantitative evaluation of physical and psychological conditions of soldiers. In addition, the innovative telemetry monitoring system (FlexiGuard system) composed of appropriate sensors is introduced. Based on previous researches and tests, FlexiGuard system and its sensors are recommended for use in military practice.

Compensation of the contrast and brightness attenuation with depth in confocal microscopy

A confocal laser scanning microscope (CLSM) captures images from a biological specimen in different depths and provides one with a stack of precisely registered fluorescent images. However, image intensities suffer from light loss distortions showing contrast and brightness degradation of images with depth. This effect causes problems in subsequent analysis and segmentation of biological objects. Therefore, we developed a post-processing method to correct this problem. It is a two step algorithm. In the first step the algorithm determines a standard histogram of the stack of images and in the second step histograms of individual images are warped according to this standard histogram. The algorithm results in more stable brightness and contrast of images through the stack.

Postural instability assessment using trunk acceleration frequency analysis

Abstract The main tools for measuring postural instability of the body during quiet stance are stabilometric platforms. Frequency domain analysis of center of pressure excursions is used for detecting and quantifying specific diseases. The disadvantage of such platforms is their higher price and large dimensions. The main aim of this work was to identify the applicability of the frequency domain analysis of the trunk acceleration measured by one-axis accelerometer. In order to test the new technique, 10 patients with degenerative cerebellar ataxia and 11 healthy subjects were chosen to participate. The trunk acceleration of each subject with opened/closed eyes was measured during quiet stance on a firm/foam surface. The distribution of the power spectral density in the frequency spectrum of acceleration in the anterior–posterior direction is a suitable tool for quantifying postural instability. The percentages of the area under the power spectral density curve of middle frequency range (2.4–3.5 Hz) of acceleration in patients and healthy subjects were compared, and significant differences were found. The finding of our research is that a single cheap one-axis accelerometer placed on trunk to measure the acceleration in AP direction, together with the method based on the power spectral density of acceleration, could be a new tool for examinations of body instability.

VOLUME OF CONVEX HULL: A TECHNIQUE FOR QUANTIFYING HUMAN POSTURAL STABILITY

Many disorders, such as nervous system disorders, can affect orientation of the body segments in 3D space negatively. Patients with these disorders often show body segments instability during stance tasks. Nowadays, 3-axis gyroscopes are about to be used to measure postural stability. The main objective of the paper is to describe a method which would be suitable for quantifying postural stability and 3D movement as a whole using a cheap 3-axis gyroscope. New method based on the volume of a 3D convex hull (CH) obtained by plotting pitch, roll and yaw angles versus each other was proposed for quantitative evaluation of 3D trunk sway. The sway was measured while patients with degenerative cerebellar disorder (Pts) and eleven healthy subjects (HSs) performed quiet stance on a firm surface (FiS) and foam surface (FoS) with open eyes (OE) and closed eyes (CE). The CH was used to identify differences in balance control, and there were significant differences found between the two groups. The median (Mdn) of the volume of Pts with OE on FiS is four times larger than the Mdn of the volume of HS with OE on FiS. The Mdn of the volume of Pts with CE on FoS is 80 times larger than the Mdn of the volume of HS with CE on FoS. It was therefore found that the volume of CH is suitable for quantifying postural sway and identifying differences in balance control.

Measuring the Response of Patients with Type I Diabetes to Stress Burden

The article presents measurement methodology and systems for measuring and evaluating the response of patients suffering from type I diabetes to stress burden. The proposed methodology and systems have been developed to recognize the effects of strain on patients’ reaction time and their work performance. Stress burden was measured by a multi-sensory monitoring system designed for this purpose. The methods used were based on monitoring physiological stress symptoms by measuring pulse rate, respiratory rate, temperature, galvanic skin resistance, and electrical activity of muscles. It was suggested to monitor the measured parameters in waveform, from initiation of stress stimuli, throughout the period of growth, and up to the point of decline. The research was conducted under the supervision of psychologists, and the proposed methodology for measuring stress burden and its impact on physiological functions of type I diabetics involved a group of patients and a control group of healthy subjects. The proposed measurement methodology would be beneficial not only in the design of systems for detecting mental stress, but also in the treatment of patients suffering from diabetes and the assessment of their physical/mental state while performing demanding work tasks.