Artur Polinski

Color transformation methods for dichromats

Color blindness is a serious perception problem. Suffering individuals cannot understand messages, which are carrying by many images, especially those, distributed by WWW. In this paper we are proposing three image processing methods to enhance image recognition and understanding by persons with dichromacy. Color difference image is introduced to represent color perception dissimilarity. Two color transformation methods are presented. Results of tests proved the usefulness of the methods for fast color transformation of images in the WWW environment.

The contribution of blood-flow-induced conductivity changes to measured impedance

The paper considers the contribution of conductivity changes undergone in an anisotropical medium to measured resistance. This was achieved by extending the relationship proposed by Geselowitz to anisotropical materials described, therefore, by a conductivity tensor. It was found that each element of a conductivity change tensor contributed to the measured resistance only if a corresponding component of the electrical field was nonzero. Numerical calculations were performed for blood-flow-associated conductivity changes. A special experiment stand was developed which allowed experiments to be performed proving the theoretical results. It was found that the absolute value of resistance change measured in the direction perpendicular to the vessel axis was much smaller than that measured along the vessel axis. The results obtained may explain the fact that the actual change of measured resistance created by changes of conductivity induced by aortic blood flow is lower than expected from simplified models.

An averaging two-electrode probe for monitoring changes in myocardial conductivity evoked by ischemia

This paper considers the applicability of effective conductivity measurements for monitoring physiological and/or pathological phenomena induced by ischemia in the myocardium. The sensitivity of a probe, calculated by means of the finite element method, to changes in the conductivity of the tissue examined is defined for this purpose. Probes developed by Schafer and collaborators (1995) and in our own departments have been examined on the basis of this sensitivity. Theoretical results were verified experimentally using a tank, enlarged models of the probes, and a specially developed electronic circuit. It follows from this study that the probe developed by Schafer et al. is characterized by positive and negative sensitivity. This can lead to misinterpretation of the measurements obtained. In contrast, the sensitivity of our probe is dominantly positive. An example of the in vivo result obtained during experimentally induced ischemia in a swine heart is included.

A probe for immittance spectroscopy based on the parallel electrode technique

This paper presents the construction of a probe for immittance spectroscopy. The probe is based on the four-electrode technique. The current application electrodes are long parallel strips and have been partitioned into three segments to measure the immittance of relatively small volumes. The probe constant has been calculated assuming anisotropy of the materials examined. The experiments, based on the measurements of KCl solutions and numerical simulations (finite element method--FEM), have shown a high degree of consistency with the theoretical value. Experimental in vivo measurements on swine gluteal tissue were performed and the conductivity and permittivity reconstructed from these measurements are presented.

Estimation of the amplitude of the signal for the active optical gesture sensor with sparse detectors

In this paper we deal with the problem of precise gesture recognition for the active optical proximity sensor with sparse 8 photodiodes. We particularly focus on developing the method of estimating the real, usually not observable, maximum signal value representing maximum intensity of light reflected from an obstacle present in the front of the sensor. Different configurations of the fingers were used as an obstacle. The Monte Carlo simulations were performed in order to cognize the accurate pattern created by fingers of considered configurations. The accurate description of curves representing finger profiles was obtained after applying the least squares method. The results of analyzes proved that finger arrangement configurations, particularly 1 finger and 2 jointed fingers, can be considered as sources of Gaussian like shapes on the face of the sensor. Therefore, data measured by 8 sparse photodiodes of the active optical gesture sensor were compared to normal distribution curves. The results of the comparison allow normalization of the measured data and the estimation of the real, usually not observable, maximum signal value. The results and discussion sections of the paper present the average detection accuracy, advantages and limitations of the proposed approach.

Sleep Apnea Detection by Means of Analyzing Electrocardiographic Signal

Obstructive sleep apnea (OSA) is a condition of cyclic, periodic obstruction (stenosis) of the upper respiratory tract. OSA could be associated with serious cardiovascular problems, such as hypertension, arrhythmias, hearth failure or peripheral vascular disease. Understanding the way of connection between OSA and cardiovascular diseases is important to choose proper treatment strategy. In this paper, we present a method for integrated measurements of biosignals for automatic OSA detection. The proposed method was implemented using a portable device with the application of the Support Vector Machine (SVM) classifier. The specific objective of this work is to analyze the minimum set of features for the ECG signal that could produce acceptable classification results. Those features can be further expanded using other biosignals, measured by the portable SleAp device. Additionally, the influence of the body movements and positions on measurement results with SleAp system are presented. The proposed system could help to determine the influence of OSA on the state of the cardiovascular system.

A six-ring probe for monitoring conductivity changes

This paper presents the construction of a six-ring probe for monitoring immittance changes. The spatial sensitivity of the probe is defined. This is used to examine the uniqueness of the probe in terms of its application to monitoring conductivity changes. A spatial distribution of the sensitivity is presented for isotropic and anisotropic cases. The latter case is restricted only to anisotropy met when measuring muscles, i.e. diagonal anisotropy. Theoretical calculations performed using the finite element method were verified experimentally using a specially developed measuring system. An example of in vivo measurements is included.

A telemedical and an outpatient thoracic impedance measurements - A validation algorithm of the electrodes placement

This paper presents the algorithm for validation of electrodes locations for the thoracic impedance measurements. In particular the presented algorithm was designed to perform the telemetric sleep apnea monitoring. One of the problems, during the clinical tests of a developed device, was to preserve the repeatability of measurements. It strongly depended on the appropriate electrodes placement on the examined persons thorax. It seems that the developed software, which allows inspecting the electrodes localization, significantly increases a possibility of impedance based sleep apnea monitoring at home. In this article, the properties of the evaluation algorithm of electrodes placement accuracy are presented.

The role of EMG module in hybrid interface of prosthetic arm

Nearly 10% of all upper limb amputations concern the whole arm. It affects the mobility and reduces the productivity of such a person. These two factors can be restored by using prosthetics. However, the complexity of human arm makes restoring its basic functions quite difficult. When the osseointegration and/or targeted muscle reinnervation (TMR) are not possible, different modalities can be used to control the prosthesis. In this paper the usability of electromyography (EMG) signals for such a control is evaluated. Method: first, the types of operations performed by the prosthetic arm that could be handled by EMG module were defined. The raw EMG signal, corresponding to the predefined gesture, was acquired from the surface of trapezius muscle. The pattern recognition neural network was trained to classify gestures based on recorded RAW data. Results: The neural network was trained using 56 signals corresponding to performed gestures. Optimal performance was achieved for 29 training cycles. The network was tested using data set of 56 gestures. The designed network was tested on gestures recorded from 10 volunteers. The gestures were correctly classified with nearly 84% accuracy. Conclusions: The EMG analysis is a reliable modality when it comes to hybrid interfaces for control over prosthetic arm.

Extending touch-less interaction with smart glasses by implementing EMG module

In this paper we propose to use temporal muscle contraction to perform certain actions. Method: The set of muscle contractions corresponding to one of three actions including “single-click”, “double-click” “click-n-hold” and “non-action” were recorded. After recording certain amount of signals, the set of five parameters was calculated. These parameters served as an input matrix for the neural network. Two-layer feedforward neural network with one hidden layer of 200 neurons was applied to classify gestures based on the input matrix. Results: The network was trained using the dataset consisted of 43 samples and then tested on the 34 samples dataset. All gestures from the test set were correctly classified.