Measurement and data processing in medicine

The MediSIG team of the ISI provides a complete solution for neurology, cardiology and medical signal analysis and other applications.

The activities of the team include the development of new non-invasive diagnostic procedures in cardiology and neurology, measurement and signal processing in medicine and the design and construction of experimental medical devices and acquisition systems. The MediSIG team cooperates with domestic and foreign hospitals and physicians. Cooperation includes the implementation of measurement and diagnostics protocols, design of recording parameters and physiological signals, data digitizing and archiving, processing and detection of physiological parameters and statistical analysis and evaluation of results. The outcomes of interdisciplinary cooperation also include joint patents and original experimental equipment and methodology.

MediSIG Cardiology – non-invasive diagnostics of cardiovascular disease

Diagnostics is focused on determining the level of risk of coronary heart disease, sudden cardiac death, arrhythmia, heart attack and heart failure, as well as ischemic disease, high blood pressure risks and heart transplant innervations. It is based on the evaluation of multi-lead ECG signal, blood pressure, impedance cardiography, heart sounds and respiration. Results include the determination of complete hemodynamic parameters, blood vessel stiffness and control properties of blood circulation.

MediSIG Neurology  – EEG signal processing, epilepsy, Parkinson’s di­sease

MediSIG provides complete processing, analysis and statistical evaluation of EEG recordings from deep brain structures. Epilepsy that cannot be pharmacologically controlled can be treated only with surgery. Intracerebral or subdural electrodes are implanted to localize epileptic sources. Unique EEG recordings from depth electrodes allow the development of new techniques for analyzing evoked processes, synchronization and desynchronization, and signal propagation directions and connectivity between different brain structures during various mental activities.

Software – methodology & processing

ScopeWin – system for measurement and data processing in medicine

Basic features:

• Data acquisition – ScopeWin communicates with the NIDAQMx library, which covers the complete series of National Instruments hardware.
• Visualization – ScopeWin includes a graphic editor that allows comfortable data inspection, signal comparison, manipulation, cursor operation etc. Data can be converted to conventional formats.
• Post-acquisition processing includes the following features: frequency analysis, digital filtering, functions for mathematical signal processing (splines, derivation, integration, digital quadrature detection and demodulation, regression, 50Hz signal detection, processing and elimination), two-dimensional analysis (time-frequency analysis – amplitude, phase and power), segmentation and averaging according to established criteria and several more. Most measurement, visualization and processing functions can be implemented as commands in the program and carried out sequentially without operator intervention.

ScopeWin signal processing in cardiology includes the following functions: ECG signal parameters detection (R wave, QT interval, heart rate, QT dispersion, T wave alternans), continuous blood pressure recordings analysis (systolic, diastolic, mean pressure, blood pressure variability, baroreflex), heart sounds (S1, S2), impedance cardiography (stroke volume and cardiac output, elasticity of blood vessels, pulse pressure wave) and respiration (breathing frequency and depth). ScopeWin provides procedures for complete evaluation of hemodynamic parameters. It also allows the implementation of new procedures and methods.

ScopeWin signal processing in neurology includes the following features: visualization of large datasets of intracranial EEG recordings, time-frequency analysis, segmentation, automatic removal of artificial segments and channels, averaging and evoked potential calculation, envelope analysis, etc.

EEG signal analysis MediSIG provides professional advice with the realization of EEG measurement and complex data analysis. We use our own software (ScopeWin, ScopeMAT) equipped with advanced methods of analysis. The software is intended for off-line data processing, especially for EEG, EKG, EMG and EOG signals analysis. Processed data are obtained from clinical and experimental intracerebral or scalp EEG recordings. Today they are recorded from up to 128 recording points with a sampling frequency of 1kHz.

Data analysis includes:

• analysis of non-repeated signals (data recorded without subject stimulation);
• analysis of repeated events (data recorded during subject stimulation: visual/sound/tac­tile/etc.);
• impact of Deep Brain Stimulation (DBS) on EEG development.

Developed software packages cover complex off-line methods suitable especially for neurological data analysis. Our software products allow:

• data blocks manipulation, data preprocessing, data analysis based on FFT, visual data representation and basic statistical data parameterization;
• statistical evaluation and automation of data processes (ScopeMAT);
• analysis of connections between brain structures based on EEG data from intracerebral electrodes;
• visualization of results on a stereotactic brain model;
• complex software for analysis and visualization – EEGVisual.

ScopeMAT software allows parametric batch data processing covering: FFT filtration, power analysis, time-frequency analysis, statistical evaluation of repeated events (Wilkoxon test, t-test, bootstrap test), automatic detection of power increase and decrease, automatic detection of statistically significant components in time or frequent domain, statistical tests for determination of repeated evoked signal differences recorded during different external conditions (subject stimulation of type A/B/etc., test for two modalities, Schoffe test for more than two modalities). Groups of subjects can also be evaluated using ScopeMAT software. We can compute „GrandAverages“ and present significant results for different contact groups transparently. The ScopeMAT software is proposed for the MATLAB environment. This solution allows quick algorithm implementation depending on application demand. The ScopeMAT software provides numerical and graphical outputs to many format types, including MS Word and MS Excel. 

Data acquisition systems

In addition to software and experimental devices MediSIG also produces complete acquisition systems. It can simultaneously record up to 128 channels, sampling up to 5MHz per channel with 16bit resolution and higher. The hardware is built on top of National Instruments PCI / PCMCIA / USB devices. For experiment control and data recording the ScopeWin program is used.

Realization examples:

• ISI Brno acquisition system.
• M&I – ISI high speed EEG recorder and analyzer (up to 200 channels, 40 kHz sampling each),
• ANNALab – acquisition system for neurology and cardiology, St. Anne’s University Hospital Brno, Mayo Clinic, USA

Experimental devices for measurement of biomedical signals

The MediSIG team mainly designs and constructs experimental devices for the measuring and data processing of biological signals. We concentrate on devices which are not available or do not yet have the desired parameters on the commercial market.

Examples of devices:

• The Detector of Vagus Nerve Stimulation. The device for detection of activity of vagus nerve stimulation is intended for independent monitoring of implanted vagus nerve stimulation. It measures the electrical potential from the patient's neck, processes it and detects activity of the stimulator.
• RECO – device for respiration control. LEDs bargraph for pacing of breathing. It is used for controlled excitation of the cardiovascular system. It enables setting of pacing frequency 1–39 min-1, various modulations – ramp and sinus with depth of 25–100%.
• The Strain Gauge Plethysmograph. The strain gauge plethysmograph, which can be used for several measurement techniques in medicine, essentially measures the changes in human limb volume directly. However, it can be also used in indirect measurement for evaluating limb blood flow, blood pressure, digital volume pulses, for measuring circumferential changes of exposed arteries and breathing. Our device can measure up to 10 channels simultaneously.
• Experimental Syringe Mixing Pump For Ultrasound Contrast Agents. The pump enables continual infusion and bolus while mixing the contents of the syringe. The control of the pump is ensured by microcontrollers and is fully programmable by the user. The device is battery operated and has a robust mechanical construction. Technical parameters: syringe 10 ml and 20 ml type, infusion flow rate 0.3..4.0 ml/min, bolus flow rate 0 .3..4.0 ml/min, bolus time max. 60 seconds, mixing rate 30 cycles/min ±180º, minimum continuous working time 4.5 hours per one full battery charge.
• Multi-Channel Impedance Cardiography. Impedance cardiography is a method based on measuring changes of thorax electrical impedance. From the changes of thorax electrical impedance it is possible to calculate important parameters of the cardiovascular system, like stroke volume or cardiac output. The monitor makes it possible to measure small changes of impedance on separate parts of the human body and to evaluate blood flow, particularly the propagation of pulse waves in the whole body. It also makes it possible to analyze vessel compliance. Commercial devices are equipped with one or two channels and the simultaneous survey of blood flow in many parts of the body is not possible. The main advantages of the monitor are the high quality of the impedance signal, coherent impedance detection in all channels, measurement of impedance phase changes and the option of stand-alone measurement without computer and supply voltage.
  • The multi-channel device consists of two-channel units. Each unit is comprised of two current generators and two voltage detectors. The device makes it possible to interconnect up to 9 units with clock and synchronization signals and to build an 18-channel device. The unit stores the impedance signal on a SD/SDHC memory card, transfers it in real-time to the PC through the USB port, and possibly represents it on analogue output.
  • The parameters of the unit are:
    • measurement frequency 30 to 70 kHz or 1 kHz to 1 MHz (optional)
    • measurement current 1 mA, adjustable
    • clock frequency of direct digital synthesis, AD converter and synchronous detector 60 MHz
    • overall dynamic range of 127 dBc/√Hz
    • phase resolution better than 0.001 degree
    • output data format 16-bit complex envelope at 10 kHz sampling
    • operating time 3 hours
• Device for microneurography. The dedicated preamplifier and amplifier with signal filtering and detection are used for monitoring the electrical activity in the nerves. The amplifies and processed signals obtained by means of microelectrodes (special insulated needle with conductive tip) directly from the desired part of nerves.
• ECG 12. Experimental 12 lead electrocardiograph amplifier with broad pass band up to 500 Hz. This device is intended to be used for special ECG measurements that cannot be performed with a standard commercial device. The amplifier is battery operated and is equipped with the 12 analog outputs, 1 monitor output and USB data acquisition unit. Figure PowerPoint 6

MediSIG has also designed and constructed a wide range of various devices for measuring biological signals like electrical amplifiers and filters, pressure measurement devices for the monitoring of breathing, pressure monitoring in lungs and esophagus, devices for phonocardiography – special microphones with dedicated amplifiers, spirometers, etc. The majority of these devices are battery operated to enable use during measurements of weak biological signals, where using AC mains operated devices cause unacceptable artifacts in the measured signal.

Contact:
Dr. Pavel Jurák
email: jurak@isibrno.cz
phone: +420 541 514 312

Detailed information: http://www.isibrno.cz 

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