Diagnostic accuracy of a novel method for detection of acute transmural myocardial ischemia based upon a self-applicable 3-lead configuration.

Background: Delayed medical attendance is a leading cause of death in patients with ST elevation myocardial infarction (STEMI).

Methods: We aimed to introduce, develop, and validate a novel method (RELF method) for detection of transmural ischemia based on a new and easy-to-use 3-lead configuration and orthonormalization of ST reference vectors (STDVN). The study included 60 patients undergoing coronary artery occlusion (CAO) during balloon inflation and 30 healthy subjects.

A shape-based quality evaluation and reconstruction method for electrical impedance tomography.

Linear methods of reconstruction play an important role in medical electrical impedance tomography (EIT) and there is a wide variety of algorithms based on several assumptions. With the Graz consensus reconstruction algorithm for EIT (GREIT), a novel linear reconstruction algorithm as well as a standardized framework for evaluating and comparing methods of reconstruction were introduced that found widespread acceptance in the community. In this paper, we propose a two-sided extension of this concept by first introducing a novel method of evaluation.

The solution for the independence of bioelectric and biomagnetic signals is confirmed.

The theoretical solution for the independence of bioelectric and biomagnetic signals rising from volume sources was published by Jaakko Malmivuo in 1995 [1]. In 2000 his research group published a clinical study on electro- and magnetocardiography which confirmed this result [2, 3]. In 2005 Iwasaki and co-workers published a clinical study on the detection of epileptic foci with electro- and magnetoencephalo-graphy [4].

Comparison of the properties of EEG and MEG in detecting the electric activity of the brain.

Since the detection of the first biomagnetic signals in 1963 there has been continuous discussion on the properties and relative merits of bioelectric and biomagnetic measurements. In this review article it is briefly discussed the early history of this controversy. Then the theory of the independence and interdependence of bioelectric and biomagnetic signals is explained, and a clinical study on ECG and MCG that strongly supports this theory is presented.

Cortical potential imaging using L-curve and GCV method to choose the regularisation parameter.

Background: The electroencephalography (EEG) is an attractive and a simple technique to measure the brain activity. It is attractive due its excellent temporal resolution and simple due to its non-invasiveness and sensor design. However, the spatial resolution of EEG is reduced due to the low conducting skull.

The significance of relative conductivity on thin layers in EEG sensitivity distributions.

Volume conductor head models contain thin tissue layers, some of which have highly contrasting conductivity values relative to neighboring tissues. We expound the cerebrospinal fluid (CSF) and the six cortical layers of the gray matter. The dual nature of the CSF competes with the well-known shunting behavior of the skull.

The influence of age and skull conductivity on surface and subdermal bipolar EEG leads.

Bioelectric source measurements are influenced by the measurement location as well as the conductive properties of the tissues. Volume conductor effects such as the poorly conducting bones or the moderately conducting skin are known to affect the measurement precision and accuracy of the surface electroencephalography (EEG) measurements. This paper investigates the influence of age via skull conductivity upon surface and subdermal bipolar EEG measurement sensitivity conducted on two realistic head models from the Visible Human Project.

EEG/MEG source imaging: methods, challenges, and open issues.

We present the four key areas of research-preprocessing, the volume conductor, the forward problem, and the inverse problem-that affect the performance of EEG and MEG source imaging. In each key area we identify prominent approaches and methodologies that have open issues warranting further investigation within the community, challenges associated with certain techniques, and algorithms necessitating clarification of their implications. More than providing definitive answers we aim to identify important open issues in the quest of source localization.

Improving the SNR of EEG generated by deep sources with weighted multielectrode leads.

We have developed a multielectrode lead technique to improve the signal-to-noise ratio (SNR) of scalp-recorded electroencephalography (EEG) signals generated deep in the brain. The basis of the method lies in optimization of the measurement sensitivity distribution of the multielectrode lead. We claim that two factors improve the SNR in a multielectrode lead: (1) the sensitivity distribution of a multielectrode lead is more specific in measuring signals generated deep in the brain and (2) spatial averaging of noise occurs when several electrodes are applied in the synthesis of a multielectrode lead.

Estimating the measuring sensitivity of unipolar and bipolar ECG with lead field method and FDM models.

New portable electrocardiogram (ECG) measurement systems are emerging into market. Some use nonstandard bipolar electrode montage and sometimes very small interelectrode distances to improve the usability of the system. Modeling could provide a straightforward method to test new electrode systems.

Correlation between signal-to-noise ratios and region of interest sensitivity ratios of bipolar EEG measurements.

We have developed a parameter, which describes how well the measurement is concentrated on the region of interest source area compared to other source areas in the volume conductor. The parameter concept is called the region of interest sensitivity ratio (ROISR). We assume that ROISR is also connected to the SNR of the measurement.

New method for analysing sensitivity distributions of electroencephalography measurements.

In this paper, we introduce a new modelling related parameter called region of interest sensitivity ratio (ROISR), which describes how well the sensitivity of an electroencephalography (EEG) measurement is concentrated within the region of interest (ROI), i.e. how specific the measurement is to the sources in ROI.

Improved detection of deep sources with weighted multielectrode EEG leads.

The purpose of the present study is to conduct preliminary experimental measurements to validate the improvement in the detection of deep EEG sources achieved with new multielectrode EEG leads. As a measurement we had brainstem auditory evoked potentials (BAEPs), which include deep generators in the brainstem and midbrain. The BAEPs were measured with a 124-channel EEG cap.

European virtual campus for biomedical engineering EVICAB.

European Commission has funded building a curriculum on Biomedical Engineering to the Internet for European universities under the project EVICAB. EVICAB forms a curriculum which will be free access and available free of charge. Therefore, in addition to the European universities, it will be available worldwide.

Contribution of the left anterior myocardium to the body surface potentials in case of apical ectopic beat.

The present paper describes a study where effects of anterior myocardium on body surface potentials were investigated. The study combines numerical lead field analysis combined with cardiac automata model. Electric fields are calculated with finite difference method in a 3-D model of male thorax.

Correlation between live and post mortem skull conductivity measurements.

The skull is a tissue with a widely controversial range of conductivity values. This article correlates live skull conductivity measurements with post mortem conductivity measurements with a scaling factor ranging between 2.5 and 4.

Measurement of noise and impedance of dry and wet textile electrodes, and textile electrodes with hydrogel.

Textile sensors, when embedded into clothing, can provide new ways of monitoring physiological signals, and improve the usability and comfort of such monitoring systems in the areas of medical, occupational health and sports. However, good electrical and mechanical contact between the electrode and the skin is very important, as it often determines the quality of the signal. This paper introduces a study where the properties of dry textile electrodes, textile electrodes moistened with water, and textile electrodes covered with hydrogel were studied with five different electrode sizes.

Effect of source depth on the specificity of bipolar EEG measurements.

The purpose of the present study was to evaluate how the brain sources located at different depths can be most effectively measured with bipolar EEG leads. The specificity of an EEG lead to detect sources was studied with a new parameter called region of interest sensitivity ratio (ROISR) by employing a spherical head model. We studied the specificity as a function of electrode distance and further as a function of scalp:skull:brain resistivity ratio.

Analysing specificity of a bipolar EEG measurement.

The objective in bioelectric measurements such as ECG and EEG is to register the signal arising from sources in the region of interest. It is also desired that signal-to-noise ratio (SNR) of a measurement is high. The sensitivity of an ideal measurement should focus on and be greater on the target areas in comparison to other areas of the volume conductor.

Heart rate variability derived from exercise ECG in the detection of coronary artery disease.

The diagnostic performance of heart rate variability (HRV) analysis from exercise ECG in the detection of coronary artery disease (CAD) is unknown. Bicycle exercise ECG recordings from The Finnish Cardiovascular Study (FINCAVAS) of angiography-proofed CAD patients (n = 112) and a patient group with a low likelihood of CAD (n = 114) were analyzed. HRV parameters (SDNN, RMSSD, Poincaré SD1 and SD2) were calculated from 1 min segments before exercise, during exercise and after exercise.

Bioelectromagnetism--relative merits of electric and magnetic measurements in cardiac studies.

This lecture gives a general overview to the relationship of bioelectric and biomagnetic phenomena: The most important issue in bioelectromagnetism is: Are the biomagnetic measurements independent on bioelectric ones and do they bring new information from the source or are they only a different modality of the same phenomenon? This issue is discussed with application on cardiac studies. The three orthogonal dipolar magnetic leads (vector magnetocardiography) are equal in the sense of diagnostic performance to the three dipolar electric leads (vector electrocardiography). Therefore the VMCG has quite the same diagnostic performance as the VECG.

Finite difference and lead field methods in designing implantable ECG monitor.

To minimize time-consuming and expensive in vitro and in vivo testing, information regarding the effects of implantation and the implants on measurements should be available during the designing of active implantable devices measuring bioelectric signals such as electrocardiograms (ECG). Modeling offers a fairly inexpensive and effective means of studying and demonstrating the effects of implantation on ECG measurements prior to any in vivo tests, and can thus provide the designer with valuable information. Finite difference model (FDM) and lead field approaches offer straightforward and effective modeling methods supporting the designing of active implantable ECG devices.

Effect of measurement noise and electrode density on the spatial resolution of cortical potential distribution with different resistivity values for the skull.

The purpose of the present theoretical study was to examine the spatial resolution of electroencephalography (EEG) by means of the accuracy of the inverse cortical EEG solution. The study focused on effect of the amount of measurement noise and the number of electrodes on the spatial resolution with different resistivity ratios for the scalp, skull and brain. The results show that if the relative skull resistivity is lower than earlier believed, the spatial resolution of different electrode systems is less sensitive to the measurement noise.

Effect of electrode density and measurement noise on the spatial resolution of cortical potential distribution.

The purpose of the present study was to examine the spatial resolution of electroencephalography (EEG) by means of inverse cortical EEG solution. The main interest was to study how the number of measurement electrodes and the amount of measurement noise affects the spatial resolution. A three-layer spherical head model was used to obtain the source-field relationship of cortical potentials and scalp EEG field.