A multimodal imaging approach to the evaluation of post-traumatic epilepsy

Object

Electroencephalography-functional magnetic resonance imaging (EEG-fMRI) coregistration and high-density EEG (hdEEG) can be combined to map noninvasively abnormal brain activation elicited by epileptic processes. By combining noninvasive imaging techniques in a multimodal approach, we sought to investigate pathophysiological mechanisms underlying epileptic activity in seven patients with severe traumatic brain injury.

Materials and methods

Standard EEG and fMRI data were acquired during a single scanning session. The EEG-fMRI data were analyzed using the general linear model and independent component analysis. Source localization of interictal epileptiform discharges (IEDs) was performed using 256-channel hdEEG. Blood oxygenation level dependent (BOLD) localizations were then compared to EEG source reconstruction.

Results

On hdEEG, focal source localization was detected in all seven patients; in six out of seven it was concordant with the expected epileptic activity as defined by EEG data and clinical evaluation; and in four out of seven in whom IEDs were recorded, BOLD signal changes were observed. These activities were partially concordant with the source localization.

Conclusion

Multimodal integration of EEG-fMRI and hdEEG combining two different methods to localize the same epileptic foci appears to be a promising tool to noninvasively map abnormal brain activation in patients with post-traumatic brain injury.     

Processing of intracardiac electrograms in atrial fibrillation

This paper presents a method for the automated processing of atrial fibrillation (AF) electrograms for the diagnosis of the electropathological substrate of AF and to monitor the effects of ablation procedures and anti-arrhythmic drug treatment on the characteristics of AF. Template matching is a well-known signal processing technique that has been proven useful in various other applications like processing of medical images and fingerprint verification. One of the advantages of this technique is that, because the involved calculations are not very complex, it can easily be applied in real time by using digital hardware. All it requires is the acquisition of fibrillation electrograms, analog-to-digital conversion, and a template matching algorithm downloaded in state-of-the-art digital signal processors. This will provide an objective characterization of fibrillation electrograms that in case of recording of multiple electrograms will produce real-time movies of the propagation of fibrillation waves through the atria. This will allow real-time identification of areas with preferential intra-atrial conduction block, rotor activity, or a focal spread of activation. The further development of algorithms for automatic analysis of fibrillation electrograms, therefore, is not only of scientific interest but may also allow individual evaluation of the atrial substrate, thus providing a basis for selecting the most appropriate treatment of AF     

A wavelet approach to detecting electrocautery noise in the ECG.

A software approach has been developed for detecting electrocautery noise in the electrocardiogram (ECG) using a wavelet decomposition of the signal. With this approach, a clinical monitoring expert system can be forewarned of potential artifacts in trend values derived from the ECG, allowing it to proceed with caution when making decisions based on these trends. In 15 operations spanning 38.5 h of ECG data, we achieved a false positive rate of 0.71% and a false negative rate of 0.33%. While existing hardware approaches detect the source of the noise without any ability to assess its impact on the measured ECG, our software approach detects the presence of noise in the signal itself. Furthermore, the software approach is cheaper and easier to implement in a clinical environment than existing hardware approaches.     

An approach to the evaluation of electromechanical transient processes in power systems

The paper presents an approach to the evaluation of electromechanical transient processes in power systems. On the basis of identification of the physical properties of the system considered, for an adequately chosen time interval, quasilinearization and decomposition of the original system of nonlinear differential equations into subsystems is performed. A linear transformation is introduced which transforms the state matrix of the sub-systems into diagonal form. These simplifications enable the use of numerical integration schemes based on difference state equations, which have an elementary form. As a result, a model is formed which is very suitable for numerical treatment. The integration is performed without numerical instability, quickly and effectively, with the desired simulation accuracy, and with low memory requirements.     

A fundamental approach to transformer thermal modeling. II. Fieldverification

For pt.I see ibid., vol.16, no.2, p.171-5 (2001). This paper has two main objectives. One is to show that the top oil rise thermal model proposed in part I is valid, for a large power transformer in service. The second is to show that there is a convenient way of estimating the parameters without removing the transformer from service. A Manitoba Hydro 250 MVA OFAF transformer was chosen and instrumented with data-gathering equipment. Two twenty-four hour test runs were performed, one in February of 1999 and the other in July of 1999. The most basic parameter to be determined was the rated top oil rise but also found were the top oil line constant and the nonlinearity exponent, commonly given the symbol n. The results are very positive     

A digital approach to the cardiac cycle

The timing diagram model could provide the cardiologist with the ways and means of quantifying interval/segment patterns. This analysis would be more exact than present use of electrocardiograms, which relies on subjective analyses of pathological events and the graph patterns they present. Improving the predictability of pathological events by filtering out overriding ventricular depolarization could identify sequential patterns of the atrial repolarization interval/segment. A healthy heart could provide a standard against which specific syndromes might be compared and contrasted for diagnostic purposes. The clinician would have yet another diagnostic tool which could identify patterns requiring aggressive preventive therapy much earlier in the clinical cycle of the patient with a family history of cardiovascular disease. Results of various treatments prescribed for the broad spectrum of cardiological pathologies could also be evaluated in relation to the manner in which these treatments bring the cardiac cycle into synchrony with normal patterns. This comparison would be accomplished by comparing the sequencing and length of time for specific interval/segment patterns demonstrated before, during, and after the treatment occurs. If successful, the proposed analysis of the ECG would ultimately contribute to more positive outcomes for patients who presently may have a poor prognosis     

A scientific approach to math

The authors demonstrate how computers can be used for mathematical discovery; they have provided two experiments as examples. The first experiment deals with the behavior of consecutive sums of integers. The second experiment allows one to generalize a property of the eigenvalues of square matrices to matrices of arbitrary dimensions. They close by explaining how to set up an experiment designed to discover something new     

A modular approach to the solution of the three-phase harmonicpower-flow

This paper describes a modular algorithm for the solution of power systems containing active nonlinear devices such as power converters. The solution is a unified real-valued Newton method allowing simultaneous solution of electrical and nonelectrical variables. The algorithm is demonstrated using the reduced equivalent of a real power system which includes both load-flow busbars and a large uncontrolled rectifier. The solution process is fast, robust and exhibits excellent convergence     

A comprehensive approach for adequacy and security evaluation ofbulk power systems

A new approach is described for assessing the adequacy and security of bulk power systems. The method takes into account generation and transmission failures, load variation, generation economic dispatch, security limits, maintenance schedules, the control actions implemented in emergencies. and the impact of different operating schemes. Reliability indices for generation adequacy, transmission adequacy, and system security are defined. The proposed method is demonstrated by application to the IEEE Reliability Test System (RTS)     

A fundamental approach to transformer thermal modeling. I. Theoryand equivalent circuit

A simple equivalent circuit to represent the thermal heat flow equations for power transformers is presented. Key features are the use of a current source analogy to represent heat input due to losses, and a nonlinear resistor analogy to represent the effect of air or oil cooling convection currents. The effect was first quantified in 1817. It is shown that the idea of “exponential response” is not the best way to think of the dynamics of the situation. It is also shown that one can consider ambient temperature to be a variable input to the system, and that it is properly represented as an ideal voltage source     

A unified approach to the analysis of single-phase induction motors

Single-phase motors are manufactured with a wide variety of capacitor/winding arrangements and interconnections. The bewildering array of motor variants is commonly analyzed using a two-axes model for each and every winding configuration. MMF harmonics are often ignored to limit the complexity. This paper describes a unified model based upon the more familiar rotating-field approach that includes MMF harmonics. Winding interconnections are modeled using simple connection matrices that do not interfere with the core motor model. The method is powerful and flexible and can be interfaced easily to a variety of techniques for determining the equivalent-circuit parameters, such as finite elements, for example. The paper illustrates the unified approach using a two-speed single-phase capacitor motor     

A project oriented approach to the teaching of machine perception

A set of computer simulation projects that have been assigned at various times during offerings of an advanced graduate level course on machine perception is discussed. The format of the projects is presented, and student results are discussed. The projects are novel in that they require advanced techniques of machine vision and are open-ended in that there are no specific solutions. The problems represent the mainstream of machine perception research without requiring more effort than is possible in a one semester course. Students have responded with algorithms developed in a variety of computer languages and on various machines