Synergy between medical informatics and bioinformatics: facilitating genomic medicine for future health care.

In this paper, we review the results of BIOINFOMED, a study funded by the European Commission (EC) with the purpose to analyse the different issues and challenges in the area where Medical Informatics and Bioinformatics meet. Traditionally, Medical Informatics has been focused on the intersection between computer science and clinical medicine, whereas Bioinformatics have been predominantly centered on the intersection between computer science and biological research. Although researchers from both areas have occasionally collaborated, their training, objectives and interests have been quite different.

Telerehabilitation needs: a survey of persons with acquired brain injury.

Objective: To survey individuals with acquired brain injury to assess multiple facets of interest, access, and familiarity necessary to implement new telerehabilitation technologies.

Design: Anonymous mail survey.

Setting: Community.

Biomagnetic 3-dimensional spatial and temporal characterization of electrical activity of human stomach.

Biomagnetic measurements are based on the noninvasive recording of magnetic signals produced by biological sources such as nervous system and muscle. The aim of this study was to obtain multichannel magnetic field recordings from the human gastrointestinal tract and to localize the sources of these signals three-dimensionally. The magnetic field was recorded in eight human healthy subjects using a sensor array with 37 superconducting quantum interference devices (SQUIDs); an electrogastrogram was recorded simultaneously.

Suppression of background brain activity influence in localizing epileptic spike sources from biomagnetic measurements.

The origin of inter-ictal epileptic activity can be localized from the magnetoencephalogram (MEG) using the Equivalent Current Dipole (ECD) as a source model. One problem with such localizations is that in many patients, the localization of an epileptic spike source becomes inaccurate because the epileptic spikes are superimposed by pathologic brain rhythmic activities. This paper proposes to use the spatial coherence of the measured magnetic field caused by the measured magnetic field to suppress its influence in the ECD localization.

MFT in complex partial epilepsy: spatio-temporal estimates of interictal activity.

Magnetic field tomography (MFT) displays three dimensional estimates of the distribution of the primary current density vector, Jp, as extracted from non-invasive, non-contact, magnetoencephalographic (MEG) measurements. MFT was used to study the spatiotemporal evolution of the interictal activity during single spike events of a patient with complex partial epilepsy. The sequences of events of the interictal spikes were analysed in sagittal sections, particularly at the depth of the temporal lobe.

Localization of evoked neuromagnetic 600 Hz activity in the cerebral somatosensory system.

Upon electrical median nerve stimulation wide-band scalp SEP recordings show a burst of high-frequency low-amplitude wavelets of uncertain origin. Digital high-pass filtering (above 400 Hz) of the primary cortical response ("N20") can separate the burst from the underlying "N20 proper" which itself is known to be generated by excitatory postsynaptic potentials (EPSPs) in area 3b. Here, neuromagnetic multichannel recordings show a close correlation between the spatial field distributions of the magnetic burst and of the magnetic "N20m" proper.

The influence of inhomogeneous volume conductor models on the ECG and the MCG.

The authors investigated the influence of human body inhomogeneities such as the lungs, blood masses and the skeletal muscle layer on the electrical body surface potential and the magnetic field. The surface potentials and magnetic fields are calculated using a boundary element method. As a rule the blood masses have a large influence on both potential and magnetic field amplitude as well as on the potential and magnetic field map orientation, but the influence on the topology of the map is less in the electric case than in the magnetic case.

Event-synchronous cancellation of the heart interference in biomedical signals.

A two-pass adaptive filtering algorithm is proposed for cancellation of recurrent interferences such as the heart interference in biomedical signals. In the first pass, an average waveform in one period of the interference is estimated by event-synchronous (QRS-synchronous) averaging of the corrupted signal. In a second pass, an adaptive Schur recursive least squares (RLS) lattice filter is used to cancel the interference by using the event synchronously repeated estimated average waveform of the interference as an artificial reference signal.

Magnetic source localization and morphological changes in temporal lobe epilepsy: comparison of MEG/EEG, ECoG and volumetric MRI in presurgical evaluation of operated patients.

Is MEG source analysis able to precisely locate the primary focal epileptic activity? 22 patients with pharmacoresistant temporal lobe epilepsy were recorded during presurgical evaluation simultaneously with multichannel MEG/EEG and invasive (subdural) electrodes to evaluate the increase of information gained by MEG concerning the localization of focal epileptic activity and lesions. With this systematic study it should become clearer how often MEG can establish a diagnostic bridge between function and morphology. In addition, MEG localization accuracy of focal epileptic activity was to be validated empirically by invasive EEG recordings and postsurgical outcome.

Experience with a multichannel system for biomagnetic study.

The components of the biomagnetic multichannel system Krenikon are described. The combination of biomagnetically yielded localizations with anatomic images gained from MR or CT is discussed as well as the enhancement of the signal-to-noise ratio by using a correlation technique. The overall localization accuracy is tested with technical phantoms.

Multichannel magneto-electroencephalography recordings of interictal and ictal activity.

A lobar or even a intralobar congruence was found when comparing the findings of magnetic source localization with presurgical evaluation (EEG, MRI and intraoperative ECoG) in temporal lobe epilepsy. The first dipolar activity that can be recognized during a spike-wave event (primary focal epileptic activity (PFA)) was localized in temporal neocortical or mesial regions. Further centres of epileptic activity could be localized by the method of spike averaging by correlation.

Magnetocardiography: three-dimensional localization of the origin of ventricular late fields in the signal averaged magnetocardiogram in patients with ventricular late potentials.

The purpose of this study was to detect ventricular late fields recorded by a biomagnetic multichannel system in patients with ventricular late potential and to determine the site of these ventricular late fields non-invasively in three dimensions. Biomagnetic signals of sinus beats during a 5-min acquisition period simultaneously recorded by a 37-channel system Krenikon were averaged in all channels. Ventricular late fields were determined in each channel according to the algorithm of Simson for ECG data.

MEG localization of interictal epileptic focal activity and concomitant stereotactic radiosurgery. A non-invasive approach for patients with focal epilepsy.

Two patients with complex partial epilepsy and tumour of the temporal lobe scheduled for gamma knife radiosurgery were evaluated pre- and postoperatively by multichannel magnetoencephalography (MEG). Centers of epileptic dipole activity found preoperatively disappeared after the focal irradiation as did the epileptic seizures. Thus, to combine stereotactic MEG and gamma knife radiosurgery seems to be a non-invasive alternative to the conventional neurosurgery in focal epilepsy.

Point and distributed current density analysis of interictal epileptic activity recorded by magnetoencephalography.

Equivalent current dipole (ECD) analysis and fully three-dimensional distributed source solutions have been applied to interictal multichannel magnetoencephalographic recordings of a patient with complex partial epilepsy (CPE). Averaged signals were used. At certain instances ECD solutions could be found with a very high cross-correlation coefficient between the measurements and the field, produced by the current dipole solution, typically in excess of 0.

Spatial differences of the duration of ventricular late fields in the signal-averaged magnetocardiogram in patients with ventricular late potentials.

Magnetocardiography (MCG) allows one to noninvasively localize cardiac electrical activity in three dimensions. It was the purpose of this study to obtain information about the spatial variations of signal-averaged ventricular late magnetic fields recorded by a biomagnetic multichannel system. Biomagnetic signals of 170-600 heart cycles obtained by the 37-channel system KRENIKON (Siemens Medical Engineering Group) were simultaneously averaged in all channels.

Ictal and interictal activity in partial epilepsy recorded with multichannel magnetoelectroencephalography: correlation of electroencephalography/electrocorticography, magnetic resonance imaging, single photon emission computed tomography, and positron emission tomography findings.

Ictal and interictal epileptic activity was recorded for the first time by multichannel magnetoencephalography (MEG) in three patients with partial epilepsy. Pre- and intra-operative localization of the epileptogenic region was compared. The interictal epileptic activity was localized at the same region of the temporal or frontal lobe as the ictal activity.

Magnetocardiographic non-invasive localization of accessory pathways in the Wolff-Parkinson-White syndrome by a multichannel system.

Electrical activity can be localized by magnetocardiography (MCG) non-invasively. In this study a 37-SQUID (Super Conducting Quantum Interference Device) sensor multi-channel system (KRENIKON) was used to assess the potential of magnetocardiography to localize accessory pathways with a multichannel system. Seven WPW patients were studied by means of magnetocardiography.

[Site and propagation of focal epileptic activity: multichannel MEG/EEG analysis].

Electrophysiological examinations provide the basis for a deeper pathophysiological understanding of focal epileptic activity. In addition to electroencephalography, magnetoencephalography from field measurements is now available for biomagnetic diagnosis. As magnetoencephalography (MEG) is basically better suited for the localization of focal epileptic activity than EEG, an increase in MEG measurements has taken place over the last years.

Biomagnetic noninvasive localization of accessory pathways in Wolff-Parkinson-White syndrome.

It was our purpose to assess the clinical relevance of noninvasive magnetocardiographic localization of accessory pathways. Nine patients with Wolff-Parkinson-White (WPW) syndrome were studied. For all of them the site of the accessory pathway was known from invasive catheter mapping.

[Magnetocardiography. Biomagnetic localization of impulse development and transmission of the heart].

Magnetocardiography is a non-invasive biomagnetic technique for measuring magnetic fields produced at the surface of the body when the heart is stimulated to beat. The measurement is contact-free and is independent of tissue resistance. For the first time, magnetocardiography employing multi-channel systems permits the accurate, non-invasive localization of accessory conduction pathways and ectopic ventricular activity.

The neocortico to mesio-basal limbic propagation of focal epileptic activity during the spike-wave complex.

In order to localize epileptogenic electrophysiological sources, a multichannel MEG system was used in 3 patients with partial epilepsy during presurgical evaluation. MEG and EEG (including scalp, sphenoidal and intracranial foramen ovale electrodes) were recorded simultaneously during a period of intensive video-EEG monitoring in order to observe single spontaneous spikes. In addition to MRI, SPECT and PET investigations were performed.

Design and performance of a biomagnetic multichannel system for MEG and MCG studies.

Considerations which have lead to the design of the Siemens biomagnetic multichannel system are discussed. Algorithms developed for data evaluation include removal of periodic signals, averaging of sporadic events, and separation of background activity. Means are described to fuse biomagnetic locations with three-dimensional medical images.

Clinical magnetocardiography: experience with a biomagnetic multichannel system.

The magnetic fields caused by the human heart's electrical activity were coherently recorded with a biomagnetic multichannel system (KRENIKON) during 1 to 10 minutes in 49 patients. 31 to 37 magnetic channels were recorded simultaneously with the ECG and respiration. Comparison of a magnetic index and the Sokolow-Lyon index to echocardiographic findings in the quantification of left ventricular hypertrophy demonstrated the superiority of the magnetocardiogram (MCG) as compared to the ECG.

Magnetic source localization in focal epilepsy. Multichannel magnetoencephalography correlated with magnetic resonance brain imaging.

Initial results of magnetic source localization by means of multichannel recording using a 10 or a 31 channel system are reported. Simultaneous magnetoencephalographic (MEG) and electroencephalographic (EEG) (scalp, sphenoidal and foramen oval) recording, as well as magnetic resonance imaging (MRI) with a fixed head position, permits the projection of brain structures and the source localized from MEG into a three-dimensional coordinate system. From 8 patients investigated it can be clearly seen that the method is of diagnostic relevance for patients with temporal lobe epilepsy.

Multichannel biomagnetic system for study of electrical activity in the brain and heart.

The authors designed a multichannel system for noninvasive measurement of the extremely weak magnetic fields generated by the brain and the heart. It uses a flat array of 37 superconducting magnetic field-sensing coils connected to sophisticated superconducting quantum interference devices. To prevent interference from external electromagnetic fields, the system is operated inside a shielded room.