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Biomedical subjects

J Edrich

Publications and source records attributed to J Edrich.

At least 19 recordsLinked to original sources
PubMed2001

Children with epilepsy after withdrawal of anticonvulsive therapy: psychiatric behaviour and neuropsychological abilities.

UNLABELLED: Do children who remain in remission with epilepsy after withdrawal of anticonvulsive therapy still exhibit a different behaviour and performance-related abilities compared to healthy children? It was the aim of this study to investigate whether these children showed deviating psychiatric behaviour and/or neuropsychological function deficits as compared with a healthy control group and with children following occasional seizures which had never been treated. The study comprised 39 children with epilepsy after withdrawal of anticonvulsive therapy, 37 children with occasional seizures, and 39 matched healthy control children who were tested with regard to psychiatric and neuropsychological criteria. The patients were aged 6-15 years; 28 had a primarily generalised epilepsy, and 11 had a focal epilepsy. The patients remained free from seizures for more than 1 year. Psychiatric testing comprised the Child Behavior Checklist by Achenbach and Edelbrock and the Mannheim Parent Interview. Neuropsychological testing included non-verbal intelligence, visual perception, short-term memory and learning ability, arithmetics, movement coordination and motor skills, fine motor skills and verbal functions. After withdrawal from anticonvulsive therapy, the children with epilepsy did not exhibit any psychiatric disturbances, whereas those with occasional seizures frequently showed behaviour problems. After withdrawal from anticonvulsive therapy, no neuropsychological deficits were found in the children with epilepsy as compared to those with occasional seizures or to healthy children. Risk factors for poorer test results were first seizures occurring before the age of 3 years, delayed development, and neonatal problems. CONCLUSION: Children with epilepsy who remained without relapse after withdrawal from the anticonvulsive therapy did not show any psychiatric abnormalities and their performance was comparable to that of healthy control children, provided no risk factors were present.

Adolescent↗
PubMed1997

Neuromagnetic focusing for selective transcranial stimulation of muscles.

A focusing method for spatially selective, fast and efficient neuromagnetic stimulation is described that is using novel excentric coil systems. Electrolytic tank phantoms indicate good subcutaneous focusing without surface stimulation at cutaneous and shallow subcutaneous levels. Preliminary in vivo tests in humans indicate that selective transcranial stimulation of such closely adjoining muscle group areas as the ones of the musculus abductor pollicis brevis (thumb) and the musculus interosseous I (index finger) is possible with at least 50% less power than with conventional systems, with higher repetition rates and with limited electronic tuning of the subcutaneous focusing depth. Use of this method might lead to new applications in neurology and rehabilitation medicine.

Electromagnetic Phenomena↗
PubMed1996

Changes in movement-related brain activity during transient deafferentation: a neuromagnetic study.

Neuromagnetic fields from the left cerebral hemisphere of three healthy, right-handed subjects were investigated preceding and during voluntary index finger movements performed every 8-15 s under two different experimental conditions: before (stage A) and during (stage B) anesthetic block of median and radial nerves at the wrist. The anesthesia caused blocking of cutaneous receptors and some of the proprioreceptors from a wide hand area, including the entire index finger. However, the index finger movements were not impaired because the muscles participating in the task were not anesthetized. The magnetic signals of the brain sources corresponding to the main components of the movement-related neuromagnetic fields (motor field, MF and movement-evoked field I, MEFI) were mapped and localized using a moving dipole model. In the three investigated subjects the MF and MEFI dipole sources were stronger (30% on average) during stage B than during stage A. No significant changes in spatial coordinates of the estimated dipole locations between stages A and B were observed. This was true for both MF and MEFI. The results show that the MEFI reflects not only proprioceptive input from the periphery but cutaneous inputs as well. In this way the results support the view that cutaneous inputs play a specific role in the cortical control of movement.

Action Potentials↗
PubMed1996

A neuromagnetic study of movement-related somatosensory gating in the human brain.

Neuromagnetic fields from the left cerebral hemisphere of five healthy, right-handed subjects were investigated under three different experimental conditions: (1) electrical stimulation of the right index finger (task S); (2) voluntary movement of the same finger (M); (3) M+S condition, consisting of voluntary movements of the right index finger triggering the electrical stimulus at the very beginning of the electromyogram. The three conditions were administered in random order every 5-8 s. In addition, the task somatosensory evoked fields (task SEFs) gathered during condition (1) were compared with control SEFs recorded at the beginning of the experiment during rest. In all subjects the overlay of somatosensory stimulation on movement provoked a decrement in brain responsiveness (gating) as determined by the amplitude of gated SEFs. The latter was found as the difference between the neuromagnetic fields during M+S condition (overlaying of movement and sensory stimulation) minus neuromagnetic fields under M condition (M only). The gating effect was found to begin approximately 30 ms after movement onset, and to last for the whole period of the ongoing movement. The theoretical locus of gating was estimated by dipole localisation of the difference between task SEFs and gated SEFS using a moving dipole model. The site of the "early" gating effect (< 40 ms) was found to be more anteriorly located than the "later" (> 40 ms) gating effect. The task SEFs were found to be larger (significant after 30 ms) than the control SEFs elicited under the basal condition. The results are discussed with respect to timing, mechanism (centrifugal and centripetal), locus and selectivity of gating. In addition, the results are discussed with regard to clinical application (measuring attentional deficits in patients with impairments of higher mental functions and measuring gating deficits in patients with disturbed sensorimotor integration.

Adult↗
PubMed1996

Reproducibility of MEG auditory evoked field source localizations in normal human subjects using a seven-channel gradiometer.

Magnetoencephalographic (MEG) auditory evoked fields (EF) were recorded from 12 normal adult subjects over both hemispheres on two separate occasions at least one week apart using a seven-channel second-order gradiometer. Stimuli were computer-generated at 25-msec duration, 1 kHz tone pips. Responses to 100 stimuli were averaged, and source estimates with confidence intervals were computed, for the 100-msec latency auditory EF component, termed M100. Root-mean-squared (rms) differences in x, y, and z locations were approximately 0.7 cm on the two occasions; strength and orientation differences were 18 nA-m and 11 degrees, respectively. This spatial accuracy using a seven-channel instrument, compares favorably with other currently available technologies for localization of brain function.

Adult↗
PubMed1995

Neuromagnetic fields of the brain evoked by voluntary movement and electrical stimulation of the index finger.

Neuromagnetic fields from the left cerebral hemisphere of five healthy, right-handed subjects were investigated under two different experimental conditions: (1) electrical stimulation of the right index finger (task somatosensory evoked fields, task SEF's), and (2) voluntary movement of the same finger referred to as movement-related fields, (MRFs). The two conditions were, performed in random order every 5-8 s. In addition, the task SEF's were compared to control SEF's recorded at the beginning of the experiment in order to find the optimal dewar position for localizing the central sulcus. The magnetic signals of the sources corresponding to the main components of the somatosensory evoked fields (early ones at 24 ms and at 34 ms, and late ones after 50 ms) and movement-related fields (motor field, MF and movement-evoked field I-MEF I) were mapped and localized by means of a moving dipole model. In four out of five subjects the MEF I dipoles were found to be located deeper than the early task SEF dipoles. In addition, all of the task SEF's components were found to exhibit larger amplitudes than the control SEF's components. The results are discussed in respect to the ability to selectively analyze contributions of mainly proprioceptive (area 3a) and cutaneous (area 3b) areas in the primary somatosensory cortex using magnetoencephalography. An additional finding of the study was that all of the task SEF's components were found to exhibit larger amplitudes than the control SEF's components.

Adult↗
PubMed1993

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. The absolute values of the filtered signals (digital, bidirectional, four-pole butterworth, bandpass filter [3-dB range, 40-250 Hz]) were calculated in each channel. The noise level was determined within the TP segment. The onset of the terminal low amplitude signals (TLAS) was defined when the signals became lower than 1/23 of Rmax of the QRS complex for the channel with the largest filtered QRS complex after filtering. The TLAS ended when the signal was lower than twice the standard deviation (2 sigma) above the mean noise level. Ventricular late fields were defined as present when the TLAS had a duration of more than 39 msec. In this study, five patients with ventricular late potentials (four with sustained ventricular tachycardia) and three healthy individuals were examined. Ventricular late fields were detected in the patient group in 2-15 MCG channels with a mean length of 49.6 msec (43-60 msec). The spatial distribution of the ventricular late fields was consistently found to exhibit maximum duration in a certain area. In the normal subjects no ventricular late fields were detected. Thus, MCG is able to detect ventricular late fields and their spatial variations. In addition to the information obtained by signal averaging from the surface ECG, averaging of biomagnetic signals with a multichannel device can reveal spatial inhomogeneity of delayed myocardial excitation.

Electrocardiography↗
PubMed1993

Biomedical engineering education in Europe.

Biomedical engineering (BME) education was started in Europe at approximately the same time as in the United States. However, it grew at a slower pace, and its undergraduate and graduate programs, its research orientation, and its relationship with industry and hospitals developed differently, exhibiting even less uniformity than in the United States. This report focusses on the programs of Central Europe, and compares them with the system in the United States. The consequences for the international job market in BME are discussed including the envisioned influence of the impending unification of the European Community in 1993.

Biomedical Engineering↗
PubMed1991

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. A 37-SQUID (superconducting quantum interference device) sensor multichannel system (KRENIKON) was used, allowing synchronous registration with all channels. The site of the electrophysiological activity at the beginning of the delta wave was determined. Magnetic resonance images of the heart were obtained to correlate the biomagnetically localized activity with the anatomy. Magnetocardiographic localization of the bypass tract corresponded with catheter mapping with a spatial difference of 0-5 cm, 1.8 cm on the average, compared to the results obtained by catheter mapping. Thus, magnetocardiography is a promising new method for noninvasive localization of accessory pathways in WPW patients. This may streamline further invasive procedures.

Adult↗
PubMed1990

Noninvasive control of microwave hyperthermia by retro-focusing.

Phased arrays for hyperthermia application have numerous advantages. They have the ability to be focused onto a desired location, and have a slightly greater depth of penetration than single applicators. Their most significant drawback has been the inability to determine the appropriate phasing necessary to focus onto a tumor location. This paper presents simulated results of a novel method, designed to overcome this problem. By precisely determining the appropriate phase coefficients and utilizing the conjugated, incoherent tumor emissions, the array can be noninvasively controlled and retro-focused onto the tumor.

Humans↗
PubMed1988

Source origin of a 50-msec latency auditory evoked field component in young schizophrenic men.

We recorded auditory evoked magnetic fields in response to 128 15-msec duration 1-KHz tone pips from both hemispheres of 6 young schizophrenic men. Auditory evoked potentials were recorded conventionally from a vertex lead. The approximately 50-msec latency component was identified in both the magnetic (M50) and electroencephalographic (EEG) (P50) recordings. Isofield topographical contour maps were used to estimate M50 source location and depth. Magnetic resonance imaging was used to identify the neuroanatomical structure(s) present at the estimated source location. M50 sources appeared to reside in the planum temporale in both left and right hemispheres in all subjects. Normal inter-hemispheric asymmetry (with respect to external bony landmarks) of the M50 source was not found in this patient group. Additionally, left (but not right) hemisphere source anatomy differed in several respects from data previously reported in normals.

Adult↗
PubMed1987

Electrosurgical dispersive electrodes heat cutaneous and subcutaneous skin layers.

Electrosurgical return electrodes can produce heating, and occasionally burns, of cutaneous and subcutaneous skin layers. Up to now, only limited aspects of modern, dispersive, polymer electrodes have been studied using infrared thermography and thermocouples. This report presents new results on a quantitative infrared study, and adds the aspects of subcutaneous effects using microwave thermography as a third dimension. In agreement with previous work in infrared thermography, average cutaneous temperature increases observed in a dozen human volunteers were 1.5 degrees C for the normal mode, and 5.7 degrees C at near-fault (with partial contact). The intradermal and/or subcutaneous microwave thermographic images exhibited slightly lower, but still significant temperature elevations which were located at a more leading location, and were more widespread. This significant heating of subcutaneous layers, particularly of the sensitive stratum germinativum, clearly suggests the need for multiple-depth (microwave and infrared) thermography in order to evaluate the thermal performance of dispersive electrosurgical return electrodes.

Adult↗