Biomedical subjects
Publications and source records attributed to S Schuy.
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In glioblastoma multiforme and high-grade astrocytomas the following procedure has been implemented to try and prevent recurrence: after extirpation of the tumour its bed is lined with metal powder and the patient's head is exposed to a high-frequency magnetic field every 4 weeks. As a result the temperature is raised by induction to +45 degrees C at the boundary between metal and brain tissue. This ought to be sufficient to prevent tumour recurrence. Varied results were achieved using this technique in 103 patients.
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The liquification of the corpus vitreum by ultrasound is a promising new alternative to presently used mechanical methods of vitrectomy. With regard to the duration time of insonation, as well as to the ultrasonic intensity, there exist thresholds, the exceeding of which causes a discontinuous breakdown of the vitreous frame in a spherical zone around the transducer tip which can be verified by ultrasonic pulse echo methods. Viscosity measurements showed that the vitreous isonified in this area has almost the same viscosity as water whereas its optical transparency remains unchanged. The dependence of the diameter of the liquified zone on insonation time was measured.
The investigations concerning the influence of supply-frequent electric fields on man have been carried out on 12 subjects in 24 single trials. A field intensity as it occurs in the height of the subjects' head under a 380 kV high voltage transmission line was used. Some physiological parameters like ECG, EEG, blood pressure, blood gas and reaction time have been recorded and analyzed. The parameters were both analogously recorded and digitally stored as indicated in Fig. 2. Some of the investigations were carried out under mental load of the subjects and showed that the changes in the heartrate due to this load cover the switch-off effect of the heartrate. For the other parameters like EEG, reaction time, blood gas and blood pressure no influence of the investigated field intensity on man could be found.
EEG was recorded simultaneously from several scalp regions in 5 normal subjects and analysed, using a PDP 11/45 computer by means of an autoregressive model. Significant intra- and interhemispheric differences in the peak frequencies within the alpha band were observed, up to 0.8 c/sec. Local modality -dependent increases in the peak frequency were also observed, which were predominant in occipital areas during visual stimulation and in central regions during acoustic stimulation. In most cases an increase in the peak frequency occurred together with a marked decrease in power, which could be interpreted as a desynchronization of slow components within the alpha band. These peak frequency differences found in the scalp EEG lead to the assumption that there might also be different alpha rhythms at the level of the cortex.
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On 12 voluntary subjects with normal visual function the intraocular pressure was increased dependent on the ophthalmic blood pressure Pm = (Ps + Pd)/2. The visual field was tested under this pressure load by means of a subjective method and the visual evoked potential was derived under light and dark adaptation. Comparison of subjective and objective investigations demonstrated that the different visual evoked potentials which are dependent on the state of adaptation are a measure for the pressure sensibility of prelaminar optic nerve fibers.
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Electroretinograms of 19 human eyes in light- and darkadapted state under normal and increased intraocular pressure (increased by a spring pressure dynamometer) were recorded (Pm = (Ps + Pd)/2). On physiological intraocular pressure the a-wave showed a low increase in amplitude after 25 min of dark adaptation, the b-wave a great one. After increasing the intraocular pressure no significant influence of the state of adaptation to the magnitude of the a- and b-wave could be found.
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