Siemens Aktiengesellschaft

Kurt Weigert

Claudius Molz

Karl Hudek, Deceased

Karl Hudek

The invention relates to equipment for magnetic resonance tomography where, for the formation of physiological test signals, an electronic measuring system with an electro-optical transducer is arranged in a shielded cabin receiving the magnetic resonance tomograph. From this transducer a beam waveguide leads to an electronic processor with an opto-electric transducer provided outside the cabin. At the input, the electronic measuring system comprises a radio-frequency filter, a following wideband amplifier and thereafter, before the electro-optical transducer, a slew rate filter.

Electro-optical isolator for magnetic resonance tomography

Current stimulation apparatus, in particular, exhibits an output stage as the current waveform generator for producing an output current through a patient's body as the load resistance. Such apparatus operates with a specifiable operating voltage and controls the patient current in a constant-current fashion in the case of a varying load resistance. Preferably, the patient current is here measured through determination of the voltage across defined resistance terminals, whereby magnitude as well as peak values can be displayed on the display units associated with the output stage. Up to the present time, the measuring and display units had been fed by power supply units which deliver a supply voltage in relation to operating potential. According to the disclosure, all units for measuring, further processing, and/or display of the patient current are decoupled from the operating voltage circuit and receive supply voltages which are directly defined in relation to ground potential.

Electromedical apparatus

In automatic EKG-analysis, for example, the occurrence of signals, such as regular QRS-complex or also extrasystoles, is monitored in adjustable time intervals. However, it also happens that regular signal complexes in a signal sequence are lacking. In accordance with an exemplary embodiment, for the recognition and display of missing individual events in the essentially periodic signal sequence corresponding to the mean signal frequency, an adjustable measuring voltage, proportional to the signal period duration, is compared with the mean value formed from the measuring voltage summed up in the preceding signal period, whereby, upon exceeding the comparison voltage value, a count signal is triggered. In this manner, asystolias, or so-called 'missed beats' of the EKG can be ascertained, while compensatory pauses after extrasystoles are eliminated.

Method and apparatus for analysis of essentially periodic signal

In an illustrative embodiment EKG normal pulses have a time separation representing a monitoring interval, and upon the occurrence of a normal event (normal pulse), circuitry is activated to determine whether further events occur during the monitoring interval. The monitoring interval can be set at a constant value or a variably concomitant value as a function of the interval between the periodic normal events. Upon switching over from constant value to concomitant value of the monitoring interval, a comparator is activated, which comparator compares a time interval value between periodic normal events determined by means of a frequency-voltage converter with the constant value of the monitoring interval. A regulating element controls the converter output voltage by means of amplification alteration in such manner that it is altered toward the direction of the constant value of monitoring interval. Upon equality, the comparator generates a shutdown signal. The voltage value of the frequency-voltage converter serves then, after shutdown of the regulation upon attainment of the now-constant amplification factor, for the concomitant setting of the monitoring interval. Thus, the setting follows largely automatically, so that the correct value sets itself.

Procedure and device for the detection of extraordinary events in a

Known current stimulation apparatus have a current waveform generator with a constant-current output stage, which operates with a relatively high operating voltage (up to several 100 Volts), in order that the necessary currents can be applied even in the case of extremely high patient resistances. In the application of large-surface electrodes, the load resistances are generally comparatively low. The operating voltage required for the necessary currents for such normal instances is here substantially lower than the high operating voltage actually available, which leads to unpleasant irritation phenomena due to an increase in the current density when the resistance is suddenly altered due to the separation of the electrodes or the like. In accordance with the illustrated embodiment, the constant-current stage and the operating voltage supply are connected to an operating voltage control circuit which, in dependence upon the load resistance and/or the current intensity, regulates the operating voltage (U.sub.B) for the constant current stage from an initial voltage value (U.sub.V) to higher values with an increasing load resistance, whereby, however, the control time constant is such that, in the case of a differential resistance change which exceeds a specifiable threshold, the change in the operating voltage proceeds less rapidly than the resistance change. In the case of rapid change, for example, due to the separation and falling-off of electrodes, the operating voltage is thus only slowly adjusted upwardly such that undesired irritation pheomena are prevented.

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Nuremberg, Germany

Kurt Weigert