Elekta Ab (publ)

Neuromag Oy

Elekta Neuromag Oy

Elekta Ab

Megin Oy

Lauri Parkkonen

Matti J Kajola

Juha T Simola

Samu Taulu

Antti I Ahonen

Juha Tuoriniemi

Sam Taulu

Antii Ahonen

The present invention describes a method enabling one to shield a device that measures weak biomagnetic signals from strong magnetic interference fields. The measurement sensors are provided with a feedback compensation loop, the difference signal of which is obtained from the measurement sensors themselves. As the actuator of the feedback function, one or more coils are responsible for eliminating, the external interference fields in the region of the sensors. Difference signals can be generated as a linear combination from the signals of two or more sensors. In the control logic, the SSS method can be used to numerically separate the biomagnetic signal being measured from the signals produced by the sources&#x2014;compensation coils and interference sources&#x2014;disposed outside the measurement region. The interference suppression can be enhanced by placing the assembly of sensors and the actuators within a magnetically shielding room.

Method for interference suppression in a measuring device

The invention relates to a method and device by means of which the location and position of an object may be determined in relation to another object by electromagnetic signals. In the arrangement in accordance with the invention there are two objects to the one of which there are attached signal sources, i.e. transmitters that generate electromagnetic signals, and the other object contains one or more receivers for measuring the transmitter signals. Usually the object containing transmitters is the one whose location or position is of interest and which is the object of the measurement. For example, in MEG measurements the object associated with the transmitters is the head of a human being on whose surface the transmitters are placed. By means of the arrangement in accordance with the invention is possible to find out the location and position of the head, in which case the location of the signals generated by the brain may be found out and utilized when examining the brain activity. The transmitters are also used to measure the signals emanating from the brain.

Determining a position of objects in a predetermined coordinate system

A method and apparatus is described for making multichannel signal measurements of weak signals in noisy environments, wherein the elimination of background interference signals from the multichannel signal measurement is performed. The method is based on an adaptive compensation technique in which the large interfering background signals are first recorded. By a statistical analysis of this multichannel measurement, independent components of the interference are determined. The apparatus is provided with compensator elements which are coupled to individual sensors for both collection and distribution of information on the interference signals during the measurement. In this way the output of a device can be made immune to the large amplitude interference components present in the device's environment. This reduces the dynamic range requirement for the data transport and storage systems.

Method and apparatus for eliminating background interference signals from multichannel signal measurements

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Lauri Parkkonen