Abstract: Disclosed is a magnetoencephalography apparatus (100) and a method. The apparatus comprises a plurality of magnetic sensors, one or more processors and one or more memories. The method comprises obtaining a reference data, calculating from the reference data a reference basis, obtaining a source basis, obtain a source data, adding together the source basis and the reference basis to form a joint basis and determine an estimate for the magnetic brain activity of the source by parametrizing the source data in the joint basis.

Abstract: The present invention introduces a method, device and a computer program for removing artifacts present in individual channels of a multichannel measurement device. At first, a basis is generated defining an n-dimensional subspace of the N-dimensional signal space, where n is smaller than N, where using in the definition of the n-dimensional basis a physical model of a Signal Space Separation method, or a statistical model based on the statistics of recorded N-dimensional signals. Thereafter, a combined (n+m)-dimensional basis is formed by adding m signal vectors to the n-dimensional basis, each of these m signal vectors representing a signal present only in a single channel of the N-channel device. After this the recorded N-dimensional signal vector is decomposed into n+m components in the combined basis, and finally, components corresponding to the m added vectors in the combined basis are subtracted from the recorded N-dimensional signal vector.

Abstract: The present invention introduces a method, device and a computer program for removing artifacts present in individual channels of a multichannel measurement device. At first, a basis is generated defining an n-dimensional subspace of the N-dimensional signal space, where n is smaller than N, where using in the definition of the n-dimensional basis a physical model of a Signal Space Separation method, or a statistical model based on the statistics of recorded N-dimensional signals. Thereafter, a combined (n+m)-dimensional basis is formed by adding m signal vectors to the n-dimensional basis, each of these m signal vectors representing a signal present only in a single channel of the N-channel device. After this the recorded N-dimensional signal vector is decomposed into n+m components in the combined basis, and finally, components corresponding to the m added vectors in the combined basis are subtracted from the recorded N-dimensional signal vector.

Abstract: The present invention introduces a method for processing multichannel measurement data achieved especially in MEG and EEG measurements. The method uses a signal space separation (SSS) method and the orthogonality of lead fields in order to calculate linear transformation from physical measurement channels to virtual channels. The geometry related to the measurement arrangement is dissipated and the number of virtual channels is clearly lower than the number of physical sensors. The concept of total information can be applied for such transformed measurement data due to orthogonality. The method offers simplified post-processing of the biomagnetic data, such as for source modelling. The total information can also be interpreted as a robust quantity describing the physiological state of a patient.

Abstract: 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—compensation coils and interference sources—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.

Abstract: 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—compensation coils and interference sources—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.

Abstract: The present invention relates to a novel manner of measuring DC fields using a multi-channel MEG or MKG measuring instrument; and on the other hand, to a manner of eliminating from the measurement result the interference signals caused by the DC currents. The invention combines the monitoring system of a testee's movement and the method for motion correction of the measured signals so that the signals produced by the DC currents of a moving testee's are visible in the final measurement result as a static signal component in a conventional MEG or MKG measurement. In that case, in the measurement, it is not necessary to beforehand prepare oneself for measuring the DC fields.

Abstract: A method and device by means of which an irrotational, sourceless vector field can be expressed by a number of physically reasonable basis vectors. In the method and device for processing a multi-channel measurement of magnetic fields of the present invention, measured signals can be unambiguously divided into signals of the irrotational, sourceless vector field that are caused by an interesting object or external interferences, as well as into a signal caused by the nonideality of the measuring device. The invention is based on the combining of two very fundamental mathematical regularities and applying in the processing of signal vectors of a multi-channel measuring device that measures an irrotational, sourceless vector field. The invention is based on the Maxwell's equations of an irrotational, sourceless vector field, as well as on the convergence characteristics of series developments.

Abstract: The present invention introduces a method for processing multichannel measurement data achieved especially in MEG and EEG measurements. The method uses a signal space separation (SSS) method and the orthogonality of lead fields in order to calculate linear transformation from physical measurement channels to virtual channels. The geometry related to the measurement arrangement is dissipated and the number of virtual channels is clearly lower than the number of physical sensors. The concept of total information can be applied for such transformed measurement data due to orthogonality. The method offers simplified post-processing of the biomagnetic data, such as for source modelling. The total information can also be interpreted as a robust quantity describing the physiological state of a patient.

Abstract: The invention relates to a method and device by means of which an irrotational, sourceless vector field can be expressed by a number of physically reasonable basis vectors as small as possible in such a manner that the measured signals can be unambiguously divided into signals of the irrotational, sourceless vector field that are caused by an interesting object or external interferences, as well as into a signal caused by the nonideality of the measuring device, which signal is not included in the model of the signal space describing an irrotational, sourceless vector field. The invention is based on the combining of two very fundamental mathematical regularities and applying in the processing of signal vectors of a multi-channel measuring device that measures an irrotational, sourceless vector field: on the Maxell's equations of an irrotational, sourceless vector field, as well as on the convergence characteristics of series developments.

Abstract: 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.

Abstract: 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.