Abstract: The invention relates to a method and a magnetoencephalography (MEG) measurement device. In the method there is determined the ending of a scheduled inactivity period of the MEG device. At the ending of the inactivity period a cryocooler of the MEG device is switched off. Helium is allowed to boil in the Dewar vessel of the MEG device when the MEG device is active and used to perform patient measurements. The boiled helium is collected via a compressor to an external storage tank. When a new inactivity period for the MEG device commences, the cryocooler is started anew and helium is let from the external storage tank in-to the Dewar vessel, where it is re-liquefied by the cryocooler. The compressor may be switched off when the cryocooler is switched on.

Abstract: The invention relates to a method and a magnetoencephalography (MEG) measurement device. In the method there is determined the ending of a scheduled inactivity period of the MEG device. At the ending of the inactivity period a cryocooler of the MEG device is switched off. Helium is allowed to boil in the Dewar vessel of the MEG device when the MEG device is active and used to perform patient measurements. The boiled helium is collected via a compressor to an external storage tank. When a new inactivity period for the MEG device commences, the cryocooler is started anew and helium is let from the external storage tank in-to the Dewar vessel, where it is re-liquefied by the cryocooler. The compressor may be switched off when the cryocooler is switched on.

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 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: 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.