Device and method for carrying out spatially directed detection of an electroencephalogram

[0001] This Application claims priority based on the following patent applications filed in Germany: Application No. 100 58 128.5, having a priority date of Nov. 22, 2000; and Application No. 10145325.6, having a priority date of Sep. 14, 2001.

[0002] The invention relates generally to medical measurement and diagnostics, and more particularly, to measuring cortical signals generated in a particular region of interest.

[0003] The latest technology knows systems that capture the EEG with suitable electrodes at predefined standardized positions and feed it to an amplifier. The disadvantageous effect is that the electrical activity can only be captured from relatively large areas of the brain.

[0004] But in many medical problems of neurology, physiology or the function diagnostic the local brain activity of certain anatomical limited areas or centers is of more essential significance. A series of extensive signal processing steps is necessary to capture the electrical activity of such areas and to free them from disturbances by the adjacent brain areas. For that the amplified EEG must be digitalized and afterwards analyzed in a computer.

[0005] One disadvantage of this procedure is that only an offline analysis is possible. Therefore, this procedure can not be used in time critical procedures either.

[0006] One aspect of the invention is to supply a procedure and an arrangement in which the local electrical activity of a spatial limited brain area is captured and can be used for further processing and/or analysis. At the same time the affecting and disrupting fields from the adjacent brain areas on the desired area to be examined shall be considerably suppressed in their projection on the deviated potential.

[0007] According to one embodiment of the invention, it is intended with an arrangement for the spatial directed capturing of an electro encephalogram, in which electrodes are attached to the skull surface of the examined person, that

• • [0008] parts of the electrodes are arranged in such a way that they capture the activity of the targeted cortical structure, and
  • [0009] other parts of the electrodes are arranged in such a way that they capture the activity of the targeted cortical structure and the activity of the surrounding areas and furthermore
  • [0010] an electronic evaluation circuit exists.

[0011] In an advantageous advancement of the arrangement according to one embodiment of the invention, the electrodes are axial symmetrically arranged around a reference electrode in an inner ring and an outer ring.

[0012] Another aspect of the invention concerns a procedure for the spatial directed capturing of the electro encephalogram, in which the electrical activity is measured

• • [0013] over the targeted cortical structure as well as
  • [0014] over the targeted cortical structure and the adjacent area and
  • [0015] the received potentials are amplified and feed to an electrical circuit.

[0016] In an advantageous advancement of the procedure according to one embodiment of the invention, it is intended that the spatial directional pattern for the capturing of the activity of a targeted cortical structure is realized with signal processing algorithms.

[0017] The arrangement on hand, according to the invention, and the procedure belonging to it is characterized in a way that the electrical activity of the targeted brain area is freed from disturbances simultaneously to the EEG capturing. In traditional capturing methods this is only possible with the help of offline analysis, meaning with methods of signal processing that are based on several repetitions of the measurement and are therefore clinically realized in a lot of cases with unacceptable delays.

[0019] The arrangement illustrated in FIG. 1 can be used for examination of the visual cortex. A double ring-shaped electrode pattern is attached on the skull surface over the visual cortex of the patient above the inion 4. The number of the used electrodes depends on the respective technical equipment. They are axial symmetrically arranged around the reference electrode 1.

[0020] The electrodes of the inner electrode ring 2 are positioned directly above the ROI (region of interest—the target area). Its measurements have to be selected depending on the known anatomical characteristics.

[0021] The electrodes of the outer electrode ring 3 additionally cover the activity of the areas surrounding the ROI. The electrode potentials of the inner ring 2 and the outer ring 3 are amplified with common EEG amplifiers 5 and 6 and fed to the electronic block 7. The electrical direction pattern of the electrode configuration and the interference suppression of adjacent brain areas is realized with a suitable analog and digital circuit technology as well as with an algorithm implemented in a micro controller or signal processor. The formed difference of the activities of both brain volumes creates an almost undisturbed activity of the examined area (ROI). The examined person can already receive diagnostically relevant information during the reception of the brain potentials.