DE202009007623U1 - Tomographic data acquisition device - Google Patents

Abstract

A tomographic data acquisition device comprising:
a plurality of electrodes arranged for attachment to a measurement subject,
a power source,
a power supply line connected to the power source and connectable to each of the plurality of electrodes;
a controller arranged to connect electrodes of a selected pair of electrodes to the power supply line to provide current between the selected pair of the plurality of electrodes; and
Sense circuits arranged to achieve voltage measurements between selected ones of the plurality of electrodes while providing current between the selected pair of electrodes.

Description

The The present invention relates to various developments in devices for the acquisition of tomographic data. But especially not exclusively, the invention relates to tomographic data acquisition systems, which can be used to obtain tomographic data from to achieve a human or animal subject, for. B. to obtain data that contributes to the function of the nervous system indicate to the human or animal subject.

The Electrical impedance tomography (BIT) is a well-known technique to obtain data showing the composition of a body specify. There are electrodes on an outer surface attached to the body, and electricity is selected between Coupled electrode pairs. While electricity between each the selected pairs of electrodes are coupled Obtained voltage measurements between other electrodes. Since the coupled Electricity is known, the voltage measurements can be used be to conductivity at certain points within of the body, as the ratio between impedance, current and voltage is known. In general you can look at tomography as a technique which is meant to be an estimate of the conductivity distribution within a body to provide data that a subset of the transimpedance ratios between the surface of the body located electrodes specify. Ie. that in general a conductivity distribution requires special transimpedance ratios. The tomography deals with the opposite problem of estimation a conductivity distribution of transimpedance ratios, indicated by a particular set of voltage and current data become.

It it has been suggested that an estimated conductivity distribution, that has been achieved using the BIT can be used to get a picture of the conductivity distribution within the To generate body, in determining the composition of the body can be useful.

The BIT has found various applications, especially in the field of industrial control. Recently, it has been suggested that clinically valuable data can be obtained by subjecting the head of a human or animal patient to such a tomographic technique. For example, European patent no. EP 1 615 550 Applicant's use of a tomography technique in determining the behavior of the human nervous system, and more particularly in determining the response of the nervous system to a particular sensory stimulus, such as a visually or acoustically evoked response stimulation.

in view of of renewed interest in the application of the EIT in clinical There is a need for improved tomographic data acquisition devices and in particular to devices that are suitable for the Use in a clinical environment.

One The first aspect of the present invention provides a tomographic Data collection device ready, comprising a variety of Electrodes arranged for attachment to a measuring subject; a power source; a power supply line connected to the power source is connected and connectable to each of the plurality of electrodes is; a controller that is arranged around the electrodes of a selected pair of electrodes to the power supply line connect to current between the selected To provide a pair of the plurality of electrodes; and measuring circuits, which are arranged to measure voltage between selected ones To achieve electrodes of the plurality of electrodes while current provided between the selected pair of electrodes becomes.

The Power supply line (also referred to here as a busbar) is therefore a convenient way to deploy of electricity between a selected pair of the plurality of electrodes. In particular, when each of the electrodes to the power supply line can be connected, it is easy to power between the selected To provide electrode pair.

The power supply line may include first and second power supply lines, and the controller may be arranged to connect a first electrode of the selected electrode pair to the first power supply line and to connect a second electrode of the selected electrode pair to the second power supply line. The power source may include first and second power sources. The first power source can be connected to the first power supply line. The second power source may be connected to the second power supply line. Thus, the controller may control the first current source to provide a first current on the first power supply line and may control the second current source to supply a second current source on the second power supply line provide. The first and second currents may be alternating currents of substantially equal magnitude but 180 degrees out of phase with each other (ie, the second current may be a reversal of the first current). The provision of the first and second currents of this kind is advantageous in view of the fact that current flow to ground is minimized, on the basis that the current flowing from the first electrode to ground is substantially equal and opposite to the current, which flows from the second electrode to earth.

at In some embodiments, each electrode of the plurality of electrodes to each of the first and second power supply lines be connected so that with respect to the pairs of electrodes, between which power can be provided can be flexible. Each electrode of the plurality of electrodes may be connected to each of the first and second power supply lines via a respective one Switch can be connected. In other embodiments Some of the variety of electrodes can only be connected to the first power supply line can be connected, and others of the plurality of electrodes only be connected to the second power supply line. The controller can be arranged to switch to control which electrode to each power supply line is connected, thereby controlling the pair of electrodes between the power is provided.

The Apparatus may further comprise current measuring circuits arranged are to make a measurement of the current between the at least one selected pair of electrodes is provided to achieve. As is known, electricity is a parameter used in the analysis and processing of voltage measurements in the manner described here be charged. The provision of current measuring circuits makes it possible to accurately determine the current and prevents that one relies on the accuracy of the power source. The current measuring circuits can be arranged to a Measuring the current to be achieved on each of the first and second Power supply lines is provided.

The Apparatus may further comprise further electrodes suitable for an attachment to a measuring subjects are arranged but not can be connected to the power supply line.

The The device may further include a processor arranged is to the voltage measurements obtained (and optionally the achieved Current measurement) to generate data having a conductivity distribution in at least part of the subject. The data can comprise at least one image having a conductivity distribution indicates.

One Second aspect of the invention provides a tomographic data acquisition device ready, comprising: a plurality of electrodes for attachment arranged on a measuring subjects; a power source that arranged is to stream between a selected pair of the variety to provide electrodes; Voltage measuring circuits arranged are to make voltage measurements between selected electrodes to achieve the variety of electrodes while the current provided between the selected pair of electrodes becomes; and current measuring circuits arranged to provide a measurement of the Current to reach between the selected pair of electrodes provided. The power source is arranged to be used as input to receive an indication of a current to be applied. The power source is arranged to approximately provide the indicated current.

To In the prior art it is known to detect voltage measurements and to use the acquired voltage measurements along with data which indicate a current that one thinks of the subject was applied (ie the current input to the power source). The present Inventors have recognized that it is useful to measure the current which is actually provided instead of assuming that the electricity provided meets expectations. The measurement of the current in this way therefore eliminates a source of error during processing of the obtained voltage measurements.

The Power source can be a first power source and a second power source comprise a first electrode of the selected pair of electrodes can be connected to the first power source, and a second Electrode of the selected pair of electrodes can be connected to the second power source to be connected. The current measuring circuits can be arranged to provide a measurement of the current achieve that for each of the first and second electrodes provided.

One Processor can be arranged to the obtained voltage measurements and process the obtained current measurement to generate data the one conductivity distribution in at least one part of the subject, and the generated data can be at least to include a picture.

One Third aspect of the invention provides a tomographic data acquisition device ready, comprising: a plurality of electrodes for attachment arranged on a measuring subjects; a power source that arranged is to generate current between a first pair of the plurality of electrodes during a Stromekkoppelzeitraums provide; and voltage sensing circuits arranged to make voltage measurements between at least a second pair of the plurality of electrodes during a part of the current injection period, referred to as Measuring period is called to achieve; the current injection period includes a first period of predetermined duration, which is a balancing period during which no voltage measurements and the measurement period is part of the electricity injection period after the settlement period; and the voltage measuring circuits comprise at least one measuring component (eg an amplifier), wherein the or each measuring component to one of the second electrode pairs is connected, and the or each measuring device has a saturation recovery time having a criterion corresponding to that with respect to Duration of the settling period is defined. The criterion can be in it insist that the saturation recovery time is shorter is the duration of the balancing period.

The Inventors have surprisingly recognized that it is in construction of a tomographic data acquisition system is important that a Measuring component, which is part of the measuring circuits, a saturation recovery time has met a criterion of the kind set out above. Such an approach improves the reliability of the Voltage measurement.

The Power source can provide an alternating current that has a frequency of about 10 kHz. The electricity input period may have a duration of 500 μs, and the settling period may be have a duration of 100 μs. The or each amplifier can have a saturation recovery time of less than 100 μs have, for. B. a saturation recovery time of less than 50 μs, such as a saturation recovery time of approximately 10 μs.

The Control unit can be arranged to power one by one between a plurality of selected pairs of the plurality of electrodes, the current between each selected pair of electrodes is provided in a respective Stromeinkoppelzeitraum. The measurement circuits can be arranged to a variety of voltage measurements between selected electrodes the plurality of electrodes during a portion of each current injection period, which is referred to as the measurement period to achieve. Each power input period may include a first period of a predetermined duration, which is referred to as Ausregelzeitraum during which no voltage measurements are obtained, and each measurement period may be part of a respective Stromeinkoppelzeitraums on the balancing period follows.

One Fourth aspect of the invention provides a tomographic data acquisition apparatus ready, which includes first and second units, where: the first Unit comprises connections to a plurality of electrodes, which are arranged for attachment to a measuring subjects; a Power source, which is arranged to current between at least one provide first pair of the plurality of electrodes, voltage measurement circuits, which are arranged to make voltage measurements between at least one while achieving the second pair of the plurality of electrodes the current is provided between one of the at least one pair of electrodes and data processing circuits arranged to to process the obtained voltage measurements to be processed Generate data and the processed data for the second Unit provide, the voltage measurements by a first data set and the processed data comprise a second amount of data, the second amount of data being smaller is considered the first dataset; and the second unit of data receiving circuits which are arranged to receive the processed data from the first unit to receive.

Consequently The first unit is both arranged to perform voltage measurements as well as the amount of data that is used to To represent voltage measurements, to reduce, where the reduced Amount of data provided by the first for the second unit becomes. Thus, the bandwidth requirements are between the first and second units reduced.

Of the Electricity can be AC. The voltage measurements between a the at least one second pair of electrodes may be a plurality of voltage values, each at a particular time be achieved. The processed data, the voltage measurements between one of the at least one second pair of electrodes, can have an in-phase value. The in-phase Value can be a correlation between the voltage measurements obtained and a reference waveform. The data processing circuits can be arranged to the in-phase value to generate the obtained voltage measurements and the reference waveform.

The processed data, the voltage measurements between the or each of the at least one second pair of electrodes can further comprising a quadrature value. The quadrature value can be a Correlation between the obtained voltage measurements and a specify phase-shifted reference waveform.

The processed data, the voltage measurements between the or each of the at least one second pair of electrodes can 32 data bits comprising a 16-bit in-phase value and a 16-bit quadrature value.

A fifth aspect of the invention provides a printed circuit board comprising a first conductor extending in a first direction in a first plane, the printed circuit board providing a shield for the first conductor, the shield comprising first and second shielding conductors located in the first Extending substantially in the first direction in the first plane, and third and fourth shielding conductors extending substantially in the first direction in respective third and fourth planes,
wherein the first, third and fourth planes are substantially parallel to each other and offset from one another, and the first plane is between the third and fourth planes.

A Such arrangement provides good shielding of the first conductor ready, both opposite ladders in one shift (resp. Level) of the printed circuit board in which it is arranged, as well as opposite Conductors in adjacent layers (or planes) of the circuit board.

It a connection between the first conductor and the first, second, third and fourth Abschirmleitern be provided, wherein the terminal is arranged to the first, second, third and fourth Shielding conductor to keep the potential of the first conductor. Of the Connection may include an amplifier.

One non-conductive material (eg a fiberglass material) may be between the first and third levels and between the first and fourth Layers are inserted. A non-conductive material can between the first conductor and the first shielding conductor in the first level and between the first conductor and the second Abschirmleiter to be inserted in the first level.

Of the Fifth aspect of the invention may also be a tomographic Providing a data collection device, comprising: a plurality of electrodes arranged for attachment to a measuring subject are; a power source that is arranged to provide power between one to provide selected pair of the plurality of electrodes; Measuring circuits arranged to measure voltage between selected ones To achieve electrodes of the plurality of electrodes while the current is provided between the selected pair of electrodes becomes; and a circuit board of the type described above, wherein the first conductor is arranged to take power from the power source for To provide electrodes of the plurality of electrodes.

The Circuit board may further comprise a second conductor which extends extending substantially in the first direction in the first plane, and the circuit board may have a shield for the second Provide ladder. In particular, the circuit board can be a shield provide for the second conductor, the fifth and sixth shielding conductor, which is essentially in the first direction extend in the first plane, and seventh and eighth shielding conductors, which are essentially in the first direction in the third and fourth levels. The second conductor can be arranged be to power from the power source for electrodes of the variety of electrodes. Each of the electrodes can be connected to each one be connectable to the first and second conductors.

The Power source may include first and second power sources, wherein the first power source to the first conductor and the second power source is connected to the second conductor. A control unit can be arranged to control the first power source to provide a first current on the first conductor, and to to control the second power source to a second power source on to provide the second conductor, wherein the first and second Streams are essentially the same size but phases that differ by about 180 degrees are (i.e., the first and second streams can Be alternating currents, which are designed such that the second stream is an inverted form of the first stream).

A sixth aspect of the invention provides a tomographic data acquisition apparatus comprising: a plurality of electrodes arranged for attachment to a measurement subject, analog circuits arranged to provide current to pairs of the electrodes, and the voltage to measure between selected electrodes; digital control circuits; and a housing defining an internal volume in which the analog and digital circuits are arranged; wherein the volume has an inner portion and an outer portion, wherein the analog circuits are disposed in the outer portion, wherein the digital circuits are disposed in the inner portion, and the electrodes are connected to the analog circuits through the housing.

Of the Sixth aspect of the invention therefore provides a tomography system ready, which has a housing in which analog and digital Components are housed practically. In particular, the analog and digital components in a practical way from each other separated. Furthermore, the location of the digital circuits in a inner part of the housing and the location of the analog circuits in an outer part of the housing a long mixed signal limit for connections between provide the analog and digital circuits.

In In fact, the device may also be digital / analog and / or Comprise analog to digital conversion circuits. The volume can further comprising an intermediate portion extending between the Interior section and the outer section is located, and the Conversion circuits may be in the intermediate section to be ordered.

Of the Exterior section can be through an exterior Limitation of the housing and a first line that is in the Generally parallel to the outer boundary of the housing extends. The intermediate section can be through the first line, which is generally parallel to extends the outer boundary of the housing, and a second line, which is generally parallel to the outer one Limiting the housing extends, defined, where the second line the inner section in a middle section of the Housing defined. The housing can be an outer Contain boundary formed by two straight parts and one curved Part that connects the two straight parts is defined. The Both straight parts can be essentially parallel to each other be.

One Seventh aspect of the invention provides a tomographic data acquisition device ready to obtain tomographic data from a human or animal subjects, the device comprising: a variety of electrodes suitable for attachment to a human or animal subjects to be arranged; Circuits that are arranged to provide power for pairs of electrodes and measure the voltage between selected electrodes; and a housing in which the circuits are arranged, the electrodes being connected to the circuits through the housing are connected through, wherein the housing has a collar defined, which is arranged in use around the neck of the human or animal subjects.

The Provision of a tomographic data acquisition device in this form is advantageous because provided a practical means is to support the neck of the subject. This is special valuable in certain clinical environments, such as operating theaters. The housing may be generally U-shaped and can define an opening around the neck of the human or animal subjects.

One eighth aspect of the invention provides a tomographic data acquisition apparatus ready, which includes first and second units, where: the first Unit includes a variety of electrodes for attachment arranged on a measuring subjects; a power source that arranged is to make electricity between at least a first pair of the plurality of electrodes, voltage measuring circuits arranged are to make voltage measurements between at least a second pair to achieve the variety of electrodes while the current between the at least one selected pair of electrodes is provided, and control circuits which are arranged to control the power source and the voltage measurement circuits, and Provide voltage measurement data for the second unit; and the second unit comprises data receiving circuits arranged are to receive voltage measurement data from the first unit, and a power supply, wherein the second unit is arranged is to recycle the energy from the energy supply is generated, and the processed energy for the first Unit to provide, with the power supply from the first Unit is isolated.

The Control circuits may be arranged to provide the service of electricity and measuring the voltage independent of the second unit to control. Ie. that the first unit essentially can work autonomously to obtain voltage measurements and Data based on the obtained voltage measurements for to provide the second unit.

The second unit may include a housing defining an interior volume, the first and second Sections, wherein the first section houses the data receiving circuits and the second section houses the power supply. Between the first and second sections, an isolation route can be provided. The second unit may further comprise a data processing interface arranged to provide received voltage measurement data to a computer. Voltage measurement data may be provided to the data processing interface from the data processing circuitry via at least one isolation switch. The second unit may be arranged to provide power to the first unit from the power supply via the isolation link. The second unit may further include an interface to a stimulus generator arranged to cause the stimulus generator to apply stimulus to the subject.

One The ninth aspect of the invention provides a tomographic data acquisition apparatus ready, comprising the first and second units, wherein: the second Unit comprises a stimulus application control unit that arranged is to induce the application of a stimulus on the measuring subjects and stimulus application data indicating the timing of the stimulus application specify to provide for the first unit; the first unit Data receiving circuits arranged to receive the stimulus application data to receive a variety of electrodes for attachment a measuring subjects are arranged, a current source, which arranged is to generate current between at least one pair of the plurality of electrodes to provide voltage sensing circuits that are arranged to stress measurements between at least a second pair of To achieve variety of electrodes while the current between the at least one selected pair of electrodes is provided, and data processing circuits arranged are the obtained voltage measurements and received stimulus application data for the second unit; and the second unit further comprises data receiving circuits arranged are to voltage measurements and the stimulus application data of the first unit to receive.

The described above, according to various aspects of the invention provided devices can be configured be that the electrodes for attachment to the human or Animal bodies are arranged to receive data from a human or animal subjects.

The described above, according to various aspects of the invention provided devices may further include a stimulus application signal generator arranged to generate a signal to a Stimulus generator to apply a stimulus to the subject. The devices can communicate with the stimulus generator stand. The stimulus generator may be arranged to provide a sensory stimulus (eg, visually or acoustically) or transcranial magnetic stimulation to create.

The described above, according to various aspects of the invention provided devices can be arranged to receive a user input that has a delay indicates and to process voltage measurements at a time after the stimulus application is achieved by the delay is determined to generate data that has an activity of the subject's nervous system at the time of stimulus application specify. Ie. that the devices are used effectively can help monitor the behavior of the Nervous system in response to a stimulus. In fact you can the voltage measurements obtained are compared with reference data, to determine if the nervous system is normal or abnormal Reaction to the applied stimulus showed. In this way Certain aspects of the invention may be considered to be functional To provide EIT system, which is a system in which tomographic Obtains and processes data that specifies a neurological function become.

The described above, according to various aspects of the invention provided devices can be configured be that the electrodes for attachment to the head of a human or animal measuring subjects are arranged, and the electrodes the or each at least one selected pair of Variety of electrodes can be arranged to be on Head substantially diametrically or nearly diametrically opposed Positions to be installed. The measuring circuits can can be arranged to measure voltage between electrodes Achieve that are arranged to be mounted side by side.

at certain embodiments will be a controller arranged to successively stream between a variety of selected To provide pairs of the plurality of electrodes, and the measuring circuits Can be arranged to a variety of voltage measurements between selected electrodes of the plurality of electrodes while achieving electricity between each of the multitude provided by selected pairs of electrodes. This process can be repeated continuously.

It is understood that those described in connection with one aspect of the invention Features can be applied to other aspects of the invention. It is further understood that the various aspects of the invention may be combined.

It It should be understood that each aspect of the invention described above also a corresponding method for obtaining tomographic data provides. Such methods can by appropriately programmed computers are running. Thus presents Each aspect of the invention further provides a method of Capture tomographic data, a computer program that arranged is to capture tomographic data, a computer-readable storage medium or a data carrier (eg a disk), which or the contains such a computer program, and a computer, programmed to capture tomographic data.

It Let now exemplary embodiments of the invention will be described with reference to the accompanying drawings. It demonstrate:

1 a schematic illustration of a functional electrical impedance tomography (BIT) system according to an embodiment of the present invention.

2 a schematic illustration showing a headset of the system 1 takes a closer look.

2A a state transition diagram, the modes of the head holder off 2 and shows transitions between these modes.

3 a circuit diagram showing a part of the circuits in the head holder 2 are included.

4 a schematic illustration showing an arrangement of electrodes on the head of a subject in a flat design.

4A to 4E schematic illustrations showing an arrangement of electrodes on the head of a subject in a three-dimensional design.

5 a schematic diagram in cross section of a portion of a printed circuit board, which is used to the circuits 3 in the head holder 2 implement.

6 a schematic diagram of a base unit of the system 1 ,

7A a flow chart showing the processing that is performed to achieve voltage measurements and process.

7B a circuit diagram of a circuit which is arranged to the processing off 7A implement.

8th a graph showing an applied current waveform.

9 a schematic illustration of a measured voltage waveform.

10 a schematic illustration of a data packet format used to extract data from the head unit for the base unit in the system 1 provide.

11 a timing diagram showing the passage of data between the head holder and the base unit in the system 1 shows.

12 a schematic diagram showing the current couplings in the system 1 shows.

13 a variety of images generated from measurements made using the tomography system 1 were achieved.

14 a schematic illustration of an alternative embodiment of the head holder from 2 ,

First, referring to 1 a tomography system is shown which is arranged to tomogra to obtain phy- sical data that make up a conductivity distribution within the head 1 a subject can be estimated. A variety of electrodes 2 is attached to the scalp of the subject. Each of the electrodes is a silver / silver chloride EEG electrode of a type having a relatively low contact impedance upon contact with the scalp.

The electrodes are electrically connected to a head holder 3 connected, each electrode via a respective cable 2a to the head holder 3 connected. The head holder 3 is to a base unit 4 and in particular to a tomography subsystem 5 connected to the base unit. The connection between the head holder 3 and the base unit 4 allows bi-directional passage of data between the head holder 3 and the base unit 4 , and also allows the provision of energy for the head holder 3 from the base unit 4 out.

The base unit 4 is to a computer 6 connected so that the tomographic data attached to the tomography subsystem 5 the base unit 4 be received, to the computer 6 can be transferred for further processing and storage.

This in 1 The system shown is arranged to provide a stimulus to a subject and to obtain and record tomographic data indicating the effect of the stimulus on the subject's nervous system. For this purpose, the base unit includes 4 a stimulus control subsystem 7 connected to a stimulation device 8th connected, which applies a stimulus to the subject, so the stimulus control subsystem 7 the operation of the stimulation device 8th controls. In one embodiment, the stimulation device provides 8th includes visual or auditory stimuli, and includes calibrated headphones to provide auditory evoked response stimulation to the subject's ears, and a pair of light emitting diodes to provide visually evoked response stimulation to the subject's eyes.

Although in 1 shown that only four electrodes are attached to the head of the patient, in some embodiments, a larger number of electrodes is used. In particular, in the embodiment described in detail below, 33 electrodes are attached to the patient's head. Thirty-two of these electrodes are used for the purpose of acquiring tomographic data, while one electrode is used as the reference electrode (here called EREF). The reference electrode provides a low impedance connection between a site on the subject (eg, the subject's neck) and a reference voltage within the head holder 3 ready. In some embodiments, the reference voltage is a local ground potential of the head holder 3 but in other embodiments, a time varying voltage may be used. Namely, the use of such time-varying voltage may be useful in canceling common mode effects. Current is coupled in series between a plurality of pairs of the 32 electrodes, and during each current injection, a plurality of voltage measurements are made between other pairs of the 32 electrodes. Methods used to obtain tomographic data are described in more detail below.

The system off 1 is suitable for use in the medical environment. In the 1 with dotted lines 9 The components shown are therefore manufactured in such a way that they comply with the relevant legislation for the safety of medical devices. For example, it may be that the head holder 3 and the stimulation device 8th are arranged for easy disinfection to prevent the spread of infection from one patient to another, and so that the head holder 3 may include a sealed enclosure meeting international protection (IP) 65. Providing the Tomography System 1 as a head holder 3 and base unit 4 allows to disconnect high voltage components from the patient by placing them in the base unit 4 and not in the head holder 3 This separation is provided by components included in the head holder 3 and the base unit 4 be used. Such an approach reduces the number and size of heat-generating components located in the vicinity of the subject. The provision of such a separation will be described in more detail below.

Because of the tomography system as a head holder 3 and base unit 4 is provided, the head holder 3 Being proximal to the subject, be small. This may be important in clinical situations where space is limited (eg in operating theaters). Furthermore, the positioning of the head holder means 3 close to the subject that the cable lengths between the head holder 3 and the electrodes 2 be minimized, reducing the noise sensitivity of the cables 2a is reduced, and what does that mean the cables 2a not necessarily shielded. Extensive and possibly dangerous parts of the tomography system are in the base unit 4 provided that are slightly away from the subject Because a single cable or cable pair (which provides data and power) can find the head holder 3 to the base unit 4 followed. Since the base unit is not near the patient, it does not need to meet standards such as the IP65 described above.

2 shows the internal structure of the head holder 3 , It can be seen that the head holder 3 has a "gravestone" shape that provides a relatively long external boundary around which the ports are 2 B to the electrodes 2 to be provided. The interior of the head holder is generally divided into three sections. A first outside section 10 is determined by the circumference of the head holder 11 and a first dotted line 12 that are essentially parallel to the circumference of the head-holder 3 extends, defines. A second interior section 13 is through a second dotted line 14 Are defined. A third boundary (or intermediate) section 15 is between the first outer section 12 and the second interior section 13 provided, and is defined by the section of the head holder between the two dotted lines 12 . 14 Are defined.

The first outer section 10 is arranged to accommodate analog circuits, the second interior section 13 is arranged to accommodate digital circuits, and the third limiting section 15 is arranged to accommodate partly analog and partly digital circuits - eg. B. Analog-to-digital converters that convert signals from analog to digital ranges. Each section of the head holder will be described in more detail below. It should be noted, however, that providing the third boundary portion 15 between the dotted lines 12 . 14 a relatively long mixed signal boundary between the first outer section 10 which accommodates analog circuits, and the second indoor section 13 , which accommodates digital circuits, provides. In particular, the composite signal boundary is long enough to readily accommodate as many analog-to-digital converters and switches as there are electrodes 2 as described below.

As described above, current becomes between pairs of the electrodes 2 coupled in ( 1 ), and as the current is coupled in, voltage measurements between other pairs of the electrodes become 2 performed. Thus, the head holder 3 arranged to supply electricity to the electrodes 2 provide and voltage between electrode pairs 2 to eat. The current for the electrodes 2 attached to the connectors 2 B are connected from a power source 16 provided in the first outer section 10 located. The electricity is connected to a power rail 17 along the head holder in the restriction section 15 extends. Each of the connections 2 B is to the power rail 17 connected via a corresponding switch, and through suitable control of the switches (discussed below) can supply power to the desired terminals 2 B to be provided.

The first outer section 10 of the head holder 3 includes protection circuits 18 , which are arranged to protect circuits in the head holder and the circuits which are connected to the head holder from electromagnetic noise, in the vicinity of the head holder 3 or near the electrodes 2 and their cables 2a may be present. Such electromagnetic noise may come from a variety of sources, e.g. B. from equipment that can be used in the execution of electrosurgery. The first outer section 10 of the head holder 3 also includes measuring circuits 19 which are operable to measure voltage between pairs of electrodes 2 to achieve that to the connections 2 B are connected, and the measuring circuits 19 will be described in more detail below.

The second interior section 13 of the head holder 3 includes a freely programmable gate (FPGA) 20 which is configured to operate the head holder 3 to control and process the received data. For example, the FPGA 20 a digital representation of a desired current waveform for the power source 16 ready, and the power source 16 then sets a current according to the desired current waveform on the bus bar 17 ready.

As stated above, will energy for the head holder 3 from the base unit 4 provided. The energy is at an energy input 21 receive. It can be seen that the energy input 21 yourself in a section of the headgear 3 located from each of the first outer section 10 , the second inner section 13 and the third boundary section 15 is disconnected, reducing the energy input 21 can be separated from other components of the head holder. The energy input 21 is arranged to filter the received energy such that the effects of noise in the received power supply are eliminated. The energy input 21 is to an analogue energy conditioning unit 22 connected, located in the first outer section 10 of the head holder 3 located. The analogue energy conditioning unit 22 is arranged to supply electrical energy to the analog circuits in the first outer section 10 to provide and also to generate a reference voltage. The generated reference voltage is used for analog-to-digital converters located in the limiting section 15 and for amplifiers that are part the measuring circuits 19 are, who are in the outer section 10 are provided. The provided reference voltage is used by the analog-to-digital converters and amplifiers in a conventional manner. The energy input 21 is also connected to a digital energy conditioning unit 23 connected. The digital energy conditioning unit 23 provides electrical power to digital components in the second interior section 13 of the head holder 3 ready.

The second interior section 13 of the head holder 3 further comprises an interface component 24 , The interface component 24 is arranged to get data from the base unit 4 to receive and to provide her. In addition, there are two input devices 25 . 26 to the interface component 24 connected.

A user input device 25 Includes a single button that is used to control the operation mode of the head holder 3 to change. In particular, the head holder 3 a plurality of modes defining a sequence and by actuating the single button provided by the user interface device 25 is provided, a user controlling the data acquisition can select one of the modes by running the sequence of modes until the desired mode in the sequence is reached. The head holder 3 has four modes of operation in 2A are shown. A first resting state is the initial state of the head-holder 3 , The head holder 3 remains at rest until the user input device 25 is activated. When the user input device 25 is activated, the head holder goes into a "measuring only" condition. In this state, voltage measurements are achieved. Another activation of the user input device 25 causes the headgear to assume an EIT state in which current is coupled between electrode pairs and voltage measurements are made between other electrodes. The head holder 3 remains in the EIT state for a predetermined time (1 minute in some embodiments), and after this predetermined time has elapsed, the head holder returns to the "measure only" state. An error condition is assumed when a subject input device 26 (described in detail below) is activated. The head holder 3 remains in the error state until the user input device is activated for at least a minimum period of time (eg, five seconds) so that the head holder returns to the idle state. The head holder 3 has a status indicator that indicates its current state. Such a status indicator may conveniently take the form of a plurality of LEDs in different colors.

The subject input device 26 is provided for use by the subject from whom data is to be collected. This second input device comprises a single button that actually serves as a "stop" button to end the data collection. The subject input interface 26 This can be useful to give comfort to a subject who collects data because it gives the subject control to stop data collection if the subject somehow feels unwell. In some embodiments, activation of the subject input device terminates 26 the application of stimuli by the stimulation device 8th not, but only influences the collection of tomographic data.

Again, with reference to 2 includes the third limiting section 15 of the head holder 3 Analog-to-digital converters that are arranged to take voltage measurements from the measurement circuits 19 and a digital representation of the received voltage measurements for the second indoor section 13 of the head holder 3 provide. In addition, the third limiting section comprises digital-to-analog conversion circuits arranged to receive data from the FPGA 20 to receive a desired current, and an analog representation of this stream to the power source 16 provide. The third boundary section 15 also includes switches arranged to select terminals 2 B to the power rail 17 to join.

The operation of the head holder 3 will now turn off with reference to the schematic 3 described in more detail. 3 shows that the busbar 17 ( 2 ) a first busbar 17a and a second busbar 17b includes. Similarly, the power source includes 16 ( 2 ) a first power source 16a , the electricity on the first power rail 17a provides, and a second power source 16b , the current on the second power rail 17b provides.

At the first busbar 17a gets power from the power source 16a through a low resistance, called resistance 27a is provided. The voltage across the low resistance 27a is through a differential amplifier 28a whose output is an analogue to digital converter 29a provided. The analog / digital converter 29a is therefore arranged to provide a digital representation of the voltage across the low resistance 27a provide. Because the resistance of the low resistance 27a It is understood that the current generated by the low-resistance Wi resistor 27a flows, can be readily derived using Ohm's Law.

An equivalent arrangement will be used in conjunction with the second bus bar 17b provided. In particular, power is for the second busbar 17b from the second power source 16b through a low resistance 27b provided by the voltage passing therethrough from a differential amplifier 28b is measured. The output of the differential amplifier 28b becomes an analogue to digital converter 29b input, which provides as output a digital representation of the voltage in question.

Regarding 2 It should be noted that the analog / digital converters 29a . 29b in the third limiting section 15 of the head holder 3 and their digital editions for the second interior section 13 provide in which digital circuits are housed.

In 3 become exemplary five electrodes 2 shown. Other electrodes with reference to 2 have been described are arranged similarly. The five illustrated electrodes comprise four measuring electrodes, E1 to E4, and the reference electrode EREF. It can be seen that each of the four mapped measuring electrodes E1 to E4 is applied to each of the two bus bars 17a . 17b through respective switches 30a . 30b connected. Thus, each of the electrodes may be connected to either the first or the second bus bar 17a . 17b be connected.

It should be noted that in alternative embodiments of the invention, some of the electrodes only contact the first bus bar 17a connectable while other electrodes only to the second busbar 17b can be connected. Such an arrangement makes it possible to couple current between any pair of electrodes having a first electrode connected to the first bus bar 17a connectable, and a second electrode connected to the second busbar 17b is connectable includes.

Each adjacent pair of measuring electrodes E1 to E4 is connected to a measuring amplifier 31 connected (which the measuring circuits 19 out 2 forms). The output of each measuring amplifier 31 is an input for a respective analog-to-digital converter 32 , This makes it possible to measure the voltage between any adjacent pair of measuring electrodes and a digital representation of the voltage for the FPGA 20 to provide 2 ). The reference electrode EREF is connected to a reference voltage VREF which, as stated above, may be a local ground potential or a time-varying voltage. The operation of the circuit 3 shall below with reference to the two 3 and 4 be described in more detail.

First, referring to 4 An embodiment of the invention is shown in which 33 electrodes are attached to the scalp of a subject in a substantially flat design. In use, an alternating current of a predetermined frequency, magnitude and phase is coupled between a pair of electrodes placed on the subject's scalp in substantially diametrically opposed positions, such as those in FIG 4 shown electrodes E1 and E17, is arranged. The current injection is achieved by the electrode E1 to the first busbar 17a and the electrode E17 to the second bus bar 17b is connected, the connections by a suitable control of the switch 30a . 30b be achieved. In use, the first power source 16a controlled to a current of a predetermined frequency, size and phase (denoted by I ₁ ) on the first busbar 17a provide while the second power source 16b is controlled to a current of the same predetermined frequency and size but with a phase which is different by 180 ° (denoted by -I1) on the second busbar 17b provide. This results in that the coupling of the desired current between the electrodes E1 and E17 is achieved while minimizing the current flowing through the reference electrode EREF to ground. Specifically, current flows from I1 from the electrode E1 to a grounded reference electrode EREF, while current from -I1 flows from the electrode E17 to the grounded reference electrode EREF. The net current flowing to the reference electrode EREF is therefore I1-I1 = 0.

The current is provided in sequence, as stated above, for each pair of electrodes that are substantially in diametrically opposite positions. During each current injection, voltage measurements are made between all adjacent pairs of electrodes. Measurements between the electrodes E22 and E23 and between the electrodes E23 and E24 are shown schematically in FIG 4 shown by way of example. It should be understood that although measurements are made between all adjacent pairs of electrodes, any measurement made between an electrode currently used for current injection (E1 and E17 in the example) and any other electrode is irrelevant and discarded can be.

It It should be noted that a coupling between diametrically opposite Electrodes and a measurement between adjacent electrodes advantageous are. This is the case because every electrode of an adjacent Couple influenced by the current injection to a similar extent which means that the resulting voltage measurement is a good idea of the impedance there. In addition, the current injection ensures between diametrically opposite electrode pairs for a good depth sensitivity for the measurements.

in the Use is the current between each pair of electrodes, the are substantially diametrically opposed, 500 μs long coupled. The injected current is an alternating current with a frequency of 10 kHz. During each coupling Voltage measurements between adjacent pairs of electrodes at the same time, and these voltage measurements are called Basis for estimating the distribution of Conductivity used in the head. While everyone Current injection of 500 μs will be a first period of 100 μs is called the settling time, while the no voltage measurements are made. During the remaining 400 μs 200 voltage measurements are made, 50 during each of the four power cycles during the 400 μs take place.

Because the same electrodes are used both for voltage measurement and for current injection, and because the amplifiers 31 are always connected to their respective electrodes, the amplifiers 31 , which are used for the voltage measurement, carefully selected. In particular, it is desirable to ensure that the amplifiers 31 are able to accurately measure the voltage between a pair of electrodes even when an electrode has been used in this pair of electrodes to inject current only a short time before (only 100 μs before in the described arrangement). Thus it is desirable that the amplifiers 31 have a saturation recovery time and a settling time which are not greater than the period of a current injection referred to as settling time (ie 100 μs in the described arrangement) and during which no voltage measurements are made. In particular, an amplifier is used which has a shorter saturation recovery time and settling time. It has z. For example, it has been found that when current injection and voltage measurement are as described above, an amplifier with a saturation recovery time of 10 μs gives good results. However, it will be understood from the foregoing discussion that the saturation recovery time required by the amplifier is dependent on the duration of the settling time in the voltage measurement process, which in turn depends on the duration of each current injection and the frequency of the applied current.

If the amplifier 31 Another factor to consider is the common mode rejection ratio of the amplifiers. In particular, since the signal common to the two electrodes is used for a measurement based on the injected current, the amplifiers should 31 be selected to properly handle this common signal. It has been stated that the injected current has a frequency of 10 kHz in the described embodiment. Thus, amplifiers capable of suppressing a common signal of this frequency are selected in the described embodiment. Those skilled in the art will understand that many amplifiers are optimized to reject common signals at much lower frequencies (eg 50 Hz). In the described embodiment of the present invention, the amplifiers become 31 is selected to have a good common mode rejection ratio on the frequency of the injected current, even if the maximum common mode rejection ratio for all frequencies is subsequently reduced.

It has turned out that with reference to 2 and 3 described arrangement can be effectively implemented when the amplifier 31 Analog Devices Precision Instrumentation Amplifiers are AD-8221 that have a settling time of 4 μs (to stabilize at 0.01% with a gain of 10). Experiments have shown that even after saturation, the settling time does not exceed 50 μs.

In an alternative embodiment of the invention, the electrodes are disposed on the scalp of the subject in a non-planar configuration as now with reference to FIG 4A to 4E is described. Generally speaking, the electrode assembly is based upon with reference to FIG 4A to 4E is described on the international 10-20 system, which is used for placement of electrodes on the head of a subject in EEG data acquisition.

4A shows in plan view the head of a subject to which 32 electrodes are attached. Four electrode groups are shown (shaded differently). A first electrode group G1 comprises eighteen electrodes arranged in a ring around the subject's head. A second electrode group G2 includes eight electrodes disposed within the electrode ring defined by the first electrode group G1. A third electrode group includes five electrodes located on the back side of the subject's head, just below the inion, and the fourth group G4 comprises a single electrode located at the vertex of the head.

4B shows the head of the subject in side view. You can see the position of the electrodes in 4A be shown on the subject's head. In particular, it can be seen that the first group G1 of eighteen electrodes extends around a relatively lower portion of the subject's head, with the second group G2 of eight electrodes extending around a relatively upper portion of the subject's head. The shares in 4B are proportions of the total distance between inion and nasion of the subject, or correspondingly between the preauricular points on each side of the subject's head.

In the following description and in 4A to 4E the 32 electrodes are numbered c1 to e32. Table 1 shows the relationship between the reference symbols used in this specification and the position information used in the international 10-20 electrode placement system. Group Electrodes no. International 10-20 position indication G1 c1 F _pz G1 e2 F _p1 G1 e3 AF ₇ G1 e4 F ₇ G1 e5 FT ₇ G1 e6 T ₇ G1 e7 P ₇ G1 e8 PO ₇ G1 e9 O ₁ G1 e10 O G1 e11 O ₂ G1 e12 PO ₈ G1 e13 P ₈ G1 e14 T ₈ G1 e15 FT ₈ G1 e16 F ₈ G1 e17 AF ₈ G1 e18 F _p2 G2 e19 F _z G2 e20 F3 G2 e21 C ₃ G2 e22 P ₃ G2 e23 P _z G2 e24 P ₄ G2 e25 C ₄ G2 e26 F4 G3 e27 - G3 e28 - G3 e29 I _z G3 e30 - G3 e31 - G4 e32 C _z TABLE

As indicated above, it is desirable to couple current between electrodes that are substantially diametrically opposite. This is achieved by coupling current between 20 different electrode pairs. 4C shows eleven current injections performed between the eighteen electrodes forming the first electrode group G1. It can be seen that each coupling is performed between a pair of electrodes located at substantially diametrically opposite locations. 4D shows four current injections between eight electrodes forming the second electrode group G2. 4E FIG. 12 shows five current injections performed between the electrode E1 located in the center on the forehead of the subject's head (aligned with the subject's nose) and the five electrodes of the third electrode group G3. It is therefore out 4C to 4E it can be seen that current is injected between twenty different electrode pairs.

The order in which current is coupled between the electrode pairs may be important. In particular, current injection between pairs of electrodes in a particular order can produce undesirable physiological symptoms. An order of current injection between the twenty electrode pairs listed above that has been found to be effective is as follows: Einkopplungsnr. electrodes 1 e1, e30 2 e1, e27 3 e22, e26 4 e9, e18 5 e7, e16 6 e3, e12 7 e1, e28 8th e8, e12 9 e5, e15 10 e1, e29 11 e4, e13 12 e8, e17 13 e7, e13 14 e20, e24 15 e6, e14 16 e1, e31 17 e1, e10 18 e2, e11 19 e21, e25 20 e19, e23 TABLE 2

When determining the order in which current is to be injected between pairs of electrodes, one symptom to be particularly considered is trigeminal neuralgia. It is unbearable pain, resulting from a stimulation of the trilling nerve. Thus, it is important that the current injection does not provide such a stimulation of the triplet nerve. The trilling nerve innervates the forehead and other areas of the face. In the arrangement with respect to 4A to 4E a number of electrodes are placed on the subject's forehead, and care must therefore be taken to ensure that the current injection involving electrodes located on the subject's forehead does not stimulate the trilling nerve. Ie. care must be taken to ensure that no current is coupled in such a way as to result in an unacceptable amplification of the signals already propagating in the trilling nerve due to previous current injections. Ie. the timing of the current injections must take into account the neural signals that are still propagating due to previous launching.

Studies using laser stimulation of the forehead have shown that the conduction velocity of nociceptive, marrow-free fibers within the trilling nerve is approximately 1.2 ms ^-1 . These non-corrosive fibers are called C-fibers, and because of their lack of myelination (which acts like a natural insulator) are particularly susceptible to stimulation by current injection on the skin. This is z. B. at Cruccu G, et al. "Unmyelinated trigeminal pathways as assessed by laser stimuli in humans", Brain 2003 Oct; 126 (Pt 10): 2246-2256 , described.

The circumference of an adult's head is typically between 53 cm and 64 cm. Studies have shown that the average circumference in men is 58 cm and the average circumference in women is 55 cm. If eight electrodes across the front of the head and assuming a conduction velocity of 1.2 ms ^-1 (as mentioned above), this implies that a current injecting stimulation pulse between 2.75 ms and 3.38 ms is required to move away from an electrode To induce action potential salvage within the trilling nerve. This means that it is desirable to avoid current injection frequencies of 296 Hz to 363 Hz between adjacent pairs located on the subject's forehead. The current injection pattern described above achieves this goal.

When referring to 4B to 4E described arrangement voltage measurements are made between consecutively numbered electrodes. In addition, two more voltage measurements are obtained by obtaining a measurement between the electrode e1 and the reference electrode EREF and the electrode e32 and the reference electrode EREF. By processing these two further voltage measurements, a voltage specification between e32 and e1 can be achieved. It has been found that the described arrangement of electrodes and current injections and voltage measurements generate data that allow relatively good estimates of the conductivity within the subject's head to be displayed.

Again, with reference to 3 it can be seen that each of the busbars 17a . 17b provided with a shield. In particular, the voltage of the first busbar 17a to an amplifier 33a passed its output to the Abschirmleitern 34a provided. A similar arrangement will be in connection with the second bus bar 17b through the amplifier 33b and the shielding conductors 34b provided.

The circuit off 3 is implemented using three layers of a printed circuit board, which in schematic cross section in 5 shown to illustrate the spatial configuration of the Abschirmanordnung. 5 shows that the circuit board comprises three conductive layers A, B, C resting on a fiberglass structure 35 are attached.

The first busbar 17a is of shielding conductors 36a . 37a . 38a . 39a surrounded, the schematically illustrated Abschirmleitern 34a out 3 correspond. It can be seen that two shielding conductors 38a . 39a parallel to and in the same plane as the first busbar 17a extend. Two shielding conductors 36a . 37a also extend parallel to the first busbar 17a but in planes that are relative to each other and to the plane in which the busbar is 17a extends, are offset, ie that while the busbar 17a and the shielding conductors 38a . 39a are provided in a first plane, which is defined by the layer B of the circuit board, the Abschirmleiter 36a provided in a plane defined by the layer C of the circuit board while the shield conductor 37a is provided in a plane defined by the layer A of the circuit board. Each of the shielding conductors is explained by referring to 3 described arrangement on the voltage of the busbar 17a held.

Each layer of the circuit board is separated by its adjacent layers by a distance of 0.18 mm, which is indicated by the arrows a. Each layer is 0.018 mm thick, which is indicated by the arrows b. The bus bar is 0.254 mm wide, which is indicated by an arrow c, and is within the plane defined by the layer B of the Abschirmleitern 38a . 39a separated by a distance of 0.2 mm, which is indicated by the arrows d. Each of the shielding conductors 38a . 39b is 1.235 mm thick, which is indicated by the arrows e. The shielding conductor 36a . 37a which extend in respective planes, in relation to the plane in which the first busbar 17a are extended, are 3.125 mm wide, which is indicated by the arrow f. It is therefore apparent that the first busbar 17a and their shielding arrangement passing through the shielding conductors 36a . 37a . 38a . 39a in each of the three layers A, B, C of the printed circuit board are 3.125 mm wide.

5 also shows the second busbar 17b together with their shielding conductors 36b . 37b . 38b . 39b , The second busbar 17b and their shielding conductors have the same dimensions as the first busbar and their shielding conductors, as indicated by the arrows marked c to f, in connection with the second busbar 17b the above with respect to the first busbar 17a represent described dimensions.

The first and second busbars 17a . 17b and their associated Abschirmanordnungen are separated in the planes of the circuit board from each other by a distance of 0.18 mm, which is indicated by an arrow g.

It is off 5 seen that creepage losses from one of the busbars 17a . 17b against one Grounding layer of the circuit board (not shown) are blocked, as well as leakage between the two busbars 17a . 17b , Creepage losses from one of the busbars 17a . 17b must be current through a relatively large area at or near the potential of the relevant busbar. The shield conductors are arranged to surround each bus bar in four directions. Thus creepage losses are minimized.

After the head holder 3 has been described in detail, will now be a description of the base unit 4 regarding 6 respectively. In 6 is shown that the base unit 4 the tomography subsystem 5 and the stimulus control subsystem 7 includes. It is also evident that the base unit 4 a filtered energy input 40 arranged to receive a supply of electrical energy. The received electrical energy is sent to a local power distribution module 41 passed, which is arranged to provide electrical power to the various components of the base unit 4 provide. More specifically, the local power distribution module comprises 41 three AC / DC converters. A first AC / DC converter receives AC electrical energy from the supply input 40 and gives DC power to the stimulus control subsystem 7 further. A second AC / DC converter receives AC power from the supply input 40 and provides DC power for an energy input 42 ready to go to the Tomography subsystem 5 belongs. In one embodiment, the second AC / DC converter is a 120W power supply unit for medical purposes. A third AC / DC converter, powered by the local power distribution module 41 is supplied receives electrical energy from the filtered power input 40 and provides DC electrical power to a data acquisition module 43 ready. The data acquisition module 43 is arranged to get data from the tomography subsystem 5 to receive and processed data to the computer 6 to pass on 1 ).

The tomography subsystem 5 shall now be described. A galvanic isolation line 43 separates the components of the tomography subsystem directly with the head holder 3 of those who are not. This provides a high degree of isolation between many of the components of the base unit 4 and the components of the head holder 3 provided, which is intended to be placed in the immediate vicinity of a human subject, possibly in a medical environment. There are only two ways through the galvanic isolation line 43 , The first is a way for the power supply to the head holder 3 , The second is a way for the bi-directional passage of data between the head holder 3 and the base unit 4 , Each of these ways will be described below. In any case, the paths that pass through the galvanic isolation path are arranged to meet all medical and other electrical safety criteria.

The insulation in the power supply for the head holder 3 is achieved by using highly insulating DC / DC converters 44 at the galvanic isolation line 43 along, wherein the DC / DC converters electrical energy from the power input 42 receive and electrical power for a headset power supply 45 provided, which is arranged to recycle the received electrical energy, before the energy for the head holder 3 provided.

The tomography subsystem 5 also includes a data interface 46 which is arranged to receive data from the head holder 3 to receive and provide him with this. It can be seen that the data interface 46 within the galvanic separation line 43 located. To ensure that the isolation is maintained, data passes through the data interface 46 have been received and have gone to the data interface, by the highly insulating optical circuit breaker 47 that are on the galvanic isolation line 43 are located. The optical circuit breaker 47 Therefore, provide the second way for the bidirectional passage of data, as already mentioned above. Data is from a digital data processing module 48 from and to the optical isolators 47 given. The digital data processing module 48 is arranged to receive data and receive data to an interface 49 the tomography subsystem, the interface 49 is arranged to data for the data acquisition module 43 provide. In some embodiments, the data acquisition module provides 43 a USB interface ready through the data for the computer 6 can be provided. For example, in one embodiment, the data acquisition module is a National Instruments USB-6221 data acquisition module.

It has been described above that the systems described herein can be used to determine a response of a nervous system to an applied stimulus at a particular time after stimulus application. To accomplish this, the stimulus control subsystem provides 7 Control commands for the stimulation device 8th ready ( 1 ) to the stimulus control subsystem 7 connected. In one embodiment, the stimulus control subsystem is a CED Micro 1401 MKII unit that includes a USB interface for the computer 6 Provides so that the stimulus application through the computer 6 can be controlled. If such commands for the stimulation device 8th provided provides the stimulus control system 7 Timing flags for a stimulus control interface 50 ready by the tomography subsystem 5 provided. These timing flags are provided by the stimulus control interface 50 to the digital data processing module 48 passed. The digital data processing module 48 again gives the received timing flags to the data interface 46 via the optical isolator 47 further. The head holder 3 is therefore provided with the timing flags and arranged to integrate the timing flags into a data stream comprising obtained voltage measurements. Thus, the digital data processing module receives 48 Data from the head holder 3 via the optical isolator 47 including both voltage measurements and an 'echo' of the stimulus timing flag provided.

It also includes the tomography subsystem 5 an optically isolated digital input 51 to which other stimulation devices can be connected. Signals indicating the application of a stimulus by a device connected to the isolated digital input 51 is connected, can specify, from the data processing module 48 are handled as signals from the stimulus control subsystem 7 to be provided. It should be noted that in this way the base unit 4 May record data indicating a point in time at which a stimulus is applied by a stimulation device, rather than relying on the time point at which an instruction to provide a stimulus to the stimulation device is provided. This is particularly useful when the stimulation device is unable to provide stimuli as requested, and is also useful when it is desired to allow the stimulation device to provide stimuli at random and to record only its application.

The operation of the head holder 3 for obtaining voltage measurements and providing obtained voltage measurements to the base unit 4 should now with reference to 7A to 11 to be discribed.

7A Figure 4 is a flow chart showing the general processing performed by the head holder 3 during the acquisition of tomographic data. In step S1, a current injection between a pair of electrodes begins. 8th shows a graph of the injected current. It can be seen that the injected current is an alternating current having a frequency of 10 kHz and that the current injection is carried out for 500 μs. As described above, the current injection time comprises a settling time of 100 μs (step S2) 7 ), wherein the voltage measurements are obtained during a measurement period of 400 μs after the settling time has elapsed (step S3) 7 ). It can be seen that 4 complete cycles of current waveform occur during the measurement period of 400 μs.

9 Figure 12 shows how the voltage between a pair of electrodes typically varies while providing current during the measurement period discussed above. As expected, the waveform is cyclic and includes four cycles during the measurement period of 400 μs. During the measurement period of 400 μs, 200 voltage measurements are obtained, ie 50 voltage measurements are made during each voltage (and current) cycle within the voltage measurement period.

In Step S3, a voltage measurement is achieved and with two reference waveforms multiplied, which will be described below in step S4, to provide two multiplication results. The multiplication results become in step S5 with the results of other multiplications calculated using the same reference waveform. In step S6, a check is made to to determine if 200 voltage measurements have been processed. If Yes, the two summation results are output in step S7. Otherwise, the processing proceeds to step S3, in which a different voltage measurement is achieved.

7B FIG. 15 shows a circuit arranged to perform the processing of steps S4 and S5 7A perform. An achieved voltage measurement is in first and second multipliers 55 . 56 entered. A reference sinusoid 60 will also be in the first multiplier 55 entered, and a reference cosine curve 61 (ie a version of the reference sinusoid 60 after a phase shift of Π / 2 or 90 degrees) is added to the second multiplier 56 entered. The reference sinusoid is generated based on the input digital current waveform provided by the FPGA 20 ( 2 ) and for the power source 16 provided.

The multiplier 55 multiplies the obtained voltage measurement by a corresponding point on the reference sinusoid 60 , A point on the reference sinusoid corresponding to each voltage measurement is determined with reference to the time at which the voltage measurement was obtained. In particular, since 200 voltage measurements are achieved within 400 μs, every 2 μs a voltage measurement is achieved. Thus, a voltage measurement that multiplies 2 μs after the beginning of the measurement period (or the beginning of any voltage cycle) is multiplied by a point on the reference sinusoid defined with respect to a time of 2 μs, and so on. In other words, since 50 measurements are taken during each cycle, each measurement becomes one point on the reference sinusoid 60 multiplied by 360/50 = 7.2 degrees in phase compared to the previous value.

Thus, in the described embodiment, the fifty measurements obtained in each cycle are processed analogously. Ie. that measurements of the reference sinusoid 60 with fifty different phase values processed four times each, once per cycle. In an alternative embodiment, 200 measurements with unique phase values can be processed. This can be accomplished by taking the times at which voltage measurements are obtained and the values of the reference sinusoid 60 at the multiplications described above.

The second multiplier 56 Similarly, it performs a received voltage measurement with a corresponding point on the reference cosine curve 61 multiplied.

The output of the first multiplier 55 forms the input for a first summation block 57 , which simply adds the input value to a running total. The output of the first summation block 57 provides an in-phase value I which is an indication of the correlation between the voltage waveform that was measured and the reference sinusoid 60 provides.

A second summation block 58 takes as input the output of the second multiplier 56 and computes the input value with a running sum. The output of the second summation block 58 provides a quadrature value Q which is an indication of the correlation between the voltage waveform that was measured and the reference cosine curve 61 provides.

It is understood that each of the summation blocks 57 . 58 200 values each corresponding to one of the voltage measurements to produce the in-phase and quadrature values.

Consequently It can be seen that the 200 voltage measurements that cause a special Pair of electrodes during a certain current injection belong, can be reduced to two numbers, which can be processed to provide the necessary voltage data to achieve.

It it is understood that the processing of step S3 to S7 for all pairs of electrodes between which voltage measurements during a certain current injection are made simultaneously be executed.

Since in the arrangements out 4A to 4E Voltage measurements are made between 33 electrode pairs during a particular current injection as described above (ie, measurements are taken between each adjacent electrode pair, including the pairs with electrodes used for current injection, although the measurements made by electrodes are for current injections may be discarded in further processing), and since current is coupled between twenty electrodes in succession in a complete measurement frame, it is understood that a large number of voltage measurements will be made in each measurement frame. In fact, all acquired voltage and current measurements provide data at a rate of 16.7 MB / s. Because the data that is generated by the head holder 3 for the base unit 4 be provided, it is desirable to increase the amount of data passing through the connection with relatively low bandwidth between the head holder 3 and the base unit 4 to transfer is to reduce. This is achieved by the processing related to 7A and 7B which means that voltage measurements between a single pair of electrodes during a single current injection are represented by two values: a quadrature value and an in-phase value.

It It should be understood that alternative methods for reducing the amount of measured data are similar can be used.

Again, with reference to 7A is determined in step S8 based on the output of one of the analog-to-digital converters 29a . 29b ( 3 ) receive a current measurement. Although the power sources 16a . 16b In order to provide a prescribed current, their accuracy is bound to have their limits, and it is therefore desirable to measure the current actually on each of the bus bars 17a . 17b ready instead of assuming that the provided current is the one for the current sources 16a . 16b was prescribed. 200 measurements of each current are made during a measurement period of 400 μs.

In step S9, the input current measurement becomes the reference sinusoid 60 and the reference cosine curve 61 as above with reference to steps S4 and 7B multiplied. In step S10, the results of the multiplications are added to the respective summations. In step S11, a check is made to determine if 200 voltage measurements have been processed. If not, the processing returns to step S8. The processing of step S8 to S11 generates in-phase values I and quadrature values Q on the basis of the 200 processed current measurements. Because the current measurements for each of the busbars 17a . 17b It will be understood that the processing of steps S8 to S11 for each of the bus bars 17a . 17b is executed in parallel.

In step S12, the processed voltage and current measurements are placed in a predetermined data packet format and from the head holder 3 for the base unit 4 provided.

In step S13, a next power injection is selected before the processing returns to step S1. 10 schematically maps a data packet format used to acquire measurement data from the head holder 3 for the base unit 4 provide. The data packet is a data packet of fixed length with a length of 152 bytes and comprises seven data fields. A synchronization code field 62 includes a synchronization code 62 with a length of 24 bits, which is used as a mark for the beginning of a data packet.

A flag field 63 includes 44 bits of data and provides various information indicating the validity of various data. In particular, 33 bits of data are used to indicate whether any of the voltage measurements are invalid, based on the fact that the particular ADC is operating outside its normal operating range. This is z. For example, it is likely that an ADC will receive a signal from an electrode currently being used for the purpose of current injection and from which no valid voltage measurement can be obtained. 8 data bits are used to specify error conditions that are related to the power sources 16a . 16b especially for an incorrect amplitude or distortion of the produced current waveforms. Two bits of data are used to indicate whether a stimulus has been applied in the time period (500 μs) associated with the data packet. The two bits may simply indicate true / false data related to a stimulus application, or may encode data relating to the type of stimulus applied.

A voltage measurement field 64 includes 32 bits of data for each of the 33 voltage measurements, giving a total of 1056 bits of data from the head holder 3 for the base unit 4 to be provided. The data representing each voltage measurement includes a 16-bit I (in-phase) value and a 16-bit Q (quadrature) value generated as described above.

A current measurement field 65 includes 64 bits of data, 32 bits for each of the two current measurements, for each of the busbars 17a . 17b be achieved. Each voltage is again represented by two 16-bit values, with a first value representing the I (in-phase) value and a second value representing a Q (quadrature) value, again generated as described above.

A stream pattern identifier field 66 includes 8 bits of data identifying the pair of electrodes between which current was injected to produce the voltage measurements obtained.

A power pattern counter field 67 includes 20 bits of data that uniquely identify a block during the measurements, that is, a particular current injection, of which there are twenty in a complete frame. The provision of 20 bits allows unique identification of all blocks within the measurements achieved during a measurement period of approximately 8 minutes. In particular, since 100 data frames per second are achieved and each frame 20 Blocks comprises 1 second measurement data 2000 blocks. One minute of measurement data comprises 120,000 blocks, while 8 minutes of measurement data comprises 960,000 blocks. Although in some embodiments measurement data is obtained only for a one-minute period, the use of 20 bits that allow measurements to be taken over an 8-minute period may be useful to allow unique identification of a block over an extended period of time , This can be useful when a measurement is interrupted.

Data is taken from the head holder 3 for the base unit 4 provided via a serial communication link. As in 11 Each data packet requires 304 μs for transmission. Since each data packet comprises data obtained over 500 μs, it is understood that no data is transmitted for 196 μs after the transmission of a data packet.

Even though 10 shows a format for a data packet that is used to get data from the head holder 3 for the base unit 4 It is understood that other data packet formats may be used.

The data collection using the methods and systems described above will now be described with reference to 12 described in a system in which electrodes are mounted on the head of a subject, and with reference to

4A to 4E is described. 12 shows a graph of Stromeinkopplungen in relation to time. Power couplings are arranged in a variety of measuring frames, of which the measuring frames 70 . 71 to be shown by way of example. In each measuring frame, current is coupled in succession between twenty pairs of electrodes while making voltage measurements between other electrodes. The twenty current injections are made between the electrode pairs listed in Table 2 above and in the order given in Table 2. As stated above, each current injection lasts 500 μs. During each current injection, 33 voltage measurements are taken simultaneously between adjacent pairs of electrodes.

The Measuring frames occur continuously. The continuous application of current couplings results in a uniform Series of voltage measurements, so that data is continuously achieved can be.

Clinically valuable information can be obtained from voltage measurements taken with a certain delay after the application of a stimulus. In general, voltage and current measurements are processed to produce data indicating an impedance distribution in the subject's head. 13 Figure 6 shows six images indicating the conductivity distributions generated from the data generated with various delays after the application of a visual stimulus. The processing of voltage and current measurements to produce images of conductivity, such as those in 13 can be carried out using known methods. Such a method is used by Polydorides, N., Lionheart WRB and McCann, H .: "Krylov Subspace Iterative Techniques: On the Detection of Brain Activity with Electrical Impedance Tomography" IEEE Transactions on Medical Imaging, Vol. 21, No. 6, June 2002, pp. 596-603 , described. Another suitable technique is included Murrieta-Lee, JC, Pomfrett CJD, Beatty, PCW, Polydorides, N., Mussel, CB, Waterfall, RC, McCann, H: Sub-second observations of EIT voltage changes to the human scalp due to brain stimulus ", Proc of the 26th Annual International Conference of the IEEE EMBS, San Francisco, 2004, pp. 1317-1320 , described. The content of these publications is hereby incorporated by reference.

The picture above left in 13 was generated from measurements made approximately 80 milliseconds after the application of visual stimulus. It is shown that the lateral knee bump (LGN) 80 at the time the data from which this image was generated was active. At this time, the LGN received information about the brightness and position of the visual stimulus that originated from the rods of the retina. The LGN receives an input from the optic nerve. The LGN is active during most of the visual processing, as seen in the six pictures of 3 is apparent.

The picture above in the middle in 13 was generated from measurements made approximately 105 milliseconds after the application of visual stimulus. The LGN 80 is still active, but at this point neurological modeling shows that information about the color of the visual stimulus coming from the suppositories of the retina is processed. Brightness and outline information will be in one area 81 processed (called area V1) processed on the back of the brain.

The top right image was generated from measurements taken approximately 137 milliseconds after the application of visual stimulus. It can be seen that the activity in the field 81 has significantly increased, with this part of the brain working to integrate color, stereo, and structural information that is ready for transmission to higher brain regions. In addition, feedback information is sent to the LGN 80 to refine its processing of future information. In this picture is an intense activity in the LGN area 80 and increased activity in the V1 region 81 specified.

The picture below left in 13 was generated from measurements made approximately 186 milliseconds after the application of visual stimulus. It can be seen that information is now available to other visual centers 82 . 83 be passed on both sides of the brain. These areas 82 . 83 are responsible for the color processing and the identification of objects.

The picture below in the middle in 13 was generated from measurements obtained 201 milliseconds after the application of visual stimulus. Big dark areas 84 . 85 . 86 correspond to the activity in the left anterior belt turn and the connected regions of the limbic system. These regions are responsible for many things, but here the feeling that comes with detecting an item is of the utmost importance. The same regions 84 . 85 . 86 are responsible for deciding whether a noxious stimulus is actually painful. In the present circumstances, it is likely that these areas of the brain will determine information in the form of "that was a flash again". Imaging using this technique is therefore able to directly represent human emotions that arise from the sensory stimulus.

The picture below right in 13 was generated from measurements obtained 248 milliseconds after the application of visual stimulus. Most of the processing is done by then, and higher brain regions determine what action to take on the information received. Large parts of the brain prepare for a possible subsequent flash, and therefore random burst sequences are necessary to prevent acclimatization as described above.

The referring to 12 The measurements described above can be used to capture images of the 13 to produce shown type. In particular, some of the voltage measurements obtained may be selected based on a time the stimulus was applied and a certain delay, and the selected voltage measurements may be used to generate the images.

Especially if a stimulus 72 At a time t _{s is} applied and measurements made after a delay t _d after the application of the stimulus are needed, voltage measurements taken during the measurement frame 71 are processed, the measuring frame 71 after the delay t _d begins.

It is understood that in the example based on the delay t _d , the measuring frame 71 begins at the time when measurements are needed (as indicated by the delay t _d ) and thus the measuring frame can 71 as the basis for the restoration of images of in 13 shown used type. It is also understood that in other examples, a measuring frame may not begin at the required time. In this case, measurements from two measurement frames can be used as the basis for the image restoration. If it is z. For example, if image recovery is desired to be based on measurements taken after a delay t _D after stimulus application at time t _s , measurements taken during current injections 73 were used as a basis for image recovery. Ie. that measurements taken during certain current injections of the measuring frame 71 and measurements made during certain current injections of the immediately subsequent measurement frame can be used, with the total number of current injections used being twenty.

As As stated above, each current injection is carried out for 500 μs. Delays after the stimulus application, in the information are required are typically of an order of magnitude the tenth of a millisecond, and thus begins a certain current injection within an acceptable tolerance of any prescribed Delay of probable size. D. H. that any prescribed delay measurements, on an activity within 0.25 ms (250 μs) based on this delay, as a basis for a picture recovery can be used, and that 0.25 ms given the size ratios the specified delay an insignificant error represent.

Alternatively, the measurement frame whose start is closest to the time indicated by the delay t _D may be used as the basis for the image restoration. In this case, one frame will always start with 5 ms of a given delay, and thus the resolution will probably be acceptable in many applications, given the general nature of the delays that are likely to be imposed.

When measurements are made continuously, as with respect to 12 described, understands it that the restoration of images representing neural activity at some point after stimulus application can be performed as an off-line process by simply selecting the appropriate measurements from the continuously obtained measurements, taking the measurements obtained based on the required Delay can be selected. Thus, it is understood that a sliding window of time may be moved over the collected measurements to monitor changes in neural activity after stimulus application.

In 12 is shown as the stimulus 72 takes place at a certain time. It is understood that the charm 72 actually has an associated duration. It can, for. For example, a visual stimulus can be applied to a subject for 30 to 50 ms. The delay after which measurements are made may be defined in relation to the onset of stimulus application.

14 shows an alternative implementation of the head holder 3 out 1 , Here is the head holder as a collar 90 implemented. This is particularly advantageous in applications where it is desired to support the neck of a patient, e.g. B. during a surgical procedure. It shows how four electrodes 2 attached to the head of the patient, and these electrodes are at respective terminals 2 B connected by the collar 90 via respective cables 2a to be provided. It will be appreciated that the provision of the collar-shaped headband not only provides a means for supporting the patient's head, but also allows for practical attachment of the electrodes to the collar with short cable lengths, thereby improving the usefulness of the device.

14 shows a connection 91 who the collar 90 to the base unit 4 followed. The internal components of the collar 90 are similar to those of the head holder described above 3 , and data will be between the head holder 3 and the base unit 4 as generally described above. Digital components, located in the interior section 13 of the head holder 3 can be located in a lower part of the collar 90 while analog components located in the outer section 10 of the head holder 3 are located in an upper part of the collar 90 can be located. An intermediate portion for accommodating analog-to-digital and digital-to-analog converter circuits may be in an intermediate portion of the collar 90 between the upper part and the lower part.

The described embodiments could be used to help diagnose a blind patient. To possible reasons for blindness, the z. B. caused by a blow to the head belong Retinal detachment or brain damage. The application a visual stimulus on the patient and the examination of a picture or multiple images of the patient's brain using the tomography technique described above, allows an analysis of the cause of the blindness. In such a Examination, the doctor knows where brain activity to expect at certain delays after stimulus application is. If any brain activity is observed, then the retina obviously did not detach because signals are sent to the brain, thus indicating that the blindness may have been caused by a brain damage. However, if no response to the stimulus is observed in the brain, The reason could be either a retinal detachment or a heavier brain damage. If some brain activity can be observed, images can be generated on Voltage measurements are based, leading to different delays after the stimulus application were achieved, so that pictures after generated a certain delay, not that show expected behavior. The doctor receives thus one Idea of the position of the brain damage.

As another example, if a patient has symptoms of stroke, one embodiment of the present invention may be used to map the brain state. Electrodes are attached to the patient's head, as in 1 and 4 pictured and as described above. The patient is presented with stimuli and the response is monitored. A nerve stimulator is placed on a patient's leg and triggered to provide a number of temporally unequally distributed stimuli. The EIT measurements obtained at a predetermined time after each stimulus are used as the basis for creating an image as described above. When this imaging process is completed, an audio stimulus is provided and a series of images is again created. Similarly, a visual stimulus is provided and a number of images are created. The three sets of images, each created in response to another type of stimulus, allow for a comprehensive assessment of brain function, allowing assessment of the severity of stroke.

The image-forming apparatus necessary for this process is relatively small and relatively inexpensive to provide, particularly in comparison to the devices used in imaging technologies such as magnetic resonance imaging and computed tomography. Thus, the device for a general practitioner can be provided so that he can quickly and easily assess whether a patient is to be referred to a neurologist.

In some embodiments of the present invention, e.g. For example, in those who are concerned with the diagnosis of the cause of blindness, only certain parts of the brain need to be imaged. With reference to a known neurological model of the brain, the specific parts of the brain to be imaged can be identified. Using this information, the number of current injections can be reduced to one or two carefully selected couplings. For example, when mapping the visual path, you can let current flow through between the front and back regions of the head. Ie. that the coupling is parallel to the visual path, which generally goes from the eyes to the back of the brain. When monitoring a response to an auditory sensation, monitor the path from the ears to the auditory cortex on the side of the brain, and thus attach electrodes at least on the side of the head. In alternative embodiments, all the current injections referred to with reference to FIG 12 can be used, but only a limited number of voltage measurements can be made for each coupling. Alternatively, both the introductions and the measurements may be selected based on a neurological model and the stimulus applied.

It may be desirable to use other stimuli that are in the environment of the patient occur whose application is not controlled instead of the targeted use of stimuli as above described. This is possible by the timing of the Occurrence of the stimulus is recorded and the recorded Time is used in the selection of voltage measurements.

Various Stimuli have been described above. In some embodiments In the invention, the stimulus applied is transcranial magnetic stimulation. d. H. a charm, the rapidly changing magnetic fields which cause a brain activity below Using the techniques described above can be observed.

at the embodiments described above have been explained that voltages between pairs of electrodes are measured while Current between a selected electrode pair is coupled. In alternative embodiments of the invention, a Voltage applied between a selected pair of electrodes and currents can be between other electrode pairs be measured while the voltage is applied.

In the embodiments described above, it has been explained that power is provided to electrodes attached to the head of a subject by placing the electrodes on two bus bars 17a . 17b be connected (see 3 ). It should be understood that some aspects of the present invention may be implemented in a system in which each electrode is provided with its own power source, thereby obviating the need for the bus bars but requiring a larger number of power sources.

Even though various embodiments have been described above, It is understood that various modifications to the described Embodiments can be applied without To leave spirit and scope of the invention.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 1615550 [0004]

Cited non-patent literature

• - Cruccu G, et al. "Unmyelinated trigeminal pathways as assessed by laser stimuli in humans", Brain 2003 Oct; 126 (Pt 10): 2246-2256 [0106]
• - N., Lionheart WRB and McCann, H .: "Krylov Subspace Iterative Techniques: On the detection of brain activity with electrical impedance tomography" IEEE Transactions on Medical Imaging, Vol. 21, No. 6, June 2002, pp. 596-603 [0151]
• - Murrieta-Lee, JC, Pomfrett CJD, Beatty, PCW, Polydorides, N., Mussel, CB, Waterfall, RC, McCann, H: Sub-second observations of EIT voltage changes to the human scalp due to brain stimulus ", Proc of 26th Annual International Conference of the IEEE EMBS, San Francisco, 2004, pp. 1317-1320 [0151]

Claims (77)

Tomographic data acquisition device, full: a variety of electrodes for attachment arranged on a measuring subject, a power source, a Power supply line connected to the power source and connectable to each of the plurality of electrodes; one Control device that is arranged to select a selected electrodes Pair of electrodes to connect to the power supply line, around current between the selected pair of the plurality of Provide electrodes; and Measuring circuits arranged are to make voltage measurements between selected electrodes to achieve the variety of electrodes while power is provided between the selected pair of electrodes. Apparatus according to claim 1, wherein the power supply line includes first and second power supply lines, and the controller is arranged to a first electrode of the selected Pair of electrodes to the first power supply line to connect and a second electrode of the selected pair of electrodes to connect to the second power supply line. Apparatus according to claim 2, wherein the power source comprising first and second current sources, the first current source is connected to the first power supply line and the second Power source connected to the second power supply line is. Apparatus according to claim 3, wherein the control device the first power source controls to make a first current on the first one To provide power supply line, and the second power source controls to a second power source on the second power supply line provide, wherein the first and second streams substantially the same size. Apparatus according to claim 4, wherein the first and second currents are alternating currents, and the first and second currents are 180 degrees out of phase with each other are. Device according to one of the claims 2-5, wherein each electrode of the plurality of electrodes is connected to each the first and second power supply lines connectable is. Apparatus according to claim 6, wherein each electrode the plurality of electrodes to each of the first and second power supply lines via a respective switch can be connected. Apparatus according to claim 7, wherein the control device is arranged to control the switches. Device according to one of the preceding claims, further comprising current measuring circuits arranged to provide a Measurement of the current between the at least one selected Electrode pair flows to achieve. Apparatus according to claim 9 in dependence of claim 2, wherein the current measuring circuits are arranged to obtain a measurement of the current on each of the first and second power supply lines. Device according to one of the preceding claims, further comprising a processor arranged to achieve the achieved To process voltage measurements to produce data that has a Indicate impedance distribution in at least part of the subject. Apparatus according to claim 11 in dependence of claim 9 or 10, wherein the processor is arranged to receive the to process the voltage measurements and the achieved current measurement, to generate data showing the distribution of conductivity in at least part of the subject. Apparatus according to claim 11 or 12, wherein the Data that has a conductivity distribution in at least specify part of the subject, include at least one image. Apparatus according to any one of the preceding claims, wherein the controller is arranged to provide flow successively between a plurality of selected pairs of the plurality of electrodes. and the sensing circuits are arranged to achieve a plurality of voltage measurements between selected ones of the plurality of electrodes while providing current between each of the plurality of selected electrode pairs. A tomographic data acquisition device comprising: a Variety of electrodes suitable for attachment to a measuring subject are arranged a power source arranged to act as Input to receive an indication of a stream that is between a to provide selected pair of the plurality of electrodes is, and a current based on the specified current between to provide the selected electrode pair; Voltage measuring circuits which are arranged to measure voltage between selected ones To achieve electrodes of the plurality of electrodes while Power provided between the selected pair of electrodes becomes; and Current measuring circuits arranged to a To achieve current measurement between the selected Electrode pair is provided. Apparatus according to claim 15, wherein the power source a first power source and a second power source, a first electrode of the at least one selected pair of electrodes connected to the first power source and a second electrode of the at least one selected pair of electrodes to the second Power source is connected, and arranged the current measuring circuits are to achieve a current measurement that is suitable for each of the at least one first electrode and the at least one second Electrode is provided. Apparatus according to claim 15 or 16, further comprising a processor arranged to achieve the achieved To process voltage measurements and the achieved current measurement, to generate data that has a conductivity distribution in at least part of the subject. Apparatus according to claim 17, wherein the data, the one impedance distribution in at least one part of the subject specify at least one image. Device according to one of the claims 15 to 18, wherein the controller is arranged to successively power between a plurality of selected pairs of the plurality to provide electrodes, and arranged the measuring circuits are selected to a variety of voltage measurements between To achieve electrodes of the plurality of electrodes while Current between each of the plurality of selected electrode pairs provided. A tomographic data acquisition device comprising: a Variety of electrodes suitable for attachment to a measuring subject are arranged a power source that is arranged to power between a first pair of the plurality of electrodes during provide a Stromeinkoppelzeitraums; and Voltage measuring circuits arranged to measure stress between at least a second one Pair of the plurality of electrodes during part of the Current injection period, which is referred to as a measurement period, too achieve; wherein the Stromeinkoppelzeitraum a first period a predetermined duration, called the settling period during which no voltage measurements are obtained, and each measurement period is part of the current injection period, which follows the settlement period; and the voltage measuring circuits comprise at least one measuring component, wherein the or each measuring component connected to one of the at least one second pair of electrodes and the or each measuring component is a saturation recovery time which satisfies a criterion related to the duration of the balancing period is defined. Apparatus according to claim 20, wherein the measuring component an amplifier is. Apparatus according to claim 20 or 21, wherein said The criterion is that the saturation recovery time is shorter is the duration of the balancing period. Apparatus according to claim 20, 21 or 22, wherein the power source provides AC power. Apparatus according to claim 23, wherein the alternating current has a frequency of about 10 kHz. Apparatus according to claim 24, wherein the Stromeinkoppelzeitraum has a duration of 500 microseconds and the Balancing period has a duration of 100 microseconds. Apparatus according to claim 25, wherein the or each amplifier has a saturation recovery time of less than 100 μs. Apparatus according to claim 26, wherein the or each amplifier has a saturation recovery time of less than 50 μs. Apparatus according to claim 27, wherein the or each amplifier has a settling time of approximately 10 μs. Device according to one of the claims 20 to 28, further comprising data processing means arranged are to process the obtained voltage measurements to data to generate a conductivity distribution in at least specify a part of the subject. Apparatus according to claim 29, wherein the data, the one conductivity distribution in at least part of the Specify subjects, include at least one image. Device according to one of the claims 20 to 30, wherein: the control unit is arranged, to stream sequentially between a variety of selected ones Providing pairs of the plurality of electrodes, wherein the current between each selected electrode pair in a respective one Current injection period is provided the measuring circuits are arranged to perform a variety of voltage measurements between selected electrodes of the plurality of electrodes during a part of each power input period, the measuring period is designated to achieve; and each power input period a first period of a predetermined duration, the is called a settling period, during which no Voltage measurements are achieved, and each measurement period is part of one respective Stromeinkoppelzeitraums is on the Ausregelzeitraum follows. Tomographic data acquisition device, comprising first and second units, wherein: the first unit connections to a plurality of electrodes adapted for attachment to a Measuring subjects are arranged; a power source that arranged is to make electricity between at least a first pair of the plurality of electrodes, voltage measuring circuits arranged are to voltage measurements between at least a second pair of electrodes to achieve the variety of electrodes while the current provided between one of the at least one pair of electrodes and data processing circuits arranged to to process the obtained voltage measurements to be processed Generate data and the processed data for the second Unit provide, the voltage measurements by a first data set and the processed data comprise a second amount of data, the second amount of data being smaller is considered the first dataset; and the second unit of data receiving circuits which are arranged to receive the processed data from the first unit to receive. Apparatus according to claim 32, wherein the stream AC is. Apparatus according to claim 33, wherein the voltage measurements between one of the at least one second electrode pair a Include a plurality of voltage values, each to a respective one Time to be achieved. Apparatus according to claim 34, wherein the processed ones Data, the voltage measurements between one of the at least one represent second pair of electrodes, include an in-phase value. Apparatus according to claim 35, wherein the in-phase Value a correlation between the obtained voltage measurements and a reference waveform. Apparatus according to claim 36, wherein the data processing circuits are arranged to the in-phase value from the obtained voltage measurements and generate the reference waveform. Apparatus according to claim 35, 36 or 37, wherein the processed data, the voltage measurements between or each of the at least one second electrode pair, further comprise a quadrature value. Apparatus according to claim 38, wherein the quadrature value a correlation between the obtained voltage measurements and a indicates a phase-shifted reference waveform. Device according to one of the claims 32 to 39, where the processed data, the voltage measurements between represent the or each of the at least one second pair of electrodes, 32 bits of data representing a 16-bit in-phase value and a 16-bit quadrature value include. Device according to one of the claims 32-40, further comprising a processor arranged to process the processed data to generate data the one impedance distribution in at least one part of the subject specify. Apparatus according to claim 41, wherein the data, the one conductivity distribution in at least part of the Specify subjects, include at least one image. Device according to one of the claims 32 to 42, wherein the controller is arranged to power successively between a plurality of selected pairs to provide the plurality of electrodes, and the measuring circuits are arranged to perform a variety of voltage measurements between to selected electrodes of the plurality of electrodes achieve power between each of the many is provided to selected pairs of electrodes. Printed circuit board comprising a first conductor which extending in a first direction in a first plane, wherein the circuit board a shield for the first conductor the shield provides first and second shield conductors which extends essentially in the first direction in the extend first level, and third and fourth shielding, the essentially in the first direction in third and fourth levels extend, wherein the first, third and fourth levels substantially to each other are parallel and offset from each other, and the first level located between the third and the fourth level. A circuit board according to claim 44, further comprising a connection between the first conductor and the first, second, third and fourth shielding conductors, wherein the terminal is arranged is to the first, second, third and fourth shielding conductor to hold onto the potential of the first conductor. The printed circuit board of claim 45, wherein the terminal includes an amplifier. A printed circuit board according to claim 44, 45 or 46, wherein a non-conductive material between the third and fourth levels and inserted between the first and fourth levels. Printed circuit board according to one of Claims 44 to 47, wherein a non-conductive material between the first conductor and the first shield conductor and between the first conductor and inserted into the second shielding conductor in the first plane is. A tomographic data acquisition device comprising: a Variety of electrodes suitable for attachment to a measuring subject are arranged a power source that is arranged to power between a selected pair of the plurality of electrodes provide; Measuring circuits that are arranged to voltage measurements between selected electrodes of the plurality of electrodes while achieving power between the selected Electrode pair is provided; and a printed circuit board after one of claims 44 to 48, wherein the first conductor arranged is to power from the power source for electrodes of the variety of electrodes. Apparatus according to claim 49, wherein the circuit board further comprises a second conductor substantially in the first direction extends in the first plane, wherein the circuit board provides a shield for the second conductor, wherein the shield comprises fifth and sixth shielding conductors, which are essentially in the first direction in the first level extend, and seventh and eighth shielding conductors, which are substantially extend in the first direction in the third and fourth planes, and the second conductor is arranged to receive power from the power source for electrodes of the plurality of electrodes. Apparatus according to claim 50, wherein each of said Electrodes can be connected to each of the first and second conductors is. Apparatus according to claim 51, wherein the power source comprising first and second current sources, the first current source to the first conductor and the second current source to the second conductor connected. The device of claim 52, further comprising a controller arranged to the first power source to control to provide a first current on the first conductor, and to control the second current source to generate a second current on the second conductor, the first and second Streams are essentially the same size have, however, phases that differ by about 180 degrees are. Device according to one of the claims 49 to 53, comprising a control unit which is arranged to stream sequentially between a variety of selected ones To provide pairs of the plurality of electrodes, and the measuring circuits are arranged to take a variety of voltage measurements between to selected electrodes of the plurality of electrodes achieve power between each of the many is provided to selected pairs of electrodes. A tomographic data acquisition device comprising: a Variety of electrodes suitable for attachment to a measuring subject are arranged analog circuits that are arranged to provide power for pairs of the electrodes and the Measure voltage between selected electrodes; digital Control circuits; and a housing that has an internal volume defined in which the analog and digital circuits are arranged are; the volume having an inner portion and an outer portion having the analog circuits in the outer portion are arranged, wherein the digital circuits in the inner portion are arranged, and the electrodes to the analog circuits are connected through the housing. Apparatus according to claim 55, further comprising Digital / analog and / or analog / digital converter circuits, wherein the volume further comprises an intermediate portion interposed between the inner portion and the outer portion is located, and the converter circuits are arranged in the intermediate section. Apparatus according to claim 56, wherein the outer portion by an outer boundary of the housing and a first line, which is generally parallel to the outer boundary of the housing extends is defined. Apparatus according to claim 57, wherein the intermediate portion through the first line, which is generally parallel to the outer boundary of the housing, and a second line that extends generally parallel to the outer boundary of the housing is defined, wherein the second line is the inner portion defined in a central portion of the housing. Device according to one of the claims 55 to 58, wherein the housing has an outer boundary characterized by two straight parts and a curved part, which connects the two straight parts is defined. Apparatus according to claim 59, wherein the two straight parts are substantially parallel to each other. Tomographic data acquisition device for Obtain tomographic data from a human or animal Subjects, the device comprising: a Variety of electrodes for attachment to a human or animal subjects are arranged; Circuits that are arranged to provide power for pairs of the electrodes and measure the voltage between selected electrodes; and a housing in which the circuits are arranged are, with the electrodes to the circuits through the housing are connected through, wherein the housing has a collar defined in use, around the neck of the human or animal subjects. Apparatus according to claim 61, wherein the housing is generally U-shaped and defines an opening to to pick up the neck of the human or animal subject. Device according to one of the claims 55 to 62, wherein the circuits are controlled to power one by one between a plurality of selected pairs of the plurality of electrodes, and a variety of voltage measurements between selected electrodes of the plurality of electrodes achieve power between each of the many is provided to selected pairs of electrodes. Tomographic data acquisition device, comprising first and second units, wherein: the first unit a variety of electrodes arranged for attachment to a measuring subject are; a power source that is arranged to supply current between at least to provide a first pair of the plurality of electrodes, voltage measurement circuits, which are arranged to make voltage measurements between at least one while achieving the second pair of the plurality of electrodes the current between the at least one selected pair of electrodes is provided, and control circuits which are arranged to control the power source and the voltage measurement circuits, and to provide voltage measurement data for the second unit, includes; and the second unit of data receiving circuits, the are arranged to voltage measurement data from the first unit received, and a power supply, wherein the second Unit is arranged to recycle energy from the power supply is generated, and the processed energy for the first unit provide, with the power supply from the first unit is isolated. Apparatus according to claim 64, wherein the second Unit comprises a housing defining an internal volume, the first and second sections, wherein the first section the data receiving circuits and the second section the power supply houses. Apparatus according to claim 65, wherein a separating line is provided between the first and second sections. Apparatus according to claim 65 or 66, wherein said second unit further comprises: a data processing interface, which is arranged to receive received voltage measurement data for to provide a computer. Apparatus according to claim 67, wherein said voltage measurement data for the data processing interface from the data processing circuits via be provided at least one circuit breaker. Device according to one of the claims 64-68, wherein the second unit is arranged to provide energy for the first unit of the power supply via the separation line provide. Device according to one of the claims 64 to 69, wherein the second unit further interfaces with a stimulus generator, which is arranged around the stimulus generator to cause a stimulus to be applied to the measuring subjects. Tomographic data acquisition device, comprising first and second units, wherein: the second unit is a stimulus application controller which is arranged to apply a stimulus to the Induce measurement subjects and provide stimulus application data, the times of stimulus application for the first unit provide; wherein the first unit of data receiving circuits arranged to receive stimulus application data, a variety of electrodes suitable for attachment to a measuring subject are arranged, a power source, which is arranged to power between at least a first pair of the plurality of electrodes to provide voltage sensing circuits that are arranged to stress measurements between at least a second pair of To provide variety of electrodes while the current between the at least one selected pair of electrodes is provided, and data processing circuits arranged are to achieved voltage measurements and received stimulus application data to provide for the second unit; and the second Unit further comprises data receiving circuits arranged are to voltage measurements and the stimulus application data of the first unit to receive. Device according to one of the claims 1 to 43 or 49 to 71, wherein the electrodes are arranged for attachment on the human or animal body to get data from to achieve a human or animal subject. Device according to one of the preceding claims, further comprising a stimulus application signal generator arranged is to generate a signal to cause a stimulus generator to apply a stimulus to the subject. The device of claim 73, wherein the stimulus generator is arranged to be a sensory stimulus or a transcranial To generate magnetic stimulation. Apparatus according to claim 73 or 74 to the: Receive a user input, which is a delay indicates; and Processing voltage measurements that lead to a Time after the stimulus application was achieved by the delay is determined to generate data that has an activity of the subject's nervous system at the time of stimulus application to create. Device according to one of the claims 1 to 43 or 49 to 75, with the electrodes for attachment to the head a human or an animal subject are arranged, and the electrodes of the or each at least one selected Pairs of the plurality of electrodes are arranged to be on the head in attached in substantially diametrically opposite positions to be. Device according to one of the claims 1 to 43 or 49 to 75, wherein the measuring circuits are arranged to To achieve voltage measurements between electrodes arranged are to be arranged next to each other.