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    • 专利摘要:
    An apparatus (1) for electro-impedance tomography (30) comprising an electrode assembly having a plurality of electrodes (33) spaced apart therefrom, a signal feed unit (51) and a signal detection unit (50), a computing and control unit (70) is configured to determine a situation with an axial displacement of the electrode assembly on a thorax (34) of a human being and to provide a control signal (79) indicating the situation with axial displacement of the electrode assembly. The computing and control unit (70) may be configured as a central unit or an array of distributed computing devices (cloud computing) to detect and provide the axial offset.
    公开号:CH713098A2
    申请号:CH01448/17
    申请日:2017-11-28
    公开日:2018-05-31
    发明作者:Gärber Yvo (Dr )
    申请人:Draegerwerk Ag & Co Kgaa；
    IPC主号:
    专利说明:

    Description: The present invention relates to an apparatus for electro-impedance tomography with a determination of an axial position of an electrode arrangement associated with the electro-impedance tomography apparatus.
    Furthermore, the present invention relates to a method for operating an apparatus for electrical impedance Tomo-graphie with a determination of an axial position of the electro-impedance tomography device associated electrode assembly.
    Devices for electro-impedance tomography (EIT) are known from the prior art. These devices are designed and intended to generate an image, a plurality of images or a continuous image sequence from signals obtained by means of electro-impedance measurements and from data and data streams obtained therefrom. These images or sequences of images show differences in the conductivity of various body tissues, bones, skin, body fluids and organs, especially the lung, which are useful for observing the patient's situation.
    For example, US Pat. No. 6,236,886 describes an electrical impedance tomograph with an arrangement of a plurality of electrodes, current supply to at least two electrodes, signal detection at the other electrodes and a method with an image reconstruction algorithm for determining the distribution of conductivities of a body such as bones, skin and blood vessels in a basic configuration with components for signal acquisition (electrodes), signal processing (amplifiers, A / D converter), power supply (generator, voltage-current converter, current limiting) and components for control.
    [0005] It is stated in US Pat. No. 5,807,251 that in the clinical application of EIT it is known to provide a set of electrodes which are arranged at a certain distance from one another, for example around the thorax of a patient in electrical contact with the skin become. For an electrical current or voltage input signal, alternating electrodes are alternately applied between different or all of the possible pairs of electrodes arranged adjacently to one another. While the input signal is applied to one of the pairs of electrodes disposed adjacent to each other, the currents or voltages between each adjacent pair of the remaining electrodes are measured and the obtained measurement data is processed in a known manner to provide a representation of the resistivity distribution over one Cross section of the patient around which the electric denring is arranged to receive and display on a screen.
    Electro-impedance tomography (EIT), in contrast to other radiological imaging methods (X-ray machines, radiological computer tomographs), has the advantage that a negative radiation load for the patient does not occur. In contrast to sonographic procedures, the EIT can be used for continuous image acquisition via a representative cross-section of the entire thorax and the patient's lungs with the help of the electrode belt. In addition, there is no need to use a contact gel, which must be applied before each examination. Electro-impedance tomography (EIT) thus offers the advantage of enabling continuous monitoring of the lungs in order to observe and document the course of therapy of a mechanically ventilated or spontaneously breathing patient.
    By means of an electrode assembly around the chest of a patient with an EIT device, as it is known for example from US 5 807 251, an impedance measurement is performed on the chest and from the impedance an image of the patient's lungs by means of a conversion to the Chest geometry generated.
    With a total of, for example, 16 electrodes mounted around the thorax of a patient, an EIT device can image in one round of current feeds to two electrodes each and record voltage measurement values (EIT measurement signals) on the remaining electrodes the lung of 32 x 32 pixels produce. In this case, a number of 208 impedance measured values at the electrodes is detected at the 16 electrodes. From these 208 impedance measured values, an amount of 1024 pixels then results with the EIT image reconstruction.
    The electrodes are arranged to carry out the electrical impedance tomography (EIT) in a horizontal arrangement around the thorax of a living being and comprehensively surrounding a region of the lungs of the living being. This results in a position in the plane of the electrode assembly which may be referred to as a thoracic-axial position of the electrode assembly at the periphery of the transverse plane of the body.
    When using an electrode belt as an electrode arrangement, in or on which the electrodes are arranged and held at fixed positions with a defined distance to each other, the possibilities for deviations in the vertical position between adjacent electrodes to each other on the chest are comparatively small. In the positioning of the electrode belt on the thorax, a vertical offset during image reconstruction, in which a horizontal sectional image through the thorax is determined as a so-called dorsal view, thus plays a comparatively minor role. The horizontal cross-sectional image is displayed inclined by only a few degrees. In addition, in the electrical supply to the electrodes not only electrical fields in the cutting plane itself, but also in Be-rich above and below about 5 to 10 centimeters of the cutting plane, which then in any case then included in the impedance measurements. Therefore, in the Tidal picture, the slightest possible inclination of the electrode belt as an effect is virtually imperceptible. In addition, a comparatively reproducible and representative horizontal position of the electrode belt in the application can be achieved by an orientation on the costal arches, so that possible errors in the horizontal attachment of the electrode belt to the thorax are rather rare.
    In contrast, the horizontal position of the electrodes is important in that for the generation of the dorsal view of the physiologically expected, deviating from the ideal circular circular or cylindrical shape, almost elliptical geometry of the thorax is important in this regard, that for inclusion of the elliptical shape in the image reconstruction information is required at which position, ie front (sternum), side (ribs) or back (spine) which electrode is attached to the rib cage. Different types of living beings, which have in common that they exchange gases with the aid of pulmonary respiration, each have per se typical circumferential shapes in the body structure surrounding the lungs (musculature, skeleton, organs, body tissue, skin). A deviation of the shape of the ribcage from an ideal circular shape is, for example, given in principle in human beings to the effect that the typical peripheral shape is usually elliptical rather than circular. In other living things, such as horses, dogs, pigs, rodents or birds, depending on the species, other typical forms of the peripheral forms arise. In this respect, the idea of the present invention with the device for electrical impedance tomography with a determination of a position of an electrode arrangement associated with the electro-impedance tomography device is not only for the application of the electrical impedance tomography in human Living beings, but also applicable to a wide biodiversity of wildlife. In human beings, in particular, the area of the electrode plane used in electro-impedance tomography (EIT), ie, the plane in the horizontal section through the thorax, is approximately in the region of the third, fourth, fifth ribs, as well as the fifth, sixth , Seventh thoracic vertebrae have a substantially elliptical peripheral shape (ellipsoid) in the region of the upper body and the thorax. In addition to the geometric shape with an anatomically predetermined elliptical design area, there are other characteristic features which influence the impedance, impedance differences and the impedance distribution measured by means of EIT and have a transversal view during image reconstruction for displaying the ventilation of the lung In the mathematically-algorithmically applied way of image reconstruction, consideration is given. Thus, in addition to the lungs, with areas perfused in the rhythm of the heartbeat and ventilated in the rhythm of the respiratory cycle, the heart, with essentially the same rhythm of the heartbeat, however, as in the same constant blooded areas, in this electrode plane also elements of the skeleton, in the front area of the The torso is located in the upper part of the body and the spinal column in the back-sided area, the impedances of which are both unaffected by the blood flow and the respiratory cycle. Rather, both the sternum and, in particular, the vertebral column have an impedance which is deviating from these and other regions (heart, skin, lung, tissue) in the electrode plane and substantially constant.
    By means of the so-called eccentricity, an ellipse can be described as a closed oval shape as a deviation from a circular shape as a dimensionless number.
    The eccentricity describes the relationship of the two perpendicular semi-axes. In the case of a circle, both half-axes are of identical length, one ellipse is defined by a shorter half-axis and one - compared to the shorter half-axis, - a longer half-axis of different lengths. Due to the elliptical shape and depending on their eccentricity, different distances result between feeding electrodes and oppositely measuring electrodes, depending on whether along the frontal plane of the human body the feeding at the front side with measurement at the back area, or feed on the back Be -rich with measurement on the front side areas or whether along the transverse axis of the human body, the feed on the left side of the body with measurement on the right side of the body, and the feed on the right side of the body with measurement on the left side of the body. In the case of the elliptical peripheral shape of the human body, the two constellations of feeds / measurements respectively opposite on the left / right side of the body represent injections / measurements on the longer half-axis and the two constellations of feeds / measurements respectively opposite to the front of the body / body back represent the elliptical one Peripheral shape of the human body feeds / measurements on the shorter half-axis dar. Only in a circular circumference, such as in a pig, affect the shape and the resulting differences in the distances between feeding and opposing electrodes are not sufficient. In this case, however, at least the elements of the skeleton or organs still cause differences in the impedances between feeding electrodes and opposing electrodes.
    A practical example is intended to illustrate the influence of how an axial rotation of a mounted in a horizontal position electrode belt effect.
    A lateral or axial displacement of the electrode belt with a number of 16 electrodes in the horizontal alignment around the thorax by a distance of an electrode results in a difference in a patient with an average diameter of the chest of 0.80 m of a human the predetermined and expected orientation of approximately 0.05 m, corresponding to a twist angle of 22.5 °. With a number of 32 electrodes, the difference correspondingly reduces to about 0.025 m, corresponding to a twist angle of 12.25 °.
    In WO 2015/048 917 A1, a system for electrical impedance tomography is shown. The EIT system is capable of detecting electrical characteristics of a patient's lungs as impedances. For this purpose, impedance values or impedance changes of the lungs are detected by means of voltage or current injection between two or more electrodes and signal detection at an electrode arrangement and further processed by means of data processing. The data processing includes a reconstruction algorithm with a data processor to determine and reconstruct the electrical properties from the impedances. When reconstructing the electrical properties from the collected measurement data, an anatomical model is selected from a variety of anatomical models based on biometric data of the patient and the reconstruction of the EIT image data is adjusted based on the anatomical model or the biometric data. This adaptation requires the user to enter biometric data into the system. Biometric data include age, gender, height, as well as a patient's chest circumference. This means that boundary conditions must be entered by the user before starting the measurement with the electro-impedance tomography system in order to be able to select and apply a suitable reconstruction model based on a selected anatomical model.
    For the operation of electroimpedance tomography systems, it is not necessarily advantageous in many application situations to measure or record and input a large number of patient data before starting the application. In particular, the requirement for data relating to the characteristics of the body such as thoracic circumference, size and weight implies that the anatomical models deposited in the device are also applicable to a large number of patients.
    In addition, the problem of how the electrode belt is applied or positioned on the body is not addressed by WO 2015/048 917 A1. Also, by inputting biometric data of the patient, it is not possible to determine a horizontal position of the belt, and in particular not an axial rotation or displacement about the vertical body axis (longitudinal or sagittal or frontal body plane). Thus, the correct positioning of the electrode belt remains the responsibility of the user, despite the use of anatomical models and consideration of biometric data.
    The present invention has been made aware of the disadvantages of the known prior art described above, a, suitable for imaging of the lung device for electrical impedance tomography (EIT) with one, the electrical impedance Indicate the tomography device associated electrode assembly, which makes it possible to determine an axial offset of the electrode assembly or an axial rotation a of the electrode assembly.
    It is another object of the present invention to provide an apparatus for imaging the lung suitable for electrical impedance tomography (EIT) with a, the electric impedance tomography device associated Elek- trodenanordnung, which makes it possible the lateral offset of individual electrodes of the electrode assembly or the axial rotation a of the electrode assembly to be considered in a determination and imaging of a Tidalbildes the lung.
    A further object of the present invention is to provide a method for operating an apparatus for imaging the lungs suitable for electro-impedance tomography (EIT), which is a determination of an axial offset of the electrode assembly or an axial rotation a of Electrode arrangement allows.
    These and other objects are achieved by the accompanying independent claims.
    According to a first aspect of the invention, the object is achieved by a device having the features of patent claim 1.
    According to a further aspect of the invention, the object is achieved by a method having the features of patent claim 10.
    Advantageous embodiments of the invention will become apparent from the dependent claims and will be explained in more detail in the following description with partial reference to the figures.
    Furthermore, the method can also be provided as a computer program or computer program product, so that the scope of protection of the present application also extends to the computer program product and the computer program.
    At the beginning, some of the terms used in this patent application will be explained in more detail.
    For the purposes of the present invention, a period of observation is to be understood as a time period in a time course. The beginning and end of such a period of observation are given either by fixed or adjustable times or by events given by the characteristics of respiration or respiration. Examples of viewing periods which are based on respiration or respiration are a respiratory cycle, multiple respiratory cycles, portions of respiratory cycles such as inspiration (inspiration), inspiratory pause, exhalation, expiratory pauses.
    For the purposes of the present invention, EIT measuring signals are to be understood as the following signals or data which can be detected with an EIT device by means of a group of electrodes or by means of an electrode belt. These include EIT measurement signals in different signal embodiments, such as electrical voltages or voltage measurement signals, electrical currents or current measurement signals, assigned to electrodes or groups of electrodes or to positions of electrodes or groups of electrodes on the electrode belt, as well as out Voltages and currents are derived electrical resistance or impedance values.
    In the context of the present invention, a measuring circulation is understood to be a signal supply to two feed electrodes, a so-called feed electrode pair, in which measurements of EIT measurement signals are made at other electrodes which are different from these two feed electrodes become.
    For the purposes of the present invention, a measuring cycle is understood to mean a sequence of feeds at a plurality of feed-electrode pairs, each with an associated measuring cycle at the remaining electrodes. Such a measurement cycle is typically referred to as a "frame" or "time frame" when processing EIT data.
    In an EIT system with a number of 16 electrodes using an adjacent data acquisition mode, in one measurement cycle, i. E. in a "time frame" a number of 208 measuring signals.
    Accordingly, a measurement cycle as part of the measurement cycle is typically referred to as a "partial frame" in the processing of EIT data. In an EIT system with a number of 16 electrodes using an adjacent data acquisition mode, in one measurement cycle, i. E. in a "partial frame" a number of 13 measurement signals.
    The use of the adjacent data acquisition mode means that in one measuring cycle, the feeds at two adjacent positioned electrodes as input-electrode pair 13 measuring signals from each two be-adjacently positioned electrodes are detected as a pair of measuring electrodes and in a measuring cycle with rotation of the feed-electrode pair with the 16 measuring cycles for each measuring electrode pair then 16 measuring signals result.
    In the context of the present invention, an EIT measuring channel is understood to mean an unambiguous assignment or constellation of in each case two signal-feeding electrodes and of the two signal-feeding electrodes different from two signal-detecting electrodes from a multiplicity of electrodes. The plurality of electrodes are embodied as part of the apparatus for impedance impedance tomography by an electrode arrangement, for example, performed as an electrode belt attached to the thorax of a patient with a certain number of electrodes. Exemplary numbers of electrodes in the electrode belt are 16, 32 or 64 electrodes. There are a variety of EIT measurement channels which include different assignments or constellations of on the one hand feeding and on the other hand different measuring electrodes. The EIT measurement channels are preferably addressed in the form of an index-based manner and the data acquired on the EIT measurement channels are preferably addressed in the form of indexed vectors, indexed data fields or indexed matrices, stored and further processed (vector operations, Matrix operations). In an EIT system with a number of 16 electrodes using an adjacent data acquisition mode, there are 208 EIT measurement channels, with one measurement channel defined as a unique assignment of a feed-electrode pair and a sample-electrode pair. In the adjacent data acquisition mode, two adjacent electrodes of the plurality of electrodes are respectively used for feeding, and adjacent two of the remaining ones of the plurality of electrodes are used for signal detection.
    According to a first aspect of the invention, an apparatus according to the invention is provided.
    The device according to the invention for electric impedance tomography for a determination of a situation, which axial offset and / or a twist angle α associated with the device, for electro-impedance tomography and horizontally disposed on the thorax of a patient electrode arrangement, indicated, an electrode arrangement comprises a signal feed unit - a signal detection unit - a calculation and control unit.
    The electrode arrangement has a multiplicity of electrodes, which are arranged at a distance from each other at the periphery of the body in the region of the thorax of a living being. The electrode assembly is arranged horizontally on or around the thorax of a patient. At least two of the electrodes of the electrode arrangement are designed to feed in an alternating current or an alternating voltage, at least two of the remaining electrodes of the electrode arrangement are designed to detect measuring signals.
    The signal feed unit is designed and provided to feed in each measuring cycle of a Messzy-klus an electrical feed signal to two cyclically and in a measuring cycle varying feeding electric-den. Preferably, an alternating current is supplied to the feeding electrodes.
    The signal detection unit is configured and provided to detect a plurality of measurement signals of the plurality of electrodes in each of the measurement cycles of the measurement cycle and to provide the calculation and control unit as well as a data storage unit as EIT measurement channels for further processing. In the preferred feeding of the alternating current to the feeding electrodes, voltage signals as measuring signals result in each case at electrode pairs at the plurality of electrodes.
    The calculation and control unit is configured and provided for performing processing of the detected plurality of measurement signals of the plurality of electrodes in each of the measurement cycles of the measurement cycle. The calculation and control unit is further configured and provided for a selection of selected measurement signals as selected EIT measurement channels from the acquired plurality of measurement signals (EIT measurement channels) and for carrying out a processing of the selected measurement signals. The computing and control unit is associated with the data storage unit, which is designed and intended to store EIT measurement channels, measurement signals, measurement signals and comparison data selected from the measurement signals, and for further processing, addressing, preferably organized into vectors, data fields ( Matrices). The computing and control unit is further configured to coordinate the data storage unit, the signal feed unit and the signal acquisition unit. This coordination is accomplished by rotating the pair of signal-sensing electrodes from the computing and control unit over the plurality n of electrodes (E ^ -. En) within each measurement cycle, and rotating the pair of signal-feeding electrodes about the number of electrodes in each measurement cycle Thorax is rotated, so that results in a number of n electrodes in a measurement (partial frame) for each feed pair a number of n-3 measurement signals and total in a measurement cycle (time frame) a number of n * (n -3) results in measurement signals. The calculation and control unit is preferably designed, for example, as a central processing unit (CPU, μΡ) or arrangement of individual or several microcontrollers (pC).
    The calculation and control unit is designed according to the invention, with the aid of selected measuring signals, which are obtained from a selection of electrodes opposite the two feeding electrodes, a situation which determines an axial offset and / or a twist angle α of the electrode arrangement indicated at the thorax, and to determine and provide a control signal which indicates the situation of the axial displacement and / or the twist angle α of the electrode arrangement at the thorax.
    This from, in each case the two feeding electrodes opposite electrodes obtained from-selected measurement signals thus represent so-called opposite EIT Messkanâle on which the determination of the axial offset and / or the angle of rotation α of the electrode assembly is based on the thorax.
    The determination of the situation which indicates the axial offset and / or the angle of rotation α of the electrode arrangement at the thorax is effected in that - by the calculation and control unit in cooperation with the data storage unit from the measuring signals of each measuring cycle of the Measuring cycle are selected and stored as selected measuring signals which have been detected at the pair of electrodes arranged opposite the thorax, - by the calculating and control unit in cooperation with the data storage unit in each measuring cycle averages of the respectively selected measuring signals each of the two feeding electrodes opposite to the thorax, electrode pairs of the respectively selected electrodes in each measuring cycle are determined and stored, - by the calculation and control unit in cooperation with the data storage unit for each ele k-trodenpaar of the selected electrodes each ratio (W) from the selected measurement signals and the averages determined for these selected electrodes are determined as a waveform (W1 ... W16), - a comparison made by the calculation and control unit in cooperation with the data storage unit the waveform (W1 ... W16) with a comparison waveform (W_0) is performed, wherein the comparison signal course (W_0) represents a waveform, which in a correct positioning of the electrodes without an axial offset or a twist angle α of the electrode assembly on the thorax - is determined by the calculation and control unit based on the comparison of the axial offset and / or the torsional angle α of the electrode assembly on the thorax, - generated and provided by the calculation and control unit, a control signal which the axial offset and / or the twist angle α de r electrode array indicated at the thorax.
    The determination of the mean values on the basis of the number of selected measurement signals of the electrodes opposite the feeding electrodes in a plurality of measuring cycles can be carried out as arithmetic, geometric or quadratic averaging, as well as non-linear averaging, for example as a median Filtering in the form of a "1 out of 3 filters" or "1 out of 5 filters".
    The comparison waveform (W_0) represents a waveform that results in correct positioning of the electrodes without axial displacement or a twist angle α of the electrode assembly on the thorax. This comparison signal profile (W_0) can be obtained both on the basis of measurement experiments on subjects with different positions of the electrodes at the thorax, as well as on the basis of theoretical considerations and / or simulation calculations.
    In a preferred embodiment of the device for electrical impedance tomography, the calculation and control unit is, in addition to the coordination of the signal feed unit, the signal acquisition unit, the data storage unit, for coordination with a in or on formed of the device for electro-impedance tomography or the device for electro-impedance tomography associated output unit.
    The output unit is for a graphical, pictorial, visual or numerical output of data and / or information of the calculation and control unit, such as, from the detected measurement signals from the calculation and control unit determined impedances, impedance changes or impedance distributions in Area of the thorax by means of-tels provided by the calculation and control unit provided control signal designed and provided. The output unit may be designed, for example, as a display device (screen, monitor, data display device) or else as a graphics interface (HDMI, VGA, PAL) in order to provide other types of data display devices (smartphones).
    Phones, tablet PCs, laptop PCs) close to the location (LON, LAN, WLAN, field bus, professional BUS, CAN, POWERLINK) or remote (Profi-NET, LAN), direct (USB, RS232) or indirect (network, ETHERNET, Intranet, Internet), wireless (WLAN, Blue-tooth) or wired (LAN).
    In a preferred embodiment of the device for electromagnetic impedance tomography of the computing and control unit in cooperation with the signal feed unit in each measuring cycle of the measuring cycle the two feeding electrodes opposite two directly adjacent electrodes as respec-ge Electrode pairs selected to acquire the selected measurement signals. Such a way of performing the electro-impedance tomography is referred to as a so-called "adjacent data acquisition mode". In the process, an overall image of the impedance distribution over the entire thorax is obtained in a regular manner, since measurement signals of all electrodes in succession in the measuring cycle of all measuring cycles contribute the respective proportion of information to the overall image. Jumping with skipping or omitting individual electrodes in the signal feed or in the signal detection takes place in the so-called "adjacent data acquisition mode" only in situations in which individual electrodes have been identified as faulty (Fault-Electrode). Furthermore, in such a so-called "adjacent data acquisition mode", the signal input is varied so that in each one measuring cycle, each of the two feeding electrodes participates at most twice in the feed in the measuring cycle and in a measuring cycle each of the selected electrodes contributes at most twice the acquisition of the selected measurement signals is taken into account.
    In a preferred embodiment of the device for electro-impedance tomography, the calculation and control unit uses a scaling in determining the ratio mass (W) from the selected measurement signals and the average values determined for these selected electrodes. The scaling used enhances or emphasizes a signal difference between the selected measurement signals and the averaged averages.
    A practical possibility in the processing of the measurement signals by the calculation and control unit by the signal difference in the determination of the ratio mass (W), i. E. The ratio of the selected measurement signals and the mean values determined for these selected electrodes by means of scaling should be emphasized or enhanced by the inclusion of a mathematical function on the ratio (W), such as the logarithm (Ig, In, log2).
    In a preferred embodiment of the device for electrical impedance tomography, the calculation and control unit uses a logarithmic scaling, preferably in logarithmic scaling, in the determination of the ratio mass (W), preferably in a signal-amplifying manner Base 10
    in logarithmic scaling to base e logarithmic scaling to base 2 In this way, in the signal paths (W1... W16), the shape of the signal curve is emphasized, resulting in pregiven forms of the signal plots (W1... W16) to the plurality of electrodes associated ratio (W). The result is a so-called "W-shape", which illustrates the difference in the propagation of the injected signals at the thorax, at which location of the elliptical peripheral shape (longer half-axis / shorter half-axis of the ellipse) the signal input to the shorter half-axis of the elliptical peripheral shape on Thorax, that is, the so-called frontal axis (sternum vertebral column) of the plane of arrangement of the plurality of electrodes or on the longer half axis of the elliptical peripheral shape on the thorax, that is, the so-called transverse axis (left side - right side) of the plane of arrangement of the plurality of electrodes, respectively took place.
    In a preferred embodiment of the device for electrical impedance tomography, a number of three, four, five or more than six electrodes of the two feeding electrodes are opposed by the computing and control unit as selected electrodes for detecting the selected measurement signals Electrodes selected. The number of selected electrodes facing the calculating and controlling unit and the feeding electrodes for detecting the selected measuring signals is different for a different number (8, 12, 16, 32, 64) of the plurality of electrodes arranged at the thorax. For example, with a number of sixteen electrodes, a choice of four, five, or six opposing electrodes is advantageous for effectively forming the ratio mass (W), highlighting the distinctive "W shape." For a number of eight electrodes, a choice of two to four, for example, three opposing electrodes to form the ratio mass (W) may be advantageous, for a number of 32 electrodes a selection of more than six, for example eight to twelve opposite Electrodes may be advantageous for forming the ratio (W).
    In a preferred embodiment of the apparatus for electro-impedance tomography, measurement signals selected by the calculation and control unit are respectively determined from mean values of the selected measurement signals of several measurement cycles. The inclusion of multiple measurement cycles to form the average provides advantages in terms of reducing the effects of noise superimposed on the measurement signals. As a result, it can be achieved, for example, that the determined "W-shape" of the signal outputs (W1... W16) is pronounced and largely free of distortions of the "W-shape" and thus the comparison with the comparison signal form (W_0) great uniqueness of the comparison result is possible. The averaging of the selected measurement signals of the electrodes opposite the feeding electrodes over several measurement cycles can be carried out as arithmetic, geometric or quadratic averaging, as well as nonlinear averaging, for example as a median filtering in the form of a "1 out of 3 filter" or "1 out of 5 filters".
    In a preferred embodiment of the apparatus for electro-impedance tomography, the calculation and control unit is designed, by means of an algorithm for image reconstruction, impedance values and / or impedance changes or impedance distributions in the thorax in the plane of the electrodes on the thorax on the basis of and a tidal image based on the calculated impedance values and / or impedance changes and / or impedance distributions in the thorax in the plane of the electrodes at the thorax and on the basis of the determined axial offset and / or the twist angle α to detect and include in the control signal and to provide the control signal for the output unit. This allows the determined determined axial offset and / or twist angle α to be determined by fitting or shifting indices in the addressing of indexed vectors, indexed data fields or indexed matrices in the EIT measurement channels with the associated impedance values in the image reconstruction for the creation of the tidal image from the EIT measuring channels.
    Corresponding to the axial offset and / or the angle of rotation α corrected and improved tidal images with the electro-impedance tomography, which ba-sieren in each on a real arrangement of the electrodes on the thorax, without that the real Arrangement of the electrodes on the thorax by the user must correspond exactly with an ideal, typical arrangement of the electrodes on the thorax.
    In a further preferred embodiment, the output unit is adapted to output and / or provide the determined axial offset and / or the twist angle α on the basis of the provided control signal. The output and / or provision preferably takes place in a numerical manner, for example as a scalar value, which represents the offset at the circumference of the thorax or the angle of rotation a of the electrode arrangement at the thorax.
    The calculation and control unit can be configured as a central unit in the device for the electrical impedance tomography, which coordinates or performs both the detection and analysis of the measurement signals and the detection and provision of the control signal as well as the consideration of the control signal the output of the corrected Tidalbildes initiated. However, it may also be an embodiment of the calculation and control unit vorteilteilhat, in which instead of a central unit several distributed units for detection, analysis and detection and provision of the control signal interact, for example in a kind of so-called cloud computing. One possible advantage of this can be achieved by the fact that the correction of the Tidalbildes and its provision can be done at a different location than the place where the measurement signals are detected.
    All the advantages that can be achieved with respect to the device described can be achieved in the same or similar manner with the method for operating an arrangement for electrical impedance tomography described as a further aspect of the invention.
    According to the further aspect of the invention, in a method according to the invention for operating an arrangement for electro-impedance tomography, a determination of an axial offset and / or a torsion angle α on the thorax of a patient is carried out with a plurality of electrodes.
    This method of operating the device for electrical impedance tomography is subdivided into a sequence of steps with the following steps: In a first step, in each measuring cycle of a measuring cycle, an electrical feed-in signal is sent to each two cyclically and in one measuring cycle fed varying feeding electrodes.
    In a second step, measurement signals selected in each measuring cycle of a measuring cycle are respectively selected on the selected electrodes, which are in each case located opposite the electrodes which are fed to the electrodes at the thorax.
    In a third step, mean values (üS6) of the respectively selected measurement signals of the respective pair of electrodes of the respectively selected electrodes arranged in the opposite direction to the two infeeding electrodes on the thorax are determined in each measurement cycle.
    In a fourth step, a ratio is determined as a logarithmic ratio of the selected measurement signals and the electrodes (determined average values (üS6) selected for them as a signal course (W1... W16).
    In a fifth step, a comparison of the specific waveform (W1 ... W16) is performed with a comparison signal course (W_0) and determines an axial offset and / or the angle of rotation α of the electrode arrangement on Tho-rax on the basis of the comparison , The comparison signal waveform (W_0) represents a signal course which results in a correct positioning of the electrodes without axial offset or a twist angle α of the electrode arrangement on the thorax.
    In a sixth step, a control signal is generated and provided which indicates the axial offset and / or the angle of rotation α of the electrode arrangement on the thorax.
    The embodiments described individually and in combination with one another constitute particular embodiments of the device according to the invention and of the method according to the invention for operating the arrangement for the electro-impedance tomography with the electrode arrangement arranged on the thorax of a patient with a multiplicity of In this case, advantages and further embodiments resulting from the combination or combinations of several embodiments are nonetheless also covered by the idea of the invention, even if not all possible combinations of embodiments are described in detail in each case.
    The above-described embodiments of the method according to the invention can also be embodied in the form of a computer-implemented method as a computer program product with a computer, the computer being made to carry out the method according to the invention described above, when the computer program is stored on the computer or on a computer Processor of the computer or a so-called "embedded system" as part of a medical device, in particular the EIT device is executed. In this case, the computer program can also be stored on a machine-readable storage medium. In an alternative embodiment, a storage medium may be provided which is intended to store the above-described computer-implemented method and is readable by a computer.
    It is within the scope of the present invention that not all steps of the method must necessarily be performed on one and the same computer instance, but they can also zen on different Computerinstan-zen, for example in a form and means of so-called cloud computing a data network system out.
    The sequence of the method steps can also be varied if necessary. It is also possible that individual sections of the method described above in a separate, for example, self-sellable unit (such as on a preferably arranged in the vicinity of the patient data analysis system) other parts on another salable unit (such as on a display and visualization unit, which is for example arranged as part of a hospital information system, preferably in a room set up to monitor a plurality of patient rooms), so to speak as a distributed system.
    The advantages described for the process according to the invention can be achieved in the same or similar manner with the device according to the invention and the described embodiments of the device. Furthermore, the described embodiments and their features and advantages of the method are transferable to the device, as well as the described embodiments of the device are transferable to the method.
    The corresponding functional features of the method are in this case formed by corresponding relevant modules of a device, in particular by hardware components (CPU, PC, DSP, MP, FPGA, AS IC, GAL), which, for example in the form of a processor, several Processors (pC, μΡ, DSP) or in the form of instructions in a memory area which are processed by the processor.
    The present invention will now be further explained with the aid of the following figures and the associated description of the figures without limitations of the general concept of the invention.
    It shows:
    1 is a schematic representation of functional elements of an electro-impedance tomography device,
    2 shows two representations of two different positions of electrode arrangements on an elliptical circumference of a thorax,
    3 shows signal outputs from two different positioning of electrode arrangements on an elliptical circumference of a thorax,
    Fig. 4 flowchart for determining a rotation of an electrode assembly on the thorax.
    FIG. 1 shows an arrangement for impedance tomography 1. In the arrangement for impedance tomography, a number of electrodes 33 are arranged on the thorax 34 of a patient 35. Of the electrodes 33, EIT data 3 are transmitted to a calculation and control unit 70 by means of a data acquisition unit 50. The transmission of the EIT data 3 from the electrodes 33 takes place by means of line connections 32. In the calculation and control unit 70, a processor unit 78 and a data memory 71 are arranged. The processing unit 78 processes the EIT data 3 provided by the signal detection unit 50. In this FIG. 1 it is shown that the EIT data 3 arrive as measuring signals 55 to the calculation and control unit 70 with the processor unit 78. The processor unit 78 determines by means of suitable calculation methods and algorithms from the measurement signals 55 signal outputs of selected measurement signals (W1... W16) 56. Selected measurement signals 56 are those measurement signals which are obtained opposite of signal-feeding electrodes 37 of selected electrodes 36. This can be seen in detail in the schematic representation 4 of signal input and signal detection. In the calculation and control unit 70, a comparison waveform (W_0) 73 is used to evaluate the signal traces of selected measurement signals (W1 ... W16) 56 by means of a comparison. As a result of the evaluation of the comparison results in a control signal 79 which indicates a rotation or an axial offset 76 (FIG. 2) of the electrodes 33 or a twist angle α 77 (FIG. 2) of the electrodes 33 combined into an electrode arrangement. The control signal 79 is provided in this FIG. 1 to an EIT device 30 with an output unit 80. The output unit 80 makes it possible to visualize 82 the impedances or the impedance changes in the horizontal plane of the thorax 34 determined by the calculation and control unit 70 in a so-called dorsal view.
    In FIG. 1, above the arrangement for impedance tomography 1, a representation 2 of an arrangement of electrodes 33 on the thorax 34 is shown schematically. A space coordinate system 5 with an X-axis 6 and a Y-axis 7 is shown. The electrodes 33 are arranged approximately uniformly distributed around the thorax 34. This representation 2 represents a horizontal section through the thorax 34 in the plane of the arrangement of the electrodes 33, that is to say the plane of representation of the dorsal view for the visualization of FIG. 82. The schematic illustration 2 shows a typical elliptical peripheral shape 20 which is typical for the majority of human beings in the field of arrangement of the electrodes 33 around the thorax34. The schematic representation of the arrangement 2 of electrodes 33 on the thorax 34 has a number of sixteen electrodes. In the schematic representation 4 of signal feed and signal detection, a current is fed to two electrodes, namely at the electrode E157 and at the electrode E1658 by means of a signal feed unit 51. On the opposite side of the two feed electrodes E157, E1658, measurement signals 55 are detected as signal outputs of selected measurement signals 56 on a selection of electrodes 36 by means of the signal detection unit 50 in one revolution of signal acquisition 53.
    In this Figure 1, the electrodes E6-E11 are shown by way of example as a selection of six electrodes 36. However, within the meaning of the present invention, it is also included that a number other than the six selected electrodes 36, for example five, four, three electrodes, which are arranged opposite the feeding electrodes 37, are used for the evaluation for determining the rotation or the axial offset 76 (FIG. 2) or a rotational angle a 77 (FIG. 2) of the electrodes 33 on the thorax 34 of the patient 35. After being fed to the electrodes E1, E16, 57, 58 by the signal feed unit 51, in this FIG. 1 shown as a counterclockwise rotation 52, the feed to the next feed pair, ie the electrodes E16 and E15, is made. The signal detection is then likewise carried out by means of a counter-clockwise rotation 53, shown in this FIG. 1, on the electrodes E5-E10 then opposite the electrodes E15 and E16. Infeed and signal acquisition rotations 52, 53 are performed in one measurement cycle for all pairs of adjacent electrodes of the 16 electrodes E1-E16. In this way, a lot of signal traces of selected measuring signals 56 (W1 ... W16) results. Thus, each electrode pair of sensing electrodes 36 is assigned a measurement signal W1, W2... W16. These measurement signals 56 obtained in the measurement cycle, each obtained from the electrodes 36 respectively facing the feeding electrodes 37, are compared by the calculation and control unit 70 as signal outputs 60 (FIG. 3) with a comparison signal profile (W_0) 73. In this case, the comparison signal profile (W_0) 73 represents a signal course which results from a correct positioning of the electrodes 33 at the thorax 34, ie when the electrodes 33 are positioned with a virtually ideal symmetrical arrangement of the sixteen electrodes E1 ... E16 with the first electrode E1 to the left of a breastbone of the patient 35 and with a position of the further feed electrode E1658 to the right of the sternum at the thorax 34. From the result of the comparison, the control signal 79 is determined. The details for determining the control signal 79 and the further processing and utilization, or use of the control signal 79, are shown in the illustrations in FIGS. 2 and 3 and the associated descriptions.
    As a result, a rotation or an axial offset 76 (FIG. 2) is determined during the positioning of the electrodes 33 on the thorax 34. This rotation or the axial offset 76 (FIG. 2) is used by means of the control signal 79 to either correct the visualization 82 in the output unit 80 by the twist angle a 77 (FIG. 2) or to give a hint to a user give the electrodes an axial offset 76 (Figure 2) on the patient's chest 34. The correction makes it possible to carry out a high-quality measurement for electric impedance tomography with the EIT device 30 even for positioning of the electrodes 33 with an axial offset 76 (FIG. 2). It is thus provided, as it were before performing further examinations or measurements with the EIT device 30, a possibility for a calibration to the actual positioning on the thorax 34 of the patient 35 to be examined. The indication allows the user to correct the placement of the electrodes 33 on the thorax 34 of the patient 35 before performing further examinations or measurements with the EIT device 30, and thus to obtain a high-quality measurement for electro-impedance tomography EIT device 30.
    FIG. 2 shows a first positioning 11 of an electrode arrangement with electrodes 33 on the thorax 34. Like elements in Figs. 1 and 2 are designated in Figs. 1 and 2 with the same reference numerals. As stated in FIG. 1, feeds are made to feed electrodes 37. In FIG. 2, the electrodes E1, 57 and E16, 58 are used for the feed. In accordance with the representation of the schematic representation 2 of
    Arrangement of electrodes on the thorax according to FIG. 1, a coordinate system 5 with an X-axis 6 and a Y-axis 7 is shown in this FIG. The signals fed in by the feed electrodes 37 pass as propagation of the feed 39 in the thorax 34 to the opposite electrodes 36 (E6 ... E11). This first positioning 11 of the electrode arrangement on the thorax shows the ideal application with a nearly ideal symmetrical arrangement of the sixteen electrodes with a position of the first electrode E1 to the left of a patient's sternum and with a position of the further supply electrode E1658 to the right of the sternum at the thorax 34 the second positioning 13 of an electrode arrangement on the thorax 34 likewise shown in FIG. 2 is given an axial offset or a rotation about a twist angle α 77 of the electrodes 33. At the same elliptical peripheral shape as in the first positioning 11, the feeding electrodes 37 'are no longer arranged on both sides of the breastbone in the second positioning 13, but the feeding electrode pair E157, E1658 is on the right side of the sternum with an axial offset 76 of the electrode arrangement on the thorax 34 arranged. Due to this axial offset or this rotation about the twisting angle α 77, the electrodes 36 ', which are now selected outward relative to the feed electrodes 37', are also arranged offset on the thorax 34. This results in this second positioning 13 of the electrode assembly on the thorax 34, a different from the first positioning 11 different propagation of the feed 39 'at the thorax 34. This results for the Signalverlufe 60, 74,74' (Fig first positioning 11 a difference to the signal paths 60, 74, 74 '(FIG. 3) of selected measuring signals of the second positioning 13 of the electrodes 33 on the thorax 34. These differences in the signal paths 60, 74, 74' (FIG. 3) are shown in FIG. 3 and explained and described in the description of FIG. 3 in more detail.
    3 shows a signal representation 60 of two signal paths 74, 74 '(W1 ... W16; W1 ... W16)
    Measuring signals 56, 56 ', which on the different positions 11, 13 of the electrode assembly on the thorax 34 of FIG. 2 result. The same elements in Figs. 1, 2, 3 are designated in Figs. 1, 2, 3 with the same reference numerals. A signal curve 74 of selected measurement signals 56 is shown, which corresponds to the first positioning 11 of the electrode arrangement 33 on the thorax 34 of FIG. 2. A further signal course 74 'of selected measuring signals 56' is shown which corresponds to the second positioning 13 of the electrode arrangement 33 on the thorax 34 according to FIG. 2. Measuring signals of 16 electrodes E157 to E1658 in the signal course 74 or 74 'are shown. The difference of the signal traces 74 and 74 ', 75 is visible as a shift of the signal traces 74, 74'. The signal processes 74, 74 'are shown in this FIG. 3 as a weighted signal ratio or weighted amplitude ratio of the measurement signals of the individual electrodes (E1... E16). In this FIG. 3, the weighted signal ratio 72 is a weighted logarithmic ratio M '= 72 of selected measurement signals 56, 56' to mean values (¾) 560 of the selected measurement signals 56, 56 'of the selected electrodes 36 (FIG. 2) the signal outputs 74, 74 '(W1 ... W16; W1' ... W16 ') are selected. The difference 75 in the signal paths 74 and 74 'can be used to determine the axial offset or the rotation with the twist angle α 77 (FIG. 2). By way of example, an evaluation may be mentioned, in which the signal curve 74, which in the first positioning 11 of the electrode arrangement 33 on the thorax 34, ie in the intended optimal arrangement of the electrodes 33 on the thorax 34 without significant Ver-rotation with centered orientation Electrodes E157 and E1658 on both sides of the sternum at the thorax 34 results, it is used that this is used as the basis of the comparison signal waveform (W_0) 73. If this comparison signal profile (W_0) 73 is stored in the data memory 71 (FIG. 1) and used as a basis for further analyzes of the signal paths 74 'of the selected electrodes 36', then the axial offset 76 (FIG Thoraxbzw. determine the twist angle a77 (Fig. 2) and based on the control signal 79 (Fig. 1) determine and ready. The provided control signal 79 (FIG. 1) may be provided by the computing and control unit 70 (FIG. 1) to a numerical output of the twist angle α 77 (FIG. 2) or a graphical or pictorial visualization 82 (FIG. 1) of the axial offset 76 (Figure 2) to the output unit 80 (Figure 1). The provided control signal 79 (FIG. 1) may further be determined by the computing and control unit 70 (FIG. 1) to correct the visualization 82 (FIG. 1) based on the measurement signals 55 (FIG. 1) and impedance values. Differences in pedestal and representation of the impedance distribution in the dorsal view (Fig. 1) by means of an adaptation with consideration of the rotation angle α 77 (Fig. 2) in the calculation rule for image reconstruction in the determination of the dorsal view (Fig.
    FIG. 4 shows a sequence 100 for operating an arrangement for electro-impedance tomography 30 (FIG. 1) having a sequence of steps 101 to 106 for determining an axial offset 76 and / or a twist angle 77 of a thorax 34 a patient 35 (Figure 1) having a plurality of electrodes 33. Like elements in Figures 1, 2, 3 and 4 are indicated in Figures 1,2, 3, 4 by the same reference numerals.
    The sequence of steps 101 to 106 starts from an ongoing measurement operation or after a startup of the arrangement for electric impedance tomography 30 (FIG. 1), that in a first step in each measurement cycle of a measurement cycle an electrical supply signal is sent to two cyclically and in a measuring cycle varying feed-in electrodes 37 is fed.
    In a second step 102, selected measuring signals 56 are detected in a measuring cycle of the measuring cycle which is selected for each of the feeding electrodes 37 on the selected electrodes 36.
    In a third step 103, mean values (ÜS6) 560 of the respectively selected measuring signals 56 of the respective electrode pairs of the respectively selected electrodes 36 in each measuring circuit arranged opposite the two feeding electrodes 37, 37 'on the thorax 34 are determined.
    In a fourth step 104, a logarithmic ratio 72, for example
    from the selected measurement signals 56 and the average values (μs &) 560 determined for these selected electrodes 36 as a waveform 60 (W1 ... W16).
    In a fifth step 105, a comparison of the signal profile 60 (W1... W16) with a comparison signal profile (W_0) 73 is carried out. By means of this comparison, an axial offset 76 and / or the angle of rotation oc 77 of the electrode arrangement at the thorax 34 (FIG. 1) are determined. The comparison signal profile (W_0) 73 represents a signal curve which results from a correct positioning of the electrodes 33 without an axial offset 76 or a twist angle α 77 of the electrode arrangement at the thorax 34 (FIG. 1).
    In a sixth step 106, a control signal 79 is generated and provided which indicates the axial offset 76 and / or the twist angle α 77 of the electrode arrangement on the thorax 34 (FIG. 1).
    LIST OF REFERENCES 1 Arrangement for Electro-Impedance Tomography 2 Schematic representation of an arrangement of electrodes on the thorax 3 EIT signals, EIT data 4 Schematic representation of signal supply and signal acquisition 5 Spatial coordinate system 6 X-axis 7 Y-axis 11 First positioning of a Electrode arrangement on the thorax 13 Second positioning of an electrode arrangement on the thorax 20 Elliptical peripheral form 30 EIT device 32 Cable connections, leads of the electrodes 33 Electrodes E1 ... E16, electrode arrangement 34 Thorax, thorax, thorax circumference 35 Patient 36 Selection of electrodes, opposite to feed electrodes 37, 37 'Infeed Electrodes 39 Infeed in Thorax 50 Signal Acquisition Unit (DAQ) 51 Signal Input Unit 52 Circulation of Signal Inputs (Measurement Cycle, Frame) 53 Circulation of Signal Acquisition (Partial Frame) 55 Measurement Signals U1 ... Un 56, 56' selected measuring signals W1 ... W16; WT ... W16 '57 Electrode E1 58 Electrode E16
    权利要求:
    Claims (12)
    [1]
    60 Signal representation 70 Calculation and control unit 71 Data memory 72 Signal ratio, weighted amplitude ratio, ratio (W) 73 Comparison signal waveform W_0 74, 74 'Wavelength / axial displacement waveform of the electrode assembly 75 Difference of the signal waveforms 74 and 74' 76 Rotation of the electrode assembly at the thorax 77 Twist angle α 78 Processor unit (μΡ, pC, CPU) 79 Control signal 80 Output unit, screen 82 Visualization 100 Sequence 101-106 Sequence of steps 560 Average values (üS6) Claims
    An apparatus for electro-impedance tomography (1) for determining a situation, which includes an axial offset and / or a rotation angle a of the device associated with the electro-impedance tomography (1) and horizontal on the thorax (34) of a patient (35) arranged electrode assembly, indicated, comprising: - an electrode assembly having a plurality of electrodes (33) spaced from each other on the body circumference in the region of the thorax (34) of a living being (35), - a signal feed unit (51), which designed and is provided to feed in each measuring cycle of a measuring cycle, an electrical feed signal to two cyclically and in a measuring cycle varying feeding electrodes (37, 37 '), - a signal detection unit (50), which is designed and intended, a To detect and provide a plurality of measurement signals (55) of the plurality of electrodes (33) in each of the measurement cycles of the measurement cycle - a calculation and control unit (70), which is designed and intended to perform a processing of the detected plurality of measurement signals (55) of the plurality of electrodes (33) and selected measurement signals (56) from the detected plurality of measurement select signals (55) and perform processing of the selected measurement signals (56), - a data storage unit (71) associated with the calculation and control unit (70) and configured to provide measurement signals selected from the measurement signals (55) (56) and comparison data (73) store and provide, wherein for determining the situation, which indicates the axial offset (76) and / or the twist angle a (77) of the electrode assembly on the thorax (34), - of the calculation and Control unit (70) in cooperation with the data storage unit (71) from the measuring signals (55) of each measuring cycle of the measuring cycle those of the measuring signals (55) as au selected and stored sensing signals (56) detected at the pair of electrodes arranged opposite the two feed electrodes (37, 37) on the thorax (34), - by the calculation and control unit (70) in cooperation with the data storage unit (56). 71) in each measuring cycle in each case average values (560) of the respectively selected measuring signals (56) of the respective pair of electrodes of the respectively selected electrodes (36, 36 ') arranged opposite the two infeed electrodes (37, 37') on the thorax (34). ) are determined and stored in each measurement cycle, by the calculation and control unit (70), in cooperation with the data storage unit (71), for each pair of electrodes of the selected electrodes (36, 36) respectively, weighting ratio (W) 72 from the selected measurement signals (56 ) and the average values (560) determined for these selected electrodes (36, 36 ') as a signal course (W1... W16) (60) t, a comparison of the signal profile (W1... W16) (60) with a comparison signal profile (W_0) (73) is carried out by the calculation and control unit (70) in cooperation with the data storage unit (71), the comparison signal profile (W_0) (73) represents a signal course which results from a correct positioning of the electrodes (33) without an axial offset (76) or a twist angle α (77) of the electrode arrangement at the thorax (34) the calculation and control unit (70) is determined on the basis of the comparison of the axial offset (76) and / or the twist angle α (77) of the electrode arrangement on the thorax (34), - a control signal (70) from the calculation and control unit (70) 79) is generated and provided, which indicates the axial offset (76) and / or the twist angle α (77) of the electrode arrangement on the thorax 34.
    [2]
    2. Device (1) according to claim 1, wherein the calculation and control unit (70) is arranged to coordinate an output unit (80), wherein the output unit (80) in or on the device for electrical impedance tomography (1). is arranged or assigned to the device for electrical impedance tomography (1).
    [3]
    The device (1) according to claim 1, wherein the computing and control unit (70), in cooperation with the signal feed unit (51), each of the two feed electrodes (37, 37) opposite two directly adjacent electrodes in each measurement cycle of the measurement cycle are selected as respective pairs of electrodes for detecting the selected measuring signals (56) and the variation of the two feeding electrodes (37, 37 ") is such that in one measuring cycle each of the two feeding electrodes (37, 37) is at most twice infeed in the measuring cycle and in each measurement cycle each of the selected electrodes (36, 36 ") is considered at most twice in the acquisition of the selected measurement signals (56).
    [4]
    4. Device (1) according to claim 1, wherein the calculation and control unit (70) in determining the ratio mass (W) (72) from the selected measurement signals (56) and the electrodes (36, 36 ') selected therefor. ) means (560) applies a scaling in a signal difference (75, 75 ') given between the selected measuring signals (56) and the ascertained mean values (560) in a manner which emphasizes or amplifies the signal difference (75, 75').
    [5]
    The apparatus (1) of claim 4, wherein the calculation and control unit (70), in determining the weight ratio (W) (72), sets a logarithmic scale as one emphasizing or enhancing the signal difference (75, 75 ') Manner, preferably in logarithmic scaling to base 10

    in logarithmic scaling to base e or in logarithmic scaling to base 2.
    [6]
    6. Device (1) according to one of the preceding claims, wherein by the calculation and control unit (70) as selected electrodes (36, 36 ') for detecting the selected measuring signals (56, 56') a number of three, four, five or more than six electrodes (33, 36, 36 ') of the electrodes (33, 36, 36') opposite the two feeding electrodes (37, 37 ') are selected.
    [7]
    7. Device according to one of the preceding claims, wherein the calculation and control unit (70) determines the selected measurement signals (56) respectively from average values of a plurality of measurement cycles.
    [8]
    8. Device (1) according to one of the preceding claims, wherein the calculation and control unit (70) is formed by means of an algorithm for image reconstruction impedance values and / or impedance changes or impedance distributions in the thorax (34) in the plane of the electrodes at the thorax (34 ) and a tidal image (82) based on the calculated impedance values and / or impedance changes and / or impedance distributions in the in-plane thorax (34) the electrodes at the thorax and on the basis of the determined axial offset (76) and / or the twist angle a (77) to determine and include in the control signal (79) and provide the control signal (79) for the output unit (80) ,
    [9]
    9. Device (1) according to one of the preceding claims, wherein the output unit (80) for outputting and / or providing the determined axial offset (76) and / or the twist angle α (77) on the basis of the provided control signal (79) is.
    [10]
    A method of operating (100) an electro-impedance tomography assembly (30) to determine an axial offset (76) and / or a twist angle (77) of an electrode assembly disposed on the thorax (34) of a patient (35) with a plurality of electrodes (33), - wherein in a first step (101) in each measuring cycle of a measuring cycle, an electrical feed signal to two cyclically and in a measuring cycle varying feeding electrodes (37, 37 ') is fed, in a second Step (102) in a each measurement cycle of a measurement cycle, each of the feeding electrical den (37, 37) on the thorax (34) opposite selected electrodes (36,36 ") selected measuring signals (56) are detected, - wherein in a third Step (103) Means (U56) (560) of the respectively selected measuring signals (56) of each of the two feeding electrodes (37, 37 ") on the thorax (34) arranged opposite electrode pairs of each selected electrodes (36, 36 ") can be determined in each measuring cycle, wherein in a fourth step (104) a logarithmic ratio (72) is determined

    from the selected measurement signals (56) and the average values (üS6) (560) determined for these selected electrodes (36, 36 ") is determined as a signal course (W1... W16) (60), wherein in a fifth Step (105) a comparison of the specific waveform (W1 ... W16) 60 is performed with a Ver-equal waveform (W_0) (73) and an axial offset (76) and / or the twist angle a (77) of the electrode assembly on the thorax 34 is determined on the basis of the comparison, wherein the comparison signal course (W_0) (73) represents a signal course resulting from correct positioning of the electrodes (33) without axial offset (76) or a twist angle α (77) of the electrode arrangement at the thorax 34 in a sixth step (106), a control signal (79) is generated and provided which indicates the axial offset (76) and / or the twist angle α (77) of the electrode arrangement on the thorax (34).
    [11]
    11. The method according to any one of the preceding method claims, wherein as selected electrodes (36, 36) for detecting the selected measuring signals (56, 56 ") a number three, four, five or more than six electrodes (33, 36, 36) of the two feed electrodes (37, 37 ") opposite electrodes (33, 36, 36") is selected.
    [12]
    12. The method according to one of the preceding method claims, wherein the selected measuring signals (56) are determined from average values of a plurality of measuring cycles.
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    法律状态:
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