Device for determining the regional distribution of a measure of lung perfusion

Abstract

Device for determining the regional distribution of a measure of lung perfusion in a sectional plane of the thorax with • an electrical impedance tomography unit with a large number of electrodes (E1, ... E N ), which can be attached to the thorax distributed around the circumference of the cutting plane, and with a control and evaluation unit (2) connected to the plurality of electrodes, which is designed to successively supply alternating current or alternating voltage to each pair of electrodes and to record voltage or current signals from the remaining electrodes as measurement signals and to reconstruct the impedance distribution in the cutting plane from the measurement signals, • a supply device (4) for the intravenous supply of a conductivity contrast medium, wherein the control and evaluation unit (2) is further configured to display the changes in the impedance distribution as a result of the supply of conductivity contrast medium as a measure of the lung perfusion in the sectional plane as a function of time, characterized in that • the supply device (4) has a controllable dosing device and the control and evaluation unit and the dosing device are connected to one another via a data connection (3) and are arranged such that at least the start and end time and amount of the delivery of a bolus of the conductivity contrast agent are available to the control and evaluation unit (2), • the control and evaluation unit (2) is configured to control the dosing device for administering a bolus of the conductivity contrast agent at a predetermined start time, with a predetermined amount and with a predetermined time course via the data connection (3) and to repeat the administration of the bolus of the conductivity contrast agent at predetermined time intervals • or the dosing device is designed to send data concerning the start time, quantity and time course of the delivery of a bolus via the data connection (3) to the control and evaluation unit (2) if the dosing device is caused to deliver a bolus repeatedly by an external device or directly by manual actuation of a switch by a user, • and that the control and evaluation unit is set up to display the temporal development of the degree of lung perfusion as a function of time as a trend representation.

Description

[0001] The present invention relates to a device for determining the regional distribution of a measure of lung perfusion in a sectional plane of the thorax of a patient, comprising an electrical impedance tomography unit with a plurality of electrodes which can be attached to the thorax distributed around the circumference of the sectional plane, and comprising a control and evaluation unit connected to the plurality of electrodes, which is configured to successively supply alternating current or alternating voltage to each pair of electrodes and to record voltage or current signals from the remaining electrodes as measurement signals and to reconstruct the impedance distribution in the sectional plane from the measurement signals, and comprising a supply device for the intravenous supply of a conductivity contrast agent, wherein the control and evaluation unit is further configured toto display the changes in the impedance distribution resulting from the administration of conductivity contrast medium as a measure of lung perfusion in the sectional plane as a function of time.

[0002] Such a device is known from the article "Determination of lung perfusion using electrical impedance tomography," Henning Luepschen et al., Biomed Tech 2010; 55 (Suppl. 1). The device comprises an electrical impedance tomography (EIT) unit, as is frequently used in medical applications. Such an EIT unit has a plurality of electrodes that can be attached to the thorax, distributed around the circumference of a cutting plane. Furthermore, a control and evaluation unit is provided, which is connected to the electrodes and is configured to successively supply alternating current or alternating voltage to each pair of the plurality of electrodes, to record the resulting voltage or current signals from the remaining electrodes as measurement signals, and to reconstruct the impedance distribution in the cutting plane from the measurement signals.More precisely, it is not the impedance that is determined absolutely, but rather its change relative to a reference distribution. Such an EIT unit is described, for example, in EP 2 228 009 A1.

[0003] Furthermore, the known device includes a manually operated delivery device (e.g., a syringe) for the intravenous administration of a conductivity contrast agent. Liquids whose conductivity differs significantly from that of blood can be used as conductivity contrast agents. After administering a bolus of the conductivity contrast agent, regional conductivity dilution curves can be recorded, i.e., the flow of the bolus through the section plane is evidenced by a rapid increase in impedance to a maximum value, followed by a slower decrease to the baseline (if the conductivity contrast agent reduces the impedance, there is a decrease in impedance to a minimum value and then a rise to the baseline). Such dilution curves can be recorded for the individual image elements of the reconstructed impedance distribution of the section plane through the thorax and displayed on a display device.For example, the determined instantaneous impedance values ​​can be shown in a spatially resolved two-dimensional representation, with the instantaneous values ​​being represented by corresponding brightness values. After administration of a bolus of conductivity contrast agent, for example, the contrast agent initially shows itself flowing into the right heart, where this results in a correspondingly increased brightness in the image of the thorax section in the region of the right heart. After this, the contrast agent leaves the right heart in the direction of the lungs, causing the right parts of the heart, which were initially shown with increased brightness, to become darker again and the lungs to become brighter. After this, the contrast agent then flows back into the left heart, which then appears on the display with correspondingly increased brightness.Instead of a time-varying representation of the instantaneous impedance value, other parameters of the dilution curves can also be displayed spatially resolved, for example, the maximum amplitude of the dilution curve or the integral value across the dilution curve. In the latter cases, a single spatially resolved representation of a measure of lung perfusion would be generated for the administration of a bolus of conductivity contrast agent. The term "measure of lung perfusion" is used here to clarify that the lung perfusion values ​​do not need to be determined absolutely, but rather only the relative proportions of the total perfusion may suffice.

[0004] When measuring lung perfusion using a conductivity contrast agent, the contrast agent must first be injected before the perfusion measurement can be started on the EIT unit. This results in two problems when performing a measurement: a) related to the administration of the contrast agent, and b) related to the lung perfusion measurement.

[0005] When administering the conductivity contrast agent, the speed at which the agent is administered can have a significant impact on the accuracy of the measurement and the comparability of different measurements. This is particularly the case if the contrast agent is applied manually without recording the exact volume and / or time. If the contrast agent is administered manually and without technical monitoring, it cannot be assumed that the in vivo concentration of the contrast agent is comparable for all measurements, and the quantifiability and comparability of EIT analyses are therefore not guaranteed.

[0006] Lung perfusion measurements also involve a time lag between the administration of the conductivity contrast agent and the start of the measurement. This time lag can lead to reduced quality of the analysis results. Furthermore, since the time lag cannot be assumed to be constant at all times, two measurements are only comparable to a limited extent, as different concentrations of the contrast agent in the blood must be assumed at the respective measurement times. The same applies to the end of the contrast agent administration, as the lung perfusion measurement must also be terminated after a defined time. Here, too, a time lag must be assumed between the end of the contrast agent administration and the end of the EIT measurement.

[0007] Because measurements obtained manually with conductivity contrast agent may vary significantly and the results are not reproducible, reliable conclusions cannot be drawn from the measured values. For example, it is not possible to determine the ventilation-perfusion ratio (V / Q ratio) in a way that allows different measurements to be compared and thus a trend to be determined.

[0008] DE 10 2007 056 481 A1 discloses a medical imaging system that uses contrast agent administration. An imaging scan is controlled by a scan protocol module. The scan protocol module also controls a contrast agent delivery device. Imaging techniques include computed tomography (CT), magnetic resonance imaging (MRI), X-ray, ultrasound, positron emission tomography, and spectroscopy. Such acquisitions are typically performed only once for a single image acquisition, which may be repeated at long intervals.

[0009] The scientific publication Frerichs et al.: "Regional lung perfusion as determined by electrical impedance tomography in comparison with electron beam CT imaging"; IEEE Transactions on Medical Imaging, June 21, 2002, 6, 646-652, describes experiments investigating pulmonary perfusion using electrical impedance tomography in comparison with computer tomography. The aim of the experiments was to test the feasibility of pulmonary perfusion imaging using functional electrical impedance tomography (EIT) and to compare EIT findings with electron beam computed tomography (EBCT) scans. Hypertonic saline or an X-ray contrast agent was administered. A series of EIT scans of the instantaneous distribution of electrical impedance in the chest were performed during each saline administration.The CT scans were performed under the same stationary conditions during administration of a radiopaque contrast agent. The results demonstrate that EIT imaging of lung perfusion is possible when using an electrical impedance contrast agent.

[0010] DE 103 01 202 B3 shows a ventilation system. This ventilation system is combined with a measurement method for electrical impedance tomography (EIT). Bidirectional data exchange is provided between the two systems. Both the ventilation system and the measurement system have a first and a second communication electronics unit, each with associated transmitting and receiving means for bidirectional data exchange.

[0011] DE 693 20 173 T2 describes agents for improving tissue / tissue contrast in electrical impedance tomography. In particular, triiodophenyl compounds, metal chelates, magnetic particles, conductive particles, and microbubbles can be used.

[0012] The object of the present invention is to design a device for determining the regional distribution of a measure of lung perfusion in such a way that improved reproducibility and comparability of successive measurements on a person can be achieved, thus allowing temporal changes to be recorded. Such temporal changes can occur, for example, during artificial respiration and provide information on the correct setting of the ventilation parameters.

[0013] The features of patent claim 1 serve to solve this problem. Advantageous embodiments of the device are specified in the subclaims.

[0014] According to the invention, the supply device for the conductivity contrast agent comprises a controllable dosing device. The control and evaluation unit and the dosing device are interconnected via a data connection and configured such that at least the start and end times and the amount of the delivery of a bolus of the conductivity contrast agent are available to the control and evaluation unit as parameters. This naturally also includes parameter sets resulting from conversion, such as the start time, amount, and injection speed or the start time, amount, and duration of the injection, etc. The control and evaluation unit can be configured to send a predetermined start time, a predetermined amount, and a predetermined time course of the infusion of the conductivity contrast agent to the controllable dosing device as control parameters via the data connection.Alternatively, the control and evaluation unit can simply start the dosing device and receive feedback from the dosing device regarding the exact start time, amount, and timing of the conductivity contrast agent infusion. Alternatively, the controllable dosing device can also be controlled by third-party devices (e.g., a ventilator or monitoring monitor) directly or indirectly via the control and evaluation unit. The dosing device then sends data regarding the start time, applied amounts, and timing of the bolus administration to the control and evaluation unit. Data communication via the data connection can be implemented either wired or wirelessly.

[0015] The control and evaluation unit is designed either to control the dosing device for administering a bolus of the conductivity contrast agent at a predefined start time, with a predefined amount and with a predefined time course via the data connection and to repeat the administration of the bolus of the conductivity contrast agent at predefined time intervals and to display a trend representation representing the temporal development of the degree of lung perfusion as a function of time

[0016] Alternatively, the dosing device is configured to send data relating to the start time, quantity and time course of the delivery of a bolus via the data connection to the control and evaluation unit if the dosing device is triggered to deliver a bolus repeatedly by an external device or directly by repeated manual actuation of a switch by a user, wherein the control and evaluation unit is configured to display the temporal development of the degree of lung perfusion as a function of time as a trend representation.

[0017] According to the invention, it is thus possible to easily detect temporal changes in lung perfusion and to identify trends.

[0018] In a preferred embodiment, the control and evaluation unit is further configured to display the measure of lung perfusion in a spatially resolved two-dimensional manner over the lung area in the sectional plane through the thorax.

[0019] In a further preferred embodiment, the control and evaluation unit is further configured to determine the perfused area in the sectional plane and to display perfused areas, each resulting from the administration of a bolus of the conductivity contrast agent, as a trend representation as a function of the time of the administration of the bolus of the conductivity contrast agent. Regions in which the measure of lung perfusion lies above a predetermined threshold value can be defined as perfused areas. In addition, a measure of the homogeneity of the lung perfusion can be determined within the perfused areas, e.g. the mean deviation from the average lung perfusion in the perfused area (=0 if the lung perfusion is the same everywhere), and displayed as a trend representation as a function of the time of the administration of the bolus.

[0020] In a preferred embodiment, the control and evaluation unit is further configured to determine the regional distribution of ventilation from the impedance distributions of the thorax section plane during periods without administration of conductivity contrast agent and to display it as a function of time. Methods for determining the intra-idal distribution of ventilation across the lung cross-section are described, for example, in EP 2 228 009 A1. In a preferred embodiment, the dosing device is provided with a temperature sensor for the conductivity contrast agent or with a temperature control device for the conductivity contrast agent that can be controlled by the control and evaluation unit.The control and evaluation unit is configured to determine the cardiac output volume based on the dilution principle from the conductivity contrast agent's temperature, which is determined or set by the temperature control device, and to calibrate the absolute lung perfusion measure based on the determined cardiac output volume. In principle, an isotonic solution can also be used for calibration; this solution does not change conductivity and is therefore not a conductivity contrast agent in the true sense.

[0021] By measuring or adjusting the temperature of the conductivity contrast agent, it is possible to calculate the cardiac ejection volume using the dilution principle (for example, the Steward-Hamilton method), thus calibrating the measured EIT values ​​with respect to lung perfusion and improving the accuracy of the measurement.

[0022] With the present invention, it is possible to increase the accuracy of the measurement, ensure the comparability of different measurements, perform cyclical, automatic measurements and reduce the possibility of incorrect operation by the user.

[0023] The conductivity contrast agent is administered under defined conditions so that the start time, volume, and speed of the injection are known to the control and evaluation unit of the EIT unit. The control and evaluation unit initiates the administration of a bolus of conductivity contrast agent with known parameters, either as a result of the actuation of a switch or at predetermined intervals, automatically or triggered by external third-party devices (such as a ventilator or monitoring monitor). At the same time, the EIT unit is prompted to repeatedly measure the regional impedance distributions in the cross-sectional plane of the thorax. Alternatively, the dosing device sends data regarding the start time, amount, and temporal progression of the bolus delivery to the control and evaluation unit if the dosing device is prompted to deliver a bolus directly or by an external device.The data connection between the control and evaluation unit of the EIT unit and third-party devices and the dosing device, as well as the control or synchronization of the EIT unit and dosing device, precisely defines the timing of a perfusion measurement. For continuous perfusion measurements, a defined volume of conductivity contrast agent can be delivered at regular intervals under defined conditions, and a corresponding EIT measurement can be triggered by the EIT unit. This increases the accuracy of the measurement and ensures the comparability of different measurements. If a timer is also integrated into the device, cyclical, automatically performed measurements are possible. The sources of error for potential incorrect operation by the user are reduced, as the user can initiate a corresponding maneuver with a single switch press.The user therefore no longer has to inject the conductivity contrast agent, initiate the EIT measurement, and possibly stop it, as is required in the current state of the art. This also makes such a device significantly easier to operate. Through the defined administration of boluses, a precise baseline for the EIT measurement can be determined using a modified Steward-Hamilton method. This method can also be considered a Steward-Hamilton method for EIT measurement. It measures not only the temperature of the injectate but also the changed conductivity in the blood. Such a procedure is described in: "Determination of Lung Perfusion Using Electrical Impedance Tomography" by H. Luepschen et al., 44th Annual Meeting of the German Society for Biomedical Engineering (BNT 2010), Rostock, Germany, October 6-8, 2010.

[0024] Since the results of the EIT measurements can be compared, a trend for cardiac output and / or lung perfusion can be calculated and displayed. The calculation and display can be done either as a regional representation, similar to an EIT ventilation image, or as a single measured value (displayed as a scalar).

[0025] For the best possible gas exchange in the lungs, the ratio between local ventilation V and lung perfusion Q must be as balanced as possible. In the literature, a ratio of V / Q = 0.8... 1.0 is therefore described as optimal. However, there is currently no way to determine this ratio regionally in real time. Due to the improvement in measurement results already presented within the scope of the present invention and their quantitative interpretation in relation to the physiological parameters, the V / Q ratio can now also be determined and displayed both with regional resolution and as an individual measured value (scalar). A comparison of intra- and inter-individual data is now also possible. This means that a trend regarding the V / Q ratio can be determined and displayed and used as a parameter for diagnosis and therapy.Based on a defined V / Q ratio, the ventilation parameters for a patient can now be optimized so that the best possible V / Q ratio is achieved. The optimal ventilation parameters can be determined in various ways. They can either be set by a doctor or nursing staff, they can be determined by another system (e.g. an expert system) and suggested to the doctor, or they can be determined by another system (e.g. an expert system) and applied automatically. In order to exchange the collected EIT perfusion data and the regional V / Q ratio values ​​with the ventilator or the other system (e.g. an expert system), a data connection can exist between the control and evaluation unit and the other system (e.g. expert system) or the ventilator.

[0026] In addition, the administration of medication can also be optimized based on a defined V / Q ratio, so that the best possible V / Q ratio is achieved. These can either be determined by a physician or nursing staff, they are determined by an expert system and suggested to the physician, or they are determined by another system (e.g., an expert system) and administered automatically. The controlled use of conductivity contrast agents opens up a new area of ​​application for EIT. The regional detection and quantification of shunts (lung areas that are perfused but not ventilated) and dead spaces (lung areas that are ventilated but not perfused) is not easily possible with conventional "difference-in-time" EIT. With the help of the device of this invention, this diagnostically and therapeutically relevant regional assessment is possible in principle.Corresponding trends can also be calculated and visualized using shunts and dead spaces in the lungs. If shunts or dead spaces are identified, appropriate treatment recommendations can be issued by the control and evaluation unit or transmitted to another system (e.g., an expert system) or the ventilator. By administering boluses at specific intervals, it is possible to "calibrate" the cardiac output and blood flow-related information, which is determined using a method such as that described in "Dynamic separation of pulmonary and cardiac changes in electrical impedance tomography," Physiol Meas. 2008 June; 29(6), pages 1-14. If this procedure is combined with a dilution measurement, the accuracy of the results can be further improved.If significant changes occur in cardiovascular data, this can indicate a change in lung perfusion or stroke volume, and a corresponding alarm can be generated. Appropriate alarm management can be provided for all of the previously mentioned measured values ​​and trends. For example, alarms can be triggered if a sufficiently large shunt or dead space is detected. The alarm thresholds for triggering them can either be entered by the user on the device or they can be automatically generated by another system (e.g., an expert system) based on appropriate clinical guidelines. An alarm can also be triggered if a corresponding change occurs, i.e., depending on the gradient of the observed measured value.

[0027] With the improvements in measured values ​​enabled by the device according to the invention, it is now also possible to perform image registration (see, for example, "A survey of image registration techniques" by LG Brown in ACM computing surveys, Volume 24, No. 4, 1992, pages 325-376, "Numerical methods for image registration", J. Modersitzki, Oxford University Press, 2004) and to insert the image information on lung perfusion and ventilation obtained using EIT into a computed tomography image, for example, thus linking the two modalities (CT and EIT). This enables physicians and staff to diagnose clinical pictures more efficiently and adapt therapy accordingly.

[0028] The improved measurement values ​​also make it possible to acquire a multi-slice EIT image of lung perfusion by successively placing the electrode ring at different heights around the thorax and taking corresponding measurements (or directly using an electrode array with the electrodes arranged in multiple rings around the thorax), thus obtaining numerous cross-sectional images at different heights. Thanks to their improved accuracy, these cross-sectional images can be combined to create a three-dimensional image of the lung. If the measurement is repeated, the change in lung perfusion over time can be visualized as a trend in three dimensions.

[0029] The improved determination of lung perfusion also makes it possible to detect possible pathologies from the temporal distribution of the bolus across the lung using a symmetry operator ("The shape of indicator dilution curves used for cardiac output measurement in man", DM Band et al., The Journal of Physiology 1997, January 1, 498 (Pt 1), 225 - 229, "Automatic gait recognition by symmetry analysis", MS Nixon, Pattern Recogn. Lett., 24(13), 2175 - 2183, 2003, and "Detection of partial symmetry using correlation with rotated-reflected images", Masuda et al., Pattern Recognition, 26(8); 1245 - 1253, 1993). It is also possible to apply this symmetry operator to the distribution of the amplitude maxima in the tomogram in order to also detect possible pathologies. The symmetry operator calculates the symmetry on the previously mentioned images and determines the symmetry between the right and left hemispheres of the lung.The axis of symmetry is not simply placed in the center of the image, but is determined automatically, for example, so that the center of gravity of the heart region is automatically determined. However, the user can also define a corresponding axis of symmetry. A score can be calculated using the symmetry operator. The smaller this score, the less symmetry between the two lung halves, and the greater the probability of lung disease. Considering the inverse of the symmetry operator, the higher the inverse of the score, the greater the probability of lung disease.

[0030] In a preferred embodiment, the control and evaluation unit is further configured to identify lung areas in which the determined ventilation is above a predetermined threshold value and the determined lung perfusion is below a further predetermined threshold value as dead spaces and to display them in the displayed cross-sectional image of the lung.

[0031] In a further preferred embodiment, the control and evaluation unit is further configured to identify lung areas where lung perfusion is above a predetermined threshold and ventilation is below another predetermined threshold as shunts and to display them in the cross-sectional view of the lung. In advantageous embodiments, the control and evaluation unit can be further configured to display the temporal development of detected shunts or dead spaces as a trend representation over a period of time.

[0032] The invention is described below using an embodiment in the figures, in which: Fig. 1 shows a schematic block diagram of the device according to the invention, Fig. 2 shows changes in impedance determined by EIT at three pixels in the plane of section through the thorax after administration of a bolus of the conductivity concentrating agent, Fig. 3 shows a measured measure of lung perfusion as a function of time as a trend plot, Fig. 4 shows the changes in impedance determined by EIT at two pixels in the plane of section through the thorax after administration of a bolus as a function of time, and Fig. 5 to 13 show the development of the impedance distributions in the cross-sectional plane through the thorax in the form of contour lines at successive time points after administration of the bolus.

[0033] In Fig. 1 shows the EIT unit with a control and evaluation unit 2 connected to measuring cables 1. The supply device 4 is a controllable dosing device. A bidirectional data connection 3 is located between the control and evaluation unit 2 and the supply device 4. The dosing device 4 is connected to a venous catheter 5, through which the conductivity contrast agent is injected. The measuring cables 1 connect the control and evaluation unit 2 to electrodes E1, ... E N , which are arranged in a ring around the thorax. The control and evaluation unit is provided with a display device 6. Both the supply device 4 and the control and evaluation unit 2 can be connected via an external data connection 8 to third-party devices, e.g., a ventilator including an expert system contained therein or a monitoring monitor.

[0034] The following is an example of the function of the device according to the invention when administering a conductance bolus. The control and evaluation unit causes the dosing device to inject a bolus of 10 ml of 1 molar NaCl solution over a period of less than 2 seconds via a central venous catheter. This bolus can be observed in the EIT image after approximately 3 seconds in the region of the heart for approximately 25 seconds and after approximately 6 seconds for approximately 20 seconds in the lungs, with the maximum of the bolus being observed after approximately 4 to 7 seconds. Fig. Figure 2 shows the impedance curves after administration of a bolus at three points in the image plane of the thorax (here in an animal experiment, young pig weighing approximately 35 kg), with the solid line curve corresponding to an image element in the region of the heart, the dotted line curve to an image element in the right lung, and the dashed line to an image element in the left lung. As can be seen from the curves in Fig. As can be seen in Figure 2, the bolus first reaches the heart and then both lungs. In this case, the relative delay between the two lung curves already indicates a possible pathology in the lung. The time difference between the two lung halves can be used to assess and indicate the severity of the pathophysiological manifestation. In this case, the time difference between the curves of the right and left lung is approximately 3 seconds. This time difference is determined from the time interval between the maxima of the two curves.

[0035] During the time the bolus is effective, the measurement accuracy of the method is particularly high, as the bolus has a direct influence on the impedance of the blood and thus directly influences the EIT measurement. Regarding the shape of the dilution curves as in Fig. 2, reference is made to the article "The shape of indicator dilution curves used for cardiac output measurement in man," DM Band et al., The Journal of Physiology, 1997, January 1; 498 (Pt 1), pages 225-229. By coupling the EIT unit and the dosing device in the device according to the invention, the temporal sequence of the maneuvers can be coordinated such that a measurement of lung perfusion is initiated as soon as the bolus administration is initiated. The measurement is controlled based on knowledge of the previously described timing such that it is only measured over the time window in which the bolus is effective. The results of this EIT measurement can be represented as lung perfusion after appropriate processing, for example using a method such as that described in the article “Dynamic separation of pulmonary and cardiac changes in electrical impedance tomography” by Deibele et al., Physiol. Meas. June 2008, 29(6), pages 1-14.If the described bolus measurement is combined with a thermodilution measurement, it is also possible to precisely determine the cardiac ejection volume at the time of the bolus measurement and to correlate this value with the value measured by EIT, so that the absolute cardiac stroke volume can subsequently be determined using EIT.

[0036] Fig. Figure 3 shows a measure of lung perfusion, here the mean lung perfusion across the thorax slice, plotted as a trend over time over many hours. Such a trend plot of lung perfusion can provide important information about the patient's development and condition.

[0037] Fig. Figure 4 shows the changes in impedance determined by EIT at two pixels in the cross-sectional plane through the thorax after administration of a bolus of the conductivity concentrating agent as a function of time. At the times marked with circles, Fig. 5 - Fig. 14 the impedance distributions in the section plane through the thorax are shown in the form of contour lines.

[0038] Fig. 5. shows representations of lung perfusion using EIT as contour lines resolved at 0.025 s (the bolus has not yet reached the heart and lung region) after bolus administration and 1.275 s after bolus administration. At 1.275 s, the bolus can be seen entering the cardiac region.

[0039] Fig. Figure 6 shows lung perfusion images using EIT resolved as contour lines at 2.525 s and 3.775 s after bolus administration. At 2.525 s, the bolus can be seen flowing from the cardiac region into the right lung. The left lung is also partially reached by the bolus. At 3.775 s, the bolus can be seen spreading further across both lung halves.

[0040] Fig. Figure 7 shows lung perfusion images using EIT resolved as contour lines at 5.025 s and 6.275 s after bolus administration. At 5.025 s, the bolus is fully distributed and begins to drain away again at 6.275 s.

[0041] Fig. Figure 8 shows lung perfusion images using EIT resolved as contour lines at 8.775 s and 10.025 s after bolus administration. The bolus flows back out of the lungs through the heart.

[0042] Fig. 9. - Fig. Figure 13 shows lung perfusion images using EIT, resolved as contour lines between 11,275 s and 21,275 s after bolus administration. The bolus flows back out of the lungs through the heart. A heartbeat can still be identified by the extent of the contour lines in the cardiac region. List of reference symbols: 1 measuring cable 2 Control and evaluation unit 3 Data connection (wired or wireless) 4 Feed device 5 catheters 6 Display device 7 Temperature sensor 8 external data connection (wired or wireless)

Claims

[1] Device for determining the regional distribution of a measure of lung perfusion in a sectional plane of the thorax with • an electrical impedance tomography unit with a large number of electrodes (E1, ... E N ), which can be attached to the thorax distributed around the circumference of the cutting plane, and with a control and evaluation unit (2) connected to the plurality of electrodes, which is designed to successively supply alternating current or alternating voltage to each pair of electrodes and to record voltage or current signals from the remaining electrodes as measurement signals and to reconstruct the impedance distribution in the cutting plane from the measurement signals, • a supply device (4) for the intravenous supply of a conductivity contrast agent, wherein the control and evaluation unit (2) is further configured to display the changes in the impedance distribution resulting from the supply of conductivity contrast agent as a measure of the lung perfusion in the sectional plane as a function of time, characterized by , that • the supply device (4) has a controllable dosing device and the control and evaluation unit and the dosing device are connected to one another via a data connection (3) and are arranged such that at least the start and end time and amount of the delivery of a bolus of the conductivity contrast agent are available to the control and evaluation unit (2), • the control and evaluation unit (2) is configured to control the dosing device for administering a bolus of the conductivity contrast agent at a predetermined start time, with a predetermined amount and with a predetermined time course via the data connection (3) and to repeat the administration of the bolus of the conductivity contrast agent at predetermined time intervals • or the dosing device is designed to send data concerning the start time, quantity and time course of the delivery of a bolus via the data connection (3) to the control and evaluation unit (2) if the dosing device is caused to deliver a bolus repeatedly by an external device or directly by manual actuation of a switch by a user, • and that the control and evaluation unit is set up to display the temporal development of the degree of lung perfusion as a function of time as a trend representation. [2] Device according to claim 1, characterized by that the control and evaluation unit (2) and / or the dosing device are designed to be triggered to administer the bolus of the conductivity contrast agent by a signal fed in by external devices via a data connection (8). [3] Device according to one of the preceding claims, characterized by that the control and evaluation unit (2) is further configured to display the measure of lung perfusion in a spatially resolved manner over the lung area in the sectional plane through the thorax in two dimensions. [4] Device according to one of the preceding claims, characterized bythat the control and evaluation unit (2) is further configured to determine areas in which the measure of lung perfusion lies above a predetermined threshold as perfused areas in the sectional plane and to display the perfused areas, which result in each case from the administration of a bolus of the conductivity contrast agent, as a trend representation as a function of the time of the administration of the boluses of the conductivity contrast agent. [5] Device according to one of the preceding claims, characterized by that the control and evaluation unit (2) is further configured to determine the regional distribution of ventilation in the sectional plane of the thorax from the impedance distributions during times without administration of conductivity contrast medium and to display it as a function of time. [6] Device according to one of the preceding claims, characterized bythat the dosing device is provided with a temperature sensor (6) for the conductivity contrast medium or with a temperature control device for the conductivity contrast medium that can be controlled by the control and evaluation unit (2), and the control and evaluation unit (2) is designed to determine the cardiac ejection volume on the basis of the dilution principle from the determined or set temperature of the conductivity contrast medium and to absolutely calibrate the measure of the lung perfusion on the basis of the determined cardiac ejection volume. [7] Device according to claim 6, characterized by that the control and evaluation unit (2) is further configured to determine the ratio of ventilation to lung perfusion (V / Q) in a spatially resolved manner and to display it two-dimensionally and / or to determine and display the ratio of ventilation to lung perfusion (V / Q) averaged over the lung region in the sectional plane of the thorax. [8] Device according to claim 7, characterized by that the control and evaluation unit (2) is further configured to determine and store the ratio of ventilation to lung perfusion (V / Q) in a spatially resolved manner for several consecutive administrations of boluses and / or to determine and store the ratio of ventilation to lung perfusion (V / Q) averaged over the lung area in the sectional plane of the thorax and to display the ratios of ventilation to lung perfusion (V / Q) together as a trend representation. [9] Device according to one of claims 5 to 8, characterized by that the control and evaluation unit (2) is further configured to identify lung areas in which the determined ventilation is above a predetermined threshold value and the determined lung perfusion is below a further predetermined threshold value as dead spaces and to display them in the cross-sectional image of the lung shown. [10] Device according to claim 5 or 9, characterized by that the control and evaluation unit (2) is further configured to determine lung areas in which the lung perfusion is above a predetermined threshold value and the ventilation is below a further predetermined threshold value as shunts and to display them in the sectional view of the lung. [11] Device according to claim 9 or 10, characterized by that the control and evaluation unit (2) is further configured to display the temporal development of detected shunts or dead spaces as a trend representation over a period of time. [12] Device according to one of the preceding claims, characterized bythat the control and evaluation unit (2) is designed to monitor the variables derived or calculated from the determined lung perfusion as mentioned in the preceding claims for predetermined criteria and to give an alarm if it is determined that a predetermined criterion is no longer met.

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