DE102016226197B4 - Reduction of radiation disturbances in heartbeat measurements - Google Patents

Abstract

A method for heartbeat measurement (M-ECG) during irradiation of a patient (P) with ionizing radiation, comprising the steps of: - determining a position (PB (t)) of an irradiation area (BB), - identifying by the ionizing radiation influenced for determining a heartbeat signal from the patient (P) arranged heartbeat sensors (S (t)) in dependence on the determined position (PB (t)) and the extent (ASD) of the irradiation area (BB), - suppressing a heartbeat Signal disturbance on the basis of the knowledge of the ionizing radiation-influenced heartbeat sensors (S (t)) in a heartbeat measurement process (M-ECG).

Description

The invention relates to a method for heartbeat measurement during irradiation of a patient with ionizing radiation. In addition, the invention relates to an imaging method. Furthermore, the invention relates to a heart rate measurement control device. Moreover, the invention relates to an imaging device.

An electrocardiogram (ECG for short) is the recording of the sum of the electrical activities of all myocardial fibers. A contraction of a heart muscle is caused by an electrical excitation, which emanates from the sinoatrial node in a healthy heart. The electrical excitation is transmitted to the other cardiac muscle cells via a proprietary electrical conduction system made of specialized cardiac muscle cells. The occurring electrical voltage changes in the heart can be measured on the body surface of a patient and recorded as a function of time.

Other methods for heart rate measurement are, for example, electro-optical methods which work with a so-called Photrode. Such a method is described in Stuart A. Kingsley, "Photodromes for Physiological Sensing", available at http://www.srico.com/files/SPIE%20Photonics%20West%202004.pdf.

Another type of heart rate measuring method is based on the principle of so-called pulse oximetry, wherein optically the movement of arteries is measured.

Various types of sensors can be used to acquire an electrocardiogram. In addition to the usual techniques of contacting patients with cables and electrodes, there are also methods in which the ECG signals are acquired purely capacitively. In this form of recording an ECG capacitive sensors in the size of about 10-100 cm ² are used, which are positioned as possible on the body of the patient that their coupling capacity with respect to the patient is maximum. For sufficient signal quality, the sensors must be placed very close to the body and completely covered by the body, but may be separated from the body by a layer of clothing a few millimeters thick.

Heartbeat measurements, for example ECG measurements, can also be used to synchronize an irradiation procedure, for example an X-ray imaging procedure, with a body movement, in particular a cardiac movement. If a capacitive detection of ECG signals is carried out during an irradiation procedure, for example an X-ray imaging method, the coupling capacity between the sensors and the patient is influenced by the ionizing effect of the X-ray irradiation. This leads to disturbances of the ECG signal, whereby the heartbeat detection can be disturbed. With a strong directivity of the X-ray radiation, the ionizing effect of the X-ray radiation is spatially limited to the effective range of the X-ray radiation, so that only sensors are influenced which lie almost directly in the beam path.

US 2016/0 074 674 A1 discloses a gating system which uses electrical impedance measurements to provide simultaneous gating for respiratory and cardiac motion. Gating is based on the change in bioimpedance that occurs during respiration and heart movement at transthoracic electrodes.

DE 10 2008 020 780 B4 discloses a correction method for correcting an ECG signal data set of an ECG signal, which was recorded in a magnetic resonance apparatus by an ECG measuring device.

Conventionally, ECG signals are detected by simultaneous X-ray irradiation with cables and electrodes. However, this detection is also susceptible to radiation interference. In addition, capacitive ECG measurement methods can be used more universally and more conveniently because direct contact with the skin of a patient is not absolutely necessary. Thus, the patient can undergo the examination dressed up, with the ECG sensors coupling capacitively through his clothing. For example, it is thus possible to produce sensor matrices which are firmly positioned in or on a holding device, such as a patient couch, for example, with the position of the individual sensors being precisely defined and known.

Another problem can be caused by movement of the patient during an ECG measurement. If the patient moves, a movement of his clothing layer occurs. This movement is extremely small, but it does cause friction on a large area between the clothing and materials in contact with it. For materials with different affinity for electrons, this results in a so-called triboelectric effect. That is, electrons are exchanged between the different materials. This leads to an electric field, which is detected by the capacitive ECG sensors and occurs as a disturbance of the ECG measurement signal.

In order to reduce the aforementioned disturbances due to the triboelectric effect, it is conventionally attempted to correlate the disturbances caused by the movement precisely with that movement of the patient using additional sensors for measuring the movement of the patient and, based on the determined movement, the movement through the motion caused noise to be removed from the ECG measurement signal. That is, the interference is not prevented, but it is subsequently attempted to remove corresponding interference signal components from the ECG measurement signal, which is not fully achieved. One such approach to correction by the application of an algorithm is described in Heuer et al., Motion Artifact Correction for Capacitive ECG Measurement, Biomedical Circuits and Systems Conference, 2009, BioCAS 2009, IEEE.

Another approach attempts to derive the triboelectrically generated charges by covering the capacitive sensors with a dissipative grid. However, this approach only allows to derive charge in the immediate vicinity of the grid and also reduces the amplitude of the ECG measurement signal. Such an approach is described in Wartzek et al., "Triboelectricity in Capacitive Biopotential Measurements" IEEE Transactions on Biomedical Engineering, Volume: 58, Issue: 5, May 2011, p. 1268-1277. Thus, it is desirable to develop a method for low-interference heartbeat measurement in the context of an irradiation process with ionizing radiation.

This object is achieved by a method for heartbeat measurement during irradiation of a patient with ionizing radiation according to claim 1, an imaging method according to claim 12, a heartbeat measurement control device according to claim 13 and an imaging device according to claim 14.

In the method according to the invention for heartbeat measurement during irradiation of a patient with ionizing radiation, a position of an irradiation area is determined. Furthermore, heartbeat sensors, which are influenced by the ionizing radiation and are arranged to detect a heartbeat signal, are identified as a function of the determined time-dependent position and the extent of the irradiation area. Finally, suppression of a heartbeat signal disturbance is based on the knowledge of the ionizing radiation-influenced heartbeat sensors in a heartbeat measurement process. The steps for avoiding radiation disorders are based on knowing the position of the heartbeat sensors for the heartbeat measurement, the extent of an irradiation area and possibly a current scan position. Advantageously, it can be predicted with the aid of this information whether, when and at which point without countermeasures a disturbance of the heartbeat signals due to irradiation of heartbeat sensors would occur. Thus, limited local and / or temporal countermeasures can be taken to suppress the signal disturbances, but at the same time the heartbeat measurement can be continued with at least part of the heartbeat sensors. In this way a more reliable synchronization of radiation, for example as part of an imaging process, is achieved, whereby the precision of the irradiation process is improved.

As ionizing radiation is any type of radiation, such as electromagnetic radiation or body noise, understood, which can cause a signal interference by ionization. An important special case is the irradiation with X-rays, which can be used for both imaging and radiotherapy. Both the imaging and the radiotherapy should be encompassed by the term "radiation" or "radiation process".

In the imaging method according to the invention, preferably an X-ray imaging method, particularly preferably a CT imaging method, heartbeat measurement signals are acquired from a patient to be examined using the heartbeat measurement method according to the invention during irradiation of a patient with ionizing radiation. In response to the detected heartbeat measurement signals, an image acquisition is then clocked by the patient. That is, the timing of the imaging, in particular triggering an imaging operation, is synchronized with the detected heartbeat measurement signals and thus with the patient's heart movement.

The imaging device according to the invention has a scanning unit for acquiring projection measurement data from an examination area of a patient. Projection measurement data includes projection-generated raw data on the basis of which image data can be generated. In the case of a CT scan unit, projection measurement data are acquired from different directions and reconstructed into image data by means of a reconstruction method. In addition, the imaging device according to the invention comprises a control device for controlling the scanning unit and for generating image data on the basis of the acquired projection measurement data, for example by means of a reconstruction method such as the filtered backprojection. Furthermore, the inventive Imaging device, a heartbeat measurement system and a heart rate measurement control device according to the invention. For example, an EKG measuring device can serve as a heartbeat measuring system. Preferably, the heartbeat measurement control device may also be part of the control device for driving the scan unit. Advantageously, in this case, data for controlling the image acquisition can also be used simultaneously for determining a position and an extent of a current radiation area in order to suppress heartbeat interference signals. The imaging device may preferably include an X-ray imaging device, particularly preferably a CT imaging device.

The essential components of the heartbeat control device according to the invention can for the most part be designed in the form of software components. This relates in particular to the position detection unit, the identification unit and the signal interference suppression unit. In principle, however, these components can also be partly realized, in particular in the case of particularly fast calculations, in the form of software-supported hardware, for example FPGAs or the like. Likewise, the required interfaces, for example, if it is only about a transfer of data from other software components, be designed as software interfaces. However, they can also be configured as hardware-based interfaces, which are controlled by suitable software.

A largely software implementation has the advantage that even previously used imaging devices can be easily retrofitted by a software update to work in the manner of the invention. In this respect, the object is also achieved by a corresponding computer program product with a computer program which can be loaded directly into a memory device of an imaging device, with program sections in order to carry out all the steps of the method according to the invention when the computer program is executed in the imaging device.

Such a computer program product may contain, in addition to the computer program, additional components such as e.g. a documentation and / or additional components, also hardware components, such as e.g. Hardware keys (dongles, etc.) for using the software include

For transport to a storage device of such an imaging device and / or for storage at the imaging device, a computer-readable medium, for example a memory stick, a hard disk or other transportable or permanently installed data carrier can be used, on which the computer program which can be read and executed by a computer unit is stored are. The computer unit may e.g. for this purpose have one or more cooperating microprocessors or the like and be part of said imaging device.

The dependent claims and the following description each contain particularly advantageous embodiments and further developments of the invention. In this case, in particular the claims of a claim category can also be developed analogously to the dependent claims of another claim category or their parts of description. In addition, in the context of the invention, the various features of different embodiments and claims can also be combined to form new embodiments.

In a variant of the method according to the invention for heartbeat measurement during irradiation of a patient with ionizing radiation, the irradiation takes place in the context of a dynamic imaging method. In this variant, therefore, the imaging process is synchronized with the heart movement by the heart movement is determined using a heartbeat signal and the imaging process is adapted to the detected heart movement. Advantageously, the interference susceptibility of the synchronization is reduced with the aid of the procedure according to the invention and thus the image quality is improved.

The heartbeat measurement may include, for example, an ECG measurement method or an electro-optical heartbeat measurement method or a pulse oximetry heartbeat measurement method.

As an ECG measuring method, for example, a classic electrode measuring method can be used in which the measuring electrodes or heartbeat sensors directly contact the body of the patient electrically. Alternatively and more preferably, the heartbeat sensors are designed as capacitive sensors. Advantageously, these capacitive sensors do not have to contact the patient's body directly. Thus, they may be located at fixed positions relative to each other and to the body of the patient, so that the positions of individual sensors need not be individually adjusted to the body of the patient. Thus, the positions of individual sensors are known in advance and a generally applicable individual patient control process can be used to turn on and off the heartbeat sensors during irradiation. In addition, the Patient should keep his clothes during an exam because direct body contact of the heartbeat sensors is not necessary in a capacitive measurement.

In one embodiment of the method according to the invention for heartbeat measurement during irradiation of a patient with ionizing radiation, suppressing a heartbeat signal disturbance comprises detecting heartbeat signals of heartbeat sensors constantly lying outside the time-dependent irradiation area during the irradiation period. In this variant, which is particularly easy to implement, only heartbeat sensors are used for measuring the cardiac movement, which lie outside the range of irradiation possibly changing its position during the irradiation over the entire time of the irradiation. Thus, there is no need to switch between different heartbeat sensors during the irradiation because the sensors used for heartbeat measurement do not change. An adaptation of the active sensor field to a moving irradiation area can thus be omitted in this constellation. For example, in imaging the heart, sensors may be positioned in the shoulder and neck area and as the opposite pole in the hip and seat area. Consequently, the sensors always remain outside the irradiation area and can be used continuously for the detection of sensor signals and for synchronizing the heart movement with the imaging process.

In a variant of the method according to the invention for heartbeat measurement during irradiation of a patient with ionizing radiation, the position of the irradiation area is determined as a time-variable position. If the position of the irradiation area changes during the irradiation process, as for example in CT imaging, the position of the irradiation area must be determined as a function of time. This can for example take place beforehand on the basis of an irradiation protocol or also take place in real time during the irradiation by determining a current position of the irradiation area, wherein this position can be determined on the basis of control data of the actuation unit of the irradiation unit, for example.

Preferably, in the method according to the invention for heartbeat measurement during irradiation of a patient with ionizing radiation, a heartbeat signal disturbance is suppressed in a time-dependent manner. This variant is particularly well suited if no sensors can be placed outside the irradiation area or image area to be detected, but there are good possibilities for positioning a plurality of sensors within this area. In this variant, the sensors are switched in the course of the irradiation depending on a position of the irradiation area so that always sensors are used, which are outside of the ionized by the irradiation area. Thus, a disturbance of the heartbeat signals due to ionization can be prevented even if all sensors are temporarily in the irradiation area. In this variant, therefore, the time-dependent suppression of a heartbeat signal interference takes place by the detection of heartbeat signals from sensors which lie outside the determined time-dependent irradiation area at a respective detection time.

In a particularly advantageous embodiment of the method according to the invention for heartbeat measurement during irradiation of a patient with ionizing radiation, the determination of a time-dependent position of an irradiation area is effected as a function of a predetermined irradiation protocol. Advantageously, it can be predicted with the aid of an irradiation protocol, for example a measurement protocol, even before the start of the irradiation process, at which point in time which sensor lies in the irradiation area and therefore has to be switched off in good time. Consequently, it is possible to dispense with monitoring of the irradiation process for establishing switching times of the sensors during the irradiation process itself, so that the control of the overall process is simplified.

In the context of a preferred variant of the method according to the invention for measuring the heartbeat during irradiation of a patient with ionizing radiation, the heartbeat signal is used to generate a triggering signal for triggering an interruption and / or a resumption of an imaging procedure. In this embodiment, therefore, imaging with the heart movement is synchronized with the aid of the heartbeat signal. For example, it may be useful to perform an imaging operation only during the resting state of the heart and to interrupt during the pumping movement of the heart. Alternatively, it may also be useful to perform an imaging operation only during a predetermined movement phase of the heart and otherwise to interrupt to map the heart or an area in the body that is synchronized with the cardiac or respiratory movement in the predetermined movement phase.

In a further variant of the method according to the invention for measuring the heartbeat during irradiation of a patient with ionizing radiation, the time-dependent suppression of a heartbeat signal disturbance takes place in that that a triggering sensitivity for a heartbeat signal from a heartbeat sensor during a determined time interval of an irradiation process is reduced. This variant is particularly suitable if only a simple set of heartbeat sensors is present, wherein the sensors are always arranged within the irradiation area. With the aid of the method according to the invention, it is now possible to predict very precisely when a possible disturbance can occur based on the position of the sensors and the knowledge of the time-dependent position of the irradiation area and its extent. This information can then be used in heartbeat detection to alter the triggering sensitivity, preferably to set the heartbeat detection algorithm to have a higher specificity. For example, the information can then be used in heartbeat detection to lower the trigger or trigger sensitivity. That is, due to the lower sensitivity in the signal evaluation, noise is not detected so easily as trigger signals, so that the risk of a faulty triggering of an irradiation process due to a noise signal is also reduced.

In a special variant of the method according to the invention for measuring the heartbeat during irradiation of a patient, the heartbeat sensors are arranged in an immovable sensor matrix. An immobile sensor matrix is to be understood as meaning a sensor matrix which does not change its position during an examination and whose sensors also do not change their relative position to one another during the examination. An immovable sensor matrix enables a reliable determination and determination of the position of the individual sensors, so that the positions of the sensors need only be determined in advance once and can be used throughout the investigation to suppress the interference signals. Such a sensor matrix can be designed, for example, as a sensor mat, which is mounted on a patient couch, on which the patient takes place for irradiation.

In one embodiment of the method according to the invention for measuring the heartbeat during irradiation of a patient with ionizing radiation, a test procedure is carried out before the irradiation in order to determine whether the patient's clothing during an irradiation procedure, for example an imaging procedure in which the patient is moved, contributes to a disturbance of a heartbeat measurement signal, preferably a heartbeat measurement signal, due to the triboelectric effect. As part of the test procedure, a time interval is determined in a heartbeat measurement signal, which corresponds to an isoelectric phase. In this context, the isoelectric phase is to be understood as meaning the cardiac phase with the lowest electrical activity and the lowest heartbeat signal amplitudes or signal amplitudes. Subsequently, the patient is moved during an isoelectric phase, preferably accelerated, and a heartbeat measurement signal is recorded during the isoelectric phase. Finally, it is determined whether an interference signal has been recorded. This determination is made by comparing the recorded heartbeat measurement signal with a reference value. The reference variable may be, for example, a heartbeat measurement signal recorded during an isoelectric phase without interference. If, during the comparison, a deviation between the two heartbeat measurement signals is determined, which exceeds a predetermined extent, then this situation is interpreted as an indication that a disorder due to the clothing of the patient occurs. In this case, the patient will be asked to remove their clothing before starting the radiation procedure.

In one embodiment of the test method according to the invention, a movement of the patient takes place during a first isoelectric phase in a first direction and during a second isoelectric phase in the opposite direction. If there is a disorder due to the clothing of the patient, this disorder also occurs in the opposite movement of the patient. A detection of a disturbance signal during the movement of the patient in the opposite direction can therefore be regarded as confirmation of the detected in the first isoelectric phase disturbance, which makes the test process even more reliable.

If capacitive measuring methods are used for the heartbeat measurement, the mentioned disturbing effects are caused by the triboelectric effect. However, the test method described can also be used in conjunction with a conventional ECG measuring method in which the measuring electrodes make direct electrical contact with the body of the patient. In this case, although the problem of a triboelectric effect due to a movement of the patient's clothing does not occur, by drawing on the ECG cable and thus pulling on the electrodes, signal interference may also occur. If the cable is subjected to a tensile load by the movement of the patient, for example due to a movement of the patient table, and is not decoupled from the electrodes, the test method likewise measures a disturbance. One possible countermeasure is to secure the electrodes against tension on the cable. For this, the cable is simply covered with medical tape at various points on the patient, with some excess cable between the Glueing and the electrodes, fixed so that a pull on the cable acts primarily on the splice.

A simple solution is to lay the cable better in most situations first. In everyday use, the problems mainly occur when the cable is unfavorable and can not move freely, but is slightly clamped.

• 1 eine schematische Darstellung einer EKG-getriggerten Röntgenbildgebungseinrichtung gemäß einem Ausführungsbeispiel der Erfindung,
• 2 ein Flussdiagramm, mit dem ein Verfahren zur EKG-Messung während einer Röntgenbestrahlung eines Patienten gemäß einem Ausführungsbeispiel der Erfindung veranschaulicht wird,
• 3 ein Blockdiagramm, mit dem eine EKG-Steuerungseinrichtung gemäß einem Ausführungsbeispiel der Erfindung dargestellt wird,
• 4 ein Flussdiagramm, welches ein Testverfahren zur Vermeidung des Auftretens eines Störsignals aufgrund des triboelektrischen Effekts gemäß einem Ausführungsbeispiel der Erfindung veranschaulicht.

The invention will be explained in more detail below with reference to the accompanying figures with reference to embodiments. Show it:

• 1 1 a schematic representation of an ECG-triggered X-ray imaging device according to an exemplary embodiment of the invention,
• 2 a flowchart illustrating a method for ECG measurement during X-irradiation of a patient according to an embodiment of the invention,
• 3 a block diagram showing an ECG control device according to an embodiment of the invention,
• 4 a flowchart illustrating a test method for avoiding the occurrence of a noise signal due to the triboelectric effect according to an embodiment of the invention.

In 1 is an ECG-triggered CT imaging device 10 shown. The CT imaging device 10 includes a CT scan unit shown in the left half of the picture 20 with a gantry 21 and a patient bed 22 and an ECG sensor unit illustrated in the right half of the drawing 30 , which by means of an ECG measurement of the heart currents of a patient (only in the right half of the picture symbolically as a layer P shown) the imaging of the scanning unit 20 with the heartbeat of the patient P synchronized. The scanning unit 20 is by means of a control device 25 controlled, which positioning commands PoB to the patient bed 22 sends to the position of the patient bed 22 during imaging, changing stepwise or continuously, thereby allowing full scan of an examination area. In addition, with the help of the control device 25 control commands AS to the scanning unit 20 which serve to perform a scanning operation of the examination area through the gantry 21 to control. Furthermore, the control device receives 25 Projection data RD from the scanning unit 20 and process them by reconstruction to image data.

The ECG sensor unit 30 includes a sensor mat M lying on the patient bed 22 is positioned and on which a patient lies during a CT imaging procedure. The sensor mat M is also shown schematically on the left edge of the right half of the image, with individual sensor elements S in the right half of the picture by dashed lines with the corresponding sensor elements S connected in the left half of the picture. The sensor mat M comprises an X-ray permeable textile layer T , a sensor cover A and a plurality of capacitive sensors S which enter the textile layer T the sensor mat M are integrated in the form of a sensor matrix. Each of the sensors S is with an active protection screen 32 Also known as guard, and an additional passive shield 31 , also referred to as shield, electrically shielded and with its own input buffer 33 electrically connected, which is a very high-impedance operational amplifier as the most important components 33a and also a very high impedance resistor 33b for the DC adjustment. The sensors S comprehensive sensor matrix is embedded in large-area contacts, which connect to a ground connection 35 as well as to one of the sensors S from controlled neutral electrode 34 Offer. The sensors S are all connected to a switching matrix 36 connected, with their help for the further signal processing certain sensors S can be selected. In the right half of the image, a clothing layer is then left on the sensor mat M K a garment of a patient presented as well as a layer P which symbolizes the patient or the body of the patient.

To the switching matrix 36 is a signal processing unit 37 connected, which generates based on received sensor signals SNS ECG signals S _ECG . The ECG signals S _ECG are sent to a trigger unit 38 transmitted, which calculates based on the ECG signals trigger signals for timing a cardiac imaging. The selection of sensors S with the help of the switching matrix 36 serves to compensate for different body shapes. There are each the sensors S used, which allows for a good coupling close to the body of each patient P lie and continue to allow a good ECG lead, which is given when the sensors S are arranged at different angles relative to the electrical heart center, so not for example both on the left shoulder of a patient P lie. The switching matrix 36 is by an ECG control device 40 the ECG sensor unit 30 with the help of control commands SB driven. The control commands SB are determined in response to position information PI, which from the controller 25 the scan unit 20 be transmitted. The position information PI include data representing a position of the patient couch 22 and thus the sensor matrix relative to the gantry 21 the scan unit 20 specify. The switching matrix 36 is determined by means of the control commands SB from the ECG control device 40 controlled such that ECG sensors, which are located in the current image recording area, are turned off, while the ECG sensors S , which are outside of a current picture-taking area, are activated. In this way, it is achieved that active sensors S are not influenced by X-radiation, so that ECG measurement errors due to the X-ray radiation can be avoided.

In 2 is a flowchart 200 which shows a method for ECG measurement during x-irradiation of a patient with a computed tomography system 10 (CT system, see 1 ) illustrated in accordance with an embodiment of the invention. At the step 2.I a position PB (t) of an irradiation area BB of the patient is determined as a function of time. The determination of the time-dependent position PB (t) of the irradiation area BB in the step 2.I For example, before starting imaging using an existing measurement protocol. Since the position PB (t) of the irradiation area BB changes in the course of imaging, a position of the irradiation area BB is calculated as a function of time. Alternatively, the position PB (t) of the irradiation area BB may also be based on the control commands AS, PoB for the scanning unit 20 of the CT system 10 (please refer 1 ) in real time. In this variant, the current position PB (t) of the irradiation area BB is always determined during the imaging. In step 2.II, the sensors S _F (t) are subsequently determined, which in each case again lie in the irradiation area BB of the CT system as a function of time. The determination can be carried out beforehand on the basis of the knowledge of a time-dependent position PB (t) of the irradiation area BB and on the basis of a previously known extent ASD of this irradiation area BB, but alternatively it can also be done in real time during image acquisition on the basis of the respective current position PB (t ) of the irradiation area BB and its extension ASD. Finally, in step 2.III, the relevant sensors S _F (t), which at a certain point in time are in the irradiation area BB, are switched off at this time or directly before this time. Sensors S, which were previously in the irradiation area BB and therefore were switched off and are no longer in the irradiation area BB, however, are turned on. Finally, in step 2.IV an ECG measurement M-ECG is carried out exclusively with the sensors S, which are not in the current irradiation area BB, so that a disturbance due to exposure of the ECG sensors S _F (t) to X-rays is prevented can.

In 3 is an ECG control device 40 shown according to an embodiment of the invention. The ECG control device 40 includes a position determination unit 41 which a position information PI detects which data is received with respect to a current position PB (t) of an irradiation area BB, for example an image acquisition area. Based on the position information PI and a previously known extent ASD of an irradiation area assigned to the irradiation area BB determines an identification unit 42 the currently lying in the irradiation area BB sensors S _F (t). The information IDI relating to the sensors S _F (t) lying in the irradiation area BB is sent to a switching matrix control unit 43 which transmits a switching matrix 36 (see also 1 ) by means of control commands SB such that the detected sensors S _F (t) are turned off. Conversely, sensors are used S , which were previously in the irradiation area BB and therefore were switched off and are currently no longer in the irradiation area BB, however, are turned on.

In 4 is a flowchart 400 which illustrates a test procedure prior to irradiation of a patient P is performed to detect an occurrence of a disturbance signal due to patient movement. For example, this test method can be done before the in 2 illustrated imaging method to avoid spurious signals due to the triboelectric effect.

At the step 4.I becomes a patient first P on a patient couch 22 (please refer 1 ), also called the patient table, is positioned in the same way as it is later arranged during the imaging procedure. In step 4.II, an ECG measurement M-ECG of the patient P is then carried out while the patient table is at rest 22 is started with capacitive ECG sensors and it is determined based on a recorded curve of the ECG signal, a time of occurrence and a period of a recurrent time interval T _iso , which corresponds to the period of an isoelectric phase. In addition, during such an isoelectric phase and with the patient table at rest 22 with an ECG measurement M-ECG (T _iso1 ) stored during a first isoelectric phase T _iso1 ECG signal stored. In step 4.III, the patient _{table is} accelerated during a second isoelectric phase T _iso2 and simultaneously _receives an ECG measurement signal from the patient P as part of an ECG measurement M-ECG (T _iso2 ) recorded. At step 4.IV the movement of the patient table becomes 22 stopped briefly. Subsequently, in the step 4.V at the next isoelectric phase T _iso3 the patient _table 22 Accelerated in the opposite direction and at the same time in turn recorded an ECG measurement signal from the patient in an ECG measurement M-ECG (T _iso3 ). Subsequently, in step 4.VI, the movement of the patient table 22 stopped again.

Subsequently, in step 4.VII, a comparison of the ECG measurement signals recorded during the table movement with the ECG measurement signal acquired when the patient table is stationary is carried out as the reference variable. Is a fault ST due to the clothing worn by the patient, it occurs in a very similar manner both in the second isoelectric phase T _iso2 and in the third isoelectric phase T _iso3 . A disturbance ST can be determined by comparing the ECG signals determined in the second and third isoelectric phase T _iso2 , T _iso3 with the ECG signal determined in the first isoelectric phase T _iso1 . Was a disorder due to the clothes detected in what 4 is marked with "j", it proceeds to step 4.VIII, in which the patient P is automatically requested to undress before the imaging process is started. In this way, an interference signal due to movement of a garment of the patient P is avoided. In the event that no interference has been detected by the clothing of the patient P, resulting in 4 is marked with "n", it proceeds to step 4.IX, where a message is issued that the imaging procedure can be started without the patient P having to be undressed.

It is finally pointed out again that the above-described methods and devices are merely preferred embodiments of the invention and that the invention can be varied by a person skilled in the art without departing from the scope of the invention, as far as it is specified by the claims. For the sake of completeness, it is also pointed out that the use of indefinite articles does not exclude "a" or "one", that the characteristics in question can also be present multiple times. Similarly, the term "unit" does not exclude that it consists of several components, which may also be spatially distributed.

Claims (16)

A method for heartbeat measurement (M-ECG) during irradiation of a patient (P) with ionizing radiation, comprising the steps of: - determining a position (PB (t)) of an irradiation area (BB), - identifying by the ionizing radiation influenced for detecting a heartbeat signal from the patient (P) arranged heartbeat sensors (S _F (t)) in dependence on the determined position (PB (t)) and the extent (ASD) of the irradiation area (BB), - suppressing a heartbeat Signal disturbance on the basis of the knowledge of the ionizing radiation-influenced heartbeat sensors (S _F (t)) in a heartbeat measurement process (M-ECG). Method according to Claim 1 , wherein the irradiation takes place in the context of an X-ray imaging method. Method according to Claim 1 or 2 in which the heartbeat measurement (M-ECG) comprises one of the following measuring methods: an ECG measuring method, an electro-optical heartbeat measuring method, a pulse oxymetric heartbeat measuring method. Method according to one of Claims 1 to 3 wherein suppressing a heartbeat signal disorder comprises detecting heartbeat signals from heartbeat sensors (S) constantly out of the irradiation area (BB) during the irradiation time. Method according to one of the preceding claims, wherein the position (PB (t)) of the irradiation area (BB) is determined as a time-varying position. Method according to one of Claims 1 . 2 . 3 and 5 wherein suppression of a heartbeat signal disturbance is time dependent. Method according to Claim 6 wherein the time-dependent suppression of a heartbeat signal disturbance comprises the detection of heartbeat signals from sensors (S) which lie outside the determined irradiation area (BB) at a respective detection time. Method according to one of the preceding claims, wherein the determination of a position (PB (t)) of an irradiation area (BB) takes place as a function of a predetermined irradiation protocol. The method of any one of the preceding claims, wherein the heartbeat signal is used to generate a trigger signal to trigger an interruption of an imaging operation. Method according to one of Claims 6 to 9 wherein the time-dependent suppression of a heartbeat signal disturbance is to reduce a triggering sensitivity for a heartbeat signal from a heartbeat sensor (S) during a determined time interval of irradiation. Method according to one of the preceding claims, wherein prior to irradiation Test _method , comprising the following steps: determining a time interval (T _iso ) which corresponds to an isoelectric phase, - moving the patient (P) during the isoelectric phase, - recording a heartbeat measurement signal during the isoelectric phase, - determining whether an interference signal has been recorded by comparing the recorded heartbeat measurement signal with a reference value. An imaging method, preferably an x-ray imaging method, comprising the steps of: - acquiring heartbeat measurement signals from a patient (P) to be examined using a method according to any one of Claims 1 to 11 , - Recording an image taken by means of ionizing radiation image recording of the patient (P) in response to the detected heartbeat measurement signals. A heartbeat measurement control device (40), comprising: - a position determination unit (41) for determining a position (PB (t)) of an irradiation area (BB), - an identification unit (42) for identifying ionizing radiation, for detecting a heartbeat signal from the patient (P) arranged heartbeat sensors (S _F (t)) in dependence on the determined position (PB (t)) and the extent (ASD) of the irradiation area (BB), - a signal interference suppression unit (43) for suppressing a heartbeat signal disorder based on the knowledge of the ionizing radiation-influenced heartbeat sensors (S _F (t)) in a heartbeat measurement process (M-ECG). Imaging device (10), preferably an X-ray imaging device, comprising: - a scan unit (20) for acquiring projection measurement data (RD) from an examination area of a patient (P), - a control device (32) for driving the scan unit (31) and for generating image data (BD) on the basis of the acquired projection measurement data (RD), - a heartbeat measurement system (30), - a heartbeat measurement control device (40) according to Claim 13 , A computer program product having a computer program which can be loaded directly into a memory unit of an imaging device (10), with program sections for carrying out all steps of the method according to one of the Claims 1 to 12 when the computer program is executed in the imaging device (10). Computer-readable medium on which program sections executable by a computer are stored in order to perform all the steps of the method according to one of Claims 1 to 12 execute when the program sections are executed by the arithmetic unit.

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