Processing of motion signals during a magnetic resonance imaging (MRI) scan

Abstract

Method for processing motion signals acquired during a magnetic resonance measurement of a patient (15), the method comprising: - Generation of RF pulses (HF1, HF2) to excite nuclear spins in the patient's body (15) by an RF transmitter unit (20) and generation of magnetic resonance signals by the excited nuclear spins, - Generation of gradient pulses for spatial encoding of the magnetic resonance signals by a gradient coil unit (18), - Detection of magnetic resonance signals by an RF receiver unit, - Detection of patient movement signals (15) by a motion detection unit (27) during the acquisition of magnetic resonance signals, - Processing of the motion signals by a processing unit (26), whereby a response of the patient (15) to a contrast agent is observed based on the motion signals.

Description

The invention relates to a method for processing movement signals which are acquired during a magnetic resonance measurement of a patient, and to a corresponding magnetic resonance apparatus and a computer program product.Magnetic Resonance Imaging (MRI). Magnetic Resonance Imaging, MRI) is a known technique for generating magnetic resonance images of a patient's interior body based on the physical phenomenon of magnetic resonance (MR). Movement of the patient during a magnetic resonance measurement can degrade the quality of the magnetic resonance images. Therefore, it is usually attempted to avoid recording magnetic resonance signals during the movement and / or to bring about periods with restricted movement, for example by air stoppage. A further possible approach is to perform a movement correction or movement compensation, as disclosed for example in the publications DE 10 2014 210 471 A1 or DE 10 2015 207 590 A1.The movement of the patient can be detected in various ways, for example by means of navigators, a respiratory belt, an ECG measuring device and / or further motion sensors. For example, the document U.S. Pat. No. 9,414,767 B2 discloses a method for correction by means of an ECG signal during magnetic resonance measurement.The invention is based on the object of more effectively processing the movement signals detected by means of one or more movement sensors in order to achieve a higher benefit.The object is achieved by the features of the independent claims. Advantageous embodiments are described in the dependent claims.Accordingly, a method for processing movement signals which are acquired during a magnetic resonance measurement of a patient is proposed. In this case, RF pulses are generated by an RF transmission unit of a magnetic resonance apparatus in order to excite nuclear spins in the body of the patient. As a rule, the excitation is effected by magnetization of the nuclear spin. Here, and also in the following, "RF" stands for "radio frequency" (RF). Magnetic resonance signals are generated by the excited nuclear spins. For the spatial encoding of the magnetic resonance signals, gradient pulses are generated by a gradient coil unit of the magnetic resonance apparatus. The magnetic resonance signals are acquired by an RF receiving unit of the magnetic resonance apparatus. Furthermore, during the acquisition of the magnetic resonance signals, movement signals of the patient are acquired by an, in particular external and / or independent, movement acquisition unit, which are processed by a processing unit. In this case, a reaction of the patient to a contrast medium is observed on the basis of the movement signals. The processing of the motion signals acquired by a motion acquisition unit allows new applications, whereby the magnetic resonance measurement can be improved.The movement detection unit can detect movement signals which characterize a movement of the patient. The movement signals are preferably acquired not only during the acquisition of the magnetic resonance signals, but also during the generation of the magnetic resonance signals, i.e. in particular during the excitation of the nuclear spins and / or waiting times for a relaxation of the nuclear spins. The movement signals are therefore preferably acquired continuously during the magnetic resonance measurement of the patient.The acquisition of the movement signals is advantageously carried out independently of the acquisition of the magnetic resonance signals. Preferably, the acquisition of the movement signals does not require a preparation of the patient. Preferably, a movement of the patient's breast, in particular a breathing movement and / or a heartbeat of the patient, is detected by the movement signals.When detecting the breathing movement, the processing unit can determine from the movement signals, for example, a breathing curve which in particular indicates whether the patient inhales or exhalations at a specific point in time. It is furthermore conceivable for a heart movement to be derived from the movement signals, so that in particular an ECG-like curve can be provided. Here, "ECG" means "electrocardiography (ECG).For example, the movement detection unit comprises at least one camera, which is preferably aligned with the patient, and / or an RF coil. The RF coil can be arranged, for example, under the patient's chest and detect the movement signals on the basis of a change in a load of the RF coil. Such a movement detection unit does not require a preparation of the patient.However, the movement detection unit can in principle also comprise other sensors, such as a breathing belt or an ECG measuring device, although a preparation of the patient is necessary here. Image-based detection of the movement signals, for example by means of a navigator, is also conceivable in principle, even if it generally requires additional measurement time and possibly has a low sensitivity.The RF transmission unit can comprise, for example, a whole body coil (body coil) which is fixedly installed in a magnetic resonance apparatus. However, it is also conceivable for the RF transmission unit to comprise one or more local coils (local coil), which can be arranged directly on the body of the patient. Furthermore, it is possible that the whole body coil and / or the one or more local coils can also receive magnetic resonance signals, i.e. the RF receiving unit can comprise the whole body coil and / or one or more local coils. The RF transmission unit and the RF reception unit can therefore also comprise common components.The generation of the RF pulses and / or the acquisition of the magnetic resonance signals and / or the generation of the gradient pulses are preferably carried out taking into account the movement signals. The magnetic resonance measurement can thus be better matched to the movement of the patient.In particular, the generation of the RF pulses and / or the acquisition of the magnetic resonance signals and / or the generation of the gradient pulses can be synchronized with the movement of the patient. Thus, the operation of the gradient coil unit and / or the RF transmission unit and / or the RF reception unit can be synchronized.In certain cases where the motion of the patient is of particular interest, the motion signals may be used to separate magnetic resonance signals originating from moving nuclear spins from magnetic resonance signals originating from static nuclear spins. Synchronization can be used advantageously in this case. More precisely, in the case of a moving nuclear spin, the carrier of the nuclear spin usually moves, namely the atomic nucleus which has the nuclear spin. Analogously, in the case of a static nuclear spin, the atomic nucleus which has the static nuclear spin is usually at rest.Synchronization on the basis of the movement signals can be carried out in principle with all elements of a magnetic resonance sequence which can relate in particular to properties of the gradient pulses, the RF pulses, the RF receiving unit and / or a reconstruction of magnetic resonance images.Such synchronization can comprise, for example, a, in particular periodic, change of an amplitude and / or duration of the gradient pulses that is generated by the gradient coil unit. Such synchronization can furthermore comprise, for example, a change, in particular a periodic change, in an amplitude and / or phase and / or frequency of the RF pulses which is generated by the RF transmission unit. Furthermore, such synchronization can comprise, for example, a, in particular periodic, change of a frequency and / or phase and / or bandwidth of the reception properties of the RF reception unit.One embodiment of the method provides that phases of the RF pulses and the RF receiving unit are synchronized on the basis of the movement signals in such a way that the relative phase between the RF pulses and the RF receiving unit, in particular an analog-to-digital converter (ADC) of the RF receiving unit, is constant for moving nuclear spins in successive measurement cycles. A measurement cycle can be understood here in particular as the time period between two successive RF pulses for exciting nuclear spins in the body of the patient by an RF transmission unit.This method can also be understood as a modified variant of so-called RF spoilering. During RF spoilers, the phases of the RF pulses of the RF receiving unit are usually changed from excitation to excitation, i.e. between two successive measurement cycles, while the relative phase of excitation and reception of the magnetic resonance signals is kept constant. As a result, signal components which still originate from preceding measurement cycles can be suppressed, which therefore have not yet decayed from one excitation to the next.By synchronizing with the movement of the patient, it can be achieved that the relative phase is constant between successive excitations only for moving nuclear spins, while the relative phase has great variations for non-moving, i.e. static, nuclear spins. Consequently, the magnetic resonance signals of the moving nuclear spins add up in the correct phase and thus contribute to the resulting magnetic resonance imaging in an amplified manner, while the magnetic resonance signals of the static nuclear spins are strongly suppressed.A further embodiment of the method provides that the gradient pulses comprise at least one bipolar gradient pulse, wherein an amplitude and / or duration and / or a direction of the at least one bipolar gradient pulse is synchronized on the basis of the movement signals, i.e. the timing, the amplitude and / or the direction of the at least one bipolar gradient pulse takes place as a function of the movement signals. Thus, the gradient moment for static nuclear spins can be suppressed.Bipolar gradient pulses are generally characterized in that their zeroth gradient moment is equal to zero and their first gradient moment is not equal to zero. Such gradient pulses usually bring about a resulting gradient moment of the moving nuclear spins, but no resulting gradient moment of the static nuclear spins. If the amplitude and / or the duration and / or the direction of these gradient pulses are advantageously synchronized with the movement of the patient, a magnetic resonance sequence can be applied which applies variable gradient moments to moving nuclear spins, but no gradient moments to static nuclear spins.In this case, the synchronization of the at least one bipolar gradient pulse on the basis of the movement signals can be used, for example, for the phase encoding of magnetic resonance signals of moving nuclear spins in order, in particular, to generate magnetic resonance images of parts of the patient's body with non-static nuclear spins.The synchronization can be used, in particular, for phase encoding of nuclear spins moving non-linearly, in particular periodically. If synchronization were also dispensed with, as in conventional flow imaging, in particular conventional phase contrast angiography, moving nuclear spins would also be phase-coded, but the strength of the effect would be random. The synchronization allows the effect to be utilized in a targeted manner and the artifacts that otherwise result to be avoided.For example, all periodically moving nuclear spins can be encoded with a same phase during a measurement. All periodically moving nuclear spins can be encoded with a predefined variable phase over the time profile of a measurement.In order that the imposed gradient moments in a periodic movement are independent of the movement, a high amplitude can be used at a low movement speed, in particular at inflection points of the periodic movement, or a low amplitude of the at least one bipolar gradient pulse can be used at a high movement speed.In order to impose specific temporal sequences of different gradient moments, the gradient moments independent of the movement can be scaled accordingly over time, e.g. a linearly increasing course.A further embodiment of the method provides that a first time series is determined on the basis of the magnetic resonance signals and a second time series is determined on the basis of the movement signals. In this case, the first time series is evaluated on the basis of the second time series. This allows, in particular, an improved evaluation of dynamic magnetic resonance measurements.In particular, it is proposed that the first and the second time series are each transformed from a time range into a frequency range, for example by means of a Fourier transformation. On the basis of the second time series transformed into the frequency range, a filter is advantageously determined, on the basis of which the first time series transformed into the frequency range is filtered. In this case, in particular on the basis of the second time series transformed into the frequency range, at least one frequency band can be determined which is used for determining the filter. The filtered first time series can be transformed back from the frequency range into the time range, for example by means of an inverse Fourier transformation. The data filtered in this way make possible an improved evaluation of the magnetic resonance data.If, for example, the magnetic resonance measurement comprises many repetitions, the time series of the magnetic resonance signals, also referred to below as image data, can be transformed from a time range into a frequency range by means of a Fourier transformation. The transformed image data often have a high signal component at low frequencies, in particular around frequency equal to zero, which usually originates from the static nuclear spins. In addition, the transformed image data often have further signal components at higher frequencies, which represent the moving nuclear spins.From the motion signals, a further time series, in particular a time-dependent motion curve, which is also referred to below as motion data, can be derived, which can likewise be transformed from the time domain into the frequency domain by means of Fourier transformation. Frequency bands can be derived from the transformed movement data, which can result, for example, from breathing movements, e.g. approximately 0.5 Hz, and / or heart beats, e.g. 1.5 Hz, of the patient. With this information, a filter in the frequency domain can be created, which can be applied to the transformed image data. In this case, for example, all image data that lie outside the one or more frequency bands can be filtered out. After an inverse Fourier transformation of the filtered image data into the time period, the back-transformed image data represent nuclear spins which can be associated with a specific movement, in particular the breathing and / or heart movement.Preferably, magnetic resonance images are generated on the basis of the first time series, in particular temporally consecutive magnetic resonance images, wherein at least one region of the plurality of magnetic resonance images is determined in which a correlation of the second time series with the first time series is established. The determined at least one region can be masked and / or marked in particular.For this purpose, a correlation threshold value can be established. Furthermore, a correlation value can be determined on the basis of the first time series and the second time series, wherein a correlation is determined by the correlation value if the correlation threshold value is exceeded. The second time series of the movement signals can comprise a movement curve of a body part of the patient, in particular of the breast and / or of the heart and / or of the finger, as is shown in the example of a functional magnetic resonance measurement below.Advantageously, at least one region of the brain is determined whose magnetic resonance images have an alternating contrast, wherein the frequency of the contrast alternation correlates with the frequency of the activity and rest phases. The correlation can be established by determining the frequency band of the periodic motion. This frequency band can then be excluded from the evaluation. This makes it possible, for example, to prevent an upward and downward movement of the head due to the breathing movement of the patient from adversely affecting the measurement results.Previous methods, in which a breathing movement is corrected by an analysis of the magnetic resonance images solely with the aid of image-based movement recognition, often suffer from the fact that the image-based movement recognition is not reliable enough. This problem can be solved with the method proposed here, since the movement detection by means of the movement detection unit can be carried out with a higher temporal resolution and / or a higher signal-to-noise ratio. In this way, in particular the breathing and the heartbeat of the patient can be resolved more reliably.According to a further example, an embodiment of the proposed method may be used to locate, in particular small, areas that are influenced mainly by movement but not by brain activity. These regions may be, for example, arteries whose contrast is influenced by the blood flow driven by the heart beat. Preferably, at least one region is determined in which the temporal contrast behavior correlates strongly with the frequency and / or amplitude of the movement curve. This region can be masked and / or marked unsuitable, for example.A further embodiment of the method provides that the movement signals are provided to a movement model, wherein the magnetic resonance signals are reconstructed on the basis of the movement model. Preferably, a movement model links a movement of at least two regions of the patient's body, for example a chest movement and / or heart movement, to a movement of an inner organ. In this case, the movement of at least one of these at least two regions can be detected with the aid of the movement detection unit.Some organs of the patient's body pulsate due to blood flow. This movement cannot usually be detected by an image-based movement detection, since this is generally very localized. If, in particular, a movement of a specific organ can be predicted, for example if it is known that the liver moves downward and upward on average by 1 mm due to the breathing movement, this information can be used in a reconstruction which resorts to such a movement model. The movement signals, in particular a timing and / or an amplitude of the movement, can then be used as input variables for the movement model, with which the magnetic resonance signals can be corrected during the reconstruction.A reaction of the patient to a contrast medium is observed on the basis of the movement signals. Many magnetic resonance measurements involve administration of a contrast agent. The administration is often carried out in the magnetic resonance apparatus during the course of the magnetic resonance measurement. Contrast agents may sometimes cause side effects, such as allergic reactions or panic attacks, in the patient.A reaction of the patient to the contrast medium can advantageously be observed by the breathing behavior and / or the heart rate, which can be determined on the basis of the movement signals. This information can be displayed to an operator of the magnetic resonance apparatus and / or used to identify unusual patient reactions. An evaluation of the movement signals can furthermore be used to prompt the operator to check the patient's presence. In particular, if the patient is unable to communicate, for example dementia syndrome, it may be highly advantageous to evaluate the condition of the patient during contrast agent administration.In addition, it is proposed that a state of the patient is observed on the basis of the movement signals, in particular during an interventional procedure.Interventional procedures are often supported by a magnetic resonance measurement. The movement signals can be used as an indicator for the medical condition of the patient. In addition, they can be used during planning and / or performance of an interventional procedure.Many patients feel discomfort before and / or during magnetic resonance measurement. Therefore, the state of health of the patient in the magnetic resonance apparatus can change during a magnetic resonance measurement. For example, a shortened breathing cycle and / or an accelerated heart beat can be indicators of discomfort of the patient, so that an interruption of the magnetic resonance measurement is recommended. Such changes can be detected with the aid of the movement detection unit and displayed to the operator.Furthermore, the movement detection unit can also be used for detecting the patient per se. Although magnetic resonance apparatuses are mostly used to examine patients, phantoms or other non-living objects are sometimes also examined. If patients, especially human patients, are measured, stringent safety regulations must usually be complied with. This may relate, for example, to a specific absorption rate (SAR) and / or magnetic field changes (dB / dt). In particular for scientific studies, it may be useful to bypass such limitations. Here, the movement signals can be used to determine whether a living, and thus generally a moving, patient is located in the magnetic resonance apparatus. If this is the case, the avoidance of the limitations can be suppressed.Furthermore, a magnetic resonance apparatus with an RF transmission unit, an RF reception unit, a gradient coil unit, a movement detection unit and a processing unit is proposed. The magnetic resonance apparatus is designed to execute a method for processing movement signals that are acquired during a magnetic resonance measurement of a patient.The advantages of the magnetic resonance apparatus according to the invention essentially correspond to the advantages of the method according to the invention, which are explained in detail above. Features, advantages or alternative embodiments mentioned here can likewise also be transferred to the other claimed subject matters and vice versa.The movement detection unit can in particular comprise a movement sensor, for example in the form of one or more cameras and / or an RF coil which is designed to detect movement signals on the basis of a change in a load of the RF coil.The RF transmission unit can in particular comprise at least one RF transmission coil and the RF reception unit can comprise at least one RF reception coil. It is also conceivable that the RF transmission unit and the RF reception coil comprise at least one combined RF transmission and reception coil, which can both transmit RF pulses, i.e. also receive magnetic resonance signals.The processing unit preferably comprises a computing unit, in particular at least one processor, and / or a memory for storing programs and / or data.In addition, a computer program product is proposed which comprises a program and can be loaded directly into a memory of a programmable arithmetic unit of a processing unit of a magnetic resonance apparatus and has program means, for example libraries and auxiliary functions, for processing a method for processing movement signals which are acquired during a magnetic resonance measurement of a patient when the computer program product is executed in the processing unit. The computer program product can comprise software with source code that still has to be compiled and bound or that only has to be interpreted, or executable software code that only has to be loaded into the evaluation unit for execution. The method can be executed in an identically repeatable and robust manner by the computer program product. The computer program product is configured such that it can carry out the method steps according to the invention by means of the processing unit. The processing unit must have the requirements such as a corresponding working memory or a corresponding logic unit, so that the respective method steps can be carried out efficiently.Further advantages, features and details of the invention are evident from the exemplary embodiments described below and on the basis of the drawings. Corresponding parts are provided with the same reference numerals in all figures.The following are shown: FIG. 1 shows a magnetic resonance apparatus according to the invention in a schematic illustration, FIG. 2 shows a block diagram of a method for processing motion signals during a magnetic resonance measurement, FIG. 3 shows an exemplary section of a magnetic resonance sequence comprising two successive measurement cycles, FIG. 4 shows an exemplary section of a magnetic resonance sequence comprising a bipolar gradient pulse, FIGS. 5-7 are block diagrams of possible method steps.FIG. 1 schematically illustrates a magnetic resonance apparatus 10. The magnetic resonance apparatus 10 comprises a magnet unit 11 which has a main magnet 12 for generating a strong and in particular temporally constant main magnetic field 13. In addition, the magnetic resonance apparatus 10 comprises a patient receiving area 14 for receiving a patient 15. In principle, however, a design of the patient receiving area 14 deviating therefrom is conceivable at any time. The patient 15 can be pushed into the patient receiving area 14 by means of a patient support device 16 of the magnetic resonance device 10. For this purpose, the patient support device 16 has a patient table 17 configured to be movable within the patient receiving area 14.The magnet unit 11 also has a gradient coil unit 18 for generating gradient pulses which are used for spatial coding during a magnetic resonance measurement. The gradient coil unit 18 is controlled by means of a gradient control unit 19 of the magnetic resonance apparatus 10. The magnetic unit 11 furthermore comprises an RF transmission unit 20, which in the present exemplary embodiment is designed as a body coil integrated firmly into the magnetic resonance apparatus 10. The RF transmission unit 20 is designed for transmitting RF pulses and a resulting excitation of nuclear spins that occurs in the main magnetic field 13 generated by the main magnet 12. The RF transmission unit 20 is controlled by a radio-frequency antenna control unit 21 of the magnetic resonance apparatus 10. The RF pulses are irradiated into an examination space which is substantially formed by a patient receiving region 14 of the magnetic resonance apparatus 10. The RF transmission unit 20 is furthermore designed to receive magnetic resonance signals, so that it simultaneously functions as part of an RF reception unit. The RF receiving unit here also comprises an RF coil 28, which can also be referred to as a local coil, since it is arranged close to the patient 15.For controlling the main magnet 12, the gradient control unit 19 and for controlling the radio-frequency antenna control unit 21, the magnetic resonance apparatus 10 has a system control unit 22. The system control unit 22 centrally controls the magnetic resonance apparatus 10, such as for example the execution of a predetermined imaging gradient echo sequence. In addition, the system control unit 22 comprises an evaluation unit, not shown in detail, for evaluating the magnetic resonance signals that are acquired during the magnetic resonance measurement. Furthermore, the magnetic resonance apparatus 10 comprises a user interface 23 which is connected to the system control unit 22. Control information such as imaging parameters, for example, and reconstructed magnetic resonance images can be displayed on a display unit 24, for example on at least one monitor, of the user interface 23 for a medical operator. Furthermore, the user interface 23 has an input unit 25, by means of which information and / or parameters can be input by the medical operating personnel during a measurement process.The magnetic resonance apparatus 10 also comprises a movement acquisition unit for acquiring movement signals of the patient during the acquisition of the magnetic resonance signals. In this example, the movement detection unit comprises a camera 27 with which optical movement signals can be detected. However, movement signals can also be detected, for example, by the RF coil 28 which is arranged under the chest of the patient, since the change over time of the state of charge of the RF coil 28 allows conclusions to be drawn about the movement, in particular the breathing movement, of the patient 15.The system control unit 22 comprises a processing unit 26 which is designed to process the movement signals. For this purpose, the processing unit preferably comprises a computing unit, in particular at least one processor, and / or a memory for storing programs and / or data.A program can be loaded directly into the processing unit 26, program means for carrying out a method for processing movement signals which are acquired during a magnetic resonance measurement of a patient, when the program is executed in the processing unit 26 of the magnetic resonance apparatus 10.In FIG. 2, an exemplary method for processing motion signals acquired during a magnetic resonance measurement of the patient 15 is illustrated. In 110, RF pulses for exciting nuclear spins in the body of the patient 15 are generated by an RF transmission unit 20 and generating magnetic resonance signals by the excited nuclear spins. In 120, gradient pulses for the spatial coding of the magnetic resonance signals are generated by a gradient coil unit 18. The magnetic resonance signals are acquired in 130 by an RF receiving unit. Meanwhile, in 140, motion signals of the patient are detected by a motion detection unit, which are processed in 150 by a processing unit.Optionally, the generation of the RF pulses and / or the acquisition of the magnetic resonance signals and / or the generation of the gradient pulses take place on the basis of the movement signals. This is illustrated in Figure 2 by the dashed lines.As a result, for example, the acquisition of the magnetic resonance signals can be adapted in such a way that only magnetic resonance signals of moving nuclear spins are effectively measured. This can be used, in particular, to generate magnetic resonance images that show only flowing blood. Furthermore, magnetic resonance signals of moving nuclear spins and magnetic resonance signals of static nuclear spins can be separated, for example, during the reconstruction of the magnetic resonance images. In this way, in particular tissue can be shown which moves during breathing and / or during the heartbeat.FIG. 3 illustrates an advantageous embodiment of the processing of the motion signals in 150, according to which the phases of the RF pulses RF 1, RF 2 and the phases of the read-out processes ADC 1, ADC 2 of the RF receiving unit are synchronized on the basis of the motion signals in such a way that the relative phase between the RF pulses RF 1, RF 2 and the read-out processes ADC 1, ADC 2 of the RF receiving unit for moving nuclear spins is constant in successive measurement cycles C 1, C 2. Here, the RF pulses RF 1, RF 2 are plotted on the axis RF and the read-out processes ADC 1, ADC 2 of the RF receiving unit are plotted on the axis ADC in time.We consider, by way of example, a moving first nuclear spin which is at the position x A during the measurement cycle C1 and at the position x B during the measurement cycle C2. In particular, the first nuclear spin can periodically move back and forth between the positions x A and x B. In contrast, a static second nuclear spin is always located at position x A.The RF pulse RF 1 of a first measurement cycle C 1 has a phase φ HF1A at the position x A and a phase φ HF1B at the position x B in this case. Analogously, the RF pulse RF 2 of a second measurement cycle C 2 following the first measurement cycle C 1 has a phase Φ HF2A for the position x A and a phase Φ HF2B for the position x B. Furthermore, the readout operation ADC 1 of the first measurement cycle C 1 has a phase Φ ACD1A for the position x A and a phase Φ ACD1B for the position x B and the readout operation ADC 2 of the second measurement cycle C 2 has a phase Φ ADC2A for the position x A and a phase Φ ADC2B for the position x B.The relative phase between the RF pulses RF 1, RF 2 and the read-out processes ADC 1, ADC 2 of the RF receiving unit can be understood to mean the difference of the location-dependent phases Φ HF1A and Φ ADC1A and Φ HF2A and Φ ADC2A and Φ HF1B and Φ ADC1B and Φ HF2B and Φ ADC2B.In order to record the moving first nuclear spin without suppression, (Φ HF1A- Φ ADC1A) - ( Φ HF2B- Φ ADC2B), advantageously holds true, i.e. the relative phase of the first nuclear spin remains constant during its movement from x A to x B so that the magnetic resonance signals add up in the correct phase.In order to suppress the magnetic resonance signal of the static second nuclear spin as strongly as possible, (Φ HF1A- Φ ADC1A) ≠(Φ HF2A- Φ ADC2A), advantageously applies, i.e. the relative phase of the second nuclear spin changes, so that the static nuclear spins add up incoherently and thus cancel one another out completely or partially.Analogous conditions naturally also preferably apply to further measurement cycles. By processing the motion signals in 150, the time sequence of the motion of the moving nuclear spins can be determined. The repetition rate of the measurement cycles and the chronological sequence of when measurement is performed at which position can thus be set such that these conditions are ideally fulfilled over the entire period of the magnetic resonance measurement.In a further variant, the gradient pulses can comprise at least one bipolar gradient pulse, wherein in 150 an amplitude and / or a direction of the at least one bipolar gradient pulse are synchronized on the basis of the movement signals. A bipolar gradient pulse G BP is illustrated in FIG. 4, which shows an exemplary section of a magnetic resonance sequence. A time profile of the bipolar gradient pulse G BP is shown on three gradient axes G x, G y, G z i.e. the amplitudes of the gradient pulse G BP are shown on three gradient axes G x, G y, G z over time. The bipolar gradient pulse G BP comprises two partial pulses, each of which has a component on each of the gradient axes G x, G y, G z. Thus, the first partial pulse comprises the components +G1, -G2 and +G3, and the second partial pulse comprises the components -G1, +G2 and -G3. The magnitudes of the time integrals of the components on a gradient axis are equal in magnitude with an unequal sign, so that the zeroth gradient moment of G BP is equal to zero. The direction of the gradient pulse G BP results from a vectorial superposition of the components of the gradient pulse G BP.By generating the bipolar gradient pulse G BP, which is characterized in particular by its timing, an amplitude and / or its direction, on the basis of the movement signals, variable gradient moments can be applied to moving nuclear spins, but no gradient moments can be applied to static nuclear spins, which can be used in particular for phase encoding of magnetic resonance signals of moving nuclear spins.FIG. 5 illustrates that in 150 a first time series can be determined in 151 on the basis of the magnetic resonance signals during the processing of the movement signals by a processing unit 26, in 152 a second time series can be determined on the basis of the movement signals and in 153 the first time series can be evaluated on the basis of the second time series.In particular, as shown in FIG. 6, the first time series can be transformed from a time domain to a frequency domain in 154 and the second time series in 155. In 156, a filter can be determined on the basis of the second time series transformed into the frequency range, on the basis of which filter the first time series transformed into the frequency range is filtered in 157.As a result, for example, movement can be filtered out of the signal dynamics. This can be used, in particular, to correct functional magnetic resonance data with respect to the breathing movement.Furthermore, it is possible that the first time series filtered in 157 is transformed back in 158 from the frequency range into the time range in order to generate one or more magnetic resonance images, for example, on the basis of the filtered and back-transformed first time series in 159.In particular, as shown in FIG. 7, magnetic resonance images can be generated 160 on the basis of the first time series and at least one region of the plurality of magnetic resonance images can be determined 161 in which a correlation of the second time series with the first time series is established. The determined at least one region can be masked and / or marked, for example 162.According to a further aspect of the invention, the movement signals can be provided to a movement model in 150, wherein the magnetic resonance signals are reconstructed on the basis of the movement model.In particular, a localized movement can be detected. This can be used, in particular, to mark and / or filter pulsating vessels during a functional magnetic resonance measurement and / or to correct magnetic resonance images by means of a motion model.It is pointed out once again that the methods described in detail above and the illustrated acquisition pattern generation unit and magnetic resonance apparatus are merely exemplary embodiments which can be modified in a wide variety of ways by the person skilled in the art without departing from the scope of the invention. Furthermore, the use of the indefinite article "a" or "an" does not exclude that the features in question can also be present multiple times. Likewise, the term "unit" does not exclude that the components in question consist of a plurality of interacting part-components, which may optionally also be spatially distributed.

Claims

Method for processing movement signals which are acquired during a magnetic resonance measurement of a patient (15), wherein the method comprises: - generation of RF pulses (RF1, RF2) for exciting nuclear spins in the body of the patient (15) by an RF transmission unit (20) and generation of magnetic resonance signals by the excited nuclear spins, - generation of gradient pulses for spatial coding of the magnetic resonance signals by a gradient coil unit (18), - acquisition of the magnetic resonance signals by an RF reception unit, - acquisition of movement signals of the patient (15) by a movement acquisition unit (27) during the acquisition of the magnetic resonance signals, - processing of the movement signals by a processing unit (26), wherein a reaction of the patient (15) to a contrast medium is observed on the basis of the movement signals.Method according to Claim 1, wherein the generation of the RF pulses (RF1, RF2) and / or the acquisition of the magnetic resonance signals and / or the generation of the gradient pulses take place taking into account the movement signals.Method according to one of claims 1 or 2, wherein phases of the RF pulses (RF1, RF2) and the RF receiving unit are synchronized on the basis of the movement signals in such a way that the relative phase between the RF pulses (RF1, RF2) and the RF receiving unit for moving nuclear spins is constant in successive measurement cycles.Method according to one of the preceding claims, wherein the gradient pulses (G BP) comprise at least one bipolar gradient pulse, wherein an amplitude and / or a duration and / or a direction of the at least one bipolar gradient pulse (G BP) are synchronized on the basis of the movement signals.Method according to one of the preceding claims, wherein a first time series is determined on the basis of the magnetic resonance signals, wherein a second time series is determined on the basis of the movement signals, wherein the first time series is evaluated on the basis of the second time series.Method according to Claim 5, wherein the first and the second time series are each transformed from a time domain into a frequency domain, wherein a filter is determined on the basis of the second time series transformed into the frequency domain, the first time series transformed into the frequency domain being used to filter said filter on the basis of said filter.Method according to one of Claims 5 or 6, wherein magnetic resonance images are generated on the basis of the first time series, at least one region of the plurality of magnetic resonance images being determined in which a correlation of the second time series of the movement signals with the first time series is established.Method according to one of the preceding claims, wherein the movement signals are provided to a movement model, wherein the magnetic resonance signals are reconstructed on the basis of the movement model.Method according to one of the preceding claims, wherein a state of the patient (15) is observed on the basis of the movement signals and / or a detection of a patient (15) is carried out.Magnetic resonance apparatus (10) having an RF transmission unit (20), an RF reception unit (18), a gradient coil unit, a movement detection unit (24) and a processing unit (26) which is designed to carry out a method according to one of Claims 1 to 9.Computer program product comprising a program and directly loadable into a memory of a programmable processing unit of a magnetic resonance apparatus (10), comprising program means for performing a method according to any one of claims 1 to 9, when said program is executed in the processing unit of the magnetic resonance apparatus.

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