DE102015207591A1 - Method for a movement correction of magnetic resonance measurement data - Google Patents

Abstract

The invention relates to a method for a movement correction of magnetic resonance measurement data, a magnetic resonance apparatus and a computer program product. In order to enable an improved movement correction of magnetic resonance measurement data, it is proposed that the method according to the invention for a movement correction of magnetic resonance measurement data acquired during a magnetic resonance imaging of an examination object by means of a magnetic resonance apparatus comprises the following method steps: - performing a reference measurement to one first time during magnetic resonance imaging, wherein a reference volume is detected, - performing an image measurement at a second time during magnetic resonance imaging, wherein magnetic resonance measurement data from an examination volume are acquired by means of a simultaneous multi-slice measurement technique in a plurality of coherently excited slice groups, - Determining a movement information from the reference volume and magnetic resonance measurement data, which detects at least one coherently excited layer group of the plurality of coherently excited layer groups wherein the movement information describes a movement of the examination object between the first time and the second time, and - movement correction of the magnetic resonance measurement data using the determined movement information.

Description

The invention relates to a method for a movement correction of magnetic resonance measurement data, a magnetic resonance apparatus and a computer program product.

In a magnetic resonance apparatus, also called a magnetic resonance tomography system, the body to be examined is usually exposed to a subject, in particular a patient, by means of a main magnet a relatively high main magnetic field, for example 1.5 or 3 or 7 Tesla. In addition, gradient circuits are played with the aid of a gradient coil unit. High-frequency high-frequency pulses, for example excitation pulses, are then emitted via a high-frequency antenna unit by means of suitable antenna devices, which results in the nuclear spins of certain atoms excited resonantly by these high-frequency pulses being tilted by a defined flip angle with respect to the magnetic field lines of the main magnetic field. During the relaxation of the nuclear spins, radio-frequency signals, so-called magnetic resonance signals, are emitted, which are received by means of suitable radio-frequency antennas and then further processed. From the thus acquired raw data finally the desired image data can be reconstructed.

For a specific measurement, therefore, a specific magnetic resonance sequence, also called pulse sequence, to be emitted, which consists of a sequence of high-frequency pulses, such as excitation pulses and Refokussierungspulsen, and coordinated to be emitted austenend gradient circuits in different gradient axes along different spatial directions. In time, readout windows are set, which specify the periods in which the induced magnetic resonance signals are detected.

During magnetic resonance imaging, movement of the examination subject may occur. For example, there may be a respiratory movement and / or a heart movement of the examination subject. There may also be voluntary movements of limbs of the examination subject. This movement of the examination object can lead to an undesired change in the magnetic resonance measurement data acquired during the magnetic resonance imaging. Thus, for example, an occurrence of motion artifacts in the acquired magnetic resonance measurement data is conceivable. The movement can also reduce the quality of the acquired magnetic resonance measurement data.

The invention is based on the object to enable improved motion correction of magnetic resonance measurement data. The object is solved by the features of the independent claims. Advantageous embodiments are described in the subclaims.

• – Durchführen einer Referenzmessung zu einem ersten Zeitpunkt während der Magnetresonanz-Bildgebung, wobei ein Referenzvolumen erfasst wird,
• – Durchführen einer Bildmessung zu einem zweiten Zeitpunkt während der Magnetresonanz-Bildgebung, wobei Magnetresonanz-Messdaten aus einem Untersuchungsvolumen mittels einer Simultanen-Mehrschichtmessung-Technik in mehreren kohärent angeregten Schichtgruppen erfasst werden,
• – Ermitteln einer Bewegungsinformation aus dem Referenzvolumen und Magnetresonanz-Messdaten, welche aus zumindest einer kohärent angeregten Schichtgruppe der mehreren kohärent angeregten Schichtgruppen erfasst werden, wobei die Bewegungsinformation eine Bewegung des Untersuchungsobjekts zwischen dem ersten Zeitpunkt und dem zweiten Zeitpunkt beschreibt, und
• – Bewegungskorrektur der Magnetresonanz-Messdaten unter Verwendung der ermittelten Bewegungsinformation.

The method according to the invention for a movement correction of magnetic resonance measurement data acquired during a magnetic resonance imaging of an examination subject by means of a magnetic resonance apparatus comprises the following method steps:

• Performing a reference measurement at a first time during magnetic resonance imaging, wherein a reference volume is detected,
• Performing an image measurement at a second time during the magnetic resonance imaging, wherein magnetic resonance measurement data from an examination volume are acquired by means of a simultaneous multi-slice measurement technique in a plurality of coherently excited slice groups,
• Determining movement information from the reference volume and magnetic resonance measurement data which are acquired from at least one coherently excited layer group of the plurality of coherently excited layer groups, wherein the movement information describes a movement of the examination object between the first time and the second time, and
• - Motion correction of the magnetic resonance measurement data using the determined motion information.

The examination object can be a patient, a training person, an animal or a phantom. Magnetic resonance imaging in the present case comprises, in particular, the use of a magnetic resonance sequence for acquiring the magnetic resonance measurement data. The reference measurement and the image measurement are then in particular a part of the magnetic resonance sequence. The first time at which the reference measurement takes place may represent a start time of the reference measurement. The first time is in particular in an initial period of the magnetic resonance sequence, advantageously before magnetic resonance measurement data are acquired according to the magnetic resonance sequence. The first time may be the time of the start of the magnetic resonance sequence. The second time at which the image measurement takes place may represent a start time of the image measurement. The second time is in particular after the first time.

In contrast, a reference measurement is carried out in particular for the magnetic resonance sequence in order to detect a reference volume at the first time. In most cases, in this case, in particular, only one reference measurement is carried out in order to produce exactly one reference volume first time to capture. It is also conceivable that a plurality of reference volumes, for example at a plurality of first times, are detected. The reference volume may also be formed as any suitable combination of two or more measurements, for example as an average over these two or more measurements. The reference volume can then serve as the basis for the motion correction for the entire magnetic resonance imaging or the entire magnetic resonance sequence. The first time can thus be regarded as the reference time, which can serve as a reference for subsequently detected movement of the examination subject. In certain cases, however, it may also be conceivable for the reference measurement to be repeated again during the magnetic resonance imaging, that is to say a further reference volume is detected at a further first time during the magnetic resonance sequence. The reference volume can only serve as a basis for the motion correction or be issued to a user. The reference volume can in particular also be detected by means of a simultaneous multi-slice measurement technique. Advantageously, the reference volume acquired during the reference measurement can likewise represent a part of the diagnostic magnetic resonance measurement data. In this way, the magnetic resonance measurement data can be detected, for example, in a time series, the reference measurement representing a first acquisition of the examination volume at the first time and the image measurement representing a further acquisition of the examination volume at the second time. In this way, acquisition of the examination volume at the beginning of a time series, in particular the first acquisition of the examination volume in the time series, can be used as the reference volume for the movement correction.

In particular, the magnetic resonance measurement data and / or magnetic resonance image data reconstructed from the magnetic resonance measurement data are to be provided, that is to say displayed to a user on a display unit, and the magnetic resonance measurement data acquired during the image measurement are diagnostic magnetic resonance measurement data / or stored in a database. In particular, the image measurement comprises a multiple recording of at least parts of the examination volume. The magnetic resonance measurement data can be detected as a time series in this way. Thus, the magnetic resonance measurement data from the two-dimensional or three-dimensional examination volume can be acquired several times at different times. Repeated measurement of the examination volume allows dynamic effects to be considered within the anatomy presented. One example of this is neuro-perfusion measurements, which can be used to examine the perfusion behavior of the brain. For this purpose, a tidal flow of contrast agent into the brain of the examination subject is examined in temporal resolution and quantitative parameters calculated from this. Another example, which will be described in more detail in any of the following sections, is a use of a functional magnetic resonance technique. Of course, it is also conceivable that the examination volume is detected only once in the image measurement in addition to the reference volume.

According to the proposed procedure, the magnetic resonance measurement data are to be acquired using the Simultaneous Multislice (Simultaneous Multislice) technique. In this way, an accelerated acquisition of the magnetic resonance measurement data can take place. The simultaneous multilayer measurement technique is known, for example, from the following document: Setsompop et al. "Blipped-controlled aliasing in parallel imaging for simultaneous multislice echo planar imaging with reduced g-factor penalty.", Magn. Reson Med. 2012, 67 (5): 1210-1224 , In particular, the simultaneous multi-slice measurement technique comprises a simultaneous, coherent excitation of multiple layers of the examination volume. The multiple layers that are excited simultaneously are typically grouped in a coherently excited layer group. The simultaneous multilayer measurement technique is typically characterized by an acceleration factor, also called a simultaneous multislice factor (SMS factor). The acceleration factor usually indicates how many layers are simultaneously attacked in a coherently excited layer group by a single high-frequency pulse. The acceleration factor is in particular integer and is at least two for accelerated measurements. With an acceleration factor of one, the measurement corresponds in particular to a conventional, sequential measurement. Typical acceleration factors are in a range of up to six and are particularly dependent on a considered body region and / or coil geometry and / or a used magnetic resonance sequence. Subsequently, the magnetic resonance signals from the multiple layers, in particular superimposed in a k-space, can be read out simultaneously.

The subsequent reconstruction of the individual layers then comprises in particular a separation of the simultaneously read out magnetic resonance signals with respect to the multiple layers. For separating the magnetic resonance signals, a known layer separation method, such as, for example, a slice-GRAPPA method in the slice direction, can be used, as described, for example, in the abovementioned document of FIG Setsompop et al. described. Thus, by means of the simultaneous multilayer measurement technique, advantageously several layers can be acquired at the same time. In particular, interleaved acquisition of the multiple layers takes place in order to minimize the influence of spatially adjacent layers by temporally successive layer measurements (possible cross-talks).

In particular, the examination volume comprises several layers, which are grouped to the several coherently excited layer groups. In particular, the several coherently excited layer groups together result in the complete examination volume. In particular, in each coherently excited layer group of the plurality of coherently excited layer groups, a number of plural layers of the plurality of layers are simultaneously excited by means of a high-frequency pulse. The high-frequency pulse thus acts in particular simultaneously on all layers of a coherently excited layer group. In this case, a coherently excited layer group of the plurality of coherently excited layer groups comprises in particular a number of layers which corresponds to the acceleration factor. All layers of a single coherently excited layer group of the plurality of coherently excited layer groups are thus excited in particular by means of a single excitation pulse and read in a single readout train. Accordingly, each high-frequency pulse in particular at the same time stimulates a number of layers, which corresponds to the acceleration factor. To excite the examination volume, in particular a number of high-frequency pulses is used, which corresponds to the number of coherently excited groups of layers. In particular, each coherently excited layer group of the plurality of coherently excited layer groups comprises the same number of layers. The total number of layers of the examination volume accordingly corresponds in particular to the product of the acceleration factor and the number of coherently excited layer groups.

By simultaneously acquiring the multiple layers, a required time to acquire the magnetic resonance measurement data can be significantly reduced. Here, a factor of time saving is approximately on the order of magnitude of the acceleration factor. In this way, on the one hand, a measurement time for the image measurement can be saved. The shortened measuring time can be invested in improved imaging parameters, for example an increased number of layers and / or an increased resolution within the layers.

The movement of the examination object can take place, in particular, between the first time and the second time. For example, there may be a respiratory movement and / or a heart movement of the examination subject. There may also be voluntary movements of limbs of the examination subject. The movement of the examination subject can be reflected in image contents of the magnetic resonance measurement data compared to image contents of the reference volume. The movement information can be determined for example by means of a registration of the magnetic resonance measurement data on the reference volume. The movement information can advantageously characterize how the examination object has moved between the first time and the second time.

Determining the motion information may include determining motion parameters. In particular, the motion parameters are designed such that they can compensate for a movement, for example when they are applied to a picture content. So that the movement information can be determined particularly quickly and robustly from the magnetic resonance measurement data and the reference volume, in particular a model assumption for the movement information is made. The model assumption may include the motion parameters of the motion information. Particularly advantageous here is a rigid model assumption for the motion information, which in particular comprises six motion parameters, namely three translation parameters and three rotation parameters. The use of a rigid model assumption has proven to be useful, in particular in the case of magnetic resonance imaging of a head of the examination subject. This is partly due to the fact that an intended movement of the brain through the surrounding skull is only possible in a rigid way. Non-rigid components, for example due to pulsation of the liquor and of the blood, are comparatively small. Of course, it is also possible to make other model assumptions for the motion information, for example non-rigid model assumptions, which appear appropriate to the person skilled in the art. The use of a non-rigid and / or non-linear motion model makes sense, in particular, for image regions for which the model assumption of a rigid motion does not apply. In the case of head imaging, for example, this can be a neck region and / or a jaw region and / or an orbital region of the examination subject. Also, by choosing a non-rigid motion model, a particularly complete detection or compensation of the contained movement may be possible. During the course of the magnetic resonance sequence, several movement information can be determined at different times. In this way, it is particularly advantageous to respond dynamically to the movement of the examination subject during magnetic resonance imaging.

The movement correction of the magnetic resonance measurement data may in particular include a prospective motion correction and / or a retrospective motion correction, as described in more detail in one of the following sections. The movement correction takes place, in particular, using the movement information which is determined from the reference volume and the diagnostic magnetic resonance measurement data, from which particular magnetic resonance images intended for display are reconstructed. Thus, the magnetic resonance measurement data is motion-corrected using the motion information obtained by using the magnetic resonance measurement data. The motion correction may include use of a method known to those skilled in the art, such as a Gauss-Newton method.

According to the proposed procedure, the motion information should already be determined on the basis of at least one coherently excited layer group of the several coherently excited layer groups. In this case, the at least one coherently excited layer group represents in particular a subset of the several coherently excited layer groups. In particular, the plurality of coherently excited layer groups beyond the at least one coherently excited layer group, which is used to determine the motion information, comprise further coherently excited layer groups. The movement information should therefore be determined in particular already after a partial recording of the examination volume. Thus, typically, the entire acquisition of the examination volume is not completed when the motion information is determined. In a particularly advantageous application, as will be described in more detail later, the motion information is determined on the basis of the reference volume and a single coherently excited layer group. Thus, after each acquisition of a coherently excited layer group of the plurality of coherently excited layer group, the layers just acquired at the same time can be considered as one unit, and the movement in the just-acquired layers relative to the reference volume can be detected.

The following is intended to explain how the proposed motion correction can exploit the advantages of the simultaneous multilayer measurement technique:
The proposed motion correction can first of all particularly advantageously exploit a consistency of the coherently excited layers of individual coherently excited layer groups of the several coherently excited layer groups. Namely, the layers of individual coherently excited layer groups are in particular acquired simultaneously. In particular, it is achieved that the layers of individual coherently excited layer groups usually do not have contradictory image contents, since there is no time interval between the acquisition of the layers from a single coherently excited layer group. Accordingly, if the motion information is determined by using a single coherently excited layer group or a smaller amount of coherently excited layer groups, then the motion information can advantageously be determined using timely and / or simultaneously measured layers having image information consistent with each other. At the same time, a movement of the examination object during the acquisition of the at least one coherently excited layer group may be smaller than a movement of the examination object during the acquisition of the entire examination volume. This fact is based on the consideration that movements of the examination object during the acquisition of individual layers are of less importance than during the acquisition of the entire examination volume. In this way, when determining the motion information, it is advantageously possible to avoid a compromise over a complete acquired examination volume. Such an error in the determination of the motion information can be advantageously minimized. It is also conceivable that an additional expenditure of a non-rigid registration can be avoided. Due to the better consistency of the considered layers of the at least one coherently excited group of layers, the movement correction can particularly advantageously reduce a distortion of an illustrated anatomy of the examination object in the magnetic resonance measurement data.

In particular, compared to known methods for determining motion information based on individual layers, so-called layer-based motion correction method, can be found with the proposed approach, which provides a determination of the motion information using coherently excited layer groups, increased robustness. The optimization methods for determining the motion information from the at least one coherently excited slice group and the reference volume can converge faster and / or better, in particular in comparison to slice-based motion correction methods. This fact is based on the consideration that when determining the movement information, multiple layers that are acquired simultaneously and that are consistent with one another can be taken into account. Particularly advantageous here is a spatial distributed arrangement of the multiple layers of the at least one coherently excited layer group over the examination volume, as described in more detail later. By means of the proposed procedure, the movement parameters of the movement information can be determined particularly robustly and / or precisely. This can therefore be particularly advantageous since small changes in the movement parameters, for example of rotational parameters, can lead to pronounced deviations from the reference volume. This may apply in particular to those layers which contain less structured anatomy, such as the outermost or topmost layers of a head of the examination subject.

In particular, the motion information may be determined repeatedly based on different sets of at least one coherently excited layer group. In this way, the movement information can be determined at different second times. In this way, it is particularly advantageous to respond dynamically to the movement of the examination subject during magnetic resonance imaging. By determining the movement information on the basis of a reduced number of coherently excited slice groups acquired, advantageously on the basis of a single coherently excited slice group, the advantage is that the motion information can be determined on shorter time scales. Such an update cycle of the movement information can be shortened and thus a movement of the examination subject on shorter time scales can be modeled. A continuous movement of the examination object can thus advantageously be modeled in sections, for example by individual rigid transformations. This is particularly advantageous in the case of a prospective motion correction described in more detail later, since the acquisition parameters can be more accurately matched to the movement of the examination subject. By considering a reduced number of layers, a calculation effort for the determination of the motion information can be further reduced.

In the following, possible embodiments of the method according to the invention and their advantages are described in more detail:
One embodiment provides that the at least one coherently excited layer group comprises a number of layer groups which are smaller than the total number of the plurality of coherently excited layer groups. The number of layer groups of the at least one coherently excited layer group is in particular less than 50 percent, advantageously less than 33 percent, particularly advantageously less than 25 percent of the total number of layers several coherently excited groups of the study volume. In this case, it is particularly advantageous that the movement information from the reference volume and magnetic resonance measurement data, which is determined from a maximum of four, advantageously a maximum of three, particularly advantageously a maximum of two, most advantageously a single coherently excited layer group of the plurality of coherently excited layer groups, is determined. In this way, the motion information can be determined particularly advantageously on a reduced number of coherently excited layer groups. The number of coherently excited layer groups, on the basis of which the motion information is determined, can be chosen here depending on the application and / or complexity of the calculation.

One embodiment provides that the movement information is determined from the reference volume and magnetic resonance measurement data which are acquired from a single coherently excited layer group of the plurality of coherently excited layer groups. Such a particularly robust motion correction using the motion information is possible, since only perfectly consistent with each other magnetic resonance measurement data for the determination of the motion information are used. In certain applications, in each case a movement information from the reference volume and each coherently excited layer group of the plurality of coherently excited layer groups can be detected. In this way, the movement of the examination object can be determined particularly accurately and / or with a particularly high time resolution.

One embodiment provides that the movement correction comprises a retrospective motion correction of the magnetic resonance measurement data using the determined motion information. The retrospective motion correction typically corrects, after acquiring the magnetic resonance measurement data, the movement of the examination subject in the magnetic resonance image data. The motion information typically contains, as described in more detail in the following section, transformation parameters, by means of which the magnetic resonance measurement data are transformed after their acquisition. By means of the proposed procedure, a particularly robust retrospective motion correction can be carried out.

One embodiment provides that the retrospective motion correction comprises determining, based on the motion information, transformation parameters that are specific to the at least one coherently excited one Layer group, and the magnetic resonance measurement data, which are detected from the at least one coherently excited layer group are transformed using the transformation parameters. In particular, it is proposed that different transformations be used for the magnetic resonance measurement data acquired from different coherently excited layer groups. In certain applications, individual transformation parameters can be determined for each coherently excited layer group of the several coherently excited layer groups. In particular, the transformation parameters should represent an optimal motion correction for the magnetic resonance measurement data acquired from the at least one coherently excited slice group. The transformation parameters may include, for example, translation parameters and / or rotation parameters and / or shear parameters and / or scaling parameters and / or non-rigid transformation parameters.

One embodiment provides that an interpolation of the transformed magnetic resonance measurement data takes place on a grid. Advantageously, the interpolation of the transformed magnetic resonance measurement data is carried out on a grid, which is configured differently from the grid on which the magnetic resonance measurement data are recorded. Advantageously, the interpolation of the transformed magnetic resonance measurement data takes place on a uniform (isotropic) grid. This is particularly relevant in the described retrospective motion correction, possibly for the reconstruction of magnetic resonance image data from the magnetic resonance measurement data. Namely, the proposed procedure typically causes no unique transformation to exist for the magnetic resonance measurement data acquired from the entire examination volume. In particular, after the movement correction, there is no uniformly sampled volume in the magnetic resonance measurement data. The interpolation method is intended to ensure that the magnetic resonance measurement data of the non-uniformly sampled volume can be interpolated onto an advantageously uniform grid (the so-called target voxel system). Interpolation methods are known to the person skilled in the art and will not be described in more detail here. For the prospective motion correction, the additional effort for the interpolation is typically not necessary, since usually only an adaptation of acquisition parameters, but no correction and / or interpolation of the acquired magnetic resonance measurement data is to take place. For the prospective motion correction described in the following sections, in particular the determination of the motion information is sufficient.

One embodiment provides that the movement correction comprises a prospective movement correction of the magnetic resonance measurement data using the determined motion information. In this case, the prospective motion correction generally comprises a detection and a correction of a movement of the examination subject during the acquisition of the magnetic resonance measurement data. The prospective motion correction can be done in certain cases, in particular almost, in real time. The prospective motion correction may comprise that, after detection of a first part of the magnetic resonance measurement data, motion parameters characterizing a movement of the examination object are determined. Then, acquisition parameters, for example a slice selection and / or a slice orientation, can be set for acquisition of a second part of the magnetic resonance measurement data on the basis of the movement parameters. In this way, the acquisition of the magnetic resonance measurement data can already be adapted during the magnetic resonance imaging to the movement of the examination subject. The recording parameters can be set in such a way that the movement of the examination object can be specifically counteracted. The movement correction of the magnetic resonance measurement data may thus include setting of acquisition parameters, which are set after the second time for the magnetic resonance imaging, depending on the movement information. In the rigid case, for example, layers of the examination volume for the magnetic resonance imaging after the second time point can be adjusted on the basis of the movement parameters, in particular on the basis of three translation parameters and three rotation parameters. In this way, a position and / or anatomy of the examination subject changed by the movement, for example a tilting of a head of the examination subject, can be compensated directly during the measurement. The adaptation of the imaging volume takes place, in particular, via an adaptation of gradient circuits which are switched during the magnetic resonance imaging after the second time, for example during excitation high-frequency pulses and / or readout windows. The adjustment of the acquisition parameters as a function of the movement information can hereby be carried out with a time offset to the acquisition of the magnetic resonance measurement data from the at least one coherently excited layer group of the several coherently excited layer groups. By means of the proposed procedure, in particular, a prospective movement correction with a fast update cycle on the basis of current image contents is possible. At the same time, the use of consistent data can lead to a particularly accurate prospective motion correction.

One embodiment provides that the prospective movement correction comprises determining, based on the movement information, acquisition parameters which are used for acquiring magnetic resonance measurement data from at least one further coherently excited layer group of the plurality of coherently excited layer groups. The detected movement can thus be incorporated into the setting of acquisition parameters for the acquisition of magnetic resonance measurement data from the at least one further coherently excited group of layers, which is different in particular from the at least one coherently excited group of layers, on the basis of which the movement information is determined.

An embodiment provides that performing the image measurement, determining the movement information and the movement correction comprises: acquiring first magnetic resonance measurement data from a first set of first coherently excited slice groups of the plurality of coherently excited slice groups, determining a first motion information from the reference volume and first magnetic resonance measurement data, movement correction of the first magnetic resonance measurement data using the first movement information, acquisition of second magnetic resonance measurement data from a second set of second coherently excited layer groups of the plurality of coherently excited layer groups, determination of a second movement information from the reference volume and the second magnetic resonance Measurement data, wherein the second movement information has other movement parameters than the first movement information and movement correction of the second magnetic resonance measurement data using the second Motion information. The first set of coherently excited layer groups comprises in particular one or more first coherently excited layer groups, while the second set of coherently excited layer groups particularly comprises one or more second coherently excited layer groups. The first amount and the second amount are advantageously formed disjoint. In this way, a continuous recording of magnetic resonance measurement data in several sub-steps with a specific motion correction for the several sub-steps is possible.

One embodiment provides that the first set of first coherently excited layer groups and the second set of second coherently excited layer groups are arranged spatially nested relative to one another. Thus, a nested acquisition (interleaved acquisition) of the coherently excited layer groups can take place. Thus, in particular spatially, between the respective layers of the first set of coherently excited layer groups, layers of the second set of the coherently excited layer groups are also positioned. In this way, a particularly robust movement correction can be made possible.

One embodiment provides that the examination volume comprises a plurality of first layers having a first layer spacing between adjacent first layers of the plurality of first layers, and a coherently excited layer group of the at least one coherently excited layer group comprising a plurality of second layers having a second layer spacing between adjacent second layers of the plurality of second layers wherein the second layer spacing is greater than the first layer spacing. The several second layers of the coherently excited layer group are advantageously arranged spatially distributed over the examination volume. Thus, a particularly robust motion information from the coherently excited layer group and the reference volume can be mentioned.

One embodiment provides that a coherently excited layer group of the at least one coherently excited layer group comprises a plurality of second layers, the plurality of second layers each being positioned as far apart as possible. This represents a particularly advantageous arrangement of the plurality of second layers for determining the movement information. The second layers can most advantageously be positioned at a maximum distance from one another in the examination volume.

One embodiment provides that a magnetic resonance sequence with first sequence parameters is used for the reference measurement and a magnetic resonance sequence with second sequence parameters is used for the image measurement, wherein the magnetic resonance sequence with the first sequence parameters is less sensitive to the movement of the examination subject than the magnetic resonance Sequence with the second sequence parameters. For the reference measurement, a different type of magnetic resonance sequence and / or other first sequence parameters can be used than for the image measurement. It is advantageous for the reference measurement to use a type of magnetic resonance sequence and / or first sequence parameters which ensure that the detected reference volume is free of movement artifacts and / or less susceptible to movement of the examination subject. This procedure is based on the consideration that usually falsifications of the reference measurements by movements of the examination object can influence the movement correction of the entire magnetic resonance measurement data. For the reference measurement can advantageously also a simultaneous multi-layer measurement technique can be used.

One embodiment provides that the examination volume comprises a brain region of the examination subject and the image measurement is performed using a functional magnetic resonance technique. In the functional magnetic resonance technique, the change in oxygenated blood compared to deoxygenated blood is typically analyzed over time using the BOLD effect. For the functional magnetic resonance technique, a time series of examination volumes is usually recorded and, as already described, the change in intensity caused by the degree of oxygenation of the blood is examined over time. During this measurement, the patient usually carries out various tasks, the so-called paradigm, for the targeted activation of individual brain areas. This may include, for example, viewing a visual stimulus, such as a flickering checkerboard pattern or images that cause emotions, motor tasks, such as finger-tapping, to auditory stimuli. The statistical evaluation of the correlation between the intensity changes and the simultaneous paradigm provides the activation of the respective brain areas in the form of statistical result maps. In the functional magnetic resonance technique even the smallest head movements of the examination object during the measurement can lead to considerable artifacts and impairments of the generated statistics maps. The motion correction thus represents a central part of the image processing in such a way, in particular for the functional magnetic resonance technique. In particular, it is conceivable that the proposed motion correction can increase a detected activation and thus the match to the paradigm by up to 20 percent and / or one size of the activation area can increase by up to 100 percent. It should be noted that the functional magnetic resonance technique is only a preferred application for the presented motion correction method. Of course, the presented method for movement correction can also be applied to regular anatomical magnetic resonance techniques and / or other body regions of the examination subject.

The magnetic resonance apparatus according to the invention comprises a reference measurement unit, an image measurement unit and a computing unit with a determination unit and a movement correction unit, wherein the magnetic resonance apparatus is designed for carrying out a method according to one of the preceding claims.

In this way, the magnetic resonance apparatus according to the invention is designed to carry out a method for a movement correction of magnetic resonance measurement data acquired during a magnetic resonance imaging of an examination subject by means of a magnetic resonance apparatus. The reference measurement unit is configured to perform a reference measurement at a first time during the magnetic resonance imaging, wherein a reference volume is detected. The image measuring unit is designed to perform an image measurement at a second point in time during the magnetic resonance imaging, wherein magnetic resonance measurement data from an examination volume are acquired by means of a simultaneous multi-slice measurement technique in a plurality of coherently excited slice groups. The determination unit is designed to determine movement information from the reference volume and magnetic resonance measurement data, which are acquired from at least one coherently excited layer group of the plurality of coherently excited layer groups, wherein the movement information describes a movement of the examination object between the first time and the second time. The movement correction unit is designed for a movement correction of the magnetic resonance measurement data using the determined motion information.

The computer program product according to the invention can be loaded directly into a memory of a programmable arithmetic unit of a magnetic resonance apparatus and has program code means for carrying out a method according to the invention when the computer program product is executed in the arithmetic unit of the magnetic resonance apparatus. The computer program product comprises in particular a computer program. As a result, the method according to the invention can be carried out quickly, identically repeatable and robust. The computer program product is configured such that it can execute the method steps according to the invention by means of the arithmetic unit. The arithmetic unit must in each case have the prerequisites such as, for example, a corresponding main memory, a corresponding graphics card or a corresponding logic unit, so that the respective method steps can be carried out efficiently. The computer program product is stored, for example, on a computer-readable medium or deposited on a network or server, from where it can be loaded into the processor of a local computing unit, which can be directly connected to the magnetic resonance apparatus or formed as part of the magnetic resonance apparatus. Furthermore, control information of the computer program product can be stored on an electronically readable data carrier. The control information of the electronically readable data carrier may be configured such that when using the data carrier in a computing unit of the magnetic resonance apparatus, they execute a method according to the invention. Examples of electronic readable data carriers are a DVD, a magnetic tape or a USB stick on which electronically readable control information, in particular software (see above), is stored. When this control information (software) is read from the data carrier and stored in a control and / or processing unit of the magnetic resonance apparatus, all the embodiments according to the invention of the previously described methods can be carried out. Thus, the invention can also emanate from the said computer-readable medium and / or the said electronically readable data carrier.

The advantages of the magnetic resonance apparatus according to the invention and of the computer program product according to the invention essentially correspond to the advantages of the method according to the invention, which are described above in detail. Features, advantages or alternative embodiments mentioned herein are also to be applied to the other claimed subject matter and vice versa. In other words, the subject-matter claims can also be developed with the features described or claimed in connection with a method. The corresponding functional features of the method are formed by corresponding physical modules, in particular by hardware modules.

In the following the invention will be described and explained in more detail with reference to the embodiments illustrated in the figures.

Show it:

1 a magnetic resonance apparatus according to the invention in a schematic representation,

2 a flow diagram of a first embodiment of a method according to the invention,

3 2 is a flow chart of a second embodiment of a method according to the invention, in particular for a retrospective movement correction,

4 a flowchart of a third embodiment of a method according to the invention, in particular for a prospective motion correction and

5 an exemplary illustration of an acquisition of layer groups according to the invention.

1 represents a magnetic resonance device according to the invention 11 schematically. The magnetic resonance apparatus 11 includes one of a magnet unit 13 formed detector unit with a main magnet 17 for generating a strong and in particular constant main magnetic field 18 , In addition, the magnetic resonance device has 11 a cylindrical patient receiving area 14 to a recording of an examination object 15 , in the present case of a patient, with the patient receiving area 14 in a circumferential direction of the magnet unit 13 is enclosed in a cylindrical shape. The patient 15 can by means of a patient support device 16 of the magnetic resonance device 11 in the patient receiving area 14 be pushed. The patient support device 16 has for this purpose a couch table, which is movable within the magnetic resonance apparatus 11 is arranged. The magnet unit 13 is by means of a housing cover 31 shielded from the magnetic resonance device to the outside.

The magnet unit 13 also has a gradient coil unit 19 for generation of magnetic field gradients used for spatial coding during imaging. The gradient coil unit 19 is by means of a gradient control unit 28 driven. Furthermore, the magnet unit 13 a high frequency antenna unit 20 which in the case shown as fixed in the magnetic resonance apparatus 10 integrated body coil is formed, and a high-frequency antenna control unit 29 to an excitation of a polarization, which is in the of the main magnet 17 generated main magnetic field 18 hangs up. The high-frequency antenna unit 20 is from the high-frequency antenna control unit 29 and radiates radiofrequency magnetic resonance sequences into an examination room, essentially from the patient receiving area 14 is formed. The high-frequency antenna unit 20 is also for the reception of magnetic resonance signals, in particular from the patient 15 , educated.

To a control of the main magnet 17 , the gradient controller 28 and the high-frequency antenna control unit 29 has the magnetic resonance device 11 an arithmetic unit 24 on. The arithmetic unit 24 centrally controls the magnetic resonance device 11 such as performing a predetermined imaging gradient echo sequence. Control information, such as imaging parameters, as well as reconstructed magnetic resonance images may be stored on a deployment unit 25 , in the present case a display unit 25 , the magnetic resonance device 11 be provided to a user. In addition, the magnetic resonance device has 11 an input unit 26 by means of which information and / or parameters can be entered by a user during a measurement process. The arithmetic unit 24 can the gradient control unit 28 and / or radio frequency antenna control unit 29 and / or the display unit 25 and / or the input unit 26 include.

The arithmetic unit 24 In the illustrated case, this includes a determination unit 33 and a motion correction unit 34 ,

The magnetic resonance device 11 further comprises a reference measurement unit 32 and an image measuring unit 30 , The reference measurement unit 32 and the image measuring unit 30 are formed in the present case by an image data acquisition unit. The image data acquisition unit in the present case of the magnet unit 13 together with the high-frequency antenna control unit 29 and the gradient control unit 28 educated. The magnetic resonance device 11 is thus together with the reference measurement unit 32 , the image measurement unit 30 and the arithmetic unit 24 designed for carrying out a method according to the invention for a movement correction of magnetic resonance measurement data.

The illustrated magnetic resonance apparatus 11 may of course include other components, the magnetic resonance devices 11 usually have. A general operation of a magnetic resonance device 11 is also known in the art, so that is dispensed with a detailed description of the other components.

2 shows a flowchart of a first embodiment of a method according to the invention for a movement correction of magnetic resonance measurement data obtained during a magnetic resonance imaging of an examination subject 15 by means of a magnetic resonance device 11 be recorded.

In a first process step 40 becomes a reference measurement at a first time during magnetic resonance imaging by means of the reference measurement unit 32 performed, wherein a reference volume is detected.

In a further process step 41 is an image measurement at a second time during the magnetic resonance imaging by means of the image measuring unit 30 performed, wherein magnetic resonance data from a study volume by means of a simultaneous multi-slice measurement technique in a plurality of coherently excited layer groups are detected.

In a further process step 42 determines the determination unit 33 a movement information from the reference volume and magnetic resonance measurement data, which are detected from at least one coherently excited layer group of the plurality of coherently excited layer groups, wherein the movement information describes a movement of the examination object between the first time and the second time.

In a further process step 43 a movement correction of the magnetic resonance measurement data takes place using the determined motion information by means of the motion correction unit 34 , The movement-corrected magnetic resonance measurement data represent in particular diagnostic magnetic resonance measurement data. The magnetic resonance measurement data and / or magnetic resonance image data which are reconstructed from the magnetic resonance measurement data can be provided, ie a user on the display unit 25 be displayed and / or stored in a database.

3 shows a flowchart of a second embodiment of a method according to the invention for a movement correction of magnetic resonance measurement data during a magnetic resonance imaging of an examination subject 15 by means of a magnetic resonance device 11 be recorded.

The following description is essentially limited to the differences from the embodiment in FIG 2 , wherein with respect to the same process steps to the description of the embodiment in 2 is referenced. Substantially the same process steps are always numbered with the same reference numerals.

In the 3 shown embodiment of the method according to the invention essentially comprises the method steps 40 . 41 . 42 . 43 the first embodiment of the inventive method according to 2 , In addition, the includes in 3 shown embodiment of the method according to the invention additional process steps and substeps. It is also possible to 3 alternative procedure, which only a part of in 3 has shown additional process steps and / or sub-steps. Of course, a too 3 alternative process sequence have additional process steps and / or sub-steps.

Im in 3 illustrated embodiment, the motion correction comprises a retrospective motion correction of the magnetic resonance measurement data in the further process step 43 using the in the further process step 42 determined movement information.

For the reference measurement in the further process step 40 can advantageously be used a magnetic resonance sequence with first sequence parameters, while for the image measurement in the further process step 41 a magnetic resonance sequence with second sequence parameters is used. This is advantageously the Magnetic resonance sequence with the first sequence parameters less sensitive to the movement of the examination subject than the magnetic resonance sequence with the second sequence parameters.

Performing the image measurement in the further process step 41 comprises in a first sub-step 41-1 acquiring first magnetic resonance measurement data from a first set of first coherently excited slice groups of the plurality of coherently excited slice groups. In a first step 42-1 the further process step 42 is a first movement information from the in the further process step 41 Reference volume and the first magnetic resonance measurement data determined. The movement correction of the first magnetic resonance measurement data using the first motion information then takes place in a first partial step 43-1 the further process step 43 , The motion corrected first magnetic resonance measurement data may then be provided to a viewer.

The retrospective motion correction of the first magnetic resonance measurement data preferably comprises that based on the first motion information first transformation parameters are determined which are specific for the first magnetic resonance measurement data. The first transformation parameters can particularly advantageously transform the acquired first set of coherently excited layer groups, since they have been specifically determined for them. In this way, the first magnetic resonance measurement data, which are acquired from the first set of coherently excited slice groups, are determined on the basis of the first transformation parameters in the first partial step 43-1 the further process step 43 transformed.

Furthermore, in a further step in a second step 41-1 second magnetic resonance measurement data from a second set of second coherently excited layer groups of the plurality of coherently excited layer groups detected. The second set of coherently excited layer groups is in particular disjoint to the first set of coherently excited layer groups. In a second step 42-1 the further process step 42 is a second movement information from the in the further process step 41 Reference volume and the second magnetic resonance measurement data determined. The movement correction of the second magnetic resonance measurement data using the second movement information then takes place in a second partial step 43-1 the further process step 43 , The motion corrected second magnetic resonance measurement data may then be provided to a viewer.

The retrospective motion correction of the second magnetic resonance measurement data preferably comprises that based on the second motion information second transformation parameters are determined, which is specific for the second magnetic resonance measurement data. The second transformation parameters can particularly advantageously transform the acquired second set of coherently excited layer groups, since they have been determined specifically for them. In this way, the second magnetic resonance measurement data, which are acquired from the second set of coherently excited slice groups, are determined based on the second transformation parameters in the second partial step 43-1 the further process step 43 transformed. Furthermore, it is possible to interpolate the transformed second magnetic resonance measurement data onto an advantageously uniform grid in a sub-step 43I of the second sub-step 43-2 respectively. Of course, this procedure is also conceivable for the first transformed magnetic resonance measurement data.

Of course, according to 3 Furthermore, further magnetic resonance measurement data from further quantities of coherently excited layer groups can be detected. This in 3 Alternatively, the described procedure can also be carried out on the basis of a single set of acquired coherently excited slice groups, ie only based on the first magnetic resonance measurement data. Particularly advantageous are according to 3 the first set of first coherently excited layer groups and the second set of second coherently excited layer groups arranged spatially nested one another.

4 shows a flowchart of a third embodiment of a method according to the invention for a movement correction of magnetic resonance measurement data obtained during a magnetic resonance imaging of an examination subject 15 by means of a magnetic resonance device 11 be recorded.

The following description is essentially limited to the differences from the embodiment in FIG 2 , wherein with respect to the same process steps to the description of the embodiment in 2 is referenced. Substantially the same process steps are always numbered with the same reference numerals.

In the 4 shown embodiment of the method according to the invention essentially comprises the method steps 40 . 41 . 42 . 43 the first embodiment of the inventive method according to 2 , In addition, the includes in 4 shown embodiment of the method according to the invention additional process steps and Sub-steps. It is also possible to 4 alternative procedure, which only a part of in 4 has shown additional process steps and / or sub-steps. Of course, a too 4 alternative process sequence have additional process steps and / or sub-steps.

Im in 4 In the exemplary embodiment illustrated, the movement correction comprises a prospective movement correction of the magnetic resonance measurement data in the further method step 43 using the in the further process step 42 determined movement information.

This is done analogously to 3 in a first step 41-1 the further process step 41 acquiring first magnetic resonance measurement data from a first set of first coherently excited slice groups of the plurality of coherently excited slice groups. Subsequently, in a sub-step 42-1 the further process step 42 a movement information from the reference volume and the first magnetic resonance measurement data determined.

In contrast to 4 now takes place in the further process step 43 a prospective motion correction of the magnetic resonance measurement data using the determined motion information. The prospective motion correction comprises that based on the motion information in a sub-step 43AP the further process step 43 Recording parameters are determined. These acquisition parameters can then be used to acquire second magnetic resonance measurement data from at least one further coherently excited layer group of the several coherently excited layer groups, which in a second sub-step 41-2 the further process step 41 be used. The acquisition parameters are set in particular for the magnetic resonance imaging after the second time. The setting of the recording parameters can be carried out such that a capture of magnetic resonance measurement data during the magnetic resonance imaging after the second time takes place such that the movement of the examination object described in the movement information 15 between the first time and the second time.

Of course, this procedure can be continued. Thus, movement information for a prospective movement correction of third magnetic resonance measurement data can also be determined on the basis of the second magnetic resonance measurement data.

In the 2 to 4 illustrated method steps of the method according to the invention are performed by the arithmetic unit. For this purpose, the arithmetic unit comprises required software and / or computer programs which are stored in a memory unit of the arithmetic unit. The software and / or computer programs comprise program means which are designed to execute the method according to the invention when the computer program and / or the software is executed in the arithmetic unit by means of a processor unit of the arithmetic unit.

5 is intended to exemplify the acquisition of several layer groups according to the invention by means of the simultaneous multilayer measurement technique. This in 5 The acquisition scheme shown by way of example can be found both in the 3 as well as in the 4 shown procedure can be used. Exemplary will be in 5 a head area of the examination object 15 examined. In this way, the examination volume VOL covers the entire head area of the examination subject 15 from. By means of the procedure according to the invention, head movements of the examination object can be particularly advantageous 15 Getting corrected. The examination volume VOL also includes a brain area of the examination subject 15 , It is conceivable that such a functional magnetic resonance technique is used during the image measurement. Of course, anatomical magnetic resonance imaging or another type of magnetic resonance imaging may also be used.

In the case shown, the examination volume VOL comprises twenty-one layers S0, S1,..., S20, which are grouped into seven coherently excited layer groups A0, A1, A2, A3, A4, A5, A6. A first coherently excited layer group A0 of the seven coherently excited layer groups A0, A1, A2, A3, A4, A5, A6 comprises three layers S0, S7, S14 of the twenty-one layers S0, S1,..., S20. In the same way, each of the seven coherently excited layer groups A0, A1, A2, A3, A4, A5, A6 respectively comprises three layers S0, S1,..., S20. The respective layers S0, S1,..., S20 belonging to a coherently excited layer group A0, A1, A2, A3, A4, A6 are measured simultaneously during the measurement of the examination volume VOL and are excited by means of an excitation pulse. In this way, the respective layers S0, S1,..., S20 belonging to a coherently excited layer group A0, A1, A2, A3, A4, A5, A6 are consistent with each other since they are recorded at the same time. In this way, these layers point S0, S1,..., S20 during a movement of the examination subject 15 the same influence of the movement. Such will be in the in 5 As an example, the examination volume VOL is shown by means of a simultaneous multi-slice measurement technique with a Acceleration factor of three and a number of coherently excited layer groups A0, A1, A2, A3, A4, A5, A6 detected by seven. The number of layers S0, S1,..., S20 of the examination volume VOL results from the product of the acceleration factor and the number of coherently excited layer groups A0, A1, A2, A3, A4, A5, A6 and is exemplary in the case shown therefore twenty-one.

The order of recording of the layers S0, S1,..., S20 of the examination volume VOL can be interleaved. Thus, coherently excited layer groups A0, A1, A2, A3, A4, A5, A6 of the examination volume VOL are advantageously never taken in succession, which have directly adjacent layers S0, S1,..., S20. This is exemplary in 5 when the coherently excited layer groups A0, A1, A2, A3, A4, A5, A6 are acquired in the order of their indices, ie first the first coherently excited layer group A0 is acquired, then the second coherently excited layer group A1 is acquired, etc In this way, interactions (cross talks) between the layers S0, S1,..., S20 during the acquisition can be reduced and / or avoided in a particularly advantageous manner during the acquisition.

The layers S0, S1,..., S20 of the examination volume VOL have a first layer spacing, which in the case shown should amount to one in arbitrary units. Between the layers S0, S1,..., S20 of a single coherently excited layer group A0, A1, A2, A3, A4, A5, A6, for example between the layers S0, S7, S14 of the first coherently excited layer group, there is a second layer spacing , This second layer spacing is greater than the first layer spacing. In the case shown, the second layer spacing in the arbitrary units is seven, which corresponds to the number of coherently excited layer groups A0, A1, A2, A3, A4, A5, A6. The individual layers of a single coherently excited layer group A0, A1, A2, A3, A4, A5, A6 are each positioned as far as possible from one another in the examination volume VOL.

According to the proposed procedure, the motion information is already determined on the basis of a subset of the acquired coherently excited slice groups A0, A1, A2, A3, A4, A5, A6. The motion information is thus determined using a number of coherently excited layer groups A0, A1, A2, A3, A4, A5, A6, which is smaller than the total number of coherently excited layer groups A0, A1, A2, A3, A4, A5, A6, im thus, the case shown is less than seven.

As an example, the case is described that the movement information from the reference volume and magnetic resonance measurement data, which consists of a single coherently excited layer group layer groups A0, A1, A2, A3, A4, A5, A6 of the plurality of coherently excited layer groups A0, A1, A2, A3, A4, A5, A6 is detected. In this way, for example, the first layers S0, S7, S14 of the first coherently excited layer group A0 shown in dashed lines (with line form: "/") are simultaneously recorded simultaneously. On the basis of these first layers S0, S7, S14 and the reference volume, a first movement information can then be determined. The movement information can be effected, for example, by means of a registration of the detected layers S0, S7, S14 on the reference volume. Of course, other possibilities for determining the movement information from the magnetic resonance measurement data and the reference volume, which appear expedient to the person skilled in the art, are also conceivable. This first movement information can then be used, for example, for the movement correction of the magnetic resonance measurement data acquired from the first layers S0, S7, S14 and / or for setting acquisition parameters for the acquisition of further coherently applied filter groups A1, A3, A4, A5, A6 , On the basis of the second slices (S1, S8, S15) of the second coherently excited slice group A1, which are acquired after the first slices S0, S7, S14, it is then possible analogously to determine second motion information, and so on For example, the simultaneous multi-slice measurement technique can be used to improve the movement correction of the magnetic resonance measurement data recorded in this way.

It should be noted that in 5 illustrated illustration of the procedure according to the invention can only be seen as an example. Of course, a different acceleration factor, different numbers of layer groups or layers, different positioning or alignments of layers can be used. Also, of course, another body region of the examination subject 15 to be examined. It can of course also a different movement of the examination object 15 , For example, a breathing movement to be compensated.

Although the invention has been further illustrated and described in detail by the preferred embodiments, the invention is nevertheless not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• Setsompop et al. "Blipped-controlled aliasing in parallel imaging for simultaneous multislice echo planar imaging with reduced g-factor penalty.", Magn Reson Med. 2012. 67 (5): 1210-1224 [0010]
• Setsompop et al. [0011]

Claims (16)

 Method for a movement correction of magnetic resonance measurement data acquired during a magnetic resonance imaging of an examination object by means of a magnetic resonance apparatus, comprising the following method steps: Performing a reference measurement at a first time during magnetic resonance imaging, wherein a reference volume is detected, Performing an image measurement at a second time during the magnetic resonance imaging, wherein magnetic resonance measurement data from an examination volume are acquired by means of a simultaneous multi-slice measurement technique in a plurality of coherently excited slice groups, Determining movement information from the reference volume and magnetic resonance measurement data which are acquired from at least one coherently excited layer group of the plurality of coherently excited layer groups, wherein the movement information describes a movement of the examination object between the first time and the second time, and - Motion correction of the magnetic resonance measurement data using the determined motion information. The method of claim 1, wherein the at least one coherently-excited layer group comprises a number of layer groups smaller than the total number of the plurality of coherently-excited layer groups. Method according to one of the preceding claims, wherein the movement information from the reference volume and magnetic resonance measurement data, which are detected from a single coherently excited layer group of the plurality of coherently excited layer groups, is determined. Method according to one of the preceding claims, wherein the movement correction comprises a retrospective motion correction of the magnetic resonance measurement data using the determined motion information.  The method of claim 4, wherein the retrospective motion correction comprises determining, based on the motion information, transformation parameters that are specific to the at least one coherently excited layer group and the magnetic resonance measurement data acquired from the at least one coherently excited layer group using the transformation parameters be transformed. The method of claim 5, wherein an interpolation of the transformed magnetic resonance measurement data is carried out on a grid. Method according to one of the preceding claims, wherein the movement correction comprises a prospective movement correction of the magnetic resonance measurement data using the determined motion information. The method of claim 7, wherein the prospective motion correction comprises determining, based on the motion information, acquisition parameters which are used for acquiring magnetic resonance measurement data from at least one further coherently excited layer group of the plurality of coherently excited layer groups. The method of any one of the preceding claims, wherein performing the image measurement, determining the motion information, and the motion correction comprises: Acquiring first magnetic resonance measurement data from a first set of first coherently excited layer groups of the plurality of coherently excited layer groups, Determining first movement information from the reference volume and the first magnetic resonance measurement data, Motion correction of the first magnetic resonance measurement data using the first motion information, Acquiring second magnetic resonance measurement data from a second set of second coherently excited layer groups of the plurality of coherently excited layer groups, Determining second movement information from the reference volume and the second magnetic resonance measurement data, the second movement information having movement parameters other than the first movement information, - Motion correction of the second magnetic resonance measurement data using the second movement information. The method of claim 9, wherein the first set of first coherently excited layer groups and the second set of second coherently excited layer groups are arranged spatially nested one another. The method of claim 1, wherein the examination volume comprises a plurality of first layers having a first layer spacing between adjacent first layers of the plurality of first layers, and a coherently excited layer group of the at least one coherently excited layer group comprising a plurality of second layers having a second layer spacing between adjacent second layers of the plurality of layers second layers, wherein the second layer spacing is greater than the first layer spacing. Method according to one of the preceding claims, wherein a coherently excited layer group of the at least one coherently excited layer group comprises a plurality of second layers, wherein the plurality of second layers are each positioned as far apart as possible. Method according to one of the preceding claims, wherein for the reference measurement, a magnetic resonance sequence with first sequence parameters and for the image measurement, a magnetic resonance sequence with second sequence parameters is used, wherein the magnetic resonance sequence with the first sequence parameters is less sensitive to the movement of the examination subject than the magnetic resonance sequence with the second sequence parameters.  Method according to one of the preceding claims, wherein the examination volume comprises a brain region of the examination subject and the image measurement is performed using a functional magnetic resonance technique. Magnetic resonance apparatus comprising a reference measurement unit, an image measurement unit and a computing unit with a determination unit and a movement correction unit, wherein the magnetic resonance apparatus is designed for carrying out a method according to one of the preceding claims. Computer program product, which is directly loadable into a memory of a programmable arithmetic unit of a magnetic resonance apparatus, with program code means for executing a method according to one of claims 1-14, when the computer program product is executed in the arithmetic unit of the magnetic resonance apparatus.

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