Method for controlling an MR apparatus

Abstract

In a method for control, input magnetic field map data is received. In this case, the input magnetic field map data for at least one magnetic field type in each case describes a magnetic field map for a state that an examination object is in at an initial location in the MR apparatus. In this case, the estimated magnetic field map data for at least one magnetic field type in each case describes at least one magnetic field map for in each case a state that the examination object is in at an alternative location that is different compared to the initial location. Control data is determined by the system control unit, using the estimated magnetic field map data or using the input magnetic field map data and the estimated magnetic field map data. The control data is suitable for controlling the MR apparatus.

Claims

1. A method for determining control data for a magnetic resonance (MR) excitation of an examination object using an MR apparatus, the method comprising: receiving input magnetic field map data, wherein the input magnetic field map data for at least one magnetic field type in each case describes a magnetic field map for a state that the examination object is in at an initial location in the MR apparatus; determining estimated magnetic field map data, wherein the estimated magnetic field map data for at least one magnetic field type in each case describes at least one magnetic field map for in each case a state that the examination object is in at an alternative location that is different compared to the initial location; and determining control data using the estimated magnetic field map data or using the input magnetic field map data and the estimated magnetic field map data, wherein the control data is suitable for the MR excitation of the examination object, and wherein the determining of the estimated magnetic field map data, the determining of the control data, or the determining of the estimated magnetic field map data and the determining of the control data take place based on an application of a trained function, an interpolation function, or the trained function and the interpolation function to the input magnetic field map data.

2. The method of claim 1, wherein the MR excitation comprises generation of at least one radio frequency (RF) transmit pulse by a transmit coil arrangement of the MR apparatus, generation of at least one gradient pulse by a gradient coil unit of the MR apparatus, or generation of the at least one radio frequency (RF) transmit pulse by the transmit coil arrangement of the MR apparatus and generation of the at least one gradient pulse by the gradient coil unit of the MR apparatus.

3. The method of claim 2, wherein the input magnetic field map data is recorded in a preliminary MR scan with the aid of the MR apparatus, and wherein after the preliminary MR scan, an MR excitation of the examination object takes place in a main MR scan by the transmit coil arrangement using the control data.

4. The method of claim 3, wherein the control data is suitable for the MR excitation in accordance with multiple excitation configurations, and wherein determining the control data comprises optimizing to the effect that each of the multiple excitation configurations comprises an MR excitation that is optimized for in each case a different location range of the examination object.

5. The method of claim 4, wherein the initial location is determined during the preliminary MR scan, wherein a current location of the examination object in the MR apparatus is determined during the main MR scan, wherein the current location relative to the initial location is assigned to one of the different location ranges, and wherein the MR excitation of the examination object takes place in accordance with the excitation configuration of the assigned location range.

6. The method of claim 5, wherein the initial location, the current location, or the initial location and the current location of the examination object is determined by a navigator scan, a pilot tone scan, a camera recording, or any combination thereof.

7. The method of claim 3, wherein the initial location is determined during the preliminary MR scan, wherein a current location of the examination object in the MR apparatus is determined during the main MR scan, and wherein at least one alternative location is determined using the current location.

8. The method of claim 1, wherein the at least one magnetic field type comprises a B1 field, a B0 field, or the B1 field and the B0 field.

9. The method of claim 1, wherein the estimated magnetic field map data for at least one magnetic field type describes multiple magnetic field maps for in each case a state that the examination object is in at a different alternative location in each case.

10. The method of claim 1, wherein at least one of the alternative locations is describable by a rotation by at least 1°, 2°, or 4°, a translation by at least 1 mm, 2 mm, or 4 mm, or a combination thereof.

11. The method of claim 1, wherein determining the control data comprises optimizing to the effect that the MR excitation is optimized for a location range that comprises the alternative locations, the initial location, or the alternative locations and the initial locations.

12. A method for provision of a trained function for determining estimated magnetic field map data, control data, or the estimated magnetic field map data and the control data, the method comprising: receiving training input data, wherein the training input data comprises training input magnetic field map data, wherein the training input magnetic field map data for at least one magnetic field type in each case describes a magnetic field map for a state that an examination object is in at an initial location in the MR apparatus; receiving training output data, wherein the training output data comprises training estimated magnetic field map data, training control data, or the training estimated magnetic field map data and the training control data for controlling an MR excitation of the examination object, wherein the training estimated magnetic field map data for at least one magnetic field type in each case describes at least one magnetic field map for in each case a state that the examination object is in at an alternative location that is different compared to the initial location; training the trained function based on the training input data and the training output data; and providing the trained function.

13. The method of claim 12, wherein the training input data, the training output data, or the training input data and the training output data are generated by scanning, simulation, or scanning and simulation of magnetic field maps.

14. A magnetic resonance (MR) apparatus comprising: a processor configured to determine control data for a magnetic resonance (MR) excitation of an examination object using the MR apparatus, the method determination of the control data comprising: receipt of input magnetic field map data, wherein the input magnetic field map data for at least one magnetic field type in each case describes a magnetic field map for a state that the examination object is in at an initial location in the MR apparatus; determination of estimated magnetic field map data, wherein the estimated magnetic field map data for at least one magnetic field type in each case describes at least one magnetic field map for in each case a state that the examination object is in at an alternative location that is different compared to the initial location; and determination of control data using the estimated magnetic field map data or using the input magnetic field map data and the estimated magnetic field map data, wherein the control data is suitable for the MR excitation of the examination object, and wherein the determination of the estimated magnetic field map data, the determination of the control data, or the determination of the estimated magnetic field map data and the determination of the control data take place based on an application of a trained function, an interpolation function, or the trained function and the interpolation function to the input magnetic field map data.

15. In a non-transitory computer-readable storage medium that stores instructions executable by one or more processors to determine control data for a magnetic resonance (MR) excitation of an examination object using an MR apparatus, the instructions comprising: receiving input magnetic field map data, wherein the input magnetic field map data for at least one magnetic field type in each case describes a magnetic field map for a state that the examination object is in at an initial location in the MR apparatus; determining estimated magnetic field map data, wherein the estimated magnetic field map data for at least one magnetic field type in each case describes at least one magnetic field map for in each case a state that the examination object is in at an alternative location that is different compared to the initial location; and determining control data using the estimated magnetic field map data or using the input magnetic field map data and the estimated magnetic field map data, wherein the control data is suitable for the MR excitation of the examination object, and wherein the determining of the estimated magnetic field map data, the determining of the control data, or the determining of the estimated magnetic field map data and the determining of the control data take place based on an application of a trained function, an interpolation function, or the trained function and the interpolation function to the input magnetic field map data.

16. The non-transitory computer-readable storage medium of claim 15, wherein the MR excitation comprises generation of at least one radio frequency (RF) transmit pulse by a transmit coil arrangement of the MR apparatus, generation of at least one gradient pulse by a gradient coil unit of the MR apparatus, or generation of the at least one radio frequency (RF) transmit pulse by the transmit coil arrangement of the MR apparatus and generation of the at least one gradient pulse by the gradient coil unit of the MR apparatus.

17. The non-transitory computer-readable storage medium of claim 15, wherein the at least one magnetic field type comprises a B1 field, a B0 field, or the B1 field and the B0 field.

18. The non-transitory computer-readable storage medium of claim 15, wherein the estimated magnetic field map data for at least one magnetic field type describes multiple magnetic field maps for in each case a state that the examination object is in at a different alternative location in each case.

19. The non-transitory computer-readable storage medium of claim 15, wherein at least one of the alternative locations is describable by a rotation by at least 1°, 2°, or 4°, a translation by at least 1 mm, 2 mm, or 4 mm, or a combination thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Parts corresponding to one another are provided with same reference characters in all figures.

(2) FIG. 1 shows one embodiment of a magnetic resonance (MR) apparatus in a schematic representation;

(3) FIG. 2 shows one embodiment of a method for determining data for controlling an MR excitation using the MR apparatus;

(4) FIG. 3 shows different locations of an examination object with assigned magnetic field maps for generating a transmit pulse;

(5) FIG. 4 shows one embodiment of an enhanced method for determining data for controlling a transmit coil arrangement of an MR apparatus;

(6) FIG. 5 shows different locations of an examination object with assigned magnetic field maps for generating multiple transmit pulses for different location ranges;

(7) FIG. 6 shows a further embodiment of a method for determining data for controlling a transmit coil arrangement of an MR apparatus;

(8) FIG. 7 shows exemplary locations, determined using a current position, of an examination object with assigned magnetic field maps for generating a transmit pulse;

(9) FIG. 8 shows an exemplary trained function for determining estimated magnetic field map data and/or control data; and

(10) FIG. 9 shows exemplary methods for providing a trained function for determining estimated magnetic field map data and/or control data.

DETAILED DESCRIPTION

(11) FIG. 1 schematically represents a magnetic resonance (MR) apparatus 10. The MR apparatus 10 includes a magnetic unit 11 that has a main magnet 12 for generating a static main magnetic field 13. The MR apparatus 10 includes a patient receiving area 14 to receive an examination object 15 (e.g., a patient). The patient receiving area 14 in the present exemplary embodiment is configured to be cylindrical and is cylindrically surrounded in a circumferential direction by the magnetic unit 11. However, in principle, a design of the patient receiving area 14 that deviates from this may be provided. The examination object 15 may be moved into the patient receiving area 14 by a patient positioning apparatus 16 of the MR apparatus 10. The patient positioning apparatus 16 has a patient table 17 that is configured to be movable inside the patient receiving area 14.

(12) The magnetic unit 11 also has a gradient coil unit 18 for generating magnetic field gradient pulses (e.g., gradient pulses). The gradient pulses are, for example, used for position encoding during imaging. The gradient coil unit 18 is controlled by a system control unit 22 of the MR apparatus 10. The magnetic unit 11 also includes a radio-frequency antenna unit 19 that, in the present exemplary embodiment, is configured as a body coil permanently integrated into the MR apparatus 10. The radio-frequency antenna unit 19, for example, includes a transmit coil arrangement 20 for transmitting and beaming radio-frequency RF transmit pulses into an examination space, which is essentially formed by a patient receiving area 14 of the MR apparatus 10. The transmit coil arrangement 20 may include multiple transmit coils (e.g., multiple transmit coil channels that may be operated in parallel; the MR apparatus 10 is pTx-enabled).

(13) In the example represented, the transmit coil arrangement 20 is part of the body coil permanently integrated into the MR apparatus 10. The transmit coil arrangement 20 may, however, also be configured as an apparatus that may be positioned locally on the examination object and that is not permanently integrated into the MR apparatus 10 (e.g., as part of a local coil). In the case of MR apparatuses 10 with a particularly strong main magnetic field 13 of, for example, more than 5 tesla, it may be advantageous to position the transmit coil arrangement 20 very close to the examination object 15.

(14) The radio-frequency antenna unit 19 is controlled by the system control unit 22 of the MR apparatus 10. By RF transmit pulses being beamed by the transmit coil arrangement 20 at the same time as magnetic field gradients are being generated by the gradient coil unit 18, an excitation of atomic nuclei occurs in the main magnetic field 13 generated by the main magnet 12. MR signals are generated thanks to relaxation of the excited atomic nuclei. The radio-frequency antenna unit 19 is also configured to receive the MR signals. The radio-frequency antenna unit 19 includes a receive coil arrangement 21. The receive coil arrangement 21 may be the same as the transmit coil arrangement 20 (e.g., the associated coils are suitable both for transmitting RF pulses and for receiving MR signals). The receive coil arrangement 21 may, however, also be characterized by a separate coil arrangement independent of the transmit coil arrangement 20.

(15) For control of the main magnet 12, of the gradient coil unit 18, and of the radio-frequency antenna unit 19, the MR apparatus 10 has a system control unit 22. The system control unit 22 controls the MR apparatus 10 centrally during an MR scan (e.g., during the performance of an imaging sequence). Moreover, the system control unit 22 includes an evaluation unit (not shown in greater detail) for evaluation of the MR signals that are detected during the MR examination. The MR apparatus 10 further includes a user interface 23 that is connected to the system control unit 22. Control information such as imaging parameters, for example, as well as reconstructed MR images, may be displayed on a display unit 24 (e.g., on at least one monitor) of the user interface 23 for medical operating personnel. Further, the user interface 23 has an input unit 25, by which information and/or parameters may be input by the medical operating personnel during a scanning operation.

(16) Represented in FIG. 2 (in conjunction with FIG. 3) is a method for determining control data for the MR excitation of the examination object 15 by the MR apparatus 10. The MR excitation may, for example, include the generation of at least one RF transmit pulse by the transmit coil arrangement 20 of the MR apparatus 10 and/or of at least one gradient pulse by a gradient coil unit 18 of the MR apparatus 10. In the following explanations, by way of example, only the generation of at least one RF transmit pulse is looked at in detail for the sake of simplicity.

(17) In S10, input magnetic field map data IMD is received. The input magnetic field map data IMD for at least one magnetic field type B0, B1 in each case describes a magnetic field map B1.sub.P0, B0.sub.P0 for a state which an examination object 15 is in at an initial location P0 in the MR apparatus 10 (e.g., in the patient receiving area 14).

(18) In S20, estimated magnetic field map data EMD is determined. The estimated magnetic field map data EMD for at least one magnetic field type B0, B1 in each case describes at least one magnetic field map B1.sub.P1, B0.sub.P1, B1.sub.P2, B0.sub.P2, B1.sub.P3, B0.sub.P3, B1.sub.P4, B0.sub.P4 for in each case a state that the examination object 15 is in at an alternative location P1, P2, P3, P4 that is different compared to the initial location.

(19) In S30, control data SD is determined using the estimated magnetic field map data EMD or using the input magnetic field map data IMD and the estimated magnetic field map data EMD. The control data SD is suitable for the MR excitation of the examination object 15 (e.g., for controlling at least one RF transmit pulse TxP that may be emitted by the transmit coil arrangement 20 of the MR apparatus 10).

(20) The determination of the estimated magnetic field map data EMD in S20 and/or of the control data in S30 takes place based on an application of a trained function and/or an interpolation function to the input magnetic field map data IMD.

(21) In S40, using the control data SD, at least one RF transmit pulse TxP is emitted by the transmit coil arrangement 20 of the MR apparatus 10. As a result, the at least one RF transmit pulse TxP is beamed into the patient receiving area 14 (e.g., into the examination object 15) for the generation of MR signals.

(22) The at least one magnetic field type may include a B1 field and/or a B0 field, which is represented in FIG. 1 as a main magnetic field 13.

(23) The estimated magnetic field map data EMD for at least one magnetic field type B0, B1 may describe multiple magnetic field maps B1.sub.P1, B0.sub.P1, B1.sub.P2, B0.sub.P2, B1.sub.P3, B0.sub.P3, B1.sub.P4, B0.sub.P4 for in each case a state that the examination object 15 is in at another alternative location P1, P2, P3, P4 in each case.

(24) By way of example, a state is represented in FIG. 3 that the examination object 15 is in at an initial location P0. For this state, input magnetic field map data IMD describes the B1 map B1.sub.P0 and the B0 map B0.sub.P0. In FIG. 3, states are represented that the examination object 15 is in at an alternative location P1, P2, P3, P4 that is different compared to the initial location, and that may be described by a rotation (e.g., about the z-axis that is orthogonal to the x-axis and the y-axis): at the alternative location P1, the examination object is rotated by −5° compared to the initial location; at the alternative location P2, the examination object is rotated by −10° compared to the initial location; at the alternative location P3, the examination object is rotated by +5° compared to the initial location; at the alternative location P4, the examination object is rotated by +10° compared to the initial location.

(25) Further, possible alternative locations may be described by a translation or a combination of rotation and translation. A rotation such as this may take place by at least 1°, 2°, or 4°, and a translation such as this may take place by at least 1 mm, 2 mm, or 4 mm.

(26) In accordance with S20, estimated magnetic field map data EMD is determined in this example based on an application of a trained function and/or an interpolation function to the input magnetic field map data IMD. In this case, the estimated magnetic field map data EMD for the B1 field describes the magnetic field map B1.sub.P1 and for the B0 field describes the magnetic field map B1.sub.P0 for the state that the examination object 15 is in at the alternative location P1. In this case, the estimated magnetic field map data EMD describes the B1 map B1.sub.P1 and the B1 map B1.sub.P1 for the state that the examination object 15 is in at the alternative location P1; further, the estimated magnetic field map data EMD describes the B1 map B1.sub.P2 and the B1 map B1.sub.P2 for the state that the examination object 15 is in at the alternative location P2. Further, the estimated magnetic field map data EMD describes the B1 map B1.sub.P3 and the B1 map B1.sub.P3 for the state that the examination object 15 is in at the alternative location P3. Further, the estimated magnetic field map data EMD describes the B1 map B1.sub.P4 and the B1 map B1.sub.P4 for the state that the examination object 15 is in at the alternative location P4.

(27) In accordance with S30, control data SD is determined using the input magnetic field map data IMD and the estimated magnetic field map data EMD in the example represented in FIG. 3. The control data SD is suitable, for example for controlling the RF transmit pulse TxP that may be emitted during an MR scan by the transmit coil arrangement 20 of the MR apparatus 10 using the control data SD.

(28) For example, the determination of the control data SD includes an optimization to the effect that the RF transmit pulse TxP is optimized for a location range A, B, C that includes the alternative locations and the initial location. In the present example, an RF transmit pulse TxP that is especially robust with respect to movements (e.g., with respect to rotations by ±10° about the z-axis) of the examination object 15 may, as a result, be generated.

(29) FIG. 4 (in conjunction with FIG. 5) shows an enhanced method, in accordance with which input magnetic field map data IMD is recorded in S05 in a preliminary MR scan with the aid of the MR apparatus 10. The emission of the at least one RF transmit pulse TxP by the transmit coil arrangement 20 using the control data SD in accordance with S40 takes place in a main MR scan after the preliminary MR scan in S05.

(30) For example, the initial location P0 may be determined in S05 during the preliminary MR scan, and a current location of the examination object 15 in the MR apparatus 10 may be determined in S40 during the main MR scan. Further, in S40, the current location relative to the initial location P0 may be assigned to one of the different location ranges A, B, C, and an RF transmit pulse TxP.sub.A, TxP.sub.B, TxP.sub.C optimized for the assigned location range A, B, C may be emitted by the transmit coil arrangement 20. The RF transmit pulses TxP.sub.A, TxP.sub.B, TxP.sub.C in each case represent, for example, a different excitation configuration that, in each case, includes an MR excitation that is optimized in each case for a different location range A, B, C of the examination object 15.

(31) In S30, the determination of the control data SD may include an optimization to the effect that multiple RF transmit pulses TxP.sub.A, TxP.sub.B, TxP.sub.C that may be emitted by the transmit coil arrangement 20 are optimized for in each case a different location range A, B, C of the examination object, such that the control data SD is suitable for controlling multiple RF transmit pulses TxP.sub.A, TxP.sub.B, TxP.sub.C that may be emitted by the transmit coil arrangement 20 of the MR apparatus 10. In one embodiment, therefore, not only is an RF transmit pulse TxP calculated in S30, but also multiple ones for a different location range A, B, C in each case.

(32) This will be explained in greater detail by way of example in FIG. 5, for which the same explanations apply as for FIG. 3, unless stipulated otherwise below. In this case, the locations P2, P1, and P0 represent a first location range A that, for example, covers a rotation range from −10° to −3° about the z-axis; the locations P1, P0, and P3 represent a second location range B that, for example, covers a rotation range from −3° to +3° about the z-axis; the locations P0, P3, and P4 represent a third location range C that, for example, covers a rotation range from +3° to +10° about the z-axis. A separate MR excitation (e.g., a separate RF transmit pulse) is optimized for each of these location ranges A, B, C in S30: the RF transmit pulse TxP.sub.A for the location range A, the RF transmit pulse TxP.sub.B for the location range B, and the RF transmit pulse TxP.sub.C for the location range C.

(33) During the MR scan (e.g., during the main scan), it is possible to determine in S40 the actual current location of the examination object 15 at present. This current location may then be assigned to one of the location ranges A, B, C. As a function of this, the RF pulse optimized for this location range may be emitted by the transmit coil arrangement 20. If, for example, the examination object 15 has rotated away from the initial location P0 by +6° about the z-axis, a current location of +6° is determined. This current location falls in the location range C that covers the rotation range from +3° to +10° about the z-axis. Consequently, in S40, the RF transmit pulse TxP.sub.C optimized for this location range C is output.

(34) By subdividing a possible overall location range into smaller location ranges A, B, C, the optimization of the RF pulses may take place more precisely than if the optimization had to take place across the overall location range.

(35) The initial location P0 and/or the current location of the examination object 15 may, for example, be determined by a navigator scan, a pilot tone scan, and/or a camera recording. For example, the MR apparatus 10 may include a camera 26 represented in FIG. 1 in order to carry out the camera recording. For example, the MR apparatus 10 may include a pilot tone transmitter not represented in FIG. 1 in order to carry out the pilot tone scan. In one embodiment, no additional apparatus is necessary for the navigator scan compared to a normal MR apparatus.

(36) According to a further variant, which is explained using FIGS. 6 and 7, the initial location P0 may be determined in S05 during the preliminary MR scan. In S15, a current location of the examination object 15 in the MR apparatus 10 is determined during the main MR scan, which includes, for example, S15, S20, S30, and S40. The at least one alternative location P5, P6, P7 is then determined in S20 using the current location.

(37) If, for example, a current location is determined that results from a rotation of +9° about the z-axis, an alternative location P6 may then be determined in accordance with which the examination object is rotated by +9° compared to the initial location P0. Further alternative locations P5, P7 around the current location may be determined, such as, for example, an alternative location P5, in accordance with which the examination object is rotated by +6° compared to the initial location P0, and an alternative location P7, in accordance with which the examination object is rotated by +12° compared to the initial location P0. The RF transmit pulse TxP then determined in the further process may be especially robust with respect to rotations of the examination object 15 in a location range from +6° to +12° about the z-axis. However, only one alternative location may, for example, be determined.

(38) Further, in accordance with this variant, estimated magnetic field map data EMD is determined in S20 based on an application of a trained function and/or an interpolation function to the input magnetic field map data IMD. The estimated magnetic field map data EMD in each case describes, for example, a B1 map and a B0 map for the state that the examination object 15 is in at the previously determined alternative locations P5, P6, P7. For example, the estimated magnetic field map data EMD for the B1 field describes the magnetic field map Blips, and for the B0 field, describes the magnetic field map Blips for the state that the examination object 15 is in at the alternative location P5. The same applies for P6 and P7.

(39) In accordance with S30, in the example represented in FIG. 7, control data SD is determined using the estimated magnetic field map data EMD. The control data SD is suitable for controlling the RF transmit pulse TxP that may be emitted by the transmit coil arrangement 20 of the MR apparatus 10 using the control data SD during an MR scan. In S40, an RF transmit pulse TxP is emitted by the transmit coil arrangement 20 of the MR apparatus 10 using the control data SD.

(40) In this variant, S15, S20, S30, and S40 may be repeatedly executed during the main MR scan (e.g., the current location is repeatedly redetermined and a corresponding RF transmit pulse TxP (optimized) is determined and emitted).

(41) In FIG. 8, a trained function is represented by way of example. The trained function includes multiple filters in the form of convolutional layers CL and multiple subsequent fully connected convolutional layers. The input data of the trained function is, for example, the input magnetic field map data IMD with the magnetic field maps B1.sub.P0 and B0.sub.P0 for the initial location P0. The output data of the trained function is, for example, the estimated magnetic field map data EMD with the magnetic field maps B1.sub.Px and B0.sub.Px for at least one alternative location Px. In one embodiment, the output data may include the control data SD for controlling an MR excitation of the examination object 15 (e.g., for controlling at least one RF transmit pulse that may be emitted by the transmit coil arrangement 20 of the MR apparatus 10).

(42) A method for the provision of a trained function for determining estimated magnetic field map data is represented in FIG. 9. In S110, training input data is received. The training input data includes training input magnetic field map data. The training input magnetic field map data for at least one magnetic field type in each case describes a magnetic field map for a state that an examination object 15 is in at an initial location P0 in the MR apparatus 10.

(43) In S120, training output data is received. The training output data includes training estimated magnetic field map data. The training estimated magnetic field map data for at least one magnetic field type in each case describes at least one magnetic field map for a state in each case that the examination object is in at an alternative location Px that is different compared to the initial location P0.

(44) In S130, the trained function is trained based on the training input data and the training output data and is provided in S140.

(45) The training input data and/or the training output data may be generated by scanning and/or simulation of magnetic field maps. A simulation such as this may be very protracted, whereas the application of a trained function is relatively fast. A protracted simulation during the MR scan for determining estimated magnetic field data or for determining control data for an optimized RF transmit pulse is scarcely possible. In one embodiment, a prior generation and provision of a trained function enables the estimated magnetic field data or the control data to be determined during the MR scan.

(46) The method described in detail above and the MR apparatus relate merely to exemplary embodiments that may be modified in various ways by the person skilled in the art without departing from the scope of the invention. Further, the use of the indefinite article “a” or “an” does not rule out that the features in question may also be present multiple times. Likewise, the term “unit” does not rule out that the components in question consist of multiple interworking subcomponents that, where appropriate, may also be spatially distributed.

(47) The elements and features recited in the appended claims may be combined in different ways to produce new claims that likewise fall within the scope of the present invention. Thus, whereas the dependent claims appended below depend from only a single independent or dependent claim, it is to be understood that these dependent claims may, alternatively, be made to depend in the alternative from any preceding or following claim, whether independent or dependent. Such new combinations are to be understood as forming a part of the present specification.

(48) While the present invention has been described above by reference to various embodiments, it should be understood that many changes and modifications can be made to the described embodiments. It is therefore intended that the foregoing description be regarded as illustrative rather than limiting, and that it be understood that all equivalents and/or combinations of embodiments are intended to be included in this description.