Method for acquiring a magnetic resonance data set, data storage medium, computer program product, and magnetic resonance system

Abstract

A method for acquiring a magnetic resonance data set of an object under examination by a magnetic resonance system using a scan sequence is provided. The scan sequence includes a succession of sequence blocks, and in each sequence block, there is at least one sub-block including an excitation section and/or a detection section. An excitation section includes at least one excitation pulse, and in a detection section, an echo signal or an echo train is acquired as a scan signal. At least one item of motion information is provided for each sub-block. The motion information contains information about a movement of the object under examination within a duration of the sub-block. Some of the sub-blocks are automatically repeated. At least the sub-blocks having motion information that exceeds a threshold value are repeated. The threshold value defines a motion amplitude.

Claims

1. A method for acquiring a magnetic resonance data set of an object under examination by a magnetic resonance system using a scan sequence, wherein the scan sequence comprises a sequence of sequence blocks, and each sequence block of the sequence of sequence blocks contains at least one sub-block comprising an excitation section, a detection section, or the excitation section and the detection section, wherein the excitation section comprises at least one excitation pulse, the method comprising: acquiring, in a respective detection section, an echo signal or an echo train as a scan signal, wherein at least one item of motion information is provided for each sub-block, wherein the motion information contains information about movement of the object under examination within a duration of the respective sub-block, wherein some of the sub-blocks are repeatedly acquired automatically based on the motion information contained in the respective sub-blocks, and wherein at least the sub-blocks having motion information that indicates motion that results in a motion artifact in an image data set reconstructed from the magnetic resonance data set are repeated.

2. In a non-transitory computer-readable storage medium that stores instructions executable by one or more processors to acquire a magnetic resonance data set of an object under examination by a magnetic resonance system using a scan sequence, wherein the scan sequence comprises a sequence of sequence blocks, and each sequence block of the sequence of sequence blocks contains at least one sub-block comprising an excitation section, a detection section, or the excitation section and the detection section, wherein the excitation section comprises at least one excitation pulse, the instructions comprising: acquiring, in a respective detection section, an echo signal or an echo train as a scan signal, wherein at least one item of motion information is provided for each sub-block, wherein the motion information contains information about movement of the object under examination within a duration of the respective sub-block, wherein some of the sub-blocks are repeatedly acquired automatically based on the motion information contained in the respective sub-blocks, and wherein at least the sub-blocks having motion information that indicates motion that allows a motion artifact in an image data set reconstructed from the magnetic resonance data set are repeated.

3. A magnetic resonance system comprising: a controller configured to acquire a magnetic resonance data set of an object under examination by a magnetic resonance system using a scan sequence, wherein the scan sequence comprises a sequence of sequence blocks, and each sequence block of the sequence of sequence blocks contains at least one sub-block comprising an excitation section, a detection section, or the excitation section and the detection section, wherein the excitation section comprises at least one excitation pulse, the acquisition of the magnetic resonance data set comprising: acquisition, in a respective detection section, of an echo signal or an echo train as a scan signal, wherein at least one item of motion information is provided for each sub-block, wherein the motion information contains information about movement of the object under examination within a duration of the respective sub-block, wherein some of the sub-blocks are repeatedly acquired automatically based on the motion information contained in the respective sub-blocks, and wherein at least the sub-blocks having motion information that indicates motion that allows a motion artifact in an image data set reconstructed from the magnetic resonance data set are repeated.

4. The method of claim 1, wherein a plurality of sub-blocks are present in a sequence block of the sequence of sequence blocks.

5. The method of claim 1, wherein all sub-blocks of a sequence block of the sequence of sequence blocks are repeated when at least one item of motion information of the sub-blocks of the sequence block indicates motion that results in a motion artifact in an image data set reconstructed from the magnetic resonance data set.

6. The method of claim 1, wherein each repeated sub-block is assigned to an originally acquired sub-block, and the data of the repeated sub-blocks replaces the data of the originally acquired sub-blocks in each case.

7. The method of claim 1, wherein each repeated sub-block is assigned to an originally acquired sub-block, and the data of the repeated sub-blocks is averaged with the data of the originally acquired sub-blocks having motion information that does not indicate motion that results in a motion artifact in an image data set reconstructed from the magnetic resonance data set.

8. The method of claim 1, wherein only sub-blocks having motion information that indicates motion that results in a motion artifact in an image data set reconstructed from the magnetic resonance data set are repeated.

9. The method of claim 8, wherein the sub-blocks are repeatedly acquired consecutively in an original order.

10. The method of claim 8, wherein the sub-blocks to be repeated are arranged in newly created sequence blocks, in each case at a same position as an originally acquired sub-block.

11. The method of claim 1, wherein the motion information is at least partially obtained by a camera.

12. The method of claim 1, wherein the motion information is obtained at least partially by navigator echoes.

13. The method of claim 1, wherein a plurality of slices are acquired, and each sub-block of a sequence block of the sequence of sequence blocks is assigned to a slice of the plurality of slices.

14. The method of claim 1, wherein the sub-blocks to be repeated are arranged in newly created sequence blocks.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows one embodiment of a magnetic resonance system;

(2) FIG. 2 shows an exemplary SE sequence diagram;

(3) FIG. 3 shows an exemplary TSE sequence diagram;

(4) FIG. 4 shows an exemplary MP-RAGE sequence diagram;

(5) FIG. 5 shows two exemplary navigator echo modules;

(6) FIG. 6 shows a schematic partial view of an exemplary scan sequence;

(7) FIG. 7 shows a schematic partial view of exemplary sequence blocks to be repeated;

(8) FIG. 8 shows a schematic partial view of newly created sequence blocks in a first embodiment;

(9) FIG. 9 shows a schematic partial view of newly created sequence blocks in a second embodiment;

(10) FIG. 10 shows a schematic partial view of newly created sequence blocks in a third embodiment; and

(11) FIG. 11 shows a flow chart of one embodiment of a method for acquiring a magnetic resonance data set.

DETAILED DESCRIPTION

(12) FIG. 1 shows one embodiment of a magnetic resonance system 1 including a scanner 2 and a control facility 3. Three gradient coils 4, 5, and 6 are mounted in the scanner 2 to generate gradient fields.

(13) The magnetic resonance system 1 also has a transmit coil arrangement 7 that may be configured as a body coil. The transmit coil arrangement 7 may also be a transmit coil array.

(14) The receive coil array 8 may also be a body coil. To increase a signal-to-noise ratio (SNR), it is also known to use local coils. For example, a coil array may be used to perform parallel imaging. A coil array enables the scan time to be reduced.

(15) A camera 9 is used to capture possible movements of a patient 10 while a scan is being performed.

(16) The control facility 3 of the magnetic resonance system 1 has a data storage medium 11 on which a computer program product 12 for carrying out the described method is stored. This is, therefore, software that is configured to evaluate motion information as described and also controls repeat scans.

(17) The computer program product 12 may be called up by scan sequences such as an SE scan sequence 13, a TSE multislice scan sequence 14, an MP-RAGE scan sequence 15, or other scan sequences or be implemented therein.

(18) SE scan sequences 13 and TSE scan sequences 14 may usually be converted from a single-slice to a multislice scan sequence by selecting the SE scan sequences 13 and the TSE scan sequences 14 in a selection field on an operator facility. Magnetic resonance data sets 16 may also be stored on the data storage medium 11.

(19) The control facility may have a monitor 17 as an output device and a keyboard 18 as an input unit.

(20) Other usual components of the magnetic resonance system 1 such as a patient couch, etc. are not shown for the sake of clarity.

(21) FIG. 2 shows an exemplary sequence diagram 19 of an SE scan sequence 13 for acquiring a magnetic resonance data set 16. The sequence diagram 19 explicitly shows, as usual, one sequence block 20 of the succession of sequence blocks; the others are indicated by the repetition arrows.

(22) The radio frequency pulses and the acquisition windows are shown along the axis ACQ. The RF pulse 21 is used as an excitation pulse. The RF pulse 21 has a flip angle of 90°. Excitation pulses flip the magnetization at least partially into the xy-plane, where the magnetization produces a signal when flipped back. The refocusing pulse 22 has a flip angle of 180°. Such pulses alone do not produce a signal, because the pulses do not flip the magnetization out of the z-direction, the direction of the main magnetic field B.sub.0. However, the refocusing pulse 22 refocuses the signal generated by the excitation pulse 21. The excitation pulse 21 and the refocusing pulse 22 produce the echo signal 23. This is also termed spin echo.

(23) A read dephase gradient 24 and a read gradient 25 are applied in the read direction G.sub.R. The read dephase gradient 24 dephases the magnetization that is rephased by the read gradient 25. In imaging experiments, the echo signal 23 is therefore a spin and gradient echo. In SE and TSE scan sequences, however, the echo signal 23 is usually referred to as spin echo.

(24) A phase encode gradient 26 is applied in the phase direction G.sub.P. The strength of the phase encode gradient 26 varies from sequence block 20 to sequence block 20, which is why the phase encode gradient 26 is shown filled with dashed lines. These indicate the varying strengths.

(25) In the slice direction G.sub.S, a slice select gradient 27 is applied simultaneously with the excitation pulse 21. This is followed by a slice rephase gradient 28.

(26) In parallel with the refocusing pulse 22, a slice select gradient 29 is applied. This is flanked by crusher gradients 30. The crusher gradients 30 are configured to compensate for imperfections of the refocusing pulse 22. Alternatively or additionally, the crusher gradients 30 may also be applied in the phase encode direction G.sub.P and/or the read direction G.sub.R.

(27) Each sequence block 20 has a plurality of sections. The excitation section 31 includes the excitation pulse 21, the slice select gradient 27, and the slice rephase gradient 28. The detection section 32 includes the rest of the sequence 20 up to the end of the read gradient 25.

(28) The number n.sub.s of slices to be acquired is at the same time the number of sub-blocks 33.

(29) After all the slices have been acquired, a wait time TW is inserted to give the magnetization time to relax. The time from the end of the first sub-block 33 to the end of the repetition time TR ranges from several hundred milliseconds to a few seconds. The wait time TW is thus determined as a function of the number n.sub.s of scanned slices.

(30) n.sub.pe is the number of phase encoding steps of the scan sequence 13 without repetitions due to excessive motion.

(31) The number n.sub.r is the number of sequence blocks 20 to be repeated. This depends on how many sub-blocks 33 and therefore, in the case of an SE scan sequence 13, how many echo signals 23 contain motion information exceeding the predefined threshold.

(32) Known variations of the sequence diagram 19 relate to the position of the read dephase gradient 24 and the phase encode gradient 26. With respect to the method described, only the n.sub.r of sequence blocks to be repeated are relevant.

(33) FIG. 3 shows an exemplary sequence diagram 34 of a TSE multislice scan sequence 14. Most of the elements have already been explained in connection with FIG. 2, which is herewith incorporated by reference.

(34) In contrast to FIG. 2, the detection section 32 includes a plurality of refocusing pulses 22 and a plurality of echo signals 23, where the echo signals 23 constitute an echo train 34. The refocusing pulse 22 is applied n.sub.E times, which provides that the echo train 34 includes n.sub.E echo signals 23.

(35) In the phase direction G.sub.P, a phase rewind gradient 36 is applied in addition to the phase encode gradient 24. The phase rewind gradient 36 compensates the gradient torque of the phase encode gradient 24 so that the total phase in the phase direction G.sub.P between two refocusing pulses 21 is zero.

(36) As n.sub.E echo signals are acquired for each echo train, only n.sub.pe/n.sub.E sequence blocks 20 are run through, without consideration of the n.sub.r of sequence blocks 20 additionally to be acquired.

(37) Here too, n.sub.s slices may be acquired, where n.sub.s≥1. In the case of n.sub.s=1 (e.g., of one slice), the sequence block has one sub-block 33. For n.sub.s>1, there are n.sub.s sub-blocks 33.

(38) FIG. 4 shows an example of a segmented scan sequence (e.g., a sequence diagram 37 of an MP-RAGE scan sequence 15). The sequence diagram 37 shows an inversion pulse 38 that flips the magnetization in the z-direction. After a wait time TIW, the magnetization is sampled with a succession of n.sub.seg spoiled gradient echo sub-blocks 33 (e.g., turbo-FLASH). Each gradient echo sub-block 33 is a sub-block 33 of a sequence block 20 of the MP-RAGE scan sequence 15. The excitation pulses 39 have a flip angle of a few degrees. The excitation pulses 39 therefore deflect the magnetization from the z-direction by only a small angle. To restore the magnetization to equilibrium, a wait time TW is introduced at the end of each sequence block 20. The gradients present are as indicated in FIGS. 2 and 3 and have the same function.

(39) In addition, a phase encode gradient 40 and a phase rewind gradient 41 are provided in the slice select direction G.sub.S, since an MP-RAGE scan sequence 15 is a T1-weighted 3D scan sequence.

(40) The presence of a plurality of sub-blocks 33 in a sequence block 20 is therefore not dependent on the use of a spin echo based scan sequence or a multislice scan.

(41) n.sub.spe is the number of phase encoding steps in the slice select direction. The phase encoding variation sequence may be reversed. It is basically irrelevant whether first the phase encode gradient 26 is stepped through in the phase direction G.sub.P and then the phase encode gradient 40 in the slice select direction G.sub.S, or vice versa.

(42) FIG. 5 shows two exemplary ways of acquiring navigator echoes. These may be placed before and/or after and/or between the imaging section consisting of the sub-block 33 or sub-blocks 33. The first embodiment of a navigator echo module 42 is positioned before the sub-blocks 33. An excitation pulse 43 having a slice thickness that is determined via a slice select gradient 44 is applied consecutively for each of the directions G.sub.R, G.sub.P, and G.sub.S. The slice rephase gradient 45 and the read dephase gradient 46 may be applied simultaneously. A navigator echo 48 is then generated using the read gradient 47 in each case. The navigator echo 48 is a 1D image and shows movements in the direction in which the read gradient 47 is applied.

(43) The imaging section including one or more sub-blocks 33 is only shown schematically.

(44) A spiral readout is shown in the navigator echo module 49 following the imaging section. By a gradient 50 and a gradient 51, a navigator echo 52 is therefore generated from which a two-dimensional image may be created. This provides that two directions may be monitored simultaneously. The gradients 50 and 51 are to be positioned or distributed in the G.sub.R, G.sub.P, and G.sub.S directions such that the desired plane or slice may be monitored.

(45) The following alternatives may be provided.

(46) A 1D navigator echo 48 may only be acquired in one of the three directions G.sub.R, G.sub.P, and G.sub.S (e.g., before and/or after a sub-block 33 or between two sub-blocks 33).

(47) If two directions are monitored, the described embodiments likewise exist.

(48) If navigator echoes 52 are generated, the navigator echoes 52 may likewise be before and/or after a sub-block 33 and/or between two sub-blocks 33.

(49) If the navigator echoes are not acquired between the sub-blocks 33, motion information is only available for one sequence block 20.

(50) Since the number of navigator modules rises as the number of sub-blocks 33 increases, the number of acquirable sub-blocks 33 decreases, as the acquirable signal decays with the relaxation time T2. It is therefore also possible to use the camera 9 to collect motion information for subsequent evaluation in addition to a navigator module before and after the sub-blocks 33 during scanning of the sub-blocks 33.

(51) Using the same navigator echo modules 42 or 49 before and after the imaging section, motion in the wait time TW may be detected in order to correct the motion prospectively. In addition, motion during the sub-blocks 33 may be detected, and re-acquisition of the sub-blocks 33 affected may be performed automatically.

(52) In principle, it is also possible to acquire different navigator echoes 48 and 52 in one sequence block 20. However, this does not allow direct comparison of these navigator echoes, which requires additional calculations to limit the time period of a movement. Therefore, selecting one or other of the navigator echo modules 42 or 49 may be provided. Whether this module is used once, twice, or even more often in a sequence block 20 depends on constraints such as the T2 relaxation time of the magnetization, the lengthening of the scan time by the modules, and other factors.

(53) FIG. 6 shows a schematic partial view of a scan sequence including a plurality of sub-blocks 33 (e.g., a TSE multislice scan sequence or an MP-RAGE scan sequence). In this case, each sub-block 33.1a to 33.3d is constituted by a block. The beginning and end of a sequence block 20.1 to 20.3 is indicated by an arrow 53, and the beginning and end of a sub-block 33 is indicated by an arrow 54. These arrows 53 and 54 may also be used as markers in a scan sequence in the form of a control instruction in order to enable the computer program product 12 to be used in a large number of scan sequences 13, 14, and 15.

(54) For the sake of clarity, each sequence block 20.1 to 20.3 has only four sub-blocks 33. In a TSE multislice scan sequence, there are four slices, and in an MP-RAGE scan sequence, it would be four echo signals with different phase encoding. The differentiation of the sub-blocks 33 into sub-blocks 33.1a to 33.3d is only intended to illustrate the different procedure for executing the repeat sequence blocks 20; the sub-blocks 33 differ only in the position in a sequence block 20.1 to 20.3 and the phase encode gradient used (see above). The first index relates to the sequence block, and the second index relates to the slice or respective sub-block. The sub-block 33.2c is therefore in the second sequence block 20.2 (e.g., the third slice).

(55) Motion information 55 is provided for each of the sub-blocks 33.1a to 33.3d (e.g., motion information 55.1a to 55.3d), which may be greater than, equal to, or less than a threshold value th. All the sub-blocks 33.1a and 33.3c with motion information 55.1b and 55.3c greater than the threshold value th are marked as to be repeated. This is indicated by a dashed border.

(56) FIG. 7 shows a first embodiment for the repetition of sub-blocks 33. Here, all the sub-blocks 33.1a to 33.1d and 33.3a to 33.3d of the sequence blocks 20.1 and 20.3, where at least one item of motion information 55.1b and 55.3c was greater than the threshold value th, are repeated. The already acquired sequence blocks 20.1 and 20.3 are therefore repeated. The sub-blocks 33.1a′ to 33.1d′ and 33.3a′ to 33.3d′ are created. These are arranged in the repeatedly acquired sequence blocks 20.1′ and 20.3′.

(57) In a first embodiment, the newly acquired sub-blocks 33.1a′ to 33.1d′ and 33.3a′ to 33.3d′ may completely replace the previous sub-blocks 33.1a to 33.1d and 33.3a to 33.3d. In an alternative, second embodiment, only the sub-blocks 33.1b and 33.3c where the movement was excessively large are replaced. The newly acquired sub-blocks 33.1a′, 33.1c′, 33.1d′, 33.3a′, 33.3b′ and 33.3d′ are each averaged with the previous sub-block 33.1a, 33.1c, 33.1d, 33.3a, 33.3b or 33.3d, which increases the SNR.

(58) FIG. 8 shows a second embodiment for the repetition of sub-blocks 33. The sub-block 33.4a has been introduced as a motion-corrupted sub-block for illustration purposes. Only the sub-blocks 33.1b, 33.3c and 33.4a in newly assembled sequence blocks 56 having motion information 55.1b, 55.3c and 55.4a that exceeds the threshold value th are repeated. In this embodiment, re-acquisition is performed irrespective of the position of the sub-blocks 33 in the original sequence block 20 but purely chronologically; for this reason, the T1 weighting may come out differently from the original sub-block 33.

(59) FIG. 9 therefore shows a third embodiment for the repetition of sub-blocks 33. Only the sub-blocks 33.1b, 33.3c, and 33.4a having motion information 55.1b, 55.3c and 55.4a that exceeds the threshold value th are repeated. However, when creating the new sequence blocks 55, the position of the sub-blocks 33 in the original sequence block 20 is maintained, thereby preserving the T1 weighting. The disadvantage of this, however, is that the slice having most sub-blocks 33 to be repeated determines the number of additional sequence blocks 55 to be acquired, where, as the repetition progresses, fewer and fewer sub-blocks 33′ are acquired in a sequence block 55.

(60) FIG. 10 therefore shows a fourth embodiment for the repetition of sub-blocks 33. Again, only the sub-blocks 33.1a, 33.1b, 33.3c, and 33.4a having motion information 55.1a, 55.1b, 55.3c and 55.4a that exceeds the threshold value th are repeated. By way of illustration, the sub-block 33.1a has been additionally introduced as motion-corrupted. A place at an original position is available for the sub-blocks 33.1a, 33.1b and 33.3c in a newly created sequence block 56. However, there would have to be another new sequence block 56 for the sub-block 33.4a. To avoid this, the sub-block 33.4a is placed at the vacant position in the newly created sequence block 56. Thus, in the present example, 75% of the newly acquired sequence blocks 33′ have original T1 weighting, but the scan time of the repeat scans was able to be halved from two sequence blocks 56 to one.

(61) FIG. 11 shows a flow chart of one embodiment of a method for acquiring a magnetic resonance data set 16 of an object under examination using a magnetic resonance system 1.

(62) In act S1, the object under examination 10 is positioned in the magnetic resonance system 1, the alignment measurements are performed, and a scan sequence is selected. Objects under examination that move are not only patients, but also animals, which are being increasingly scanned. Flow phantoms may have movements as well as other inanimate objects under examination that may slip due to vibrations.

(63) An example of a TSE multislice scan sequence 14 will now be discussed. In act S2, a sequence block 20 is run through. In act S2.1, the phase encode gradient of this sequence block 20 is determined. In act S2.2, a first navigator echo 49 is acquired. Thereafter, as act 2.3, the sub-block 33 of a slice is acquired, and then, as act 2.4, a second navigator echo 49 is acquired. Acts 2.3 and 2.4 are repeated n.sub.s times (e.g., for each slice). As a result, one item of motion information 55 is available for each sequence block 33.

(64) Act S2 including sub-acts S2.1 to S2.4 is repeated n.sub.pe or n.sub.pe/n.sub.E times depending on the scan sequence until the scan data set 16 is acquired.

(65) Any movement that occurs cannot be corrected during actual data acquisition, only before the individual sequence blocks 20.

(66) If the movement of the object under examination 10 within a sub-block 33 is too large, that sub-block 33 is to be repeated. A corresponding metric for the strength of the movement is used. The repetition information is stored in a buffer for this purpose. As the repetition of a sub-block 33 is possible within the structure of a sequence block 20, this may be carried out following the actual acquisition of a scan sequence in three ways:

(67) 1.) In the simplest form, the sub-blocks 33 affected, which are to be repeated due to excessive motion, are arranged in one or more repeat sequence blocks 20′. Here the order of the sub-blocks 33′ to be repeated may be a simple sorting scheme (e.g., chronological), as shown in FIG. 7. In contrast to the following two versions, taking the example of the TSE multislice scan sequence 14, it would not be guaranteed that exactly the same image contrast would be acquired. However, averaging effects might possibly make this limitation acceptable in some cases.

(68) 2.) Each sequence block 20 that contains a sub-block 33 corrupted by excessive motion is repeated unchanged. There are two alternatives for using the resulting scan signals.

(69) A) The scan signals (e.g., echo signals or echo trains) of motion-corrupted sub-blocks 33 are replaced by the newly acquired sub-blocks 33′. The scan signals of non-motion-corrupted sub-blocks 33 are averaged. This also produces an improved SNR.

(70) B) The scan signals of all the sub-blocks 33 of repeated sequences 20 are replaced by the newly acquired sub-blocks 33′.

(71) 3.) If there are a very large number of sub-blocks 33 to be repeated, new sequence blocks 56 may be created using the information from the motion-corrupted sub-blocks 33, as shown also in FIG. 10. Instead of repeating all three sequence blocks 20.1, 20.3, and 20.4 again, a new sequence block 56 is created from the required k-space lines that were acquired by the corrupt sub-blocks 33.1a, 33.1b, 33.3c and 33.4a using the corresponding sub-blocks 33′ (e.g., 33.1a′, 33.1b′, 33.3c′ and 33.4a′).

(72) The free positions of sub-blocks 33′ in the newly created sequence blocks 56 may then be skipped. Echo signals 23′ or echo trains 34′ may be acquired from any other sub-blocks 33′ at the same position in a sequence block 20′ for averaging Echo signals 23′ or echo trains 34′ may be acquired from specific other sub-blocks 33 where the amount of movement was below but close to the rejection limit. Echo signals 23′ or echo trains 34′ may be acquired from any other sub-blocks 33′ at another position in a sequence block 20 for averaging. However, the position in the sequence block 56 is only to be shifted by no more than one position or another previously defined value. In addition, the k-space center is not to be in one of the shifted echo trains 34′.

(73) The re-acquisition time may thus be reduced accordingly.

(74) In act S3, sequence blocks 20′ to be repeated or sequence blocks 56 to be re-acquired are defined according to one of the described alternatives. This may be done in parallel with or after act S2.

(75) In act S4, the sequences 20′ to be repeated or sequences 55 to be re-acquired are acquired. Repetition of a sequence block 20 is as described if all the sub-blocks 33 of the original sequence block 20 are included, and re-acquisition is as described if a new sequence block 56 is combined with sub-blocks 33′ that differ from the original sub-blocks 33.

(76) As act S5, the newly acquired echo signals are inserted into scan dataset 16 or averaged with corresponding echo signals 23 to obtain a motion-corrected scan dataset 16.

(77) The advantage of the method described resides in completely automatic re-acquisition of suboptimally motion-corrected scan signals by an existing motion correction module. For this purpose, a scan sequence may provide markers 54 and/or 55 so that the computer program product 12 may recognize that sections are possibly allowed to be repeated (e.g., whether always only complete sequence blocks 20 are repeated or also sub-blocks 33). Otherwise, this process runs completely identically for all scan sequences.

(78) Advantageous in the case of the third embodiment for repeating sub-blocks 33 is the concept of how sub-blocks 33 may be optimally re-acquired in a time-optimized manner. The advantage here is the significant time saving for re-acquisition.

(79) New scan sequences may therefore be very quickly adapted to this method.

(80) 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.

(81) 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.