Correction of MR object movements

Abstract

A method for correcting magnetic resonance (MR) object movements includes performing a recording of an MR object with multiple echo trains. k-space data pertaining to an echo train regarded as impaired by an MR object movement is corrected by linking the k-space data to corresponding k-space data reconstructed from k-space data of other echo trains by a PPA method.

Claims

1. A method for correcting magnetic resonance (MR) object movements, the method comprising: performing a recording of an MR object with multiple echo trains; correcting k-space data pertaining to an echo train of the multiple echo trains regarded as impaired by a movement of the MR object, the correcting comprising linking to corresponding k-space data reconstructed by a PPA method at least from k-space data of other echo trains of the multiple echo trains; correcting the k-space data of only one echo train of the multiple echo trains from a k-space of all measured k-space data; storing a corrected k-space that includes k-space data present after the correcting of the k-space data of only the one echo train; repeating the correcting of the k-space data of only the one echo train and the storing for each echo train of the multiple echo trains; and constructing an MR image from the corrected k-spaces.

2. The method of claim 1, wherein the recording is a TSE recording.

3. The method of claim 1, wherein the reconstructed k-space data is generated by a GRAPPA method.

4. The method of claim 3, wherein reconstructed k-space points of the reconstructed k-space data are generated by a 3×4 GRAPPA kernel.

5. The method of claim 1, wherein the linkage comprises a replacement of the k-space data pertaining to an impaired echo train by corresponding reconstructed k-space data.

6. The method of claim 1, wherein at least one movement-impaired echo train has been identified prior to the performance of the correction.

7. The method of claim 1, further comprising: correcting corresponding original k-space data of the echo train; determining a size of a deviation of the corrected k-space data of the echo train from the corresponding original k-space data; retaining the corrected k-space data when the size of the deviation exceeds a predefined amount or retaining the original k-space data; and repeating, for all echo trains of the number of echo trains, the correcting of the corresponding original k-space data of the echo train, the determining, and the retaining.

8. The method of claim 1, wherein storing the corrected k-space comprises generating an associated corrected MR image from the k-space and saving the associated corrected MR image, and wherein constructing the MR image comprises generating a final MR image by overlaying the previously stored corrected MR images.

9. The method of claim 1, further comprising recording k-space data identified as or assumed to be movement-impaired afresh when a predefined condition is satisfied.

10. A data processing device comprising: a processor configured to correct magnetic resonance (MR) object movements, the correction comprising: performance of a recording of an MR object with multiple echo trains; correction of k-space data pertaining to an echo train of the multiple echo trains regarded as impaired by a movement of the MR object, the correction comprising linkage to corresponding k-space data reconstructed by a PPA method at least from k-space data of other echo trains of the multiple echo trains; correction of the k-space data of only one echo train of the multiple echo trains from a k-space of all measured k-space data; storage of a corrected k-space that includes k-space data present after the correction of the k-space data of only the one echo train; repetition of the correction of the k-space data of only the one echo train and the storage for each echo train of the multiple echo trains; and construction of an MR image from the corrected k-spaces.

11. In a non-transitory computer-readable storage medium that stores instructions executable by one or more processors to correct magnetic resonance (MR) object movements, the instructions comprising: performing a recording of an MR object with multiple echo trains; correcting k-space data pertaining to an echo train of the multiple echo trains regarded as impaired by a movement of the MR object, the correcting comprising linking to corresponding k-space data reconstructed by a PPA method at least from k-space data of other echo trains of the multiple echo trains; correcting the k-space data of only one echo train of the multiple echo trains from a k-space of all measured k-space data; storing a corrected k-space that includes k-space data present after the correcting of the k-space data of only the one echo train; repeating the correcting of the k-space data of only the one echo train and the storing for each echo train of the multiple echo trains; and constructing an MR image from the corrected k-spaces.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above-described characteristics, features and advantages of this invention, as well as the manner in which these are realized, will become more clearly and easily intelligible in connection with the following schematic description of exemplary embodiments, which are explained in more detail with reference to the drawings. For clarity of illustration, identical elements, or elements having an identical effect, may be given identical reference characters.

(2) FIG. 1 shows a flow diagram of a first exemplary embodiment of a method;

(3) FIG. 2 shows a sketch of a variant of the first exemplary embodiment with a 3×4 GRAPPA kernel;

(4) FIG. 3 shows a flow diagram of a second exemplary embodiment of the method; and

(5) FIG. 4 shows a flow diagram of a third exemplary embodiment of the method.

DETAILED DESCRIPTION

(6) FIG. 1 shows a flow diagram of a first embodiment of a method.

(7) The flow diagram includes a first act S11, in which a turbo spin echo (TSE) recording of a magnetic resonance (MR) object with multiple TSE sequences or echo trains is performed.

(8) In a second act S12, information about which echo train(s), if any, is movement-impaired is received. As a result, at least one movement-impaired echo train may be identified prior to the performance of the correction. The information may, for example, be obtained by external hardware (e.g., a camera, a pilot tone method, or a respiratory sensor) or sequence-inherent navigators.

(9) In a third act S13, k-space rows pertaining to movement-impaired echo trains are replaced by k-space rows reconstructed by a GRAPPA method. The remaining, non-movement-impaired k-space rows are retained without change.

(10) In act S14, an MR image may be generated from the k-space resulting from act S13.

(11) After act S13, it is possible to check in an optional act S15 whether the MR image is improved by the replacement of the k-space rows classified as movement-impaired. This may be implemented, for example, in that a size of a deviation of the corrected k-space rows from the corresponding uncorrected k-space rows is determined. If the size of the deviation exceeds a predefined amount, the uncorrected k-space rows of the echo train classified as movement-impaired are replaced by the corresponding corrected k-space rows, or the replacement is retained. Otherwise, the uncorrected k-space rows are retained, or the replacement is reversed by the corresponding corrected k-space rows.

(12) At least the acts S13 to S15 may be carried out by a correspondingly set up (e.g., programmed) data processing device D. The data processing device D may represent a part of an MR system, by which the acts S11 and S12 may also be carried out.

(13) FIG. 2 shows a sketch of a variant of the first exemplary embodiment, in which reconstructed k-space points of a k-space row are generated by a 3×4 GRAPPA kernel. In this case, an original, uncorrected two-dimensional k-space or portion thereof is represented on the left-hand side, while on the right-hand side, a GRAPPA-corrected two-dimensional k-space or portion thereof is represented. The coil dimension k.sub.z is not represented but is optionally present. A 3×4 GRAPPA kernel applied to the uncorrected k-space is indicated in enlarged form between the two k-spaces.

(14) The k-spaces have k-space rows {k.sub.x}|.sub.ky=const. that each represent spin echoes of an echo train. The k-space rows of the spin echoes of an identical echo train are arranged spaced evenly apart in the ky direction and are represented separately from k-space rows of the spin echoes of other echo trains. A TSE recording with five echo trains with eight spin echoes in each case is represented in this case by a k-space purely by way of example. The third echo train (drawn in dashed form) is assumed to be or is classified as movement-impaired here.

(15) Each k-space row has multiple k-space points (k.sub.i, k.sub.j) distributed along a k.sub.x axis, where i=[1, . . . , xmax] and j=y=const.

(16) By the 3×4 GRAPPA kernel, the k-space points of the k-space rows of the movement-impaired third echo train (drawn in dashed form in the left-hand k-space) are reconstructed from k-space points of the k-space rows adjacent thereto of the first, second, fourth, and fifth echo trains and are then replaced by the reconstructed k-space points (drawn with dotted lines in the right-hand k-space). By way of example, k.sub.1 here designates the first k-space row of the first echo train, k.sub.2 designates the first k-space row of the second echo train, . . . , k.sub.6 designates the second k-space row of the first echo train, etc. In this case, the 3×4 GRAPPA kernel is applied to the first k-space rows of the five echo trains such that an i-th point (k.sub.i, k.sub.3) of the first k-space row k.sub.3 of the movement-impaired third echo train is reconstructed in each case by three points (k.sub.i−1,k.sub.m), (k.sub.i,k.sub.m), (k.sub.i+1,k.sub.m) of the four k-space rows k.sub.m, where m=1, 2, 4 and 5.

(17) The 3×4 GRAPPA kernel is shifted by one place from i to the right for the reconstruction of the (i+1)-th point (k.sub.i, k.sub.3) of the first k-space row k.sub.3.

(18) FIG. 3 shows a flow diagram of a second exemplary embodiment of the method.

(19) In a first act S21, a TSE recording of an MR object with multiple TSE sequences or echo trains is performed.

(20) In a second act S22, a particular “first” echo train of the k-space is selected.

(21) In a third act S23, k-space rows reconstructed by GRAPPA are generated for k-space rows pertaining to this echo train. In a variant, these may then be linked to the corresponding original k-space rows in order to generate corrected k-space rows.

(22) In a fourth act S24, the corrected k-space rows are compared with the originally recorded k-space rows. For example, a size of a deviation of the corrected k-space rows from the originally recorded, uncorrected k-space rows may be determined.

(23) In a fifth act S25, it is determined whether a significant deviation exists between the corrected and the originally recorded k-space rows. For example, it may be determined whether the size of the deviation exceeds a predefined amount. The result of the comparison thus corresponds to a determination or decision whether the originally recorded k-space rows were or were not movement-impaired.

(24) If this is the case (“Y”), the corrected k-space data is retained or the originally recorded k-space rows of the echo train are replaced by the corrected k-space rows in act S26.

(25) However, if there is no significant deviation between the corrected and the originally recorded k-space rows (“N”), the originally recorded k-space rows are retained.

(26) In act S27, a further echo train of the k-space is selected, and the acts S22 to S26 are performed afresh for the further echo train.

(27) This procedure is continued until the acts S22 to S26 have been applied to the k-space rows of all echo trains of a TSE recording.

(28) At least the acts S22 to S27 may be carried out by a correspondingly set up (e.g., programmed) data processing device D. The data processing device D may represent a part of an MR system, by which act S21 may also be carried out.

(29) FIG. 4 shows a flow diagram of a third exemplary embodiment of the method.

(30) In a first act S31, a TSE recording of an MR object with multiple TSE sequences or echo trains is performed.

(31) In a second act S32, a particular “first” echo train of the k-space is selected.

(32) In a third act S33, the k-space rows pertaining to this echo train are replaced by k-space rows reconstructed by GRAPPA.

(33) In a fourth act S34, a corresponding corrected MR image is generated from the thus generated “corrected” k-space and is saved.

(34) In a fifth act S32, a check is made to see whether a further, as yet uncorrected echo train is present.

(35) If the answer is yes (“Y”), a further, as yet uncorrected echo train is selected in act S36, and the acts S33 and S34 are applied to this echo train or the associated k-space.

(36) If the answer is no (“N”), a final MR image is generated from the corrected MR images in act S37 (e.g., by pixel-by-pixel average value formation of corresponding pixels of all corrected MR images, etc.).

(37) At least the acts S32 to S37 may be carried out by a correspondingly set up (e.g., programmed) data processing device D. The data processing device D may represent a part of an MR system, by which act S31 may also be carried out.

(38) Although the invention has been illustrated and described in detail by the exemplary embodiments shown, the invention is not restricted thereto, and other variations may be derived therefrom by a person skilled in the art without departing from the protective scope of the invention.

(39) In general, “a”, “an”, etc. may be understood as singular or plural, in particular in the sense of “at least one” or “one or more”, etc., provided this is not explicitly excluded (e.g., by the expression “exactly one”, etc.).

(40) A numerical value may also include the given value as a typical tolerance range, provided this is not explicitly excluded.

(41) 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.

(42) 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.