METHOD FOR PERFORMING A MAGNETIC RESONANCE MEASUREMENT, A MAGNETIC RESONANCE APPARATUS, AND A COMPUTER PROGRAM PRODUCT

Abstract

A method for performing a magnetic resonance measurement includes selecting a first set of coil elements from a plurality of coil elements and a second set of coil elements from the plurality of coil elements, and performing a magnetic resonance measurement. During the magnetic resonance measurement with the first set of coil elements and the second set of coil elements, magnetic resonance signals and pilot tone signals are received. The method includes ascertaining at least one magnetic resonance image solely with the assistance of magnetic resonance signals received with the first set of coil elements during performance of the magnetic resonance measurement, and ascertaining patient movement information solely with the assistance of pilot tone signals received with the second set of coil elements during performance of the magnetic resonance measurement. The first set of coil elements is not congruent with the second set of coil elements.

Claims

1. A method for performing a magnetic resonance measurement of a patient using a magnetic resonance apparatus comprising a plurality of coil elements for receiving RF signals, the method comprising: selecting a first set of coil elements from the plurality of coil elements and a second set of coil elements from the plurality of coil elements; performing the magnetic resonance measurement, wherein magnetic resonance signals and pilot tone signals are received during the magnetic resonance measurement with the first set of coil elements and the second set of coil elements; ascertaining at least one magnetic resonance image solely with assistance of magnetic resonance signals received with the first set of coil elements during performance of the magnetic resonance measurement; and ascertaining patient movement information solely with assistance of pilot tone signals received with the second set of coil elements during performance of the magnetic resonance measurement, wherein the first set of coil elements is not congruent with the second set of coil elements.

2. The method of claim 1, wherein the selecting of the first set of coil elements proceeds prior to the selecting of the second set of coil elements.

3. The method of claim 1, wherein the selecting of the second set of coil elements proceeds prior to the selecting of the first set of coil elements.

4. The method of claim 1, wherein the first set of coil elements and the second set of coil elements are jointly selected.

5. The method of claim 4, wherein a weighting factor that describes a relative prioritization of a probable quality of the at least one magnetic resonance image to be ascertained compared with a quality of the patient movement information to be ascertained is defined, and wherein the joint selection of the first set of coil elements and the second set of coil elements proceeds with assistance of the weighting factor.

6. The method of claim 1, further comprising ascertaining, at least for a part of the plurality of coil elements of the magnetic resonance apparatus, a position of the part of the plurality of coil elements relative to the magnetic resonance apparatus, relative to the patient, or relative to the magnetic resonance apparatus and relative to the patient, and wherein selecting the first set of coil elements, the second set of coil elements, or the first set of coil elements and the second set of coil elements in each case proceeds as a function of the respectively ascertained position.

7. The method of claim 6, wherein the positions of the coil elements are ascertained using: evaluation of a stored item of coil-specific information that describes a position of at least one coil element relative to the receive coil, which comprises the at least one coil element; evaluation of magnetic resonance signals that were received during an adjustment measurement with the coil elements; evaluation of a video signal that was captured with at least one camera; evaluation of a sensor signal that was acquired with at least one position sensor; or any combination thereof.

8. The method of claim 1, wherein selecting the first set of coil elements, the second set of coil elements, or the first set of coil elements and the second set of coil elements takes place fully automatically, semi-automatically, manually, or any combination thereof, wherein, in the case of fully automatic selecting of coil elements, an operator of the magnetic resonance apparatus plays no part in selection of the coil elements, and wherein, in the case of semi-automatic selecting of coil elements, a set of coil elements is automatically proposed to the operator, and the coil elements are selectable by the operator based on the proposal.

9. The of claim 1, wherein selecting the second set of coil elements proceeds with the assistance of: one type of at least one receive coil that comprises at least one part of the plurality of coil elements of the magnetic resonance apparatus; a relative position of the coil elements within at least one receive coil that comprises at least one part of the plurality of coil elements of the magnetic resonance apparatus; at least one characteristic of the patient; positioning of the patient in the magnetic resonance apparatus; or any combination thereof.

10. The method of claim 1, wherein in each case one adjustment pilot tone signal is captured with at least one part of the plurality of coil elements of the magnetic resonance apparatus, wherein the adjustment pilot tone signals are evaluated in terms of respective contribution to ascertaining the patient movement information, wherein a maximum number K of coil elements of the second set of coil elements is ascertained, and wherein K coil elements that make a biggest contribution to ascertaining the patient movement information are selected, proposed, or selected and proposed.

11. The method of claim 10, wherein the at least one part of the plurality of coil elements of the magnetic resonance apparatus, with which in each case an adjustment pilot tone signal is captured, is determined with the assistance of: one type of at least one receive coil that comprises at least one part of the plurality of coil elements of the magnetic resonance apparatus; a relative position of the coil elements within at least one coil that comprises at least one part of the plurality of coil elements of the magnetic resonance apparatus; at least one characteristic of the patient; positioning of the patient in the magnetic resonance apparatus; or a combination thereof.

12. The method of claim 1, further comprising: for selecting the first set of coil elements from the plurality of coil elements and the second set of coil elements from the plurality of coil elements, displaying an avatar of the patient to an operator, together with at least one part of the plurality of coil elements of the magnetic resonance apparatus correctly positioned in relation to the avatar; and displaying whether a displayed coil element is assigned to the first set of coil elements, the second set of coil elements, or the first set of coil elements and the second set of coil elements.

13. The method of claim 12, further comprising displaying an imaging region to the operator for coil element selection.

14. A magnetic resonance apparatus for performing a magnetic resonance measurement of a patient, the magnetic resonance apparatus comprising: a processor; and a plurality of coil elements for receiving RF signals, wherein the processor is configured to select a first set of coil elements from the plurality of coil elements and a second set of coil elements from the plurality of coil elements, wherein the plurality of coil elements are configured to perform the magnetic resonance measurement, wherein the first set of coil elements and the second set of coil elements are configured to receive magnetic resonance signals and pilot tone signals during the magnetic resonance measurement, wherein the processor is further configured to: ascertain at least one magnetic resonance image solely with assistance of magnetic resonance signals received with the first set of coil elements during performance of the magnetic resonance measurement; and ascertain patient movement information solely with assistance of pilot tone signals received with the second set of coil elements during performance of the magnetic resonance measurement, and wherein the first set of coil elements is not congruent with the second set of coil elements.

15. In a non-transitory computer-readable storage medium that stores instructions executable by one or more processors to perform a magnetic resonance measurement of a patient using a magnetic resonance apparatus comprising a plurality of coil elements for receiving RF signals, the instructions comprising: selecting a first set of coil elements from the plurality of coil elements and a second set of coil elements from the plurality of coil elements; performing a magnetic resonance measurement, wherein magnetic resonance signals and pilot tone signals are received during the magnetic resonance measurement with the first set of coil elements and the second set of coil elements; ascertaining at least one magnetic resonance image solely with assistance of magnetic resonance signals received with the first set of coil elements during performance of the magnetic resonance measurement; and ascertaining patient movement information solely with assistance of pilot tone signals received with the second set of coil elements during performance of the magnetic resonance measurement, wherein the first set of coil elements is not congruent with the second set of coil elements

16. The non-transitory computer-readable storage medium of claim 15, wherein the selecting of the first set of coil elements proceeds prior to the selecting of the second set of coil elements.

17. The non-transitory computer-readable storage medium of claim 15, wherein the selecting of the second set of coil elements proceeds prior to the selecting of the first set of coil elements.

18. The non-transitory computer-readable storage medium of claim 15, wherein the first set of coil elements and the second set of coil elements are jointly selected.

19. The non-transitory computer-readable storage medium of claim 18, wherein a weighting factor that describes a relative prioritization of a probable quality of the at least one magnetic resonance image to be ascertained compared with a quality of the patient movement information to be ascertained is defined, and wherein the joint selection of the first set of coil elements and the second set of coil elements proceeds with assistance of the weighting factor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Further advantages, features, and details of the invention are revealed by the exemplary embodiments described below with reference to the drawings. Mutually corresponding parts are provided with the same reference numerals in all the figures.

[0073] FIG. 1 is a schematic representation of one embodiment of a magnetic resonance apparatus;

[0074] FIG. 2 is a block diagram of one embodiment of a method for performing magnetic resonance measurement; and

[0075] FIG. 3 shows one embodiment of a display for the selection of coil elements.

DETAILED DESCRIPTION

[0076] FIG. 1 is a schematic representation of one embodiment of a magnetic resonance apparatus 10. The magnetic resonance apparatus 10 includes a magnet unit 11 that includes a main magnet 12 for generating a strong and, for example, time-constant main magnetic field 13. The magnetic resonance apparatus 10 also includes a patient accommodation zone 14 for accommodating a patient 15. In the present exemplary embodiment, the patient accommodation zone 14 is of cylindrical construction and is cylindrically surrounded in a circumferential direction by the magnet unit 11. In principle, however, the patient accommodation zone 14 may at any time be formed in a manner that differs therefrom. The patient 15 may be advanced into the patient accommodation zone 14 by a patient positioning apparatus 16 of the magnetic resonance apparatus 10. The patient positioning apparatus 16 includes, for example, a patient table 17 that is movable within the patient accommodation zone 14.

[0077] The magnet unit 11 also has a gradient coil unit 18 for generating magnetic field gradients that are used for spatial encoding during imaging. The gradient coil unit 18 is controlled by a gradient control unit 19 of the magnetic resonance apparatus 10. The magnet unit 11 further includes a radio-frequency antenna unit 20 that is configured in the present exemplary embodiment as a body coil permanently integrated into the magnetic resonance apparatus 10. The radio-frequency antenna unit 20 is controlled by a radio-frequency antenna control unit 21 of the magnetic resonance apparatus 10 and during magnetic resonance measurement irradiates radio-frequency pulses into an investigation chamber (e.g., into an imaging region FOV) according to a predetermined magnetic resonance sequence. In this way, excitation of atomic nuclei is established in the main magnetic field 13 generated by the main magnet 12. Magnetic resonance signals are generated by relaxation of the excited atomic nuclei. The radio-frequency antenna unit 20 is configured to receive magnetic resonance signals.

[0078] The magnetic resonance apparatus 10 includes a system control unit 22 for controlling the main magnet 12 and the gradient control unit 19 and for controlling the radio-frequency antenna control unit 21. The system control unit 22 provides central control of the magnetic resonance apparatus 10, such as, for example, the performance of a predetermined imaging magnetic resonance sequence. In addition, the system control unit 22 includes a system control unit, not shown in greater detail, for evaluating the magnetic resonance signals that are acquired during the magnetic resonance examination. The magnetic resonance apparatus 10 further includes a user interface 23 that is connected to the system control unit 22. Control information, such as, for example, imaging parameters, and reconstructed magnetic resonance images may be displayed on a display unit 24 (e.g., on a screen) of the user interface 23 for a medical operator. The user interface 23 also includes an input unit 25, by which information and/or parameters may be input by the medical operator during a measurement procedure.

[0079] The magnetic resonance apparatus further includes three receive coils 23a, 23b, 23c, that are arranged directly on the patient 15. The receive coils 23a, 23b, 23c are thus local coils. Each of the three receive coils 23a, 23b, 23c includes a plurality of coil elements 27 that are conventionally integrated into the respective receive coil 23a, 23b, 23c. The coil elements are capable of receiving RF signals (e.g., magnetic resonance signals and/or pilot tone signals). The received signals may be transmitted to the system control unit 22. With the assistance of the magnetic resonance signals, magnetic resonance images of the patient 15 may be reconstructed by the system control unit 22. With the assistance of the pilot tone signals, information may, for example, be ascertained by the system control unit 22 about movements of the patient 15. The receive coil 23c, for example, includes a pilot tone signal generator (not shown here) that emits an RF signal. This RF signal enters into interaction with the patient 15. For example, the RF signal is influenced by movement of the patient 15. For example, the RF signal may have a different amplitude and/or phase depending on the movement state of the patient 15. The RF signal is received as a pilot tone signal by the coil elements 27 and forwarded to the system control unit 22 for evaluation (e.g., for ascertaining movement information).

[0080] FIG. 2 shows one possible method for performing magnetic resonance measurement on the patient 15 using the magnetic resonance apparatus 10.

[0081] In S10, a first set A and a second set B of coil elements are selected from the plurality of coil elements 27. The first set A is in this case not congruent with the second set B (e.g., A≠B). Selection may proceed fully automatically, semi-automatically, and/or manually (e.g., with the assistance of the system control unit 22).

[0082] In S20, magnetic resonance measurement is performed, where, during the magnetic resonance measurement with the first set and the second set of coil elements (e.g., with the union of the first and second sets A∪B), magnetic resonance signals and pilot tone signals are received.

[0083] In S30, patient 15 movement information is determined solely with the assistance of pilot tone signals received in S20 with the second set of coil elements B during performance of the magnetic resonance measurement. Any pilot tone signals that were received with coil elements of the difference A\B are thus not used for ascertaining the movement information.

[0084] The movement information may, for example, be ascertained during the magnetic resonance measurement. The ascertained movement information may, for example, be used for control of the magnetic resonance measurement (e.g., for a prospective movement correction). In this case, a magnetic resonance sequence underlying the magnetic resonance measurement may be adapted in real time and/or on-the-fly (e.g., by the system control unit 22 adapting a position of a slice to be captured).

[0085] In step S40, at least one magnetic resonance image of the patient 15 is determined solely with the assistance of magnetic resonance signals received in S20 with the second set of coil elements B during performance of the magnetic resonance measurement. Any pilot tone signals that were received with coil elements of the difference B\A are thus not used for ascertaining the least one magnetic resonance image.

[0086] Possible embodiments of the selection of the first set A and second set B are explained in greater detail below. According to a first embodiment, first, the first set A is selected, which is to be used for imaging, prior to selection of the second set B. The first set A may, for example, be performed manually by the operator of the magnetic resonance apparatus 10 or proceed automatically.

[0087] In this case, N coil elements are selected from the plurality of coil elements, for example. In one exemplary magnetic resonance apparatus with M receive channels, L=M−N channels remain as receive channels for other applications than imaging, such as, for example, for receiving dedicated pilot tone signals.

[0088] Selection of the second set B may, for example, proceed fully automatically (e.g., in a “concealed” manner, unnoticed by the operator). Selection of the second set B and ascertainment of the movement information may, for example, be triggered by the operator activating respiratory monitoring or triggering (e.g., in the context of adjustment of the magnetic resonance measurement).

[0089] The magnetic resonance apparatus may automatically detect which of coil elements 27 are particularly favorable for respiratory monitoring. In an upstream adjusting step, adjustment data (e.g., adjustment pilot tone signals) may be captured by potentially favorable receive coils.

[0090] Potentially favorable receive coils are, for example, coils that are arranged in the region of the abdomen and/or thorax of the patient. Typically, these are dedicated receive coils, such that selection of the second set B may also proceed with the assistance of the type of at least one receive coil.

[0091] In one embodiment, coil elements of specific coil types that lie and are used in the abdomen/thorax region (e.g., a spinal column coil and/or a body matrix coil) are selected.

[0092] In one embodiment, a relative position of the receive coils 26a, 26b, 26c (e.g., the coil elements 27 of the receive coils 26a, 26b, 26c) is ascertained. In this case, coil elements lying on the inside in the right-left direction are more important than those on the outside. Selection of the second set B may thus, for example, proceed from a relative position of the coil elements within at least one receive coil.

[0093] For example, prior information obtained from registration of the patient 15 may be used to ascertain where the coil elements with the highest signal contributions may probably be located. Such prior information may, for example, include positioning (e.g., planned positioning) of the patient 15 in the magnetic resonance apparatus 10 (e.g., whether the patient is introduced into the patient accommodation zone 14 head first or feet first). Further, the prior information may, for example, include at least one characteristic of the patient 15 (e.g., their height, weight, and/or sex).

[0094] If the magnetic resonance apparatus has a sufficient number of receive channels, adjustment data may be captured from all the coil elements (e.g., relevant coil elements). If not, a preselection of the above-described information and/or criteria may be put together. The elements may also be captured in a number of groups one after the other or in temporally interleaved manner.

[0095] The adjustment data is examined (e.g., with a principal component analysis) with regard to how great is the contribution of the individual coil elements to detection of the movement information (e.g., a respiratory signal). In this way, an order of precedence of the particularly suitable coil elements may be drawn up.

[0096] The first L coil elements from this selection may, for example, be selected by the magnetic resonance apparatus 10 for receiving pilot tone signals, without the first set A, including the coil elements for the imaging, being limited. In addition to the first L coil elements, the second set B may, for example, also include suitable coil elements from the first set A. For example, a maximum number K of coil elements of the second set B may be ascertained, such that in addition to the first L coil elements, still further K−L coil elements from the first set A may additionally be selected.

[0097] If L is very small or zero or no signal has been found that is sufficiently strong for a movement (e.g., respiration), it may, for example, be displayed to the operator that pilot tone-based monitoring has been deactivated.

[0098] A coil element used in magnetic resonance measurement in S20 may thus belong only to set A, only to set B, or to both sets. For example, information is transmitted to the hardware of the magnetic resonance apparatus 10, for performance of the magnetic resonance measurement, about which coil elements are selected (e.g., the union A∪B of sets A and B). The software of the magnetic resonance apparatus 10 may, for example, distinguish to which end a coil element was selected (e.g., whether a coil element belongs only to set A, only to set B, or to set A∪B).

[0099] For example, the display unit 24 may display to the operator only the coil elements of set A for imaging, but not the coil elements of set B for movement detection.

[0100] According to one further embodiment, selection of the second set B proceeds manually by the operator. To this end, possible coil elements are displayed (e.g., via the display unit 24) to the operator, who may assign the possible coil elements the second set B, for example, by clicking on the possible coil elements. This selection option may be configured such that it is clear to the operator that, with the received signals of the coil elements to be selected, no image reconstruction is to proceed; rather, the received signals merely serve to ascertain the movement information with the assistance of the pilot tone signals received thereby.

[0101] According to one further embodiment, the second set B of coil elements is fully automatically selected (e.g., on activation of pilot tone functionality). For example, the fully automatically selected coil elements cannot be deselected again by the operator. The operator may then, insofar as permitted by the number of available receive channels of the magnetic resonance apparatus, manually select additional coil elements for imaging. Alternatively, the coil elements are fully automatically selected for imaging (e.g., based on imaging geometry). Selection of the second set of coil elements thus proceeds, for example, prior to selection of the first set of coil elements.

[0102] FIG. 3 shows a representation, by way of example, that is displayed to the operator by the display unit 24 on selection of the coil elements. In this case, a patient avatar 15A and receive coils 26a, 26b, positioned correctly relative thereto, with their coil elements 270-279 are displayed, which may be used during the following magnetic resonance measurement. The receive coil 26a, which is, for example, a head coil, includes the coil elements 270, 271, 272, 273; the receive coil 26a, which is, for example, a spinal column coil, includes the coil elements 274, 275, 276, 277, 278, 279. The position of the receive coils 26a, 26b or their coil elements 270-279 may, for example, be ascertained by an adjustment measurement that precedes the actual magnetic resonance measurement and during which magnetic resonance signals are conventionally evaluated to determine the position. Further, in the case of stationary receive coils, such as, for example, typically a head coil, the positions of the coil elements may be stored in a coil-specific file. Further, to determine the position of the receive coils and/or of the coil elements, 2D and/or 3D cameras, for example, and/or sensors attached to the receive coil (e.g., Hall sensors) may be used.

[0103] It is further displayed whether a displayed coil element is assigned to the first set of coil elements and/or the second set of coil elements. For example, it is depicted which coil elements belong to the second set B (e.g., are provided for ascertaining movement information), and which coils elements belong to the first set A (e.g., are provided for imaging). If a coil element belongs to the first set A, this is represented by “MR” in conjunction with a check mark; if a coil element belongs to the second set B, this is represented by “PT” in conjunction with a check mark. If a coil element does not belong to the first set A, this is represented by “MR” in conjunction with a cross; if a coil element does not belong to the second set B, this is represented by “PT” in conjunction with a cross. If a coil element belongs to the union A∪B (e.g., is to receive any RF signals), this is represented by its coil number in conjunction with a check mark; otherwise, this is represented by a cross. In the case shown, coil elements 270, 271, 272, 273 belong to the first set A; the magnetic resonance signals received thereby are particularly well suited to ascertaining therefrom at least one magnetic resonance image of the patient 15. Coil elements 274, 275, 276, 277 belong to the second set B; the pilot tone signals received thereby are particularly well suited to detecting therefrom the movement of the heart and/or the abdomen of the patient 15. Coil elements 278, 279, in contrast, are not used in magnetic resonance measurement.

[0104] Selection of the coil elements may, for example, proceed with the assistance of one characteristic of the displayed coil element (e.g., its position): if the display is then supplemented by the depiction of an imaging region FOV (e.g., an imaging volume), it immediately becomes clear which coil element is suitable for which purpose. Above all, the coil elements that are located within the imaging region FOV or close to the imaging region FOV contribute to the image. The criterion of the position of the receive coils relative to the imaging region FOV may also lead, after performance of the magnetic resonance measurement, to the removal of coil elements from the first set A (e.g., the magnetic resonance signals that were received with such remote coil elements are then not used to ascertain the at least one magnetic resonance image).

[0105] In one embodiment, the coil elements are selected with the assistance of geometric criteria. Additionally or alternatively, the coil symbols outside the imaging region FOV may also be modified to display that the coil symbols do not represent imaging coil elements of set A. The modification may be limited to an interface with the operator; in other parts of the magnetic resonance apparatus 10, the two coil types would not advantageously need to be distinguished.

[0106] To summarize, it may be noted that the method of the present embodiments makes pilot tone-based monitoring possible also in areas of the body in which coil elements are not used for imaging (e.g., when measuring the head of the patient 15 with heartbeat and/or respiratory synchronization). In one embodiment, the operator does not herself need to select such coil elements.

[0107] The method described above in detail and the depicted magnetic resonance apparatus are merely exemplary embodiments that may be modified in the most varied manner by a person skilled in the art without departing from the scope of the invention. Further, use of the indefinite article “a” does not rule out the possibility of a plurality of the features in question also being present. Likewise, the term “unit” does not rule out the possibility of the components in question consisting of a plurality of interacting subcomponents that may optionally also be spatially distributed.

[0108] 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.

[0109] 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.