METHOD FOR CALCULATING AN OPERATING PARAMETER OF A MAGNETIC RESONANCE SEQUENCE, MAGNETIC RESONANCE APPARATUS AND COMPUTER PROGRAM PRODUCT

Abstract

A method for calculating an operating parameter of a magnetic resonance sequence, a magnetic resonance apparatus, and a computer program product are disclosed. According to the method, at least one initial sequence parameter of a radio-frequency (RF) transmit pulse of the magnetic resonance sequence is provided. In addition, at least one test RF transmit pulse is determined, (e.g., calculated and/or modeled and/or simulated), wherein the at least one test RF transmit pulse is adapted based on the at least one initial sequence parameter to a specified, in particular geometric, standard shape. The at least one operating parameter is determined, (e.g., calculated), with the assistance of the at least one test RF transmit pulse. It is in particular assumed in this respect that the at least one test RF transmit pulse is applied on performance of the magnetic resonance sequence.

Claims

1. A computer-implemented method for calculating at least one operating parameter of a magnetic resonance sequence, the method comprising: providing at least one initial sequence parameter of a radio-frequency (RF) transmit pulse of the magnetic resonance sequence; determining at least one test RF transmit pulse, wherein the at least one test RF transmit pulse is adapted based on the at least one initial sequence parameter to a specified standard shape; and determining the at least one operating parameter of the magnetic resonance sequence using the at least one test RF transmit pulse.

2. The method of claim 1, wherein the specified standard shape is a rectangular shape.

3. The method of claim 2, wherein the at least one initial sequence parameter comprises a pulse duration that corresponds to a width of the rectangular shape.

4. The method of claim 3, wherein the pulse duration is a maximum pulse duration, and wherein the width of the rectangular shape is a maximum width of the rectangular shape.

5. The method of claim 2, wherein the at least one initial sequence parameter comprises an amplitude that corresponds to a height of the rectangular shape.

6. The method of claim 5, wherein the amplitude is a maximum amplitude, and wherein the height of the rectangular shape is a maximum height of the rectangular shape.

7. The method of claim 1, wherein the at least one operating parameter comprises a power requirement applicable to a magnetic resonance apparatus during operation of the magnetic resonance sequence.

8. The method of claim 7, wherein the power requirement is applicable to a RF amplifier of the magnetic resonance apparatus.

9. The method of claim 1, wherein the at least one operating parameter comprises a specific absorption rate to which a patient is exposed during operation of the magnetic resonance sequence.

10. The method of claim 1, further comprising: providing at least one constraint for the at least one operating parameter; and determining at least one adapted sequence parameter by adapting the at least one initial sequence parameter to comply with the at least one constraint.

11. The method of claim 10, further comprising: determining at least one measurement RF transmit pulse based on the at least one adapted sequence parameter.

12. The method of claim 11, wherein the at least one measurement RF transmit pulse is a dynamic pulse.

13. The method of claim 11, wherein the at least one measurement RF transmit pulse is a pTx pulse.

14. The method of claim 11, wherein the at least one adapted sequence parameter comprises a constraint for determining the at least one measurement RF transmit pulse.

15. The method of claim 14, wherein the constraint for determining the at least one measurement RF transmit pulse comprises a maximum pulse duration.

16. The method of claim 14, wherein the constraint for determining the at least one measurement RF transmit pulse comprises a maximum amplitude.

17. A magnetic resonance apparatus comprising: at least one processor configured to: provide at least one initial sequence parameter of a radio-frequency (RF) transmit pulse of a magnetic resonance sequence; determine at least one test RF transmit pulse, wherein the at least one test RF transmit pulse is adapted based on the at least one initial sequence parameter to a specified standard shape; and determine the at least one operating parameter of the magnetic resonance sequence using the at least one test RF transmit pulse.

18. A computer program product that comprises a program and is directly loadable into a memory of a programmable system control unit of a magnetic resonance apparatus, wherein the program, when executed by the programmable system control unit, is configured to cause the magnetic resonance apparatus to: provide at least one initial sequence parameter of a radio-frequency (RF) transmit pulse of a magnetic resonance sequence; determine at least one test RF transmit pulse, wherein the at least one test RF transmit pulse is adapted based on the at least one initial sequence parameter to a specified standard shape; and determine the at least one operating parameter of the magnetic resonance sequence using the at least one test RF transmit pulse.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Further advantages, features, and details of the disclosure are revealed by the embodiments described below with reference to the drawings. Mutually corresponding parts are provided with the same reference characters in all the figures.

[0044] FIG. 1 is a schematic representation of an example of a magnetic resonance apparatus.

[0045] FIG. 2 is a block diagram of an example of a method for calculating an operating parameter of a magnetic resonance sequence.

[0046] FIG. 3 depicts an example of rectangular test RF transmit pulses and a measurement RF transmit pulse.

DETAILED DESCRIPTION

[0047] FIG. 1 is a schematic representation of a magnetic resonance apparatus 10. The magnetic resonance apparatus 10 includes a magnet unit 11 that has a main magnet 12 for generating a strong and in particular time-constant main magnetic field 13. The magnetic resonance apparatus 10 additionally includes a patient receiving region 14 for accommodating a patient 15. In the present embodiment, the patient receiving region 14 has a cylindrical construction and is cylindrically surrounded in a circumferential direction by the magnet unit 11. In principle, however, a different configuration of the patient receiving region 14 is conceivable. The patient 15 may be advanced into the patient receiving region 14 by way of a patient positioning apparatus 16 of the magnetic resonance apparatus 10. The patient positioning apparatus 16 includes a patient table 17 that is movable within the patient receiving region 14.

[0048] The magnet unit 11 furthermore includes 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, which is configured in the present 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 emits radio-frequency transmit pulses, (e.g., at least one test RF transmit pulse and/or measurement RF transmit pulse), into an examination space that is substantially formed by a patient receiving region 14 of the magnetic resonance apparatus 10. 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.

[0049] To transmit suitable electrical signals to the radio-frequency antenna unit 20, the radio-frequency antenna control unit 21 includes one or more radio-frequency amplifiers (not shown here) that may amplify a control signal of the system control unit 22 into a power signal. The radio-frequency amplifier is configured to temporarily store an electrical charge, in particular precharge, which it then draws from on amplification of a transmit pulse. This enables the radio-frequency amplifier to amplify transmit pulses with a high edge steepness. To store the electrical charge, the radio-frequency amplifier may include at least one capacitor.

[0050] The radio-frequency antenna unit 20 may include a plurality of transmit antennas. In particular, the radio-frequency antenna unit 20 may be configured to generate, in particular transmit, dynamic pulses. Radio-frequency antenna unit 20 may additionally or alternatively include a local transmit coil (not shown here) with one or more transmit antennas, which may be arranged directly on the patient 15. This is advantageous above all with magnetic resonance apparatuses 10 with a strong main magnetic field 13, (e.g., 7 Tesla or more).

[0051] 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 centrally controls the magnetic resonance apparatus 10, such as the performance of a magnetic resonance sequence. The system control unit 22 may be configured to calculate at least one operating parameter of the magnetic resonance sequence according to the method according to FIG. 2. In addition, the system control unit 22 includes an evaluation unit, not shown in any more detail, for evaluating the magnetic resonance signals that are acquired during the magnetic resonance examination. The magnetic resonance apparatus 10 furthermore includes a user interface 23 connected to the system control unit 22. Control information, (e.g., imaging parameters), and reconstructed magnetic resonance images may be displayed on a display unit 24, (e.g., on at least one monitor), of the user interface 23 for a medical operator. The user interface 23 furthermore includes an input unit 25, by way of which information and/or parameters may be input by the medical operator during a measurement procedure.

[0052] According to the method shown in FIG. 2, in S10, at least one initial sequence parameter of an RF transmit pulse of a magnetic resonance sequence is provided. Provision may proceed by loading the at least one initial sequence parameter from a database and/or by input of the at least one initial sequence parameter by the operator by the user interface 23. A magnetic resonance sequence may be loaded from the database for which the at least one sequence parameter, (e.g., a pulse duration), is specified. Transfer of the at least one sequence parameter, (e.g., the pulse duration), may run automatically in the background and/or may not be visible or may only be indirectly visible to the operator.

[0053] Furthermore, provision of the at least one initial sequence parameter of the RF transmit pulse may include the provision of an, in particular maximum, amplitude of the RF transmit pulse. This is determined, for example, from an amplitude maximally generable by the magnetic resonance apparatus and/or from a reference voltage of the patient 15, which reference voltage is established in at least one possible prior measurement. Provision of the amplitude may also proceed automatically and/or in a manner not or only indirectly visible to the operator.

[0054] In S20, at least one test RF transmit pulse is produced, the at least one test RF transmit pulse being adapted based on the at least one initial sequence parameter to a specified standard shape.

[0055] The standard shape may be a rectangular shape. In this respect, the at least one initial sequence parameter provided in S10 may include a pulse duration, (e.g., a maximum pulse duration), which corresponds to a width, (e.g., a maximum width), of the rectangular shape. Furthermore, the at least one initial sequence parameter may include an, in particular maximum, amplitude, which corresponds to a height, (e.g., a maximum height), of the rectangular shape.

[0056] In S30, at least one operating parameter is determined with the assistance of the at least one test RF transmit pulse. The at least one operating parameter may include a power requirement applicable to the magnetic resonance apparatus 10, (e.g., to a radio-frequency amplifier of the magnetic resonance apparatus 10), which requirement is to be met on performance of the magnetic resonance sequence by the magnetic resonance apparatus, in particular by the radio-frequency amplifier. Furthermore, the at least one operating parameter may include a specific absorption rate to which a patient 15 is exposed on performance of the magnetic resonance sequence.

[0057] In S40, at least one constraint, (e.g., a power limit of the radio-frequency amplifier and/or an SAR limit value), is provided to the at least one operating parameter. In certain examples, S40 may also take place before S10, S20, or S30 and/or at the same time as S10, S20, or S30.

[0058] In S50, at least one adapted sequence parameter is determined by adapting the at least one initial sequence parameter to comply with the provided at least one constraint.

[0059] In S60, at least one measurement RF transmit pulse, (e.g., a dynamic pulse), is determined with the assistance of the at least one adapted sequence parameter.

[0060] In S70, a magnetic resonance measurement is performed according to a magnetic resonance sequence, the magnetic resonance sequence including the at least one measuring RF transmit pulse, such that the at least one measurement RF transmit pulse is applied at least once during the magnetic resonance measurement. The magnetic resonance signals may advantageously be received by the magnetic resonance measurement, at least one magnetic resonance image being produced, (e.g., reconstructed), from the magnetic resonance signals.

[0061] The proposed method is particularly suitable for determining dynamic pulses. This is further clarified based on FIG. 3, in which an initial rectangular pulse R.sub.i is shown as a test RF transmit pulse determined in S20. The width thereof corresponds to an initial pulse duration T.sub.i as a first initial sequence parameter, and the height thereof corresponds to an initial amplitude A.sub.i as a second initial sequence parameter, which initial sequence parameters are in each case provided in S10.

[0062] The at least one operating parameter is determined in S30 based on the initial rectangular pulse R.sub.i. In particular, the situation is simulated of the radio-frequency antenna unit 20 emitting the rectangular pulse R.sub.i as an RF transmit pulse, in order to determine the resultant at least one operating parameter. This at least one operating parameter may then be compared with the at least one constraint provided in S40. If the at least one constraint is complied with, the at least one initial sequence parameter, (e.g., the initial pulse duration T.sub.i and/or the initial amplitude A.sub.i), are used unchanged to determine the at least one measurement RF transmit pulse.

[0063] If, however, the at least one constraint is not complied with, in S50, the method determines whether at least one adapted sequence parameter complies with the provided at least one constraint. For example, the amplitude is adapted to the value A.sub.f and the pulse duration to the value T.sub.f. This adaptation may proceed iteratively, (i.e., a modification of the sequence parameter may be repeatedly carried out), with subsequent checking of the at least one constraint, until the at least one adapted sequence parameter complies with at least one constraint.

[0064] If the at least one constraint is complied with on application of a rectangular pulse with the values T.sub.f (for the pulse duration) and A.sub.f (for the amplitude), then these values may be used in S60 as adapted sequence parameters as constraints, (e.g., as maximum pulse duration and maximum amplitude), to determine the at least one measurement RF transmit pulse. Then, for example, a dynamic pulse P may be determined that is shorter than the maximum pulse duration and lower than the maximum amplitude.

[0065] It is thus proposed, in particular, to approximate the dynamic pulse P in the calculations with a rectangular pulse that may have the same length as the resultant dynamic pulse and an amplitude that corresponds to the maximum amplitude of the dynamic pulse, and to calculate the actual dynamic pulse only in the final test act after a performable solution has been found.

[0066] This is therefore advantageously possible because dynamic pulses conventionally have a very high and virtually constant amplitude over the pulse profile. By approximating this pulse with a rectangular pulse, the actual pulse is indeed overestimated, but only to a small extent.

[0067] In particular, it is proposed to approximate dynamic pulses for calculations of a power requirement applicable to a radio-frequency amplifier and/or an SAR by a rectangular pulse and only after these calculations or in the final test act to calculate the dynamic pulse with the required constraints. This prevents time-consuming recalculation of the dynamic pulses during the, in particular iterative, calculation acts of such calculations being constantly started from scratch.

[0068] It should finally once again be noted that 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 disclosure. Furthermore, 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 including a plurality of interacting subcomponents that may optionally also be spatially distributed.

[0069] It is to be understood that 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 disclosure. Thus, whereas the dependent claims appended below depend on 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, and that such new combinations are to be understood as forming a part of the present specification.

[0070] While the present disclosure has been described above by reference to various embodiments, it may be understood that many changes and modifications may 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.