Magnetic resonance apparatus and method for operation thereof with an accelerated progression of a repeating pulse sequence with an optimized gradient curve

Abstract

In a method for an accelerated progression of a repeating pulse sequence with an optimized gradient curve (that has at least one pulse) for a magnetic resonance examination by operation of a magnetic resonance apparatus, boundary conditions for a first gradient pulse of a first progression of the pulse sequence are detected, and the boundary conditions of the first gradient pulse of the first progression of the pulse sequence are compared with boundary conditions of a previous gradient pulse of a previous progression of the pulse sequence. An optimized gradient curve of the first gradient pulse of the first progression of the pulse sequence is determined from the gradient curve of the previous gradient pulse when agreement of the boundary conditions of the first gradient pulse with the boundary conditions of the previous gradient pulse exists.

Claims

1. A method for operating a magnetic resonance apparatus comprising a gradient system, with a repeating pulse sequence in which said gradient system is operated to activate an optimized gradient curve for a magnetic resonance data acquisition, said method comprising: detecting boundary conditions for a first gradient pulse of a first repetition of said pulse sequence; in a processor, comparing the boundary conditions of the first gradient pulse of the first repetition of the pulse sequence with boundary conditions of a previous gradient pulse activated during a previous repetition of the pulse sequence; in said processor, if agreement exists between the boundary conditions of the first gradient pulse and the boundary conditions of the previous gradient pulse, determining an optimized gradient curve for the first gradient pulse of the first repetition of the pulse sequence from an optimized gradient curve of said previous gradient pulse; and operating said gradient system of said magnetic resonance apparatus in said first repetition of said pulse sequence by activating said first gradient pulse with said optimized gradient curve.

2. A method as claimed in claim 1 comprising developing the optimized gradient curve of the first gradient pulse from the optimized gradient curve of the previous gradient pulse upon agreement of said boundary conditions of the first gradient pulse with the boundary conditions of the previous gradient pulse.

3. A method as claimed in claim 1 comprising using at least one boundary condition of said first gradient pulse and said previous gradient pulse selected from the group consisting of a duration of the respective gradient pulse, a gradient moment of the respective gradient pulse, a starting point in time of the respective gradient pulse, and an end point in time of the respective gradient pulse.

4. A method as claimed in claim 1 comprising storing the optimized gradient curve of the previous gradient pulse in a memory that is accessible by said processor when determining said optimized gradient curve of said first gradient pulse in said first repetition of said pulse sequence.

5. A method as claimed in claim 4 comprising storing the boundary conditions of the pervious gradient pulse in said memory together with said optimized gradient curve of the previous gradient pulse.

6. A method as claimed in claim 1 comprising calculating the optimized gradient curve of the first gradient pulse independently of the optimized gradient curve of the previous gradient pulse if the comparison of the boundary conditions of the first gradient pulse and the boundary condition of the previous gradient pulse shows a dissimilarity between the boundary conditions of the first gradient pulse and the boundary conditions of the previous gradient pulse.

7. A method as claimed in claim 6 comprising storing the optimized gradient curve of the first gradient pulse together with the boundary conditions of the first gradient pulse in a memory.

8. A method as claimed in claim 6 comprising calculating the optimized gradient curve of the first gradient pulse by a spline interpolation.

9. A magnetic resonance apparatus comprising: a magnetic resonance data acquisition unit comprising a gradient system; a processor configured to detect boundary conditions for a first gradient pulse of a first repetition of said pulse sequence; said processor being configured to compare the boundary conditions of the first gradient pulse of the first repetition of the pulse sequence with boundary conditions of a previous gradient pulse activated during a previous repetition of the pulse sequence; said processor being configured, if agreement exists between the boundary conditions of the first gradient pulse and the boundary conditions of the previous gradient pulse, to determine an optimized gradient curve for the first gradient pulse of the first repetition of the pulse sequence from an optimized gradient curve of said previous gradient pulse; and said processing being configured to operate said gradient system of said magnetic resonance apparatus in said first repetition of said pulse sequence by activating said first gradient pulse with said optimized gradient curve.

10. A non-transitory, computer-readable data storage medium encoded with programming instructions, said storage medium being loaded into a control and processing system of a magnetic resonance apparatus, that also comprises a gradient system, said programming instructions causing said computerized control and processing system to: detect boundary conditions for a first gradient pulse of a first repetition of said pulse sequence; compare the boundary conditions of the first gradient pulse of the first repetition of the pulse sequence with boundary conditions of a previous gradient pulse activated during a previous repetition of the pulse sequence; if agreement exists between the boundary conditions of the first gradient pulse and the boundary conditions of the previous gradient pulse, determine an optimized gradient curve for the first gradient pulse of the first repetition of the pulse sequence from an optimized gradient curve of said previous gradient pulse; and operate said gradient system of said magnetic resonance apparatus in said first repetition of said pulse sequence by activating said first gradient pulse with said optimized gradient curve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a flowchart of an embodiment of the method according to the invention for an accelerated progression of a repeated pulse sequence.

(2) FIG. 2 schematically illustrates a magnetic resonance apparatus that implements the method shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(3) A magnetic resonance apparatus 10 according to the invention is schematically shown in FIG. 2. The magnetic resonance apparatus 10 has a magnet unit 11 with a patient examination region 12 cylindrically surrounded by the magnet unit 11. An examination subject (in particular a patient) 14 can be introduced into the patient examination region 12 by a patient support device 13 of the magnetic resonance apparatus 10. The patient support device 13 can be designed so as to be movable relative to the magnet unit 11 within the patient examination region 12.

(4) Significant components of the magnet unit 11 are a basic field magnet 15, a gradient system 16 and a radio-frequency system 17. The gradient system 16 includes magnetic field gradient coils to generate magnetic field gradients in the x-direction 18, in the y-direction 19 and in the z-direction 20. The individual magnetic field gradient coils in the x-direction 18, y-direction 19 and z-direction 20 can be controlled independently of one another so that a gradient field can be applied in arbitrary spatial directions (for example in the slice selection direction, in the phase coding direction or in the readout direction). These directions depend on a selected slice orientation. In the exemplary embodiment, the radio-frequency system 17 is a whole-body radio-frequency coil that emits radio-frequency signals. The reception of magnetic resonance signals induced in the examination subject can take place via the whole-body radio-frequency coil.

(5) The individual components of the magnet unit 11 are controlled by a system control unit 21. For this purpose, the system control unit 21 includes at least one computer. The system control unit 21 is connected via a terminal interface with an operator terminal 22 via which an operator can control the entire magnetic resonance apparatus 10. In the present case, as a computer this operator terminal 22 is equipped with keyboard, one or more monitors, and additional input devices, such that a graphical user interface is provided to the operator.

(6) A gradient control unit 23 of the magnetic resonance apparatus 10 is controlled by the system control unit 21. From this gradient control unit 23, the individual magnetic field gradient coils are fed with control signals according to a gradient pulse sequence. Gradient pulses are activated at precisely set time positions and with a precisely set time curve during a magnetic resonance measurement.

(7) Moreover, a radio-frequency transmission unit 24 of the magnetic resonance apparatus 10 is controlled by the system control unit 21 in order to feed radio-frequency pulses into the whole-body radio-frequency coil according to a predetermined radio-frequency pulse sequence. In addition, the magnetic resonance apparatus 10 has a radio-frequency reception unit 25 that is designed to read out and further process the magnetic resonance signals received by the whole- body radio-frequency coil.

(8) Furthermore, the system control unit 21 includes a reconstruction unit (not shown in detail) that reconstructs image data from the magnetic resonance signals.

(9) A pulse sequence or, respectively, a magnetic resonance sequence is initially selected for a measurement (data acquisition) of the magnetic resonance apparatus. The selection can take place automatically and/or independently via the system control unit 21. Additionally, individual parameters that are important for the selection of the pulse sequence can be selected and/or entered by an operator via the operator terminal 22.

(10) The system control unit 21 furthermore has a pulse sequence optimization unit 26 that is designed for optimization of the gradient pulses during a progression of a pulse sequence.

(11) For this purpose, the pulse sequence optimization unit has a memory unit 27 in which are stored software and/or computer programs that are required for the optimization of the gradient pulses. In addition, the pulse sequence optimization unit 26 has a processor unit 28 that executes the software and/or computer programs stored in the memory unit 27 are executed during a progression of the selected pulse sequence.

(12) A method according to the invention for an accelerated progression of a repeating pulse sequence with an optimized gradient curve is shown in FIG. 1. The magnetic resonance examination of the patient 14 is initially started with the selected pulse sequence, and this pulse sequence is executed repeatedly for the magnetic resonance examination. A start signal for the magnetic resonance examination can be input, for example manually by an operator via the operator terminal 22. The execution of the pulse sequence takes place by means of the system control unit 21 together with the gradient control unit 23 and the radio-frequency control unit 24.

(13) For a first progression of the pulse sequence, boundary conditions for a first gradient pulse are initially detected by the pulse sequence optimization unit 26 in a first method step 100. The boundary conditions include duration of the gradient pulse and/or a gradient moment of the gradient pulse and/or a start point in time of the gradient pulse and/or an end point in time of the gradient pulse.

(14) For an accelerated progression of an optimization of the first gradient pulse, a query 101 initially takes place—by means of the pulse sequence optimization unit 26—as to whether a data set of an additional gradient pulse of a previous progression of a gradient pulse is already stored within the memory unit 27. This data set for an additional gradient pulse includes at least one optimized curve of the additional gradient pulse and also the four boundary conditions that have led to this optimized curve of the additional gradient pulse. The optimized curve of the additional gradient pulse is preferably stored, together with the four boundary conditions, within a data array of the memory unit 27.

(15) If the query 101 indicates that no stored data set with an optimized curve of an additional gradient pulse of a previous progression of the pulse sequence is present, for the first gradient pulse, the optimized curve must be calculated by means of the pulse sequence optimization unit 26 using the four boundary conditions. The calculation of the optimized gradient curve of the first gradient pulse takes place in a further method step 102 by means of a spline interpolation that is executed by the pulse sequence optimization unit 26 (in particular the processor unit 28 of the pulse sequence optimization unit 26). The calculated, optimized gradient curve of the first gradient pulse is stored, together with the four boundary conditions, within the data array of the memory unit 27 in a method step 103 that follows this. In addition, in a further method step 104 the calculated optimized gradient curve for the first gradient pulse is applied to the magnetic field gradient coils.

(16) If the query 101 indicates that a stored data set with an optimized curve of an additional gradient pulse of a previous progression of the pulse sequence is already present within the memory unit 27, a comparison of the boundary conditions of the first gradient pulse of the first progression of the pulse sequence with the boundary conditions of the additional gradient pulse of the previous progression of the pulse sequence takes place by means of the pulse sequence optimization unit 26 in a further method step 105. Each boundary condition of the first gradient pulse is hereby separately compared by the pulse sequence optimization unit 26 with the corresponding boundary condition of the additional gradient pulse.

(17) Following this, an optimized gradient curve of the first gradient pulse of the first progression of the pulse sequence is determined by means of the pulse sequence optimization unit 26, wherein the determination of the optimized gradient curve of the first gradient pulse takes place depending on an agreement of the boundary conditions of the first gradient pulse with the boundary conditions of the additional gradient pulse. A query 106 initially takes place as to whether the boundary conditions of the first gradient pulse agree with the boundary conditions of the additional gradient pulse. Insofar as the query 106 yields that an agreement of the boundary conditions of the first gradient pulse with the boundary conditions of the additional gradient pulse exists, in a method step 107 following this the optimized gradient curve of the first gradient pulse of the first progression of the pulse sequence is calculated from the optimized gradient curve of the additional gradient pulse. The optimized gradient curve of the additional gradient pulse is read out from the memory unit 27 by the pulse sequence optimization unit, and this optimized gradient curve is adopted for the first gradient pulse.

(18) Given an agreement of the boundary conditions of the first gradient pulse with the boundary conditions of the additional gradient pulse, each of the boundary conditions (for example the duration of the first gradient pulse or a gradient moment of the first gradient pulse or a start or end point in time of the first gradient pulse) must independently agree exactly with the respective boundary condition (in particular the duration or a gradient moment or a start or end point in time of the additional gradient pulse). Only if all four boundary conditions of the first gradient pulse agree exactly with the four boundary conditions of the additional gradient pulse are the conditions for execution of method step 107 satisfied.

(19) After the method step 107, in the further method step 104 the determined optimized gradient curve for the first gradient pulse is applied to the magnetic field gradient coils.

(20) If the query 106 indicates that dissimilarity exists between the boundary conditions of the first gradient pulse and the boundary conditions of the additional gradient pulse, the method step 102 is executed again by the pulse sequence optimization unit 26 and the optimized gradient curve for the first gradient pulse is calculated. Following this, the calculated optimized gradient curve (together with the boundary conditions) is stored within the data array of the memory unit 27 in the method step 103. Furthermore, in the further method step 104 the determined optimized gradient curve for the first gradient pulse is applied to the magnetic field gradient coils.

(21) The method described with regard to FIG. 1 for an accelerated progression of a repeating pulse sequence with an optimized gradient curve repeats with every progression of the pulse sequence. Only when the magnetic resonance measurement is ended is the method described above for an accelerated progression of a repeating pulse sequence with an optimized gradient curve ended as well.

(22) The software and/or computer programs stored in the memory unit of the pulse sequence optimization unit 26 include a computer program that can be loaded directly into a memory unit of a pulse sequence optimization unit 26, with program code segments in order to execute all steps of a method for an accelerated progression of a repeating pulse sequence with an optimized gradient curve when the program is executed in the processor unit 28 of the pulse sequence optimization unit 26.

(23) Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art.