Method and magnetic resonance apparatus for optimization of a magnetic resonance sequence

Abstract

In a method to optimize a magnetic resonance sequence of a magnetic resonance apparatus and a magnetic resonance apparatus operated according to such a method, optimization of the timing of the magnetic resonance sequence is implemented by adopting a magnetic resonance sequence as a starting sequence includes a first time interval set of one or more first time intervals and a second time interval set of one or more second time intervals, wherein the first time intervals of the first time interval set are to be left unmodified with regard to an optimization of the duration. The magnetic resonance sequence is automatically analyzed to identify the first time intervals of the first time interval set and the second time intervals of the second time interval set in the magnetic resonance sequence. The duration of at least one second time interval of the second time interval set is then automatically optimized.

Claims

1. A method to optimize a magnetic resonance (MR) sequence for operating a magnetic resonance apparatus, comprising: entering a starting magnetic resonance sequence into a computer, said starting magnetic resonance sequence comprising a first time interval set comprising at least one time interval, and a second time interval set, comprising at least one second time interval; in said computer, automatically analyzing said starting magnetic resonance sequence to identify said at least one first time interval in the first time interval set and said at least one second time interval in the second time interval set in said starting magnetic resonance sequence; in said computer, automatically optimizing a duration of said at least one second time interval of said second time interval set, and making no modification to a duration of said at least one first time interval of said first time interval set, in order to produce an optimized magnetic resonance sequence; from said computer, controlling a magnetic resonance apparatus with said optimized magnetic resonance sequence in order to acquire magnetic resonance data from a subject; and In said computer, reconstructing image data from the acquired magnetic resonance data, and displaying an image, represented by said image data, at a display in communication with said computer.

2. A method as claimed in claim 1 comprising automatically optimizing said duration of said at least one second time interval using an optimization criterion that causes the optimized duration of said at least one second time interval to be minimized.

3. A method as claimed in claim 2 wherein said optimization criterion is a first optimization criterion, and wherein said magnetic resonance apparatus comprises a gradient coil arrangement having gradient coil arrangement specification parameters associated therewith, and wherein said starting magnetic resonance sequence comprises a gradient switching set comprising at least one gradient switching implemented by said gradient coil arrangement, and comprising automatically optimizing the duration of said at least one second time interval according to a second optimization criterion that an adaptation of at least one gradient switching of said gradient switching set, which takes place in said starting magnetic resonance sequence during said at least one second time interval, to the optimized duration of said at least one second time interval, is possible while complying with said gradient coil arrangement specification parameters.

4. A method as claimed in claim 3 comprising using, as said gradient coil arrangement specification parameters, at least one of a maximum allowable gradient amplitude and a maximum allowable slew rate.

5. A method as claimed in claim 1 wherein said starting magnetic resonance sequence comprises a gradient switching set comprising at least one gradient switching, and comprising, in said computer, automatically adapting said at least one gradient switching, which takes place during said at least one second time interval in said starting magnetic resonance sequence, to the optimized duration of said at least one second time interval.

6. A method as claimed in claim 5 comprising automatically adapting said at least one gradient switching while adhering to an adaptation criterion that a gradient switching moment of said at least one gradient switching in said optimized magnetic resonance sequence is kept to be the same as the gradient moment of said at least one gradient switching in said starting magnetic resonance sequence.

7. A method as claimed in claim 5 comprising automatically adapting said at least one gradient switching while adhering to an adaptation criterion that a gradient amplitude of said at least one gradient switching at fixed points in time of said optimized magnetic resonance sequence is maintained to be the same as the gradient amplitude of said at least one gradient switching at said fixed points in said starting magnetic resonance sequence, wherein said fixed points are edge values at time interval boundaries of said at least one second time interval, with an adjoining first time interval of said first time interval set.

8. A method as claimed in claim 1 comprising identifying said at least one first time interval in said magnetic resonance sequence as a time interval in which at least one event takes place that is selected from the group consisting of emission of a radio frequency pulse, readout of raw data, switching of a flow compensation gradient, and switching of a diffusion gradient.

9. A method as claimed in claim 1 comprising identifying a time interval within said starting magnetic resonance sequence as being said at least one first time interval or said at least one second time interval, by an analysis selected from the group consisting of analysis of pulse transmission times of radio frequency pulses in said starting magnetic resonance sequence, analysis of readout times in said starting magnetic resonance sequence, analysis of a shape of gradients in said starting magnetic resonance sequence, and analysis of identifiers in a parameter set associated with a gradient activation in said starting magnetic resonance sequence.

10. A method as claimed in claim 1 comprising identifying a time interval in said starting magnetic resonance sequence as a first time interval, as being a time interval in which a change in the duration thereof results in a change of at least one of an echo time produced in said starting magnetic resonance sequence and a change in a repetition time of said starting magnetic resonance sequence.

11. A method as claimed in claim 1 comprising implementing said optimization of said starting magnetic resonance sequence in said computer dependent on a manually-entered input into said computer.

12. A method as claimed in claim 1 wherein said magnetic resonance sequence comprises a gradient switching set comprising at least one gradient switching and, in said computer, also optimizing said at least one gradient switching.

13. A method as claimed in claim 12 wherein said magnetic resonance apparatus comprises a gradient coil arrangement that implements said at least one gradient switching, said gradient coil arrangement having gradient coil arrangement specification parameters associated therewith, and comprising, after optimizing said at least one gradient switching, checking, in said computer, to ensure compliance of the optimized at least one gradient switching with said gradient coil arrangement specification parameters.

14. A magnetic resonance apparatus, comprising: a magnetic resonance data acquisition unit; a computer provided with a starting magnetic resonance sequence, said starting magnetic resonance sequence comprising a first time interval set comprising at least one time interval, and a second time interval set, comprising at least one second time interval; said computer being configured to automatically analyze said starting magnetic resonance sequence to identify said at least one first time interval in the first time interval set and said at least one second time interval in the second time interval set in said starting magnetic resonance sequence; said computer being configured to automatically optimize a duration of said at least one second time interval of said second time interval set, and make no modification to a duration of said at least one first time interval of said first time interval set, in order to produce an optimized magnetic resonance sequence; said computer being configured to operate said magnetic resonance data acquisition unit with said optimized magnetic resonance sequence in order to acquire magnetic resonance data from a subject; and said computer being configured to reconstruct image data from the acquired magnetic resonance data, and display an image, represented by said image data, at a display in communication with said computer.

15. A non-transitory, computer-readable data storage medium encoded with programming instructions, said storage medium being loaded into a computerized control unit of a magnetic resonance apparatus, and said programming instructions causing said computerized control unit to: receive a starting magnetic resonance sequence into a computer, said starting magnetic resonance sequence comprising a first time interval set comprising at least one time interval, and a second time interval set, comprising at least one second time interval; analyze said starting magnetic resonance sequence to identify said at least one first time interval in the first time interval set and said at least one second time interval in the second time interval set in said starting magnetic resonance sequence; optimize a duration of said at least one second time interval of said second time interval set, and make no modification to a duration of said at least one first time interval of said first time interval set, in order to produce an optimized magnetic resonance sequence; control said magnetic resonance apparatus with said optimized magnetic resonance sequence in order to acquire magnetic resonance data from a subject; and reconstruct image data from the acquired magnetic resonance data, and display an image, represented by said image data, at a display in communication with said computer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a magnetic resonance apparatus according to the invention for execution of a method according to the invention, in a schematic presentation.

(2) FIG. 2 is a flowchart of an embodiment of a method according to the invention.

(3) FIG. 3 is a sequence diagram of a magnetic resonance sequence to be optimized in its chronological workflow according to the method according to the invention.

(4) FIG. 4 shows the sequence diagram according to FIG. 3, subdivided into first and second time intervals.

(5) FIG. 5 shows the sequence diagram according to FIG. 4 after optimization of the duration of the second time intervals.

(6) FIG. 6 shows the sequence diagram according to FIG. 3 before an optimization of gradient switchings according to one embodiment of the method according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) FIG. 1 shows, in a schematic presentation, a magnetic resonance apparatus 11 according to the invention for execution of a method according to the invention. The magnetic resonance apparatus 11 has a data acquisition unit (formed by a magnet unit 13) with a basic field magnet 17 to generate a strong and constant basic magnetic field 18. In addition, the magnetic resonance apparatus 11 has a cylindrical patient acquisition region 14 for an acquisition of a patient 15, wherein the patient acquisition region 14 is cylindrically enclosed by the magnet unit 13 in a circumferential direction. The patient 15 can be slid into the patient acquisition region 14 by a patient support device 16 of the magnetic resonance apparatus 11. For this purpose, the patient bearing device 16 has a patient table that is arranged so as to be movable within the magnetic resonance apparatus 11. The magnet unit 13 is externally shielded by a housing casing 31 of the magnetic resonance apparatus.

(8) Furthermore, the magnet unit 13 has a gradient coil unit 19 to generate magnetic field gradients that are used for a spatial coding during an imaging. The gradient coil unit 19 is controlled by means of a gradient control unit 28. The magnetic field gradients are generated in the x-, y- and z-directions. The gradient coils of the gradient coil unit 19 can be controlled independently of one another in the x-, y- and z-directions so that, with a predetermined combination, gradients can be applied in arbitrary spatial directions (for example in the slice selection direction, in the phase coding direction or in the readout direction), wherein these directions normally depend on the chosen slice orientation. The spatial directions of the gradient switchings can likewise also coincide with the x-, y- and z-directions; for example, the slice selection direction points in the z-direction, the phase coding direction points in the y-direction and the readout direction points in the x-direction. The x-direction is that direction situated horizontally orthogonal to the direction of the basic magnetic field 18 (the z-direction). The y-direction is that direction situated vertically orthogonal to the z-direction, and orthogonal to the x-direction.

(9) Furthermore, the magnet unit 13 has a radio-frequency antenna unit 20 (which, in the shown case, is designed as a body coil permanently integrated into the magnetic resonance apparatus 10) and a radio-frequency antenna control unit 29 for an excitation of a polarization that arises in the basic magnetic field 18 generated by the basic magnet 17. The radio-frequency antenna unit 20 is controlled by the radio-frequency antenna control unit 29 and radiates high-frequency radio-frequency pulses into an examination space that is essentially formed by the patient acquisition region 14.

(10) The magnetic resonance apparatus 11 has a control unit 24 to control the basic magnet 17, the gradient control unit 28 and the radio-frequency antenna control unit 29. The control unit 24 centrally controls the magnetic resonance apparatus 11, for example the implementation of magnetic resonance sequences. Control information (for example imaging parameters) and reconstructed magnetic resonance images can be displayed for a user at a display unit 25 (for example on at least one monitor) of the magnetic resonance apparatus 11. In addition, the magnetic resonance apparatus 11 has an input unit 26 via which information and/or imaging parameters can be entered by a user during a measurement process. The control unit 24 can include the gradient control unit 28 and/or radio-frequency antenna control unit 29 and/or the display unit 25 and/or the input unit 26. The magnetic resonance apparatus furthermore has a sequence optimization unit 30 which has a computer (not shown further) for optimization of imaging parameters of magnetic resonance sequences. In addition, the sequence optimization unit 30 furthermore comprises an input interface 32, an analysis unit 33 and a duration optimization unit 34.

(11) The shown magnetic resonance apparatus 11 can naturally have additional components that magnetic resonance apparatuses 11 conventionally have. A general functionality of a magnetic resonance apparatus 11 is additionally known to those skilled in the art, such that a detailed description of the additional components is not necessary herein.

(12) FIG. 2 is a flowchart of an embodiment of a method according to the invention. In a first method step 200, a selection and preparation of the magnetic resonance sequence is initially implemented in a typical manner. This means that, via the input unit 26, a user typically establishes the type of magnetic resonance sequence and/or searches for a corresponding protocol in which a specific magnetic resonance sequence is defined. The protocols thereby include various imaging parameters for the respective magnetic resonance sequence. Among these imaging parameters are specific ground rules for the desired magnetic resonance sequence, for example the type of magnetic resonance sequence, i.e. whether it is a spin echo sequence, a turbo spin echo sequence etc. Furthermore, counting amount these are the imaging parameters of: slice thickness; slice intervals; number of slices; resolution; repetition times; the echo times in a spin echo sequence; whether the magnetic resonance sequence should be executed with a minimum echo time and/or a minimum repetition time etc. With the use of the input unit 26, the user can modify a portion of these imaging parameters in order to create an individual magnetic resonance sequence for a currently desired measurement. For this, modifiable imaging parameters are offered to the user for modification, for example at a graphical user interface of the input unit 26.

(13) In a further method step 201, the precise timing and the workflow of the magnetic resonance sequence are then calculated with the predetermined defined imaging parameters. The magnetic resonance sequence can be calculated in the control unit 24 that, for example, can be realized in the form of software components in a computer system of the magnetic resonance apparatus 11.

(14) In a further method step 202, the relaying of the magnetic resonance sequence that is ready for transmission but not yet optimized takes place in the form of time intervals (also called event blocks). A direct relaying of the time intervals to the gradient control unit 28 and the radio-frequency antenna control unit 29 does not take place. Rather, in a further method step 202 the magnetic resonance sequence is initially relayed from the control unit 24 to the sequence optimization unit 30 for optimization of the magnetic resonance sequence before being relayed to the gradient control unit 28 and the radio-frequency antenna control unit 29. The input interface 32 of the sequence optimization unit 30 is designed to accept the magnetic resonance sequence that is actually finished, ready for transmission, but is to be optimized.

(15) In a further method step 203, the analysis unit 33 of the sequence optimization unit 30 analyzes the magnetic resonance sequence and thereby identifies first time intervals and second time intervals of the magnetic resonance sequence. This is depicted as an example in the transition from FIG. 3 to FIG. 4. The first time intervals are thereby to be left unmodified relative to an optimization of the duration. The durations of the second time intervals may be optimized. In particular, during the automatic analysis of the magnetic resonance sequence a defined time interval within the magnetic resonance sequence is identified as a first time interval by then analysis unit 33 at least whenaccording to the magnetic resonance sequenceat least one of the following events should take place in the defined time interval: emission of a radio-frequency pulse, readout of raw data, switching of a flow compensation gradient switching, and switching of a diffusion gradient switching.

(16) For this, to identify a time interval within the magnetic resonance sequence as a first time interval or as a second time interval, the analysis unit 33 uses at least one of the following methods: analysis of the radio-frequency pulse transmission times, analysis of the readout times, analysis of the shape of the gradient switchings, and analysis of the identifiers included in a parameter set belonging to a gradient switching.

(17) Furthermore, during the automatic analysis of the magnetic resonance sequence a defined time interval within the magnetic resonance sequence is identified by the analysis unit 33 as a first time interval at least whenaccording to the magnetic resonance sequencea change of the duration of the defined time interval leads to a change of an echo time and/or a change of a repetition time of the magnetic resonance sequence.

(18) In a further method step 204, an optimization of the duration of at least one time interval takes place by means of the duration optimization unit 34 of the sequence optimization unit 30. In particular, the optimization of the duration of the at least one second time interval takes place under the optimization criterion that the duration of the at least one second time interval is minimized. Furthermore, the automatic optimization of the duration of the at least one second time interval takes place under the optimization criterion that an adaptation of the gradient switchings whichaccording to the magnetic resonance sequenceshould take place during the at least one second time interval to the optimized duration of the at least one time-optimized second time interval is possible while complying with system specification parameters, in particular a maximum allowable gradient amplitude and/or a maximum allowable slew rate. Various optimization criteria and the associated rules can be stored in a memory. These optimization criteria can optionally be offered to the user for selection on a monitor of the display unit 25, wherein the user then implements the selection via the input unit 26.

(19) In a further method step 205, if necessary the start times of the first and second time intervals are adapted to the modified duration of the at least one time interval by the sequence optimization unit 30.

(20) In a further method step 206, an automatic adaptation of the gradient switchings of the gradient switching set whichaccording to the magnetic resonance sequenceshould take place during the at least one second time interval to the optimized duration of the at least one time-optimized second time interval is implemented by the sequence optimization unit 30. This is implemented under the adaptation criteria that the gradient switching moment is kept constant, and that the amplitude of the gradient switchings is kept constant at fixed points, wherein the fixed points include edge values at time interval boundaries of the at least one second time interval with adjoining first time intervals. Method steps 204, 205 and 206 are shown as examples in the transition from FIG. 4 to FIG. 5.

(21) In a further method step 207, an automatic optimization of at least one gradient switching of the gradient switching set takes place. The additional method step 207 is hereby optional and can also take place before the additional method step 204, for example. The example optimization of at least one gradient switching is shown in the transition from FIG. 6 to FIG. 3.

(22) In a further method step 208, after an optimization and/or adaptation of at least one gradient switching of the gradient switching set the at least one optimized and/or adapted gradient switching is checked for compliance with system specification parameters, in particular the compliance with a maximum allowable gradient amplitude and/or a maximum allowable slew rate. The maximum allowable gradient amplitude and/or maximum allowable slew rate are system specification parameters which can be stored in a memory, for example. Additional system specification parameters can also be used to check the at least one optimized and/or adapted gradient switching.

(23) In a further method step 209, the optimized magnetic resonance sequence (with the optimized at least one second time interval, the adapted gradient switchings, the possibly optimized gradient switchings and the additional first and second time intervals which are possibly adapted in their start time) is finally passed to the gradient control unit 28 and the radio-frequency antenna control unit 29. From the optimized magnetic resonance sequence, the gradient coil unit 28 and the radio-frequency antenna control unit 29 generate the corresponding control commands and pass these to the radio-frequency antenna unit 20 and the gradient coil unit 19 so that the entire optimized magnetic resonance sequence is executed in the correct chronological order, with a timing that is improved relative to before the optimization, for acquisition of magnetic resonance image data by means of the magnetic resonance apparatus 11.

(24) The method steps of the method according to the invention that are shown in FIG. 2 are executed by the sequence optimization unit 30 together with the magnetic resonance apparatus 11. For this, the sequence optimization unit 30 comprises corresponding software and/or computer programs that are stored in a memory unit of the sequence optimization unit 30. The software and/or computer programs include code designed to cause the method according to the invention to be executed when the computer program and/or software is executed in said sequence optimization unit 30 by a processor unit of the magnetic resonance apparatus 11.

(25) As an example, FIG. 3 shows a sequence diagram of a portion of a very simplified magnetic resonance sequence (a gradient echo sequence) that is subdivided into time intervals Z.sub.1, Z.sub.2, Z.sub.3, . . . , Z.sub.8 (in FIG. 3, only the first seven time intervals are shown entirely, and the eighth is shown nearly entirely). In this sequence diagram, the readout window W, the radio-frequency pulses RF.sub.1, RF.sub.2, RF.sub.3 and the gradient switchings are respectively shown depending on the time t in a typical manner on different time axes situated one over another. The readout window W is thereby shown on the uppermost readout time axis ADC. The amplitudes of the radio-frequency pulses RF.sub.1, RF.sub.2, RF.sub.3 are shown on the second-uppermost radio-frequency pulse time axis RF. The gradient switchings Gx.sub.1, Gx.sub.2, Gx.sub.3, Gx.sub.4, Gx.sub.5 are shown un the underlying gradient switching time axis Gx. These are the gradient switchings in the readout direction. On the second-lowermost gradient switching time axis Gy, the gradient switchings Gy.sub.1, Gy.sub.2, Gy.sub.3, Gy.sub.4 are shown which are switched in the phase coding direction. The gradient switchings Gz.sub.1, Gz.sub.2, Gz.sub.3, Gz.sub.4, Gz.sub.5, Gz.sub.6 in the slice selection direction are shown on the lowermost gradient switching time axis Gz. The position of the time axis respectively indicates the zero line, meaning that the gradient switchings can have negative or positive amplitudes in the gradients depending on whether their amplitudes extend downward or upward from the gradient switching time axis Gx, Gy, Gz. In all sequence diagrams, for simplification the scaling in the time direction and in amplitude directions takes place only in arbitrary units.

(26) The first time interval Z.sub.1 and second time interval Z.sub.2 of this magnetic resonance sequence should induce a fat saturation. Therefore, a relatively strong radio-frequency pulse RF.sub.1 is initially emitted in a first time interval Z.sub.1, during which radio-frequency pulse RF.sub.1 no gradient switching is executed so that the radio-frequency pulse RF.sub.1 does not act slice-selectively. Immediately after the end of this radio-frequency pulse RF.sub.1, three gradient switchings Gx.sub.1, Gy.sub.1, Gz.sub.1 follow in all three spatial axes in the following time interval Z.sub.2, which gradient switchings Gx.sub.1, Gy.sub.1, Gz.sub.1 serve to dephase an unwanted transversal magnetization that is generated by the fat saturation. The gradient switchings Gx.sub.1, Gy.sub.1, Gz.sub.1 simultaneously serve as pre-spoilers in Z.sub.2. These pre-spoilers also serve to effectively dephase transversal residual magnetization that is possibly present.

(27) The third time interval Z.sub.3, fourth time interval Z.sub.4 and fifth time interval Z.sub.5 form a gradient echo sequence in which magnetic resonance signals are acquired in a defined volume or a defined slice. In Z.sub.3, the volume is thereby excited via a radio-frequency pulse RF.sub.2 with simultaneous execution of a defined gradient Gz.sub.2 in a slice selection direction Gz, and in Z.sub.5 a readout window W is placed while switching a defined gradient Gx.sub.3 in the readout direction, which means that the ADC is switched to receive. In Z.sub.4 there are additional gradient switchings Gx.sub.2, Gy.sub.2, Gz.sub.3, Gz.sub.4 which serve to dephase transversal magnetization generated by the excitation pulse in order to not generate unwanted echoes in the following time intervals.

(28) A sixth time interval Z.sub.6 then follows these gradient echo time intervals, during which sixth time interval Z.sub.6 three gradient switchings Gx.sub.4, Gy.sub.3, Gz.sub.5 are switched in parallel in the x-, y- and z-direction, which gradient switchings Gx.sub.4, Gy.sub.3, Gz.sub.5 serve as spoiler gradients for dephasing of the magnetization.

(29) The acquisition cycle subsequently begins again from the start in that a radio-frequency pulse RF.sub.3 that is not slice-selective is emitted in a seventh time interval Z.sub.7, wherein all gradients are set to zero and additional gradient switchings Gx.sub.5, Gy.sub.4, Gz.sub.6 are subsequently emitted again in all three spatial directions in the eighth time interval Z.sub.8. Additional time intervals can then subsequently follow, for example a new pre-spoiler, an additional repetition, a gradient echo time interval etc.

(30) Some of these time intervals Z.sub.1, Z.sub.2, Z.sub.3, . . . , Z.sub.8 can be optimized with regard to their duration, and thus second time intervals I.sub.2. Here these are the time intervals that do not fall under the criteria described above that identify a time interval as not a first time interval I.sub.1 that can be optimized in the duration. Z.sub.1, Z.sub.3 and Z.sub.7 are thus first time intervals I.sub.1 since radio-frequency pulses RF.sub.1, RF.sub.2, RF.sub.3 are emitted during them. Z.sub.5 is likewise a first time interval I.sub.1 since a readout window W is switched during Z.sub.5. In the shown case, it has been predetermined by the user that the echo time should be kept constant while a change of the repetition time is allowed due to an optimization of the second time intervals I.sub.2. Z.sub.4 is thus a first time interval I.sub.1 since a change of the duration of Z.sub.4 would lead to a change of the echo time, the time between the radio-frequency pulse RF.sub.2 and the center of the readout window W. In the simplified sequence that is shown here, specific gradient switchings such as flow compensation gradient switchings or diffusion gradient switchings are not included and thus cannot be used as criteria to identify a time interval as a first time interval I.sub.1. Time intervals Z.sub.2, Z.sub.6 and Z.sub.8 are optimizable with regard to the duration and thus are to be identified as second time intervals I.sub.2. This is based on the fact that none of the cited criteria apply to the time intervals Z.sub.2, Z.sub.6 and Z.sub.8, and a change of the duration of Z.sub.2, Z.sub.6 and Z.sub.8, would keep the echo time constant. In particular, time interval Z.sub.6 is identified as a second time interval I.sub.2 since Z.sub.6 includes a spoiler gradient.

(31) FIG. 4 shows the sequence diagram of the magnetic resonance sequence from FIG. 3. Here the first time intervals I.sub.1 that have been determined (by the analysis unit 33) to not be optimizable in the further method step 203 are respectively covered by a cross-striped pattern. The optimizable second time intervals I.sub.2 are not covered by a cross-striped pattern. The optimizable second time intervals I.sub.2 are not covered by a cross-striped pattern.

(32) FIG. 5 shows the sequence diagram of the magnetic resonance sequence from FIG. 3 and FIG. 4. The duration of the second time intervals Z.sub.2, Z.sub.4 and Z.sub.6 was hereby optimized. The duration of the second time intervals I.sub.2 was minimized under the optimization criteria of a maximum allowable gradient amplitude and slew rate of the gradient switchings, while the optimizable second time intervals I.sub.2 are minimized by means of the duration optimization unit 34 in the further method step 204.

(33) In a further method step 206, the gradient switchings Gx.sub.1, Gy.sub.1 and Gz.sub.1 were simultaneously adapted due to the shortened duration of the time interval Z.sub.2, whereby new gradient switchings Gx.sub.1, Gy.sub.1 and Gz.sub.1 are created. The amplitude values of the gradient switchings at the boundaries at Z.sub.1 and Z.sub.3 have respectively been held constant as fixed points. Furthermore, the adaptation of the gradient switchings has been implemented such that the gradient switching moment of the gradient switchings in Z.sub.2 is the same before and after the optimization. The gradient switchings Gx.sub.4, Gy.sub.3 and Gz.sub.5 were similarly adapted to adapted gradient switchings Gx.sub.4, Gy.sub.3 and Gz.sub.5 due to the shortened duration of Z.sub.6. Similarly, the gradient switchings Gx.sub.5, Gy.sub.4 and Gz.sub.6 were similarly adapted to adapted gradient switchings Gx.sub.5, Gy.sub.4 and Gz.sub.6 due to the shortened duration of Z.sub.8.

(34) As was shown in FIG. 5, by the optimization of the duration of the second time intervals I.sub.2 it has been achieved that the excitation pulse RF.sub.2 was shifted closer to the saturation pulse RF.sub.1, whereby the effect of the saturation pulse RF.sub.1 was improved in the excitation of the magnetization. Furthermore, the duration of the spoiler gradient in Z.sub.6 can be shortened. Overall, the repetition time of the magnetic resonance sequence could thus be reduced by approximately 20 percent, and thus a distinct savings of measurement time could be achieved.

(35) Finally, together with FIG. 3, FIG. 6 shows the optimization of gradient switchings of the magnetic resonance sequence according to one embodiment of the method according to the invention. FIG. 6 thus depicts the magnetic resonance sequence of FIG. 3, but without gradient switchings having been optimized. An optimization of the gradient switchings was implemented in the further method step 207 between FIG. 6 and FIG. 3. As was already noted, this optimization of the gradient switchings is optional with regard to the method according to the invention. The method according to the invention can thus proceed from the magnetic resonance sequence shown in FIG. 3 without an optimization of the gradient switchings being necessary.

(36) With regard to the optimization of the gradient switchings, different time intervals also result, namely fixed point time intervals I.sub.F (shown with shading) in which no gradient switchings may be optimized and modifiable time intervals I.sub.0 (not shown with shading) in which the gradient switchings may be optimized. Here, specifically the time intervals Z.sub.1, Z.sub.3, Z.sub.5 and Z.sub.7 in which the radio-frequency pulses RF.sub.1, RF.sub.2, RF.sub.3 are emitted or the readout window W is switched in parallel have been identified by means of the analysis unit 33 as fixed point time intervals I.sub.F that cannot be optimized. In these time intervals, the gradients must remain at the exact predetermined amplitude values. With regard to the optimization of the gradient switchings, Z.sub.4 is a modifiable time interval I.sub.0 since the echo time is kept constant given the optimization of the gradient switchings.

(37) In the modifiable time intervals I.sub.0, the gradient switchings (in particular the gradient curve of the gradient switchings) may be varied arbitrarily under the following boundary conditions: the amplitude values must be maintained at the border points with the adjoining time intervals that include the fixed point time intervals I.sub.F that cannot be optimized. The first derivative at these border points must be zero. The total moment of the gradient switchings in the respective optimizable time intervals I.sub.0 must be identical before and after the optimization.

(38) The optimizable time intervals Z.sub.2, Z.sub.4, Z.sub.6, Z.sub.8 are optimized under the boundary conditions that were just cited, wherein the gradient switchings from FIG. 3 result. The optimization takes place using a spline interpolation method, wherein the amplitude values at the borders are respectively viewed as fixed points, and under the cited boundary conditions (reaching the fixed points, 1st derivative at the fixed points=0, and keeping the integral below the gradient switching curve the same) a spline leads to a desired smooth gradient switching in the respective optimizable time intervals I.sub.0.

(39) In comparison, between FIG. 6 and FIG. 1 it can be seen how adjoining, relatively angular gradient switchings Gx.sub.1, Gx.sub.2, Gx.sub.4, Gx.sub.5, Gx.sub.6, Gy.sub.1, Gy.sub.2, Gy.sub.3, Gy.sub.4, Gy.sub.5, Gy.sub.6, Gz.sub.1, Gz.sub.2, Gz.sub.3, Gz.sub.4, Gz.sub.5, Gz.sub.6 with steep edges have been converted into gradient switchings that transition into one another with shapes Gx.sub.1, Gx.sub.2, Gx.sub.3, Gx.sub.4, Gx.sub.5, Gy.sub.1, Gy.sub.2, Gy.sub.3, Gy.sub.4, Gz.sub.1, Gz.sub.2, Gz.sub.3, Gz.sub.4, Gz.sub.5, Gz.sub.6 that are common in part. The optimized gradient switchings are relatively smooth, therefore provide significantly smaller loads for the gradient coils and thus significantly reduce the noise exposure. As an example for the merging of gradient switchings, in particular the merging of the gradient switchings Gy.sub.1, Gy.sub.2 in the original magnetic resonance sequence according to FIG. 6 into a common gradient switching Gy.sub.1 in the optimized sequence according to FIG. 3 is noted, as well as the gradient switchings Gz.sub.1 through Gz.sub.3 that would now be replaced by a common shape Gz.sub.1, Gz.sub.2, Gz.sub.3 that even extends over three time intervals Z.sub.2, Z.sub.3, Z.sub.4. In particular, here it is to be heeded that the gradient amplitude has not changed during the time interval Z.sub.3 in which a slice-selective radio-frequency pulse RF.sub.2 is emitted in parallel, which means thatexactly in this regionthe original part of the gradient switching Gz.sub.3 from FIG. 6 precisely corresponds to the gradient switching Gz.sub.2 from FIG. 3 that is present in the time interval Z.sub.3. Using FIG. 3 and FIG. 6 it can be seen howwith the optimization of the gradient switchings according to the embodiment of the method according to the inventioneach magnetic resonance sequence can be very quickly optimized in an effective manner, with regard to noise exposure and loading of the gradient switchings, immediately before the execution.

(40) The present invention encompasses a method to operate a magnetic resonance apparatus, comprising entering a starting magnetic resonance sequence into a computer, said starting magnetic resonance sequence comprising a first time interval set comprising at least one time interval, and a second time interval set, comprising at least one second time interval; in said computer, automatically analyzing said starting magnetic resonance sequence to identify said at least one first time interval in the first time interval set and said at least one second time interval in the second time interval set in said starting magnetic resonance sequence; in said computer, automatically optimizing a duration of said at least one second time interval of said second time interval set, and making no modification to a duration of said at least one first time interval of said first time interval set, in order to produce an optimized magnetic resonance sequence; and making said optimized magnetic resonance sequence available in electronic form at an output of said computer, and operating said magnetic resonance apparatus with said optimized magnetic resonance sequence.

(41) The present invention also encompasses a sequence optimization unit for optimizing a magnetic resonance sequence of a magnetic resonance apparatus, comprising, a computer having an input that receives a starting magnetic resonance sequence, said starting magnetic resonance sequence comprising a first time interval set comprising at least one time interval, and a second time interval set, comprising at least one second time interval; said computer being configured to automatically analyze said starting magnetic resonance sequence to identify said at least one first time interval in the first time interval set and said at least one second time interval in the second time interval set in said starting magnetic resonance sequence; said computer being configured to automatically optimize a duration of said at least one second time interval of said second time interval set, and make no modification to a duration of said at least one first time interval of said first time interval set, in order to produce an optimized magnetic resonance sequence; and said computer comprising an output, and being configured to make said optimized magnetic resonance sequence available in electronic form at said output of said computer, in a format for controlling a magnetic resonance apparatus.

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