Method and magnetic resonance tomography apparatus for diffusion imaging

Abstract

In a method and magnetic resonance tomography apparatus for diffusion imaging, coherences are determined in a processor, which would occur during the diffusion imaging measurement, and an implicit spoil moment M.sub.A resulting from a diffusion gradient pulse is determined in the processor. A spoiler moment M.sub.S is established in the processor as a function of a comparison value and threshold value formed from the implicit spoil moment M.sub.A and the suppression moment M. Depending on whether this comparison value lies below or above the threshold value, different calculation techniques are applied for the spoiler moment M.sub.S. Diffusion gradient pulses and spoiler gradient pulses in accordance with the moments M.sub.A and M.sub.S in a pulse sequence for operating the magnetic resonance tomography apparatus.

Claims

1. A method to control a magnetic resonance (MR) tomography apparatus for diffusion imaging, comprising: in a processor, determining coherences that occur during measurement of raw data in an execution of a diffusion imaging sequence by an MR scanner and, also in said processor, determining a suppression moment M needed for suppression of said coherences; in said processor, determining an amplitude A.sub.D and an application time T.sub.D of a predetermined diffusion gradient pulse GD in conjunction with a predetermined diffusion encoding produced by said diffusion imaging sequence, and determining an implicit spoil moment M.sub.A resulting from said diffusion gradient pulse GD; in said processor, establishing a spoiler moment M.sub.S as a function of a comparison value and a threshold value formed from the implicit spoil moment M.sub.A and the suppression M, and, depending on whether said comparison value is below or above said threshold value, applying different types of calculations for the spoiler M.sub.S; in said processor, determining an amplitude A.sub.S of a spoiler gradient pulse and an application time S.sub.T of the spoiler gradient pulse GS from the determined spoiler moment M.sub.S; and in said processor, generating a final form of said diffusion imaging sequence that comprises diffusion gradient pulses GD and spoiler gradient pulses GS with respective application times T.sub.D and T.sub.S, and providing control signals from said processor to said MR scanner representing said final form of said diffusion imaging sequence and thereby operating said MR scanner so as to acquire raw data by execution of said final form or said diffusion imaging sequence.

2. A method as claimed in claim 1 comprising determining the suppression moment M from a readout gradient GR in said diffusion imaging sequence, and a known factor F1 using the formula:
M>FGR(t)dt.

3. A method as claimed in claim 1 comprising determining the suppression moment M from a known field of view FOV of said MR scanner, and from a known number of pixels PX per row of a diffusion image to be generated from said raw data, and a known factor F1, according to: $M=2F\frac{\mathrm{PX}}{\mathrm{FOV}}.$

4. A method as claimed in claim 1 comprising determining the implicit spoil moment M.sub.A from a known diffusion gradient pulse having an amplitude A.sub.D and application time TD according to: $M_A={}_0^{T_A}{A}_D\left(t\right)\mathrm{dt}.$

5. A method as claimed in claim 1 comprising determining the diffusion gradient pulses respectively on Cartesian axes x, y and z, with partial moments MA.sub.x, MA.sub.y, and MA.sub.z, on the respective axes, according to: $M_A=\sqrt{\frac{1}{3}}\left(M_{A_x}^2+M_{A_y}^2+M_{A_z}^2\right).$

6. A method as claimed in claim 1 wherein each of said spoiler gradient pulses has an associated direction, and determining said spoiler gradient pulses GS in relation to the respective directions so as to support said implicit spoiler M.sub.A of the diffusion gradient pulses GD.

7. A method as claimed in claim 1 comprising determining said spoiler gradient pulses so as to be activated individually on a plurality of different physical gradient axes.

8. A method as claimed in claim 1 comprising determining said spoiler gradient pulses GS so as to be respectively activated along same axes as the diffusion gradient pulses GD.

9. A method as claimed in claim 1 comprising: determining said comparison value from the difference M.sub.D=MM.sub.A, or from a value derived from M.sub.D; determining said threshold to be reached if M=M.sub.A or M.sub.D=0; defining said spoiler moment MS, when M.sub.A<M, as M.sub.D or said value derived from M.sub.D; and setting the spoiler moment to zero if M.sub.AM.

10. A method as claimed in claim 1 comprising: starting from a time sequence of said gradient pulses, determining a threshold of a b value in said diffusion imaging sequence, with which an implicit spoil moment M.sub.A=M is achieved; in said processor, determining a current b value; if the current b value is below said threshold, setting said spoiler moment M.sub.S so as to suppress said coherences; and when said b value is above or at said threshold, setting said spoiler moment M.sub.S to be zero.

11. A method as claimed in claim 1 wherein said diffusion imaging sequence comprises a radio-frequency (RF) excitation pulse and an RF refocusing pulse, and producing said final form of said diffusion imaging sequence so that a spoiler gradient pulse GS is activated before said RF refocusing pulse and so that another spoiler gradient pulse GS is activated after said RF refocusing pulse.

12. A method as claimed in claim 11 comprising generating said final form of said diffusion imaging sequence so that at least one of a further RF refocusing pulse or a restoration pulse is activated after said RF refocusing pulse that is preceded and followed by respective spoiler gradient pulses GS, with said at least one further RF refocusing pulse not being assigned to any diffusion gradient pulse GD.

13. A method as claimed in claim 11 comprising: generating said final form of said diffusion pulse sequence so that said diffusion gradient pulses GD are given an insignificant zero moment by one of: activating diffusion gradient pulses GD before said RF refocusing pulse and activating further diffusion gradient pulses GD after said RF refocusing pulse that are the same as the diffusion gradient pulses GD activated before the RF refocusing pulse; activating diffusion gradient pulses GD before said RF refocusing pulse and activating further diffusion gradient pulses GD after said RF refocusing pulse that are different from the diffusion gradient pulses GD that were activated before said RF refocusing pulse; activating oscillating diffusion gradient pulses before said RF refocusing pulse and activating further oscillating diffusion gradient pulses after said RF refocusing pulses that have a same number of periods as the oscillating diffusion gradient pulses activated before said RF refocusing pulse; activating oscillating diffusion gradient pulses before said RF refocusing pulse and activating further oscillating diffusion gradient pulses after said RF refocusing pulse that have a different number of periods from the oscillating diffusion gradient pulses GD activated before the RF refocusing pulse; activating pairs of diffusion gradient pulses GD before said RF refocusing pulse and activating further pairs of diffusion gradient pulses after said RF refocusing pulse, with said further pairs of diffusion gradient pulses GD being in the same directions as the pairs of diffusion gradient pulses GD activated before the RF refocusing pulse; and activating pairs of diffusion gradient pulses before said RF refocusing pulse and activating further pairs of diffusion gradient pulses after said RF refocusing pulse, with the further pairs of diffusion gradient pulses having different directions from the pairs of diffusion gradient pulses activated before the RF refocusing pulse.

14. A method as claimed in claim 1 comprising generating said final form of said diffusion imaging sequence with said spoiler gradient pulses GS activated separated in time from said diffusion gradient pulses GD.

15. A method as claimed in claim 1 comprising generating said final form of said diffusion imaging sequence with said spoiler gradient pulses GS activated overlapping in time from said diffusion gradient pulses GD.

16. A computer to control a magnetic resonance (MR) tomography apparatus for diffusion imaging, said computer comprising: a spoiler gradient pulse adaptation processor configured to determine coherences that occur during measurement of raw data in an execution of a diffusion imaging sequence by an MR scanner and also to determine a suppression moment M needed for suppression of said coherences; said spoiler gradient pulse adaptation processor being configured to determine an amplitude A.sub.D and an application time T.sub.D of a predetermined diffusion gradient pulse GD in conjunction with a predetermined diffusion encoding produced by said diffusion imaging sequence, and to determine an implicit spoil moment M.sub.A resulting from said diffusion gradient pulse GD; said spoiler gradient pulse adaptation processor being configured to establish a spoiler moment M.sub.S as a function of a comparison value and a threshold value formed from the implicit spoil moment M.sub.A and the suppression M, and, depending on whether said comparison value is below or above said threshold value, to apply different types of calculations for the spoiler M.sub.S; said spoiler gradient pulse adaptation processor being configured to determine an amplitude A.sub.S of a spoiler gradient pulse and an application time S.sub.T of the spoiler gradient pulse GS from the determined spoiler moment M.sub.S; said spoiler gradient pulse adaptation processor being configured to generate a final form of said diffusion imaging sequence that comprises diffusion gradient pulses GD and spoiler gradient pulses GS with respective application times T.sub.D and T.sub.S; and an output interface configured to provide control signals from said spoiler gradient pulse adaptation processor to said MR scanner representing said final form of said diffusion imaging sequence and thereby to operate said MR scanner so as to acquire raw data by execution of said final form or said diffusion imaging sequence.

17. A magnetic resonance (MR) tomography apparatus comprising: an MR scanner; a spoiler gradient pulse adaptation processor configured to determine coherences that occur during measurement of raw data in an execution of a diffusion imaging sequence by an MR scanner and also to determine a suppression moment M needed for suppression of said coherences; said spoiler gradient pulse adaptation processor being configured to determine an amplitude A.sub.D and an application time T.sub.D of a predetermined diffusion gradient pulse GD in conjunction with a predetermined diffusion encoding produced by said diffusion imaging sequence, and to determine an implicit spoil moment M.sub.A resulting from said diffusion gradient pulse GD; said spoiler gradient pulse adaptation processor being configured to establish a spoiler moment M.sub.S as a function of a comparison value and a threshold value formed from the implicit spoil moment M.sub.A and the suppression M, and, depending on whether said comparison value is below or above said threshold value, to apply different types of calculations for the spoiler M.sub.S; said spoiler gradient pulse adaptation processor being configured to determine an amplitude A.sub.S of a spoiler gradient pulse and an application time S.sub.T of the spoiler gradient pulse GS from the determined spoiler moment M.sub.S; said spoiler gradient pulse adaptation processor being configured to generate a final form of said diffusion imaging sequence that comprises diffusion gradient pulses GD and spoiler gradient pulses GS with respective application times T.sub.D and T.sub.S; and an output interface configured to provide control signals from said spoiler gradient pulse adaptation processor to said MR scanner representing said final form of said diffusion imaging sequence and thereby to operate said MR scanner so as to acquire raw data by execution of said final form or said diffusion imaging sequence.

18. A non-transitory, computer-readable data storage medium encoded with programming instructions, said storage medium being loaded into a computer of a magnetic resonance (MR) tomography apparatus comprising an MR scanner, and said programming instructions causing said computer to: determine coherences that occur during measurement of raw data in an execution of a diffusion imaging sequence by an MR scanner, and determine a suppression moment M needed for suppression of said coherences; determine an amplitude A.sub.D and an application time T.sub.D of a predetermined diffusion gradient pulse GD in conjunction with a predetermined diffusion encoding produced by said diffusion imaging sequence, and determine an implicit spoil moment M.sub.A resulting from said diffusion gradient pulse GD; establish a spoiler moment M.sub.S as a function of a comparison value and a threshold value formed from the implicit spoil moment M.sub.A and the suppression M, and, depending on whether said comparison value is below or above said threshold value, apply different types of calculations for the spoiler M.sub.S; determine an amplitude A.sub.S of a spoiler gradient pulse and an application time S.sub.T of the spoiler gradient pulse GS from the determined spoiler moment M.sub.S; and generate a final form of said diffusion imaging sequence that comprises diffusion gradient pulses GD and spoiler gradient pulses GS with respective application times T.sub.D and T.sub.S, and provide control signals to said MR scanner representing said final form of said diffusion imaging sequence, and thereby operate said MR scanner so as to acquire raw data by execution of said final form or said diffusion imaging sequence.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an example of a pulse sequence that can be produced by the inventive method.

(2) FIG. 2 shows a diagram of the relevant moments for the case in which M.sub.A<M.

(3) FIG. 3 shows a diagram of the relevant moments for the case in which M.sub.A>M.

(4) FIG. 4 shows a part of an example of a pulse sequence that can be produced by the inventive method,

(5) FIG. 5 shows an alternate part of an example of a pulse sequence that can be produced by the inventive method,

(6) FIG. 6 shows a further part of an example of a pulse sequence that can be produced by the inventive method,

(7) FIG. 7 shows a flowchart for the execution sequence of the inventive method,

(8) FIG. 8 shows a schematic diagram of a magnetic resonance tomography apparatus according to an exemplary embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(9) Very simplified diagrams of pulse sequences are shown below. For better understanding of the invention the various pulses are shown as a function of the time t on a single time line. Normally in a pulse diagram of a gradient echo sequence the radio frequency pulses (the RF pulses HA, HR) to be emitted, as well as the gradient pulses GD, GS, are shown on different time axes lying above one another. Usually the RF pulses HA, HR are shown on one radio-frequency pulse time axis and the gradient pulses GD, GS on three gradient pulse time axes, which correspond to three spatial directions. The gradient pulses, spoiler gradient pulses GS and diffusion gradient pulses GD shown below can thus be shown in relation to their amplitudes distributed on the three gradient axes, and thus be oriented in space as per requirements. In such cases the spoiler gradient pulses GS do not have to be aligned absolutely identically to the diffusion gradient pulses GD, but such an alignment is part of a preferred form of embodiment.

(10) In the following figures only elements significant for the invention or helpful for your understanding are depicted. Thus for example no slice selection gradients are shown, although they can certainly be present in the pulse sequence.

(11) FIG. 1 shows an example of a pulse sequence PS, to which the inventive method can be applied. Time t runs from left to right in FIG. 1. Initially the pulse sequence PS comprises an RF excitation pulse HA with a duration usual for this type of pulse. The RF excitation pulse HA is followed by an RF refocusing pulse HR of usual duration, which is framed by diffusion gradient pulses GD and spoiler gradient pulses GS. In this example gradient pulses of the same type, i.e. the two diffusion gradient pulses GD and the two spoiler gradient pulses GS, each have the same polarity, the same amplitude and the same duration. The RF refocusing pulse HR forms a spin echo, which in the example shown is read out with an EPI echo read-out train EA, containing a number of read-out windows.

(12) FIG. 1 shows the case in which the implicit spoil moment M.sub.A is smaller than the suppression moment M needed for suppression of coherences (see FIG. 2). Therefore it is necessary to apply the spoiler gradient pulses GS shown, which bring about a specific spoiler moment M.sub.S. In the example shown the RF refocusing pulse HR is framed by two spoiler gradient pulses GS, which are applied with the spoiler application time T.sub.S. The two spoiler gradient pulses GS in their turn are framed by two diffusion gradient pulses GD, which are applied for their part with the diffusion application time T.sub.D.

(13) The amplitude AS of the spoiler gradient pulses GS and their spoiler application time T.sub.S are produced from the established spoiler moment M.sub.S. In an idealized case, in which the amplitude AS of the spoiler gradient pulses GS is predetermined as a constant by the type of construction of the apparatus, the spoiler application times T.sub.S would be produced in accordance with the formula T.sub.S=A.sub.S/M.sub.S.

(14) FIG. 2 depicts the relevant moments for the case in which the implicit spoil moment M.sub.A is smaller than the suppression moment M needed for suppression of coherences (M.sub.A<M). In this case an additional spoiler moment M.sub.S is needed, which in this example is established from M.sub.S=MM.sub.A. Such a spoiler moment M.sub.S can be introduced into the system via application of the spoiler gradient pulses GS shown in FIG. 1 with the spoiler application time T.sub.S.

(15) FIG. 3 depicts the relevant moments for the case in which the implicit spoil moment M.sub.A is greater than the suppression moment M needed for suppression of coherences M (M.sub.A>M). In this case an additional spoiler moment M.sub.S is not needed. A corresponding part of a pulse sequence, which differs from that shown in FIG. 1, is shown in FIG. 4.

(16) FIG. 4 shows an alternate pulse sequence PS based on that shown in FIG. 1 in the case in which the implicit spoil moment M.sub.A is greater than the suppression moment M needed for suppression of coherences M. In this case it is not necessary to apply spoiler gradient pulses GS, since an additional spoiler moment M.sub.S is not needed. In the example shown the RF refocusing pulse HR is therefore merely framed by two diffusion gradient pulses GD, which are each applied with the diffusion application time T.sub.D. The diffusion gradient pulses DG shown here can have a fixed distance from the RF refocusing pulse HR. If necessary, this distance can be filled with spoiler gradient pulses.

(17) FIG. 5 shows an alternate part of an example of a pulse sequence based on FIG. 1. The difference between the embodiment of FIG. 5 and the sequence shown in FIG. 1 is that the RF refocusing pulse HR shown in FIG. 1 comprises two RF refocusing pulses HRa here. This represents the case, for example, in which two 90 pulses rather than one 180 pulse are used as the refocusing pulse. No gradients are applied in this case between the two RF refocusing pulses HRa. They are viewed together as being representative of an RF refocusing pulse HR and are framed by diffusion gradient pulses GD and if necessary by spoiler gradient pulses GS.

(18) FIG. 6 shows a further part of an example of a pulse sequence, using FIG. 1 as its starting point. Here, by contrast with FIG. 1, a further RF refocusing pulse HR is applied, which for its part, is framed by two spoiler gradient pulses GS. These could be used for refocusing, e.g. for a repeated recording of data within the framework of a turbo spin echo recording (TSE) or of a gradient and spin echo recording (GRASE). Theoretically the application of further RF refocusing pulses HR would be possible in accordance with a corresponding scheme. Instead of the RF refocusing pulses HR shown here, a restoration pulse could also be applied to establish a longitudinal magnetization.

(19) FIG. 7 shows a flowchart for the execution sequence of the inventive method for control of a magnetic resonance tomography apparatus 1 (see FIG. 8) for diffusion imaging, in particular for showing the Intra-Voxel Incoherent Motion (IVIM). The block diagram in this case illustrates the most important method steps.

(20) In step I the determination of an amplitude and an application time TD of a diffusion gradient pulse GD in conjunction with a predetermined diffusion encoding for a pulse sequence PS takes place and an implicit spoil moment M.sub.A resulting from the diffusion gradient pulse GD is determined from this. In an ideal case of a constant diffusion gradient pulse GD with negligible rise time, the implicit spoil moment M.sub.A would be calculated in accordance with M.sub.A=G.sub.D.Math.T.sub.D.

(21) In step II the determination of coherences that would occur during the measurement takes place and a suppression moment M need for suppression of these coherences is established (see e.g. formulas (2) or (3) above). For example, with a factor F and a constant read-out gradient moment M.sub.R, the suppression moment would be calculated for M=F.Math.M.sub.R.

(22) In step III it is established whether the implicit spoil moment M.sub.A is greater or smaller than the suppression moment M. In the case of M.sub.AM, path W1 is selected for the further procedure, in the case M.sub.A<M path W1 is selected for the further procedure.

(23) In step IV, for the case in which M.sub.AM, no additional spoiler moment M.sub.S is needed. Thus no spoiler gradient pulse GS is applied in the pulse sequence, or expressed in numerical terms, the amplitude of the spoiler gradient pulse of GS A.sub.S=0 is set and/or the spoiler application time of T.sub.S=0 is set.

(24) In step V, for the case in which MA<M, an additional spoiler moment M.sub.S is established. It is calculated for example in accordance with M.sub.S=MM.sub.A.

(25) In step VI the spoiler amplitude A.sub.S and the necessary spoiler application time T.sub.S of the spoiler gradient pulses GS to be applied are calculated from the established spoiler moment M.sub.S. In an ideal case of a constant spoiler gradient pulse GS with negligible rise time and a constant spoiler amplitude A.sub.S predetermined by the device, the spoiler application time T.sub.S would be calculated in accordance with T.sub.S=M.sub.S/A.sub.S.

(26) In step VII a pulse sequence PS consisting of RF excitation pulse HA, RF refocusing pulse HR, diffusion gradient pulses GD and the spoiler gradient pulses GS, provided the latter produce a spoiler moment >0, is created with the corresponding application times T.sub.S, T.sub.D in each case and is used for controlling the image recording of a magnetic resonance tomography system.

(27) FIG. 8 shows a schematic illustration of a magnetic resonance tomography apparatus 1. This includes the magnetic resonance scanner 2 with an examination space 3 or patient tunnel, in which a patient or test object, in the body of which the actual examination object O is located, is positioned on a couch 8. Although, in the example shown, the examination object O is imaged in the torso, diffusion tensor imaging is also often used for recordings of the brain, since it is particularly well suited for imaging of neurological structures.

(28) The magnetic resonance scanner 2 is equipped in the usual way with a basic field magnet 4, a gradient coil arrangement 6 and an RF transmit antenna system 5 and an RF receive antenna system 7. In the exemplary embodiment shown, the RF transmit antenna system 5 is a whole body coil permanently built into the magnetic resonance scanner 2, while the RF receive antenna system 7 is composed of local coils arranged on the patient or test object (symbolized in FIG. 8 by just a single local coil). Basically, however, the whole body coil can also be used as an RF receive antenna system and the local coils as an RF transmit antenna system, provided these coils are able to be switched over into different operating modes in each case. The basic field magnet 4 here is embodied in the usual way so that it creates a basic magnetic field in the longitudinal direction of the patient, i.e. along the longitudinal axis running in the z-direction of the magnetic resonance scanner 2. In the usual way the gradient coil arrangement 6 has individually activatable gradient coils, in order to be able to switch gradients in the x-direction, y-direction, and the z-direction independently of one another. In addition the magnetic resonance scanner 2 contains shim coils (not shown), which can be embodied in the usual way.

(29) The magnetic resonance tomography apparatus 1 shown in FIG. 8 involves a whole-body system with a patient tunnel, into which a patient can be introduced completely. However, the invention can also be used in other magnetic resonance tomography apparatuses, e.g. with a C-shaped housing open at the side. The only significant factor is that corresponding recordings of the examination object O can be produced.

(30) The magnetic resonance tomography apparatus 1 further has a central control computer 13, for controlling the MR apparatus 1. This central control computer 13 has a sequence controller 14, with which the sequence of radio-frequency pulses (RF pulses) and gradient pulses is controlled as a function of a selected pulse sequence PS, or a sequence of a number of pulse sequences for recording a number of slices in a volume region of interest of the examination object is controlled within a measurement session. Such a pulse sequence PS can be predetermined and parameterized for example within a measurement or control protocol P. Usually different control protocols P for different measurements or measurement sessions are held in a memory 19 and can be selected by an operator (and if required changed if necessary) and then be used for carrying out the measurement. In the present case the control computer 13 contains pulse sequences for acquisition of the raw data.

(31) To emit the individual RF pulses of a pulse sequence PS, the central control computer 13 has a radio-frequency transmit device 15, which creates the RF pulses, amplifies them and feeds them via a suitable interface (not shown in detail) into the RF transmit antenna system 5. For control of the gradient coils of the gradient coil arrangement 6, in order to switch the gradient pulses in an appropriate manner according to the predetermined pulse sequence PS, the control computer 13 has a gradient system interface 16. Via this gradient system interface 16 the diffusion gradient pulses and spoiler gradient pulses could be applied. The sequence controller 14 communicates in a suitable way, e.g. by sending out sequence control data SD, with the radio-frequency transmit device 15 and the gradient system interface 16 for carrying out the pulse sequence PS.

(32) The control computer 13 also has a radio-frequency receive device 17 (likewise communicating in a suitable way with the sequence controller 14), in order to receive magnetic resonance signals within the read-out window predetermined by the pulse sequence PS coordinated by the RF receive antenna system 7 and in this way to acquire the raw data.

(33) A reconstruction computer 18 accepts the acquired raw data here and reconstructs magnetic resonance image data from the acquired raw data. This reconstruction is also done as a rule on the basis of parameters that can be predetermined in the respective measurement or control protocol P. The image data can then be stored in a memory 19 for example.

(34) The details of how suitable raw data can be acquired by the radiation of RF pulses and the switching of gradient pulses and how MR images or parameter maps can be reconstructed therefrom are basically known to those skilled in the art, and therefore need not be explained in more detail herein.

(35) The spoiler gradient pulse adaptation processor 20 is in communication with other units for the exchange of data, in particular with the gradient system interface 16 and the sequence controller 14. As an alternative, it can be a part of the sequence controller 14. The spoiler gradient pulse adaptation processor 20 has a number of units for determining or establishing different values. A determination unit 21 is designed for determining an implicit spoil moment M.sub.A from a diffusion gradient pulse GD and its application time T.sub.D. A determination unit 22 is designed for determining a suppression moment M for suppression of coherences, which would occur during a measurement. An establishment unit 23 is designed to establish a spoiler moment M.sub.S as a function of a comparison value and threshold value from the implicit spoiler moment M.sub.A and the suppression moment M, wherein, depending on whether this comparison value lies below or above the threshold value, different ways of calculation for the spoiler moment M.sub.S are applied. A determination unit 24 is designed for determination of a spoiler gradient pulse GS and its application time T.sub.S from the previously determined spoiler moment M.sub.S.

(36) The central control computer 13 can be operated via a terminal 11 with an input unit 10 and a display unit 9, via which the entire magnetic resonance tomography apparatus 1 can thus also be operated by an operator. Magnetic resonance tomography images can also be displayed on the display unit 9, and measurements can be planned and started and in particular control protocols P selected and if necessary modified by means of the input unit 10, if necessary in combination with the display unit 9

(37) The inventive magnetic resonance tomography apparatus 1 and in particular the control computer 13 can also have a number of further components, not shown herein in detail, which are usually present in systems of this type, such as a network interface, in order to connect the entire system to a network and be able to exchange raw data and/or image data or parameter maps, but also further data, such as for example patient-relevant data or control protocols.

(38) A wide diversity of measurement sequences, such as EPI measurement sequences or other measurement sequences for creation of diffusion-weighted images, are fundamentally known to those person skilled in the art.

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