CN104688228B - A kind of MR imaging method and equipment - Google Patents
A kind of MR imaging method and equipment Download PDFInfo
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- CN104688228B CN104688228B CN201510126269.9A CN201510126269A CN104688228B CN 104688228 B CN104688228 B CN 104688228B CN 201510126269 A CN201510126269 A CN 201510126269A CN 104688228 B CN104688228 B CN 104688228B
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves
- A61B5/055—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/01—Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
- A61B5/7225—Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
- A61B5/7235—Details of waveform analysis
- A61B5/7253—Details of waveform analysis characterised by using transforms
- A61B5/7257—Details of waveform analysis characterised by using transforms using Fourier transforms
Abstract
Embodiments of the present invention provide a kind of MR imaging method, the method includes: by periodically carrying out a magnetic resonance imaging pulse sequence, interleaved acquisition echo translation signal and stable state precession time reversal signal within the adjacent repetition period, this sequence includes that the first level putting on level selection direction selects gradient A, the second level selection gradient B, third layer face to select gradient C, the 4th level selection gradient D, layer 5 face to select gradient E, and meet relation MB+MC=MD+ME, MA/2+MB+MC+MA+MD=0, MA/2+MD+ME–MB=0.By the method for the above-mentioned embodiment of the present invention, can gather simultaneously echo translation signal and stable state precession time reversal signal, the method needed for the repetition period short, it is thus achieved that picture quality good, be one MR imaging method easily and fast.Additionally, embodiments of the present invention provide a kind of MR imaging apparatus.
Description
Technical field
Embodiments of the present invention relate to mr imaging technique field, and specifically, embodiments of the present invention relate to a kind of magnetic
Resonant imaging method and equipment.
Background technology
This part is it is intended that the embodiments of the present invention stated in claims provide background or context.Description herein
Not because being included in this part just recognize it is prior art.
Stable state precession time reversal (Time-reversed Fast Imaging with Steady-state Precession, time
Reversed FISP, or PSIF, or Contrast Enhanced Fourier Acquired Steady state, CE-FAST) signal
It it is the gtadient echo signal of a kind of heavy T2 weighting.Compared to tradition based on fast spin echo T2 weighted signal, it has collection
Speed is fast, the advantages such as selective absorbing rate is low.
Echo translation (Echo Shift, ES) signal is the gtadient echo signal of a kind of heavy T2* weighting, when it has long echo
Between the feature of (Echo Time, TE), the most sensitive for phase place change, be generally used for magnetic resonance temperature imaging etc. real
Time monitoring field.
Industry is typically to utilize two kinds of different magnetic resonance imaging pulse sequences at present, respectively acquisition time reversion stable state precession letter
Number and echo translate signal.
Summary of the invention
Monitor field in real time at some, in order to obtain temperature information and tissue T 2 change information, need to gather echo translation simultaneously
Signal and stable state precession time reversal signal, current industry utilize two kinds of different magnetic resonance imaging pulse sequences gather respectively with
The mode of upper two kinds of signals cannot meet this needs.
To this end, be highly desirable to the MR imaging method of a kind of improvement, echo translation signal and time can be gathered to meet simultaneously
The needs of reversion stable state precession signal.
In the present context, embodiments of the present invention expectation provides a kind of MR imaging method and equipment.
In the first aspect of embodiment of the present invention, it is provided that a kind of MR imaging method, for example, it is possible to include:
According to a working cycle, periodically carry out a step, until the total number of cycles performing described step reaches default phase
Position encoded number；
While periodically performing described step, utilize obtain time reversal stable state precession signal and echo translation signal fill out
Fill k-space；
After filling, the data of described k-space are carried out Fourier transformation, obtains magnetic resonance image (MRI)；
Described step includes sub-step 11～sub-step 18:
Sub-step 11, applies radio-frequency pulse, applies the first level simultaneously and selects gradient A；
Sub-step 12, applies the second level selection gradient B, first phase coding gradient U and the first pre-dephasing of reading
Gradient F；
Sub-step 13, applies the first readout gradient G, simultaneously collecting magnetic resonance signal, to the magnetic resonance letter currently collected
Number carry out analog digital conversion, obtain stable state precession time reversal signal；
Sub-step 14, applies the first reading rephasing gradient H, the first rephasing gradient V, third layer face selection gradient C；
Sub-step 15, applies described radio-frequency pulse, applies the first level simultaneously and selects gradient A；
Sub-step 16, applies the 4th level selection gradient D, first phase coding gradient U and the second pre-dephasing of reading
Gradient J；
Sub-step 17, applies the second readout gradient P, simultaneously collecting magnetic resonance signal, to the magnetic resonance letter currently collected
Number carry out analog digital conversion, obtain echo translation signal；
Sub-step 18, applies the second reading rephasing gradient Q, the first rephasing gradient V, layer 5 face selection gradient E；
Wherein, described the first level select gradient A, the second level selection gradient B, third layer face select gradient C, the 4th layer
Face selects gradient D, layer 5 face to select gradient E all to put on level selection direction, and meets following relation:
MB+MC=MD+ME,
MA/2+MB+MC+MA+MD=0,
MA/2+MD+ME–MB=0,
MAIt is the square of the first level selection gradient A,
MBIt is the square of the second level selection gradient B,
MCIt is the square of third layer face selection gradient C,
MDIt is the square of the 4th level selection gradient D,
MEIt is the square of layer 5 face selection gradient E,
Described first phase coding gradient U, the first rephasing gradient V all put on phase-encoding direction, and meet following relation:
MU=-MV,
MUIt is the square of first phase coding gradient U,
MVIt it is the square of the first rephasing gradient V；
Described first reads pre-dephasing gradient F, the first readout gradient G, the first reading rephasing gradient H, the second pre-dephasing of reading
Gradient J, the second readout gradient P, the second reading rephasing gradient Q all put on readout direction, and meet following relation:
First pre-dephasing gradient F of reading, the first reading rephasing gradient H and opposite polarity of the first readout gradient G, described second
Read pre-dephasing gradient J, the second reading rephasing gradient Q and opposite polarity of the second readout gradient P,
MF+MG+MH=0,
MJ+MP+MQ=0,
MFIt is the square of the first reading pre-dephasing gradient F,
MGIt is the square of the first readout gradient G,
MHIt is the square of the first reading rephasing gradient H,
MJIt is the square of the second reading pre-dephasing gradient J,
MPIt is the square of the second readout gradient P,
MQIt it is the square of the second reading rephasing gradient Q；
The described working cycle includes two repetition periods；
When performing described step, within first repetition period of working cycle, perform described sub-step 11～sub-step 14 successively,
Described sub-step 15～sub-step 18 is performed successively within second repetition period of working cycle, or, in the working cycle
Perform described sub-step 15～sub-step 18 in first repetition period successively, depend within second repetition period of working cycle
The described sub-step of secondary execution 11～sub-step 14；Further, often complete a working cycle, change described first phase coding ladder
Degree U and the square of the first rephasing gradient V.
In the second aspect of embodiment of the present invention, it is provided that a kind of MR imaging apparatus, such as, may include that process
Device, gradient coil, impulse ejection coil, reception of impulse coil, analog-digital converter, output device；
Described processor includes:
First processing unit, is arranged to control described impulse ejection coil transmissions radio-frequency pulse, controls described ladder simultaneously
Degree coil applies the first level and selects gradient A；
Second processing unit, is arranged to control described gradient coil and applies the second level selection gradient B, first phase volume
Code gradient U and first reads pre-dephasing gradient F；
3rd processing unit, is arranged to control described gradient coil and applies the first readout gradient G, control described arteries and veins simultaneously
Rush receiving coil collecting magnetic resonance signal, control the described analog-digital converter magnetic resonance signal to currently collecting and carry out mould
Number conversion is to obtain stable state precession time reversal signal；
Fourth processing unit, is arranged to control described gradient coil and applies the first reading rephasing gradient H, first time poly-ladder
Degree V, third layer face select gradient C；
5th processing unit, is arranged to control described impulse ejection coil transmissions radio-frequency pulse, controls described ladder simultaneously
Degree coil applies the first level and selects gradient A；
6th processing unit, is arranged to control described gradient coil and applies the 4th level selection gradient D, first phase volume
Code gradient U and second reads pre-dephasing gradient J；
7th processing unit, is arranged to control described gradient coil and applies the second readout gradient P, control described arteries and veins simultaneously
Rush receiving coil collecting magnetic resonance signal, control the described analog-digital converter magnetic resonance signal to currently collecting and carry out mould
Number conversion is to obtain echo translation signal；
8th processing unit, is arranged to control described gradient coil and applies the second reading rephasing gradient Q, first time poly-ladder
Degree V, layer 5 face select gradient E；
Wherein, described the first level select gradient A, the second level selection gradient B, third layer face select gradient C, the 4th layer
Face selects gradient D, layer 5 face to select gradient E all to put on level selection direction, and meets following relation:
MB+MC=MD+ME,
MA/2+MB+MC+MA+MD=0,
MA/2+MD+ME–MB=0,
MAIt is the square of the first level selection gradient A,
MBIt is the square of the second level selection gradient B,
MCIt is the square of third layer face selection gradient C,
MDIt is the square of the 4th level selection gradient D,
MEIt it is the square of layer 5 face selection gradient E；
Described first phase coding gradient U, the first rephasing gradient V all put on phase-encoding direction, and meet following relation:
MU=-MV,
MUIt is the square of first phase coding gradient U,
MVIt it is the square of the first rephasing gradient V；
Described first reads pre-dephasing gradient F, the first readout gradient G, the first reading rephasing gradient H, the second pre-dephasing of reading
Gradient J, the second readout gradient P, the second reading rephasing gradient Q all put on readout direction, and meet following relation:
First pre-dephasing gradient F of reading, the first reading rephasing gradient H and opposite polarity of the first readout gradient G, described second
Read pre-dephasing gradient J, the second reading rephasing gradient Q and opposite polarity of the second readout gradient P,
MF+MG+MH=0,
MJ+MP+MQ=0,
MFIt is the square of the first reading pre-dephasing gradient F,
MGIt is the square of the first readout gradient G,
MHIt is the square of the first reading rephasing gradient H,
MJIt is the square of the second reading pre-dephasing gradient J,
MPIt is the square of the second readout gradient P,
MQIt it is the square of the second reading rephasing gradient Q；
Described processor also includes:
Performance element, being arranged to a working cycle periodically works, and the described working cycle includes two
Repetition period, performance element triggers the first processing unit～everywhere within first repetition period of its working cycle successively
Reason unit, triggers the 5th processing unit～the 8th processing unit within second repetition period of its working cycle successively, or,
Performance element triggers the 5th processing unit～the 8th processing unit within first repetition period of its working cycle successively,
The first processing unit～fourth processing unit is triggered successively in second repetition period of its working cycle；
Cycling element, is arranged to control described performance element and periodically works, until what described performance element completed
Total number of cycles reaches default phase code number, wherein, when described performance element often completes a working cycle,
Cycling element changes described first phase coding gradient U and the square of the first rephasing gradient V；
Clock, provides clock signal for described performance element and described cycling element, so that described performance element and described
Cycling element determines initial time and the finish time of each repetition period；
Fill unit, be arranged to utilize described analog-digital converter to obtain time reversal stable state precession signal and echo put down
Shifting signal fills k-space；
Fourier transform unit, is arranged to the data to filling in complete k-space and carries out Fourier transformation, obtain magnetic
Resonance image；
Described output device, is arranged to export described magnetic resonance image (MRI).
MR imaging method according to embodiment of the present invention and equipment, can be by periodically performing a magnetic resonance imaging pulse
Sequence is interleaved acquisition echo translation signal and stable state precession time reversal signal within the adjacent repetition period, reaches to gather simultaneously
The purpose of both signals, further, utilizes the echo collected translation signal and stable state precession time reversal signal to carry out
Nuclear magnetic resonance；Needed for the MR imaging method of embodiment of the present invention, the repetition period is short, and signal collected signal to noise ratio is high,
The picture quality obtained is good, is one MR imaging method easily and fast.
Accompanying drawing explanation
In order to be illustrated more clearly that the embodiment of the present invention or technical scheme of the prior art, institute in embodiment being described below
The accompanying drawing used is needed to be briefly described, it should be apparent that, the accompanying drawing in describing below is only some enforcements of the present invention
Example, for those of ordinary skill in the art, on the premise of not paying creative work, it is also possible to according to these accompanying drawings
Obtain other accompanying drawing.
Fig. 1 schematically shows a magnetic resonance imaging pulse sequence of embodiment of the present invention；
Fig. 2 schematically shows another magnetic resonance imaging pulse sequence of embodiment of the present invention；
Fig. 3 schematically shows the structural representation of the MR imaging apparatus of embodiment of the present invention；
Fig. 4 schematically shows the structural representation of the processor of embodiment of the present invention；
Fig. 5 schematically shows a kind of working cycle of embodiment of the present invention；
Fig. 6 schematically shows the another kind of working cycle of embodiment of the present invention；
Fig. 7 schematically shows the schematic flow sheet of the MR imaging method of embodiment of the present invention；
Fig. 8 is four magnetic resonance image (MRI) of the exemplary case study on implementation acquisition of embodiment of the present invention.
Detailed description of the invention
Principle and the spirit of the present invention are described below with reference to some illustrative embodiments.Should be appreciated that and provide these in fact
The mode of executing is only used to make those skilled in the art better understood when and then realize the present invention, and the most by any way
Limit the scope of the present invention.On the contrary, it is provided that these embodiments are to make the disclosure more thorough and complete, and can
The scope of the present disclosure is intactly conveyed to those skilled in the art.
Art technology skilled artisan knows that, embodiments of the present invention can be implemented as a kind of system, device, equipment, side
Method or computer program.Therefore, the disclosure can be to be implemented as following form, it may be assumed that hardware, completely completely
Software (includes firmware, resident software, microcode etc.), or the form that hardware and software combines.
According to the embodiment of the present invention, it is proposed that a kind of MR imaging method and equipment.
In this article, it is to be understood that:
1, alphabetical A, B, C, D, E, F, G, H, J, P, Q, U, V, S, T in literary composition and in accompanying drawing the most only use
In differentiation, and not there is any limitation.
2, gradient: include putting on the gradient in level selection direction, putting on the gradient of phase-encoding direction and apply
Gradient in readout direction.
3, the first level selects gradient A: put on level selection direction, matches to excite organism certain with radio-frequency pulse
One layer (i.e. excitation layer), the first level selects the persistent period of gradient A, the time dependent function of gradient fields by excitation layer
Thickness and the parameter such as bandwidth of radio-frequency pulse determine.
3, first phase coding gradient U: put on phase-encoding direction, for the nuclear magnetic resonance of two dimension, make in excitation layer
Be positioned on same two dimensional surface possesses different initial phases from copper plate, to distinguish the position of different voxel.
4, the first rephasing gradient V: put on phase-encoding direction, for the nuclear magnetic resonance of two dimension, makes to be positioned in excitation layer
The phase place from copper plate on same two dimensional surface is returned poly-, and the first rephasing gradient V encodes the intensity phase of gradient U with first phase
Same, opposite polarity.
5, second phase coding gradient S: put on level selection direction, for three-dimensional nuclear magnetic resonance, make in excitation layer
Be perpendicular on two dimensional surface direction possesses different initial phases from copper plate, to distinguish different two dimensional surfaces.
6, the second rephasing gradient T: put on level selection direction, for three-dimensional nuclear magnetic resonance, makes in excitation layer vertical
The phase place from copper plate on two dimensional surface direction is returned poly-, and the second rephasing gradient T encodes the intensity phase of gradient S with second phase
Same, opposite polarity.
7, phase code number: depend on the resolution of magnetic resonance image (MRI), the total number of cycles of performance element periodic duty (or
Periodically perform the total number of cycles of this process of magnetic resonance pulse sequence) corresponding with phase code number.
8, the first readout gradient G: matching with RF receiving coil and invert stable state precession signal with acquisition time, first reads
The persistent period of gradient G, the time dependent function of gradient fields are big by the visual field of sampling number, acquisition bandwidth and readout direction
The parameter such as little determines.
9, the second readout gradient P: match with RF receiving coil to gather echo translation signal, the second readout gradient P's
Persistent period, the time dependent function of gradient fields are by parameters such as the visual field sizes of sampling number, acquisition bandwidth and readout direction
Determine.
10, output device: output magnetic resonance image (MRI), can be the device such as display, printer.
Summary of the invention
At present at magnetic resonance imaging arts, it is common that utilize two kinds of different magnetic resonance imaging pulse sequences, acquisition time respectively
Reversion stable state precession signal and echo translation signal, but monitor field in real time at some, in order to obtain temperature information and tissue T 2
Change information, needs to gather echo translation signal and stable state precession time reversal signal simultaneously, and current industry utilizes two kinds of differences
Magnetic resonance imaging pulse sequence gather the mode of both the above signal respectively and cannot meet this needs.
To this end, the invention provides a kind of MR imaging method, in the method, by periodically carrying out a magnetic resonance
Imaging pulse sequence, can believe within the adjacent repetition period in interleaved acquisition echo translation signal and stable state precession time reversal
Number, further, utilize the both signals collected to fill k-space, and the k-space filled carried out Fourier transformation,
Can be obtained by corresponding magnetic resonance image (MRI).
With reference to Fig. 1, the magnetic resonance imaging pulse sequence performed for the present invention, perform magnetic resonance imaging pulse sequence shown in Fig. 1
Process can be to comprise the steps that (first acquisition time inverts stable state precession signal within the adjacent repetition period, then gathers back
Popin shifting signal):
Step S11, applies radio-frequency pulse, applies the first level simultaneously and selects gradient A；
Step S12, applies the second level selection gradient B, first phase coding gradient U and the first pre-dephasing gradient F of reading；
Step S13, applies the first readout gradient G, simultaneously collecting magnetic resonance signal, obtains stable state precession time reversal signal；
Step S14, applies the first reading rephasing gradient H, the first rephasing gradient V, third layer face selection gradient C；
Step S15, applies described radio-frequency pulse, applies the first level simultaneously and selects gradient A；
Step S16, applies the 4th level selection gradient D, first phase coding gradient U and the second pre-dephasing gradient J of reading；
Step S17, applies the second readout gradient P, simultaneously collecting magnetic resonance signal, obtains echo translation signal；
Step S18, applies the second reading rephasing gradient Q, the first rephasing gradient V, layer 5 face selection gradient E.
In Fig. 1, the first level selects gradient A, the second level selection gradient B, third layer face to select gradient C, the 4th aspect
Select gradient D, layer 5 face to select gradient E all to put on level selection direction, and meet following relation:
MB+MC=MD+ME,
MA/2+MB+MC+MA+MD=0,
MA/2+MD+ME–MB=0.
Alternatively, the magnetic resonance imaging pulse sequence that the present invention uses can also is that the form shown in Fig. 2, performs magnetic shown in Fig. 2
The process of resonance image-forming pulse train can be to comprise the steps (first to gather echo translation letter within the adjacent repetition period
Number, then acquisition time reversion stable state precession signal):
Step s11, applies described radio-frequency pulse, applies the first level simultaneously and selects gradient A；
Step s12, applies the 4th level selection gradient D, first phase coding gradient U and the second pre-dephasing gradient J of reading；
Step s13, applies the second readout gradient P, simultaneously collecting magnetic resonance signal, obtains echo translation signal；
Step s14, applies the second reading rephasing gradient Q, the first rephasing gradient V, layer 5 face selection gradient E；
Step s15, applies radio-frequency pulse, applies the first level simultaneously and selects gradient A；
Step s16, applies the second level selection gradient B, first phase coding gradient U and the first pre-dephasing gradient F of reading；
Step s17, applies the first readout gradient G, simultaneously collecting magnetic resonance signal, obtains stable state precession time reversal signal；
Step s18, applies the first reading rephasing gradient H, the first rephasing gradient V, third layer face selection gradient C.
In Fig. 2, the first level selects gradient A, the second level selection gradient B, third layer face to select gradient C, the 4th aspect
Select gradient D, layer 5 face to select gradient E all to put on level selection direction, and meet following relation:
MB+MC=MD+ME,
MA/2+MB+MC+MA+MD=0,
MA/2+MD+ME–MB=0.
After the ultimate principle describing the present invention, introduce the various non-limiting embodiment of the present invention in detail below.
Application scenarios overview
During nuclear magnetic resonance, MR imaging apparatus applies RF pulse-to-pulse according to magnetic resonance imaging pulse sequence pair organism
Punching and magnetic field gradient, make the atomic nucleus generation precession in bio-tissue and energy level transition, MR imaging apparatus detection atom
The magnetization vector that core produces in this motor process, using testing result as magnetic resonance signal, finally utilizes magnetic resonance signal
Carry out nuclear magnetic resonance.
MR imaging apparatus can be any type being exemplified below out: magneto or electromagnetic type are (according to magnetic field producing method
Classification), open type magnetic build, closed magnet type or distinctive appearance magnet type (according to the form class of main magnet) are low
Field, midfield, High-Field or super high field strong type (classifying according to the field intensity of main magnet).
Example devices
Below in conjunction with application scenarios, the MR imaging apparatus of exemplary embodiment of the invention is introduced.
It should be noted that above-mentioned application scenarios is for only for ease of and understand that spirit and principles of the present invention illustrate, the present invention
Embodiment the most unrestricted.On the contrary, embodiments of the present invention can apply to any scene being suitable for.
For example, with reference to Fig. 3, the MR imaging apparatus structural representation provided for the embodiment of the present invention.As it is shown on figure 3, magnetic
Resonance image-forming equipment may include that processor 31, gradient coil 32, impulse ejection coil 33, reception of impulse coil 34, mould
Number converter 35, output device 36.
Seeing Fig. 4, processor 31 has 31 bodies and may include that at first processing unit the 311, second processing unit the 312, the 3rd
Reason unit 313, fourth processing unit the 314, the 5th processing unit the 315, the 6th processing unit the 316, the 7th processing unit 317,
8th processing unit 318, and performance element 31-Z, cycling element 31-X, clock 31-S, filling unit 31-T and Fourier
Converter unit 31-F.
The work process of the MR imaging apparatus that the embodiment of the present invention provides is as follows:
Operator start MR imaging apparatus, various parameters that MR imaging apparatus sets according to operator (such as:
The field range of readout direction, the thickness of excitation layer, the resolution of magnetic resonance image (MRI), the flip angle of radio-frequency pulse, repetition week
The duration etc. of phase) start working.
After startup, the clock 31-S signal that cycling element 31-X and performance element 31-Z provides according to clock 31-S determines each
The initial time of individual repetition period and finish time, cycling element 31-X controls performance element 31-Z and periodically works, and right
The cycle that performance element completes counts, until the total number of cycles that performance element completes reaches default phase code number.
Performance element 31-Z each cycle sex work once experiences two repetition periods, for convenience of introducing, below by every for performance element 31-Z
Periodic duty is once referred to as a working cycle (including two repetition periods), introduces performance element 31-Z below with reference to Fig. 5
The detailed process of each working cycle, as it is shown in figure 5, time shaft express time direction from left to right.
(1) the performance element 31-Z initial time first repetition period triggers the first processing unit 311.First processes list
Unit 311, after triggering, controls impulse ejection coil 33 immediately and launches radio-frequency pulse, control gradient coil 32 in aspect simultaneously
Choice direction applies the first level and selects gradient A.
(2), after performance element 31-Z triggers the first processing unit 311, the second processing unit 312 is triggered.Second processing unit
312 after triggering, and controls gradient coil 32 immediately and applies the second level selection gradient B in level selection direction, compiles in phase place
Code direction applies first phase coding gradient U, and applies the first pre-dephasing gradient F of reading in readout direction.
(3), after performance element 31-Z triggers the second processing unit 312, the 3rd processing unit 313 is triggered.3rd processing unit
313 after triggering, and controls gradient coil 32 immediately and applies the first readout gradient G in readout direction, controls reception of impulse simultaneously
Coil 34 collecting magnetic resonance signal, and control the analog-digital converter 35 magnetic resonance signal to currently collecting carry out analog digital conversion
To obtain stable state precession time reversal signal.
(4), after performance element 31-Z triggers the 3rd processing unit 313, fourth processing unit 314 is triggered.Fourth processing unit
314 after triggering, and controls gradient coil 32 immediately and applies the first reading rephasing gradient H in readout direction, in phase code side
To applying the first rephasing gradient V, and apply third layer face selection gradient C in level selection direction.
So far, first repetition period terminates, and enters second repetition period.
(5) the performance element 31-Z initial time second repetition period triggers the 5th processing unit 315.5th processes list
Unit 315, after triggering, controls impulse ejection coil 33 immediately and launches radio-frequency pulse, control gradient coil 32 in aspect simultaneously
Apply the first level in choice direction and select gradient A.
(6), after performance element 31-Z triggers the 5th processing unit 315, the 6th processing unit 316 is triggered.6th processing unit
316 after triggering, and controls gradient coil 32 immediately and applies the 4th level selection gradient D on level selection direction, in phase place
Coding staff upwards applies first phase coding gradient U, and applies the second pre-dephasing gradient J of reading in the readout direction.
(7), after performance element 31-Z triggers the 6th processing unit 316, the 7th processing unit 317 is triggered.7th processing unit
317 after triggering, and controls gradient coil 32 immediately and applies the second readout gradient P in readout direction, controls reception of impulse simultaneously
Coil 34 collecting magnetic resonance signal, controls the analog-digital converter 35 magnetic resonance signal to currently collecting and carries out analog digital conversion to obtain
Signal is translated to echo.
(8), after performance element 31-Z triggers the 7th processing unit 317, the 8th processing unit 318 is triggered.8th processing unit
318 after triggering, and controls gradient coil 32 immediately and applies the second reading rephasing gradient Q in readout direction, in phase code side
To applying the first rephasing gradient V, and apply layer 5 face selection gradient E in level selection direction.
So far, second repetition period also terminates, and performance element 31-Z enters the subsequent work cycle.
In working cycle shown in Fig. 5, each gradient needs to meet following condition:
MB+MC=MD+ME
MA/2+MB+MC+MA+MD=0
MA/2+MD+ME–MB=0
MU=-MV
MF+MG+MH=0
MJ+MP+MQ=0
MAIt is the square of the first level selection gradient A,
MBIt is the square of the second level selection gradient B,
MCIt is the square of third layer face selection gradient C,
MDIt is the square of the 4th level selection gradient D,
MEIt is the square of layer 5 face selection gradient E,
MUIt is the square of first phase coding gradient U,
MVIt is the square of the first rephasing gradient V,
MFIt is the square of the first reading pre-dephasing gradient F,
MGIt is the square of the first readout gradient G,
MHIt is the square of the first reading rephasing gradient H,
MJIt is the square of the second reading pre-dephasing gradient J,
MPIt is the square of the second readout gradient P,
MQIt is the square of the second reading rephasing gradient Q,
Further, first reads pre-dephasing gradient F, the first reading rephasing gradient H and opposite polarity of the first readout gradient G, the
Two read pre-dephasing gradient J, the second reading rephasing gradient Q and opposite polarity of the second readout gradient P.
While performance element 31-Z periodically works, fill unit 31-T and be utilized respectively the time that analog-digital converter 35 obtains
Reversion stable state precession signal and echo translation signal fill k-space.
After filling k-space is complete, the Fourier transform unit 31-F k-space to utilizing stable state precession time reversal signal to fill
In data carry out Fourier transformation, obtain the magnetic resonance image (MRI) that stable state precession time reversal signal is corresponding, and, Fourier
Data in the converter unit 31-F k-space to utilizing echo translation signal to fill carry out Fourier transformation, obtain echo translation letter
Number corresponding magnetic resonance image (MRI).
Finally, output device 36 exports both magnetic resonance image (MRI).
It should be noted that be make collection time reversal stable state precession signal and echo translation signal cover whole k-space with
Reaching the purpose of two-dimensional imaging, cycling element 31-X is controlling while performance element 31-Z periodically works, be also responsible for as
Lower work: performance element 31-Z often completes a working cycle, cycling element 31-X changes first phase coding gradient U and the
The square of one rephasing gradient V, say, that first phase coding gradient U in any one working cycle and the first rephasing gradient
V is identical, and often experiences a working cycle, and first phase coding gradient U and the first rephasing gradient V occur one-shot change.
Working cycle shown in Fig. 5, obtain stable state precession time reversal signal first repetition period, second repetition
Cycle obtains echo translation signal.
Alternatively, in the working cycle of performance element 31-Z, it is also possible to obtain echo translation signal first repetition period,
Obtain stable state precession time reversal signal second repetition period, introduce such working cycle below in conjunction with Fig. 6.
(1) the performance element 31-Z initial time second repetition period triggers the 5th processing unit 315.5th processes list
Unit 315, after triggering, controls impulse ejection coil 33 immediately and launches radio-frequency pulse, control gradient coil 32 in aspect simultaneously
Apply the first level in choice direction and select gradient A.
(2), after performance element 31-Z triggers the 5th processing unit 315, the 6th processing unit 316 is triggered.6th processing unit
316 after triggering, and controls gradient coil 32 immediately and applies the 4th level selection gradient D on level selection direction, in phase place
Coding staff upwards applies first phase coding gradient U, and applies the second pre-dephasing gradient J of reading in the readout direction.
(3), after performance element 31-Z triggers the 6th processing unit 316, the 7th processing unit 317 is triggered.7th processing unit
317 after triggering, and controls gradient coil 32 immediately and applies the second readout gradient P in readout direction, controls reception of impulse simultaneously
Coil 34 collecting magnetic resonance signal, controls the analog-digital converter 35 magnetic resonance signal to currently collecting and carries out analog digital conversion to obtain
Signal is translated to echo.
(4), after performance element 31-Z triggers the 7th processing unit 317, the 8th processing unit 318 is triggered.8th processing unit
318 after triggering, and controls gradient coil 32 immediately and applies the second reading rephasing gradient Q in readout direction, in phase code side
To applying the first rephasing gradient V, and apply layer 5 face selection gradient E in level selection direction.
So far, first repetition period terminates, and enters second repetition period.
(5) the performance element 31-Z initial time first repetition period triggers the first processing unit 311.First processes list
Unit 311, after triggering, controls impulse ejection coil 33 immediately and launches radio-frequency pulse, control gradient coil 32 in aspect simultaneously
Choice direction applies the first level and selects gradient A.
(6), after performance element 31-Z triggers the first processing unit 311, the second processing unit 312 is triggered.Second processing unit
312 after triggering, and controls gradient coil 32 immediately and applies the second level selection gradient B in level selection direction, compiles in phase place
Code direction applies first phase coding gradient U, and applies the first pre-dephasing gradient F of reading in readout direction.
(7), after performance element 31-Z triggers the second processing unit 312, the 3rd processing unit 313 is triggered.3rd processing unit
313 after triggering, and controls gradient coil 32 immediately and applies the first readout gradient G in readout direction, controls reception of impulse simultaneously
Coil 34 collecting magnetic resonance signal, and control the analog-digital converter 35 magnetic resonance signal to currently collecting carry out analog digital conversion
To obtain stable state precession time reversal signal.
(8), after performance element 31-Z triggers the 3rd processing unit 313, fourth processing unit 314 is triggered.Fourth processing unit
314 after triggering, and controls gradient coil 32 immediately and applies the first reading rephasing gradient H in readout direction, in phase code side
To applying the first rephasing gradient V, and apply third layer face selection gradient C in level selection direction.
So far, second repetition period also terminates, and performance element 31-Z enters the subsequent work cycle.
In working cycle shown in Fig. 6, each gradient is also required to meet following condition:
MB+MC=MD+ME
MA/2+MB+MC+MA+MD=0
MA/2+MD+ME–MB=0
MU=-MV
MF+MG+MH=0
MJ+MP+MQ=0
Further, first reads pre-dephasing gradient F, the first reading rephasing gradient H and opposite polarity of the first readout gradient G, the
Two read pre-dephasing gradient J, the second reading rephasing gradient Q and opposite polarity of the second readout gradient P.
During it should be noted that performance element 31-Z periodically works, can always use the working cycle shown in Fig. 5, also
Can always use the working cycle shown in Fig. 6, it is also possible to sometimes use the working cycle shown in Fig. 5, sometimes use Fig. 6 institute
The working cycle shown.
If the free induction decay of radio-frequency pulse (Free Induction Decay, FID) signal is not because decay is held completely
Continue the period of collecting magnetic resonance signal, collecting magnetic resonance signal will have been interfered.Alternatively, so that radio frequency
The free induction decay signal of pulse does not affect collecting magnetic resonance signal, and the first level selects gradient A, the second level selection ladder
Spend B, the 4th level selection gradient D also needs to meet following condition:
∣MA/2+MB∣≧∣MA/ 2, MA/2+MD∣≧∣MA/ 2 (conditions 1)
Alternatively, in order to meet above-mentioned condition 1, can make the first level select gradient A, the second level selection gradient B, the
Three level selection gradients C, the 4th level selection gradient D, layer 5 face select gradient E to meet following relation:
MB=MA,
MC=MA/ 2,
MD=0,
ME=3MA/2。
Alternatively, in order to meet above-mentioned condition 1, it is also possible to make the first level select gradient A, the second level selection gradient B,
Third layer face selects gradient C, the 4th level selection gradient D, layer 5 face to select gradient E to meet following relation:
MB=MA/ 2,
MC=MA/ 2,
MD=3MA/ 2,
ME=3MA/2。
(stable state precession signal time reversal and echo translation is corresponded respectively in order to ensure the two width magnetic resonance image (MRI) finally given
Signal) there is identical resolution, and have the compensation effect that preferably flows, alternatively, make the first reading pre-dephasing gradient F,
First readout gradient G, the first reading rephasing gradient H, the second pre-dephasing gradient J of reading, the second readout gradient P, the second reading
Rephasing gradient Q meets following relation: MF=MJ=MH=MQ=MG/ 2=MP/2。
In order to obtain the magnetic resonance image (MRI) of three-dimensional, alternatively, when the second processing unit 312 and the 6th processing unit 316 are triggered
Also controlling gradient coil 32 and apply second phase coding gradient S in level selection direction, fourth processing unit 314 and the 8th processes
Also control gradient coil 32 when unit 318 is triggered and apply the second rephasing gradient T in level selection direction；Wherein, second phase
The square M of coding gradient SS, the square M of the second rephasing gradient TTMeet following relation: MS=-MT, and, for making collection
Time reversal stable state precession signal and echo translation signal under three-dimensional situation, cover whole k-space to reach the mesh of three-dimensional imaging
, cycling element 31-X, while control performance element 31-Z periodically works, is also responsible for working as follows: in performing list
When unit 31-Z often completes a working cycle, change described second phase coding gradient S and the square of the second rephasing gradient T, the most just
Being to say, first phase coding gradient U and the first rephasing gradient V in any one working cycle are identical, and often experience a work
Making the cycle, there is one-shot change in first phase coding gradient U and the first rephasing gradient V.
Illustrative methods
After the equipment describing exemplary embodiment of the invention, it follows that with reference to Fig. 1, Fig. 2 and Fig. 7 to the present invention
The MR imaging method of illustrative embodiments is introduced.
The schematic flow sheet of the MR imaging method that Fig. 7 provides for the embodiment of the present invention.Referring to this figure, magnetic resonance is become
The flow process of image space method is described.
Step 701, starts MR imaging apparatus.
Step 702, processor reads various parameters, such as: the field range of readout direction, the thickness of excitation layer, magnetic resonance
The resolution of image, the flip angle of radio-frequency pulse, the duration of repetition period, the encoded number of phase code and perform list
Unit's employing what type of working cycle (gather echo translation signal after first acquisition time reversion stable state precession signal, or, first
Gather acquisition time reversion stable state precession signal after echo translation signal) etc..
Step 703, performance element, according to the parameter read, determines the type (two select) of current operating cycle, if such as
Type (gathering echo translation signal after first acquisition time reversion stable state precession signal) shown in Fig. 5, then perform step 704,
If type as shown in Figure 6 (first gathers acquisition time reversion stable state precession signal after echo translation signal), then perform step
Rapid 705.Alternatively, parameter could be arranged to: performance element always works according to the working cycle as shown in Figure 5, it is also possible to
Always work according to the working cycle as shown in Figure 6, it is also possible to sometimes work according to the working cycle as shown in Figure 5, sometimes press
Work according to the working cycle as shown in Figure 6.
Step 704 includes:
Step 7041, impulse ejection coil applies radio-frequency pulse, and gradient coil applies first in level selection direction simultaneously
Level selection gradient A.
Step 7042, gradient coil applies the second level selection gradient B, executes at phase-encoding direction in level selection direction
Add first phase coding gradient U, and apply the first pre-dephasing gradient F of reading in readout direction.Alternatively, gradient line
Circle can also apply second phase coding gradient S in level selection direction, and applies in level selection direction second time to gather
Gradient T.
Step 7043, gradient coil applies the first readout gradient G in readout direction, and the magnetic of reception of impulse signals collecting simultaneously is altogether
Shake signal, and the analog-digital converter magnetic resonance signal to currently collecting carries out analog digital conversion, obtains stable state time reversal and enters
Dynamic signal.
Step 7044, gradient coil applies the first reading rephasing gradient H in readout direction, applies the at phase-encoding direction
One rephasing gradient V, applies third layer face and selects gradient C in level selection direction.
Step 705 includes:
Step 7051, impulse ejection coil applies described radio-frequency pulse, and gradient coil applies in level selection direction simultaneously
The first level selects gradient A.
Step 7052, gradient coil applies the 4th level selection gradient D, executes at phase-encoding direction in level selection direction
Add first phase coding gradient U, and apply the second pre-dephasing gradient J of reading in readout direction.Alternatively, gradient line
Circle can also apply second phase coding gradient S in level selection direction, and applies in level selection direction second time to gather
Gradient T.
Step 7053, gradient coil applies the second readout gradient P in readout direction, and reception of impulse coil gathers magnetic altogether simultaneously
Shake signal, and the analog-digital converter magnetic resonance signal to currently collecting carries out analog digital conversion, obtains echo translation signal；
Step 7054, gradient coil applies the second reading rephasing gradient Q in readout direction, applies the at phase-encoding direction
One rephasing gradient V, applies layer 5 face and selects gradient E in level selection direction.
Step 706, fills unit and utilizes the stable state precession time reversal signal obtained to fill k-space, and utilize
The echo translation signal obtained fills k-space.
Step 707, whether Fourier transform unit real-time judge k-space fills complete, if filling complete, then in k-space
Data carry out Fourier transformation, obtain correspondence magnetic resonance image (MRI).
Step 708, cycling element is according to the parameter read, it is judged that whether the total number of cycles that performance element completes reaches phase place is compiled
The encoded number of code, if it is not, then perform step 709, the most then nuclear magnetic resonance terminates.
Step 709, changes first phase coding gradient U and the square of the first rephasing gradient V, and returns step 703.Alternatively,
When being applied with second phase coding gradient S and the second rephasing gradient T in step 704 or step 705, step 709 also needs to change
Become second phase coding gradient S and the square of the second rephasing gradient T.
Exemplary case study on implementation
After the equipment describing exemplary embodiment of the invention and method, it follows that illustrate that the present invention shows with reference to Fig. 8
The magnetic resonance image (MRI) effect that example case study on implementation obtains.
This exemplary case study on implementation utilizes same MR imaging apparatus to carry out three nuclear magnetic resonance processes, respectively:
1, use illustrative methods of the present invention acquisition time reversion stable state precession signal simultaneously and echo translation signal, obtain Fig. 8
In the magnetic resonance image (MRI) that shows of (a), (b).
2, use the magnetic resonance imaging pulse sequence acquisition stable state time reversal precession signal that current industry is conventional, obtain in Fig. 8
C magnetic resonance image (MRI) that () shows.
3, use the magnetic resonance imaging pulse sequence acquisition echo translation signal that current industry is conventional, obtain that (d) in Fig. 8 show
Magnetic resonance image (MRI).
When MR imaging apparatus carries out above three nuclear magnetic resonance processes, the identical parameters having is:
The field range of readout direction: 384mm
The field range of phase directional: 384mm
The thickness of excitation layer: 5mm
The resolution of magnetic resonance image (MRI): 384*384
The flip angle of radio-frequency pulse: 20degree
Repetition period: 4.5ms
Echo time: 2.35ms
Acquisition bandwidth: 592Hz/pixel
Although it should be noted that, be referred to some unit of MR imaging apparatus in above-detailed, but this division
The most enforceable.It practice, according to the embodiment of the present invention, the feature of two or more unit above-described
Can embody in a unit with function.Otherwise, feature and the function of an above-described unit can be drawn further
It is divided into and being embodied by multiple unit.
Although additionally, describe the operation of the inventive method in the accompanying drawings with particular order, but, this does not requires that or secretly
Show and must operate to perform these according to this particular order, or having to carry out the most shown operation could realize desired knot
Really.Additionally or alternatively, it is convenient to omit some step, multiple steps are merged into a step and performs, and/or by one
Step is decomposed into multiple step and performs.
Although describing spirit and principles of the present invention by reference to some detailed description of the invention, it should be appreciated that, the present invention
Being not limited to disclosed detailed description of the invention, the division to each side does not means that the feature in these aspects can not combine yet
To be benefited, this division merely to statement convenience.It is contemplated that contain spirit and scope of the appended claims
Various amendments included by and equivalent arrangements.
Those skilled in the art are it will also be appreciated that the various illustrative components, blocks (illustrative that list of the embodiment of the present invention
Logical block), unit, and step can pass through electronic hardware, computer software, or both combinations realize.For
Clearly show that the replaceability (interchangeability) of hardware and software, above-mentioned various illustrative components (illustrative
Components), unit and step the most universally describe their function.Such function is by hardware or soft
Part realizes depending on specifically applying the design requirement with whole system.Those skilled in the art can be specific for every kind
Application, it is possible to use the function described in the realization of various methods, but this realization is understood not to protect beyond the embodiment of the present invention
The scope protected.
Various illustrative logical block described in the embodiment of the present invention, or unit, or device can pass through general procedure
Device, digital signal processor, special IC (ASIC), field programmable gate array or other programmable logic device,
Discrete gate or transistor logic, discrete hardware components, or the design of any of the above described combination realize or operate described function.
General processor can be microprocessor, alternatively, this general processor can also be any traditional processor, controller,
Microcontroller or state machine.Processor can also realize by calculating the combination of device, such as digital signal processor and micro-
Processor, multi-microprocessor, one or more microprocessors one Digital Signal Processor Core of associating, or other class any
As configure and realize.
Method or the step of algorithm described in the embodiment of the present invention can be directly embedded into hardware, the software mould of processor execution
Block or the combination of both.Software module can be stored in RAM memory, flash memory, ROM memory, EPROM
Other arbitrary shape in memorizer, eeprom memory, depositor, hard disk, moveable magnetic disc, CD-ROM or this area
In the storage medium of formula.Exemplarily, storage medium can be connected with processor, so that processor can be from storage medium
Middle reading information, it is possible to deposit write information to storage medium.Alternatively, storage medium can also be integrated in processor.Place
Reason device and storage medium can be arranged in ASIC, and ASIC can be arranged in user terminal.Alternatively, processor and depositing
Storage medium can also be arranged in the different parts in user terminal.
In one or more exemplary designs, the above-mentioned functions described by the embodiment of the present invention can hardware, software,
The combination in any of firmware or this three realizes.If realized in software, these functions can store the matchmaker with computer-readable
On Jie, or it is transmitted on the medium of computer-readable with one or more instructions or code form.Computer readable medium includes computer
Store medium and be easy to so that allowing computer program transfer to the telecommunication media in other place from a place.Storage medium can be
Any general or special computer can be with the useable medium of access.Such as, such computer readable media can include but not
It is limited to RAM, ROM, EEPROM, CD-ROM or other optical disc storage, disk storage or other magnetic storage device,
Other any may be used for carrying or storage with instruction or data structure and other can by general or special computer or general or
Special processor reads the medium of the program code of form.Additionally, any connection can be properly termed computer-readable
Medium, such as, if software is by coaxial cable, a light from a web-site, server or other remote resource
Fiber-optic cable, twisted-pair feeder, Digital Subscriber Line (DSL) or with the wireless way for transmittings such as the most infrared, wireless and microwave also by
It is included in defined computer readable medium.Described video disc (disk) and disk (disc) include Zip disk, radium-shine
Dish, CD, DVD, floppy disk and Blu-ray Disc, disk is generally with magnetic duplication data, and video disc generally carries out light with laser
Learn and replicate data.Combinations of the above can also be included in computer readable medium.
Claims (12)
1. a MR imaging method, wherein, including:
According to a working cycle, periodically carry out a step, until the total number of cycles performing described step reaches default phase
Position encoded number；
While periodically performing described step, utilize obtain time reversal stable state precession signal and echo translation signal fill out
Fill k-space；
After filling, the data of described k-space are carried out Fourier transformation, obtains magnetic resonance image (MRI)；
Described step includes sub-step 11～sub-step 18:
Sub-step 11, applies radio-frequency pulse, applies the first level simultaneously and selects gradient A；
Sub-step 12, applies the second level selection gradient B, first phase coding gradient U and the first pre-dephasing of reading
Gradient F；
Sub-step 13, applies the first readout gradient G, simultaneously collecting magnetic resonance signal, to the magnetic resonance letter currently collected
Number carry out analog digital conversion, obtain stable state precession time reversal signal；
Sub-step 14, applies the first reading rephasing gradient H, the first rephasing gradient V, third layer face selection gradient C；
Sub-step 15, applies described radio-frequency pulse, applies the first level simultaneously and selects gradient A；
Sub-step 16, applies the 4th level selection gradient D, first phase coding gradient U and the second pre-dephasing of reading
Gradient J；
Sub-step 17, applies the second readout gradient P, simultaneously collecting magnetic resonance signal, to the magnetic resonance letter currently collected
Number carry out analog digital conversion, obtain echo translation signal；
Sub-step 18, applies the second reading rephasing gradient Q, the first rephasing gradient V, layer 5 face selection gradient E；
Wherein, described the first level select gradient A, the second level selection gradient B, third layer face select gradient C, the 4th layer
Face selects gradient D, layer 5 face to select gradient E all to put on level selection direction, and meets following relation:
MB+MC=MD+ME,
MA/2+MB+MC+MA+MD=0,
MA/2+MD+ME–MB=0,
MAIt is the square of the first level selection gradient A,
MBIt is the square of the second level selection gradient B,
MCIt is the square of third layer face selection gradient C,
MDIt is the square of the 4th level selection gradient D,
MEIt is the square of layer 5 face selection gradient E,
Described first phase coding gradient U, the first rephasing gradient V all put on phase-encoding direction, and meet following relation:
MU=-MV,
MUIt is the square of first phase coding gradient U,
MVIt it is the square of the first rephasing gradient V；
Described first reads pre-dephasing gradient F, the first readout gradient G, the first reading rephasing gradient H, the second pre-dephasing of reading
Gradient J, the second readout gradient P, the second reading rephasing gradient Q all put on readout direction, and meet following relation:
First pre-dephasing gradient F of reading, the first reading rephasing gradient H and opposite polarity of the first readout gradient G, described second
Read pre-dephasing gradient J, the second reading rephasing gradient Q and opposite polarity of the second readout gradient P,
MF+MG+MH=0,
MJ+MP+MQ=0,
MFIt is the square of the first reading pre-dephasing gradient F,
MGIt is the square of the first readout gradient G,
MHIt is the square of the first reading rephasing gradient H,
MJIt is the square of the second reading pre-dephasing gradient J,
MPIt is the square of the second readout gradient P,
MQIt it is the square of the second reading rephasing gradient Q；
The described working cycle includes two repetition periods；
When performing described step, within first repetition period of working cycle, perform described sub-step 11～sub-step 14 successively,
Described sub-step 15～sub-step 18 is performed successively within second repetition period of working cycle, or, in the working cycle
Perform described sub-step 15～sub-step 18 in first repetition period successively, depend within second repetition period of working cycle
The described sub-step of secondary execution 11～sub-step 14；Further, often complete a working cycle, change described first phase coding ladder
Degree U and the square of the first rephasing gradient V.
MR imaging method the most according to claim 1, wherein, described the first level selects gradient A, the second layer
Face selects gradient B, the 4th level selection gradient D also to meet following relation:
∣MA/2+MB∣≧∣MA/ 2,
∣MA/2+MD∣≧∣MA/2∣。
MR imaging method the most according to claim 2, wherein, described the first level selects gradient A, the second layer
Face selects gradient B, third layer face to select gradient C, the 4th level selection gradient D, layer 5 face to select gradient E satisfied as follows
Relation:
MB=MA,
MC=MA/ 2,
MD=0,
ME=3MA/2。
MR imaging method the most according to claim 2, wherein, described the first level selects gradient A, the second layer
Face selects gradient B, third layer face to select gradient C, the 4th level selection gradient D, layer 5 face to select gradient E satisfied as follows
Relation:
MB=MA/ 2,
MC=MA/ 2,
MD=3MA/ 2,
ME=3MA/2。
MR imaging method the most according to claim 1, wherein, described first read pre-dephasing gradient F, first
Readout gradient G, first read rephasing gradient H, second read pre-dephasing gradient J, the second readout gradient P, second reads back gather
Gradient Q meets following relation:
MF=MJ=MH=MQ=MG/ 2=MP/2。
MR imaging method the most according to claim 1, wherein,
Described sub-step 12 and sub-step 16 also include: apply second phase coding gradient S in level selection direction；
Described sub-step 14 and sub-step 18 also include: apply the second rephasing gradient T in level selection direction；
Wherein, described second phase encodes gradient S, the second rephasing gradient T meets following relation:
MS=-MT,
MSIt is the square of second phase coding gradient S,
MTIt it is the square of the second rephasing gradient T；
Described MR imaging method also includes: often complete a working cycle, change described second phase coding gradient S and
The square of the second rephasing gradient T.
7. a MR imaging apparatus, wherein, including: processor, gradient coil, impulse ejection coil, pulse connect
Take-up circle, analog-digital converter, output device；
Described processor includes:
First processing unit, is arranged to control described impulse ejection coil transmissions radio-frequency pulse, controls described ladder simultaneously
Degree coil applies the first level and selects gradient A；
Second processing unit, is arranged to control described gradient coil and applies the second level selection gradient B, first phase volume
Code gradient U and first reads pre-dephasing gradient F；
3rd processing unit, is arranged to control described gradient coil and applies the first readout gradient G, control described arteries and veins simultaneously
Rush receiving coil collecting magnetic resonance signal, control the described analog-digital converter magnetic resonance signal to currently collecting and carry out mould
Number conversion is to obtain stable state precession time reversal signal；
Fourth processing unit, is arranged to control described gradient coil and applies the first reading rephasing gradient H, first time poly-ladder
Degree V, third layer face select gradient C；
5th processing unit, is arranged to control described impulse ejection coil transmissions radio-frequency pulse, controls described ladder simultaneously
Degree coil applies the first level and selects gradient A；
6th processing unit, is arranged to control described gradient coil and applies the 4th level selection gradient D, first phase volume
Code gradient U and second reads pre-dephasing gradient J；
7th processing unit, is arranged to control described gradient coil and applies the second readout gradient P, control described arteries and veins simultaneously
Rush receiving coil collecting magnetic resonance signal, control the described analog-digital converter magnetic resonance signal to currently collecting and carry out mould
Number conversion is to obtain echo translation signal；
8th processing unit, is arranged to control described gradient coil and applies the second reading rephasing gradient Q, first time poly-ladder
Degree V, layer 5 face select gradient E；
Wherein, described the first level select gradient A, the second level selection gradient B, third layer face select gradient C, the 4th layer
Face selects gradient D, layer 5 face to select gradient E all to put on level selection direction, and meets following relation:
MB+MC=MD+ME,
MA/2+MB+MC+MA+MD=0,
MA/2+MD+ME–MB=0,
MAIt is the square of the first level selection gradient A,
MBIt is the square of the second level selection gradient B,
MCIt is the square of third layer face selection gradient C,
MDIt is the square of the 4th level selection gradient D,
MEIt it is the square of layer 5 face selection gradient E；
Described first phase coding gradient U, the first rephasing gradient V all put on phase-encoding direction, and meet following relation:
MU=-MV,
MUIt is the square of first phase coding gradient U,
MVIt it is the square of the first rephasing gradient V；
Described first reads pre-dephasing gradient F, the first readout gradient G, the first reading rephasing gradient H, the second pre-dephasing of reading
Gradient J, the second readout gradient P, the second reading rephasing gradient Q all put on readout direction, and meet following relation:
First pre-dephasing gradient F of reading, the first reading rephasing gradient H and opposite polarity of the first readout gradient G, described second
Read pre-dephasing gradient J, the second reading rephasing gradient Q and opposite polarity of the second readout gradient P,
MF+MG+MH=0,
MJ+MP+MQ=0,
MFIt is the square of the first reading pre-dephasing gradient F,
MGIt is the square of the first readout gradient G,
MHIt is the square of the first reading rephasing gradient H,
MJIt is the square of the second reading pre-dephasing gradient J,
MPIt is the square of the second readout gradient P,
MQIt it is the square of the second reading rephasing gradient Q；
Described processor also includes:
Performance element, being arranged to a working cycle periodically works, and the described working cycle includes two
Repetition period, performance element triggers the first processing unit～everywhere within first repetition period of its working cycle successively
Reason unit, triggers the 5th processing unit～the 8th processing unit within second repetition period of its working cycle successively, or,
Performance element triggers the 5th processing unit～the 8th processing unit within first repetition period of its working cycle successively,
The first processing unit～fourth processing unit is triggered successively in second repetition period of its working cycle；
Cycling element, is arranged to control described performance element and periodically works according to the described working cycle, directly
The total number of cycles completed to described performance element reaches default phase code number, wherein, every in described performance element
When completing a working cycle, cycling element changes described first phase coding gradient U and the square of the first rephasing gradient V；
Clock, provides clock signal for described performance element and described cycling element, so that described performance element and described
Cycling element determines initial time and the finish time of each repetition period；
Fill unit, be arranged to utilize described analog-digital converter to obtain time reversal stable state precession signal and echo put down
Shifting signal fills k-space；
Fourier transform unit, is arranged to the data to filling in complete k-space and carries out Fourier transformation, obtain magnetic
Resonance image；
Described output device, is arranged to export described magnetic resonance image (MRI).
MR imaging apparatus the most according to claim 7, wherein, described the first level selects gradient A, the second layer
Face selects gradient B, the 4th level selection gradient D also to meet following relation:
∣MA/2+MB∣≧∣MA/ 2,
∣MA/2+MD∣≧∣MA/2∣。
MR imaging apparatus the most according to claim 8, wherein, described the first level selects gradient A, the second layer
Face selects gradient B, third layer face to select gradient C, the 4th level selection gradient D, layer 5 face to select gradient E satisfied as follows
Relation:
MB=MA,
MC=MA/ 2,
MD=0,
ME=3MA/2。
MR imaging apparatus the most according to claim 8, wherein, described the first level selects gradient A, the second layer
Face selects gradient B, third layer face to select gradient C, the 4th level selection gradient D, layer 5 face to select gradient E satisfied as follows
Relation:
MB=MA/ 2,
MC=MA/ 2,
MD=3MA/ 2,
ME=3MA/2。
11. MR imaging apparatus according to claim 7, wherein, described first read pre-dephasing gradient F, first
Readout gradient G, first read rephasing gradient H, second read pre-dephasing gradient J, the second readout gradient P, second reads back gather
Gradient Q meets following relation:
MF=MJ=MH=MQ=MG/ 2=MP/2。
12. MR imaging apparatus according to claim 7, wherein,
Described second processing unit and described 6th processing unit are also configured to: control described gradient coil and apply second phase
Coding gradient S；
Described fourth processing unit and described 8th processing unit are also configured to: control the applying of described gradient coil and gather for second time
Gradient T,
Wherein, described second phase coding gradient S, described second rephasing gradient T all put on level selection direction, and meet
Following relation:
MS=-MT,
MSIt is the square of second phase coding gradient S,
MTIt it is the square of the second rephasing gradient T；
Described cycling element is also configured to: when described performance element often completes a working cycle, changes described second phase
Position coding gradient S and the square of the second rephasing gradient T.
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