CN104523274A - Magnetic resonance imaging method based on steady-state free procession sequence - Google Patents
Magnetic resonance imaging method based on steady-state free procession sequence Download PDFInfo
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Abstract
The invention provides a magnetic resonance imaging method based on a steady-state free procession sequence and belongs to the technical field of magnetic resonance imaging. The magnetic resonance imaging method based on the steady-state free procession sequence comprises the steps that excitation pulses and a first-level selection gradient A are applied at the same time; a second-level selection gradient B and a first phase encoding gradient U are applied, and a phase pre-dispersing gradient J is read; a first reading gradient G is applied, and an echo horizontal-movement signal is acquired at the same time; a third-level selection gradient D is applied; a second reading gradient H is applied, and a time reversed steady-state procession signal is acquired at the same time; a reading back-gathering gradient F, a second phase encoding gradient V and a fourth-level selection gradient C are applied, wherein the moment of the gradient A, the moment of the gradient B, the moment of the gradient C and the moment of the gradient D meet the relation: MC=-MA/2 and 2MB-MD=MA; a k space is filled with obtained signals, and Fourier transformation is conducted, so that a magnetic resonance image is obtained. According to the magnetic resonance imaging method based on the steady-state free procession sequence, the time reversed steady-state procession signal and the time reversed steady-state procession signal can be acquired at the same time, and imaging time is shortened.
Description
Technical field
The present invention relates to mr imaging technique field, particularly, relate to a kind of MR imaging method utilizing steady state free precession.
Background technology
Stable state precession time reversal (Time-reversed Fast Imaging with Steady-state Precession, timereversed FISP, or PSIF, or Contrast Enhanced Fourier Acquired Steady state, CE-FAST) signal is a kind of gtadient echo signal of heavy T2 weighting.Compared to tradition based on fast spin echo T2 weighted signal, it is fast that it has picking rate, the advantages such as selective absorbing rate is low.
Echo translation (Echo Shift, ES) signal is a kind of gtadient echo signal of heavy T2* weighting, and it has the feature of long echo time (Echo Time, TE), also very responsive for phase place change, be generally used for the real-time monitoring fields such as magnetic resonance temperature imaging.
Current industry normally utilizes corresponding sequence to gather respectively to these two kinds of signals, and monitors field in real time at some, needs to gather echo translation signal and stable state precession time reversal signal, to obtain temperature information and tissue T 2 change information simultaneously.
Summary of the invention
The main purpose of the embodiment of the present invention is to provide a kind of MR imaging method utilizing steady state free precession, to solve in prior art the problem that can not gather echo translation signal and stable state precession time reversal signal simultaneously.
To achieve these goals, the embodiment of the present invention provides a kind of MR imaging method utilizing steady state free precession, comprising:
Circulation execution one steady state free precession; Wherein, the process performing this steady state free precession comprises:
Step 1, applies excitation pulse, applies the first level simultaneously and selects gradient A;
Step 2, after the described the first level of applying selects gradient A, applies the second level selection gradient B, first phase encode gradient U and reads pre-loose phase gradient J;
Step 3, after applying described second level selection gradient B, first phase encode gradient U and the pre-loose phase gradient J of reading, applies the first readout gradient G;
Step 4, collecting magnetic resonance signal while the described first readout gradient G of applying, obtains echo translation signal;
Step 5, after collecting echo translation signal, applies third layer face and selects gradient D;
Step 6, after gradient D is selected in the described third layer face of applying, applies the second readout gradient H;
Step 7, collecting magnetic resonance signal while the described second readout gradient H of applying, obtains stable state precession time reversal signal;
Step 8, after collecting stable state precession time reversal signal, applies to read rephasing gradient F, second phase encode gradient V, the 4th level selection gradient C;
Wherein, described the first level selects gradient A, the second level selection gradient B, the 4th level selection gradient C, third layer face to select gradient D to meet following relation:
M
C＝-M
A/2，
2M
B–M
D＝M
A，
M
athe square that the first level selects gradient A,
M
bthe square of the second level selection gradient B,
M
cthe square of the 4th level selection gradient C,
M
dit is the square that gradient D is selected in third layer face;
Wherein, described first phase encode gradient U, second phase encode gradient V meet following relation:
M
U＝-M
V，
M
uthe square of first phase encode gradient U,
M
vit is the square of second phase encode gradient V;
The echo translation signal utilizing the described steady state free precession of circulation execution to obtain and stable state precession time reversal signal fill k-space;
Fourier transformation is carried out to the data of described k-space, obtains magnetic resonance image (MRI).
By means of technique scheme, the present invention devises a kind of new steady state free precession, perform this sequence and can gather echo translation signal and stable state precession time reversal signal simultaneously, compared to prior art, the present invention can meet the needs simultaneously gathering echo translation signal and stable state precession time reversal signal, obtain temperature information and tissue T 2 change information, obviously shorten the nuclear magnetic resonance time.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, below the accompanying drawing used required in describing embodiment is briefly described, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.
Fig. 1 is the MR imaging method schematic flow sheet utilizing steady state free precession provided by the invention;
Fig. 2 is a kind of steady state free precession example schematic for magnetic resonance two-dimensional imaging provided by the invention;
Fig. 3 is the steady state free precession example schematic of another kind provided by the invention for magnetic resonance two-dimensional imaging;
Fig. 4 is a kind of steady state free precession example schematic for magnetic resonance three-dimensional imaging provided by the invention;
In Fig. 5, (a) is the echo displacement images that the present invention collects; B () is the stable state precession time reversal image that the present invention collects; C () is the echo displacement images utilizing separately echo translation sequence to collect; D () is the stable state precession time reversal image utilizing separately stable state precession time reversal sequence scanning.
Detailed description of the invention
Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.
The invention provides a kind of MR imaging method utilizing steady state free precession, as shown in Figure 1, the method comprises:
Step S1, circulation execution one steady state free precession.
Steady state free precession comprises excitation pulse, the gradient of level selection direction (Z-direction), the gradient of phase-encoding direction (Y-direction), the gradient of readout direction (X-direction).
Concrete, the cycle-index performing steady state free precession in step S1 is corresponding with the coded number of phase code, depends on the resolution (sweep parameter) of magnetic resonance image (MRI).
In step S1, single performs steady state free precession and specifically comprises as follows step by step:
Step S11, applies excitation pulse, applies the first level simultaneously and selects gradient A.
Concrete, excitation pulse is the pulse signal of one group of equidistant, identical flip angle.The first level selects gradient A to put on level selection direction.
Step S12, after applying the first level selects gradient A, applies the second level selection gradient B, first phase encode gradient U and reads pre-loose phase gradient J.
Concrete, the second level selection gradient B puts on level selection direction; First phase encode gradient U puts on phase-encoding direction; Read pre-loose phase gradient J and put on readout direction.
Step S13, after applying second level selection gradient B, first phase encode gradient U and the pre-loose phase gradient J of reading, applies the first readout gradient G.
Concrete, the first readout gradient G puts on readout direction.
Step S14, collecting magnetic resonance signal while applying first readout gradient G, obtains echo translation signal.
Step S15, after collecting echo translation signal, applies third layer face and selects gradient D.
Concrete, third layer face selects gradient D to put on level selection direction.
Step S16, after gradient D is selected in applying third layer face, applies the second readout gradient H.
Concrete, the second readout gradient H puts on readout direction.
Step S17, collecting magnetic resonance signal while applying second readout gradient H, obtains stable state precession time reversal signal.
Step S18, after collecting stable state precession time reversal signal, applies to read rephasing gradient F, second phase encode gradient V, the 4th level selection gradient C.
Concrete, read rephasing gradient F and put on readout direction; Second phase encode gradient V puts on phase-encoding direction; 4th level selection gradient C puts on level selection direction.
In order to reach the object gathering echo translation signal and stable state precession time reversal signal simultaneously, in the present invention, the first level selects gradient A, the second level selection gradient B, the 4th level selection gradient C, third layer face to select gradient D should meet following relation:
M
C＝-M
A/2，
2M
B–M
D＝M
A，
M
athe square that the first level selects gradient A,
M
bthe square of the second level selection gradient B,
M
cthe square of the 4th level selection gradient C,
M
dit is the square that gradient D is selected in third layer face.
Concrete, the first level selects gradient A to coordinate excitation pulse for exciting the gradient of certain one deck of acquisition target, and it is determined by parameters such as exciting the bandwidth of thickness and excitation pulse.
The present invention is applicable to magnetic resonance two-dimensional imaging and magnetic resonance three-dimensional imaging.
In magnetic resonance two-dimensional imaging, in each repetition period, only apply first phase encode gradient U and second phase encode gradient V at phase-encoding direction (Y-direction).Wherein, the object applying first phase encode gradient U makes to possess different initial phases from copper plate, to distinguish the position of corresponding voxel, for magnetic resonance two-dimensional imaging, but before the next repetition period arrives, all phase places from copper plate need be made to return poly-, will apply and first phase encode gradient U intensity identical, opposite polarity second phase encode gradient V (i.e. rephasing gradient) for this reason.That is, first phase encode gradient U, second phase encode gradient V should meet relation: M
u=-M
v, M
uthe square of first phase encode gradient U, M
vit is the square of second phase encode gradient V.
In magnetic resonance three-dimensional imaging, in each repetition period,, also need to apply third phase encode gradient S and the 4th phase encoding gradient T in level selection direction (Z-direction) except first phase encode gradient U and second phase encode gradient V except applying at phase-encoding direction.Wherein, applying third phase encode gradient S is after applying the first level selects gradient A, before applying the first readout gradient G; Applying the 4th phase encoding gradient T is after collecting stable state precession time reversal signal; Further, third phase encode gradient S, the 4th phase encoding gradient T should meet relation: M
s=-M
t, M
sthe square of third phase encode gradient S, M
tit is the square of the 4th phase encoding gradient T.
Step S2, the echo translation signal utilizing circulation execution steady state free precession to obtain and stable state precession time reversal signal fill k-space.
Step S3, carries out Fourier transformation to the data of k-space, obtains magnetic resonance image (MRI).
Perform this steady state free precession, apply different phase encoding gradients in each repetition period to cover whole k-space, the signal of k-space is done Fourier transformation and can obtain corresponding image information.
If the free induction decay of excitation pulse (Free Induction Decay, FID) signal is not decayed completely, and has entered in the acquisition window of echo translation signal, interference will be caused to collection echo translation signal.Consider this point, in the present invention, do not affect to make the FID signal of excitation pulse and gather echo translation signal, level selection gradient A, B, C, D also should meet relation: ∣ M
a/ 2+M
b∣≤M
a/ 2, decay very soon completely to make the FID signal of excitation pulse.
In a kind of preferred embodiment, make M
b=– M
a, M
d=M
a, Shang can meeting, state Guan Xi ∣ M
a/ 2+M
b∣≤M
a/ 2.
The invention provides the steady state free precession example that a kind of method shown in Fig. 1 that can be applicable to as shown in Figure 2 carries out magnetic resonance two-dimensional imaging, this sequence comprises excitation pulse, the gradient in level selection direction, the gradient of phase-encoding direction, the gradient of readout direction.
In Fig. 2, excitation pulse is the pulse signal of one group of equidistant, identical flip angle α.ADC#1 represents collection echo translation signal while applying first readout gradient G.ADC#2 represents acquisition time reversion stable state precession signal while applying second readout gradient H.
Based on Fig. 2, in each repetition period, after applying first readout gradient G, and before applying the second readout gradient H, also comprise: apply to read back poly-pre-loose phase gradient E, further, the reading in Fig. 2 in advance loose phase gradient J, the first readout gradient G, reads back poly-fall apart in advance phase gradient E, the second readout gradient H, reading rephasing gradient F meets following relation:
M
J＝-M
G/2，
M
E＝-(M
G+M
H)/2，
M
F＝-M
H/2，
M
jthe square reading pre-loose phase gradient J,
M
gthe square of the first readout gradient G,
M
ethe square reading back poly-pre-loose phase gradient E,
M
hthe square of the second readout gradient H,
M
fit is the square reading rephasing gradient F.
Concrete, the first readout gradient G, the second readout gradient H need mating die number converter to perform the work of collecting magnetic resonance signal, and their size is determined by the parameter such as visual field size of sampling number, acquisition bandwidth and readout direction.
Below for performing work process and the principle of steady state free precession shown in Fig. 2:
In each repetition period:
(1) excitation pulse is applied on acquisition target by radio-frequency coil, coordinates the first level to select gradient A simultaneously, makes all being excited from copper plate in certain plane in space;
(2) apply first phase encode gradient U, make to possess certain different initial phase, for magnetic resonance two-dimensional imaging from copper plate;
(3) apply to read pre-loose phase J;
(4) apply the first readout gradient G, open analog-digital converter, collecting magnetic resonance signal simultaneously, the magnetic resonance signal now collected is echo translation signal;
(5) apply to read back poly-pre-loose phase gradient E;
(6) apply the second readout gradient H, open analog-digital converter, collecting magnetic resonance signal simultaneously, the signal now collected is stable state precession time reversal signal.
Based on the sequence shown in Fig. 2, the present invention bound fraction echo (asymmetric) technology can also reduce the repetition period, shortens the time of nuclear magnetic resonance.Due to partial echo technology make echo center not readout gradient G the center of magnetic resonance signal (echo-signal stable state precession time reversal signal) of H and collection, decrease the persistent period of readout gradient G and H, thus can the repetition period be shortened.In this case, the gradient of readout direction only needs to meet: M
j+ M
e+ M
f+ M
g+ M
h=0; Wherein the polarity of gradient J, E, F is identical; Gradient G, H are contrary with the polarity of gradient J, E, F.
The invention provides the steady state free precession example that the another kind of method shown in Fig. 1 that can be applicable to as shown in Figure 3 carries out magnetic resonance two-dimensional imaging, this sequence comprises excitation pulse, the gradient in level selection direction, the gradient of phase-encoding direction, the gradient of readout direction.Wherein, gradient J, G, H, F meet relation: M
j+ M
f+ M
g+ M
h=0; Further, the polarity of the first readout gradient G and the second readout gradient H is contrary.
Compared with the steady state free precession shown in Fig. 2, in the sequence shown in Fig. 3, after applying the first readout gradient G, and before applying the second readout gradient H, do not apply to read back poly-pre-loose phase gradient E.This is because the sequence shown in Fig. 3 uses the mode of ambipolar reading to remove to read back poly-pre-loose phase gradient E, to reach the effect reducing the repetition period, shorten the time of nuclear magnetic resonance.
The invention provides the steady state free precession example that a kind of method shown in Fig. 1 that can be applicable to as shown in Figure 4 carries out magnetic resonance three-dimensional imaging, this sequence comprises excitation pulse, the gradient in level selection direction, the gradient of phase-encoding direction, the gradient of readout direction.
In Fig. 4, excitation pulse is the pulse signal of one group of equidistant, identical flip angle α.ADC#1 represents collection echo translation signal while applying first readout gradient G.ADC#2 represents acquisition time reversion stable state precession signal while applying second readout gradient H.
Based on Fig. 4, in each repetition period, after the described the first level of applying selects gradient A, before applying the first readout gradient G, also comprise: apply third phase encode gradient S in level selection direction; And, after collecting stable state precession time reversal signal, also comprise: apply the 4th phase encoding gradient T in level selection direction.
In a kind of preferred embodiment, the third phase encode gradient S of Fig. 4 can merge with the second level selection gradient B, and the 4th phase encoding gradient T can merge with the 4th level selection gradient C.
In Fig. 5, (a) is the two-dimentional echo displacement images that the present invention collects; B two-dimensional time reversion stable state precession image that () the present invention collects; C () is the echo displacement images utilizing separately echo translation sequence to collect; D () is the stable state precession time reversal image utilizing separately stable state precession time reversal sequence scanning.
Basic common acquisition parameter is:
Field range: 384mm*384mm
Thickness: 5mm
Resolution: 384*384
Pulse flip angle: 20degree
The sequence that the present invention proposes:
Repetition time/echo time: 8ms/2.4ms, acquisition bandwidth: 610Hz/pixel
Echo translation sequence:
Repetition time/echo time: 5ms/2.5ms, acquisition bandwidth: 592Hz/pixel
Stable state precession time reversal sequence:
Repetition time/echo time: 5ms/2.5ms, acquisition bandwidth: 592Hz/pixel
Comparison diagram 5 (a) ~ (d) is known, and the image of collection of the present invention has similar contrast to the image utilizing separately echo translation sequence and stable state precession time reversal sequence to collect respectively.But the present invention can meet the needs gathering echo translation signal and stable state precession time reversal signal simultaneously, obtain temperature information and tissue T 2 change information, obviously shorten the nuclear magnetic resonance time.
Above-described specific embodiment; object of the present invention, technical scheme and beneficial effect are further described; be understood that; the foregoing is only specific embodiments of the invention; the protection domain be not intended to limit the present invention; within the spirit and principles in the present invention all, any amendment made, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.
Those skilled in the art can also recognize the various illustrative components, blocks (illustrativelogical block) that the embodiment of the present invention is listed, unit, and step can pass through electronic hardware, computer software, or both combinations realize.For the replaceability (interchangeability) of clear displaying hardware and software, above-mentioned various illustrative components (illustrativecomponents), unit and step have universally described their function.Such function is the designing requirement realizing depending on specific application and whole system by hardware or software.Those skilled in the art for often kind of specifically application, can use the function described in the realization of various method, but this realization can should not be understood to the scope exceeding embodiment of the present invention protection.
Various illustrative logical block described in the embodiment of the present invention, or unit, or device can pass through general processor, 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 above-mentioned any combination realizes or operates described function.General processor can be microprocessor, and alternatively, this general processor also can be any traditional processor, controller, microcontroller or state machine.Processor also can be realized by the combination of accountant, such as digital signal processor and microprocessor, multi-microprocessor, and a Digital Signal Processor Core combined by one or more microprocessor, or other similar configuration any realizes.
The software module that method described in the embodiment of the present invention or the step of algorithm directly can embed hardware, processor performs or the combination of both.Software module can be stored in the storage medium of other arbitrary form in RAM memorizer, flash memory, ROM memorizer, eprom memory, eeprom memory, depositor, hard disk, moveable magnetic disc, CD-ROM or this area.Exemplarily, storage medium can be connected with processor, with make processor can from storage medium reading information, and write information can be deposited to storage medium.Alternatively, storage medium can also be integrated in processor.Processor and storage medium can be arranged in ASIC, and ASIC can be arranged in user terminal.Alternatively, processor and storage medium also can be arranged in the different parts in user terminal.
In one or more exemplary design, the above-mentioned functions described by the embodiment of the present invention can realize in the combination in any of hardware, software, firmware or this three.If realized in software, these functions can store on the medium with computer-readable, or are transmitted on the medium of computer-readable with one or more instruction or code form.Computer readable medium comprises computer storage medium and is convenient to make to allow computer program transfer to the telecommunication media in other place from a place.Storage medium can be that any general or special computer can the useable medium of access.Such as, such computer readable media can include but not limited to RAM, ROM, EEPROM, CD-ROM or other optical disc storage, disk storage or other magnetic storage device, or other anyly may be used for carrying or store the medium that can be read the program code of form with instruction or data structure and other by general or special computer or general or special processor.In addition, any connection can be properly termed computer readable medium, such as, if software is by a coaxial cable, fiber optic cables, twisted-pair feeder, Digital Subscriber Line (DSL) or being also comprised in defined computer readable medium with wireless way for transmittings such as such as infrared, wireless and microwaves from a web-site, server or other remote resource.Described video disc (disk) and disk (disc) comprise Zip disk, radium-shine dish, CD, DVD, floppy disk and Blu-ray Disc, and disk is usually with magnetic duplication data, and video disc carries out optical reproduction data with laser usually.Above-mentioned combination also can be included in computer readable medium.
Claims (7)
1. utilize a MR imaging method for steady state free precession, it is characterized in that, comprising:
Circulation execution one steady state free precession; Wherein, the process performing this steady state free precession comprises:
Step 1, applies excitation pulse, applies the first level simultaneously and selects gradient A;
Step 2, after the described the first level of applying selects gradient A, applies the second level selection gradient B, first phase encode gradient U and reads pre-loose phase gradient J;
Step 3, after applying described second level selection gradient B, first phase encode gradient U and the pre-loose phase gradient J of reading, applies the first readout gradient G;
Step 4, collecting magnetic resonance signal while the described first readout gradient G of applying, obtains echo translation signal;
Step 5, after collecting echo translation signal, applies third layer face and selects gradient D;
Step 6, after gradient D is selected in the described third layer face of applying, applies the second readout gradient H;
Step 7, collecting magnetic resonance signal while the described second readout gradient H of applying, obtains stable state precession time reversal signal;
Step 8, after collecting stable state precession time reversal signal, applies to read rephasing gradient F, second phase encode gradient V, the 4th level selection gradient C;
Wherein, described the first level selects gradient A, the second level selection gradient B, the 4th level selection gradient C, third layer face to select gradient D to meet following relation:
M
C＝-M
A/2，
2M
B–M
D＝M
A，
M
athe square that the first level selects gradient A,
M
bthe square of the second level selection gradient B,
M
cthe square of the 4th level selection gradient C,
M
dit is the square that gradient D is selected in third layer face;
Wherein, described first phase encode gradient U, second phase encode gradient V meet following relation:
M
U＝-M
V，
M
uthe square of first phase encode gradient U,
M
vit is the square of second phase encode gradient V;
The echo translation signal utilizing the described steady state free precession of circulation execution to obtain and stable state precession time reversal signal fill k-space;
Fourier transformation is carried out to the data of described k-space, obtains magnetic resonance image (MRI).
2. method according to claim 1, is characterized in that, described the first level selects gradient A, the second level selection gradient B, the 4th level selection gradient C, third layer face to select gradient D also to meet relation: ∣ M
a/ 2+M
b∣≤M
a/ 2.
3. method according to claim 2, is characterized in that, described the first level selects gradient A, the second level selection gradient B, third layer face selects gradient D to meet relation:
M
B＝–M
A，
M
D＝M
A。
4. method according to claim 1, is characterized in that, after the described first readout gradient G of applying, before applying described second readout gradient H, the process of described this steady state free precession of execution also comprises: apply to read back poly-pre-loose phase gradient E;
Wherein, described reading in advance loose phase gradient J, the first readout gradient G, reads back poly-fall apart in advance phase gradient E, the second readout gradient H, reading rephasing gradient F meets following relation:
M
J＝-M
G/2，
M
E＝-(M
G+M
H)/2，
M
F＝-M
H/2，
Further, the polarity of described first readout gradient G, the second readout gradient H is identical;
M
jthe square reading pre-loose phase gradient J,
M
gthe square of the first readout gradient G,
M
ethe square reading back poly-pre-loose phase gradient E,
M
hthe square of the second readout gradient H,
M
fit is the square reading rephasing gradient F.
5. method according to claim 4, is characterized in that, described reading in advance loose phase gradient J, the first readout gradient G, reads back poly-fall apart in advance phase gradient E, the second readout gradient H, reading rephasing gradient F also meets relation: M
j+ M
e+ M
f+ M
g+ M
h=0;
Further, described reading in advance loose phase gradient J, reads back the poly-phase gradient E that falls apart in advance, reading rephasing gradient F polarity identical; Described first readout gradient G, the second readout gradient H and described reading in advance loose phase gradient J, reads back the poly-phase gradient E that falls apart in advance, to read the polarity of rephasing gradient F contrary.
6. method according to claim 1, is characterized in that, described reading in advance loose phase gradient J, the first readout gradient G, the second readout gradient H, reading rephasing gradient F meets relation:
M
J+M
F+M
G+M
H＝0；
Further, the polarity of described first readout gradient G, the second readout gradient H is contrary;
M
jthe square reading pre-loose phase gradient J,
M
gthe square of the first readout gradient G,
M
hthe square of the second readout gradient H,
M
fit is the square reading rephasing gradient F.
7. method according to claim 1, it is characterized in that, after the described the first level of applying selects gradient A, before applying the first readout gradient G, the process of described this steady state free precession of execution also comprises: apply third phase encode gradient S in level selection direction;
After collecting stable state precession time reversal signal, the process of described this steady state free precession of execution also comprises: apply the 4th phase encoding gradient T in level selection direction;
Wherein, described third phase encode gradient S, the 4th phase encoding gradient T meet following relation:
M
S＝-M
T，
M
sthe square of third phase encode gradient S,
M
tit is the square of the 4th phase encoding gradient T.
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| CN108245158B (en) * | 2016-12-29 | 2021-05-11 | 中国科学院深圳先进技术研究院 | Magnetic resonance temperature measuring method and device |
| CN108245158A (en) * | 2016-12-29 | 2018-07-06 | 中国科学院深圳先进技术研究院 | A kind of magnetic resonance temperature measuring method and device |
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| CN107728090B (en) * | 2017-08-29 | 2019-10-18 | 深圳先进技术研究院 | A kind of method and apparatus of optimization balance steady state free precession |
| CN107728090A (en) * | 2017-08-29 | 2018-02-23 | 深圳先进技术研究院 | A kind of method and apparatus for optimizing balance steady state free precession |
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| CN111310529A (en) * | 2018-12-12 | 2020-06-19 | 深圳先进技术研究院 | Target area identification and necrotic tissue assessment method, device, medium and system |
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| CN117233674A (en) * | 2023-03-27 | 2023-12-15 | 广东省人民医院 | MR imaging method and system based on single-excitation BUDA acquisition and combined constraint reconstruction |
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