CN103110421B - Method and system for improving signal-to-noise ratio of magnetic resonance imaging - Google Patents
Method and system for improving signal-to-noise ratio of magnetic resonance imaging Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 27
- 238000002595 magnetic resonance imaging Methods 0.000 title claims abstract description 22
- 238000011084 recovery Methods 0.000 claims abstract description 106
- 238000003384 imaging method Methods 0.000 claims description 40
- 238000005481 NMR spectroscopy Methods 0.000 claims description 39
- 238000002059 diagnostic imaging Methods 0.000 abstract description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 8
- 239000011574 phosphorus Substances 0.000 description 8
- 238000010586 diagram Methods 0.000 description 7
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 6
- 230000005415 magnetization Effects 0.000 description 6
- 238000005457 optimization Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 230000007547 defect Effects 0.000 description 2
- 238000001208 nuclear magnetic resonance pulse sequence Methods 0.000 description 2
- -1 phosphorus compound Chemical class 0.000 description 2
- 230000002490 cerebral effect Effects 0.000 description 1
- 238000003759 clinical diagnosis Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 210000004884 grey matter Anatomy 0.000 description 1
- 238000013421 nuclear magnetic resonance imaging Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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Abstract
The invention is suitable for the technical field of medical imaging, and provides a method and a system for improving the signal-to-noise ratio of magnetic resonance imaging, wherein the method comprises the following steps: and (3) signal-to-noise ratio curve drawing step: drawing a signal-to-noise ratio-recovery pulse time-repetition time curve in unit time; acquiring a parameter range: acquiring a recovery pulse time range and a repetition time range in a maximum value area on the curve; determining parameter values: and setting the pulse recovery time, the repetition time and the repetition times of the current scanning according to the pulse recovery time range and the repetition time range and the given current scanning time. Therefore, the signal-to-noise ratio of the magnetic resonance imaging is improved.
Description
Technical field
The present invention relates to Medical Imaging Technology field, particularly relate to a kind of method and the system thereof that improve nuclear magnetic resonance signal to noise ratio.
Background technology
Since year at the beginning of the eighties in last century, First medical nuclear magnetic resonance imaging instrument came out, NMR (Nuclear Magnetic Resonance)-imaging obtains development at full speed as important clinical examination means, plays an important role in clinical diagnosis work.Meanwhile, the imaging technique of nuclear magnetic resonance, NMR also all enters with day, and from the object of imaging, device hardware, pulse train, to image reconstruction, all emerges much new technology.Wherein the development of magnetic resonance imaging pulse sequence is in core status, just because of the development of pulse train, the application of medical magnetic resonance imaging instrument could improve to the image information of diagnostician each side.
In magnetic resonance imaging pulse sequence, there is a class sequence to be called as driven equilibrium sequence, in some document, be also referred to as fast quick-recovery pulse train.Such sequence is after the readout gradient carrying out data acquisition applies, giving 180 degree of Y pulses allows remaining magnetization intensity vector meet again, the magnetization intensity vector of meeting again on applying 90 degree of-X pulses allow horizontal direction in the echo time is turned to vertical direction, is namely ordered about the inceptive direction getting back to magnetization intensity vector.Driven equilibrium sequence can combine with the sequence such as GRE sequence, SE sequence, FSE sequence, to shorten the time that these sequences return to equilibrium state after obtaining signal.Based on GRE sequence driven equilibrium pulse train waveform schematic diagram as shown in Figure 1.
The recovery efficiency of driven equilibrium sequence and imaging parameters Tfr, Tfr be first 90 ° of driving pulse and last drive interval between 90 ° of pulses recovering, namely burst length, TR (repetitiontime is recovered, repetition time) and the relaxation constant T1 (relaxation constant of check object) of check object, T2 (relaxation constant of check object) is relevant.Under normal circumstances for T2 at 100ms less than mono-, T1 at below 2000ms, the recovery efficiency of driven equilibrium adopts short Tfr and short TR can be relatively high.List of references 1:SylvainMiraux, EricThiaudi_ere, PaulCanioni, etal, Magnetizationrecoveryforsignalenhancement:afastimagingDE FT-basedtechnique, JMagRes, 2004 (166): 28-34 (the magnetization intensity vector recoveries for signal strengthens: according to the fast imaging techniques based on driven equilibrium, magnetic resonance magazine, 2004 (166): 28-34.) driven equilibrium pulse train is described in detail to the raising efficiency of signal to noise ratio and imaging parameters Tfr, TR, relation between relaxation time T1 and T2.But, when driven equilibrium sequence is applied to the very weak phosphorus imaging of signal intensity, because phosphorus compound T1 is longer, concentration is very low, cause read bandwidth and TR very large to SNR influence, need when determining driven equilibrium parameter to consider to read bandwidth, T2* decays, the relation between TR and number of repetition.
In summary, in actual use, obviously there is inconvenience and defect, so be necessary to be improved in existing mr imaging technique.
Summary of the invention
For above-mentioned defect, the object of the present invention is to provide a kind of method and the system thereof that improve nuclear magnetic resonance signal to noise ratio, to improve the signal to noise ratio of nuclear magnetic resonance.
To achieve these goals, the invention provides a kind of method improving nuclear magnetic resonance signal to noise ratio, comprise the steps:
Signal to noise ratio curve plotting step: draw signal to noise ratio in the unit interval-recovery burst length-repetition time curve;
The scope that gets parms step: the maximum region on described curve obtains recovers burst length scope and repetition time scope;
Determine parameter value step: according to described recovery burst length scope and repetition time scope, and the recovery burst length of given present scan set of time present scan, repetition time and number of repetition.
According to described method, described determine parameter value step after also comprise:
Within the described given present scan time, perform magnetic resonance imaging according to recovery burst length of described present scan, repetition time and number of repetition.
According to described method, described signal to noise ratio curve plotting step comprises:
To separate based on Bloch equations, obtain described signal to noise ratio and the relation recovering burst length, repetition time and number of repetition;
According to described relation, draw in the unit interval after having revised described recovery burst length and repetition time factor two-dimentional signal to noise ratio-recovery burst length-repetition time signal to noise ratio curve;
The described scope step that gets parms comprises:
Described signal to noise ratio-recovery burst length-repetition time signal to noise ratio curve on maximum region obtain and recover burst length scope and repetition time scope.
According to described method, describedly determine that parameter value step comprises:
The optimal region searching described signal to noise ratio in described maximum region, and read corresponding recovery burst length and repetition time in any point of described optimal region; Or
In described maximum region, search described signal to noise ratio peak, and read corresponding recovery burst length and repetition time at described peak;
According to recovery burst length and the repetition time of described correspondence, and the number of repetition of given described present scan set of time present scan.
According to described method, described nuclear magnetic resonance is the imaging of driven equilibrium pulse train.
Present invention also offers a kind of system improving nuclear magnetic resonance signal to noise ratio to realize another goal of the invention of the present invention, comprising:
Signal to noise ratio curve plotting module, for draw signal to noise ratio in the unit interval-recovery burst length-repetition time curve;
Get parms range module, obtains recover burst length scope and repetition time scope for the maximum region on described curve;
Determine parameter value module, for according to described recovery burst length scope and repetition time scope, and the recovery burst length of given present scan set of time present scan, repetition time and number of repetition.
According to described system, described system also comprises:
Scan module, within the described given present scan time, performs magnetic resonance imaging according to recovery burst length of described present scan, repetition time and number of repetition.
According to described system, described signal to noise ratio curve plotting module comprises:
Parameters relationship determination submodule, for separate based on Bloch equations, obtains described signal to noise ratio and the relation recovering burst length, repetition time and number of repetition;
Signal to noise ratio curve plotting submodule, for according to described relation, draw two-dimentional signal to noise ratio in the unit interval after having revised described recovery burst length and repetition time factor-recovery burst length-repetition time signal to noise ratio curve;
Described get parms module described signal to noise ratio-recovery burst length-repetition time signal to noise ratio curve on maximum region obtain and recover burst length scope and repetition time scope.
According to described system, describedly determine that parameter value module comprises:
First parameter value determination submodule, for the optimal region searching described signal to noise ratio in described maximum region, and reads corresponding recovery burst length and repetition time in any point of described optimal region; Or
Second parameter value determination submodule, for searching described signal to noise ratio peak in described maximum region, and reads corresponding recovery burst length and repetition time at described peak;
Number of repetition determination submodule, for according to recovery burst length of described correspondence and repetition time, and the number of repetition of given described present scan set of time present scan.
According to described system, described nuclear magnetic resonance is the imaging of driven equilibrium pulse train.
The present invention by draw signal to noise ratio in the unit interval-recovery burst length-repetition time curve; Then the maximum region on described curve obtains recovers burst length scope and repetition time scope; And according to described recovery burst length scope and repetition time scope, and the recovery burst length of given present scan set of time present scan, repetition time and number of repetition.Thus achieve by obtaining optimal recovery pulse application time, read bandwidth, the combination of repetition time and number of repetition reaches the object improving signal to noise ratio.In addition, in the nuclear magnetic resonance of driven equilibrium class pulse train, the driven equilibrium GRE best distribution region of sequence unit time signal to noise ratio is given; Can image quality be improved under this distribution is instructed, shorten sweep time.Concrete, reference recovery burst length and repetition time are on the impact of imaging signal to noise ratio, and the two relation mutually retrained with readout gradient and number of repetition again, utilize based on Bloch equations emulation, draw with revises read signal to noise ratio after bandwidth sum number of repetition factor-recovery burst length-repetition time two-dimentional unit interval signal to noise ratio curve, this curve obtains signal to noise ratio peak recovery burst length-reading bandwidth, repetition time-number of repetition combination, reach and obtain best signal to noise ratio object within preset time.The method for weak imaging signal, as the multinuclear imagings such as phosphorus imaging have clear improvement signal to noise ratio effect.
Accompanying drawing explanation
Fig. 1 is the schematic diagram of driven equilibrium gradin-echo in prior art;
Fig. 2 is the system structure schematic diagram of the raising nuclear magnetic resonance signal to noise ratio that first embodiment of the invention provides;
Fig. 3 be the present invention second and third, the system structure schematic diagram of raising nuclear magnetic resonance signal to noise ratio that provides of four embodiments;
Fig. 4 is the method flow diagram of the raising nuclear magnetic resonance signal to noise ratio that fifth embodiment of the invention provides;
Fig. 5 be one embodiment of the invention provide unit interval signal to noise ratio-fast quick-recovery burst length-repetition time two-dimensional curve figure
Fig. 6 be one embodiment of the invention provide Phos imaging unit interval signal to noise ratio-fast quick-recovery burst length-repetition time two-dimensional curve figure
Fig. 7 is the sequential chart of the GE3TSigna scanner unit execution SPSP_DE_GRE pulse train that one embodiment of the invention provides
Fig. 8 is the employing parameters optimization SPSP_DE_GRE pulse scanning result schematic diagram that one embodiment of the invention provides;
Fig. 9 is SPSP_GRE pulse scanning result schematic diagram in prior art.
Detailed description of the invention
In order to make object of the present invention, technical scheme and advantage clearly understand, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.
See Fig. 2, in the first embodiment of the present invention, provide a kind of system 100 improving nuclear magnetic resonance signal to noise ratio, comprising:
Signal to noise ratio curve plotting module 10, for draw signal to noise ratio in the unit interval-recovery burst length-repetition time curve;
Get parms range module 20, obtains recover burst length scope and repetition time scope for the maximum region on described curve;
Determine parameter value module 30, for according to described recovery burst length scope and repetition time scope, and the recovery burst length of given present scan set of time present scan, repetition time and number of repetition.
In this embodiment, first by signal to noise ratio curve plotting module 10 draw signal to noise ratio in the unit interval-recovery burst length-repetition time curve; This curve be normalizated unit time signal to noise ratio-recovery burst length-drafting of repetition time curve.Then, the maximum region of the range module that gets parms 20 on described curve obtains recovers burst length scope and repetition time scope, and this scope comprises the optimum value region of recovering burst length and repetition time.Finally, by determining that parameter value module 30 is according to described recovery burst length scope and repetition time scope, and the recovery burst length of given present scan set of time present scan, repetition time and number of repetition.Because described recovery burst length scope and repetition time scope are the optimum value region of recovering burst length and repetition time, recovery burst length of the present scan therefore finally determined, repetition time and number of repetition also will be optimize to obtain, therefore the nuclear magnetic resonance parameter by the optimization of the system 100 of above-mentioned raising nuclear magnetic resonance signal to noise ratio, finally reaching the object improving nuclear magnetic resonance signal to noise ratio.Preferably, described nuclear magnetic resonance is the imaging of driven equilibrium pulse train.
See Fig. 3, in the second embodiment of the present invention, the system 100 improving nuclear magnetic resonance signal to noise ratio also comprises:
Scan module 40, within the described given present scan time, performs magnetic resonance imaging according to recovery burst length of described present scan, repetition time and number of repetition.
In this embodiment, scan module 40 is according to recovery burst length of described present scan, repetition time and number of repetition, magnetic resonance imaging is performed within the described given present scan time, in concrete nuclear magnetic resonance process, the optimization of nuclear magnetic resonance signal to noise ratio can be realized thus.
See Fig. 3, in the third embodiment of the present invention, signal to noise ratio curve plotting module 10 comprises:
Parameters relationship determination submodule 11, for separate based on Bloch (Bloch) equation, obtains described signal to noise ratio and the relation recovering burst length, repetition time and number of repetition;
Signal to noise ratio curve plotting submodule 12, for according to described relation, draw two-dimentional signal to noise ratio in the unit interval after having revised described recovery burst length and repetition time factor-recovery burst length-repetition time signal to noise ratio curve;
The module that gets parms 20 described signal to noise ratio-recovery burst length-repetition time signal to noise ratio curve on maximum region obtain and recover burst length scope and repetition time scope.
In this embodiment, parameters relationship determination submodule 11 is to separate the relevant parameter obtaining nuclear magnetic resonance signal to noise ratio based on Bloch equation.Bloch equation is that classical mechanics describes one of of paramount importance theoretical basis of nmr phenomena.The relation of described recovery burst length and repetition time and signal to noise ratio can be revised by separating Bloch equation.By signal to noise ratio curve plotting submodule 12 according to parameters relationship determination submodule 11 draw two-dimentional signal to noise ratio in the relevant unit interval-recovery burst length-repetition time signal to noise ratio curve.
See Fig. 3, in the fourth embodiment of the present invention, determine that parameter value module 30 comprises:
First parameter value determination submodule 31, for the optimal region searching described signal to noise ratio in described maximum region, and reads corresponding recovery burst length and repetition time in any point of described optimal region; Or
Second parameter value determination submodule 32, for searching described signal to noise ratio peak in described maximum region, and reads corresponding recovery burst length and repetition time at described peak;
Number of repetition determination submodule 33, for according to recovery burst length of described correspondence and repetition time, and the number of repetition of given described present scan set of time present scan.
In this embodiment, the subregion in the maximum region in described signal to noise ratio curve can be defined as the optimal region of described signal to noise ratio by the first parameter value determination submodule 31, the concrete value parameter setting that concrete determination can be arranged according to operator.Recovery burst length and the repetition time parameter of this magnetic resonance imaging can be read as in recovery burst length corresponding to any point of this optimal region and repetition time.In addition, preferably, the second parameter value determination submodule 32 will search recovery burst length and the repetition time parameter that recovery burst length corresponding to described signal to noise ratio peak and repetition time are read as this magnetic resonance imaging in described maximum region; The recovery burst length that last number of repetition determination submodule 33 can be determined according to above-mentioned two submodules and repetition time arrange the number of repetition of this magnetic resonance imaging.
In above-mentioned multiple embodiment, the system 100 improving nuclear magnetic resonance signal to noise ratio can software unit, hardware cell or software and hardware combining unit.And this system can be arranged in magnetic resonance imaging equipment.
See Fig. 4, in the fifth embodiment of the present invention, provide a kind of method improving nuclear magnetic resonance signal to noise ratio, comprise the steps:
In step S401, signal to noise ratio curve plotting module 10 draw signal to noise ratio in the unit interval-recovery burst length-repetition time curve; This step is signal to noise ratio curve plotting step;
In step S402, the maximum region of the range module that gets parms 20 on described curve obtains recovers burst length scope and repetition time scope; This step is the scope step that gets parms:
In step S403, determine that parameter value module 30 is according to described recovery burst length scope and repetition time scope, and the recovery burst length of given present scan set of time present scan, repetition time and number of repetition; This step is for determining parameter value step.
In this embodiment, optimizing magnetic resonance parameters by obtaining, making the time efficiency that can significantly improve imaging in the non-proton imaging that signal to noise ratio is lower, improving image quality.
In the sixth embodiment of the present invention, also comprise after described step S403:
Scan module 40, within the described given present scan time, performs magnetic resonance imaging according to recovery burst length of described present scan, repetition time and number of repetition.
In the sixth embodiment of the present invention, comprise at described step S401:
Parameters relationship determination submodule 11, to separate based on Bloch equation, obtains described signal to noise ratio and the relation recovering burst length, repetition time and number of repetition;
Signal to noise ratio curve plotting submodule 12 according to described relation, draw in the unit interval after having revised described recovery burst length and repetition time factor two-dimentional signal to noise ratio-recovery burst length-repetition time signal to noise ratio curve;
Described step S402 comprises:
The module that gets parms 20 described signal to noise ratio-recovery burst length-repetition time signal to noise ratio curve on maximum region obtain and recover burst length scope and repetition time scope.
In this embodiment, MR imaging sequences is driven equilibrium sequence.Based on when being applied to the very weak phosphorus imaging of signal intensity when driven equilibrium sequence, because phosphorus compound T1 is longer, concentration is very low, cause read bandwidth and TR very large to SNR influence, need when determining driven equilibrium parameter to consider to read bandwidth, T2* decays, the relation between TR and number of repetition.Consider the correction relation proposing signal to noise ratio and Tfr, TR, T1 and T2, optimum magnetic resonance imaging parameter is determined on this relation basis.Concrete method implementation procedure is as follows:
First, be normalized unit interval signal to noise ratio-recovery burst length-drafting of repetition time curve
(1) SNR (Signal/Noise, signal to noise ratio) and each imaging parameters relation;
Existing under driven equilibrium pulse situation, by separating Bloch equation, can obtain
M in formula
xysteady state levels direction magnetization intensity vector, M
0be original state magnetization intensity vector, TE is the echo time.Due to signal intensity and the M of MRI (MagneticResonanceImaging, nuclear magnetic resonance)
xybe directly proportional, and in noise level and above formula, each parameter has nothing to do, so can represent the signal to noise ratio of driven equilibrium nuclear magnetic resonance with above formula.
Because in driven equilibrium pulse train, Tfr is subject to the restriction of sensing tape wide bandwidth, when all the other image-forming conditions are identical, magnetic resonance signal to noise ratio with the pass reading bandwidth is:
Bandwidth and readout time window have following relation:
In pre-loose gradient mutually, under phase encoding gradient gets the minima situation that hardware system can provide, the minimum echo time, TE can regard as:
TE=0.5 × Tread+ Δ Tmin (formula 4)
And in reunion gradient, under each equilibrium gradient all gets the minima situation that hardware system can provide, readout time window and Tfr relation be approximately:
Tfr=(Tread+ Δ Tmin) × 2 (formula 5)
Neglect Δ T, TE gets the minimum echo time, has
TE=Tfr/4 (formula 7)
Consider the mutual constraint between NEX (numberofexcitation, number of repetition) and TR again, this constraint represents with unit interval signal to noise ratio uSNR:
(formula 8)
In sum, unit interval signal to noise ratio meets following relation:
(formula 9)
Object when the T2* dependence T2 in formula, imaging in coil and the quality of shimming, and there is between T2 following relation:
Known
Section 2 in the good situation of shimming in denominator is about about 10ms.
(2) programming curve plotting;
According to co-relation, be certain concrete T1 in imaging object, T2, during T2* value (as on 3TMRI scanner unit, cerebral gray matter T1=1820ms, T2=99ms), with TR and Tfr for independent variable, unit interval signal to noise ratio is dependent variable, draws two-dimensional curve figure as shown in Figure 5, and in figure, the Dark grey part of top is the optimum part of unit signal to noise ratio.Each color gray level is 0.001/ms.
(3) T1, T2 are on the impact of two-dimensional curve figure;
SNR/UnitTime – Tfr – TR scattergram changes with the difference of T1, T2.Also Just because of this, for different T1, T2, scattergram can help to determine optimum Tfr and TR.
In the seventh embodiment of the present invention, described step S402 comprises:
The optimal region of searching described signal to noise ratio of the first parameter value determination submodule 31 in described maximum region, and read corresponding recovery burst length and repetition time in any point of described optimal region; Or
Second parameter value determination submodule 32 searches described signal to noise ratio peak in described maximum region, and reads corresponding recovery burst length and repetition time at described peak;
Number of repetition determination submodule 33 is according to the recovery burst length of described correspondence and repetition time, and the number of repetition of given described present scan set of time present scan.
In one embodiment of the invention, by obtaining the optimal recovery burst length (Tfr), reading the object that the combination of bandwidth, repetition time TR and number of repetition (NEX) reaches raising signal to noise ratio.In the nuclear magnetic resonance of driven equilibrium class pulse train, Tft and TR has a significant impact imaging signal to noise ratio (SNR), mutually retrains again simultaneously with readout gradient and number of repetition.Based on the emulation of Bloch equation, draw and read the two-dimentional unit interval signal to noise ratio curve of SNR-Tft & TR after bandwidth sum NEX factor to revise, the Tfr-that this curve obtains SNR peak reads bandwidth TR-NEX combination, reaches the object obtaining best SNR within preset time.This technical scheme for weak imaging signal, as the multinuclear imagings such as phosphorus imaging have clear improvement SNR effect.Concrete extremal region of choosing determines being operating as of optimum imaging parameters with nearby principle: under given imaging time and imaging array situation, take Fig. 5 as reference, in dark gray areas, select suitable Tfr and TR, select number of repetition in conjunction with given imaging time.Preferably, this dark gray areas value of comprising TR 200 ~ 1800 range areas.
See Fig. 6 ~ Fig. 9, in a preferred embodiment of the invention, be the nuclear magnetic resonance of driven equilibrium pulse train Phos in this embodiment.The execution platform of imaging sequence is 3TGESignaHDxscanner (GEHealthcare, Waukesha, WI).Sweep object is the 100mMNa of radius 6cm
2hPO
4spherical water mould.Implementation is as follows:
1, use proton coil to be 3_plane and locate scanning phase;
2, switch to phosphorus coil, use the SpectralPrescan option in GE2Dfidcsi sequence to carry out prescan, imaging pattern is chosen as wave spectrum (Mode=1).By optimum configurations, sequence used is set to a frequency selectivity radio-frequency pulse.Regulate shimming gradient, make signal attenuation the slowest, estimate T2* (also can measure T2* by other sequence or be obtained by correlation experience) simultaneously;
3, Phos T1, T2 and above-mentioned T2* are substituted into formula, draw out curve chart.The T1=6900ms of Phos Pi, T2=153ms under 3T.It is 60ms that T2* tests preliminary surveying.Be plotted as unit interval signal to noise ratio-fast quick-recovery burst length-repetition time two-dimensional curve figure as shown in Figure 6.
4, from Fig. 6, obtain maximum region, preferably, maximum region comprises the dark gray areas in Fig. 6, namely TR value 500 ~ 3500 range areas.Finally determine that the optimal region of Tfr and TR is between 1000 to 1800 at TR, Tfr is between 20 to 40;
5, load there is the SPSP_DE_GRE pulse of selective excitation, according to sweep time (supposition is herein no more than 6 minutes) and optimal T fr and TR scope, TR is set, the relevant parameters such as NEX, Tfr.Consider that larger signal intensity is easy to observe, getting TR is 1800ms, and corresponding Tfr is taken as 35ms, and Matrix32*32, NEX are 6.Total scanning time 5 points 46 seconds;
6, wherein load SPSP_DE_GRE pulse, pulse train as shown in Figure 7:
7, the SPSP_GRE pulse not having driven equilibrium module is used, TR=6000ms, NEX=2, imaging time 6 points 24 seconds, scanogram signal to noise ratio contrasts, and result is respectively shown in Fig. 8 and Fig. 9, parameters optimization SPSP_DE_GRE pulse is adopted to scan the result obtained, SNR=12 in Fig. 8; For the result that the SPSP_GRE pulse contrasted obtains in Fig. 9, SNR=8.The method of raising nuclear magnetic resonance signal to noise ratio provided by the invention and system thereof can significantly improve nuclear magnetic resonance signal to noise ratio as can be seen here.
In one embodiment of the invention, improve the method for nuclear magnetic resonance driven equilibrium pulse train signal to noise ratio, realized by following multiple step: the drafting of (a) SNR-Tft & TR two dimension unit interval signal to noise ratio curve; B () utilizes SNR-Tft & TR two dimension unit interval signal to noise ratio curve acquisition optimal recovery pulse application time (Tfr) to combine with sensing tape wide array and repetition time TR and number of repetition (NEX); The concrete bandwidth (or readout time) that reads in certain TR situation in (a) revises SNR-Tft curve; And in certain Tfr situation, unit interval signal to noise ratio correction (UnittimeSNR)-Tft curve is read in (a); Revise by reading bandwidth (or readout time) method that SNR-Tft curve improves MRI signal to noise ratio in (b) certain TR situation; And in (b) certain Tfr situation, the method for MRI signal to noise ratio is improved by unit interval signal to noise ratio (UnittimeSNR)-Tft curve.
In sum, the present invention by draw signal to noise ratio in the unit interval-recovery burst length-repetition time curve; Then the maximum region on described curve obtains recovers burst length scope and repetition time scope; And according to described recovery burst length scope and repetition time scope, and the recovery burst length of given present scan set of time present scan, repetition time and number of repetition.Thus achieve by obtaining optimal recovery pulse application time, read bandwidth, the combination of repetition time and number of repetition reaches the object improving signal to noise ratio.In addition, in the nuclear magnetic resonance of driven equilibrium class pulse train, the driven equilibrium GRE best distribution region of sequence unit time signal to noise ratio is given; Can image quality be improved under this distribution is instructed, shorten sweep time.Concrete, reference recovery burst length and repetition time are on the impact of imaging signal to noise ratio, and the two relation mutually retrained with readout gradient and number of repetition again, utilize based on the emulation of Bloch equation, draw with revises read signal to noise ratio after bandwidth sum number of repetition factor-recovery burst length-repetition time two-dimentional unit interval signal to noise ratio curve, this curve obtains signal to noise ratio peak recovery burst length-reading bandwidth, repetition time-number of repetition combination, reach and obtain best signal to noise ratio object within preset time.The method for weak imaging signal, as the multinuclear imagings such as phosphorus imaging have clear improvement signal to noise ratio effect.
Certainly; the present invention also can have other various embodiments; when not deviating from the present invention's spirit and essence thereof; those of ordinary skill in the art are when making various corresponding change and distortion according to the present invention, but these change accordingly and are out of shape the protection domain that all should belong to the claim appended by the present invention.
Claims (10)
1. improve a method for nuclear magnetic resonance signal to noise ratio, it is characterized in that, comprise the steps:
Signal to noise ratio curve plotting step: draw signal to noise ratio in the unit interval-recovery burst length-repetition time curve;
The scope that gets parms step: the maximum region on described curve obtains recovers burst length scope and repetition time scope;
Determine parameter value step: according to described recovery burst length scope and repetition time scope, and the recovery burst length of given present scan set of time present scan, repetition time and number of repetition.
2. method according to claim 1, is characterized in that, described determine parameter value step after also comprise:
Within the described given present scan time, perform magnetic resonance imaging according to recovery burst length of described present scan, repetition time and number of repetition.
3. method according to claim 1, is characterized in that, described signal to noise ratio curve plotting step comprises:
To separate based on Bloch equations, obtain described signal to noise ratio and the relation recovering burst length, repetition time and number of repetition;
According to described relation, draw in the unit interval after having revised described recovery burst length and repetition time factor two-dimentional signal to noise ratio-recovery burst length-repetition time signal to noise ratio curve;
The described scope step that gets parms comprises:
Described signal to noise ratio-recovery burst length-repetition time signal to noise ratio curve on maximum region obtain and recover burst length scope and repetition time scope.
4. method according to claim 3, is characterized in that, describedly determines that parameter value step comprises:
Described signal to noise ratio-recovery burst length-repetition time signal to noise ratio curve on maximum region in search the optimal region of described signal to noise ratio, and read corresponding recovery burst length and repetition time in any point of described optimal region; Or
Described signal to noise ratio-recovery burst length-repetition time signal to noise ratio curve on maximum region in search described signal to noise ratio peak, and read corresponding recovery burst length and repetition time at described peak;
According to recovery burst length and the repetition time of described correspondence, and the number of repetition of given described present scan set of time present scan.
5. the method according to any one of Claims 1 to 4, is characterized in that, described nuclear magnetic resonance is the imaging of driven equilibrium pulse train.
6. improve a system for nuclear magnetic resonance signal to noise ratio, it is characterized in that, comprising:
Signal to noise ratio curve plotting module, for draw signal to noise ratio in the unit interval-recovery burst length-repetition time curve;
Get parms range module, obtains recover burst length scope and repetition time scope for the maximum region on described curve;
Determine parameter value module, for according to described recovery burst length scope and repetition time scope, and the recovery burst length of given present scan set of time present scan, repetition time and number of repetition.
7. system according to claim 6, is characterized in that, described system also comprises:
Scan module, within the described given present scan time, performs magnetic resonance imaging according to recovery burst length of described present scan, repetition time and number of repetition.
8. system according to claim 6, is characterized in that, described signal to noise ratio curve plotting module comprises:
Parameters relationship determination submodule, for separate based on Bloch equations, obtains described signal to noise ratio and the relation recovering burst length, repetition time and number of repetition;
Signal to noise ratio curve plotting submodule, for according to described relation, draw two-dimentional signal to noise ratio in the unit interval after having revised described recovery burst length and repetition time factor-recovery burst length-repetition time signal to noise ratio curve;
Described get parms range module described signal to noise ratio-recovery burst length-repetition time signal to noise ratio curve on maximum region obtain and recover burst length scope and repetition time scope.
9. system according to claim 8, is characterized in that, describedly determines that parameter value module comprises:
First parameter value determination submodule, for described signal to noise ratio-recovery burst length-repetition time signal to noise ratio curve on maximum region in search the optimal region of described signal to noise ratio, and read corresponding recovery burst length and repetition time in any point of described optimal region; Or
Second parameter value determination submodule, for described signal to noise ratio-recovery burst length-repetition time signal to noise ratio curve on maximum region in search described signal to noise ratio peak, and read corresponding recovery burst length and repetition time at described peak;
Number of repetition determination submodule, for according to recovery burst length of described correspondence and repetition time, and the number of repetition of given described present scan set of time present scan.
10. the system according to any one of claim 6 ~ 9, is characterized in that, described nuclear magnetic resonance is the imaging of driven equilibrium pulse train.
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