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CN107219484A - What multilayer excited Diffusion Imaging parallel excites flip angle to determine method and apparatus - Google Patents

What multilayer excited Diffusion Imaging parallel excites flip angle to determine method and apparatus Download PDF

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Publication number
CN107219484A
CN107219484A CN201610165939.2A CN201610165939A CN107219484A CN 107219484 A CN107219484 A CN 107219484A CN 201610165939 A CN201610165939 A CN 201610165939A CN 107219484 A CN107219484 A CN 107219484A
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imaged
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diffusion
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CN107219484B (en
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刘薇
周堃
肖楠
张琼
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Siemens Shenzhen Magnetic Resonance Ltd
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Siemens Shenzhen Magnetic Resonance Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/48—NMR imaging systems
    • G01R33/58—Calibration of imaging systems, e.g. using test probes, Phantoms; Calibration objects or fiducial markers such as active or passive RF coils surrounding an MR active material
    • G01R33/583—Calibration of signal excitation or detection systems, e.g. for optimal RF excitation power or frequency
    • G01R33/586—Calibration of signal excitation or detection systems, e.g. for optimal RF excitation power or frequency for optimal flip angle of RF pulses

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  • High Energy & Nuclear Physics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)

Abstract

What embodiment of the present invention disclosed that a kind of multilayer excites Diffusion Imaging parallel excites flip angle to determine method and apparatus.Method includes：The first region to be imaged and the second region to be imaged are determined, wherein first region to be imaged and second region to be imaged have different longitudinal relaxation times；It is determined that when execution multilayer excites Diffusion Imaging parallel, the picture contrast function between first region to be imaged and second region to be imaged；Flip angle is excited based on what described image contrast function determined the diffusion-weighting sequence.Using embodiment of the present invention, it can be obtained when multilayer excites Diffusion Imaging parallel and excite the same or similar image tissue contrast of Diffusion Imaging with individual layer.

Description

What multilayer excited Diffusion Imaging parallel excites flip angle to determine method and apparatus
Technical field
The present invention relates to Diffusion Imaging technical field, what more particularly to multilayer excited Diffusion Imaging parallel excites flip angle to determine method and apparatus.
Background technology
Magnetic resonance (Magnetic Resonance, MR) imaging be with computer technology, electronic circuit technology, the development of superconduction body technique and it is fast A kind of biomagnetism nuclear spin imaging technique that speed grows up.It makes the proton (i.e. H+) of precession in tissue using magnetic field and radio-frequency pulse Generation vibration produces radiofrequency signal, handles and is imaged through computer.Be placed on when object in magnetic field, with appropriate electromagnetic wave irradiation it, be allowed to altogether Shake, then analyze the electromagnetic wave that it discharges, it is possible to learn the nuclear position for constituting this object and species, can be depicted as accordingly in object The accurate stereo-picture in portion.
Disperse process of the MR by H+ magnetization come mark molecule without disturbing it.Diffusion gradient is added in any conventional MR imaging sequences to dash forward Go out dispersion effect, you can perform diffusion-weighted imaging (diffusion-weighted MR imaging, DWI), can be to hydrone in tissue more Scattered behavior is directly detected.
In the recent period, the parallel excitation technique of multilayer has been successfully introduced Single-shot echo planar image (ss-EPI) and has read direction sectional plan echo-wave imaging (rs-EPI) in, so as to reduce the sweep time of diffusion-weighted imaging.By exciting n-layer simultaneously, (n is that layer accelerates to the parallel excitation technique of multilayer The factor) carry out accelerated scan to reduce all layers of repetition time (TR) of scanning, in theory sweep time can be down to n/mono-.Generally, disperse Excite flip angle using 90 degree in weighted imaging and maximize signal intensity, therefore in order that Mz can be replied fully after excitation To equilibrium state, the repetition time (TR) needs the longitudinal relaxation time (T1) much larger than image tissue.
However, if the Mz of some image tissues could not be replied completely, then in ensuing scanning, the letter of these image tissues It number will decay to influence final picture contrast.
The content of the invention
Embodiment of the present invention proposes that what a kind of multilayer excited Diffusion Imaging parallel excites angle determination method and device, so as to improve picture contrast.
The technical scheme of embodiment of the present invention is as follows：
According to the one side of embodiment of the present invention, what a kind of multilayer excited Diffusion Imaging parallel excites flip angle to determine method, including：
Determine the first region to be imaged and the second region to be imaged, wherein first region to be imaged and second region to be imaged have it is different Longitudinal relaxation time；
It is determined that when execution multilayer excites Diffusion Imaging parallel, the picture contrast between first region to be imaged and second region to be imaged Function；
Flip angle is excited based on what described image contrast function determined diffusion-weighting sequence.
In one embodiment, it is described to excite flip angle to include based on what picture contrast function determined diffusion-weighting sequence：
It is determined that when execution individual layer excites Diffusion Imaging, the image contrast value between first region to be imaged and second region to be imaged；
It is determined that exciting flip angle when the functional value of described image contrast function is equal to described image contrast value.
In one embodiment, the diffusion-weighting sequence is reading direction sectional plan echo imaging sequence；
It is described to excite flip angle to be θ1opt, wherein：
E is the nature truth of a matter；TRshortExcite the repetition time of Diffusion Imaging parallel for the multilayer；TRlongDiffusion Imaging is excited for the individual layer Repetition time；T1AFor the longitudinal relaxation time in the first region to be imaged；T1BFor the longitudinal relaxation time in the second region to be imaged.
In one embodiment, it is described to excite flip angle to include based on what picture contrast function determined the diffusion-weighting sequence：
It is determined that exciting flip angle when the functional value of described image contrast function is maximum；Or
It is determined that exciting flip angle when the functional value of described image contrast function is predetermined value.
In one embodiment, it is described to determine when performing multilayer and exciting Diffusion Imaging parallel, the first region to be imaged and the second region to be imaged it Between picture contrast function include：
Repetition time based on the diffusion-weighting sequence, the echo time of the diffusion-weighting sequence, the longitudinal relaxation in first region to be imaged Time and the T2 in first region to be imaged, determine the signal intensity function in the first region to be imaged；
Repetition time based on the diffusion-weighting sequence, the echo time of the diffusion-weighting sequence, the longitudinal relaxation in second region to be imaged Time and the T2 in second region to be imaged, determine the signal intensity function in the second region to be imaged；
Signal intensity function and the signal intensity function in the described second region to be imaged based on the described first region to be imaged, determine that described image is contrasted Spend function.
According to the one side of embodiment of the present invention, what a kind of multilayer excited Diffusion Imaging parallel excites flip angle determining device, including：
Area determination module to be imaged, for determining the first region to be imaged and the second region to be imaged, wherein first region to be imaged and second Region to be imaged has different longitudinal relaxation times；
Picture contrast function determination module, for determining when performing multilayer and exciting Diffusion Imaging parallel, first region to be imaged and described the Picture contrast function between two regions to be imaged；
Flip angle determining module is excited, flip angle is excited for determine the diffusion-weighting sequence based on described image contrast function.
In one embodiment, flip angle determining module is excited, for determining that described first is to be imaged when execution individual layer excites Diffusion Imaging Image contrast value between region and second region to be imaged；It is determined that when the functional value of described image contrast function is contrasted equal to described image Flip angle is excited during angle value.
In one embodiment, the diffusion-weighting sequence is reading direction sectional plan echo imaging sequence；
It is described to excite flip angle to be θ1opt, wherein：
E is the nature truth of a matter；TRshortExcite the repetition time of Diffusion Imaging parallel for the multilayer；TRlongDiffusion Imaging is excited for the individual layer Repetition time；T1AFor the longitudinal relaxation time in the first region to be imaged；T1BFor the longitudinal relaxation time in the second region to be imaged.
In one embodiment, flip angle determining module is excited, for determining when the functional value of described image contrast function is maximum Excite flip angle；Or, determine to excite flip angle when the functional value of described image contrast function is predetermined value.
In one embodiment, picture contrast function determination module, adds for the repetition time based on the diffusion-weighting sequence, the disperse The T2 of the echo time of Weight train, the longitudinal relaxation time in first region to be imaged and first region to be imaged, determine The signal intensity function in one region to be imaged；It is repetition time based on the diffusion-weighting sequence, the echo time of the diffusion-weighting sequence, described The longitudinal relaxation time in the second region to be imaged and the T2 in second region to be imaged, determine the signal intensity in the second region to be imaged Function；Signal intensity function and the signal intensity function in the described second region to be imaged based on the described first region to be imaged, determine described image pair Than degree function.
It can be seen from the above technical proposal that in embodiments of the present invention, the first region to be imaged and the second region to be imaged are determined, wherein first Region to be imaged and the second region to be imaged have different longitudinal relaxation times；It is determined that when execution multilayer excites Diffusion Imaging parallel, first treats into As the picture contrast function between region and the second region to be imaged；Flip angle is excited based on what picture contrast function determined diffusion-weighting sequence. As can be seen here, embodiment of the present invention will not excite flip angle to be defined to 90 degree, but determine diffusion-weighting sequence by picture contrast function Excite flip angle, can obtain exciting the same or similar image tissue contrast of Diffusion Imaging with individual layer when multilayer excites Diffusion Imaging parallel.
Moreover, embodiment of the present invention can be applied not only to rs-EPI sequences, other diffusion-weighting sequences such as ss-EPI sequences can also be applied to. In addition, embodiment of the present invention can be widely applied in the diffusion-weighted scanning of different parts.
Brief description of the drawings
Fig. 1 is the flow chart for exciting angle determination method for exciting diffusion-weighted imaging parallel according to embodiment of the present invention multilayer；
Fig. 2 is the sequence chart of the rs-EPI sequences of monopole dispersion pattern；
Fig. 3 is the exemplary comparison diagram according to the collection master drawing of embodiment of the present invention and the collection master drawing of prior art；
Fig. 4 is the structure chart for exciting angle setting unit for exciting Diffusion Imaging parallel according to the multilayer of embodiment of the present invention.
Embodiment
In order that technical scheme and advantage are more clearly understood, below in conjunction with drawings and the embodiments, the present invention is carried out further detailed Explanation.It should be appreciated that embodiment described herein is only to the illustrative explanation present invention, the protection model being not intended to limit the present invention Enclose.
In order to succinct and directly perceived on describing, hereafter the solution of the present invention is illustrated by describing some representational embodiments.Embodiment party Substantial amounts of details is only used for help and understands the solution of the present invention in formula.However, it will be apparent that technical scheme can be not limited to these when realizing Details.In order to avoid unnecessarily having obscured the solution of the present invention, some embodiments are not described meticulously, but only give framework. Hereinafter, " comprising " refers to " include but is not limited to ", " according to ... " refer to " according at least to ..., but be not limited to according only to ... ".Due to The speech habits of Chinese, when being hereinafter not specifically stated the quantity of composition, it is meant that it can also be multiple that the composition, which can be one, or can It is interpreted as at least one.
In the multilayer of prior art excites Diffusion Imaging parallel, generally excite flip angle using 90 degree and maximize signal intensity.In order that vertical Equilibrium state can be fully returned to after excitation to magnetization vector, and the repetition time (TR) needs the T1 much larger than image tissue.If some imagings The Mz of tissue can not be replied completely, then in ensuing scanning, and the signal of these image tissues will decay, so as to influence most Whole picture contrast.It can be seen that, in actual scanning, TR reduction is not only relevant with layer accelerated factor, and the reply also with Mz has Close.
For example, in head individual layer excites Diffusion Imaging, in order to obtain suitable contrast in tissue, TR at least needs to be more than 3 seconds.However, adopting Excited parallel after Diffusion Imaging with multilayer, the TR needed for exciting all layers may be much smaller than 3 seconds.In order to ensure in diffusion-weighted imaging b0 or low T2 contrasts under b values, multilayer excites the minimum TR of Diffusion Imaging not to be utilized parallel, and TR still depends on interested group in actual scanning The T1 values knitted.
It is found by the applicant that：When multilayer excites Diffusion Imaging (i.e. short TR Diffusion Imagings) parallel, flip angle is excited to accelerate longitudinal direction by reduction The reply of magnetization vector, so as to increase the contrast between signal intensity or the specific image tissue of maximization.
In fact, in current multilayer excites Diffusion Imaging parallel, not based on exciting upset angle and optimizing to keep contrast in tissue interested Technical scheme.
Applicant further found that：Flip angle is excited by optimization, obtains exciting with individual layer when can excite Diffusion Imaging (i.e. short TR) parallel in multilayer Diffusion Imaging (i.e. long TR Diffusion Imagings) same or similar image tissue contrast.
Fig. 1 is the flow chart for exciting angle determination method for exciting Diffusion Imaging parallel according to embodiment of the present invention multilayer.
As shown in figure 1, this method includes：
Step 101：The first region to be imaged and the second region to be imaged are determined, wherein the first region to be imaged and the second region to be imaged have difference Longitudinal relaxation time.
Herein, the first region to be imaged and the second region to be imaged can be the respective image tissue with different longitudinal relaxation times.Such as, First region to be imaged and the second region to be imaged can be respectively cinereum matter and cerebrospinal fluid, etc..
Step 102：It is determined that when execution multilayer excites Diffusion Imaging parallel, the image between the first region to be imaged and second region to be imaged Contrast function.
Picture contrast function between first region to be imaged and the second region to be imaged, the signal intensity and for reflecting the first region to be imaged Contrast degree between the signal intensity in two regions to be imaged.
In one embodiment, step 102 is specifically included：
First, the repetition time based on diffusion-weighting sequence, the echo time of diffusion-weighting sequence, the longitudinal relaxation time in the first region to be imaged and The T2 in the first region to be imaged, determines the signal intensity in the first region to be imaged；Repetition time, disperse based on diffusion-weighting sequence The T2 of the echo time of weighting sequence, the longitudinal relaxation time in the second region to be imaged and the second region to be imaged, determine that second treats into As the signal intensity in region.
Then, signal intensity and the signal intensity in the second region to be imaged based on the first region to be imaged, determine that the first region to be imaged is treated with second Picture contrast function between imaging region.Such as, by the signal intensity in the first region to be imaged compared with the signal intensity in the second region to be imaged, So as to obtain the picture contrast function between the first region to be imaged and the second region to be imaged.
Step 103：Flip angle is excited based on what picture contrast function determined diffusion-weighting sequence.
In one embodiment, step 103 includes：It is determined that when performing individual layer and exciting Diffusion Imaging, the first region to be imaged and second to be imaged Image contrast value between region；It is determined that exciting flip angle when the functional value of picture contrast function is equal to the image contrast value.
Specifically, the image comparison between the first region to be imaged and the second region to be imaged when performing individual layer and exciting Diffusion Imaging can be determined first Angle value, then by the functional value of picture contrast function be equal to the image contrast value, and determine now excite flip angle.So, determine Excite flip angle to ensure the image contrast value in the first region to be imaged and the second region to be imaged when multilayer excites Diffusion Imaging parallel, etc. It is same as the image contrast value between the first region to be imaged and the second region to be imaged when individual layer excites Diffusion Imaging.
Therefore, after using embodiment of the present invention, it can also be obtained when short TR is scanned and scan equivalent or similar image tissue figure with long TR Image contrast, consequently facilitating staff is divided the short TR images scanned based on the existing graphical analysis experience scanned for long TR Analysis.
In one embodiment, step 102 is specifically included：It is determined that exciting flip angle when the functional value of picture contrast function is maximum.
Flip angle is excited when herein, by calculating the functional value of picture contrast function for maximum, it is ensured that obtained when short TR is scanned Highest image tissue picture contrast is obtained, consequently facilitating staff preferably observes and analyzed scan image.
In one embodiment, step 102 is specifically included：It is determined that exciting flip angle when the functional value of picture contrast function is predetermined value.
Flip angle is excited when herein, by calculating the functional value of picture contrast function for predetermined value, what can be set based on staff is pre- Definite value scans corresponding image contrast value, consequently facilitating staff, which is based on respective picture contrast, perceives custom, short TR is scanned Image is analyzed.
In one embodiment, diffusion-weighting sequence is reading direction sectional plan echo-wave imaging (rs-EPI) sequence；
It is θ to excite flip angle1opt, wherein：
Wherein e is the nature truth of a matter；TRshortExcite the repetition time of Diffusion Imaging parallel for multilayer；TRlongThe repetition of Diffusion Imaging is excited for individual layer Time；T1AFor the longitudinal relaxation time in the first region to be imaged；T1BFor the longitudinal relaxation time in the second region to be imaged.
In embodiments of the present invention, diffusion-weighting sequence can also be embodied as single-shot echo planar imaging in addition to it may be embodied as rs-EPI sequences The others diffusion-weighted series such as imaging sequence.
Determined based on method shown in Fig. 1 after exciting flip angle, you can excited parallel more with exciting flip angle to perform specific multilayer according to this Astigmatic image is scanned.Multilayer excites Diffusion Imaging scan process to be this area mature technology parallel, and embodiment of the present invention is repeated no more to this.
The signal of diffusion-weighted collection can be derived from the Mz at sequence different time.Below with using monopole dispersion pattern Exemplified by rs-EPI sequences, progress refinement description is implemented to embodiment of the present invention.
Fig. 2 is the sequence chart of the rs-EPI sequences of monopole dispersion pattern.As shown in Fig. 2 in rs-EPI sequence acquisitions, the stable state of different time points Mz can be marked with A-G.Assuming that because presence and T1 relaxation when can ignore radio frequency (RF) pulse excitation of damage gradient, So the Mxy at G points can be ignored.
If Mz during stable state is M0；Mz at A points is MA；Mz at B points is MB；At C points Mz be Mc；Mz at D points is MD；Mz at E points is ME；Longitudinal magnetization arrow at F points Measure as MF；Mz at G points is MG；θ1To excite flip angle；θ2For reunion pulse angle.So：
MB=MAcosθ1
MC=MBE1+M0(1-E1)
MD=MCcosθ2
ME=MDE2+M0(1-E2)
MF=MEcosθ2
MG=MFE3+M0(1-E3)
Wherein：
E1=e-TE1/2T1；E2=e-TE2/2T1；E is natural logrithm；TE1 and TE2 are respectively rs-EPI The echo time of sequence；T1 is longitudinal relaxation time.
Utilize the condition M of stable stateA=MG, and set θ2Mz M at=180 degree, G pointsGWith signal intensity S nowdiffusionCan To be represented with following formula：
Sdiffusion=MGDinθ1sin2(θ2/2)e-TE1/T2e-bD。
Wherein:T2 is T2；B is disperse sensitive factor, and D is the dispersion coefficient on added Diffusion gradient direction.Herein, second Individual time poly- pulse is used to obtain navigation data to carry out phasing, therefore only influences the reply of Mz, does not have an impact to signal intensity.
Therefore, one includes tissue A (region A i.e. to be imaged) and the tissue B (contrasts between the tissue of interest pair of (region B i.e. to be imaged) Degree can be represented with following formula：
Wherein MGA(T1A,TR,TE1,TE2,θ1) it is Mzs of the tissue A at G points, independent variable includes T1A,TR,TE1,TE2,θ1； MGB(T1B,TR,TE1,TE2,θ1) it is Mzs of the tissue B at G points, independent variable includes T1B,TR,TE1,TE2,θ1；T1AFor group Knit A T1 values；T1BTo organize B T1 values；T2ATo organize A T2 values；T2BTo organize B T2 values；DAIt is tissue A added Dispersion coefficient on Diffusion gradient direction；DBIt is dispersion coefficients of the tissue B on added Diffusion gradient direction.It can be based onCalculate MGA(T1A,TR,TE1,TE2,θ1) and MGB(T1B,TR,TE1,TE2,θ1)。
Set θ1Optimal conditions be：Long TR (TRlong) and θ1Contrast during equal to 90 degree, equal to short TR (TRshort) and θ1To be optimal When contrast.
If TE1, TE2<<TR, can obtain following optimal flip angle θ1opt：
Wherein：E is the nature truth of a matter；TRshortExcited parallel for multilayer The repetition time of Diffusion Imaging；TRlongThe repetition time of Diffusion Imaging is excited for individual layer；T1AFor the T1 values in the first region to be imaged；T1BFor second The T1 values in region to be imaged.
Above by taking rs-EPI sequences as an example, the optimal flip angle θ of calculating is described in detail1optSpecific formula.Skilled person realizes that： By being simply adapted to back the number of poly- pulse, ss-EPI disperses can also be generalized to by deriving the optimal method for exciting flip angle based on rs-EPI sequences In sequence.Generally speaking, embodiment of the present invention suitable for all the negligible sequence of Mxy before exciting again.
It is proposed by the present invention to excite flip angle optimized algorithm to be widely applied to multilayer to excite in Diffusion Imaging, obtain under short TR parallel With same or analogous picture contrast under traditional long TR so that the minimum TR under multilayer is excited parallel may apply in actual scanning.
During the present invention is embodied, by adjusting corresponding parameter in the parameter card of diffusion-weighting sequence (such as, in optimization Option Box The middle adjustment T1 values of a pair of tissue of interest, long TR values and it is expected that hope optimizes obtained equivalent contrast), can be with based on above-mentioned derivation Automatically calculate and optimal excite flip angle.
Such as：The present invention is realized using rs-EPI sequences, wherein the parameter in head scanning is as follows：
TE=79ms；The visual field is 252mm × 252mm；With a width of 530Hz/Pixel；Thickness is 5mm；Acquisition matrix is 224 × 224；Scanning slice Number is 20；Segments is 11；Echo separation is 0.36ms；Dispersion pattern (Diffusion Mode) is 4-scan-trace；Disperse scheme (Diffusion Scheme) it is monopole (Monopolar)；B=0,1000s/mm2；The general automatic calibrated section parallel acquisition factor (GRAPPA factor) in aspect For 2；Layer accelerated factor is 2.
Using prior art bilayer it is parallel excite acquisition scheme (TR=4800) as referring to, its total scanning time be 4 points 12 seconds；In TR=2000 Bilayer excite parallel in collection, be respectively adopted 90 the degree of prior art and excite flip angle optimal to excite flip angle, total scanning time with of the invention Be 1 point 52 seconds.
Fig. 3 is the exemplary comparison diagram according to the collection master drawing of embodiment of the present invention and the collection master drawing of prior art.Fig. 3 includes subgraph 3 (A) -3 (H), altogether eight subgraphs.In figure 3, under the different TR of rs-EPI sequences, excite flip angle be 90 degree when bilayer excite parallel Collection master drawing with it is optimal excite flip angle when the master drawing that collects contrasted.
Fig. 3 (A) is to excite the image that Diffusion Imaging is collected, wherein TR=4800ms parallel using the bilayer of prior art, and sweep time is 4 Divide 12 seconds, b=0s/mm2, it is 90 degree to excite flip angle；Fig. 3 (B) is to excite Diffusion Imaging to be collected parallel using the bilayer of prior art Image, wherein TR=2000ms, sweep time=1 point 52 seconds, b=0s/mm2, it is 90 degree to excite flip angle；Fig. 3 (C) is used after the present invention, Using the optimal parallel image for exciting Diffusion Imaging to be collected of bilayer for exciting flip angle calculated, wherein TR is 2000ms, sweep time For 1 point of 52 seconds, b=0s/mm2, T1AFor 1500ms, T1BFor 4000ms, long TR is 4800ms, optimal to excite flip angle to be 49 degree；Fig. 3 (D) The image that corresponding ss-EPI is collected, acquisition matrix=192*192, TR=5200ms, sweep time be 1 point 14 seconds.Fig. 3 (E)-Fig. 3 (F) High b values image corresponding to respectively Fig. 3 (A)-Fig. 3 (D), wherein b is equal to 1000s/mm2.All subgraphs in Fig. 3 are with automatic window width window Position display.
As shown in Fig. 3 (B), with TR reduction, the contrast of cinereum matter and cerebrospinal fluid also accordingly declines.Employ and optimal excite upset angle and optimizing Afterwards, short TR bilayer excites rs-EPI to obtain the picture contrast similar with long TR parallel, so as to further reduction sweep time.
It is worth noting that：Under high b values, the present invention is similarly obvious (being marked in figure 3 with white circle) for the improvement of picture contrast. By gathering corresponding ss-EPI diffusion weighted images, it is found that optimization excites the bilayers of the short TR after flip angle to excite rs-EPI can be similar parallel Sweep time in obtain being substantially better than ss-EPI picture quality.
Based on above-mentioned analysis, angle setting unit is excited the invention also provides what a kind of multilayer excited Diffusion Imaging parallel.
Fig. 4 is the structure chart for exciting angle setting unit for exciting Diffusion Imaging parallel according to the multilayer of embodiment of the present invention.
As shown in figure 4, the device 400 includes：
Area determination module 401 to be imaged, for determining the first region to be imaged and the second region to be imaged, wherein the first region to be imaged and second Region to be imaged has different longitudinal relaxation times；
Picture contrast function determination module 402, for determining that the first region to be imaged is treated with second when execution multilayer excites Diffusion Imaging parallel Picture contrast function between imaging region；
Flip angle determining module 403 is excited, flip angle is excited for determine diffusion-weighting sequence based on picture contrast function.
In one embodiment, flip angle determining module 403 is excited, for determining that first is to be imaged when execution individual layer excites Diffusion Imaging Image contrast value between region and the second region to be imaged；It is determined that exciting when the functional value of picture contrast function is equal to image contrast value Flip angle.
In one embodiment, diffusion-weighting sequence is reading direction sectional plan echo imaging sequence；
It is θ to excite flip angle1opt, wherein：
E is the nature truth of a matter；TRshortExcite the repetition time of Diffusion Imaging parallel for multilayer；TRlongThe repetition time of Diffusion Imaging is excited for individual layer； T1AFor the T1 values in the first region to be imaged, T1BFor the T1 values in the second region to be imaged.
In one embodiment, flip angle determining module 403 is excited, for determining when the functional value of picture contrast function is maximum Excite flip angle；Or, determine to excite flip angle when the functional value of picture contrast function is predetermined value.
In one embodiment, picture contrast function determination module 402, for the repetition time based on diffusion-weighting sequence, diffusion-weighted sequence The T2 of the echo time of row, the longitudinal relaxation time in the first region to be imaged and the first region to be imaged, determine the first region to be imaged Signal intensity function；The echo time of repetition time, diffusion-weighting sequence based on diffusion-weighting sequence, the longitudinal relaxation in the second region to be imaged Time and the T2 in the second region to be imaged, determine the signal intensity function in the second region to be imaged；Letter based on the first region to be imaged Number intensity function and the signal intensity function in the second region to be imaged, determine picture contrast function.
In one embodiment, diffusion-weighting sequence includes rs-EPI or ss-EPI sequences.
The application programming interfaces of certain specification can be followed, what the multilayer that embodiment of the present invention is proposed excited Diffusion Imaging parallel excites angle true The method of determining is written as the plug-in card program being installed in the Diffusion MR Images control main frame, PC, mobile terminal etc., can also be encapsulated for Application program uses so that user voluntarily downloads.
What the storing mode multilayer that be proposed embodiment of the present invention that can be stored by instruction or instruction set excited Diffusion Imaging parallel excites angle Degree determination method is stored on various storage mediums.These storage mediums include but is not limited to：Floppy disk, CD, DVD, hard disk, flash memory etc..
Furthermore it is also possible to the multilayer that embodiment of the present invention is proposed excite Diffusion Imaging parallel excite angle determination method to be applied to based on flash memory In the storage medium of (Nand flash), such as USB flash disk, CF cards, SD card, SDHC cards, mmc card, SM cards, memory stick, xD cards etc..
In summary, in embodiments of the present invention, the first region to be imaged and the second region to be imaged are determined, wherein the first region to be imaged and Two regions to be imaged have different longitudinal relaxation times；It is determined that when execution multilayer excites Diffusion Imaging parallel, first region to be imaged and institute State the picture contrast function between the second region to be imaged；Flip angle is excited based on what picture contrast function determined the diffusion-weighting sequence. It can be seen that, embodiment of the present invention can obtain exciting the same or similar image tissue pair of Diffusion Imaging with individual layer when multilayer excites Diffusion Imaging parallel Than.
Moreover, the present invention can be applied not only to rs-EPI sequences, it can also be applied in other diffusion-weighting sequences.Moreover, the present invention can be with It is widely used in the scanning of the diffusion-weighted of different parts, as long as the T1 values of tissue of interest pair can be known.
It is described above, it is only the better embodiment of the present invention, is not intended to limit the scope of the present invention.It is all the present invention spirit and Within principle, any modification, equivalent substitution and improvements made etc. should be included in the scope of the protection.

Claims (10)

  1. What 1. a kind of multilayer excited Diffusion Imaging parallel excites flip angle to determine method, it is characterised in that including：
    Determine the first region to be imaged and the second region to be imaged, wherein first region to be imaged and second region to be imaged have it is different Longitudinal relaxation time；
    It is determined that when execution multilayer excites Diffusion Imaging parallel, the picture contrast between first region to be imaged and second region to be imaged Function；
    Flip angle is excited based on what described image contrast function determined diffusion-weighting sequence.
  2. What 2. multilayer according to claim 1 excited Diffusion Imaging parallel excites flip angle to determine method, it is characterised in that described to be based on What picture contrast function determined diffusion-weighting sequence excites flip angle to include：
    It is determined that when execution individual layer excites Diffusion Imaging, the image contrast value between first region to be imaged and second region to be imaged；
    It is determined that exciting flip angle when the functional value of described image contrast function is equal to described image contrast value.
  3. What 3. multilayer according to claim 2 excited Diffusion Imaging parallel excites flip angle to determine method, it is characterised in that the disperse Weighting sequence is reading direction sectional plan echo imaging sequence；
    It is described to excite flip angle to be θ1opt, wherein：
    <mrow> <msub> <mi>&amp;theta;</mi> <mrow> <mn>1</mn> <mi>o</mi> <mi>p</mi> <mi>t</mi> </mrow> </msub> <mo>=</mo> <mi>&amp;pi;</mi> <mo>-</mo> <mi>arccos</mi> <mrow> <mo>(</mo> <mfrac> <mrow> <mi>a</mi> <mo>+</mo> <mi>c</mi> <mo>-</mo> <mi>a</mi> <mi>b</mi> <mo>-</mo> <mn>1</mn> </mrow> <mrow> <mi>b</mi> <mo>-</mo> <mi>a</mi> <mi>c</mi> <mo>-</mo> <mi>b</mi> <mi>c</mi> <mo>+</mo> <mi>a</mi> <mi>b</mi> <mi>c</mi> </mrow> </mfrac> <mo>)</mo> </mrow> <mo>;</mo> </mrow>
    <mrow> <mi>a</mi> <mo>=</mo> <mfrac> <mrow> <mn>1</mn> <mo>-</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mfrac> <mrow> <msub> <mi>TR</mi> <mrow> <mi>l</mi> <mi>o</mi> <mi>n</mi> <mi>g</mi> </mrow> </msub> </mrow> <msub> <mi>T</mi> <mrow> <mn>1</mn> <mi>A</mi> </mrow> </msub> </mfrac> </mrow> </msup> </mrow> <mrow> <mn>1</mn> <mo>-</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mfrac> <mrow> <msub> <mi>TR</mi> <mrow> <mi>l</mi> <mi>o</mi> <mi>n</mi> <mi>g</mi> </mrow> </msub> </mrow> <msub> <mi>T</mi> <mrow> <mn>1</mn> <mi>B</mi> </mrow> </msub> </mfrac> </mrow> </msup> </mrow> </mfrac> <mo>;</mo> <mi>b</mi> <mo>=</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <msub> <mi>TR</mi> <mrow> <mi>s</mi> <mi>h</mi> <mi>o</mi> <mi>r</mi> <mi>t</mi> </mrow> </msub> <mo>/</mo> <msub> <mi>T</mi> <mrow> <mn>1</mn> <mi>B</mi> </mrow> </msub> </mrow> </msup> <mo>;</mo> <mi>c</mi> <mo>=</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <msub> <mi>TR</mi> <mrow> <mi>s</mi> <mi>h</mi> <mi>o</mi> <mi>r</mi> <mi>t</mi> </mrow> </msub> <mo>/</mo> <msub> <mi>T</mi> <mrow> <mn>1</mn> <mi>A</mi> </mrow> </msub> </mrow> </msup> <mo>;</mo> </mrow>
    E is the nature truth of a matter；TRshortExcite the repetition time of Diffusion Imaging parallel for the multilayer；TRlongDiffusion Imaging is excited for the individual layer Repetition time；T1AFor the longitudinal relaxation time in the first region to be imaged；T1BFor the longitudinal relaxation time in the second region to be imaged.
  4. What 4. multilayer according to claim 1 excited Diffusion Imaging parallel excites flip angle to determine method, it is characterised in that described to be based on What picture contrast function determined diffusion-weighting sequence excites flip angle to include：
    It is determined that exciting flip angle when the functional value of described image contrast function is maximum；Or
    It is determined that exciting flip angle when the functional value of described image contrast function is predetermined value.
  5. What 5. the multilayer according to any one of claim 1-4 excited Diffusion Imaging parallel excites flip angle to determine method, it is characterised in that
    It is described to determine when execution multilayer excites Diffusion Imaging parallel, the picture contrast function between the first region to be imaged and the second region to be imaged Including：
    Repetition time based on the diffusion-weighting sequence, the echo time of the diffusion-weighting sequence, the longitudinal relaxation in first region to be imaged Time and the T2 in first region to be imaged, determine the signal intensity function in the first region to be imaged；
    Repetition time based on the diffusion-weighting sequence, the echo time of the diffusion-weighting sequence, the longitudinal relaxation in second region to be imaged Time and the T2 in second region to be imaged, determine the signal intensity function in the second region to be imaged；
    Signal intensity function and the signal intensity function in the described second region to be imaged based on the described first region to be imaged, determine that described image is contrasted Spend function.
  6. What 6. a kind of multilayer excited Diffusion Imaging parallel excites flip angle determining device, it is characterised in that including：
    Area determination module to be imaged, for determining the first region to be imaged and the second region to be imaged, wherein first region to be imaged and second Region to be imaged has different longitudinal relaxation times；
    Picture contrast function determination module, for determining when performing multilayer and exciting Diffusion Imaging parallel, first region to be imaged and described the Picture contrast function between two regions to be imaged；
    Flip angle determining module is excited, flip angle is excited for determine diffusion-weighting sequence based on described image contrast function.
  7. What 7. multilayer according to claim 6 excited Diffusion Imaging parallel excites flip angle determining device, it is characterised in that
    Flip angle determining module is excited, for determining that first region to be imaged and described second is treated into when execution individual layer excites Diffusion Imaging As the image contrast value between region；It is determined that exciting flip angle when the functional value of described image contrast function is equal to described image contrast value Degree.
  8. What 8. multilayer according to claim 7 excited Diffusion Imaging parallel excites flip angle determining device, it is characterised in that the disperse Weighting sequence is reading direction sectional plan echo imaging sequence；
    It is described to excite flip angle to be θ1opt, wherein：
    <mrow> <msub> <mi>&amp;theta;</mi> <mrow> <mn>1</mn> <mi>o</mi> <mi>p</mi> <mi>t</mi> </mrow> </msub> <mo>=</mo> <mi>&amp;pi;</mi> <mo>-</mo> <mi>arccos</mi> <mrow> <mo>(</mo> <mfrac> <mrow> <mi>a</mi> <mo>+</mo> <mi>c</mi> <mo>-</mo> <mi>a</mi> <mi>b</mi> <mo>-</mo> <mn>1</mn> </mrow> <mrow> <mi>b</mi> <mo>-</mo> <mi>a</mi> <mi>c</mi> <mo>-</mo> <mi>b</mi> <mi>c</mi> <mo>+</mo> <mi>a</mi> <mi>b</mi> <mi>c</mi> </mrow> </mfrac> <mo>)</mo> </mrow> <mo>;</mo> </mrow>
    <mrow> <mi>&amp;alpha;</mi> <mo>=</mo> <mfrac> <mrow> <mn>1</mn> <mo>-</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mfrac> <mrow> <msub> <mi>TR</mi> <mrow> <mi>l</mi> <mi>o</mi> <mi>n</mi> <mi>g</mi> </mrow> </msub> </mrow> <msub> <mi>T</mi> <mrow> <mn>1</mn> <mi>A</mi> </mrow> </msub> </mfrac> </mrow> </msup> </mrow> <mrow> <mn>1</mn> <mo>-</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mfrac> <mrow> <msub> <mi>TR</mi> <mrow> <mi>l</mi> <mi>o</mi> <mi>n</mi> <mi>g</mi> </mrow> </msub> </mrow> <msub> <mi>T</mi> <mrow> <mn>1</mn> <mi>B</mi> </mrow> </msub> </mfrac> </mrow> </msup> </mrow> </mfrac> <mo>;</mo> <mi>b</mi> <mo>=</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <msub> <mi>TR</mi> <mrow> <mi>s</mi> <mi>h</mi> <mi>o</mi> <mi>r</mi> <mi>t</mi> </mrow> </msub> <mo>/</mo> <msub> <mi>T</mi> <mrow> <mn>1</mn> <mi>B</mi> </mrow> </msub> </mrow> </msup> <mo>;</mo> <mi>c</mi> <mo>=</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <msub> <mi>TR</mi> <mrow> <mi>s</mi> <mi>h</mi> <mi>o</mi> <mi>r</mi> <mi>t</mi> </mrow> </msub> <mo>/</mo> <msub> <mi>T</mi> <mrow> <mn>1</mn> <mi>A</mi> </mrow> </msub> </mrow> </msup> <mo>;</mo> </mrow>
    E is the nature truth of a matter；TRshortExcite the repetition time of Diffusion Imaging parallel for the multilayer；TRlongDiffusion Imaging is excited for the individual layer Repetition time；T1AFor the longitudinal relaxation time in the first region to be imaged；T1BFor the longitudinal relaxation time in the second region to be imaged.
  9. What 9. multilayer according to claim 6 excited Diffusion Imaging parallel excites flip angle determining device, it is characterised in that
    Flip angle determining module is excited, for determining to excite flip angle when the functional value of described image contrast function is maximum；Or, It is determined that exciting flip angle when the functional value of described image contrast function is predetermined value.
  10. What 10. the multilayer according to any one of claim 6-9 excited Diffusion Imaging parallel excites flip angle determining device, it is characterised in that
    Picture contrast function determination module, for the repetition time based on the diffusion-weighting sequence, the echo time of the diffusion-weighting sequence, The longitudinal relaxation time in first region to be imaged and the T2 in first region to be imaged, determine the signal in the first region to be imaged Intensity function；Repetition time based on the diffusion-weighting sequence, the echo time of the diffusion-weighting sequence, second region to be imaged it is vertical To relaxation time and the T2 in second region to be imaged, the signal intensity function in the second region to be imaged is determined；Based on described first The signal intensity function in region to be imaged and the signal intensity function in the described second region to be imaged, determine described image contrast function.
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