CN108152769A - A kind of angle and T based on hyperpolarized gas wave spectrum1Measuring method simultaneously - Google Patents
A kind of angle and T based on hyperpolarized gas wave spectrum1Measuring method simultaneously Download PDFInfo
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- CN108152769A CN108152769A CN201711405510.7A CN201711405510A CN108152769A CN 108152769 A CN108152769 A CN 108152769A CN 201711405510 A CN201711405510 A CN 201711405510A CN 108152769 A CN108152769 A CN 108152769A
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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]
- G01R33/448—Relaxometry, i.e. quantification of relaxation times or spin density
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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]
- G01R33/46—NMR spectroscopy
Abstract
The invention discloses a kind of angles and T based on hyperpolarized gas wave spectrum1Measuring method simultaneously, collects hyperpolarized gas first；Research object obtains hyperpolarized gas；In single-breath hold, the excitation angle, θ of fixed RF pulse, acquire the Magnetic Resonance Spectrum of the hyperpolarized gas of research object, obtain the free induction decay signal FID1 of hyperpolarized gas of the research object under the variable repetition time TR1 and free induction decay signal FID2 of the hyperpolarized gas under fixed repetition time TR2；By FID1, FID2 processing, the excitation angle, θ of practical radio-frequency pulse is obtainedrWith the longitudinal relaxation time constant T of the hyperpolarized gas of research object1.The present invention can obtain angle and T simultaneously1Analytic solutions, and shorten the sampling time, reduce the requirement to hardware, Project Realization and data processing are simple and practicable.
Description
Technical field
The present invention relates to magnetic resonance spectroscopy techniques fields, and in particular to a kind of angle and T based on hyperpolarized gas wave spectrum1
Measuring method simultaneously.Angle is excited accurately to control suitable for the radio-frequency pulse using hyperpolarized gas as contrast agent, T1Measure etc..
Background technology
Observing nuclear of the Magnetic Resonance Spectrum (Magnetic Resonance Spectroscopy, MRS) in sample is in magnetic
The phenomenon that nuclear magnetic resonance is occurred by the excitation of radio frequency (radiofrequency, RF) pulse in, is connect using electronic system
The magnetic resonance signal of sample generation is received, gained digital signal is subjected to Spectrum Conversion, Magnetic Resonance Spectrum can be reconstructed.It is conventional
MRS be chiefly used in H atom in water or lipid.For intert-gas atoms, the method for usually utilizing spin-exchange optical pumping so that
Magnetization vector during its thermal nonequilibrium is far above stable state, i.e. inert gas core obtains higher polarizability, and this method is known as
Hyperpolarized gas technology.H2At ambient temperature, nuclear spin polarization degree is generally 10 for gas and inert gas-6Magnitude, and hyperpolarization
The nuclear spin polarization degree of inert gas can be increased 4-5 magnitude by technology.But at this moment hyperpolarized gas is in unstable state, by
In SPIN-LATTICE RELAXATION (T1Relaxation) and radio-frequency pulse excitation, thermal nonequilibrium polarizability can decay rapidly, and irrecoverable.
This causes hyperpolarized gas MRS to be different from conventional proton MRS.
In hyperpolarized gas magnetic resonance experiments, RF pulse modules need to export specific voltage value to realize to observing nuclear
The excitation of controllable flip angle, and the T of sample1Accurate voltage control is also required in measurement.In addition, on the one hand, by instrument
Hardware limitation can only set the RF pulses of finite number difference excitation angle in experiment；On the other hand, in human body and animal lung
In hyperpolarization experiment, it usually needs gathered data of holding one's breath, this needs short acquisition time.Currently used measurement RF pulse angles
The method of θ is easily by T1Relaxation influences, and the sampling time is long, and error of fitting is larger, needs to set multiple excitation angles, will to hardware
Ask higher.
In addition, also have the excitation angle measurement that hyperpolarized gas is carried out using MR imaging method, but these methods
It needs repeatedly to hold one's breath, causes acquisition time longer and easily by the different different influences of lower gas flow of holding one's breath.Therefore, for
The above problem needs to develop a kind of angle and T for hyperpolarized gas wave spectrum1Method for fast measuring.
Invention content
It is a kind of based on hyperpolarized gas wave spectrum the purpose of the present invention is in view of the above-mentioned problems existing in the prior art, providing
Angle and T1Measuring method simultaneously.
The above-mentioned purpose of the present invention is achieved through the following technical solutions：
A kind of angle and T based on hyperpolarized gas wave spectrum1Measuring method simultaneously, includes the following steps：
Step 1 collects hyperpolarized gas；
Step 2, research object obtain hyperpolarized gas；
Step 3, in single-breath hold, the excitation angle, θ of fixed RF pulse acquires the hyperpolarized gas of research object
Magnetic Resonance Spectrum obtains the free induction decay signal FID1 of hyperpolarized gas of the research object under variable repetition time TR1,
And the FID signal FID2 of the hyperpolarized gas under fixed repetition time TR2,
Wherein, variable repetition time TR1 is defined as TR1 (i), TR1 (i)=a (i-1)+b, i=1,2 ..., N, N >=2, a>
0, b>0, and i, N, a, b are real number, N excites number for radio-frequency pulse,
Definition fixed repetition time TR2 is TR2 (j), TR2 (j)=b, j=1,2 ..., N+1, and j is real number；
Step 4, will be at the free induction decay signal FID1 that obtained in step 3 and free induction decay signal FID2
Reason, obtains the excitation angle, θ of practical radio-frequency pulserIt is normal with the spin-lattice relaxation time of the hyperpolarized gas of research object
Number T1, specifically include following steps：
Free induction decay signal FID1, free induction decay signal FID2 are combined and sorted by step 4.1, are studied
The free induction decay signal FID3 of hyperpolarized gas of the object under set repetition time TR3,
Definition set repetition time TR3 is TR3 (k), in 1≤k≤N, TR3 (k)=a (k-1)+b, in N<k≤2N+1
When, TR3 (k)=b, k=1,2 ..., 2N+1, and k is real number,
It is FID3 (k) to define free induction decay signal FID3, in 1≤k≤N, FID3 (k)=FID1, in N<k≤2N
When+1, TR3 (k)=FID2；
Free induction decay signal FID3 progress Fast Fourier Transform is obtained research object in set weight by step 4.2
The wave spectrum F1 of hyperpolarized gas under multiple time TR3, and phasing is carried out to the wave spectrum F1 of hyperpolarized gas, obtain phase school
The wave spectrum F2 of hyperpolarized gas of the research object under set repetition time TR3 after just calculates the real part integrated value of wave spectrum F2
M defines real part integrated value M as M (p), p=1,2 ..., 2N+1, and P is real number；
Step 4.3 carries out real part integrated value M from normalizing, and obtains research object under the variable repetition time TR4 that adds up
Hyperpolarized gas signal S1；
Definition signal S1 be S1 (i), S1 (i)=(M (i+1+N) * M (1))/(M (i+1) * M (N+1)),
Step 4.4 normalizes before being carried out to the signal S1 of hyperpolarized gas to oneself, obtains research object in regressive Weight variable
The relaxation signals S2 of hyperpolarized gas under multiple time TR5,
Wherein, it is S2 (i) to define relaxation signals S2, during i=1, during S2 (1)=S1 (1)/S1 (1), 2≤i≤N, and S2 (i)
=S1 (i)/S1 (i-1),
The definition regressive variable repetition time is TR5 (i), TR5 (i)=TR1 (i)-TR2 (i)；
Step 4.5 carries out relaxation signals S2 natural logrithm is asked to calculate, and obtains natural logrithm signal S3；
Step 4.6 defines natural logrithm signal S3 as S3 (i), to natural logrithm signal S3 according to formula S 3 (i)=(1/
T1) * TR5 (i) progress least square fittings, obtain the spin-lattice relaxation time constant T of the hyperpolarized gas of research object1；
Step 4.7 normalizes the rear N+1 progress of real part integrated value M certainly, obtains the hyperpolarized gas of research object
Radio-frequency pulse deamplification S4；
Wherein, it is S4 (j), S4 (j)=M (j+N)/M (N+1) to define radio-frequency pulse deamplification S4；
Step 4.8 defines radio-frequency pulse and declines according to radio-frequency pulse deamplification S4, acquisition radio-frequency pulse deamplification S5
Cut signal S5 is S5 (i), during i=1, during S5 (1)=S4 (1)/S4 (1), 2≤i≤N,
Step 4.9, to radio-frequency pulse deamplification S5 according to formula S 5 (i)=(cos θr)i-1Carry out least square fitting,
Obtain the excitation angle, θ of practical radio-frequency pulser。
The present invention has the advantages that relative to the prior art：
The 1st, the repetition time of multiple length need not be set, significantly reduce the sampling time.Also, hyperpolarization can be measured simultaneously
The spin-lattice relaxation time constant T of gas1With the excitation angle, θ of radio-frequency pulse；
2nd, using single excitation angle, the requirement to hardware is reduced；
3rd, Project Realization and data processing method are simple and practicable.
Description of the drawings
Fig. 1 is the flow diagram of the method for the present invention.Wherein TR is the repetition time, T1It is the hyperpolarized gas of research object
Spin-lattice relaxation time constant.
Specific embodiment
The specific implementation process and effect of the present invention is provided with reference to specific example.
A kind of angle and T based on hyperpolarized gas wave spectrum disclosed by the invention1Measuring method simultaneously, including following step
Suddenly：
Step 1 collects hyperpolarized gas.Wherein hyperpolarized gas includes3He or129Xe or131Xe or83Kr etc..It collects
To hyperpolarized gas save as gaseous state or solid-state, wherein solid-state is distilled when in use as gaseous state.
Step 2, research object obtain hyperpolarized gas.Research object include liquid or solid or biological tissue or animal or
People etc..
Step 3, in single-breath hold, the excitation angle, θ of fixed RF pulse acquires the hyperpolarized gas of research object
Magnetic Resonance Spectrum obtains free induction decay (FID) signal of hyperpolarized gas of the research object under variable repetition time TR1
The FID signal FID2 of FID1 and the hyperpolarized gas under fixed repetition time TR2.Specifically include following steps,
Step 3.1, the excitation angle, θ of fixed RF pulse obtain super of the research object under variable repetition time TR1
Change the free induction decay signal FID1 of gas.Wherein, variable repetition time TR1 is defined as TR1 (i), TR1 (i)=a (i-1)+
B, i=1,2 ..., N, N >=2, a>0,b>0, and i, N, a, b are real number, N excites number for radio-frequency pulse；
Step 3.2, the excitation angle, θ of fixed RF pulse obtain super of the research object under fixed repetition time TR2
Change the free induction decay signal FID2 of gas.Wherein, it defines and fixes repetition time TR2 as TR2 (j), TR2 (j)=b, j=1,
2 ..., N+1, and j is real number.
Step 4, will be at the free induction decay signal FID1 that obtained in step 3 and free induction decay signal FID2
Reason, obtains the excitation angle, θ of practical radio-frequency pulserIt is normal with the spin-lattice relaxation time of the hyperpolarized gas of research object
Number T1.Specifically include following steps,
Free induction decay signal FID1, free induction decay signal FID2 are combined and sorted by step 4.1, are studied
The free induction decay signal FID3 of hyperpolarized gas of the object under set repetition time TR3.
Wherein, it is TR3 (k) to define set repetition time TR3, in 1≤k≤N, TR3 (k)=a (k-1)+b, in N<k≤
During 2N+1, TR3 (k)=b, k=1,2 ..., 2N+1, and k is real number；It is FID3 (k) to define free induction decay signal FID3,
In 1≤k≤N, FID3 (k)=FID1, in N<During k≤2N+1, TR3 (k)=FID2；
Free induction decay signal FID3 progress Fast Fourier Transform is obtained research object in set weight by step 4.2
The wave spectrum F1 of hyperpolarized gas under time TR3 again, and pass through the side that real part integrates maximum value to the wave spectrum F1 of hyperpolarized gas
Method carries out phasing, obtains the wave spectrum of hyperpolarized gas of the research object after phasing under set repetition time TR3
F2 calculates the real part integrated value M of the wave spectrum F2 of hyperpolarized gas, defines real part integrated value M as M (p), p=1,2 ..., 2N+1,
And P is real number；
Step 4.3 carries out real part integrated value M from normalizing, and obtains research object under the variable repetition time TR4 that adds up
Hyperpolarized gas signal S1,
Wherein, definition signal S1 be S1 (i), S1 (i)=(M (i+1+N) * M (1))/(M (i+1) * M (N+1)),I=1,2 ..., N, and i is real number；
Step 4.4 normalizes before being carried out to the signal S1 of hyperpolarized gas to oneself, obtains research object in regressive Weight variable
The relaxation signals S2 of hyperpolarized gas under multiple time TR5,
Wherein, it is S2 (i) to define relaxation signals S2, during i=1, during S2 (1)=S1 (1)/S1 (1), 2≤i≤N, and S2 (i)
=S1 (i)/S1 (i-1),
The definition regressive variable repetition time is TR5 (i), TR5 (i)=TR1 (i)-TR2 (i), i=1,2 ..., N, and i is
Real number；
Step 4.5 carries out relaxation signals S2 natural logrithm is asked to calculate, and obtains natural logrithm signal S3；
Step 4.6 defines natural logrithm signal S3 as S3 (i), to natural logrithm signal S3 according to formula S 3 (i)=(1/
T1) * TR5 (i) and least-square fitting approach, fitting obtain the spin-lattice relaxation time of the hyperpolarized gas of research object
Constant T1；
Step 4.7 normalizes the rear N+1 progress of real part integrated value M certainly, obtains the hyperpolarized gas of research object
Radio-frequency pulse deamplification S4, wherein, it is S4 (j), S4 (j)=M (j+N)/M (N+1), j to define radio-frequency pulse deamplification S4
=1,2 ..., N+1, and j is real number；
Step 4.8 defines radio-frequency pulse and declines according to radio-frequency pulse deamplification S4, acquisition radio-frequency pulse deamplification S5
Cut signal S5 is S5 (i), during i=1, during S5 (1)=S4 (1)/S4 (1), 2≤i≤N,And i is
Real number；
Step 4.9, to radio-frequency pulse deamplification S5 according to formula S 5 (i)=(cos θr)i-1, i=1,2 ..., N, and i
For real number, least square fitting is carried out, obtains the excitation angle, θ of practical radio-frequency pulser；
By with result it is found that the excitation angle, θ of practical radio-frequency pulse can be obtained simultaneously using the method for the inventionr
With the spin-lattice relaxation time constant T of the hyperpolarized gas of research object1。
In conclusion the present invention a kind of angle and T based on hyperpolarized gas wave spectrum1Measuring method simultaneously, is collected first
Hyperpolarized gas；Research object obtains hyperpolarized gas；In single-breath hold, the excitation angle, θ of fixed RF pulse, acquisition is ground
Study carefully the Magnetic Resonance Spectrum of the hyperpolarized gas of object, obtain hyperpolarized gas of the research object under variable repetition time TR1
The free induction decay signal of free induction decay signal FID1 and the hyperpolarized gas under fixed repetition time TR2
FID2；By FID1, FID2 processing, the excitation angle, θ of practical radio-frequency pulse is obtainedrWith the hyperpolarized gas of research object
Spin-lattice relaxation time constant T1.Specific advantage is as follows：
1st, the spin-lattice relaxation time constant T of the hyperpolarized gas of the excitation angle, θ and research object of radio-frequency pulse1
It is respectively provided with analytic solutions.It is related to θ and T1Equation be single type elementary function, therefore with analytic solutions.
2nd, θ and T can be measured simultaneously1, and shorten the sampling time.Due to the method using the set repetition time, without setting
It puts the repetition time of multiple length, therefore the sampling time can be significantly reduced.
3rd, using single excitation angle, the requirement to hardware is reduced.In sampling angle is excited with 1 fixed radio-frequency pulse
Degree, it is only necessary to which 1 radio-frequency pulse object module can be achieved with.
4th, Project Realization and data processing method are simple and practicable.In sampling using 1 fixed radio-frequency pulse excitation angle,
The variable and fixed repetition time, it is only necessary to which the sequential for adjusting pulse train module can be achieved with.During data processing, by T1With θ points
It can be handled from rear based on elementary function, it is simple and practicable.
Specific embodiment described herein is only an example for the spirit of the invention.Technology belonging to the present invention is led
The technical staff in domain can do various modifications or additions to described specific embodiment or replace in a similar way
In generation, however, it does not deviate from the spirit of the invention or beyond the scope of the appended claims.
Claims (1)
1. a kind of angle and T based on hyperpolarized gas wave spectrum1Measuring method simultaneously, which is characterized in that include the following steps：
Step 1 collects hyperpolarized gas；
Step 2, research object obtain hyperpolarized gas；
Step 3, in single-breath hold, the excitation angle, θ of fixed RF pulse, the magnetic for acquiring the hyperpolarized gas of research object is total to
Vibration wave compose, obtain hyperpolarized gas of the research object under variable repetition time TR1 free induction decay signal FID1 and
The FID signal FID2 of hyperpolarized gas under fixed repetition time TR2,
Wherein, variable repetition time TR1 is defined as TR1 (i), TR1 (i)=a (i-1)+b, i=1,2 ..., N, N >=2, a>0, b>
0, and i, N, a, b are real number, N excites number for radio-frequency pulse,
Definition fixed repetition time TR2 is TR2 (j), TR2 (j)=b, j=1,2 ..., N+1, and j is real number；
Step 4, by the free induction decay signal FID1 obtained in step 3 and free induction decay signal FID2 processing,
Obtain the excitation angle, θ of practical radio-frequency pulserWith the spin-lattice relaxation time constant T of the hyperpolarized gas of research object1,
Specifically include following steps：
Free induction decay signal FID1, free induction decay signal FID2 are combined and sorted by step 4.1, obtain research object
The free induction decay signal FID3 of hyperpolarized gas under set repetition time TR3,
Definition set repetition time TR3 is TR3 (k), in 1≤k≤N, TR3 (k)=a (k-1)+b, in N<During k≤2N+1,
TR3 (k)=b, k=1,2 ..., 2N+1, and k is real number,
It is FID3 (k) to define free induction decay signal FID3, in 1≤k≤N, FID3 (k)=FID1, in N<k≤2N+1
When, TR3 (k)=FID2；
Free induction decay signal FID3 progress Fast Fourier Transform is obtained research object when set repeats by step 4.2
Between hyperpolarized gas under TR3 wave spectrum F1, and phasing is carried out to the wave spectrum F1 of hyperpolarized gas, after obtaining phasing
Hyperpolarized gas of the research object under set repetition time TR3 wave spectrum F2, calculate the real part integrated value M of wave spectrum F2, it is fixed
Adopted real part integrated value M is that M (p), p=1,2 ..., 2N+1, and P are real number；
Step 4.3 carries out real part integrated value M, from normalizing, it is super under the variable repetition time TR4 that adds up to obtain research object
The signal S1 of polarized gas；
Definition signal S1 be S1 (i), S1 (i)=(M (i+1+N) * M (1))/(M (i+1) * M (N+1)),
Step 4.4, the signal S1 of hyperpolarized gas is carried out before to from normalizing, obtain research object regressive is variable repeat when
Between hyperpolarized gas under TR5 relaxation signals S2,
Wherein, it is S2 (i) to define relaxation signals S2, during i=1, during S2 (1)=S1 (1)/S1 (1), 2≤i≤N, and S2 (i)=S1
(i)/S1 (i-1),
The definition regressive variable repetition time is TR5 (i), TR5 (i)=TR1 (i)-TR2 (i)；
Step 4.5 carries out relaxation signals S2 natural logrithm is asked to calculate, and obtains natural logrithm signal S3；
Step 4.6 defines natural logrithm signal S3 as S3 (i), to natural logrithm signal S3 according to formula S 3 (i)=(1/T1)*
TR5 (i) carries out least square fitting, obtains the spin-lattice relaxation time constant T of the hyperpolarized gas of research object1；
Step 4.7 normalizes the rear N+1 progress of real part integrated value M certainly, obtains the radio frequency of the hyperpolarized gas of research object
Impulse attenuation signal S4；
Wherein, it is S4 (j), S4 (j)=M (j+N)/M (N+1) to define radio-frequency pulse deamplification S4；
Step 4.8, according to radio-frequency pulse deamplification S4, obtain radio-frequency pulse deamplification S5, define radio-frequency pulse attenuation letter
Number S5 is S5 (i), during i=1, during S5 (1)=S4 (1)/S4 (1), 2≤i≤N,
Step 4.9, to radio-frequency pulse deamplification S5 according to formula S 5 (i)=(cos θr)i-1Least square fitting is carried out, is obtained
The excitation angle, θ of practical radio-frequency pulser。
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