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CN108294753B - Method and device for acquiring magnetic resonance quantitative information map - Google Patents

Method and device for acquiring magnetic resonance quantitative information map Download PDF

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CN108294753B
CN108294753B CN201810005157.1A CN201810005157A CN108294753B CN 108294753 B CN108294753 B CN 108294753B CN 201810005157 A CN201810005157 A CN 201810005157A CN 108294753 B CN108294753 B CN 108294753B
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CN108294753A (en
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黄峰
徐威
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Shanghai Neusoft Medical Technology Co Ltd
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Abstract

The embodiment of the application discloses a method and a device for acquiring a magnetic resonance quantitative information map, wherein the method is used for constructing a plurality of unknown numbers T based on two groups of echoes in two different repetition times acquired when a three-dimensional gradient multi-echo sequence is operated1、
Figure DDA0001538376600000011
And/or proton density, and ensuring that the number of constructed linear equations is not less than the number of unknowns in the linear equations, and obtaining T by solving the solutions of the linear equations1A quantitative graph,
Figure DDA0001538376600000012
A quantification map and a proton density quantification map. Therefore, the method for acquiring the magnetic resonance quantitative information map provided by the embodiment of the application converts the process of acquiring the quantitative information map into the process of solving a linear equation set, and has the characteristics of acquiring data once and acquiring 3 quantitative information maps simultaneously. When each quantitative information graph is obtained, only one-time collection is needed for the patient, and the patient does not need to be scanned for multiple times, so that a large amount of data collection time is saved, and the data collection rate is improved.

Description

Method and device for acquiring magnetic resonance quantitative information map
Technical Field
The present application relates to the field of magnetic resonance imaging technologies, and in particular, to a method and an apparatus for acquiring a magnetic resonance quantitative information map.
Background
The basic principle of Magnetic Resonance Imaging (MRI) is as follows: hydrogen nuclei (hydrogen atoms) in human tissue have a spin motion to generate a magnetic moment. Under the action of a strong uniform main magnetic field, spin hydrogen proton spin magnetic moments which are irregularly arranged can be arranged along the direction of the main magnetic field to form macroscopic magnetic moments. Under the excitation of radio frequency pulses, the macroscopic magnetization vector is turned to the direction vertical to the main magnetic field and can be received by a radio frequency receiving system in the precession rotation process, so that electromagnetic induction signals are generated, and various magnetic resonance images are formed through corresponding data reconstruction.
Conventional magnetic resonance images mainly comprise qualitative images of different contrast properties, such as T1Weighting, T2Weighting, proton density weighting, diffusion weighting, susceptibility weighting, and the like. Magnetic resonance images can provide far more than this qualitative information, but they can also provide quantitative magnetic resonance information. The magnetic resonance quantitative information is more important for disease diagnosis, especially in the aspects of brain neuroscience research and clinical application. Comparison with differentQualitative image mapping of the magnetic resonance quantitative information map including T1Quantitative information map (T)1mapping)，T2Quantitative information map (T)2mapping), proton density map (PD mapping), diffusion apparent diffusion coefficient map (ADC mapping), and the like.
Prior art magnetic resonance quantitative techniques have all focused on the measurement of information of a single magnetic resonance quantitative parameter, e.g. fitting the T using multiple acquisitions alone1Quantitative, or separate acquisition of multiple echo time-corresponding magnetic resonance data to obtain T2And (4) quantifying. One of the disadvantages of these techniques is that only a single quantitative information map can be obtained at a time, and a plurality of quantitative information maps cannot be comprehensively used for accurate diagnosis; the second disadvantage is that the acquisition time is too long, sometimes can be as long as half an hour, and the tolerance of the patient is very high; particularly, when a plurality of quantitative information maps need to be obtained, a plurality of sequences need to be acquired separately, and the required acquisition time is the sum of the individual acquisition times of the quantitative information maps. In addition, the data acquisition time is too long, and the patient may generate involuntary movement in the data acquisition process, and the involuntary movement can seriously affect the registration among the quantitative information maps, so that the quantitative analysis diagnosis is troublesome.
Disclosure of Invention
In view of the above, the present application provides a method and an apparatus for acquiring a magnetic resonance quantitative information map, so as to obtain a plurality of quantitative information simultaneously in one acquisition process and shorten data acquisition time.
In order to solve the technical problem, the embodiment of the application adopts the following technical scheme:
a method for obtaining a magnetic resonance quantitative information map, wherein the magnetic resonance quantitative information map comprises T1A quantitative graph,
Figure BDA0001538376580000021
A quantification map and a proton density quantification map, the method comprising:
acquiring a first group of echoes acquired within a first repetition time and a second group of echoes acquired within a second repetition time of a three-dimensional gradient multi-echo sequence operation; the first and second sets of echoes each comprise magnetic resonance gradient echoes of N different echo times; the echo time of each magnetic resonance gradient echo in the first group of echoes and the second group of echoes at the corresponding acquisition position is the same; the acquisition parameters of the echoes at the corresponding acquisition positions in the first group of echoes and the second group of echoes are completely the same except that the flip angles are different; n is not less than 3 and is an integer;
each magnetic resonance gradient echo is related to the T of the tissue1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000022
Respectively converting the relation into the ratio of the magnetic resonance gradient echo to the flip angle sine value and T1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000023
The relationship of (1);
according to the ratio of the magnetic resonance gradient echo to the sine value of the flip angle and T1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000024
Constructing a plurality of linear equations according to the relationship; solving the linear equation to obtain T1A quantitative graph,
Figure BDA0001538376580000025
A quantification map and a proton density quantification map, wherein,
Figure BDA0001538376580000026
is composed of
Figure BDA0001538376580000027
The reciprocal of (c).
Optionally, the ratio of the sine value of the magnetic resonance gradient echo and the flip angle according to each magnetic resonance gradient and T1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000028
Constructing a plurality of linear equations according to the relationship; solving the linear equation to obtain T1A quantitative graph,
Figure BDA0001538376580000029
The quantitative map and the proton density quantitative map specifically include:
according to the ratio of the magnetic resonance gradient echo to the sine value of the flip angle and T1Relaxation time, proton density and tissue decay time
Figure BDA00015383765800000210
Is unknown as T1N first linear equations of (a);
performing simultaneous solution on N first linear equations to obtain T1Thereby obtaining T1A quantitative map;
t obtained by solving1Substituting a quantitative map into the ratio of the sine value of each magnetic resonance gradient echo and the flip angle in the first group of echoes or the second group of echoes and T1Relaxation time, proton density and tissue decay time
Figure BDA00015383765800000211
In the relationship of (1), the unknown number is obtained as
Figure BDA00015383765800000212
And N equations for proton density;
for unknown number of
Figure BDA00015383765800000213
And performing mathematical operation on the N equations of the proton density to obtain unknown number
Figure BDA00015383765800000214
And N second linear equations of proton density;
performing simultaneous solution on the N second linear equations to obtain
Figure BDA0001538376580000031
And proton density, thereby obtaining
Figure BDA0001538376580000032
A quantification map and a proton density quantification map.
Optionally, the ratio of the sine value of the magnetic resonance gradient echo and the flip angle is determined according to the T1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000033
Is unknown as T1The N first linear equations specifically include:
the ratio of the magnetic resonance gradient echo with the same echo time in the second group of echoes and the echo time in the first group of echoes to the sine value of the flip angle is compared with T1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000034
Are subtracted to obtain N T1A first linear equation that is an unknown.
Alternatively, for unknowns of
Figure BDA0001538376580000035
And performing mathematical operation on the N equations of the proton density to obtain unknown number
Figure BDA0001538376580000036
And N second linear equations of proton density, including in particular:
for unknown number of
Figure BDA0001538376580000037
And carrying out logarithm operation on N equations of the sum proton density to obtain an unknown number of
Figure BDA0001538376580000038
And N second linear equations for proton density.
Optionally, the solving of the linear equation specifically includes:
the solution of the linear equation is solved by the least squares method.
Optionally, the method further comprises comparing each magnetic resonance gradient echo with T1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000039
Respectively converting the relation into the ratio of the magnetic resonance gradient echo to the flip angle sine value and T1Relaxation time, proton density and tissue decay time
Figure BDA00015383765800000310
The relationship (2) specifically includes:
converting the relation (I) into a relation (II);
wherein, the relation formula (I) is specifically as follows:
Figure BDA00015383765800000311
the relation (II) is specifically as follows:
Figure BDA00015383765800000312
wherein S is a magnetic resonance gradient echo, theta is a flip angle, and rho0Proton density, TR repetition time, TE echo time, T1In order to be able to determine the relaxation time,
Figure BDA00015383765800000313
is the decay time of the tissue; e1＝exp(-TR/T1)。
An acquisition device of a magnetic resonance quantitative information map, wherein the magnetic resonance quantitative information map comprises T1A quantitative graph,
Figure BDA00015383765800000314
A quantitation map and a proton density quantitation map, the apparatus comprising:
the echo acquisition unit is used for acquiring a first group of echoes acquired in a first repetition time of a three-dimensional gradient multi-echo sequence operation and a second group of echoes acquired in a second repetition time; the first and second sets of echoes each comprise magnetic resonance gradient echoes of N different echo times; the echo time of each magnetic resonance gradient echo in the first group of echoes and the second group of echoes at the corresponding acquisition position is the same; the acquisition parameters of the echoes at the corresponding acquisition positions in the first group of echoes and the second group of echoes are completely the same except that the flip angles are different; n is not less than 3 and is an integer;
a relationship transformation unit for correlating each magnetic resonance gradient echo with T of the tissue1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000041
Respectively converting the relation into the ratio of the magnetic resonance gradient echo to the flip angle sine value and T1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000042
The relationship of (1);
an equation construction solving unit for solving the equation construction problem according to the ratio of the magnetic resonance gradient echo to the flip angle sine value and T1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000043
Constructing a plurality of linear equations according to the relationship; solving the linear equation to obtain T1A quantitative graph,
Figure BDA0001538376580000044
A quantification map and a proton density quantification map, wherein,
Figure BDA0001538376580000045
is composed of
Figure BDA0001538376580000046
The reciprocal of (c).
Optionally, the relationship conversion unit specifically includes:
a first constructing subunit, configured to, according to the ratio of the magnetic resonance gradient echo to the flip angle sine value and T1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000047
Is unknown as T1N first linear equations of (a);
a first calculating subunit, configured to perform simultaneous solution on the N first linear equations to obtain T1Thereby obtaining T1A quantitative map;
a substitution subunit for substituting the solved T1Substituting a quantitative map into the ratio of the sine value of each magnetic resonance gradient echo and the flip angle in the first group of echoes or the second group of echoes and T1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000048
In the relationship of (1), the unknown number is obtained as
Figure BDA0001538376580000049
And N equations for proton density;
a mathematical operation subunit for performing an operation on the unknown number
Figure BDA00015383765800000410
And performing mathematical operation on the N equations of the proton density to obtain unknown number
Figure BDA00015383765800000411
And N second linear equations of proton density;
a second calculation subunit, configured to perform simultaneous solution on the N second linear equations to obtain
Figure BDA00015383765800000412
And the density of the protons,thereby obtaining
Figure BDA00015383765800000413
A quantification map and a proton density quantification map.
Optionally, the first building subunit specifically includes: the ratio of the magnetic resonance gradient echo with the same echo time in the second group of echoes and the echo time in the first group of echoes to the sine value of the flip angle is compared with T1Relaxation time, proton density and tissue decay time
Figure BDA00015383765800000414
Are subtracted to obtain N T1A linear equation of unknowns.
Optionally, the mathematical operation subunit specifically includes: for unknown number of
Figure BDA0001538376580000051
And carrying out logarithm operation on N equations of the sum proton density to obtain an unknown number of
Figure BDA0001538376580000052
And N second linear equations for proton density.
Compared with the prior art, the method has the following beneficial effects:
based on the above technical solutions, the method for acquiring a magnetic resonance quantitative information map provided in the embodiment of the present application constructs a plurality of unknowns T based on two sets of echoes acquired during running a three-dimensional gradient multi-echo sequence within two different repetition times1、
Figure BDA0001538376580000053
And/or proton density, and ensuring that the number of constructed linear equations is not less than the number of unknowns in the linear equations, and obtaining T by solving the solutions of the linear equations1A quantitative graph,
Figure BDA0001538376580000054
A quantification map and a proton density quantification map. Therefore, the temperature of the molten metal is controlled,the acquisition method of the magnetic resonance quantitative information graph provided by the embodiment of the application converts the process of obtaining the quantitative information graph into the process of solving a linear equation set, and has the characteristics of acquiring data once and obtaining 3 quantitative information graphs simultaneously. Therefore, compared with the prior art, the method provided by the embodiment of the application can obtain 3 quantitative information graphs through one-time data acquisition without respectively acquiring data of each quantitative information graph, and the method provided by the embodiment of the application only needs to acquire the patient once without scanning the patient for multiple times when each quantitative information graph is acquired, so that a large amount of data acquisition time is saved, and the data acquisition rate is improved.
In addition, the data of a plurality of quantitative information maps obtained by the method is acquired when a three-dimensional gradient multi-echo sequence allows, namely after excitation, so that the problem of image mismatching caused by patient motion does not exist among the obtained quantitative information maps, and the obtained quantitative information maps are completely matched, so that a clinician can be helped to make a more accurate diagnosis by comparing the quantitative information maps.
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In order that the detailed description of the present application may be clearly understood, a brief description of the drawings that will be used when describing the detailed description of the present application will be provided.
FIG. 1 is a schematic diagram of a three-dimensional gradient multi-echo sequence as is commonly used in the industry;
fig. 2 is a flowchart of a method for acquiring a magnetic resonance quantitative information map according to an embodiment of the present application;
FIG. 3 is a schematic diagram of a three-dimensional gradient multi-echo sequence shown in an embodiment of the present application;
fig. 4 is a schematic flowchart of a specific manner of step S23 provided by the embodiment of the present application;
fig. 5A to 5C are T acquired by the method for acquiring a magnetic resonance quantitative information map provided in the embodiment of the present application1Quantification map, proton density quantification map and
Figure BDA0001538376580000061
a quantitative map;
fig. 6 is a schematic structural diagram of a control device for executing a method for acquiring a magnetic resonance quantitative information map according to an embodiment of the present application;
fig. 7 is a schematic structural diagram of an apparatus for acquiring a magnetic resonance quantitative information map according to an embodiment of the present application.
Detailed Description
In order to clearly understand the embodiments of the present application, technical terms used in the embodiments of the present application will be described below.
T1The time is T when the magnetization vector of the vertical axis increases from 0 to 63%1Relaxation time (also known as longitudinal magnetization vector).
T2The relaxation time is the time required for the transverse magnetization vector to decay from a maximum to 37%.
Figure BDA0001538376580000062
The time is the time required for the magnetization vector intensity to decay from the maximum value to 37% after faster phase dispersion due to factors such as non-uniformity of magnetic field during transverse magnetization decay
Figure BDA0001538376580000063
T less than tissue2The relaxation time.
Figure BDA0001538376580000064
Is composed of
Figure BDA0001538376580000065
The reciprocal of (2) can also be used
Figure BDA0001538376580000066
The attenuation of the transverse magnetization vector is measured.
Gradient echo (GRE) is an echo signal generated by a reversal of the direction of the relevant gradient field. Gradient echoes, also called field echoes, differ from spin echoes mainly in the way they are excited differently. The GRE sequence always starts with an RF pulse of less than 90 deg..
In the GRE sequence, a negative-then-positive gradient field is applied in the readout gradient direction as soon as the RF excitation pulse ends. The change in direction of the gradient pulse is customarily referred to as gradient inversion. Therefore, the proton groups are subjected to a process of dephasing-phase reunion, thereby generating echo signals.
The repetition Time (TR) refers to the time required for a pulse sequence to perform a pass and is also the time elapsed from the occurrence of one RF excitation pulse to the occurrence of the same pulse in the next cycle. In milliseconds. TR determines the time between one RF pulse and the next. TR is a determining factor of the scanning speed and also the image contrast (T)1、T2And proton density contrast). .
The echo Time (TE) is the time required from the first RF pulse to the echo signal generation, and the time from the RF pulse to the occurrence of the first echo signal in a multi-echo sequence is called TE1The time to the second echo signal is called TE2. And so on. TE and TR together determine the contrast of the map comparison.
For a clear understanding of the various concepts in the three-dimensional gradient multi-echo sequence, please refer to the three-dimensional gradient multi-echo sequence schematic diagram shown in fig. 1. In the sequence shown in fig. 1, two pulse periods, i.e. two repetition times TR1 and TR2, are illustrated. In each repetition time, 4 echo acquisition windows are arranged, and the echo time corresponding to each echo acquisition window is TE respectively1、TE2、TE3And TE4。
T1Quantitative graph (T)1mapping) can describe the organization T1Change in relaxation time.
Proton density quantification (PD mapping) can describe the change in water content in tissue.
Figure BDA0001538376580000071
mapping for groupsThe factors causing the change of magnetic susceptibility, such as the change of iron element, are very sensitive. So comprehensively utilize T1A quantitative map, a proton density quantitative map,
Figure BDA0001538376580000072
The three quantitative information of the quantitative map are very helpful for the diagnosis of tissue pathology, in particular to the accurate diagnosis of nervous system lesion.
In the field of magnetic resonance imaging, when obtaining each quantitative information map by the conventional magnetic resonance acquisition method, a plurality of scans are required to be carried out on a patient, for example, T is required to be obtained1In mapping, the conventional magnetic resonance acquisition method needs to run a plurality of acquisition sequences to acquire magnetic resonance signals under a plurality of flip angles to obtain T through fitting1The value is obtained. Need to obtain T2During mapping, a plurality of acquisition sequences are required to be operated to acquire magnetic resonance signals under a plurality of different echo times in the conventional magnetic resonance acquisition method, and then T is obtained through fitting of a signal attenuation curve2Moreover, when the number of acquired echoes is small, the fitted quantitative value is only an approximate value and is inaccurate, so that a large number of echo data need to be acquired in order to acquire accurate quantification, and therefore, the conventional magnetic resonance signal acquisition method for quantitative information map data is time-consuming. And when a plurality of quantitative information maps need to be acquired simultaneously, the required acquisition time is often the sum of the individual acquisition times of the quantitative information maps. Thus, the existing magnetic resonance data acquisition method has too long acquisition time, sometimes as long as half an hour, and is a great test for the tolerance of patients; particularly, when a plurality of quantitative information maps need to be obtained, a plurality of sequences need to be acquired separately, and the required acquisition time is the sum of the individual acquisition times of the quantitative information maps.
In addition, since the data of each quantitative information map is acquired separately, the patient may generate involuntary movement during the data acquisition process, and the involuntary movement may seriously affect the registration between the quantitative information maps, which is troublesome for quantitative analysis and diagnosis.
Based on this, the embodiment of the application is based on two acquired when running a three-dimensional gradient multi-echo sequenceTwo groups of echoes in different repetition times have the same acquisition parameters except different flip angles, and a plurality of unknowns T are constructed based on the two groups of echoes1、
Figure BDA0001538376580000081
And/or proton density, and ensuring that the number of constructed linear equations is not less than the number of unknowns in the linear equations, and obtaining T by solving the solutions of the linear equations1A quantitative graph,
Figure BDA0001538376580000082
A quantification map and a proton density quantification map. Therefore, the method for acquiring the magnetic resonance quantitative information map provided by the embodiment of the application converts the process of acquiring the quantitative information map into the process of solving a linear equation set, and has the characteristics of acquiring data once and acquiring 3 quantitative information maps simultaneously. Therefore, compared with the prior art, the method provided by the embodiment of the application can obtain 3 quantitative information graphs through one-time data acquisition without respectively acquiring data of each quantitative information graph, and the method provided by the embodiment of the application only needs to acquire the patient once without scanning the patient for multiple times when each quantitative information graph is acquired, so that a large amount of data acquisition time is saved, and the data acquisition rate is improved.
In addition, the data of a plurality of quantitative information maps obtained by the method is acquired when a three-dimensional gradient multi-echo sequence allows, namely after excitation, so that the problem of image mismatching caused by patient motion does not exist among the obtained quantitative information maps, and the obtained quantitative information maps are completely matched, so that a clinician can be helped to make a more accurate diagnosis by comparing the quantitative information maps.
It should be noted that the magnetic resonance quantitative information map described in the embodiment of the present application includes a T1 quantitative map and R2 quantitative map*A quantification map and a proton density quantification map.
The following detailed description of specific embodiments of the present application is provided in conjunction with the accompanying drawings.
Fig. 2 is a flowchart illustrating a method for acquiring a magnetic resonance quantitative information map according to an embodiment of the present application, and referring to fig. 2, the method includes:
s21: a first set of echoes acquired during a first repetition time and a second set of echoes acquired during a second repetition time of a three-dimensional gradient multi-echo sequence run are acquired.
Specific implementations of this step are described in detail below in connection with the three-dimensional gradient multi-echo sequence schematic shown in fig. 3.
The embodiment of the application is provided with N acquisition windows in the first repetition time TR1 and the second repetition time TR2 of the three-dimensional gradient multi-echo sequence operation, and each acquisition window can acquire the echo corresponding to the position. The embodiment of the application refers to the N echoes acquired in the same repetition time as a group of echoes. Specifically, the embodiment of the present application refers to N echoes acquired in the first repetition time as a first group of echoes, and refers to N echoes acquired in the second repetition time as a second group of echoes.
Wherein each magnetic resonance gradient echo in the first set of echoes may be represented by E11、E12…E1nIndicating that the echo time corresponding to each magnetic resonance gradient echo is TE11、TE12…TE1nAnd (4) showing. The individual magnetic resonance gradient echoes of the second set of echoes may be represented by E21、E22…E2nIndicating that the echo time corresponding to each magnetic resonance gradient echo is TE21、TE22…TE2nAnd (4) showing.
For convenience of subsequently constructing a linear equation, the echo time of each magnetic resonance gradient echo in the first group of echoes and the second group of echoes at the corresponding acquisition position is the same. That is, TE11＝TE12，TE12＝TE22，…，TE1n＝TE2n。
In the embodiment of the present application, the flip angles corresponding to the N echoes in the first group of echoes are the same and are all θ1Indicating that N echoes of the second set of echoes correspondAre all equal in flip angle theta2And (4) showing. Due to T1The relaxation time is related to the flip angle of the echo signal, and T can be determined by collecting the echo signals with different flip angles1The relaxation time. Based on this, to obtain T1Relaxation time, acquisition parameters of the echoes of the first and second sets of echoes at the corresponding acquisition positions other than the flip angle (i.e. theta)1≠θ2) Other acquisition parameters are identical except for the following parameters: the repetition time TR and the corresponding echo time TE.
In addition, the acquisition parameters of the first group of echoes and the second group of echoes at the corresponding acquisition positions are completely the same except for the flip angle, so that the images of the echoes are completely registered, and fast and accurate quantitative information is provided for accurate magnetic resonance diagnosis.
Furthermore, it is intended to be constructed with T in the examples of the present application1、
Figure BDA0001538376580000091
And simultaneous equations with proton density as unknowns by solving the equations to obtain solutions to the unknowns to obtain T1、
Figure BDA0001538376580000092
And proton density, and then T is obtained1A quantitative graph,
Figure BDA0001538376580000093
A quantification map and a proton density quantification map. Therefore, the number of equations of the simultaneous equations must not be smaller than the number of unknowns, and thus the number of equations of the simultaneous equations must not be smaller than 3. In the embodiment of the present application, an equation may be constructed for an echo corresponding to one echo time, so that at least three echoes corresponding to the echo time are required, and therefore, in the embodiment of the present application, at least three echoes corresponding to the echo time are to be acquired within one repetition time, so that N is greater than or equal to 3, and N is an integer.
S22: each magnetic resonance gradient echo is related to the T of the tissue1Relaxation ofTime, proton density and decay time of tissue
Figure BDA0001538376580000094
Respectively converting the relation into the ratio of the magnetic resonance gradient echo to the flip angle sine value and T1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000095
The relationship (2) of (c).
In the embodiment of the application, the acquired magnetic resonance gradient echo signals and the T of the tissue1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000101
There is a relationship, which can be described by the relation (1), as follows:
Figure BDA0001538376580000102
wherein S is a magnetic resonance gradient echo, theta is a flip angle, and rho0For tissue proton density, TR is the repetition time, T1Is T of tissue1The relaxation time, TE, is the echo time,
Figure BDA0001538376580000103
is organized
Figure BDA0001538376580000104
Decay time, p0、T1And
Figure BDA0001538376580000105
these three parameters are the relative density parameter and the relaxation parameter of the tissue that needs to be solved quantitatively.
To simplify the calculation, subsequent conversion to unknown values of rho is facilitated0、T1And
Figure BDA0001538376580000106
the linear equation of (1) may be obtained by dividing sin θ by sin θ on both sides of the linear equation to obtain a relation (2), and further may be obtained by multiplying 1-cos θ exp (-TR/T) by sin θ on both sides of the relation (2) simultaneously1) Relation (1) can be converted as follows:
Figure BDA0001538376580000107
furthermore, the two sides of the relation (2) can be simultaneously multiplied by 1-cos theta x exp (-TR/T)1) And to further simplify the relational expression, T that needs to be solved quantitatively may be1Information E1Indicates, setting E1＝exp(-TR/T1) Further, relation (3) is obtained as follows:
Figure BDA0001538376580000108
adding the equal sign of the relation (3) at the same time
Figure BDA0001538376580000109
Relation (4) can be obtained as follows:
Figure BDA00015383765800001010
the above relation (4) can be regarded as the ratio of the converted magnetic resonance gradient echo to the flip angle sine value and T1Relaxation time, proton density and tissue decay time
Figure BDA00015383765800001011
The relationship (2) of (c).
In this step, each magnetic resonance gradient echo, which can be represented by the relation (1), can be correlated with the T of the tissue1Relaxation time, proton density and tissue decay time
Figure BDA00015383765800001012
Respectively converted into the ratio of the magnetic resonance gradient echo to the flip angle sine value and T shown in the relation (4)1Relaxation time, proton density and tissue decay time
Figure BDA00015383765800001013
The relationship (2) of (c). That is, a relational expression as shown in relational expression (1) may be established for each of the first and second sets of echoes, and a relational expression as shown in relational expression (4) may be obtained by further conversion. In this way, the relationship shown in the relational expression (4) corresponding to 2N magnetic resonance gradient echoes can be obtained in total. In relation (4), except for E1、ρ0And
Figure BDA0001538376580000111
in addition, other parameters are known.
S23: according to the ratio of the sine value of each magnetic resonance gradient echo and the flip angle and T1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000112
The relationship of (A) and (B) is used for constructing a plurality of linear equations, and the plurality of linear equations are simultaneously solved, so that T is obtained1A quantitative graph,
Figure BDA0001538376580000113
A quantification map and a proton density quantification map.
The step may specifically be: by performing various mathematical operations on the relationship expressed by the expression (4) corresponding to the 2N magnetic resonance gradient echoes obtained in the above step S22, a plurality of unknowns T are constructed1、
Figure BDA0001538376580000114
And a linear equation with proton density as an unknown.
Note that T is1The value is related to the flip angle and can be obtained by setting different flip angles, thus, as an example of the present application, T1The value can be obtained by solving two groups of echoes corresponding to two different flip angles. When T is1After the value is solved, the T can be obtained1Into relation (4) so that the unknown is obtained only including
Figure BDA0001538376580000115
And an equation of proton density, which is converted into a linear relation by processing and converting the equation. Therefore, the calculation amount can be simplified, and the calculation efficiency can be improved.
Based on this, as one possible implementation manner of the present application, as shown in fig. 4, step S23 may specifically include the following steps:
s231: constructing unknown number E according to 2N relational expressions (4)1N first linear equations.
As described above, in the embodiment of the present application, among the acquired 2N magnetic resonance gradient echoes, the echo E acquired in the first repetition time is due to11～E1nThe corresponding echo time is respectively corresponding to the echo E acquired in the second repetition time21～E2nThe corresponding echo time is the same, and the flip angle is different. That is, TE11＝TE21，TE12＝TE22，…，TE1n＝TE2n，θ1≠θ2. And the first repetition time is equal to the second repetition time.
Based on this, E11And E21The second term on the right side of the equal sign of the corresponding relation (4) is
Figure BDA0001538376580000116
Same, E12And E22The second terms on the right side of the equal sign of the corresponding relation (4) are the same, E11And E21The second terms on the right side of the equal sign of the corresponding relation (4) are the same, and so on, E1nAnd E2nThe second terms on the right side of the equal sign of the corresponding relational expression (4) are the same. Therefore, the N echoes collected in the first repeating time are subtracted from the N echoes at the corresponding positions in the second repeating time to obtain N echoes and E echoes1The associated linear equation, as follows:
Figure BDA0001538376580000121
for convenience of understanding, equation (5) can also be expressed by a general equation shown in equation (6), and the results are as follows:
a2-a1＝E1*(b2-b1) (6)
wherein, a1、a2、b1And b2Can be regarded as a coefficient relating to the echo signal and its flip angle etc.
S232: simultaneously solving N first linear equations to obtain E1。
To obtain more accurate E1The value of the first equation set can be solved by the least square method in the step, so that the value E can be accurately obtained1The value is obtained.
Wherein the least square method is only for the above unknown number as E1In other possible implementation manners of the embodiment of the present application, other methods may also be used to solve the first linear equation, and the embodiment of the present application does not limit this.
S233: according to E1And T1Is solved to obtain T1。
According to E1＝exp(-TR/T1) To obtain T1Of the formula, i.e. T1＝-TR/lnE1. Thus, the solution E according to the first linear equation1Can be solved to obtain T1. According to T obtained by solving1Can obtain T1And (4) quantifying the graph.
S234: t obtained by solving1The values are respectively substituted into the relations shown in the formula (4) corresponding to the N magnetic resonance gradient echoes in the first group of echoes or the second group of echoes to respectively obtain N unknowns of
Figure BDA0001538376580000122
And the equation for proton density.
When T is1After the value is obtained by solving, the relation (4) is divided by rho0And
Figure BDA0001538376580000123
other numbers are known.
To construct the unknown number p0And
Figure BDA0001538376580000124
because the echo times TE in different repetition times are different, the unknown number can be constructed from the echoes corresponding to the different echo times in the same repetition time (i.e., the echoes in the same group of echoes)
Figure BDA0001538376580000125
And the equation for proton density.
Based on this, the embodiment of the present application will solve the obtained T1The values are respectively substituted into the relations shown in the formula (4) corresponding to the N magnetic resonance gradient echoes of the first group of echoes or the second group of echoes to respectively obtain N unknowns
Figure BDA0001538376580000126
And the equation for proton density.
As an example, the resulting T will be solved for1The values are respectively substituted into the relation shown in the formula (4) corresponding to the N magnetic resonance gradient echoes of the first group of echoes to respectively obtain N unknowns of
Figure BDA0001538376580000131
And proton density, as follows:
Figure BDA0001538376580000132
s235: for each unknown number of
Figure BDA0001538376580000133
And the equation of the proton density is subjected to logarithm operation to respectively obtain N unknowns of
Figure BDA0001538376580000134
And a second linear equation for proton density.
Since there is an exponentiation operation in the relational expression (4), the relational expression (4) can be converted into a relational expression having a linear relationship by taking a logarithm operation for the sake of simplification of the operation.
To simplify the relation, the first term to the left of the middle sign in relation (4) may be preceded by a log-taking operation
Figure BDA0001538376580000135
Move to the left of the equal sign, resulting in relation (8):
Figure BDA0001538376580000136
setting up
Figure BDA0001538376580000137
Thereby, the relation (8) is equivalently converted into the relation (9).
Figure BDA0001538376580000138
Then, the relation (9) is subjected to a natural logarithm operation to obtain a relation (10).
Figure BDA0001538376580000139
Due to the fact that
Figure BDA00015383765800001310
Therefore, the relation (10) can be converted into the relation (11):
Figure BDA00015383765800001311
in relation (11) of each echo, except for proton density ρ0And
Figure BDA00015383765800001312
in addition, other parameters are known. Therefore, the second linear equations with the relation of N shown in (10) can be constructed by N echoes in the first set of echoes or the second set of echoes.
Taking the first group of echoes as an example, the obtained N second linear equations are respectively:
Figure BDA0001538376580000141
in the relation (12), Sc11Is an echo E11Corresponding Sc value, Sc12Is an echo E12Corresponding Sc value, … …, Sc1NIs an echo E1NThe corresponding Sc value.
It should be noted that the above example has a pair of unknowns of
Figure BDA0001538376580000142
The logarithm operation of the equation for sum of proton density is performed only on the unknowns of
Figure BDA0001538376580000143
And proton density, an example of a mathematical operation. In fact, the embodiment of the present application is not limited to the logarithm operation shown above, but may also be other operations capable of setting the unknown number as the logarithm
Figure BDA0001538376580000144
And the equation for proton density is converted to other mathematical operations of a linear equation.
S236: simultaneously solving N second linear equations to obtain
Figure BDA0001538376580000145
And proton density ρ0。
To obtain more accurate
Figure BDA0001538376580000146
And proton density ρ0In the embodiment of the present application, a least square method may be adopted to solve the solution of the second linear equation to obtain
Figure BDA0001538376580000147
And proton density ρ0。
It should be noted that the least squares method is only for unknowns of
Figure BDA0001538376580000148
And an implementation manner of simultaneous solution of the second linear equation of proton density, in other possible implementation manners of the embodiment of the present application, other methods may also be used to perform the solution, which is not limited in the embodiment of the present application.
In the specific implementation manner, based on two groups of echoes acquired in two different repetition times during running of the three-dimensional gradient multi-echo sequence, acquisition parameters of the two groups of echoes are the same except for different flip angles, and a plurality of unknown numbers T are constructed based on the two groups of echoes1、
Figure BDA0001538376580000149
And/or proton density, and ensuring that the number of constructed linear equations is not less than the number of unknowns in the linear equations, and obtaining T by solving the solutions of the linear equations1A quantitative graph,
Figure BDA00015383765800001410
A quantification map and a proton density quantification map. Therefore, the method for acquiring the magnetic resonance quantitative information map provided by the embodiment of the application converts the process of acquiring the quantitative information map into the process of solving a linear equation set, and has the characteristics of acquiring data once and acquiring 3 quantitative information maps simultaneously. Therefore, compared with the prior art, the method provided by the embodiment of the application can obtain 3 quantitative information maps through one-time data acquisition without dividing each quantitative information mapIn addition, when each quantitative information image is obtained, the method provided by the embodiment of the application only needs to collect the patient once without scanning the patient for multiple times, so that a large amount of data collection time is saved, and the data collection rate is improved.
In addition, the data of a plurality of quantitative information maps obtained by the method is acquired when a three-dimensional gradient multi-echo sequence allows, namely after excitation, so that the problem of image mismatching caused by patient motion does not exist among the obtained quantitative information maps, and the obtained quantitative information maps are completely matched, so that a clinician can be helped to make a more accurate diagnosis by comparing the quantitative information maps.
In addition, the acquisition method of the magnetic resonance quantitative information map provided by the application is proved to be feasible through sufficient experiments and verification, and the obtained T1Quantitative graph (T)1mapping), proton density quantitation map (PDmapping),
Figure BDA0001538376580000151
quantitative graph (A)
Figure BDA0001538376580000152
mapping) are shown in fig. 5A to 5C, respectively. Compared with the existing quantitative empirical value, the calculation result of the quantitative value obtained by the embodiment of the application is more accurate, so that a plurality of quantitative graphs obtained by the method can help a clinician to make a more accurate diagnosis.
The method for acquiring the magnetic resonance quantitative information map of the above embodiment may be performed by the control apparatus shown in fig. 6. The control device shown in fig. 6 includes a processor (processor)610, a communication Interface (Communications Interface)520, a memory (memory)630, and a bus 640. The processor 610, the communication interface 620, and the memory 630 communicate with each other via the bus 640.
The memory 630 may store logic instructions for acquiring the magnetic resonance quantitative information map, and the memory may be a non-volatile memory (non-volatile memory), for example. The processor 610 may invoke logic instructions to perform the magnetic resonance image reconstruction in the memory 630 to perform the magnetic resonance quantitative information map acquisition method described above. As an embodiment, the logic instruction for acquiring the magnetic resonance quantitative information map may be a program corresponding to control software, and when the processor executes the instruction, the control device may correspondingly display a functional interface corresponding to the instruction on the display interface.
The functions of the logic instructions for acquiring the magnetic resonance quantitative information map may be stored in a computer-readable storage medium if they are implemented in the form of software functional units and sold or used as independent products. Based on such understanding, the technical solutions of the present disclosure may be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the methods according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
The logic instructions for acquiring the magnetic resonance quantitative information map may be referred to as "an apparatus for acquiring a magnetic resonance quantitative information map", and the apparatus may be divided into various functional blocks. See in particular the examples below.
The following describes a specific implementation of the apparatus for acquiring a magnetic resonance quantitative information map provided in the embodiments of the present application.
Fig. 7 is a schematic structural diagram of an apparatus for acquiring a magnetic resonance quantitative information map according to an embodiment of the present application. As shown in fig. 6, the apparatus for acquiring a magnetic resonance quantitative information map includes:
an echo acquisition unit 71 for acquiring a first group of echoes acquired during a first repetition time and a second group of echoes acquired during a second repetition time of a three-dimensional gradient multi-echo sequence operation; the first and second sets of echoes each comprise magnetic resonance gradient echoes of N different echo times; the echo time of each magnetic resonance gradient echo in the first group of echoes and the second group of echoes at the corresponding acquisition position is the same; the acquisition parameters of the echoes at the corresponding acquisition positions in the first group of echoes and the second group of echoes are completely the same except that the flip angles are different; n is not less than 3 and is an integer;
a relation transforming unit 72 for relating each magnetic resonance gradient echo to the T of the tissue1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000161
Respectively converting the relation into the ratio of the magnetic resonance gradient echo to the flip angle sine value and T1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000162
The relationship of (1);
an equation construction solving unit 73 for solving the equation construction problem according to the ratio of the magnetic resonance gradient echo to the flip angle sine value and T1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000163
Constructing a plurality of linear equations according to the relationship; solving the linear equation to obtain T1A quantitative graph,
Figure BDA0001538376580000164
A quantification map and a proton density quantification map, wherein,
Figure BDA0001538376580000165
is composed of
Figure BDA0001538376580000166
The reciprocal of (c).
As an example of the present application, the relationship conversion unit 72 may specifically include:
a first construction subunit for constructing a magnetic resonance image from the respective magnetic resonance gradient echoes and flipsRatio of angle sine value to T1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000167
Is unknown as T1N first linear equations of (a);
a first calculating subunit, configured to perform simultaneous solution on the N first linear equations to obtain T1Thereby obtaining T1A quantitative map;
a substitution subunit for substituting the solved T1Substituting a quantitative map into the ratio of the sine value of each magnetic resonance gradient echo and the flip angle in the first group of echoes or the second group of echoes and T1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000171
In the relationship of (1), the unknown number is obtained as
Figure BDA0001538376580000172
And N equations for proton density;
a mathematical operation subunit for performing an operation on the unknown number
Figure BDA0001538376580000173
And performing mathematical operation on the N equations of the proton density to obtain unknown number
Figure BDA0001538376580000174
And N second linear equations of proton density;
a second calculation subunit, configured to perform simultaneous solution on the N second linear equations to obtain
Figure BDA0001538376580000175
And proton density, thereby obtaining
Figure BDA0001538376580000176
A quantification map and a proton density quantification map.
As a specific example of the present application, the firstA building subunit may specifically comprise: the ratio of the magnetic resonance gradient echo with the same echo time in the second group of echoes and the echo time in the first group of echoes to the sine value of the flip angle is compared with T1Relaxation time, proton density and tissue decay time
Figure BDA0001538376580000177
Are subtracted to obtain N T1A linear equation of unknowns.
As another specific example of the present application, the mathematical operation subunit may specifically include: for unknown number of
Figure BDA0001538376580000178
And carrying out logarithm operation on N equations of the sum proton density to obtain an unknown number of
Figure BDA0001538376580000179
And N second linear equations for proton density.
It should be noted that the apparatus for acquiring a magnetic resonance quantitative information map provided in the embodiment of the present application corresponds to the method for acquiring a magnetic resonance quantitative information map provided in the embodiment of the present application, and the technical effects achieved by the method also correspond to the technical effects achieved by the acquisition method. For the sake of brevity, detailed description is omitted here, please refer to the technical effects corresponding to the above-mentioned exemplary acquisition method.
The above is a specific implementation manner of the embodiment of the present application.

Claims (10)

1. A method for acquiring a magnetic resonance quantitative information map, characterized in that the magnetic resonance quantitative information map comprises T1A quantitative graph,
Figure FDA0002889317770000011
A quantification map and a proton density quantification map, the method comprising:
acquiring a first group of echoes acquired within a first repetition time and a second group of echoes acquired within a second repetition time of a three-dimensional gradient multi-echo sequence operation; the first and second sets of echoes each comprise magnetic resonance gradient echoes of N different echo times; the echo time of each magnetic resonance gradient echo in the first group of echoes and the second group of echoes at the corresponding acquisition position is the same; the acquisition parameters of the echoes at the corresponding acquisition positions in the first group of echoes and the second group of echoes are completely the same except that the flip angles are different; n is not less than 3 and is an integer;
each magnetic resonance gradient echo is related to the T of the tissue1Relaxation time, proton density and tissue decay time
Figure FDA0002889317770000012
Respectively converting the relation into the ratio of the magnetic resonance gradient echo to the flip angle sine value and T1Relaxation time, proton density and tissue decay time
Figure FDA0002889317770000013
The relationship of (1);
according to the ratio of the magnetic resonance gradient echo to the sine value of the flip angle and T1Relaxation time, proton density and tissue decay time
Figure FDA0002889317770000014
Constructing a plurality of linear equations according to the relationship; solving the linear equation to obtain T1A quantitative graph,
Figure FDA0002889317770000015
A quantification map and a proton density quantification map, wherein,
Figure FDA0002889317770000016
is composed of
Figure FDA0002889317770000017
The reciprocal of (c).
2. The acquisition method according to claim 1, characterized in that said method is based on a respective instituteThe ratio of the magnetic resonance gradient echo to the flip angle sine value and T1Relaxation time, proton density and tissue decay time
Figure FDA0002889317770000018
Constructing a plurality of linear equations according to the relationship; solving the linear equation to obtain T1A quantitative graph,
Figure FDA0002889317770000019
The quantitative map and the proton density quantitative map specifically include:
according to the ratio of the magnetic resonance gradient echo to the sine value of the flip angle and T1Relaxation time, proton density and tissue decay time
Figure FDA00028893177700000110
Is unknown as T1N first linear equations of (a);
performing simultaneous solution on N first linear equations to obtain T1Thereby obtaining T1A quantitative map;
t obtained by solving1Substituting a quantitative map into the ratio of the sine value of each magnetic resonance gradient echo and the flip angle in the first group of echoes or the second group of echoes and T1Relaxation time, proton density and tissue decay time
Figure FDA00028893177700000111
In the relationship of (1), the unknown number is obtained as
Figure FDA00028893177700000112
And N equations for proton density;
for unknown number of
Figure FDA00028893177700000113
And performing mathematical operation on the N equations of the proton density to obtain unknown number
Figure FDA00028893177700000114
And N second linear equations of proton density;
performing simultaneous solution on the N second linear equations to obtain
Figure FDA00028893177700000115
And proton density, thereby obtaining
Figure FDA00028893177700000116
A quantification map and a proton density quantification map.
3. The acquisition method according to claim 2, wherein the ratio of each of the magnetic resonance gradient echoes to the sine of the flip angle is T1Relaxation time, proton density and tissue decay time
Figure FDA0002889317770000021
Is unknown as T1The N first linear equations specifically include:
the ratio of the magnetic resonance gradient echo with the same echo time in the second group of echoes and the echo time in the first group of echoes to the sine value of the flip angle is compared with T1Relaxation time, proton density and tissue decay time
Figure FDA0002889317770000022
Are subtracted to obtain N T1A first linear equation that is an unknown.
4. The acquisition method according to claim 2, characterized in that the pair of unknowns is
Figure FDA0002889317770000023
And performing mathematical operation on the N equations of the proton density to obtain unknown number
Figure FDA0002889317770000024
And N of proton densityThe second linear equation specifically includes:
for unknown number of
Figure FDA0002889317770000025
And carrying out logarithm operation on N equations of the sum proton density to obtain an unknown number of
Figure FDA0002889317770000026
And N second linear equations for proton density.
5. The acquisition method according to any one of claims 1 to 4, characterized in that said solving of the solution of the linear equation comprises in particular:
the solution of the linear equation is solved by the least squares method.
6. The acquisition method according to any one of claims 1 to 4, wherein each magnetic resonance gradient echo is associated with T1Relaxation time, proton density and tissue decay time
Figure FDA0002889317770000027
Respectively converting the relation into the ratio of the magnetic resonance gradient echo to the flip angle sine value and T1Relaxation time, proton density and tissue decay time
Figure FDA0002889317770000028
The relationship (2) specifically includes:
converting the relation (I) into a relation (II);
wherein, the relation formula (I) is specifically as follows:
Figure FDA0002889317770000029
the relation (II) is specifically as follows:
Figure FDA00028893177700000210
wherein S is a magnetic resonance gradient echo, theta is a flip angle, and rho0Proton density, TR repetition time, TE echo time, T1In order to be able to determine the relaxation time,
Figure FDA00028893177700000211
is the decay time of the tissue; e1＝exp(-TR/T1)。
7. An apparatus for acquiring a magnetic resonance quantitative information map, wherein the magnetic resonance quantitative information map comprises T1A quantitative graph,
Figure FDA00028893177700000212
A quantitation map and a proton density quantitation map, the apparatus comprising:
the echo acquisition unit is used for acquiring a first group of echoes acquired in a first repetition time of a three-dimensional gradient multi-echo sequence operation and a second group of echoes acquired in a second repetition time; the first and second sets of echoes each comprise magnetic resonance gradient echoes of N different echo times; the echo time of each magnetic resonance gradient echo in the first group of echoes and the second group of echoes at the corresponding acquisition position is the same; the acquisition parameters of the echoes at the corresponding acquisition positions in the first group of echoes and the second group of echoes are completely the same except that the flip angles are different; n is not less than 3 and is an integer;
a relationship transformation unit for correlating each magnetic resonance gradient echo with T of the tissue1Relaxation time, proton density and tissue decay time
Figure FDA0002889317770000031
Respectively converting the relation into the ratio of the magnetic resonance gradient echo to the flip angle sine value and T1Relaxation time, proton density and tissue decay time
Figure FDA0002889317770000032
The relationship of (1);
an equation construction solving unit for solving the equation construction problem according to the ratio of the magnetic resonance gradient echo to the flip angle sine value and T1Relaxation time, proton density and tissue decay time
Figure FDA0002889317770000033
Constructing a plurality of linear equations according to the relationship; solving the linear equation to obtain T1A quantitative graph,
Figure FDA0002889317770000034
A quantification map and a proton density quantification map, wherein,
Figure FDA0002889317770000035
is composed of
Figure FDA0002889317770000036
The reciprocal of (c).
8. The obtaining apparatus according to claim 7, wherein the equation construction solving unit specifically includes:
a first constructing subunit, configured to, according to the ratio of the magnetic resonance gradient echo to the flip angle sine value and T1Relaxation time, proton density and tissue decay time
Figure FDA0002889317770000037
Is unknown as T1N first linear equations of (a);
a first calculating subunit, configured to perform simultaneous solution on the N first linear equations to obtain T1Thereby obtaining T1A quantitative map;
a substitution subunit for substituting the solved T1Substituting a quantitative map into the ratio of the sine value of each magnetic resonance gradient echo and the flip angle in the first group of echoes or the second group of echoes and T1The relaxation time,Proton density and tissue decay time
Figure FDA0002889317770000038
In the relationship of (1), the unknown number is obtained as
Figure FDA0002889317770000039
And N equations for proton density;
a mathematical operation subunit for performing an operation on the unknown number
Figure FDA00028893177700000310
And performing mathematical operation on the N equations of the proton density to obtain unknown number
Figure FDA00028893177700000311
And N second linear equations of proton density;
a second calculation subunit, configured to perform simultaneous solution on the N second linear equations to obtain
Figure FDA00028893177700000312
And proton density, thereby obtaining
Figure FDA00028893177700000313
A quantification map and a proton density quantification map.
9. The obtaining apparatus according to claim 8, wherein the first building subunit specifically includes: the ratio of the magnetic resonance gradient echo with the same echo time in the second group of echoes and the echo time in the first group of echoes to the sine value of the flip angle is compared with T1Relaxation time, proton density and tissue decay time
Figure FDA00028893177700000314
Are subtracted to obtain N T1A linear equation of unknowns.
10. According toThe obtaining apparatus of claim 8, wherein the mathematical operation subunit specifically includes: for unknown number of
Figure FDA0002889317770000041
And carrying out logarithm operation on N equations of the sum proton density to obtain an unknown number of
Figure FDA0002889317770000042
And N second linear equations for proton density.
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