WO2021098690A1 - 定量磁共振成像参数确定方法、装置、设备及存储介质 - Google Patents

定量磁共振成像参数确定方法、装置、设备及存储介质 Download PDF

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WO2021098690A1
WO2021098690A1 PCT/CN2020/129571 CN2020129571W WO2021098690A1 WO 2021098690 A1 WO2021098690 A1 WO 2021098690A1 CN 2020129571 W CN2020129571 W CN 2020129571W WO 2021098690 A1 WO2021098690 A1 WO 2021098690A1
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magnetic resonance
voxel
signal
radio frequency
mrf
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PCT/CN2020/129571
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English (en)
French (fr)
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王海峰
邹莉娴
刘新
梁栋
郑海荣
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深圳先进技术研究院
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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
    • G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console

Definitions

  • This application relates to the field of magnetic resonance imaging technology, and in particular to a method, device, equipment, and storage medium for determining quantitative magnetic resonance imaging parameters.
  • Quantitative magnetic resonance imaging has tissue specificity for the detection of human pathological tissues, which can help doctors better distinguish between healthy tissues and pathological tissues, and has very important clinical diagnosis and research value.
  • Magnetic Resonance Fingerprinting is a new type of rapid quantitative magnetic resonance imaging parameter determination technology.
  • MRF uses a set of pseudo-randomly varying pulse sequences to scan the subject, so that different tissue types (using voxels as a carrier) from the subject exhibit unique signal evolution (ie fingerprint). Then, the obtained fingerprint is matched with multiple dictionary entries in the pre-acquired dictionary to obtain the quantitative value of multiple organization attribute parameters of each organization type.
  • Tissue attribute parameters include longitudinal relaxation time (hereinafter referred to as T1) and lateral relaxation time (hereinafter referred to as T2).
  • the MRF pulse sequence is mainly based on the steady-state free precession sequence of reversal recovery.
  • the reversal recovery sequence is particularly sensitive to T1, and the steady-state free precession sequence has a relatively high signal-to-noise ratio, so it is based on the pulse sequence pair Obtaining the organizational attribute parameters of different subjects has certain advantages.
  • the magnetic resonance images obtained based on the current MRF pulse sequence are not sensitive to the T2 differences of various tissue types, resulting in low accuracy of the obtained T2.
  • the embodiments of the present application provide a method, device, equipment, and storage medium for determining quantitative magnetic resonance imaging parameters to solve the technical problem of inaccurate transverse relaxation time in quantitative magnetic resonance imaging in the prior art.
  • an embodiment of the present application provides a method for determining quantitative magnetic resonance imaging parameters, including:
  • the MRF pulse sequence includes multiple radio frequency pulse trains that are sequentially excited, and the radio frequency pulse train is used to excite the magnetization vector of the subject;
  • the dictionary includes multiple analog signals generated by the signal simulation evolution of the MRF pulse sequence , And the transverse relaxation time corresponding to each analog signal one-to-one.
  • the radio frequency pulse train includes 90° excitation pulses, at least one 180° excitation pulse, and -90° excitation pulses that are sequentially excited.
  • the interval time between two adjacent excitation pulses in the radio frequency pulse train is the same.
  • the duration of each radio frequency pulse train is the dwell time after the magnetization vector is flipped to the transverse plane, and the duration of multiple radio frequency pulse trains increases in sequence.
  • each radio frequency pulse train is followed by a radio frequency pulse for sampling, and the flip angle of each radio frequency pulse is less than or equal to 10°.
  • determining the lateral relaxation time of the tissue represented by each voxel according to the analog signal in the preset dictionary that best matches the evolution signal of each voxel including:
  • the lateral relaxation time corresponding to the analog signal with the highest matching degree of the evolution signal of the voxel is taken as the lateral relaxation time of the voxel.
  • the MRF pulse sequence further includes a gradient echo sequence based on inversion recovery.
  • an apparatus for determining quantitative magnetic resonance imaging parameters including:
  • the pre-imaging module is used to acquire multiple magnetic resonance images of the subject based on a preset MRF pulse sequence; wherein the MRF pulse sequence includes multiple radio frequency pulse trains that are sequentially excited, and the radio frequency pulse train is used to excite the magnetization of the subject Vector
  • the signal acquisition module is used to extract the evolution signal of each voxel from multiple magnetic resonance images; wherein, the evolution signal is used to characterize the change of the signal intensity of each voxel in the multiple magnetic resonance images;
  • the parameter determination module is used to determine the transverse relaxation time of the tissue represented by each voxel according to the analog signal that best matches the evolution signal of each voxel in the preset dictionary; the dictionary includes the signal simulation evolution of the MRF pulse sequence Generate multiple analog signals, and the transverse relaxation time corresponding to each analog signal one-to-one.
  • an embodiment of the present application provides a quantitative magnetic resonance imaging parameter determination device, which includes a memory, a processor, and a computer program stored in the memory and running on the processor.
  • the processor implements the above-mentioned first when the computer program is executed. On the one hand, the steps of any method.
  • an embodiment of the present application provides a computer-readable storage medium, and the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of any one of the methods in the first aspect are implemented.
  • the embodiments of the present application provide a computer program product, which when the computer program product runs on a terminal device, causes the terminal device to execute the method in any one of the above-mentioned first aspects.
  • the method for determining quantitative magnetic resonance imaging parameters acquires multiple magnetic resonance images of a subject based on a preset MRF pulse sequence; extracts the evolution signal of each voxel from the multiple magnetic resonance images, and extracts the evolution signal of each voxel from the multiple magnetic resonance images.
  • the analog signal in the dictionary that matches the evolution signal of each voxel determines the transverse relaxation time of the tissue represented by each voxel, realizing the quantification of the transverse relaxation time in magnetic resonance imaging.
  • the MRF sequence in the embodiment of the present application includes a plurality of radio frequency pulse trains that are sequentially excited.
  • each radio frequency pulse train is The radio frequency pulse causes the hydrogen nucleus of the subject’s internal tissues to flip to generate a transverse magnetization vector, and during the duration of the radio frequency pulse train, the transverse magnetization vector is re-excited to achieve the weighting of T2 relaxation. Therefore, the embodiment of the present application provides The quantitative magnetic resonance imaging parameter determination method improves the sensitivity of lateral relaxation time detection, and can obtain accurate lateral relaxation time.
  • FIG. 1 is a schematic structural diagram of a quantitative magnetic resonance imaging system provided by an embodiment of the present application
  • FIG. 2 is a schematic flowchart of a method for determining quantitative magnetic resonance imaging parameters according to an embodiment of the present application
  • Fig. 3 is a schematic diagram of a radio frequency pulse train provided by an embodiment of the present application.
  • Fig. 4 is an evolution signal of a single voxel provided by an embodiment of the present application.
  • FIG. 5 is a schematic diagram of a process for determining the lateral relaxation time of a voxel according to an embodiment of the present application
  • Fig. 6 is a schematic diagram of a pulse sequence provided by another embodiment of the present application.
  • FIG. 7 is a schematic diagram of a pseudo-randomly changing flip angle and repetition time provided by an embodiment of the present application.
  • FIG. 8 is a schematic diagram of a dictionary provided by an embodiment of the present application.
  • FIG. 9 is a schematic diagram of the composition of a quantitative magnetic resonance imaging parameter determination device provided by an embodiment of the present application.
  • FIG. 10 is a schematic structural diagram of a quantitative magnetic resonance imaging parameter determination device provided by an embodiment of the present application.
  • Magnetic resonance imaging The basic principle of Resonance Imaging (MRI) is that the spin motion of hydrogen atoms in the tissue generates magnetic moments. Under the action of a strong and uniform main magnetic field, the originally irregularly arranged hydrogen atom spin magnetic moments will be arranged along the direction of the main magnetic field to form a macroscopic magnetization vector (including longitudinal magnetization vector and transverse magnetization vector). Under the excitation of the radio frequency pulse, the macroscopic magnetization vector will flip to the direction perpendicular to the main magnetic field. The magnetization vector cuts the radio frequency coil during the precession and rotation of the hydrogen atom to generate electromagnetic induction signals, which are reconstructed to form a magnetic resonance image.
  • MRI Resonance Imaging
  • Magnetic Resonance Fingerprinting It is a fast, quantitative magnetic resonance imaging method that can obtain multiple tissue attribute parameters at the same time.
  • Pulse sequence Sequence refers to the combination of radio frequency pulse, spatial coding, and echo sampling in a certain time sequence.
  • Repetition Time refers to the time interval between two adjacent excitation pulses in a pulse sequence.
  • Echo time Time refers to the time between the excitation of the excitation pulse and the acquisition of the echo signal.
  • T1 Longitudinal relaxation time, the time required for the longitudinal magnetization vector to recover from zero to two-thirds of the total signal strength.
  • T2 Transverse relaxation time, the time required for the transverse magnetization vector to decay from 100% to 1/3.
  • Quantitative magnetic resonance imaging parameter determination refers to determining the value of the tissue attribute parameter of the subject, where the tissue attribute parameter of the subject includes T1, T2, proton density, and so on. Quantitative tissue attribute parameters can help doctors better distinguish between healthy tissues and pathological tissues in an absolute sense, and it is also convenient for doctors to compare different examinations more objectively in follow-up research. Currently, the most widely used organization attribute parameters include T1 and T2.
  • MRF Magnetic resonance fingerprint imaging
  • T1 and T2 quantitative methods MRF can obtain the parameter values of multiple tissue attribute parameters at the same time.
  • MRF mainly includes the following steps: in each excitation of the pulse sequence, different TR and FA are used to collect data of the area of interest of the subject; then according to the parameters of the pulse sequence, a dictionary is generated based on the classic one-step Bloch model.
  • the dictionary includes multiple analog time signals and the corresponding tissue attribute parameter values of each analog time signal; finally, after the collected data is reconstructed, the evolution signal (ie, "fingerprint") of a single voxel over time is obtained; The evolution signal of each voxel is compared with the analog time signal contained in the dictionary, the best matching analog time signal of each voxel is searched in the dictionary, and the tissue attribute parameter value corresponding to the best matching analog time signal is taken as The tissue attribute parameter value of the voxel. Since the tissue attribute parameters of different tissue types of the subject are different, different evolution signals of different tissue types can be obtained based on the same pulse sequence. Repeat the above process to obtain the tissue attribute parameter values of different tissue types (all voxels) of the subject .
  • FIG. 1 is a schematic structural diagram of a quantitative magnetic resonance imaging system provided by an embodiment of the application. As shown in FIG. 1, the quantitative magnetic resonance imaging system includes a magnetic resonance device 10 and an image reconstruction device 20.
  • the magnetic resonance device 10 For executing scan instructions input by the user and acquiring magnetic resonance data, the magnetic resonance device 10 includes a display, one or more input devices, and a processor.
  • the display provides a user input interface for receiving a scan instruction input by the user, and the scan instruction is used to generate a pulse sequence.
  • the magnetic resonance device 10 may be connected to the image reconstruction device 20 through a communication system for sending processing instructions and magnetic resonance data input by the user to the image reconstruction device 20.
  • the communication system includes a wired or wireless network connection.
  • the image reconstruction device 20 is a server, which receives the magnetic resonance data and processing instructions sent by the magnetic resonance device 10, and processes the magnetic resonance data according to the processing instructions to generate a reconstructed magnetic resonance image, and determines tissue attribute parameters based on the magnetic resonance image
  • Processing instructions include Fourier transform of magnetic resonance data, image reconstruction, pattern matching, and dictionary generation.
  • the image reconstruction device 20 may also include a display and one or more input devices for receiving scan instructions or processing instructions input by the user.
  • the quantitative magnetic resonance imaging parameter determination system may also include one or more networked user terminals, such as mobile phones, smart computers, and so on.
  • the networked user terminal can be connected to the magnetic resonance device 10 through a communication system to realize remote access and control of the magnetic resonance device 10.
  • the magnetic resonance device 10 receives the scan instruction input by the user and generates the corresponding pulse signal, which specifically includes generating the gradient waveform used to perform the specified scan and controlling the radio frequency generator to generate the desired frequency, phase, and pulse amplitude waveform Radio frequency pulse.
  • the magnetic resonance device 10 acquires magnetic resonance data and sends the magnetic resonance data to the image reconstruction device 20.
  • the image reconstruction device 20 performs image reconstruction and pattern matching in magnetic resonance fingerprint imaging (MRF) to determine the tissue The quantitative value of the attribute parameter.
  • MRF magnetic resonance fingerprint imaging
  • FIG. 2 is a schematic flowchart of a method for determining quantitative magnetic resonance imaging parameters provided by an embodiment of the application, and mainly relates to the process of how to accurately quantify T2 in MRF.
  • the method for determining quantitative magnetic resonance imaging parameters includes:
  • S201 Acquire multiple magnetic resonance images of the subject based on a preset MRF pulse sequence; wherein the MRF pulse sequence includes multiple radio frequency pulse trains that are sequentially excited, and the radio frequency pulse train is used to excite the magnetization vector of the subject.
  • the subject includes a number of different tissue types. Based on the same pulse sequence scanning the subject, different tissue types can obtain different evolution signals. Exemplarily, the subject may include imitations, living bodies (animals or humans), isolated organs or tissues, and the like.
  • the resonance characteristics of different tissue types are different.
  • the tissue type may include water, fat, bone, muscle, blood, and the like.
  • the MRF pulse sequence is a pulse sequence generated based on the MRF framework. Unlike conventional magnetic resonance imaging, the MRF framework uses a series of changing sequence blocks to generate the target pulse sequence. These sequence blocks generate radio frequency pulses that are sequentially excited and applied to different tissue types to generate different signal evolutions.
  • the MRF pulse sequence includes multiple radio frequency pulse trains that are sequentially excited, and the multiple radio frequency pulse trains are used to excite the magnetization vector of the subject to prepare for T2 magnetization.
  • T2 magnetization preparation refers to the preparation of transverse magnetization of the hydrogen nucleus of the subject to improve the sensitivity of T2 detection. Since T2 is used to characterize the attenuation characteristics of the transverse magnetization vector, the magnetization preparation can be multiple focusing on the transverse magnetization vector to encode the specific transverse relaxation of the subject multiple times.
  • the transverse magnetization vector is the macroscopic representation of the magnetic moments of multiple hydrogen nuclei of the subject in the transverse plane.
  • the magnetization vector includes a longitudinal magnetization vector and a transverse magnetization vector.
  • the direction of the magnetization vector is parallel to the main magnetic field
  • the magnetization vector parallel to the main magnetic field direction is the longitudinal magnetization vector
  • the magnetization vector perpendicular to the direction of the magnetic field is the transverse magnetization vector.
  • each radio frequency pulse train includes an excitation pulse, a 180° flip pulse, and a 90° flip pulse that are sequentially excited, where the excitation pulse is used to flip the magnetization vector to the transverse plane to obtain a larger transverse magnetization vector; °The flipping pulse is used to flip the direction of all the magnetic moments constituting the transverse magnetization vector by 180°; the flipping pulse is used to flip the relaxed transverse magnetization vector back to the longitudinal plane.
  • the excitation pulse of the radio frequency pulse and the 90° flipping pulse each time the 180° flipping pulse is excited, the vector direction of the current transverse magnetization vector is 180° flipped, which can achieve multiple encodings specific to the transverse relaxation and improve The sensitivity of T2 detection. Among them, there can be one or more 180° flip pulses.
  • the radio frequency pulse train includes 90° excitation pulses, at least one 180° excitation pulse, and -90° excitation pulses that are sequentially excited; wherein, the 90° excitation pulse is the aforementioned excitation pulse, and the 180° excitation pulse is the aforementioned The 180° reversal pulse, and the -90° excitation pulse is the above-mentioned 90° reversal pulse.
  • the interval time between two adjacent excitation pulses in the radio frequency pulse train is the same. Among them, there can be multiple 180° excitation pulses, and each 180° excitation pulse performs a reversal of the transverse magnetization vector in the transverse plane. By setting multiple 180° excitation pulses, the transverse relaxation specificity can be encoded multiple times. .
  • FIG. 3 is a schematic diagram of a radio frequency pulse train provided by this embodiment.
  • the pulse train includes two radio frequency pulse trains, and each radio frequency pulse train includes a sequence of 90° excitation. Excitation pulse, one 180° excitation pulse and one -90° excitation pulse. The interval time between the 90° excitation pulse and the 180° excitation pulse is the same as the interval time between the 180° excitation pulse and the -90° excitation pulse.
  • the 90° excitation pulse directly flips the magnetization vector to the transverse plane and obtains the largest transverse magnetization vector. After the 90 excitation pulse is excited, the transverse magnetization vector enters a relaxed state and begins to attenuate.
  • the vector direction of all the magnetic moments in the current transverse magnetization vector is reversed by 180°, and the reversed transverse magnetization vector is obtained.
  • the reversed transverse magnetization vector continues to attenuate until the -90° excitation pulse will attenuate the transverse magnetization.
  • the vector is flipped back to the longitudinal plane, and the T2 magnetization preparation of the subject is completed.
  • each radio frequency pulse train is the dwell time after the magnetization vector flips to the transverse plane, which is specifically embodied as the interval time between the excitation pulse and the flip pulse of the radio frequency pulse train; for example, as shown in Fig. 3, each The duration of each radio frequency pulse train is the interval time between the 90° excitation pulse and the -90° excitation pulse.
  • each radio frequency pulse train can be different. Since the T2 of the tissue represented by different voxels is different, the preparation time for T2 sensitivity of different voxels is also different.
  • the duration of each radio frequency pulse train is set as a preparation time sensitive to T2 of the tissues represented by different voxels, and the duration of multiple radio frequency pulse trains increases sequentially.
  • the radio frequency excitation pulse train includes three, and the duration of the three radio frequency excitation pulse trains is 5 milliseconds, 25 milliseconds, and 35 milliseconds, respectively.
  • the duration of the RF excitation pulse train generally does not exceed 100 milliseconds.
  • the video burst is used for the T2 preparation of the test subject. Therefore, after each radio frequency burst, a radio frequency pulse for sampling can be set, and the flip angle of each radio frequency pulse is less than or equal to 10° . In practical applications, after each RF excitation pulse train is finished, a RF pulse is applied. At this time, each voxel generates an echo, and the echo signal is collected through a sampling window (analog-to-digital conversion device A/D).
  • the subject is scanned to obtain the magnetic resonance image of the subject, which specifically includes S2011 to S2013:
  • the pulse sequence parameter is used to characterize the combination of the radio frequency pulse train of the MRF pulse sequence and the radio frequency pulse used for sampling.
  • the pulse sequence parameters also include the flip angle FA, repetition time TR, echo time TE of each pulse, and the phase change of the radio frequency pulse in each excitation.
  • S2012 Send the pulse sequence parameters to the magnetic resonance device, so that the magnetic resonance device generates a pulse signal based on the pulse sequence parameters, and acquires multiple sampling data of the subject.
  • the manner in which the magnetic resonance equipment obtains the sampling data based on the pulse sequence parameters can be implemented based on the existing technology, which will not be repeated here.
  • S2013 Receive a plurality of sampled data, and perform Fourier transform on each sampled data to generate a magnetic resonance image of the subject corresponding to each sampled data.
  • the magnetic resonance equipment stores the sampled data obtained by sampling in a certain arrangement to form a sampled data space. According to the signal intensity of each sampling point and its location in the sampling data space, a magnetic resonance image is generated. Specifically, for the data obtained by linear sampling, the data is evenly distributed on the grid points. After inverse Fourier transformation, the two-dimensional plane can be obtained. According to the signal intensity of each voxel, it is converted into the corresponding gray Degree value, the magnetic resonance image is obtained.
  • Each voxel has different signal intensity at different sampling times, which is reflected in the magnetic resonance image as a different gray value. Obtain the signal intensity of each voxel point from multiple magnetic resonance images, and sort and combine them according to the sampling time of the magnetic resonance image, that is, obtain the evolution signal of each voxel.
  • FIG. 4 is an evolution signal of a single voxel provided by an embodiment of the application.
  • the sampling time point is preset to 1000, and the MRF pulse sequence is executed at each sampling time point to obtain 1000 under-sampled magnetic resonance images.
  • the pixel points in the magnetic resonance image correspond to the voxels of the subject one-to-one.
  • S203 Determine the transverse relaxation time of the tissue represented by each voxel according to the analog signal that best matches the evolution signal of each voxel in the preset dictionary; wherein, the dictionary includes signals generated by performing signal simulation evolution on the MRF pulse sequence. Multiple analog signals, and the transverse relaxation time corresponding to each analog signal one-to-one.
  • the dictionary may be obtained in advance, and the dictionary includes a plurality of analog signals generated by signal simulation evolution based on the above-mentioned MRF pulse sequence, and a transverse relaxation time corresponding to each analog signal one-to-one.
  • the signal simulation evolution can be obtained by simulation calculation of Bloch model.
  • Each analog signal is a dictionary entry in the dictionary, and each dictionary entry corresponds to a T2.
  • the T2 is divided unevenly according to the physiological characteristics of the subject.
  • the range of T2 is set to 0-500 milliseconds.
  • the T2 that is less than 100 milliseconds is increased with a gradient of 2 milliseconds
  • the portion greater than 100 milliseconds and less than 200 milliseconds is increased with a gradient of 5 milliseconds
  • the portion greater than 200 milliseconds is increased with a gradient of 50 milliseconds to generate multiple sets of T2.
  • the Bloch model is used to simulate and calculate the simulated time signal.
  • the Bloch model represents the change of the proton magnetization vector with the relaxation time under the action of a magnetic field.
  • Figure 5 mainly relates to how to determine the T2 of each voxel.
  • the transverse relaxation of each voxel is determined according to the analog signal matching the evolution signal of each voxel in the preset dictionary. Henan time, specifically including S501 and S502:
  • S501 Compare the time signal of each voxel with all the analog signals in the preset dictionary, and obtain the analog signal with the highest matching degree with the magnetic resonance signal of each voxel in the dictionary.
  • the introduction of the dictionary allows the MRF to incorporate some of the system parameters of the magnetic resonance equipment, such as the inhomogeneity of the main magnetic field and the inhomogeneity of the radio frequency pulse, which improves the robustness of the MRF and makes it suitable for different tissue locations and different times
  • the quantitative magnetic resonance imaging parameters of the segment are determined.
  • the method for determining quantitative magnetic resonance imaging parameters acquires multiple magnetic resonance images of a subject based on a preset MRF pulse sequence; extracts the evolution signal of each voxel from the multiple magnetic resonance images, and extracts the evolution signal of each voxel from the multiple magnetic resonance images.
  • the analog signal in the dictionary that matches the evolution signal of each voxel determines the transverse relaxation time of the tissue represented by each voxel, realizing the quantification of the transverse relaxation time in magnetic resonance imaging.
  • the MRF sequence in the embodiment of the present application includes a plurality of radio frequency pulse trains that are sequentially excited.
  • each radio frequency pulse train is The radio frequency pulse causes the hydrogen nucleus of the subject’s internal tissues to flip to generate a transverse magnetization vector, and during the duration of the radio frequency pulse train, the transverse magnetization vector is re-excited to achieve the weighting of T2 relaxation. Therefore, the embodiment of the present application provides The quantitative magnetic resonance imaging parameter determination method improves the sensitivity of lateral relaxation time detection, and can obtain accurate lateral relaxation time.
  • the MRF pulse sequence is a pulse sequence generated based on the MRF framework. Unlike conventional magnetic resonance imaging, the MRF framework uses a series of changing sequence blocks to generate the target pulse sequence. These sequence blocks generate radio frequency pulses that are sequentially excited and applied to different tissue types to generate different signal evolutions. And according to the evolution of the signal, the parameter values of multiple tissue attribute parameters can be obtained at the same time. Among them, the tissue attribute parameters may include longitudinal relaxation time T1, main magnetic field strength B0, and so on.
  • the dictionary may include multiple analog signals generated by signal simulation evolution based on the MRF pulse sequence, and characteristic physical parameters corresponding to each analog signal on a one-to-one basis.
  • the characteristic physical parameters can also include the longitudinal relaxation time T1, the main magnetic field strength B0, and so on. Then, according to the analog signal that best matches the evolution signal of each voxel in the preset dictionary, the characteristic physical parameters of the tissue represented by each voxel are determined.
  • FIG. 6 is a schematic diagram of a pulse sequence provided by another embodiment of the application.
  • the MRF pulse sequence includes two sequentially excited radio frequency pulse trains, an inversion recovery pulse, and a steady state equilibrium. Automatic precession sequence.
  • the MRF may include a T2 preparation sequence block, which is used to generate multiple radio frequency pulse trains that are sequentially excited, and the MRF may also include an inversion recovery pulse sequence block, which is used to generate inversion recovery pulses. MRF realizes the rapid addition of multiple pulse sequence blocks through the frame design of sequence blocks.
  • the MRF pulse sequence may also include a gradient echo sequence based on inversion recovery.
  • the gradient echo sequence based on inversion recovery includes sequentially excited inversion recovery pulses and gradient echo sequence pulses, which can be implemented by adding an inversion recovery sequence block and a gradient echo acquisition sequence block to the MRF framework.
  • the inversion recovery sequence is sensitive to T1, and the sensitivity of the magnetic resonance signal to T1 can be improved by setting the inversion recovery sequence, and the accuracy T1 value can be obtained.
  • Inversion recovery pulse Recovery includes sequential excitation of 180° RF pulses and 90° RF pulses. The interval between two RF pulses is the reversal waiting time. When in use, the magnetization vector is first excited based on a 180° RF pulse, and then after a period of time (inversion time TI), a 90° RF pulse is used for excitation here, and the two RF pulses form an echo.
  • the magnetization vector is excited by the reversal recovery 180° pulse, and the magnetization vector is reversed by 180°, and then waits for the first T1 time, at which time the longitudinal magnetization vector will be partially recovered, and then multiple small-angle radio frequency pulses are applied ( (With 90° pulse component) invert the current magnitude of the longitudinal magnetization vector to the horizontal coordinate for data acquisition.
  • multiple small-angle radio frequency pulses are applied (With 90° pulse component) invert the current magnitude of the longitudinal magnetization vector to the horizontal coordinate for data acquisition.
  • the longitudinal magnetization vector is completely restored to the steady state, repeat the above operation by changing the value of the inversion time TI, choosing a different inversion time, which can reduce the chemical shift artifacts and obtain a more accurate T1 value.
  • the gradient echo sequence is used for echo sampling, and the gradient echo sequence can be a balanced steady-state free precession sequence.
  • the characteristic of the equilibrium steady-state free precession sequence is that both the transverse magnetization vector and the longitudinal magnetization vector reach a steady state after multiple radio frequency excitations. Since the excited radio frequency angle can be small and the TR can be set very short, the scanning time of the balanced steady-state free precession sequence is greatly reduced compared to the scanning time of the ordinary gradient echo sequence.
  • MRF can be obtained by changing the pulse sequence parameters at each acquisition time point to obtain spatially incoherent and or temporally incoherent evolution signals.
  • the pulse sequence parameters that can be changed include the reversal angle FA, pulse phase, repetition time TR, echo time TE, and sampling mode of each pulse.
  • the repetition time TR and the flip angle FA bit of the balanced steady-state automatic precession sequence are randomly changed to obtain spatially incoherent evolution signals. That is, the evolution signal of each voxel.
  • the repetition time TR and the random change curve of the flip angle FA position of the balanced steady-state automatic precession sequence can be seen in Figure 7.
  • the subject is scanned based on the MRF pulse sequence of this embodiment, and the steps for acquiring the magnetic resonance image of the subject are the same as S2011 to S2013, only the pulse sequence parameters are different.
  • the pulse sequence parameters are used to characterize the timing combination of the radio frequency pulse train of the MRF pulse sequence, the radio frequency pulse used for sampling, the reverse recovery pulse, and the balance steady-state automatic precession pulse.
  • the pulse sequence parameters also include the flip angle FA, repetition time TR, echo time TE of each pulse, and the phase change of the radio frequency pulse in each excitation.
  • the flip angle FA and the repetition time TR of the balanced steady-state automatic precession pulse change pseudo-randomly with time.
  • the evolution signal of each voxel of the subject is extracted from the multiple magnetic resonance images; among them, the evolution signal is used to characterize the signal of each voxel in multiple magnetic resonance images Changes in intensity. Then determine the tissue attribute parameter value of each voxel according to the analog signal matching the evolution signal of each voxel in the preset dictionary; the dictionary includes multiple simulations generated by signal simulation evolution of the MRF pulse sequence shown in Figure 6 Signal, and the tissue attribute parameter value corresponding to each analog signal one-to-one.
  • Organization attribute parameter values include T1 and T2.
  • the dictionary can be obtained by pre-calculation through Bloch model simulation.
  • the range of T1 is set to 0-5000 milliseconds
  • the range of T2 is set to 0-500 milliseconds.
  • FIG. 8 is a schematic diagram of a dictionary provided by an embodiment of the application. As shown in FIG. 8, each group of tissue attribute parameter values corresponds to an analog signal.
  • the organization attribute parameters include T1 and T2, and the number of dictionary entries in the dictionary is determined by the number of permutations and combinations of T2 and T1. It should be understood that the tissue attribute parameters may also include other tissue attribute parameters such as proton density.
  • the MRF pulse sequence includes not only the radio frequency pulse sequence used to excite the magnetization vector, but also the gradient echo sequence based on inversion recovery.
  • the FA and TR of the gradient echo sequence change pseudo-randomly, so the signal of each voxel of the subject can be spatially encoded.
  • the MRF pulse sequence can obtain accurate T1 and T2 at the same time by setting the radio frequency pulse train and the inversion recovery pulse.
  • some system parameters of the magnetic resonance equipment can be incorporated, such as the inhomogeneity of the main magnetic field and the inhomogeneity of the radio frequency pulse, which improves the robustness of the MRF and makes it suitable for Quantitative magnetic resonance imaging of different tissue types and different time periods.
  • the embodiment of the present invention further provides an embodiment of an apparatus for realizing the foregoing method embodiment.
  • FIG. 9 is a schematic diagram of the composition of a quantitative magnetic resonance imaging parameter determination device provided by an embodiment of the application.
  • the quantitative magnetic resonance imaging parameter determination device 90 includes: a pre-imaging module 901, a signal acquisition module 902 and a parameter determination module 903.
  • the pre-imaging module 901 is used to acquire multiple magnetic resonance images of the subject based on a preset MRF pulse sequence; wherein the MRF pulse sequence includes multiple radio frequency pulse trains that are sequentially excited, and the radio frequency pulse train is used to excite the subject’s Magnetization vector
  • the signal acquisition module 902 is used to extract the evolution signal of each voxel from multiple magnetic resonance images; wherein, the evolution signal is used to characterize the change of the signal intensity of each voxel in the multiple magnetic resonance images;
  • the parameter determination module 903 is used to determine the transverse relaxation time of the tissue represented by each voxel according to the analog signal that best matches the evolution signal of each voxel in the preset dictionary; wherein the dictionary includes signal simulation of the MRF pulse sequence The multiple analog signals generated by the evolution, and the transverse relaxation time corresponding to each analog signal one-to-one.
  • the radio frequency pulse train includes 90° excitation pulses, at least one 180° excitation pulse, and -90° excitation pulses that are sequentially excited.
  • the interval time between two adjacent excitation pulses in the radio frequency pulse train is the same.
  • the duration of each radio frequency pulse train is the dwell time after the magnetization vector flips to the transverse plane, and the duration of multiple radio frequency pulse trains increases in sequence.
  • Each radio frequency pulse train is followed by a radio frequency pulse for sampling, and the flip angle of each radio frequency pulse is less than or equal to 10°.
  • the MRF pulse sequence also includes a gradient echo sequence based on inversion recovery.
  • the parameter determination module 903 is specifically configured to:
  • the dictionary includes the signal simulation evolution of the MRF pulse sequence The generated multiple analog signals, and the correspondence between each analog signal and the transverse relaxation time.
  • the lateral relaxation time corresponding to the analog signal with the highest matching degree of the evolution signal of the voxel is taken as the lateral relaxation time of the voxel.
  • the quantitative magnetic resonance imaging parameter determination device acquires multiple magnetic resonance images of the subject based on a preset MRF pulse sequence; extracts the evolution signal of each voxel from the multiple magnetic resonance images, and extracts the evolution signal of each voxel from the multiple magnetic resonance images, and extracts the evolution signal of each voxel from the multiple magnetic resonance images, according to the preset MRF pulse sequence.
  • the analog signal matching the evolution signal of each voxel in the dictionary determines the transverse relaxation time of the tissue represented by each voxel, and realizes the quantification of the transverse relaxation time in magnetic resonance imaging.
  • the MRF sequence in the embodiment of the present application includes a plurality of radio frequency pulse trains that are sequentially excited.
  • each radio frequency pulse train is The radio frequency pulse causes the hydrogen nucleus of the subject’s internal tissues to flip to generate a transverse magnetization vector, and during the duration of the radio frequency pulse train, the transverse magnetization vector is re-excited to achieve the weighting of T2 relaxation. Therefore, the embodiment of the present application provides The quantitative magnetic resonance imaging parameter determination method improves the sensitivity of lateral relaxation time detection, and can obtain accurate lateral relaxation time.
  • the device for determining quantitative magnetic resonance imaging parameters provided by the embodiment shown in FIG. 9 can be used to implement the technical solutions in the foregoing method embodiments, and its implementation principles and technical effects are similar, and will not be repeated here in this embodiment.
  • FIG. 10 is a schematic diagram of a quantitative magnetic resonance imaging image reconstruction device provided by an embodiment of the present application.
  • the quantitative magnetic resonance imaging parameter determination terminal device 10 of this embodiment includes: at least one processor 1001, a memory 1002, and a computer program stored in the memory 1002 and running on the processor 1001.
  • the quantitative magnetic resonance imaging image reconstruction device further includes a communication component 1003, wherein the processor 1001, the memory 1002, and the communication component 1003 are connected by a bus 1004.
  • the processor 1001 executes the computer program
  • the steps in the above embodiments of the method for determining quantitative magnetic resonance imaging parameters are implemented, for example, steps S201 to S203 in the embodiment shown in FIG. 2.
  • the processor 1001 executes the computer program
  • the functions of the modules/units in the foregoing device embodiments for example, the functions of the modules 901 to 903 shown in FIG. 9 are realized.
  • the computer program may be divided into one or more modules/units, and one or more modules/units are stored in the memory 1002 and executed by the processor 1001 to complete the application.
  • the one or more modules/units may be a series of computer program instruction segments capable of completing specific functions, and the instruction segments are used to describe the execution process of the computer program in the quantitative magnetic resonance imaging image reconstruction device 100.
  • the quantitative magnetic resonance imaging image reconstruction device may be a cloud server or a user terminal.
  • the user terminal can be, but is not limited to, various personal computers, notebook computers, smart phones, etc. that can run applications.
  • the cloud server can be a server that implements a single function or a server that implements multiple functions. Specifically, it can be an independent physical server or a cluster of physical servers.
  • FIG. 12 is only an example of the quantitative magnetic resonance imaging parameter determination device and does not constitute a limitation on the quantitative magnetic resonance imaging image reconstruction device, and may include more or fewer components than shown in the figure, or Combine certain components, or different components, such as input and output devices, network access devices, buses, etc.
  • the processor 1001 may be a central processing unit (Central Processing Unit). Unit, CPU), other general-purpose processors, digital signal processors (Digital Signal Processor, DSP), Application Specific Integrated Circuit (Application Specific Integrated Circuit, ASIC), ready-made programmable gate array (Field-Programmable Gate Array, FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.
  • the general-purpose processor may be a microprocessor or the processor may also be any conventional processor or the like.
  • the memory 1002 may be an internal storage unit of the quantitative magnetic resonance imaging image reconstruction device, or an external storage device of the quantitative magnetic resonance imaging image reconstruction device, such as a plug-in hard disk, a smart memory card (Smart Media Card, SMC), and a secure digital (Secure Digital, SD) card, flash card (Flash Card), etc.
  • the memory 1002 is used to store the computer program and other programs and data required by the quantitative magnetic resonance imaging image reconstruction device.
  • the memory 1002 can also be used to temporarily store data that has been output or will be output.
  • the bus may be an industry standard architecture (Industry Standard Architecture, ISA) bus, a peripheral device interconnect (Peripheral Component, PCI) bus, or an extended industry standard architecture (Extended Industry Standard Architecture, EISA) bus, etc.
  • ISA Industry Standard Architecture
  • PCI peripheral device interconnect
  • EISA Extended Industry Standard Architecture
  • the bus can be divided into address bus, data bus, control bus and so on.
  • the buses in the drawings of this application are not limited to only one bus or one type of bus.
  • the embodiments of the present application also provide a computer-readable storage medium, and the computer-readable storage medium stores a computer program.
  • the computer program is executed by a processor, the steps in the foregoing method embodiments can be realized.
  • the embodiments of the present application provide a computer program product.
  • the quantitative magnetic resonance imaging parameter determination device can realize the steps in the foregoing method embodiments when the quantitative magnetic resonance imaging parameter determination device is executed.
  • the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer readable storage medium.
  • the computer program can be stored in a computer-readable storage medium.
  • the computer program can be stored in a computer-readable storage medium.
  • the steps of the foregoing method embodiments can be implemented.
  • the computer program includes computer program code, and the computer program code may be in the form of source code, object code, executable file, or some intermediate forms.
  • the computer-readable medium may include at least: any entity or device capable of carrying the computer program code to the quantitative magnetic resonance imaging image reconstruction equipment, recording medium, computer memory, read-only memory (ROM, Read-Only Memory), Random Access Memory (RAM, Random Access Memory), electrical carrier signals, telecommunications signals, and software distribution media.
  • ROM read-only memory
  • RAM Random Access Memory
  • electrical carrier signals telecommunications signals
  • software distribution media For example, U disk, mobile hard disk, floppy disk or CD-ROM, etc.
  • computer-readable media cannot be electrical carrier signals and telecommunication signals.
  • the disclosed apparatus/network equipment and method may be implemented in other ways.
  • the device/network device embodiments described above are only illustrative.
  • the division of the modules or units is only a logical function division, and there may be other divisions in actual implementation, such as multiple units.
  • components can be combined or integrated into another system, or some features can be omitted or not implemented.
  • the displayed or discussed mutual coupling or direct coupling or communication connection may be indirect coupling or communication connection through some interfaces, devices or units, and may be in electrical, mechanical or other forms.
  • the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the objectives of the solutions of the embodiments.

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Abstract

一种定量磁共振成像参数确定方法、装置、设备及存储介质。方法包括基于预设的MRF脉冲序列获取被试对象的多个磁共振图像（S201），从多个磁共振图像中提取每个体素的演变信号（S202）；根据预设的字典中与每个体素的演变信号匹配的模拟信号，确定每个体素的横向弛豫时间（S203）；其中，MRF脉冲序列包括顺序激发的多个射频脉冲串，射频脉冲串用于激发被试对象的横向磁化矢量；演变信号用于表征每个体素在多个磁共振图像中信号强度的变化。定量磁共振成像参数确定方法增加了对横向弛豫时间检测的灵敏度，提高了基于MRF检测组织横向弛豫时间的准确度。

Description

定量磁共振成像参数确定方法、装置、设备及存储介质 技术领域
本申请涉及磁共振成像技术领域，尤其涉及一种定量磁共振成像参数确定方法、装置、设备及存储介质。
 背景技术
定量磁共振成像对于人体病理组织的检测具有组织特异性，可以帮助医生更好地区分健康组织和病理组织，具有非常重要的临床诊断和研究价值。
磁共振指纹成像（Magnetic Resonance Fingerprinting，MRF）是一种新型的快速定量磁共振成像参数确定技术。 MRF采用一组伪随机变化的脉冲序列扫描被试对象，使得来自被试对象不同的组织类型（以体素为载体）呈现特有的信号演变（即指纹）。然后将得到的指纹与预先获取的字典中的多个字典条目进行匹配，以得到各组织类型多个组织属性参数的定量值。组织属性参数包括纵向弛豫时间（以下简称T1）和横向弛豫时间（以下简称T2）。
目前，MRF的脉冲序列主要是基于反转恢复的稳态自由进动序列，反转恢复序列对T1特别敏感，而稳态自由进动序列具有相对高的信噪比，因此基于该脉冲序列对获取不同被试对象的组织属性参数具有一定的优势。但是由于磁场的不均匀性以及T2持续时间较短，基于当前的MRF脉冲序列获得的磁共振图像中，对各组织类型T2差异不敏感，导致获得的T2准确度较低。
 技术问题
有鉴于此，本申请实施例提供了一种定量磁共振成像参数确定方法、装置、设备及存储介质，以解决现有技术中定量磁共振成像中横向弛豫时间不准确的技术问题。
 技术解决方案
第一方面，本申请实施例提供了一种定量磁共振成像参数确定方法，包括：
基于预设的MRF脉冲序列获取被试对象的多个磁共振图像；其中，MRF脉冲序列包括顺序激发的多个射频脉冲串，射频脉冲串用于激发被试对象的磁化矢量；
从多个磁共振图像中提取每个体素的演变信号；其中，演变信号用于表征每个体素在多个磁共振图像中信号强度的变化；
根据预设的字典中与每个体素的演变信号最匹配的模拟信号，确定每个体素所代表组织的横向弛豫时间；其中，字典包括对MRF脉冲序列进行信号模拟演变生成的多个模拟信号，以及与每个模拟信号一一对应的横向弛豫时间。
在第一方面的一种可能的实现方式中，射频脉冲串包括顺序激发的90°激发脉冲、至少一个180°激发脉冲和-90°激发脉冲。
在第一方面的一种可能的实现方式中，射频脉冲串中的相邻两个激发脉冲之间的间隔时间相同。
在第一方面的一种可能的实现方式中，每个射频脉冲串的持续时间为磁化矢量翻转至横向平面后的停留时间，多个所述射频脉冲串的持续时间依次递增。
在第一方面的一种可能的实现方式中，每个射频脉冲串之后跟随有一个用于采样的射频脉冲，每个射频脉冲的翻转角均小于等于10°。
在第一方面的一种可能的实现方式中，根据预设的字典中与每个体素的演变信号最匹配的模拟信号，确定每个体素所代表组织的横向弛豫时间，包括：
将每个体素的时间信号与预设的字典中所有的模拟信号进行比较，获得字典中与各体素的磁共振信号匹配度最高的模拟信号；
针对每个体素，将与体素的演变信号匹配度最高的模拟信号对应的横向弛豫时间作为体素的横向弛豫时间。
在第一方面的一种可能的实现方式中，MRF脉冲序列还包括基于反转恢复的梯度回波序列。
第二方面，本申请实施例提供了一种定量磁共振成像参数确定装置，包括：
预成像模块，用于基于预设的MRF脉冲序列获取被试对象的多个磁共振图像；其中，MRF脉冲序列包括顺序激发的多个射频脉冲串，射频脉冲串用于激发被试对象的磁化矢量；
信号获取模块，用于从多个磁共振图像中提取每个体素的演变信号；其中，演变信号用于表征每个体素在多个磁共振图像中信号强度的变化；
参数确定模块，用于根据预设的字典中与每个体素的演变信号最匹配的模拟信号，确定每个体素所代表组织的横向弛豫时间；其中，字典包括对MRF脉冲序列进行信号模拟演变生成的多个模拟信号，以及与每个模拟信号一一对应的横向弛豫时间。
第三方面，本申请实施例提供了一种定量磁共振成像参数确定设备，包括存储器、处理器以及存储在存储器中并可在处理器上运行的计算机程序，处理器执行计算机程序时实现上述第一方面任一项方法的步骤。
第四方面，本申请实施例提供了一种计算机可读存储介质，计算机可读存储介质存储有计算机程序，计算机程序被处理器执行时实现上述第一方面任一项方法的步骤。
第五方面，本申请实施例提供了一种计算机程序产品，当计算机程序产品在终端设备上运行时，使得终端设备执行上述第一方面中任一项的方法。
本申请实施例提供的定量磁共振成像参数确定方法，基于预设的MRF脉冲序列获取被试对象的多个磁共振图像；从多个磁共振图像中提取每个体素的演变信号，根据预设的字典中与每个体素的演变信号匹配的模拟信号，确定每个体素所代表组织的横向弛豫时间，实现了磁共振成像中横向弛豫时间的定量。与现有技术中的MRF脉冲序列相比，本申请实施例中的MRF序列包括顺序激发的多个射频脉冲串，在MRF序列被执行以进行磁共振成像过程中，每个射频脉冲串中的射频脉冲使得被试对象的体内组织的氢核翻转产生横向磁化矢量，并在射频脉冲串的持续时间内，对横向磁化矢量进行再次激发，实现了T2驰豫的加权，因此本申请实施例提供的定量磁共振成像参数确定方法，提高了横向弛豫时间检测的灵敏度，可获得准确的横向弛豫时间。
 有益效果
可以理解的是，上述第二方面至第五方面的有益效果可以参见上述第一方面中的相关描述，在此不再赘述。
 附图说明
为了更清楚地说明本申请实施例中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1是本申请一实施例提供的定量磁共振成像系统的架构示意图；
图2是本申请一实施例提供的定量磁共振成像参数确定方法的流程示意图；
图3是本申请一实施例提供的射频脉冲串的示意图；
图4是本申请一实施例提供的单个体素的演变信号；
图5是本申请一实施例提供的确定体素横向弛豫时间的流程示意图；
图6是本申请另一实施例提供的脉冲序列的示意图；
图7是本申请一实施例提供的伪随机变化的翻转角和重复时间示意图；
图8是本申请一实施例提供的字典示意图；
图9是本申请一实施例提供的定量磁共振成像参数确定装置的组成示意图；
图10是本申请一实施例提供的定量磁共振成像参数确定设备的结构示意图。
 本发明的最佳实施方式
以下描述中，为了说明而不是为了限定，提出了诸如特定系统结构、技术之类的具体细节，以便透彻理解本申请实施例。然而，本领域的技术人员应当清楚，在没有这些具体细节的其它实施例中也可以实现本申请。在其它情况中，省略对众所周知的系统、装置、电路以及方法的详细说明，以免不必要的细节妨碍本申请的描述。
应当理解，当在本申请说明书和所附权利要求书中使用时，术语“包括”指示所描述特征、整体、步骤、操作、元素和/或组件的存在，但并不排除一个或多个其它特征、整体、步骤、操作、元素、组件和/或其集合的存在或添加。
另外，在本申请说明书和所附权利要求书的描述中，术语“第一”、“第二”等仅用于区分描述，而不能理解为指示或暗示相对重要性。
首先，对本申请中的涉及到的概念进行解释如下：
磁共振成像（Magnetic Resonance Imaging ，MRI）基本原理为：组织的氢原子自旋运动产生磁矩。在强均匀的主磁场作用下，原本无规律排列的氢原子自旋磁矩会沿主磁场方向排列，形成宏观磁化矢量（包括纵向磁化矢量和横向磁化矢量）。在射频脉冲激励下，宏观磁化矢量将翻转到与主磁场垂直的方向，氢原子进动旋转中磁化矢量切割射频线圈，产生电磁感应信号，经过数据重建形成磁共振图像。
磁共振指纹成像（Magnetic Resonance Fingerprinting，MRF）：是一种快速、可同时获得多个组织属性参数的定量磁共振成像方法。
脉冲序列（Pulse Sequence）是指射频脉冲、空间编码、回波采样在一定时序上的组合。
重复时间（ Repetition Time，TR）指脉冲序列中两次相邻激发脉冲之间的时间间隔。
回波时间（Echedelay Time，TE）指激发脉冲激发后到采集回波信号之间的时间。
弛豫：在激发脉冲的激发下，被试对象内的质子吸收能量处于激发状态；激发脉冲终止后，处于激发状态的质子恢复到其原始状态的过程称为弛豫。
T1：纵向弛豫时间，纵向磁化矢量从零恢复至总信号强度的三分之二所需的时间。
T2：横向弛豫时间，横向磁化矢量从百分百衰减至三分之一所需的时间。
翻转角（Flip Angle, FA）：激发脉冲使磁化矢量沿主磁场方向偏离的角度。FA为90°时，磁化矢量垂直于主磁场方向，翻转至横向平面。
定量磁共振成像参数确定是指确定被试对象的组织属性参数的值，其中被试对象的组织属性参数包括T1、T2、质子密度等。定量组织属性参数在绝对意义上可以帮助医生更好地区分健康组织和病理组织，也便于医生在后续研究中更客观地比较不同的检查。目前应用最广泛的组织属性参数包括T1和T2。
磁共振指纹成像（以下简称MRF）是一种快速定量磁共振成像参数确定方法。相比于传统的T1、T2定量方法，MRF可以同时获得多个组织属性参数的参数值。MRF主要包括以下步骤：在脉冲序列的每一次激发中采用不同的TR和FA进行被试对象感兴趣区域的数据采集；然后根据脉冲序列的参数，基于经典的一阶梯布洛赫模型生成字典，其中，字典中包括多个模拟时间信号和各个模拟时间信号对应的组织属性参数值；最后将采集到的数据重建后，获取单个体素的随时间变化的演变信号（也即“指纹”）；将每个体素的演变信号与字典中包含的模拟时间信号进行一一比较，从字典中查找获得各体素的最佳匹配模拟时间信号，将最佳匹配模拟时间信号对应的组织属性参数值作为体素的组织属性参数值。由于被试对象不同组织类型的组织属性参数不同，基于相同的脉冲序列可以获得的不同组织类型的不同演变信号，重复上述过程可获得被试对象不同组织类型（所有体素）的组织属性参数值。
图1为本申请一实施例提供的定量磁共振成像系统的架构示意图，如图1所示，定量磁共振成像系统包括磁共振设备10和图像重建设备20。
其中磁共振设备10 用于执行用户输入的扫描指令并获取磁共振数据，磁共振设备10包括显示器、一个或多个输入设备以及处理器。显示器提供用户输入界面，用于接收用户输入的扫描指令，该扫描指令用于生成脉冲序列。
磁共振设备10可以通过通信系统与图像重建设备20连接，用于将用户输入的处理指令以及磁共振数据发送至图像重建设备20，通信系统包括有线或无线的网络连接。
图像重建设备20为服务器，其接收磁共振设备10发送的磁共振数据和处理指令，并根据处理指令来处理磁共振数据，以生成重建的磁共振图像，并根据该磁共振图像确定组织属性参数的定量值。处理指令包括磁共振数据的傅里叶变换、图像重建、模式匹配以及字典生成等。
图像重建设备20也可以包括显示器、一个或多个输入设备，用于接收用户输入的扫描指令或处理指令。
定量磁共振成像参数确定系统还可以包括一个或多个联网用户终端，例如，移动手机、智能计算机等。联网用户终端可以通过通信系统与磁共振设备10连接，以实现磁共振设备10的远程访问和控制。
实际应用中，磁共振设备10接收用户输入的扫描指令，并生成相应的脉冲信号，具体包括产生用于执行规定扫描的梯度波形以及用于控制射频发生器产生期望的频率、相位和脉冲振幅波形的射频脉冲。
当时激发脉冲终止后，磁共振设备10采集获得磁共振数据并将该磁共振数据发送图像重建设备20,图像重建设备20执行磁共振指纹成像（MRF）中的图像重建以及模式匹配工作，确定组织属性参数的定量值。
为使本发明实施例的目的、技术方案和优点更加清楚，下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行示例性地描述，显然，所描述的实施例是本发明一部分实施例，而不是全部的实施例。基于下文中列举的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。
图2为本申请一实施例提供的定量磁共振成像参数确定方法的流程示意图，主要涉及在MRF中如何准确定量T2的过程。如图1所示，该定量磁共振成像参数确定方法包括：
S201、基于预设的MRF脉冲序列获取被试对象的多个磁共振图像；其中，MRF脉冲序列包括顺序激发的多个射频脉冲串，射频脉冲串用于激发被试对象的磁化矢量。
被试对象包括多个不同组织类型，基于相同的脉冲序列扫描被试对象，不同组织类型可以获得不同演变信号。示例性的，被试对象可以包括仿体、活体（动物或人体），离体器官或组织等。
其中，不同组织类型的共振特性不同。示例性的，组织类型可以包括水、脂肪、骨头、肌肉、血液等。
MRF脉冲序列为基于MRF框架生成的脉冲序列。不同于常规的磁共振成像，MRF框架采用一系列变化的序列块来生成目标的脉冲序列，这些序列块产生射频脉冲顺序激发并施加到不同组织类型中以产生不同的信号演变。
在本实施例中，MRF脉冲序列包括顺序激发的多个射频脉冲串，多个射频脉冲串用于激发被试对象的磁化矢量以进行T2磁化准备。
其中，T2磁化准备是指对被试对象的氢核进行横向磁化准备，以提高T2检测的灵敏度。由于T2用于表征横向磁化矢量的衰减特性，该磁化准备可以为对横向磁化矢量进行多次聚焦，以对被试对象的横向弛豫特异性进行多次编码。
其中，横向磁化矢量为被试对象的多个氢核的磁矩在横向平面的宏观表现。当被试对象进入主磁场后，被试对象的多个氢核的磁矩绕着主磁场的方向章动。每个磁矩都是矢量，所有磁矩的矢量和即为磁化矢量。磁化矢量包括纵向磁化矢量和横向磁化矢量。在没有激励脉冲的情况下，磁化矢量的方向是平行于主磁场的，平行于主磁场方向的磁化矢量为纵向磁化矢量，而垂直于磁场方向的磁化矢量为横向磁化矢量。
在本实施例中，每个射频脉冲串包括顺序激发的激励脉冲、180°翻转脉冲以及90°翻转脉冲，其中激励脉冲用于将磁化矢量翻转至横向平面，获得较大的横向磁化矢量；180°翻转脉冲用于将构成横向磁化矢量的所有磁矩的方向进行180°翻转；翻转脉冲用于将弛豫后的横向磁化矢量翻转回纵向平面。在射频脉冲的激励脉冲和90°翻转脉冲之间，180°翻转脉冲每激发一次，即对当前横向磁化矢量的矢量方向进行180°翻转，可以实现对横向弛豫特异性的多次编码，提高T2检测的灵敏度。其中，180°翻转脉冲可以为一个或多个。
在一种实施方式中，射频脉冲串包括顺序激发的90°激发脉冲、至少一个180°激发脉冲和-90°激发脉冲；其中，90°激发脉冲为上述的激励脉冲，180°激发脉冲为上述的180°翻转脉冲，-90°激发脉冲为上述的90°翻转脉冲。射频脉冲串中的相邻两个激发脉冲之间的间隔时间相同。其中， 180°激发脉冲可以有多个，每一个180°激发脉冲进行一次横向磁化矢量在横向平面的翻转，通过设置多个180°激发脉冲，可以对横向弛豫特异性进行多次编码。。
请一并参阅图3，图3为本实施例提供的一种射频脉冲串的示意图，如图3所示，脉冲序列包括两个射频脉冲串，每个射频脉冲串均包括顺序激发的90°激发脉冲、一个180°激发脉冲和一个-90°激发脉冲。90°激发脉冲和180°激发脉冲之间的间隔时间，与180°激发脉冲和-90°激发脉冲之间的间隔时间相同。基于该脉冲序列扫描被试对象时，90°激发脉冲直接将磁化矢量完全翻转至横向平面，获得了最大的横向磁化矢量，90激发脉冲激发完毕后，横向磁化矢量进入弛豫状态，开始衰减，直至180°激发脉冲将当前横向磁化矢量中所有磁矩的矢量方向进行180°翻转，获得翻转后横向磁化矢量，翻转后的横向磁化矢量继续衰减，直至-90°激发脉冲将衰减后的横向磁化矢量翻转回纵向平面，至此完成被试对象的T2磁化准备。
每个射频脉冲串的持续时间为磁化矢量翻转至横向平面后的停留时间，具体体现为该射频脉冲串的激励脉冲和翻转脉冲之间的间隔时间；示例性的，如图3所示，每个射频脉冲串的持续时间为90°激发脉冲和-90°激发脉冲之间的间隔时间。
每个射频脉冲串的持续时间可以不同，由于不同体素所代表的组织的T2不同，对不同体素的T2的敏感的准备时间也不同。将每个射频脉冲串的持续时间设置为对不同体素所代表的组织的T2敏感的准备时间，多个射频脉冲串的持续时间依次递增。示例性的，射频激发脉冲串包括3个，3个射频激发脉冲串的持续时间分别为5毫秒，25毫秒以及35毫秒。射频激发脉冲串的持续时间一般不超过100毫秒。
在本实施例中，视频脉冲串用于进行被试对象的T2准备，因此每个射频脉冲串之后，可以设置一个用于采样的射频脉冲，其中每个射频脉冲的翻转角均小于等于10°。实际应用中，每一个射频激发脉冲串结束后，施加一个射频脉冲，此时每个体素产生一个回波，通过一个采样窗（模数转换装置A/D）进行回波信号的采集。
本实施中，基于上述MRF脉冲序列，进行被试对象的扫描，获取被试对象的磁共振图像，具体包括S2011至S2013：
S2011、获取MRF脉冲序列的脉冲序列参数；
脉冲序列参数用于表征MRF脉冲序列的射频脉冲串、用于采样的射频脉冲在时序上的组合。同时，脉冲序列参数还包括了各脉冲的翻转角FA、重复时间TR、回波时间TE以及射频脉冲在每一次激发中的相位变化。
S2012、将脉冲序列参数发送至磁共振设备，以使磁共振设备基于脉冲序列参数生成脉冲信号，并获取被试对象的多个采样数据。
磁共振设备基于脉冲序列参数获取采样数据的方式可以基于现有技术实现，在此不再赘述。
S2013、接收多个采样数据，并对每个采样数据进行傅里叶变换，生成对应每个采样数据的被试对象的磁共振图像。
磁共振设备将采样得到的采样数据按一定的编排方式进行存放，构成采样数据空间。根据采样数据空间每一个采样点的信号强度及其所在的位置，生成磁共振图像。具体地，对于直线式采样得到的数据，其数据均匀分布网格点上，经过傅里叶逆变换就可以得到二维平面内上，根据每个体素的信号强度，将其转换为相应的灰度值，就得到磁共振图像。
S202、从多个磁共振图像中提取每个体素的演变信号；其中，演变信号用于表征每个体素在多个磁共振图像中信号强度的变化。
每个体素在不同的采样时间信号强度不同，体现到磁共振图像上体现为灰度值大小不同。从多个磁共振图像中获取每个体素点的信号强度，并按照磁共振图像的采样时间进行排序组合，即获得每个体素的演变信号。
请一并参阅图4，图4为本申请一实施例提供的单个体素的演变信号。实际应用中，预先设置采样时间点为1000，在每一个采样时间点执行该MRF脉冲序列，即得到1000张欠采样的磁共振图像。将1000张磁共振图像中每个像素点的信号强度按照时间进行组合，获得每个像素点的演变信号曲线，即各体素的演变信号。应理解的是，磁共振图像中的像素点与被试对象的体素一一对应。
S203、根据预设的字典中与每个体素的演变信号最匹配的模拟信号，确定每个体素所代表组织的横向弛豫时间；其中，字典包括对所述MRF脉冲序列进行信号模拟演变生成的多个模拟信号，以及与每个模拟信号一一对应的横向弛豫时间。
字典可以预先获得，字典包括基于上述MRF脉冲序列进行信号模拟演变生成的多个模拟信号，以及与每个模拟信号一一对应的横向弛豫时间。
信号模拟演变可以通过布洛赫模型模拟计算获得。每一个模拟信号为字典中的一个字典条目，每条字典条目对应一个T2。
示例性的，首先根据被试对象生理特性，将T2不均匀划分。例如，为了覆盖被试对象，T2的范围设置为0-500毫秒。将小于100毫秒的T2以2毫秒的梯度增加，大于100毫秒小于200毫秒的部分以5毫秒的梯度增加，大于200毫秒部分以50毫秒的梯度增加，生成多组T2。然后根据步骤S201中的MRF脉冲序列的参数集合，用布洛赫模型模拟计算获得模拟时间信号，每变换一组T2，则获得一个字典条目，直至所有组T2都进行模拟计算，生成包含多个字典条目的字典。其中，布洛赫模型表示的是质子在磁场作用下磁化矢量随弛豫时间的变化。
请一并参阅图5，图5主要涉及如何确定每个体素的T2，如图5所示，根据预设的字典中与每个体素的演变信号匹配的模拟信号，确定每个体素的横向弛豫时间，具体包括S501和S502：
S501、将每个体素的时间信号与预设的字典中所有的模拟信号进行比较，获得所述字典中与各体素的磁共振信号匹配度最高的模拟信号。
S502、针对每个体素，将与所述体素的演变信号匹配度最高的模拟信号对应的横向弛豫时间作为所述体素的横向弛豫时间。
首先，对字典中的每一个字典条目进行归一化处理。然后基于点乘操作进行比较。具体地，在获得字典以及每个体素的演变信号后，针对每个体素，将该体素的演变信号与预设字典中每一个字典条目一一进行比较，获得字典中与该体素的演变信号匹配度最高的字典条件；将该字典条目对应的T2作为体素的T2。字典的引入，使得MRF可以融入一些磁共振设备的系统参数，如主磁场的不均匀性以及射频脉冲的不均匀性的，提高了MRF的鲁棒性，使其适用于不同组织位置和不同时间段的定量磁共振成像参数确定。
本申请实施例提供的定量磁共振成像参数确定方法，基于预设的MRF脉冲序列获取被试对象的多个磁共振图像；从多个磁共振图像中提取每个体素的演变信号，根据预设的字典中与每个体素的演变信号匹配的模拟信号，确定每个体素所代表组织的横向弛豫时间，实现了磁共振成像中横向弛豫时间的定量。与现有技术中的MRF脉冲序列相比，本申请实施例中的MRF序列包括顺序激发的多个射频脉冲串，在MRF序列被执行以进行磁共振成像过程中，每个射频脉冲串中的射频脉冲使得被试对象的体内组织的氢核翻转产生横向磁化矢量，并在射频脉冲串的持续时间内，对横向磁化矢量进行再次激发，实现了T2驰豫的加权，因此本申请实施例提供的定量磁共振成像参数确定方法，提高了横向弛豫时间检测的灵敏度，可获得准确的横向弛豫时间。
MRF脉冲序列为基于MRF框架生成的脉冲序列。不同于常规的磁共振成像，MRF框架采用一系列变化的序列块来生成目标的脉冲序列，这些序列块产生射频脉冲顺序激发并施加到不同组织类型中以产生不同的信号演变。并根据该信号演变，可以同时获得多个组织属性参数的参数值。其中，组织属性参数可以包括纵向弛豫时间T1、主磁场强度B0等。
具体地，字典可以包括基于MRF脉冲序列进行信号模拟演变生成的多个模拟信号，以及与每个模拟信号一一对应的特征物理参数。其中特征物理参数除了包括横向弛豫时间之外，还可以包括纵向弛豫时间T1，主磁场强度B0,等。然后根据预设的字典中与每个体素的演变信号最匹配的模拟信号，确定每个体素所代表组织的特征物理参数。
请一并参阅图6，图6为本申请另一实施例提供的脉冲序列的示意图，如图6所示，MRF脉冲序列包括两个顺序激发的射频脉冲串、反转恢复脉冲和平衡稳态自动进动序列。
本实施例中，MRF可以包括T2准备序列块，T2准备序列块用于产生顺序激发的多个射频脉冲串，MRF还可以包括反转恢复脉冲序列块，用于产生反转恢复脉冲。MRF通过序列块的框架设计，实现了多个脉冲序列块的快速添加。
在本实施例中，MRF脉冲序列还可以包括基于反转恢复的梯度回波序列。在MRF脉冲序列每一次激发中，基于反转恢复的梯度回波序列的重复时间和翻转角均不相同。其中，基于反转恢复的梯度回波序列包括顺序激发的反转恢复脉冲和梯度回波序列脉冲，可以通过在MRF框架中添加一个反转恢复序列块和一个梯度回波采集序列块实现。反转恢复序列对T1敏感，通过设置反转恢复序列可以提高磁共振信号对T1的灵敏度，获得准确度T1值。
反转恢复脉冲（inversion recovery ，IR）包括顺序激发180°射频脉冲和90°射频脉冲。两个射频脉冲之间的间隔为反转等待时间。使用时，首先基于180°射频脉冲激发磁化矢量，然后等待一段时间（反转时间TI）后使用90°射频脉冲在此进行激发，两个射频脉冲形成回波。
示例性的，首先通过反转恢复180°脉冲激发磁化矢量，使其反转180°，之后等待第一个T1的时间，此时纵向磁化矢量将部分恢复，然后施加多个小角度射频脉冲（具有90°脉冲分量）将目前大小的纵向磁化矢量反转到横向坐标，以进行数据采集。待纵向磁化矢量完全恢复稳态之后，改变反转时间TI的值的大小重复以上操作，选择不同反转时间，可以降低化学移位伪影，获得较准确的T1值。
梯度回波序列用于进行回波采样，梯度回波序列可以为平衡稳态自由进动序列。平衡稳态自由进动序列的特征是横向磁化矢量和纵向磁化矢量均在多个射频激发之后达到稳态。由于激发的射频角度可以很小，TR可以设置的很短，因此平衡稳态自由进动序列的扫描时间相对于普通的梯度回波序列的扫描时间大大减少。
实际应用中，MRF可以通过在每个采集时间点改变脉冲序列参数获得来在空间上不相干和或时间上不相干的演变信号。能够改变的脉冲序列参数包括各脉冲的反转角FA、脉冲相位、重复时间TR、回波时间TE以及采样模式。示例性的，在本实施例中，在MRF脉冲序列的每一次激发中，平衡稳态自动进动序列的重复时间TR和翻转角FA位随机变化，以获得在空间上不相干的演变信号，即各体素的演变信号。平衡稳态自动进动序列的重复时间TR和翻转角FA位随机变化曲线可以参阅图7。
基于本实施例的MRF脉冲序列进行被试对象的扫描，获取被试对象的磁共振图像的步骤与S2011至S2013相同，仅脉冲序列参数不同。具体地，脉冲序列参数用于表征MRF脉冲序列的射频脉冲串、用于采样的射频脉冲、反转恢复脉冲以及平衡稳态自动进动脉冲在时序上的组合。同时，脉冲序列参数还包括了各脉冲的翻转角FA、重复时间TR、回波时间TE以及射频脉冲在每一次激发中的相位变化。示例性的，平衡稳态自动进动脉冲的翻转角FA和重复时间TR随时间伪随机变化。
当获取被试对象的多个磁共振图像后，从多个磁共振图像中提取被试对象的每个体素的演变信号；其中，演变信号用于表征每个体素在多个磁共振图像中信号强度的变化。然后根据预设的字典中与每个体素的演变信号匹配的模拟信号，确定每个体素的组织属性参数值；其中，字典包括对图6所示MRF脉冲序列进行信号模拟演变生成的多个模拟信号，以及与每个模拟信号一一对应的组织属性参数值。组织属性参数值包括T1和T2。
其中，字典可以通过布洛赫模型模拟预先计算获得。
示例性的，将T1的范围设置为0-5000毫秒，T2的范围设置为0-500毫秒。首先对组织参数值进行排列组合，生成多组组织参数值，其中每组组织参数包括T1和T2，且每组组织参数的T2和T1不完全相同；然后根据步骤S201中的MRF脉冲序列的参数集合，用布洛赫模型模拟计算获得模拟时间信号，每变换一组组织参数值，则获得一个字典条目，直至所有组的组织参数值都进行模拟计算，生成包含多个字典条目的字典。其中，布洛赫模型表示的是质子在磁场作用下磁化矢量随弛豫时间的变化。
请一并参阅图8，图8为本申请实施例提供的字典示意图，如图8所示，每一组组织属性参数值对应一个模拟信号。组织属性参数包括T1和T2，字典的字典条目数目由T2和T1的排列组合数确定。应理解的是，组织属性参数还可以包括质子密度等其他组织属性参数。
本实施例提供的定量磁共振成像方法中，MRF脉冲序列不仅包括用于进行激发磁化矢量的射频脉冲串，还包括基于反转恢复的梯度回波序列，在MRF脉冲序列的每一次激发中，该梯度回波序列的FA和TR伪随机变化，故可以实现被试对象的各体素的信号在空间上编码。一方面，该MRF脉冲序列通过射频脉冲串和反转恢复脉冲的设置，能够同时获得准确的T1和T2。另一方面，MRF方案中通过字典的设计，可以融入一些磁共振设备的系统参数，如主磁场的不均匀性以及射频脉冲的不均匀性等，提高了MRF的鲁棒性，使其适用于不同组织类型和不同时间段的定量磁共振成像。
应理解，上述实施例中各步骤的序号的大小并不意味着执行顺序的先后，各过程的执行顺序应以其功能和内在逻辑确定，而不应对本申请实施例的实施过程构成任何限定。
基于上述实施例所提供的定量磁共振成像参数确定，本发明实施例进一步给出实现上述方法实施例的装置实施例。
图9为本申请一实施例提供的定量磁共振成像参数确定装置的组成示意图。如图9所示，定量磁共振成像参数确定装置90包括：预成像模块901、信号获取模块902以及参数确定模块903。
预成像模块901，用于基于预设的MRF脉冲序列获取被试对象的多个磁共振图像；其中，MRF脉冲序列包括顺序激发的多个射频脉冲串，射频脉冲串用于激发被试对象的磁化矢量；
信号获取模块902，用于从多个磁共振图像中提取每个体素的演变信号；其中，演变信号用于表征每个体素在多个磁共振图像中信号强度的变化；
参数确定模块903，用于根据预设的字典中与每个体素的演变信号最匹配的模拟信号，确定每个体素所代表组织的横向弛豫时间；其中，字典包括对MRF脉冲序列进行信号模拟演变生成的多个模拟信号，以及与每个模拟信号一一对应的横向弛豫时间。
可选地，预成像模块901中，射频脉冲串包括顺序激发的90°激发脉冲、至少一个180°激发脉冲和-90°激发脉冲。
射频脉冲串中的相邻两个激发脉冲之间的间隔时间相同。
每个射频脉冲串的持续时间为磁化矢量翻转至横向平面后的停留时间，多个射频脉冲串的持续时间依次递增。
每个射频脉冲串之后跟随有一个用于采样的射频脉冲，每个射频脉冲的翻转角均小于等于10°。
MRF脉冲序列还包括基于反转恢复的梯度回波序列。
可选地，参数确定模块903，具体用于：
将每个体素的时间信号与预设的字典中所有的模拟信号进行比较，获得字典中与各体素的磁共振信号匹配度最高的模拟信号；其中，字典包括对MRF脉冲序列进行信号模拟演变生成的多个模拟信号，以及每个模拟信号与横向弛豫时间之间的对应关系。
针对每个体素，将与体素的演变信号匹配度最高的模拟信号对应的横向弛豫时间作为体素的横向弛豫时间。
本实施例提供的定量磁共振成像参数确定装置，基于预设的MRF脉冲序列获取被试对象的多个磁共振图像；从多个磁共振图像中提取每个体素的演变信号，根据预设的字典中与每个体素的演变信号匹配的模拟信号，确定每个体素所代表组织的横向弛豫时间，实现了磁共振成像中横向弛豫时间的定量。与现有技术中的MRF脉冲序列相比，本申请实施例中的MRF序列包括顺序激发的多个射频脉冲串，在MRF序列被执行以进行磁共振成像过程中，每个射频脉冲串中的射频脉冲使得被试对象的体内组织的氢核翻转产生横向磁化矢量，并在射频脉冲串的持续时间内，对横向磁化矢量进行再次激发，实现了T2驰豫的加权，因此本申请实施例提供的定量磁共振成像参数确定方法，提高了横向弛豫时间检测的灵敏度，可获得准确的横向弛豫时间。
图9所示实施例提供的定量磁共振成像参数确定装置，可用于执行上述方法实施例中的技术方案，其实现原理和技术效果类似，本实施例此处不再赘述。
所属领域的技术人员可以清楚地了解到，为了描述的方便和简洁，仅以上述各功能单元、模块的划分进行举例说明，实际应用中，可以根据需要而将上述功能分配由不同的功能单元、模块完成，即将所述装置的内部结构划分成不同的功能单元或模块，以完成以上描述的全部或者部分功能。实施例中的各功能单元、模块可以集成在一个处理单元中，也可以是各个单元单独物理存在，也可以两个或两个以上单元集成在一个单元中，上述集成的单元既可以采用硬件的形式实现，也可以采用软件功能单元的形式实现。另外，各功能单元、模块的具体名称也只是为了便于相互区分，并不用于限制本申请的保护范围。上述系统中单元、模块的具体工作过程，可以参考前述方法实施例中的对应过程，在此不再赘述。
图10是本申请一实施例提供的定量磁共振成像图像重建设备的示意图。如图10所示，该实施例的定量磁共振成像参数确定终端设备10包括：至少一个处理器1001、存储器1002以及存储在存储器1002中并可在处理器1001上运行的计算机程序。定量磁共振成像图像重建设备还包括通信部件1003，其中，处理器1001、存储器1002以及通信部件1003通过总线1004连接。
处理器1001执行计算机程序时实现上述各个定量磁共振成像参数确定方法实施例中的步骤，例如图2所示实施例中的步骤S201至步骤S203。或者，处理器1001执行所述计算机程序时实现上述各装置实施例中各模块/单元的功能，例如图9所示模块901至903的功能。
示例性的，计算机程序可以被分割成一个或多个模块/单元，一个或者多个模块/单元被存储在存储器1002中，并由处理器1001执行，以完成本申请。所述一个或多个模块/单元可以是能够完成特定功能的一系列计算机程序指令段，该指令段用于描述计算机程序在定量磁共振成像图像重建设备100中的执行过程。
在本实施例中，定量磁共振成像图像重建设备可以为云端服务器或用户终端。用户终端可以是但不限于各种能运行应用的个人计算机、笔记本电脑、智能手机等。云端服务器可以是实现单一功能的服务器，也可以是实现多种功能的服务器，具体可以是独立的物理服务器，也可以是物理服务器集群。
本领域技术人员可以理解，图12仅仅是定量磁共振成像参数确定装置设备的示例，并不构成对定量磁共振成像图像重建设备的限定，可以包括比图示更多或更少的部件，或者组合某些部件，或者不同的部件，例如输入输出设备、网络接入设备、总线等。
处理器1001可以是中央处理单元(Central Processing Unit，CPU)，还可以是其他通用处理器、数字信号处理器 (Digital Signal Processor，DSP)、专用集成电路 (Application Specific Integrated Circuit，ASIC)、现成可编程门阵列 (Field-Programmable Gate Array，FPGA) 或者其他可编程逻辑器件、分立门或者晶体管逻辑器件、分立硬件组件等。通用处理器可以是微处理器或者该处理器也可以是任何常规的处理器等。
存储器1002可以是定量磁共振成像图像重建设备的内部存储单元，也可以是定量磁共振成像图像重建设备的外部存储设备，例如插接式硬盘，智能存储卡（Smart Media Card，SMC），安全数字（Secure Digital，SD）卡，闪存卡（Flash Card）等。所述存储器1002用于存储所述计算机程序以及定量磁共振成像图像重建设备所需的其他程序和数据。所述存储器1002还可以用于暂时地存储已经输出或者将要输出的数据。
总线可以是工业标准体系结构（Industry Standard Architecture，ISA）总线、外部设备互连（Peripheral Component，PCI）总线或扩展工业标准体系结构（Extended Industry Standard Architecture，EISA）总线等。总线可以分为地址总线、数据总线、控制总线等。为便于表示，本申请附图中的总线并不限定仅有一根总线或一种类型的总线。
本申请实施例还提供了一种计算机可读存储介质，计算机可读存储介质存储有计算机程序，计算机程序被处理器执行时实现可实现上述各个方法实施例中的步骤。
本申请实施例提供了一种计算机程序产品，当计算机程序产品在定量磁共振成像参数确定设备上运行时，使得定量磁共振成像参数确定设备执行时实现可实现上述各个方法实施例中的步骤。
所述集成的单元如果以软件功能单元的形式实现并作为独立的产品销售或使用时，可以存储在一个计算机可读取存储介质中。基于这样的理解，本申请实现上述实施例方法中的全部或部分流程，可以通过计算机程序来指令相关的硬件来完成，所述的计算机程序可存储于一计算机可读存储介质中，该计算机程序在被处理器执行时，可实现上述各个方法实施例的步骤。其中，所述计算机程序包括计算机程序代码，所述计算机程序代码可以为源代码形式、对象代码形式、可执行文件或某些中间形式等。所述计算机可读介质至少可以包括：能够将计算机程序代码携带到定量磁共振成像图像重建设备的任何实体或装置、记录介质、计算机存储器、只读存储器（ROM，Read-Only Memory）、随机存取存储器（RAM，Random Access Memory）、电载波信号、电信信号以及软件分发介质。例如U盘、移动硬盘、磁碟或者光盘等。在某些司法管辖区，根据立法和专利实践，计算机可读介质不可以是电载波信号和电信信号。
在上述实施例中，对各个实施例的描述都各有侧重，某个实施例中没有详述或记载的部分，可以参见其它实施例的相关描述。
本领域普通技术人员可以意识到，结合本文中所公开的实施例描述的各示例的单元及算法步骤，能够以电子硬件、或者计算机软件和电子硬件的结合来实现。这些功能究竟以硬件还是软件方式来执行，取决于技术方案的特定应用和设计约束条件。专业技术人员可以对每个特定的应用来使用不同方法来实现所描述的功能，但是这种实现不应认为超出本申请的范围。
在本申请所提供的实施例中，应该理解到，所揭露的装置/网络设备和方法，可以通过其它的方式实现。例如，以上所描述的装置/网络设备实施例仅仅是示意性的，例如，所述模块或单元的划分，仅仅为一种逻辑功能划分，实际实现时可以有另外的划分方式，例如多个单元或组件可以结合或者可以集成到另一个系统，或一些特征可以忽略，或不执行。另一点，所显示或讨论的相互之间的耦合或直接耦合或通讯连接可以是通过一些接口，装置或单元的间接耦合或通讯连接，可以是电性，机械或其它的形式。
所述作为分离部件说明的单元可以是或者也可以不是物理上分开的，作为单元显示的部件可以是或者也可以不是物理单元，即可以位于一个地方，或者也可以分布到多个网络单元上。可以根据实际的需要选择其中的部分或者全部单元来实现本实施例方案的目的。
以上所述实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的精神和范围，均应包含在本申请的保护范围之内。

Claims (10)

  1. 一种定量磁共振成像参数确定方法，其特征在于，包括：
    基于预设的MRF脉冲序列获取被试对象的多个磁共振图像；其中，所述MRF脉冲序列包括顺序激发的多个射频脉冲串，所述射频脉冲串用于激发所述被试对象的磁化矢量；
    从所述多个磁共振图像中提取每个体素的演变信号；其中，所述演变信号用于表征每个体素在所述多个磁共振图像中信号强度的变化；
    根据预设的字典中与每个体素的演变信号最匹配的模拟信号，确定每个体素所代表组织的横向弛豫时间；其中，所述字典包括对所述MRF脉冲序列进行信号模拟演变生成的多个模拟信号，以及与每个模拟信号一一对应的横向弛豫时间。
  2. 如权利要求1所述的定量磁共振成像参数确定方法，其特征在于，所述射频脉冲串包括顺序激发的90°激发脉冲、至少一个180°激发脉冲和-90°激发脉冲。
  3. 如权利要求2所述的定量磁共振成像参数确定方法，其特征在于，所述射频脉冲串中的相邻两个激发脉冲之间的间隔时间相同。
  4. 如权利要求1所述的定量磁共振成像参数确定方法，每个所述射频脉冲串的持续时间为所述磁化矢量翻转至横向平面后的停留时间，多个所述射频脉冲串的持续时间依次递增。
  5. 如权利要求1所述的定量磁共振成像参数确定方法，其特征在于，每个射频脉冲串之后跟随有一个用于采样的射频脉冲，每个所述射频脉冲的翻转角均小于等于10°。
  6. 如权利要求1-5任一项所述的定量磁共振成像参数确定方法，其特征在于，所述根据预设的字典中与每个体素的演变信号最匹配的模拟信号，确定每个体素所代表组织的横向弛豫时间，包括：
    将每个体素的时间信号与预设的字典中所有的模拟信号进行比较，获得所述字典中与各体素的磁共振信号匹配度最高的模拟信号；
    针对每个体素，将与所述体素的演变信号匹配度最高的模拟信号对应的横向弛豫时间作为所述体素的横向弛豫时间。
  7. 如权利要求1所述的定量磁共振成像参数确定方法，其特征在于，所述MRF脉冲序列还包括基于反转恢复的梯度回波序列。
  8. 一种定量磁共振成像参数确定装置，其特征在于，包括：
    预成像模块，用于基于预设的MRF脉冲序列获取被试对象的多个磁共振图像；其中，MRF脉冲序列包括顺序激发的多个射频脉冲串，射频脉冲串用于激发被试对象的磁化矢量；
    信号获取模块，用于从多个磁共振图像中提取每个体素的演变信号；其中，演变信号用于表征每个体素在多个磁共振图像中信号强度的变化；
    参数确定模块，用于根据预设的字典中与每个体素的演变信号最匹配的模拟信号，确定每个体素所代表组织的横向弛豫时间；其中，字典包括对MRF脉冲序列进行信号模拟演变生成的多个模拟信号，以及与每个模拟信号一一对应的横向弛豫时间。
  9. 一种定量磁共振成像参数确定设备，包括存储器、处理器以及存储在所述存储器中并可在所述处理器上运行的计算机程序，其特征在于，所述处理器执行所述计算机程序时实现如权利要求1至7任一项所述方法的步骤。
  10. 一种计算机可读存储介质，所述计算机可读存储介质存储有计算机程序，其特征在于，所述计算机程序被处理器执行时实现如权利要求1至7任一项所述方法的步骤。
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