Magnetic resonance imaging method, device and storage medium

Abstract

The present invention provides a magnetic resonance imaging method, device, and storage medium. The method includes: obtaining an imaging region of an object to be imaged; invoking a spoiled gradient echo sequence for radial acquisition, and using dummy scans to make the magnetic resonance physical signals in the imaging region reach a transient steady state; continuously and cyclically performing the following first operation and second operation n*N y times. The first operation: exciting a magnetization preparation pulse and then waiting for a preset time period to achieve magnetization preparation corresponding to the magnetic resonance quantitative parameters of the magnetic resonance physical signals. The second operation: using the spoiled gradient echo sequence for radial acquisition to perform N z excitations on the imaging region; based on the property that the magnetic resonance physical signals enter a transient steady state after the second operation in the acquisition sequence, generating a magnetic resonance image of the magnetic resonance quantitative parameters according to the sampled magnetic resonance physical signals. Thus, the time efficiency of magnetic resonance imaging is improved while ensuring the accuracy and precision of the magnetic resonance image.

Description

Technical Field

[0001] The present invention relates to the field of medical imaging, and more specifically to a magnetic resonance imaging method, device and storage medium. Background Art

[0002] Magnetic resonance imaging technology uses the phenomenon of nuclear magnetic resonance to image the human body and has become a common medical imaging examination method. This technology provides an important reference for the diagnosis of diseases and is often used to detect parts of the body such as the brain, heart, liver and joint cartilage.

[0003] Quantitative magnetic resonance imaging technology developed in recent years directly measures the basic physical parameters of magnetic resonance to achieve quantitative tissue evaluation. Magnetic resonance quantitative parameters include T1 (spin lattice relaxation time, also known as longitudinal relaxation time), T2 (spin-spin relaxation time, also known as transverse relaxation time) and ADC (apparent diffusion coefficient). The first two are time constants that describe the recovery of the longitudinal magnetization vector and the attenuation of the transverse magnetization vector. The latter is a parameter used to describe the diffusion speed and range of different water molecules in magnetic resonance diffusion-weighted imaging. Magnetic resonance quantitative parameters are determined by the composition of biological tissues, the existing structural form and the magnetic field strength. Under a certain magnetic field strength, different tissues have specific physical parameter values. When biological tissues change, the physical parameter values ​​will also change accordingly. Therefore, these physical parameter values ​​can be used as characteristic parameters to identify the characteristics of biological tissues.

[0004] The current magnetic resonance imaging technology has a long imaging time. "Liu, JV, Bock, NA and Silva, AC, 2011. Rapid high-resolution three-dimensional mapping of T1 and age-dependent variations in the non-human primate brain using magnetization-prepared rapid gradient-echo (MPRAGE) sequence. Neuroimage, 56 (3), pp. 1154-1163." discloses a technology for T1 imaging based on a 3TI-MPRAGE sequence structure of a sequence framework of a rapid gradient echo sequence (MPRAGE). Taking this technology as an example, in the current sequence, after the sampling of the magnetic resonance physical signal is completed, a certain waiting time (or delay time) is required before the next sequence can be started. In this way, it is ensured that the sum of the inversion time and the waiting time in the T1 magnetization preparation module in each sequence is the same. Due to the existence of the waiting time, this method requires a long imaging time.

[0005] To solve the above problems, a new magnetic resonance imaging method is needed to improve the imaging speed. Summary of the invention

[0006] The present invention has been made in view of the above-mentioned problems.

[0007] According to one aspect of the present invention, there is provided a magnetic resonance imaging method, comprising:

[0008] Acquire a to-be-imaged area of ​​the to-be-imaged object;

[0009] The spoiled gradient echo sequence of radial acquisition is called, and the magnetic resonance physical signal of the area to be imaged is made to reach a temporary steady state by using an empty scan;

[0010] Loop the following first and second operations n*N continuously y Second-rate,

[0011] The first operation is to excite a magnetization preparation pulse and then wait for a preset period of time to achieve magnetization preparation corresponding to the magnetic resonance quantitative parameters of the magnetic resonance physical signal.

[0012] The second operation is to use the radially acquired spoiled gradient echo sequence to perform N z times of excitation, where N z The first N times of stimulation z1 times of excitation, and N consecutive z1 Sampling of magnetic resonance physical signals;

[0013] The first operation and the second operation are performed in each cycle N y times, change the duration of the preset time period, n is an integer greater than or equal to 3, N y Indicates the number of Y-direction phase encodings in the layer, N z1 Indicates the number of inter-layer Z-direction phase encodings, N z is an integer greater than or equal to the number threshold;

[0014] Based on the property that the magnetic resonance physical signal enters a transient steady state after the second operation in the acquisition sequence, a magnetic resonance image of magnetic resonance quantitative parameters is generated according to the sampled magnetic resonance physical signal.

[0015] For example, N z1 =N z .

[0016] For example, in the second operation, the first N z1 After the first excitation, the radially acquired spoiled gradient echo sequence is called, and the magnetic resonance physical signal is brought into a transient steady state by using an empty scan.

[0017] Exemplarily, the magnetic resonance quantitative parameter is the longitudinal relaxation time,

[0018] Based on the property that the magnetic resonance physical signal enters a transient steady state after the second operation in the acquisition sequence, a magnetic resonance image of a magnetic resonance quantitative parameter is generated according to the sampled magnetic resonance physical signal, including:

[0019] Parameter fitting is performed based on the following formula to generate magnetic resonance images:

[0020]

[0021] Among them, S(TI n ) indicates that the duration of the preset time periods are TI1, TI2…TI n , T1 represents the longitudinal relaxation time, and a and b represent the fitting parameters.

[0022] Exemplarily, based on the property that the magnetic resonance physical signal enters a transient steady state after the second operation in the acquisition sequence, generating a magnetic resonance image of the magnetic resonance quantitative parameter according to the sampled magnetic resonance physical signal includes:

[0023] Based on the property that the magnetic resonance physical signal enters a transient steady state after the second operation in the acquisition sequence, determining a magnetic resonance quantitative parameter according to the sampled magnetic resonance physical signal;

[0024] The magnetic resonance quantitative parameters are corrected to generate magnetic resonance images.

[0025] Exemplarily, correcting the magnetic resonance quantitative parameters to generate a magnetic resonance image includes:

[0026] When the magnetic resonance quantitative parameter is lower than the first parameter threshold or higher than the second parameter threshold, the magnetic resonance quantitative parameter is set to 0, wherein the second parameter threshold is greater than the first parameter threshold.

[0027] Exemplarily, the magnetic resonance quantitative parameter is the longitudinal relaxation time, the transverse relaxation time or the apparent diffusion coefficient.

[0028] Exemplarily, the k-space filling mode of the radially acquired spoiled gradient echo sequence is any one of the following modes: radial Cartesian sampling, radial radial sampling, and radial spiral sampling.

[0029] According to another aspect of the present invention, there is also provided a magnetic resonance imaging device, comprising a processor and a memory, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, they are used to execute the magnetic resonance imaging method as described above.

[0030] According to yet another aspect of the present invention, a storage medium is provided, on which program instructions are stored, and the program instructions are used to execute the magnetic resonance imaging method as described above when running.

[0031] In the above technical solution, after the second operation of each acquisition sequence is completed, the magnetic resonance physical signal enters a transient steady state, thereby directly entering the next acquisition sequence without waiting time. Therefore, while ensuring the accuracy and precision of the magnetic resonance image, the time efficiency of the magnetic resonance imaging is improved.

[0032] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and other purposes, features and advantages of the present invention will become more apparent by describing the embodiments of the present invention in more detail in conjunction with the accompanying drawings. The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings, the same reference numerals generally represent the same signals or pulses, etc.

[0034] Figure 1 A schematic flow chart of a magnetic resonance imaging method according to an embodiment of the present invention is shown;

[0035] Figure 2 A structural diagram of a T1 quantitative magnetic resonance sequence according to an embodiment of the present invention is shown;

[0036] Figure 3 A schematic flow chart of generating a magnetic resonance image of magnetic resonance quantitative parameters according to sampled magnetic resonance physical signals according to an embodiment of the present invention is shown;

[0037] Figure 4 A comparison diagram of IRSE, 3TI-MPRAGE and phantom experimental results of imaging sequences according to an embodiment of the present invention is shown;

[0038] Figure 5 A histogram comparison diagram of IRSE, 3TI-MPRAGE and the imaging sequence of the embodiment of the present invention is shown;

[0039] Figure 6 The T1 magnetic resonance quantitative images of two human brain tissues of the imaging sequence of the above embodiment of the present invention are shown;

[0040] Figure 7 A schematic block diagram of a magnetic resonance imaging device according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the present invention more obvious, the exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments of the present invention, and it should be understood that the present invention is not limited to the exemplary embodiments described herein. Based on the embodiments of the present invention described in the present invention, all other embodiments obtained by those skilled in the art without creative work should fall within the protection scope of the present invention.

[0042] In order to improve the speed of magnetic resonance imaging, an embodiment of the present invention provides a magnetic resonance imaging method for generating magnetic resonance images of magnetic resonance quantitative parameters. The magnetic resonance imaging method uses the transient steady-state signal of the radially collected spoiled gradient echo sequence as a reference point, and completes different quantitative parameter imaging through the cooperation between the magnetization preparation module and the signal sampling module. The magnetic resonance quantitative parameters can be: longitudinal relaxation time, transverse relaxation time or apparent diffusion coefficient. The longitudinal relaxation time indicates the time required for the longitudinal magnetization vector to recover to 63% of the original magnetization vector in the normal polarization state. The transverse relaxation time indicates the time required when the magnetic resonance physical signal decays to 36.8% of the original signal. The apparent diffusion coefficient indicates that in the magnetic resonance imaging that uses the change of the diffusion coefficient of water molecules in the imaging plane to generate image contrast, it reflects the diffusion effect of tissue in a certain direction at a certain moment. Through different cooperation between the magnetization preparation module and the signal sampling module, the imaging of the above-mentioned different magnetic resonance quantitative parameters can be achieved.

[0043] Figure 1 FIG. 1 is a schematic flow chart of a magnetic resonance imaging method 100 according to an embodiment of the present invention. It is understood that the magnetic resonance imaging method 100 can be used for various magnetic resonance quantitative parameters. However, for the convenience of description, the magnetic resonance quantitative parameter is described as the longitudinal relaxation time T1. Figure 1 As shown, the magnetic resonance imaging method 100 includes the following steps.

[0044] Step S110, obtaining the to-be-imaged area of ​​the to-be-imaged object.

[0045] Exemplarily, the area to be imaged may be gray matter or white matter in the brain, cartilage in joints, and other human tissues. On the magnetic resonance operating table, the user can locate the imaging area of ​​the object to be imaged through the magnetic resonance imaging operating software, thereby determining the area to be imaged. Optionally, the environmental parameters may also be corrected, wherein the operations for correcting the environmental parameters include but are not limited to radio frequency power correction, field shimming, and tuning.

[0046] After acquiring the imaging area of ​​the object to be imaged, the compiled imaging sequence can be imported. The imaging sequence parameters are set according to the different tissues to which the imaging area belongs. The imaging sequence parameters may include the field of view, resolution, waiting time period for magnetization preparation, etc. Then, the imaging sequence is executed to complete the data sampling. Figure 2 FIG. 1 shows a structure diagram of a T1 quantitative magnetic resonance sequence according to an embodiment of the present invention. Figure 2 The following description is given.

[0047] Step S120, calling the spoiled gradient echo sequence acquired in radial direction, and using empty scanning to make the magnetic resonance physical signal of the area to be imaged reach a temporary steady state.

[0048] Specifically, the radially acquired spoiled gradient echo sequence may include a radio frequency pulse sequence RF, a layer selection direction phase encoding gradient sequence G s , the phase encoding gradient sequence G in the slice direction p , read direction frequency encoding timing G r . Figure 2 The steady-state preparation module 1 shown is used to implement the step S120, wherein the four time sequences mentioned above correspond from top to bottom. In this step, a certain number of empty scans are used to make the magnetic resonance physical signal of the area to be imaged reach the signal transient steady state of the pre-scan. During the empty scan, although the spoiled gradient echo sequence is called, the magnetic resonance physical signal is not collected, only to make the magnetic resonance physical signal reach the transient steady state.

[0049] Step S130, continuously and cyclically execute the following first operation and second operation n*N y times, n is an integer greater than or equal to 3, N y Indicates the number of Y-direction phase encodings in the plane. In the first operation, a magnetization preparation pulse is excited and then a preset time period is waited to achieve magnetization preparation corresponding to the magnetic resonance quantitative parameters of the magnetic resonance physical signal. In the second operation, a radially acquired spoiled gradient echo sequence is used to perform N z times of excitation, where N z The first N times of stimulation z1 times of excitation, and N consecutive z1 The sampling of magnetic resonance physical signals. z1 Indicates the number of inter-layer Z-direction phase encodings, N z is an integer greater than or equal to the number threshold. The first operation and the second operation are performed N times per cycle y times, change the duration of the preset time period.

[0050] For example, Figure 2The T1 magnetization preparation module shown is used to perform the first operation described in the above step S130. After the magnetic resonance physical signal of the imaging area reaches the signal transient state of the pre-scan, first, the magnetic resonance physical signal is excited by an excitation pulse, for example, a spatially non-selectable adiabatic excitation pulse is used to achieve a T1 magnetization preparation effect with a reversal angle of 180 degrees. Then wait for a preset time period (which can be referred to as the reversal time), and use the spoiler gradient applied to each axis to reduce the residual of the magnetic resonance physical signal on the XY plane. Thus, the magnetic resonance quantitative parameter weighting is performed on the magnetic resonance physical signal that has reached the transient state, and the magnetization preparation is completed.

[0051] In the second operation, the region to be imaged is subjected to N z N times incentive. z is greater than or equal to the number threshold, thereby ensuring that the magnetic resonance physical signal is within N z After N times of stimulation, the image can return to the transient state. The number threshold can be set based on experience for the area to be imaged. For example, for the brain area, the number threshold can be 128. z The first N times of stimulation z1 times of excitation, and N consecutive z1 The sampling of magnetic resonance physical signals. z1 It indicates the number of inter-layer Z-direction phase encodings. It can be understood that N z1 Less than or equal to N z .

[0052] The following describes in detail the above-mentioned first N z1 The sub-excitation process is the signal sampling process. Figure 2 The signal acquisition module shown is used to perform the signal sampling part of the second operation in the above step S130. After the magnetization preparation is completed in the first operation, the signal acquisition module executes a spoiled gradient echo sequence for radial acquisition, excites the magnetic resonance physical signal and performs continuous radial k-space signal acquisition. Specifically, k-space represents the space filled with the original data of the magnetic resonance physical signal with spatial positioning encoding information. In the phase axis direction of the layer, the sampling of the magnetic resonance physical signal can be accelerated based on technologies such as parallel imaging technology or compressed sensing technology. Each time the T1 magnetization preparation module is started, an inversion cycle begins. During each radial k-space sampling process, the gradient encoding in the layer direction of each k-line will be updated, and the gradient encoding within the layer will remain consistent until the next inversion cycle begins.

[0053] Exemplarily, the k-space filling mode of the radially acquired spoiled gradient echo sequence is any one of the following: radial sampling modes such as radial Cartesian sampling, radial radial sampling, and radial spiral sampling. Selecting the filling mode of radial Cartesian sampling, radial radial sampling, or radial spiral sampling for k-space filling can significantly improve the quantitative contrast of the signal, thereby ensuring the accuracy of magnetic resonance quantitative imaging.

[0054] In step S130, the first operation and the second operation are executed in a continuous cycle, that is, after the second operation, there is no waiting time, and the first operation of the next inversion cycle is directly executed. In other words, there is no time interval between each inversion cycle, and each inversion cycle is continuous. The first operation and the second operation are executed N times per cycle. y times, that is, every time N y The duration of the preset time period of the T1 magnetization preparation module is changed at least twice, thereby obtaining magnetic resonance physical signals sampled under the conditions of at least three different preset time periods.

[0055] Step S140 , based on the property that the magnetic resonance physical signal enters a transient steady state after the second operation in the acquisition sequence, a magnetic resonance image of magnetic resonance quantitative parameters is generated according to the sampled magnetic resonance physical signal.

[0056] After each acquisition sequence completes signal acquisition, the magnetic resonance physical signal reaches a transient steady state. Using this property, parameter fitting can be performed to generate a magnetic resonance image of magnetic resonance quantitative parameters, such as a T1 image, based on the sampled magnetic resonance physical signal.

[0057] In the above technical solution, after the second operation of each acquisition sequence is completed, the magnetic resonance physical signal enters a transient steady state, thereby directly entering the next acquisition sequence without waiting time. Therefore, while ensuring the accuracy and precision of the magnetic resonance image, the time efficiency of the magnetic resonance imaging is improved.

[0058] Those skilled in the art will appreciate that, although the above description is based on the longitudinal relaxation time, imaging of other magnetic resonance quantitative parameters may be achieved through different coordination between the magnetization preparation module and the signal sampling module.

[0059] As mentioned above, in the second operation described in step S130, N z1 Can be equal to N z For N z1 Equal to N z In the case of , sampling of the magnetic resonance physical signal is performed in each excitation of the second operation.

[0060] Therefore, when N z1 =N z When Nz1 After the signal acquisition is completed, it will directly enter the next cycle, which improves the magnetic resonance imaging rate.

[0061] Alternatively, N z1 Can be less than N z In the second operation described in step S130, the first N z1 After the first excitation, the magnetic resonance physical signal may not have reached a transient steady state, so the radial acquisition spoiled gradient echo sequence is continued to be called, and the current magnetic resonance physical signal is brought into a transient steady state by using an empty scan. z -N z1 ) No sampling of magnetic resonance physical signals is performed in the second excitation. This process can be used Figure 2 The steady-state preparation module 2 shown in is implemented.

[0062] Therefore, in N z1 After completing signal acquisition under the excitation, perform an empty scan until reaching N z The second excitation ensures that the magnetic resonance physical signal can enter a transient steady state after the second operation in the current acquisition sequence, which ensures better accuracy of magnetic resonance imaging.

[0063] Exemplarily, the magnetic resonance quantitative parameter is the longitudinal relaxation time T1. The above step S140 generates a magnetic resonance image of the magnetic resonance quantitative parameter according to the sampled magnetic resonance physical signal based on the property that the magnetic resonance physical signal enters a transient steady state after the second operation in the acquisition sequence, including: performing parameter fitting based on the following formula to generate a magnetic resonance image Among them, S(TI n ) indicates that the duration of the preset time periods are TI1, TI2…TI n , T1 represents the longitudinal relaxation time, and a and b represent the fitting parameters.

[0064] Specifically, in each repetition time (TR) of the signal acquisition module, the longitudinal magnetization vector M of the i-th excitation i , and the previous M i-1 Related, it can be expressed as:

[0065]

[0066] Among them, θ represents the flip angle of the set magnetic resonance excitation, M0 represents the steady-state magnetization vector under the normal polarization state, and T1 represents the longitudinal relaxation time of the imaging area under the current magnetic field. It can be understood that the value range of i is [1,N z ], where N z Indicates the total number of excitations in the second operation.

[0067] By iterating based on formula (1), the longitudinal magnetization vector M after each excitation pulse is i The evolution of can be expressed as:

[0068]

[0069] Among them, M z0 represents the longitudinal magnetization vector before the first data acquisition.

[0070] For the T1 magnetization preparation module of the next cycle, after the inversion pulse with efficiency α, the longitudinal magnetization vector M in the next cycle z1 Undergoing free relaxation in the absence of any RF excitation:

[0071]

[0072] Where TI represents the inversion time after the inversion pulse excitation, n represents the total number of samples after an inversion cycle, and can also represent the number of phase encodings in the Z direction, n = N z .

[0073] Let i=n in formula (2), and substitute formula (2) into formula (3), and then simplify the formula to obtain:

[0074]

[0075] In the case of a transient steady state, the longitudinal magnetization vector M z1 In the current cycle with M z0 The same, thus obtaining the following simultaneous formula:

[0076]

[0077] Further simplifying formula (5) yields:

[0078]

[0079] Among them, M ss represents the longitudinal magnetization vector of the magnetic resonance physical signal of the transient steady state under the current sequence, where,

[0080]

[0081] According to an embodiment of the present invention, a radially acquired spoiled gradient echo sequence is used to perform radial sampling of magnetic resonance physical signals. The sampled magnetic resonance physical signals can be expressed as:

[0082]

[0083] Where S represents the voxel value of the T1-weighted image sampled at the current inversion time. represents the transverse relaxation time.

[0084] Substituting the above formula (6) into formula (8), we can obtain the expression for estimating T1 relaxation time:

[0085]

[0086] Among them, S(TI j ) indicates that the duration of the reversal time (preset time period) is TI1, TI2…TI n The magnetic resonance physical signal sampled under the condition of , the value interval of j is [1,n], T1 represents the longitudinal relaxation time, and a and b represent the fitting parameters.

[0087] In formula (9),

[0088] Based on the above derivation, it can be known that the T1 values ​​at different inversion times can be obtained based on the fitting formula (9) to generate a quantitative magnetic resonance image of T1. The T1 quantitative fitting based on the above formula (9) is not affected by the uniformity of the radio frequency field and does not rely on perfect phase spoiling technology. The accuracy of T1 quantification is greatly improved.

[0089] As described above, in the above step S140, based on the property that the magnetic resonance physical signal enters a transient steady state after the second operation in the acquisition sequence, a magnetic resonance image of magnetic resonance quantitative parameters is generated according to the sampled magnetic resonance physical signal. This step S140 may include the following sub-steps. Figure 3 A schematic flow chart of generating a magnetic resonance image of magnetic resonance quantitative parameters according to sampled magnetic resonance physical signals according to an embodiment of the present invention is shown.

[0090] Step S141 : determining a magnetic resonance quantitative parameter according to the sampled magnetic resonance physical signal based on the property that the magnetic resonance physical signal enters a transient steady state after the second operation in the acquisition sequence.

[0091] For example, during the signal acquisition process of each acquisition sequence, the acquired magnetic resonance physical signals have reached a transient steady state, and this feature is used to determine the magnetic resonance quantitative parameters according to the magnetic resonance physical signals during the sampling process. This process has been explained in the above description, and for the sake of brevity, it will not be repeated here.

[0092] Step S142: calibrate the magnetic resonance quantitative parameters to generate a magnetic resonance image.

[0093] Due to various factors such as sampling noise, the magnetic resonance quantitative parameters determined in step S141 may be inaccurate. For this reason, the magnetic resonance quantitative parameters obtained in the above step S141 are corrected. According to the corrected magnetic resonance quantitative parameters, a corresponding color mapping is established, for example, a corresponding color table of the corresponding relationship between the T1 value range corresponding to the tissue in the imaging area and the color assigned to the value range. Finally, different colors of the displayed color image are used to represent different magnetic resonance quantitative parameters of the tissue, thereby generating a magnetic resonance image.

[0094] Therefore, by correcting the magnetic resonance quantitative parameters, a magnetic resonance image with higher accuracy can be obtained.

[0095] Exemplarily, step S142, correcting the magnetic resonance quantitative parameter to generate a magnetic resonance image, includes: when the magnetic resonance quantitative parameter is lower than a first parameter threshold or higher than a second parameter threshold, setting the magnetic resonance quantitative parameter to 0. The second parameter threshold is greater than the first parameter threshold. The first parameter threshold and the second parameter threshold can be the lower limit and upper limit of the magnetic resonance quantitative parameter of the area to be imaged, respectively, which are set based on experience. If the magnetic resonance quantitative parameter is lower than the set first parameter threshold or higher than the second parameter threshold, the magnetic resonance quantitative parameter can be considered as noise and thus discarded.

[0096] Therefore, the above solution removes the noise in the magnetic resonance quantitative parameters in a simple and easy-to-implement manner. The magnetic resonance image generated based on the corrected magnetic resonance quantitative parameters is more accurate.

[0097] In a specific embodiment according to the present invention, magnetic resonance imaging is performed for T1.

[0098] First, the phantoms used in the experiment were prepared. Four cylindrical phantoms were used for the phantom T1 quantification experiment, with a diameter of 5 cm and a height of 15 cm. Each water-containing phantom was doped with gadolinium chloride at a concentration of [18, 30, 48, 72] μmol / kg and agarose at a concentration of [0.6, 1.0, 1.2, 1.6]%.

[0099] Then, the sequence parameters of the inversion recovery spin echo sequence (IRSE) are set. IRSE does not have high requirements on the performance of each system, and the measurement data is accurate and robust. It is the gold standard in magnetic resonance T1 quantification. However, the IRSE scanning time is too long to be used for clinical diagnosis. The two-dimensional IRSE method was implemented using non-selective inversion pulses to serve as a reference standard for the T1 values ​​of the phantom. The two-dimensional IRSE parameters are: TR / TE=1550 / 10ms, slice thickness=4mm, TI=[3053010301530]ms, bandwidth=20kHz, field of view=280*280mm 2, matrix = 220*220. The total IRSE scanning time for a single layer is 23.5 minutes.

[0100] Furthermore, the parameters required for the imaging sequence according to the embodiment of the present invention are set. The experimental parameters include: TR / TE=5.8 / 2.5ms, TI=[66861506]ms, bandwidth=10kHz, field of view=280*280*360mm 3 , matrix = 220*220*128. 1.8 times GRAPPA parallel imaging acceleration is used in the phase encoding direction in the 2D plane to reduce the scanning time. In this embodiment, the total scanning time is 9.1 minutes.

[0101] In addition, the sequence parameters of 3TI-MPRAGE based on the fast echo sequence were set. The sequence parameters of 3TI-MPRAGE were: TR / TE = 5.8 / 2.5 ms, TI = [6346756] ms, TD = [7504100] ms, bandwidth = 10 kHz, field of view = 280*280*360 mm 3 , matrix = 220*220*128. In the 2D in-plane phase encoding direction, 1.8 times GRAPPA parallel imaging acceleration was used to reduce the scanning time. The total scanning time of this method was also 9.1 minutes.

[0102] Then, three groups of sequences are run separately for data sampling.

[0103] Finally, the sampled magnetic resonance physical signals are used to generate T1 mapping comparison images.

[0104] Figure 4 The figure shows the comparison of the phantom experiment results of IRSE, 3TI-MPRAGE and the imaging sequence according to the embodiment of the present invention. The four phantoms of different colors represent the different T1 values ​​of the phantoms themselves. For the phantom experiment, the corresponding T1 histogram is calculated using a bin width of 10ms and smoothed by a spline filter. Figure 4 The phantom test results based on the IRSE sequence show the most uniformity, the phantom test results of the embodiment of the present invention show relatively uniformity, and the phantom test results of 3TI-MPRAGE show unevenness. The image accuracy of the embodiment of the present invention is close to the accuracy of IRSE, which is significantly better than 3TI-MPRAGE.

[0105] Figure 5The figure shows a histogram comparison chart obtained by analyzing IRSE, 3TI-MPRAGE and the imaging sequence of the embodiment of the present invention based on the image T1 value. The ordinate represents the frequency of the T1 value, and the abscissa represents the T1 value. The higher the frequency, the sharper the envelope in the histogram, which means that there are more pixels presenting the T1 value, and the better the prediction accuracy. The dotted line is the T1 value histogram of IRSE, the solid line is the T1 value histogram of the imaging sequence of the embodiment of the present invention, and the dotted line is the T1 value histogram of 3I-MPRAGE.

[0106] Table 1 is Figure 5 The phantom experimental data comparison table of the imaging sequences of IRSE, 3TI-MPRAGE and the embodiment of the present invention is shown. As shown in Table 1, within the same scanning time, compared with 3TI-MPRAGE, the standard deviation of the phantom T1 value measured by the embodiment of the present invention is lower, indicating that the accuracy of the embodiment of the present invention is higher. At the same time, with IRSE as a reference, the accuracy analysis of the other two quantitative magnetic resonance sequences based on MP-RAGE was performed. In the T1 histogram, the embodiment method of the present invention and the IRSE method have frequency peaks at 442ms, 666ms, 939ms and 1355ms. As shown in the data in Table 1, the maximum relative error obtained by the embodiment of the present invention is about 4%, while the maximum relative error obtained by 3TI-MPRAGE exceeds 25%. Therefore, the embodiment method of the present invention also has better accuracy than the 3TI-MPRAGE method.

[0107] Table 1

[0108]

[0109] *: Mean ± standard deviation

[0110] According to another embodiment of the present invention, imaging of human brain tissue signals is performed. In this embodiment, magnetic resonance scanning is performed on the brains of two healthy volunteers, both of whom are male and aged 24 and 28 respectively.

[0111] The parameters of the sequence in this embodiment are consistent with the parameters used in the above-mentioned phantom embodiment, and the sequence is run to perform data sampling. For the sampled magnetic resonance physical signals, after stripping the skull signals, the magnetic resonance physical signals of the basic brain tissue are extracted. Since the current sequence inversion time is set to a large value, the tissue signals of the cerebrospinal fluid are filtered out, and the T1 magnetic resonance quantitative image is obtained after processing. Figure 6 The T1 magnetic resonance quantitative images of two human brain tissues of the imaging sequence of the above embodiment of the present invention are shown. Figure 6 The two groups of human brain data shown in the figure extracted the regions of interest of gray matter and white matter for statistical analysis of T1 values.

[0112] Table 2 is a table of gray matter and white matter data analysis results of two healthy subjects. According to Table 2, the T1 values ​​of gray matter and white matter in the brain are 1040±148ms and 668±52ms, which are close to the T1 values ​​of brain tissue reported in known literature and are in line with expectations. The results show that the above embodiment of the present invention has high T1 measurement accuracy for gray matter and white matter in human brain experiments.

[0113] Table 2

[0114]

[0115] *: Mean ± standard deviation

[0116] According to yet another aspect of the present invention, a magnetic resonance imaging device is provided. Figure 7 FIG. 2 shows a schematic block diagram of a magnetic resonance imaging device 700 according to an embodiment of the present invention. The magnetic resonance imaging device 700 includes a processor and a memory. Figure 7 As shown, the magnetic resonance imaging device 700 may include a processor 710 and a memory 720. The processor 710 is used to run the computer program instructions stored in the memory to perform the corresponding steps of the magnetic resonance imaging method according to the embodiment of the present invention. The memory 720 stores the computer program instructions for implementing the various steps in the magnetic resonance imaging method according to the embodiment of the present invention.

[0117] According to another aspect of the present invention, a storage medium is also provided, on which program instructions are stored, and when the program instructions are executed by a computer or a processor, the computer or the processor executes the corresponding steps of the magnetic resonance imaging method of the embodiment of the present invention, and is used to implement the corresponding modules in the magnetic resonance imaging device according to the embodiment of the present invention. The storage medium may include, for example, a storage component of a tablet computer, a hard disk of a personal computer, a read-only memory (ROM), an erasable programmable read-only memory (EPROM), a portable compact disk read-only memory (CD-ROM), a USB memory, or any combination of the above storage media. The computer-readable storage medium may be any combination of one or more computer-readable storage media.

[0118] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0119] Similarly, it should be understood that in order to streamline the present invention and help understand one or more of the various inventive aspects, in the description of the exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, the method of the present invention should not be interpreted as reflecting the following intention: the claimed invention requires more features than the features explicitly stated in each claim. More specifically, as reflected in the corresponding claims, the inventive point is that the corresponding technical problem can be solved with less than all the features of a single disclosed embodiment. Therefore, the claims following the specific embodiment are hereby expressly incorporated into the specific embodiment, wherein each claim itself serves as a separate embodiment of the present invention.

[0120] It will be understood by those skilled in the art that, except for mutually exclusive features, all features disclosed in this specification (including the accompanying claims, abstracts and drawings) and all processes or units of any method or device disclosed in this specification may be combined in any combination. Unless otherwise expressly stated, each feature disclosed in this specification (including the accompanying claims, abstracts and drawings) may be replaced by an alternative feature that provides the same, equivalent or similar purpose.

[0121] In addition, those skilled in the art will appreciate that, although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present invention and form different embodiments. For example, in the claims, any one of the claimed embodiments may be used in any combination.

[0122] It should be noted that the word "comprising" does not exclude the presence of elements or steps not listed in the claims. The use of the words first, second and third etc. does not indicate any order. These words may be interpreted as names. The words one, two, third etc. are here equivalent to the numbers 1, 2, 3 etc. respectively corresponding thereto. Thus, first, second and third etc. are equivalent to the 1st, 2nd and 3rd etc. respectively corresponding thereto.

[0123] The above is only a specific embodiment of the present invention or an explanation of a specific embodiment, and the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. The protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A magnetic resonance imaging method, characterized in that: The following steps are involved: Acquire a to-be-imaged area of ​​the to-be-imaged object; Invoking a radially acquired spoiled gradient echo sequence, and using an empty scan to make the magnetic resonance physical signal of the area to be imaged reach a temporary steady state; Loop the following first and second operations n*N continuously y Second-rate, The first operation is to excite a magnetization preparation pulse and then wait for a preset period of time to achieve magnetization preparation corresponding to the magnetic resonance quantitative parameter of the magnetic resonance physical signal. The second operation is to use the radially acquired spoiled gradient echo sequence to perform N z times excitation, where in the N z The first N times of stimulation z1 times of excitation, and N consecutive z1 sampling of the magnetic resonance physical signal; The first operation and the second operation are performed in each cycle N y times, changing the duration of the preset time period, n is an integer greater than or equal to 3, N y Indicates the number of Y-direction phase encodings in the layer, N z1 Indicates the number of inter-layer Z-direction phase encodings, N z is an integer greater than or equal to the number threshold; Based on the property that the magnetic resonance physical signal enters a transient steady state after the second operation in the acquisition sequence, a magnetic resonance image of the magnetic resonance quantitative parameter is generated according to the sampled magnetic resonance physical signal.

2. The method of claim 1, wherein: N z1 =N z 。 3. The method of claim 1, wherein: In the second operation, in the first N z1 After the second excitation, the spoiled gradient echo sequence acquired in the radial direction is called, and the magnetic resonance physical signal is made to reach a temporary steady state by using an empty scan.

4. The method according to any one of claims 1 to 3, wherein: The magnetic resonance quantitative parameter is the longitudinal relaxation time, The method of generating the magnetic resonance image of the magnetic resonance quantitative parameter according to the sampled magnetic resonance physical signal based on the property that the magnetic resonance physical signal enters a transient steady state after the second operation in the acquisition sequence comprises: Parameter fitting is performed based on the following formula to generate the magnetic resonance image: Among them, S(TI n ) indicates that the durations of the preset time periods are TI1, TI2, ...TI n : The magnetic resonance physical signal sampled in the case of , T1 represents the longitudinal relaxation time, a and b represent the fitting parameters.

5. The method according to any one of claims 1 to 3, wherein: The method of generating the magnetic resonance image of the magnetic resonance quantitative parameter according to the sampled magnetic resonance physical signal based on the property that the magnetic resonance physical signal enters a transient steady state after the second operation in the acquisition sequence comprises: Based on the property that the magnetic resonance physical signal enters a transient steady state after the second operation in the acquisition sequence, determining the magnetic resonance quantitative parameter according to the sampled magnetic resonance physical signal; The magnetic resonance quantitative parameters are corrected to generate the magnetic resonance image.

6. The method of claim 5, wherein: The step of correcting the magnetic resonance quantitative parameter to generate the magnetic resonance image comprises: When the magnetic resonance quantitative parameter is lower than a first parameter threshold or higher than a second parameter threshold, the magnetic resonance quantitative parameter is set to 0, wherein the second parameter threshold is greater than the first parameter threshold.

7. The method according to any one of claims 1 to 3, wherein: The magnetic resonance quantitative parameter is longitudinal relaxation time, transverse relaxation time or apparent diffusion coefficient.

8. The method according to any one of claims 1 to 3, wherein: The k-space filling mode of the radially acquired spoiled gradient echo sequence is any one of the following modes: radial Cartesian sampling, radial radial sampling, and radial spiral sampling.

9. A magnetic resonance imaging device, comprising a processor and a memory, wherein: The memory stores computer program instructions, which are used by the processor to execute the magnetic resonance imaging method according to any one of claims 1 to 8 when executed.

10. A storage medium having program instructions stored thereon, wherein the program instructions are used to execute the magnetic resonance imaging method according to any one of claims 1 to 8 when run.

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