Longitudinal relaxation time constant determination method and device and magnetic resonance imaging equipment

Abstract

The invention relates to a longitudinal relaxation time constant determination method and device and magnetic resonance imaging equipment, and the method comprises the steps: obtaining a plurality of first amplitude images corresponding to a plurality of inversion recovery moments; wherein the sizes of the plurality of first amplitude images are the same; determining an amplitude image with the minimum amplitude at a preset target position point in the plurality of first amplitude images as a target amplitude image; selecting an image except the target amplitude image in the plurality of first amplitude images as a second amplitude image; and determining a longitudinal relaxation time constant of the target position point according to the second amplitude image. According to the invention, the problem of inaccurate calculation of the longitudinal relaxation time constant in the prior art is solved.

Description

Technical Field

[0001] The present application relates to the field of magnetic resonance technology, and in particular, to a method and apparatus for determining a longitudinal relaxation time constant and a magnetic resonance imaging device. Background Art

[0002] In existing methods for measuring the longitudinal relaxation time constant, the longitudinal magnetization vector is often flipped by an inversion recovery pulse, and then data is collected at different times using a spin echo sequence and reconstructed to obtain images with different inversion recovery times. However, since the longitudinal magnetization vector is inverted to the negative direction after applying the inversion recovery sequence and then gradually returns to the positive steady-state value. And currently, the images reconstructed by the conventional spin echo sequence often have a positive amplitude map. Therefore, it is necessary to first invert a part of the data and then perform fitting. However, since the data close to zero cannot be determined whether it is positive or negative, it is often processed by taking all of them as positive or all as negative, which leads to incorrect data processing at this point, resulting in an error in the fitted longitudinal relaxation time constant and inaccurate calculation of the longitudinal relaxation time constant. Summary of the Invention

[0003] In this embodiment, a method, apparatus and magnetic resonance imaging device for determining a longitudinal relaxation time constant are provided to solve the problem of inaccurate calculation of the longitudinal relaxation time constant in the prior art.

[0004] In a first aspect, in this embodiment, a method for determining a longitudinal relaxation time constant is provided, and the method includes:

[0005] Obtaining a plurality of first amplitude images corresponding to a plurality of inversion recovery times; wherein, the plurality of first amplitude images have the same size;

[0006] Determining the amplitude image with the smallest amplitude at a preset target position point in the plurality of first amplitude images as the target amplitude image;

[0007] Selecting the images in the plurality of first amplitude images except the target amplitude image as the second amplitude images;

[0008] Determining the longitudinal relaxation time constant of the target position point according to the second amplitude image.

[0009] In some of these embodiments, the determining the longitudinal relaxation time constant of the target position point according to the second amplitude image includes:

[0010] Obtaining the target inversion recovery time corresponding to the target amplitude image;

[0011] Determine multiple inversion recovery times before the target inversion recovery time as the first inversion recovery times, and determine multiple inversion recovery times after the target inversion recovery time as the second inversion recovery times;

[0012] Determine the correction value of the target position point according to the second amplitude image corresponding to the first inversion recovery time and the second amplitude image corresponding to the second inversion recovery time;

[0013] Determine the longitudinal relaxation time constant of the target position point according to the correction value.

[0014] In some embodiments, the correction value includes a first correction value and a second correction value; the first correction value is the negative value of the corresponding second amplitude image, and the second correction value is the corresponding second amplitude image; the step of determining the correction value of the target position point according to the second amplitude image corresponding to the first inversion recovery time and the second amplitude image corresponding to the second inversion recovery time includes:

[0015] Determine that the correction value of the first inversion recovery time at the target position point is the first correction value;

[0016] Determine that the correction value of the second inversion recovery time at the target position point is the second correction value.

[0017] In some embodiments, the step of determining the longitudinal relaxation time constant of the target position point according to the correction value includes:

[0018] Determine the longitudinal relaxation time constant of the target position point according to the first correction value, the second correction value, the first inversion recovery time, and the second inversion recovery time.

[0019] In some embodiments, the step of determining the longitudinal relaxation time constant of the target position point according to the correction value includes:

[0020] Determine the longitudinal relaxation time constant of the target position point according to the first correction value, the second correction value, the first inversion recovery time, the second inversion recovery time, and a known signal recovery function.

[0021] In some embodiments, the method further includes:

[0022] Determine the longitudinal relaxation time constants of all position points in the first amplitude image.

[0023] In some embodiments, the step of obtaining multiple first amplitude images corresponding to multiple inversion recovery times includes:

[0024] After executing the preparation pulse sequence, an acquisition pulse sequence is executed according to multiple inversion recovery times; the preparation pulse sequence is an inversion recovery pulse sequence; the acquisition pulse sequence is an imaging pulse sequence, which can acquire echo signals to image an object;

[0025] After executing the acquisition pulse sequence to acquire the corresponding echo signals, wait for a preset time; the preset time is determined according to an estimated value of the longitudinal relaxation time constant;

[0026] After the preset time arrives, execute the preparation pulse sequence of the next cycle;

[0027] According to the echo signals, generate multiple first amplitude images corresponding to the multiple inversion recovery times.

[0028] In a second aspect, in this embodiment, a device for determining the longitudinal relaxation time constant is provided. The device includes:

[0029] An acquisition module, configured to acquire multiple first amplitude images corresponding to multiple inversion recovery times; wherein, the multiple first amplitude images have the same size;

[0030] A first determination module, configured to determine that the amplitude image with the smallest amplitude at a preset target position point among the multiple first amplitude images is the target amplitude image;

[0031] A selection module, configured to select the images other than the target amplitude image among the multiple first amplitude images as the second amplitude images;

[0032] A second determination module, configured to determine the longitudinal relaxation time constant of the target position point according to the second amplitude images.

[0033] In a third aspect, in this embodiment, a magnetic resonance imaging device is provided, including:

[0034] Multiple radio frequency coils, configured to respectively acquire multiple echo signals of anatomical slices of an imaging object;

[0035] An image data processor, which includes at least one processing device adjusted to perform the following:

[0036] Generate a first amplitude image according to the multiple echo signals;

[0037] Acquire multiple first amplitude images corresponding to multiple inversion recovery times; wherein, the multiple first amplitude images have the same size;

[0038] Determine that the amplitude image with the smallest amplitude at a preset target position point among the multiple first amplitude images is the target amplitude image;

[0039] Select the images among the multiple first magnitude images except the target magnitude image as the second magnitude images;

[0040] Determine the longitudinal relaxation time constant of the target position point according to the second magnitude images.

[0041] In a fourth aspect, a computer-readable storage medium is provided in this embodiment, on which a computer program is stored. When the computer program is executed by a processor, the steps of the method for determining the longitudinal relaxation time constant in the first aspect are implemented.

[0042] Compared with the prior art, in the method, device, magnetic resonance imaging equipment and storage medium for determining the longitudinal relaxation time constant provided in this embodiment, by obtaining the minimum value of the magnitude image values collected at multiple inversion recovery times, since the positive or negative of the magnetic resonance signal at the inversion recovery time corresponding to this minimum value cannot be determined, after removing this minimum value, the images collected at other inversion recovery times are used to calculate the longitudinal relaxation time constant, solving the problem of inaccurate calculation of the longitudinal relaxation time constant in the prior art.

[0043] Details of one or more embodiments of the present application are set forth in the following drawings and description to make other features, objects, and advantages of the present application more concise and understandable. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The drawings described herein are used to provide a further understanding of the present application and form a part of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation of the present application. In the drawings:

[0045] Figure 1 is a hardware structure block diagram of a terminal for implementing the method for determining the longitudinal relaxation time constant according to an embodiment of the present application;

[0046] Figure 2 is a flowchart of the method for determining the longitudinal relaxation time constant according to an embodiment of the present application;

[0047] Figure 3 is a step flowchart of determining the longitudinal relaxation time constant of the target position point according to the second magnitude image in an embodiment of the present application;

[0048] Figure 4 is a step flowchart of obtaining multiple first magnitude images corresponding to multiple inversion recovery times in an embodiment of the present application;

[0049] Figure 4a is a timing schematic diagram of executing a preparation pulse sequence and an acquisition pulse sequence in an embodiment of the present application;

[0050] Figure 4bIt is a timing schematic diagram of another execution preparation pulse sequence and acquisition pulse sequence in an embodiment of the present application;

[0051] Figure 4c It is a timing schematic diagram of another execution preparation pulse sequence and acquisition pulse sequence in an embodiment of the present application;

[0052] Figure 5 It is a function schematic diagram of a known signal recovery function in an embodiment of the present application;

[0053] Figure 6 It is a schematic diagram of an amplitude diagram corresponding to an inversion recovery time in an embodiment of the present application;

[0054] Figure 7 It is a schematic diagram of a calculated image in an embodiment of the present application;

[0055] Figure 8 It is a schematic diagram of a calculated image in the prior art;

[0056] Figure 9 It is a structural schematic diagram of a magnetic resonance imaging device in an embodiment of the present application;

[0057] Figure 10 It is a structural block diagram of a longitudinal relaxation time constant determination device in an embodiment of the present application. Detailed implementation manners

[0058] To understand the purpose, technical solution, and advantages of the present application more clearly, the present application is described and illustrated below with reference to the accompanying drawings and embodiments.

[0059] Unless otherwise defined, technical terms or scientific terms involved in this application shall have the general meanings understood by those with ordinary skills in the technical field to which this application belongs. In this application, words such as "a", "an", "one kind", "the", "these", etc. do not indicate a limitation in quantity, and they can be singular or plural. The terms "include", "comprise", "have" and any variants thereof involved in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product or device including a series of steps or modules (units) is not limited to the listed steps or modules (units), but may include unlisted steps or modules (units), or may include other steps or modules (units) inherent in these processes, methods, products or devices. The words such as "connect", "be connected", "couple" and the like involved in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The "plurality" involved in this application means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" may represent: A exists alone, A and B exist simultaneously, and B exists alone. Usually, the character " / " indicates that the objects associated before and after are in an "or" relationship. The terms "first", "second", "third", etc. involved in this application are only used to distinguish similar objects and do not represent a specific order for the objects.

[0060] The method embodiments provided in this embodiment may be executed on a terminal, a computer or a similar computing device. For example, when running on a terminal, Figure 1 is a hardware structure block diagram of a terminal for executing a method for determining a longitudinal relaxation time constant according to an embodiment of this application. As Figure 1 shown, the terminal may include one or more ( Figure 1 only one is shown in the figure) processors 102 and a memory 104 for storing data. Among them, the processor 102 may include, but is not limited to, a processing device such as a microprocessor MCU or a programmable logic device FPGA. The above terminal may also include a transmission device 106 for communication functions and an input / output device 108. Those of ordinary skill in the art can understand that Figure 1 the structure shown is only schematic and does not limit the structure of the above terminal. For example, the terminal may also include more or fewer components than those shown in Figure 1 the figure, or have a different configuration from that shown in Figure 1 the figure.

[0061] The memory 104 can be used to store computer programs, such as software programs and modules of application software, such as the computer program corresponding to a longitudinal relaxation time constant determination method in this embodiment. The processor 102 executes various functional applications and data processing by running the computer program stored in the memory 104, that is, implements the above method. The memory 104 can include a high-speed random access memory, and can also include a non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memories. In some instances, the memory 104 can further include a memory remotely set relative to the processor 102, and these remote memories can be connected to the terminal through a network. Examples of the above network include but are not limited to the Internet, intranet, local area network, mobile communication network, and combinations thereof.

[0062] The transmission device 106 is used to receive or send data via a network. The above network includes a wireless network provided by a communication provider of the terminal. In one instance, the transmission device 106 includes a network adapter (Network Interface Controller, abbreviated as NIC), which can be connected to other network devices through a base station and thus communicate with the Internet.

[0063] In this embodiment, a longitudinal relaxation time constant determination method is provided. Figure 2 It is a flowchart of a longitudinal relaxation time constant determination method according to an embodiment of the present application, as Figure 2 shown, and this process includes the following steps:

[0064] Step S210, obtain a plurality of first amplitude images corresponding to a plurality of inversion recovery times; wherein, the sizes of the plurality of first amplitude images are the same.

[0065] Specifically, a plurality of inversion recovery times are preset, such as N inversion recovery times. The magnetic resonance device executes a pulse sequence. After each application of the preparation radio frequency pulse sequence, at different inversion recovery times, an acquisition pulse sequence is applied to acquire an echo signal, and according to the acquired echo signal, N first amplitude images corresponding to N inversion recovery times are generated. Wherein, N is a positive integer, and here the inversion recovery time can be understood as the signal acquisition time, and the number N of inversion recovery times can be set according to the measurement accuracy requirements of the longitudinal relaxation time constant. The specific values of the plurality of inversion recovery times can be determined according to the specific form of the magnetic resonance signal generated by the magnetic resonance device after applying the radio frequency pulse. Further, obtain a known signal recovery function of the magnetic resonance signal after applying the radio frequency pulse with respect to time, and according to this known signal recovery function, determine the specific values of the N inversion recovery times. The sizes of the N first amplitude images are the same, that is, each first amplitude image has the same number of pixel points. Further, the N first amplitude images acquire image data of the same part of the imaging object.

[0066] In some of these embodiments, the pulse sequence in the present application may include five parts, namely, a radio frequency pulse, a slice selection gradient field, a phase encoding gradient field, a frequency encoding gradient field, and a signal collector. In addition, the acquisition pulse sequence in the embodiments of the present application may be a combination of one or more of a free induction decay (FID) sequence, a fast spin echo sequence, a gradient-echo sequence (GRE), a hybrid sequence, etc., and specific limitations are not made herein. The acquisition time window of the signal collector for each period can be set according to different inversion recovery times, so as to realize the acquisition of echo signals at different inversion recovery times.

[0067] Step S220: Determine the amplitude image with the smallest amplitude at a preset target position point among the multiple first amplitude images as the target amplitude image.

[0068] Specifically, the pixel points in the first amplitude image are sequentially set as the preset target position points, and the N first amplitude images are sorted according to the amplitudes of the N first amplitude images at the preset target position points. The first amplitude image with the smallest amplitude at the preset target position point is determined as the target amplitude image. Here, the first amplitude image may be the amplitude of the image reconstructed by the magnetic resonance device from the acquired echo signal. The pixel points in the first amplitude image can be sequentially set as the preset target position points in a preset order, such as sequentially setting the pixel points in the first amplitude image as the preset target position points in the order from top to bottom and from left to right, or sequentially setting the pixel points in the first amplitude image as the preset target position points in the order from the center to the edge, and specific limitations are not made herein.

[0069] Step S230: Select the images other than the target amplitude image among the multiple first amplitude images as the second amplitude images.

[0070] Specifically, select N-1 other first magnitude images except the target magnitude image as the second magnitude image. After applying the inversion recovery radio frequency pulse, the magnitude of the magnetic resonance signal will reverse. For example, if the magnetic resonance signal is positive before applying the radio frequency pulse, after applying the inversion recovery radio frequency pulse, the magnetic resonance signal changes from positive to negative. During the signal recovery time, the magnetic resonance signal will recover, changing from negative to positive, and the magnitude of the magnetic resonance signal will recover to the magnitude before applying the radio frequency pulse. There is a known signal recovery function between the magnetic resonance signal and time, and the longitudinal relaxation time constant is the unknown in this known signal recovery function. Calculate the longitudinal relaxation time constant based on the measured values of the magnetic resonance signal and time corresponding to each other. The magnitude of each pixel point in the first magnitude image represents the magnetic resonance signal. However, since the magnitude of each pixel point in the first magnitude image only represents the magnitude and has no positive or negative sign, it is impossible to determine the sign corresponding to the measured value of the magnetic resonance signal. Therefore, it is necessary to correct the first magnitude image first, and determine the signal value of the magnetic resonance signal based on the corrected image. Remove the first magnitude image with the smallest magnitude as the target magnitude image, and determine the longitudinal relaxation time constant based on the remaining N-1 first magnitude images after removal.

[0071] Step S240, determine the longitudinal relaxation time constant of the target position point according to the second magnitude image.

[0072] Specifically, remove the first magnitude image with the smallest magnitude as the target magnitude image, and determine the longitudinal relaxation time constant based on the remaining N-1 first magnitude images after removal. According to the relationship between the N-1 inversion recovery times corresponding to the N-1 first magnitude images except the target magnitude image and the inversion recovery time corresponding to the target magnitude image, and the second magnitude image, determine the signal value of the magnetic resonance signal and the time corresponding to this signal value, and determine the longitudinal relaxation time constant of the target position point based on the determined signal value of the magnetic resonance signal and the time corresponding to this signal value. Further, determine the correction value of the second magnitude image according to the relationship between the N-1 inversion recovery times corresponding to the N-1 first magnitude images except the target magnitude image and the inversion recovery time corresponding to the target magnitude image, and the second magnitude image, and determine the longitudinal relaxation time constant of the magnetic resonance signal according to this correction value. Exemplarily, assume that the inversion recovery time corresponding to the target magnitude image is t1. When calculating the signal value of the magnetic resonance signal based on the magnitude of the target position point in the first magnitude image, the negative value of the magnitude corresponding to the inversion recovery time less than t1 can be used as the signal value of the magnetic resonance signal at this inversion recovery time, and the magnitude corresponding to the inversion recovery time greater than t1 can be used as the signal value of the magnetic resonance signal at this inversion recovery time. Based on the determined N-1 signal values of the magnetic resonance signal and the corresponding times, and the known signal recovery function between the magnetic resonance signal and time, determine the unknown longitudinal relaxation time constant in the known signal recovery function.

[0073] In this embodiment, by obtaining the minimum value of the amplitude image values collected at multiple inversion recovery times, since the positive or negative of the magnetic resonance signal at the inversion recovery time corresponding to this minimum value cannot be determined, after removing this minimum value, the images collected at other inversion recovery times are used to calculate the longitudinal relaxation time constant, solving the problem of inaccurate calculation of the longitudinal relaxation time constant in the prior art.

[0074] In some of these embodiments, as Figure 3 shown, determining the longitudinal relaxation time constant of the target position point according to the second amplitude image includes the following steps:

[0075] Step S310, obtaining the target inversion recovery time corresponding to the target amplitude image.

[0076] Specifically, after determining the target amplitude image, obtain the inversion recovery time for collecting the target amplitude image, and determine the inversion recovery time for collecting the target amplitude image as the target inversion recovery time.

[0077] Step S320, determining multiple inversion recovery times before the target inversion recovery time as the first inversion recovery time, and determining multiple inversion recovery times after the target inversion recovery time as the second inversion recovery time.

[0078] Specifically, let the target inversion recovery time be t2, determine multiple inversion recovery times before t2, that is, multiple inversion recovery times less than t2, as the first inversion recovery time, and determine multiple inversion recovery times after t2, that is, multiple inversion recovery times greater than t2, as the second inversion recovery time.

[0079] Step S330, determining the correction value of the target position point according to the second amplitude image corresponding to the first inversion recovery time and the second amplitude image corresponding to the second inversion recovery time.

[0080] Specifically, the correction value includes a first correction value and a second correction value. The first correction value is the negative value of the corresponding second amplitude image, and the second correction value is the positive value of the corresponding second amplitude image (i.e., the second amplitude image itself). Determine the correction value of the first inversion recovery time at the target position point as the first correction value, and determine the correction value of the second inversion recovery time at the target position point as the second correction value. That is, determine the correction value of the first inversion recovery time at the target position point as the negative value of the second amplitude image corresponding to the first inversion recovery time, and determine the correction value of the second inversion recovery time at the target position point as the second amplitude image corresponding to the second inversion recovery time.

[0081] Step S340, determining the longitudinal relaxation time constant of the target position point according to the correction value.

[0082] Specifically, according to the first correction value, the second correction value, the first inversion recovery time, and the second inversion recovery time, the longitudinal relaxation time constant of the target position point is determined. Further, according to the first correction value, the second correction value, the first inversion recovery time, the second inversion recovery time, and the known signal recovery function, the longitudinal relaxation time constant of the target position point is determined.

[0083] In this embodiment, a plurality of inversion recovery times before the target inversion recovery time are determined as the first inversion recovery time, and a plurality of inversion recovery times after the target inversion recovery time are determined as the second inversion recovery time. According to the second amplitude image corresponding to the first inversion recovery time and the second amplitude image corresponding to the second inversion recovery time, the correction value of the target position point is determined as the second amplitude image or the negative value of the second amplitude image. According to the determined correction value, the longitudinal relaxation time constant of the target position point is determined, thus solving the problem that the images reconstructed by the current conventional spin echo sequence are often amplitude images, and their values are all positive. Therefore, it is necessary to first invert a part of the data and then perform fitting. Since the data close to zero cannot be determined whether it is positive or negative, and all of them are taken as positive or all taken as negative, resulting in incorrect data processing at this point, which will lead to errors in the fitted longitudinal relaxation time constant and inaccurate calculation of the longitudinal relaxation time constant.

[0084] In some of the embodiments, the method for determining the longitudinal relaxation time constant further includes: determining the longitudinal relaxation time constant of all position points in the first amplitude image.

[0085] In some of the embodiments, the parameters of the acquired echo signal can also be set according to the pre-estimated longitudinal relaxation time constant of all position points, that is, the pre-estimated value of the longitudinal relaxation time constant, and the echo signal is acquired. Then the echo signal is reconstructed to obtain an amplitude image. The accurate value of the longitudinal relaxation time constant needs to be calculated. First, a rough value of the longitudinal relaxation time constant, that is, the pre-estimated value of the longitudinal relaxation time constant, is obtained based on experience and prior knowledge. According to this pre-estimated value, a reasonable inversion recovery time and a preset waiting time are set, so as to acquire a high-quality amplitude image for fitting and calculating the inversion recovery time, thereby obtaining an accurate longitudinal relaxation time constant.

[0086] In some of the embodiments, as Figure 4 shown, obtaining a plurality of first amplitude images corresponding to a plurality of inversion recovery times includes the following steps:

[0087] Step S410, after executing the preparation pulse sequence, execute the acquisition pulse sequence according to a plurality of inversion recovery times.

[0088] Specifically, prepare a pulse sequence as an inversion recovery pulse sequence and an acquisition pulse sequence as an imaging pulse sequence, and echo signals can be acquired to image an object. Set the signal acquisition time of the current period according to multiple inversion recovery times, and execute the acquisition pulse sequence at the signal acquisition time to acquire echo signals. It can be understood that for N inversion recovery times, N cycles of acquisition pulse sequences can be used for signal acquisition, and the interval between the inversion recovery pulse and the acquisition pulse sequence within each cycle can be the inversion recovery time. For example, if the N inversion recovery times are TI1, TI2, TI3... TI N , that is, the times for executing the acquisition pulse sequences of N signals are TI1, TI2, TI3... TI N , that is, for N cycles, at TI1, TI2, TI3... TI after applying the inversion recovery pulse respectively N execute the acquisition pulse sequence to acquire echo signals.

[0089] Step S420, after executing the acquisition pulse sequence to acquire the corresponding echo signals, wait for a preset time.

[0090] Specifically, the preset time is determined according to the estimated value of the longitudinal relaxation time constant. After executing the acquisition pulse sequence to acquire echo signals, it is necessary to wait for a preset time for the magnetic resonance signal to recover to the positive steady-state value. Obtain the estimated value of the longitudinal relaxation time constant. Here, the estimated value of the longitudinal relaxation time constant can be the estimated value set by the user according to experience. If the object contains different tissues, there are multiple estimated values of the longitudinal relaxation time constant, and the maximum value of these estimated values can be selected as the estimated value of the longitudinal relaxation time constant of the entire object. Determine the preset waiting time according to the estimated value of the longitudinal relaxation time constant. Exemplarily, the waiting time after executing the acquisition pulse sequence is determined to be N1 times the estimated value of the longitudinal relaxation time constant, where N1 is an integer greater than or equal to 5.

[0091] Step S430, after the preset time arrives, execute the preparation pulse sequence of the next cycle.

[0092] Specifically, preset N inversion recovery times, apply the acquisition pulse sequence at the current inversion recovery time, wait for a preset time after obtaining all the echo signals of the corresponding magnetic resonance K-space; the preset time is determined according to the estimated value of the longitudinal relaxation time constant; after the preset time arrives, apply the inversion recovery pulse of the next cycle; when the inversion recovery time of the next cycle arrives, apply the acquisition pulse sequence to obtain all the echo signals of the magnetic resonance K-space corresponding to the next inversion recovery time. Figure 4aSchematic diagram of the timing for preparing the pulse sequence and acquiring the pulse sequence. Taking three inversion recovery times TI1, TI2, and TI3 as an example, where t3 is the preset waiting time, M1 is the inversion recovery pulse, i.e., the preparation pulse sequence, and M2 is the acquisition pulse sequence. It should be noted that the M2 module can, according to different categories of acquisition pulse sequences, acquire all the echo signals of the magnetic resonance K-space corresponding to the current inversion recovery time at one time (such as Figure 4a ); it can also acquire a part of the echo signals of the current magnetic resonance K-space; for the case of only acquiring a part of the echo signals at a time, it is necessary to repeat the M1 module and the corresponding inversion recovery time and change the phase encoding gradient in the acquisition pulse sequence M2 module until all the echo signals of the current magnetic resonance K-space are acquired, Figure 4b and Figure 4c schematically show two waveforms of the sequences for acquiring all the echo signals of the magnetic resonance K-space corresponding to each inversion recovery time multiple times, but it is not limited to these two methods. As long as all the echo signals of the magnetic resonance K-space corresponding to each inversion recovery time can be acquired completely. Taking three inversion recovery times TI1, TI2, and TI3, and acquiring the echo signals 2 times for each inversion recovery time as an example, where, Figure 4b after the echo signals corresponding to a set of inversion recovery times (TI1, TI2, and TI3) are acquired, then acquire the echo signals corresponding to the next set of inversion recovery times (TI1, TI2, and TI3); Figure 4c first acquire the echo signals corresponding to TI1 2 times, then acquire the echo signals corresponding to TI2 2 times, and finally acquire the echo signals corresponding to TI3 2 times, to complete the acquisition of the echo signals 2 times for each of the three inversion recovery times TI1, TI2, and TI3. It should be noted that here only the example of acquiring 2 times for three inversion recovery times is used for illustration. It can be understood that the number of inversion recovery times can be multiple, such as 4, 5, etc., and the number of acquisitions for each inversion recovery time can also be multiple, such as 3 times, 4 times, etc., and no specific limitation is made here.

[0093] Step S440, generate multiple first amplitude images corresponding to multiple inversion recovery times according to the echo signals.

[0094] Specifically, generate N first amplitude images corresponding to N inversion recovery times according to the echo signals of the magnetic resonance K-space acquired in the periods corresponding to N inversion recovery times.

[0095] In this embodiment, set the execution times of multiple acquisition pulse sequences according to multiple inversion recovery times, acquire the echo signals, and thus obtain multiple first amplitude images corresponding to multiple inversion recovery times.

[0096] The following describes and illustrates this embodiment through specific examples.

[0097] Let the radio frequency pulse of the preparation pulse sequence be an inversion recovery pulse. The known signal recovery function is shown in Formula (1), where T1 is the longitudinal relaxation time constant, S(t) is the intensity of the longitudinal magnetization vector at time t after applying the inversion recovery pulse, that is, the magnetic resonance signal, M is the intensity of the longitudinal magnetization vector in the equilibrium state, and b is the inherent deviation of the system.

[0098] S(t) = M(1 - 2e -t / T1 ) + b (1)

[0099] After applying the inversion recovery pulse, taking b = 0 as an example, the signal value of the magnetic resonance signal will change from +M to -M, and then recover until it returns to the equilibrium state of +M and remains unchanged. This recovery process satisfies the exponential function shown in Formula (1), that is, the known signal recovery function is an exponential function, and the function graph of this exponential function is as Figure 5 shown. After each application of the inversion recovery pulse, the echo signal is measured using the acquisition pulse sequence at different times, and these different times are the inversion recovery (TI) times. As Figure 5 shown, 5 TI times are selected, where TI3 is the position where the signal value of the magnetic resonance signal is closest to 0. The horizontal axis is the time t, and the vertical axis is S(t).

[0100] Suppose there are N inversion recovery times (denoted as TI1, TI2, TI3... TI N ), and the amplitude images reconstructed by the corresponding acquisition pulse sequences are Im1, Im2, Im3... Im N , and the size of each amplitude image is [Nx, Ny], where Nx and Ny are positive integers. Here, the amplitude image is the first amplitude image described in the foregoing embodiment.

[0101] Denote 1 <= i <= Nx, 1 <= j <= Ny, and the pixel value of the current pixel point A(i, j) of the kth image is Im k (i, j), where 1 <= k <= N. Traverse the pixel values of the corresponding points on all images, that is, find the minimum value among Im1(i, j) ~ Im N (i, j) and denote it as Im h (i, j), and record the order of the image corresponding to this minimum value point as h, where 1 <= h <= N. Among them, i, j, k, and h are all positive integers.

[0102] Use the order of the image corresponding to the minimum value point to correct the image. Denote the corrected inversion recovery times as TIC1, TIC2, TIC3... TIC N-1 , where TIC1 ~ TIC h-1 = TI1 ~ TI h-1 , TIC h ~ TICN-1 = TI h+1 ~ TI N , that is, TI in the inversion recovery time is h eliminated. Similarly, the point Im h (i, j) in the image is also eliminated, and the values before this point are negated while the values after this point remain unchanged. Denote the corrected images as ImC1, ImC2, ImC3... ImC N-1 , where, ImC1(i, j) ~ ImC h-1 (i, j) = -Im1(i, j) ~ -Im h-1 (i, j), ImC h (i, j) ~ ImC N-1 (i, j) = Im h+1 (i, j) ~ Im N (i, j).

[0103] According to the corrected inversion recovery time TIC and the corrected image ImC r (i, j), where 1 <= r <= N - 1 and r is a positive integer, perform the least - squares fitting of formula (2) to obtain M0(i, j) and T1(i, j) at this time, where T1(i, j) is the longitudinal relaxation time constant T1 value of the current pixel point A.

[0104]

[0105] Traverse i and j to calculate the longitudinal relaxation time constant T1 values corresponding to all pixel points on the amplitude image.

[0106] The following gives a set of results of the longitudinal relaxation time constant T1 values calculated after using the inversion recovery time TI = [100, 200, 350, 600, 1000, 1600, 2400, 3600, 5000, 6800, 9000, 12000] ms and collecting the corresponding 12 amplitude images at these 12 inversion recovery times using the spin - echo sequence. Figure 6 is the amplitude image corresponding to the inversion recovery time of 350 ms, where each circle is a uniform phantom with basically the same T1 value; different circles correspond to different phantoms with different corresponding T1 values. Figure 7 is a longitudinal relaxation time constant calculation image in an embodiment of the present application, and the longitudinal relaxation time constant used in this calculation image is determined according to the longitudinal relaxation time constant determination method in the embodiment of the present application. Figure 8A longitudinal relaxation time constant calculation image in the prior art. In the method for calculating the longitudinal relaxation time constant in the prior art, the image is not corrected accordingly. For data close to zero, it is impossible to determine whether it is positive or negative, and all of them are processed as positive or all as negative, resulting in incorrect data processing at this point, leading to errors in the fitted longitudinal relaxation time constant and inaccurate calculation of the longitudinal relaxation time constant. As Figure 8 described, there are noise points in the image of the longitudinal relaxation time constant calculated according to this inaccurate method in some phantoms.

[0107] It should be noted that the steps shown in the above process or the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. And although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0108] In this embodiment, a magnetic resonance imaging device is also provided. Figure 9 It is a schematic structural diagram of a magnetic resonance imaging device according to an embodiment of the present application. As Figure 9 shown, the magnetic resonance imaging device includes: a magnetic resonance scanning device 620 and an image data processor 640. The image data processor 640 is communicatively connected to the magnetic resonance scanning device 620. The image data processor 640 is configured to obtain a plurality of first amplitude images based on a plurality of echo signals. The magnetic resonance scanning device 620 includes a plurality of radio frequency coils for respectively acquiring a plurality of echo signals of an anatomical slice of an imaging object; the image data processor 640 includes at least one processing device adjusted to perform the following: generating a first amplitude image based on a plurality of echo signals; obtaining a plurality of first amplitude images corresponding to a plurality of inversion recovery times; wherein the sizes of the plurality of first amplitude images are the same; determining the amplitude image with the smallest amplitude at a preset target position point among the plurality of first amplitude images as the target amplitude image; selecting the images other than the target amplitude image among the plurality of first amplitude images as the second amplitude images; and determining the longitudinal relaxation time constant of the target position point according to the second amplitude images.

[0109] In some of these embodiments, the image data processor 640 is further configured to obtain the target inversion recovery time corresponding to the target amplitude image; determine a plurality of inversion recovery times before the target inversion recovery time as the first inversion recovery times, and determine a plurality of inversion recovery times after the target inversion recovery time as the second inversion recovery times; determine a correction value of the target position point according to the second amplitude images corresponding to the first inversion recovery times and the second amplitude images corresponding to the second inversion recovery times; and determine the longitudinal relaxation time constant of the target position point according to the correction value.

[0110] In some of these embodiments, the image data processor 640 is further configured to determine that the correction value of the first inversion recovery time at the target position point is the first correction value; and determine that the correction value of the second inversion recovery time at the target position point is the second correction value.

[0111] In some of these embodiments, the image data processor 640 is further configured to determine the longitudinal relaxation time constant of the target position point according to the first correction value, the second correction value, the first inversion recovery time, and the second inversion recovery time.

[0112] In some of these embodiments, the image data processor 640 is further configured to determine the longitudinal relaxation time constant of the target position point according to the first correction value, the second correction value, the first inversion recovery time, the second inversion recovery time, and a known signal recovery function.

[0113] In some of these embodiments, the image data processor 640 is further configured to determine the longitudinal relaxation time constant of all position points in the first amplitude image.

[0114] In some of these embodiments, the image data processor 640 is further configured to, after executing a preparation pulse sequence, execute an acquisition pulse sequence according to a plurality of inversion recovery times; the preparation pulse sequence is an inversion recovery pulse sequence; the acquisition pulse sequence is an imaging pulse sequence, which can acquire echo signals to image an object; after executing the acquisition pulse sequence to acquire corresponding echo signals, wait for a preset time; the preset time is determined according to a predicted value of the longitudinal relaxation time constant; after the preset time arrives, execute the preparation pulse sequence of the next cycle; and generate a plurality of first amplitude images corresponding to the plurality of inversion recovery times according to the echo signals.

[0115] In this embodiment, a longitudinal relaxation time constant determination device is further provided. This device is used to implement the above embodiments and preferred implementation manners, and those that have been described will not be repeated here. The following terms such as "module", "unit", "sub-unit", etc. can be a combination of software and / or hardware that can achieve a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, implementation in hardware, or a combination of software and hardware is also possible and contemplated.

[0116] Figure 10 is a structural block diagram of a longitudinal relaxation time constant determination device according to an embodiment of the present application, as Figure 10 shown, this device includes:

[0117] An acquisition module 710, configured to acquire a plurality of first amplitude images corresponding to a plurality of inversion recovery times; wherein, the sizes of the plurality of first amplitude images are the same;

[0118] The first determination module 720 is configured to determine, as the target amplitude image, the amplitude image with the minimum amplitude at a preset target position point among multiple first amplitude images;

[0119] The selection module 730 is configured to select, as the second amplitude image, the images among multiple first amplitude images except the target amplitude image;

[0120] The second determination module 740 is configured to determine the longitudinal relaxation time constant of the target position point according to the second amplitude image.

[0121] It should be noted that the above-mentioned each module can be a functional module or a program module, and can be implemented either by software or by hardware. For the modules implemented by hardware, the above-mentioned each module can be located in the same processor; or the above-mentioned each module can also be located in different processors in any combined form.

[0122] In this embodiment, an electronic device is further provided, including a memory and a processor. A computer program is stored in the memory, and the processor is configured to run the computer program to execute the steps in any one of the above method embodiments.

[0123] Optionally, the above-mentioned electronic device may further include a transmission device and an input / output device, wherein the transmission device is connected to the above-mentioned processor, and the input / output device is connected to the above-mentioned processor.

[0124] Optionally, in this embodiment, the above-mentioned processor may be configured to execute the following steps through a computer program:

[0125] S1. Obtain multiple first amplitude images corresponding to multiple inversion recovery times; wherein, the sizes of the multiple first amplitude images are the same;

[0126] S2. Determine, as the target amplitude image, the amplitude image with the minimum amplitude at a preset target position point among multiple first amplitude images;

[0127] S3. Select, as the second amplitude image, the images among multiple first amplitude images except the target amplitude image;

[0128] S4. Determine the longitudinal relaxation time constant of the target position point according to the second amplitude image.

[0129] It should be noted that the specific examples in this embodiment can refer to the examples described in the above embodiment and the optional implementation manners, and will not be elaborated in this embodiment.

[0130] In addition, in combination with the method for determining the longitudinal relaxation time constant provided in the above embodiments, a storage medium can also be provided in this embodiment to implement it. A computer program is stored on the storage medium; when the computer program is executed by a processor, any of the methods for determining the longitudinal relaxation time constant in the above embodiments is implemented.

[0131] It should be understood that the specific embodiments described here are only used to explain this application, rather than to limit it. According to the embodiments provided in this application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of this application.

[0132] Obviously, the accompanying drawings are only some examples or embodiments of this application. For those of ordinary skill in the art, this application can also be applied to other similar situations based on these drawings without creative work. In addition, it can be understood that although the work done during the development process here may be complex and time-consuming, for those of ordinary skill in the art, certain design, manufacturing, or production changes based on the technical content disclosed in this application are only conventional technical means and should not be regarded as insufficient disclosure of this application.

[0133] The term "embodiment" in this application means that the specific features, structures, or characteristics described in combination with the embodiments can be included in at least one embodiment of this application. The phrase appears in various positions in the specification does not necessarily mean the same embodiment, nor does it mean being independent or alternative to other embodiments and mutually exclusive. Those of ordinary skill in the art can clearly or implicitly understand that the embodiments described in this application can be combined with other embodiments without conflict.

[0134] The above-described embodiments only represent several implementation manners of this application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of patent protection. It should be noted that for those of ordinary skill in the art, without departing from the concept of this application, several modifications and improvements can still be made, and these all belong to the protection scope of this application. Therefore, the protection scope of this application should be subject to the appended claims.

Claims

1. A method for determining the longitudinal relaxation time constant, characterized in that The method includes: Obtaining a plurality of first amplitude images corresponding to a plurality of inversion recovery times; wherein, the sizes of the plurality of first amplitude images are the same; Determining the amplitude image with the smallest amplitude at a preset target position point among the plurality of first amplitude images as the target amplitude image; Selecting the images among the plurality of first amplitude images except the target amplitude image as the second amplitude images; Determining the longitudinal relaxation time constant of the target position point according to the second amplitude images.

2. The method for determining the longitudinal relaxation time constant according to claim 1, wherein The determining the longitudinal relaxation time constant of the target position point according to the second amplitude images includes: Obtaining the target inversion recovery time corresponding to the target amplitude image; Determining a plurality of inversion recovery times before the target inversion recovery time as the first inversion recovery times, and determining a plurality of inversion recovery times after the target inversion recovery time as the second inversion recovery times; Determining a correction value of the target position point according to the second amplitude images corresponding to the first inversion recovery times and the second amplitude images corresponding to the second inversion recovery times; Determining the longitudinal relaxation time constant of the target position point according to the correction value.

3. The method for determining the longitudinal relaxation time constant according to claim 2, wherein The correction value includes a first correction value and a second correction value; the first correction value is the negative value of the corresponding second amplitude image, and the second correction value is the corresponding second amplitude image; the determining the correction value of the target position point according to the second amplitude images corresponding to the first inversion recovery times and the second amplitude images corresponding to the second inversion recovery times includes: Determining the correction value of the first inversion recovery time at the target position point as the first correction value; Determining the correction value of the second inversion recovery time at the target position point as the second correction value.

4. The method for determining the longitudinal relaxation time constant according to claim 3, characterized in that, The determining the longitudinal relaxation time constant of the target position point according to the correction value includes: Determining the longitudinal relaxation time constant of the target position point according to the first correction value, the second correction value, the first inversion recovery time and the second inversion recovery time.

5. The method for determining the longitudinal relaxation time constant according to claim 3, wherein The determining the longitudinal relaxation time constant of the target position point according to the correction value includes: Determining the longitudinal relaxation time constant of the target position point according to the first correction value, the second correction value, the first inversion recovery time, the second inversion recovery time and a known signal recovery function.

6. The method for determining the longitudinal relaxation time constant according to any one of claims 1 to 5, characterized in that, The method further includes: Determining the longitudinal relaxation time constants of all position points in the first amplitude image.

7. The method for determining the longitudinal relaxation time constant according to any one of claims 1 to 5, characterized in that, The obtaining a plurality of first amplitude images corresponding to a plurality of inversion recovery times includes: After executing a preparation pulse sequence, executing an acquisition pulse sequence according to a plurality of inversion recovery times; the preparation pulse sequence is an inversion recovery pulse sequence; the acquisition pulse sequence is an imaging pulse sequence, which can collect echo signals to image an object; After executing the acquisition pulse sequence to collect the corresponding echo signals, waiting for a preset time; the preset time is determined according to a pre-estimated value of the longitudinal relaxation time constant; After the preset time arrives, executing the next cycle of the preparation pulse sequence; Generating a plurality of first amplitude images corresponding to the plurality of inversion recovery times according to the echo signals.

8. A longitudinal relaxation time constant determination device, characterized in that The device includes: An acquisition module, configured to acquire a plurality of first magnitude images corresponding to a plurality of inversion recovery times; wherein, the sizes of the plurality of first magnitude images are the same; A first determination module, configured to determine that the magnitude image with the smallest magnitude at a preset target position point among the plurality of first magnitude images is the target magnitude image; A selection module, configured to select the images other than the target magnitude image among the plurality of first magnitude images as the second magnitude images; A second determination module, configured to determine the longitudinal relaxation time constant of the target position point according to the second magnitude images.

9. A magnetic resonance imaging device, characterized in that, Comprising: A plurality of radio frequency coils, configured to respectively acquire a plurality of echo signals of an anatomical slice of an imaging object; An image data processor, which includes at least one processing device adjusted to perform the following: Generate a first magnitude image according to the plurality of echo signals; Acquire a plurality of the first magnitude images corresponding to a plurality of inversion recovery times; wherein, the sizes of the plurality of first magnitude images are the same; Determine that the magnitude image with the smallest magnitude at a preset target position point among the plurality of first magnitude images is the target magnitude image; Select the images other than the target magnitude image among the plurality of first magnitude images as the second magnitude images; Determine the longitudinal relaxation time constant of the target position point according to the second magnitude images.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the longitudinal relaxation time constant determination method according to any one of claims 1 to 7.

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