Magnetic resonance center frequency correction method, device, storage medium and medical equipment

Abstract

The present invention discloses a method, device, storage medium and medical equipment for correcting the center frequency of magnetic resonance, wherein the correction method includes obtaining a respiratory signal; determining the baseline position information of the region of interest corresponding to the respiratory signal and the real-time position information corresponding to the current level of the region of interest according to the corresponding relationship between the respiratory signal and the position time information of the region of interest; obtaining the offset of the isocenter distance corresponding to the current level according to the baseline position information and the real-time position information; and correcting the center frequency of the pulse of the current level according to the offset. The present invention updates the corrected center frequency to the center frequency of the pulse of the current level, so that the accuracy and image quality of the image data collected by the corrected center frequency of the pulse are higher.

Description

Technical Field

[0001] The present invention belongs to the field of magnetic resonance technology, and in particular relates to a method, a device, a storage medium and a medical device for correcting the center frequency of magnetic resonance. Background Art

[0002] Magnetic resonance imaging has excellent soft tissue imaging capabilities, which can provide many unique contrasts for clinical diagnosis. However, due to the slow scanning speed during MRI, it is easily affected by the patient's respiratory movement. The patient's respiratory movement can cause large movements of organs along the head and feet direction and non-rigid deformation of organs, which can cause artifacts such as ghosting, blurring, and double imaging in MRI images.

[0003] Although existing MRI machines use respiratory-triggered acquisition for motion compensation, the effectiveness of this method depends on whether the patient's respiratory state is stable. When the patient's respiratory movement is unstable, the patient's respiratory state at different times when the acquisition is triggered by the respiratory gating device is inconsistent, resulting in different actual acquisition positions of the same k-space data in the head-foot direction, and problems such as ghosting, blurring and double imaging will still exist. Summary of the invention

[0004] In view of this, the present invention provides a method, device, storage medium and medical equipment for correcting the center frequency of magnetic resonance, the main purpose of which is to correct the center frequency of the pulse at the current level so that the accuracy and image quality of the image data collected by the corrected center frequency of the pulse at the current level are higher.

[0005] In a first aspect, the present invention provides a method for calibrating a magnetic resonance center frequency, comprising:

[0006] Get breathing signals;

[0007] Determine, according to the correspondence between the respiratory signal and the position time information of the region of interest, the baseline position information of the region of interest corresponding to the respiratory signal and the real-time position information corresponding to the current level of the region of interest;

[0008] Obtaining an offset of an isocenter distance corresponding to the current level according to the baseline position information and the real-time position information;

[0009] The center frequency of the pulses at the current level is corrected according to the offset.

[0010] Furthermore, before acquiring the breathing signal, the correction method further includes:

[0011] Acquire a sample respiration signal and a preset time resolution signal of a sample region of interest corresponding to the sample respiration signal;

[0012] Acquire a position-time curve of the sample region of interest according to the preset time resolution signal;

[0013] Establishing a functional mapping relationship between the position-time curve and the sample breathing signal;

[0014] The function mapping relationship is used as the corresponding relationship between the respiratory signal and the position time information of the region of interest.

[0015] Further, the acquiring of the sample respiration signal and a preset time resolution signal of a sample region of interest corresponding to the sample respiration signal includes:

[0016] Combined with respiratory gating, obtaining a preset time resolution signal of the sample region of interest in a direction perpendicular to the diaphragm, wherein the preset time resolution signal is a one-dimensional signal; or,

[0017] Combined with respiratory gating, a preset time resolution signal of the sample region of interest on the coronal plane is obtained, wherein the preset time resolution signal is a two-dimensional signal.

[0018] Furthermore, the preset time resolution signal is a signal obtained in a direction perpendicular to the diaphragm, and obtaining the position-time curve of the sample region of interest according to the preset time resolution signal includes:

[0019] Performing FFT transformation on the preset time resolution signal to obtain a one-dimensional image of the sample region of interest corresponding to the acquisition time;

[0020] Based on the gray value information of the one-dimensional image, acquiring the position information of the diaphragm in the one-dimensional image;

[0021] A correspondence between the position information and the acquisition time is established to obtain the position and time information of the sample region of interest.

[0022] Furthermore, the preset time resolution signal is a signal obtained on the coronal plane, and obtaining the position-time curve of the sample region of interest according to the preset time resolution signal includes:

[0023] Performing FFT transformation on the preset time resolution signal to obtain a two-dimensional image of the region of interest corresponding to the acquisition time;

[0024] Based on the gray value information of the two-dimensional image, obtaining the position information of the center of the sample region of interest in the two-dimensional image;

[0025] A corresponding relationship between the position information and the acquisition time is established to obtain a position-time curve of the sample region of interest.

[0026] Further, the position-time information of the region of interest includes the position information of the sample region of interest in the moving direction, and the function mapping relationship includes a mapping relationship between the sample breathing signal and the position-time curve of the sample region of interest in the moving direction.

[0027] Furthermore, the sample respiration signal and the preset time resolution signal of the sample region of interest include signals obtained by pre-scanning the region of interest, or signals obtained based on historical scanning data of a patient.

[0028] Further, determining the baseline position information of the region of interest corresponding to the respiratory signal according to the corresponding relationship between the respiratory signal and the position time information of the region of interest includes:

[0029] Performing weighted averaging on the respiratory signal within a preset acquisition window to obtain a baseline value of the respiratory signal when the respiratory signal is acquired;

[0030] Determining weighted position information of a region of interest corresponding to the respiratory signal baseline value according to the corresponding relationship;

[0031] The weighted position information of the region of interest is used as the baseline position information of the region of interest.

[0032] Further, the correcting the center frequency of the pulse of the current level according to the offset includes:

[0033] Based on the isocenter distance corresponding to the current level and the offset, a predetermined formula is used to calculate and obtain the center frequency of the pulse of the current level;

[0034] The predetermined calculation formula is:

[0035] Among them, freq n is the center frequency of the pulse at the current level; γ is the magnetic gyrometry ratio; Δz n is the isocenter distance corresponding to the current level; D n -D acq is the offset; Gss is the layer selection gradient value corresponding to the current level.

[0036] Furthermore, the region of interest is at least one of the liver, kidney and spleen.

[0037] In a second aspect, the present invention provides a device for correcting a magnetic resonance center frequency, comprising:

[0038] A signal acquisition module, used for acquiring a respiratory signal;

[0039] a position information determination module, configured to determine the baseline position information of the region of interest corresponding to the respiratory signal and the real-time position information corresponding to the current level of the region of interest according to the corresponding relationship between the respiratory signal and the position time information of the region of interest;

[0040] An offset determination module, used to obtain an offset of the isocenter distance corresponding to the current level according to the baseline position information and the real-time position information;

[0041] The center frequency correction module is used to correct the center frequency of the pulse of the current level according to the offset.

[0042] In a third aspect, the present invention provides a storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method for correcting the magnetic resonance center frequency in the first aspect or any possible implementation of the first aspect.

[0043] In a fourth aspect, the present invention provides a medical device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of the method for correcting the magnetic resonance center frequency in the first aspect or any possible implementation of the first aspect are implemented.

[0044] By means of the above technical solution, the technical solution provided by the embodiment of the present invention has at least the following advantages:

[0045] The present invention provides a method, device, storage medium and medical equipment for correcting the center frequency of magnetic resonance. The method determines the baseline position information of the region of interest corresponding to the respiratory signal and the real-time position information corresponding to the current level of the region of interest according to the corresponding relationship between the respiratory signal and the position time information of the region of interest; then obtains the offset of the isocenter distance corresponding to the current level according to the baseline position information and the real-time position information; finally, corrects the center frequency of the pulse of the current level according to the offset. The accuracy and image quality of the image data collected by the corrected center frequency of the pulse are higher.

[0046] 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

[0047] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0048] Figure 1 A block diagram of the magnetic resonance system is shown;

[0049] Figure 2 A trigger acquisition schematic diagram of a respiratory gating device is shown;

[0050] Figure 3 A flow chart of a method for correcting a magnetic resonance center frequency provided by an embodiment of the present invention is shown;

[0051] Figure 4 A schematic diagram of multi-layer scanning of a region of interest of a patient provided by an embodiment of the present invention is shown;

[0052] Figure 5 Magnetic resonance images simulated and corrected for motion are shown;

[0053] Figure 6 A flow chart showing another method for correcting the magnetic resonance center frequency provided by an embodiment of the present invention;

[0054] Figure 7 A schematic diagram of positioning for exciting a high time resolution signal to the diaphragm provided by an embodiment of the present invention is shown;

[0055] Figure 8 A schematic diagram showing a high time resolution signal provided by an embodiment of the present invention after FFT transformation is shown;

[0056] Fig. 9 A flow chart showing the determination of baseline position information of a region of interest corresponding to a respiratory signal according to a corresponding relationship provided by an embodiment of the present invention;

[0057] Fig.10 A block diagram showing a magnetic resonance center frequency correction device provided by an embodiment of the present invention;

[0058] Fig.11 A block diagram showing another magnetic resonance center frequency correction device provided by an embodiment of the present invention is shown;

[0059] Fig.12 A schematic diagram of the physical structure of a medical device provided by an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0060] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples of devices and methods consistent with some aspects of the present invention as detailed in the appended claims.

[0061] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, device, product or server that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0062] Magnetic resonance imaging (MRI) is one of the main imaging methods in modern medical imaging. Figure 1 The basic principle is to use the magnetic resonance phenomenon, use the gradient field to encode the spatial position, then use radio frequency excitation to excite the hydrogen protons in the human body, then use the receiving coil to receive the signal with position information, and finally reconstruct the image information through Fourier transform.

[0063] The existing MRI monitors the patient's respiratory signals and triggers the scan at the end of breathing, hoping to collect signals at the end of breathing when the movement is slow. Figure 2 Before the respiratory triggered scan begins, the system will calculate the respiratory cycle and the maximum slope point. The scanning technician can set a fixed trigger delay time and scanning window length for normal scanning by observing the patient's respiratory signal curve and the position of the maximum slope point to ensure that the scanning window falls in the interval where the end-respiratory signal is the most stable.

[0064] However, the scanning time of MRI high-resolution imaging sequences is relatively long. The patient's respiratory state may change in the later stage of the scan, such as changes in the respiratory cycle and / or respiratory amplitude, but the sequence is not adjusted accordingly, resulting in different positions of the imaged organs corresponding to the excitation (shot) of the early scan and the excitation (shot) of the later scan. The signals collected at these different positions are used to reconstruct the same image, which will produce artifacts.

[0065] Based on this, an embodiment of the present application provides a method for correcting the center frequency of magnetic resonance, by determining the baseline position information of the region of interest corresponding to the respiratory signal and the real-time position information of the region of interest corresponding to the respiratory signal of the current level based on the correspondence established between the respiratory signal and the position-time information of the region of interest; then, based on the baseline position information and the real-time position information, obtaining the offset of the isocenter distance corresponding to the current level; finally, correcting the center frequency of the pulse of the current level based on the offset, the accuracy and image quality of the image data collected by the corrected center frequency of the pulse of the current level are higher.

[0066] The following describes a method for calibrating the center frequency of magnetic resonance in the present application. Figure 3 Said, including:

[0067] 301. Obtain a breathing signal.

[0068] In this embodiment, the respiratory signal can be obtained based on a respiratory gating device or a 3D camera device, and the respiratory signal can reflect the movement amplitude and movement state of the region of interest. Under normal circumstances, combined with respiratory gating, MRI scanning can well remove artifacts caused by respiratory movement. However, after the patient controls the respiratory movement for a long time, the respiratory cycle and / or the amplitude of breathing may change.

[0069] 302. Determine, according to a correspondence between the respiratory signal and the position-time information of the region of interest, baseline position information of the region of interest corresponding to the respiratory signal and real-time position information corresponding to a current level of the region of interest.

[0070] See also Figure 4 When scanning the region of interest, the region of interest is scanned in multiple layers through the repetition time TR, wherein each repetition time TR will obtain multiple layers of one excitation (shot) data, and each single layer of k-space data is composed of data collected by multiple excitations (shot). The respiratory cycles in which the multiple excitations are located are different. Since the respiratory signals of the patient in different respiratory cycles may be different, that is, the movement of the region of interest of the scanned person caused by the respiratory movement is different, the same excitation frequency leads to different excitation level positions. In other words, the same excitation frequency is used, and the acquired data belongs to different levels. The region of interest may include at least one of the liver, kidneys, or spleen.

[0071] In this embodiment, by analyzing the respiratory signal and the location information of the region of interest in advance, a corresponding relationship between the two is established, that is, a corresponding relationship between the respiratory signal and the location time information of the region of interest. When acquiring the respiratory signal, the location information of the region of interest corresponding to the determined respiratory signal can be inferred based on the established corresponding relationship. The location relationship includes the baseline location information D of the region of interest corresponding to the respiratory signal. acq , and the real-time location information D corresponding to the current level of the area of ​​interest n .

[0072] 303. Obtain an offset of the isocenter distance corresponding to the current level according to the baseline position information and the real-time position information.

[0073] The central frequency of the pulse for the nth level of excitation in the patient's area of ​​interest is calculated as freq n =γ*Δz n *Gss, where γ is the magnetogyroscopic ratio, Δz n is the theoretical isocenter distance of the nth level in the layer direction, which is applicable when the respiratory signal has good consistency, and Gss is the layer-selected gradient value; since the gyroscopic ratio and the layer-selected gradient value are fixed values, the isocenter distance of the nth level in the layer direction shifts with the patient's respiratory movement. Therefore, in order to accurately obtain the value of the isocenter distance corresponding to the current level, the offset of the isocenter distance corresponding to the current level is calculated according to the corresponding relationship between the isocenter distance corresponding to the current level and the baseline position information and the real-time position information. The offset of the isocenter distance can be the difference between the real-time position and the baseline position, that is, D n -D acq , so as to enable the real-time correction of the center frequency of the pulse of the current level according to the offset in the following step 304.

[0074] 304. Correct the center frequency of the pulse at the current level according to the offset.

[0075] By obtaining the offset of the isocenter distance corresponding to the current level, correct the isocenter distance of the current level, Δz n校正 is Δz n -(D n -D acq ), through the corrected isocenter distance Δz n校正 By correcting the center frequency of the pulse at the current level in real time, the corrected center frequency can be used as the center frequency of the pulse at the current level for updating, thereby correcting the movement deviation of the pulse in the layer direction corresponding to the current level excitation in the region of interest.

[0076] By updating the center frequency of the pulses corresponding to each level of the region of interest, the motion between different levels of the region of interest can be simulated, thereby obtaining better image quality. Figure 5 As shown in (a), the image obtained at the center frequency of the uncorrected pulse has artifacts and blur, such as Figure 5 As shown in (b) and 5(c), the images obtained at the center frequency of the corrected pulse and the images without inter-layer motion have good image quality.

[0077] An embodiment of the present invention provides a method for correcting the center frequency of magnetic resonance, by determining the baseline position information of the region of interest corresponding to the respiratory signal and the real-time position information corresponding to the current level of the region of interest based on a pre-established correspondence between the respiratory signal and the position-time information of the region of interest; then, based on the baseline position information and the real-time position information, obtaining the offset of the isocenter distance corresponding to the current level; finally, correcting the center frequency of the pulse of the current level based on the offset, so that the accuracy and image quality of the image data collected by the corrected center frequency of the pulse are higher.

[0078] The embodiment of the present invention provides another method for correcting the center frequency of magnetic resonance, including establishing a corresponding relationship between the respiratory signal and the position time information of the region of interest, such as Figure 6 As shown, the method specifically includes:

[0079] 601. Acquire a sample respiration signal and a high time resolution signal of a sample region of interest corresponding to the sample respiration signal.

[0080] The preset time resolution signal of the sample respiratory signal and the sample region of interest includes a signal obtained by pre-scanning the region of interest or a signal obtained based on the scanning data of historical patients. In the case of obtaining the sample region of interest by pre-scanning, the sample region of interest is actually the region of interest. Before the region of interest is formally scanned, the sample respiratory signal and the high time resolution signal of the sample region of interest are obtained by pre-scanning. In this case, it is equivalent to each patient establishing a corresponding relationship between his own respiratory signal and the position time information of the region of interest, which may be the same or different between different patients. In the case of obtaining the sample respiratory signal and the sample region of interest based on the scanning data of historical patients, the sample respiratory signal and the sample region of interest are not obtained by pre-scanning, but are obtained based on the historical patient medical records. The sample region of interest may not be the region of interest of the patient to be scanned, but belongs to the same position of different patients. For example, the region of interest is the liver, and the sample region of interest is the liver of other patients. In this case, it is equivalent to multiple patients using the same corresponding relationship between the respiratory signal and the position time information of the region of interest to correct the isocenter distance.

[0081] For the embodiment of the present invention, the sample breathing signal and sample region of interest obtained by pre-scanning the region of interest are used as an example for explanation. When the gating device starts to collect the patient's sample breathing signal, a set of preset time resolution signal scans of the patient's region of interest are obtained, that is, the preset time resolution signal of the sample region of interest. The preset time resolution signal can preferably be a signal with low spatial resolution, and the spatial resolution of the preset time resolution signal is 32-64, and the time resolution is about 100ms. The preset time resolution signal can be applied to scanning organs with larger layer thickness. In the embodiment of the present invention, the preset time resolution signal can be called a high time resolution signal, and the high time resolution signal can meet the requirements of obtaining the position time information of the region of interest, which is not limited here. For example, the time resolution of the preset time resolution signal can reach milliseconds.

[0082] Acquiring a preset time-resolution signal of a sample region of interest requires position localization.

[0083] In one example, the diaphragm is used as a positioning position. Figure 7 The diaphragm is a thin membrane separating the thoracic cavity and the abdominal cavity. It is located below the heart and the bilateral lungs, above the liver, spleen, and stomach, and lies flat inside the body to separate the thoracic and abdominal cavities. It can move up and down with the breathing movement. When collecting the patient's breathing signal, the position information of the diaphragm changes relatively obviously. Therefore, obtaining the sample breathing signal and the preset time resolution signal of the sample region of interest corresponding to the sample breathing signal may include: combining respiratory gating to obtain the preset time resolution signal of the sample region of interest in the direction perpendicular to the diaphragm, wherein the preset time resolution signal is a one-dimensional signal. The preset time resolution signal may be obtained by exciting a layer or by exciting a line through a pencil beam, and then collecting the preset time resolution signal perpendicular to the diaphragm direction. The preset time resolution signal perpendicular to the diaphragm direction corresponds to at least one respiratory cycle. In order to meet the preset time resolution requirement, the acquisition sequence may adopt a GRE sequence, and the time resolution reaches several milliseconds. The preset time resolution signal may be a preset time resolution FID signal, the FID signal is a nuclear magnetic resonance free induction decay signal, and the GRE sequence is a gradient echo pulse sequence.

[0084] In another example, the center position of the coronal plane image of the region of interest is taken as the positioning position. Since the liver, kidneys or spleen can move significantly with the breathing of the human body, when collecting the patient's respiratory signal, the change in the position information of the liver, kidneys or spleen is relatively obvious, which can be reflected in the coronal plane image of the liver, kidneys or spleen, wherein the reference position on the coronal plane can select the center position of the region of interest. Therefore, obtaining a sample respiratory signal and a preset time resolution signal of the sample region of interest corresponding to the sample respiratory signal may include: combining respiratory gating to obtain a preset time resolution signal of the sample region of interest on the coronal plane, wherein the preset time resolution signal is a two-dimensional signal. The preset time resolution signal on the coronal plane can excite a layer, and in order to ensure the time resolution, a GRE sequence may be used.

[0085] In other embodiments, the preset time resolution signal may also be a preset time resolution ECHO signal, and the acquisition sequence may also use a GRE sequence. Compared with the FID signal, the acquisition of the ECHO signal includes a prephase gradient process, and the acquisition time is longer.

[0086] Since the preset time resolution signal is collected along with the respiratory motion in the time dimension, the preset time resolution signal contains the motion information of the sample region of interest related to the sample respiratory signal. Different respiratory signals may result in different preset time resolution signals at different time points.

[0087] 602. Acquire a position-time curve of the sample region of interest according to the preset time resolution signal.

[0088] Since the preset time resolution signal contains the motion information of the region of interest with breathing, the preset time resolution signal is analyzed to extract the position information related to the motion, so as to obtain the position time information of the region of interest corresponding to the sample breathing signal.

[0089] In one example, the preset time resolution signal is a signal obtained in a direction perpendicular to the diaphragm, and based on the preset time resolution signal, a position-time curve of the sample region of interest is obtained, including: performing FFT transformation on the preset time resolution signal to obtain a one-dimensional image of the sample region of interest corresponding to the acquisition time; based on the gray value information of the one-dimensional image, obtaining the position information of the diaphragm in the one-dimensional image; establishing a corresponding relationship between the position information and the acquisition time to obtain the position-time information of the sample region of interest.

[0090] In this embodiment, the preset time resolution signal is subjected to FFT transformation to obtain image data of the sample region of interest, which may also be referred to as spatial domain data. Since the preset time resolution signal is a one-dimensional signal, the image data of the sample region of interest is a one-dimensional image corresponding to different acquisition times. Obtaining the position information of the diaphragm in the one-dimensional image may specifically include: obtaining the position of the grayscale value in the one-dimensional image based on the grayscale value of the diaphragm. Establishing a correspondence between the position information and the acquisition time to obtain the position-time information of the sample region of interest may specifically include: arranging the obtained position information in sequence along the acquisition time, that is, obtaining the position-time information of the region of interest. For example, see Figure 8 , the horizontal axis is the acquisition time, the vertical axis represents the gray value distribution in the direction perpendicular to the diaphragm, and the vertical axis information corresponding to each acquisition time can represent a one-dimensional image. Among them, the intersection position of black and white gray values ​​is the location of the diaphragm, and the information of the intersection position changing over time is the position time information of the sample area of ​​interest.

[0091] Here, the position time information includes the position information corresponding to the signal change of the region of interest in the foot-to-head direction. The foot-to-head direction is a direction perpendicular to the diaphragm and is also the movement direction of the sample region of interest.

[0092] In another example, the preset time resolution signal is a signal obtained on the coronal plane, and obtaining the position-time curve of the sample region of interest based on the preset time resolution signal may include: performing FFT transformation on the preset time resolution signal to obtain a two-dimensional image of the region of interest corresponding to the acquisition time; obtaining the position information of the sample region of interest in the two-dimensional image based on the grayscale value information of the two-dimensional image; and establishing a corresponding relationship between the position information and the acquisition time to obtain the position-time curve of the sample region of interest.

[0093] In this embodiment, the preset time resolution signal is subjected to FFT transformation to obtain image data of the sample region of interest, and the image data can also be called spatial domain data. Since the preset time resolution signal is a two-dimensional signal, the image data of the sample region of interest is a two-dimensional image corresponding to different acquisition times, that is, a tomographic image. Based on the gray value information, obtaining the position information of the sample region of interest in the two-dimensional image can specifically include: based on the gray value information, extracting the contour of the sample region of interest, and the position information of the contour in the two-dimensional image is the position information of the sample region of interest in the two-dimensional image. Or, based on the gray value information, obtaining the characteristic position of the sample region of interest, and the position information of the characteristic position in the two-dimensional image is the position information of the sample region of interest in the two-dimensional image. Establishing a corresponding relationship between the position information and the acquisition time to obtain the position time information of the sample region of interest can specifically include: arranging the obtained position information in sequence along the acquisition time, that is, obtaining the position time information of the region of interest. Taking the liver as an example, based on the gray value information, extracting the liver contour, determining the position information of the liver contour in different two-dimensional images, and then arranging the position information in the order of the acquisition time, that is, obtaining the position time information of the sample region of interest.

[0094] Here, the position time information includes the position information corresponding to the signal change of the coronal plane of the sample region of interest in the foot-to-head direction, and the foot-to-head direction is the movement direction of the sample region of interest.

[0095] 603. Establish a function mapping relationship between the position-time curve and the sample breathing signal.

[0096] Here, a linear or second-order model is used to establish a functional mapping relationship between the sample breathing signal and the position and time information of the sample region of interest through polynomial fitting.

[0097] In some embodiments, the position-time information of the sample region of interest includes position information of the sample region of interest in a moving direction, and the function mapping relationship includes a mapping relationship between the sample breathing signal and a position-time curve of the sample region of interest in a moving direction.

[0098] Among them, the functional relationship between the position information D of the sample area of ​​interest in the direction from foot to head and the function mapping relationship F of the breathing signal I is, D=F(I), where F is a mapping relationship between the sample breathing signal I and the position information-time curve D of the sample area of ​​interest in the direction of movement.

[0099] 604. Use the function mapping relationship as a corresponding relationship between the respiratory signal and the position and time information of the region of interest.

[0100] When the functional relationship corresponding to the function mapping relationship is the above-mentioned D=F(I), the corresponding relationship between the respiratory signal and the position and time information of the region of interest is D=F(I).

[0101] 605. Determine the baseline position information of the region of interest corresponding to the respiratory signal and the real-time position information corresponding to the current level of the region of interest according to the corresponding relationship between the respiratory signal and the position time information of the region of interest.

[0102] It should be noted that, assuming that the current level is the nth level, the breathing signal I of the current level n During the acquisition, the real-time position information of the region of interest corresponding to the respiratory signal at the current level is calculated according to the corresponding relationship between the respiratory signal and the position time information of the region of interest, that is, D = F (I). The real-time position information obtained is D n =F(I n ).

[0103] Since, when the patient's region of interest is scanned hierarchically, the patient's region of interest will move in the direction of movement (from the feet to the head) with the patient's breathing movement, and the movement of the acquired region of interest in the direction of movement will inevitably produce an offset due to environmental factors or equipment factors, therefore, in order to accurately obtain the offset of the isocenter distance corresponding to different levels, it is also necessary to determine the baseline position information of the region of interest corresponding to the patient's breathing signal when the patient's breathing signal is collected. Therefore, according to the correspondence between the respiratory signal and the position time information of the region of interest, the baseline position information of the region of interest is determined, see Fig. 9 , which may include:

[0104] 6051. Perform weighted averaging on the respiratory signal within a preset acquisition window to obtain a baseline value of the respiratory signal when the respiratory signal is acquired.

[0105] Here, according to the respiratory signal obtained in the learning cycle and the size of the preset acquisition window set by the user, the respiratory signal in the preset acquisition window is determined, and then the respiratory signal in the preset acquisition window is weighted averaged to obtain the respiratory signal baseline value.

[0106] 6052. Determine weighted position information of a region of interest corresponding to the respiratory signal baseline value according to the corresponding relationship.

[0107] Here, the baseline value of the respiratory signal is set to I acq , using the functional relationship D=F(I) corresponding to the function mapping relationship in step 604, the weighted position information of the region of interest is calculated as D acq =F(I acq), the weighted position information of the region of interest here serves as the baseline position information of the region of interest in the following step 6053.

[0108] 6053. Use the weighted position information of the region of interest as the baseline position information of the region of interest.

[0109] Since, when the gating device collects the patient's breathing signal, the gating device automatically analyzes the signal within the learning cycle, the gating device can analyze the breathing signal within the preset collection window within the learning cycle. Here, by performing weighted averaging calculation on the breathing signal within the preset collection window, the baseline value of the breathing signal corresponding to the breathing signal within the preset collection window can be obtained; then, based on the functional mapping relationship between the breathing signal and the position-time information of the region of interest, the weighted position information of the region of interest corresponding to the baseline value of the breathing signal is determined to obtain the baseline position information of the region of interest, so as to calculate the offset of the equivalent center distance in the following step 606.

[0110] 606. Obtain an offset of the isocenter distance corresponding to the current level according to the baseline position information and the real-time position information.

[0111] Here, the real-time location information is D n =F(I n ), the baseline position information is D acq =F(I acq ), then the isocenter distance Δz corresponding to the current level n The offset is D n -D acq .

[0112] 607. Correct the center frequency of the pulse at the current level according to the offset.

[0113] In one example, the correcting the center frequency of the pulse of the current level according to the offset includes: based on the isocenter distance corresponding to the current level and the offset, using a predetermined formula to calculate the center frequency of the pulse of the current level; the predetermined calculation formula is: Among them, freq n is the center frequency of the pulse at the current level; γ is the magnetic gyrometry ratio; Δz n is the isocenter distance corresponding to the current level; D n -D acq is the offset; Gss is the layer selection gradient value corresponding to the current level.

[0114] It should be noted that the offset is used to calculate the isocenter distance Δz corresponding to the current level. nCorrection is performed to obtain the corrected isocenter distance Δz in the layer direction corresponding to the pulse used to excite the current layer n , which is to convert Δz n Corrected to Δz n -(D n -D acq ), and then the corrected Δz n Substitute the formula freq used to calculate the center frequency of the pulse at the current level n =γ*Δz n * In Gss, the center frequency of the pulse at the current level can be corrected.

[0115] The present invention provides a method for correcting the center frequency of magnetic resonance. The method comprises the following steps: scanning and pre-scanning a region of interest to obtain a preset time resolution signal of the region of interest, that is, a preset time resolution signal of a sample region of interest; positioning and analyzing the preset time resolution signal to obtain position-time information of the sample region of interest; and establishing a function mapping relationship between the sample breathing signal and the position-time information of the sample region of interest based on the position-time information of the sample region of interest, and using the function mapping relationship between the breathing signal and the position-time information of the region of interest during normal scanning; and accurately determining the baseline position information of the region of interest and the real-time position information of the region of interest at the current level by acquiring the real-time breathing signal and the above-mentioned function mapping relationship. Then, the offset of the isocenter distance corresponding to the current level obtained through the real-time position information and the baseline position information is used to correct the center frequency of the pulse based on the offset, so that the center frequency of the pulse at the corrected current level is more accurate.

[0116] Furthermore, as a response to the above Figure 3 In order to realize the method shown in the figure, the embodiment of the present invention provides a correction device for the center frequency of magnetic resonance, such as Fig.10 As shown, the device comprises:

[0117] A signal acquisition module 1001 is used to acquire a respiratory signal;

[0118] A position information determination module 1002 is used to determine the baseline position information of the region of interest corresponding to the respiratory signal and the real-time position information corresponding to the current level of the region of interest according to the corresponding relationship between the respiratory signal and the position time information of the region of interest;

[0119] An offset determination module 1003 is used to obtain an offset of the isocenter distance corresponding to the current level according to the baseline position information and the real-time position information;

[0120] The center frequency correction module 1004 is used to correct the center frequency of the pulse of the current level according to the offset.

[0121] An embodiment of the present invention provides a device for correcting the center frequency of magnetic resonance. The device determines the baseline position information of the region of interest corresponding to the respiratory signal and the real-time position information corresponding to the current level of the region of interest based on the correspondence between the respiratory signal and the position-time information of the region of interest; then obtains the offset of the isocenter distance corresponding to the current level based on the baseline position information and the real-time position information; finally, corrects the center frequency of the pulse of the current level based on the offset, so that the accuracy and image quality of the image data collected by the corrected center frequency of the pulse are higher.

[0122] As the above Figure 6 In order to realize the method shown in the figure, the embodiment of the present invention provides another device for correcting the center frequency of magnetic resonance, such as Fig.11 As shown, the device comprises:

[0123] An acquisition module 1101 is used to acquire a sample respiration signal and a preset time resolution signal of a sample region of interest corresponding to the sample respiration signal;

[0124] A position-time curve acquisition module 1102 is used to acquire a position-time curve of the sample region of interest according to the preset time resolution signal;

[0125] A function mapping relationship establishing module 1103, used to establish a function mapping relationship between the position time curve and the sample breathing signal;

[0126] A correspondence determination module 1104, configured to use the function mapping relationship as a correspondence relationship between the respiratory signal and the position time information of the region of interest;

[0127] A position information determination module 1105, configured to determine, according to the corresponding relationship, the baseline position information of the region of interest corresponding to the respiratory signal, and the real-time position information of the region of interest corresponding to the respiratory signal at the current level;

[0128] An offset determination module 1106, configured to obtain an offset of the isocenter distance corresponding to the current level according to the baseline position information and the real-time position information;

[0129] The center frequency correction module 1107 is used to correct the center frequency of the pulse of the current level according to the offset.

[0130] Furthermore, the region of interest is at least one of the liver, kidney and spleen.

[0131] Furthermore, the acquisition module 1101 includes:

[0132] A first scanning unit, used for acquiring a preset time resolution signal of the sample region of interest in a direction perpendicular to the diaphragm in combination with respiratory gating, wherein the preset time resolution signal is a one-dimensional signal;

[0133] A second scanning unit, used for acquiring a preset time resolution signal of the sample region of interest on the coronal plane in combination with respiratory gating, wherein the preset time resolution signal is a two-dimensional signal;

[0134] In one example, the position-time curve acquisition module 1102 includes:

[0135] An image acquisition unit, used for performing FFT transformation on the preset time resolution signal to acquire a one-dimensional image of the sample region of interest corresponding to the acquisition time;

[0136] a corresponding relationship establishing unit, configured to obtain position information of the diaphragm in the one-dimensional image based on the gray value information of the one-dimensional image;

[0137] The position information time acquisition unit is used to establish a corresponding relationship between the position information and the acquisition time, and obtain the position time information of the sample area of ​​interest.

[0138] Furthermore, in another example, the position-time curve acquisition module 1102 includes:

[0139] An image acquisition unit, used for performing FFT transformation on the preset time resolution signal to obtain a two-dimensional image of the region of interest corresponding to the acquisition time;

[0140] A corresponding relationship establishing unit, configured to obtain the position information of the center of the sample region of interest in the two-dimensional image based on the gray value information of the two-dimensional image;

[0141] The position-time curve acquisition unit is used to establish a corresponding relationship between the position information and the acquisition time to obtain the position-time curve of the sample region of interest.

[0142] Further, the position-time information of the region of interest includes position information of the region of interest in a moving direction, and the function mapping relationship includes a mapping relationship between the respiratory signal and a position-time curve of the region of interest in a moving direction.

[0143] Furthermore, the location information determination module 1105 further includes:

[0144] A respiratory signal baseline value acquisition unit, used to perform weighted averaging on the respiratory signal within a preset acquisition window to obtain a respiratory signal baseline value when the respiratory signal is acquired;

[0145] A weighted position information acquisition unit, used to determine the weighted position information of the region of interest corresponding to the respiratory signal baseline value according to the corresponding relationship;

[0146] The baseline position information determining unit is configured to use the weighted position information of the region of interest as the baseline position information of the region of interest.

[0147] Furthermore, the center frequency correction module 1107 includes:

[0148] A calculation unit, configured to calculate the center frequency of the pulse of the current level by using a predetermined formula based on the isocenter distance corresponding to the current level and the offset;

[0149] The predetermined calculation formula is:

[0150] Among them, freq n is the center frequency of the pulse at the current level; γ is the magnetic gyrometry ratio; Δz n is the isocenter distance corresponding to the current level; D n -D acq is the offset; Gss is the layer selection gradient value corresponding to the current level.

[0151] An embodiment of the present invention provides another device for correcting the center frequency of magnetic resonance. The device obtains a preset time resolution signal of the region of interest, that is, a preset time resolution signal of the sample region of interest, by performing a pre-scan on the region of interest; then the preset time resolution signal is positioned and analyzed to obtain the position-time information of the sample region of interest; and based on the position-time information of the sample region of interest, a function mapping relationship between the sample breathing signal and the position-time information of the sample region of interest is established, and used as the function mapping relationship between the breathing signal and the position-time information of the region of interest during normal scanning; by acquiring the real-time breathing signal and the above-mentioned function mapping relationship, the baseline position information of the region of interest and the real-time position information of the region of interest at the current level can be accurately determined, and then the offset of the isocenter distance corresponding to the current level is obtained through the real-time position information and the baseline position information, and the center frequency of the pulse is corrected based on the offset, so that the center frequency of the pulse at the corrected current level is more accurate.

[0152] Based on the same inventive concept, an embodiment of the present application further provides a storage medium on which a computer program is stored, and when the program is executed by a processor, the steps of the method for correcting the magnetic resonance center frequency in any possible implementation manner described above are implemented.

[0153] Alternatively, the storage medium may be a non-transitory computer-readable storage medium, for example, the non-transitory computer-readable storage medium may be a ROM, a random access memory (RAM), a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, and the like.

[0154] Based on the above Figure 3 The method shown and Fig.10 The embodiment of the device shown in the figure, the embodiment of the present invention also provides a physical structure diagram of a medical device, such as Fig.12 As shown, the medical device includes: a processor 1201, a memory 1202, and a computer program stored in the memory 1202 and executable on the processor, wherein the memory 1202 and the processor 1201 are both arranged on a bus 1203, and when the processor 1201 executes the program, the following steps are implemented: obtaining a respiratory signal; determining the baseline position information of the region of interest corresponding to the respiratory signal and the real-time position information corresponding to the current level of the region of interest based on the correspondence between the respiratory signal and the position-time information of the region of interest; obtaining the offset of the isocenter distance corresponding to the current level based on the baseline position information and the real-time position information; and correcting the center frequency of the pulse of the current level based on the offset.

[0155] Through the technical solution of the present invention, the present invention can determine the baseline position information of the region of interest corresponding to the respiratory signal and the real-time position information of the region of interest corresponding to the respiratory signal of the current level according to the corresponding relationship established between the respiratory signal and the position-time information of the region of interest; then obtain the offset of the isocenter distance corresponding to the current level according to the baseline position information and the real-time position information; finally, correct the center frequency of the pulse of the current level according to the offset, and the accuracy and image quality of the image data collected by the corrected center frequency of the pulse of the current level are higher.

[0156] Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, and optionally, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, and in some cases, the steps shown or described can be executed in a different order than here, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0157] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for calibrating a magnetic resonance center frequency, characterized in that: include: Get breathing signals; Determine, according to the correspondence between the respiratory signal and the position time information of the region of interest, the baseline position information of the region of interest corresponding to the respiratory signal and the real-time position information corresponding to the current level of the region of interest; Obtaining an offset of an isocenter distance corresponding to the current level according to the baseline position information and the real-time position information; The center frequency of the pulses at the current level is corrected according to the offset.

2. The calibration method according to claim 1, characterized in that: Before acquiring the breathing signal, the correction method further includes: Acquire a sample respiration signal and a preset time resolution signal of the sample region of interest corresponding to the sample respiration signal; Acquire a position-time curve of the sample region of interest according to the preset time resolution signal; Establishing a functional mapping relationship between the position-time curve and the sample breathing signal; The function mapping relationship is used as the corresponding relationship between the respiratory signal and the position time information of the region of interest.

3. The calibration method according to claim 2, characterized in that: The step of acquiring a sample respiration signal and a preset time resolution signal of a sample region of interest corresponding to the sample respiration signal comprises: Combined with respiratory gating, obtaining a preset time resolution signal of the sample region of interest in a direction perpendicular to the diaphragm, wherein the preset time resolution signal is a one-dimensional signal; or, Combined with respiratory gating, a preset time resolution signal of the sample region of interest on the coronal plane is obtained, wherein the preset time resolution signal is a two-dimensional signal.

4. The calibration method according to claim 3, characterized in that: The preset time resolution signal is a signal obtained in a direction perpendicular to the diaphragm. According to the preset time resolution signal, a position-time curve of the sample region of interest is obtained, including: Performing FFT transformation on the preset time resolution signal to obtain a one-dimensional image of the sample region of interest corresponding to the acquisition time; Based on the gray value information of the one-dimensional image, acquiring the position information of the diaphragm in the one-dimensional image; A corresponding relationship between the position information and the acquisition time is established to obtain the position and time information of the sample region of interest.

5. The calibration method according to claim 3, characterized in that: The preset time resolution signal is a signal obtained on the coronal plane, and obtaining the position time curve of the sample region of interest according to the preset time resolution signal includes: Performing FFT transformation on the preset time resolution signal to obtain a two-dimensional image of the region of interest corresponding to the acquisition time; Based on the gray value information of the two-dimensional image, obtaining the position information of the center of the sample region of interest in the two-dimensional image; A corresponding relationship between the position information and the acquisition time is established to obtain a position-time curve of the sample region of interest.

6. The calibration method according to claim 2, characterized in that: The position-time information of the region of interest includes the position information of the sample region of interest in the moving direction, and the function mapping relationship includes the mapping relationship between the sample breathing signal and the position-time curve of the sample region of interest in the moving direction.

7. The calibration method according to claim 2, characterized in that: The sample respiration signal and the preset time resolution signal of the sample region of interest include signals obtained by pre-scanning the region of interest, or signals obtained based on historical scanning data of a patient.

8. The calibration method according to claim 1, characterized in that: Determining the baseline position information of the region of interest corresponding to the respiratory signal according to the corresponding relationship between the respiratory signal and the position time information of the region of interest includes: Performing weighted averaging on the respiratory signal within a preset acquisition window to obtain a baseline value of the respiratory signal; Determining weighted position information of a region of interest corresponding to the respiratory signal baseline value according to the corresponding relationship; The weighted position information of the region of interest is used as the baseline position information of the region of interest.

9. The calibration method according to claim 1, characterized in that: The step of correcting the center frequency of the pulse at the current level according to the offset comprises: Based on the isocenter distance corresponding to the current level and the offset, a predetermined formula is used to calculate and obtain the center frequency of the pulse of the current level; The predetermined calculation formula is: Among them, freq n is the center frequency of the pulse at the current level; γ is the magnetic gyrometry ratio; Δz n is the isocenter distance corresponding to the current level; D n -D acq is the offset; Gss is the layer selection gradient value corresponding to the current level.

10. The calibration method according to any one of claims 1 to 9, characterized in that: The region of interest is at least one of the liver, kidneys and spleen.

11. A device for correcting the center frequency of magnetic resonance, characterized in that: include: A signal acquisition module, used for acquiring a respiratory signal; a position information determination module, configured to determine the baseline position information of the region of interest corresponding to the respiratory signal and the real-time position information corresponding to the current level of the region of interest according to the corresponding relationship between the respiratory signal and the position time information of the region of interest; An offset determination module, used to obtain an offset of the isocenter distance corresponding to the current level according to the baseline position information and the real-time position information; The center frequency correction module is used to correct the center frequency of the pulse of the current level according to the offset.

12. A storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 8 are implemented.

13. A medical device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps of the method according to any one of claims 1 to 8 are implemented.

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