Free-breathing abdominal chemical exchange saturation transfer imaging method and system

Abstract

The application relates to the technical field of medical equipment, in particular to a free-breathing abdominal chemical exchange saturation transfer imaging method and system, wherein the method comprises the following steps: collecting a respiratory motion signal of an imaging object; if a preset specific position of the respiratory motion signal is detected, triggering a water signal suppression sequence application module after a delay target time length, so that a water signal starts longitudinal relaxation recovery from 0; applying a CEST saturation pulse for a second preset time length after a delay first preset time length, and performing MR signal reading on the imaging object after the CEST saturation pulse application is completed, to obtain an MR image of the imaging object. Therefore, the problems that related technologies cannot overcome the influence of respiratory motion on abdominal CEST, have low implementation, poor usability, low accuracy and the like are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of medical equipment, in particular to a free-breathing abdominal chemical exchange saturation transfer imaging method and system. BACKGROUND

[0002] Chemical Exchange Saturation Transfer (CEST) Magnetic Resonance Imaging (MRI) is a molecular imaging method, which can be used to detect molecules such as proteins, polypeptides, sugars, lipids, phosphocreatine, glutamic acid, etc. in tissues, and can also be used to image molecular probes containing "exchangeable protons", which has great application prospects in tumors, cerebral ischemia, and neurological disorders. The reliability of CEST imaging is easily affected by tissue motion, so it is mainly used for imaging of static tissues such as brain and muscle, and the technology is not mature enough and the application is still relatively small in moving organs such as liver, kidney, and heart.

[0003] The technical difficulty of abdominal CEST imaging is to overcome the influence of respiratory motion on CEST signal. At present, a few studies use the method of making the person receiving scanning (hereinafter referred to as the subject) hold breath, and the saturation pulse and MR signal reading are applied in the breath-holding state, but the current breath-holding method has obvious shortcomings:

[0004] (1) CEST needs to collect images at multiple offset frequencies (usually more than 10), and in order to obtain high-resolution or large-range images, the data of each offset frequency may also be collected through multiple excitations, so multiple breath-holdings are required. This is less implementable for patients with obvious breathing difficulties or serious illness;

[0005] (2) Between different breath-holdings, it is difficult for the subject to control the position of the abdomen at the same level, so the motion artifacts or image misalignment between different offset frequencies are still difficult to effectively overcome.

[0006] Another method to overcome the influence of respiratory motion on abdominal CEST is to use a motion detection device (such as a respiratory belt) to monitor the respiratory motion state of the subject in real time during imaging, and trigger the operation of the imaging sequence according to the changes in the respiratory motion state, so as to collect MR signals in a specific respiratory phase (such as the expiratory phase). However, due to the fluctuations in the subject's breathing cycle, the length of the saturation pulse applied before each MR signal collection is also fluctuating, resulting in different exchange times of hydrogen protons and different longitudinal relaxation recovery degrees of free water, thereby reducing the comparability of the MR signals collected in different times and the accuracy of the final CEST imaging. SUMMARY

[0007] The application provides a free-breathing abdominal chemical exchange saturation transfer imaging method and device to solve the problems of the related art, such as the inability to overcome the influence of respiratory motion on abdominal CEST, low implementation, poor usability, and low accuracy.

[0008] The first aspect of the application provides a free-breathing abdominal chemical exchange saturation transfer imaging method, including the following steps: acquiring a respiratory motion signal of an imaging object; if a preset specific position of the respiratory motion signal is detected, triggering a water signal suppression sequence module after a target delay time, so that the water signal starts longitudinal relaxation recovery from 0; applying a CEST saturation pulse for a second preset time after a first preset time is delayed; and reading MR signals of the imaging object after the CEST saturation pulse is applied, to obtain an MR image of the imaging object.

[0009] Optionally, before the target delay time, the method further includes: estimating a next respiratory cycle parameter according to the respiratory motion signal before the current time; and calculating the target time according to the respiratory cycle parameter, a time length of the water signal suppression sequence module, a preset expected respiratory phase of MR signal reading, the first preset time, and the second preset time.

[0010] Optionally, triggering the water signal suppression sequence module after the target delay time includes: detecting a trigger signal according to the respiratory motion signal; and timing according to the trigger signal until the target delay time is delayed, and then applying the water signal suppression sequence module.

[0011] Optionally, reading MR signals of the imaging object after the CEST saturation pulse is applied, to obtain an MR image of the imaging object, includes: calculating a real respiratory phase at the MR signal reading time according to the respiratory motion signal; if a difference between the real respiratory phase and an expected respiratory phase is greater than a preset threshold, discarding the MR signal corresponding to the MR signal reading and reacquiring; or if the respiratory motion of the imaging object is relatively stable, not discarding the MR signal.

[0012] The second aspect of the application provides a free-breathing abdominal chemical exchange saturation transfer imaging system, including: a respiratory motion detection module, configured to acquire a respiratory motion signal of an imaging object; a water signal suppression module, configured to trigger a water signal suppression sequence module after a target delay time if a preset specific position of the respiratory motion signal is detected, so that the water signal starts longitudinal relaxation recovery from 0; a CEST saturation module, configured to apply a CEST saturation pulse for a second preset time after a first preset time is delayed; and an MR signal reading module, configured to read MR signals of the imaging object after the CEST saturation pulse is applied, to obtain an MR image of the imaging object.

[0013] Optionally, the method further comprises: calculating a next breathing cycle parameter according to the breathing motion signal before a target time delay; and calculating the target time delay according to the breathing cycle parameter, a time length of the water signal suppression sequence module, a preset expected breathing phase of MR signal reading, the first preset time length and the second preset time length.

[0014] Optionally, the water signal suppression module is further configured to: detect a trigger signal according to the breathing motion signal; and apply the water signal suppression sequence module after the target time delay according to the timing of the trigger signal.

[0015] Optionally, the MR signal reading module is further configured to: calculate an actual breathing phase of the MR signal reading time according to the breathing motion signal; if a difference between the actual breathing phase and an expected breathing phase is greater than a preset threshold, discard the corresponding MR signal and perform resampling; or if the breathing motion of the imaging subject is relatively balanced, not discard the MR signal.

[0016] The third aspect of the present application provides a medical device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the free-breathing abdominal chemical exchange saturation transfer imaging method according to the above embodiments.

[0017] The fourth aspect of the present application provides a computer readable storage medium having a computer program stored thereon, wherein the program is executable by a processor to implement the free-breathing abdominal chemical exchange saturation transfer imaging method according to the above embodiments.

[0018] Therefore, the present application has at least the following beneficial effects:

[0019] The embodiments of the present application can use the detected breathing motion signal to perform breathing motion compensation, and the subject can breathe freely during the imaging process, without the need for breath holding, so the ease of use is high and the embodiments are easy to promote in the clinic; real-time and adaptive trigger delay time adjustment is performed according to the breathing motion state, so that MR signal reading only occurs at a specific breathing phase, and finally the effectiveness of the data is judged and it is decided whether to perform resampling according to the actual breathing phase, which can effectively overcome the problems of CEST image artifacts and image misalignment caused by breathing motion; and by introducing water signal suppression, the influence of breathing cycle fluctuation on CEST signal is removed, the comparability of the acquired signals under different offset frequencies is improved, and the accuracy of CEST is improved. Therefore, the technical problems of the related art, such as the inability to overcome the influence of breathing motion on abdominal CEST, low implementation, poor ease of use, and low accuracy, are solved.

[0020] Additional aspects and advantages of the present application will be made apparent from the following description with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0021] The above and / or additional aspects and advantages of the present application will become apparent and be more readily understood from the following description, taken in conjunction with the accompanying drawings, in which:

[0022] Figure 1 is a schematic diagram of a CEST imaging sequence in the related art;

[0023] Figure 2 is a schematic diagram of a Z-spectrum in the related art;

[0024] Figure 3 is a schematic diagram of applying a CEST saturation pulse in the related art;

[0025] Figure 4 is a flow chart of a free-breathing abdominal chemical exchange saturation transfer imaging method according to an embodiment of the present application;

[0026] Figure 5 is a schematic diagram of a CEST imaging sequence according to an embodiment of the present application;

[0027] Figure 6 is a schematic diagram of a free-breathing abdominal chemical exchange saturation transfer imaging system according to an embodiment of the present application;

[0028] Figure 7 is a schematic diagram of a medical device according to an embodiment of the present application. DETAILED DESCRIPTION

[0029] Embodiments of the present application are described in detail below with reference to the attached drawing figures, wherein the same or like reference numerals and characters are used throughout the figures to denote like components. The embodiments described below are illustrative only and are not intended to be limiting to the scope of the present application, as defined by the appended claims.

[0030] In MRI, by applying radio frequency pulse signal of a specific frequency, hydrogen protons in the tissue can be resonated, and then signals are generated, received by coils, input to image reconstruction algorithm, and finally images are generated. CEST mainly involves two types of hydrogen protons, one is hydrogen protons in water molecules, and the other is hydrogen protons in molecules to be detected (such as proteins, glycogen, etc.). Due to the difference in chemical environment, the resonance frequencies of the two types of hydrogen protons are different, and the resonance frequencies of hydrogen protons in different molecules to be detected are also different. The content of hydrogen protons in water in living tissues is much higher than that of hydrogen protons in other molecules, and conventional MRI mainly images hydrogen protons in water. It should be noted that there is a continuous exchange between the two types of hydrogen protons concerned in the above CEST, and the existence of this exchange process is the basis of CEST imaging. Like traditional MRI technology, CEST is also to collect signals of hydrogen protons in water. But before signal collection, a radio frequency pulse with a frequency consistent with the hydrogen protons of the molecule to be detected is applied to saturate the hydrogen protons in the molecule to be detected. Due to the exchange process, this saturation effect will be transferred to the hydrogen protons in water, causing the signal to be weakened. Therefore, CEST indirectly reflects the content of the molecule to be detected by observing the degree of reduction of water signal.

[0031] As shown in Figure 1 The main components of the CEST imaging sequence include a CEST saturation module for saturating the hydrogen protons of the molecule to be detected and exchanging with the hydrogen protons of water, and a signal reading module. In order to saturate enough water hydrogen protons and obtain high detection sensitivity, the saturation of the hydrogen protons of the molecule to be detected needs to last for a long time (for example, 2 seconds). In order to detect multiple molecules, multiple "CEST saturation-signal reading" imaging processes need to be performed, and in each imaging, the CEST saturation module acts on different offset frequencies (corresponding to the hydrogen protons of different molecules to be detected). Taking the offset frequency as the horizontal axis and the water signal as the vertical axis, the resulting curve is called Z spectrum, and the signal dip and dip degree on the Z spectrum can reflect the content of the molecule at the corresponding frequency, as shown in Figure 2 Motion of the tissue can cause motion artifacts in a single CEST image, and also cause images of different offset frequencies to be misaligned in space, resulting in fluctuations and non-true dips on the Z spectrum.

[0032] In the related art, the influence of respiratory motion on abdominal CEST is overcome by the following method, but there are different defects:

[0033] 1. The subject undergoing the scan (hereinafter referred to as the subject) holds their breath while a saturation pulse and MR signal are applied and read. However, CEST requires acquiring images at multiple offset frequencies (usually more than 10), and to obtain high-resolution or large-area images, data for each offset frequency may require multiple excitations and acquisitions, thus necessitating multiple breath-holds. This is less feasible for patients with significant respiratory distress or severe illness; between different breath-holds, the subject has difficulty maintaining the same abdominal position, so motion artifacts or image misalignment between different offset frequencies remain difficult to overcome effectively.

[0034] 2. During the imaging process, motion detection equipment (e.g., breathing belts) is used to monitor the subject's respiratory motion in real time, and the imaging sequence is triggered based on changes in respiratory motion to acquire MR signals during specific respiratory phases (e.g., expiration). To improve acquisition efficiency, this technique continuously applies CEST saturation pulses during non-signal readout periods, such as... Figure 3 As shown. However, due to fluctuations in the respiratory cycle of the subjects, the length of the CEST saturation pulse applied before different MR signal readings also fluctuates, resulting in different hydrogen proton exchange times and different degrees of longitudinal relaxation recovery of free water. This reduces the comparability of MR signals acquired from different times and the final accuracy of CEST imaging.

[0035] The following describes a method and system for abdominal chemical exchange saturation transfer imaging (CEST) with free breathing, based on embodiments of the present application, with reference to the accompanying drawings. Addressing the problems of low feasibility, poor usability, and low accuracy associated with methods mentioned in the background art for overcoming the influence of respiratory motion on abdominal CEST image acquisition, this application provides a method for abdominal CEST with free breathing. In this method, detected respiratory motion signals are used for respiratory motion compensation. The subject can breathe freely during the imaging process without breath-holding, resulting in high usability. Real-time, adaptive trigger delay time adjustments can be made based on the respiratory motion state, ensuring that MR signal readings occur only during specific respiratory phases. Finally, the validity of the data and the decision to re-acquire are based on the actual respiratory phase. A water signal suppression module is introduced to remove the influence of respiratory cycle fluctuations on the CEST signal, improving the comparability of signals acquired at different bias frequencies and enhancing the accuracy of CEST. Therefore, this method solves the problems of related technologies, such as the inability to overcome the influence of respiratory motion on abdominal CEST, low feasibility, poor usability, and low accuracy.

[0036] Specifically, Figure 4 This is a schematic flowchart of a free-breathing abdominal chemical exchange saturation transfer imaging method provided in an embodiment of this application.

[0037] like Figure 4As shown, the free-breathing abdominal chemical exchange saturation transfer imaging method comprises the following steps:

[0038] In step S101, a respiratory motion signal of an imaging subject is collected.

[0039] The imaging subject can be a person receiving scanning, i.e., a subject.

[0040] The respiratory motion signal can be collected by a respiratory belt or obtained by monitoring the movement of the abdomen by an optical camera. The collection method is not limited, and those skilled in the art can select the collection method according to the actual situation.

[0041] In step S102, if a preset specific position of the respiratory motion signal is detected, a water signal suppression sequence module is triggered after a delay target time length, so that the water signal starts longitudinal relaxation recovery from 0.

[0042] The preset specific position of the respiratory motion signal can be obtained by a signal processing algorithm. The preset specific position of the respiratory motion signal can be a peak point (a transition point between the inspiration period and the expiration period), a peak valley point (a transition point from the expiration period to the inspiration period), or a midpoint of an uphill section or a downhill section (a midpoint of the inspiration period or the expiration period), or other calculated specific points. These specific positions are used as references for subsequent synchronous respiratory motion and imaging sequences.

[0043] The target time length (t d ≥ 0) is a trigger delay time, which can be calculated. The specific calculation method is described in the following embodiments.

[0044] It can be understood that the embodiments of the present application can use the water signal suppression sequence module after a delay target time length when the specific position of the respiratory motion signal of the imaging subject is detected, so that the water signal starts longitudinal relaxation recovery from 0.

[0045] It should be noted that the CEST (such as Figure 5 ) of the present application compared with the traditional CEST sequence, the new sequence adds a water signal suppression module in front of the CEST saturation module, so that the water signal starts longitudinal relaxation recovery from 0.

[0046] In the embodiments of the present application, before the delay target time length, the method further comprises: estimating a next respiratory cycle parameter according to the respiratory motion signal before the current time; and calculating the target time length according to the respiratory cycle parameter, the length of the water signal suppression sequence module, the expected respiratory phase of the preset MR signal reading, the first preset time length, and the second preset time length.

[0047] The respiratory cycle parameter includes the length of the inspiration period and the length of the expiration period.

[0048] wherein, the expected respiratory phase of MR signal reading is preset and fixed (such as 50% of expiration phase); the first preset time length (t wd ≥0) is as shown in the following formula (1) : Figure 5 The second preset time length (t cest ≥0) can be set according to specific conditions, as shown in the following formula (2) : Figure 5

[0049] It can be understood that, according to the respiratory motion signal before the current time, the respiratory parameters (inspiration length and expiration length) of the next respiratory cycle can be estimated, according to the two length values, the preset expected respiratory phase of MR signal reading, the time length of the water signal suppression sequence module, t wd and t cest , the target time length is calculated, and the target time length is adjusted in real time.

[0050] It should be noted that, the estimation of the inspiration length and expiration length of the next cycle does not only depend on the last respiratory cycle, but also depends on multiple previous respiratory cycles, for example, the average inspiration length and expiration length of the previous multiple respiratory cycles are taken as the estimated values of the next respiratory cycle, and the specific estimation method is not limited in the present application.

[0051] In the embodiments of the present application, the water signal suppression sequence module is triggered after the delay target time length, including: detecting a trigger signal according to the respiratory motion signal; counting according to the trigger signal until the delay target time length, and then applying the water signal suppression sequence module.

[0052] It can be understood that, according to the real-time collected respiratory motion signal, a trigger signal (such as the middle of inspiration) can be detected, and the trigger signal is counted until the delay target time length, and then the water signal suppression sequence module is triggered.

[0053] In step S103, the CEST saturation pulse of the second preset time length is applied after the delay of the first preset time length, and the MR signal reading of the imaging target is performed after the application of the CEST saturation pulse is completed, to obtain the MR image of the imaging target.

[0054] The imaging target is a certain abdominal organ of the imaging subject, such as liver, kidney or other organs.

[0055] It can be understood that, after the water signal suppression sequence module of the above steps is completed, the CEST saturation pulse of the second preset time length t cest is applied after the delay of the first preset time length t wd , so that the MR signal reading of the imaging target is performed, to obtain the MR image of the imaging target. ​

[0056] It should be noted that the present application adds a water signal suppression module before the CEST saturation pulse. The use of the water signal suppression module makes the signal evolution of the sequence only related to the sequence module after the module, and not related to t d and the length of the respiratory cycle, thereby overcoming the influence of respiratory cycle fluctuations on the CEST signal, improving the comparability of the acquired signal under different offset frequencies, and improving the accuracy of CEST. Traditional CEST imaging will perform a long delay time after MR signal reading, so that the longitudinal magnetization vector of water is fully recovered before the CEST saturation module is applied, reducing the influence on the quantitative analysis of the CEST signal. In the present application, the use of the water signal suppression module makes the longitudinal magnetization vector of water not fully recovered before the CEST saturation module is applied. The effect of this on CEST quantification can be corrected using the QUASS technique.

[0057] In the embodiment of the present application, MR signal reading is performed on the imaging target after the CEST saturation pulse is applied, and an MR image of the imaging target is obtained, including: calculating the real respiratory phase at the MR signal reading time according to the respiratory motion signal; if the difference between the real respiratory phase and the expected respiratory phase is greater than a preset threshold, discarding the corresponding MR signal and performing resampling; or if the respiratory motion of the imaging object is relatively stable, not discarding the MR signal.

[0058] It should be noted that the preset threshold can be set according to specific circumstances, and is not limited.

[0059] It can be understood that the embodiment of the present application will calculate the real respiratory phase at the MR signal reading time according to the respiratory motion signal after performing MR signal reading. When the real respiratory phase and the expected respiratory phase deviate greatly, the acquired MR signal will be discarded and resampled, thereby sufficiently reducing the CEST image artifacts and image position misalignment problems caused by respiratory motion.

[0060] It should be noted that after MR signal reading, it is determined whether the data is valid according to the actual respiratory phase, and then it is determined whether to perform data resampling. However, data validity judgment and resampling (i.e. the data acquired is always valid by default) can also not be performed. As long as the subject's breathing is relatively stable during scanning, the image quality is basically acceptable without data resampling.

[0061] Figure 5The midpoint of the uphill section of the respiratory motion signal (midpoint of the inspiration period) is used as a reference to trigger the imaging sequence (i.e., the timing of the water signal suppression module, the CEST saturation module, and the MR signal reading module). Therefore, the application time of the water signal suppression sequence module and the CEST saturation pulse module and the MR signal reading module is determined at one time, rather than being determined separately (i.e., no need to make a judgment of the inhalation signal and then make a judgment of the exhalation signal). If t cest , t wd , and the duration of the MR signal reading module is short, significantly shorter than the exhalation period, then the triggering can be performed during the exhalation period (i.e., using the exhalation period respiratory motion signal position as a reference).

[0062] The free-breathing abdominal chemical exchange saturation transfer imaging method according to the embodiments of the present application can use the detected respiratory motion signal for respiratory motion compensation, the subject can freely breathe during the imaging process, and therefore the method has high ease of use and is convenient for promotion in the clinic; the real-time and adaptive trigger delay time adjustment according to the respiratory motion state causes the MR signal reading to occur only at a specific respiratory phase, and finally the actual respiratory phase is used to judge the validity of the data and determine whether to perform resampling, which can effectively overcome the CEST image artifacts and image misalignment caused by respiratory motion; and the water signal suppression module is introduced, which removes the influence of respiratory cycle fluctuations on the CEST signal, improves the comparability of the acquired signals at different offset frequencies, and improves the accuracy of CEST.

[0063] Next, the free-breathing abdominal chemical exchange saturation transfer imaging system according to the embodiments of the present application is described with reference to the accompanying drawings.

[0064] Figure 6 is a block schematic diagram of the free-breathing abdominal chemical exchange saturation transfer imaging system according to the embodiments of the present application.

[0065] As shown in Figure 6 , the free-breathing abdominal chemical exchange saturation transfer imaging system 10 includes a respiratory motion detection module 101, a water signal suppression module 102, a CEST saturation module 103, and an MR signal reading module 104.

[0066] The respiratory motion detection module 101 is configured to acquire the respiratory motion signal of the imaging object. The water signal suppression module 102 is configured to, if the preset specific position of the respiratory motion signal is detected, trigger the application of the water signal suppression sequence module after a delay target duration, so that the water signal starts longitudinal relaxation recovery from 0. The CEST saturation module 103 is configured to apply a CEST saturation pulse for a second preset duration after a delay of a first preset duration. The MR signal reading module 104 is configured to perform MR signal reading on the imaging target after the application of the CEST saturation pulse is completed, to obtain an MR image of the imaging target.

[0067] In the embodiments of the present application, the system 10 further comprises a calculation module.

[0068] The calculation module is configured to estimate a next breathing cycle parameter according to the breathing motion signal before a target delay duration, and calculate the target duration according to the breathing cycle parameter, a duration of the water signal suppression sequence module, a preset expected breathing phase of MR signal reading, a first preset duration and a second preset duration.

[0069] In the embodiments of the present application, the MR signal reading module 104 is further configured to calculate a real breathing phase of the MR signal reading time according to the breathing motion signal, discard the corresponding MR signal and perform resampling if the difference between the real breathing phase and the expected breathing phase is greater than a preset threshold, or not discard the MR signal if the breathing motion of the imaging object is relatively stable.

[0070] In the embodiments of the present application, the water signal suppression module 102 is further configured to detect a trigger signal according to the breathing motion signal, and apply the water signal suppression sequence module after the target delay duration according to the timing of the trigger signal.

[0071] It should be noted that the foregoing description of the embodiment of the abdomen chemical exchange saturation transfer imaging method under free breathing also applies to the abdomen chemical exchange saturation transfer imaging system under free breathing of this embodiment, which will not be described here.

[0072] The abdomen chemical exchange saturation transfer imaging system under free breathing according to the embodiments of the present application adds a water signal suppression module before the CEST saturation pulse, and combines with the MR respiratory gating technology, so that the signal change of the tissue is no longer affected by the breathing cycle fluctuation, the comparability of the acquired signals under different bias frequencies is improved, and the accuracy of the CEST is improved; the detected breathing motion signal can be used for breathing motion compensation, the subject can breathe freely during the imaging process, and therefore the ease of use is high, and the system is easy to promote in the clinic; the real-time and adaptive trigger delay time adjustment is performed according to the breathing motion state, so that the MR signal reading only occurs at a specific breathing phase, and finally the effectiveness of the data is judged and it is determined whether resampling is performed according to the actual breathing phase, which can effectively overcome the CEST image artifacts and image misalignment caused by the breathing motion.

[0073] Figure 7 The medical device provided in the embodiments of the present application has the structure shown in the schematic diagram. The medical device can include:

[0074] The memory 701, the processor 702, and the computer program stored in the memory 701 and executable on the processor 702.

[0075] The processor 702 implements the free-breathing abdominal chemical exchange saturation transfer imaging method provided in the above embodiments when executing a program.

[0076] Further, the medical device further comprises:

[0077] The communication interface 703 is configured to communicate between the memory 701 and the processor 702.

[0078] The memory 701 is configured to store a computer program executable on the processor 702.

[0079] The memory 701 can include a high-speed RAM (Random Access Memory) memory, and can also include a nonvolatile memory, for example, at least one disk memory.

[0080] If the memory 701, the processor 702 and the communication interface 703 are implemented independently, the communication interface 703, the memory 701 and the processor 702 can be connected through a bus and communicate with each other. The bus can be an ISA (Industry Standard Architecture) bus, a PCI (Peripheral Component) bus or an EISA (Extended Industry Standard Architecture) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For the convenience of representation, Figure 7 Only one thick line is used in the figure, but it does not mean that there is only one bus or only one type of bus.

[0081] Optionally, in a specific implementation, if the memory 701, the processor 702 and the communication interface 703 are integrated on a chip, the memory 701, the processor 702 and the communication interface 703 can communicate with each other through an internal interface.

[0082] The processor 702 can be a CPU (Central Processing Unit), or an ASIC (Application Specific Integrated Circuit), or one or more integrated circuits configured to implement the embodiments of the present application.

[0083] The embodiments of the present application also provide a computer readable storage medium, which stores a computer program, and the program is executed by a processor to implement the free-breathing abdominal chemical exchange saturation transfer imaging method as above.

[0084] In the description of the application, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the application. In the description of the application, the illustrative description of the above terms is not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or N embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the description and the features of the different embodiments or examples, without contradiction.

[0085] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the application, the meaning of "N" is at least two, for example, two, three, etc., unless otherwise specifically limited.

[0086] Any process or method descriptions in flow charts or otherwise described herein can be understood as representing code modules, segments, or portions of code that include one or more executable instructions for implementing specific logic functions (or steps) in the process, and the various embodiments of the application contemplate that the modules, segments, or portions of code may, in some embodiments, be implemented by hardware, software, firmware, or any combination thereof. The various embodiments of the application contemplate that the order of the steps in the processes described herein can be altered, that other steps can be added, and that some steps can be eliminated, without departing from the scope of the application.

[0087] It should be understood that portions of the application can be implemented in hardware, software, firmware, or combinations thereof. In the above embodiments, the N steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. As in another embodiment, if implemented in hardware, any of the following technologies known in the art or their combinations can be used: discrete logic circuit with logic gate circuit for implementing logic functions on data signals, application specific integrated circuit with suitable combination logic gate circuit, programmable gate array, field programmable gate array, etc.

[0088] Those skilled in the art of the present technology can understand that all or part of the steps carried out by the above-mentioned embodiment method can be completed by a program instructing the relevant hardware, and the program can be stored in a computer readable storage medium. The program, when executed, includes one of the steps of the method embodiment or a combination thereof.

[0089] Although the embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary, and are not to be interpreted as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A free-breathing abdominal chemical exchange saturation transfer imaging method, characterized by, The method comprises the following steps: acquiring a respiratory motion signal of an imaging object; if a preset specific position of the respiratory motion signal is detected, triggering a water signal suppression sequence module after a target delay time, so that the water signal starts longitudinal relaxation recovery from 0; before the target delay time, further comprising: estimating a next respiratory cycle parameter according to the respiratory motion signal before the current time; calculating the target time according to the respiratory cycle parameter, the length of the water signal suppression sequence module, a preset expected respiratory phase of MR signal reading, a first preset time and a second preset time; applying a CEST saturation pulse of the second preset time after delaying the first preset time, and performing MR signal reading on the imaging object after the CEST saturation pulse is applied to obtain an MR image of the imaging object.

2. The method of claim 1, wherein, The MR signal reading on the imaging object after the CEST saturation pulse is applied to obtain an MR image of the imaging object comprises: calculating a real respiratory phase at the MR signal reading time according to the respiratory motion signal; if the difference between the real respiratory phase and the expected respiratory phase is greater than a preset threshold, discarding the MR signal corresponding to the MR signal reading and re-sampling; or if the respiratory motion of the imaging object is relatively stable, not discarding the MR signal.

3. The method of claim 1, wherein, The triggering of the water signal suppression sequence module after the target delay time comprises: detecting a trigger signal according to the respiratory motion signal; counting according to the trigger signal until the target delay time is delayed, and then applying the water signal suppression sequence module.

4. A free-breathing abdominal chemical exchange saturation transfer imaging system, comprising: It comprises: a respiratory motion detection module for acquiring a respiratory motion signal of an imaging object; a water signal suppression module for triggering the application of a water signal suppression sequence module after a target delay time if a preset specific position of the respiratory motion signal is detected, so that the water signal starts longitudinal relaxation recovery from 0; a CEST saturation module for applying a CEST saturation pulse of a second preset time after delaying a first preset time; an MR signal reading module for performing MR signal reading on the imaging object after the CEST saturation pulse is applied to obtain an MR image of the imaging object; a calculation module for estimating a next respiratory cycle parameter according to the respiratory motion signal before the current time before the target delay time; calculating the target time according to the respiratory cycle parameter, the length of the water signal suppression sequence module, a preset expected respiratory phase of MR signal reading, the first preset time and the second preset time.

5. The system of claim 4, wherein, The MR signal reading module is further used for: calculating a real respiratory phase at the MR signal reading time according to the respiratory motion signal; if the difference between the real respiratory phase and the expected respiratory phase is greater than a preset threshold, discarding the MR signal corresponding to the MR signal reading and re-sampling; or if the respiratory motion of the imaging object is relatively stable, not discarding the MR signal.

6. The system of claim 4, wherein, The water signal suppression module is further used for: detecting a trigger signal according to the respiratory motion signal; counting according to the trigger signal until the target delay time is delayed, and then applying the water signal suppression sequence module.

7. A medical device, characterized by It comprises: - a memory, a processor and a computer program stored on the memory and runable on the processor, the processor executing the program to implement the free-breathing abdominal chemical exchange saturation transfer imaging method according to any one of claims 1-3.

8. A computer-readable storage medium having stored thereon a computer program, characterized in that, The program is executed by the processor for implementing the free-breathing abdominal chemical exchange saturation transfer imaging method according to any one of claims 1-3.

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