Methods and magnetic resonance imaging systems for acquiring magnetic resonance imaging data

Abstract

Embodiments of the present invention provide a magnetic resonance imaging system and a method for acquiring magnetic resonance imaging data. The method includes: applying a fat suppression pulse before the start of any repetition time in an imaging sequence; performing multiple echoes during the repetition time, wherein during each echo in the multiple echoes, first image data when water and fat are in phase and second image data when water and fat are out of phase are acquired; and acquiring fat-suppressed image data based on the first image data and the second image data.

Description

Technical Field

[0001] The embodiments disclosed in this invention relate to medical imaging technology, and more specifically to a method and a magnetic resonance imaging system for acquiring magnetic resonance imaging data. Background Technology

[0002] Magnetic resonance imaging (MRI), a medical imaging modality, can acquire images of the human body without using X-rays or other ionizing radiation. MRI utilizes a magnet with a strong magnetic field to generate a static magnetic field B0. When the area to be imaged is positioned within the static magnetic field B0, the nuclear spins associated with the hydrogen nuclei in the tissue become polarized, resulting in a longitudinal magnetization vector on a macroscopic scale. When a radio frequency field B1 is applied, intersecting the direction of the static magnetic field B0, the direction of proton rotation changes, resulting in a transverse magnetization vector on a macroscopic scale. After the radio frequency field B1 is removed, the transverse magnetization vector decays in a spiral pattern until it returns to zero. During this decay process, a free-inductance decay signal is generated, which can be acquired as an MRI signal. Based on this acquired signal, an image of the tissue area to be imaged can be reconstructed.

[0003] The precession frequencies of protons in water and fat in human tissues differ, which can cause chemical shift artifacts during magnetic resonance imaging. To remove chemical shift artifacts or other artifacts caused by fat tissue, or to meet certain clinical diagnostic needs, various fat suppression methods have been proposed in the current technology. However, it is still difficult to obtain ideal images of water tissue, especially when the static magnetic field B0 or ​​radio frequency field B1 is not uniform.

[0004] While existing techniques propose an improved fat suppression method—acquiring image data of water and fat tissue in phase during one repetition time of the imaging sequence and out of phase during another repetition time—and then using image processing algorithms to obtain pure water image data, this method, although capable of acquiring water tissue images with better image quality, requires two repetition times to obtain the desired image, resulting in a longer scanning time and hindering process optimization.

[0005] Therefore, there is a need for a new method for acquiring magnetic resonance imaging data that can acquire images with a shorter scan time and effectively remove various artifacts caused by chemical shifts in the images. Summary of the Invention

[0006] An embodiment of the present invention provides a method for acquiring magnetic resonance imaging data, comprising: applying a fat suppression pulse before the start of any repetition time of an imaging sequence; performing multiple echoes during the repetition time, wherein during each echo of the multiple echoes, first image data when water and fat are in phase and second image data when water and fat are out of phase are acquired; and acquiring fat suppression image data based on the first image data and the second image data.

[0007] An embodiment of the present invention provides a magnetic resonance imaging system, comprising: a scanner for acquiring data of an imaging object; a controller unit coupled to the scanner and configured to control the scanner to execute an imaging sequence, wherein: a fat suppression pulse is applied before the start of any repetition time of the imaging sequence; multiple echoes are executed during the repetition time, wherein first image data when water and fat are in phase and second image data when water and fat are out of phase are acquired during each echo of the multiple echoes; and a data processing unit configured to acquire fat suppression image data based on the first image data and the second image data.

[0008] It should be understood that the brief description provided above is intended to introduce some concepts further described in the detailed embodiments in a simplified form. This is not intended to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims following the detailed description. Furthermore, the claimed subject matter is not limited to the implementation of any shortcomings mentioned above or in any paragraph of this disclosure. Attached Figure Description

[0009] The invention will be better understood by referring to the accompanying drawings and by reading the following description of non-limiting embodiments, in which:

[0010] Figure 1 This is a block diagram of a magnetic resonance imaging system according to one embodiment.

[0011] Figure 2 This is a flowchart of a method for acquiring magnetic resonance image data according to an embodiment of the present invention.

[0012] Figure 3 This is a schematic diagram of analyzing first and second image data with opposite chemical shift directions.

[0013] Figure 4 It is used according to the embodiments of the present invention. Figure 2 An example of an imaging sequence for the method shown.

[0014] Figure 5 This is a flowchart of a method for acquiring magnetic resonance imaging data based on the MRI system 1 according to an embodiment of the present invention.

[0015] Figure 6 It is a set of human tissue images obtained using existing fat suppression techniques.

[0016] Figure 7 and Figure 8 These are a set of human tissue images obtained using the methods described in the embodiments of the present invention. Detailed Implementation

[0017] The various embodiments described below include those using imaging systems (such as, Figure 1 A method for acquiring data from an imaging object (e.g., the human body) using a magnetic resonance imaging (MRI) system, thereby enabling the image reconstructed based on that data to have better fat suppression, for example, reducing artifacts caused by fat signals, such as chemical shift artifacts, chemical shift edge artifacts, etc.

[0018] Figure 2 A flowchart illustrating a method for acquiring medical image data according to one embodiment is shown. Figure 2 As shown, the method includes steps S21, S22 and S23.

[0019] In step S21, a fat suppression pulse is applied before the start of any repetition time of the imaging sequence.

[0020] Those skilled in the art will understand that the aforementioned imaging sequence refers to a combination of pulses with specific amplitude, width, direction, and timing applied during MRI, which may include, for example, radio frequency pulses and gradient pulses. The radio frequency pulse may include, for example, radio frequency excitation pulses used to excite protons in the human body to resonate, and the gradient pulse may include, for example, slice selection gradient pulses, phase-coded gradient pulses, frequency-coded gradient pulses, etc. In one embodiment, the repetition time mentioned above refers to the time interval between two adjacent radio frequency excitation pulses of the imaging sequence.

[0021] In step S22, multiple echoes are performed within the repetition time, wherein during each of the multiple echoes, first image data when water and fat are in phase and second image data when water and fat are out of phase are acquired.

[0022] In step S23, fat suppression image data is obtained based on the first image data and the second image data described above.

[0023] In embodiments of the present invention, a fat suppression pulse is applied before the repetition time, so that the fat tissue signal is suppressed or its intensity is reduced during the repetition time, thereby producing no or a weaker magnetic resonance signal of fat tissue. Furthermore, by acquiring both first image data when water and fat are in phase and second image data when they are out of phase within the same repetition time, it is possible to acquire both types of data in a shorter time and obtain image data of one type of tissue suppressed based on the two types of data, thereby achieving a better artifact removal effect without increasing the scanning time.

[0024] In one embodiment, during each echo, a first gradient readout pulse is applied when the water and fat are in phase to acquire the first image data, and a second gradient readout pulse is applied when the water and fat are out of phase to acquire the second image data. The aforementioned gradient readout pulse is a frequency-coded gradient pulse, which is used to acquire magnetic resonance signals with positional information.

[0025] Furthermore, the chemical shift directions in the first and second image data acquired during each echo are opposite. This allows for further removal of chemical shift edge artifacts. Because the chemical shift of water and adipose tissue causes the adipose tissue in the image to shift to one side, acquiring two types of image data at the same repetition time results in one side of the imaged area being a bright signal and the other side a dark signal at the edge. Figure 3 For example, by reversing the chemical shift direction, water and fat signals are present on each edge (e.g., (W+F) / 2 instead of (F+F) / 2 on the left side of the data, and (WF) / 2 instead of (WW) / 2 on the right side of the data), reducing the brightness difference at the edges and making the image more uniform.

[0026] For example, fat-suppressed image data can be obtained using the following formulas (1) to (3).

[0027] I1=F1+W+F+W2 (1)

[0028] I2=W1+WF-F2 (2)

[0029] I3=(I1+I2) / 2=(F1+W1) / 2+2*W / 2+(W2-F2) / 2 (3)

[0030] Wherein, I1 and I2 are the first image data and the second image data, respectively; I3 is the water tissue image data after suppressing adipose tissue; W represents the water tissue signal in the middle region of the image; F represents the adipose tissue signal in the middle region of the image; W1 and W2 represent the water tissue signals at the edges of the two sides of the image (such as the left and right sides), respectively; F1 and F2 represent the adipose tissue signals at the edges of the two sides of the image (such as the left and right sides), respectively.

[0031] Furthermore, since a fat suppression pulse is applied before the repetition time, the fat signals F1 and F2 are extremely low when the fat tissue signal intensity is extremely low. At this time, I3≈W1 / 2+W+W2 / 2, so higher quality images can be obtained. Among them, the fat suppression effect is better, effectively removing chemical shift artifacts, chemical shift edge artifacts and other image problems caused by fat signals.

[0032] In one embodiment, the first gradient readout pulse and the second gradient readout pulse can be made to have opposite directions, so that the chemical shift directions in the first image data and the second image data are opposite.

[0033] Furthermore, the first and second gradient readout pulses are applied consecutively. This design enables the simultaneous acquisition of first and second image data within one echo cycle, reducing scan time.

[0034] Furthermore, a first gradient readout pulse is applied during each echo period, and two second gradient readout pulses are applied before and after the first gradient readout pulse, respectively. This symmetrical approach ensures a balanced readout gradient area and allows for the simultaneous acquisition of first and second image data within one echo cycle, reducing scanning time.

[0035] When two second image data are acquired by applying two second gradient readout pulses during each echo, fat suppression image data is obtained based on the average image data of the two second image data obtained when applying the two second gradient pulses and the first image data. Specifically, the second image data I2 mentioned in the above formulas (1) and (3) is obtained by averaging the image data obtained under the same gradient readout pulses.

[0036] Figure 4 This is an example of an imaging sequence for the method described above according to an embodiment of the present invention, wherein at least a portion of the sequence waveform at at least one repetition time of the imaging sequence is shown.

[0037] like Figure 4As shown, the imaging sequence includes a fat suppression pulse P41 applied before any repetition time TR, and within that repetition time TR, after the applied radio frequency excitation pulse P42 ends, gradient readout pulses P43, P44, and P45 are applied sequentially. Preferably, the amplitude and width of gradient readout pulses P43, P44, and P45 are the same, and the direction of gradient readout pulse P44 is opposite to the directions of gradient readout pulses P43 and P45. Gradient readout pulse P44 can serve as the first gradient pulse, applied when water and fat are in phase, and gradient readout pulses P43 and P45 can serve as the second gradient pulses, applied when water and fat are out of phase.

[0038] The imaging sequence in this example can also include other pulses, which may be located, for example, in... Figure 3 Between any two adjacent pulses, for example, the radio frequency refocusing pulse P46 applied after the end of the radio frequency excitation pulse P41. The examples of this invention are for illustrative purposes only. Figure 3 The timing relationships between the individual pulses are shown, but the timing relationships between these pulses and other pulses not shown are not limited.

[0039] In the above example, the radio frequency excitation pulse can be, for example, a 90-degree radio frequency pulse, and the fat suppression pulse can be one or more of the following: a frequency-selective suppression pulse, a spatial presaturation pulse, an inverted fat suppression pulse, or an adiabatic pulse.

[0040] Figure 4 Only one form of imaging sequence that can be applied to the above methods is shown, and it is not intended to limit the scope of protection of the present invention.

[0041] The above-described method for acquiring magnetic resonance image data can be achieved through, for example... Figure 1 The magnetic resonance (MRI) system 1 shown is used to implement this. In other embodiments, the MRI system 1 described above is only an example. In other embodiments, the MRI system 1 can have various variations, as long as it can acquire image data from the imaging object.

[0042] like Figure 1As shown, the MRI system 1 includes at least a scanner 10, a controller unit 20, and a data processing unit 30. The scanner 10 can be used to acquire data of the imaging object. The controller unit 20 is coupled to the scanner 10 to control the operation of the scanner 10, for example, controlling the scanner 10 to perform the steps S21-S22 described above, wherein: a fat suppression pulse is applied before the start of any repetition time in the imaging sequence; multiple echoes are executed during the repetition time, wherein during each echo in the multiple echoes, first image data when water and fat are in phase and second image data when water and fat are out of phase are acquired. The data processing unit 30 can be used to acquire fat-suppressed image data based on the first and second image data.

[0043] In one example, scanner 10 may include components disposed between scanning chambers and devices, such as a main magnet 11, an RF transmitting coil 12, an RF generator 13, a gradient coil system 17, a gradient coil driver 18, and an RF receiving coil 19.

[0044] The main magnet 11 typically includes, for example, a toroidal superconducting magnet mounted within a toroidal vacuum container. This toroidal superconducting magnet defines a cylindrical space surrounding the object 100 and generates a constant static magnetic field, such as a static magnetic field B0, along the Z-direction of the cylindrical space. The MRI system 1 utilizes the generated static magnetic field B0 to transmit a magnetic field pulse signal to the object 16 placed in the imaging space, thereby ordering the precession of protons within the object 16 and generating a longitudinal magnetization vector.

[0045] The radio frequency generator 13 is used to generate radio frequency pulses, which may include radio frequency excitation pulses. These excitation pulses are amplified (e.g., by a radio frequency power amplifier (not shown)) and applied to the RF transmitting coil 12, causing the RF transmitting coil 12 to emit an RF magnetic field B1 orthogonal to the static magnetic field B0 to the object 16 to excite the atomic nuclei in the object 16, and the longitudinal magnetization vector is transformed into a transverse magnetization vector.

[0046] After the radio frequency excitation pulse ends, the transverse magnetization vector of object 16 gradually recovers to zero, generating a free induction decay signal, which is the magnetic resonance signal that can be acquired.

[0047] Radiofrequency pulses may also include pulses with other functions, such as radiofrequency pulses used to suppress signals from specific tissues. More specifically, for example, fat suppression pulses. When a fat suppression pulse is applied before the radiofrequency excitation pulse, the adipose tissue is not excited after the radiofrequency excitation pulse is applied, so the acquired magnetic resonance signal does not contain adipose tissue signals or contains only small adipose tissue signals.

[0048] The radio frequency generator 13 can be used to generate the aforementioned radio frequency excitation pulse or fat suppression pulse in response to the imaging sequence control signal issued by the controller unit 20.

[0049] In one embodiment, the RF transmitting coil 12 can be a body coil that can be connected to a transmit / receive (T / R) switch (not shown). By controlling the transmit / receive switch, the body coil can be switched between transmit and receive modes. In the receive mode, the body coil can be used to receive magnetic resonance signals from the object 16.

[0050] The scanner 10 may also include a gradient coil system 17 and a gradient driver 18. The gradient coil system 17 forms a gradient magnetic field in the imaging space to provide three-dimensional position information for the magnetic resonance signal. The magnetic resonance signal can be received by an RF receiving coil 19 or a body coil in receiving mode. The data processing unit 30 can process the received magnetic resonance signal to obtain the desired image or image data.

[0051] Specifically, the gradient coil system 17 may include three gradient coils, each of which generates a gradient magnetic field tilted to one of three mutually perpendicular spatial axes (e.g., the X-axis, Y-axis, and Z-axis), and generates gradient fields in each of the slice selection direction, phase encoding direction, and frequency encoding direction according to the imaging conditions. More specifically, the gradient coil system 17 applies a gradient field in the slice selection direction of the object 16 to select a slice; and the RF transmit coil 12 transmits an RF excitation pulse to the selected slice of the object 16 and excites the slice. The gradient coil system 17 also applies a gradient field in the phase encoding direction of the object 16 to perform phase encoding of the magnetic resonance signal of the excited slice. The gradient coil system 17 then applies a gradient field in the frequency encoding direction of the object 16 to perform frequency encoding of the magnetic resonance signal of the excited slice.

[0052] The gradient coil driver 18 is used to provide appropriate power signals to the three gradient coils respectively in response to the sequence control signals issued by the controller unit 30.

[0053] The scanner 10 may also include a data acquisition unit 14 for acquiring magnetic resonance signals received by the RF surface coil 19 or the volume coil. The data acquisition unit 14 may include, for example, an RF preamplifier (not shown), a phase detector (not shown), and an analog-to-digital converter (not shown). The RF preamplifier is used to amplify the magnetic resonance signals received by the RF surface coil 19 or the volume coil, the phase detector is used to perform phase detection on the amplified magnetic resonance signals, and the analog-to-digital converter is used to convert the phase-detected magnetic resonance signals from analog signals to digital signals.

[0054] The digitized magnetic resonance signals described above can be processed, such as calculated and reconstructed, by the data processing unit 30. The data processing unit 30 may include a computer and a storage medium on which a predetermined data processing program to be executed by the computer is recorded. The data processing unit 30 may be connected to the controller unit 20 and execute data processing based on control signals received from the controller unit 20. The data processing unit 30 may also be connected to the data acquisition unit 14 to receive the magnetic resonance signals output by the data acquisition unit 14 in order to perform the aforementioned data processing.

[0055] The controller unit 20 may include a computer and a storage medium for storing programs executable by the computer. When the computer executes the program, it can cause multiple components of the scanner 11 to perform operations corresponding to the imaging sequence described above. It can also cause the data processing unit 30 to perform predetermined data processing.

[0056] The storage media of the controller unit 20 and the data processing unit 30 may include, for example, ROM, floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, or non-volatile memory card.

[0057] The MRI system 1 also includes a stage 40 for placing the object 16 thereon. The object 16 can be moved into or out of the imaging space by moving the stage 26 based on control signals from the controller unit 20.

[0058] The MRI system 1 also includes an operation console 50 connected to the controller unit 20. The operation console 50 can be located in the operating room or scanning room. The controller unit 20 receives and processes operation signals input to the operation console 50, and controls the operating states of components such as the stage 40 and the scanner 10 based on these operation signals. The operation signals may include, for example, scanning protocols and parameters selected manually or automatically. The scanning protocol may include the aforementioned imaging sequence. The controller unit 20 also controls the data processing unit 30 based on the operation signals received from the operation console 50 to obtain the desired image.

[0059] The operation console 50 may include user input devices, such as a keyboard and mouse, through which the operator can input operation signals / control signals to the controller unit 20.

[0060] The MRI system 1 may also include a display unit 60, which can be connected to the operation console 50 to display the operation interface, and can also be connected to the data processing unit 30 to display images.

[0061] Figure 5 This is a flowchart of a method for acquiring magnetic resonance imaging data based on the MRI system 1 according to an embodiment of the present invention.

[0062] In step S501, in response to an operation signal from the operation console 50, the stage 40 is moved to position the imaging object (e.g., the patient) 16 in the imaging space.

[0063] In step S502, the controller unit 20 receives operator input regarding patient information and the imaging protocol. Specifically, the operator can select the protocol based on the anatomical structures to be scanned. The imaging protocol may include the region of interest (ROI), field of view (FOV), imaging sequences to be performed, etc.

[0064] In step S503, the stage 40 is moved to position the area to be scanned of the imaging object 16 at the scanning center.

[0065] In step S504, the radio frequency generator 13, in response to the requirements of the timing, amplitude, and angle of the radio frequency pulses in the imaging sequence issued by the controller unit 20, transmits a fat suppression pulse P41 to the radio frequency transmitting coil 12.

[0066] In step S505, the radio frequency generator 13 responds to the requirements of the imaging sequence issued by the controller unit 20 regarding the timing, amplitude, and angle of the radio frequency pulses and transmits a radio frequency excitation pulse P42 to the radio frequency transmitting coil 12. The radio frequency excitation pulse P42 can be transmitted immediately after the fat suppression pulse P41 ends.

[0067] In step S506, the radio frequency generator 13, in response to the requirements of the imaging sequence issued by the controller unit 20 regarding the timing, amplitude, and angle of the radio frequency pulses, transmits a radio frequency refocusing pulse P46 to the radio frequency transmitting coil 12.

[0068] In step S507, the gradient coil driver 18, in response to the requirements of the imaging sequence of the controller unit 20 regarding the timing, amplitude, and width of the gradient pulses, transmits slice selection gradient pulses to the gradient coil system 17.

[0069] In step S508, the gradient coil driver 18 transmits phase-coded gradient pulses to the gradient coil system 17 in response to the requirements of the timing, amplitude, and width of the gradient pulses in the imaging sequence issued by the controller unit 20.

[0070] In step S509, the gradient coil driver 18, in response to the requirements of the imaging sequence issued by the controller unit 20 regarding the timing, amplitude, and width of the gradient pulses, transmits three symmetrical frequency-coded gradient pulses (e.g., gradient readout pulses P43, P44, and P45) to the gradient coil system 17. The magnetic resonance signal of the object is received via the radio frequency surface coil 19 or the volume coil, respectively, in response to these three symmetrical frequency-coded gradient pulses.

[0071] In step S510, the data acquisition unit 14 responds to the data acquisition control signal issued by the controller unit 20 to acquire and preprocess the magnetic resonance signal received in each echo, so as to obtain the first image data and the second image data respectively.

[0072] The above step S509 can be repeated multiple times until the current repetition time ends. After the current repetition time ends, steps S504 to S510 are repeated to execute the next repetition time of the imaging sequence.

[0073] In step S511, the data processing unit 30 responds to the data processing control signal issued by the controller unit 20 and performs calculation processing and image reconstruction processing on the first image data and the second image data to obtain fat suppression image data.

[0074] In step S512, the data processing unit 30 responds to the image display signal sent by the controller unit 20 and displays the image obtained by reconstruction based on the first image data, the second image data, or the fat suppression image data through the display unit 60.

[0075] Based on the above description, embodiments of the present invention can provide an improved magnetic resonance imaging system, comprising:

[0076] A scanner, used to acquire data about an image object;

[0077] A controller unit, coupled to the scanner, is used to control the scanner to execute an imaging sequence, wherein: a fat suppression pulse is applied before the start of any repetition time of the imaging sequence; multiple echoes are executed during the repetition time, wherein first image data when water and fat are in phase and second image data when water and fat are out of phase are acquired during each echo in the multiple echoes; and,

[0078] A data processing unit is used to acquire fat-suppressed image data based on first image data and second image data.

[0079] Furthermore, the chemical shift directions in the first and second image data acquired during each echo are opposite.

[0080] Furthermore, during each echo, the controller unit controls the scanner to apply a first gradient readout pulse when water and fat are in phase to obtain first image data, and to apply a second gradient readout pulse when water and fat are out of phase to obtain second image data, wherein the first gradient readout pulse and the second gradient readout pulse are in opposite directions.

[0081] Furthermore, the first gradient readout pulse and the second gradient readout pulse are applied consecutively.

[0082] Furthermore, the controller unit controls the scanner to apply a first gradient pulse once during each echo and to apply two second gradient pulses before and after the first gradient pulse, respectively.

[0083] Furthermore, the data processing unit is used to acquire the average image data of the two second image data obtained when the second gradient pulse is applied twice, and to acquire fat suppression image data based on the first image data and the average image data.

[0084] Figure 6 These are a set of human tissue images obtained using existing fat suppression techniques. Due to the unsatisfactory fat suppression effect, obvious bright signal artifact areas appeared, resulting in uneven images.

[0085] Figure 7 and Figure 8 These are a set of human tissue images obtained using the method described in the embodiments of the present invention, wherein Figure 7 The image shown is obtained by acquiring both first image data when water and fat are in phase and second image data when water and fat are out of phase during a repetition period. Figure 8 Further images obtained when fat suppression pulses were applied before the repetition time are shown for comparison. Figure 6 and Figure 7 , Figure 8 , Figure 7 , Figure 8 The images shown clearly show the elimination of chemical shift artifacts and chemical shift edge artifacts. (Comparison) Figure 7 , Figure 8 As indicated by the middle arrow, Figure 8 The images in the image further eliminated chemical shift edge artifacts.

[0086] As used herein, elements or steps described in the singular and prefixed with the words “a” or “an” should be understood to not exclude a plural of said elements or steps unless such exclusion is explicitly stated. Furthermore, reference to “one embodiment” of the invention is not intended to be construed as excluding the existence of additional embodiments that simultaneously incorporate the described features. Moreover, unless explicitly stated otherwise, embodiments “comprising,” “including,” or “having” elements or multiple elements having a particular property may include additional such elements that do not have that property. The terms “including” and “in which” are used as concise linguistic equivalents to the corresponding terms “comprising” and “wherein.” Furthermore, in the appended claims, the terms “first,” “second,” and “third,” etc., are used merely as designations and are not intended to impose numerical requirements or a particular order of position on their objects.

[0087] This written description uses examples to disclose the invention, including the best mode, and enables those skilled in the art to implement the invention, including making and using any device or system and performing any covered methods. The scope of patent protection for this invention is defined by the claims and may include other examples known to those skilled in the art. Such other examples are intended to fall within the scope of the claims if they have structural elements that are not indistinguishable from the literal language of the claims, or if they include equivalent structural elements that are not substantially indistinguishable from the literal language of the claims.

Claims

1. A method for acquiring magnetic resonance imaging data, comprising: A fat suppression pulse is applied before the start of any repetition time in the imaging sequence; Multiple echoes are performed within the repetition time, wherein during each echo of the multiple echoes, first image data when water and fat are in phase and second image data when water and fat are out of phase are acquired. Fat suppression image data is obtained based on the first image data and the second image data. Specifically, a first gradient pulse is applied once during each echo period, and two second gradient pulses are applied before and after the first gradient pulse, respectively. The step of obtaining fat suppression image data based on the first image data and the second image data includes: Fat suppression image data is obtained based on the first image data and the average image data of the two second image data obtained when the two second gradient pulses are applied.

2. The method as described in claim 1, characterized in that, The chemical shift directions in the first and second image data acquired during each echo are opposite.

3. The method as described in claim 2, characterized in that, During each echo, a first gradient readout pulse is applied when water and fat are in phase to obtain the first image data, and a second gradient readout pulse is applied when water and fat are out of phase to obtain the second image data, wherein the first gradient readout pulse and the second gradient readout pulse are in opposite directions.

4. The method as described in claim 3, characterized in that, The first gradient readout pulse and the second gradient readout pulse are applied consecutively.

5. A magnetic resonance imaging system, comprising: A scanner, used to acquire data of an image object; A controller unit, coupled to the scanner, is configured to control the scanner to execute an imaging sequence, wherein: a fat suppression pulse is applied before the start of any repetition time of the imaging sequence; multiple echoes are executed within the repetition time, wherein during each echo of the multiple echoes, first image data when water and fat are in phase and second image data when water and fat are out of phase are acquired; and, A data processing unit is configured to acquire fat suppression image data based on the first image data and the second image data. The controller unit controls the scanner to apply a first gradient pulse once during each echo and to apply two second gradient pulses before and after the first gradient pulse, respectively. The data processing unit is used to acquire the average image data of the two second image data obtained when the second gradient pulse is applied twice, and to acquire fat suppression image data based on the first image data and the average image data.

6. The system as described in claim 5, characterized in that, The chemical shift directions in the first and second image data acquired during each echo are opposite.

7. The system as described in claim 6, characterized in that, During each echo, the controller unit controls the scanner to apply a first gradient readout pulse when water and fat are in phase to obtain the first image data, and to apply a second gradient readout pulse when water and fat are out of phase to obtain the second image data, wherein the first gradient readout pulse and the second gradient readout pulse are in opposite directions.

8. The system as described in claim 7, characterized in that, The first gradient readout pulse and the second gradient readout pulse are applied consecutively.

Images