Magnetic resonance imaging method, system, electronic device and medium for lungs

Abstract

The present invention provides a method, system, electronic device, and medium for magnetic resonance imaging of the lungs. The method includes: applying a gradient magnetic field in a layer direction to a target to be imaged; when the gradient of the gradient magnetic field begins to climb, hard pulse excitation is performed on the target to be imaged, and the hard pulse is frequency modulated based on a preset frequency modulation range to generate a magnetic resonance signal; when the hard pulse excitation is stopped, spiral acquisition is performed on the magnetic resonance signal to obtain raw imaging data of the target to be imaged; based on preset reconstruction rules, the raw imaging data is reconstructed to obtain target imaging. The method, system, electronic device, and medium for magnetic resonance imaging of the lungs provided by the present invention can effectively shorten the echo time and imaging time, and have a high signal-to-noise ratio and high resolution.

Description

Technical Field

[0001] The present invention relates to the field of magnetic resonance imaging technology, and in particular to a magnetic resonance imaging method, system, electronic equipment and medium for lungs. Background Art

[0002] Currently, the primary method for clinical lung imaging is computed tomography (CT). CT uses the varying X-ray absorption and transmittance of different tissues to obtain cross-sectional images of the body. However, CT is radioactive and is particularly unsuitable for children, pregnant women, and those requiring longitudinal follow-up lung imaging.

[0003] Compared to CT, magnetic resonance imaging (MRI) technology can achieve imaging without invasion and ionizing radiation. In recent years, MRI technology has achieved relatively rapid development and is considered to be an imaging technology with great application prospects.

[0004] The existing magnetic resonance imaging technologies for the lungs mainly include the following schemes: 1. Half-pulse excitation ultrashort echo sequence, that is, the first half of the pulse uses a positive slice selection gradient, and the second half uses a gradient of equal size and opposite direction. The two halves of the pulse excitation are combined to form a complete raw data. However, the disadvantage of this scheme is that separate excitation may introduce artifacts caused by volume and physiological motion between the two separate excitations, low signal-to-noise ratio, low resolution, and large imaging errors. 2. Pulse-excited ultrashort echo sequence, that is, the entire area is excited by pulses, no layer selection gradient is required, and three-dimensional trajectory acquisition is required. The spoke-shaped acquisition method is generally used. The disadvantage is that a large number of radial projections are required to meet the Nyquist sampling theorem, which greatly prolongs the imaging time. 3. Use selective radio frequency pulses and layer selection gradients to excite part of the target to be imaged. The disadvantage is that layer encoding and in-plane encoding require a lot of phase encoding time, which prolongs the echo time. Summary of the Invention

[0005] The present invention provides a method, system, electronic device and medium for magnetic resonance imaging of the lungs, which are used to solve the problems of low signal-to-noise ratio, low resolution, long imaging time and long echo time in magnetic resonance imaging solutions for the lungs in the prior art.

[0006] The present invention provides a method for magnetic resonance imaging of the lungs, comprising:

[0007] Applying a gradient magnetic field in a slice direction to the target to be imaged;

[0008] When the gradient of the gradient magnetic field starts to climb, hard pulse excitation is performed on the target to be imaged, and the hard pulse is frequency modulated based on a preset frequency modulation range, thereby generating a magnetic resonance signal;

[0009] When the hard pulse excitation is stopped, spirally acquiring the magnetic resonance signal to obtain original imaging data of the target to be imaged;

[0010] Based on a preset reconstruction rule, the original imaging data is reconstructed to obtain target imaging.

[0011] Optionally, before the step of performing hard pulse excitation on the target to be imaged when the gradient of the gradient magnetic field starts to rise, the method further includes:

[0012] Determining an expected maximum echo time based on a preset maximum hardware gradient field strength, a maximum hardware gradient switching rate, and a hard pulse duration;

[0013] Determining an estimated minimum echo time based on a preset radio frequency switching time and the hard pulse duration;

[0014] Determine whether the expected maximum echo time and the expected minimum echo time meet the preset echo time threshold range, obtain the judgment result and provide feedback; and, based on the expected maximum echo time and / or the expected minimum echo time, determine the echo time verification range, the echo time verification range is used to verify the actual echo time obtained when the magnetic resonance signal acquisition is completed, and adjust the hard pulse excitation-related parameters and the spiral acquisition-related parameters based on the verification result.

[0015] Optionally, based on a preset maximum hardware gradient field strength, a maximum hardware gradient switching rate, and a hard pulse duration, a mathematical expression for determining the expected maximum echo time is:

[0016] TE max =2×(G / Slew rate)+ΔT Hard / 2

[0017] Among them, TE max represents the expected maximum echo time, G represents the maximum hardware gradient field strength, Slew rate represents the maximum hardware gradient switching rate, ΔT Hard Indicates the hard pulse duration;

[0018] Based on the preset RF switching time and the hard pulse duration, the mathematical expression for determining the expected minimum echo time is:

[0019] TE min =ΔT Hard / 2+T s

[0020] Among them, TE min Indicates the expected minimum echo time, T s Indicates the RF switching time.

[0021] Optionally, when the gradient of the gradient magnetic field begins to climb, the step of performing hard pulse excitation on the target to be imaged includes:

[0022] When the gradient of the gradient magnetic field starts to climb, hard pulse excitation of the target to be imaged begins;

[0023] During the hard pulse excitation process, based on a preset moving step size and number of movements, the hard pulse is controlled to move gradually toward a target direction; the target direction includes: a first target direction and a second target direction. When the gradient of the gradient magnetic field is positive, the hard pulse is controlled to move gradually toward the first target direction; when the gradient of the gradient magnetic field is negative, the hard pulse is controlled to move gradually toward the second target direction.

[0024] Optionally, the step of frequency modulating the hard pulse based on a preset frequency modulation range to generate a magnetic resonance signal includes:

[0025] Based on a preset frequency modulation range, the original frequency range preset for the hard pulse is expanded to obtain a target frequency range;

[0026] Based on the target frequency range, hard pulse excitation is performed on the target to be imaged, thereby generating the magnetic resonance signal with an expanded excitation range.

[0027] Optionally, when the hard pulse excitation is stopped, the step of performing spiral acquisition on the magnetic resonance signal to obtain raw imaging data of the target to be imaged includes:

[0028] When the hard pulse excitation is stopped, the magnetic resonance signal is spirally acquired according to a preset signal acquisition rule to obtain the magnetic resonance signal, wherein the signal acquisition rule includes: the number of spiral acquisition arms, the number of sampling points of the spiral acquisition arms, the spiral acquisition time, the repetition time and the spiral acquisition trajectory;

[0029] The acquired magnetic resonance signal is converted into digital form to obtain a digital magnetic resonance signal, and the digital magnetic resonance signal is used as the original imaging data.

[0030] Optionally, the step of reconstructing the original imaging data based on a preset reconstruction rule to obtain target imaging includes:

[0031] Based on a preset orthogonal gridding rule, performing an orthogonal transformation on the raw imaging data to obtain orthogonal raw k-space data;

[0032] Reconstructing the orthogonal original k-space data based on a preset Fourier transform rule to obtain a reconstructed multi-channel image;

[0033] The target imaging is acquired by merging the multi-channel images.

[0034] The present invention also provides a magnetic resonance imaging system for lungs, comprising:

[0035] A gradient module, used for applying a gradient magnetic field in a layer direction to the target to be imaged;

[0036] a hard pulse excitation module, configured to perform hard pulse excitation on the target to be imaged when the gradient of the gradient magnetic field begins to climb, and frequency modulate the hard pulse based on a preset frequency modulation range, thereby generating a magnetic resonance signal;

[0037] an acquisition module, configured to perform spiral acquisition on the magnetic resonance signal to obtain raw imaging data of the target to be imaged when the hard pulse excitation is stopped;

[0038] The reconstruction module is used to reconstruct the original imaging data based on a preset reconstruction rule to obtain target imaging.

[0039] The present invention also provides an electronic 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 magnetic resonance imaging method for the lung as described above is implemented.

[0040] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements any of the above-described magnetic resonance imaging methods for the lungs.

[0041] The present invention provides a magnetic resonance imaging method, system, and electronic device medium for the lungs, which applies a gradient magnetic field in a layer direction to the target to be imaged; when the gradient of the gradient magnetic field begins to climb, hard pulse excitation is performed on the target to be imaged, and the hard pulse is frequency modulated based on a preset frequency modulation range to generate a magnetic resonance signal; when the hard pulse excitation is stopped, the magnetic resonance signal is spirally collected to obtain original imaging data of the target to be imaged; based on preset reconstruction rules, the original imaging data is reconstructed to obtain target imaging; the echo time and imaging time can be effectively shortened, and the signal-to-noise ratio and resolution are high. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0043] Figure 1 1 is a schematic flow chart of a magnetic resonance imaging method for lungs provided by the present invention;

[0044] Figure 2 It is a schematic diagram of the process of performing hard pulse excitation in the magnetic resonance imaging method for lungs provided by the present invention;

[0045] Figure 3 1 is a schematic diagram of the timing of hard pulse excitation, frequency modulation and applied gradient in the magnetic resonance imaging method for the lung provided by the present invention;

[0046] Figure 4 1 is a schematic diagram of a process for frequency modulation in a magnetic resonance imaging method for lungs provided by the present invention;

[0047] Figure 5 Schematic diagram of the principle of frequency modulation in the magnetic resonance imaging method for lungs provided by the present invention;

[0048] Figure 6 It is a schematic diagram of the process of obtaining raw imaging data in the magnetic resonance imaging method for lungs provided by the present invention;

[0049] Figure 7 It is a schematic diagram of the process of obtaining target imaging in the magnetic resonance imaging method for lungs provided by the present invention;

[0050] Figure 8 1. It is a schematic diagram comparing the layer-wise encoding time in the magnetic resonance imaging method for the lung provided by the present invention and the layer-wise encoding time in the traditional method;

[0051] Figure 9 This is a comparison diagram of the radio frequency field (magnetic field formed by hard pulse excitation) with and without frequency modulation;

[0052] Figure 10 This is a comparison chart of the frequency range of hard pulses with and without frequency modulation;

[0053] Figure 11 This is a comparison chart of signal strength with and without frequency modulation;

[0054] Figure 12This is a comparison chart of the signal-to-noise ratio of healthy volunteers' lungs imaged using the magnetic resonance imaging method for the lungs provided by the present invention and the signal-to-noise ratio using a traditional method;

[0055] Figure 13 This is a fitting result diagram of T2* obtained by measuring a sponge phantom using the magnetic resonance imaging method for the lung provided by the present invention;

[0056] Figure 14 1 is a schematic structural diagram of a magnetic resonance imaging system for lungs provided by the present invention;

[0057] Figure 15 It is a structural schematic diagram of the electronic device provided by the present invention. DETAILED DESCRIPTION

[0058] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0059] In the following examples, Figures 1-15 The present invention describes a method, system, electronic device and medium for magnetic resonance imaging of the lungs.

[0060] Please refer to Figure 1 The present embodiment provides a method for magnetic resonance imaging of the lungs, comprising:

[0061] S101: Applying a gradient magnetic field in a slice direction to the target to be imaged.

[0062] Specifically, the target to be imaged refers to a target object that needs to undergo magnetic resonance imaging. The layer direction refers to the layer selection direction (usually referred to as the Z-axis direction or the inter-layer direction), and corresponding to it, there are also intra-layer directions (usually referred to as X and Y directions). It can be understood that the layer direction (Z-axis direction) runs through each layer (which can be understood as each cross-section of the target to be imaged for imaging data encoding), and each layer has corresponding encoding data in the X and Y directions. The X direction usually refers to the frequency encoding direction, and the Y direction usually refers to the phase encoding direction. Gradient refers to a magnetic field with different magnetic field strengths applied in the layer direction. By applying a gradient magnetic field in the layer direction to the target to be imaged, spatial positioning can be facilitated, and subsequent hard pulse excitation of the target to be imaged based on the gradient magnetic field can be facilitated.

[0063] S102: When the gradient of the gradient magnetic field starts to climb, hard pulse excitation is performed on the target to be imaged, and the hard pulse is frequency modulated based on a preset frequency modulation range, thereby generating a magnetic resonance signal.

[0064] It should be noted that by immediately performing a hard pulse excitation on the target to be imaged as the gradient of the gradient magnetic field begins to rise, and frequency modulating the hard pulse within a preset frequency modulation range, the excitation range can be expanded to a certain extent. Generally, the shorter the duration of a radio frequency pulse, the wider its frequency range after Fourier transform, and such a pulse is generally referred to as a hard pulse. The longer the duration of a radio frequency pulse, the narrower its frequency range after Fourier transform, i.e., the narrower the transmission bandwidth, and such a pulse is generally referred to as a soft pulse. In this step, hard pulse excitation is employed. Among different types of radio frequency pulses of the same amplitude, the hard pulse has the shortest duration, minimizing the echo time (the interval between the excitation pulse and the generated echo) and enabling 3D excitation. Furthermore, in this step, frequency modulation of the hard pulse within a preset frequency modulation range simultaneously with the hard pulse excitation can effectively expand the excitation range and improve the signal-to-noise ratio. Furthermore, based on or in combination with frequency modulation, hard pulse excitation is performed on the target to be imaged, generating a magnetic resonance signal with an expanded excitation range.

[0065] S103: When the hard pulse excitation is stopped, spirally acquiring the magnetic resonance signal to obtain original imaging data of the target to be imaged.

[0066] It should also be noted that when hard pulse excitation is stopped, helical acquisition of the generated magnetic resonance signals can significantly shorten the echo time. Compared to traditional magnetic induction signal acquisition methods such as Cartesian acquisition, helical acquisition has higher acquisition efficiency and can effectively shorten imaging time. The raw imaging data is the imaging data stored in a preset raw k-space.

[0067] S104: reconstructing the original imaging data based on a preset reconstruction rule to obtain target imaging.

[0068] Specifically, by reconstructing the original imaging data based on a preset reconstruction rule, it is possible to obtain target imaging with higher accuracy.

[0069] In order to shorten the echo time as much as possible, in some embodiments, before the step of performing hard pulse excitation on the target to be imaged when the gradient of the gradient magnetic field begins to climb, the method further includes:

[0070] Determining an estimated maximum echo time based on a preset maximum hardware gradient field strength, a maximum hardware gradient switching rate, and a hard pulse duration; determining an estimated minimum echo time based on a preset radio frequency switching time and the hard pulse duration;

[0071] Determine whether the expected maximum echo time and the expected minimum echo time meet the preset echo time threshold range, obtain the judgment result and provide feedback; and, based on the expected maximum echo time and / or the expected minimum echo time, determine the echo time verification range, the echo time verification range is used to verify the actual echo time obtained when the magnetic resonance signal acquisition is completed, and adjust the hard pulse excitation-related parameters and the spiral acquisition-related parameters based on the verification result.

[0072] Specifically, the maximum hardware gradient field strength refers to the maximum value of the gradient field strength of the hardware device (magnetic resonance device), such as 80 mT / m (milliTesla / meter). The maximum hardware gradient switching rate refers to the maximum value of the gradient switching rate of the hardware device. The echo time threshold range can be set according to actual conditions. For example, if an ultrashort echo sequence generally requires an echo time less than 100 ms (microseconds), the echo time threshold range can be set to (0, 100) microseconds. By determining whether the current expected maximum echo time and expected minimum echo time are within the preset echo time threshold range, obtaining the judgment result and providing feedback, it is possible to better control the echo time required for the current magnetic resonance imaging process. Furthermore, by determining the echo time verification range based on the expected maximum echo time and / or the expected minimum echo time, and using the echo time verification range to verify the actual echo time obtained when the magnetic resonance information acquisition is subsequently completed, it is possible to better adjust the hard pulse excitation-related parameters and spiral acquisition-related parameters, further shortening the echo time. The echo time verification range can be determined by adding or subtracting a preset parameter value from the estimated maximum echo time. Alternatively, the echo time verification range can be determined by adding or subtracting a preset parameter value from the estimated minimum echo time. Alternatively, the echo time verification range can be determined by taking the average of the estimated maximum echo time and the estimated minimum echo time, and then adding or subtracting a preset parameter value from the average to determine the echo time verification range. The method for obtaining the echo time verification range is not limited herein.

[0073] In some embodiments, the hard pulse excitation associated parameters include: hard pulse frequency, hard pulse amplitude, hard pulse phase, hard pulse duration, hard pulse movement step and number of movements, etc.; the spiral acquisition associated parameters include: number of spiral acquisition arms, number of spiral acquisition arm sampling points, spiral acquisition time, repetition time and spiral acquisition trajectory, etc.

[0074] It should be noted that, based on the preset maximum hardware gradient field strength, the maximum hardware gradient switching rate, and the hard pulse duration, the mathematical expression for determining the expected maximum echo time is:

[0075] TE max =2×(G / Slew rate)+ΔT Hard / 2

[0076] Among them, TE max represents the expected maximum echo time, G represents the maximum hardware gradient field strength, Slew rate represents the maximum hardware gradient switching rate, ΔT Hard Indicates the hard pulse duration.

[0077] It should also be noted that, based on the preset RF switching time and the hard pulse duration, the mathematical expression for determining the expected minimum echo time is:

[0078] TE min =ΔT Hard / 2+T s

[0079] Among them, TE min Indicates the expected minimum echo time, T s Indicates the RF switching time. The RF switching time refers to the time required for the hard pulse to turn on or off.

[0080] Please refer to Figure 2 In some embodiments, when the gradient of the gradient magnetic field begins to climb, the step of performing hard pulse excitation on the target to be imaged includes:

[0081] S201: When the gradient of the gradient magnetic field starts to rise, hard pulse excitation is started for the target to be imaged. That is, when the gradient of the gradient magnetic field starts to rise, hard pulses are started to perform hard pulse excitation on the target to be imaged.

[0082] S202: During the hard pulse excitation process, based on a preset movement step size and number of movements, the hard pulse is controlled to gradually move toward a target direction. The target directions include a first target direction and a second target direction. When the gradient of the gradient magnetic field is positive, the hard pulse is controlled to gradually move toward the first target direction. When the gradient of the gradient magnetic field is negative, the hard pulse is controlled to gradually move toward the second target direction. The first target direction and the second target direction are different arbitrary directions. In a specific implementation, two opposite directions can be selected as the first target direction and the second target direction, respectively, which can accelerate the encoding speed in the layer direction to a certain extent.

[0083] It is understood that when applying a gradient to an imaging target, the gradient may be positive or negative. By controlling the hard pulse to gradually move toward the target during hard pulse excitation, the slice encoding speed can be effectively increased, thereby helping to shorten the echo time. For example, when the gradient of the gradient magnetic field is positive, the hard pulse is controlled to gradually move to the right, and when the gradient of the gradient magnetic field is negative, the hard pulse is controlled to gradually move to the left.

[0084] Figure 3 The diagram shows a timing diagram of hard pulse excitation, frequency modulation, and applied gradients (intra-plane direction, slice direction) in the magnetic resonance imaging method for the lungs provided by the present invention.

[0085] Figure 3 There are four timing curves, namely the timing curve of hard pulse (RF pulse), the timing curve of frequency modulation, the timing curve of intra-layer gradient, and the timing curve of layer direction gradient. Figure 3 As can be seen, when the gradient of the gradient magnetic field begins to climb, a hard pulse is applied to the imaging target. The rectangle in the hard pulse (RF pulse) timing curve represents the hard pulse, and the arrows represent the gradual movement of the hard pulse. Simultaneously with the start of hard pulse excitation, frequency modulation of the hard pulse begins, expanding the excitation range and improving the signal-to-noise ratio. The timing curve of the intra-slice gradient indicates that after the slice gradient is applied or terminated, the corresponding gradient magnetic field is applied in the intra-slice directions (X and Y directions).

[0086] Please refer to Figure 4 In some embodiments, the step of frequency modulating the hard pulse based on a preset frequency modulation range to generate a magnetic resonance signal includes:

[0087] S401: Expanding the original frequency range preset for the hard pulse based on a preset frequency modulation range to obtain a target frequency range. For example, based on the preset frequency modulation range, increasing the upper limit of the original frequency range preset for the hard pulse and / or decreasing the lower limit of the original frequency range to obtain an expanded target frequency range.

[0088] S402: Based on the target frequency range, hard pulse excitation is performed on the target to be imaged, thereby generating the magnetic resonance signal with an expanded excitation range. By frequency modulating the hard pulse, the excitation range can be expanded and the signal-to-noise ratio can be improved.

[0089] Figure 5 The schematic diagram showing the principle of frequency modulation is shown in Figure 5 , Figure 5 The two lines in the figure represent the applied gradient field strength G z,1 , G z,2(Unit: millitesla per meter) After that, the spatial coordinates correspond to the Larmor precession frequency. The horizontal axis represents position (Position), and the vertical axis represents the different Larmor precession frequencies (Frequency) corresponding to different positions. Without frequency modulation, the original frequency range of the hard pulse is Δf, and the excitation ranges are ΔZ1 and ΔZ2 respectively. However, if frequency modulation is added, it means that the frequency of the hard pulse becomes Δf + ΔM (frequency modulation range). Intuitively, the excitation range corresponding to the hard pulse has been significantly expanded.

[0090] Please refer to Figure 6 In some embodiments, when the hard pulse excitation is stopped, the step of performing spiral acquisition on the magnetic resonance signal to obtain raw imaging data of the target to be imaged includes:

[0091] S601: When the hard pulse excitation is terminated, the magnetic resonance signals are spirally acquired according to preset signal acquisition rules. The signal acquisition rules include the number of spiral acquisition arms, the number of sampling points in the spiral acquisition arms, the spiral acquisition time, the repetition time, and the spiral acquisition trajectory. By immediately acquiring magnetic resonance signals upon terminating the hard pulse excitation, the echo time can be shortened to a certain extent.

[0092] S602: Perform analog-to-digital conversion on the acquired magnetic resonance signals to obtain digital magnetic resonance signals, and use the digital magnetic resonance signals as the raw imaging data. It will be appreciated that the acquired magnetic resonance signals are analog signals, and this step facilitates subsequent processing of the digital magnetic resonance signals by performing analog-to-digital conversion on the acquired magnetic resonance signals.

[0093] Please refer to Figure 7 In some embodiments, the step of reconstructing the original imaging data based on a preset reconstruction rule to obtain target imaging includes:

[0094] S701: Based on a preset orthogonal gridding rule, perform an orthogonal transformation on the original imaging data to obtain orthogonal original k-space data.

[0095] It should be noted that since the acquisition method used in the present invention is non-uniform sampling, if the data obtained by non-uniform sampling is to be reconstructed, it will consume a lot of computing power and require the construction of a relatively complex algorithm. Therefore, in order to reduce the complexity and difficulty of data reconstruction, S701 performs an orthogonal transformation on the original imaging data based on a preset orthogonal gridding rule to obtain orthogonal original k-space data, which facilitates subsequent data reconstruction and reduces the complexity of data reconstruction. The orthogonal gridding rule can use interpolation sampling and other methods to evenly distribute the originally unevenly distributed original imaging data to a preset k-space (k-space) to generate orthogonal original k-space data.

[0096] S702: Reconstruct the orthogonal original k-space data based on a preset Fourier transform rule to obtain a reconstructed multi-channel image. The Fourier transform rule can adopt an existing Fourier calculation formula, etc., which will not be described in detail here.

[0097] S703: Acquire the target imaging by merging the multi-channel images. The target imaging has high accuracy and high resolution.

[0098] In order to more clearly demonstrate the differences and gaps between the present invention and the traditional method, the relevant effects of the magnetic resonance method provided by the present invention are explained in a comparative manner below.

[0099] Figure 8 The figure shows a comparison between the layer direction encoding time in the magnetic resonance imaging method for the lungs provided by the present invention and the layer direction encoding time in the traditional method. Figure 8 As shown, Figure 8 The horizontal coordinate K in z =1 / L z , K z The unit is m -1 , m means meter, L z It indicates the size of the field of view in the slice direction. Experiments have shown that the time taken for slice direction encoding in the magnetic resonance imaging method provided by the present invention is much shorter than that taken for slice direction encoding in traditional methods.

[0100] Figure 9 The figure shows a comparison diagram of the radio frequency field with frequency modulation and the traditional radio frequency field without frequency modulation (magnetic field formed by hard pulse excitation). Figure 9 It can be seen that the magnitude of the RF field (induced magnetic field generated after adding hard / RF pulses) with frequency modulation is the same as that of the traditional RF field without RF modulation. Figure 10 The figure shows a comparison of the frequency range of hard pulses with those without frequency modulation. Figure 10 As shown in FIG, the frequency modulation range after adding frequency modulation is much larger than the frequency range of the traditional hard pulse without adding frequency modulation. Figure 11 The figure shows the signal strength comparison between adding frequency modulation and traditional signal strength comparison without frequency modulation. Figure 11 After adding frequency modulation, the signal intensity in different slice directions is significantly higher than that of the traditional method without frequency modulation. In summary, adding frequency modulation can expand the hard pulse excitation or stimulation range, facilitate more comprehensive acquisition of magnetic resonance signals, and improve the signal-to-noise ratio.

[0101] Figure 12The figure shows a comparison of the signal-to-noise ratio obtained by using the magnetic resonance imaging method for lungs provided by the present invention to perform lung imaging tests on healthy volunteers and the signal-to-noise ratio obtained by using the traditional method. Figure 12 ,It has been proved through multiple experiments that the ,signal-to-noise ratio of the magnetic resonance imaging method provided by ,the present invention is significantly higher than that of the ,traditional methods. Figure 12 The three images in the figure correspond to different layers of the same experimental object. The horizontal axis represents the spatial cross-section (per pixel), and the vertical axis represents the signal intensity at the corresponding position.

[0102] In order to verify that the magnetic resonance imaging method for the lungs provided by the present invention can achieve magnetic resonance imaging with a short transverse relaxation time, this embodiment tests the T2* (transverse relaxation time) of the sponge phantom. For an example of experimental data, please refer to Figure 13 .exist Figure 13 In the figure, by statistics of echo time and signal-to-noise ratio (au), the transverse relaxation time T2* of the magnetic resonance imaging method provided by the present invention is fitted to be 2.209 milliseconds, indicating that the magnetic resonance imaging method provided by the present invention can achieve magnetic resonance imaging with a short transverse relaxation time.

[0103] The actual experiment / application process of the magnetic resonance imaging method for the lungs of the present invention will be further described below by way of specific embodiments.

[0104] Example 1:

[0105] In order to prove that the magnetic resonance imaging method for lungs provided by the present invention can achieve magnetic resonance imaging with short transverse relaxation time, and to verify the difference in image signal-to-noise ratio between the method of the present invention and the traditional magnetic resonance imaging method. In this embodiment, the lungs of healthy volunteers are used as imaging targets, and magnetic resonance imaging of the lungs of the healthy volunteers is performed using the magnetic resonance imaging method for lungs provided by the present invention and the traditional magnetic resonance imaging method. The experimental results show that the image signal-to-noise ratio of the magnetic resonance imaging method provided by the present invention is significantly higher than that of the traditional magnetic resonance imaging method. The signal-to-noise ratio comparison chart can be referred to Figure 12 In the specific implementation process, the relevant parameters involved can be set according to the actual situation, such as the echo time TE is set to 0.07 milliseconds, the repetition time TR is set to 65 milliseconds, the flip angle is set to 10 degrees, and the FOV (field of view, referring to the single plane imaging range) is set to 180×180mm. 2 , the imaging resolution is set to 1.2×1.2×7mm 3 The number of spiral acquisition arms is set to 64, the number of spiral acquisition readout points is set to 3500, etc., which will not be repeated here. In this embodiment, the magnetic resonance imaging method for the lung provided by the present invention uses the same parameters as the traditional method.

[0106] Example 2:

[0107] In order to prove that the magnetic resonance imaging method for the lungs provided by the present invention can achieve magnetic resonance imaging with short transverse relaxation time, and to verify the difference in image signal-to-noise ratio between the method of the present invention and the traditional magnetic resonance imaging method. In this example, a sponge phantom is used as the imaging target, and magnetic resonance imaging is performed on the sponge phantom using the magnetic resonance imaging method for the lungs provided by the present invention and the traditional magnetic resonance imaging method. Please refer to Figure 13 The experimental results show that the method provided by the present invention can achieve magnetic resonance imaging with a short transverse relaxation time. In the specific implementation process, the relevant parameters involved can be set according to the actual situation. Please refer to the description of the parameter setting in Example 1, which will not be repeated here. The magnetic resonance imaging method for the lungs provided by the present invention in this embodiment uses the same parameters as the traditional method.

[0108] The magnetic resonance imaging system for the lungs provided by the present invention is described below by way of example. The magnetic resonance imaging system for the lungs described below and the magnetic resonance imaging method for the lungs described above can be referenced to each other.

[0109] Please refer to Figure 14 , the magnetic resonance imaging system for lungs provided in this embodiment includes:

[0110] The gradient module 1401 is used to apply a gradient magnetic field in a slice direction to the target to be imaged.

[0111] The hard pulse excitation module 1402 is configured to perform hard pulse excitation on the target to be imaged when the gradient of the gradient magnetic field starts to climb, and frequency modulate the hard pulse based on a preset frequency modulation range to generate a magnetic resonance signal.

[0112] The acquisition module 1403 is configured to perform spiral acquisition on the magnetic resonance signal when the hard pulse excitation is stopped, so as to obtain original imaging data of the target to be imaged.

[0113] Reconstruction module 1404 is configured to reconstruct the raw imaging data based on preset reconstruction rules to obtain target images. The gradient module 1401, hard pulse excitation module 1402, acquisition module 1403, and reconstruction module 1404 are connected. The magnetic resonance imaging system provided in this embodiment can effectively shorten echo time and imaging time, and achieve a high signal-to-noise ratio and high resolution.

[0114] In some embodiments, before the step of performing hard pulse excitation on the target to be imaged when the gradient of the gradient magnetic field begins to climb, the method further includes:

[0115] The expected maximum echo time is determined based on the preset maximum hardware gradient field strength, the maximum hardware gradient switching rate, and the hard pulse duration.

[0116] An estimated minimum echo time is determined based on a preset radio frequency switching time and the hard pulse duration.

[0117] Determine whether the expected maximum echo time and the expected minimum echo time meet the preset echo time threshold range, obtain the judgment result and provide feedback; and, based on the expected maximum echo time and / or the expected minimum echo time, determine the echo time verification range, the echo time verification range is used to verify the actual echo time obtained when the magnetic resonance signal acquisition is completed, and adjust the hard pulse excitation-related parameters and the spiral acquisition-related parameters based on the verification result.

[0118] In some embodiments, based on the preset maximum hardware gradient field strength, the maximum hardware gradient switching rate, and the hard pulse duration, the mathematical expression for determining the expected maximum echo time is:

[0119] TE max =2×(G / Slew rate)+ΔT Hard / 2

[0120] Among them, TE max represents the expected maximum echo time, G represents the maximum hardware gradient field strength, Slew rate represents the maximum hardware gradient switching rate, ΔT Hard Indicates the hard pulse duration.

[0121] Based on the preset RF switching time and the hard pulse duration, the mathematical expression for determining the expected minimum echo time is:

[0122] TE min =ΔT Hard / 2+T s

[0123] Among them, TE min Indicates the expected minimum echo time, T s Indicates the RF switching time.

[0124] In some embodiments, when the gradient of the gradient magnetic field begins to rise, the hard pulse excitation module 1402 performs hard pulse excitation on the target to be imaged, including:

[0125] When the gradient of the gradient magnetic field starts to climb, hard pulse excitation of the target to be imaged begins.

[0126] During the hard pulse excitation process, based on a preset moving step size and number of movements, the hard pulse is controlled to move gradually toward a target direction; the target direction includes: a first target direction and a second target direction. When the gradient of the gradient magnetic field is positive, the hard pulse is controlled to move gradually toward the first target direction; when the gradient of the gradient magnetic field is negative, the hard pulse is controlled to move gradually toward the second target direction.

[0127] In some embodiments, the hard pulse excitation module 1402 performs frequency modulation on the hard pulse based on a preset frequency modulation range to generate a magnetic resonance signal, including:

[0128] Based on the preset frequency modulation range, the original frequency range preset for the hard pulse is expanded to obtain a target frequency range.

[0129] Based on the target frequency range, hard pulse excitation is performed on the target to be imaged, thereby generating the magnetic resonance signal with an expanded excitation range.

[0130] In some embodiments, when the hard pulse excitation is stopped, the acquisition module 1403 performs spiral acquisition on the magnetic resonance signal to obtain raw imaging data of the target to be imaged, including:

[0131] When the hard pulse excitation is stopped, the magnetic resonance signal is spirally acquired according to a preset signal acquisition rule to obtain the magnetic resonance signal, wherein the signal acquisition rule includes: the number of spiral acquisition arms, the number of sampling points of the spiral acquisition arms, the spiral acquisition time, the repetition time and the spiral acquisition trajectory;

[0132] The acquired magnetic resonance signal is converted into digital form to obtain a digital magnetic resonance signal, and the digital magnetic resonance signal is used as the original imaging data.

[0133] In some embodiments, the reconstruction module 1404 reconstructs the original imaging data based on a preset reconstruction rule, and the step of obtaining the target imaging includes:

[0134] Based on a preset orthogonal gridding rule, the raw imaging data is orthogonally transformed to obtain orthogonal raw k-space data.

[0135] Based on a preset Fourier transform rule, the orthogonal original k-space data is reconstructed to obtain a reconstructed multi-channel image.

[0136] The target imaging is acquired by merging the multi-channel images.

[0137] Figure 15 An example of a physical structure diagram of an electronic device is shown below. Figure 15As shown, the electronic device may include: a processor 1510, a communication interface 1520, a memory 1530, and a communication bus 1540, wherein the processor 1510, the communication interface 1520, and the memory 1530 communicate with each other via the communication bus 1540. The processor 1510 may call the logic instructions in the memory 1530 to execute a magnetic induction imaging method for the lungs, the method comprising: applying a gradient magnetic field in a layer direction to the target to be imaged; when the gradient of the gradient magnetic field begins to climb, performing hard pulse excitation on the target to be imaged, and frequency modulating the hard pulse based on a preset frequency modulation range to generate a magnetic resonance signal; when the hard pulse excitation is stopped, performing spiral acquisition on the magnetic resonance signal to obtain raw imaging data of the target to be imaged; and reconstructing the raw imaging data based on a preset reconstruction rule to obtain target imaging.

[0138] In addition, the logic instructions in the above-mentioned memory 1530 can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when sold or used as an independent product. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0139] On the other hand, the present invention also provides a computer program product, which includes a computer program, which can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the magnetic induction imaging method for the lungs provided by the above methods, the method including: applying a gradient magnetic field in a layer direction to the target to be imaged; when the gradient of the gradient magnetic field begins to climb, performing hard pulse excitation on the target to be imaged, and frequency modulating the hard pulse based on a preset frequency modulation range to generate a magnetic resonance signal; when the hard pulse excitation is stopped, spirally acquiring the magnetic resonance signal to obtain the original imaging data of the target to be imaged; reconstructing the original imaging data based on a preset reconstruction rule to obtain target imaging.

[0140] On the other hand, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, is implemented to execute the magnetic induction imaging method for the lungs provided by the above-mentioned methods, the method comprising: applying a gradient magnetic field in a layer direction to the target to be imaged; when the gradient of the gradient magnetic field begins to climb, performing hard pulse excitation on the target to be imaged, and frequency modulating the hard pulse based on a preset frequency modulation range to generate a magnetic resonance signal; when the hard pulse excitation is stopped, spirally acquiring the magnetic resonance signal to obtain the original imaging data of the target to be imaged; and reconstructing the original imaging data based on a preset reconstruction rule to obtain target imaging.

[0141] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, i.e., they may be located in one location or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of the present embodiment. Persons of ordinary skill in the art will be able to understand and implement the present invention without inventive effort.

[0142] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, or of course, by hardware. Based on this understanding, the essence of the above technical solution or the part that contributes to the existing technology can be embodied in the form of a software product. The computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or certain parts of the embodiments.

[0143] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for magnetic resonance imaging of the lungs, characterized in that: include: Applying a gradient magnetic field in a slice direction to the target to be imaged; When the gradient of the gradient magnetic field starts to climb, hard pulse excitation is performed on the target to be imaged, and the hard pulse is frequency modulated based on a preset frequency modulation range, thereby generating a magnetic resonance signal; When the hard pulse excitation is stopped, spirally acquiring the magnetic resonance signal to obtain original imaging data of the target to be imaged; Reconstructing the original imaging data based on a preset reconstruction rule to obtain target imaging; Before the step of performing hard pulse excitation on the target to be imaged when the gradient of the gradient magnetic field begins to rise, the method further includes: Determining an expected maximum echo time based on a preset maximum hardware gradient field strength, a maximum hardware gradient switching rate, and a hard pulse duration; Determining an estimated minimum echo time based on a preset radio frequency switching time and the hard pulse duration; Determine whether the expected maximum echo time and the expected minimum echo time meet the preset echo time threshold range, obtain the judgment result and provide feedback; and, based on the expected maximum echo time and / or the expected minimum echo time, determine the echo time verification range, the echo time verification range is used to verify the actual echo time obtained when the magnetic resonance signal acquisition is completed, and adjust the hard pulse excitation-related parameters and the spiral acquisition-related parameters based on the verification result.

2. The magnetic resonance imaging method for lungs according to claim 1, wherein: Based on the preset maximum hardware gradient field strength, maximum hardware gradient switching rate, and hard pulse duration, the mathematical expression for determining the expected maximum echo time is: TE max =2×(G / Slew rate)+ΔT Hard / 2 Among them, TE max represents the expected maximum echo time, G represents the maximum hardware gradient field strength, Slew rate represents the maximum hardware gradient switching rate, ΔT Hard Indicates the hard pulse duration; Based on the preset RF switching time and the hard pulse duration, the mathematical expression for determining the expected minimum echo time is: TE min =ΔT Hard / 2+T s Among them, TE min Indicates the expected minimum echo time, T s Indicates the RF switching time.

3. The magnetic resonance imaging method for lungs according to claim 1, wherein: When the gradient of the gradient magnetic field begins to climb, the step of performing hard pulse excitation on the target to be imaged includes: When the gradient of the gradient magnetic field starts to climb, hard pulse excitation of the target to be imaged begins; During the hard pulse excitation process, based on a preset moving step size and number of movements, the hard pulse is controlled to move gradually toward a target direction; the target direction includes: a first target direction and a second target direction. When the gradient of the gradient magnetic field is positive, the hard pulse is controlled to move gradually toward the first target direction; when the gradient of the gradient magnetic field is negative, the hard pulse is controlled to move gradually toward the second target direction.

4. The magnetic resonance imaging method for lungs according to claim 1, wherein: The step of frequency modulating the hard pulse based on a preset frequency modulation range to generate a magnetic resonance signal includes: Based on a preset frequency modulation range, the original frequency range preset for the hard pulse is expanded to obtain a target frequency range; Based on the target frequency range, hard pulse excitation is performed on the target to be imaged, thereby generating the magnetic resonance signal with an expanded excitation range.

5. The magnetic resonance imaging method for lungs according to claim 1, wherein: When the hard pulse excitation is stopped, the step of performing spiral acquisition on the magnetic resonance signal to obtain raw imaging data of the target to be imaged includes: When the hard pulse excitation is stopped, the magnetic resonance signal is spirally acquired according to a preset signal acquisition rule to obtain the magnetic resonance signal, wherein the signal acquisition rule includes: the number of spiral acquisition arms, the number of sampling points of the spiral acquisition arms, the spiral acquisition time, the repetition time and the spiral acquisition trajectory; The acquired magnetic resonance signal is converted into digital form to obtain a digital magnetic resonance signal, and the digital magnetic resonance signal is used as the original imaging data.

6. The magnetic resonance imaging method for lungs according to claim 1, wherein: The steps of reconstructing the original imaging data based on a preset reconstruction rule to obtain target imaging include: Based on a preset orthogonal gridding rule, performing an orthogonal transformation on the raw imaging data to obtain orthogonal raw k-space data; Reconstructing the orthogonal original k-space data based on a preset Fourier transform rule to obtain a reconstructed multi-channel image; The target imaging is acquired by merging the multi-channel images.

7. A magnetic resonance imaging system for lungs, characterized in that include: A gradient module, used for applying a gradient magnetic field in a layer direction to the target to be imaged; a hard pulse excitation module, configured to perform hard pulse excitation on the target to be imaged when the gradient of the gradient magnetic field begins to climb, and frequency modulate the hard pulse based on a preset frequency modulation range, thereby generating a magnetic resonance signal; an acquisition module, configured to perform spiral acquisition on the magnetic resonance signal to obtain raw imaging data of the target to be imaged when the hard pulse excitation is stopped; A reconstruction module, configured to reconstruct the original imaging data based on a preset reconstruction rule to obtain a target image; Before the step of performing hard pulse excitation on the target to be imaged when the gradient of the gradient magnetic field begins to rise, the method further includes: Determining an expected maximum echo time based on a preset maximum hardware gradient field strength, a maximum hardware gradient switching rate, and a hard pulse duration; Determining an estimated minimum echo time based on a preset radio frequency switching time and the hard pulse duration; Determine whether the expected maximum echo time and the expected minimum echo time meet the preset echo time threshold range, obtain the judgment result and provide feedback; and, based on the expected maximum echo time and / or the expected minimum echo time, determine the echo time verification range, the echo time verification range is used to verify the actual echo time obtained when the magnetic resonance signal acquisition is completed, and adjust the hard pulse excitation-related parameters and the spiral acquisition-related parameters based on the verification result.

8. An electronic 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 magnetic resonance imaging method for the lung according to any one of claims 1 to 6 is implemented.

9. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the magnetic resonance imaging method for the lung according to any one of claims 1 to 6 is implemented.

Images