Multi-echo data magnetic resonance imaging scanning method, apparatus and magnetic resonance imaging system
By applying an offset gradient in the readout direction during MR imaging and acquiring automatically calibrated data during the astigmatic gradient plateau period, the problems of TR oscillation and insufficient data continuity were solved, achieving high-quality image reconstruction.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SIEMENS SHENZHEN MAGNETIC RESONANCE
- Filing Date
- 2024-11-29
- Publication Date
- 2026-05-29
AI Technical Summary
In existing multi-echo data MR imaging techniques, insufficient continuity between TR oscillation and automatic calibration data and imaging data leads to artifacts in the reconstructed images.
When the plateau signal of the first readout gradient is applied in the readout direction, the offset gradient is applied in the phase encoding direction, and automatic calibration data is acquired during the plateau period of the astigmatic gradient in the readout direction. By integrating the acquisition of automatic calibration data and imaging data within the same TR, the continuity of data is ensured.
This avoids increasing the TR length, reduces artifacts in the reconstructed image, enables continuous acquisition of automatic calibration data and imaging data, and improves image quality.
Smart Images
Figure CN122109955A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of medical imaging technology, and in particular to multi-echo data magnetic resonance imaging scanning methods, apparatus and magnetic resonance imaging systems. Background Technology
[0002] Multi-echo data MR (Magnetic Resonance) imaging refers to scanning the target and acquiring multiple echo MR signals. Each echo signal constructs a separate K-space, and the image is reconstructed using signals from each K-space. These multiple images are then merged to obtain the final MR image. This echo-independent reconstruction method is frequently used in parallel imaging or other image reconstructions involving K-space interpolation. Sequences used in multi-echo data MR imaging include MEDIC (Multi-Echo Data Imaging Combination) sequences.
[0003] Figure 1 This is an example diagram of a typical MEDIC sequence. Wherein:
[0004] 11 represents the RF (Radio Frequency) sequence, 111 represents the RF pulse, and the time interval between two adjacent RF pulses is one TR (Time Repetition).
[0005] 12 is the gradient sequence in the Par (Partition) direction, 121 is the layer selection gradient, and 122 and 123 are the convergence gradients of 121, which also have flow compensation function.
[0006] 13 is the gradient sequence in the PE (Phase Encoding) direction, 131 is the PE gradient, and 132 is the convergence gradient of 131.
[0007] 14 is the gradient sequence in the RO (Read Out) direction, 141 and 142 are pre-dispersive gradients with flow compensation function, 143, 145, 147 and 149 are readout gradients, 144, 146 and 148 are dispersive gradients of 143, 145 and 147 respectively, and 140 is the damage gradient.
[0008] Each gradient signal consists of a rising edge, a falling edge, and a plateau period signal in between;
[0009] 15 represents the ADC (Analog-to-Digital Converter) sequence, specifically the echo sampling control sequence. 151-154 correspond to the sampling control signals for echoes 1-4, respectively. It can be seen that each TR contains four echoes: echoes 1-4. A K-space is constructed for each echo, resulting in a total of four K-spaces. Signals from the same echo acquired within all TRs are filled into the K-space of that echo.
[0010] To accelerate scanning, undersampling is typically used to acquire imaging data. Therefore, image reconstruction requires recovering the undersampling data. When recovering any undersampling data point (or simply undersampled point) in any K-space, the undersampled point is recovered by interpolating the sampling points in its neighborhood. The interpolation factor is calculated using ACS (Auto Calibrating Signal). ACS acquisition methods include the following two:
[0011] The first method is the integrated acquisition method. That is, when acquiring imaging data, the data at the center of the K-space is sampled in full, and all or part of the data in the fully sampled area at the center of the K-space is used as the ACS.
[0012] Figure 2 This diagram illustrates the acquisition of an ACS (Acoustic Scanner Array) using an integrated acquisition method. X represents a sampling point, and 0 represents an undersampled point. 21 represents the acquired imaging data of a specific two-dimensional plane. The horizontal direction of this plane is the PE direction, the vertical direction is the Par direction, and the direction perpendicular to this two-dimensional plane is the RO direction. 211 represents the acquired ACS; it can be seen that the ACS is the imaging data of the central region in K-space. 212 represents the imaging data along a specific Par direction within this two-dimensional plane. 2121 is a schematic diagram of 212 on the two-dimensional plane formed by the PE and RO directions. Each line in 2121 from top to bottom corresponds to a line along the RO direction of each point in 212 from left to right. For example, the four green lines in 2121 correspond to lines along the RO direction of the four sampling points located at the center of 212.
[0013] The disadvantage of this method is that in some scenarios, preparatory scans are required before imaging, such as scans related to fat saturation or region saturation. If an integrated acquisition method is used to acquire ACS, the size of the data acquired within each TR will not be the same, such as... Figure 2As shown, data was acquired within 6 echoes in the first 1-2 TRs, and within 8 echoes in the third-6 TRs. Then, in the seventh-8 TRs, the acquisition time returned to 6 echoes. This causes oscillations in the TR length, meaning that the lengths of the first 1-2 and seventh-8 TRs are the same, while the lengths of the third-6 TRs are the same but greater than the lengths of the first 1-2 and seventh-8 TRs. These oscillations in the TR length ultimately lead to artifacts in the reconstructed image.
[0014] The second method is independent acquisition. That is, ACS is acquired separately using a full sampling method before or after the acquisition of imaging data.
[0015] Figure 3 This diagram illustrates the acquisition of an ACS (Autocorrelation Acquisition System) using an independent acquisition method. X represents a sampling point, and 0 represents an undersampled point. 31 represents the acquired ACS on a specific two-dimensional plane, and 32 represents the acquired imaging data of that two-dimensional plane. The horizontal direction of this two-dimensional plane is the PE direction, the vertical direction is the Par direction, and the direction perpendicular to the two-dimensional plane is the RO direction. It is evident that the ACS and imaging data are acquired independently. 311 represents the ACS on a specific Par within this two-dimensional plane, and 3111 is a schematic diagram of 311 on the two-dimensional plane formed by the PE and RO directions. Each line from top to bottom in 3111 corresponds to a point on the left-to-right side of 311. 321 represents the imaging data on a specific Par direction within this two-dimensional plane, and 3211 is a schematic diagram of 321 on the two-dimensional plane formed by the PE and RO directions. Each line from top to bottom in 3211 corresponds to a line on the RO direction where each point on the left-to-right side of 321 is located.
[0016] The disadvantage of this approach is that since the ACS and imaging data are acquired independently, the continuity between the ACS and imaging data is insufficient. As a result, when using the ACS to restore undersampled imaging data, restoration errors may occur, ultimately leading to artifacts in the reconstructed image. Summary of the Invention
[0017] In view of this, embodiments of the present invention propose, on the one hand, a multi-echo data MR imaging scanning method and apparatus to avoid TR oscillation during multi-echo data MR imaging scanning and to achieve continuity of automatically calibrated data and imaging data acquired during multi-echo data MR imaging scanning; on the other hand, an MR imaging system is proposed to avoid TR oscillation during multi-echo data MR imaging scanning and to achieve continuity of automatically calibrated data and imaging data acquired during multi-echo data MR imaging scanning.
[0018] A multi-echo data magnetic resonance imaging scanning method, the method comprising:
[0019] During multi-echo magnetic resonance imaging (MRI) scans of the target, for any repetition time:
[0020] If automatic calibration data needs to be acquired within the current repetition time, and the position of the automatic calibration data in K-space is inconsistent with the position of any imaging data to be acquired within the current repetition time in K-space, then:
[0021] When the plateau signal of the first readout gradient is applied in the readout direction, an offset gradient is applied in the phase encoding direction, wherein the first readout gradient is any readout gradient in the readout direction other than the last readout gradient;
[0022] Furthermore, during the plateau period of the isophagic gradient signal in which the first readout gradient is applied in the readout direction, automatic calibration data is acquired.
[0023] During the plateau period signal of the dephasing gradient of the first readout gradient applied in the readout direction, automatic calibration data is acquired, including:
[0024] During the plateau period of the isophagic gradient of the first readout gradient applied in the readout direction, automatic calibration data is acquired, and the acquisition duration is less than or equal to the application duration of the plateau period of the isophagic gradient of the first readout gradient.
[0025] After acquiring automatic calibration data during the plateau period signal of the dephasing gradient of the first readout gradient applied in the readout direction, the process further includes:
[0026] After the phase gradient of the first readout gradient is applied, the convergence gradient of the offset gradient is applied in the phase encoding direction, and the time when the application of the convergence gradient is completed is the time when the application of the plateau signal of the second readout gradient begins. The area of the convergence gradient is equal to the area of the offset gradient, and the second readout gradient is the next readout gradient after the first readout gradient.
[0027] The area of the offset gradient is equal to the reciprocal of the product of the length of the field of view in the phase encoding direction, the levitation ratio, and 2π.
[0028] The method further includes: acquiring imaging data during the plateau signal of each readout gradient applied in the readout direction within the current repetition time;
[0029] Furthermore, once the imaging data of the imaging target has been acquired, the undersampled imaging data is recovered based on the acquired automatic calibration data.
[0030] A multi-echo data magnetic resonance imaging scanning device, comprising: a scanning control module and an automatic calibration data acquisition module, wherein:
[0031] The scanning control module is used to: during the multi-echo data magnetic resonance imaging scanning of the imaging target, for any repetition time: if automatic calibration data needs to be acquired within the current repetition time, and the position of the automatic calibration data in K-space is inconsistent with the position of any imaging data to be acquired within the current repetition time in K-space, then: when the plateau signal of the first readout gradient is applied in the readout direction, an offset gradient is applied in the phase encoding direction, wherein the first readout gradient is any readout gradient in the readout direction other than the last readout gradient;
[0032] The automatic calibration data acquisition module is used to acquire automatic calibration data during the plateau period signal of the isophagic gradient of the first readout gradient applied in the readout direction.
[0033] The automatic calibration data acquisition module acquires automatic calibration data during the plateau period signal of the isophagic gradient of the first readout gradient applied in the readout direction, including:
[0034] During the plateau period of the isophagic gradient of the first readout gradient applied in the readout direction, automatic calibration data is acquired, and the acquisition duration is less than or equal to the application duration of the plateau period of the isophagic gradient of the first readout gradient.
[0035] The scanning control module is further used for:
[0036] After the phase gradient of the first readout gradient is applied, the convergence gradient of the offset gradient is applied in the phase encoding direction, and the time when the application of the convergence gradient is completed is the time when the application of the plateau signal of the second readout gradient begins. The area of the convergence gradient is equal to the area of the offset gradient, and the second readout gradient is the next readout gradient after the first readout gradient.
[0037] The area of the convergence gradient of the offset gradient applied by the scanning control module in the phase encoding direction is equal to the reciprocal of the product of the length of the field of view in the phase encoding direction, the levitation ratio, and 2π.
[0038] The device further includes: an imaging data acquisition module and an undersampled imaging data recovery module, wherein:
[0039] The imaging data acquisition module is used to: acquire imaging data during the plateau signal when each readout gradient is applied in the readout direction within the current repetition time;
[0040] The undersampled imaging data recovery module is used to recover the undersampled imaging data based on the acquired automatic calibration data after the imaging data of the imaging target has been acquired.
[0041] A magnetic resonance imaging system, the system comprising a multi-echo data magnetic resonance imaging scanning apparatus as described in any of the above.
[0042] In this embodiment of the invention, during the multi-echo MR imaging scan of the imaging target, for any TR: if automatic calibration data needs to be acquired within the current TR, and the position of the automatic calibration data to be acquired within the current TR in K-space is inconsistent with the position of any imaging data to be acquired within the current TR in K-space, then within the current TR: when the plateau signal of the first readout gradient is applied in the RO direction, an offset gradient is applied in the PE direction. The first readout gradient is any readout gradient in the RO direction other than the last readout gradient. During the plateau signal of the astigmatic gradient of the first readout gradient applied in the RO direction, automatic calibration data is acquired. This ensures that automatic calibration data is acquired simultaneously with imaging data, achieving integrated acquisition of imaging data and automatic calibration data. Furthermore, the length of the TR is not increased, avoiding TR oscillations, which ultimately reduces artifacts in the reconstructed image. Also, since the automatic calibration data and imaging data are acquired within the same TR in the same sequence, they are continuous, which also ultimately reduces artifacts in the reconstructed image. Attached Figure Description
[0043] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which will make the above and other features and advantages of the present invention more apparent to those skilled in the art. In the drawings:
[0044] Figure 1 An example diagram of a typical MEDIC sequence;
[0045] Figure 2 This is a schematic diagram of ACS data acquisition using an integrated acquisition method;
[0046] Figure 3 This is a schematic diagram of ACS data acquisition using an independent acquisition method;
[0047] Figure 4 This is a flowchart of a multi-echo data MR imaging scanning method provided in an embodiment of the present invention;
[0048] Figure 5 In an application example of the present invention, when automatic calibration data needs to be acquired within a TR, and the position of the automatic calibration data to be acquired in K-space is inconsistent with the position of any imaging data to be acquired within the TR in K-space, an example diagram of the MEDIC sequence used within the TR is shown.
[0049] Figure 6 This is a schematic diagram of imaging data and automatic calibration data collected in an application example of the present invention.
[0050] Figure 7This is a schematic diagram of the evolution curve of the echo signal when performing MR imaging using a MEDIC sequence.
[0051] Figure 8 This is a schematic diagram showing how to obtain a discrete function f(n) by sampling a continuous function f(t) using a sampling function;
[0052] Figure 9 The relationship diagram between F(t), f(n), F(jw), and F(jnw0);
[0053] Figure 10 Example images of parallel imaging of a certain layer of the knee joint using a two-dimensional MEDIC sequence, respectively, using existing independent acquisition methods and the integrated acquisition method provided in this embodiment of the invention;
[0054] Figure 11 This is a schematic diagram of the structure of a multi-echo data MR imaging scanning device provided in an embodiment of the present invention.
[0055] The reference numerals in the attached figures are as follows:
[0056]
[0057]
[0058]
[0059] Detailed Implementation
[0060] To make the objectives, technical solutions, and advantages of the present invention clearer, the following embodiments are provided to further illustrate the present invention in detail.
[0061] Figure 4 This is a flowchart of a multi-echo data MR imaging scanning method according to an embodiment of the present invention. Figure 4 As shown, the specific steps are as follows:
[0062] Step 401: During the multi-echo MR imaging scan of the imaging target, for any TR: if automatic calibration data needs to be acquired within the current TR, and the position of the automatic calibration data to be acquired within the current TR in K-space is inconsistent with the position of any imaging data to be acquired within the current TR in K-space, then proceed to steps 402-403:
[0063] The determination of which TRs (Tracking Zones) require automatic calibration data acquisition, and whether the location of the automatic calibration data in K-space coincides with the location of any imaging data to be acquired within that TR, is determined by the size of the central region of the automatic calibration data in K-space and the fact that automatic calibration data is fully sampled while imaging data is undersampled. Automatic calibration data is always located in the central region of K-space; therefore, it only needs to be acquired within the TRs corresponding to the central region of K-space. The size of the central region of K-space occupied by the automatic calibration data is preset. Once the size of this central region is determined, the TRs in which automatic calibration data needs to be acquired are also determined. Furthermore, since automatic calibration data requires full sampling, the location of each automatic calibration data point in K-space can be determined once the size of its central region is determined. Imaging data, on the other hand, is undersampled; once the undersampling rate of the imaging data is determined, the sampling and undersampling locations of the imaging data are also determined. So, for a certain TR, if automatic calibration data needs to be collected within the TR, and the full sampling position of the automatic calibration data is exactly the undersampling position of the imaging data, then it belongs to the case where automatic calibration data needs to be collected within the TR, and the position of the automatic calibration data in K-space is inconsistent with the position of any imaging data to be collected within the TR in K-space.
[0064] Step 402: When the plateau signal of the first readout gradient is applied in the RO direction, an offset gradient is applied in the PE direction, wherein the first readout gradient is any readout gradient in the RO direction other than the last readout gradient.
[0065] In one optional embodiment, in step 402, the area of the offset gradient applied in the PE direction is equal to the reciprocal of the product of the length of the FOV (Field of View) in the PE direction, the levitation ratio, and 2π.
[0066] Step 403: Acquire automatic calibration data during the plateau period of the isophagic gradient signal in which the first readout gradient is applied in the RO direction.
[0067] In one optional embodiment, in step 403, the acquisition duration of the automatic calibration data is less than or equal to the application duration of the plateau period signal of the first readout gradient's phase gradient.
[0068] In one optional embodiment, after step 403, the method further includes: after the application of the dephasing gradient of the first readout gradient is completed, applying the convergence gradient of the offset gradient in step 402 in the PE direction, and the completion time of the application of the convergence gradient is the start time of the application of the plateau signal of the second readout gradient, wherein the area of the convergence gradient is equal to the area of the offset gradient in step 402, and the second readout gradient is the next readout gradient after the first readout gradient.
[0069] In practical applications, imaging data is acquired during the plateau period signal of each readout gradient applied in the RO direction within the current TR; and when the imaging data of the imaging target is acquired, the undersampled imaging data is recovered based on the acquired automatic calibration data.
[0070] In the above embodiments, during the multi-echo MR imaging scan of the imaging target, for any TR: if automatic calibration data needs to be acquired within the current TR, and the position of the automatic calibration data to be acquired within the current TR in K-space is inconsistent with the position of any imaging data to be acquired within the current TR in K-space, then within the current TR: when the plateau signal of the first readout gradient is applied in the RO direction, an offset gradient is applied in the PE direction. The first readout gradient is any readout gradient in the RO direction other than the last readout gradient. During the plateau signal of the astigmatic gradient of the first readout gradient applied in the RO direction, automatic calibration data is acquired. This ensures that: automatic calibration data is acquired simultaneously with imaging data, i.e., integrated acquisition of imaging data and automatic calibration data is achieved. At the same time, the length of the TR is not increased, avoiding TR oscillation, which ultimately reduces artifacts in the reconstructed image. Furthermore, since the automatic calibration data and imaging data are acquired within the same TR in the same sequence, the automatic calibration data and imaging data are continuous, which also ultimately reduces artifacts in the reconstructed image.
[0071] Figure 5 This is an example diagram of the MEDIC sequence used in a TR when automatic calibration data needs to be acquired within a TR, and the position of the automatic calibration data to be acquired in K-space is inconsistent with the position of any imaging data to be acquired within the TR in K-space.
[0072] like Figure 5 As shown, with Figure 1Compared to the MEDIC sequence shown, when the plateau signal of the first readout gradient 143 is applied in the RO direction corresponding to 14, an offset gradient 133 is applied in the PE direction corresponding to 13. During the application of the dephasing gradient 144 of the first readout gradient 143 in the RO direction corresponding to 14, an echo sampling control signal 155 is applied to acquire automatic calibration data, wherein the acquisition duration of the automatic calibration data is less than or equal to the application duration of the dephasing gradient 144. Then, after the dephasing gradient 144 is applied, a convergence gradient 134 of the offset gradient 133 is applied in the PE direction corresponding to 13. The completion time of the convergence gradient 134 is the start time of the application of the plateau signal of the second readout gradient 145, wherein the area of the convergence gradient 134 is equal to the area of the offset gradient 133.
[0073] In practical applications, an offset gradient 133 can be applied in the PE direction corresponding to 13 after the plateau signal of any of the readout gradients (excluding the last readout gradient) in the RO direction corresponding to 14 has been applied. For example... Figure 5 As shown:
[0074] When the plateau signal of readout gradient 143 is applied, an offset gradient 133 can be applied in the PE direction corresponding to 13. Then, during the plateau signal of the dephasing gradient 144 of readout gradient 143, an echo sampling control signal 155 is applied in the ADC direction corresponding to 15. After the dephasing gradient 144 is applied, the convergence gradient 134 of offset gradient 133 is applied in the PE direction corresponding to 13.
[0075] Alternatively, after the plateau signal of readout gradient 145 is applied, an offset gradient 133-2 can be applied in the PE direction corresponding to 13. Then, during the plateau signal of the dephasing gradient 146 of readout gradient 145, an echo sampling control signal 155-2 can be applied in the ADC direction corresponding to 15. After the dephasing gradient 146 is applied, a convergence gradient 134-2 of offset gradient 133-2 can be applied in the PE direction corresponding to 13.
[0076] Alternatively, after the plateau signal of readout gradient 147 is applied, an offset gradient 133-3 can be applied in the PE direction corresponding to 13. Then, during the plateau signal of the dephasing gradient 148 of readout gradient 147, an echo sampling control signal 155-3 can be applied in the ADC direction corresponding to 15. After the dephasing gradient 148 is applied, a convergence gradient 134-3 of offset gradient 133-3 can be applied in the PE direction corresponding to 13.
[0077] When automatic calibration data needs to be acquired within a certain TR, and the position of the acquired automatic calibration data in K-space coincides with the position of any imaging data to be acquired within that TR in K-space, then the MEDIC sequence used within that TR is as follows: Figure 1 As shown. At this point, all or part of all imaging data acquired within the TR (a part located in the central region of K-space) can be directly used as the automatic calibration data in the RO direction corresponding to the TR.
[0078] Figure 6 This diagram illustrates the imaging data and automatic calibration data collected in an application example of the present invention. 61 represents the imaging data and automatic calibration data collected on a specific two-dimensional plane. X represents a sampling point of the imaging data, 0 represents an undersampled point of the imaging data, and Y represents a sampling point of the automatic calibration data. The horizontal direction is the PE direction, the vertical direction is the Par direction, and the direction perpendicular to the two-dimensional plane is the RO direction. X(Y) indicates that imaging data was collected at this point, and all or part of this imaging data can be used as automatic calibration data.
[0079] 611 represents the imaging data and automatic calibration data in a certain Par direction within this two-dimensional plane. 6111 is a schematic diagram of 611 on the two-dimensional plane formed by the PE and RO directions. Each line in 6111 from top to bottom corresponds to each point in 611 from left to right. For example, the four green lines in 6111 correspond to a line in the RO direction where the four automatic calibration data sampling points located at the center of 611 are located.
[0080] like Figure 6 As shown in Figure 611, 611 corresponds to a certain Par direction and a certain RO direction in three-dimensional K-space. In 611, automatic calibration data is acquired starting from the 5th position along the PE direction. This position is the same as the 3rd sampling position of the imaging data. Then, the MEDIC sequence applied at this position is... Figure 1 The same applies; the 6th position is the undersampled position of the imaging data but the sampling position of the automatic calibration data. Therefore, an application is applied at the 6th position as follows: Figure 5 The MEDIC sequence shown is such that an echo sampling control signal is applied during the plateau period signal in which an offset gradient is applied in the PE direction and then a dephasing gradient is applied in the RO direction, thereby achieving automatic calibration data acquisition at the 6th position.
[0081] It should be noted that, for any TR: if automatic calibration data needs to be acquired within the current TR, and the position of the automatic calibration data in K-space is inconsistent with the position of any imaging data to be acquired within the TR in K-space, the automatic calibration data and imaging data acquired within the TR using the MEDIC sequence provided in this embodiment of the invention are continuous. The specific analysis is as follows:
[0082] Figure 7 The evolution curves of the echo signal when using MEDIC sequences for MR imaging are presented. Figure 7 MEDIC sequences and Figure 1 Similarly, 16 represents the echo signal evolution sequence. Each TR contains four echoes: e1 to e4, and the corresponding time functions can be expressed as: e1(t) to e4(t). s1(t), s2(t), and s3(t) are the signals that undergo precession and relaxation processes after e1(t), e2(t), and e3(t), respectively. t0, t1, t2, t3, t4, t5, t6, and t7 represent the start and end times of echoes e1, e2, e3, and e4.
[0083] Taking e1(t) as an example, it is known that: e1(t)∝M1x(t)+iM1y(t), t∈[t0,t1]
[0084] Where ∝ means "proportional to"; M1x(t) is the horizontal component of the transverse magnetization vector, which is the real part; M1y(t) is the vertical component of the transverse magnetization vector, which is the imaginary part.
[0085] Similarly: s1(t)∝M2x(t)+iM2y(t), t∈[t1,t2]
[0086] And because:
[0087]
[0088] Where M1z(t) is the longitudinal magnetization vector;
[0089] but:
[0090]
[0091] Furthermore, due to:
[0092]
[0093] and:
[0094]
[0095] Where β(t)=r∫γGdt
[0096] Where T2 is the transverse relaxation time, T1 is the longitudinal relaxation time, r is the spatial position of the magnetization vector, γ is the gyromagnetic ratio, G is the gradient corresponding to the field inhomogeneity, and ∫ is the integral sign.
[0097] Therefore, we can conclude that:
[0098]
[0099] That is, e1(t1) = s1(t1), meaning that e1(t) and s1(t) combine to form a continuous function; thus, it can be concluded that the segmented signals e1(t), s1(t), e2(t), s2(t), ..., s3(t) and e4(t) form a continuous function f(t), that is, there is continuity between the automatic calibration data acquired within the TR and the imaging data acquired within the TR.
[0100] According to sampling theory, after sampling f(t) using a sampling function, a discrete function f(n) is obtained, which will generate a periodic function in the transform domain. Figure 8 This diagram illustrates how a continuous function f(t) is sampled using a sampling function to obtain a discrete function f(n), where 81 represents the continuous function f(t), 82 represents the sampling function, and 83 represents the discrete function f(n).
[0101] Let F(jW) be a function in the transform domain obtained by performing a Fourier transform on F(t), that is:
[0102] F(jw)=∫f(t)*e - jwt dt
[0103] Let F(jnw0) be a function in the transform domain obtained by performing a discrete Fourier transform on F(n). Figure 9 The relationships between f(t), f(n), F(jw), and F(jnw0) are given, where 911 is f(t), 921 is F(jw); 912 is the sampling function, 922 is the function in the transform domain obtained after performing a Fourier transform on the sampling function; 913 is f(n), 923 is F(jnw0); 924 is the function obtained after performing a rectangular filter on F(jnw0), i.e., F(jw), and 914 is the function obtained after performing an inverse Fourier transform on 924, i.e., f(t). Therefore, 914 can be expressed as: sinc() is the sinc operator. Therefore, we can conclude the following:
[0104] Any point f(q) in a continuous function f(t) can be calculated using sinc interpolation of a discrete function f(n), that is:
[0105]
[0106] Where N0 is the number of discrete points in f(n), f(i) represents the i-th point in f(n), and W′ i Let W' be the interpolation factor for f(i). i It is unique; regardless of which point in f(t) needs to be recovered, this interpolation factor W′ can be used. iRecovery is then performed. Therefore, it can be determined that the interpolation factor W′ can be calculated using the fully sampled automatic calibration data. i Then through the interpolation factor W′ i To recover undersampled imaging data.
[0107] Figure 10 Examples of images obtained by parallel imaging of a specific layer of the knee joint using a two-dimensional MEDIC sequence, employing both existing independent acquisition methods and the integrated acquisition method provided in this embodiment of the invention. Some scanning parameters are as follows:
[0108] FOV = 240mm * 240mm, layer thickness = 2mm, image size = 256 * 256, acquisition bandwidth of imaging data = 488Hz / pixel, TE (Time Echo) / TR = 27ms / 40ms, acquisition bandwidth of automatic calibration data = 700Hz / pixel.
[0109] 101 represents the MR images of each echo in each channel obtained by using an independent acquisition method, that is, by acquiring undersampled imaging data using a MEDIC sequence, and then directly using the undersampled imaging data for image reconstruction. Here, c represents the channel, e represents the echo, c1-c4 represent channels 1-4 respectively, and e1-e3 represent echoes 1-3 respectively.
[0110] 102 represents the MR images of each channel obtained by image reconstruction using the automatic calibration data acquired through the integrated acquisition method provided in this embodiment of the invention.
[0111] 103 is the MR image of each echo obtained by recovering the undersampled imaging data from the automatic calibration data acquired using the integrated acquisition method provided in the embodiment of the present invention, and then performing image reconstruction on the recovered imaging data.
[0112] In this example, the GRAPPA (GeneRalized Autocalibrating Partially Parallel Acquisitions) method is used for image reconstruction.
[0113] It is obvious that the image quality of 103 is significantly better than that of 101.
[0114] Figure 11 This is a schematic diagram of the structure of a multi-echo data MR imaging scanning device 110 provided in an embodiment of the present invention. Figure 11 As shown, the device 110 mainly includes: a scanning control module 111 and an automatic calibration data acquisition module 112, wherein:
[0115] The scanning control module 111 is used to: during the multi-echo data MR imaging scanning of the imaging target, for any TR: if automatic calibration data needs to be acquired in the current TR, and the position of the automatic calibration data in the K space is inconsistent with the position of any imaging data to be acquired in the current TR in the K space, then: when the plateau signal of the first readout gradient is applied in the RO direction, an offset gradient is applied in the PE direction, wherein the first readout gradient is any readout gradient in the RO direction other than the last readout gradient.
[0116] The automatic calibration data acquisition module 112 is used to acquire automatic calibration data during the plateau period signal of the isophagic gradient of the first readout gradient applied in the RO direction.
[0117] In one optional embodiment, the automatic calibration data acquisition module 112 acquires automatic calibration data during the plateau period signal of the isophagic gradient of the first readout gradient applied in the RO direction, including: acquiring automatic calibration data during the plateau period signal of the isophagic gradient of the first readout gradient applied in the RO direction, wherein the acquisition duration is less than or equal to the application duration of the plateau period signal of the isophagic gradient of the first readout gradient.
[0118] In an optional embodiment, the scan control module 111 is further configured to: after the first gradient is applied, apply the back-convergence gradient of the offset gradient in the PE direction, and the time when the back-convergence gradient is applied is the time when the plateau signal of the second readout gradient is applied, wherein the area of the back-convergence gradient is equal to the area of the offset gradient, and the second readout gradient is the next readout gradient after the first readout gradient.
[0119] In one optional embodiment, the area of the convergence gradient of the offset gradient applied by the scanning control module 111 in the PE direction is equal to the reciprocal of the product of the length of the FOV in the PE direction, the levitation ratio, and 2π.
[0120] In an optional embodiment, the above-mentioned device 110 further includes: an imaging data acquisition module 113 and an undersampled imaging data recovery module 114, wherein:
[0121] Imaging data acquisition module 113 is used to: acquire imaging data during the plateau period signal when each readout gradient is applied in the RO direction within the current TR;
[0122] The undersampled imaging data recovery module 114 is used to: recover the undersampled imaging data based on the collected automatic calibration data after the imaging data of the imaging target has been acquired.
[0123] This invention also provides an MR imaging system, which includes the multi-echo data MR imaging scanning device 110 as described above.
[0124] It should be noted that the multi-echo data MR imaging scanning method, apparatus, and MR imaging system provided in the embodiments of the present invention can all be methods, apparatus, and systems applied in medical imaging.
[0125] This invention also provides a computer program product, including a computer program or instructions, which, when executed by a processor, implement the steps of the multi-echo data MR imaging scanning method as described in any of the above embodiments.
[0126] This invention also provides a computer-readable storage medium storing instructions that, when executed by a processor, can perform the steps of the multi-echo data MR imaging scanning method described above. In practical applications, the computer-readable medium may be included in the devices / apparatus / systems described above, or it may exist independently and not assembled into the device / apparatus / system. The computer-readable storage medium stores instructions that, when executed by a processor, can perform the steps of the multi-echo data MR imaging scanning method described above.
[0127] This invention also provides an electronic device. The electronic device may include a processor with one or more processing cores, a memory of one or more computer-readable storage media, and a computer program stored in the memory and executable on the processor. When the program in the memory is executed, the aforementioned multi-echo data MR imaging scanning method can be implemented.
[0128] Those skilled in the art will understand that the features described in the various embodiments and / or claims disclosed in this application can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this application. In particular, without departing from the spirit and teachings of this application, the features described in the various embodiments and / or claims of this application can be combined and / or combined in various ways, and all such combinations and / or combinations fall within the scope of this application.
[0129] This document uses specific embodiments to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the methods and core ideas of this application, and are not intended to limit this application. For those skilled in the art, changes can be made to the specific implementation methods and application scope based on the ideas, spirit and principles of this application. Any modifications, equivalent substitutions, improvements, etc., made should be included within the scope of protection of this application.
Claims
1. A multi-echo data magnetic resonance imaging scanning method, characterized in that, The method includes: During multi-echo magnetic resonance imaging (MRI) scans of the target, for any repetition time: If automatic calibration data needs to be acquired within the current repetition time, and the position of the automatic calibration data in K-space is inconsistent with the position of any imaging data to be acquired within the current repetition time in K-space, then: When the plateau signal of the first readout gradient is applied in the readout direction, an offset gradient is applied in the phase encoding direction, wherein the first readout gradient is any readout gradient in the readout direction other than the last readout gradient; Furthermore, during the plateau period of the isophagic gradient signal in which the first readout gradient is applied in the readout direction, automatic calibration data is acquired.
2. The method according to claim 1, characterized in that, During the plateau period signal of the dephasing gradient of the first readout gradient applied in the readout direction, automatic calibration data is acquired, including: During the plateau period of the isophagic gradient of the first readout gradient applied in the readout direction, automatic calibration data is acquired, and the acquisition duration is less than or equal to the application duration of the plateau period of the isophagic gradient of the first readout gradient.
3. The method according to claim 1, characterized in that, After acquiring automatic calibration data during the plateau period signal of the dephasing gradient of the first readout gradient applied in the readout direction, the process further includes: After the phase gradient of the first readout gradient is applied, the convergence gradient of the offset gradient is applied in the phase encoding direction, and the time when the application of the convergence gradient is completed is the time when the application of the plateau signal of the second readout gradient begins. The area of the convergence gradient is equal to the area of the offset gradient, and the second readout gradient is the next readout gradient after the first readout gradient.
4. The method according to claim 1, characterized in that, The area of the offset gradient is equal to the reciprocal of the product of the length of the field of view in the phase encoding direction, the levitation ratio, and 2π.
5. The method according to claim 1, characterized in that, The method further includes: acquiring imaging data during the plateau signal of each readout gradient applied in the readout direction within the current repetition time; Furthermore, once the imaging data of the imaging target has been acquired, the undersampled imaging data is recovered based on the acquired automatic calibration data.
6. A multi-echo data magnetic resonance imaging scanning device, characterized in that, The device includes: a scanning control module and an automatic calibration data acquisition module, wherein: The scanning control module is used to: during the multi-echo data magnetic resonance imaging scanning of the imaging target, for any repetition time: if automatic calibration data needs to be acquired within the current repetition time, and the position of the automatic calibration data in K-space is inconsistent with the position of any imaging data to be acquired within the current repetition time in K-space, then: when the plateau signal of the first readout gradient is applied in the readout direction, an offset gradient is applied in the phase encoding direction, wherein the first readout gradient is any readout gradient in the readout direction other than the last readout gradient; The automatic calibration data acquisition module is used to acquire automatic calibration data during the plateau period signal of the isophagic gradient of the first readout gradient applied in the readout direction.
7. The apparatus according to claim 6, characterized in that, The automatic calibration data acquisition module acquires automatic calibration data during the plateau period signal of the isophagic gradient of the first readout gradient applied in the readout direction, including: During the plateau period of the isophagic gradient of the first readout gradient applied in the readout direction, automatic calibration data is acquired, and the acquisition duration is less than or equal to the application duration of the plateau period of the isophagic gradient of the first readout gradient.
8. The apparatus according to claim 6, characterized in that, The scanning control module is further used for: After the phase gradient of the first readout gradient is applied, the convergence gradient of the offset gradient is applied in the phase encoding direction, and the time when the application of the convergence gradient is completed is the time when the application of the plateau signal of the second readout gradient begins. The area of the convergence gradient is equal to the area of the offset gradient, and the second readout gradient is the next readout gradient after the first readout gradient.
9. The apparatus according to claim 8, characterized in that, The area of the convergence gradient of the offset gradient applied by the scanning control module in the phase encoding direction is equal to the reciprocal of the product of the length of the field of view in the phase encoding direction, the levitation ratio, and 2π.
10. The apparatus according to claim 6, characterized in that, The device further includes: an imaging data acquisition module and an undersampled imaging data recovery module, wherein: The imaging data acquisition module is used to: acquire imaging data during the plateau signal when each readout gradient is applied in the readout direction within the current repetition time; The undersampled imaging data recovery module is used to recover the undersampled imaging data based on the acquired automatic calibration data after the imaging data of the imaging target has been acquired.
11. A magnetic resonance imaging system, characterized in that, The system includes a multi-echo data magnetic resonance imaging scanning apparatus as described in any one of claims 6 to 10.