Electromagnetic interference acquisition method in open magnetic resonance imaging

Abstract

The application discloses an electromagnetic interference collection method in open magnetic resonance imaging, and comprises the following steps: (1) sensing coil design and manufacture; (2) sensing coil deployment; (3) signal collection; (4) signal correlation analysis; (5) judging the correlation analysis result; (6) optimizing the sensing coil deployment. Based on the application, only one sensing coil can be used to collect electromagnetic interference signals with a correlation higher than 99.5% in the open magnetic resonance imaging coil, and the cost of the electromagnetic interference elimination related method in the open magnetic resonance imaging and the complexity of data processing are greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of medical device technology, and in particular to a method for acquiring electromagnetic interference in open magnetic resonance imaging. Background Technology

[0002] In recent years, academia and industry have focused on low-field (i.e., <0.3T) magnetic resonance imaging strategies to drive a paradigm shift from traditional MRI scanners to point-of-care systems. This type of low-field MRI offers advantages such as low cost, portability, and open access. However, a significant factor limiting the deployment of low-field MRI equipment outside shielded areas is the unavoidable electromagnetic interference during the imaging process.

[0003] Most existing solutions for electromagnetic interference in open low-field magnetic resonance imaging (MRI) employ multiple (≥2) detectors (coils and / or electrodes) to collect electromagnetic interference, and then use numerical calculations or deep learning methods to eliminate electromagnetic interference components in the MRI coil signal. Typically, these detectors have low detection performance, and it is necessary to compensate for the lack of detector performance by increasing the number of detectors.

[0004] However, an excessive number of detectors increases the cost and hardware complexity of low-field magnetic resonance imaging (MRI) equipment. Therefore, it is necessary to propose a method for detecting electromagnetic interference (EMI) signals in MRI that utilizes only a single sensing coil to detect EMI signals during the MRI process, while also meeting the signal correlation requirements of EMI cancellation methods. Summary of the Invention

[0005] In view of the above-mentioned defects or deficiencies in existing methods, the present invention provides an electromagnetic interference acquisition method for open magnetic resonance imaging, which can capture electromagnetic interference signals with a correlation of more than 99.5% with the magnetic resonance imaging coil using only one sensing coil, thereby significantly reducing the cost and hardware complexity of open magnetic resonance equipment.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for acquiring electromagnetic interference in open-type magnetic resonance imaging includes the following steps:

[0008] Step 1: Design and fabrication of the sensing coil, including,

[0009] Step 1.1: Design the shape and size of the sensing coil;

[0010] Step 1.2: Fabricate and tune the sensing coil;

[0011] Step 2: Deployment of sensing coils, including,

[0012] Step 2.1: Connect the sensing coil to the radio frequency receiving channel of the magnetic resonance imaging device;

[0013] Step 2.2: Place the sensing coil above or below the subject's body;

[0014] Step 2.3: Adjust the position and orientation of the sensing coil;

[0015] Step 3: Signal acquisition, including,

[0016] Step 3.1: Set the radio frequency gain of the magnetic resonance imaging device to 0;

[0017] Step 3.2: The magnetic resonance imaging equipment coil and sensing coil synchronously acquire signals;

[0018] Step 4: Signal correlation analysis, including,

[0019] Step 4.1: Extract the first frequency encoding line from the k-space data acquired by the sensing coil and the magnetic resonance imaging device coil, respectively;

[0020] Step 4.2: Calculate the one-dimensional modulus data or one-dimensional frequency data for the two frequency coding lines;

[0021] Step 4.3: Calculate the correlation between the one-dimensional modulus data or one-dimensional frequency data of the two frequency coding lines using the one-dimensional data correlation analysis method;

[0022] Step 4.4: Repeat steps 4.1-4.3 to calculate the correlation between every two frequency coding lines in the k-space data acquired by the sensing coil and the magnetic resonance imaging device coil, and take the average value;

[0023] Step 5: Determine whether the mean value meets the design target. If it does, proceed to step 7; otherwise, proceed to step 6.

[0024] Step 6: Optimize the deployment of sensing coils;

[0025] Step 7: Finish the design.

[0026] Furthermore, the sensing coil mentioned in step 1 is a surface coil; the resonant frequency of the sensing coil is the same as that of the magnetic resonance imaging coil.

[0027] Furthermore, in step 2, the sensing coil is oriented towards the opening of the magnet of the magnetic resonance imaging device, the sensing coil is positioned close to the opening of the magnet of the magnetic resonance imaging device, and the sensing coil does not have a coupling effect with the coil of the magnetic resonance imaging device; placing the sensing coil above or below the subject's body includes embedding the sensing coil in the bed board and being located below the subject's body, or placing it above the non-imaging area of ​​the subject's body.

[0028] Furthermore, during the signal acquisition process described in step 3, the gradient power amplifier and RF power amplifier of the magnetic resonance imaging device are kept on and the RF gain is set to 0 in the console software; the magnetic resonance imaging coil and the sensing coil synchronously acquire the signal of each frequency encoding line and fill the k space; the magnetic resonance imaging coil and the sensing coil can only acquire electromagnetic interference signals.

[0029] Furthermore, the design specifications include that the average correlation of the modulus signal or frequency signal of the frequency encoding line of the k-space data acquired by the magnetic resonance imaging coil and the sensing coil is higher than 99.5%.

[0030] Furthermore, step 6 optimizes the location and orientation of the sensing coil deployment.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] In view of the fact that the performance of electromagnetic interference detectors in the existing technology is weak and the number of detectors is large, which leads to the increase in cost and hardware complexity of low-field magnetic resonance imaging equipment, this method uses only one sensing coil as an electromagnetic interference detector. It can capture electromagnetic interference signals with a correlation higher than 99.5% with the magnetic resonance imaging coil and can meet the requirements of signal correlation in electromagnetic interference elimination correlation methods. Attached Figure Description

[0033] Figure 1 This is a flowchart of an electromagnetic interference acquisition method in open magnetic resonance imaging provided by an embodiment of the present invention;

[0034] Figure 2 A physical diagram of the sensing coil provided in an embodiment of the present invention;

[0035] Figure 3 A physical diagram of the magnetic resonance imaging coil provided in an embodiment of the present invention;

[0036] Figure 4 A schematic diagram illustrating the deployment range of the magnetic resonance imaging device and sensing coil provided in an embodiment of the present invention;

[0037] Figure 5 A schematic diagram of the signal acquisition sequence and radio frequency gain control provided in an embodiment of the present invention;

[0038] Figure 6 The modulus diagram of electromagnetic interference signals collected by the magnetic resonance imaging coil and sensing coil provided in the embodiments of the present invention;

[0039] Figure 7 Frequency diagram of electromagnetic interference signals collected by magnetic resonance imaging coils and sensing coils provided in embodiments of the present invention;

[0040] Figure 8This is a diagram illustrating the effect of an open magnetic resonance imaging electromagnetic interference cancellation method based on the present invention.

[0041] Figure 9 This is an illustration of the effect of another open magnetic resonance imaging electromagnetic interference cancellation method based on the present invention. Detailed Implementation

[0042] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0043] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0044] Example

[0045] like Figure 1 The flowchart shown illustrates a method for acquiring electromagnetic interference in open-type magnetic resonance imaging, comprising the following steps:

[0046] Step 1: Design and fabrication of the sensing coil, including,

[0047] Step 1.1: Design the shape and size of the sensing coil;

[0048] The coil is a surface coil and can be designed in a rectangular or circular shape. This embodiment uses the following... Figure 2 The rectangular surface coil shown is used as a sensing coil, and its dimensions are 15cm × 18cm.

[0049] Step 1.2: Fabrication and tuning of the sensing coil.

[0050] The fabricated sensing coil is tuned so that its resonant frequency matches that of the magnetic resonance imaging coil, thereby enabling both the sensing coil and the magnetic resonance imaging coil to capture electromagnetic interference within the same frequency band. This embodiment employs... Figure 3 The magnetic resonance imaging device coil shown.

[0051] Step 2: Deployment of sensing coils, including,

[0052] Step 2.1: Connect the sensing coil to the radio frequency receiving channel of the magnetic resonance imaging device.

[0053] Step 2.2: Place the sensing coil above or below the subject's body. The sensing coil can be embedded in the bed board below the subject's body, or it can be placed above the non-imaging area of ​​the subject's body, ensuring that it does not affect the normal imaging process and the subject's experience.

[0054] Step 2.3: Adjust the position and orientation of the sensing coil, such as... Figure 4 As shown, 401 is the magnetic resonance imaging (MRI) device, 402 is the bed, and 403 is the non-imaging area of ​​the subject's body, i.e., the deployment range of the sensing coil. The sensing coil is positioned as close as possible to the opening of the magnet in the open MRI device, ensuring no coupling effect occurs between it and the MRI coil. In this embodiment, the direction of the sensing coil is consistent with the opening of the magnet.

[0055] Step 3: Signal acquisition, including,

[0056] Step 3.1: As Figure 5 As shown, the radio frequency pulse, slice selection gradient, phase encoding gradient, and frequency encoding gradient during the signal acquisition process are the same as those during the imaging process. The difference is that the radio frequency gain is set to 0 during the signal acquisition process, while the radio frequency gain is set to a non-zero value N during the imaging process.

[0057] When the RF gain is set to 0, only electromagnetic interference signals can be captured by the magnetic resonance imaging coil and the sensing coil. At this time, the RF power amplifier and the gradient power amplifier remain on to ensure that the electromagnetic interference signals generated by the RF power amplifier and the gradient power amplifier can be captured by the magnetic resonance imaging coil and the sensing coil.

[0058] Step 3.2: The magnetic resonance imaging coil and the sensing coil acquire signals synchronously.

[0059] The signal acquisition process is the same as the imaging process, the difference being whether the magnetic resonance signal is excited. The magnetic resonance imaging coil and the sensing coil synchronously acquire electromagnetic interference signals, ensuring a sufficiently high correlation between the electromagnetic interference signals between the coils.

[0060] Step 4: Signal correlation analysis, including,

[0061] Step 4.1: Extract the first frequency encoding line from the k-space data acquired by the sensing coil and the magnetic resonance imaging coil, respectively. The k-space data of the sensing coil and the magnetic resonance imaging coil are K... sensing and K MRI .

[0062] Step 4.2: Calculate the one-dimensional modulus data or one-dimensional frequency data of the two frequency coding lines.

[0063] The one-dimensional modulus and one-dimensional frequency data of the first frequency-encoded line acquired by the sensing coil and magnetic resonance imaging coil are as follows:

[0064]

[0065]

[0066] Among them, Amp sensingFre sensing These represent the one-dimensional modulus data and one-dimensional frequency data of the frequency encoding line acquired by the sensing coil, respectively. MRI Fre MRI These represent the one-dimensional modulus data and one-dimensional frequency data of the frequency encoding line acquired by the magnetic resonance imaging coil, respectively.

[0067] Step 4.3: Calculate the correlation between the one-dimensional modulus data or one-dimensional frequency data of the two frequency coding lines using the one-dimensional data correlation analysis method.

[0068] In this embodiment, the Spearman correlation coefficient is used to calculate the correlation between the two frequency coding lines. The correlation between the one-dimensional modulus data and the one-dimensional frequency data of the two frequency coding lines can be expressed as:

[0069] Correlation Amp =spearman(Amp) sensing Amp MRI ).

[0070] Correlation Fre =spearman(Fre sensing ,Fre MRI ).

[0071] Figure 6 This is a modulus diagram of the electromagnetic interference signals collected by the magnetic resonance imaging device coil and sensing coil in this embodiment. 601 is the modulus data of a frequency encoding line in the k-space of the magnetic resonance imaging coil, and 602 is the modulus data of a frequency encoding line in the k-space of the sensing coil.

[0072] Figure 7 This is a frequency diagram of the electromagnetic interference signal collected by the magnetic resonance imaging coil and the sensing coil in this embodiment. 701 is the frequency data of a frequency encoding line in the k-space of the magnetic resonance imaging coil, and 702 is the frequency data of a frequency encoding line in the k-space of the sensing coil.

[0073] Figure 6 and Figure 7 The correlation between the two sets of one-dimensional data exceeds 99.8%.

[0074] Step 4.4: Repeat steps 4.1-4.3 to calculate the correlation between every two frequency-coded lines in the k-space data acquired by the sensing coil and the magnetic resonance imaging coil, and take the average value. The average value of the correlation between the frequency-coded lines in the two k-spaces is used as the correlation analysis result.

[0075] Step 5: Determine whether the mean value meets the design specifications. If it does, proceed to Step 7; otherwise, proceed to Step 6. The average correlation of the frequency coding lines in the two k-spaces should be greater than 99.5%. If it is lower than this standard, the deployment of the sensing coils needs to be optimized.

[0076] Step 6: Optimize the deployment of sensing coils. Adjust the position and orientation of the sensing coils.

[0077] Step 7: Finish the design.

[0078] In one embodiment, after deploying the sensing coil based on the present invention, the radio frequency gain is adjusted to a non-zero value so that the magnetic resonance signal of the imaging target can be excited. Then, the magnetic resonance imaging coil and the sensing coil simultaneously acquire signals, wherein the magnetic resonance imaging coil acquires magnetic resonance signals and electromagnetic interference signals, and the sensing coil acquires electromagnetic interference signals that are highly correlated with the electromagnetic interference signals in the magnetic resonance imaging coil. After the scan is completed, using the k-space data of the sensing coil, the electromagnetic interference in the k-space of the magnetic resonance imaging coil is eliminated using numerical calculation methods. Figure 8 The images show the results of a numerically computed-based open-loop magnetic resonance imaging (MRI) electromagnetic interference cancellation method. Image 801 is the reconstructed k-space image of the sensing coil. Image 802 is the reconstructed k-space image of the MRI coil. Image 803 is the reconstructed image after electromagnetic interference cancellation of the MRI coil's k-space.

[0079] In another embodiment, based on the present invention, highly correlated electromagnetic interference signals are acquired using the coils and sensing coils of a magnetic resonance imaging (MRI) device to construct a dataset and train a deep learning model. During imaging, the radio frequency gain is adjusted to a non-zero value so that the magnetic resonance signal of the imaging target can be excited. The electromagnetic interference captured in the sensing coil is used to predict the electromagnetic interference component in the MRI coil. Subtracting the predicted value of the electromagnetic interference component from the signal acquired by the MRI coil yields a magnetic resonance signal free of electromagnetic interference, thereby achieving electromagnetic interference elimination in open low-field MRI. Figure 9 The images show the results of an open-source electromagnetic interference cancellation method for magnetic resonance imaging (MRI) based on deep learning. Image 901 is the reconstructed k-space image of the sensing coil. Image 902 is the reconstructed k-space image of the MRI coil. Image 903 is the reconstructed image after electromagnetic interference cancellation of the k-space of the MRI coil.

[0080] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for acquiring electromagnetic interference in open-type magnetic resonance imaging, characterized in that, Includes the following steps: Step 1: Design and fabrication of the sensing coil, including, Step 1.1: Design the shape and size of the sensing coil; Step 1.2: Fabricate and tune the sensing coil; Step 2: Deployment of sensing coils, including, Step 2.1: Connect the sensing coil to the radio frequency receiving channel of the magnetic resonance imaging device; Step 2.2: Place the sensing coil above or below the subject's body; Step 2.3: Adjust the position and orientation of the sensing coil; Step 3: Signal acquisition, including, Step 3.1: Set the radio frequency gain of the magnetic resonance imaging device to 0; Step 3.2: The magnetic resonance imaging equipment coil and sensing coil synchronously acquire signals; Step 4: Signal correlation analysis, including, Step 4.1: Extract any frequency encoding line from the k-space data acquired by the sensing coil and the magnetic resonance imaging device coil, respectively; Step 4.2: Calculate the one-dimensional modulus data of the two frequency coding lines; Step 4.3: Calculate the correlation between the one-dimensional modulus values ​​of the two frequency coding lines using one-dimensional data correlation analysis; Step 4.4: Repeat steps 4.1-4.3 to calculate the correlation between every two frequency coding lines in the k-space data acquired by the sensing coil and the magnetic resonance imaging device coil, and take the average value; Step 5: Determine whether the mean value meets the design target. If it does, proceed to step 7; otherwise, proceed to step 6. Step 6: Optimize the deployment of sensing coils; Step 7: Finish the design.

2. The electromagnetic interference acquisition method in open magnetic resonance imaging according to claim 1, characterized in that, The sensing coil mentioned in step 1 is a surface coil; the resonant frequency of the sensing coil is the same as that of the magnetic resonance imaging device coil.

3. The electromagnetic interference acquisition method in open magnetic resonance imaging according to claim 1, characterized in that, In step 2, the sensing coil is oriented toward the opening of the magnet of the magnetic resonance imaging device, and the sensing coil is positioned close to the opening of the magnet of the magnetic resonance imaging device. The sensing coil and the magnetic resonance imaging device coil do not have a coupling effect. Placing the sensing coil above or below the subject's body includes embedding the sensing coil in the bed board and being located below the subject's body, or placing it above the non-imaging area of ​​the subject's body.

4. The electromagnetic interference acquisition method in open magnetic resonance imaging according to claim 1, characterized in that, During the signal acquisition process described in step 3, the gradient power amplifier and RF power amplifier of the magnetic resonance imaging device are kept on and the RF gain is set to 0 in the console software; the magnetic resonance imaging coil and sensing coil synchronously acquire the signal of each frequency encoding line and fill the k space, and the magnetic resonance imaging coil and sensing coil can only acquire electromagnetic interference signals.

5. The electromagnetic interference acquisition method in open magnetic resonance imaging according to claim 1, characterized in that, The design specifications include that the average correlation of the modulus signal or frequency signal of the frequency encoding line of the k-space data acquired by the magnetic resonance imaging coil and the sensing coil is higher than 99.5%.

6. The electromagnetic interference acquisition method in open magnetic resonance imaging according to claim 1, characterized in that, The optimized deployment of sensing coils includes optimizing the position and orientation of the sensing coils.

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