A method for improving signal-to-noise ratio and contrast of magnetic resonance images

Abstract

The present invention discloses a method for improving the signal-to-noise ratio and contrast of magnetic resonance images, and specifically relates to the field of magnetic resonance imaging. The method for improving the signal-to-noise ratio and contrast of magnetic resonance images is as follows: setting an echo chain value in an engineer debugging interface, calculating a central echo value according to the echo chain value, and then setting an effective echo value, calculating the number of effective echo forward echoes, and converting a 90-degree echo to a 90-degree echo. o The ETL echoes collected after the RF pulse excitation are placed in the echo list 1, and the echoes in the echo list 1 are reordered according to the effective echo advance number, and the result is placed in the newly created echo list 2, and the obtained echo list 2 is applied in the multi-echo sequence acquisition and reconstruction process. The present invention adopts the above method to keep the echo chain, imaging acquisition time and image resolution unchanged, and the image weighted properties meet the requirements, and by reasonably reducing the effective TE time, the MR signal intensity of the central echo is improved, and finally the signal-to-noise ratio and contrast of the image are improved.

Description

Technical Field

[0001] The invention relates to the technical field of magnetic resonance imaging, and in particular to a method for improving the signal-to-noise ratio and contrast of a magnetic resonance image. Background Art

[0002] K space, also known as Fourier space, is a space filled with the original digital data of the magnetic resonance (MR) signal with spatial positioning encoding. The echo filling the center of the K space will mainly determine the image contrast. In the sequential imaging of multiple echo chains, any echo in the echo chain can be filled in the center of the K space. o The time interval from the midpoint of the pulse to the midpoint of the echo at the center of the K space is defined as the effective TE. When the effective TE is very short, the attenuation of the magnetic resonance signal is small, the collected MRI signal is high, and thus the signal-to-noise ratio is high, but the influence of the tissue's T2 relaxation on the image contrast is basically eliminated; when the effective TE is very long, a heavily weighted T2WI will be obtained. Therefore, in the T2-weighted imaging of the multi-echo chain sequence, when the echo chain is determined and unchanged, how to select the appropriate effective TE time within the T2-weighted effective TE range is crucial to ensure that the image scanning time and image resolution remain unchanged and to improve the image's signal-to-noise ratio and contrast. Summary of the invention

[0003] The present invention mainly provides a method for improving the signal-to-noise ratio and contrast of magnetic resonance images, which can solve the shortcomings of the prior art. Under the premise of keeping the echo chain, imaging acquisition time and image resolution unchanged and the image weighted properties meeting the requirements, the effective TE time is reasonably reduced, the MR signal intensity of the central echo is improved, and finally the signal-to-noise ratio and contrast of the image are improved.

[0004] To achieve the above object, the present invention provides a method for improving the signal-to-noise ratio and contrast of a magnetic resonance image, the steps of which are as follows:

[0005] Step 1: Set the echo chain (ETL) value in the MRI equipment engineer debugging interface.

[0006] Step 2: Calculate the center echo value (Center_Echo) based on the ETL value:

[0007] If ETL is an odd number, Center_Echo = (ETL+1) / 2;

[0008] If ETL is even, Center_Echo=(ETL / 2) +1.

[0009] Step 3: Set the effective echo value (Efect_Echoe) in the engineer debugging interface, where the Efect_Echoe value is not greater than the Center_Echo value.

[0010] Step 4: Calculate the number of effective echo front echoes as n1 = Center_Echo - Efect_Echoe.

[0011] Step 5: 90 o The ETL echoes collected after the RF pulse excitation are placed in the echo list 1 in sequence.

[0012] Step 6: Reorder the echoes in echo list 1 according to the number of effective echo advances, and place the results in the newly created echo list 2; the specific sorting process is: place the (n1+1)th echo in echo list 1 at the 1st position in echo list 2, the (n1+2)th echo in echo list 1 at the 2nd position in echo list 2, ..., and so on, the ETLth echo in echo list 1 is placed at the (ETL-n1)th position in the new echo list 2; then place the 1st echo in echo list 1 at the (ETL-n1+1)th position in echo list 2, ..., and so on, and finally place the n1th echo in echo list 1 at the last position in echo list 2.

[0013] Step 7: Apply the obtained echo list 2 to the multi-echo sequence acquisition and reconstruction process to obtain the original MRI data, and then reconstruct the original data to obtain the final MRI image.

[0014] The beneficial effects of the present invention are:

[0015] In the process of multi-echo sequence acquisition, the image weighted properties are guaranteed to meet the requirements, and under the premise that the echo chain, imaging acquisition time and image resolution remain unchanged, the signal-to-noise ratio and contrast of the image are improved by reducing the effective TE value.

[0016] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a flow chart of a method for improving the signal-to-noise ratio and contrast of magnetic resonance images.

[0018] Figure 2 It is a schematic diagram of filling the K space when the effective echo is moved forward by one K space in an embodiment of the present invention.

[0019] Figure 3 It is a schematic diagram of filling two K spaces with effective echo advance in an embodiment of the present invention.

[0020] Figure 4 Schematic diagram of echo signal strength at different positions after the effective echo is moved forward in an embodiment of the present invention.

[0021] Figure 5This is an image obtained without using the imaging method of the present invention.

[0022] Figure 6 This is an image obtained by using the effective echo advance of the present invention.

[0023] Figure 7 These are two images obtained by using the effective echo forward shift of the present invention. DETAILED DESCRIPTION

[0024] The following is a further description of the embodiments of the present invention in conjunction with the accompanying drawings. In this embodiment, a method for improving the signal-to-noise ratio and contrast of a magnetic resonance image according to the present invention is described in detail by taking the acquisition of a T2-weighted image by a Fast Spin Echo (FSE) sequence with an echo train length of 9, a sampling bandwidth of 12.5 KHz, and a slice number of 14 as an example. The process is as follows: Figure 1 As shown, the specific steps are as follows:

[0025] Step 1: Set the echo chain (ETL) value in the MRI equipment engineer debugging interface.

[0026] Step 2: Calculate the center echo value (Center_Echo) based on the ETL value:

[0027] If ETL is an odd number, Center_Echo = (ETL+1) / 2;

[0028] If ETL is an even number, Center_Echo=(ETL / 2) +1.

[0029] Step 3: Set the effective echo value (Efect_Echoe) in the engineer debugging interface, where the Efect_Echoe value is not greater than the Center_Echo value.

[0030] Step 4: Calculate the number of effective echo advance echoes:

[0031] n1= Center_Echo-Efect_Echoe.

[0032] Step 5: 90 o The ETL echoes collected after the RF pulse excitation are placed in the echo list 1 in sequence.

[0033] Step 6: Reorder the echoes in echo list 1 according to the number of effective echo advances, and place the result in the newly created echo list 2; the specific sorting process is: place the (n1+1)th echo in echo list 1 at the first position in echo list 2, the (n1+2)th echo in echo list 1 at the second position in echo list 2, ..., and so on, the ETLth echo in echo list 1 is placed at the (ETL-n1)th position in the new echo list 2; then place the first echo in echo list 1 at the (ETL-n1+1)th position in echo list 2, ..., and so on, and finally place the n1th echo in echo list 1 at the last position in echo list 2. The specific example is as follows: Figure 2-Figure 4 shown.

[0034] Figure 2 This is a schematic diagram of K-space filling when the effective echo is moved forward by one in the embodiment. Step 2 is executed to obtain a central echo of 5. If the effective echo is set to 5, the effective echo is not moved forward, and the K-space filling method is as shown in echo list 1; if the effective echo is set to 4, steps 4 to 6 are executed, and the final space filling method is as shown in echo list 2. Compared with echo list 1, it can be clearly seen that the echo signal position is moved forward by one.

[0035] Figure 3 If the effective echo is set to 3, and steps 4 to 6 are executed, the final space filling method is shown in echo list 2. Compared with echo list 1, it can be clearly seen that the echo signal position is moved forward by 2.

[0036] Figure 4 Schematic diagram of the echo signal strength at different positions after the effective echo is moved forward in the embodiment. When the effective echo value is equal to the central echo value, the K-space echo signal filling method is as follows: Figure 2 and Figure 3 As shown in the echo list 1, the echo signal strength at different positions is obtained as follows Figure 4 As shown in 4-1, the position with the maximum signal strength is at 5; when the effective echo moves forward by 1, the K-space echo signal filling method is as follows Figure 2 When the echo list 2 is shown, the echo signal strength position is obtained as follows Figure 4 As shown in 4-2, the position with the maximum signal intensity is at 4; when the effective echo moves forward by 2, the K-space echo signal is filled as follows Figure 3 As shown in echo list 2, the echo signal strength position is obtained as follows Figure 4 As shown in Figure 4-3, the position with the highest signal strength is at 3.

[0037] Step 7: Apply the obtained echo list 2 to the multi-echo sequence acquisition and reconstruction process to obtain the original MRI data, and then reconstruct the original data to obtain the final MRI image. The final MRI image is as follows Figure 5 to Figure 7 As shown, Figure 5 to Figure 7 All of them are test images on a 0.16T conventional magnetic resonance imaging system. Figure 5 to Figure 7 It can be seen that after applying the method of the present invention, the signal-to-noise ratio and contrast of the magnetic resonance image are significantly improved.

[0038] Figure 5 is an image obtained without using the imaging method of the present invention, where TR = 4250, TE = 155. It can be seen from the figure that the mean value of the signal of the region of interest in the phantom is 646.6, and the average value of the standard deviation of the background signal at the four corners is 14.2, so the signal-to-noise ratio of the water phantom image is 30.053.

[0039] Figure 6 This is an image obtained by using the imaging method provided by the present invention to move the effective echo forward by one, wherein TR = 4250, TE = 124.2. It can be seen from the figure that the mean value of the signal of the region of interest in the phantom is 628.2, and the average value of the standard deviation of the background signal at the four corners is 10.45, so the signal-to-noise ratio of the water phantom image is 39.676.

[0040] Figure 7 This is an image obtained by using the imaging method provided by the present invention to move the effective echo forward by two. TR=4260, TE=93.4. It can be seen from the figure that the mean value of the signal of the region of interest in the phantom is 640.2, and the average value of the standard deviation of the background signal at the four corners is 8.9, so the signal-to-noise ratio of the water phantom image is 47.476.

[0041] The method of the present invention is simple and can ensure that the image weighted properties meet the requirements during the multi-echo sequence acquisition process. Under the premise that the echo chain, imaging acquisition time and image resolution remain unchanged, the signal-to-noise ratio and contrast of the image are improved by reducing the effective TE value, thereby improving the image quality.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for improving the signal-to-noise ratio and contrast of a magnetic resonance image, characterized in that: Here are the steps: Step 1: Set the echo chain (ETL) value in the MRI equipment engineer debugging interface; Step 2: Calculate the center echo value (Center_Echo) based on the ETL value. If ETL is an odd number, Center_Echo=(ETL+1) / 2; If ETL is an even number, Center_Echo=(ETL / 2)+1; Step 3: Set the effective echo value (Efect_Echoe) in the MRI equipment engineer debugging interface, where the Efect_Echoe value is not greater than the Center_Echo value; Step 4: Calculate the number of effective echo front echoes as n1=Center_Echo-Efect_Echoe; Step 5: 90 o The ETL echoes collected after the RF pulse excitation are placed in echo list 1; Step 6: Re-sort the echoes in echo list 1 according to the number of effective echo forward echoes, and place the result in the newly created echo list 2. The specific sorting process is: put the (n1+1)th echo in echo list 1 in the first position in echo list 2, the (n1+2)th echo in echo list 1 in the second position in echo list 2, ..., and so on, the ETLth echo in echo list 1 is placed in the (ETL-n1)th position in the new echo list 2; then put the first echo in echo list 1 in the (ETL-n1+1)th position in echo list 2, ..., and so on, and finally put the n1th echo in echo list 1 in the last position in echo list 2; Step 7: Apply the obtained echo list 2 to the multi-echo sequence acquisition and reconstruction process to obtain the original MRI data, and then reconstruct the original data to obtain the final MRI image.

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