Non-contrast agent injection tumor glucose CEST weighted imaging acquisition and post-processing method

Abstract

The invention discloses a non-contrast agent injection tumor glucose CEST weighted imaging acquisition and post-processing method, and relates to the technical field of magnetic resonance imaging, and the method is characterized in that a 16-channel phased array coil is used on a 3.0 T MR scanner to obtain MRI; by means of the obtained MRI, a 3D glucose CEST (glucoCEST) image is obtained by means of a 3D single TSE-mDixon sequence and SPIR fat suppression; post-processing is carried out on the 3D (three-dimensional) glucoCEST image, and an MTRasym image is obtained; the change of the glucose CEST weighted signal is analyzed through MTRasym imaging, the change of the in-vivo glucose concentration is obtained, and the detection of the in-vivo glucose signal is completed. According to the magnetic resonance imaging technology based on chemical exchange saturation transfer, the contrast agent is replaced with the magnetic resonance saturation pulse for specifically inhibiting the glucose signal, in-vivo glucose signal detection can be achieved, meanwhile, the obtained image is high in resolution and low in cost, and repeated detection and clinical popularization are facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic resonance imaging, and more specifically, it relates to a method for collecting and post-processing tumor glucose CEST-weighted imaging without contrast agent injection. Background Art

[0002] Glucose is the main source of energy for most organisms, and its abnormal uptake is associated with many pathological conditions, including cancer, diabetes, and obesity, etc. Therefore, it is very necessary to develop a method capable of non-invasively detecting glucose metabolism in tissues.

[0003] So far, people mainly use 18 18F-FDG positron emission tomography (PET) imaging technology to detect the uptake of glucose in vivo. PET is a metabolic imaging technology that uses a radioactive tracer 18 18F-fluorodeoxyglucose ( 18 18F-FDG) to identify the presence and severity of diseases; since the proliferation activity and metabolism of most malignant tumors are higher than those of normal tissues, the glycolysis and glucose transport rate in their cells will increase, so 18 the uptake of 18F-FDG will also increase. In addition to PET, there are also some other technologies for detecting glucose uptake or metabolism in vivo, such as hyperpolarized MRI ( 13 13C-labeled D-glucose), stimulated Raman scattering, mass spectrometry, and fluorescence imaging, etc. However, these technologies are all in the experimental stage and have not entered the clinical application stage.

[0004] Although PET has been widely used in clinical research, however, the PET method has a high cost, a long detection time, a low image resolution, and requires injection of a contrast agent, and the contrast agent is radioactive. The PET results are also affected by factors such as blood glucose concentration, and hyperpolarized MRI (13C-labeled D-glucose) requires additional hardware and uses a hyperpolarizer to generate a hyperpolarized contrast agent for injection in real time to improve the resolution and signal-to-noise ratio of the results. Moreover, optical imaging methods also require injection of a contrast agent. Although the reagent is convenient to use and has a high cost-effectiveness, its tissue penetration is weak and a high dose is required during detection.

[0005] Therefore, the present invention aims to provide a method for collecting and post-processing tumor glucose CEST-weighted imaging without contrast agent injection to solve the above problems. Summary of the Invention

[0006] The object of the present invention is to provide a method for collecting and post-processing tumor glucose CEST-weighted imaging without contrast agent injection. The present invention is based on the magnetic resonance imaging technology of chemical exchange saturation transfer, and by using a magnetic resonance saturation pulse that specifically suppresses the glucose signal to replace the contrast agent, it can realize the detection of glucose signals in vivo.

[0007] The above technical object of the present invention is achieved through the following technical solutions: A method for collecting and post-processing tumor glucose CEST weighted imaging without contrast agent injection, comprising the following steps:

[0008] S1. Obtain MRI using a 16-channel phased array body coil on a 3.0T MR scanner;

[0009] S2. Utilize the obtained MRI, adopt a 3D single-shot TSE-mDixon sequence, and perform SPIR fat suppression to obtain 3D glucoCEST images;

[0010] S3. Post-process the 3D glucoCEST images to obtain MTRasym imaging;

[0011] S4. Analyze the change of glucose CEST weighted signal through MTRasym imaging to obtain the change of in-vivo glucose concentration, and complete the detection of in-vivo glucose signal.

[0012] The present invention is further configured as: The MRI in step S1 includes 2D fast spin echo images with different saturation frequencies including glucose frequency.

[0013] The present invention is further configured as: The 2D fast spin echo images are processed by using self-developed matlab code to obtain 2D original images based on glucose CEST weighting.

[0014] The present invention is further configured as: When adopting the 3D single-shot TSE-mDixon sequence and performing SPIR fat suppression in step S2, the saturation frequency and duration of the radiofrequency saturation pulse sequence of the glucose cest sequence are 1.2 ppm and 1 s respectively, and the B1 root mean square is 2.0 μT.

[0015] The present invention is further configured as: The process of post-processing the 3D glucoCEST images in step S3 is: Read in the original data, adopt a B0 inhomogeneity correction method to obtain a z-spectrum, and generate a glucose CEST weighted map.

[0016] The present invention is further configured as: The z-spectrum is obtained through 9 saturation frequency offset imagings at -1.5, -1.2, -0.8, -0.25, 0, 0.25, 0.8, 1.2, 1.5 and S0 imaging under an offset far from the resonance frequency.

[0017] The present invention is further configured as: The calculation formula of the glucose CEST weighted signal in step S4 is:

[0018] MTRasym(1.2ppm) = [S sat (-1.2ppm) - Ssat (+1.2 ppm)] / S0

[0019] Among them, S sat represents the signal intensity of the applied saturation pulse, and S0 represents the signal intensity without the applied saturation pulse.

[0020] In summary, the present invention has the following beneficial effects:

[0021] 1. Based on the magnetic resonance imaging technology of chemical exchange saturation transfer, the present invention can achieve in-vivo glucose signal detection by using a magnetic resonance saturation pulse that specifically inhibits glucose signals instead of a contrast agent;

[0022] 2. Compared with the traditional PET method, the present invention can achieve in-vivo glucose signal detection without injecting a contrast agent, and at the same time, the obtained images have high resolution, low cost, which is conducive to repeated detection and clinical promotion. Description of the Drawings

[0023] Figure 1 is a schematic flow chart of the non-contrast agent injection tumor glucose CEST weighted imaging acquisition and post-processing method in Embodiment 1 of the present invention;

[0024] Figure 2 is the glucose CEST weighted map in Embodiment 2 of the present invention;

[0025] Figure 3 is the z-spectrum map in Embodiment 2 of the present invention;

[0026] Figure 4 is the T1 / T2 mapping map in Embodiment 2 of the present invention;

[0027] Figure 5 is a comparison chart of the DWI image, glucose CEST image, and contrast-enhanced image of high-grade rectal cancer in Embodiment 3 of the present invention;

[0028] Figure 6 is a comparison chart of the DWI image, glucose CEST image, and contrast-enhanced image of low-grade rectal cancer in Embodiment 3 of the present invention. Detailed Embodiments

[0029] The following further elaborates on the present invention in conjunction with the attached Figure 1-6 drawings for a more detailed description.

[0030] Embodiment 1: A non-contrast agent injection tumor glucose CEST weighted imaging acquisition and post-processing method, including the following steps:

[0031] S1. Obtain MRI on a 3.0T MR (Ingenia 3.0T, Philips Healthcare, Best, Netherlands) scanner using a 16-channel phased array body coil; the MRI includes 2D fast spin echo images with different saturation frequencies including glucose frequency, and the 2D fast spin echo images are processed using self-developed Matlab code to obtain 2D raw images based on glucose CEST weighting.

[0032] S2. Using the obtained MRI, set the saturation frequency and duration of the glucose CEST sequence radiofrequency saturation pulse sequence to 1.2 ppm and 1 s respectively, set the B1 root mean square (B1, rms) to 2.0 μT, and use a 3D single-shot TSE-mDixon sequence with SPIR fat suppression to obtain 3D glucoCEST images.

[0033] S3. Post-process the 3D glucoCEST images. By reading in the raw data, use a B0 inhomogeneity correction method to obtain a z-spectrum through imaging at 9 saturation frequency offsets of -1.5, -1.2, -0.8, -0.25, 0, 0.25, 0.8, 1.2, 1.5 and S0 imaging at an offset far from the resonance frequency, generate a glucose CEST weighted map, and obtain MTRasym(1.2 ppm) imaging.

[0034] S4. Analyze the change of the glucose CEST weighted signal through MTRasym(1.2 ppm) imaging to obtain the change of in-vivo glucose concentration and complete the detection of in-vivo glucose signal. The calculation formula of the glucose CEST weighted signal is:

[0035] MTRasym(1.2 ppm) = [S sat (-1.2 ppm) - S sat (+1.2 ppm)] / S0

[0036] where S sat represents the signal intensity with the saturation pulse applied, and S0 represents the signal intensity without the saturation pulse applied.

[0037] The technical principle of this embodiment is: after applying a saturation pulse to glucose, due to the magnetization transfer effect, the free water signal decreases. By comparing the change of the free water signal before and after applying the saturation pulse, the change of glucose concentration is indirectly reflected.

[0038] Example 2: In-vitro model experiment on the acquisition and post-processing method of tumor glucose CEST weighted imaging without contrast agent injection

[0039] In this embodiment, a 5% glucose injection solution was used. In a 50 ml centrifuge tube, 5 ml, 10 ml, 15 ml and 20 ml of the 5% glucose injection solution were added respectively, and then PBS was added to fill the test tube; T1 / T2 mapping was collected as Figure 4 shown, the glucose CEST weighted image was as Figure 2 shown, and the z-spectrum was as Figure 3 shown.

[0040] Conclusion: This embodiment verified the feasibility and accuracy of the 2D glucose CEST weighted image in detecting glucose signals at different concentrations in Embodiment 1.

[0041] Embodiment 3: In-vivo tumor experiment on the acquisition and post-processing method of non-contrast-agent-injected tumor glucose CEST weighted imaging

[0042] In this embodiment, one case of high-grade rectal cancer and one case of low-grade rectal cancer confirmed by pathology were collected respectively. DWI images, glucose CEST images and contrast-enhanced images were collected respectively, as Figure 5 、 Figure 6 shown.

[0043] Conclusion: In this embodiment, it was found that the glucose CEST signal at the lesion of high-grade rectal cancer was higher, at 5%, while the glucose CEST signal at the lesion of low-grade rectal cancer was -0.3%. The change of the glucose CEST weighted signal at the positions of low-grade and high-grade tumors was detected through this embodiment, verifying that the present invention has practical clinical value.

[0044] This specific embodiment is only an explanation of the present invention and is not a limitation thereof. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present invention, it is protected by the patent law.

Claims

1. A method for acquisition and post-processing of tumor glucose CEST-weighted imaging without contrast agent injection, characterized by: The following steps are involved: S1, MRI was obtained using a 16-channel phased array body coil on a 3.0T MR scanner; S2. Using the acquired MRI, a 3D single-shot TSE-mDixon sequence and SPIR fat suppression were used to obtain 3D glucoCEST images; S3, post-processing the 3D glucoCEST image to obtain MTRasym imaging; S4. Analyze the changes in the glucose CEST weighted signal through MTRasym imaging to obtain the changes in the in vivo glucose concentration and complete the detection of the in vivo glucose signal.

2. The method for collecting and post-processing tumor glucose CEST-weighted imaging without contrast agent injection according to claim 1, characterized in that: In step S1, the MRI includes 2D fast spin echo images of different saturation frequencies including the glucose frequency.

3. The method for collecting and post-processing tumor glucose CEST-weighted imaging without contrast agent injection according to claim 2, characterized in that: The 2D fast spin echo image is processed by using a self-developed matlab code to obtain a 2D original image based on glucose CEST weighting.

4. The method for collecting and post-processing tumor glucose CEST-weighted imaging without contrast agent injection according to claim 1, characterized in that: In the step S2, a 3D single-shot TSE-mDixon sequence is used. During SPIR fat suppression, the saturation frequency and duration of the glucose cest sequence radio frequency saturation pulse sequence are 1.2 ppm and 1 s respectively, and the B1 root mean square is 2.0 μT.

5. The method for collecting and post-processing tumor glucose CEST-weighted imaging without contrast agent injection according to claim 1, characterized in that: The process of post-processing the 3D glucoCEST image in step S3 is: reading the original data, using the B0 inhomogeneity correction method, obtaining the z spectrum, and generating the glucose CEST weighted map.

6. The method for collecting and post-processing tumor glucose CEST-weighted imaging without contrast agent injection according to claim 5, characterized in that: The z spectrum was obtained by imaging at nine saturation frequency offsets of -1.5, -1.2, -0.8, -0.25, 0, 0.25, 0.8, 1.2, 1.5 and S0 imaging at one offset away from the resonance frequency.

7. The method for collecting and post-processing tumor glucose CEST-weighted imaging without contrast agent injection according to claim 1, characterized in that: The calculation formula of the glucose CEST weighted signal in step S4 is: MTRasym(1.2ppm)=[S sat (-1.2ppm)-S sat (+1.2ppm)] / S0 Among them, S sat S0 represents the signal intensity when a saturation pulse is applied, and S1 represents the signal intensity when a saturation pulse is not applied.

Images