Rat caudal vertebra magnetic resonance image acquisition device and method

Abstract

The invention provides a rat caudal vertebra magnetic resonance image acquisition device and method, and the device comprises a nuclear magnetic resonance spectrometer, a fixing material, and an elimination filling material. The fixing material is fixed at the bottom of a scanning radio frequency coil of the nuclear magnetic resonance spectrometer, a groove is formed in the fixing material, and the groove is matched with the caudal vertebra and the hip of a rat to be detected in position; the elimination filling material is an adaptive material, the elimination filling material and the fixing material fix the position of the to-be-detected rat, and a magnetic resonance image is obtained through scanning of a nuclear magnetic resonance spectrometer. The fixing material used in the invention has certain plasticity, can effectively fill irregular space around a scanning area, reduces magnetic sensitive artifacts, and improves the imaging definition. The rat caudal vertebra scanning device is simple in structure, free of filling materials, non-toxic, odorless, high in plasticity, light in texture and moderate in viscosity, can stabilize the caudal vertebra scanning area of a rat to be detected, does not cause extra burden to animals, ensures that the position of the rat is fixed in the imaging process, and ensures the accuracy of images.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic resonance imaging technology, and particularly to a device and method for obtaining magnetic resonance images of rat caudal vertebrae. Background Art

[0002] Rats are common experimental small animals because of their low price, strong reproductive ability and easy breeding. Their caudal vertebrae are very convenient for researchers to operate because they are exposed and have multiple segments, and are ideal research objects in the field of orthopedic spine research. After researchers perform modeling or treatment on the intervertebral discs of rat caudal vertebrae, they need to regularly understand the evolution of the diseased intervertebral discs. CT and X-ray examinations are sensitive to bone lesions, but the intervertebral disc belongs to soft tissue and cannot be imaged under X-rays. Magnetic resonance scanning is the most ideal examination method for observing soft tissue lesions, but current existing technical means are still difficult to obtain magnetic resonance images of the caudal vertebrae of live rats. The reasons are as follows: 1. When the buttocks of a rat transition to the caudal vertebrae, the tissue structure suddenly becomes thinner, resulting in severe susceptibility artifacts. 2. The caudal vertebrae of rats are slender, and the magnetic resonance signal itself is weak, and the device cannot start the scanning program. 3. The caudal vertebrae of rats are relatively long and usually curved. It must be straightened and displayed on a plane to facilitate device scanning and data analysis. 4. The magnetic resonance scanning time is long and sensitive to movement. Even if a live rat is anesthetized in advance, there are still physiological movements such as respiratory movement and intestinal peristalsis, as well as anesthesia recovery, etc. Summary of the Invention

[0003] Based on this, it is necessary to provide a device and method for obtaining magnetic resonance images of rat caudal vertebrae in view of the above technical problems.

[0004] A device for obtaining magnetic resonance images of rat caudal vertebrae includes: a nuclear magnetic resonance instrument, a fixing material, and an eliminating and filling material;

[0005] The fixing material is fixed at the bottom of the scanning radiofrequency coil of the nuclear magnetic resonance instrument. A groove is provided on the fixing material, and the groove is adapted to the positions of the caudal vertebrae and buttocks of the rat to be measured; the eliminating and filling material is an adaptable material, which together with the fixing material fixes the position of the rat to be measured, and magnetic resonance images are obtained by scanning with the nuclear magnetic resonance instrument.

[0006] In one embodiment, it further includes: a signal enhancing material;

[0007] The signal enhancing material is fixed inside the scanning radiofrequency coil of the nuclear magnetic resonance instrument, specifically above the caudal vertebrae of the rat to be measured, and is used to enhance the magnetic resonance signal intensity of the scanning area.

[0008] In one embodiment, the signal enhancing material is made through the following steps:

[0009] Weigh the first raw material according to a preset ratio; wherein, the first raw material includes: a filler, liquid paraffin, and glycerol;

[0010] Mix the first raw material evenly, pack it into small bags and evacuate to obtain a signal enhancement material.

[0011] In one embodiment, the fixing material is made through the following steps:

[0012] Weigh the second raw material according to a preset ratio; wherein, the second raw material includes: a base polymer, a plasticizer, a filling material, a thixotropic agent, and a stabilizer;

[0013] Mix the base polymer and the plasticizer, and stir at 80 - 120 °C for 10 - 30 minutes to form a homogeneous colloid;

[0014] Add the inorganic filler, the thixotropic agent, and the stabilizer to the homogeneous colloid, and knead in a mixer at a speed of 50 - 100 rpm for 15 - 45 minutes to obtain a mixed material;

[0015] Transfer the mixed material to a vacuum degassing device, and degas at a pressure of -0.06 to -0.09 MPa for 5 - 20 minutes to obtain a degassed material;

[0016] Form the degassed material into a sheet or block through a calender, and cool it to room temperature to obtain a fixing raw material with a Shore A hardness of 20 - 50 and a temperature resistance range of -30 °C to 120 °C;

[0017] Lay the fixing raw material flat in the scanning radiofrequency coil of the nuclear magnetic resonance instrument, try to cover the bottom of the scanning radiofrequency coil as much as possible, and leave a space for the test white rat to lie prone;

[0018] Place the test white rat prone on the fixing raw material, with the head facing forward to ensure unobstructed breathing; gently press the back and buttocks of the test white rat, straighten the tail vertebra of the test white rat and press it on the fixing raw material, so that the body shape characteristics of the test white rat are retained on the fixing raw material to obtain a fixing material.

[0019] In one embodiment, the elimination filling material is made through the following steps:

[0020] Weigh the third raw material according to a preset ratio; wherein, the third raw material includes: foamed microspheres, an adhesive, a plasticizer, a light filler, a moisturizing agent, and deionized water;

[0021] Mix the adhesive and the deionized water, and stir at 60 - 80 °C until completely dissolved to form a transparent glue solution;

[0022] Add the plasticizer and the humectant to the transparent adhesive liquid in sequence, maintain the temperature at 40-50 °C, and stir until evenly mixed to obtain a mixed adhesive liquid;

[0023] Add the foaming microspheres and the light filler to the mixed adhesive liquid in sequence, and stir at a speed of 200-400 rpm for 10-30 minutes to form a uniform paste;

[0024] Place the uniform paste in a vacuum degassing machine, and degas it at a pressure of -0.08 to -0.1 MPa for 5-15 minutes to obtain a filling material free of air bubbles.

[0025] In one of the embodiments, obtaining a magnetic resonance image by scanning with the nuclear magnetic resonance instrument includes:

[0026] Step S1: Use the spin echo sequence as the basic sequence, set the T2 weighted imaging parameters, and generate a T2 contrast image;

[0027] Step S2: Introduce an echo train in the T2 weighted sequence formed in Step S1, and set the acceleration factor to 5-11 to obtain an accelerated TSE-T2 weighted image;

[0028] Step S3: Based on applying the frequency selective fat suppression technique, apply a presaturation pulse in the TSE sequence formed in Step S2 to suppress the normal vertebral body fat signal to a low signal while retaining the water signal, and generate a fat-suppressed TSE-T2 weighted image;

[0029] Step S4: On the basis of Step S3, through the SPAIR technique, set the frequency offset to 200 Hz, and adjust the arrival mode and power of the 180° refocusing radio frequency pulse to further suppress the residual fat signal and obtain a high-contrast SPAIR-TSE-T2 weighted image;

[0030] Step S5: Apply a negative 90° radio frequency pulse at the end of the sequence echo train formed in Step S4 to force the longitudinal magnetization vector to recover and generate a time-optimized DRIVE-SPAIR-TSE-T2 weighted image;

[0031] Step S6: For the rat scanning area, adjust the gradient coil parameters to reduce the inhomogeneity of the main magnetic field, thereby further reducing the susceptibility artifacts and obtaining the final magnetic resonance image.

[0032] In one of the embodiments, configuring the T2 weighted imaging parameters includes:

[0033] Based on the sagittal plane image scanning of the coccyx, set the repetition time TR to 2000 - 6000 ms; set the echo time TE to 60 - 120 ms; set the phase encoding direction to anterior-posterior; set the frequency encoding direction to cephalocaudal; set the scan matrix to 288 * 368; set the voxel size to 0.3 * 0.3 mm; set the number of excitations to 2 - 4 times; set the scan slice thickness to 1 - 2.5 mm per slice; set the number of slices to 7 - 11 slices;

[0034] Based on the axial plane image scanning of the intervertebral disc, set the repetition time TR to 2000 - 6000 ms; set the echo time TE to 60 - 120 ms; set the phase encoding direction to anterior-posterior; set the frequency encoding direction to left-right; set the scan matrix to 288 * 288; set the voxel size to 0.3 * 0.3 mm; set the number of excitations to 2 - 4 times; set the scan slice thickness to 1 - 1.5 mm per slice; set the number of slices to 3 - 5 slices.

[0035] A method for obtaining a magnetic resonance image of a rat coccyx, used for the device for obtaining a magnetic resonance image of a rat coccyx as described above, includes:

[0036] Fix the fixing material at the bottom of the scanning radiofrequency coil of the nuclear magnetic resonance instrument. There are grooves on the fixing material, and the grooves are adapted to the positions of the coccyx and buttocks of the rat to be measured. Place the position of the coccyx of the rat to be measured in the groove, place the elimination filling material on the coccyx of the rat to be measured, fill the remaining gap between the coccyx of the rat to be measured and the fixing material, and try to expel all the air. Fix the position of the rat to be measured, and obtain a magnetic resonance image by scanning with the nuclear magnetic resonance instrument.

[0037] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: The fixing material used in the present invention has certain plasticity, can effectively fill the irregular space around the scanning area, reduce magnetic susceptibility artifacts, and improve the clarity of imaging. The elimination filling material is non-toxic, odorless, has strong plasticity, is light in texture, and has moderate viscosity. It can not only stabilize the scanning area of the coccyx of the rat to be measured, but also will not cause additional burden to the animal, ensuring that the position of the rat remains fixed during imaging and guaranteeing the accuracy of the image. Place a signal enhancement material above the scanning area of the anesthetized rat coccyx. The signal enhancement material helps to enhance the magnetic resonance signal intensity of the scanning area and is almost invisible after the fat suppression technique, with almost no interference to the image. Scan through the nuclear magnetic resonance instrument, and the DRIVE + TSE imaging realizes fast scanning. The SPAIR + high-order shimming technique further reduces magnetic susceptibility artifacts, thereby obtaining the magnetic resonance image of the rat coccyx, providing a more reliable theoretical basis for subsequent medical research and detection, and can also be extended to the spinal imaging scenarios of other small animals (mice, rabbits). Description of the Drawings

[0038] Figure 1 Schematic diagram of the structure of a rat caudal vertebra magnetic resonance image acquisition device in an embodiment;

[0039] Figure 2 Schematic diagram of the shaping process of the fixing material in an embodiment;

[0040] Figure 3 Schematic diagram of the SE sequence pulse in an embodiment;

[0041] Figure 4 Schematic diagram of the TSE pulse in an embodiment;

[0042] Figure 5 Schematic diagram of the SPAIR sequence in an embodiment;

[0043] Figure 6 Schematic diagram of the sequence after DRIVE processing in an embodiment;

[0044] Figure 7 Schematic diagram of the magnetic resonance image in an embodiment;

[0045] Figure 8 Schematic diagram of a failed image with severe susceptibility artifacts in an embodiment. Detailed implementation manners

[0046] Before describing the detailed implementation manners of the present invention, the overall concept of the present invention is described as follows:

[0047] The present invention mainly focuses on the research and development of the process for obtaining magnetic resonance images of the sacral and caudal regions of live small animals (such as rats). At present, it is difficult to obtain magnetic resonance images of the caudal vertebrae of live rats by existing technical means.

[0048] Therefore, the present invention proposes a rat caudal vertebra magnetic resonance image acquisition device. The anesthetized rat is fixed by a fixing material and an elimination filling material, scanned by a nuclear magnetic resonance instrument, and rapid scanning is achieved through DRIVE + TSE imaging. The SPAIR + high-order shimming technology further reduces susceptibility artifacts, which can meet the safety requirements of live rats and can also be extended to the spinal imaging scenarios of other small animals (mice, rabbits).

[0049] After introducing the overall concept of the present invention, in order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below through specific implementation manners in conjunction with the accompanying drawings.

[0050] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in one or more embodiments of this specification should have the ordinary meanings understood by those of ordinary skill in the art to which the present invention pertains. The terms "first", "second" and similar words used in one or more embodiments of this specification do not denote any order, quantity or importance, but are only used to distinguish different components. Words such as "including" or "comprising" mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. Words such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Upper", "lower", "left", "right", etc. are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0051] For ease of understanding, the following explains the nouns involved in the embodiments of the present invention:

[0052] SE (Spin Echo) sequence: Spin echo sequence, the most commonly used basic sequence in magnetic resonance imaging, which can be used to generate T1-weighted, T2-weighted and proton density-weighted images.

[0053] T2WI: T2-weighted imaging.

[0054] SPAIR (Spectral Attenuated Inversion Recovery) fat suppression technique: Frequency attenuation inversion recovery technique, a fat suppression technique based on frequency selectivity and inversion recovery principles.

[0055] TSE (Turbo Spin Echo): Fast spin echo.

[0056] STIR (Short TI Inversion Recovery) fat suppression technique: Short time inversion recovery sequence, also a commonly used fat suppression technique in MRI imaging.

[0057] SPIR (Spectral Presaturation with Inversion Recovery) fat suppression technique: Frequency presaturation inversion recovery fat suppression technique.

[0058] PROSET (PRinciple Of Selective Excitation Technique) fat suppression technique: Selective water excitation fat suppression technique.

[0059] DRIVE (DRIVen Equilibrium) technology: Drive Equilibrium technology.

[0060] In one embodiment, as Figure 1 shown, a device for acquiring magnetic resonance images of rat caudal vertebrae is provided, including: a nuclear magnetic resonance instrument 10, a fixing material 11, and an eliminating filling material 12;

[0061] The fixing material 11 is fixed to the bottom of the scanning radiofrequency coil of the nuclear magnetic resonance instrument 10. A groove is provided on the fixing material 11, and the groove is adapted to the positions of the caudal vertebrae and buttocks of the rat to be measured. The eliminating filling material 12 is an adaptable material. The position of the rat to be measured is fixed by the fixing material 11 and the eliminating filling material 12, and magnetic resonance images are acquired by scanning with the nuclear magnetic resonance instrument 10. In the present invention, a Philips Ingenia 3.0T nuclear magnetic resonance instrument is used to scan the rats. Any other instrument that can achieve the scanning function can also be used, and it is not limited to this instrument. If other devices are used, the scanning principle and parameter design are similar to those of this device, but the names may be different for different manufacturers.

[0062] In this embodiment, neither the fixing material nor the eliminating filling material itself generates magnetic resonance signals and has no interference with the images. The fixing material has a certain plasticity and is not prone to generating bubbles during shaping. The eliminating filling material is non-toxic, odorless, highly plastic, light in texture, and moderately sticky, causing no harm to the rats. After the scanning is completed, it is easy to peel off and clean from the rats.

[0063] The fixing material 11 is made through the following steps:

[0064] Weigh the second raw materials according to a preset ratio; wherein, the second raw materials include: 30 - 50% of a base polymer, 15 - 30% of a plasticizer, 20 - 40% of a filling material, 1 - 5% of a thixotropic agent, and 0.5 - 8% of a stabilizer;

[0065] Mix the base polymer and the plasticizer, and stir at 80 - 120 °C for 10 - 30 minutes to form a homogeneous colloid;

[0066] Add inorganic fillers, a thixotropic agent, and a stabilizer to the homogeneous colloid, and mix in a mixer at a rotation speed of 50 - 100 rpm for 15 - 45 minutes to obtain a mixed material;

[0067] Transfer the mixed material to a vacuum degassing device, and degas at a pressure of -0.06 to -0.09 MPa for 5 - 20 minutes to obtain a degassed material;

[0068] Form the degassed material into a sheet or block through a calender, and cool it to room temperature to obtain a fixing raw material with a Shore A hardness of 20 - 50 and a temperature resistance range of -30 °C to 120 °C;

[0069] Lay the fixed raw materials flat in the scanning RF coil of the nuclear magnetic resonance instrument, trying to cover the bottom of the scanning RF coil as much as possible, leaving a space for the to-be-tested rat to lie prone.

[0070] As Figure 2 shown, place the to-be-tested rat prone on the fixed raw materials, with the head facing forward to ensure unobstructed breathing; gently press the back and buttocks of the to-be-tested rat, straighten the caudal vertebra of the to-be-tested rat and press it on the fixed raw materials, so that the body shape characteristics of the to-be-tested rat are retained on the fixed raw materials, obtaining the fixed material.

[0071] Specifically, the base polymer is selected from at least one of styrene-butadiene rubber, silicone rubber, and polyvinyl chloride (PVC), and the molecular weight is 50,000 - 200,000.

[0072] The inorganic filler is at least one of calcium carbonate, talcum powder, or kaolin, with a particle size of 1 - 50 μm, and the surface is modified by a silane coupling agent.

[0073] The plasticizer is at least one of phthalate esters, epoxidized soybean oil, or polyester plasticizers, and the mass ratio to the base polymer is 1:2 to 1:4.

[0074] The thixotropic agent is fumed silica or organobentonite.

[0075] The elimination filler 12 is made through the following steps:

[0076] Weigh the third raw materials according to a preset ratio; the third raw materials include: 5 - 15% foaming microspheres, 20 - 40% binder, 10 - 25% plasticizer, 10 - 30% light filler, 2 - 8% humectant, and the balance is deionized water.

[0077] Mix the binder with deionized water, and stir at 60 - 80 °C until completely dissolved to form a transparent glue solution;

[0078] Add the plasticizer and the humectant to the transparent glue solution in sequence, keep the temperature at 40 - 50 °C, and stir until evenly mixed to obtain a mixed glue solution;

[0079] Add the foaming microspheres and the light filler to the mixed glue solution in sequence, and stir at a speed of 200 - 400 rpm for 10 - 30 minutes to form a uniform paste;

[0080] Place the uniform paste in a vacuum degassing machine, and degas at a pressure of -0.08 to -0.1 MPa for 5 - 15 minutes to obtain the elimination filler 12.

[0081] Specifically, the foaming microspheres are thermally expandable microspheres, with a particle size range of 20 - 100 μm and an expansion temperature of 80 - 120 °C.

[0082] The light filler is selected from at least one of hollow glass microspheres, nano-silica, or mica powder, and has a particle size of 1-50 μm.

[0083] The humectant is at least one of sorbitol, propylene glycol, or polyethylene glycol.

[0084] The plasticizer is at least one of phthalate esters, epoxy soybean oil, or polyester plasticizers.

[0085] On this basis, it further includes: a signal enhancement material;

[0086] The signal enhancement material is fixed inside the scanning radiofrequency coil of the nuclear magnetic resonance instrument, specifically above the caudal vertebra of the to-be-tested white rat, and is used to enhance the magnetic resonance signal intensity in the scanning area.

[0087] The signal enhancement material is made through the following steps:

[0088] Weigh the first raw material according to a preset ratio; among them, the first raw material includes: 50-70% filler, 10-20% liquid paraffin, and 10-30% glycerol;

[0089] After mixing the first raw material evenly, pack it into small bags and evacuate to obtain the signal enhancement material.

[0090] Specifically, the filler can be at least one of calcium carbonate powder, talcum powder, kaolin, diatomaceous earth, mica powder, and starch.

[0091] In one embodiment, the signal enhancement material can also use a grease block, such as a beef tallow block. The composition of beef tallow has a certain similarity to human fat and can simulate the signal characteristics of biological tissues.

[0092] Specifically, place the signal enhancement material above the scanning area of the caudal vertebra of the anesthetized white rat, aiming to enhance the magnetic resonance signal intensity in the scanning area, and after the fat suppression technique, it is almost invisible and has almost no interference with the image.

[0093] On this basis, obtaining the magnetic resonance image by scanning with the nuclear magnetic resonance instrument includes:

[0094] Step S1, using the spin echo sequence as the basic sequence, set the T2 weighted imaging parameters to generate a T2 contrast image;

[0095] Step S2, introduce an echo train in the T2 weighted sequence formed in Step S1, and set the acceleration factor to 5-11 to obtain an accelerated TSE-T2 weighted image;

[0096] Step S3: Select a fat suppression technique based on the applied frequency, and apply a presaturation pulse in the TSE sequence formed in Step S2 to suppress the normal vertebral body fat signal to a low signal while retaining the water signal, generating a fat-suppressed TSE-T2 weighted image;

[0097] Step S4: On the basis of Step S3, through the SPAIR technique, set the frequency offset to 200 Hz, and adjust the arrival mode and power of the 180° insulating radiofrequency pulse to further suppress the residual fat signal and obtain a high-contrast SPAIR-TSE-T2 weighted image;

[0098] Step S5: Apply a negative 90° radiofrequency pulse at the end of the sequence echo train formed in Step S4 to force the recovery of the longitudinal magnetization vector and generate a time-optimized DRIVE-SPAIR-TSE-T2 weighted image;

[0099] Step S6: For the rat scanning area, adjust the gradient coil parameters to reduce the inhomogeneity of the main magnetic field, thereby further reducing the susceptibility artifacts and obtaining the final magnetic resonance image.

[0100] Specifically, select the Spin Echo (SE) sequence. The characteristic of the SE sequence is that after the 90° radiofrequency pulse excitation, a 180° refocusing pulse is used to refocus the dephased protons to generate a spin echo signal. Compared with other sequences such as the gradient echo sequence, the SE sequence has the following advantages: relatively simple sequence structure; good image signal-to-noise ratio and tissue contrast; low sensitivity to the inhomogeneity of the main magnetic field, relatively light susceptibility artifacts; easy interpretation of signal changes. The pulse schematic diagram of the SE sequence is as Figure 3 shown.

[0101] Select the T2-weighted imaging (T2WI) sequence. The T2WI sequence generates signals of different levels according to the transverse relaxation differences between different tissues. Normal intervertebral discs are water-containing soft tissues and present high signals on the T2WI sequence, while diseased intervertebral discs and vertebral bodies present medium to low signals on the T2WI. Usually, the sagittal view of the coccyx is scanned for easy observation and measurement analysis. According to the characteristics of the T2WI sequence, the repetition time TR is set to 2000 - 6000 ms; the echo time TE is set to 60 - 120 ms; the phase encoding direction is set to anterior-posterior; the frequency encoding direction is set to head-foot; scan matrix: 288 * 368 (phase encoding * frequency encoding); voxel size: 0.3 * 0.3 mm; number of excitations: 2 - 4 times; scan slice thickness: 1 - 2.5 mm per slice; number of slices: 7 - 11 slices. For diseased intervertebral discs, the T2WI axial sequence can be added for scanning. According to the characteristics of the T2WI sequence, the repetition time TR is set to 2000 - 6000 ms; the echo time TE is set to 60 - 120 ms; the phase encoding direction is set to anterior-posterior; the frequency encoding direction is set to left-right; scan matrix: 288 * 288 (phase encoding * frequency encoding); voxel size: 0.3 * 0.3 mm; number of excitations: 2 - 4 times; scan slice thickness: 1 - 1.5 mm per slice; number of slices: 3 - 5 slices. At this time, the device will display the total scanning time. Even if only the sagittal plane of the coccyx is scanned, the total time will reach 10 - 30 minutes, which is very likely to generate motion artifacts and there is a possibility of anesthetic awakening.

[0102] Use the fast spin echo (Turbo Spin Echo, TSE) acceleration technique to accelerate it. The acceleration factor (TSE factor) is set to 5 - 11. Since the spin echo sequence has a disadvantage that the longitudinal relaxation takes a relatively long time and one echo data is acquired per excitation, the total acquisition time is relatively long and it is more sensitive to the movement of the object being detected. Although the live rats are anesthetized, there are still physiological movements such as respiratory movement and intestinal peristalsis, as well as random muscle twitching movements. The total scanning time cannot be too long, otherwise the image is very likely to appear motion artifacts and it also wastes the working time of the researchers. The TSE sequence uses multiple 180° refocusing pulses to refocus the signals after one radiofrequency pulse excitation, and multiple phase encoding lines of the K space can be filled at one time. The larger the value of the acceleration factor, the corresponding reduction in the scanning time. By setting a reasonable TSE factor, the scanning time in a single direction can be reduced to within 4 minutes. However, the use of the TSE technique will cause the vertebral bodies that are rich in fat and should originally present medium signals to become high signals, and at this time, it will be difficult to distinguish between normal vertebral bodies, diseased vertebral bodies, and intervertebral discs. Specifically, the schematic diagram of the TSE pulse is as Figure 4 shown.

[0103] The TSE sequence is further optimized using fat signal suppression technology. Since the vertebral bodies are rich in fat, after using the accelerated TSE sequence, they all show high signals on T2WI. Therefore, it is difficult to distinguish among normal vertebral bodies, water-containing pathological vertebral bodies, and water-containing intervertebral discs, which all show high signals.

[0104] Fat suppression is performed using fat suppression technology that utilizes the difference in the precession frequencies of hydrogen protons in fat and water protons, enabling normal vertebral bodies to appear as low signals for easier differentiation. Currently, commonly used fat suppression technologies include the (Short TI Inversion Recovery, STIR) fat suppression technology that utilizes the difference in the longitudinal relaxation times of hydrogen protons in fat and water protons, and the fat suppression technology that utilizes the difference in the precession frequencies of hydrogen protons in fat and water protons. Although the STIR technology has less susceptibility artifact, it causes too much decrease in the signal-to-noise ratio of the image and may suppress the signals of tissues with longitudinal relaxation times of hydrogen protons in fat that are not very different, affecting the analysis of the image. Therefore, the fat suppression technology that utilizes the difference in the precession frequencies of hydrogen protons in fat and water protons is selected - the chemical shift of their precession frequencies in the main magnetic field is 3.5 ppm.

[0105] According to the formula the resonance peak frequency offset between hydrogen protons in fat and water protons can be calculated under different main magnetic field strengths. Among them, is a constant term, and B 0 is related to the strength of the main magnetic field. Taking a 3.0T main magnetic field as an example, the theoretically calculated offset frequency according to the formula is 383.22 Hz. This value is also related to the actual temperature at the operation site (the temperature in the experimental computer room is generally fixed at 20 - 22°) and the temperature of the object to be detected. The measured body temperature of the tested rats is usually about 40°, slightly higher than the human body temperature, and because the rats are small in size, the temperature will further rise during the scanning process. Therefore, this value is corrected to 400 - 430 Hz according to different situations.

[0106] The SPAIR fat suppression technology is used for further optimization. The 180° adiabatic inversion pulse of the SPAIR sequence precisely targets adipose tissue, is insensitive to the inhomogeneity of the magnetic resonance radiofrequency field, has a high fat signal suppression efficiency, and relatively less susceptibility artifact compared to the SPIR and PROSET technologies. The schematic diagram of the SPAIR sequence is as Figure 5 shown.

[0107] Set the frequency offset parameter to 200 Hz. The frequency offset is the frequency segment by which the flip prepulse is offset relative to the fat peak. If set too small, the frequency segment offset is small, the bandwidth of the emitted 180° refocusing pulse is small, and fat suppression deteriorates; if set too large, the frequency segment offset is large, the bandwidth of the emitted 180° refocusing pulse is large, and fat suppression is more thorough, but it will also cause some water signals (intervertebral disc signals) to be suppressed. Setting it to 200 Hz can ensure that adipose tissue is fully flipped while ensuring that water signals are not affected.

[0108] When using a frequency-selective refocusing pulse in the SPAIR sequence, it is possible to choose to slowly rotate until reaching the target angle of 180°, and it is possible to choose to increase the RF power as much as possible. This will make the object to be detected less sensitive to the inhomogeneity of the MR RF field, further reducing susceptibility artifacts, but the scan time will increase slightly.

[0109] Adopt the (DRIVen Equilibrium, DRIVE) technique to further control the scan duration. If the use of the SPAIR technique causes the scan time of a single sequence to increase again beyond 4 minutes, it may increase the risk of motion artifacts in the rats again. Since the TSE factor cannot be increased indefinitely, otherwise it will lead to an aggravated image blurring effect. Since the scan time in the TSE sequence is proportional to the repetition time TR, in order to shorten the scan time, TR can be appropriately reduced. However, when TR decreases, when the next RF pulse is excited, the longitudinal magnetization vector of the tissue has not fully recovered. Not only will the image signal-to-noise ratio decrease, but insufficient TR will also affect the T2 contrast of the image. At this time, the DRIVE technique can be adopted, that is, a negative 90° RF pulse is added after the last 180° refocusing pulse to flip the remaining magnetization vector in the horizontal direction back to the longitudinal axis direction, forcing the tissue to quickly complete longitudinal relaxation. At this time, the sequence diagram is as Figure 6 shown.

[0110] Use shimming techniques to make the magnetic field in the area to be scanned at the sacral tail of the rat more uniform. When the buttocks of the rat transition to the caudal vertebra, the tissue structure suddenly becomes thinner, which will produce severe susceptibility artifacts. Although it has been processed by embedding with cancellation materials, there is still a possibility of producing a small amount of susceptibility artifacts. First, apply appropriate currents on the gradient coils in the X, Y, and Z axes, which are superimposed on the original main magnetic field to compensate for the inhomogeneity of the original main magnetic field (first-order active shimming); then apply appropriate currents in the active shimming coils inside the gradient coils (second-order active shimming). The two work together to make the magnetic field in the scanned area more uniform.

[0111] Through the reasonable combination and use of the above technical means, the finally obtained scan image is as Figure 7 shown. The failed image with severe susceptibility artifacts is asFigure 8 as shown

[0112] The rat caudal vertebra magnetic resonance image acquisition device provided by the present invention eliminates magnetic susceptibility artifacts through an elimination filling material, precisely fixes with a fixing material, and enhances the magnetic resonance signal intensity of the scanning area with a grease block. Combining the high signal-to-noise ratio of the spin echo (SE) sequence and the excellent tissue contrast of T2-weighted imaging (T2WI), the fast spin echo (TSE) technique (acceleration factor 5 - 11) compresses the scanning time to within 4 minutes, effectively controlling the physiological motion artifacts of live rats; the fat suppression technique based on the fat-water frequency difference combines with SPAIR to precisely eliminate the vertebral fat signal, making the contrast between the low signal of normal vertebrae and the signal of the lesion area distinct. At the same time, the DRIVE technique forces the recovery of the longitudinal magnetization vector to maintain the T2 contrast and further shortens the scanning duration; combining the first-order and second-order shimming techniques further reduces the inhomogeneity of the main magnetic field in the scanning area, significantly improving the uniformity of image fat suppression, and finally realizing fast, high-resolution, and low-artifact imaging of the rat caudal vertebra in vivo, with high efficiency, diagnostic accuracy, and operation safety. It can meet the safety requirements of live rats and can also be extended to the spinal imaging scenarios of other small animals (mice, rabbits).

[0113] Based on the same inventive concept, corresponding to the device of any of the above embodiments, the present invention also provides a method for acquiring rat caudal vertebra magnetic resonance images, including:

[0114] Fix the fixing material at the bottom of the scanning radiofrequency coil of the nuclear magnetic resonance instrument. There is a groove on the fixing material, and the groove is adapted to the positions of the caudal vertebra and buttocks of the rat to be measured. Place the position of the caudal vertebra of the rat to be measured in the groove, place the elimination filling material on the caudal vertebra of the rat to be measured, fill the remaining gap between the caudal vertebra of the rat to be measured and the fixing material, and try to expel all the air. Fix the position of the rat to be measured, and obtain magnetic resonance images through the scanning of the nuclear magnetic resonance instrument.

[0115] The method of the above embodiment is used for the corresponding rat caudal vertebra magnetic resonance image acquisition device in any of the foregoing embodiments, and has the beneficial effects of the corresponding method embodiment, which will not be elaborated here.

[0116] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the protection scope of the present invention.

[0117] Embodiment 1

[0118] A manufacturing method of a fixing material 11 is provided:

[0119] This embodiment uses 50% styrene-butadiene rubber, 25% phthalate esters, 20% calcium carbonate, 2% fumed silica, and 3% stabilizer;

[0120] Mix the styrene-butadiene rubber and phthalate esters, and stir at 100 °C for 25 minutes to form a homogeneous colloid;

[0121] Add calcium carbonate, fumed silica, and stabilizer to the homogeneous colloid, first mix at a low speed of 50 - 80 rpm for 10 minutes in a Banbury mixer, and then increase the speed to 80 - 100 rpm for high-speed mixing for 15 minutes to obtain a mixed material;

[0122] Transfer the mixed material to a vacuum degassing device, and degas at a pressure of -0.08 MPa for 20 minutes to obtain a degassed material;

[0123] Form the degassed material into sheets or blocks through a calender, and cool to room temperature to obtain a fixed raw material with a Shore A hardness of 20 - 50 and a temperature resistance range of -30 °C to 120 °C;

[0124] Lay the fixed raw material flat in a small coil such as a special coil for rats or a human wrist joint coil, and try to fill all the gaps at the bottom of the coil as much as possible, leaving a space for the test rat to lie prone.

[0125] Place the test rat prone on the fixed raw material, with the head facing forward to ensure unobstructed breathing; because the fixed raw material has a certain plasticity, gently press the back and buttocks of the test rat, straighten the caudal vertebra of the test rat and press it on the fixed raw material, so that the body shape characteristics of the test rat are retained on the fixed raw material to obtain a fixed material.

[0126] Example Two

[0127] A method for manufacturing the filling material 12 is provided:

[0128] This embodiment uses 10% foamed microspheres, 25% polyvinyl alcohol binder, 20% glycerol plasticizer, 20% mica powder, 8% polyethylene glycol, and 17% deionized water.

[0129] Mix the polyvinyl alcohol binder and deionized water, and stir at 70 °C until completely dissolved to form a transparent glue solution.

[0130] Add glycerol plasticizer and polyethylene glycol to the transparent glue solution in sequence, keep the temperature at 50 °C, and stir until evenly mixed to obtain a mixed glue solution.

[0131] Add foamed microspheres and mica powder to the mixed glue solution in sequence, first mix at a low speed of 200 rpm for 10 minutes, and then increase the speed to 400 rpm for high-speed stirring for 10 minutes to form a uniform paste.

[0132] Place the uniform paste in a vacuum degassing machine and degas it for 15 minutes under a pressure of -0.1 MPa to obtain the filling material 12 without air bubbles.

[0133] Example 3

[0134] A method for manufacturing a signal enhancement material is provided:

[0135] In this example, 60% calcium carbonate powder, 20% liquid paraffin, and 20% glycerol are used.

[0136] Mix the above materials evenly at room temperature, pack them into small bags of 1*5*12 cm, and evacuate to obtain the signal enhancement material.

[0137] Those of ordinary skill in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the present invention (including the claims) is limited to these examples; within the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the embodiments of the present invention as described above, which are not provided in detail for the sake of brevity.

[0138] In addition, in the case where specific details are set forth to describe the exemplary embodiments of the present invention, it will be apparent to those skilled in the art that the present invention can be practiced without these specific details or with variations of these specific details. Therefore, these descriptions should be considered illustrative rather than restrictive. Although the present invention has been described in connection with specific embodiments of the present invention, many substitutions, modifications, and variations of these embodiments will be apparent to those of ordinary skill in the art based on the foregoing description.

[0139] The embodiments of the present invention are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the embodiments of the present invention shall be included within the protection scope of the present invention.

Claims

1. A device for acquiring magnetic resonance images of rat tail vertebrae, characterized in that: include: MRI machines, fixation materials, and elimination of filling materials; The fixing material is fixed to the bottom of the nuclear magnetic resonance scanning radio frequency coil, and a groove is provided on the fixing material, and the groove is adapted to the position of the coccyx and buttocks of the rat to be tested; the eliminating filling material is an adaptable material, and together with the fixing material, the position of the rat to be tested is fixed, and a magnetic resonance image is obtained by scanning with the nuclear magnetic resonance apparatus.

2. The device for acquiring magnetic resonance images of rat coccyx according to claim 1, characterized in that: Also includes: Signal enhancement materials; The signal enhancement material is fixed in the scanning radio frequency coil of the nuclear magnetic resonance apparatus, specifically located above the tail vertebra of the rat to be tested, and is used to enhance the intensity of the magnetic resonance signal in the scanning area.

3. The device for acquiring magnetic resonance images of rat coccyx according to claim 2, characterized in that: The signal enhancement material is prepared by the following steps: Weigh the first raw material according to a preset ratio; wherein the first raw material includes: filler, liquid paraffin and glycerin; The first raw materials are mixed evenly, put into a small bag and evacuated to obtain a signal enhancement material.

4. The rat tail vertebra magnetic resonance image acquisition device according to claim 1, characterized in that: The fixing material is made by the following steps: Weigh the second raw material according to a preset ratio; wherein the second raw material includes: a base polymer, a plasticizer, a filler material, a thixotropic agent and a stabilizer; The base polymer and the plasticizer are mixed and stirred at 80-120° C. for 10-30 minutes to form a homogeneous colloid; Adding the inorganic filler, the thixotropic agent and the stabilizer to the homogeneous colloid, and mixing them in an internal mixer at a speed of 50-100 rpm for 15-45 minutes to obtain a mixed material; The mixed material is transferred to a vacuum degassing device and degassed at a pressure of -0.06 to -0.09 MPa for 5 to 20 minutes to obtain a degassed material; The deaerated material is formed into a sheet or block by a calender, and cooled to room temperature to obtain a fixed raw material with a hardness of Shore A20-50 and a temperature resistance range of -30°C to 120°C; The fixed material is spread flatly in the nuclear magnetic resonance scanning radio frequency coil, and the bottom of the scanning radio frequency coil is covered as much as possible, and a space is reserved for the rat to be tested to lie prone; The rat to be tested is placed prone on the fixing material with its head facing forward to ensure unimpeded breathing; the back and buttocks of the rat to be tested are lightly pressed, and the tail vertebrae of the rat to be tested are straightened and pressed on the fixing material so that the body shape characteristics of the rat to be tested are retained on the fixing material to obtain a fixing material.

5. The device for acquiring magnetic resonance images of rat coccyx according to claim 1, characterized in that: The eliminating filling material is prepared by the following steps: Weigh the third raw material according to a preset ratio; wherein the third raw material includes: foamed microspheres, adhesive, plasticizer, lightweight filler, moisturizer and deionized water; Mixing the adhesive with the deionized water, stirring at 60-80° C. until completely dissolved to form a transparent adhesive solution; Add the plasticizer and the moisturizer to the transparent glue solution in sequence, keep the temperature at 40-50° C., and stir until the mixture is uniform to obtain a mixed glue solution; Add the foaming microspheres and the lightweight filler to the mixed glue solution in sequence, and stir at a speed of 200-400 rpm for 10-30 minutes to form a uniform paste; The uniform paste is placed in a vacuum degassing machine and degassed for 5-15 minutes at a pressure of -0.08 to -0.1 MPa to obtain a filler-eliminating material.

6. The device for acquiring magnetic resonance images of rat coccyx according to claim 1, characterized in that: The obtaining of a magnetic resonance image by scanning with the nuclear magnetic resonance apparatus comprises: Step S1, using a spin echo sequence as a basic sequence, setting T2 weighted imaging parameters, and generating a T2 contrast image; Step S2, introducing an echo chain into the T2-weighted sequence formed in step S1, setting the acceleration factor to 5-11, and obtaining an accelerated TSE-T2-weighted image; Step S3, selecting fat suppression technology based on the applied frequency, applying a pre-saturation pulse in the TSE sequence formed in step S2, so that the normal vertebral fat signal is suppressed to a low signal, while the water signal is retained, and a fat-suppressed TSE-T2 weighted image is generated; Step S4, based on step S3, using the SPAIR technology, setting the frequency offset to 200 Hz, adjusting the arrival mode and power of the 180° insulating radio frequency pulse, further suppressing the residual fat signal, and obtaining a high-contrast SPAIR-TSE-T2 weighted image; Step S5, applying a negative 90° radio frequency pulse at the end of the sequence echo chain formed in step S4 to force the longitudinal magnetization vector to recover and generate a time-optimized DRIVE-SPAIR-TSE-T2 weighted image; Step S6, adjusting the gradient coil parameters for the rat scanning area to reduce the inhomogeneity of the main magnetic field, thereby further reducing magnetic susceptibility artifacts and obtaining a final magnetic resonance image.

7. The device for acquiring magnetic resonance images of rat coccyx according to claim 6, characterized in that: The configuration of T2 weighted imaging parameters includes: Based on the sagittal image scan of the coccyx, the repetition time TR is set to 2000-6000ms; the echo time TE is set to 60-120ms; the phase encoding direction is set to front and back; the frequency encoding direction is set to head and foot; the scanning matrix is ​​set to 288*368; the voxel size is set to 0.3*0.3mm; the number of excitations is set to 2-4 times; the scanning layer thickness is set to 1-2.5mm per layer; the number of layers is set to 7-11 layers; Based on the axial image scan of the intervertebral disc, the repetition time TR is set to 2000-6000ms; the echo time TE is set to 60-120ms; the phase encoding direction is set to front and back; the frequency encoding direction is set to left and right; the scanning matrix is ​​set to 288*288; the voxel size is set to 0.3*0.3mm; the number of excitations is set to 2-4 times; the scanning layer thickness is set to 1-1.5mm per layer; and the number of layers is set to 3-5 layers.

8. A method for acquiring a magnetic resonance image of a rat's coccygeal vertebrae, characterized in that: The device for acquiring magnetic resonance images of the rat coccyx as claimed in any one of claims 1 to 7 comprises: The fixing material is fixed to the bottom of the radio frequency coil of the nuclear magnetic resonance apparatus. A groove is provided on the fixing material. The groove is adapted to the position of the caudal vertebrae and buttocks of the rat to be tested. The caudal vertebrae of the rat to be tested is placed in the groove. The remaining gap between the caudal vertebrae of the rat to be tested and the fixing material is filled with a filling material. All air is exhausted as much as possible. The position of the rat to be tested is fixed, and a magnetic resonance image is obtained by scanning with the nuclear magnetic resonance apparatus.

Images