Rat tail vertebrae magnetic resonance image acquisition apparatus and method

Abstract

The present application provides a mouse tail vertebrae magnetic resonance image acquisition device and method, wherein the device comprises a nuclear magnetic resonance instrument, a fixing material and an elimination filling material; the fixing material is fixed to the bottom of the nuclear magnetic resonance instrument scanning radio frequency coil, and a groove is arranged on the fixing material, which is adapted to the position of the tail vertebrae and the hips of the mouse to be measured; the elimination filling material is an adaptable material, which, together with the fixing material, fixes the position of the mouse to be measured, and the magnetic resonance image is acquired through the nuclear magnetic resonance instrument scanning. The fixing material used in the present application has certain plasticity, can effectively fill the irregular space around the scanning area, reduce the magnetic susceptibility artifact, and improve the imaging clarity. The elimination filling material is non-toxic and odorless, has strong plasticity and light texture, and has moderate viscosity, which can stabilize the scanning area of the tail vertebrae of the mouse to be measured, and will not cause additional burden to the animal, so as to ensure that the position of the mouse is fixed during the imaging process, and the accuracy of the image is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of magnetic resonance imaging technology, and in particular to a mouse caudal vertebrae magnetic resonance image acquisition device and method. BACKGROUND

[0002] Mice are common experimental small animals due to their low price, strong reproductive ability and easy feeding. The caudal vertebrae of mice are exposed and have multiple segments, which are very convenient for researchers to operate, and are ideal research objects in the field of orthopedic spine research. After modeling the intervertebral disc of the caudal vertebrae of the mouse or after treatment, researchers need to regularly understand the evolution of the diseased intervertebral disc. CT and X-ray examination is more sensitive to bone lesions, but the intervertebral disc belongs to soft tissue and cannot be imaged under X-ray. Nuclear magnetic resonance scanning is the most ideal method for observing soft tissue lesions, but it is still difficult to obtain the magnetic resonance image of the caudal vertebrae of the live mouse by the existing technical means. The reasons are as follows: 1. The tissue structure of the mouse suddenly becomes thin when the hip transitions to the caudal vertebrae, which will produce serious magnetic susceptibility artifacts; 2. The caudal vertebrae of the mouse is thin, and the magnetic resonance signal itself is weak, so the equipment cannot start the scanning program. 3. The caudal vertebrae of the mouse is long and usually curved, so it must be straightened to be displayed in a plane to facilitate equipment scanning and data analysis. 4. Magnetic resonance scanning takes a long time and is sensitive to movement. Even if the live mouse is anesthetized in advance, there are still physiological movements such as respiratory movement, intestinal peristalsis, and anesthesia recovery. SUMMARY

[0003] Therefore, it is necessary to provide a mouse caudal vertebrae magnetic resonance image acquisition device and method aiming at the above technical problems.

[0004] The mouse caudal vertebrae magnetic resonance image acquisition device comprises a nuclear magnetic resonance instrument, a fixing material and a elimination filling material.

[0005] The fixing material is fixed to the bottom of the scanning radio frequency coil of the nuclear magnetic resonance instrument, and a groove is arranged on the fixing material, which is adapted to the position of the caudal vertebrae and hip of the mouse to be measured. The elimination filling material is an adaptable material, which, together with the fixing material, fixes the position of the mouse to be measured, and obtains a magnetic resonance image by scanning the nuclear magnetic resonance instrument.

[0006] In one embodiment, it further comprises a signal enhancement material.

[0007] The signal enhancement material is fixed in the scanning radio frequency coil of the nuclear magnetic resonance instrument, and is specifically located above the caudal vertebrae of the mouse to be measured, and is used for enhancing the magnetic resonance signal strength of the scanning area.

[0008] In one embodiment, the signal enhancement material is made by the following steps:

[0009] The first raw material is weighed according to a preset proportion, wherein the first raw material comprises a filler, liquid paraffin and glycerol;

[0010] The first raw material is mixed uniformly, filled into a small bag and vacuumized to obtain a signal enhancement material.

[0011] In one embodiment, the fixing material is prepared by the following steps:

[0012] The second raw material is weighed according to a preset proportion, wherein the second raw material comprises a base polymer, a plasticizer, a filler, a thixotropic agent and a stabilizer;

[0013] The base polymer and the plasticizer are mixed and stirred at 80-120℃ for 10-30 minutes to form a homogeneous colloid;

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

[0015] The mixed material is transferred to a vacuum defoaming device and defoamed at a pressure of-0.06 to-0.09 MPa for 5-20 minutes to obtain a defoamed material;

[0016] The defoamed material is formed into a sheet or a block by a calender and cooled to room temperature to obtain a fixing raw material with a hardness of Shore A 20-50 and a temperature resistance range of-30℃ to 120℃;

[0017] The fixing raw material is laid flat in a scanning radio frequency coil of the nuclear magnetic resonance instrument, and the scanning radio frequency coil bottom is as full as possible, leaving a space for a mouse to lie on its stomach;

[0018] The mouse to be tested is placed on the fixing raw material on its stomach with the head facing forward, and the back and hips of the mouse are pressed and the tail vertebrae of the mouse are straightened and pressed on the fixing raw material, so that the body shape characteristics of the mouse to be tested are reserved on the fixing raw material to obtain a fixing material.

[0019] In one embodiment, the elimination filler is prepared by the following steps:

[0020] The third raw material is weighed according to a preset proportion, wherein the third raw material comprises foamed microspheres, an adhesive, a plasticizer, a light filler, a humectant and deionized water;

[0021] The adhesive and the deionized water are mixed and stirred at 60-80℃ until completely dissolved to form a transparent glue solution;

[0022] The plasticizer and the humectant are sequentially added into the transparent glue solution, and the temperature is kept at 40-50 DEG C, and the mixture is stirred until uniform, to obtain a mixed glue solution;

[0023] The foaming microspheres and the light filler are sequentially added into the mixed glue solution, and the mixture is stirred at a speed of 200-400 rpm for 10-30 minutes, to form a uniform paste;

[0024] The uniform paste is placed in a vacuum defoaming machine, and is defoamed at a pressure of-0.08 to-0.1 MPa for 5-15 minutes, to obtain a filling material.

[0025] In one of the embodiments, the magnetic resonance image obtained by scanning the nuclear magnetic resonance instrument comprises:

[0026] In step S1, a T2-weighted imaging parameter is set based on a spin echo sequence as a basic sequence, and a T2 contrast image is generated;

[0027] In step S2, an echo chain is introduced into the T2-weighted sequence formed in step S1, and an acceleration factor is set to 5-11, to obtain an accelerated TSE-T2-weighted image;

[0028] In step S3, a fat suppression technique based on an applied frequency is used, and a presaturation pulse is applied to the TSE sequence formed in step S2, so that the normal vertebral fat signal is suppressed to a low signal, and the water signal is retained, to generate a fat-suppressed TSE-T2-weighted image;

[0029] In step S4, based on step S3, an SPAIR technique is used, a frequency offset is set to 200 Hz, the arrival mode and power of the 180° insulating radio frequency pulse are adjusted, the residual fat signal is further suppressed, and a high-contrast SPAIR-TSE-T2-weighted image is obtained;

[0030] In step S5, a negative 90° radio frequency pulse is applied at the end of the echo chain of the sequence formed in step S4, to force the longitudinal magnetization vector to recover, and a time-optimized DRIVE-SPAIR-TSE-T2-weighted image is generated;

[0031] In step S6, for the scanning area of the rat, the gradient coil parameters are adjusted, the inhomogeneity of the main magnetic field is reduced, and the magnetic susceptibility artifacts are further reduced, to obtain a final magnetic resonance image.

[0032] In one of the embodiments, configuring the T2-weighted imaging parameter comprises:

[0033] Based on the sagittal image scanning of the tail vertebra, 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 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*0.3 mm; the number of excitations is set to 2-4 times; the scanning layer thickness is set to 1-2.5 mm per layer; and the number of layers is set to 7-11 layers.

[0034] Based on the axial image scanning of the intervertebral disc, 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 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*0.3 mm; the number of excitations is set to 2-4 times; the scanning layer thickness is set to 1-1.5 mm per layer; and the number of layers is set to 3-5 layers.

[0035] The method for acquiring a magnetic resonance image of a tail vertebra of a rat, which is used in the device for acquiring a magnetic resonance image of a tail vertebra of a rat as described above, comprises the following steps:

[0036] The fixing material is fixed to the bottom of the scanning radio frequency coil of the nuclear magnetic resonance instrument, and a groove is arranged on the fixing material, which is adapted to the position of the tail vertebra and the hip of the rat to be measured. The position of the tail vertebra to be measured is placed in the groove, and the elimination filling material is placed on the tail vertebra to be measured to fill the remaining gap between the tail vertebra to be measured and the fixing material, and all the air is discharged as much as possible to fix the position of the rat to be measured. The magnetic resonance image is acquired by scanning through the nuclear magnetic resonance instrument.

[0037] Compared with the prior art, the advantages and beneficial effects of the present application are that the fixing material used in the present application has a certain plasticity, can effectively fill the irregular space around the scanning area, reduce the magnetic susceptibility artifact, and improve the clarity of imaging. The elimination filling material is non-toxic, odorless, has strong plasticity, light texture, moderate viscosity, can stabilize the scanning area of the tail vertebra of the rat to be measured, and will not cause additional burden to the animal, so as to ensure that the position of the rat is fixed during the imaging process and guarantee the accuracy of the image. The signal enhancement material is placed above the tail vertebra scanning area of the rat after anesthesia, which helps to enhance the magnetic resonance signal intensity of the scanning area and is almost not developed after the fat suppression technology, and has almost no interference to the image. The nuclear magnetic resonance instrument is scanned, DRIVE+TSE imaging is realized for rapid scanning, and SPAIR+high-order shimming technology is further used to reduce the magnetic susceptibility artifact, so as to acquire the magnetic resonance image of the tail vertebra of the rat, provide a more reliable theoretical basis for subsequent medical research and detection, and can be extended to other small animal (mouse, rabbit) spine imaging scenes. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 Fig. 1 is a structural schematic diagram of a mouse caudal vertebrae magnetic resonance image acquisition device in an embodiment;

[0039] Figure 2 Fig. 2 is a schematic diagram of a fixed material shaping process in an embodiment;

[0040] Figure 3 Fig. 3 is a schematic diagram of an SE sequence pulse in an embodiment;

[0041] Figure 4 Fig. 4 is a schematic diagram of a TSE pulse in an embodiment;

[0042] Figure 5 Fig. 5 is a schematic diagram of a SPAIR sequence in an embodiment;

[0043] Figure 6 Fig. 6 is a schematic diagram of a DRIVE post-processing sequence in an embodiment;

[0044] Figure 7 Fig. 7 is a schematic diagram of a magnetic resonance image in an embodiment;

[0045] Figure 8 Fig. 8 is a schematic diagram of a failed image with severe susceptibility artifacts in an embodiment. DETAILED DESCRIPTION

[0046] Before the specific embodiment of the present application is described, the overall concept of the present application is described as follows:

[0047] The present application is mainly developed for the magnetic resonance image acquisition process of live small animals (such as mice), and it is difficult to obtain the magnetic resonance image of the caudal vertebrae of a live mouse by using the existing technical means.

[0048] Therefore, the present application provides a mouse caudal vertebrae magnetic resonance image acquisition device, which fixes the anesthetized mouse through a fixing material and a filling material, performs scanning through a nuclear magnetic resonance instrument, realizes rapid scanning through DRIVE+TSE imaging, further reduces magnetic susceptibility artifacts through SPAIR+high-order shimming technology, and can meet the safety requirements of live rats and can be extended to other small animal (mouse, rabbit) spine imaging scenarios.

[0049] After the overall concept of the present application is introduced, in order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application is further described in detail through specific embodiments combined with the drawings.

[0050] It should be noted that, unless otherwise defined, the technical or scientific terms used in one or more embodiments of this specification should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in one or more embodiments of this specification do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word covers the element or object listed following the word and its equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0051] For ease of understanding, the terms used in the embodiments of this invention are explained below:

[0052] SE (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 technology: a fat suppression technology based on the principles of frequency selectivity and inversion recovery.

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

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

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

[0058] PROSET (Principle of Selective Excitation Technique) Fat Inhibition Technology: Selective water-excited fat inhibition technology.

[0059] DRIVE (DRiven Equilibrium) technique: driven equilibrium technique.

[0060] In one embodiment, as shown in Figure 1 a mouse tail vertebrae magnetic resonance image acquisition device is provided, comprising: a nuclear magnetic resonance instrument 10, a fixing material 11 and a elimination filling material 12;

[0061] The fixing material 11 is fixed to the bottom of the scanning radio frequency coil of the nuclear magnetic resonance instrument 10, and the fixing material 11 is provided with a groove which is adapted to the position of the tail vertebrae and the hip of the mouse to be measured; the elimination filling material 12 is an adaptable material, and the fixing material 11 fixes the position of the mouse to be measured, and the magnetic resonance image is acquired by scanning through the nuclear magnetic resonance instrument 10. In the present application, the mouse is scanned by using the Philips Ingenia 3.0T nuclear magnetic resonance instrument, and the remaining instruments which can realize the scanning function can also be used, and are not limited to this instrument. For example, if other devices are used, the scanning principle and parameter design are similar to those of the device, but the names of different manufacturers may be different.

[0062] In the present embodiment, neither the fixing material nor the elimination filling material generates a magnetic resonance signal by itself and does not interfere with the image. The fixing material has a certain plasticity and is not easy to generate bubbles when being shaped. The elimination filling material is non-toxic, non-smelly, has strong plasticity, light texture and moderate viscosity, does not harm the mouse, and is easy to peel off and clean from the mouse after the scanning is completed.

[0063] The fixing material 11 is prepared by the following steps:

[0064] The second raw material is weighed according to a predetermined proportion; wherein the second raw material comprises: 30-50% base polymer, 15-30% plasticizer, 20-40% filling material, 1-5% thixotropic agent and 0.5-8% stabilizer;

[0065] The base polymer and the plasticizer are mixed and stirred at 80-120℃ for 10-30 minutes to form a homogeneous colloid;

[0066] The inorganic filling material, the thixotropic agent and the stabilizer are added to the homogeneous colloid, and the mixture is mixed in a banbury mixer at a speed of 50-100 rpm for 15-45 minutes to obtain a mixed material;

[0067] The mixed material is transferred to a vacuum defoaming device and defoamed at a pressure of -0.06 to -0.09 MPa for 5-20 minutes to obtain a defoamed material;

[0068] The defoamed material is formed into a sheet or a block by a calendering machine, and cooled to room temperature to obtain a fixing raw material with a hardness of Shore A 20-50 and a temperature resistance range of -30℃ to 120℃;

[0069] The fixed raw material is laid in the nuclear magnetic resonance instrument scanning radio frequency coil, and the bottom of the scanning radio frequency coil is as full as possible, leaving a space for the mouse to lie down;

[0070] As shown in the figure, the mouse to be tested is placed on the fixed raw material, with the head facing forward, and the breathing is ensured to be unobstructed; the back and hips of the mouse to be tested are lightly pressed, and the tail vertebrae of the mouse to be tested are straightened and pressed on the fixed raw material, so that the fixed material retains the body characteristics of the mouse to be tested, and the fixed material is obtained. Figure 2

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

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

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

[0074] The thixotropic agent is fumed silica or organic bentonite.

[0075] The elimination filling material 12 is made by the following steps:

[0076] The third raw material is weighed according to a predetermined proportion; the third raw material includes 5-15% foaming microspheres, 20-40% adhesive, 10-25% plasticizer, 10-30% light filler, 2-8% humectant, and the balance is deionized water.

[0077] The adhesive is mixed with deionized water, and stirred at 60-80°C until completely dissolved to form a transparent glue solution;

[0078] The plasticizer and the humectant are sequentially added to the transparent glue solution, the temperature is kept at 40-50°C, and the stirring is performed until the mixture is uniformly mixed to obtain a mixed glue solution;

[0079] The foaming microspheres and the light filler are sequentially added to the mixed glue solution, and the stirring is performed at a speed of 200-400 rpm for 10-30 minutes to form a uniform paste;

[0080] The uniform paste is placed in a vacuum defoaming machine and defoamed at a pressure of -0.08 to -0.1 MPa for 5-15 minutes to obtain the elimination filling material 12.

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

[0082] ​The light filler is selected from at least one of hollow glass microbeads, 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, the signal enhancement material is further included;

[0086] The signal enhancement material is fixed in a radio frequency coil of a nuclear magnetic resonance instrument, and is specifically located above the tail vertebra of the mouse to be measured, and is used for enhancing the magnetic resonance signal intensity of the scanning area.

[0087] The signal enhancement material is prepared by the following steps:

[0088] The first raw material is weighed according to a preset proportion, wherein the first raw material includes 50-70% of the filler, 10-20% of the liquid paraffin and 10-30% of the glycerol;

[0089] After the first raw material is mixed uniformly, it is loaded into a small bag and vacuumized to obtain the signal enhancement material.

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

[0091] In an embodiment, the signal enhancement material can also use a fat block, for example, a beef tallow block. The composition of beef tallow has certain similarity with human body fat, and can simulate the signal characteristics of biological tissues.

[0092] Specifically, the signal enhancement material is placed above the tail vertebra scanning area of the mouse after anesthesia, so as to enhance the magnetic resonance signal intensity of the scanning area, and after the fat suppression technology, it is almost not developed and has almost no interference to the image.

[0093] On this basis, the magnetic resonance image is obtained by scanning the nuclear magnetic resonance instrument, and includes:

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

[0095] Step S2, introducing an echo chain in the T2 weighted sequence formed in step S1, setting an acceleration factor of 5-11 to obtain an accelerated TSE-T2 weighted image;

[0096] Step S3, based on the fat suppression technology of applying frequency, pre-saturation pulse is applied in the TSE sequence formed in step S2, so that the normal vertebral fat signal is suppressed to low signal, while the water signal is reserved, generating fat-suppressed TSE-T2 weighted image;

[0097] Step S4, on the basis of step S3, by SPAIR technology, the frequency offset is set to 200Hz, the arrival mode and power of 180° insulation radio frequency pulse are adjusted, the residual fat signal is further suppressed, and high-contrast SPAIR-TSE-T2 weighted image is obtained;

[0098] Step S5, a negative 90° radio frequency pulse is applied at the end of the echo chain formed in step S4, the longitudinal magnetization vector is forced to recover, and a time-optimized DRIVE-SPAIR-TSE-T2 weighted image is generated;

[0099] Step S6, for the scanning area of the rat, the gradient coil parameters are adjusted, the inhomogeneity of the main magnetic field is reduced, and the magnetic susceptibility artifacts are further reduced, so as to obtain the final magnetic resonance image.

[0100] Specifically, a spin echo (SE) sequence is selected. The SE sequence has the following advantages compared with other sequences such as gradient echo sequence: the sequence structure is relatively simple; the image signal-to-noise ratio and tissue contrast are good; the inhomogeneity sensitivity to the main magnetic field is low, the magnetic susceptibility artifacts are relatively light; and the signal change is easy to explain. The SE sequence pulse diagram is shown in Figure 3 .

[0101] The T2 weighted imaging (T2WI) sequence is selected. The T2WI sequence produces different signals according to the transverse relaxation difference between different tissues. The normal intervertebral disc is a water-containing soft tissue, and presents a high signal on the T2WI sequence. The diseased intervertebral disc and the vertebral body present a low signal on the T2WI sequence. Usually, the sagittal plane of the tail vertebra is scanned to facilitate 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 front and back; the frequency encoding direction is set to head and foot; the scanning matrix is 288*368 (phase encoding*frequency encoding); the voxel size is 0.3*0.3 mm; the number of excitations is 2-4 times; the scanning layer thickness is 1-2.5 mm per layer; and the number of layers is 7-11 layers. The T2WI axial sequence can be added for the diseased intervertebral disc. 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 front and back; the frequency encoding direction is set to left and right; the scanning matrix is 288*288 (phase encoding*frequency encoding); the voxel size is 0.3*0.3 mm; the number of excitations is 2-4 times; the scanning layer thickness is 1-1.5 mm per layer; and the number of layers is 3-5 layers. At this time, the device will display the total scanning time. Even if only the sagittal plane of the tail vertebra is scanned, the total time will reach 10-30 minutes, which is extremely prone to motion artifacts and anesthesia recovery.

[0102] The fast spin echo (Turbo Spin Echo, TSE) acceleration technique is used to accelerate it, and the acceleration factor (TSE factor) is set to 5-11. The spin echo sequence has a disadvantage that the longitudinal relaxation time is relatively long. One echo data is collected in one excitation, so the total collection time is relatively long, and the motion of the detected object is relatively sensitive. Although the live mouse is anesthetized, there are still physiological movements such as respiratory movement, intestinal peristalsis, and muscle random twitch movement. The total scanning time cannot be too long, otherwise the image is prone to motion artifacts, and the researcher's working time is wasted. The TSE sequence uses multiple 180° recombination pulses to recombine the signal after one radio frequency pulse excitation, and can fill multiple K-space phase encoding lines at a time. The larger the acceleration factor value, the shorter the scanning time. A reasonable TSE factor is set to reduce the scanning time in a single direction to within 4 minutes. However, the use of TSE technology will cause the vertebral body rich in fat to change from a medium signal to a high signal, and at this time it will be difficult to distinguish between the normal vertebral body, the diseased vertebral body and the intervertebral disc. Specifically, the TSE pulse diagram is as shown in Figure 4 .

[0103] Further optimization of TSE sequence is performed using fat signal suppression technique. Because the vertebral body is rich in fat, the T2WI image of the vertebral body using TSE sequence after acceleration shows high signal, so it is difficult to distinguish the normal vertebral body, the lesion vertebral body containing water and the intervertebral disc containing water.

[0104] The fat suppression technique using the difference in precession frequency of hydrogen protons in fat and water can suppress fat and make the normal vertebral body show low signal for easy distinction. The commonly used fat suppression techniques include the Short TI Inversion Recovery (STIR) fat suppression technique using the difference in longitudinal relaxation time of hydrogen protons in fat and water and the fat suppression technique using the difference in precession frequency of hydrogen protons in fat and water. The STIR technique has less magnetic susceptibility artifacts, but it can cause too much decline in image signal-to-noise ratio and can suppress the signal of tissues with little difference in longitudinal relaxation time of hydrogen protons in fat, affecting image analysis. Therefore, the fat suppression technique using the difference in precession frequency of hydrogen protons in fat and water is selected, and the chemical shift of the precession frequency of hydrogen protons in fat and water in the main magnetic field is 3.5 ppm.

[0105] According to the formula The resonance peak frequency offset of hydrogen protons in fat and water in different main magnetic field strengths can be calculated. Wherein, is a constant term, B0 is related to the main magnetic field strength, and the theoretical offset frequency calculated according to the formula is 383.22 Hz at a main magnetic field of 3.0T. The value is also related to the actual temperature of the operation site (the temperature of the experimental room is generally fixed at 20-22°) and the temperature of the object to be detected. The body temperature of the white rat to be detected is usually about 40°, which is slightly higher than the human body temperature, and the temperature will further rise during the scanning process due to the small size of the white rat. Therefore, the value is corrected to 400-430 Hz according to different conditions.

[0106] Further optimization is performed using SPAIR fat suppression technique. The 180° insulating flip pulse of SPAIR sequence accurately targets fat tissue and is not sensitive to the inhomogeneity of magnetic resonance radio frequency field, so the fat signal suppression efficiency is high and the magnetic susceptibility artifacts are relatively light compared with SPIR and PROSET techniques. The SPAIR sequence diagram is shown in Figure 5 .

[0107] Set the frequency offset parameter to 200 Hz. The frequency offset is the frequency offset of the fat peak from the flip pulse. If it is set too small, the frequency offset is small, the 180° insulating pulse emitted has a small bandwidth, and the fat suppression is poor; if it is set too large, the frequency offset is large, the 180° insulating pulse emitted has a large bandwidth, and the fat suppression is more thorough, but it can cause part of the water signal (intervertebral disc signal) to be suppressed as well. Setting it to 200 Hz can ensure that the fat tissue is sufficiently flipped, and can also ensure that the water signal is not affected.

[0108] When the frequency-selective insulating flip pulse is used in the SPAIR sequence, a slow precession can be selected until the target angle of 180° is reached, and the radio frequency power can be selected to be as high as possible. This makes the object to be detected less sensitive to the inhomogeneity of the magnetic resonance radio frequency field, further reducing the magnetic susceptibility artifact, but the scan time is slightly increased.

[0109] The (DRIVEN Equilibrium, DRIVE) technique is used to further control the scan time. If the use of the SPAIR technique again increases the scan time of a single sequence to more than 4 minutes, it can again increase the risk of motion artifacts in the rat, because the TSE factor cannot be increased indefinitely, otherwise the image blurring effect will be aggravated. Since the scan time in the TSE sequence is proportional to the repetition time TR, in order to shorten the scan time, the TR can be appropriately reduced. However, when the next radio frequency pulse is excited, the longitudinal magnetization vector of the tissue has not fully recovered, not only the image signal-to-noise ratio will be reduced, but also the insufficient TR will affect the T2 contrast of the image. At this time, the DRIVE technique can be used, that is, a negative 90° radio frequency pulse is added after the last 180° re-focusing pulse, which will force the horizontal residual magnetization vector to return to the longitudinal axis direction, and the tissue will quickly complete the longitudinal relaxation. At this time, the sequence diagram is as shown in Figure 6

[0110] The shim technique is used to make the magnetic field of the rat sacrococcygeal region to be scanned more uniform. Because the hip of the rat suddenly becomes thin when it transitions to the tail vertebra, a serious magnetic susceptibility artifact can be generated, and although the embedding treatment of the elimination material is used, there is still a possibility of generating a small amount of magnetic susceptibility artifact. First, appropriate currents are applied to the gradient coils in the X, Y, and Z directions to superimpose on the original main magnetic field and thereby compensate for the inhomogeneity of the original main magnetic field (first-order active shim); then appropriate currents are applied to the active shim coils in the gradient coils (second-order active shim). The two work together to make the magnetic field of the scan region more uniform.

[0111] Through the reasonable use of the above technical means, the final scan image is as shown in Figure 7 The failed image with a more serious magnetic susceptibility artifact is as shown in​Figure 8 As shown.

[0112] The large mouse tail vertebra magnetic resonance image acquisition device provided by the application eliminates the magnetic susceptibility artifacts by eliminating the filling material, accurately fixes the material, and enhances the magnetic resonance signal strength of the scanning area by the grease block, combines the high signal-to-noise ratio of the spin echo (SE) sequence and the excellent tissue contrast of T2 weighted imaging (T2WI), and compresses the scanning time to 4 minutes by the fast spin echo (TSE) technology (acceleration factor 5-11), so as to effectively control the physiological motion artifacts of the living rat; the fat suppression technology based on the fat-water frequency difference is combined with the SPAIR to accurately eliminate the vertebral fat signal, so that the signal contrast between the normal vertebral low signal and the lesion area is clear, and the DRIVE technology forcibly restores the longitudinal magnetization vector to maintain the T2 contrast and further shorten the scanning time; the first-order and second-order uniform field technology is combined to further reduce the non-uniformity of the main magnetic field of the scanning area, significantly improve the fat suppression uniformity of the image, and finally realize the living rat tail vertebra imaging with fast speed, high resolution and low artifacts, and have high efficiency, diagnostic accuracy and operation safety. It can meet the safety requirements of the living large mouse and can be extended to other small animal (mouse, rabbit) spine imaging scenes.

[0113] Based on the same inventive concept, the application also provides a large mouse tail vertebra magnetic resonance image acquisition method corresponding to any of the above-mentioned embodiment devices, which comprises:

[0114] The fixing material is fixed at the bottom of the nuclear magnetic resonance instrument scanning radio frequency coil, a groove is arranged on the fixing material, the groove is adapted to the tail vertebra and the hip position of the large mouse to be measured, the tail vertebra position of the large mouse to be measured is placed in the groove, the elimination filling material is placed on the tail vertebra of the large mouse to be measured, the remaining gap between the tail vertebra of the large mouse to be measured and the fixing material is filled, all the air is discharged as much as possible, the position of the large mouse to be measured is fixed, and the magnetic resonance image is acquired by scanning the nuclear magnetic resonance instrument.

[0115] The method of the above-mentioned embodiment is used in the large mouse tail vertebra magnetic resonance image acquisition device of any of the above-mentioned embodiments, and has the beneficial effects of the corresponding method embodiment, which will not be described here.

[0116] The technical solutions in the application will be clearly and completely described below with reference to the embodiments in the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0117] Embodiment one

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

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

[0120] Styrene-butadiene rubber and phthalate are mixed and stirred at 100°C for 25 minutes to form a homogeneous colloid;

[0121] Calcium carbonate, fumed silica and stabilizer are added to the homogeneous colloid, and the mixture is mixed at a low speed of 50-80 rpm for 10 minutes in an internal mixer, and then mixed at a high speed of 80-100 rpm for 15 minutes to obtain a mixed material;

[0122] The mixed material is transferred to a vacuum degassing device and degassed at a pressure of -0.08 MPa for 20 minutes to obtain a degassed material;

[0123] The degassed 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 A 20-50 and a temperature resistance range of -30°C to 120°C;

[0124] The fixed raw material is laid flat in a small coil such as a mouse special coil or a human wrist joint coil, and the coil bottom is filled as much as possible. A space is reserved for the mouse to lie down.

[0125] The mouse to be tested is placed on the fixed raw material with its head facing forward, ensuring unobstructed breathing. Because the fixed raw material has a certain plasticity, the back and hips of the mouse to be tested are lightly pressed, and the tail vertebrae of the mouse to be tested are straightened and pressed onto the fixed raw material, so that the fixed material retains the body features of the mouse to be tested, and the fixed material is obtained.

[0126] Example Two

[0127] A method for making a filling material 12 is provided:

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

[0129] The polyvinyl alcohol adhesive is mixed with deionized water and stirred at 70°C until completely dissolved to form a transparent glue solution.

[0130] Glycerol plasticizer and polyethylene glycol are added to the transparent glue solution in sequence, the temperature is kept at 50°C, and the mixture is stirred until uniform to obtain a mixed glue solution.

[0131] Foamed microspheres and mica powder are added to the mixed glue solution in sequence, first mixed at a low speed of 200 rpm for 10 minutes, and then stirred at a high speed of 400 rpm for 10 minutes to form a uniform paste.

[0132] The uniform paste is placed in a vacuum defoaming machine and defoamed at -0.1 MPa pressure for 15 minutes to obtain the filler material 12.

[0133] Example Three

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

[0135] This example uses 60% calcium carbonate powder, 20% liquid paraffin and 20% glycerol.

[0136] The above materials are mixed uniformly at room temperature, vacuum-packed in a 1*5*12 cm bag to obtain the signal enhancement material.

[0137] It should be understood by those of ordinary skill in the art that the above discussion of any of the embodiments is merely exemplary and is not intended to suggest the scope of the present application (including the claims) is limited to these examples; the embodiments or technical features between different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes to the aspects of the embodiments of the present application as described above, which are not provided in detail. In order to be brief.

[0138] In addition, in the case of describing specific details to describe the exemplary embodiments of the present application, it is obvious to those skilled in the art that the embodiments of the present application can be implemented without these specific details or with changes to these specific details. Therefore, these descriptions should be considered as illustrative rather than limiting. Although the present application has been described in conjunction with specific embodiments thereof, many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description.

[0139] The embodiments of the present application are intended to cover all such alternatives, modifications and variations as falling within the broad scope of the appended claims. Accordingly, any omission, modification, equivalent replacement, improvement, etc. made in the spirit and principle of the embodiments of the present application should be included in the scope of protection of the present application.

Claims

1. A device for acquiring magnetic resonance images of the rat's tail vertebrae, characterized in that, include: Nuclear magnetic resonance spectrometer, fixation material, and removal filler material; The fixation material is fixed to the bottom of the scanning radio frequency coil of the MRI scanner. The fixation material has grooves that are adapted to the position of the tailbone and buttocks of the rat to be tested. The elimination filling material is an adaptable material that, together with the fixation material, fixes the position of the rat to be tested. Magnetic resonance images are obtained by scanning with the MRI scanner. The elimination filling material is made from a third raw material, which includes: 5-15% foamed microspheres, 20-40% binder, 10-25% plasticizer, 10-30% lightweight filler, 2-8% humectant, and the balance being deionized water.

2. The rat tail vertebra magnetic resonance image acquisition device according to claim 1, characterized in that, Also includes: Signal enhancement materials; The signal enhancement material is fixed inside the scanning radio frequency coil of the MRI scanner, specifically located above the tailbone of the rat under test, to enhance the magnetic resonance signal intensity in the scanning area.

3. The rat tail vertebra magnetic resonance image acquisition device according to claim 2, characterized in that, The signal enhancement material is prepared by the following steps: The first raw material is weighed according to a preset ratio; wherein, the first raw material includes: filler, liquid paraffin and glycerin; The first raw material is mixed evenly, packed into a small bag, and vacuum-sealed 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 prepared by the following steps: The second raw material is weighed according to a preset ratio; wherein, the second raw material includes: base polymer, plasticizer, filler, thixotropic agent and stabilizer; The base polymer and the plasticizer are mixed and stirred at 80-120°C for 10-30 minutes to form a homogeneous colloid; The filler, the thixotropic agent, and the stabilizer are added to the homogeneous colloid, and the mixture is kneaded in an internal mixer at 50-100 rpm for 15-45 minutes to obtain a mixture. The mixture is transferred to a vacuum degassing device and degassed for 5-20 minutes under a pressure of -0.06 to -0.09 MPa to obtain degassed material; The degassed material is formed into sheets or blocks by calendering and cooled to room temperature to obtain a fixed raw material with a Shore A hardness of 20-50 and a temperature resistance range of -30℃ to 120℃. The fixative material is laid flat inside the scanning radio frequency coil of the nuclear magnetic resonance spectrometer, covering the bottom of the scanning radio frequency coil as much as possible, while leaving a space for the rat to lie prone. Place the rat to be tested prone on the fixation material with its head facing forward to ensure unobstructed breathing; gently press the back and buttocks of the rat to be tested, straighten the tailbone of the rat to be tested and press it onto the fixation material, so that the body shape characteristics of the rat to be tested are preserved on the fixation material, thus obtaining the fixation material.

5. The rat tail vertebra magnetic resonance image acquisition device according to claim 1, characterized in that, The filler removal material is prepared through the following steps: The third raw material is weighed according to a preset ratio; wherein, the third raw material includes: foamed microspheres, adhesive, plasticizer, lightweight filler, humectant and deionized water; The adhesive is mixed with the deionized water and stirred at 60-80°C until completely dissolved to form a transparent adhesive solution; Add the plasticizer and the humectant to the transparent adhesive solution in sequence, maintain the temperature at 40-50℃, and stir until the mixture is uniform to obtain a mixed adhesive solution; The foamed microspheres and the lightweight filler are added sequentially to the mixed adhesive solution, and the mixture is stirred at 200-400 rpm for 10-30 minutes to form a uniform paste. The uniform paste was placed in a vacuum degassing machine and degassed for 5-15 minutes under a pressure of -0.08 to -0.1 MPa to obtain the filler-free material.

6. The rat tail vertebra magnetic resonance image acquisition device according to claim 1, characterized in that, The process of acquiring magnetic resonance images by scanning with the nuclear magnetic resonance spectrometer includes: Step S1: Using the spin echo sequence as the base sequence, set the T2 weighted imaging parameters and generate a T2 contrast image; Step S2: Introduce an echo train into the T2 weighted sequence formed in step S1, and set the acceleration factor to 5-11 to obtain the accelerated TSE-T2 weighted image; Step S3: Based on the frequency-selective fat suppression technique, a pre-saturation pulse is applied to the TSE sequence formed in step S2 to suppress the normal vertebral fat signal to a low signal while preserving the water signal, thereby generating a fat-suppressed TSE-T2 weighted image. Step S4: Based on step S3, using SPAIR technology, the frequency offset is set to 200 Hz, and the arrival mode and power of the 180° insulated radio frequency pulse are adjusted to further suppress fat signal residue and obtain a high-contrast SPAIR-TSE-T2 weighted image. Step S5: Apply a negative 90° radio frequency pulse to the end of the echo train formed in step S4 to force longitudinal magnetization vector recovery and generate a time-optimized DRIVE-SPAIR-TSE-T2 weighted image; Step S6: Adjust 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 the final magnetic resonance image.

7. The rat tail vertebra magnetic resonance image acquisition device according to claim 6, characterized in that, The setting of T2-weighted imaging parameters includes: Based on sagittal image scanning of the coccyx, the repetition time (TR) was set to 2000-6000 ms; the echo time (TE) was set to 60-120 ms; the phase encoding direction was set to anterior-posterior; the frequency encoding direction was set to cephalothorax; the scan matrix was set to 288*368; the voxel size was set to 0.3*0.3 mm; the number of excitations was set to 2-4; the slice thickness was set to 1-2.5 mm per slice; and the number of slices was set to 7-11. For axial image scanning of the intervertebral disc, the repetition time (TR) was set to 2000-6000ms; the echo time (TE) was set to 60-120ms; the phase encoding direction was set to anterior-posterior; the frequency encoding direction was set to lateral; the scan matrix was set to 288*288; the voxel size was set to 0.3*0.3mm; the number of excitations was set to 2-4; the slice thickness was set to 1-1.5mm per slice; and the number of slices was set to 3-5.

8. A method for acquiring magnetic resonance images of the caudal vertebrae of a rat, characterized in that, The rat tail vertebra magnetic resonance image acquisition device as described in any one of claims 1-7 includes: A fixation material is fixed to the bottom of the scanning radio frequency coil of the MRI scanner. The fixation material has a groove that is adapted to the position of the tailbone and buttocks of the rat to be tested. The tailbone of the rat to be tested is placed in the groove, and the remaining gap between the tailbone of the rat to be tested and the fixation material is filled with a filling material to remove as much air as possible. The position of the rat to be tested is fixed, and the MRI scanner is used to scan and obtain magnetic resonance images.

Images