CN113156350B - Non-invasive light opaque micron-sized living tissue magnetic resonance tomography method and system - Google Patents

Abstract

A non-invasive optical opaque micron-scale living tissue magnetic resonance tomography method is realized by controlling the following three conditions: A. A uniform and single-direction main magnetic field with ultra-high magnetic field strength is applied to the living biological tissue; B. On the basis of the main magnetic field Above, for the three directions of X, Y, and Z, the superimposed gradient magnetic field with the intensity gradient distribution of more than 10000 mT/m is used to spatially encode the elements with spin angular momentum, so that the spin frequencies of elements in different spatial positions are Different; C. The radio frequency electromagnetic field perpendicular to the main magnetic field is used to excite the imaging object with the radio frequency electromagnetic field, and after the excitation is withdrawn, the energy level converted radio frequency signal emitted by the imaging object is picked up, and the radio frequency signal is reconstructed and decoded to obtain a tomographic image. It can realize non-invasive living tissue tomography with a spatial resolution of 1 micron scale and the ability to resolve subcellular structures.

Description

Non-invasive optical opaque micron-scale living tissue magnetic resonance tomography method and system

technical field

The invention relates to the technical field of biomedical in vivo imaging, in particular to a non-invasive optical opaque micron-scale in vivo magnetic resonance tomography imaging method and a system thereof.

Background technique

In the field of biomedical imaging, for biological tissues and/or cells, the main imaging technologies are optical imaging, ultrasound imaging, X-ray imaging (including X-ray CT), nuclear medicine imaging, photoacoustic imaging, electromagnetic microwave imaging, magnetic resonance imaging Wait.

Using optical imaging techniques such as confocal laser imaging, subcellular structures (ie, intracellular organelles) can be observed, but the observed objects must be independent single cells that have been separated from non-transparent tissues. For optically opaque living biological tissue, since light cannot penetrate the imaging object, it is impossible to use optical imaging methods to image individual cells in the living tissue. Under normal circumstances, light cannot penetrate the bodies of rats and mice, let alone the human body.

Although ultrasonic imaging has a certain penetrating power and can penetrate tissues with a thickness of tens of centimeters or more, due to various limitations such as ultrasonic emission beams and ultrasonic detectors, it is impossible to observe every single cell in living tissue. . The ultra-high frequency ultrasound imaging currently under development, although it can achieve a resolution of less than 1 mm, still cannot achieve in vivo imaging at the level of 1 micron resolution; and its penetrating ability declines sharply with the increase of frequency. , the use of ultrasonic imaging techniques cannot achieve tomographic imaging at the 1-micron resolution level of living tissue in rats and mice.

X-ray imaging includes two types of X-ray projection imaging and X-ray tomography (X-ray CT). The existing X-ray CT technology can achieve a resolution of about 1 mm, but cannot achieve a resolution of 1 micron. In addition, the soft tissue resolution of X-rays is relatively poor, and it is impossible to achieve tomographic imaging at the 1-micron resolution level of living tissue in rats and mice.

Nuclear medicine imaging has the advantage of relatively high sensitivity, but its imaging spatial resolution is poor, which is lower than the spatial resolution of CT imaging, and is far from the spatial resolution required for tomography at the 1-micron resolution level.

Photoacoustic imaging uses light as the excitation source to excite tissue to generate ultrasound, and realizes imaging by detecting ultrasound, and its resolution does not essentially exceed that of ultrasound imaging.

The advantage of electromagnetic microwave imaging is that there is no ionizing radiation, but its resolution is poor, often in the order of centimeters or even rougher, and a high-resolution practical system cannot be formed at present.

Magnetic resonance imaging has the advantages of strong penetration and high resolution of soft tissue imaging, but the resolution of the existing magnetic resonance imaging system cannot achieve tomography at the level of 1 micron resolution in vivo, and the highest resolution small animal magnetic resonance imaging system The spatial resolution of _20-40um can be achieved at most, and at this resolution, multiple cells will appear as one pixel on the image.

In a word, so far, the existing biomedical imaging techniques have not been able to non-invasively achieve tomography at the level of 1 micron resolution on the living body, and none of them can non-invasively observe and measure the morphology and function of individual cells on the living body. .

Therefore, in view of the deficiencies of the prior art, it is necessary to provide a non-invasive optical opaque micron-scale living tissue magnetic resonance tomography imaging method to overcome the deficiencies of the prior art.

SUMMARY OF THE INVENTION

The purpose of the present invention is to avoid the deficiencies of the prior art and provide a non-invasive optical opaque micron-scale living tissue magnetic resonance tomography method, which can non-invasively achieve 1-micron-level tomography on the living tissue level.

The object of the present invention is achieved by the following technical measures.

A non-invasive optical opaque micron-scale living tissue magnetic resonance tomography method is provided, which is realized by controlling the following three conditions:

A. The main magnetic field with a uniform and single-direction ultra-high magnetic field strength is applied to the living biological tissue as the imaging object;

B. On the basis of the main magnetic field, a gradient field is applied in the 1-micron-scale imaging area according to the imaging standard with an imaging spatial resolution of 1-micron scale, specifically: for the three directions of X, Y, and Z, the intensity is 10000 mT/m respectively. The superimposed gradient magnetic field of the above intensity gradient distribution performs spatial encoding on the elements with spin angular momentum, so that the spin frequencies of elements in different spatial positions are different;

C. Use the radio frequency electromagnetic field perpendicular to the main magnetic field to excite the imaging object with the radio frequency electromagnetic field, and pick up the energy level conversion radio frequency signal emitted by the imaging object after the excitation is cancelled, reconstruct and decode the radio frequency signal, and obtain the tomographic imaging.

Preferably, in the above non-invasive optical opaque micron-scale living tissue magnetic resonance tomography method, in A, the magnetic field strength of the main magnetic field is not lower than 9.4 Tesla.

Preferably, in the above non-invasive optical opaque micron-scale living tissue magnetic resonance tomography method, in B, a gradient field is applied according to an imaging standard with an imaging spatial resolution of 1 micron, specifically:

In the Z direction, the frequency selection bandwidth is narrowed to below 20KHz, and the superimposed gradient magnetic field with the intensity of 10000mT/m to 50000mT/m is used to realize the layer selection in the Z direction with a resolution of 1 micron thickness;

In the X direction, a superimposed gradient magnetic field with an intensity of 20000mT/m to 50000mT/m is used, and a receiving spectrometer with a frequency resolution of 0.8KHz to 3.0KHz is used to achieve a resolution of 1 micron pixel in the X direction;

Among them, the frequency resolution of the spectrometer satisfies the formula (1):

Δf=γ*(G _x *Δx)... Formula (1);

In formula (1), Δf is the frequency resolution of the spectrometer, γ is the gyromagnetic ratio, _Gx is the gradient field strength of the superimposed gradient magnetic field in the X direction, and Δx is the scale that reaches the pixel resolution in the X direction;

In the Y direction, a superimposed gradient magnetic field with an intensity of 10000mT/m to 50000mT/m is used to control the gradient opening time in the Y direction, and the step size is set to 4.7us to 4.7*5us to achieve a phase resolution of 1 micron-scale pixels. coding;

Among them, the gradient opening time in the Y direction satisfies the formula (2):

为Y方向上梯度打开时间。In formula (2), G _y is the gradient field strength of the superimposed gradient magnetic field in the Y direction, Δy is the scale that reaches the pixel resolution in the Y direction, Δy is not greater than 1 μm,

Turns on time for the gradient in the Y direction.

Preferably, in the above non-invasive optical opaque micron-scale living tissue magnetic resonance tomography method, in B, in the X direction, a superimposed gradient magnetic field with an intensity of 20,000 mT/m is used, and a receiving spectrometer with a frequency resolution of 852 Hz is used. A resolution of 1 micron pixel is achieved.

Preferably, in the above non-invasive optical opaque micron-scale living tissue magnetic resonance tomography method, in B, in the X direction, a superimposed gradient magnetic field with an intensity of 50,000 mT/m is used, and a receiving spectrometer with a frequency resolution of 2.5 KHz is used. Orientation achieves pixel resolution at 1 micron scale.

Preferably, the above-mentioned non-invasive optical opaque micron-scale living tissue magnetic resonance tomography method, in B,

In the Y direction, a superimposed gradient magnetic field with a strength of 10000mT/m is used, the gradient opening time in the Y direction is controlled at 2.35ms, and the step size is set at 4.7us; or

In the Y direction, a superimposed gradient magnetic field with an intensity of 50000 mT/m is used, the gradient opening time in the Y direction is controlled at 2.35 ms, and the step size is set at 4.7*5us.

Preferably, the above-mentioned non-invasive optical opaque micron-scale living tissue magnetic resonance tomography imaging method adopts an imaging area co-transformation tomography imaging method for the overall imaging object. Conditioning for tomography;

The tomographic imaging range is 10±5cm. When the required imaging range is large, the Zoom out (zoomed out) mode is used for imaging; on the contrary, when the required imaging range is small, the Zoom in (zoomed in) mode imaging is used; at least the selected area of interest is used for imaging. As a 1-micron-scale imaging area and applying a gradient field with the standard of a 1-micron-scale imaging area, the imaging spatial resolution of the region of interest is 1-micron scale, and the upper limit of the data size of a single tomographic image is controlled between 100kB-100MB between.

Preferably, when the imaging range is large, the Zoom out mode is used for imaging, and the initial region of interest is obtained by using the imaging result of the Zoom out mode;

Then judge whether the initial region of interest satisfies the 1-micron-scale imaging conditions, if so, perform tomographic imaging with a resolution of 1-micron scale on the initial region of interest; if not, divide the initial region of interest into multiple 1-micron-scale imaging Sub-imaging areas of scale imaging conditions, tomographic imaging with a resolution of 1 micron scale is performed on multiple sub-imaging areas respectively;

1-micron-scale imaging conditions are: the upper limit of the data size of a single tomographic image obtained by imaging at 1-micron scale is between 100kB-100MB;

Specifically, the tomographic imaging with a resolution of 1 μm is to apply a gradient field and perform imaging according to the imaging standard with an imaging spatial resolution of 1 μm.

Preferably, 1 micron scale refers to a resolution range of 0.1 micron to 2 microns.

Preferably, in the above non-invasive optical opaque micron-scale living tissue magnetic resonance tomography method, the signal enhancement sequence used in condition C is: adding a positive 90-degree radio frequency pulse before the next negative 90-degree radio frequency pulse to shorten the TR time and reduce the T2 signal. Attenuate and improve the signal-to-noise ratio.

Preferably, in the above non-invasive optically opaque micron-scale living tissue magnetic resonance tomography method, the tomographic imaging range is 10±2 cm.

The non-invasive optical opaque micron-scale living tissue magnetic resonance tomography method of the present invention is realized by controlling the following three conditions: A. a uniform and single-direction main magnetic field with ultra-high magnetic field strength is applied to the living biological tissue; B. in the main magnetic field On the basis, for the three directions of X, Y and Z, the superimposed gradient magnetic field with the intensity gradient distribution of more than 10000 mT/m is respectively used to spatially encode the elements with spin angular momentum, so that the spins of elements in different spatial positions can be encoded. The frequencies are different; C. The radio frequency electromagnetic field perpendicular to the main magnetic field is used to excite the imaging object with the radio frequency electromagnetic field, and after the excitation is withdrawn, the energy level converted radio frequency signal emitted by the imaging object is picked up, and the radio frequency signal is reconstructed and decoded to obtain the tomographic image. The invention can non-invasively realize tomography at the level of 1 micron resolution on the level of optically opaque living tissue, and can realize non-invasive living tissue tomography with a spatial resolution of 1 micron and the ability to resolve subcellular structures. The technical problem of non-invasively realizing tomographic imaging at the level of 1 micron resolution at the living tissue level, which cannot be achieved by the existing biomedical imaging technology means, is solved.

Instruction drawings

The present invention will be further described by using the accompanying drawings, but the content in the accompanying drawings does not constitute any limitation to the present invention.

1 is a sequence diagram of a signal enhancement sequence of a non-invasive optically opaque micron-scale living tissue magnetic resonance tomography method of the present invention.

Detailed ways

The present invention will be further described with reference to the following examples.

Example 1.

A non-invasive optical opaque micron-scale living tissue magnetic resonance tomography method is realized by controlling the following three conditions: A, B, and C.

A. The main magnetic field with ultra-high magnetic field strength in a uniform single direction is applied to the living biological tissue. It should be noted that the main magnetic field with ultra-high magnetic field strength mentioned in the present invention refers to the main magnetic field with a magnetic field strength not lower than 9.4 Tesla, such as 9.4T, 10.5T, 16T and so on. The realization of the main magnetic field with the ultra-high magnetic field strength can be realized by the relevant magnetic resonance equipment, which belongs to the well-known technology in the art, and will not be repeated here.

The micron-scale scale of the present invention refers to the resolution of imaging at about 1 micron, and specifically refers to the resolution range of 0.1 micron to 2 microns, such as 1 micron resolution or slightly less than 1 micron resolution. Elements containing spin angular momentum in living biological tissues, including protons, phosphorus elements, sodium elements, etc. Using a main magnetic field with a uniform and single-direction ultra-high magnetic field strength, the spin direction alignment process can be performed on elements with spin angular momentum contained in living biological tissues. When biological tissue is under the action of a strong external magnetic field, the vector direction of the spin angular momentum of elements with spin angular momentum will be consistent with the direction of the external magnetic field (or 180 degrees opposite). The design of the condition of item A is a key to ensure the realization of micron-scale resolution tomography.

B. On the basis of the main magnetic field, when the target area to be imaged needs to achieve 1-micron-scale tomography (the target area is the 1-micron-scale imaging area), apply a gradient field according to the imaging standard with an imaging spatial resolution of 1-micron scale , specifically: for the three directions of X, Y, and Z, respectively use superimposed gradient magnetic fields with an intensity gradient distribution of more than 10000 mT/m to spatially encode elements with spin angular momentum, so that the elements in different spatial positions are The rotation frequency is different.

Specifically, in the Z direction, the frequency selection bandwidth is narrowed to below 20KHz, and a superimposed gradient magnetic field with an intensity of 10000mT/m to 50000mT/m is used to achieve Z direction layer selection with a resolution of 1 micron thickness.

In the X direction, according to the relationship of formula (1), a superimposed gradient magnetic field with an intensity of 20000mT/m to 50000mT/m is used, and a receiving spectrometer with a frequency resolution of 0.8KHz to 3.0KHz is used to achieve a pixel of 1 in the X direction. micron-scale resolution;

Among them, the frequency resolution of the spectrometer satisfies the formula (1):

Δf=γ*(G _x *Δx)... Formula (1);

In formula (1), Δf is the frequency resolution of the spectrometer, γ is the gyromagnetic ratio, _Gx is the gradient field strength of the superimposed gradient magnetic field in the X direction, and Δx is the scale that reaches the pixel resolution in the X direction.

For example, in the X direction, for hydrogen nuclei, the gyromagnetic ratio is γ=42.6MHzT ^-1 , to achieve a resolution of 1 micron pixel in the X direction, for frequency encoding, according to the gradient field strength G _x is greater than 20000mT/ m is calculated by using the gradient frequency coding rule. When the pixel is 1 micron, the corresponding frequency resolution of the spectrometer is:

Δf=γ*(G _x *Δx)=42.6×10 ⁶ HzT ^-1 ×20Tm ^-1 ×10 ^-6 m=852Hz, the above result means that if the frequency resolution of the receiving spectrometer can reach 852Hz (about 1KHz) , the frequency encoding with a pixel of 1 micron (imaging in the X direction) can be achieved, and the current spectrometer can fully achieve this level of frequency resolution; if the gradient field strength G _x continues to increase to 50000mT/m, the frequency of the receiving spectrometer will be The resolution requirement is lower, about 2.5KHz.

It should be noted that, according to the relationship of formula (1), by adjusting the gradient field strength of the superimposed gradient magnetic field in the X direction and the frequency resolution of the spectrometer, 1-micron-scale spatial resolution imaging can be achieved. The method of the present invention is suitable not only for hydrogen nuclei, but also for other elements having spin properties that are compatible with magnetic resonance.

In the Y direction, according to the relationship of formula (2), a superimposed gradient magnetic field with an intensity of 10000mT/m to 50000mT/m is used to control the gradient opening time in the Y direction, and the step size is set to 4.7us to 4.7*5us to achieve resolution. Rate of phase encoding of 1-micron-scale pixels;

Among them, the gradient opening time in the Y direction satisfies the formula (2):

为Y方向上梯度打开时间。In formula (2), G _y is the gradient field strength of the superimposed gradient magnetic field in the Y direction, Δy is the scale that reaches the pixel resolution in the Y direction, Δy is not greater than 1 μm,

Turns on time for the gradient in the Y direction.

是y方向上梯度打开持续时间，同样要求成像的分辨率为1um，则需要满足：For example, in the Y direction, also for hydrogen nuclei, the gyromagnetic ratio γ=42.6MHzT ^-1 , the gradient field intensity Gy in the Y direction is calculated as 10000mT/m, and the linear length in the Y direction of the imaging area is within the range of r=1mm ,

is the gradient opening duration in the y direction, and the resolution of the imaging is also required to be 1um, then it needs to meet:

意味着只需要将梯度打开时间控制在2.35ms，步长可设定为4.7us，就可以实现分辨率为1um的像素的相位编码需要。y方向上梯度强度一般在10000mT/m至50000mT/m之间。如果增加G_y至50000mT/m，则可相应放宽步长的要求，使得步长为4.7us*5。which is:

It means that only the gradient opening time can be controlled to 2.35ms, and the step size can be set to 4.7us, and the phase encoding needs of pixels with a resolution of 1um can be achieved. The gradient strength in the y direction is generally between 10000 mT/m and 50000 mT/m. If G _y is increased to 50000mT/m, the step size requirement can be relaxed accordingly, so that the step size is 4.7us*5.

It should be noted that, according to the relationship of formula (2), by adjusting the gradient field strength, gradient opening time, and step size of the superimposed gradient magnetic field in the Y direction, 1-micron-scale spatial resolution imaging can be achieved. The method of the present invention is suitable not only for hydrogen nuclei, but also for other elements having spin properties that are compatible with magnetic resonance.

C. Use the radio frequency electromagnetic field perpendicular to the main magnetic field to excite the imaging object with the radio frequency electromagnetic field, and pick up the energy level conversion radio frequency signal emitted by the imaging object after the excitation is cancelled, reconstruct and decode the radio frequency signal, and obtain the tomographic imaging; The range is 10±5 cm, the preferred range is 10±2 cm, and the imaging spatial resolution of the region of interest is 1 micron scale.

The RF electromagnetic field adopts the design method of integrated transceiver, and the specific winding can adopt the 8-channel or 16-channel cage structure, the cylindrical coil partially overlaps the surrounding structure, etc., covering the entire imaging object.

For the whole imaging object, the imaging area CT imaging method is adopted. The imaging area co-transformation tomography method is to perform tomography imaging by dynamic adjustment of imaging area and imaging resolution. That is, the imaging area and imaging resolution are dynamically adjusted, and the upper limit of the data size of a single tomographic image is controlled between 100kB-100MB.

When the required imaging range is large, use the Zoom out (zoom out) mode for imaging; on the contrary, when the required imaging range is small, use the Zoom in (zoom in) mode for imaging; at least the selected area of interest is used as a 1-micron-scale imaging area and is The standard applied gradient field of the 1-micron-scale imaging area, the imaging spatial resolution of the region of interest is 1-micron scale, and the upper limit of the data size of a single tomographic image is controlled between 100kB-100MB.

This method is proposed by the applicant for the first time, and its most essential feature is that the imaging area is linked with the imaging resolution, and the image data size of the formed tomographic imaging is controlled within the required range. Specifically, when the required imaging range is large, the gradient coils and current control and driving modes corresponding to the Zoom out mode (zoom out mode) are used; on the contrary, when the required imaging range is small, the Zoom in mode (zoom in mode) corresponding to gradient coils and current control and drive modes. The Zoomout mode can provide positioning assistance for the Zoom in mode, and the gradient field strength in the Zoom out mode is smaller than the gradient field strength corresponding to the Zoom in mode. In this innovative tomographic imaging mode, corresponding to different imaging area (FOV) and imaging resolution requirements, different parameter combinations are set. The setting rule is: control the data of each tomographic image, within the set image data size range In general, the data size of a single tomographic image is set between 100kB-100MB. For example, if the imaging FOV is set to 5cm*5cm*5cm, if the entire FOV range is directly reconstructed with a horizontal resolution of 1um*1um, the pixel size of each tomographic image will reach 2500MB, which is obviously inappropriate. To this end, by controlling the gradient change, we segment large FOVs into small FOVs, similar to the process of "imaging area connected tomography", to achieve a reasonable matching of reconstructed image pixel size and resolution requirements.

The imaging method of the present invention takes into account the problem of calculation amount. For a specific imaging target, if the data of a single tomographic image is too large, the processing amount of the image operation performed by the computer will increase geometrically, so that the method of this scheme cannot be effectively implemented. The invention designs a tomographic imaging method of "interchangeable imaging area", which dynamically adjusts the imaging area and the corresponding resolution according to the actual situation of the imaging range, so as to reduce the calculation amount of the picture. For those with a small imaging range, the magnification mode is used for imaging, and the relevant gradient fields can be set at this time to achieve tomographic imaging with a resolution of 1 μm. When the imaging range is large, avoid performing tomographic imaging with a resolution of 1 micron in the whole range, but select the region of interest, and perform tomography imaging with a resolution of 1 micron only for the region of interest, and can perform tomography for the non-interested region. Larger-scale resolution tomography. For the selection of the region of interest, the Zoom out mode imaging can be used to provide a reference function for positioning the region of interest.

The following is an example of a region of interest and the imaging setting process when the imaging range is large: when the imaging range is large, the Zoom out mode is used for imaging, and the initial region of interest is obtained by using the imaging results of the Zoom out mode;

Then judge whether the initial region of interest satisfies the 1-micron-scale imaging conditions, if so, perform tomographic imaging with a resolution of 1-micron scale on the initial region of interest; if not, divide the initial region of interest into multiple 1-micron-scale imaging Sub-imaging areas of scale imaging conditions, tomographic imaging with a resolution of 1 micron scale is performed on multiple sub-imaging areas respectively;

Among them, the 1-micron-scale imaging conditions are: the upper limit of the data size of a single tomographic image obtained by the image spatial resolution of 1-micron-scale imaging is between 100kB-100MB;

Specifically, the tomographic imaging with a resolution of 1 μm is to apply a gradient field and perform imaging according to the imaging standard with an imaging spatial resolution of 1 μm.

It should be noted that the size of the imaging range can be flexibly set according to actual needs. The method of the present invention is generally suitable for an imaging range of 10±5cm. The boundary between the large imaging range and the small imaging range can be flexibly set according to actual needs. For example, in some cases, it may be set that the imaging range is less than or equal to 5 cm as the case where the imaging range is small, and the imaging range is larger than 5 cm as the case where the imaging range is large.

In terms of the method for realizing the imaging technology, in addition to the conventional manner, the present invention also improves the signal-to-noise ratio of imaging by adopting an acquisition sequence with a high signal-to-noise ratio. On the premise of meeting the resolution requirements, consider the scan time of the sequence. The signal enhancement sequence used in Condition C is: adding a positive 90 degree radio frequency pulse before the next negative 90 degree radio frequency pulse to shorten the TR time, reduce the attenuation of the T2 signal, and improve the signal-to-noise ratio. The timing diagram of the signal enhancement sequence of the present invention is shown in Fig. 1, where slice refers to layer thickness, phase refers to phase encoding, read is readout gradient, RF radio frequency pulse, TE echo time, and TR is repetition time. In this sequence, the TR time can be greatly shortened, the attenuation of the T2 signal can be reduced, and the signal-to-noise can be improved by adding a 90-degree RF pulse (combination: minus 90 degrees + plus 90 degrees) before the next 90-degree radio frequency (RF) pulse. ratio, which not only ensures the signal-to-noise ratio, but also improves the imaging speed.

For optically opaque living tissue or organs, none of today's existing biomedical imaging techniques can non-invasively achieve 1-micron resolution tomography at the living tissue level. The specific reasons for the above shortcomings: If you want to achieve non-invasive tomography at the level of 1 micron resolution at the living level, you must technically meet the following three requirements: (1) The key media for imaging (such as : light, X-ray, ultrasound, electromagnetic waves, etc.), which requires non-invasive, light-opaque living tissue; (2) the spatial resolution reaches 1 micron or less than 1 micron; (3) simultaneously obtains the imaging area, 1 At a resolution level of micrometers or less than 1 micrometer, all imaged individual cells correspond to information. Looking at all the current technical means, none of them can meet the technical requirements of the above three aspects at the same time. Therefore, today's existing biomedical imaging technology means cannot non-invasively achieve tomography at the level of 1 micron resolution at the level of living tissue.

The non-invasive optical opaque micron-scale living tissue magnetic resonance tomography method of the present invention is designed through the three conditions of A, B and C. It can non-invasively achieve tomography at the level of 1 micron resolution on the level of optically opaque living tissue, and can achieve non-invasive living tissue tomography with a spatial resolution of 1 micron and the ability to resolve subcellular structures. The technical problem of non-invasively realizing tomographic imaging at the level of 1 micron resolution at the living tissue level, which cannot be achieved by the existing biomedical imaging technology means, is solved.

Example 2.

Using the non-invasive optically opaque micron-scale living tissue magnetic resonance tomography method of the present invention, the optically opaque living organism, the oviparous fertilized egg, is subjected to ultra-high resolution of 1 micron or less than 1 micron, including all imaging areas. Tomographic imaging of the structure and function of single cells.

According to the above-mentioned design techniques, a high magnetic field strength, such as a 16T static magnetic field, is selected. On the basis of this static magnetic field, a strong gradient magnetic field in the three directions of X, Y, and Z is applied. The gradient field strength is in the Z direction, and the strength is For superimposed gradient magnetic fields above 10000mT/m, by narrowing the frequency selection bandwidth to 20KHz or below, the Z-direction layer selection with a thickness of 1 micron can be achieved;

The gradient field strength is in the X direction, using a superimposed gradient magnetic field with a strength of more than 20000mT/m, the frequency resolution of the receiving spectrometer can reach 852Hz (about 1KHz), and the resolution in the X direction with a resolution of 1 micron can be achieved. ;

The gradient field strength is in the Y direction, and a superimposed gradient magnetic field with a strength of more than 10000mT/m is used. To control the gradient opening time to 2.35ms and the step size to 4.7us, the phase encoding of pixels with a resolution of 1um can be realized. .

The imaging method of "imaging area co-transformation tomography" is adopted, and a high signal-to-noise ratio acquisition sequence is used to improve the imaging signal-to-noise ratio. The imaging area and imaging resolution are co-transformed, and the image data size of the tomographic imaging formed is controlled within The required range is generally within 100MB.

Through a series of innovative technical means and combinations, the present invention non-invasively realizes the structure and the Functional, tomographic techniques.

It should be noted that, the method of the present invention can non-invasively achieve high-resolution imaging at a scale of 1 micrometer on living organisms that are opaque to light, such as mice, fruit flies, and oviparous fertilized eggs.

Example 3.

It is necessary to observe the cells in the mouse brain, and perform 1-micron-scale tomography on the brain of the mouse. The head size of a mouse is roughly 3cm*3cm*3cm.

The thickness of the longitudinal tomography is 1 micron, the imaging range of the XY plane is 3cm*3cm, and imaging with a spatial resolution of 1 micron is also performed. At this time, the upper limit of the data size of a single tomographic image is in the range of 100kB-100MB.

Select a static magnetic field with a high magnetic field strength of 10.5T. On the basis of this static magnetic field, apply a strong gradient magnetic field in the three directions of X, Y, and Z. The gradient field strength is in the Z direction, and a superimposed gradient with a strength of more than 10000 mT/m is used. Magnetic field, narrow the frequency selection bandwidth to 20KHz, and achieve the Z-direction layer selection with a thickness of 1 micron.

The gradient field strength is in the X direction, using a superimposed gradient magnetic field with a strength of more than 20000mT/m, the frequency resolution of the receiving spectrometer is 1KHz, and the resolution in the X direction with a resolution of 1 micron is achieved.

The gradient field strength is in the Y direction, and a superimposed gradient magnetic field with a strength of more than 30000mT/m is used. To control the gradient opening time to 2.35ms and the step size to 4.7*3us, the phase of the pixel with a resolution of 1um can be achieved. coding.

The radio frequency electromagnetic field perpendicular to the main magnetic field is used to excite the imaging object with radio frequency electromagnetic field. Since the upper limit of the data size of a single tomographic image is in the range of 100kB-100MB, the calculation amount is small, and micron-level imaging can be realized.

In terms of the imaging technology implementation method, in addition to the conventional practice, the present invention also improves the imaging signal-to-noise ratio by adopting a high signal-to-noise ratio acquisition sequence. On the premise of meeting the resolution requirements, consider the scan time of the sequence. The signal enhancement sequence used in Condition C is: adding a positive 90 degree radio frequency pulse before the next negative 90 degree radio frequency pulse to shorten the TR time, reduce the attenuation of the T2 signal, and improve the signal-to-noise ratio. The timing diagram of the signal enhancement sequence of the present invention is shown in FIG. 1 . In this sequence, the TR time can be greatly shortened, the attenuation of the T2 signal can be reduced, and the signal-to-noise can be improved by adding a 90-degree RF pulse (combination: minus 90 degrees + plus 90 degrees) before the next 90-degree radio frequency (RF) pulse. ratio, which not only ensures the signal-to-noise ratio, but also improves the imaging speed.

The method of the present invention can perform micron-level imaging on a living object in a non-traumatic state. It can observe and analyze the cellular structure of living tissue on the basis of cell level, which provides an advanced analysis method for cell research.

Example 4.

It is necessary to observe and study the somatic cell condition of a larger object. Some positions of the object to be measured, such as the size of the hand, are smaller, and some parts of the object are larger in size, such as the chest.

The size of one of the smaller parts to be observed is approximately 2cm*2cm*1cm, and the size of one of the larger parts to be observed is approximately 20cm*20cm*20cm.

For imaging small-sized parts, the thickness of the longitudinal tomography can be controlled to 1 micron scale, the imaging range of the XY plane is 2cm*2cm, and imaging with a spatial resolution of 1 micron is also performed, which meets the upper limit of the data size of a single tomographic image. In the 100kB-100MB range.

For larger parts, the thickness of the longitudinal tomography can be controlled to 1 micron scale, and the imaging range of the XY plane is 20cm*20cm, the data size of a single tomographic image will reach 40,000MB, so the data volume of the tomographic image will be very large, and the imaging results cannot be effectively obtained. Therefore, for a larger part, through the imaging area combined tomography imaging method of the present invention, the region of interest is found as a 1-micron-scale imaging region and a gradient field is applied based on the standard of a 1-micron-scale imaging region, and the imaging spatial resolution of the region of interest is: 1 micron scale, and the upper limit of the data size of a single tomographic image is controlled between 100kB-100MB.

In the process of finding a region of interest, the Zoom out mode imaging is used to provide a reference function for positioning the region of interest. First, image the imaging range in Zoom out mode, and use the imaging results in Zoom out mode to obtain the initial region of interest;

Then judge whether the initial region of interest satisfies the 1-micron-scale imaging conditions, if so, perform tomographic imaging with a resolution of 1-micron scale on the initial region of interest; if not, divide the initial region of interest into multiple 1-micron-scale imaging In the sub-imaging area of the scale imaging condition, tomographic imaging with a resolution of 1 μm is performed on the multiple sub-imaging areas respectively.

It should be noted that two non-passing imaging ranges are used as examples for description here. For different positions of the actual imaging objects, according to the imaging region linked tomographic imaging method of the present invention, the imaging region and the spatial resolution are dynamically linked. Change, adjust the corresponding applied gradient field to achieve at least 1-micron-scale imaging of the region of interest; 1-micron-scale imaging can be selected for non-interested regions, or a higher-resolution imaging method can be used.

In terms of the imaging technology implementation method, in addition to the conventional practice, the present invention also improves the imaging signal-to-noise ratio by adopting a high signal-to-noise ratio acquisition sequence. On the premise of meeting the resolution requirements, consider the scan time of the sequence. The signal enhancement sequence used in Condition C is: adding a positive 90 degree radio frequency pulse before the next negative 90 degree radio frequency pulse to shorten the TR time, reduce the attenuation of the T2 signal, and improve the signal-to-noise ratio. The timing diagram of the signal enhancement sequence of the present invention is shown in FIG. 1 . In this sequence, the TR time can be greatly shortened, the attenuation of the T2 signal can be reduced, and the signal-to-noise can be improved by adding a 90-degree RF pulse (combination: minus 90 degrees + plus 90 degrees) before the next 90-degree radio frequency (RF) pulse. ratio, which not only ensures the signal-to-noise ratio, but also improves the imaging speed.

This embodiment can non-invasively achieve 1-micron-level resolution tomography on the level of optically opaque living tissue, and can achieve non-invasive living tissue tomography with 1-micron spatial resolution and subcellular structure resolution capability.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should The technical solutions of the present invention may be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention.

Claims (7)

1. a non-invasive optical opaque micron-level living tissue magnetic resonance tomography method, is characterized in that, realizes by controlling following three conditions: A. The main magnetic field with a uniform and single-direction ultra-high magnetic field strength is applied to the living biological tissue as the imaging object; B. On the basis of the main magnetic field, a gradient field is applied in the 1-micron-scale imaging area according to the imaging standard with an imaging spatial resolution of 1-micron scale, specifically: for the three directions of X, Y, and Z, the intensity is 10000 mT/m respectively. The superimposed gradient magnetic field of the above intensity gradient distribution performs spatial encoding on the elements with spin angular momentum, so that the spin frequencies of elements in different spatial positions are different; C. Use the radio frequency electromagnetic field perpendicular to the main magnetic field to excite the imaging object with the radio frequency electromagnetic field, and pick up the energy level conversion radio frequency signal emitted by the imaging object after the excitation is cancelled, reconstruct and decode the radio frequency signal, and obtain the tomographic imaging; In A, the magnetic field strength of the main magnetic field is not less than 9.4 Tesla; In B, the gradient field is applied according to the imaging standard with an imaging spatial resolution of 1 μm, specifically: In the Z direction, the frequency selection bandwidth is narrowed to below 20KHz, and the superimposed gradient magnetic field with the intensity of 10000mT/m to 50000mT/m is used to realize the layer selection in the Z direction with a resolution of 1 micron thickness; In the X direction, according to the relationship of formula (1), a superimposed gradient magnetic field with an intensity of 20000mT/m to 50000mT/m is used, and a receiving spectrometer with a frequency resolution of 0.8KHz to 3.0KHz is used to achieve a pixel of 1 in the X direction. micron-scale resolution; Among them, the frequency resolution of the spectrometer satisfies the formula (1): Δf=γ*(G _x *Δx)... Formula (1); In formula (1), Δf is the frequency resolution of the spectrometer, γ is the gyromagnetic ratio, _Gx is the gradient field strength of the superimposed gradient magnetic field in the X direction, and Δx is the scale that reaches the pixel resolution in the X direction; In the Y direction, according to the relationship of formula (2), a superimposed gradient magnetic field with an intensity of 10000mT/m to 50000mT/m is used to control the gradient opening time in the Y direction, and the step size is set to 4.7us to 4.7*5us to achieve resolution. The rate of phase encoding of 1-micron-scale pixels; Among them, the gradient opening time in the Y direction satisfies the formula (2):

In formula (2), G _y is the gradient field strength of the superimposed gradient magnetic field in the Y direction, Δy is the scale that reaches the pixel resolution in the Y direction, Δy is not greater than 1 μm,

Turns on time for the gradient in the Y direction. 2. The non-invasive optical opaque micron-scale living tissue magnetic resonance tomography method according to claim 1, wherein in B, in the X direction, a superimposed gradient magnetic field with an intensity of 20000 mT/m is used, and the frequency resolution is The 852Hz receiver spectrometer achieves a resolution of 1 micron pixel in the X direction. 3. The non-invasive optical opaque micron-scale living tissue magnetic resonance tomography method according to claim 1, wherein in B, in the X direction, a superimposed gradient magnetic field with an intensity of 50000 mT/m is used, and a frequency resolution of 50000 mT/m is used. The 2.5KHz receiver spectrometer achieves a resolution of 1 micron pixel in the X direction. 4. The non-invasive optical opaque micron-scale living tissue magnetic resonance tomography method according to any one of claims 1 to 3, wherein: in B, In the Y direction, a superimposed gradient magnetic field with a strength of 10000mT/m is used, the gradient opening time in the Y direction is controlled at 2.35ms, and the step size is set at 4.7us; or In the Y direction, a superimposed gradient magnetic field with an intensity of 50000 mT/m is used, the gradient opening time in the Y direction is controlled at 2.35 ms, and the step size is set at 4.7*5us. 5. The non-invasive optically opaque micron-scale living tissue magnetic resonance tomography method according to any one of claims 1 to 3, characterized in that: for the overall imaging object, an imaging area linkage tomography method is adopted, and the imaging area is connected The variable tomography method is to perform tomography by dynamic adjustment of the imaging area and the imaging resolution; When the required imaging range is large, use the Zoom out mode for imaging; on the contrary, when the required imaging range is small, use the Zoom in mode for imaging; at least the selected region of interest is used as the 1-micron-scale imaging area and the 1-micron-scale imaging area is used for imaging. The gradient field is applied as standard, the imaging spatial resolution of the region of interest is 1 micron scale, and the upper limit of the data size of a single tomographic image is controlled between 100kB-100MB. 6. The non-invasive optical opaque micron-scale living tissue magnetic resonance tomography method according to claim 5, wherein: When the imaging range is large, the Zoom out mode is used for imaging, and the initial region of interest is obtained by using the imaging results of the Zoom out mode; Then judge whether the initial region of interest satisfies the 1-micron-scale imaging conditions, if so, perform tomographic imaging with a resolution of 1-micron scale on the initial region of interest; if not, divide the initial region of interest into multiple 1-micron-scale imaging Sub-imaging areas of scale imaging conditions, tomographic imaging with a resolution of 1 micron scale is performed on multiple sub-imaging areas respectively; 1-micron-scale imaging conditions are: the upper limit of the data size of a single tomographic image obtained by imaging at 1-micron scale is between 100kB-100MB; Specifically, the tomographic imaging with a resolution of 1 μm is to apply a gradient field and perform imaging according to the imaging standard with an imaging spatial resolution of 1 μm. 7 . The non-invasive optical opaque micron-scale living tissue magnetic resonance tomography method according to claim 5 , wherein: 1 micron scale refers to a resolution range of 0.1 μm to 2 μm. 8 .

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