Multimodal Imaging System and Method Based on Low-Coherence Optical Interference Field

Abstract

The application discloses a multi-modal imaging system and method based on an optical low-coherence interference field. The application can realize efficient interference signal collection and imaging under various OCT imaging modes in one set of system and imaging mechanism, and can realize mapping of imaging coordinate systems of various modes through linear transformation by combining the OCT axial imaging characteristics and the scanning setting under the same galvanometer mirror, so that the fusion display of multi-dimensional information in tissues can be completed without complex offline registration. The application can provide wide-area positioning imaging in a large depth range, structure imaging with high resolution and high signal-to-noise ratio, blood flow velocity detection and angiography with a large dynamic range, fast elastic imaging, and can also provide a real-time structure imaging mode with a large lateral field of view, so that a user can observe and operate according to the above information in a dynamic scene. The application has great significance for biomedical application scenes with multi-tissue information requirements.

Description

Technical Field

[0001] This invention belongs to the field of biomedical optical imaging technology, and in particular to a multimodal imaging system and method based on low-coherence optical interference fields. Background Technology

[0002] Utilizing multimodal fusion imaging to acquire multidimensional information about living organisms is a research hotspot in the field of imaging. Current multimodal imaging techniques generally involve first obtaining tomographic structures using CT, then acquiring functional information using PET / SPECT, followed by offline registration to form a 3D multimodal fusion image, and finally introducing in vivo molecular imaging to locate lesions on the offline fusion image. This method requires multiple radiation sources and different imaging mechanisms, cannot image simultaneously, and exhibits significant differences in resolution, depth, and contrast among modalities, necessitating complex offline data processing. This results in a localization accuracy of only tens of micrometers in tissue layers, severely limiting its application in life sciences. Another approach is optical multimodal imaging using methods such as confocal imaging, multiphoton imaging, light sheet imaging, and super-resolution. This method requires labeling samples with fluorescent proteins / dyes, thus exhibiting biotoxicity. Coupled with limited imaging depth, it is primarily used for ex vivo imaging or animal studies, unsuitable for humans. Therefore, it can be seen that existing multimodal imaging is trapped in the fundamental constraints of piling up multiple imaging mechanisms and relying on offline image registration and image processing.

[0003] Optical coherence tomography (OCT) is a non-invasive, high-resolution tomographic imaging technique that utilizes the principle of low-coherence interference of light to obtain high-resolution tomographic images of living tissues (at the micrometer scale). Besides obtaining the basic imaging mode of tissue structure by detecting the intensity of light returning from different depths of the tissue, it can also perform functional imaging of tissues by fully utilizing the amplitude and phase signals of the low-coherence interference signal: non-invasive blood flow imaging can be achieved by detecting changes in the interference signal at the same location, including OCT angiography (OCTA) and blood flow velocity detection (Doppler OCT, D-OCT); by applying a known external force and combining it with tissue deformation extracted from OCT images, OCT elastography (OCE) can obtain biomechanical parameters such as Young's modulus of the tissue. Furthermore, OCT can acquire multi-dimensional information within the tissue under the same imaging mechanism without the need for additional offline registration, making it an ideal multimodal imaging technique.

[0004] However, different OCT imaging modes emphasize different physical parameters, making it difficult to efficiently implement multiple functions in the same system. For example, deep and wide-area localization imaging relies on high duty cycle and low-speed frequency sweep; high-resolution and high signal-to-noise ratio fine structure imaging relies on high-bandwidth light source and low-speed frequency sweep; OCTA, blood flow detection, OCE and other functions require repeated scanning of the same location, which places certain requirements on imaging speed. Among them, blood flow detection has a limited dynamic range at the same frequency sweep speed, which means it is difficult to achieve high sensitivity (low flow velocity detection) and high flow velocity detection at the same time. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art by providing a multimodal imaging technology based on optical low-coherence interference signals with multiple sweep rates. The low sweep rate interference signal is used for wide-area imaging and positioning, the medium speed is used for high-quality structural imaging and high-sensitivity blood flow imaging, the high speed is used for high-velocity blood flow imaging and elastic imaging, and the ultra-high speed is used for real-time three-dimensional structural imaging and functional imaging.

[0006] The technical solution to achieve the purpose of this invention is: a multimodal imaging system based on optical low-coherence interference field, the system comprising a multi-frequency sweep laser module, an optical / electrical selection module, a fiber optic interference module, a reference arm, a sample arm, a photodetector, a data acquisition unit, and a host computer;

[0007] The multi-scan laser module includes multiple lasers with different scan rates for emitting lasers or triggering signals; wherein, the scan frequency can divide the system into low-speed imaging mode, medium-speed imaging mode and high-speed imaging mode.

[0008] The optical / electric selection module is used to select a laser to emit a laser to the fiber optic interferometer module under the control of the host computer, and at the same time, select a laser to emit a trigger signal to the signal acquisition trigger port of the data acquisition unit under the control of the host computer, so as to realize the synchronization of low coherence interference signal acquisition and sample arm scanning.

[0009] The fiber optic interferometer module is used to split the light output from the laser into two beams, which are then transmitted to the reference arm and the sample arm, respectively.

[0010] The light returned from the reference arm and the sample arm converges and interferes in the fiber optic interferometry module.

[0011] The photodetector is used to convert the interference signal into an analog electrical signal;

[0012] The data acquisition unit is used to convert the analog electrical signal into a digital signal and transmit it to the host computer.

[0013] The host computer is also used for data processing and imaging.

[0014] Furthermore, the duty cycle of the effective spectrum of all lasers in the multi-frequency sweep laser module is greater than 50%.

[0015] Furthermore, the optical / electric selection module includes an optical switch, a controller, and an electrical switch. Under the control of the host computer, the controller and the optical switch select the light emitted by one laser in the multi-frequency sweep laser module to be transmitted to the fiber optic interferometer module. Under the control of the host computer, the controller and the electrical switch select the trigger signal emitted by one laser in the multi-frequency sweep laser module to be transmitted to the signal acquisition trigger port of the data acquisition unit.

[0016] Furthermore, the reference arm includes a first collimator, a reflector, and a high-precision displacement stage; the first collimator converts the light output from the laser into spatial light, which then reaches the reflector, which is mounted on the high-precision displacement stage; the high-precision displacement stage can adjust the optical path of the reference arm under the control of the host computer.

[0017] Furthermore, the sample arm includes a second collimator, a two-dimensional galvanometer galvanometer mirror, and an objective lens. The second collimator converts the light output from the laser into spatial light, which is then laterally deflected by the two-dimensional galvanometer galvanometer mirror and finally focused onto the sample by the objective lens.

[0018] On the other hand, a multimodal imaging method based on a low-coherence optical interference field is provided based on the aforementioned multimodal imaging system, the method comprising:

[0019] During the following steps, the galvanometer mirrors of the two-dimensional galvanometer should be set with the same transverse scanning midpoint;

[0020] Step 1: The laser is selected via the optical / electrical selection module and the host computer to put the system into a low-speed imaging mode; simultaneously, the data acquisition unit is set to a high sampling rate mode, and the wavenumber of the high-frequency interference signal is linearized by combining a time-domain interpolation algorithm. The reflection signals at different axial positions are reconstructed by fast Fourier transform to achieve large-depth wide-area imaging of the sample area; based on the large-depth wide-area imaging results, the optical path of the reference arm is adjusted by a high-precision displacement stage to move the region of interest to a position close to zero frequency, where the zero-frequency position is the position where the optical paths of the reference arm and the sample arm are equal.

[0021] Step 2: The laser is selected via the optical / electrical selection module and the host computer to put the system into a medium-speed imaging mode. Each frequency sweep cycle, the data acquisition unit covers all effective wavelengths of the laser to achieve optimal axial resolution tomographic imaging I. Using a two-dimensional galvanometer galvanometer, the interference amplitude signal at the same lateral position of the sample is acquired multiple times to calculate the flow velocity-related parameter D1. Then, the actual blood flow velocity distribution map v is obtained through flow velocity calibration. 低流速 (D1);

[0022] Step 3: The laser is selected via the optical / electrical selection module and the host computer to put the system into high-speed imaging mode. Multiple acquisitions of interference amplitude signals at the same lateral position of the sample are performed using a two-dimensional galvanometer galvanometer mirror. The flow velocity-related parameter D2 is calculated, and then the actual blood flow velocity distribution map v is obtained through flow velocity calibration. 高流速 (D2), where the parameters set by scanning with a two-dimensional galvanometer galvanometer must be consistent with the scanning parameters set in step 2; at the same time, the OCT elastic imaging method is used to obtain the tomographic map E of the Young's modulus distribution of the sample;

[0023] Step 4: Register and fuse the image coordinate systems of the various imaging modalities mentioned above;

[0024] Step 5: Achieve multimodal imaging display by quickly switching or overlaying the display.

[0025] Furthermore, in step 2, the velocity-related parameter D1 is calculated using the following formula:

[0026]

[0027] In the formula, A t,H A t+1,H These represent the signal strengths collected at position H at time t and time t+1, respectively, where T is the number of repeated sampling times, and H is the signal strength at position H. noise M represents the location of the system noise region where there is no signal, and M is the total number of points occupied by the system noise region. To determine the position H at time t noise The acquired signal strength; where the first term is the decorrelation value of the current position in the logarithmic domain, the second term is the signal strength term at the current position, and the third term is the system noise term, which is theoretically a fixed value.

[0028] Furthermore, in step 3, the flow velocity correlation parameter D2 is calculated using a traditional decorrelation algorithm:

[0029]

[0030] In the formula, A t,H A t+1,H The positions H are at time t and t+1, respectively, where T is the number of repeated sampling times.

[0031] Furthermore, step 4, which involves registering and fusing the image coordinate systems of the various imaging modes, specifically includes:

[0032] (1) In the longitudinal scanning direction, record the tomographic structure imaging I and the actual blood flow velocity distribution map v. 低流速 (D1), Actual blood flow velocity distribution map v 高流速(D2) The maximum window depths of the fault map E of Young's modulus distribution are Z1, Z2, Z3, and Z4, respectively, and the total number of pixels are n1, n2, n3, and n4, respectively.

[0033] The value at the vertical numerical position z is F q (z), where z = 0 represents the zero-frequency position, and the longitudinally registered image F of each imaging modality is obtained according to the following formula. q ′(z):

[0034]

[0035] Where a and z satisfy the following conditions:

[0036]

[0037] (2) In the horizontal scanning direction, the two orthogonal horizontal scanning positions x and y are registered in the following manner;

[0038] For the lateral scan position x, record the tomographic structure imaging I and the actual blood flow velocity distribution map v. 低流速 (D1), Actual blood flow velocity distribution map v 高流速 (D2) The transverse scanning ranges of the fault map E of Young's modulus distribution are X1, X2, X3, and X4, respectively, and the total number of pixels are m1, m2, m3, and m4, respectively.

[0039] The value at the horizontal numerical position x is F. q (x), where x = 0 represents the midpoint of the horizontal scan, and the value of F of the registered horizontal digital position x is calculated according to the following formula. q ′(x):

[0040]

[0041] Where b and x satisfy the following conditions:

[0042]

[0043] Similarly, the value F of the horizontal digital position y after registration is obtained. q ′(y);

[0044] Combined with F q ′(z), that is, the image F obtained after registration and fusion of various imaging modes. q ′(x,y,z).

[0045] Furthermore, the method also includes:

[0046] For dynamic imaging scenarios, the system is put into ultra-high-speed mode by selecting the laser through the optical / electric selection module and the host computer, so as to obtain a large lateral field of view and real-time three-dimensional OCT structural imaging, and use the multimodal imaging information in step 5 as an aid; the scanning frequency of the ultra-high-speed mode is much greater than the scanning frequency corresponding to the high-speed mode.

[0047] Compared with the prior art, the significant advantages of this invention are:

[0048] (1) This invention enables efficient interferometric signal acquisition and imaging under multiple OCT imaging modalities within a single system and imaging mechanism. Simultaneously, by combining OCT axial imaging characteristics with the same galvanometer galvanometer, linear transformation is used to map the imaging coordinate systems of each modality, achieving fusion display of multi-dimensional information within tissues without complex offline registration. This invention provides wide-area localization imaging with a depth range, high-resolution, high signal-to-noise ratio structural imaging, large dynamic range blood flow velocity detection and angiography, and rapid elastography. It also provides a real-time structural imaging mode with a large lateral field of view, allowing users to observe and operate within dynamic scenes by comparing the above information.

[0049] (2) Non-invasive imaging: All imaging modes do not require interventional methods such as injection of contrast agents, and multimodal registration does not require the placement of physical markers.

[0050] (3) Large dynamic blood flow imaging: By combining the medium speed mode with the signal-to-noise ratio adaptive logarithmic domain blood flow algorithm and the high speed mode with the conventional blood flow algorithm, the problem of the contradiction between the blood flow velocity detection sensitivity and the maximum measurable velocity under the same algorithm, sweep rate and scan setting parameters is solved.

[0051] (4) Simple and efficient implementation: Different modes share the same imaging optical path, and the acquisition of interference signals required for different modal imaging can be achieved through optical / electrical switches.

[0052] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of a multimodal imaging system based on a low-coherence optical interference field in one embodiment.

[0054] Figure 2 This is a flowchart of a multimodal imaging method based on low-coherence optical interference fields in one embodiment.

[0055] Figure 3 This is a comparison image of OCT mouse brain angiography results from one embodiment, in which... Figure 3 Image (a) in the image is an angiography image generated by the traditional decorrelation method. Figure 3 (b) is the angiography image formed by the method proposed in step 2 of this invention.

[0056] Figure 4 This is a comparison image of 3DOCT imaging results of mouse brains in one embodiment, where... Figure 4 (a) in the image represents OCT high-resolution structural imaging of blood vessels. Figure 4 (b) in the image is an OCT angiography image. Figure 4 (c) and (d) in the figure are the fused images from different perspectives after coordinate system registration. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0058] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0059] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0060] In one embodiment, combined Figure 1 A multimodal imaging system based on low-coherence optical interference field is provided. The system includes a multi-frequency sweep laser module 1, an optical / electrical selection module 2, a fiber optic interference module 3, a reference arm 4, a sample arm 5, a photodetector 6, a data acquisition unit 7, and a host computer 8.

[0061] The multi-scanning laser module 1 includes multiple lasers with different scanning rates for emitting lasers or triggering signals; wherein, the scanning frequency can divide the system into low-speed imaging mode, medium-speed imaging mode and high-speed imaging mode.

[0062] The optical / electric selection module 2 is used to select a laser to emit a laser to the fiber optic interference module 3 under the control of the host computer 8, and at the same time, select a laser to emit a trigger signal to the signal acquisition trigger port of the data acquisition unit 7 under the control of the host computer 8, so as to realize the synchronization of low coherence interference signal acquisition and sample arm 5 scanning.

[0063] The fiber optic interference module 3 is used to split the light output from the laser into two beams and transmit them to the reference arm 4 and the sample arm 5 respectively.

[0064] The light returned from the reference arm 4 and the sample arm 5 converges and interferes in the fiber optic interferometry module 3.

[0065] The photodetector 6 is used to convert the interference signal into an analog electrical signal;

[0066] The data acquisition unit 7 is used to convert the analog electrical signal into a digital signal and transmit it to the host computer 8;

[0067] The host computer 8 is also used for data processing and imaging.

[0068] Preferably, the data acquisition unit is a data acquisition card.

[0069] Preferably, in some embodiments, the duty cycle of the effective spectrum of all lasers in the multi-scan laser module 1 is greater than 50%.

[0070] Preferably, in some embodiments, the optical / electrical selection module 2 includes an optical switch 21, a controller 22, and an electrical switch 23. Under the control of the host computer 8, the controller 22 and the optical switch 21 select the light emitted by one laser in the multi-frequency sweep laser module 1 to be transmitted to the fiber optic interferometer module 3. Under the control of the host computer 8, the controller 22 and the electrical switch 23 select the trigger signal emitted by one laser in the multi-frequency sweep laser module 1 to be transmitted to the signal acquisition trigger port of the data acquisition unit 7.

[0071] Preferably, in some embodiments, the reference arm 4 includes a first collimator 41, a reflector 42, and a high-precision displacement stage 43; the first collimator 41 converts the light output from the laser into spatial light, which then reaches the reflector 42, which is mounted on the high-precision displacement stage 43; the high-precision displacement stage 43 can adjust the optical path of the reference arm 4 under the control of the host computer 8.

[0072] Preferably, in some embodiments, the sample arm 5 includes a second collimator 51, a two-dimensional galvanometer galvanometer 52, and an objective lens 53. The second collimator 51 converts the light output from the laser into spatial light, which is then laterally deflected by the two-dimensional galvanometer galvanometer 52 and finally focused onto the sample 54 by the objective lens 53.

[0073] In one embodiment, combined Figure 2 A multimodal imaging method based on low-coherence optical interference fields is provided, the method comprising:

[0074] During the following steps, the same transverse scanning midpoint should be set for the two-dimensional galvanometer galvanometer mirror 52;

[0075] Step 1: The laser is selected via the optical / electrical selection module 2 and the host computer 8 to put the system into a low-speed imaging mode; simultaneously, the data acquisition unit 7 is set to a high sampling rate mode (internal clock of the acquisition card, sampling rate ≥ 1 GSPS), and the wavenumber linearization of the high-frequency interference signal is achieved by combining the time-domain interpolation algorithm. The reflection signals at different axial positions are reconstructed by fast Fourier transform to achieve large-depth wide-area imaging of the sample area; based on the large-depth wide-area imaging results, the optical path of the reference arm 4 is adjusted by the high-precision displacement stage 43 to move the region of interest to a position close to zero frequency, where the zero frequency position is the position where the optical paths of the reference arm 4 and the sample arm 5 are equal;

[0076] Here, the low-speed imaging mode has a sweep rate ≤100kHz;

[0077] Step 2: The laser is selected via the optical / electrical selection module 2 and the host computer 8 to put the system into medium-speed imaging mode. Each frequency sweep cycle, the data acquisition unit 7 covers all effective wavelengths of the laser to achieve optimal axial resolution tomographic imaging I. The interference amplitude signal at the same lateral position of the sample is acquired multiple times using the two-dimensional galvanometer galvanometer 52, and the flow velocity-related parameter D1 is calculated. Then, the actual blood flow velocity distribution map v is obtained through flow velocity calibration. 低流速 (D1); (where D represents the angiography image)

[0078] Here, the medium-speed imaging mode has a sweep rate of 200kHz;

[0079] Step 3: The laser is selected via the optical / electrical selection module 2 and the host computer 8 to put the system into high-speed imaging mode. The interference amplitude signal at the same lateral position of the sample is acquired multiple times using the two-dimensional galvanometer galvanometer mirror 52. The flow velocity-related parameter D2 is calculated, and then the actual blood flow velocity distribution map v is obtained through flow velocity calibration. 高流速 (D2), where the scanning parameters set by the two-dimensional galvanometer 52 must be consistent with the scanning parameters set in step 2; at the same time, the OCT elastic imaging method is used to obtain the tomographic map E of the Young's modulus distribution of the sample;

[0080] Here, the high-speed imaging mode has a sweep rate of 400kHz;

[0081] Step 4: Register and fuse the image coordinate systems of the various imaging modes (because the laser, acquisition settings and scanning settings are inconsistent under various imaging modes, different imaging spaces will result in different imaging spaces, so it is necessary to register the image coordinate systems of multiple modes).

[0082] Step 5: Achieve multimodal imaging display by quickly switching or overlaying the display.

[0083] Furthermore, in one embodiment, the flow velocity-related parameter D1 is calculated in step 2 using the following formula:

[0084]

[0085] In the formula, A t,H A t+1,H These represent the signal strengths collected at position H at time t and time t+1, respectively, where T is the number of repeated sampling times, and H is the signal strength at position H. noise M represents the location of the system noise region where there is no signal, and M is the total number of points occupied by the system noise region. To determine the position H at time t noise The acquired signal strength; where the first term is the decorrelation value of the current position in the logarithmic domain, the second term is the signal strength term at the current position, and the third term is the system noise term, which is theoretically a fixed value.

[0086] Here, the medium-speed mode combined with the above formula can obtain a highly sensitive blood flow detection capability, while not being affected by the signal-to-noise ratio of the current location.

[0087] For example, Figure 3 These are the results of OCT mouse brain angiography comparisons, among which... Figure 3 (a) in the image is an angiography image generated by the traditional decorrelation method; Figure 3 (b) is an angiography image formed by the method proposed in step 2 of this invention. Compared with the traditional method, more microvessels can be seen (especially the vessels corresponding to the red triangles), that is, the blood flow sensitivity is higher.

[0088] Furthermore, in one embodiment, step 3 uses a conventional decorrelation algorithm to calculate the flow velocity correlation parameter D2:

[0089]

[0090] In the formula, A t,H A t+1,H The positions H are at time t and t+1, respectively, where T is the number of repeated sampling times.

[0091] Furthermore, in one embodiment, step 4, which involves registering and fusing the image coordinate systems of the various imaging modes, specifically includes:

[0092] (1) In the longitudinal scanning direction, record the tomographic structure imaging I and the actual blood flow velocity distribution map v. 低流速 (D1), Actual blood flow velocity distribution map v 高流速 (D2) The maximum window depths of the fault map E of Young's modulus distribution are Z1, Z2, Z3, and Z4, respectively, and the total number of pixels are n1, n2, n3, and n4, respectively.

[0093] The value at the vertical numerical position z is F q (z), where z = 0 represents the zero-frequency position, and the longitudinally registered image F of each imaging modality is obtained according to the following formula. q ′(z):

[0094]

[0095] Where a and z satisfy the following conditions:

[0096]

[0097] (2) In the horizontal scanning direction, the two orthogonal horizontal scanning positions x and y are registered in the following manner;

[0098] For the lateral scan position x, record the tomographic structure imaging I and the actual blood flow velocity distribution map v. 低流速 (D1), Actual blood flow velocity distribution map v 高流速 (D2) The transverse scanning ranges of the fault map E of Young's modulus distribution are X1, X2, X3, and X4, respectively, and the total number of pixels are m1, m2, m3, and m4, respectively.

[0099] The value at the horizontal numerical position x is F. q (x), where x = 0 represents the midpoint of the horizontal scan, and the value of F of the registered horizontal digital position x is calculated according to the following formula. q ′(x):

[0100]

[0101] Where b and x satisfy the following conditions:

[0102]

[0103] Similarly, the value F of the horizontal digital position y after registration is obtained. q ′(y);

[0104] Combined with F q ′(z), that is, the image F obtained after registration and fusion of various imaging modes.q ′(x,y,z).

[0105] Here, the maximum window depth and horizontal scanning range are obtained through traditional OCT calibration methods, the total number of vertical pixels is determined by the acquisition mode setting of the acquisition card 7, and the total number of horizontal pixels is determined by the scanning settings of the two-dimensional galvanometer galvanometer 52 and the acquisition mode of the acquisition card 7.

[0106] For example, Figure 4 These are the results of 3DOCT imaging comparisons of mouse brains, among which... Figure 4 (a) in the image represents OCT high-resolution structural imaging of blood vessels. Figure 4 (b) in the image is an OCT angiography image. Figure 4 (c) and (d) are the fused images from different perspectives after coordinate system registration (the transparency of the high-resolution structure diagram has been adjusted for ease of display).

[0107] Furthermore, in one embodiment, the method further includes:

[0108] For dynamic imaging scenarios, the laser is selected by the optical / electric selection module 2 and the host computer 8 to put the system into ultra-high speed mode, so as to obtain a large lateral field of view and real-time three-dimensional OCT structural imaging, and use the multimodal imaging information in step 5 as an aid; the scanning frequency of the ultra-high speed mode is much greater than the scanning frequency corresponding to the high speed mode.

[0109] The dynamic imaging requirements include, but are not limited to, intraoperative navigation imaging.

[0110] In summary, this invention is of great significance for biomedical applications with multi-organizational information needs.

[0111] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention without departing from its spirit and scope should be included within the protection scope of the present invention.

Claims

1. A method of multi-modal imaging based on optical low-coherence interferometry, characterized in that, The multi-modal imaging method is realized based on a multi-modal imaging system, and the multi-modal imaging system comprises a multi-swept frequency laser module (1), an optical / electrical selection module (2), a fiber-optic interference module (3), a reference arm (4), a sample arm (5), a photoelectric detector (6), a data acquisition unit (7) and an upper computer (8); The multi-swept frequency laser module (1) comprises a plurality of lasers with different swept frequency rates, and is used for emitting laser or trigger signals; wherein the swept frequency rate can divide the system into a low-speed imaging mode, a medium-speed imaging mode and a high-speed imaging mode; The optical / electrical selection module (2) is used for selecting a certain laser to emit laser to the fiber-optic interference module (3) under the control of the upper computer (8), and simultaneously selecting a certain laser to emit a trigger signal to a signal acquisition trigger port of the data acquisition unit (7) under the control of the upper computer (8), so as to realize synchronization of low-coherence interference signal acquisition and scanning of the sample arm (5); The fiber-optic interference module (3) is used for dividing the light output by the laser into two beams and transmitting the two beams to the reference arm (4) and the sample arm (5) respectively; The light returned by the reference arm (4) and the sample arm (5) is combined in the fiber-optic interference module (3) and interferes; The photoelectric detector (6) is used for converting the interference signal into an analog electrical signal; The data acquisition unit (7) is used for converting the analog electrical signal into a digital signal and transmitting the digital signal to the upper computer (8); The upper computer (8) is also used for data processing and imaging; The duty cycle of the effective spectrum output by all the lasers in the multi-swept frequency laser module (1) is greater than 50%; The optical / electrical selection module (2) comprises an optical switch (21), a controller (22) and an electrical switch (23); under the control of the upper computer (8), the controller (22) and the optical switch (21) are used to select the light emitted by one of the lasers in the multi-swept frequency laser module (1) to be transmitted to the fiber-optic interference module (3); under the control of the upper computer (8), the controller (22) and the electrical switch (23) are used to select the trigger signal emitted by one of the lasers in the multi-swept frequency laser module (1) to be transmitted to the signal acquisition trigger port of the data acquisition unit (7); The reference arm (4) comprises a first collimator (41), a mirror (42) and a high-precision displacement table (43); the first collimator (41) converts the light output by the laser into spatial light, and then the spatial light reaches the mirror (42), which is installed on the high-precision displacement table (43); the high-precision displacement table (43) can adjust the optical path of the reference arm (4) under the control of the upper computer (8); The sample arm (5) comprises a second collimator (51), a two-dimensional galvanometer mirror (52) and an objective lens (53); the second collimator (51) converts the light output by the laser into spatial light, and then the spatial light is deflected laterally by the two-dimensional galvanometer mirror (52) and finally focused on a sample (54) through the objective lens (53); During the following steps, the two-dimensional galvanometer mirror (52) should be set with the same lateral scanning midpoint; The multi-modal imaging method specifically comprises: Step 1, through the light / electricity selection module (2) and the upper computer (8), select the laser to make the system in a low-speed imaging mode; at the same time, set the data acquisition unit (7) in a high sampling rate mode, combine a time domain interpolation algorithm to realize wave number linearization of a high-frequency interference signal, and through fast Fourier transform reconstruction of reflection signals at different axial positions, realize large-depth wide-area imaging of a sample region; based on the large-depth wide-area imaging result, through the high-precision displacement table (43), adjust the optical path of the reference arm (4), and move the region of interest to a position close to a zero frequency position, the zero frequency position being a position with equal optical paths of the reference arm (4) and the sample arm (5); Step 2, select the laser by the light / electricity selection module (2) and the host computer (8) to make the system in the medium-speed imaging mode, the data acquisition unit (7) covers all effective wave bands of the laser in each sweep cycle to achieve the tomographic structure imaging I with the optimal axial resolution; through the two-dimensional galvanometer mirror (52), the interference amplitude signals of the same lateral position of the sample are collected multiple times, the flow rate related parameters D1 are calculated, and then the actual blood flow velocity distribution map v is obtained through the flow rate calibration 低流速 (D1); Step 3, select the laser through the light / electricity selection module (2) and the host computer (8) to make the system in high-speed imaging mode, collect the interference amplitude signals of the same lateral position of the sample multiple times through the two-dimensional galvanometer mirror (52), calculate the flow rate related parameter D2, and then obtain the actual blood flow rate distribution map v through the flow rate calibration 高流速 (D2), wherein the scanning setting parameters through the two-dimensional galvanometer mirror (52) need to be consistent with the scanning parameter setting in step 2; at the same time, the OCT elastic imaging method is adopted to obtain the tomogram E of the Young's modulus distribution of the sample; Step 4, register and fuse image coordinate systems of various imaging modes; Step 5, realize multi-modal imaging display through fast switching or superimposed display.

2. The method for multi-modal imaging based on optical low-coherence interferometric field according to claim 1, characterized in that, In step 2, a flow rate related parameter D1 is calculated by the following formula: In the formula, A t,H , A t+1,H are signal strengths collected at time t and time t+1 respectively for position H, T is the number of repeated collection times, H noise is the position of the system noise region without signal, M is the total number of points occupied by the system noise region, is the signal strength collected at time t for position H noise ; wherein the first term is the strength decorrelation value of the current position in the logarithmic domain, the second term is the signal strength term of the current position, and the third term is the system noise term.

3. The method for multi-modal imaging based on optical low-coherence interferometric field according to claim 1, characterized in that, In step 3, a conventional decorrelation algorithm is used to calculate a flow rate related parameter D2: In the formula, A t,H , A t+1,H are respectively the positions at time t, time t+1, and T is the number of repeated acquisition times.

4. The method for multi-modal imaging based on optical low-coherence interferometric field according to claim 1, characterized in that, In step 4, the image coordinate systems of various imaging modes are registered and fused, specifically comprising: (1) In the longitudinal scanning direction, the tomographic structure is imaged I, the actual blood flow velocity distribution map v 低流速 (D1), the actual blood flow velocity distribution map v 高流速 (D2), the maximum window depth of the tomographic map E of the Young's modulus distribution is Z1, Z2, Z3, Z4, respectively, and the total number of pixels is n1, n2, n3, n4, respectively. The value of the longitudinal digital position z is F q (z), where z = 0 represents the zero frequency position, the images F q ′(z) of each imaging modality after longitudinal registration are computed according to the following formula Wherein, a and z satisfy the following conditions: (2) in the lateral scanning direction, two orthogonal lateral scanning positions x and y are registered in the following manner respectively; For the transverse scanning position x, the tomographic structure imaging I, the actual blood flow velocity distribution v 低流速 (D1), the actual blood flow velocity distribution v 高流速 (D2), the transverse scanning range of the tomographic image E of the Young's modulus distribution is X1, X2, X3, X4, and the total number of pixels is m1, m2, m3, m4, respectively. The value of the registered lateral digital position x is F q (x), where x = 0 represents the midpoint of the lateral scan, the value of the registered lateral digital position x is calculated as F q ′(x): Wherein, b and x satisfy the following conditions: Similarly, the value F of the registered transverse digital position y is obtained q '(y); F q ′(z), i.e. the image F q ′(x,y,z) is obtained.

5. The method for multi-modal imaging based on optical low-coherence interferometric field according to claim 1, characterized in that, The method further comprises: For a dynamic imaging requirement scene, through the light / electricity selection module (2) and the upper computer (8), select the laser to make the system in a super-high-speed mode, acquire a large lateral field of view, real-time three-dimensional OCT structure imaging, and take the multi-modal imaging information in step 5 as auxiliary; the scanning frequency of the super-high-speed mode is much larger than the scanning frequency corresponding to the high-speed mode.

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