CN112957037A - DCS-NIRS-based multi-modal brain function measuring method and device - Google Patents
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Abstract
The invention discloses a DCS-NIRS based multi-mode brain function measuring method and device. The device comprises a long coherent near-infrared laser light source, a plurality of multimode optical fibers and a single-mode optical fiber, wherein the multimode optical fibers transmit near-infrared light with a plurality of wavelengths, the multimode optical fibers passing through an optical switch and the multimode optical fibers used for cerebral blood flow measurement are nested into a two-in-one optical fiber through an optical fiber lantern ring, the optical switch is switched and then sequentially irradiated to the surface of a brain, and meanwhile, the optical fibers used for cerebral blood flow continuously irradiate to the surface of the brain. The single-mode optical fiber receives the photons diffused by the surface of the brain due to the light passing through the brain tissue, converts the photons into electric signals by using the single-photon counter, and sends the electric signals to the personal computer and the related arithmetic unit. Based on the counting of electric signals and the light intensity autocorrelation operation, the brain blood oxygen is calculated by utilizing the light intensity attenuation of two different wavelengths, the light intensity autocorrelation function is used for fitting the brain blood flow, and meanwhile, the multi-modal brain function detection and imaging are realized. The invention is non-invasive, non-radiative, highly efficient, and has low cost and high portability.
Description
Technical Field
The invention relates to the field of brain imaging, in particular to a method and a device for measuring brain functions of multi-mode brain blood oxygen, brain blood oxygen and the like.
Background
The characteristics of cerebral blood flow, blood oxygen, and the respective functional connectivity are important for the diagnosis and assessment of cerebrovascular or cellular disorders. Imaging techniques have been developed to measure tissue hemodynamics, including magnetic resonance imaging, positron emission tomography, single photon emission computed tomography, and the like, but have many limitations, such as large size, high cost, poor flexibility, presence of ionizing radiation, and the like. Near infrared spectroscopy (NIRS) is a simple, fast, portable, low cost non-invasive measurement method for biological blood oxygen. Conventional NIRS measures the light absorption of chromophores (mainly oxyhemoglobin, deoxyhemoglobin) using low absorption spectra (water, fat, etc.) and strong penetration of the organism in the near infrared band (650-1050nm) for blood oxygenation measurements. Diffuse Correlation Spectroscopy (DCS) is an emerging dynamic near-infrared technique for measuring blood flow in deep microvasculature. The DCS technique uses long-coherence near-infrared light to measure the light intensity perturbation caused by biological tissue scatterers (mainly red blood cells in biological tissue) to further extract blood flow indices. At present, a DCS technology is combined with an NIRS technology to form a mixing instrument, so that blood oxygen and blood flow are measured on the same instrument, but the mixing instrument measures the blood oxygen and the blood flow in a time-sharing manner, and is large in size, high in cost and long in time consumption.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, realize the combination of DCS technology and NIRS technology and multi-mode brain function measurement, and provide a multi-mode brain function measurement method and device based on DCS-NIRS.
The purpose of the invention is realized by the following technical scheme:
a DCS-NIRS based multi-modal brain function measuring device, comprising: the device comprises a light source A, a light source B, a light source C, an optical switch, an optical fiber lantern ring A, a measuring probe, an optical fiber lantern ring B, an optical fiber lantern ring C, an optical fiber lantern ring D, an optical fiber lantern ring E, a single photon calculator, a correlation calculator, a personal computer, a multi-mode light source optical fiber and a single-mode detection optical fiber;
the light source A, the light source B and the light source C are laser light sources of long coherent near infrared with different wavelengths, the light source B and the light source C are coupled with multimode light source optical fibers and then connected with an optical switch, and the light source C and the optical switch are connected with a measuring probe through a two-in-one optical fiber consisting of an optical fiber lantern ring A and irradiate the surface of a brain;
the optical switch is used for switching the light source B and the light source C and switching different light source wavelengths;
the optical fiber lantern ring is used for realizing nesting of a multi-mode light source optical fiber and a single-mode detection optical fiber to form a two-in-one optical fiber and enable the measuring probe to be approximately incident or emergent at the same point, and the incident point or the emergent point is ensured to belong to the same brain functional unit; the optical fiber lantern ring A is used for nesting the end of an optical switch optical fiber used for measuring the cerebral blood oxygen with a light source A used for measuring the cerebral blood flow to form a two-in-one multi-mode light source optical fiber, the optical fiber lantern ring B, the optical fiber lantern ring C, the optical fiber lantern ring D and the optical fiber lantern ring E are respectively used for nesting a single-mode detection optical fiber used for detecting photons for calculating the cerebral blood oxygen and a single-mode optical fiber used for detecting photons for calculating the cerebral blood flow to form a corresponding two-in-one single-mode detection optical fiber, and the plurality of single-mode optical fibers;
the measuring probe is fixed on the surface of the brain and used for arranging and fixing the multimode light source optical fiber and the single-mode detection optical fiber; the multiple measuring probes realize the measurement of different brain areas;
the single photon counter is used for receiving the photons diffused and emitted by the brain tissue after being irradiated by the light source, and is coupled with the single-mode detection optical fiber to realize photon counting at different positions;
the correlation arithmetic unit is a cerebral blood flow measuring module, is connected with a partial channel of the single photon counter, outputs a normalized light intensity autocorrelation function according to the photon sequence operation, and transmits the normalized light intensity autocorrelation function to a personal computer to wait for further cerebral blood flow calculation;
the personal computer realizes the pairing based on a Diffusion Correlation Spectroscopy (DCS) algorithm and a near infrared spectroscopy (NIRS) algorithmPhoton counting, normalized light intensity autocorrelation function (g)2) And multi-mode imaging of brain blood oxygen, brain blood flow and respective functional connectivity.
The wavelength ranges of the light source A, the light source B and the light source C are 650nm-1050nm, the coherence length of the light source is more than 5m, and the central wavelength is preferably 690nm, 785nm and 850 nm.
The optical switch is Nx 1, wherein N >1 and is used for switching different light source wavelengths.
The optical fiber lantern ring A2 multiplied by 1 is characterized in that the front end of the optical fiber lantern ring A2 multiplied by 1 is provided with two multimode light source optical fibers, the rear end of the optical fiber lantern ring is provided with a two-in-one multimode light source optical fiber, and the diameter D of the optical fiber lantern ring is larger than or equal to the sum of the diameters of the two multimode light source optical fibers; the optical fiber lantern ring B, the optical fiber lantern ring C, the optical fiber lantern ring D and the optical fiber lantern ring E are all 2 x 1 optical fiber lantern rings, the front end is provided with two multimode light source optical fibers, the rear end is provided with a two-in-one multimode light source optical fiber, and the diameter D of the optical fiber lantern ring is larger than or equal to the sum of the diameters of the two single-mode detection optical fibers.
The photon counter has photon detection efficiency of over 50% in 690-830nm band and counting rate of 1.5 Mc/s.
The diameter of the fiber core of the multimode light source optical fiber is more than 50 microns; the diameter of the fiber core of the single-mode detection fiber is 4.2 microns, and the end face of the single-mode detection fiber is provided with bandpass filters with different central wavelengths.
A measurement method of a multi-mode brain function measurement device based on DCS-NIRS comprises the following steps:
1) two long coherent near infrared laser sources are connected with a2 multiplied by 1 path optical switch through a multimode light source optical fiber to realize wavelength switching, one long coherent near infrared laser source is directly connected with an optical fiber lantern ring, and then the long coherent near infrared laser source is irradiated to the surface of a brain through a two-in-one multimode light source optical fiber probe;
2) the single photon counter receives photons emitted from the surface of the tested brain after the irradiation of the light source in the step 1), counts the photons, converts the photons into electric signals and transmits the electric signals to a personal computer and a related arithmetic unit;
3) the correlation operator normalizes the light intensity autocorrelation function (g) by the electric signal sequence2) The calculation of (a) is performed,and uploading to a personal computer;
4) the personal computer calculates the cerebral blood oxygen parameter by the attenuation of the light intensity with different wavelengths, namely the attenuation of the electric signals: oxyhemoglobin concentration (HbO)2) And a deoxyhemoglobin concentration (Hb), the formula for calculating the brain blood oxygen being:
wherein C isHbIs the concentration of the deoxygenated hemoglobin,
is the oxyhemoglobin concentration, epsilonHbAnd
the extinction coefficients of the deoxyhemoglobin and the oxyhemoglobin at a certain wavelength are respectively, the DPF is a difference path length coefficient of light with a certain wavelength transmitted in the brain tissue and depends on the specific structure and optical properties of the brain tissue, and d is the physical distance between the light source probe and the detection probe;
normalized light intensity autocorrelation function (g)2) Fittable calculation of α DBAs a cerebral blood flow index BFI, the cerebral blood oxygen and cerebral blood flow measurement is finally realized; wherein the normalized light intensity autocorrelation function (g)2) The calculation formula of (2) is as follows:
where beta is a constant, depending on the nature of the fiber optic probe,<I>2is the mean value of light intensity, the autocorrelation function of the electric field G1；
5) Obtaining the cerebral blood oxygen and the cerebral blood flow through the step 4), and obtaining the cerebral blood oxygen cerebral functional connectivity (HbO) through the personal computer through the Pearson correlation calculation2-RSFC, Hb-RSFC), brain-function connectivity (BFI-RSFC), and finally completing the multi-modal brain function measurements;
6) the position of the measuring probe is changed, and the number of the measuring probes is increased, so that the different brain areas can be measured simultaneously.
The measuring method is characterized in that two light sources for measuring cerebral blood oxygen are switched by a light switch to irradiate the surface of the brain in a pulse mode, and the light source for measuring cerebral blood flow continuously irradiates the surface of the brain.
The fitting mathematical model of the cerebral blood flow index BFI is as follows:
according to the diffusion equation and the brownian motion semi-infinite model,
wherein
Optical parameter mu's、μaτ is the delay time, wave vector k0Is known as r1Is the distance between the isotropic source and the probe point, r2Is the distance between the mirror source and the detection point above the medium.
The calculation formula of the brain function connectivity is as follows:
in the above equation, cov represents covariance, σ represents standard deviation, and x and y represent cerebral blood oxygen or cerebral blood flow sequences at different detection positions.
Compared with the prior art, the invention has the following beneficial effects:
the invention adopts different wavelength long coherent near infrared light sources as detection light sources, combines an optical switch and an optical fiber lantern ring to form a two-in-one light source detection optical fiber, and realizes simultaneous multi-channel measurement; the optical property of biological tissues is fully utilized, the light intensity is acquired through the single photon counter, the normalized light intensity autocorrelation function is calculated through the correlation arithmetic unit, the diffusion correlation spectrum technology and the near infrared spectrum technology are effectively combined, a multi-mode solution is provided, and the multi-channel cerebral blood oxygen and cerebral blood flow and the respective functional connectivity can be measured simultaneously. Compared with the prior art, the method has the characteristics of non-invasion, no radiation, high efficiency and the like, and the device has the advantages of low cost, high portability and the like.
Drawings
FIG. 1 is a system diagram of a DCS-NIRS based multi-modal brain function measurement method and apparatus of the present invention.
The system comprises a light source A, a light source B, a light source C, a 4-optical switch, a 5-optical fiber lantern ring A, a 6-measuring probe, a 7-brain, an 8-optical fiber lantern ring B, a 9-optical fiber lantern ring C, a 10-optical fiber lantern ring D, an 11-optical fiber lantern ring E, a 12-single photon counter, a 13-correlation arithmetic unit, a 14-personal computer, a 15-multimode light source detection optical fiber, a 16-single mode detection optical fiber and a 17-cable.
FIG. 2 is a schematic diagram showing the arrangement and distribution of light source fibers and detection fibers in a measurement probe of the DCS-NIRS-based multi-modal brain function measurement method and apparatus of the present invention.
Wherein, represents a single mode detection fiber probe,
representing a multimode source fiber optic probe.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without any creative efforts shall fall within the protection scope of the present invention.
A multi-mode brain function measuring device based on DCS-NIRS, figure 1 shows a system schematic diagram of the multi-mode brain function measuring device based on DCS-NIRS, and the device mainly comprises: the device comprises a light source A (1), a light source B (2), a light source C (3), an optical switch 4, an optical fiber sleeve ring A (5), a measuring probe (6), an optical fiber sleeve ring B (8), an optical fiber sleeve ring C (9), an optical fiber sleeve ring D (10), an optical fiber sleeve ring E (11), a single photon calculator 12, a correlation calculator 13, a personal computer 14, a multi-mode light source optical fiber 15 and a single-mode detection optical fiber 16.
The light source A (1), the light source B (2) and the light source C (3) are laser light sources with long coherent near infrared different wavelengths, the light source B (2) and the light source C (3) are coupled with a multimode light source optical fiber 15 and then connected with an optical switch 4, and the light source C (3) and the optical switch 4 are connected with a measuring probe 6 through a two-in-one optical fiber consisting of an optical fiber lantern ring A (5) and irradiate the surface of a brain.
Further, in this embodiment, the central wavelength of the light source a (1) is 850nm, the central wavelength of the light source B (2) is 690nm, the central wavelength of the light source C (3) is 785nm, the coherence length is greater than 5m, the wavelength of the near-infrared light can be selected according to actual requirements, and the number of the light sources can be increased.
The optical switch 4 is used for switching between the light source B (2) and the light source C (3) and switching different light source wavelengths. Further, the optical switch 4 is N × 1 in the present embodiment, where N >1, and is used for switching different light source wavelengths.
The optical fiber lantern ring is used for realizing nesting of a multi-mode light source optical fiber and a single-mode detection optical fiber to form a two-in-one optical fiber and enable the measuring probe to be approximately incident or emergent at the same point, and the incident point or the emergent point is ensured to belong to the same brain functional unit; optical fiber lantern ring A (5) will be used for measuring the 4 optic fibre ends of photoswitch of brain blood oxygen and the light source A (1) nestification that is used for measuring the brain blood flow, form the multimode light source optic fibre of two unifications, optical fiber lantern ring B (8), optical fiber lantern ring C (9), optical fiber lantern ring D (10), optical fiber lantern ring E (11) are all the single mode detection optic fibre that will be used for surveying the photon of calculating brain blood oxygen and are used for surveying the single mode optic fibre nestification of the photon of calculating the brain blood flow, form the single mode detection optic fibre of two unifications that correspond, the detection of different positions is realized to a plurality of single mode optic.
Further, in this embodiment, the optical fiber ferrule a (5) is a2 × 1 optical fiber ferrule, the front end is two multimode light source optical fibers, and the rear end is a two-in-one multimode light source optical fiber, wherein the diameter D of the optical fiber ferrule is greater than or equal to the sum of the diameters of the two multimode light source optical fibers.
Further, in this embodiment, the optical fiber ferrule B (8), the optical fiber ferrule C (9), the optical fiber ferrule D (10), and the optical fiber ferrule E11 are all 2 × 1 optical fiber ferrules, the front end is a two-in-one single-mode detection optical fiber, and the rear end is two single-mode detection optical fibers, where the diameter D of the optical fiber ferrule is greater than or equal to the sum of the diameters of the two single-mode detection optical fibers.
The measuring probe 6 is fixed on the surface of the brain and used for arranging and fixing the multimode light source optical fiber and the single-mode detection optical fiber; the multiple measuring probes can realize the measurement of different brain areas.
Further, in the present embodiment, as shown in the arrangement distribution schematic diagram of fig. 2, the light source fiber in the measurement probe is placed at the center of the 4 detection fibers to form 4 detection channel pairs. The number of the measuring probes can be correspondingly increased according to the actual number of the light sources, so that the requirement for measuring more brain areas is met.
Furthermore, the core diameter of the multimode light source fiber 15 is more than 50 microns. In this embodiment, the core diameter of the multimode source fiber is 50 microns.
Further, the core diameter of the single mode detection fiber 16 may be 4.2 microns, 5 microns, 9 microns. And the end face of the single-mode detection optical fiber is provided with band-pass filters with different central wavelengths. In this embodiment, the fiber core diameter of the single-mode detection fiber is 4.2 microns, for the single-mode detection fiber for detecting cerebral blood oxygen, the end face of the fiber incident end of the single-mode detection fiber is provided with a 680-790nm band-pass filter, and for the single-mode detection fiber for detecting cerebral blood flow, the end face of the fiber incident end of the single-mode detection fiber is provided with a 850nm narrow-band-pass filter.
And the single photon counter 12 is used for receiving the photons diffused and emitted by the brain tissue after being irradiated by the light source, and is coupled with the single-mode detection optical fiber 16 to realize photon counting at different positions.
Further, the single photon counter 12 has a photon detection efficiency of 50% or more and a count rate of 1.5Mc/s in the 690-830nm band. In order to satisfy the simultaneous measurement of cerebral blood oxygen and cerebral blood flow, the present embodiment adopts a combination of 2 4-channel photon counters, wherein the photon counter for measuring cerebral blood flow needs to be connected to the correlation arithmetic unit 13 and then connected to the personal computer 14, and the photon counter for measuring cerebral blood oxygen is directly connected to the personal computer 14.
The correlation arithmetic unit 13 is a module for measuring cerebral blood flow, is connected with a part of channels of the single photon counter 12, outputs a normalized light intensity autocorrelation function according to the photon sequence operation, and transmits the normalized light intensity autocorrelation function to the personal computer 14 to wait for further cerebral blood flow calculation. The personal computer 14 performs photon counting and normalization of the light intensity autocorrelation function (g) based on the Diffuse Correlation Spectroscopy (DCS) and near infrared spectroscopy (NIRS) algorithms2) And multi-modal imaging of brain blood oxygenation, brain blood flow and respective functional connectivity.
Further, the personal computer 14 calculates the cerebral blood oxygen and cerebral blood flow of each channel, and when the functional connectivity of the cerebral blood oxygen and cerebral blood flow is calculated, the functional connectivity of each channel is calculated by performing the calculation of each channel, and finally a functional connectivity matrix is formed.
A DCS-NIRS based multi-modal brain function measuring method comprises the following steps:
(1) two long coherent near infrared laser sources are connected with a2 multiplied by 1 optical switch through multimode light source optical fibers to realize wavelength switching, one long coherent near infrared laser source is directly connected with an optical fiber lantern ring, and then the long coherent near infrared laser source irradiates the surface of a brain through a two-in-one multimode light source optical fiber probe.
(2) And (3) the single photon counter receives photons emitted from the surface of the tested brain after the irradiation of the light source in the step (1), counts the photons, converts the photons into electric signals and transmits the electric signals to a personal computer and a related arithmetic unit.
(3) The correlation operator normalizes the light intensity autocorrelation function (g) by the electric signal sequence2) And uploading to a personal computer.
(4) The personal computer calculates the cerebral blood oxygen parameter by the attenuation of the light intensity with different wavelengths, namely the attenuation of the electric signals: oxyhemoglobin concentration (HbO)2) And deoxyhemoglobin concentration (Hb), normalized light intensity autocorrelation function (g)2) Fittable calculation of α DBAs a cerebral blood flow index BFI, the cerebral blood oxygen and cerebral blood flow measurement is finally realized; wherein the normalized light intensity autocorrelation function (g)2) The calculation formula of (2) is as follows:
where beta is a constant, depending on the nature of the fiber optic probe,<I〉2is the mean value of light intensity, the autocorrelation function of the electric field G1。
(5) Obtaining the cerebral blood oxygen and the cerebral blood flow through the step (4), and obtaining the cerebral blood oxygen cerebral functional connectivity (HbO) through the personal computer through the Pearson correlation calculation2-RSFC, Hb-RSFC), brain function connectivity to the bloodstream brain (BFI-RSFC), and finally completing the multi-modal brain function measurements.
Furthermore, there are two ways of illuminating the surface of the brain in step (1), two light sources for measuring the blood oxygen content of the brain are switched on and off to illuminate the surface of the brain in a pulse mode, and the light source for measuring the blood flow of the brain is continuously illuminated on the surface of the brain.
Further, in the step (4), the specific calculation process of the two parameters of the cerebral blood oxygen is as follows:
in the formula, CHbIs the concentration of the deoxygenated hemoglobin,
is the concentration of oxygenated hemoglobin,
and
deoxyhemoglobin and oxyhemoglobin, respectively, at a wavelength λaExtinction coefficient of (d), DPF (λ)a) Is the wavelength lambdaaThe differential path length coefficient of light transmitted in the brain tissue depends on the characteristics of the brain tissueBulk structure and optical properties, likewise corresponding to the wavelength λaAlso with the above parameters, d is the physical distance between the light source probe and the probing probe.
Furthermore, the concentration C of the deoxygenated hemoglobin can be calculated by combining the two calculation formulasHbAnd oxyhemoglobin concentration
These two concentrations are relative change concentrations, and the calculation result is as follows:
wherein,
further, in the step (4), the specific calculation process of the cerebral blood flow index BFI is as follows:
the normalized light intensity autocorrelation function expression obtained by calculation in the correlation operator (14) is
Where beta is a constant, depending on the nature of the fiber optic probe,<I〉2is the mean value of light intensity, the autocorrelation function of the electric field G1。
Further, the brain is generally considered to be a semi-infinite model, based on the diffusion equation and a semi-infinite model of brownian motion,
wherein
Optical parameter mu's、μaτ is the delay time, wave vector k0Is known as r1Is the distance between the isotropic source and the probe point, r2The distance between a mirror image source above the medium and a detection point is used, and the mathematical expression quantity of the blood flow index BFI can be obtained by a fitting method: alpha DBWhere α is the probability of a photon to undergo a scattering event, DBIs the brownian motion diffusion coefficient.
Further, in the step (5), the functional connectivity calculation formula is
In the above equation, cov represents covariance, σ represents standard deviation, and x and y represent cerebral blood oxygen or cerebral blood flow sequences of different probe channels.
All the possible combinations of the technical features of the above embodiments are not described for the sake of brevity, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features. It will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. The scope of the invention is to be determined by the appended claims.
Claims (10)
1. A multi-modal brain function measuring device based on DCS-NIRS, characterized by comprising: the device comprises a light source A (1), a light source B (2), a light source C (3), an optical switch (4), an optical fiber sleeve ring A (5), a measuring probe (6), an optical fiber sleeve ring B (8), an optical fiber sleeve ring C (9), an optical fiber sleeve ring D (10), an optical fiber sleeve ring E (11), a single photon calculator (12), a correlation calculator (13), a personal computer (14), a multi-mode light source optical fiber (15) and a single-mode detection optical fiber (16);
the light source A (1), the light source B (2) and the light source C (3) are laser light sources with long coherent near infrared and different wavelengths, the light source B (2) and the light source C (3) are coupled with a multimode light source optical fiber (15) and then connected with an optical switch (4), and the light source C (3) and the optical switch (4) are connected with a measuring probe (6) through a two-in-one optical fiber consisting of an optical fiber lantern ring A (5) and irradiate the surface of a brain;
the optical switch (4) is used for switching between the light source B (2) and the light source C (3) and switching different light source wavelengths;
the optical fiber lantern ring is used for realizing nesting of a multi-mode light source optical fiber and a single-mode detection optical fiber to form a two-in-one optical fiber and enable the measuring probe to be approximately incident or emergent at the same point, and the incident point or the emergent point is ensured to belong to the same brain functional unit; the optical fiber lantern ring A (5) is used for nesting an optical fiber end of an optical switch (4) for measuring brain blood oxygen with a light source A (1) for measuring brain blood flow to form two-in-one multi-mode light source optical fibers, the optical fiber lantern ring B (8), the optical fiber lantern ring C (9), the optical fiber lantern ring D (10) and the optical fiber lantern ring E (11) are used for nesting a single-mode detection optical fiber for detecting photons for calculating brain blood oxygen and a single-mode optical fiber for detecting photons for calculating brain blood flow to form corresponding two-in-one single-mode detection optical fibers, and the single-mode optical fibers realize detection at different positions;
the measuring probe (6) is fixed on the surface of the brain and used for arranging and fixing the multimode light source optical fiber and the single-mode detection optical fiber; the multiple measuring probes realize the measurement of different brain areas;
the single photon counter (12) is used for receiving the photons diffused and emitted by the brain tissue after being irradiated by the light source, and is coupled with the single-mode detection optical fiber (16) to realize photon counting at different positions;
the correlation arithmetic unit (13) is a cerebral blood flow measuring module, is connected with a partial channel of the single photon counter (12), outputs a normalized light intensity autocorrelation function according to photon sequence operation, and transmits the normalized light intensity autocorrelation function to a personal computer for waiting further cerebral blood flow calculation; the personal computer (14) counts photons and normalizes the light intensity autocorrelation function (g) based on the Diffusion Correlation Spectroscopy (DCS) and near infrared spectroscopy (NIRS) algorithm2) And multi-mode imaging of brain blood oxygen, brain blood flow and respective functional connectivity.
2. The DCS-NIRS based multi-modal brain function measuring device of claim 1, wherein the light source A (1), the light source B (2) and the light source C (3) have a wavelength range of 650nm to 1050nm, a light source coherence length of 5m or more, and a center wavelength of 690nm, 785nm and 850nm is preferred.
3. The DCS-NIRS based multimodal brain function measuring device according to claim 1, characterised in that the light switch (4) is nx1, where N >1, for switching different light source wavelengths.
4. The DCS-NIRS based multi-modal brain function measuring device of claim 1, wherein the optical fiber ferrule A (5) is a2 x 1 optical fiber ferrule with two multi-mode light source optical fibers at the front end and a two-in-one multi-mode light source optical fiber at the rear end, wherein the diameter D of the optical fiber ferrule is larger than or equal to the sum of the diameters of the two multi-mode light source optical fibers; the optical fiber ferrule B (8), the optical fiber ferrule C (9), the optical fiber ferrule D (10) and the optical fiber ferrule E (11) are all 2 x 1 optical fiber ferrules, the front end is provided with two multimode light source optical fibers, the rear end is provided with a two-in-one multimode light source optical fiber, and the diameter D of the optical fiber ferrule is larger than or equal to the sum of the diameters of the two single-mode detection optical fibers.
5. The DCS-NIRS based multi-modal brain function measuring device of claim 1, wherein the single photon counter (12) has a photon detection efficiency of 50% or more and a count rate of 1.5Mc/s in the 690-830nm band.
6. The DCS-NIRS based multi-modal brain function measuring device of claim 1, wherein the multi-mode light source fiber (15) has a core diameter of more than 50 microns; the diameter of the fiber core of the single-mode detection fiber (16) is 4.2 microns, and the end face of the single-mode detection fiber is provided with bandpass filters with different central wavelengths.
7. A method of measuring based on a DCS-NIRS multi-modal brain function measuring device according to claim 1, comprising the steps of:
1) two long coherent near infrared laser sources are connected with a2 multiplied by 1 path optical switch through a multimode light source optical fiber to realize wavelength switching, one long coherent near infrared laser source is directly connected with an optical fiber lantern ring, and then the long coherent near infrared laser source is irradiated to the surface of a brain through a two-in-one multimode light source optical fiber probe;
2) the single photon counter receives photons emitted from the surface of the tested brain after the irradiation of the light source in the step 1), counts the photons, converts the photons into electric signals and transmits the electric signals to a personal computer and a related arithmetic unit;
3) the correlation operator normalizes the light intensity autocorrelation function (g) by the electric signal sequence2) And uploading to a personal computer;
4) the personal computer calculates the cerebral blood oxygen parameter by the attenuation of the light intensity with different wavelengths, namely the attenuation of the electric signals: oxyhemoglobin concentration (HbO)2) And a deoxyhemoglobin concentration (Hb), the formula for calculating the brain blood oxygen being:
wherein C isHbIs the concentration of the deoxygenated hemoglobin,
is the oxyhemoglobin concentration, EHbAnd
the extinction coefficients of the deoxyhemoglobin and the oxyhemoglobin at a certain wavelength are respectively, the DPF is a difference path length coefficient of light with a certain wavelength transmitted in the brain tissue and depends on the specific structure and optical properties of the brain tissue, and d is the physical distance between the light source probe and the detection probe;
normalized light intensity autocorrelation function (g)2) Fittable calculation of α DBAs a cerebral blood flow index BFI, the cerebral blood oxygen and cerebral blood flow measurement is finally realized; wherein the normalized light intensity autocorrelation function (g)2) The calculation formula of (2) is as follows:
where beta is a constant, depending on the nature of the fiber optic probe,<I>2is the mean value of light intensity, the autocorrelation function of the electric field G1；
5) Obtaining the cerebral blood oxygen and the cerebral blood flow through the step 4), and obtaining the cerebral blood oxygen cerebral functional connectivity (HbO) through the personal computer through the Pearson correlation calculation2-RSFC, Hb-RSFC), brain-function connectivity (BFI-RSFC), and finally completing the multi-modal brain function measurements;
6) the position of the measuring probe is changed, and the number of the measuring probes is increased, so that the different brain areas can be measured simultaneously.
8. The method of claim 7, wherein the two light sources for measuring cerebral blood oxygen are switched by a light switch to illuminate the surface of the brain in a pulse mode, and the light source for measuring cerebral blood flow is continuously illuminated on the surface of the brain.
9. The measurement method according to claim 8, wherein the fitted mathematical model of the cerebral blood flow indicator BFI is: according to the diffusion equation and the brownian motion semi-infinite model,
wherein
Optical parameter mu's、μaτ is the delay time, wave vector k0Is known as r1Is the distance between the isotropic source and the probe point, r2Is the distance between the mirror source and the detection point above the medium.
10. The measurement method according to claim 9, wherein the calculation formula of brain functional connectivity is:
in the above equation, cov represents covariance, σ represents standard deviation, and x and y represent cerebral blood oxygen or cerebral blood flow sequences at different detection positions.
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