Functional near infrared spectrum imaging system

Abstract

The invention discloses a functional near-infrared spectrum imaging system which comprises an optical fiber, a light source, a detector, a multi-channel near-infrared spectrometer and a display terminal. The detector and the light source are connected through an optical fiber and are fixed on the head of a detected person; in the measuring process, the light source illuminates the head area, and diffuse reflection signals of the head are captured by the detector and transmitted to the multi-channel near-infrared spectrometer through the optical fiber to be processed and analyzed. The core advantage of the invention lies in the spectral resolution capability, multi-channel infrared signal capture can be realized in a low power consumption state without light intensity modulation and demodulation methods, and the circuit complexity of the system is greatly reduced. By combining the advantages of the multi-channel optical fiber and the imaging spectrometer, the complexity of the detection system is simplified, the power consumption is reduced, and the system has remarkable advantages in the aspects of portability and high-density detection. The system has the potential of realizing high-density portable fN IRS monitoring, and is particularly suitable for dynamic activities such as walking.

Description

Technical Field

[0001] The present invention belongs to the technical field of brain imaging, and relates to a functional near-infrared spectroscopy imaging system for detecting human brain blood oxygen signals in a motion state. Background Art

[0002] The human brain is the most complex organ in the body, playing an important role in perception, motor control and advanced cognition. In recent years, brain cognition research has become an interdisciplinary emerging field, covering sensory functions such as vision, hearing, and smell, as well as emotional expression, language comprehension and advanced psychological functions. Brain function is crucial to human life activities, and various physiological activities are closely related to the brain. Therefore, researchers have conducted in-depth research on the brain through various technologies and means. The brain has a huge demand for oxygen, accounting for about one-fifth of the total oxygen consumption of the human body. It is also very sensitive to cerebral blood oxygen concentration, and even a short lack of oxygen can cause irreversible damage. The nervous system of a newborn is in the development stage, and hypoxia may cause serious damage or even brain death. Therefore, cerebral blood oxygen concentration detection has become an important research direction in the field of brain cognition. This demand has promoted the development of more accurate and convenient brain imaging technologies, especially those that can be used in motion, to meet the needs of brain function monitoring in dynamic environments. This background provides an important technical basis and application scenario for the research and development of the present invention.

[0003] Brain imaging technology was first applied to electroencephalography (EEG) and magnetoencephalography (MEG), which can directly reflect the electrical activity of the central nervous system, have high temporal resolution, and are easy to use and maintain. However, the spatial resolution of EEG is limited, and there is a certain uncertainty in interpreting EEG data. Although magnetoencephalography (MEG) has a high spatial resolution, its wide application is limited by the high cost of equipment and complex maintenance. Functional magnetic resonance imaging (fMRI) is a technology that can accurately locate the function of brain regions and has a high spatial resolution. However, its low temporal resolution, bulky equipment, and high sensitivity to the environment make fMRI unsuitable for portable and dynamic brain function monitoring.

[0004] Functional near-infrared spectroscopy (fNIRS) is based on blood oxygen imaging technology and has many significant advantages. First, the cost of the fNIRS system is low, which is more economical than expensive imaging equipment such as MEG and fMRI. Secondly, fNIRS is a non-invasive technology that does not harm the subjects, which makes it particularly suitable for research on special populations (such as newborns, the elderly, and individuals with specific diseases). In addition, fNIRS devices are usually lightweight and suitable for portable use, and can be monitored during dynamic activities such as walking and running.

[0005] These advantages make fNIRS provide new research perspectives and tools for cognitive neuroscience. Its ability to efficiently capture brain functional activities in a dynamic environment provides broad application prospects for neuroscience research, brain disease diagnosis and treatment monitoring. Therefore, further improving the performance of the fNIRS system, especially its applicability in a dynamic environment, has become an important direction of current research. This is also the problem that the present invention is committed to solving. Through innovative design, a more efficient and convenient fNIRS system is provided to meet the needs of brain blood oxygen signal monitoring in dynamic activities.

[0006] Although existing Chinese patents, such as CN201110286531.8 and CN200410096007.X, can effectively detect blood oxygen information, they have obvious limitations in module design and system integration. First, the light source system in these patents uses expensive lasers, which not only increases the overall cost, but also greatly reduces the flexibility of the system due to the limitation of wavelength selection. In a multi-channel detection system, each channel needs to be equipped with at least two light sources of different wavelengths, so multiple lasers must be equipped and the light source must be integrated through a complex coupler. This design further increases the cost and increases the complexity of the system, thus affecting its convenience and feasibility in practical applications. Secondly, in terms of the detector module, although a photomultiplier tube with extremely high sensitivity is selected, the high cost, large size, susceptibility to mechanical impact damage of this detector, and the non-uniformity and fatigue of the sensitivity of the photocathode surface greatly limit its wide application. In addition, due to its low sensitivity, traditional silicon photodiodes are difficult to detect weak light signals scattered by the brain. In terms of probe design, the unreasonable channel arrangement and adaptive probe design of these two patents also greatly affected the system performance. These design and technical defects, coupled with the limitations of data acquisition technology, resulted in the overall system failing to efficiently meet data acquisition requirements and failing to fully utilize the potential advantages of near-infrared spectral imaging technology.

[0007] Based on the significant difference in the absorption spectra of HbO and HbR, the fNIRS system uses a multi-wavelength detection method to achieve more accurate brain blood oxygen signal detection. In order to make full use of this difference, 2 to 3 LEDs of different wavelengths are usually integrated in the light source module. Each pair of light source modules and detector modules together constitute a detection channel. However, the current detector technology cannot distinguish between light of different wavelengths. If all LEDs in a light source module are driven by a constant current source at the same time and continuously irradiated onto the scalp, the detector will not be able to distinguish the light intensity of each wavelength. In order to maintain the time efficiency of detection, traditional fNIRS systems usually use light intensity modulation technology, which sets different light intensity frequencies for LEDs of different wavelengths and combines the high-speed detection and demodulation algorithm of photoelectric sensors to distinguish and detect light intensities of different wavelengths. For example, the system mentioned in patent CN103156620 A uses an avalanche photodiode as a detector and uses optical fiber to monitor multi-channel brain blood oxygen. However, this modulation and demodulation technology will lead to a corresponding increase in power requirements as the number of channels increases. At the same time, when used with detectors such as avalanche diodes, the power consumption and number of detectors of the device will also increase sharply, making it difficult for the overall device to be compact and portable.

[0008] In summary, the need for high operating voltage limits the application of avalanche photodiodes or photomultiplier tubes in compact or wearable devices, especially in scenarios where high-density detection is required. In addition, although silicon photodiodes (SiPDs) are suitable for wearable devices due to their small size and low operating voltage, their low sensitivity and sensitivity to ambient temperature changes often require additional temperature control measures during use to ensure that the device can still operate stably under changing environmental conditions.

[0009] Further considering the progress and limitations of existing portable fNIRS systems, we found that these systems usually use low-density detector configurations, which to some extent limits the range and resolution of brain activity capture. With the increasing demand for scientific research and the continuous advancement of related technologies, the demand for high-density detectors is also growing. High-density fNIRS systems are defined as having more optical detectors per square centimeter of measurement area, and the density of detectors is usually between 0.5 and 2 cm per square centimeter, or even higher. Faced with this increase in technical requirements, a series of technical challenges need to be addressed in the design of high-density portable fNIRS systems. First, the layout and integration of high-density detectors must not only consider the portability of the device, but also ensure the comfort of the wearer. This requires the development of new materials and design methods to achieve lightweight and ergonomic optimization of the device. Second, as the number of detectors and light sources increases, the complexity and cost of the system also increase. This not only increases the production cost, but also increases the power consumption of the device. Therefore, designing an effective power management system and solving the problem of large amounts of data transmission have become important challenges that must be faced. Summary of the invention

[0010] The purpose of the present invention is to provide a functional near-infrared spectroscopy imaging system, which is designed and developed based on a high-throughput fiber optic spectrometer. This system can synchronously complete the operation of multi-channel fNIRS, capture the diffuse reflection signal detected by the optical fiber in the brain nerve activity, and convert it into an accurate detection of the concentration of oxygenated hemoglobin and deoxygenated hemoglobin. The development of this system not only improves the spatial resolution and sensitivity of the fNIRS technology, but also optimizes the stability and accuracy of the signal by using advanced fiber optic technology, thereby expanding its application potential in the field of cerebral hemodynamics research.

[0011] The technical solution to achieve the purpose of the present invention is: Functional near-infrared spectral imaging system, including: optical fiber, light source, detector, multi-channel near-infrared spectrometer and display terminal; The detector and light source are connected by optical fiber and fixed on the head of the subject. During the measurement process, the light source illuminates the head area, the diffuse reflection signal of the head is captured by the detector, and transmitted to the multi-channel near-infrared spectrometer through the optical fiber for processing and analysis. The test results are transmitted in real time and displayed on the display terminal, and the operator can obtain the data immediately and make adjustments or analyses.

[0012] Preferably, it also includes a headband and a shoulder strap; the headband is used to fix the detector and the light source on the head of the subject; and the shoulder strap is used to fix the multi-channel near-infrared spectrometer on the back of the subject.

[0013] Preferably, it further comprises an optical fiber holder for fixing the optical fiber; the optical fiber holder comprises a first cap, a first socket, a first spring and a first base; The first base is worn on the head, and a semicircular groove is provided at the front end. The optical fiber passes through the semicircular groove of the base. The first socket is inserted into the first base to fix the optical fiber. The first spring is placed between the first socket and the first base. The first cap is put on the first socket to cover the upper part of the optical fiber probe.

[0014] Preferably, it further comprises a light source holder for fixing the light source; the light source holder comprises a second cap, a second socket, a second spring and a second base; The light source includes a three-wavelength LED, which is fixed on the second hat. The second hat is connected to the second socket for fine-tuning the angle and position of the LED; the second socket is inserted into the second base, and the second spring is placed between the second socket and the second base; the second base is worn on the head.

[0015] Preferably, the three wavelengths of the LED all belong to the near-infrared wavelength of 600nm to 870nm.

[0016] Preferably, the multi-channel near-infrared spectrometer comprises: an optical fiber bundle, a first sleeve, an angled connector, a second sleeve, a CMOS camera, a focusing lens, a grating and a collimating lens; The optical fiber bundle comprises an optical fiber bundle proximal end and an optical fiber bundle distal end, wherein the optical fiber bundle distal end is composed of N optical fibers and is responsible for transmitting the optical signal received from the head; The proximal end of the optical fiber bundle is connected to one end of the first sleeve, the other end of the first sleeve is connected to one end of an angled connector, the other end of the connector is connected to one end of the second sleeve, and the other end of the second sleeve is connected to a CMOS camera; a collimating lens and a grating are placed in the first sleeve in sequence, and a focusing lens is placed in the second sleeve.

[0017] Preferably, the optical signal is transmitted into the first sleeve through the proximal end of the optical fiber bundle, and then transmitted forward to the collimating lens, ensuring that the light is collimated after passing through the grating and dispersed along the vertical direction of the optical fiber bundle; through the angled connector, the scattered light in the optical fiber bundle is focused to the focusing lens after first-order diffraction, and finally projected to the CMOS camera.

[0018] Preferably, the CMOS camera receives spectral energy on its focal plane, detects the intensity and wavelength position of the spectrum, and converts the optical signal into an electrical signal; subsequently, the signal is amplified, measured and recorded to obtain the distribution data of the light intensity, and is processed by a computer to finally output the spectral image in the form of a grayscale image.

[0019] Preferably, there are three light sources and five detectors, the three light sources are respectively deployed at the left, middle and right centers of the frontal lobe, and the five detectors are distributed around the three light sources, so as to realize nine-channel brain blood oxygen concentration monitoring; Time division multiplexing technology is used to switch between the three light sources to achieve a continuous lighting effect; the three light sources are activated in a continuous cycle within 0.1 seconds, and during the activation of each light source, the three surrounding detectors monitor the three channels of the light source respectively.

[0020] Preferably, the multi-channel near-infrared spectrometer captures diffuse reflectance signals returned from the brain; the video frames correspond to the diffuse reflectance signals at a specific moment, and an image processing method interprets these signals: In the image, the frame number shows the signal intensity emitted by the brain at a specific moment, where the horizontal axis represents the channel number included in the system, with a total of N channels; the vertical axis of the image represents the wavelength associated with the emitted light, from which the distribution of diffuse reflection signals at different wavelengths is observed; the grayscale value of each pixel in the image represents the intensity of the captured diffuse reflection light; the intensity information changes over time, and by analyzing these changes, the dynamic changes in brain blood oxygen concentration are calculated based on the modified Beer-Lambert law.

[0021] Compared with the prior art, the present invention has the following significant advantages: (1) First, based on the advanced optical structure of the imaging spectrometer, this system has developed a functional near-infrared spectrometer module that can synchronously obtain spectral information from multiple continuous detection positions, showing great potential in high-density cerebral blood oxygen detection. In addition, the multi-channel fiber bundle we designed can independently collect diffuse reflection signals from different positions on the head. These signals are transmitted to the CMOS sensor in the imaging spectrometer via multiple optical fibers, and then diffracted into multiple independent spectral bands, achieving effective distinction between wavelength signals in different detection channels. This design allows the LED to be directly driven by a universal constant current source without the need for light intensity modulation, simplifying the system design.

[0022] (2) On this basis, the multi-channel fiber bundle not only transmits the scattered light to the entrance of the imaging spectrometer, but also uses a large-area global exposure CMOS chip to synchronously capture the spectral signals transmitted by all fibers in a low-power operation mode. The design of the imaging spectrometer can accurately distinguish the spectrum without modulating the LED intensity, thereby further reducing the complexity and energy consumption of the system.

[0023] (3) The system is compact in size, has high-throughput spectral acquisition capabilities, and is flexible and portable, providing a new tool for future brain function research and clinical applications. Theoretically, the system can simultaneously acquire diffuse reflectance spectral signals from 20 different wavelength channels and has the ability to quantitatively measure blood oxygen saturation with high precision.

[0024] (4) Most importantly, the portability and high-density detection capability of the system enable it to perform multi-channel brain blood oxygen signal monitoring in unstructured environments (such as hospitals, outdoors, etc.) and is suitable for a variety of states (such as walking, exercising, etc.). BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is an overall schematic diagram of the functional near-infrared spectroscopy imaging system in Example 1; Figure 2 is a schematic diagram of an optical fiber fixture in Example 2; Figure 3 This is a schematic diagram of a light source fixture in Example 3; Figure 4 This is a schematic diagram of the multi-channel near-infrared spectrometer in Example 4; Figure 5 This is a schematic diagram of using a spectrometer to achieve high-density cerebral blood oxygen detection in Example 5; Figure 6 This is a schematic diagram illustrating the channel layout in Example 6. DETAILED DESCRIPTION

[0026] In order to enable the public to more clearly understand the technical essence and beneficial effects of the present invention, the applicant will provide detailed descriptions in the form of embodiments below. However, the descriptions of the embodiments are not limitations on the scheme of the present invention. Any equivalent changes made based on the concept of the present invention that are merely formal and not substantial should be regarded as within the scope of the technical scheme of the present invention. Example

[0027] The following is combined with Figure 1 The overall structure of the functional near-infrared spectral imaging system of the present invention is further described.

[0028] As attached Figure 1 As shown, the present invention constructs a complete set of functional near-infrared spectroscopy imaging system, including the following key components: optical fiber 1, light source 2, detector 3, headband 4, multi-channel near-infrared spectrometer 5, shoulder strap 6 and tablet computer 7. The working principle of the system is as follows: the detector 3 and the light source 2 are connected by optical fiber 1 and are firmly fixed to the head of the subject with the help of headband 4. During the measurement process, the light source 2 is activated and adjusted to an appropriate light intensity to ensure that the head area can be fully illuminated. The diffuse reflection signal of the head is captured by the detector 3 and transmitted to the multi-channel near-infrared spectrometer 5 through optical fiber 1 for processing and analysis. The shoulder strap 6 is used to fix the multi-channel near-infrared spectrometer 5 on the back of the subject. The system design takes into account the convenience of user operation, so the test results can be transmitted in real time and displayed on the tablet computer 7, so that the operator can instantly obtain data and make necessary adjustments or analyses.

[0029] Example 2 When the wearer performs actual scene applications, such as walking, running and other experiments involving large movements, there may be gaps between the fiber optic probe and the scalp or motion artifacts due to shaking, which will cause the optical test experimental data to be overexposed or too dark, thereby affecting the accuracy of the experiment. To solve this problem, we propose to add a "fixer" to the light source and the fiber optic probe to improve the stability of the system and the reliability of the data.

[0030] The following is combined with Figure 2 The optical fiber holder of the present invention is further described.

[0031] As attached Figure 2 As shown, it includes a first cap 201, a first socket 202, a first spring 203 and a first base 204; the first base 204 is worn on the head, and a semicircular groove is provided at the front end, and the optical fiber passes through the semicircular groove of the base, and the first socket 202 is inserted into the first base 204 to fix the optical fiber; the first spring 203 is placed between the first socket 202 and the first base 204 to provide the necessary tension to adapt to different head shapes and movement states. The first cap 201 is put on the first socket 202 to cover the upper part of the optical fiber probe.

[0032] The first base 204 is made of epoxy resin material through 3D printing technology and is designed to be fixed on a nylon cloth belt for easy wearing on the head. During wearing, the reaction force of the scalp will compress the first spring 203 to generate tension, so that the probe is firmly fixed on the head, effectively reducing signal interference caused by head movement and enhancing the stability and accuracy of experimental data. Example

[0033] In portable high-density fNIRS systems, the fixation and setting of the light source are crucial to ensure that the system works properly in diverse environments.

[0034] The following is combined with Figure 3 The light source holder in the present invention is described in detail.

[0035] The light source holder includes a second cap 302, a second socket 303, a second spring 304 and a second base 305. A three-wavelength LED 301 is mounted at the front end of the light source, and the LED 301 is fixed on a special second cap 302, which is designed to maintain the stability and correct positioning of the light source during use. The second socket 303 is connected to the second cap 302 as a support point for the LED 301, and the angle and position of the LED 301 can be fine-tuned to ensure the optimal light projection direction. The second socket 303 is inserted into the second base 305, and the second spring 304 is placed between the second socket 303 and the second base 305 to provide the necessary elasticity so that the light source can adapt to the wearer's head movement, reduce vibration and deviation during movement, and ensure that the light is accurately irradiated to the target area. The second base 305 is fixed to the headband and is made of a lightweight but stable material to increase overall comfort and convenience of wearing.

[0036] Through this design, the light source holder not only ensures the stability of the light source in a dynamic environment, but also improves the applicability and flexibility of the system, enabling it to perform optimally in different experimental conditions and daily application scenarios. A useful example uses wavelengths of 730nm, 810nm, and 860nm. Example

[0037] During operation, the light source detector fixed on the head emits near-infrared light, which penetrates the scalp and enters the head tissue and is scattered. The main form of scattering is backscattering, in which the scattered photons escape the cortex and are received by the fiber optic detector in the head holder. These optical fibers transmit the captured light signals to the multi-channel near-infrared spectrometer, which further converts the light signals into electrical signals to obtain data about the absorption of near-infrared light sources by the brain. Thanks to the efficient design of the imaging spectrometer and the innovative conversion design of the front-end fiber optic bundle from linear array to planar array, the system can achieve multi-channel synchronous information acquisition.

[0038] The following is combined with Figure 4The multi-channel near-infrared spectrometer of the present invention is further described. The key components of the multi-channel near-infrared spectrometer 5 are an optical fiber bundle 500, a first sleeve 502, an angled connector 503, a second sleeve 504, a CMOS camera 505, a focusing lens 506, a grating 507 and a collimating lens 508; the optical fiber bundle 500 includes an optical fiber bundle proximal end 501 and an optical fiber bundle distal end 509, and the optical fiber bundle distal end 509 is composed of N optical fibers 1, which are responsible for transmitting the optical signal received from the head; the optical fiber bundle proximal end 501 is connected to one end of the first sleeve 502, and the other end of the first sleeve 502 is connected to one end of the angled connector 503, and the other end of the connector 503 is connected to one end of the second sleeve 504, and the other end of the second sleeve 504 is connected to the CMOS camera 505; the collimating lens 508 and the grating 507 are placed in the first sleeve 502 in sequence, and the focusing lens 506 is placed in the second sleeve 504.

[0039] The optical fiber bundle 500 is responsible for transmitting the optical signal received from the head. Each optical fiber 1 at the distal end 509 of the optical fiber bundle is fixed to the head by the optical fiber fixture described in Example 2, and is used to receive the scattered light signal. The optical signal is transmitted into the sleeve 502 through the proximal end 501 of the optical fiber bundle, and then transmitted forward to the collimating lens 508 to ensure that the light is collimated after passing through the grating 507 and dispersed along the vertical direction of the optical fiber bundle. Through the angled connector 503, the scattered light in the optical fiber bundle is focused to the focusing lens 506 after the first-order diffraction, and finally projected to the CMOS camera 505. The synergistic effect of this series of components ensures that the functional near-infrared spectrometer can accurately capture the optical information inside the biological tissue. The CMOS camera 505 receives spectral energy on its focal plane, detects the intensity and wavelength position of the spectrum, and converts the optical signal into an electrical signal. Subsequently, the signal is amplified, measured and recorded to obtain the distribution data of the light intensity, and is processed by a computer to finally output the spectral image in the form of a grayscale image. This system improves the accuracy, sensitivity and speed of detection, and facilitates digital and automated analysis.

[0040] Example 5 In low-density fNIRS systems, the above method is still applicable due to the limited number of detection channels. However, as the number of detection channels increases, the corresponding hardware requirements also increase, which makes it more difficult to implement a high-density portable fNIRS system. At present, there are no reports on the use of a spectrometer to extract light intensities of different wavelengths to achieve fNIRS applications. This example is intended to show that even with a small number of light sources and detectors, multi-channel brain blood oxygen concentration monitoring can be achieved through innovative design, thereby illustrating the potential of the present invention in achieving high-density portable characteristics.

[0041] The following is combined with Figure 5 The present invention further illustrates a schematic diagram of using a spectrometer to achieve high-density cerebral blood oxygen detection.

[0042] The system is designed to use three light sources 2 and five detectors 3. Figure 5 The middle circle represents the light source, the numbers 1, 2, and 3 in the circle represent the light source serial number, the hexagon represents the detector, and the numbers 1-5 in the hexagon represent the detector serial number; each light source has three channels with different wavelengths. This configuration realizes nine-channel brain blood oxygen concentration monitoring. Using time-division multiplexing technology, the system can quickly switch between the three light sources to achieve the effect of continuous illumination. The three light sources are strategically deployed in the left, middle, and right centers of the frontal lobe, while the five detectors are distributed around these light sources, and each detector is about 3 cm away from the corresponding light source. This layout helps to monitor nine different channels simultaneously. Light source 1 is activated within 0.1 seconds, followed by light source 2 in another 0.1 seconds, and then light source 3 is activated within 0.1 seconds, forming a continuous cycle. During the activation of light source 1, detectors 1, 2, and 3 monitor channels 1, 2, and 3 respectively. When light source 2 is activated, detectors 1, 3, and 5 monitor channels 4, 5, and 6 respectively. Finally, when light source 3 is activated, detectors 1, 4, and 5 monitor channels 7, 8, and 9, respectively. This design enables the system to capture changes in blood oxygen concentration in the capillaries of the cerebral cortex, which are affected by oxygen metabolism and hemodynamics and usually appear as slowly changing signals. Although this system has a lower temporal resolution due to its time-division multiplexing acquisition method, its design ensures sufficient analysis of the characteristics of cerebral blood oxygen changes, demonstrating the possibility of achieving high-density detection in a portable fNIRS system. Example

[0043] like Figure 6 As shown in the figure, in the fNIRS system, the infrared imaging spectrometer captures the diffuse reflection signal returned from the brain. The video frame corresponds to the diffuse reflection signal at a specific moment. In order to interpret these signals, we use a specific image processing method. In the image, frame 1 shows the signal intensity emitted by the brain at a specific moment, where the horizontal axis represents the channel number contained in the system, with a total of N channels. The vertical axis of the image represents the wavelength associated with the emitted light, so that the distribution of diffuse reflection signals at different wavelengths can be observed. In this imaging technique, the grayscale value of each pixel in the image represents the intensity of the captured diffuse reflection light. This intensity information changes over time, and by analyzing these changes, the dynamic changes in the blood oxygen concentration in the brain can be calculated according to the Modified Beer-Lambert Law. This law provides a method to estimate the concentration of certain components (such as oxygenated or deoxygenated hemoglobin) in the tissue by measuring the attenuation of light intensity passing through the biological tissue.

[0044] The system uses the high resolution and sensitivity of the imaging spectrometer to accurately capture and analyze changes in light intensity in different channels and wavelengths. This precise data capture and processing technology enables the fNIRS system to provide a real-time and detailed view of the blood oxygen status of the brain, providing a powerful tool for neuroscience research and clinical diagnosis. The premise of the fNIRS system measurement is to calculate the concentrations of oxyhemoglobin (HbO) and deoxyhemoglobin (HbR). The main basis for calculating the concentrations of these two in current research on biological tissue spectroscopy technology is the Lambert-Beer law and the modified Lambert-Beer law. The Beer-Lambert law can be defined as: when a light beam of a certain wavelength passes vertically through a solution of uniform concentration, the intensity of the transmitted light is related to the absorbance of the solution substance, the concentration of the absorbing substance, and the thickness of the solution. This law can be expressed by a mathematical formula: ,Formula (1) In this formula, represents absorbance, Represents the intensity of incident light. Represents the intensity of the emitted light. Represents the absorption coefficient of a substance. Represents the thickness of the solution. is the concentration of the solution.

[0045] When using near-infrared acquisition equipment, the distance between the light source and the detector is much smaller than the actual optical path. This is because when the light is received by the detector, it has been scattered multiple times in the human tissue, and the Beer-Lambert law is no longer applicable. Therefore, Cope et al. proposed a modified Beer-Lambert law in 1988. In their experiments, Cope et al. showed that when light passes through a highly scattering medium, the basic Beer-Lambert law still applies, but the optical path length d is not simply the distance from the light source to the detector. So in 1988, Delpy proposed the introduction of the concepts of differential path length factor (DPF) and average optical path L.

[0046] The trajectory of photons in brain tissue is "banana-shaped", and its path length is greater than the straight-line distance d between the light source and the detector. L can be expressed as: When using near-infrared acquisition equipment, the distance between the light source and the detector is much smaller than the actual optical path. This is because when the light is received by the detector, it has been scattered multiple times in the human tissue, and the Beer-Lambert law is no longer applicable. Therefore, Cope et al. proposed a modified Beer-Lambert law in 1988. In their experiments, Cope et al. showed that when light passes through a highly scattering medium, the basic Beer-Lambert law still applies, but the optical path length d is not simply the distance from the light source to the detector. So in 1988, Delpy proposed the introduction of the concepts of differential path length factor (DPF) and average optical path L.

[0047] The trajectory of photons in brain tissue is "banana-shaped", and its path length is greater than the straight-line distance d between the light source and the detector. L can be expressed as: ,Formula (2) Among them, DPF is the differential path factor, and then the modified Lambert-Beer law is obtained: ,Formula (3) in, represents absorbance, represents the absorption coefficient of the substance, represents the concentration of the absorbing substance, and G is a constant correction factor. Near-infrared light (NIR) is the part of the spectrum with a longer wavelength, between visible light and infrared light. When near-infrared light passes through human tissue, some substances in the blood (oxyhemoglobin (HbO), deoxyhemoglobin (HbR), water, and collagen) can absorb this light, and n is oxyhemoglobin (HbO), deoxyhemoglobin (HbR), water, and collagen. In the wavelength range from 600 to 900 nm, the absorption of near-infrared light is dominated by these chromophores. Among them, oxyhemoglobin (HbO) and deoxyhemoglobin (HbR) are the main chromophores, and water also has a certain degree of absorption in this wavelength range. This experiment uses a four-wavelength light source. In order to have more accurate data and results, the absorption of water is taken into account. The calculation formula at this time is: ,Formula (4) in, Represents the thickness of the solution at wavelength λ. The absorption coefficient of blood to light can be regarded as a constant. , since the concentration of other tissues in the blood does not change in a short time, we can calculate the absorbed light intensity in a short time interval: Absorption intensity at time T0: ,Formula (5) is the differential path factor at wavelength λ; Absorption intensity at time T1: ,Formula (6) By subtracting the two equations, the constant G is eliminated, which reduces the complexity of the calculation and the resulting formula is: ,Formula (7) This eliminates the effects of scattering. Since oxygenated and deoxygenated hemoglobin have a specific extinction coefficient and different differential path length factors, two different wavelengths are used. , The light is measured: ,Formula (8) in, ,Formula (9) ,Formula (10) ,Formula (11) and It is expressed as: , formula (12) ,Formula (13) Thus, the concentration of oxygenated and deoxygenated hemoglobin can be obtained : ,Formula (14) The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacement modes and shall be included in the protection scope of the present invention.

Claims

1. A functional near-infrared spectroscopy imaging system, characterized in that: include: Optical fiber (1), light source (2), detector (3), multi-channel near-infrared spectrometer (5) and display terminal (7); The detector (3) and the light source (2) are connected via an optical fiber (1) and fixed on the head of the subject. During the measurement process, the light source (2) illuminates the head area, and the diffuse reflection signal of the head is captured by the detector (3) and transmitted to the multi-channel near-infrared spectrometer (5) via the optical fiber (1) for processing and analysis. The test results are transmitted in real time and displayed on a display terminal (7), and the operator can obtain the data immediately and make adjustments or analyses.

2. The functional near-infrared spectroscopy imaging system according to claim 1, characterized in that: It also comprises a headband (4) and a shoulder strap (6); the headband (4) is used to fix the detector (3) and the light source (2) on the head of the subject; and the shoulder strap (6) is used to fix the multi-channel near-infrared spectrometer (5) on the back of the subject.

3. The functional near-infrared spectroscopy imaging system according to claim 1, characterized in that: It also includes an optical fiber holder for fixing the optical fiber (1); the optical fiber holder includes a first cap (201), a first socket (202), a first spring (203) and a first base (204); The first base (204) is worn on the head, and a semicircular groove is provided at the front end, through which the optical fiber passes; the first socket (202) is inserted into the first base (204) to fix the optical fiber; the first spring (203) is placed between the first socket (202) and the first base (204); the first cap (201) is put on the first socket (202) to cover the upper part of the optical fiber probe.

4. The functional near-infrared spectroscopy imaging system according to claim 1, characterized in that: It also includes a light source holder for fixing the light source (2); the light source holder includes a second cap (302), a second socket (303), a second spring (304) and a second base (305); The light source (2) comprises a three-wavelength LED (301), the LED (301) is fixed on a second hat (302), the second hat (302) is connected to a second socket (303) for fine-tuning the angle and position of the LED (301); the second socket (303) is inserted into a second base (305), and a second spring (304) is placed between the second socket (303) and the second base (305); and the second base (305) is worn on the head.

5. The functional near-infrared spectroscopy imaging system according to claim 4, characterized in that: The three wavelengths of the LED (301) all belong to the near-infrared wavelength of 600nm to 870nm.

6. The functional near-infrared spectroscopy imaging system according to claim 4, characterized in that: The multi-channel near-infrared spectrometer (5) comprises: an optical fiber bundle (500), a first sleeve (502), an angled connector (503), a second sleeve (504), a CMOS camera (505), a focusing lens (506), a grating (507) and a collimating lens (508); The optical fiber bundle (500) comprises an optical fiber bundle proximal end (501) and an optical fiber bundle distal end (509), wherein the optical fiber bundle distal end (509) is composed of N optical fibers (1) and is responsible for transmitting the optical signal received from the head; The proximal end (501) of the optical fiber bundle is connected to one end of a first sleeve (502), the other end of the first sleeve (502) is connected to one end of an angled connector (503), the other end of the connector (503) is connected to one end of a second sleeve (504), and the other end of the second sleeve (504) is connected to a CMOS camera (505); a collimating lens (508) and a grating (507) are sequentially placed in the first sleeve (502), and a focusing lens (506) is placed in the second sleeve (504).

7. The functional near-infrared spectroscopy imaging system according to claim 6, characterized in that: The optical signal is transmitted into the first sleeve (502) through the proximal end (501) of the optical fiber bundle, and then transmitted forward to the collimating lens (508), ensuring that the light is collimated after passing through the grating (507) and dispersed along the vertical direction of the optical fiber bundle; through the angled connector (503), the scattered light in the optical fiber bundle is focused to the focusing lens (506) after first-order diffraction, and finally projected to the CMOS camera (505).

8. The functional near-infrared spectroscopy imaging system according to claim 7, characterized in that: The CMOS camera (505) receives spectral energy on its focal plane, detects the intensity and wavelength position of the spectrum, and converts the optical signal into an electrical signal; subsequently, the signal is amplified, measured and recorded to obtain light intensity distribution data, which is processed by a computer and finally outputs a spectral image in the form of a grayscale image.

9. The functional near-infrared spectroscopy imaging system according to claim 4, characterized in that: There are three light sources (2) and five detectors (3), the three light sources (2) are respectively arranged at the left, middle and right centers of the frontal lobe, and the five detectors (3) are distributed around the three light sources (2), so as to realize nine-channel brain blood oxygen concentration monitoring; The time division multiplexing technology is used to switch between the three light sources (2) to achieve a continuous lighting effect; the three light sources (2) are activated in a continuous cycle within 0.1 seconds respectively, and during the activation of each light source (2), the three surrounding detectors (3) respectively monitor the three channels of the light source (2).

10. The functional near-infrared spectroscopy imaging system according to claim 1, characterized in that: The multi-channel near-infrared spectrometer (5) captures diffuse reflection signals returning from the brain; a video frame corresponds to the diffuse reflection signals at a specific moment, and an image processing method interprets these signals: In the image, the frame number shows the signal intensity emitted by the brain at a specific moment, where the horizontal axis represents the channel number included in the system, with a total of N channels; the vertical axis of the image represents the wavelength associated with the emitted light, from which the distribution of diffuse reflection signals at different wavelengths is observed; the grayscale value of each pixel in the image represents the intensity of the captured diffuse reflection light; the intensity information changes over time, and by analyzing these changes, the dynamic changes in brain blood oxygen concentration are calculated based on the modified Beer-Lambert law.

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