CN117257290A - Time domain functional near infrared spectrum system based on phase control and wearable equipment - Google Patents

Abstract

The invention relates to a phase control-based time domain functional near infrared spectroscopy (TD-fNIRS) system and a wearable device, and relates to the technical field of biological sensing. The light source is used for providing picosecond pulse light with two wavelengths, the light modulation module comprises an optical switch, optical attenuation and optical coupling, the time domain delay module is used for separating incident light signals of different channels and emergent light signals of different wavelengths in the time domain so as to achieve the purpose of phase control, the sensing probe adopts hexagonal design and compact arrangement, high-resolution plane detection is realized, and the signal detection and processing module is used for detecting light signals carrying brain information and processing the light signals so as to visualize the information. The system can finely perform functional partitioning on the brain, and the light source phase control scheme solves the crosstalk problem of multi-light source detection, realizes the maximum utilization of the probe and the light source, and realizes high spatial resolution and high integration level.

Description

Time-domain functional near-infrared spectroscopy system and wearable devices based on phase control

Technical field

The invention belongs to the technical field of near-infrared spectrum brain imaging, and relates to a phase-controlled time-domain functional near-infrared spectrum system and a wearable device.

Background technique

Near-Infrared Spectroscopy (NIRS) is a non-invasive spectral analysis technology that is widely used in biomedicine, agriculture, food quality testing and other fields. Time-Domain Functional Near-Infrared Spectroscopy (TD-fNIRS), as a form of NIRS, uses the time-of-flight (TOF) measurement principle to detect oxygenated hemoglobin and deoxygenated hemoglobin in the human cerebral cortex. The concentration of hemoglobin reflects the neural activity information of the human brain.

Compared with obtaining the optical properties of the measured substance by measuring the intensity and wavelength of light based on frequency domain or continuous wave light sources, time-domain functional near-infrared spectroscopy technology is mainly used to measure the flight time of light in biological tissues and can provide more accurate information. High temporal and depth resolution.

However, the existing time domain system has low utilization rate of light sources and the detection area is not flexible. If the light source utilization rate is improved, that is, when multiple detectors are used to detect a light source at the same time, more serious light source crosstalk will occur. Most existing time domain systems use one detector to detect one light source. Not only is the light source utilization rate low, but also loss Information scattered by brain tissue in other areas. For the detection area, a fixed source-detector distance is generally used, which limits the planar spatial resolution of the system.

Therefore, it is necessary to provide a time-domain functional near-infrared spectroscopy system and wearable devices based on phase control to solve the limitations of the existing technology and meet the needs of practical applications.

Contents of the invention

In order to make up for the problems of low light source utilization and inflexible detection area in the existing technology, the present invention provides a time-domain functional near-infrared spectroscopy system and wearable device based on phase control, which utilizes the clever layout of the probe and the phase control technology of the light source. Solve the above defects of the existing technology.

Technical solutions

A time-domain functional near-infrared spectroscopy system based on phase control, which is different from most TD-fNIRS systems. The present invention inputs a pulse sequence with a number of pulses N, and sets up 7 light source points. The same pulse sequence is time-divided into four phases. Entering the 7 light source setting points, 42 detectors complete the time-sharing detection of the 7 light source points. Internal integrated devices using this system can be configured as wearable devices, including:

The phase-controlled time-domain functional near-infrared spectroscopy system includes a light source, a light modulation module, a time-domain delay module, a sensing probe, and a signal detection and processing module; the light source is used to provide near-infrared picosecond pulse light to target the brain. Cortical tissue is detected; the optical modulation module includes an optical switch for controlling the input of pulses, an optical attenuator for adjusting the power of the input light, and an optical coupler for coupling the input light into multiple sensing fibers; the time domain delay module includes at least An optical delay element used to separate multiple channels of sensing light in time sequence. The optical delay element allows light sources from different detection points to enter the cerebral cortex with a certain time difference, so that the light sources located at different positions on the cerebral cortex detect Information can be processed independently; the signal detection and processing module includes the reception and amplification of optical signals, counting single photons and generating histograms, and subsequent control circuits and processors to store and process data, and finally visualize brain neural activity.

The optical switch in the optical modulation module switches every other pulse sequence. Assume that the number of pulses in a single pulse sequence is N, the time interval between two pulses is P, and the number of phase controls is 4 phases. Then the optical switch turns on N×P After the time, turn off the 3N×P time and alternate in sequence to ensure that the number of pulses in each pulse sequence reaches the level of detecting brain neural activity and that the detection results of each pulse sequence do not interfere with each other.

The optical coupler in the optical modulation module is a 1×7 coupler, which divides multi-wavelength pulse light of two or more wavelengths into 7 channels and enters the sensing fiber.

The time domain module divides 7 channels of sensing light into four phases. Each phase is separated into the cerebral cortex sequentially according to the time difference of N×P. According to the arrangement position of the light source, the input sequence of the light source is sorted to complete the phase control of the light source.

The sensing probe adopts a hexagonal design, the light source is arranged in the center of the probe, and six detectors are equally spaced around the light source to complete the detection of the central light source.

The sensing probe takes advantage of the hexagonal angle, and each probe is closely arranged at very short intervals. The detectors of adjacent probes detect brain activity in the second and third plane areas of the central light source.

Different detection areas in the sensing probe have different numbers of detection channels. The first, second and third layer detection areas have 42, 24 and 36 detection channels respectively, and the entire system has a total of 102 detection channels.

The closely arranged hexagonal probe uses light source phase control. According to the arrangement position of the light source, the light source is coded. The upper left and lower right are 1, the lower left and upper right are 2, the center is 3, and the upper and lower are 4. According to the coding Performs 4-phase control.

The signal detection and processing module independently detects optical signals of different wavelengths in each channel. Each channel corresponds to a detector. Signals of different phases are separated from each other to complete the time-sharing detection of multiple light sources by the detector. After receiving and amplifying , visualize brain neural activity after counting, storage and processing.

The information acquisition method of the phase-controlled time-domain functional near-infrared spectroscopy system is to utilize the permeability of near-infrared light to human skin and the absorption characteristics of oxygenated hemoglobin and deoxygenated hemoglobin in the cerebral cortex in the near-infrared band. , using the photon time-of-flight measurement principle to detect the concentration of oxygenated hemoglobin and deoxygenated hemoglobin in the human cerebral cortex to reflect human brain neural activity information.

The wearable device is internally integrated with a time-domain functional near-infrared spectroscopy system based on phase control as described above.

beneficial effects

Compared with the existing technology, the phase-controlled time-domain functional near-infrared spectroscopy system disclosed by the present invention uses optical switches, delay lines and clever probe layout to complete the refined control of the light source and realize the integration of the light source and probe. Maximize utilization. The hexagonal probe design and close arrangement method achieve high-resolution planar detection, which can more accurately divide the brain's functions.

In addition, the phase-controlled time-domain functional near-infrared spectroscopy system disclosed by the present invention integrates the light source and detection module on one side of the probe through integrated circuit design and optical parameter calculation, which can realize device miniaturization and facilitate wearable measurement. Applied to various wearable devices such as VR.

Description of the drawings

Figure 1 is a schematic diagram of a phase-controlled time-domain functional near-infrared spectroscopy system and a wearable device provided by the present invention.

Figure 2 is a probe design scheme and a layered diagram of the detection area provided by the present invention.

Figure 3 shows the light source encoding and phase control scheme provided by the present invention.

Figure 4 is a four-phase input time domain diagram provided by the present invention.

Specific implementation methods

The present invention will now be further described with reference to the embodiments and drawings. Obviously, the described embodiments are only preferred embodiments of the present invention and do not limit the patent scope of the present invention. Based on the embodiments of the present invention, for those in the field, Other similar technical problems are included in the patent protection scope of the present invention.

In order to solve the shortcomings of the existing time domain system, such as low integration, low light source utilization, inflexible detection area and serious light source crosstalk, embodiments of the present invention disclose a time domain functional near-infrared spectroscopy system based on phase control. and wearable devices, as shown in Figure 1, mainly including

Light source 10 is used to provide near-infrared picosecond pulse light to detect cerebral cortex tissue;

The optical modulation module 20 includes an optical switch 21 for controlling the input of pulses, an optical attenuator 22 for adjusting the power of the input light, and an optical coupler 23 for coupling the input light into the multi-channel sensing optical fiber 40;

The time domain delay module 30 is used to separate multiple channels of sensing light in time sequence to ensure that the light sources at different detection points enter the cerebral cortex with a certain time difference, so that the information detected by the light sources located at different positions on the cerebral cortex can be processed independently. ;

The sensing probe 50 is used to couple the sensing light into the cerebral cortex 60 and fix the positions of the light source and detector;

The signal detection and processing module 70 includes the reception and amplification of optical signals, counting single photons and generating histograms, and subsequent storage and processing of data by control circuits and processors, and finally visualizing brain neural activity.

In order to make the above-mentioned objects, solutions and advantages of the present invention more obvious and easy to understand, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments:

As shown in Figure 1, the light source 10 emits pulsed light of <100ps at a repetition rate of MHz. The pulsed light contains two or more light wavelengths. Taking two as an example, the operating wavelengths are around 690nm and 830nm respectively.

Using the simultaneous detection of near-infrared light of two wavelengths, a linear equation system can be formed to measure the content of oxygenated hemoglobin and deoxygenated hemoglobin in the cerebral cortex and characterize the activity of neurons.

Furthermore, the near-infrared light of two wavelengths enters the light modulation module 20 at the same time according to the same pulse. Because the propagation and scattering of pulsed light in tissues will cause signal intensity attenuation and time delay, it is usually necessary to input multiple pulsed lights to detect activity information of the cerebral cortex. Therefore, in this embodiment, a pulse sequence is used as the sensing light, and a single pulse The number of pulses in the sequence ranges from tens to hundreds of pulses.

Here, the number of pulses in a single pulse sequence is N, the time interval between two pulses is P, and the number of phase controls is 4 phases.

In order to achieve the purpose of phase control, the optical switch 21 is turned on for N×P time to incident N optical pulses, that is, a pulse sequence is incident. The pulse sequence is divided into 7 pulses by the optical coupler 23 after adjusting the power by the optical attenuator 22 sequence into the sensing fiber. In addition, the switching time of the optical switch can be operated by an external control signal.

Further, seven identical pulse sequences generate different time delays after passing through the time domain delay module 30. Each light corresponds to a light source point on a hexagonal probe. The seven light sources are divided into four phases and are incident sequentially, that is, they are incident sequentially in four periods of time. , specifically as shown in Figure 4, there are intervals between the first phase pulse sequence and the second phase pulse sequence, between the second phase pulse sequence and the third phase pulse sequence, and between the third phase pulse sequence and the fourth phase pulse sequence. Both are N×P time. In this way, the incident optical signals at different time periods will be detected in a time-sharing manner, thereby reducing the crosstalk problem between each other during detection.

The time domain delay module specifically adopts the optical path delay method, that is, by introducing optical delay elements, such as delay lines, optical fibers, etc., to delay the propagation time of optical pulses, and by controlling the length and refractive index of optical elements or introducing the length of optical fibers to achieve delay and Control the delay time. Since four-phase delay is required, four delay lines or optical fibers with different parameters need to be set up. The two lights in the first item do not need to be processed, and the two lights in the second phase are delayed by N×P time based on the first phase. , one light of the third phase is delayed by N×P time based on the second phase, and the two lights of the fourth phase are delayed by N×P time based on the third phase. It is necessary to accurately set the delay elements on each path to achieve four-phase incidence of the light source.

In addition, in the embodiment, only seven probes are used as an example, and seven paths of light are incident, so the four-phase solution in this embodiment is optimal. If the material resources are sufficient, a seven-phase or other solution larger than four phases can be used. Achieve higher accuracy. It is worth mentioning that if the probes continue to be closely arranged around the seven probes in this embodiment, the phase control scheme needs to be re-planned. In short, four-phase control is only the preferred solution for this embodiment. The present invention is not limited to four phases. The phase control solution can be flexibly selected according to the probe layout and light source incident mode.

In order to enable the information of each pulse to be independently detected, it is necessary to ensure that the interval between pulses and the interval between pulse sequences is large enough, that is, the time interval between two pulses must be greater than the pulse width after broadening of a single pulse. Two-phase pulses The time interval between sequences should be greater than the overall pulse width after all the single-phase pulse sequences are broadened.

Generally, the repetition frequency of a laser diode or other laser is between tens of MHz and hundreds of MHz, so the time interval between two generated pulses is inherently larger than the pulse width after broadening of a single pulse, so in this embodiment, time is used The interval P is used to distinguish the two pulses before or after broadening. The time interval P is the reciprocal of the laser repetition frequency.

In special cases, when the repetition frequency of the laser is very high or the broadening effect is obvious, that is, when the time interval between two pulses is less than the broadened pulse width of a single pulse, each phase is processed as N× the broadened pulse width.

In fact, the original light source only fired one pulse sequence, but produced scattered light signals at four times, and the signal detection is uninterrupted, so the next pulse sequence should be received after all the information of the previous pulse sequence is received. Enter immediately. That is to say, the time interval between two pulse sequences successively driven by the original light source is greater than the overall time of the four-phase pulse sequence.

In the embodiment, the optical switch 21 is turned on for N×P time and then turned off for 3N×P time, alternating with this, then the time interval between the two pulse sequences actually driven by the original light source is 4N×P.

Further, seven lines of light enter the cerebral cortex 60 in four phases along the sensing optical fiber 40, and the sensing probe 50 is used for coupling in the middle.

Specifically, the sensing probe adopts a hexagonal probe design and close arrangement, as shown in Figure 2. For a hexagonal probe, the light source is arranged in the center of the probe, and six detectors are equally spaced around the light source. For multiple hexagonal probes, a close arrangement is used, with six hexagonal probes distributed around the central hexagonal probe.

In the embodiment, the distance between the light source and the detector of the hexagonal probe is 1cm, the distance between the detector and the corresponding side of the hexagon is 0.25cm, and the distance between the central hexagonal probe and the peripheral hexagonal probe is 0.5cm. As shown in Figure 2, the distance between the centermost light source and the six detectors numbered 1 is 1cm, the distance from the six detectors numbered 2 is 2cm, and the distance from the 12 detectors numbered 3 is In fact, these three layers of detectors are enough to achieve high-resolution two-dimensional plane detection. The intensity of the light signals detected by the 18 detectors on the next layer is also very weak and is generally not considered for use.

Among them, the six detectors of a single probe realize the response to the central light source and complete the detection of detection area 1, as shown in the inner line 1 in Figure 2. The response of the detectors of adjacent probes to the central light source can realize the detection of brain activity in the second plane detection area, such as line 2. From the analogy of line 1-line 2-line 3, it can be concluded that clever arrangement of detector positions can complete high-resolution planar detection.

It is thus obtained that the total number of channels of the TD-fNIRS system in this embodiment is 42+24+36. Specifically, the detection channel is shown in Figure 2. The detection channel 1 is the detector in this probe that completes the detection of the light source in this probe. There are 42 channels in total; the detection channel 2 is the detector on the second layer that completes the detection of the light source in the adjacent probe. Detection, this is also applicable to the 6 edge probes, a total of 24 channels; detection channel 3, that is, the detector on the 3rd layer completes the detection of the light source in the adjacent probe, is also applicable to the 6 edge probes, a total of 36 channels .

Therefore, although the phase-controlled time-domain functional near-infrared spectroscopy system disclosed by the present invention has only 42 detection lines, each detection line corresponding to a detector, it has a total of 102 channels, including the signals from different areas of the brain at the same time. High resolution activity information.

It is worth noting that the positions of these detectors, light sources and probes can be adjusted by themselves. When they are closer together, the spatial resolution and temporal resolution are higher, but the depth and penetration of the measurement are limited. When they are farther apart, the opposite will be true. .

In addition, because a detector needs to detect multiple light sources, that is, it must detect the light source at the center of the probe and the light sources of adjacent probes, so there is a crosstalk problem caused by multiple light sources.

To solve this problem, a light source phase control scheme is specifically adopted. As shown in Figure 3, the light source phase control scheme is coded according to the arrangement position of the light source. The upper left and lower right probes are 1, the lower left and upper right probes are 2, the centermost probe is 3, and the upper and lower probes are 4. Combined with the input time domain scheme in Figure 4, the light source is finely regulated through four-phase control to complete the light source phase control, ultimately maximizing the utilization of the probe and light source and achieving high spatial resolution. Compared with the existing technology, the source-detector distance is generally fixed, and the detection area is also relatively fixed, which limits the spatial resolution of its detection. However, the source-detector distance of this embodiment can be flexibly changed according to the probe settings, and the same The light source can be detected simultaneously by multiple probes in different detection areas, greatly improving its spatial resolution.

It can be found that detectors in the same phase do not detect multiple light sources at the same time, and detectors in different phases complete the detection of information with a very short time difference in the time domain. The change time of brain blood sample level is on the order of seconds, and the interval between two pulse sequences is on the order of microseconds. Therefore, multiple pulse sequences are used for intermittent incidence, and the phased incidence of a single pulse sequence is sufficient to reflect multiple information of the brain at the same time. This ensures that the implementation of the phase control scheme does not affect the time resolution of the detection system.

Then, the optical signals of all phases and channels enter the signal detection and processing module 70 through 42 identical detection lines. In the embodiment, an ordinary single photon detection system is used for detection. These optical signals carrying brain information are first detected by silicon photomultiplier tubes. Receive and amplify, and then count by a single photon counter. Use gated single photon counting to generate a time window and a histogram at the same time, and restore the measured light waveform through the histogram. The subsequent control circuit and processor store and process the data, evaluate the absorption and scattering characteristics of the cerebral cortex tissue, and finally visualize the brain neural activity. The number of time windows that can be divided in this module determines the depth resolution of the detection system. .

Specifically, the emitted light of one phase is emitted through 42 detection lines, and the scattering signals at 42 detector positions are recorded. The optical signal intensity of the detector in the fourth layer detection area is significantly smaller than other signals, and can be eliminated in subsequent processing. These signals, and the signals in the first three layers of detection areas are recorded and stored. Then the same is true for the outgoing light of the second phase, and the relevant signal is recorded and stored in the next new time period. After all four-phase signals are stored, the four-phase recording of the second pulse sequence begins, and so on. In the final processing, the four-phase information can be clearly distinguished according to time, and the signals in different detection areas can be clearly distinguished according to light intensity. The signals in the corresponding areas can be independently selected for processing and analysis to complete the detection of neural activity in different brain areas. .

The phase-controlled time-domain functional near-infrared spectroscopy system disclosed by the invention is a non-invasive spectrum analysis technology based on time-domain near-infrared spectroscopy technology. It uses the time-of-flight measurement principle to detect oxygenated hemoglobin and oxygen-containing hemoglobin in the human cerebral cortex. The concentration of deoxyhemoglobin reflects the neural activity information of the human brain.

The probe designed in the present invention integrates a light source and a detection module on one side of the probe through integrated circuit design and optical parameter calculation, so that the device can be miniaturized and used for wearable measurement.

The phase-controlled time-domain functional near-infrared spectroscopy system and wearable device disclosed in the present invention can achieve refined control of the light source using only optical switches and delay lines, thereby maximizing the utilization of the light source. The hexagonal probe design and tight arrangement achieve high-resolution planar detection and are perfectly adapted to the phase control scheme of the light source. The system is highly flexible and can independently select the required channels and brain areas to be observed. It can also detect multiple brain areas simultaneously to achieve more refined brain functional partitioning. Wearable devices using this system have high integration and high spatial resolution, and can be applied to larger areas of the human brain and more detailed physiological monitoring in medical diagnosis, as well as more comprehensive physiological status monitoring during military training and combat in military activities. .

Claims (12)

1. A time-domain functional near-infrared spectroscopy system based on phase control, which is characterized in that it includes a light source, a light modulation module, a time-domain delay module, a sensing probe, and a signal detection and processing module; The light source is used to provide near-infrared picosecond pulse light to detect cerebral cortex tissue; The optical modulation module includes an optical switch for controlling the input of pulses, an optical attenuator for adjusting the power of the input light, and an optical coupler for coupling the input light into multiple sensing fibers; The time domain delay module includes at least one optical delay element for temporally separating multiple sensing lights. The optical delay element allows light sources from different detection points to enter the cerebral cortex with a certain time difference, so that the light sources located on the cerebral cortex Information detected by light sources at different locations can be processed independently; The sensing probe is used to couple the sensing light into the cerebral cortex and fix the positions of the light source and detector; The signal detection and processing module includes the reception and amplification of optical signals, counting single photons and generating histograms, and subsequent control circuits and processors to store and process data, and finally visualize brain neural activity. 2. A time-domain functional near-infrared spectroscopy system based on phase control according to claim 1, characterized in that: the optical switch in the light modulation module switches every other pulse sequence, assuming a single pulse sequence. The number of medium pulses is N, the time interval between two pulses is P, and the number of phase controls is 4 phases. Then the optical switch is turned on for N×P time and then turned off for 3N×P time, alternating in sequence to ensure that the number of pulses in each pulse sequence reaches the detection level. The level of brain neural activity and the detection results of each pulse sequence do not interfere with each other. 3. A time-domain functional near-infrared spectroscopy system based on phase control according to claim 1, characterized in that: the optical coupler in the light modulation module is a 1×7 coupler, combining two or more The multi-wavelength pulsed light is divided into 7 channels and enters the sensing fiber. 4. A time-domain functional near-infrared spectroscopy system based on phase control according to claim 3, characterized in that: the time-domain module divides 7 channels of sensing light into four phases, and each phase is based on N×P The time difference is separated into the cerebral cortex in sequence, and the light source input sequence is sorted according to the arrangement position of the light source to complete the light source phase control. 5. A phase-controlled time-domain functional near-infrared spectroscopy system according to claim 1, characterized in that: the sensing probe adopts a hexagonal design, the light source is arranged in the center of the probe, and six detectors are equally spaced around it. Around the light source, complete the detection of the central light source. 6. A time-domain functional near-infrared spectroscopy system based on phase control according to claim 5, characterized in that: the sensing probes are provided with 7, and each probe is closely spaced at very short intervals by taking advantage of the hexagonal angle. Arrangement, that is, the six peripheral probes are closely arranged near the six sides of the central probe to complete the detection of the light source of the central probe by the detectors of the adjacent probes. 7. A phase-controlled time-domain functional near-infrared spectroscopy system according to claims 5 and 6, characterized in that: the sensing probe has four layers of detection areas, and a circle of detectors is closest to the central light source. It constitutes the first layer of detection area, and the circle of detectors among adjacent probes that is closest to the central light source forms the second layer of detection area, increasing by distance, and the other two circles of detectors respectively constitute the third and fourth layer of detection areas, using The first three layers of detection area detection. 8. A time-domain functional near-infrared spectroscopy system based on phase control according to claim 7, characterized in that: different detection areas in the sensing probe have different detection channel numbers, one, two and three. The layer detection areas have 42, 24 and 36 detection channels respectively, and the entire system has a total of 102 detection channels. 9. A time-domain functional near-infrared spectroscopy system based on phase control according to claims 4 and 6, characterized in that: the closely arranged hexagonal probe adopts light source phase control, and according to the arrangement position of the light source, Code the light source, the upper left and lower right are 1, the lower left and upper right are 2, the center is 3, the upper and lower are 4, and the 4-phase control is performed according to the encoding. 10. A time-domain functional near-infrared spectroscopy system based on phase control according to claim 1, characterized in that: the signal detection and processing module independently detects optical signals of different wavelengths in each channel, and each channel Corresponding to a detector, signals of different phases are separated from each other, completing the detector's time-sharing detection of multiple light sources. After receiving, amplifying, counting, storing and processing, the brain's neural activity is visualized. 11. Apply the time-domain functional near-infrared spectroscopy system based on phase control according to any one of claims 1-10, and its information acquisition method is: utilizing the permeability of near-infrared light to human skin and the oxygen content in the cerebral cortex The absorption characteristics of hemoglobin and deoxygenated hemoglobin in the near-infrared band are used to detect the concentration of oxygenated hemoglobin and deoxygenated hemoglobin in the human cerebral cortex through the principle of photon flight time measurement to reflect the information on human brain nerve activity. 12. A wearable device, characterized in that the phase-controlled time-domain functional near-infrared spectroscopy system used in any one of claims 1 to 10 is internally integrated.