Single photon counting circuit and detection device based on time-domain near infrared spectrum

Abstract

The application discloses a kind of single-photon counting circuit and detection device based on time-domain near infrared spectrum, circuit includes: pulse light module, for generating near infrared light to cerebral cortex tissue is irradiated;Light signal receiving amplification module, for receiving after the light signal of diffusion absorption of the cerebral cortex tissue, after amplification conversion into electrical signal;Single-photon counting module, including counting window generation unit and D flip-flop one, for in the counting window of generation, through D flip-flop one output electrical signal's counting waveform;Control module, including counter, for receiving electrical signal's counting waveform, and according to counting waveform carries out counting, generates histogram.The single-photon counting circuit of time-domain near infrared brain function imaging disclosed in the application is low in cost, simple in structure, high in integration, and can effectively solve the shortcomings of existing timing instrument, such as complexity and high cost, and the limitation brought by conversion time.

Description

Technical Field

[0001] The present invention relates to the technical field of near-infrared spectroscopy brain imaging, and more particularly to a single-photon counting circuit and detection device based on time-domain near-infrared spectroscopy. Background Art

[0002] Near-infrared functional brain imaging, also known as near-infrared spectroscopy, is a powerful technique for obtaining non-invasive in vivo measurements of tissue composition and structure. It uses the low absorption coefficient of near-infrared light in biological tissue to determine the concentrations of oxygenated and deoxygenated hemoglobin, thereby revealing information about human tissue.

[0003] Measurements are generally performed based on continuous wave (CW), frequency domain (FD), and time domain (TD) near-infrared spectroscopy. Since time domain near-infrared spectroscopy (TD) provides more information and data during measurement, it is more widely used.

[0004] However, existing time-domain systems are not highly integrated, are bulky, and lack portability. Furthermore, the timing instruments used to provide picosecond resolution for single-photon counting in traditional near-infrared brain imaging systems are typically complex and expensive, and the conversion time (i.e., the time required to calculate the arrival time of a single event) is non-negligible, which limits the maximum acquisition rate of the entire detection system.

[0005] Therefore, how to provide a low-cost and highly integrated single-photon counting circuit and detection device for time-domain near-infrared brain functional imaging is an urgent problem that needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides a single photon counting circuit and detection device based on time-domain near-infrared spectroscopy to solve the above-mentioned defects in the prior art.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] In one aspect, the present application discloses a single photon counting circuit based on time-domain near-infrared spectroscopy, comprising:

[0009] A pulse light emitting module is used to generate near-infrared light to irradiate the cerebral cortex tissue;

[0010] an optical signal receiving and amplifying module, configured to receive the optical signal diffused and absorbed by the cerebral cortex tissue, amplify the optical signal, and convert it into an electrical signal;

[0011] A single-photon counting module includes a counting window generating unit and a D-type flip-flop 1, wherein the counting window generating unit is used to generate a counting window according to a signal synchronized with the near-infrared light frequency, and the D-type flip-flop 1 is used to output a counting waveform of the number of photons in the electrical signal within the counting window;

[0012] The control module includes a counter for receiving a counting waveform of the number of photons in the electrical signal, and performing counting according to the counting waveform to generate a histogram.

[0013] Preferably, the pulse light emitting module includes a high-frequency pulse transmitting circuit, a VCESL driver and a VCESL connected in sequence. The high-frequency pulse generated by the high-frequency pulse transmitting circuit generates periodic near-infrared light through the VCESL driver and the VCESL.

[0014] Preferably, the optical signal receiving and amplifying module adopts a Sipm silicon photomultiplier tube to receive and detect the optical signal after being diffused and absorbed by the cerebral cortex tissue.

[0015] Preferably, the counting window generating unit is connected to the D end of the D trigger one, the electrical signal is connected to the CK end of the D trigger one as a clock signal, the Q end of the D trigger one is used to output a counting waveform of the number of photons in the electrical signal, and is reversely connected to the R end of the D trigger one through a fixed delay chip.

[0016] Preferably, the delay time of the fixed delay chip is 4ns.

[0017] Preferably, the control module further includes a control circuit for providing the counting window generating unit with a signal synchronized with the near-infrared light frequency.

[0018] Preferably, the counting window generating unit includes a programmable delay chip 1, a programmable delay chip 2 and a D trigger 2. The programmable delay chip 1 receives a signal synchronized with the near-infrared light frequency, and after a delay of T, inputs the signal to the CK end of the D trigger. The programmable delay chip 2 receives a signal synchronized with the near-infrared light frequency, and after a delay of T+t, inputs the signal to the R end of the D trigger 2. The Q end of the D trigger 2 outputs a waveform signal containing a counting window, and the step size of the counting window is t.

[0019] Preferably, the triggering mode of the D trigger 1 and the D trigger 2 is edge triggering.

[0020] On the other hand, the present application also discloses a detection device based on time-domain near-infrared spectroscopy, which mainly includes a pulse light-emitting module and an optical signal processing module. The pulse light-emitting module is used to generate near-infrared light to irradiate cerebral cortical tissue;

[0021] The optical signal processing module uses any of the single photon counting circuits based on time-domain near-infrared spectroscopy as described above, and is used to output a histogram of the number of photons in a counting window based on the optical signal after diffusion and absorption by cerebral cortical tissue.

[0022] Preferably, the device further comprises a waveform restoration evaluation module for restoring the waveform signal after diffusion and absorption of the brain cortex tissue according to the histogram, and evaluating the absorption and scattering performance of the brain cortex tissue according to the waveform signal.

[0023] According to the technical solution, compared with the prior art, the single photon counting circuit for time-domain near-infrared brain function imaging disclosed by the application does not need to use complex instruments, has low cost, simple structure and high integration, uses gated single photon counting, and can effectively improve the acquisition rate. The histogram is used to represent the probability distribution function of photons in time, the detection light waveform is restored through the histogram, the absorption and scattering characteristics of the brain cortex tissue can be evaluated from the pulse peak of the waveform, time, area and width, etc.

[0024] In addition, the duration can be programmed to be as low as several nanoseconds or hundreds of picoseconds in synchronization with the excitation laser, so as to ensure that the waveform of the emitted pulsed light after passing through the tissue reaches the detection point, and ensure the accuracy of the restored waveform.

[0025] On the other hand, the detection device based on time-domain near-infrared spectrum disclosed by the application can be provided in a wearable structure, and has small volume and is convenient to carry. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0027] Figure 1 The single photon counting circuit diagram provided by the application;

[0028] Figure 2 The pin waveform signal diagram of the D flip-flop one provided by the application;

[0029] Figure 3 The histogram of the single counting window output by the control module provided by the application;

[0030] Figure 4 The histogram of the multiple counting windows output by the control module provided by the application;

[0031] Figure 5 The pin waveform signal diagram of the D flip-flop two provided by the application. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] First, to address the shortcomings of single-photon counting in traditional near-infrared brain imaging systems, which require complex and expensive timing instruments to provide picosecond resolution and whose conversion time limits the maximum acquisition rate of the entire detection system, the present invention discloses a single-photon counting circuit based on time-domain near-infrared spectroscopy, which mainly includes:

[0034] A pulse light emitting module is used to generate near-infrared light to irradiate the cerebral cortex tissue;

[0035] The optical signal receiving and amplifying module includes a transimpedance amplifier and a comparator, which is used to receive the optical signal after diffusion and absorption by the cerebral cortex tissue, amplify it and convert it into an electrical signal;

[0036] The single-photon counting module includes a counting window generating unit and a D-type flip-flop. The counting window generating unit is used to generate a counting window according to a signal synchronized with the near-infrared light frequency. The D-type flip-flop is used to output a counting waveform of the number of photons in the electrical signal within the counting window.

[0037] The control module includes a counter for receiving a counting waveform of the electrical signal, and performing counting according to the counting waveform to generate a histogram.

[0038] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] First, if Figure 1 As shown, the pulse light emitting module includes a high-frequency pulse transmitting circuit, a VCESL driver and a VCESL connected in sequence. The high-frequency pulse generated by the high-frequency pulse transmitting circuit generates periodic near-infrared light through the VCESL driver and the VCESL.

[0040] In one embodiment, the pulse light emitting module can generate near-infrared light with a frequency of more than 155 MHz.

[0041] The generated near-infrared light is irradiated on the cerebral cortex tissue, and then absorbed and diffused by the cerebral cortex tissue and received by the optical signal receiving and amplifying module.

[0042] In one embodiment, a novel photodetector device—a silicon photomultiplier (SIPM) tube—is used to receive light signals. The signals are then amplified by a transimpedance amplifier and converted into a measurable pulse signal by a comparator. Specifically, the comparator shapes the pulse signal amplified by the amplifier to produce the differential electrical signal PHOTONIN required by a D-type flip-flop. Specifically, the received light signal is converted using a reference voltage in the comparator as a threshold. The comparator's reference voltage must be slightly greater than the voltage generated by dark current, which is the current drawn by the photodetector when no light is present.

[0043] Furthermore, the converted electrical signal enters the single-photon counting module, which counts the number of photons in the electrical signal within a set counting window. The present invention uses gated single-photon counting technology to ignore photons outside the window and count within a well-defined counting window, which can effectively improve the acquisition rate and reduce costs.

[0044] Specifically includes a counting window generating unit and a D flip-flop.

[0045] The counting window generation unit is connected to the D terminal of D flip-flop 1, and the electrical signal is connected to the CK terminal of D flip-flop 1 as a clock signal. The Q terminal of D flip-flop 1 is used to output the counting waveform of the electrical signal and is reversely connected to the R terminal of D flip-flop 1 through a fixed delay chip. D flip-flop 1 uses an edge-triggered triggering mode; in one embodiment, the fixed delay is 4ns.

[0046] In the counting window, as long as the electrical signal changes from low to high, the D flip-flop will output a high level 1, indicating that a photon has arrived at the SIPM. The output passes through the fixed delay chip and reaches the R terminal of the D flip-flop, causing the output to be reset to 0 and wait for the next count.

[0047] In one embodiment, the D flip-flop is rising edge triggered, that is, when the clk rises, the D flip-flop is triggered, and the output waveform signal at the Q end is as follows: Figure 2 shown.

[0048] Then, the counting waveform signal passes through the counter in the control module to be counted and a histogram is generated. Figure 3 By restoring the detected light waveform using a histogram, the absorption and scattering characteristics of the cerebral cortex tissue can be evaluated based on the pulse peak of the waveform and its time, area, and width.

[0049] Furthermore, by changing the adjustable delay T, another counting window is obtained. After multiple counting and multiple modulations of T, the following is obtained: Figure 4 The histogram shown.

[0050] Adjusting T changes the timing of the counting window relative to the pulsed light emission, obtaining detection data at the same location at different times relative to the pulsed light emission to restore the final waveform. Specifically, T is adjusted based on the optical path lengths of the emission and reception.

[0051] It's important to note that each window must be counted several times, for example, 100,000 times at a frequency of 40 trillion times per second. However, the pulses are very narrow. After passing through brain tissue and skull, most of them are absorbed. Photons are scattered, and a 100-ps incident pulse will be stretched to a few nanoseconds by the time it is received. Therefore, the probability of detecting a pulse in each window is less than 1. In other words, the probability of each counting window outputting a high level (detecting a photon) is much less than 1. This principle can be used to determine whether the system is operating properly.

[0052] In addition, the present invention can set multiple counting windows in the circuit, thereby reducing the conversion time by increasing the circuit scale.

[0053] At the same time, the control module also includes a control circuit for providing a SYNC signal synchronized with the near-infrared light frequency to the counting window generating unit to ensure that the waveform of the emitted pulse light reaching the detection point after passing through the tissue is consistent, thereby ensuring the accuracy of the restored waveform.

[0054] Specifically, the counting window generating unit includes a programmable delay chip 1, a programmable delay chip 2 and a D trigger 2. The programmable delay chip 1 receives the SYNC signal with a delay of T and inputs it to the CK end of the D trigger 2. The programmable delay chip 2 receives the SYNC signal with a delay of T+t and inputs it to the R end of the D trigger 2. The Q end of the D trigger 2 outputs a waveform signal containing the counting window, that is, the counting window is t.

[0055] In one embodiment, the D terminal is always set to a high level, and its trigger mode is rising edge trigger. At this time, the output waveform signal of the Q terminal is as follows: Figure 5 shown.

[0056] That is to say, the control module gives a SYNC signal synchronized with the laser pulse, which is connected to the CLK port of the trigger after an adjustable delay T. The D trigger is triggered by the rising edge. Because the D port has been set to high level 1, the trigger starts to output a high level. Because the other branch of SYNC enters the R port of the trigger after an adjustable delay T+t, the D trigger is set to 0. The time difference t is the counting window.

[0057] This invention uses a time delay based on a signal consistent with the near-infrared light frequency generated by the pulse emission module. This facilitates statistical analysis of the time distribution of photon arrival, thereby measuring the absorption and scattering characteristics of brain tissue based on the principle that absorption causes a decrease in received light intensity, while scattering causes pulse broadening. Furthermore, the use of a histogram further clearly demonstrates the temporal distribution characteristics. Furthermore, based on this, the present application can flexibly adjust the circuit scale and cost by adjusting the serial port width.

[0058] In one embodiment, the single photon counting circuit further includes a power supply module for providing required voltages to other modules in the circuit.

[0059] The present invention uses gated single-photon counting, which is synchronized with the excitation laser, and the duration can be programmed as low as a few nanoseconds or hundreds of picoseconds. At the same time, by placing the counting window at an appropriate delay position relative to the waveform to be collected, various curve parameters can be extracted. For example, the light intensity curve of pulsed near-infrared light at the same location on human skin at different times after passing through human tissue. When the delay T is adjusted and the counting window is changed relative to the time after the pulse light is emitted, a combination of multiple counting windows with different delays can restore the light intensity curve.

[0060] Furthermore, the single photon counting circuit for time-domain near-infrared brain functional imaging disclosed in the present invention has low cost, simple structure, and high integration, effectively solving the shortcomings of the timing instruments in the prior art that are complex and expensive.

[0061] On the other hand, an embodiment of the present invention also discloses a wearable near-infrared brain imaging detection device. The device is based on near-infrared spectroscopy technology and is a non-invasive solvent characterization and monitoring technology. It retrieves the concentration of oxygenated hemoglobin and deoxygenated hemoglobin by taking advantage of the low absorption coefficient of near-infrared spectral light exhibited by biological tissue, thereby reflecting human tissue information.

[0062] The device can be used for brain function detection and can also be used for detection of other parts of the body. It specifically includes a pulse light emitting module and an optical signal processing module. The pulse light emitting module and the optical signal processing module apply any of the single photon counting circuits based on time-domain near-infrared spectroscopy as described above.

[0063] Specifically, the pulse light emitting module is used to generate near-infrared light to irradiate the cerebral cortex tissue;

[0064] The optical signal processing module is used to output a histogram of the number of photons in the counting window according to the optical signal after diffusion and absorption by the cerebral cortex tissue.

[0065] The near-infrared brain imaging device disclosed in this invention can be configured as a helmet. However, due to the extremely short pulses, direct ADC acquisition requires a very high data rate and extremely high circuit costs, making it impractical for wearable devices. However, this invention utilizes a compact SIPM, VCSE, and PCB circuits, eliminating the need for larger, more complex instruments. This allows for a compact, wearable near-infrared brain imaging device without increasing costs. Furthermore, the use of a histogram distribution method reduces circuit size and cost.

[0066] In addition, the detection device of the present invention also includes a waveform restoration evaluation module, which is used to restore the waveform signal after diffusion and absorption by the cerebral cortex tissue according to the histogram, and evaluate the absorption and scattering properties of the cerebral cortex tissue based on the waveform signal.

[0067] The wearable brain imaging detection device based on a single-photon counting circuit for time-domain near-infrared brain functional imaging disclosed in the present invention is compact and easy to carry, and can effectively overcome the problems of large size, low integration and inconvenient wear of downstream near-infrared brain imaging detection systems. The device uses a histogram to represent the probability distribution function of photons in time, and restores the detection light waveform through the histogram, so that the absorption and scattering characteristics of cerebral cortical tissue can be evaluated from aspects such as the pulse peak of the waveform and its time, area and width.

[0068] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0069] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A single photon counting circuit based on time-domain near-infrared spectroscopy, characterized in that: include: A pulse light emitting module is used to generate near-infrared light to irradiate the cerebral cortex tissue; an optical signal receiving and amplifying module, configured to receive the optical signal diffused and absorbed by the cerebral cortex tissue, amplify the optical signal, and convert it into an electrical signal; A single-photon counting module includes a counting window generating unit and a D-type flip-flop 1, wherein the counting window generating unit is used to generate a counting window according to a signal synchronized with the near-infrared light frequency, and the D-type flip-flop 1 is used to output a counting waveform of the number of photons in the electrical signal within the counting window; The counting window generating unit is connected to the D terminal of the D flip-flop 1, the electrical signal is connected to the CK terminal of the D flip-flop 1 as a clock signal, the Q terminal of the D flip-flop 1 is used to output a counting waveform of the number of photons in the electrical signal, and is reversely connected to the R terminal of the D flip-flop 1 through a fixed delay chip; The counting window generating unit includes a programmable delay chip 1, a programmable delay chip 2 and a D flip-flop 2, wherein the programmable delay chip 1 receives a signal synchronized with the near-infrared light frequency, delays the signal to the CK terminal of the D flip-flop 2 after a delay of T, and the programmable delay chip 2 receives a signal synchronized with the near-infrared light frequency, delays the signal to the R terminal of the D flip-flop 2 after a delay of T+t, and the Q terminal of the D flip-flop 2 outputs a waveform signal containing a counting window, and the step size of the counting window is t; The control module includes a counter for receiving a counting waveform of the number of photons in the electrical signal, and performing counting according to the counting waveform to generate a histogram.

2. The single photon counting circuit based on time-domain near-infrared spectroscopy according to claim 1, characterized in that: The pulse light emitting module includes a high-frequency pulse transmitting circuit, a VCESL driver and a VCESL connected in sequence. The high-frequency pulse generated by the high-frequency pulse transmitting circuit generates periodic near-infrared light through the VCESL driver and the VCESL.

3. The single photon counting circuit based on time-domain near-infrared spectroscopy according to claim 1, characterized in that: The optical signal receiving and amplifying module adopts a Sipm silicon photomultiplier tube to receive and detect the optical signal after being diffused and absorbed by the cerebral cortex tissue.

4. The single photon counting circuit based on time-domain near-infrared spectroscopy according to claim 1, characterized in that: The delay time of the fixed delay chip is 4ns.

5. The single photon counting circuit based on time-domain near-infrared spectroscopy according to claim 1, characterized in that: The control module further includes a control circuit for providing the counting window generating unit with a signal synchronized with the near-infrared light frequency.

6. The single photon counting circuit based on time-domain near-infrared spectroscopy according to claim 5, characterized in that: The triggering mode of the D trigger 1 and the D trigger 2 is edge triggering.

7. A detection device based on time-domain near-infrared spectroscopy, characterized in that: A single photon counting circuit based on time-domain near-infrared spectroscopy according to any one of claims 1 to 6 is applied, wherein the detection device includes a pulse light emitting module and an optical signal processing module. The pulse light emitting module is used to generate near-infrared light to irradiate the cerebral cortex tissue; The optical signal processing module is used to output a histogram of the number of photons in a counting window according to the optical signal after diffusion and absorption by the cerebral cortex tissue.

8. The detection device based on time-domain near-infrared spectroscopy according to claim 7, characterized in that: It also includes a waveform restoration and evaluation module, which is used to restore the waveform signal after diffusion and absorption by the cerebral cortex tissue according to the histogram, and evaluate the absorption and scattering properties of the cerebral cortex tissue according to the waveform signal.

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