Multi-channel fNIRS signal acquisition system based on time domain interference modulation

Abstract

The invention provides a multichannel fNIRS signal acquisition system based on time domain interference modulation, which relates to the technical field of data acquisition and comprises a processor and a plurality of signal acquisition modules, the signal acquisition module comprises a detector, a first light source and a second light source; the detector, the first light source and the second light source are sequentially arranged on the same straight line; performing interference modulation on a first modulation optical carrier signal emitted by the first light source and a second modulation optical carrier signal emitted by the second light source at a position to be measured to obtain a time domain interference signal; the time domain interference signal is irradiated to a to-be-detected substance in a to-be-detected position, diffused and then received by a detector, and an fNIRS signal is obtained; and the processor demodulates the fNI RS signal to obtain a blood oxygen signal. Time domain interference modulation is realized through double light sources, artifact signals and fNIRS signals can be distinguished, artifact suppression in the acquisition process is realized, and 1 / f noise in the signals can be eliminated.

Description

Technical Field

[0001] The present invention relates to the technical field of data acquisition, and in particular to a multi-channel fNIRS signal acquisition system based on time domain interferometric modulation. Background Art

[0002] The acquisition of fNIRS needs to be based on at least one set of light sources and light detectors containing two different wavelengths, and reflects neural activity by measuring the changes in the properties of photons after diffusion in the tissue. In a typical detection structure, near-infrared photons will first pass through the artifact area of ​​non-neural activity before modulation of neural activity-related signals can be achieved. Since the light intensity will decay with the increase of the diffusion path, the blood oxygen signal generated by the artifact will account for the largest proportion after demodulation. Finally, there will be strong non-neural activity artifacts in the collected blood oxygen signal, which will affect the measurement effect.

[0003] To address the above problems, a common solution is to estimate the artifact components and suppress the estimated artifact components from the acquired signal to achieve noise filtering. However, there are some problems with the current solution. First, since the generation of artifacts is accidental and related to physiological activities, it is difficult to accurately estimate the artifact components and cannot guarantee complete filtering of artifact signals. Secondly, the separation process of the traditional solution needs to rely on statistical analysis methods and estimate the artifact characteristics from the trend of the time series, which cannot be processed in real time.

[0004] On the other hand, since the location of the artifact during detection is different from the target signal, the introduction of artifacts can be avoided by distinguishing and extracting signals at different scales in space. However, photon diffusion is continuous in space, and the introduction of artifacts cannot be simply avoided without invasiveness.

[0005] At the same time, due to the inherent characteristics of the detector transistor, flicker noise, also known as 1 / f noise, naturally exists in the low-frequency passband. Therefore, flicker noise often exists in the acquired functional near-infrared spectroscopy (fNRIS) signal, such as Figure 3 As shown in Figure 1, the density distribution of flicker noise is inversely proportional to the frequency, and is mainly composed of low-frequency narrowband noise below 100 Hz. In addition, the probability distribution of flicker noise is the result of the superposition of multiple noise distributions. In order to remove flicker noise, the commonly used method in the prior art is to improve the flicker noise density of the device itself, but this makes the detector expensive. Summary of the invention

[0006] The purpose of the present invention is to provide a multi-channel fNIRS signal acquisition system based on time domain interferometry modulation. By realizing time domain interferometry modulation through dual light sources, artifact signals can be distinguished from fNIRS signals, artifacts can be suppressed during the acquisition process, and 1 / f noise in the signal can be eliminated.

[0007] A multi-channel fNIRS signal acquisition system based on time domain interferometric modulation, comprising: a processor and a plurality of signal acquisition modules; the number of the signal acquisition modules is the same as the number of channels;

[0008] The signal acquisition module includes a detector, a first light source and a second light source;

[0009] The detector, the first light source and the second light source are sequentially arranged on the same straight line; a perpendicular line is drawn from the position to be measured to the straight line, and the intersection of the perpendicular line and the straight line is the center point between the detector and the first light source; a first modulated optical carrier signal emitted by the first light source and a second modulated optical carrier signal emitted by the second light source are interferometrically modulated at the position to be measured to obtain a time domain interference signal;

[0010] The first modulated optical carrier signal includes a first wavelength modulated optical carrier signal and a second wavelength modulated optical carrier signal, the second modulated optical carrier signal includes a third wavelength modulated optical carrier signal and a fourth wavelength modulated optical carrier signal, and the time domain interference signal includes a first wavelength time domain interference signal and a second wavelength time domain interference signal;

[0011] The first wavelength modulated optical carrier signal and the third wavelength modulated optical carrier signal have the same wavelength, and the first wavelength modulated optical carrier signal and the third wavelength modulated optical carrier signal are interferometrically modulated at a position to be measured to obtain the first wavelength time domain interference signal;

[0012] The second wavelength modulated optical carrier signal and the fourth wavelength modulated optical carrier signal have the same wavelength, and the second wavelength modulated optical carrier signal and the fourth wavelength modulated optical carrier signal are interferometrically modulated at a position to be measured to obtain the second wavelength time domain interference signal;

[0013] Let i=1, i∈K, K is the number of signal acquisition modules;

[0014] The controller controls the i-th signal acquisition module to generate the first wavelength time domain interference signal and the second wavelength time domain interference signal;

[0015] The i-th time domain interference signal of the first wavelength is irradiated to the material to be detected in the position to be detected, and then diffuses and is received by the detector, so as to obtain a first wavelength fNIRS signal; the i-th time domain interference signal of the second wavelength is irradiated to the material to be detected in the position to be detected, and then diffuses and is received by the detector, so as to obtain a second wavelength fNIRS signal;

[0016] The processor performs envelope center demodulation on the first wavelength fNIRS signal to obtain an initial oxygenated hemoglobin signal, and the processor performs envelope center demodulation on the second wavelength fNIRS signal to obtain an initial deoxygenated hemoglobin signal;

[0017] The processor performs envelope center demodulation on the initial oxygenated hemoglobin signal to obtain an oxygenated hemoglobin signal, and the processor performs envelope center demodulation on the initial deoxygenated hemoglobin signal to obtain a deoxygenated hemoglobin signal;

[0018] The processor judges i, and if i<K, it sets i=i+1 and returns to "the controller controls the i-th signal acquisition module to generate the first wavelength time domain interference signal and the second wavelength time domain interference signal", and if i≥K, K oxygenated hemoglobin signals and K deoxygenated hemoglobin signals are obtained.

[0019] Optionally, expressions of the first modulated optical carrier signal and the second modulated optical carrier signal are:

[0020]

[0021] Where: E 1 (t) is the first modulated optical carrier signal, E 2 (t) is the second modulated optical carrier signal, a is the amplitude of the first modulated optical carrier signal, b is the amplitude of the second modulated optical carrier signal, N 1 is the DC component of the first modulated optical carrier signal, N 2 is the DC component of the second modulated optical carrier signal, f 1 is the frequency of the first modulated optical carrier signal, f 2 is the frequency of the second modulated optical carrier signal, and t is time.

[0022] Optionally, the expression of the time domain interference signal is:

[0023]

[0024] Where: E tot is the time domain interference signal.

[0025] Optionally, the detection depth of the first wavelength modulated optical carrier signal is greater than the vertical distance between the position to be measured and the straight line, and the detection depth of the second wavelength modulated optical carrier signal is greater than the vertical distance between the position to be measured and the straight line.

[0026] Optionally, the detection depth expression of the first wavelength modulated optical carrier signal is:

[0027]

[0028] Where: Z max is the detection depth of the first wavelength modulated optical carrier signal, and d is the distance between the first light source and the detector.

[0029] Optionally, the expression of the first wavelength fNIRS signal is:

[0030]

[0031] Where: S(t) is the first wavelength fNIRS signal, ρ 1 (t) is the initial oxygenated hemoglobin signal;

[0032] Optionally, the initial oxygenated hemoglobin signal expression is:

[0033]

[0034] Where: 2 (t) is the oxygenated hemoglobin signal;

[0035] Optionally, the oxygenated hemoglobin signal is:

[0036]

[0037] Where: c is the amplitude of the oxygenated hemoglobin signal, A(t) is the AC component of the oxygenated hemoglobin signal, N 3 is the DC component of the oxygenated hemoglobin signal.

[0038] Optionally, the processor obtains an oxygenated blood oxygen value according to the oxygenated hemoglobin signal, and the processor obtains a deoxygenated blood oxygen value according to the deoxyhemoglobin signal;

[0039] Optionally, the oxygen-containing blood oxygen value expression is:

[0040]

[0041] Where: 2 (t) is the oxygenated hemoglobin signal, and X(t) is the oxygenated blood oxygen value.

[0042] The effects of the present invention are as follows:

[0043] The multi-channel fNIRS signal acquisition system based on time domain interferometric modulation in the present invention extracts the blood oxygen component of the spatial position of the target signal based on the position difference between the artifact generation and the target signal and utilizes the time domain interferometric carrier generated by the overlapping position of the photon diffusion path to filter out the artifact signal.

[0044] The multi-channel fNIRS signal acquisition system based on time domain interferometric modulation of the present invention can filter out artifact signals without estimating artifact features and statistical classification.

[0045] A multi-channel fNIRS signal acquisition system based on time domain interferometric modulation is invented. The original blood oxygen signal is modulated by modulating the optical carrier signal so that the passband of the original blood oxygen signal is shifted, thereby migrating the low-frequency original blood oxygen signal to a high bandwidth and removing the 1 / f noise in the original blood oxygen signal.

[0046] The multi-channel fNIRS signal acquisition system based on time domain interferometric modulation of the present invention avoids the influence of carrier oscillation when light source is switched by central sampling during time-sharing modulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a principle diagram of the time domain interferometric modulation of the present invention;

[0048] Figure 2 Schematic diagram of the frequency band migration of the original blood oxygen signal of the present invention;

[0049] Figure 3 Schematic diagram of flicker noise in functional near-infrared spectroscopy. DETAILED DESCRIPTION

[0050] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0051] Figure 1 FIG. 1 is a schematic diagram of the time domain interferometric modulation of the present invention. Figure 1 As shown, the present invention provides a multi-channel fNIRS signal acquisition system based on time domain interferometric modulation, which includes: a processor and a plurality of signal acquisition modules; the number of the signal acquisition modules is the same as the number of channels.

[0052] The signal acquisition module includes a detector, a first light source and a second light source.

[0053] The detector, the first light source and the second light source are arranged in sequence on the same straight line; a perpendicular line is drawn from the position to be measured to the straight line, and the intersection of the perpendicular line and the straight line is the center point between the detector and the first light source; a first modulated optical carrier signal emitted by the first light source and a second modulated optical carrier signal emitted by the second light source are interferometrically modulated at the position to be measured to obtain a time domain interference signal.

[0054] The time domain interference signal modulates the original blood oxygen signal, so that the frequency band of the original blood oxygen signal is migrated, thereby migrating the low-frequency original blood oxygen signal to a high bandwidth and eliminating the 1 / f noise of the original blood oxygen signal. Figure 2 shown.

[0055] Specifically, the expressions of the first modulated optical carrier signal and the second modulated optical carrier signal are:

[0056]

[0057] Where: E 1 (t) is the first modulated optical carrier signal, E 2 (t) is the second modulated optical carrier signal, a is the amplitude of the first modulated optical carrier signal, b is the amplitude of the second modulated optical carrier signal, N 1 is the DC component of the first modulated optical carrier signal, N 2 is the DC component of the second modulated optical carrier signal, f 1 is the frequency of the first modulated optical carrier signal, f 2 is the frequency of the second modulated optical carrier signal, and t is time.

[0058] The expression of the time domain interference signal is:

[0059]

[0060] Where: E tot is the time domain interference signal.

[0061] The first modulated optical carrier signal includes a first wavelength modulated optical carrier signal and a second wavelength modulated optical carrier signal, the second modulated optical carrier signal includes a third wavelength modulated optical carrier signal and a fourth wavelength modulated optical carrier signal, and the time domain interference signal includes a first wavelength time domain interference signal and a second wavelength time domain interference signal. The first wavelength time domain interference signal and the second wavelength time domain interference signal can refer to the time domain interference signal. The detection depth of the first wavelength modulated optical carrier signal is greater than the vertical distance between the position to be measured and the straight line, and the detection depth of the second wavelength modulated optical carrier signal is greater than the vertical distance between the position to be measured and the straight line.

[0062] The detection depth expression of the first wavelength modulated optical carrier signal is:

[0063]

[0064] Where: Z max is the detection depth of the first wavelength modulated optical carrier signal, and d is the distance between the first light source and the detector.

[0065] The detection depth of the second wavelength modulated optical carrier signal refers to the detection depth of the first wavelength modulated optical carrier signal.

[0066] The first wavelength modulated optical carrier signal and the third wavelength modulated optical carrier signal have the same wavelength. The first wavelength modulated optical carrier signal and the third wavelength modulated optical carrier signal are interferometrically modulated at the position to be measured to obtain a first wavelength time domain interference signal.

[0067] The second wavelength modulated optical carrier signal and the fourth wavelength modulated optical carrier signal have the same wavelength, and the second wavelength modulated optical carrier signal and the fourth wavelength modulated optical carrier signal are interferometrically modulated at the position to be measured to obtain a second wavelength time domain interference signal.

[0068] Let i=1, i∈K, K is the number of signal acquisition modules.

[0069] The controller controls the i-th signal acquisition module to generate a first wavelength time domain interference signal and a second wavelength time domain interference signal.

[0070] The i-th first wavelength time domain interference signal is irradiated to the material to be detected in the position to be measured, causing diffusion and then being received by the detector, thereby obtaining a first wavelength fNIRS signal; the i-th second wavelength time domain interference signal is irradiated to the material to be detected in the position to be measured, causing diffusion and then being received by the detector, thereby obtaining a second wavelength fNIRS signal.

[0071] Preferably, the expression of the first wavelength fNIRS signal is:

[0072]

[0073] Where: S(t) is the first wavelength fNIRS signal, ρ 1 (t) is the initial oxygenated hemoglobin signal.

[0074] The second wavelength fNIRS signal can refer to the first wavelength fNIRS signal.

[0075] The processor performs envelope center demodulation on the first wavelength fNIRS signal to obtain an initial oxygenated hemoglobin signal, and the processor performs envelope center demodulation on the second wavelength fNIRS signal to obtain an initial deoxygenated hemoglobin signal.

[0076] Furthermore, the initial oxygenated hemoglobin signal expression is:

[0077]

[0078] Where: 2 (t) is the oxygenated hemoglobin signal.

[0079] The initial deoxyhemoglobin signal may refer to the initial oxygenated hemoglobin signal.

[0080] The processor performs envelope center demodulation on the initial oxygenated hemoglobin signal to obtain the oxygenated hemoglobin signal, and the processor performs envelope center demodulation on the initial deoxygenated hemoglobin signal to obtain the deoxygenated hemoglobin signal.

[0081] Specifically, the oxygenated hemoglobin signal is:

[0082]

[0083] Where: c is the amplitude of the oxygenated hemoglobin signal, A(t) is the AC component of the oxygenated hemoglobin signal, N 3 is the DC component of the oxygenated hemoglobin signal.

[0084] The deoxyhemoglobin signal can be referred to the oxygenated hemoglobin signal.

[0085] The processor judges i. If i<K, it sets i=i+1 and returns to "the controller controls the i-th signal acquisition module to generate a first wavelength time domain interference signal and a second wavelength time domain interference signal". If i≥K, K oxygenated hemoglobin signals and K deoxygenated hemoglobin signals are obtained.

[0086] Preferably, the processor obtains the oxygenated blood oxygen value according to the oxygenated hemoglobin signal, and the processor obtains the deoxygenated blood oxygen value according to the deoxygenated hemoglobin signal.

[0087] The expression of oxygenated blood oxygen value is:

[0088]

[0089] Where: 2 (t) is the oxygenated hemoglobin signal, and X(t) is the oxygenated blood oxygen value.

[0090] Figure 1 In this example, the number of signal acquisition modules is 8, λ 1 is the first wavelength, λ 2 is the second wavelength, S1-S8 represent 8 groups of light sources, each group of light sources includes the first light source and the second light source, each channel modulates the time domain interference signal of time length T in turn, and the cycle of completing the blood oxygen solution of all channels is 16T. Y is the first wavelength fNIRS signal.

[0091] The above embodiments are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A multi-channel fNIRS signal acquisition system based on time domain interferometric modulation, characterized in that: It includes: A processor and several signal acquisition modules; The number of the signal acquisition modules is the same as the number of channels; The signal acquisition module includes a detector, a first light source and a second light source; The detector, the first light source and the second light source are sequentially arranged on the same straight line; a perpendicular line is drawn from the position to be measured to the straight line, and the intersection of the perpendicular line and the straight line is the center point between the detector and the first light source; a first modulated optical carrier signal emitted by the first light source and a second modulated optical carrier signal emitted by the second light source are interferometrically modulated at the position to be measured to obtain a time domain interference signal; The first modulated optical carrier signal includes a first wavelength modulated optical carrier signal and a second wavelength modulated optical carrier signal, the second modulated optical carrier signal includes a third wavelength modulated optical carrier signal and a fourth wavelength modulated optical carrier signal, and the time domain interference signal includes a first wavelength time domain interference signal and a second wavelength time domain interference signal; The first wavelength modulated optical carrier signal and the third wavelength modulated optical carrier signal have the same wavelength, and the first wavelength modulated optical carrier signal and the third wavelength modulated optical carrier signal are interferometrically modulated at a position to be measured to obtain the first wavelength time domain interference signal; The second wavelength modulated optical carrier signal and the fourth wavelength modulated optical carrier signal have the same wavelength, and the second wavelength modulated optical carrier signal and the fourth wavelength modulated optical carrier signal are interferometrically modulated at a position to be measured to obtain the second wavelength time domain interference signal; Let i=1, i∈K, K is the number of signal acquisition modules; The controller controls the i-th signal acquisition module to generate the first wavelength time domain interference signal and the second wavelength time domain interference signal; The i-th time domain interference signal of the first wavelength is irradiated to the material to be detected in the position to be detected, and then diffuses and is received by the detector, so as to obtain a first wavelength fNIRS signal; the i-th time domain interference signal of the second wavelength is irradiated to the material to be detected in the position to be detected, and then diffuses and is received by the detector, so as to obtain a second wavelength fNIRS signal; The processor performs envelope center demodulation on the first wavelength fNIRS signal to obtain an initial oxygenated hemoglobin signal, and the processor performs envelope center demodulation on the second wavelength fNIRS signal to obtain an initial deoxygenated hemoglobin signal; The processor performs envelope center demodulation on the initial oxygenated hemoglobin signal to obtain an oxygenated hemoglobin signal, and the processor performs envelope center demodulation on the initial deoxygenated hemoglobin signal to obtain a deoxygenated hemoglobin signal; The processor judges i, and if i<K, sets i=i+1 and returns to "the controller controls the i-th signal acquisition module to generate the first wavelength time domain interference signal and the second wavelength time domain interference signal", and if i≥K, obtains K oxygenated hemoglobin signals and K deoxygenated hemoglobin signals.

2. The multi-channel fNIRS signal acquisition system based on time domain interferometric modulation according to claim 1, characterized in that: The expressions of the first modulated optical carrier signal and the second modulated optical carrier signal are: Wherein: E1(t) is the first modulated optical carrier signal, E2(t) is the second modulated optical carrier signal, a is the amplitude of the first modulated optical carrier signal, b is the amplitude of the second modulated optical carrier signal, N1 is the DC component of the first modulated optical carrier signal, N2 is the DC component of the second modulated optical carrier signal, f1 is the frequency of the first modulated optical carrier signal, f2 is the frequency of the second modulated optical carrier signal, and t is time.

3. The multi-channel fNIRS signal acquisition system based on time domain interferometric modulation according to claim 2, characterized in that: The expression of the time domain interference signal is: Where: E tot is the time domain interference signal.

4. The multi-channel fNIRS signal acquisition system based on time domain interferometric modulation according to claim 1, characterized in that: The detection depth of the first wavelength modulated optical carrier signal is greater than the vertical distance between the position to be measured and the straight line, and the detection depth of the second wavelength modulated optical carrier signal is greater than the vertical distance between the position to be measured and the straight line.

5. The multi-channel fNIRS signal acquisition system based on time domain interferometric modulation according to claim 4, characterized in that: The detection depth expression of the first wavelength modulated optical carrier signal is: Where: Z max is the detection depth of the first wavelength modulated optical carrier signal, and d is the distance between the first light source and the detector.

6. The multi-channel fNIRS signal acquisition system based on time domain interferometric modulation according to claim 2, characterized in that: The expression of the first wavelength fNIRS signal is: Where: S(t) is the first wavelength fNIRS signal, ρ1(t) is the initial oxygenated hemoglobin signal.

7. The multi-channel fNIRS signal acquisition system based on time domain interferometric modulation according to claim 6, characterized in that: The initial oxygenated hemoglobin signal expression is: Where: ρ2(t) is the oxygenated hemoglobin signal.

8. The multi-channel fNIRS signal acquisition system based on time domain interferometric modulation according to claim 7, characterized in that: The oxygenated hemoglobin signal is: Wherein: c is the amplitude of the oxygenated hemoglobin signal, A(t) is the AC component of the oxygenated hemoglobin signal, and N3 is the DC component of the oxygenated hemoglobin signal.

9. The multi-channel fNIRS signal acquisition system based on time domain interferometric modulation according to claim 1, characterized in that: The processor obtains an oxygenated blood oxygen value according to the oxygenated hemoglobin signal, and the processor obtains a deoxygenated blood oxygen value according to the deoxygenated hemoglobin signal.

10. The multi-channel fNIRS signal acquisition system based on time domain interferometric modulation according to claim 9, characterized in that: The oxygen-containing blood oxygen value expression is: Where: ρ2(t) is the oxygenated hemoglobin signal, and X(t) is the oxygenated blood oxygen value.

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