CN110361357A - A kind of single array element photoacoustic spectrum signal acquisition system and method for skin detection - Google Patents

Abstract

The invention relates to a system and method for acquiring a single-array photoacoustic spectrum signal for skin detection. The system body includes: a computer, a pulse laser, an optical fiber bundle, a beam splitter, a focusing lens, an aperture, a needle hydrophone, and a water tank , black body, single array element detection transducer, amplifier and oscilloscope, the method specifically includes: the pulsed laser light shaped by the focusing lens adjusts the size of the light spot through the diaphragm, and vertically irradiates the sample tissue to be tested to generate a photoacoustic signal; The pulsed laser light shaped by the focusing lens is irradiated on the black body immersed in the water tank, and the photoacoustic signal generated by the black body is collected by the transducer; after signal collection and signal processing, the photoacoustic energy absorption spectrum of the sample to be tested is obtained; the characteristic wavelength is selected The photoacoustic power spectrum of the photoacoustic sound is used to perform a linear fitting, and the obtained linear fitting parameters are used to provide diverse quantitative information for skin detection. Compared with the prior art, the invention has the advantages of high sensitivity, deep detection depth and the like.

Description

A single array element photoacoustic spectrum signal acquisition system and method for skin detection

technical field

The invention relates to the technical field of medical equipment, in particular to a single-array element photoacoustic spectrum signal acquisition system and method for skin detection.

Background technique

The skin is the largest organ of the human body and plays a particularly important protective role in the health of the human body.

Non-invasive imaging diagnostic methods currently used in the diagnosis of skin diseases include optical imaging and ultrasound imaging. Optical imaging can provide relatively high imaging resolution, but due to the strong scattering of light in biological tissues, the penetration depth is limited, resulting in insufficient imaging depth. Accurate pathological diagnosis. Compared with optical imaging, ultrasound imaging can provide deeper imaging depth and can determine the thickness of skin lesions, but its imaging is based on the difference in acoustic impedance of biological tissues, so it is often difficult to distinguish lesions with different chemical properties but similar physical properties In addition, ultrasound imaging lacks the analysis of chemical information and can provide less effective lesion information, which cannot be used as a basis for diagnosis; in addition, these imaging diagnostic methods cannot Provide quantitative information.

The single-array photoacoustic spectroscopy method for skin detection combines the advantages of optics and acoustics, and can achieve sufficient resolution at a certain imaging depth. At the same time, this method makes up for the limitation that the current imaging diagnostic methods can only provide information from a single aspect of physics or chemistry, and cannot provide quantitative information. It can analyze the nature, content, and microstructural changes of biological tissue components from the chemical tissue level. , providing more accurate objective quantitative information. The ability to comprehensively acquire organizational structure and function information will also be an inevitable trend in the development of medical and biological sciences.

Chinese patent CN201510935010 provides an ultrasonic photoacoustic photoacoustic spectrum imaging system and method. The method uses an array of ultrasonic probes for skin spectral imaging detection. However, this method has low sensitivity and is prone to missing high-frequency information; and the obtained photoacoustic spectrum information is The photoacoustic two-dimensional spectrogram can only judge the tissue qualitatively, and cannot obtain quantitative information, so it can make an objective and accurate judgment on the tissue.

Contents of the invention

The object of the present invention is to provide a single array element photoacoustic spectrum signal acquisition system and method for skin detection in order to overcome the above-mentioned defects in the prior art.

The purpose of the present invention can be achieved through the following technical solutions:

A single array element photoacoustic spectrum signal acquisition system for skin detection, the system comprising:

The computer is used to control the pulse laser to emit multi-wavelength pulse laser.

Pulse laser, used to receive computer instructions to emit pulse laser.

Multimode fiber optic bundles for guiding pulsed laser light from pulsed lasers.

Water tank for soaking the black body and coupling the acoustic signal.

The beam splitter is used for splitting the pulsed laser light guided by the multimode fiber bundle, and respectively irradiating it onto the tissue sample to be tested and onto the black body immersed in the water tank.

The focusing lens is used to focus the split pulsed laser beam.

The aperture is used for adjusting the size of the focused pulsed laser light, and adjusting the size of the light spot irradiated on the tissue sample to be tested.

The needle hydrophone is used to collect the photoacoustic signal generated by the tissue sample to be tested.

The transducer, immersed in the water tank, is used to collect the photoacoustic signal generated by the black body.

The amplifier is used to respectively amplify the photoacoustic signals collected by the needle hydrophone and the transducer.

The oscilloscope is used for displaying and collecting the photoacoustic signals collected by the needle hydrophone and the transducer.

A single array element photoacoustic spectrum signal acquisition method for skin detection, the method comprises the following steps:

S1. Wrap the tissue sample to be tested with coupling agent, immerse the black body in the water tank, and split the multi-wavelength pulsed laser light through the beam splitter.

S2. Focus and irradiate the split pulsed laser light on the tissue sample to be tested and the black body immersed in the water tank through the focusing lens, determine the size of the area to be detected to adjust the size of the aperture, and determine the spot size irradiated on the tissue sample to be tested. .

S3. Using the needle hydrophone to receive the photoacoustic signal generated by the sample through the coupling agent, place the transducer in the water tank and align it with the black body, and receive the photoacoustic signal generated by the black body.

S4. Perform energy normalization of the photoacoustic signal generated by the tissue sample to be measured to the photoacoustic signal generated by the blackbody to perform laser energy calibration, and simultaneously perform frequency response calibration on the needle hydrophone.

S5. Process the energy normalized and calibrated signal to obtain an optical absorption energy spectrum of the tissue sample to be tested.

Preferably, the welch processing is performed on the energy normalized and calibrated signal to obtain the light absorption energy spectrum of the tissue sample to be tested.

S6. Select a plurality of characteristic absorption light wavelengths according to the light absorption energy spectrum, and perform a linear fitting of the photoacoustic power spectrum. Specific steps include:

1) Compare the obtained light energy absorption spectrum with the light energy absorption spectrum of known pure tissue components, and select multiple characteristic light absorption wavelengths, such as hemoglobin, collagen, lipid, melanin and other characteristic light absorption wavelengths;

2) Extract the photoacoustic signal at the characteristic light absorption wavelength, perform signal processing, obtain the photoacoustic power spectrum at the corresponding light wavelength, and perform a linear fitting.

S7. Extract linear fitting parameters including slope, intercept, and median according to the fitting result in step S6.

S8. Using the obtained fitting parameters to provide diverse quantitative information for skin disease detection.

Compared with the prior art, the present invention has the following advantages:

1. The present invention adopts the method of photoacoustic spectrum detection, and uses photoacoustic signals to carry information such as the nature, content and microstructure changes of biological tissues on chemical tissue components, and can realize the use of photoacoustic power spectrum at specific wavelengths. Linear fitting parameters for quantitative detection, deep penetration depth, high sensitivity, and not easy to lose high-frequency information;

2. The focusing method adopted in the present invention is weak focusing with a certain size, so that the entire sample tissue is irradiated by the light source to generate photoacoustic signals, and the biological information of the entire tissue sample can be obtained, including chemical tissue composition and tissue microstructure information, etc. ;Using coupling agent to wrap all the tissue samples to be tested except in the direction of illumination ensures that the photoacoustic signal of the entire sample can be obtained, which helps to obtain more comprehensive molecular chemistry, microstructure and other information of the tissue samples to be tested, which is different from traditional imaging Compared with medical diagnostic methods, the present invention can provide quantitative information, and can provide physical microstructure information and chemical composition information at the same time;

3. The present invention uses the needle type hydrophone to rotate for multi-point signal acquisition, which can obtain richer information, and can reconstruct a two-dimensional image, and obtain quantified information corresponding to each position, with high sensitivity and wide bandwidth;

4. The present invention immerses the black body in a water tank, and generates a photoacoustic signal after being excited by pulsed laser irradiation. The generated photoacoustic signal is used to normalize the light energy of the multi-wavelength pulsed laser, and has high stability. Inherent limitations of different energies at optical wavelengths;

5. The present invention avoids the influence of the system itself on the data by using the needle hydrophone for frequency response calibration, and can effectively remove system noise.

Description of drawings

Fig. 1 is the structural representation of the system of the present invention;

Fig. 2 is a schematic flow sheet of the inventive method;

As indicated by the labels in Figure 1:

1. Computer, 2. Pulse laser, 3. Multimode fiber bundle, 4. Beam splitter, 5. Focusing lens, 6. Aperture, 7. Needle hydrophone, 8. Black body, 9. Water tank, 10. Changing energy device, 11, amplifier, 12, oscilloscope, 13, tissue sample to be tested.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. Apparently, the described embodiments are some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

As shown in Figure 1, the present invention relates to a single-array element photoacoustic spectrum signal acquisition system for skin detection, the system includes a computer 1, a pulsed laser 2, a multimode fiber bundle 3, a beam splitter 4, a focusing lens 5, Aperture 6, needle hydrophone 7, water tank 9, transducer 10, amplifier 11 and oscilloscope 12. The computer 1 is connected with the pulsed laser 2, the pulsed laser 2 emits the pulsed laser and is guided by the multimode fiber bundle 3, the beam splitter 4 splits the pulsed laser guided by the multimode fiber bundle 3, and then irradiates the pulsed laser through the focusing lens 5 respectively. The tissue sample 13 to be tested is irradiated onto the black body 8 . The black body 8 is immersed in a water tank 9 filled with water, and after being excited by pulsed laser irradiation, a photoacoustic signal is generated, and the generated photoacoustic signal is used to normalize the light energy of the multi-wavelength pulsed laser.

The diaphragm 6 is used to adjust the size of the focused pulsed laser light, and to adjust the size of the light spot irradiated on the tissue sample 13 to be measured. The needle hydrophone 7 detects and collects the photoacoustic signal generated by the tissue sample 13 to be tested, and uses the amplifier 11 to amplify the collected signal and then displays and collects it on the oscilloscope 12 . The transducer 10 detects and collects the photoacoustic signal generated by the black body 8 , and uses the amplifier 11 to amplify the collected signal and then displays the collected signal on the oscilloscope 12 .

Using the focusing lens to weakly focus the laser pulse can not only increase the optical energy density, thereby improving the photoacoustic signal-to-noise ratio, but also realize the complete irradiation of light on the tissue sample to be tested, so that the entire sample tissue can generate photoacoustic signals; The aperture can adjust the spot size according to the size of the sample tissue, which increases the flexibility of the system; the multi-wavelength pulsed laser scanning range is 690-950nm and 1200-1800nm, covering the characteristic absorption wavelengths of various tissue components, which can be more Fully reflect the optical characteristics of the sample to be tested.

Preferably, the needle hydrophone 7 is a needle hydrophone with high sensitivity and wide frequency band (preferably 1-20 MHz), so as to better receive the photoacoustic signal generated by the sample.

The present invention also relates to a single-array element photoacoustic spectrum signal acquisition method for skin detection. The method is based on the above system and includes the following steps:

Step 1. Build the experimental optical path, use multi-wavelength pulsed laser to irradiate the area to be tested, wrap the tissue sample to be tested with medical coupling agent, immerse the black body in the water tank, and pass the multi-wavelength pulsed laser through the beam splitter.

Step 2. Focus and irradiate the split pulsed laser light on the tissue sample to be tested and the black body immersed in the water tank respectively through the focusing lens, determine the size of the area to be detected to adjust the size of the aperture, and determine the light spot irradiated on the tissue sample to be tested size.

Step 3. Make the pulsed laser weakly focus through the focusing lens, adjust the spot size through the diaphragm, and then irradiate the tissue sample to be tested, and use the needle hydrophone to receive the photoacoustic signal from the sample through coupling agent coupling; The detector is placed in the water tank and aimed at the black body, and receives the photoacoustic signal generated by the black body.

Step 4. Normalize the energy of the photoacoustic signal generated by the tissue sample to the photoacoustic signal generated by the black body to calibrate the laser energy, and at the same time perform frequency response calibration on the needle hydrophone to remove the system influence.

Step 5, performing welch processing on the normalized and calibrated photoacoustic signal to obtain the light absorption energy spectrum of the tissue sample to be tested.

Step 6. Obtain the linear fitting parameters of the photoacoustic power spectrum at the characteristic light absorption wavelength:

Compare the obtained light absorption energy spectrum with the light energy absorption spectrum of known pure tissue components, and select multiple characteristic light absorption wavelengths, such as hemoglobin, collagen, lipid, melanin and other characteristic light absorption wavelengths.

Extract the photoacoustic signal at the corresponding characteristic light absorption wavelength, perform signal processing, obtain the photoacoustic power spectrum at the corresponding optical wavelength, and perform a linear fitting; extract a linear fitting parameter, including slope, intercept, median etc. for quantitative evaluation.

Step 7, using the obtained fitting parameters to provide diversified quantitative information for skin disease detection.

For the photoacoustic effect, the focusing method adopted in the present invention is a weak focus with a certain size, so that the entire sample tissue is irradiated by the light source to generate photoacoustic signals, and the biological information of the entire tissue sample can be obtained, including chemical tissue components and Tissue microstructure information, etc.

Photoacoustic is a detection technology of light in and sound out. The photoacoustic effect describes a method that uses pulsed laser or modulated electromagnetic waves as the acoustic wave excitation source to irradiate the tissue, and the macromolecular chromophore in the tissue produces radiation due to the thermoelastic effect. The process of sound energy. Photoacoustics combines the advantages of optics on an ultrasound platform to detect deeper depths while retaining high sensitivity. At the same time, based on the characteristic spectral absorption and morphological structure of the absorbing group in the tissue, the photoacoustic signal can simultaneously carry the physical, chemical, and microstructure information of the detected sample. Compared with many current intraoperative boundary detection technologies, it can more accurately define the boundary. The following formula is the photoacoustic equation, indicating that when the tissue is subjected to time-varying heating (illumination), it will radiate sound waves outward:

where β is the coefficient of thermal expansion, is heat function, η _th is heat conversion efficiency, is the specific optical power deposition of the irradiated area of the biological tissue, is the luminous flux, C _p is the constant pressure specific heat capacity, is the sound pressure generated at r at time t, is the Laplace operator, c is the speed of sound, and V is the volume.

In step 1, the coupling agent is used to wrap all the tissue samples to be tested except in the direction of light, which ensures that the photoacoustic signal of the entire sample can be obtained, and helps to obtain more comprehensive molecular chemistry, microstructure and other information of the tissue samples to be tested; The hydrophone has high sensitivity and wide bandwidth (1-20MHz); at the same time, rotating the needle hydrophone for multi-point signal acquisition can obtain richer information, and can even reconstruct a two-dimensional image to obtain the corresponding Quantitative information about the location.

In step 3 and step 4, the photoacoustic signal generated by the black body is used to normalize the light energy of the tissue sample to be tested, which has high stability and removes the inherent limitation of the laser itself having different energy under different light wavelengths; The frequency response calibration of the hydrophone avoids the influence of the system itself on the data to remove system noise.

In step 5, use the pWelch function in the Matlab software (the smoothing average window is 30000, and the signal overlap rate is 90%) to perform time-frequency conversion, calculate the power spectrum of the signal, and obtain the light absorption energy spectrum of the tissue sample to be measured, where the abscissa Is the light absorption wavelength (690-950nm, 1200-1800nm), and the ordinate is the normalized energy amplitude of the photoacoustic signal generated by absorbing the laser (the characteristic absorption peak wavelength of water is 1450nm as the normalized point); the obtained light absorption The energy spectrum is compared with the light energy absorption spectrum of known pure tissue components (oxygenated hemoglobin, anoxygenated hemoglobin, collagen, lipid, melanin, water, etc.), and multiple characteristic light absorption wavelengths (absorption peaks, or far Higher than the light absorption wavelength of other substances), such as hemoglobin, collagen, lipid, melanin and other characteristic light absorption wavelengths, to analyze the changes in the content and microstructure of these tissue components in the tissue sample to be tested.

In step 6, extract the photoacoustic signal at the characteristic light absorption wavelength of the corresponding tissue composition, perform signal processing, obtain the photoacoustic power spectrum at the corresponding light wavelength, and perform a linear fitting; obtain a linear fitting parameter, including the slope , intercept, median, etc. Among them, the intercept and the median value are the evaluation of the tissue component content, and the intercept reflects the evaluation of the tissue content corresponding to the low-frequency size in the tissue; the median value is also called the medium-frequency intensity, which is a reflection of the intensity of the average signal of the tissue; the slope It reflects the relative distribution of tissue size corresponding to high and low frequencies in the tissue, and is an evaluation of the uniformity and heterogeneity of the tissue. For example, tumor tissue is often accompanied by abnormal proliferation of blood vessels, then compared with normal tissue, the hemoglobin content will increase, and the corresponding linear fitting parameters, intercept and median value of the characteristic light absorption wavelength of hemoglobin will usually become larger. The slope will become smaller. Therefore, the fitting parameters of the photoacoustic acoustic power spectrum can be used for quantitative evaluation to provide diverse quantitative information for skin disease detection.

The present invention adopts the method of photoacoustic spectrum detection, uses the photoacoustic signal to carry information such as the nature, content and microstructure changes of the biological tissue analyzed on the chemical tissue composition, and can realize the linearity of the photoacoustic power spectrum at a specific wavelength. Fitting parameters for quantitative detection, deep penetration depth, high sensitivity, and no loss of information.

The above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any worker familiar with the technical field can easily think of various equivalents within the technical scope disclosed in the present invention. Modifications or replacements shall all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (4)

1. a kind of single array element photoacoustic spectrum signal acquisition system for skin detection characterized by comprising

Computer, for controlling pulse laser transmitting multi-Wavelength Pulses laser；

Pulse laser, for receiving computer instruction emission pulse laser；

Multimode fiber-optic bundle, the pulse laser for the transmitting of pilot pulse laser；

Sink, for impregnating black matrix and coupling acoustical signal；

Light splitting piece for the pulse laser after multimode fiber-optic bundle guides to be divided, and exposes to test serum sample respectively In sheet and be irradiated to immerse sink in black matrix on；

Condenser lens, for being focused to the pulse laser beam after light splitting；

It is big to adjust the hot spot being irradiated on test serum sample for carrying out size adjusting to the pulse laser after focusing for diaphragm It is small；

Pin type hydrophone, for acquiring the photoacoustic signal of test serum sample generation；

Energy converter immerses in sink, for acquiring the photoacoustic signal of black matrix generation；

Amplifier is amplified for the photoacoustic signal respectively to pin type hydrophone, energy converter acquisition；

Oscillograph, for the pin type hydrophone and the collected photoacoustic signal of energy converter to be shown and acquired.

2. a kind of signal acquisition using single array element photoacoustic spectrum signal acquisition system described in claim 1 for skin detection Method, which is characterized in that this method includes the following steps:

1) test serum sample is wrapped up using couplant, black matrix is immersed in sink, by multi-Wavelength Pulses ray laser through excessive Mating plate light splitting；

2) pulsed light laser after light splitting is passed through into condenser lens focusing illumination in test serum sample respectively and is immersed in sink Black matrix on, determine area to be tested size to adjust diaphragm size, determine the spot size being irradiated on test serum sample；

3) it is coupled to receive the photoacoustic signal generated from sample using coupled dose of pin type hydrophone, energy converter is placed in sink And it is directed at black matrix, receive the photoacoustic signal that black matrix generates；

4) photoacoustic signal for generating test serum sample carries out energy normalizing to the photoacoustic signal that black matrix generates, to carry out laser Energy calibration, while frequency response calibration is carried out to pin type hydrophone；

5) signal after the calibration of energy normalizing is handled, obtains the light absorption energy spectrogram of test serum sample；

6) multiple characteristic absorption optical wavelength are chosen according to light absorption energy spectrogram, carries out the fitting of optoacoustic power sound spectrum once linear；

7) the once linear fitting parameter including slope, intercept, intermediate value is extracted.

3. a kind of single array element photoacoustic spectrum signal acquiring method for skin detection according to claim 2, feature exist In in step 5), to the signal progress welch processing after the calibration of energy normalizing, the light absorption energy of acquisition test serum sample Spectrogram.

4. a kind of single array element photoacoustic spectrum signal acquiring method for skin detection according to claim 3, feature exist In, step 6) specifically includes the following steps:

61) the energy absorption spectrogram of acquisition and the energy absorption spectrogram of known pure structural constituent are compared, is chosen multiple Feature light absorption wavelength；

62) photoacoustic signal under feature light absorption wavelength is extracted, signal processing is carried out, obtains the optoacoustic sound function under corresponding optical wavelength Rate spectrum, and carry out once linear fitting.