CN112022093A

CN112022093A - Skin imaging system

Info

Publication number: CN112022093A
Application number: CN202010828577.7A
Authority: CN
Inventors: 莫建华; 陈洁雯; 戴佳宁
Original assignee: Suzhou University
Current assignee: Suzhou University
Priority date: 2020-08-17
Filing date: 2020-08-17
Publication date: 2020-12-04
Anticipated expiration: 2040-08-17
Also published as: CN112022093B

Abstract

The invention discloses a skin imaging system, which comprises an OCT subsystem, an HSI subsystem and an image processing unit, wherein the OCT subsystem is used for emitting a light signal, the light signal is reflected to form reference light and sample light of a skin area, the sample light and the reference light are interfered to form interference spectrum information, the HSI subsystem is used for emitting a white light signal to the skin area, reflected light generated by the white light signal irradiating the skin area is split and converged to obtain a spectrogram in all wavelength ranges, the image processing unit is used for generating a depth image of the skin area according to the interference spectrum information, reconstructing and correcting the spectrogram to obtain a hyperspectral image of the skin area, and the depth image and the hyperspectral image are fused to obtain the skin image. The invention utilizes the double imaging of the OCT technology and the hyperspectral technology, not only can make up the defects of the respective imaging technologies, but also can realize advantage complementation.

Description

Skin imaging system

[ technical field ] A method for producing a semiconductor device

The invention relates to the field of biomedical imaging, in particular to a skin imaging system.

[ background of the invention ]

Two novel biomedical Optical Imaging technologies, namely an Optical Coherence Tomography (OCT) Imaging technology and a Hyper-spectral Imaging (HSI) Imaging technology, can realize nondestructive Imaging of in-vivo biological tissues, and have the advantages of high sensitivity, high resolution, non-invasion, no radiation and the like. These two techniques have been widely used in biomedical fields, and become important means for clinical outpatient examinations. However, in the actual diagnosis process, the two technologies have imaging defects respectively, for example, OCT imaging has the disadvantages of contradiction between image resolution and imaging range and almost no molecular information acquisition; the hyperspectral imaging has the defect of poor capability of acquiring depth information of a biological sample.

To this end, we propose a skin imaging system.

[ summary of the invention ]

The invention mainly aims to provide a skin imaging system, an OCT system and an HSI system for biomedical imaging are combined into a set of dual-mode imaging system, the advantages of the OCT system and the HSI system are complemented, and the problems in the technical background are effectively solved.

In order to achieve the purpose, the invention adopts the technical scheme that:

a skin imaging system comprises an OCT subsystem, an HSI subsystem and an image processing unit;

the OCT subsystem: the light signal is used for forming reference light and sample light of the skin area through reflection, and meanwhile the sample light and the reference light are interfered to form interference spectrum information;

the HSI subsystem is used for emitting a white light signal to the skin area, and splitting and converging reflected light generated by irradiating the skin area with the white light signal so as to obtain spectrograms in all wavelength ranges;

an image processing unit: the system is used for generating a depth image of the skin area according to the interference spectrum information, reconstructing and correcting the spectrogram to obtain a hyperspectral image of the skin area, and fusing the depth image and the hyperspectral image to obtain the skin image.

Optionally, the OCT subsystem comprises:

sweeping the light source: for emitting a laser signal;

a first fiber coupler: the device is used for splitting the laser signal output by the sweep frequency light source and enabling the split optical signal to be respectively injected into the reference arm and the sample arm;

a reference arm: the light source is used for reflecting the received incident light to form generated reference light;

sample arm: for emitting the received incident light to the area of skin to be imaged and forming sample light upon reflection;

a second fiber coupler: the interference light source is used for enabling the sample light and the reference light to interfere to form interference spectrum information;

balancing the detector: the interference spectrum information is detected and output to the image processing unit.

Optionally, the sample arm includes a scanning galvanometer and a first achromatic lens, and the incident light entering the sample arm is redirected by the scanning galvanometer and then focused on the skin area through the first achromatic lens.

Optionally, the scanning galvanometer is configured with a high speed analog output device capable of outputting an analog signal to control the scanning galvanometer to effect scanning of the skin region.

Optionally, the front end of the scanning galvanometer is further configured with a first optical fiber collimator for collimating an optical signal incident into the scanning galvanometer.

Optionally, the reference arm includes a second fiber collimator, a third fiber collimator, a first plane mirror and a second plane mirror, and incident light entering the reference arm enters the third fiber collimator after being collimated by the second fiber collimator and reflected by the first plane mirror and the second plane mirror.

Optionally, the HSI subsystem comprises:

white light source: for emitting a white light signal to the skin area;

front-end optical system: the device is used for achromatizing reflected light generated by irradiating a skin area by a white light signal and enabling the reflected light to pass through a preset incident slit through focusing treatment;

a spectrometer: the device is used for performing push-broom according to a preset step length, and performing light splitting and convergence processing on reflected light passing through the incident slit to obtain spectrums in all wavelength ranges of the skin area; wherein the step size is equal to the width of the entrance slit;

a CCD camera: for detecting the spectrum of the spectrometer output to form a spectrogram.

Optionally, the spectrometer is configured with a motorized translation stage for driving the spectrometer into operation to complete the push-broom operation.

Optionally, the pre-optical system comprises at least two coaxially arranged second achromats.

Optionally, a dichroic mirror is further included, and the dichroic mirror is configured to focus the optical signals emitted by the OCT subsystem and the HSI subsystem on the skin region, and simultaneously configured to reflect the optical signals reflected by the skin region to the OCT subsystem and the HSI subsystem, respectively.

Compared with the prior art, the invention has the following beneficial effects:

the skin imaging system comprises an OCT subsystem, an HSI subsystem and an image processing unit, and by utilizing double imaging of the OCT technology and the hyperspectral technology, the defects of respective imaging technologies can be overcome, advantage complementation can be realized, high resolution is met, and meanwhile, a large imaging depth can be obtained.

[ description of the drawings ]

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention.

Fig. 1 is an overall configuration diagram of an embodiment of the present skin imaging system.

Fig. 2 is a pigmented nevus sample in an embodiment of the present skin imaging system.

FIG. 3 is a comparison graph before and after denoising of a normal skin spectrum in an embodiment of the skin imaging system.

Fig. 4 is a real map of HSI subsystem spectral resolution in an embodiment of the present skin imaging system.

FIG. 5 is a result of various clustering algorithms and a contrast map in an embodiment of the present skin imaging system.

Fig. 6 is a 3D reconstruction of a pigmented nevus sample in an embodiment of the skin imaging system.

FIG. 7 is a B-scan and flattened B-scan of the skin in an embodiment of the present skin imaging system.

Fig. 8 is a graph of a-scan comparison of normal skin and pigmented nevus samples in an embodiment of the present skin imaging system.

Fig. 9 shows the result of the fitting of attenuation coefficients in an embodiment of the skin imaging system.

Figure 10 is a B-scan diagram of the OCT subsystem in an embodiment of the present skin imaging system.

In the figure: 1. sweeping a light source; 2. a first fiber coupler; 3. a second fiber coupler; 4. a first fiber collimator; 5. a first plane mirror; 6. a second plane mirror; 7. a second fiber collimator; 8. a balance detector; 9. a third fiber collimator; 10. scanning a galvanometer; 11. a first achromatic lens; 12. a sample; 13. a white light source; 14. a second achromatic lens; 15. a front optical system; 16. an entrance slit; 17. a spectrometer; 18. a CCD camera; 19. an image processing unit; 20. a dichroic mirror.

[ detailed description ] embodiments

In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, but not all embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the following OCT subsystems refer to optical coherence tomography imaging subsystems and HSI subsystems refer to hyperspectral imaging subsystems.

As shown in FIG. 1, the skin imaging system provided by the present invention comprises an OCT subsystem, an HSI subsystem and an image processing unit 19;

the OCT subsystem emits optical signals, the optical signals form reference light and sample light of a skin area through reflection, and meanwhile the sample light and the reference light are interfered to form interference spectrum information;

the HSI subsystem emits a white light signal to the skin area, and splits and converges reflected light generated by irradiating the skin area with the white light signal so as to obtain spectrograms in all wavelength ranges;

the image processing unit 19 generates a depth image of the skin region according to the interference spectrum information formed by the OCT subsystem, performs reconstruction and correction according to the spectrogram obtained by the HSI subsystem to obtain a hyperspectral image of the skin region, and finally fuses the depth image and the hyperspectral image to obtain the skin image.

The operation of the OCT subsystem and the HSI subsystem is not limited in sequence, and the OCT subsystem can be operated firstly, and the HSI subsystem can be operated later; or the HSI subsystem operates first, the OCT subsystem operates later, or the OCT subsystem and the HSI subsystem operate simultaneously.

In some embodiments, the OCT subsystem includes a swept optical source 1, a reference arm, a sample arm, a first fiber coupler 2, a second fiber coupler 3, and a balanced detector 8;

in this embodiment, swept source 1 may be model SS-OCT1060, Axsun Technology Inc, with a source center wavelength of 1060nm, a bandwidth of 110nm, and a sweep rate of 100 kHz; the balanced probe 8 may be model PDB471C, Thorlabs; it should be noted that the models of the swept-frequency light source 1 and the balanced detector 8 are not limited to the model of the embodiment.

Firstly, light emitted by a sweep frequency light source 1 is split by a first optical fiber coupler 2; then, the light enters a sample arm (50%) and a reference arm (50%), incident light received by the reference arm is reflected to form generated reference light, and the incident light received by the sample arm is changed in direction to realize focusing of a skin area to be imaged and reflected to form sample light; finally, the sample light in the sample arm and the reference light in the reference arm perform light interference in the second fiber coupler 3 to form interference spectrum information, the balance detector 8 detects the interference spectrum information and outputs the interference spectrum information to the image processing unit 19 for processing, specifically, the interference spectrum signal detected in the balance detector 8 is filtered by a low pass filter (model can be SLP-150+, Mini-circuits) to remove other signals with frequency higher than 155MHz, and then is output to the image processing unit 19 through a 12-bit dual channel data acquisition card (model is ATS9351, alazarth).

In some embodiments, the sample arm comprises a scanning galvanometer 10 and a first achromatic lens 11;

the model of the scanning galvanometer 10 can be GVGM 002/M, Thorlabs; first acromatic lens 11 may be of the type AC254-125-B-ML, Thorlabs;

the light incident on the sample arm is redirected by the scanning galvanometer 10 and focused on the skin area by the first achromatic lens 11.

In some embodiments, the scanning galvanometer 10 is configured with a high speed analog output device;

the model of the high-speed analog output device can be PCIe-6363, National Instruments;

the high-speed analog output device can output analog signals to control and drive the scanning galvanometer 10 to realize scanning in X and Y directions, and finally, data are analyzed and visualized through the image processing unit 19.

In some embodiments, the sample arm is further configured with a first fiber collimator 4 at the front end of the scanning galvanometer 10, and the first fiber collimator 4 is configured to collimate the optical signal incident to the scanning galvanometer 10.

In some embodiments, the reference arm includes a second fiber collimator 7, a third fiber collimator 9, a first plane mirror 5, and a second plane mirror 6, and incident light entering the reference arm enters the third fiber collimator 9 after being collimated by the second fiber collimator 7 and then reflected by the first plane mirror 5 and the second plane mirror 6.

The incident light entering the reference arm sequentially passes through the second optical collimator 7, the first plane mirror 5, the second plane mirror 6 and the third optical collimator 9 to change the direction of the incident light.

In some embodiments, the HSI subsystem includes a white light source 13, a front-end optics system 15, a spectrometer 17, and a CCD camera 18;

the white light source 13 emits a white light signal to the skin area, the preposed optical system 15 achromatizes the reflected light generated by irradiating the skin area by the white light signal, and the reflected light can pass through an incident slit 16 preset by a spectrometer 17 through focusing treatment;

the spectrometer 17 is arranged on the mobile device and performs push-broom based on a preset step length, and meanwhile, the spectrometer 17 performs light splitting and convergence processing on reflected light passing through the entrance slit 16 to obtain spectra in all wavelength ranges of a skin area;

the step size is equal to the width of the entrance slit 16, so that each push-sweep of the spectrometer 17 will obtain a spectrogram of the skin region in all wavelength ranges;

the CCD detection camera acquires the spectrogram, and the spectrogram is subjected to data processing on a computer at the later stage and is reconstructed and corrected to obtain biological tissue images at all wavelengths;

in this embodiment, 2 60W wide beam LED spotlights can be used as the white light source 13, and the CCD detection camera model is MANTA G-201-30FPS, Allied Vision.

In some embodiments, spectrometer 17 is configured with a motorized translation stage for driving spectrometer 17 to operate to perform a push-scan operation, specifically, spectrometer 17 is fixed on the motorized translation stage for push-scanning.

In some embodiments, the front optical system 15 includes at least two coaxially disposed second achromatic lenses 14, and the second achromatic lenses 14 achromatize and focus reflected light generated by the white light signal illuminating the skin region so as to allow the reflected light to pass through the predetermined entrance slit 16.

In this embodiment, the width of the slit is 22 μm.

In some embodiments, the skin imaging system further includes a dichroic mirror 20, the dichroic mirror 20 focuses the light signals emitted by the OCT subsystem and the HSI subsystem on the skin region, and simultaneously reflects the light signals reflected by the skin region to the OCT subsystem and the HSI subsystem, respectively;

the imaging performance parameters of the system are as follows: the A-scan speed of the OCT system reaches 100kHz, the imaging depth is 5mm (in air), and the axial resolution and the transverse resolution are respectively 8 mu m and 70.3 mu m; the imaging spectral range of the HSI system is 465-630nm, the spectral resolution and the spatial resolution are respectively 2.1nm and 31.3 mu m, and particularly, referring to FIG. 4, an actual measurement diagram of the spectral resolution of the hyperspectral subsystem.

The image processing unit 19 includes a basic information processing apparatus such as a computer;

the image processing unit 19 in the system comprises time sequence control, data acquisition, image reconstruction, image real-time display, image preprocessing and the like of an OCT subsystem and an HSI subsystem, and meanwhile, the software part of the image processing unit 19 is realized based on mixed programming of Labview and Matlab;

parameters during data acquisition are set on a front panel of the Labview, a B-scan image, an original interference spectrum and the like of an OCT part, a spectrum image and the like of a hyperspectral part are displayed in real time, and image preprocessing mainly comprises spectrum shaping, Fourier transform, fixed pattern noise removal and the like of an OCT subsystem and wavelength calibration of the hyperspectral subsystem.

Specific experiments and analyses thereof:

the experiment is to detect, study and analyze pigmented nevus of skin;

the experimental sample is shown in fig. 2, the hyperspectral image size is set to be 240 × 150 pixels, the spectral dimension is 900 dimensions, and the field of view size is 5.28mm × 3.3 mm; the En-face image size of OCT is 2000 × 300 pixels, and the field of view size is 12mm × 4 mm.

Performing smooth denoising, multivariate scattering correction, dimension reduction and clustering processing on the hyperspectral data and then analyzing;

the smoothing and denoising method adopts a Gaussian weighting filter, the smoothing window is set to be 5, and the result is shown in FIG. 3; the dimension reduction method is a PCA method, wherein 900 dimensions are reduced to 100 dimensions, and the dimension reduction accuracy reaches 90% (shown in Table 1);

the clustering method comprises K-means, GMM and HAC algorithms, the obtained processing results are shown in FIG. 5 and Table 2, the system data can obtain more than 90% of accuracy and higher Dice coefficient under three algorithms, wherein the accuracy and Dice coefficient obtained by the HAC algorithm are highest, the accuracy is 92.61%, and the Dice coefficient is 94.53%.

In fig. 5:

wherein, (a) gold standard; (b) the result is; (c) comparing;

wherein 1 represents a K-means algorithm; 2 represents the GMM algorithm; and 3 represents the HAC algorithm.

TABLE 1

Principal component	Rate of contribution	Cumulative contribution rate
			1	0.5679	0.5679
2	0.1442	0.7121
			3	0.0638	0.7759
…	…	…
			99	0.006	0.8995
100	0.006	0.9001

TABLE 2

	Rate of accuracy	Sensitivity of the composition	Specificity of	False negative rate	False positive rate	Dice coefficient
							K-means	0.9023	0.8529	0.9354	0.1471	0.0646	0.8751
GMM	0.9182	0.8793	0.9443	0.1207	0.0557	0.9045
							HAC	0.9261	0.9373	0.8852	0.0627	0.1148	0.9453

On the other hand, a three-dimensional image of the detection region (fig. 6) is reconstructed using the OCT data and the difference between the pigmented nevus region and the normal skin region is quantitatively analyzed by the attenuation coefficient and the fractal dimension.

In fig. 6: (a) a skin surface map; (b) a pigmented nevus profile.

In the measurement of the attenuation coefficient, the study was fitted in three layers from the skin surface down, the first layer was 1-50 pixels, the second layer was 51-150 pixels, and the third layer was 151-250 pixels, and the fitting results are shown in FIG. 9; to make the fitting error smaller, both curves are averaged from 300 adjacent a-scans (axial scans) within the region of interest; as can be seen from fig. 8, due to the different scattering properties of normal skin and moles, normal skin tissue has a higher a-scan gray value than lesion tissue in the first 150 pixels, the a-scan first reflection peak of normal tissue appears later than the a-scan of lesion tissue, lags behind about 25 pixels, the attenuation coefficient of moles is higher than that of normal skin in the first and second layers, and the a-scan curves of both are almost coincident in the third layer, see table 3 for specific experimental results;

in the measurement of fractal dimension, 20B-scans at 5 intervals were selected for analysis, and the area size was 64 × 64 pixels, and the results are shown in fig. 10 and table 4, as can be seen from table 4, the fractal dimension of the nevus pigmentosus area was significantly different from that of normal skin tissue (P <0.05), and the fractal dimension value was increased by 3.56%, which indicates that the cells in the nevus pigmentosus area were more disordered and irregular, and the internal composition was more complex.

FIG. 7 is a B-scan plot of the skin and a B-scan plot after flattening;

in fig. 7: (a) a B-scan acquisition map of the skin, wherein the raised part is a display of a pigmented nevus area on the B-scan; (b) based on the B-scan image after the skin surface is flattened, the left dotted frame part is an A-scan interested area of normal skin, and the right dotted frame part is an A-scan interested area of pigmented nevi.

In fig. 10: the region of interest of normal skin tissue is in the upper dotted frame, and pigmented nevi are in the lower dotted frame.

TABLE 3

TABLE 4

In conclusion, the experimental results obtained through the experiment prove that the dual-mode system can be used for obtaining more information of the pigmented nevus and identifying the pigmented nevus lesion tissues, so that a better effect is achieved.

The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. A skin imaging system is characterized by comprising an OCT subsystem, an HSI subsystem and an image processing unit;

the HSI subsystem: the device is used for emitting a white light signal to the skin area, and splitting and converging reflected light generated by irradiating the skin area with the white light signal so as to obtain spectrograms in all wavelength ranges;

the image processing unit: the system is used for generating a depth image of the skin area according to the interference spectrum information, reconstructing and correcting the spectrogram to obtain a hyperspectral image of the skin area, and fusing the depth image and the hyperspectral image to obtain the skin image.

2. The skin imaging system of claim 1, wherein the OCT subsystem comprises:

sweeping the light source: for emitting a laser signal;

3. The skin imaging system of claim 2, wherein the sample arm comprises a scanning galvanometer and a first achromatic lens, and wherein incident light entering the sample arm is redirected by the scanning galvanometer and then focused on the skin area through the first achromatic lens.

4. A skin imaging system according to claim 3, wherein the scanning galvanometer is configured with a high speed analog output device capable of outputting an analog signal to control the scanning galvanometer to effect scanning of the skin region.

5. The skin imaging system of claim 3, wherein the front end of the scanning galvanometer is further configured with a first fiber collimator for collimating the light signal incident on the scanning galvanometer.

6. The skin imaging system of claim 2, wherein the reference arm comprises a second fiber collimator, a third fiber collimator, a first plane mirror and a second plane mirror, and incident light entering the reference arm enters the third fiber collimator after being collimated by the second fiber collimator and reflected by the first plane mirror and the second plane mirror.

7. The skin imaging system of claim 1, wherein the HSI subsystem comprises:

white light source: for emitting a white light signal to the skin area;

8. The skin imaging system of claim 7, wherein the spectrometer is configured with a motorized translation stage for driving operation of the spectrometer to complete the push-broom operation.

9. Skin imaging system according to claim 7, characterized in that the front optical system comprises at least two coaxially arranged second achromatic lenses.

10. The skin imaging system of claim 1, further comprising a dichroic mirror for focusing the light signals from the OCT subsystem and the HSI subsystem onto the skin region, and for reflecting the light signals reflected from the skin region to the OCT subsystem and the HSI subsystem, respectively.