PS-OCT-based detection method for physiological and functional characteristics of hard tissue of tooth body

Abstract

The invention provides a method for detecting physiological and functional characteristics of tooth hard tissue based on PS-OCT (Pressure Swing-Optical Coherence Tomography). The method comprises the following steps: acquiring an interference signal of tooth hard tissue by using a PS-OCT system; calculating the complex amplitude of the PS-OCT interference signal, and further calculating to obtain a PS-OCT intensity image and various polarization images; based on the PS-OCT phase delay image, calculating and outputting a density parameter of the tooth hard tissue; on the basis of the PS-OCT optical axis image, calculating and outputting a structural confusion degree parameter of the tooth hard tissue; and based on the PS-OCT polarization uniformity image, calculating and outputting a depolarization parameter of the tooth hard tissue. Compared with the prior art, the system and the method have the advantages that high-resolution and large-view-field imaging can be carried out on in-vivo tooth tissue in a real-time and lossless mode by using the PS-OCT technology, intensity images and various polarization images can be obtained at the same time, and physiological and functional characteristics of tooth hard tissue are represented by various parameters.

Description

Technical Field

[0001] This invention belongs to the field of polarization-sensitive optical coherence tomography (PS-OCT) technology, specifically, it relates to a method for detecting the physiological and functional characteristics of dental hard tissues based on PS-OCT. Background Technology

[0002] Oral health has always been a major social concern. Oral tissues include the hard tissues of the teeth and the mucous membranes of the lips, cheeks, and palate. The development and health of the hard tissues of the teeth directly affect people's quality of life. Common diseases include dental caries, periodontitis, and pulpitis. These diseases seriously impact people's quality of life. For example, dental caries often causes inflammation at the root apex and other areas, and in severe cases, local swelling can occur, potentially leading to sepsis or bacteremia. Therefore, a method for detecting the physiological and functional characteristics of the hard tissues of the teeth is needed to achieve early diagnosis of diseases.

[0003] Currently, the primary method for detecting dental diseases is visual inspection. However, this is highly dependent on the dentist's experience, and early-stage lesions usually occur inside the tooth and cannot be identified from the tooth's exterior. Another method is to use X-ray technology to image the hard tissues of the tooth, which can provide structural features of the tooth. However, low-resolution X-ray imaging technology cannot detect early lesions. High-resolution X-ray micro-CT imaging technology has micron-level resolution, but due to high levels of radioactive contamination, it cannot be used for in vivo tooth examination.

[0004] Optical coherence tomography (OCT), as a non-invasive, high-resolution, and non-contact imaging technique, has become a routine diagnostic technique in ophthalmology. Polarization technology, by detecting changes in the polarization state of light after reflection or scattering through biological tissue, can obtain more functional information about the tissue than just its structural information. Polarization-sensitive OCT (PS-OCT), combined with polarization technology, can obtain more information about dental hard tissues by analyzing the polarization characteristics of the sample, in addition to acquiring tissue structural information.

[0005] For example, tooth enamel is an anisotropic crystalline material. Its crystal structure causes birefringence when light passes through it. This birefringence not only reveals the crystal arrangement and internal structural characteristics of enamel but also provides a new perspective for studying the biological characteristics and pathological changes of teeth. Normal tooth hard tissue has an ordered crystal structure and exhibits significant birefringence. When tooth hard tissue is diseased, such as through caries, the hydroxyapatite crystal structure in the enamel is disrupted, increasing the internal air or liquid content and altering its birefringence. This results in changes in the density of the tooth hard tissue, the disorder of the internal crystal structure arrangement, and its depolarization characteristics. Therefore, PS-OCT, as a polarization imaging method, can effectively observe changes in the physiological and functional characteristics of tooth hard tissue during disease processes. For example, phase delay (δ) describes the magnitude of birefringence in dental hard tissue, characterizes the density of the internal crystal structure arrangement, and reflects the hardness of dental hard tissue; optical axis (θ) describes the direction of the optical axis of dental hard tissue, indicating the arrangement direction of its internal crystal structure; and polarization uniformity (DOPU) describes the depolarization characteristics of dental hard tissue, characterizing the degree of multiple scattering of light within the tissue. Previous studies have found that dental caries lesions cause strong changes in DOPU (Depth-to-Pearl Detection and Detection of Dental Caries), and DOPU has been used as a parameter to detect dental caries lesions (Jonas Golde, Florian Tetschke, Julia Walther, Tobias Rosenauer DDS, Franz Hempel, Christian Hannig DDS, Edmund Koch, Lars Kirsten, "Detection of cariouslesions utilizing depolarization imaging by polarization sensitive opticalcoherence tomography," J. Biomed. Opt. 23(7)071203(2018)). However, this method only uses DOPU as a parameter to detect dental caries lesions, making it difficult to describe the physiological and functional characteristics of dental hard tissues in more detail. Currently, it is still necessary to fully explore the information in PS-OCT images to effectively characterize the physiological and functional properties of dental hard tissues. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing methods and provide a method for detecting the physiological and functional characteristics of dental hard tissues based on PS-OCT. This method can perform non-contact and non-destructive detection of dental hard tissues and fully utilize the intensity and polarization images of PS-OCT to analyze different regions of dental hard tissues, thereby obtaining the typical physiological and functional characteristics of dental hard tissues.

[0007] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0008] A method for detecting physiological and functional characteristics of dental hard tissues based on PS-OCT, the specific steps of which include:

[0009] Step 1: Use a polarization-sensitive optical coherence tomography (PS-OCT) system to probe the hard tissue of the tooth, and obtain two PS-OCT interference signals I with mutually perpendicular polarization directions. H and I V The subscripts H and V indicate that the polarization direction is horizontal and vertical, respectively.

[0010] Step 2: Based on the two PS-OCT interference signals of the dental hard tissue, calculate and output the corresponding intensity image and various polarization images of the dental hard tissue, including but not limited to: phase delay image, optical axis image, and polarization uniformity image; the specific calculation method is as follows:

[0011] Step 2.1: Process the two PS-OCT interference signals I obtained in Step 1. H and I V After performing background spectrum subtraction, zero-padding, and inverse Fourier transform sequentially, two complex amplitudes corresponding to the PS-OCT interference signals were obtained. and Represented as:

[0012]

[0013] Among them, A and These represent the amplitude and phase of the complex amplitude, respectively.

[0014] Step 2.2: Calculate the PS-OCT intensity image, phase delay image, optical axis image, and polarization uniformity image based on the complex amplitude, as shown below:

[0015]

[0016]

[0017]

[0018]

[0019] Where I represents intensity, δ represents phase delay, θ represents optical axis, and DOPU represents polarization uniformity (Degree of Polarization Uniformity, DOPU). I is used to describe the structural characteristics of dental hard tissue; δ is used to describe the cumulative phase delay change of dental hard tissue from the surface to the detection depth, reflecting the magnitude of birefringence of dental hard tissue; θ is used to describe the cumulative optical axis change of dental hard tissue from the surface to the detection depth, reflecting the alignment direction of crystal structures in dental hard tissue; DOPU is used to describe the overall degree of polarization of dental hard tissue within a selected window, reflecting the depolarization characteristics of dental hard tissue.

[0020] Step 3: Based on the PS-OCT phase delay image obtained in Step 2, calculate and output the density parameters of the tooth hard tissue to reflect the hardness characteristics of the tooth hard tissue. The specific method is as follows:

[0021] Step 3.1: Divide the hard tissue of the tooth into different regions in the PS-OCT phase delay image, extract the phase delay image values ​​of each region, and obtain the phase delay parameters;

[0022] Based on the phase delay parameters of dental hard tissue, calculate the local density parameters of various regions of dental hard tissue, including but not limited to: the regional mean parameters of phase delay. The specific calculation steps are as follows:

[0023]

[0024] in The mean parameter representing the phase delay of a region reflects the local hardness characteristics of the tooth hard tissue in various regions, where m represents the m-th pixel in the region, and δ m This represents the phase delay value of the m-th pixel within the region, where n represents the total number of pixels in the region.

[0025] Step 3.2: Based on the PS-OCT phase delay parameters obtained in Step 3.1, the image is divided into high-hardness and low-hardness regions using a selected threshold. The overall density parameters of the tooth hard tissue are calculated, including but not limited to: the width parameter and the normalized area parameter of the high-hardness region. The specific steps are as follows:

[0026] h = P t -P e

[0027]

[0028] Where h is the width parameter of the high-hardness region, P t To distinguish the boundary locations of high and low hardness regions using a threshold, P e The location is the edge of the hard tissue of the tooth; T is the normalized area parameter of the high-hardness region, and S is the edge of the hard tissue of the tooth.H S represents the area of ​​the high-hardness region. L is the area of ​​the low-hardness region; h represents the distance from the edge of the high-hardness region in the tooth hard tissue, determined according to the threshold, to the edge of the tooth hard tissue; T represents the proportion of the high-hardness region area to the total area of ​​the tooth hard tissue. Together, they reflect the overall hardness characteristics of the tooth hard tissue.

[0029] Step 4: Based on the PS-OCT optical axis image obtained in Step 2, calculate and output the structural disorder parameter of the tooth hard tissue, which is used to reflect the consistency of the crystal structure of the tooth hard tissue. The specific method is as follows:

[0030] Divide the hard tissue of the tooth into different regions in the PS-OCT optical axis image, extract the optical axis image values ​​of each region, and obtain the optical axis parameters;

[0031] Based on the optical axis parameters of dental hard tissue, calculate the local structural disorder parameters of various regions of dental hard tissue, including but not limited to: the regional standard deviation parameter σ of the optical axis. θ The specific calculation steps are as follows:

[0032]

[0033] Where σ θ The regional standard deviation parameter representing the optical axis reflects the consistency of the crystal structure of the hard dental tissue in different regions. θ represents the regional mean of the optical axis parameter. m This represents the optical axis value of the m-th pixel within the region, where n represents the total number of pixels in the region and m represents the m-th pixel in the region.

[0034] Step 5: Based on the PS-OCT polarization uniformity image obtained in Step 2, calculate and output the depolarization parameters of the tooth hard tissue to reflect the degree of multiple scattering of the tooth hard tissue. The specific method is as follows:

[0035] Divide the hard tissue of the tooth into different regions in the PS-OCT polarization uniformity image, extract the polarization uniformity image values ​​of each region, and obtain the polarization uniformity parameters.

[0036] Based on the polarization uniformity parameters of dental hard tissue, calculate the local depolarization parameters of various regions of dental hard tissue, including but not limited to: the regional mean parameters of polarization uniformity. The specific calculation steps are as follows:

[0037]

[0038] in The mean parameter representing polarization uniformity reflects the degree of multiple scattering of dental hard tissue in various regions, x DOPUmThis represents the polarization uniformity value of the m-th pixel within the region, where n represents the total number of pixels in the region and m represents the m-th pixel in the region.

[0039] The advantages or beneficial effects of this invention compared with the prior art are:

[0040] (1) The PS-OCT system used in this invention can perform non-invasive and non-destructive detection of dental hard tissues, obtain high-resolution three-dimensional tomographic PS-OCT images, and simultaneously obtain PS-OCT intensity images and multiple polarization images for calculating physiological and functional characteristics in one imaging session.

[0041] (2) The method for detecting the physiological and functional characteristics of dental hard tissue based on PS-OCT proposed in this invention makes full use of the information of PS-OCT images and can comprehensively describe the physiological and functional characteristics of dental hard tissue from multiple dimensions at the same time.

[0042] (3) The method for detecting the physiological and functional characteristics of dental hard tissue based on PS-OCT proposed in this invention calculates the density, structural disorder and degree of depolarization of dental hard tissue based on the obtained PS-OCT intensity image and various polarization image information, which can quantitatively describe the physiological and functional characteristics of dental hard tissue in various ways. Attached Figure Description

[0043] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope.

[0044] Figure 1 This is a flowchart of a method for detecting physiological and functional characteristics of dental hard tissues based on PS-OCT, as described in this invention.

[0045] Figure 2 This is a schematic diagram of the PS-OCT sweep source system used in this embodiment;

[0046] Figure 3 The images shown are intensity enface images of a healthy tooth (a) and a defective tooth (b) obtained by the PS-OCT system used in this embodiment.

[0047] Figure 4 The images shown are phase-delayed en-face images of healthy teeth (a) and defective teeth (b) obtained by the PS-OCT system used in this embodiment, and the output local density parameters (c).

[0048] Figure 5The images shown are phase-delayed en-face images of healthy teeth (a) and defective teeth (b) obtained by the PS-OCT system used in this embodiment, and the overall density parameters (c) output.

[0049] Figure 6 The images shown are the optical axis enface images of a healthy tooth (a) and a defective tooth (b) obtained by the PS-OCT system used in this embodiment, and the output structural disorder parameters (c).

[0050] Figure 7 The images show the polarization uniformity enface images of healthy teeth (a) and defective teeth (b) obtained by the PS-OCT system used in this embodiment, as well as the output depolarization parameters (c). Detailed Implementation

[0051] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings in the embodiments of the present invention;

[0052] The method for detecting physiological and functional characteristics of dental hard tissues based on PS-OCT proposed in this invention can use a time-domain PS-OCT system, a spectral-domain PS-OCT system, or a swept-frequency source PS-OCT system.

[0053] This embodiment uses a sweep frequency source PS-OCT system to detect healthy teeth and defective teeth, and calculates the physiological and functional characteristics of the hard tissues of the teeth based on the imaging results, thereby demonstrating the effect of the proposed method.

[0054] like Figure 2 The diagram shows the schematic of the sweep frequency source PS-OCT system used in this embodiment. The system includes: a broadband light source 101, a polarization controller 102, a circulator 103, a polarization beam splitter 104, a polarization-maintaining coupler 105, a collimator 106, a quarter-wave plate 107, a dispersion compensator 108, an aperture 109, a mirror 110, a second collimator 111, a second quarter-wave plate 112, a scanning galvanometer 117, an objective lens 118, the hard tissue of the tooth to be tested 119, a second polarization beam splitter 113, a first balanced detector 114, a second balanced detector 115, and a computer 116. Specifically, the broadband light source 101 uses a sweep frequency source with a wavelength of 1300nm.

[0055] for Figure 2The sweep frequency source PS-OCT system shown in the diagram outputs linearly polarized light vertically from the broadband light source 101 after passing through the polarization controller 102. This linearly polarized light enters the circulator 103, and the light exiting the circulator 103 is split into a reference beam and a sample beam after passing through the polarization beam splitter 104 and the polarization-maintaining coupler 105a (50:50). The reference beam passes through the collimator 106, a quarter-wave plate 107 (22.5° angle between the fast axis and the vertical direction), the dispersion compensator 108, and the aperture 109, and is reflected back to the polarization-maintaining coupler 105c by the mirror 110. The sample beam passes through the collimator 111 and a quarter-wave plate 112 (45° angle between the fast axis and the vertical direction), causing the sample beam to change from linearly polarized to circularly polarized. The sample beam then passes through the scanning mirror 11. 7 and objective lens 118 probe the hard tissue of the tooth 119. The light scattered from the hard tissue of the tooth returns to the polarization-maintaining coupler 105d along the original path. The reference light entering the polarization-maintaining coupler 105c and the sample light entering the polarization-maintaining coupler 105d interfere. The interfered light exits from the polarization-maintaining coupler 105a and b. The light exiting from the polarization-maintaining coupler 105a enters the polarization beam splitter 104. The vertical light passes through the circulator 103 and enters the balanced detector 114, while the horizontal light enters the balanced detector 115. The light exiting from the polarization-maintaining coupler 105b passes through the polarization beam splitter 113. The vertical light enters the balanced detector 114, while the horizontal light enters the balanced detector 115. The balanced detectors 114 and 115 receive the light and convert it into electrical signals, which are then transmitted to the computer 116.

[0056] Figure 1 This is a flowchart of a method for detecting the physiological and functional characteristics of dental hard tissues based on PS-OCT, as described in this invention. The specific steps include:

[0057] Step 1: Use a polarization-sensitive optical coherence tomography (PS-OCT) system to probe the hard tissue of the tooth, and obtain two PS-OCT interference signals with mutually perpendicular polarization directions. H and I V The subscripts H and V indicate that the polarization direction is horizontal and vertical, respectively.

[0058] Step 2: Based on the two PS-OCT interference signals of the dental hard tissue, calculate and output the corresponding intensity image, phase delay image, optical axis image, and polarization uniformity image of the dental hard tissue. The specific calculation method is as follows:

[0059] Step 2.1: Process the two PS-OCT interference signals I obtained in Step 1. H and IV After performing background spectrum subtraction, zero-padding, and inverse Fourier transform sequentially, the complex amplitudes of the two PS-OCT interferometric signals were obtained. and Represented as:

[0060]

[0061] Among them, A and These represent the amplitude and phase of the complex amplitude, respectively.

[0062] Step 2.2: Calculate the PS-OCT intensity image, phase delay image, optical axis image, and polarization uniformity image based on the complex amplitude, as shown below:

[0063]

[0064] Where I represents intensity, δ represents phase delay, θ represents optical axis, and DOPU represents polarization uniformity (DOPU). I is used to describe the structural characteristics of dental hard tissue; δ is used to describe the cumulative phase delay change of dental hard tissue from the surface to the detection depth, reflecting the magnitude of birefringence of dental hard tissue; θ is used to describe the cumulative optical axis change of dental hard tissue from the surface to the detection depth, reflecting the arrangement direction of crystal structure in dental hard tissue; DOPU is used to describe the overall polarization degree of dental hard tissue within a selected window, reflecting the depolarization characteristics of dental hard tissue; in this embodiment, the measurement range of δ is [0, π / 2], the measurement range of θ is [-π / 2, π / 2], and the measurement range of DOPU is [0, 1].

[0065] Figure 3 (a) and Figure 3 (b) are PS-OCT intensity enface images of healthy and defective teeth obtained using the system, with the slice position 1 mm below the surface of the tooth hard tissue. Figure 3 The box in (b) indicates the defective area. The intensity map shows the structural features of the hard tissue of the tooth and can identify defective areas at different depths below the surface.

[0066] Step 3: Based on the PS-OCT phase delay image obtained in Step 2, calculate and output the density parameters of the tooth hard tissue to reflect the hardness characteristics of the tooth hard tissue. The specific method is as follows:

[0067] Step 3.1: Divide the hard tissue of the tooth into different regions in the PS-OCT phase delay image, extract the phase delay image values ​​of each region, and obtain the phase delay parameters;

[0068] Based on the phase delay parameters of dental hard tissue, calculate the local density parameters of various regions of dental hard tissue, including but not limited to: the regional mean parameters of phase delay. The specific calculation steps are as follows:

[0069]

[0070] in The mean parameter representing the phase delay of a region reflects the local hardness characteristics of the tooth hard tissue in various regions, where m represents the m-th pixel in the region, and δ m This represents the phase delay value of the m-th pixel within the region, where n represents the total number of pixels in the region.

[0071] Figure 4 (a) and Figure 4 (b) These are PS-OCT phase-delayed enface images obtained by imaging healthy and defective teeth using the system. The image size is 500 pixels × 500 pixels, and the slice position is 1 mm below the surface of the tooth hard tissue. Regions 1, 2, and 3 in the image represent the middle, lower, and left sides of the tooth hard tissue, respectively, with pixel counts n of 180 × 130, 220 × 130, and 40 × 130, respectively. Figure 4 (b) Area 3 is a defective area. Figure 4 (c) shows the local average phase delay values ​​of different regions, reflecting the hardness of different regions of the tooth hard tissue. It can be seen that the phase delay value of the middle part of the tooth hard tissue is lower than that of the edge region, reflecting that the hardness of the tooth is greater at the edge than at the center. Furthermore, the phase delay value of the defective region is lower than that of the normal edge region, indicating that defects will reduce the hardness of the tooth hard tissue.

[0072] Step 3.2: Based on the PS-OCT phase delay parameters obtained in Step 3.1, the image is divided into high-hardness and low-hardness regions using a selected threshold. The overall density parameters of the tooth hard tissue are calculated. In this embodiment, the threshold is set to 0.7, meaning that regions with a phase delay parameter greater than 0.7 are high-hardness regions, and regions with a phase delay parameter less than 0.7 are low-hardness regions. The overall density parameters of the tooth hard tissue include, but are not limited to, the width parameter of the high-hardness region and the normalized area parameter of the high-hardness region. The specific steps are as follows:

[0073] h = P t -P e

[0074]

[0075] Where h is the width parameter of the high-hardness region, P t To distinguish the boundary locations of high and low hardness regions using a threshold, P eThe location is the edge of the hard tissue of the tooth; T is the normalized area parameter of the high-hardness region, and S is the edge of the hard tissue of the tooth. H S represents the area of ​​the high-hardness region. L is the area of ​​the low-hardness region; h represents the distance from the edge of the high-hardness region in the tooth hard tissue, determined according to the threshold, to the edge of the tooth hard tissue; T represents the proportion of the high-hardness region area to the total area of ​​the tooth hard tissue. Together, they reflect the overall hardness characteristics of the tooth hard tissue.

[0076] Figure 5 (a) and Figure 5 (b) are PS-OCT phase delay enface images of healthy and defective teeth obtained by imaging with the system, with the slice position 1 mm below the surface of the hard tissue of the tooth, and the width of the high hardness region determined by the threshold is marked. Figure 5 (c) represents the width and normalized area of ​​the high-hardness region in the tooth hard tissue, reflecting the overall hardness characteristics of the tooth hard tissue. It can be seen that the overall hardness of a healthy tooth is greater than that of a defective tooth. The overall hardness of the tooth hard tissue is not only related to defects but also to its inherent hardness characteristics.

[0077] Step 4: Based on the PS-OCT optical axis image obtained in Step 2, calculate and output the structural disorder parameter of the tooth hard tissue, which is used to reflect the consistency of the crystal structure of the tooth hard tissue. The specific method is as follows:

[0078] Divide the hard tissue of the tooth into different regions in the PS-OCT optical axis image, extract the optical axis image values ​​of each region, and obtain the optical axis parameters;

[0079] Based on the optical axis parameters of dental hard tissue, calculate the local structural disorder parameters of various regions of dental hard tissue, including but not limited to: the regional standard deviation parameter σ of the optical axis. θ The specific calculation steps are as follows:

[0080]

[0081] Where σ θ The regional standard deviation parameter representing the optical axis reflects the consistency of the crystal structure of the hard dental tissue in different regions. θ represents the regional mean of the optical axis parameter. m This represents the optical axis value of the m-th pixel within the region, where n represents the total number of pixels in the region and m represents the m-th pixel in the region.

[0082] Figure 6 (a) and Figure 6 (b) are PS-OCT optical axis enface images of healthy teeth and defective teeth obtained using the system, with an image size of 500 pixels × 500 pixels and a slice position 1 mm below the surface of the tooth hard tissue. Figure 6The box in (b) indicates the defective area, and the total number of pixels n in this area is 40×110. Figure 6 (c) is the standard deviation of the optical axis region of the output, reflecting the consistency characteristics of the crystal structure arrangement inside the hard tissue of the tooth. It can be seen that Figure 6 In the optical axis diagram of the healthy tooth shown in (a), the optical axis orientation of the hard tissue of the tooth shows a "rice" - shaped distribution, indicating an ordered arrangement of the crystal structure in the hard tissue of the tooth. Therefore, the standard deviation of the region in the box - indicated area is small; while in Figure 6 In the defective area indicated by the box in (b), the ordered arrangement of the crystal structure is disrupted, and the standard deviation value of the region of the optical axis diagram increases significantly.

[0083] Step 5: Based on the PS - OCT polarization uniformity image obtained in Step 2, calculate and output the depolarization parameter of the hard tissue of the tooth, which is used to reflect the multiple - scattering degree of the hard tissue of the tooth. The specific method is as follows:

[0084] Divide different regions of the hard tissue of the tooth in the PS - OCT polarization uniformity image, extract the values of the polarization uniformity image of each region, and obtain the polarization uniformity parameter;

[0085] Based on the polarization uniformity parameter of the hard tissue of the tooth, calculate the local depolarization parameters of each region of the hard tissue of the tooth, including but not limited to: the regional mean parameter of polarization uniformity The specific calculation steps are as follows:

[0086]

[0087] Where represents the regional mean parameter of polarization uniformity, reflecting the multiple - scattering degree of the hard tissue of the tooth in each region. x DOPUm represents the polarization uniformity value of the m - th point in the region, n represents the total number of pixels in the divided region, and m represents the m - th pixel point in the region;

[0088] Figure 7 (a) and Figure 7 (b) are respectively the PS - OCT polarization uniformity enface images obtained by imaging healthy teeth and defective teeth using the system. The image size is 500 pixels × 500 pixels, and the slicing position is 1 mm below the surface of the hard tissue of the tooth. Figure 7 The box in (b) indicates the defective area, and the total number of pixels n in this area is 40×110. Figure 7 (c) is the overall and regional mean parameter of the output polarization uniformity, reflecting the multiple - scattering degree of the hard tissue of the tooth. It can be seen that due to the damage of the tooth hard tissue structure at the defective part, obvious depolarization characteristics are shown, the value of DOPU decreases, and the multiple - scattering degree of the tissue increases.

[0089] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for detecting physiological and functional characteristics of dental hard tissues based on PS-OCT, characterized in that, The physiological and functional characteristics of dental hard tissues are detected by utilizing the results of light scattering and polarization state modulation by biological tissues. Specific steps include: Step 1: Use a polarization-sensitive optical coherence tomography (PS-OCT) system to probe the hard tissue of the tooth, and obtain two PS-OCT interference signals I with mutually perpendicular polarization directions. H and I V The subscripts H and V indicate that the polarization direction is horizontal and vertical, respectively. Step 2: Based on the two PS-OCT interference signals of the dental hard tissue, calculate and output the intensity image and multiple polarization images of the corresponding dental hard tissue, wherein the multiple polarization images include, but are not limited to: phase delay image, optical axis image and polarization uniformity image; Step 3: Based on the PS-OCT phase delay image obtained in Step 2, calculate and output the density parameters of the tooth hard tissue to reflect the hardness characteristics of the tooth hard tissue. Step 4: Based on the PS-OCT optical axis image obtained in Step 2, calculate and output the structural disorder parameter of the hard tooth tissue to reflect the consistency of the crystal structure of the hard tooth tissue. Step 5: Based on the PS-OCT polarization uniformity image obtained in Step 2, calculate and output the depolarization parameters of the tooth hard tissue to reflect the degree of multiple scattering of the tooth hard tissue.

2. The method for detecting physiological and functional characteristics of dental hard tissues based on PS-OCT as described in claim 1, characterized in that, The specific calculation methods for the intensity image and multiple polarization images mentioned in step 2 are as follows: Step 2.1: Process the two PS-OCT interference signals I obtained in Step 1. H and I V After performing background spectrum subtraction, zero-padding, and inverse Fourier transform sequentially, the complex amplitudes corresponding to the PS-OCT interference signals were obtained. and Represented as: Among them, A and These represent the amplitude and phase of the complex amplitude, respectively. Step 2.2: Calculate the PS-OCT intensity image, phase delay image, optical axis image, and polarization uniformity image based on the complex amplitude, as shown below: Where I represents intensity, δ represents phase delay, θ represents optical axis, and DOPU represents polarization uniformity (Degree of Polarization Uniformity, DOPU). I is used to describe the structural characteristics of dental hard tissue; δ is used to describe the cumulative phase delay change of dental hard tissue from the surface to the detection depth, reflecting the magnitude of birefringence of dental hard tissue; θ is used to describe the cumulative optical axis change of dental hard tissue from the surface to the detection depth, reflecting the alignment direction of crystal structures in dental hard tissue; and DOPU is used to describe the overall polarization degree of dental hard tissue within a selected window, reflecting the depolarization characteristics of dental hard tissue.

3. The method for detecting physiological and functional characteristics of dental hard tissues based on PS-OCT as described in claim 1, characterized in that, The density parameters of the hard dental tissue mentioned in step 3 are calculated using the following method: Step 3.1: Divide the hard tissue of the tooth into different regions in the PS-OCT phase delay image, extract the phase delay image values ​​of each region, and obtain the phase delay parameters; Based on the phase delay parameters of dental hard tissue, calculate the local density parameters of various regions of dental hard tissue, including but not limited to: the regional mean parameters of phase delay. The specific calculation steps are as follows: in The mean parameter representing the phase delay of a region reflects the local hardness characteristics of the tooth hard tissue in various regions, where m represents the m-th pixel in the region, and δ m This represents the phase delay value of the m-th pixel within the region, where n represents the total number of pixels in the region. Step 3.2: Based on the PS-OCT phase delay parameters obtained in Step 3.1, the image is divided into high-hardness and low-hardness regions using a selected threshold. The overall density parameters of the tooth hard tissue are calculated, including but not limited to: the width parameter and the normalized area parameter of the high-hardness region. The specific steps are as follows: h=P t -P e Where h is the width parameter of the high-hardness region, P t To distinguish the boundary locations of high and low hardness regions using a threshold, P e The location is the edge of the hard tissue of the tooth; T is the normalized area parameter of the high-hardness region, and S is the edge of the hard tissue of the tooth. H S represents the area of ​​the high-hardness region. L denoted as the area of ​​the low-hardness region; h represents the distance from the edge of the high-hardness region (determined by a threshold) to the edge of the tooth hard tissue; and T represents the proportion of the high-hardness region area to the total area of ​​the tooth hard tissue. Together, they reflect the overall hardness characteristics of the tooth hard tissue.

4. The method for detecting physiological and functional characteristics of dental hard tissues based on PS-OCT as described in claim 1, characterized in that, The structural disorder parameter of the hard dental tissue mentioned in step 4 is specifically calculated as follows: Divide the hard tissue of the tooth into different regions in the PS-OCT optical axis image, extract the optical axis image values ​​of each region, and obtain the optical axis parameters; Based on the optical axis parameters of dental hard tissue, calculate the local structural disorder parameters of various regions of dental hard tissue, including but not limited to: the regional standard deviation parameter σ of the optical axis. θ The specific calculation steps are as follows: Where σ θ The regional standard deviation parameter representing the optical axis reflects the consistency of the crystal structure of the hard dental tissue in different regions. θ represents the regional mean of the optical axis parameter. m This represents the optical axis value of the m-th pixel within the region, where n represents the total number of pixels in the region and m represents the m-th pixel in the region.

5. The method for detecting physiological and functional characteristics of dental hard tissues based on PS-OCT as described in claim 1, characterized in that, The regression parameters of the tooth hard tissue mentioned in step 5 are specifically calculated as follows: Divide the hard tissue of the tooth into different regions in the PS-OCT polarization uniformity image, extract the polarization uniformity image values ​​of each region, and obtain the polarization uniformity parameters. Based on the polarization uniformity parameters of dental hard tissue, calculate the local depolarization parameters of various regions of dental hard tissue, including but not limited to: the regional mean parameters of polarization uniformity. The specific calculation steps are as follows: in The mean parameter representing polarization uniformity reflects the degree of multiple scattering of dental hard tissue in various regions, x DOPUm This represents the polarization uniformity value of the m-th pixel within the region, where n represents the total number of pixels in the region and m represents the m-th pixel in the region.

Images