System, method and program for analyzing measurement result

Abstract

To provide a technology that improves accuracy when automatically telling a tissue.SOLUTION: A measurement result analyzing system includes: a measurement information acquisition unit for acquiring measurement information that indicates a measurement result of a measurement object by a polarization-sensitive OCT; a parameter acquisition unit for acquiring a plurality of types of parameters that indicates polarization properties for respective positions of the measurement objects on the basis of the measurement information; and an identification unit for identifying types of tissues for respective positions on the basis of values of the plurality of types of parameters.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a measurement result analysis system, a measurement result analysis method, and a measurement result analysis program. [Background technology]

[0002] Conventionally, polarization-sensitive OCT (Polarization-Sensitive Optical Coherence Tomography) has been known. Polarization-sensitive OCT has a function of measuring the polarization characteristics of a measurement object. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6463051 Summary of the Invention [Problem to be solved by the invention]

[0004] When a measurement object such as an eye is photographed using polarization-sensitive OCT, the three-dimensional structure of the measurement object and the polarization characteristics at each position can be identified. Conventionally, in order to inspect the measurement object, the biological tissue of the measurement object has been distinguished by evaluating the area of ​​the part with strong birefringence or by performing artificial manipulation based on the photographed image. However, it has been difficult to distinguish tissues easily and accurately. The present invention has been made in consideration of the above-mentioned problems, and has an object to improve the accuracy in automatically distinguishing tissues. [Means for solving the problem]

[0005] In order to achieve the above-mentioned objective, the measurement result analysis system includes a measurement information acquisition unit that acquires measurement information indicating the measurement results of the measurement object using polarization-sensitive OCT, a parameter acquisition unit that acquires multiple types of parameters that indicate the polarization characteristics for each position of the measurement object based on the measurement information, and an identification unit that identifies the type of tissue for each position based on the values ​​of the multiple types of parameters.

[0006] According to the polarization-sensitive OCT, it is possible to obtain multiple types of parameters that indicate the polarization characteristics of the measurement object. It is considered that the tissue of the measurement object has various polarization characteristics, and if the type of tissue is the same, the polarization characteristics are considered to be the same (or similar). In addition, if the types of tissue are different, the polarization characteristics of a certain type may be similar, but the possibility of distinguishing between the tissues increases by combining multiple types of polarization characteristics. Therefore, if the type of tissue is identified based on multiple types of parameters, the accuracy of distinction can be improved compared to a configuration in which the type of tissue is identified based on one type of parameter. [Brief description of the drawings]

[0007] [Figure 1] 1 is a diagram showing a measurement result analysis system according to an embodiment of the present invention. [Diagram 2] 1 is a schematic diagram illustrating the configuration of an optical system of a polarization-sensitive OCT according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a block diagram showing in detail the configuration of a sampling trigger / clock generator according to the present embodiment. [Figure 4] FIG. 11 is a diagram illustrating an example of type-specific information. [Diagram 5] 13 is a flowchart of a measurement result analysis process. [Figure 6] 13 is a flowchart of an eyelid removal process. [Figure 7] 7A is a surface shape map in a Cartesian coordinate system, FIG. 7B is a surface shape map in a polar coordinate system, FIG. 7C is a surface gradient map showing the radial direction, and FIG. 7D is a binarized surface gradient map. [Figure 8]FIG. 8A is a surface gradient map showing gradient values ​​in the angular direction, FIG. 8B is a binarized surface gradient map, FIG. 8C is a diagram showing the result of combining the binarized surface gradient maps, and FIG. 8D is a diagram showing a mask for excluding the eyelids. [Figure 9] FIG. 9A shows scar tissue identified without eyelid removal, and FIG. 9B shows scar tissue identified with eyelid removal. [Figure 10] FIG. 2 is a schematic diagram showing a tomographic image of a bleb wall. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Here, the embodiments of the present invention will be described in the following order. (1) Measurement result analysis system configuration: (1-1) Configuration of polarization-sensitive OCT: (2) Analysis and processing of measurement results: (3) Other embodiments:

[0009] (1) Measurement result analysis system configuration: FIG. 1 is a diagram showing a measurement result analysis system 1000 that functions as a measurement result analysis system according to one embodiment of the present invention. A polarization-sensitive OCT 2000, a storage medium 3000, an input unit 4000, and a display unit 5000 are connected to the measurement result analysis system 1000 according to this embodiment. The polarization-sensitive OCT 2000 is an apparatus that performs optical coherence tomography by splitting light from a light source into reference light and measurement light, and measuring the interference between the reference light returned by a mirror or the like and the measurement light returned by the subject's eye. However, the polarization-sensitive OCT 2000 can acquire measurement information including the polarization characteristics of the measurement object. In this embodiment, the polarization-sensitive OCT 2000 measures the subject's eye as the measurement object to generate measurement information and output it to the measurement result analysis system 1000.

[0010] The storage medium 3000 is a non-volatile storage medium such as a hard disk drive (HDD) or a solid state drive (SSD). Various data can be stored in the storage medium 3000, and the measurement result analysis system 1000 can store data in the storage medium 3000 at any timing and can read out the data stored in the storage medium 3000. In this embodiment, the storage medium 3000 stores measurement information 3000a obtained by photographing the subject's eye.

[0011] The input unit 4000 is a device operated by a user such as an examiner, and is a device for making various inputs to the measurement result analysis system 1000. The form of the input unit 4000 is not particularly limited, and examples thereof include a keyboard and a mouse. The display unit 5000 is a display device that displays various information, and displays various images such as characters and images generated by the measurement result analysis system 1000.

[0012] The measurement result analysis system 1000 includes a control unit 1100, a communication interface (I / F) 1200, and a display I / F 1300. The communication I / F 1200 is an interface that connects the measurement result analysis system 1000 to an external device. In this embodiment, a polarization-sensitive OCT 2000, a storage medium 3000, and an input unit 4000 are connected to the measurement result analysis system 1000 via the communication I / F 1200. The communication I / F 1200 may be of various standards, such as the USB standard, PCI-Express standard, Thunderbolt standard, and Ethernet standard (which are registered trademarks).

[0013] The display I / F 1300 is an interface that connects the measurement result analysis system 1000 and the display unit 5000. The display I / F 1300 may be of various standards, such as HDMI (High-Definition Multimedia Interface: registered trademark) and DVI (Digital Visual Interface). Of course, the communication I / F 1200 and the display I / F 1300 are not limited and may be wireless communication interfaces, etc.

[0014] The control unit 1100 includes a CPU, RAM, and ROM (not shown), and can execute various programs stored in the storage medium 3000, ROM, etc. The programs executed by the control unit 1100 include various programs. In this embodiment, the programs include a measurement result analysis program 1110 for performing analysis based on the measurement information 3000a. Functions executed by the control unit 1100 by the measurement result analysis program 1110 include a measurement information acquisition unit 1110a, a parameter acquisition unit 1110b, an identification unit 1110c, and an output unit 1110d.

[0015] The measurement information acquisition unit 1110a has a function of acquiring measurement information 3000a indicating the measurement result of the measurement object by the polarization-sensitive OCT 2000. That is, the control unit 1100 controls the polarization-sensitive OCT 20 to acquire the measurement information 3000a obtained by measuring the subject's eye, and stores the measurement information 3000a in the storage medium 3000. In this embodiment, the measurement information 3000a is a Jones matrix indicating the polarization characteristics of the subject's eye, which is the measurement object.

[0016] (1-1) Configuration of polarization-sensitive OCT: Here, a configuration example of a polarization-sensitive OCT 2000 for measuring the Jones matrix will be described. Here, an example will be described in which the polarization-sensitive OCT 2000 is a wavelength-swept Fourier domain type (so-called SS-OCT type) device using a wavelength-swept light source. However, the OCT type is not limited to SS-OCT, and other types using the Fourier domain type, such as SD-OCT (spectral domain OCT) and types other than the Fourier domain type (such as the time domain type) can also be used.

[0017] As shown in FIG. 2, the polarization-sensitive OCT 2000 of this embodiment includes a light source 11, a measurement light generation unit (21-29, 31, 32) that generates measurement light from the light of the light source 11, a reference light generation unit (41-46, 51) that generates reference light from the light of the light source 11, interference light generation units 60, 70 that generate interference light by combining reflected light from the measurement object 30 generated by the measurement light generation unit with the reference light generated by the reference light generation unit, and interference light detection units 80, 90 that detect the interference light generated by the interference light generation unit.

[0018] (light source) The light source 11 is a wavelength sweep type light source, and the wavelength (wave number) of the emitted light changes at a predetermined period. Since the wavelength of the light irradiated to the measurement object 30 changes (sweeps), the intensity distribution of the light reflected from each part in the depth direction of the measurement object 30 can be obtained by performing Fourier analysis on the signal obtained from the interference light between the reflected light from the measurement object 30 and the reference light.

[0019] A polarization control device 12 and a fiber coupler 13 are connected to the light source 11, and a PM (Polarization Maintaining) coupler 14 and a sampling trigger / clock generator 100 are connected to the fiber coupler 13. Therefore, the light output from the light source 11 is input to each of the PM coupler 14 and the sample trigger / clock generator 100 via the polarization control device 12 and the fiber coupler 13. The sampling trigger / clock generator 100 uses the light from the light source 11 to generate sampling triggers and sampling clocks for each of signal processors 83 and 93, which will be described later.

[0020] (Measurement light generation section) The measurement light generating unit (21 to 29, 31, 32) includes a PM coupler 21 connected to the PM coupler 14, two measurement light paths S1, S2 branched from the PM coupler 21, a polarized beam combiner / splitter 25 connecting the two measurement light paths S1, S2, and a light path extension unit 306, a collimator lens 26, galvanometer mirrors 27, 28, and a lens 29 connected to the polarized beam combiner / splitter 25. The measurement light path S1 includes an optical path length difference generating unit 22 and a circulator 23. The measurement light path S2 includes a circulator 24. Therefore, the optical path length difference Δl between the measurement light path S1 and the measurement light path S2 is generated by the optical path length difference generating unit 22. The optical path length difference Δl may be set to be longer than the measurement range in the depth direction of the measurement object. This makes it possible to prevent interference light having different optical path length differences from overlapping. The optical path length difference generating unit 22 may use, for example, an optical fiber or an optical system such as a mirror or a prism. In this embodiment, a 1 m PM fiber is used for the optical path length difference generating unit 22. The measurement light generating unit further includes PM couplers 31 and 32. The PM coupler 31 is connected to the circulator 23. The PM coupler 32 is connected to the circulator 24.

[0021] One of the beams (i.e., the measurement beam) split by the PM coupler 14 is input to the measurement beam generating unit (21-29, 31, 32). The PM coupler 21 splits the measurement beam input from the PM coupler 14 into a first measurement beam and a second measurement beam. The first measurement beam split by the PM coupler 21 is guided to a measurement beam path S1, and the second measurement beam is guided to a measurement beam path S2. The first measurement beam guided to the measurement beam path S1 passes through the optical path length difference generating unit 22 and the circulator 23 and is input to the polarization beam combiner / splitter 25. The second measurement beam guided to the measurement beam path S2 passes through the circulator 24 and is input to the polarization beam combiner / splitter 25.

[0022] The PM fiber 304 is connected to the polarized beam combiner / splitter 25 in a state rotated 90 degrees in the circumferential direction with respect to the PM fiber 302. As a result, the second measurement light input to the polarized beam combiner / splitter 25 becomes light having a polarization component orthogonal to the first measurement light. Since the optical path length difference generating unit 22 is provided in the measurement optical path S1, the first measurement light is delayed relative to the second measurement light by the distance of the optical path length difference generating unit 22 (i.e., an optical path length difference Δl is generated). The polarized beam combiner / splitter 25 superimposes the input first measurement light and second measurement light.

[0023] The light output from the polarized beam combiner / splitter 25 (light obtained by superimposing the first measurement light and the second measurement light) is irradiated onto the measurement object 30 via the collimator lens 26, the galvanometer mirrors 27 and 28, and the lens 29. An optical path extension section 306 may be disposed between the collimator lens 26 and the galvanometer mirror 27. For example, a PM fiber of about 60 m may be used for the optical path extension section 306 as shown in FIG. 2. This makes it possible to suppress the occurrence of crosstalk between two modes of the PM fiber. The light irradiated onto the measurement object 30 is scanned in the xy directions by the galvanometer mirrors 27 and 28. The x and y directions are orthogonal to each other in a plane perpendicular to the optical axis.

[0024] The light irradiated to the measurement object 30 is reflected by the measurement object 30. Here, the light reflected by the measurement object 30 is scattered on the surface of the measurement object 30 or inside the measurement object. The reflected light and scattered light from the measurement object 30 pass through the lens 29, the galvanometer mirrors 28 and 27, and the collimator lens 26 in the opposite direction to the incident path, and are input to the polarized beam combiner / splitter 25. The polarized beam combiner / splitter 25 splits the input reflected light into horizontally polarized reflected light (horizontally polarized component) and vertically polarized reflected light (vertically polarized component), which are polarized components orthogonal to each other, and guides the horizontally polarized reflected light to the measurement optical path S1 and the vertically polarized reflected light to the measurement optical path S2, respectively.

[0025] The optical path of the horizontally polarized reflected light is changed by the circulator 23 and input to the PM coupler 31. The PM coupler 31 branches the input horizontally polarized reflected light and inputs it to each of the PM couplers 61 and 71. Therefore, the horizontally polarized reflected light input to the PM couplers 61 and 71 contains a reflected light component due to the first measurement light and a reflected light component due to the second measurement light.

[0026] The vertically polarized reflected light has its optical path changed by the circulator 24 and is input to the PM coupler 32. The PM coupler 32 branches the input vertically polarized reflected light and inputs it to each of the PM couplers 62 and 72. Therefore, the vertically polarized reflected light input to the PM couplers 62 and 72 contains a reflected light component due to the first measurement light and a reflected light component due to the second measurement light.

[0027] (Reference light generation section) The reference light generating unit (41 to 46, 51) includes a circulator 41 connected to the PM coupler 14, a reference delay line (42, 43) connected to the circulator 41, a PM coupler 44 connected to the circulator 41, two reference light paths R1, R2 branched from the PM coupler 44, a PM coupler 46 connected to the reference light path R1, and a PM coupler 51 connected to the reference light path R2. An optical path length difference generating unit 45 is disposed in the reference light path R1. No optical path length difference generating unit is provided in the reference light path R2. Therefore, the optical path length difference Δl' between the reference light path R1 and the reference light path R2 is generated by the optical path length difference generating unit 45. For example, an optical fiber is used for the optical path length difference generating unit 45. The optical path length difference Δl' of the optical path length difference generating unit 45 may be the same as the optical path length difference Δl of the optical path length difference generating unit 22. By making the optical path length differences Δl and Δl' equal, the depth positions of the multiple interference lights described below with respect to the measurement object become the same, which means that there is no need to align the multiple tomographic images to be acquired.

[0028] The other light (i.e., reference light) branched by the PM coupler 14 is input to the reference light generating unit (41 to 46, 51). The reference light input from the PM coupler 14 is input to the reference delay line (42, 43) through the circulator 41. An optical path length extension unit 308 may be disposed between the optical circulator 41 and the reference delay line (42, 43). A PM fiber of about 60 m may be used for the optical path length extension unit 308 as shown in FIG. 2. The reference delay line (42, 43) is composed of a collimator lens 42 and a reference mirror 43. The reference light input to the reference delay line (42, 43) is irradiated to the reference mirror 43 via the collimator lens 42. The reference light reflected by the reference mirror 43 is input to the circulator 41 via the collimator lens 42. Here, the reference mirror 43 is movable in a direction toward or away from the collimator lens 42. In this embodiment, before starting measurement, the position of the reference mirror 43 is adjusted so that the optical path length (measurement optical path length) from the PM coupler 14 to the object to be measured 30 via the second measurement optical path S2 matches the optical path length (reference optical path length) from the PM coupler 14 to the reference mirror 43.

[0029] The reference light reflected by the reference mirror 43 has its optical path changed by the circulator 41 and is input to the PM coupler 44. The PM coupler 44 splits the input reference light into a first reference light and a second reference light. The first reference light is guided to the reference optical path R1, and the second reference light is guided to the reference optical path R2. The first reference light is input to the PM coupler 46 through the optical path length difference generating unit 45. The reference light input to the PM coupler 46 is split into a first branched reference light and a second branched reference light. The first branched reference light is input to the PM coupler 61 through the collimator lens 47 and the lens 48. The second branched reference light is input to the PM coupler 62 through the collimator lens 49 and the lens 50. The second reference light is input to the PM coupler 51 and split into a third branched reference light and a fourth branched reference light. The third branched reference light is input to the PM coupler 71 through the collimator lens 52 and the lens 53. The fourth branched reference light passes through a collimator lens 54 and a lens 55 and is input to a PM coupler 72 .

[0030] (Interference light generation unit) The interference light generating units 60 and 70 include a first interference light generating unit 60 and a second interference light generating unit 70. The first interference light generating unit 60 includes PM couplers 61 and 62. As described above, the PM coupler 61 receives the horizontally polarized reflected light from the measurement light generating unit and the first branched reference light (light having an optical path length difference Δl) from the reference light generating unit. Here, the horizontally polarized reflected light includes a reflected light component due to the first measurement light (light having an optical path length difference Δl) and a reflected light component due to the second measurement light. Therefore, in the PM coupler 61, the reflected light component due to the first measurement light (light having an optical path length difference Δl) of the horizontally polarized reflected light and the first branched reference light are combined to generate the first interference light (horizontally polarized component).

[0031] Further, the PM coupler 62 receives the vertically polarized reflected light from the measurement light generating unit, and receives the second branched reference light (light having optical path length difference Δl) from the reference light generating unit. Here, the vertically polarized reflected light includes a reflected light component due to the first measurement light (light having optical path length difference Δl) and a reflected light component due to the second measurement light. Therefore, in the PM coupler 62, the reflected light component due to the first measurement light (light having optical path length difference Δl) of the vertically polarized reflected light is combined with the second branched reference light to generate a second interference light (vertically polarized component).

[0032] The second interference light generating unit 70 has PM couplers 71 and 72. As described above, the horizontally polarized reflected light is input from the measurement light generating unit to the PM coupler 71, and the third branched reference light (light not having an optical path length difference Δl) is input from the reference light generating unit. Therefore, in the PM coupler 71, the reflected light component (light not having an optical path length difference Δl) by the second measurement light out of the horizontally polarized reflected light is combined with the third branched reference light to generate the third interference light (horizontally polarized component).

[0033] Further, the PM coupler 72 receives the vertically polarized reflected light from the measurement light generating unit, and receives the fourth branched reference light (light having no optical path length difference Δl) from the reference light generating unit. Therefore, in the PM coupler 72, the reflected light component (light having no optical path length difference Δl) by the second measurement light of the vertically polarized reflected light is combined with the fourth branched reference light to generate a fourth interference light (vertically polarized component). The first interference light and the second interference light correspond to the measurement light that has passed through the measurement optical path S1, and the third interference light and the fourth interference light correspond to the measurement light that has passed through the measurement optical path S2.

[0034] (Interference light detection section) The interference light detection units 80, 90 include a first interference light detection unit 80 that detects the interference light (first interference light and second interference light) generated by the first interference light generation unit 60, and a second interference light detector 90 that detects the interference light (third interference light and fourth interference light) generated by the second interference light generation unit 70.

[0035] The first interference light detection unit 80 includes balanced photodetectors 81 and 82, and a signal processor 83 connected to the balanced photodetectors 81 and 82. The PM coupler 61 is connected to the balanced photodetector 81, and the signal processor 83 is connected to the output terminal of the balanced photodetector 81. The PM coupler 61 splits the first interference light into two interference lights having a phase difference of 180 degrees, and inputs them to the balanced photodetector 81. The balanced photodetector 81 performs differential amplification and noise reduction processing on the two interference lights having a phase difference of 180 degrees input from the PM coupler 61, converts them into an electrical signal (first interference signal), and outputs the first interference signal to the signal processor 83. That is, the first interference signal is an interference signal HH of the horizontally polarized reflected light from the measurement object due to the horizontally polarized measurement light and the reference light.

[0036] Similarly, the PM coupler 62 is connected to the balanced photodetector 82, and the signal processor 83 is connected to the output terminal of the balanced photodetector 82. The PM coupler 62 splits the second interference light into two interference lights with a phase difference of 180 degrees, and inputs them to the balanced photodetector 82. The balanced photodetector 82 performs differential amplification and noise reduction processing on the two interference lights with a phase difference of 180 degrees, converts them into an electrical signal (second interference signal), and outputs the second interference signal to the signal processor 83. That is, the second interference signal is an interference signal HV of the vertically polarized reflected light from the measurement object due to the horizontally polarized measurement light and the reference light. The signal processor 83 samples the first interference signal (signal due to the first interference light) and the second interference signal (signal due to the second interference light) based on the sampling trigger and sampling clock input from the sampling trigger / clock generator 100. The first interference signal and the second interference signal sampled by the signal processor 83 are input to a calculation unit 202 described later. The signal processor 83 may be a known data acquisition device (so-called DAQ).

[0037] The second interference light detector 90, like the first interference light detection unit 80, includes balanced photodetectors 91 and 92 and a signal processor 93 connected to the balanced photodetectors 91 and 92. The PM coupler 71 is connected to the balanced photodetector 91, and the signal processor 93 is connected to the output terminal of the balanced photodetector 91. The PM coupler 71 splits the third interference light into two interference lights having a phase difference of 180 degrees and inputs them to the balanced photodetector 91. The balanced photodetector 91 performs differential amplification and noise reduction processing on the two interference lights having a phase difference of 180 degrees, converts them into an electrical signal (third interference signal), and outputs the third interference signal to the signal processor 93. That is, the third interference signal is an interference signal VH of the horizontally polarized reflected light from the measurement object and the reference light due to the vertically polarized measurement light.

[0038] Similarly, the PM coupler 72 is connected to the balanced photodetector 92, and the signal processor 93 is connected to the output terminal of the balanced photodetector 92. The PM coupler 72 splits the fourth interference light into two interference lights with a phase difference of 180 degrees, and inputs them to the balanced photodetector 91. The balanced photodetector 92 performs differential amplification and noise reduction processing on the two interference lights with a phase difference of 180 degrees, converts them into an electrical signal (fourth interference signal), and outputs the fourth interference signal to the signal processor 93. That is, the fourth interference signal is an interference signal VV of the vertically polarized reflected light of the measurement object and the reference light due to the vertically polarized measurement light. The signal processor 93 samples the third interference signal (signal due to the third interference light) and the fourth interference signal (signal due to the fourth interference light) based on the sampling trigger and sampling clock input from the sampling trigger / clock generator 100. The third interference signal and the fourth interference signal sampled by the signal processor 93 are input to a calculation unit 202 described later. A known data acquisition device (so-called DAQ) can also be used for the signal processor 93. With this configuration, interference signals representing the four polarization characteristics of the measurement object 30 can be acquired.

[0039] Next, the configuration of a control system of the polarization-sensitive OCT 2000 according to this embodiment will be described. As shown in Fig. 3, the polarization-sensitive OCT 2000 is controlled by a calculation device 200. The calculation device 200 is composed of a calculation unit 202, a first interference light detection unit 80, and a second interference light detector 90. The first interference light detection unit 80, the second interference light detector 90, and the calculation unit 202 are connected to a measurement unit 10. The calculation unit 202 outputs a control signal to the measurement unit 10 and drives the light source 11 and the galvanometer mirrors 27 and 28 to scan the incident position of the measurement light on the measurement object 30.

[0040] The first interference light detector 80 acquires first sampling data based on the sampling clock 1 input from the measurement unit 10, using the sampling trigger 1 as a trigger, for the interference signal (interference signal HH and interference signal HV) input from the measurement unit 10, and outputs the first sampling data to the calculation unit 202. The calculation unit 202 performs a predetermined calculation process on the first sampling data to generate the HH component and the HV component of the Jones matrix. The second interference light detector 90 acquires second sampling data based on the sampling clock 2 input from the measurement unit 10, using the sampling trigger 2 as a trigger, for the interference signal (interference signal VH and interference signal VV) input from the measurement unit 10, using the sampling trigger 2 as a trigger, and outputs the second sampling data to the calculation unit 202. The calculation unit 202 performs a predetermined calculation process on the second sampling data to generate the VH component and the VV component of the Jones matrix. The HH, HV, VH, and VV components of the Jones matrix are the 1st row, 1st column, the 1st row, 2nd column, the 2nd row, 1st column, and the 2nd row, 2nd column of the 2 row, 2 column Jones matrix, respectively. If the 1st row, 1st column is denoted as a, the 1st row, 2nd column is denoted as b, the 2nd row, 1st column is denoted as c, and the 2nd row, 2nd column is denoted as d, the Jones matrix J(x,y,z) of any coordinates (x,y,z) can be expressed by the following formula (1).

number

[0041] In the Jones matrix J(x,y,z) measured as described above, each of the components a, b, c, and d is a complex number. The Jones matrix also depends on the position of the object in the depth direction (optical axis direction) and the position in the direction perpendicular to the optical axis. Note that here, the two orthogonal directions in the plane perpendicular to the optical axis are defined as the x direction and the y direction, and the optical axis direction is defined as the z direction.

[0042] In this embodiment, the Jones matrix defined for each position in three-dimensional space is the measurement information 3000a. When the polarization-sensitive OCT 2000 measures the subject's eye, the polarization-sensitive OCT 2000 transmits the measurement information 3000a to the measurement result analysis system 1000. The control unit 1100 acquires the measurement information 3000a via the communication I / F 1200 and stores it in the storage medium 3000.

[0043] Returning to FIG. 1, the description will be continued. The parameter acquisition unit 1110b is a function of acquiring a plurality of types of parameters indicating the polarization characteristics for each position of the object to be measured based on the measurement information. That is, the control unit 1100 acquires parameters indicating the polarization characteristics for each of the coordinates (x, y, z) indicated by the measurement information 3000a based on the Jones matrix. The parameters indicating the polarization characteristics may be various parameters, but in this embodiment, the control unit 1100 acquires a parameter indicating the strength of birefringence for each position of the object to be measured, a parameter indicating the depolarization property of the object to be measured, and a parameter indicating the spatial uniformity of the orientation of the birefringence axis of the object to be measured. Specifically, the control unit 1100 acquires a local phase retardation amount indicating the strength of birefringence for each position of the object to be measured based on the measurement information 3000a. In addition, the control unit 1100 acquires a polarization entropy indicating the depolarization property of the object to be measured based on the measurement information 3000a. Furthermore, the control unit 1100 acquires OAxU (Optic Axis Uniformity) based on the measurement information 3000a. The acquired parameters for each position are stored as parameter information 3000b in the storage medium 3000. The acquisition of these parameters will be described in detail later.

[0044] The identification unit 1110c is a function for identifying the type of tissue for each position based on the values ​​of multiple types of parameters. The polarization-sensitive OCT 2000 according to this embodiment can be used for various purposes. Here, an example is assumed in which the polarization-sensitive OCT 2000 is used for postoperative management of trabeculectomy. The treatment for glaucoma that has solid evidence at present is to lower intraocular pressure, and trabeculectomy is performed as an effective means of treating intraocular pressure. Trabeculectomy is a surgical procedure in which a part of the trabecula and iris of the eye is removed and a scleral flap is formed to form an artificial aqueous humor drainage path from the anterior chamber between the conjunctiva and the sclera. In addition, in this surgical procedure, a pool for temporarily storing aqueous humor is formed between the conjunctiva and the sclera.

[0045] This pool is called a filtering bleb, and the wall of the bleb, which was originally the conjunctiva, is called the bleb wall. Because the aqueous humor drainage pathway, including the bleb formed by this surgical procedure, is artificial, it often happens that the drainage pathway closes due to wound healing, and the intraocular pressure lowering effect is no longer functioning. In particular, scar tissue made of collagen fibers often develops in the bleb wall, preventing the drainage of aqueous humor. If it is confirmed that the intraocular pressure lowering function is impaired due to scar tissue in the bleb wall, the scar tissue is removed by filtering bleb reconstruction.

[0046] Conventionally, scarring of the bleb wall has been evaluated based on the subjective judgment of the examiner. In this embodiment, therefore, a polarization-sensitive OCT 2000 is used to objectively quantitatively evaluate whether or not the bleb wall is scarred. In order to detect scarring of the bleb wall, in this embodiment, the identifying unit 1110c identifies the type of tissue for each position of the subject's eye. For this purpose, in this embodiment, a plurality of types of tissue to be analyzed in the subject's eye are determined in advance. Then, a range of values ​​of a plurality of types of parameters is associated with each type of tissue, and stored in the storage medium 3000 as type identifying information 3000c.

[0047] Fig. 4 is a diagram illustrating the type specifying information 3000c. In Fig. 4, the type of tissue of the subject's eye is shown at the left end of the table. In this example, the types of tissue are bleb wall, scar tissue, sclera, uvea, and extraocular muscle. That is, in this embodiment, the type specifying information 3000c is defined so that tissues that may be present around the bleb wall can be distinguished in trabeculectomy.

[0048] For a test eye whose tissues are known in advance, the parameters of each tissue are obtained and compared, and if the magnitude of the parameter value of each tissue is classified as Low when it is relatively small and as High when it is relatively large, it was found that the range of values ​​is as shown in Figure 4. For example, when the local phase delay amounts for the bleb wall, scar tissue, sclera, uvea, and extraocular muscles were compared, the results were Low, High, High, Random, and High-Very High.

[0049] In addition, Random indicates that various values ​​can be taken from Low to High, and High-Very High indicates that a value that is very large compared to other tissues can be taken. In addition, Moderate-High indicates that a value can be taken from the middle between Low and High to High. In FIG. 4, the range of the relative size of each tissue is also shown for the intensity of the measurement information 3000a. The intensity is not a parameter indicating the polarization characteristics, and does not need to be used to identify the tissue. However, if the intensity of the measurement information 3000a is low, analysis based on the image becomes difficult, so in this embodiment, the intensity is also taken into consideration when identifying the tissue.

[0050] The range of each parameter, i.e., distinction between Low and High, may be determined in advance for each parameter. For example, when the possible range of each parameter is V1 to V2, the (V2-V1) / 2 may be used as a threshold value to determine Low and High, or a statistical value such as the average or median of the distribution of the parameter values ​​may be used as a threshold value to determine Low and High, and various configurations may be adopted. When there are three or more ranges, two types of thresholds may be set. For example, thresholds Th1 and Th2 may be determined in advance for the local phase delay amount, and the local phase delay amount may be regarded as Low when the value is Th1 or less, High when it is greater than Th1 and less than Th2, and Very High when it is greater than Th2. Also, for example, thresholds Th3 and Th4 may be determined in advance for the polarization entropy, and the polarization entropy may be regarded as Low when the value is Th3 or less, Moderate when it is greater than Th3 and less than Th4, and High when it is greater than Th4. In the case of Random, the parameter does not need to be referred to when identifying the type of tissue.

[0051] In a state where type identification information 3000c indicating the threshold value defined as above is stored in storage medium 3000, identification unit 1110c refers to parameter information 3000b and identifies the parameter value at each of the coordinates (x, y, z). Then, when each of the parameter values ​​is included in a range corresponding to a specific organization among the organizations indicated by type identification information 3000c, identification unit 1110c determines that the organization at that position is the specific organization. With the above configuration, identification unit 1110c can identify which of the types of organizations shown in FIG. 4 an organization at any coordinate (x, y, z) is.

[0052] As described above, according to this embodiment, it is possible to identify which of multiple tissues the tissue at any position in the test eye is. However, since this embodiment is used for post-operative management of trabeculectomy, the identification unit 1110c identifies the coordinates (x, y, z) where the intensity is High, the local phase delay is High, the polarization entropy is Low, and the OAxU is High, and identifies the tissue at the coordinates as scar tissue.

[0053] In the present embodiment according to the above configuration, the tissue is identified based on three parameters indicating the polarization characteristics. Therefore, compared with a configuration in which the tissue is identified based only on a specific parameter, the accuracy of automatically distinguishing the tissue can be improved. For example, when trying to identify the tissue based only on the amount of local phase delay, it is difficult to automatically distinguish between the sclera and scar tissue. For this reason, in the past, it was necessary to distinguish the tissue by performing an artificial operation based on the captured image. However, in the present embodiment, since the type of tissue is identified based on multiple parameters, it is possible to automatically distinguish the tissue with high accuracy.

[0054] The output unit 1110d is a function that displays information indicating the result identified by the identification unit 1110c. In this embodiment, an example is assumed in which information for performing postoperative management of trabeculectomy is provided to the examiner by identifying scar tissue. For this reason, the output unit 1110d generates information on the identified scar tissue, for example, information for distinguishing the scar tissue from other tissues at each of the coordinates (x, y, z) and information indicating the volume, area, etc. of the scar tissue. Then, the output unit 1110d controls the display unit 5000 via the display I / F 1300 and causes the display unit 5000 to display the generated information. As a result, the examiner can determine the presence or absence of scar tissue in the subject's eye, the degree of scarring, the need for bleb reconstruction, etc.

[0055] (2) Analysis and processing of measurement results: Next, the measurement result analysis process performed by the control unit 1100 in the above-mentioned configuration will be described in detail. FIG. 5 is a flowchart showing the measurement result analysis process. The measurement result analysis process is executed after the subject places the subject's eye at the measurement position of the polarization-sensitive OCT 2000. When the measurement result analysis process is started, the control unit 1100 acquires measurement information by the function of the measurement information acquisition unit 1110a (step S100). That is, the control unit 1100 controls the polarization-sensitive OCT 20 to acquire measurement information 3000a obtained by measuring the subject's eye and store it in the storage medium 3000. In this embodiment, the measurement information 3000a is expressed by a Jones matrix for each coordinate (x, y, z) in a three-dimensional space.

[0056] Next, the control unit 1100 acquires the intensity I(x, y, z) for each position by the function of the parameter acquisition unit 1110b (step S105). The acquired intensity I(x, y, z) is stored in the storage medium 3000 as parameter information 3000b. The intensity I(x, y, z) is specified, for example, by the following formula (2). Here, a, b, c, and d are the components of the Jones matrix shown in formula (1). The intensity I(x, y, z) is also used when visualizing the measurement information 3000a as a measurement image, but when visualizing an image based on the intensity, it is preferable to perform processing such as expressing the intensity logarithmically and expressing a specific range as a gradation value.

number

[0057] Next, the control unit 1100 uses the function of the identification unit 1110c to identify the position Io where Imin<intensity I(x, y, z) (step S110). Here, Imin is a threshold for distinguishing between low and high intensity I(x, y, z) and is determined in advance. A flag indicating that the intensity is at a high level is associated with the position Io. According to the above process, as shown in FIG. 4, positions where the tissue is the uvea are excluded from the position Io. In addition, some positions where the tissue is the bleb wall and some positions where the tissue is the extraocular muscle are also excluded from the position Io.

[0058] Next, the control unit 1100 acquires the local phase delay amount R(x, y, z) by the function of the identification unit 1110c (step S115). The acquired local phase delay amount R(x, y, z) is stored in the storage medium 3000 as parameter information 3000b. The local phase delay amount R(x, y, z) is identified based on, for example, the following formulas (3) and (4).

number

number

[0059] In addition, in equation (3), the left side is the local Jones matrix J localized with a length of δz in the optical axis direction at the coordinates (x, y, z). L (z, δz), and J on the right hand side is the Jones matrix. The Jones matrix also depends on the coordinates (x, y), but for simplicity, the notation for x and y is omitted here.

[0060] In equation (4), the local Jones matrix J defined by equation (3) L The local phase delay amount R(z) is defined as ξ1(z, δz) and ξ2(z, δz) which are eigenvalues ​​obtained by diagonalizing (z, δz). Note that in equation (4), the superscript asterisk represents a complex conjugate, and arg represents the argument of the complex number which is the argument. For simplicity, notation for x and y is omitted in equation (4).

[0061] The local phase delay R(x,y,z) is a parameter that indicates the strength of birefringence at each position of the object being measured. When light is incident on a non-isotropic medium, multiple refracted light beams appear. Birefringence can also occur when the medium is a tissue in a living body. Most of the birefringence observed in living bodies is due to form birefringence of fibrous tissue. For example, collagen fibers, nerve fibers, and muscle fibers all have a periodic structure as an assembly of cylinders with a size (nanometer order) that is sufficiently smaller than the wavelength of light. Such periodic structures act in complex ways on electromagnetic fields, and the medium behaves as a kind of metamaterial and exhibits birefringence. The strength of this birefringence depends on various factors, but generally speaking, the higher the fiber density, the stronger the birefringence.

[0062] The main component of the sclera, bleb wall (conjunctiva), and scar tissue is collagen fiber, but their structures are different. The collagen fiber in the bleb wall has weak orientation and periodicity in its microstructure, so its birefringence is weak. The collagen fiber in the sclera has strong orientation and periodicity in its microstructure, so its birefringence is strong. The scar tissue in the bleb wall has collagen fibers with strong orientation. Therefore, if the local phase delay R, which is a parameter corresponding to the strength of birefringence, is obtained, it can be used as an element for distinguishing the tissues of the test eye.

[0063] The strength of birefringence is a property that includes the concept of magnitude defined by the difference between two refractive indices depending on polarization, and the direction of the axis defined by the direction of the polarization state where the refractive index is minimum and maximum. Therefore, the strength of birefringence may be evaluated by the magnitude of birefringence, or may be evaluated by an index including the direction of the axis. In this embodiment, the former, that is, the local phase delay amount R(x, y, z), which is the phase difference of the output light in the axis where the refractive index is minimum and maximum, is used as a parameter for identifying the type of tissue. In the case of structural birefringence possessed by fibrous tissue of a living body, the slow axis where the refractive index is maximum generally coincides with the fiber direction.

[0064] Next, the control unit 1100 uses the function of the identification unit 1110c to identify a position Ro where Rmin<local phase delay amount R(x,y,z)≦Rmax (step S120). Here, Rmin is a threshold for distinguishing between Low and High of the local phase delay amount R(x,y,z), and Rmax is a threshold for distinguishing between High and Very High of the local phase delay amount R(x,y,z). These thresholds are determined in advance. A flag indicating that the local phase delay amount is at a High level is associated with the position Ro. According to the above process, the position where the tissue is a bleb wall is excluded from the position Ro, as shown in FIG. 4.

[0065] Next, the control unit 1100 acquires the polarization entropy H(x, y, z) by the function of the identification unit 1110c (step S125). The acquired polarization entropy H(x, y, z) is stored in the storage medium 3000 as parameter information 3000b. A method for calculating the polarization entropy H(x, y, z) is described in, for example, the following document. M. Yamanari, S. Tsuda, T. Kokubun, Y. Shiga, K. Omodaka, N. Aizawa, Y. Yokoyama, N. Himori, S. Kunimatsu-Sanuki, K. Maruyama, H. Kunikata, and T. Nakazawa, "Estimation of Jones matrix, birefringence and entropy using Cloude-Pottier decomposition in polarization-sensitive optical coherence tomography," Biomed. Opt. Express 7(9), 3551-3573 (2016).

[0066] The calculation method for the polarization entropy can be simply described as follows: a 2-by-2 Jones matrix is ​​rearranged into a 1-by-4 vector, its covariance matrix is ​​calculated, the ensemble average of the covariance matrix is ​​calculated for a certain spatial range, and the entropy is calculated from its eigenvalues. As an actual example, the calculation can be performed based on the following formulas (5), (6), and (7).

number

number

number

[0067] The polarization entropy H(x,y,z) is expressed by Equation (6), where λ' i are the normalized eigenvalues ​​of the covariance matrix T, and the eigenvalue λ jHere, the polarization entropy H depends on the coordinates (x, y, z) in equation (6), but for simplicity, the notation for x, y, and z is omitted here.

[0068] Polarization entropy H(x,y,z) is a parameter that indicates the depolarization of the object being measured. In polarization-sensitive OCT, depolarization refers to the disorder of the spatial polarization characteristics of the object being measured (depolarization). Melanin pigments and melanosomes are known as biological tissues that have depolarization. For example, the iris pigmented epithelium and uvea contain melanosomes, so the value of the parameter indicating depolarization is large. In addition, depolarization occurs due to the folded structure of collagen fibers in the sclera, and the value of the parameter indicating depolarization is large.

[0069] The polarization entropy is one of the indices for evaluating the depolarization property described above. There are various other definitions for such indices. In this embodiment, the control unit 1100 acquires the polarization entropy H(x,y,z) for each position in order to identify the type of tissue using the polarization entropy H(x,y,z).

[0070] Next, the control unit 1100 uses the function of the identification unit 1110c to identify the position Ho where the polarization entropy H(x, y, z)≦Hmax (step S130). Here, Hmax is a threshold value for distinguishing between Low and High of the polarization entropy H(x, y, z) and is determined in advance. A flag indicating that the polarization entropy H is at a Low level is associated with the position Ho. According to the above process, as shown in FIG. 4, the positions where the tissue is the sclera, the positions where the tissue is the bleb wall, and the positions where the tissue is the extraocular muscle are excluded from the position Ho.

[0071] Next, the control unit 1100 acquires OAxU(x, y, z) by the function of the identification unit 1110c (step S135). The acquired OAxU(x, y, z) is stored in the storage medium 3000 as parameter information 3000b. Here, OAxU is optical axis uniformity, and is disclosed in the following document. M. Yamanari, K. Ishii, S. Fukuda, Y. Lim, L. Duan, S. Makita, M. Miura, T. Oshika, and Y. Yasuno, "Optical Rheology of Porcine Sclera by Birefringence Imaging," PLoS One 7(9), e44026 (2012). J. Willemse, MGO Grafe, JA van de Kreeke, F. Feroldi, FD Verbraak, and JF de Boer, "Optic axis uniformity as a metric to improve the contrast of birefringent structures and analyze the retinal nerve fiber layer in polarization-sensitive optical coherence tomography," Opt. Lett. 44(15), 3893-3896 (2019).

[0072] OAxU can be calculated, for example, based on the following equation (8).

number

[0073] Here, Qm, Um, and Vm are Stokes parameters indicating the direction of the birefringence axis, averaged by a kernel of a predetermined size centered at the m-th position. The Stokes parameters can be obtained, for example, from the eigenvectors of the Jones matrix localized in the optical axis direction of the object. The eigenvectors can be calculated by applying matrix diagonalization to the localized Jones matrix. In Equation (8), OAxU depends on the coordinates (x, y, z), but here, for simplicity, the notation for x, y, and z is omitted.

[0074] OAxU(x, y, z) is a parameter indicating the spatial uniformity of the direction of the birefringence axis of the measurement object. Indicators representing depolarization properties such as polarization entropy become stronger as the biological tissue changes the incident polarized light more randomly. On the other hand, as disclosed in the above-mentioned literature, OAxU is an indicator for evaluating the spatial uniformity of the direction of the birefringence axis. In the case of OAxU, the magnitude of birefringence is not the object of evaluation, but in tissues with strong axial orientation due to birefringence, such as muscle fibers and scar tissue, OAxU becomes large. In tissues with strong birefringence and fibers overlapping in various axial directions, such as the sclera, OAxU becomes small. When calculating OAxU for a medium with zero or very weak birefringence, such as the bleb wall (conjunctiva), the birefringence axis is greatly affected by noise, so OAxU becomes small. In the present embodiment, the control unit 1100 acquires OAxU(x, y, z) for each position in order to identify the type of tissue using OAxU(x, y, z).

[0075] Next, the control unit 1100 specifies the position Uo where OAxUmin < OAxU(x, y, z) by the function of the specifying unit 1110c (step S140). Here, OAxUmin is a threshold value for distinguishing Low and High of OAxU(x, y, z) and is predetermined. For the position Uo, a flag indicating that OAxU is at the High level is associated. According to the above processing, as shown in FIG. 4, the positions where the tissue is the bleb wall, the positions where the tissue is the sclera, and the positions where the tissue is the iris are excluded from the position Uo.

[0076] Next, the control unit 1100 uses the function of the identification unit 1110c to identify a position So that corresponds to all of the positions Io, Ro, Ho, and Uo (step S145). That is, the control unit 1100 refers to the flags associated with the coordinates (x, y, z), and identifies the position to which all of the flags in steps S110, S120, S130, and S140 correspond as the position So. Since the intensity I is at a high level, the local phase delay amount is at a high level, the polarization entropy is at a low level, and OAxU is at a high level, the position can be said to be scar tissue as shown in FIG. 4.

[0077] Next, the control unit 1100 performs a noise removal process using the function of the identification unit 1110c (step S150). The noise removal process may be performed by various methods. Scar tissue is cellular tissue and is considered to spread over a certain size, and when the size of the detected scar tissue is extremely small, it is considered to be noise. In addition, it is considered that there is little need to detect extremely small scar tissue in the postoperative management of trabeculectomy. Therefore, in this embodiment, when the position So does not spread over a volume or area equal to or greater than a threshold value, the detection result for the position So is considered to be noise and not scar tissue.

[0078] Next, the control unit 1100 performs an eyelid removal process using the function of the identification unit 1110c (step S155). In the polarization-sensitive OCT 2000 used by the applicant, the eyelids around the subject eye are included in the imaging range, and the position of the cells of the eyelids may be detected as the position So. It is relatively easy to distinguish the eyelids from scar tissue, but in this embodiment, the process of removing the eyelids is automatically performed.

[0079] Specifically, FIG. 6 is a flowchart of the eyelid removal process. When the eyelid removal process is started, the control unit 1100 acquires a surface shape map (step S200). The surface shape map is information indicating the height of the subject's eye and the tissues around it in the optical axis direction. The control unit 1100 identifies the position of the tissue that is closest to the corneal apex in the optical axis direction, that is, the tissue that is closest to the surface, based on the measurement information 3000a. The control unit 1100 also plots the position of each tissue on a two-dimensional plane perpendicular to the optical axis. Here, the two-dimensional plane is defined by a two-dimensional coordinate system obtained by omitting z, which is the optical axis direction, in the three-dimensional coordinate system that defines the above-mentioned coordinates (x, y, z).

[0080] Fig. 7A is a surface topography map that defines gradation values ​​on a two-dimensional plane such that the gradation values ​​are larger closer to the corneal apex and smaller closer to the fundus. In the surface topography map, as shown in Fig. 7A, the state in which the eyelid L is present around the spherical test eye E can be grasped. In Fig. 7A, the X-axis and Y-axis for defining the x-coordinate and y-coordinate, respectively, are shown superimposed on the surface topography map. The position of the corneal apex on the XY plane is the origin of the X-axis and the Y-axis.

[0081] Next, the control unit 1100 converts the surface shape map into polar coordinates (step S205). That is, the control unit 1100 converts any position on a two-dimensional plane into coordinates expressed by a distance r from the origin and a clockwise angle θ from a predetermined direction (the negative direction of the Y axis in this embodiment). FIG. 7B shows the surface shape map after the polar coordinate conversion of the surface shape map shown in FIG. 7A. Here, the negative direction of the Y axis shown in FIG. 7A is set to 0°, and the angle is defined clockwise. Therefore, the negative direction of the X axis shown in FIG. 7A is 90°. In FIG. 7A, angles are added to the axes. Since the surface shape map shown in FIG. 7A is rectangular, the directions of angles θ of 45°, 135°, 225°, and 315° are diagonal directions, and r is the maximum value. Therefore, in FIG. 7B, when the angle θ after the polar coordinate conversion is 45°, 135°, 225°, and 315°, r in the vertical axis direction is the maximum value.

[0082] After the polar coordinate conversion, the control unit 1100 acquires a gradient value in the radial direction (step S210). That is, the control unit 1100 acquires a gradient value indicating the amount of change in the surface shape map after the polar coordinate conversion in the direction of the distance r from the origin. The gradient value may be acquired by various methods, and may be a differential in the direction of the distance r, or may be acquired by various filters for acquiring the gradient value. FIG. 7C is a surface gradient map indicating the gradient value of each coordinate, and the larger the gradient value, the larger the gradation value. In FIG. 7C, the surface gradient map is shown by an image in which the brightness increases as the gradation value increases.

[0083] Since the test eye is approximately spherical, as shown in Fig. 7A, the surface shape of the test eye E changes smoothly, but the surface shape changes suddenly at the boundaries between the test eye E and the eyelid L, which are located above and below the test eye E. That is, the gradation value indicating the surface shape changes suddenly at the boundaries. Moreover, the surface shape of the eyelid L changes more suddenly than the surface shape of the test eye E, and the change in gradation value is greater.

[0084] The surface gradient map shown in Fig. 7C reflects such a change in surface shape, with large (white) gradation values ​​distributed on the surface of the eyelid L, and small (black) gradation values ​​distributed on the surface of the subject's eye E. Therefore, the control unit 1100 performs binarization based on the radial gradient value (step S215). That is, the control unit 1100 compares the gradation value of the surface gradient map acquired in step S210 with a threshold value for binarization (e.g., the median value of the gradation range) to binarize the surface gradient map. Fig. 7D is a diagram showing the surface gradient map after binarization, with coordinates with large gradient values ​​shown in white and coordinates with small gradient values ​​shown in black.

[0085] Next, the control unit 1100 acquires a gradient value in an angular direction (step S220). That is, the control unit 1100 acquires a gradient value indicating the amount of change in the surface shape map after the polar coordinate transformation in the direction of the angle θ from a predetermined axis. Here, too, the gradient value may be acquired by various methods. FIG. 8A is a surface gradient map indicating the gradient value of each coordinate, and the surface gradient map is represented by an image in which the larger the gradient value, the larger the gradation value, and the larger the gradation value, the greater the brightness.

[0086] The surface gradient map indicated by the gradient value in the angular direction also reflects such a change in the surface shape, with parts with large gradation values ​​(white) distributed on the surface of the eyelid L and parts with small gradation values ​​(black) distributed on the surface of the subject's eye E. Therefore, the control unit 1100 performs binarization based on the gradient value in the angular direction (step S225). That is, the control unit 1100 compares the gradation value of the surface gradient map acquired in step S220 with a threshold value for binarization (e.g., the median value of the gradation range) to binarize the surface gradient map. FIG. 8B is a diagram showing the surface gradient map after binarization, with coordinates with large gradient values ​​indicated by white and coordinates with small gradient values ​​indicated by black.

[0087] Next, the control unit 1100 synthesizes the binarized images (step S230). That is, the control unit 1100 synthesizes the image obtained in step S215 and the image obtained in step S225 by OR operation. Next, the control unit 1100 performs noise removal (step S235). It can be estimated that the eyelid is an area of ​​continuous white parts in the binarized image after synthesis. In addition, the eyelid is considered to have a certain size. Therefore, the control unit 1100 removes white parts of a predetermined area or less as noise in the binarized image after synthesis. FIG. 8C shows the binarized image after noise removal.

[0088] Next, the control unit 1100 identifies the eyelids (step S240). That is, the control unit 1100 performs a conversion inverse to the conversion in step S205 on the binarized image after noise removal, converting it from polar coordinates to Cartesian coordinates. Fig. 8D shows an image in which the eyelids are colored black and the other parts are colored white in the converted coordinates.

[0089] Through the above process, the subject eye portion and the eyelid portion are identified. The control unit 1100 excludes positions that are estimated to be eyelids from the positions So. That is, the control unit 1100 removes the positions So whose (x, y) coordinates match the eyelid portion shown in black in FIG. 8D. Next, the control unit 1100 identifies the remaining positions So after the eyelids are removed as scar tissue (step S160).

[0090] According to the above process, even if the scar tissue and the eyelid tissue cannot be distinguished by the parameters indicating the polarization characteristics, the eyelid tissue is not mistaken for the scar tissue. FIG. 9A is a schematic diagram showing the intensity I obtained in step S105 for a portion that is visually recognized when the test eye is viewed along the optical axis direction. The central part of FIG. 9A is the test eye E, and the eyelid L is present above and below the test eye E. The test eye E includes a pupil P and an iris IR, and the conjunctiva is present between the outside of the iris IR and the eyelid L. A part of the conjunctiva is a bleb wall B. In this image, the position So obtained in step S145 is indicated by a marker M. As shown in FIG. 9A, when the scar tissue is identified by the parameters indicating the polarization characteristics, the tissue of the eyelid L may also include a portion that has been identified as the scar tissue.

[0091] 9B is a schematic diagram of the position So after the eyelid removal process in step S155 is performed for the same image as in FIG. 9A. As shown in FIG. 9B, when the eyelid removal process is performed, there is no position on the eyelid that is identified as scar tissue. Therefore, the accuracy of identifying the type of tissue can be improved compared to when the eyelid removal process is not performed.

[0092] A schematic diagram of a tomographic image at the dashed line DL in Figure 9B is shown in Figure 10. Figure 10 shows the eyelid L, conjunctiva and bleb wall CJ / BW, marker M, sclera S, scleral flap SF, and water space WC. In Figure 10, marker M is also the area where scar tissue was detected. In this way, by using this method, scar tissue can be detected three-dimensionally in a tomographic image or volume.

[0093] Next, the control unit 1100 displays information about the scar tissue by using the function of the output unit 1110d (step S165). That is, the control unit 1100 performs a predetermined analysis process based on the position So after the eyelid removal process to generate information to be displayed. The information to be displayed may be various information, such as the area of ​​the scar tissue in an amphasic state (projected onto a plane perpendicular to the optical axis direction), the volume of the scar tissue, the area of ​​the scar tissue on an arbitrary cross section, the thickness of the scar tissue in an arbitrary direction, etc. Of course, the statistical values ​​(average value, etc.) of these areas, etc. may be displayed, or the relative values ​​(such as the ratio between the area of ​​the subject eye and the area of ​​the scar tissue) may be displayed.

[0094] When the information to be displayed is generated, the control unit 1100 controls the display unit 5000 via the display I / F 1300 to display the information on the display unit 5000. According to the above process, the examiner can perform postoperative management of trabeculectomy based on the displayed content.

[0095] (3) Other embodiments: The above embodiment is an example for carrying out the present invention, and various other embodiments can be adopted. For example, the device configuration of the measurement result analysis system is not limited to the configuration shown in FIG. 1. The devices shown in FIG. 1 may be fewer devices sharing functions, or may be more devices. Specifically, the measurement result analysis system 1000 may be a device integrated with at least one of the polarization-sensitive OCT 2000, the storage medium 3000, the input unit 4000, and the display unit 5000. Also, the measurement result analysis system 1000 may be distributed among more devices, such as at least a part of which is configured by a server.

[0096] 5 and 6 are merely examples, and various omissions, additions, replacements, etc. may be performed. For example, the order of acquiring the intensity in step S105 and the parameters in steps S115, S125, and S135 may be arbitrary. Furthermore, in the eyelid removal process, since the subject's eye is substantially spherical, it is considered that the polar coordinate system is easier to capture the characteristics of the surface shape map than the Cartesian coordinate system, and thus polar coordinate transformation is used. However, a gradient map may be generated using a surface shape map in a Cartesian coordinate system. Furthermore, in the eyelid removal process, gradient values ​​in two directions are acquired, but a configuration in which a gradient value in one direction is acquired may also be used.

[0097] The measurement information acquisition unit may acquire measurement information indicating the measurement result of the measurement object by the polarization-sensitive OCT. That is, the measurement information acquisition unit acquires measurement information for calculating a plurality of types of parameters indicating the polarization characteristics. The measurement object is not limited to the subject's eye, and any object can be the measurement object as long as it can be measured by the interference between the reference light and the measurement light using the OCT. In addition, the measurement information may be information indicating the measurement result reflecting the polarization characteristics of the measurement object, and is not limited to the Jones matrix as in the above-mentioned embodiment. For example, the measurement information may be a Jones vector of the interference light measured by the polarization-sensitive OCT.

[0098] The parameter acquisition unit may acquire a plurality of types of parameters that indicate the polarization characteristics for each position of the object based on the measurement information. That is, the parameter acquisition unit may acquire a plurality of types of parameters that can distinguish the tissues of the object. The types of parameters are not limited to the above-mentioned local phase delay, polarization entropy, and OAxU.

[0099] For example, the magnitude of birefringence defined by the difference in refractive index in different axial directions, various evaluation indices of depolarization (degree of polarization uniformity, depolarization index, depolarization power, etc.), various indices indicating the spatial uniformity of the orientation of the birefringence axis of the measurement object, etc. may be used. Furthermore, the types of parameters used in the analysis are not limited to three types, and may be two types, or four or more types.

[0100] For example, as shown in FIG. 4, in scar tissue, the local phase delay is at a high level and the polarization entropy is at a low level. Furthermore, there is no tissue other than scar tissue in which the local phase delay is at a high level and the polarization entropy is at a low level. Therefore, the type of tissue may be identified based on the local phase delay and the polarization entropy. Furthermore, there is no tissue other than scar tissue in which the polarization entropy is at a low level and the OAxU is at a high level. Therefore, the type of tissue may be identified based on the polarization entropy and the OAxU.

[0101] The identification unit may identify the type of tissue for each position based on the values ​​of multiple types of parameters. That is, the identification unit may identify that a combination of parameter values ​​is a combination of parameters for a specific type of tissue from the values ​​of multiple types of parameters defined for each position, and identify the tissue for each position. Of course, the tissue to be identified is not limited to scar tissue, and may be a bleb wall, sclera, uvea, extraocular muscle, etc., or may be configured to identify which of multiple tissues the tissue at each position is.

[0102] Furthermore, the technique for identifying the type of tissue for each position based on the values ​​of multiple types of parameters can also be applied as a method or program invention. Also, the above-mentioned system, method, and program can be realized as a standalone device or as part of a device having multiple functions, and include various aspects. [Explanation of symbols]

[0103] 10... measurement unit, 11... light source, 12... polarization control device, 13... fiber coupler, 14... PM coupler, 21... PM coupler, 22... optical path length difference generating unit, 23... circulator, 24... circulator, 25... splitter, 26... collimator lens, 27... galvanometer mirror, 28... galvanometer mirror, 29... lens, 30... measurement object, 31... PM coupler, 32... PM coupler, 41... circulator, 42... collimator a reference mirror, 43, a reference mirror, 44, a PM coupler, 45, an optical path length difference generating section, 46, a PM coupler, 47, a collimator lens, 48, a lens, 49, a collimator lens, 50, a lens, 51, a PM coupler, 52, a collimator lens, 53, a lens, 54, a collimator lens, 55, a lens, 60, a first interference light generating section, 61, a PM coupler, 62, a PM coupler, 70, a second interference light generating section, 71, a PM coupler , 72...PM coupler, 80...first interference light detector, 81...balanced photodetector, 82...balanced photodetector, 83...signal processor, 90...second interference light detector, 91...balanced photodetector, 92...balanced photodetector, 93...signal processor, 100...clock generator, 200...arithmetic unit, 202...arithmetic unit, 302...PM fiber, 304...PM fiber, 306...optical path extension unit, 308...optical path length extension unit, 100 0...measurement result analysis system, 1100...control unit, 1110...measurement result analysis program, 1110a...measurement information acquisition unit, 1110b...parameter acquisition unit, 1110c...identification unit, 1110d...output unit, 1200...communication I / F, 1300...display I / F, 3000...storage medium, 3000a...measurement information, 3000b...parameter information, 3000c...type identification information, 4000...input unit, 5000...display unit

Claims

1. a measurement information acquisition unit that acquires measurement information indicating a measurement result of the measurement object by the polarization-sensitive OCT; a parameter acquisition unit that acquires a plurality of types of parameters that indicate polarization characteristics for each position of the measurement object based on the measurement information; An identification unit that identifies a type of tissue for each position based on values ​​of the multiple types of parameters; A measurement result analysis system comprising:

2. The measurement object is an eye, The identifying portion identifies a location of scar tissue. The measurement result analysis system according to claim 1 .

3. The plurality of types of parameters include a parameter indicating the strength of birefringence for each position of the measurement object.

3. The measurement result analysis system according to claim 1.

4. The plurality of types of parameters includes a parameter indicating the depolarization property of the object to be measured.

3. The measurement result analysis system according to claim 1.

5. The plurality of types of parameters includes a parameter indicating spatial uniformity of the orientation of the birefringence axis of the measurement object.

3. The measurement result analysis system according to claim 1.

6. A range of values ​​of the plurality of types of parameters is associated with each of the types of tissue; The identification unit is If each of the values ​​of the plurality of types of parameters is within the range corresponding to a predetermined type of tissue, the tissue at that position is identified as the predetermined type of tissue.

3. The measurement result analysis system according to claim 1.

7. The identification unit is Identifying tissue types at locations of the eye excluding the eyelid; The measurement result analysis system according to claim 2 .

8. a measurement information acquisition step of acquiring measurement information indicating a measurement result of the measurement object by the polarization-sensitive OCT; a parameter acquiring step of acquiring a plurality of types of parameters indicating polarization characteristics for each position of the measurement object based on the measurement information; a step of identifying a type of tissue for each position based on values ​​of the plurality of types of parameters; A measurement result analysis method comprising:

9. Computer, A measurement information acquisition unit that acquires measurement information indicating a measurement result of the measurement object by the polarization-sensitive OCT; a parameter acquisition unit that acquires a plurality of types of parameters that indicate polarization characteristics for each position of the measurement object based on the measurement information; An identification unit that identifies the type of tissue for each position based on values ​​of the multiple types of parameters; A measurement result analysis program that functions as a

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