JP7352162B2 - Ophthalmological image processing method and ophthalmological image processing program - Google Patents

Description

The present disclosure relates to an ophthalmologic image processing method and an ophthalmologic image processing program that process OCT data of tissues of a subject's eye.

In recent years, in the field of ophthalmology, optical coherence tomography (OCT), which is a device that takes tomographic images of tissues in the eye to be examined, has been attracting attention.

In SD-OCT, which is relatively popular in ophthalmology, the effective imaging range in the depth direction is approximately 2 mm to 3 mm from the origin position (zero delay position) in OCT data. When displaying OCT data captured by such a device, the entire imaging range is displayed as is (for example, see Patent Document 1).

On the other hand, various attempts have been made to improve the depth of penetration in OCT data (that is, to expand the imaging range in the depth direction).

In recent years, it has been reported in Non-Patent Document 1 that the photographing range can be significantly improved by improving the light source and the like. Non-Patent Document 1 reports that it is effective to improve penetration depth by employing a light source called VCSEL that emits light with a long coherence length as an OCT light source.

Japanese Patent Application Publication No. 2016-55122

Ireneusz Grulkowski. et al. (2013) High-precision, high-accuracy ultralong-range swept-source optical coherence tomography using vertical cavity surface emitting laser light source, Opt Lett. 2013 Mar 1; 38(5): 673-675.

The higher the depth of penetration in the OCT data (the wider the imaging range in the depth direction), the relatively narrower the image of the subject is depicted in the OCT data. Therefore, when the same display method as in Patent Document 1 is adopted, it becomes difficult to observe the tissue.

The present disclosure has been made based on the problems of the prior art, and provides an ophthalmological image processing method and an ophthalmic image processing program that enable good observation of a desired tissue using OCT data with high penetration depth. , as a technical issue.

An ophthalmologic image processing method according to a first aspect of the present disclosure is an ophthalmologic image processing method performed by a computer, which includes an acquisition step of acquiring OCT data obtained by photographing a tissue of a subject 's eye, and storing the photographed results in a memory in advance. a setting step of setting a part of the depth region of the data in one direction from the zero delay position in the OCT data that has been set as an extraction region, the step of setting the A setting step of setting a depth region including the image position of the tissue as the extraction region, and extracting OCT data corresponding to the extraction region in a predetermined display region on the viewer screen where the captured image is displayed. an ophthalmological image processing method, comprising: a display control step of extracting and displaying the OCT data from the OCT data.

The ophthalmologic image processing program according to the second aspect of the present disclosure is executed by a processor of a computer, so that the ophthalmologic image processing method according to the first aspect is executed by the computer.

According to the present disclosure, it is easy to observe a desired tissue well using OCT data with high penetration depth.

1 is a diagram showing a schematic configuration of an OCT system according to an example. It is a diagram showing an OCT optical system according to an example. FIG. 3 is a diagram for explaining OCT data. It is a flowchart explaining the operation. It is a figure showing an example of a viewer screen. 6 is a diagram showing the viewer screen in a state where the extraction area has been changed in comparison with FIG. 5. FIG. FIG. 3 is a diagram showing an example of a viewer screen when anterior segment OCT is displayed. FIG. 7 is a diagram showing a display mode of extracted OCT data according to a modified example.

"overview"
Embodiments of the present disclosure will be described. Note that the items classified in <> below can be used independently or in conjunction.

<Overall configuration>
One embodiment of the present disclosure will be described below. First, an OCT system according to an embodiment will be described. The OCT system is used to photograph a subject's eye and display OCT data that is the photographed result.

In this embodiment, the OCT system includes at least an OCT optical system, an image processor, and a computer (see FIG. 1). The ophthalmologic image processing program according to the embodiment is stored in a nonvolatile memory that can be read by a computer processor. The OCT optics, image processor, and computer may be integrated as an OCT device (see, eg, Examples). Also, some of the OCT optical system, image processor, and computer may be separate from other parts.

<OCT optical system>
The OCT optical system (see FIG. 2) is used to capture OCT data of the eye to be examined. The OCT optical system detects a spectral interference signal between the measurement light guided to the tissue of the eye to be examined and the reference light.

In this embodiment, an OCT optical system suitable for acquiring OCT data with high penetration depth may be used. For example, the OCT optical system may be a wavelength swept OCT (SS-OCT) optical system. In this case, the OCT optical system may include a wavelength swept light source (wavelength scanning light source) as an OCT light source that is a light source for measurement light and reference light. A wavelength swept light source changes the emission wavelength rapidly over time. For example, since a VCSEL type wavelength swept light source has a long coherence length, when used as an OCT light source, a wider imaging range in the depth direction can be enjoyed. For example, a photographing range of about 10 mm or more can be achieved. This makes it possible to photograph a plurality of tissues at different depths in the eye to be examined at one time. As a specific example, both the fundus and the transparent body may be photographed at one time. Further, it is preferable that the wavelength swept light source performs wavelength sweeping in a so-called 1 μm band (wavelength sweeping is performed centered on about 1050 nm). It is known that the so-called 1 μm band exhibits a higher depth of penetration into the tissue of the eye to be examined than other wavelength bands.

Further, the OCT optical system may include at least one of a light splitting section, a scanning section (also referred to as an optical scanner), and a detector. The light splitter splits the light from the OCT light source into measurement light and reference light. The scanning unit is a device for scanning measurement light on the tissue of the eye to be examined. The scanning unit may be, for example, a combination of two optical scanners with mutually different scanning directions. The detector outputs a spectral interference signal by receiving the measurement light and the reference light guided to the eye to be examined. The OCT optical system may scan the measurement light along a plurality of predetermined scan lines on the tissue of the eye to be examined, and may capture OCT data for each of the plurality of scan lines. The scan line may be set at any position based on instructions from the examiner. Further, by selecting one of a plurality of predetermined scan patterns, a scan line corresponding to the scan pattern may be set. Various scan patterns are known, such as line, cross, multi, map, radial, and circle.

<Image processor>
The image processor processes the spectral interference signal output from the OCT optical system to obtain OCT data of the eye to be examined. The image processor may be shared by a control section that controls the operation of the entire OCT device, or may be an image processing device separate from the control section.

<OCT data>
The OCT data may be signal data or visualized image data. For example, OCT data includes tomographic image data showing the reflection intensity characteristics of the eye to be examined, OCT angio data (for example, OCT motion contrast data) of the eye to be examined, Doppler OCT data showing the Doppler characteristics of the eye to be examined, and polarization characteristics of the eye to be examined. It may be at least one of the polarization characteristic data shown in FIG.

In addition, OCT data includes B scan data (e.g. B scan tomographic image data, two-dimensional OCT angio data, etc.), en face data (e.g. OCT en face data, front motion contrast data, etc.), three-dimensional The data may be at least one of data (for example, three-dimensional tomographic image data, three-dimensional OCT angio data, etc.).

<Computer>
The computer acquires OCT data of the subject's eye generated by the image processor and displays it on the monitor. A computer includes at least a processor (arithmetic control unit). The arithmetic control unit may be configured by a CPU, RAM, ROM, etc. When the processor executes the ophthalmological image observation program, the computer executes each step described below. The ophthalmologic image observation program may be stored in a nonvolatile storage medium that is accessible from the arithmetic control unit.

<Acquisition step>
First, the eye to be examined is photographed through an OCT optical system, and as a result of the photographing, an image processor generates OCT data of the eye to be examined. Thereafter, the OCT data generated by the image processor is acquired by the computer 1. "Acquisition" here means that target data (here, OCT data) is stored in a memory that is accessible from the processor.

<Setting step>
In the setting step, an extraction region is set for a part of the depth region in the OCT data.

Here, the extraction area in this embodiment will be explained using FIG. 3. FIG. 3 shows image data G of a tomographic image, which is an example of visualized OCT data. The image data G consists of first image data G1 corresponding to the back side of the zero delay position Z, and second image data G2 corresponding to the front side of the zero delay position Z, which are symmetrical to each other with respect to the zero delay position Z. It is an image. Specifically, a real image and a virtual image of the fundus are formed symmetrically with respect to the zero delay position Z.

In the setting step, an extraction area is set for data in one direction from the zero delay position Z (in FIG. 3, either the first image data G1 or the second image data G2). At this time, a depth region including the image position of the tissue is set as an extraction region. In other words, the distance between one or both of the upper and lower ends of the extraction region and the zero delay position is adjusted so that the image position of the tissue is included between the upper and lower ends of the extraction region.

Here, in the setting step, the image position of the tissue in the OCT data may be detected. In this case, the distance between one or both of the upper and lower ends of the extraction area and the zero delay position may be adjusted based on the detected image position. In this case, for example, by adjusting the relationship between the reference position in the extraction region and the tissue image position in the OCT data, the distance between one or both of the upper and lower ends of the extraction region and the zero delay position is adjusted. may be adjusted.

In order to observe from the retinal surface to the choroid in the center of the fundus (between the macula and papilla), a depthwise imaging range of several millimeters (for example, 2 mm to 3 mm) is sufficient, whereas wavelength-swept OCT In this case, a photographing range (photographing range in one direction from the zero delay position) that is more than twice as large as that can be realized. In this case, when the central part of the fundus is displayed in the extracted OCT data, it is preferable that the length of the extracted region in the depth direction is less than half the imaging range of the OCT data that is the extraction source.

<Application of full range technology>
Full range techniques may be applied to OCT data. Various techniques for removing virtual images in OCT data are called full-range techniques. In this embodiment, any full-range technique may be applied, and thereby it may be possible to obtain OCT data over a wider range from which virtual images are selectively removed. In this case, the extraction area can be set at any depth position from the combined area of the first image data G1 and the second image data G2.

Examples of full-range techniques include a technique that removes a virtual image (also called a mirror image) using additional hardware (for example, see Non-Patent Document 2), a technique that corrects it by software without using additional hardware (for example, , see Patent Document 2).
Wojtkowski, M. et al. (2002) Full range complex spectral optical coherence tomography technique in eye imaging, Optics Letters, 27(16), p. 1415. Japanese Patent Application No. 2015-506772 In addition, in an application filed by the present applicant (Japanese Patent Application No. 2019-014771), based on multiple OCT data having different optical path lengths when detecting a spectral interference signal, real images and virtual images in OCT data are analyzed. Yet another full-range technique has been proposed that performs at least interpolation processing on the overlapping region with the .

<Display control step>
In the display control step, extracted OCT data corresponding to the extraction area is extracted from the OCT data and displayed in a predetermined display area on the monitor. Therefore, in this embodiment, even if OCT data with high penetration depth is acquired, a depth region including the tissue image position is extracted from the OCT data and displayed, rather than the entire OCT data. Therefore, the image of the tissue of the eye to be examined is displayed in a more enlarged manner with respect to the predetermined display area. As a result, the state of the tissue of the eye to be examined can be better understood through the extracted OCT data.

<Display of information indicating the location of the extraction area>
Further, in the display control step, information indicating the positional relationship of the extraction area with respect to the OCT data that is the extraction source may be displayed on the monitor together with the extracted OCT data. Displaying such information makes it easier to understand, for example, the position of the tissue of the eye to be examined included in the extracted OCT data.

Information indicating the positional relationship of the extraction region with respect to the OCT data that is the extraction source may be displayed, for example, as a graphic, as text, or as a combination of both. The graphic may be a thumbnail image of the OCT data that is the extraction source, or may be any other image. When a thumbnail image of OCT data is displayed, the extraction area may be further highlighted on the thumbnail image. Furthermore, the graphic may indicate the positional relationship between the tissue included in the OCT data that is the extraction source and the extraction region (for example, see FIG. 8). Furthermore, the graphic may be an indicator such as the following: The indicator is a bar or a number line that indicates the imaging range of OCT data, and the range corresponding to the extraction area is highlighted in a distinguishable manner from other ranges. Alternatively, it may be an indicator that indicates, by color, the positional relationship between the tissue included in the OCT data that is the extraction source and the extraction region. For example, the color of the indicator may be changed to green when tissue is included in the extraction region, and red when tissue is not included.

<Change step>
In the changing step, an operation input for changing at least one of the depth position and range of the extraction region with respect to the OCT data is accepted. Furthermore, at least one of the depth position and range of the extraction region is changed based on the operation input.

The operation input may be input via various input interfaces connected to the computer.

A graphic indicating the position of the extraction area may be used as a widget for accepting operation input in the changing step. In this case, an operation input for changing the extraction area may be input via the above-mentioned graphic. As one specific example, an operation to move a highlighted portion on a thumbnail image or an indicator may be input as an operation input for changing the extraction area. Note that the widget here is a general term for GUI interface parts (UI parts), and is also called a control. As specific examples of widgets, commonly used widgets include buttons, sliders, check boxes, text boxes, and the like.

If at least one of the depth position and range of the extraction region is changed in the changing step, in the subsequent display control step, the extracted OCT data displayed in a predetermined display area corresponds to the changed extraction region. You can switch to what you want.

Thereby, the tissue included in the OCT data and located at a desired depth position can be observed on the monitor.

Furthermore, if at least one of the depth position and range of the extraction region is changed in the changing step, the display mode of the extracted OCT data on the monitor will be changed according to the changed extraction region in the subsequent display control step. may be changed.

In this embodiment, the display mode may be changed, for example, by changing the layout of the extracted OCT data on the monitor. In this case, the layout may be changed by changing any one of the position, size, and shape of the display area where the extracted OCT data is displayed. Furthermore, the display mode may be changed by changing at least one of the scale and aspect ratio of the extracted OCT data in the display area according to the extraction area. Furthermore, the display mode may be changed by changing the coordinate system within the display area according to the extraction area. In this case, the extracted OCT data is transformed (deformed) in accordance with the coordinate system. Furthermore, some of the above examples may be combined.

In this embodiment, in the acquisition step, OCT data including images of a plurality of tissues located at mutually different depth positions in the eye to be examined may be acquired. In this case, in the display control step, the display mode of the extracted OCT data may be changed depending on the type of tissue included in the extraction region. For example, the display mode may be changed at least between a case where only the fundus tissue is included in the extraction region and a case where a transparent body is included in the extraction region. Furthermore, the display mode may be changed depending on the number of tissue types included in the extraction area.

<Sequential display of multiple scan lines of OCT data>
In the acquisition step, a plurality of OCT data for each of a plurality of predetermined scan lines may be acquired. In order to capture a plurality of OCT data, a plurality of scan lines may be continuously scanned by the OCT optical system. The plurality of scan lines may be set at positions close to each other (for example, at positions approximately one pixel apart) by raster scanning.

In this case, in the setting step, processing for setting the extraction region for each OCT data may be performed so that the position of the extraction region with respect to the image position of the subject is matched among the plurality of OCT data. Moreover, in the display control step, extracted OCT extracted from each of the plurality of OCT data may be sequentially displayed in the display area. At this time, a plurality of extracted OCT data may be switched and displayed so that the position on the tissue displayed by the extracted OCT data changes in one direction. As a result, the position of the tissue image with respect to the display area is maintained in the sequential display of a plurality of extracted OCT data in the display area.

However, it is not necessarily limited to this. In the setting step, an extraction region setting process may be performed for each OCT data so that the depth position of the extraction region is matched among the plurality of OCT data. When a plurality of extracted OCT data are switched and displayed so that the position on the tissue displayed by the extracted OCT data changes in one direction, the image position of the tissue is displaced within the display area. As a result, the three-dimensional shape of the tissue becomes easier to grasp in the sequential display.

<Real-time display>
Each time new OCT data is photographed via the OCT optical system, real-time extracted OCT data may be displayed in the above-described sequential display.
In this case, for example, in the acquisition step, each time OCT data is generated by the image processor by scanning each scan line by the OCT optical system, the OCT data is acquired as new OCT data. Further, an extraction area is set in the new OCT data, and the extracted OCT data corresponding to the extraction area is displayed in real time in the display area.

<Follow-up display>
Furthermore, the following process may be performed for follow-up using a plurality of OCT data whose scan line positions match each other and whose imaging dates differ.

For example, in the acquisition step, a plurality of OCT data may be acquired in which the scanning line positions match each other and the imaging dates are different from each other.

Furthermore, in the setting step, processing for setting the extraction region for each OCT data may be performed so that the position of the extraction region with respect to the image position of the subject is matched among the plurality of OCT data. Further, in the display control step, extracted OCT extracted from each of the plurality of OCT data may be sequentially displayed (switched and displayed) in the display area. In the display area, extracted OCT data with different imaging dates are switched and displayed with the positions of the tissue images substantially coincident, making it easy for the examiner to observe changes over time in the tissue of interest.

<Display of composite OCT data>
The OCT data in which the extraction region is set may be synthetic OCT data. The composite OCT data is generated by combining a plurality of OCT data having mutually different depth positions (for example, see Patent Document 3 below by the present applicant). The composite OCT data may include at least OCT data of the anterior segment and the fundus. Furthermore, OCT data of the equatorial region may also be included.
JP, 2012-75640, A Since individual tissues are difficult to observe even in synthetic OCT data, an extraction area may be set in a desired area and the area may be enlarged and displayed in a predetermined display area.

<Reduction of data other than the extraction area>
With OCT data that penetrates more deeply, the data capacity of the OCT data may become large. On the other hand, in OCT data with high depth penetration, the depth region occupied by the tissue of the eye to be examined may be the same as before. Therefore, in this embodiment, data in areas other than the extraction area may be reduced (deleted or compressed) from the OCT by setting the extraction area. As a result, the extracted region data (ie, extracted OCT data) may be stored in memory instead of the original OCT data.

"Example"
Hereinafter, as an example, an OCT system (optical coherence tomography system) shown in FIGS. 1 and 2 will be described.

As shown in FIG. 1, the OCT system according to the embodiment includes at least an optical unit 10 and a control unit 50 corresponding to the computer of the embodiment. In this embodiment, the optical unit 10 and the control unit 50 are integrated as an OCT device. The OCT system (OCT device) according to this embodiment has a basic configuration of wavelength swept OCT (SS-OCT).

The optical unit 10 includes an OCT optical system 100 (see FIG. 2). Further, the control unit 50 is a computer in this embodiment, and includes at least an arithmetic control section (processor) 70 that controls the entire OCT system. The arithmetic control unit (hereinafter simply referred to as a control unit) 70 includes, for example, a CPU and a memory. As an example, in this embodiment, the control unit 70 also serves as an image processor in the OCT system.

In addition, the OCT system may be provided with a storage unit (memory) 72, an input interface (operation unit) 75, a monitor 80, and the like. Each section is connected to a control section 70.

Various programs, initial values, etc. for controlling the operation of the OCT apparatus may be stored in the memory 72. For example, a hard disk drive, a flash ROM, a USB memory that is removably attached to the OCT apparatus, or the like can be used as the memory 72. Further, the memory 72 may store various information related to imaging in addition to OCT images generated from OCT data. The monitor 80 may display OCT data (OCT images).

<OCT optical system>
Next, referring to FIG. 2, the OCT optical system 100 in this embodiment will be explained. The OCT optical system 100 guides measurement light to the eye E through a light guiding optical system 150. OCT optical system 100 guides reference light to reference optical system 110. The OCT optical system 100 causes a detector (light receiving element) 120 to receive interference signal light obtained by interference between the measurement light reflected by the eye E and the reference light. The OCT optical system 100 is mounted in a casing (device body) not shown, and the casing can be moved three-dimensionally with respect to the eye E using a well-known alignment movement mechanism via an operating member such as a joystick. Alignment with respect to the eye to be examined may be performed by.

In this embodiment, the OCT optical system 100 uses the SS-OCT method. In this case, the OCT optical system 100 has a wavelength swept light source as the OCT light source 102. Further, the OCT optical system 100 has a point detector as the detector 120.

In the wavelength swept light source, the emission wavelength is temporally swept. The OCT light source 102 may be a VCSEL wavelength swept light source. The VCSEL wavelength swept light source includes a VCSEL that performs laser oscillation and a MEMS that achieves high-speed scanning.

In this embodiment, the detector 120 is an equilibrium detector that performs equilibrium detection using a plurality of (for example, two) detectors. The control unit 70 samples the interference signal of the return light of the reference light and the measurement light according to the change in the emission wavelength by the wavelength swept light source, and generates OCT data of the eye to be examined based on the interference signal at each wavelength obtained by sampling. get.

A coupler (splitter) 104 is used as a first light splitter and splits the light emitted from the light source 102 into a measurement optical path and a reference optical path. For example, the coupler 104 guides the light from the light source 102 to the optical fiber 152 on the measurement optical path side, and also guides the light to the reference optical system 110 on the reference optical path side.

<Light guiding optical system>
The light guide optical system 150 is provided to guide measurement light to the eye E. The light guiding optical system 150 may be sequentially provided with, for example, an optical fiber 152, a collimator lens 153, a focusing lens 155, an optical scanner 156, and an objective lens system 158 (objective optical system in this embodiment). In this case, the measurement light is emitted from the output end of the optical fiber 152 and becomes a parallel beam by the collimator lens 153. Thereafter, the light passes through a focusing lens 155 and heads toward an optical scanner 156 . The focusing lens 155 is movable along the optical axis by a drive unit (not shown), and is used to adjust the state of light condensation on the fundus of the eye. The light that has passed through the optical scanner 156 is irradiated onto the eye E via the objective lens system 158. A first pivot point P1 is formed at a position conjugate with the optical scanner 156 with respect to the objective lens system 158. By positioning the anterior segment of the eye at this pivot point P1, the measurement light reaches the fundus without vignetting. Further, the measurement light is scanned on the fundus according to the operation of the optical scanner 156. At this time, the measurement light is scattered and reflected by the tissue of the fundus.

The optical scanner 156 may scan the measurement light on the eye E in the XY direction (transverse direction). The optical scanner 156 is, for example, two galvano mirrors, the reflection angle of which is arbitrarily adjusted by a drive mechanism. The direction of reflection (travel) of the light beam emitted from the light source 102 is changed, and the fundus is scanned in an arbitrary direction. As the optical scanner 156, for example, in addition to a reflecting mirror (galvano mirror, polygon mirror, resonant scanner), an acousto-optic element (AOM) that changes the direction of propagation (deflection) of light, etc. may be used.

The scattered light (reflected light) from the eye E due to the measurement light goes back along the path at the time of light projection, enters the optical fiber 152, and reaches the coupler 104. Coupler 104 directs the light from optical fiber 152 into an optical path toward detector 120 .

<Reference optical system>
The reference optical system 110 generates a reference light that is combined with the fundus reflected light of the measurement light. The reference light that has passed through the reference optical system 110 is combined with the light from the measurement optical path at a coupler 148 and interferes with the light from the measurement optical path. The reference optical system 110 may be of a Michelson type or a Mach-Zehnder type.

The reference optical system 110 shown in FIG. 2 is formed by a transmission optical system, as an example. In this case, the reference optical system 110 guides the light from the coupler 104 to the detector 120 by transmitting it without returning it. However, the reference optical system 110 is not limited to this, and may be formed of a reflective optical system, for example, and guide the light from the coupler 104 to the detector 120 by reflecting the light from the coupler 104 with the reflective optical system. In this embodiment, an optical path length difference adjustment section 145 and a polarization adjustment section 147 are arranged on the optical path from the coupler 104 to the detector 120.

The optical path length difference adjustment section 145 is used to adjust the optical path length difference between the measurement light and the reference light. In this embodiment, a mirror 145a having two perpendicular surfaces is provided on the reference optical path. By moving this mirror 145a in the direction of the arrow by the actuator 145b, the optical path length of the reference optical path can be increased or decreased. Of course, the configuration in which the difference in optical path length between the measurement light and the reference light is adjusted is not limited to this. For example, in the light guide optical system 150, the collimator lens 153 and the coupler are moved integrally to adjust the optical path length of the measurement light, and as a result, the difference in optical path length between the measurement light and the reference light is adjusted. It's okay.

In this embodiment, the polarization adjustment section 147 adjusts the polarization of the reference light. The polarization adjustment section may be placed on the measurement optical path.

<Acquisition of depth information>
The control unit 70 processes (Fourier analysis) the spectrum signal detected by the detector 120 to obtain OCT data of the eye to be examined.

The spectral signal (spectral data) may be rewritten as a function of wavelength λ and converted into a function I(k) equally spaced with respect to wave number k (=2π/λ). Alternatively, it may be obtained from the beginning as a function I(k) that is equally spaced with respect to the wave number k (K-CLOCK technique). The arithmetic controller may obtain OCT data in the depth (Z) domain by Fourier transforming the spectral signal in wave number k space.

Furthermore, the information after Fourier transformation may be expressed as a signal including a real component and an imaginary component in Z space. The control unit 70 may obtain the OCT data by determining the absolute values of the real component and the imaginary component of the signal in the Z space.

Note that it is necessary to control the reference optical path adjustment unit 145 to adjust in advance the optical path length difference between the measurement optical path and the reference optical path, which is related to the axial length of the eye E to be examined. In this embodiment, for example, the mirror 145a is moved within a predetermined adjustment range, the interference signal at each position is acquired, and the position of the mirror 145a is determined based on the position where the intensity of the interference signal is the highest. You can do it like this. If the adjustment range of the optical path length in the reference optical path adjustment section 145 is sufficiently small compared to the optical path length difference between the first branched optical path and the second branched optical path, the interference signal is The position of the intensity peak can be uniquely identified.

In addition, in the insertion state, the measurement light reflected from the fundus periphery is weaker than the reflected light from the center of the fundus, so the zero delay position between the measurement optical path and the reference optical path is set at the fundus periphery. The reference optical path adjustment unit 145 may adjust the optical path length difference between the measurement optical path and the reference optical path so that they overlap with the desired fundus tissue (for example, retina, choroid, sclera, etc.).

<Dispersion correction by software>
Note that in this embodiment, the control unit 70 may perform dispersion correction processing using software on the spectrum data output from the detector 120. The control unit 70 obtains OCT data based on the spectrum data after dispersion correction. Therefore, a difference occurs in image quality between the real image and the virtual image (see FIG. 3).

That is, in this embodiment, the difference in the amount of dispersion of the optical system between the measurement optical path and the reference optical path is corrected by signal processing. Specifically, this is performed by applying correction values stored in advance in the memory 72 in the above-mentioned spectral signal processing.

The control unit 70 acquires the spectral intensity of light based on the light reception signal output from the detector 120, and rewrites it as a function of the wavelength λ. Next, the spectral intensity I(λ) is converted into a function I(k) equally spaced with respect to the wave number k (=2π/λ).

The influence of dispersion mismatch between the measurement light and the reference light shifts the phase of the interference component, lowers the peak of the combined signal of each wavelength, and gives the signal a spread (resolution decreases). Therefore, in dispersion correction, the phase shifted for each wavelength is returned to correct the decrease in resolution due to the decrease in interference signal. In this case, the amount of phase shift φ(k) as a function of wave number k is obtained, and the phase shift is returned for each value of k using I(k)·exp-iφ(k). Here, the phase φ(k) to be corrected for dispersion may be determined in advance by calibration, or the phase φ(k) corresponding to the acquired tomographic image may be determined. The memory 72 stores parameters for dispersion correction (for example, phase φ(k)).

Thereafter, the control unit 70 obtains OCT data by Fourier transforming the dispersion-corrected spectral intensity I(k) corrected by the set dispersion correction data.

For example, a first dispersion correction value (for a normal image) is acquired from the memory 72 as a dispersion correction value for correcting the influence of dispersion on the real image, and the spectrum data output from the detector 120 is used as the first dispersion correction value. The corrected spectral intensity data is Fourier transformed to form OCT data. The real image R is acquired as an image with high sensitivity and high resolution, and the virtual image M (mirror image) is acquired as a blurred image with low resolution due to the difference in dispersion correction value.

As a result, when a real image is acquired in the first image area G1, the real image is acquired as a high-sensitivity, high-resolution image, and the virtual image (mirror image) is dispersion-corrected in the second image area G2. A low-resolution, blurred image is obtained due to the difference in values. On the other hand, when a real image is acquired in the second image area G2, the virtual image is acquired in the first image area G1 as a low-resolution, blurred image due to the difference in dispersion correction values.

Of course, the present invention is not limited to this, and software dispersion correction for the virtual image M may be performed. In this case, the virtual image M is acquired as a high-sensitivity, high-resolution image, and the real image R is acquired as a low-resolution, blurred image.

For details of the method of performing dispersion correction using software as described above, please refer to US Pat. Also, please refer to Japanese Patent Application Laid-Open No. 2010-29648.

When dispersion correction processing is performed by software, when obtaining OCT data at the center of the fundus, for example, the control unit 70 extracts the image data of the real image and the virtual image, whichever has higher sensitivity and resolution. Bye.

<Operation explanation>
Next, an ophthalmologic image processing method executed by the OCT system of the embodiment will be described along the flowchart shown in FIG. 4. Each process in the flowchart may be executed by the control unit 70 based on an ophthalmologic image processing program. In this embodiment, by executing each process in the flowchart, at least extracted OCT data is displayed in the manner shown in FIGS. 5 and 6.

For convenience, the screens shown in FIGS. 5 and 6 will be referred to as viewer screens, and it is assumed that OCT data will be displayed after imaging is completed. Furthermore, for convenience, all OCT data in the following description is B-scan data. Further, OCT data corresponding to a scan line is also referred to as a slice.

<S1: Acquisition step>
First, after various adjustments are made to the OCT optical system 100, OCT data of the eye to be examined is photographed. OCT data may be captured using any one of a plurality of predetermined scan patterns.

The photographed OCT data may be stored (saved) in the memory of the apparatus in association with identification information indicating the scanning position and the date and time of photographing. Thereby, the photographed OCT data is acquired by the control unit 70 as a photographed image (S1). When multiple slices are captured at once, each slice may be acquired in step S1.

At this time, in this embodiment, a predetermined one of the first image area G1 and the second image area G2 sandwiching the zero delay position Z is extracted and acquired as a photographed image. At this time, as a result of the above-mentioned dispersion correction, one image area acquired as a photographed image includes an image of the eye to be examined that is depicted with higher sensitivity and higher resolution than the other image area. There is.

<S2: Selection of display target>
Next, when a plurality of slices are acquired, the slice that is displayed first on the screens shown in FIGS. 5 and 6 is selected. The first slice to be displayed may be determined in advance for each scan pattern.

As an example, the examples shown in FIGS. 5 and 6 show display examples of slices taken using a "multi" scan pattern. In this case, each slice is acquired based on a horizontal scan. The scan lines 231 to 233 corresponding to each slice are set to be different from each other in the vertical direction. In this case, as shown in FIGS. 5 and 6, the slice corresponding to the scan line 231 passing through the fovea may be predetermined to be selected as the first slice to be displayed.

<S3: Automatic setting of extraction area (setting step of this embodiment)>
Next, an extraction area in the slice selected as a display target is set (S3). In this embodiment, the image of the fundus included in the slice may be detected by image processing, and the extraction region may be set based on the detected position of the image of the fundus.

The image of the fundus may be detected, for example, based on the signal intensity distribution in the depth direction of OCT data, or may be detected based on the feature amount of the image, or may be detected by other detection methods. Good too.

The size of the extraction area set in step S2 may be determined in advance. In this case, the distance between the zero delay position and the extraction area is adjusted so that the detected image position is included between the upper and lower ends of the extraction area.

<S4: Display of extracted OCT data>
After setting the extraction area, display of the extracted OCT data is started. As an example, display is performed in the manner shown in FIGS. 5 and 6.

As shown in FIGS. 5 and 6, extracted OCT data is displayed in a predetermined first display area 210 on the viewer screen.

In the viewer screen shown in FIGS. 5 and 6, a second display area 220 is provided at a different position from the first display area 210. The second display area 220 is also referred to as a thumbnail table area. The entire slice from which the extracted OCT data was extracted is displayed in the second display area 220 as a thumbnail. That is, in this embodiment, the extracted OCT data and the OCT data from which the extracted OCT data is extracted are displayed simultaneously in different display areas. At this time, the extracted OCT data is displayed enlarged relative to the thumbnail.

In the second display area 220, a selection frame 221 is displayed along with the thumbnail. The extraction position of the extracted OCT data is graphically indicated by a selection frame 221. In this embodiment, the selection frame 221 indicates the positional relationship of the extraction area with respect to the OCT data that is the extraction source.

Furthermore, text information indicating the depth position of the extraction area may be displayed on the viewer screen. The text information may indicate the position of the extraction area with respect to the origin position (zero delay position), for example, the Z coordinate of the extraction area, or the optical path from the origin position to the extraction area. It may be long.

Additionally, a front image of the fundus may be displayed in the third display area 230 on the viewer screen. A scan line may be superimposed on the front image. In FIGS. 5 and 6, a scan line 231 corresponding to the currently displayed slice, and scan lines 232 and 233 corresponding to other slices that can be displayed by switching from the currently displayed slice are displayed on the front image, respectively. Ru.

<S5: Reception of various operation inputs>
With the viewer screen displayed, the control unit 70 can accept various instructions based on operational inputs to the input interface 75 (S5). For example, various widgets may be selectable by moving the pointer C via the input interface 75. Various operation inputs are input via various widgets.

<Changing the extraction area>
In this embodiment, while the viewer screen is displayed, the control unit 70 may receive a change instruction to change the extraction area while maintaining the slice to be displayed. The instruction to change the extraction area may be received based on an operation input via the above-mentioned selection frame 221 (an example of a widget). If the instruction to change the extraction area is accepted (S6: Yes), the extraction area is updated (newly set) in accordance with the instruction (S7).

For example, the position of the extraction area may be changeable based on instructions. In this case, the selection frame 221 may be movable up and down on the screen based on an operation via the input interface. By inputting an operation to move the selection frame 221, the position of the extraction region in the OCT data may be changed while maintaining the size and shape of the selection frame 221.

Further, for example, the size of the extraction area may be changeable based on an instruction. In this case, the size of the selection frame 221 may be changeable on the screen based on an operation input to each control point of the selection frame 221.

The operation input for changing the position of the extraction area and the operation input for changing the size of the extraction area may be different. At this time, since the extraction area (in other words, the area inside the selection frame 221) and the selection frame 221 itself are set as widgets that can be individually selected (designated) as operation targets, the above two types It may also be possible to input the operation inputs individually.

When the extraction area is updated (newly set) in response to the extraction area change instruction (S7), the extracted OCT data corresponding to the updated extraction area is newly displayed in the first display area 210 (S4). ). As a result, even from OCT data that is long in the depth direction, a portion desired by the examiner can be enlarged and observed in the first display area 210.

As an example, by changing the depth position of the extraction region in the OCT data to a deeper position with respect to FIG. 5, a new screen as shown in FIG. 6 will be displayed.

Note that when the size of the extraction area is changed, the layout of the first display area 210 on the screen may be adjusted according to the changed size. For example, the range occupied by the first display area 210 on the screen may be adjusted. Further, the range occupied by the first display area 210 on the screen may be constant, and the vertical and horizontal scales of the extracted OCT data may be changed individually according to the shape of the first display area 210.

When the position of the extraction area is changed, the amount of displacement between the changed extraction area and the extraction area set in the process of S3 may be stored in the memory 72. Further, when the size of the extraction area is changed, information specifying the size after the change may be stored in the memory 72.

<Change of OCT data to be displayed>
In this embodiment, while the viewer screen is displayed, the control unit 70 may receive a change instruction to select a new slice as a display target. In this embodiment, an instruction to change OCT data may be accepted based on an operation input to select a scan line corresponding to a new slice on the front image and an operation input to the forward buttons 211 to 214.

If a slice change instruction is received (S8: Yes), a new slice according to the instruction is selected as a display target (S9).

Next, an extraction area is set for a new slice (OCT data). At this time, in this embodiment, the extraction area setting method differs depending on whether the Auto button 219 shown as a check box in FIGS. 5 and 6 is turned on or off.

If the Auto button 219 has been turned on in advance (S10: Yes), the process of setting the extraction area for the new slice is performed so that the position of the extraction area with respect to the image position of the fundus matches the slices before and after the change. (S3)

Specifically, if the Auto button 219 is turned on in advance (S10: Yes), the extraction region is automatically set based on the image position of the fundus image in the new OCT data.

At this time, in this embodiment, it is conceivable that the extraction area in the immediately preceding (currently displayed) OCT data has been changed from its original setting position based on an instruction to change the extraction area. In this case, the position of the extraction region with respect to the new OCT data may be set in consideration of the amount of displacement of the extraction region before and after the change, which is stored in the memory in step S7. For example, the extraction region may be set at a position offset from the image position of the fundus image in the new OCT data according to the displacement amount stored in the process of S7.

Alternatively, the amount of displacement may be determined by performing a matching process between the immediately preceding OCT data and the new OCT data, and the extraction area for the new OCT data may be set based on this amount of displacement.

As a result, the part to be enlarged and observed using the extracted OCT data is maintained before and after the OCT data to be displayed is changed, making it easier to concentrate on observing a specific part.

On the other hand, if the Auto button 219 is turned off in advance (S10: No), the extraction area setting process for the new slice is performed so that the depth position of the extraction area is the same between the slices before and after the change. (S11). The depth position of the extraction area in the previous (currently displayed) OCT data (for example, the Z coordinate of the extraction area or the optical path length from the origin position to the extraction area) is the depth position of the extraction area in the new OCT data. will be taken over as. As a result, before and after changing the slice, the appearance position of the fundus image in the extracted OCT data may change depending on the actual fundus shape. This makes it easy for the examiner to grasp the three-dimensional shape of the fundus tissue from the appearance position of the fundus image in the extracted OCT data.

<End of display>
Furthermore, for example, in this embodiment, an instruction to end the display of the viewer screen may be accepted. If the instruction is received (S12: Yes), the control unit 70 ends the display of the viewer screen.

"Transformation example"
Although the present disclosure has been described above based on the embodiments and examples, it is not necessarily limited thereto, and various modifications are allowed.

For example, in the above embodiment, a case has been described in which extracted OCT data is displayed when OCT data is displayed after imaging is completed. However, it is not necessarily limited to this. For example, the extracted OCT data may be displayed based on the OCT data acquired in real time while the OCT data is being photographed or while the OCT optical system 100 is being adjusted during the photographing.

Furthermore, in the embodiment described above, it is assumed that OCT data of the fundus is photographed via the OCT optical system 100. However, it is not necessarily limited to this. In the OCT with high penetration depth (wide imaging range in the depth direction) shown in the embodiment, it is conceivable that imaging may be performed by switching or simultaneously using one device.

In this case, as shown in FIG. 7, extracted OCT data regarding the anterior segment may be displayed. The depth range (width in the vertical direction) of the extraction region set for the anterior segment OCT data that is the extraction source may be different from the extraction region set for the fundus OCT data. Further, the extracted OCT data regarding the anterior segment may be displayed in the first display area 210 at a scale different from that of the fundus. In this way, the extraction region is automatically set according to the region of the eye to be examined included in the OCT data, making it easier to observe each region well.

Further, in the operation input, it is not necessarily necessary to move the pointer C. For example, the setting position of the extraction region with respect to OCT data or the slice to be displayed may be changed by scrolling the mouse wheel.

In addition, in the above embodiment, the positional relationship of the extraction area with respect to the OCT data that is the extraction source is shown through the thumbnail (image displayed in the second display area 220) of the OCT data that is the extraction source. There is. However, the present invention is not necessarily limited to this, and the positional relationship of the extraction area to the OCT data that is the extraction source may be shown on the screen without using thumbnails. As an example, as shown in FIG. 8, a graphic 240 displayed in the first display area 210 may indicate the positional relationship of the extraction area with respect to the OCT data that is the extraction source. In FIG. 8, when the OCT data that is the extraction source includes images of the anterior segment of the eye and the fundus, the extraction region is set between the anterior segment and the fundus. In this case, the arrows and text shown as graphics 240 indicate the tissue that exists above and below the extraction region. In this case, the examiner can grasp the position of the extraction region even if the extraction region does not include a tissue image. As a result, the examiner can easily adjust the position of the extraction area so that the desired tissue is displayed in the first display area 210.

In this embodiment, an ophthalmological photographing apparatus for photographing OCT data of the subject's eye E has been described as an example, but the present invention is not limited to this. For example, the present embodiment may be applied to an apparatus for photographing OCT data of a subject. For example, the test object may be a living body such as an eye, skin, or blood vessel, or may be a non-living sample such as a resin body.

50 Control unit 70 Control section 80 Monitor 102 OCT light source 100 OCT optical system 120 Detector 210 First display area

Claims (8)

An ophthalmological image processing method performed by a computer, the method comprising:
an acquisition step of acquiring OCT data in which tissues of the eye to be examined are photographed ;
a setting step of setting a partial depth region of data in one direction from a zero delay position in the OCT data stored in a memory in advance as a result of imaging , as an extraction region; a setting step of setting a depth region including the image position of the tissue as the extraction region according to the image position of the tissue ;
a display control step of extracting extracted OCT data corresponding to the extraction area from the OCT data and displaying the extracted OCT data in a predetermined display area on the viewer screen where the captured image is displayed;
Ophthalmology image processing method. In the setting step, the image position of the tissue in the OCT data is detected, and the distance between the zero delay position and at least one of the upper end and the lower end of the extraction area is adjusted based on the detected image position. The ophthalmological image processing method according to claim 1. A changing step of receiving an instruction to change at least one of a depth position and a range of the extraction region with respect to the OCT data, and changing at least one of the depth position and the range of the extraction region based on the instruction. including,
In the display control step, when at least one of the depth position and range of the extraction region is changed based on the instruction, the extracted OCT data displayed in the display area is configured to correspond to the changed extraction region. The ophthalmological image processing method according to claim 1 or 2, wherein the ophthalmological image processing method is switched to a method in which the image is processed. In the display control step, when at least one of the depth position and the range of the extraction region is changed based on the instruction, the display mode of the extracted OCT data on the viewer screen is changed to the changed extraction region. 4. The ophthalmological image processing method according to claim 3, wherein the method is changed according to. In the acquisition step, the OCT data including images of a plurality of tissues located at different positions in the eye to be examined is acquired;
5. The ophthalmologic image processing method according to claim 4, wherein in the display control step, the display mode is changed depending on the type of the image included in the extracted OCT data. In the acquisition step, acquire a plurality of OCT data for each of a plurality of predetermined scanning lines,
In the setting step, the position of the extraction region with respect to the image position of the subject is matched among the plurality of OCT data,
6. The ophthalmologic image processing method according to claim 1, wherein in the display control step, the extracted OCT data for each plurality of OCT data are sequentially displayed in the display area. The ophthalmologic image processing method according to any one of claims 1 to 6 , further comprising performing a reduction step of reducing data in areas other than the extraction area in the OCT data . An ophthalmologic image processing program that, when executed by a processor of the computer, causes the ophthalmologic image processing method according to any one of claims 1 to 7 to be executed by the computer.

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