JP5543536B2 - Tomographic imaging apparatus, tomographic imaging method and program - Google Patents

Description

  The present invention relates to a tomographic imaging apparatus and a tomographic imaging method, and more particularly to a tomographic imaging apparatus and a tomographic imaging method used for ophthalmic medical care and the like.

  An ocular tomographic imaging apparatus using an optical coherence tomography (OCT) or the like is capable of three-dimensionally observing the state inside the retinal layer and more accurately diagnoses the disease. It has attracted attention in recent years because of its usefulness.

FIG. 5 shows a schematic diagram of an OCT measurement range on the fundus and a corresponding tomographic image of the retina. In FIG. 5, 501 represents a fundus image, and R _XY represents a two-dimensional measurement range of OCT on the fundus plane (x axis: horizontal direction, y axis: vertical direction). In the example of FIG. 5, _RXY is a rectangular area. T _{1 to} T _n are two-dimensional tomographic images (B-Scan images) of the macular portion obtained by imaging the depth direction of the retina with respect to the measurement range R _XY . One tomographic image is composed of scan lines (hereinafter referred to as A-scan lines) for scanning the depth direction of a plurality of retinas. The z-axis represents the direction of this A-scan, and R _Z represents the one-dimensional measurement range in the OCT depth direction in the z-axis direction. The imaging OCT, sequentially raster scan set measurement range R _XY respect fundus (x-axis direction of the scan in the main scanning is called a scan in the y-axis direction and sub-scanning) it is, these tomographic images group 3D data can be acquired at once. M represents the fovea, A represents the inner limiting membrane, and B represents the retinal pigment epithelial layer boundary. Since the anatomical features of diseases such as glaucoma and age-related macular degeneration that are the main causes of blindness appear in the region of the retinal layer between the inner boundary membrane A and the retinal pigment epithelium layer boundary B, a tomogram of OCT Very useful for the diagnosis used. Therefore, when capturing a tomographic image, it is important to capture the region so that this region is not interrupted from the upper end and the lower end in the depth direction of the tomographic image.

In a general OCT apparatus, only one or several tomographic images passing through the center of the measurement range _RXY are acquired and displayed in real time during observation of the subject's eye before imaging three-dimensional data. . By doing this, it was visually confirmed whether or not the area of the retinal layer was contained in the tomographic image, and the imaging position was adjusted appropriately. Further, in Patent Document 1, by analyzing one tomographic image acquired at the time of observing the subject eye and determining whether or not the retinal layer is captured, a position where the retinal layer is automatically captured so that the retinal layer is captured in the tomographic image. The technology to adjust is introduced.

JP 2008-154939 A

However, if the above method, since the photographer or is not recognized by the computer only a few tomographic image passing through the center of the measurement range R _XY, when tested eye observation, retinal layers fit properly in the three-dimensional data to be subsequently captured Could not be determined. In particular, when imaging a myopic eye in which the curvature of the retinal layer is severe, even if the retinal layer is contained in a tomographic image that passes through the center of the measurement range _RXY when observing the subject eye, the retinal layer is appropriate in the tomographic image at a position away from the center. May not fit in. In such a case, imaging failed, and as a result, a tomographic image had to be taken again.

  The present invention has been made in view of the above problems, and in an imaging apparatus using an optical coherence tomography, it is possible to easily and appropriately set the imaging position in the depth direction of a tomographic image within a set measurement range. For the purpose.

In order to achieve the above object, a tomographic imaging apparatus according to one aspect of the present invention has the following configuration. That is,
A tomographic imaging apparatus for taking a tomographic image of the fundus using an optical coherence tomography,
An acquisition means for acquiring a tomographic image of the position of the center and the opposite end of the two-dimensional measurement range on the fundus;
A plurality of tomographic images acquired by the acquisition means are displayed side by side on the screen of a display device, and a tomographic image display form in which the retinal layer included in the tomographic image covers either the upper end or the lower end of the tomographic image the and a display control unit that displays a different display mode from other tomographic images.

  According to the present invention, in an imaging apparatus using an optical coherence tomography, it is possible to easily and appropriately set an imaging position in the depth direction of a tomographic image within a set measurement range.

The figure which shows the function structure of the tomogram imaging apparatus which concerns on embodiment. The figure which shows the apparatus and functional structure of the tomogram acquisition part 103. FIG. The flowchart which shows the process sequence which concerns on embodiment. The flowchart which shows the process sequence of step S310. The figure which shows the measurement range of the OCT in a fundus, and the imaged three-dimensional data. The figure which shows a tomogram acquisition position and the acquired tomogram. The figure which shows an example of the display method which arranges and displays the image data (no interruption | interruption) of a tomogram. The figure which shows an example of the display method which arranges and displays the image data (with a discontinuity) of a tomogram. The figure which shows the warning display when an inner boundary film breaks. The figure which shows the warning display when the retinal pigment epithelium layer boundary is interrupted. The figure which shows the positional relationship of the estimated line of a retinal layer which interrupted, and a tomogram. The figure which shows the apparatus structure of the tomogram imaging apparatus which concerns on embodiment. The figure which shows the position of the center corresponding to a measurement range, and an edge part. The figure explaining the break of a retina layer.

[First Embodiment]
In the present embodiment, when a tomographic image of the subject eye is captured by an optical coherence tomography (hereinafter referred to as OCT), the measurement target is included in the captured image by displaying while repeatedly scanning a plurality of parts in the measurement range. It is possible to adjust to. More specifically, the tomographic image capturing apparatus of this embodiment, during the previous test eye observation for imaging a three-dimensional data for diagnosis OCT, the position of the center and the end portion of the eye of the measurement range R _XY Tomographic images are acquired and displayed side by side on the confirmation screen in real time. At this time, since the three-dimensional shape of the retina can be approximated to an ellipsoid, the difference in the position of the retina in the depth (z-axis) direction with respect to the center increases monotonously from the center of the measurement range _RXY. . This property allows the photographer to always recognize whether or not the retinal layer fits in the three-dimensional data that is subsequently captured by making it possible to refer to the state of the tomographic image at the center and end positions of the measurement range _RXY. to enable. Here, the position of the center and the end portion of the measurement range R _XY, respectively, position and through the center of the measurement range R _XY, represents the position including a region of the outermost end of the measurement range R _XY. Some specific examples are shown below.

FIG. 13 is a diagram illustrating the positions of the center and the end corresponding to the measurement range _RXY . FIGS. 13A and 13B are two types of diagrams showing the positions of the center and the end when the measurement range _RXY is rectangular. (C) And (d) is 2 types of figures which show the position of the center and edge part in case measurement range _RXY is a parallelogram. (E) and (f) are two types of diagrams showing the positions of the center and the end when the measurement range _RXY is circular. In each of the drawings (a) to (f), 1301 is a fundus image, and _RXY is a two-dimensional measurement range. Further, 1302,1306,1310,1314,1318,1321 indicates the center position of the measurement range _{R XY.} Reference numerals 1303 and 1304, 1307 and 1308, 1311 and 1312, 1315 and 1316, 1319, and 1322 indicate end positions. Further, P ₁ , P ₂ , P ₃ , and P ₄ in (c) and (d) indicate four vertices of the measurement range R _XY . At this time, the positions of the center and the end in each figure are all positions that satisfy the above definition. When the measurement range _RXY is rectangular, the positions of the center and the end may be respectively a line segment parallel to the x axis in the figure as shown in (a), or parallel to the y axis as shown in (b). It may be a straight line segment. When the measurement range R _XY is a parallelogram, the center and end positions may be line segments parallel to the side P ₁ P ₄ in the figure as shown in (c), or as shown in (d). Alternatively, a line segment parallel to the side P ₁ P _{2 in the} drawing may be used. When the measurement range R _XY is circular, the center position of the measurement range R _XY may be a line segment parallel to the x axis in the drawing as shown in (e), or the y axis as shown in (f). It is good also as a line segment parallel to. The position of the end is the circumferential position of the measurement range _RXY . That is, a tomographic image obtained by scanning the circumference is used. In the present embodiment described below, the case of FIG. 13A is specifically described as an example, but the shape of the measurement range and the positions of the center and the end are not limited to this example.

  Then, by displaying the tomographic images at the center and both ends in real time, the user can easily determine whether or not the retinal layer protrudes from the measurement range in the depth direction (discontinuity in the depth direction). In addition, since the OCT reference mirror can be moved while viewing the tomographic images at the center and both ends displayed in real time, the reference mirror can be easily set at an appropriate position. Further, it is detected from the above tomographic image whether or not the retinal layer is interrupted in the depth direction of the measurement range, and when it is interrupted, the photographer recognizes the disconnection of the retinal layer by presenting a warning to that effect. Try to provide support. Here, the discontinuity in the depth direction of the retinal layer is detected, for example, by determining whether the retinal layer is in contact with or intersects with the upper side or the lower side of the tomographic image. Furthermore, the position of the retinal layer in the tomographic image is recognized, and the measurement depth in the z-axis direction can be automatically adjusted so that the retinal layer is not interrupted from the tomographic image, reducing the burden on the photographer and preventing imaging errors. . A specific example will be described below.

FIG. 14 is a diagram for explaining the interruption of the retinal layer. (A) and (b) of FIG. 14 are diagrams showing an example of discontinuity of the retinal layer on the upper side and the lower side of the tomographic image, respectively. 1401 and 1402 are tomographic images in which the retinal layer is interrupted in the images in the cases (a) and (b), respectively. In each figure, the x-axis is the main scanning direction, and the z-axis is the A-scanning direction. As shown in the figure, the coordinate ranges on the tomographic image are 0 ≦ x ≦ x _max and 0 ≦ z ≦ z _max . A in (a) is the inner boundary membrane of the fundus. In (a), since the straight line of x = 0 (upper side of the tomographic image) and the inner boundary film A intersect, the inner boundary film A is in a state of being interrupted. B in (b) is the retinal pigment epithelium layer boundary. In (b), since the retinal pigment epithelium boundary B intersects with the straight line x = x _max (the lower side of the tomographic image), the retinal pigment epithelium layer boundary B is discontinuous. Thus, the interruption of the retinal layer in the present embodiment specifically indicates the interruption of the inner boundary membrane or the boundary of the retinal pigment epithelium layer.

  Next, with reference to the block diagram of FIG. 1 and the flowchart of FIG. 3, the configuration of the tomographic imaging apparatus 10 of the present embodiment and the specific processing procedure executed by the tomographic imaging apparatus 10 will be described.

In step S301, the measurement range acquisition unit 101 acquires the instruction information by the operator for the instruction acquisition unit 100 sets the two-dimensional measurement range R _XY for fundus of a subject, identifying a measurement range R _XY. This instruction information is input by an operator via a keyboard or mouse (not shown) provided in the tomographic imaging apparatus 10. As an instruction of the measurement range R _XY on the fundus, for example, an instruction such as designation of a region or position on the fundus of the tomographic image acquisition target (this is defined as instruction 1) is acquired. Based on the contents of the instruction 1, a rectangular measurement range _RXY is specified. The specified measurement range R _XY is transmitted to the tomographic image acquisition position setting unit 102.

In step S302, the tomographic image acquisition position setting unit 102 acquires the measurement range R _XY from the measurement range acquisition unit 101, a position of obtaining the tomographic image from among the measurement range (hereinafter, referred to as a tomographic image acquisition position P) Set. As the tomographic image acquisition position P, a plurality of predetermined positions smaller than that for diagnostic imaging are set. In this step, as the tomographic image acquisition position P, for example, the center and end positions of the measurement range _RXY are set. Of course, the tomographic image acquisition position P is not limited to this combination. For example, one acquisition position may be added between the center and both ends, and the number of tomographic image acquisition positions P may be five.

FIG. _6A is a diagram illustrating a tomographic image acquisition position P in the measurement range _RXY . Reference numeral 601 represents a fundus image, and R _XY in the fundus image 601 represents a two-dimensional measurement range. C in the measurement range R _XY is the measurement range R _XY center parallel to the x axis in street view a line segment (hereinafter referred to as central portion), U is the measurement range R _XY of the upper side (hereinafter, an upper end called), L represents the measurement range _{R XY} of the lower side (hereinafter, referred to as the lower end), respectively. In the present embodiment, as a position indicating the center portion and both end portions of the measurement range R _XY, applying the central portion C of the measurement range R _XY, upper portion U, the three positions of the lower end L. These positions correspond to (a) of FIG. 13 (1302-1304). During the tomographic image acquisition described later, so that the central station C, a top end U, relative to the position of the lower end L, obtaining a tomographic image obtained by scanning a region of the measurement range R _Z in the z-axis direction. However, as described above, the positions of the center and the end of the measurement range _RXY are not limited to this, and may be positions such as (b) to (f) in FIG. Thus, the set tomographic image acquisition position P (center C, upper end U, lower end L) is transmitted to the tomographic image acquisition unit 103.

  In step S <b> 303, the movement amount setting unit 109 acquires instruction information from the operator for manually setting the measurement position in the depth direction of the retina from the instruction acquisition unit 100. This instruction is input by an operator using a user interface (not shown). As an instruction for setting the measurement position, here, a movement amount of the measurement position in the depth direction (z-axis direction) (hereinafter referred to as a depth direction movement amount D) is acquired. Then, the set value of the depth direction movement amount D is transmitted to the tomographic image acquisition unit 103.

  In step S304, the tomographic image acquisition unit 103 captures a tomographic image of the subject eye based on the tomographic image acquisition position P acquired from the tomographic image acquisition position setting unit 102 and the depth direction movement amount D acquired from the movement amount setting unit 109. To do.

  In the present embodiment, the tomographic image acquisition unit 103 is composed of Fourier domain OCT. FIG. 2 shows the function and apparatus configuration of the tomographic image acquisition unit 103. The tomographic image acquisition unit 103 controls the galvano mirror driving mechanism 203 according to the tomographic image acquisition position P to drive the galvano mirror 204. The galvanometer mirror driving mechanism 203 drives the galvanometer mirror 204 so as to scan the signal light in the main scanning and sub-scanning directions (the x-axis and y-axis directions in FIG. 6). Here, since the three positions of the central portion C, the upper end portion U, and the lower end portion L in FIG. 6 are imaged in real time, control is performed so that these three locations are simultaneously scanned in one main scan. Specifically, in the sub-scanning direction, when the main scanning is performed with the sub-scanning position fixed by switching the scanning position between the central part C, the upper end U, and the lower end L at high speed. Control is performed to scan in the main scanning direction at a sampling interval of 1/3. In addition, the tomographic image acquisition unit 103 controls the reference mirror drive mechanism 209 according to the depth direction movement amount D and drives the reference mirror 202.

  Then, the light beam from the low-coherence light source 200 is split by the half mirror 201 into signal light traveling toward the object to be measured 211 via the objective lens 210 and reference light traveling toward the reference mirror 202. Next, interference light is generated by superimposing the signal light and the reference light reflected by the measured object 211 and the reference mirror 202, respectively. The interference light is split into wavelength components of wavelengths λ1 to λn by the diffraction grating 205, and each wavelength component is detected by the one-dimensional photosensor array 206. Each photosensor constituting the one-dimensional photosensor array 206 outputs a detection signal of the detected light intensity of the wavelength component to the image reconstruction unit 208.

  Based on the detection signal of each wavelength component of the interference light output from the one-dimensional photosensor array 206, the image reconstruction unit 208, the wavelength-light intensity relationship for this interference light, that is, the light intensity distribution of the interference light ( Wavelength spectrum). The obtained wavelength spectrum of the interference light is Fourier transformed to reconstruct a tomographic image of the retina.

FIG. 6B is a diagram illustrating a tomographic image acquired at the center C, the upper end U, and the lower end L. R _Z represents a one-dimensional measurement range in the z-axis direction as in FIG. The measurement range _RZ is a range in the depth direction (depth direction) of the tomographic image determined based on the position of the controlled and moved reference mirror 202. T _C tomographic image corresponding to the center portion C of (a) 6 (hereinafter referred to as the central portion tomographic images), T _U is the upper end portion tomographic image corresponding to the U (or later (a) of FIG. 6, _TL represents a tomographic image corresponding to the lower end L in FIG. 6A (hereinafter referred to as a lower end tomographic image). The image data of the captured tomographic image is transmitted to the storage unit 104.

  Next, in step S305, the display method setting unit 105 acquires the tomographic image data stored in the storage unit 104, and sets the tomographic image data side by side as a display method (display method). 1).

FIG. 7 shows an example of the display method 1. T _U is the upper end portion tomographic image, _{T C} is the central portion tomographic image, _{T L} represents the lower end tomogram. Similarly to FIG. 5, A in each tomogram represents the inner boundary membrane, and B represents the retinal pigment epithelial layer boundary. As shown in FIG. 7, in the present embodiment, a method of displaying the upper-end tomographic image T _U , the central tomographic image T _C , and the lower-end tomographic image _TL in order from the top is applied. However, the display method of the tomographic image is not limited to this method as long as the tomographic images can be simultaneously confirmed in a state where the tomographic images are arranged. For example, these tomographic images may be displayed side by side or diagonally. FIG. 8 shows an example of the display method 1 when the retinal layer is interrupted. 8, T _U , T _C , T _L , A, and B represent the upper end tomographic image, the central tomographic image, the lower end tomographic image, the inner boundary membrane, and the retinal pigment epithelium layer boundary, respectively. . 8, at the upper end tomographic image T _U and the lower end portion tomographic image T _L, the inner limiting membrane A is interrupted from the top. The arrangement of the tomographic images is the same as in FIG.

  In this way, by displaying the tomographic images at the center and the edge side by side, the user can check whether the retinal layer is interrupted from the tomographic image, and the retinal layer is interrupted from the three-dimensional data after imaging. You can judge whether or not. Then, the set display method 1 data and tomographic image data to be displayed are transmitted to the display unit 106.

  The next processing in steps S306 to S308 is processing for warning by detecting a discontinuity of the retinal layer in the tomographic image and making the display form of the tomographic image in which the discontinuity is detected different from other tomographic images. First, in step S306, the retinal layer extraction unit 107 acquires tomographic image data stored in the storage unit 104, and extracts a retinal layer from each of the tomographic images by image analysis.

In this step, two layers of the inner boundary membrane A and the retinal pigment epithelium layer boundary B in FIG. Since the inner boundary film A is a boundary sandwiched between the vitreous region above it depicted as a low luminance region on the image and the nerve fiber layer below it depicted as a high luminance region, There is a property in which the upper brightness gradient is increased. Therefore, in this embodiment, for one A- scan lines, the pixel of interest from the image upper end in the z-axis positive direction is sequentially scanned, the image gradients around the target pixel stops scanning at the position beyond the predetermined threshold value T _A Thus, the pixel at the stop position is extracted as a pixel of the inner boundary film. By repeating this for all A-scan lines, the inner boundary film is extracted from the tomographic image.

In addition, the region (retinal pigment epithelium layer) sandwiched between the retinal pigment epithelium layer boundary B and the one-upper boundary of the photoreceptor inner / outer segment joint (IS / OS) is also a part of the retinal layer. It is depicted as a particularly bright area. On the other hand, since the upper area of IS / OS has a relatively low luminance, the luminance gradient on the image in IS / OS has a property of increasing. Therefore, in this embodiment, for one A- scan lines, the position of the boundary layer A among extracted by scanning the target pixel in the positive direction of the z-axis as a base point, the image gradients around the target pixel is greater than a predetermined threshold value T _I By stopping scanning at the position, the pixel at the stop position is extracted as an IS / OS pixel. By repeating this operation for all A-scan lines, an IS / OS layer is extracted from the tomographic image.

Then, for one A- scan lines, by scanning the further the pixel of interest in the positive direction of the z-axis the IS / OS as a base point, the luminance value stops scanning at lower position than the predetermined threshold value T _B, the stop position Are extracted as pixels of the retinal pigment epithelium layer boundary B. By repeating this operation for all A-scan lines, the layer of the retinal pigment epithelium layer boundary B is extracted. The tomographic image data and the extracted retinal layer data (the three boundary data of the inner boundary membrane, IS / OS, and retinal pigment epithelium layer boundary) are transmitted to the retinal layer break detection unit 108.

  In step S307, the retinal layer break detection unit 108 detects a retinal layer break based on the tomographic image data and retinal layer data acquired from the retinal layer extraction unit 107, and detects the retinal layer data from which the retinal layer break is detected. Generate. This data is defined as retinal layer break detection data. If it is detected that there is a break, that is, the retinal layer protrudes from the measurement range in the depth direction, a flag indicating that the retinal layer is broken is set to True, and if it is not detected, it is set to False. To do. This flag is defined as a break detection flag E. When the break detection flag E = True, the value of the break detection flag E and the retinal layer break detection data are transmitted to the storage unit 104, and the process proceeds to step S308. When the break detection flag E = False, only the value of the break detection flag E is transmitted to the storage unit 104, and the process proceeds to step S312.

In this step, a break in the retinal layer is detected by the following method. First, a method for detecting a break in the inner boundary film A on the tomographic image in FIG. 8 will be described. In one A- scan lines, to a point on the boundary layer A inner is detected with p _A at step S306. At this time, a fixed region (for example, about 3 pixels) on the upper side (z axis negative direction) with respect to the point p _A is defined as a reference region X. Then, when the luminance value of the reference region X falls within a certain range from the luminance value of the vitreous region originally present on the upper side of the inner boundary film A, it is determined that there is no interruption, and when it does not, it is determined that the luminance value is interrupted. This conditional expression is expressed by the following expression.

In the formula (1), the average luminance value of _{V X} is the reference area _{X, V Corpus} the average luminance value of the vitreous region is _{T A} is a positive constant that indicates the width of constant luminance value. As described above, when Expression (1) is not satisfied, another point that is not adjacent to the vitreous region is detected as the point p _A. Therefore, the inner boundary film A is not reflected on the A-scan line and the fault is detected. It can be regarded as being interrupted from the top of the image. Also, if the pixel on the upper side of the point p _A is not present, since the point p _A located upper side of the tomographic image is determined to be interrupted.

Next, a method for detecting a break in the retinal pigment epithelium layer boundary B will be described. In one A-scan line, a point on the retinal pigment epithelium layer boundary B detected in step S306 is set as p _B , and a point on the IS / OS is set as p _I. At this time, we are defining a region between the point p _I and p _B and the reference region Y. If the luminance value of the reference area Y falls within a certain range from the luminance value of the retinal pigment epithelium layer region originally sandwiched between the IS / OS and the retinal pigment epithelium layer boundary, it is not interrupted. Is determined. This conditional expression is expressed by the following expression.

In the formula (2), the average luminance value of V _Y reference region Y, V _RPE is an average luminance value of the retinal pigment epithelium, T _B are positive constants indicating the width of constant luminance value. In this way, when the expression (2) is not satisfied, since another point not adjacent to the region of the retinal pigment epithelium layer is detected as the points p _B and p _I , the retinal pigment epithelium layer on the A-scan line. Is not reflected and can be regarded as broken from the bottom of the tomographic image. Further, even when not satisfy the equation (2), if the pixels do not exist on the lower side of the point p _B, since the point p _B is located lower side of the tomographic image is determined to be interrupted.

  As described above, retinal layer data obtained by combining retinal layer data (inner boundary membrane A or retinal pigment epithelial layer boundary B) determined to be interrupted for each A-scan line and tomographic image data is obtained. Detected data.

  Next, in step S308, the display method setting unit 105 acquires the data of the break detection flag E = True and the retinal layer break detection data from the storage unit 104, and displays a warning for the display method (this is called the display method 2). Define). As will be described below, in the display method 2, the display form of the tomographic image in which it is detected that the retinal layer protrudes in the depth direction is changed from the display form of another tomographic image (the tomographic image in which the retinal layer does not protrude). Display form).

FIG. 9 is a diagram showing a warning display when the inner boundary film is interrupted as an example of the display method 2. This display method is applied when the retinal layer break detection data is data of the inner boundary membrane. The display method 2 in FIG. 9 corresponds to a method in which each part of the display method 1 in FIG. 8 is changed for warning display. In Figure 9, _{T U} is the upper end portion tomographic image, _{T C} is the central portion tomographic image, _{T L} represents the lower end tomogram. Reference numeral 901 indicates a warning display that informs in writing that the inner boundary film is interrupted, and 902 indicates an arrow that indicates the position of the end point of the inner boundary film where the interruption occurs. Further, A in each tomographic image represents a thickly highlighted inner boundary film where a break occurs. In FIG. 9, the tomographic image in which the inner boundary film has been interrupted, such as _TU and _TL , is enlarged and the tomographic image in which no interruption has occurred, such as _TC , is displayed in a reduced manner.

FIG. 10 is a diagram showing a warning display when the boundary of the retinal pigment epithelium layer is interrupted as an example of the display method 2. This display method is applied when the retinal layer break detection data is retinal pigment epithelium layer boundary data. In FIG. 10, _{T U} is the upper end portion tomographic image, _{T C} is the central portion tomographic image, _{T L} represents the lower end tomogram. Reference numeral 1001 indicates a warning display that informs in writing that the boundary of the retinal pigment epithelium layer is interrupted, and 1002 indicates an arrow that indicates the position of the end point of the boundary of the retinal pigment epithelium layer where the disconnection occurs. Further, B in each tomographic image represents the retinal pigment epithelium layer boundary where the break is generated and highlighted. In Figure 10, T _U and tomogram break the retinal pigment epithelium boundary occurs as T _L is enlarged, the tomogram interrupted as from T _C is not generated is collapsed.

  In this way, the fact that the retinal layer is interrupted is indicated by the text display, the display of the interrupted part, the layer highlighting display, and the enlarged display of the tomographic image, thereby assisting the observer to recognize the disconnection of the retinal layer. It can be carried out. Then, the data of the display method 2 is transmitted to the display unit 106. In step S309, the display unit 106 acquires display method 2 data from the display method setting unit 105, and performs display control so that the data is displayed on a monitor (not illustrated).

  Next, in step S310, the movement amount setting unit 109 determines whether or not an input from the operator for instructing automatic adjustment of the measurement depth is acquired from the instruction acquisition unit 100 when the break detection flag E = True. judge. This instruction is input by an operator using a user interface (not shown). At this time, if the movement amount setting unit 109 has received an input for instructing automatic adjustment, the process proceeds to step S311. If not acquired, the process proceeds to step S303.

  In step S311, the movement amount setting unit 109 sets a movement amount for automatically adjusting the measurement depth in the depth direction with respect to the retina based on the retinal layer break detection data acquired in step S310. Next, based on the set movement amount, the tomographic image acquisition unit 103 acquires tomographic image data. Next, the display method setting unit 105 sets the display method of the acquired tomographic image to display method 1. Then, the set data of the display method 1 is transmitted to the storage unit 104. Details of the processing in this step will be described later in detail using the flowchart shown in FIG.

  In step S <b> 312, the display unit 106 acquires display method 1 data from the display method setting unit 105 and performs display control so that the data is displayed on a monitor (not shown). In step S <b> 313, the instruction acquisition unit 100 acquires an instruction from the outside as to whether to end the tomographic image analysis / display processing by the tomographic imaging apparatus 10. This instruction is input by an operator using a user interface (not shown). If the point of interest on the fundus image is designated without terminating the process, the process returns to step S301. When an instruction to end the process is acquired, the tomographic imaging apparatus 10 ends the process.

Next, the automatic adjustment processing of the measurement depth in step S311 will be described with reference to FIG.
In step S401, the movement amount setting unit 109 acquires and analyzes the retinal layer interruption detection data from the retinal layer interruption detection unit 108, and sets a necessary movement amount (this is defined as a depth direction movement amount D ′). . When the tomographic image is captured, the reference mirror 202 moves by the depth direction movement amount D, whereby a tomographic image of the measurement range RZ is obtained. When the depth direction movement amount D ′ is set, the movement start position of the depth direction movement amount D of the reference mirror 202 is shifted by D ′ and the measurement range RZ is shifted by D ′ when the tomographic image is captured. In this step, if the retinal layer break detection data is data indicating the break of the inner boundary membrane, the measurement range _RZ is moved in the negative z-axis direction because the upper side of the retinal layer is broken (depth direction). The movement amount D ′ becomes a negative value). Conversely, when the retinal layer break detection data is data of the retinal pigment epithelium layer boundary, the lower retinal layer is broken, and therefore the measurement range R _Z is moved in the positive z-axis direction (depth direction movement amount). D ′ becomes a positive value).

First, a method for setting the depth direction movement amount D ′ when the inner boundary film is interrupted (when the depth direction movement amount D ′ is a negative value) will be described. In the present embodiment, the positive constant may be set as d _C , and the depth direction movement amount D ′ = − d _C may be set, or the distance d _X (positive value) necessary for the retinal layer not to be interrupted is calculated. to the depth direction movement amount D '= - may be set as d _X. how to set d _X described below.

(A) of FIG. 11 is a figure which shows the positional relationship of the estimated line of a broken inner boundary film, and a tomogram. Reference numeral 1101 denotes an end tomogram (upper end tomogram or lower end tomogram), and A denotes an inner boundary film. A ′ represents an estimated line of the interrupted inner boundary membrane estimated by extrapolating the contour of the inner boundary membrane A. D ₁ represents the distance between the estimated line A ′ and the left edge of the upper side of the tomographic image, and d ₂ represents the distance between the estimated line A ′ and the right edge of the upper side of the tomographic image.

  As an estimation method of the estimated line A ′, for example, a curve obtained by fitting the elliptical shape to the detected inner boundary film A is estimated by using the fact that the three-dimensional shape of the retina can be approximated to an ellipsoid. The method applied is used. Any other estimation method that takes into account the shape of the retina is not limited to this method.

Then, the distance d _X having a larger value among the distance d ₁ and the distance d ₂ is employed. In the example of FIG. 11A, d ₁ > d ₂ holds, so d _X = d ₁ . Thus, from the position on the farthest are estimated line A 'from the upper side of the tomographic image, the distance to the upper side of the tomographic image can be set as a distance d _X. Therefore, by moving the measurement range R _Z in the direction of the z-axis negative distance d _X, it is possible to keep the inner limiting membrane A tomographic image.

Next, a method of setting the depth direction movement amount D ′ when the retinal pigment epithelium layer boundary is interrupted will be described. In this case, the sign may be reversed from that in the case where the inner boundary film is interrupted, and D ′ = d _C or D ′ = d _X. how to set d _X described below.

FIG. 11B is a diagram showing the positional relationship between the estimated line of the discontinuous retinal pigment epithelium layer and the tomographic image. Reference numeral 1102 denotes a tomographic image at the end (upper end tomographic image or lower end tomographic image), and B represents a retinal pigment epithelium layer boundary. B ′ represents an estimated line obtained by exteriorizing the outline of the boundary of the discontinuous retinal pigment epithelium layer, and d ₃ represents the distance between the position of the estimated line B ′ having the largest z coordinate and the lower side of the tomographic image. Represent. Since the retinal pigment epithelium layer boundary is also a part of the retina, the estimated line B ′ is also obtained by the same method as the estimated line A ′. By setting the distance d _X = d ₃ , the measurement range R _Z can be moved by d _{X in the} positive z-axis direction, and the retinal pigment epithelium layer boundary B can be included in the tomographic image. Thus, the set value of the depth direction movement amount D ′ is transmitted to the tomographic image acquisition unit 103.

  In step S402, the tomographic image acquisition unit 103 examines the subject eye based on the depth direction movement amount D ′ acquired from the movement amount setting unit 109 and the tomographic image acquisition position P set by the tomographic image acquisition position setting unit 102 in step S302. A tomographic image is taken. The details of the process are the same as in step S303, and will be omitted. The image data of the captured tomographic image is transmitted to the storage unit 104.

  In step S403, the retinal layer extraction unit 107 acquires tomographic image data stored in the storage unit 104, and extracts a retinal layer by image analysis. The details of the process are the same as in step S306, and will be omitted. The tomographic image data and the extracted retinal layer data are transmitted to the retinal layer break detecting unit 108. In step S404, the retinal layer break detecting unit 108 detects a retinal layer break based on the tomographic image data acquired from the retinal layer extracting unit 107 and the extracted retinal layer data. The details of the process are the same as those in step S307, and will be omitted. When the break detection flag E = True, the value of the break detection flag E and the retinal layer break detection data are transmitted to the storage unit 104, and the process proceeds to step S401. When the break detection flag E = False, only the value of the break detection flag E is transmitted to the storage unit 104, and the process proceeds to step S405.

  In step S405, the display method setting unit 105 acquires the tomographic image data stored in the storage unit 104 and the value of the break detection flag E = False, and displays the tomographic image data side by side simultaneously, that is, Set to display method 1. The details of the process are the same as those in step S304, and will be omitted. The set display method 1 data and tomographic image data to be displayed are transmitted to the display unit 106.

The measurement depth is automatically adjusted by the above procedure. However, when the depth direction movement amount D ′ = − d _C is set in step S401 (when the inner boundary film is interrupted), a tomographic image in which the reference mirror is moved by a certain amount is acquired in step S402. Therefore, this process and the procedure of checking the interruption of the retinal layer in step S404 are repeated many times (steps S401 to S404), and the process proceeds to the next process when the interruption of the retina is no longer detected.

On the other hand, the depth direction movement amount D '= in step S401 - If set to d _X, acquires the tomographic image interrupted moves the reference mirror as necessary to not occur at step S402. Therefore, after checking the retinal layer break once in step S404, the process proceeds to the next process. Alternatively, in this case, since the reference mirror is moved as much as necessary, the confirmation processing in steps S403 and S404 may be omitted.

According to the configuration described above, since the three-dimensional shape of the retina can be approximated to an ellipsoid, the tomograms at the center and the end in the measurement range _RXY of the subject eye can be referred to in real time. Whether or not the retinal layer fits in the entire three-dimensional data obtained can be determined during observation of the subject's eye. Then, when the retinal layer break is detected, a warning is presented so that the photographer can assist in recognizing the retinal layer break. Furthermore, when a break in the retinal layer is detected, the state of the retinal layer break is analyzed according to the photographer's instruction, and the measurement depth in the depth direction of the retina is automatically adjusted so that the retinal layer does not break from the tomographic image. Thus, it is possible to reduce the burden of the photographer adjusting the position and to prevent a photographing error.

  On the other hand, when a break in the retinal layer is detected, a manual input of the measurement depth can be acquired when the photographer does not give an instruction for automatic adjustment. With this configuration, the photographer can manually align the measurement depth (alignment of the reference mirror 202) while referring to a warning display indicating a break in the retinal layer. At this time, the result of the alignment of the reference mirror 202 is displayed in real time by the display method 2, and when the retinal layer break is eliminated, display by the display method 1 is executed.

Further, in FIG. 1, by omitting the display method 2 in the retinal layer extraction unit 107, the retinal layer break detection unit 108, and the display method setting unit 105, only the display method 1 is applied in the display method setting unit 105. Can be configured to be displayed in real time. In this case, since detection of a break in the retinal layer is not performed, only a manual measurement depth instruction from the photographer is input to the movement amount setting unit 109. Therefore, the photographer can manually adjust the measurement depth while referring to the tomographic images as they are at the positions of the center and both ends of the measurement range _RXY in real time. In this case, S303 to S305 in FIG. 3 are repeatedly executed.

  In addition, when performing automatic adjustment, the user does not need to check a tomogram. Therefore, the display method in the display method setting unit 105 may display only one central tomographic image. In this way, it is also possible to adopt a configuration in which the movement amount setting unit 109 automatically adjusts the measurement depth when the retinal layer is interrupted without displaying the tomographic image display and the retinal layer interruption warning display at both ends. In this case, since the photographer is not presented with the state of the tomograms at both ends, the photographer is not aware of the state of the tomograms at the edges, and is three-dimensional with no photographing errors based on the position automatically adjusted by the computer. Data can be acquired. In this configuration, when a break occurs in the retina, an instruction from the photographer is automatically acquired after notifying the photographer of the occurrence of the break using any notification means (such as voice notification) other than tomographic image presentation. It may be adjusted or may be automatically adjusted without notification.

(Other embodiments)
In each of the above embodiments, the present invention is realized as an imaging apparatus. However, the embodiment of the present invention is not limited only to the imaging apparatus. In the present embodiment, a configuration for realizing the present invention as software that operates on a computer will be described. FIG. 12 is a diagram illustrating a basic configuration of a computer for realizing the functions of the respective units of the tomographic imaging apparatus 10 with software.

  The CPU 1201 controls the entire computer using computer programs and data stored in the RAM 1202 and the ROM 1203. Further, the execution of software corresponding to each unit of the tomographic imaging apparatus 10 is controlled to realize the function of each unit. The RAM 1202 includes an area for temporarily storing computer programs and data loaded from the external storage device 1204, and also includes a work area required for the CPU 1201 to perform various processes. The function of the storage unit 104 is realized by the RAM 1202. The ROM 1203 generally stores a computer BIOS and setting data. The external storage device 1204 is a device that functions as a large-capacity information storage device such as a hard disk drive, and stores an operating system, a computer program executed by the CPU 1201, and the like. Information known in the description of the present embodiment is stored here, and loaded into the RAM 1202 as necessary. The monitor 1205 is configured by a liquid crystal display or the like. For example, the content output by the display unit 106 can be displayed. A keyboard 1206 and a mouse 1207 are input devices, and the operator can use them to give various instructions to the tomographic imaging apparatus 10. The interface 1208 is an interface for exchanging data with the tomographic image acquisition unit 103. Note that an interface configured by IEEE 1394, USB, Ethernet (registered trademark) port, or the like for exchanging various types of data with an external device may be provided. Data acquired via the interface 1208 is taken into the RAM 1202. Each component described above is connected to each other by a bus 1209.

  In addition, the function of each part of the tomographic imaging apparatus 10 in this embodiment is implement | achieved when CPU1201 runs the computer program which implement | achieves the function of each part, and controls the whole computer. In the above embodiment, it is assumed that the program code according to the flowchart is already loaded from the external storage device 1204 to the RAM 1202, for example.

As described above, according to the above embodiment, since the tomographic images at the center and end positions in the measurement range of the subject eye are displayed side by side in real time, is the retinal layer fit in the three-dimensional data to be imaged thereafter? Whether or not can be determined at the time of observation of the test eye. Alternatively, the imaging range in the depth direction is automatically adjusted so that the retinal layer does not protrude from the imaging range in the depth direction in the tomographic image. Therefore, it is possible to prevent an imaging error that the retinal layer is interrupted in the tomographic image after the three-dimensional data imaging.
(Other embodiments)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program. It is a process to be executed.

  Note that the description in this embodiment described above is an example of a suitable image processing apparatus according to the present invention, and the present invention is not limited to this.

Claims (7)

A tomographic imaging apparatus for taking a tomographic image of the fundus using an optical coherence tomography,
An acquisition means for acquiring a tomographic image of the position of the center and the opposite end of the two-dimensional measurement range on the fundus;
A plurality of tomographic images acquired by the acquisition means are displayed side by side on the screen of a display device, and a tomographic image display form in which the retinal layer included in the tomographic image covers either the upper end or the lower end of the tomographic image the tomographic image capturing apparatus characterized by having a display control unit that displays a different display mode from other tomographic images.   The tomographic imaging apparatus according to claim 1, wherein the display control unit displays tomographic images at both ends of a two-dimensional measurement range on the fundus side by side on the screen of the display device.   The tomographic imaging apparatus according to claim 1, wherein the two-dimensional measurement range is a quadrangle.   Before displaying the three-dimensional image obtained based on the information of the tomographic image captured in the two-dimensional measurement range on the screen of the display device, any one of the center part and the end part of the two-dimensional measurement range is displayed. The tomographic imaging apparatus according to claim 1, wherein the tomographic image at the above position is displayed. The acquisition means includes
A low coherence light source,
A first optical member for branching low coherence light generated from the light source to the eye side to be examined and the reference mirror side;
A second optical member for irradiating the low-coherence light branched by the optical member while scanning the fundus of the eye to be examined;
A component that configures a tomographic image of the subject eye by causing optical interference between the return light of the low-coherence light from the fundus of the subject eye and the return light from the moved reference mirror;
5. The tomographic image according to claim 1, wherein the second optical member scans at least two positions of a central portion and an end portion of the two-dimensional measurement range. Imaging device. A tomographic imaging method for taking a tomographic image of the fundus using an optical coherence tomography,
An acquisition step of acquiring a tomographic image of the position of the center and the opposite end of the two-dimensional measurement range on the fundus;
A plurality of tomographic images acquired in the acquisition step are displayed side by side on the screen of a display device, and a display form of tomographic images in which the retinal layer included in the tomographic image is applied to either the upper end or the lower end of the tomographic image the tomographic image capturing method characterized by having a display control step that displays a different display form and the other tomographic image.   The program for making a computer perform each process of the tomographic image imaging method described in Claim 6.

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