JP2010110656A - Tomographic image photographing apparatus, tomographic image photographing method, program and program storing medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mechanism that detects displacement or distortion of images due to movements or blinking of the subject eye and easily determines an accuracy of optical tomographic images while photographing the eye by means of an optical coherence tomograph. <P>SOLUTION: An image processing section 252 acquires information showing a continuity of tomographic images of the subject eye. A determination section 253 determines a photographic state of the subject eye on the basis of the information acquired by the image processing section 252. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a tomographic imaging system that supports imaging of an eye part, and more particularly to a tomographic imaging system using a tomographic image of an eye part.

  Eye examinations are widely performed for the purpose of early diagnosis of lifestyle-related diseases and various diseases that account for the top causes of blindness. In medical examinations and the like, since it is required to find a disease in the entire eye part, examination using an image over a wide range of the eye part (hereinafter referred to as a wide area image) is essential. The wide area image is captured using, for example, a fundus camera or a scanning laser opthalmoscope (SLO). On the other hand, an ophthalmic tomographic imaging apparatus such as an optical coherence tomography (OCT) can observe the state inside the retinal layer three-dimensionally, and thus diagnoses the disease more accurately. It is expected to be useful. Hereinafter, an image captured by OCT is referred to as tomographic image and tomographic image volume data.

  When taking an image of the eye with an optical coherence tomography, it takes some time from the start to the end of the acquisition, so if the subject's eye moves suddenly or blinks during this time, Although distortion may occur, they may not be noticed during shooting. Further, in the photographing data confirmation work after photographing, the amount of image data is enormous, so it may be overlooked. And since this confirmation work is not easy, the diagnosis workflow of a doctor was inefficient.

  To solve these problems, a technique for detecting blinking at the time of photographing (see Patent Document 1) and a technique for correcting a positional shift of a tomographic image due to movement of an eye to be examined (see Patent Document 2) are disclosed.

JP-A-62-281923 JP 2007-130403 A

  However, the conventional techniques have the following problems.

  The method described in Patent Document 1 described above is to detect a blink with the eyelid opening / closing detector and take a picture after a predetermined time set by the delay time setting device when switching from the eyelid level to the eyelid level. . Therefore, although blinking can be detected, it is not possible to detect image shift or distortion due to the movement of the eye to be examined. Therefore, it is not possible to acquire the imaging state including the movement of the eye to be examined.

  In addition, the method described in Patent Document 2 performs alignment between two or more tomographic images using a reference image (one tomographic image orthogonal to two or more tomographic images or a fundus image). For this reason, when the eye moves greatly, the tomographic image is corrected and an accurate image cannot be created. In addition, there is no idea of capturing a photographing state that is a state of an eye to be examined at the time of photographing.

In order to achieve the above object, a tomographic imaging apparatus according to one aspect of the present invention has the following arrangement. That is, image processing means for acquiring information indicating continuity of tomographic images of the eye to be examined;
Determination means for determining a photographing state of the eye to be examined based on information acquired by the image processing means;
Acquisition means for acquiring an instruction as to whether or not to image the eye to be examined again;
Is provided.

Further, a tomographic imaging method for determining the imaging state of the eye to be examined according to another aspect of the present invention,
An image processing step for acquiring information indicating continuity of tomographic images of the eye to be examined;
A determination step of determining a photographing state of the eye to be examined based on the information acquired in the image processing step;
An acquisition step of acquiring an instruction as to whether or not to image the eye to be examined again;
Is provided.

  With the configuration of the present invention, it is possible to determine either continuity or accuracy of tomographic images. Alternatively, the photographing state of the eye to be examined can be determined.

1 is a diagram illustrating a configuration of a device connected to an image processing system 10. FIG. 1 is a diagram illustrating a functional configuration of an image processing system 10. FIG. 3 is a flowchart showing a processing procedure of the image processing system 10. It is a figure which shows an example of a tomogram and an integration image. It is a figure which shows an example of an integration image. It is a figure which shows an example of a screen display. It is a figure which shows the relationship between an imaging | photography state, a blood vessel concentration degree, and a similarity degree. 1 is a diagram illustrating a basic configuration of an image processing system 10. FIG. It is a figure which shows an example of an integration image and a gradient image. It is a figure which shows an example of an integration image and a power spectrum. It is a flowchart which shows a process sequence. It is a figure for demonstrating the characteristic of a tomogram. It is a flowchart which shows a process sequence. It is a figure which shows an example of an integration image and a partial image. It is a figure which shows an example of a blood vessel model and a partial model. It is a figure which shows an example of a screen display.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

(First embodiment)
The image processing apparatus according to the present embodiment creates an integrated image from tomographic volume data when acquiring a tomographic image of an eye to be examined (an eye to be inspected), and uses the continuity of image characteristics obtained from the integrated image. Determine the accuracy of the captured image.

  FIG. 1 is a configuration diagram of devices connected to the image processing system 10 according to the present embodiment. As shown in FIG. 1, the image processing system 10 is connected to a tomographic imaging apparatus 20 and a data server 40 via a local area network (LAN) 30 such as Ethernet (registered trademark). Note that these devices may be connected via an interface such as an optical fiber, USB, or IEEE1394. Further, they are connected via an interface such as an optical fiber, USB, IEEE 1394 or the like. The tomographic imaging apparatus 20 is connected to a data server 40 via a local area network (LAN) 30 such as Ethernet (registered trademark). The connection with these devices may be configured to be connected via an external network such as the Internet.

  The tomographic image capturing apparatus 20 is an apparatus that captures a tomographic image of an eye part, and includes, for example, a time domain type OCT or a Fourier domain type OCT. The tomographic image capturing apparatus 20 three-dimensionally captures a tomographic image of an eye not shown (not shown) in response to an operation by an operator (not shown). Then, the obtained tomographic image is transmitted to the image processing system 10.

  The data server 40 is a server that holds a tomographic image of the eye to be examined, information acquired from the eye to be examined, and the like. The data server 40 stores the tomographic image of the eye to be examined output from the tomographic imaging apparatus 20 and the result output from the image processing system 10. Further, in response to a request from the image processing system 10, past data relating to the eye to be examined is transmitted to the image processing system 10.

  Next, the functional configuration of the image processing system 10 according to the present embodiment will be described with reference to FIG. FIG. 2 is a functional block diagram of the image processing system 10. As shown in FIG. 2, the image processing system 10 includes an eye information acquisition unit 210, an image acquisition unit 220, an instruction acquisition unit 230, a storage unit 240, an image processing device 250, a display unit 260, and a result output unit 270. Composed.

  The eye information acquisition unit 210 acquires information for identifying the eye to be examined from the outside. Here, the information for identifying the eye to be examined is, for example, a subject identification number assigned to each eye to be examined. In addition to this, as the information for identifying the eye to be examined, the identification number of the subject and an identifier indicating whether the examination target is the right eye or the left eye may be used in combination.

  Information for identifying the eye to be examined is input by the operator. In addition, when the data server 40 holds information for identifying the eye to be examined, the information may be acquired from the data server 40.

  The image acquisition unit 220 acquires a tomographic image transmitted from the tomographic imaging apparatus 20. In the following description, it is assumed that the tomographic image acquired by the image acquisition unit 220 is that of the eye to be examined that is identified by the eye information acquisition unit 210. In addition, various parameters related to tomographic image acquisition are attached to the tomographic image as information.

  The instruction acquisition unit 230 acquires a process instruction input by the operator. For example, an instruction to start, interrupt, end, or re-shoot a shooting process, an instruction on whether to save a shot image, an instruction on a storage location, or the like is acquired. The contents of the instruction acquired by the instruction acquisition unit 230 are transmitted to the image processing apparatus 250 and the result output unit 270 as necessary.

  The storage unit 240 temporarily holds information on the eye to be examined acquired by the eye information acquiring unit 210. Further, the tomographic image of the eye to be examined acquired by the image acquisition unit 220 is temporarily stored. Furthermore, the information acquired from the tomogram by the image processing apparatus 250 described later is temporarily stored. These data are transmitted to the image processing device 250, the display unit 260, and the result output unit 270 as necessary.

  The image processing apparatus 250 obtains tomographic images held in the storage unit 240 and executes processing for determining the continuity of tomographic image volume data on the tomographic images. The image processing apparatus 250 includes an integrated image creation unit 251, an image processing unit 252, and a determination unit 253.

  The integrated image creation unit 251 creates an integrated image obtained by integrating the tomographic images in the depth direction. The integrated image creation unit 251 performs a process of integrating each of the n two-dimensional tomographic images captured by the tomographic imaging apparatus 20 in the depth direction. Here, the two-dimensional tomographic image is referred to as a cross-sectional image. The cross-sectional image includes, for example, a B-scan image and an A-scan image. Details of specific processing executed by the integrated image creation unit 251 will be described in detail later.

  The image processing unit 252 extracts information for determining three-dimensional continuity from the tomographic image. Details of specific processing executed by the image processing unit 252 will be described in detail later.

  The determination unit 253 determines the continuity of tomographic volume data (hereinafter also referred to as tomographic image) based on the information extracted by the image processing unit 252. If the determination unit 253 determines that the tomographic volume data is discontinuous, the display unit 260 displays the result. Details of specific processing executed by the determination unit 253 will be described in detail later. Further, the determination unit 253 determines the degree of eye movement and the presence or absence of blinking based on the information extracted by the image processing unit 252.

  The display unit 260 displays the tomographic image acquired by the image acquisition unit 220 and the result of processing the tomographic image by the image processing device 250 on the monitor. Specific display contents on the display unit 260 will be described in detail later.

  The result output unit 270 associates the examination date and time, information for identifying the eye to be examined, the tomographic image of the eye to be examined, and the analysis result obtained by the image processing unit 220, and sends the information to the data server 40 as information to be stored. Send.

  FIG. 8 is a diagram illustrating a basic configuration of a computer for realizing the functions of the respective units of the image processing system 10 by software.

  The CPU 701 controls the entire computer using programs and data stored in the RAM 702 and the ROM 703. Further, the execution of software corresponding to each part of the image processing system 10 is controlled to realize the function of each part. The program can also be stored in the RAM 702 or ROM 703 from the program storage medium.

  The RAM 702 includes an area for temporarily storing programs and data loaded from the external storage device 704 and a work area required for the CPU 701 to perform various processes. The function of the storage unit 240 is realized by the RAM 702.

  The ROM 703 generally stores a computer BIOS and setting data. The external storage device 704 is a device that functions as a large-capacity information storage device such as a hard disk drive, and stores an operating system, a program executed by the CPU 701, and the like. Information known in the description of the present embodiment is stored here, and loaded into the RAM 702 as necessary.

  The monitor 705 is configured by a liquid crystal display or the like. For example, the contents output by the display unit 260 can be displayed.

  A keyboard 706 and a mouse 707 are input devices, and an operator can give various instructions to the image processing system 10 by using these devices. The functions of the eye information acquisition unit 210 and the instruction acquisition unit 230 are realized via these input devices.

  The interface 708 is for exchanging various data between the image processing system 10 and an external device, and includes an IEEE 1394, USB, Ethernet (registered trademark) port, or the like. Data acquired via the interface 708 is taken into the RAM 702. The functions of the image acquisition unit 220 and the result output unit 270 are realized via the interface 708.

  Each component described above is connected to each other by a bus 709.

  Next, the processing procedure of the image processing system 10 of the present embodiment will be described with reference to the flowchart of FIG. Note that the function of each unit of the image processing system 10 in the present embodiment is realized by the CPU 701 executing a program for realizing the function of each unit and controlling the entire computer. It is assumed that the program code according to the flowchart is already loaded from, for example, the external storage device 704 to the RAM 702 in the previous stage of performing the following processing.

<Step S301>
In step S301, the eye information acquisition unit 210 acquires a subject identification number from the outside as information for identifying the eye to be examined. This information is input by an operator via a keyboard 706, a mouse 707, or a card reader (not shown). And the information regarding the said to-be-examined eye which the data server 40 hold | maintains based on a test subject identification number. For example, the name, age, and sex of the patient are acquired as the information related to the eye to be examined. Furthermore, when there is measurement data such as visual acuity, axial length, and intraocular pressure as other examination information, the measurement data may be acquired. Then, the acquired information is transmitted to the storage unit 240.

  In step S301, in the case of re-shooting with the same eye, this processing may be skipped, and when there is information to be newly added, that information is acquired.

<Step S302>
In step S <b> 302, the image acquisition unit 220 acquires a tomographic image transmitted from the tomographic imaging apparatus 20. Then, the acquired information is transmitted to the storage unit 240.

<Step S303>
In step S303, the integrated image creation unit 251 creates an integrated image obtained by integrating cross-sectional images (for example, B-scan images) in the depth direction.

Hereinafter, the processing of the integrated image creation unit 251 will be described with reference to FIG. FIG. 4 is a diagram illustrating an example of a cross-sectional image and an integrated image. 4A is a cross-sectional image T _{1 to} T _n of the macular portion, and FIG. 4B is an integrated image P created from the cross-sectional images T _{1 to} T _n . The depth direction is the z direction in FIG. 4A, and integrating in the depth direction is a process of adding the light intensity (luminance value) at each depth position in the z direction in FIG. 4A. The integrated image P may be a value obtained by simply adding the luminance values at the respective depth positions, or may be an average value obtained by dividing the added value by the number of additions. In the integrated image P, it is not necessary to add the luminance values of all the pixels in the depth direction, and only an arbitrary range may be added. For example, the entire retinal layer may be detected in advance and only the retinal layer may be added. Furthermore, you may add only the arbitrary layers in a retina layer. The integrated image creation unit 251 performs a process of integrating each of the _n cross-sectional images T _{1 to} T _n photographed by the tomographic imaging apparatus 20 in the depth direction, and creates an integrated image P. The integrated image in FIG. 4B is represented such that the luminance value is brighter as the integrated value is larger, and the luminance value is darker as the integrated value is smaller. A curve V in the integrated image P in FIG. 4B indicates a blood vessel, and a circle M at the center of the image indicates a macular portion. The tomographic image capturing apparatus 20 captures cross-sectional images T _{1 to} T _n of the eye by receiving reflected light of light emitted from the low-coherence light source with a light receiving element. In a place where there is a blood vessel, the reflected light intensity at a position deeper than the blood vessel tends to be weak, and the value integrated in the z direction is smaller than that in a place where there is no blood vessel. Therefore, by creating the integrated image P, it is possible to obtain an image having contrast between the blood vessel and the rest.

<Step S304>
In step S304, the image processing unit 252 extracts the acquired information for determining the continuity of tomographic volume data from the integrated image.

  The image processing unit 252 detects a blood vessel as information for determining the continuity of tomographic volume data from the integrated image. The blood vessel detection method is a generally known technique and will not be described in detail. The blood vessel detection method need not be limited to one method, and a plurality of methods may be combined.

<Step S305>
In step S305, the determination unit 253 performs processing on the blood vessel acquired in step S304 to determine the continuity of the tomographic volume data.

Hereinafter, specific processing of the determination unit 253 will be described with reference to FIG. FIG. 5 is a diagram showing an example of the integrated image. 5 (a) shows a macula lutea integrated image P _a for successful imaging, FIG. 5 (b) shows an example of a macula lutea integrated image P _b a Failed shooting. In the case of FIG. 5, the scanning direction during OCT imaging is assumed to be parallel to the x direction. Since the blood vessels in the eye part are concentrated on the optic disc and the blood vessels run from the optic disc to the macula, the blood vessels are concentrated near the macula. In addition, the end portion of the blood vessel is hereinafter referred to as a blood vessel end. The end of the blood vessel in the tomographic image may be captured as the end of the subject's blood vessel or the end of the subject's blood vessel may be captured as the end of the blood vessel, such as the movement of the subject's eyeball during imaging.

  The image processing unit 252 tracks each blood vessel from blood vessels concentrated near the macula, and attaches a tracked label to the tracked blood vessel. The tracked blood vessel end position coordinates are stored in the storage unit 240 as position information. Then, the position coordinates of the blood vessel ends existing on the same straight line parallel to the scanning direction (x direction) during OCT imaging are counted together. This is representative of the number of blood vessel ends on the cross-sectional image.

For example, the points (x ₁ , y _i ), (x ₂ , y _i ), (x ₃ , y _i ) (x _n−1 , y _i ), (x _n , y _i ) are counted together. When the OCT imaging is successful as shown in FIG. 5A, the coordinates of the blood vessel end are rarely concentrated on the same straight line parallel to the scanning direction during the OCT imaging. However, when the OCT imaging has failed as shown in FIG. 5B, the position shift occurs between the cross-sectional images (B-scan images), so the blood vessels are on the same straight line at the boundary where the position shift has occurred. The edges are concentrated. Therefore, when there are a plurality of blood vessel end coordinates on the same straight line parallel to the scanning direction (x direction) during OCT imaging, there is a high possibility of imaging failure. The determination unit 253 determines the imaging failure based on the threshold Th of the concentration frequency at the blood vessel end. For example, the determination is made based on the following formula (1). Here, _Cy is the concentration degree of the blood vessel end, the subscript represents the y coordinate, and Y represents the image size. If the concentration frequency at the end of the blood vessel is equal to or greater than the threshold, it is determined that the blood vessel end is discontinuous. That is, if the number of blood vessel ends on the cross-sectional image is equal to or greater than the threshold value, it is determined that the discontinuity occurs.

For this purpose, the threshold Th may be a fixed threshold based on the number, or the ratio of the number of blood vessel end coordinates on the same straight line to the total number of blood vessel end coordinates may be used as the threshold. Alternatively, a threshold value may be set based on statistical data, or a threshold value may be set based on patient information (age, sex, race). The degree of concentration of the blood vessel ends need not be limited to the same straight line, and may be determined using two or more consecutive blood vessel end coordinates on the same straight line in consideration of variations in blood vessel detection. Furthermore, when the end of the blood vessel is positioned at the end of the image size, the coordinate point may be excluded from the count, assuming that the blood vessel is connected outside the image. Here, the end of the blood vessel is positioned at the end of the image size. When the image size is (X, Y), the blood vessel end coordinates are (0, y _j ), (X-1, y _j ) or (x _j , 0 ), (X _j , Y−1). In this case, it is not necessary to limit to the edge of the image, and a margin may be provided on the inside of several pixels from the edge of the image.

<Step S306>
In step S306, the display unit 260 displays the tomographic image and cross-sectional image acquired in step S302 on the monitor 705. For example, an image as schematically shown in FIGS. 4A and 4B is displayed. Here, since the tomographic image is three-dimensional data, what is actually displayed on the monitor 705 is a cross-sectional image obtained by cutting out any one of the cross-sections of interest, and becomes a two-dimensional tomographic image. The cross-sectional image to be displayed is preferably configured to be arbitrarily selectable by the operator via a GUI (slider or button) not shown. Moreover, the structure which can arrange and display the patient data acquired by step S301 may be sufficient.

In step S306, when the determination unit 253 determines the discontinuity of the tomographic image volume data in step S305, the display unit 260 displays that effect. FIG. 6 is a diagram illustrating an example of a screen display. In FIG. 6, tomographic images T _m−1 and T _m before and after the boundary at which the discontinuity is detected are displayed, and the integrated image P _b and the marker S indicating the position shift position are displayed. The display example need not be limited to this, and either a tomographic image of the boundary where the discontinuity is detected may be displayed, or only the fact that the discontinuity is detected may be displayed without displaying the image. good.

  (A) of FIG. 7 has shown the location where the eyeball moved, with the arrow, (B) has shown the location where blinking was shown with the arrow. (C) is a diagram showing the relationship between the value of the degree of blood vessel concentration, which is the number on the cross-sectional image of the blood vessel end, and the state of the eye to be examined. The degree will be higher. Further, since the blood vessel position on the cross-sectional images fluctuates between the cross-sectional images as the eye moves higher, the blood vessel concentration tends to increase. That is, the blood vessel concentration degree indicates a photographing state such as movement of the eye to be examined and blinking. The image processing unit 252 can also calculate the similarity between cross-sectional images. For the similarity, for example, a correlation value between cross-sectional images is used. The correlation value is calculated from the value for each pixel of the cross-sectional image. When the similarity is 1, it is shown that the cross-sectional images are the same, and the eyeball moves as the similarity decreases. When there is a blink, the similarity approaches 0. Therefore, it is possible to acquire the photographing state such as the degree of movement of the eye to be examined and the presence or absence of blinking from the similarity between the cross-sectional images. FIG. 7D shows the relationship between the similarity and the position of the cross-sectional image.

  As described above, the determination unit 253 determines the continuity of tomographic images and the imaging state such as the movement of the eye to be examined and blinking.

<Step S307>
In step S307, the instruction acquisition unit 230 acquires an instruction from the outside as to whether or not to image the eye to be examined again. This instruction is input by the operator via the keyboard 706 or the mouse 707, for example. If re-shooting is instructed, the process returns to step S301 to re-process the same eye. If reshooting is not instructed, the process proceeds to step S308.

<Step S308>
In step S308, the instruction acquisition unit 230 acquires an instruction from the outside as to whether or not to save the result of the current process relating to the eye to be examined in the data server 40. This instruction is input by the operator via the keyboard 706 or the mouse 707, for example. If storage is instructed, the process proceeds to step S309. If storage is not instructed, the process proceeds to step 310.

<Step S309>
In step S309, the result output unit 270 associates the examination date and time, information for identifying the eye to be examined, the tomographic image of the eye to be examined, and the information obtained by the image processing unit 220, and stores the data server as information to be stored. 40.

<Step S310>
In step S310, the instruction acquisition unit 230 acquires an instruction from the outside as to whether or not the tomographic image processing by the image processing system 10 is to be ended. This instruction is input by the operator via the keyboard 706 and the mouse 707. When an instruction to end the process is acquired, the image processing system 10 ends the process. On the other hand, if an instruction to continue the process is acquired, the process returns to step S301, and the process for the next eye to be examined (or reprocessing for the same eye to be examined) is executed.

  As described above, the processing of the image processing system 10 is performed.

  According to the configuration described above, the continuity of tomographic images is determined from the integrated image created from the tomographic image volume data, and the result is presented to the doctor. Therefore, the doctor can easily determine the accuracy of the tomographic image in the eye, and the efficiency of the doctor's diagnosis workflow can be improved. Furthermore, it is possible to acquire imaging states such as eye movement and blinking during OCT imaging.

(Second Embodiment)
In the present embodiment, the processing content of the image processing unit 252 is different, and the description of the same processing as in the first embodiment is omitted.

  The image processing unit 252 detects an edge region from the integrated image, and detects the edge region parallel to the scanning direction at the time of capturing the tomographic image, thereby quantifying the similarity between the cross-sectional images constituting the tomographic image volume data.

  When an integrated image is created using tomographic volume data obtained by imaging the distant position of the retina due to eye movement at the time of imaging, the integrated value differs depending on the difference in retinal layer thickness, etc., at a position that is misaligned.

  Alternatively, when a blink occurs during shooting, the integrated value is 0 or extremely low. For this reason, a luminance difference occurs at a position shift or a blinking boundary. FIG. 9 is a diagram illustrating an example of the integrated image and the gradient image.

In FIG. 9, the scan direction during tomographic image capturing is parallel to the x direction. FIG. 9A shows an integrated image P _b that is displaced, and FIG. 9B shows an example of an edge image P _b ′ created from the integrated image P _b . In FIG. 9B, the symbol E represents an edge region parallel to the scan direction (x direction) during tomographic image capturing. The edge image P _b ′ is created by applying a smoothing filter to the integrated image P _b to remove noise components and applying an edge detection filter such as a Sobel filter or a Canny filter. The filter applied here may be a filter having no directionality or a filter considering the directionality. However, when considering the directivity, it is desirable to apply a filter that emphasizes a component parallel to the scan direction during OCT imaging.

Then, the image processing unit 252 detects, from the edge image P _b ′, a range in which a certain number of edge regions that are parallel to the OCT imaging scan direction (x direction) and that are equal to or greater than the threshold value continue. By detecting a certain number of edge regions E parallel to the scan direction (x direction), it can be distinguished from blood vessel edges and noise.

  In determining the continuity of tomographic images and the imaging state of the eye to be examined, the image processing unit 252 quantifies the length of a certain number of consecutive edge regions E.

  Then, the determination unit 253 determines the continuity of tomographic images and the imaging state of the eye to be examined by comparing with the threshold value Th ′.

  For example, it determines based on the following formula | equation (2). Here, E represents the length of the continuous edge region. The threshold value Th ′ may be a fixed value, may be set based on statistical data, or may be set based on patient information (age, sex, race). Further, it is desirable that the threshold Th ′ is dynamically changed according to the image size. For example, the smaller the image size, the smaller the threshold Th ′. Further, it is not necessary to limit the range of the edge region that is continuous for a certain number to the same parallel line, and the determination may be made using the range of the edge region that is continuous for a certain number on two or more consecutive parallel lines.

(Third embodiment)
In the present embodiment, the image processing unit 252 performs frequency analysis by Fourier transform and extracts frequency features, and the determination unit 253 determines the continuity of tomographic image volume data based on the intensity of the frequency domain.

FIG. 10 is a diagram illustrating an example of an integrated image and a power spectrum. FIG. 10A shows an integrated image P _b that has failed to be photographed due to a positional shift, and FIG. 10B shows a power spectrum P _b ″ of the integrated image P _b . When the eye moves during imaging and the position is shifted, or when blinking during imaging, a spectrum is detected in a direction orthogonal to the scanning direction during OCT imaging.

  Then, the determination unit 253 determines the continuity of tomographic images and the imaging state of the eye to be examined using these results.

(Fourth embodiment)
The image processing system 10 according to the first embodiment acquires a tomographic image of the eye to be examined, creates an integrated image from the tomographic image volume data, and uses a continuity of image features obtained from the integrated image to capture a captured image. Judging the accuracy of. The image processing apparatus according to the present embodiment is similar to the first embodiment in that the acquired tomographic image of the eye to be examined is processed. However, this embodiment is different from the first embodiment in that the continuity of tomographic images and the imaging state of the eye to be examined are determined from image features obtained from the tomographic images without creating an integrated image.

  Next, the processing procedure of the image processing system 10 of the present embodiment will be described with reference to the flowchart of FIG. Note that the processing in steps S1001, S1002, S1005, S1006, S1007, S1008, and S1009 is the same as steps S301, S302, S306, S307, S308, S309, and S310 in the first embodiment. Is omitted.

<Step S1003>
In step S1003, the image processing unit 252 extracts the acquired information for determining the continuity of tomogram volume data from the tomogram.

The image processing unit 252 detects the photoreceptor layer from the tomogram as a feature for determining the continuity of the tomogram volume data, and detects a region having a low luminance value in the photoreceptor cell layer. Hereinafter, specific processing of the image processing unit 252 will be described with reference to FIG. FIG. 12 is a diagram for explaining the characteristics of a tomographic image. Left side of FIG. 12 (a) shows a two-dimensional tomographic image T _i, right figure shows the profile of the image along the A-scan in vascular no position on the left. That is, the left figure shows the relationship between the coordinates on the line indicated by A-scan and the luminance value.

FIG. 12B is a view similar to FIG. 12A and illustrates a case where there is a blood vessel. In the two-dimensional tomograms T _i and T _j , 1 is the inner boundary membrane, 2 is the nerve fiber layer boundary, 3 is the retinal pigment epithelial layer, 4 is the photoreceptor inner / outer node junction, 5 is the photoreceptor layer, and 6 is the photoreceptor layer. A blood vessel region 7 represents a region under the blood vessel.

  The image processing unit 252 detects a layer boundary from the tomographic image. Here, the three-dimensional tomographic image to be processed is considered as a set of cross-sectional images (for example, B-scan images), and the following two-dimensional image processing is executed for each cross-sectional image. First, smoothing filter processing is performed on the cross-sectional image of interest to remove noise components. Then, edge components are detected from the tomogram, and some line segments are extracted as layer boundary candidates based on the connectivity. Then, the uppermost line segment is selected as the inner boundary film 1 from these candidates. Further, the line segment immediately below the inner boundary film 1 is selected as the nerve fiber layer boundary 2, and the lowest line segment is selected as the retinal pigment epithelium layer boundary 3. Then, the line segment immediately above the retinal pigment epithelium layer boundary 3 is selected as the photoreceptor inner / outer node junction 4. The region surrounded by the photoreceptor inner / outer joint junction 4 and the retinal pigment epithelium layer boundary 3 is defined as a photoreceptor layer 5. When the change in luminance value is small and an edge component equal to or greater than the threshold value cannot be detected by A-scan, the boundary of each layer may be interpolated using the coordinate points of the left and right or the entire detection point group.

  Furthermore, the detection accuracy may be improved by applying a dynamic contour method such as a Snake or a level set method using these line segments as initial values. Further, a layer boundary may be detected using a technique such as graph cut. Note that the boundary detection using the dynamic contour method or the graph cut may be performed three-dimensionally for a three-dimensional tomographic image, or the three-dimensional tomographic image to be processed is considered as a set of cross-sectional images, respectively. It may be applied two-dimensionally to the cross-sectional image. Note that the method for detecting the layer boundary is not limited to these, and any method may be used as long as the layer boundary can be detected from the tomographic image of the eye.

  As shown in FIG. 12B, the luminance value of the region 7 under the blood vessel is lowered as a whole. Therefore, a blood vessel can be detected by detecting a region in the photoreceptor cell layer 5 in which the luminance value is generally lowered in the A-scan direction.

  In the above, a region where the luminance value in the photoreceptor layer 5 is low is detected, but the blood vessel feature is not limited to this. A blood vessel may be detected by detecting the thickness between the inner boundary membrane 1 and the nerve fiber layer boundary 2 (in other words, the nerve fiber layer) and the thickness change between the left and right. For example, as shown in FIG. 12B, when the thickness change of the layer is observed in the x direction, the thicknesses of the inner boundary membrane 1 and the nerve fiber layer boundary 2 are rapidly increased in the blood vessel portion. By detecting it, a blood vessel can be detected. Furthermore, a blood vessel may be detected by combining the above processes.

<Step S1004>
In step S1004, the image processing unit 252 performs processing on the blood vessel acquired in step S1003, and determines the continuity of the tomographic image volume data.

The image processing unit 252 tracks the blood vessel from the blood vessel end near the macula, and attaches a tracked label to the tracked blood vessel. Then, the tracked blood vessel end coordinates are stored in the storage unit 240. Then, the coordinates of the blood vessel ends existing on the same parallel line parallel to the scanning direction during OCT imaging are counted together. In the case of FIG. 12, for example, if the scanning direction during OCT imaging is parallel to the x direction, a point existing at the same y coordinate is a cross-sectional image (for example, a B-scan image). Accordingly, in FIG. 12B, (x ₁ , y _j , z ₁ ), (x ₂ , y _j , z ₂ )... (X _n , y _j , z _n ) are counted together. When there is a change in the imaging state of the eye to be inspected, a positional deviation occurs between the cross-sectional images (B-scan images), so that the blood vessel ends are concentrated on the same straight line at the boundary where the positional deviation has occurred. Since the subsequent processing is the same as that of the first embodiment, detailed description thereof is omitted.

  According to the configuration described above, the continuity of the tomographic image is determined from the tomographic image volume data, and the result is presented to the doctor. Therefore, the doctor can easily determine the accuracy of the ocular tomographic image, and the efficiency of the diagnosis workflow of the doctor can be improved.

(Fifth embodiment)
This embodiment explains in detail the method of calculating the similarity according to the first embodiment. The image processing unit 252 further includes a similarity calculation unit 254 (not shown), and calculates the similarity or dissimilarity between cross-sectional images. The determination unit 253 uses the similarity or dissimilarity to determine the continuity of tomographic images and The imaging state of the eye to be examined is determined. In the following description, the similarity is described.

  The similarity calculation unit 254 calculates the similarity between successive cross-sectional images. The similarity between images can be calculated by the sum of squares of brightness difference (SSD) or the sum of brightness differences (SAD). Alternatively, mutual information (MI) may be obtained. Note that the method for calculating the similarity between cross-sectional images is not limited to these, and any method may be used as long as the similarity between images can be calculated. For example, the image processing unit 252 extracts the mean and variance of density values as color and density features, extracts Fourier features, density co-occurrence matrices, etc. as texture features, and forms layer features, blood vessels as shape features. Extract shape etc. Then, the similarity calculation unit 254 may determine the similarity by calculating a distance in the image feature space. The distance may be calculated using the Euclidean distance, Mahalanobis distance, or the like.

  The determination unit 253 determines that continuous cross-sectional images (B-scan images) have been captured normally if the similarity obtained by the similarity calculation unit 254 is equal to or greater than a threshold value. The threshold of similarity may be changed according to the distance between two-dimensional tomographic images and the scan speed. For example, when a shooting range of 6 × 6 mm is shot with 128 slices (B-scan image) and when shot with 256 slices (B-scan image), the similarity between cross-sectional images is 256 slices. Get higher. The threshold value for similarity may be set to a fixed value, may be set based on statistical data, or may be set based on patient information (age, sex, race). When the similarity is less than or equal to the threshold value, it is assumed that continuous cross-sectional images are discontinuous. Thereby, it is possible to detect a positional shift or blink at the time of shooting.

(Sixth embodiment)
The image processing apparatus according to the present embodiment is the same as the first embodiment in that the acquired tomographic image of the eye to be examined is processed. However, each of the above-mentioned points is that the image feature obtained from tomographic images taken at different time points of the same patient in the past and the image feature obtained from currently taken tomographic images are detected for positional deviation and blinking at the time of photographing. This is different from the embodiment.

  The functional block of the image processing system 10 according to the present embodiment is different from the first embodiment (FIG. 2) in that the image processing apparatus 250 has a similarity calculation unit 254 (not shown). .

  Next, a processing procedure of the image processing system 10 of the present embodiment will be described with reference to the flowchart of FIG. In this embodiment, S1207, S1208, S1209, and S1210 are the same as steps S307, S308, S309, and S310 in the first embodiment, respectively, and thus the description thereof is omitted.

<Step S1201>
In step S1201, the eye information acquisition unit 210 acquires a subject identification number from the outside as information for identifying the eye. This information is input by an operator via a keyboard 706, a mouse 707, or a card reader (not shown). Then, based on the eye identification number to be examined, information on the eye to be examined held by the data server 40 is acquired. For example, a patient's name, age, sex, etc. are acquired. Furthermore, a tomographic image of the eye to be inspected in the past is acquired. If there is measurement data such as visual acuity, axial length and intraocular pressure as other examination information, the measurement data may be acquired. Then, the acquired information is transmitted to the storage unit 240.

  In step S1201, in the case of re-imaging with the same eye, this processing may be stepped, and when there is information to be newly added, that information is acquired.

<Step S1202>
In step S <b> 1202, the image acquisition unit 220 acquires a tomographic image transmitted from the tomographic imaging apparatus 20. Then, the acquired information is transmitted to the storage unit 240.

<Step S1203>
In step S1203, the integrated image creation unit 251 creates an integrated image obtained by integrating cross-sectional images (for example, B-scan images) in the depth direction. The integrated image creation unit 251 acquires the past tomographic image acquired by the eye information acquisition unit 210 in step S1201 and the past tomographic image acquired by the image acquisition unit 220 in step S1202 from the storage unit 240. Then, an integrated image of each tomographic image is created. The specific method of creating the integrated image is the same as that in the first embodiment, and detailed description thereof is omitted.

<Step S1204>
In step S1204, the similarity calculation unit 254 calculates the similarity between integrated images created from tomographic images taken at different times.

Hereinafter, specific processing of the similarity calculation unit 254 will be described with reference to FIG. FIG. 14 is a diagram illustrating an example of the integrated image and the partial image. In FIG. 14 (a) integrated image _{P a} created from tomograms captured in the past, FIG. 14 (b) integrated image _{P a} partial integrated image created from _P a1 _{to P an,} FIG. 14 (c) it is integrated image P _b created from the current captured tomogram. Here, partial integrated image P _a1 to P _an, it is desirable that the same straight line parallel to the scanning direction at the time of image capturing OCT are in the same area. Further, the division number n of the partial integration image may be an arbitrary number, and may be dynamically changed according to the tomographic image size (X, Y, Z).

  The similarity between images can be obtained using the sum of squares of luminance differences, the sum of luminance differences, and the mutual information amount. Note that the method for calculating the similarity between the integrated images is not limited to these, and any method may be used as long as the similarity between images can be calculated.

Determination unit 253, when calculating the similarity of parts integrated image P _a1 to P _an, and the integrated image P _b, movement of the eyeball has been successfully reduced shooting if the similarity of all partial integrated image threshold or Judge.

  If there is a partial integrated image whose similarity is equal to or less than the threshold, the partial integrated image is further divided into m pieces, and the place where the similarity is high and the similarity are calculated. These processes are repeated until it cannot be divided, or until a section between low-similarity cross-sectional images can be identified. Since the accumulated image created from the tomographic image when the eyeball moves or blinks is spatially misaligned, there is no part of the partially accumulated image that has been successfully photographed. For this reason, the determination unit 253 determines whether the similarity is high even when the division of the partial integrated image is repeated or the similarity is equal to or less than the threshold, or in a place where the position is inconsistent (the order of the partial integrated images is changed). Then, it is determined that the partial integrated image does not exist.

<Step S1205>
The determination unit 253 determines that a continuous two-dimensional tomographic image is normally captured if the similarity obtained by the similarity calculation unit 254 is equal to or greater than a threshold value. It is assumed that the tomographic image is discontinuous when the similarity is equal to or less than the threshold value. Also, it is determined that there has been a position shift or blinking during shooting.

<Step S1206>
In step S1206, the display unit 260 displays the tomographic image acquired in step S1202 on the monitor 705. The contents displayed on the monitor 705 are the same as those shown in step S306 of the first embodiment. However, in addition to these, tomographic images taken at different times on the same eye to be examined acquired in step S1201 may be displayed on the monitor 705.

  In this embodiment, an integrated image is created from tomographic images, and similarity is calculated to determine continuity. However, similarity is calculated between tomographic images without creating an integrated image from tomographic images. Sex may be determined.

  According to the configuration described above, the continuity of tomographic images is determined from the similarity between integrated images created from tomographic images taken at different times, and the results are presented to the doctor. Therefore, the doctor can easily determine the accuracy of the ocular tomographic image, and the efficiency of the diagnosis workflow of the doctor can be improved.

(Seventh embodiment)
In the present embodiment, the similarity calculation unit 254 calculates the similarity between the blood vessel models created from the tomograms taken at different times, and the determination unit 253 uses the similarity to determine the continuity of the tomographic image volume data. judge.

Since the blood vessel detection method in the image processing unit 252 is the same as that in step S304 of the first embodiment, the description thereof is omitted. The blood vessel model is, for example, a binarized image in which the blood vessel is 1 and other tissues are 0, or a multi-valued image in which only the blood vessel portion is grayscale and other tissues are 0. . FIG. 15 shows an example of a blood vessel model. FIG. 15 is a diagram illustrating an example of a blood vessel model and a partial model. In FIG. 15 (a) vessel model _{V a} created from tomograms captured in the past, FIG. 15 (b) the partial blood vessel models _V a1 _{~V an,} created from the blood vessel model _{V a,} FIG. 15 (c) is It is the blood vessel model _Vb created from the tomogram currently image | photographed. Here, in the partial blood vessel models V _{a1 to} V _an, it is desirable that the same straight line parallel to the scan direction during OCT imaging is included in the same region. Further, the division number n of the partial blood vessel model may be an arbitrary number, and may be dynamically changed according to the tomographic image size (X, Y, Z).

  Then, similarly to steps S1204 and S1205 of the third embodiment, the continuity of tomographic volume data is determined from the similarity between features obtained from tomographic images taken at different times.

(Eighth embodiment)
In each of the embodiments described above, the determination unit 253 determines by combining similarity evaluation and blood vessel end detection. For example, using the partial integrated image _P a1 _{to P an,} or the partial blood vessel models _V a1 _{~V an,,} to assess the similarity of the tomograms captured at different times. Then, blood vessel tracking and blood vessel end detection are performed only in the partial integrated images P _{a1 to} P _an or the partial blood vessel models V _{a1 to} V _an whose similarity is equal to or less than the threshold value, and the continuity of the tomographic image volume data is determined. May be.

(Other embodiments)
In each of the above-described embodiments, it may be automatically determined whether or not to image the subject's eye again. For example, if the determination unit 253 determines discontinuity, the image is automatically captured again. Alternatively, when the location determined to be discontinuous is within a certain range from the center of the image, re-photographing is automatically performed. Alternatively, if a discontinuity is determined at a plurality of locations, the image is automatically re-captured. Alternatively, the amount of positional deviation is estimated from the blood vessel pattern, and if the degree of positional deviation is greater than or equal to the threshold value, re-imaging is automatically performed. The estimation of the amount of displacement is not limited to the blood vessel pattern, and may be estimated from a comparison with a past image. Alternatively, if a discontinuity is determined in the case of a diseased eye depending on whether it is a normal eye or a diseased eye, the image is automatically re-taken. Alternatively, when a discontinuity is determined at a location where a lesion (white spot or bleeding) is present as compared with past data, re-imaging is automatically performed. Alternatively, it may be configured to automatically re-photograph when the location where the operator has instructed photographing is misaligned. Note that these processes are not necessarily performed independently, and may be performed in combination.

  If it is determined that re-taking has been performed, the processing is returned to perform reprocessing on the same eye to be examined.

In each of the above embodiments, the display example on the display unit 260 is not limited to that shown in FIG. For example, another example will be described with reference to FIG. FIG. 16 is a schematic diagram illustrating an example of a screen display. FIG. 16 (a), and estimates the positional deviation amount from a blood vessel pattern, an example in which explicitly shown in the integrated image P _b the positional deviation amount. The S ′ area indicates the estimated unphotographed area. FIG. 16B shows an example in which discontinuities due to misalignment or blinking are detected at a plurality of locations. In that case, the boundary tomographic image of all the locations may be displayed simultaneously, the boundary tomographic image of the location where the displacement is large may be displayed at the same time, the vicinity of the center or the location where there was a disease The boundary tomographic image at may be displayed simultaneously. When displaying a tomographic image at the same time, it is desirable that the operator knows which part the displayed tomographic image corresponds to using a color or a numerical value. In addition, the boundary tomographic image to be displayed is configured to be freely changeable by the operator using a GUI (not shown). FIG. 16C shows a slider S ″ and a knob S ′ ″ for manipulating the tomographic images displayed as tomographic volume data T _{1 to} T _n, and the marker S is a place where discontinuity is detected from the tomographic volume data. Further, the positional deviation amount S ′ or the like may be explicitly displayed on the slider, and when there is a past image or a wide area image in addition to the above image, it may be displayed at the same time. .

  In each of the above-described embodiments, analysis processing is performed on an image in which a macular portion is photographed. However, the location where the image processing unit determines continuity is not limited to the image in which the macular portion is photographed, and the same processing may be performed on the image in which the optic nerve head is photographed. Furthermore, processing may be performed on an image in which the macular portion and the optic disc are captured simultaneously.

  In each of the embodiments described above, analysis processing is performed on the entire acquired three-dimensional tomographic image. However, the configuration may be such that a notable cross section is selected from the three-dimensional tomographic image and the selected two-dimensional tomographic image is processed. For example, the process may be performed on a cross section including a predetermined specific part (for example, fovea) of the fundus. In this case, the detected layer boundary, normal structure, normal data, etc. are all two-dimensional data on the cross section.

  The continuity determination of the tomographic volume data of the image processing system 10 described in each of the above embodiments is not necessarily performed independently, and may be performed in combination. For example, the degree of concentration of the blood vessel end obtained from the integrated image created from the tomographic image as in Example 1 and the similarity and image feature amount between consecutive tomographic images as in Example 2 are evaluated together. The continuity of tomographic volume data may be determined. For example, each detection result and image feature amount may be learned from a tomographic image having no positional deviation and a tomographic image having a positional deviation, and the continuity of tomographic image volume data may be determined by a discriminator. In addition, it goes without saying that any of the embodiments may be combined.

  In each of the above embodiments, the tomographic imaging apparatus 20 does not necessarily have to be connected to the image processing system 10. For example, the tomographic image to be processed may be stored in the data server 40 in a state where the tomographic image has already been captured, and may be read and processed. In this case, the image acquisition unit 220 requests the data server 40 to transmit a tomogram, acquires the tomogram transmitted from the data server 40, and performs layer boundary detection and quantification processing. Further, the data server 40 does not necessarily have to be connected to the image processing system 10, and the external storage device 704 of the image processing system 10 may be configured to play its role.

  An object of the present invention is to supply a storage medium storing software program codes for realizing the functions of the above-described embodiments to a system or apparatus. Needless to say, this can also be achieved by the computer (or CPU or MPU) of the system or apparatus reading and executing the program code stored in the storage medium.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.

  As a storage medium for supplying the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

  Further, by executing the program code read by the computer, an OS (operating system) operating on the computer performs part or all of the actual processing based on the instruction of the program code. Needless to say, the process includes the case where the functions of the above-described embodiments are realized.

  Furthermore, it goes without saying that the function expansion board inserted into the computer or the function expansion unit connected to the computer performs part or all of the processing, and the functions of the above-described embodiments are realized by the processing. . In this case, the program code read from the storage medium is written in a memory provided in the function expansion board or function expansion unit. Then, a CPU or the like provided in the function expansion board or function expansion unit executes actual processing based on the instruction of the program code.

  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.

250 Image Processing Device 251 Integrated Image Creation Unit 252 Image Processing Unit 253 Determination Unit 254 Similarity Determination Unit 260 Display Unit

Claims (15)

Image processing means for acquiring information indicating continuity of tomographic images of the eye to be examined;
Determination means for determining a photographing state of the eye to be examined based on information acquired by the image processing means;
Acquisition means for acquiring an instruction as to whether or not to image the eye to be examined again;
A tomographic imaging apparatus comprising:   The image processing means acquires a similarity between cross-sectional images constituting the tomographic image, and the determination means determines the imaging state of the eye to be examined based on the similarity between the cross-sectional images. The tomographic imaging apparatus according to claim 1.   The image processing means acquires blood vessel edge position information from the tomographic image, and the determining means is based on the number of blood vessel edges on a cross-sectional image that is a two-dimensional tomographic image of the tomographic image. The tomographic imaging apparatus according to claim 1, wherein an imaging state is determined. The image processing means obtains the similarity between tomograms taken at different points in time of the eye;
The tomography apparatus according to claim 1, wherein the determination unit determines an imaging state of the eye to be examined based on a similarity between the tomograms.   The tomography apparatus according to claim 2, wherein the determination unit determines the degree of movement of the eye to be examined and the presence or absence of blinking based on the similarity between the cross-sectional images.   The tomography apparatus according to claim 3, wherein the determination unit determines the degree of movement of the eye to be examined and the presence or absence of blinking based on the number of blood vessel ends in the cross-sectional image. A cumulative image creating means for creating a cumulative image obtained by integrating the tomographic images in the depth direction;
The tomographic imaging apparatus according to claim 1, wherein the image processing unit acquires either the similarity or the number of blood vessel ends from the integrated image.   7. The tomography according to claim 1, wherein the determination unit determines either the degree of movement of the eye to be examined or the presence or absence of blinking based on information acquired by the image processing unit. Image taking device. Image processing means for acquiring information indicating continuity of tomographic images of the eye to be examined;
Determination means for determining a photographing state of the eye to be examined based on information acquired by the image processing means;
An acquisition means for acquiring an instruction as to whether or not to save the result of the current processing relating to the eye to be examined in the data server;
A tomographic imaging apparatus comprising: Image processing means for acquiring information indicating continuity of tomographic images of the eye to be examined;
Determination means for determining a photographing state of the eye to be examined based on information acquired by the image processing means;
Obtaining means for obtaining an instruction as to whether or not to end the photographing process;
A tomographic imaging apparatus comprising: An image processing step for acquiring information indicating continuity of tomographic images of the eye to be examined;
A determination step of determining a photographing state of the eye to be examined based on the information acquired in the image processing step;
An acquisition step of acquiring an instruction as to whether or not to image the eye to be examined again;
A tomographic imaging method comprising: An image processing step for acquiring information indicating continuity of tomographic images of the eye to be examined;
A determination step of determining the imaging state of the eye to be examined based on information acquired by the image processing means;
An acquisition step of acquiring an instruction as to whether or not to store the result of the current process relating to the eye to be examined in the data server;
A tomographic imaging method comprising: An image processing step for acquiring information indicating continuity of tomographic images of the eye to be examined;
A determination step of determining the imaging state of the eye to be examined based on information acquired by the image processing means;
An acquisition step of acquiring an instruction as to whether or not to end the photographing process;
A tomographic imaging method comprising:   A program for causing a computer to execute the image processing method according to claim 11.   A storage medium storing a program for causing a computer to execute the image processing method according to claim 14.

Images