JP2017121576A - Information processing device, and method and program for controlling information processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical interference tomography apparatus which facilitates observation of highly-reliable analysis image data and for which enhanced inspection efficiency is expected.SOLUTION: The tomography apparatus is provided with: acquisition means for acquiring a tomographic image of an inspection object; specifying means for specifying an image area corresponding to an inspection site of the inspection object in the tomographic image; discrimination means for determining a region of significance and a region of non-significance on the basis of a positional relationship between a peripheral edge part of the image area and the tomographic image; and display control means for designating a display mode for displaying both image data based on the tomographic image and data relating to the region of non-significance and allowing display means to display both the data.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an information processing apparatus that processes information obtained from, for example, an optical coherence tomography device typified by an ophthalmic apparatus, a control method for the information processing apparatus, and a program.

  Currently, various types of ophthalmic equipment using optical equipment are used. For example, various apparatuses such as an anterior ocular segment photographing machine, a fundus camera, and a confocal laser scanning ophthalmoscope (Scanning Laser Ophthalmoscope: SLO) are used as optical instruments for observing eyes. Among them, an optical tomographic imaging apparatus based on optical coherence tomography (OCT) using multiwavelength lightwave interference is an apparatus that can obtain a tomographic image of a sample with high resolution. For this reason, it is becoming an indispensable device for specialized retina outpatients as an ophthalmic device. Moreover, it is used not only for ophthalmology but also for endoscopes and the like. Hereinafter, this is referred to as an OCT apparatus. The OCT apparatus is widely used in ophthalmologic diagnosis and the like to acquire a tomographic image of the retina at the fundus of the eye to be examined and a tomographic image of the anterior segment such as the cornea.

  The OCT apparatus divides measurement light, which is low-coherent light, into reference light and measurement light, irradiates the inspection light with the measurement light, causes the return light from the inspection object to interfere with the reference light, It is possible to measure the tomography of the inspection object from the spectrum information. In a current OCT apparatus, a spectrum domain (SD) -OCT that can obtain information in the depth direction from the spectrum information of the interference light is generally used. Hereinafter, in the present invention, the SD-OCT apparatus is simply referred to as an OCT apparatus.

  The OCT apparatus can obtain a high-resolution tomographic image by scanning the measurement light on the sample, and obtain a two-dimensional image by performing one-dimensional scanning of the measurement light on a specific region. A three-dimensional image (volume data) is obtained by repeatedly acquiring a one-dimensional scan for acquiring a two-dimensional tomographic image while shifting the position.

  Here, it is known that the retina of a human eye is composed of a plurality of layers. In ophthalmologic diagnosis, the layer structure is interpreted based on volume data, and the state of a lesion is confirmed. In addition, in order to confirm the state of the lesion in the volume image data of the retina, it is effective to display a tomogram, analyze the layer structure of the retina, and display a layer thickness graph, layer thickness map, etc. (Patent Document 1). Furthermore, comparing the calculated layer thickness with normal eye layer thickness data (Normal Data Base: NDB) is also effective in confirming the state of the lesion.

  However, when attempting to obtain a tomographic image of an object to be inspected using spectral information, due to the characteristics of the Fourier transform performed during the calculation, a normal tomogram based on the position where the measurement optical path called the gate and the reference optical path are equal It is known that a folded image is generated with respect to the image. When the tomographic image of the inspection object crosses the gate position, the normal tomographic image and the folded tomographic image overlap to form a double image.

  When the tomographic image is a double image, it is difficult to identify the layer structure of the sample by image analysis. For this reason, there is a possibility that the layer thickness analysis data of the region that has become a double image cannot be properly presented to the user. Therefore, in Patent Document 1, an ophthalmic apparatus that issues a warning when a tomographic image of an object to be inspected appears outside the proper image capturing range in order to prevent a folded image from being captured in a state where it overlaps a normal tomographic image. Is disclosed.

JP 2012-071113 A JP 2011-092290 A

  However, even when the ophthalmologic apparatus disclosed in Patent Document 2 is used, there is a possibility that the user may take a picture with a folded image. This is because the tomographic image becomes unclear due to a decrease in the signal intensity as the distance from the gate position increases, and the user may intentionally bring the target region close to the gate position for imaging. In addition, since the retina of the human eye has a curved shape rather than a flat surface, there is a possibility that a tomographic image crosses the gate position and a folded image is generated in a region away from the focused region. In addition, when the retina is strongly curved, such as intense myopia, it may be difficult to capture the entire retina without a folded image.

  Therefore, in view of the above problems, the present invention provides an information processing apparatus that appropriately presents layer thickness data to a user and processes information expected to improve inspection efficiency, a control method for the information processing apparatus, and a program The purpose is to do.

  In order to achieve the above object, an optical coherence tomographic apparatus according to an aspect of the present invention includes an acquisition unit that acquires a tomographic image of an object to be inspected, and an image display corresponding to an inspection site of the object to be inspected in the tomographic image. Specifying means for specifying an area; discriminating means for determining a significant area and an insignificant area based on a positional relationship between a peripheral portion of the image area and the tomographic image; and image data based on the tomographic image and the insignificant area Display control means for designating a display form for displaying the data and displaying it on the display means.

  According to the information processing apparatus, the control method for the information processing apparatus, and the program according to the present invention, the user can be highly reliable because the area where the aliasing image may affect the analysis image data can be clearly indicated. It is possible to focus only on the analysis image data, which leads to improvement in diagnosis efficiency.

It is explanatory drawing of the layer thickness map which concerns on this invention. (A) is an overall schematic diagram of the optical coherence tomography apparatus according to the present invention, (b) is a block diagram of the optical coherence tomography apparatus according to the present invention, and (c) is an image acquisition unit of the optical coherence tomography apparatus according to the present invention. It is explanatory drawing of a certain measurement optical system. It is explanatory drawing of the imaging | photography screen which displays the real-time image (moving image) before the imaging of the optical coherence tomography apparatus which concerns on this invention. It is explanatory drawing of the report screen which displays the tomographic image of the optical coherence tomography apparatus which concerns on this invention in detail. It is explanatory drawing of the retina structure of a human eye. (A) is a flow chart for generating a layer thickness map according to the present invention, and (b) and (c) are explanatory diagrams of a method for determining a significant region according to the present invention. It is explanatory drawing of the modification of the layer thickness map display which concerns on this invention. It is explanatory drawing of the significant area | region identification method of IS / OS-RPE. (A) And (c)-(e) is explanatory drawing of the comparison layer thickness map which concerns on this invention, (b) is a production | generation flow of the comparison layer thickness map which concerns on this invention. (A) And (c)-(g) is explanatory drawing of the sector layer thickness data based on this invention, (b) is the production | generation flow of sector layer thickness data. (A) is explanatory drawing of the comparison sector layer thickness data based on this invention, (b) is a production | generation flow of the comparison sector layer thickness data.

(Body structure)
FIG. 2A is a side view of the optical tomographic imaging apparatus according to the present embodiment. 200 is an optical coherence tomography apparatus, 900 is an acquisition unit (measurement optical system) for acquiring an anterior ocular segment image, a two-dimensional image and a tomographic image of the eye to be examined, 950 is a stage unit as a moving unit, and an image acquisition unit 900 Can be moved in the XYZ directions using a motor (not shown). Reference numeral 951 denotes a base unit incorporating a spectroscope described later.

  As will be described in detail later, the image acquisition unit 900 scans the subject with light for acquiring an image of the subject and captures the subject to acquire the image of the subject.

  Reference numeral 925 denotes a personal computer that controls the configuration of the tomographic image, the stage portion, and the alignment operation. Further, an image area specification and a layer structure analysis described later, a significant area specification, generation of analysis image data, display control on a monitor, and the like are performed. A hard disk 926 serves as a patient information storage unit that stores patient information and various types of imaging data, and stores a tomographic program and reference layer thickness data in advance.

  Reference numeral 928 denotes a monitor as a display unit, and reference numeral 929 denotes an input unit for instructing a personal computer, and specifically includes a keyboard and a mouse. That is, the monitor 928 is a single common monitor that time-divides a shooting screen and a report screen, which will be described later, and is provided not on the image acquisition unit 900 side but on the personal computer 925 side.

  Reference numeral 323 denotes a face holder, which includes a chin rest 324 that can be moved up and down by a motor (not shown), a forehead support 325, and an eye height line 326 that is provided at the center of the movement range of the objective lens described later in the height direction. By placing the subject's chin on the chin rest 324, placing the forehead on the forehead 325, and fixing the subject's face so that the height of the subject's eyes substantially coincides with the eye height line 326, The eye to be examined can be roughly positioned on the acquisition unit 900.

(Block Diagram)
A block diagram illustrating the configuration of the information processing apparatus according to the present embodiment will be described with reference to FIG. Details of each operation for performing information processing according to the present embodiment will be described later.

  Reference numeral 930 denotes a tomographic image generation unit that generates a tomographic image based on a reference light signal (to be described later) obtained by the acquisition unit 900.

  Reference numeral 931 denotes an image range specifying unit that analyzes the tomographic image formed by the tomographic image generation unit 930 and specifies an image region corresponding to a predetermined part of the inspection object. The image area indicates an area of an image displayed on the monitor 928, and the size of the image area is, for example, constant. The image range specifying unit 931 corresponds to specifying means for specifying, in the present invention, a portion corresponding to an inspection site of an inspection object to be inspected in a tomographic image as an image region.

  A layer structure analysis unit 932 analyzes the tomographic image formed by the tomographic image generation unit 930 and identifies the layer structure of the inspection object. The layer structure analysis unit 932 corresponds to analysis means in the present invention.

  Reference numeral 933 denotes a significant area discriminating unit which sets a significant area based on the image area formed by the image range specifying unit 931 and the layer structure formed by the layer structure analyzing unit 932. Here, the significant region is a characteristic configuration in the present invention, and details will be described later. The significant area discriminating unit 933 corresponds to a discriminating unit that determines a significant area and an insignificant area based on the positional relationship between the area periphery of the image area and the tomographic image in the present invention. Details of this positional relationship will be described later.

  Reference numeral 934 denotes an analysis image generation unit, which stores the image region formed by the image range specifying unit 931, the layer structure formed by the layer structure analysis unit 932, the significant region formed by the significant region determination unit 934, and the storage unit 926. Analysis image data is generated based on the obtained reference layer thickness data. Here, the analysis image data includes a layer thickness map that displays the layer thickness of the object to be inspected as a color map, or an average of specific layer thicknesses in each region (sector) by dividing the object to be inspected into several regions. For example, sector layer thickness data for displaying value data. The analysis image generation unit 935 corresponds to generation means in the present invention.

  Reference numeral 935 denotes a display control unit that performs control to display the analysis image data generated by the analysis image generation unit 934 on a monitor 928 that is a display unit. Further, as will be described later, the display control means designates a display form for displaying both the image data based on the tomographic image and the data relating to the insignificant region, and causes the monitor 928 to display the display form.

(Configuration of measurement optical system and spectrometer)
The configuration of the measurement optical system and the spectroscope of this embodiment will be described with reference to FIG. First, the inside of the image acquisition unit 900 will be described. An objective lens 135-1 is installed facing the eye 107, and a first dichroic mirror 132-1 and a second dichroic mirror 132-2 are disposed on the optical axis. By these dichroic mirrors, the optical path 351 of the OCT optical system, the SLO optical system that combines observation of the eye to be examined and acquisition of the two-dimensional image, the optical path 352 for the fixation lamp, and the optical path 353 for the anterior eye observation are provided for each wavelength band. Fork.

  The optical path 352 for the SLO optical system and the fixation lamp includes SLO scanning means 133, lenses 135-3 and 135-4, a mirror 132-5, a third dichroic mirror 132-3, a photodiode 173, an SLO light source 174, and a fixation lamp. 191. The mirror 132-5 is a prism on which a perforated mirror or a hollow mirror is deposited, and separates illumination light from the SLO light source 174 and return light from the eye to be examined. The third dichroic mirror 132-3 separates the optical path for each wavelength band into the optical path to the SLO light source 174 and the fixation lamp 191. The SLO scanning unit 133 scans the light emitted from the SLO light source 174 and the fixation lamp 191 on the eye 107 to be examined, and includes an X scanner that scans in the X direction and a Y scanner that scans in the Y direction. Yes. In this embodiment, since the X scanner needs to perform high-speed scanning, the Y scanner is constituted by a polygon mirror and the Y scanner is constituted by a galvanometer mirror. The lens 135-3 is driven by a motor (not shown) for focusing the SLO optical system and the fixation lamp. The SLO light source 174 generates light having a wavelength near 780 nm. The photodiode 173 detects return light from the eye to be examined. The fixation lamp 191 generates visible light to promote fixation of the subject.

  The light emitted from the SLO light source 174 is reflected by the third dichroic mirror 132-3, passes through the mirror 132-5, passes through the lenses 135-4 and 135-3, and is scanned on the eye 107 by the SLO scanning unit 133. Is scanned. The return light from the eye 107 to be examined returns through the same path as the projection light, is reflected by the mirror 132-5, and is guided to the photodiode 173. The fixation lamp 191 passes through the third dichroic mirror 132-3 and the mirror 132-5, passes through the lenses 135-4 and 135-3, and is scanned on the eye 107 by the SLO scanning unit 133. At this time, by flashing the fixation lamp 191 in accordance with the movement of the SLO scanning means, an arbitrary shape is created at an arbitrary position on the subject's eye 107 to prompt the subject to fixate.

  In the optical path 353 for anterior eye observation, 135-2 and 135-10 are lenses, 140 is a split prism, and 171 is a CCD for anterior eye observation that detects infrared light. The CCD 171 has sensitivity at a wavelength of irradiation light for anterior eye observation (not shown), specifically, around 970 nm. The split prism 140 is disposed at a position conjugate with the pupil of the eye 107 to be detected, and can detect the distance in the Z direction (front-back direction) of the image acquisition unit 900 with respect to the eye 107 as a split image of the anterior eye. it can.

  The optical path 351 of the OCT optical system forms the OCT optical system as described above, and is for capturing a tomographic image of the eye 107 to be examined. More specifically, an interference signal for forming a tomographic image is obtained. Reference numeral 134 denotes an XY scanner for scanning light on the eye to be examined. The XY scanner 134 is illustrated as a single mirror, but is a galvanometer mirror that performs scanning in the XY biaxial directions.

  Reference numerals 135-5 and 135-6 denote lenses, and the lens 135-5 is for focusing the light from the OCT light source 101 emitted from the fiber 131-2 connected to the optical coupler 131 on the eye 107 to be examined. Are driven by a motor (not shown). By this focusing, the return light from the eye 107 to be inspected is incident on the tip of the fiber 131-2 in the form of a spot.

  Next, the configuration of the optical path from the OCT light source 101, the reference optical system, and the spectrometer will be described. Reference numeral 101 denotes an OCT light source, 132-4 denotes a reference mirror, 115 denotes dispersion compensation glass, 131 denotes an optical coupler, 131-1 to 4 denote a single mode optical fiber connected to the optical coupler, and 135-7 denotes a lens. , 180 is a spectroscope.

  The Michelson interference system is configured by these configurations. The light emitted from the OCT light source 101 is split into the measurement light on the optical fiber 131-2 side and the reference light on the optical fiber 131-3 side through the optical coupler 131 through the optical fiber 131-1. The measurement light is irradiated to the eye 107 to be examined through the OCT optical system optical path 351 described above, and reaches the optical coupler 131 through the same optical path due to reflection and scattering by the eye to be examined.

  By the optical coupler 131, the measurement light and the reference light are combined to become interference light. Here, interference occurs when the optical path length of the measurement light and the optical path length of the reference light are substantially the same. The reference mirror 132-4 is held so as to be adjustable in the optical axis direction by a motor and a driving mechanism (not shown), and the optical path length of the reference light can be adjusted to the optical path length of the measurement light that changes depending on the eye 107 to be examined. The interference light is guided to the spectroscope 180 via the optical fiber 131-4.

  Reference numeral 139-1 denotes a measurement light side polarization adjusting unit provided in the optical fiber 131-2. Reference numeral 139-2 denotes a reference light side polarization adjustment unit provided in the optical fiber 131-3. These polarization adjusting units have several portions in which the optical fiber is looped. By rotating this loop-shaped portion around the longitudinal direction of the fiber, the fiber can be twisted, and the polarization states of the measurement light and the reference light can be adjusted and matched.

  The spectroscope 180 includes lenses 135-8 and 135-9, a diffraction grating 181, and a line sensor 182. The interference light emitted from the optical fiber 131-4 becomes parallel light via the lens 135-8, is then split by the diffraction grating 181, and is imaged on the line sensor 182 by the lens 135-9.

  The OCT optical system described above corresponds to acquisition means for acquiring a tomographic image by irradiating the inspection object with measurement light in the present invention.

  Next, the periphery of the OCT light source 101 will be described. The OCT light source 101 is an SLD (Super Luminescent Diode) which is a typical low coherent light source. The center wavelength is 855 nm and the wavelength bandwidth is about 100 nm. Here, the bandwidth is an important parameter because it affects the resolution of the obtained tomographic image in the optical axis direction.

  As the type of light source, SLD is selected here, but it is sufficient that low-coherent light can be emitted, and ASE (Amplified Spontaneous Emission) or the like can be used. Near-infrared light is suitable for the center wavelength in view of measuring the eye. Moreover, since the center wavelength affects the lateral resolution of the obtained tomographic image, it is desirable that the center wavelength be as short as possible. For both reasons, the center wavelength was set to 855 nm.

  In this embodiment, a Michelson interference system is used as the interference system, but a Mach-Zehnder interference system may be used. It is desirable to use a Mach-Zehnder interference system when the light amount difference is large and a Michelson interference system when the light amount difference is relatively small, depending on the light amount difference between the measurement light and the reference light.

  With the configuration as described above, a tomographic image of the eye to be examined can be obtained, and a two-dimensional image of the eye to be examined having high contrast can be obtained even with near infrared light.

(Tomographic imaging method)
A tomographic image capturing method using the optical coherence tomography apparatus 200 will be described. The optical coherence tomography apparatus 200 can take a tomographic image of a predetermined part of the eye 107 to be examined by controlling the XY scanner 134. Here, the trajectory of scanning the tomographic image acquisition light in the eye to be examined is called a scan pattern (scanning pattern). This scan pattern includes, for example, a cross scan that scans in a vertical and horizontal cross about one point and a 3D scan that scans to fill the entire area and obtains a three-dimensional tomogram (volume image) as a result. A cross scan is suitable for detailed observation of a specific part, and a 3D scan is suitable for observation of the layer structure and layer thickness of the entire retina.

  Here, an imaging method when 3D scanning is executed will be described. First, the measurement light is scanned in the X direction in the figure, and a predetermined number of pieces of information are imaged by the line sensor 182 from the imaging range of the eye to be examined in the X direction. The luminance distribution of the line sensor 182 obtained at a certain position in the X direction is subjected to a fast Fourier transform (FFT), and the linear luminance distribution obtained by the FFT is converted into density information for display on the monitor 928. . This is called an A-scan image.

  A two-dimensional image in which a plurality of A-scan images are arranged is called a B-scan image. After capturing a plurality of A scan images for composing one B scan image, a plurality of B scan images are obtained by moving the scan position in the Y direction and scanning in the X direction again.

  By displaying a plurality of B-scan images or a three-dimensional image (volume data) constructed from a plurality of B-scan images on the monitor 928 described below, the examiner can use it for diagnosis of the eye to be examined. Here, an example is shown in which a three-dimensional image is obtained by obtaining a plurality of B-scan images in the X direction, but a three-dimensional image may be obtained by obtaining a plurality of B-scan images in the Y direction.

  At this time, a tomographic image having a target shape based on a specific position, specifically, a position where the measurement optical path length and the reference optical path length are equal (gate position) is formed based on the principle characteristic of Fourier transform. . In addition, a periodic tomographic image is formed with reference to the gate position. For this reason, in order to obtain a tomographic image that can be easily observed by the examiner, it is necessary to cut out and display a specific region (image region).

(Configuration of shooting screen)
A shooting screen 2000 according to the present embodiment will be described with reference to FIG. The imaging screen 2000 is a screen for performing various settings and adjustments to obtain a desired eye image, and is a screen displayed on the monitor 928 before imaging.

  Reference numeral 2400 denotes a patient information display unit, which displays information on a patient to be imaged on this screen, such as patient ID, patient name, age, and sex. Reference numeral 2001 denotes a button for switching the left and right of the eye to be examined. By pressing the L and R buttons, the image acquisition unit 900 is moved to the initial position of the left and right eyes. Reference numeral 2101 denotes an anterior ocular segment observation screen obtained by the anterior ocular segment observation CCD 171. By clicking an arbitrary point on the anterior ocular segment observation screen 2101 with the mouse, the image is set to the center of the screen. The acquisition unit 900 is moved to align the image acquisition unit 900 and the eye 107 to be examined. A scan pattern display screen 2012 displays an outline of a scan pattern to be performed at the time of shooting. 2201 is a two-dimensional image display screen of the eye to be examined obtained by the photodiode 173, and 2301 is a tomographic image display screen for confirming the acquired tomographic image. Reference numeral 2004 denotes a start button. When this button is pressed, acquisition of a tomographic image and a two-dimensional image is started, and the acquired eye image is displayed in real time on the two-dimensional image display screen 2201 and the tomographic image display screen 2301. At this time, a frame 2202 displayed in the two-dimensional image display screen 2201 is a range in which a tomographic image is acquired at the time of photographing. Further, a horizontal arrow line 2203 at the center in the vertical direction indicates the position on the eye to be examined and the scan direction from which the tomographic image displayed on the tomographic image display screen 2301 is acquired.

  Here, the outer frame body 2302 of the tomographic image display screen 2301 indicates an image region in the present invention. The left side and the right side of the image area 2302 in the figure are the same boundary as the scan range 2202, the upper side is a position (gate position) where the measurement optical path length is equal to the reference optical path length, and the lower side is a position away from the upper side by a predetermined length. It is.

  A slider arranged in the vicinity of each image is used for adjustment. The slider 2103 adjusts the position of the acquisition unit in the Z direction with respect to the eye to be examined, the slider 2203 adjusts the focus, and the slider 2303 adjusts the position of the coherence gate. The focus adjustment is an adjustment for moving the lenses 135-3 and 135-5 in the direction shown in the drawing in order to adjust the focus on the fundus. The coherence gate adjustment is an adjustment in which the reference mirror 132-4 is moved in the illustrated direction so that the tomographic image is observed at a desired position on the tomographic image display screen. Thereby, since the optical path length difference between the tomographic image and the reference optical path in the OCT optical system is changed, the tomographic image on the tomographic image display screen 2301 moves in the vertical direction, and the examiner moves the tomographic image. The image region can be specified so that the examination site is arranged at a desired position on the tomographic image display screen.

  By these adjustment operations, the examiner creates a state in which optimum imaging can be performed. Reference numeral 2003 denotes an imaging button. When various adjustments are completed, a desired imaging is performed by pressing this button.

(Report screen configuration)
A report screen 4000 according to the present embodiment will be described with reference to FIG. The report screen 4000 is a screen displayed on the monitor 928, and is a screen for confirming the captured eye image and image analysis data in detail.

  Reference numeral 4001 denotes a patient information display unit that displays patient information displayed on the screen, such as patient ID, patient name, date of birth, sex, race, and the like. Reference numeral 4100 denotes a two-dimensional image display screen on which an SLO image or a projection image which is an eye image reconstructed or reconstructed from the acquired tomographic image is displayed. Reference numeral 4200 denotes a tomographic image display screen on which the acquired tomographic image is displayed. On the two-dimensional image display screen 4100, a schematic diagram of a scanning locus when the tomographic image displayed on the tomographic image display screen 4200 is acquired is superimposed and displayed as an arrow 4102. Furthermore, a grid 4103 that is the basis of sector data to be described later is superimposed and displayed.

  Reference numeral 4300 is a layer thickness map, 4400 is a comparative layer thickness map, 4500 is sector layer thickness data, and 4600 is comparative sector layer thickness data. These will be described in detail below.

(Layer thickness map)
The layer thickness map according to the present embodiment will be described with reference to FIG.

  Here, as shown in FIG. 5, the human retina has a vitreous body, an inner limiting membrane (ILM), a nerve fiber layer (NFL), a ganglion cell layer (GCL), an inner plexiform layer (IPL), an inner granule layer ( INL), outer reticulate layer (OPL), outer granule layer (ONL), IS / OS-RPE (visual cell inner-node outer-junction junction-retinal pigment epithelium), and the like. For example, it is known that the thickness distribution of a layer called a ganglion cell complex (GCC, registered trademark) combining NFL, GCL and IPL is important for diagnosis of glaucoma. Image analysis data called a layer thickness map is effective for the diagnosis. In this case, the thickness of a specific layer is displayed as a color change.

  The layer thickness map will be described with reference to FIG. Here, a layer thickness map generated in the case of volume data of a tomographic image including a folded image as shown in FIG. FIG. 1C is a schematic diagram of a layer thickness map when a significant region that is characteristic in the present invention is not set. Reference numeral 4301 denotes a two-dimensional image, 4300 denotes a layer thickness map, and 4310 denotes a color scale indicating a color corresponding to the layer thickness. In the region of the layer thickness map 4300, the layer thickness based on the layer thickness analysis result of a specific layer is expressed by a color corresponding to the color scale 4310. Thereby, the user can observe the distribution of the layer thickness easily and intuitively, and can perform diagnosis efficiently. In FIG. 1C, the color to be painted is a semi-transparent color and is displayed superimposed on the two-dimensional image 4301.

  However, since it is difficult to analyze the layer structure at the part where the tomographic image is folded back, it may be displayed as 0 μm like the peripheral part of 4300, or it may become discontinuous data. The reliability may be low data. When such data is presented to the user, the user must sequentially confirm whether the layer thickness is abnormal or whether the layer thickness calculation is failed by the folded image, resulting in a decrease in diagnostic efficiency. There is a fear.

  On the other hand, FIG. 1B shows a layer thickness map when a significant region characteristic in the present invention is set. Reference numeral 4301 denotes a two-dimensional image, 4300 denotes a layer thickness map, 4310 denotes a color scale indicating a color corresponding to the layer thickness, and 4320 denotes an indicator indicating a region other than a significant region (masking region). As indicated by a masking area 4303 in the layer thickness map 4300, the user can easily recognize only highly reliable data by identifying the wrapping area and clearly indicating it to the user. For this reason, it is not necessary to confirm the failure of the layer thickness calculation due to the folded image, and it is possible to focus only on the part that is truly abnormal, and the diagnostic efficiency can be improved.

  Next, a generation flow of the layer thickness map according to the present embodiment will be described with reference to FIG. First, after starting in step S1, volume data of a tomogram is acquired by the acquisition unit 900 in step S2, and a tomogram is generated by the tomogram generation unit 930.

  Next, in step S3, the image range specifying unit 931 sets an image region for the tomographic image generated in step S2. Here, the image region is a region that is cut out from a periodic tomographic image generated by the Fourier transform at the time of tomographic image generation as described above, and the outer frame of the tomographic image display screen 4200 in the report screen 4000, and This is an outer frame 4302 of the layer thickness map 4300. That is, the image region is equivalent to an image display region that is a region where a tomographic image is displayed on the monitor 928.

  Next, in step S4, the layer structure analysis unit 932 analyzes the layer structure of the inspection object. In the analysis of the layer structure, each layer can be identified by utilizing the fact that the signal intensity varies depending on the reflectance of each layer.

  Next, in step S5, the significant region determination unit 933 specifies a significant region. The significant area determination unit 933 sets a significant area based on the positional relationship between the specific layer and the image area. Here, a specific operation of the significant area determination unit will be described with reference to FIG. Here, an example in which the positional relationship between the ILM and the upper side of the image area is calculated using GCC as the layer thickness measurement target will be described. T1, T2, T3,..., T (n−1), Tn indicate tomographic images constituting volume data. Here, attention is paid to the tomographic image T1. First, the significant area determination unit 933 sets a center position C1 in the left-right direction in the figure of the tomographic image. Next, intersections between the ILM and the upper side of the image area are obtained from the center position C1 in the horizontal direction in the figure. The coordinates of the left and right intersections are M1L and M1R. The region between M1L and M1R is a significant region where no folded image is generated, and is a region where a highly reliable layer thickness can be obtained. On the other hand, since the folded image is generated in the region outside the significant region and is a double image with the normal image, the reliability of the obtained layer thickness may be low. The intersection of the ILM and the upper side of the image area is obtained by, for example, a predetermined layer (for example, ILM) included in the tomographic image at the peripheral edge (for example, the upper end) of the image display area that is an area where the tomographic image is displayed on the monitor 928. Equivalent to finding the point where is touching.

  Using the same method as described above, intersections M2L, M3L,..., MnL and M2R, M3R,. Here, when the target layer and the upper side of the image area do not intersect like the tomographic image T3, the left and right boundaries of the image area are set as intersections such as M3L and M3R, respectively. Further, when the layer of interest is a folded image in the entire region as in the tomographic image Tn, the layer structure analysis unit 932 cannot identify the ILM, so that the center point Cn is MnL and MnR, respectively. Is set as an intersection. As described above, after setting intersection points for all tomographic images constituting volume data, the intersection points are connected to obtain a significant region 1000 and a region 1001 outside the significant region as shown in FIG. 6C. it can.

  After the significant region discriminating unit 933 identifies the significant region in step S5 by the above-described method, the process proceeds to step S6, and the analysis image generating unit 934 includes the layer structure obtained in step S4 and the significant region obtained in step S5. Based on the above, layer thickness map data is generated. Specifically, for the A scan data in the significant region, the thickness of a specific layer, here GCC, is measured based on the layer structure, and the corresponding color data is held. On the other hand, for A scan data outside the significant area, color data or a pattern indicating the masking area is held. After the layer thickness map data is generated in step S6, it is displayed on the report screen 4000 in step S7, and the process ends in step S8.

  By generating a layer thickness map according to the above flow, the user can instantly determine a region where the aliasing image may have an effect on the layer thickness analysis data, and create a layer thickness map useful for ophthalmic diagnosis. Because it can be observed, the diagnostic efficiency is improved.

  Here, the layer thickness measurement is not performed on the masking region in step S6 described above, but the layer thickness measurement may be performed also on the masking region. At this time, the color data is also held in the masking area, and the color data or pattern indicating the masking area is superimposed on the masking area in a translucent manner. An example of this display is shown in FIG. By using the layer thickness map as shown in FIG. 7A, the user can confirm the layer thickness distribution of the entire image region and identify a highly reliable significant region.

  Further, the masking area may not be filled with a specific color or pattern, and as shown in FIG. 7B, only the boundary line 4304 may be drawn in the layer thickness map so that the display can be identified by the user. .

  In the above description of the layer thickness map, the GCC layer thickness has been described as an example, but layers other than the GCC may be used. Ophthalmic diagnosis often focuses on the IS / OS-RPE layer in addition to the GCC. This is because observation of the presence or absence of choroidal neovascularization in RPE is effective for diagnosis of age-related macular degeneration and the like. Therefore, it is desirable that a layer to be analyzed can be selected by a layer selection unit (not shown).

  A method for specifying a significant range in this case will be described with reference to FIG. When a significant range is set for the IS / OS-RPE layer, according to the above flow, an intersection 1100 between the IS / OS line and the image range is obtained, and a significant region is set therefrom. However, since the folded image crosses the normal tomographic image between the intersection 1101 between the IS / OS line and the ILM folded image and the intersection 1100, it is difficult to analyze the layer thickness. Therefore, it is desirable to set a significant region based on the point 1101 where the IS / OS line intersects the ILM folded image. Here, an example of how to obtain the intersection 1101 is introduced.

  First, an intersection 1102 between the ILM and the upper side of the image area is obtained. Next, an intersection 1103 with the IS / OS line at the same X position as 1102 is obtained. Then, an intersection 1104 between the Z position and the ILM is obtained. Here, assuming that each layer of the retina viewed locally approximates a straight line and that each layer is parallel, the distance 1106 between the intersection 1102 and the intersection 1101 is half of the distance 1105 between the intersection 1102 and the intersection 1104. is there. The intersection 1101 can be estimated by the above calculation. For layer thickness analysis that does not have ILM, by setting the significant region by the method as described above, the significant region can be removed while efficiently removing the region that may affect the layer thickness measurement by the aliasing image. It is possible to present as much as possible to the user.

(Layer thickness map NDB)
Next, the comparative layer thickness map 4400 will be described with reference to FIG. The comparative layer thickness map displays the result of comparing the reference layer thickness map with the layer thickness map. Here, the reference layer thickness map is a standard layer thickness map of the human eye retina, a past layer thickness map of the same patient, and a layer thickness map of the other left and right eyes of the same patient. It is remembered.

  The configuration of the comparative layer thickness map will be described with reference to FIG. Reference numeral 4400 is a comparison layer thickness map, 4410 is a color scale indicating a color corresponding to the comparison layer thickness data, and 4420 is an indicator indicating a region other than a significant region (masked region or masking region).

  Also in the comparative layer thickness map 4400, as indicated by the masking region 4403, as in the layer thickness map, the user can easily recognize only reliable data by identifying the folded region and clearly indicating it to the user. .

  Next, a flow for creating a comparative layer thickness map will be described with reference to FIG. Steps S101 to S105 are the same as steps S1 to S5 of the above-described layer thickness map, and thus description thereof is omitted.

  After setting a significant region in step S105, the analysis image generation unit 934 calls a reference layer thickness map from the storage unit 926 in step S106. In step S107, the analysis image generation unit 934 generates a layer thickness map from the layer structure generated in S104, and performs the reference layer thickness based on the thickness of the reference layer thickness map called in S106 for the layer thickness at each position. The ratio is calculated, and data that is the basis of the comparative layer thickness map is generated.

  Then, in combination with the significant region generated in step S105, a comparative layer thickness map using a color map is generated in the same manner as the layer thickness map described above. An example of this comparative layer thickness map is shown in FIG. FIG. 9A shows an example in which the masking area is filled with a pattern. Similar to the above-described layer thickness map, a display method for superimposing a translucent pattern on color data (FIG. 9C). ) Or only the boundary line (FIG. 9D) may be used. In the above description, the ratio data with respect to the reference layer thickness data is generated. However, difference amount data may be generated and displayed as shown in FIG.

  The data used as the reference layer thickness data includes layer thickness data for healthy eyes, past examination data for the same eye, left and right other eye data for the same patient, and the like. The thickness data of healthy eyes is called Normal Data Base (NDB), and is the thickness data of healthy eyes according to race and age. By comparing this NDB with the layer thickness of the corresponding patient, it is possible to easily confirm an abnormality in the layer thickness of the patient. In particular, it is known that it is very effective for diagnosis of glaucoma by paying attention to the layer thickness of GCC.

  In addition, past examination data of the same eye is useful for follow-up observation, and it is possible to easily confirm a change in layer thickness over time. For this reason, it is used for diagnosis of the progress of glaucoma. Furthermore, using the left and right other eyes of the same patient as reference layer thickness data is useful when there is an abnormality in one eye.

  As described above, by setting a significant region for the comparative layer thickness map and presenting it to the user, the ophthalmologist can easily discriminate highly reliable data without a folded image. A comparison layer thickness map useful for diagnosis can be observed, which leads to improvement in diagnosis efficiency.

(Sector data)
Next, the configuration of sector layer thickness data will be described with reference to FIG. Reference numeral 4501 in FIG. 10A denotes sector layer thickness data indicating the layer thickness average value in each sector when the object to be measured is divided by the grid 4103 described above. Reference numeral 4502 in FIG. 10A denotes sector layer thickness data indicating an average layer thickness value in each sector when a plurality of adjacent sector regions are combined. Reference numeral 4503 in FIG. 10A denotes sector layer thickness data indicating an average layer thickness value in the sector when all the sector regions are combined.

  Next, an operation flow for generating and displaying sector layer thickness data will be described with reference to FIG. Steps S201 to S205 are the same as steps S1 to S5 of the above-described layer thickness map, and thus description thereof is omitted. After setting a significant area in step S205, in step S206, the analysis image generation unit 934 generates a sector based on the layer structure obtained in step S204 and the data of the grid 4103, and all layers constituting the sector are generated. The average value of the layer thickness of each sector is calculated from the thickness data. Next, sector layer thickness data is generated in step S206 based on the significant area information generated in step S205, and displayed in step S207.

  Here, the display method of the sector layer thickness data is not limited to the display of only the numbers shown in FIG. For example, as shown in FIG. 10C, each sector may be displayed so as to be filled with a color corresponding to the layer thickness. Further, as shown in FIG. 10 (d), it may be displayed in a form superimposed on a two-dimensional image or the aforementioned layer thickness map.

  Next, the case where the sector area and the area outside the significant area (masking area) overlap will be described. As shown in FIG. 10E, when the masking area 4511 is over the sector area 4510, the layer thickness is displayed by the folded image by displaying in the format as shown in FIGS. 10F and 10G. Data that may have an impact on data and data that is not so can be identified instantaneously. The sector 4521 in FIG. 10F indicates that all the sector areas are included in the masking area by the color information in the sector. That is, the display color is changed between the sector area included in the significant area and the sector area other than the included sector area. Further, the sector 4522 in FIG. 10F indicates that a part of the sector area overlaps the masking area by color information in the sector.

  Here, although the sector 4512 and the sector 4513 are displayed in different colors, the same display color may be used if it is only necessary to identify whether or not they overlap with the masking area. By using such a display method, the user can determine at a glance whether or not there is a possibility of an influence due to the folded image. FIG. 10G shows an example in which the number display form is changed. The sector 4531 in FIG. 10G indicates that all the sector areas are included in the masking area by using the enclosed characters in the numbers indicating the layer thickness data in the sectors. In addition, the sector 4532 in FIG. 10G indicates that a part of the sector region overlaps the masking region by using parentheses in the numbers indicating the layer thickness data in the sector. By adopting such a display method, it is possible to provide easy-to-see sector layer thickness data even when displayed in a form superimposed on a two-dimensional image or a layer thickness map.

  Here, an example in which the average value is calculated from all the layer thickness data constituting the sector when calculating the sector layer thickness average value in the above step S206 is shown, but only the layer thickness data in the sector and in the significant region is shown. The average value may be calculated using. As a result, the influence of the folded image on the layer thickness data can be eliminated, so that the sector layer thickness data with high reliability can be obtained. In this case, it is desirable to notify the user that the data to be used for calculation is selected by the masking area by the display method as shown in FIGS.

(Sector NDB)
Next, the comparative sector layer thickness data 4600 will be described with reference to FIG. Here, the reference sector layer thickness data (reference layer thickness) includes standard human eye retina sector layer thickness data, past sector layer thickness data of the same patient, and other sector layers of the left and right eyes of the same patient. The thickness data is stored in the storage unit 926 in advance.

  The comparative sector layer thickness data will be described with reference to FIG. Reference numeral 4601 in FIG. 11A compares the sector layer thickness data indicating the layer thickness average value in each sector and the corresponding reference sector layer thickness data when the object to be measured is divided by the grid 4103 described above. , That percentage is displayed.

  Reference numeral 4602 in FIG. 11A compares the sector layer thickness data indicating the average layer thickness in each sector when a plurality of adjacent sector regions are combined with the corresponding reference sector layer thickness data. , That percentage is displayed. Reference numeral 4503 in FIG. 11A compares the sector layer thickness data indicating the layer thickness average value in the sector and the corresponding reference sector layer thickness data when all sector regions are combined, and displays the ratio. doing.

  Next, an operation flow for generating and displaying sector layer thickness data will be described with reference to FIG. Steps S301 to S305 are the same as steps S1 to S5 of the above-described layer thickness map, and thus description thereof is omitted. After setting the significant area in step S305, the analysis image generation unit 934 calls the reference sector layer thickness data from the storage unit 926 in step S306.

  Next, in step S307, the analysis image generation unit generates sector layer thickness data in the same manner as in the above-described S206, and references based on the thickness of the reference sector layer thickness data called in S306 for the layer thickness at each sector position. A ratio with respect to the layer thickness is calculated, and data as a basis for the comparative sector layer thickness data is generated. Then, in combination with the significant area generated in step S305, comparative sector layer thickness data is generated. This data is displayed in step S308.

  Here, in addition to FIG. 11A, the display method of the comparative layer thickness data is a display method in which the sector area is filled with a color corresponding to the calculated value as shown in FIG. As described above, there is a display method for superimposing on a two-dimensional image or a layer thickness map.

  In the case where the masking area overlaps with the sector area, a method of changing the color information in the sector as shown in FIG. 10 (f) depending on the positional relationship between the sector area and the masking area, As described above, there is a method of changing the character display form.

  Here, in addition to FIG. 11A, the display method of the comparative layer thickness data is a display method in which the sector area is filled with a color corresponding to the calculated value as shown in FIG. As described above, there is a display method for superimposing on a two-dimensional image or a layer thickness map.

  Although the example in which the ratio data with respect to the reference sector layer thickness data is generated has been described above, the difference amount data may be generated and displayed in the same manner as the comparative layer thickness map described above.

  The data used as the reference layer thickness data includes layer thickness data for normal eyes, past examination data for the same eye, left and right eye data for the same patient, etc., as in the comparison layer thickness map.

  Furthermore, when calculating the sector layer thickness average value in the above step S206, an example in which the average value is calculated from all layer thickness data constituting the sector has been shown. The average value may be calculated using only the thickness data.

  As described above, in the layer thickness map and sector layer thickness data, the user can pay attention to the lesion site of the eye to be examined, and the diagnostic efficiency can be improved Can be made.

  As described above, according to the present invention, even if the object to be inspected is composed of a plurality of layers, an appropriate layer thickness can be presented to the user for each layer, and further the display in the layer thickness map By displaying the method by color or boundary line, it is possible to easily recognize a region where the folded image may affect the layer thickness analysis data.

In addition, according to the present invention, by displaying the display method in the sector layer thickness data in character form or color, it is possible to easily recognize a region where the folded image may affect the layer thickness analysis data. it can.
Furthermore, according to the present invention, the influence of the folded image on the sector layer thickness data can be removed, so that the reliability of the sector layer thickness data can be improved.

[Other Examples]
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, or the like) of the system or apparatus reads the program. The processing to be executed also constitutes one aspect of the present invention.

  Furthermore, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made without departing from the spirit of the present invention. For example, in the above embodiment, the case where the object to be measured is the eye is described, but the present invention can also be applied to the object to be measured such as skin or organ other than the eye. In this case, the present invention has an aspect as a medical device such as an endoscope other than the ophthalmologic apparatus. Therefore, it is preferable that the present invention is grasped as an inspection apparatus exemplified by an ophthalmologic apparatus, and the eye to be examined is grasped as one aspect of the object to be inspected.

107 .. Eye to be examined, 101... OCT light source, 133... SLO scanner, 134... OCT scanner, 174 ... SLO light source, 900 ... Image acquisition unit, 925 ... PC, 926 ... Hard disk, 928 ... Monitor, 930... Image generation unit, 931... Image range specifying unit, 932 .. Layer structure analysis unit, 933... Significant region discrimination unit, 934 .. Analytical image generation unit, 935. .Stage section, 4000 ..Report screen, 4300 ..Layer thickness map, 4302 ..Image area, 4303 ..Masking area, 4310 ..Color scale, 4320 ..Masking area indicator, 4400. 4500 ・ ・ Sector layer thickness data 4600 ・ ・ Comparative sector layer thickness data

Claims (26)

An acquisition means for acquiring a tomographic image of the inspection object;
Discriminating means for discriminating a significant region and an insignificant region based on a positional relationship between a peripheral portion of an image display region where the tomographic image is displayed and the tomographic image;
Generating means for generating analysis image data that enables identification of the significant region based on the significant region and a specific layer included in the tomographic image;
An information processing apparatus comprising: a display control unit that causes the display unit to display the analysis image data generated by the generation unit. A selection means for selecting the specific layer from the layer structure of the tomographic image;
The information processing apparatus according to claim 1, wherein the determination unit determines the significant area and the insignificant area based on a positional relationship between the selected specific layer and the image display area.   The information processing apparatus according to claim 1, wherein the generation unit generates the analysis image data without using the specific layer in the insignificant region. The analysis image data includes data indicating a layer thickness map for the specific layer,
The information processing apparatus according to claim 1, wherein the generation unit generates data indicating the layer thickness map that enables the significant region to be identified. Further comprising storage means for storing a reference layer thickness map for said particular layer;
The analysis image data includes a ratio or difference amount of a layer thickness map related to the specific layer corresponding to the reference layer thickness map,
The information processing apparatus according to claim 4, wherein the generation unit generates the ratio or the difference amount that enables the significant region to be identified. The generating means generates the layer thickness map of the significant region as a color map,
The information processing apparatus according to claim 4, wherein the color map is generated by superimposing a color or a pattern different from the layer thickness map of the significant area on the layer thickness map of the insignificant area. .   The information processing apparatus according to claim 4, wherein the generation unit generates the layer thickness map in which a boundary line is drawn on a peripheral portion of the significant region. The analysis image data is calculated based on a plurality of layer thickness data included in the sector region as data for a sector region obtained by dividing the data indicating the layer thickness map by a predetermined grid,
The information according to any one of claims 4 to 7, wherein the generation unit generates analysis image data in which a display method is changed based on a positional relationship between the sector region and the significant region. Processing equipment. The analysis image data is calculated based on a plurality of layer thickness data included in the sector region as data for a sector region obtained by dividing the data indicating the layer thickness map by a predetermined grid,
The information processing apparatus further comprises storage means for previously storing reference sector layer thickness data corresponding to the predetermined sector area of the inspection object,
The analysis image data calculates a ratio or difference amount of sector layer thickness data of the inspection object corresponding to the reference sector layer thickness data,
The information according to any one of claims 4 to 7, wherein the generation unit generates analysis image data in which a display method is changed based on a positional relationship between the sector region and the significant region. Processing equipment. The generation means generates analysis image data for displaying data corresponding to the sector area as numbers,
9. The analysis image data in which the number of displayed numbers is changed between the sector area included in the significant area and a sector area other than the included sector area is generated. 9. The information processing apparatus according to 9. The generation means generates analysis image data for displaying the magnitude of data corresponding to the sector area as a color change,
11. The analysis image data in which the display color is changed between the sector area included in the significant area and a sector area other than the included sector area is generated. The information processing apparatus according to any one of claims.   9. The generation unit according to claim 8, wherein the generation unit holds data calculated based on only the layer thickness data included in the significant region among the plurality of layer thickness data included in the sector region. The information processing apparatus according to any one of 11. Obtaining means for obtaining data indicating a region where a folded image is generated among a plurality of tomographic images of the eye to be examined;
An information processing apparatus comprising: a display control unit that causes a display unit to display a layer thickness map based on the plurality of tomographic images based on the acquired data.   The information processing apparatus according to claim 13, wherein the display control unit changes a display method of the layer thickness map based on the acquired data.   The information processing apparatus according to claim 13, wherein the tomographic image is a tomographic image of the fundus of the eye to be examined.   The information processing apparatus according to claim 13, wherein the layer thickness map is generated based on a layer thickness of a predetermined layer included in each of the plurality of tomographic images.   The layer thickness map is generated based on a ratio or a difference amount between a layer thickness of a predetermined layer and a reference layer thickness included in each of the plurality of tomographic images. The information processing apparatus according to claim 1. Further comprising generating means for generating the layer thickness map;
The information processing apparatus according to claim 16, wherein the generation unit does not use the layer thickness of the predetermined layer in the region where the folded image is generated to generate the layer thickness map.   The acquisition unit acquires the data based on a layer obtained from each of the plurality of tomographic images and a position where the optical path length of the measurement light and the optical path length of the reference light match in the OCT apparatus. The information processing apparatus according to any one of claims 13 to 18.   20. The display control unit according to claim 13, wherein the display control unit causes the display unit to display a mask generated based on the acquired data so as to be superimposed on the layer thickness map. The information processing apparatus described.   The display control means displays the layer thickness map based on the acquired data so that the display means does not display the layer thickness of the region where the folded image is generated. The information processing apparatus according to any one of 13 to 19. Obtaining means for obtaining data indicating a region where a folded image is generated among a plurality of tomographic images of the eye to be examined;
Display control for displaying on the display means a layer thickness map based on the plurality of tomographic images capable of distinguishing between a region where the folded image is generated and a region where the folded image is not generated based on the acquired data And an information processing apparatus. An acquisition step of acquiring a tomographic image of the inspection object;
A determination step of determining a significant region and a non-significant region based on a positional relationship between a peripheral portion of an image display region of the display unit on which the tomographic image is displayed and the tomographic image;
A generation step of generating analysis image data that enables identification of the significant region based on the significant region and a specific layer included in the tomographic image;
A display control step of displaying on the display means the analysis image data generated by the generation step, and a control method for the information processing apparatus. Obtaining data indicating a region where a folded image is generated among a plurality of tomographic images of the eye to be examined; and
And a step of displaying a layer thickness map based on the plurality of tomographic images on a display unit based on the acquired data. Obtaining data indicating a region where a folded image is generated among a plurality of tomographic images of the eye to be examined; and
Displaying, on a display means, a layer thickness map based on the plurality of tomographic images capable of distinguishing a region where the folded image is generated from a region where the folded image is not generated based on the acquired data; And a method of controlling the information processing apparatus.   A program causing a computer to execute each step of the control method according to any one of claims 23 to 25.