Patent Publication Number: US-2022230307-A1

Title: Image processing method, image processing device, image processing program

Description:
TECHNICAL FIELD 
     The present invention relates to an image processing method, an image processing device, and an image processing program. 
     BACKGROUND ART 
     US Patent Application Laid-Open No. 2009/0136100 discloses a device and method for synthesizing a panoramic fundus image. There remains demand for an effective image synthesizing method for analysis of structures in a fundus-peripheral portion. 
     SUMMARY OF INVENTION 
     An image processing method of a first aspect of technology disclosed herein includes acquiring a first direction fundus image imaged in a state in which an examined eye is directed in a first direction, and a second direction fundus image imaged in a state in which the examined eye is directed in a second direction different to the first direction, generating a combined image for analyzing a fundus-peripheral portion of the examined eye by combining the first direction fundus image and the second direction fundus image, and outputting the combined image. 
     An image processing device of a second aspect of technology disclosed herein includes an acquisition section configured to acquire a first direction fundus image imaged in a state in which an examined eye is directed in a first direction, and a second direction fundus image imaged in a state in which the examined eye is directed in a second direction different to the first direction, a generation section configured to generate a combined image for analyzing a fundus-peripheral portion of the examined eye by combining the first direction fundus image and the second direction fundus image, and an output section configured to output the combined image. 
     An image processing program of a third aspect of technology disclosed herein causes a computer to function as an acquisition section configured to acquire a first direction fundus image imaged in a state in which an examined eye is directed in a first direction, and a second direction fundus image imaged in a state in which the examined eye is directed in a second direction different to the first direction, a generation section configured to generate a combined image for analyzing a fundus-peripheral portion of the examined eye by combining the first direction fundus image and the second direction fundus image, and an output section configured to output the combined image. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram illustrating an ophthalmic system  100 . 
         FIG. 2  is a schematic configuration diagram illustrating an overall configuration of an ophthalmic device  110 . 
         FIG. 3A  is a first diagram to illustrate an imaging range of a fundus of an examined eye  12  by the ophthalmic device  110 . 
         FIG. 3B  illustrates an image of a fundus obtained by the ophthalmic device  110 , and is a second diagram to illustrate an imaging range of the fundus of the examined eye  12  by the ophthalmic device  110 . 
         FIG. 3C  is a third diagram to illustrate an imaging range of the fundus of the examined eye  12  by the ophthalmic device  110 . 
         FIG. 4  is a block diagram illustrating functionality of a CPU  22  of the ophthalmic device  110 . 
         FIG. 5  is a flowchart illustrating processing during image capture of the fundus of the examined eye  12  as executed by the CPU  22  of the ophthalmic device  110 . 
         FIG. 6A  is a diagram of a plane running parallel to an up-down direction and passing through a pupil and an eyeball center to illustrate an imaging range (spanning between Ul and D 1 ) of a fundus in a case in which an optical axis of the examined eye  12  is directed in an oblique upward direction relative to the ophthalmic system  100 . 
         FIG. 6B  is a diagram of a plane running parallel to an up-down direction and passing through the pupil and the eyeball center to illustrate an imaging range (spanning between U 2  and D 2 ) of a fundus in a case in which the optical axis of the examined eye  12  is directed in an oblique downward direction relative to the ophthalmic system  100 . 
         FIG. 7A  is a diagram illustrating a UWF upward-looking fundus image GU obtained by upward-looking imaging at step  304  in  FIG. 5 . 
         FIG. 7B  is a diagram illustrating a UWF downward-looking fundus image GD obtained by downward-looking imaging at step  308  in  FIG. 5 . 
         FIG. 8  is a block diagram illustrating an electrical configuration of a server  140 . 
         FIG. 9  is a block diagram illustrating functionality of a CPU  262  of the server  140 . 
         FIG. 10  is a flowchart illustrating montage image creation processing executed by the CPU  262  of the server  140 . 
         FIG. 11  is a flowchart illustrating positional alignment processing between images at step  324  in  FIG. 10 . 
         FIG. 12A  is a diagram illustrating a line segment LGU set in the UWF upward-looking fundus image GU. 
         FIG. 12B  is a diagram illustrating a line segment LGD set in the UWF downward-looking fundus image GD. 
         FIG. 13  is a diagram to explain generation of a montage image GM. 
         FIG. 14  is a diagram illustrating a first display mode of a display screen  400  of a display  256  of a viewer  150 . 
         FIG. 15  is a diagram illustrating a second display mode of the display screen  400  of the display  256  of the viewer  150 . 
         FIG. 16  is a diagram illustrating a third display mode of the display screen  400  of the display  256  of the viewer  150 . 
         FIG. 17  is a diagram illustrating a fourth display mode of the display screen  400  of the display  256  of the viewer  150 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Detailed explanation follows regarding an exemplary embodiment of the present invention, with reference to the drawings. 
     Explanation follows regarding configuration of an ophthalmic system  100 , with reference to  FIG. 1 . As illustrated in  FIG. 1 , the ophthalmic system  100  includes an ophthalmic device  110 , an eye axial length measurement instrument  120 , a server device (referred to hereafter as a “server”)  140 , and a display device (referred to hereafter as a “viewer”)  150 . The ophthalmic device  110  acquires images of a fundus. The eye axial length measurement instrument  120  measures the eye axial length of a patient. The server  140  stores plural fundus images and eye axial lengths obtained by imaging the fundi of plural patients with the ophthalmic device  110 , in association with patient IDs. The viewer  150  displays fundus images and analysis results acquired from the server  140 . 
     The server  140  is an example of an “image processing device” of technology disclosed herein. 
     The ophthalmic device  110 , the eye axial length measurement instrument  120 , the server  140 , and the viewer  150  are connected together over a network  130 . 
     Note that other ophthalmic equipment (examination equipment for measuring a field of view, measuring intraocular pressure, or the like) and/or a diagnostic support device that analyzes images using artificial intelligence (AI) may be connected to the ophthalmic device  110 , the eye axial length measurement instrument  120 , the server  140 , and the viewer  150  over the network  130 . 
     Next, explanation follows regarding configuration of the ophthalmic device  110 , with reference to  FIG. 2 . As illustrated in  FIG. 2 , the ophthalmic device  110  includes a control unit  20 , a display/operation unit  30 , and a SLO unit  40 . The ophthalmic device  110  images a posterior eye portion (fundus) of an examined eye  12 . The ophthalmic device  110  may further include a non-illustrated OCT unit to acquire OCT data for the fundus. SLO is an acronym for Scanning Laser Ophthalmoscopy. OCT is an acronym standing for Optical Coherence Tomography. 
     The control unit  20  includes a computer provided with a CPU  22 , memory  24 , a communication interface (I/F)  26 , and the like. The display/operation unit  30  is a graphical user interface that displays images obtained by imaging and also accepts various instructions, including imaging instructions, and includes a display  32  and an input/instruction device  34 . 
     The CPU  22  executes an image capture processing program so as, as illustrated in  FIG. 4 , to cause the CPU  22  to function as a SLO controller  180  (including a fixation light control section  1802 , an SLO light source control section  1804 , and a scanner control section  1806 ), an image processing section  182 , a display control section  184 , and a processing section  186 . 
     The memory  24  is stored with the image capture processing program used to perform image capture processing when imaging the fundus of the examined eye  12 , as described later. 
     The SLO unit  40  includes a G light source  42  (green light: wavelength 530 nm), a R light source  44  (red light: wavelength 650 nm), and an IR light source  46  (infrared radiation (near-infrared light), wavelength 800 nm). The respective light sources  42 ,  44 ,  46  emit light in response to commands from the control unit  20 . Note that the light sources  42 ,  44 ,  46  may employ LED light sources or laser light sources. Note that explanation follows regarding an example in which laser light sources are employed. 
     The SLO unit  40  includes optical systems  50 ,  52 ,  54 ,  56  that either reflect or transmit the light from the light sources  42 ,  44 ,  46  so as to guide the light onto a single light path. The optical systems  50 ,  56  are configured by mirrors, whereas the optical systems  52 ,  54  are configured by beam splitters, specifically dichroic mirrors, half-mirrors, or the like. 
     The G light is reflected by the optical systems  50 ,  54 , the R light is transmitted through the optical systems  52 ,  54 , and the IR light is reflected by the optical systems  52 ,  56 , such that the G light, the R light, and the IR light are each guided onto a single light path. 
     The SLO unit  40  includes a wide-angle optical system  80  that scans the light from the light sources  42 ,  44 ,  46  across the posterior eye portion (fundus) of the examined eye  12  in a two-dimensional pattern. The SLO unit  40  includes a beam splitter  58  that, out of the light from the posterior eye portion (fundus) of the examined eye  12 , reflects G light and transmits light other than the G light. The SLO unit  40  also includes a beam splitter  60  that, out of the light transmitted through the beam splitter  58 , reflects R light and transmits light other than the R light. The SLO unit  40  also includes a beam splitter  62  that, out of the light transmitted through the beam splitter  60 , reflects IR light. Dichroic mirrors, half-mirrors, or the like may be employed as the beam splitters  58 ,  60 ,  62 . 
     The SLO unit  40  includes a G light detection element  72  that detects the G light reflected by the beam splitter  58 , a R light detection element  74  that detects the R light reflected by the beam splitter  60 , and an IR light detection element  76  that detects the IR light reflected by the beam splitter  62 . For example, avalanche photodiodes (APDs) may be employed as the light detection elements  72 ,  74 ,  76 . 
     Moreover, the SLO unit  40  includes a fixation target control device  90  that is controlled by the control unit  20  so as to illuminate an upper fixation light  92 U and a lower fixation light  92 D (as well as a non-illustrated central fixation light). The orientation (gaze direction) of the examined eye  12  can be changed by illuminating the central fixation light, the upper fixation light  92 U, and the lower fixation light  92 D respectively. 
     The wide-angle optical system  80  includes an X direction scanning device  82  configured by polygonal mirrors so as to scan the light from the light sources  42 ,  44 ,  46  in an X direction, a Y direction scanning device  84  configured by mirror galvanometers so as to scan the light from the light sources  42 ,  44 ,  46  in a Y direction, and an optical system  86  configured by a lens system made up of a concave mirror such as an elliptical mirror and plural lenses so as to illuminate an Ultra-Wide Field (UWF) with the scanned light. The respective scanning devices of the X direction scanning device  82  and the Y direction scanning device  84  may employ Micro Electro Mechanical System (MEMS) mirrors. Alternatively, instead of providing separate scanners for the X direction and the Y direction, a single MEMS mirror may be configured capable of two-dimensional scanning. Note that in cases in which the ophthalmic device  110  is installed on a horizontal plane, the X direction corresponds to a horizontal direction, and the Y direction corresponds to a direction perpendicular to the horizontal plane. A direction connecting the center of the pupil at an anterior eye portion of the examined eye  12  and the center of the eyeball of the examined eye  12  is referred to as a Z direction. The X direction, the Y direction, and the Z direction are therefore mutually perpendicular to one another. 
     The wide-angle optical system  80  has an ultra-wide angle Field of View (FOV) with respect to the fundus, and is capable of imaging a region spanning from a posterior pole of the fundus and crossing an equatorial portion of the examined eye  12 . 
     Explanation follows regarding an equatorial portion  174 , with reference to  FIG. 3A . The eyeball (examined eye  12 ) is a spherical structure with a diameter of approximately  24  mm and an eyeball center  170 . A straight line joining an anterior pole  175  to a posterior pole  176  is referred to as an ocular axis  172 , a line running along an intersection between a plane orthogonal to the ocular axis  172  and the eyeball surface is referred to as a line of latitude, and an equator  174  corresponds to the line of latitude with the greatest length. Portions of the retina and the choroid coinciding with the position of the equator  174  configure the equatorial portion  178 . The equatorial portion  178  corresponds to one part of a fundus-peripheral portion. 
     The ophthalmic device  110  is capable of imaging a region covered by an internal irradiation angle of 200° with respect to the position of the eyeball center  170  of the examined eye  12 . Note that an internal irradiation angle of 200° corresponds to an external irradiation angle of 167° relative to the pupil of the eyeball of the examined eye  12 . Namely, the wide-angle optical system  80  irradiates laser light through the pupil at an angle of view corresponding to an external irradiation angle of 167° in order to image a fundus region over an internal irradiation angle of 200°. 
       FIG. 3B  illustrates an SLO image  179  obtained by imaging with the ophthalmic device  110  that is capable of scanning over an internal irradiation angle of 200°. As illustrated in  FIG. 3B , the equatorial portion  174  corresponds to an internal irradiation angle of 180°, and the location indicated by the dotted line  178   a  in the SLO image  179  corresponds to the equatorial portion  178 . In this manner, the ophthalmic device  110  is capable of imaging a fundus-peripheral region spanning from a posterior pole portion including the posterior pole  176  and crossing the equatorial portion  178  in a single take (either a single image or a single scan). Namely, the ophthalmic device  110  is capable of capturing from a central portion of the fundus to a peripheral portion of the fundus in a single take. 
     The ophthalmic device  110  is an example of an “imaging device” of technology disclosed herein. 
       FIG. 3C  is a diagram illustrating a positional relationship between a choroid  12 M and vortex veins  12 V 1 ,  12 V 2  of the eyeball. 
     In  FIG. 3C , choroid blood vessels of the choroid  12 M are illustrated in a mesh pattern. The choroid blood vessels carry blood around the entire choroid. Blood flows out from the eyeball through plural (usually from four to six) vortex veins of the examined eye  12 .  FIG. 3C  illustrates an upper vortex vein V 1  and a lower vortex vein V 2  present on one side of the eyeball. Vortex veins are frequently present in the vicinity of the equatorial portion  178 . Accordingly, the ophthalmic device  110  that is capable of scanning the fundus-peripheral portion over a broad range with an internal irradiation angle of 200° as described above is employed in order to image the vortex veins and the choroid blood vessels peripheral to the vortex veins in the examined eye  12 . 
     An SLO fundus image obtained by imaging the examined eye  12  using the ophthalmic device  110  that is capable of scanning over an internal irradiation angle of 200° is referred to as a UWF fundus image. 
     The configuration of the ophthalmic device  110  provided with the wide-angle optical system as described above may employ the configuration described in International Application No. PCT/EP 2017/075852. The disclosure of International Application No. PCT/EP 2017/075852 (International Publication No. WO2018/069346), filed internationally on Oct. 10, 2017, is incorporated in its entirety by reference herein. 
     Explanation follows regarding imaging of upward-looking and downward-looking UWF fundus images using the ophthalmic device  110 . 
     First, the input/instruction device  34  is used to input the ophthalmic device  110  with information including patient attribute information such as a patient ID and patient name, as well as information to indicate whether the examined eye to be imaged is a left eye or a right eye. If the patient has existing medical records, patient attribute information recorded in the server  140  is read when the patient ID is input. 
     Next, the ophthalmic device  110  displays on the display  32  a menu screen to prompt selection of either a normal imaging mode in which the central fixation light is illuminated and the fundus is imaged over a broad range, or a montage image capture mode used to analyze structures in a fundus-peripheral portion (for example including vortex veins and choroid blood vessels in the vicinity of the vortex veins). Using the input/instruction device  34 , a user is able to select the mode using the menu screen displayed on the display  32 . 
     When the user selects the montage image capture mode, the CPU  22  of the ophthalmic device  110  executes the image capture processing program in order to implement image capture processing as illustrated by the flowchart in  FIG. 5 . 
     When the user has selected the montage image capture mode, the SLO controller  180  performs alignment and focus adjustment. 
     At step  302  in  FIG. 5 , the fixation light control section  1802  controls the fixation target control device  90  so as to illuminate the upper fixation light  92 U in order to direct the gaze of the patient in an oblique upward direction. As illustrated in  FIG. 6A , the gaze of the patient is thus directed in the oblique upward direction, namely a direction running from the eyeball center toward the upper fixation light  92 U. In addition to illuminating the upper fixation light  92 U, the operator of the ophthalmic device  110  may also give an instruction such as “please look upward” to direct the gaze of the patient in the oblique upward direction and thereby achieve a state in which the gaze of the examined eye is directed in the oblique upward direction 
     The oblique upward direction is an example of a “first direction” of technology disclosed herein. 
     At step  304 , the fundus is imaged in an upward-looking state, in which the gaze of the patient is directed in the oblique upward direction. Specifically, the SLO light source control section  1804  causes the G light source  42  and the R light source  44  to emit G light and R light respectively. The scanner control section  1806  controls the X direction scanning device  82  and the Y direction scanning device  84 . The G light and the R light scanned in the X direction and the Y direction are reflected by the fundus of the examined eye. 
     Since a G light, which wavelength corresponds to green light, is reflected by the retina, structural information relating to the retina is included. The G light reflected from the examined eye  12  is detected by the G light detection element  72 . The image processing section  182  generates image data for a UWF upward-looking fundus image G based on a signal from the G light detection element  72 . Similarly, R light reflected from the examined eye  12  is detected by the R light detection element  74 . Since red laser light (R light) is reflected at the choroid, this being deeper than the retina, structural information relating to the choroid is included. The image processing section  182  generates image data for a UWF upward-looking fundus image R based on a signal from the R light detection element  74 . The image processing section  182  then generates image data for a UWF upward-looking fundus image RG by combining the UWF upward-looking fundus image and the UWF upward-looking fundus image R at a predetermined mixing ratio. 
     Note that the UWF upward-looking fundus image G, the UWF upward-looking fundus image R, and the UWF upward-looking fundus image RG are referred to collectively as UWF upward-looking fundus images when not drawing a distinction therebetween. 
     The UWF upward-looking fundus images are examples corresponding to a “first direction fundus image” of technology disclosed herein. 
     When the fundus is imaged in a state in which the optical axis of the ophthalmic system  100  aligns with the optical axis of the examined eye  12 , a UWF en face fundus image of the fundus of the examined eye  12  thus obtained captures a region spanning between an upper position U 0  and a lower position D 0  of the fundus in the Y-Z plane illustrated in  FIG. 6A . 
     The upward-looking fundus images are obtained by imaging the fundus while looking upward. As illustrated in  FIG. 6A , due to the gaze of the patient being directed in the oblique upward direction, each upward-looking fundus image corresponds to an image of a region spanning between an upper position U 1  above the upper position U 0 , and a lower position D 1 . Accordingly, each upward-looking fundus image includes an image of a region MU 01  that is not included in the en face image.  FIG. 7A  illustrates a UWF upward-looking fundus image for a right eye. This UWF upward-looking fundus image GU includes a vortex vein  12 V 1  on the nose side (on the right side of the drawing) and a vortex vein  12 V 3  on the ear side (on the left side of the drawing), the vortex veins  12 V 1  and  12 V 3  being present in the vicinity of an eyeball upper side of the equatorial portion, positioned toward the upper side of the UWF upper side fundus image GU. Moreover an optical nerve head ONH and a macula M present in a fundus central portion are positioned toward the lower side of the UWF upper side fundus image GU. 
     At step  306 , the fixation light control section  1802  controls the fixation target control device  90  so as to illuminate the upper fixation light  92 D in order to direct the gaze of the patient in an oblique downward direction. As illustrated in  FIG. 6B , the gaze of the patient is thus directed in the oblique downward direction, namely a direction running from the eyeball center toward the lower fixation light  92 D. In addition to illuminating the upper fixation light  92 D, the operator of the ophthalmic device  110  may also give an instruction such as “please look downward” to direct the gaze of the patient in the oblique downward direction and thereby achieve a state in which the gaze of the examined eye is directed in the oblique downward direction. 
     The oblique downward direction is an example of a “second direction” of technology disclosed herein. 
     At step  308 , the fundus is imaged in a downward-gazing state, in which the gaze of the patient is directed in the oblique downward direction. Similarly to at step  304 , the SLO light source control section  1804  causes the G light source  42  and the R light source  44  to emit G light and R light respectively. The scanner control section  1806  controls the X direction scanning device  82  and the Y direction scanning device  84  so as to scan the G light and the R light in the X direction and the Y direction. Similarly to at step  304 , the image processing section  182  generates image data for a UWF downward-looking fundus image G, a UWF downward-looking fundus image R, and a UWF downward-looking fundus image RG. 
     Note that the UWF downward-looking fundus image G, the UWF downward-looking fundus image R, and the UWF downward-looking fundus image RG are referred to collectively as UWF downward-looking fundus images when not drawing a distinction therebetween. 
     The UWF downward-looking fundus images are an example of a “second direction fundus image” of technology disclosed herein. 
     The downward-looking fundus images are obtained by imaging the fundus while looking downward. As illustrated in  FIG. 6B , due to the gaze of the patient being directed in the oblique downward direction, each downward-looking fundus image corresponds to an image of a region spanning between a lower position D 2  below the lower position D 0  and an upper position U 2 . Accordingly, each downward-looking fundus image includes an image of a region MD 02  that is not included in the UWF en face fundus image.  FIG. 7B  illustrates a UWF downward-looking fundus image GD for a right eye. This UWF downward-looking fundus image GD includes a vortex vein  12 V 2  on the nose side (on the right side of the drawing) and a vortex vein  12 V 4  on the ear side (on the left side of the drawing), the vortex veins  12 V 2  and  12 V 4  being present in the vicinity of the equatorial portion at the eyeball upper side thereof, positioned toward the lower side of the UWF downward-looking fundus image GD. An optical nerve head ONH and a macula M present in a fundus central portion are positioned toward the upper side of the UWF downward-looking fundus image GD. 
     At step  310 , the processing section  186  transmits image data for the UWF upward-looking fundus images and the UWF downward-looking fundus images to the server  140  via the communication interface (IIF)  26 . The processing section  186  also transmits the patient ID and the patient attribute information (patient name, age, information indicating whether each fundus image corresponds to a left eye or a right eye, visual acuity, imaging date and time, and the like) to the server  140  when transmitting the image data to the server  140 . 
     The server  140  stores the received image data, patient ID, and patient attribute information in association with each other in a storage device  254 , described later. 
     Note that the display control section  184  may display the UWF upward-looking fundus images and the UWF downward-looking fundus images on the display  32 . 
     When the user has selected the normal imaging mode, in which the fundus is imaged over a broad range while looking straight ahead, the SLO controller  180  performs alignment and focus adjustment. The fixation light control section  1802  then controls the fixation target control device  90  so as to illuminate the central fixation light. The gaze of the patient is thus fixed straight ahead, and a UWF en face fundus image such as that illustrated in  FIG. 3B  is imaged. 
     In cases in which UWF en face fundus images have been acquired, at step  310  the processing section  186  transmits image data of the UWF en face fundus images in a similar manner to that described above. 
     Note that similarly to the UWF upward-looking fundus images and the UWF downward-looking fundus images, the UWF en face fundus images generated include a UWF en face fundus image G, a UWF en face fundus image R, and a UWF en face fundus image RG. 
     In order to analyze structures in the fundus-peripheral portion (for example vortex veins and choroid blood vessels in the vicinity of the vortex veins), it is necessary to image a fundus region including the periphery of the equatorial portion and crossing the equatorial portion in the direction of the anterior eye portion. During wide-angle imaging performed while looking straight ahead, the eyelids and eyelashes of the examinee, as well as casing of the ophthalmic device  110  may enter the image, with the result that the fundus-peripheral portion cannot be imaged. In such cases, it would not be possible to image the vortex veins and the choroid blood vessels in the vicinity of the vortex veins, with the result that an image including all of the vortex veins in the fundus-peripheral portion or peripheral to the equatorial portion cannot be acquired. 
     Accordingly, in the present exemplary embodiment the UWF upward-looking fundus image GU is acquired in a state in which the gaze of the patient is directed upward and the UWF downward-looking fundus image GD is acquired in a state in which the gaze of the patient is directed downward. These two images are then combined in order to generate a montage image, thereby reliably capturing a broader region than that captured in a single UWF en face fundus image. Employing a montage image in this manner enables a montage image to be obtained including vortex veins and choroid blood vessels in the vicinity of the vortex veins, from which the eyelids and eyelashes of the examinee, as well as any casing of the ophthalmic device  110  have been removed. Such a montage image is well-suited to the detection of pathological lesions and above regions in the fundus-peripheral portion, as well as the detection of vortex veins and choroid blood vessels in the vicinity of the vortex veins. 
     Explanation follows regarding generation of a montage image by the server  140 . 
     Explanation follows regarding configuration of the server  140 , with reference to  FIG. 8 . As illustrated in  FIG. 8 , the server  140  includes a computer unit  252 . The computer unit  252  includes a CPU  262 , RAM  266 , ROM  264 , and an input/output (I/O) port  268 . The storage device  254 , a display  256 , a mouse  255 M, a keyboard  255 K, and a communication interface (a)  258  are connected to the input/output (I/O) port  268 . The storage device  254  is, for example, configured by non-volatile memory. The input/output (I/O) port  268  is connected to the network  130  via the communication interface (I/F)  258 . Accordingly, the server  140  is capable of communicating with the ophthalmic device  110 , the eye axial length measurement instrument  120 , and the viewer  150 . The storage device  254  is stored with a montage image creation processing program, described later. Note that the montage image creation processing program may be stored in the ROM  264 . 
     The montage image creation processing program is an example of an “image processing program” of technology disclosed herein. 
     The CPU  262  of the server  140  executes the montage image creation processing program so as to cause the CPU  262  to function as an image acquisition section  1410 , an image processing section  1420  (including a position alignment section  1421 , a binarization processing section  1422 , a combined image generation section  1424 , and a vortex vein analysis section  1425 ), a display control section  1430 , and an output section  1440 , as illustrated in  FIG. 9 . 
     The image acquisition section  1410  is an example of an “acquisition section” of technology disclosed herein. The image processing section  1420  is an example of a “generation section” of technology disclosed herein. The output section  1440  is an example of an “output section” of technology disclosed herein. 
     Next, detailed explanation follows regarding montage image creation processing executed by the CPU  262  of the server  140 , with reference to  FIG. 10 . The CPU  262  of the server  140  executes the montage image creation processing program in order to implement the montage image creation processing illustrated by the flowchart in  FIG. 10 . 
     The montage image creation processing is an example of an “image processing method” of technology disclosed herein. 
     A user (for example an ophthalmologist) turns on a non-illustrated montage image display button in order to instruct display on the viewer  150  of a fundus image (montage image) of the examined eye  12  of a patient for the purpose of diagnosing the examined eye  12 . When this is performed, the operator inputs the patient ID to the viewer  150 . The viewer  150  then outputs montage image creation instruction data to the server  140  together with the patient ID. Having received the montage image creation instruction data and the patient ID, the server  140  executes the montage image creation processing program. 
     Note that the montage image creation processing program may be executed at the point in time when UWF upward-looking fundus images and UWF downward-looking fundus images imaged by the ophthalmic device  110  are transmitted to the server  140 . 
     At step  320  in the flowchart of  FIG. 10 , the image acquisition section  1410  acquires the UWF upward-looking fundus images and the UWF downward-looking fundus images from the storage device  254 . At step  322 , the binarization processing section  1422  performs processing to emphasize blood vessels in the UWF upward-looking fundus images and the UWF downward-looking fundus images. The binarization processing section  1422  then executes binarization processing so as to perform binarization about a predetermined threshold value. Blood vessels of the ftmdus are emphasized in white as a result of the binarization processing. 
     At step  324 , the position alignment section  1421  performs positional alignment between the UWF upward-looking fundus images and the UWF downward-looking fundus images. Explanation follows regarding positional alignment processing performed at step  324 , with reference to the flowchart of  FIG. 11 . Here, explanation will be given regarding a case in which the UWF downward-looking fundus images are transformed with reference to the UWF upward-looking fundus images (namely, a case in which only the UWF downward-looking fundus images are transformed, and the UWF upward-looking fundus images are not transformed). 
     At step  340  in  FIG. 11 , the position alignment section  1421  performs image processing to extract a feature point group  1  from the UWF upward-looking fundus image GU. As illustrated in  FIG. 7A , the feature point group  1  includes plural feature points in the fundus image, including the optical nerve head ONHU, a macula MU, and a retinal blood vessel junction VBU. Note that a junction between choroid blood vessels may also be extracted as a feature point. The position alignment section  1421  extracts only structural information regarding the choroid from the UWF upward-looking fundus image G that includes structural information relating to the retina and the UWF upward-looking fundus image R that includes structural information relating to the choroid, by removing the structural information relating to the retina from the UWF upward-looking fundus image R. The position alignment section  1421  then extracts a retinal blood vessel junction from the UWF upward-looking fundus image G, and extracts a choroid blood vessel junction from the structural information relating only to the choroid. The respective feature points are configured by the pixel with the maximum brightness in an optical nerve head ONHU region, the pixel with the minimum brightness in a macula MU region, and pixels positioned at retinal blood vessel junctions and choroid blood vessel junctions. Coordinates of these pixels are extracted as feature point data. In addition to retinal blood vessel junctions and choroid blood vessel junctions, a region including a distinctive blood vessel layout pattern may be extracted and the central point of the region including this pattern then taken as a feature point. 
     Note that terminal points, bend points, or meander points of retinal blood vessels and choroid blood vessels may also be extracted as feature points. 
     Feature point detection algorithms such as Scale Intevariant Feature Transform (SIFT) or Speed Upped Robust Feature (SURF) may be employed in the processing relating to the feature points. 
     In order to perform positional alignment at high precision, preferably at least four of the feature points are extracted. The UWF upward-looking fundus image GU includes only a single optical nerve head and a single macula of the examined eye. Four or more feature points  1  can therefore be extracted from the UWF upward-looking fundus image GU by extracting two or more junctions VBU of retinal blood vessels and choroid blood vessels. 
     The optical nerve head, macula, retinal blood vessels, and choroid blood vessels present in the fundus central portion are captured in both the UWF upward-looking fundus image GU and the UWF downward-looking fundus image GD, and therefore make suitable selection targets for feature points to be used in positional alignment. Namely, it is preferable to select feature points from the fundus central portion that configures a common region present in both the UWF upward-looking fundus image GU and the UWF downward-looking fundus image GD. 
     At step  340 , the position alignment section  1421  extracts the feature point group  1  by performing image processing on the fundus central portion, namely a region at the lower side of the center of the UWF upward-looking fundus image GU. 
     The vortex veins  12 V 1  and  12 V 3  that are present in the fundus-peripheral portion and that appear in the UWF upward-looking fundus image GU are eliminated from selection as feature points. Since this fundus-peripheral portion is not a region common to both the WF upward-looking fundus image GU and the UWF downward-looking fundus image GD, structures in this fundus-peripheral portion are eliminated from selection as feature points. 
     At step  342 , the position alignment section  1421  extracts a feature point group  2  corresponding to the feature point group  1  from the UWF downward-looking fundus image GD. As illustrated in  FIG. 7B , the feature point group  2  includes the optical nerve head ONHD and the macula MD, as well as a retinal blood vessel junction VBD. Since the eye is the same eye in both cases, the optical nerve head ONHD corresponds to the optical nerve head ONHU, and the macula MD corresponds to macula MU. The junction VBD corresponds to the blood vessel junction VUB, and a junction location exhibiting the same junction pattern as the junction pattern of the junction VBU is extracted using image recognition processing or the like. 
     At step  344 . the position alignment section  1421  employs the feature point group  1  and the feature point group  2  to generate a projection transformation grid to geometrically transform the UWF downward-looking fundus image GD. The projection transformation grid is a grid used to map the UWF downward-looking fundus image GD onto the UWF upward-looking fundus image GU. The projection transformation grid is set using at least four feature points. 
     At step  346 , the generated projection transformation grid is employed to transform the UWF downward-looking fundus image GD (see  FIG. 7B ) in order to obtain a post-transformation UWF downward-looking fundus image GDC (see  FIG. 12B ). After performing transformation using the projection transformation grid, the feature point group  1  and the feature point group  2  are brought to matching positions to complete the positional alignment processing. As a result of this transformation, the UWF downward-looking fundus image GDC is larger (has a greater area) than the UWF downward-looking fundus image GD. 
     In the foregoing explanation, the projection transformation grid is generated in order to map the UWF downward-looking fundus image GD onto the UWF upward-looking fundus image GU, and the UWF downward-looking fundus image GD is then transformed. Conversely, a projection transformation grid may be generated in order to map the UWF upward-looking fundus image GU onto the UWF downward-looking fundus image GD, before transforming the UWF upward-looking fundus image GU. 
     This completes the processing to align positions between the images, namely step  324  in  FIG. 10 , after which the montage image creation processing proceeds to step  326 . 
     At step  326  in  FIG. 10 , the combined image generation section  1424  combines the UWF upward-looking fundus image GU with the post-transformation UWF downward-looking fundus image GDC in order to generate a montage image GM. 
     First, as illustrated in  FIG. 12A , a line segment LGU is set in the UWF upward-looking fundus image GU so as to pass through the optical nerve head ONHU and the macula MU. Similarly, as illustrated in  FIG. 12B , a line segment LGD is set in the post-transformation UWF downward-looking fundus image GDC so as to pass through the optical nerve head ONHD and the macula MD. 
     Next, the combined image generation section  1424  performs weighting processing for a region where the UWF upward-looking fundus image GU and the UWF downward-looking fundus image GDC overlap. As illustrated in  FIG. 13 , the combined image generation section  1424  applies a weighting of “1” to an upper UWF upward-looking fundus image GUx region that is a region on the upper side of the line segment LGU in the UWF upward-looking fundus image GU. The combined image generation section  1424  applies a weighting of “0” to a region on the upper side of the line segment LGU. The combined image generation section  1424  also applies a weighting of “1” to a lower UWF downward-looking fundus image GDCx region on the lower side of the line segment LGD in the post-transformation UWF downward-looking fundus image, and applies a weighting of “0” to a region on the upper side of the line segment LGD. 
     The combined image generation section  1424  performs weighting processing on the UWF upward-looking fundus image GU and the UWF downward-looking fundus image GDC in this manner in order to generate the montage image GM in which the UWF upward-looking fundus image GUx and the UWF downward-looking fundus image GDCx are combined. As illustrated in  FIG. 13 , a line segment LG is a line segment joining the optical nerve head OMH and the macula M, the UWF upward-looking fundus image GUx is at the upper side of the line segment LG, and the UWF downward-looking fundus image GDCx is at the lower side of the line segment LG. The montage image is an example of a “combined image” of technology disclosed herein. 
     Note that the weighting relating to overlapping portions of the UWF upward-looking fundus image GU and the UWF downward-looking fundus image GDC is not limited to the above example, and various values may be employed in the mixing ratio between the UWF upward-looking fundus image GU and the UWF downward-looking fundus image GDC. 
     The UWF upward-looking fundus image GU and the UWF downward-looking fundus image GDC are positionally aligned and combined in the above manner. Combining in this manner enables a fundus image to be obtained for analyzing vortex veins and choroid blood vessels peripheral to the vortex veins, or for analyzing abnormalities or pathological lesions at positions in the fundus-peripheral portion or a fundus equatorial portion, without blood vessels of the fundus appearing discontinuous. 
     At the next step  328 , the vortex vein analysis section  1425  uses the montage image GM to analyze the positions of vortex veins and blood vessel diameters of blood vessels in the vicinity of the vortex veins. Vortex vein information obtained as a result of this analysis includes information relating to the number of vortex veins, the positions of the vortex veins, the number of blood vessels connected to the vortex veins, and the blood vessel diameters of blood vessels surrounding the vortex-shaped film. 
     At step  330 , the display control section  1430  generates a display screen  400 , described later, reflecting both the montage image and the patient attribute information (patient name, age, information indicating whether each fundus image corresponds to a left eye or a right eye, visual acuity, imaging date and time, and the like) corresponding to the patient ID. 
     At step  332 , the output section  1440  outputs the montage image GM and vortex vein analysis information obtained by the vortex vein analysis to the storage device  254  of the server  140 . The montage image GM and the vortex vein analysis information obtained by the vortex vein analysis are then stored in the storage device  254  of the server  140 . 
     Also at step  5332 , the output section  1440  outputs image data corresponding to the display screen  400  to the viewer  150 . 
     Note that the display control section  1430  may perform output so as to display the montage image GM on the display  256 . 
     Explanation has been given according to the flowcharts of  FIG. 10  and  FIG. 11 , in which the UWF downward-looking fundus image is transformed with reference to the UWF upward-looking fundus image. However, there is no limitation thereto, and the UWF upward-looking fundus image may be transformed with reference to the UWF downward-looking fundus image. 
     Although the montage image is generated employing binarized images, a similar technique may be applied to generate a montage image employing the color UWF upward-looking fundus image RG and UWF downward-looking fundus image RG that have not yet been subjected to binarization. In such cases, binarization processing may be performed on the montage image after performing montage combining processing. 
     Explanation follows regarding a graphical user interface (GUI) in which the montage image is employed. 
     As described above, at step  332  in  FIG. 10 , the server  140  outputs image data compatible with the display screen  400  to the viewer  150 . 
     Having received the image data output from the server  140 , the viewer  150  displays the display screen  400  on a non-illustrated display (monitor). 
     As illustrated in  FIG. 14 , the display screen  400  includes an information display region  402  and an image display region  404  ( 404 A). Note that  FIG. 14  illustrates an image display region  404 A corresponding to a first display mode of the image display region  404 . The information display region  402  includes a patient ID display region  412 , a patient name display region  414 , an age display region  416 , a left eye/right eye display region  418 , an eye axial length display region  420 , a visual acuity display region  422 , and an imaging date and time display region  424 . The viewer  150  displays various information in the respective display regions from the patient ID display region  412  to the imaging date and time display region  424  based on the received information. 
     The information display region  402  is also provided with a select image icon  430  and a switch display icon  440 . 
     The image display region  404 A includes a montage image display region  450  and a related image display region  460 . When the select image icon  430  has been selected, a pull-down menu is displayed. The pull-down menu displayed when the select image icon  430  has been selected is a menu for selecting a related image for display in the related image display region  460 . For example, the pull-down menu displays selection candidates including an animation of previously-acquired fluorescence images of the fundus of the examined eye  12  (for example indocyanine green angiography images (IA images)), a still IA image, and a UWF en face fundus image.  FIG. 14  illustrates a case in which the montage image GM is being displayed in the montage image display region  450  and an animation GA of IA images is being displayed in the related image display region  460 . 
     The line segment LG is a line segment joining the optical nerve head ONH and the macula M in the montage image GM. The animation GA of IA images displayed in the related image display region  460  is displayed such that the positions of the optical nerve head and the macula in the animation GA are aligned so as to lie on the line segment LG. 
     The user is able to select whether the line segment LG is displayed or hidden. 
     Marks to indicate vortex veins may be displayed in the montage image and the related image at positions corresponding to the vortex veins. 
     For example, as illustrated in  FIG. 14 , in the montage image GM the positions of the vortex veins  12 V 1 ,  12 V 2 ,  12 V 3 ,  12 V 4  may be detected and marks to indicate the vortex veins may be displayed at the detected positions in the montage image GM. 
     Moreover, the vortex vein analysis information (the number of vortex veins, the positions of the vortex veins, the number of blood vessels connected to the vortex veins, and the blood vessel diameters of blood vessels surrounding the vortex veins) may also be displayed on the display screen  400 . 
     When the switch display icon  440  has been selected, a pull-down menu is displayed. The pull-down menu includes menu options relating to image display in the image display region  404 . Specifically, the pull-down menu includes a menu option to display the montage image and the IA image alongside each other, menu options to divide and combine display of the montage image and the IA image respectively, and a menu option to display the montage image alongside a 3D image obtained using a 3D model, namely by projecting the montage image onto the 3D model.  FIG. 14  illustrates a case in which the menu option to display the montage image and the IA image alongside each other has been selected. 
     On the other hand,  FIG. 15  illustrates a case in which the menu option to divide and combine display of the montage image and the IA image has been selected from the pull-down menu of the switch display icon  440 . As illustrated in  FIG. 15 , a dividing line LK is employed as a boundary, with an IA image (animation or still image) GA being displayed at the upper side of the dividing line LK, and a montage image GM being displayed at the lower side of the dividing line LK in an image display region  404 B. By moving the dividing line LK up or down using an icon L the dividing line LK changes the regions in which the IA image GA and the montage image GM are displayed. For example, when the icon I is moved toward the upper side, the dividing line LK is moved toward the upper side, and only portions of the IA image GA lying at the upper side of the dividing line LK after moving toward the upper side are displayed, whereas portions of the montage image GM lying between the former position of the dividing line LK and the new position of the dividing line LK are displayed. 
       FIG. 16  illustrates a case in which the menu option to display the montage image alongside a 3D image has been selected from the pull-down menu of the switch display icon  440 . As illustrated in  FIG. 16 , an image display region  404 C includes the montage image display region  450  and a 3D image display region  470  displaying a 3D image obtained by projecting the montage image onto a 3D model of an eyeball. Note that the 3D model of an eyeball may first be corrected based on the eye axial length data of the patient as received from the server  140  in order to project the montage image onto a 3D model corresponding to the examined eye. 
     Note that a menu option to display all may be added to the pull-down menu of the switch display icon  440 , such that two or more of the image display region  404 A to the image display region  404 C illustrated in  FIG. 14  to  FIG. 16  are displayed simultaneously or sequentially on a single screen. 
     Instead of employing the montage image GM after binarization, configuration may be made to display a montage image obtained by combining the UWF upward-looking fundus image and the UWF downward-looking fundus image prior to binarization on the  3 D model. 
     As described above, in the present exemplary embodiment, the montage image is generated by combining the UWF upward-looking images and the UWF downward-looking images, thereby enabling an ophthalmologist to diagnose the examined eye of the patient more accurately using the montage image, in which regions corresponding to both the fundus equatorial portion and the fundus-peripheral portion are captured. In particular, the montage image can be generated without the eyelid, eyelashes, or equipment appearing in the image. This enables the ophthalmologist to ascertain the state of both upper and lower vortex veins. Moreover, it is possible to diagnose whether or not pathological lesions are present in the fundus equatorial portion and the fundus-peripheral portion. Moreover, it is possible to deduce not only pathological lesions in the fundus equatorial portion and the fundus-peripheral portion, but also advance indicators of pathological lesions in the fundus central portion from the states of the upper and lower vortex veins. 
     Next, explanation follows regarding various modified examples. 
     FIRST MODIFIED EXAMPLE 
     In the exemplary embodiment described above, montage image creation processing is executed by the CPU  262  of the server  140 . However, technology disclosed herein is not limited thereto. For example, montage image creation processing may be executed by the CPU  22  of the ophthalmic device  110 , executed by a CPU of the viewer  150 , or executed by a CPU of another computer connected over the network  130 . 
     SECOND MODIFIED EXAMPLE 
     In the exemplary embodiment described above, the UWF upward-looking fundus images and the UWF downward-looking fundus images are acquired in the following manner. Namely, the upper fixation light  92 U is illuminated and the UWF upward-looking fundus image GU of the examined eye  12  is acquired in a state in which the gaze of the patient is directed upward. The lower fixation light  92 D is then illuminated and the UWF downward-looking fundus image GD of the examined eye  12  is acquired in a state in which the gaze of the patient is directed downward. However, technology disclosed herein is not limited thereto. For example, the SLO unit  40  may be configured so as to be capable of swinging in an up-down direction centered on the center of the pupil of the examined eye  12 . 
     When acquiring an upward image, the SLO unit  40  is swung toward the lower side centered on the center of the pupil of the examined eye  12 . In this state, the SLO unit  40  on the lower side acquires an image of the fundus through the pupil of the examined eye  12  on the upper side. When this is performed, the upper fixation light  92 U may also be illuminated to direct the gaze of the patient upward. 
     When acquiring a downward image, the SLO unit  40  is swung toward the upper side centered on the center of the pupil of the examined eye  12 . In this state, the SLO unit  40  on the upper side acquires an image of the fundus through the pupil of the examined eye  12  on the lower side. When this is performed, the lower fixation light  92 D may also be illuminated to direct the gaze of the patient downward. 
     Moreover, there is no limitation to directing the gaze of the patient in the up-down direction or swinging the SLO unit  40  in the up-down direction centered on the center of the pupil of the examined eye  12 . 
     For example, fixation lights may be provided to guide the gaze of the examined eye  12  toward an oblique upper right side, an oblique upper left side, an oblique lower right side, and an oblique lower left side, and fundus images may be acquired with the gaze in respective corresponding states and then combined to generate a montage image. 
     Furthermore, the SLO unit  40  may be configured capable of swinging toward an oblique upper right side, an oblique upper left side, an oblique lower right side, and an oblique lower left side centered on the center of the pupil of the examined eye  12  to enable imaging of the fundus through the pupil of the examined eye  12 . The SLO unit  40  may acquire UWF fundus images corresponding to each direction by imaging the fundus from each method, which are then combined to generate a montage image. In such cases, respective fixation lights disposed on the oblique upper right side, the oblique upper left side, the oblique lower right side, and the oblique lower left side may be illuminated to guide the gaze of the examined eye  12  in each of the directions. 
     THIRD MODIFIED EXAMPLE 
     As well as visualizing vortex veins, the montage image generated by the server  140  may by subjected to processing to analyze retinal structures or analyze blood vessels or to detect abnormal regions (pathological lesions) in the fundus-peripheral portion (fundus equatorial portion). The generated montage image may be employed to deduce the presence of pathological lesions (or the possibility of pathological lesions developing) in the fundus central portion, for example diabetic retinopathy, age-related macular degeneration, and the like. Factoring in image information from the fundus-peripheral portion (fundus equatorial portion) in the montage image enables image analysis of the fundus central portion image to be used to deduce pathological lesions in consideration of information relating to the fundus-peripheral portion. 
     Moreover, artificial intelligence (AI) based analysis may be employed for structural analysis and blood vessel analysis, or as analysis to deduce pathological lesions. 
     Processing to perform structural analysis of the retina, to analyze blood vessels, or to detect abnormal regions (pathological lesions) in the fundus-peripheral portion (fundus equatorial portion) may be carried out using the functionality of the vortex vein analysis section  1425 , or may be implemented by another, non-illustrated, image analysis section. 
     FOURTH MODIFIED EXAMPLE 
     In the exemplary embodiment described above, the CPU  262  of the server  140  executes the montage image creation processing, and the positional alignment processing is performed automatically. In cases in which the montage image creation processing is performed by the viewer  150 , extraction of the feature point group  1  from the UWF upward-looking fundus images and extraction of the feature point group  2  from the UWF downward-looking fundus images may be performed manually by a user. 
     Specifically, the following processing may be executed in place of steps  340 ,  342  in  FIG. 11 . 
     Image data of the UWF upward-looking fundus image GU and the UWF downward-looking fundus image GD are transmitted from the server  140  to the viewer  150 . 
     Having received the image data, the viewer  150  detects the macula MU, MD and the optical nerve head ONHU, ONHD in the UWF upward-looking fundus image GU and the UWF downward-looking fundus image GD respectively. As illustrated in  FIG. 17 , the viewer  150  displays the UWF upward-looking fundus image GU and the UWF downward-looking fundus image GD alongside each other, positionally aligned such that a line segment joining the macula MU and the optical nerve head ONHU in the UWF upward-looking fundus image GU and a line segment joining the macula MID and the optical nerve head ONHD in the UWF downward-looking fundus image GD line up with each other to configure a line segment LGM. The viewer  150  then sets a feature point extraction region upper limit LU and a feature point extraction region lower limit LD running parallel to the line segment LGM at positions at predetermined distances to the upper side and the lower side of the line segment LGM. 
     The user then sets the feature point group  1  between the upper limit LU and the lower limit LD in the UWF upward-looking fundus image GU. The user then extracts the feature point group  2  corresponding to the feature point group  1  between the upper limit LU and the lower limit LD in the UWF downward-looking fundus image GD. The viewer  150  then transmits data indicating the positions of the feature point group  1  and the feature point group  2  to the server  140 . Having received the data indicating the positions of the feature point group  1  and the feature point group  2 , at step  344  ( FIG. 11 ) the position alignment section  1421  of the server  140  creates the projection transformation grid described above using the received feature point group  1  and feature point group  2  (see  FIG. 11 ). 
     OTHER MODIFIED EXAMPLES 
     The montage image creation processing and the processing when displaying the montage image described above are merely examples. Obviously, unnecessary steps may be removed, additional steps may be introduced, and the processing sequence may be changed within a range not departing from the spirit thereof. 
     The ophthalmic device  110  has functionality to image a region with an internal irradiation angle of 200° relative to the position of the eyeball center  170  of the examined eye  12  (an external irradiation angle of 167° relative to the pupil of the eyeball of the examined eye  12 ). However, the angle of view is not limited thereto. The internal irradiation angle may be set to 200° or greater (and the external irradiation angle may be set to from 167° to) 180°. 
     Moreover, specifications may be adjusted such that the internal irradiation angle is set to less than 200° (the external irradiation angle is set to less than 167°). For example, an angle of view with an internal irradiation angle of approximately 180° (an external irradiation angle of approximately 140°), an internal irradiation angle of approximately 156° (an external irradiation angle of approximately 120°), or an internal irradiation angle of approximately 144° (an external irradiation angle of approximately 110°) may be adopted. These values are merely examples, and any angle of view enabling the fundus-peripheral portion and the fundus central portion in which vortex veins and the like are present to be captured in a single take may be adopted. 
     In the respective examples described above, tomographic image generation processing is implemented by a software configuration using a computer. However, technology disclosed herein is not limited thereto. For example, tomographic image generation processing may be implemented solely by a hardware configuration such as a field-programmable gate array (FPGA) or an application specific integrated circuit (ASIC) instead of by a software configuration using a computer. Alternatively, some of the tomographic image generation processing may be implemented by a software configuration, with the remaining processing being implemented by a hardware configuration.