JP2016040005A - Blood flow information generation apparatus, blood flow information generation method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform blood flow measurement with high accuracy.SOLUTION: A blood flow information generation apparatus comprises an acquisition unit, a blood vessel region identification unit, and a blood flow information generation unit. The acquisition unit acquires a tomographic image showing time-series variation of a form of a cross section crossing a target blood vessel of a living body, which is formed by executing optical coherence tomography (OCT) to the cross section, and a phase image showing time-series variation of a phase difference. The blood vessel region identification unit identifies blood vessel regions corresponding to the target blood vessel for each of the tomographic image and the phase image. The blood flow information generation unit generates blood flow information on the target blood vessel on the basis of the blood vessel region of the tomographic image and the time-series variation of the phase difference in the blood vessel region of the phase image.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an apparatus, a method, and a program for performing blood flow measurement based on an image obtained using optical coherence tomography (OCT).

  In recent years, OCT that forms an image representing the surface form or internal form of an object to be measured using a light beam from a laser light source or the like has attracted attention. Since OCT has no invasiveness to the human body like X-ray CT, it is expected to be applied particularly in the medical field and the biological field. For example, in the field of ophthalmology, an apparatus for forming an image of the fundus oculi or cornea has been put into practical use.

  Patent Document 1 discloses an apparatus using a so-called “Fourier Domain OCT (Fourier Domain OCT)” technique. That is, this apparatus irradiates the object to be measured with a beam of low coherence light, superimposes the reflected light and the reference light to generate interference light, acquires the spectral intensity distribution of the interference light, and performs Fourier transform. By performing the conversion, the form of the object to be measured in the depth direction (z direction) is imaged. Further, this apparatus includes a galvanometer mirror that scans a light beam (signal light) in one direction (x direction) orthogonal to the z direction, thereby forming an image of a desired measurement target region of the object to be measured. It has become. An image formed by this apparatus is a two-dimensional tomographic image in the depth direction (z direction) along the scanning direction (x direction) of the light beam. Note that this technique is also called a spectral domain.

  In Patent Document 2, a plurality of two-dimensional tomographic images in the horizontal direction are formed by scanning (scanning) the signal light in the horizontal direction (x direction) and the vertical direction (y direction), and based on the plurality of tomographic images. A technique for acquiring and imaging three-dimensional tomographic information of a measurement range is disclosed. As this three-dimensional imaging, for example, a method of displaying a plurality of tomographic images side by side in a vertical direction (referred to as stack data or the like), volume data (voxel data) based on the stack data is rendered, and a three-dimensional image is rendered. There is a method of forming.

  Patent Documents 3 and 4 disclose other types of OCT apparatuses. In Patent Document 3, the wavelength of light irradiated to a measured object is scanned (wavelength sweep), and interference intensity obtained by superimposing reflected light of each wavelength and reference light is detected to detect spectral intensity distribution. And an OCT apparatus for imaging the form of an object to be measured by performing Fourier transform on the obtained image. Such an OCT apparatus is called a swept source type. The swept source type is a kind of Fourier domain type.

  In Patent Document 4, the traveling direction of light is obtained by irradiating the object to be measured with light having a predetermined beam diameter, and analyzing the component of interference light obtained by superimposing the reflected light and the reference light. An OCT apparatus for forming an image of an object to be measured in a cross-section orthogonal to is described. Such an OCT apparatus is called a full-field type or an en-face type.

  Patent Document 5 discloses a configuration in which OCT is applied to the ophthalmic field. Prior to the application of OCT, a fundus camera, a slit lamp, or the like was used as an apparatus for observing the eye to be examined (see, for example, Patent Document 6 and Patent Document 7). A fundus camera is a device that shoots the fundus by illuminating the subject's eye with illumination light and receiving the fundus reflection light. A slit lamp is a device that acquires an image of a cross-section of the cornea by cutting off a light section of the cornea using slit light.

  An apparatus using OCT has an advantage over a fundus camera or the like in that a high-definition image can be acquired, and further, a tomographic image or a three-dimensional image can be acquired.

  As described above, an apparatus using OCT can be applied to observation of various parts of an eye to be examined, and can acquire high-definition images, and thus has been applied to diagnosis of various ophthalmic diseases.

  The OCT is used not only for measuring the form of the object to be measured but also for measuring blood flow of blood flowing through a blood vessel in a living body (for example, see Patent Documents 8 and 9). Blood flow measurement using OCT is applied to fundus blood flow measurement and the like.

JP 11-325849 A JP 2002-139421 A JP 2007-24677 A JP 2006-153838 A JP 2008-73099 A JP-A-9-276232 JP 2008-259544 A JP 2009-165710 A Special table 2010-523286

  Since changes in blood flow also occur in early diseases, it is considered possible to use blood flow measurement for the diagnosis. However, with the conventional blood flow measurement, it has been difficult to achieve sufficient accuracy for use in early diagnosis.

  Accordingly, an object of the present invention is to provide a technique capable of performing blood flow measurement with high accuracy.

The blood flow information generation device according to the embodiment includes a tomographic image representing a time-series change in morphology in the cross section formed by executing optical coherence tomography (OCT) on a cross section intersecting a target blood vessel of a living body. An acquisition unit that acquires a phase image representing a time-series change in phase difference; a blood vessel region specifying unit that specifies a blood vessel region corresponding to the target blood vessel for each of the tomographic image and the phase image; and A blood flow information generation unit configured to generate blood flow information related to the blood vessel of interest based on the blood vessel region and a time-series change in phase difference in the blood vessel region of the phase image;
The blood flow information generation device according to another embodiment includes an acquisition unit that acquires data obtained by executing optical coherence tomography (OCT) on a cross section that intersects a target blood vessel of a living body, and the acquisition unit. Based on the acquired data, an image forming unit that forms a tomographic image representing a time-series change in form in the cross section and a phase image representing a time-series change in phase difference, and each of the tomographic image and the phase image A blood vessel region specifying unit that specifies a blood vessel region corresponding to the blood vessel of interest, and a time-series change in phase difference between the blood vessel region of the tomographic image and the blood vessel region of the phase image. A blood flow information generation unit that generates blood flow information.

  According to the present invention, the blood flow measurement is performed using the tomographic image having the same cross section as the phase image and the time-series change of the phase difference, so that the blood flow measurement with high accuracy can be realized.

It is a schematic diagram showing an example of composition of a fundus oculi observation device (optical image measurement device) concerning an embodiment. It is a schematic diagram showing an example of composition of a fundus oculi observation device concerning an embodiment. It is a schematic block diagram showing an example of composition of a fundus oculi observation device concerning an embodiment. It is a schematic block diagram showing an example of composition of a fundus oculi observation device concerning an embodiment. It is the schematic showing an example of operation | movement of the fundus observation apparatus which concerns on embodiment. It is the schematic showing an example of operation | movement of the fundus observation apparatus which concerns on embodiment. It is a flowchart showing the operation example of the fundus oculi observation device concerning an embodiment.

  An example of an embodiment of an optical image measurement device according to the present invention will be described in detail with reference to the drawings. The optical image measurement device according to the present invention forms a tomographic image or a three-dimensional image of a living body using OCT. In this specification, images acquired by OCT may be collectively referred to as OCT images. In addition, a measurement operation for forming an OCT image may be referred to as OCT measurement. In addition, it is possible to use suitably the description content of the literature described in this specification as the content of the following embodiment.

  In the following embodiments, a fundus oculi observation device that performs OCT measurement of the fundus using a Fourier domain type OCT with a measurement target of a living body as an eye to be examined (fundus) will be described. In particular, the fundus oculi observation device according to the embodiment can acquire both the fundus OCT image and the fundus oculi image using the spectral domain OCT technique, similarly to the device disclosed in Patent Document 5. Note that the configuration according to the present invention can be applied to an optical image measurement apparatus using a type other than the spectral domain, for example, a swept source OCT technique. In this embodiment, an apparatus combining an OCT apparatus and a fundus camera will be described. However, this embodiment may be applied to a fundus imaging apparatus other than a fundus camera, for example, an SLO (Scanning Laser Ophthalmoscope), a slit lamp, an ophthalmic surgical microscope, and the like. It is also possible to combine an OCT apparatus having the configuration according to the above. In addition, the configuration according to this embodiment can be incorporated into a single OCT apparatus. The configuration of this embodiment can also be applied to an OCT apparatus that measures a biological part other than the fundus. Such a living body part is an arbitrary part to be inspected for a blood flow state.

[Constitution]
As shown in FIG. 1, the fundus oculi observation device 1 includes a fundus camera unit 2, an OCT unit 100, and an arithmetic control unit 200. The retinal camera unit 2 has almost the same optical system as a conventional retinal camera. The OCT unit 100 is provided with an optical system for acquiring an OCT image of the fundus. The arithmetic control unit 200 includes a computer that executes various arithmetic processes and control processes.

[Fundus camera unit]
The fundus camera unit 2 shown in FIG. 1 is provided with an optical system for obtaining a two-dimensional image (fundus image) representing the surface form of the fundus oculi Ef of the eye E to be examined. The fundus image includes an observation image and a captured image. The observation image is, for example, a monochrome moving image formed at a predetermined frame rate using near infrared light. The captured image may be, for example, a color image obtained by flashing visible light, or a monochrome still image using near infrared light or visible light as illumination light. The fundus camera unit 2 may be configured to be able to acquire images other than these, such as a fluorescein fluorescent image, an indocyanine green fluorescent image, a spontaneous fluorescent image, and the like.

  The retinal camera unit 2 is provided with a chin rest and a forehead support for supporting the subject's face. Further, the fundus camera unit 2 is provided with an illumination optical system 10 and a photographing optical system 30. The illumination optical system 10 irradiates the fundus oculi Ef with illumination light. The photographing optical system 30 guides the fundus reflection light of the illumination light to an imaging device (CCD image sensor (sometimes simply referred to as a CCD) 35, 38). The imaging optical system 30 guides the signal light from the OCT unit 100 to the fundus oculi Ef and guides the signal light passing through the fundus oculi Ef to the OCT unit 100.

  The observation light source 11 of the illumination optical system 10 is constituted by a halogen lamp, for example. The light (observation illumination light) output from the observation light source 11 is reflected by the reflection mirror 12 having a curved reflection surface, passes through the condensing lens 13, passes through the visible cut filter 14, and is converted into near infrared light. Become. Further, the observation illumination light is once converged in the vicinity of the photographing light source 15, reflected by the mirror 16, and passes through the relay lenses 17 and 18, the diaphragm 19 and the relay lens 20. Then, the observation illumination light is reflected at the peripheral portion (region around the hole portion) of the aperture mirror 21, passes through the dichroic mirror 46, and is refracted by the objective lens 22 to illuminate the fundus oculi Ef. An LED (Light Emitting Diode) can also be used as the observation light source.

  The fundus reflection light of the observation illumination light is refracted by the objective lens 22, passes through the dichroic mirror 46, passes through the hole formed in the central region of the perforated mirror 21, passes through the dichroic mirror 55, and is a focusing lens. It is reflected by the mirror 32 via 31. Further, the fundus reflection light passes through the half mirror 40, is reflected by the dichroic mirror 33, and forms an image on the light receiving surface of the CCD image sensor 35 by the condenser lens 34. The CCD image sensor 35 detects fundus reflected light at a predetermined frame rate, for example. On the display device 3, an image (observation image) based on fundus reflection light detected by the CCD image sensor 35 is displayed. When the photographing optical system is focused on the anterior segment, an observation image of the anterior segment of the eye E is displayed.

  The imaging light source 15 is constituted by, for example, a xenon lamp. The light (imaging illumination light) output from the imaging light source 15 is applied to the fundus oculi Ef through the same path as the observation illumination light. The fundus reflection light of the imaging illumination light is guided to the dichroic mirror 33 through the same path as that of the observation illumination light, passes through the dichroic mirror 33, is reflected by the mirror 36, and is reflected by the condenser lens 37 of the CCD image sensor 38. An image is formed on the light receiving surface. On the display device 3, an image (captured image) based on fundus reflection light detected by the CCD image sensor 38 is displayed. Note that the display device 3 that displays the observation image and the display device 3 that displays the captured image may be the same or different. In addition, when similar imaging is performed by illuminating the eye E with infrared light, an infrared captured image is displayed. It is also possible to use an LED as a photographing light source.

  An LCD (Liquid Crystal Display) 39 displays a fixation target and an eyesight measurement index. The fixation target is an index for fixing the eye E to be examined, and is used at the time of fundus photographing or OCT measurement.

  A part of the light output from the LCD 39 is reflected by the half mirror 40, reflected by the mirror 32, passes through the focusing lens 31 and the dichroic mirror 55, passes through the hole of the perforated mirror 21, and is dichroic. The light passes through the mirror 46, is refracted by the objective lens 22, and is projected onto the fundus oculi Ef.

  By changing the display position of the fixation target on the screen of the LCD 39, the fixation position of the eye E can be changed. As the fixation position of the eye E, for example, a position for acquiring an image centered on the macular portion of the fundus oculi Ef, or a position for acquiring an image centered on the optic disc as in the case of a conventional fundus camera And a position for acquiring an image centered on the fundus center between the macula and the optic disc. It is also possible to arbitrarily change the display position of the fixation target.

  Further, the fundus camera unit 2 is provided with an alignment optical system 50 and a focus optical system 60 as in a conventional fundus camera. The alignment optical system 50 generates an index (alignment index) for performing alignment (alignment) of the apparatus optical system with respect to the eye E. The focus optical system 60 generates an index (split index) for focusing on the fundus oculi Ef.

  The light (alignment light) output from the LED 51 of the alignment optical system 50 is reflected by the dichroic mirror 55 via the apertures 52 and 53 and the relay lens 54, passes through the hole of the aperture mirror 21, and reaches the dichroic mirror 46. And is projected onto the cornea of the eye E by the objective lens 22.

  The cornea-reflected light of the alignment light passes through the objective lens 22, the dichroic mirror 46, and the hole, part of which passes through the dichroic mirror 55, passes through the focusing lens 31, and is reflected by the mirror 32. 40 is reflected by the dichroic mirror 33 and projected onto the light-receiving surface of the CCD image sensor 35 by the condenser lens 34. The light reception image (alignment index) by the CCD image sensor 35 is displayed on the display device 3 together with the observation image. The user performs alignment by performing the same operation as that of a conventional fundus camera. Further, the arithmetic control unit 200 may perform alignment by analyzing the position of the alignment index and moving the optical system (auto-alignment function).

  When performing the focus adjustment, the reflecting surface of the reflecting rod 67 is obliquely provided on the optical path of the illumination optical system 10. The light (focus light) output from the LED 61 of the focus optical system 60 passes through the relay lens 62, is separated into two light beams by the split indicator plate 63, passes through the two-hole aperture 64, and is reflected by the mirror 65, The light is focused on the reflecting surface of the reflecting bar 67 by the condenser lens 66 and reflected. Further, the focus light passes through the relay lens 20, is reflected by the perforated mirror 21, passes through the dichroic mirror 46, is refracted by the objective lens 22, and is projected onto the fundus oculi Ef.

  The fundus reflection light of the focus light is detected by the CCD image sensor 35 through the same path as the cornea reflection light of the alignment light. A light reception image (split index) by the CCD image sensor 35 is displayed on the display device 3 together with the observation image. The arithmetic control unit 200 analyzes the position of the split index and moves the focusing lens 31 and the focus optical system 60 to perform focusing as in the conventional case (autofocus function). Alternatively, focusing may be performed manually while visually checking the split indicator.

  The dichroic mirror 46 branches the optical path for OCT measurement from the optical path for fundus photography. That is, the optical path for fundus imaging and the optical path for OCT measurement are configured coaxially by the dichroic mirror 46 and share the optical path on the eye E side with respect to the dichroic mirror 46. The dichroic mirror 46 reflects light in a wavelength band used for OCT measurement and transmits light for fundus photographing. In this optical path for OCT measurement, a collimator lens unit 40, an optical path length changing unit 41, a galvano scanner 42, a focusing lens 43, a mirror 44, and a relay lens 45 are provided in this order from the OCT unit 100 side. It has been.

  The optical path length changing unit 41 is movable in the direction of the arrow shown in FIG. 1 and changes the length of the optical path for OCT measurement. This change in the optical path length is used for correcting the optical path length according to the axial length of the eye E or adjusting the interference state. The optical path length changing unit 41 includes, for example, a corner cube and a mechanism for moving the corner cube.

  The galvano scanner 42 changes the traveling direction of light (signal light LS) passing through the optical path for OCT measurement. Thereby, the fundus oculi Ef can be scanned with the signal light LS. The galvano scanner 42 includes, for example, a galvano mirror that scans the signal light LS in the x direction, a galvano mirror that scans in the y direction, and a mechanism that drives these independently. Thereby, the signal light LS can be scanned in an arbitrary direction on the xy plane. The galvano scanner 42 is an example of a “scanning unit”.

[OCT unit]
An example of the configuration of the OCT unit 100 will be described with reference to FIG. The OCT unit 100 is provided with an optical system for acquiring an OCT image of the fundus oculi Ef. This optical system has the same configuration as a conventional spectral domain type OCT apparatus. That is, this optical system divides low-coherence light into reference light and signal light, and generates interference light by causing interference between the signal light passing through the fundus oculi Ef and the reference light passing through the reference optical path. It is configured to detect spectral components. This detection result (detection signal) is sent to the arithmetic control unit 200.

  In the case of a swept source type OCT apparatus, a wavelength swept light source is provided instead of a light source that outputs a low coherence light source, and an optical member that spectrally decomposes interference light is not provided. In general, for the configuration of the OCT unit 100, a known technique according to the type of optical coherence tomography can be arbitrarily applied.

  The light source unit 101 outputs a broadband low-coherence light L0. The low coherence light L0 includes, for example, a near-infrared wavelength band (about 800 nm to 900 nm) and has a temporal coherence length of about several tens of micrometers. Note that near-infrared light having a wavelength band that cannot be visually recognized by the human eye, for example, a center wavelength of about 1040 to 1060 nm, may be used as the low-coherence light L0.

  The light source unit 101 includes a light output device such as a super luminescent diode (SLD), an LED, or an SOA (Semiconductor Optical Amplifier).

  The low-coherence light L0 output from the light source unit 101 is guided to the fiber coupler 103 by the optical fiber 102 and split into the signal light LS and the reference light LR.

  The reference light LR is guided by the optical fiber 104 and reaches the optical attenuator (attenuator) 105. The optical attenuator 105 automatically adjusts the amount of the reference light LR guided to the optical fiber 104 under the control of the arithmetic control unit 200 using a known technique. The reference light LR whose light amount has been adjusted by the optical attenuator 105 is guided by the optical fiber 104 and reaches the polarization adjuster (polarization controller) 106. The polarization adjuster 106 is, for example, a device that adjusts the polarization state of the reference light LR guided in the optical fiber 104 by applying a stress from the outside to the optical fiber 104 in a loop shape. The configuration of the polarization adjuster 106 is not limited to this, and any known technique can be used. The reference light LR whose polarization state is adjusted by the polarization adjuster 106 reaches the fiber coupler 109.

  The signal light LS generated by the fiber coupler 103 is guided by the optical fiber 107 and converted into a parallel light beam by the collimator lens unit 105. Further, the signal light LS reaches the dichroic mirror 46 via the optical path length changing unit 41, the galvano scanner 42, the focusing lens 43, the mirror 44, and the relay lens 45. Then, the signal light LS is reflected by the dichroic mirror 46, refracted by the objective lens 11, and irradiated onto the fundus oculi Ef. The signal light LS is scattered (including reflection) at various depth positions of the fundus oculi Ef. The backscattered light of the signal light LS from the fundus oculi Ef travels in the same direction as the forward path in the reverse direction, is guided to the fiber coupler 103, and reaches the fiber coupler 109 via the optical fiber 108.

  The fiber coupler 109 causes the backscattered light of the signal light LS to interfere with the reference light LR that has passed through the fiber coupler 104. The interference light LC generated thereby is guided by the optical fiber 110 and emitted from the emission end 111. Further, the interference light LC is converted into a parallel light beam by the collimator lens 112, dispersed (spectral decomposition) by the diffraction grating 113, condensed by the condenser lens 114, and projected onto the light receiving surface of the CCD image sensor 115. The diffraction grating 118 shown in FIG. 2 is a transmission type, but other types of spectroscopic elements such as a reflection type diffraction grating can also be used.

  The CCD image sensor 115 is a line sensor, for example, and detects each spectral component of the split interference light LC and converts it into electric charges. The CCD image sensor 115 accumulates this electric charge, generates a detection signal, and sends it to the arithmetic control unit 200.

  In this embodiment, a Michelson type interferometer is employed, but any type of interferometer such as a Mach-Zehnder type can be appropriately employed. Further, in place of the CCD image sensor, another form of image sensor such as a CMOS (Complementary Metal Oxide Semiconductor) image sensor can be used.

[Calculation control unit]
The configuration of the arithmetic control unit 200 will be described. The arithmetic control unit 200 analyzes the detection signal input from the CCD image sensor 115 and forms an OCT image of the fundus oculi Ef. The arithmetic processing for this is the same as that of a conventional spectral domain type OCT apparatus.

  The arithmetic control unit 200 controls each part of the fundus camera unit 2, the display device 3, and the OCT unit 100. For example, the arithmetic control unit 200 displays an OCT image of the fundus oculi Ef on the display device 3.

  As the control of the fundus camera unit 2, the arithmetic control unit 200 controls the operation of the observation light source 11, the imaging light source 15 and the LEDs 51 and 61, the operation control of the LCD 39, the movement control of the focusing lenses 31 and 43, and the reflector 67. Movement control, movement control of the focus optical system 60, movement control of the optical path length changing unit 41, operation control of the galvano scanner 42, and the like are performed.

  As control of the OCT unit 100, the arithmetic control unit 200 performs operation control of the light source unit 101, operation control of the optical attenuator 105, operation control of the polarization adjuster 106, operation control of the CCD image sensor 120, and the like.

  The arithmetic control unit 200 includes, for example, a microprocessor, a RAM, a ROM, a hard disk drive, a communication interface, etc., as in a conventional computer. A computer program for controlling the fundus oculi observation device 1 is stored in a storage device such as a hard disk drive. The arithmetic control unit 200 may include various circuit boards, for example, a circuit board for forming an OCT image. The arithmetic control unit 200 may include an operation device (input device) such as a keyboard and a mouse, and a display device such as an LCD.

  The fundus camera unit 2, the display device 3, the OCT unit 100, and the calculation control unit 200 may be configured integrally (that is, in a single housing) or separated into two or more housings. It may be.

[Control system]
The configuration of the control system of the fundus oculi observation device 1 will be described with reference to FIGS.

(Control part)
The control system of the fundus oculi observation device 1 is configured around the control unit 210. The control unit 210 includes, for example, the aforementioned microprocessor, RAM, ROM, hard disk drive, communication interface, and the like. The control unit 210 is provided with a main control unit 211 and a storage unit 212.

(Main control unit)
The main control unit 211 performs the various controls described above. In particular, the main control unit 211 controls the focusing drive unit 31A, the optical path length changing unit 41, and the galvano scanner 42 of the fundus camera unit 2, and further the light source unit 101, the optical attenuator 105, and the polarization adjuster 106 of the OCT unit 100. To do.

  The focusing drive unit 80 moves the focusing lens 31 in the optical axis direction. Thereby, the focus position of the photographic optical system 30 is changed. The main control unit 211 can also move an optical system provided in the fundus camera unit 2 in a three-dimensional manner by controlling an optical system drive unit (not shown). This control is used in alignment and tracking. Tracking is to move the apparatus optical system in accordance with the eye movement of the eye E. When tracking is performed, alignment and focusing are performed in advance. Tracking is a function of maintaining a suitable positional relationship in which the alignment and focus are achieved by causing the position of the apparatus optical system to follow the eye movement.

  Further, the main control unit 211 performs processing for writing data into the storage unit 212 and processing for reading data from the storage unit 212.

(Memory part)
The storage unit 212 stores various data. Examples of the data stored in the storage unit 212 include OCT image image data, fundus image data, and examined eye information. The eye information includes information about the subject such as patient ID and name, and information about the eye such as left / right eye identification information. The storage unit 212 stores various programs and data for operating the fundus oculi observation device 1.

(Image forming part)
The image forming unit 220 forms tomographic image data and phase image data of the fundus oculi Ef based on the detection signal from the CCD image sensor 115. These images will be described later. The image forming unit 220 includes, for example, the circuit board and the microprocessor described above. In this specification, “image data” and “image” based thereon may be identified. The image forming unit 220 includes a tomographic image forming unit 221 and a phase image forming unit 222.

  In this embodiment, two types of scanning (first scanning and second scanning) are performed on the fundus oculi Ef. In the first scan, the first cross section that intersects the target blood vessel of the fundus oculi Ef is repeatedly scanned with the signal light LS. In the second scan, the second cross section that intersects the blood vessel of interest and is located in the vicinity of the first cross section is scanned with the signal light LS. Here, the first cross section and the second cross section are preferably oriented so as to be orthogonal to the traveling direction of the blood vessel of interest. As shown in the fundus oculi image D of FIG. 5, in this embodiment, one first cross section C0 and two second cross sections C1 and C2 intersect a predetermined blood vessel Db in the vicinity of the optic disc Da of the fundus oculi Ef. Set to do. One of the two second cross sections C1 and C2 is located upstream of the target blood vessel Db with respect to the first cross section C0, and the other is located downstream.

  Note that the first scan is preferably performed over at least one cardiac cycle of the patient's heart. Thereby, blood flow information in all time phases of the heart is obtained. The time for executing the first scan may be a predetermined time set in advance, or may be a time set for each patient or for each examination. In the former case, a time longer than a general cardiac cycle is set (for example, 2 seconds). In the latter case, examination data such as a patient's electrocardiogram is referred to. Here, factors other than the cardiac cycle can be considered. Examples of this factor include time required for examination (a burden on the patient), response time of the galvano scanner 42 (scan interval), response time of the CCD 115 (scan interval), and the like.

(Tomographic image forming part)
The tomographic image forming unit 221 forms a tomographic image (first tomographic image) representing a time-series change in form in the first cross section based on the detection result of the interference light LC obtained by the first scanning. This process will be described in more detail. In the first scanning, the first cross section C0 is repeatedly scanned as described above. Detection signals are sequentially input from the CCD 115 of the OCT unit 100 to the tomographic image forming unit 221 in accordance with the first scan. The tomographic image forming unit 221 forms one tomographic image of the first cross section C0 based on the detection signal corresponding to each scan of the first tomographic image. The tomographic image forming unit 221 forms a series of tomographic images along a time series by repeating this process as many times as the first scan is repeated. Here, these tomographic images may be divided into a plurality of groups, and the tomographic images of each group may be superimposed to improve the image quality.

  In addition, the tomographic image forming unit 221 includes a tomographic image (second tomographic image) representing a form in the second cross section C1, based on the detection result of the interference light LC obtained by the second scanning with respect to the second cross sections C1 and C2. A tomographic image (second tomographic image) representing the form in the second cross section C2 is formed. This process is executed in the same manner as in the case of the first tomogram. The first tomographic image is a series of tomographic images along time series, but the second tomographic image may be a single tomographic image. The second tomographic image may be an image obtained by superimposing a plurality of tomographic images obtained by scanning each of the second cross sections C1 and C2 a plurality of times to improve image quality.

  The processing for forming such a tomographic image includes processing such as noise removal (noise reduction), filter processing, FFT (Fast Fourier Transform), and the like, similarly to the conventional spectral domain type optical coherence tomography. In the case of another type of OCT apparatus, the tomographic image forming unit 221 executes a known process corresponding to the type.

(Phase image forming unit)
The phase image forming unit 222 forms a phase image representing a time-series change of the phase difference in the first cross section based on the detection result of the interference light LS obtained by the first scanning. The detection result used in this process is the same as that used for the first tomographic image forming process by the tomographic image forming unit 221. Therefore, it is possible to perform alignment between the first tomographic image and the phase image. That is, it is possible to naturally associate the pixels of the first tomographic image with the pixels of the phase image.

  An example of a phase image forming method will be described. The phase image in this example is obtained by calculating the phase difference between adjacent A-line complex signals (signals corresponding to adjacent scanning points). In other words, the phase image of this example is formed based on the time series change of the pixel value (luminance value) of each pixel of the first tomographic image. For an arbitrary pixel, the phase image forming unit 222 considers a graph of a time-series change in luminance value. The phase image forming unit 222 obtains a phase difference Δφ between two time points t1 and t2 (= t1 + Δt) separated by a predetermined time interval Δt in this graph. The phase difference Δφ is defined as the phase difference Δφ (t1) at the time point t1 (more generally, any time point between the two time points t1 and t2). By executing this process for each of a number of preset time points, a time-series change in phase difference at the pixel can be obtained.

  The phase image represents the value of the phase difference at each time point of each pixel as an image. This imaging process can be realized, for example, by expressing the value of the phase difference with the display color or brightness. At this time, the display color (for example, red) when the phase increases along the time series and the display color (for example, blue) when it decreases can be changed. Also, the magnitude of the phase change amount can be expressed by the darkness of the display color. By adopting such an expression method, the direction and size of the blood flow can be clearly indicated by the display color. A phase image is formed by executing the above processing for each pixel.

  The time-series change of the phase difference is obtained by ensuring the phase correlation by sufficiently reducing the time interval Δt. At this time, oversampling in which the time interval Δt is set to a value less than the time corresponding to the resolution of the tomographic image in the scanning of the signal light LS is executed.

(Image processing unit)
The image processing unit 230 performs various types of image processing and analysis processing on the image formed by the image forming unit 220. For example, the image processing unit 230 executes various correction processes such as image brightness correction and dispersion correction. The image processing unit 230 performs various types of image processing and analysis processing on the image (fundus image, anterior eye image, etc.) obtained by the fundus camera unit 2.

  The image processing unit 230 executes known image processing such as interpolation processing for interpolating pixels between tomographic images to form image data of a three-dimensional image of the fundus oculi Ef. Note that the image data of a three-dimensional image means image data in which pixel positions are defined by a three-dimensional coordinate system. As image data of a three-dimensional image, there is image data composed of voxels arranged three-dimensionally. This image data is called volume data or voxel data. When displaying an image based on volume data, the image processing unit 230 performs rendering processing on the volume data to form image data of a pseudo three-dimensional image when viewed from a specific line-of-sight direction. . This pseudo three-dimensional image is displayed on a display device such as the display unit 240A.

  It is also possible to form stack data of a plurality of tomographic images as image data of a three-dimensional image. The stack data is image data obtained by three-dimensionally arranging a plurality of tomographic images obtained along a plurality of scanning lines based on the positional relationship of the scanning lines. That is, stack data is image data obtained by expressing a plurality of tomographic images originally defined by individual two-dimensional coordinate systems by one three-dimensional coordinate system (that is, by embedding them in one three-dimensional space). is there.

  The image processing unit 230 includes a blood vessel region specifying unit 231 and a blood flow information generating unit 232. The blood flow information generation unit 232 includes an inclination calculation unit 233, a blood flow velocity calculation unit 234, a blood vessel diameter calculation unit 235, and a blood flow rate calculation unit 236. Further, the image processing unit 230 has a cross-section setting unit 237. Hereinafter, each of these units 231 to 237 will be described.

(Vessel region specific part)
The blood vessel region specifying unit 231 specifies a blood vessel region corresponding to the target blood vessel Db for each of the first tomographic image, the second tomographic image, and the phase image. This processing can be performed by analyzing the pixel value of each image (for example, threshold processing).

  It should be noted that the first tomogram and the second tomogram have sufficient resolution to perform analysis processing, but the phase image may not have enough resolution to identify the boundary of the blood vessel region. However, as long as blood flow information is generated based on the phase image, it is necessary to specify the blood vessel region with high accuracy and high accuracy. Therefore, for example, it is desirable to specify the blood vessel region of the phase image more accurately by performing the following processing.

  As described above, the first tomographic image and the phase image are formed based on the same detection signal, and the correspondence between the pixels can be made. Using this, first, the first tomogram is analyzed to obtain a blood vessel region, and an image region in a phase image composed of pixels corresponding to the pixels included in this blood vessel region is set as the blood vessel region. Thereby, the blood vessel region of the phase image can be specified with high accuracy and high accuracy.

(Blood flow information generator)
The blood flow information generation unit 232 determines the blood flow related to the target blood vessel Db based on the distance between the first cross section and the second cross section, the result of specifying the blood vessel region, and the time-series change of the phase difference in the blood vessel region of the phase image. Generate information. Here, the distance between the first cross section and the second cross section (inter-section distance) is determined in advance. One example will be described later in the description of the cross-section setting unit 237. The blood vessel region is obtained by the blood vessel region specifying unit 231. The time series change of the phase difference in the blood vessel region of the phase image is obtained as the time series change of the phase difference for the pixels in the blood vessel region of the phase image. Hereinafter, an example of a configuration for executing this process will be described. As described above, the blood flow information generation unit 232 includes the inclination calculation unit 233, the blood flow velocity calculation unit 234, the blood vessel diameter calculation unit 235, and the blood flow rate calculation unit 236.

(Inclination calculator)
The inclination calculation unit 233 calculates the inclination of the target blood vessel Db in the first cross section based on the distance between cross sections and the result of specifying the blood vessel region. First, the reason for calculating the inclination of the target blood vessel Db will be described. Blood flow information is obtained by the Doppler OCT technique (see Patent Documents 8 and 9). The blood flow velocity component contributing to the Doppler shift is a component in the irradiation direction of the signal light LS. Therefore, even if the blood flow velocity is the same, the Doppler shift received by the signal light LS changes according to the angle formed by the blood flow direction (that is, the direction of the blood vessel Db of interest) and the signal light LS, and thus blood obtained Flow information will also change. In order to avoid such inconvenience, it is necessary to obtain the inclination of the target blood vessel Db and reflect this in the blood flow velocity calculation process.

  A method of calculating the inclination of the target blood vessel Db will be described with reference to FIG. Reference numerals G0, G1, and G2 respectively indicate a first tomogram in the first section C0, a second tomogram in the second section, and a second tomogram in the second section C2. Reference numerals V0, V1, and V2 denote a blood vessel region of the first tomographic image G0, a blood vessel region of the second tomographic image G1, and a blood vessel region of the second tomographic image G2, respectively. In FIG. 6, the z coordinate axis is directed downward in the drawing, and this substantially coincides with the irradiation direction of the signal light LS. Also, let d be the interval between adjacent tomographic images.

  The inclination calculation unit 233 calculates the inclination A of the target blood vessel Db in the first cross section C0 based on the positional relationship between the three blood vessel regions V0, V1, and V2. This positional relationship is obtained, for example, by connecting three blood vessel regions V0, V1, and V2. More specifically, the inclination calculation unit 233 identifies the feature positions of the three blood vessel regions V0, V1, and V2, and connects these feature positions. Examples of the characteristic position include a center position, a center of gravity position, an uppermost portion (a position having the smallest z coordinate value), and a lowermost portion (a position having the largest z coordinate value). In addition, as a method of connecting these feature positions, there are a method of connecting with a line segment, a method of connecting with an approximate curve (spline curve, Bezier curve, etc.), and the like.

  Further, the inclination calculation unit 233 calculates the inclination A based on a line connecting these feature positions. When connected by line segments, for example, the slope of the first line segment connecting the feature position of the first cross section C0 and the feature position of the second cross section C1, the feature position of the first cross section C0, and the feature position of the second cross section C2 The slope A is calculated based on the slope of the second line segment connecting the two. As an example of this calculation process, the average value of the slopes of two line segments can be obtained. Further, as an example of connecting with an approximate curve, the slope of the approximate curve at the intersection position of the approximate curve and the first cross section C0 can be obtained. Note that the cross-sectional distance d is used when embedding the tomographic images G0 to G2 in the xyz coordinate system in the process of obtaining line segments and approximate curves.

  In this example, the blood vessel region in the three cross sections is considered, but it is also possible to obtain the inclination in consideration of the two cross sections. As a specific example, the inclination of the first line segment or the second line segment can be set as a target inclination. In this example, one inclination is obtained, but the inclination may be obtained for each of two or more positions (or areas) in the blood vessel region V0. In this case, two or more obtained slope values can be used separately, or one value (for example, an average value) statistically obtained from these slope values can be used as the slope A.

(Blood velocity calculation part)
The blood flow velocity calculation unit 234 calculates the blood flow velocity in the first cross section C0 of the blood flowing in the blood vessel Db based on the time series change of the phase difference obtained as the phase image. This calculation target may be a blood flow velocity at a certain point in time, or a time-series change (blood flow velocity change information) of this blood flow velocity. In the former case, for example, it is possible to selectively acquire the blood flow velocity in a predetermined time phase (for example, R wave time phase) of the electrocardiogram. The time range in the latter is the entire time or a part of the time when the first cross section C0 is scanned.

  When the blood flow velocity change information is obtained, the blood flow velocity calculator 234 can calculate a statistical value of the blood flow velocity in the time range. The statistical values include an average value, standard deviation, variance, median value, maximum value, minimum value, maximum value, minimum value, and the like. It is also possible to create a histogram for blood flow velocity values.

  The blood flow velocity calculation unit 234 calculates the blood flow velocity using the Doppler OCT method as described above. At this time, the inclination A of the target blood vessel Db in the first cross section C0 calculated by the inclination calculation unit 233 is considered. Specifically, the inclination calculation unit 233 uses the following equation.

here:
Δf represents the Doppler shift received by the scattered light of the signal light LS;
n represents the refractive index of the medium;
v represents the flow velocity (blood flow velocity) of the medium;
θ represents the angle formed by the irradiation direction of the signal light LS and the flow vector of the medium;
λ represents the center wavelength of the signal light LS.

  In this embodiment, n and λ are known, Δf is obtained from a time-series change in phase difference, and θ is obtained from slope A (or θ is obtained as slope A). By substituting these values into the above formula, the blood flow velocity v is calculated.

(Vessel diameter calculator)
The blood vessel diameter calculation unit 235 calculates the diameter of the target blood vessel Db in the first cross section C0. Examples of this calculation method include a first calculation method using a fundus image and a second calculation method using a tomographic image.

  When the first calculation method is applied, imaging of a part of the fundus oculi Ef including the position of the first cross section C0 is performed in advance. The fundus image obtained thereby may be an observation image (frame) or a captured image. When the captured image is a color image, an image constituting the captured image (for example, a red free image) may be used.

  The blood vessel diameter calculation unit 235 determines the relationship between the scale on the image and the scale in the real space, such as the shooting angle of view (shooting magnification), working distance, and information on the eyeball optical system. Set the scale. This scale represents the length in real space. As a specific example, this scale associates an interval between adjacent pixels with a scale in real space (for example, an interval between pixels = 10 μm). It is also possible to calculate in advance the relationship between various values of the above factor and the scale in the real space, and store information expressing this relationship in a table format or a graph format. In this case, the blood vessel diameter calculation unit 235 selectively applies a scale corresponding to the factor.

  Furthermore, the blood vessel diameter calculation unit 235 calculates the diameter of the target blood vessel Db in the first cross section C0, that is, the diameter of the blood vessel region V0, based on this scale and the pixels included in the blood vessel region V0. As a specific example, the blood vessel diameter calculation unit 235 obtains the maximum value and the average value of the diameters of the blood vessel region V0 in various directions. In addition, the blood vessel region 235 can approximate the outline of the blood vessel region V0 in a circle or an ellipse, and obtain the diameter of the circle or the ellipse. If the blood vessel diameter is determined, the area of the blood vessel region V0 can be (substantially) determined (that is, the two can be substantially associated one-to-one). You may make it calculate.

  A second calculation method will be described. In the second calculation method, a tomographic image of the fundus oculi Ef in the first cross section C0 is used. This tomographic image may be a first tomographic image or may be obtained separately.

  The scale in this tomographic image is determined according to the scanning mode of the signal light LS. In this embodiment, the first cross section C0 is scanned as shown in FIG. The length of the first cross section is determined based on various factors that determine the relationship between the scale on the image and the scale in the real space, such as working distance and information on the eyeball optical system. For example, the blood vessel diameter calculation unit 235 obtains the interval between adjacent pixels based on this length, and calculates the diameter of the blood vessel Db of interest in the first cross section C0 in the same manner as in the first calculation method.

(Blood flow calculation unit)
The blood flow rate calculation unit 236 calculates the flow rate of the blood flowing in the target blood vessel Db based on the blood flow velocity calculation result and the blood vessel diameter calculation result. An example of this process will be described below.

  It is assumed that the blood flow in the blood vessel is a Hagen-Poiseille flow. Further, when the blood vessel diameter is w and the maximum value of the blood flow velocity is Vm, the blood flow rate Q is expressed by the following equation.

  The blood flow rate calculation unit 236 substitutes the calculation result w of the blood vessel diameter by the blood vessel diameter calculation unit 235 and the maximum value Vm based on the calculation result of the blood flow velocity by the blood flow velocity calculation unit 234 into this equation. A target blood flow rate Q is calculated.

(Cross section setting part)
The main control unit 211 displays a fundus image on the display unit 240A. This fundus image may be an observation image or a captured image. Further, the fundus image may be an image constituting a captured image. The user operates the operation unit 240B to designate the first cross section C0 for the displayed fundus image. The cross section setting unit 237 sets the second cross sections C1 and C2 based on the designated first cross section C0 and the fundus image. As described above, the first cross section CO is designated so as to cross the desired blood vessel Db.

  The operation of designating the first cross section C0 as a fundus image is performed using, for example, a pointing device. When the display unit 240A is a touch panel, the user designates the first cross section C0 by touching a desired position of the displayed fundus image. In this case, the parameters (direction, length, etc.) of the first cross section C0 are set manually or automatically.

  As an example of manual operation, a predetermined interface for setting parameters can be used. This interface may be hardware such as a switch or software such as a graphical user interface (GUI).

  As an example of an automatic case, the cross-section setting unit 237 sets parameters based on the position designated by the user for the fundus image. For the automatic length setting, a predetermined value may be applied, or the designated position and the position of a blood vessel in the vicinity thereof may be considered. The former value is designated based on, for example, a general distance between a predetermined blood vessel of interest and a blood vessel in the vicinity thereof. This distance information can be generated based on clinical data. The same applies to the latter case. In any case, the length of the first cross section C0 is set so as to cross the target blood vessel Db and not cross the other blood vessels (particularly thick blood vessels).

  For automatic setting of the orientation of the first cross section C0, a predetermined orientation may be applied, or the orientation of the target blood vessel Db may be taken into account. In the former case, information indicating the inclination of each position of a predetermined blood vessel of interest is generated in advance and is referred to. This information can be generated based on clinical data. In the latter case, the traveling direction of the target blood vessel Db at the designated position is obtained and set based on the traveling direction. The process for obtaining the traveling direction is performed using, for example, a thinning process for the blood vessel Db of interest. In any case, it is desirable that the direction of the first cross section C0 is set to be orthogonal to the traveling direction.

  Next, processing for setting the second cross sections C1 and C2 will be described. The cross-section setting unit 237 sets the second cross-sections C1 and C2 at positions separated from the first cross-section C0 by a predetermined distance. This distance is set to 100 μm, for example. This distance is specified as described above, for example. Further, the length and / or orientation of the second cross sections C1 and C2 are set in the same manner as in the case of the first cross section C0.

  In this embodiment, the cross sections C0 to C2 (that is, the scanning position of the signal light LS) are set based on the fundus image. For this purpose, it is necessary to associate the fundus image with the scanning position. As for this association, as in this embodiment, it is desirable that the fundus imaging optical system and the OCT measurement optical system share a part of each other's optical path. With this coaxial configuration, the position in the fundus image and the scanning position can be associated with each other based on the optical axis. In this association, fundus image display magnification (including at least one of so-called optical zoom and digital zoom) may be taken into consideration.

  In the case of such a coaxial configuration, the fundus image and the scanning position can be associated based on the fundus image and the projection image obtained by OCT measurement. Note that the projection image is an image representing the form of the surface of the fundus oculi Ef obtained by integrating three-dimensional images obtained by a three-dimensional scan described later in the depth direction (z direction). By using such a projection image, the position between the fundus image and the projection image can be associated using, for example, image correlation, and the fundus image and the scanning position can be associated using this association. However, in consideration of the influence of eye movement (fixed eye movement, etc.) of the eye E, it is considered that a coaxial configuration capable of performing both imaging substantially without time lag is desirable.

  The image processing unit 230 that functions as described above includes, for example, the aforementioned microprocessor, RAM, ROM, hard disk drive, circuit board, and the like. In a storage device such as a hard disk drive, a computer program for causing the microprocessor to execute the above functions is stored in advance.

(User interface)
The user interface 240 includes a display unit 240A and an operation unit 240B. The display unit 240A includes the display device of the arithmetic control unit 200 and the display device 3 described above. The operation unit 240B includes the operation device of the arithmetic control unit 200 described above. The operation unit 240B may include various buttons and keys provided on the housing of the fundus oculi observation device 1 or outside. For example, when the fundus camera unit 2 has a housing similar to that of a conventional fundus camera, the operation unit 240B may include a joystick, an operation panel, or the like provided on the housing. The display unit 240 </ b> A may include various display devices such as a touch panel provided on the housing of the fundus camera unit 2.

  The display unit 240A and the operation unit 240B do not need to be configured as individual devices. For example, a device in which a display function and an operation function are integrated, such as a touch panel, can be used. In that case, the operation unit 240B includes the touch panel and a computer program. The operation content for the operation unit 240B is input to the control unit 210 as an electrical signal. Further, operations and information input may be performed using the GUI displayed on the display unit 240A and the operation unit 240B.

[Scanning signal light and OCT images]
Here, the scanning of the signal light LS and the OCT image will be described.

  Examples of scanning modes of the signal light LS by the fundus oculi observation device 1 include horizontal scanning, vertical scanning, cross scanning, radiation scanning, circular scanning, concentric scanning, and spiral (vortex) scanning. These scanning modes are selectively used as appropriate in consideration of the observation site of the fundus, the analysis target (such as retinal thickness), the time required for scanning, the precision of scanning, and the like.

  The horizontal scan scans the signal light LS in the horizontal direction (x direction). The horizontal scan also includes an aspect in which the signal light LS is scanned along a plurality of horizontal scanning lines arranged in the vertical direction (y direction). In this aspect, it is possible to arbitrarily set the scanning line interval. Further, the above-described three-dimensional image can be formed by sufficiently narrowing the interval between adjacent scanning lines (three-dimensional scanning). The same applies to the vertical scan.

  In the cross scan, the signal light LS is scanned along a cross-shaped trajectory composed of two linear trajectories (straight trajectories) orthogonal to each other. In the radiation scan, the signal light LS is scanned along a radial trajectory composed of a plurality of linear trajectories arranged at a predetermined angle. The cross scan is an example of a radiation scan.

  In the circle scan, the signal light LS is scanned along a circular locus. In the concentric scan, the signal light LS is scanned along a plurality of circular trajectories arranged concentrically around a predetermined center position. A circle scan is an example of a concentric scan. In the spiral scan, the signal light LS is scanned along a spiral (spiral) locus while the radius of rotation is gradually reduced (or increased).

  Since the galvano scanner 42 is configured to scan the signal light LS in directions orthogonal to each other, it can independently scan the signal light LS in the x direction and the y direction, respectively. Further, by simultaneously controlling the directions of the two galvanometer mirrors included in the galvano scanner 42, the signal light LS can be scanned along an arbitrary locus on the xy plane. Thereby, various scanning modes as described above can be realized.

  By scanning the signal light LS in the above-described manner, a tomographic image on a plane stretched by the direction along the scanning line (scanning trajectory) and the fundus depth direction (z direction) can be acquired. In addition, the above-described three-dimensional image can be acquired particularly when the scanning line interval is narrow.

  A region on the fundus oculi Ef to be scanned with the signal light LS as described above, that is, a region on the fundus oculi Ef to be subjected to OCT measurement is referred to as a scanning region. The scanning area in the three-dimensional scan is a rectangular area in which a plurality of horizontal scans are arranged. The scanning area in the concentric scan is a disk-shaped area surrounded by the locus of the circular scan with the maximum diameter. In addition, the scanning area in the radial scan is a disk-shaped (or polygonal) area connecting both end positions of each scan line.

[Operation]
The operation of the fundus oculi observation device 1 will be described. FIG. 7 illustrates an example of the operation of the fundus oculi observation device 1.

(S1: Preparation for measurement)
As preparation for OCT measurement, input of a patient ID, selection designation of an operation mode (blood flow measurement mode) of the present embodiment, and the like are performed.

(S2: alignment, focusing)
Next, a near-infrared moving image (observation image) of the fundus oculi Ef is acquired by continuously illuminating the fundus oculi Ef with illumination light from the observation light source 11. The main control unit 211 displays this observation image on the display unit 240A.

  At this time, a fixation target by the LCD 39, an alignment index by the alignment optical system 50, and a split index by the focus optical system 60 are projected onto the eye E. Thereby, the alignment index and the split index are drawn on the displayed observation image. These indices are used for alignment and focusing. In this embodiment, a fixation target for observing the optic disc is used. Here, tracking for the optic nerve head may be started.

(S3: Designation of measurement position)
Subsequently, the user designates a position where blood flow is measured with respect to the displayed fundus image. The first section is designated here. Note that the fundus image may be an observation image or a captured image (including an image constituting the fundus image). The method for specifying the first cross section has been described above.

(S4: Setting of cross section near measurement position)
When the first cross section is designated, the cross section setting unit 237 sets the second cross section based on the first cross section.

(S5: Confirmation of OCT image)
The main control unit 211 performs OCT measurement by controlling the light source unit 101, the galvano scanner 42, and the like. This OCT measurement may be performed on the first cross section, the second cross section, or any other cross section. With reference to this OCT image, it is confirmed whether a suitable image is obtained. This confirmation may be performed visually by the user, or may be automatically performed by the fundus oculi observation device 1.

  When performing visually, the main control part 211 displays this OCT image on the display part 240A. The user evaluates the display position and image quality of the OCT image in the frame, and inputs the confirmation result using the operation unit 240B. When a suitable image is not obtained, measurement conditions are adjusted. When the image display position is not appropriate, the optical path length changing unit 41 changes the optical path length of the signal light LS. If the image quality is not appropriate, the optical attenuator 105 and the polarization adjuster 106 are adjusted.

  When performing automatically, the display position and image quality of an image are evaluated with reference to a predetermined evaluation standard, and the measurement conditions are adjusted based on the evaluation result in the same manner as in the manual case.

(S6: Start of blood flow measurement)
Blood flow measurement is started in response to a predetermined trigger.

(S7: Execution of OCT measurement)
In blood flow measurement, first, a first tomographic image, a second tomographic image, and a phase image are formed by performing OCT measurement on the first cross section and the second cross section.

(S8: Identification of blood vessel region)
The blood vessel region specifying unit 231 specifies a blood vessel region for each of the first tomographic image, the second tomographic image, and the phase image.

(S9: Calculation of inclination of target blood vessel)
The inclination calculation unit 233 calculates the inclination of the target blood vessel in the first cross section based on the distance between cross sections and the result of specifying the blood vessel region.

(S10: Calculation of blood flow velocity)
The blood flow velocity calculation unit 234 calculates the blood flow velocity in the first cross section of the blood flowing in the blood vessel of interest based on the time series change of the phase difference obtained as the phase image and the inclination of the blood vessel of interest.

(S11: Calculation of blood vessel diameter)
The blood vessel diameter calculator 235 calculates the diameter of the target blood vessel in the first cross section based on the fundus image or the tomographic image (first tomographic image or the like).

(S12: Calculation of blood flow)
The blood flow rate calculation unit 236 calculates the flow rate of the blood flowing in the target blood vessel based on the blood flow velocity calculation result and the blood vessel diameter calculation result.

(S13: Display and storage of measurement results)
The main control unit 211 causes the display unit 240A to display blood flow information including a blood flow velocity calculation result, a blood flow volume calculation result, and the like. In addition, the main control unit 211 stores blood flow information in the storage unit 212 in association with the patient ID. This is the end of the processing related to blood flow measurement in this embodiment.

[effect]
The effect of the fundus oculi observation device 1 will be described.

  The fundus oculi observation device 1 includes an optical system for OCT measurement, a galvano scanner 42, an image forming unit 220, a blood vessel region specifying unit 231, and a blood flow information generating unit 232.

  The optical system for OCT measurement divides the light from the light source unit 101 into the signal light LS and the reference light LR, and the interference light LC between the scattered light of the signal light LS by the fundus oculi Ef and the reference light LR via the reference light path. Is detected.

  The galvano scanner 42 performs the first scan. In the first scan, the first cross section intersecting the target blood vessel of the fundus oculi Ef is repeatedly scanned with the signal light LS.

  The image forming unit 220 forms a first tomographic image and a phase image. The first tomographic image is an image representing a time-series change in the form in the first cross section, and is formed based on the detection result of the interference light LC obtained by the optical system in the first scanning. The phase image is an image representing a time-series change of the phase difference in the first cross section, and is formed based on the detection result of the interference light LC obtained by the optical system in the first scan.

  The blood vessel region specifying unit 231 specifies a blood vessel region corresponding to the target blood vessel for each of the first tomographic image and the phase image.

  The blood flow information generation unit 232 generates blood flow information related to the target blood vessel based on the time-series change of the phase difference between the blood vessel region of the first tomogram and the blood vessel region of the phase image. The above is the basic operation of this embodiment.

  The galvano scanner 42 may perform the second scan in addition to the first scan. In the second scan, the second cross section that intersects the target blood vessel and is located in the vicinity of the first cross section is scanned with the signal light LS. In this case, the image forming unit 220 forms a second tomographic image in addition to the first tomographic image and the phase image. The second tomographic image is an image representing the form in the second cross section, and is formed based on the detection result of the interference light LC obtained by the optical system in the second scanning. Furthermore, the blood vessel region specifying unit 231 also specifies a blood vessel region corresponding to the blood vessel of interest for this second tomographic image. The blood flow information generation unit 232 changes the distance between the first cross section and the second cross section, the blood vessel region of the first tomographic image, the blood vessel region of the second tomographic image, and the phase difference represented by the phase image over time. Based on the above, blood flow information is generated.

  The blood flow information generation unit 232 may be configured as follows: (1) the distance between the first cross section and the second cross section, the blood vessel region of the first tomogram, and the second tomogram An inclination calculating unit 233 for calculating the inclination of the target blood vessel in the first cross section based on the blood vessel region; (2) generating blood flow information based on the calculation result of the inclination and the time-series change of the phase difference. .

  The second cross section may include an upstream cross section and a downstream cross section of the target blood vessel with respect to the first cross section.

  The inclination calculation unit 233 may be configured to calculate the inclination of the target blood vessel in the first cross section based on the position of the blood vessel region in the first tomographic image and the position of the blood vessel region in the second tomographic image.

  The blood flow information generation unit 232 calculates the blood flow velocity in the first cross section of the blood flowing in the blood vessel of interest based on the calculation result of the inclination of the blood vessel of interest by the inclination calculation unit 233 and the time-series change of the phase difference. A blood flow velocity calculation unit 234 may be included.

  The blood flow velocity calculation unit 234 may be configured to generate blood flow velocity change information representing a time-series change in blood flow velocity based on a time-series change in phase difference.

  The blood flow velocity calculation unit 234 may be configured to calculate a statistical value of the blood flow velocity based on the blood flow velocity change information.

  The fundus camera unit 2 photographs a part of the fundus oculi Ef including the position of the first cross section. In this case, the blood vessel diameter calculation unit 235 and the blood flow rate calculation unit 236 of the blood flow information generation unit 232 function as follows. That is, the blood vessel diameter calculation unit 235 calculates the diameter of the target blood vessel in the first cross section based on the image captured by the fundus camera unit 2. In addition, the blood flow rate calculation unit 236 calculates the flow rate of blood flowing in the target blood vessel based on the blood flow velocity change information and the diameter calculation result.

  Instead, the blood flow rate calculation unit 235 calculates the diameter of the blood vessel of interest in the first cross section based on the first tomogram, and the blood flow rate calculation unit 236 calculates the blood flow rate change information and the diameter calculation result. Based on the above, the flow rate of the blood flowing in the blood vessel of interest may be calculated.

  The blood vessel region specifying unit 231 analyzes the first tomographic image to specify the blood vessel region, specifies the image region of the phase image corresponding to the position of the blood vessel region in the first tomographic image, and uses this as the blood vessel region of the phase image. It may be configured to set.

  The first scan can be configured to occur during at least one cardiac cycle of the patient. In particular, when the above [Equation 2] is used in the calculation of the blood flow, the maximum value of the blood flow velocity obtained during one cardiac cycle is used.

  The first cross section and the second cross section can be set in the vicinity of the optic disc on the fundus. In blood flow measurement using a conventional laser Doppler, due to its characteristics, the blood vessel of interest is measured at a position away from the optic nerve head by the diameter of the nipple (more than the distance). However, when OCT is used as in this embodiment, measurement can be performed at a position closer to the optic nerve head. Thereby, it is considered that measurement with higher accuracy and higher accuracy becomes possible.

  The fundus oculi observation device 1 according to such an embodiment is configured to perform blood flow measurement using the first tomographic image having the same cross section as the phase image and the time-series change of the phase difference. Accurate blood flow measurement can be realized.

  The fundus oculi observation device 1 has the following characteristics. That is, the fundus oculi observation device 1 includes an OCT measurement optical system, a galvano scanner 42, an image forming unit 220, a fundus camera unit 2, a blood vessel region specifying unit 231, a blood flow velocity calculating unit 234, and a blood vessel diameter. A calculation unit 235 and a blood flow rate calculation unit 236 are included.

  The optical system for OCT measurement divides the light from the light source unit 101 into the signal light LS and the reference light LR, and the interference light LC between the scattered light of the signal light LS by the fundus oculi Ef and the reference light LR via the reference light path. Is detected.

  The galvano scanner 42 performs a first scan and a second scan. In the first scan, the first cross section intersecting the target blood vessel of the fundus oculi Ef is repeatedly scanned with the signal light LS. In the second scan, the second cross section that intersects the target blood vessel and is located near the first cross section is scanned with the signal light LS.

  The image forming unit 220 forms a first tomographic image, a phase image, and a second tomographic image. The first tomographic image is an image representing a time-series change in the form in the first cross section, and is formed based on the detection result of the interference light LC obtained by the optical system in the first scanning. The phase image is an image representing a time-series change of the phase difference in the first cross section, and is formed based on the detection result of the interference light LC obtained by the optical system in the first scan. The second tomographic image is an image representing the form in the second cross section, and is formed based on the detection result of the interference light LC obtained by the optical system in the second scanning.

  The fundus camera unit 2 photographs a part of the fundus oculi Ef including the position of the first cross section.

  The blood vessel region specifying unit 231 specifies a blood vessel region corresponding to the target blood vessel for each of the first tomographic image, the phase image, and the second tomographic image.

  The blood flow velocity calculation unit 234 calculates the blood flow velocity in the first cross section of the blood flowing in the blood vessel of interest based on the time-series change of the phase difference and the result of specifying the blood vessel region (the inclination of the blood vessel of interest obtained from the blood vessel region). Is calculated.

  The blood vessel diameter calculation unit 235 calculates the diameter of the blood vessel of interest in the first cross section based on the captured image of the fundus oculi Ef by the fundus camera unit 2.

  The blood flow rate calculation unit 236 calculates the flow rate of the blood flowing in the target blood vessel based on the blood flow velocity calculation result and the blood vessel diameter calculation result. The above is the basic operation of this embodiment.

  The first scan can be configured to occur during at least one cardiac cycle of the patient. In particular, when the above [Equation 2] is used in the calculation of the blood flow, the maximum value of the blood flow velocity obtained during one cardiac cycle is used.

  The first cross section and the second cross section can be set in the vicinity of the optic disc on the fundus. In blood flow measurement using a conventional laser Doppler, due to its characteristics, the blood vessel of interest is measured at a position away from the optic nerve head by the diameter of the nipple (more than the distance). However, when OCT is used as in this embodiment, measurement can be performed at a position closer to the optic nerve head. Thereby, it is considered that measurement with higher accuracy and higher accuracy becomes possible.

  The photographing optical system 30 of the fundus camera unit 2 shares a part of the optical path with the OCT measurement optical system. An image captured by the fundus camera unit 2 is displayed on the display unit 240A. When the user uses the operation unit 240B to specify the first cross section for the displayed captured image, the cross section setting unit 237 sets the second cross section based on the specified first cross section and the captured image. The galvano scanner 42 performs the first scan on the designated first cross section, and performs the second scan on the set second cross section.

  According to the fundus oculi observation device 1 according to such an embodiment, blood flow measurement can be performed using the first tomographic image having the same cross section as the phase image and the time-series change of the phase difference. Further, the fundus oculi observation device 1 calculates the blood flow velocity based on the time-series change of the phase difference and the result of specifying the blood vessel region, calculates the diameter of the target blood vessel based on the captured image, and calculates the blood flow velocity. The blood flow rate is calculated based on the calculation result of the blood vessel diameter. Therefore, it is possible to realize blood flow measurement with high accuracy.

[Modification]
The configuration described above is merely an example for favorably implementing the present invention. Therefore, arbitrary modifications (omitted, replacement, addition, etc.) within the scope of the present invention can be made as appropriate.

  A modified example of the blood flow calculation method will be described. In this modification, the blood flow velocity calculation unit 234 generates information (blood flow velocity change information) that represents a time-series change in blood flow velocity for each pixel included in the blood vessel region of the phase image. In this process, for example, a process of associating a plurality of phase image pixels along the time series for each pixel position, and generating blood flow velocity change information based on the plurality of pixels along the time series corresponding to each pixel position. And processing to be performed. By this processing, the blood flow velocity in the blood vessel region of the first cross section can be obtained for each position.

  The blood flow rate calculation unit 236 calculates the blood flow rate for each pixel by integrating the blood flow rate change information of each pixel included in the blood vessel region along a time series. By this process, the blood flow rate in the blood vessel region of the first cross section can be obtained for each position.

  Furthermore, the blood flow rate calculation unit 236 calculates the flow rate of blood flowing through the target blood vessel by adding the blood flow rates for these pixels. By this process, the blood flow volume at each position obtained in the previous process is added, and the total amount of blood flowing through the blood vessel region of the first cross section is obtained.

  In the above embodiment, the optical path length difference between the optical path of the signal light LS and the optical path of the reference light LR is changed by changing the position of the optical path length changing unit 41, but this optical path length difference is changed. The method is not limited to this. For example, it is possible to change the optical path length difference by disposing a reflection mirror (reference mirror) in the optical path of the reference light and moving the reference mirror in the traveling direction of the reference light to change the optical path length of the reference light. Is possible. Further, the optical path length difference may be changed by moving the fundus camera unit 2 or the OCT unit 100 with respect to the eye E to change the optical path length of the signal light LS. In particular, when the measured object is not a living body part, the optical path length difference can be changed by moving the measured object in the depth direction (z direction).

  A computer program for realizing the above embodiment can be stored in any recording medium readable by a computer. Examples of the recording medium include a semiconductor memory, an optical disk, a magneto-optical disk (CD-ROM / DVD-RAM / DVD-ROM / MO, etc.), a magnetic storage medium (hard disk / floppy (registered trademark) disk / ZIP, etc.), and the like. Can be used.

  It is also possible to transmit / receive this program through a network such as the Internet or a LAN.

1 Fundus observation device (optical image measurement device)
2 fundus camera unit 10 illumination optical system 30 photographing optical system 31 focusing lens 31A focusing drive unit 41 optical path length changing unit 42 galvano scanner 50 alignment optical system 60 focus optical system 100 OCT unit 101 light source unit 105 optical attenuator 106 polarization Adjuster 115 CCD image sensor 200 Arithmetic control unit 210 Control unit 211 Main control unit 212 Storage unit 220 Image forming unit 221 Tomographic image forming unit 222 Phase image forming unit 230 Image processing unit 231 Blood vessel region specifying unit 232 Blood flow information generating unit 233 Inclination calculator 234 Blood flow velocity calculator 235 Blood vessel diameter calculator 236 Blood flow rate calculator 237 Cross-section setting unit 240A Display unit 240B Operation unit E Eye to be examined Ef Fundus LS Signal light LR Reference light LC Interference light

Claims (7)

A tomographic image representing a time-series change in morphology in the cross-section and a phase image representing a time-series change in phase difference, which are formed by performing optical coherence tomography (OCT) on a cross-section intersecting a target blood vessel of a living body And an acquisition unit for acquiring
For each of the tomographic image and the phase image, a blood vessel region specifying unit that specifies a blood vessel region corresponding to the blood vessel of interest;
A blood flow information generation device including: a blood flow information generation unit that generates blood flow information related to the blood vessel of interest based on a time-series change in phase difference between the blood vessel region of the tomographic image and the blood vessel region of the phase image . An acquisition unit that acquires data obtained by performing optical coherence tomography (OCT) on a cross section that intersects a target blood vessel of a living body;
Based on the data acquired by the acquisition unit, an image forming unit that forms a tomographic image representing a time-series change in form in the cross section and a phase image representing a time-series change in phase difference;
For each of the tomographic image and the phase image, a blood vessel region specifying unit that specifies a blood vessel region corresponding to the blood vessel of interest;
A blood flow information generation device including: a blood flow information generation unit that generates blood flow information related to the blood vessel of interest based on a time-series change in phase difference between the blood vessel region of the tomographic image and the blood vessel region of the phase image . The blood vessel region specifying unit analyzes the tomographic image to specify the blood vessel region, specifies an image region of the phase image corresponding to a position of the blood vessel region in the tomographic image, and determines the image region as the phase image. The blood flow information generation device according to claim 1, wherein the blood flow region is the blood vessel region. A method for generating blood flow information of a living body,
A tomographic image representing a time-series change in morphology in the cross-section and a phase image representing a time-series change in phase difference, which are formed by performing optical coherence tomography (OCT) on a cross-section intersecting a target blood vessel of a living body And get the
For each of the tomographic image and the phase image, specify a blood vessel region corresponding to the blood vessel of interest,
A blood flow information generation method for generating blood flow information related to the blood vessel of interest based on a time-series change in phase difference between the blood vessel region of the tomographic image and the blood vessel region of the phase image. A method for generating blood flow information of a living body,
Acquire data obtained by performing optical coherence tomography (OCT) on a cross section intersecting the target blood vessel of the living body,
Based on the acquired data, obtain a tomographic image representing a time-series change in morphology in the cross section and a phase image representing a time-series change in phase difference,
For each of the tomographic image and the phase image, specify a blood vessel region corresponding to the blood vessel of interest,
A blood flow information generation method for generating blood flow information related to the blood vessel of interest based on a time-series change in phase difference between the blood vessel region of the tomographic image and the blood vessel region of the phase image. A computer for processing images formed using optical coherence tomography (OCT);
An acquisition unit that acquires a tomographic image representing a time-series change in morphology and a phase image representing a time-series change in phase difference formed by executing OCT on a cross-section intersecting a target blood vessel of a living body ,
For each of the tomographic image and the phase image, a blood vessel region specifying unit that specifies a blood vessel region corresponding to the blood vessel of interest, and
A program that functions as a blood flow information generation unit that generates blood flow information related to the blood vessel of interest based on a time-series change in phase difference between the blood vessel region of the tomographic image and the blood vessel region of the phase image. A computer for processing images formed using optical coherence tomography (OCT);
An acquisition unit for acquiring data obtained by executing OCT on a cross section intersecting a target blood vessel of a living body;
Based on the data acquired by the acquisition unit, an image forming unit that forms a tomographic image representing a time-series change in form in the cross section and a phase image representing a time-series change in phase difference,
For each of the tomographic image and the phase image, a blood vessel region specifying unit that specifies a blood vessel region corresponding to the blood vessel of interest, and
A program that functions as a blood flow information generation unit that generates blood flow information related to the blood vessel of interest based on a time-series change in phase difference between the blood vessel region of the tomographic image and the blood vessel region of the phase image.

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