JP6776313B2 - Blood flow measuring device - Google Patents

Description

The present invention relates to a blood flow measuring device.

Optical Coherence Tomography (OCT) is used not only to measure the morphology of an object, but also to measure its function. For example, a device for measuring blood flow in a living body using OCT is known. Blood flow measurement using OCT is applied to blood vessels in the fundus and the like.

Japanese Unexamined Patent Publication No. 2013-184018 JP-A-2009-165710 Special Table 2010-523286

In blood flow measurement, a phase image showing the time course of the phase difference in this cross section is formed from the data collected by repeatedly scanning the cross section intersecting the blood vessel. To obtain a suitable phase image, the intervals between scanning points (A scans) for scanning the cross section are sufficiently close and the scanning repetition rate is sufficiently fast (for example, in one heartbeat). Sampling intervals should be close enough).

Such dense, fast scans limit the width of the cross section. Therefore, it is difficult to measure the blood flow of multiple blood vessels with a single scan (especially, it is difficult to measure the blood flow of a wide range of blood vessels with a single scan). For example, in the measurement of blood flow in the fundus, it is practically impossible to increase the width of the cross section because the amount of light applicable to the eye to be examined is limited, and such a problem becomes remarkable.

However, there is a desire to measure blood flow in multiple blood vessels (distributed over a wide area). For example, in order to grasp the overall blood flow state in the fundus, it may be desired to measure the blood flow of a plurality of blood vessels distributed around the optic nerve head. In such cases, it is possible to repeatedly perform a circle scan around the optic nerve head, but considering the length of the circle scan path (scan width), the dense scan point spacing and high repeat rate It is difficult to achieve both.

An object of the present invention is to provide a technique capable of suitably performing blood flow measurement of a plurality of blood vessels.

The blood flow measuring device of the embodiment has an image acquisition unit that acquires a frontal image or a three-dimensional image of the fundus of a living body, and an image region identification that identifies a plurality of blood vessel regions by analyzing the frontal image or the three-dimensional image. A unit, a measurement position setting unit that sets a plurality of measurement positions intersecting the plurality of blood vessel regions, and a scanning unit that scans a plurality of cross sections of the fundus corresponding to the plurality of measurement positions using optical coherence stromography. And a blood flow information generation unit that generates blood flow information regarding the fundus of the eye based on the data acquired by the scanning. The blood flow information generation unit obtains an angle formed by a blood vessel of interest in the plurality of blood vessel regions and a measurement position intersecting the blood vessel of interest , and applies a trigonometry using the obtained angle to obtain the blood. Includes a correction unit that corrects flow information.

According to the embodiment, it is possible to suitably measure the blood flow of a plurality of blood vessels.

It is the schematic which shows an example of the structure of the blood flow measuring apparatus which concerns on embodiment. It is the schematic which shows an example of the structure of the blood flow measuring apparatus which concerns on embodiment. It is the schematic which shows an example of the structure of the blood flow measuring apparatus which concerns on embodiment. It is the schematic which shows an example of the structure of the blood flow measuring apparatus which concerns on embodiment. It is the schematic which shows an example of the operation of the blood flow measuring apparatus which concerns on embodiment. It is the schematic which shows an example of the operation of the blood flow measuring apparatus which concerns on embodiment. It is the schematic which shows an example of the operation of the blood flow measuring apparatus which concerns on embodiment. It is the schematic which shows an example of the operation of the blood flow measuring apparatus which concerns on embodiment. It is a flowchart which shows an example of the operation of the blood flow measuring apparatus which concerns on embodiment. It is the schematic which shows an example of the operation of the blood flow measuring apparatus which concerns on embodiment. It is the schematic which shows an example of the operation of the blood flow measuring apparatus which concerns on embodiment.

An exemplary embodiment of the present invention will be described in detail with reference to the drawings. In addition, the description contents of the document cited in this specification can be incorporated into the embodiment.

The blood flow measuring device uses OCT to acquire information on the blood flow of a living body. In addition, the blood flow measuring device can acquire an image of a living body by using OCT. Hereinafter, a case where blood flow measurement of the fundus is performed using a Fourier domain OCT (particularly, a spectral domain OCT) will be described. The target of blood flow measurement does not have to be the fundus, and may be any biological part such as skin or internal organs. Further, the type of OCT is not limited to the spectral domain OCT, and may be any type such as a Swept source OCT or a time domain OCT. Further, in the following embodiment, a device in which an OCT device and a fundus camera are combined will be described. It is possible to apply the same configuration as. Further, the same configuration as that of the embodiment can be applied to an apparatus having only an OCT function.

[Constitution]
As shown in FIG. 1, the blood flow measuring device 1 includes a fundus camera unit 2, an OCT unit 100, and an arithmetic control unit 200. The fundus camera unit 2 includes a configuration for photographing the fundus Ef. The OCT unit 100 includes a configuration for acquiring an OCT image of the fundus Ef. The calculation control unit 200 includes a configuration for executing various calculations and controls.

[Fundus camera unit]
The fundus camera unit 2 acquires a two-dimensional image (fundus image) showing the surface morphology of the fundus Ef. The fundus image includes an observed image and a photographed image. The observation image is, for example, a monochrome moving image acquired at a predetermined frame rate using near-infrared light. The captured image includes a color image obtained by flashing visible light, a monochrome image obtained by using near-infrared light or visible light (for example, a fluorescein fluorescent image, an indocyanine green fluorescent image, a spontaneous fluorescent image, etc.). Fluorescent image) and so on.

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 eye E to be inspected with illumination light. The photographing optical system 30 detects the return light (reflected light from the fundus of the eye, reflected light from the corneal reflex, fluorescence, etc.) of the illumination light from the eye E to be inspected. Further, the fundus camera unit 2 guides the measurement light from the OCT unit 100 to the eye E to be inspected, and guides the return light of the measurement light from the eye E to the OCT unit 100.

The light (observation illumination light) output from the observation light source 11 of the illumination optical system 10 is reflected by the reflection mirror 12 having a curved reflecting surface, passes through the condenser lens 13, and passes through the visible cut filter 14. It becomes near infrared light. Further, the observation illumination light is once focused in the vicinity of the photographing light source 15, reflected by the mirror 16, passes through the relay lenses 17 and 18, the diaphragm 19, and the relay lens 20, and is peripheral to the perforated mirror 21 (hole). It is reflected by the area around the lens, passes through the dichroic mirror 46, is refracted by the objective lens 22, and is irradiated to the eye E to be inspected.

The return light of the observation illumination light from the eye E to be inspected 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, and passes through the dichroic mirror 55. , It is reflected by the mirror 32 via the focusing lens 31, is transmitted through the half mirror 40, is reflected by the dichroic mirror 33, and is imaged on the light receiving surface of the area sensor 35 by the condenser lens 34. The area sensor 35 detects the return light at a predetermined frame rate. As a result, an observation image of the fundus Ef and the anterior segment of the eye can be obtained.

The light output from the photographing light source 15 (photographing illumination light) is applied to the eye E (fundus Ef) to be inspected through the same path as the observation illumination light. The return light (reflected from the fundus of the eye, fluorescence, etc.) of the photographing 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 a condenser lens. The image is formed on the light receiving surface of the area sensor 38 by the 37. As a result, a photographed image of the fundus Ef or the like can be obtained.

The LCD (Liquid Crystal Display) 39 displays a fixation target and a visual acuity measurement target. 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. It passes through the mirror 46, is refracted by the objective lens 22, and is projected onto the eye E (fundus Ef) to be inspected. By changing the display position of the fixation target by the LCD 39, the fixation position of the eye E to be inspected can be changed.

The fundus camera unit 2 is provided with an alignment optical system 50 and a focus optical system 60. The alignment optical system 50 generates an index (alignment index) for aligning the device optical system with respect to the eye E to be inspected (alignment). The focus optical system 60 generates an index (split index) for focusing (focusing) on the fundus Ef.

The near-infrared light (alignment light) output from the LED 51 of the alignment optical system 50 passes through the diaphragms 52 and 53 and the relay lens 54, is reflected by the dichroic mirror 55, and passes through the hole portion of the perforated mirror 21. It passes through the dichroic mirror 46 and is projected onto the eye E (corneal membrane) to be inspected by the objective lens 22. The return light of the alignment light is detected by the area sensor 35 through the same path as the return light of the observation illumination light. The detected image (alignment index image) by the area sensor 35 is drawn in the observation image. The user or the arithmetic control unit 200 can perform alignment based on the position of the alignment index image in the same manner as the conventional fundus camera.

When adjusting the focus, the reflecting surface of the reflecting rod 67 is obliquely provided in the optical path of the illumination optical system 10. The near-infrared 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 index plate 63, passes through the two-hole aperture 64, and reaches the mirror 65. It is reflected, once imaged on the reflecting surface of the reflecting rod 67 by the condenser lens 66, reflected, passed through the relay lens 20, reflected by the perforated mirror 21, transmitted through the dichroic mirror 46, and refracted by the objective lens 22. It is projected onto the eye to be inspected E (fundus Ef). The return light of the focus light is detected by the area sensor 35 through the same path as the return light of the alignment light. The detection image (split index image) by the area sensor 35 is drawn in the observation image. The user or the arithmetic control unit 200 performs focusing by moving the focusing lens 31 and the focus optical system 60 based on the position of the split index image, as in the conventional fundus camera. The focusing lens 31 is moved by the focusing drive unit 31A shown in FIG. 3, and the focus optical system 60 is moved by a drive mechanism (not shown).

After the alignment (and focusing) is completed, tracking can be performed to move the device optical system according to the eye movement of the eye E to be inspected.

The dichroic mirror 46 synthesizes an optical path for fundus photography and an optical path for OCT measurement (called a measurement arm, a sample arm, or the like). The dichroic mirror 46 reflects light in the wavelength band used for OCT measurement and transmits light for fundus photography. The optical path for OCT measurement is provided with a collimator lens unit 40, an optical path length changing unit 41, an optical scanner 42, a focusing lens 43, a mirror 44, and a relay lens 45 in order from the OCT unit 100 side. ing.

The optical path length changing unit 41 changes the length of the measuring arm. The optical path length changing unit 41 includes, for example, a corner cube that can move in the direction of the arrow shown in FIG. The change of the optical path length of the measuring arm is used for adjusting the optical path length according to the axial length of the eye E to be inspected, adjusting the interference state, and the like.

The optical scanner 42 has a configuration capable of two-dimensionally deflecting the light passing through the measurement arm (measurement light LS). For example, the optical scanner 42 is configured to be able to independently scan the measurement light LS in directions orthogonal to each other (x direction and y direction). As a result, various scanning patterns are realized. When the configuration for the anterior segment OCT (lens system attachment or the like) is applied, the anterior segment is scanned by the measurement light LS. The optical scanner 42 includes, for example, a galvano mirror, a MEMS mirror, a resonant mirror, and the like.

[OCT unit]
FIG. 2 shows a configuration example of the OCT unit 100. The OCT unit 100 has a configuration according to the type of OCT. FIG. 2 shows an example of the configuration when the spectral domain OCT is applied. Spectral domain OCTs are generally provided with a low coherence light source and a spectroscope. In Swept Source OCT, for example, a wavelength sweep light source and a balanced photodiode are provided.

In the spectral domain OCT, the light L0 output from the light source unit 101 is wideband low coherence light. Light L0 includes, for example, a wavelength band in the near infrared region (about 800 nm to 900 nm), and has a temporal coherence length of about several tens of micrometers. Further, for example, near-infrared light having a central wavelength of about 1040 to 1060 nm may be used as the light L0. The light source unit 101 includes an optical output device such as a super luminescent diode (SLD), an LED, and an SOA (Semiconductor Optical Amplifier).

The light L0 output from the light source unit 101 is guided by the optical fiber 102 to the fiber coupler 103 and divided into the measurement light LS and the reference light LR.

The reference optical LR is guided by the optical fiber 104 and reaches the optical attenuator (attenuator) 105. The optical attenuator 105 automatically adjusts the amount of light of the reference light LR guided to the optical fiber 104 under the control of the arithmetic control unit 200 by using a known technique. The reference light LR whose light amount is adjusted by the optical attenuator 105 is guided by the optical fiber 104 and reaches the polarization regulator 106. The polarization adjuster 106 adjusts the polarization state of the reference light LR guided to the optical fiber 104 under the control of the arithmetic control unit 200 by using a known technique. The polarized light LR whose polarization state is adjusted reaches the fiber coupler 109.

On the other hand, the measurement light LS generated by the fiber coupler 103 is guided by the optical fiber 107 and converted into a parallel luminous flux by the collimator lens unit 105. Further, the measurement light LS is reflected by the dichroic mirror 46 via the optical path length changing unit 41, the optical scanner 42, the focusing lens 43, the mirror 44, and the relay lens 45, and is refracted by the objective lens 11 to be inspected. (Focus Ef) is irradiated. The measurement light LS is scattered and reflected at various depth positions of the fundus Ef. The return light (backscattered light, reflected light, fluorescence, etc.) of the measurement light LS travels in the same direction as the outward path in the opposite direction, is guided to the fiber coupler 103, and reaches the fiber coupler 109 via the optical fiber 108. .. The focusing lens 43 is moved by the focusing drive unit 43A shown in FIG.

The fiber coupler 109 interferes with the return light of the measurement light LS and the reference light LR that has passed through the fiber coupler 104. The interfering light LC generated thereby is guided by the optical fiber 110 and emitted from the exit end 111, is converted into a parallel light beam by the collimator lens 112, is separated by the diffraction grating 113 (spectral decomposition), and is collected by the condenser lens 114. It is illuminated and projected onto the light receiving surface of the light detector 115. The photodetector 115 is, for example, a line sensor, and detects each spectral component of the dispersed interference light LC to generate an electric signal (detection signal). The generated detection signal is sent to the arithmetic control unit 200.

[Calculation control unit]
The arithmetic control unit 200 controls the fundus camera 2, the display device 3, and the OCT unit 100, performs various arithmetic processing, and executes OCT image forming processing. Further, the arithmetic control unit 200 includes a user interface such as a display device, an input device, and an operation device. The configuration of the arithmetic control unit 200 will be described in the following description of the control system of the control system.

[Control system]
The control system of the blood flow measuring device 1 will be described with reference to FIGS. 3 and 4.

(Control unit)
The control system of the blood flow measuring device 1 is mainly composed of the control unit 210. 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 controls the fundus camera unit 2, the OCT unit 100, and the arithmetic control unit 200. Further, the main control unit 211 performs a process of writing data to the storage unit 212 and a process of reading data from the storage unit 212.

(Memory)
The storage unit 212 stores various types of data. The data stored in the storage unit 212 includes, for example, an OCT image, a fundus image, and eye examination information. The eye test information is information about the eye to be tested or the subject, and includes, for example, input information such as a patient ID and medical information such as an electronic medical record. Further, the storage unit 212 stores programs and data for operating the blood flow measuring device 1.

(Image forming part)
The image forming unit 220 forms the image data of the tomographic image of the fundus Ef and the image data of the phase image based on the detection signal from the photodetector 115. These image data will be described later. In this specification, the "image data" and the "image" output based on the "image data" may be equated. The image forming unit 220 has a tomographic image forming unit 221 and a phase image forming unit 222.

In this embodiment, two types of scans (first scan and second scan) are performed on the fundus Ef. In the first scan, the first cross section intersecting the blood vessel of interest of the fundus Ef is repeatedly scanned with the measurement light LS. In the second scan, the second cross section intersecting the blood vessel of interest is scanned with the measurement light LS. The second cross section is set in the vicinity of the first cross section. Here, it is desirable that the first cross section and the second cross section are oriented so as to be orthogonal to the traveling direction of the blood vessel of interest.

Specific examples of the first cross section and the second cross section are shown in FIG. The fundus image D shown in FIG. 5 shows a first cross section C0 and a second cross section C1 set in the vicinity of the optic nerve head Da of the fundus Ef. The first cross section C0 and the second cross section C1 are set to intersect the predetermined blood vessel Db of interest. The second cross section C1 may be set on the upstream side of the blood vessel Db of interest with respect to the first cross section C0, or may be set on the downstream side. The second cross section may include two or more cross sections.

It is desirable that the first and second scans be performed over at least one cardiac cycle of the patient's heart. Thereby, blood flow information in all time phases of the heart can be obtained. The time for executing the first scan may be a predetermined fixed time, or may be a time set for each patient or each examination. In the former case, it is possible to set a shorter time than before. For example, conventionally, a time sufficiently longer than the cardiac cycle (for example, 2 seconds) is applied in order to reliably collect data over one cardiac cycle. On the other hand, in the present embodiment, for example, by monitoring the change over time of the phase difference represented by the phase image, a predetermined time phase is detected, and data collection is started from that time phase. It is possible to apply for a period of time (eg 1 second) or slightly longer. In the latter case, examination data such as an electrocardiogram of a patient can be referred to. Here, it is also possible to consider factors other than the cardiac cycle. Examples of this factor include the time required for the examination (burden on the patient), the response time of the optical scanner 42 (scanning interval), the response time of the photodetector 115 (scanning interval), and the like.

(Tomographic image formation part)
The tomographic image forming unit 221 forms a tomographic image (first tomographic image) showing a change over time in the morphology of 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. The first scan repeatedly scans the first cross section C0 as described above. Detection signals are sequentially input to the tomographic image forming unit 221 from the photodetector 115 of the OCT unit 100 in response to the first scan. The tomographic image forming unit 221 forms one tomographic image of the first cross section C0 based on the detection signals corresponding to each scan of the first cross section C0. The tomographic image forming unit 221 forms a series of tomographic images in chronological order by repeating the above process for the number of repetitions of the first scan. Here, these tomographic images may be divided into a plurality of groups, and the tomographic images of each group may be superposed (added and averaged) to improve the image quality.

Further, the tomographic image forming unit 221 forms a tomographic image (second tomographic image) representing the morphology in the second cross section C1 based on the detection result of the interference light LC obtained by the second scanning on the second cross section C1. This process is performed in the same manner as for the first tomographic image. The first tomographic image is a series of tomographic images in chronological order, but the second tomographic image may be a single tomographic image. Further, the second tomographic image may be one obtained by superimposing (adding and averaging) a plurality of tomographic images obtained by scanning the second cross section C1 a plurality of times to improve the image quality.

The process of forming such a tomographic image includes processes such as noise removal (noise reduction), filtering, and FFT (Fast Fourier Transform), as in the conventional spectral domain type optical coherence tomography. In the case of other types of OCT devices, the tomographic image forming unit 221 performs a known process according to the type.

(Phase image forming part)
The phase image forming unit 222 forms a phase image showing a change with time 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 in the process of forming the first tomographic image by the tomographic image forming unit 221. Therefore, it is possible to align 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 method for forming a phase image will be described. The phase image of this example is obtained by calculating the phase difference of adjacent A-line complex signals (signals corresponding to adjacent scanning points). In other words, the phase image of this example is formed for each pixel of the first tomographic image based on the time course of the pixel value (luminance value) of the pixel. For any pixel, the phase image forming unit 222 considers a graph of changes in its luminance value over time. The phase image forming unit 222 obtains the phase difference Δφ between two time points t1 and t2 (= t1 + Δt) separated by a predetermined time interval Δt in this graph. Then, this 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 at each of a large number of preset time points, a time-dependent change in the phase difference in 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 in display color or brightness. At this time, the display color when the phase increases along the time series (for example, red) and the display color when the phase decreases (for example, blue) can be changed. In addition, the magnitude of the amount of phase change can be expressed by the density of the display color. By adopting such an expression method, it is possible to clearly indicate the direction and size of blood flow with a display color. A phase image is formed by executing the above processing for each pixel.

The change in phase difference with time can be obtained by sufficiently reducing the time interval Δt described above to ensure phase correlation. At this time, in scanning of the measurement light LS, oversampling is executed in which the time interval Δt is set to a value less than the time corresponding to the resolution of the tomographic image.

(Data processing unit)
The data processing unit 230 executes various data processing. For example, the data processing unit 230 performs various image processing and analysis processing on the image formed by the image forming unit 220. The data processing unit 230 can execute various correction processes such as image brightness correction and dispersion correction. In addition, the data processing unit 230 performs various image processing and analysis processing on the images (fundus image, anterior ocular segment image, etc.) obtained by the fundus camera unit 2.

The data processing unit 230 includes a setting processing unit 231, a blood flow information generation unit 232, and a blood vessel discrimination unit 233.

(Setting processing unit)
The setting processing unit 231 executes a process for setting a position (measurement position) for measuring blood flow. This process is performed by analyzing the image of the fundus Ef. The image to be analyzed may be a frontal image of the fundus Ef, a tomographic image, or a three-dimensional image. Further, the image to be analyzed may be an observation image (frame), a photographed image, or an OCT image. The setting processing unit 231 includes an image area specifying unit 2311 and a measurement position setting unit 2312.

(Image area identification part)
The image region specifying unit 2311 identifies an image region corresponding to a predetermined portion of the fundus Ef by analyzing the image of the fundus Ef. Examples of the specified image region include an image region corresponding to a blood vessel (vascular region) and an image region corresponding to the optic nerve papilla (papillary region). It is also possible to configure the image region (lesion region) corresponding to the lesion to be specified. The analysis process for specifying such an image region may be a known technique, for example, a process based on a pixel value (luminance value or the like) (threshold value process or the like), a pattern analysis (pattern matching or the like), or the like. It may include a feature detection process (edge detection process), an arbitrary filter process, and the like.

The process of identifying the vascular region will be described. The image region identification unit 2311 identifies a plurality of blood vessel regions by analyzing the image of the fundus Ef. The number of specified vascular regions may be preset or may be an arbitrary number according to the analysis process. The former may be a default value or a value preset by the user or the like. As an example of the latter, it is possible to select a vascular region that meets the predetermined conditions. Examples of this condition include the width of the vascular region (blood vessel diameter) and the position of the vascular region. The position of the blood vessel region includes, for example, the distance of the fundus Ef from a predetermined site (optic disc, etc.) and the orientation with respect to the predetermined site (upper side, lower side, ear side, lower side, etc.).

The process of calculating the width of the blood vessel region may be an arbitrary process for calculating the width of the band-shaped or tubular image region. This process includes, for example, the following series of processes: a process for detecting the boundary of the blood vessel region (edge detection, etc.); a process for identifying the central axis of the blood vessel region (thinning, etc.); a line segment orthogonal to the central axis. A process of identifying two intersections that intersect a boundary; a process of calculating the distance between these intersections.

The vascular region can be ranked based on a predetermined condition, and a plurality of vascular regions can be selected according to the ranking. For example, it is possible to rank in descending order of width, select a predetermined number of blood vessel regions from the higher rank, or select blood vessel regions having a predetermined width or more. Alternatively, it is possible to preferentially select the vascular region located in a predetermined orientation, or to select the vascular region so as to be averaged with respect to the orientation. Further, when the number of blood vessel regions satisfying the predetermined conditions does not reach the predetermined number, the blood vessels are included so as to include all the blood vessel regions satisfying the predetermined conditions and some blood vessel regions not satisfying the predetermined conditions. You can select the area.

(Measurement position setting unit)
The measurement position setting unit 2312 sets a plurality of measurement positions that intersect the plurality of blood vessel regions specified by the image region identification unit 2311. Here, the number of measurement positions set is equal to or less than the number of a plurality of blood vessel regions.

It should be noted that each of the plurality of measurement positions referred to here may be a concept indicating the above-mentioned first cross section. In that case, the measurement position setting unit 2312 also executes the setting of the second cross section for each first cross section in addition to the setting of the plurality of first cross sections. Alternatively, the plurality of measurement positions referred to here may be a concept including a first cross section and a second cross section. In that case, two or more measurement positions are assigned to each blood vessel region.

The measurement position setting unit 2312 sets the measurement position (only the first cross section or both the first cross section and the second cross section) within a predetermined distance from a predetermined portion of the fundus Ef, for example. Here, the predetermined distance is defined as, for example, a distance from an arbitrary feature portion (center position, center of gravity position, boundary, etc.) of a predetermined portion.

FIG. 6 shows an example of a plurality of measurement positions set by the measurement position setting unit 2312. In this example, the predetermined site of the fundus Ef is the optic nerve head. The symbol F0 indicates the papilla region. Reference numeral F1 indicates a range (setting range) within a predetermined distance from the center of the papillary region F0. Reference numerals B1 to B6 indicate a plurality of blood vessel regions specified by the image region identification unit 2311.

The measurement position setting unit 2312 sets a plurality of measurement positions so as to intersect all the blood vessel regions B1 to B6. That is, each measurement position is set to intersect at least one blood vessel region Bi. In this example, five measurement positions L1 to L5 are set so as to intersect the six blood vessel regions B1 to B6. Specifically, the measurement position L1 is set so as to intersect the two blood vessel regions B1 and B2, the measurement position L2 is set so as to intersect the blood vessel region B3, and the measurement position L3 is set so as to intersect the blood vessel region B4. Is set, the measurement position L4 is set so as to intersect the blood vessel region B5, and the measurement position L5 is set so as to intersect the blood vessel region B6. The measurement position may be set individually for each blood vessel region, or any measurement position may be set so as to intersect two or more blood vessel regions. Further, each measurement position Lj indicates a first cross section in which measurement for acquiring a phase image is performed. The second cross section in which the measurement for determining the inclination of the blood vessel is performed is set in the vicinity of the first cross section as described above (not shown).

The shape of the measurement position is arbitrary, and may be arcuate or linear as shown in FIG. 6, for example. The shapes of the plurality of measurement positions may all be the same or may be different. Also, the length of the measurement position may be arbitrary (for example, a default length). The lengths of the plurality of measurement positions may all be the same or may be different. In addition, the maximum value (maximum length) of the length of the measurement position can be set in advance, and a plurality of measurement positions can be set based on the distribution (interval) and the maximum length of a plurality of blood vessel regions. it can.

Each measurement position Lj (j = 1 to 5) is set within the setting range F1. Here, each measurement position Lj (j = 1 to 5) can be set on the boundary of the setting range F1. In this case, the measurement position setting unit 2312 can specify the intersection position between each blood vessel region Bi and the boundary of the setting range F1 and set the measurement position so as to pass through the specified plurality of intersection positions.

Each measurement position Lj is set so as to be orthogonal to, for example, the blood vessel region Bi. When one measurement position intersects two or more blood vessel regions, it is possible to set a measurement position having a shape orthogonal to all of these blood vessel regions, and optimize the arrangement of measurement positions having a predetermined shape (measurement position). It is also possible to optimize the position and orientation of the placement.

(Blood flow information generator)
The blood flow information generation unit 232 is information on blood flow in the blood vessels of the fundus Ef (blood flow information) based on the data acquired by OCT executed based on the plurality of measurement positions set by the measurement position setting unit 2312. To generate. The blood flow information generation unit 232 includes a blood vessel cross-section identification unit 2321, an inclination calculation unit 2322, a blood flow velocity calculation unit 2323, a blood vessel diameter calculation unit 2324, a blood flow rate calculation unit 2325, and a correction unit 2326.

The blood vessel cross-section specifying unit 2321, the inclination calculation unit 2322, the blood flow velocity calculation unit 2323, the blood vessel diameter calculation unit 2324, and the blood flow rate calculation unit 2325 will describe each measurement position Lj set by the measurement position setting unit 2312 later. Execute the process. In the following description, the blood vessel Db of interest corresponds to each blood vessel region Bi.

(Vessel cross-section identification part)
The blood vessel cross-section specifying unit 2321 identifies the blood vessel cross-section corresponding to the blood vessel Db of interest for each of the first tomographic image, the second tomographic image, and the phase image. This processing can be performed by analyzing the pixel values of each image (for example, threshold processing).

It is considered that the first tomographic image and the second tomographic image have sufficient resolution for performing the analysis process, but the phase image does not have enough resolution to specify the boundary of the blood vessel cross section. However, since blood flow information is generated based on the phase image, it is necessary to specify the blood vessel cross section with high accuracy and high accuracy. Therefore, for example, the blood vessel cross section of the phase image can be more accurately specified 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 a natural correspondence between the pixels of each other is possible. Utilizing this, first, the first tomographic image is analyzed to obtain a blood vessel cross section, and an image region in a phase image composed of pixels corresponding to the pixels included in the blood vessel cross section is defined as the blood vessel cross section. Thereby, the blood vessel cross section of the phase image can be specified with high accuracy and high accuracy.

(Slope calculation unit)
The inclination calculation unit 2322 calculates the inclination of the blood vessel Db of interest in the first cross section based on the distance between the first cross section and the second cross section (distance between cross sections) and the specific result of the blood vessel cross section. The inter-cross-section distance is determined in advance as the distance between the first cross-section and the second cross-section set by the measurement position setting unit 2312.

The reason for calculating the slope of the blood vessel Db of interest will be described. Blood flow information is obtained by the Doppler OCT method. The velocity component of blood flow that contributes to the Doppler shift is a component in the irradiation direction of the measurement light LS. Therefore, even if the blood flow velocity is the same, the Doppler shift received by the measurement 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 measurement light LS, and thus the blood obtained. The flow information also changes. In order to avoid such inconvenience, it is necessary to obtain the inclination of the blood vessel Db of interest and reflect this in the calculation process of the blood flow velocity.

The method of calculating the inclination of the blood vessel Db of interest will be described with reference to FIG. 7. Reference numeral G0 indicates a first tomographic image in the first cross section C0, and reference numeral G1 indicates a second tomographic image in the second cross section C1. Further, reference numeral V0 indicates a blood vessel cross section in the first tomographic image G0, and reference numeral V1 indicates a blood vessel cross section in the second tomographic image G1. In FIG. 7, the z coordinate axis points downward on the paper surface, which substantially coincides with the irradiation direction of the measurement light LS. The distance between cross sections is indicated by d.

The inclination calculation unit 2322 calculates the inclination A of the blood vessel Db of interest in the first cross section C0 based on the positional relationship between the two blood vessel cross sections V0 and V1. This positional relationship is obtained, for example, by connecting two blood vessel cross sections V0 and V1. More specifically, the inclination calculation unit 2322 specifies the feature positions of the two blood vessel cross sections V0 and V1 and connects the two specified feature positions with a line segment. The feature positions include a center position, a center of gravity position, a top portion (a position having a minimum z coordinate value), and a bottom portion (a position having a maximum z coordinate value).

Further, the slope calculation unit 2322 calculates the slope A based on the line segment connecting the two feature positions. More specifically, the slope calculation unit 2322 calculates the slope of the line segment connecting the feature position of the first cross section C0 and the feature position of the second cross section C1, and sets this calculated value as the slope A. The cross-sectional distance d is used when embedding two tomographic images G0 and G1 in the xyz coordinate system in the process of obtaining a line segment.

In this example, one inclination value is obtained, but the inclination may be obtained for each of two or more positions (or regions) in the blood vessel cross section V0. In this case, the obtained two or more 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 flow velocity calculation unit)
The blood flow velocity calculation unit 2323 calculates the blood flow velocity in the first cross section C0 of the blood flowing in the blood vessel Db of interest based on the phase image (change over time of the phase difference) and the inclination A of the blood vessel Db of interest. The calculation target may be the blood flow velocity at a certain point in time, or may be a change over time in the blood flow velocity (blood flow velocity change information). In the former case, for example, it is possible to selectively acquire the blood flow velocity in a predetermined time phase of the electrocardiogram (for example, the time phase of the R wave). Further, the time range in the latter is the whole or an arbitrary 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 calculation unit 2323 can calculate the statistical value of the blood flow velocity in the time range. The statistical values include mean value, standard deviation, variance, median value, maximum value, minimum value, maximum value, and minimum value. It is also possible to create a histogram of blood flow velocity values.

The blood flow velocity calculation unit 2323 calculates the blood flow velocity by using the Doppler OCT method as described above. At this time, the inclination A of the blood vessel Db of interest in the first cross section C0 calculated by the inclination calculation unit 2322 is taken into consideration. Specifically, the blood flow velocity calculation unit 2323 uses the following equation to obtain the blood flow velocity.

here:
Δf represents the Doppler shift received by the scattered light of the measurement 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 measurement light LS and the flow vector of the medium;
λ represents the center wavelength of the measurement light LS.

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

Considering the change of the parameter with time, it is expressed as Doppler shift Δf = Δf (t) and angle θ = θ (t). Here, t is a variable representing time. The blood flow velocity calculation unit 2323 can obtain the blood flow velocity v (t) at an arbitrary time t and the change over time of the blood flow velocity v (t) by using the following equation.

(Blood vessel diameter calculation unit)
The blood vessel diameter calculation unit 2324 calculates the diameter of the blood vessel Db of interest 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, the portion of the fundus Ef including the position of the first cross section C0 is photographed in advance. The fundus image obtained thereby may be an observation image (frame) or a photographed image. When the captured image is a color image, an image (for example, a red-free image) constituting the captured image may be used.

The blood vessel diameter calculation unit 2324 sets the fundus image based on various factors that determine 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 the spacing between adjacent pixels with the scale in real space (for example, the spacing between pixels = 10 μm). It is also possible to calculate in advance the relationship between various values of the above factors and the scale in 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 2324 selectively applies the scale corresponding to the above factor.

Further, the blood vessel diameter calculation unit 2324 calculates the diameter of the blood vessel Db of interest in the first cross section C0, that is, the diameter of the blood vessel cross section V0, based on this scale and the pixels included in the blood vessel cross section V0. As a specific example, the blood vessel diameter calculation unit 2324 obtains the maximum value and the average value of the diameters of the blood vessel cross sections V0 in various directions. Further, the blood vessel diameter calculation unit 235 can approximate the contour of the blood vessel cross section V0 by a circle or an ellipse, and obtain the diameter of the circle or the ellipse. Since the area of the blood vessel cross section V0 can be determined (substantially) once the blood vessel diameter is determined (that is, both can be associated with each other substantially one-to-one), the area is calculated instead of obtaining the blood vessel diameter. It may be calculated.

The second calculation method will be described. In the second calculation method, a tomographic image of the fundus Ef in the first cross section C0 is used. This tomographic image may be a first tomographic image, a phase image, or may be acquired separately from these.

The scale in this tomographic image is determined according to the scanning mode of the measurement light LS. In this embodiment, the first cross section C0 is scanned as shown in FIG. The length of this first cross section is determined based on various factors that determine the relationship between the scale on the image and the scale in real space, such as working distance and information on the eyeball optical system. The blood vessel diameter calculation unit 2324 obtains, for example, 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. It is also possible to determine the change over time in the blood vessel diameter.

(Blood flow calculation unit)
The blood flow rate calculation unit 2325 calculates the flow rate of blood flowing in the blood vessel Db of interest based on the calculation result of the blood flow velocity and the calculation result of the blood vessel diameter. An example of this process will be described below.

It is assumed that the blood flow in the blood vessel is the Hagen-Poiseuille flow. Further, assuming that 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 2325 substitutes the blood vessel diameter calculation result w by the blood vessel diameter calculation unit 2324 and the maximum value Vm based on the blood flow rate calculation result by the blood flow rate calculation unit 2323 into this mathematical formula. Calculate the target blood flow rate Q. As another method, the blood flow rate can be calculated by integrating the product (or integral value) of the time-dependent change in blood flow velocity and the blood vessel diameter (the time-dependent change) with time. The unit of blood flow is, for example, μL / min.

By the above treatment, the blood vessel diameter, blood flow velocity, and blood flow rate for each blood vessel region Bi can be obtained. The blood flow rate calculation unit 2325 can obtain the total blood flow rate based on the plurality of blood flow rates calculated for the plurality of blood vessel regions B1 to B6. The total blood flow rate may be a simple sum of the calculated blood flow rates or a weighted sum. Alternatively, considering that the sum of the plurality of blood flow rates is less than the sum of the blood flow rates of all the blood vessels of the fundus Ef, the total blood flow rate is obtained by adding or multiplying the sum of the plurality of blood flow rates by a predetermined factor. You may do so. This factor is calculated, for example, based on one of the following values: the number of all blood vessels that can be identified from the fundus or OCT images and the number of blood vessels considered to calculate blood flow. Ratio (or difference) to blood vessel diameter; clinically (statistically) blood vessel and blood flow data; test data obtained in the past for the subject (or subject).

(Correction part)
The correction unit 2326 corrects the calculated blood flow information (blood flow velocity, blood vessel diameter, blood flow volume, etc.). This correction process is executed based on, for example, the angle formed by the blood vessel of interest (blood vessel region Bi) and the cross section (measurement position Lj) intersecting the blood vessel of interest. The correction unit 2326 calculates this angle. Alternatively, when a configuration for calculating the angle is applied in the processing of the previous stage, the calculated angle is input to the correction unit 2326.

The process of calculating the angle includes, for example, the following series of processes: the central axis Axi of the vascular region Bi is obtained by performing image processing such as thinning the vascular region Bi; the central axis Axi and the measurement position Lj Find the intersection Pij; find the tangential direction Hi of the central axis Axi at the intersection Pij (if necessary, find the approximate curve of the central axis Axi); find the normal direction Nj of the measurement position Lj at the intersection Pij (or the intersection) Find the direction orthogonal to the tangential direction of the measurement position Lj in Pij); Find the angle αij formed by the tangential direction Hi and the normal direction Nj.

As described above, it is desirable to set the measurement position Lj so as to be orthogonal to the traveling direction of the blood vessel region Bi. In other words, it is desirable to set the measurement position Lj so that the normal direction Nj coincides with the tangential direction Hi of the blood vessel region Bi (that is, the value of the angle αij is preferably small). Therefore, the angle αij is a parameter indicating the suitability of the set measurement position Lj.

The correction unit 2326 can determine the suitability of the measurement position Lj based on the calculated angle αij. For example, the correction unit 2326 compares the calculated angle αij with a predetermined threshold value. When the angle αij is smaller than the threshold value, the correction unit 2326 does not correct the blood flow information regarding the blood vessel region Bi. On the other hand, when the angle αij is equal to or greater than the threshold value, the correction unit 2326 corrects the blood flow information acquired for the blood vessel region Bi. This correction process includes, for example, a process of converting the value of blood flow information by applying a triangular method using an angle αij.

The method of using the angle αij is not limited to the correction of blood flow information. For example, when the angle αij is equal to or greater than the threshold value, the measurement position Lj can be configured to be reset. Alternatively, the angle αij or a value calculated from the angle αij can be provided to the user as an evaluation value indicating the reliability of the blood flow information.

(Blood vessel discriminator)
The blood vessel discrimination unit 233 determines whether the blood vessel region Bi is an image region (arterial region) corresponding to an artery or an image region (vein region) corresponding to a vein. This discrimination process is executed, for example, based on the pixel value of the fundus image (see JP-A-2007-319403, etc.). Alternatively, the blood vessel region may be discriminated based on the blood vessel distribution in the fundus Ef and the phase image. Specifically, the blood vessel discrimination unit 233 obtains the path of the blood vessel region Bi from the optic nerve head to the measurement position Lj based on the blood vessel distribution represented in the fundus image, and based on the phase image, the blood vessel at the measurement position Lj. The blood flow direction of the region Bi is obtained, and it is determined whether the blood vessel region Bi is an arterial region or a venous region based on the obtained route and the blood flow direction.

Based on the discrimination result by the blood vessel discrimination unit 233, the blood flow rate calculation unit 2325 can separately obtain the total blood flow rate for the arterial region and the total blood flow rate for the venous region.

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

(User interface)
The user interface 240 includes a display unit 241 and an operation unit 242. The display unit 241 includes the display device and the display device 3 of the arithmetic control unit 200 described above. The operation unit 242 includes the operation device of the arithmetic control unit 200 described above. The operation unit 242 may include various buttons and keys provided on the housing of the blood flow measuring device 1 or on the outside. For example, when the fundus camera unit 2 has a housing similar to that of a conventional fundus camera, the operation unit 242 may include a joystick, an operation panel, and the like provided on the housing. Further, the display unit 241 may include various display devices such as a touch panel provided on the housing of the fundus camera unit 2.

The display unit 241 and the operation unit 242 do not need to be configured as separate devices. For example, it is possible to use a device such as a touch panel in which a display function and an operation function are integrated. In that case, the operation unit 242 is configured to include the touch panel and a computer program. The operation content for the operation unit 242 is input to the control unit 210 as an electric signal. Further, the GUI displayed on the display unit 241 and the operation unit 242 may be used to perform operations and information input.

[motion]
Some examples of the operation of the blood flow measuring device 1 will be described.

(First operation example)
An example of the operation of the blood flow measuring device 1 is shown in FIG. Preliminary processing such as input of patient ID and selection designation of operation mode (blood flow measurement mode) is performed in advance.

(S1: Acquisition of fundus image)
First, the blood flow measuring device 1 acquires an image (setting image) of the fundus Ef for setting the measurement position. The set image is an image obtained by photographing the fundus Ef using the blood flow measuring device 1 or another fundus imaging device, and is, for example, an observation image, a photographed image, or an OCT image of the fundus Ef. When the set image acquired by another fundus photography device is used, the blood flow measuring device 1 acquires the set image from the fundus photography device or the image server. Further, the set image may be an image acquired in real time by the blood flow measuring device 1 (for example, an observation image or an OCT image), or an image acquired in the past by the blood flow measuring device 1 or another fundus photography device. (For example, observed image, photographed image or OCT image).

(S2: Identification of blood vessel region)
The image region specifying unit 2311 identifies a plurality of blood vessel regions Bi by analyzing the set image acquired in step S1. Here, the papillary region and the like can be further specified.

(S3: Setting of measurement position)
Next, the measurement position setting unit 2312 sets a plurality of measurement positions Lj (first cross section) intersecting the plurality of blood vessel regions Bi specified in step S2. Further, the measurement position setting unit 2312 sets a second cross section in the vicinity of each measurement position Lj.

The main control unit 211 can display the set image and information indicating a plurality of measurement positions Lj (and the second cross section) on the display unit 241. The user can adjust any measurement position Lj, delete any measurement position Lj, or add a new measurement position.

(S4: Preparation for OCT measurement)
Next, preparation for OCT measurement (blood flow measurement) is executed. This process includes, for example, alignment and focusing. In addition, tracking can be started. If the OCT measurement is executed in step S1, such processing is executed in step S1.

In addition, it is possible to execute a process for specifying the scanning position of the fundus Ef corresponding to the measurement position Lj (first cross section) and the second cross section set for the set image. In this process, for example, the process of acquiring the observation image of the fundus Ef in real time, the image matching between the observation image (frame) and the set image, and the measurement position Lj (first cross section) based on this image matching. ) And the process of specifying the position (scanning position) in the observation image corresponding to the second cross section. The OCT measurement in step S5 is executed for the plurality of scanning positions identified in this way.

At this stage, the OCT measurement can be optimized. In this optimization process, for example, the main control unit 211 controls the light source unit 101, the optical scanner 42, and the like to execute preliminary OCT measurement. This preliminary OCT measurement is performed for any of the measurement positions (first cross section, second cross section) set in step S3, or any other cross section. It is determined whether the image obtained by this preliminary OCT is suitable. This determination may be made visually by the user or automatically by the blood flow measuring device 1.

When visually performed, the main control unit 211 causes the display unit 241 to display the OCT image. The user evaluates the display position, image quality, and the like of a predetermined tissue (blood vessel, retinal surface, etc.) in the OCT image. If a suitable image is not obtained, the user adjusts the measurement conditions. For example, when the display position of the image is not appropriate, the optical path length changing unit 41 is operated to change the optical path length of the measurement light LS. If the image quality is not appropriate, the optical attenuator 105 and the polarization adjuster 106 are adjusted.

When it is performed automatically, the display position and image quality of a predetermined tissue 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.

(S5: Execution of OCT measurement)
When the optimization process of step S4 is completed, the main control unit 211 executes OCT measurement (blood flow measurement). In this operation example, repetitive scanning (first scanning) for the plurality of measurement positions Lj (first cross section) and scanning for the plurality of second cross sections (second scanning) are executed. This process includes a plurality of first scans and a plurality of second scans, and the order in which they are executed is preset.

(S6: Image formation)
The image forming unit 220 forms a plurality of images based on the data acquired in step S5. In this operation example, the tomographic image forming unit 221 forms a first tomographic image T1i representing each measurement position Li (first cross section) and a second tomographic image T2i representing each second cross section. Further, the phase image forming unit 222 forms a phase image Ui representing each measurement position Li (first cross section).

(S7: Identification of blood vessel cross section)
The blood vessel cross-section specifying unit 2321 identifies the blood vessel cross-section corresponding to the blood vessel region Bi for each of the first tomographic image T1i, each second tomographic image T2i, and each phase image Ui formed in step S6.

(S8: Calculation of blood vessel inclination)
For each blood vessel region Bi, the inclination calculation unit 2322 is based on the blood vessel cross section specified in step S7 and the distance between the measurement position Lj (first cross section) and the second cross section (intersection distance). The slope of the blood vessel region Bi (blood vessel of interest) in the cross section is calculated.

(S9: Calculation of blood flow velocity)
The blood flow velocity calculation unit 2323 determines the blood vessel region of interest for each blood vessel region Bi (blood vessel of interest) based on the temporal change of the phase difference obtained as the phase image Ui and the inclination of the blood vessel region Bi calculated in step S8. The blood flow velocity at the measurement position Lj (first cross section) of the blood flowing inside is calculated.

(S10: Calculation of blood vessel diameter)
The blood vessel diameter calculation unit 2324 calculates the diameter of the blood vessel of interest at the measurement position Lj (first cross section) for each blood vessel region Bi (blood vessel of interest) based on the first tomographic image T1i (or phase image Ui). Instead of the first tomographic image, the fundus image may be analyzed to obtain the blood vessel diameter.

(S11: Calculation of blood flow rate)
The blood flow calculation unit 2325 determines the flow rate (μL) of blood flowing in the blood vessel of interest for each blood vessel region Bi (blood vessel of interest) based on the blood flow velocity calculated in step S9 and the blood vessel diameter calculated in step S10. / Min) is calculated.

(S12: Correction of blood flow information)
The correction unit 2326 calculates the angle αij formed by each blood vessel region Bi (blood vessel of interest) and the measurement position Lj (first cross section) intersecting the angle αij, and based on the calculated angle αij, the blood flow related to the blood vessel region Bi. Correct information (blood flow velocity, vessel diameter and / or blood flow).

(S13: Calculation of total blood flow)
The blood flow rate calculation unit 2325 calculates the total blood flow rate based on the plurality of blood flow rates calculated in step S11 (or the blood flow rate corrected in step S12).

Here, the blood vessel region Bi may be classified into an arterial region and a venous region by the blood vessel discriminating unit 233, and the total blood flow rate for the arterial region and the total blood flow rate for the venous region may be obtained.

(S14: Display and storage of measurement results)
The main control unit 211 causes the display unit 241 to display blood flow information including the blood flow velocity, the blood vessel diameter, the blood flow volume, etc. obtained for the plurality of blood vessel regions Bi, and the total blood flow rate calculated in step S13. The blood flow information may include information (position information) indicating a plurality of measurement positions Lj, a setting image, and the like. Further, the main control unit 211 stores the blood flow information in the storage unit 212 in association with the patient ID input in step S1. This is the end of the process related to this operation example.

(Second operation example)
The process of presenting a plurality of blood vessel regions Bi using the tomographic image acquired by OCT will be described.

In this operation example, for example, in the OCT measurement in step S5 of the first operation example, scanning of a single cross section including a plurality of measurement positions Li is additionally executed. An example of this single cross section is shown in FIG. The scanning pattern shown in FIG. 10 is a circle scan that passes through a plurality of measurement positions L1 to L5 and surrounds the papillary region F0.

By executing such a circle scan, a tomographic image showing the morphology of all the measurement positions Lj (first cross section) can be obtained. A cross section of each blood vessel region Bi is depicted in this tomographic image. The main control unit 211 can display this cross-sectional image on the display unit 241 and display information (blood vessel position information) indicating the cross section of each blood vessel region Bi on the cross-sectional image.

An example of the information displayed in this way is shown in FIG. Reference numeral Z indicates a tomographic image based on the data collected by the circle scan of FIG. The tomographic image Z represents a strip-shaped cross section obtained by cutting open a cylindrical scanning cross section corresponding to a circle scan. The position at which the cylindrical scanning section is cut open may be arbitrary. The tomographic image Z shown in FIG. 11 is obtained by cutting open a cylindrical scanning cross section at the 12 o'clock position “S” in FIG. As is generally used, "S" represents the upper side (superior), "T" represents the ear side (temporal), "I" represents the lower side (inferior), and "N" represents the nose. Represents the side (nasal). Further, on the tomographic image Z, blood vessel position information (also indicated by reference numerals B1 to B6) indicating blood vessel regions B1 to B6 (cross sections) is displayed.

The user can specify the desired blood vessel position information Bi by using the operation unit 242. The main control unit 211 can display the blood flow information corresponding to the designated blood vessel position information Bi (blood vessel region Bi).

It is possible to configure the same process so that the front image of the fundus Ef can be executed. This front image may be, for example, a setting image or a separately acquired image. The main control unit 211 displays the front image and displays the blood vessel position information on the front image. When the user specifies the desired blood vessel position information, the main control unit can display the F blood flow information corresponding to the designated blood vessel position information.

[effect]
The effect of the blood flow measuring device according to the embodiment will be described.

The blood flow measuring device according to the embodiment includes an image acquisition unit, an image area identification unit, a measurement position setting unit, an operation unit, and a blood flow information generation unit.

The image acquisition unit includes, for example, a function of photographing a living body. In the present embodiment, the configuration for acquiring the observation image, the photographed image, and / or the OCT image of the fundus corresponds to the image acquisition unit. Alternatively, the image acquisition unit includes a function of acquiring an image from an external device (another fundus photography device, an image server, etc.). This function is realized by a configuration including a communication interface. The image region identification unit (2311) identifies a plurality of blood vessel regions by analyzing the image acquired by the image acquisition unit. The measurement position setting unit (2312) sets a plurality of measurement positions that intersect the plurality of blood vessel regions specified by the image region identification unit. The scanning unit scans a plurality of cross sections of a living body corresponding to a plurality of measurement positions set by the measurement position setting unit using OCT. In the present embodiment, the configuration for acquiring the OCT image of the fundus corresponds to the scanning unit. The blood flow information generation unit (232) generates blood flow information regarding the living body based on the data acquired by the scanning unit. The blood flow information includes, for example, the blood flow rate, the blood flow velocity, the blood vessel diameter, and the like for each blood vessel region specified by the image region specifying portion.

According to such a blood flow measuring device, blood flow measurement of a plurality of blood vessels can be performed in a plurality of stages (that is, a plurality of measurement positions), so that a close scanning point interval and a high-speed repetition rate can be achieved at the same time. It is possible. Therefore, even when a plurality of blood vessels distributed over a wide area are targeted, blood flow measurement can be suitably performed.

In the embodiment, the image region identification unit calculates the width of the blood vessel region in the image acquired by the image acquisition unit, and includes a blood vessel region whose calculated width is equal to or larger than a predetermined threshold value. It may be configured to make an identification. According to this configuration, it is possible to automatically select a major blood vessel and measure blood flow.

In the embodiment, the image region specifying unit may be configured to specify an image region corresponding to a predetermined part of a living body by analyzing an image acquired by the image acquisition unit. An example of this image area is the optic disc of the fundus. Further, the measurement position setting unit may be configured to set a plurality of measurement positions within a range within a predetermined distance from the image area specified by the image area identification unit. According to this configuration, blood flow measurement can be performed within a predetermined range. This range may be arbitrarily set in clinical practice or research. Further, it is possible to configure this range so that it can be changed arbitrarily.

In the embodiment, the measurement position setting unit may be configured to set a plurality of measurement positions so as to be orthogonal to at least a part of the plurality of blood vessel regions. According to this configuration, suitable blood flow measurement can be easily performed.

In embodiments, the scanning section may be configured to scan a single cross section, including a plurality of cross sections. Further, the blood flow measuring device may include a tomographic image forming unit and a control unit. The tomographic image forming unit (221) forms a tomographic image representing the morphology of this single cross section based on the data acquired by scanning the single cross section. The control unit (210) causes the display means to display this tomographic image and blood vessel position information indicating the positions of a plurality of blood vessels for which blood flow information is generated. The display means may be provided in the blood flow measuring device (display unit 241) or may be an external device. According to this configuration, it is possible to clearly show the blood vessel in which the blood flow measurement is performed together with the image showing the cross-sectional morphology of the living body.

In the embodiment, the blood flow information generation unit may include a correction unit (2326). The correction unit obtains the angle formed by the blood vessel region and the measurement position intersecting the blood vessel region, and corrects the blood flow information based on the obtained angle. According to this configuration, it is possible to improve the reliability of the acquired blood flow information.

In the embodiment, the blood flow information generation unit may be configured to obtain the total blood flow rate based on the plurality of flow rates obtained for the plurality of cross sections. Further, the blood flow measuring device of the embodiment includes a discriminating unit (blood vessel discriminating unit 233) for discriminating whether the blood vessel region is an arterial region or a venous region, and the blood flow information generating unit is a total blood flow volume related to the arterial region. It may be configured to determine the total blood flow with respect to the venous region.

[Modification example]
The configuration described above is only an example for preferably carrying out the present invention. Therefore, any modification (omission, replacement, addition, etc.) within the scope of the gist of the present invention can be appropriately applied.

A modified example of the method for calculating the blood flow rate will be described. In this modification, the blood flow velocity calculation unit 2323 generates information (blood flow velocity change information) indicating a change over time in the 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 the pixels of a plurality of phase images along the time series for each pixel position and a process of generating blood flow velocity change information based on a plurality of pixels along the time series corresponding to each pixel position. It can be configured to include processing to be performed. By this process, 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 2325 calculates the blood flow rate for each pixel by integrating the blood flow velocity change information of each pixel included in the blood vessel region in chronological order. By this treatment, the blood flow rate in the blood vessel region of the first cross section can be obtained for each position.

Further, the blood flow rate calculation unit 2325 can calculate the flow rate of blood flowing through the blood vessel of interest by adding the blood flow rates for these pixels. By this treatment, the blood flow rate for each position obtained in the previous step treatment 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 measurement 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, the optical path length difference can be changed by arranging 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. It 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 be inspected and changing the optical path length of the measurement light LS.

1 Blood flow measuring device 2 Fundus camera unit 41 Optical path length changing unit 42 Optical scanner 100 OCT unit 200 Calculation 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 Data Processing unit 231 Setting processing unit 2311 Image area identification unit 2312 Measurement position setting unit 232 Blood flow information generation unit 2321 Blood vessel cross-section identification unit 2322 Inclination calculation unit 2323 Blood flow velocity calculation unit 2324 Blood flow velocity calculation unit 2325 Blood flow volume calculation unit 2326 Correction unit 233 Blood vessel discrimination unit 241 Display unit 242 Operation unit E Eye to be inspected Ef Fundus

Claims (4)

An image acquisition unit that acquires a frontal image or a three-dimensional image of the fundus of a living body,
An image region specifying unit that identifies a plurality of blood vessel regions by analyzing the front image or the three-dimensional image, and
A measurement position setting unit that sets a plurality of measurement positions that intersect the plurality of blood vessel regions,
A scanning unit that scans a plurality of cross sections of the fundus corresponding to the plurality of measurement positions using optical coherence tomography.
A blood flow information generation unit that generates blood flow information regarding the fundus based on the data acquired by the scanning is provided.
The blood flow information generation unit obtains an angle formed by a blood vessel of interest in the plurality of blood vessel regions and a measurement position intersecting the blood vessel of interest , and applies a trigonometry using the obtained angle to obtain the blood. A blood flow measuring device characterized by including a correction unit that corrects flow information. The image region specifying unit calculates the width of the blood vessel region in the front image or the three-dimensional image, and specifies the plurality of blood vessel regions so as to include the blood vessel region whose calculated width is equal to or larger than a predetermined threshold value. The blood flow measuring device according to claim 1, wherein the blood flow measuring device is characterized. The image region specifying unit identifies an image region corresponding to a predetermined portion of the fundus by analyzing the front image or the three-dimensional image.
The blood flow measuring device according to claim 1 or 2, wherein the measuring position setting unit sets the plurality of measuring positions within a range within a predetermined distance from the image area. The blood according to any one of claims 1 to 3, wherein the measurement position setting unit sets the plurality of measurement positions so as to be orthogonal to at least a part of the plurality of blood vessel regions. Flow measuring device.