JP7068366B2 - 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 Japanese Unexamined Patent Publication No. 2009-165710 Special Table 2010-523286 Gazette

It is desirable to measure blood flow at a site where a pulse wave can be clearly obtained. Typically, the blood vessel to be measured is an artery located in an orientation in which a suitable Doppler signal can be obtained. Currently, the search for arteries is performed by the following method. In the first method, the user specifies a cross section across a desired blood vessel, blood flow measurement of the blood vessel is performed, and the obtained data is analyzed to determine whether the blood vessel is an artery. In this method, a series of processes such as selection of blood vessels, designation of cross sections, blood flow measurement, and data analysis must be repeated until a suitable artery is found, which takes time and effort.

In the second method, live OCT is used. Live OCT is an imaging method in which a cross section of a living body is repeatedly scanned at a predetermined repetition rate, and a moving image based on the obtained data is displayed in real time. In this method, a morphological image and a phase image of a cross section crossing a desired blood vessel are displayed as moving images. In the phase image, arteries are represented as regions where light and dark changes periodically and relatively large, and veins are represented as regions where light and dark changes are relatively small. By observing the phase image, the user determines whether the blood vessel is an artery or a vein. This determination relies on the user's experience and is inferior in accuracy and reproducibility. Furthermore, a series of processes such as selection of blood vessels, designation of cross sections, measurement of blood flow, and determination by observation must be repeated until a suitable artery is found.

In particular, when measuring blood flow in the fundus, it is not easy to select a blood vessel because an infrared observation image having poor visibility is generally used.

One of the objects of the present invention is to facilitate and shorten the setting of the target site for blood flow measurement.

An embodiment is a blood flow measuring device that measures blood flow in a living body using optical coherence stromography, and includes a front image acquisition unit, a data acquisition unit, a phase image forming unit, and a processing unit. The front image acquisition unit acquires a front image of the living body. The data acquisition unit repeatedly scans the cross section of the living body to acquire data. The phase image forming unit forms a phase image in this cross section based on this data. The processing unit identifies the arterial region based on the phase image, generates measurement site information for setting the target site for blood flow measurement based on the identified arterial region, and combines the front image and the measurement site information. Based on this, any of the arterial regions is specified as the blood vessel of interest, and the cross section of interest to be measured for blood flow is set so as to intersect the blood vessel of interest at a position where the direction of the blood vessel of interest is within a predetermined range .

According to the embodiment, it is possible to facilitate and shorten the setting of the target site for blood flow measurement.

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

The blood flow measuring device according to the embodiment will be described in detail with reference to the drawings. The blood flow measuring device of the embodiment uses OCT to form a tomographic image or a three-dimensional image of a living body. The contents of the cited references described herein may be incorporated into embodiments.

In the following embodiment, a blood flow measuring device capable of measuring the fundus of a living eye using a Fourier domain OCT (particularly, a spectral domain OCT) will be described. The type of OCT is not limited to the spectral domain and may be, for example, a swept source OCT. The blood flow measuring device of the embodiment is a device in which an OCT device and a fundus camera are combined, but a fundus imaging device other than the fundus camera and an OCT device may be combined. Examples of such a fundus photography device include an SLO (Scanning Laser Ophthalmoscope), a slit lamp, a microscope for ophthalmic surgery, and the like. In general, it is sufficient that the blood flow measuring device of the embodiment has an OCT function.

<First Embodiment>
[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 an optical system for photographing the fundus and acquiring a front image. This optical system is almost the same as that of a conventional fundus camera. The OCT unit 100 includes an optical system for performing OCT of the fundus and acquiring data. The arithmetic control unit 200 includes a computer that executes various arithmetics and controls.

(Fundus camera unit 2)
The fundus camera unit 2 shown in FIG. 1 is provided with an optical system for acquiring a two-dimensional image (fundus image) showing the surface morphology of the fundus Ef of the eye to be inspected E. The fundus image includes an observation image and a photographed image. The observation image is, for example, a monochrome moving image formed at a predetermined frame rate using near-infrared light. The captured image is, 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 able to acquire images other than these, such as a fluorescein fluorescent image, an indocyanine green fluorescent image, and a spontaneous fluorescent image.

The fundus camera unit 2 is provided with a chin rest and a forehead pad for supporting the face of the subject. 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 Ef with illumination light. The photographing optical system 30 guides the fundus reflected light of this illumination light to an image pickup device (CCD image sensor (sometimes simply referred to as CCD) 35, 38). Further, the photographing optical system 30 guides the measurement light from the OCT unit 100 to the fundus Ef, and guides the return light of the measurement light from the fundus Ef to the OCT unit 100.

The observation light source 11 of the illumination optical system 10 includes, for example, a halogen lamp or an LED (Light Emitting Diode). The light output from the observation light source 11 (observation illumination light) is reflected by the reflection mirror 12 having a curved reflecting surface, passes through the condenser lens 13, passes through the visible cut filter 14, and becomes near-infrared light. Become. Further, the observation illumination light is once focused in the vicinity of the photographing light source 15, reflected by the mirror 16, and passes through the relay lenses 17, 18, the diaphragm 19, and the relay lens 20. Then, the observation illumination light is reflected at the peripheral portion of the perforated mirror 21 (the region around the perforated portion), passes through the dichroic mirror 46, is refracted by the objective lens 22, and illuminates the fundus Ef.

The fundus reflected 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 passes through 31 and is reflected by the mirror 32, transmitted through the half mirror 40, reflected by the dichroic mirror 33, and is imaged on the light receiving surface of the CCD image sensor 35 by the condenser lens 34. The CCD image sensor 35 detects the fundus reflected light at a predetermined frame rate. An image (observation image) based on the fundus reflected light detected by the CCD image sensor 35 is displayed on the display device 3. When the photographing optical system 30 is focused on the anterior eye portion, an observation image of the anterior eye portion of the eye E to be inspected is displayed.

The photographing light source 15 includes, for example, a xenon lamp or an LED. The light output from the photographing light source 15 (photographing illumination light) is applied to the fundus Ef through the same path as the observation illumination light. The fundus reflected light 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 reflected by the condenser lens 37 of the CCD image sensor 38. An image is formed on the light receiving surface. An image (photographed image) based on the fundus reflected light detected by the CCD image sensor 38 is displayed on the display device 3.

The LCD (Liquid Crystal Display) 39 displays a fixative and an index for measuring visual acuity. The fixative is an index for fixing the eye E to be inspected, and is used at the time of fundus photography, OCT, and the like. By changing the display position of the fixative on the screen of the LCD 39, the fixative position of the eye E to be inspected can be changed.

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 reflected by the objective lens 22, and is projected onto the fundus Ef.

Further, the fundus camera unit 2 is provided with an alignment optical system 50 and a focus optical system 60, as in the conventional fundus camera. 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. The focus optical system 60 generates an index (split index) for focusing on the fundus 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 diaphragms 52 and 53 and the relay lens 54, passes through the holes of the perforated mirror 21, and passes through the holes of the perforated mirror 21. Is transmitted and projected onto the eye E to be inspected by the objective lens 22.

The return light of the alignment light is detected by the CCD image sensor 35. The received light image (alignment index image) by the CCD image sensor 35 is displayed together with the observed image. The user can perform the alignment while referring to the alignment index image as in the case of the conventional fundus camera. Further, the arithmetic control unit 200 can analyze the position of the alignment index image and move the optical system to perform alignment (auto alignment function).

When adjusting the focus, 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 index plate 63, passes through the two-hole aperture 64, and is reflected by the mirror 65. The condenser lens 66 once forms an image on the reflecting surface of the reflecting rod 67 and reflects the image. 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 Ef.

The return light of the focus light is detected by the CCD image sensor 35. The received light image (split index image) by the CCD image sensor 35 is displayed together with the observation image and the alignment index image. The arithmetic control unit 200 can analyze the position of the split index and move the focusing lens 31 and the focus optical system 60 to perform focusing (autofocus function) as in the conventional case. Further, focusing may be performed manually while referring to the position of the split index image.

The dichroic mirror 46 synthesizes an optical path (measurement optical path, measurement arm) of measurement light for OCT with an optical path for fundus photography. That is, the optical path for fundus photography and the measurement optical path are coaxially configured by the dichroic mirror 46, and share the optical path on the eye E side of the dichroic mirror 46. The dichroic mirror 46 reflects light in the wavelength band used for OCT and transmits light for fundus photography. The measurement optical path 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 this order from the OCT unit 100 side.

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 measured optical path. This change in the optical path length is used for correcting 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 path length changing unit 41 includes, for example, a corner cube and a mechanism for moving the corner cube.

The optical scanner 42 changes the traveling direction of the measurement light LS passing through the measurement optical path. Thereby, the fundus Ef can be scanned by the measurement light LS. The optical scanner 42 includes, for example, a galvano mirror that scans the measurement light LS in the x direction and a galvano mirror that scans the measurement light LS in the y direction, and is configured to be able to deflect the measurement light LS in any direction on the xy plane.

(OCT unit 100)
A configuration example of the OCT unit 100 will be described with reference to FIG. The optical system provided in the OCT unit 100 divides the low coherence light into the reference light and the measurement light, and separates the return light and the reference light path of the measurement light from the eye E to be inspected, like the conventional spectral domain type OCT device. It is configured to interfere with the passing reference light to generate interference light and detect the spectral component of this interference light. This detection result (detection signal) is sent to the arithmetic control unit 200.

When a swept source type OCT device is applied, a wavelength sweep light source is provided instead of the low coherence light source, and a balanced photodiode or the like is provided instead of the device (spectrometer) for detecting the spectral component. In general, the OCT unit 100 may have known configurations depending on the type of OCT.

The light source unit 101 outputs low coherence light L0 (broadband light). The low coherence 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. Alternatively, near-infrared light having a center wavelength of 1040 to 1060 nm may be used as the low coherence light L0.

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

The low coherence 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 changes the amount of light of the reference light LR guided to the optical fiber 104 under the control of the arithmetic control unit 200 or by manual operation. 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 (polarization controller) 106. The polarization regulator 106 changes the polarization state of the reference light LR guided in the optical fiber 104. The reference light LR whose polarization state has been adjusted by the polarization regulator 106 reaches the fiber coupler 109.

The measurement light LS generated by the fiber coupler 103 is guided by the optical fiber 107 and is converted into a parallel luminous flux by the collimator lens unit 105. Further, the measurement light LS reaches 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. Then, the measurement light LS is reflected by the dichroic mirror 46, refracted by the objective lens 11, and incident on the eye E to be inspected. The measured light LS is reflected and scattered at various depth positions of the fundus Ef. The return light (backscattered light, reflected light, fluorescence, etc.) of the measured light LS from the fundus Ef travels in the same path as the outward path in the opposite direction and is guided to the fiber coupler 103, and is guided to the fiber coupler 103 via the optical fiber 108. Reach 109.

The fiber coupler 109 interferes with the return light of the measurement light LS and the reference light LR. As a result, the interference light LC is generated. The interference light LC 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, spectrally decomposed by the diffraction grating 113, condensed by the condenser lens 114, and projected onto the light receiving surface of the CCD image sensor 115. Although the diffraction grating 118 shown in FIG. 2 is a transmission type, it is also possible to use a spectroscopic element of another form such as a reflection type diffraction grating.

The CCD image sensor 115 is, for example, a line sensor, and detects each spectral component of the interference light LC and converts it into an electric charge. The CCD image sensor 115 accumulates this charge, generates a detection signal, and sends the detection signal to the arithmetic control unit 200. Instead of the CCD image sensor, another image sensor, for example, a CMOS (Complementary Metal Oxide Sensor) image sensor may be used.

(Operation control unit 200)
The arithmetic control unit 200 analyzes the detection signal input from the CCD image sensor 115 to form an OCT image. The arithmetic processing for that is the same as that of the conventional spectral domain OCT.

Further, the arithmetic control unit 200 controls the fundus camera unit 2, the display device 3, and the OCT unit 100. The control of the fundus camera unit 2 includes operation control of each of the observation light source 11, the photographing light source 15, the LCD 39, the optical scanner 42, and the LEDs 51 and 61, the focusing lenses 31 and 43, the optical path length changing unit 41, and the focus optical system. There are movement control of each of 60 and the reflection rod 67. The control of the OCT unit 100 includes operation control of each of the light source unit 101, the optical attenuator 105, the polarization adjuster 106, and the CCD image sensor 120.

The arithmetic control unit 200 includes a processor, RAM, ROM, a hard disk drive, a communication interface, and the like. Further, 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. In the present specification, the "processor" is, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), a programmable logic device (for example, a SPLD), a programmable logic device (for example, a SPLD). It means a circuit such as (Complex Program Logic Device), FPGA (Field Programbulmable Gate Array)) and the like. The arithmetic control unit 200 realizes the function according to the embodiment by reading and executing a program stored in a storage circuit or a storage device, for example.

[Control system]
3 and 4 show a configuration example of the control system of the blood flow measuring device 1.

(Control unit 210)
The control unit 210 includes, for example, a processor, RAM, ROM, a hard disk drive, a communication interface, and the like. The control unit 210 is provided with a main control unit 211 and a storage unit 212. The storage unit 212 stores various data and computer programs.

The main control unit 211 performs various controls. For example, as shown in FIG. 3, the main control unit 211 controls the CCDs 35 and 38 of the fundus camera unit 2, the focusing drive unit 31A, the optical path length changing unit 41, the optical scanner 42, and the focusing drive unit 43A. .. Further, the main control unit 211 controls the light source unit 101, the optical attenuator 105, the polarization adjuster 106, and the CCD 115 of the OCT unit 100.

The focusing drive unit 31A moves the focusing lens 31 in the optical axis direction. As a result, the focusing position of the photographing optical system 30 changes. Further, the focusing drive unit 43A moves the focusing lens 43 in the optical axis direction. As a result, the in-focus position of the measurement light LS (the in-focus position of the OCT measurement) changes. The main control unit 211 can control an optical system drive unit (not shown) to move the optical system provided in the fundus camera unit 2 three-dimensionally. The movement control of this optical system is used in alignment and tracking. Tracking is a process of moving the device optical system according to the eye movement of the eye E to be inspected. Alignment and focus adjustments are performed prior to tracking. Tracking is a function of keeping the alignment and focus in focus by making the position of the optical system of the device follow the eye movement.

(Image forming unit 220)
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 CCD image sensor 115. The image forming unit 220 includes a processor. In this specification, "image data" and "image" based on the "image data" may be equated with each other. The image forming unit 220 has a tomographic image forming unit 221 and a phase image forming unit 222.

In this embodiment, scanning for setting a target site for blood flow measurement (preliminary measurement) and scanning for acquiring blood flow information about the set site from the result of preliminary measurement (blood flow measurement) are executed. Will be done.

In the preliminary measurement, a plurality of cross sections of the fundus Ef are repeatedly scanned with the measurement light LS. Scanning a plurality of cross sections is, for example, a raster scan along a plurality of scanning lines parallel to each other. The number of scanning lines in the raster scan is, for example, 128, whereby the three-dimensional region of the fundus Ef is scanned (three-dimensional scan). The number of scanning patterns and scanning lines is not limited to this example.

In the blood flow measurement, two types of scans (first scan and second scan) are executed based on the site of the fundus Ef set from the result of the preliminary measurement. The part set from the result of the preliminary measurement is called the part of interest. The site of interest includes the blood vessel of interest and the cross section of interest. The blood vessel of interest is a blood vessel of the fundus Ef set from the result of preliminary measurement. The blood vessel of interest may be a blood vessel in which a pulse wave is clearly observed, for example, an artery. The cross section of interest is a cross section that intersects the blood vessel of interest. Further, the region of interest may include one or more cross sections located in the vicinity of the cross section of interest. This one or more cross sections is the target of an OCT scan for determining the inclination of the blood vessel of interest.

In the first scan, two or more cross sections intersecting the blood vessel of interest are scanned by the measurement light LS. The data acquired by the first scan is used to determine the inclination (orientation) of the blood vessel of interest in the cross section of interest. On the other hand, in the second scan, the cross section of interest intersecting the blood vessel of interest is repeatedly scanned by the measurement light LS. The cross section in which the first scan is performed is arranged in the vicinity of the cross section of interest. The second scan is Doppler measurement using OCT.

It is desirable that the target cross sections of the first scan and the second scan are oriented so as to be orthogonal to the traveling direction of the blood vessel of interest on the xy plane. As shown in the fundus image D of FIG. 5, in the present embodiment, for example, two cross sections C11 and C12 in which the first scan is performed and a cross section C2 of interest in which the second scan is performed are provided in the vicinity of the optic disc Da. It is set to intersect the blood vessel Db of interest. One of the two cross sections C11 and C12 is located on the upstream side of the blood vessel Db of interest with respect to the cross section of interest C2, and the other is located on the downstream side of the blood vessel Db of interest. The distance (distance between cross sections) of each cross section C11 and C12 with respect to the cross section C2 of interest is determined in advance.

The second 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 can be obtained. The execution time of the second scan may be a predetermined fixed time (for example, 2 seconds), or may be a time set for each patient or each examination. In one example of the latter, the patient's heart rate data obtained using an electrocardiograph can be utilized.

(Tomographic image forming part 221)
The tomographic image forming unit 221 forms a tomographic image based on the data obtained by OCT scanning the fundus Ef. The tomographic image forming unit 221 can form a tomographic image based on the data acquired in the preliminary measurement. Further, the tomographic image forming unit 221 can form a tomographic image based on the data acquired by the blood flow measurement (first scan and / or second scan). For example, the tomographic image forming unit 221 has a tomographic image showing the morphology of the cross section C11 and a tomographic image showing the morphology of the cross section C12 based on the detection result of the interference light LC obtained by the first scan for the cross sections C11 and C12. To form. At this time, the cross section C11 can be scanned once to form one tomographic image, and the cross section C12 can be scanned once to form one tomographic image. Alternatively, one tomographic image is acquired based on a plurality of tomographic images obtained by scanning the cross section C11 multiple times, and one tomographic image is obtained based on the plurality of tomographic images obtained by scanning the cross section C12 multiple times. A tomographic image can be obtained. Examples of the process of acquiring one tomographic image from a plurality of tomographic images include a process of averaging a plurality of tomographic images to improve image quality and a process of selecting the optimum one from a plurality of tomographic images.

Further, the tomographic image forming unit 221 forms a tomographic image group representing a time-series change in the morphology of the tomographic cross section C2 based on the detection result of the interference light LC obtained by the second scan for the tomographic cross section C2. This process will be described in more detail. In the second scan, the cross section C2 of interest is repeatedly scanned as described above. Detection signals are sequentially input to the tomographic image forming unit 221 from the CCD 115 of the OCT unit 100 in response to the second scan. The tomographic image forming unit 221 forms one tomographic image of the cross section C2 of interest based on the detection signal group corresponding to one scan of the cross section C2 of interest. The tomographic image forming unit 221 forms a series of tomographic images along the time series by repeating this process for the number of repetitions of the second scan. Here, these tomographic images may be divided into a plurality of groups, and the tomographic images of each group may be averaged to improve the image quality.

The processing executed by the tomographic image forming unit 221 includes noise removal (noise reduction), filtering processing, FFT (Fast Fourier Transform) and the like, as in the conventional spectral domain OCT. When another type of OCT is applied, the tomographic image forming unit 221 performs a known process according to the type.

(Phase image forming unit 222)
The phase image forming unit 222 forms a phase image based on the data obtained by repeatedly performing an OCT scan on a predetermined portion of the fundus Ef. The phase image forming unit 222 forms a phase image showing the time-series change of the phase difference in the scanned cross section based on the data acquired in the preliminary measurement. In the preliminary measurement, a plurality of cross sections of the fundus Ef are repeatedly scanned. The phase image forming unit 222 forms a phase image in each of these cross sections based on the data acquired by the preliminary measurement.

Further, the phase image forming unit 222 forms a phase image based on the data acquired by the second scan of the blood flow measurement. For example, the phase image forming unit 222 forms a phase image showing the time-series change of the phase difference in the cross section C2 of interest based on the detection result of the interference light LS obtained by the second scan with respect to the cross section C2 of interest.

The data used to form the phase image may be the same as the data used by the tomographic image forming unit 221 to form the tomographic image. In this case, the tomographic image of the scanned cross section and the phase image can be easily aligned. That is, it is possible to naturally associate the pixels of the tomographic image and the pixels of the phase image with respect to the tomographic image and the phase image formed based on the same data.

An example of a method of 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 tomographic image of the scanned cross section based on the time-series change of the pixel value (luminance value) of the pixel. For any pixel, the phase image forming unit 222 considers a graph of time-series changes in its luminance value. The phase image forming unit 222 obtains the phase difference Δφ between two time points t1 and t2 (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-series 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 by the display color or the brightness. At this time, the color indicating that the phase has increased along the time series (for example, red) and the color indicating that the phase has decreased (for example, blue) can be different. In addition, the magnitude of the amount of change in phase can be expressed by the depth of the display color. By adopting such an expression method, it becomes possible to present the direction and size of blood flow in color and density. A phase image is formed by executing the above processing for each pixel.

The time-series change of the phase difference can be obtained by sufficiently reducing the time interval Δt to ensure the 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 230)
The data processing unit 230 includes a processor that executes various data processing. For example, the data processing unit 230 performs image processing and analysis processing on the image formed by the image forming unit 220. As a specific example, there are various correction processes such as luminance correction and dispersion correction. Further, the data processing unit 230 performs image processing and analysis processing on the images (fundus image, anterior eye portion image, etc.) obtained by the fundus camera unit 2. The data processing unit 230 includes a preliminary measurement processing unit 231 and a blood flow measurement processing unit 232.

(Preliminary measurement processing unit 231)
The preliminary measurement processing unit 231 processes the data acquired in the preliminary measurement for setting the site where the blood flow measurement is performed. In this example, the preliminary measurement processing unit 231 generates information (measurement site information) for setting a region of interest to be measured for blood flow based on the phase image formed from the data by the preliminary measurement. The preliminary measurement processing unit 231 includes a profile generation unit 2311, an arterial region identification unit 2312, and an information generation unit 2313.

(Profile generation unit 2311)
The profile generation unit 2311 integrates (integrates) each frame of the phase image formed based on the preliminary measurement in the z direction. That is, the profile generation unit 2311 integrates the pixel values of the frames of the phase image in the A-line direction (axis direction). As a result, a plurality of integrated value profiles (time-related integrated value profiles) arranged in time series are obtained for each cross section on which the preliminary measurement is performed. It should be noted that the integration of pixel values may include a process of adding the values of a plurality of pixels arranged along the A line (luminance values representing reflection intensities), and may include an operation of processing the obtained integrated values. An example of this processing operation is scale conversion (conversion of gradation range).

A specific example of the process executed by the profile generation unit 2311 will be described. See FIGS. 6A and 6B. FIG. 6A represents a frame F of a phase image for a cross section on which preliminary measurements have been performed. An image region (blood vessel region) Fa corresponding to a cross section of a blood vessel is represented in the frame F. The vascular region Fa represents a cross section of an artery. The frame F is composed of a plurality of A scan images Ak ( _k = 1, 2, 3, ..., K: for example, K = 512). Each A scan image _Ak is a one-dimensional luminance image along the z direction (A line direction). A plurality of _A scan images A1 to _AK are arranged along an arbitrary direction in the xy plane. Therefore, the position of the A scan image _{Ak on the xy plane is specified as the position of the pixel P k located} at the intersection of the xy plane and the A scan image _Ak .

The profile generation unit 2311 integrates the values (luminance values) of a plurality of pixels included in the A scan image Ak for each A scan image _Ak , and associates the _{obtained integrated values with the pixels P k .} As a result, the correspondence between the integrated values for the plurality of _A scan images A1 to _AK and the plurality of pixels _P1 to _PK can be obtained. When this correspondence is graphed, the integrated value profile P as shown in FIG. 6B can be obtained. The horizontal axis of the integrated value profile P represents the positions of the pixels corresponding to the plurality of _A scan images A1 to _AK , and the vertical axis represents the magnitude of the integrated value. In the integrated value profile P, the integrated value obtained from the A scan image _Ak is associated with the pixel P _k . Such an integrated value profile is created for each frame constituting each phase image of the plurality of cross sections for which preliminary measurement has been performed. Thereby, a time-lapse integrated value profile for each cross section is obtained.

In the present embodiment, the values of all the pixels included in the A-scan image are integrated, but it is also possible to integrate only a part of the pixel values of a plurality of pixels included in the A-scan image. Is. That is, the profile generation unit 2311 may be configured to integrate the pixel values of at least a part of the plurality of pixels constituting the frame of the phase image. The case where only some pixels are targeted will be described later.

(Arterial region identification part 2312)
A part Pa of the integrated value profile P corresponds to the blood vessel region Fa. When the blood vessel region Fa corresponds to a vein, the change in the luminance value of the blood vessel region Fa is small, but when the blood vessel region Fa corresponds to an artery, the luminance value of the blood vessel region Fa changes significantly with time. do. Therefore, by analyzing the integrated value profile over time, it is possible to determine whether the blood vessel passing through the cross section is an artery or a vein. Utilizing such a fact, the arterial region specifying portion 2312 identifies an image region (arterial region) corresponding to an artery. An example of the process performed by the arterial region identification unit 2312 will be described below.

In the determination of blood vessels, the degree (magnitude) of the change over time in the luminance value can be taken into consideration. That is, the arterial region specifying portion 2312 can discriminate blood vessels based on changes over time in the integrated value profile (variations over time in the integrated values). As a specific example, the arterial region specifying unit 2312 can obtain the difference between different integrated value profiles included in the time-dependent integrated value profile, and can discriminate the blood vessel based on the magnitude of the obtained difference. If the difference is relatively large, the blood vessel is determined to be an artery. Further, the arterial region specifying unit 2312 can obtain an evaluation value of the magnitude of the change with time of the integrated value for each pixel position (for each pixel _Pk ), and can discriminate the blood vessel based on this evaluation value. be. If the cumulative change over time is relatively large, the blood vessel is determined to be an artery. In addition, the arterial region specifying unit 2312 can obtain statistical values (standard deviation, variance, etc.) of variations in the integrated values in each integrated value profile, and can discriminate blood vessels based on these statistical values. When the variation of the integrated value is relatively large, the blood vessel is determined to be an artery.

In addition, the magnitude (absolute value) of the luminance value can be taken into consideration in the determination of blood vessels. For example, the arterial region identification unit 2312 can determine that the blood vessel is an artery when there is an integrated value profile including a group of pixels (blood vessel region) associated with a relatively large integrated value. In this example, the magnitude of the representative value in the integrated value profile is referred to. This representative value is, for example, a maximum value or a maximum value in the integrated value profile.

In the above description, "relatively" refers to a comparison between the arterial region and the venous region. Whether a value is "relatively" large is determined, for example, by comparison with a threshold for distinguishing between the arterial region and the venous region.

(Information generation unit 2313)
The information generation unit 2313 generates measurement site information for setting a target site for blood flow measurement based on the arterial region specified by the arterial region identification unit 2312. The form of the measurement site information is arbitrary.

For example, the measurement site information may include information indicating whether the blood vessel passing through the cross section where the preliminary measurement was performed is an artery or a vein. When two or more vessels pass through one cross section (ie, two or more vascular regions are identified within the frame), the information generator 2313 tells each vessel whether it is an artery or a vein. It is possible to generate information indicating whether or not. Specific examples of measurement site information will be described later.

(Blood flow measurement processing unit 232)
The blood flow measurement processing unit 232 processes the data acquired by the blood flow measurement of the site set based on the preliminary measurement. In this example, the blood flow measurement processing unit 232 obtains the inclination of the blood vessel of interest in the cross section of interest based on the data acquired by the first scan. Further, the blood flow measurement processing unit 232 obtains blood flow information regarding the blood flow of interest based on the inclination of the blood vessel of interest obtained by the first scan and the data acquired by the second scan. Blood flow information includes, for example, blood flow velocity and blood flow volume. The blood flow measurement processing unit 232 includes a blood vessel region specifying unit 2321, an inclination calculation unit 2322, a blood flow velocity calculation unit 2323, a blood vessel diameter calculation unit 2324, and a blood flow volume calculation unit 2325.

(Vessel region identification part 2321)
The blood vessel region specifying unit 2321 identifies the blood vessel region corresponding to the blood vessel of interest in the tomographic image formed by the tomographic image forming unit 221. Further, the blood vessel region specifying unit 2321 identifies the blood vessel region corresponding to the blood vessel of interest in the phase image formed by the phase image forming unit 222. The blood vessel region is specified by analyzing the pixel value of each image (for example, threshold processing).

When a tomographic image and a phase image are created from the same data, the identification of the vascular region in the tomographic image where the cross-sectional morphology is depicted relatively clearly is first performed, and then the identification of the vascular region in the phase image corresponding to the identified vascular region is performed. The region can be identified using the natural registration of the tomographic image and the phase image described above. In addition, even if the tomographic image and the phase image are created from different data, if their registration is possible directly or indirectly, the specific result of the blood vessel region of one image is obtained from the other. It can be used to identify the blood vessel region of the image.

(Inclination calculation unit 2322)
The inclination calculation unit 2322 calculates the inclination of the blood vessel Db of interest in the cross section C2 of interest based on the data acquired by the first scan. At this time, it is also possible to further use the data obtained by the second scan. The inclination calculation unit 2322 calculates the inclination of the blood vessel Db of interest in the section of interest C2 based on the distance between the cross sections and the specific result of the blood vessel region. The cross-section distance may include the distance between the cross-sections C11 and the cross-section C12. Further, the inter-section distance may include a distance between the cross-section C11 and the section of interest C2 and a distance between the section C12 and the section of interest C2.

An example of a method for calculating the inclination of the blood vessel Db of interest will be described with reference to FIG. 7. The tomographic images G11 and G12 are a tomographic image representing the cross section C11 to which the first scan is applied and a tomographic image representing the cross section C12, respectively. Further, the tomographic image G2 is a tomographic image representing a cross section of interest C2 to which the second scan is applied. Reference numerals V11, V12 and V2 indicate a blood vessel region in the tomographic image G11, a blood vessel region in the tomographic image G12, and a blood vessel region in the tomographic image G2, respectively. These blood vessel regions correspond to the cross section of the blood vessel Db of interest. In FIG. 7, the z coordinate axis points downward, which substantially coincides with the irradiation direction of the measurement light LS (the direction of the optical axis of the optical path of the measurement light LS, the axis direction, and the A-line direction). .. Further, let L be the interval between adjacent tomographic images (cross sections).

In one example, the inclination calculation unit 2322 calculates the inclination U of the blood vessel Db of interest in the cross section C2 of interest based on the positional relationship of the three blood vessel regions V11, V12, and V2. This positional relationship is obtained, for example, by connecting three vascular regions V11, V12 and V2. Specifically, the inclination calculation unit 2322 identifies the feature points of each of the three blood vessel regions V11, V12, and V2, and connects these feature points. The feature points include a center position, a center of gravity position, a top portion (a position where the z coordinate value is the minimum), and a bottom portion (a position where the z coordinate value is the maximum). Further, as a method of connecting these feature points, 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 2322 calculates the inclination U based on the line connecting these feature points. When a line segment is used, for example, the inclination of the first line segment connecting the feature point of the blood vessel region V2 in the cross section C2 of interest and the feature point of the blood vessel region V11 in the cross section C11, and the feature point of the blood vessel region V2. The slope U is calculated based on the slope of the second line segment connecting the feature points of the blood vessel region V12 in the cross section C12. As an example of this calculation process, the average value of the slopes of the 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 cross section of interest C2 can be obtained. The intersection distance L is used when embedding these tomographic images G11, G12, and G2 in the xyz coordinate system in the process of obtaining a line segment or an approximate curve.

In this example, the blood vessel regions in the three cross sections are taken into consideration, but it is also possible to obtain the inclination in consideration of the blood vessel regions in the two cross sections. As a specific example, it can be configured to obtain the inclination U of the blood vessel Db of interest in the cross section C2 of interest based on the blood vessel region V11 in the cross section C11 and the blood vessel region V12 in the cross section C12. Alternatively, the slope of the first line segment or the second line segment can be used as the slope U.

The method for calculating the inclination of the blood vessel of interest in the cross section of interest is not limited to the above. For example, the following method can be applied. First, an OCT scan is performed on a cross section that intersects the cross section of interest and is along the blood vessel of interest. Next, a tomographic image is formed based on the data acquired by this OCT scan, and the tomographic image is segmented to identify an image region (layer region) corresponding to a predetermined tissue. The specified layer region is, for example, a layer region (ILM region) corresponding to the internal limiting membrane. The internal limiting membrane is the tissue of the retina that defines the boundary between the retina and the vitreous and is relatively clearly depicted. Further, a line segment that approximates the shape of the specified layer region is obtained, and the slope thereof is obtained. The slope of the approximate line segment is expressed, for example, as an angle with respect to the z-axis or as an angle with respect to the xy plane (that is, a plane orthogonal to the z-axis).

(Blood flow velocity calculation unit 2323)
The blood flow velocity calculation unit 2323 calculates the blood flow velocity in the attention section C2 of the blood flowing in the blood vessel Db of interest based on the time-series change of the phase difference obtained as the phase image. The calculation target may be the blood flow velocity at a certain point in time, or may be a time-series change (blood flow velocity change information) of the blood flow velocity. In the former case, for example, it is possible to selectively acquire the blood flow velocity in a predetermined time phase of an electrocardiogram (for example, the time phase of an R wave). Also, the time range in the latter is the whole or any part of the time scanned in the section of interest C2.

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 the value of blood flow velocity.

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 U of the blood vessel Db of interest in the cross section of interest C2 calculated by the inclination calculation unit 2322 is taken into consideration. Specifically, the inclination calculation unit 2322 uses the following equation.

here:
Δf represents the Doppler shift received by the scattered light of the measurement light LS;
n represents the refractive index of the medium (blood);
v represents the flow velocity (blood flow velocity) of the medium;
θ represents the angle formed by the incident direction of the measurement light LS and the flow direction (slope U) 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 series change of the phase difference, θ is obtained from the slope U (or θ is obtained as the slope U). By substituting these values into the equation (1), the blood flow velocity v is calculated.

(Blood vessel diameter calculation unit 2324)
The blood vessel diameter calculation unit 2324 calculates the diameter of the blood vessel Db of interest in the cross-section of interest C2 by analyzing the fundus image or the OCT image. When a fundus image is used, a portion of the fundus Ef including the position of the fundus section C2 is imaged, and the fundus image obtained by the image (for example, a color fundus image, a red-free image, etc.) is used as a basis for the fundus image of interest. The diameter of the blood vessel Db of interest, that is, the diameter of the blood vessel region V2 is calculated. When an OCT image is used, the OCT image is, for example, a tomographic image formed based on the second scan or an image formed based on preliminary measurement. Such calculation of the blood vessel diameter is performed in the same manner as before.

(Blood flow rate calculation unit 2325)
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 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 volume 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 velocity calculation result by the blood flow velocity calculation unit 2323 into the equation (2). , Calculate the blood flow Q.

(User interface 240)
The user interface 240 includes a display unit 241 and an operation unit 242. The display unit 241 includes a display device and a display device 3 of the arithmetic control unit 200. The operation unit 242 includes an operation device of the arithmetic control unit 200. The user interface 240 may include a device having a display function and an operation function, such as a touch panel.

[motion]
The operation of the blood flow measuring device 1 will be described. FIG. 8 shows an example of the flow of operations executed by the blood flow measuring device 1. It is assumed that the input of the patient ID and the preparatory operations such as alignment and focusing have already been performed.

(S1: Preliminary measurement)
First, the user or the blood flow measuring device 1 sets the scan range of the preliminary measurement. In setting the scan range, for example, an infrared observation image of the fundus Ef acquired in real time or data of the fundus Ef acquired in the past (fundus image, OCT image, SLO image, phase image, etc.) is referred to. To.

The blood flow measuring device 1 executes a preliminary measurement for a set scan range (a plurality of cross sections). As an example, the scan range to be set is a three-dimensional area, and the raster scan of this three-dimensional area is repeatedly executed. The phase image forming unit 222 forms a phase image for each of the plurality of cross sections based on the data acquired by the preliminary measurement.

(S2: Generation of time-series integrated value profile)
The profile generation unit 2311 integrates the pixel values of each frame of each phase image formed in step S1 in the A-line direction to generate a temporal integrated value profile for each cross section on which preliminary measurement has been performed.

(S3: Identification of arterial region)
The arterial region specifying unit 2312 identifies the arterial region by analyzing the time-lapse integrated value profile generated in step S2. If no arterial region is obtained, it is possible to return to the setting of the scan range in step S1. Here, a sufficiently large scan range can be set from the beginning so that the arterial region can be obtained. Also, by setting the scan range near the optic disc, the possibility of obtaining an arterial region can be increased.

(S4: Generation of measurement site information)
The information generation unit 2313 generates measurement site information for setting a target site for blood flow measurement based on the arterial region specified in step S3.

(S5: Display of information for setting the measurement part)
The control unit 210 causes the display unit 241 to display information (setting support information) for setting a target site for blood flow measurement based on the measurement site information generated in step S4. The setting support information may include information that enables the distinction between arteries and veins. In particular, the setting support information may include information indicating the position of the artery.

In one example, the control unit 210 displays a frontal image of the fundus Ef and displays setting support information that identifiablely presents an arterial region in the frontal image. The front image is, for example, an infrared observation image acquired in real time or an image acquired in the past. The setting support information is, for example, information superimposed on the front image, and includes an arrow image pointing to the arterial region and an image of a predetermined display color arranged on the arterial region.

(S6: Setting the cross section of interest, etc.)
The user refers to the information displayed in step S5 and sets a cross section (attention cross section C2) to be measured for blood flow. For example, the user designates a desired arterial region (attention blood vessel Db) in the frontal image by referring to the setting support information displayed together with the frontal image of the fundus Ef.

In this example, the cross section C2 of interest is set manually, but the present invention is not limited to this. For example, the blood vessel Db of interest and the cross section C2 of interest can be automatically set based on the infrared observation image of the fundus Ef and the measurement site information. The setting of the blood vessel Db of interest is performed, for example, by selecting one of the arterial regions (eg, the thickest one). Further, the cross section C2 of interest is set so as to be orthogonal to the traveling direction of the blood vessel Db of interest, for example, at a position where the direction of the blood vessel Db of interest is within a predetermined allowable range.

Further, the user or the blood flow measuring device 1 (for example, the data processing unit 230) sets the cross sections C11 and C12 to be the target of the first scan.

(S7: First scan of blood flow measurement)
The blood flow measuring device 1 executes an OCT scan of the cross sections C11 and C12 set in step S6 (first scan). The tomographic image forming unit 221 forms tomographic images G11 and G12 corresponding to the cross sections C11 and C12 based on the data acquired by the first scan. The data processing unit 230 (blood vessel region specifying unit 2321 and inclination calculation unit 2322) calculates the inclination U of the blood vessel Db of interest in the cross section C2 of interest. When the slope U is calculated by adding the data acquired by the second scan, the calculation of the slope U is executed after the second scan.

(S8: Second scan of blood flow measurement)
The blood flow measuring device 1 performs a repetitive OCT scan of the cross section of interest C2 set in step S6 (second scan). The phase image forming unit 222 forms a phase image of the cross section of interest C2 based on the data acquired by the second scan. Further, the tomographic image forming unit 221 forms a tomographic image of the cross section of interest C2 based on the data. The data processing unit 230 (blood vessel region specifying unit 2321, blood vessel diameter calculating unit 2324, etc.) obtains the diameter of the blood vessel Db of interest in the cross-section of interest C2.

(S9: Generation of blood flow information)
The blood flow velocity calculation unit 2323 calculates the blood flow velocity in the cross section C2 of interest based on the inclination U calculated based on the first scan of step S7 and the phase image acquired by the second scan of step S8. .. Further, 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 obtained in step S8.

The main control unit 211 causes the display unit 241 to display blood flow information including the calculation result of the blood flow velocity, the calculation result of the blood flow volume, 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. This is the end of the operation related to this example.

[Action / Effect]
The operation and effect of the blood flow measuring device according to the embodiment will be described.

The blood flow measuring device of the embodiment measures the blood flow of a living body (fundus Ef or the like) using OCT, and includes a data acquisition unit, a phase image forming unit, and a processing unit.

The data acquisition unit repeatedly scans a plurality of cross sections of a living body to acquire data. That is, the data acquisition unit executes preliminary measurement. In the above embodiment, the data acquisition unit includes a configuration for executing OCT, such as an OCT unit 100 and a group of optical elements arranged in the optical path of the measurement light LS.

The phase image forming unit (222) forms a phase image in each of a plurality of cross sections for which preliminary measurement has been performed, based on the data acquired by the data acquisition unit.

The processing unit (preliminary measurement processing unit 231) integrates the values of at least a part of the pixels in each frame of the phase image formed by the phase image forming unit in each of the plurality of cross sections where the preliminary measurement is performed. Generate an integrated value profile over time. Further, the processing unit generates measurement site information for setting a target site for blood flow measurement based on the generated time-lapse integrated value profile.

In the embodiment, the processing unit analyzes a time-dependent integrated value profile to specify an arterial region (arterial region specifying unit 2312) and information for generating measurement site information based on the specified arterial region. It may include a generator (2313).

Further, the region specifying unit may be configured to obtain information indicating the degree of change over time in the integrated value profile over time by analyzing the integrated value profile over time, and to specify the arterial region based on this information.

Further, the region specifying portion may be configured to specify the arterial region based on the magnitude of the representative value in the time-lapse integrated value profile.

The blood flow measuring device of the embodiment may further include a front image acquisition unit, a display control unit, and an operation unit. The front image acquisition unit acquires a front image of the living body. In the above embodiment, the front image acquisition unit includes a configuration for photographing the fundus Ef, such as the fundus camera unit 2. Further, the front image acquisition unit may be configured to acquire a front image stored in the blood flow measuring device or another device. For example, the front image acquisition unit may be configured to acquire a front image from an image filing system via a network. The display control unit (control unit 210) causes the display means to display the front image and the measurement site information. The display means may be included in the blood flow measuring device or may be a display device connected to the display device. The operation unit (242) is used to set a target cross section (attention cross section C2) for blood flow measurement.

According to such an embodiment, measurement site information is generated based on a phase image group acquired by performing an OCT scan of a plurality of cross sections, and a target site for blood flow measurement is set based on the measurement site information. be able to. Therefore, it is not necessary to perform trial and error for searching the target blood vessel (blood vessel of interest) for blood flow measurement, and the target blood vessel can be set without relying on the user's experience. Therefore, it is possible to facilitate the setting of the target site for blood flow measurement and shorten the time. The embodiment also contributes to improving the accuracy and reproducibility of the setting of the target blood vessel.

<Second Embodiment>
In the first embodiment, the values of all the pixels constituting the frame of the phase image are integrated in order to generate the integrated value profile over time. On the other hand, in the second embodiment, a case where only a part of the pixels in the frame of the phase image are integrated will be described.

A configuration example of this embodiment is shown in FIG. The blood flow measuring device of the present embodiment has almost the same configuration as that of the first embodiment, but is different from the first embodiment in that the layer region specifying unit 2314 is provided in the preliminary measurement processing unit 231. Unless otherwise specified, the drawings of the first embodiment will be referred to.

The layer region specifying unit 2314 identifies the layer region in the OCT image by analyzing the OCT image. The layered region is, for example, an image region corresponding to any tissue of the fundus Ef, or an image region corresponding to a boundary between adjacent tissues. The layered region may be an image region corresponding to the tissue of the retina. Tissues that can be identified as layered regions include the internal limiting membrane (ILM), nerve fiber layer (NFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), and outer plexiform layer (. OPL), outer nuclear layer (ONL), inner plexiform photoreceptor, outer plexiform junction (IS / OS), retinal pigment epithelial layer (RPE), Bruch's membrane (BM), internal limiting membrane-strong membrane boundary (CSI), and the like.

The process of dividing an OCT image into a plurality of layer areas is called segmentation. Segmentation is performed based on the pixel value (luminance value) of the two-dimensional tomographic image or the three-dimensional image. Each layered tissue of the fundus Ef has a characteristic reflectance, and the image region of the layered tissue also has a characteristic luminance value. In segmentation, a target image area is specified based on such characteristic luminance values.

The layer region specifying unit 2314 performs segmentation of the frame of the phase image obtained by the preliminary measurement. Therefore, the layer region specifying unit 2314 can analyze only the phase image or both the phase image and the tomographic image. As an example of the latter, segmentation can be performed on the tomographic image and the result can be reflected in the phase image. Further, the blood vessel region can be specified based on the phase image, and the partial region (one or more layer regions) including the blood vessel region can be specified. For example, as shown in FIG. 10, a partial region Fb including a blood vessel region Fa is specified in the frame F.

The profile generation unit 2311 generates an integrated value profile for the frame by integrating the values of the pixels included in the layer region specified by the layer region specifying unit 2314 (for example, in the A-line direction). In a plurality of frames, the integrated range may be the same or different.

According to such an embodiment, it is possible to reduce the noise included in the integrated value profile. For example, since the integrated value profile can be generated by excluding the data of the portion irrelevant to the arterial / vein discrimination such as the vitreous body, it is expected that the accuracy and accuracy of the arterial / vein determination will be improved.

<Third Embodiment>
When two or more blood vessels are located side by side in the z direction, in OCT, only the data of the blood vessel closest to the retinal surface is preferably acquired, and the data on other blood vessels is often not sufficiently acquired. When the pixel values of the A scan image passing through such a portion are integrated, the accuracy of the obtained integrated value may be low. In the present embodiment, a configuration for generating an integrated value profile by excluding such an inappropriate portion will be described.

A configuration example of this embodiment is shown in FIG. The blood flow measuring device of the present embodiment has almost the same configuration as that of the first embodiment, but is different from the first embodiment in that the preliminary measurement processing unit 231 is provided with the partial area specifying unit 2315. Unless otherwise specified, the drawings of the first embodiment will be referred to.

The partial region specifying unit 2315 identifies a partial region corresponding to a predetermined portion of the eye E to be inspected in the frame of the phase image obtained by the preliminary measurement. The predetermined site may include an inappropriate site as described above. The partial region specifying unit 2315 identifies a partial region by analyzing only the phase image or both the phase image and the tomographic image. As an example of the latter, the partial region specifying unit 2315 can specify a region corresponding to a predetermined portion in the tomographic image and specify a partial region in the phase image corresponding to this region. Further, the blood vessel region may be specified based on the phase image, and it may be determined whether or not some of the specified blood vessel regions are aligned in the z direction.

The profile generation unit 2311 generates an integrated value profile for the frame by integrating the values of the pixels included in the region other than the partial region specified by the partial region specifying unit 2315 (for example, in the A-line direction). In a plurality of frames, the integrated range may be the same or different.

According to such an embodiment, it is possible to reduce the noise included in the integrated value profile as in the second embodiment.

<Modification example>
The configuration described above is merely an example of an embodiment of the present invention. Therefore, it is possible to make arbitrary modifications (omission, substitution, addition, etc.) within the scope of the gist of the present invention.

For example, in the above typical embodiment, data is acquired by repeatedly scanning a plurality of cross sections of a living body, a phase image is formed in each of the plurality of cross sections, and a time-lapse integrated value profile in each of the plurality of cross sections is obtained. It is generated, and the measurement site information is generated based on it. However, the number of cross sections to be processed is not limited to two or more, and may be one. That is, in the embodiment, a "single" cross section of a living body is repeatedly scanned to acquire data, a phase image in this cross section is formed, a time-lapse integrated value profile in this cross section is generated, and this time-lapse integrated value is generated. It may be configured to generate measurement site information based on the profile.

In addition, considering that the blood flow velocity in any cross section is the same for both arteries and veins as long as they are the same blood vessel, and the pulsatile state is also the same, the arterial region and the venous region can be discriminated in a single cross section. It is possible to do. Even in that case, the arterial region and the venous region can be specified in the same manner as in the above embodiment. However, when the treatment is applied to a single cross section, only the blood vessels that intersect this cross section can be discriminated. Therefore, when discriminating multiple blood vessels, the position and number of these blood vessels are determined. It is necessary to apply the treatment to the number of cross sections.

From the above, in the blood flow measuring device according to the embodiment, the data acquisition unit may be configured to repeatedly scan one or more cross sections of the living body to acquire data, and the phase image forming unit may be configured to acquire the acquired data. Based on this, it may be configured to form a phase image in each of the one or more cross sections, and the processing unit may integrate the values of at least a part of the pixels in each frame of the phase image to form a phase image in each of the one or more cross sections over time. It may be configured to generate a target integrated value profile and generate measurement site information for blood flow measurement based on this temporal integrated value profile.

Also in this configuration, the processing unit can generate a time-dependent integrated value profile by segmentation and integration of pixel values in the layer region, as in the above embodiment. Alternatively, the processing unit can generate a time-dependent integrated value profile by specifying a partial region in the phase image and integrating the pixel values of the region other than the partial region, as in the above embodiment. Further, it is also possible to display a front image of the living body and information on the measurement site and to accept the setting of the target cross section for blood flow measurement.

In the above typical embodiment, the arterial region is selectively specified in order to set the target site for blood flow measurement, but it is also possible to specify the venous region. That is, in the embodiment, the region specifying portion may be configured to identify at least one of the arterial region and the venous region by analyzing the cumulative value profile over time. The identification of the venous region can be performed in the same manner as the identification of the arterial region. For example, the region specifying unit is configured to obtain information indicating the degree of change over time (variation over time of the integrated value) by analyzing the integrated value profile over time, and to specify the vein region based on this information. May be done. Alternatively, the region specifying unit may be configured to specify the venous region based on the size of a representative value (eg, maximum value, maximum value, etc.) in the integrated value profile over time.

The type of specific target blood vessel can be manually or automatically selected. For example, if it is effective to consider arterial blood flow for diagnosis or screening, the artery is selected as a specific target. Conversely, if it is useful to consider venous blood flow for diagnosis or screening, arteries are selected as the specific target. In addition, when it is necessary to analyze both arterial blood flow and venous blood flow sent to the whole body for diagnosis and screening, both arterial and venous blood flows are selected as specific targets. The region identification unit operates to identify the region corresponding to the artery and / or vein selected as the identification target. The determination of blood vessels according to the embodiment can be applied to other than blood flow measurement. For example, blood vessel discrimination can be applied to determine the shape and distribution of arteries and veins.

In this way, the information generation unit can generate measurement site information based on at least one of the arterial region and the vein region specified by the region identification unit.

In the above typical embodiment, the values of at least a part of the pixels in the frame (two-dimensional cross section) of the phase image are integrated in the A-line direction in order to generate the integrated value profile over time. However, the direction in which the pixel values are integrated is not limited to the A-line direction. For example, the pixel values can be integrated in the direction orthogonal to the A-line direction (horizontal scan direction) in the frame. Alternatively, it is also possible to configure the pixel values to be integrated in an arbitrary direction different from the A-line direction and the lateral scan direction.

Further, the frame of the phase image is not limited to the two-dimensional cross section. For example, when a phase image in a three-dimensional region is obtained, it is possible to generate a pixel value profile over time by integrating the pixel values in an arbitrary direction in the three-dimensional region.

Further, when the frame of the phase image is a two-dimensional cross section, the two-dimensional cross section is not limited to a plane. For example, when a circle scan is applied, the frame of the phase image corresponds to a cylindrical cross section. In such a case, it is possible to generate a time-dependent integrated value profile by integrating the pixel values in an arbitrary direction in the cross section. More generally, the direction in which the pixel values are integrated is not limited to a linear direction (constant direction), and may be a direction along an arbitrary path such as a curved direction.

It is also possible to integrate pixel values in a plurality of directions in one frame. For example, it is possible to generate a plurality of integrated value profiles over time by integrating pixel values in each of a plurality of directions. Then, it is possible to select and use one of a plurality of time-lapse integrated value profiles, or to use data obtained by integrating two or more of the plurality of time-lapse integrated value profiles.

1 Blood flow measuring device 100 OCT unit 222 Phase image forming unit 231 Preliminary measurement processing unit

Claims (6)

A blood flow measuring device that measures blood flow in a living body using optical coherence tomography.
A front image acquisition unit that acquires a front image of the living body,
A data acquisition unit that repeatedly scans the cross section of the living body to acquire data,
Based on the data, a phase image forming unit that forms a phase image in the cross section,
An arterial region is specified based on the phase image, and measurement site information for setting a target site for blood flow measurement is generated based on the identified arterial region, and the front image and the measurement site information are combined. Based on this, any of the arterial regions of interest is specified as a blood vessel of interest, and a cross section of interest to be measured for blood flow so as to intersect the blood vessel of interest at a position where the direction of the blood vessel of interest is within a predetermined range. A blood flow measuring device equipped with a processing unit to be set. As the range of repeated scanning for acquiring the data by the data acquisition unit, a range having a sufficient width is set so that the arterial region can be obtained.
The blood flow measuring device according to claim 1. The range of repeated scanning for acquiring the data by the data acquisition unit is set in the vicinity of the optic disc of the fundus of the living body.
The blood flow measuring device according to claim 1 or 2, wherein the blood flow measuring device is characterized by the above. The blood flow measuring device according to any one of claims 1 to 3 , wherein the processing unit sets the cross section of interest so as to intersect the thickest arterial region in the front image. The blood flow measuring device according to any one of claims 1 to 4, wherein the processing unit sets the cross section of interest so as to be orthogonal to the traveling direction of the blood vessel of interest . The processing unit generates a temporal integrated value profile in the cross section by integrating the values of at least a part of the pixels in each frame of the phase image, and the measurement site information is based on the temporal integrated value profile. The blood flow measuring apparatus according to any one of claims 1 to 5, wherein the blood flow measuring apparatus is generated.

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