JP5752538B2 - Optical coherence tomographic image processing method and apparatus - Google Patents

Description

  The present invention relates to an optical coherence tomographic image processing method and apparatus, and more particularly, to extract a specific structure such as a blood vessel from tomographic information acquired by a tomographic method represented by optical coherence tomography (OCT). The present invention relates to a suitable image processing technique.

  In recent years, for example, in the medical field, OCT measurement has been used as one of non-invasive methods for obtaining tomographic information inside a living body. OCT measurement has an advantage that the resolution is about 10 μm higher than ultrasonic measurement, and detailed tomographic information (tomographic image) inside the living body can be obtained. In addition, it is possible to obtain tomographic information of a three-dimensional region by connecting the tomographic information acquired at a plurality of positions while shifting the position of acquiring the tomographic information.

  Currently, it is required to acquire detailed tomographic information of a living body for the purpose of cancer diagnosis and the like. As a method therefor, a time domain OCT (Time domain OCT) that obtains tomographic information on a subject by scanning light output from a low coherent light source has been proposed (Patent Document 1).

  Further, in recent years, an improved type that solves the problems that the optimum signal / noise ratio (S / N ratio), which is a disadvantage of the time domain OCT, cannot be obtained, the imaging frame rate is low, and the penetration depth (observation depth) is poor. The frequency domain OCT (Frequency domain OCT) which is OCT is utilized (patent document 2). Frequency domain OCT (Frequency domain OCT) is also used in diagnostic regions other than cancer and is widely used in clinical practice.

  Typical examples of the apparatus configuration for performing frequency domain OCT measurement include an SD-OCT (Spectral Domain OCT) apparatus and an SS-OCT (Swept SourceOCT). The SD-OCT apparatus uses broadband low-coherent light such as SLD (Super Luminescence Diode), ASE (Amplified Spontaneous Emission) light source, white light as a light source, and uses Michelson interferometer to generate broadband low-coherent light. After splitting into measurement light and reference light, irradiate the measurement light on the object to be measured, cause the reflected light and reference light that have returned at that time to interfere with each other, and decompose this interference light into frequency components using a spectrometer. Then, the interference light intensity for each frequency component is measured using a detector array in which elements such as photodiodes are arranged in an array, and the resulting spectrum interference intensity signal is Fourier-transformed by a computer. Information is acquired.

  On the other hand, the SS-OCT apparatus uses a laser that temporally sweeps the optical frequency as a light source, causes reflected light and reference light to interfere at each wavelength, and measures the time waveform of the signal corresponding to the temporal change of the optical frequency. The tomographic information is obtained by Fourier-transforming the spectral interference intensity signal thus obtained with a computer.

  In addition, the OCT apparatus can acquire three-dimensional information of the subject (measurement target) together with the tomographic information in the depth direction by scanning the optical axis of the measurement light two-dimensionally. Patent Document 3 discloses an image diagnostic apparatus that not only generates a tomographic image of one cross section by OCT but also draws a three-dimensional image by performing three-dimensional scanning, and three-dimensionally diagnoses a lesion. Has been. By combining OCT measurement and three-dimensional computer graphic technology, it is possible to display a three-dimensional structure model composed of structure information of a measurement object having a resolution of the order of micrometers.

JP 2000-131222 A Special table 2007-510143 gazette JP 2010-68865 A

  In general, in order for cancer cells to grow, nutrients for growth are required, and thus cancer cells have a feature that many new blood vessels are concentrated. Therefore, if a blood vessel image can be displayed three-dimensionally based on the tomographic information acquired by OCT measurement, it is very effective for cancer diagnosis.

  By the way, the intensity | strength of the measurement light which reaches | attains deeper than the structure | tissue becomes small with respect to the structure | tissue where attenuation | damping of measurement light in OCT measurement is large like a blood vessel. For this reason, in the region from the blood vessel to the deep part, a shadow (blood vessel reflection) in which the tail is drawn from the blood vessel occurs. When a three-dimensional image or the like of a blood vessel is displayed using tomographic information of a three-dimensional region obtained by OCT, such a shadow region is also displayed as a three-dimensional image, so that the state of the blood vessel is difficult to understand. There is a problem. Therefore, it is desirable to identify the blood vessel region from the tomographic information, remove the shadow, and display only the blood vessel image.

  However, the value of tomographic information (tomographic data value) obtained by OCT varies depending on measurement conditions such as the intensity of measurement light and the distance from the probe to the measurement target, and is absolute for a specific subject such as a blood vessel. It does not indicate a correct value. In addition, since signal components such as electrical and optical noise at the time of OCT measurement are included, the position (region) of a specific subject such as a blood vessel is specified only from the value or change of tomographic data. There was a problem that it was difficult.

  The present invention has been made in view of such circumstances, and can accurately specify the position (region) of a specific subject such as a blood vessel from tomographic information (tomographic data) inside a living body acquired by OCT measurement. An object of the present invention is to provide an optical coherence tomographic image processing method and apparatus.

  In order to achieve the above object, the present invention provides tomographic data acquisition for acquiring tomographic data at each position indicating tomographic information of a three-dimensional region of the inner wall obtained by optical coherence tomography measurement on the inner wall of the living body. Means, an integrated image generating means for generating an integrated image obtained by integrating the tomographic data in the depth direction of the inner wall, and a predetermined image on the integrated image based on the integrated image generated by the integrated image generating means. A subject candidate region extraction unit that extracts a region where an image of a subject region where the subject is present exists as a subject candidate region; and each point in the subject candidate region extracted by the subject candidate region extraction unit Profile generating means for generating a contrast profile indicating a variation distribution of the tomographic data in the depth direction in the depth direction, the depth at each point in the subject candidate region Obtaining a profile in the subject candidate region indicating the distribution of the tomographic data in the direction, and obtaining a profile indicating the distribution of the tomographic data in the depth direction at a predetermined reference point outside the candidate subject region as a reference profile, Profile generation means for generating a difference between the profile in the object candidate area at each point in the object candidate area and the reference profile as a contrast profile at each point; and a contrast profile generated by the profile generation means And a subject depth position determining means for determining a position range in the depth direction of the subject region in the subject candidate region.

  According to the present invention, a position range related to a two-dimensional direction orthogonal to the depth direction of the subject region where the subject exists is identified as an object candidate region by the integral image, and the depth direction of the subject region is determined by the contrast profile. A position range is specified. Accordingly, the position of the subject occupying the three-dimensional region of the inner wall is determined. In addition, in order to determine the position range of the subject region in the depth direction, the profile of the subject candidate region where the subject region exists in the depth direction and the subject candidate region where the subject region does not exist in the depth direction Since a contrast profile that is compared with an external reference profile is used, only a unique profile indicated by the subject can be extracted, and the location of the subject can be specified accurately and easily. And regions (noise, shadows) other than the subject region can be easily removed.

  In the present invention, it is desirable that the profile generation means sets a position that is close to each of the points from which the object candidate in-region profile is acquired as a reference point for acquiring the reference profile. According to this, in the position range in the depth direction other than the subject region, the specimen candidate region profile and the reference profile are approximated, and thus the subject profile can be appropriately obtained in the contrast profile obtained by these differences. .

  In the present invention, it is preferable that the profile generation means sets a profile obtained by further averaging the reference profiles acquired at a plurality of points as the reference profile. According to this, the influence of noise included in the reference profile obtained at each point can be reduced.

  In the present invention, the subject depth position determining means acquires the position in the depth direction of the outer peripheral surface that is the surface side of the inner wall portion of the subject region in the subject candidate region based on the contrast profile. And determining the position in the depth direction of the outer peripheral surface on the opposite side to the surface of the inner wall portion of the subject region based on the acquired position and the thickness information of the subject, It is desirable to determine the position range of the subject region in the depth direction. In this embodiment, the position range in the depth direction of the subject is determined based on the contrast profile. Further, it is desirable that the information on the thickness of the subject is acquired from the integral image. According to this, information regarding the thickness of the subject can be accurately obtained, and the position in the depth direction of the subject can be accurately identified.

  In the present invention, the subject depth position determining means, based on the contrast profile, an effective region where the subject actually exists in the depth direction in the subject candidate region, and the subject in the depth direction. It is desirable to discriminate from a noise region where no specimen exists and to remove the noise region from the subject candidate region. Further, whether the region is an effective region or a noise region can be determined based on the presence or absence of a shadow region generated on the subject.

  In the present invention, a position range in the two-dimensional direction orthogonal to the depth direction of the subject candidate region extracted by the subject candidate region extraction unit, and the subject determined by the subject depth position determination unit. A three-dimensional subject that generates a three-dimensional image of the subject based on a position range of the subject region that occupies a three-dimensional region of the inner wall determined by the position range in the depth direction of the subject region It is preferable that the apparatus includes an image generation unit and a display unit that displays the three-dimensional image of the subject generated by the three-dimensional subject image generation unit. In this embodiment, a three-dimensional image of a subject is generated and displayed based on the specified position of the subject.

  In the present invention, the three-dimensional object image generation means generates the three-dimensional image of the object by visualizing the tomographic data, and at the time of the generation, the depth of the object candidate region It is desirable to replace the tomographic data other than the subject region in the direction with the tomographic data of the reference profile. According to this, the tomographic data of the noise area and the shadow area can be removed from the tomographic data, and when the tomographic data is visualized and displayed in three dimensions, these areas are removed from the image, and the 3 of the subject is removed. Only a dimensional image is displayed.

  In the present invention, it is desirable that the three-dimensional object image generation unit generates a three-dimensional image of the object colored with a different color according to a position in the depth direction of the object. According to this, the position in the depth direction of each part of the subject can be grasped also by the color information.

  In the present invention, the subject can be a blood vessel. The present invention is suitable as a device for specifying the position of a blood vessel occupying an inner wall portion inside a living body.

  The present invention also provides a tomographic data acquisition step of acquiring tomographic data at each position indicating tomographic information of a three-dimensional region of the inner wall obtained by optical coherence tomography measurement on the inner wall of the living body, and the inner wall An integrated image generating step for generating an integrated image obtained by integrating the tomographic data in the depth direction, and an object in which a predetermined subject exists on the integrated image based on the integrated image generated by the integrated image generating step. A subject candidate region extraction step for extracting a region where an image of the sample region exists as a subject candidate region; and the depth direction at each point in the subject candidate region extracted by the subject candidate region extraction step A profile generation step of generating a contrast profile indicating a variation distribution of tomographic data, wherein the tomographic data distribution in the depth direction at each point in the subject candidate region A profile indicating the distribution of tomographic data in the depth direction at a predetermined reference point outside the subject candidate region is acquired as a reference profile, and a profile within the subject candidate region is acquired. A profile generation step of generating a difference between the profile in the subject candidate region at each point and the reference profile as a contrast profile at each point, and the subject based on the contrast profile generated by the profile generation step An object depth position determining step for determining a position range in the depth direction of the object area in the candidate area.

  According to the present invention, a position range related to a two-dimensional direction orthogonal to the depth direction of the subject region where the subject exists is identified as an object candidate region by the integral image, and the depth direction of the subject region is determined by the contrast profile. A position range is specified. Therefore, the position range of the subject region in the three-dimensional region of the inner wall is determined. In addition, in order to determine the position range of the subject region in the depth direction, the profile of the subject candidate region where the subject region exists in the depth direction and the subject candidate region where the subject region does not exist in the depth direction Since a contrast profile that is compared with an external reference profile is used, only a unique profile indicated by the subject can be extracted, and the location of the subject can be specified accurately and easily. And regions (noise, shadows) other than the subject region can be easily removed.

  In the present invention, it is desirable that in the profile generation step, a position that is close to each point from which the in-subject candidate region profile is acquired is used as a reference point for acquiring the reference profile. According to this, in the position range in the depth direction other than the subject region, the specimen candidate region profile and the reference profile are approximated, and thus the subject profile can be appropriately obtained in the contrast profile obtained by these differences. .

  In the present invention, it is preferable that the profile generation step sets a profile obtained by further averaging the reference profiles acquired at a plurality of points as the reference profile. According to this, the influence of noise included in the reference profile obtained at each point can be reduced.

  In the present invention, the subject depth position determining step acquires the position in the depth direction of the outer peripheral surface on the surface side of the inner wall portion of the subject region in the subject candidate region based on the contrast profile. And determining the position in the depth direction of the outer peripheral surface on the opposite side to the surface of the inner wall portion of the subject region based on the acquired position and the thickness information of the subject, It is desirable to determine the position range of the subject region in the depth direction. In this embodiment, the position range in the depth direction of the subject is determined based on the contrast profile. Further, it is desirable that the information on the thickness of the subject is acquired from the integral image. According to this, information regarding the thickness of the subject can be accurately obtained, and the position in the depth direction of the subject can be accurately identified.

  In the present invention, the subject depth position determining step includes, based on the contrast profile, an effective region where the subject actually exists in the depth direction in the subject candidate region, and the subject in the depth direction. It is desirable to discriminate from a noise region where no specimen exists and to remove the noise region from the subject candidate region. Further, whether the region is an effective region or a noise region can be determined based on the presence or absence of a shadow region generated on the subject.

  In the present invention, a position range in the two-dimensional direction perpendicular to the depth direction of the subject candidate region extracted by the subject candidate region extraction step, and the subject determined by the subject depth position determination step. A three-dimensional subject that generates a three-dimensional image of the subject based on a position range of the subject region that occupies a three-dimensional region of the inner wall determined by the position range in the depth direction of the subject region It is desirable to include an image generation step and a display step for displaying the three-dimensional image of the subject generated by the three-dimensional subject image generation step. In this embodiment, a three-dimensional image of a subject is generated and displayed based on the specified position of the subject.

  In the present invention, the three-dimensional subject image generation step generates a three-dimensional image of the subject by visualizing the tomographic data, and at the time of the generation, the depth of the subject candidate region. It is desirable to replace the tomographic data other than the subject region in the direction with the tomographic data of the reference profile. According to this, the tomographic data of the noise area and the shadow area can be removed from the tomographic data, and when the tomographic data is visualized and displayed in three dimensions, these areas are removed from the image, and the 3 of the subject is removed. Only a dimensional image is displayed.

  In the present invention, it is desirable that the three-dimensional object image generation step generates a three-dimensional image of the object colored with a different color according to a position in the depth direction of the object. According to this, the position in the depth direction of each part of the subject can be grasped also by the color information.

  In the present invention, the subject can be a blood vessel. The present invention is suitable as a method for specifying the position of a blood vessel occupying an inner wall portion inside a living body.

  According to the present invention, the position (region) of a subject such as a blood vessel can be accurately identified from tomographic information (reflection intensity data) acquired by OCT measurement.

1 is an external view of an image diagnostic apparatus to which a tomographic image processing apparatus according to an embodiment of the present invention is applied. The block diagram which shows the internal structure of the OCT processor of FIG. Sectional view of the OCT probe of FIG. The figure which shows the scanning surface of a tomographic image in case optical scanning is radial scanning with respect to a measuring object The figure which shows the three-dimensional volume data constructed | assembled by the tomographic image of FIG. The figure which shows a mode that a tomographic image is acquired using the OCT probe derived | led-out from the forceps opening | mouth of the endoscope of FIG. The block diagram which shows the structure of the signal processing part of FIG. Flow chart of 3D blood vessel structure extraction process Flow chart showing a procedure for generating a blood vessel contrast profile Diagram illustrating the blood vessel structure of the measurement site The figure which illustrated the volume data acquired with respect to FIG. (A) is a diagram reconstructing volume data as a slice image of a cross section parallel to the XY plane, and (B) is a diagram showing an integral image. Diagram used to describe profile Diagram used to describe blood vessel contrast profile The figure which expanded the integral image of FIG. The figure which showed the example which displayed the three-dimensional image of the blood vessel

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is an external view of an image diagnostic apparatus to which an optical coherence tomographic image processing apparatus according to an embodiment of the present invention is applied. As shown in FIG. 1, the diagnostic imaging apparatus 10 mainly includes an endoscope 100, an endoscope processor 200, a light source device 300, an OCT processor 400 as a tomographic image processing apparatus, and a monitor device 500. Note that the endoscope processor 200 may be configured to incorporate the light source device 300.

  The endoscope 100 includes a hand operation unit 112 and an insertion unit 114 that is connected to the hand operation unit 112. The surgeon grasps and operates the hand operation unit 112 and performs observation by inserting the insertion unit 114 into the body of the subject.

  The hand operation part 112 is provided with a forceps insertion part 138, and the forceps insertion part 138 communicates with the forceps port 156 of the distal end part 144. In this embodiment, the OCT probe 600 is led out from the forceps opening 156 by inserting the OCT probe 600 from the forceps insertion portion 138. The OCT probe 600 is inserted into the OCT processor 400 via the insertion portion 602 inserted from the forceps insertion portion 138 and led out from the forceps opening 156, the operation portion 604 for the operator to operate the OCT probe 600, and the connector 610. It consists of a cable 606 to be connected.

  At the distal end portion 144 of the endoscope 100, an observation optical system 150, an illumination optical system 152, and a CCD (not shown) are disposed.

  The observation optical system 150 forms an image of a subject on a light receiving surface (not shown) of the CCD, and the CCD converts the subject image formed on the light receiving surface into an electric signal by each light receiving element. The CCD of this embodiment is a color CCD in which three primary color red (R), green (G), and blue (B) color filters are arranged for each pixel in a predetermined arrangement (Bayer arrangement, honeycomb arrangement). is there. Reference numeral 154 denotes a cleaning nozzle for supplying cleaning liquid and pressurized air toward the observation optical system 150.

  The light source device 300 causes visible light to enter a light guide (not shown). One end of the light guide is connected to the light source device 300 via the LG connector 120, and the other end of the light guide faces the illumination optical system 152. The light emitted from the light source device 300 is emitted from the illumination optical system 152 via the light guide, and illuminates the visual field range of the observation optical system 150.

  An image signal output from the CCD is input to the endoscope processor 200 via the electrical connector 110. The analog image signal is converted into a digital image signal in the endoscope processor 200, and necessary processing for displaying on the screen of the monitor device 500 is performed.

  In this manner, observation image data obtained by the endoscope 100 is output to the endoscope processor 200, and an image is displayed on the monitor device 500 connected to the endoscope processor 200.

  FIG. 2 is a block diagram showing an internal configuration of the OCT processor of FIG. The OCT processor 400 and the OCT probe 600 shown in FIG. 2 are for acquiring tomographic information (tomographic image) to be measured by an optical coherence tomography (OCT) measurement method.

  The OCT processor 400 emits light La for measurement, a first light source unit (first light source unit) 12, and the light La emitted from the first light source unit 12 is measured light (first light flux). An optical fiber coupler (branching / combining unit) 14 for branching into L1 and reference light L2 and combining the return light L3 and the reference light L2 from the measurement target S, which is the subject, to generate interference light L4; The measurement light L1 branched by the fiber coupler 14 is guided to the optical connector 18 of the OCT probe 600, and the fixed-side optical fiber FB2 that guides the return light L3 guided by the rotation-side optical fiber FB1 in the OCT probe 600; The interference light detection unit 20 that detects the interference light L4 generated by the optical fiber coupler 14 as an interference signal, and processes the interference signal detected by the interference light detection unit 20 to obtain tomographic information ( A signal processing unit 22 for acquiring layer image). The tomographic information acquired by the signal processing unit 22 is imaged and displayed on the monitor device 500.

  Further, the OCT processor 400 adjusts the optical path length of the second light source unit (second light source unit) 13 that emits aiming light (second light flux) Le for indicating a mark of measurement, and the reference light L2. Detection that detects return light (interference light) L4 and L5 combined by the optical fiber coupler 14, and an optical fiber coupler 28 that splits the light La emitted from the first light source unit 12, and an optical path length adjustment unit 26 Sections 30a and 30b, and an operation control section 32 for inputting various conditions to the signal processing section 22, changing settings, and the like.

  The OCT probe 600 connected to the OCT processor 400 guides the measurement light L1 guided through the fixed optical fiber FB2 to the measurement target S and also guides the return light L3 from the measurement target S. An optical fiber FB1 and an optical connector 18 that rotatably connects the rotation side optical fiber FB1 to the fixed side optical fiber FB2 and transmits the measurement light L1 and the return light L3 are provided.

  In the OCT processor 400 and the OCT probe 600 shown in FIG. 2, various light including the above-described emission light La, aiming light Le, measurement light L1, reference light L2, return light L3, etc. Various optical fibers FB (FB3, FB4, FB5, FB6, FB7, FB8, etc.) including the rotation side optical fiber FB1 and the fixed side optical fiber FB2 are used as light paths for guiding and transmitting between the components. It is used.

  The first light source unit 12 emits light for OCT measurement (for example, wavelength-variable laser light in the infrared region or low-coherence light). The first light source unit 12 of this example emits a laser beam La (for example, a laser beam centered on a wavelength of 1.3 μm) while sweeping the optical frequency (wavelength) at a constant period in the infrared wavelength region. It is a variable light source.

  The first light source unit 12 includes a light source 12a that emits laser light or low-coherence light La, and a lens 12b that condenses the light La emitted from the light source 12a. Further, as will be described in detail later, the light La emitted from the first light source unit 12 is divided into the measurement light L1 and the reference light L2 by the optical fiber coupler 14 via the optical fibers FB4 and FB3, and the measurement light L1 is Input to the optical connector 18.

  The second light source unit 13 emits visible light so as to make it easy to confirm the measurement site as the aiming light Le. For example, red semiconductor laser light having a wavelength of 660 nm, He—Ne laser light having a wavelength of 630 nm, blue semiconductor laser light having a wavelength of 405 nm, or the like can be used. The second light source unit 13 in this embodiment includes, for example, a semiconductor laser 13a that emits red, blue, or green laser light, and a lens 13b that condenses the aiming light Le emitted from the semiconductor laser 13a. . The aiming light Le emitted from the second light source unit 13 is input to the optical connector 18 through the optical fiber FB8.

  In the optical connector 18, the measurement light (first light beam) L 1 and the aiming light (second light beam) Le are combined and guided to the rotation side optical fiber FB 1 in the OCT probe 600.

  The optical fiber coupler (branching / combining unit) 14 is composed of, for example, a 2 × 2 optical fiber coupler, and is optically connected to the fixed-side optical fiber FB2, the optical fiber FB3, the optical fiber FB5, and the optical fiber FB7, respectively. ing.

  The optical fiber coupler 14 divides the light La incident from the first light source unit 12 via the optical fibers FB4 and FB3 into measurement light (first light flux) L1 and reference light L2, and the measurement light L1 is fixed. The light is incident on the optical fiber FB2, and the reference light L2 is incident on the optical fiber FB5.

  Further, the optical fiber coupler 14 includes a reference light L2 that is incident on the optical fiber FB5 and is frequency-shifted and changed in optical path length by an optical path length adjusting unit 26, which will be described later, and returned to the optical fiber FB5. The acquired light L3 guided from the fixed side optical fiber FB2 is multiplexed and emitted to the optical fiber FB3 (FB6) and the optical fiber FB7.

  The OCT probe 600 is connected to the fixed optical fiber FB2 via the optical connector 18, and the measurement light L1 combined with the aiming light Le is rotated from the fixed optical fiber FB2 via the optical connector 18. The light enters the side optical fiber FB1. The measurement light L1 combined with the incident aiming light Le is transmitted by the rotation side optical fiber FB1, and is irradiated to the measurement object S. Then, the return light L3 from the measuring object S is acquired, the acquired return light L3 is transmitted by the rotation side optical fiber FB1, and is emitted to the fixed side optical fiber FB2 via the optical connector 18.

  The interference light detection unit 20 is connected to the optical fibers FB6 and FB7, and uses the interference lights L4 and L5 generated by combining the reference light L2 and the return light L3 by the optical fiber coupler 14 as interference signals. It is to detect.

  A detector 30a for detecting the light intensity of the interference light L4 is provided on the optical path of the optical fiber FB6 branched from the optical fiber coupler 28, and the light intensity of the interference light L5 is detected on the optical path of the optical fiber FB7. A detector 30b is provided. The interference light detection unit 20 generates an interference signal based on the detection results of the detectors 30a and 30b.

  The signal processing unit 22 acquires tomographic information from the interference signal detected by the interference light detection unit 20, and outputs a tomographic image obtained by imaging the acquired tomographic information to the monitor device 500. In this embodiment, based on the interference signal detected by the interference light detection unit 20, a blood vessel region is extracted from the tomographic information to generate a three-dimensional blood vessel image, and an image showing the three-dimensional structure of the blood vessel is displayed on the monitor device 500. Is output. A detailed configuration of the signal processing unit 22 for realizing this will be described later.

  The optical path length adjustment unit 26 for changing the optical path length of the reference light L2 is disposed on the emission side of the reference light L2 of the optical fiber FB5 (that is, the end of the optical fiber FB5 opposite to the optical fiber coupler 14). ing.

  The optical path length adjustment unit 26 includes a first optical lens 80 that converts the light emitted from the optical fiber FB5 into parallel light, a second optical lens 82 that condenses the light converted into parallel light by the first optical lens 80, and The reflection mirror 84 that reflects the light collected by the second optical lens 82, the base 86 that supports the second optical lens 82 and the reflection mirror 84, and the base 86 are moved in a direction parallel to the optical axis direction. And a mirror moving mechanism 88. By changing the distance between the first optical lens 80 and the second optical lens 82, the optical path length of the reference light L2 is adjusted.

  The first optical lens 80 converts the reference light L2 emitted from the core of the optical fiber FB5 into parallel light, and condenses the reference light L2 reflected by the reflection mirror 84 on the core of the optical fiber FB5.

  The second optical lens 82 condenses the reference light L2 converted into parallel light by the first optical lens 80 on the reflection mirror 84 and makes the reference light L2 reflected by the reflection mirror 84 parallel light. Thus, the first optical lens 80 and the second optical lens 82 form a confocal optical system.

  Further, the reflection mirror 84 is disposed at the focal point of the light collected by the second optical lens 82 and reflects the reference light L2 collected by the second optical lens 82.

  As a result, the reference light L2 emitted from the optical fiber FB5 becomes parallel light by the first optical lens 80 and is condensed on the reflection mirror 84 by the second optical lens 82. Thereafter, the reference light L2 reflected by the reflection mirror 84 becomes parallel light by the second optical lens 82 and is condensed by the first optical lens 80 on the core of the optical fiber FB5.

  The base 86 fixes the second optical lens 82 and the reflecting mirror 84, and the mirror moving mechanism 88 moves the base 86 in the optical axis direction of the first optical lens 80 (the direction of arrow A in FIG. 2). .

  By moving the base 86 in the direction of arrow A with the mirror moving mechanism 88, the distance between the first optical lens 80 and the second optical lens 82 can be changed, and the optical path length of the reference light L2 can be adjusted. Can do.

  The operation control unit 32 includes input means such as a keyboard and a mouse, and control means for managing various conditions based on input information, and is connected to the signal processing unit 22. The operation control unit 32 inputs, sets, and changes various processing conditions and the like in the signal processing unit 22 based on an operator instruction input from the input unit.

  Note that the operation control unit 32 may display the operation screen on the monitor device 500, or may provide a separate display unit to display the operation screen. The operation control unit 32 controls the operation of the first light source unit 12, the second light source unit 13, the optical connector 18, the interference light detection unit 20, the optical path length, the detection units 30a and 30b, and sets various conditions. You may do it.

  FIG. 3 is a cross-sectional view of the OCT probe 600. As shown in FIG. 3, the distal end portion of the insertion portion 602 includes a probe outer tube (sheath) 620, a cap 622, a rotation side optical fiber FB1, a spring 624, a fixing member 626, and an optical lens 628. doing.

  The probe outer cylinder 620 is a flexible cylindrical member, and is made of a material that transmits the measurement light L1 combined with the aiming light Le and the return light L3 in the optical connector 18. The probe outer cylinder 620 is a tip through which the measurement light L1 (aiming light Le) and the return light L3 pass (the tip of the rotation side optical fiber FB1 opposite to the optical connector 18, hereinafter referred to as the tip of the probe outer cylinder 620). It is only necessary that a part of the side is made of a material that transmits light over the entire circumference (transparent material), and parts other than the tip may be made of a material that does not transmit light.

  The cap 622 is provided at the distal end of the probe outer cylinder 620 and closes the distal end of the probe outer cylinder 620.

  The rotation-side optical fiber FB1 is a linear member and is accommodated in the probe outer cylinder 620 along the probe outer cylinder 620. The rotation-side optical fiber FB1 guides the measurement light L1 combined with the optical connector 18 and the aiming light Le to the optical lens 628 and irradiates the measurement target S with the measurement light L1 (aiming light Le). The return light L3 from the measuring object S acquired by the lens 628 is guided to the optical connector 18. The return light L3 enters the fixed side optical fiber FB2 via the optical connector 18. The rotation-side optical fiber FB1 is disposed so as to be rotatable with respect to the probe outer cylinder 620 and movable in the axial direction of the probe outer cylinder 620.

  The spring 624 is fixed to the outer periphery of the rotation side optical fiber FB1. The rotation side optical fiber FB1 and the spring 624 are connected to the optical connector 18 together with the rotation cylinder 656.

  The optical lens 628 is disposed at the measurement-side tip of the rotation-side optical fiber FB1 (tip of the rotation-side optical fiber FB1 opposite to the optical connector 18). The distal end portion (light emission surface) of the optical lens 628 is formed in a substantially spherical shape for condensing the measurement light L1 (aiming light Le) emitted from the rotation-side optical fiber FB1 onto the measurement target S. .

  The optical lens 628 irradiates the measurement target S with the measurement light L1 (aiming light Le) emitted from the rotation side optical fiber FB1, collects the return light L3 from the measurement target S, and enters the rotation side optical fiber FB1. .

  The fixing member 626 is disposed on the outer periphery of the connection portion between the rotation side optical fiber FB1 and the optical lens 628, and fixes the optical lens 628 to the end portion of the rotation side optical fiber FB1. The fixing method of the rotation side optical fiber FB1 and the optical lens 628 by the fixing member 626 is not particularly limited, and the fixing member 626, the rotation side optical fiber FB1 and the optical lens 628 may be bonded and fixed by an adhesive. It may be fixed with a mechanical structure using bolts or the like. Any fixing member 626 may be used as long as it is used for fixing, holding or protecting the optical fiber, such as a zirconia ferrule or a metal ferrule.

  The rotation-side optical fiber FB1 and the spring 624 are connected to the rotation cylinder 656. By rotating the rotation-side optical fiber FB1 and the spring 624 by the rotation cylinder 656, the optical lens 628 is moved with respect to the probe outer cylinder 620 by the arrow R2. Rotate in the direction (rotation direction with the optical axis of the rotation side optical fiber FB1 as the rotation center). The optical connector 18 includes a rotary encoder. Based on the signal from the rotary encoder, the irradiation position of the measuring light L1 is detected from the position information (angle information) of the optical lens 628. That is, the measurement position is detected by detecting the angle of the rotating optical lens 628 with respect to the reference position in the rotation direction.

  Further, the rotation-side optical fiber FB1, the spring 624, the fixing member 626, and the optical lens 628 are moved inside the probe outer cylinder 620 in the directions indicated by arrows S1 (forceps opening direction) and S2 (outside the probe) by a drive mechanism including a motor 660. It is configured to be movable in the direction of the tip of the cylinder 620.

  On the left side of FIG. 3, a schematic configuration of a drive mechanism such as the rotation-side optical fiber FB1 in the operation unit 604 of the OCT probe 600 is shown.

  The probe outer cylinder 620 is fixed to the fixing member 670, while the rotation-side optical fiber FB 1 and the base end portion of the spring 624 are connected to the rotation cylinder 656. The rotating cylinder 656 is configured to rotate via a gear 654 in accordance with the rotation of the motor 652. The rotary cylinder 656 is connected to the optical connector 18, and the measurement light L1 and the return light L3 are transmitted between the rotation side optical fiber FB1 and the fixed side optical fiber FB2 via the optical connector 18.

  The frame 650 including the rotary cylinder 656, the motor 652, the gear 654, and the optical connector 18 includes a support member 662. The support member 662 has a screw hole (not shown), and a ball screw 664 for advancing / retreating is engaged with the screw hole. A motor 660 is connected to the ball screw 664 for advancing / retreating movement. By rotating and driving the motor 660, the frame 650 is moved back and forth, whereby the rotation-side optical fiber FB1, the spring 624, the fixing member 626, and the optical lens 628 are moved in the S1 and S2 directions in FIG. , That is, the direction along the optical axis of the rotation-side optical fiber FB1).

  The OCT probe 600 is configured as described above, and the measurement light emitted from the optical lens 628 by rotating the rotation-side optical fiber FB1 and the spring 624 in the direction of the arrow R2 in FIG. L1 (aiming light Le) is irradiated onto the measuring object S while scanning in the direction of arrow R2 (circumferential direction of the probe outer cylinder 620), and the return light L3 is acquired. The aiming light Le is applied to the measuring object S as, for example, blue, red, or green spot light. The reflected light of the aiming light Le (reflected light from the measuring object S) is also displayed as a bright spot on the observation image displayed on the monitor device 500.

  By such optical scanning along the rotation direction, a desired part of the measuring object S can be accurately captured on the entire circumference of the probe outer cylinder 620 in the circumferential direction, and the return light L3 reflected from the measuring object S is obtained. Can be acquired.

  Furthermore, when acquiring tomographic information of a three-dimensional area for generating three-dimensional volume data, the end of the movable range of the rotation side optical fiber FB1 and the optical lens 628 in the direction of the arrow S1 is driven by a drive mechanism including a motor 66. And move to the end of the movable range while alternately acquiring the tomographic information and moving the predetermined amount in the S2 direction while acquiring the tomographic information.

  In this way, three-dimensional volume data can be obtained by acquiring tomographic information in a desired range for the measurement target S.

  FIG. 4 is a diagram showing a scan surface of tomographic information when the optical scanning is radial scan with respect to the measurement target S, and FIG. 5 is a diagram showing three-dimensional volume data constructed by the tomographic information of FIG. . By acquiring tomographic information in the depth direction (Z direction) of the measurement target S from the interference signal, the measurement target S is scanned (radial scan) in the direction of arrow R2 (circumferential direction of the probe outer cylinder 620) in FIG. As shown in FIG. 4, tomographic information on the scan plane composed of the Z direction and the X direction orthogonal to the Z direction can be acquired. Furthermore, by moving the scan plane along the Y direction orthogonal to the scan plane, as shown in FIG. 5, tomographic information of a three-dimensional area for generating three-dimensional volume data can be acquired.

  FIG. 6 is a diagram illustrating a state in which tomographic information is obtained using the OCT probe 600 derived from the forceps port 156 of the endoscope 100. As shown in FIG. 6, tomographic information is obtained by bringing the distal end portion of the insertion portion 602 of the OCT probe 600 close to a desired portion of the measurement target S. When acquiring tomographic information of a desired three-dimensional region, it is not always necessary to move the OCT probe 600 main body, and the optical lens 628 may be moved within the probe outer cylinder 620 by the drive mechanism described above.

  FIG. 9 is a block diagram showing a configuration of the signal processing unit 22 of FIG.

  As illustrated in FIG. 7, the signal processing unit 22 of the present embodiment is a processing unit that performs signal processing for generating an image output to the monitor device 500 from the interference signal input from the interference light detection unit 20. , Mainly including a Fourier transform unit 410, a logarithmic transform unit 420, a tomographic image construction unit 450, a three-dimensional blood vessel structure extraction processing unit 460, and a control unit 490. The control unit 490 controls each unit of the signal processing unit 22 based on the operation signal from the operation control unit 32.

  The interference light detection unit 20 is obtained when the light emitted from the first light source unit 12 serving as a wavelength swept light source is divided into measurement light and reference light, and the measurement light S is irradiated from the OCT probe 600 to the measurement target S. The interference light when the reflected light and the reference light are combined is input. The interference light detection unit 20 converts an input interference light (optical signal) into an interference signal (electric signal), and converts the interference signal generated by the interference signal generation unit 20a from an analog signal to a digital signal. It comprises an AD conversion unit 20b that converts it into a signal.

  In the AD conversion unit 20b, for example, conversion from an analog signal to a digital signal is performed with a sampling rate of about 80 MHz and a resolution of about 14 bits. However, the value is not particularly limited to these values. The interference signal converted into a digital signal by the AD conversion unit 20 b is input to the Fourier transform unit 410 of the signal processing unit 22.

  The Fourier transform unit 410 performs frequency analysis by FFT (Fast Fourier Transform) on the interference signal converted into the digital signal in the AD conversion unit 20b of the interference light detection unit 20, and the reflected light at each depth position of the measurement target S ( Return light) The intensity of L3, that is, the reflection intensity data in the depth direction is generated. The reflection intensity data Fourier-transformed by the Fourier transform unit 410 is logarithmically transformed by the logarithmic transform unit 420. The logarithmically converted reflection intensity data is input to the tomographic image construction unit 450.

  The tomographic image construction unit 450 performs luminance conversion, contrast adjustment, resampling according to the display size, coordinate conversion according to a scanning method such as radial scanning, etc. on the reflection intensity data logarithmically converted by the logarithmic conversion unit 420. The reflection intensity data is constructed as data for visualizing as a tomographic image. Further, the reflection intensity data obtained for the three-dimensional area in this way is assigned as pixel data of each voxel arranged three-dimensionally, and the tomographic information data of the three-dimensional area is three-dimensionally obtained. Arranged three-dimensional volume data (simply referred to as volume data) is generated. The data at each position indicating the tomographic information of the three-dimensional area, that is, the reflection intensity data assigned as the pixel data of each voxel of the volume data is hereinafter referred to as tomographic data.

  The three-dimensional blood vessel structure extraction processing unit 460 obtains the volume data constructed by the tomographic image construction unit 450, extracts blood vessel information based on the obtained volume data, and displays a three-dimensional image of the blood vessel. A three-dimensional blood vessel image is generated. Details of processing contents of the three-dimensional blood vessel structure extraction processing unit 460 will be described later.

  The three-dimensional blood vessel image generated in this way is output to a monitor device 500 such as an LCD monitor. In addition, in place of the display output of the three-dimensional blood vessel image or together with the display of the three-dimensional blood vessel image, another image (three-dimensional image, tomographic image, etc.) based on the volume data constructed by the tomographic image construction unit 450 is monitored. 500 can also be displayed.

  FIG. 8 is a flowchart of the three-dimensional blood vessel structure extraction process in this embodiment. This processing is performed by the three-dimensional blood vessel structure extraction processing unit 460 in FIG.

  In step S10, volume data (tomographic data) is acquired. Volume data generated by the tomographic image construction unit 450 in FIG. 7 is input to the three-dimensional blood vessel structure extraction processing unit 460. As volume data acquired at this time, for example, volume data obtained by OCT measurement of the inner wall 900 having a structure as shown in FIG. 10 in the lumen of the digestive system is taken as an example. In the inner wall portion 900 shown in FIG. 10, there is a region 904 in which normal cells continue substantially uniformly below the inner wall surface 902 (the positive direction of the Z-axis from the surface 902 to the deep portion of the inner wall 900). Assume that a blood vessel 906 exists in the region 904. At this time, the volume data obtained by the OCT measurement has a structure as shown in FIG. As shown in the figure, the volume data includes a blood vessel region 908 composed of tomographic data of the blood vessel 906 and a shadow region composed of tomographic data that is a reflection (shadow) of the blood vessel 906 below the blood vessel region 908. 910 exists.

  That is, during the OCT measurement, the measurement light L1 that has entered the Z direction (the positive direction of the Z axis) from the upper side of the surface 902 to the inside of the inner wall portion 900 is greatly attenuated by strong reflection at the blood vessel 906, and the blood vessel region The intensity of the measurement light L1 traveling to the region below 908 is lower than the intensity of the measurement light L1 that has passed through the non-blood vessel region 912 where the blood vessel 906 does not exist in the Z direction. Therefore, the tomographic data (reflection intensity data) obtained below the blood vessel region 908 is smaller than the tomographic data obtained in the non-blood vessel region 912 at the same depth position. Therefore, a shadow region 910 made of tomographic data having a value greatly different from the non-blood vessel region 912 is formed in the entire region below the blood vessel region 908.

  From this, when the shadow region 910 exists, it indicates that the blood vessel region 908 exists above it. However, since the shaded area 910 is not an area where the blood vessel 906 itself exists, it is removed from the image when displaying the three-dimensional blood vessel image by the process described later.

  In addition, due to noise components included in the tomographic data, a false shadow region (noise) consisting of tomographic data having specific values as indicated by reference numerals 914 and 916 in FIG. Region) may be formed. Since such false shadow areas 914 and 916 do not form a continuous area in the Z direction and the like, they are neither the blood vessel area 908 nor the shadow area 910 and are unnecessary information for displaying a three-dimensional blood vessel image. It is removed from the image by a process described later.

  In step S12, based on the volume data acquired in step S10, an integrated image is generated by integrating the volume data in the depth direction (Z direction). Here, at the time of OCT measurement, volume data as shown in FIG. 11 is obtained by arranging tomographic images made of tomographic data obtained at positions parallel to the XZ plane at positions at predetermined intervals in the Y direction. Is generated. On the other hand, by cutting the volume data at a predetermined interval in the Z direction along a plane parallel to the XY plane, a tomographic image including tomographic data of a cross section parallel to the XY plane as shown in FIG. Assume that (slice images S (1) to S (N)) are reconfigured into a slice image sequence S arranged in the Z direction. In FIG. 12A, the same reference numerals are assigned to regions corresponding to the blood vessel region 908, the shadow region 910, the non-blood vessel region 912, and the false shadow regions 914 and 916 shown in FIGS.

  For each slice image S (1) to S (N) reconstructed in this way, the tomographic data at the point where the X coordinate value and the Y coordinate value (XY coordinate value) match is added to obtain the integral value. That is, for the sake of explanation, assuming that a Z line 930 indicating a position on a line in the Z direction where the XY coordinate value is a constant value with respect to the position of an arbitrary Z coordinate value is assumed, each slice image S (1) to S (1) -S. In (N), an integral value obtained by adding all the tomographic data of the points on the Z line 930 is obtained. Then, the pixel value of a point that coincides with the XY coordinate value at the position where the Z line 930 is assumed on the image plane (XY coordinate plane) of one image as an integral image is set as the integral value. In this way, by obtaining the pixel value of each XY coordinate value of the integral image by changing the XY coordinate value of the position assuming the Z line 930, an integral image in which the volume data is integrated in the Z direction is generated. At this time, an integral image 932 as shown in FIG. 12B is obtained for the volume data (slice image sequence S) as shown in FIGS. 11 and 12A.

  In FIG. 12B, the same reference numerals are assigned to regions formed on the integrated image due to the blood vessel region 908, the non-blood vessel region 912, and the false shadow regions 914 and 916. Note that the tomographic data of points on the Z line is added to the volume data (integrated in the Z direction) without reconstructing the volume data as shown in FIG. 11 into the slice image sequence S as shown in FIG. Thus, the integral image 932 as shown in FIG. 12B can be directly obtained, and the processing using the slice image sequence S will not be referred to below.

  In step S14, based on the integrated image obtained in step S12, a region where an image showing the blood vessel 906 (blood vessel region 908) exists is extracted as a blood vessel candidate region. For example, in the integrated image, an XY coordinate value range of a region where the pixel value indicates a value within a predetermined range is extracted as a blood vessel candidate region.

  Here, the range of pixel values to be extracted as a blood vessel candidate region in the integrated image is obtained empirically from the actual pixel value range of the image region formed on the integrated image due to the region where the blood vessel region 908 actually exists. You can decide in advance. It is also possible to set a pixel value range of a non-blood vessel candidate region that is not extracted as a blood vessel candidate region and extract a pixel value region that does not belong to the range as a blood vessel candidate region. Furthermore, an edge whose pixel value changes abruptly in the integrated image is extracted as a boundary between the blood vessel candidate region and the non-blood vessel candidate region, and a region on either side of the boundary is extracted as a blood vessel candidate region depending on the magnitude relationship of the pixel values. Any image processing technique for analyzing the image configuration can be used.

  According to this processing, in the integrated image as shown in FIG. 12B, an image region resulting from the blood vessel region 908 is extracted as a blood vessel candidate region 940. That is, an area on the integrated image corresponding to the range of the XY coordinate values where the blood vessel region 908 exists in the Z direction in the volume data is extracted as the blood vessel candidate region 940.

  In addition to the blood vessel candidate region 940, a region where the blood vessel region 908 does not actually exist in the Z direction, such as an image region caused by the false shadow regions 914 and 916, may be extracted as the blood vessel candidate region 940. The pseudo-shadow regions 914 and 916 are extracted as blood vessel candidate regions 940 for the following explanation. The non-blood vessel region 912 excluding the false shadow regions 914 and 916 can be substantially excluded from the blood vessel candidate region 940 and becomes a non-blood vessel candidate region 942. However, regions that may be determined to be blood vessel candidate regions even though the blood vessel region 908 does not exist in the Z direction, such as the non-blood vessel region 912, are volume data such as the false shadow regions 914 and 916. This is not limited to the case where the tomographic data at a specific position is a unique value, and may occur as a result of adding a plurality of tomographic data when generating an integral image.

  In step S16, a blood vessel contrast profile is generated. A blood vessel contrast profile is a profile in a blood vessel candidate region compared with a profile in a non-blood vessel candidate region (reference profile). The profile is a distribution of tomographic data in the Z direction. When attention is paid to the position of a predetermined XY coordinate value with respect to the volume data, the position of the focused XY coordinate value in the Z direction, that is, the position on the Z line (Z coordinate value at each point), and the volume data This shows the relationship with the fault data.

  First, the profile will be described. The profile is represented by a graph as shown in FIG.

  In the figure, the horizontal axis indicates the Z coordinate value (position in the depth direction) on the Z line assumed at the position of a predetermined XY coordinate value, and the vertical axis indicates the value of tomographic data. One profile is generated for any one point on the XY coordinates (XY coordinate value), and the profile obtained for the focused XY coordinate value is referred to as a profile at that XY coordinate value. .

  In the volume data as shown in FIG. 11 and FIG. 12A, paying attention to the XY coordinate value of the Z line 930A passing through the non-blood vessel region 912 (excluding the false shadow regions 914 and 916), Is created, a graph such as a curve C1 in FIG. 13 is obtained. That is, in the Z coordinate value (Z0) where the surface 902 of the inner wall portion 900 is located, the tomographic data increases rapidly, and the tomographic data gradually decreases as the depth from the surface 902 increases.

  On the other hand, when attention is paid to the XY coordinate value of the Z line 930B (see FIG. 12A) passing through the blood vessel region 908 (and the shadow region 910) and a profile with the XY coordinate value is created, FIG. A graph like curve C2 is obtained. That is, as with the curve C1, in the Z coordinate value (Z0) of the surface 902 of the inner wall 900, the tomographic data increases rapidly, and the range from the surface 902 to the depth of the Z coordinate value (Z1) where the blood vessel region 908 exists. As with the curve C1, the tomographic data gradually decreases. When the depth of the Z coordinate value (Z1) where the blood vessel region 908 is present, the tomographic data increases on the surface (blood vessel wall) of the blood vessel 906, and when it becomes deeper, the tomographic data decreases rapidly due to the attenuation of the measurement light L1. After that, it gradually decreases while showing a smaller value than the curve C1.

  Further, when attention is paid to the XY coordinate value of the Z line 930C passing through the false shadow region 914 (916) and a profile with the XY coordinate value is created, a graph like a curve C3 in FIG. 13 is obtained. The curve C3 shows a form that is approximately approximate to the curve C1, but a relatively large tomographic data value variation that does not exist in the curve C1 occurs in a partial range of the Z coordinate value (range indicated by Z2).

  Next, the blood vessel contrast profile generated in step S16 will be described. In the blood vessel candidate region 940 extracted based on the integrated image in step S14 as shown in FIG. 12B, a blood vessel region 908 actually exists in the Z direction. The effective region extracted appropriately and the invalid region (noise region) extracted by the presence of the regions such as the false shadow regions 914 and 916 without the blood vessel region 908 in the Z direction are included.

  Therefore, it is necessary to determine a noise region (noise determination process) in the blood vessel candidate region 940 and remove the noise region. Further, it is necessary to specify the position in the Z direction where the blood vessel region 908 actually exists (Z coordinate value range) with respect to the effective region (blood vessel depth position calculation processing). Therefore, noise discrimination and blood vessel depth position calculation processing are performed using profiles having different forms depending on the difference in the region through which the Z line passes as described above.

  Further, when such processing is performed, it passes through the non-blood vessel region 912 as shown by the curve C1 in FIG. 13 rather than analyzing the form of only the profile at each XY coordinate value in the blood vessel candidate region 940. The profile at the XY coordinate value of the Z line, that is, the profile at the XY coordinate value in the non-blood vessel candidate region 942 is used as a reference profile, and the profile at each XY coordinate value in the blood vessel candidate region 940 is compared with the reference profile. The analysis can be performed accurately and easily.

  Therefore, a profile obtained by the difference between the profile at each XY coordinate value in the blood vessel candidate region 940 and the reference profile is referred to as a blood vessel contrast profile, and a blood vessel contrast profile at each XY coordinate value in the blood vessel candidate region 940 is generated in step S16. To do.

  The blood vessel contrast profile shows a graph as shown in FIG. When the XY coordinate value focused on in the blood vessel candidate region 940 is the XY coordinate value of the Z line 930B passing through the blood vessel region 908 (and the shadow region 910), a profile as shown by the curve C2 in FIG. 13 is generated. At this time, the blood vessel contrast profile shows a graph like a curve C21 in FIG.

  On the other hand, when the XY coordinate value focused on in the blood vessel candidate region 940 is the XY coordinate value of the Z line 930B passing through the false shadow regions 914 and 916, a profile as shown by the curve C3 in FIG. 13 is generated. The blood vessel contrast profile shows a graph like a curve C31 in FIG. Specific descriptions thereof will be described later.

  Further, the reference profile can be a profile with an arbitrary XY coordinate value in the non-blood vessel candidate region 942 that does not include the blood vessel region 908 and the false shadow regions 914 and 916. However, with respect to the profile with the XY coordinate value of interest in the blood vessel candidate region 940, the range of Z coordinate values other than the blood vessel region 908 and the shadow region 910 in the profile, or Z other than the false shadow regions 914 and 916 It is desirable to show as similar a profile as possible in the range of coordinate values. Therefore, it is preferable to use a profile with the XY coordinate values in the non-blood vessel candidate region 942 in the vicinity of the XY coordinate values of interest in the blood vessel candidate region 940 as the reference file. Also, since the profile includes a noise component at the time of OCT measurement, a plurality of XY coordinate values in the non-blood vessel candidate region 942 that are in the vicinity range with respect to the XY coordinate value of interest in the blood vessel candidate region 940 are selected, It is more preferable that the average of the profiles at the plurality of XY coordinate values is used as the reference file.

  Therefore, in the present embodiment, the blood vessel contrast profile generation processing in step S16 is performed as shown in the flowchart of FIG.

  In step S30, a position (XY coordinate value for generating a reference profile) for obtaining a plurality of profiles for generating a reference profile is set as a non-blood vessel candidate area for a predetermined XY coordinate value of interest in the blood vessel candidate area 940. Select from 942. The number to be selected is a predetermined number (for example, 5 points, 10 points, etc.). Referring to the integrated image of FIG. 15 that shows the enlarged integrated image of FIG. 12B, the XY coordinate value of a predetermined point A in the blood vessel candidate region 940 extracted based on the integrated image is focused. Then, the minimum distance r from the point A to the closest border line of the blood vessel candidate region 940 is obtained. That is, the radius r of a circle 950 that is drawn within the range of the blood vessel candidate region 940 with the point A as the center and that touches any boundary line of the blood vessel candidate region 940 is obtained. Then, a predetermined value α is added to the minimum distance r (circle radius r), and within a range where the distance from the point A is within the distance r + α (range of the circle 952 having the radius r + α), A predetermined number of XY coordinate values are selected as XY coordinate values for generating a reference profile from a range 954 to be a non-blood vessel candidate region 942.

  In step S32, a profile with the XY coordinate value of interest in the blood vessel candidate region 940 and a profile with each XY coordinate value selected in step S30 are generated based on the volume data acquired in step S10.

  In step S34, an average of profiles at each XY coordinate value selected in step 30 is obtained, and a reference profile is generated. That is, all the tomographic data at the same Z coordinate value of the profile at each XY coordinate value is added, and the value obtained by the addition is divided by the number of selected XY coordinate values. A reference profile is generated using the values at the respective Z coordinate values thus obtained as new tomographic data.

  In step S <b> 36, a blood vessel contrast profile is generated at the XY coordinate value focused on in the blood vessel candidate region 940. That is, the difference between the profile at the XY coordinate value focused on in the blood vessel candidate region 940 obtained in step S32 and the reference profile obtained in step S34 is obtained. Specifically, the tomographic data at each Z coordinate value of the reference profile is subtracted by the tomographic data at the same Z coordinate value of the profile at the focused XY coordinate value. A profile in which the value at each Z coordinate value obtained in this way is used as new tomographic data is generated. As a result, a blood vessel contrast profile as shown in FIG. 14 is generated.

  In step S38, it is determined whether or not a blood vessel contrast profile has been generated for all XY coordinate values in the blood vessel candidate region 940. If NO, in step S40, the focused XY coordinate value is changed to an unfocused XY coordinate value in the blood vessel candidate region 940, and the processes in steps S30 to S36 are performed. If YES, the blood vessel contrast profile generation process in this flowchart is terminated.

  As described above, the reference profile is not used for each blood vessel contrast profile at each XY coordinate value, but is used for all or a common XY coordinate value range. It may be. In addition, the reference profile with a plurality of XY coordinate values is not averaged, but may be a reference profile with XY coordinate values at one point.

  When the blood vessel contrast profile generation process is completed as described above, the process proceeds to step S18 in FIG.

  In step S18, profile analysis is performed on the blood vessel contrast profile generated in step S16. Thus, as described above, the noise discrimination process for discriminating the effective area and the noise area in the blood vessel candidate area 940 is performed, and the blood vessel depth position calculation process for specifying the depth position of the blood vessel area 908 is performed.

  That is, the blood vessel contrast profile at the XY coordinate values of the Z line that passes through the blood vessel region 908 in the blood vessel candidate region 940 shows a shape like the curve C21 shown in FIG. 14 without passing through the blood vessel region 908. The blood vessel contrast profile at the XY coordinate values of the Z line passing through the false shadow areas 914 and 916 shows a shape like a curve C31 in FIG.

  The difference between the shapes of the curves C21 and C31 is obvious, and a shape feature amount that defines the difference between these shapes is defined. For example, when the value of the tomographic data exceeds a predetermined threshold value ds in a continuous range of Z coordinate values, the length of the range of the Z coordinate values is used as the shape feature amount. At this time, in the blood vessel contrast profile at the focused XY coordinate value, when the shape feature amount Z21 is equal to or larger than the predetermined threshold value Zs as shown by the curve C21 in FIG. 14, the XY coordinate value is the blood vessel in the Z direction. It is determined that the area 908 belongs to an existing effective area.

  On the other hand, when the shape feature amount Z31 is less than the threshold value Zs as shown by the curve C31 in FIG. 14, the XY coordinate value is determined to belong to the noise region. That is, the shape feature amount defined here is the existence of the shadow region 910 in consideration that the shadow region 910 exists below the blood vessel region 908 in the blood vessel candidate region 940 in the Z direction. In this case, the threshold value Zs is defined to be equal to or greater than the threshold value Zs, and the effective region or the noise region is determined based on the presence or absence of the shadow region 910. However, the shape feature amount may be based on another definition.

  In this way, by determining whether each XY coordinate value in the blood vessel candidate region 940 belongs to the effective region or the noise region based on the blood vessel contrast profile at each XY coordinate value in the blood vessel candidate region 940, The blood vessel candidate region 940 can be divided into an effective region and a noise region.

  In addition, the blood vessel contrast profile with the XY coordinate values focused on in the region determined to be an effective region among the blood vessel candidate regions 940 has a shape like a curve C21 in FIG. 14 and is the upper end portion of the blood vessel region 908. As the Z coordinate value increases from the coordinate value Z1, the value of the tomographic data greatly decreases to the negative side, then rapidly increases to the positive side, and then gradually decreases while maintaining the positive value. . Therefore, there is a minimum point P in the vicinity of the Z coordinate value Z1 that is the upper end of the blood vessel region 908. Therefore, the Z coordinate value ZMIN of the minimum point P is set as the upper end position of the blood vessel region 908. Even if the Z coordinate value ZMIN of the local minimum point P is other than the Z coordinate value ZMIN when the tomographic data becomes zero when the tomographic data changes from a negative value to a positive value, the upper end of the blood vessel region 908 on the graph A Z coordinate value indicating a characteristic point that can be regarded as a part can also be set as the position of the upper end of the blood vessel region 908.

  On the other hand, the Z coordinate value serving as the lower end of the blood vessel region 908 is determined based on the Z coordinate value ZMIN of the upper end of the blood vessel region 908 on the assumption that the cross section of the blood vessel is circular. For example, when the above processing is executed for each XY coordinate value of the effective region of the blood vessel candidate region 940, the Z coordinate value of the upper end of the blood vessel region 908 at the position of each XY coordinate value is determined. That is, of the outer surface of the blood vessel wall of the blood vessel 906, the Z coordinate value of the outer peripheral surface on the surface 902 side of the inner wall portion 900 is determined. Further, the thickness (diameter) of the blood vessel 906 is detected from the width of each part of the blood vessel candidate region 940 (effective region) in the integrated image, and based on this, the surface 902 side of the outer surface of the blood vessel wall of the blood vessel 906 is detected. The Z coordinate value of the lower outer peripheral surface which is the opposite side is calculated. Accordingly, since the position range of the blood vessel region 908 in the Z direction is determined, the position range of the blood vessel region 908 in the three-dimensional region is determined based on the range of the XY coordinate values of the effective region of the blood vessel candidate region 940. Note that the thickness of the blood vessel 906 is not detected from the integrated image, but may be specified by the user, or the thickness information of the blood vessel 906 is not used, but the surface of the blood vessel wall of the blood vessel 906 is used. The Z coordinate value of the outer peripheral surface opposite to the surface 902 may be calculated from the Z coordinate value of the outer peripheral surface on the 902 side.

  In step S20, the noise area and the shadow area are removed from the volume data based on the profile analysis result in step S18. For example, the tomographic data of each Z coordinate value in the Z line of the XY coordinate value determined as the noise region in step S18 is replaced with the tomographic data of the reference profile used when generating the blood vessel contrast profile with the XY coordinate value. . As a result, noise such as false shaded areas 914 and 916 is removed from the volume data.

  On the other hand, for each Z coordinate value of the Z line of the XY coordinate value determined as the effective region, the tomographic data value of the reference profile used when generating the blood vessel contrast profile with the XY coordinate value is used. The values of tomographic data other than the area 908 are replaced. As a result, the volume data is removed from the shadow region 910 formed below the blood vessel region 908.

  In step S22, a three-dimensional blood vessel image is generated and displayed on the monitor device 500 based on the volume data from which the shadow area 910 and the false shadow areas 914 and 916 are removed in step S20. As a result, a three-dimensional image of the blood vessel 906 without a shadow or noise image is displayed as shown in FIG.

  It is also possible to generate and display a three-dimensional blood vessel image using only the information on the position (XYZ coordinate value) of the blood vessel region 908 specified by the profile analysis in step S18 without using the tomographic data of the volume data. In this case, the process for removing the false shadow areas 914 and 916 and the shadow area 910 as in step S20 is unnecessary.

  Further, when generating a three-dimensional blood vessel image, the blood vessel region 908 is colored with a different color depending on the position in the Z direction so that the depth of each part of the blood vessel region 908 can be displayed visually. Good.

  As described above, in the above three-dimensional blood vessel structure extraction process, after generating blood vessel contrast profiles for all XY coordinate values of the blood vessel candidate region 940 in step S16, profile analysis in step S18 and noise and shadow regions in step S20 are performed. Although the removal process is performed, the process of step S18 and step S20 may be performed each time the blood vessel contrast profile is obtained with one XY coordinate value of the blood vessel candidate region 940.

  Further, the above-described three-dimensional vascular structure extraction processing may be applied not to the entire area in the depth direction of the volume data but limited to a partial position range in the depth direction. Further, it may be divided into a plurality of position ranges in the depth direction, and the blood vessel region in each position range may be specified by applying the three-dimensional blood vessel structure extraction process for each position range.

  Further, in the above embodiment, the case where the position of the blood vessel inside the living body is specified and displayed is described, but the present invention specifies the position of the subject occupying the inside of the living body using a tissue other than the blood vessel as the subject. However, the present invention can be similarly applied to the case where a three-dimensional image of the subject is displayed.

  In the above embodiment, the SS-OCT (Swept Source OCT) apparatus has been described as the OCT processor 400. However, the present invention is not limited to this, and the OCT processor 400 can also be applied as an SD-OCT (Spectral Domain OCT) apparatus. It is.

  Further, the present invention is not limited to the above examples, and it is needless to say that various improvements and modifications may be made without departing from the gist of the present invention.

  DESCRIPTION OF SYMBOLS 10 ... Image diagnostic apparatus, 12 ... 1st light source part, 20 ... Interference light detection part, 20a ... Interference signal generation part, 20b ... AD conversion part, 22 ... Signal processing part, 100 ... Endoscope, 200 ... Endoscope Mirror processor, 300 ... light source device, 400 ... OCT processor, 410 ... Fourier transform unit, 420 ... logarithmic transformation unit, 450 ... tomographic image construction unit, 460 ... three-dimensional blood vessel structure extraction processing unit, 490 ... control unit, 500 ... monitor Device: 600 ... OCT probe, 900 ... inner wall, 906 ... blood vessel, 908 ... blood vessel region, 910 ... shadow region, 912 ... non-blood vessel region, 914, 916 ... pseudo shadow region

Claims (22)

A tomographic data acquisition means for acquiring tomographic data at each position indicating tomographic information of a three-dimensional region of the inner wall obtained by optical coherence tomography measurement on the inner wall of the living body;
An integrated image generating means for generating an integrated image obtained by integrating the tomographic data in the depth direction of the inner wall portion;
Based on the integrated image generated by the integrated image generating means, a subject candidate region extracting means for extracting a region where an image of a subject region where a predetermined subject exists on the integrated image is present as a subject candidate region When,
Profile generating means for generating a contrast profile indicating a variation distribution of tomographic data in the depth direction at each point in the subject candidate area extracted by the subject candidate area extracting means, the subject candidate area The object candidate area profile indicating the distribution of the tomographic data in the depth direction at each point within the object is acquired, and the distribution of the tomographic data in the depth direction at a predetermined reference point outside the candidate object area is indicated. Profile generating means for acquiring a profile as a reference profile, and generating a difference between the reference profile in the subject candidate area at each point in the subject candidate area and the reference profile as a contrast profile at each point;
Subject depth position determining means for determining a position range in the depth direction of the subject region in the subject candidate region based on the contrast profile generated by the profile generating means;
An optical coherence tomographic image processing apparatus.   2. The light according to claim 1, wherein the profile generation unit uses a position that is close to each of the points from which the in-subject candidate region profile is acquired as a reference point for acquiring the reference profile. Coherent tomographic image processing device.   3. The optical coherence tomographic image processing apparatus according to claim 1, wherein the profile generation unit uses, as the reference profile, a profile obtained by further averaging the reference profiles acquired at a plurality of points.   The subject depth position determining means acquires the position in the depth direction of the outer peripheral surface on the surface side of the inner wall portion of the subject region in the subject candidate region based on the contrast profile, and acquires the position And determining the position in the depth direction of the outer peripheral surface opposite to the surface of the inner wall portion of the subject region based on the measured position and the thickness information of the subject. The optical coherence tomographic image processing apparatus according to claim 1, wherein a position range in the depth direction is determined.   The optical coherence tomographic image processing apparatus according to claim 4, wherein the information on the thickness of the subject is acquired from the integrated image.   The subject depth position determining means is based on the contrast profile, and in the subject candidate region, the effective region where the subject actually exists in the depth direction and the subject does not exist in the depth direction. The optical coherence tomographic image processing apparatus according to claim 1, wherein the optical coherence tomographic image processing apparatus according to claim 1 is discriminated from a noise area and removed from the subject candidate area.   The optical coherence tomographic image processing apparatus according to claim 6, wherein the subject depth position determination unit determines the effective region and the noise region based on the presence or absence of a shadow region generated with respect to the subject. A position range of the subject candidate region extracted by the subject candidate region extracting unit in a two-dimensional direction orthogonal to the depth direction, and the subject region determined by the subject depth position determining unit. Three-dimensional object image generation means for generating a three-dimensional image of the subject based on the position range of the subject region occupying in the three-dimensional region of the inner wall portion determined by the position range in the depth direction; ,
Display means for displaying a three-dimensional image of the subject generated by the three-dimensional subject image generating means;
The optical coherence tomographic image processing apparatus according to claim 1, wherein the optical coherence tomographic image processing apparatus is provided.   The three-dimensional subject image generation means generates the three-dimensional image of the subject by visualizing the tomographic data, and at the time of the generation, the subject in the depth direction of the subject candidate region. 9. The optical coherence tomographic image processing apparatus according to claim 8, wherein tomographic data other than the specimen region is replaced with tomographic data of the reference profile.   The three-dimensional object image generation unit generates the three-dimensional image of the object colored with a different color according to a position in the depth direction of the object. Optical coherence tomographic image processing device.   The optical coherence tomographic image processing apparatus according to claim 1, wherein the subject is a blood vessel. A tomographic data acquisition step of acquiring tomographic data at each position indicating tomographic information of a three-dimensional region of the inner wall obtained by optical coherence tomography measurement on the inner wall of the living body;
An integrated image generating step for generating an integrated image obtained by integrating the tomographic data in the depth direction of the inner wall,
Based on the integral image generated by the integral image generation step, a subject candidate region extraction step of extracting a region where an image of a subject region where a predetermined subject exists on the integral image is present as a subject candidate region When,
A profile generation step of generating a contrast profile indicating a variation distribution of the tomographic data in the depth direction at each point in the subject candidate region extracted by the subject candidate region extraction step, wherein the subject candidate region The object candidate area profile indicating the distribution of the tomographic data in the depth direction at each point within the object is acquired, and the distribution of the tomographic data in the depth direction at a predetermined reference point outside the candidate object area is indicated. A profile generation step of acquiring a profile as a reference profile, and generating a difference between the reference profile in the subject candidate area at each point in the subject candidate area and the reference profile as a contrast profile at each point;
A subject depth position determining step for determining a position range in the depth direction of the subject region in the subject candidate region based on the contrast profile generated by the profile generating step;
An optical coherence tomographic image processing method comprising:   13. The light according to claim 12, wherein the profile generation step uses, as a reference point for acquiring the reference profile, a position that is close to each of the points at which the in-subject candidate region profile is acquired. Coherent tomographic image processing method.   The optical coherence tomographic image processing method according to claim 12 or 13, wherein the profile generation step uses a profile obtained by further averaging the reference profiles acquired at a plurality of points as the reference profile.   The object depth position determining step acquires the position in the depth direction of the outer peripheral surface that is the surface side of the inner wall portion of the object region in the object candidate region based on the contrast profile, and acquires the position And determining the position in the depth direction of the outer peripheral surface opposite to the surface of the inner wall portion of the subject region based on the measured position and the thickness information of the subject. The optical coherence tomographic image processing method according to claim 12, wherein a position range in the depth direction is determined.   The optical coherence tomographic image processing method according to claim 15, wherein the information on the thickness of the subject is acquired from the integrated image.   In the subject depth position determining step, based on the contrast profile, in the subject candidate region, the effective region where the subject actually exists in the depth direction and the subject does not exist in the depth direction. The optical coherence tomographic image processing method according to any one of claims 12 to 16, wherein a noise region is discriminated and the noise region is removed from the subject candidate region.   The optical coherence tomographic image processing method according to claim 17, wherein the object depth position determining step determines the effective area and the noise area based on the presence or absence of a shadow area generated with respect to the object. A position range of the subject candidate region extracted in the subject candidate region extraction step in a two-dimensional direction orthogonal to the depth direction, and the subject region determined in the subject depth position determination step. A three-dimensional object image generation step for generating a three-dimensional image of the subject based on the position range of the subject region occupying in the three-dimensional region of the inner wall portion determined by the position range in the depth direction; ,
A display step of displaying a three-dimensional image of the subject generated by the three-dimensional subject image generation step;
The optical coherence tomographic image processing method according to any one of claims 12 to 18, further comprising:   The three-dimensional subject image generation step generates a three-dimensional image of the subject by visualizing the tomographic data, and at the time of the generation, the subject in the depth direction of the subject candidate region. The optical coherence tomographic image processing method according to claim 19, wherein tomographic data other than the specimen region is replaced with tomographic data of the reference profile.   21. The three-dimensional object image generation step generates a three-dimensional image of the object colored with a different color according to a position in the depth direction of the object. Optical coherence tomographic image processing method.   The optical coherence tomographic image processing method according to any one of claims 12 to 21, wherein the subject is a blood vessel.

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