Operation method of optical tomography device

Abstract

The operation method of the optical tomography apparatus of the present invention includes: an initial setting step, setting the initial positions of a reference mirror and the ends of optical components; a photography step, after the initial setting step, photographing a tubular element of a biological organism; a reference mirror adjustment step, after the photography step, reducing the image portion of artifacts caused by reflected light from the optical components by moving the reference mirror, while magnifying the image portion formed by reflected light from the tubular element of the biological organism and the image portion formed by reflected light from the tube, converging the image portion of artifacts to the inside of the image portion generated by reflected light from the tube; a magnification adjustment step, after the reference mirror adjustment step, returning the image portion formed by reflected light from the tubular element of the biological organism and the image portion formed by reflected light from the tube to their state before magnification; and a display step, after the magnification adjustment step, displaying the image portion formed by reflected light from the tubular element of the biological organism and the image portion formed by reflected light from the tube, now in their state before magnification, on an image display unit.

Description

Technical Field

[0001] This invention relates to a method for operating an optical tomography apparatus. Background Technology

[0002] Patent Document 1 discloses a swept-source optical coherence tomography (SS-OCT) system for imaging tomographic images of various tubular elements of biological tissues, including the digestive tract, pancreatic and bile ducts, fallopian tubes, urethra, trachea, blood vessels, and lymphatic vessels. This SS-OCT system comprises a swept-source light source that emits light by sequentially switching wavelengths, a reference mirror, and an optical probe that illuminates the tubular elements of the biological tissue with light emitted from the swept-source light source. During imaging, with the optical probe inserted into a blood vessel, light emitted from the swept-source light source is irradiated onto the reference mirror and the optical probe, thereby obtaining interference light between the reference mirror-reflected light and the blood vessel-reflected light reflected by the optical probe. By detecting this interference light and performing a Fourier transform, a radial tomographic image of the blood vessel can be obtained.

[0003] However, when multiple optical components are assembled and optically coupled within an optical probe, light is reflected or scattered at the boundary surfaces of these components (e.g., the light incident surface and light exit surface of the optical components). This reflected or scattered light sometimes appears as artifacts in tomographic images. Artifacts not only reduce image sharpness but can also make accurate diagnosis difficult if they overlap with tissue images.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Patent Publication No. 2016 / 047773 Summary of the Invention

[0007] Therefore, the present invention provides a method for preventing artifacts from overlapping with images of tubular features of a biological organism in tomographic images.

[0008] To achieve this objective, in the operation method of the optical tomography apparatus according to embodiments of the present invention, the optical tomography apparatus comprises:

[0009] light source;

[0010] A splitter that separates light emitted from the light source into a first light and a second light;

[0011] A translucent tube that is inserted into the tubular elements of a living organism;

[0012] The imaging unit has an optical fiber whose base end is optically connected to the separator and an optical component disposed at the end of the optical fiber. The first light, which is guided to the optical fiber, is emitted from the optical component through the tube to the inner wall of the tubular element of the organism. On the other hand, the reflected light of the first light returning from the tubular element of the organism through the tube is obtained from the optical component via the optical fiber.

[0013] An optical distance adjustment unit has a movable reference mirror, which obtains a reference light by reflecting the second light onto the reference mirror, and adjusts the optical distance of the second light by moving the reference mirror;

[0014] An interference section that causes the reflected light and the reference light to interfere to obtain interference light;

[0015] The detection unit detects the interference light between the reflected light and the reference light;

[0016] The conversion unit converts the interference light detected by the detection unit into an electrical signal;

[0017] The Fourier transform unit performs a Fourier transform on the electrical signal obtained through the transform unit to obtain the light intensity distribution relative to the optical distance difference between the optical distance of the reflected light and the optical distance of the reference light.

[0018] The image processing unit removes the image portion of the image captured (photographed) by the photographing unit from the image to obtain an image without the artifacts;

[0019] Image display unit;

[0020] The control unit controls the photography unit, the optical distance adjustment unit, the image processing unit, and the image display unit.

[0021] In the operation method of the optical tomography device

[0022] The control unit performs the following procedures:

[0023] (a) In the initial setting process, the optical distance adjustment unit is controlled to set the optical distance of the reference light from the light emitted from the light source to the detection unit after being reflected by the reference mirror, to be approximately equal to the optical distance of the reflected light after the sum of the first optical distance from the light source to the end of the optical component and the second optical distance from the end of the optical component to the detection unit.

[0024] (b) Photography process: After the initial setup process, the photography unit is operated to photograph the tubular elements of the organism.

[0025] (c) In the reference mirror adjustment process, after the photographing process, the optical distance adjustment unit is controlled to move the reference mirror so that the optical distance of the reference light is shorter than the optical distance of the reflected light. This reduces the image portion of the artifact caused by the reflected light from the optical component. On the other hand, the image portion formed by the reflected light from the tubular element of the organism and the image portion formed by the reflected light from the tube are magnified, converging the image portion of the artifact to the inside of the image portion formed by the reflected light from the tube.

[0026] (d) Magnification adjustment process: After the reference mirror adjustment process, the image processing unit is controlled to return (restore) the image portion formed by reflected light from the tubular element of the organism and the image portion formed by reflected light from the tube to their pre-magnification state.

[0027] (e) Display process: After the magnification adjustment process, the image portion formed by reflected light from the tubular element of the organism and the image portion formed by reflected light from the tube, which have returned to the state before magnification, are displayed on the image display unit.

[0028] Invention Effects

[0029] According to the method of the present invention, artifacts caused by optical components do not overlap with tomographic images of tubular elements of a biological organism. Therefore, it is possible to perform appropriate diagnoses using tomographic images. Attached Figure Description

[0030] Figure 1 This is a diagram showing a schematic structure of an optical tomography apparatus according to an embodiment of the present invention.

[0031] Figure 2 yes Figure 1 A cross-sectional view of the optical probe included in the optical tomography apparatus shown.

[0032] Figure 3 Through Figure 1 The intensity distribution of the OCT signal obtained by the optical tomography device shown.

[0033] Figure 4 (a) is a tomographic image showing tubular features of a organism containing artifacts caused by optical components. Figure 4 (b) is a diagram showing the state of reduced artifacts in tomographic images of tubular features of an organism. Figure 4 (c) indicates from Figure 4 (a) A tomographic image of tubular features of an organism after artifact removal. Detailed Implementation

[0034] Hereinafter, embodiments of the optical tomography method of the present invention and the optical tomography apparatus using the method will be described with reference to the accompanying drawings.

[0035] [Optical Tomography Device]

[0036] Figure 1 This section outlines the wavelength sweep optical tomography (SS-OCT) apparatus according to the embodiments.

[0037] The SS-OCT100 has an optical section 200 and a signal processing section 400.

[0038] [Optics Department]

[0039] The optical unit 200 includes multiple optical elements. These optical elements include: a wavelength sweep light source 210, a first optical coupler 212, a first optical circulator 214, a second optical circulator 216, a second optical coupler 218, a biological tubular element imaging unit 220, an optical distance adjustment unit 222, and a detection unit 224. As will be described below, these optical elements are coupled via light transmission elements such as fiber optics.

[0040] [Wavelength swept frequency light source]

[0041] The wavelength-sweeping light source 210 outputs light required for photographing cross-sections of tubular elements in organisms. The wavelength-sweeping light source 210 is configured to periodically change the wavelength of the output light, for example, sweeping the wavelength from 1260 nm to 1360 nm at a frequency of 100 kHz.

[0042] [First optical coupler]

[0043] The first optical coupler (splitter) 212 is a component that optically couples two parallel optical fibers by heating and melting portions of each fiber. One of the two optical fibers is optically coupled to the first optical coupler 212 and the first optical circulator 214, while the other optical fiber is optically coupled to the wavelength-sweeping light source 210 and the second optical circulator 216 via the first optical coupler 212. Therefore, the light output from the wavelength-sweeping light source 210 is branched into two beams by the first optical coupler 212; one beam is sent to the first optical circulator 214, and the other beam is sent to the second optical circulator 216.

[0044] [First Optical Circulator]

[0045] The first optical circulator 214 is a 3-port optical circulator. The first port is connected to the first optical coupler 212, the second port is connected to the second optical coupler 218, and the third port is connected to the biological tubular element imaging unit 220. Light from the wavelength sweep light source 210, which is sent to the first optical circulator 214 via the first optical coupler 212, is sent to the biological tubular element imaging unit 220, and light returning from the biological tubular element imaging unit 220 is sent to the second optical coupler 218.

[0046] [Second optical circulator]

[0047] The second circulator 216 is a 3-port optical circulator. The first port is connected to the first optical coupler 212, the second port is connected to the second optical coupler 218, and the third port is connected to the optical distance adjustment unit 222. Light sent from the wavelength sweep light source 210 to the second optical circulator 216 via the first optical coupler 212 is sent to the optical distance adjustment unit 222, and light returned from the optical distance adjustment unit 222 is sent to the second optical coupler 218.

[0048] [Second optical coupler]

[0049] The second optical coupler 218 (interference section) is a part that optically couples the optical fiber with one end (base end) connected to the first optical circulator 214 and the optical fiber with one end (base end) connected to the second optical circulator 216 by heating and melting them midway. This causes the light (reflected light) sent from the biological tubular element imaging unit 220 to the second optical coupler 218 via the first optical circulator 214 and the light (reference light) sent from the optical distance adjustment unit 222 to the second optical coupler 218 via the second optical circulator 216 to coincide, thereby obtaining interference light.

[0050] [Biological Tubular Element Photography Department]

[0051] The biological tubular element imaging unit 220 includes: a base 226, and a component relative to the base 226 along a predetermined direction ( Figure 1 A linear moving part (pull-back part) 228 moves linearly in the left-right direction. The linear moving part 228 is connected to a linear moving motor 230 provided on the base 226 and is configured to move forward or backward in a predetermined direction based on the drive of the linear moving motor 230. The base end of a hollow cylindrical flexible tube (hereinafter referred to as "sheath") 232 made of light-transmitting resin is detachably fixed to the base 226 by a retainer 233. As shown in the figure, the base end of the sheath 232 is open and the end is closed.

[0052] A base-side collimating lens 234 and an end-side collimating lens 236 are provided on the linear moving part 228. The base-side collimating lens 234 and the end-side collimating lens 236 are arranged at a certain interval on an optical axis, and the light passing through the base-side collimating lens 234 passes through the optical axis of the end-side collimating lens 236.

[0053] The base-side collimating lens 234 is fixed on the linear moving part 228 and is optically connected to the first optical circulator 214 via an optical fiber.

[0054] The end-side collimating lens 236 is supported by a rotating part 238 provided on the linear moving part 228. The rotating part 238 is rotatably supported on the linear moving part 228 with the optical axis of the base-side collimating lens 234 and the end-side collimating lens 236 as the center, while keeping the distance between the base-side collimating lens 234 and the end-side collimating lens 236 at a constant state.

[0055] The rotating part 238 is driven and connected to the rotary motor 240 fixed to the linear moving part 228 via a rotary transmission mechanism (not shown) including, for example, gears and toothed belts.

[0056] An optical probe 300 is detachably connected to the rotating part 238. The optical probe 300 has an optical fiber 310 and an optical component 312. The optical component 312 is connected to the end of the optical fiber 310. The base end of the optical fiber 310 is detachably connected to the rotating part 238 via a connector 242, configured such that the optical fiber 310 rotates as the rotating part 238 rotates, and light focused by the end-side collimating lens 236 enters the core of the optical fiber 310 from its base end.

[0057] The optical component 312, connected to the end of the optical fiber 310, includes multiple optical elements. In one embodiment, the multiple optical elements include a glass rod (first lens) 314, a Green lens (second lens) 316, and a prism 318 as a deflection component (see reference). Figure 2 The glass rod 314, the green lens 316, and the prism 318 are arranged sequentially from the base end to the end end, and adjacent optical elements are mechanically and optically connected to each other by fusion or by an adhesive of light-transmitting resin.

[0058] A cylindrical glass rod 314 and a cylindrical lens 316 are coaxial with respect to the extension of the optical axis of the optical fiber 310. A prism 318, serving as a deflection component, is a roughly right-angled triangular prism, with one of its two roughly right-angled sides (excluding the hypotenuse) connected to the end face of the lens 316. Therefore, light emitted from the end of the optical fiber 310 passes through the glass rod 314 and the lens 316, entering the prism 318 from one side (face) on the base side. The light entering the prism 318 is reflected by the inclined surface (hypotenuse) and travels in a direction orthogonal to the optical axis, exiting in a radial direction from the other side (face) on the end side. Conversely, light entering the prism 318 from the other side (face) on the end side is reflected by the inclined surface (hypotenuse) and passes sequentially through the lens 316 and the glass rod 314, before entering the optical fiber 310.

[0059] In order to suppress as much as possible the light transmitted through the optical fiber 310 that is reflected back to the optical fiber 310 by the end faces of the optical fiber 310 and the optical component 312, the end face of the optical fiber 310, the base-side end face and the end-side end face of the glass rod 314, the base-side end face of the Green lens 316, and the base-side end face of the prism 318 are preferably slightly inclined relative to the plane perpendicular to the optical axis (for example, preferably about 8° to about 10°).

[0060] To suppress the diffusion of light emitted from prism 318 along the optical axis, for example, the inclined surface of prism 318 may be formed as a curved surface convex outward with an axis orthogonal to the optical axis as its center. To suppress the diffusion of light emitted from prism 318 in the circumferential direction centered on the optical axis, for example, another edge (surface) on the end side of prism 318 may also be a curved surface convex outward with an axis parallel to the optical axis of the light propagating in optical fiber 310 as its center.

[0061] The aforementioned sheath 232 and optical probe 300 are provided with the optical probe 300 inserted into the sheath 232. In use, the optical fiber 310 of the optical probe 300 is connected to the rotating part 238 via the connector 242, and the base end of the sheath 232 is fixed to the base 226 by the retainer 233.

[0062] Therefore, driven by the linear motion motor 230, the linear motion unit 228 and the optical probe 300 move forward and backward relative to the base 226. On the other hand, the sheath 232 is held on the base 226. Therefore, driven by the linear motion motor 230, the optical probe 300 moves forward and backward within the sheath 232. In addition, driven by the rotary motor 240, the rotary unit 238 rotates about the optical axis. At this time, since the optical probe 300 is connected to the rotary unit 238 via the connector 242, it rotates together with the rotary unit 238. As a result, the light sent from the first optical circulator 214 to the imaging unit 220 is incident on the optical fiber 310 via the base-side collimating lens 234 and the end-side collimating lens 236, and then emitted from the optical fiber 310 in the radial direction via the optical component 312, and the emitted light scans at a certain speed in the circumferential direction centered on the optical axis.

[0063] The size of the sheath 232 and the optical probe 300 housed within it are appropriately determined based on the size of the tubular biological element being photographed. To ensure stable rotation of the optical probe 300 within the sheath 232, the inner diameter of the sheath 232 and the outer diameter of the optical probe 300 housed therein are determined to be, for example, approximately 50 μm larger than the maximum outer diameter of the glass rod 314, the Green lens 316, the prism 318, and the metal tube (not shown) holding these optical elements. For example, when the maximum outer diameter of the glass rod 314, the Green lens 316, the prism 318, and the metal tube holding these optical elements is approximately 200–500 μm, the inner diameter of the sheath 232 is approximately 250–550 μm.

[0064] [Optical distance adjustment unit]

[0065] The optical distance adjustment unit 222 includes a collimating lens 243 and a reference mirror 244. The collimating lens 243 is fixed immovably. The reference mirror 244 has a reflecting surface (mirror surface) perpendicular to the optical axis of the collimating lens 243. The reference mirror 244 is supported on a linear motion unit 246. The linear motion unit 246 is movable along the optical axis of the collimating lens 243. The linear motion unit 246 is also connected to a linear motion motor 248, configured to move forward and backward toward the collimating lens 243 based on the drive of the linear motion motor 248, thereby adjusting the optical distance (optical distance) of the reference light.

[0066] [Testing Department]

[0067] The detection unit 224 is an optical component that receives light transmitted from the second optical coupler 218 and performs photoelectric conversion, and in particular, is a dual-balanced detector with two light input sections. The dual-balanced detector has two photodiodes that detect the light (interference light) transmitted from the second optical coupler 218, and these two photodiodes are respectively connected to the ends of the two optical fibers constituting the second optical coupler 218. The detection unit 224 is further configured to, after converting the light input from the two optical fibers into electrical signals respectively, mutually cancel out the DC components contained in these electrical signals, and extract only the electrical signal based on the interference light.

[0068] [Signal Processing Department]

[0069] The signal processing unit 400 includes: a control unit 410, an image adjustment unit 412, an analog-to-digital (A / D) conversion unit 414, a Fourier transform unit 416, an image processing unit (artifact removal unit) 418, and an image display unit (monitor) 420. In the figure, the image adjustment unit 412, A / D conversion unit 414, Fourier transform unit 416, and image processing unit 418 represent functional blocks, which do not need to be physical structures and may also be part of the program stored in the storage unit of the control unit 410 (described later).

[0070] [Control Department]

[0071] The control unit 410 includes a control unit (not shown), an arithmetic unit, and a storage unit. The storage unit can temporarily store programs required for executing the processes described later, as well as various data (e.g., image data) generated during the processes described later. The arithmetic unit executes the operations that should be performed during the processes described later, according to the programs stored in the storage unit.

[0072] Although not shown, the control unit 410 is configured to communicatively connect to the various devices included in the optical unit 200 (wavelength sweep light source 210, optical probe rotary motor 240, optical probe linear motion motor 230, and reference mirror linear motion motor 248), and to drive and control these devices according to the program in the storage unit. The control unit 410 is also configured to communicatively connect to the image adjustment unit 412, the analog-to-digital (A / D) conversion unit 414, the Fourier transform unit 416, the image processing unit (artifact removal unit) 418, and the image display unit (monitor) 420, and to transmit and receive signals with these components.

[0073] Although not shown, the control unit 410 is configured to connect to the input unit and perform the processing described below based on the signals input from the input unit. The input unit can be any one of a keyboard, indicator device, touch screen, mouse, joystick, trackball, scanner, OCR, OMR, voice input device, graphics tablet, etc.

[0074] [Image Adjustment Department]

[0075] The image adjustment unit 412 moves the reference reflector 244 by driving the linear motion motor 248 of the optical distance adjustment unit 222, thereby adjusting the optical distance of the reference light. In this embodiment, in the initial state, the image adjustment unit 412 sets the optical distance from the light emitted from the light source 210 to the detection unit 224 after being reflected by the reference reflector 244 to be equal to the sum of the optical distance from the light source 210 to the prism tilt surface 320 and the optical distance from the prism tilt surface 320 to the detection unit 224.

[0076] Hereinafter, the position of the reference mirror 244 in its initial state will be referred to as the "reference position". Therefore, for example, when the reference mirror 244 is moved toward the collimating lens 243, the point on the light path of the reflected light corresponding to the position of the reference mirror 244 after the movement (hereinafter referred to as the "corresponding point 330 after movement") moves toward the front side of the inclined surface 320 of the prism 318 (reference position). Figure 2 As a result, as will be described later, when the reference mirror 244 is moved toward the collimating lens 243, the distance from the moving corresponding point 330 on the optical path of the reflected light to the sheath 232 and the tubular element 500 of the organism increases, while the distance from the moving corresponding point 330 to the joint surface of the optical elements (the joint surface of the glass rod 314, the Green lens 316, and the prism 318) decreases.

[0077] [A / D Conversion Unit]

[0078] The A / D conversion unit 414 converts the analog signal (electrical signal based on interference light) output from the detection unit 224 into a digital signal.

[0079] [Fourier Transform Section]

[0080] The Fourier transform unit 416 performs a Fourier transform (e.g., high-speed Fourier transform, discrete Fourier transform) on the digital signal output from the A / D transform unit 414 to obtain the intensity (power spectrum) of the interference light relative to the difference (optical distance difference) between the optical distance of the reflected light and the optical distance of the reference light.

[0081] Figure 3 (a) indicates that it will be as follows Figure 2The figure shows the relationship between optical distance difference and intensity when the optical probe 300, covered by sheath 232, is inserted into a tubular element 500 (e.g., a blood vessel) of a biological organism. In this figure, the horizontal axis represents the optical distance difference on a linear scale, and the vertical axis represents the intensity on a logarithmic scale. The intensity distribution shown by symbol 610 corresponds to the interference of reflected light from the tubular element 500 with a reference light, and the intensity distribution shown by symbol 612 corresponds to the interference of reflected light from the sheath 232 with a reference light. The intensity distribution shown by symbol 614 corresponds to the interference of light reflected or scattered at or near the interface of the optical elements constituting the optical probe 300 (the interface of the glass rod 314, the Green lens 316, and the prism 318) with a reference light (the aforementioned artifact 700'). For ease of understanding, in Figure 3 (a) shows the intensity distribution 610 of the tubular element 500 of the organism and the intensity distribution 614 of the artifact 700', but in the actual obtained power spectrum, it is represented as two synthesized intensity distributions 610 and 614. Furthermore, in Figure 3 In (a), the intensity distribution 610 of the biological tubular element 500 and the intensity distribution 614 of the artifact 700' represent regions with the same optical distance difference (overlapping) because the optical distance from the prism tilt surface 320 (reference surface) to the biological tubular element 500 and the optical distance from the prism tilt surface 320 to the joint surface of the optical element (the joint surface of the glass rod 314, the Green lens 316, and the prism 318) are approximately equal.

[0082] Image Processing Department

[0083] The image processing unit 418 receives the power spectrum of the spectral components 610 and 612 of the biological tubular element 500 and the sheath 232 and the spectral component 614 of the artifact 700 from the Fourier transform unit 416, and outputs image information according to each rotation angle of the light probe 300 based on the intensity distributions 610, 612 and 614 of the biological tubular element 500, sheath 232 and artifact 700 in the power spectrum.

[0084] Furthermore, as will be explained in detail later, the image processing unit 418 deletes the image portion (specifically, artifacts) of the instructed area within the photographic image based on instructions from the control unit 410.

[0085] [Image Display Section]

[0086] The image display unit 420 is a typical monitor.

[0087] For reference only. Figure 4 (a) indicates that it will be as follows Figure 2The image shown is a photographic image obtained when the optical probe 300, covered by a sheath 232, is inserted into a tubular element 500 of a living organism (e.g., a blood vessel). In the figure, symbol 500' is the image portion corresponding to the tubular element 500 of the living organism, symbol 232' is the image portion corresponding to the sheath 232, and symbol 700' is the image portion corresponding to light reflected or scattered at or near the interface of the optical element (hereinafter referred to as "artifact").

[0088] Optical tomography

[0089] The optical tomography using the SS-OCT100 described above will be explained.

[0090] The optical probe 300, together with the sheath 232, is inserted into the radiographic location of tubular elements (digestive tract, pancreatic duct, fallopian tube, urethra, trachea, blood vessels, or lymphatic vessels) of a human or animal. For example, in the case of photographing a cross-section of a human blood vessel, after inserting a guidewire through the ulnar cutaneous vein of the upper arm, the optical probe 300 and sheath 232 are inserted along the guidewire to the target site.

[0091] When the light probe 300 is moving, the operator inputs the necessary signals to the control unit 410 via an input section (not shown). Upon receiving the signal, the control unit 410 drives the linear motion motor 230 of the biological tubular element imaging unit 220, causing the linear motion unit 228 to move forward or backward.

[0092] Next, based on the drive start signal from the input unit (not shown), the control unit 410 drives the rotary motor 240 of the biological tubular element imaging unit 220 to make the light probe 300 rotate at a speed of, for example, 180 revolutions per second.

[0093] Next, the control unit 410 drives the wavelength sweep light source 210 to emit light of a specified wavelength. The light emitted from the wavelength sweep light source 210 is separated by the first optical coupler 212 into first light entering the biological tubular element imaging unit 220 and second light entering the optical distance adjustment unit 222.

[0094] The separated first light is sent to the biological tubular element imaging unit 220 via the first optical circulator 214, and then incident on the optical fiber 310 of the optical probe 300 via the base-side collimating lens 234 and the end-side collimating lens 236. After passing through the core of the optical fiber 310, the light incident on the optical fiber 310 passes through the glass rod 314 and the Green lens 316, and reaches the inclined surface 320 (reference surface) of the prism 318, where it is reflected. The light reflected by the inclined surface 320 of the prism 318 is emitted in a radial direction from the outer peripheral surface 322 of the prism. The light emitted from the prism 318 moves circumferentially based on the rotation of the optical probe 300, and passes through the sheath 232 to irradiate the entire circumference of the inner wall of the biological tubular element 500. Light reflected from the tubular bio-element 500 and its surrounding ecological tissue enters the prism 318 via the outer peripheral surface 322. After being reflected by the inclined surface 320, it is sent to the first optical circulator 214 via the Green lens 316, glass rod 314, optical fiber 310, end-side collimating lens 236, and base-side collimating lens 234. The first optical circulator 214 sends the reflected light from the bio-element imaging unit 220 toward the second optical coupler 218.

[0095] The reflected light sent to the first light circulator 214 includes, in addition to the reflected light from the tubular element 500 and the sheath 232, unwanted reflected and scattered light from the junction of the glass rod 314, the Green lens 316, and the prism 318 (see reference). Figure 3 (a) Figure 4 (a)).

[0096] The second light separated by the first optical coupler 212 is sent from the second optical circulator 216 to the optical distance adjustment unit 222. After exiting the collimating lens 243, it is reflected by the reference mirror 244 opposite to it and sent back to the second optical circulator 216 via the collimating lens 243. The second optical circulator 216 sends the reference light from the optical distance adjustment unit 222 toward the second optical coupler 218.

[0097] The reflected light and reference light sent to the second optical coupler 218 are combined to obtain interference light. The interference light is split into two beams, which are then incident on the detection unit 224.

[0098] The detection unit 224 performs photoelectric conversion on the interference light to generate an analog signal corresponding to the interference light. The generated analog signal is sent to the A / D conversion unit 414 to be converted into a digital signal.

[0099] Figure 4(a) shows an image generated based on a digital signal (an unprocessed image containing artifacts). As shown, the unprocessed image, in addition to the image portion 500' of the biological tubular element 500 and the image portion 232' of the sheath 232, also includes an image portion (artifact) 700' of light reflected or scattered from or near the optical element bonding surface of the light probe 300. In this embodiment, the distance from the prism tilt surface (reference surface) 320 to the biological tubular element 500 and the distance from the prism tilt surface (reference surface) 320 to the bonding surfaces of the optical elements (the bonding surfaces of the glass rod 314, the Green lens 316, and the prism 318) are set to be approximately equal. Therefore, the artifact 700' overlaps with the image portion 500' of the biological tubular element 500 of interest, making the image portion 500' unclear.

[0100] As described above, a digital signal containing information about the artifact 700' is sent to the Fourier transform unit 416. The Fourier transform unit 416 performs a Fourier transform (Fast Fourier Transform or Discrete Fourier Transform) on the digital signal. Thus, as... Figure 3 As shown in (a), the intensity distribution (power spectrum) of the interference light corresponding to the optical distance difference between the optical distance of the reference light and the optical distance of the reflected light can be obtained. As described above, since the distance from the prism tilt surface (reference surface) 320 to the biological tubular element 500 is approximately equal to the distance from the prism tilt surface (reference surface) 320 to the junction surface of the optical element, the intensity distribution 614 of the artifact 700' represents the same optical distance difference region as the intensity distribution 610 of the biological tubular element 500. Therefore, as... Figure 4 As shown in (a), the artifact 700' is superimposed on the image 500' of the organism tubular element 500.

[0101] To remove artifacts 700' and make the image 500' of the biological tubular element 500 clear, the control unit 410 drives the linear motion motor 248 of the optical distance adjustment unit 222 via the image adjustment unit 412, bringing the reference mirror 244 closer to the collimating lens 243. As a result, the optical distance from the reference light reflected by the reference mirror 244 to the detection unit 224 decreases. Consequently, the difference between the optical distance of the reflected light from the biological tubular element 500 and the sheath 232 and the optical distance of the reference light increases, while the difference between the optical distance of the reflected or scattered light from the mating surface of the optical component 312 in the light probe 300 and the optical distance of the reference light decreases. Therefore, as... Figure 4As shown in (b), the image portion 500” of the tubular element 500 and the image portion 232” of the sheath 232 are enlarged, while the image portion 700” of the artifact is reduced, and the image portion 700” of the artifact is converged to the inside of the image portion 232” of the sheath 232. Therefore, the power spectrum obtained by performing a Fourier transform on the interference light after optical distance adjustment is as follows: Figure 3 As shown in (b), the intensity distributions 610 and 612 of the tubular element 500 and the sheath 232 of the organism move to the right side of the figure, and the intensity distribution 614 of the artifact caused by light reflected or scattered at and near the junction of the optical element moves to the left side of the figure. The intensity distributions 610, 612 and 614 are separated into non-overlapping ones.

[0102] The distance by which the reference mirror 244 is moved will be explained. In the SS-OCT100, the size (inner diameter, outer diameter) of the sheath 232 and the size (length in the optical axis direction) of the optical elements (glass rod 314, Green lens 316, and prism 318) of the light probe 300 are determined according to their models, and this information is stored in the storage unit of the control unit 410. Therefore, the control unit 410 determines the moving distance of the reference mirror 244 according to the models of the sheath 232 and the probe 300, so that the moving point 330 ( ) is located on the optical path of the reflected light corresponding to the position of the moved reference mirror 244. Figure 2 The optical distance from the sheath 232 to the probe 300 is greater than the optical distance from the corresponding point 330 after the movement to the joint surface of the optical elements, such as the joint surface of the Green lens 316 and the prism 318. This movement distance can also be stored according to the model of the sheath 232 and the probe 300, and the control unit 410 moves the reference mirror 244 according to the stored value.

[0103] Next, the control unit 410 starts the image processing unit 418, from Figure 4 (b) The image portion 700” containing the reduced artifact is deleted from the image shown. Specifically, the image data located inside the annular image portion 232” of the sheath 232 (corresponding to the image portion 700” of the artifact) is deleted, i.e., the image data containing... Figure 3 Image data of the optical distance difference range of intensity distribution 614 in (b). The optical distance difference range corresponding to the image data to be deleted corresponds to the moving distance of the aforementioned reference mirror 244, and together with this moving distance, is predetermined according to the model of the sheath 232 and the probe 300 and stored in the storage unit.

[0104] Next, the control unit 410 displays the magnified image after removing the image data containing artifacts (see...). Figure 4 (b)) Return to Figure 4 (a) shows the magnification of the image before magnification. Figure 4 (c) represents the image without artifacts after magnification return.

[0105] Finally, the control unit 410 displays on the display unit 420. Figure 4 The image shown in (c) illustrates this. As described above, the image portion with artifacts has been removed from the image displayed on the display unit 420. Therefore, a clear tomographic image of the tubular features of a biological organism without artifacts can be obtained. As a result, the reliability of the obtained image is increased, and the reliability of the diagnosis using the image is improved.

[0106] Furthermore, in the above description, for the sake of easy understanding of the invention, in Figure 4 (a) shows an image containing artifacts. Figure 4 (b) shows that Figure 4 (a) is an enlarged image, but in an actual device, these images are not displayed on the display unit 420. Of course, to indicate the presence of artifacts, they can also be displayed on the display unit 420. Figure 4 (a) or Figure 4 Image (b).

[0107] [Other Implementation Methods]

[0108] In the above embodiment, the control unit 410 starts the image processing unit 418, and from... Figure 4 (b) The enlarged image shown has the image portion 700” with the reduced artifact deleted, but it is also possible not to delete the image portion 700” with the reduced artifact. In this case, even if the control unit 410... Figure 4 The magnified image shown in (b) returns as Figure 4 (a) shows the magnification of the image before magnification. Since the image portion 700” of the artifact still converges to the inside of the image portion 232” of the sheath 232, the image portion 500” of the biological tubular element 500 and the image portion 700” of the artifact do not overlap. Therefore, even without deleting the image portion 700” of the reduced artifact, the reliability of the obtained image is increased, and the reliability of the diagnosis using the image is improved.

[0109] Additionally, to continuously acquire images, the control unit 410 can also perform a pull-back operation that rotates the optical probe 300 while retracting the linear motion unit 228. In this case, the control unit 410... Figure 4After the image shown in (c) is displayed on the display unit 420, the bio-tubular element imaging unit 220 is operated to photograph the bio-tubular element 500 while the light probe 300 is retracted along the sheath 232 by a pull-back operation. At this time, since the position of the reference mirror 244 has been adjusted, as described above, the image portion of the bio-tubular element 500 and the image portion of the sheath 232 are enlarged, while the image portion of the artifact is reduced and converges to the inside of the image portion of the sheath 232. After the photograph is taken by this pull-back operation, the control unit 410, using the same method as described above, returns the magnified image after removing the image data of the artifact, or the magnified image in the state where the image portion of the artifact is still converged to the inside of the image portion of the sheath 232, to the magnification of the original image, and then displays the image at the magnification of the original image on the display unit 420. As described above, the control unit 410 can continuously acquire images by repeatedly performing the process of taking pictures based on the pull-back operation, returning the magnified image to the magnification of the original image, and displaying the image at the magnification of the original image on the display unit 420.

[0110] In the above embodiment, the optical probe 300 includes a glass rod 314, a Green lens 316, and a prism 318, but the optical components constituting the optical probe 300 are not limited to these. For example, an optical element replacing a prism can be formed by obliquely processing the core tip of the optical fiber, and light is emitted from the oblique tip towards the radiation direction. Alternatively, the optical probe can also be composed of an optical fiber and a glass or plastic rod with an oblique end face. Or, the optical probe can also be composed of an optical fiber and a spherical lens with an oblique end face.

[0111] In the above embodiment, the inclined surface 320 of the prism 318 is used as a reference surface to set the optical distance of the reference light, but the outer peripheral surface 322 of the prism 318 can also be used as a reference surface.

[0112] Alternatively, the image processing unit 418 may also include a change detection unit (not shown) that detects the change in the optical distance difference between the optical distance of the reference light and the optical distance of the reflected light during image acquisition. In the imaging of the SS-OCT 100, this change detection unit automatically detects, for example, the change in the optical distance difference between the optical distance of the reference light and the optical distance of the reflected light caused by the extension or retraction of the fiber optic cable 310, and sends a command based on this change to the image adjustment unit 412 via the control unit 410. Based on the command, the image adjustment unit 412 moves the reference mirror 244 by driving the linear motion motor 248 of the optical distance adjustment unit 222, automatically adjusting the optical distance of the reference light. Therefore, the optical distance difference between the optical distance of the reference light and the optical distance of the reflected light is automatically maintained. As a result, during imaging, the change in the optical distance difference between the optical distance of the reference light and the optical distance of the reflected light does not change, and artifacts can be reliably removed from the tomographic image.

[0113] Symbol Explanation

[0114] 100: Optical tomography (SS-OCT) for tubular features of organisms

[0115] 210: Wavelength sweep frequency light source

[0116] 212: Splitter (First Optical Coupler)

[0117] 218: Interference section (second optical coupler)

[0118] 220: Photographic Department of Tubular Elements in Organisms

[0119] 222: Optical distance adjustment unit

[0120] 224: Testing Department

[0121] 232: Transparent tube (sheath)

[0122] 310: Fiber optic

[0123] 312: Optical components

[0124] 410: Control Department

[0125] 412: Image Adjustment Unit

[0126] 414: A / D Conversion Unit

[0127] 416: Fourier Transform Section

[0128] 418: Image Processing Department

[0129] 420: Display Unit

[0130] 500: Tubular elements of organisms

[0131] 700', 700”: artifacts

Claims

1. A method for operating an optical tomography apparatus, the optical tomography apparatus comprising: light source; A splitter that separates light emitted from the light source into a first light and a second light; A translucent tube that is inserted into the tubular elements of a living organism; The imaging unit has an optical fiber whose base end is optically connected to the splitter and an optical component disposed at the end of the optical fiber. The first light guided to the optical fiber is emitted from the optical component through the tube toward the inner wall of the tubular element of the organism. On the other hand, the reflected light of the first light returning from the tubular element of the organism through the tube is obtained from the optical component via the optical fiber. An optical distance adjustment unit has a movable reference mirror, which obtains a reference light by reflecting the second light onto the reference mirror, and adjusts the optical distance of the second light by moving the reference mirror; An interference section that causes the reflected light and the reference light to interfere to obtain interference light; The detection unit detects the interference light between the reflected light and the reference light; The conversion unit converts the interference light detected by the detection unit into an electrical signal; The Fourier transform unit performs a Fourier transform on the electrical signal obtained through the transform unit to obtain the light intensity distribution relative to the optical distance difference between the optical distance of the reflected light and the optical distance of the reference light. An image processing unit removes the image portion of the image captured by the photographing unit that suffers from artifacts caused by the optical components, thereby obtaining an image free of the artifacts; Image display unit; The control unit controls the photography unit, the optical distance adjustment unit, the image processing unit, and the image display unit. Among them, the operation method of the optical tomography device, The control unit performs the following procedures: (a) In the initial setting process, the optical distance adjustment unit is controlled to set the optical distance of the reference light from which the light emitted from the light source is reflected by the reference mirror and reaches the detection unit, to be equal to the optical distance of the reflected light, which is the sum of the first optical distance from the light source to the end of the optical component and the second optical distance from the end of the optical component to the detection unit. (b) Photography process: After the initial setup process, the photography unit is operated to photograph the tubular elements of the organism. (c) In the reference mirror adjustment process, after the photographing process, the optical distance adjustment unit is controlled to move the reference mirror so that the optical distance of the reference light is shorter than the optical distance of the reflected light. This reduces the image portion of the artifact caused by the reflected light from the optical component. On the other hand, the image portion formed by the reflected light from the tubular element of the organism and the image portion formed by the reflected light from the tube are magnified, converging the image portion of the artifact to the inside of the image portion formed by the reflected light from the tube. (d) Magnification adjustment process: After the reference mirror adjustment process, the image processing unit is controlled to return the image portion formed by the reflected light from the tubular element of the organism and the image portion formed by the reflected light from the tube to the state before magnification. (e) Display process: After the magnification adjustment process, the image portion formed by reflected light from the tubular element of the organism and the image portion formed by reflected light from the tube, which have returned to the state before magnification, are displayed on the image display unit.

2. The operation method of the optical tomography apparatus as described in claim 1, characterized in that, After the reference mirror adjustment process and before the magnification adjustment process, an artifact removal process is performed to control the image processing unit to remove the image portion of the image after the reduction in size.

3. The method of operating the optical tomography apparatus as described in claim 1 or 2, characterized in that, The optical tomography apparatus includes a pull-back section that moves the optical components of the imaging unit along the tube. Following the display process, a pull-back imaging process is performed whereby the optical component is moved along the tube by the pull-back unit, and the imaging unit is operated to take pictures of the tubular elements of the organism. After the pull-back photography process, the magnification adjustment process and the display process are performed. The pull-back photography process, the magnification adjustment process, and the display process are performed in sequence and repeatedly.

4. The method of operating the optical tomography apparatus as described in claim 1 or 2, characterized in that, The optical component has a prism. The prism is a right-angle prism having a first side and a second side connected at a right angle at one end, and an inclined side connecting the other end of the first side and the other end of the second side. The first side of the right-angle prism is optically coupled to the end of the optical fiber. Light emitted from the end of the optical fiber is reflected by the hypotenuse and then emitted through the second side. Light reflected by the tubular element of the organism is incident on the right-angle prism from the second side, reflected by the oblique side, and then incident on the optical fiber via the first side.

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