Patent Publication Number: US-2017354315-A1

Title: Endoscopic diagnosis apparatus, image processing method, program, and recording medium

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of PCT International Application No. PCT/JP2016/ 053120 filed on Feb. 3, 2016, which claims priority under 35 U.S.C §119(a) to Japanese Patent Application No. 2015-070715 filed on Mar. 31, 2015. Each of the above application(s) is hereby expressly incorporated by reference, in its entirety, into the present application. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an endoscopic diagnosis apparatus having a function of measuring the size of a lesion portion or the like in the case of inserting an endoscope into a subject and observing the inside of the subject, and to an image processing method, and a non-transitory computer-readable recording medium. 
     2. Description of the Related Art 
     An endoscopic diagnosis apparatus is used to observe the inside of a subject. In the case of observing the inside of a subject, an endoscope is inserted into a body cavity of the subject, white light, for example, is emitted from a distal end portion of the endoscope onto a region of interest, reflected light thereof is received, and thereby an endoscopic image is captured. The captured endoscopic image is displayed on a display unit and observed by an operator of the endoscopic diagnosis apparatus. 
     There is a demand for measuring the size of a lesion portion such as a tumor portion for the purpose of, for example, removing a tumor if the tumor is larger than a predetermined size and conserving the tumor for monitoring if the tumor has the predetermined size or less, as well as determining the presence or absence of a lesion portion by viewing an endoscopic image captured inside a subject. 
     A method for measuring the size of a lesion portion by using a surgical instrument such as measuring forceps is known. In this method, measuring forceps are inserted from a forceps inlet of an endoscope and are protruded from a forceps outlet at a distal end portion of the endoscope. A tip portion of the measuring forceps has scales for measuring size. The tip portion, which is flexible, is pressed against a region of interest so as to bend, and the scales on the tip portion are read to measure the size of a tumor or the like in the region of interest. 
     The related art documents related to the present invention include JP2011-183000A (hereinafter referred to as PTL 1) and JP2008-245838 A(hereinafter referred to as PTL 2). 
     PTL 1 relates to an endoscope apparatus. PTL 1 describes ejecting water streams onto a lesion portion from two openings at a distal end portion of an insertion section of an endoscope and determining, on the basis of the distance between the two water streams being equal to the distance between the two openings, whether or not the lesion portion is larger than or equal to a treatment reference value. 
     PTL 2 relates to a robotic arm system mounted on an endoscope apparatus. PTL 2 describes setting a plurality of measurement points around a lesion portion by using a tip portion of a surgical instrument or the like, and obtaining the size of the lesion portion through computation on the basis of coordinate information on the measurement points. 
     SUMMARY OF THE INVENTION 
     In this method, however, inserting the measuring forceps into a forceps channel of the endoscope is required only for measuring the size of a lesion portion. This operation is not only time-consuming but also complex and cumbersome. Furthermore, since the measurement is performed by pressing the tip portion of the measuring forceps against a region of interest of a subject so as to bend the tip portion, measurement accuracy is low. In some portions of a subject, it may be difficult to perform measurement, that is, it may be difficult to press the tip portion against the region of interest of the subject. 
     Furthermore, the endoscope apparatus according to PTL 1 involves an issue that a special endoscope including two openings for ejecting two water streams from the distal end portion of the insertion section is required, and that only this endoscope is capable of measuring the size of a lesion portion. 
     In addition, the endoscope apparatus according to PTL 2 involves an issue that a robot arm is required to measure the size of a lesion portion, and that it is necessary to set a plurality of measurement points around the lesion portion by operating the complex robot ann. 
     An object of the present invention is to solve the issues according to the related art and to provide an endoscopic diagnosis apparatus, image processing method, and a non-transitory computer-readable recording medium that enable easy measurement of the size of a lesion portion or the like based on an endoscopic image captured through a normal operation without a special operation. 
     To achieve the object, the present invention provides an endoscopic diagnosis apparatus including an imaging unit that has a plurality of pixels and captures an endoscopic image of a subject from a distal end portion of an endoscope; a display unit that displays the endoscopic image; an input unit that receives an instruction to designate a position in the endoscopic image, the instruction being input by an operator; a region detecting unit that detects, from the position in the endoscopic image, a region having a periodic structure of living tissue of the subject in response to the instruction to designate the position; an imaging size calculating unit that calculates, in number of pixels, an imaging size in the endoscopic image equivalent to a period in the periodic structure of the living tissue in the region having the periodic structure of the living tissue; a size information holding unit that holds information of an actual size equivalent to the period in the periodic structure of the living tissue; a pixel size calculating unit that calculates an actual size corresponding to one pixel of the endoscopic image on the basis of the imaging size and the information of the actual size; a scale generating unit that generates scales indicating an actual size of the subject in the endoscopic image on the basis of the actual size corresponding to the one pixel of the endoscopic image; and a control unit that causes the endoscopic image and the scales to be combined and displayed on the display unit. 
     Preferably, the imaging size calculating unit calculates the imaging size on the basis of a ratio of pixel values of individual pixels in a spectral image having different color components of the endoscopic image. 
     Preferably, the imaging size calculating unit calculates the imaging size on the basis of a frequency characteristic of a distribution of pixel values of individual pixels within the region having the periodic structure of the living tissue. 
     Preferably, the frequency characteristic is a power spectrum. 
     Preferably, the input unit receives an instruction to designate two positions in the endoscopic image, and the region detecting unit detects, as the region having the periodic structure of the living tissue, a region between the two positions in the endoscopic image in response to the instruction to designate the two positions. 
     Preferably, the imaging size calculating unit calculates a ratio of pixel values of individual pixels in a spectral image having two color components of the endoscopic image, sets a linear region in the region between the two positions, calculates a power spectrum of a ratio of pixel values of individual pixels in the linear region, detects frequency peaks from the power spectrum, and calculates the imaging size in accordance with an interval between the frequency peaks. 
     Preferably, the imaging size calculating unit calculates an average of intervals between a plurality of the frequency peaks in the linear region and regards the average as the imaging size. 
     Preferably, the imaging size calculating unit sets a plurality of linear regions in the region between the two positions, calculates, for each linear region, an average of intervals between a plurality of the frequency peaks in the linear region, further calculates an average of averages of intervals between the frequency peaks in the plurality of linear regions, and regards the average of the averages as the imaging size. 
     Preferably, the input unit further receives an instruction to start detecting the region having the periodic structure of the living tissue and an instruction to finish detecting the region having the periodic structure of the living tissue before and after receiving the instruction to designate the position, respectively, and the region detecting unit starts detecting the region in response to the instruction to start detecting the region and finishes detecting the region in response to the instruction to finish detecting the region. 
     Preferably, the input unit further receives an instruction to start detecting the region having the periodic structure of the living tissue before receiving the instruction to designate the position, and the region detecting unit starts detecting the region in response to the instruction to start detecting the region and finishes detecting the region after a predetermined time period elapses from when the endoscopic image and the scales are combined and displayed on the display unit. 
     Preferably, the periodic structure of the living tissue is a microvasculature of a glandular structure of a large intestine, and the period in the periodic structure of the living tissue is an interval between microvessels in the microvasculature of the glandular structure of the large intestine. 
     Preferably, the periodic structure of the living tissue is a microvasculature in an outermost layer of a mucous membrane of an esophagus, and the period in the periodic structure of the living tissue is an interval between microvessels in the microvasculature in the outermost layer of the mucous membrane of the esophagus. 
     The present invention also provides an image processing method including a step of holding, with a size information holding unit, information of an actual size equivalent to a period in a periodic structure of living tissue of a subject; a step of causing, with a control unit, an endoscopic image of the subject captured by an imaging unit having a plurality of pixels from a distal end portion of an endoscope to be displayed on a display unit; a step of receiving, with an input unit, an instruction to designate a position in the endoscopic image, the instruction being input by an operator; a step of detecting, with a region detecting unit, a region having the periodic structure of the living tissue from the position in the endoscopic image in response to the instruction to designate the position; a step of calculating in number of pixels, with an imaging size calculating unit, an imaging size in the endoscopic image equivalent to the period in the periodic structure of the living tissue in the region having the periodic structure of the living tissue; a step of calculating, with a pixel size calculating unit, an actual size corresponding to one pixel of the endoscopic image on the basis of the imaging size and the information of the actual size; a step of generating, with a scale generating unit, scales indicating an actual size of the subject in the endoscopic image on the basis of the actual size corresponding to the one pixel of the endoscopic image; and a step of causing, with the control unit, the endoscopic image and the scales to be combined and displayed on the display unit. 
     Preferably, the imaging size calculating unit calculates the imaging size on the basis of a ratio of pixel values of individual pixels in a spectral image having different color components of the endoscopic image. 
     Preferably, the imaging size calculating unit calculates the imaging size on the basis of a frequency characteristic of a distribution of pixel values of individual pixels within the region having the periodic structure of the living tissue. 
     Preferably, the frequency characteristic is a power spectrum. 
     Preferably, the input unit receives an instruction to designate two positions in the endoscopic image, and the region detecting unit detects, as the region having the periodic structure of the living tissue, a region between the two positions in the endoscopic image in response to the instruction to designate the two positions. 
     Preferably, the imaging size calculating unit calculates a ratio of pixel values of individual pixels in a spectral image having two color components of the endoscopic image, sets a linear region in the region between the two positions, calculates a power spectrum of a ratio of pixel values of individual pixels in the linear region, detects frequency peaks from the power spectrum, and calculates the imaging size in accordance with an interval between the frequency peaks. 
     Preferably, the imaging size calculating unit calculates an average of intervals between a plurality of the frequency peaks in the linear region and regards the average as the imaging size. 
     Preferably, the imaging size calculating unit sets a plurality of linear regions in the region between the two positions, calculates, for each linear region, an average of intervals between a plurality of the frequency peaks in the linear region, further calculates an average of averages of intervals between the frequency peaks in the plurality of linear regions, and regards the average of the averages as the imaging size. 
     The present invention also provides a non-transitory computer-readable recording medium on which a program is recorded, the program causing a computer to execute the individual steps of the image processing method described above. 
     According to the present invention, the size of a lesion portion or the like can be easily measured by using an endoscopic image captured through a normal operation, not by using an endoscopic image captured for the purpose of measuring the size of a lesion portion or the like. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an external view of an embodiment illustrating the configuration of an endoscopic diagnosis apparatus according to the present invention; 
         FIG. 2  is a block diagram illustrating the internal configuration of the endoscopic diagnosis apparatus illustrated in  FIG. 1 ; 
         FIG. 3  is a conceptual diagram illustrating the configuration of a distal end portion of an endoscope; 
         FIG. 4  is a graph illustrating an emission spectrum of blue laser light emitted by a blue laser light source and of light obtained by converting the wavelength of the blue laser light by using fluorescent bodies; 
         FIG. 5  is a conceptual diagram illustrating an endoscopic image of a large intestine; 
         FIG. 6  is a conceptual diagram illustrating a state of a microvasculature of a glandular structure of the large intestine; 
         FIG. 7  is a conceptual diagram illustrating a state in which a region of the microvasculature is designated; 
         FIG. 8  is a graph illustrating a power spectrum of a ratio of pixel values of individual pixels in a linear region set in the region of the microvasculature; and 
         FIG. 9  is a conceptual diagram illustrating an endoscopic image of a microvasculature in an outermost layer of a mucous membrane of an esophagus. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, an endoscopic diagnosis apparatus, image processing method, and a non-transitory computer-readable recording medium according to the present invention will be described in detail on the basis of preferred embodiments illustrated in the attached drawings. 
       FIG. 1  is an external view of an embodiment illustrating the configuration of the endoscopic diagnosis apparatus according to the present invention, and  FIG. 2  is a block diagram illustrating the internal configuration thereof The endoscopic diagnosis apparatus  10  illustrated in these figures is constituted by a light source device  12 , an endoscope  14  that captures an endoscopic image of a region of interest of a subject by using light emitted by the light source device  12 , a processor device  16  that performs image processing on the endoscopic image captured by the endoscope  14 , a display device  18  that displays the endoscopic image that has undergone the image processing and has been output from the processor device  16 , and an input device  20  that receives an input operation. 
     The light source device  12  is constituted by a light source control unit  22 , a laser light source LD, and a coupler (optical splitter)  26 . 
     In this embodiment, the laser light source LD emits narrowband light having a center wavelength of 445 nm in a predetermined blue wavelength range (for example, the center wavelength±10 nm). The laser light source LD is a light source that emits, as illumination light, excitation light for causing fluorescent bodies described below to generate white light (pseudo white light). ON/OFF (light-up/light-down) control and light amount control of the laser light source LD are performed by the light source control unit  22 , which is controlled by a control unit  68  of the processor device  16  described below. 
     As the laser light source LD, an InGaN-based laser diode of a broad area type can be used. Alternatively, an InGaNAs-based laser diode, a GaNAs-based laser diode, or the like can be used. 
     A white light source for generating white light is not limited to a combination of excitation light and fluorescent bodies, and any light source that emits white light may be used. For example, a xenon lamp, halogen lamp, white LED (light-emitting diode), or the like can be used. The wavelength of the laser light emitted by the laser light source LD is not limited to the foregoing example, and laser light with a wavelength that plays a similar role can be selected as appropriate. 
     The laser light emitted by the laser light source LD enters an optical fiber through a condenser lens (not illustrated) and is then transmitted to a connector section  32 A after being split into two branches of light by the coupler  26 . The coupler  26  is constituted by a half-mirror, reflection mirror, or the like. 
     The endoscope  14  is an electronic endoscope having an illumination optical system that emits two branches (two beams) of illumination light from a distal end surface  46  of an endoscope insertion section that is to be inserted into a subject, and an imaging optical system of a single system (single lens) type that captures an endoscopic image of a region of interest. The endoscope  14  includes the endoscope insertion section  28 , an operation section  30  that is operated to bend a distal end of the endoscope insertion section  28  or to perform observation, and connector sections  32 A and  32 B for connecting the endoscope  14  to the light source device  12  and the processor device  16  in a detachable manner. 
     The endoscope insertion section  28  is constituted by a flexible portion  34  having flexibility, a bending portion  36 , and a distal end portion (hereinafter also referred to as an endoscope distal end portion)  38 . 
     The bending portion  36  is disposed between the flexible portion  34  and the distal end portion  38  and is configured to be freely bent by a rotational operation of an angle knob  40  located at the operation section  30 . The bending portion  36  can be bent in an arbitrary direction or at an arbitrary angle in accordance with a portion or the like of a subject for which the endoscope  14  is used, and accordingly the endoscope distal end portion  38  can be oriented toward a desired portion of interest. 
     As illustrated in  FIG. 3 , two illumination windows  42 A and  42 B for emitting light onto a region of interest, one observation window  44  for gathering reflected light from the region of interest, a forceps outlet  74  serving as an exit for a surgical instrument or the like that is inserted into a forceps channel disposed inside the endoscope insertion section  28 , an air/water supply channel opening  76  serving as an exit of an air/water supply channel, and so forth are located on the distal end surface  46  of the endoscope insertion section  28 . 
     The observation window  44 , the forceps outlet  74 , and the air/water supply channel opening  76  are located in a center portion of the distal end surface  46 . The illumination windows  42 A and  42 B are located on both sides of the observation window  44  so as to sandwich the observation window  44 . 
     An optical fiber  48 A is accommodated behind the illumination window  42 A. The optical fiber  48 A extends from the light source device  12  to the endoscope distal end portion  38  through the connector section  32 A. A fluorescent body  54 A is located in front of a tip portion (on the illumination window  42 A side) of the optical fiber  48 A, and in addition an optical system such as a lens  52 A is attached in front of the fluorescent body  54 A. Likewise, an optical fiber  48 B is accommodated behind the illumination window  42 B. A fluorescent body  54 B and an optical system such as a lens  52 B are located in front of a tip portion of the optical fiber  48 B. 
     The fluorescent bodies  54 A and  54 B contain a plurality of kinds of fluorescent substances (for example, a YAG-based fluorescent substance or a fluorescent substance such as BAM (BaMgAl 10 O 17 )) that absorb a part of blue laser light emitted by the laser light source LD and that are excited to emit light in the green to yellow spectrum. When the fluorescent bodies  54 A and  54 B are irradiated with excitation light, light in the green to yellow spectrum (fluorescent light) emitted by the fluorescent bodies  54 A and  54 B as a result of excitation is combined with blue laser light that has passed through the fluorescent bodies  54 A and  54 B without being absorbed, and thereby white light (pseudo white light) for observation is generated. 
       FIG. 4  is a graph illustrating an emission spectrum of blue laser light emitted by the blue laser light source and of light obtained by converting the wavelength of the blue laser light by using fluorescent bodies. The blue laser light emitted by the laser light source LD is expressed by an emission line having a center wavelength of 445 nm, and the light emitted by the fluorescent bodies  54 A and  54 B as a result of excitation caused by the blue laser light has a spectral intensity distribution in which the emission intensity increases in a wavelength range of about 450 to 700 nm. Composite light of the light emitted as a result of excitation and the blue laser light forms the foregoing pseudo white light. 
     The white light according to the present invention is not limited to light strictly including all wavelength components of visible light and may be, for example, light including light in specific wavelength bands, for example, wavelength bands of R (red), G (green), and B (blue) as reference colors, as well as the foregoing pseudo white light. That is, the white light according to the present invention includes, in a broad sense, light including green to red wavelength components, light including blue to green wavelength components, and the like. 
     In the illumination optical system, the configuration and operation of the illumination window  42 A side and the illumination window  42 B side are equivalent to each other, and basically equivalent illumination light beams are simultaneously emitted from the illumination windows  42 A and  42 B. Alternatively, different illumination light beams may be emitted from the illumination windows  42 A and  42 B. It is not required to have an illumination optical system that emits two branches of illumination light. For example, an equivalent function may be implemented by an illumination optical system that emits one or four branches of illumination light. 
     An optical system, such as an objective lens unit  56 , for gathering image light of a region of interest of a subject is disposed behind the observation window  44 . Furthermore, an imaging device  58 , such as a CCD (Charge Coupled Device) image sensor or CMOS (Complementary Metal-Oxide Semiconductor) image senor, for obtaining image information on the region of interest is attached behind the objective lens unit  56 . The imaging device  58  corresponds to an imaging unit according to the present invention that has a plurality of pixels and captures an endoscopic image of a subject from the distal end portion of the endoscope  14 . 
     The imaging device  58  receives, at its imaging surface (light receiving surface), light from the objective lens unit  56 , photoelectrically converts the received light, and outputs an imaging signal (analog signal). The imaging surface of the imaging device  58  is provided with red (about 580 to 760 nm), green (about 450 to 630 nm), and blue (about 380 to 510 nm) color filters having spectral transmittance for splitting a wavelength range of about 370 to 720 nm of visible light into three bands, and a plurality of sets of pixels, each set formed of pixels of three colors, R pixel, G pixel, and B pixel, are arranged in a matrix on the imaging surface. 
     The light beams guided by the optical fibers  48 A and  48 B from the light source device  12  are emitted from the endoscope distal end portion  38  toward a region of interest of a subject. Subsequently, an image depicting a state of the region of interest irradiated with the illumination light is formed on the imaging surface of the imaging device  58  by the objective lens unit  56  and is captured through photoelectric conversion by the imaging device  58 . An imaging signal (analog signal) of the captured endoscopic image of the region of interest of the subject is output from the imaging device  58 . 
     The imaging signal (analog signal) of the endoscopic image output from the imaging device  58  is input to an A/D converter  64  through a scope cable  62 . The A/D converter  64  converts the imaging signal (analog signal) from the imaging device  58  to an image signal (digital signal). The image signal obtained through the conversion is input to an image processing unit  70  of the processor device  16  through the connector section  32 B. 
     The processor device  16  includes the image processing unit  70 , a region detecting unit  78 , an imaging size calculating unit  80 , a size information holding unit  82 , a pixel size calculating unit  84 , a scale generating unit  86 , the control unit  68 , and a storage unit  72 . The display device  18  and the input device  20  are connected to the control unit  68 . The processor device  16  controls the light source control unit  22  of the light source device  12  and also performs image processing on an image signal of an endoscopic image received from the endoscope  14  and outputs the endoscopic image that has undergone the image processing to the display device  18 , in response to an instruction input through an imaging switch  66  of the endoscope  14  or the input device  20 . 
     The display device  18  corresponds to a display unit according to the present invention that displays an endoscopic image. The input device  20  and a button or the like located in the operation section  30  of the endoscope  14  correspond to an input unit according to the present invention that receives various instructions input by an operator. 
     The image processing unit  70  performs various kinds of image processing, set in advance, on an image signal of an endoscopic image received from the endoscope  14  and outputs an image signal of the endoscopic image that has undergone the image processing. The image signal of the endoscopic image that has undergone the image processing is transmitted to the control unit  68 . 
     The region detecting unit  78  detects, from a position in an endoscopic image corresponding to the image signal of the endoscopic image, a region having a periodic structure of living tissue of a subject in response to an instruction to designate the position in the endoscopic image, which will be described below. 
     Here, the periodic structure of living tissue is a structure in which specific living tissues are arranged at a constant period in a normal portion of living tissue. There is no periodic structure in a lesion portion of living tissue due to the influence of a lesion, but a normal portion includes a portion in which specific living tissues are arranged at a constant period. For example, microvessels in the microvasculature of a glandular structure of the large intestine or in the microvasculature in an outermost layer of a mucous membrane of the esophagus are arranged at a substantially constant interval (distance) regardless of person, sex, or age. 
     The periodic structure of living tissue is not limited to the above-described example, and any periodic structure of living tissue may be applied as long as an actual size equivalent to a period in the periodic structure of living tissue is known and as long as the periodic structure is in a region of a normal portion of living tissue that can be imaged together with a region of interest at the time of capturing an endoscopic image. 
     The imaging size calculating unit  80  calculates, in number of pixels, an imaging size (distance) in the endoscopic image equivalent to a period in the periodic structure of living tissue in the region that has the periodic structure of living tissue and has been detected by the region detecting unit  78 . 
     Here, the imaging size is, in the case of the microvasculature of a glandular structure of the large intestine or the microvasculature in an outermost layer of a mucous membrane of the esophagus, the number of pixels in the endoscopic image corresponding to an interval between microvessels in the microvasculature. 
     A method for calculating, by using the imaging size calculating unit  80 , an imaging size in the endoscopic image equivalent to a period in the periodic structure of living tissue in the region having the periodic structure of living tissue is not limited. For example, the imaging size can be calculated on the basis of the ratio of pixel values of individual pixels in a spectral image having different color components of the endoscopic image or a frequency characteristic of a distribution of pixel values of individual pixels in the region having the periodic structure of living tissue, for example, a power spectrum or the like. 
     The size information holding unit  82  holds information of an actual size (distance) equivalent to a period in the periodic structure of living tissue. 
     Here, the actual size equivalent to the period in the periodic structure of living tissue is, in the case of the microvasculature of a glandular structure of the large intestine or the microvasculature in an outermost layer of a mucous membrane of the esophagus, an actual size equivalent to an interval between microvessels in the microvasculature. 
     The pixel size calculating unit  84  calculates an actual size (distance) corresponding to one pixel of the endoscopic image on the basis of the imaging size calculated by the imaging size calculating unit  80  in number of pixels and the information of the actual size held by the size information holding unit  82 . 
     For example, if the imaging size is X pixels and the actual size is Y mm, the actual size corresponding to one pixel of the endoscopic image can be calculated as Y/X. 
     The scale generating unit  86  generates scales, such as a scale bar, indicating the actual size of the subject in the endoscopic image, on the basis of the actual size corresponding to one pixel of the endoscopic image calculated by the pixel size calculating unit  84 . 
     The control unit  68  causes the display device  18  to display the endoscopic image that has undergone image processing. In this case, the endoscopic image and the scales generated by the scale generating unit  86  can be combined and displayed on the display device  18  under control of the control unit  68 . In addition, the control unit  68  controls the operation of the light source control unit  22  of the light source device  12  and causes, for example, the storage unit  72  to store endoscopic images in units of images (in units of frames) in response to an instruction from the imaging switch  66  of the endoscope  14  or the input device  20 . 
     Next, a description will be given of an operation of the endoscopic diagnosis apparatus  10 . 
     First, a description will be given of an operation in the case of capturing an endoscopic image. 
     At the time of capturing an endoscopic image, the laser light source LD is lit up with a constant amount of light set in advance under control of the light source control unit  22 . Laser light having a center wavelength of 445 nm and emitted by the laser light source LD is applied onto the fluorescent bodies  54 A and  54 B, and white light is emitted by the fluorescent bodies  54 A and  54 B. The white light emitted by the fluorescent bodies  54 A and  54 B is applied onto a subject, the reflected light thereof is received by the imaging device  58 , and thereby an endoscopic image of a region of interest of the subject is captured. 
     An imaging signal (analog signal) of the endoscopic image output from the imaging device  58  is converted to an image signal (digital signal) by the AID converter  64 , various kinds of image processing are performed by the image processing unit  70 , and the image signal of the endoscopic image that has undergone the image processing is output. Subsequently, the control unit  68  causes the display device  18  to display an endoscopic image corresponding to the image signal of the endoscopic image that has undergone the image processing, and if necessary, causes the storage unit  72  to store the image signal of the endoscopic image. 
     Next, a description will be given of an operation in the case of measuring the actual size of a region of interest of a subject. 
     First, a description will be given of, as a first embodiment, the case of measuring the actual size of a subject in an endoscopic image by using a microvasculature of a glandular structure of a large intestine. 
     First, an operator of the endoscopic diagnosis apparatus  10  inputs through the input device  20  information of an actual size equivalent to an interval between microvessels in a microvasculature of a glandular structure of a large intestine. The information of the actual size equivalent to the interval between the microvessels is held by the size information holding unit  82 . 
     Subsequently, the operator inserts the endoscope  14  into a subject and moves the distal end portion of the endoscope  14  to a region of interest of the large intestine while checking an endoscopic image displayed on the display device  18 . 
     If a lesion portion such as a tumor portion is found in the region of interest during observation of the large intestine, for example, as encompassed by a dotted line in  FIG. 5 , the operator performs observation such that the microvasculature of the glandular structure of the large intestine in the lesion portion and a normal portion around the lesion portion is included in the endoscopic image. As illustrated in  FIG. 6 , the microvessels in the microvasculature of the glandular structure of the large intestine in the normal portion are arranged at an interval of 20 to 30 μm. 
     After moving the distal end portion of the endoscope  14  to the region of interest, the operator presses a button or the like located in the operation section  30  of the endoscope  14  to input an instruction to start detecting a region having a periodic structure of living tissue. 
     After inputting the instruction to start detecting the region, the operator further inputs through the input device  20  an instruction to designate two positions  88  and  90  that sandwich the microvasculature of the glandular structure of the large intestine in the endoscopic image displayed on the display device  18  as illustrated in  FIG. 7 , so as to designate the region of the microvasculature of the glandular structure of the large intestine. 
     Upon input of the instruction to designate the two positions  88  and  90  in the endoscopic image, the region detecting unit  78  starts detecting the region of the microvasculature of the glandular structure of the large intestine from the two positions  88  and  90  in the endoscopic image. 
     In this case, the region detecting unit  78  detects, as the region of the microvasculature of the glandular structure of the large intestine, a region  92  that is between the two positions in the endoscopic image and encompassed by a dotted line in  FIG. 7  in response to the instruction to designate the two positions  88  and  90 . 
     Subsequently, the imaging size calculating unit  80  calculates, in number of pixels, an imaging size in the endoscopic image equivalent to an interval between microvessels in the microvasculature in the region of the microvasculature of the glandular structure of the large intestine detected by the region detecting unit  78 . 
     The imaging size calculating unit  80  is capable of calculating the imaging size in the endoscopic image equivalent to the interval between the microvessels in the microvasculature of the glandular structure of the large intestine in the following manner, for example. 
     First, the imaging size calculating unit  80  calculates the ratio of pixel values of individual pixels in a spectral image having two color components of the endoscopic image. 
     For example, the imaging size calculating unit  80  calculates the ratio G/B of pixel values of individual pixels in a spectral image having G (green) and B (blue) components of the endoscopic image. Accordingly, a characteristic structure of living tissue, in the case of this embodiment, the microvasculature of the glandular structure of the large intestine, can be made stand out and extracted. 
     The spectral image is not limited to a spectral image having individual color components of a white light image that is captured by using white light, and a special optical image that is captured by using special light such as short-wavelength laser light of BLI (Blue Laser Imaging) can also be used. 
     Subsequently, as illustrated in  FIG. 7 , the imaging size calculating unit  80  sets a linear region  94  in the region  92  that is between the two positions  88  and  90  in the endoscopic image and has been detected by the region detecting unit  78 , that is, in the region of the microvasculature of the glandular structure of the large intestine, in response to the instruction to designate the two positions  88  and  90  in the endoscopic image. 
     Subsequently, the imaging size calculating unit  80  calculates the power spectrum of the ratio of pixel values of individual pixels in the linear region  94  set in the region of the microvasculature of the glandular structure of the large intestine. 
     As illustrated in  FIG. 8 , in which the lateral axis represents the position in the linear region  94  and the vertical axis represents the ratio G/B of pixel values of individual pixels in a spectral image having two color components, the amount of B component is small and the value of the ratio G/B is large at the position of a blood vessel, and thus upward frequency peaks appear at a substantially constant period. 
     Subsequently, the imaging size calculating unit  80  detects the frequency peaks from the power spectrum and calculates, in accordance with an interval between the frequency peaks, an imaging size in the endoscopic image equivalent to an interval between the microvessels in the microvasculature of the glandular structure of the large intestine. 
     For example, the imaging size calculating unit  80  is capable of calculating an average of intervals between a plurality of frequency peaks in the linear region  94  and regarding the average as the imaging size in the endoscopic image equivalent to the interval between the microvessels in the microvasculature of the glandular structure of the large intestine. Accordingly, the imaging size can be calculated accurately. 
     Alternatively, the imaging size calculating unit  80  may set a plurality of linear regions  94  in the region  92  between the two positions  88  and  90 , may calculate, for each linear region  94 , an average of intervals between a plurality of frequency peaks in the linear region  94 , and may further calculate an average of averages of intervals between the frequency peaks in the plurality of linear regions  94 . In addition, the imaging size calculating unit  80  may regard the average of the averages as the imaging size in the endoscopic image equivalent to the interval between the microvessels in the microvasculature of the glandular structure of the large intestine. Accordingly, the imaging size can be calculated more accurately. 
     Subsequently, the pixel size calculating unit  84  calculates an actual size corresponding to one pixel of the endoscopic image, on the basis of the imaging size equivalent to the interval between the microvessels in the microvasculature of the glandular structure of the large intestine calculated in number of pixels by the imaging size calculating unit  80 , and on the basis of the information of the actual size equivalent to the interval between the microvessels in the microvasculature of the glandular structure of the large intestine held by the size information holding unit  82 . 
     Subsequently, the scale generating unit  86  generates scales indicating the actual size of the subject in the endoscopic image on the basis of the actual size corresponding to one pixel of the endoscopic image. 
     Subsequently, under control of the control unit  68 , the endoscopic image and the scales are combined and displayed on the display device  18 . As the scales, for example, a scale bar in which the length of 1 mm can be seen is displayed on the screen of the display device  18  as illustrated in  FIG. 5 . 
     Subsequently, the operator presses a button or the like located in the operation section  30  of the endoscope  14  to input an instruction to finish detecting the region having the periodic structure of living tissue to the endoscopic diagnosis apparatus  10 . 
     Upon input of the instruction to finish detecting the region, the region detecting unit  78  finishes detecting the region of the microvasculature of the glandular structure of the large intestine from the two positions in the endoscopic image. Accordingly, the scales displayed on the display device  18  disappear. 
     Instead of the finish instruction being input, the region detecting unit  78  may finish detecting the region of the microvasculature of the glandular structure of the large intestine from the two positions in the endoscopic image after a predetermined time period elapses from when the endoscopic image and the scales are combined and displayed on the display device  18 . 
     Next, a description will be given of, as a second embodiment, the case of measuring the actual size of a subject in an endoscopic image by using a microvasculature in an outermost layer of a mucous membrane of an esophagus. 
     First, as in the case of the first embodiment, an operator inputs through the input device  20  information of an actual size equivalent to an interval between microvessels in a microvasculature in an outermost layer of a mucous membrane of an esophagus, and the information is held by the size information holding unit  82 . 
     Subsequently, the operator inserts the endoscope  14  into a subject and moves the distal end portion of the endoscope  14  to a region of interest of the esophagus while checking an endoscopic image displayed on the display device  18 . 
     Here, if a lesion portion such as a tumor portion is found in the region of interest during observation of the esophagus, the operator performs observation such that the microvasculature in the outermost layer of the mucous membrane of the esophagus in the lesion portion and a normal portion around the lesion portion is included in the endoscopic image. As illustrated in  FIG. 9 , the microvessels in the microvasculature in the outermost layer of the mucous membrane of the esophagus in the normal portion are arranged at an interval of 100 to 200 μm. 
     After moving the distal end portion of the endoscope  14  to the region of interest, the operator presses a button or the like located in the operation section  30  of the endoscope  14  to input an instruction to start detecting a region having a periodic structure of living tissue. 
     After inputting the instruction to start detecting the region, the operator further inputs through the input device  20  an instruction to designate the two positions  88  and  90  that sandwich the microvasculature in the outermost layer of the mucous membrane of the esophagus in the endoscopic image displayed on the display device  18  as illustrated in  FIG. 7 , so as to designate the region of the microvasculature in the outermost layer of the mucous membrane of the esophagus. 
     Upon input of the instruction to designate the two positions  88  and  90  in the endoscopic image, the region detecting unit  78  starts detecting the region of the microvasculature in the outermost layer of the mucous membrane of the esophagus from the two positions  88  and  90  in the endoscopic image. 
     In this case, the region detecting unit  78  detects, as the region of the microvasculature in the outermost layer of the mucous membrane of the esophagus, the region  92  that is between the two positions in the endoscopic image and encompassed by the dotted line in  FIG. 7  in response to the instruction to designate the two positions  88  and  90 . 
     Subsequently, the imaging size calculating unit  80  calculates, in number of pixels, an imaging size in the endoscopic image equivalent to an interval between microvessels in the microvasculature in the region of the microvasculature in the outermost layer of the mucous membrane of the esophagus detected by the region detecting unit  78 . 
     Subsequently, the pixel size calculating unit  84  calculates an actual size corresponding to one pixel of the endoscopic image, on the basis of the imaging size equivalent to the interval between the microvessels in the microvasculature in the outermost layer of the mucous membrane of the esophagus calculated in number of pixels by the imaging size calculating unit  80 , and on the basis of the information of the actual size equivalent to the interval between the microvessels in the microvasculature in the outermost layer of the mucous membrane of the esophagus held by the size information holding unit  82 . 
     The subsequent operation is similar to that in the case of the first embodiment. Under control of the control unit  68 , the endoscopic image and the scales are combined, and a scale bar in which the length of 1 mm can be seen is displayed on the screen of the display device  18 , for example, as illustrated in  FIG. 9 . 
     In this way, the endoscopic diagnosis apparatus  10  is capable of easily measuring the size of a lesion portion or the like by using an endoscopic image captured through a normal operation, not by using an endoscopic image captured for the purpose of measuring the size of a lesion portion or the like. 
     In the apparatus according to the present invention, each element included in the apparatus may be constituted by dedicated hardware, or each element may be constituted by a programmed computer. 
     The method according to the present invention can be implemented by a program that causes a computer to execute individual steps of the method, as described above. Furthermore, a non-transitory computer-readable recording medium on which the program is recorded can be provided. 
     The present invention is basically as above. 
     The present invention has been described in detail above. The present invention is not limited to the above-described embodiments, and various improvements and changes can of course be made without deviating from the gist of the present invention. 
     REFERENCE SIGNS LIST 
       10  endoscopic diagnosis apparatus 
       12  light source device 
       14  endoscope 
       16  processor device 
       18  display device 
       20  input device 
       22  light source control unit 
       26  coupler (optical splitter) 
       28  endoscope insertion section 
       30  operation section 
       32 A,  32 B connector section 
       34  flexible portion 
       36  bending portion 
       38  distal end portion 
       40  angle knob 
       42 AD  42 B illumination window 
       44  observation window 
       46  distal end surface 
       48 A,  48 B optical fiber 
       52 A,  52 B lens 
       54 A,  54 B fluorescent body 
       56  objective lens unit 
       58  imaging device 
       62  scope cable 
       64  AID converter 
       66  imaging switch 
       68  control unit 
       70  image processing unit 
       72  storage unit 
       74  forceps outlet 
       76  air/water supply channel opening 
       78  region detecting unit 
       80  imaging size calculating unit 
       82  size information holding unit 
       84  pixel size calculating unit 
       86  scale generating unit 
       88 ,  90  position 
       92  region 
       94  linear region 
     LD laser light source