Patent Publication Number: US-2020302610-A1

Title: Medical image processing device, medical observation device, method of processing image, and computer readable recording medium

Description:
This application claims priority from Japanese Application No. 2019-055737, filed on Mar. 22, 2019, the contents of which are incorporated by reference herein in its entirety. 
     BACKGROUND 
     The present disclosure relates to a medical image processing device, a medical observation device, a method of processing image, and a computer readable recording medium. 
     In a medical device that captures an image of an object to be observed, a configuration including a switch with which a user such as a doctor adjusts brightness has been known (see, for example, JP 2006-15078 A). For example, when observing a deep part, the user brightens the entire screen by increasing a brightness level. 
     SUMMARY 
     When a brightness level of the entire screen is increased, for example, a white area such as a nerve or a tumor in the deep part has a desired brightness, while a red part such as blood in an area that is in the vicinity of the deep part and is not the deep part becomes brighter than necessary to become a light color, such that it is not only impossible to reproduce an original color, but it is also difficult to distinguish from the white area. 
     There is a need for a medical image processing device, a medical observation device, a method of processing image, and a computer readable recording medium capable of providing an image with good color reproducibility by performing appropriate adjustment for each color component at the time of performing brightness adjustment. 
     According to one aspect of the present disclosure, there is provided a medical image processing device including circuitry configured to: divide a color space into at least two areas by a hue when an instruction signal for changing a brightness level of an image signal captured by a medical observation device is received, the color space being a color space indicating a signal value of the image signal and being determined by a luminance signal and a color difference signal; and perform different signal processing on the image signal for each divided area of the color space. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view schematically illustrating a medical observation system according to an embodiment; 
         FIG. 2  is a block diagram illustrating a functional configuration of a medical observation device according to an embodiment; 
         FIG. 3  is a flowchart illustrating an outline of processing performed by a medical image processing device according to an embodiment; and 
         FIG. 4  is a flowchart illustrating an outline of processing performed by a medical image processing device according to a modification of an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, a mode (hereinafter referred to as an “embodiment”) for carrying out the present disclosure will be described with reference to the accompanying drawings. 
       FIG. 1  is a view schematically illustrating a medical observation system according to an embodiment. A medical observation system  1  illustrated in  FIG. 1  includes a medical observation device  2  and a display device  3 . 
     The medical observation device  2  includes a microscope device  4  and a control device  5 . The microscope device  4  has a function as an imaging device that captures an image of an object to be observed to acquire an image signal. The control device  5  has a function as a medical image processing device that performs image processing on the image signal captured by the microscope device  4 . The medical observation device  2  according to the present embodiment is a microscope for a surgical operation. 
     The display device  3  receives an image signal for display generated by the control device  5  from the control device  5 , and displays an image corresponding to the image signal. The display device  3  has a display panel made of liquid crystal or organic electro luminescence (EL). 
     An appearance configuration of the microscope device  4  will be described. The microscope device  4  includes a microscope unit  6  that magnifies a microstructure of an object to be observed and captures an image of the magnified microstructure, a support unit  7  that supports the microscope unit  6 , a base unit  8  that holds a proximal end of the support unit  7  and incorporates the control device  5 . 
     The microscope unit  6  has a cylindrical portion that forms a columnar shape. A cover glass is provided on an aperture surface at a lower end portion of a body portion (not illustrated). The cylindrical portion may be gripped by a user, and has a size at which it may be moved while being gripped by the user at the time of changing an imaging field of view of the microscope unit  6 . Note that a shape of the cylindrical portion is not limited to a cylindrical shape, and may be a polygonal cylindrical shape. 
     The support unit  7  has a plurality of arm portions, and adjacent arm portions are rotatably connected to each other through joint portions. A transmission cable transmitting various signals between the microscope unit  6  and the control device  5  and a light guide transmitting illumination light generated by the control device  5  to the microscope unit  6  passes through a hollow portion formed inside the support unit  7 . 
       FIG. 2  is a block diagram illustrating a functional configuration of the medical observation device  2 . First, a functional configuration of the microscope device  4  will be described. The microscope device  4  includes an imaging unit  41 , an input unit  42 , a brake unit  43 , and a control unit  44 . 
     The imaging unit  41  includes an optical system that has focus and zoom functions and an imaging element that generates an image signal by receiving an image of an object to be observed imaged by the optical system and performing photoelectric conversion. The optical system and the imaging element are provided inside the cylindrical portion of the microscope unit  6 . The imaging element is configured using an image sensor such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS). The image signal generated by the imaging unit  41  is transmitted to the control device  5  through the transmission cable. Note that the imaging unit  41  may include two imaging elements each having a predetermined parallax in each field of view and generate a three-dimensional image signal. 
     The input unit  42  receives an input such as an operation signal of the optical system of the imaging unit  41  or an operation signal of the brake unit  43 . The input unit  42  is provided at a position where it may be operated by the user in a state where he/she holds the microscope unit  6 , on a side surface of the cylindrical portion of the microscope unit  6 . Note that the input unit  42  may receive an input of an instruction signal for changing a brightness level of an image displayed by the display device  3 . In addition, the input unit  42  may be configured by further using a foot switch that the user may operate with his/her foot. 
     The brake unit  43  has a plurality of electromagnetic brakes provided, respectively, at a plurality of joint portions of the support unit  7 . The electromagnetic brake is released when the input unit  42  receives an input of a release instruction. When the electromagnetic brake is released, one of two arms whose movement is regulated by the electromagnetic brake becomes rotatable with respect to the other of the two arms. Note that an actuator that assists the movement of the arm may be further provided at the joint portion. 
     The control unit  44  controls an operation of the microscope device  4  in cooperation with a control unit  55  of the control device  5 . The control unit  44  is configured using at least one processor such as a central processing unit (CPU), a field programmable gate array (FPGA), and an application specific integrated circuit (ASIC). 
     Next, a functional configuration of the control device  5  will be described. The control device  5  includes an acquiring unit  51 , an input unit  52 , a light source unit  53 , a signal processing unit  54 , the control unit  55 , and a storage unit  56 . 
     The acquiring unit  51  acquires an image signal captured by the microscope device  4  and transmitted through the transmission cable. The image signal includes information related to image capturing, such as a focus position, a zoom, an exposure time, and an imaging time at the time of capturing an image. 
     The input unit  52  receives an input of various types of information including an instruction signal for changing a brightness level of the image. The input unit  52  is configured using a user interface such as a keyboard, a mouse, a touch panel, and a foot switch. Note that the input unit  52  may have at least some of the functions of the input unit  42  of the microscope device  4 . 
     The light source unit  53  generates illumination light supplied to the microscope device  4  through the light guide. The light source unit  53  is configured using a discharge lamp such as a xenon lamp or a metal halide lamp, a solid light emitting element such as a light emitting diode (LED) or a laser diode (LD), a light emitting member such as a laser light source or a halogen lamp, or the like. 
     The signal processing unit  54  generates an image signal for display by performing signal processing on the image signal acquired by the acquiring unit  51 , and outputs the generated image signal to the display device  3 . The signal processing unit  54  is configured using at least one processor such as a CPU, an FPGA, and an ASIC. 
     The signal processing unit  54  performs conversion processing of a signal value on the image signal acquired by the acquiring unit  51 . Specifically, the signal processing unit  54  converts a signal value (a signal value in an RGB color space) of the image signal acquired by the acquiring unit  51  into a signal value in a color space (hereinafter, referred to as a luminance-color difference color space) expressed using a luminance signal and two color difference signals. This conversion is defined by, for example, linear conversion. Specific examples of the luminance-color difference color space may include a YCbCr space or a YPbPr space. 
     The signal processing unit  54  performs signal processing for changing a luminance signal value in the luminance-color difference color space by different amounts for each area divided by an area dividing unit  57  of the control unit  55  to be described later. The signal processing unit  54  may change a luminance signal value in at least one of the divided areas. An amount of change in the luminance signal value may be stored in advance in the storage unit  56 , or may be calculated by a predetermined calculation stored by the storage unit  56  based on information on an intensity of the illumination light generated by the light source unit  53  or an exposure time when the imaging unit  41  captures an image. The signal processing unit  54  generates an image signal for display by converting the signal value in the luminance-color difference color space into a signal value in an RGB space after changing the luminance signal value of the luminance-color difference color space. 
     The control unit  55  includes the area dividing unit  57  that divides the luminance-color difference color space into two areas according to a brightness level after being adjusted when the input unit  52  receives an input of an adjustment signal of the brightness level. For example, when the input unit  52  receives an input of an adjustment signal for increasing the brightness level, the control unit  55  divides the luminance-color difference color space into a first area including an area in which a hue is red and a second area other than the first area. A boundary between the first area and the second area divided by the area dividing unit  57  may be changed according to the brightness level after being adjusted. 
     The control unit  55  controls an operation of the control device  5 , and controls an operation of the medical observation device  2  in cooperation with the control unit  44  of the microscope device  4 . Specifically, for example, the control unit  55  controls light emission of the light source unit  53  by detecting the image signal acquired by the acquiring unit  51 , and controls the exposure time in the imaging unit  41 . In addition, the control unit  55  controls the display device  3  to display the image signal for display generated by the signal processing unit  54 . The control unit  55  is configured using at least one processor such as a CPU, an FPGA, and an ASIC. Note that the signal processing unit  54  and the control unit  55  may be configured using a common processor. 
     The storage unit  56  stores information on the areas of the luminance-color difference color space divided by the area dividing unit  57  or information on an change amount for each hue when the signal processing unit  54  changes the luminance signal value in association with the brightness level. Note that the information stored by the storage unit  56  may be changeable by inputting settings by the user through the input unit  52 . 
     The storage unit  56  stores various programs including a medical image processing program executed by the control device  5 , and temporarily stores data that is being arithmetically processed by the control device  5 . The storage unit  56  is configured using a read only memory (ROM), a random access memory (RAM), or the like. Note that the medical image processing program may be recorded on a computer-readable recording medium such as a hard disk, a flash memory, a CD-ROM, a DVD-ROM, or a flexible disc to be widely distributed. 
       FIG. 3  is a flowchart illustrating an outline of processing performed by the control device  5 . First, when the input unit  52  receives the input of the instruction signal for changing the brightness level (step S 1 : Yes), the signal processing unit  54  converts the signal value of the image signal, that is, the signal value in the RGB color space into the signal value in the luminance-color difference color space (step S 2 ). When the input unit  52  does not receive the input of the instruction signal for changing the brightness level (step S 1 : No), the control device  5  repeats step S 1 . 
     After step S 2 , the area dividing unit  57  divides the luminance-color difference color space into two areas according to a hue determined based on a signal value of the color difference signal with reference to the storage unit  56  (step S 3 ). For example, the area dividing unit  57  divides the luminance-color difference color space into a first area that is an area (red area) in which a hue includes red and a second area other than the first area. 
     Then, the signal processing unit  54  changes the luminance signal value by different amounts for each divided area with reference to the storage unit  56  (step S 4 ). For example, when the brightness level is increased in a case of dividing the luminance-color difference color space into the first and second areas described above, the signal processing unit  54  decreases a luminance signal value of the first area, but does not change a luminance signal value of the second area. Thus, it is possible to decrease lightness of a red hue portion to adjust the red hue portion to an appropriate color and suppress a change in a color associated with a change in a brightness level, such that color reproducibility is improved and a contrast in a screen is increased. 
     Then, the signal processing unit  54  converts the signal value of the image signal from the signal value in the luminance-color difference color space into the signal value in the RGB color space to generate the image signal for display, and outputs the image signal for display to the display device  3  (step S 5 ). 
     According to the embodiment described above, when the input of the instruction signal for changing the brightness level of the image signal is received, the color space determined by the luminance signal and the color difference signal is divided into the two areas by the hue, and different signal processing is performed on the divided two areas according to the brightness level. Therefore, it is possible to provide an image having good color reproducibility by performing appropriate adjustment for each color component at the time of performing brightness adjustment. 
     In addition, according to the present embodiment, when the instruction signal includes an instruction to increase the brightness level, the signal processing unit decreases a luminance signal value of an area that is one of the two areas and including a red hue portion. Therefore, it is possible to decrease the lightness of the red hue portion to adjust the red hue portion to the appropriate color and suppress the change in the color associated with the change in the brightness level, such that the color reproducibility is improved and the contrast in the screen is increased. As a result, for example, it becomes easy for the user to see a boundary between a tumor portion and a blood portion. 
     Modification 
       FIG. 4  is a flowchart illustrating an outline of processing performed by a medical image processing device (control device  5 ) according to a modification of the present embodiment. Steps S 11  to S 13  correspond, respectively, to steps S 1  to S 3  described with reference to  FIG. 3 . 
     In step S 14 , the signal processing unit  54  converts the signal value of the image signal from the signal value in the luminance-color difference color space to the signal value in the RGB color space (step S 14 ). 
     Then, the signal processing unit  54  generates an image signal for display by performing different signal processing according to the areas divided in the luminance-color difference color space at each point in the RGB color space, and outputs the image signal to the display device  3  (step S 15 ). For example, in the first area including the red hue portion, the signal value in RGB color space is changed so that the luminance signal value in the luminance-color difference color space is decreased, while in the second area, the signal value in RGB color space is changed so that the luminance signal value in the luminance-color difference color space is not changed. 
     The modification described above has the same effect as that of the embodiment. 
     Although the mode for carrying out the present disclosure has been described hereinabove, the present disclosure should not be limited only by the embodiment described above. For example, the medical observation system according to the present disclosure may be a medical endoscope system including a medical endoscope inserted into the object to be observed and capturing an image of the inside of the object to be observed. 
     Moreover, the area dividing unit  57  may divide the luminance-color difference color space into three areas or more than three areas, and the signal processing unit  54  may perform different signal processing on each of the divided areas. 
     According to the present disclosure, it is possible to provide an image with good color reproducibility by performing appropriate adjustment for each color component at the time of performing brightness adjustment. 
     Although the disclosure has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.