JP2017189608A - Image processing apparatus and image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing apparatus and an image processing method with which accuracy in inspection using an image can be improved.SOLUTION: An image processing apparatus according to the embodiment includes an acquisition unit, a region specifying unit, a conversion unit, and an image generation unit. The acquisition unit acquires a first image in which each pixel is shown in first gradation. The region specifying unit specifies a partial region in the first image. The conversion unit converts a step in the first gradation of each pixel included in the partial region in the first image into a corresponding display pattern, on the basis of association information in which each step of the first gradation and display patterns of a plurality of pixels in the display unit displaying an image in second gradation lower than the first gradation are associated with each other. The image generation unit generates a second image in which a plurality of pixels included in the partial region in the first image are shown in the display pattern converted by the conversion unit.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to an image processing apparatus and an image processing method.

  The X-ray diagnostic apparatus irradiates the subject with X-rays, and generates an X-ray image showing the difference in attenuation of the X-rays in the subject in black and white based on the transmitted X-rays. Such an X-ray image is displayed on various displays and is observed, for example, when performing a contrast examination such as angiography or an interventional treatment. Here, the black and white gradation in the X-ray image generated by the X-ray diagnostic apparatus is converted into a gradation expressed on the display when displayed on the display.

JP 2011-023895 A JP 2001-061063 A JP 2000-330530 A

  The problem to be solved by the present invention is to provide an image processing apparatus and an image processing method capable of improving the accuracy of an inspection using an image.

  The image processing apparatus according to the embodiment includes an acquisition unit, a region designation unit, a conversion unit, and an image generation unit. The acquisition unit acquires a first image in which each pixel is indicated by a first gradation. The area designating unit designates a partial area in the first image. The conversion unit associates each stage of the first gradation with a display pattern of a plurality of pixels in the display unit that displays an image with a second gradation smaller than the first gradation. Based on the above, the stage in the first gradation of each pixel included in the partial area in the first image is converted into the corresponding display pattern. An image generation part produces | generates the 2nd image which showed the some pixel contained in the said one part area | region of the said 1st image with the said display pattern converted by the said conversion part.

FIG. 1 is a block diagram showing an example of the configuration of the X-ray diagnostic apparatus according to the first embodiment. FIG. 2 is a diagram for explaining display of an X-ray image. FIG. 3 is a diagram for explaining display of an X-ray image. FIG. 4 is a diagram for explaining the display of the X-ray image according to the first embodiment. FIG. 5 is a diagram for explaining the pseudo gradation processing according to the first embodiment. FIG. 6 is a diagram for explaining the pseudo gradation processing according to the first embodiment. FIG. 7 is a diagram for explaining the pseudo gradation processing according to the first embodiment. FIG. 8 is a diagram for explaining the gradation interpolation mode according to the first embodiment. FIG. 9 is a flowchart for explaining a series of processing steps of the X-ray diagnostic apparatus according to the first embodiment. FIG. 10 is a diagram for explaining the gradation interpolation mode according to the second embodiment. FIG. 11 is a diagram for explaining the gradation interpolation mode according to the second embodiment. FIG. 12 is a flowchart for explaining a series of processing steps of the X-ray diagnostic apparatus according to the second embodiment.

  Hereinafter, an image processing apparatus and an image processing method according to embodiments will be described with reference to the drawings. In the following, an X-ray diagnostic apparatus including the image processing apparatus according to the embodiment will be described as an example. In the following, an X-ray image will be described as an example of an image to be subjected to image processing by the image processing apparatus according to the embodiment.

(First embodiment)
First, an example of the configuration of the X-ray diagnostic apparatus 1 according to the first embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing an example of the configuration of the X-ray diagnostic apparatus 1 according to the first embodiment. As shown in FIG. 1, the X-ray diagnostic apparatus 1 according to the first embodiment includes a high voltage generator 101, an X-ray source 102, a top plate 103, an X-ray detector 104, a holding arm 105, A display 106, an input circuit 107, a storage circuit 108, and a processing circuit 109.

  The high voltage generator 101 generates a high voltage under the control of the processing circuit 109 and supplies the generated high voltage to the X-ray source 102. The X-ray source 102 includes an X-ray tube 102a and an X-ray diaphragm 102b. The X-ray tube 102 a generates X-rays using the high voltage supplied from the high voltage generator 101. The X-ray stop 102b controls the X-ray irradiation field for the purpose of reducing the exposure amount to the subject P and improving the image quality.

  The top plate 103 is a bed on which the subject P is placed, and is placed on a bed (not shown). The X-ray detector 104 has a plurality of X-ray detection elements, detects signal intensity distribution data for X-rays transmitted through the subject P, and transmits the detected distribution data to the processing circuit 109. The holding arm 105 holds the X-ray source 102 and the X-ray detector 104 so as to face each other with the subject P interposed therebetween.

  The display 106 is a monitor referred to by the operator, and displays various X-ray images under the control of the processing circuit 109. The display 106 may be a stationary monitor or a display of a portable terminal (a portable PC such as a notebook PC (Personal Computer) or a tablet PC, a PDA (Personal Digital Assistant), a mobile phone, etc.). It may be a screen. For example, the display 106 displays an X-ray image that has undergone pseudo gradation processing or an X-ray image that has not undergone pseudo gradation processing. The X-ray image displayed on the display 106 and the pseudo gradation processing will be described later. In the following, as an example, a case will be described in which the display 106 is a color monitor that displays an image with gradation of “8 bits (256 gradations)” for each color of RGB (Red Green Blue).

  The input circuit 107 includes a mouse, a keyboard, a trackball, a switch, a button, a joystick, and the like used for inputting various instructions and various settings, and transfers instructions and setting information from the operator to the processing circuit 109. For example, the input circuit 107 receives an operation for designating a partial area for the X-ray image displayed on the display 106 from the operator. For example, the input circuit 107 receives a display mode switching operation from the operator. Note that the designation of some areas and the display mode will be described later.

  The storage circuit 108 stores data used when the processing circuit 109 controls the entire processing performed by the X-ray diagnostic apparatus 1. For example, the storage circuit 108 stores each program executed by the processing circuit 109. The storage circuit 108 stores various image data. In addition, the storage circuit 108 stores correspondence information that associates each gradation level of the X-ray image with a display pattern of a plurality of pixels on the display 106. The correspondence information will be described later.

  The processing circuit 109 executes a control function 109a, an image generation function 109b, a conversion function 109c, a display control function 109d, an area designation function 109e, a reception function 109f, and a region of interest setting function 109g. In the embodiment in FIG. 1, each processing function performed by the component control function 109a, the image generation function 109b, the conversion function 109c, the display control function 109d, the area designation function 109e, the reception function 109f, and the region of interest setting function 109g These are recorded in the storage circuit 108 in the form of a program that can be executed by a computer. The processing circuit 109 is a processor that realizes a function corresponding to each program by reading the program from the storage circuit 108 and executing the program. In other words, the processing circuit 109 in a state where each program is read has each function shown in the processing circuit 109 of FIG. In FIG. 1, the control function 109a, the image generation function 109b, the conversion function 109c, the display control function 109d, the region designation function 109e, the reception function 109f, and the region of interest setting function 109g are performed by a single processing circuit. Although the processing function has been described as being realized, a processing circuit may be configured by combining a plurality of independent processors, and the function may be realized by each processor executing a program.

  The term “processor” used in the above description is, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an application specific integrated circuit (ASIC), a programmable logic device (for example, It means circuits such as a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA). The processor implements a function by reading and executing a program stored in the storage circuit 108. Instead of storing the program in the storage circuit 108, the program may be directly incorporated in the processor circuit. In this case, the processor realizes the function by reading and executing the program incorporated in the circuit. Note that each processor of the present embodiment is not limited to being configured as a single circuit for each processor, but may be configured as a single processor by combining a plurality of independent circuits to realize the function. Good. Furthermore, a plurality of components in FIG. 1 may be integrated into one processor to realize the function.

  The image generation function 109b in the first embodiment is an example of an image generation unit in the claims. The conversion function 109c in the first embodiment is an example of a conversion unit in the claims. Further, the display control function 109d in the first embodiment is an example of a display control unit in the claims. Further, the area designating function 109e in the first embodiment is an example of an area designating unit in the claims. Further, the reception function 109f in the first embodiment is an example of a reception unit in the claims. The region-of-interest setting function 109g in the first embodiment is an example of a region-of-interest setting unit in the claims.

  The processing circuit 109 controls the entire processing by the X-ray diagnostic apparatus 1. The process performed by the X-ray diagnostic apparatus 1 is a series of processes related to an examination using an X-ray image, such as taking an X-ray image and displaying an X-ray image. For example, the processing circuit 109 controls the projection data collection process. For example, the processing circuit 109 generates an X-ray image using the collected projection data. Then, the processing circuit 109 stores the generated various X-ray images in the storage circuit 108.

  Further, the processing circuit 109 designates a partial area in the X-ray image stored in the storage circuit 108. Further, the processing circuit 109 converts the gradation level of each pixel included in a partial region in the generated X-ray image into a corresponding display pattern based on the correspondence information stored in the storage circuit 108. In addition, the processing circuit 109 generates an X-ray image in which a plurality of pixels included in a partial region of the X-ray image generated based on the projection data are represented by a display pattern converted based on the correspondence information. In addition, the processing circuit 109 causes the display 106 to display the X-ray image indicated by the display pattern. This point will be described later.

  The overall configuration of the X-ray diagnostic apparatus 1 according to the first embodiment has been described above. With this configuration, the X-ray diagnostic apparatus 1 according to the first embodiment uses the predetermined correspondence information to determine the gradation of each pixel in the X-ray image generated based on the X-ray transmitted through the subject P. By converting to a corresponding display pattern and generating an X-ray image in which pixels are shown in the display pattern, the accuracy of inspection using the X-ray image is improved.

  Here, first, the gradation conversion when displaying an X-ray image on the display 106 will be described. For example, the X-ray diagnostic apparatus 1 generates an X-ray image for display with “10 bits (1024 gradations)” and displays an “8 bits (256 gradations)” display 106 (for example, each of RGB 8 bits (256 colors)). When displaying on a display), an X-ray image in which the brightness of black and white is expressed in “1024 steps” is converted into the brightness of “256 steps”. That is, the “4-level” brightness in the X-ray image is converted to the “1-level” brightness, and pixels having different brightness levels in the X-ray image are expressed on the display 106 with the same brightness.

  When the color is reduced at the display stage in this way, the original gradation information is lost in the image observed by the observer, and in some cases, it may appear as a white spot or contour line. Therefore, in the X-ray diagnostic apparatus 1 according to the first embodiment, pseudo gradation processing is performed on the X-ray image before displaying the X-ray image on the display 106, and the original gradation information is obtained in a pseudo manner. The displayed X-ray image is displayed on the display 106.

  Here, first, details of gradation conversion executed by the X-ray diagnostic apparatus 1 will be described. FIG. 2 is a diagram for explaining display of an X-ray image. In FIG. 2, processing on the main body side of the X-ray diagnostic apparatus 1 (internal processing) is shown in the upper stage, and processing (external processing) on the display system (for example, display 106) side is shown in the lower stage. For example, the X-ray diagnostic apparatus 1 performs image processing on pixel data (projection data) detected by the X-ray detector 104 and applies an internal LUT, as shown in the upper part of FIG. A gradation X-ray image is generated. That is, on the main body side of the X-ray diagnostic apparatus 1, for example, as illustrated in the upper part of FIG. 2, processing is performed with “10-bit” data from pixel data to an X-ray image. In the X-ray diagnostic apparatus 1, the data stored by the storage circuit 108 also remains “10 bits”.

  When the generated X-ray image is displayed on the display 106, the display system receives the multi-gradation X-ray image, applies the display color-reduction LUT, and executes the monitor γ processing. Is converted from “10 bits” to “8 bits”. Then, an X-ray image of the video card “8 bits” is output from the display 106. As described above, in the X-ray diagnostic apparatus 1, when displaying an X-ray image having more gradations than the gradation displayed on the display 106, the gradations are simply thinned out according to the LUT held by the display 106. To display an X-ray image.

  In the X-ray diagnostic apparatus 1 according to the first embodiment, the pseudo-gradation process is performed on the X-ray image and the display color reduction LUT is applied before the gradation conversion process. An X-ray image holding key information is displayed. Thereby, for example, information that has become invisible in the gradation conversion process by simple thinning can be displayed. FIG. 3 is a diagram for explaining display of an X-ray image. In FIG. 3, the original data of the X-ray image before being displayed on the display 106 (in the stage of internal processing) is shown on the left side, and the X-ray image displayed by simple thinning is shown on the right side.

  For example, it is assumed that the character “A” is included as information in the generated X-ray image as shown in the left diagram of FIG. In this case, since the original data has multiple gradations, the gradation level differs between the character “A” and the background, resulting in different colors. However, if tone conversion is simply performed on the original data, the character “A” and the background are converted to the same color and identified as information, as shown on the right side of FIG. I can't. Therefore, the X-ray diagnostic apparatus 1 can identify information even if the display 106 is converted to gradation by performing pseudo gradation processing before conversion to the gradation of the display 106. Display line images. That is, when the X-ray diagnostic apparatus 1 displays the X-ray image of FIG. 3 on the display 106, the X-ray image that allows the character “A” to be identified is displayed on the display 106. Hereinafter, processing performed by the X-ray diagnostic apparatus 1 according to the first embodiment will be described in detail.

  First, the control function 109a controls the imaging system including the high voltage generator 101, the X-ray source 102, the top plate 103, the X-ray detector 104, and the holding arm 105, and collects projection data. Specifically, the control function 109a controls the imaging system so that the subject P is exposed to X-rays and the X-rays transmitted through the subject P are detected by the X-ray detector 104. Then, the control function 109a generates projection data using the electric signal converted from the X-ray by the X-ray detector 104, and stores the generated projection data in the storage circuit 108. For example, the control function 109a performs current / voltage conversion, A (Analog) / D (Digital) conversion, and parallel / serial conversion on the electrical signal received from the X-ray detector 104, and performs projection data (pixel data). Is generated.

  Next, the image generation function 109b generates an X-ray image using the collected projection data (pixel data). Specifically, the image generation function 109b performs various types of image processing on the projection data (pixel data), and generates an X-ray image by applying an internal LUT. Hereinafter, the X-ray image generated by the image generation function 109b based on the X-rays transmitted through the subject P is also referred to as a first X-ray image. The first X-ray image is an example of the first image in the claims.

  In addition, the conversion function 109c associates each stage of the first gradation with a display pattern of a plurality of pixels in the display 106 that displays an image with a second gradation smaller than the first gradation. Based on the information, the stage in the first gradation of each pixel in the first X-ray image is converted into a corresponding display pattern. The display control function 109d causes the display 106 to display an X-ray image indicating a plurality of pixels included in a partial region of the first X-ray image with a display pattern converted by the conversion function 109c. Hereinafter, these processes will be described with reference to FIG. In the following, a case where the first X-ray image is a monochrome image having a gradation of “10 bits (1024 gradations)” will be described as an example. Here, the gradation of the monochrome image refers to the gradation regarding the brightness of the hue expressed in the X-ray image. Hereinafter, the gradation indicated by each pixel of the first X-ray image is also referred to as a first gradation. Hereinafter, the gradation indicated by each pixel of the display 106 is also referred to as a second gradation. In the following, a case where the first gradation is higher than the second gradation will be described.

  As shown in FIG. 4, when the image generation function 109b generates the first X-ray image, the conversion function 109c performs pseudo gradation processing prior to outputting the first X-ray image to the display 106. If it is determined whether or not pseudo gradation processing is to be performed, pseudo gradation processing is performed on the first X-ray image. Here, the pseudo gradation processing executed by the conversion function 109c is to express the first gradation of each pixel of the first X-ray image using the second gradation displayed on the display 106. Thus, it refers to a process of representing on the display 106 the gradation information that each pixel of the first X-ray image has. FIG. 4 is a diagram for explaining the display of the X-ray image according to the first embodiment. In FIG. 4, processing on the main body side of the X-ray diagnostic apparatus 1 (internal processing) is shown in the upper stage, and processing (external processing) on the display system (for example, display 106) side is shown in the lower stage. Hereinafter, an example of the pseudo gradation processing executed by the conversion function 109c will be described with reference to FIG. Here, FIG. 5 is a diagram for explaining the pseudo gradation processing according to the first embodiment. 5 shows a part of the gradation of the display 106. Further, in FIG. 5, for convenience of explanation, “four levels” of “256 gradations” are shown, but the following contents are actually applied to all “256 gradations”.

  For example, the first 10-bit X-ray image generated by the image generation function 109b is expressed in 1024 steps (black and white shades). When the first X-ray image is converted to “8 bits” by the display color reduction LUT, the color is reduced to 256 stages. That is, the original gradation information is “1/4”. Therefore, as the correspondence information in this case, a display pattern for expressing each of “1024 steps” using 256 steps is used. For example, as shown in FIG. 5, there are four displays for “four steps (four colors)” of the first X-ray image that is reduced to “one step (one color)” of the gradation of the display 106. A display pattern associated with the pattern is stored in advance by the storage circuit 108. Here, since the display pattern shown in FIG. 5 is expressed by the gradation of the display 106, four pixels are used to express four times the gradation information. By converting the gradation information of the first X-ray image using such a display pattern, the original gradation information can be expressed using the gradation of the display 106. The conversion function 109c refers to the correspondence information stored in the storage circuit 108, and converts each pixel of the first X-ray image into a display pattern corresponding to the color of the pixel.

  In FIG. 5, the case where four times the number of pixels is used to express the information of “1024 colors” in “256 colors” has been described as an example, but the embodiment is not limited thereto. Absent. That is, corresponding information is generated according to the gradation of the display 106 and the gradation of the first X-ray image, and stored in the storage circuit 108. For example, the storage circuit 108 stores display pattern correspondence information using 16 times the number of pixels in order to represent “256 colors” and “4096 colors” information. The conversion function 109c selects correspondence information to be used based on the gradation of the first X-ray image and the gradation of the display 106 that is the display destination, and executes conversion processing using the selected correspondence information.

  First, the conversion function 109c obtains correspondence information that associates each stage of the first gradation with the display pattern of a plurality of pixels in the display 106 that displays an image at the second gradation from the storage circuit 108. get. Here, each stage of the first gradation is, for example, each stage of “1024 gradations” in the first X-ray image. Further, the display pattern indicates each stage of the gradation of the original X-ray image by using the gradation of the display 106 shown in the left figure of FIG. 5, as shown in the right figure of FIG. . In the following, the process of converting each stage of the first gradation into the corresponding display pattern using the correspondence information is also referred to as a dither process.

  That is, the conversion function 109c can express the gradation of each pixel of the first X-ray image using the gradation displayed by each pixel of the display 106 by dither processing. For example, the conversion function 109c uses the “256-step” color of the “8-bit” gradation displayed on the display 106, and the “10-bit” gradation of each pixel of the first X-ray image. A color of “1024 steps” can be expressed. In other words, the conversion function 109c can express, for example, a first X-ray image having a gradation of “10 bits” with “8 bits” by dither processing.

In addition, the X-ray image in which each pixel is converted into the “1024 ways” pattern is displayed on the display 106 by the display control function 109d. Here, the “1024 patterns” patterns are recognized as “1024-step” colors due to the visual effect when the operator observes the image. In other words, the X-ray image seen by the operator is actually an “8-bit” image displayed on the display 106, but is recognized as a “10-bit” image due to visual effects.

  Accordingly, the conversion function 109c can express a grayscale intermediate color by a dither process. In addition, the conversion function 109c increases the apparent gray scale by dither processing, for example, the “10 bit” of each pixel of the first X-ray image on the “8 bit” display 106. "Can be expressed. In the following description, an X-ray image expressed as “8 bits” by dithering an “10-bit” X-ray image is referred to as a “pseudo 10-bit” X-ray image.

  The X-ray image converted to “pseudo 10 bits” is already “8 bits” when viewed in pixel units. Therefore, the X-ray image that has undergone the pseudo gradation processing is displayed on the display 106 without being subjected to color reduction by the display color reduction LUT included in the display 106 and having information corresponding to the gradation information of “10 bits”. . Further, the “pseudo 10-bit” X-ray image subjected to the pseudo gradation processing and the “10-bit” X-ray image before the pseudo gradation processing are stored in the storage circuit 108.

  In the above-described example, a case has been described in which the conversion function 109c expresses the “256-level” color as the “1024-level” color by the dither processing in which each pixel of the first X-ray image is expressed by four pixels. . However, the embodiment is not limited to this. For example, the conversion function 109c performs “256” by performing dither processing in which each pixel of the first X-ray image is expressed by nine “3 × 3” pixels. The “stage” color can be expressed as the “2304 stage” color. In addition, for example, the conversion function 109c converts the “256-step” color into the “4096-step” color by dither processing that expresses each pixel of the first X-ray image by 16 pixels of “4 × 4”. Can be expressed.

  As described above, the conversion function 109c can prevent the information included in the original data from being lost by artificially increasing the number of gradations by the pseudo gradation processing. Furthermore, the conversion function 109c can reduce staircase noise by pseudo gradation processing. Here, the step-like noise reduction by the pseudo gradation processing will be described with reference to FIG. FIG. 6 is a diagram for explaining the pseudo gradation processing according to the first embodiment. For example, when the original data of the “eight steps” color shown in the upper diagram of FIG. 6 is displayed on the display 106 without performing the pseudo gradation processing, as shown in the middle diagram of FIG. By the simple color reduction at, an image reduced to “four levels” is displayed. On the other hand, when the original data of “8 levels” color shown in the upper diagram of FIG. 6 is displayed on the display 106 by performing pseudo gradation processing as shown in the lower diagram of FIG. Although the points displayed in color are the same, by expressing the intermediate color by the display pattern, it is possible to reduce staircase noise and display a smooth image as a whole.

  Further, as described above, the dither processing executed by the conversion function 109c is processing for converting the gradation of each pixel of the first X-ray image into a display pattern that is a combination of colors of a plurality of pixels. Therefore, when the dither process is executed, as shown in FIG. 7, the number of pixels of the X-ray image is increased. FIG. 7 is a diagram for explaining the pseudo gradation processing according to the first embodiment. For example, the number of pixels of the X-ray image that has been subjected to dither processing that expresses “1 pixel” of the X-ray image shown in the left diagram of FIG. 7 by “4 pixels” of “2 × 2” shown in the right diagram of FIG. Increases up to 4 times the original image.

  Here, depending on the number of pixels of the X-ray image, there may be a case where the effect of increasing the number of apparent gradations due to the dither processing cannot be obtained. That is, since the dither process is a process of expressing each pixel of the first X-ray image by a plurality of pixels on the display 106, depending on the number of pixels of the first X-ray image with respect to the number of pixels of the display 106, Each pixel of the first X-ray image cannot be displayed by a plurality of pixels on the display 106, and the visual effect by the dither process may not be obtained.

  Therefore, the conversion function 109c performs a process for determining whether or not to perform the pseudo gradation process prior to the execution of the pseudo gradation process. First, the conversion function 109c, for example, performs pseudo gray level processing on the first X-ray image having the number of pixels “512 × 512” and the number of gradations “10 bits” to have the number of pixels “1024 × 1024”. And is converted into an X-ray image having the number of gradations of “pseudo 10 bits”. Here, for example, when the total number of pixels of the display 106 is “512 × 512”, “4 pixels” in the converted X-ray image (“1 pixel” in the first X-ray image before conversion) is set. This is expressed by “one pixel” on the display 106. In this case, since the X-ray image after the dither process cannot be displayed on the display 106, the conversion function 109c determines that the pseudo gradation process is not performed in the determination process.

  On the other hand, for example, when the display 106 is a large-screen monitor or a high-resolution monitor and can display an X-ray image after pseudo gradation processing, the number of pixels of the X-ray image increases by performing dither processing. Can be displayed on the display 106. Therefore, when the number of pixels of the display 106 is sufficiently large, the conversion function 109c determines in the determination process that an X-ray image interpolated with the number of gradations can be displayed, and performs pseudo gradation processing. In other words, in the determination process, the conversion function 109c determines whether or not an X-ray image obtained by interpolating the number of gradations can be displayed based on the relationship between the number of pixels of the display 106 and the number of pixels of the X-ray image. In some cases, pseudo gradation processing is performed. Note that the conversion function 109c determines that the pseudo gradation process is not necessary in the determination process, for example, when the number of gradations of the first X-ray image is smaller than the number of gradations displayed on the display 106. It is determined that pseudo gradation processing is not performed.

  When the X-ray image displayed on the display 106 by the display control function 109d is not the entire X-ray image generated by the image generation function 109b but a partial area of the X-ray image, the conversion function 109c is Then, a determination process is performed on a part of the X-ray image, and a pseudo gradation process is performed on pixels included in the part of the X-ray image. For example, when enlarging and displaying only a part of the entire X-ray image, the conversion function 109c is based on the relationship between the number of pixels corresponding to the part of the display area and the number of pixels of the display 106. It can be determined whether or not an X-ray image interpolating the number of gradations can be displayed. Hereinafter, the pseudo gradation process with the enlarged display of the X-ray image will be described with reference to FIG. FIG. 8 is a diagram for explaining the gradation interpolation mode according to the first embodiment.

  For example, first, the display control function 109d causes the display 106 to display the entire X-ray image that has not been subjected to the pseudo gradation processing, as shown in the upper left diagram of FIG. In other words, the display control function 109d causes the display 106 to display an X-ray image obtained by replacing each step of the first gradation of each pixel in the first X-ray image with a step corresponding to the second gradation.

  Next, the reception function 109f replaces each step of the first gradation of each pixel in the first X-ray image with a step corresponding to the second gradation, and performs processing on the X-ray image displayed on the display 106. An operation is received from the operator. For example, the accepting function 109f accepts designation of a part of the entire X-ray image to be displayed from the operator who refers to the X-ray image shown in the upper left diagram of FIG. For example, the reception function 109f receives a rectangular area shown in the upper left diagram of FIG. 8 that is adjusted through a mouse operation included in the input circuit 107 as a partial area to be enlarged.

  Next, the area designating function 109e designates a part of the area in the first X-ray image based on the operation accepted by the accepting function 109f. For example, when the operator performs an operation for designating the rectangular region shown in the upper left diagram of FIG. 8, the region designation function 109e uses the rectangular region shown in the upper left diagram of FIG. Designated as a part area.

  Further, the conversion function 109c determines whether or not a part of the entire X-ray image subjected to the enlargement operation can be displayed on the display 106 by performing pseudo gradation processing. Here, when it is determined that the partial area subjected to the pseudo gradation processing can be displayed on the display 106, the conversion function 109c determines the first of each pixel included in the partial area based on the correspondence information. Each stage in the gradation is converted into a corresponding display pattern. In other words, the conversion function 109c performs pseudo gradation processing on a specified part of the area, and converts the X-ray image into “pseudo 10 bits”.

  Next, the image generation function 109b generates an X-ray image (hereinafter, also referred to as a second X-ray image) indicating a plurality of pixels included in a partial area with a display pattern converted by the conversion function 109c. To do. For example, the image generation function 109b generates a “pseudo 10-bit” second X-ray image from a “10-bit” first X-ray image. Note that the second X-ray image may be an image corresponding to only a partial area of the first X-ray image, or may correspond to an area of the first X-ray image including the partial area. It may be an image. The second X-ray image is an example of a second image in the claims.

  Then, the display control function 109d causes the display 106 to display the second X-ray image generated by the image generation function 109b, as shown in the lower right diagram of FIG. In other words, the display control function 109 d displays a “pseudo 10-bit” X-ray image on the display 106. In FIG. 8, the second X-ray image is an image corresponding to only a partial region of the first X-ray image.

  On the other hand, when the number of pixels is insufficient or when the setting is not performed for the pseudo gradation process, the conversion function 109c does not perform the pseudo gradation process for the area subjected to the enlargement operation in the entire X-ray image, and displays The control function 109d enlarges and displays the “8-bit” X-ray image, as shown in the upper right diagram of FIG. Hereinafter, a mode for displaying an X-ray image subjected to pseudo gradation processing (that is, a mode for displaying a second X-ray image) is referred to as a gradation interpolation mode, and X-ray processing without pseudo gradation processing is performed. A mode for displaying a line image is referred to as a normal mode.

  Hereinafter, the X-ray image displayed on the display 106 by the display control function 109d in the normal mode is also referred to as a third X-ray image. For example, the X-ray image shown in the upper right diagram of FIG. 8 is a third X-ray image. The third X-ray image may be an image corresponding to only a partial region of the first X-ray image, or an image corresponding to a region of the first X-ray image including the partial region. There may be. The third X-ray image in FIG. 8 is an image corresponding to only a partial region of the first X-ray image. The third X-ray image is an example of a third image in the claims.

  For example, as shown in the lower right diagram of FIG. 8, the conversion function 109c automatically switches to the gradation interpolation mode when displaying a part of the X-ray image in an enlarged manner, and the display control function 109d , A “pseudo 10-bit” X-ray image is displayed on the display 106. Note that switching between the normal mode and the gradation interpolation mode may be automatic or may be performed by an operator. For example, the display control function 109d can switch the image display mode in response to pressing of a button included in the input circuit 107.

  Hereinafter, the pseudo gradation processing accompanied with the enlargement operation of the X-ray image will be described more specifically. In the following, as an example, the total number of pixels of the display 106 is “512 × 512”, and the total number of pixels of the first X-ray image generated by the image generation function 109b is “512 × 512”. The case will be described. For example, in the upper left diagram of FIG. 8, the display 106 displays the entire first X-ray image, and “1 pixel” of the display 106 displays “1 pixel” of the first X-ray image. In the following, as an example, a case will be described in which the display control function 109d enlarges the designated part of the entire first X-ray image to “2 times” and displays it on the display 106. . For example, in the upper right view of FIG. 8, the display 106 displays a “¼” region of the entire first X-ray image, and the “2 × 2” “4 pixels” of the display 106 is “1 pixel” of one X-ray image is displayed.

  For example, first, the conversion function 109c executes pseudo gradation processing on a part of the region specified by the operator in the entire X-ray image shown in the upper left diagram of FIG. For example, the conversion function 109c executes pseudo gradation processing for expressing “1 pixel” in the first X-ray image by “4 pixels” of “2 × 2”. Next, the image generation function 109b outputs a second X-ray in which a plurality of pixels included in a partial region of the X-ray image illustrated in the upper left diagram of FIG. 8 is displayed with a display pattern converted by pseudo gradation processing. Generate an image. Next, the display control function 109d displays the second X-ray image generated by the image generation function 109b on the display 106 as shown in the lower right diagram of FIG.

  As described above, when displaying a part of the entire X-ray image that has been subjected to the enlargement operation, the number of pixels of the X-ray image to be displayed is reduced with respect to the number of pixels of the display 106. There is a margin for displaying the X-ray image on the display 106. Therefore, for example, the entire X-ray image subjected to dither processing cannot be displayed due to a limitation on the number of pixels of the display 106 (for example, when the number of pixels of the X-ray image is large or when the number of pixels of the display 106 is small). Even in this case, it is possible to display the X-ray image subjected to the dither process by enlarging and displaying a part of the X-ray image.

  In addition, the conversion function 109c can determine the content of the pseudo gradation processing based on the relationship between the number of pixels of the display 106 and the number of pixels of the X-ray image to be displayed. For example, the display control function 109d displays the X-ray image in the gradation interpolation mode by adjusting the magnification for enlarging the X-ray image even when the number of gradations of the original data is further increased from “10 bits”. Can do. In FIG. 8, a specified part of the entire X-ray image is enlarged to “2 ×” (display magnification for displaying “¼” of the entire first X-ray image). When the display function is displayed on the display 106, the conversion function 109c performs pseudo gradation processing for expressing “1 pixel” of the first X-ray image using “4 pixels” on the display 106. . Here, for example, a specified part of the entire X-ray image is enlarged to “4 times” (display magnification for displaying “1/16” of the entire first X-ray image). When the image is displayed on the display 106, the conversion function 109c displays “1 pixel” of the first X-ray image using “16 pixels” of “4 × 4” on the display 106. Processing can be performed. That is, when displaying the “12-bit” X-ray image on the “8-bit” display 106, the conversion function 109 c represents “1 pixel” in the first X-ray image as “16 pixels” on the display 106. The X-ray image is converted from “12 bits” to “pseudo 12 bits” by gradation processing. Then, for example, the display control function 109d enlarges a part of the X-ray image to “4 times” and displays the X-ray image on the display 106 and also displays the “pseudo 12-bit” X-ray image.

  Next, an example of a processing procedure performed by the X-ray diagnostic apparatus 1 will be described with reference to FIG. FIG. 9 is a flowchart for explaining a series of processing steps of the X-ray diagnostic apparatus 1 according to the first embodiment. Step S101, step S102 and step S110 are steps corresponding to the control function 109a. Step S103 is a step corresponding to the image generation function 109b. Step S106 is a step corresponding to the conversion function 109c and the image generation function 109b. Step S104, step S107, step S108, and step S109 are steps corresponding to the display control function 109d. Step S105 is a step corresponding to the area designation function 109e and the reception function 109f.

  First, the processing circuit 109 determines whether an inspection start request has been received from the operator (step S101). When the inspection start request is not accepted (No at Step S101), the processing circuit 109 enters a standby state. On the other hand, when the examination start request is accepted (Yes at Step S101), the processing circuit 109 performs imaging on the subject P (Step S102), and generates an X-ray image based on the signal collected from the subject P (Step S102). Step S103).

  Next, the processing circuit 109 displays the entire generated X-ray image on the display 106 (Step S104), receives an enlargement operation from the operator, and designates a partial region in the X-ray image (Step S105). Then, the processing circuit 109 performs pseudo gradation processing on a specified part of the entire X-ray image, and generates a second X-ray image (step S106). Further, the processing circuit 109 displays the X-ray image (second X-ray image) on which the pseudo gradation processing has been executed on the display 106 (step S107).

  Here, the processing circuit 109 determines whether or not a display mode switching operation has been received (step S108). When a display mode switching operation is received (Yes at step S108), the processing circuit 109 performs an X-ray image on which pseudo gradation processing has been performed or an X-ray image on which pseudo gradation processing has not been performed, depending on the content of the operation. Is displayed on the display 106 (step S109). On the other hand, when the display mode switching operation is not accepted (No at Step S108), the processing circuit 109 determines whether an end command is accepted from the operator (Step S110). When the end command is not accepted (No at Step S110), the processing circuit 109 proceeds to Step S108 again. On the other hand, when an end command is received (Yes at step S110), the processing circuit 109 ends the process.

  In step S107, the processing circuit 109 may display an X-ray image that has not been subjected to the pseudo gradation processing on the display 106. In addition, although the case where the pseudo gradation process is performed on a part of the region subjected to the enlargement operation in step S106 has been described, the pseudo gradation process is performed on the entire first X-ray image in advance, and the first X-ray process is performed. The second X-ray image may be generated according to a part of the entire line image subjected to the enlargement operation. The processing circuit 109 may determine whether or not the X-ray image subjected to the pseudo gradation process can be displayed on the display 106 prior to the pseudo gradation process in step S106.

  As described above, according to the first embodiment, the image generation function 109b generates a first X-ray image in which each pixel is indicated by the first gradation based on the X-ray transmitted through the subject P. Generate. The area specifying function 109e specifies a part of the area in the first X-ray image. In addition, the conversion function 109c associates each stage of the first gradation with a display pattern of a plurality of pixels in the display 106 that displays an image with a second gradation smaller than the first gradation. Based on the information, the stage in the first gradation of each pixel included in a partial region in the first X-ray image is converted into a corresponding display pattern. Further, the image generation function 109b generates a second X-ray image in which a plurality of pixels included in a partial region of the first X-ray image are indicated by a display pattern converted by the conversion function 109c. The display control function 109d causes the display 106 to display the second X-ray image generated by the image generation function 109b. Therefore, the X-ray diagnostic apparatus 1 according to the first embodiment presents information that is lost due to simple color reduction on the display 106 to the operator, thereby improving the accuracy of the examination using the X-ray image. it can.

  In addition, as described above, the display control function 109d according to the first embodiment displays a pseudo-scale on the display 106, which is a color monitor that displays an image with “8 bits (256 gradations)” for each of the RGB colors. It is possible to display an X-ray image that has been subjected to tonal processing. Therefore, the X-ray diagnostic apparatus 1 according to the first embodiment uses an “8-bit” color monitor that has recently been used for displaying X-ray images due to low price and high resolution. Even when an X-ray image is displayed, an examination using an X-ray image is performed by presenting to the operator gradation information contained in an X-ray image having gradations such as “10 bits” and “12 bits”. Accuracy can be improved.

  As described above, the conversion function 109c according to the first embodiment executes pseudo gradation processing on the X-ray image, and the display control function 109d displays the X-ray image subjected to pseudo gradation processing. 106 is displayed. Therefore, the X-ray diagnostic apparatus 1 according to the first embodiment reduces the staircase noise from the X-ray image displayed on the display 106 and presents an X-ray image with improved overall appearance to the operator. Thus, the accuracy of the inspection using the X-ray image can be improved.

  Further, as described above, the conversion function 109c according to the first embodiment executes pseudo gradation processing on the X-ray image before receiving simple color reduction by the display color reduction LUT in the monitor. Therefore, the X-ray diagnostic apparatus 1 according to the first embodiment differs from anti-aliasing or the like in which the resolution of the X-ray image is lowered by blurring the boundary line of the X-ray image that has undergone simple color reduction. An X-ray image that effectively uses the gradation information contained in the data can be displayed, and the accuracy of the inspection can be improved.

  As described above, the conversion function 109c according to the first embodiment performs the pseudo gradation process on the X-ray image after performing the determination process. Therefore, the X-ray diagnostic apparatus 1 according to the first embodiment has a dither processing level even if an X-ray image subjected to pseudo gradation processing is displayed on the display 106 in relation to the number of pixels of the display 106. When the effect of the key interpolation cannot be obtained, the calculation load can be reduced by not performing the dither processing.

  Further, as described above, the display control function 109d according to the first embodiment enlarges and displays the X-ray image subjected to the pseudo gradation processing on the display 106. Therefore, the X-ray diagnostic apparatus 1 according to the first embodiment is not limited to the case where the display 106 is a high resolution monitor or a large screen monitor, and presents an X-ray image subjected to pseudo gradation processing to the operator. The accuracy of the inspection using the X-ray image can be improved.

  Further, as described above, the display control function 109d according to the first embodiment enlarges and displays the X-ray image subjected to the pseudo gradation processing on the display 106. Therefore, the X-ray diagnostic apparatus 1 according to the first embodiment has the number of pixels of the display 106 even when the gradation of the X-ray image is multi-gradation such as “12 bits” or “14 bits”. The accuracy of inspection using X-ray images is determined by determining the contents of dither processing and display magnification in relation to the above, and presenting the operator with an X-ray image that has been subjected to dither processing that maximizes the effect of gradation interpolation. Can be improved.

  In addition, as described above, the display control function 109d according to the first embodiment displays the gradation interpolation mode for displaying the X-ray image subjected to the pseudo gradation process and the X-ray image not subjected to the pseudo gradation process. The normal mode to be displayed can be switched. Therefore, the X-ray diagnostic apparatus 1 according to the first embodiment enables display and comparison as usual using original image data, and further displays and compares using an X-ray image interpolated with gradation. And the accuracy of inspection can be improved.

  In FIG. 8, the display control function 109 d has been described with respect to a case where a specified part of the area is displayed on the entire display 106, but the embodiment is not limited thereto. For example, the display control function 109d displays the entire X-ray image on the display 106, enlarges an area surrounded by an icon (for example, a “magnifying glass” tool) that moves on the X-ray image, and displays the entire X-ray image. It may be a case where the image is displayed so as to be superimposed on a part of the image. The display control function 109d can display, for example, a partial region of the pseudo-gradation X-ray image on a part of the entire X-ray image that is not pseudo-gradation.

  In FIG. 8, the case where the area specifying function 109e specifies a part of the area in the first X-ray image based on the operation received by the receiving function 109f has been described. However, the embodiment is limited to this. Is not to be done. Hereinafter, another example of designating a part of the area by the area designating function 109e will be described.

  First, a case will be described in which a device is included in the first X-ray image and a partial area is designated based on device information in the first X-ray image. For example, after the image generation function 109b generates a first X-ray image, the region-of-interest setting function 109g sets a region of interest including a device in the first X-ray image. Note that the region of interest may be a region along the outline of the device, a rectangular region including the device, or a region of another shape.

  Here, the setting of the region of interest will be described as an example where the device included in the first X-ray image is a stent. The stent is, for example, a metal mesh, and is placed in a stenosis site in the blood vessel of the subject P in interventional treatment, and is used to reduce the restenosis rate of the stenosis site.

  For example, the region-of-interest setting function 109g sets a region of interest based on a stent marker indicating the position of the stent. Here, the stent marker is, for example, a radiopaque metal. For example, in an interventional treatment for a stenosis site using a balloon catheter, stent markers are attached to two locations of the balloon portion. In this case, since the stent is inserted into the subject while being in close contact with the outside of the balloon portion of the balloon catheter, the stent marker attached to the balloon portion substantially indicates the position of the stent. The catheter is a tube used for medical purposes. For example, in interventional treatment, a balloon portion of a catheter with a balloon is inserted to a stenosis site, and liquid is injected into the balloon through the catheter, whereby the balloon is expanded and the stenosis site is expanded.

  Since the stent marker appears clearly in the first X-ray image as compared with the body tissue or stent of the subject P, the region-of-interest setting function 109g cannot directly identify the position of the stent from the first X-ray image. Even in this case, the position of the stent can be specified based on the stent marker. Hereinafter, points used for specifying the position of the device in the first X-ray image, such as a stent marker included in the first X-ray image, are also referred to as feature points.

  Note that the shape and size of the region of interest based on the position of the stent marker may be set using information regarding the shape and size of the stent, or preset settings may be used. The region-of-interest setting function 109g may be a case where the region of interest is set from the image of the device in the first X-ray image without using a feature point such as a stent marker.

  Next, the region designation function 109e determines whether or not to designate the region of interest as a partial region according to the information on the device included in the region of interest. The device information may be information acquired from the first X-ray image or may be information input by the operator. Here, the determination as to whether or not the region of interest is designated as a partial region will be described as an example in which the device included in the first X-ray image is a stent.

  For example, the region specifying function 109e first acquires stent information based on the stent image in the first X-ray image. Here, the stent information is information related to the configuration of the stent, such as the roughness of the mesh of the stent. For example, the region specifying function 109e acquires the thickness and interval of the linear metal constituting the mesh from the stent image as stent information.

  Here, when the mesh of the stent is fine (for example, when the linear metal constituting the mesh is thin or when the interval is close), the contrast of the stent in the first X-ray image is small. When the first X-ray image including such a stent is subjected to color reduction by the display color reduction LUT in the monitor, the stent is expressed with a smaller number of gradations and visibility is reduced.

  Accordingly, when the stent mesh is fine, the region designating function 109e designates the region of interest including the stent as a partial region to be subjected to dither processing. For example, the region specifying function 109e calculates a value indicating the roughness of the mesh of the stent (such as the thickness of the metal constituting the mesh and the interval) from the stent image in the first X-ray image, and calculates the calculated value and the threshold value. To determine whether or not to designate the region of interest as a partial region.

  Alternatively, the region specifying function 109e calculates contrast (lightness) for the stent image in the first X-ray image, and determines whether or not to specify the region of interest as a partial region based on the calculated contrast. To do. For example, the region specifying function 109e calculates the ratio or difference between the minimum value and the maximum value of the pixel values in the stent image as contrast, and compares the calculated contrast with a threshold value, thereby determining the region of interest as a partial region. Determine whether to specify.

  The contrast for the stent image may be calculated for the image in the region of interest, or may be calculated for the image of the portion of the region of interest that includes the stent image. For example, when the region of interest is a rectangular region including a stent, the region specifying function 109e can calculate the contrast for the region along the contour of the stent.

  Further, when the first X-ray image is a plurality of images collected in time series such as a fluoroscopic image used in interventional treatment, the image is an image of the same subject P and the same stent. However, the contrast of the stent image may change due to changes in imaging angle, contrast medium distribution, stent position, and the like. In such a case, the region specifying function 109e may calculate the contrast for determining whether or not the region of interest is specified as a partial region for each image, or calculate one value for a plurality of images. May be. For example, the region specifying function 109e calculates the contrast for the stent image in each of the plurality of first X-ray images, and determines whether or not the region of interest is specified as a partial region for each image. In addition, for example, the region specifying function 109e is configured such that the contrast of the stent image in the first image among the plurality of first X-ray images collected in time series, and each of the plurality of first X-ray images. Whether or not to designate the region of interest in each of the plurality of first X-ray images as a partial region is uniformly determined based on the average value of the contrast for the stent image at.

  Further, the region designating function 109e may determine whether to designate the region of interest as a partial region based on the stent information input by the operator. For example, first, information that determines whether or not to designate a partial region for each stent (for example, for each stent standard or product name) or for each value indicating the roughness of the mesh is stored in the storage circuit 108. Stored in Such information may be set by the area specifying function 109e or may be set by the operator.

  Next, the input circuit 107 receives an operation for inputting stent information from the operator. Here, the information on the stent that accepts the input operation may be a standard or product name of the stent, or may be a value indicating the roughness of the mesh. Then, the region designating function 109e determines whether or not the region of interest is designated as a partial region by comparing the information that determines whether or not to designate a partial region with the input stent information. To decide.

  When the region of interest is designated as a partial region, the conversion function 109c converts the stage in the first gradation of each pixel included in the region of interest into a corresponding display pattern, and the image generation function 109b A second X-ray image is generated in which the pixels included in the region of interest of the X-ray image are shown in a display pattern. Here, the second X-ray image may be an image corresponding only to the region of interest, or may be an image corresponding to part or all of the first X-ray image including the region of interest.

  That is, by converting each pixel included in the region of interest into a display pattern and increasing the number of pixels, a plurality of pixels of the second X-ray image are displayed on one pixel of the display 106, and dither processing is performed. In some cases, the visual effect of gradation interpolation cannot be obtained. In such a case, the image generation function 109b generates the second X-ray image as an image corresponding to only the region of interest or an image corresponding to a part of the first X-ray image including the region of interest. Therefore, when the second X-ray image is displayed on the display 106, the visual effect of gradation interpolation by dither processing can be obtained. On the other hand, when the display 106 is a large-screen monitor, a high-resolution monitor, or the like, the image generation function 109b generates the second X-ray image as an image corresponding to the entire first X-ray image. When the second X-ray image is displayed on the display 106, it is possible to obtain a visual effect of gradation interpolation by dither processing.

  Next, a case where a region of interest in the first X-ray image is set regardless of whether or not a device is included in the first X-ray image will be described. For example, the region-of-interest setting function 109g may set the region of interest based on an operation received by the reception function 109f from the operator, or may be set in a preset range (for example, in the center of the first X-ray image). A range having a predetermined shape and size) may be set as the region of interest.

  After the region of interest is set, the region designation function 109e determines whether or not to designate the region of interest as a partial region depending on the presence or absence of a device in the region of interest. Here, regarding the determination of whether or not to designate the region of interest as a partial region, the first X-ray image is a fluoroscopic image used in interventional treatment, and a doctor who performs a procedure using a catheter selects the fluoroscopic image. The case of referring will be described as an example.

  A doctor who refers to a fluoroscopic image mainly focuses on the catheter when the catheter is included in the region of interest. Here, since the catheter is clearly expressed with sufficient contrast in the first X-ray image, the doctor can sufficiently view the catheter without using the dither processing. Therefore, the region specifying function 109e does not specify the region of interest as a partial region when the region of interest includes a catheter.

  On the other hand, when the region of interest does not include a catheter, the doctor focuses on the body tissue of the subject P, for example. Here, the body tissue in the first X-ray image has a smaller contrast than that of the catheter, and when the first X-ray image is subjected to color reduction by the display color reduction LUT in the monitor, the body tissue has a smaller gradation. This means that the visibility is reduced. Therefore, the region designating function 109e designates the region of interest as a partial region when the region of interest does not include a catheter.

  Although the catheter has been described as an example, the region designating function 109e can determine whether or not to designate the region of interest as a partial region depending on the presence or absence of a linear device other than the catheter. Here, the linear device is a device that is expressed in the first X-ray image with a contrast that can be visually recognized without using dither processing. Including esophageal echocardiography).

  When the region of interest is designated as a partial region, the conversion function 109c converts the stage in the first gradation of each pixel included in the region of interest into a corresponding display pattern, and the image generation function 109b A second X-ray image is generated in which the pixels included in the region of interest of the X-ray image are shown in a display pattern. Here, the second X-ray image may be an image corresponding only to the region of interest, or may be an image corresponding to part or all of the first X-ray image including the region of interest. Further, the second X-ray image may be a display pattern showing each pixel included in the region of interest, or a display pattern for each of the plurality of pixels included in the region of interest. May be.

  That is, when the number of pixels is increased by converting each pixel included in the region of interest into a display pattern, the conversion function 109c may be used to convert a plurality of pixels included in the region of interest. By converting to a display pattern for each pixel, an increase in the number of pixels can be avoided and a visual effect of gradation interpolation by dithering can be obtained.

  For example, when the first gradation is “10 bits” and the second gradation is “8 bits”, the conversion function 109 c includes four pixels included in the “2 × 2” area of the region of interest. Each time, the average value of the pixel values in the first gradation is calculated, and the pixels in the “2 × 2” area are converted into a display pattern corresponding to the calculated average value. Then, the image generation function 109b generates a second X-ray image indicated by a display pattern for each pixel in the “2 × 2” area included in the region of interest. In such a second X-ray image, four pixels in the first X-ray image are used as one display pattern in the second X-ray image, so that the spatial resolution is reduced, but the density resolution is maintained by dithering. Be drunk.

  The conversion function 109c converts each pixel included in the region of interest into a display pattern or converts each pixel included in the region of interest into a display pattern depending on whether spatial resolution or density resolution is prioritized. It is good also as switching whether to do. In addition, when each pixel included in the region of interest is converted into a display pattern, the image generation function 109b supports the second X-ray image only for the region of interest in order to reduce the number of pixels of the second X-ray image. Or an image corresponding to a part of the first X-ray image including the region of interest.

  Next, a case where a part of the area is designated based on the annotation information added to the first X-ray image will be described. Here, the annotation information is, for example, a mark or a comment attached to a lesion site such as a tumor by an engineer or an interpreting doctor who refers to the first X-ray image. Further, for example, the annotation information is a mark or a comment that is detected by a computer-aided diagnosis (CAD) and attached to the first X-ray image as a lesion site.

  For example, when the mark attached to the lesion site is a circle or rectangle surrounding the lesion site, the area designating function 109e designates the area surrounded by the mark as a partial area. Further, for example, the area designating function 109e designates a part of the area based on the position where a mark or a comment is added. For example, the region designating function 109e performs a process of determining that a pixel having a pixel value difference equal to or less than a threshold value from a pixel at a position where a mark or a comment is attached is a pixel included in the lesion site. A region adjacent to the lesion site is calculated by sequentially performing processing on pixels adjacent to the pixel determined to be a pixel included in the region, and the calculated region is designated as a partial region.

  When a partial area is designated based on the annotation information, the conversion function 109c converts the stage in the first gradation of each pixel included in the partial area into a corresponding display pattern, and the image generation function 109b. Generates a second X-ray image in which pixels included in a partial region of the first X-ray image are indicated by a display pattern. Here, the second X-ray image may be an image corresponding to only a partial area in the first X-ray image, or a part of the first X-ray image including the partial area or The image corresponding to all may be sufficient. The second X-ray image may be a display pattern showing each pixel included in a part of the region, or a display pattern for each of a plurality of pixels included in the part of the region. It may be.

  For example, in a conference or a report system (Report System), in order to observe a tumor in the subject P, when an interpretation using a color monitor of “8 bits (256 gradations)” is performed, it is included in some areas. By converting each of the plurality of pixels into a display pattern and giving priority to the density resolution over the spatial resolution, the visibility of the tumor can be improved.

(Second Embodiment)
In the first embodiment described above, the case where the pseudo gradation processing is performed on a specified part of the region has been described. In contrast, in the second embodiment, a case will be described in which pseudo gradation processing is performed on pixels (pixels) that have the same color during color reduction. Note that the X-ray diagnostic apparatus 1 according to the second embodiment has the same configuration as that of the X-ray diagnostic apparatus 1 according to the first embodiment shown in FIG. 1, and includes a conversion function 109c and an image generation function 109b. Processing is partially different. Therefore, points having the same functions as those in the configuration described in the first embodiment are denoted by the same reference numerals as those in FIG.

  First, the conversion function 109c according to the second embodiment searches for a region having the same color when displayed on the display 106 from the first X-ray image generated by the image generation function 109b. For example, the conversion function 109c extracts the color of each pixel of the first X-ray image (the stage in the gradation of the image), and acquires the converted color when the display color reduction LUT is applied. Then, the conversion function 109c extracts a region where the converted colors are the same color. The region extracted here is a region in which pixels having the same color after conversion are continuous and have a predetermined size. For example, the conversion function 109c extracts a region where a predetermined number of pixels of the same color are continuous. Next, the conversion function 109c pseudo-gradates an area that has the same color during color reduction. For example, the conversion function 109c converts the gradation of the pixels included in the extracted region into a display pattern based on the correspondence information.

  Here, the gradation interpolation mode according to the second embodiment will be described with reference to FIG. FIG. 10 is a diagram for explaining the gradation interpolation mode according to the second embodiment. The left figure of FIG. 10 shows the image before a process, and the right figure of FIG. 10 shows the image after a process. For example, the conversion function 109c searches for an area having the same color when the display color reduction LUT is applied to the X-ray image generated by the image generation function 109b, and extracts the area R shown in FIG. Next, the conversion function 109c performs pseudo gradation processing on the pixels included in the extracted region R. Then, the image generation function 109b generates a second X-ray image indicating the region R with a display pattern converted by the pseudo gradation process. As a result, the region R of the image displayed by the display control function 109d becomes an image including the original gradation information as shown in the right diagram of FIG.

  The region having the same color is replaced with the same level in the gradation of the display 106 when gradation conversion is performed in the display color reduction LUT included in the display 106 among the pixels of the first X-ray image. An area corresponding to a pixel to be processed. For example, when an X-ray image that was “10 bits” at the original data stage is displayed on the “8-bit” display 106, the floor at the original data stage as shown in the region R in the left diagram of FIG. 10. In some cases, the pixels in the regions shown in a plurality of stages are replaced with the same stage in the gradation of the display 106 and displayed on the display 106 as the same color. In the following, an area having the same color (for example, an area R shown in the left diagram of FIG. 10) is also referred to as an identical replacement area.

  Details of processing by the conversion function 109c according to the second embodiment will be described below with reference to FIG. FIG. 11 is a diagram for explaining the gradation interpolation mode according to the second embodiment. In FIG. 11, the X-ray image generated by the image generation function 109b is shown in units of pixels. For example, as shown in the upper diagram of FIG. 11, the conversion function 109c sequentially extracts “2 × 2” areas from the end of the X-ray image, and all the pixels included in the extracted areas are displayed on the floor of the display 106. When the same color is obtained by reducing the color to “8 bits”, which is the key, the pixels included in the extracted area are specified as the pixels that are the same color when the color is reduced. In the following, the color of each pixel is described by a numerical value in binary number.

  For example, as shown in the lower diagram of FIG. 11, the colors of four pixels included in the “2 × 2” area are “0101”, “0100”, “0100” at the original data stage of “10 bits”, respectively. ”And“ 0111 ”. Here, when simple color reduction is performed by the display color reduction LUT in order to output the original data of “10 bits” to the display 106 of “8 bits”, as shown in the lower diagram of FIG. As a result of the replacement, the conversion function 109c identifies the four pixels shown in the lower diagram of FIG. 11 as pixels that have the same color when color is reduced.

  Next, the conversion function 109c calculates the average value of the specified four pixels at “10 bits” at the stage of the original data of “10 bits”. For example, as shown in FIG. 11, the conversion function 109c calculates the average value “((0101 + 0100 + 0100 + 0111) / 4) = 0101” of the four pixels. Next, the conversion function 109c replaces the calculated average value “0101” with the corresponding display pattern of “8 bits”. For example, as shown in the lower diagram of FIG. 11, the conversion function 109c displays the average value “0101” as the display pattern in which the colors of the four pixels are “02”, “01”, “01”, and “01”, respectively. Replace with. That is, as shown in the lower diagram of FIG. 11, the conversion function 109 c executes pseudo gradation processing, for example, by combining four pixels included in the “2 × 2” area in the first X-ray image. . Therefore, the conversion function 109c can perform pseudo gradation processing without changing the matrix (number of pixels) from the original image data.

  That is, the conversion function 109c divides the pixels included in the same replacement area into a plurality of pixel groups based on the correspondence information, and divides the plurality of pixels included in the pixel group by the pixel group. Replace with the display pattern corresponding to the key step. For example, the conversion function 109c first divides the pixels included in the area shown in the upper diagram of FIG. 11 into a plurality of pixel groups for each “4 pixels” that is the number of pixels in the display pattern. Next, the conversion function 109c converts the divided “4 pixels” into a display pattern corresponding to the gradation level indicated by “4 pixels” (for example, “0101” which is an average value of the colors of “4 pixels”). Replace with. Then, the image generation function 109b generates a second X-ray image indicating the same replacement area in the first X-ray image with the display pattern converted by the conversion function 109c.

  Next, an example of a processing procedure performed by the X-ray diagnostic apparatus 1 will be described with reference to FIG. FIG. 12 is a flowchart for explaining a series of processing steps of the X-ray diagnostic apparatus 1 according to the second embodiment. Step S201, step S202, and step S210 are steps corresponding to the control function 109a. Step S203 is a step corresponding to the image generation function 109b. Steps S205 and S206 are steps corresponding to the conversion function 109c and the image generation function 109b. Step S204, step S207, step S208, and step S209 are steps corresponding to the display control function 109d.

  First, the processing circuit 109 determines whether or not an inspection start request has been received from the operator (step S201). When the inspection start request is not accepted (No at Step S201), the processing circuit 109 enters a standby state. On the other hand, when the examination start request is received (Yes at Step S201), the processing circuit 109 performs imaging on the subject P (Step S202), and generates an X-ray image based on the signal collected from the subject P (Step S202). Step S203).

  Next, the processing circuit 109 displays the entire generated X-ray image on the display 106 (step S204). In addition, the processing circuit 109 searches the entire generated X-ray image for pixels that have the same color during color reduction (step S205), and executes pseudo gradation processing for the region that has the same color during color reduction on the X-ray image. Then, a second X-ray image is generated (step S206). Further, the processing circuit 109 causes the display 106 to display the second X-ray image that has been subjected to the pseudo gradation processing (step S207).

  Here, the processing circuit 109 determines whether or not a display mode switching operation has been received (step S208). When a display mode switching operation is received (Yes at step S208), the processing circuit 109 performs an X-ray image that has been subjected to pseudo gradation processing or an X-ray image that has not been subjected to pseudo gradation processing, depending on the content of the operation. Is displayed on the display 106 (step S209). On the other hand, when the display mode switching operation is not accepted (No at Step S208), the processing circuit 109 determines whether an end command is accepted from the operator (Step S210). When the end command is not accepted (No at Step S210), the processing circuit 109 proceeds to Step S208 again. On the other hand, when an end command is received (Yes at step S210), the processing circuit 109 ends the process.

  As described above, according to the second embodiment, the image generation function 109b generates a first X-ray image in which each pixel is indicated by the first gradation based on the X-ray transmitted through the subject P. Generate. In addition, the conversion function 109c associates each stage of the first gradation with a display pattern of a plurality of pixels in the display 106 that displays an image with a second gradation smaller than the first gradation. Based on the information, the pixels included in the same replacement region that are replaced at the same stage in the second gradation in the first X-ray image are divided into a plurality of pixel groups according to the number of pixels in the display pattern. Are converted into a display pattern corresponding to the stage in the first gradation indicated by the pixel group. In addition, the image generation function 109b generates a second X-ray image in which the same replacement area in the first X-ray image is indicated by the display pattern converted by the conversion function 109c. Further, the display control function 109d causes the display 106 to display the second X-ray image. Therefore, the X-ray diagnostic apparatus 1 according to the second embodiment presents information that is lost by simple color reduction on the display 106 to the operator, and can improve the accuracy of the examination using the X-ray image. it can.

  In addition, as described above, the conversion function 109c according to the second embodiment searches for pixels having the same color by color reduction on the display 106, and performs pseudo gradation processing on the region having the same color in the entire X-ray image. Run. Therefore, the X-ray diagnostic apparatus 1 according to the second embodiment does not use pseudo-levels for areas that do not become the same color by the display color reduction LUT in the display 106 (for example, areas other than the area R in the left diagram of FIG. 10). Conventional display and comparison using original image data can be performed without performing tone processing.

  Further, the conversion function 109c according to the second embodiment executes the pseudo gradation process while maintaining the number of pixels (matrix size) of the X-ray image. Therefore, the X-ray diagnostic apparatus 1 according to the second embodiment is difficult to display on the display 106 when the number of pixels of the X-ray image increases in the relationship between the number of pixels of the display 106 and the number of pixels of the X-ray image. Even in this case, the X-ray image subjected to the pseudo gradation process can be presented to the operator, and the inspection accuracy can be improved.

  In the first and second embodiments described above, the case where the pseudo gradation process is performed on the first X-ray image has been described. In contrast, in the third embodiment, a plurality of correction images are generated based on a plurality of first X-ray images generated in time series, and pseudo gradation processing is performed on the generated correction images. Will be described. The X-ray diagnostic apparatus 1 according to the third embodiment has a feature point position detection function described later, compared to the X-ray diagnostic apparatus 1 according to the first embodiment shown in FIG. And a correction image generation function. In addition, the X-ray diagnostic apparatus 1 according to the third embodiment is compared with the X-ray diagnostic apparatus 1 according to the first embodiment shown in FIG. Part of the processing at 109e is different. Points having the same functions as those of the configuration described in the first embodiment are denoted by the same reference numerals as those in FIG. 1 and description thereof is omitted.

  The feature point position detection function in the third embodiment is an example of a feature point position detection unit in the claims. The corrected image generation function in the third embodiment is an example of a corrected image generation unit in the claims.

  First, the feature point position detection function in the processing circuit 109 detects the position of the feature point in each of the plurality of first X-ray images generated in time series by the image generation function 109b. Here, the feature point is, for example, a stent marker included in the first X-ray image. For example, the feature point position detection function calculates the coordinates on the image where the stent marker is located for each of the plurality of first X-ray images. Next, the corrected image generation function generates a plurality of corrected images in which the positions of the feature points in the image are substantially the same based on the plurality of first X-ray images.

  For example, the corrected image generation function generates a plurality of corrected images by correcting the plurality of first X-ray images so that the coordinates of the stent marker coincide with each other. For example, the corrected image generation function uses the coordinates of the stent marker in an arbitrary X-ray image (for example, the first X-ray image in time series) among the plurality of first X-ray images as reference coordinates, Image movement processing such as parallel movement and rotational movement, affine transformation, etc. with respect to each of the plurality of first X-ray images so that the coordinates of the stent marker in each of the first X-ray images coincide with the reference coordinates. A plurality of corrected images are generated by performing the image deformation process.

  Alternatively, the corrected image generation function performs alignment processing on a plurality of X-ray images included in the plurality of first X-ray images based on the positions of feature points in the image, thereby adding a plurality of corrected images. Is generated. In other words, the corrected image generation function generates a plurality of corrected images by applying a recursive filter to the plurality of first X-ray images. The recursive filter is an example of a high frequency noise reduction filter.

  For example, the corrected image generation function first corrects the plurality of first X-ray images so that the coordinates of the stent markers in the image coincide with each other. Next, the corrected image generation function generates a plurality of corrected images by performing processing such as addition averaging on a plurality of X-ray images among the plurality of corrected first X-ray images. For example, when the plurality of first X-ray images are three X-ray images of “X-ray image at time T1,” “X-ray image at time T2,” and “X-ray image at time T3.” The function is a correction image obtained by adding the “X-ray image at time T1” and the “X-ray image at time T2”, and the correction image obtained by adding “X-ray image at time T2” and “X-ray image at time T3”. Generate an image.

  Note that the number of X-ray images used to generate one corrected image among the plurality of first X-ray images is arbitrary, and may be set by the operator or may be a preset value. Alternatively, the corrected image generation function may be set based on the magnitude of the change in the coordinates of the stent marker between the first X-ray images before correction. In addition, when the corrected image is generated by adding the first X-ray image, the pixel values of the pixels constituting the first X-ray image may be weighted. For example, the corrected image generation function performs an addition process so that the weights of the plurality of first X-ray images collected in time series increase as the time is closer.

  Next, the area designation function 109e designates some areas in the plurality of corrected images. Here, the area specifying function 109e may specify a partial area for each of the plurality of corrected images, or may specify one partial area for the plurality of corrected images. For example, since the coordinates of the stent marker in the plurality of correction images match each other, the area designating function 109e has an area based on the coordinates of the stent marker (for example, centered on the coordinates of the stent marker and has a predetermined size). And a region having a shape, etc.) can be specified, so that some regions in a plurality of corrected images can be specified.

  Next, the conversion function 109c associates each stage of the first gradation with a display pattern of a plurality of pixels in the display 106 that displays an image with a second gradation smaller than the first gradation. Based on the correspondence information, the stage in the first gradation of each pixel included in a partial region in the plurality of corrected images is converted into a corresponding display pattern. Note that in the third embodiment, the gradation indicated by each pixel in the corrected image generated by the corrected image generation function is referred to as a first gradation. The gradation indicated by each pixel of the first X-ray image may be the same as the first gradation indicated by each pixel of the correction image.

  Then, the image generation function 109b generates a second X-ray image in which a plurality of pixels included in a partial area of the plurality of corrected images are indicated by a display pattern converted by the conversion function 109c. In other words, the image generation function 109b displays, in a display pattern, pixels in a partial area of a plurality of corrected images generated by correcting the plurality of first X-ray images so that the coordinates of the stent marker coincide with each other. A plurality of X-ray images generated by aligning the second X-ray image or a plurality of X-ray images included in the plurality of first X-ray images based on the positions of the feature points in the image and adding them. A second X-ray image in which pixels in a partial area of the corrected image are shown in a display pattern is generated. Further, the display control function 109d causes the display 106 to display the second X-ray image.

  Up to now, as an example of generating a second X-ray image by applying a recursive filter and dither processing to the first X-ray image, a plurality of images aligned based on the position of the stent marker have been added. Although the case where the correction image is generated and the dither process is performed on a part of the generated correction image has been described, the embodiment is not limited thereto. For example, for a plurality of first X-ray images, a correction image is generated by performing alignment based on the position of the stent marker, and after a dither process is performed on a partial region of the generated correction image, the dither process is performed. The correction image may be added.

  When the recursive filter is applied, the background portion other than the stent marker in the image is subjected to addition processing in a shifted state, and thus the visibility of the background portion may be reduced. In particular, the more images to be added, the lower the visibility of the background portion. In the recursive filter, dithering is performed after applying the recursive filter to the plurality of first X-ray images, or by applying the recursive filter after applying the dither processing to the plurality of first X-ray images. The number of images to be added can be reduced. For example, in the case where staircase noise shown in FIG. 6 occurs, high-frequency noise may become noticeable due to color reduction at the display stage, but information on gradations lost due to color reduction is displayed on the display 106 by dither processing. By expressing, high frequency noise can be reduced. Therefore, since high frequency noise can be sufficiently removed even if the number of images to be added is reduced, the number of images to be added by the recursive filter can be reduced, and the visibility of the background portion can be improved.

  In the first to third embodiments described above, the case has been described in which the display 106 is a color monitor that displays an image with 8 bits (256 tones) for each of the RGB colors. However, the embodiment is not limited thereto. Is not to be done. For example, the display 106 may be a monochrome monitor, and the number of gradations is not limited to 8 bits.

  In the first to third embodiments described above, the display control function 109d causes the display 106 to display the second X-ray image after the image generation function 109b generates the second X-ray image. Although described, the embodiment is not limited to this. For example, after the image generation function 109b generates the second X-ray image, the second X-ray image may be stored in the storage circuit 108 without displaying the second X-ray image. . The second X-ray image stored in the storage circuit 108 is read by, for example, the X-ray diagnostic apparatus 1 or another apparatus and displayed on the display 106 or another display.

  In the above-described first to third embodiments, the case where the processing circuit 109 performs image processing on the first X-ray image generated by the image generation function 109b has been described. It is not limited. For example, the processing circuit 109 acquires a first X-ray image from another X-ray diagnostic apparatus, a PACS (Picture Archiving and Communication Systems) database, an electronic medical record system database, or the like, and acquires the acquired first X-ray. It may be a case where image processing is executed on an image.

  In other words, the processing circuit 109 has an acquisition function for acquiring the first X-ray image. The image generation function 109 b that generates the first X-ray image is an example of an acquisition function in the processing circuit 109. The acquisition function is an example of an acquisition unit in the claims. The processing circuit 109 applies an image to the first X-ray image generated based on the X-ray transmitted through the subject, or the first X-ray image acquired from another X-ray diagnostic apparatus or various databases. Processing can be executed.

  The image processing method described above may be performed by an image processing apparatus installed independently of the X-ray diagnostic apparatus. For example, the image processing method having the same function as the processing circuit 109 shown in FIG. 1 uses the image data acquired from the X-ray diagnostic apparatus or the PACS database or the database of the electronic medical record system as described above. May be performed.

  For example, an image processing apparatus independent of the X-ray diagnostic apparatus acquires a first X-ray image from another X-ray diagnostic apparatus or a database such as PACS, and performs dither processing on the acquired first X-ray image. By applying, the second X-ray image is generated, and the generated second X-ray image is displayed on an arbitrary display. For example, an image processing apparatus independent of the X-ray diagnostic apparatus is installed in a room where a conference is held or is brought in and connected to a display used for displaying an image at the conference. Then, the image processing apparatus determines whether dither processing is necessary according to the gradation that can be displayed by the connected display. For example, when the acquired first X-ray image is “10 bits” and the connected display is an “8 bit” color monitor, the image processing apparatus determines that dither processing is necessary, and A second X-ray image subjected to dither processing is generated and displayed on the display.

  The image processing apparatus described above may be a so-called video card (also referred to as a graphic board). For example, a video card is added to a PC with a display. In such a case, the video card performs dither processing on the first X-ray image acquired from the PC, generates a second X-ray image, and outputs it to the display.

  In the case where the display 106 is a display screen of a portable terminal such as a tablet, the above-described image processing method may be performed in a device separate from the portable terminal, or the above-mentioned in the portable terminal. An image processing method may be performed.

  Each component of each device according to the first to third embodiments is functionally conceptual and does not necessarily need to be physically configured as illustrated. In other words, the specific form of distribution / integration of each device is not limited to that shown in the figure, and all or a part thereof may be functionally or physically distributed or arbitrarily distributed in arbitrary units according to various loads or usage conditions. Can be integrated and configured. Further, all or a part of each processing function performed in each device may be realized by a CPU and a program that is analyzed and executed by the CPU, or may be realized as hardware by wired logic.

  The image processing methods described in the first to third embodiments can be realized by executing a prepared image processing program on a computer such as a personal computer or a workstation. This image processing program can be distributed via a network such as the Internet. The image processing program can also be executed by being recorded on a computer-readable recording medium such as a hard disk, a flexible disk (FD), a CD-ROM, an MO, or a DVD, and being read from the recording medium by the computer. .

  According to at least one embodiment described above, it is possible to improve the accuracy of inspection using an X-ray image.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 X-ray diagnostic apparatus 109 Processing circuit 109a Control function 109b Image generation function 109c Conversion function 109d Display control function 109e Area designation function 109f Reception function 109g Area of interest setting function

Claims (20)

An acquisition unit for acquiring a first image in which each pixel is indicated by a first gradation;
An area designating unit for designating a partial area in the first image;
Based on correspondence information that associates each stage of the first gradation with a display pattern of a plurality of pixels in a display unit that displays an image with a second gradation smaller than the first gradation, A conversion unit that converts the stage in the first gradation of each pixel included in the partial area in the first image into the corresponding display pattern;
An image processing apparatus comprising: an image generation unit configured to generate a second image indicated by the display pattern obtained by converting a plurality of pixels included in the partial region of the first image by the conversion unit. The image processing apparatus further includes a receiving unit that replaces each step of the first gradation of each pixel in the first image with a corresponding step in the second gradation and receives an operation on the image displayed on the display unit. ,
The image processing apparatus according to claim 1, wherein the region specifying unit specifies the partial region based on an operation received by the receiving unit. A region of interest setting unit for setting a region of interest in the first image;
The image processing apparatus according to claim 1, wherein the region designating unit determines whether to designate the region of interest as the partial region according to information on a device included in the region of interest. The device is a stent;
The image processing device according to claim 3, wherein the region designating unit determines whether or not to designate the region of interest as the partial region based on an image of the stent in the region of interest.   The region designating unit obtains a roughness of the stent mesh from the stent image in the region of interest, and determines whether to designate the region of interest as the partial region based on the roughness. The image processing apparatus according to claim 4. An input unit that receives an input operation from an operator;
The device is a stent;
The input unit accepts an input operation of the information of the stent,
The image processing apparatus according to claim 3, wherein the region designating unit determines whether or not to designate the region of interest as the partial region based on the input information on the stent.   The image processing device according to claim 3, wherein the region-of-interest setting unit sets the region of interest based on a feature point included in the first image. A region of interest setting unit for setting a region of interest in the first image;
The image processing apparatus according to claim 1, wherein the region designating unit determines whether or not to designate the region of interest as the partial region according to presence or absence of a device in the region of interest. The device is a linear device;
The image processing apparatus according to claim 8, wherein the region designating unit designates the region of interest as the partial region when the region of interest does not include the linear device.   The image processing apparatus according to claim 1, wherein the region designating unit designates the partial region based on annotation information added to the first image.   The image processing apparatus according to claim 10, wherein the annotation information is information indicating a mass or information detected by computer-aided diagnosis. An acquisition unit for acquiring a first image in which each pixel is indicated by a first gradation;
Based on correspondence information that associates each stage of the first gradation with a display pattern of a plurality of pixels in a display unit that displays an image with a second gradation smaller than the first gradation, Of the first image, pixels included in the same replacement region that are replaced at the same stage in the second gradation are divided into a plurality of pixel groups according to the number of pixels in the display pattern, and are included in the pixel group. A converter that converts a plurality of pixels into a display pattern corresponding to a stage in the first gradation indicated by the pixel group;
An image processing apparatus comprising: an image generation unit configured to generate a second image in which the same replacement area in the first image is represented by the display pattern converted by the conversion unit.   13. The conversion unit according to claim 12, wherein the conversion unit sets an average value of a stage in the first gradation of each of a plurality of pixels included in the pixel group as a stage in the first gradation indicated by the pixel group. The image processing apparatus described.   A third image obtained by replacing each step of the first gradation of each pixel in the first image with a corresponding step in the second gradation in response to a switching operation of an image display mode; The image processing apparatus according to claim 1, further comprising a display control unit configured to switch a second image and display the second image on the display unit. An acquisition unit for acquiring a plurality of first images generated in time series;
A feature point position detection unit for detecting a position of a feature point in each of the plurality of first images;
Based on the plurality of first images, a plurality of correction images in which the positions of the feature points in the image are substantially the same, each pixel having a plurality of correction images indicated by a first gradation A corrected image generation unit to generate,
An area designating unit for designating a partial area in the plurality of corrected images;
Based on correspondence information that associates each stage of the first gradation with a display pattern of a plurality of pixels in a display unit that displays an image with a second gradation smaller than the first gradation, A conversion unit that converts a stage in the first gradation of each pixel included in the partial area in the plurality of corrected images into the corresponding display pattern;
An image processing apparatus comprising: an image generation unit configured to generate a second image indicated by the display pattern obtained by converting a plurality of pixels included in the partial area of the plurality of corrected images by the conversion unit.   The corrected image generation unit generates the plurality of corrected images by performing alignment processing on the plurality of images included in the plurality of first images based on the positions of the feature points in the image and adding the processed images. The image processing apparatus according to claim 15.   The image processing apparatus according to any one of claims 1 to 16, wherein the first gradation and the second gradation are gradations for lightness of a hue expressed in an image.   The image processing apparatus according to claim 1, wherein the display unit is a display screen of a portable terminal. An acquisition step in which each pixel acquires a first image indicated by a first gradation;
A designating step of designating a partial area in the first image;
Based on correspondence information that associates each stage of the first gradation with a display pattern of a plurality of pixels in a display unit that displays an image with a second gradation smaller than the first gradation, A conversion step of converting a stage in the first gradation of each pixel included in the partial area in the first image into the corresponding display pattern;
An image generation method comprising: an image generation step of generating a second image indicated by the display pattern obtained by converting the plurality of pixels included in the partial region of the first image in the conversion step. An acquisition step in which each pixel acquires a first image indicated by a first gradation;
Based on correspondence information that associates each stage of the first gradation with a display pattern of a plurality of pixels in a display unit that displays an image with a second gradation smaller than the first gradation, Of the first image, pixels included in the same replacement region that are replaced at the same stage in the second gradation are divided into a plurality of pixel groups according to the number of pixels in the display pattern, and are included in the pixel group. A conversion step of converting a plurality of pixels into a display pattern corresponding to the stage in the first gradation indicated by the pixel group;
An image processing method comprising: an image generation step of generating a second image indicating the same replacement area in the first image by the display pattern converted in the conversion step.