JP5513749B2 - X-ray imaging apparatus and X-ray image processing method - Google Patents

Description

  The present invention relates to an X-ray imaging apparatus and an X-ray image processing method having an auto window function for appropriately adjusting and displaying the density and contrast of an X-ray image.

  Conventionally, X-ray imaging apparatuses and X-ray CT apparatuses have been widely used as medical image diagnostic apparatuses, and various types of medical image data can be generated by using computer technology. Further, in an X-ray imaging apparatus, for example, a digital general imaging apparatus or a digital mammography apparatus, gradation processing is performed in order to adjust density and contrast to an appropriate state when observing an image. The gradation processing can be manually adjusted by a user (doctor, engineer, etc.) operating a mouse or the like.

  In addition, since manual adjustment for each image takes time and effort, there is an automatic window function that automatically analyzes a pixel value histogram of an image at the time of image collection and automatically performs gradation processing. Patent Document 1 discloses an example of an X-ray diagnostic apparatus having an auto window function.

  On the other hand, in the X-ray imaging apparatus, the captured image is displayed on the display unit and the imaging result is observed, but if the imaging is not performed well and it is determined that the imaging has failed, the imaging is performed again. For this reason, the X-ray imaging apparatus is provided with a “re-imaging” button, and when re-imaging is performed, the re-imaging is started by operating the “re-imaging” button.

  For example, a “re-photograph” button is displayed on the display screen, and re-photographing starts by clicking this “re-photograph” button. When re-photographing is started, the photographed failed image is deleted or moved to the deleted image folder and is not used for observation. In addition, since auto window processing is not perfect, an image whose density is shifted may be displayed in rare cases because histogram analysis or gradation calculation processing is omitted.

  However, even if the image density is deviated, there is no problem in the image data, and the gradation processing is often deviated. In this case, if the gradation is manually adjusted, an image sufficient for diagnosis can be obtained, but there are users (doctors, engineers, etc.) who determine that an image whose density is shifted is unsuccessful. For example, if the user has little experience in image processing, it is easy to determine that the image is a failed image even if the gradation is adjusted manually. For this reason, the “re-photograph” button may be pressed without manually adjusting the gradation of the image to start re-photographing, which increases unnecessary exposure.

JP 2002-102212 A

  In a conventional X-ray imaging apparatus, a captured image is displayed on a display unit, and an imaging result is observed. If imaging is not performed well and it is determined that imaging has failed, re-imaging is performed, but there is no problem with the image data. In many cases, the gradation processing is merely shifted. In addition, a user with little experience may determine that the image is a failed image and start re-shooting even if the gray level is adjusted manually. For this reason, useless exposure was increased.

  In view of such circumstances, the present invention prevents unnecessary re-shooting by displaying an image in which the window level of the image to be deleted is shifted in several stages before starting re-shooting. An object is to provide a radiographic apparatus and an X-ray image processing method.

The X-ray imaging apparatus according to the first aspect of the present invention is a data collection unit that collects images captured by an X-ray imaging unit, an operation unit that instructs execution of imaging and re-imaging by the X-ray imaging unit, First window calculation means for analyzing a captured image collected by the data collection unit to calculate a first window level, and a plurality of different second window levels with the window level shifted stepwise. Two window calculation means, a first image obtained by gradation processing the captured image based on the first window level, and a gradation process performed on the captured image based on the second window level. A gradation processing unit that generates a plurality of second images whose density changes sequentially, a display unit that displays an output image from the gradation processing unit, and the first image displayed on the display unit. And To, when an instruction for the re-photographed by the operation means is characterized by comprising a display control means for displaying a second image of the plurality.

The X-ray image processing method of the present invention according to claim 8 collects images captured by an X-ray imaging unit, analyzes the collected captured images, calculates a first window level, and calculates the first window level. When a first image obtained by performing gradation processing on the captured image based on the window level is displayed on the display unit, and when the redisplay is instructed by the operation means while the first display image is displayed, , Gradation processing is performed on the captured image based on a plurality of different second window levels whose window levels are shifted in stages, and a plurality of second images whose density has been sequentially changed are displayed on the display unit, If there is an image suitable for diagnosis in the second image, it can be selected, and if there is no image applicable to diagnosis, the second image is shifted to the re-imaging mode according to the instruction.

  According to the present invention, even when an auto window process is shifted and an image with an inappropriate density or the like is displayed, an image with the window level shifted in several stages is displayed, so that it can be used for diagnosis. Whether or not there is an image can be confirmed, and unnecessary exposure to the patient can be reduced.

1 is an overall configuration diagram of an X-ray imaging apparatus according to an embodiment of the present invention. The block diagram centering on the image data processing part which concerns on the same embodiment. Explanatory drawing which shows the example of a display of the image after the gradation process which concerns on the same embodiment. Explanatory drawing which shows the other example of a display of the image after the gradation process which concerns on the same embodiment. Explanatory drawing explaining the shift operation | movement of the window which concerns on the same embodiment. 6 is a flowchart showing image display processing according to the embodiment. Explanatory drawing explaining the shift operation | movement of the window which concerns on other embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing the overall configuration of the X-ray imaging apparatus of the present invention. In FIG. 1, the X-ray imaging apparatus 10 includes an X-ray imaging unit 11 and a computer system 20. The X-ray imaging unit 11 two-dimensionally detects the X-ray irradiation unit including the X-ray tube 12 and the X-ray diaphragm 13 and the X-ray transmitted through the subject P, and X-ray projection data based on the detection result. The X-ray detector 14 is generated.

  The X-ray tube 12 is a vacuum tube that generates X-rays, and accelerates electrons emitted from a cathode (filament) by a high voltage to collide with a tungsten anode to generate X-rays. The X-ray diaphragm 13 is provided for the purpose of reducing the exposure dose to the subject P and improving the image quality by irradiating only the region to be imaged with X-rays. The X-ray detector 14 detects an X-ray image by X-rays that has passed through the opening formed by the X-ray diaphragm 13 and has passed through the region of interest of the subject P.

  As the X-ray detector 14, an FPD (Flat Panel Detector) capable of digital processing is used and provided on the imaging table 15 on which the subject P is placed. The X-ray detector 14 converts X-rays transmitted through the region of interest of the subject into electric charges and accumulates them, and minute detection elements that detect X-rays are arranged two-dimensionally in the column direction and the line direction. Configured.

  Each detection element senses X-rays and generates a charge according to the incident X-ray dose, a charge storage capacitor that stores the charge generated in the photoelectric film, and a predetermined charge stored in the charge storage capacitor TFT (thin film transistor) that is read out at the timing shown in FIG. The X-ray image detection method includes a method of converting X-rays into light and then converting them into charges in addition to a method of directly converting X-rays into charges.

  The electric charge read from the X-ray detector 14 is converted into a voltage, and further converted into a digital signal by an A / D converter and output. A digital signal from the X-ray detector 14 is read out via the data acquisition unit 16 and transmits digital projection data (X-ray image data) to the bus line 21 of the computer system 20. Note that a high voltage generator 17 is connected to the X-ray tube 12, and a tube voltage and a tube current are supplied from the high voltage generator 17 to the X-ray tube 12.

  The computer system 20 includes a system control unit 22, an operation unit 23, a display unit 24, an image data processing unit 25, and a data storage unit 26 connected to the bus line 21. The system control unit 22 includes a CPU, a ROM, and the like, and comprehensively controls each unit of the X-ray imaging apparatus 10.

  The operation unit 23 is used by a user such as a doctor to input various commands. The operation unit 23 is an interactive device including an input device such as an operation console, a keyboard, a trackball, a joystick, a mouse, and a mouse wheel, a display panel, and various switches. Interface.

  The operation unit 23 inputs subject information and a control signal for the X-ray diaphragm 13. In addition, the position of the imaging table 15, the X-ray irradiation conditions including the tube voltage and tube current of the X-ray tube 12 are set. The display unit 24 displays image data and the like.

  The image data processing unit 25 generates diagnostic image data based on the X-ray image data from the data collection unit 16. The data storage unit 26 stores the generated image data. Processing of image data in the image data processing unit 25, storage of image data in the data storage unit 26, and reading of image data are performed under the control of the system control unit 22.

  The system control unit 22 includes a high voltage control unit 27 that controls the high voltage generation unit 17, an aperture control unit 28 that controls the X-ray diaphragm 13, and a control unit that controls the position of the imaging table 15 (see FIG. The high voltage control unit 27, the aperture control unit 28, and the like are controlled by the system control unit 22.

  The high voltage generation unit 17 generates a voltage to be applied between the anode and the cathode in order to accelerate the thermoelectrons generated from the cathode of the X-ray tube 12, and the high voltage control unit 27 includes the operation unit 23. The tube current / tube voltage of the high voltage generator 17, the irradiation time, the irradiation repetition period, and the like are controlled based on the X-ray irradiation conditions input from.

  Next, the image data processing unit 25 which is a characteristic part of the present invention will be described with reference to FIG. FIG. 2 is a block diagram showing the X-ray imaging apparatus 10 of the present invention centering on the image data processing unit 25.

  The image data processing unit 25 includes a histogram creation unit 31, an image processing unit 32, an auto window calculation unit 33, a shift window calculation unit 34, a gradation processing unit 35, and a display interface (I / F) 36. A display interface (I / F) 36 is connected to the display unit 24, and an operation unit 23 is connected to the display I / F 36. The display I / F 36 operates under the control of the system control unit 22 and displays various images on the display unit 24 according to the operation of the operation unit 23, and constitutes a display control unit.

  The histogram creation unit 31 and the image processing unit 32 are connected to the bus line 21, and the auto window calculation unit 33 and the shift window calculation unit 34 are connected to the gradation processing unit 35. The gradation processing unit 35 is connected to the display I / F 36.

  The histogram creating unit 31 creates a histogram of pixel values of the X-ray image data collected by the data collecting unit 16, analyzes the shape of the histogram, statistics, etc., and identifies the direct line part, human body part, and diaphragm part. . The direct line portion represents a component in which the X-ray from the X-ray tube 12 is directly incident on the X-ray detector 14 without passing through the subject P, and the stop portion has the X-ray hitting the X-ray stop 13. Represents the possible shadow component.

  The image processing unit 32 performs image processing other than gradation processing such as frequency enhancement, noise reduction, and dynamic range compression of collected X-ray image data. The auto window calculation unit 33 calculates a window suitable for the human body part when displaying the image of the human body part identified by the histogram creation unit 31, and sets the standard window width WW so that the density and contrast of the image are appropriate. A standard window level (first window level) WL is calculated.

  The shift window calculation unit 34 is a block for displaying an image with a fixed window width and shifted window levels by several stages when a “re-photograph” button (described later) representing re-photographing is pressed. The window width to be applied to the display image and several shift window levels (a plurality of different second window levels) are calculated.

  The gradation processing unit 35 performs gradation processing on the image data input from the image processing unit 32 using the window values (window width and window level) calculated by the auto window calculation unit 33 or the shift window calculation unit 34.

  The operation unit 23 includes an operation console, a keyboard, a mouse, and the like, and performs various instructions such as operation of a “re-photograph” button displayed on the display unit 24, image selection, display, processing change, and transfer. These operations are input to the gradation processing unit 35 and the shift window calculation unit 34 by the display I / F 36 and reflected on the image.

  Next, the operation of the image data processing unit 25 will be described with reference to FIGS. FIG. 3A shows a display screen when the image data subjected to gradation processing by the gradation processing unit 35 is displayed on the display unit 24. At this time, gradation processing is performed based on the calculation result of the auto window calculation unit 31, and the density and contrast are adjusted. However, since auto window processing is not perfect, histogram analysis and gradation calculation processing are rarely performed, and an image with a shifted density may be displayed. FIG. 3A shows an example of an image whose density is shifted (abnormally high density).

  In this case, depending on the user, it may be determined that it cannot be used for diagnosis as it is. In other words, due to circumstances such as shortly after the X-ray imaging apparatus has been digitized, for example, a user who is accustomed to filming with a film apparatus has a film sensation. It is easy to judge. For this reason, the “re-photograph” button 41 is pushed to re-photograph. When the “re-imaging” button 41 is pressed, the X-ray imaging apparatus 10 deletes a captured image or moves to a deleted image folder and shifts to a re-imaging mode.

  However, even if the image density is deviated, there is no problem in the image data, and the gradation processing is often deviated. In this case, if the gradation is adjusted manually, an image sufficient for diagnosis can be obtained. However, inexperienced users sometimes re-photograph without being aware of it.

  Therefore, the shift window calculation unit 34 calculates a shift window that shifts the window level in several steps around a standard window width (WW) and window level (WL) registered in advance in the inspection protocol. . When the “re-photograph” button 41 is pressed, the gradation processing unit 35 executes gradation processing based on the shift window level based on the calculation result. Here, the window level shift amount is also registered in the inspection protocol in advance. As a result, a series of images in which the contrast is constant and the density sequentially changes can be formed.

  The gradation-processed image data is supplied to the display unit 24 via the display I / F 36. As a result, as shown in FIG. 3B, the display unit 24 displays a series of images whose density has been sequentially changed as thumbnail images. Therefore, the user can confirm the presence or absence of candidate images that can be used for diagnosis by observing the thumbnail images.

  That is, the thumbnail image is a message image that notifies the user that there is an image that can be used for diagnosis by adjusting the gradation. It is also desirable to display a message 42 such as “Please select an image” on the screen. If the user selects an image suitable for diagnosis from a plurality of candidate images, the selected image is enlarged and displayed as shown in FIG. In this example, the case where the image enclosed with the dotted line of FIG.3 (b) is selected is shown.

  An “OK” button 43 is displayed on the screen of FIG. 3C, and the selected image is selected by pressing the “OK” button 43 and used for diagnosis. In addition, re-shooting is stopped. Further, the user may press the “OK” button 43 after finely adjusting the gradation as necessary. Fine adjustment of the gradation can be performed by operating the operation unit 23. A “return” button (not shown) may be provided on the screen of FIG. 3C to return to the thumbnail image display screen of FIG. Thereby, it is possible to select another candidate image after confirming it again.

  With the above process, even a user who determines that the image data is normal but the image of which the density is shifted is determined to have failed to be photographed and re-photographs can be prevented from being deleted unnecessarily. If it is determined that there is a cause different from gradation processing, such as inappropriate X-ray irradiation conditions or a patient moving, and that an image suitable for diagnosis cannot be obtained even if the window level is shifted. Then, the “re-photograph” button 41 is pressed to take another picture.

  Note that when displaying thumbnail images as shown in FIG. 3B, there is a limit to the number of images that can be displayed on one screen, so it is preferable to scroll a plurality of images and switch the displayed images sequentially. .

  Also, as shown in FIG. 4, images with shifted windows are switched at predetermined time intervals and sequentially displayed one by one, and if there is an image suitable for diagnosis, an “OK” button 43 is selected. It may be.

  FIG. 5 is an explanatory diagram for explaining the window shift operation. In FIG. 5, the horizontal axis indicates the input value before the gradation processing, that is, the data input value from the image processing unit 32, and the vertical axis indicates the output value after the gradation processing. If the standard window width and window level (thick line 50) registered in advance in the inspection protocol are the center, the window width is constant, and the window level is shifted stepwise in the right or left direction in the figure, the output The value changes sequentially.

  If the window level shift amount is also registered in the inspection protocol in advance, a window shifted in several steps as shown in FIG. 5 is prepared. Therefore, if the captured image data is subjected to gradation processing in each window, a candidate image having a constant contrast and a stepwise change in density can be obtained.

  The above operation will be described with reference to the flowchart of FIG. The process of FIG. 6 is performed under the control of the system control unit 22. In step S1, a patient is selected from the list of patients scheduled to be examined on the day, and the examination is started. Step S2 is a patient positioning step, in which the X-ray tube 12 and the X-ray detector 14 are positioned in accordance with the examination site of the patient.

  In step S 3, shooting is performed, and in step S 4, image processing of the collected captured image is performed, gradation processing is performed based on the calculation data calculated by the auto window calculation unit 31, and the image is displayed on the display unit 24. The next step S5 is a step of confirming the display image by the user (for example, an operator). If the image is a good image (YES), the inspection is terminated in step S6.

  Here, since the auto window process is not perfect, the histogram analysis and the gradation calculation process are rarely performed, and an image with a shifted density may be displayed. In this case, the user determines that it cannot be used for diagnosis as it is.

  If the user has a good understanding of the digital general photographing apparatus and the digital mammography apparatus, it can be determined that there is a high possibility that there is no problem in the image data simply because the gradation processing is shifted. Adjust the key. If it is determined in step S8 that the adjusted image is good (YES), the process proceeds to step S6 and the inspection is terminated. If it is determined in step S8 that the X-ray condition is inappropriate or the patient has moved, etc., and it is not suitable for diagnosis even if the gradation is adjusted, the “re-photograph” button is displayed in the next step S9. 41 is pushed, and it returns to step S2 and transfers to the mode of re-photographing.

  On the other hand, a user who has become familiar with the conventional film apparatus and has a film sensation determines that the shooting has failed when the density of the display image is deviated, and presses the “re-shoot” button in step S10. Then, in step S11, a shift window for shifting the window level in several steps is calculated around the standard window width and window level registered in advance in the inspection protocol, and gradation processing is executed using this. . As a result, the gradation-processed image is displayed as a thumbnail as a candidate image, and a message image that prompts confirmation is displayed as to whether there is an image that can be used for the inspection.

  In step S12, if there is an image suitable for diagnosis, the image is selected, and if necessary, the gradation is finely adjusted. If it is determined in step S13 that there is a good image (YES), the process proceeds to step S6 and the inspection is terminated. . If it is determined that there is a cause other than the gradation processing such as improper X-ray conditions or patient movement, and it is determined that an image suitable for diagnosis cannot be obtained even if the window is shifted, “re-photographing is performed in step S14. "Button 41 is pressed, and the process returns to step S2 to perform photographing again.

  As described above, according to an embodiment of the present invention, even if the image data is normal but the image of which the density is shifted is erroneously determined as failed shooting, the message image is displayed before the re-shooting is performed. It is possible to present the presence or absence of an image applicable to. Therefore, it is possible to effectively use the image without deleting it wastefully.

  Next, a second embodiment of the present invention will be described. The second embodiment is characterized by a method for determining the direction of the window level shift and the amount of shift at the window level. That is, as the standard window width and the standard window level (first window level), the values calculated by the auto window are used, but the shift direction of the second window level is determined by the gradation at the standard window width and the standard window level. Depending on the average pixel value in the region of interest (ROI) of the processed image data, it is determined whether to shift to the low density side, to both the low density side and the high density side, or to the high density side To do.

  Here, the pixel value at the boundary for determining the ROI and the shift direction is registered in advance in the inspection protocol. Further, the shift amount of the window level is determined based on the average pixel value in the ROI of the image data subjected to gradation processing at the standard window width and the standard window level, and the shift amount for each average pixel value is registered in the inspection protocol.

  FIG. 7 is an explanatory diagram for explaining a window level shift operation in the second embodiment. FIG. 7A illustrates an image 51 having a low average pixel value in the ROI and an image 52 having a high average pixel value in the ROI. Since the image 51 having a low average pixel value in the ROI is originally high in density (dark), in the state where the average pixel value is lower than a certain threshold value, the image only becomes black even if the window level is shifted to the high density side. is there. On the contrary, the image 52 having a high average pixel value in the ROI originally has a low density (bright). Therefore, when the average pixel value is higher than a certain threshold value, the image becomes white even if the window level is shifted to the low density side. Only.

  Therefore, as shown in FIG. 7B, for the image 51 having a low average pixel value in the ROI, the window level is shifted to the low density side, that is, the image is gradually brightened. In addition, the shift amount is fixed when the average pixel value in the ROI is equal to or less than a predetermined threshold (for example, h1), and the density is not further increased (blackened).

  Further, as shown in FIG. 7B, for the image 52 having a high average pixel value in the ROI, the window level is shifted to the high density side, that is, the image is gradually darkened. In addition, the shift amount is fixed when the average pixel value in the ROI is equal to or greater than a predetermined threshold (for example, h2), and the density is not further lowered (whitened).

  Further, as shown in FIG. 7B, for an image whose average pixel value in the ROI is within a predetermined range (h01 to h02) around the intermediate level h0, the window level is set to the low density side and the high density side. When the average pixel value is near the intermediate level h0, the shift amount is reduced. Thereby, an image suitable for diagnosis can be found more quickly.

  As described above, according to the present invention, it is possible to display a candidate image having a constant contrast and a stepwise change in density before re-shooting. This makes it possible to make a determination and prevent unnecessary re-shooting. Moreover, useless exposure to a patient can be reduced.

  In addition, it is not limited to the above embodiment, A various deformation | transformation is possible in the range which does not deviate from a claim.

DESCRIPTION OF SYMBOLS 10 ... X-ray imaging apparatus 11 ... X-ray imaging part 12 ... X-ray tube 13 ... X-ray restrictor 14 ... X-ray detector 15 ... Imaging stand 16 ... Data collection part 17 ... High voltage generation part 20 ... Computer system 21 ... Bus line 22 ... System control unit 23 ... Operation unit 24 ... Display unit 25 ... Image data processing unit 26 ... Data storage unit 27 ... High voltage control unit 28 ... Aperture control unit 31 ... Histogram creation unit 32 ... Image processing unit 33 ... Auto Window calculation unit 34 ... shift window calculation unit 35 ... gradation processing unit 36 ... display interface (I / F)

Claims (12)

Data collection means for collecting images taken by the X-ray imaging unit;
Operation means for instructing execution of imaging and reimaging in the X-ray imaging unit;
A first window calculating means for analyzing a captured image collected by the data collecting unit and calculating a first window level;
Second window calculation means for calculating a plurality of different second window levels obtained by shifting the window level in stages;
A first image obtained by performing gradation processing on the captured image based on the first window level is generated, and gradation processing is performed on the captured image based on the second window level. Gradation processing means for generating a plurality of second images;
A display unit for displaying an output image from the gradation processing means;
Display control means for displaying the plurality of second images when the re-photographing instruction is given by the operation means while displaying the first image on the display section;
An X-ray imaging apparatus comprising: The operation means displays an instruction button for instructing the re-photographing together with the first image on the display unit, and the display control means replaces the first image when the instruction button is selected. The X-ray imaging apparatus according to claim 1, wherein the second image is displayed.   2. The X-ray imaging according to claim 1, wherein the display control means deletes the first and second images when the re-imaging instruction is given after the second image is displayed. apparatus.   The X-ray imaging apparatus according to claim 1, wherein a plurality of thumbnail images whose density sequentially changes are displayed as the second image.   The X-ray imaging apparatus according to claim 1, wherein the second image is displayed by switching a plurality of images whose density has been sequentially changed at predetermined time intervals.   The gradation processing means calculates an average pixel value of a region of interest (ROI) of the first image, and when the average pixel value is outside a preset range, the second window level is set to an intermediate level. The second image is generated by shifting in both directions around the intermediate level when the average pixel value is within a preset range. X-ray imaging device.   The gradation processing means calculates an average pixel value of a region of interest (ROI) of the first image, and when the average pixel value is outside a preset range, the shift amount of the second window level is calculated. The X-ray imaging apparatus according to claim 1, wherein the X-ray imaging apparatus is increased and the shift amount is decreased when the average pixel value is within a preset range. Collect images taken by the X-ray unit,
Analyzing the collected captured image to calculate a first window level;
Displaying a first image obtained by performing gradation processing on the captured image based on the first window level on a display unit;
When an instruction for re-shooting is given by the operating means while the first display image is being displayed, the shot image is displayed on the basis of a plurality of different second window levels whose window levels are shifted stepwise. A plurality of second images whose density has been sequentially changed are displayed on the display unit,
X-ray image processing characterized in that if there is an image suitable for diagnosis in the second image, it can be selected, and if there is no image applicable for diagnosis, it shifts to a re-imaging mode according to an instruction. Method.   9. The X-ray image processing method according to claim 8, wherein a plurality of thumbnail images whose densities are sequentially changed are displayed as the second image.   9. The X-ray image processing method according to claim 8, wherein a plurality of images whose density has been sequentially changed are displayed as the second image while being shifted every predetermined time. The average pixel value of the region of interest (ROI) of the first image is calculated, and when the average pixel value is outside the preset range, the second window level is shifted in the direction of the intermediate level,
9. The X-ray image processing method according to claim 8, wherein when the average pixel value is within a preset range, shifting is performed in both directions around the intermediate level.   An average pixel value of a region of interest (ROI) of the first image is calculated, and when the average pixel value is outside a preset range, the shift amount of the second window level is increased, and the average pixel value 9. The X-ray image processing method according to claim 8, wherein the shift amount is reduced when is within a preset range.