JP2009189667A - X-ray image diagnostic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray image diagnostic apparatus capable of displaying an X-ray image after image processing at a stable density by allowing an operator to easily change-determine the region of interest (ROI) with respect to the X-ray image. <P>SOLUTION: The X-ray image diagnostic apparatus for obtaining the transmission X-rays of a subject 1 as image data and image-processing the image data includes: a histogram generating means 12; a ROI setting means 13; and a ROI display control means 14. The histogram generating means 12 generates the histogram of a pixel value in the image data. The ROI setting means 13 sets a specified pixel value width, which is selected by the operator, based on the acquired histogram in order to determine the ROI in the image processing. The ROI display control means 14 allows a display means 9 to display an X-ray image, so as to display the specified region of the X-ray image corresponding to the specified pixel value width in a way visually different from that of the other region. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an X-ray diagnostic imaging apparatus that obtains an X-ray image by irradiating a subject with X-rays. In particular, the present invention relates to an X-ray diagnostic imaging apparatus that can confirm, change, and determine a region of interest when performing image processing.

  Conventionally, an apparatus for irradiating an object with X-rays and detecting an X-ray intensity distribution transmitted through the object to obtain an X-ray image has been widely used in industrial nondestructive inspection and medical diagnosis. Yes. As such an imaging technique, an X-ray image is obtained by converting transmitted X-rays of a subject into an electrical signal using an imaging plate or an image intensifier, and performing image processing on the electrical signal and reproducing it as a visible image on a CRT or the like. Devices for obtaining are known. In addition, an apparatus for taking an X-ray image in the same manner using a flat detector (flat panel detector) has been developed. These apparatuses have a much wider dynamic range than conventional X-ray imaging apparatuses using a photosensitive film, and have the advantage that a stable X-ray image can be obtained that is not affected by fluctuations in the amount of X-ray exposure. Have.

  Among these X-ray detectors, the flat detector has a structure in which charges are accumulated as noise in the storage capacitor by dark current even when X-rays are not irradiated. It is necessary to subtract (offset correction) this dark current amount from the data. In addition, since the gain of each pixel is not constant in the flat panel detector, gain correction for each pixel is required to obtain a uniform output image with respect to the input image. Furthermore, since a flat detector usually has a defective pixel for which no pixel value is output, correction of the defective pixel is also required. In general, various types of image processing are performed on the image data corrected by these basic corrections. For example, display gradation processing that stabilizes the density of the region of interest in the X-ray image, image processing such as dynamic range compression processing and frequency enhancement processing that easily output the structure of the human body and the shadow of the lesion are performed.

  In these image processes, a region of interest is often determined from image data that has been subjected to basic correction, and various types of processing are performed on the image data using the feature amount of the region of interest. For example, as a technique for determining processing conditions for display gradation processing, a reference image signal range (region of interest) is determined based on a characteristic value of a cumulative histogram of a captured image region, and the range becomes a predetermined electrical image signal range. A technique for setting gradation processing conditions so as to correspond (for example, see Patent Document 1) has been proposed. In this technology, a constant width before and after the signal value at which the cumulative frequency of the cumulative histogram is 50% is determined as the reference image signal range.

JP 63-31641 A

  However, the above-described conventional technique is a uniform method in which the region of interest is set around a signal value at which the cumulative frequency of the cumulative histogram is 50%, and a certain width before and after that is determined as the reference image signal range. Therefore, when the determined region of interest is not appropriate, the surgeon cannot appropriately reset the optimum region of interest.

  For example, in the X-ray image of the front of the trunk such as the front of the abdomen as shown in FIG. 10, the entire image is generally the subject region 30, and the peak as shown in FIG. Appear in Therefore, it is relatively easy to estimate the image portion necessary for diagnosis even in the conventional technology. However, depending on the imaging region, the positioning of the subject, etc., there is no need for diagnosis, such as an X-ray aperture that restricts X-ray irradiation of the subject region, or a direct line region where X-rays reach the detector without passing through the subject. The portion to be processed may be included in the image. For this reason, when the image processing is performed by determining the region of interest with the conventional technique for an image including an X-ray aperture region or a direct line region, a stable display gradation processing image is obtained due to the influence of the region that is not necessary for diagnosis. May not be obtained.

  For example, in an X-ray image of a trunk side surface such as a lumbar side surface, an operator may or may not insert an X-ray diaphragm. FIG. 12 shows an image composed of the subject region 30 and the aperture region 40 by inserting an X-ray aperture. FIG. 13 shows an image distinguished from the subject region 30 by excluding the direct line region 50 in advance using the histogram (or cumulative histogram) without inserting the X-ray stop and displaying in black. A cumulative histogram of these images is shown in FIG. In this cumulative histogram, a solid line indicates a case where an X-ray diaphragm is inserted and a broken line is not inserted. As shown in FIG. 13, in the image from which the direct line region 50 is removed, the boundary portion (skin line region) between the subject region 30 and the direct line region 50 necessary for diagnosis has high brightness. Therefore, as shown in FIG. 14, the cumulative histogram becomes a straight line with a gentle slope as compared with the case where an X-ray diaphragm is inserted, and the setting of the region of interest according to the conventional technique cannot be set appropriately. Many.

  Further, in the X-ray image of the cervical spine as shown in FIG. 15, not only the influence of the direct X-ray but also a part unnecessary for the diagnosis such as the jaw and the shoulder exists, so the surgeon does the X-ray diaphragm. In the case of not inserting (FIG. 15) and the case of inserting (FIG. 16), the cumulative histogram is as shown in FIG. 17 (the solid line indicates the case where the X-ray diaphragm is inserted and the broken line does not indicate the case). In such a case as well, similarly, when the X-ray diaphragm is not inserted, the curve of the cumulative histogram becomes a gentle straight line, and it is difficult to narrow down the region of interest appropriately with the conventional technology. For this reason, image processing cannot be performed based on an appropriate region of interest, and the processed image may not be displayed with a stable density.

  The present invention has been made in view of such circumstances, and one of its purposes is that an operator can easily change / determine a region of interest for each X-ray image, thereby enabling post-image processing. An object of the present invention is to provide an X-ray image diagnostic apparatus capable of displaying an X-ray image at a stable density.

  An X-ray diagnostic imaging apparatus according to the present invention is disposed opposite to an X-ray source that irradiates a subject with X-rays, detects the transmitted X-rays of the subject, and outputs the detected data as image data. An X-ray diagnostic imaging apparatus comprising: an X-ray detector; an image processing unit that performs image processing using the image data; and a display unit that displays an X-ray image based on the image data. A histogram creation means for creating a histogram of pixel values in the image, a region-of-interest setting means for setting a specific pixel value width from the obtained histogram to determine a region of interest in the image processing, and an X corresponding to the specific pixel value width A region-of-interest display control unit that displays a specific region of the line image so as to be visually different from other regions is provided.

  According to such a configuration, the region of interest can be arbitrarily changed / set by the region-of-interest setting unit while the operator looks at the X-ray image. Therefore, not only in the case of an image composed of subject areas necessary for diagnosis, but also in the case of an image including areas not necessary for diagnosis such as aperture areas, direct line areas, subject areas unnecessary for diagnosis, etc. An appropriate region of interest can be set according to individual images. The region-of-interest display control means changes the region of interest while viewing the X-ray image so that the surgeon can visually display the specific region of the X-ray image corresponding to the specific pixel value width with respect to other regions.・ Easy to set. Various image processing such as display gradation processing, dynamic range compression processing, and frequency enhancement processing can be performed based on the image feature amount of the appropriate region of interest. Therefore, an X-ray image having a stable density can always be displayed on the display means regardless of the imaging conditions such as the imaging target region and positioning.

  In the X-ray image diagnostic apparatus of the present invention, it is preferable that the region-of-interest setting unit displays on the display unit a pixel value width display unit for changing the specific pixel value width.

  The surgeon can select the region of interest easily and appropriately by operating the pixel value width display unit while confirming the image displayed on the display means. In addition to a scroll bar that can be operated with a mouse pointer, a scroll bar or a rotary knob that is displayed on a touch panel and can be operated by touching the surface of the panel can be used as the pixel value width display unit.

  In the X-ray image diagnostic apparatus of the present invention, the region of interest display control means may display the specific region of the X-ray image corresponding to the specific pixel value width in a translucent manner.

  In this way, the specific region (the currently selected region of interest) can be clearly visually recognized and selected without generating a portion that becomes invisible in the entire image. In addition, instead of the translucent display, the specific area may be surrounded by a specific line such as a broken line.

  The X-ray diagnostic imaging apparatus according to the present invention includes an initial region setting unit that sets a pixel value width of a reference region of interest determined in advance according to an imaging technique as an initial pixel value width, and a pixel value width of a specific region by the region of interest setting unit This setting may be performed by changing the initial pixel value width.

  In this way, since a desired region of interest can be set with reference to the reference region of interest displayed as an initial setting, the region of interest can be easily set. The pixel value width of the reference region of interest is prepared for each imaging target region and imaging direction. For example, in the front of the abdomen, regions of interest that are judged to be preferable are manually selected and set for X-ray images of several hundreds of subjects, and the average pixel value width of those regions of interest is the value of the cumulative histogram. % To what percentage may be obtained and used as the initial pixel value width.

  In the X-ray image diagnostic apparatus of the present invention, the image processing condition is selected on the basis of the image feature amount obtained in the region of interest appropriately set by the region of interest setting unit. Regardless of the imaging conditions, an X-ray image having a stable density can always be displayed.

  Hereinafter, an X-ray diagnostic imaging apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a basic configuration of an X-ray image diagnostic apparatus. This X-ray diagnostic imaging apparatus is an apparatus that captures an X-ray image of a subject 1, and includes an X-ray tube 2, an X-ray diaphragm 3, a grid 4, an X-ray flat detector 5, and a flat detector basic. A correction unit 6, an image storage unit 7, an image processing unit 8, and a display unit 9 are provided.

  The X-ray tube 2 is an X-ray source that irradiates the subject 1 with X-rays. The X-ray diaphragm 3 limits irradiation of the subject 1 with X-rays irradiated from the X-ray tube 2. The grid 4 removes scattered radiation components generated when X-rays pass through the subject 1. The X-ray flat panel detector 5 includes a large number of pixels, is arranged to face the X-ray tube 2, detects X-rays transmitted through the subject 1 (transmitted X-rays), and outputs them as image data. The flat detector basic correction means 6 performs basic correction (dark current correction, gain correction, etc.) of the image data output from the X-ray flat detector 5. The image storage means 7 stores the image data output from the flat detector basic correction means 6. The image processing unit 8 performs image processing such as display gradation processing, dynamic range compression processing, and frequency enhancement processing on the image data stored in the image storage unit 7. The display means 9 displays the image data subjected to basic correction and the image data subjected to image processing.

  Further, the apparatus includes an X-ray aperture calculation unit 10, a direct X-ray calculation unit 11, a histogram creation unit 12, a region of interest setting unit 13, a region of interest display control unit 14, and an initial region setting unit 15. I have.

  The X-ray diaphragm calculation unit 10 detects the position of the X-ray diaphragm 3 from the position information of the X-ray diaphragm 3. The direct X-ray calculation means 11 calculates the direct line area of the X-ray flat panel detector 5. The histogram creation means 12 calculates the subject area by removing the aperture area and the direct line area in the image from the calculation results of the direct X-ray calculation means 11 and the X-ray aperture calculation means 10, and creates a cumulative histogram of the subject area. . As a specific processing procedure for removing the aperture region and the direct line region, a known technique can be used. The region-of-interest setting means 13 uses the cumulative histogram to change / set the specific pixel value width selected by the operator. More specifically, as will be described later, a scroll bar for changing the pixel value histogram and the pixel value width is displayed on the screen of the display means. The region-of-interest display control unit 14 displays the X-ray image on the display unit so that the specific region (the currently selected region of interest) of the X-ray image corresponding to the specific pixel value width is visually different from other regions. Is displayed. Here, the specific area is made translucent and the area other than the specific area is displayed as a normal X-ray image. The initial region setting unit 15 stores the pixel value width of the reference region of interest determined in advance according to the shooting technique in the storage unit as the initial pixel value width, and sets the reference region of interest in accordance with the procedure selected from the anatomical program. The pixel value width is read from the storage means. Then, the pixel value width read from the storage unit is set as the initial pixel value width of the reference region of interest in the region of interest setting unit.

  A basic processing process from the start of X-ray imaging to display of an X-ray image in such an X-ray image diagnostic apparatus will be described based on the flowchart of FIG. First, X-ray imaging is performed (S1). Then, the transmitted X-ray is detected by the X-ray flat detector 5 and converted into detection data and output. Next, the detection data is subjected to basic correction by the flat detector basic correction means 6 (S2), and then transferred to the image storage means 7 as image data. Next, the position of the X-ray diaphragm 3 is detected by the X-ray diaphragm calculator 10 based on the position information of the X-ray diaphragm 3 (S3), and the direct X-ray calculator 11 directly detects the position of the X-ray flat panel detector 5. A line region is calculated (S4). The X-ray aperture calculation means 10 performs image processing such as straight line detection (Hough transform) and pattern matching, or acquires the position of the X-ray aperture 3 from the X-ray tube 2 side. Further, the direct X-ray calculation means 11 estimates the pixel value of the direct X-ray from the X-ray imaging conditions (tube voltage, tube current, imaging time, imaging distance, grid, additional filter, etc.) for the subject 1. The direct line area is calculated. Then, the histogram creation means 12 calculates a subject area using the calculation results of the X-ray aperture calculation means 10 and the direct X-ray calculation means 11, and creates a cumulative histogram of the subject area (S5).

  Next, the region of interest is set by operating the region of interest setting unit 13 on the display unit 9 by the operator using the cumulative histogram created by the histogram creating unit 12 (S6). Based on the image feature amount obtained from the set region of interest, image processing conditions such as display gradation processing, dynamic range compression processing, frequency enhancement processing, etc. are selected, and from the image storage means 7 based on the image processing conditions. Image processing is performed on the read image data by the image processing means 8 (S7). Then, the processed X-ray image is displayed on the display means 9 (S8).

  Next, the setting of the region of interest by the region of interest setting means 13 will be described in detail with reference to the flowchart of FIG. 3 and FIGS. S11, S17, and S18 of the flowchart of FIG. 3 are the same processes as S1, S7, and S8 of the flowchart of FIG.

  After performing X-ray imaging (S11) by irradiating the subject 1 with X-rays from the X-ray tube 2, first, as shown in FIG. 4, according to a control command from the region-of-interest display control means 14, An image of the subject area (overall image) calculated using the X-ray aperture calculation means 10 and the direct X-ray calculation means 11 is displayed on the display means 9 (S12). This image is an entire image representing all of the subject area subjected to logarithmic conversion. As shown in FIGS. 4 to 7, the display means 9 includes “initial range”, “confirm”, “return” buttons 20, 21, 22, “scroll bar” S, and “histogram” of the subject area. "H" is displayed. The “scroll bar” S includes a horizontal bar extending from the low density (left) side to the high density (right) side, and a minimum density band knob SL and a maximum density band knob SH that can be slid on the horizontal bar with a mouse pointer ( FIG. 8). By sliding the knobs SL and SH, the minimum density band and the maximum density band can be changed, and the range of both bands is the pixel value width of the region of interest currently selected. The “scroll bar” S and the “histogram” H are displayed side by side so that the density of the “scroll bar” S corresponds to the horizontal axis of the “histogram” H, that is, the pixel value.

  Next, by pressing down the “initial range” button 20, the control command from the region of interest display control means 14 via the initial area setting means 15 corresponds to the initial pixel value width as shown in FIG. The specific region of the X-ray image is displayed as a reference region of interest on the display means 9 in a translucent manner (S13). In order to make a part of the image translucent, the pixel value of the reference region of interest may be increased as a whole. Here, for convenience of explanation, the translucent area is surrounded by a broken line and displayed, but such a line such as a broken line may be used to actually display the area of interest. If the reference region of interest is displayed in a translucent manner, the region of interest can be clearly visually recognized without generating a portion where the image cannot be seen.

  If the surgeon determines that the reference region of interest is inappropriate as the region of interest when performing image processing, the region of interest can be arbitrarily changed from the reference region of interest using the “scroll bar” S.

  For example, when the initial pixel value width is shifted to the low density side, as shown in FIG. 6, for example, the minimum density band knob SL and the maximum density band knob SH are shifted to the left, that is, to the low density side (S14). . By this shift, the pixel value width defined between the knobs SL and SH after the shift becomes a new pixel value width, and a specific region corresponding to the new pixel value width is determined by a control command from the region-of-interest display control means 14. A new region of interest is displayed on the display means 9 in a translucent manner (FIG. 6).

  Conversely, when shifting the initial pixel value width to the high density side, as shown in FIG. 7, for example, the minimum density band knob SL and the maximum density band knob SH are shifted to the right, that is, to the high density side (S14). ). By this shift, the pixel value width defined between the knobs SL and SH after the shift becomes a new pixel value width, and the specific region corresponding to the new pixel value width is made translucent to the display means 9 as a new region of interest. Is displayed (FIG. 7).

  Then, when the operator confirms the image on the screen of the display unit 9 and determines that the set region of interest is appropriate, the “confirm” button 21 is pressed down. When the “confirm” button 21 is pressed, the region of interest is determined (S15), and the image processing conditions are determined (S16). Based on the determined image processing conditions, the image processing unit 8 performs image processing on the image data read from the image storage unit 7 (S17). Then, the processed X-ray image is displayed on the display means 9 (S18).

  On the other hand, when the user wants to review the region of interest again after pressing the “OK” button, the “RETURN” button 22 is pressed down. As a result, the confirmation of the image processing conditions is once canceled, and the region of interest may be reset by operating the knobs SL and SH described above again.

  According to the apparatus of the present invention described above, the operator can change the region of interest serving as a reference for image processing for each image while confirming the X-ray image on the screen. The image processing can be performed based on the above. Therefore, it is possible to always obtain an X-ray image having a stable density regardless of the imaging conditions such as the imaging target region and the positioning of the subject.

  Further, as shown in FIG. 8 and the like, by displaying the histogram H in the vicinity of the scroll bar S, the currently displayed pixel value width can be confirmed by the histogram, so that the operability is improved. In that case, if the pixel value width operated by the scroll bar S is displayed on the histogram H in real time, the operability is further improved.

  Note that the initial pixel value width may be determined as follows, for example. In a region in front of the abdomen, a region of interest determined to be preferable for X-ray images of several hundred subjects is manually selected and set on the screen as shown in FIG. Here, the selected region of interest is surrounded by a broken line. Then, what percentage to what percentage of the cumulative histogram the average pixel value width of the region of interest in the plurality of examples is obtained and set as the initial pixel value width by the initial region setting means 15. Such initial settings may be made by the manufacturer.

  Further, the present invention is not limited to the above-described embodiment, and can be freely improved, changed, etc. as necessary without departing from the gist of the invention. For example, in the present embodiment, a scroll bar as shown in FIG. 8 is used to shift the density band for the region of interest setting operation. In addition, the density band is shifted by a track bar, a button, or the like. May be.

  Furthermore, in the above embodiment, the cumulative histogram is created by the histogram creating means for changing the pixel value width, but the pixel value width may be changed based on a normal histogram.

  In addition, the X-ray detector transmitted through the subject may be a combination of an image intensifier and a camera, or an imaging plate, instead of the flat panel detector.

  The X-ray diagnostic imaging apparatus of the present invention can display an X-ray image having a stable density at all times regardless of imaging conditions such as an imaging target region and positioning, and therefore can be suitably applied for medical use.

1 is a block diagram showing a basic configuration of an X-ray image diagnostic apparatus according to an embodiment of the present invention. It is an example of the flowchart. It is an example of another flowchart. It is explanatory drawing which shows an example of the display means. It is explanatory drawing which shows an example of the display means. It is explanatory drawing which shows an example of the display means. It is explanatory drawing which shows an example of the display means. It is explanatory drawing which shows an example of the scroll bar. It is explanatory drawing of the manual setting of the same region of interest. It is explanatory drawing for demonstrating the problem in the conventional image processing. It is another explanatory view. It is another explanatory view. It is another explanatory view. It is another explanatory view. It is another explanatory view. It is another explanatory view. It is another explanatory view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Subject 2 X-ray tube 3 X-ray aperture 4 Grid 5 X-ray plane detector 6 Plane detector basic correction means 7 Image storage means 8 Image processing means 9 Display means 10 X-ray aperture calculation means 11 Direct X-ray calculation means 11 DESCRIPTION OF SYMBOLS 12 Histogram preparation means 13 Region of interest setting means 14 Region of interest display control means 15 Initial area setting means H Histogram S Scroll bar SL Minimum density band knob SH Maximum density band knob 20 Initial range button 21 Confirm button 22 Return button 30 Subject area 40 Aperture Area 50 Direct line area

Claims (4)

An X-ray source that irradiates the subject with X-rays, an X-ray detector that is arranged opposite to the X-ray source, detects transmitted X-rays of the subject, and outputs the detected image data as image data, and the image data An X-ray diagnostic imaging apparatus comprising: an image processing unit that performs image processing using a display; and a display unit that displays an X-ray image based on the image data,
A histogram creating means for creating a histogram of pixel values in the image data;
A region of interest setting means for setting a specific pixel value width from the obtained histogram in order to determine a region of interest in the image processing;
An X-ray image diagnosis apparatus comprising: a region-of-interest display control unit configured to display a specific region of an X-ray image corresponding to the specific pixel value width so as to be visually different from other regions. The X-ray image diagnosis apparatus according to claim 1, wherein the region-of-interest setting unit causes the display unit to display a pixel value width display unit for changing the specific pixel value width. The X-ray image diagnosis apparatus according to claim 1, wherein the region-of-interest display control unit displays the specific region of the X-ray image corresponding to the specific pixel value width in a translucent manner. An initial region setting means for setting a pixel value width of a reference region of interest determined in advance according to a shooting technique as an initial pixel value width;
2. The X-ray image diagnosis apparatus according to claim 1, wherein the setting of the pixel value width of the specific region by the region-of-interest setting unit is performed by changing the initial pixel value width.