JP5468362B2 - Mammography equipment - Google Patents

Description

  The present invention relates to an apparatus for imaging a subject using radiation, and more particularly to a mammography apparatus having a blackening processing function suitable for imaging a breast image.

  Conventionally, a mammography apparatus is known as a radiographic image capturing apparatus for capturing a breast image in the medical field. A mammography apparatus irradiates radiation (eg, X-rays) that does not harm the health of a subject from a radiation source toward the subject's breast, detects the radiation that has passed through the subject, and acquires digital image data. is there.

  The mammography apparatus is a modality that is generally very fine and has a low subject contrast, and the luminance of the Schaukasten and the monitor used at the time of interpretation is higher than that of other modalities. Therefore, when a mammography image photographed by the mammography apparatus is displayed positively, a portion of the direct line region (white portion of the image) from which light is directly extracted is felt very dazzling for the examiner. Therefore, normally, even if negative / positive reversal is performed, a blackening process that always displays a white portion (direct line area) of the image in black is performed on the diagnostic image.

  By the way, as a conventional technique for blackening processing, a method for detecting a skin line of a breast and making the nipple side a target for blackening processing from this, and detecting a minimum pixel value of a direct line region from a histogram and calculating a pixel value larger than this. A method for blackening processing is known. In the latter case, for example, a threshold value is obtained from a boundary point between the peak of the breast region and the peak of the direct line region appearing in the histogram of the mammography image, and the binarization process is performed on the basis of this threshold to separate the breast region and the direct line region. A nipple detection device is known (see Patent Document 1).

  In mammography using a mammography apparatus, when imaging a subject, a marker is placed at a position that does not overlap the subject in the irradiation field. The marker is a symbol that indicates the imaging direction and whether it is the left breast or the right breast, etc., and appears on the reproduced captured image, and is usually made of a metal such as lead that does not transmit radiation. .

  In some cases, a scale made of a metal that does not transmit radiation is placed in order to display the dimensions of the mammography image.

  When such a marker or scale is imaged at the time of subject imaging, blackening processing for skinline detection may cause blackening processing targets such as markers and scales to be necessary. In addition, the blackening process based on the histogram detection has a problem that foreign matters such as dust in the direct line area are not targeted for the blackening process. An image processing apparatus is known in which a marker region is detected and an intermediate pixel value is detected in order to suppress a decrease in the discrimination capability of the observer due to the marker (see Patent Document 2). However, in this case, it is necessary to detect the marker region.

JP 2006-68373 A JP 2006-68372 A

  The present invention has been made in order to solve the above-described problems, and does not detect the marker region, and does not impair the image of a necessary radiation non-transparent material such as a marker or scale in the direct line region. An object of the present invention is to provide a mammography apparatus capable of performing the digitization process.

According to claim 1 of the present invention, mammography means for irradiating a subject with radiation from a radiation source, detecting radiation transmitted through the subject and acquiring digital image data, and processing the digital image data A skin line detecting means for detecting a skin line in the breast region and obtaining skin line coordinates, and obtaining a histogram in the non-breast region obtained based on the skin line coordinates in the digital image data. Threshold setting means for obtaining a threshold value by setting the pixel value on the maximum side of the profile indicating the marker region in the histogram, and blackening processing for performing blackening processing on the non-breast region of the digital image data based on the threshold value And a mammography device.

  According to the present invention, it is possible to obtain a mammography apparatus that can perform a blackening process without detecting a marker area and without damaging an image of a necessary non-transparent material such as a marker or a scale in a direct line area. Have

It is a common block diagram of the mammography apparatus concerning the embodiment of the present invention. It is a block diagram of the blackening process of the mammography apparatus which concerns on the same embodiment. It is a mammography image of the mammography device concerning a 1st embodiment of the present invention, (a) shows an image before blackening processing, and (b) shows an image after blackening processing. It is a flowchart of the blackening process of the mammography apparatus which concerns on the 1st Embodiment of this invention. It is a histogram of B area | region of the mammography apparatus which concerns on the 1st Embodiment of this invention. It is a flowchart of the blackening process of the mammography apparatus which concerns on the 2nd Embodiment of this invention. It is a mammography image of each step in the blackening process flow of the mammography apparatus concerning the 2nd embodiment of the present invention. (A) shows the original image, (b) shows the image after removing the minute object image, (c) shows the image after blackening processing, and (d) shows the image after replacement. It is an example of the original image before the morphological process which concerns on the 2nd Embodiment of this invention. It is an example of an image after various morphological processes concerning a 2nd embodiment of the present invention. (A) is Dilation, (b) is Erosion, (c) is Opening, and (d) is each image after Closing processing. It is a histogram of the original image of the mammography apparatus concerning a 2nd embodiment of the present invention.

  Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram of a mammography apparatus according to an embodiment of the present invention.

  In FIG. 1, reference numeral 100 denotes a mammography apparatus, which includes a mammography unit 110 for imaging a breast and a computer system 120 that performs imaging control and image output.

  The mammography unit 110 includes an X-ray tube (radiation source) 111 attached to one end (upper end) of an arm (not shown), and a top plate 112 attached to the other end (lower end) of the arm. An X-ray detector 113 is provided in the plate 112. A compression plate 114 for compressing the subject P (breast) is attached between the X-ray tube 111 and the top plate 112 so as to be movable in the vertical direction.

  The X-ray detector (radiation detector) 113 is, for example, a flat panel detector (FPD: Flat Panel Detector), and is formed by arranging a plurality of pixels arranged two-dimensionally in a matrix. The X-ray detector 113 detects X-rays (radiation) transmitted through the subject P by each pixel, and converts the detected X-rays into electric signals. The X-ray detector 113 includes an amplifier that amplifies the electric signal and an A / D converter that converts the amplified electric signal (analog signal) into a digital signal. The top plate 112 faces the X-ray tube 111, and the subject P placed on the top plate 112 is sandwiched between the top plate 112 and the compression plate 114 to perform imaging.

  The X-ray tube 111 is supplied with a high voltage from the high voltage generator 115 and generates X-rays. X-rays transmitted through the subject P are detected by the X-ray detector 113 and converted into electrical signals. The converted electrical signal is read out via the data collection unit 116 and transmitted to the computer system 120 as digital projection data (digital image data).

  The computer system 120 includes a bus line 121, and a system control unit 122, a data storage unit 123, a data processing unit 124, an operation unit 125, a display unit 126, and an irradiation control unit 127 are connected to the bus line 121. Yes.

  The system control unit 122 controls the overall operation of the computer system 120. The data storage unit 123 stores the digital image data sent from the data collection unit 116. The data processing unit 124 processes the image data stored in the data storage unit 123 to generate mammography image data.

  The operation unit 125 and the display unit 126 constitute a user interface together with the system control unit 122. The operator operates the operation unit 125, and the operation unit 125 outputs various operation information such as an X-ray exposure instruction and imaging start. The display unit 126 displays the image generated by the data processing unit 124.

  Further, the mammography unit 110 is provided with an irradiation region restriction device 117 that restricts the X-ray irradiation range by the X-ray tube 111, and the irradiation region restriction device 117 is controlled by the irradiation control unit 127. The irradiation control unit 127 controls the irradiation region limiting device 117 to limit the X-ray irradiation range according to the subject P.

  FIG. 2 is a diagram illustrating a configuration example of a blackening processing unit that performs blackening processing in the data processing unit 124. The blackening processing unit acquires an image from the data storage unit 123 via the bus line 121, processes the digital image data, detects a skin line in the breast region, and acquires skin line coordinates. Skinline detection unit 22, region separation unit 23 that separates digital image data from the skinline coordinates into a breast region and a non-breast region, and a removal that removes an image of an unnecessary object reflected in the non-breast region by a minute object disappearance process Threshold setting for creating a histogram for the entire area of the digital image data or the area separated by the area separation unit and setting a threshold value of a pixel value serving as a reference for binarization processing from the histogram Pixel value replacement that replaces the pixel value for the whole area of the image digital data or the non-breast region separated by the region separation unit 26, an output unit 27 for outputting the processed blackening processed image with the pixel value replacing unit 26 to the bus line 121.

  The minute object disappearance process performed by the removal unit 24 is a process of reducing an image and then enlarging it, or a morphological process. By this process, an image of a small unnecessary object can be erased.

  In FIG. 2, thick arrows indicate the flow of image data, and dotted arrows indicate the flow of parameters necessary for image processing.

<First Embodiment>
FIG. 3 is a mammography image of the mammography apparatus according to the first embodiment of the present invention. FIG. 3A shows an image before the blackening process, and FIG. 3B shows an image after the blackening process. Hereinafter, the case where the mammography image is a positive image will be described with reference to FIGS. 1 and 2.

  As shown in FIG. 3A, the mammography image before the blackening process is divided into a region A indicating a breast region and a region B indicating a direct line region with a breast skin line 30 as a boundary line. Usually, cleaning is performed with great care so that dust is not photographed when the breast is photographed, but the dust 31 attached to the top 112 or the compression plate 114 may still appear. In addition, a marker 32 (left L is shown here) indicating the left and right of the breast is displayed in black in the positive image because it does not transmit X-rays. In the blackening process, as shown in FIG. 3 (b), it is required that only an unnecessary image such as dust is targeted for blackening and the marker is not blackened.

  FIG. 4 is a flowchart of the blackening process of the mammography apparatus according to the first embodiment of the present invention. The blackening process is performed by the data processing unit 124. First, the data processing unit 124 takes the image data stored in the data storage unit 123 into the image input unit 21 (S401). In the image data captured in step S401, the skin line detection unit 22 detects the skin line 30 as a breast region (S402), and the region separation unit 23 uses the coordinates for forming the skin line 30 based on the coordinates. The mammography image is separated into a breast region (A region) and a direct line region (B region). In the next step S403, a histogram is calculated for the separated B region.

  An example of the histogram of the B region processed by the threshold setting unit 25 is shown in FIG. In this figure, the horizontal axis represents pixel values (luminance) and the vertical axis represents frequency. In the histogram of the B area, the breast area (A area) is separated from the original image, so its constituent elements are divided into three areas (profiles): a marker area, a dust area, and a direct line area.

  A marker region that does not transmit X-rays made of lead or the like appears as a mountain profile in the low pixel value region. For the direct line region, a high peak profile is obtained in the high pixel value region. A dust region profile appears between the two profiles.

  In step S404, the point (pixel value) where the mountain profile in the marker area and the profile in the dust area overlap is set as the threshold (Th).

  The pixel value replacement unit 26 classifies pixels existing in the A area and the B area from the skin line coordinates acquired in step S402, and applies blackening processing to pixels in the B area having a pixel value equal to or greater than Th. For the marker area having a pixel value equal to or less than Th, a process of converting to white or a gray color having an arbitrary luminance is performed (S405).

  By performing such binarization processing, as shown in FIG. 3B, only images of unnecessary objects such as dust are obtained without blackening the images of necessary radiopaque objects such as markers and scales. Can be blackened.

  In the above-described embodiment, the histogram of the non-breast region is analyzed, and the threshold value (Th) for binarizing the marker pixel region and the other regions is obtained from this histogram. However, this threshold value (Th) is not obtained by analyzing the histogram, but an optimum threshold value (Th) is obtained in advance by changing the X-ray imaging conditions, and a threshold value (Th) corresponding to the imaging conditions is set. You may make it do.

<Second Embodiment>
FIG. 6 is a flowchart of the blackening process of the mammography apparatus according to the second embodiment of the present invention. FIG. 7 is a mammography image corresponding to each step in the blackening process flow of the embodiment. 7 (a) shows the original image, FIG. 7 (b) shows the image after removing the unnecessary image, FIG. 7 (c) shows the image after blackening processing, and FIG. 7 (d) shows the image after replacement. Each image is shown.

  The blackening process of this embodiment will be described based on FIG. 6 with reference to FIGS. 1, 2, and 7. The blackening process in the present embodiment is performed by the data processing unit 124 as in the first embodiment. The data processing unit 124 takes the image data stored in the data storage unit 123 into the image input unit 21 (S601).

  As shown in FIG. 7A, the original image data captured by the image input unit 21 detects the skin line 30 in the skin line detection unit 22, and the region separation unit 23 determines the breast based on the skin line coordinates. A region (A region) and a direct line region (B region) are separated (S602).

  On the other hand, as shown in FIG. 7B, the removing unit 24 creates an image obtained by removing unnecessary minute objects such as dust from the original image in FIG. For example, microscopic objects are removed by using enlargement / reduction processing, morphological processing, or the like (S603).

  Various specific methods of enlargement / reduction processing can be considered. For example, by simply sampling pixel values according to the reduction ratio and thinning out the pixels, or by using the average value of the pixel values in the reduction source area, A process of removing and returning to the original image is performed. The size of an image of a minute object such as dust 31 to be removed can be adjusted by changing the reduction ratio.

  Morphological processing will be described with reference to a cited document (Medical Imaging Technology Vol.12 No.1 January 1994).

  FIG. 8 shows an example of an original image before morphological processing. FIG. 8A shows the original image A, and FIG. 8B shows the structural element B. The morphological process is defined by a set operation between the original image A to be processed and the structural element B. For example, a case where a circle with a radius r having the center at the origin is made to act as the structural element B on the original image A having holes, protrusions, cuts, and the like will be described.

  FIG. 9 is an image example after various morphological processes. 9A shows Dilation, FIG. 9B shows Erosion, FIG. 9C shows Opening, and FIG. 9D shows each image example after Closing processing.

  The Dilation in FIG. 9A is also called Max, and indicates the maximum area when the center of the structural element B is moved along the periphery of the original image A. That is, the original image A is a figure that is widened outward by a width r. In particular, an inner hole having a radius smaller than r disappears. Similarly, the bay-shaped portion cut into thin portions is generally buried and disappears. In the original image A, the separated figures are fused.

  Erosion in FIG. 9B is also called Min, and indicates the minimum area when the center of the structural element B is moved along the periphery of the original image A. That is, the original image A becomes a figure reduced inward by the width r. In particular, the inner hole is further expanded in radius by r.

  Since the outside of the original image A is reduced to the inside and the inner hole is enlarged to the outside, the original image A is separated at a narrow isthmus. Small figures disappear. In this embodiment, in particular, by using this erosion, it is possible to remove an image of a minute unnecessary object such as dust. Further, the size of the unnecessary image that can be removed can be changed depending on the size of the structural element B.

  Opening shown in FIG. 9C is a process in which Dilation (Max) processing is performed after Erosion (Min). The Dilation and Erosion described in FIGS. 9A and 9B have an effect of removing an object smaller than the structural element B from the image. However, Dilation enlarges the figure and Erosion reduces the figure. End up. In Opening, smoothing is performed while maintaining the overall size, and a portion where the structural element B cannot enter is removed.

  Closing shown in FIG. 9D is for performing Erosion (Min) processing after Dilation (Max). This Closing is also smoothed while maintaining the overall size, and the portions where the structural element B cannot enter are connected.

  As described above, the size of the structural element B and one or a plurality of these four processes can be appropriately combined to remove minute objects. For example, as a simple example, when it is desired to remove even relatively large dust, the structure element B itself is enlarged or the process of Erosion (Min) is repeated a predetermined number of times so that dust larger than the structure element B is also removed. It can be removed. Also, when it is desired to leave an object larger than the structural element B as an image without processing it as dust, an Opening process or the like is performed.

  On the other hand, the threshold setting unit 25 acquires a histogram of the original image in order to detect a threshold (a direct line pixel threshold) to be blackened (S604). FIG. 10 shows an example of the histogram of the original image of the mammography apparatus. Since this histogram includes the breast region, the marker region and dust region profiles observed in FIG. 5 are observed as a histogram that overlaps the breast region profile (the dust region is hidden). As shown in FIG. 10, the local minimum point where the profile of the direct line region and the profile of the breast region overlap is set as the pixel value threshold Th of the direct line region (S605).

  The pixel value replacement unit 26 applies blackening processing to pixels having a pixel value equal to or greater than the threshold value Th obtained in step S605 to the image shown in FIG. 7B obtained in step S603 (S606). ). Further, for a pixel having a lower pixel value, for example, a process of replacing it with white or a gray color having an arbitrary luminance is performed (S607). As a result, an image as shown in FIG. 7C is obtained. Here, the breast region is defined as an A ′ region, and the region obtained by blackening the direct line region is defined as a B ′ region.

  Next, the breast area (A area) of the original image is obtained based on the skin line coordinates obtained in step S602, and the breast area (A 'area) of the image obtained in step S606 (FIG. 7C). (S607). In other words, in the original image, the non-breast area is replaced with the processed image. In this way, a blackened image as shown in FIG. 7D is obtained.

  According to the second embodiment, in the removal of the minute object image reflected in the direct line area, the size of the structure that can be removed is adjusted by variously selecting the size of the structural element B and the removal processing method. There are advantages that can be made.

  As described above, according to the embodiment of the present invention, it is possible to blacken an image of a small unnecessary object without blackening a necessary radiopaque image such as a marker or a scale in a direct line region. There is an effect that can.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, the constituent elements over different embodiments may be appropriately combined. As long as the technical idea of the present invention is used, these modified examples are also included in the present invention.

100 ... Mammography device,
110: Mammography unit,
111 ... X-ray tube,
112 ... top plate,
113 ... X-ray detector,
114 ... compression plate,
115 ... high pressure generator,
116: Data collection unit,
117 ... Irradiation area limiting unit,
120 ... computer system,
121 ... Bus line,
122... System control unit,
123: Data storage unit,
124: Data processing unit,
125 ... operation unit,
126 ... display section,
127 ... irradiation control part,
21: Image input unit,
22 ... skin line detection unit,
23 ... area separation part,
24 ... removal part,
25 ... Threshold setting unit,
26: Pixel value replacement unit,
27: Image output unit.

Claims (5)

Mammography means for irradiating a subject with radiation from a radiation source, detecting radiation transmitted through the subject and acquiring digital image data;
Skin line detection means for processing the digital image data to detect a skin line in the breast region and obtaining skin line coordinates;
A threshold value is obtained by obtaining a histogram in a non-breast area obtained based on the skin line coordinates in the digital image data, and using the maximum pixel value of a profile indicating a marker area in the histogram based on the histogram. Threshold setting means;
Blackening processing means for performing blackening processing of the non-breast region of the digital image data based on the threshold;
A mammography apparatus comprising: The blackening processing means includes
The mammography apparatus according to claim 1, wherein the non-breast region is blackened after removing an unnecessary image reflected in the digital image data. The mammography apparatus according to claim 2 , wherein the threshold value is further set to a threshold value determined in advance from imaging conditions of the digital image. Mammography means for irradiating a subject with radiation from a radiation source, detecting radiation transmitted through the subject and acquiring digital image data;
Skin line detection means for processing the digital image data to detect a skin line in the breast region and obtaining skin line coordinates;
Region separating means for separating the digital image data into a breast region and a non-breast region from the skinline coordinates;
A removal means for removing an image of an unnecessary object reflected in the non-breast area by a microscopic object disappearance process that is a scaling process or a morphological process ,
Create a histogram of the entire digital image data, and based on this histogram, set the threshold value of the pixel value that serves as a reference for binarization by setting the pixel value on the maximum side of the profile indicating the marker region in the histogram , Blackening processing means for obtaining a binary image of this area;
A pixel value replacement unit that replaces the pixel value of the non-breast region obtained by the region separation unit of the digital image data with a pixel value obtained by the blackening processing unit;
A mammography apparatus comprising:   5. The mammography apparatus according to claim 4, wherein the threshold value is a pixel value of a minimum point where a profile of a direct line region and a profile of a breast region in the histogram overlap.

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