JP5541989B2 - Radiation image processing apparatus and method, and program - Google Patents

Description

  The present invention relates to a radiation image processing apparatus and method for performing image processing on a radiation image such as a breast image, and a radiation image processing program.

  In recent years, in order to promote early detection of breast cancer, image diagnosis using a radiographic imaging apparatus (called mammography) for imaging a breast has attracted attention. A radiation image (breast image) of a breast imaged by mammography is subjected to image processing by a dedicated operation terminal, and then transmitted to a server or a browsing terminal via a network. The doctor examines the presence or absence of a lesion such as a tumor or calcification by projecting and interpreting the breast image transmitted to the viewing terminal.

  Here, the above-described image processing is performed in order to facilitate interpretation of a breast image. Specifically, in image processing, image characteristics such as density, contrast, gradation, dynamic range, frequency characteristics, and noise of the region to be interpreted are appropriate, and a breast image having a desired image quality is obtained. As described above, the breast image is analyzed to determine the image processing condition, and the breast image is subjected to image processing based on the determined image processing condition.

  Various techniques for performing image processing suitable for such breast images have been proposed. For example, a technique has been proposed in which a breast area is detected from a breast image, a pectoral muscle area is detected from the breast area, and the density of the breast area is adjusted based on the average density of the pectoral muscle area (see Patent Document 1). . Also proposed is a method of extracting a mammary gland region from a breast image, setting multiple local regions centered on the mammary gland region, calculating the contrast of the local region, and performing image processing on the breast image based on the calculated contrast (See Patent Document 2).

  By the way, for example, breast reconstruction surgery after breast cancer surgery and breast augmentation surgery for beauty may be performed on the breast to be imaged. May have an implant. The image quality of a breast image acquired by imaging differs greatly between a breast in which such an implant is embedded and a breast that is not embedded, depending on the presence or absence of the implant. In particular, since the implant appears as a high-luminance region in the breast image, the brightness of the breast image varies greatly depending on the presence or absence of the implant.

  For this reason, in mammography, a method of performing exposure control so that the implant portion has an appropriate brightness (see Patent Document 3) and a method of controlling the exposure dose when there is an implant (see Patent Document 4) are proposed. Has been. According to the methods of Patent Documents 3 and 4, by controlling the exposure or exposure dose, a breast image can be obtained so as to have appropriate brightness even if an implant is included in the breast.

JP 2010-017370 A JP 2009-247521 A Special table 2009-507595 JP 2007-236524 A

  Here, in the breast image acquired by the method of patent document 3 and 4, the area | region of an implant becomes appropriate brightness. However, since the luminance of the region other than the implant region is lowered, there is a possibility that the region necessary for the diagnosis is difficult to see. In addition, although the implant region has appropriate brightness, it is still brighter than other regions. For this reason, even if the images are acquired by the methods of Patent Documents 3 and 4, if the image processing conditions are set based on the breast image including the implant, the image processing conditions are affected by the region of the implant, and preferable image quality is obtained. In some cases, image processing cannot be performed.

  The present invention has been made in view of the above circumstances, and an object thereof is to appropriately perform image processing on a breast image including an implant.

The radiological image processing apparatus according to the present invention includes an implant region extracting means for extracting a region of the implant from a breast image including the implant,
Image processing condition setting means for setting image processing conditions for image processing based on an area other than the implant area in the breast image;
Image processing means for performing image processing on the breast image according to the image processing conditions is provided.

  In the radiographic image processing apparatus according to the present invention, the image processing means may further include means for converting the implant region into a predetermined density.

  In the radiographic image processing apparatus according to the present invention, when the image processing condition setting unit compares the breast image including the implant with another breast image, the breast image including the implant and the image of the other breast image It is good also as a means to set process conditions based on area | regions other than the said implant area | region.

  As the “other breast image”, for example, a breast image acquired at the same time for the same patient, a breast image on the opposite side to the breast image including the implant, and a past breast image acquired at a different time for the same patient are used. be able to.

The radiological image processing method according to the present invention extracts a region of an implant from a breast image including the implant,
Based on regions other than the implant region in the breast image, set image processing conditions for image processing,
Image processing is performed on the breast image according to the image processing conditions.

  The radiographic image processing method according to the present invention may be provided as a program for causing a computer to execute the method.

  According to the present invention, the region of the implant is extracted from the breast image including the implant, the image processing condition for image processing is set based on the region other than the implant region in the breast image, and the set image processing condition Image processing is performed on the breast image. For this reason, even if the breast image includes an implant, image processing can be performed so that the breast region has high image quality without being affected by the implant region.

  Further, by converting the implant region to a predetermined density, the implant region does not become brighter, so that the observer does not feel dazzling when displaying the processed breast image.

  Further, when comparing a breast image including an implant with another breast image, comparison is performed by setting image processing conditions of the breast image including the implant and the other breast image based on a region other than the implant region 2 Image processing can be performed so that the appearances of two breast images are matched without being affected by the implant region. Therefore, comparative interpretation using two breast images can be performed with high accuracy.

Schematic block diagram showing the configuration of a system including a radiation image processing apparatus according to the present embodiment Schematic showing the configuration of the mammography device Internal configuration diagram of imaging stand in mammography apparatus Schematic block diagram showing functions of an image processing program performed by the radiation image processing apparatus Diagram showing breast image Diagram showing an image of a breast image divided into regions A flowchart showing processing performed in the present embodiment

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram showing the configuration of a system including a radiation image processing apparatus according to the present embodiment. As shown in FIG. 1, this system includes a radiographic image processing apparatus 10 according to the present invention, a mammography imaging apparatus 40 installed in a medical facility, an operation console 42 for operating the mammography imaging apparatus 40, and the mammography imaging. It comprises an image database (image DB) 44 for storing breast images taken by the device 40 and a doctor's terminal device 46 for interpretation, having a high-definition monitor (not shown).

  The radiographic image processing apparatus 10 is configured by a computer such as a workstation, and mainly stores a central processing unit (CPU) 12 that controls the operation of each component, and a control program for the apparatus, and works when the program is executed. A main memory 14 serving as a region, a graphic board 16 for controlling display of a monitor device 28 such as a liquid crystal display or a CRT display, a communication interface (communication I / F) 18 connected to a network 50 of a medical facility, and the present invention A hard disk device 20 that stores various application software including a radiographic image processing program, a CD-ROM drive 22, a keyboard controller 24 that detects key operations of the keyboard 30 and outputs them to the CPU 12 as instruction inputs, and position input Mau as a device And it is configured to detect the 32 states of the signal state of the position or the mouse 32 of the mouse pointer on the monitor device 28 from the mouse controller 26 for output to the CPU 12.

  FIG. 2 is a schematic diagram showing the configuration of the mammography photographing apparatus 40. As shown in FIG. As shown in FIG. 2, the mammography imaging apparatus 40 includes a base 112 that is installed in an upright state, an arm member 116 that is fixed to a turning shaft 114 that is disposed at a substantially central portion of the base 112, and a subject. 118 X-ray sources for exposing radiation (X-rays) to 118 breasts are stored, an X-ray source storage unit 120 fixed to one end of the arm member 116, and X-rays transmitted through the breasts are detected. A detector for storing X-ray image information is housed, and an imaging table 122 fixed to the other end of the arm member 116, and a compression plate 124 for pressing the breast against the imaging table 122 are provided.

  The arm member 116 to which the X-ray source storage unit 120, the imaging table 122, and the compression plate 124 are connected is configured to be adjustable in the imaging direction with respect to the breast of the subject 118 by rotating in the direction of arrow A about the rotation axis 114. Is done. The compression plate 124 is disposed between the X-ray source storage unit 120 and the imaging table 122 while being connected to the arm member 116, and is configured to be displaceable in the arrow B direction.

  The X-ray source storage unit 120 is provided with a face guard sheet 128 made of a member that blocks X-rays in order to protect the vicinity of the face of the subject 118 from X-ray exposure. Further, on the base 112, imaging information such as the imaging region and imaging direction of the subject 118, ID information of the subject 118, and the like are displayed, and the compressed state of the breast by the compression plate 124 is released as necessary. A display 130 is provided for displaying information relating to the remaining compression time.

  FIG. 3 is an internal configuration diagram of the imaging stand 122 in the mammography imaging apparatus 40, and shows a state in which a breast 136 that is an imaging site of the subject 118 is disposed between the imaging stand 122 and the compression plate 124. Reference numeral 138 indicates the chest wall of the subject 118.

  The X-ray image information based on the X-rays transmitted through the breast 136 is accumulated in the imaging table 122, and the detector 140 that outputs the information as an electrical signal, and the X-ray image information accumulated and recorded in the detector 140 are read. In addition, a reading light source unit 142 for irradiating the detector 140 with reading light and a dose detection for detecting an X-ray dose transmitted through the breast 136 in order to determine an exposure time which is one of the X-ray exposure conditions. In order to remove unnecessary charges accumulated in the detector 140 (hereinafter referred to as an “AEC (Automatic Exposure Control) sensor 144”) and an automatic exposure control X-ray detector. And an erasing light source unit 146 for irradiating.

  The detector 140 is an X-ray detector of direct conversion type and optical readout type, and accumulates X-ray image information based on X-rays transmitted through the breast 136 as an electrostatic latent image and reads from the reading light source unit 142. By scanning with light, a current corresponding to the electrostatic latent image is generated.

  The reading light source unit 142 includes, for example, a line light source configured by arranging a plurality of LED chips in a line and an optical system that linearly irradiates the reading light output from the line light source onto the detector 140, and detects the light source. The detector 140 is moved by moving the line light source in which the LED chips are arranged in the direction orthogonal to the extending direction of the linear electrode, which is the second conductive layer of the detector 140, in the extending direction (arrow C direction) of the linear electrode. Are exposed and scanned.

  The AEC sensor 144 is configured to be movable in the direction of arrow C along the detector 140 so that the X-ray dose can be detected by moving the AEC sensor 144 to a portion corresponding to a portion of the breast 136 where the breast density is high. The erasing light source unit 146 can be configured by two-dimensionally arranging LED chips that emit and extinguish light in a short time and have very little afterglow.

  X-rays transmitted through the breast 136 are detected as X-ray image information by the detector 140, and an X-ray image (breast image) of the breast 136 is formed by an X-ray image forming unit (not shown). On the other hand, the detector 140 from which the X-ray image information has been read is irradiated with erasing light from the erasing light source unit 146, thereby erasing the remaining X-ray image information.

  When mammography of the subject 118 is performed, the subject 118 is positioned and the operator console 42 (FIG. 1) is operated for imaging. The console 42 includes input means for inputting subject identification information (subject ID) for identifying a subject and a photographer ID for identifying a photographer. The subject ID and photographer ID input here are input. Are associated with the breast image photographed by the mammography photographing apparatus 40 and stored in the image DB 44.

  The breast image can be stored in the image DB 44 as, for example, a DICOM (Digital Image and Communication in Medicine) standard image file (DICOM file). In this case, the subject ID and imaging are included in the header of the DICOM file. In addition to the person ID, information such as the shooting date and the shooting facility is recorded.

  The detector 140 is not limited to a direct conversion type and optical readout type X-ray detector, but may be an imaging plate (storable phosphor sheet) IP having a stimulable phosphor, A flat panel X-ray detector (flat panel detector) FPD in which a very large number of X-ray detection elements using a semiconductor or the like are two-dimensionally arranged on the X-ray detection surface may be used.

  Next, the positioning and imaging procedures of the subject 118 will be described. The photographer (radiologist) sets the mammography apparatus 40 in a predetermined state according to the designated imaging method. For example, as the imaging direction of the breast 136, head-to-tail (CC) imaging in which radiation X is irradiated from above, lateral (ML) imaging in which radiation X is irradiated from the side, and oblique direction There is an inside / outside oblique (MLO) imaging in which imaging is performed by irradiating with radiation X, and the arm member 116 is pivoted about the pivot axis 114 in accordance with these imaging directions. FIG. 2 shows a case where head-to-tail (CC) imaging is performed.

  After the above preparatory work is completed, the subject 118 is guided to the mammography apparatus 40 and positioning of the breast 136 is started. That is, after placing the breast 136 on the imaging table 122, the radiologist turns on a compression plate moving switch (not shown) and moves the compression plate 124 in the direction of arrow B (FIG. 2) with respect to the imaging table 122. The breast 136 is gradually compressed.

  When it is detected by a pressure sensor (not shown) that the compression pressure has reached the pressure required for photographing, the movement of the compression plate 124 is stopped and a photographing permission is output. Therefore, when the radiation engineer turns on an exposure switch (not shown), radiation imaging of the breast 136 is performed.

  When the mammography is completed, the compression of the breast 136 is released by moving the compression plate 124 away from the imaging table 122. In imaging of the breast 136, a single subject 118 is subjected to multiple imaging such as CC imaging, ML imaging, and MLO imaging of the left and right breasts 136.

  Next, image processing performed by the radiation image processing apparatus 10 will be described. FIG. 4 is a schematic block diagram showing functions of an image processing program executed by the radiation image processing apparatus 10. As shown in FIG. 4, the function of the image processing program performed by the radiation image processing apparatus 10 is executed by the area dividing unit 200 and the image processing unit 202. The region dividing unit 200 corresponds to an implant region detecting unit.

  Here, as a result of breast reconstruction or breast augmentation, the image quality of the breast image differs greatly between the breast in which the implant such as silicon is embedded and the breast that is not embedded. In particular, since the implant appears as a high-luminance region in the breast image, the brightness of the breast image varies greatly depending on the presence or absence of the implant. In this case, when the image processing condition is set based on the breast image including the implant, the image processing condition is affected by the region of the implant, and the image processing condition may not be set so as to obtain a preferable image quality. For this reason, in this embodiment, image processing is performed in consideration of the implant region.

  For this purpose, the region dividing unit 200 divides the breast image into regions. FIG. 5 shows a breast image, and FIG. 6 shows a region-divided breast image. The breast image shown in FIG. 5 is divided into regions of each structure (whole breast region, mammary gland region, fat region, greater pectoral muscle region, implant region, and missing region (non-breast region)) as shown in FIG. be able to. Note that whether or not an implant is embedded in the breast of the patient is known from the patient to the photographer before imaging, so that it can be determined whether or not the breast image includes an implant during imaging.

  First, the region dividing unit 200 divides a breast image into a breast region and a missing region using, for example, a method described in JP-A-2005-65855. Since the background missing region exhibits a particularly high density on the image, the peak appearing on the high density side in the density histogram of the entire image corresponds to the background missing region. The region dividing unit 200 divides the breast image into a breast region and a missing region by performing binarization processing using a value obtained by subtracting a certain value from the peak value as a threshold value. Alternatively, a search may be performed from the high density side in the density histogram, and binarization processing may be performed using a point that first becomes a predetermined value or less as a threshold value.

  Next, the region dividing unit 200 extracts a skin line that is an outline of the breast region. A skin line can be extracted by sequentially searching for a boundary point between a breast region and a missing region and connecting the searched pixels.

  On the other hand, for the large pectoral muscle region, the edge between the pectoral muscle region and the fat region has a relatively clear edge, so scanning with a differential operator from the skin line toward the chest wall side has a large differential value. A point is extracted as a boundary point of the greater pectoral muscle region. Then, a curve connecting the extracted boundary points is calculated, and the chest wall side (on the opposite side to the blank region) with respect to the curve is detected as the greater pectoral muscle region.

  Then, the region dividing unit 200 calculates a threshold value for separating the mammary gland and the fat region from the density values of the greater pectoral muscle region and its neighboring fat region. By setting parameters so that this threshold value is a slightly larger value, it is possible to reliably extract pixels composed only of adipose tissue. Based on this threshold value, the breast region is divided into a mammary gland region and a fat region.

  Depending on the breast image, the greater pectoral muscle region may not exist. Therefore, more simply, without extracting the great pectoral muscle region, a known threshold value determination method (such as discriminant analysis) is used to perform threshold processing on the pixel value to make the breast region a mammary gland region. You may make it divide | segment into a fat area | region.

  Furthermore, the region dividing unit 200 calculates a threshold value for extracting an implant region in the breast region. Here, the implant is made of silicon or the like, and has a relatively high luminance (that is, low density) in the breast image. For this reason, the region dividing unit 200 sets a threshold value lower than the average density value of the fat region, and extracts pixels having a density lower than the threshold value, thereby extracting the implant region.

  As shown in FIG. 5, the implant has a shape clearly different from other tissues in the breast region. For this reason, a template having the shape of an implant may be used, and an implant region may be extracted by template matching using this template.

  The image processing unit 202 analyzes the breast image, calculates pixel values and contrast values in the breast region, and sets image processing conditions for image processing to be performed on the breast image. At this time, a histogram analysis is performed using only pixels other than the implant region in the breast region, for example, pixels in the breast region or pixels having a breast content in the breast region equal to or higher than a predetermined threshold, and image processing conditions are set. Set up. Note that. The image processing condition is set by determining the gradation shift amount so that the calculated pixel value of the breast region becomes a predetermined value, or by determining the gradient of the gradation according to the calculated contrast value (level). Key parameters). Other parameters such as a density parameter that determines the brightness of the entire breast image, a frequency processing parameter that sets a frequency processing condition, and a noise removal parameter that sets a noise removal condition are set. Further, the intensity of the dynamic range compression process is set as a dynamic range parameter so that overexposure and underexposure do not occur in pixel values in the breast region. The image processing unit 202 performs image processing on the breast image according to an image processing condition including various parameters that have been set, and generates a processed image. In addition, since the lesion cannot be confirmed in the tissue overlapping with the implant region, there is no problem even if the implant region of the breast image is blown out by image processing.

  Further, the image processing unit 202 converts the implant region so as to have a predetermined density. Specifically, the pixel value of the implant region is converted so that the concentration is higher than that of the fat tissue or the mammary gland tissue.

  The CPU 12 functions as the area dividing unit 200 and the image processing unit 202 of the radiation image processing apparatus 10 by executing the image processing program.

  Next, processing performed in the present embodiment will be described. FIG. 7 is a flowchart showing processing performed in the present embodiment. When imaging of the breast is completed and a breast image is acquired, the CPU 12 starts processing, divides the breast image into regions (step ST1), and extracts an implant region from the breast image (step ST2). Then, the CPU 12 sets an image processing condition using pixels in a region other than the implant region (image processing condition setting considering the implant region, step ST3), and performs image processing on the breast image according to the set image processing condition. (Step ST4), and further, the density of the implant region is converted (step ST5) to generate a processed breast image. The CPU 12 transmits the processed breast image to the image DB 44 (step ST6), and ends the process.

  Thereafter, in accordance with an instruction from the terminal device 46, the breast image stored in the image DB 44 is transmitted to the terminal device 46 and used for interpretation by a doctor.

  As described above, in the present embodiment, an implant region is extracted from a breast image including an implant, and image processing is performed on the breast image in consideration of the implant region. For this reason, even if the breast image includes an implant, image processing can be appropriately performed on the breast image.

  Further, by setting image processing conditions for image processing based on regions other than the implant region in the breast region, image processing is performed so that the breast region has high image quality without being affected by the implant region. be able to.

  Further, by converting the implant region to a predetermined concentration, the implant region does not become brighter, and thus the observer does not feel dazzling when displaying the processed breast image.

  In the above embodiment, image processing conditions are set based on regions other than the implant region in the breast region. However, when the implant region is relatively small, the implant region may not be considered. is there. For this reason, the ratio of the implant area to the breast area may be calculated, and the image processing condition considering the implant area may be set only when the calculated ratio is larger than a predetermined threshold value.

  In some cases, a breast image including an implant is compared with a past breast image of the same patient whose imaging time is different. In such a case, the same image processing condition is set so that the two breast images look the same based on the region other than the implant region in the past breast image, and the set image processing condition is set. Thus, it is preferable to perform image processing on two breast images. When the past breast image does not include an implant, the two breast images may be subjected to image processing according to the image processing conditions set based on the current breast image including the implant. Furthermore, using either the image processing condition obtained from the breast image including the current implant or the image processing condition obtained from the breast image not including the past implant, the past breast image and the current breast image are used. You may make it select whether to perform image processing.

  In addition, when the implant is embedded only in one of the left and right breasts, image processing conditions are set based on the breast image not including the implant, and image processing is performed on both breast images according to the set image processing conditions. May be applied. Conversely, image processing conditions may be set based on the breast image including the implant, and image processing may be performed on both breast images according to the set image processing conditions.

  The present invention is not limited to the above examples, and it goes without saying that various improvements and modifications may be made without departing from the scope of the present invention.

10 radiation image processing device 12 central processing unit (CPU)
14 Main Memory 18 Communication Interface 20 Hard Disk Device 28 Monitor Device 30 Keyboard 32 Mouse 40 Mammography Camera 44 Image DB
200 Region division unit 202 Image processing unit

Claims (6)

An implant region extracting means for extracting a region of the implant from a breast image including the implant;
Image processing condition setting means for setting image processing conditions for image processing based on an area other than the implant area in the breast image;
Wherein by the image processing conditions for the breast images to facilities the image processing, the image processing means and the radiographic image processing apparatus characterized by comprising a further converting the implant region to a predetermined concentration. An implant region extracting means for extracting a region of the implant from a breast image including the implant;
Upon comparing the breast image including the implant and other breast image, the image processing conditions for image processing on the breast image and said other breast image containing the implant, set based on the region other than the implant area Image processing condition setting means for
An image processing means for performing image processing on the breast image according to the image processing conditions. Extracting a region of the implant from a breast image containing the implant;
Based on regions other than the implant region in the breast image, set image processing conditions for image processing,
The image processing condition by and facilities the image processing, further radiographic image processing method characterized by converting the implant region to a predetermined concentration with respect to the breast image. Extracting a region of the implant from a breast image containing the implant;
Upon comparing the breast image including the implant and other breast image, the image processing conditions for image processing on the breast image and said other breast image containing the implant, set based on the region other than the implant area And
A radiation image processing method, wherein image processing is performed on the breast image according to the image processing conditions. Extracting a region of the implant from a breast image including the implant;
A procedure for setting image processing conditions for image processing based on regions other than the implant region in the breast image;
Wherein said image processing conditions for the breast images to facilities the image processing, the radiographic image processing program for causing further the implant region to execute the steps of converting a predetermined concentration to the computer. Extracting a region of the implant from a breast image including the implant;
Upon comparing the breast image including the implant and other breast image, the image processing conditions for image processing on the breast image and said other breast image containing the implant, set based on the region other than the implant area And the steps to
A radiation image processing program for causing a computer to execute a procedure for performing image processing on the breast image according to the image processing conditions.

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