JP5145170B2 - Medical image evaluation device - Google Patents

Description

The present invention relates to relates to the evaluation equipment of the medical image, in particular a medical image such as captured breast image is evaluated whether or not useful in diagnostic techniques.

[Breast radiography]
In breast cancer image diagnosis by mammography (mammography), a difference in X-ray absorption between a lesion and normal tissue is extremely small, and a diagnosis of a minute lesion is required. Therefore, a high-quality image is required. Among the factors affecting the image quality, the influence of the imaging technique is particularly great, and the poor compression of the whole mammary gland tissue at the time of positioning and imaging can cause a deep lesion or a light minute lesion to be overlooked.

  On the other hand, (1) The breast size, shape, mammary gland density, and body type of the examinee are all different, and (2) Mammography is a special imaging in which the mammary gland is fully expanded and compressed. Because of this, there was a problem that mammography was very difficult.

  That is, mammography has the following differences and difficulty in imaging from general imaging such as chest and bone.

<Differences between mammography and general radiography>
(1) Compression imaging In mammography, it is necessary to depict a structure (tumor) with a small difference in X-ray absorption that does not exist in other parts. Therefore, the mammary gland is compressed with the breasts expanded, so that the mammary glands do not overlap.

(2) Imaging of soft tissue In order to depict the entire mammary gland, it is necessary to move the movable tissue sufficiently to the fixed tissue side. There is a problem in that a defective area is generated simply by sandwiching a breast with a compression plate.

<Difficulty of mammography>
Since mammography has the above-mentioned specialities, not only the points of positioning in general radiography (the standing position and orientation of the examinee, the imaging range), but also (a) imaging with the mammary gland sufficiently expanded, (b) There are so many points to be aware of in order to minimize the occurrence of missing areas.

  Breasts are said to have the largest individual differences among human organs, and it is necessary to devise positioning according to individual differences such as breast size, shape, and mammary gland content, as well as the physical size of the examinee. .

  For the above reasons, mammography is very difficult and advanced imaging techniques are required.

[Positioning evaluation of medical images]
The basis of positioning in mammography is to properly compress and stretch the entire mammary tissue where the lesion occurs.

  Conventionally, an anatomical structure is extracted from a captured medical image, and whether or not the medical image is appropriate for diagnosing the diagnostic region captured in the medical image on the basis of the extracted structure. An apparatus for determining and displaying the determination result has been proposed (Patent Document 1).

  In this patent document, the quality of a breast image is judged based on the area ratio of the pectoralis major region to the whole breast area, or the breast is determined based on the positional relationship between the position of the lower end of the pectoral muscle region and the nipple. A method for determining the quality of an image is disclosed.

  By the way, according to the NPO corporation mammography screening accuracy management central committee facility image evaluation, the positioning is evaluated with a total of 6 points, 4 points, and a total of 24 points. Evaluation items are shown in [Table 1] below.

FIG. 11 is cited from Non-Patent Document 1 and shows the site of each item in the above [Table 1].
JP 2007-105264 A Author: Tokiko Endo, Publisher: Medical Science, p.18

[Problem 1]
The quality of the positioning (medical image) needs to be comprehensively evaluated based on the plurality of items.

  However, the method described in Patent Document 1 focuses only on the evaluation items relating to the greater pectoral muscle, and has a problem that it is difficult to obtain sufficient accuracy for positioning evaluation.

  For example, even if the depiction of the greater pectoral muscle is appropriate, the depiction of the mammary gland and nipple is not always appropriate. In breast imaging, it is necessary to take an image with the movable tissue properly moved to the fixed tissue, but if this movement is insufficient, the fat behind the mammary gland is not depicted and the mammary gland is behind the pectoral muscle. Hidden or nipples tend to face down. That is, even if the evaluation items (the position of the pectoralis muscle, the size) corresponding to the specific structure are good, there is a possibility that the case where the positioning is inappropriate as a whole cannot be evaluated correctly.

  In addition, it is difficult for the following people to depict the pectoralis muscle properly, and it is said that it will place a heavy burden on the examinee if the pectoral pectoral muscle is forcibly drawn.

a) People with bent backs (old people, etc.)
b) Person who does not raise his arm
c) Person with sternum in front
d) People who are lean and have large breasts In such cases, it is important to achieve proper positioning as a whole at the expense of rendering the pectoralis major muscle, but the method described in Patent Document 1 is inappropriate. May be evaluated as a correct image. In other words, even if the positioning is appropriate as a whole, it is impossible to consider the case where the value of a specific evaluation item is beyond the normal range due to the circumstances of the examinee (body shape, breast size, etc.).

[Problem 2]
Since the positioning technique varies greatly depending on the photographer, it is desirable to be able to weight which evaluation item is important depending on the photographer and the facility. For example, in the case of a photographer who knows an item that is not good, the accuracy of positioning evaluation is improved by raising the evaluation score for a specific evaluation item. In the method described in Patent Document 1, only the quality of the positioning is determined based on a predetermined evaluation criterion, and therefore, an important item for each photographer cannot be reflected.

The present invention has been made in view of such circumstances, and can improve the accuracy of evaluation of positioning at the time of photographing a medical image, and can perform comprehensive evaluation of positioning according to a request from a photographer or the like. an object of the present invention is to provide an evaluation equipment of the medical image.

In order to achieve the above object, a medical image evaluation apparatus according to claim 1, an image acquisition unit that acquires a medical image obtained by radiographing a region including a diagnosis target region of a subject, and analyzes the acquired medical image A structure extraction means for extracting a plurality of anatomical structures, and evaluating a plurality of positioning evaluation items at the time of taking the medical image based on the extraction results of the extracted structures, and scoring for each evaluation item Scoring means for each evaluation item , wherein the medical image is a breast image taken by a mammography apparatus, and the structure extraction means includes at least a breast, a mammary gland, and a pectoral muscle as the structure to be extracted. And the scoring means for each evaluation item is used for the first positioning evaluation item related to the left-right symmetry of the breast image, and for rendering the teat in the breast image. A second positioning evaluation item, a third positioning evaluation item related to the rendering of the pectoralis major muscle in the breast image, and a fourth positioning evaluation item related to the drawing of the adipose tissue behind the mammary gland in the breast image A plurality of evaluation items of the fifth positioning evaluation item related to the depiction of the lower abdominal tissue in the breast image and the sixth positioning evaluation item related to the extensibility of the mammary gland in the breast image. It is characterized by evaluating and scoring each .
The medical image evaluation apparatus according to claim 2 includes an image acquisition unit that acquires a medical image obtained by radiographing a region including a diagnosis target region of a subject, and an anatomical structure obtained by analyzing the acquired medical image. A plurality of structure extracting means for extracting, and a plurality of evaluation item scoring means for evaluating a plurality of positioning evaluation items at the time of photographing the medical image based on the extraction result of the extracted structures and scoring for each evaluation item The medical image is a breast image taken by a mammography apparatus, and the structure extraction means includes at least a plurality of breasts, mammary glands, pectoral muscles, and nipples as the structure to be extracted. And the scoring means for each evaluation item is related to the first positioning evaluation item related to the left-right symmetry of the breast image and the rendering of the nipple in the breast image. A second positioning evaluation item, a third positioning evaluation item related to the rendering of the pectoralis major muscle in the breast image, a fourth positioning evaluation item related to the drawing of adipose tissue behind the mammary gland in the breast image, The plurality of structures of the fifth positioning evaluation item related to the depiction of the abdominal tissue under the breast in the breast image and the sixth positioning evaluation item related to the extensibility of the mammary gland in the breast image It is characterized in that a plurality of evaluation items corresponding to each is evaluated and scored.

  That is, by positioning the positioning at the time of photographing for each of a plurality of evaluation items, the plurality of evaluation items can be comprehensively evaluated, and the accuracy of positioning evaluation can be improved.

In the evaluation apparatus of the medical image according to claim 1 or 2 as shown in claim 3, comprising an evaluation itemized weight setting means for respectively setting an arbitrary weights to the plurality of evaluation items, by the evaluation items The scoring means weights the score for each evaluation item scored based on the extraction result of the extracted structure based on the set weight for each evaluation item, and scores for each of the plurality of evaluation items It is characterized by performing.

  As a result, the score for each evaluation item can be weighted according to which evaluation item is emphasized by the photographer or the radiographer, and a comprehensive evaluation of positioning according to the request of the photographer or the like can be performed. .

In the evaluation apparatus of the medical image according to any one of claims 1-3 as indicated in claim 4, wherein the evaluation items by scoring means by scoring and a plurality of evaluation items different points, and the total score An image determining means for determining whether or not the medical image is appropriately captured based on at least one of them is provided.

  The image determination means may determine whether a medical image is obtained when the evaluation score does not reach the reference point for each evaluation item or the total score does not reach the reference point even in one item among the scores for the plurality of evaluation items. It can be determined that the image is not properly captured.

According to a fifth aspect of the present invention, in the medical image evaluation apparatus according to any one of the first to fourth aspects, the scores for each of the plurality of evaluation items scored by the scoring means for each evaluation item, and the total points thereof It is characterized by providing a presentation means for presenting at least one of them.

  Thus, the photographer can check which evaluation item of the positioning is low, which positioning item should be noted, and the like.

In the evaluation apparatus of the medical image according to any one of claims 1-5 as indicated in claim 6, wherein the evaluation items by scoring means by scoring and a plurality of evaluation items different points, and the total score A warning means for generating a warning prompting re-photographing based on at least one of them is provided.

  The warning means may not only display a warning prompting re-photographing on the screen but also transmit the warning by voice.

In the evaluation apparatus of the medical image according to any one of 6 claim 1 as indicated in claim 7, and the medical image, a plurality of which are scored by the evaluation items by scoring means against said medical image It is characterized by comprising a recording means for recording in association with at least one of the score for each evaluation item and the total score.

  The information recorded in the recording means can be used, for example, when searching for medical images in the order from the lowest evaluation score for positioning, and can be used for a study session of the photographer.

In the evaluation apparatus of the medical image according to claim 7, as shown in claim 8, comprising a photographer information means for obtaining photographic identification information for identifying the photographer who photographed medical images in which the acquired, the The recording means records the acquired photographer identification information in association with the medical image.

  The information recorded in the recording means can be used for, for example, calculation of the average score of positioning evaluations for each photographer, and thereby grasping positioning defects and improvement points for each photographer. it can.

In the evaluation apparatus of the medical image according to claim 7 or 8 as shown in claim 9, comprising a shooting date obtaining means for obtaining photography date of the acquired medical images, the recording means is associated with the medical image The acquired shooting date is recorded.

  The information recorded in the recording means can be used, for example, for calculating the transition of the evaluation score of the positioning for every month, thereby easily grasping the improvement effect of the positioning technique.

In the evaluation apparatus of the medical image according to claim 1 as shown in claim 109, wherein the evaluation items by scoring means, the area ratio of the right and left breasts extracted from the breast image, the left and right breast The symmetry is evaluated on the basis of the area ratio of the left and right pectoralis major muscles, and the evaluation of the first positioning evaluation item is scored by the sum thereof.

In the evaluation apparatus of the medical image according to any one of 10 claims 1 as shown in claim 11, wherein the evaluation items by scoring means, nipple of the left and right from the breast image based on whether or not each extracted The evaluation of the second positioning evaluation item is scored. If the nipple is not extracted to the side, the nipple may overlap with the mammary gland and may be mistaken for an abnormality in the mammary gland, or a lesion directly under the nipple may be overlooked.

In the evaluation apparatus of the medical image according to any one of claims 1 to 11 as shown in claim 12, wherein the evaluation items by scoring means, the lower end position of the pectoralis major muscle extracted from the breast image, pectoralis major The evaluation of the third positioning evaluation item is scored based on the shape of the breast and the area ratio of the pectoralis major to the breast. For example, the lower pectoral position of the pectoral muscle is shown to the level of the nipple, the pectoral muscle has a slightly convex arc, and is not too large relative to the size of the breast. If too much is put in, the pressure on the mammary gland will weaken or the entire mammary gland will not enter the irradiation field.

In the evaluation apparatus of the medical image according to any one of 12 claims 1 as shown in claim 13, wherein the evaluation items by scoring means, pectoralis major boundaries and chest wall side of the image extracted from the breast image The evaluation of the fourth positioning evaluation item is scored based on the length of the line composed of the ends and the length of the mammary gland that is extracted from the breast image. Thereby, it is evaluated that the adipose tissue behind the mammary gland is depicted without interruption (whether the whole mammary gland is depicted).

The medical image evaluation apparatus according to any one of claims 1 to 13 , wherein the scoring unit for each evaluation item includes a detection unit for detecting a skin line of the breast image, as shown in claim 14. The fifth positioning evaluation item is scored based on the detected shape of the skin line. This evaluates whether abdominal tissue is contained (whether the lower end of the mammary gland is within the imaging range).

In evaluation assistance device of the medical image according to any one of claims 1 to 14 as shown in claim 15, wherein the evaluation items by scoring means calculates a mammary gland in contrast value of the mammary gland extracted from the breast image A calculating means for scoring the evaluation of the sixth positioning evaluation item based on the area ratio between the breast and the mammary gland excluding the great pectoral muscle extracted from the breast image, and the calculated intramammary contrast value; It is characterized by doing. This evaluates whether the mammary gland is sufficiently compressed and extended. In addition, there is a correlation between the area ratio of the breast and mammary gland excluding the great breast muscle (mammary gland ratio) and the contrast value in the mammary gland. It seems to be lacking.

  According to the present invention, scoring is performed for each of a plurality of evaluation items, so that the accuracy of positioning evaluation at the time of taking a medical image can be improved. Further, depending on which evaluation item is emphasized depending on the photographer or the facility, the score for each evaluation item can be weighted, and the overall evaluation of positioning according to the request of the photographer or the like can be performed.

Hereinafter, preferred embodiments of the evaluation equipment in a medical image will be described according to the present invention with reference to the accompanying drawings.

[Device configuration]
FIG. 1 is a system configuration diagram including a medical image evaluation apparatus according to the present invention.

  This system includes a medical image evaluation device 10 according to the present invention, a photographing device 40 for photographing a medical image installed in a medical facility, a console 42 for operating the photographing device 40, and the photographing device 40. It is composed of an image database (image DB) 44 for storing taken medical images and the like.

  The evaluation device 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, a control program for the device, and a work area during program execution. A main memory 14, a graphic board 16 for controlling display on 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 Detects key operations on a medical image evaluation program, various application software including an image analysis program, a hard disk device 20 that stores a database (DB) of positioning evaluation results, which will be described later, a CD-ROM drive 22, and a keyboard 30 CPU1 as an instruction input And a mouse controller 26 that detects the state of the mouse 32 as a position input device and outputs signals such as the position of the mouse pointer on the monitor device 28 and the state of the mouse 32 to the CPU 12. ing.

  In this embodiment, the imaging device 40 is a mammography imaging device that radiographs a breast image.

<Mamography device>
FIG. 2 is a configuration diagram showing an embodiment of an imaging apparatus (mammography imaging apparatus) 40.

  The mammography imaging apparatus 40 radiates radiation to the breast 112 of the subject 118, the base 112 installed in an upright state, the arm member 116 fixed to the pivot shaft 114 disposed in the substantially central portion of the base 112. A radiation source storage unit 120 that stores a radiation source that exposes the radiation and that is fixed to one end of the arm member 116, and a solid state detector that acquires radiation image information by detecting radiation that has passed through the breast are stored. An imaging table 122 fixed to the other end of the member 116 and a compression plate 124 that compresses the breast against the imaging table 122 are provided.

  The arm member 116, to which the radiation source storage unit 120, the imaging table 122, and the compression plate 124 are connected, is configured so that the imaging direction with respect to the breast of the subject 118 can be adjusted by rotating in the arrow A direction about the rotation axis 114. The The compression plate 124 is disposed between the radiation 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 radiation source storage unit 120 is provided with a face guard sheet 128 made of a member that blocks radiation in order to protect the vicinity of the face of the subject 118 from radiation exposure. The base 112 displays imaging information such as the imaging region and imaging direction of the subject 118, ID information of the subject 118, and the like, and if necessary, until the compressed state of the breast by the compression plate 124 is released. A display 130 for displaying information related to the remaining compression time is provided.

  FIG. 3 is an internal configuration diagram of the imaging stand 122 in the mammography imaging apparatus 40, and shows a state where a breast 136 that is an imaging region 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.

  In the imaging table 122, radiation image information based on the radiation X transmitted through the breast 136 is accumulated and output as an electrical signal. The solid-state detector 140 (radiation image information detector) is stored and recorded in the solid-state detector 140. In order to read the radiation image information, the reading light source unit 142 that irradiates the solid detector 140 with the reading light, and the radiation that has passed through the breast 136 to determine the exposure time that is one of the exposure conditions of the radiation X A dose detector (radiation detector for automatic exposure control, hereinafter referred to as “AEC (Automatic Exposure Control) sensor 144”) for detecting a dose of X and an unnecessary charge accumulated in the solid state detector 140 are removed. And an erasing light source unit 146 for irradiating the solid state detector 140 with erasing light.

  The solid state detector 140 is a direct conversion type and optical readout type radiation solid state detector that accumulates radiographic image information based on the radiation X transmitted through the breast 136 as an electrostatic latent image and reads it 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 solid state detector 140, By moving a line light source in which LED chips are arranged in a direction orthogonal to the extending direction of the linear electrode, which is the second conductive layer of the solid state detector 40, in the extending direction (arrow C direction) of the linear electrode. The entire surface of the solid state detector 140 is exposed and scanned.

  The AEC sensor 144 is configured to be movable in the direction of arrow C along the solid detector 140 so that the dose of the radiation X 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.

  The radiation X transmitted through the breast 136 is detected as radiation image information by the solid state detector 140, and a radiation image of the breast 136 is formed by a radiation image forming unit (not shown). On the other hand, when the radiation image information is read, the solid state detector 140 is irradiated with erasing light from the erasing light source unit 146, whereby the erasing process of the remaining radiation image information is performed.

  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. And the medical image photographed by the photographing device 40 are stored in the image DB 44 in association with each other.

  The medical 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, In addition to the photographer ID, information such as a photographing date, a photographing facility, and a photographing part is recorded.

  Next, the positioning and imaging procedures of the subject 118 will be described.

  The photographer (radiologist) sets the mammography apparatus 40 to 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 photographing in the head-to-tail direction (CC) 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 necessary for photographing, the movement of the compression plate 124 is stopped and photographing permission is output.

  Therefore, when the radiologist turns on an exposure switch (not shown), radiography 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 plurality of imaging such as CC imaging, ML imaging, and MLO imaging of the left and right breasts 136 are performed on one subject 118.

  Returning to FIG. 1, the evaluation apparatus 10 acquires the acquired image (breast image) directly from the imaging apparatus 40 or from the image DB 44 via the network 50 and the communication I / F 18, and this acquisition. Analyzing the breast image to extract anatomical structures (whole breast area, mammary gland area, fat area, pectoral muscle area, nipple area), and extraction results of these extracted structures This is a means to evaluate whether breast images have been properly captured based on the evaluation item, which evaluates the positioning at the time of radiography according to multiple evaluation items (scores) and outputs the evaluation results for each item Scoring means.

  The evaluation apparatus 10 includes a presentation means for presenting the score for each of the plurality of evaluation items scored by the scoring means for each evaluation item, and a total score thereof to the monitor device 28, and a plurality of evaluation items for each of the plurality of evaluation items for positioning. Based on the score and the total score, image determination means for determining whether or not a breast image is properly captured, and when it is determined that a breast image is not properly captured, the photographer is re-photographed. Warning means for displaying an urging warning on the monitor device 28 or generating a voice message is further provided.

  Furthermore, the evaluation apparatus 10 creates a DB that associates the score for each of the plurality of evaluation items and the total score (evaluation result) of the positioning scored by the evaluation item scoring means with the breast image to be evaluated. DB creation means for recording is provided.

  Further, the DB creation means can create a DB in which a subject ID indicating a subject and a photographer of the breast image, a photographer ID, and a photographing date are associated with the breast image. As described above, when the breast image (medical image) is a DICOM file, the subject ID, the photographer ID, and the photographing date can be acquired from the header. When the subject ID and the photographer ID are not recorded in the header of the image file, the subject ID, the photographer ID, etc. are input by the keyboard 30 or the mouse 32, and the DB creating means And a DB in which a breast image is associated with each other.

  The CPU 12 functions as each unit of the evaluation apparatus 10 by executing a medical image evaluation program. Further, in this embodiment, the DB created by the DB creating means is stored in the hard disk device 20, but may be stored in the image DB 44.

[Method for evaluating medical images]
Next, a medical image evaluation method will be described. FIG. 4 is a diagram showing a procedure for evaluating a medical image.

  In FIG. 4, first, a medical image (breast image) to be evaluated is captured (FIG. 4A). Subsequently, the captured breast image is analyzed, and anatomical structures (whole breast region, mammary gland region, fat region, greater pectoral muscle region, nipple region) are extracted from the breast image (FIG. 4B).

  Here, the “anatomical structure” refers to a structure such as an organ constituting a human body such as the pectoralis major muscle or the breast. Since each structure appears on the image with its own density value, shape, and position, it can be extracted according to information such as the density value, shape, and position.

  FIG. 5A shows an original image of a breast image, and FIG. 5B shows an image in which regions are divided for each structure extracted from the original image.

Specifically, each structure is extracted in the following order. (For details, see Japanese Patent Application Laid-Open Nos. 2005-65855 and 2006-68373 filed by the present applicant)
(i) The image is divided into a breast region and a blank region. Since the missing area has 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 missing area. Binarization processing is performed using a value obtained by subtracting a certain value from the peak value as a threshold value, thereby dividing the breast region and the missing region.

  (ii) Extracting the outline of the breast region (hereinafter referred to as skin line). A boundary point between the breast region and the unexposed region is sequentially searched, and a skin line is extracted by connecting the searched pixels.

  (iii) Extract the greater pectoral muscle region. Since the border between the pectoral muscle region and the fat region is relatively clear, the differential operator scans from the skin line toward the chest wall, and the point with a large differential value is the boundary point of the pectoral muscle region. Extract as A curve connecting the extracted boundary points is calculated, and the chest wall side (opposite to the unplugged region) is extracted as a greater pectoral muscle region with respect to the curve.

  (iv) A threshold for extracting the mammary gland region is calculated from the concentration values of the greater pectoral muscle region and the fat region in the vicinity thereof, and the mammary gland region is extracted.

  (v) Detect the nipple. A smoothed skin line obtained by smoothing the skin line is acquired, and a nipple is detected based on the distance between the smoothed skin line and the skin line. If it cannot be detected, the highest point is taken as the nipple.

  By extracting multiple structures, it is possible to grasp the characteristics (position, shape, size, etc.) of each structure from the relationship with other structures, and perform subsequent positioning evaluation with high accuracy. Can do.

  Next, breast image evaluation (scoring for a plurality of evaluation items) is performed based on the extraction result of the extracted structure (FIG. 4C). Evaluation of each positioning item is performed as shown below.

(1) Evaluation of left-right symmetry Assess the overall breast symmetry (2 points), mammary gland symmetry (1 point), and pectoral muscle symmetry (1 point), and total the points (4 points maximum) Evaluate left-right symmetry. If the positioning is the same on the left and right, the area of each structure in the left and right breast images should be approximately the same, and the symmetry is evaluated based on the area ratio of the left and right as shown in the following equation.

  In the above [Expression 1], (Area A) represents the area of each structure in the right breast image, and (Area B) represents the area of each structure in the left breast image. The symmetry of the whole breast is scored by the result of the above formula x2. In addition, when the evaluation score calculated by the formula [1] becomes negative, the score is 0.

(2) Evaluation of the laterality of the nipple. If the nipple can be detected, 2 points will be given, and if it cannot be detected, the nipple will be completely contained within the nipple. Evaluation is performed on each of the left and right breasts, and the evaluation is performed with the total score (full score of 4).

(3) Evaluation of greater pectoral muscles The position of the lower pectoral muscle (1 point), shape (0.5 points), and area (0.5 points) were evaluated, and the total points (2 points on each side, 4 points in total) ) To evaluate the pectoralis major muscle. First, it is the position of the lower end of the greater pectoral muscle, but it is desirable that it is reflected almost to the height of the nipple. Based on the position of the lower end of the pectoralis muscle and the nipple, evaluation is performed based on the following formula.

  Here, (length A) represents the length from the upper end of the image to the lower end of the pectoralis major muscle, and (length B) represents the length from the upper end of the image to the nipple. In addition, when the evaluation score calculated by the formula [2] becomes negative, it is set to 0 point.

  Further, it is desirable that the shape of the greater pectoral muscle is a convex shape. If the pectoral muscle is concave, it means that the pectoral muscle has not been properly moved inward during positioning, or that the pectoral muscle has been tightened by raising or abducting the subject's upper arm. Since the shape of the greater pectoral muscle can be expressed by a quadratic function, it can be determined whether the shape is convex or concave with respect to the chest wall side based on the coefficient. The shape evaluation point is calculated as 0.5 point for the convex shape and 0 point for the concave shape.

  As described in Patent Document 2, the area of the greater pectoral muscle is desirably in the range of 10% to 50% with respect to the entire breast area. Therefore, the area evaluation score is calculated as 0.5 point when it is within the range and 0 point when it is outside the range.

(4) Evaluation of the post-mammary space This is an evaluation item of whether the entire mammary gland is depicted, and analyzes whether fat is depicted behind the mammary gland. Specifically, the evaluation of the post-mammary space is performed by the following equation based on the overlap between the mammary gland and the line indicated by the dotted line in FIG. 6 (the border of the great pectoral muscle and the image end on the chest wall side).

  Here, the length of the dotted line in FIG. 6 is (length A), and the length excluding the length of the portion overlapping the mammary gland on the dotted line is (length B (= B1 + B2)). Moreover, an evaluation score is calculated for each of the left and right, and the post-mammary space is evaluated with the total score (full score of 4).

(5) Evaluation of the lower part of the breast Whether or not abdominal tissue is contained can be judged from the shape of the breast. Specifically, the determination is made based on whether the skin line has reached the lower end of the image. If it has reached it, it will be 2 points, otherwise it will be 0 point. An evaluation score is calculated for each of the left and right, and the lower part of the breast is evaluated using the total score (full score of 4).

(6) Evaluation of mammary gland extensibility Mammary gland extensibility is evaluated by calculating the area ratio of the mammary gland region to the entire breast (hereinafter referred to as “mammary gland ratio”) and the intramammary contrast value. Here, the mammary gland ratio is calculated by the following equation.

[Equation 4]
Breast ratio = (Area of the mammary gland area) / (Area of the entire breast excluding the great pectoral muscle)
Further, the intramammary contrast can be calculated from a local dispersion value in the mammary gland region as described below.

  First, as shown in FIG. 7, a small square area centered on pixels belonging to the mammary gland area 70 is set as a local area 80. The size of the local region 80 is set to a size that includes both the mammary gland structure and the background. Empirically, it is preferable that the size is about 5 × 5 mm. Then, the entire mammary gland region 70 is scanned as indicated by arrows in FIG.

  When the local region 80 is set, the variance of the signal value is calculated in each local region 80 in order to calculate the contrast value of the mammary gland structure in the local region 80. Note that it is not necessary to calculate the variance value for all the pixels in the mammary gland region 70, and it is sufficient to empirically have about 500 points.

  In addition, if the local region 80 includes the blank region 78, the fat region 74 near the skin, or the pectoral muscle region 76, the variance value may become extremely large. Only signal values of fat regions 72 other than 70 and the vicinity of the skin are used, and signal values of other regions are excluded.

  By calculating the variance value in the local region 80 as described above, it becomes possible to consider the local mammary gland structure and the legibility of the lesion. Further, by calculating not only the signal value in the mammary gland region 70 but also the signal value in the fat region 72 other than the vicinity of the skin, it is possible to consider the contrast between the mammary gland and the surrounding region (the fat region 72). It becomes.

  In addition, in order to calculate the contrast value in the local region, the variance of the signal value in the local region is calculated. However, the method is not limited to the method using the variance, and the difference between the maximum value and the minimum value The difference between the average signal values of each class when it is divided into two classes by the discriminant analysis method may be obtained.

  Then, an intramammary contrast value is calculated. When the variance value is calculated in each local region 80, the contrast value in the mammary gland of the image is calculated by integrating them. Here, a median value of a plurality of dispersion values is calculated and used as an intramammary contrast value.

  As a result of the study by the present inventor, it was found that there is a correlation between the mammary gland ratio and the intramammary contrast value, as shown in FIG. And, in the case of intramammary contrast below a certain value with respect to the mammary gland ratio, it is considered that the mammary gland is not sufficiently stretched or compressed. Therefore, the average value and standard deviation of the intramammary contrast value for each mammary gland ratio are calculated from a large number of images in advance, and the standard deviation corresponding to the mammary gland ratio calculated by the equation [4] and the intramammary contrast value are calculated. The relationship evaluates the extensibility of the mammary gland according to the following [Expression 5], [Expression 6], and [Expression 7].

[Equation 5]
Intramammary contrast value <mean value-(3 x standard deviation)
[Equation 6]
Average value− (3 × standard deviation) ≦ Contrast value in mammary gland <Average value−standard deviation [Equation 7]
Average value−standard deviation ≦ contrast value in the mammary gland In the case of the above [Equation 5], the extensibility of the mammary gland is 0 point, in the case of the [Equation 6], 1 point, and in the case of the [Equation 7], Two points. An evaluation score is calculated for each of the left and right sides, and the extensibility of the mammary gland is evaluated by the total score (full score of 4).

  Since the image contrast changes depending on the X-ray exposure conditions, the average value and the standard deviation may be obtained for each exposure condition.

  FIG. 9 is a chart summarizing each positioning evaluation item and its evaluation score as described above, and shows a case where 6 items are 4 points in total and 24 points in total.

<Weighting for each evaluation item for positioning>
As shown in FIG. 10, for a plurality of positioning evaluation items, a large weight (a value larger than 1) is assigned to an important item, and a small weight (a value smaller than 1) is assigned to an unimportant item. Set the weight to be given.

  The weighting for each positioning evaluation item can be set as appropriate by an input means such as the keyboard 30. When weighting is set, the total weight set for each evaluation item is set to 6. According to this, when the score of all evaluation items is a perfect score, it can be set to 24 points regardless of weighting.

  The example shown in FIG. 10 is an example of weighting set for a photographer who is not good at pulling out the mammary gland, and the weight of the evaluation item of the post-mammary space is increased. Here, depending on the examinee, it may be impossible to draw the nipple directly to the side, so the weight of the evaluation item for the laterality of the nipple is reduced.

  The score obtained for each of the plurality of evaluation items for positioning is weighted by multiplying the weight for each evaluation item set as described above. When the weight of the evaluation item for the positioning that is emphasized is increased, the quality of the positioning of the evaluation item that is emphasized greatly affects the overall evaluation (total score). Therefore, the photographer needs a large weight to increase the total score. You will be more careful with the positioning of the assigned evaluation items.

  In this example, the weighting for each positioning evaluation item is set according to the photographer. However, the weighting is not limited to this, and may be set according to the radiographer, the imaging device, or the subject. .

<Determining the quality of positioning>
Based on the scores of the plurality of positioning evaluation items, the quality of the positioning is determined. For example, if the total score is less than 20 points and the total score is less than 20 points and one item out of 6 items is less than (full score / 2), it is judged as “dangerous for interpretation” as it is, Warning to prompt the user to re-shoot. Thus, the quality of the breast image can be accurately determined by making a comprehensive determination based on the total score and the score for each item.

  In addition, as described above, when weighting is performed for each evaluation item of a plurality of positioning, a weight may be applied when calculating the evaluation score of each item, or a weight may be applied when determining the quality of positioning. good.

  In the warning display, not only the re-photographing is promoted, but also a score for each of the plurality of evaluation items may be displayed so that it can be understood which item has a low score. In addition to displaying on the screen, it may be transmitted by voice.

<Application example>
According to the present invention, scoring is performed for each of a plurality of evaluation items, so that the accuracy of positioning evaluation at the time of taking a breast image can be improved, but the present invention is further used for improving the positioning technique. You can also.

  Specifically, at the time of registration of a breast image, a photographer ID (including the photographer's name), a DB in which the breast image and the positioning evaluation result are stored in association with each other, the following Is possible.

  (1) Make it possible to search for images in descending order of positioning evaluation score. It can be used for photographer study sessions.

  (2) Enter the photographer ID, extract the score or total score for each evaluation item registered corresponding to the photographer ID, and calculate the average score for each evaluation item and the average score of the total score And display. As a result, it is possible to grasp the wrinkles and improvement points for each photographer, and to evaluate the photographing technique for each photographer.

  (3) The photographer ID is input, and the score or total score for each evaluation item registered corresponding to the photographer ID is extracted every predetermined period (for example, one month). Then, the average score for each evaluation item and the average score of the total points for each month are calculated and displayed. According to this, the transition of the positioning evaluation score every month can be displayed, and the improvement effect of the positioning technique can be easily grasped.

<Others>
In this embodiment, as shown in [Table 1], a case has been described in which evaluation is performed on a total of 24 points, including 6 items as 4 evaluation points, as a plurality of evaluation items of a breast image. The type of items, the distribution of points for each evaluation item, and the method of assigning points are not limited to this embodiment.

  In addition, the positioning evaluation result presented on the monitor device 28 of the evaluation device 10, a warning prompting re-photographing, and the like can be confirmed on the console 42 of the photographing device 40, other terminals connected to the network 50, and the like. Also good.

  Furthermore, the present invention is not limited to breast images but can be applied to medical images of other parts. For example, a score may be given for each of a plurality of evaluation items (a lung field area, a slope of each of the left and right lung field regions, etc.) of a chest image as shown in Patent Document 1 and presented.

  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.

FIG. 1 is a system configuration diagram including a medical image evaluation apparatus according to the present invention. FIG. 2 is a configuration diagram showing an embodiment of an imaging apparatus (mammography imaging apparatus). FIG. 3 is an internal configuration diagram of a photographing stand in the mammography photographing apparatus. FIG. 4 is a diagram showing an evaluation procedure in the medical image evaluation method according to the present invention. FIG. 5A shows an original image of a breast image, and FIG. 5B shows an image in which regions are divided for each structure extracted from the original image. FIG. 6 is a diagram used for explaining the evaluation of the retromammary space. FIG. 7 is a diagram showing how a local region is set for a mammary gland region. FIG. 8 is a diagram showing the relationship between the mammary gland ratio and intramammary contrast value. FIG. 9 is a chart summarizing each evaluation item for positioning and its evaluation points. FIG. 10 is a chart showing an example of weights set for a plurality of positioning evaluation items. FIG. 11 is a diagram showing each part relating to the positioning evaluation item of the breast image.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Evaluation apparatus, 12 ... Central processing unit (CPU), 14 ... Main memory, 18 ... Communication interface, 20 ... Hard disk device, 28 ... Monitor device, 30 ... Keyboard, 32 ... Mouse, 40 ... Imaging device (mammography imaging device) ), 42 ... console, 44 ... image DB

Claims (15)

An image acquisition means for acquiring a medical image obtained by radiographing a region including a diagnosis target region of a subject;
A structure extraction means for analyzing the acquired medical image and extracting a plurality of anatomical structures;
A plurality of evaluation items for positioning at the time of photographing the medical image based on the extraction result of the extracted structure, and a scoring unit for each evaluation item for scoring for each evaluation item ,
The medical image is a breast image taken by a mammography apparatus,
The structure extracting means extracts at least a breast, a mammary gland, a great pectoral muscle, and a nipple as the structure to be extracted.
The scoring means for each evaluation item includes: a first positioning evaluation item related to left-right symmetry of the breast image; a second positioning evaluation item related to rendering of a nipple in the breast image; For the third positioning evaluation item related to the depiction of the pectoralis major muscle, the fourth positioning evaluation item related to the drawing of the adipose tissue behind the mammary gland in the breast image, and the abdominal tissue under the breast in the breast image A medical image characterized by evaluating a plurality of evaluation items among a related fifth positioning evaluation item and a sixth positioning evaluation item related to extensibility of the mammary gland in the breast image, respectively. Evaluation device. An image acquisition means for acquiring a medical image obtained by radiographing a region including a diagnosis target region of a subject;
A structure extraction means for analyzing the acquired medical image and extracting a plurality of anatomical structures;
  A plurality of evaluation items for positioning at the time of photographing the medical image based on the extraction result of the extracted structure, and a scoring unit for each evaluation item for scoring for each evaluation item,
The medical image is a breast image taken by a mammography apparatus,
The structure extraction means extracts a plurality of structures of at least a breast, a mammary gland, a great pectoral muscle, and a nipple as the structure to be extracted,
The scoring means for each evaluation item includes: a first positioning evaluation item related to left-right symmetry of the breast image; a second positioning evaluation item related to rendering of a nipple in the breast image; For the third positioning evaluation item related to the depiction of the pectoralis major muscle, the fourth positioning evaluation item related to the drawing of the adipose tissue behind the mammary gland in the breast image, and the abdominal tissue under the breast in the breast image Of the fifth positioning evaluation item related and the sixth positioning evaluation item related to the extensibility of the mammary gland in the breast image, a plurality of evaluation items respectively corresponding to the plurality of structures are evaluated, respectively. A medical image evaluation apparatus characterized by scoring. A weight setting unit for each evaluation item that sets an arbitrary weight for each of the plurality of evaluation items,
The evaluation item-specific scoring means weights the scores for each evaluation item scored based on the extraction result of the extracted structure based on the set weights for each evaluation item, and performs a plurality of evaluations. evaluation device for a medical image according to claim 1 or 2, characterized in that the itemized scored. It is determined whether or not the medical image has been appropriately captured based on at least one of a plurality of positioning evaluation item scores scored by the evaluation item scoring unit and a total score thereof. evaluation device for a medical image according to any one of claims 1 to 3, characterized by comprising an image determination unit. The evaluation items by scoring means by scoring and a plurality of evaluation items different number, and any one of claims 1-4, characterized in that it comprises presentation means for presenting at least one of their total The medical image evaluation apparatus according to claim 1. A warning means for generating a warning prompting re-photographing based on at least one of the scores for each of the plurality of evaluation items scored by the score for each evaluation item and the total score thereof is provided. evaluation device for a medical image according to any one of claims 1 to 5. Recording means for recording the medical image in association with at least one of the score for each evaluation item scored by the scoring means for each evaluation item and the total score for the medical image. evaluation device for a medical image according to any one of claims 1 6, characterized in that the. Photographer information means for acquiring photographer identification information for identifying a photographer who photographed the obtained medical image,
The medical image evaluation apparatus according to claim 7 , wherein the recording unit records the acquired photographer identification information in association with the medical image. A photographing date acquisition means for acquiring a photographing date of the acquired medical image;
It said recording means, evaluating device of a medical image according to claim 7 or 8, characterized in that for recording the acquired shooting date in association with the medical image. The scoring means for each evaluation item evaluates the symmetry based on the area ratio of the left and right breasts extracted from the breast image, the area ratio of the left and right mammary glands, and the area ratio of the left and right pectoralis major muscles, and the total evaluation device for a medical image according to any one of claims 1-9, characterized by scoring the evaluation of the first positioning evaluation item by. The evaluation items by scoring means, according to claim 1 to 10, characterized in that the nipple of the left and right from the breast image is scored a rating of the second positioning evaluation items based on whether or not each extracted The medical image evaluation apparatus according to any one of the above. The scoring unit for each evaluation item evaluates the third positioning evaluation item based on the lower pectoral position of the pectoralis major muscle, the shape of the pectoralis major muscle, and the area ratio of the pectoralis major to the breast extracted from the breast image. 12. The medical image evaluation apparatus according to claim 1 , wherein the medical image is scored. The scoring means for each evaluation item includes a length of a line consisting of a pectoral muscle boundary extracted from the breast image and an image end on the chest wall side, and a length overlapping with the line of the mammary gland extracted from the breast image. evaluation device for a medical image according to any one of claims 1 to 12, characterized in that the scoring evaluation of the fourth positioning evaluation items based on. The scoring unit for each evaluation item has a detecting unit for detecting a skin line of the breast image, and scoring the fifth positioning evaluation item based on the shape of the detected skin line. The medical image evaluation apparatus according to claim 1 . The scoring means for each evaluation item has calculation means for calculating an intramammary contrast value of the mammary gland extracted from the breast image, and an area ratio between the breast and the mammary gland excluding the great pectoral muscle extracted from the breast image; the evaluation apparatus of the medical image according to any one of claims 1 to 14, characterized in that the scoring evaluation of the sixth positioning evaluation items on the basis of the mammary gland in contrast value the calculated.

Images