KR101787713B1 - Digital breast tomosynthesis for detecting position angle and correcting trace of x-ray focal spot - Google Patents

Abstract

The digital mammogram synthesizer according to the present invention includes an X-ray generator for generating X-rays; An X-ray detector that is irradiated by the X-ray generator and converts the X-rays that have passed through the breast into image information, and an X-ray detector that is provided between the X-ray detector and the X-ray detector, Ray detector, wherein the X-ray detector obtains an image from a different X-ray focus (FS) according to rotation of the X-ray generator, and wherein the marker of the marker on the image Based on the positional change, the position angle of the X-ray focus FS is detected. According to this, since the accurate position angle of the X-ray focus can be measured and the locus of the X-ray focus can be corrected without adding a complicated and expensive configuration, a reliable and high quality projection image can be obtained.

Description

Technical Field [0001] The present invention relates to a digital mammographic tomographic image synthesizer capable of correcting a locus of an X-

The present invention relates to a digital mammographic tomographic image synthesizer capable of correcting the locus of the X-ray focus and measuring the position angle of the X-ray focus.

Cancer that develops due to infinite proliferation of cells includes liver cancer, colon cancer, stomach cancer, and lung cancer. Breast cancer that is especially a female disease is a very fatal disease and needs periodic diagnosis and management. Westernized eating habits are raising the incidence of breast cancer in Asia. Therefore, in each country, it is recommended that women with a certain age or older be diagnosed with breast cancer at regular intervals.

Breast ultrasound (Breast Ultrasonography), Breast MRI (Breast MRI), etc. are available for diagnosis of breast cancer, but digital breast tomography image synthesizer using X-ray is typically used. The digital mammographic tomographic image synthesizer acquires an X-ray image of the breast from the image receptor after exposing an appropriate amount of X-ray to the automatic exposure control device (Automatic Exposure Control, AEC).

X-ray image acquisition of the breast is generally performed by FFDM (Full Field Digital Mammography), Digital Breast Tomosynthesis, and BCT (Breast Computed Tomography). The FFDM acquires a 2D image, and the DBT reconstructs the image using the acquired image while the X-ray generator rotates. The BCT rotates the X-ray generator and the X-ray detector to form a three-dimensional image.

Particularly, in order to obtain a projection image, the DBT for obtaining a 3D image rotates the focal spot of the X-ray about the breast, and the locus of the focus of the X- That is, the patient's chest wall). However, commercially available digital mammographic tomographic image synthesizers tend to be designed to ignore the trajectory of the X-ray focus, even though it should be traveling straight in the horizontal plane.

When a projection image is obtained without designing the rotation accuracy of the rotation axis of the digital breast tomographic image synthesizer, the X-ray focus position of each projection image is not aligned on the horizontal plane with the chest wall of the breast. That is, unlike the desired straight line trajectory of the X-ray focus, the trajectory of the actual X-ray focus is not horizontal to the chest wall, but has an uneven trajectory depending on the position of the X-ray focus. If 3D reconstruction is performed using the projection image obtained in this state, the quality of the 3D image is inevitably poor. That is, when reconstructing an image using a projection image, it is difficult to obtain a proper 3D image because an image reconstruction algorithm is performed while assuming that the trajectory of the X-ray focus moves in a straight line.

In order to reconstruct the image, it is necessary to precisely grasp the position angle at which the X-ray focus is located. However, it is difficult to accurately measure the position angle of the X-ray focus . Reliable position There is a blind spot in that the measurement requires an additional component such as an encoder or a high-precision angle meter, which leads to an increase in manufacturing cost. If the image reconstruction is performed appropriately with an approximate value rather than an accurate position angle of the X-ray focus, the quality of the 3D image is inevitably poor.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a high-quality, high-reliability Dimensional image synthesizer for acquiring a 3D image.

According to an aspect of the present invention, there is provided a digital mammography apparatus comprising: an X-ray generator for generating an X-ray; An X-ray detector which is irradiated by the X-ray generator and converts the X-ray passing through the breast into image information; And a reference table unit provided between the X-ray generator and the X-ray detector and having a marker for obtaining an image by the X-ray detector, wherein the X- Acquires an image from different X-ray foci (FS) according to rotation of the X-ray generator, and detects the position angle of the X-ray focus (FS) based on the positional change of the marker on the image.

The reference table portion may be provided at a predetermined height from the surface of the X-ray detector.

And a distance (SID) from the X-ray detector to the surface of the X-ray detector and a distance from the X-ray detector to the surface of the X-ray detector, And the position angle of the X-ray focus FS can be detected.

Also, a correction value for the locus of the X-ray focus (FS) is calculated on the basis of the locus of the marker appearing in the image obtained while the X-ray generator rotates, The image can be corrected.

And a storage unit for storing a reference trajectory of the X-ray focus (FS), wherein the correction value can be generated based on a y-axis deviation of the reference trajectory stored in the storage unit and the trajectory of the marker have.

The reference table portion having the marker may be detachably attached to the digital mammogram image synthesizer.

According to the digital breast tomographic image synthesizer of the present invention having the above-described configuration, the accurate position angle of the X-ray focus can be measured and the X-ray focus can be corrected without adding a complicated and expensive configuration, It is possible to acquire high-quality and reliable 3D X-ray images.

1 is a perspective view of a digital mammogram image synthesizer according to an embodiment of the present invention.
2 is a view for explaining a trajectory correction method of a digital mammogram image synthesizer according to an embodiment of the present invention.
3 is a view for explaining a position angle detection method of a digital mammogram image synthesizer according to an embodiment of the present invention.
4A and 4B are views for explaining a position angle measurement method of a digital mammogram image synthesizer according to an embodiment of the present invention.
5 is a view for explaining a method of calculating an X-ray focus position angle of a digital mammogram image synthesizer according to an embodiment of the present invention.

The present invention will now be described in detail with reference to the accompanying drawings, which show specific embodiments in which the present invention may be practiced. For a specific embodiment shown in the accompanying drawings, those skilled in the art will be described in detail so as to be sufficient for practicing the present invention. Other embodiments than the particular embodiment need not be mutually exclusive but different from each other. It is to be understood that the following detailed description is not to be taken in a limiting sense.

The detailed description of the specific embodiments shown in the accompanying drawings is read in conjunction with the accompanying drawings, which are considered a part of the description of the entire invention. The reference to direction or orientation is for convenience of description only and is not intended to limit the scope of the invention in any way.

Specifically, terms indicating positions such as "lower, upper, horizontal, vertical, upper, lower, upper, lower, upper, lower ", or their derivatives (e.g.," horizontally, Etc.) should be understood with reference to both the drawings and the associated description. In particular, such a peer is merely for convenience of description and does not require that the apparatus of the present invention be constructed or operated in a specific direction.

It should also be understood that the term " attached, attached, connected, connected, interconnected ", or the like, refers to a state in which the individual components are directly or indirectly attached, And it should be understood as a term that encompasses not only a movably attached, connected, fixed state but also a non-movable state.

The thicknesses and sizes of the respective components shown in the accompanying drawings are exaggerated, omitted, or schematically shown for convenience and clarity of explanation. That is, the size of each component does not entirely reflect the actual size.

1 is a perspective view of a digital mammogram generating apparatus 100 according to an exemplary embodiment of the present invention. 1, a digital mammography apparatus 100 according to an exemplary embodiment of the present invention includes an X-ray detector 110, a compression paddle 120, an X-ray generator 130, a gantry 140 A rotary part 150, and a reference table part 160. [

The X-ray detector 110 has a function of converting the X-ray passing through the breast U into image information and can simultaneously perform a function as a bucky for placing the patient's breast U . However, in another embodiment, a separate configuration for accommodating the X-ray detector 110 may be further included.

The X-ray detector 110 may be implemented with various types of detectors such as a screen-film detector, an indirect conversion digital detector, a direct conversion digital detector, and the like. Although not shown in FIG. 1, a grid (not shown) for removing scattered X-rays may be provided on the upper surface of the X-ray detector 110.

The push paddle 120 is designed to be movable up and down, and may be provided between the X-ray generator 130 and the X-ray detector 110. The pushing paddle 120 is preferably made of a material that does not affect the X-ray image acquisition of the breast U, and the up-and-down movement can be controlled so as not to be damaged by the pressing. For example, when a force exceeding a threshold value is applied to the patient's breast U, the downward movement of the pushing paddle 120 may be stopped or controlled to reduce the urging force. At this time, in order to obtain a clear X-ray image, the breast U needs to be evenly compressed.

The X-ray generator 130 is provided above the X-ray detector 110. Although FIG. 1 shows the X-ray generator 130, in another embodiment, the X-ray generator 130 may be referred to as a C-arm and may be designed to have an X- Do. The X-ray generator 130 includes a high voltage generator (not shown) for supplying energy, an X-ray tube (not shown) for converting energy into X-rays, a collimator City), and the like.

Ray detector 130. The patient's breast U is placed on the upper surface of the X-ray detector 110 and the breast U is compressed by the compression pad 120. The X- The line passes through the compressed breast U and reaches the X-ray detector 110. The X-ray detector 110 generates a signal for the position of the X-ray and the incident amount, and this information can acquire an X-ray image of the breast U by an image reconstruction algorithm. At this time, the position angle with respect to the X-ray focus is used for image processing, and the process of measuring the accurate position angle will be described in detail below. Various conventional methods can be applied to image processing of an X-ray image. Therefore, in order not to obscure the essence of the present invention, a detailed description related to the image processing will be omitted here.

It is preferable that the locus of the X-ray focus due to the rotation of the X-ray generator 130, that is, the locus of the X-ray focus, lies on a straight line in a plane horizontal to the chest wall of the breast U, It is necessary to correct the error of the locus of the vehicle.

1, the gantry 140 includes a rotation unit 150 for rotating the X-ray generator 130. When the rotation unit 150 is operated, the X-ray detector 110, The X-ray generator 120 maintains its position, and only the X-ray generator 130 can be rotated within a predetermined range.

Except for the external (e.g., bucky) of the X-ray detector 110, which optionally supports the push paddle 120 and the breast U and the breast U, the X- The X-ray generator 110 and the X-ray generator 130 may rotate integrally. The rotation of each configuration may be designed to allow selective rotation, or it may be designed to be controlled through conversion of the mode (manual or automatic).

The digital mammography apparatus 100 according to an exemplary embodiment of the present invention further includes a reference table 160 between the X-ray detector 110 and the X-ray generator 130. The reference table portion 160 is spaced a predetermined distance from the surface of the X-ray detector 110. In addition, the reference table portion 160 includes a marker 161 having a predetermined shape (e.g., a cross shape).

The markers 161 generate an image on the X-ray detector 110 while the X-rays irradiated from the X-ray generator 130 pass. Accordingly, the marker 161 can be printed, deposited or inserted into a material having a high specific gravity such as lead (pb).

On the other hand, the region other than the markers 161 of the reference table portion 160 is preferably formed of a material having a high X-ray transmittance. Therefore, when the X-ray passes through the reference table portion 160, only the shape of the marker 161 is detected as an X-ray image by the X-ray detector 110.

At this time, the size of the marker 161 and the height of the reference table portion 160 can be appropriately selected so as to be distinguishable from the projection image acquired by the X-ray detector 110. In addition, the position can be adjusted according to the distance (SID, Source to Image-Receptor Distance) from the X-ray focus to the surface of the X-ray detector 110.

Since the area occupied by the image detected by the X-ray detector 110 becomes too large if the thickness of the marker 161 is too large (for example, when the horizontal line and the vertical line are too thick in the cross-shaped marker 161) It is difficult to find the center point. This results in making it difficult to recognize the moving distance of the image of the marker 161, which will be described later.

Therefore, it is preferable that the thickness of the marker 161 is appropriately thin. But it is not limited thereto. The height of the reference table portion 160 may vary depending on the thickness of the marker 161. The height of the reference table portion 160 may be set to about 10 to 20 pixels in the projection image obtained by the X- The position of the food portion 160 can be selected. However, this is merely an embodiment, and in another embodiment, the height of the reference table portion 160 may be set so that the number of pixels is larger or smaller than the size of the range.

FIG. 2 is a view for explaining a locus correcting operation of an X-ray focus of a digital mammogram image synthesizer 100 according to an embodiment of the present invention. Since the digital mammographic tomographic image synthesizer currently in use is designed without considering the rotation accuracy of the rotation axis, the locus of the X-ray focus, that is, the locus of the X-ray focus detected by the X-ray detector, is not straight. In view of the above, the digital mammographic tomographic image synthesizer 100 according to the present invention is configured such that the X-ray focus locus in the X-ray detector 110, which is detected while rotating the X-ray generator 130, , We propose a method that can calibrate to obtain the same effect as making it straight.

That is, the digital breast tomographic image synthesizer 100 according to the present invention does not need software of a complicated algorithm or hardware that causes an increase in cost, so that it is possible to use the markers 161 of the reference table portion 160 only very easily, The error of the locus of the X-ray focus of the image can be corrected.

The ideal X-ray focus trajectory is straight in a direction horizontal to the patient's chest wall, such as the RL shown by the dotted line in FIG. This means that the X-ray generator 130 rotates horizontally without an error in the vertical direction. When the projection image generated by the ideal rotation of the X-ray generator 130 passes through an image reconstruction algorithm, the quality (resolution) of the finally generated 3D image is very good.

In the storage unit (not shown) of the digital breast tomographic image synthesizer 100 according to the present invention, an ideal trajectory of the X-ray focus may be stored. This may be data quantized so as to have a constant y coordinate value with respect to the x coordinate, or image data expressed linearly.

The digital mammography apparatus 100 according to the present invention is capable of detecting an X-ray focal point (numerical data, image date, etc.) stored in a storage unit (not shown) The projection image obtained using the trajectory is corrected to be the projection image obtained by using the ideal X-ray focus trajectory. At this time, the actually detected X-ray focus locus corresponds to the image locus of the marker 161 detected by the X-ray detector 110.

The digital mammogram generating unit 100 generates a digital mammogram based on the locus of the marker 161 displayed on the projection image detected by the X-ray detector 110 in accordance with the rotation of the X-ray generator 130, Thereby correcting the projection image so as to be in the ideal horizontal position. At this time, an error is detected by comparing numerically the stored X-ray locus RL of the storage unit (not shown) and the locus XL of the marker 161 or by comparing deviations on the image.

Specifically, the X-ray locus RL (ideal reference locus) stored in the storage unit (not shown) is located at a predetermined height in the y-axis direction and lies on a straight line in the x-axis direction. The correction value? Y _n of the y coordinate for each projection image according to the position of each X-ray focus FS with respect to the locus XL of the marker 161 and the stored X-ray locus RL, Which is a natural number of 1 or more, which means the sequence number of the projection image). The correction value? Y _n corresponds to a deviation between the y coordinate value of the locus XL of the marker 161 and the y coordinate value of the stored X-ray locus RL.

In FIG. 2, the locus XL of the marker 161 is shown continuously, but may be substantially discrete, when all the projection images are viewed in succession. In case of a discrete image, points that have not been shot directly may be interpolated to calculate the y-coordinate value, or a straight line connecting the points to find the y-coordinate value of the point. This is only an example, and the trajectory XL of the actual marker 161 can be obtained in various ways.

Even as a concept, such as in 2 for each projection image according to the position of each shot point, that is X- ray focus in accordance with the position of the marker 161 shown in the image correction value of the y coordinate (Δy _n, where n is a natural number of 1 or more projection And the correction can be performed by moving all the pixel values of each projection image by a correction value (y _n ) of the y coordinate.

As described above, the digital breast tomographic image synthesizer 100 according to the present invention can correct the vertical direction error (corresponding to the y-axis in FIG. 2) due to the rotation of the X-ray generator 130. Since the error in the left-right direction (corresponding to the x-axis in Fig. 2) is corrected by the position angle measurement described later, it is not necessary to perform another correction.

FIG. 3 is a diagram for explaining a position detection method of the digital mammogram image synthesizer 100 according to an embodiment of the present invention. 3, the reference table portion 160 is positioned at a predetermined height from the X-ray detector 110 and the marker 161 printed, deposited or inserted into the reference table portion 160 is transferred to an X- 130 are rotated to form an image on the X-ray detector 110. At this time, the circumferential points (FS) shown in FIG. 3 represent the X-ray focus.

The X-ray generator 130 is rotated about the rotation center A by the rotation unit 150 and the X-ray focus FS is rotated by the rotation of the X- Move in the interval.

Although the center of rotation A is shown as being on the surface of the X-ray detector 130 in FIG. 3, it may alternatively be located at a distance from the X-ray detector 130 a predetermined distance, It can be adjusted properly when designing a tomographic image synthesizer.

The position angle to be measured in the digital mammographic tomographic image synthesizer 100 according to an embodiment of the present invention is determined by the angle at which the X-ray focus FS is positioned with respect to a line segment perpendicular to the rotation center A angle indicated by?).

The positional shift of the X-ray focus FS causes the movement of the marker 161 in the projection image, and the digital mammogram image synthesizer 100 according to the present invention causes the X-ray detector 110 to detect the marker The position angle alpha of the X-ray focus FS can be calculated according to the positional shift of the X-ray focusing point 161.

4A, when the patient's breast U is pressed between the X-ray detector 110 and the pushing paddle 120, the X-ray generator 130 is rotated by the rotation unit 150 X-rays are generated at the position. The X-ray detector 110 detects the X-ray image of the breast U and the image of the marker 161 in accordance with the movement of the X-ray focus FS. It can be seen that the image of the marker 161 detected by the X-ray detector 110 has shifted from a to a 'as shown in FIG. 4B. The digital mammographic tomographic image synthesizer 100 according to the present invention can detect the position angle alpha of the X-ray focus FS based on the positional change on the image of the marker 161 acquired by the X- .

Although the X-ray image of the crisscross marker 161 is shown as being clearly detected in FIG. 4B, in practice, the X-ray image of the marker 161 may be relatively blurry.

At this time, the distance of the image of the marker 161 can be confirmed in such a manner that the center of the crisscross marker 161 is found based on the brightness and darkness of the detected image, and the moving distance of the center thereof is detected. However, the present invention is not limited to this method, and it is possible to detect the moving distance in various ways without difficulty.

FIG. 5 is a view for explaining a position angle detection method of the digital breast tomographic image synthesizer 100 according to the present invention. Where D is the X-ray focus, A is the rotation center of the X-ray focus, C is the position of the marker 161, B is the X-ray focus center position, E is the X- The position of the marker 161 detected by the X-ray detector 110 is indicated. On the other hand, the line segment AD is a distance (SID) from the X-ray focus D to the surface of the X-ray detector 110, and is a predetermined value in designing the digital mammogram image synthesizer. The position of the reference table portion 160 can be determined according to the distance SID to the surface of the X-ray detector 110. For example, when the SID is 65 cm, the position of the reference table portion 160 is determined by the X- Lt; RTI ID = 0.0 > cm. ≪ / RTI > Of course, the present invention is not limited to such distances as mentioned above.

The digital mammographic tomographic image synthesizer 100 according to the present invention can calculate the position angle alpha of the X-ray focus using the following equation.

In the above equation, since the line AC (= the height of the marker 161) and the line segment AD (= SID) are predetermined values already known by the user, the position of the marker 161 on the X- By acquiring only the value of the change line segment AE, the position angle alpha of the X-ray focus can be calculated.

The digital breast tomographic image synthesizer 100 according to the present invention adds only the reference table type portion 160 on which the markers 161 are displayed without adding a complicated configuration to measure the accurate position angle of the X- The locus of the X-ray focus can be corrected. It is used to acquire high quality 3D X-ray images.

The reference table portion 160 included in the digital mammographic image synthesizer 100 according to the present invention may be detachably fixed. That is, after the trajectory of the X-ray focus FS is corrected, only the correction value may be stored in a storage unit (not shown), and the stored correction value may be applied to a projection image to be generated in the future. At this time, the reference table portion 160 may be removed from the digital breast tomographic image synthesizer 100.

After all the position angles of the X-ray focus FS are detected, the detected position angles are stored in a storage unit (not shown), and a position angle corresponding to the rotation angle of the X-ray generator 130 is stored (Not shown), and may be used for image reconstruction. That is, the reference table portion 160 used in the digital mammogram synthesizer 100 according to the present invention may be attached only when necessary, and used for locus correction and position angle measurement of the X-ray focus.

Although the present invention has been described in terms of specific embodiments including the preferred embodiments of the present invention, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, It can be predicted. In addition, various structural and functional modifications can be made without departing from the scope and spirit of the present invention. Accordingly, the spirit and scope of the present invention may be widely understood as set forth in the claims appended hereto.

100 ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥
110 ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ X
120 ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥
130 ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ X-
140 ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ Gantry
150 ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥
160 ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥
161 ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ Markers

Claims (6)

An X-ray generator for generating X-rays;
An X-ray detector which is irradiated by the X-ray generator and converts the X-ray passing through the breast into image information; And
And a reference table provided between the X-ray generator and the X-ray detector and having a marker for obtaining an image by the X-ray detector,
The X-ray detector acquires an image from different X-ray focuses (FS) according to the rotation of the X-ray generator,
And detects a position angle of the X-ray focus (FS) based on a change in position of the marker on the image obtained from the X-ray detector. The method according to claim 1,
Wherein the reference table portion is provided at a predetermined height from a surface of the X-ray detector. 3. The method of claim 2,
Ray detector, based on a change amount of the position of the marker, a distance from the surface of the X-ray detector to the reference table portion, and a distance (SID) from the X-ray focus FS to the surface of the X- A digital mammographic tomographic image synthesizer for detecting a position angle of a line focus (FS). The method according to claim 1,
And a correction value for the trajectory of the X-ray focus (FS) is calculated based on the locus of the marker appearing in the image obtained while the X-ray generator rotates, and the corrected image is calculated using the calculated correction value Digital mammographic tomographic image synthesizer. 5. The method of claim 4,
And a storage unit for storing a reference locus of the X-ray focus FS,
Wherein the correction value is generated based on a locus of the marker and a y-axis deviation of a reference locus stored in the storage unit. The method according to claim 1,
Wherein the reference table having the marker is detachably attached to the digital mammography.

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