JP5297247B2 - Radiation imaging equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of suitably correcting the detection value of each radiation dose information detector without retaking correction data used in biopsy imaging every time of stereo imaging. <P>SOLUTION: The radiation image capturing device includes: a plurality of AEC sensors 64 for detecting the dose of radiation Xray transmitted through the breast 28 of a subject 27 and acquiring a detection value for AEC; a weighting coefficient imparting part 88 for multiplying the detection value by a weighting coefficient corresponding to the position of each AEC sensor 64; and a radiation source control part 76 for controlling the radiation dose to be exposed from a radiation source 30 on the basis of the detection value multiplied by the weighting coefficient. The radiation image capturing device is provided with: a reference value holding part 90 for holding the weighting coefficient determined on the basis of a reference geometric imaging condition as a reference weighting coefficient; a geometric imaging condition acquisition part 92 for acquiring a geometric imaging condition related to the position of the radiation source 30, a solid state detector 60 or the plurality of AEC sensors 64; and a weighting coefficient correction part 94 for correcting the reference weighting coefficient on the basis of the reference geometric imaging condition, the reference weighting coefficient and the geometric imaging condition. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a radiographic image capturing apparatus for acquiring radiographic image information of a subject.

  In the medical field, radiation imaging is performed in which radiation is exposed to a subject (patient) from a radiation source, radiation transmitted through the subject is detected by a solid-state detector, and radiation image information is acquired based on the detected detection signal. The device is widely used.

  As one of such radiographic imaging devices, a mammography device used for breast cancer screening or the like is known. The mammography apparatus, for example, is equipped with a panel-shaped solid detector, supports a breast that is a photographing part of a subject, and a pressure table that is disposed opposite to the photographing base and presses the breast against the photographing base. A plate and a radiation source for exposing the breast to radiation through the compression plate.

  In addition, a mammography stereotaxic device has been developed that incorporates a mechanism that can collect a tissue of a lesion site and perform a precise examination for diagnosing diseases, etc., against a mammography device that acquires a radiographic image of the mammogram of the subject. Has been. In such a mammography localization apparatus, a radiographic imaging method called stereo imaging is often used. Here, stereo imaging refers to an imaging method in which a breast is imaged from angles in a plurality of directions and an accurate three-dimensional lesion position for insertion with a biopsy needle is determined.

  Furthermore, in this type of radiographic imaging apparatus, it is necessary to ensure good radiographic image quality while minimizing the radiation dose of the subject. Therefore, in order to acquire appropriate radiological image information of the region of interest in the subject, it is necessary to set an exposure control condition so that a desired amount of radiation is exposed to the region of interest. In view of this, a radiographic imaging apparatus including an automatic exposure control (AEC) system that controls the radiation dose emitted from the radiation source based on the detection result of the radiation dose transmitted through the subject has been proposed.

  For example, in the X-ray inspection apparatus disclosed in Patent Document 1, a radiation dose is detected at a plurality of measurement positions in an X-ray detector, and a portion of interest (preferably not overexposed or underexposed) based on each detected value. A suitable measurement region can be performed.

Special Table 2000-513869 Japanese Patent Laid-Open No. 5-200126

  However, the following adverse effects may occur when performing stereo imaging using the AEC using a mammography localization apparatus.

  By correcting the detection values of a plurality of AEC sensors arranged in the left-right direction of the imaging table, it is possible to perform imaging while reducing the influence of variation such as the geometrical influence of the distance between the tube and the AEC sensor and the AEC sensor sensitivity. . Generally, a method is used in which correction data is created based on the input value of the AEC sensor when irradiation is performed in front image shooting (so-called scout shooting) with a stereo angle of 0 °.

  However, when performing stereo photography related to biopsy (photographing with a stereo angle other than 0 °), the difference in the geometric photography conditions of the photography system, specifically, the distance between the tube and each AEC sensor. There arises a problem that the AEC may not function sufficiently as a result of the relative distortion occurring and making it difficult to accurately estimate the radiation dose.

  Here, a stereotactic radiotherapy apparatus that fixes the lesion to the treatment table so as to coincide with the rotation center point of the treatment gantry and controls the radiation dose rate so as to obtain a constant radiation dose (Patent Document) 2) is known, and it is considered that the present invention can be used as it is in solving this problem.

  However, since a general mammography localization apparatus has a plurality of AEC sensors and it is impossible to position all the AEC sensors at the rotation center of the radiation source, the invention described in Patent Document 2 is used. Cannot be used as is.

  In order to solve this problem, a method of acquiring correction data corresponding to various stereo angles for biopsy imaging is also conceivable.

  In such a case, not only the change of the stereo angle but also the optimum correction data corresponding to the geometric imaging conditions such as the distance of the SID (Source Indicator Distance) and the AEC sensor position must be acquired each time. As a result, not only will the amount of exposure be increased, but also the time and effort required for shooting and data management will be increased.

  The present invention has been made in order to solve the above-described problems. For example, the detection values of a plurality of radiation dose information detectors are preferably obtained without re-correcting correction data used for biopsy imaging at every stereo imaging. A method of correcting is provided.

  A breast radiographic imaging device according to the present invention detects a radiation source that is supported rotatably about a rotation axis and that exposes radiation to an imaging region of a subject, and a dose of the radiation that has passed through the imaging region. A radiation detection unit, a radiation image formation unit that acquires image information about the imaging region based on the radiation dose detected by the radiation detection unit, and forms a radiation image based on the image information, and a plurality of measurements A radiation dose information detector for detecting radiation dose transmitted through the imaging region at a position and acquiring radiation dose information for exposure control; and the measurement for each radiation dose information measured at the plurality of measurement positions. A weighting factor applying unit that multiplies a weighting factor according to a position, and a radiation that is exposed from the radiation source based on the radiation dose information multiplied by the weighting factor. A radiation source control unit that controls a dose, a reference value holding unit that holds the weighting coefficient determined based on a reference geometric imaging condition as a reference value, the radiation source, A radiation detection unit, or a geometric imaging condition acquisition unit that acquires a geometric imaging condition related to the position of the radiation dose information detector; the reference geometric imaging condition; the reference value; and the geometric imaging condition And a weighting coefficient correction unit that corrects the weighting coefficient based on the first aspect (Invention of Claim 1).

  Furthermore, the geometric imaging condition may be a rotation angle of the radiation source, the plurality of measurement positions, a rotation center position of the radiation source, and a position in a normal direction of a detection surface related to the radiation detection unit. Preferred (invention of claim 2).

  Furthermore, it is preferable to hold the weighting coefficient so as to be a function of the rotation angle of the radiation source.

  Further, the reference geometric imaging condition may be a geometric imaging condition set by setting the optical axis of the radiation to be a normal direction of a detection surface related to the radiation detection unit. Preferred (invention of claim 4).

  Furthermore, the imaging region is a subject's breast, and it is preferable to use it for mammography.

  According to the present invention, when a predetermined radiation dose measurement position is selected from a plurality of measurement positions from which radiation dose information is detected, each radiation dose information is added to the measurement position while taking into account geometric imaging conditions. Since the calculation process of multiplying the corresponding weighting coefficient is performed, the detection value of each radiation dose information detector can be suitably corrected without re-correcting correction data used for biopsy imaging every time stereo imaging is performed.

It is a perspective explanatory view of the mammography device of this embodiment. It is principal part explanatory drawing which shows the internal structure of the imaging stand in the mammography apparatus shown in FIG. FIG. 3 is a partially omitted perspective view showing an internal configuration of the photographing stand shown in FIG. 2. It is an AEC circuit block diagram which comprises the mammography apparatus shown in FIG. It is a drive control circuit block diagram of the biopsy hand part which comprises the mammography apparatus shown in FIG. It is an operation | movement flowchart of the mammography apparatus of this embodiment. FIG. 7A is a relationship diagram of the arrangement positions of the AEC sensors according to the mammography apparatus of the present embodiment. FIG. 7B is a table showing an example of a suitable reference weighting coefficient according to the mammography apparatus of the present embodiment. It is explanatory drawing of the stereo imaging | photography which concerns on the mammography apparatus of this embodiment. 9A and 9B are diagrams illustrating specific examples of geometric imaging conditions according to the mammography apparatus of the present embodiment. FIG. 10A is a table showing an example of a suitable correction coefficient related to stereo shooting (θ = −45 °) of the mammography apparatus of the present embodiment. FIG. 10B is a table showing an example of a suitable weighting coefficient for stereo shooting (θ = −45 °) of the mammography apparatus of the present embodiment. FIG. 11A is a table showing an example of a suitable correction coefficient related to stereo shooting (θ = + 45 °) of the mammography apparatus of the present embodiment. FIG. 11B is a table showing an example of a suitable weighting coefficient for stereo shooting (θ = + 45 °) of the mammography apparatus of the present embodiment. It is a graph which shows an example of the weighting coefficient suitable for tomosynthesis which concerns on the mammography apparatus of this embodiment.

  FIG. 1 is a configuration diagram of a mammography apparatus 20 according to an embodiment of a radiographic image capturing apparatus according to the present invention.

  The mammography apparatus 20 includes a base 22 that is installed in an upright state, an arm member 26 that is fixed to a rotary shaft 24 that is disposed at a substantially central portion of the base 22, and a breast 28 (examination target region) of a subject 27. 2), the radiation source 30 (FIG. 2) that irradiates the radiation Xray is accommodated, and the radiation source accommodation part 32 fixed to one end of the arm member 26 and the radiation Xray transmitted through the breast 28 are detected. A solid state detector 60 (radiation detector, FIG. 2 and FIG. 3) is housed, and an imaging table 36 fixed to the other end of the arm member 26, and a compression that compresses and holds the breast 28 against the imaging table 36 A plate 38 and a biopsy hand unit 40 that is attached to the compression plate 38 and collects a necessary tissue from a biopsy site of the breast 28 are provided. The base 22 displays a photographing part of the subject 27, photographing information such as a photographing direction, ID information of the subject 27, and the like, and a display operation unit 42 that can set the information as necessary is disposed. Is done.

  The arm member 26 that connects the radiation source storage unit 32 and the imaging table 36 is configured to be adjustable about the imaging direction of the subject 27 with respect to the breast 28 by rotating about the rotation shaft 24. The radiation source storage unit 32 is connected to the arm member 26 via a hinge unit 35 and is configured to be rotatable independently of the imaging table 36 in the direction of the arrow θ. The compression plate 38 is disposed between the radiation source storage unit 32 and the imaging table 36 while being connected to the arm member 26, and is configured to be displaceable in the arrow Z direction.

  The compression plate 38 is formed with an opening 44 for tissue collection using the biopsy hand unit 40. The biopsy hand unit 40 includes a post 46 fixed to the compression plate 38, a first arm 48 that is pivotally supported at one end of the post 46 and rotatable along the surface of the compression plate 38, and the first arm 48. One end is pivotally supported by the end, and a second arm 50 that is rotatable along the surface of the compression plate 38 is provided. A biopsy needle 52 that can move in the arrow Z direction is attached to the other end of the second arm 50. As shown in FIG. 2, the biopsy needle 52 includes a collection unit 56 that sucks and collects the tissue of the biopsy site 54 of the breast 28. The collection unit 56 of the biopsy needle 52 moves the first arm 48 and the second arm 50 of the biopsy hand unit 40 in the XY plane along the surface of the compression plate 38 and moves the biopsy needle 52 in the arrow Z direction. By moving it, it can be placed near the biopsy site 54.

  FIG. 2 is a main part explanatory diagram showing an internal configuration of the imaging stand 36 in the mammography apparatus 20, and shows a state in which the breast 28 that is an imaging region (region of interest) of the subject 27 is arranged between the imaging table 36 and the compression plate 38. Show. Reference numeral 29 indicates the chest wall of the subject 27.

  A solid-state detector 60 that accumulates radiation image information captured based on the radiation Xray emitted from the radiation source 30 built in the radiation source storage unit 32 and outputs the radiation image information as an electrical signal inside the imaging table 36. In order to read the radiation image information accumulated and recorded in the solid state detector 60, a reading light source unit 62 that irradiates the solid state detector 60 with reading light is housed. Furthermore, in order to determine the radiation Xray exposure control conditions, a plurality of radiation dose information detectors (hereinafter referred to as “radiation Xray”) that detect the radiation dose of the radiation Xray that has passed through the breast 28 and the solid state detector 60 are provided inside the imaging table 36. In order to remove unnecessary charges accumulated in the solid state detector 60, an erasing light source unit 66 that irradiates the solid state detector 60 with erasing light is housed.

  The solid state detector 60 is a direct conversion type and optical readout type radiation solid state detector. The solid state detector 60 accumulates radiation image information based on the radiation Xray transmitted through the breast 28 as an electrostatic latent image, and reads from the reading light source unit 62. By scanning with light, a current corresponding to the electrostatic latent image is generated.

  For example, the solid state detector 60 having a structure disclosed in Japanese Patent Application Laid-Open No. 2004-154409 can be used. Specifically, the solid state detector 60 is formed on a glass substrate and transmits a radiation Xray. The recording photoconductive layer that generates a charge when exposed to radiation Xray and the latent image polar charge charged in the first conductive layer act as an insulator while being opposite to the latent image polar charge. A charge transport layer that acts as a substantially conductive material for the polar transport polar charge, a read photoconductive layer that exhibits electrical conductivity when irradiated with read light, and a second that transmits radiation Xray. A conductive layer is sequentially stacked. A power storage unit is formed at the interface between the recording photoconductive layer and the charge transport layer.

  The first conductive layer and the second conductive layer each constitute an electrode. The electrode of the first conductive layer is a two-dimensional flat plate electrode, and the electrode of the second conductive layer is a plurality of lines having a predetermined pixel pitch for detecting recorded radiographic image information as an image signal. Configured as an electrode. The arrangement direction of the linear electrodes corresponds to the main scanning direction, and the extending direction of the linear electrodes corresponds to the sub scanning direction.

  The reading light source unit 62 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 60, The line light source in which the 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 60 is moved in the extending direction of the linear electrode (arrow C direction in FIG. 3). By doing so, the entire surface of the solid state detector 60 is exposed and scanned.

  As shown in FIG. 3, the erasing light source 66 is configured by arranging a large number of LED chips 68 on the panel 70 that emit and extinguish light in a short time and have very little afterglow. The panel 70 is stored in the imaging stand 36 in a state of being arranged in parallel with the solid state detector 60.

  As shown in FIGS. 2 and 3, a plurality of AEC sensors 64 (16 in the case of this embodiment) are arranged on the sensor substrate 72 and formed on the panel 70 constituting the erasing light source unit 66. The direction of the solid detector 60 is directed from the hole 73. Each AEC sensor 64 is arranged in a state surrounded by a rectangular cylindrical member (not shown) extending from the hole 73 toward the AEC sensor 64 side along the radiation Xray direction from the radiation source 30. Is done.

  Such an AEC sensor 64 is arranged on the sensor substrate 72 so as to correspond to the breast 28 in a state where the breast 28 is positioned and fixed on the imaging table 36 (see FIG. 3).

  FIG. 4 is an AEC circuit block diagram constituting the mammography apparatus 20.

  The control circuit of the mammography apparatus 20 is housed in the radiation source housing unit 32, and can be set by inputting the radiation condition control unit 76 that controls the radiation source 30 that emits the radiation Xray by operating the exposure switch 74 and the imaging conditions. Radiation detected by the display operation unit 42, a drive control unit 78 that drives and controls the position and rotation angle of the radiation source 30, the position of the imaging table 36, and the like based on the imaging conditions that have been input and set, and a plurality of AEC sensors 64. Based on the radiation dose of Xray, a measurement position selector 80 that selects an AEC sensor (radiation dose information detector) 64 estimated near the breast position (region of interest) of the breast 28, and the radiation Xray detected by the AEC sensor 64 Based on the radiation dose exposed per unit time, an appropriate exposure time of the radiation Xray from the radiation source 30 is calculated, and the exposure is performed. And a exposure time calculator 82 supplies the radiation source controller 76 as control condition.

  The control circuit of the mammography apparatus 20 acquires radiation image information (image information) based on the radiation Xray dose detected by the solid state detector (radiation detection unit) 60, and forms a radiation image. 84 and a display unit 86 for displaying the radiation image. As described above, the solid state detector 60 functions as a radiation image generation unit that detects radiation exposed from the radiation source 30 and generates a radiation image. The display unit 86 displays an image representing position information indicating the AEC sensor 64 selected by the measurement position selection unit 80 or the specified breast position superimposed on the radiation image.

  Further, the control circuit of the mammography apparatus 20 uses a weighting coefficient adding unit 88 that multiplies each detection value (radiation dose information) from each AEC sensor 64 by a weighting coefficient, and a scout imaging condition (standard geometric imaging condition). A reference value holding unit 90 that holds a reference weighting coefficient (reference value) determined based on the geometric imaging conditions (position and rotation angle of the radiation source 30, position of the imaging table 36) supplied from the display operation unit 42. And the like, and the same information supplied to the drive control unit 78.) The geometric imaging condition acquisition unit 92 that acquires the reference weighting coefficient based on the scout imaging condition and the geometric imaging condition And a weighting coefficient correction unit 94 that supplies the corrected weighting coefficient to the weighting coefficient adding unit 88.

  As described above, the mammography apparatus 20 according to the present embodiment is estimated to be near the region of interest of the breast 28 by the measurement position selection unit 80 based on the radiation dose detected by the AEC sensor 64 that is the radiation dose information detection unit. The AEC sensor 64 is selected, and the AEC (automatic exposure control) system is configured in which the radiation source controller 76 controls the radiation source 30.

  FIG. 5 is a drive control circuit block diagram of the biopsy hand unit 40 constituting the mammography apparatus 20.

  The mammography apparatus 20 includes an imaging condition setting unit 96 for setting imaging conditions such as a tube current, a tube voltage, a type of target and filter set in the radiation source 30, an irradiation dose of radiation X, an irradiation time, and the like. The radiation source control unit 76 that drives and controls the radiation source 30 according to the above, the biopsy needle drive control unit 98 that moves the biopsy needle 52 to a predetermined position via the biopsy hand unit 40, and the compression that moves the compression plate 38 in the arrow Z direction The plate drive control unit 100, the detector control unit 102 that controls the solid state detector 60 that detects and converts the radiation Xray transmitted through the breast 28 into image information, and the image information converted by the solid state detector 60 is stored. Image information storage unit 104 and CAD (Computer Aided Diagnosis) that automatically detects biopsy site 54 by processing image information ) A processing unit 106 and a display unit 86 that displays a radiographic image of the breast 28 including the biopsy site 54 that is automatically detected.

  In addition, the mammography apparatus 20 selects the biopsy site selection unit 108 that selects the biopsy site 54 from the radiation transmission image displayed on the display unit 86 using a pointing device such as a mouse, and the acquired image information is selected. The biopsy site position information calculation unit 110 that calculates the position information of the biopsy site 54 and the necessary amount of movement of the breast 28 with respect to the movable range of the biopsy needle 52 or the amount of movement of the biopsy needle 52 with respect to the biopsy site 54 are calculated. And a movement amount calculation unit 112 for calculating.

  The mammography apparatus 20 of the present embodiment is basically configured as described above. Next, the workflow and apparatus operation will be described with reference to the flowchart shown in FIG.

[Step S1]
First, the engineer uses the imaging condition setting unit 96 to restrict subject information relating to the age, sex, body type, subject identification number, etc. of the subject 27, imaging conditions of radiographic image information, imaging method, and movement of the biopsy hand unit 40. The processing conditions such as the movement restriction amount and the length of the biopsy needle 52 are set. These processing conditions can be confirmed by displaying them on the display operation unit 42 of the mammography apparatus 20.

  Among the processing conditions set by the imaging condition setting unit 96, imaging conditions such as the tube current of the radiation source 30, the tube voltage, the radiation X irradiation dose, and the irradiation time are set in the radiation source control unit 76. Of the processing conditions, geometric imaging conditions such as SID and stereo angle are supplied to the drive controller 78 to perform a predetermined drive operation.

  Further, information related to the movement limit amount of the biopsy hand unit 40 and the length of the biopsy needle 52 is set in the biopsy needle drive control unit 98.

[Step S2]
Next, the engineer positions the breast 28 of the subject 27 in accordance with the designated imaging method. In this embodiment, the engineer performs setting for scout shooting. Scout imaging is imaging performed by setting the optical axis of the radiation Xray to be in the normal direction with respect to the imaging table 36 without rotating the radiation source storage unit 32.

  As shown in FIG. 1, when photographing the breast 28, the arm member 26 is rotated by a predetermined angle around the rotation axis 24 (hereinafter, this angle is referred to as “stereo angle”) and set to a predetermined angular position. To do. Further, the breast 28 on the right side of the subject 27 is positioned with respect to the mammography apparatus 20. In this case, after placing the right breast 28 on the mounting surface of the imaging table 36, the compression plate 38 is pushed down to hold the breast 28 between the imaging table 36 and the compression plate 38 (see FIG. 2). That is, with the outer side (right arm side) of the right breast 28 in contact with the imaging table 36, the compression plate 38 is pressed and held from the inner side (left breast 28 side).

[Step S3]
Next, the engineer sets an exposure control condition in the mammary gland region as a region of interest by setting the radiation dose of the radiation Xray to be exposed to the breast 28 to be small (hereinafter referred to as “pre-exposure”). I do. When the technician depresses the exposure switch 74, the radiation Xray is exposed to the breast 28, and thereafter, a suitable weighting factor and exposure control condition to be applied to each AEC sensor 64 are automatically set to the reference value holding unit 90, the memory, respectively. (Not shown). Thus, the engineer can make settings necessary for a suitable AEC without being conscious of the internal processing of the mammography apparatus 20.

  Hereinafter, the operation of the mammography apparatus 20 corresponding to step S3 will be described.

  The AEC sensor 64 detects the radiation amount of the radiation Xray that has passed through the compression plate 38, the breast 28, and the solid detector 60, and supplies it to the measurement position selection unit 80. The measurement position selection unit 80 calculates the radiation dose to be exposed per unit time from the radiation dose of the radiation Xray detected at a predetermined sampling time by the AEC sensor 64, and estimates the mammary gland position based on the radiation dose. To do. In other words, the measurement position selection unit 80 selects the one that detects the minimum radiation dose from the plurality of AEC sensors 64 arranged on the sensor substrate 72 and estimates the vicinity of the mammary gland position to thereby obtain a predetermined radiation dose. A position having the highest breast density as a measurement position can be detected as a breast position (region of interest).

  Here, the detection value of each AEC sensor 64 is not used as it is, but a weighting coefficient corresponding to the sensitivity characteristic of each AEC sensor, imaging position condition, breast positioning mode, etc. is used as the detection value of each AEC sensor 64. You can ride. Hereinafter, details of the weighting coefficient supplied to the measurement position selection unit 80 will be described.

  As the weighting coefficient, for example, a value that uniformly corrects the radiation dose accompanying the sensor sensitivity variation and the radiation optical path difference of each AEC sensor 64 can be used. In such a case, it is possible to select a suitable AEC sensor 64 that reduces the effects of differences in sensor sensitivity and shooting position information.

  As the weighting coefficient, for example, a value that is set in advance in the mammography apparatus 20 and that is already held in the reference value holding unit 90 can be used. If the geometric imaging conditions related to the pre-exposure are not always the same in the operation of the imaging, the geometric imaging conditions related to the pre-exposure are input and set by the display operation unit 42, and a weighting suitable for the condition is set. A coefficient can also be selected.

Next, an example of calculating a suitable weighting coefficient to be given to each AEC sensor 64 will be described. As shown in FIG. 7A, the plurality of AEC sensors 64 are arranged in a grid pattern on the sensor substrate 72 (25 in total, 5 rows in the X direction and 5 rows in the Y direction). The weighting coefficient to be given to each AEC sensor 64 can be determined based on the following equation (1).
Iout (i, j) = Iin (i, j) × W1 (i, j) × W2 (i, j) (1)

  Here, i = −2, −1,..., +2, j = −2, −1,..., +2, and (i, j) is an identification number associated with the AEC sensor 64, The AEC sensor 64 disposed in the center (third row, third column) is defined as (0, 0). In addition, Iin (i, j), W1 (i, j), W2 (i, j), and Iout (i, j) are the detection values in the AEC sensor 64 of the identification number (i, j) and the sensor sensitivity variations. , A weighting coefficient derived from geometric imaging conditions, and a detection value after the weighting coefficient is given. For example, the weighting coefficient due to the sensor sensitivity variation based on the sensitivity characteristic of the AEC sensor 64 with the identification number (0, 0) disposed in the center is W1 (i, j) = Iin (i, j) / Iin (0, 0).

  FIG. 7B is a table showing an example of suitable weighting factors (W1 × W2) to be given to the plurality of AEC sensors 64 shown in FIG. 7A under the scout imaging conditions. By using such weighting coefficients at the time of scout imaging, it is possible to perform suitable AEC in which the influence of differences in sensor sensitivity and geometric imaging conditions is reduced.

  It is also a preferable aspect that the operator can automatically set the weighting coefficient in advance by the AEC sensor correction function when the mammography apparatus 20 is installed in a hospital or the like. For example, the operator can switch between the normal photographing mode and the sensor correction mode by the display operation unit 42.

  In the case of the sensor correction mode, the radiation Xray is exposed from the radiation source 30 in the state where the subject 27 is not present on the imaging table 36, so-called solid exposure is performed. At this time, each AEC sensor 64 detects the radiation amount of the radiation Xray transmitted through the solid state detector 60. Based on the detected value, it is possible to calculate a reference weighting coefficient to be given to each AEC sensor 64 that conforms to the above-described mathematical expression. Further, the reference value holding unit 90 holds the weighting coefficient obtained by this pre-exposure work as a suitable reference weighting coefficient in scout imaging.

  Hereinafter, the geometric imaging condition and the weighting coefficient relating to the pre-exposure are referred to as a reference geometric imaging condition and a reference weighting coefficient, respectively.

  In this embodiment, the reference geometric imaging condition is set to the scout imaging condition (stereo angle = 0 °), but the reference condition is changed to an imaging condition other than the scout imaging condition (for example, stereo angle ≠ 0 °). In such a case, it is preferable to maintain not only the weighting coefficient related to pre-exposure but also the geometric imaging conditions.

  Further, the weighting coefficient assigning unit 88 is installed on the AEC sensor 64 that is installed closer to the center than the peripheral part of the breast 28 and closer to the nipple side than the chest wall 29 side. It is also a preferred aspect that a value obtained by further multiplying the detection value of each AEC sensor 64 by the weighting coefficient set so that it can be preferentially selected at is supplied to the measurement position selector 80. In such a case, it is effectively prevented that the installation position of the AEC sensor 64 that overlaps the pectoral muscle that tends to have a larger radiation absorption coefficient than the mammary gland region is erroneously selected as the mammary gland location (region of interest).

  As described above, when the AEC sensor 64 estimated to be in the vicinity of the mammary gland position is selected by the measurement position selection unit 80, the exposure time calculation unit 82 performs the per unit time detected by the AEC sensor 64 at the mammary gland position. Based on the radiation dose, an exposure time for exposing the radiation dose necessary to obtain appropriate radiation image information of the mammary gland region of the breast 28 is calculated as an exposure control condition.

  In this way, by setting the radiation dose of the radiation Xray to be exposed to the breast 28 to be small by pre-exposure, it is possible to determine the exposure control condition in the mammary gland region that is the target region.

[Step S4]
Next, the engineer drives the radiation source 30 and performs stereo imaging of the breast 28. In this case, the radiation source storage portion 32 is moved around the hinge portion 35 (FIG. 1), and the radiation source 30 is disposed at the position A as shown in FIG. Photographing is performed while being held by the compression plate 38. When the engineer presses the exposure switch 74, imaging is started, and after the radiation Xray is exposed based on the exposure time calculated by the exposure time calculation unit 82, a radiation image relating to the breast 28 is automatically formed. Is done. Similarly, as shown in FIG. 8, when the radiation source 30 is arranged at the B position and imaging is started, a radiation image relating to the breast 28 is automatically formed.

  Hereinafter, the operation of the mammography apparatus 20 corresponding to step S4 will be described.

  By arranging the radiation source 30 at the A position and the B position and irradiating the radiation Xray, the radiation Xray transmitted through the breast 28 is detected as a radiation dose by the solid state detector 60 of the imaging table 36. The detector control unit 102 controls the solid state detector 60 to acquire radiation image information from the radiation dose of the breast 28 at the A position and the B position, and the radiation image information is supplied to the radiation image forming unit 84. The

  On the other hand, the AEC sensor 64 detects the radiation dose of the radiation Xray transmitted through the compression plate 38, the breast 28 and the solid detector 60. The weighting coefficient assigning unit 88 assigns a weighting coefficient to the detected value and supplies the weighting coefficient to the measurement position selecting unit 80. The measurement position selection unit 80 calculates an exposure time for exposing a radiation dose necessary for obtaining appropriate radiographic image information of the mammary gland region of the breast 28 as an exposure control condition, and a radiation source control unit as necessary. 76 exposure times can be updated. The details of the method for calculating the exposure time after the detection value of the AEC sensor 64 is supplied to the measurement position selection unit 80 are the same as described above, and will be omitted.

  Further, the detection value of each AEC sensor 64 is supplied to the radiation image forming unit 84 and can be used as a parameter relating to image processing including CAD processing described later (step S5). Further, various pieces of photographing information such as detection values and exposure times of the respective AEC sensors 64 can be displayed together with images, or can be made into a database. Thereby, the engineer or the doctor can utilize the history of the exposure information of the patient stored in the database for subsequent diagnosis and treatment.

  Here, in order to effectively use the detection value of each AEC sensor 64, the reference weighting coefficient held in the reference value holding unit 90 is not used as it is, but according to the geometric imaging conditions of each stereo shooting. It is desirable to use a suitable weighting factor.

  Hereinafter, the weighting coefficient correction method will be described in detail. The geometric imaging condition acquisition unit 92 acquires the geometric imaging condition to be used for correcting the weighting coefficient from the display operation unit 42. Next, the weighting coefficient correction unit 94 determines the reference value based on the reference geometric imaging condition supplied from the reference value holding unit 90 and the geometric imaging condition supplied from the geometric imaging condition acquisition unit 92. The reference weighting coefficient held by the holding unit 90 is corrected, and the corrected weighting coefficient is supplied to the weighting coefficient adding unit 88.

Here, according to geometric considerations, the weighting coefficient to be given to each AEC sensor 64 can be corrected based on the following equations (2) and (3).
Iout (i, j) = Iin (i, j) × W (i, j) (2)
W (i, j) = K (i, j) × W1 (i, j) × W2 (i, j) (3)

  As described above, i = −2, −1,..., +2, j = −2, −1,..., +2, and (i, j) is an identification number related to the AEC sensor 64, A plurality of AEC sensors 64 arranged at the center (third row, third column) are defined as (0, 0). In addition, Iin (i, j), W (i, j), and Iout (i, j) are the original detection value, the corrected reference weighting coefficient, and the correction in the AEC sensor 64 with the identification number (i, j), respectively. The detected value after the given reference weighting coefficient is given. Further, K (i, j), W1 (i, j), and W2 (i, j) are derived from the weighting coefficient correction coefficient and pre-exposure in the AEC sensor 64 with the identification number (i, j), respectively. This represents a weighting coefficient caused by variation and a weighting coefficient caused by geometric imaging conditions derived by pre-exposure.

  The correction coefficient K (i, j) is derived based on the reference weighting coefficient (W1 × W2), the geometric imaging conditions related to scout imaging and stereo imaging. Hereinafter, an example of setting the correction coefficient K (i, j) will be described in detail.

  FIG. 9 is a diagram illustrating a specific example of the geometric imaging condition according to the mammography apparatus 20. FIG. 9A shows a plan view of the imaging stand 36. When the radiation source 30 is rotated around the rotation axis 24, the trajectory of the intersection point where the perpendicular line is drawn from the radiation source 30 to the plane of the imaging table 36 is taken as the X axis (Y = 0), and the scout imaging condition (stereo angle θ Is the origin O (0,0). At this time, if the coordinates where the AEC sensor 64 is disposed are (x, y), x and y correspond to the geometric imaging conditions.

  9B is a Y-axis direction cross-sectional view (XZ plan view) of the positional relationship among the radiation source 30, the imaging stand 36, and the AEC sensor 64. The plane formed by the solid state detector 60 (or imaging table 36) is Z = 0, and the distance between the radiation source 30 and the solid state detector 60 (or imaging table 36) under the scout imaging condition (θ = 0 °) is D. To do. The radiation source 30 can be driven so as to draw a circular orbit having a radius R around the isocenter O ′ (0, DR), which is one point on the rotating shaft 24. Furthermore, the AEC sensor 64 is installed at the position of coordinates (x, z). At this time, θ, D, R, x, and z correspond to geometric imaging conditions.

  The geometric imaging conditions include the stereo angle θ, the position (x, y, z) of the AEC sensor 64, the position of the isocenter O ′ (0, 0, DR), and the imaging table 36 (or a solid state detector). 60), which is composed of four parameters of the position (Z = 0) in the normal direction of the detection surface. However, even imaging conditions other than the four parameters can be used as parameters for determining the geometric imaging conditions as long as the four parameters can be uniquely derived. For example, in FIG. 9B, D (corresponding to the SID at the time of scout imaging) is used as a parameter for determining the geometric imaging condition, instead of the position in the normal direction of the detection surface related to the isocenter O ′ and the solid state detector 60. Can also be used.

  10 and 11 are diagrams illustrating examples of suitable weighting coefficients.

  10A shows a matrix of K (i, j) at θ = −45 ° (position of 45 ° counterclockwise with θ = 0 ° as a reference), and FIG. 10B shows a weighting factor W (i, j) after correction. It is a table | surface which shows. 11A shows a matrix of K (i, j) at θ = + 45 ° (position of 45 ° clockwise with θ = 0 ° as a reference), and FIG. 11B shows a weighting factor W (i, j) after correction. It is a table | surface which shows. As described above, (i, j) in the table is an identification number related to the AEC sensor 64.

  In this way, at the time of stereo shooting, the correction coefficient K (i, j) is derived based on the geometric shooting conditions related to the shooting, and the weighting coefficient is corrected by multiplying this value by the reference weighting coefficient. The As a result, it is possible to perform a suitable correction of the AEC sensor 64 without performing pre-exposure every time of stereo shooting (shooting with a changed stereo angle) and acquiring a weighting coefficient suitable for the shooting.

[Step S5]
Next, the technician performs a necessary GUI operation using a mouse, a touch panel, or the like, so that the radiation image forming unit 84 performs CAD processing.

  As shown in FIG. 8, after imaging by rotating the radiation source 30 to the A position and the B position, these two pieces of radiation image information are temporarily stored in the image information storage unit 104 to create a stereo image. Are displayed on the display unit 86. The CAD processing unit 106 extracts an abnormal candidate site by performing quantitative image processing on the image information stored in the image information storage unit 104.

[Step S6]
Next, the engineer performs a necessary GUI operation using a mouse, a touch panel, or the like, thereby displaying an image on the display unit 86.

  The abnormal candidate portion extracted by the CAD processing unit 106 is displayed on the display unit 86 together with the radiation transmission image of the breast 28. It is preferable to display the radiation transmission image of the breast 28, the marker indicating the abnormal candidate site extracted by the CAD process, and the image of the opening 44 of the compression plate 38 on the display unit 86.

[Step S7]
Next, the engineer instructs the biopsy site 54 from the stereo image displayed on the display unit 86 using the biopsy site selection unit 108. The biopsy site selection unit 108 can be configured by a GUI such as a mouse or a touch panel.

  Thereafter, the operation of the mammography apparatus 20 corresponding to the following steps S8 to S10 is automatically performed based on an operation of starting biopsy site collection by an engineer.

[Step S8]
Next, an operation for calculating biopsy site position information is performed (step S8). The biopsy site position information calculation unit 110 calculates the position information of the biopsy site 54 based on the biopsy site 54 instructed by the engineer and the two pieces of radiation image information stored in the image information storage unit 104. To do. This position information is three-dimensional position information of the biopsy site 54. The calculated position information of the biopsy site 54 is supplied to the biopsy needle drive control unit 98. The position information of the biopsy site 54 calculated by the biopsy site position information calculation unit 110 is supplied to the movement amount calculation unit 112.

  Thereafter, the movement amount calculation unit 112 calculates a movement amount for moving the biopsy needle 52 to the biopsy site 54 using the position information of the biopsy site 54. In this case, the amount of movement of the biopsy needle 52 is set in the biopsy needle drive control unit 98 as the amount of movement in the X direction and the amount of movement in the Y direction on the basis of the coordinates of the center of the opening 44, for example. The movement amount of the biopsy needle 52 calculated by the movement amount calculation unit 112 is supplied to the biopsy needle drive control unit 98.

[Step S9]
Next, a biopsy needle moving operation is performed (step S9). The biopsy needle drive control unit 98 controls the biopsy needle 52 to move to a predetermined position according to the movement amount of the biopsy needle 52 supplied from the movement amount calculation unit 112. The biopsy hand unit 40 moves the first arm 48 and the second arm 50 in the XY plane according to the position information of the biopsy site 54 in the X direction and the Y direction, and moves the biopsy needle 52 above the biopsy site 54. Position to. Next, the biopsy needle 52 is moved in the Z direction, and an operation of inserting the biopsy needle 52 into the breast 28 through the opening 44 formed in the compression plate 38 is started.

  The position information of the biopsy needle 52 in the Z direction is sequentially calculated by the biopsy site position information calculation unit 110 and supplied to the biopsy needle drive control unit 98. The biopsy needle 52 is moved in the Z direction by the biopsy needle drive control unit 98 in accordance with the position information of the biopsy needle 52 in the Z direction and the movement limit amount of the biopsy hand unit 40 that has been set, and the sampling unit 56 ( 2) is brought to the vicinity of the biopsy site 54. In this case, since the movement of the biopsy needle 52 in the XY plane is restricted, the biopsy needle 52 does not inadvertently move greatly in the X direction or the Y direction in the inserted state, and the breast 28 A situation in which tissue is damaged can be avoided.

[Step S10]
Finally, a biopsy site collection operation is performed (step S10). When the collection part 56 of the biopsy needle 52 reaches the vicinity of the biopsy site 54, suction processing by the biopsy needle 52 is started, and the biopsy site 54 is collected. Thereafter, by moving the biopsy needle 52 in the Z direction, the biopsy needle 52 is extracted from the breast 28, and the operation is completed.

  As described above, the mammography apparatus 20 according to the above-described embodiment includes the radiation source 30 that exposes the radiation Xray to the breast 28 of the subject 27 and is supported rotatably about the rotation axis (hinge portion 35). A solid state detector 60 that detects a dose of radiation Xray that has passed through the breast 28 of the subject 27; and image information relating to the breast 28 of the subject 27 based on the dose of radiation Xray detected by the solid state detector 60; A radiographic image forming unit 84 that forms a radiographic image based on image information, and a plurality of AECs that detect radiation Xray doses that have passed through the breast 28 of the subject 27 and obtain detection values for AEC at a plurality of measurement positions. A weighting unit that multiplies the detection values measured at the positions of the sensors 64 and the plurality of AEC sensors 64 by a weighting coefficient corresponding to the positions. A mammography apparatus 20 having a provision unit 88 and a radiation source control unit 76 that controls a radiation dose emitted from the radiation source 30 based on the detection value multiplied by a weighting coefficient. A reference value holding unit 90 that holds a weighting coefficient determined based on an imaging condition as a reference weighting coefficient, and a geometric imaging condition regarding the positions of the radiation source 30, the solid state detector 60, or the plurality of AEC sensors 64 are acquired. A geometric imaging condition acquisition unit 92 and a weighting coefficient correction unit 94 that corrects the reference weighting coefficient based on a reference geometric imaging condition, a reference weighting coefficient, and a geometric imaging condition are arranged. .

  As described above, since the reference weighting coefficient is corrected based on the reference geometric imaging condition, the reference weighting coefficient, and the geometric imaging condition, the weighting coefficient used for biopsy in the mammography apparatus 20 is set. The detection value correction of each AEC sensor 64 can be suitably performed without re-taking every time of stereo shooting.

  The geometric imaging conditions were set so as to be determined by the rotation angle of the radiation source 30, the positions where the plurality of AEC sensors 64 were disposed, and the radiation source 30 (hinge portion 35) and the predetermined positions of the solid state detector 60. Therefore, it is possible to easily and accurately correct the detection value deviation of each AEC sensor 64 caused by the difference in stereo angle, that is, the detection value deviation of each AEC sensor 64 caused by geometric distortion.

  Furthermore, since the geometric imaging conditions related to scout imaging are set as reference geometric imaging conditions, the weighting coefficient is not corrected in normal mammography imaging (imaging imaging without using the biopsy function), which is a general aspect. Since the reference weighting factor can be used directly, the most suitable weighting factor to be applied to each AEC sensor 64 can be selected.

  Furthermore, since the mammography apparatus 20 uses the breast 28 as an imaging region, a breast tissue biopsy can be performed.

  This embodiment can be applied not only to a mammography localization apparatus but also tomosynthesis imaging.

  Here, tomosynthesis imaging is an imaging method in which radiation is emitted from a radiation source to a subject at a plurality of different stereo angles. By this tomosynthesis imaging, each radiation transmitted through the subject is detected by a radiation detector and converted into radiation image data, respectively, and the converted image data is reconstructed to reconstruct the subject at an arbitrary tomographic position. A tomographic image can be generated.

  However, a reconstructed tomographic image is generated by reconstructing image data of a few tens of stereo angles. Usually, in order to acquire several tens of image data, photographing at several tens of different stereo angles is required, and a weighting coefficient of the AEC sensor 64 suitable for each stereo angle is required. Therefore, if the mammography apparatus 20 according to the present embodiment is used, the detection value correction of each AEC sensor 64 can be suitably performed without performing pre-exposure every time the stereo angle is changed.

  In such a case, it is preferable that the above-described correction coefficient K (i, j) is obtained as a function of the stereo angle, and the reference weighting coefficient can be corrected by multiplying the reference weighting coefficient by the correction coefficient.

  FIG. 12 is a graph showing an example of a weighting coefficient suitable for tomosynthesis. The geometric imaging conditions are: D = 1.0 [m], R = 0.5 [m], Δx = 0.15 [m], Δy = 0.10 [m], z = −0.05 [m]. m]. Here, Δx and Δy mean the distances in the x direction and y direction (lattice spacing) of the adjacent AEC sensors 64, respectively.

  The correction coefficient K (0,0) associated with the AEC sensor identification number (0,0) is a symmetric function with respect to the θ = 0 ° axis, with the stereo angle θ = 0 ° being the peak. Further, the correction coefficient K (-1, -1) associated with the AEC sensor identification number (-1, -1) is an asymmetric function with respect to the θ = 0 ° axis having a peak around θ = + 20 °. Further, the correction coefficient K (+2, +2) related to the AEC sensor identification number (+2, +2) is an asymmetric function with respect to the θ = 0 ° axis, with a peak around θ = −25 °.

  In this way, a suitable correction factor K (i, j) for each AEC sensor 64 can be held as a function of the stereo angle θ.

  Moreover, it is preferable that the data format of the weighting coefficient supplied to the weighting coefficient providing unit 88 is a common data format regardless of the values of variables such as geometric conditions and stereo angles. If comprised in this way, regardless of the difference of a variable, the common hardware / software arithmetic processing can be performed in the weighting coefficient provision part 88. FIG.

  In addition, this invention is not limited to embodiment mentioned above, Of course, it can change freely in the range which does not deviate from the main point of this invention.

  For example, the weighting coefficient described in the above embodiment (see FIG. 7B and FIGS. 10 to 12) is changed as appropriate according to the apparatus and method to which the present invention is applied. Of course, it can be changed.

  Moreover, although the case where the solid state detector 60 was used was demonstrated in the said embodiment, it replaces with the solid state detector 60 and the radiographic image imaging comprised so that a storage fluorescent substance panel is detachable with respect to the imaging stand 36 is possible. An apparatus may be used.

In the above-described embodiment, the so-called optical scanning method in which the electrostatic latent image accumulated in the solid state detector 60 is scanned with the reading light from the reading light source unit 62 to generate current has been described as an example. However, it may be configured such that the charge of the electrostatic latent image can be read by the TFT method without using the reading light source unit 62 as described above. Furthermore, a radiation solid detector capable of generating an image by directly converting without using the reading light source unit 62 as described above can be used.

  In the above-described embodiment, the solid state detector 60 that is an image sensor and the AEC sensor 64 that is a radiation dose information detector are illustrated and described as separate bodies. In this case, a part of the image sensor can be used as a radiation dose information detector. In this case, the radiation dose information detector can be replaced by an image sensor. In such a case, a radiographic image obtained by pre-exposure performed before stereo imaging can be used. An appropriate region of interest is derived by applying various image processing algorithms to the radiation image, and exposure control of the radiation source 30 is performed based on the number, position, and size of the region of interest. it can.

DESCRIPTION OF SYMBOLS 20 ... Mammography apparatus 22 ... Base 24 ... Rotating shaft 26 ... Arm member 27 ... Subject 28 ... Breast 29 ... Chest wall 30 ... Radiation source 32 ... Radiation source storage part 36 ... Imaging stand 38 ... Compression plate 42 ... Display operation part 60 ... Solid detector 64 ... AEC sensor 74 ... Exposure switch 76 ... Radiation source control unit 78 ... Drive control unit 80 ... Measurement position selection unit 82 ... Exposure time calculation unit 84 ... Radiation image forming unit 86 ... Display unit 88 ... Weighting coefficient Giving unit 90 ... reference value holding unit 92 ... geometric imaging condition acquisition unit 94 ... weighting coefficient correction unit

Claims (7)

A radiation source for exposure to radiation in the shooting site of the Utsushitai,
A radiation detector that detects a dose of the radiation transmitted through the imaging region;
A radiation image forming unit that acquires image information related to the imaging region based on the radiation dose detected by the radiation detection unit, and forms a radiation image based on the image information;
A radiation amount information detecting means for acquiring radiation amount data for exposure control by detecting the dose of radiation transmitted through the pre SL imaging site by the measuring position,
A weighting coefficient applying unit that multiplies each radiation dose information measured by the radiation dose information detecting means by a weighting coefficient corresponding to the measurement position;
A radiation source control unit that controls a radiation dose exposed from the radiation source based on each radiation dose information multiplied by the weighting coefficient,
The radiation source is supported rotatably about a rotation axis and emits the radiation to the imaging region from a plurality of positions relatively different from the radiation dose information detection unit,
When the imaging condition regarding the position of the radiation source, the radiation detection unit, or the radiation dose information detection means is referred to as a geometric imaging condition, the reference geometric imaging condition corresponding to the reference position among the plurality of positions is used. A reference value holding unit that holds the weighting coefficient determined based on a reference value;
A geometric imaging condition acquisition unit that acquires a geometric imaging condition corresponding to a position other than the reference position among the plurality of positions ;
Based on the geometric imaging condition acquired by the geometric imaging condition acquisition unit and the reference geometric imaging condition , the weighting coefficient that is the reference value held by the reference value holding unit is A weighting coefficient correction unit to correct,
A radiographic imaging apparatus comprising: The radiographic imaging apparatus according to claim 1,
The radiographic image capturing apparatus according to claim 1, wherein the geometric imaging condition includes an angle of the radiation source with respect to the radiation detection unit. In the radiographic imaging device of Claim 2 ,
The geometric imaging conditions, the rotation angle of the radiation source, before Kihaka fixed position, the rotation center position of the radiation source, and to include the normal direction of the position of the detection surface according to the radiation detector A radiographic imaging device as a feature. In the radiographic imaging device of any one of Claims 1 thru | or 3 ,
The weighting coefficient correction unit corrects the weighting coefficient using a function having a rotation angle of the radiation source as a variable. In the radiographic imaging apparatus according to any one of claims 1 to 4,
The reference geometric imaging condition is a geometric imaging condition performed by setting the optical axis of the radiation to be a normal direction of a detection surface of the radiation detection unit. Shooting device. In the radiographic imaging apparatus according to any one of claims 1 to 5,
The radiographic image capturing apparatus, wherein the imaging part is a breast of a subject. In the radiographic imaging device of any one of Claims 1 thru | or 6,
The radiation image photographing apparatus, wherein the radiation dose information detecting means is integrated with or separate from the radiation detecting unit.

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