JP2008079923A - Radiographic photographing equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve dose insufficiency caused by that a diagnosis object region becomes out of a sensor disposition range by controlling the amount of the radiation irradiation in response to the output of each sensor in radiographic photographing equipment having a plurality of sensors for automatic exposure control. <P>SOLUTION: A mammography equipment 1 determines whether patterns of output values of the respective sensors constituting an AEC (Automatic Exposure Control) sensor section 13 have resemblance to a sensor pattern A or a sensor pattern B, when determining to have resemblance to the sensor pattern A, determines an irradiation time T corresponding to the mean mammary gland content of the AEC sensor section 13 and, after the lapse of the irradiation time T, stops the radiation irradiation from a radiation source 6. When determining to have resemblance to the sensor pattern B, the equipment determines a time T(1+α) obtained by adding a prescribed extra time to the radiation irradiation time T and, after the lapse of the irradiation time T(1+α), stops the radiation irradiation from the radiation source 6. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a radiographic image capturing apparatus, and more particularly to a radiographic image capturing apparatus capable of capturing a phase contrast image.

  A breast image obtained by imaging a breast using radiation is widely used as a medical image for diagnosis. Proper control of the radiation dose irradiated in mammography is important in order to prevent an excessive exposure dose to the subject. In addition, radiation dose and image quality are very closely related, and if the dose is not appropriate, the granularity of the image will increase, so the imaging performance of the subject will deteriorate and the diagnostic performance will deteriorate, so the radiation dose to be irradiated will be controlled appropriately This is also important for ensuring diagnostic performance of images. Therefore, an imaging device that performs mammography is equipped with an automatic exposure control device (AEC) and is controlled so that the radiation dose is appropriate.

  In the radiographic imaging device, the radiation amount transmitted through the subject is measured on the opposite side of the surface facing the radiation source of the radiation image detector that detects the radiation transmitted through the subject held on the opposite side across the radiation source and the subject. It has a sensor (AEC sensor) to detect. In the automatic exposure control, the radiation irradiation time is controlled in accordance with the radiation dose detected by this sensor. Since most breast cancers originate from mammary tissue, it is the main diagnostic area in the breast image and it is important to irradiate the mammary tissue with an optimal dose of radiation. Therefore, in order to irradiate the region of the mammary gland with an optimal dose of radiation, the radiographer needs to position the sensor so that the position of the sensor for detecting the radiation dose corresponds to the portion having the highest breast density. .

  As an aid to this automatic exposure control, for example, in Patent Document 1, a sensor position is projected onto the breast to indicate where the sensor is located on the breast before X-ray irradiation. Is described.

  In addition, as described in Non-Patent Document 1, in recent years, it has a plurality of sensors that detect the amount of radiation that has passed through the subject, and calculates the mammary gland content of the entire subject from the detection values of the plurality of sensors, There has also been proposed an imaging apparatus having a function of controlling the radiation dose applied to the subject based on the mammary gland content.

The technique described in Non-Patent Document 1 does not require an operation for aligning the sensor position with the portion having the highest mammary gland density by the imaging technician, and can improve imaging efficiency.
JP-A-8-80295 Rad Fan Vol. 3 NO. 5 (2005) (pp. 63-64)

  By the way, in the radiographic imaging apparatus having a plurality of sensors that detect the radiation dose transmitted through the subject as described in Non-Patent Document 1, the structure of the radiographic image detector is taken into consideration when arranging the sensors. There is a need. For example, when a member that does not transmit radiation is used for the back plate or the like of the radiation image detector, the sensor cannot be disposed at a position corresponding to this member. Furthermore, since there are many types and sizes of radiological image detectors, in order to make these usable in the same radiographic image capturing device, a sensor arrangement area common to each type and size is searched. It is necessary to arrange a plurality of sensors. That is, in the radiographic imaging device, the sensor cannot be arranged corresponding to the entire surface of the radiographic image detector, and there is a limit to the area where the sensor can be arranged.

  For this reason, as shown in FIG. 8, for example, the subject H is large in size, and the subject does not fit in the region where the sensor (indicated by SE in FIGS. 8 and 9) is placed. When a region having a high rate (indicated by M in FIGS. 8 and 9) has been arranged, the region having a high actual mammary gland content rate is not included in the calculation of the average mammary gland content rate of a plurality of sensors. When the radiation dose is controlled in accordance with the mammary gland content of the entire subject calculated from the plurality of sensors, there is a problem that a sufficient dose of radiation cannot be irradiated to a portion having a high mammary gland density. Further, when performing phase contrast imaging, as shown in FIGS. 9A and 9B, the relationship between the position of the radiation image and the sensor differs depending on the enlargement ratio. There was a similar problem when going out of range.

  An object of the present invention is to provide a radiographic imaging apparatus having a plurality of sensors for automatic exposure control, by controlling the radiation dose according to the output of each sensor, so that the diagnosis target area is outside the sensor arrangement area. It is to be able to solve the shortage of dose due to the accident.

In order to solve the above-mentioned problem, the invention described in claim 1
A radiation source for irradiating the subject with radiation;
Detector holding means for holding a radiographic image detector for detecting radiation from the radiation source;
Detecting means for detecting a radiation amount transmitted through the radiation image detector held by the detector holding means;
Control means for controlling the radiation dose from the radiation based on the detection result by the detection means;
In a radiographic imaging apparatus comprising:
The detection means is configured by arranging a plurality of sensors in a planar area in an area area smaller than the area occupied by the radiation image detector,
The control means variably controls the radiation dose from the radiation source according to the output of each sensor in the plurality of sensors.

The invention according to claim 2 is the invention according to claim 1,
Whether the control unit includes the diagnosis target region of the subject of the radiographic image detected by the radiological image detector in the arrangement region of the plurality of sensors based on the outputs of the individual sensors in the plurality of sensors. It is characterized by determining whether or not, and variably controlling the radiation dose from the radiation source according to the determination result.

The invention according to claim 3 is the invention according to claim 1 or 2,
The radiographic imaging device is an imaging device capable of phase contrast imaging,
A magnification setting means for setting a shooting magnification; a shooting direction setting means for setting a shooting direction of the subject;
With
The control means further variably controls the radiation dose from the radiation source based on the photographing direction set by the photographing direction setting means and / or the photographing magnification set by the magnification setting means. It is characterized by.

  According to the first and second aspects of the present invention, since the radiation dose is variably controlled according to the output of each of the plurality of sensors of the detection means, the diagnosis target region is a sensor according to the output of each sensor. It is possible to determine whether the region is out of the arrangement region, and to variably control the radiation irradiation amount according to the result, and to solve the shortage of dose due to the diagnosis target region being out of the sensor arrangement region.

  According to the third aspect of the present invention, the radiation dose can be variably controlled with higher accuracy in accordance with the imaging direction and / or the imaging magnification.

A breast image capturing apparatus 1 according to the present embodiment is a radiographic image capturing apparatus that performs phase contrast imaging. Hereinafter, the configuration of the breast image capturing apparatus 1 will be described with reference to the drawings.
1 and 2 show a configuration example of the breast image photographing apparatus 1. FIG. 1 is a diagram illustrating an example of an external configuration of the breast image photographing apparatus 1, and FIG. 2 is a diagram schematically illustrating an internal configuration of the photographing apparatus main body 2 of the breast image photographing apparatus 1 illustrated in FIG. In FIG. 2, the AEC sensor unit 13, the operation device 14, the power supply unit 15, the drive device 17, and the drive device 19 are connected to the control device 16 (shown in FIG. 3) of the main body unit 9. do not do. As shown in FIG. 1, in the mammography apparatus 1, a support base 3 is provided on a main body 9 so as to be movable up and down, and a support shaft 4 provided on the support base 3 is attached to the support base 3. The imaging device main body 2 is supported through the support. The support base 3 is moved up and down by being driven by a drive device 17 constituted by a motor or the like. The imaging device main body 2 can be raised and lowered by raising and lowering the support base 3 by the drive device 17, and can be rotated by the drive device 17 about the support shaft 4.

  A radiation source 6 for emitting radiation is provided on the upper part of the imaging apparatus main body 2, and the radiation source 6 is connected to the main body 9 via the support shaft 4 and the support base 3. It is connected to the. The radiation source 6 is applied with a tube voltage and a tube current by the power supply unit 15. The radiation source of the radiation source 6 is provided with a throttle port of a diaphragm device 7 as an irradiation field adjustment device that adjusts the radiation field, so that the radiation field can be opened and closed.

  The radiation source 6 is preferably a rotary anode X-ray tube. In this rotary anode X-ray tube, X-rays are generated when an electron beam emitted from the cathode collides with the anode. This is incoherent (incoherent) like natural light, and is not divergent X-rays but divergent light. If the electron beam continues to hit the place where the anode is fixed, the anode is damaged by the generation of heat. Therefore, in an X-ray tube that is usually used, the anode is rotated to prevent the anode from being shortened. An electron beam is made to collide with a plane of a certain size of the anode, and the generated X-rays are emitted toward the subject H from the plane of the certain size of the anode. This plane is called a focus. The focal point size D (μm) indicates the length of one side when the focal point is a square, the short side when the focal point is a rectangle or a polygon, and the diameter when the focal point is a circle.

  As the focal spot size D increases, the amount of radiation applied increases. Since a radiation dose of a certain level or more is practically required to pass through the human body, the breast image capturing apparatus 1 can irradiate the radiation dose necessary for photographing the human body, and the focal spot size D is D ≧ 30 (μm). The radiation source 6) is preferred.

  A detector holder 12 that holds a cassette containing a stimulable phosphor sheet, for example, as a radiographic image detector that detects radiation transmitted through the subject H is provided below the subject table 10 below the imaging apparatus main body 2. At a position extending substantially perpendicularly from the radiation source 6, it is attached so as to face the radiation source 6. The uppermost surface of the radiation image detector held by the detector holding unit 12 coincides with the uppermost surface of the detector holding unit 12. The radiation source 6 and the detector holding unit 12 are attached to a holding member 8 as shown in FIG. 2, and the distance L (R1 + R2 described later) between the radiation source 6 and the detector holding unit 12 is set by the holding member 8. It is maintained at a certain distance. The holding member 8 can be moved up and down by driving a driving device 19 composed of a motor or the like. The raising and lowering of the holding member 8 by the driving device 19 keeps the radiation source 6 and the detector holding unit 12 at a constant distance. It is designed to go up and down. The relative distance between the radiation source 6 and the detector holding unit with respect to the subject table 10 can be adjusted by raising and lowering the radiation source 6 and the detector holding unit 12 by driving the driving device 19. That is, the drive device 19 functions as an adjustment unit. Note that the distance L between the radiation source 6 and the detector holding unit 12 is L from the viewpoint of the visibility of the edge enhancement effect (phase contrast effect) when the captured image is output when the focus size D ≧ 30 (μm). It is preferable that ≧ 0.95 (m).

As the radiation image detector, for example, a screen (intensifying screen) / film, an FPD (flat panel detector), or the like may be used in addition to the cassette containing the photostimulable phosphor sheet.

  At the position below the radiation source 6 and above the detector holding unit 12 in the imaging apparatus main body 2 and extending substantially perpendicularly from the radiation source 6, the subject table 10 and the subject H that hold the subject H from below are provided. A compression plate 11 is arranged for pressing and fixing from above. As shown in FIG. 2, the subject table 10 is attached to the holder 5 of the photographing apparatus main body 2 and moves up and down in accordance with the raising and lowering of the photographing apparatus main body 2 by the driving device 17. Thereby, the height of the subject table 10 can be adjusted according to the position of the subject H (breast position). The compression plate 11 is configured to be movable up and down along a support shaft (not shown) provided in the photographing apparatus main body 2.

  The position of the compression plate 11 is detected by a position detection unit 18 (shown in FIG. 3) and output to the control device 16 of the main body unit 9. As the position detection unit 18, a method using photometry using infrared rays, a method in which a line resistance is provided on the rail of the support shaft that slides the compression plate 11, and a position is determined based on the resistance value measurement can be employed.

  An AEC sensor unit serving as a detection unit that detects the amount of radiation that has passed through the radiation image detector held by the detector holding unit 12 is provided on the surface of the detector holding unit 12 opposite to the surface facing the subject table 10. 13 is provided. The AEC sensor unit 13 is a sensor configured by, for example, a photomultiplier, an ion chamber, or a semiconductor.

  FIG. 4 shows a sensor arrangement example of the AEC sensor unit 13. In the AEC sensor unit 13, a plurality of sensors are arranged in a planar shape in an area region smaller than the area occupied by the radiation image detector held by the detector holding unit 12.

  Each of the plurality of sensors has a conversion unit (not shown) that converts the detection value of the radiation dose of the sensor into the mammary gland content rate. In the conversion unit of each sensor, the transmitted dose when each dose (each dose in the range to be irradiated in mammography) is irradiated to the breast of each mammary content is stored as data in advance. This is data obtained by measuring in advance using an experimental phantom of a breast of each mammary gland content rate. The conversion unit of each sensor measures the transmitted dose of the subject that has reached the sensor in n microseconds after the start of irradiation based on the detected value for n microseconds after the start of irradiation from the sensor. The detected value of the sensor is converted into the mammary gland content rate of the breast portion on the sensor based on the radiation dose (input from the control device 16) and the pre-measured data of each mammary gland content rate stored in advance. It outputs to the control apparatus 16 as a sensor output value. The mammary gland content is output in the range of 0 to 100 (%). When the mammary gland content is 0, it indicates that there is no mammary gland at a position corresponding to this sensor, and the higher the value, the more The mammary gland density at the position corresponding to the sensor is high.

The main body 9 includes a CPU (Central Processing Unit), ROM (Read Only Memory), RA
A control device 16 composed of M (Random Access Memory) is provided. FIG. 3 shows a functional configuration example of the breast image capturing apparatus 1. As shown in FIG. 3, the control device 16 includes an AEC sensor unit 13, a keyboard and a touch panel for setting shooting conditions such as an enlargement ratio and a shooting direction as a shooting direction setting unit and a magnification setting unit, and a subject table 10. An input device 14a having a position adjustment switch (upward adjustment switch for upward adjustment, downward adjustment switch for downward adjustment) for adjusting the position, and an operation device 14 having a display device 14b such as a CRT display or a liquid crystal display. , A power source 15 that is a power source of the apparatus, a driving device 17 that moves the imaging apparatus main body 2 up and down by rotating the support base 3 and rotates the imaging apparatus main body 2, and a position detection unit that detects the position of the compression plate 11. 18 and a drive device 19 for raising and lowering the holding member 8 are connected via a bus 20. The ROM of the control device 16 stores various control programs including an imaging control processing program for controlling each part of the mammography apparatus 1 and data necessary for executing the program. In cooperation with the program, the operation of each part of the mammography apparatus 1 is comprehensively controlled to perform phase contrast imaging.

  In the ROM of the control device 16, as shown in FIG. 5, the imaging direction of the breast (right breast oblique direction; MLO-R, left breast oblique direction; MLO-L, vertical direction of the right breast and left breast) ; For each combination of CC) and magnification rate, sensor pattern A and sensor pattern B for determining whether or not a region having a high mammary gland content rate is included in the sensor arrangement region at the time of imaging are stored. The region having a high mammary gland content of the subject here refers to a region corresponding to a region having the highest mammary gland density of the subject in a radiographic image transmitted through the subject. The sensor pattern A is a sensor at each position in the sensor arrangement area when a region having a high mammary gland content of the subject is included in the sensor arrangement area of the AEC sensor unit 13 in each combination of the photographing direction and the enlargement ratio. This is a reference pattern of output values. The sensor pattern B is a sensor at each position in the sensor arrangement area when an area with a high mammary gland content of the subject is arranged outside the sensor arrangement area of the AEC sensor unit 13 in each combination of the imaging direction and the magnification ratio. This is a reference pattern of output values.

  FIG. 5A shows an example of sensor patterns A and B of CC with an enlargement ratio of 1.75 times. FIG. 5B shows an example of sensor patterns A and B of MLO-R with an enlargement ratio of 1.75 times. FIG. 5C shows an example of sensor patterns A and B with an enlargement ratio of 1.75 times and MLO-L. FIG. 5D shows an example of the sensor patterns A and B of CC with an enlargement ratio of 1.46. In addition, although not shown in the drawings, the sensor patterns A and B of MLO-R with an enlargement ratio of 1.75 times and the sensor patterns A and B of MLO-L with an enlargement ratio of 1.75 times are also stored in the same manner. In addition, the rectangle shown in FIG. 5 shows each sensor arrange | positioned in the sensor arrangement | positioning area | region of the AEC sensor part 13, and the numerical value in each rectangle shows the mammary gland content rate which is an output value of each sensor.

  Here, the principle of phase contrast imaging will be described with reference to FIG. Phase contrast imaging is to obtain an edge-enhanced (refractive contrast-enhanced) image resulting from the refraction of radiation as shown in FIG. 6 by providing a certain distance R2 between the subject H and the radiation image detector. is there. As schematically depicted in FIG. 6, radiation is refracted when passing through the object, and the radiation density inside the boundary of the object becomes sparse, and the outside of the object overlaps with radiation that does not pass through the object. To rise. In this way, the edge that is the subject boundary portion is enhanced as an image. This is a phenomenon resulting from the difference in refractive index between the object and air with respect to radiation. This is an edge-enhanced image.

  Further, not only the edge enhancement at the boundary between air and the subject shown in principle in FIG. 6 but also the same effect can be obtained at the boundary portion having a different refractive index in the object. The subject boundary portion in the present invention can be expressed as a boundary portion with a substance having a different refractive index of radiation.

  When phase contrast imaging is performed, if the distance from the radiation source 6 to the subject H is R1, and the distance between the subject H and the radiographic image detector is R2, the magnification ratio = (R1 + R2) / R1 is magnified at the imaging magnification. . Here, with respect to R1, the starting point is the position of the focal point of the radiation source 6, and the location is clearly shown in the ordinary commercially available radiation source 6. The end point is the center line of the subject H fixed by the subject table 10 that fixes the subject position. Here, the position that is equidistant from the subject table 10 and the compression plate 11 is the center line of the subject H. For R2, the starting point is the center line of the subject H, and the ending point is the uppermost surface of the plane that receives the radiation of the radiation image detector, that is, the uppermost surface of the detector holding unit 12.

  In the present embodiment, it is assumed that the breast image capturing apparatus 1 performs phase contrast imaging at any magnification ratio (imaging magnification) of 1.46 times or 1.75 times.

Next, the operation of the mammography apparatus 1 will be described.
FIG. 7 shows photographing control processing executed by the control device 16. The control means is realized by executing the processing.

  First, shooting conditions including a shooting direction are set and input from the input device 14a (step S1), then the positions of the subject table 10 and the compression plate 11 are adjusted, and the positions of the subject table 10 and the compression plate 11 are set. (Step S1). Specifically, it is determined whether or not the photographing direction input from the input device 14a is a photographing direction that requires rotation of the photographing device main body 2, and when the photographing direction requires rotation, for example, In the case of MLO (Medio-Lateral Oblique) in which the breast is imaged from the oblique direction, the driving device 17 is controlled, and the entire imaging device body 2 is rotated by a predetermined amount. When the position adjustment switch of the input device 14a is operated, the drive device 17 is controlled according to the operation of the position adjustment switch, and the position of the subject table 10 is adjusted. In addition, the operator H such as a photographing engineer adjusts the position of the compression plate 11 and presses and fixes the subject H. After the adjustment, the input device 14a inputs an instruction to set the subject table 10 and the compression plate 11 to the adjusted position, thereby completing the setting.

  After the positions of the subject table 10 and the compression plate 11 are set, when the enlargement factor (imaging magnification) is set and input by the input device 14a (step S3), the radiation source for the subject table 10 is set according to the input imaging magnification. 6 and the detector holding unit 12 are calculated, and the driving device 19 is controlled, whereby the distances from the subject table 10 to the radiation source 6 and the detector holding unit 12 are calculated. The holding member 8 is moved to this position, and the relative distance between the radiation source 6 and the detector holding unit 12 with respect to the subject table 10 is adjusted (step S4).

  Next, the sensor patterns A and B stored in the ROM of the control device 16 corresponding to the shooting direction and the enlargement ratio are read into the RAM (step S5), and a shooting instruction from the input device 14a is awaited.

  When an imaging instruction is input from the input device 14a (step S6; YES), a tube voltage and a tube current are applied to the radiation source 6 by the power supply unit 15 to start radiation irradiation (step S7). The output value (mammary gland content rate) of each sensor is acquired (step S8), and the average mammary gland content rate of the entire subject is calculated based on the output value from the AEC sensor unit 13 (step S9). When there is a defect sensor whose value is not output, a value obtained by interpolation from the mammary gland content output from the surrounding normal sensors is used as the mammary gland content of the defect sensor.

  Next, a pattern of output values output from the individual sensors of the AEC sensor unit 13 (pattern consisting of output values output from the sensors at the respective sensor positions in the sensor arrangement region) is read into the RAM. It is determined whether the pattern A or the sensor pattern B is similar (step S10). Here, the two-dimensional normalized cross-correlation values of the output value pattern output from each sensor of the AEC sensor unit 13 and the sensor pattern A and sensor pattern B read out to the RAM are respectively obtained by the template matching method. It is determined that the pattern of the output value output from each sensor of the AEC sensor unit 13 is similar to the sensor pattern having the larger correlation value. Here, as shown in FIG. 5, the sensor pattern A is a pattern in which the sensor output value near the center of the sensor placement area is high. If the sensor pattern A is similar to the sensor pattern A, the sensor pattern A has a high mammary gland content rate. Is included in the sensor placement region. As shown in FIG. 5, the sensor pattern B is a pattern in which the sensor output value is high at the edge of the sensor arrangement region. If the sensor pattern B is similar to the sensor pattern B, the region having a high mammary gland content is the sensor placement. It is determined that it exists outside the area. Note that the irradiation time of radiation is about 2 seconds on average, and the time required for the determination in step S10 is about 100 milliseconds.

  When it is determined that the pattern of output values output from each sensor of the AEC sensor unit 13 is similar to the sensor pattern A (step S11; YES), based on the average mammary gland content calculated in step S9. The irradiation time T by the radiation source 6 is determined (step S12). The ROM of the control device 16 is associated in advance with an average mammary gland content rate and a radiation irradiation time required for irradiating a radiation dose necessary for obtaining an image suitable for diagnosis at the average mammary gland content rate. A table is stored, and by referring to the table stored in the ROM, the radiation irradiation time T corresponding to the average mammary gland content calculated in step S9 is determined as the radiation irradiation time.

  When the irradiation time T is determined, the process waits until the irradiation time T elapses. When it is determined that the irradiation time T has elapsed (step S13; YES), the radiation irradiation from the radiation source 6 is stopped (step S16). ), This process ends.

  On the other hand, if it is determined that the pattern of output values output from each sensor of the AEC sensor unit 13 is similar to the sensor pattern B (step S11; NO), the average mammary gland content calculated in step S9 is obtained. Based on this, the irradiation time T (1 + α) from the radiation source 6 is determined (step S14).

  As described above, the ROM of the control device 16 previously stores the average mammary gland content rate and the radiation exposure time required to irradiate the radiation dose necessary for obtaining an image suitable for diagnosis at the average mammary gland content rate. Are stored in the associated table. However, when the pattern of output values output from each sensor is similar to the sensor pattern B, it is estimated that a region having a high mammary gland content rate exists outside the sensor arrangement region.

  Here, the breast is mainly composed of mammary gland tissue and other adipose tissue that spreads from the nipple toward the chest wall, and the mammary gland tissue has a characteristic that it easily absorbs radiation, and the adipose tissue easily transmits radiation. Yes. Since mammary tissue is likely to develop lesions such as cancer, an image suitable for diagnosis cannot be obtained unless radiation of a dose corresponding to the mammary gland content of the subject is irradiated, and this affects the diagnosis. When the region having a high mammary gland content rate exists outside the sensor arrangement region, the average mammary gland content rate calculated in step S9 is calculated based on the region having a low mammary gland content rate of the subject. Even if the irradiation time is calculated based on the average mammary gland content rate, the dose is insufficient for the region of high mammary gland content that is the main region of interest (diagnostic region), and the resulting image has graininess (roughness). And an image suitable for diagnosis cannot be obtained.

  Therefore, in step S14, the table stored in the ROM is referred to obtain the radiation irradiation time T corresponding to the average mammary gland content calculated in step S9, and the radiation irradiation time T is extended by a certain amount. A time T (1 + α) obtained by adding the times is determined as the radiation irradiation time. The extension time is 20 to 30 percent of T and is predetermined. The extension time may be configured to be appropriately set.

  When the irradiation time T is determined, the process waits until the irradiation time T (1 + α) elapses. When it is determined that the irradiation time T (1 + α) elapses (step S15; YES), the radiation irradiation from the radiation source 6 is performed. Is stopped (step S16), and this process ends.

  As described above, according to the mammography apparatus 1, it is determined whether the pattern of the output value of each sensor constituting the AEC sensor unit 13 is similar to the sensor pattern A or the sensor pattern B, When it is determined that the pattern is similar to the sensor pattern A, it is determined that a region having a high mammary gland content is included in the sensor arrangement region, and the irradiation time T corresponding to the average mammary gland content of the AEC sensor unit 13 is determined. Then, after the irradiation time T has elapsed, the radiation irradiation from the radiation source 6 is stopped. When it is determined that the pattern is similar to the sensor pattern B, it is determined that a region having a high mammary gland content rate is also present outside the sensor arrangement region, and an irradiation time T corresponding to the average mammary gland content rate of the AEC sensor unit 13 is obtained. A time T (1 + α) obtained by adding a certain extension time to the radiation irradiation time T is determined as the radiation irradiation time, and after the irradiation time T (1 + α) has elapsed, the radiation irradiation from the radiation source 6 is stopped.

  Therefore, even when a region having a high mammary gland content that is a diagnosis target region exists outside the sensor placement region, a sufficient radiation dose can be irradiated, and a region having a high mammary gland content is determined to be outside the sensor region. This makes it possible to eliminate the shortage of dose.

  In addition, the sensor patterns A and B for determining whether or not a region having a high mammary gland content is included in the sensor arrangement region are prepared according to the shooting direction and the shooting magnification. It is possible to control the radiation dose with high accuracy according to the magnification.

In addition, the description content in the said embodiment is a suitable example of the mammography apparatus 1 which concerns on this invention, and is not limited to this.
For example, in the above embodiment, the detection values of the individual sensors of the AEC sensor unit 13 are converted into the mammary gland content rate and output to the control device 16. However, if the processing speed of the control device 16 is sufficiently high. For example, the detection values of the individual sensors may be output to the control device 16, and the control device 16 may calculate the mammary gland content of each sensor.

  In the above embodiment, the average mammary gland content of the entire subject is calculated by averaging the output values of the sensors of the AEC sensor unit 13, and the irradiation time is determined based on the average mammary gland content. However, it is also possible to calculate the mammary gland content of the entire subject by weighting an area where the mammary gland content is high in the sensor arrangement area, and to determine the radiation irradiation time based on the calculated mammary gland content. Good. In the above embodiment, the irradiation time is determined based on whether or not the region having a high mammary gland content is within the sensor arrangement region and the average mammary gland content of the subject, and only the determined radiation irradiation time is determined. Although the radiation dose is controlled by irradiating the radiation, the radiation dose to be irradiated may be determined and the radiation dose may be controlled.

Further, when it is determined that the pattern is similar to the sensor pattern B in step S11 described above, the correlation value is considered as a reliability for the determination that the region having a high mammary gland content rate exists outside the sensor arrangement region, and the correlation value Based on the above, the radiation irradiation time may be determined.
Further, in order to shorten the calculation time of the correlation value, the correlation value may be calculated after averaging the values of a plurality of adjacent sensors into one value and reducing the sample points. In this case, it is better to hold the reference pattern (sensor patterns A and B) after reducing the sample points.
Further, the correlation value may be obtained by using all the sensors of the AEC sensor unit 13, or the correlation value may be calculated by using only a part of the sensors (for example, half of the nipple side).

In the above embodiment, the sensor pattern A and the sensor pattern B are stored in advance, and it is determined whether or not the region where the subject's mammary gland content is high is within the sensor placement region, depending on which is similar. However, it is not limited to this.
For example, if the number of sensors of the AEC sensor unit 13 is large and the number of quantization bits of the sensor output value is large, a curved surface formed by the sensor output value for each sensor position is extrapolated by a method such as polynomial approximation, etc. The output value of the virtual sensor corresponding to the position outside the arrangement area may be estimated, and the radiation output time or the radiation dose may be controlled using the estimated sensor output value. At this time, only when the mammary gland content value of the virtual sensor is estimated to be higher than the mammary gland content rate in the sensor placement region, the irradiation time or the radiation dose is increased according to the estimated mammary gland content value. You may let them.

  In addition, the virtual sensor output value is estimated only when it is determined that the sensor pattern B is similar to the sensor pattern B in the above-described embodiment, that is, a region having a high mammary gland content rate exists outside the sensor arrangement region. Depending on the value of the mammary gland content, the irradiation time or the irradiation amount may be increased.

  In the imaging control process, when an output value is output from each sensor of the AEC sensor unit 13, the sensor located on the outermost side excluding the chest wall side has a mammary gland content of 0 (direct radiation has been irradiated). It is determined whether or not there is a sensor in the blank region). If there is a sensor having a mammary gland content rate of 0, it is determined that a sensor is present outside the breast region, and steps S10 and S11 are performed. It is good also as irradiating with the irradiation time T defined beforehand according to the average mammary gland content rate computed by step S9, without performing determination.

  In the above-described embodiment, the mammography apparatus 1 has been described as performing magnified imaging by phase contrast imaging. However, the present invention can be applied to a close-contact imaging apparatus that captures an actual subject. Of course. In such a photographing apparatus, since it is not necessary to consider the enlargement ratio in the sensor pattern stored in the ROM, a sensor pattern may be provided for each photographing direction.

  In enlarged spot photography, the area to be diagnosed that is compressed by the spot compression plate matches the sensor placement area. Therefore, during magnified spot photography, the area where the subject's mammary gland content is high is included in the sensor placement area. The function of determining whether or not is OFF may be turned off, and radiation may be irradiated for an irradiation time corresponding to the average mammary gland content rate.

  For example, when the radiation image detector is an FPD device, the function of the AEC sensor described above can be built in the FPD device, or the output value of a predetermined pixel of the FPD device can be substituted. The image detector also serves as the detection means.

  In addition, the detailed configuration and detailed operation of the mammography apparatus 1 can be changed as appropriate without departing from the spirit of the present invention.

It is a figure which shows the structural example of the mammography apparatus 1 which concerns on this invention. It is a figure which shows typically the internal structure of the imaging device main-body part 2 of the breast image imaging device 1. FIG. 2 is a block diagram showing a functional configuration of the breast image capturing apparatus 1. FIG. It is a figure which shows the example of sensor arrangement | positioning of the AEC sensor part. (A) is a figure which shows an example of sensor pattern A and B of magnifying power 1.75 times, CC, (b) shows an example of sensor pattern A and B of magnifying power 1.75 times, MLO-R. (C) is a figure which shows an example of sensor pattern A and B of magnifying power 1.75 times, MLO-L, (d) is an example of sensor pattern A and B of magnifying power 1.46 times. FIG. It is a figure for demonstrating the principle of phase contrast imaging. 3 is a flowchart showing a photographing control process executed by a control device 16; It is a figure which shows the relationship between the arrangement | positioning area | region of a sensor (SE) in case the size of a to-be-photographed object (H) is large, and the area | region (M) with a high mammary gland content rate in an image. It is a figure which shows the relationship between the arrangement | positioning area | region of a sensor (SE) when image | photographed with 1.46 times of magnifications, and 1.75 times, and the area | region (M) with a high mammary gland content rate in an image.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mammography apparatus 2 Imaging apparatus main-body part 3 Support base 4 Support axis 6 Radiation source 7 Diaphragm apparatus 8 Holding member 9 Main-body part 10 Subject base 11 Pressure plate 12 Detector holding part 13 AEC sensor part 14 Operation apparatus 14a Input apparatus 14b Display device 15 Power supply unit 16 Control device 17 Drive device 18 Position detection unit 19 Drive device 20 Bus

Claims (3)

A radiation source for irradiating the subject with radiation;
Detector holding means for holding a radiographic image detector for detecting radiation from the radiation source;
Detecting means for detecting a radiation amount transmitted through the radiation image detector held by the detector holding means;
Control means for controlling the radiation dose from the radiation based on the detection result by the detection means;
In a radiographic imaging apparatus comprising:
The detection means is configured by arranging a plurality of sensors in a planar area in an area area smaller than the area occupied by the radiation image detector,
The radiographic imaging apparatus characterized in that the control means variably controls the radiation dose from the radiation source in accordance with the output of each sensor in the plurality of sensors.   Whether the control unit includes the diagnosis target region of the subject of the radiographic image detected by the radiological image detector in the arrangement region of the plurality of sensors based on the outputs of the individual sensors in the plurality of sensors. 2. The radiographic imaging apparatus according to claim 1, wherein the radiographic imaging apparatus determines whether or not, and variably controls the radiation dose from the radiation source according to the determination result. The radiographic imaging device is an imaging device capable of phase contrast imaging,
A magnification setting means for setting a shooting magnification; a shooting direction setting means for setting a shooting direction of the subject;
With
The control means further variably controls the radiation dose from the radiation source based on the photographing direction set by the photographing direction setting means and / or the photographing magnification set by the magnification setting means. The radiographic imaging device according to claim 1 or 2.

Images