JP2008167928A - Radiation image capturing apparatus and radiation image capturing method - Google Patents

Abstract

Provided is a radiographic imaging apparatus that suppresses exposure of a subject by irradiating only a minimum necessary part during pre-exposure.
A subject is placed on a top plate arranged opposite to the radiation source, the placed subject is irradiated with radiation from the radiation source, and the radiation transmitted through the subject is detected by a radiation detector. A mammography unit that performs measurement, a measurement unit that measures the size of the subject placed on the top, and a radiation irradiation region that is irradiated from the radiation source toward the radiation detector according to the measurement result of the measurement unit. An irradiation area limiting means for limiting, and an AEC circuit that performs pre-exposure by irradiating radiation within the area limited by the irradiation area limiting means and calculates a radiation dose suitable for the subject.
[Selection] Figure 2

Description

  The present invention captures a subject using radiation (X-rays), and particularly relates to a radiation image capturing apparatus and a radiation image capturing method suitable for capturing a breast image.

  Conventionally, a mammography apparatus is known as a radiographic image capturing apparatus for capturing a breast image in the medical field. The mammography device irradiates radiation (e.g., X-rays) that does not harm the health of the subject from the radiation source toward the subject (breast), and detects the radiation that has passed through the subject with a digital radiation detector, Radiation images are acquired.

  Patent Document 1 describes an X-ray detection apparatus used for mammography and the like.

  Some radiographic imaging apparatuses have an AEC (Automatic Exposure Control) function. AEC calculates radiation time for each subject according to the subject in order to emit radiation at an appropriate dose, and controls to stop the radiation at an appropriate timing during radiation exposure. It is. In order to calculate the appropriate dose, it is necessary to measure the size of the breast for each subject. For this reason, conventionally, test exposure called pre-exposure is performed in order to calculate the exposure amount by AEC.

  In pre-exposure, radiation from a radiation source is irradiated toward the entire radiation detector, radiation that has passed through the subject (breast) is detected by the radiation detector, and the size of the breast is measured. The appropriate dose is calculated based on this.

However, when calculating an appropriate exposure time by AEC, an image detected by the entire radiation detector is not required, and it is only necessary to acquire a part of the image, that is, an image of the breast part, and the other part of the image is diagnosed and It does not contribute to the calculation of AEC. Therefore, it was exposed to the part which was not necessary conventionally, and there was a risk of harming the health of the subject.
JP 2001-330679 A

  Conventionally, pre-exposure has been performed to calculate an appropriate exposure time by AEC, but radiation is also applied to parts that do not contribute to the calculation or diagnosis of AEC. There was a problem of fear of harm.

  The present invention has been made in view of the above circumstances, and a radiation image capturing apparatus and a radiation image capturing that suppress radiation of a subject as much as possible by irradiating only a minimum necessary part during pre-exposure. It aims to provide a method.

  The radiographic imaging device according to the first aspect of the present invention is configured such that a subject is placed on a top plate disposed opposite to a radiation source, and radiation from the radiation source is placed on the subject placed on the top plate. A mammography unit that irradiates and detects radiation transmitted through the subject with a radiation detector, a measuring unit that measures the size of the subject placed on the top plate, and a measurement result of the measuring unit Accordingly, an irradiation area limiting means for limiting an irradiation area of radiation irradiated from the radiation source toward the radiation detector, and pre-exposure by irradiating the area within the area limited by the irradiation area limiting means And an AEC circuit for calculating a radiation dose suitable for the subject.

  The radiographic imaging method of the present invention according to claim 8 is a mammographic imaging method in which a subject is placed on a top plate arranged opposite to a radiation source, and radiation transmitted through the subject is detected by a radiation detector. Radiation is irradiated from the radiation source toward the radiation detector by measuring the size of the placed object in advance. Pre-exposure is performed by limiting the area according to the measurement result, and a radiation dose suitable for the subject is calculated using the detection result of the radiation detector by the pre-exposure. The region restriction is removed, and the radiation dose to the subject is controlled based on the calculation result.

  According to the present invention, X-rays are irradiated to the minimum necessary range during pre-exposure, so that the exposure dose of the subject can be reduced.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram showing the overall configuration of an embodiment of a radiographic image capturing apparatus of the present invention. In FIG. 1, reference numeral 10 denotes a radiographic image capturing apparatus, which includes a mammography unit 11. The mammography unit 11 includes an X-ray tube 13 attached to one end (upper end) of an arm 12 and a top plate 14 attached to the other end (lower end) of the arm 12. A detector 15 is provided. A compression plate 16 for compressing the subject P (breast) is movably attached in the vertical direction between the X-ray tube 13 and the top plate 14.

The X-ray detector 15 is a flat-type detector (flat panel detector), in which a plurality of two-dimensionally arranged pixels are arranged in a matrix, and the subject P is transmitted through each pixel. X-rays are detected, respectively, and the detected X-rays are converted into electrical signals. The X-ray detector 15 includes an amplifier that amplifies the electric signal and an A / D converter that converts the amplified electric signal (analog signal) into a digital signal.

The top plate 14 is opposed to the X-ray tube 13. The subject is placed on the top plate 14, and the subject is sandwiched between the top plate 14 and the compression plate 16 and pressed to perform imaging. . A pressure sensor 17 is fixed to the surface of the compression plate 16 that faces the top plate 14. Alternatively, the distance sensor 18 may be provided on the surface of the top 14 on which the subject P is placed instead of the pressure sensor 17. The roles of the pressure sensor 17 and the distance sensor 18 will be described later.

  FIG. 2 is a block diagram illustrating a hardware configuration of the radiographic image capturing apparatus 10 of the present invention.

  In FIG. 2, the mammography unit 11 includes an X-ray tube 13 and an X-ray detector 15, and the X-ray tube 13 generates X-rays with a high voltage supplied from a high voltage generation unit 21. X-rays that have passed through the subject P are detected by the X-ray detector 15 and converted into electrical signals. The air signal is read out via the data collection unit 22 and the digital projection data is transmitted to the computer system 30.

  The computer system 30 includes a bus line 31, and a system control unit 32, a data processing unit 33, a data storage unit 34, an operation unit 35, and a display unit 36 are connected to the bus line 31.

  The system control unit 32 controls the overall operation of the computer system 30. The data processing unit 33 processes the digital projection data sent from the data collecting unit 22 to generate predetermined image data. The data storage unit 34 stores image data.

  The operation unit 35 is operated by an operator, and gives various kinds of operation information such as pre-exposure and main exposure instructions and imaging start by operation of the operation unit 35. The display unit 36 displays the image generated by the data processing unit 33. The operation unit 35 and the display unit 36 together with the system control unit 32 constitute a user interface.

  In addition, an AEC circuit 37 (Automatic Exposure Control circuit) and an irradiation control unit 38 are connected to the bus line 31.

  The AEC circuit 37 calculates the X-ray exposure time individually according to the subject in order to expose the X-rays at an appropriate dose. In calculating the exposure time, first, pre-exposure is performed, and an appropriate X-ray dose is calculated for each subject based on the data of the subject P obtained by the pre-exposure. Output to.

  Further, the output of the pressure sensor 17 or the distance sensor 18 described above is supplied to the sensor circuit 23, and the sensor circuit 23 measures the size of the subject P using the output of the pressure sensor 17 or the distance sensor 18. Measurement data from the sensor circuit 23 is supplied to the irradiation controller 38.

  Further, the mammography unit 11 is provided with an irradiation region limiting unit 24 for limiting the X-ray irradiation range by the X-ray tube 13, and the irradiation region limiting unit 24 is controlled by the irradiation control unit 38. Based on the measurement data from the sensor circuit 23, the irradiation control unit 38 controls the irradiation region limiting unit 24 during pre-exposure to limit the X-ray irradiation range according to the subject P.

  The high pressure generation unit 21 controls the exposure time in response to the calculation result of the AEC circuit 37, stops the exposure when a predetermined time elapses from the start of exposure when performing the main imaging, and becomes an appropriate X-ray dose. To control.

An imaging operation of the radiographic imaging apparatus of the present invention will be schematically described. Before performing actual imaging (main imaging), the subject's subject P is first pressed against the top plate 14 by the compression plate 16 to compress the subject's breast. Next, the size of the subject P (the width X and the width Y of the breast) is measured by the pressure sensor 17 (or the distance sensor 18) and the sensor circuit 23.

  Data representing the size of the subject P measured by the sensor circuit 23 is sent to the irradiation control unit 38, and the irradiation control unit 38 controls the irradiation range limiting device 24 to set the X-ray irradiation range to the size of the subject P. Then, the X-ray is pre-exposed.

  Detection data of the subject P detected by the X-ray detector 15 by pre-exposure is sent to the computer system 30 via the data collection unit 22, and the AEC circuit 37 is suitable for the subject based on the detection data. Calculate the radiation dose (exposure time).

  Thus, after calculating an appropriate dose by the AEC circuit 23, the process shifts to the main imaging. In the main imaging, the limitation of the irradiation range by the irradiation range limiting device 24 is released, the entire X-ray detector 15 is irradiated with X-rays, and a breast image is captured. Further, at the time of X-ray exposure, the exposure is stopped at an appropriate timing based on the result calculated by the AEC circuit 23 to prevent the X-ray from being excessively irradiated to the subject.

  Data detected by the X-ray detector 15 in the main imaging is collected by the data collection unit 22, sent to the computer system 30, subjected to image processing by the data processing unit 22, and image information is displayed on the display unit 36.

  Next, the AEC circuit 37, the sensor circuit 23, and the irradiation range limiting means 24, which are features of the present invention, will be described with reference to FIGS.

The AEC circuit 37 calculates the time for individually irradiating the radiation in accordance with the subject P in order to expose the radiation at an appropriate dose, and for each subject to calculate the appropriate dose. When performing pre-exposure, the sensor circuit 23 first measures the size of the subject P (breast) and determines the X-ray irradiation range.

  In FIG. 3, 151 indicates a detection range of the X-ray detector 15, and 131 indicates an irradiation range of the X-ray tube 13. P indicates a subject (breast) placed on the top 16. When pre-exposure is performed and the exposure time by AEC is calculated, a region 152 necessary for AEC calculation is a portion corresponding to the substantially central portion of the subject P, and this range 152 corresponds to the size of the subject P. Change.

  Next, an example of measuring the size of the subject P using the output of the pressure sensor 17 will be described with reference to FIG. FIG. 4A is a side view showing a state in which the pressure sensor 17 is provided on the compression plate 16 and the subject P is compressed toward the top plate 14 by the compression plate 16.

  In this case, since the subject P is pushed against the top plate 14 by the compression plate 16, the pressure sensor 17 senses pressure at a portion in contact with the subject P. The sensor circuit 23 obtains the width (X, Y) of the subject P in the horizontal direction and the vertical direction, as shown in FIG. The output of the sensor circuit 23 is supplied to the irradiation control unit 38, and the irradiation control unit 38 controls the irradiation range limiting unit 24 according to the size (X, Y) of the subject P.

  FIG. 5 shows a configuration of the mammography unit 11 using the aperture mechanism 241 as the irradiation range limiting unit 24. The aperture mechanism 241 limits the X-ray irradiation range from the X-ray tube 13, and the irradiation control unit 38 changes the aperture amount of the aperture mechanism 241 at the time of pre-exposure and depends on the size of the subject P. To limit the X-ray irradiation range.

  The detection data detected by the X-ray detector 15 during pre-exposure is sent to the AEC circuit 37 via the data collection unit 22 and the bus line 31. The AEC circuit 37 calculates an appropriate exposure amount (exposure time) for each subject, and controls the exposure time so that an appropriate dose is obtained when X-rays are exposed to the subject P during the main imaging. To do.

  Thereby, when performing pre-exposure, since X-rays are irradiated within the minimum necessary range, exposure of the subject can be suppressed.

  Next, an example of measuring the size of the subject P using the output of the distance sensor 18 will be described with reference to FIG. FIG. 6 is a plan view illustrating an example in which the distance sensor 18 is provided on the top board 14 and the width (X1, Y1) of the subject P is measured in the horizontal direction and the vertical direction.

  The distance sensor 18 is formed by arranging a plurality of pairs of light receiving elements and light emitting elements 181 to 18n along one side of the top plate 14 (the side opposite to the side facing the subject), and receives light from the light emitting elements. The reflected light from the subject P is applied to the sample P with the same pair of light receiving elements, and the distance between the subject P and the light receiving element is obtained based on the detection result.

  When the vertical width of the top plate 14 is Y0, for example, if the distance between the center of the subject P and the distance sensor 18 is Y2, the size Y1 of the central portion of the subject P in the vertical direction is Y1. = Yo-Y2. Similarly, the distance between the periphery of the subject P and the distance sensor 18 can be obtained.

  When obtaining the size in the horizontal direction, the sensor circuit 23 obtains a region where the reflected light from the subject P cannot be received or a region X0 where the measured distance Y2 exceeds Y0, and this region X0 is determined to be other than the breast. Then, the region X1 in which the reflected light can be received is determined as the horizontal size of the subject P.

  Thus, the sensor circuit 23 obtains the horizontal and vertical sizes (X1, Y1) of the subject P and supplies the obtained data to the irradiation control unit 38. As shown in FIG. 5, the irradiation control unit 38 controls the aperture amount of the aperture mechanism 241 according to the size (X, Y) of the breast P to limit the X-ray irradiation range.

  The detection data detected by the X-ray detector 15 at the time of pre-exposure is sent to the AEC circuit 37 via the bus line 31 via the data collection unit 22, and an appropriate exposure dose (exposure) according to the subject. Time) is calculated.

  7 and 8 are diagrams for explaining another embodiment of the irradiation range limiting means 24. FIG.

  FIG. 7 shows a mask plate 41 disposed opposite to the exit of the X-ray tube 13 when the subject is irradiated with X-rays from the X-ray tube 13. The mask plate 41 is provided with a mask portion 42 that blocks X-rays and a transmission window 43 that transmits X-rays. A plurality of mask plates 41 having different shapes (sizes and shapes) of the transmission windows 43 are prepared. To do.

  Since the shape of the transmission window 43 of each mask plate 41 is different, the mask plate 41 having the transmission window 43 having the shape closest to the size of the subject P measured by the sensor circuit 23 is selected, and the X-ray tube 13 is selected. It is arranged opposite to the exit port portion. Thereby, the X-ray irradiation range can be limited by the transmission window 43.

  FIG. 8A shows the configuration of the mammography unit 11 using a mask plate 41 as the irradiation range limiting means 24. Reference numeral 242 denotes an irradiation range limiting device.

  As shown in FIG. 8 (b), the irradiation range limiting device 242 has a transparent disk 44 that can be rotated by a motor 45. A plurality of mask plates 41 shown in FIG. Has been. The rotation of the motor 45 is controlled by the irradiation control unit 38, and any one of the mask plates 41 is selected so as to face the exit port portion of the X-ray tube 13.

  Data of the transmission windows 43 of the plurality of mask plates 41 are registered in advance in a memory (not shown) provided in the irradiation control unit 38, and are registered in the memory and the size of the subject P measured by the sensor circuit 23. By comparing the data of the transmission window 43, the mask plate 41 having the transmission window 43 closest to the measurement result can be selected.

  Therefore, the rotation range of the X-ray can be limited by controlling the rotation of the transparent disk 45 by the irradiation control unit 38 and disposing the selected mask plate 41 opposite to the X-ray tube 13. In addition, when performing actual imaging, the mask plate 41 having the largest transmission window may be selected so that the entire surface of the X-ray detector 15 is irradiated with X-rays.

  As described above, according to the present invention, X-rays are irradiated to the minimum necessary range at the time of pre-exposure, so that the exposure dose of the subject can be reduced.

  Various modifications can be made without departing from the scope of the claims.

The block diagram which shows one Embodiment of the radiographic imaging apparatus of this invention. The block diagram which shows the hardware constitutions of the radiographic imaging apparatus of this invention. Explanatory drawing explaining the irradiation range of the X-ray at the time of the main imaging | photography and pre-exposure in this invention. The side view and top view explaining operation | movement of the pressure sensor used for the radiographic imaging apparatus of this invention. The block diagram which shows the structure of the mammography part which used the aperture mechanism in this invention. The top view explaining operation | movement of the distance sensor used for this invention. The top view explaining the mask board used for this invention. The block diagram and perspective view which show the structure of the mammography part using the irradiation range restriction | limiting apparatus in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Radiation imaging device 11 ... Mammography part 12 ... Arm 13 ... Radiation source (X-ray tube)
14 ... top 15 ... radiation detector (X-ray detector)
DESCRIPTION OF SYMBOLS 16 ... Compression plate 17 ... Pressure sensor 18 ... Distance sensor 21 ... High pressure generation part 22 ... Data collection part 23 ... Sensor circuit 24 ... Irradiation range restriction means 241 ... Diaphragm mechanism 242 ... Irradiation range restriction device 30 ... Computer system 31 ... System control Unit 32 ... Data collection unit 37 ... AEC circuit 38 ... Irradiation control unit 41 ... Mask plate 42 ... Shielding unit 43 ... Transmission etc. 44 ... Rotating disk 45 ... Motor

Claims (12)

A subject is placed on a top plate disposed opposite to the radiation source, the subject placed on the top plate is irradiated with radiation from the radiation source, and the radiation transmitted through the subject is detected by a radiation detector. A mammography unit detected by
Measuring means for measuring the size of the subject placed on the top plate;
In accordance with the measurement result of the measurement unit, an irradiation region limiting unit that limits an irradiation region of radiation irradiated from the radiation source toward the radiation detector;
An AEC circuit that performs pre-exposure by irradiating radiation within an area limited by the irradiation area limiting means, and calculates a radiation dose suitable for the subject;
The radiographic imaging device characterized by comprising.   2. The radiation according to claim 1, wherein the mammography unit releases the restriction of the irradiation area at the time of main imaging, and controls the radiation dose to the subject based on a calculation result calculated by the AEC circuit. Image shooting device. The mammography unit includes a compression plate that compresses the subject toward the top plate,
The measurement means includes a pressure sensor disposed on a surface of the compression plate that contacts the subject, and measures the size of the subject using a pressure-sensitive output of the pressure sensor. Item 2. The radiographic imaging device according to Item 1.   The measurement means includes a distance sensor provided on a side opposite to the side facing the subject of the top plate, calculates a distance between the distance sensor and the subject, and uses the distance data The radiographic image capturing apparatus according to claim 1, wherein the size of the subject is measured.   The irradiation region limiting unit is a diaphragm mechanism that limits an irradiation range of radiation radiated from the radiation source, and the diaphragm amount of the diaphragm mechanism is variable according to a measurement result of the measuring unit. Item 2. The radiographic imaging device according to Item 1.   The irradiation area limiting unit includes a plurality of mask plates each having a radiation transmission window having a different size, and selects the mask plate according to the measurement result of the measurement unit and disposes the mask plate opposite to the emission port of the radiation source. The radiographic imaging apparatus according to claim 1.   The irradiation area limiting means includes a rotating disk in which the plurality of mask plates are arranged concentrically, and rotates the rotating disk according to the measurement result of the measuring means, and is arranged to face the exit of the radiation source. The radiographic imaging apparatus according to claim 6, wherein a plate is selected. A mammography unit that is disposed opposite to a radiation source, places a subject on a top plate, and detects radiation transmitted through the subject with a radiation detector;
Place the subject on the top plate, measure the size of the placed subject in advance,
Perform pre-exposure by limiting the irradiation area of the radiation irradiated from the radiation source toward the radiation detector according to the measurement result,
Calculate the radiation dose suitable for the subject using the detection result of the radiation detector by the pre-exposure,
A radiographic imaging method, wherein, during main imaging, the restriction of the irradiation area is released and the radiation dose to the subject is controlled based on the calculation result. The mammography unit includes a compression plate that compresses the subject toward the top plate, and a pressure sensor disposed on a surface of the compression plate that contacts the subject,
The radiographic imaging method according to claim 8, wherein when measuring the size of the subject placed on the top board, measurement is performed using a pressure-sensitive output of the pressure sensor. The mammography unit includes a distance sensor provided on a side opposite to a side facing the subject of the top plate,
The distance between the distance sensor and the subject is calculated when measuring the size of the subject placed on the top board, and the distance data is used for measurement. 8. The radiographic imaging method according to 8. The mammography unit has a diaphragm mechanism that limits an irradiation range of radiation emitted from the radiation source,
The radiographic image capturing method according to claim 8, wherein when the pre-exposure is performed, the aperture amount is varied according to a measurement result of the subject. The mammography unit includes a plurality of mask plates each having a radiation transmission window having a different size,
The radiographic image capturing method according to claim 8, wherein the mask plate is selected according to the measurement result of the subject and is made to face the exit of the radiation source.

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