JP2009291472A - Radiation image capturing apparatus and adjustment method thereof - Google Patents

Abstract

A radiation image capturing apparatus capable of easily and accurately setting an irradiation field in an arbitrary range at an arbitrary position of a radiation conversion panel and an adjustment method thereof.
The present invention relates to a radiographic image capturing apparatus and an adjustment method thereof, parameters P1, P2 are set, a collimator 32 is adjusted, X-rays are irradiated to a radiation conversion panel 38, parameters P1, Calculate each position a1, b1, c1, d1 and a2, b2, c2, d2 of the shielding plates 44a to 44d with respect to P2, and then from each position a1, b1, c1, d1 and a2, b2, c2, d2, A parameter P to be a desired irradiation field 116 is calculated by linear interpolation. Then, the collimator 32 is adjusted according to the calculated parameter P.
[Selection] Figure 6

Description

  The present invention relates to a radiographic imaging apparatus that performs imaging by adjusting a radiation field in a radiation conversion panel and an adjustment method thereof.

  2. Description of the Related Art In the medical field, a radiation image capturing apparatus that irradiates a subject with radiation and guides the radiation transmitted through the subject to a radiation conversion panel to capture a radiation image is widely used.

  In this case, as a radiation conversion panel, a stimulable phosphor panel is known in which radiation energy as a radiation image is accumulated in the phosphor and the radiation image can be extracted as stimulated emission light by irradiating excitation light. . The stimulable phosphor panel on which the radiation image is recorded is supplied to a reading device and subjected to reading processing, whereby a radiation image as a visible image can be obtained.

  Further, in a medical field such as an operating room, it is required that the radiation image information can be read and displayed immediately from the radiation conversion panel in order to perform a quick and accurate treatment on the patient. Radiation conversion using a solid-state detector that converts radiation directly into an electrical signal, or converts radiation into visible light with a scintillator and then converts it into an electrical signal and reads it as a radiation conversion panel that can meet such requirements Panels are being developed.

  In a radiographic imaging apparatus that captures radiographic images using these radiation conversion panels, radiation is applied to a desired area of the radiation conversion panel in order to avoid exposure of unnecessary parts of the subject. In order to obtain appropriate images, a collimator that defines the radiation field is installed in the vicinity of the radiation source.

  Normally, the irradiation field is adjusted by irradiating the radiation conversion panel with radiation to acquire a radiation image, and adjusting the collimator while visually confirming the radiation image.

  However, the operator may be exposed to radiation while performing such adjustment work. In view of this, a radiographic imaging apparatus capable of performing collimator adjustment work in a short time has been proposed (see Patent Document 1).

  In this prior art, the radiation conversion panel is irradiated with radiation through a collimator, and the deviation and inclination between the irradiation field by the collimator and the center position of the light receiving surface of the radiation conversion panel are calculated from the obtained radiation image information. Is adjusted by translating and rotating in a two-dimensional plane along the radiation conversion panel.

JP 2006-122488 A

  In this case, the information on the center position of the radiation conversion panel is used to make adjustment so that the center of the irradiation field and the center of the radiation conversion panel coincide with each other. It is not intended to adjust.

  In order to effectively use the image detection area of the radiation conversion panel, the irradiation field is usually set in a slightly wider range than the detection area. However, the conventional technique cannot adjust the range of the irradiation field.

  The present invention has been made to solve the above-described problem, and a radiographic imaging apparatus capable of easily and accurately setting an irradiation field in an arbitrary range at an arbitrary position of a radiation conversion panel and adjustment thereof. It aims to provide a method.

The present invention comprises a radiation source that outputs radiation;
A radiation conversion panel that is irradiated with the radiation transmitted through the subject and converts the radiation into radiation image information of the subject;
A collimator disposed between the radiation source and the radiation conversion panel and defining an irradiation field of the radiation with respect to the radiation conversion panel;
Configuring the collimator, moving at least one shielding plate that shields part of the radiation irradiated to the radiation conversion panel, and adjusting the irradiation field; and
Using the irradiation field information obtained by irradiating the radiation conversion panel with the radiation via the collimator and the image detection area of the radiation conversion panel, a shielding plate position where a desired irradiation field can be obtained. A shielding plate position calculation unit for calculating;
The irradiation field adjustment unit adjusts the irradiation field by moving the shielding plate according to the calculated shielding plate position.

Further, the present invention provides a radiation image capturing apparatus that irradiates a radiation conversion panel with radiation output from a radiation source via a collimator and captures a radiation image of a subject.
The collimator is configured, a shielding plate that shields a part of the radiation irradiated on the radiation conversion panel is set at a first adjustment position, and the radiation conversion panel is irradiated with the radiation in the state to perform the first irradiation. Obtaining field information;
Setting the shielding plate to a second adjustment position different from the first adjustment position, and irradiating the radiation conversion panel in that state to obtain second irradiation field information;
Using the first irradiation field information and the second irradiation field information to calculate an adjustment position of the shielding plate capable of obtaining a desired irradiation field;
And the shielding plate is set at the adjustment position.

  In the present invention, an irradiation field in an arbitrary range including a range wider than the image detection area of the radiation conversion panel can be easily and accurately set at an arbitrary position of the radiation conversion panel.

  FIG. 1 is a mammography apparatus 10 to which a radiographic imaging apparatus and an adjustment method thereof according to the present invention are applied. The mammography apparatus 10 is an apparatus that captures a radiographic image of a breast of a subject 12. The mammography apparatus 10 includes a radiation source storage unit 18 disposed at one end of an arm member 16 that is pivotally connected to a base 14, and an arm. An imaging table 20 disposed at the other end of the member 16, a compression plate 22 configured to be movable in the arrow direction with respect to the imaging table 20, and a display unit 24 for displaying subject information, imaging conditions, and the like. Prepare.

  FIG. 2 is an explanatory diagram of the internal structure of the radiation source storage unit 18 and the imaging stand 20. A radiation source 30 having a cathode 26 that outputs an electron beam when a high voltage is applied to the radiation source storage unit 18 and a target 28 such as Mo that generates X-rays when the electron beam collides is output from the target 28. A collimator 32 that defines the irradiated X-ray field and a filter 34 that adjusts the X-ray energy according to the imaging conditions and the imaging target are housed. The imaging table 20 houses a radiation conversion panel 38 that converts X-rays transmitted through the breast 36 of the subject 12 into radiation image information as charge information.

  FIG. 3 is a configuration diagram of the collimator 32. The collimator 32 includes a substrate 42 having an opening 40, and four rectangular shielding plates 44a to 44d that are attached to the substrate 42 and can move independently in the arrow X direction and the arrow Y direction. One end of the shielding plates 44a and 44b is movably engaged with the guide rail 46, and racks 48a and 48b are formed at the other end. Pinions 52a and 52b rotated by motors 50a and 50b mesh with the racks 48a and 48b. Similarly, the shield plates 44c and 44d have one end movably engaged with the guide rail 54, and the racks 48c and 48d are formed at the other end. Pinions 52c and 52d rotated by motors 50c and 50d mesh with racks 48c and 48d. The shielding plates 44a to 44d define the position and area of the opening 56 through which X-rays pass.

  FIG. 4 is a circuit configuration diagram of the radiation conversion panel 38 housed in the imaging table 20.

  In the radiation conversion panel 38, a photoelectric conversion layer 58 made of a material such as amorphous selenium (a-Se) that senses radiation and generates charges is arranged on an array of thin film transistors (TFTs) 60 in a matrix form. After the generated charge is stored in the storage capacitor 62, the TFT 60 is sequentially turned on for each row, and the charge is read out as an image signal. In FIG. 4, only the connection relationship between one pixel 64 including the photoelectric conversion layer 58 and the storage capacitor 62 and one TFT 60 is shown, and the configuration of the other pixels 64 is omitted. Amorphous selenium must be used within a predetermined temperature range because its structure changes and its function decreases at high temperatures. Therefore, it is preferable to provide means for cooling the radiation conversion panel 38 in the imaging table 20.

  A gate line 66 extending parallel to the row direction and a signal line 68 extending parallel to the column direction are connected to the TFT 60 connected to each pixel 64. Each gate line 66 is connected to a line scanning drive unit 70, and each signal line 68 is connected to a multiplexer 72 constituting a reading circuit.

  Control signals Von and Voff for controlling on / off of the TFTs 60 arranged in the row direction are supplied from the line scanning drive unit 70 to the gate line 66. In this case, the line scan driving unit 70 includes a plurality of switches SW1 for switching the gate lines 66 and an address decoder 74 for outputting a selection signal for selecting one of the switches SW1. An address signal is supplied from the panel control unit 76 to the address decoder 74.

  Further, the charge held in the storage capacitor 62 of each pixel 64 flows out to the signal line 68 through the TFTs 60 arranged in the column direction. This charge is amplified by an amplifier 78. A multiplexer 72 is connected to the amplifier 78 via a sample and hold circuit 80. The multiplexer 72 includes a plurality of switches SW2 for switching the signal line 68 and an address decoder 82 for outputting a selection signal for selecting one of the switches SW2. An address signal is supplied to the address decoder 82 from the panel control unit 76. An A / D converter 84 is connected to the multiplexer 72, and radiation image information converted into a digital signal by the A / D converter 84 is supplied to the panel controller 76.

  FIG. 5 is a control circuit block diagram of the mammography apparatus 10.

  The control circuit of the mammography apparatus 10 includes a radiation source drive unit 88 that drives the radiation source 30 and a collimator drive unit 90 that drives the motors 50a to 50d of the collimator 32 according to the operation of the exposure switch 87 by the technician (irradiation field adjustment A compression plate drive unit 92 that moves the compression plate 22, and a panel control unit 76 that controls the radiation conversion panel 38.

  In addition, the control circuit includes an imaging condition setting unit 96 that sets imaging conditions including tube voltage, tube current, and X-ray irradiation time for the object 12 that are imaging conditions according to the subject 12 and its imaging region. These imaging conditions are set in the radiation source driving unit 88. The control circuit also includes a parameter setting unit 98 that sets parameters for arranging the shielding plates 44a to 44d of the collimator 32 at predetermined positions, a collimator control unit 100 that controls movement of the collimator 32 according to the set parameters, According to the operation of the compression plate movement switch 102 by the engineer, the compression plate control unit 104 that controls the movement of the compression plate 22, the image processing unit 106 that performs image processing on the radiation image information acquired from the panel control unit 76, and the image processing And a shielding plate position calculation unit 108 that calculates the positions of the shielding plates 44a to 44d with respect to the radiation conversion panel 38 based on the irradiation field information that is the radiation image information and the image detection region of the radiation conversion panel 38. The shielding plate position calculation unit 108 calculates parameters for adjusting the shielding plates 44a to 44d to a predetermined position from the calculated positions of the shielding plates 44a to 44d and sets them in the parameter setting unit 98.

  The mammography apparatus 10 of the present embodiment is basically configured as described above. Next, the operation of driving the collimator 32 and adjusting the X-ray irradiation field on the radiation conversion panel 38 will be described. This will be described with reference to the flowchart shown in FIG.

  First, as shown in FIG. 7, the parameter setting unit 98 sets a parameter P1 (FIG. 8) in which the X-ray irradiation field 112 surely enters the image detection region 110 of the radiation conversion panel 38 (step S1). The parameter P1 is supplied to the collimator controller 100. The parameter P1 can be set independently for each of the shielding plates 44a to 44d. The collimator control unit 100 controls the collimator driving unit 90 according to the supplied parameter P1 to drive the motors 50a to 50d and move the shielding plates 44a to 44d (step S2).

  The motors 50a to 50d rotate the pinions 52a to 52d, and the shielding plates 44a to 44d move through the racks 48a to 48d engaged with the pinions 52a to 52d, so that an opening 56 corresponding to the irradiation field 112 is formed. The

  After being set to the above state, the radiation source driving unit 88 drives the radiation source 30 to irradiate the radiation conversion panel 38 with X-rays (step S3). That is, the radiation source driving unit 88 applies a high voltage to the cathode 26 of the radiation source 30. An electron beam is output from the cathode 26 to which a high voltage is applied, and this electron beam collides with the target 28 to generate X-rays. X-rays generated from the target 28 are applied to the radiation conversion panel 38 via the collimator 32 whose opening 56 is adjusted according to the parameter P1, and are applied to the irradiation field 112 shown in FIG.

  The radiation conversion panel 38 irradiated with X-rays in the irradiation field 112 converts the X-rays into radiation image information. The process of converting X-rays to radiation image information will be described later.

  The image processing unit 106 acquires radiation image information as first irradiation field information (step S4), and performs necessary image processing. The shielding plate position calculation unit 108 follows the first irradiation field information supplied from the image processing unit 106, and positions of the shielding plates 44a to 44d based on the positions A to D of the image detection region 110 of the radiation conversion panel 38. a1, b1, c1, and d1 (first adjustment positions) are calculated (step S5). FIG. 8 shows only the position a1 of the shielding plate 44a. The positions b1, c1, and d1 of the other shielding plates 44b to 44d are calculated in the same manner.

  Next, in order to calculate the next positions a2, b2, c2, and d2 (second adjustment positions) of the shielding plates 44a to 44d (step S6), the parameter setting unit 98, as shown in FIG. After setting the parameter P2 (P1 ≠ P2) (FIG. 8) in which the X-ray irradiation field 114 surely enters the image detection region 110 (step S7) and supplying the parameter P2 to the collimator control unit 100, step By repeating the processes of S2 to S5, the radiation image information as the second irradiation field information is acquired. And the shielding board position calculation part 108 uses this 2nd irradiation field information, and position a2, b2 of each shielding board 44a-44d on the basis of each position AD of the image detection area | region 110 of the radiation conversion panel 38. FIG. , C2 and d2 are calculated (step S5).

  The shielding plate position calculation unit 108 uses the calculated positions a1, b1, c1, d1 and positions a2, b2, c2, d2 of the shielding plates 44a to 44d to the image detection area 110 of the radiation conversion panel 38. A parameter P that can set the predetermined irradiation field 116 is calculated (step S8).

  That is, as shown in FIG. 8, a straight line L is determined from the position a1 of the shielding plate 44a when the parameter P1 is set and the position a2 of the shielding plate 44a when the parameter P2 is set, and this straight line L is used. Then, a parameter P that can set the position of the shielding plate 44a to a3 is calculated by linear interpolation. The parameter P that allows the positions of the other shielding plates 44b to 44d to be b3, c3, d3 can be obtained in the same manner.

  The collimator controller 100 adjusts the positions of the shielding plates 44a to 44d using the parameter P calculated as described above (step S9). In this case, since each shielding plate 44a-44d can adjust each position independently, arbitrary irradiation fields 116 can be set to the image detection region 110 of the radiation conversion panel 38. Moreover, since the positions a1, b1, c1, d1 and the positions a2, b2, c2, d2 of the shielding plates 44a to 44d are obtained with reference to the image detection region 110 of the radiation conversion panel 38, the shielding plates 44a to 44d are positioned. The parameter P that can be set to a3, b3, c3, d3 can be calculated easily and with high accuracy.

  After the collimator 32 is adjusted to an appropriate position as described above, imaging of the breast 36 is started.

  Therefore, after placing the breast 36 of the subject 12 on the imaging table 20, the operator operates the compression plate movement switch 102. When the compression plate moving switch 102 is operated, the compression plate control unit 104 controls the compression plate drive unit 92, and compression of the breast 36 by the compression plate 22 is started.

  After the breast 36 is brought into a predetermined compression state, the operator operates the exposure switch 87. When the exposure switch 87 is operated, the radiation source driving unit 88 causes the imaging conditions set by the imaging condition setting unit 96, for example, the tube voltage according to the age of the subject 12, the state of the breast 36, the imaging method, and the like. Based on the tube current, irradiation time, etc., the radiation source 30 is driven to irradiate the breast 36 with X-rays.

  The X-rays output from the radiation source 30 are adjusted to the irradiation field 116 shown in FIG. 7 by the collimator 32 and then irradiated to the radiation conversion panel 38 through the filter 34, the compression plate 22 and the breast 36.

  The photoelectric conversion layer 58 of each pixel 64 constituting the radiation conversion panel 38 converts the incident X-rays into an electric signal, and the electric signal is held in the storage capacitor 62 as an electric charge. Next, the charge information that is radiation image information of the breast 36 held in each storage capacitor 62 is read according to the address signal supplied from the panel control unit 76 to the line scan driving unit 70 and the multiplexer 72.

  That is, the address decoder 74 of the line scan driving unit 70 outputs a selection signal in accordance with the address signal supplied from the panel control unit 76 to select one of the switches SW1 and the TFT 60 connected to the corresponding gate line 66. A control signal Von is supplied to the gate. On the other hand, the address decoder 82 of the multiplexer 72 outputs a selection signal in accordance with the address signal supplied from the panel control unit 76 to sequentially switch the switch SW2, and is connected to the gate line 66 selected by the line scan driving unit 70. Radiation image information, which is charge information held in the storage capacitor 62 of the pixel 64, is sequentially read out via the signal line 68.

  The radiation image information read from the storage capacitor 62 of each pixel 64 connected to the selected gate line 66 of the radiation conversion panel 38 is amplified by each amplifier 78 and then sampled by each sample and hold circuit 80. The signal is supplied to the A / D converter 84 via the multiplexer 72 and converted into a digital signal. The radiation image information converted into the digital signal is supplied to the image processing unit 106 by the panel control unit 76.

  Similarly, the address decoder 74 of the line scan driving unit 70 sequentially switches the switch SW1 according to the address signal supplied from the panel control unit 76, and holds it in the storage capacitor 62 of each pixel 64 connected to each gate line 66. The radiographic image information, which is the charge information, is read via the signal line 68 and supplied to the image processing unit 106 via the multiplexer 72, the A / D converter 84 and the panel control unit 76.

  The image processing unit 106 performs image processing on the radiation image information. The processed radiation image information is displayed by, for example, a viewer and used for interpretation interpretation by a doctor.

  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, in the above-described embodiment, the four shielding plates 44a to 44d can be moved independently and set to an arbitrary irradiation field. However, at least one of the shielding plates 44a to 44d can be moved. The irradiation field may be set as

  Further, in the mammography apparatus 10, the target 28, the filter 34, or the X-ray focal spot size may be changed, and a parameter P for adjusting the collimator may be set for each. Further, a parameter P may be obtained in advance for the combination of the target 28, the filter 34, and / or the X-ray focal spot size and tabulated, and the parameter P may be set with reference to this table.

  Further, instead of the radiation conversion panel 38 for recording radiation image information, a radiation conversion panel using a solid-state detection element that converts radiation to visible light after being converted into visible light by a scintillator, and a radiation image on a phosphor. The storage phosphor panel can be used that can store the radiation energy and extract the radiation image as the stimulated emission light by irradiating the excitation light.

It is a block diagram of the mammography apparatus to which the radiographic imaging apparatus of this invention and its adjustment method are applied. It is explanatory drawing of the internal structure of the radiation source storage part and imaging stand in the mammography apparatus shown in FIG. It is a block diagram of the collimator shown in FIG. It is a circuit block diagram of the radiation conversion panel used for a mammography apparatus. It is a control circuit block diagram of a mammography apparatus. It is a flowchart of the adjustment work of the collimator in a mammography apparatus. It is a positional relationship explanatory drawing of the image detection area of a radiation conversion panel, and the X-ray irradiation field. It is explanatory drawing of the calculation method of the parameter which determines the position of the shielding board which comprises a collimator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Mammography apparatus 12 ... Subject 18 ... Radiation source storage part 20 ... Imaging stand 22 ... Compression plate 30 ... Radiation source 32 ... Collimator 36 ... Breast 38 ... Radiation conversion panels 44a-44d ... Shielding plate 90 ... Collimator drive part 98 ... Parameter Setting unit 100 ... collimator control unit 106 ... image processing unit 108 ... shielding plate position calculation unit 110 ... image detection regions 112, 114, 116 ... irradiation field

Claims (5)

A radiation source that outputs radiation;
A radiation conversion panel that is irradiated with the radiation transmitted through the subject and converts the radiation into radiation image information of the subject;
A collimator disposed between the radiation source and the radiation conversion panel and defining an irradiation field of the radiation with respect to the radiation conversion panel;
Configuring the collimator, moving at least one shielding plate that shields part of the radiation irradiated to the radiation conversion panel, and adjusting the irradiation field; and
Using the irradiation field information obtained by irradiating the radiation conversion panel with the radiation via the collimator and the image detection area of the radiation conversion panel, a shielding plate position where a desired irradiation field can be obtained. A shielding plate position calculation unit for calculating;
The radiation field adjustment unit adjusts the irradiation field by moving the shielding plate according to the calculated shielding plate position. The apparatus of claim 1.
The shielding plate constituting the collimator is composed of four shielding plates that can be independently moved by the irradiation field adjusting unit, and the irradiation field is defined by an opening surrounded by the four shielding plates. A radiographic imaging device characterized by the above. The apparatus of claim 1.
The radiographic image capturing apparatus is a mammography apparatus. In a radiographic imaging apparatus that irradiates a radiation conversion panel with radiation output from a radiation source via a collimator,
The collimator is configured, a shielding plate that shields a part of the radiation irradiated on the radiation conversion panel is set at a first adjustment position, and the radiation conversion panel is irradiated with the radiation in the state to perform the first irradiation. Obtaining field information;
Setting the shielding plate to a second adjustment position different from the first adjustment position, and irradiating the radiation conversion panel in that state to obtain second irradiation field information;
Using the first irradiation field information and the second irradiation field information to calculate an adjustment position of the shielding plate capable of obtaining a desired irradiation field;
And adjusting the shielding plate at the adjustment position. The method of claim 4, wherein
The adjustment position of a radiographic imaging apparatus, wherein the adjustment position is obtained by linearly interpolating the first irradiation field information and the second irradiation field information.

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