JP2001176692A - X-ray equipment - Google Patents

Abstract

(57) [Problem] To provide an X-ray imaging apparatus capable of obtaining an appropriate X-ray fluoroscopic image according to an imaging part. An X-ray automatic exposure detector includes a small-field detection unit, a medium-field detection unit, and a large-field detection unit. When the X-ray irradiation field is small, the small-field detection unit is used. Automatic exposure control of the X-ray fluoroscopic image is performed in accordance with the integrated value of the detection values of only 10a, and when the X-ray irradiation field is medium, the detection value sum of the small-field detection unit 10a and the medium-field detection unit 10b is calculated. Automatic exposure control of the X-ray fluoroscopic image is performed according to the integral value. Further, when the X-ray irradiation field is large, the automatic exposure control of the X-ray fluoroscopic image is performed in accordance with the integrated value of the sum of the detection values of the small-field detection unit 10a, the medium-field detection unit 10b, and the large-field detection unit 10c. Is made. This makes it possible to perform exposure control based on an accurate measurement of the X-ray dose transmitted through the imaging region,
A good photographed image can be obtained for each photographed part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray imaging apparatus having an X-ray automatic exposure control function for automatically and optimally controlling the density of a fluoroscopic image during X-ray imaging.

[0002]

2. Description of the Related Art X-ray imaging, which irradiates a subject with X-rays and detects the transmitted X-rays with X-ray detecting means such as a film to obtain an X-ray image, is performed in the medical field. In order to obtain a good X-ray image, it is necessary to control so that an appropriate X-ray dose is irradiated on a film or the like.

For this reason, in radiography and the like, X
An X-ray imaging apparatus having an automatic X-ray exposure function is widely used. The X-ray automatic exposure function detects a part of transmitted X-rays and automatically controls an imaging time according to the detected value. And the integrated amount of transmitted X-rays applied to a film or the like is set to a desired value.

FIG. 7 shows a schematic configuration of a conventional X-ray imaging apparatus having an automatic X-ray exposure function. In the figure,
The X-ray emitted from the X-ray tube 1 is narrowed down by the X-ray diaphragm 2 so that a predetermined imaging field of view can be obtained according to the imaging region.
The subject 3 placed on the sample is irradiated. A part of the X-rays transmitted through the subject 3 are detected by the automatic exposure X-ray detector 5 and irradiated on the film in the cassette 6. The X-ray high-voltage device 7 integrates the value detected by the automatic exposure X-ray detector 5, and when the integrated value becomes a value suitable for a photographed image corresponding to the film in the cassette 6, the X-ray The X-ray emitted from the tube 1 is stopped. As a result, X-ray automatic exposure control for the film in the cassette 6 becomes possible, and an appropriate X-ray image of the subject 3 is obtained.

[0005]

However, in the conventional X-ray imaging apparatus, as shown in FIG. 8, only one X-ray detecting section 5a in the X-ray detector 5 for automatic exposure is arranged at the center of the imaging. Since the size of the lighting field for detecting the X-rays is fixed, the X-ray irradiation field defined by the X-ray diaphragm 2 according to the imaging site is detected by the detection unit 5a as shown in FIG. In contrast, when it is wide, only the average dose in a limited part of the imaging site can be measured, and an appropriate imaging image may not be obtained.

Further, as shown in FIG. 8B, when the X-ray irradiation field is narrow, a part where the X-ray cannot be detected occurs in the detection unit 5a. Since the X-ray dose cannot be measured, an appropriate photographed image may not be obtained in some cases.

The present invention has been made in order to solve these problems, and an appropriate X is selected according to the region to be imaged.
It is an object of the present invention to provide an X-ray imaging apparatus capable of obtaining a fluoroscopic image.

[0008]

According to the first aspect of the present invention, X
In an X-ray imaging apparatus that captures a transmission image by irradiating a subject with X-rays, two or more X-ray detectors that detect transmitted X-rays in different fields of view, and among the two or more X-ray detectors, Detector selection means for selecting an X-ray detector suitable for the imaging region and outputting the detected value; integrating the detected value of the selected X-ray detector; Automatic exposure control means for stopping the irradiation of X-rays when the exposure time has elapsed.

According to the first aspect of the present invention, there are provided two or more X-ray detectors for detecting transmitted X-rays having different visual fields, respectively.
Since the X-ray detector suitable for the imaging region is selected, the difference between the size of the imaging region and the size of the X-ray field is reduced. For this reason, it is possible to perform exposure control based on an accurate measurement value of the X-ray dose transmitted through the imaging region, and a good captured image can be obtained for each imaging region.

According to a second aspect of the present invention, in the X-ray imaging apparatus according to the first aspect, the two or more X-ray detectors include at least a first X-ray detector disposed at the center of imaging, A second X-ray detector surrounding the first X-ray detector;
1 or the first and second X-ray detectors.
It is characterized by outputting the sum of the detection values of the line detector.

According to the second aspect of the present invention, a first X-ray detector is provided at the center of imaging, and a second X-ray detector is provided so as to surround the first X-ray detector. Since the sum of the detection values of the two detectors is used as the detection value when the region to be imaged becomes large, the disposed X-ray detector can be used effectively.

According to a third aspect of the present invention, in the X-ray imaging apparatus according to the second aspect, an X-ray aperture for limiting an X-ray irradiation range according to an imaging region and an X-ray irradiation range suitable for the imaging region are provided. The X-ray aperture is controlled to obtain
X-ray irradiation field control means for controlling the detector selection means so that the X-ray detector is appropriately selected in accordance with the X-ray irradiation range, wherein the X-ray irradiation range is selected by the X-ray detector. It is characterized by at least a size that can be accommodated.

According to the third aspect of the present invention, the X-ray aperture is controlled so as to obtain an X-ray irradiation range suitable for the region to be imaged, and the X-ray detector is appropriately provided in accordance with the selected X-ray irradiation range. Since the detector selection means is controlled so as to be selected, when the X-ray irradiation field is wide, the transmitted X-ray of the imaging region can be accurately detected, and even when the X-ray irradiation field is narrow. By selecting an X-ray detector suitable for the irradiation field, it becomes possible to accurately detect the amount of X-ray transmitted through the irradiation field. Therefore, the amount of exposure of the subject can be minimized according to the imaging region, and exposure control based on an accurate measurement value of the X-ray dose transmitted through the imaging region can be performed. An image is obtained.

[0014]

FIG. 1 shows a schematic configuration of an X-ray imaging apparatus according to an embodiment of the present invention. In the figure, the X-ray radiated from the X-ray tube 20 has its irradiation range narrowed by an X-ray diaphragm 21 and irradiates the subject 11.
The X-ray transmitted through the subject 11 is detected by the X-ray automatic exposure detector 10.
And a part thereof is detected, and the X-ray film in the cassette 12 is irradiated to obtain an X-ray image.

FIG. 2 is a schematic view of the X-ray automatic exposure detector 10 observed from the X-ray irradiation direction. As shown in FIG. The circular small-field detection unit 10a provided, the ring-shaped medium-field detection unit 10b provided around the small-field detection unit 10b, and the ring-shaped large-field detection unit provided around the medium-field detection unit 10b It comprises a detection unit 10c, and each detection value is output via a connector 10d.

The small-field detection unit 10a is used for imaging the smallest imaging region, and is formed to have a size that can be accommodated in the smallest X-ray irradiation field. The middle-field detection unit 10b is used for photographing a medium-sized imaging region.
c is used for imaging a large part. In the present embodiment, three detectors are used. However, as the number of detectors is increased, it is possible to flexibly correspond to various target sites.

FIG. 3 is a schematic diagram showing a cross section taken along line AA in FIG. Here, the detector for automatic X-ray exposure includes a fluorescent daylighting type, an ionization chamber type, a semiconductor type, and the like. In the present invention, any of them may be used. 1 shows an embodiment of a line automatic exposure detector. In FIG. 3, a detector 10 for automatic exposure of X-rays is provided in a chamber formed by a frame 100 forming the periphery thereof and an A1 plate 100a and an A2 plate 100b respectively covering the X-ray input side and output side, respectively. A detection unit 10a for a visual field, a detection unit 10b for a middle visual field, and a detection unit 10c for a large visual field are formed.

The small-field-of-view detecting unit 10a is provided in a circular space partitioned by a ring-shaped spacer 101a.
Circular insulating plates 102a and 102a 'are respectively provided on the inner surfaces of the A1 plate 100a and the A2 plate 100b, and electrodes 104a and 104a' having the same shape are provided on the surfaces thereof.
An ionization space 103a is formed by applying a DC voltage between the electrodes 04a and 104a '. Further, the ring-shaped spacer 101a raises the X-ray detection accuracy by holding the A1 plate 100a and the A2 plate 100b so that the distance between the electrodes 104a and 104a 'is always constant.

In the ring-shaped space defined by the ring-shaped spacer 101a and the ring-shaped spacer 101b surrounding the ring-shaped spacer 101a, the inner field of the A1 plate 100a and the A2 plate 100b are respectively provided with ring-shaped insulating members. Plates 102b and 102b 'and electrodes 104b and 104b' having the same shape are provided on the surfaces thereof, respectively.
An ionization space 103b is formed by applying a DC voltage between the electrodes 04b and 104b '. The ring-shaped spacers 101a and 101b are connected to the electrodes 104b and 1b.
A1 plate 100a so that the distance between the substrates 04b 'is always constant.
By holding the A2 plate 100b, X-ray detection accuracy is increased.

Further, in the ring-shaped space partitioned by the ring-shaped spacer 101b and the ring-shaped spacer 101c surrounding the ring-shaped spacer 101b, the large-field detection unit 10c is formed on the inner surfaces of the A1 plate 100a and the A2 plate 100b, respectively. The electrodes 104c, 104c 'having the same shape are respectively provided on the insulating plates 102c, 102c' and the surface thereof, and an ionization space 103c is formed by applying a DC voltage between the electrodes 104c, 104c '. The ring-shaped spacers 101b and 101c are the electrodes 1
A1 so that the distance between 04b and 104b 'is always constant.
By holding the plate 100a and the A2 plate 100b, X-ray detection accuracy is increased.

In the X-ray automatic exposure detector 10 having the above-described structure, the frame 100, the A1 plate 100a, and the A2 plate 100b are formed of aluminum having a low X absorption rate, and the spacers 101a, 101b, and
1c is formed of a resin having a low X-ray absorption rate. Further, the electrodes 104a, 104a 'and the electrodes 104b, 104
Since b 'and the electrodes 104c, 104c' are made of aluminum foil, X-ray absorption in the X-ray automatic exposure detector 10 is reduced. Therefore, even if the X-ray automatic exposure detector 10 is disposed in front of the cassette 12, there is almost no artifact on the X-ray image photographed on the film in the cassette 12.

In FIG. 1, X-ray irradiation field control means 13
Determines the X-ray irradiation field according to the imaging region of the subject 11, controls the X-ray aperture 21 so as to obtain the determined irradiation field, and selects the detector so that the corresponding detector is selected. The circuit 14 is controlled.

Under the control of the X-ray irradiation field control means 13, the detector selection circuit 14 controls the small-field detection section 10a of the X-ray automatic exposure detector 10 shown in FIGS. The detection unit 10b and the large-field detection unit 10c are appropriately selected, and the outputs of the selected detectors are added and output to the integration circuit 15a.

FIG. 4 is a block diagram showing a schematic configuration of the detector selection circuit 14, which comprises an addition circuit 14a and switch means 14b. When the detector selection circuit 14 receives an instruction to select the small-field detection unit 10a corresponding to the small-field based on the instruction of the X-ray irradiation field control unit 13, the switch unit 14b detects the small-field detection. Part 10a
Are connected, and when an instruction to select the small-field detection unit 10a and the medium-field detection unit 10b corresponding to the medium-field is received, the switch unit 14b connects the small-field detection unit 10a with the medium-field detection unit 10b. When the output of the detection unit 10b is connected, and the instruction to select the detection unit 10a for the small visual field, the detection unit 10b for the middle visual field, and the detection unit 10c for the large visual field corresponding to the large visual field is received, the switch In the means 14b, all outputs of the small-field detection unit 10a, the medium-field detection unit 10b, and the large-field detection unit 10c are connected. And
The addition circuit 14a adds the outputs of the connected detectors and outputs the result to the integration circuit 15a. As a result, it is possible to obtain a lighting field for detecting three different sizes of X-rays in three different visual fields.

In FIG. 1, an X-ray automatic exposure control device 15
Calculates the integrated value of the X-ray dose emitted from the X-ray tube 20 based on the output of the detector selection circuit 14, and activates the X-ray high-voltage device 19 when the integrated value becomes a value suitable for imaging. The X-ray irradiation of the X-ray tube 20 is stopped via the X-ray tube.

The X-ray automatic exposure control device 15 compares the output of the integration circuit 15a with the value set by the density setting circuit 15c, and compares the output of the integration circuit 15a with the value set by the density setting circuit 15c. When the output reaches the set value, a signal to that effect is output to the X-ray cutoff signal generator 15d, and the X-ray cutoff signal generator 15d cuts off the X-rays emitted from the X-ray tube 20. A signal for controlling the X-ray high voltage device 19 is output. Here, the density setting circuit 15
c is a detection unit 10 for a small visual field selected according to an imaging region.
a, the integrated value of the sum output of the small-field detection unit 10a and the medium-field detection unit 10b, and the small-field detection unit 10a, the medium-field detection unit 10b, and the large-field detection unit 10
The standard values Xa, Xb, and Xc, which are the optimum values for the integrated value of the sum output of c to obtain a captured image of each imaging region, are stored as set values, respectively. The set value corresponding to the instruction to select the X-ray detector is output to the comparator 15b.

Thus, as shown in FIG. 5, when only the detection unit 10a for the small visual field is selected, the density setting circuit 15c outputs the standard value Xa, so that the total transmitted X-ray dose becomes Xa. When the X-ray irradiation is completed at the time and the detection unit 10a for the small visual field and the detection unit 10b for the middle visual field are selected in the same manner, when the total transmitted X-ray dose becomes the standard value Xb, When the detection unit 10a, the detection unit 10b for the middle field of view, and the detection unit 10c for the large field of view are selected, the X-ray irradiation ends when the total transmitted X-ray dose reaches the standard value Xc.
An optimal X-ray fluoroscopic image according to the radiation field can be obtained.

The standard values Xa, Xb and Xc set by the density setting circuit 15c are set by the set value changing means 15e according to the photographer's preference after the respective values are set or in advance. It is configured so that it can be changed via the Internet.

Next, the operation of this embodiment will be described with reference to FIG. First, when there is an instruction from a not-shown instruction unit to the X-ray irradiation field control unit 13 for imaging a small imaging region, for example, a small visual field corresponding to a limb such as a hand or a foot, the X-ray irradiation field control unit 13 is used. Controls the X-ray aperture 21 to select the X-ray irradiation field corresponding to the imaging region, and instructs the detector selection circuit 14 to select the small-field detection unit 10a. For the density setting circuit 15c, a standard value Xa corresponding to the output of the small-field detection unit 10a
Instruct the user to select Thus, only the detection value of the small-field detection unit 10a after the X-ray irradiation is applied to the integration circuit 1
When the integrated value reaches the standard value Xa, the comparator 15b issues an instruction to the X-ray cutoff signal generator 15d to that effect, and the X-ray The radiation is shut off.

Further, when an instruction to shoot a medium-sized imaging region, for example, a medium field corresponding to the head and thigh, is given, and for a large imaging region, for example, a large field of view corresponding to the chest and abdomen. The same operation is performed when an instruction is issued, and when the integrated value of the sum output of the selected detectors reaches a predetermined value, X-ray irradiation is cut off.

In the above embodiment, the selected small-field detection unit 10a or the small-field detection unit 10a to the large-field detection unit 10c are set in the X-ray irradiation field selected according to each imaging region. The combination of the detectors for the respective X-ray irradiation fields specified by the X-ray irradiation field control means 13 may be specified as follows so that the combination of the X-ray irradiation fields surely falls within the X-ray irradiation field.

That is, the correspondence table shown in FIG. 6A is stored in the X-ray irradiation field control means 13, and when the X-ray irradiation field is from S1 to S2, the X-ray detector selects only the detection unit 10a for the small visual field. Then, the density setting circuit 15c is instructed to set the standard value Xa. Similarly, when the X-ray irradiation field is from S2 to S3, the small-field detection unit 10a and the middle-field detection unit 10b are selected, and the density is determined. The setting circuit 15c is instructed to set the standard value Xb, and when the X-ray irradiation field is equal to or more than S3, the small-field detection unit 10a, the medium-field detection unit 10b, and the large-field detection unit 10c are selected. Then, it is sufficient to instruct the density setting circuit 15c to set the standard value Xc. Note that FIG.
As shown in the figure, the irradiation field S1 is a minimum irradiation field which is normally set and is small enough to just fit the small-field detection unit 10a. Similarly, the irradiation field S2 is a medium-field detection unit 1
The size of the irradiation field S3 is set to a size that just fits the large field of view detection unit 10c. Further, the small-field-of-view detection unit 10a is configured to have a size corresponding to the smallest part required for imaging. For example, the small-field detector 10a has a diameter of about 5 cm, the middle-field detector 10b has a diameter of about 7 cm,
In addition, the large-field detection unit 10c can be about 10 cm in diameter.

Thus, even when the X-ray irradiation field is narrowed, transmitted X-rays in the irradiation field can be reliably detected, so that highly accurate automatic exposure control can be performed.

In the above-described embodiment, the X-ray automatic exposure detector 10 includes a circular small-field detector 10a and a ring-shaped medium-field detector 10b surrounding the detector.
And the large-field-of-view detection unit 10c.
A shape similar to the X-ray irradiation field defined by the line stop,
For example, a square shape may be used.

[0035]

According to the X-ray imaging apparatus of the present invention,
Since two or more X-ray detectors that detect transmitted X-rays in different fields of view are provided, and an X-ray detector suitable for the imaging region is selected, the difference between the size of the imaging region and the size of the X-ray field can be reduced. Exposure can be controlled based on an accurate measurement value of the X-ray dose transmitted through the imaging region, and a good fluoroscopic image can be obtained for each imaging region.

Further, when a first X-ray detector disposed at the center of radiography and a second X-ray detector are disposed so as to surround the first X-ray detector, the size of the radiographed part becomes larger. By using the sum of the detection values of the two detectors as the detection value, it is possible to effectively use the X-ray detector provided.

Further, the X-ray aperture is controlled so as to obtain an X-ray irradiation range suitable for the imaging region, and the detector selection means is controlled so that an X-ray detector suitable for the imaging region is selected. Therefore, when the X-ray irradiation field is wide, it is possible to accurately detect transmitted X-rays at the imaging site, and even when the X-ray irradiation field is narrow, select an X-ray detector suitable for the irradiation field By doing so, it becomes possible to accurately detect the X-ray dose transmitted through the irradiation field. Exposure control based on the accurate measurement of the X-ray dose transmitted through the imaging site becomes possible,
A good photographed image can be obtained for each photographed part.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an X-ray imaging apparatus according to the present invention.

FIG. 2 is a schematic view of an X-ray detector for automatic exposure according to the present invention observed from an X-ray irradiation direction.

FIG. 3 is a schematic view showing a cross section of the X-ray detector for automatic exposure according to the present invention.

FIG. 4 is a block diagram illustrating a detector selection unit according to the present invention.

FIG. 5 is a view showing an X-ray dose accumulated in an X-ray detector for automatic exposure.

FIG. 6 is a table showing X-ray detectors for automatic exposure and density setting values selected according to the X-ray irradiation field.

FIG. 7 is a diagram showing a conventional X-ray imaging apparatus.

FIG. 8 is a diagram showing a relationship between an X-ray irradiation field and a lighting field in a conventional X-ray imaging apparatus.

[Explanation of symbols]

 10: X-ray detector for automatic exposure 10a: X-ray detector for small visual field 10b: X-ray detector for medium visual field 10c: X-ray detector for large visual field

Claims (3)

[Claims] An X-ray imaging apparatus configured to irradiate a subject with an X-ray to capture a transmission image of the subject, comprising: two or more X-ray detectors for detecting transmission X-rays having different visual fields; A detector selecting means for selecting an X-ray detector suitable for the imaging region among the X-ray detectors and outputting the detected value; integrating a detection value of the selected X-ray detector; An automatic exposure control means for stopping the irradiation of X-rays when the X-ray dose becomes suitable for the X-ray. 2. The X-ray imaging apparatus according to claim 1, wherein the two or more X-ray detectors include a first X-ray detector disposed at least at a center of imaging, and the first X-ray detector. No. surrounding the detector
2 X-ray detectors, the detector selection means, the detection value of the first X-ray detector, or the first and second X-ray detector according to the size of the imaging region Output the sum of the detected values of X
X-ray equipment. 3. The X-ray imaging apparatus according to claim 2, wherein the X-ray stop restricts the X-ray irradiation range according to the imaging region, and the X-ray irradiation range suitable for the imaging region is obtained. X-ray irradiation field control means for controlling the line stop and controlling the detector selection means so that an X-ray detector is appropriately selected according to the X-ray irradiation range, An X-ray imaging apparatus characterized in that the size of the X-ray detector is at least large enough to accommodate the selected X-ray detector.