JP3538286B2 - X-ray equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an X-ray apparatus,
In particular, the present invention relates to a technique that is effective when applied to an exposure control device that appropriately controls X-ray conditions during imaging in X-ray diagnosis.

[0002]

2. Description of the Related Art The X-ray automatic exposure control method in an X-ray apparatus has been devised and improved from a long time ago, but it is difficult to set appropriate X-ray conditions due to the influence of a contrast agent, a bone and the like when transmitted through a subject. In gastrointestinal diagnosis, which is frequently used, there is a strong demand for improvement.

A conventional X-ray automatic exposure control method is disclosed in, for example, Japanese Patent Application Laid-Open No. 57-88698.
There is a line automatic exposure device.

In this X-ray automatic exposure apparatus, a part of an X-ray transmission image of a subject is detected by a plurality of photodiodes, and detection of some selected photodiodes among the plurality of photodiodes is performed. This is a method of controlling the irradiation time of X-rays at the time of X-ray imaging based on the output of the device.

That is, in this automatic X-ray exposure apparatus, the X-ray irradiation time during X-ray imaging can be controlled in real time based on the output signal of the photodiode. Control that is not affected can be performed.

As another X-ray automatic exposure control method, there is an X-ray diagnostic apparatus described in JP-A-62-15800.

This X-ray diagnostic apparatus obtains an average thickness and a minimum / maximum thickness of a subject from a video signal output from an X-ray detector during fluoroscopy of the subject. An X-ray imaging condition that maximizes the contrast of the X-ray imaging image of the sample is determined and imaging is controlled.

That is, the X-ray imaging condition of the subject is determined using the video signal output from the X-ray detector.
It is not necessary to prepare a photodiode as in the case of Japanese Patent Application Laid-Open No. 57-88698, and X-ray imaging conditions can be controlled with a simple device configuration.

In general, when performing exposure control using a video signal, it is necessary to control the photographing time on a time scale shorter than the reading speed of the video signal, so that real-time control is impossible.

For this reason, the above-mentioned Japanese Patent Application Laid-Open No. Sho 62-1580 has been disclosed.
As described in Japanese Patent Publication No. 0, it is necessary to determine the X-ray imaging conditions of the subject in advance.

[0011]

The present inventor has found the following problems as a result of studying the above prior art.

X described in JP-A-57-88698
The line automatic exposure apparatus requires a large number of photodiodes to perform accurate exposure control, and thus has a problem that the cost increases.

In addition, a control device for controlling a large number of photodiodes and controlling exposure based on a large number of inputs becomes complicated with an increase in the number of photodiodes.

Furthermore, there is a problem in that accurate exposure control becomes difficult due to the difference in light sensitivity characteristics between the photodiode and the X-ray detector.

On the other hand, X-ray scattering that occurs when X-rays pass through the inside of the subject is generally caused by the tube voltage of the X-ray tube, the type of X-ray filter, the thickness of the subject, the subject and the X-ray detection. Depending on the distance from the input surface of the vessel (hereinafter referred to as air gap) and the type of X-ray grid, the scattering intensity and scattering distribution change and are affected by the size of the X-ray irradiation area. It has been known.

In an apparatus using an X-ray image intensifier (hereinafter, referred to as X-ray II) as a detector, glare scattering generated when converting an X-ray image into an optical image causes a detection area to be reduced. I. I. It is known that the scattering intensity and the scattering distribution change according to the mode.

Therefore, the X-ray I.D. I. In an apparatus using a TV camera and an X-ray I.D. I. In addition to direct X-rays and scattered X-rays incident on I. The result including the glare scattering generated in the above is taken by the television camera, that is, converted into a video signal.

On the other hand, in the X-ray diagnostic apparatus described in Japanese Patent Application Laid-Open No. Sho 62-15800, the influence of X-ray scattering and glare scattering is not taken into account when performing exposure control using video signals. The exact thickness of the specimen cannot be determined,
As a result, there is a problem that X-ray imaging conditions cannot be determined accurately.

As a method for solving the above problem, there is an "X-ray apparatus" described in Japanese Patent Application No. 8-214466 filed by the same applicant.

In this X-ray apparatus, first, the relationship between the intensity of direct X-rays and the video signal output which is the output of the television camera,
In addition, the point spread of the X-ray scattered by the subject is measured in advance, and the result is stored in a storage device.

In the case of performing X-ray fluoroscopy and performing X-ray imaging based on the fluoroscopy result, the X-ray apparatus requires the X-ray fluoroscopic conditions,
From the point spread of the scattered X-rays and the contents stored in the storage means, a television camera (including an X-ray image intensifier)
Of the incident light amount of the television camera due to the scattered X-rays, that is, the amount of incident light amount of the TV camera due to the scattered X-rays, is determined to determine the imaging conditions.

Specifically, first, the intensity distribution of the output image when the subject has a predetermined thickness is calculated from the imaging conditions at the time of fluoroscopy. Next, a relationship between the intensity distribution of the output image at the time of fluoroscopy and the thickness of the subject is obtained, and from this relationship, a region of interest (hereinafter, ROI: Region Of Inter) of the operator.
est) is determined by function fitting using, for example, the well-known least squares method. Next, the average subject thickness in the ROI is calculated from the average output signal, and a part of the imaging conditions (tube voltage, X-ray filter type, etc.) is determined.

Next, other photographing conditions (air gap, grid type, image intensifier mode, etc.) under the decided photographing conditions are determined, and the intensity of the output image when photographing is performed under these conditions. A relationship between the distribution and the thickness of the subject is determined, and an average output signal within the ROI is determined from the relationship.

Finally, from the above-mentioned average output signal during fluoroscopy and the average output signal during imaging, the final or actual imaging conditions (tube current amount of X-ray tube, optical aperture area, television camera, etc.) Is obtained, and X-ray imaging is performed.

However, this X-ray apparatus needs to calculate the intensity distribution of an output image accompanied by a two-dimensional convolution operation when calculating the average output signal in the ROI.
There is a problem that it takes a lot of time to determine the imaging conditions at the time of imaging.

An object of the present invention is to provide an X-ray imaging apparatus capable of determining an imaging condition of an appropriate density level in a short time when determining an imaging condition for X-ray imaging from an imaging condition for X-ray fluoroscopy.
Wire device.

Another object of the present invention is to provide an X-ray imaging apparatus capable of determining the imaging conditions in consideration of the influence of X-ray scattering when determining the imaging conditions for X-ray imaging from the imaging conditions for X-ray fluoroscopy. Wire device.

Another object of the present invention is to provide a technique capable of realizing a low-cost X-ray apparatus with a simple apparatus configuration.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0030]

Means for Solving the Problems Of the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

[0031] (1) Display and X-ray tube for generating X-rays, and X-ray collimator for limiting the irradiation area of X-ray, and means detect you imaging an X-ray image of the subject, the X-ray image materials which have at the X-ray device having a display unit, simulating the object to be
The relationship among the output value I of the detection means, the tube voltage V of the X-ray tube, the tube current Q, the gain G of the detection means, and the thickness t of the subject , obtained by using With the tube voltage V as a variable
First approximation using the polynomials Po (V) and μ (V)
I = QGPo (V) exp (−μ (V) t)
Obtained values of the polynomial coefficients of Po (V) and μ (V)
First storage means for storing the size of the irradiation area,
The rate of change of the output value I of the detection means with respect to the
The tube voltage V of the tube, the thickness t of the subject, and the
A second approximation formula consisting of a polynomial with size and variables
The second case that stores the value of the polynomial coefficient obtained by approximating
Storage means, and the distance between the subject and the input surface of the detection means
The change rate of the output value I of the detection means with respect to the change of
The tube voltage V of the X-ray tube, the thickness t of the subject, and the subject
And the distance between the input means of the detection means and the polynomial
Polynomial relation obtained by approximation with the third approximation formula
A third storage unit for storing a value of the number;
Output approximation function expressed by the product of similar expressions
X-ray tube voltage V, tube current Q, and size of the irradiation area
And the distance between the subject and the input surface of the detection means and the
The thickness t of the subject based on the value of the gain G of the output means.
First calculating means for calculating, and the first calculating means
The calculated thickness t of the subject, the output approximation function,
The predetermined tube voltage V of the X-ray tube at the time of shadow
The size of the irradiation area and the input of the subject and the detection means
The tube current Q at the time of photographing based on the distance from the
Second calculating means for calculating the gain G of the output means;
Controlling the photographing based on the calculation result of the calculating means
X-ray apparatus comprising a step .

(2) In the X-ray apparatus according to (1), an X-ray filter for changing the energy distribution of X-rays
And / or when X-rays pass through the subject
X-ray grid to remove scattered X-rays
X-ray filters and / or a plurality of said X-ray grids
The first to third approximate expressions determined for the combinations of
The values of the polynomial coefficients of the first to third storage means, respectively.
Stores .

(3) In the X-ray apparatus according to (1 ), the second approximate expression is a constant value.

[0034] (4) In the X-ray apparatus according to the aforementioned (1), the third approximate expression is a constant value.

(5) In the X-ray apparatus according to the above ( 1 ), the first calculating means may be configured so that the first calculation means performs the tube operation during fluoroscopy.
The values of the voltage V, the tube current Q and the gain G are preset.
Determining means for determining whether the value is within the range of the allowable value.
The judging means has the tube voltage V, the tube current amount Q,
And that the gain G is not included in the range of the allowable value.
When set, the tube current Q or the gain G at the time of photographing
The second calculating means includes an output value correcting means for multiplying by a predetermined value.
Be prepared.

[0036]

[0037]

[0038]

[0039]

[0040]

According to the above-mentioned means (1), the subject is
The relationship between the output value I of the detecting means, the tube voltage V of the X-ray tube, the tube current Q, the gain G of the detecting means, and the thickness t of the subject , obtained by using the material to be simulated , Polynomial as variable
First approximation formula I = QG using Po (V) and μ (V)
Po (V) exp (−μ (V) t)
The values of the polynomial coefficients of Po (V) and μ (V) are stored in the first storage means. In addition, changes in the size of the irradiation area
The rate of change of the output value I of the detection means with respect to the tube voltage of the X-ray tube
V, the thickness t of the subject, and the size of the irradiation area are variables.
A polynomial obtained by approximation with a second approximation formula composed of polynomials
The value of the term equation coefficient is stored in the second storage means.

Further, the distance between the subject and the input surface of the detecting means is determined.
The rate of change of the output value I of the detection means with respect to the change of the distance is expressed by X
The tube voltage V of the tube, the thickness t of the subject, the
The third consisting of a polynomial with the distance to the input surface as a variable
The value of the polynomial coefficient obtained by approximation with the approximation formula is stored in the third storage unit.

At the time of use, that is, at the time of fluoroscopic imaging, first, fluoroscopy is performed under imaging conditions based on the operator and the setting conditions set by the automatic fluoroscopic control, and the imaging region of the subject is determined.

Next, when the transition to the shooting from the perspective is, first
The first calculating means is first represented by the product of the first to third approximate expressions.
Output approximation function and the tube voltage V of the X-ray tube during fluoroscopy.
The tube current Q, the size of the irradiation area,
Based on the distance to the force surface and the value of the gain G of the detecting means,
The thickness t of the specimen is calculated. Next, the second calculating means calculates the first
And the output approximation calculated by the calculation means
Function and tube voltage of X-ray tube preset at the time of imaging
V, the size of the irradiation area, the object, and the input surface of the detection means.
Based on the distance, the tube current Q at the time of photographing and the detection means
Calculate the gain G. After this, the control means makes the second calculation
The imaging conditions such as the tube voltage and tube current of the X-ray tube for controlling the imaging based on the calculation result of the stage and the gain of the X-ray detecting means are controlled, so that the imaging conditions of an appropriate density level can be obtained in a short time. X-ray imaging is possible.

According to the above-mentioned means (2), X-ray energy
An X-ray filter that changes the energy distribution, and / or
Eliminates scattered X-rays generated when X-rays pass through the subject
A plurality of X-ray filters, and / or
Is calculated for multiple X-ray grid combinations.
The values of the polynomial coefficients of the first to third approximate expressions are
By -3 storage means stores, you can consider the effect on the output value of the detection means by the X-ray scattering Runode can shoot an X-ray image of the subject in the imaging condition in consideration of the influence of X-ray scattering.

[0046]

[0047]

[0048]

According to the above-mentioned means ( 3 ), the second neighborhood
By approximating the Nishiki a constant value, it is possible to omit the measurement of the size <br/> variation of irradiation morphism region, it can be omitted measuring mechanism for measuring the amount of change in the size of the irradiation morphism region .

Therefore, the X-ray apparatus can be manufactured at low cost.

According to the above-mentioned means ( 4 ), the third neighborhood
By approximating the similar expression with a constant value, it is possible to omit the measurement using the distance from the subject to the input surface of the X-ray detecting means as a variable, so that the distance from the subject to the input surface of the X-ray detecting means is changed. The measurement mechanism for measuring the output value of the X-ray detecting means when the detection is performed can be omitted.

Therefore, the X-ray apparatus can be manufactured at low cost.

[0053]

[0054]

[0055]

[0056]

[0057]

[0058] According to the measure of the aforementioned (5), based on the determination result of the determine the constant means, the output value correction means the gain G of the tube current quantity Q or X-ray detector of the X-ray tube at the time of photographing a predetermined Therefore, for example, even when the gain G of the X-ray detecting means during fluoroscopy cannot be increased to an appropriate level due to a large thickness of the subject, the imaging conditions at the time of imaging are accurately calculated. it can.

[0059]

[0060]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings together with embodiments (examples) of the invention.

In all of the drawings for describing the embodiments of the present invention, components having the same functions are denoted by the same reference numerals, and their repeated description will be omitted.

FIG. 1 is a block diagram showing a schematic configuration of an X-ray apparatus according to an embodiment of the present invention. The X-ray tube 1, X-ray filter 2, X-ray collimator 3, bed top 5, X-ray Grid 6, X-ray image intensifier (hereinafter abbreviated as X-ray II) 7, optical lens system 8, television camera 9, monitor (display means) 10, remote console 11, console 12, X X-ray controller 100, X-ray filter controller 10
1. X-ray collimator controller 102, fluoroscopic / imaging position controller 103, I.I. I. Mode controller 104, optical aperture controller 105, television camera controller 106, amplifier 107,
A / D converter 108, image processing device 109, fluoroscopy condition calculation device 110, fluoroscopy condition storage memory 111, imaging condition calculation device (imaging condition calculation device) 112, imaging condition storage memory 113, table (storage device) 114 And so on. It should be noted that known devices and mechanisms are used.

In FIG. 1, the X-ray detector is an X-ray I.D.
I. 7, an optical lens system 8 and a television camera 9. The X-ray detection system (X-ray detection means) has a configuration in which an amplifier 107 is added to the X-ray detector described above. Therefore, the gain and output value of the X-ray detection system are the gain and output value of the amplifier 107, respectively. The imaging system includes an X-ray tube 1, an X-ray filter 2, an X-ray collimator 3, an X-ray grid 6, and the aforementioned X-ray detector. The control system (control means) includes the controllers 100 to 106, the amplifier 107, and the imaging condition storage memory 113 that stores and outputs control information of each controller. In addition, the subject 4 is located on the couchtop 5 and can change the imaging position in various ways. Then, an operator (not shown) sets a part of the subject 4 to be imaged near the center of the visual field of the X-ray detector.

The X-ray tube 1 and the X-ray I.D. I. 7 is 120 cm, the thickness of the subject 4 is t, and the upper surface of the couchtop 5 and the X-ray I.I. I. The distance from the input surface 7 (hereinafter referred to as an air gap) is L.

T changes variously depending on the individual difference or the body position of the subject 4. In addition, the air gap L is
It changes according to the setting of the position. X-ray I.I. I. The diameter of the X-ray input surface of No. 7 is 30.48 [cm]. The (x, y) coordinate system is an X-ray I.D. I. 7 defined on the input surface of X-ray I.7.
I. 7, the body axis direction is defined as the y-axis, and the direction orthogonal to the y-axis is defined as the x-axis. X-ray grid 6 is X
Line I. I. 7 is fixed on the input surface. TV camera 9
Uses a high-resolution CCD device as a photographing device.

Next, the outline of each of the above-described parts will be described with reference to FIG. 1. The X-ray controller 100 controls the tube voltage of the X-ray tube 1 during X-ray fluoroscopy (hereinafter, referred to as fluoroscopic tube voltage) and A tube current amount (hereinafter referred to as a fluoroscopic tube current) is read from the fluoroscopic condition storage memory 111, and based on the read value,
The X-ray generation of the X-ray tube 1 is controlled in real time. Also, X
At the time of X-ray imaging, a tube voltage (hereinafter, referred to as an imaging tube voltage), a tube current amount (hereinafter, referred to as an imaging tube current) and an imaging time of the X-ray tube 1 are read from the imaging condition storage memory 113, and based on the read values. Thus, X-ray generation of the X-ray tube 1 is controlled.

The X-ray filter controller 101 performs X-ray fluoroscopy
The type and presence / absence of the X-ray filter 2 at the time of imaging are read from the fluoroscopic condition storage memory 111 and the imaging condition storage memory 113, respectively.
The type and presence / absence of the line filter 2 are controlled. The X-ray filter 2 is used to change the energy distribution of X-rays emitted from the X-ray tube 1.

The X-ray collimator controller 102 controls the X-ray for setting the X-ray irradiation area 13 during X-ray fluoroscopy and imaging.
The position of the line collimator 3 is read from the fluoroscopic condition storage memory 111 and the imaging condition storage memory 113, and the position of the X-ray collimator 3 is controlled based on the read value.
However, the X-ray irradiation area 13 has the X-ray I.O. I. 7 is defined as an X-ray irradiation area on the input surface. The X-ray collimator 3 can change the X-ray irradiation area 13 in the x-axis and y-axis directions. The amount of change is axially symmetric with respect to the x-axis and the y-axis, respectively, and the sizes of the X-ray irradiation regions in the x-axis direction and the y-axis direction are represented by Ax and Ay, respectively.

The fluoroscopic position controller 103 is a device for controlling the X-ray fluoroscopic position of the subject 4. The control of the fluoroscopy / imaging position is performed by moving the entire imaging system with respect to the fixed couch top 5, or by moving the couch top 5 with respect to the fixed imaging system, or This is done by combining both.

I. I. The mode controller 104 controls the X-ray I.D. I. I.7. I. Mode
Each of the X-ray I.V. I. I.7. I.
Control the mode. However, I. I. The mode is X-ray I.O. I. 7 defines an X-ray detection area. X-ray I.I. I. 7 has I.I. I. The modes are, for example, 7,
9, 12-inch mode is provided, and X-ray I. I.
On the input surface of No. 7, X-rays are detected in an area inside a circle having a diameter of approximately each inch (1 inch is 2.54 [cm]).

The optical aperture controller 105 stores the optical aperture area of the optical lens system 8 at the time of X-ray fluoroscopy / imaging, in the fluoroscopy condition storage memory 111 and the imaging condition storage memory 1, respectively.
13 and controls a well-known aperture mechanism (not shown) based on the read value.

The TV camera controller 106 controls the X-ray fluoroscopy
Scanning conditions of the television camera 9 at the time of shooting are stored in a fluoroscopic condition storage memory 111 and a shooting condition storage memory 1, respectively.
13 and controls the scanning conditions of the television camera 9 based on the read value. Further, the television camera controller 106 controls the timing of scanning of the television camera 9. However, in the present embodiment, the standard scanning mode at the time of X-ray fluoroscopy of the television camera 9 is 30 frames per second and the number of scanning lines is 1050, but fluoroscopy with 60 frames per second and 525 scannings is also possible. The standard number of scanning lines at the time of X-ray imaging of the television camera 9 is 21.
Although the number of scanning lines is 00, shooting with 1050 scanning lines and 525 scanning lines is also possible.

The amplifier 107 stores the gain of the output signal of the television camera 9 at the time of X-ray fluoroscopy / photographing, into the fluoroscopic condition storage memory 111 and the radiographing condition storage memory 113, respectively.
And control.

X-ray irradiation area 13 during fluoroscopy / imaging
X-ray fluoroscopy / imaging position, type of X-ray grid 6, I. I.
The mode and the scanning conditions of the television camera 9 are set by the operator (not shown) by the remote control console 11 or the console 1.
Set manually through 2. At the time of fluoroscopy / imaging, the tube voltage and tube current of the X-ray tube 1, the type of the X-ray filter 2, the optical aperture area, and the gain of the amplifier 107 are controlled by a worker (not shown) through the remote operation console 11 or the operation console 12, respectively. It can be set manually as well as automatically. However, the shooting time at the time of shooting is automatically set by a method (procedure) described later. Remote control console 11
Alternatively, in addition to the above-described settings, the console 12 sets the imaging target site (for example, the chest and abdomen) of the subject 4 and
Settings such as the divided shooting mode can be made. As the division mode at this time, there are prepared no division, up / down and left / right two division modes, and four division mode.

In the following description, the tube voltage V of the X-ray tube 1
Alternatively, the tube current amount Q (however, the tube current amount Q is equal to the tube current of the X-ray tube 1 and the tube current
On the other hand, as the product of the frame reading time, on the other hand, in the case of X-ray imaging, it is defined as the product of the tube current of the X-ray tube 1 and the imaging time), the type of the X-ray filter 2, and Ax expressing the X-ray irradiation area 13 Ay, air gap L, type of X-ray grid 6, I.I. I. Mode, optical aperture area Ω, scanning conditions of the television camera 9, and gain G of the amplifier 107
X-ray fluoroscopy and X-ray
The set values of the above parameters at the time of radiography are referred to as X-ray fluoroscopic conditions and X-ray radiographic conditions, respectively. X at this time
The fluoroscopy condition and the X-ray imaging condition are recorded in the fluoroscopic condition storage memory 111 and the imaging condition storage memory 113, respectively.

Next, the operation of the X-ray apparatus according to the present embodiment will be described with reference to FIG. At the time of X-ray fluoroscopy and imaging, the X-rays generated in the X-ray tube 1 are first changed in energy distribution by the X-ray filter 2 and then after the X-ray collimator 3 limits the X-ray irradiation area 13. The subject 4 is irradiated.

When the X-ray radiated to the subject passes through the subject 4, a part thereof is scattered by the subject 4. Most of the scattered X-rays are blocked by the X-ray grid 6, but some of the scattered X-rays pass through the X-ray grid 6 without being blocked. The scattered X-rays transmitted through the X-ray grid 6 and the direct X-rays transmitted through the subject 4 without being scattered are simultaneously X-rays.
Line I. I. 7 and converted into an optical image. X-ray I. I. The optical image converted at 7 and emitted from the output surface is adjusted in light quantity by a well-known optical aperture (not shown) in an optical lens system 8 and formed on a television camera 9.
The television camera 9 converts this optical image into a video signal,
Output to the amplifier 107. The video signal input to the amplifier 107 is converted from an analog signal to a digital signal in the A / D converter 108 after the signal intensity is adjusted by the amplifier 107. The video signal converted into the digital signal is displayed on the display screen of the monitor 10 after being subjected to predetermined image processing by the image processing device 109.

At this time, at the time of X-ray fluoroscopy, the video signal output from the image processing device 109 is input to the fluoroscopy condition calculation device 110.

Next, the fluoroscopy condition calculating device 110 sets the above-mentioned video signal output to a preset value (an appropriate value), the fluoroscopic tube voltage V of the X-ray tube 1, the tube current Q, and the optical aperture area Ω.
Then, the respective values of the gain G of the amplifier 107 are calculated in real time, and are overwritten on the storage locations of the respective values in the fluoroscopic condition storage memory 111. At this time, the appropriate value of the signal output of the video signal at the time of fluoroscopy differs depending on the subject region to be imaged and the division mode, and these values are stored in the table 114 in advance. Therefore,
The fluoroscopy condition calculation device 110 refers to the table 114 based on the setting values of the subject region and the division mode input 111 to the fluoroscopy condition storage memory through the remote console 11 or the console 12 by an operator (not shown), and Set an appropriate value for the signal output of the video signal.

The fluoroscopy condition calculating device 110 selects an appropriate X-ray filter from the set value of the subject and the fluoroscopy tube voltage V recorded in the input 111 in the fluoroscopy condition storage memory, and selects an appropriate X-ray filter in the fluoroscopy condition storage memory 111. Overwrite the storage location of. An example of a method of selecting an X-ray filter at this time is, for example, electromedica 62 (1994) no. 1 p19-22.
And the like.

The fluoroscopy condition storage memory 111 stores the fluoroscopy tube voltage V of the X-ray tube 1 input from the fluoroscopy condition calculation device 110,
The values of the tube current Q, the optical aperture area Ω, and the gain G of the amplifier 107, and the X-ray irradiation area A input by a worker (not shown) through the remote console 11 or the console 12
x, Ay, X-ray fluoroscopy / imaging position, type of X-ray grid,
I. I. Information such as the mode, the value of the scanning condition of the television camera 9, the set value of the subject part, and the set value of the imaging division mode is stored. Each controller controls each device in real time according to the information described above, and the control result is reflected on the video signal intensity and fed back to the fluoroscopy condition calculation device 110.

An operator (not shown) uses the remote operation console 11 or the operation console 12 to perform the fluoroscopy position so that the desired part of the subject 4 is located at an appropriate position on the display screen of the monitor 10 during X-ray fluoroscopy. Are adjusted, and when the positions are aligned, the remote control console 11 or the console 1
2 is used to generate an X-ray imaging start signal to perform imaging.

Simultaneously with the generation of the photographing start signal, X
The X-ray controller 100 stops X-ray generation and ends X-ray fluoroscopy. At the same time, the X-ray imaging condition calculation device 112
X-ray fluoroscopic conditions at the end of fluoroscopy are stored in fluoroscopic condition storage memory 11
1, X-ray irradiation areas A'x, A'y at the time of radiography (hereinafter referred to as setting values of radiographing conditions) which are input in advance by an operator (not shown) through the remote console 11 or the console 12. Prime to '
To distinguish them from the set values of the fluoroscopic conditions), I. I. Information on the mode and the scanning condition of the television camera 9 is read from the shooting condition storage memory 113. Further, the X-ray imaging condition calculation device 112, based on the read information,
4, the tube voltage V ′ and the tube current Q ′ at the time of photographing, the optical aperture area Ω ′,
The respective values of the gain G ′ of the amplifier 107 are calculated, and the calculation results are stored in the photographing condition storage memory 113. At the same time that the calculation result is stored in the photographing condition storage memory 113, each controller stores the photographing condition in the photographing condition storage memory 113.
And performs each setting according to the set value. Upon completion of the setting, the X-ray controller 100 sends an X-ray generation signal to the X-ray tube 1 to perform X-ray imaging. The X-ray image obtained by the imaging is converted into a digital signal by the A / D converter 108 and then stored in a frame memory (not shown).

FIG. 2 is a block diagram showing a schematic configuration of the imaging condition calculation device of the present embodiment. The imaging condition calculation device 112 includes a subject thickness calculating means (average subject thickness calculating means).
201, an imaging tube voltage determining means 202, a Q'Ω'G 'calculating means 203, a saturation monitoring means (allowable value determining means, output value correcting means) 204, and a Q'Ω'G' determining means 205.

In the present embodiment, each means shown in FIG. 2 is realized by a program executed on a known information processing apparatus.

In FIG. 2, the subject thickness calculating means 201
Is means for calculating the subject thickness of the subject 4 from the relationship between the subject thickness at the time of fluoroscopy and the video signal output of the amplifier 107. The details will be described later.

The photographing tube voltage determining means 202 outputs X
This is a means for determining a so-called imaging tube voltage applied to the tube 1. In the present embodiment, the subject thickness determining means 20
Based on the subject thickness t and the imaging region determined in step 1, the determination is made by referring to the corresponding imaging tube voltage from the table 114b. The details will be described later.

The Q′Ω′G ′ calculating means 203 includes a subject thickness calculating means 201 and an imaging tube voltage determining means 202, and an imaging input by an operator (not shown) using the remote operation console 11 or the operation console 12. The tube current amount Q ′, the optical aperture area Ω ′, and the gain G ′ of the amplifier 107 are calculated so that the average signal output of the output image based on the condition and the average signal output of the output image during fluoroscopy have the same value. This will be described in detail later.

The saturation monitoring means 204 includes a tube voltage V, a tube current Q, an optical aperture area Ω, and a
It is determined whether or not each of the gains G of 7 is set to the maximum allowable value, that is, whether or not the imaging condition at the time of fluoroscopy is saturated. Based on the result, the following process is executed. It is a means to do.

If the above value is not set to the maximum allowable value, the tube voltage determining means 202 and Q '
The tube voltage V ', tube current Q', optical aperture area Ω 'and amplifier 1
The value of the gain G ′ of 07 is set as the value at the time of shooting.

On the other hand, when the above values are set to the maximum allowable values, the tube current amount Q ′ determined by the Q′Ω′G ′ calculating means 203, the optical aperture area Ω ′, and the amplifier 107 Is multiplied by (appropriate value of signal output during photographing) / (average signal output of output image based on calculated value). The details will be described later.

The Q'Ω'G 'determining means 205 calculates Q', Ω ',
After obtaining each value of G ′, the value is recorded in the photographing condition storage memory 113 as a set value 315 by automatic photographing control.

Next, FIG. 3 shows a processing flow for explaining the processing from the generation of the X-ray imaging start signal to the determination of all the imaging conditions. 2 will be described.

First, an outline of the entire processing flow will be described.
At the start of this processing flow, a photographing button provided on the remote operation console 11 or the operation console 12 is turned on by an operator (not shown) (step 301).

When the ON of the radiographing button is detected, the subject thickness calculating means 201 of the radiographing condition calculation unit 112 reads out all the fluoroscopic conditions recorded in the fluoroscopic condition storage memory 111 at the end of fluoroscopy, and stores the table 114a and the table 11
The average subject thickness t in the X-ray irradiation area of the subject 4 is calculated with reference to 4c (Step 302). However, the above-mentioned fluoroscopy conditions are, specifically, the remote control console 11,
Set value 310 input from console 12 or others
Setting 311 in, and common setting 313 in fluoroscopy / photographing
And a set value 314 by automatic fluoroscopic control.

Next, the imaging tube voltage determining means 202 determines an appropriate imaging tube voltage V ′ with reference to the table 114b with respect to the value of the average object thickness t and the set value of the object region.
It is recorded in the photographing condition storage memory 113 (specifically, the set value 315 by automatic photographing control) (step 303).

Next, the Q'Ω'G 'calculating means 203 calculates the values of the subject thickness t and the imaging tube voltage V' and the fluoroscopic and imaging conditions stored in the fluoroscopic condition storage memory 111 and the imaging condition storage memory 113. Are read out, and the table 11
A value Q'Ω'G 'of the product of the tube current amount Q', the optical aperture area Ω 'and the gain G' at the time of photographing is calculated with reference to 4c (step 304). However, the photographing conditions in this step are, specifically, the set value 310 input from the remote console 11, the console 12, or others, and the set value 314 by the automatic fluoroscopic control.

Here, the saturation monitoring means 204 determines whether the set value 314 by the automatic fluoroscopic control is set to a value that maximizes the signal strength of the output image, that is,
It is determined whether the fluoroscopic conditions are saturated (step 3).
05), when not saturated, Q ′ already determined
It is determined that the value of Ω'G 'is appropriate, and the next step 30
Proceed to 7. On the other hand, if the value is saturated, the determined value of Q'Ω'G 'is evaluated to be smaller than the appropriate value, as described later. 306), and then proceed to the next step 307. Here, the value of k is determined by a method described later using the value of the signal intensity 323 of the output image obtained at the end of the fluoroscopy.

Finally, the Q′Ω′G ′ determining means 205 determines the values of Q ′, Ω ′,
The values of G ′ are individually obtained, and the respective values are recorded in the photographing condition storage memory 113 as set values 315 by the photographing automatic control (step 307), and the photographing condition calculating device 112
The setting of the photographing conditions according to is completed.

Next, the photographing condition calculation device 1 of the present embodiment
The processing in each of the twelve means will be specifically described with reference to FIGS.

To calculate the average subject thickness t in the X-ray irradiation field of the subject 4 by the subject thickness calculating means 201, the subject thickness and the signal intensity of the output image under fluoroscopic imaging conditions are related. The following equation 1 (first function) is used.

[0102]

(Equation 1)

In Equation 1, the average signal output Ic is A / D
The average value of the output signal intensity near the center of the image output from the converter 108 is shown.

In the following description, Ic is defined as the average value of the output signal in the area (length of one side) of the center 1/4 of the output image (for example, scanning is performed with 2100 scanning lines). , For an image sampled by A / D conversion, the average value of output signals in the center 525 pixels square) is not limited thereto.

FC and FI are the scan mode of TV camera 9 and I.F. I. This is a coefficient determined by the mode. The FC and FI values are determined for all scan modes and for I.F. I. Pre-measured for the mode. Po
(V) is an average signal output function with respect to air, and when the subject 4 does not exist, X is detected through the air.
Represents the average signal output of the line. In general, Po (V) changes depending on the tube voltage V, and 2 (
It can be approximated by the following function:

[0106]

(Equation 2)

In equation (2), the coefficient a of the quadratic function
The values of p, bp, and cp can be measured in advance. μ
(V) is a function of the X-ray absorption coefficient of the subject 4. Generally, μ (V) changes depending on the tube voltage V.
Can be approximated by a quadratic function such as

[0108]

[Equation 3]

In equation (3), the coefficient a of the quadratic function
The values of m, bm, and cm are measured in advance for a material simulating the subject 4, such as an acrylic plate or water. FF
(V, t, Ax, Ay) is a function of the change rate of the average signal output with respect to the change of the X-ray irradiation area. Generally, FF
The amount of change of (V, t, Ax, Ay) with respect to the X-ray irradiation areas Ax, Ay depends on the tube voltage V and the subject thickness t, and can be approximated by the following equation (third function). .

[0110]

(Equation 4)

In equation (4), FF (V, t, Ax, A
The values of the coefficient KF and the tube voltage VF characterizing y) are measured in advance for a material simulating the subject 4 such as an acrylic plate or water. Ao is the X-ray irradiation area A
These values are set as standard sizes of x and Ay. Number 4
FF (V, t, Ax, Ay) is 1 when the X-ray irradiation areas Ax, Ay have the standard value Ao. Therefore, Equation 4 shows the change in the X-ray irradiation areas Ax, Ay. For
It shows the rate of change of the average signal output. FL (V, t,
L) is a function of the rate of change of the average signal output with changes in the air gap. In general, the amount of change of FL (V, t, L) with respect to the air gap L depends on the tube voltage V and the thickness t of the subject, and can be approximated by the following equation 5 (fourth function).

[0112]

(Equation 5)

In Equation 5, the values of the coefficient KL and the tube voltage VL characterizing FL (V, t, L) are measured in advance for a material simulating the subject 4, such as an acrylic plate or water. Lo is a value set as a standard size of the air gap L. Looking at Equation 5, FL (V,
(t, L) is 1 when the air gap L is the standard value Lo, and therefore, Equation 5 represents the rate of change of the average signal output with respect to the change of the air gap L. Number 1 above
Of the parameters characterizing ~ 5, the values of FC and FI are
It is measured in advance for a specific combination of the X-ray filter 2 and the X-ray grid 6, and is stored in the table 114c. Also, ap, bp, cp, am, bm, cm, K
The values of F, VF, KL, and VL are measured in advance for all combinations of the X-ray filter 2 and the type of the X-ray grid 6, and are stored in the table 114c. Note that,
The method of deriving the parameters and measuring the parameter values stored in the table 114c will be described later.

As described above, the fluoroscopy condition calculation device 110
The perspective control is performed so that the average signal output Ic is maintained at an appropriate value Ico. The appropriate value of Ico is measured in advance for a material simulating the subject 4, such as an acrylic plate or water. Ico is set as a different value depending on the subject region and the division mode, and these values are set in the table 114a.
Is stored in

When calculating the average subject thickness t of the subject 4 by the subject thickness calculating means 201, first, the fluoroscopic conditions stored in the fluoroscopic condition storage memory 111, that is, the remote operation console 11, Perspective setting 311, perspective / photographing common setting 313 in setting value 310 input from desk 12 or other, and setting value 3 by automatic fluoroscopic control
14 are read out. Next, the camera mode and I.P. I. Table 11
4c, read the values of FC and FI. Further, for the set values of the grid type and the X-ray filter type in the fluoroscopic conditions, ap, bp, cp, a
The values of m, bm, cm, KF, VF, KL and VL are read. Further, the setting value Ico of the average signal output is read from the table 114a with respect to the setting values of the subject part setting and the division mode setting in the fluoroscopic conditions. At this time,
Since the values of all parameters other than the average subject thickness t are read out and determined on the right side of Equation 1, it is possible to determine the average subject thickness t using the average signal output of the left side of Equation 1 as Ico. it can. Specifically, t that satisfies Equation 1 can be calculated by using a numerical calculation method such as Newton's method or dichotomy. As another calculation method, for example, 5, 10, 15, 20 [c
m] etc., and then calculate these by the exponential function a × e
xp (-bt) for least square fitting (however,
a and b are variables determined by fitting), and the subject thickness t is t = (log a−log Ico) /
b can be easily obtained.

As another method for obtaining the average object thickness t, the actual average signal output I from the fluoroscopic image at the end of fluoroscopy is used.
There is a method of calculating c to obtain an average signal output Ic on the left side of Expression 1. In this method, since the calculation is performed using the actually measured value of the average signal output, a more accurate thickness t of the subject can be obtained. However, the fluoroscopic image at the end of fluoroscopy is center 1 /
If halation occurs in the region 4 (length of one side), accurate Ic cannot be obtained. Therefore, the presence or absence of this halation is determined, and if the halation exists, the average signal output on the left side of Equation 1 is calculated as Ic
It is necessary to calculate the average subject thickness t using the method described above as o.

In the imaging tube voltage determining means 202, the imaging tube voltage V ′ is determined according to the subject thickness t determined by the subject thickness calculating means 201. Here, an appropriate value of the imaging tube voltage V ′ for each subject thickness t is set in the table 114b in advance in consideration of the contrast and noise of the captured image, the preferences of the examiner, and the like. In addition, since such settings are different depending on the object part (since the distribution of the X-ray absorption coefficient differs for each object part), a table value can be prepared according to each imaging part of the object.

In the Q'Ω'G 'calculating means 203,
The value of Q'Ω'G 'is calculated so that the average signal output of the output image and the average signal output of the captured image at the end of the fluoroscopy have the same value Ic. At this time, since the signal output of the fluoroscopic image at the end of fluoroscopy has an appropriate value by the automatic fluoroscopy control, it is possible to perform imaging so that the signal output of the captured image becomes an appropriate value. From Equation 1, such Q '
The value of Ω'G 'is obtained by the following equation (6).

[0119]

(Equation 6)

The values of the parameters on the right side of Equation 6 include the subject thickness t, the imaging tube voltage V ', the set value 310 input from the console / others, the set value 314 by automatic fluoroscopy control, and the table 114c. Can be calculated by referring to the equation (6).

The calculation by the Q'Ω'G 'calculating means 203 is based on the premise that the signal output of the fluoroscopic image at the end of fluoroscopy has an appropriate value by automatic fluoroscopic control. However, when the subject 4 is thick or when a contrast agent is used, the automatic fluoroscopic control may not be properly performed. This is because the X-ray absorption of the subject 4 is large and the tube voltage V, the tube current amount Q,
This is because the signal output of the fluoroscopic image at the time of fluoroscopy is less than an appropriate value, although the respective values of the optical aperture area Ω and the gain G are all set to the maximum values allowed. In this case, since the average signal output Ic of the fluoroscopic image takes a small value with respect to the appropriate value Ico, the value of Q'Ω'G 'at the time of shooting is changed so that the signal output in the shot image takes the appropriate value Ico. It is necessary to perform correction by multiplying k = Ico / Ic.

The saturation monitoring means 204 reads the set value 314 by the automatic fluoroscopic control, and sets the values of the tube voltage V, the tube current Q, the optical aperture area Ω, and the gain G during fluoroscopy to the maximum allowable values. Is determined, that is, whether the fluoroscopic conditions are saturated. Here, the maximum values of the tube voltage V and the tube current Q are determined by the heat capacity of the X-ray tube 1. The maximum value of the optical stop area Ω is determined by the aperture of the lens used in the optical system 8. Furthermore, the maximum value of the gain G of the amplifier 107 is set in advance by limiting the SN ratio of the fluoroscopic output image. When the fluoroscopic conditions are not saturated, the automatic fluoroscopic control is properly performed, and the value of Q'Ω'G 'calculated by the Q'Ω'G' calculating means 203 can be used as it is. When the fluoroscopic conditions are saturated, the automatic fluoroscopic control is not properly performed, and the value of Q′Ω′G ′ is set to k = Ico so that the signal output of the captured image takes an appropriate value Ico. /
It is multiplied by Ic (step 306). Here, the value of the appropriate value Ico of the signal output is determined by the table 114a in step 302.
Can be used.

In step 307, the determined Q'Ω '
The values of Q ', Ω', and G 'are individually determined for the value of G'. Here, the above-mentioned determination is automatically performed in consideration of the exposure dose of the subject 4, the spatial resolution of the captured image, the SN ratio of the captured image, or the like, or partially manually determined in advance by an operator (not shown). Is done. Generally, tube current Q '
Increases the exposure dose of the subject 4, increases the optical aperture area Ω ′, reduces the spatial resolution of the captured image, and increases the camera gain G ′ to decrease the SN ratio of the captured image. descend. Therefore, when photographing is performed with emphasis on the image quality of the photographed image, the optical aperture area Ω ′ and the camera gain G ′ may be reduced, and conversely, the tube current amount Q ′ may be increased. In addition, when imaging is performed with emphasis on reducing the exposure dose of the subject 4, the optical aperture area Ω ′ and the camera gain G ′ may be increased, and conversely, the tube current amount Q ′ may be decreased.

Next, FIG. 4 is a diagram for explaining the relationship between the thickness of the subject and the tube voltage and the average signal output of the output image. FIG. 5 is a diagram showing changes in the air gap L and the X-ray irradiation area A and the output image. FIG. 6 is a diagram for explaining the relationship between the average signal output of the X-ray irradiation area A and FIG. 6 is a diagram for explaining the relationship between the change of the air gap L and the average signal output of the output image.
FIG. 4 is a diagram for explaining a relationship between a change in x and Ay and an average signal output of an output image. Hereinafter, based on FIGS. 4 to 7, fluoroscopic conditions, a subject thickness, and a signal intensity of an output image will be described. Derivation of equations 1 to 5 to be related and parameters ap, bp, cp, am, bm, cm, K in equations 1 to 5
A method for measuring F, VF, KL, and VL will be described.

First, the fluoroscopy / imaging conditions, the subject thickness,
Of Equation 1 relating the signal strength of the output image,
The relationship between the subject thickness t and the tube voltage V and the average signal output of the output image will be described with reference to FIG. However, in the following description, all parameters other than the subject thickness t and the tube voltage V, that is, the tube current amount Q, the camera aperture Ω, the amplifier gain G, the camera mode, the I.V. I. Standard values are set for the mode, the X-ray irradiation areas Ax and Ay, and the air gap L. An example of a standard value for each parameter is, for example, as shown in FIG. In the measurement described below, the values shown in FIG. 4A are all used as standard values. In the following description, a standard aluminum filter having a thickness of 0.5 [mm] is used as the type of the X-ray filter 2, a standard distance of 120 [cm] is used as the type of the X-ray grid, and a grid ratio of 1:12 is used. A standard acrylic plate is used as a material for simulating a large grid and a subject. Further, the X-ray irradiation areas Ax, A
If Ax = Ay = A is maintained for y, this is abbreviated as X-ray irradiation area A for simplicity.
In all the following description relating to FIG. 4, all the aforementioned parameters having standard values are fixed to standard values. At this time, FF (V, t, Ax, Ay) and FL
The value of (V, t, L) is 1, and Po, which characterizes the relationship between the subject thickness t and the tube voltage V, and the signal strength of the output image.
(V) and μ (V) can be measured.

FIG. 4B shows that the tube voltage V = 70, 85, 1
In each case of 00 and 115 [kV], the measured value of the average signal output Ic is plotted when the thickness t of the subject is changed every 5 [cm] from 5 to 25 [cm]. FIG. 4B also shows the result of least-squares fitting of the above plot values with an exponential function Po × exp (−μt). The parameters Po and μ characterizing the exponential function are determined by the above-described fitting.
Po and μ have a tube voltage dependency, and Po (V) and μ
(V). Po (V) and μ determined for each tube voltage V from FIG.
The results obtained by plotting (V) are shown in FIG.
It is shown in (D). 4 (C) and 4 (D) also show the results of least square fitting of the above-mentioned plot values with quadratic functions expressed by Equations 2 and 3, respectively. Equation 2,
Parameters ap, bp, cp and a characterizing equation 3
The values of m, bm, and cm are determined by the aforementioned fitting. Since the values of these parameters depend on the tube voltage V of the X-ray tube 1, that is, the energy distribution of the radiated X-rays, generally, an X-ray filter or an X-ray grid that changes the energy distribution of the X-rays is used. Is changed, the value of the parameter also changes. Therefore, it is necessary to measure ap, bp, cp, am, bm, and cm in advance for all combinations of X-ray filters and grid types used, and store the results as a table. 4 (B) to 4 (D), it can be seen that the fitting is performed almost appropriately by the fitting function that least squares each plot value. However, the fitting function is not limited to the above example, but may be replaced with a more appropriate one according to the measured value.

Next, the fluoroscopy / imaging conditions, the thickness of the subject,
Of Equation 1 relating the signal strength of the output image,
The relationship between the change in the air gap L and the X-ray irradiation area A and the average signal output of the output image will be described with reference to FIG.

FIG. 5A shows that the tube voltage V is set to 110 [KV].
While keeping the air gap L at L = 5, 15, 25
FIG. 9 is a diagram illustrating a state of a change in an average output signal Ic when the average output signal Ic is changed to [cm]. However, the value of the average output signal Ic is
The value of the average output signal Ic at the standard value 5 [cm] of the air gap L is normalized as 1 and therefore, FIG.
(A) is a diagram showing the rate of change of the average output signal Ic. As is apparent from FIG. 5A, generally, as the air gap L increases, the average signal output decreases. This is because as the air gap L increases, the X-ray I.O. I. This is because the amount of scattered X-rays incident on 7 decreases. FIG. 5 (A) also shows the results obtained by simultaneously examining the dependency of the change rate on the thickness of the subject and the dependency on the X-ray irradiation area. FIG. 5A shows that the rate of change increases as the thickness t of the subject changes to 5, 10, 15 [cm]. This is because the ratio of the scattered X-rays to the direct X-rays increases as the thickness t of the subject increases. According to FIG. 5A, even if the X-ray irradiation area A is changed to 12, 9.6, 7.2 [inch] square, the change rate of the average output signal is not so affected. You can see that.

FIG. 5B shows that the tube voltage V is set to 110 [KV].
, The X-ray irradiation area A is L = 12, 9.6,
Average output signal I when changed to 7.2 [inch] square
It is a figure showing a situation of change of c. However, the value of the average output signal Ic is the standard value 12 [inc
h], the value of the average output signal Ic is normalized as 1.

As is clear from FIG. 5B, generally, as the X-ray irradiation area A becomes smaller, the average signal output becomes smaller. This is because as the X-ray irradiation area A becomes smaller, it is scattered around the X-ray irradiation area and the X-ray I.I. I.
This is because the amount of scattered X-rays incident near the center of 7 decreases. FIG. 5 (B) also shows the results of simultaneous investigation of the above-described dependency of the rate of change on the subject thickness and the air gap. As a result, according to FIG. 5B, it is understood that the rate of change increases as the thickness t of the subject changes to 5, 10, 15 [cm]. This is because the ratio of the scattered X-rays to the direct X-rays increases as the thickness t of the subject increases. According to FIG. 5B,
It can be seen that changing the air gap L to 5, 15, 25 [cm] does not significantly affect the rate of change of the average output signal.

As described above, according to FIGS. 5A and 5B, the change in the average signal output Ic depends on the air gap L and the X-ray irradiation area A.
Can be considered almost independent of changes in

Therefore, in equation (1), the function FF of the rate of change of the average signal output with respect to the change of the X-ray irradiation area is given.
(V, t, Ax, Ay) and a function FL (V, t, L) of the rate of change of the average signal output with respect to the change of the air gap are separated as independent functions.

Based on FIG. 6, among the expressions 1 relating the fluoroscopic / radiographic conditions and the thickness of the subject to the signal intensity of the output image, in particular, the relationship between the change in the air gap L and the average signal output of the output image. Will be described. In FIG. 6, in particular,
The change rate of the average output signal Ic is shown as the signal strength of the output image, and the expression method is basically the same as that in FIG.

FIG. 6A shows the tube thickness dependence of the change rate of the average output signal Ic, and FIG. 6B shows the subject thickness dependence of the change rate of the average output signal Ic. is there.
As is clear from FIGS. 6A and 6B, the rate of change of the average output signal Ic depends on the tube voltage and the thickness of the subject. This is because the ratio of the scattered X-ray to the direct X-ray changes as the thickness of the subject and the tube voltage change. In FIG. 6A, the subject thickness t is 2
5 [cm], tube voltage V = 70, 90, 110
For each case of [kV], the air gap L was changed to 5, 12, 19, 26 [cm], and the plot values in the figure represent experimental values. As is apparent from the plot values, the average output signal Ic changes almost linearly with the change in the air gap L. Further, it can be seen that the average output signal Ic changes almost linearly with respect to the tube voltage V.

In FIG. 6B, the tube voltage V is set to 110 [k].
V], and the air gap L is set to 5, 12, and 25 for each case where the subject thickness t = 5, 15, 25 [cm].
19 and 26 [cm], and the plot values in the figure represent experimental values. As is apparent from the plot values, the average output signal Ic changes almost linearly with the change in the air gap L. Moreover,
It can be seen that the average output signal Ic changes almost linearly with the thickness t of the subject.

As described above, the function FL (V, t, L) of the rate of change of the average signal output Ic with respect to the change of the air gap L is approximated by the following equation (5). At this time, the value of VL characterizing Equation 5 is represented by two plots (t = 25 [cm],
L = 26 [cm], V = 70, 110 [kV]) were measured, and FL (V, t = 25) was obtained from the above measured value and Equation 5.
[Cm], L = 26 [cm]) = 1, and is obtained by calculating the value of VL. Also, KL characterizing Equation 5
Are the values of t = 25 [cm] and L =
A measured value at 26 [cm] and V = 110 [kV];
It is easily calculated from the value of VL already obtained by using Expression 5. The values of these parameters are the tube voltage V of the X-ray tube 1.
That is, since there is a dependency on the energy distribution of the radiated X-rays, generally, when the X-ray filter or the X-ray grid that changes the energy distribution of the X-rays is changed, the value of the parameter also changes. For this reason, for all combinations of the types of X-ray filters and grids used, VL
And KL need to be measured and stored as a table. FIGS. 6A and 6B simultaneously show the value of the average signal output Ic calculated using Equation 5 with respect to KL and VL obtained by the above-described method. FIG. 6 (A),
According to (B), it can be seen that the change in the average output signal Ic with respect to the change in the air gap L is approximately approximated using Equation 5. In Equation 5, the average output signal I
Although the change with respect to the air gap L, the subject thickness t, and the tube voltage V of c was linearly approximated as being linear, the above-described approximate function is not limited to only the above-described example, but depends on the measured value. Can be replaced with something more appropriate.

Based on FIG. 7, among the equations 1 relating the fluoroscopic conditions and the subject thickness to the signal intensity of the output image, in particular, the change of the X-ray irradiation areas Ax and Ay and the average signal output of the output image Will be described. FIG. 7 is a diagram showing the rate of change of the average output signal Ic. The expression method is basically the same as that of FIG.

FIG. 7A shows the dependence of the change rate of the average output signal Ic on the tube thickness, and FIG. 7B shows the dependence of the change rate of the average output signal Ic on the thickness of the subject. Each is shown. As is clear from FIGS. 7A and 7B,
The above-described rate of change of the average output signal Ic depends on the tube voltage and the subject thickness. This is because the ratio of the scattered X-ray to the direct X-ray changes as the thickness of the subject and the tube voltage change.

In FIG. 7A, the subject thickness t is 25 [c].
m], and the tube voltage V = 70, 90, 110 [kV]
In each case, the X-ray irradiation area A is set to 12, 1
0, 8, and 6 [inch], and the plot values in the figure represent experimental values. According to this plot value, it can be seen that the average output signal Ic changes almost linearly with the change in the X-ray irradiation area A. Further, it can be seen that the average output signal Ic changes almost linearly with respect to the tube voltage V.

In FIG. 7B, the tube voltage V is set to 110 [k].
V], and the X-ray irradiation area A is set to 12, 1 for each case where the object thickness t = 5, 15, 25 [cm].
0, 8, and 6 [inch], and the plot values in the figure represent experimental values. As is apparent from the plot values, the average output signal Ic changes almost linearly with the change in the X-ray irradiation area A. Also, the average output signal I
It can be seen that c changes almost linearly with the thickness t of the subject.

FIG. 7 (C) shows a case where the X-ray irradiation dose range is changed simultaneously in the x and y directions, and a case where only the x direction is changed (in this case, the y direction is fixed to a standard value of 12 [inch]).
5 shows changes in the average output signal Ic for each of the above cases. In FIG. 7 (C), the object thickness t and the tube voltage V are fixed at 25 [cm] and 90 [kV], respectively, and the X-ray irradiation areas A and Ax are 12, 10, 8, and
6 [inch], and the plot values in the figure represent experimental values. As is clear from the plot values, X
The change amount of the average output signal Ic when the X-ray irradiation area is changed only in the x direction is almost half of the change amount of the average output signal Ic when the X-ray irradiation area is changed simultaneously in the x and y directions. I have. Therefore, it is considered that the value of the average output signal Ic changes approximately in proportion to the sum of the change amount of Ax and the change amount of Ay.

As described above, the function FF (V, V,
t, Ax, Ay) are approximated by Equation 4. At this time, the value of VF that characterizes Equation 4 is obtained by plotting two points (t = 25 [cm], A = 6 [inch], V = 70,
110 [kV]), and FF (V, t = 25 [cm], Ax = 6 [inc] from the measured value and Equation 4
h], Ay = 6 [inch]) = 1 to calculate the value of VF. Also, KF characterizing Equation 4
Is t = 25 [cm] and A = 6 of the measured values.
[Inch], it can be easily calculated from the measured value at V = 110 [kV] and the value of VF already obtained by using Expression 4. Since the values of these parameters depend on the tube voltage V of the X-ray tube 1, that is, the energy distribution of the radiated X-rays, generally, when an X-ray filter or an X-ray grid that changes the energy distribution of the X-rays is changed, , The parameter values also change. For this reason, it is necessary to measure VF and KF in advance for all combinations of X-ray filters and grid types used, and to store them as a table.
FIGS. 7A to 7C simultaneously show the value of the average signal output Ic calculated using Equation 4 with respect to KF and VF obtained by the above-described method.

According to FIGS. 7A to 7C, it can be seen that the change of the average output signal Ic with respect to the change of the X-ray irradiation areas Ax and Ay is approximately approximated by using Equation 4. In addition,
In Equation 4, the X-ray irradiation area A of the average output signal Ic
Although the changes with respect to x, Ay, the subject thickness t, and the tube voltage V were each linearly approximated by a linear function, this approximate function is not limited to only the above-described example.
It can be replaced with a more appropriate one according to the measured value.

As described above, with reference to FIGS. 4 to 7, derivation of equations 1 to 5 and parameters ap, bp, cp, a
The method for measuring m, bm, cm, KF, VF, KL, and VL has been described. In addition, in Equation 1, the parameter F
C and FI, which are the coefficients for the camera mode and the X-ray I.D. I. I. I. The coefficients for the modes are shown. FC and FI are standard camera mode and standard I.F. I. 1 in mode. The measurement of FC and FI is performed under standard conditions and an appropriate thickness t of the subject, a tube voltage V (for example, t = 15 [cm], V = 90
[KV]), the camera mode and the I.D. I. It can be easily measured by changing only the mode from the standard condition and measuring the change rate of the average output signal Ic.

In Equations 1 and 6, the correction term FF (V, t,
Ax, Ay) and FL (V, t, L) can be omitted either or both. That is, FF (V,
t, Ax, Ay) = 1 or FL (V, t, L) = 1
And At this time, accuracy in deriving the thickness t of the subject or determining X-ray imaging conditions is degraded. However, since a mechanism for measuring an X-ray irradiation area or an air gap is not required, the apparatus configuration can be relatively simplified. Can be. In particular,
Regarding the correction term FL (V, t, L) of the air gap,
Since the air gap L does not change at the time of X-ray fluoroscopy and at the time of imaging, the omission of this omission has little effect on the calculation accuracy.
For example, when FL (V, t, L) is omitted, the value of Q'Ω'G 'determined by Expression 6 is the tube voltage V of the fluoroscopy and imaging tube.
Can be calculated within an error range of about 5% if the difference between the two is within about 20 [kV].

In the present embodiment, the values shown in FIG. 4A are used as the standard values of each parameter, but the present invention is not limited to this. In particular, the air gap L and the X-ray irradiation area A
It is desirable to set the standard values of x and Ay to the most frequently used values of the respective parameters. At this time, the FFs (V, t, Ax,
Ay) and the approximation error of FL (V, t, L), or the frequency of occurrence of calculation error due to omission can be suppressed.

As described above, according to the X-ray apparatus of the present embodiment, the relationship between the subject thickness and the signal intensity of the output image (average signal output Ic) under fluoroscopy conditions is approximated by Equation 1. First, values for specifying FC and FI, which are parameters of Equation 1, and Po (V),
μ (V), FF (V, t, Ax, Ay) and FL
Ap, bp, cp, am, bm, cm, KF, V, which are parameters of equations 2 to 5 for calculating (V, t, L)
F, KL, and VL, and imaging conditions at the time of fluoroscopy and imaging conditions at the instruction of the operator are stored in a table 11 respectively.
4a to c, the fluoroscopic condition storage memory 111 and the imaging condition storage memory 113 are stored in advance.

When an instruction for imaging is given, first, the subject thickness calculating means 201 calculates the subject thickness based on the imaging conditions at the time of fluoroscopy.

Next, after the imaging tube voltage determination means 202 determines the tube voltage of the X-ray tube 1, the Q'Ω'G 'calculation means 203
Determines the imaging conditions at the time of imaging by simple calculations based on the values stored in Equations 2 to 6, tables 114a to 114c, perspective condition storage memory 111, and imaging condition storage memory 113.

Next, the saturation monitoring means 204 determines whether there is any saturated item in the imaging conditions for fluoroscopy (set value 314 by automatic fluoroscopy control), and the imaging conditions for fluoroscopy are not saturated. In this case, it is considered that the automatic fluoroscopic control is properly performed, and the Q ′ calculated by the Q′Ω′G ′ calculating means 203.
The value of Ω'G 'is used as it is. On the other hand, when the imaging conditions at the time of fluoroscopy are saturated, it is considered that automatic fluoroscopy control has not been properly performed, and the signal output of the captured image is set to the appropriate value I.
so that the value of Q'Ω'G 'is k = Ico / I
The value multiplied by c is used.

The Q′Ω′G ′ determining means 205 individually obtains the values of Q ′, Ω ′, and G ′ with respect to the value of Q′Ω′G ′ output from the saturation monitoring means 204, respectively. Each value is recorded in the photographing condition storage memory 113 as a set value 315 by the automatic photographing control, and based on the set value, each of the controllers 100 to 106 and the amplifier 107 controls the corresponding device to perform X-ray When performing imaging, that is, when determining X-ray imaging conditions from X-ray fluoroscopic conditions and video signals during fluoroscopy, a simple function is used to determine the scattered X-ray dose that changes with changes in the X-ray irradiation area, air gap, and the like. The X-ray imaging conditions can be determined in consideration of changes in the amount of scattered X-rays. Therefore, it is possible to perform more appropriate X-ray imaging while eliminating the influence of X-ray scattering.

Further, X-ray imaging can be performed in a short time under an imaging condition of an appropriate density level.

The tube current amount Q ', the tube current amount, the optical aperture area Ω' and the gain G 'of the amplifier 107, which are imaging conditions at the time of photographing.
In the equation (6), the correction relating to the X-ray scattering is corrected by FF (V, t, Ax, Ay) and FL (V,
t, L) and FF (V ', t, Ax', Ay ') at the time of shooting
And FL (V ', t, L), the X-ray image of the subject can be captured under imaging conditions that take into account the effects of X-ray scattering.

Further, the photographing condition calculating device 112 calculates the values stored in the tables 114a to 114c, the fluoroscopic condition storing memory 111 and the photographing condition storing memory 113,
Since the imaging conditions at the time of imaging are calculated by Expressions 2 to 6 based on the approximate expression of the output value shown in FIG.

Since the imaging conditions at the time of photographing can be determined only by the product operation, a low-cost operation device having no high-speed operation capability can be used. Therefore, the X-ray apparatus can be manufactured at low cost.

The subject thickness calculating means 201 approximates and calculates the subject thickness of the subject 4 based on the equation (1) and the tables 114a and 114b. For example, the subject enters the X-ray detector during fluoroscopy. Even when the X-ray intensity exceeds the range that can be properly detected by the X-ray detector, the thickness of the subject can be accurately calculated.

Therefore, for example, even when a halo occurs in a fluoroscopic image (perspective image), the thickness of the subject can be calculated accurately, so that the imaging conditions at the time of radiography can be accurately determined. .

Also, based on the thickness of the object obtained by the calculation by the object thickness calculating means 201, the Q'Ω'G 'calculating means 20
3 calculates the imaging conditions at the time of shooting, so that the imaging conditions can be calculated more appropriately.

In the X-ray apparatus according to the present embodiment, the function unique to the apparatus is approximated by the product of Equations 4 and 5, and the parameters KF, VF, KL, and VL of Equations 4 and 5 are stored in a table 114c. For example, measurement for adjustment or the like for periodic inspection or the like can be performed in a short time, and the device can be easily adjusted by changing the above-described parameters.

The saturation monitoring means 204 monitors whether there is a saturated item in the imaging conditions at the time of fluoroscopy. If the item is saturated, it is regarded that the automatic fluoroscopic control has not been properly performed, and The value of Q'Ω'G 'multiplied by k = Ico / Ic is set as the imaging condition at the time of imaging so that the signal output takes an appropriate value Ico, for example, because the thickness of the subject 4 is large. Even when the gain of the amplifier 107 cannot be increased to an appropriate level during fluoroscopy, the imaging conditions during imaging can be accurately calculated.

Further, the standard values (tube current Q, camera aperture Ω, amplifier gain G, camera mode, II mode, X-ray irradiation area Ax, Ay, air gap L) shown in FIG. ) Is, for example, a value that is used most frequently during fluoroscopy, there is also the effect that errors in determining imaging conditions during imaging due to approximation errors of Equations 4 and 5 can be reduced. .

The effect described above is particularly effective when the amount of scattered X-ray is large, that is, when the thickness of the subject is large and the tube voltage of the X-ray tube is high.

As an example of this, as a subject, the thickness 28c
The case where the photographing control is performed using the acrylic of m is shown below. The fluoroscopic conditions at this time are as follows: tube voltage V =
120 [kV (kilovolt)], X-ray irradiation area Ax = A
y = 7 [inch], imaging conditions include a tube voltage V ′ of the X-ray tube = 108 [kV], and an X-ray irradiation area Ax = Ay = 1
2 [inch]. The other conditions (X-ray filter type, X-ray grid type, II mode, camera aperture, camera mode, amplifier gain, and air gap) are the same under fluoroscopy and radiography. did. In particular, the X-ray filter type and the X-ray grid type are the same as those used in the experiments shown in FIGS.
I. I. The mode, camera aperture, camera mode, and amplifier gain were set to the standard values shown in FIG. Also,
The air gap L was set to L = 25 [cm].

Under these conditions, radiographing conditions were obtained by the X-ray apparatus of the present invention, and radiographing was actually performed, and a fluoroscopic image and a radiographic image were compared.

As a result, the average signal output of the fluoroscopic image was 10
When 0% is set, the average signal output of the captured image is 95 to 10
The photographing was performed with an error of about 5%, that is, about 5%.

On the other hand, when imaging control is performed by the conventional method described in Japanese Patent Application Laid-Open No. Sho 62-15800 without considering the error of the scattered X-ray dose during fluoroscopy and imaging. The average signal output of the captured image is 140 to 150
%, Resulting in an error of 40 to 50%. The main cause of such a large error is a change in the X-ray irradiation area and a change in the scattered X-ray dose accompanying a deviation from the standard value of the air gap. Since such a large error causes halation in a photographed image, it is impossible to perform photographing at an appropriate density level using the conventional method. It was confirmed that shooting could be performed at the level.

In the present embodiment, the operation and effects of the X-ray apparatus have been described. However, the present invention is not limited to the X-ray apparatus, and other general X-ray fluoroscopic apparatuses, X-ray imaging apparatus, stereoscopic X-ray imaging apparatus, DSA apparatus (Digital Subtraction Ang)
It is needless to say that the present invention can also be applied to an iography device or the like.

As described above, the invention made by the present inventors is described below.
Although specifically described based on the embodiments of the present invention, the present invention is not limited to the embodiments of the present invention, and it is needless to say that various modifications can be made without departing from the gist of the present invention. .

For example, in the above-described embodiment of the present invention, a system including an X-ray image intensifier 7, an optical lens system 8, and a television camera 9 is used as an X-ray detector. Will not be done, X
Even if this is substituted by an X-ray detector using an X-ray flat sensor or the like (imaging means) capable of directly converting a line signal into an electric signal,
Needless to say, the above-described effects can be obtained. As an example of the X-ray flat sensor, a TFT (Thin Film) is used.
A method using a transistor is described in “Large
Area, Flat-Panel, Amorphous Silicon Imagers; LEAnto
nuk, et al.SPIE, Vol.2432, Physics of Medical Imagin
g, pp. 216-217 ".

[0170]

The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows.

(1) When determining imaging conditions for X-ray imaging from imaging conditions for X-ray fluoroscopy, imaging conditions with an appropriate density level can be determined in a short time.

(2) When determining the imaging conditions for X-ray imaging from the imaging conditions for X-ray fluoroscopy, imaging conditions can be determined in consideration of the influence of X-ray scattering.

(3) Since the X-ray apparatus can be manufactured with a simple configuration, the manufacturing cost of the X-ray apparatus can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a block diagram illustrating a schematic configuration of a photographing condition calculation device according to the present embodiment.

FIG. 3 is a processing flow for describing processing from generation of an X-ray imaging start signal to determination of all imaging conditions.

FIG. 4 is a diagram for explaining a relationship between a subject thickness and a tube voltage and an average signal output of an output image.

FIG. 5 is a diagram for explaining a relationship between a change in an air gap and an X-ray irradiation area and an average signal output of an output image.

FIG. 6 is a diagram for explaining a relationship between a change in an air gap and an average signal output of an output image.

FIG. 7 is a diagram for explaining a relationship between a change in an X-ray irradiation area and an average signal output of an output image.

[Explanation of symbols]

1. X-ray tube, 2. X-ray filter, 3. X-ray collimator,
5: bed top, 6: X-ray grid, 7: X-ray image intensifier, 8: optical lens system, 9: television camera, 10: monitor, 11: remote control console, 12: operation console,
100: X-ray controller, 101: X-ray filter controller, 1
02: X-ray collimator controller; 103: fluoroscopy position controller; 104: I. I. Mode controller, 105: optical aperture controller, 106: television camera controller, 107: amplifier, 108: A / D converter, 109: image processing device, 1
DESCRIPTION OF SYMBOLS 10 ... Perspective condition calculation device, 111 ... Perspective condition storage memory, 112 ... Imaging condition calculation device, 113 ... Imaging condition storage memory, 114 ... Table, 201 ... Subject thickness calculation means, 202 ... Imaging tube voltage determination means, 203 ... Q'Ω '
G 'calculation means, 204: saturation monitoring means, 205: Q'
Ω'G 'determining means.

──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Ken Ishikawa 1-1-1 Uchikanda, Chiyoda-ku, Tokyo Inside Hitachi Medical Corporation (72) Inventor Takashi Ishiguro 1-11-1 Uchikanda, Chiyoda-ku, Tokyo (56) References JP-A-6-189946 (JP, A) JP-A-6-14911 (JP, A) JP-A-63-82627 (JP, A) Jpn. JP, U) JP 4-77440 (JP, B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05G 1/00-2/00 A61B 6/00-6/14 JSTPlus file ( JOIS)

Claims (5)

(57) [Claims] 1. An X-ray tube for generating X-rays, an X-ray collimator for limiting an X-ray irradiation area, a detection unit for capturing an X-ray image of a subject, and a display unit for displaying the X-ray image And an output value I of the detection means, a tube voltage V of the X-ray tube, a tube current Q, and a gain of the detection means obtained by using a material simulating the subject. The relationship between G and the thickness t of the object is determined by using the tube voltage V as a variable.
First approximation formula I = using terms Po (V) and μ (V)
QGPo (V) exp (−μ (V) t)
The values of the polynomial coefficients of Po (V) and μ (V)
First storage means for storing, and a change in the size of the irradiation area
The change rate of the output value I of the detection means with respect to
Tube voltage V, the thickness t of the subject, and the size of the irradiation area.
And a second approximation formula consisting of a polynomial
Second storage means for storing values of polynomial coefficients obtained similarly
A step and a change in a distance between the subject and the input surface of the detection means.
The rate of change of the output value I of the detection means with respect to
The tube voltage V of the tube, the thickness t of the subject, and the
And a distance between the input means of the detection means and the input surface.
Of the polynomial coefficient obtained by approximation with the third approximation
Third storage means for storing a value, and the first to third approximate expressions
Output approximation function expressed by the product of
Tube voltage V, tube current Q, size of the irradiation area, and
The distance between the subject and the input surface of the detection means and the detection means
Calculating the thickness t of the subject based on the value of the gain G of the step
First calculating means for performing the calculation by the first calculating means
The thickness t of the subject, the output approximation function, and the time of imaging
The tube voltage V of the X-ray tube preset in
The size of the projection area, the subject, and the input surface of the detection means
Tube current amount Q at the time of photographing based on the distance
Second calculating means for calculating the gain G of the stage;
Control means for controlling photographing based on the calculation result of the calculation means;
An X-ray apparatus comprising: 2. The X-ray apparatus according to claim 1, wherein X
An X-ray filter that changes the energy distribution of the rays, and / or
Or, scattered X generated when X-rays pass through the subject
An X-ray grid for removing lines;
Luta and / or a combination of multiple said X-ray grids
Polynomial relation of the first to third approximation formulas determined for
An X-ray apparatus , wherein the first to third storage means store numerical values . 3. The X-ray apparatus according to claim 1, wherein said second approximate expression is a constant value . 4. The X-ray apparatus according to claim 1 , wherein said third approximate expression is a constant value. In X-ray apparatus according to claim 5] according to claim 1, before
The first calculating means calculates the tube voltage V during fluoroscopy,
The values of the storage current Q and the gain G are preset allowable values.
Having a determination means for determining whether or not it is within the range of,
The determining means determines the tube voltage V, the tube current Q, and the
When it is determined that the gain G is not included in the range of the allowable value.
In this case, the tube current Q or the gain G at the time of photographing is multiplied by a predetermined value.
An X-ray apparatus , wherein the second calculating means includes output value correcting means .