JPH10201746A - X-ray image diagnostic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust a semi-automatic setting of nearly γ-corrective coefficient using for offering a diagnosis without a gray level control by an operator as much as possible. SOLUTION: This device is constructed by providing X-rays tube ball 1 irradiating a subject 3 with X-rays, an I.I. 4 to detect the X-rays passing through the subject 3 and to output converting to an optical image, an arm part 18 holding both of the X-ray tube 1 and I.I. 4 to be opposed to each other, a holder 19 holding rotatably the arm part 18 in an optional angle, and a gray level operation part 9 to calculate the γ-corrective coefficient for displaying an optical image on a TV monitor 11. In this case, the operating part 9 of the γ-corrective coefficient calculate the rcoorective coefficient from a combination with at least each one of a parameter selected from a group consisting of a voltage parameter impressing the X-rays tube ball 1, a parameter of effective distance between the X-ray tube 1 and the I.I. 4, an angle parameter made by the arm part 18 and the holder 19, and a parameter size of a X-ray sensitive area of the I.I. 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray diagnostic imaging apparatus having a gamma correction coefficient calculating section for displaying an optical image converted and output by an X-ray detection system on an image monitor, and more particularly to the gamma correction coefficient. The present invention relates to an X-ray diagnostic imaging apparatus improved so that a calculation unit can be adjusted to a substantially appropriate value in real time.

[0002]

2. Description of the Related Art A conventional X-ray diagnostic imaging apparatus uses an X-ray
An X-ray generation system that emits X-rays, an X-ray detection system that detects X-rays transmitted through the subject, converts the X-rays into an optical image, and outputs the optical image, and positions the X-ray generation system and the X-ray detection system in opposing positions. An arm that supports the arm so as to be rotatable at an arbitrary angle, and a gamma correction coefficient calculator that calculates a gamma correction coefficient for displaying the optical image on an image monitor. ing.

The X-ray generating system includes an X-ray tube, and the X-ray detecting system includes an image intensifier (hereinafter referred to as “I.
I. "). In this type of X-ray image diagnostic apparatus, a gamma correction coefficient for displaying the optical image on an image monitor is calculated based on a voltage applied to an X-ray tube (hereinafter, referred to as “tube voltage”). Also,
Japanese Patent Application Laid-Open No. HEI 8-11818 also discloses that a gradation conversion characteristic is changed by a tube voltage.

[0004]

However, in the above-described method of calculating the gamma correction coefficient using the tube voltage, there is a case where only an approximate value as an appropriate gamma correction coefficient which is easy to diagnose in actual X-ray imaging is calculated. Many,
Some exceptional imaging modes (eg, gastrointestinal imaging)
Except for the above, it is necessary to adjust the gradation by actually displaying an image visually by an operator (also referred to as an “operator”), and the adjustment must be confirmed while viewing the actual image display. And the amount of adjustment differs for each shooting mode, there is a problem that such an operation is complicated.

[0005] In addition, when performing the above adjustment, the patient (subject)
Irradiating the subject with X-rays, and there is a problem that the subject may increase the X-ray exposure dose. The present invention is to solve at least one of these problems, and an object of the present invention is to calculate an appropriate gamma correction coefficient in actual X-ray imaging and to perform a tone adjustment by an operator as little as possible. Another object of the present invention is to provide an X-ray diagnostic imaging apparatus capable of semi-automatically setting a substantially appropriate gamma correction coefficient for use in diagnosis.

[0006]

An object of the present invention is to provide a method for measuring a subject
An X-ray generation system that emits X-rays, an X-ray detection system that detects X-rays transmitted through the subject, converts the X-rays into an optical image, and outputs the optical image, and positions the X-ray generation system and the X-ray detection system in opposing positions. An arm that supports the arm so as to be rotatable at an arbitrary angle, and a gamma correction coefficient calculator that calculates a gamma correction coefficient for displaying the optical image on an image monitor. In the X-ray image diagnostic apparatus, the gamma correction coefficient calculation unit includes a voltage parameter to be applied to the X-ray generation system, an effective distance parameter between the X-ray generation system and the X-ray detection system, the arm unit and the support unit. Calculating a gamma correction coefficient from a combination of at least one of an angle parameter with the detector and a size parameter of an X-ray receiving area of the X-ray detection system.
This is achieved by a line image diagnostic apparatus.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the X-ray image diagnostic apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the X-ray image diagnostic apparatus according to the present invention, and FIG. 2 is a block diagram showing an example of the configuration of a gradation calculation unit in FIG.

As shown in FIG. 1, an X-ray image diagnostic apparatus according to the present invention comprises an X-ray tube 1, a table 2, an I.D. I. 4, a distributor 5, a TV camera 6, an A / D converter 7, an operation unit 8, a gradation operation unit 9, a D / A conversion unit 10, and a TV monitor 1.
1, a high-voltage generator 12, an X-ray controller 13, a table controller 14, a support controller 15, and a system controller 1.
6, a console 17, an arm 18, and a support 19.

The X-ray tube 1 irradiates the subject 3 with X-rays.
The table 2 places the subject 3 thereon. I. I. Reference numeral 4 denotes an X-ray tube which is arranged to face the X-ray tube 1 and detects X-rays transmitted through the subject 3, converts the X-ray into an optical image, and outputs the optical image. The distributor 5 splits and outputs a component detected by a photomultiplier and a component input to the TV camera 6 so that the optical image can be input to the TV camera 6 with an appropriate amount of light. The photomultiplier is connected to an X-ray controller 13 and transmitted to an X-ray generation system so that feedback control can be performed. The TV camera 6 inputs the optical image of the component input from the distributor 5 to the TV camera 6, converts the optical image into a first analog signal, and outputs the first analog signal. The A / D converter 7 converts the first analog signal into a first digital signal and outputs it. The arithmetic unit 8 performs image processing on the first digital signal so as to display an image which can be easily diagnosed by performing a filtering process or the like, and outputs a second digital signal. For example, if the bit depth of the image is 16 bits, the gradation calculator 9 converts the second digital signal of 65536 gradations into 256 gradations that can be displayed on the TV monitor 11 and outputs the converted digital signals as a third digital signal. Along with
The effective focus of the X-ray tube 1 and I.I. I. 4 (generally referred to as "Source Image Distance", hereinafter abbreviated as "SID"), the angle formed between the arm 18 and the support 19, and the I.D.
I. The gamma correction coefficient relating to the gradation conversion is calculated by combining each parameter of the size of the X-ray receiving area of No. 4, the tube voltage parameter, and the input image data from the photomultiplier. The D / A converter 10 converts the third digital signal into a second digital signal.
And output it. The TV monitor 11 displays the second video signal as an X-ray image. The high voltage generator 12 is a power supply that supplies a high voltage (on the order of tens to hundreds of kilovolts) and a current (on the order of several to several hundred milliamps) to the X-ray tube 1. The X-ray controller 13 adjusts the voltage and current of the high-voltage generator 12 so that the X-ray
Adjust the amount of line energy. Although not shown in detail, the table controller 14 controls the table 2 so that the table 2 can be moved in at least one of the height direction of the apparatus installation floor, the height direction of the subject 3, and the vertical direction. The support control unit 15 controls the rotation of the arm 18 with respect to the support 19 and detects the angle between them. The system controller 16 gives a control amount to the table controller 14 and the supporter controller 15. The operator of the console 17 inputs various parameters necessary for the imaging mode based on the control amount to the system controller 16 by the operator. The arm part 18 is X
The tube 1 and I. I. 4, a mechanism for adjusting the SID (not shown in detail) is provided. The support 19 supports the arm 18 and, although not shown in detail, the arm 18 and the support 19.
Can be freely rotated to form an arbitrary angle.

Next, the configuration of the tone calculating section 9 will be described with reference to FIG.
This will be described with reference to FIG. The gradation calculation unit 9 includes a latch 25, a central processing unit (CPU) 26, and a gradation conversion processing unit 27.

The latch 25 stores information on a tube voltage value (tube voltage information), information on a SID distance (SID information) stored by a timing signal when the input image data is collected, an arm unit 18 and a support unit 19. Of angle (angle information) formed by I. I. The various parameters of the information (II size information) of the size of the X-ray receiving area of No. 4 are stored.
The CPU 26 calculates a gamma correction coefficient for calculating a gradation conversion value from various parameters. Gradation conversion processing unit 2
7 outputs a third digital signal by performing gradation conversion of the second digital signal based on the gamma correction coefficient calculated by the CPU 26.

Next, the principle of calculation of the gamma correction coefficient derived by the inventor will be described. I. I. The optical image output from 4 increases the amount of X-rays transmitted through the subject when the tube voltage is set high, so that the overall brightness is high and the contrast of the optical image is insufficient. In order to compensate for the insufficient contrast, a gamma correction coefficient is set so as to emphasize the luminance value area of the insufficient part. In this setting, since the luminance region that appears as a halation phenomenon increases, the increase in the luminance value of the gamma correction coefficient in the high luminance region (where there are many transmitted X-rays) where the halation phenomenon is likely to occur is suppressed.

The main cause is that the X-ray absorption amount of the subject increases as the thickness of the subject increases, or a high-absorber such as bone absorbs a large amount of X-rays inside the subject. It is considered that the subject suddenly enters the X-ray irradiation field due to body movement such as respiration. In this case, the tube voltage is controlled so that a photomultiplier is provided as a sensor for detecting the light quantity of the irradiation field, and is set to be increased based on the detected light quantity of the photomultiplier. The subject receiving the X-rays from the tube apparatus and the I.D. I. The inventor has verified that it greatly fluctuates depending on the positional relationship between the two.

For example, the subject 3 and the I.P. I. There are respective imaging modes in which a high-definition image is obtained when the X-ray tube 4 is in close contact, while an enlarged image of the object is obtained when the X-ray tube is close to the object. When an enlarged image is obtained, even if the tube voltage is set to a certain value, the scattered component of the X-ray radiated to the subject 3 becomes I.D. I. 4 is equivalent to a voltage lower than the actually applied tube voltage.
Also, by changing the SID, the X-ray tube 1 can be relatively separated from the subject 3 to obtain an enlarged image. At this time, I. I. Since the amount of received X-rays per unit area incident on 4 decreases, the setting control is performed so that the tube voltage increases. In such a case, I.I. I. Although the high absorber does not enter the X-ray receiving surface of No. 4, the tube voltage must be increased.

Next, the case where the angle formed between the arm 18 and the support 19 is changed will be considered. First, the subject 3 is laid on the table 2, and the X-ray tube 1 is placed vertically above the subject 3. I. 4 is positioned vertically below the subject 3 (hereinafter referred to as “frontal photographing”), and the X-ray tube 1 and the I.D. I. 4 is changed from the vertical direction with respect to the subject 3, and the X-ray tube 1 and the I.D. I. 4
Are taken in the horizontal direction (hereinafter referred to as “lateral photography”). In this case, since the effective body thickness of the subject 3 increases as the front imaging is shifted to the lateral imaging at an angle, the tube voltage must be set higher.

The main causes of the fluctuation of the setting of the tube voltage as described above include the magnification, the scattered radiation, and the thickness of the subject. I. 4 have different luminance distributions of the optical images.

Further, there is a factor that greatly varies depending on information received from the photomultiplier of the distributor 5. For example, the chest is I. I. When the front side is photographed with a relatively large field of view of about 12 inches on one side of the light receiving surface of No. 4, the field of view includes the spine almost completely. In such a case, the I.P. I. Since the light field of the photomultiplier from the photomultiplier 4 is obtained and the light field is overlapped with the region of the subject 3 having the spine, the amount of light input to the photomultiplier is reduced. I have to go.

On the other hand, I. I. When the front side of the light receiving surface of the subject 4 is photographed with a relatively small field of view of about 7 inches, the light receiving field and the spine of the subject 3 rarely overlap. Although the lighting field overlaps with the sternum, since the sternum itself has a low X-ray absorptivity and there is little space between the sternum, the lighting field of the photomultiplier is less obstructed. Since it does not decrease so much, the tube voltage does not need to be set so much higher as compared with the above-described imaging with a large field of view.

In other words, an image in which the tube voltage is set to be increased in imaging in a large field of view and an image in which the tube voltage is set to be increased due to enlargement in imaging in a small field of view are, of course, the most suitable for diagnosis. The gamma correction coefficient will be different. Therefore, how to set a gamma correction coefficient for a parameter that fluctuates with the verified tube voltage will be described for each item.

(1) I. I. The size of the field of view with respect to the light receiving surface of a large field of view (a side of the light receiving surface of II.4 is 16 inches, 12 inches, etc.) I. 4 has a large light-receiving area and, as a result, receives a wide range of transmitted X-rays from the subject, so that the X-rays individually pass through many organs of the subject having different X-ray absorptances. Since the dynamic range of the optical image at the location where the absorption coefficient is small and the location where the X-ray absorption coefficient is large become large, the gradient of the gamma correction coefficient is set on average over almost the entire dynamic range.

In the case of a small field of view (one side of the light receiving surface of II.4 is 9 inches, 7 inches, etc.) I. 4, the light receiving area is narrower than the large visual field, and as a result, the range of transmitted X-rays from the subject is narrow, so that the dynamic range is often compressed as compared to the large visual field. Since many regions of interest are included in the field of view, the gradient of the gamma correction coefficient is set steep to sharpen the display gradation.

(2) Size of SID When SID is large I. Since the X-ray dose per unit area of the X-ray receiving surface of No. 4 becomes smaller, I. I. In many cases, the amount of light of the optical image 4 is insufficient, and the gradient of the gamma correction coefficient is set steep to sharpen the display gradation.

When the SID is small Since the light quantity is not insufficient, the gradient of the gamma correction coefficient is set averagely over substantially the entire image.

(3) The angle between the arm 18 and the support 19 (the angle is 0 ° when the X-ray tube 1 and II. When it is located, the angle is 90 °.
The 90 ° direction is called large and the 0 ° direction is called small)

When the angle is large, the effective body thickness of the subject 3 increases, so that the tube voltage must be set higher in order to secure the transmitted energy of X-rays, and the gamma correction coefficient must be increased in order to sharpen the display gradation. Set the gradient steeply.

In the case where the angle is small, the gradient of the gamma correction coefficient may be averagely set over substantially the entire image because the effective body thickness changes in the direction of decreasing.

Next, a case where the X-ray dose detected by the photomultiplier and applied to the subject is controlled will be considered.

When a high-absorber such as the spine which absorbs X-rays well falls on the light receiving area of the photomultiplier, the amount of light received by the photomultiplier decreases, and the tube voltage is set higher to increase the amount of X-ray transmission. The subject is irradiated with X-rays of energy corresponding to the set tube voltage, and the blackening of the image of the spine and the like is reduced. It tends to be. In addition, when a lighting field enters the space between the sternum and the like, the amount of incident light of the photomultiplier increases, so that the gradation of the optical image becomes clear, but the high absorber such as the spine tends to be displayed in black. .

As described above, the tube voltage and the I.V. I. Of the field of view, the size of the SID, and the arm 1
The gamma correction coefficient is calculated by combining the angle formed by 8 and the support 19.

Next, an example in which a characteristic curve (hereinafter abbreviated as "characteristic curve") of the gamma correction coefficient input to the gradation calculating section 9 is specifically applied will be described with reference to FIGS. FIG. 3 shows the tube voltage rise setting, I.V. I. X-ray receiving area constant, predetermined SI
D, a graph showing an example of a typical characteristic curve at the time of front photographing, FIG. I. FIG. 5 is a graph showing an example of a typical characteristic curve at the time of X-ray receiving area constant, SID increased from a predetermined value, and front photographing, and FIG. I. FIG. 6 is a graph showing an example of a typical characteristic curve at the time of X-ray receiving area constant, predetermined SID, and lateral imaging of FIG.
I. Is a graph showing an example of a typical characteristic curve when the X-ray receiving area is larger than the predetermined value, a predetermined SID, and frontal photographing. FIG. I. X-ray receiving area constant, predetermined SI
D is a graph showing an example of a representative characteristic curve at the time of front photographing.

The tube voltage is set to increase, and I.V. I. In the case where the X-ray receiving area is constant, the SID is set to a predetermined distance, and a frontal image is taken. In this case, it is imagined that a high-absorbent material such as a bone blocks the lighting field in the image. Since it is expected that halation tends to occur in a lung field or the like where absorption is small, a characteristic curve that suppresses output data of a high luminance portion as shown in FIG. 3 is selected.

The tube voltage is set to increase, and I.V. I. In the case where the X-ray receiving area is constant, the SID is increased from the above-mentioned predetermined distance, and frontal photographing is performed. In this case, the I.D. I. Since the incident dose of X-rays to the X-ray is reduced, a characteristic curve that slightly emphasizes the intermediate luminance value as shown in FIG. 4 is selected.

The tube voltage is set to increase, and I.V. I. X-ray receiving area is constant, and the SID is set to the predetermined distance,
When lateral imaging is performed When the angle formed between the arm and the supporter increases and the effective body thickness of the subject increases, the amount of X-ray transmitted through the subject is insufficient. I. Since a large number of optical images in a low-luminance region are output from, a characteristic curve that emphasizes a low-luminance portion as shown in FIG. 5 is selected.

The tube voltage is set to increase, and I.V. I. In the case where the X-ray receiving area is larger than the above-mentioned fixed value, the SID is set to a predetermined distance, and the front image is taken. In this case, the X-ray dose per unit area decreases because the receiving area increases. Since a low-luminance area is hardly drawn and a portion where the effective body thickness of the subject is thin tends to be halation, a characteristic curve which emphasizes the low-luminance part as shown in FIG. 6 is selected.

The tube voltage is set to drop, and I.V. I. In the case where the X-ray receiving area is constant, the SID is set to a predetermined distance, and the front image is taken. In this case, since the optical image includes many low-luminance parts, FIG.
The characteristic curve is selected such that the low density portion is brightened as shown in FIG.

In the case where the tube voltage is set to decrease and the above-mentioned one is excluded, a special characteristic curve is not required.
In addition, factors may actually overlap. As an example, when the SID and the angle increase, the respective characteristic curves are combined and calculated. Specifically, the calculation may be performed in consideration of the characteristic points of the low luminance region, the medium luminance region, and the high luminance region of the characteristic curve to be synthesized.

In this embodiment, X-ray information, SID information, angle information, I.D. I. The optimum characteristic curve to be used for diagnosis is obtained from the information on the size of the light receiving area of FIG.
The image feature amount of the input image data may be adopted as the determination means. Examples of the image feature amount include halation detection and histogram data. There is also a method of calculating the optimal gamma correction coefficient to be used for diagnosis from only image information such as histogram data.However, when performing feedback control based on the captured image, a time delay occurs in this control. When the distribution and the data distribution of the next time phase are significantly different, there is a problem that the calculated characteristic curve does not match the currently displayed image data of the next time phase. For this reason, in shooting in which the image data distribution has a lot of fluctuation, rather than feedback control for each image,
In some cases, it is easier to see the fluctuation of the image data distribution, to input a certain allowable range to the console, and to roughly control the gamma correction coefficient.

Next, the operation of the X-ray diagnostic imaging apparatus of the present invention will be described with reference to FIGS.

X-ray tube 1 supported by arm 18
The X-rays emitted from the I.P. I. 4 is input. I. I. At 4, the X-ray information is converted into optical information, and is converted to a first video signal by the TV camera 6 via the distributor 5. The A / D converter 7 digitizes the video signal, performs various kinds of image processing in the arithmetic unit 8, performs display gradation processing in the gradation control unit 9, and then performs digital / analog conversion to display it on the TV monitor 11. . The table 2 and the arm unit 18 are controlled by a table control unit 14 and a support unit control unit 15, respectively. The system controller 16 operated from an operation console 17 instructs the operation thereof. The X-ray generation conditions are set by the X-ray controller 13 controlling the high-voltage generator 12 and real-time control is performed so that the light amount from the photomultiplier built in the distributor 14 becomes constant. . The display gradation is calculated by the gradation calculation unit 9 and the output is output from the D / A converter 10.
And is displayed on the TV monitor 11. X-ray information such as a tube voltage, a current flowing through the X-ray tube 1 (referred to as “tube current”), an exposure time, and the like are input from the X-ray controller 13 to the gradation calculation unit 9. SID,
I. I. The information of the X-ray receiving area, angle, and the like are input.

As shown in FIG. 2, the input image data is input to the gradation processing table 25, and the table is written into the gradation processing table 25 by the CPU 26. X-ray information, SID information, angle information,
I. X-ray receiving area of the CPU 26 via the latch 27
To calculate an optimal gamma curve.

Further, the present invention may be implemented by a memory circuit storing a plurality of characteristic curves without using a CPU. A large amount of data on the characteristic curve must be created and stored assuming that a plurality of conditions overlap, but since the hardware is mostly composed of a memory circuit, it has a simple configuration, Since it is only necessary to select and read the matched characteristic curve, the processing speed can be increased as compared with the case where the processing time until the setting of the gamma correction coefficient is sequentially calculated.

According to this embodiment, in addition to X-ray information such as tube voltage, tube current, and exposure time, SID, angle information, I.D.
I. The optimal gamma correction coefficient to be used for diagnosis can be controlled in real time by using each piece of information of the X-ray receiving area of the X-ray receiving area, so that the operator can efficiently proceed with examination and treatment,
Exposure of the subject can also be reduced.

[0043]

The X-ray image diagnostic apparatus according to the present invention has the above-described configuration. Since these configurations operate as described above, an appropriate gamma correction coefficient can be set in actual X-ray imaging. The present invention has the effect of providing an X-ray image diagnostic apparatus capable of semi-automatically setting an approximately appropriate gamma correction coefficient for use in diagnosis without calculating and performing tone adjustment by the operator as much as possible.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a gradation calculation unit in FIG. 1;

FIG. 3 is a diagram showing an example of a characteristic curve of a gamma correction coefficient when a front view is taken with a predetermined SID and a tube voltage is set to increase.

FIG. 4 is a diagram illustrating an example of a characteristic curve of a gamma correction coefficient when the front is photographed with the SID larger than that in FIG. 3;

FIG. 5 is a diagram illustrating an example of a characteristic curve of a gamma correction coefficient when lateral shooting is performed using a predetermined SID.

FIG. 6 is a diagram illustrating an example of a gamma curve when the tube voltage is reduced in a standard state of the SID.

FIG. I. The figure which shows the example of the gamma curve when a size becomes large and a tube voltage falls.

FIG. 8 is a diagram showing an example in which an image feature amount of input image data is also incorporated as a determination unit.

[Explanation of symbols]

 1 X-ray tube 2 Table 4 I. I. 9 Gradation calculation unit 13 X-ray controller 14 Table control unit 15 Support unit control unit 18 Arm unit 19 Support unit

Claims (1)

[Claims] An X-ray generation system that irradiates a subject with X-rays,
An X-ray detection system that detects X-rays that have passed through the subject, converts the X-rays into an optical image, and outputs the X-rays; an arm unit that supports the X-ray generation system and the X-ray detection system so as to face each other; An X-ray diagnostic imaging apparatus comprising: a support for rotatably supporting an arm at an arbitrary angle; and a gamma correction coefficient calculator for calculating a gamma correction coefficient for displaying the optical image on an image monitor. The coefficient calculation unit includes a voltage parameter applied to the X-ray generation system, an effective distance parameter between the X-ray generation system and the X-ray detection system, an angle parameter between the arm unit and the support, and the X-ray detection. An X-ray diagnostic imaging apparatus characterized in that a gamma correction coefficient is calculated from a combination of at least one of the size parameters of the X-ray light receiving area of the system.