JP3465424B2 - X-ray equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an analog or digital X-ray apparatus and, more particularly, to an X-ray apparatus having a plurality of different focal sizes. The present invention relates to an X-ray imaging apparatus. 2. Description of the Related Art X-ray imaging apparatuses are roughly classified into an analog type for recording on a film or the like, and an X-ray image signal obtained using an image intensifier and a television camera, and converted into a digital image. There is a digital type that converts and records. In these X-ray imaging apparatuses, those having a plurality of focal points having different focal point sizes and having an X-ray tube capable of switching between the focal points are used. [0003] If the size of the X-ray focus is increased, a large current can flow, so that the exposure time can be shortened. However, the penumbra becomes large, and the sharpness of the photographed image decreases. In particular,
In the X-ray geometric system, when the enlargement ratio determined by the distance from the X-ray focal point to the subject and the distance to the imaging surface is large, penalty blur increases, which is a problem. On the other hand, when the focal point size is small, penumbra is small, but the tube current cannot be increased, so that the exposure time becomes long, and if there is a motion of the subject, the motion causes blur. In general, when a subject is thick, an X-ray condition (tube voltage or the like) is increased for imaging. Therefore, a large X-ray focal point is selected, and a large current and short-time imaging are performed. Conversely, when the subject is thin and the X-ray conditions are small or the magnification is large, blurring due to motion is ignored and small-focus, small-current, and long-time shooting are performed. Conventionally, such selection of the X-ray focal point size has been performed by an operator's manual operation. That is,
The operator considers various conditions such as X-ray conditions, magnification, subject thickness, and whether or not the subject is moving,
An X-ray focal spot size is determined and operated to select it. However, it is very troublesome for an operator to select an X-ray focal spot size and manually set it as in the prior art, and it is necessary for the operator to perform appropriate settings. And it is easy to make setting mistakes.
There is a problem. SUMMARY OF THE INVENTION In view of the above, the present invention provides an X-ray imaging system which is capable of automatically taking an optimum X-ray image with the least amount of penumbra regardless of the thickness of the subject or the magnification.
An object of the present invention is to provide a radiographic apparatus. In order to achieve the above object, in an X-ray imaging apparatus according to the present invention, an X-ray tube having a plurality of X-ray focal points having different sizes, and these focal points are defined. A focus selection circuit for selecting, an image intensifier for receiving an X-ray transmitted through a subject and converting the X-ray transmitted image into a visible light image, a television camera to which the visible light image is guided, and the television An image monitor device that transmits an image signal from a camera to display an X-ray fluoroscopic image, an X-ray power supply device that supplies a high voltage to the X-ray tube, and a field-of-view size by controlling the image intensifier. At the same time, the luminance signal of the X-ray image signal when the image monitor device is displaying the X-ray fluoroscopic image is transmitted, and the X-ray power supply device is controlled so that the luminance becomes constant, and the X-ray condition is controlled. To Performs automatic brightness adjustment to adjust, and further selects the maximum focus size when the X-ray condition determined by the automatic brightness adjustment during fluoroscopy is larger than a threshold as the focus size at the time of transition from fluoroscopy to imaging. If the former is smaller than the latter, the size of the penumbra defocus calculated from the X-ray focal spot size and the magnification is compared with the resolution of the image to be photographed. An X-ray controller is provided for controlling the focus selection circuit so as to select a size and to select a smaller focus size when the former is greater than or equal to the latter. [0009] Even if penumbra blurs, it does not affect the sharpness of the image if it is lower than the resolution of the image to be photographed. Therefore, the size of the penumbra is calculated from the size of the X-ray focal point and the enlargement ratio, and by comparing this with the resolution of the image to be photographed, the image is adversely affected. Not know the size of the focus. If the largest focus size that does not adversely affect the image is used, shooting can be performed with a larger current and for a shorter time, and a good image can be shot. Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In FIG. 1, a subject 10 is placed on a medical examination table 11 and an X-ray tube 12
X-rays are emitted through the collimator 13. The X-ray transmitted through the subject 10 is incident on an image intensifier (II) 14, and the transmitted X-ray image is converted into a visible light image. This visible light image is guided to the television camera 17 via the optical system 15 and the aperture device 16, and an image signal is obtained. This X-ray image signal is transmitted to the image processing device 2
The X-ray image is sent to the image monitor device 22 through 1 and an X-ray fluoroscopic image is displayed. The image processing device 21 converts an input image signal into digital image data and performs various image processing. The recording device 23 records a captured image. The X-ray controller 31 includes a mechanical drive 32
Is controlled, the height of the examination table 11 and the height of the X-ray tube 12 are controlled. Also, the collimator 13
Is controlled by the collimator driving device 33 under the control of the X-ray control device 31. X-ray tube 12
Is supplied with a high voltage from the X-ray power supply 34. In this embodiment, the X-ray tube 12 has focal points of three sizes, large, medium, and small.
5 is selected. The X-ray controller 31 is, in addition to the above,
The X-ray power supply 34, the focus selection circuit 35, the aperture device 16, and the like are controlled. Further, the X-ray control device 31 controls the image intensifier 14 to switch its visual field size. Normally, a fluoroscopic image is displayed on the image monitor 22 to perform so-called X-ray fluoroscopy, and the operator observes the displayed image and obtains appropriate timing to obtain X-rays.
Perform radiography. At the time of this fluoroscopy, a luminance signal of an X-ray image signal is sent from the image processing device 21 and the X-ray control device 31
The automatic brightness adjustment for adjusting the X-ray conditions (such as the tube voltage) is performed so that the brightness becomes constant. Therefore, when the thickness of the subject 10 is large, X-ray conditions suitable for the thickness, such as an increase in the X-ray tube voltage, are automatically set. When an X-ray imaging command is input by an operator, the focus at the time of imaging is selected according to the fluoroscopic conditions. This is performed inside the X-ray control device 31 according to the procedure shown in FIG. First, the fluoroscopic condition is set to a predetermined threshold (A
). If this is greater than or equal to A, it means that the subject is thick. In this case, in order to reduce the blur due to the movement of the subject as compared with the penumbra, a large focus is selected in order to perform a large current and short time shooting. When the fluoroscopic condition is smaller than the threshold value A,
The focus size is selected to be "medium", and the calculation of Xh = (M-1) .Xf is performed. Here, Xh is the size of penumbra, Xf
Is the focal size. M is the magnification, and the X-ray tube 12
From the X-ray focal point to the subject 10 and the image receiving of the image intensifier 14 from the X-ray focal point determined from the height of the subject 10, the height of the subject 10 (examination table 11), and the height of the image intensifier 14. It is the ratio to the distance to the surface. If the size Xh of the penumbra determined by this calculation is smaller than the size of one pixel of the image matrix (the size of the image intensifier 14 on the image receiving surface), the penumbra will decrease the sharpness of the image. Has no effect. Incidentally, the size of one pixel of the image matrix on the image receiving surface of the image intensifier 14 is such that the field size is Is (inch) and the matrix size is Ms
Then, it is obtained by (Is · 25.4) / Ms. Therefore, the size Xh of the penumbra is compared with this, and if the former is smaller, the middle focus is selected as it is. Conversely, when the penumbra blur size Xh is equal to or larger than the one pixel size obtained by the above calculation, the minimum focus size is selected. X-rays are emitted from the focal point selected in this way, and the image intensifier 14 and the television camera 1
7, an image signal of an X-ray transmission image is obtained. This image signal is taken into the image processing device 21, converted into digital image data, stored in an internal memory, and output to the recording device 23 for recording. In addition, instead of such digital photography,
The focus is automatically switched as described above even in a method of recording an analog image signal without converting it into digital image data or a method of shooting a film by sending the film to the front of the image intensifier 14. be able to. In these cases, the calculation is performed using the image resolution instead of the pixel size (the pixel size is also a kind of the image resolution). Further, when the X-ray focal point is automatically selected by the calculation as described above, the load of the X-ray tube at the focal point is calculated and controlled so as not to be overloaded (in the case of overload). May increase the focus by one step). In addition, the calculation of the enlargement ratio may be performed by applying a predetermined correction to the height of the examination table 11. As described above, as described in the embodiment,
ADVANTAGE OF THE INVENTION According to the X-ray imaging apparatus of this invention, the optimal X-ray focal point size can always be automatically selected regardless of a subject thickness, an enlargement ratio, the size of a screen, etc. X-ray images can be taken.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of one embodiment of the present invention. FIG. 2 is an exemplary flowchart showing the procedure of processing in the embodiment. DESCRIPTION OF SYMBOLS 10 Subject 11 Examination table 12 X-ray tube 13 Collimator 14 Image intensifier 15 Optical system 16 Aperture device 17 Television camera 21 Image processing device 22 Image monitor device 23 Recording device 31 X-ray control device 32 Mechanical Drive device 33 Collimator drive device 34 X-ray power supply device 35 Focus selection circuit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H05G 1/00-2/00

Claims (1)

(57) [Claim 1] An X-ray tube having a plurality of X-ray focal points of different sizes, a focus selecting circuit for selecting these focal points,
An X-ray transmitted through the subject enters, an image intensifier that converts the X-ray transmission image into a visible light image, a television camera to which the visible light image is guided, and an image signal from the television camera. An image monitor for displaying an X-ray fluoroscopic image, an X-ray power supply for supplying a high voltage to the X-ray tube, and controlling the image intensifier to switch the size of the visual field, and the image monitor. A luminance signal of an X-ray image signal when is displaying an X-ray fluoroscopic image is transmitted, and an automatic luminance adjustment for controlling the X-ray power supply device and adjusting the X-ray condition so that the luminance is constant is performed. Then, when the X-ray condition determined by the automatic luminance adjustment during the fluoroscopy is larger than a threshold value, the maximum focus size is selected as the focal size at the time of the transition from the fluoroscopy to the radiography. When the former is smaller than the latter, a larger focus size other than the maximum focus size is selected if the size of the penumbra calculated from the X-ray focus size and the magnification is compared with the resolution of the image to be captured. And an X-ray control device for controlling the focus selection circuit so as to select a smaller focus size when the former is greater than the latter.