JP2674443B2 - X-ray equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray apparatus used for generating X-rays in the fields of medical diagnosis or non-destructive material inspection, and more particularly to an X-ray image intensifier and a television image pickup tube. The present invention relates to an X-ray device suitable for use in an X-ray television system in which the above are combined.

[0002]

2. Description of the Related Art In a conventional medical diagnostic X-ray television system, in order to reduce the skin dose to a subject (human body), an X-ray tube and an X-ray collimator are provided with a filter made of an aluminum plate having a certain thickness. Inserting.

[0003]

However, the conventional X-ray apparatus using such a filter has a problem that the skin dose to the subject increases when the tube voltage decreases.

That is, in a normal X-ray television system, the X-ray intensity is generally controlled by an automatic brightness adjusting circuit so that the brightness of the display image becomes constant.
According to this, when using an image intensifier with a large field of view, or for a subject with a small body thickness, the stable tube voltage drops. Then, the soft X-rays increase, but the soft X-rays do not contribute to the light emission of the image intensifier due to the quality dependence of the light emission efficiency of the image intensifier. Therefore, in the low tube voltage region, the proportion of soft X-rays that do not contribute to light emission in the incident X-rays of the image intensifier increases, so that the entire incident X-ray dose, that is, the skin dose of the subject increases. .

In view of the above, an object of the present invention is to provide an X-ray apparatus improved so as to remove soft X-rays in a low tube voltage region.

[0006]

In order to achieve the above object, in the X-ray apparatus according to the present invention, the X-ray tube, the X-ray image intensifier, and the luminance of the X-ray image signal obtained by the television camera are used. According to the tube voltage control signal from the automatic brightness adjusting circuit that controls the X-ray tube voltage accordingly, the effective filter thickness is continuously increased as the tube voltage decreases. Is continuously controlled, and a movable filter device mounted near the X-ray emission port of the X-ray tube.

[0007]

When the tube voltage decreases, the proportion of soft X-rays increases. Therefore, the proportion of X-rays contributing to the light emission of the image intensifier decreases, and the X-ray dose incident on the image intensifier increases in the low tube voltage region. That is, the wasted X-ray dose increases and the skin dose of the subject increases. On the other hand, the automatic brightness adjustment circuit
It controls the X-ray tube voltage according to the brightness of the X-ray image intensifier and the brightness of the X-ray image signal obtained by the television camera to make the brightness constant. When it becomes thin, a control signal for lowering the tube voltage is generated. Therefore, if the effective filter thickness of the movable filter device is controlled according to this tube voltage control signal and the effective filter thickness becomes thicker as the tube voltage becomes lower, the subject (human body) at low tube voltage
The skin dose can be automatically reduced. That is, it is possible to appropriately and simultaneously perform the automatic adjustment of the brightness when the tube voltage is low and the automatic reduction of the exposure dose. Moreover, since the effective filter thickness is controlled so as to continuously change, optimum control for automatically reducing the skin dose to the subject is possible in conjunction with automatic adjustment of the brightness.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, a lead cone 2 is provided at the X-ray irradiation port of the X-ray tube 1 to limit the irradiation field. Then, a collimator 3 for X-rays is attached near the lead cone 2. The collimator 3 is provided with a movable filter device 4, and a tube voltage signal (kV) from an X-ray controller (not shown) is provided.
It operates according to the signal).

That is, the movable filter device 4 has a wedge-shaped thickness change 2 as shown in FIG. 2, for example.
It has two aluminum plates 41 and 42. By simultaneously moving these in the opposite directions as shown by the arrow by an appropriate mechanism (not shown), the entry into the X-ray irradiation field
It is retracted to change its effective thickness. Drive 4
3 moves the aluminum plates 41 and 42 according to the kV signal.

Since the movable filter device 4 only needs to have a change in the effective thickness for the X-rays that pass therethrough, other configurations are possible, for example, in the X-ray irradiation field as shown in FIG. Alternatively, the aluminum plate 44 having a constant thickness may be rotated.

The movable filter device 4 thus constructed controls the effective filter thickness to increase as shown in FIG. 4 when the tube voltage decreases. When the tube voltage becomes high, the filter thickness is controlled so as to decrease, but the control is performed so that it does not fall below a certain value so as not to fall below the JIS standard for radiation protection.

As a result, the filter thickness increases in the low tube voltage region, soft X-rays that do not contribute to the light emission of the image intensifier can be reduced, and the skin dose can be reduced.

That is, in an X-ray television system having an automatic brightness adjustment circuit, an image signal is obtained by a combination of an image intensifier and a television camera, and this is sent to a television monitor device, and X
When a line image is displayed, the X-ray intensity is controlled by changing the tube voltage so that the brightness of the displayed image is constant. Therefore, in an X-ray television system having such an automatic brightness adjustment circuit, an experiment as to how the image intensifier incident dose changes when the subject thickness changes is as shown in FIG. Data is obtained. As shown in this figure, it can be seen that the tube voltage decreases according to the thickness of the acrylic plate used as the subject, and the incident X-ray dose increases accordingly. This is because the proportion of soft X-rays that do not contribute to the light emission of the image intensifier increases in the low tube voltage region.

Further, FIG. 5 also shows data when the thickness of the aluminum plate used as the filter is changed or the material is changed. That is, the curve 51 shows the case where the thickness of the aluminum plate is 2.5 mm, the curve 52 shows the case where the thickness of the aluminum plate is 4.0 mm, and the curve 53 shows the case where the thickness of the aluminum plate is 2.5 mm. It shows the case where the one having a thickness of 20 μm is used.
It can be seen that the incident X-ray dose of the image intensifier is reduced by increasing the filter thickness. This is a soft X due to increasing the filter thickness.
This is because the line has been reduced.

Therefore, by controlling the filter thickness so as to increase in the low tube voltage region, the soft X-rays that do not contribute to the light emission of the image intensifier can be reduced and the skin dose can be reduced. .

As described above, it is premised on the use in the X-ray television system having the automatic brightness adjusting circuit, and the effective filter thickness of the movable filter device 4 is controlled according to the tube voltage control signal from the automatic brightness adjusting circuit. Since the effective filter thickness is made thicker as the tube voltage becomes lower, the skin dose to the subject (human body) when the tube voltage is low can be automatically reduced. That is, it is possible to appropriately and simultaneously perform the automatic adjustment of the brightness when the tube voltage is low and the automatic reduction of the exposure dose. Moreover, since the effective filter thickness is controlled so as to continuously change, optimum control for automatically reducing the skin dose to the subject is possible in conjunction with automatic adjustment of the brightness.

Although the movable filter device 4 is incorporated in the collimator 3 in the above description, it is also possible to separate the movable filter device 4 from the collimator 3 and install it on the lead cone 2 as a single unit.

[0018]

As described above, according to the X-ray apparatus of the present invention, the effective filter thickness is controlled according to the tube voltage control signal from the automatic brightness adjusting circuit, and the effective filter thickness decreases as the tube voltage decreases. By reducing the soft X-rays by increasing the thickness, the skin dose to the subject (human body) at a low tube voltage can be automatically reduced. That is, the brightness can be automatically adjusted at the time of low tube voltage and the exposure dose can be automatically reduced in cooperation with the brightness adjustment and the brightness adjustment.
Moreover, since the effective filter thickness is controlled so as to continuously change, optimum control for automatically reducing the skin dose to the subject is possible in conjunction with automatic adjustment of the brightness.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a schematic view showing a movable filter device portion of the same embodiment.

FIG. 3 is a schematic view showing another example of the movable filter device.

FIG. 4 is a graph showing the effective filter thickness with respect to the tube voltage.

FIG. 5 is a graph showing experimental data on image intensifier incident dose with respect to subject thickness.

[Explanation of symbols]

 1 X-ray tube 2 Lead cone 3 Collimator 4 Movable filter device 41, 42, 44 Aluminum plate 43 Drive device

Claims (1)

(57) [Claims] 1. An X-ray tube, and an automatic brightness adjustment for keeping the brightness constant by controlling the X-ray tube voltage according to the brightness of an X-ray image intensifier and an X-ray image signal obtained by a television camera. According to a tube voltage control signal from the circuit, the effective filter thickness is continuously controlled so that the lower the tube voltage is, the thicker the effective filter thickness is continuously controlled. X-ray device comprising a movable filter device provided.