JPH03108299A - X-ray automatic exposure control device - Google Patents

Abstract

PURPOSE:To make a fluoroscopic image and a photographic image to coincide and prevent a diagnostic trouble by applying fluoroscopy and photography within the preset tube current range, and changing the tube voltage for fluorosco py and photography when the tube current is outside this range. CONSTITUTION:In an automatic exposure control device, an erecting bed 1 supports a body under test 2, its movement is controlled by an erection control ler 3, and an X-ray tube 4 is arranged below the body under test 2. An X-ray generator 5 driving the X-ray tube 4 is controlled by an X-ray controller 6. The controller 6 determines the center value of the tube current and the maxi mum and minimum tube currents for the thickness of the average body to be tested. Fluoroscopy and photography can be applied while the tube current is changed in the preset tube current range for the thickness of the average body to be tested and the tube voltage is kept constant. When the thickness of the tested body is small, the tube voltage is automatically decreased, and when the thickness of the tested body is large, the tube voltage is automatically increased. The fluoroscopic image and the photographic image are made to coincide, thus a diagnostic trouble can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an X-ray automatic exposure control device that displays a fluoroscopic image of a subject on a monitor and performs spot imaging as necessary.

(Prior Art) For example, when performing an X-ray examination of the digestive organs using an automatic X-ray exposure control device, spot imaging is performed as necessary while displaying and observing a fluoroscopic image of the digestive organs on a monitor. There is. This X-ray automatic exposure control device has automatic exposure control (AUL), which includes a function to automatically adjust the monitor brightness during fluoroscopy, and a photo timer to keep the film at a constant density during imaging.

Exposure Control) function is provided.

Among these, the F-ABC function mainly uses tube voltage control for ease of control and reduction of exposure dose, and the automatic exposure control function uses shooting time control for the sake of accuracy, ease of control, and image quality. Each of these functions is configured to be independently controlled.

In addition, the F-ATR (F-ATR) automatically determines the tube voltage and tube current during imaging based on the fluoroscopic conditions.
py-A auto TubevollageRe
gulator (fluoroscopic automatic tube voltage adjustment) function is implemented. FIG. 4 is a characteristic diagram showing a control method when performing fluoroscopy and imaging of a subject using such an F-ATR function. The vertical axis is the fluoroscopy tube voltage VT [kv], and the left horizontal axis is the fluoroscopy tube voltage VR kv], and the right horizontal axis indicates the object thickness T. First, the fluoroscopic tube voltage V is sequentially increased according to the thickness T of the object to be examined. The tube current ■ is set as a parameter, for example O-5mA and 1 mA.

The case where three types of 2 mA are selected is shown.

For each of these tube currents, a value is selected that maximizes the X-ray tube capacity with respect to the imaging tube voltage vR.

As the object thickness T increases, the fluoroscopy tube voltage V also increases, and the imaging tube voltage VR increases in proportion to this fluoroscopy tube voltage vl.
will also rise. However, in order to particularly reduce deterioration in image quality during imaging, the change in the imaging tube voltage VR is designed to be smaller than the change in the fluoroscopic tube voltage V. For example, as shown in FIG. 4, the fluoroscopic tube voltage V is 90 [kv], 125 [kv]
In the case of kv, the photographing tube voltage v3 is 80 [kv
It seems to be set at 90 [kv].

(Problem to be Solved by the Invention) However, in the conventional X-ray automatic exposure control device, the fluoroscopic tube voltage and the imaging tube voltage are different when a subject of the same thickness is examined. There is a problem in that the image and the photographed image do not match, which poses a problem in diagnosis.

That is, regarding the F-ABC function, since this function mainly performs tube voltage control, the fluoroscopic tube voltage (2) also changes greatly according to the change in the object thickness T based on the characteristics shown in FIG. As V increases, the contrast of the object decreases, and conversely, as V decreases, latitude (tolerance) increases.
decreases, making it difficult to obtain appropriate image quality. This is noticeable in direct shooting, so as mentioned above,
- Although the ATR function is designed to make the change in the imaging tube voltage VR smaller than the change in the fluoroscopy tube voltage V, this is not sufficient. As a result, the fluoroscopic tube voltage and the imaging tube voltage differ even for objects with the same thickness, and there are cases where what is seen in the fluoroscopic image is not captured on the photographic film, and the fluoroscopic image and the photographed image do not match. I will not do it.

The present invention has been made in response to the above-mentioned problems.
It is an object of the present invention to provide an automatic X-ray exposure control device that matches a fluoroscopic image and a photographed image.

[Structure of the Invention] (Means for Solving the Problem) To achieve the above object, the present invention provides an In an automatic radiation exposure control device, X-rays are seen through the X-ray tube by changing the tube current according to the thickness of the subject with a constant X-ray tube voltage within the range of the X-ray tube current set in advance based on the average subject. means for transmitting X-rays by changing the tube voltage with a constant tube current when the thickness of the subject falls outside the range of the tube current; The present invention is characterized by comprising means for performing imaging for a fixed period of time using a tube current having a value obtained by multiplying the tube current by a coefficient.

(Function) The range of X-ray tube current is set in advance based on the average subject.
Fluoroscopy is performed by keeping the tube voltage constant and varying the tube current within that range. Furthermore, for a subject that falls outside the tube current range, fluoroscopy is performed by decreasing or increasing the tube voltage while keeping the tube current constant. Next, imaging is performed for a certain period of time using a tube current that is the same as the predetermined tube voltage in the fluoroscopy and has a value obtained by multiplying the predetermined tube current by a certain coefficient. As a result, in the case of a subject within the tube current range, fluoroscopy or imaging can be performed with a constant tube voltage, and in the case of a subject outside the tube current range, the tube voltage is decreased or increased. Therefore, since the fluoroscopic tube voltage and the photographing tube voltage can be made to match, the fluoroscopic image and the photographed image match.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a configuration diagram showing an embodiment of the automatic X-ray exposure control device of the present invention, in which reference numeral 1 denotes a tilting table that supports a subject 2, the movement of which is controlled by a tilting controller 3, and the position below the subject 2 is shown in FIG. is X
A wire tube 4 is arranged.

Reference numeral 5 denotes an X-ray generator that drives the X-ray tube 4 and is controlled by an X-ray controller 6. 7 is a photography tube voltage automatic setting circuit (F-AT
R), 8 is a fluoroscopic tube voltage automatic setting circuit (F-A B C
) respectively control the X-ray controller 6.

Reference numeral 9 denotes a cassette disposed opposite to the tilting table 1 with the subject 2 interposed therebetween, and contains an X-ray film therein.

10 is 1.1 (image intensifier), 1
1 is a TV camera that shoots the optical image displayed on 1.110, 12 is an automatic exposure control circuit (AEC) that keeps the film density constant during shooting, 13 is a TV left camera control circuit, 1
4 is a TV monitor that displays a perspective image.

The X-ray controller 6 sets the tube current range in advance in consideration of the average subject and corresponds to this body thickness. The current ■.1n and the maximum tube current■.1K are set so that the tube current changes continuously within this range.Also, the fluoroscopic tube voltage V is set so that appropriate brightness can be obtained at this center current.
, is set. - As an example, as shown in FIG. 2, the average value of the object thickness T is set to 20 cm, and the corresponding center value C of the tube current is set to 1. 5mA, minimum tube current■. ,. 0,
5mA, maximum tube current I mmx 4. OmA and fluoroscopic tube voltage V are set to 80 kv.

Next, a control method for performing fluoroscopy and imaging according to this embodiment will be explained with reference to FIG. When the thickness of the subject is 20 cm, fluoroscopy is performed under a corresponding tube current of 1.5 mA and tube voltage of 80 kV. In addition, the tube current decreases in the entrance direction, and when the tube current becomes thicker than 20 cm, the tube current increases in the B direction, and fluoroscopy is performed under a tube voltage of 80 kV.Next, the tube current If it becomes even smaller than point A of 0.5 mA, the tube current is fixed at 0.5 mA and fluoroscopy is performed with the tube voltage reduced below 80 kV.Conversely, if the specimen thickness is lower than the tube current of 4.0 mA If the current becomes larger than point B, the tube current is fixed at 4.0 mA and fluoroscopy is performed with the tube voltage increased above 80 kV. This shows that the tube current (2) always does not exceed a preset range regardless of changes in the thickness T of the subject.

When photographing is to be performed next, photographing conditions are set in advance in the F-ATR as follows.

V R [kv co = V, [kv co
・ (1) I R [mA co = ■,
[mA] × α ... (2) Here VR:
Imaging tube voltage ■, : Fluoroscopic tube voltage ■ R = Imaging tube current ■, : Fluoroscopic tube current α: Coefficient Therefore, by performing imaging based on the above formulas (1) and (2), imaging can be performed in approximately constant time. I can do it.

If the tube current (2) exceeds the maximum current of the device, select the maximum current and use the phototimer to automatically compensate for the shortage.

According to this embodiment of the present invention, in the case of an average thickness of the subject, fluoroscopy and imaging can be performed by changing the tube current within a preset tube current range and keeping the tube voltage constant.

Further, when the thickness of the subject becomes small, the tube voltage can be automatically reduced to perform fluoroscopy and imaging, so it is possible to prevent the imaging time from becoming extremely short. Furthermore, when the thickness of the subject increases, the tube voltage can be automatically increased to prevent the imaging time from increasing.

This makes it possible to match the fluoroscopic tube voltage and the imaging tube voltage even for objects with the same thickness, so that the fluoroscopic image and the photographed image can be made to match. Therefore, since there is no problem in diagnosis, the efficiency of diagnosis can be improved.

Further, according to this embodiment, since no particularly complicated control circuit is required, the purpose can be achieved at low cost.

In the embodiments, the values of the tube current and tube voltage are explained by giving an example, but the values can be arbitrarily set depending on the purpose, use, etc.

[Effects of the Invention] As described above, according to the present invention, fluoroscopy and imaging are performed within a preset tube current range, and when the tube current is outside this range, fluoroscopy and imaging are performed by changing the tube voltage. Therefore, since the fluoroscopic image and the photographed image match, problems in diagnosis can be eliminated.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an embodiment of the automatic X-ray exposure control device of the present invention, and Fig. 2 is a characteristic diagram showing the relationship between the thickness of the subject and the fluoroscopic tube voltage to explain the operation of the device of this embodiment. , FIG. 3 is a characteristic diagram showing the relationship between the object thickness and tube current corresponding to FIG. 2, and FIG. 4 is a characteristic diagram for explaining a conventional control method for performing fluoroscopy and imaging. 2... Subject, 4... X-ray tube, 6... X-ray controller, 7... Imaging tube voltage automatic setting circuit, 8... Fluoroscopic tube voltage automatic setting circuit, 12... Automatic exposure control circuit. Figure 1

Claims (1)

[Claims] In an automatic X-ray exposure control device that displays a fluoroscopic image on a monitor while viewing a subject with X-rays and performs spot imaging as necessary, the X-ray tube current is A means for transmitting X-rays by changing the tube current according to the thickness of the object under constant X-ray tube voltage, and changing the tube voltage under constant tube current when the object thickness is outside the range of the tube current. and a means for performing imaging for a certain period of time using a tube current that is the same as a predetermined tube voltage in each of the fluoroscopic means and has a value obtained by multiplying a predetermined tube current by a coefficient. An automatic X-ray exposure control device characterized by: