JPS5845779B2 - X-ray source device - Google Patents

Description

[Detailed description of the invention] The present invention relates to an X-ray source device using an X-ray tube.

The X-ray source device of this invention combines an X-ray tube or a container containing an X-ray tube (including a monotank) with a device that limits and adjusts the aperture of the X-ray irradiation field as necessary. Refers to something that is designed to take out.

As is well known, an X-ray radiation device generally includes an X-ray tube and an X-ray diaphragm called a collimator in order to extract the X-rays emitted from the anode target of the X-ray tube in a desired direction and in a desired irradiation field. It is used in conjunction with a device that limits the irradiation field by shielding the radiation from undesired directions and areas of X-rays.

FIGS. 1 and 2 illustrate an example of an apparatus using a rotating anode type X-ray tube.

In the figure, numeral 21 is an X-ray tube, 22a is an anode target, 22b is a cathode for electron beam generation, 23 is a container housing the X-ray tube, 24 is an X-ray emission window formed in the container, 25
26 is a collimator, and 26 is an X-ray aperture piece.

This collimator 25 is firmly fixed to a flange 27 of the radiation window portion of the container 23.

From such an X-ray source device, X-rays having a direction and an irradiation field determined by an X-ray emission window and a collimator are extracted to the outside.

The collimator is usually assembled so that its central axis X intersects at right angles to the tube axis O of the X-ray tube, and is used in a fixed manner.

The X-ray irradiation field is determined by adjusting the X-ray aperture of the collimator as necessary.

By the way, in such an X-ray source device, as shown in Fig. 2, the real focus (hereinafter simply referred to as the real focus) of the electron beam formed on the anode target is the shape seen from the top perpendicular to the target surface. For Eo, the X-ray center radiation direction, that is, the center line X of the X-ray field to be extracted.
X-ray effective focus viewed from the direction (hereinafter simply referred to as effective focus)
The shape changes significantly in response to changes in the electron beam width.

For example, even if the effective focal point Si is square when the input is large and the focal point is large, if the input is reduced and the electron beam from the same cathode is narrowed to obtain a small focal point, the effective focal point S is usually elongated.
It becomes 2.

This causes the shape of the effective focal point to be significantly distorted, and the recent 0
．． 1mm to 1.2m or 2. This is not suitable for the characteristics of variable focus X-ray tubes up to Orran.

For this reason, the reality is that X-ray tubes are prepared or replaced for each required effective focus.

In FIG. 2, the shapes of the effective focal points S1 and S2 are shown by copying the shapes of the actual focal points on the anode target in the radial direction X in front of the paper.

By the way, a proposal to solve this problem is to use an X-ray tube having an anode target with two or more angles, as shown in USP 2,942,126, and to selectively irradiate each inclined surface with an electron beam. There is something that makes you guess.

However, this makes it difficult to manufacture the anode target, and there are only a number of choices that correspond to the number of tilted target surfaces.Furthermore, since the electron beam is applied to each tilted surface at a different location, the focal position is different and the irradiation field is different. However, there is a serious drawback in that each individual item is misaligned.

By the way, the maximum input power of an X-ray tube increases as the size of the actual focal point, that is, the electron beam impact area on the target surface increases.

Here, the size of the actual focal spot has a one-to-one relationship with the effective focal spot size, depending on the target angle of the X-ray tube.
Directly affects the quality of the X-shot shooting image.

As long as the effective focal spot size is kept constant, the maximum manpower for a particular X-ray tube is naturally determined.

The effective focal spot size and the maximum input power are inseparable in a single X-ray tube, and in order to obtain a larger input power for each effective focal spot, it is generally necessary to use multiple real focal spots with different nominal dimensions. I am trying to tie them selectively at the same position.

An example is shown below.

As shown in Fig. 3, in the case of a rotating anode X-ray tube with a target angle θ of 16° and a focal orbit radius r of 42 mm, the small focus S
The effective focal length of a is 1. The maximum input for OXl and Omm is 1
It is 260 mA at 00 kV-0 and 1 sec.

If more input is required under the same operating conditions, use another large focal point sb installed in parallel, for example 2
, OX2. Use Omm.

2. OX2. The maximum human power in the case of Omm is 350mA, and the usable range is wider in terms of input.

However, in terms of image quality, the focal size (one side) is 1. Since the increase is 2.0 rrun from the OR, it is inevitable that the quality will deteriorate, which is a serious drawback.

Therefore, if you want to obtain a larger input with the same effective focus (1.OR in the early example), you will have to replace and use a different type of X-ray tube with a different structure and performance, as already mentioned. There is a problem.

Examples of X-ray tubes that fall under this category are as follows.

With a rotating anode tube with a target angle of 12 degrees and a focal orbit radius of 42 wφ, at 100 kV -0.1 sec, the maximum input with an effective focal length of 1.0 m is 350 mA.

In other words, if you replace it with a similar X-ray tube with a target angle of 12°, the focus will be 1.0m, and the 2.0rran in the previous example will be reduced.
A maximum input of 350 mA, which is equivalent to the focal point, is obtained.

However, it is generally not possible to replace the X-ray tube in a short period of time even if it is not an emergency.

The present invention was made in view of the above-mentioned circumstances, and is fundamentally different from the conventional structure, and the effective focal shape is always kept in the optimum state with maximum input efficiency (power input to the target by the electron beam). An object of the present invention is to provide an X-ray source device using an X-ray tube that can be maintained in a stable manner.

That is, the characteristics of this X-ray tube are that it is possible to form a plurality of real focal points of electron beams arranged in the radial direction on a single angular surface of the anode target surface of the X-ray tube; The intersection angle between the ray tube and a device such as a collimator that limits the X-ray irradiation field can be adjusted.

Examples thereof will be described below with reference to the drawings.

Identical parts are designated by the same reference numerals.

The X-ray source device of the embodiment shown in FIGS. 4 and 5 has the following structure.

An X-ray tube 32 is housed and fixed inside a storage container 31, which is generally called a Haube. A radiation window 34 is formed.

The outer surface of the surrounding seven flange 35 constituting the radiation window 34 is formed into a cylindrical curved shape.

A device for limiting the X-ray irradiation direction and irradiation field, ie, a collimator 36, is attached so as to be rotatable along the cylindrical curved surface of the flange 350.

This collimator 36 has a built-in X-ray diaphragm (not shown) for determining the X-ray irradiation field as desired, and its central axis X1
is a circular arc that is centered at or near the real focal point E formed on the anode target of the X-ray tube and intersects with the X-ray tube central axis O to the left and right of the figure along a plane that includes the real focal point and the tube central axis. In this way, it is possible to move.

Therefore, the X-ray tube 32 forms, for example, three actual electron beam focal points Ea, Eb, and Ec lined up in the radial direction of the target on a surface forming a single angle θ formed on the target 33. It looks like this.

Correspondingly, therefore, the cathode 31 has three electron-emitting filaments 37a, 37b, and 37c.

Each of these filaments can operate independently.

In addition, the three real focal points Ea, Eb, and Ee all have the same width dimension t, and when mutually adjacent radial ends form focal points at the same time, the electron density distribution becomes almost uniform at each boundary. Do it like this.

In other words, at least they are arranged so that they are not discontinuously distributed, or they are arranged so that they are adjacent to each other, or that they are adjacent to each other so that there is no discontinuous distribution.

Note that the symbol θ represents the tangent to the inclined surface of the target, which also corresponds to the target inclination angle.

X-rays generated from the focal point are taken out to the outside through an X-ray emission window and a collimator.

In this case, it is a matter of course that the X-rays are not emitted outward from the tangent .theta. to the inclined target surface, and therefore the irradiation field of the collimator is also limited within this region.

The essence of this device is to make the relative angle between the anode target surface of the X-ray tube and the collimator variable.For convenience, the collimator is moved relative to the X-ray tube storage container in the explanation. I recommend an explanation.

However, when actually used for medical purposes, the collimator should be fixed to the base of the X-ray device, and the X-ray tube or X-ray tube storage container should be assembled so that it can rotate. is practical.

Now, the present invention having the structure as described above exhibits effects.

First, the apparatus of the present invention can maximize the input power of the electron beam to the target while keeping the focal shape optimal, and can relatively increase the amount of X-rays extracted.

This point will be further explained with reference to FIGS. 4 and 6.

First, the electron beam current is set to 260mA and 1. OXl, 0
In the case where a square effective focus of rItjrL is not obtained, one of the three cathodes, for example the central cathode 3,
7b is operated to form an actual focal point Eb on the target surface.

At this time, the width t of the actual focal point is 1.0 mm, and the length t is longer than the width t.

In this case, the central axis X1 of the collimator (indicated by a dotted line 36b in FIG. 4) is positioned at a large angle θ1 with respect to the tangent θ to the target inclined surface.

Note that the irradiation field xb may be arbitrary.

This is where the actual focal point shape viewed from the central axis X1, that is, the effective focal point S1 is square and has the most extreme shape.

Next, increase the electron beam current to three times that of the above case, or about 780 m
I will talk about the case where it is used with a large input of A.

In this case, all three cathodes are ignited to form three real focal points E a ) E b IEc radially adjacent to each other on the target surface.

The length of the actual focal point is about three times the length mentioned above.

However, the width t does not change. At this time, the central axis of the collimator
2 to a position where the angle θ2 is smaller than the previous θ1.

At this position, the shape of the three adjoining real focal points, ie, the effective focal point S2, as seen from the central axis X2, is also square and has an optimal shape.

Similarly, when the electron beam current is 520 mA, for example, the two cathodes are operated and the central axis of the collimator is moved to set the effective focus S3 to a square.

In this way, a plurality of electron beam focal points, that is, real focal points, can be operated independently to form one or a plurality of adjacent real focal points, and correspondingly, the tangent to the target inclined surface and the X-ray By changing the angle with respect to the radiation center line, ie, the central axis of the collimator, the most efficient operation can be obtained while optimizing the effective focus.

Of course, the effective focal point shape is not limited to a square, and it goes without saying that X-rays can be extracted in any shape.

It should be noted that the actual focal point should not be fixed at one in three, but finely divided in the length direction, that is, in the radial direction. The central radiation can be selected, and by simultaneously forming one or several real foci adjacent to each other in the longitudinal direction so that the effective focus size in this direction conforms to the nominal value, it is always possible to achieve optimal conditions. It is possible to obtain the highest maximum input value with .

Although the above example is for one type of effective focal spot size, it can be implemented in exactly the same way in the case of an X-ray tube that combines two or more types of focal spots.

The individual lengths of the real focal points do not need to be in a constant ratio relationship to each other.

Further, these individual actual focal widths and dimensions do not need to be strictly the same, but it is sufficient that the effective focal dimensions when combined at the same time fall within the tolerance range of the nominal dimensions in the desired central radial direction.

The purpose of varying the radiation direction as contemplated by the present invention can be achieved sufficiently within a plane that is approximately parallel to the tube axis and includes the actual focal point. It is also possible to freely change the radiation direction within the range.

As described above, as a method for freely changing the central radiation angle at or near the actual focal point, the joint surface of the X-ray tube device and the collimator is set at or near the actual focal point and perpendicular to the tube axis. In addition to a cylindrical curved surface that can be slid relative to each other, a spherical convex surface centered on the real focal point may be slidably variable.

Specifically, if both the X-ray tube container radiation window and the collimator radiation port mounting part are curved, and when the collimator is attached via an adapter, the radiation port mounting part of the adapter and the radiation port mounting part of the tube container should be curved. and into a curved surface.

Alternatively, the X-ray tube housing may remain in its conventional shape, and the collimator itself may be configured to change radiation direction near the actual focal point, or may be configured to change direction at the interface between the collimator and the adapter. do.

Furthermore, the above combination may be used so that the adapter itself can change the direction of the collimator.

In addition to the above-mentioned structures, means for freely selecting the X-ray emission direction of the X-ray source device in any direction around the actual focal point position do not necessarily require the use of the radiation port as a support. , tube container support, X-ray bed, etc., when incorporating X-ray equipment,
The structure may be such that the X-ray tube device can be rotated around the focal point position by supporting various structures close to the collimator, or the structure may be individually designed to suit the purpose of use.

Note that the present invention is not limited to an anode target having a single inclination angle, but may have a plurality of inclination angles, and the point is that a plurality of electron beam focuses (actually (focal point).

As explained above, according to the present invention, an X-ray source device with great practical value can be provided.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the main parts of a general X-ray source device, FIGS. 2 and 3 are schematic diagrams showing the operating mode of the device shown in FIG. 1, and FIG. 4 shows an embodiment of the present invention. FIG. 5 is a schematic perspective view showing the main part of the device shown in FIG. 3, and FIG. 6 is a schematic diagram showing the operating mode thereof. 32...X-ray tube, 33...target, 36...
Collimator (X-ray irradiation field limiting device), 31... cathode,
E a , E b , E c . . . real focal point, θ . . . target surface line X1, X 2 . . . collimator central axis.

Claims (1)

[Claims] 1. An anode target provided at a predetermined tangential angle to the tube axis, and an electron beam focus elongated in the radial direction with respect to the tube axis on this target, and the dimensions of this electron beam focus can be varied. An X-ray tube having a built-in cathode having an electron emitting part, an X-ray tube housing container housing the X-ray tube and having an X-ray radiation window, and In an X-ray source device comprising an externally mounted X-ray field confinement device, the target forms a single angle and a plurality of radially adjacent electron beam focal points are each independent of each other on the target plane. and an X-ray irradiation field limiting device is installed such that the direction of its central axis can be changed with respect to the X-ray tube housing container to limit the X-ray irradiation field to the target surface line. An X-ray source device characterized in that the angle of intersection with the central axis of the device is configured to be variable. 2. The X-ray source device according to claim 1, wherein the X-ray source device is configured to change the intersection angle with respect to the X-ray focal position formed on the target of the X-ray tube.