JPH0922800A - Linear accelerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an beam takeout window for electron-ray irradiation from being destroyed by an electron ray for X-ray irradiation by providing deflection magnet portions separately on both sides of one accelerating tube, one for X-ray irradiation and the other for electron-ray irradiation. SOLUTION: An electron gun 12 for electron-ray irradiation is provided at one end of a standing-wave accelerating tube 11, and an electron gun 13 for X-ray irradiation is provided at the other end. A deflection magnet portion 14 for electron-ray irradiation is provided at the end where the electron gun 13 for X-ray irradiation is provided, and a deflection magnet portion 15 for X-ray irradiation is provided at the end where the electron gun 12 for electron- ray irradiation is provided. A target 16 is provided at the deflection magnet portion 1 5 for X-ray irradiation, and a beam takeout window 17 made of a thin metal film is provided at the deflection magnet portion 14 for electron-ray irradiation, with a scatter 18 provided opposite to the takeout window 17. Therefor a large beam current for X-ray irradiation does not pass through the thin metal film of the beam takeout window 17, damage to the beam takeout window 17 can be prevented, and a linear accelerator whose reliability is enhanced is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear accelerator which is used for, for example, radiation therapy and which irradiates an electron beam and an X-ray.

[0002]

2. Description of the Related Art FIG. 17 is a block diagram showing an example of a conventional linear accelerator for radiotherapy. In the figure, 1 is an accelerating tube, 2 is an electron gun provided at one end of the accelerating tube 1, 3
Is provided at the other end of the accelerating tube 1, and is a deflection magnet section for deflecting the electron beam (here, approximately 270 °), and 4 is a beam extraction window for extracting the electron beam from the deflection magnet section 3. The window 4 is made of a metal thin film in which the electron beam is weakly attenuated, and supports the atmospheric pressure outside the deflection magnet unit 3.

Reference numeral 5 is a metal target which is provided outside the deflection magnet section 3 so as to face the beam extraction window 4 and generates X-rays by electron beam irradiation. 6 and the target 5 are interchangeable in position. Is a scatterer, a collimator 7 defines an X-ray irradiation field (irradiation area), and an accessory 8 defines an electron beam irradiation field.

Next, the operation will be described. Electrons emitted from the electron gun 2 at one end of the accelerating tube 1 are accelerated by the microwave electric field by passing through the vacuum accelerating tube 1 in which microwave flows. The accelerated electron beam has its course bent in a usable direction by the deflection magnet section 3 at the other end of the acceleration tube 1, and is taken out from the beam extraction window 4.

At the time of X-ray irradiation, the extracted electron beam is collided with a metal called a target 5 to convert it into braking X-rays, and an irradiation field is defined and irradiated by a diaphragm called a collimator 7. On the other hand, during electron beam irradiation, the target 5
And the scatterer 6 are replaced with each other, and the electron beam is appropriately scattered by passing therethrough, and the irradiation field is defined and irradiated by the dedicated accessory 8. Here, at the time of X-ray irradiation, a beam current far larger than that at the time of electron beam irradiation needs to be emitted from the electron gun 2 and taken out from the beam extraction window 4.

[0006]

In the conventional linear accelerator configured as described above, the metallic thin film for blocking the vacuum space in the deflection magnet section 3 and the outside of the atmospheric pressure, that is, the beam extraction window 4 is provided. Since a large beam current for X-rays passes therethrough, the beam extraction window 4 is easily damaged, which breaks the vacuum and may require replacement of other main parts in some cases. . Further, due to a malfunction of the CPU, if the target 5 is not placed on the beam flux even though the beam current for X-rays is flowing, there is a possibility that more electron beams may be irradiated than necessary. there were.

The present invention has been made to solve the above-mentioned problems, and a linear accelerator capable of preventing the beam extraction window from being damaged and eliminating a target placement error. Aim to get.

[0008]

A linear accelerator according to the invention of claim 1 is provided with an accelerating tube, an electron beam irradiating electron gun provided at one end of the accelerating tube, and the other end of the accelerating tube. Of the X-ray irradiation electron gun and the accelerating tube, which are provided at the other end of the accelerating tube and deflect the electron beam emitted from the electron beam irradiating electron gun and accelerated by the accelerating tube. An X-ray irradiation deflection magnet unit provided at one end for deflecting an electron beam emitted from an X-ray irradiation electron gun and accelerated by an accelerating tube, a target provided in the X-ray irradiation deflection magnet unit, and an electron. This is provided with an accelerator main body having a beam extraction window made of a metal thin film provided in a beam irradiation deflection magnet section, and a scatterer facing the beam extraction window.

According to a second aspect of the present invention, in the linear accelerator, a gantry portion rotatable about a gantry rotation axis, and a gantry portion mounted on the gantry portion and having an accelerator body mounted thereon are arranged to rotate at right angles to the gantry rotation axis. And a C-arm portion rotatable about an axis.

In the linear accelerator according to the third aspect of the present invention, the high energy target and the low energy target are mounted side by side on the X-ray irradiation deflection magnet section.

A linear accelerator according to a fourth aspect of the present invention is provided so as to face a target for high energy and a target for low energy, and at the time of X-ray irradiation from the target for high energy and at the time of X-ray irradiation from the target for low energy. It is equipped with a collimator that can be moved so as to match the deviation of the irradiation field.

In the linear accelerator according to a fifth aspect of the present invention, a high-energy target and a low-energy target are mounted side by side on the X-ray irradiation deflection magnet section, and the gantry section is provided with respect to the C arm section. The independently movable collimator is attached.

In the linear accelerator according to a sixth aspect of the present invention, the length of a node of the accelerating tube can be adjusted according to the direction of the electron beam.

In the linear accelerator according to a seventh aspect of the present invention, the size of the entrance / exit between the electron passage of the acceleration tube and the cavity can be adjusted in accordance with the length of one node.

[0015]

According to the invention of claim 1, since the X-ray irradiation deflection magnet section and the electron beam irradiation deflection magnet section are separately provided on both sides of one acceleration tube, the beam extraction for electron beam irradiation is taken out. The window is prevented from being destroyed by the electron beam for X-ray irradiation, and the electron beam for X-ray irradiation is also prevented from being irradiated without passing through the target.

According to the second aspect of the present invention, the electron beam and X-ray irradiating portions can be smoothly moved to their respective predetermined positions by the combination of the driving of the gantry portion and the driving of the C arm portion.

According to the third aspect of the present invention, the high-energy target and the low-energy target are attached side by side to the X-ray irradiation deflection magnet section.
The energy of X-rays can be switched in multiple stages.

In the invention of claim 4, by moving the collimator, it is possible to match the deviation of the irradiation field between the X-ray irradiation from the high energy target and the X-ray irradiation from the low energy target. At the same time, the geometric penumbra can be reduced.

In the invention of claim 5, a high energy target and a low energy target are mounted side by side on the X-ray irradiation deflection magnet section, and the gantry section is independently movable with respect to the C arm section. By attaching a collimator, it is possible to match the deviation of the irradiation field between the X-ray irradiation from the high energy target and the X-ray irradiation from the low energy target, and reduce the geometric penumbra. it can.

According to the sixth aspect of the invention, the length of one section of the accelerating tube is adjusted according to the direction of the electron beam,
Even if the direction of the electron beam changes, the electron beam can be efficiently accelerated.

According to the invention of claim 7, the size of the entrance / exit between the passage of electrons of the acceleration tube and the cavity is adjusted according to the length of one node, so that the volume of the cavity changes. Resonance can be easily maintained.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. 1 is a configuration diagram showing an accelerator body of a linear accelerator according to Embodiment 1 of the present invention. In the figure, 11 is a standing wave accelerating tube mounted in a gantry section (not shown), 12 is an electron beam irradiation electron gun provided at one end of the accelerating tube 11, and 13 is another accelerating tube 11. An electron gun for X-ray irradiation provided at the end, 14 is a deflection magnet unit for electron beam irradiation provided at the other end of the acceleration tube 11, and 15 is an X provided at one end of the acceleration tube 11. Deflection magnet unit for beam irradiation, 16 is a target provided in the deflection magnet unit for X-ray irradiation, 17 is a beam extraction window made of a metal thin film provided in the deflection magnet unit for electron beam irradiation, and 18 is a beam. A scatterer, C, which faces the take-out window 17, is an isocenter.

The accelerating tube 11 is arranged so as to be perpendicular to the gantry rotation axis, and its central portion is closest to the gantry rotation axis. Further, each of the deflection magnet units 14 and 15 deflects the electron beam by an angle smaller than 270 °, so that the beam can be directed to a point on the gantry rotation axis.

In such a linear accelerator, since the target 16 for X-ray irradiation and the beam extraction window 17 for electron beam irradiation are separately provided at both ends of the accelerating tube 11, they are large for X-ray irradiation. The beam current does not pass through the metal thin film of the beam extraction window 17, so that the damage of the beam extraction window 17 is prevented. Further, it is also prevented that the electron beam for X-ray irradiation is irradiated without passing through the target 16.

Embodiment 2 FIG. 2 is a block diagram showing a linear accelerator according to Embodiment 2 of the present invention, and FIG. 3 is a perspective view of FIG. In the figure, reference numeral 21 denotes a gantry portion in which an arcuate guide portion 21a is formed inside, and reference numeral 22 denotes a C arm portion rotatable along the guide portion 21a. The same accelerator body as that of No. 1 is installed. Further, in FIG. 3, 21A is a gantry rotation shaft which is the rotation center of the gantry portion, and 22A is C at the position shown in the figure.
It is the rotation axis of the arm part.

With such a structure, the electron beam irradiating section and the X-ray irradiating section can be smoothly moved to predetermined positions, and the irradiation target can be irradiated with the electron beam and X-ray respectively from the predetermined directions. Further, a part of the mechanical technology of the C-arm linac can be incorporated.

Embodiment 3 FIG. Next, a third embodiment of the present invention will be described. Conventionally, when the energy of X-rays is multistage, a target for high energy and a target for low energy are prepared, and the irradiation mode is set to high energy X.
Rays, low energy X-rays, and electron beams were used to replace the two types of targets and scatterers. However, when the target 16 is fixed to the accelerating tube 11 as in the first embodiment, The replacement becomes difficult.

Therefore, in the third embodiment, as shown in FIG. 4, the high energy target 16a and the low energy target 16b are placed in the same plane perpendicular to the gantry rotation axis in order to make the X-ray multi-stage. They are mounted side by side at points equidistant from the gantry rotation axis. In this case, by controlling the magnetic field of the X-ray irradiating deflection magnet unit 15, the electron beams can hit the predetermined targets 16a and 16b, respectively, and the respective extension lines can pass through the same point on the gantry rotation axis. .

The displacement of the irradiation field due to this is adjusted by driving the collimator leaf 24 as shown in FIGS. More specifically, the collimator 23 is an irradiation field limiting means, and has a lead piece as shown in FIG. 5, that is, an assembly of collimator leaves 24 therein. These collimator leaves 24
The irradiation field is shaped by opening and closing (driving) as shown in FIGS. 5A and 5B according to the shape of the irradiated portion.

Normally, the irradiated portion 25 is fixed at the position of the isocenter C in FIG. 3, whereas if the X-ray emission position is changed as in the third embodiment, the irradiation field is displaced. I will end up. Therefore, in the third embodiment, as shown in FIGS. 6 and 7, the opening position of the collimator leaf 24 is set to 23A,
It changes like 23B. At this time, strictly speaking,
Since the appearance of the irradiated portion 25 viewed from the side of the targets 16a and 16b is different, the opening manner of the collimator leaf 24 is slightly changed.

Embodiment 4 FIG. Although the deviation of the irradiation field is adjusted by driving the collimator leaf 24 in the third embodiment, the collimator 23 can be adjusted as shown in FIGS.
The irradiation field may be adjusted by moving the whole, and the geometric penumbra caused by the collimator leaf 24 can be reduced.

Here, the geometric penumbra is caused by the X-rays emitted from a certain point on the targets 16a and 16b being blocked by the collimator leaf 24 as shown in FIG. As shown in FIG. 11, the surface that determines the irradiation field of the collimator leaf 24 is always the targets 16a and 16b regardless of the position of the collimator leaf 24.
There is something that happens about things that are not a collection of line segments in a straight line passing through the center of. That is, as shown in FIG. 11, the end surface of the collimator leaf 24 is changed to the alternate long and short dash line depending on the driving method and the cross section method, and the target 16
There is a point on the isocenter plane where the X-rays emitted from the centers of a and 16b pass through inside the lead at a distance that is not sufficient to be shielded and attenuate and arrive. It is difficult to avoid the element shown in FIG. 10 among the elements of the geometric penumbra.

Generally, in the multi-leaf type collimator 23 as shown in FIG. 5, as shown in FIG. 12, a taper type collimator leaf 24 in which the contact surfaces 24a of the leaves are conical surfaces excluding the center is used. Used and eliminates the element of geometric penumbra. In FIG. 12, 2
3A is a leaf drive rotating shaft common to each leaf. However, in the apparatus as shown in FIG.
When the firing position of the line is changed, a geometrical penumbra appears even if the collimator leaf 24 is opened in a different manner.

On the other hand, by moving the entire collimator 23 as in the case of the fourth embodiment, the geometric penumbra can be made small in any of the targets 16a and 16b.

Embodiment 5 FIG. Next, FIG. 13 is a configuration diagram showing a linear accelerator according to a fifth embodiment of the present invention. In the fifth embodiment, the high energy target 16a and the low energy target 16b are arranged in order to make the X-rays multistage.
They are arranged side by side at points equidistant from the isocenter C in the plane of rotation of the C arm portion 22. Then, the collimator 23
Is directly attached to the gantry section 21 and C
It is movable independently of the arm portion 22.

In such a structure, first, low energy X
At the time of line irradiation, as shown in FIG. 13, the C arm portion 22 and the collimator 23 are arranged so that the low energy target 16b faces the collimator 23. Further, at the time of high energy X-ray irradiation, the C arm portion 22 and the collimator 23 are arranged as shown in FIG. Further, at the time of electron beam irradiation, the C arm portion 22 and the collimator 23 are arranged as shown in FIG.
Is fully opened and the accessory 8 is attached to the bottom of the collimator 23.
(FIG. 17) is attached.

With such a linear accelerator, the geometric penumbra caused by the collimator leaf 24 can be reduced as in the case of the fourth embodiment.

Embodiment 6 FIG. Next, FIG. 16 is a longitudinal sectional view of an accelerating tube of a linear accelerator according to a sixth embodiment of the present invention. In the figure, 31 is an outer cylinder that holds an internal vacuum, 32 is a wall part that is provided in the outer cylinder 31 and forms an electric field, and these wall parts 33 can be adjusted in their mutual spacing, that is, one section. It is long but adjustable. 33 is a passage through which the electron beam passes,
34 is a cavity provided around the passage 32, 35 is an opening / closing means for opening and closing an entrance / exit between the passage 32 and the cavity 34,
Reference numeral 36 is a drive contact provided between the adjacent wall portions 33.

Usually, when a section in the accelerating tube has a predetermined length proportional to the speed of the electron, the electron beam is efficiently accelerated. Therefore, the length of a section in the acceleration tube is short on the side close to the electron gun and long on the side close to the irradiation unit. On the other hand, in the sixth embodiment, the length of one node is changed and the volume of the cavity 34 is changed in response to the change in the direction of the electron beam in the acceleration tube. Further, the size of the entrance / exit between the passage 32 and the cavity 34 is adjusted by the opening / closing means so that resonance is maintained even if the volume of the cavity 34 changes. Therefore, the electron beam can be efficiently accelerated even if the direction of the electron beam changes.

[0040]

As described above, according to the linear accelerator of the invention of claim 1, the X-ray irradiation deflection magnet section and the electron beam irradiation deflection magnet section are separately provided on both sides of one accelerating tube. Therefore, it is possible to prevent the beam extraction window for electron beam irradiation from being destroyed by the electron beam for X-ray irradiation.
Further, it is possible to prevent the electron beam for X-ray irradiation from being irradiated without passing through the target, and it is possible to improve reliability.

In the linear accelerator of the second aspect of the present invention, a gantry portion rotatable about a gantry rotation axis is provided with a C arm portion rotatable about a rotation axis orthogonal to the gantry rotation axis. Since the accelerator body is installed in the section,
In addition to the same effect as the invention of claim 1, by combining the driving of the gantry unit and the driving of the C-arm unit, the electron beam and X-ray irradiation units can be smoothly moved to respective predetermined positions. Has the effect.

In the linear accelerator of the third aspect of the present invention, since the high energy target and the low energy target are mounted side by side on the X-ray irradiation deflection magnet section, in addition to the effect similar to that of the first aspect, X The effect is that the energy of the wire can be switched in multiple stages.

In the linear accelerator of the fourth aspect of the present invention, the collimator can be moved. Therefore, in addition to the same effect as that of the third aspect of the invention, in addition to the X-ray irradiation from the high energy target and the low energy target. There is an effect that the deviation of the irradiation field can be matched with the time of X-ray irradiation from and the geometric penumbra can be reduced.

In the linear accelerator of the fifth aspect of the present invention, the high-energy target and the low-energy target are mounted side by side on the X-ray irradiation deflection magnet section, and the gantry section moves independently of the C-arm section. Since a possible collimator is attached, in addition to the same effect as that of the invention of claim 2, there is a difference in the irradiation field between X-ray irradiation from the high energy target and X-ray irradiation from the low energy target. There is an effect that the geometric penumbra can be made small while being able to match.

In the linear accelerator according to the invention of claim 6, the length of one section of the accelerating tube can be adjusted according to the direction of the electron beam. Therefore, in addition to the same effect as the invention of claim 1, Even if the direction of the line is changed, the electron beam can be efficiently accelerated.

In the linear accelerator according to the invention of claim 7, the size of the entrance / exit between the passage of electrons in the accelerator tube and the cavity can be adjusted in accordance with the length of one node. In addition to the same effect as the invention, there is an effect that the resonance can be easily maintained even if the volume of the cavity changes.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an accelerator body of a linear accelerator according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a linear accelerator according to a second embodiment of the present invention.

FIG. 3 is a perspective view of FIG. 2.

FIG. 4 is an enlarged configuration diagram showing a main part of a linear accelerator according to a third embodiment of the present invention.

FIG. 5 is an explanatory diagram for explaining an opening / closing operation of a collimator leaf used in the third embodiment.

FIG. 6 is an explanatory diagram for explaining a method for preventing deviation of an irradiation field in the third embodiment.

FIG. 7 is an explanatory diagram showing a state of the collimator leaf of FIG.

FIG. 8 is a configuration diagram showing an accelerator body of a linear accelerator according to a fourth embodiment of the present invention.

9 is an explanatory view showing an enlarged main part of FIG.

FIG. 10 is an explanatory diagram showing the generation of a general geometric penumbra.

FIG. 11 is an explanatory diagram showing the generation of geometric penumbra in the collimator as shown in FIG.

FIG. 12 is an explanatory diagram for explaining a method of preventing a geometric penumbra by a general multileaf type collimator.

FIG. 13 is a configuration diagram showing a state of a linear accelerator according to a fifth embodiment of the present invention during low energy X-ray irradiation.

14 is a configuration diagram showing a state at the time of high energy X-ray irradiation in FIG.

15 is a configuration diagram showing a state at the time of electron beam irradiation in FIG.

FIG. 16 is a vertical sectional view of an accelerating tube of a linear accelerator according to a sixth embodiment of the present invention.

FIG. 17 is a configuration diagram showing an example of a conventional linear accelerator.

[Explanation of symbols]

11 standing wave accelerator, 12 electron gun for electron beam irradiation, 13
X-ray irradiation electron gun, 14 Electron beam irradiation deflection magnet section, 15 X-ray irradiation deflection magnet section, 16 target, 16a High energy target, 16b
Low energy target, 17 beam extraction window, 18
Scatterer, 21 gantry part, 22 C arm part, 23 collimator, 33 passage, 34 cavity.

Claims (7)

[Claims] 1. An accelerating tube, an electron beam irradiating electron gun provided at one end of the accelerating tube, an X-ray irradiating electron gun provided at the other end of the accelerating tube, and the other accelerating tube. A deflection magnet unit for electron beam irradiation, which is provided at an end and deflects an electron beam emitted from the electron gun for electron beam irradiation and accelerated by the acceleration tube, and the X-ray irradiation provided at one end of the acceleration tube. To the deflection magnet unit for X-ray irradiation, which deflects the electron beam emitted from the electron gun and accelerated by the acceleration tube, the target provided in the deflection magnet unit for X-ray irradiation, and the deflection magnet unit for electron beam irradiation. A linear accelerator comprising: an accelerator main body having a beam extraction window made of a metal thin film and a scatterer facing the beam extraction window. 2. A gantry section rotatable about a gantry rotation axis, and an accelerator body provided on the gantry section and mounted on the gantry section, and rotatable about a rotation axis orthogonal to the gantry rotation axis. The linear accelerator according to claim 1, further comprising a C-arm portion. 3. The linear accelerator according to claim 1, wherein a high energy target and a low energy target are mounted side by side on the X-ray irradiation deflection magnet portion. 4. The irradiation field is provided so as to face the high-energy target and the low-energy target, and the irradiation field shifts when the X-ray is irradiated from the high-energy target and the X-ray is irradiated from the low-energy target. 4. The linear accelerator according to claim 3, further comprising a collimator movable so as to be aligned with each other. 5. A high-energy target and a low-energy target are mounted side by side on the X-ray irradiation deflection magnet section, and a gantry section is provided with a collimator movable independently of the C-arm section. The linear accelerator according to claim 2, wherein the linear accelerator is mounted. 6. The linear accelerator according to claim 1, wherein the accelerating tube is configured so that the length of a node can be adjusted according to the direction of the electron beam. 7. The linear accelerator according to claim 6, wherein the size of the entrance / exit between the passage through which electrons pass and the cavity is adjustable in accordance with the length of a node.