JP3098937B2 - Linear accelerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear accelerator used for, for example, radiotherapy and irradiating electron beams and X-rays.

[0002]

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

[0005] Reference numeral 5 denotes a metal target provided outside the deflection magnet unit 3 so as to face the beam extraction window 4 and generates X-rays by irradiating an electron beam. Reference numeral 6 denotes a target whose position can be interchanged with the target 5. , A scatterer 7 for defining an X-ray irradiation field (irradiation area), and 8 an accessory for defining an electron beam irradiation field.

Next, the operation will be described. The 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 through which the microwave flows. The path of the accelerated electron beam is bent in a usable direction by the deflection magnet unit 3 at the other end of the acceleration tube 1, and is extracted from the beam extraction window 4.

At the time of X-ray irradiation, the taken-out electron beam hits a metal called a target 5 to be converted into a braking X-ray, and is irradiated with an irradiation field defined by a stop called a collimator 7. On the other hand, during electron beam irradiation, the target 5
And the scatterer 6 are exchanged, and the electron beam is appropriately scattered by passing therethrough. Here, at the time of X-ray irradiation, a beam current much larger than at the time of electron beam irradiation needs to be emitted from the electron gun 2 and extracted from the beam extraction window 4.

[0006]

In the conventional linear accelerator constructed as described above, the metal thin film that blocks the vacuum space in the deflecting 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, the beam extraction window 4 is easily damaged, which breaks the vacuum, and in some cases, requires replacement of other main parts. . Further, there is also a problem that if the target 5 is not placed on the beam flux even though the X-ray beam current is flowing due to a malfunction of the CPU, an unnecessary electron beam may be irradiated. there were.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to prevent a beam extraction window from being damaged and to eliminate a target placement error. The purpose is to obtain.

[0008]

A linear accelerator according to the present invention is provided with an acceleration tube, an electron gun for irradiating an electron beam provided at one end of the acceleration tube, and another end of the acceleration tube. An electron gun for X-ray irradiation, a deflection magnet unit for electron beam irradiation, which is provided at the other end of the accelerating tube and deflects an electron beam emitted from the electron gun for electron beam irradiation and accelerated by the accelerating tube; An X-ray deflecting magnet unit provided at one end for deflecting an electron beam emitted from the X-ray irradiating electron gun and accelerated by the accelerating tube; a target provided on the X-ray irradiating deflection magnet unit; It is provided with a beam extraction window made of a metal thin film provided in the beam irradiation deflection magnet section, and an accelerator body having a scatterer facing the beam extraction window.

According to a second aspect of the present invention, there is provided a linear accelerator which is rotatable about a gantry rotation axis, and which is provided in the gantry section and has an accelerator main body mounted thereon, and which rotates at right angles to the gantry rotation axis. And a C-arm portion rotatable about an axis.

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

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, at the time of X-ray irradiation from a target for high energy and at the time of X-ray irradiation from a target for low energy. And a collimator that can be moved so as to adjust the deviation of the irradiation field.

In a 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 a deflection magnet for X-ray irradiation. An independently movable collimator is attached.

A linear accelerator according to a sixth aspect of the present invention is configured such that the length of one node of the accelerating tube can be adjusted according to the direction of the electron beam.

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

[0015]

According to the first aspect of the present invention, the X-ray irradiating deflecting magnet and the electron beam irradiating deflecting magnet are separately provided on both sides of the single accelerating tube. The window is prevented from being destroyed by the X-ray irradiation electron beam, and the X-ray irradiation electron beam is prevented from being irradiated without passing through the target.

According to the second aspect of the present invention, the electron beam and the X-ray irradiation unit can be smoothly moved to the predetermined positions by combining the driving of the gantry unit and the driving of the C-arm unit.

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.
X-ray energy can be switched in multiple stages.

According to the fourth aspect of the present invention, the displacement of the irradiation field can be matched between the time of X-ray irradiation from the high energy target and the time of X-ray irradiation from the low energy target by moving the collimator. At the same time, the geometric penumbra can be reduced.

According to the fifth aspect of the present invention, a high energy target and a low energy target are mounted side by side on the deflection magnet for X-ray irradiation, and the gantry is movable independently of the C-arm. By attaching a collimator, it is possible to match the deviation of the irradiation field between X-ray irradiation from the high energy target and X-ray irradiation from the low energy target, and to reduce the geometric penumbra. it can.

According to the sixth aspect of the present invention, by adjusting the length of one node of the accelerating tube according to the direction of the electron beam,
Even if the direction of the electron beam changes, the electron beam can be efficiently accelerated.

In the invention according to claim 7, the size of the entrance and exit between the cavity and the passage of electrons of the accelerating tube is adjusted according to the length of the knot, so that the volume of the cavity changes. Resonance can be easily maintained.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

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

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

In such a linear accelerator, 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, so that the large target for X-ray irradiation is provided. The beam current does not pass through the metal thin film of the beam extraction window 17, so that damage of the beam extraction window 17 is prevented. In addition, it is possible to prevent the electron beam for X-ray irradiation from being irradiated without passing through the target 16.

Embodiment 2 FIG. FIG. 2 is a configuration 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 having an arc-shaped guide portion 21a formed inside, and 22 denotes a C-arm portion rotatable along the guide portion 21a. The same accelerator body as that of No. 1 is mounted. In FIG. 3, reference numeral 21A denotes a gantry rotation axis which is the center of rotation of the gantry portion, and 22A denotes C at the position shown in FIG.
This is the rotation axis of the arm.

With such a configuration, the electron beam irradiation unit and the X-ray irradiation unit can be smoothly moved to a predetermined position, and the object to be irradiated with the electron beam and the X-ray can be irradiated from the respective predetermined directions. In addition, a part of the mechanical technology of the C-arm linac can be used.

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 high energy X-ray.
Although the two types of targets and the scatterer were exchanged depending on whether the target was a ray, a low energy X-ray, or an electron beam, when the target 16 was fixed to the accelerator tube 11 as in the first embodiment, The replacement becomes difficult.

Therefore, in the third embodiment, as shown in FIG. 4, in order to make the X-rays multistage, the high energy target 16a and the low energy target 16b are placed in the same plane perpendicular to the gantry rotation axis. Are mounted 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 beam 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. These collimator leaves 24
It is opened and closed (driven) as shown in FIGS. 5A and 5B in accordance with the shape and the like of the irradiated portion to form an irradiation field.

Normally, the irradiated portion 25 is fixed at the position of the isocenter C in FIG. 3, but if the emission position of the X-ray changes as in the third embodiment, a shift occurs in the irradiation field. I will. 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 is changed like 23B. At this time, strictly speaking,
Since the illuminated portion 25 looks different from the targets 16a and 16b, the opening of the collimator leaf 24 is slightly changed.

Embodiment 4 FIG. In the third embodiment, the displacement of the irradiation field is adjusted by driving the collimator leaf 24. However, for example, as shown in FIGS.
The irradiation field may be adjusted by moving the whole, and the geometric penumbra by the collimator leaf 24 can be reduced.

As shown in FIG. 10, the geometric penumbra is caused by an X-ray emitted from a point on the targets 16a and 16b being blocked by the collimator leaf 24. As shown in FIG. 11, the surfaces that determine the irradiation field of the collimator leaf 24 always have the targets 16a and 16b regardless of the position of the collimator leaf 24.
May occur for those that are not a set of line segments within a straight line passing through the center of That is, as shown in FIG. 11, the end face of the collimator leaf 24 is in the state of a dashed line due to the driving and the way of taking the cross section, 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 the inside of the lead for a distance that is not enough to be shielded and attenuate and reach. Among the elements of the geometric penumbra, it is difficult to avoid the elements as shown in FIG.

Usually, in a 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 between the leaves are conical except for the center. Used to eliminate geometric penumbra elements. In FIG. 12, 2
3A is a leaf drive rotation axis common to each leaf. However, in the device as shown in FIG.
If the emission position of the line is changed, a geometric penumbra will appear even if an attempt is made to change the opening of the collimator leaf 24.

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

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

In such a configuration, first, the low energy X
At the time of line irradiation, the C-arm unit 22 and the collimator 23 are arranged such that the low energy target 16b faces the collimator 23 as shown in FIG. When irradiating with high energy X-rays, the C-arm 22 and the collimator 23 are arranged as shown in FIG. Further, at the time of electron beam irradiation, the C-arm unit 22 and the collimator 23 are arranged as shown in FIG.
Is fully opened, and the accessory 8 is located below the collimator 23.
(FIG. 17) is attached.

Also with such a linear accelerator, the geometric penumbra by the collimator leaf 24 can be reduced as in the fourth embodiment.

Embodiment 6 FIG. Next, FIG. 16 is a longitudinal sectional view of an acceleration tube of a linear accelerator according to Embodiment 6 of the present invention. In the figure, reference numeral 31 denotes an outer cylinder that holds an internal vacuum, 32 denotes a plurality of walls provided in the outer cylinder 31 to form an electric field, and the distance between the walls 33 is adjustable. The length is adjustable. 33 is a passage through which the electron beam passes,
34 is a cavity provided around the passage 32, 35 is opening / closing means for opening / closing an entrance / exit between the passage 32 and the cavity 34,
Reference numeral 36 denotes 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 electrons, the electron beam is efficiently accelerated. Therefore, the length of each node in the accelerating tube is shorter on the side closer to the electron gun and longer on the side closer to the irradiation unit. On the other hand, in the sixth embodiment, the length of the node is changed and the volume of the cavity 34 is changed in accordance with the change in the direction of the electron beam in the acceleration tube. Further, the size of the entrance and exit between the passage 32 and the cavity 34 is adjusted by the opening and closing means so that resonance is maintained even when the volume of the cavity 34 changes. Therefore, even if the direction of the electron beam changes, the electron beam can be efficiently accelerated.

[0040]

As described above, in the linear accelerator according to the first aspect of the present invention, a deflection magnet section for X-ray irradiation and a deflection magnet section for electron beam irradiation 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,
In addition, it is possible to prevent the electron beam for X-ray irradiation from being irradiated without passing through the target, and to improve the reliability.

According to a second aspect of the present invention, there is provided a linear accelerator, wherein a gantry section rotatable about a gantry rotation axis is provided with a C-arm section 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 first aspect of the present invention, the electron beam and the X-ray irradiation unit can be smoothly moved to respective predetermined positions by a combination of the driving of the gantry unit and the driving of the C-arm unit. This has the effect.

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 deflection magnet unit for X-ray irradiation. The effect is that the energy of the line can be switched in multiple stages.

In the linear accelerator according to a fourth aspect of the present invention, the collimator can be moved. Therefore, in addition to the same effects as those of the third aspect of the present invention, the linear accelerator can be used for X-ray irradiation from a high energy target and for a low energy target. This makes it possible to adjust the deviation of the irradiation field between the irradiation with the X-ray and the effect of reducing the geometric penumbra.

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 a deflection magnet for X-ray irradiation, and move independently of a C-arm on a gantry. Since a possible collimator is attached, in addition to the same effect as the invention of the above-mentioned claim 2, the deviation of the irradiation field between the time of X-ray irradiation from the high energy target and the time of X-ray irradiation from the low energy target is reduced. This has the effect of being able to match and to reduce the geometric penumbra.

In the linear accelerator according to the sixth aspect of the present invention, the length of the joint of the accelerating tube can be adjusted in accordance with the direction of the electron beam. Even if the direction of the line changes, an effect that the electron beam can be efficiently accelerated is exerted.

According to the linear accelerator of the present invention, the size of the entrance and exit between the electron passage and the cavity of the accelerating tube can be adjusted in accordance with the length of the knot. In addition to the same effects as the invention, there is an effect that resonance can be easily maintained even if the volume of the cavity changes.

[Brief description of the drawings]

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

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

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

FIG. 4 is a configuration diagram showing an enlarged main part of a linear accelerator according to Embodiment 3 of the present invention.

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

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

FIG. 7 is an explanatory diagram showing a state of the collimator leaf in FIG. 6;

FIG. 8 is a configuration diagram showing an accelerator main body of a linear accelerator according to Embodiment 4 of the present invention.

FIG. 9 is an explanatory view showing an enlarged main part of FIG. 8;

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

FIG. 11 is an explanatory diagram showing the occurrence of a geometric penumbra in the collimator as shown in FIG. 5;

FIG. 12 is an explanatory diagram for describing a method of preventing a geometric penumbra by a general multi-leaf type collimator.

FIG. 13 is a configuration diagram showing a state of a linear accelerator according to Embodiment 5 of the present invention at the time of 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 longitudinal sectional view of an acceleration tube of a linear accelerator according to Embodiment 6 of the present invention.

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

[Explanation of symbols]

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

Claims (7)

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