JPH0747051B2 - Beam expanding device for charged heavy particle beam by deflecting static magnetic field - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam expanding device for a charged heavy particle beam by a deflecting static magnetic field.

[0002]

Radiation therapy has been an important part of cancer therapy. By the way, as the radiation used for this purpose, in addition to conventional X-rays, gamma rays, electron beams, and the like, there are proton rays and heavy ion rays which have been actively researched recently. In the radiation treatment with proton beam or heavy ion beam, the lesion of the patient to be irradiated has a cross-sectional area of, for example, about 15 cm × 15 cm. However, since the proton beam and the heavy ion beam obtained from the accelerator are thin beams as they are, it is necessary to expand the beam cross-sectional area in order to irradiate a lesion having a specific cross-sectional area.

A technique for changing the beam emitted from the accelerator to be suitable for a patient is called irradiation field formation. Among them, the technique for expanding the beam in the direction perpendicular to the beam traveling direction as described above is called beam expansion.

Conventionally, a method of using a scatterer and a method of scanning a beam have been used for beam expansion. The scatterer method expands the cross-sectional area of the beam by utilizing the fact that the direction of heavy charged particles is gradually bent by the electric field around the atomic nucleus. The beam scanning method is a method in which a relatively thin beam is scanned by changing the magnetic field of an electromagnet to obtain a beam having a large cross-sectional area as a time average.

The above-mentioned conventional method has the following problems.

In the scatterer system using a single scatterer, the scattering angle has a substantially normal distribution, and therefore the intensity distribution in the beam width direction also has a substantially normal distribution. The use efficiency of the beam is poor because a part of this normal distribution is almost flat, and there are many neutrons generated by the unused heavy charged particles. There is a problem.

In order to reduce this problem, a method using a plurality of scatterers is used, but it is theoretically impossible to dramatically increase the beam utilization efficiency. Also, since heavy particles such as heavy ion beams do not scatter very much, it is not possible to expand the beam cross section only by the scatterers.

In the scanning method, the constant beam intensity is a problem and cannot be used for pulsed beams. In addition, since there is a non-uniform dose even if there is a temporal change in the beam intensity for a continuous beam, there is a problem that the requirement for the constant beam intensity is strict, and therefore the requirement for the performance of the accelerator becomes large. .

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the conventional beam expanding method, and an object thereof is to provide a simpler beam expanding apparatus for a charged heavy particle beam. And

[0010]

A beam expanding device of the present invention for solving the above-mentioned problems includes a first distribution forming means for forming an energy distribution in a charged particle beam and a charged particle beam having the energy distribution. A beam is incident, and the charged particle beam is expanded linearly in a first direction based on a difference in energy of the charged particle beam.
And the expanded charged particle beam beam output from the first deflection electromagnet means,
A first uniforming means for uniformizing the energy of the expanded charged particle beam is provided.

Further, the present invention may further comprise means for scanning the beam from the first uniforming means and expanding it into a planar beam.

Furthermore, in the present invention, a second beam forming an energy distribution in the beam from the first uniforming means is formed.
Of the charged particle beam and the charged particle beam beam is incident on the charged particle beam beam based on the difference in energy of the charged particle beam beam.
Second deflection electromagnet means for linearly expanding in a second direction different from the direction and outputting a planar beam, and the planarly expanded charged particle beam output from the second deflection electromagnet means. A second uniform means for injecting a beam and homogenizing the energy of the charged particle beam beam expanded in the plane may be further provided.

Further, according to the present invention, the first distribution forming means is arranged upstream of the first distribution forming means, and the charged particle beam is scanned in a second direction different from the first direction to form the first distribution forming means. It may further comprise scanning means leading to the means.

[0014]

If the above-mentioned structure is adopted, the charged particle beam can be linearly expanded in the first direction based on the difference in energy. Furthermore, since the means for scanning the beam in the second direction different from the first direction or the means for linearly expanding the beam in the second direction is provided, the beam can be expanded in the plane and a planar irradiation field is formed. can do. Therefore,
The proton beam / heavy ion beam obtained from the accelerator is a thin beam as it is, but the cross-sectional area of the beam can be expanded so that a lesion having a cross section of a specific size can be irradiated.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a beam expanding apparatus for charged heavy particle beams by a static deflection magnetic field according to the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view of the beam expanding device according to the first embodiment. The beam expanding device 2 linearly spreads a narrow beam 4 incident from the left side of FIG. 1 to form a linear beam 6. . This beam expansion device includes an energy distribution generator 8, a deflection electromagnet 10, and an energy distribution corrector 12.

The energy distribution generator 8 is an element having a non-uniform thickness depending on the location, and is made of a substance having a low atomic number, for example, a polymer substance such as graphite or acrylic resin. The energy distribution generator 8 has a structure as shown in FIG. 2, FIG. 3 or FIG. 4, and FIG. 2 (b) and FIG. 3 (b) are A of FIG. 2 (a) and FIG. 3 (a), respectively. 4B is a side view of FIG. 4A, and FIG. 4B is a cross-sectional view taken along line A-B and line B-B. When the charged particle beam (thin beam) 4 passes through the energy distribution generator 8, the energy loss of the charged particle beam 4 varies depending on the location, so that the energy distribution of the charged particles can be obtained.

Charged particle beam 4 having this energy distribution
Is incident on the deflecting electromagnet 10, the degree of bending due to the energy of the charged particle beam 4 is different, so that a linearly expanded beam 14 as shown in FIG. 1 is obtained.
This beam 14 is guided to the energy distribution corrector 12 and transmitted therethrough, thereby reducing the energy distribution.

The energy distribution compensator 12 has the same structure as that of the energy distribution generator 8 shown in FIG. 3, and thickens places where high energy particles come and thin places where small energy particles enter. ing.

By using such a beam expanding device, the thin beam 4 can be linearly expanded in the first direction to form a linear beam 6, and the linear beam 6 is scanned in the second direction perpendicular to the paper surface. Then, as shown in FIG. 5, the beam can be expanded in a plane and the irradiation field 16 can be formed.

Next, with reference to FIGS. 6 and 7, a second embodiment of the beam expanding device of the present invention will be described. FIG. 7 is a side view of FIG. 6 viewed from the left side of the drawing. In this embodiment, in addition to the beam expanding device 2 shown in FIG. 1, a second beam expanding device 20 is further provided to expand the narrow beam 4 in a plane as shown in FIG. That is, the beam 6 expanded in the first direction by the first beam expanding device 2 as shown in FIG.
Is magnified in the second direction shown in FIG. 7 by the second magnifying device 20, and the planar irradiation field 16 as shown in FIG.
To form. As shown in FIGS. 6 and 7, the second direction is a direction orthogonal to the first direction.

The second beam expanding device 20 has the same structure as the first beam expanding device 2 and comprises an energy distribution generator 28 on which the beam 6 is incident, a deflection electromagnet 30, and an energy distribution corrector 32. Become. Second beam expansion device 2
0 is the first so that the beam 6 emitted from the first beam expansion device 2 and expanded in the first direction is expanded in the second direction.
The beam expanding device 2 has a configuration rotated by 90 degrees. The energy distribution creator 28 and the energy distribution corrector 32 have the same configuration as that shown in FIG. 3 or FIG. 4, like the energy distribution creator 8 and the energy beam corrector 12.

Since the other structure is the same as that of the first embodiment, the same parts are designated by the same reference numerals and detailed description thereof will be omitted. This device is also effective for expanding the pulse beam in a plane.

Next, a third embodiment of the beam expanding device of the present invention will be described with reference to FIGS. FIG. 9 is a side view of FIG. 8 viewed from the left side of the drawing. In this embodiment, the incident beam is scanned by the scanning electromagnet 40 in the second direction perpendicular to the paper surface, and the scanned beam 44 is incident on the energy distribution generator 8. Then, the beam is sent to the energy distribution corrector 12 via the deflection electromagnet 10 and the beam is expanded in a plane in the first direction of FIG. 8 and the second direction of FIG. Then, the irradiation field 16 as shown in FIG. 5 is formed.

Since the other structure is the same as that of the first embodiment, the same portions are designated by the same reference numerals and the detailed description thereof will be omitted.

According to this embodiment, since the beam output from the deflection electromagnet 10 can be directly sent to the patient via the energy distribution corrector 12, the distance from the output part of the beam expanding device to the patient can be shortened. There is.

Although the present invention has been described based on the embodiments, the present invention is not limited to the above embodiments. Various modifications can be implemented.

[0028]

According to the present invention, the heavy charged particle beam can be expanded, and the beam utilization efficiency can be almost 100%.

When two sets of the energy distribution generator, the deflection electromagnet, and the energy distribution corrector are used, the beam can be expanded even for the pulse beam.

Even when a set of energy distribution generator / deflection electromagnet / energy distribution compensator is used to linearly spread and scanning this with a scanning electromagnet, it is already linearly expanded. The requirement for constant intensity is smaller than that of conventional scanning methods.

Furthermore, if the beam is scanned at a right angle to the traveling direction before being made incident on the energy distribution generator, and then the energy distribution is formed and expanded by the deflecting electromagnet in the direction perpendicular to the scanning direction, The distance from the beam expander to the patient can be shortened.

[Brief description of drawings]

FIG. 1 is a schematic view of a beam expansion device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a structure of an energy distribution generator,
(A) is a top view, (b) is sectional drawing which followed the AA line.

FIG. 3 is a diagram showing another structure of the energy distribution generator and the structure of the energy distribution compensator, FIG.
(B) is sectional drawing which followed the BB line.

FIG. 4 is a diagram showing still another structure of the energy distribution generator, (a) is a plan view and (b) is a side view.

FIG. 5 is a diagram showing an irradiation field of a beam enlarged in a plane.

FIG. 6 is a schematic view of a beam expanding device according to a second embodiment of the present invention.

7 is a side view of the device of FIG. 6 as viewed from the left of the drawing.

FIG. 8 is a schematic view of a beam expanding device according to a third embodiment of the present invention.

9 is a side view of the device of FIG. 8 as viewed from the left side of the drawing.

[Explanation of symbols]

2 ... Beam expanding device, 4 ... Narrow beam, 6 ... Linear beam, 8 ... Energy distribution generator, 10 ... Bending electromagnet, 1
2 ... Energy distribution corrector, 14 ... Expanded beam

Claims (4)

[Claims] 1. A first distribution forming means for forming an energy distribution in a charged particle beam, and a charged particle beam having the energy distribution is incident, and the charged particle beam is charged on the basis of a difference in energy of the charged particle beam. First deflecting electromagnet means for linearly expanding the particle beam in a first direction, and the expanded charged particle beam output from the first deflecting electromagnet means are incident to the expanded charged particles. A charged particle beam beam expanding apparatus using a static magnetic field for deflection, comprising: a first uniform means for uniformizing the energy of the beam. 2. The apparatus according to claim 1, further comprising means for scanning the beam from the first uniform means to expand it into a planar beam. 3. A second distribution forming means for forming an energy distribution on the beam from the first uniforming means, and a charged particle beam beam incident from the second distribution forming means, The charged particle beam may be changed to a second direction different from the first direction based on the difference in energy of
The second which linearly expands in a direction and outputs a planar beam
Of the deflecting electromagnet means and the planarly expanded charged particle beam beam output from the second deflecting electromagnet means are made incident, and the energy of the planarly expanded charged particle beam beam is made uniform. The apparatus of claim 1, further comprising: second uniform means. 4. A scan which is arranged upstream of the first distribution forming means, scans the charged particle beam in a second direction different from the first direction, and guides it to the first distribution forming means. The apparatus of claim 1, further comprising means.