U.S. patent application number 14/098026 was filed with the patent office on 2014-04-03 for energy degrader and charged particle beam irradiation system equipped therewith.
This patent application is currently assigned to Sumitomo Heavy Industries, Ltd.. The applicant listed for this patent is Sumitomo Heavy Industries, Ltd.. Invention is credited to Takuya Miyashita, Takamasa Ueda.
Application Number | 20140091238 14/098026 |
Document ID | / |
Family ID | 47295852 |
Filed Date | 2014-04-03 |
United States Patent
Application |
20140091238 |
Kind Code |
A1 |
Miyashita; Takuya ; et
al. |
April 3, 2014 |
ENERGY DEGRADER AND CHARGED PARTICLE BEAM IRRADIATION SYSTEM
EQUIPPED THEREWITH
Abstract
An energy degrader includes a plurality of attenuating members
configured to attenuate the energy of an incident charged particle
beam, the plurality of attenuating members having different amounts
of energy to be attenuated. A low-energy-side attenuating member
that is the attenuating member with a larger amount of energy to be
attenuated is made of a material having a higher transmittance of
the charged particle beam than that of a high-energy-side
attenuating member that is the attenuating member with a smaller
amount of energy to be attenuated.
Inventors: |
Miyashita; Takuya; (Ehime,
JP) ; Ueda; Takamasa; (Ehime, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sumitomo Heavy Industries, Ltd. |
Tokyo |
|
JP |
|
|
Assignee: |
Sumitomo Heavy Industries,
Ltd.
Tokyo
JP
|
Family ID: |
47295852 |
Appl. No.: |
14/098026 |
Filed: |
December 5, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2012/059585 |
Apr 6, 2012 |
|
|
|
14098026 |
|
|
|
|
Current U.S.
Class: |
250/492.3 ;
250/505.1 |
Current CPC
Class: |
G21K 1/10 20130101; A61N
5/1042 20130101; A61N 2005/1095 20130101; A61N 2005/1087 20130101;
A61N 5/1048 20130101 |
Class at
Publication: |
250/492.3 ;
250/505.1 |
International
Class: |
G21K 1/10 20060101
G21K001/10; A61N 5/10 20060101 A61N005/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 6, 2011 |
JP |
2011-126342 |
Claims
1. An energy degrader comprising: a plurality of attenuating
members configured to attenuate the energy of an incident charged
particle beam, the plurality of attenuating members having
different amounts of energy to be attenuated, wherein a
low-energy-side attenuating member that is the attenuating member
with a larger amount of energy to be attenuated is made of a
material having a higher transmittance of the charged particle beam
than that of a high-energy-side attenuating member that is the
attenuating member with a smaller amount of energy to be
attenuated.
2. The energy degrader according to claim 1, wherein only the
low-energy-side attenuating member with the largest amount of
energy to be attenuated among the plurality of attenuating members
is made of a material having a high transmittance.
3. The energy degrader according to claim 1, wherein the
low-energy-side attenuating member is formed from beryllium, and
the high-energy-side attenuating member is formed from
graphite.
4. A charged particle beam irradiation system including the energy
degrader according to claims 1 and irradiating the charged particle
beam, the charged particle beam irradiation system comprising: an
accelerator configured to accelerate charged particles introduced
into the energy degrader; and an irradiation device configured to
irradiate the charged particle beam having energy attenuated by the
energy degrader.
Description
INCORPORATION BY REFERENCE
[0001] Priority is claimed to Japanese Patent Application No.
2011-126342, filed Jun. 6, 2011, and International Patent
Application No. PCT/JP2012/059585, the entire content of each of
which is incorporated herein by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention relates to an energy degrader that
attenuates the energy of a charged particle beam, and a charged
particle beam irradiation system equipped therewith.
[0004] 2. Description of the Related Art
[0005] There are known facilities that irradiate a patient with a
charged particle beam, such as a proton beam, to perform cancer
treatment. These types of facilities include a cyclotron
(accelerator) that accelerates ions (charged particles) generated
by an ion source, a transportation line that transports the charged
particles accelerated by the cyclotron, and a rotatable irradiation
device (rotating gantry) that irradiates a patient with a charged
particle beam from arbitrary directions.
[0006] A degrader in which a beam absorber (attenuating material)
is inserted into a beam line (transportation line) to attenuate
beam energy is disclosed in a technique described in the related
art.
SUMMARY
[0007] According to an embodiment of the present invention, there
is provided an energy degrader including a plurality of attenuating
members with different amounts of energy to be attenuated
configured to attenuate the energy of an incident charged particle
beam, the plurality of attenuating members. A low-energy-side
attenuating member which is the attenuating member with a larger
amount of energy to be attenuated is made of a material having a
higher transmittance of the charged particle beam than that of a
high-energy-side attenuating member that is the attenuating member
with a smaller amount of energy to be attenuated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is an arrangement view of a particle beam treatment
system related to an embodiment of the invention.
[0009] FIG. 2 is a schematic view showing an energy degrader
related to the embodiment of the invention.
[0010] FIG. 3 is a schematic view showing an energy degrader
related to another embodiment of the invention.
[0011] FIG. 4 is a schematic view showing an energy degrader
related to a further embodiment of the invention.
[0012] FIG. 5 is a schematic view showing an energy degrader
related to a still further embodiment of the invention.
DETAILED DESCRIPTION
[0013] In charged particle beam irradiation systems of the related
art, the energy of the charged particle beam is adjusted based on
the irradiation position (depth) of a body to be irradiated. An
energy degrader having an attenuating material is used for the
adjustment of energy of the charged particle beam. Generally, as
the attenuating material, graphite that is not easily
radioactivated and is inexpensive is adopted. In the related art,
the amount of energy to be attenuated is adjusted by changing a
length by which the charged particle beam is transmitted through
the attenuating material made of the same material.
[0014] Additionally, in recent years, request for using a charged
particle beam having lower energy than usual has been increasing.
If the attenuating material is thickened in order to increase the
amount of energy attenuation, scattering of the charged particle
beam becomes large and the number (=transmittance) of charged
particles capable of being transmitted through the attenuating
material decreases.
[0015] It is desirable to provide an energy degrader that can
mitigate a reduction in the transmittance of a low-energy charged
particle beam, and a charged particle beam irradiation system
equipped therewith.
[0016] In the energy degrader related to the embodiment of the
invention, the plurality of attenuating members having different
amounts of energy attenuation are provided, and the low-energy-side
attenuating member with a larger amount of energy attenuation is
formed from a material having a higher transmittance than the
high-energy-side attenuating member with a smaller amount of energy
attenuation. Therefore, a reduction in the transmittance of the
low-energy-side proton beam can be mitigated. As a result, in a low
energy region (for example, 70 MeV or lower), a reduction in the
number of protons that are transmitted through the attenuating
members can be suppressed. When the amount of energy attenuation is
large, as compared with a case where the amount of energy
attenuation is small, the energy of the charged particle beam after
being transmitted through the attenuating members becomes low.
[0017] Additionally, only the low-energy-side attenuating member
with the largest amount of energy to be attenuated among the
plurality of attenuating members may be made of a material having a
high transmittance. In this way, only the attenuating member with
the largest amount of energy attenuation can be made of a material
having a higher transmittance compared to the other attenuating
members.
[0018] Additionally, the low-energy-side attenuating member can be
formed from beryllium, and the high-energy-side attenuating member
can be formed from graphite. By adopting beryllium as the
low-energy-side attenuating member in the aforementioned way, the
number of charged particles that are transmitted through and the
number of attenuating members can be increased in the low energy
region.
[0019] Additionally, according to another embodiment of the
invention, there is provided a charged particle beam irradiation
system including the above energy degrader and irradiating the
charged particle beam. The charged particle beam irradiation system
includes an accelerator configured to accelerate charged particles
introduced into the energy degrader; and an irradiation device
configured to irradiate the charged particle beam having energy
attenuated by the energy degrader.
[0020] The charged particle beam irradiation system related to the
embodiment of the invention includes the energy degrader that
attenuates the energy of an incident charged particle beam. In this
energy degrader, the plurality of attenuating members having
different amounts of energy attenuation are provided, and the
low-energy-side attenuating member with a larger amount of energy
attenuation is formed from a material having a higher transmittance
than the high-energy-side attenuating member with a smaller amount
of energy attenuation. Therefore, the transmittance of the
low-energy-side charged particle beam can be improved. As a result,
in the low energy region, the number of charged particles that are
transmitted through the attenuating members can be increased.
[0021] Hereinafter, preferred embodiments of an energy degrader and
a charged particle beam irradiation system equipped therewith
related to the invention will be described referring to the
drawings. In the present embodiment, a case where a particle beam
treatment system is used as the charged particle beam irradiation
system.
[0022] Charged Particle Beam Irradiation System
[0023] The particle beam treatment system, which is, for example, a
device that is used in cancer treatment, irradiates a tumor (target
to be irradiated) inside a patient' s body with a proton beam
(charged particle beam).
[0024] As shown in FIG. 1, the particle beam treatment system 1
includes a cyclotron (particle accelerator) 2 that accelerates ions
(positive ions of hydrogen) generated in an ion source (not shown)
to generate a proton beam, a rotatable rotating gantry (irradiation
device) 3 that irradiates a patient with the proton beam from
arbitrary directions, and a transportation line 4 that transports
the proton beam (charged-particle beam accelerated by the
cyclotron) generated by cyclotron 2 to the rotating gantry 3.
[0025] The proton beam accelerated by the cyclotron 2 is deflected
along the transportation line 4 and transported to the rotating
gantry 3. The transportation line 4 is provided with a deflecting
magnet for deflecting the proton beam. Additionally, the
transportation line 4 is provided with an energy degrader 10 that
attenuates the energy of charged particles (will be described below
in detail).
[0026] Moreover, an energy selection system (ESS) 30 is provided at
a rear stage (downstream) of the energy degrader 10 in the
transportation line 4. The ESS 30 selectively takes out a proton
beam with a desired energy width from the proton beam with a
predetermined energy distribution that has been transported. In the
ESS 30, the energy width of the proton beam is selected so as to
become a desired range.
[0027] The rotating gantry 3 includes a treatment table on which
the patient lies, and an irradiation unit that irradiates a patient
with the proton beam. The charged particle beam having energy
attenuated by the energy degrader 10 is emitted from the
irradiation unit and irradiates to a target region of the
patient.
[0028] Energy Degrader
[0029] FIG. 2 is a schematic view showing the energy degrader
related to the embodiment of the invention. The energy degrader 10
shown in FIG. 2 is provided on a path (on a beam line) of a proton
beam B to attenuate the energy of the proton beam B. The energy
degrader 10 includes a plurality of attenuating members 11A to 11G
that attenuate the energy of the proton beam B to be transmitted.
In addition, when it is not necessary to distinguish the
attenuating members 11A to 11G, these attenuating members are
written as the attenuating members 11.
[0030] In the energy degrader 10, the attenuating members 11 having
mutually different thicknesses are arranged in order of thickness
in one direction. In the present embodiment, the attenuating
members are arranged so as to increase in thickness in order from
the attenuating member 11A to the attenuating member 11G in a
direction X intersecting the path of the proton beam B. In
addition, the term "thickness" means the length of the charged
particle beam in its transmission direction. For example, the
attenuating members 11 are arranged so that the end surfaces
thereof on an outlet side from which the proton beam B is emitted
are aligned, and are arranged so that the end surfaces thereof on
an opposite inlet side constitute a stair shape. In addition, the
attenuating members 11 may not be arranged in order of thickness.
Additionally, the attenuating members are arranged so that the end
surfaces thereof on the outlet side constitute a stair shape, or
may have other arrangements.
[0031] The attenuating members 11 are integrally supported by a
supporting member (not shown). Additionally, the energy degrader 10
includes a drive source (for example, a drive motor) that applies a
driving force to the attenuating members 11, guide means (for
example, a guide rail) for guiding movement of the attenuating
members 11, or the like. Also, the energy degrader 10 moves the
attenuating members 11 that transmits the proton beam B
therethrough, on the path of the proton beam B, thereby changing
the amount of energy attenuation of the proton beam B. The energy
degrader 10 decelerates the proton beam B at different decelerated
velocities based on the thicknesses of the attenuating members 11
through which the proton beam B is transmitted. The kinetic energy
of the proton beam B is reduced and attenuated.
[0032] Here, in the energy degrader 10, a low-energy-side
attenuating member that is the attenuating member 11 with a larger
amount of energy to be attenuated is formed from a material having
a higher transmittance of the proton beam B than a high-energy-side
attenuating member that is the attenuating member 11 with a smaller
amount of energy to be attenuated. In other words, a substance with
a small atomic number is adopted for the low-energy-side
attenuating member rather than the high-energy-side attenuating
member. Since scattering of the proton beam B spreads more greatly
as the atomic number of attenuating materials is larger, this
results from the decrease in the number of protons capable of being
transmitted.
[0033] In the energy degrader 10 of the present embodiment, only
the attenuating member 11G with the largest amount of energy to be
attenuated is formed from a material having a higher transmittance
than the other attenuating members 11A to 11F. The materials of the
attenuating members 11 include, for example, carbon (C), beryllium
(Be), or the like. In the present embodiment, beryllium that is a
stable solid substance with a small atomic number is adopted for
the lowest-energy-side attenuating member 11G, and carbon
(graphite) is adopted for the other attenuating members 11A to
11F.
[0034] In addition, a material having a higher transmittance than
the remaining attenuating members 11A to 11E may be adopted for two
low-energy-side attenuating members 11G and 11F. Additionally, the
material having a high transmittance may not be adopted for the
lowest-energy-side attenuating member 11G. For example, a material
having a higher transmittance than the remaining attenuating
members 11A to 11E may be adopted for the low-energy-side
attenuating member 11F, and the lowest-energy-side attenuating
member 11G and the attenuating members 11A to 11D may be formed
from the same material.
[0035] Operation of Energy Degrader and Particle Beam Treatment
System
[0036] In the particle beam treatment system 1, the proton beam B
is accelerated by the cyclotron 2 and the accelerated proton beam B
(for example, having an energy range of 230 MeV.+-.several MeV) is
introduced into the energy degrader 10. In the energy degrader 10,
the attenuating members 11 are driven and moved by driving means,
and a desired attenuating member 11 is arranged on the path of the
proton beam B. The proton beam B passed through this attenuating
member 11 is decelerated by the attenuating member 11 and the
energy thereof is attenuated (for example, 200 MeV.+-.ten and
several MeV).
[0037] The proton beam B passed through the energy degrader 10 is
introduced into the ESS 30. The proton beam B with a desired energy
range out of the proton beam B introduced into the ESS 30 is taken
out selectively (for example, 200 MeV.+-.1 MeV). The proton beam B
with a selected energy width is transported by the transportation
line 4, is introduced into the rotating gantry 3, and is irradiated
to a body to be irradiated. This allows the proton beam B to be
irradiated so as to reach a predetermined depth position inside the
body to be irradiated. When the proton beam B is irradiated so as
to reach a deep position inside the body to be irradiated, the
amount of attenuation using the energy degrader 10 is made small,
and when the proton beam B is irradiated so as to reach a shallow
position inside the body to be irradiated (for example, near a body
surface), the amount of attenuation due to the energy degrader 10
is made large.
[0038] According to such energy degrader and particle beam
treatment system equipped therewith of the present embodiment, the
plurality of attenuating members 11 are included, and the energy of
the proton beam B that enters the attenuating members 11 can be
attenuated. In the energy degrader 10, the low-energy-side
attenuating member 11G with a larger amount of energy attenuation
is formed from a material having the higher transmittance than a
high-energy-side attenuating member with a smaller amount of energy
attenuation. Therefore, a reduction in the transmittance of the
low-energy-side proton beam B can be mitigated. As a result, in a
low energy region, scattering of the proton beam B can be
suppressed and a reduction in the number of protons that can be
transmitted through the attenuating members 11 can be
suppressed.
[0039] Additionally, since only the low-energy-side attenuating
member 11G with the largest amount of energy to be attenuated among
the plurality of attenuating members 11 is formed from beryllium
that is expensive and has a high transmittance, a reduction in the
number of protons that are transmitted through the low-energy-side
attenuating member 11G can be suppressed, while suppressing an
increase in the manufacturing cost. That is, a reduction in the
number of protons to be irradiated can be suppressed. This enables
the proton beam B to be effectively irradiated to the shallow
position near the body surface and enables the reliable particle
beam treatment system 1 to be realized.
[0040] The following Table 1 shows transmittances at individual
levels of energy of the proton beam B. The transmittances in Table
1 are values measured at the outlet of the ESS 30. All the
materials of the attenuating members at this time are the same, and
are graphite.
TABLE-US-00001 TABLE 1 Energy of Proton Beam Transmittance [MeV]
(.phi.5 mm, 32.pi.) [%] 70 0.36 110 1.66 150 5.54 190 17.29 230
46.50
[0041] The following Table 2 shows the comparison between the
materials of the attenuating members with respect to the
transmittance of the proton beam B. Measurement is made in cases
where the energy of the proton beam B is 70 [MeV] and beam
diameters are .phi.5 mm and .phi.2 mm.
TABLE-US-00002 TABLE 2 Attenuation Rate Attenuation Rate Material:
Carbon Material: Beryllium Beam Diameter (.phi.5 mm, 32.pi.) [%]
(.phi.5 mm, 32.pi.) [%] .phi.5 mm 0.358 0.578 .phi.2 mm 0.478
0.744
Second Embodiment
[0042] Next, an energy degrader 10B related to a second embodiment
will be described with reference to FIG. 3. The energy degrader 10B
shown in FIG. 3 is different from the energy degrader 10 shown in
FIG. 2 in that each of the attenuating members 12A to 12G have
different thicknesses. In this way, each of the attenuating members
12A to 12G may be configured to have a plurality of
thicknesses.
Third Embodiment
[0043] Next, an energy degrader 10C related to a third embodiment
will be described with reference to FIG. 4. As shown in FIG. 4, the
energy degrader 10C has a pair of attenuating members 13 and 14
that are arranged to face each other. The attenuating members 13
and 14 form a wedge shape and are arranged such that mutual
inclined surfaces 13a and 14a face each other. The attenuating
members 13 and 14 are configured so as to be movable in an X
direction intersecting a traveling direction of the proton beam B.
The amount of energy attenuation of the proton beam B is controlled
by moving the attenuating members 13 and 14 in the X direction and
changing a length by which the proton beam B is transmitted through
the attenuating members 13 and 14. In addition, a configuration may
be adopted in which the beam diameter of the proton beam B is
controlled by driving any one of the attenuating members 13 and 14
in the traveling direction of the proton beam B to adjust the gap
between the attenuating members 13 and 14.
[0044] The attenuating members 13 and 14 include a plurality of
attenuating members 13A, 13B, 14A, and 14B having different amounts
of energy to be attenuated. Here, the low-energy-side attenuating
members 13B and 14B with larger amounts of energy to be attenuated
are formed from a material having a higher transmittance of the
proton beam B than the high-energy-side attenuating members 13A and
14A with smaller amounts of energy to be attenuated. For example, a
material (beryllium) with a high transmittance is adopted only for
a portion where the energy of the proton beam B is attenuated to 70
[MeV].
[0045] Even in the energy degrader 10C of the aforementioned third
embodiment, similar to the energy degrader 10 of the above
embodiment, in a low energy region, scattering of the proton beam B
can be suppressed and a reduction in the number of protons that are
transmitted through the attenuating members 13B and 14B can be
suppressed.
Fourth Embodiment
[0046] Next, an energy degrader 10D related to a fourth embodiment
will be described with reference to FIG. 5. FIG. 5 is a front view
of the energy degrader, and is shown from the traveling direction
of the proton beam B. The energy degrader 10D shown in FIG. 5
includes a plurality of attenuating members 15A and 15B having
different thicknesses, and the plurality of attenuating members 15A
and 15 are arranged spirally. For example, the plurality of
attenuating members 15A and 15B are arranged so as to become thin
on a central side thereof and become thick on an outer side
thereof. For example, the plurality of attenuating members 15A and
15B may be arranged so as to become thick on the central side
thereof and become thin on the outer side thereof.
[0047] A rotating shaft 16 extending parallel to the traveling
direction of the proton beam B is arranged at the center of the
energy degrader 10D. The rotating shaft 16 is configured so as to
be rotatable around an axis and movable in the direction
intersecting the traveling direction of the proton beam. As the
rotating shaft 16 rotates and moves in a predetermined direction,
desired attenuating members 15A and 15B are arranged on the path of
the proton beam.
[0048] Here, even in the energy degrader 10D of the fourth
embodiment, the low-energy-side attenuating member 15B with a
larger amount of energy to be attenuated is formed from a material
having a higher transmittance of the proton beam than the
high-energy-side attenuating member 15A with a smaller amount of
energy to be attenuated. Even in the energy degrader 10D of such a
fourth embodiment, similar to the energy degrader 10 of the above
embodiment, in a low energy region, scattering of the proton beam B
can be suppressed and a reduction in the number of protons that are
transmitted through the attenuating members 13B and 14B can be
suppressed.
[0049] Although the invention has been specifically described above
on the basis of the embodiments, the invention is not limited to
the above embodiments.
[0050] Additionally, the arrangement of the energy degrader 10 is
not limited to that immediately after the cyclotron 2, a
configuration may be adopted in which the energy degrader 10 is
provided in the irradiation nozzle installed at the rotating gantry
3.
[0051] Additionally, the accelerator is not limited to the
cyclotron 2, and may be, for example, other accelerators, such as a
synchro-cyclotron. Additionally, the charged particle beam is not
limited to the proton beam, and may be a carbon beam (baryon beam)
or the like.
[0052] Additionally, the material of the low-energy-side
attenuating member is not limited to beryllium, and other
attenuating materials may be adopted.
[0053] Additionally, the particle beam treatment system 1 may not
use the rotating gantry but may use stationary irradiation.
[0054] The energy degrader and the charged particle beam
irradiation system equipped therewith of the invention can mitigate
a reduction in the transmittance of the low-energy charged particle
beam and can suppress a reduction in the number of charged
particles that are transmitted through the low-energy-side
attenuating member.
[0055] It should be understood that the invention is not limited to
the above-described embodiment, but may be modified into various
forms on the basis of the spirit of the invention. Additionally,
the modifications are included in the scope of the invention.
* * * * *