JP6025227B2 - Neutron irradiation equipment for neutron capture therapy - Google Patents

Description

The present invention relates to a neutron beam irradiation equipment for neutron capture therapy.

As one of radiotherapy in cancer treatment or the like, boron neutron capture therapy (BNCT: BoronNCT) that performs cancer treatment by irradiation of neutron rays is known. Boron neutron capture therapy is attracting attention as a therapy capable of selectively treating cancer cells by reacting neutrons with a boron compound such as ¹⁰ B previously incorporated into cancer cells. In this neutron beam generating apparatus for performing boron neutron capture therapy, a neutron beam is generated by irradiating a target made of beryllium Be or the like with a charged particle beam, and a neutron is generated by a moderator provided with a storage chamber for storing the target. Decelerate the line to the appropriate energy level. In this type of apparatus, since the target is consumed due to the generation of neutrons, it is necessary to periodically replace the target.

  Patent Document 1 describes a target recovery device that recovers a used target in a neutron beam generator. In this target recovery apparatus, the target is exposed by pulling out the speed reducer provided with a storage chamber in which the target is stored so as to be separated from the target, and the target is recovered.

JP 2009-204428 A

  By the way, at the time of maintenance of the neutron beam generator, the influence of radiation on the worker becomes a problem. At this time, in the neutron beam generating apparatus, not only the target but also the members around the target including the moderator are activated, and therefore it is preferable to perform work such as target replacement with the target and the peripheral members separated.

  However, in the configuration in which the speed reducer is pulled away from the target to expose the target as in the conventional target recovery device described above, a space for pulling out the speed reducer is required, so the area of the room in which the speed reducer is installed Will become bigger.

Accordingly, the present invention is to reduce the influence of radiation workers receive during maintenance, to provide a neutron beam irradiation equipment for neutron capture therapy can suppress an increase in the area of the room to install a moderator Objective.

In order to solve the above problems, the present invention provides a neutron beam irradiation apparatus that irradiates a neutron beam for neutron capture therapy to irradiate an irradiated object in an irradiation chamber, and accelerates charged particles to generate charged particle beams. Connects the accelerator to be emitted, a neutron beam generator that generates a neutron beam when irradiated with a charged particle beam, and the accelerator and the neutron beam generator, and the charged particle beam emitted from the accelerator is connected to the neutron beam generator. A decelerator that decelerates the neutron beam generated at the neutron beam generator and reduces the energy of the neutron beam irradiated to the irradiated body, and the decelerator is adjacent to the irradiation chamber. The neutron beam generator is movable along the duct to the upstream side of the duct so as to be separated from the moderator .

According to neutron beam irradiation apparatus according to the present invention, by moving the neutron beam generator during maintenance along the duct to the upstream side of the duct, neutrons while avoiding adverse effects from moderator and its peripheral members and activation It becomes possible to perform operations such as generating unit replacement. Moreover, unlike the conventional configuration in which the speed reducer is moved, there is no need to provide a large space for moving the speed reducer in the room. Therefore, according to this neutron beam irradiation apparatus, it is possible to reduce the influence of the radiation received by the worker during maintenance and to suppress an increase in the area of the room where the speed reducer is installed.

The neutron beam irradiation apparatus for neutron capture therapy according to the present invention further includes a radiation shield capable of shielding radiation emitted from the moderator to the neutron beam generator , and the moderator can accommodate the neutron generator. has a receiving chamber, neutron beam generating unit, by moving to the upstream side of the duct along the duct, be taken from the state of being accommodated in the accommodating chamber of the moderator to the outside of the deceleration member is be possible The radiation shield is disposed between the moderator and the neutron beam generator when the neutron beam generator is taken out of the moderator, and the neutron beam generator is accommodated in the moderator housing chamber. In this case , it is preferable to arrange at a position retracted from between the moderator and the neutron beam generation unit .
According to this neutron capture therapy for neutron beam irradiation device, by disposing the ray shield release between the neutron generator of the separated state from the moderator and moderator, effectively radiation from moderator It can be shielded, and the influence of radiation on the operator can be greatly reduced.

In the neutron beam irradiation apparatus for neutron capture therapy according to the present invention, the radiation shield includes a position of the neutron beam generating unit and a moderator when the neutron beam generating unit is taken out of the moderator in the duct extending direction. It is preferable that it is possible to move in a direction intersecting with the duct extending direction .

In the neutron beam irradiation apparatus for neutron capture therapy according to the present invention, the duct preferably has a desorption part capable of changing the duct length by desorption.
According to the neutron beam irradiation apparatus for neutron capture therapy , the neutron beam generation unit can be separated from the moderator by shortening the duct length by removing the desorption unit. In addition, since the movement of the neutron beam generation unit can be realized with a simple structure, it is advantageous in reducing the cost of the apparatus.

In the neutron beam irradiation apparatus for neutron capture therapy according to the present invention, the moderator includes the accelerator and the dashes. Between the accelerator room where the target is placed and the irradiation room where the treatment table is placed. It is preferable to be provided.

  ADVANTAGE OF THE INVENTION According to this invention, while reducing the influence of the radiation which an operator receives at the time of a maintenance, the increase in the area of the room which installs a deceleration body can be suppressed.

It is a top view which shows the core wire irradiation apparatus which concerns on 1st Embodiment. It is a side view which shows the core wire irradiation apparatus of FIG. It is a top view which shows the maintenance state of the core wire irradiation apparatus which concerns on 1st Embodiment. FIG. 4 is a side view showing the core beam irradiation device of FIG. 3. It is a side view which shows an example of a duct support structure. It is a top view which shows the core wire irradiation apparatus which concerns on 2nd Embodiment. It is a side view which shows the core wire irradiation apparatus of FIG. It is a top view which shows the maintenance state of the core wire irradiation apparatus which concerns on 2nd Embodiment. It is a side view which shows the core-line irradiation apparatus of FIG. It is a top view which shows the core wire irradiation apparatus which concerns on 3rd Embodiment. It is a top view which shows the maintenance state of the core wire irradiation apparatus which concerns on 3rd Embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same or an equivalent part, and the overlapping description is abbreviate | omitted. The terms “upstream” and “downstream” mean upstream (cyclotron side) and downstream (patient side) of the emitted charged particle beam and neutron beam, respectively.

[First Embodiment]
As shown in FIGS. 1 and 2, the neutron beam irradiation apparatus 1 according to the first embodiment is an apparatus used for cancer treatment or the like by neutron capture therapy (NCT). The neutron beam irradiation apparatus 1 performs treatment by irradiating the affected part (irradiated body) of the patient on the treatment table 100 provided in the irradiation room Rm with neutron beams.

  The neutron beam irradiation apparatus 1 generates a neutron beam N by causing a charged particle beam P emitted from a cyclotron (accelerator) 2 in the accelerator chamber Ra to collide with a target (neutron beam generation unit) 3. The cyclotron 2 is an accelerator that accelerates charged particles such as protons and emits a proton beam (proton beam) as a charged particle beam P. The charged particle beam P emitted from the cyclotron 2 is sent to the target 3 through the vacuum duct 4.

  The target 3 is a disk-shaped member formed from beryllium Be, for example. The target 3 generates a neutron beam N by being irradiated with the charged particle beam P emitted from the cyclotron 2. Since the target 3 is gradually consumed due to generation of the neutron beam N, periodic replacement is required. The target 3 is detachably attached to the downstream end of the vacuum duct 4 through which the charged particle beam P passes, and is accommodated in the accommodation chamber 5a of the moderator (decelerator) 5 in this state.

The moderator 5 is a device that decelerates the neutron beam N generated at the target 3. The neutron beam N generated from the target 3 is irradiated by the moderator 5 with the energy suppressed to a level suitable for treatment by being moderated. Inside the moderator 5, moderator 5A for decelerating neutrons line N (e.g., iron Fe, aluminum Al, laminate consisting of calcium fluoride CaF _2, etc.) and lead to prevent the leakage of neutrons N A shielding material 5B made of the like is provided. The shielding material 5B shields not only the neutron beam N but also gamma rays generated when the neutron beam N collides with the shielding material 5B. A collimator C for shaping the neutron beam N into a predetermined shape (beam diameter) is provided on the exit side of the neutron beam N in the moderator 5.

  In the building where the neutron beam irradiation apparatus 1 is provided, an accelerator room Ra and an irradiation room Rm are provided. A cyclotron 2 and a part of the vacuum duct 4 are provided in the accelerator chamber Ra. In the irradiation chamber Rm, a target 3, a part of the vacuum duct 4, a moderator 5, and a treatment table 100 are provided. The boundary between the accelerator chamber Ra and the irradiation chamber Rm may be the moderator 5 instead of the vacuum duct 4. In other words, the cyclotron 2, the target 3, the vacuum duct 4, and a part of the moderator 5 may be provided in the accelerator chamber Ra.

  The vacuum duct 4 transports the charged particle beam P emitted from the cyclotron 2 to the target 3. The vacuum duct 4 connects the upstream cyclotron 2 and the downstream target 3. The vacuum duct 4 is connected to decompression means (for example, a vacuum pump) (not shown), and the inside of the vacuum duct 4 is maintained in a vacuum state, thereby suppressing the attenuation and divergence of the charged particle beam P being transported.

  Further, around the vacuum duct 4, a deflecting magnet (not shown) for changing the direction of the charged particle beam P along the vacuum duct 4 and a converging magnet for converging the charged particle beam P that gradually diffuses by transport ( A plurality of (not shown) are arranged. In addition, the shape of the vacuum duct 4 is not restricted to a linear thing, According to the arrangement | positioning condition of an installation, it takes a curve shape and other suitable shapes.

  This vacuum duct 4 has a bellows part (extensible part) 4a that can be freely extended and contracted. As shown in FIGS. 1 and 3, when the bellows portion 4 a of the vacuum duct 4 is contracted, the target 3 moves in a direction away from the moderator 5 (in the direction of the arrow S <b> 1), and between the target 3 and the moderator 5. A space is formed. Moreover, when the bellows part 4a extends, the target 3 moves so as to approach the moderator 5, and the target 3 is housed in the housing chamber 5a. Thus, in the neutron beam irradiation apparatus 1, the target 3 can be separated from the moderator 5 by configuring the target 3 to be movable with respect to the installation floor and the cyclotron 2. Further, according to this configuration, the target 3 can be moved upstream of the vacuum duct 4 along the vacuum duct 4. If the expansion / contraction amount of the bellows part 4a is 1-2 m, for example, the target 3 can be sufficiently separated from the moderator 5.

  Hereinafter, the state in which the target 3 is accommodated in the accommodation chamber 5a of the moderator 5 as shown in FIGS. 1 and 2 is referred to as an irradiable state, and the target 3 is separated from the moderator 5 as shown in FIGS. The state is called a maintenance state.

  As shown in FIGS. 3 and 4, the movable radiation shield 6 is disposed between the target 3 and the moderator 5 in the maintenance state. The radiation shield 6 is composed of two shields 6A and 6B, and the shields 6A and 6B are opened and closed like a sliding door along a rail 7 provided on the floor surface. The shields 6 </ b> A and 6 </ b> B are configured to open and close in a direction intersecting with the vacuum duct 4.

  The shields 6A and 6B are opened to the left and right of the vacuum duct 4 in the irradiation enabled state shown in FIGS. 1 and 2, and are arranged between the target 3 and the moderator 5 in the maintenance state shown in FIGS. Closed state. The opening / closing direction of the shields 6A and 6B is not limited to the left / right direction (horizontal direction) but may be the vertical direction (vertical direction) or the like.

  As shown in FIGS. 2 and 4, the neutron beam irradiation apparatus 1 includes duct pedestals 8 and 9 that support the vacuum duct 4. The duct cradle 8 is a pedestal that supports the upstream side of the bellows portion 4 a, that is, the fixed side, of the vacuum duct 4. On the other hand, the duct pedestal 9 supports the downstream side, that is, the moving side of the vacuum duct 4 from the bellows portion 4a, and a rail 10 is provided at the upper end thereof. The rail 10 supports the downstream side of the vacuum duct 4 movably in the direction of arrow S1 (see FIG. 3).

  Various structures can be adopted as a support structure that movably supports the downstream side of the vacuum duct 4. Here, FIG. 5 is a diagram illustrating an example of a support structure of the vacuum duct 4. In the support structure shown in FIG. 5, a duct base 12 having a horizontally long shape is provided along the vacuum duct 4 instead of the duct base 9 shown in FIG. 2. A rail 13 extending along the vacuum duct 4 is provided at the upper end of the duct cradle 12.

  Roller portions 14 and 15 are attached to the downstream side of the vacuum duct 4, and the roller portions 14 and 15 are configured to be slidable with respect to the rail 13. The roller portions 14 and 15 may be configured to move the downstream side of the vacuum duct 4 to the upstream side by driving a motor, or may be configured to manually move the downstream side of the vacuum duct 4. According to such a support structure, the target 3 can be moved along the vacuum duct 4 to the upstream side of the vacuum duct 4 with a simple configuration.

  Next, a maintenance method for the neutron beam irradiation apparatus 1 according to the first embodiment will be described. When performing maintenance such as target replacement, the neutron beam irradiation apparatus 1 shifts from the irradiation enabled state shown in FIGS. 1 and 2 to the maintenance state shown in FIGS. 3 and 4.

  In the neutron beam irradiation apparatus 1, first, a target moving step is performed in which the target is moved in the direction indicated by the arrow S1 in FIG. In the target moving step, the target 3 is moved away from the moderator 5 by contracting the bellows portion 4a of the vacuum duct 4 as compared with the positional relationship between the target 3 and the moderator 5 in the irradiation enabled state. The target 3 is moved along the vacuum duct 4 to the upstream side of the vacuum duct 4. At this time, since the downstream side of the bellows portion 4a of the vacuum duct 4 is supported by the rail 10 so as to be movable, the target 3 can be smoothly moved with a small amount of work.

  Next, in the neutron beam irradiation apparatus 1, a shield arrangement process shown as an arrow S2 in FIG. 3 is performed. In the shield arrangement step, the movable radiation shield 6 is arranged between the target 3 and the moderator 5 by closing the shields 6A and 6B. Thereby, the radiation emitted from the moderator 5 to the target 3 side can be shielded. Thereafter, in the neutron beam irradiation apparatus 1, a target exchange process for exchanging the target 3 is performed.

  According to the neutron beam irradiation apparatus 1 and the maintenance method described above, the target 3 can be replaced while moving the target 3 away from the moderator 5 during maintenance, thereby avoiding adverse effects from the activated moderator 5 and its peripheral members. Etc. can be performed. Moreover, unlike the conventional configuration in which the moderator 5 is moved, it is not necessary to provide a large space for moving the moderator in the irradiation chamber Rm. Therefore, according to this neutron beam irradiation apparatus 1, while reducing the influence of the radiation which an operator receives at the time of a maintenance, the increase in the area of irradiation chamber Rm can be suppressed.

  Further, in this neutron beam irradiation apparatus 1, a movable radiation shield 6 is arranged between the target 3 and the moderator 5 that are separated from the moderator 5 as compared with the positional relationship between the target 3 and the moderator 5 in the irradiation enabled state. By doing so, the radiation from the moderator 5 can be effectively shielded, and the influence of the radiation received by the operator can be greatly reduced.

  Furthermore, according to this neutron beam irradiation apparatus 1, since the target 3 moves upstream along the vacuum duct 4, when the target 3 moves, the space provided with the vacuum duct 4 can be used effectively. In order to move the target 3, it can suppress that a building enlarges.

  According to this neutron beam irradiation apparatus 1, the target 3 can be separated from the moderator 5 by contracting the bellows part 4 a of the vacuum duct 4, so that the target 3 can be easily moved and the maintenance time can be shortened. Can be planned. This also leads to a reduction in the effects of radiation received by workers.

[Second Embodiment]
As shown in FIG.6 and FIG.7, the neutron beam irradiation apparatus 21 which concerns on 2nd Embodiment replaces the vacuum duct 22 with the bellows part 4a compared with the neutron beam irradiation apparatus 1 which concerns on 1st Embodiment. The point which has the attachment / detachment part 23 differs.

  Specifically, the vacuum duct 22 of the neutron beam irradiation apparatus 21 has a detachable part 23 that can be detached. The detachable part 23 is a member that constitutes a part of the vacuum duct 22 in the length direction.

  Here, FIG.6 and FIG.7 is the top view and side view which show the neutron beam irradiation apparatus 21 of the irradiation possible state. 8 and 9 are a plan view and a side view showing the neutron beam irradiation apparatus 21 in the maintenance state. 6 and 7, the detachable portion 23 is attached to the vacuum duct 22 by bolting the flange portions 23a at both ends to the flange portion 22a on the main body side.

  On the other hand, in the maintenance state shown in FIGS. 8 and 9, the detachable portion 23 is removed by releasing the connection of the flange portions 22a and 23a. Thereafter, by connecting the flange portions 22 a to each other, the duct length of the vacuum duct 22 is shortened, and the target 3 is moved away from the moderator 5. The length of the desorption part 23 is preferably, for example, 1 to 2 m.

  Next, a maintenance method for the neutron beam irradiation apparatus 21 according to the second embodiment will be described. When performing maintenance such as target replacement, the neutron beam irradiation apparatus 21 shifts from the irradiation enabled state shown in FIGS. 6 and 7 to the maintenance state shown in FIGS. 8 and 9.

  In the neutron beam irradiation apparatus 21, first, a target moving process is performed in which the target 3 is moved away from the moderator 5. The target moving process according to the second embodiment includes an attaching / detaching portion removing process shown as an arrow S11 in FIG. 8 and a duct connecting process shown as an arrow S12 in FIGS.

  In the detaching part removing step, the detaching part 23 is removed from the vacuum duct 22 by releasing the connection of the flange parts 22a and 23a. Thereafter, in the duct connecting step, the downstream side of the vacuum duct 22 is moved to the upstream side, and the downstream side and upstream side flange portions 22a are connected. At this time, since the downstream side of the vacuum duct 22 is movably supported by the rail 10 of the duct cradle 9, it can be moved smoothly with a small amount of work. The target 3 attached to the downstream end of the vacuum duct 22 is moved away from the moderator 5 by performing the above-described detachment part removal process and duct connection process.

  Next, in the neutron beam irradiation apparatus 21, a shield arrangement step shown as an arrow S13 in FIG. 8 is performed. In the shield arrangement step, the movable radiation shield 6 is arranged between the target 3 and the moderator 5 by closing the shields 6A and 6B. Thereby, radiation can be shielded between the moderator 5 and the target 3. Thereafter, in the neutron beam irradiation apparatus 21, a target exchange process for exchanging the target 3 is performed.

  According to the neutron beam irradiation apparatus 21 and the maintenance method thereof according to the second embodiment described above, the target 3 is separated from the moderator 5 by shortening the duct length of the vacuum duct 22 by removing the desorption part 23. Can do. In addition, since the movement of the target 3 can be realized with a simple structure, it is advantageous in reducing the cost of the apparatus.

[Third Embodiment]
As shown in FIG.10 and FIG.11, the neutron beam irradiation apparatus 31 which concerns on 3rd Embodiment compared with the neutron beam irradiation apparatus 1 which concerns on 1st Embodiment, instead of the bellows part 4a, a bending bellows part ( The difference is that it has a stretchable part 32a.

  Specifically, the vacuum duct 32 of the neutron beam irradiation apparatus 31 has a bent bellows portion 32a configured to be bent in the left-right direction. The bending direction of the bent bellows portion 32a is not limited to the left-right direction (horizontal direction), and may be bent in the up-down direction (vertical direction). The bent bellows portion 32a is bent by shrinking the inner side and extending the outer side with respect to the bending direction. In the vacuum duct 32, the downstream side of the vacuum duct 32 can be moved with the bent bellows portion 32a as the bending center.

  Further, the moderator 5A of the moderator 5 of the neutron beam irradiation device 31 is formed with a notch 5b for allowing the downstream side of the vacuum duct 32 to pass therethrough.

  Next, a maintenance method for the neutron beam irradiation apparatus 31 according to the third embodiment will be described. When performing maintenance such as target replacement, the neutron beam irradiation apparatus 31 shifts from the irradiation enabled state shown in FIG. 10 to the maintenance state shown in FIG.

  In the neutron beam irradiation apparatus 31, first, a target moving process is performed in which the target is moved in the direction indicated by the arrow S <b> 21 in FIG. 11. In the target moving step, the target 3 is moved away from the moderator 5 by bending the downstream side of the vacuum duct 32 around the bent bellows portion 32a as compared with the positional relationship between the target 3 and the moderator 5 in the irradiation enabled state. Let

  Next, in the neutron beam irradiation apparatus 31, a shield arrangement process shown as an arrow S22 in FIG. 11 is performed. In the shield arrangement step, the movable radiation shield 6 is arranged between the target 3 and the moderator 5 by closing the shields 6A and 6B. Thereby, the radiation emitted from the moderator 5 to the target 3 side can be shielded. Thereafter, in the neutron beam irradiation apparatus 31, a target exchange process for exchanging the target 3 is performed.

  According to the neutron beam irradiation apparatus 31 and the maintenance method thereof according to the third embodiment described above, the target 3 is removed from the moderator 5 by bending the downstream side of the vacuum duct 32 around the bent bellows portion 32a during maintenance. It can be moved apart. Moreover, since the length of the bending bellows part 32a can be shortened compared with the neutron beam irradiation apparatus 1 which concerns on 1st Embodiment, the deformation | transformation site | part where durability tends to fall can be decreased.

  The present invention is not limited to the embodiment described above.

  For example, the accelerator that emits the charged particle beam P is not limited to a cyclotron, and a synchrotron, a synchrocyclotron, a linear accelerator, or the like may be used. Further, the expansion and contraction of the vacuum duct 4 and the movement of the movable radiation shield 6 are not necessarily performed manually by an operator, and may be configured to be remotely operated or automatically controlled by providing an actuator or the like.

  The radiation shield 6 is not necessarily composed of the two shields 6A and 6B, may be composed of one or three or more shields, and the movement mode is limited to the sliding door shape. I can't.

  Furthermore, the expansion / contraction part of the vacuum duct 4 is not limited to the bellows part 4a. For example, instead of the bellows portion 4a, a cylindrical slider portion that can be expanded and contracted by sliding inside or outside of a double-structured tube may be employed.

DESCRIPTION OF SYMBOLS 1, 21, 31 ... Neutron beam irradiation apparatus 2 ... Cyclotron (accelerator) 3 ... Target (neutron beam generating part) 4 , 22, 32 ... Vacuum duct 4a ... Bellows part (expandable part) 5 ... Moderator (decelerator) 5A ... Moderator 5B ... Shielding material 5a ... Storage chamber 6 ... Radiation shield 6A, 6B ... Shield 7 ... Rail 8, 9 ... Duct base 10 ... Rail 22a, 23a ... Flange 23 ... Detachment 32a ... Bent bellows ( C ... Collimator N ... Neutron beam P ... Charged particle beam Ra ... Accelerator chamber Rm ... Irradiation chamber

Claims (5)

A neutron irradiation apparatus for neutron capture therapy that irradiates an irradiated object in an irradiation chamber with a neutron beam,
An accelerator that accelerates charged particles and emits charged particle beams;
A neutron beam generator that generates a neutron beam by being irradiated with the charged particle beam;
A duct for connecting the accelerator and the neutron beam generator, and transporting the charged particle beam emitted from the accelerator to the neutron beam generator,
A moderator that reduces the energy of the neutron beam irradiated to the irradiated body by decelerating the neutron beam generated by the neutron beam generating unit;
With
The moderator is a boundary between the irradiation room and another adjacent room,
The neutron beam generation unit is capable of moving along the duct to the upstream side of the duct so as to be separated from the moderator . A radiation shield capable of shielding radiation emitted from the moderator to the neutron beam generation unit side;
The speed reducer has a storage chamber capable of storing the neutron beam generation unit,
The neutron beam generating part can be taken out of the speed reducer from the state accommodated in the accommodating chamber of the speed reducer by moving to the upstream side of the duct along the duct,
The radiation shield is disposed between the moderator and the neutron beam generator when the neutron beam generator is taken out of the moderator, and the neutron beam generator is disposed on the moderator. The neutron beam irradiation apparatus for neutron capture therapy according to claim 1, wherein the neutron beam irradiation apparatus for neutron capture therapy according to claim 1, wherein the neutron beam irradiation apparatus is disposed at a position retracted from between the moderator and the neutron beam generator when housed in the housing chamber. The radiation shield is
In the extending direction of the duct, provided between the position of the neutron beam generation unit and the moderator when the neutron beam generation unit is taken out of the moderator,
The neutron beam irradiation apparatus for neutron capture therapy according to claim 2, wherein the neutron irradiation apparatus is capable of moving in a direction crossing an extending direction of the duct. The said duct has a desorption part which can change a duct length by desorption. The neutron beam irradiation apparatus for neutron capture therapy as described in any one of Claims 1-3 characterized by the above-mentioned. The said deceleration body is provided in the boundary of the accelerator chamber in which the said accelerator and the said duct are provided, and the said irradiation chamber in which the treatment table in which the said to-be-irradiated body is mounted is provided. 5. The neutron beam irradiation apparatus for neutron capture therapy according to any one of 4 above.

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