JP6938627B2 - Neutron capture therapy system - Google Patents

Description

The present invention relates to a neutron capture therapy system.

In a neutron capture therapy system that irradiates a patient who is an irradiated object with a neutron beam, a neutron beam detector for measuring the neutron beam is used. For example, Patent Document 1 shows a configuration in which a scintillator of a neutron beam detector is provided in a collimator for shaping a neutron beam irradiation field. In a neutron beam detector, the dose of a neutron beam can be measured by converting radiation into light in a scintillator, propagating the light through an optical fiber, and detecting it in a subsequent photodetector.

Japanese Unexamined Patent Publication No. 2003-260490

Attempting to place the above neutron detector in an irradiation chamber that irradiates a patient with neutrons causes the following problems. First, since the dose of radiation such as neutron rays is high in the irradiation chamber, if a photodetector provided after the scintillator is placed in the irradiation chamber, the photodetector may deteriorate. On the other hand, if the photodetector is arranged outside the irradiation room in order to prevent deterioration of the photodetector, the optical fiber connecting the scintillator and the photodetector becomes long, which may cause a problem in handleability.

The present invention has been made in view of the above, and an object of the present invention is to provide a neutron capture therapy system including a neutron beam detector with improved handleability while suppressing radiation deterioration of the photodetector.

In order to achieve the above object, the neutron capture therapy system according to one embodiment of the present invention is a neutron capture therapy system that irradiates an irradiated body with neutron rays, and blocks the radiation of the neutron rays from indoors to outdoors. The irradiation chamber surrounded by the shielding wall and irradiating the irradiated body with the neutron beam, the neutron beam generating unit that generates the neutron beam, and the neutron beam generated by the neutron beam generating unit are irradiated. It has a neutron beam irradiation unit that irradiates a room and a neutron beam detector that detects the dose of the neutron beam. The optical detector has an optical detector that converts an electric signal, an optical fiber that propagates the light from the scintillator to the optical detector, and a shielding portion that covers the optical detector and shields radiation. And the shielding portion is provided in the irradiation chamber or the shielding wall.

According to the above-mentioned neutron capture therapy system, since the photodetector and the shielding portion of the neutron beam detector are provided in the irradiation chamber or the shielding wall constituting the irradiation chamber, the optical fiber connected to the photodetector is provided. It can be shortened and can be handled more easily as a neutron beam detector. In addition, the periphery of the photodetector is covered with a shielding portion. Therefore, even when the photodetector is provided in the irradiation chamber or in the shielding wall constituting the irradiation chamber, the radiation deterioration of the photodetector can be prevented by the shielding portion. Therefore, in the above-mentioned neutron capture therapy system, the handleability as the neutron beam detector 4 is improved while suppressing the radiation deterioration of the photodetector.

Here, the neutron beam detector is provided outside the irradiation chamber and has a signal processing unit that processes an electric signal and an electric signal cable that transmits an electric signal emitted from the photodetector to the signal processing unit. And, the optical fiber can be shorter than the electrical signal cable.

As described above, by making the optical fiber shorter than the electric signal cable, it is possible to reduce the risk of damage to the optical fiber, which is considered to have a higher risk of breakage than the electric signal cable.

In addition, the photodetector and the shielding portion may be installed on a treatment table on which the irradiated body is placed.

When the photodetector and the shielding portion are installed on the treatment table as described above, the distance between the photodetector and the scintillator can be shortened, so that the optical fiber can be shortened. Therefore, the handleability of the neutron detection unit can be improved and damage to the optical fiber can be prevented.

Further, the photodetector and the shielding portion are fixed in the irradiation chamber or in the shielding wall constituting the irradiation chamber, and the treatment table on which the irradiated object is placed is inside and outside the irradiation chamber. The optical fiber may be in a mode that is movable between the optical fibers and has a length that can follow the moving range of the treatment table.

With the above configuration, even if the treatment table moves, the optical fiber follows and the connection between the photodetector fixed in the irradiation room or the shielding wall and the scintillator is maintained, so that the treatment can be performed. It is not necessary to remove the scintillator and the optical fiber according to the movement of the table, and the workability is improved.

According to the present invention, there is provided a neutron capture therapy system including a neutron beam detector with improved handleability while suppressing radiation deterioration of the photodetector.

It is a top view which shows typically the neutron capture therapy system. It is an enlarged plan view around the irradiation chamber. It is a figure explaining the neutron beam detector. It is sectional drawing explaining the light detection part of a neutron beam detector. It is a figure explaining the 1st modification. It is a figure explaining the 2nd modification. It is a figure explaining the 3rd modification.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate description will be omitted.

The neutron capture therapy system will be described with reference to FIG. The neutron capture therapy system according to the present embodiment is a system for performing cancer treatment using Boron Neutron Capture Therapy (BNCT). Boron neutron capture therapy is to treat cancer by irradiating a neutron beam at the position where boron is accumulated in a patient who has been administered a substance that accumulates in cancer cells (for example, boron (10B)). ..

The neutron capture therapy system 1 has an irradiation chamber 2 for irradiating a patient P (irradiated body) restrained by the treatment table 3 with a neutron beam N to treat the patient P with cancer.

Preparatory work such as restraining patient P on the treatment table 3 is performed in a preparation room (not shown) outside the irradiation room 2, and the treatment table 3 on which patient P is restrained is moved from the preparation room to the irradiation room 2. .. Further, the neutron capture therapy system 1 includes a neutron beam generation unit 10 that generates a neutron beam N for treatment, and a neutron beam irradiation unit that irradiates the patient P restrained by the treatment table 3 in the irradiation chamber 2 with the neutron beam N. 20 and. The irradiation chamber 2 is covered with a concrete shielding wall W1 that blocks the radiation of neutron rays from the room to the outside, but a passage and a door 25 may be provided for a patient, a worker, or the like to pass through. .. The door 25 shown in FIG. 1 is provided between the preparation room and the irradiation room 2.

The neutron beam generation unit 10 scans the accelerator 11 that accelerates the charged particles and emits the charged particle beam L, the beam transport path 12 that transports the charged particle beam L emitted by the accelerator 11, and the charged particle beam L. A charged particle beam scanning unit 13 that controls the irradiation position of the charged particle beam L with respect to the target 8, a target 8 that causes a nuclear reaction when the charged particle beam L is irradiated to generate a neutron beam N, and a charged particle beam. A current monitor 16 for measuring the current of L is provided. The accelerator 11 and the beam transport path 12 are arranged in a room of a charged particle beam generation chamber 14 having a substantially rectangular shape, and the charged particle beam generation chamber 14 is a space covered with a concrete shielding wall W. .. The charged particle beam generation chamber 14 may be provided with a passage and a door 27 for a worker for maintenance to pass through. The charged particle beam generation chamber 14 is not limited to a substantially rectangular shape, and may have another shape. For example, when the path from the accelerator to the target is L-shaped, the charged particle beam generation chamber 14 may also be L-shaped. Further, the charged particle beam scanning unit 13 controls, for example, the irradiation position of the charged particle beam L with respect to the target 8, and the current monitor 16 measures the current of the charged particle beam L irradiated to the target 8.

The accelerator 11 accelerates a charged particle to generate a charged particle beam L. In this embodiment, a cyclotron is adopted as the accelerator 11. As the accelerator 11, instead of the cyclotron, another accelerator such as a synchrotron, a synchrocyclotron, or a linac may be used.

One end (upstream end) of the beam transport path 12 is connected to the accelerator 11. The beam transport path 12 includes a beam adjusting unit 15 that adjusts the charged particle beam L. The beam adjusting unit 15 has a horizontal steering electromagnet and a horizontal and vertical steering electromagnet that adjust the axis of the charged particle beam L, a quadrupole electromagnet that suppresses the divergence of the charged particle beam L, and a four-way shape that shapes the charged particle beam L. It has a slit and the like. The beam transport path 12 may have a function of transporting the charged particle beam L, and the beam adjusting unit 15 may not be provided.

The charged particle beam L transported by the beam transport path 12 is irradiated to the target 8 by controlling the irradiation position by the charged particle beam scanning unit 13. The charged particle beam scanning unit 13 may be omitted, and the same portion of the target 8 may always be irradiated with the charged particle beam L.

The target 8 generates a neutron beam N by being irradiated with the charged particle beam L. The target 8 is made of, for example, beryllium (Be), lithium (Li), tantalum (Ta), or tungsten (W), and has a plate shape. The target 8 is not limited to a plate shape, and may be, for example, a liquid (liquid metal). The neutron beam N generated by the target 8 is irradiated toward the patient P in the irradiation chamber 2 by the neutron beam irradiation unit 20.

The neutron beam irradiation unit 20 includes a moderator that slows down the neutron beam N emitted from the target 8 and a shield that shields radiation such as the neutron beam N and gamma rays. The moderator is composed of the moderator and the shield. The moderator has, for example, a laminated structure composed of a plurality of different materials, and the moderator material is appropriately selected depending on various conditions such as the energy of the charged particle beam L. Specifically, for example, when the output from the accelerator 11 is a proton beam of 30 MeV and a beryllium target is used as the target 8, the moderator material can be lead, iron, aluminum or calcium fluoride.

The shield is provided so as to surround the moderator, and has a function of shielding the neutron beam N and radiation such as gamma rays generated by the generation of the neutron beam N from being emitted to the outside of the shield. Further, a wall body 21 forming a part of the side wall surface of the irradiation chamber 2 is provided between the irradiation chamber 2 and the shield. A collimator 31 for defining the irradiation field of the neutron beam N is fixed to the wall body 21 at the output port of the neutron beam N. The collimator 31 may be attached to the treatment table 3 described later.

In the above neutron beam irradiation unit 20, the charged particle beam L is irradiated to the target 8, and the target 8 generates the neutron beam N accordingly. The neutron beam N generated by the target 8 is decelerated while passing through the moderator, and the neutron beam N emitted from the moderator passes through the collimator 31 and irradiates the patient P on the treatment table 3. NS. Here, as the neutron beam N, a thermal neutron beam having a relatively low energy or an extrathermal neutron beam can be used.

The treatment table 3 functions as a mounting table used in neutron capture therapy, and can move between the preparation room (not shown) and the irradiation room 2 with the patient P placed on it. The treatment table 3 is provided on the base portion and has a top plate on which the patient P is placed and a drive unit for moving the top plate relative to the base portion. If the base portion can be moved with respect to the floor, it can be easily moved between the irradiation chamber 2 and the preparation chamber.

Further, the neutron capture therapy system 1 has a neutron beam detector 4. The neutron beam detector 4 is used, for example, to measure the dose of the neutron beam in the vicinity of the irradiation target position when irradiating the patient P with the neutron beam. The neutron beam detector 4 is also used during system inspection work and the like. FIG. 2 schematically shows the periphery of the irradiation chamber 2 of the neutron capture therapy system 1. As shown in FIG. 2, the neutron beam detector 4 includes a scintillator 41, an optical fiber 42, an optical detection unit 43, a cable 44, and a signal processing unit 45. Further, as shown in FIG. 3, the light detection unit 43 includes a photodetector 46, a first shielding unit 47, and a second shielding unit 48.

The scintillator 41 is attached to the patient or the phantom at or near the placement position of the patient P on the treatment table 3. Further, the light detection unit 43 is arranged in the irradiation chamber 2 or on the shielding wall W1 constituting the irradiation chamber 2. In the present embodiment, as shown in FIG. 2, the light detection unit 43 and the cable 44 are provided in a place different from the inside of the irradiation chamber 2, that is, inside the shielding wall W1 surrounding the irradiation chamber 2 or outside the irradiation chamber 2. Further, the signal processing unit 45, which is operated by an operator or the like, is provided outside the irradiation chamber 2. FIG. 2 shows an example in which the light detection unit 43 and the cable 44 are provided inside the shielding wall W1, and the signal processing unit 45 is provided outside the shielding wall W1.

The scintillator 41 is a phosphor that converts incident radiation (neutron rays N, gamma rays) into light. In the scintillator 41, the internal crystal is excited according to the dose of the incident radiation, and scintillation light is generated. The scintillator 41 has, for example, a cubic shape having a side of about 0.2 mm. The scintillator 41 emits light when neutron rays N or gamma rays are incident on the scintillator 41. The scintillator 41 ^may employ 6 Li glass scintillator, LiCAF ^{scintillator,} a plastic scintillator coated with 6 ^LiF, a 6 LiF / ZnS scintillators like.

The scintillator 41 can be used to detect only the neutron beam N. However, gamma rays are generated when the neutron beam N is generated or when the neutron beam N is decelerated by the moderator. The scintillator 41 may also detect this gamma ray.

The optical fiber 42 functions as a light guide for propagating the light generated by the scintillator 41. The length of the optical fiber 42 is, for example, about 10 m. The outer diameter, core diameter, etc. of the optical fiber 42 are not particularly limited as long as they can function as a light guide. When performing neutron capture therapy, the treatment table 3 is promptly moved from the irradiation room 2 to the preparation room after irradiating the patient with the neutron beam N. Therefore, the scintillator 41 attached to the patient or phantom on the treatment table 3 moves to the preparation room together with the treatment table 3 as it is. On the other hand, the light detection unit 43 is fixed in the shielding wall W1. Therefore, the length of the optical fiber 42 can always connect between the scintillator 41 and the photodetector 43 (photodetector 46) following the movement of the treatment table 3 even when the treatment table 3 moves. It is said to be the length.

Further, the optical fiber 42 may be attached to, for example, a take-up reel having an automatic take-up function so that the optical fiber 42 does not interfere with the work performed in the irradiation chamber 2 such as the movement of the treatment table 3. .. When the optical fiber 42 is attached to the take-up reel, for example, after removing the scintillator 41 from the patient or phantom on the treatment table 3, the optical fiber 42 can be automatically accommodated in the take-up reel. Therefore, the winding work of the optical fiber 42 and the like becomes unnecessary, and the exposure dose of the operator can be reduced.

The photodetector 43 has a function of detecting the light transmitted through the optical fiber 42. As shown in FIG. 3, the light detection unit 43 includes a photodetector 46, a first shielding unit 47, and a second shielding unit 48. As the photodetector 46, various photodetectors such as a photomultiplier tube and a phototube can be adopted. The photodetector 46 outputs an electric signal (detection signal) at the time of light detection. The first shielding portion 47 and the second shielding portion 48 are provided around the photodetector 46, and the details will be described later.

The cable 44 is composed of a high voltage cable and an electric signal cable. The high-voltage cable has a function of supplying a current to the photodetector 46 of the photodetector 43. Further, the electric signal cable has a function of transmitting an electric signal output from the photodetector 46 to the signal processing unit 45. In the present embodiment, these plurality of cables are collectively shown as the cable 44, but the two cables may be grouped together or may have a shape that can be handled individually.

The signal processing unit 45 has a function of receiving an electric signal transmitted via the signal cable included in the cable 44 and calculating the dose of the neutron beam detected by the scintillator 41 from the electric signal. The signal processing unit 45 can be configured as an electronic control unit composed of a CPU, ROM, RAM, and the like.

The light detection unit 43 will be described with reference to FIGS. 3 and 4. FIG. 3 is a diagram schematically showing the light detection unit 43, and FIG. 4 is a diagram schematically showing a cross section of the light detection unit 43. In the light detection unit 43, a first shielding unit 47 and a second shielding unit 48 are provided around the photodetector 46. The first shielding portion 47 and the second shielding portion 48 cover the photodetector 46 with a so-called two-layer structure. That is, the outside is the first shielding portion 47, and the second shielding portion 48 is provided inside the first shielding portion 47.

As shown in FIG. 4, the first shielding portion 47 except for the portion of the photodetector 46 to which the optical fiber 42 and the cable 44 are attached and the opening for wiring for connecting the optical fiber 42 and the cable 44 to the photodetector 46. And covered by the second shield 48. However, the neutron beam basically scatters from the collimator 31 into the irradiation chamber 2. Therefore, when the mounting position of the photodetector 46 is determined (the arrangement of the photodetector 46 at the time of neutron irradiation is determined), the first shielding portion 47 and the first shielding portion 47 and only on the side irradiated with the neutron beam. A second shielding portion 48 may be provided. Therefore, for example, when the surface of the photodetector 46 connecting the optical fiber 42 is the surface receiving the neutron beam, a region where the photodetector 46 is exposed is formed on the surface side connecting the cable 44. You may be.

The first shielding unit 47 has a function of shielding neutron rays. As the first shielding portion 47, for example, polyethylene (PE), LiF-containing polyethylene, or the like can be used. However, the material of the first shielding portion 47 is not limited to the above, and a known material having a neutron beam shielding function can be used. The thickness of the first shielding portion 47 is appropriately changed depending on the material, but for example, when LiF-containing polyethylene is used, it can be about 1 cm to 3 cm.

The second shielding unit 48 has a function of shielding gamma rays. As the second shielding portion 48, for example, lead (Pb) or the like can be used. However, the material of the second shielding portion 48 is not limited to the above, and a known material having a gamma ray shielding function can be used. The thickness of the second shielding portion 48 is appropriately changed depending on the material, but for example, when lead is used, it can be about 2 cm.

In the light detection unit 43 of the present embodiment, the second shielding unit 48 is inside the first shielding unit 47. When the neutron beam is shielded by the first shielding unit 47, gamma rays are secondarily emitted. The gamma rays emitted by the first shielding portion 47 can also be shielded by the second shielding portion 48 arranged inside the first shielding portion 47. Therefore, according to the above configuration, radiation shielding can be performed more preferably.

Instead of the two-layer structure of the first shielding portion 47 and the second shielding portion 48, for example, a shielding portion having a single-layer structure made of a material having a shielding ability against neutron rays and gamma rays such as concrete is used. May be good. However, as described in the present embodiment, the combination of the first shielding unit 47 for neutron beam shielding and the second shielding unit 48 for gamma ray shielding is a smaller shielding unit. Radiation (neutron rays and gamma rays) can be suitably shielded. The shielding portion may be made of a material capable of shielding at least one of a neutron beam and a gamma ray.

As described above, in the neutron capture therapy system according to the present embodiment, in the neutron beam detector 4 that detects the neutron beam, the photodetector 43 including the photodetector 46 shields the inside of the irradiation chamber 2 or the irradiation chamber 2. It is provided in the wall W1. Therefore, in the neutron beam detector 4, the handleability is improved while suppressing the radiation deterioration of the photodetector 46.

Conventionally, in order to prevent radiation deterioration of the photodetector 46, the photodetector 46 is arranged in a preparation room or the like outside the irradiation chamber 2, but in this case, the photodetector 46 and the scintillator 41 are connected. Since the optical fiber 42 becomes long, there is a possibility that the work may be hindered if the handling is not appropriate. In addition, it was considered that the longer the optical fiber, the higher the risk of breakage during work.

On the other hand, in the neutron beam detector 4 according to the present embodiment, since the photodetector 46 is provided in the irradiation chamber 2 or in the shielding wall W1 constituting the irradiation chamber 2, it is connected to the photodetector 46. The optical fiber 42 to be formed can be shortened, and the handleability as the neutron beam detector 4 is improved. On the other hand, in the photodetector 43, the periphery of the photodetector 46 is covered with a shield (first shield 47 and second shield 48). Therefore, even when the photodetector 46 of the neutron beam detector 4 is provided in the irradiation chamber 2 or in the shielding wall W1 constituting the irradiation chamber 2, the shielding portion prevents the radiation deterioration of the photodetector 46. Therefore, the handleability as the neutron beam detector 4 is improved while suppressing the radiation deterioration of the photodetector 46.

When the photodetector 46 and the shielding portion (the first shielding portion 47 and the second shielding portion 48) are housed in the shielding wall W1 constituting the irradiation chamber 2, light detection is performed as in the above embodiment. Radiation deterioration of the vessel 46 is further suppressed.

Further, in the above embodiment, since the light detection unit 43 including the photodetector 46 can be arranged closer to the treatment table 3 as compared with the conventional configuration, the length of the optical fiber 42 is set in the cable 44. It is possible to make it shorter than the electric signal cable of. By making the length of the optical fiber 42 shorter than that of the electric signal cable in this way, it is possible to reduce the risk of damage to the optical fiber 42, which is considered to have a higher risk of breakage than the electric signal cable.

Further, in the above embodiment, the photodetector 46 and the light detection unit 43 including the shielding unit are fixed in the irradiation chamber 2 or the shielding wall W1, and the treatment table 3 is inside and outside the irradiation chamber 2 (for example,). It is movable to and from the preparation room), and the optical fiber 42 has a length that can follow the moving range of the treatment table 3. With such a configuration, even if the treatment table 3 moves, the optical fiber 42 follows and the connection between the photodetector 46 and the scintillator 41 is maintained, so that the connection between the photodetector 46 and the scintillator 41 is maintained. It is not necessary to remove the scintillator 41 and the optical fiber 42, which improves workability.

(Modification example)
Next, a modified example of the neutron beam detector 4 in the neutron capture therapy system 1 according to the present embodiment will be described.

FIG. 5 is a diagram illustrating an installation state of the neutron beam detector 4A according to the first modification. In the neutron beam detector 4A shown in FIG. 5, the arrangement of the photodetector 43 is different from that of the neutron beam detector 4. That is, the light detection unit 43 is arranged not in the shielding wall W1 but in the treatment table 3.

In the neutron beam detector 4A, since the photodetector 43 is provided on the treatment table 3, the distance between the scintillator 41 attached to the patient P or the phantom on the treatment table 3 and the treatment table 3 can be shortened. Further, even when the treatment table 3 is moved to the preparation room, for example, it is possible to prevent the distance between the photodetector 46 and the scintillator 41 from becoming long. Therefore, the length of the optical fiber 42 can be shortened as compared with the neutron beam detector 4.

The photodetector 43 including the photodetector 46, the first shield 47, and the second shield 48 may be attached to any of the base, drive, and top plate of the treatment table 3. For example, if the position is the same as that of the patient placed on the top plate, such as the back of the top plate, the photodetector 43 (photodetector 46) and the scintillator 41 are placed even when the treatment table 3 is operated. The optical fiber 42 can be designed to be shorter because the distance between the optical fiber 42 and the optical fiber 42 does not change.

When the photodetector 43 is arranged on the treatment table 3 like the neutron detector 4A, the cable 44 connected to the photodetector 46 of the photodetector 43 is compared with the neutron detector 4. become longer. In the example shown in FIG. 5, the cable 44 connected to the signal processing unit 45 is housed in the shielding wall W1, and a part of the cable 44 extends from the shielding wall W1 and is connected to the photodetector 46 of the photodetector unit 43. .. Here, when the treatment table 3 moves to the preparation room or the like, the light detection unit 43 moves together with the treatment table 3, so that the cable 44, not the optical fiber 42, needs to follow the movement of the treatment table 3. Therefore, the length of the cable 44 is set so that the light detection unit 43 and the signal processing unit 45 can be connected even when the treatment table 3 moves. At this time, the cable 44 may be attached to, for example, a take-up reel having an automatic take-up function so that the cable 44 does not interfere with the work performed in the irradiation chamber 2 such as the movement of the treatment table 3.

When the photodetector 43 is arranged on the treatment table 3 as in the neutron detector 4A, the radiation dose received by the photodetector 43 is higher than that when the photodetector 43 is housed in the shielding wall W1. growing. Therefore, the thickness of the first shielding portion 47 and the second shielding portion 48 of the photodetector 43 is larger than the thickness of the first shielding portion 47 and the second shielding portion 48 of the light detection unit 43 in the neutron beam detector 4. can do.

FIG. 6 shows an example in which the photodetector 43 is housed in the storage case 50 as a second modification. The light detection unit 43 may be housed in the storage case 50 in this way to improve portability.

Since the radiation is shielded by the first shielding portion 47 and the second shielding portion 48 of the light detection unit 43, the material of the storage case 50 is not particularly limited.

Further, the shape and the like of the storage case 50 are not particularly limited, and for example, the storage case 50 may have a handle or the like for carrying on the surface thereof. Further, the volume of the storage case 50 can be changed as appropriate. Therefore, an amplifier for amplifying the electric signal output from the photodetector 46 is housed in the storage case 50, and the amplified electric signal output from the amplifier is transmitted by the electric signal cable of the cable 44. It may be configured. Further, when the amplifier or the like is housed in the storage case 50, the storage case 50 may be provided with a vent or the like for the purpose of heat dissipation or the like.

Further, as shown in FIG. 6, a connector 51 is provided in the storage case, and the cable 44 connecting the light detection unit 43 and the signal processing unit 45 is connected to the cable 44A in the front stage of the connector 51 and the cable 44 in the rear stage of the connector 51. It may be configured to be divided into the cable 44B. With such a configuration, the portability of the cable 44A, the photodetector 43, the optical fiber 42, and the scintillator 41 in front of the connector 51 can be improved.

In this way, the shape, configuration, and the like of the storage case 50 can be appropriately changed for carrying the light detection unit 43.

FIG. 7 is a diagram for explaining the shape of the shielding portion as a third modification. FIG. 7 shows a cross-sectional view when the photodetector 46 has a cylindrical shape (see FIG. 3). In FIG. 7A, the cross section of the inner peripheral surface of the second shielding portion 48 is circular and the cross section of the outer peripheral surface is circular so as to cover the outer circumference of the light detector 46 with respect to the light detector 46 having a circular cross section. Is provided so as to have a quadrangular shape, and the first shielding portion 47 on the outer side thereof is also provided so that the cross section of the outer peripheral surface has a quadrangular shape. FIG. 7B shows an example in which the cross section of the inner peripheral surface of the second shielding portion 48 in FIG. 7A is a quadrangular shape. FIG. 7C shows an example in which the cross sections of the outer peripheral surfaces of both the second shielding portion 48 and the first shielding portion 47 are circular. Further, FIG. 7D shows an example in which the cross section of the outer peripheral surface of the second shielding portion 48 is circular, whereas the cross section of the outer peripheral surface of the outer first shielding portion 47 is quadrangular. There is. As shown in FIGS. 7 (a) to 7 (d), the shapes of the first shielding portion 47 and the second shielding portion 48 can be appropriately changed. Further, as shown in FIG. 7B, a gap may be formed between the photodetector 46 and the second shielding portion 48. Further, a gap may be formed between the first shielding portion 47 and the second shielding portion 48. Further, in the above embodiment, the case where the photodetector 46 has a cylindrical shape has been described, but the shape of the photodetector 46 can be changed as appropriate. Further, the shapes of the first shielding portion 47 and the second shielding portion 48 may be changed according to the shape of the photodetector 46.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments.

For example, in the above embodiment, the case where the light detection unit 43 is arranged inside the shielding wall W1 and the case where the light detection unit 43 is arranged on the treatment table 3 has been described, but the light detection unit 43 is the same as the treatment table 3 in the irradiation chamber 2. May be placed in different positions. Further, since the ceiling and floor of the irradiation chamber 2 are also composed of the shielding wall W1, the light detection unit 43 may be arranged on the shielding wall W1 of the ceiling or floor of the irradiation chamber 2. The lengths of the optical fiber 42 and the cable 44 are appropriately changed according to the arrangement of the photodetector 43.

Further, in the present embodiment, the case where the light detection unit 43 of the neutron beam detector 4 is fixed at a predetermined position (inside the shielding wall W1 or the treatment table 3) to detect the neutron beam has been described. In the line detector 4, the arrangement of the light detection unit 43 may be changed each time a neutron beam is detected. In that case, the lengths of the optical fiber 42 and the cable 44 are appropriately changed in consideration of the movement of the photodetector 43. However, if the arrangement of the photodetector 43 at the time of neutron beam detection is fixed in advance, the lengths of the optical fiber 42 and the cable 44 can be set shorter while considering the movement of the treatment table 3 and the like. , The handleability can be improved and the risk of breakage can be reduced.

1 ... Neutron capture therapy system, 2 ... Irradiation room, 3 ... Treatment table, 4 ... Neutron beam detector, 10 ... Neutron beam generator, 20 ... Neutron beam irradiation unit, 41 ... Scintillator, 42 ... Optical fiber, 43 ... Light Detection unit, 44 ... cable, 45 ... signal processing unit, 46 ... photodetector, 47 ... first shielding unit, 48 ... second shielding unit, W1 ... shielding wall.

Claims (4)

A neutron capture therapy system that irradiates an irradiated body with neutron rays.
An irradiation room surrounded by a shielding wall that blocks the radiation of the neutron beam from the room to the outside, and the irradiated body is irradiated with the neutron beam.
The neutron beam generator that generates the neutron beam and
A neutron irradiation unit that irradiates the irradiation chamber with the neutron beam generated by the neutron beam generation unit, and a neutron irradiation unit.
A neutron beam detector that detects the dose of the neutron beam and
Have,
The neutron detector is
A scintillator that emits light when a neutron beam is incident,
A photodetector that converts the light into an electrical signal,
An optical fiber that propagates the light from the scintillator to the photodetector,
It has a shielding portion that covers the photodetector and shields radiation.
A neutron capture therapy system in which the photodetector and the shielding portion are provided in the irradiation chamber or the shielding wall. The neutron beam detector is provided outside the irradiation chamber and has a signal processing unit that processes an electric signal and an electric signal cable that transmits an electric signal emitted from the photodetector to the signal processing unit. Have and
The neutron capture therapy system according to claim 1, wherein the optical fiber is shorter than the electric signal cable. The neutron capture therapy system according to claim 1 or 2, wherein the photodetector and the shielding portion are installed on a treatment table on which the irradiated body is placed. The photodetector and the shielding portion are fixed in the irradiation chamber or in the shielding wall constituting the irradiation chamber.
The treatment table on which the irradiated body is placed can be moved between the inside and the outside of the irradiation chamber.
The neutron capture therapy system according to claim 1 or 2, wherein the optical fiber has a length that can follow the moving range of the treatment table.

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