JP2014190754A - Neutron dosimetry device and neutron capture therapy device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a neutron dosimetry device capable of measuring the dose of neutron rays during irradiation and suppressing deterioration of irradiation accuracy of neutron rays by a detector, and provide a neutron capture therapy device.SOLUTION: A neutron dosimetry device 10 for measuring the dose of neutron rays N includes: a first scintillator 21 having an opening T through which the neutron rays N pass; a second scintillator 22 provided so as to surround the first scintillator 21 from the outside; and a control unit S for calculating the dose of the neutron rays N having passed through the opening T on the basis of the detection results of the first and second scintillators 21 and 22.

Description

  The present invention relates to a neutron dosimetry apparatus and a neutron capture therapy apparatus.

  As one of radiotherapy in cancer treatment or the like, there is neutron capture therapy in which a tumor is treated by neutron irradiation. In neutron capture therapy, a neutron capture element compound having tumor accumulation properties is administered to a patient in advance. Thereafter, by irradiating the patient's tumor with neutrons, the neutron and the neutron capture element compound react to generate radiation, and the tumor is treated.

  In neutron capture therapy, it is necessary to irradiate the tumor with an appropriate dose of neutron radiation. For example, Japanese Patent Application Laid-Open No. 2004-233168 is known as a technical document relating to such neutron dose measurement. In this publication, a gold wire is attached to the surface of an affected area of a patient, and after irradiation with a neutron beam, a part of the gold wire is pulled out and the activation amount of the gold wire is measured, whereby the dose of the irradiated neutron beam A method of measuring is shown.

JP 2004-233168 A

  In neutron capture therapy, it is strongly required to measure the dose of neutron radiation during irradiation. However, with the conventional measurement method described above, the dose could be measured only after neutron irradiation. Further, in the conventional measurement method described above, since a gold wire is placed on the neutron beam irradiation field, there is a problem that the irradiation accuracy of the neutron beam is lowered due to the influence of the gold wire (the dose does not become as planned).

  Accordingly, an object of the present invention is to provide a neutron dosimetry apparatus and a neutron capture therapy apparatus that can measure a neutron beam dose during irradiation and avoid a decrease in neutron beam irradiation accuracy due to the arrangement of detectors. And

  In order to solve the above-mentioned problems, the present invention is a neutron dosimetry apparatus for measuring a neutron beam dose, and includes a first neutron detector having an opening through which a neutron beam passes, and the first neutron detector outside. Calculation to calculate the dose of the neutron beam that has passed through the opening based on the detection result of the second neutron detector, the detection result of the first neutron detector, and the detection result of the second neutron detector And means.

  According to the neutron dosimetry apparatus according to the present invention, the second neutron detector is provided so as to surround the first neutron detector having an opening through which the neutron beam passes from the outside (opposite the opening). From the relationship between the distance (radius) from the aperture of each detector and the dose detected by each detector, it is possible to calculate the dose of neutron radiation that has passed through the aperture, and measure the neutron dose during irradiation. It can be carried out. Moreover, according to this neutron dosimetry apparatus, since the neutron beam toward the patient's tumor and the like passes through the opening without being obstructed by the detector, it is possible to avoid a decrease in neutron beam irradiation accuracy due to the arrangement of the detector. .

In the neutron dosimetry apparatus according to the present invention, the first neutron detector may have an annular shape when viewed from the traveling direction of the neutron beam passing through the opening.
According to this neutron dosimetry apparatus, by configuring the first neutron detector in an annular shape having a predetermined radius from the center of the opening, the first neutron detector radius (distance from the opening) and the first The relationship between the doses detected by the neutron detector is simplified, and calculations relating to the dose measurement of the neutron beam that has passed through the aperture can be facilitated.

Alternatively, in the neutron dosimetry apparatus according to the present invention, the first neutron detector may have a frame shape having a polygonal opening as viewed from the traveling direction of the neutron beam passing through the opening.
According to this neutron dosimetry apparatus, since the first neutron detector has a frame shape having a polygonal opening, the configuration can be simplified and the manufacture becomes easy. Moreover, according to this neutron dose measuring apparatus, a 1st neutron detector can be easily comprised, for example by combining several rod-shaped detection elements.

In the neutron dosimetry apparatus according to the present invention, the first neutron detector has a plurality of detection elements that form openings, and at least one of the plurality of detection elements is a neutron beam that passes through the openings. It may be movable in a direction orthogonal to the traveling direction.
According to this neutron dosimetry apparatus, since the first neutron detector is composed of a plurality of detection elements forming the aperture, at least one detection element is moved in a direction orthogonal to the traveling direction of the neutron beam. Thus, the size of the opening can be adjusted. Thus, when forming an irradiation field of a different size according to the affected area of the patient, the aperture of the first neutron detector is appropriately adjusted so that the irradiation field of the neutron beam is not hindered with sufficient accuracy. Dose and dose distribution can be calculated.

The neutron capture therapy apparatus according to the present invention includes any one of the neutron dosimetry apparatuses described above.
According to this neutron capture therapy apparatus, it becomes possible to calculate the dose of the neutron beam that has passed through the opening of the first neutron detector, and the dose of the neutron beam can be measured during irradiation. Moreover, according to this neutron capture therapy apparatus, since the neutron beam toward the irradiated body such as a patient passes through the opening, the detector does not interfere with irradiation, and the irradiation accuracy of the neutron beam is reduced due to the arrangement of the detector. Can be avoided.

The neutron capture therapy apparatus according to the present invention further includes a collimator for shaping the irradiation field of the neutron beam, and the first neutron detector and the second neutron detector of the neutron dosimetry apparatus are arranged on the downstream side of the collimator. May be.
According to this neutron capture therapy apparatus, since the first neutron detector and the second neutron detector of the neutron dosimetry apparatus are arranged on the downstream side of the collimator, the first neutron detector and the second neutron Compared to the case where the detector is placed upstream of the collimator, the dose is not reduced by shaping the irradiation field with the collimator after measurement, and the neutron dose can be measured closer to the patient. Therefore, the dose of neutrons irradiated to the patient can be measured with high accuracy. Further, it is possible to avoid excessive incidence of neutron beams on the first neutron detector and the second neutron detector.

  According to the neutron dosimetry apparatus and the neutron capture therapy apparatus according to the present invention, it is possible to measure the neutron beam dose during irradiation, and to avoid a decrease in neutron beam irradiation accuracy due to the arrangement of the detector.

It is a schematic sectional drawing which shows the neutron capture therapy apparatus which concerns on 1st Embodiment. It is a figure which shows the neutron dose measuring apparatus which concerns on 1st Embodiment. It is a figure for demonstrating the neutron beam N which passes the opening T. FIG. 4 is a graph for explaining measurement of a dose of neutron beam N that has passed through an opening T. It is a perspective view which shows the neutron dose measuring apparatus which concerns on 2nd Embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
As shown in FIG. 1, the neutron capture therapy apparatus 1 according to the first embodiment is an apparatus used for performing cancer treatment using boron neutron capture therapy (BNCT). The neutron beam N is irradiated to the tumor F of the patient 50 to which boron ( ¹⁰ B) is administered.

  The neutron capture therapy apparatus 1 includes a cyclotron 2. The cyclotron 2 is an accelerator that generates charged particle beams R by accelerating charged particles such as negative ions. The cyclotron 2 has a capability of generating a charged particle beam R having a beam radius of 40 mm and 60 kW (= 30 MeV × 2 mA), for example. The accelerator is not limited to a cyclotron, and may be a synchrotron, a synchrocyclotron, a linac, or the like.

  The charged particle beam R emitted from the cyclotron 2 travels toward the target 6 through the beam duct 3. A plurality of quadrupole electromagnets 4 and scanning electromagnets 5 are provided along the beam duct 3. The plurality of quadrupole electromagnets 4 adjust the beam axis of the charged particle beam R using, for example, an electromagnet. The scanning electromagnet 5 scans the charged particle beam R and controls irradiation of the charged particle beam R to the target 6. The scanning electromagnet 5 controls the irradiation position of the charged particle beam R with respect to the target 6.

  The neutron capture therapy apparatus 1 generates a neutron beam N by irradiating the target 6 with the charged particle beam R and emits the neutron beam N toward the patient 50. The neutron capture therapy device 1 includes a target 6, a shield 7, a moderator 8, a collimator 9, and a neutron dose measurement device 10.

  Further, the neutron capture therapy apparatus 1 includes a control unit (calculation means) S. The control unit S is an electronic control unit including a CPU [Central Processing Unit], a ROM [Read Only Memory], a RAM [Random Access Memory], and the like, and comprehensively controls the neutron capture therapy apparatus 1.

  The control unit S includes a current monitor M that measures the current value of the charged particle beam R irradiated to the target 6 (that is, the charge and the irradiation dose rate) in real time. As the current monitor M, for example, a non-destructive type DCCT [Direct Current Current Transformer] that can be measured without affecting the charged particle beam R is used.

  The target 6 generates a neutron beam N when irradiated with the charged particle beam R. The target 6 here is made of, for example, beryllium (Be), lithium (Li), tantalum (Ta), or tungsten (W), and has a disk shape with a diameter of 160 mm.

  The shield 7 shields the generated neutron beam N and the gamma rays generated by the generation of the neutron beam N so as not to be emitted to the outside. The moderator 8 decelerates (attenuates) the energy of the neutron beam N and is provided inside the shield 7. The moderator 8 is composed of a first moderator 8A that mainly decelerates fast neutrons contained in the neutron beam N, and a second moderator 8B that mainly decelerates epithermal neutrons contained in the neutron beam N. It has a laminated structure.

  The collimator 9 shapes the irradiation field of the neutron beam N (irradiation range in a plane orthogonal to the traveling direction of the neutron beam N), and has an opening 9a through which the neutron beam N passes. The neutron beam N generated at the target 6 passes through the moderator 8 and then is partially shaped into a predetermined irradiation field by passing through the opening 9 a of the collimator 9.

  The neutron dose measuring device 10 is a device that measures the dose and dose distribution of the neutron beam N irradiated to the patient 50 on the treatment table 51. Here, FIG. 2 is a diagram showing the neutron dose measuring apparatus 10. The neutron dosimetry apparatus 10 shown in FIG. 2 includes a scintillator unit 20 that emits light upon incidence of a neutron beam N, a light guide unit 30 that transmits light generated by the scintillator unit 20, and light transmitted by the light guide unit 30. And a light detection unit 40 that detects and outputs an electrical signal.

  The scintillator unit 20 is a phosphor that converts incident neutron beams N into light. The scintillator unit 20 is arranged on the downstream side of the collimator 9 (downstream side in the traveling direction of the neutron beam N). The scintillator unit 20 generates scintillation light by causing the internal crystal to be excited according to the dose of the incident neutron beam N.

The scintillator portion 20 is formed in an annular shape, and has an opening T at the center thereof. The opening T is formed larger than the opening 9 a of the collimator 9. The neutron beam N that has passed through the opening 9a of the collimator 9 passes through this opening T and travels toward the patient 50. Figure 2 shows the traveling direction N _F neutron N passing through the aperture T. Advancing direction N _F shows the main traveling direction of the neutrons N passing through the aperture T, in fact neutrons N is present proceed to various angles. The traveling direction of the neutron beam in the claims means the main traveling direction of the neutron beam N. The main traveling direction of the neutron beam N is the traveling direction of the charged particle beam R when the target 6 is irradiated (more precisely, the traveling direction of the charged particle beam R when nothing is scanned by the scanning electromagnet 5). It is.

  The light guide part 30 is a member that transmits light generated in the scintillator part 20. The light guide part 30 is comprised from the bundle | flux of a flexible optical fiber etc., for example.

  The light detection unit 40 detects light generated in the scintillator unit 20 through the light guide unit 30 and outputs an electrical signal. For the light detection unit 40, various light detection devices such as a photomultiplier tube and a photoelectric tube can be employed. The light detection unit 40 is connected to the control unit S and outputs an electronic signal to the control unit S when detecting light.

FIG. 3 is a diagram for explaining the neutron beam N passing through the opening T. FIG. As shown in FIG. 3, neutrons N, after the irradiation field is shaped through an opening 9a of the collimator 9 is also to spread radially with the progress (the direction perpendicular to the traveling direction N _F), neutron A part of the line N enters the scintillator unit 20 without passing through the opening T provided in the scintillator unit 20. When the neutron beam N is incident on the scintillator unit 20 and the internal crystal of the scintillator unit 20 is excited, light corresponding to the dose of the neutron beam N is generated, and light is detected by the light detection unit 40 through the light guide unit 30. . The light detection unit 40 outputs an electrical signal to the control unit S according to the detected light.

Next, the configuration of the scintillator unit 20, the light guide unit 30, and the light detection unit 40 will be described with reference to FIG. As shown in FIG. 2, the scintillator unit 20 includes four scintillators 21 to 24. The scintillator 21 to 24 is a member having an annular shape as viewed from the traveling direction N _F neutron N, each of which passes through the opening T. The scintillator 21 to 24 are arranged concentrically in a plane perpendicular to the traveling direction N _F. The circular shape is not limited to a perfect circular shape, and includes an annular shape such as an ellipse or an ellipse.

The scintillators 21 to 24 have a large radius in the order of the first scintillator 21, the second scintillator 22, the third scintillator 23, and the fourth scintillator 24. The radial thicknesses of the scintillators 21 to 24 may be the same or different. The scintillator 21 to ^24, can be adopted 6 Li glass scintillator, LiCAF ^{scintillator,} a plastic scintillator coated with 6 ^LiF, a 6 LiF / ZnS scintillators like. Note that the scintillators 21 to 24 are not necessarily the same kind of scintillators.

  The first scintillator 21 is a scintillator having the smallest radius annular shape. An opening T is formed in the center of the first scintillator 21. The first scintillator 21 is connected to the first light guide 31 constituting the light guide portion 30. The first light guide 31 is connected to a first light detector 41 constituting the light detection unit 40. When the neutron beam N is incident on the first scintillator 21, light generated in the first scintillator 21 is detected by the first photodetector 41 through the first light guide 31, and an electric signal is output to the control unit S. Is done.

  The second scintillator 22 is an annular scintillator provided so as to surround the first scintillator 21 from the outside. The second scintillator 22 is disposed along the outer periphery of the first scintillator 21, and the inner peripheral surface thereof is in contact with the outer peripheral surface of the first scintillator 21. The space between the second scintillator 22 and the first scintillator 21 is shielded from light, and the light of the first scintillator 21 does not enter the second scintillator 22. The first scintillator 21 and the second scintillator 22 may be provided so as to be separated from each other to form a predetermined gap.

  The second scintillator 22 is connected to a second light guide 32 that constitutes the light guide portion 30. The second light guide 32 is connected to a second photodetector 42 that constitutes the photodetector 40. When the neutron beam N is incident on the second scintillator 22, the light generated in the second scintillator 22 is detected by the second photodetector 42 through the second light guide 32, and an electric signal is output to the control unit S. Is done. The first scintillator 21 and the second scintillator 22 respectively correspond to a first neutron detector and a second neutron detector described in the claims.

  The third scintillator 23 is an annular scintillator provided so as to surround the second scintillator 22 from the outside. The third scintillator 23 is disposed along the outer periphery of the second scintillator 22, and the inner peripheral surface thereof is in contact with the outer peripheral surface of the second scintillator 22. The space between the third scintillator 23 and the second scintillator 22 is shielded from light, and the light from the second scintillator 22 does not enter the third scintillator 23. The second scintillator 22 and the third scintillator 23 may be provided so as to be separated from each other to form a predetermined gap.

  The third scintillator 23 is connected to a third light guide 33 constituting the light guide portion 30. The third light guide 33 is connected to a third light detector 43 constituting the light detection unit 40. When the neutron beam N is incident on the third scintillator 23, the light generated in the third scintillator 23 is detected by the third photodetector 43 through the third light guide 33 and an electric signal is output to the control unit S. Is done.

  Similarly, the fourth scintillator 24 is an annular scintillator having the largest radius and is provided so as to surround the third scintillator 23 from the outside. The fourth scintillator 24 is disposed along the outer periphery of the fourth scintillator 24, and the inner peripheral surface thereof is in contact with the outer peripheral surface of the fourth scintillator 24. The fourth scintillator 24 and the third scintillator 23 are shielded from light, and the light from the third scintillator 23 does not enter the fourth scintillator 24. The third scintillator 23 and the fourth scintillator 24 may be provided so as to be separated from each other to form a predetermined gap.

  The fourth scintillator 24 is connected to a fourth light guide 34 that constitutes the light guide portion 30. The fourth light guide 34 is connected to a fourth light detector 44 constituting the light detection unit 40. When the neutron beam N is incident on the fourth scintillator 24, light generated in the fourth scintillator 24 is detected by the fourth photodetector 44 through the fourth light guide 34, and an electric signal is output to the control unit S. Is done.

  In the neutron dosimetry apparatus 10 configured as described above, the number of neutrons of the neutron beam N incident on the scintillators 21 to 24 around the opening T is detected, and the radius of each scintillator 21 to 24 (distance from the center of the opening T). ) And the number of neutrons detected by each of the scintillators 21 to 24, the dose and dose distribution of the neutron beam N that has passed through the aperture T are calculated (measured).

  The scintillators 21 to 24 are configured to be detachable from each other. For example, when it is desired to enlarge the opening T, the inside of the second scintillator 22 can be made a new opening T by removing the first scintillator 21. In addition, the number of scintillators is not limited to four, but may be two or more, and may be five or more.

  FIG. 4 is a graph for explaining the calculation (measurement) of the dose of the neutron beam N that has passed through the opening T. The vertical axis of the graph shown in FIG. 4 indicates the number of neutrons, and the horizontal axis indicates the radius of the scintillator. In FIG. 4, P1 is the detection result of the first scintillator 21, P2 is the detection result of the first scintillator 22, P3 is the detection result of the first scintillator 23, and P4 is the detection result of the first scintillator 24. Moreover, the calculation result of the neutron number of the neutron beam N which passed the opening T is shown as Q1 and Q2.

  As shown in FIG. 4, the neutron beam N has a greater number of neutrons as it is closer to the center of the beam diameter, and a smaller number of neutrons the further away from the center of the beam diameter. Therefore, the control unit S derives a fit function related to the number of detected neutrons and the distance from the center of the aperture T (the center of the beam diameter) based on the detection results P1 to P4 of the scintillators 21 to 24, and uses this fit function. The calculation results Q1 and Q2 of the number of neutrons of the neutron beam N that has passed through the opening T are acquired. The control unit S obtains the dose and dose distribution of the neutron beam N that has passed through the opening T (distribution of the dose of the neutron beam N with respect to the distance from the center of the opening T) based on the calculation results Q1 and Q2.

  Note that the method of calculating the dose and dose distribution of the neutron beam N that has passed through the opening T is not limited to the above-described method. For example, the calculation results Q1, Q2, the dose, and the like may be obtained from the detection results P1 to P4 of the scintillators 21 to 24 by a known mathematical method. In addition, the control unit S stores in advance a data map indicating the correspondence relationship between the detection results P1 to P4 of the scintillators 21 to 24 and the dose of the neutron beam N that has passed through the opening T, and using this data map, The dose of the neutron beam N that has passed through the opening T may be calculated.

  Next, the effect of the neutron capture therapy apparatus 1 (neutron dose measuring apparatus 10) according to the first embodiment described above will be described.

  According to the neutron capture therapy apparatus 1 according to the first embodiment, the scintillators 22 to 24 are provided so as to surround the first scintillator 21 having the opening T through which the neutron beam N passes from the outside. From the relationship between the radii of 21 to 24 and the number of neutrons detected by each of the scintillators 21 to 24, the dose and dose distribution of the neutron beam N that has passed through the aperture T can be calculated (measured). Moreover, in this neutron capture therapy apparatus 1, in order to measure the dose and dose distribution of the neutron beam N, it is not necessary to stop the irradiation of the neutron beam N, and the dose of the neutron beam N is measured in real time during the irradiation. Can do. Furthermore, according to this neutron capture therapy apparatus 1, since the neutron beam N irradiated to the tumor F of the patient 50 passes through the opening T without being blocked by the scintillators 21-24, the neutron beam by the arrangement of the scintillators 21-24. The decrease in N irradiation accuracy can be suppressed.

  Further, according to the neutron dose measuring apparatus 1, the scintillator 20 has an opening T through which the neutron beam N passes, so that one or two neutron detectors are arranged outside the irradiation field of the neutron beam N. Therefore, the measurement accuracy of the dose of neutron beam N can be greatly improved as compared with the case where measurement is performed.

Further, according to the neutron capture therapy apparatus 1, since each of the scintillator 21 to 24 forms a circular shape having a center of radius from a predetermined opening T when viewed from the traveling direction N _F neutron N, each The relationship between the radius of the scintillators 21 to 24 (distance from the center of the opening T) and the detection results P1 to P4 of each of the scintillators 21 to 24 becomes simple, and a fitting function and the like can be easily derived. Calculation related to measurement of dose distribution can be facilitated.

  Furthermore, according to this neutron capture therapy apparatus 1, since the scintillators 21 to 24 are disposed on the downstream side of the collimator 9, measurement is performed as compared with the case where the scintillators 21 to 24 are disposed on the upstream side of the collimator 9. The dose of the neutron beam N is not reduced later by shaping the irradiation field by the collimator 9, and the dose of the neutron beam N can be measured at a position closer to the patient 50. As a result, the dose and dose distribution of the neutron beam N irradiated to the patient 50 can be measured with high accuracy. Moreover, in this neutron capture therapy apparatus 1, since the scintillators 21-24 are arrange | positioned in the downstream of the collimator 9, compared with the case where the scintillators 21-24 are arrange | positioned in the upstream of the collimator 9, the neutron beam N Is excessively incident on the scintillators 21-24.

[Second Embodiment]
As shown in FIG. 5, the neutron capture therapy apparatus according to the second embodiment differs from the neutron capture therapy apparatus 1 according to the first embodiment in the configuration of the scintillator unit 60 in the neutron dose measurement apparatus. Yes.

  The scintillator section 60 according to the second embodiment shown in FIG. 5 is configured in a cross beam shape (frame shape) having a quadrangular opening T at the center. The scintillator unit 60 includes a first scintillator 70, a second scintillator 80, a third scintillator 90, and a fourth scintillator 100. These scintillators 70, 80, 90, 100 are each configured by combining bar-shaped scintillator elements in a cross beam shape. The scintillators 70, 80, 90, 100 are provided in order of the first scintillator 70, the second scintillator 80, the third scintillator 90, and the fourth scintillator 100 from the inner side (opening T side) to the outer side. Yes.

  The first scintillator 70 is formed in a cross beam shape by four rod-like scintillator elements (detection elements) 71 to 74, and forms a central opening T. Specifically, the first scintillator element 71 and the second scintillator element 72 extend in a predetermined direction (for example, the horizontal direction) and are arranged in parallel to each other, and the third scintillator element 73 and the fourth scintillator element 73 The scintillator elements 74 extend in a direction orthogonal to a predetermined direction (for example, the vertical direction) and are arranged in parallel to each other. That is, the scintillator elements 71 to 74 form each side of the rectangular opening T.

  Light guides 111 to 114 are connected to the scintillator elements 71 to 74, respectively. The light guides 111 to 114 are connected to four photodetectors (not shown), and the light generated by the scintillator elements 71 to 74 is transmitted to the photodetectors through the light guides 111 to 114.

  The second scintillator 80 is provided so as to surround the first girder-shaped first scintillator 70 from the outside. The second scintillator 80 is formed in a cross beam shape by four rod-like scintillator elements (detection elements) 81 to 84, and these scintillator elements 81 to 84 constitute scintillator elements 71 to 74 constituting the first scintillator 70. Is disposed outside (opening T opposite side).

  Specifically, the first scintillator element 81 in the second scintillator 80 is disposed along the outside of the first scintillator element 71, and the second scintillator element 82 is the second scintillator element 72. It is arranged along the outside. Similarly, the third scintillator element 83 is disposed along the outside of the third scintillator element 73, and the fourth scintillator element 84 is disposed along the outside of the fourth scintillator element 74. .

  Light guides 121 to 124 are connected to the scintillator elements 81 to 84, respectively. The light guides 121 to 124 are respectively connected to four photodetectors (not shown), and light generated by the scintillator elements 81 to 84 is transmitted to the photodetectors through the light guides 121 to 124. The first scintillator 70 and the second scintillator 80 correspond to a first neutron detector and a second neutron detector described in the claims, respectively.

  In addition, the third scintillator 90 is provided so as to surround the cross-shaped second scintillator 80 from the outside. The third scintillator 90 is formed in a cross beam shape by four rod-like scintillator elements (detection elements) 91 to 94, and these scintillator elements 91 to 94 constitute scintillator elements 81 to 84 that constitute the second scintillator 80. Is disposed outside (opening T opposite side).

  Light guides 131 to 134 are connected to the scintillator elements 91 to 94, respectively. The light guides 131 to 134 are respectively connected to four photodetectors (not shown), and light generated by the scintillator elements 91 to 94 is transmitted to the photodetectors through the light guides 131 to 134.

  Similarly, the fourth scintillator 100 is a scintillator that is provided on the outermost side and surrounds the third scintillator 90 having a cross beam shape from the outside. The fourth scintillator 100 is formed in a cross beam shape by four rod-like scintillator elements (detection elements) 101 to 104, and these scintillator elements 101 to 104 constitute scintillator elements 91 to 94 that constitute a third scintillator 90. Is disposed outside (opening T opposite side).

  Light guides 141 to 144 are connected to the scintillator elements 101 to 104, respectively. The light guides 141 to 144 are respectively connected to four photodetectors (not shown), and light generated by the scintillator elements 101 to 104 is transmitted to the photodetectors through the light guides 141 to 144.

The scintillator unit 60 according to the second embodiment includes linear motors (moving means) 151 to 154 that move the scintillators 70, 80, 90, and 100 in a predetermined direction. Linear motors 151 to 154 are used to move the respective scintillator 70,80,90,100 in a direction perpendicular to the traveling direction _{N F} neutron N.

  Specifically, the first linear motor 151 integrally moves the first scintillator elements 71, 81, 91, 101 in the direction indicated by the arrow A1. The second linear motor 152 integrally moves the second scintillator elements 72, 82, 92, 102 in the direction indicated by the arrow A2. The third linear motor 153 moves the third scintillator elements 73, 83, 93, 103 integrally in the direction indicated by the arrow A3. The fourth linear motor 154 integrally moves the fourth scintillator elements 74, 84, 94, 104 in the direction indicated by the arrow A4. The scintillator unit 60 may include a linear guide for linearly moving each scintillator element.

  According to the neutron capture therapy apparatus according to the second embodiment described above, since the scintillators 80, 90, 100 are provided so as to surround the first scintillator 70 that forms the opening T from the outside, each scintillator 70 is provided. , 80, 90, 100, the dose from the center of the opening T and the number of neutrons detected by each of the scintillators 70, 80, 90, 100 and the dose distribution of the neutron beam N passing through the opening T are measured. Is possible. Moreover, in this neutron capture therapy apparatus, in order to measure the dose and dose distribution of the neutron beam N, it is not necessary to stop the irradiation of the neutron beam N, and the dose of the neutron beam N can be measured in real time during the irradiation. it can. Furthermore, according to this neutron capture therapy apparatus, since the neutron beam N irradiated to the tumor F of the patient 50 passes through the opening T without being blocked by the scintillators 70, 80, 90, 100, the scintillators 70, 80, 90 , 100 can suppress a decrease in irradiation accuracy of the neutron beam N.

  Further, according to this neutron capture therapy apparatus, the configuration can be simplified by making the scintillator section 60 into a cross-girder shape having a square opening T, and the scintillator section 60 can be easily combined with a rod-shaped scintillator element. Can be manufactured.

Further, according to the neutron capture therapy apparatus, since constitute a scintillator 70,80,90,100 from a plurality of scintillator elements forming the opening T, perpendicular to the scintillator element to the traveling direction N _F neutron N By moving in the direction, the size of the opening T can be adjusted. Thereby, when forming the irradiation field of a different size according to the tumor F of the patient 50, the dose and the dose can be accurately adjusted without disturbing the irradiation field of the neutron beam N by appropriately adjusting the opening T. Distribution measurements can be made.

  As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to embodiment mentioned above. For example, the neutron detector need not be a scintillator but may be an ionization chamber. Further, the shape of the scintillator portion according to the first embodiment may be a polygonal frame shape (frame shape) including a quadrangular frame shape or a triangular frame shape instead of an annular shape. The shape of the central opening may be a polygonal shape or other shapes in addition to a circular shape. Further, the scintillators constituting the scintillator portion do not have to be unified in a frame shape including an annular shape, a polygonal frame shape, and a cross beam shape, and these may be mixed. That is, a quadrangular scintillator may surround the outside of the annular scintillator, and vice versa.

  Even when the scintillator has an annular shape, the scintillator may be composed of a plurality of scintillator elements (for example, arc-shaped scintillator elements). In this case, the size of the opening can be adjusted by making it possible to move at least one of the scintillator elements forming the opening in a direction orthogonal to the traveling direction of the neutron beam. Note that it is not always necessary to provide a linear motor for moving the scintillator element, and it may be adjusted manually. In addition, it is not always necessary to configure all of the scintillator elements to be movable, as long as at least one scintillator element forming the opening is configured to be movable.

  DESCRIPTION OF SYMBOLS 1 ... Neutron capture therapy apparatus 2 ... Cyclotron 3 ... Beam duct 4 ... Quadrupole electromagnet 5 ... Scanning electromagnet 6 ... Target 7 ... Shielding body 8 ... Moderator 9 ... Collimator 9a ... Opening 10 ... Neutron dose measuring device 20 ... Scintillator part 21 ... 1st scintillator (1st neutron detector) 22 ... 2nd scintillator (2nd neutron detector) 23 ... 3rd scintillator 24 ... 4th scintillator 30 ... Light guide part 31 ... 1st light guide 32 ... 2nd light guide 33 ... 3rd light guide 34 ... 4th light guide 40 ... Photodetection part 41 ... 1st photodetector 42 ... 2nd photodetector 43 ... 3rd photodetector 44 ... 4th photodetector 50 ... Patient 51 ... Treatment table 60 ... Scintillator part 70 ... 1st scintillator (1st neutron detector) 7 , 81, 91, 101 ... first scintillator element (detection element) 72, 82, 92, 102 ... second scintillator element (detection element) 73, 83, 93, 103 ... third scintillator element (detection element) 74, 84, 94, 104 ... fourth scintillator element (detection element) 80 ... second scintillator (second neutron detector) 90 ... third scintillator 100 ... fourth scintillator F ... tumor N ... neutron beam NF ... Traveling direction R ... Charged particle beam S ... Control part (calculation means) T ... Opening

Claims (6)

A neutron dosimetry device that measures the dose of neutron radiation,
A first neutron detector having an aperture through which a neutron beam passes;
A second neutron detector provided to surround the first neutron detector from the outside;
A calculation means for calculating a dose of neutron beam that has passed through the opening based on a detection result of the first neutron detector and a detection result of the second neutron detector;
A neutron dosimetry apparatus comprising:   2. The neutron dosimetry apparatus according to claim 1, wherein the first neutron detector has an annular shape when viewed from a traveling direction of a neutron beam passing through the opening.   2. The neutron dosimetry apparatus according to claim 1, wherein the first neutron detector has a frame shape having the polygonal opening as viewed from a traveling direction of a neutron beam passing through the opening. The first neutron detector has a plurality of detection elements forming the opening,
The neutron dosimetry apparatus according to any one of claims 1 to 3, wherein at least one of the plurality of detection elements is movable in a direction orthogonal to a traveling direction of a neutron beam passing through the opening.   A neutron capture therapy apparatus comprising the neutron dosimetry apparatus according to any one of claims 1 to 4. A collimator for shaping the neutron radiation field;
The neutron capture therapy apparatus according to claim 5, wherein the first neutron detector and the second neutron detector of the neutron dosimetry apparatus are arranged on the downstream side of the collimator.

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