JP6465677B2 - Boron Neutron Capture Therapy System - Google Patents

Description

  The present invention relates to a boron neutron capture therapy system, and more particularly to a boron neutron capture therapy system that treats cancer by reacting neutrons generated using a charged particle accelerator with a boron preparation administered to a patient.

Conventionally, as a cancer treatment method, boron neutron capture therapy using α-rays and lithium nuclei generated by a reaction between boron ( ¹⁰ B) administered to a patient and neutrons irradiated from the outside for destruction of tumor cells. (BNCT: Boron Neutron Capture Therapy) is known. Since the range of alpha rays and lithium nuclei is about one cell, tumor cells can be destroyed without damaging normal cells.

  Since a medical reactor for obtaining neutrons is subject to various regulations, an inexpensive and simple accelerator system for BNCT using an accelerator that can be installed in a medical facility has been desired.

As an neutron generation method using an accelerator, a ⁷ Li (p, n) ⁷ Be reaction with protons having acceleration energy of about 2.5 MeV or less is used, and ⁹ Be (p, n) ⁹ B using protons with acceleration energy of 4 MeV. Those utilizing a reaction, those utilizing a nuclear fragmentation reaction of tungsten, tantalum, or the like with protons having acceleration energy of 30 MeV or more are being studied.

  As a treatment device for boron neutron capture therapy using an accelerator, for example, a treatment device has been proposed in which a linear accelerator is used and neutrons can be irradiated from multiple directions to the treatment site according to the treatment site (for example, Patent Document 1).

JP 2008-22920 A

  However, in the conventional treatment apparatus for boron neutron capture therapy, since the acceleration energy of protons is large, most of the neutrons are forward projected, and the change of the neutron irradiation direction requires the deflection of the proton beam.

  Also, even when neutrons are irradiated to the whole body of a patient after adjusting to a predetermined neutron energy spectrum, the irradiation equipment is large and expensive, such as the need to attach the irradiation unit to the rotating gantry and move the irradiation unit relative to the whole body It will become something.

  Accordingly, the main object of the present invention is to provide a boron neutron capture therapy system that does not require a change in the irradiation direction of the charged particle beam, and that can be reduced in size and cost.

  In order to achieve the above object, a boron neutron capture therapy system according to the present invention includes a plurality of linear accelerators for accelerating deuterons to a predetermined energy, and installed at respective terminal portions of the plurality of linear accelerators. And a neutron irradiation section that is provided so as to surround the plurality of targets and that irradiates the fast neutrons generated by the targets at a reduced speed.

  The acceleration tubes of the plurality of linear accelerators are preferably arranged in parallel with each other around the neutron irradiation space.

  The neutron irradiation unit includes a neutron absorber that collectively surrounds the plurality of targets, a neutron reflector provided inside the neutron absorber, a neutron moderator provided inside the neutron reflector, And a gamma ray shielding material provided inside the neutron moderator.

  It is preferable that the neutron absorber, the neutron reflector, the neutron moderator, and the gamma ray shielding material are provided in layers.

  The neutron irradiation part is preferably cylindrical.

  The plurality of linear accelerators are preferably arranged in an annular shape.

  The plurality of linear accelerators may be arranged side by side.

  It is preferable that the plurality of linear accelerators are arranged so that their targets face each other.

  It is preferable to further comprise a bed that is neutron permeable and on which the patient is placed.

  It is preferable that the bed is movably provided.

  It is preferable that the acceleration tubes of the plurality of linear accelerators are arranged in a vertical direction and further provided with a lifting platform for carrying a patient.

  It is preferable to generate isotropic neutrons from the target by exothermic neutron-generating nuclear reaction by accelerating deuterons to a predetermined energy (for example, 200 keV to 1 MeV) by the linear accelerator.

  According to the present invention, the amount of high-energy neutrons generated can be reduced using the exothermic neutron nuclear reaction, and the speed reduction system can be reduced. In addition, since deuteron acceleration energy is reduced in the exothermic neutron nuclear reaction and neutrons are isotropically irradiated from the target, deuteron beam deflection is not necessary.

It is a schematic block diagram which shows 1st Embodiment of the boron neutron capture therapy system which concerns on this invention, (a) is a front view, (b) is a side view. The internal structure of the boron neutron capture therapy system of FIG. 1 is shown, (a) is a center longitudinal front view, (b) is a bb center longitudinal side view of (a). The internal structure of the other example of the boron neutron capture therapy system of FIG. 1 is shown, (a) is a center longitudinal front view, (b) is a bb center longitudinal side view of (a). It is a schematic block diagram which shows 2nd Embodiment of the boron neutron capture therapy system which concerns on this invention, (a) is a front view, (b) is a top view. It is a front view which shows schematic structure of 3rd Embodiment of the boron neutron capture therapy system which concerns on this invention. It is a schematic block diagram which shows 4th Embodiment of the boron neutron capture therapy system which concerns on this invention, (a) is a front view, (b) is a side view.

  An embodiment of a boron neutron capture therapy system according to the present invention will be described below with reference to FIGS. Throughout the drawings and all the embodiments, the same or similar components are denoted by the same reference numerals.

  FIG. 1 shows a first embodiment of a boron neutron capture therapy system according to the present invention. As shown in FIG. 1, the boron neutron capture therapy system 1 includes a plurality of linear accelerators 2 for accelerating deuterons to predetermined energy, a target 3 installed at each terminal end of the plurality of linear accelerators 2, and And a neutron irradiation unit 4 provided so as to surround the plurality of targets 3.

  The linear accelerator 2 includes an ion source 5, a polyethylene accelerator tube 6, a SiC high voltage pulse generator (not shown), and the like. The acceleration tubes 6 of the plurality of linear accelerators 2 are arranged in parallel and annularly around the neutron irradiation space. Deuteron ions generated in the ion source 5 are accelerated to 200 keV to 1 MeV (for example, 480 keV or 960 keV) in the polyethylene acceleration tube 6.

The accelerated deuteron beam generates fast neutrons in the target 3 made of beryllium. The neutron generation reaction at this time is a so-called exothermic neutron generation nuclear reaction, and the reaction formula is represented by ⁹ Be + d → ¹⁰ B + n + 4.35 MeV (d is deuteron and n is neutron).

  As shown in FIG. 2 or 3, the neutron irradiation unit 4 includes a neutron absorber 4a that encloses a plurality of targets 3 from the outside, a neutron reflector 4b provided inside the neutron absorber 4a, A neutron moderator 4c provided inside the reflector 4b and a gamma ray shielding material 4d provided inside the neutron moderator 4c are provided. The target 3 can be embedded in the neutron moderator 4c. The neutron irradiation unit 4 in FIG. 2 shows a deceleration system for decelerating fast neutrons to thermal neutrons, and the neutron irradiation unit 4 in FIG. 3 shows a deceleration system for decelerating fast neutrons to epithermal neutrons. A heat sink 7 is attached to the target 3.

  These neutron absorber 4a, neutron reflector 4b, neutron moderator 4c, and gamma ray shielding material 4d can be provided in layers, and can be formed in a cylindrical shape as in the illustrated example. The central cavity portion of the neutron irradiation section 4 formed into an annular shape becomes the neutron irradiation space X.

  A bed 8 (FIG. 1) on which a patient D is placed in the neutron irradiation space X is disposed. The bed 8 can be moved in the horizontal direction along the length direction of the acceleration tube 6 by a drive mechanism (not shown).

  Fast neutrons generated by the target 3 are decelerated to thermal neutrons or epithermal neutrons by a neutron moderator 4 c provided so as to surround the target 3. The generated thermal neutrons or epithermal neutrons are reflected by the neutron reflector 4b provided on the outer periphery of the plurality of targets 3 arranged in an annular shape and guided to the neutron irradiation space in the center of the ring. It is burned.

  The neutron absorber 4a can be formed of boron-containing polyethylene, preferably 10% boron-containing polyethylene. The neutron reflector 4b can be formed of graphite.

  Heavy water is used for the neutron moderator 4c when decelerating fast neutrons to thermal neutrons. As the neutron moderator 4c when decelerating fast neutrons to epithermal neutrons, aluminum, aluminum fluoride, a mixed material of aluminum and aluminum fluoride, or the like is used.

  When decelerating fast neutrons to thermal neutrons, the neutron permeable gamma ray shielding material has a double structure as shown in FIG. 2, and lead fluoride or the like is used for the outer gamma ray shielding material 4d (A). Bismuth or the like is used for the inner gamma ray shielding material 4d (B).

  When decelerating fast neutrons to epithermal neutrons, lead or the like is used as the neutron permeable gamma ray shielding material 4d. When decelerating fast neutrons to epithermal neutrons, a thermal neutron absorber 4e formed of cadmium or the like is further provided between the neutron permeable gamma ray shielding material 4d and the neutron moderator 4c as shown in FIG. obtain.

  The boron neutron capture therapy system having the above configuration uses an exothermic neutron-generating nuclear reaction between deuteron ions of 1 MeV or less and beryllium instead of proton ions, and therefore generates a small amount of high-energy neutrons. Since the generation amount of high energy neutrons is small, the speed reduction system can be made small. Even if the amount of neutrons generated by a single accelerator is small, the total amount of neutrons can be increased by using a plurality of accelerators in combination.

  In addition, since the acceleration energy of deuterons is small, neutrons are irradiated isotropically from the target, and the deuteron beam need not be deflected. A high neutron flux is formed at the center of the ring from a plurality of targets arranged in an annular shape without providing a mechanical drive mechanism, and irradiation to the whole body becomes possible. Neutrons isotropically irradiated from each of the plurality of targets are superimposed at the center of the irradiation region surrounded by each target.

  Furthermore, the spatial distribution of neutrons optimal for treatment can be formed by individually adjusting the outputs of a plurality of accelerators. Therefore, the effect of irradiation can be expected even for tumors with a size of several mm or less that do not appear in PET.

  In the above embodiment, neutrons can be irradiated from the circumferential direction of an arbitrary cross section of the patient while the patient is laid down. Since the bed 8 is neutron-permeable, it can also irradiate neutrons from the back. By moving the bed 8 in the horizontal direction, the whole body can be irradiated with neutrons.

  FIG. 4 shows a second embodiment of the boron neutron capture therapy system. The second embodiment is different from the first embodiment in that the acceleration tube 6 of the linear accelerator 2 is arranged vertically and a lifting platform 10 on which a patient is placed is installed in the neutron irradiation space. Although not shown, a chair made of a neutron permeable material can be installed on the elevator 10. In the second embodiment, neutrons can be irradiated from the circumferential direction of an arbitrary cross section of the patient while the patient is standing or sitting on a chair. Further, the entire body can be irradiated with neutrons by moving the elevator 10 in the vertical direction.

  FIG. 5 shows a third embodiment of the boron neutron capture therapy system. In the third embodiment, the linear accelerator 2 is disposed so that the targets 3 face each other, and the linear accelerator 2 is disposed on both sides. In the third embodiment, the patient's whole body can be irradiated with neutrons without providing a drive mechanism that moves the patient in the horizontal direction while the patient is laid down. Moreover, since the bed 8 is neutron-permeable, it can also irradiate neutrons from the back. With respect to the second embodiment, the third embodiment can be applied to form a combination of two sets in the vertical direction.

  FIG. 6 shows a fourth embodiment of the boron neutron capture therapy system. In the fourth embodiment, a plurality of linear accelerators 2 are arranged side by side in two upper and lower stages. In the illustrated example, three linear accelerators 2 are arranged side by side in the upper stage, and three linear accelerators 2 are arranged side by side in the lower stage. The neutron permeable bed 8 is movable in the XY direction. According to the fourth embodiment, neutrons can be irradiated from the upper and rear surfaces of the patient while the patient is laid down. Since the bed has high neutron permeability, it can irradiate neutrons from the back. Further, neutrons can be irradiated to the whole body by moving the bed 8 in the XY direction.

  The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Boron neutron capture therapy system 2 Linear accelerator 3 Target 4 Neutron irradiation part 5 Ion source 6 Accelerating tube 8 Bed 10 Lift platform

Claims (12)

A plurality of linear accelerators that accelerate deuterons to a predetermined energy;
A target made of beryllium installed at each end of the plurality of linear accelerators;
A neutron irradiation unit that is provided so as to surround the plurality of targets and irradiates the fast neutrons generated by the targets at a reduced speed;
A boron neutron capture therapy system comprising:   2. The boron neutron capture therapy system according to claim 1, wherein the acceleration tubes of the plurality of linear accelerators are arranged in parallel to each other around a neutron irradiation space.   The neutron irradiation unit includes a neutron absorber that collectively surrounds the plurality of targets, a neutron reflector provided inside the neutron absorber, a neutron moderator provided inside the neutron reflector, The boron neutron capture therapy system according to claim 1, further comprising a gamma ray shielding material provided inside the neutron moderator.   4. The boron neutron capture therapy system according to claim 3, wherein the neutron absorber, the neutron reflector, the neutron moderator, and the gamma ray shielding material are provided in layers.   The boron neutron capture therapy system according to claim 3 or 4, wherein the neutron irradiation unit is cylindrical.   The boron neutron capture therapy system according to claim 2, wherein the plurality of linear accelerators are annularly arranged.   The boron neutron capture therapy system according to claim 2, wherein the plurality of linear accelerators are arranged side by side.   The boron neutron capture therapy system according to any one of claims 1 to 7, wherein the plurality of linear accelerators are arranged so that their targets face each other.   The boron neutron capture therapy system according to any one of claims 1 to 8, further comprising a bed that is neutron permeable and on which a patient is placed.   The boron neutron capture therapy system according to claim 9, wherein the bed is movably provided.   The boron neutron capture therapy system according to any one of claims 1 to 8, wherein the acceleration tubes of the plurality of linear accelerators are arranged in a vertical direction, and further includes a lifting platform for carrying a patient. The boron neutron capture therapy system according to any one of claims 1 to 11, wherein neutrons are generated isotropically from the target using an exothermic neutron-generating nuclear reaction.

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