Beam shaping assembly for neutron capture therapy
A beam shaping assembly for neutron capture therapy includes a beam inlet, a target having nuclear reaction with an incident proton beam from the beam inlet to produce neutrons forming a neutron beam, a moderator adjoining to the target, a reflector surrounding the moderator, a thermal neutron absorber adjoining to the moderator, a radiation shield arranged inside the beam shaping assembly and a beam outlet. The material of the moderator is subjected to a powder sintering process using a powder sintering device so as to change powders or a power compact into blocks. The reflector leads the neutrons deviated from the main axis back. The thermal neutron absorber is used for absorbing thermal neutrons so as to avoid overdosing in superficial normal tissue during therapy. The radiation shield is used for shielding leaking neutrons and photons so as to reduce dose of the normal tissue not exposed to irradiation.
1. A beam shaping assembly for neutron capture therapy comprising:
a beam inlet;
a target, wherein the target has nuclear reaction with an incident proton beam from the beam inlet to produce neutrons, and wherein the neutrons form a neutron beam defining a main axis;
a moderator adjoining to the target, wherein the neutrons are moderated by the moderator to epithermal neutron energies, and the material of the moderator is prepared by mixing a mixture containing one or more of PbF 4 , Al 2 O 3 , AlF 3 , CaF 2 and MgF 2 and a 6 Li element-containing material accounting for 0.1 to 5% in percentage by weight of the mixture;
a reflector surrounding the moderator, wherein the reflector leads the neutrons deviated from the main axis back to enhance epithermal neutron beam intensity;
a thermal neutron absorber adjoining to the moderator, wherein the thermal neutron absorber absorbs thermal neutrons so as to avoid overdosing in superficial normal tissue during therapy;
a radiation shield arranged inside the beam shaping assembly, wherein the radiation shield shields leaking neutrons and photons so as to reduce dose of the normal tissue not exposed to irradiation; and
a beam outlet.
2. The beam shaping assembly for neutron capture therapy according to claim 1 , wherein the incident proton beam is accelerated by means of an accelerator and generate nuclear reaction with the target made of a metal material to produce neutrons.
3. The beam shaping assembly for neutron capture therapy according to claim 1 , wherein the reflector is made of a material having a high neutron reflection ability, and the thermal neutron absorber is made of a material having a cross section for acting with thermal neutrons.
4. The beam shaping assembly for neutron capture therapy according to claim 3 , wherein the reflector is made of at least one of Pb or Ni, and the thermal neutron absorber is made of 6 Li, and wherein an air passage is arranged between the thermal neutron absorber and the beam outlet.
5. The beam shaping assembly for neutron capture therapy according to claim 1 , wherein an outer surface of the moderator includes a first tapered section and a second tapered section adjoining to the first tapered section, and a tapering direction of the first tapered section is opposite to a tapering direction of the second tapered section, and wherein the first tapered section includes a first side and a second side facing away from the beam outlet and is tapered gradually from the second side towards the first side, and the second tapered section includes a third side and a fourth side facing the beam outlet and is tapered gradually from the third side towards the fourth side.
6. The beam shaping assembly for neutron capture therapy according to claim 5 , wherein the first side defines a first diameter perpendicularly to the main axis, the second side and the third side defines a second diameter perpendicularly to the main axis and the fourth side defines a third diameter perpendicularly to the main axis, the first diameter is 1 cm to 20 cm in length, the second diameter is 30 cm to 100 cm in length, the third diameter is 1 cm to 50 cm in length, and wherein multiple sintered blocks are connected to form the moderator and a density of the moderator is 80 to 100 percent of theoretical density.
7. A beam shaping assembly for neutron capture therapy comprising:
a beam inlet;
a target, wherein the target has nuclear reaction with an incident proton beam from the beam inlet to produce neutrons, and wherein the neutrons form a neutron beam defining a main axis;
a moderator adjoining to the target, wherein the neutrons are moderated by the moderator to epithermal neutron energies, and the material of the moderator is prepared from a material containing at least one of LiF, Li 2 CO 3 , Al 2 O 3 , AlF 3 , CaF 2 and MgF 2 ;
a reflector surrounding the moderator, wherein the reflector leads the neutrons deviated from the main axis back to enhance epithermal neutron beam intensity;
a thermal neutron absorber adjoining to the moderator, wherein the thermal neutron absorber absorbs thermal neutrons so as to avoid overdosing in superficial normal tissue during therapy;
a radiation shield arranged inside the beam shaping assembly, wherein the radiation shield shields leaking neutrons and photons so as to reduce dose of the normal tissue not exposed to irradiation; and
a beam outlet;
wherein the outer surface of the moderator includes the first tapered section and a second tapered section adjoining to the first tapered section, and a tapering direction of the first tapered section is opposite to a tapering direction of the second tapered section, and wherein the first tapered section includes a first side and a second side facing away from the beam outlet and is tapered gradually from the second side towards the first side, and the second tapered section includes a third side and a fourth side facing the beam outlet and is tapered gradually from the third side towards the fourth side; and
wherein the first side defines a first diameter perpendicularly to the main axis, the second side and the third side defines a second diameter perpendicularly to the main axis and the fourth side defines a third diameter perpendicularly to the main axis, the first diameter is 1 cm to 20 cm in length, the second diameter is 30 cm to 100 cm in length, the third diameter is 1 cm to 50 cm in length, and wherein multiple sintered blocks are connected to form the moderator and a density of the moderator is 80 to 100 percent of theoretical density.