CN108295385B - Neutron capture therapeutic device - Google Patents
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- CN108295385B CN108295385B CN201710017520.7A CN201710017520A CN108295385B CN 108295385 B CN108295385 B CN 108295385B CN 201710017520 A CN201710017520 A CN 201710017520A CN 108295385 B CN108295385 B CN 108295385B
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- 238000011282 treatment Methods 0.000 claims abstract description 58
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Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N5/1001—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy using radiation sources introduced into or applied onto the body; brachytherapy
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
- A61K41/00—Medicinal preparations obtained by treating materials with wave energy or particle radiation ; Therapies using these preparations
- A61K41/009—Neutron capture therapy, e.g. using uranium or non-boron material
- A61K41/0095—Boron neutron capture therapy, i.e. BNCT, e.g. using boronated porphyrins
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N5/1001—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy using radiation sources introduced into or applied onto the body; brachytherapy
- A61N5/1007—Arrangements or means for the introduction of sources into the body
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N5/1048—Monitoring, verifying, controlling systems and methods
- A61N5/1071—Monitoring, verifying, controlling systems and methods for verifying the dose delivered by the treatment plan
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
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- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N5/1077—Beam delivery systems
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N5/1001—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy using radiation sources introduced into or applied onto the body; brachytherapy
- A61N2005/1019—Sources therefor
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N2005/1085—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy characterised by the type of particles applied to the patient
- A61N2005/109—Neutrons
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N2005/1092—Details
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N2005/1092—Details
- A61N2005/1094—Shielding, protecting against radiation
Abstract
The invention discloses a neutron capture treatment device which comprises a neutron generating part, a retarder, a reflector, a beam outlet and a flexible shielding body, wherein the neutron generating part is used for generating neutrons, the retarder retards a neutron beam generated by the neutron generating part to an epithermal neutron beam, the reflector is used for reflecting the neutrons diffused around back to the neutron beam, the neutron beam reaches a patient through the beam outlet, and the patient is protected by the flexible shielding body. The present invention reduces the damage to a patient from exposure to additional neutron doses and gamma rays during a neutron capture therapy by providing such a solution.
Description
Technical Field
The present invention relates to a radiation therapy apparatus, and more particularly, to a neutron capture therapy apparatus.
Background
With the development of atomic science, radiation therapy such as cobalt sixty, linac, electron beam, etc. has become one of the main means for cancer therapy. However, the traditional photon or electron treatment is limited by the physical condition of the radioactive rays, and a large amount of normal tissues on the beam path can be damaged while killing tumor cells; in addition, due to the different sensitivity of tumor cells to radiation, traditional radiotherapy often has poor therapeutic effects on malignant tumors with relatively high radiation resistance (such as glioblastoma multiforme (glioblastoma multiforme) and melanoma (melanoma)).
In order to reduce radiation damage to normal tissue surrounding a tumor, the concept of target treatment in chemotherapy (chemotherapy) has been applied to radiotherapy; for tumor cells with high radiation resistance, radiation sources with high relative biological effects (relative biological effectiveness, RBE) such as proton therapy, heavy particle therapy, neutron capture therapy, etc. are also actively developed. The neutron capture treatment combines the two concepts, such as boron neutron capture treatment, and provides better cancer treatment selection than the traditional radioactive rays by means of the specific aggregation of boron-containing medicaments in tumor cells and the accurate neutron beam regulation.
Various radioactive rays, such as gamma rays and neutron beams, are generated in the neutron capture treatment process, and the radioactive rays can cause different degrees of damage to a human body, wherein the gamma rays have extremely strong penetrating power, and when the human body is irradiated by the gamma rays, the gamma rays can generate ionization action with cells in the body, and the ions generated by ionization can destroy main components such as protein, nucleic acid and the like which form living cell tissues, so that the cells can die seriously; neutron radiation can cause hematopoietic organ failure, damage to the digestive and central nervous systems, and can also produce genetic effects that affect the development of offspring of the irradiated subject. Therefore, the reasonable and effective shielding of the radioactive rays in the neutron capture treatment process and the protection of patients from the injury of the radioactive rays become a problem to be solved.
Disclosure of Invention
In order to solve the injury of radioactive rays generated in the neutron capture treatment process to operators or patients, the invention provides a neutron capture treatment device which comprises a neutron generating part, a retarder, a reflector, a beam outlet and a flexible shielding body, wherein the neutron generating part is used for generating neutrons, the neutrons form a neutron beam, and the neutron beam comprises fast neutrons; the retarder is adjacent to the neutron generating part and retards fast neutrons generated by the neutron generating part to epithermal neutrons; the reflector surrounds the retarder for reflecting neutrons diffusing to the surroundings back to the neutron beam; the beam outlet is used for enabling the neutron beam retarded by the retarder to pass through and irradiate a patient; the flexible shielding body is used for covering a part of the patient which does not need to receive neutron irradiation in the process of carrying out neutron capture treatment so as to shield neutron rays in the treatment process, and can be attached to the outline of the part under the action of external force.
The flexible shielding body is an object which can deform under the action of external force and is attached to the outline of a patient, and the object can be a soft object with deformation disappeared after the external force is eliminated; the deformation state of the object can be maintained after the external force is eliminated, and the external force is required to be additionally applied in the state to eliminate the deformation. The flexible shielding body can be attached to a part of a patient which is not required to be irradiated by neutrons under the action of external force in the neutron capturing treatment process so as to shield various neutron rays existing in the treatment process, wherein the external force comprises gravity.
Preferably, in the neutron capture treatment device, the neutron capture treatment device includes a collimator and a thermal neutron absorber, wherein the collimator is adjacent to the outer side of the beam outlet and is used for converging the neutron beam coming out of the beam outlet; the thermal neutron absorber is adjacent to the retarder and is used for absorbing thermal neutrons so as to avoid excessive dose to shallow normal tissues during treatment.
The neutron beam energy generated by the neutron generating part is different, and epithermal neutrons are used in the treatment process, the thermal neutrons generated by the neutron generating part or the thermal neutrons retarded by the retarder can cause neutron pollution to the surrounding environment, the thermal neutron absorber can effectively reduce the content of thermal neutrons in the neutron beam; the collimator can converge neutron beam, so that the neutron beam has better beam quality and treatment effect.
Preferably, in the neutron capture treatment device, the flexible shield is selected from paraffin, lead, polyethylene or a boron-containing composition, wherein the boron element in the boron-containing composition is 10 B。
The boron-containing composition preferably comprises silica gel and a boron-containing composition 10 Composition of neutron capture material of B element, which contains 10 The neutron capture material of the B element accounts for 10-50% of the weight of the boron-containing composition. The shielding effect of the flexible shielding body on the neutron rays is mainly derived from the components 10 Neutron capture material of element B, in particular 10 B element, thus containing 10 The higher the content of B element, the better the shielding effect of the flexible shielding on the neutron rays, but if it contains 10 The content of the B element is too high, the content of corresponding silica gel is reduced, and then the flexibility of the flexible shielding body is greatly reduced, so that the use effect is influenced.
The boron-containing composition comprises, in addition to silica gel and a boron-containing composition 10 In addition to the neutron capture material of element B, a suitable amount of curing agent may be added to provide a flexible shield with a certain morphology, as is well known to those skilled in the art.
Further, the said contains 10 The neutron capture material of the B element is preferably 10 BN or 10 B 4 C。
Still more preferably, the thickness of the flexible shield is 1cm or less. On the premise of fixed materials and proportions for forming the flexible shielding body, the thicker the thickness of the flexible shielding body is, the better the shielding wire effect on the neutron rays is, but the flexibility of the flexible shielding body is reduced along with the increase of the thickness, and in order to avoid the influence of the excessive thickness of the flexible shielding body on the flexibility of the flexible shielding body and to alleviate the uncomfortable feeling of the heavier flexible shielding body on a patient, the thickness of the flexible shielding body is preferably less than or equal to 1cm, and is preferably 0.5cm, 0.7cm and 1cm.
During neutron capture treatment, the part to be irradiated of the patient needs to be as close to the beam outlet of the collimator as possible to improve the treatment effect, and the shortest distance between the flexible shielding body and the collimator is preferably less than or equal to 20cm.
It is further preferred that in the neutron capture therapy device, the flexible shield has elasticity, and that the flexible shield is held against the patient's contour by the elasticity during neutron capture therapy.
Preferably, in the neutron capture treatment device, any opening of the flexible shielding body is provided with a tightening structure, and the tightening structure enables the flexible shielding body to be attached to the outline of the patient at the opening, so that neutron rays are prevented from entering from a gap between the opening and the outline of the patient, and normal tissues of the patient are injured.
In the neutron capture treatment device, the normal tissue covered by the flexible shield receives a radiation dose of less than 18Gy/h during neutron capture treatment.
The flexible shielding body is used for covering a part of a patient which is not required to be irradiated by neutrons in the treatment process, and can be cut into a clothes shape or other shapes capable of protecting the patient from being injured by the neutrons.
Note that: the epithermal neutron energy region is between 0.5eV and 40keV, the thermal neutron energy region is less than 0.5eV, and the fast neutron energy region is more than 40keV.
The invention has the beneficial effect of providing the neutron capture treatment device which can effectively reduce the extra damage of the neutron rays to the patient.
Drawings
FIG. 1 is a schematic diagram of an accelerator type neutron capture therapy device;
FIG. 2 is a schematic diagram of a reactor type neutron capture therapy device;
FIG. 3 is a schematic diagram of measuring the shielding effect of a flexible shield on a neutron ray;
fig. 4 is a flexible shield cut into a garment shape.
Detailed Description
Neutron capture therapy has been increasingly used in recent years as an effective means for treating cancer, and among them, boron neutron capture therapy is most commonly used, and neutron capture therapy devices can be classified into nuclear reactor type neutron capture therapy devices or accelerator type neutron capture therapy devices according to neutron generation units. The basic components of an accelerator boron neutron capture therapy device as shown in fig. 1 generally include an accelerator 11a for accelerating charged particles (e.g., protons, deuterons, etc.), a target T, a beam shaping body 30a, a collimator 40a, and a body 51b to be irradiated wrapped with a flexible shield 50, wherein the accelerated charged particles P react with the metal target T to produce neutrons, and suitable nuclear reactions are selected based on the desired neutron yield and energy, available energy and current of the accelerated charged particles, physical and chemical properties of the metal target, etc., with the nuclear reactions being discussed 7 Li(p,n) 7 Be and Be 9 Be(p,n) 9 And B, performing an endothermic reaction. The energy threshold values of the two nuclear reactions are respectively 1.881MeV and 2.055MeV, because the ideal neutron source for boron neutron capture treatment is epithermal neutrons with the energy level of keV, in theory, if protons with the energy only slightly higher than the threshold value are used for bombarding a metal lithium target material, relatively low-energy neutrons can Be generated, the nuclear reactions can Be clinically used without too much slowing treatment, however, the proton action cross sections of the two targets of lithium metal (Li) and beryllium metal (Be) and the threshold energy are not high, and in order to generate enough neutron flux, protons with higher energy are generally selected for initiating the nuclear reactions.
The ideal target should have the characteristics of high neutron yield, close neutron energy distribution generated to the epithermal neutron energy region (which will be described in detail later), no too much strong penetrating radiation generation, safety, low cost, easy operation, high temperature resistance, etc., but practically no nuclear reaction meeting all the requirements can be found, and the target is made of lithium metal in the embodiment of the invention. However, it is well known to those skilled in the art that the material of the target may be made of other metallic materials than those mentioned above.
The requirements for the heat removal system will vary depending on the chosen nuclear reaction, e.g 7 Li(p,n) 7 Be has lower requirements for heat removal systems due to the lower melting point and thermal conductivity of the metal target (lithium metal) 9 Be(p,n) 9 B is high. In the embodiment of the invention adopts 7 Li(p,n) 7 Nuclear reaction of Be.
Whether the neutron source of the boron neutron capture treatment is from nuclear reaction of charged particles of a nuclear reactor or an accelerator and a target, the generated mixed radiation field is that the beam contains neutrons and photons with low energy to high energy; for boron neutron capture treatment of deep tumors, the more radiation content, except for epithermal neutrons, the greater the proportion of non-selective dose deposition of normal tissue, and therefore the less radiation that will cause unnecessary doses.
The international atomic energy organization (IAEA) gives five air beam quality factor suggestions for neutron sources for clinical boron neutron capture treatment, and the five suggestions can be used for comparing the advantages and disadvantages of different neutron sources and serve as reference bases for selecting neutron production paths and designing beam shaping bodies. These five suggestions are as follows:
epithermal neutron beam flux Epithermal neutron flux>1x 10 9 n/cm 2 s
Fast neutron contamination Fast neutron contamination<2x 10 -13 Gy-cm 2 /n
Photon pollution Photon contamination<2x 10 -13 Gy-cm 2 /n
The ratio thermal to epithermal neutron flux ratio of thermal neutron to epithermal neutron flux is less than 0.05
Neutron current to flux ratio epithermal neutron current to flux ratio >0.7
Note that: the epithermal neutron energy region is between 0.5eV and 40keV, the thermal neutron energy region is less than 0.5eV, and the fast neutron energy region is more than 40keV.
1. Epithermal neutron beam flux:
the neutron beam flux and the boron-containing drug concentration in the tumor together determine the clinical treatment time. If the concentration of the boron-containing medicament in the tumor is high enough, the requirement on the neutron beam flux can be reduced; conversely, if the boron-containing drug concentration in the tumor is low, a high flux epithermal neutron is required to administer a sufficient dose to the tumor. IAEA requires a epithermal neutron beam flux of greater than 10 epithermal neutrons per square centimeter per second 9 The neutron beam at this flux can generally control the treatment time to within one hour for current boron-containing drugs, and short treatment times can more effectively utilize the limited residence time of boron-containing drugs within tumors in addition to advantages for patient positioning and comfort.
2. Fast neutron contamination:
since fast neutrons cause unnecessary normal tissue doses, which are positively correlated with neutron energy, as a matter of pollution, the fast neutron content should be minimized in the neutron beam design. Fast neutron contamination is defined as the fast neutron dose accompanied by a unit epithermal neutron flux, with IAEA recommended for fast neutron contamination as less than 2x 10 -13 Gy-cm 2 /n。
3. Photon pollution (gamma) radiation contamination):
gamma rays belonging to the intense penetrating radiation can cause non-selective dose deposition of all tissues on the beam path, so reducing the gamma ray content is also an essential requirement for neutron beam design, gamma ray pollution is defined as the gamma ray dose accompanied by the unit epithermal neutron flux, and the proposal of IAEA on gamma ray pollution is less than 2x 10 -13 Gy-cm 2 /n。
4. Ratio of thermal neutron to epithermal neutron flux:
because of high thermal neutron attenuation speed and poor penetrating capacity, most of energy is deposited on skin tissues after entering a human body, and thermal neutrons are required to be used as neutron sources for boron neutron capture treatment for superficial tumors such as melanoma and the like, so that the thermal neutron content is required to be reduced for deep tumors such as brain tumors and the like. The IAEA to thermal neutron to epithermal neutron flux ratio is recommended to be less than 0.05.
5. Neutron current to flux ratio:
the ratio of neutron current to flux represents the directionality of the beam, the larger the ratio is, the better the frontage of the neutron beam is, the high frontage neutron beam can reduce the surrounding normal tissue dose caused by neutron divergence, and the treatable depth and the posture setting elasticity are improved. IAEA is recommended to have a neutron current to flux ratio greater than 0.7.
The dose distribution in the tissue is obtained by using the prosthesis, and the quality factor of the prosthesis beam is deduced according to the dose-depth curve of normal tissue and tumor. The following three parameters can be used to make comparisons of the therapeutic benefits of different neutron beams.
1. Effective treatment depth:
the tumor dose is equal to the depth of the maximum dose of normal tissue, and at a position behind the depth, the tumor cells obtain a dose smaller than the maximum dose of normal tissue, i.e. the advantage of boron neutron capture is lost. This parameter represents the penetration capacity of the neutron beam, with a greater effective treatment depth indicating a deeper treatable tumor depth in cm.
2. Effective therapeutic depth dose rate:
i.e. the tumor dose rate at the effective treatment depth, is also equal to the maximum dose rate of normal tissue. Because the total dose received by normal tissues is a factor affecting the total dose size that can be given to a tumor, a larger effective treatment depth dose rate indicates a shorter irradiation time in cGy/mA-min, as the parameters affect the length of treatment time.
3. Effective therapeutic dose ratio:
the average dose ratio received from the brain surface to the effective treatment depth, tumor and normal tissue, is referred to as the effective treatment dose ratio; calculation of the average dose can be obtained from the integration of the dose-depth curve. The larger the effective therapeutic dose ratio, the better the therapeutic benefit of the neutron beam.
In order to make the beam shaping body have a comparative basis in design, besides the five IAEA suggested beam quality factors in air and the three parameters mentioned above, the following parameters for evaluating the neutron beam dose performance are also used in the embodiment of the present invention:
1. the irradiation time is less than or equal to 30min (the proton current used by the accelerator is 10 mA)
2. 30.0RBE-Gy with therapeutic depth of 7cm or more
3. The maximum tumor dose is more than or equal to 60.0RBE-Gy
4. The maximum dose of normal brain tissue is less than or equal to 12.5RBE-Gy
5. The maximum skin dose is less than or equal to 11.0RBE-Gy
Note that: RBE (Relative Biological Effectiveness) is a relative biological effect, which is different due to photons and neutrons, the dose terms above are each multiplied by the relative biological effects of the different tissues to find the equivalent dose.
Neutron capture therapy has been increasingly used in recent years as an effective means for treating cancer, with boron neutron capture therapy being the most common, and the invention will be described in further detail below with reference to the accompanying drawings so that those skilled in the art can practice the invention in light of the description.
It will be understood that terms such as "having," "including," and "comprising," as used herein, do not preclude the presence or addition of one or more other ingredients or combinations thereof.
Neutrons used in the neutron capture treatment device are generated by a neutron generating part, different neutron generating parts are an accelerator type neutron generating part and a reactor type neutron generating part according to the principle of neutron generation, and no matter whether a neutron source of the boron neutron capture treatment is from nuclear reactor or nuclear reaction of charged particles of an accelerator and a target material, the generated neutron is a mixed radiation field, namely the beam contains neutrons and photons with low energy to high energy; for boron neutron capture treatment of deep tumors, the more radiation content, except for epithermal neutrons, the greater the proportion of non-selective dose deposition of normal tissue, and therefore the less radiation that will cause unnecessary doses.
Example 1 ]
The accelerator type neutron capture treatment device shown in fig. 1 comprises an accelerator type neutron generating part 10a, a beam shaping body 30a, a collimator 40a and a flexible shielding body 50, wherein the accelerator type neutron generating part 10a comprises an accelerator 11a and a neutron generating body 12a embedded in the beam shaping body 30a, and a target material T is arranged inside the neutron generating body 12 a; the accelerator 11a is used to accelerate charged particles P, which act with the target T to generate neutrons. The beam shaping body 30a comprises a reflector 31a, a retarder 32a and a thermal neutron absorber 33a, neutrons generated by the accelerator type neutron generating part 10a need to reduce the neutron content of other types as far as possible to avoid hurting operators or patients except epithermal neutrons to meet treatment requirements due to a wide energy spectrum, so neutrons coming out of the neutron generating part 10a need to adjust fast neutron energy in the neutrons to an epithermal neutron energy region through the retarder 32a, and one or a plurality of combinations of compounds containing elements such as Al, mg, ca, pb, F and the like can be used as materials of the retarder 32 a; the reflector 31a surrounds the retarder 32a and reflects neutrons diffused around the retarder 32a back to the neutron beam N to improve the neutron utilization rate, the thermal neutron absorber 33a is arranged at the rear part of the retarder 32a and is used for absorbing thermal neutrons passing through the retarder 32a to reduce the content of thermal neutrons in the neutron beam N, the beam outlet 34a is arranged at the rear part of the thermal neutron absorber 33a and is used for allowing the neutron beam N to pass through, in addition, a collimator 40 is arranged outside the beam outlet 34a and is used for converging the neutron beam, so that the neutron beam has higher targeting property in the treatment process; the neutron beam is converged by the collimator 40 and irradiates the patient 51, and when the neutron beam passing through the collimator 40 and gamma rays mixed in the neutron beam irradiate the part of the patient which is not required to be treated, serious damage is often caused to the patient, so that the part of the patient 51 which is not required to be irradiated by epithermal neutrons is shielded by the flexible shielding body 50 in preparation for treatment, the flexible shielding body 50 plays a role of exposing the part 52 to be irradiated to the irradiation range of the neutron beam and protecting the patient from being damaged by more neutron rays, the flexible shielding body 50 surrounds the normal part of the patient body and can be attached to the body of the patient 51 under the action of external force, the flexible shielding device and the patient shown in fig. 1 have a certain distance only for illustrating that the shape of the flexible shielding device can be changed at will according to the outline of the patient body, the flexible shielding body has no limitation meaning on whether the flexible shielding body is attached to the patient, and conversely, when the flexible shielding body is attached to the patient, the damage to the human body can be better prevented from being caused by changing the propagation direction of the neutron rays in the flexible shielding body. The flexible shield 51 may have elasticity to be closely attached to the patient's body by its own elasticity.
Example 2 ]
The reactor type neutron capture treatment device shown in fig. 2 comprises a reactor type neutron generating part 10b, a beam shaping body 30b, a collimator 40b and a flexible shielding body 50, wherein neutrons generated by the reactor are mixed radiation fields, a retarder 32b in the beam shaping body 30b is used for retarding fast neutrons in the mixed radiation fields into epithermal neutrons, a reflector 31b reflects neutrons diffused around back to a neutron beam N, and a thermal neutron absorber 33b is used for absorbing thermal neutrons in the neutron beam retarded by the retarder 32b so as to improve the content of epithermal neutrons in the neutron beam; the epithermal neutron beam passes through the beam outlet 34b to the patient 51, wherein a collimator 40b located at the beam outlet 34b is used to converge the neutron beam N to improve the accuracy of the treatment. The flexible shield 50 exposes the portion 52 of the patient 51 to be irradiated to the neutron beam to cover the portion of the patient not to be treated, so that normal tissue of the patient 51 is protected from gamma rays in the neutron beam and the mixed neutron beam.
Example 3 ]
When a patient is treated by the neutron capture treatment device, the neutron beam N' converged by the collimator irradiates the patient part of the patient, and the part which does not need to be irradiated is protected by the flexible shielding body.
FIG. 3 is a schematic view showing the measurement of the shielding effect of the flexible shielding on the neutron rays, N' is the neutron beam after being converged by the collimator in the accelerator type neutron capture therapy device or the reactor type neutron capture therapy device, 50 in FIG. 3Shown is a flexible shield of thickness 1cm, wherein the flexible shield comprises a silicone gel and 10 BN, the embodiment selects and uses respectively 10 Materials having BN weights of 10%, 20%, 30%, 40% and 50% of the weight of the flexible shield were calculated as different contents, respectively, as the flexible shield 10 Shielding effect of the flexible shield of BN on the neutron rays. Shown at 53 in figure 3 is a detector for measuring neutron reactivity,
the detector detects the neutron reaction rate according to the reaction of the copper sheet and neutrons and generates gamma rays, and the quantity of the generated gamma rays and the neutron flux passing through the copper sheet are in direct proportion, and the detector determines the neutron reaction rate by measuring the quantity of the gamma rays.
The present embodiment evaluates the shielding effect of the flexible shield on the neutron rays with parameter a, wherein,
A＝RR/RR ref
wherein RR is the neutron reaction rate detected by the detector when the detector is in the position shown in FIG. 3, and a flexible shielding body is arranged between the detector and the neutron beam;
RR ref in order to provide a detector in the position shown in fig. 3, a flexible shield is not provided between the detector and the neutron beam, and the neutron reactivity detected by the detector.
It follows that the smaller the value of a, the better the shielding effect of the flexible shield against neutrons.
Detectors measure RR and RR ref When it is fixed in position relative to the collimator.
Under the above experimental conditions, when the flexible shield contains 10%, 20%, 30%, 40% and 50%, respectively 10 BN, the corresponding a values are respectively: 8.3%, 7.5%, 6.2%, 5.4%/and 4.9%, whereby the addition of flexible shield material is visible 10 BN is effective in shielding neutron rays and, as 10 The increase of BN content strengthens the shielding effect of the flexible shielding body on the neutron rays.
Example 4 ]
To enhance patient comfort during treatment, the flexible shield may be cut into various shapes as needed to protect the patient, preferably the flexible shield is cut into a garment shape (as shown in fig. 4), and the flexible shield may be cut to expose the patient's area where the neutron beam is to be irradiated.
The neutron capture therapy device disclosed in the present invention is not limited to the above embodiments and the structures shown in the drawings. Obvious changes, substitutions, or modifications to the materials, shapes, and positions of the components therein are made on the basis of the present invention, and are within the scope of the present invention as claimed.
Claims (9)
1. A neutron capture therapy device, characterized in that: the neutron capture treatment device comprises a neutron generating part, a retarder, a reflector, a beam outlet and a flexible shielding body, wherein the neutron generating part is used for generating neutrons, the neutrons form a neutron beam, and the neutron beam comprises fast neutrons; the retarder is adjacent to the neutron generating part and retards fast neutrons generated by the neutron generating part to epithermal neutrons; the reflector surrounds the retarder for reflecting neutrons diffusing to the surroundings back to the neutron beam; the beam outlet is used for enabling the neutron beam retarded by the retarder to pass through and irradiate a patient; the flexible shielding body is used for covering a part of the patient which does not need to receive neutron irradiation in the process of carrying out neutron capture treatment so as to shield neutron rays in the treatment process, and can be attached to the outline of the part under the action of external force; the flexible shield is selected from paraffin, polyethylene or a boron-containing composition, wherein the boron element in the boron-containing composition is 10 B。
2. The neutron capture therapy device of claim 1, wherein the neutron capture therapy device includes a collimator and a thermal neutron absorber, wherein the collimator is adjacent to the outside of the beam outlet for converging the neutron beam exiting the beam outlet; the thermal neutron absorber is adjacent to the retarder and is used for absorbing thermal neutrons so as to avoid excessive dose to shallow normal tissues during treatment; the neutron capture therapy device includes a nuclear reactor neutron capture therapy device or an accelerator neutron capture therapy device.
3. The neutron capture therapy device of claim 1, wherein the boron-containing composition comprises silica gel and a boron-containing composition 10 A neutron capturing material of B element, which contains 10 The neutron capture material of the B element accounts for 10-50% of the weight of the boron-containing composition.
4. The neutron capture therapy device of claim 3, wherein the containment 10 The neutron capture material of the B element is 10 BN or 10 B 4 C。
5. The neutron capture therapy device of any one of claims 1-4, wherein the external force comprises gravity and the flexible shield has a thickness of less than or equal to 1cm.
6. The neutron capture therapy device of claim 2, wherein the flexible shield is at a distance of less than or equal to 20cm from the collimator nearest the collimator during neutron capture therapy.
7. The neutron capture therapy device of any one of claims 1-4, wherein the flexible shield has elasticity, the flexible shield conforming to the contours of the patient under the influence of the elasticity during neutron capture therapy.
8. The neutron capture therapy device of any one of claims 1-4, wherein any one of the openings of the flexible shield is provided with a constriction structure, the constriction structure conforming the flexible shield to the contours of the patient at the opening.
9. The neutron capture therapy device of any one of claims 1-4, wherein the normal tissue covered by the flexible shield receives a radiation dose less than 18Gy/h during neutron capture therapy.
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