Method for measuring radiation intensity

Abstract

A method for measuring radiation intensity includes measuring the radiation intensity received by the protein in a radiation field based on degree of protein degradation in the radiation field, wherein the degree of degradation is a ratio of the molecular weight of the protein before and after irradiation. The measuring method is simple in operation, small in number of steps, small in error, and capable of measuring radiation doses of various radiation fields or even mixed radiation fields. Use of a biological dosimeter for measuring the radiation intensity by the method in a neutron capture therapy system can not only assess radiation contamination in the irradiation chamber, but also evaluate the neutron dose.

Claims

1. A method for measuring radiation intensity, comprising: measuring the radiation intensity received by a protein in a radiation field based on degree of protein degradation in the radiation field, wherein the degree of degradation is a ratio of the molecular weight of the protein before and after irradiation; wherein the radiation field comprises: a gamma radiation field, a proton radiation field, a heavy ion radiation field, or a mixed radiation field of neutron and gamma; wherein when the radiation field is a mixed radiation field of neutron and gamma, the method further comprises: utilizing the degree of protein degradation in the gamma radiation field to draw a standard curve and calculating the radiation intensity corresponding to the degree of protein degradation Xi as the relative radiation intensity of the protein in the gamma radiation field Di=Mj+Nj, wherein Mj is gamma intensity, Nj is equivalent intensity of neutron relative to gamma, the neutron intensity actually received by the protein is ratio of the equivalent intensity of neutron relative to gamma to the conversion coefficient Ki at the protein degradation concentration, and the conversion coefficient Ki is ratio of the gamma intensity to the neutron intensity at a particular degree of protein degradation.

2. The method according to claim 1 further comprising: formulating a plurality of sets of protein solutions of the same concentration, respectively placing the protein solutions in a radiation field and exposing them to radiation of different intensities, terminating the radiation, and measuring the radiation intensity received by each group of protein solutions and analyzing the degree of protein degradation after irradiation, and plotting and fitting a standard curve of radiation intensity and degree of protein degradation.

3. The method according to claim 1, wherein the protein is a radiation sensitive protein when the radiation intensity for measurement is less than 1000 Gy, and the radiation sensitive protein is a protein having a ratio of the molecular weight after irradiation to the molecular weight of the protein before irradiation of less than 0.8 at a concentration of less than 1 g/L when exposed to a radiation intensity of 1000 Gy.

4. The method according to claim 1, wherein the protein is a bovine serum albumin solution having a concentration of 0.2 g/L to 0.6 g/L when the radiation intensity for measurement is 100 Gy to 500 Gy.

5. The method according to claim 2 further comprising: formulating a protein solution of the same concentration as in claim 2, placing the protein solution in a radiation environment to be measured for receiving radiation, terminating radiation and measuring the degree of protein degradation after irradiation, and calculating the radiation intensity received by the protein during the irradiation of the radiation by the standard curve.

6. The method according to claim 5, wherein the step of placing the protein solution in the radiation environment to be measured for receiving radiation further comprises: adjusting the time during which the protein solution is subjected to radiation exposure such that the radiation intensity received by the protein solution is in the range of the radiation intensity used in the standard curve.

7. The method for measuring radiation intensity according to claim 1 for use in a neutron capture therapy system, wherein the method is provided in a biological dosimeter for measuring radiation dose of the protein.

8. The method according to claim 7, wherein when the radiation dose for measurement is 100 Gy to 500 Gy, the protein used is a bovine serum albumin solution at a concentration of 0.2 g/L to 0.6 g/L.

9. The method according to claim 8, wherein the bovine serum albumin solution of 0.2 g/L to 0.6 g/L is configured to measure a radiation dose of 100 Gy to 500 Gy.

10. The method according to claim 7, wherein the molecular weight of the protein before and after irradiation with radiation is measured by SDS-gel electrophoresis and the degree of protein degradation after irradiation with radiation is calculated.

11. The method according to claim 7, wherein the degree of protein degradation is quantified by the ratio of the molecular weight of the protein after irradiation with radiation to the molecular weight of the protein before irradiation with radiation.

12. The method according to claim 7, wherein the biological dosimeter performs measurement of the radiation dose by the following steps: formulating a plurality of sets of protein solutions, respectively placing the protein solutions in the radiation field and exposing them to radiation of different doses, terminating the radiation, measuring the radiation dose received by each group of protein solutions and analyzing the degree of protein degradation after exposure to radiation, and plotting and fitting a standard curve of radiation dose and degree of protein degradation; and formulating a protein solution of the same concentration as in the above step, placing the protein solution in a radiation environment to be measured for receiving radiation, terminating radiation and measuring the degree of protein degradation after irradiation, and calculating the radiation intensity received by the protein during the irradiation of the radiation by the standard curve, and substituting a numerical value capable of reflecting the degree of protein degradation into the above standard curve to calculate the radiation dose that the protein receives during the irradiation of the radiation.

13. The method for measuring radiation intensity according to claim 1 for use in a neutron capture therapy system, wherein the method is provided in a biological dosimeter in a neutron capture therapy system, wherein the neutron capture therapy system comprises: a neutron source configured to generate a neutron beam, a beam shaping assembly located at the rear of the neutron source for adjusting the fast neutrons in the neutron beam with a broad energy spectrum generated by the neutron source to epithermal neutrons, a collimator located at the rear of the beam shaping assembly for converging the epithermal neutrons, and the biological dosimeter disposed at the rear of the collimator for measuring the radiation dose at the location of the biological dosimeter.

14. The method according to claim 13, wherein the neutron source is an accelerator neutron source or a reactor neutron source.

15. The method according to claim 13, wherein the beam shaping assembly comprises a reflector and a moderator, wherein the reflector surrounds the moderator for reflecting neutrons diffused outside the beam shaping assembly back to the moderator, and the moderator is used to moderating fast neutrons into epithermal neutrons.

16. The method according to claim 13, wherein the epithermal neutron energy region is between 0.5 eV and 40 keV, and the fast neutron energy region is greater than 40 keV.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a standard curve of a bovine serum albumin solution at a concentration of 0.3 g/L in a gamma radiation field.

(2) FIG. 2 is a standard curve of a bovine serum albumin solution at a concentration of 0.2 g/L in a gamma radiation field.

(3) FIG. 3 is a standard curve of a bovine serum albumin solution at a concentration of 0.5 g/L in a gamma radiation field.

(4) FIG. 4 is a standard curve of a bovine serum albumin solution at a concentration of 0.6 g/L in a gamma radiation field.

(5) FIG. 5 is a neutron capture therapy system containing a biological dosimeter.

DETAILED DESCRIPTION

(6) The present disclosure will be further described in detail below with reference to the accompanying drawings, so that those skilled in the art can follow the instructions to implement the present disclosure. The above description and the following detailed description are to be considered as illustrative and not restrictive to the subject matter of the present disclosure.

(7) It is to be understood that the terms “having”, “comprising” and “including” do not exclude the presence or addition of one or more other components or combinations thereof.

(8) In order to clearly illustrate the technical solution of the present disclosure, the terms present in the present disclosure are defined as follows:

(9) The degree of protein degradation is the ratio of the molecular weight of the protein before and after exposure to radiation;

(10) The numerical value calculated by substituting the value of the degree of protein degradation in the radiation field to be measured into the standard curve is called the radiation dose;

(11) When the radiation field to be measured is different from the radiation field used to draw the standard curve, the radiation dose is called a relative dose:

(12) When the radiation field to be measured and the radiation field used to draw the standard curve belong to the same kind of radiation field, the radiation dose is called the actual dose;

(13) The biological dosimeter provided by the present disclosure can measure the radiation dose of various radiation fields (including mixed radiation fields) by utilizing the degree of degradation of proteins in the radiation field, and the method of using the biological dosimeter comprises two steps;

(14) a step of drawing a standard curve: formulating a plurality of sets of protein solutions, respectively placing the protein solutions in the radiation field and exposing them to radiation of different doses, terminating the radiation, measuring the radiation dose received by each group of protein solutions and analyzing the degree of protein degradation after exposure to radiation, and plotting and fitting a standard curve of radiation dose and degree of protein degradation.

(15) a step of measuring the dose of the radiation field to be measured: formulating a protein solution of the same concentration as in the above step, placing the protein solution in a radiation environment to be measured for receiving radiation, terminating radiation and measuring the degree of protein degradation after irradiation, and calculating the radiation intensity received by the protein during the irradiation of the radiation by the standard curve, and substituting a numerical value capable of reflecting the degree of protein degradation into the standard curve to calculate the radiation dose that the protein receives during the irradiation of the radiation.

(16) Use of the biological dosimeter and drawing of a standard curve of the biological dosimeter will be specifically described below by way of examples with reference to the accompanying drawings:

<Embodiment 1> Drawing of a Standard Curve of a Biological Dosimeter

(17) The standard curve drawn by the biological dosimeter provided by the present disclosure can be drawn according to the degree of protein degradation in any kind of radiation field. In this embodiment, a standard curve is drawn by the degree of degradation of bovine serum albumin in the gamma radiation field to illustrate a method of drawing the standard curve.

(18) Different concentrations of proteins have different degree of degradation in the radiation field. Protein concentration is a factor that affects the degree of degradation in the radiation field. It is further illustrated in the following by the standard curve drawn by the degradation degree of different concentrations of protein in the gamma radiation field.

(19) Drawing of a Standard Curve of a Bovine Serum Albumin Solution at a Concentration of 0.3 g/L in the Gamma Radiation Field:

(20) 0.03 g of BSA was dissolved in 100 g of distilled water to formulate a BSA solution having a concentration of 0.3 g/L, and the BSA solution was uniformly mixed and divided into several equal portions, and 6 parts of the BSA solutions were placed in a gamma radiation field to receive different doses of gamma radiation and the dose of each BSA solution in the radiation field was measured by Gafchromic film to be 118 Gy, 258 Gy, 337 Gy, 358 Gy, 370 Gy and 405 Gy.

(21) The molecular weights of the protein without radiation irradiation and the protein exposed to different doses in the radiation field were calculated by SDS-gel electrophoresis in combination with Image J, and the ratio of the molecular weight of the protein after irradiation to the molecular weight of the protein before irradiation is used to describe the degree of protein degradation under the action of the radiation dose. The results are shown in Table 1:

(22) TABLE-US-00001 TABLE 1 Degree of degradation of 0.3 g/L bovine serum albumin under different doses of gamma radiation Radiation dose received by protein (Gy) Degree of protein degradation 118 0.75 258 0.42 337 0.25 358 0.22 370 0.19 405 0.11

(23) From the above experimental data, a function curve between the degree of protein degradation and the radiation dose received by the protein is fitted as shown in FIG. 1. From the fitted standard curve of 0.3 g/L bovine serum albumin shown in FIG. 1, it can be seen that there is a good linear relationship between the degree of protein degradation and its corresponding radiation dose in the range of radiation doses from 118 Gy to 405 Gy.

(24) The same methods and steps were used to calculate the degree of degradation of bovine serum albumin solutions at concentrations of 0.2 g/L, 0.5 g/L, and 0.6 g/L in the gamma radiation field, as shown in Table 2, Table 3, and Table 4, respectively.

(25) TABLE-US-00002 TABLE 2 Degree of degradation of 0.2 g/L bovine serum albumin under different doses of gamma radiation Radiation dose received by protein (Gy) Degree of protein degradation 133 0.49 258 0.27 358 0.1 370 0.06 380 0.03

(26) TABLE-US-00003 TABLE 3 Degree of degradation of 0.5 g/L bovine serum albumin under different doses of gamma radiation Radiation dose received by protein (Gy) Degree of protein degradation 142 0.85 258 0.49 324 0.31 383 0.15

(27) TABLE-US-00004 TABLE 4 Degree of degradation of 0.6 g/L bovine serum albumin under different doses of gamma radiation Radiation dose received by protein (Gy) Degree of protein degradation 118 0.86 249 0.62 328 0.46 405 0.25

(28) TABLE-US-00005 TABLE 5 Degree of degradation of 0.1 g/L bovine serum albumin under different doses of gamma radiation Radiation dose received by protein (Gy) Degree of protein degradation 118 0.37 133 0.28 142 0.22 215 0.1

(29) TABLE-US-00006 TABLE 6 Degree of degradation of 1 g/L bovine serum albumin under different doses of gamma radiation Radiation dose received by protein (Gy) Degree of protein degradation 249 0.87 258 0.83 328 0.78 358 0.67 405 0.58 419 0.55

(30) According to the experimental data in Tables 2 to 4, the standard curves of the degree of degradation of different concentrations of protein in the radiation field are respectively plotted as shown in FIG. 2 to FIG. 4, and it can be seen from the figures that the degree of degradation of different concentrations of protein in the radiation field has a good linear relationship with the radiation dose it receives.

(31) Tables 5 and 6 show the degradation of bovine serum albumin at concentrations of 0.1 g/L and 1 g/L, respectively, under different doses of gamma radiation. From the data in these two tables, it can be found that the degree of protein degradation in the radiation field has a linear relationship with the radiation dose it receives, indicating that a protein solution with a concentration lower than 0.2 g/L or a protein solution with a concentration higher than 0.6 g/L can also be used as a biological dosimeter.

(32) The standard curve can be used to detect the radiation dose of the same concentration of protein in a radiation field of unknown intensity and unknown type, and the radiation dose calculated by substituting it into the standard curve is expressed by the dose of gamma rays. When the unknown type of radiation field is a gamma radiation field, the calculated radiation dose is the same as the actual radiation dose received by the protein in the radiation field to be measured. When the unknown type of radiation field is not a gamma radiation field, the calculated radiation dose is the relative dose of the protein in the unknown radiation field. It is needed to calculate the conversion coefficient between the gamma radiation field and the radiation field to be measured through experiments.

<Embodiment 2> Method for Measuring Actual Radiation Dose of Mixed Radiation Field of Neutron and Gamma by Biological Dosimeter

(33) When measuring the radiation intensity field with a biological dosimeter, the standard curve between the degree of protein degradation and the radiation dose can be determined in advance by the type of radiation field to be measured. It is also possible to measure the actual radiation dose of the radiation field to be measured by using a standard curve determined from a radiation field which is not to be measured and the conversion coefficient between the radiation field to be measured and the radiation field used for the standard curve.

(34) The conversion coefficient between the radiation fields needs to be further confirmed by experiments. In this embodiment, the calculation method of the conversion coefficient between the gamma radiation field and the neutron radiation field is taken as an example to illustrate the calculation method of the conversion coefficient between different radiation fields.

(35) According to <Embodiment 1>, a certain concentration of the protein solution is formulated, and the protein solution is placed in a gamma radiation field to receive different doses (Dγ.sub.1, Dγ.sub.2 . . . Dγ.sub.n) of gamma ray irradiation, and the degree of protein degradation X.sub.1, X.sub.2 . . . X.sub.n at the dose of Dγ.sub.1, Dγ.sub.2 . . . Dγ.sub.n was calculated, respectively.

(36) Protein solutions of the above specific concentrations were formulated and placed in a neutron irradiation field for irradiation. When the degree of protein degradation in the neutron radiation field is consistent with the degree of protein degradation in the gamma radiation field (i.e., when the degradation degree of the protein in the neutron radiation field is X.sub.1, X.sub.2 . . . X.sub.n, respectively), the neutron doses Dn.sub.1, Dn.sub.2 . . . Dn.sub.n received by the proteins are read.

(37) The ratio of the gamma dose to the neutron dose of the protein at a particular degree of degradation is set as the conversion coefficient between the neutron and gamma for the degree of protein degradation:
K.sub.i=Dγ.sub.i/Dn.sub.i,(wherein i takes values from 1 to n)

(38) A curve is drawn between the degree of protein degradation and the conversion coefficient corresponding to the degree of degradation, and the curve function is fitted:
Ki=f(Xi)

(39) When the relative radiation dose of the protein in the neutron radiation field is calculated by the standard curve made by the gamma radiation field, first, the conversion coefficient at the degree of degradation is calculated according to substituting the degree of protein degradation into the function Ki=f(Xi). Then, the neutron radiation dose actually received by the protein in the neutron radiation field is calculated based on the conversion coefficient and the relative radiation dose calculated from the standard curve. The neutron radiation dose actually received by the protein in the neutron radiation field is a ratio of the relative radiation dose to the conversion coefficient.

(40) The dose received by the protein in the radiation field in this embodiment was measured by Radiochromic film, and can also be measured by other methods known to those skilled in the art which are able to measure the amount of radiation received by the protein at the site of irradiation.

(41) When the radiation field to be measured is a mixed radiation field of neutron and gamma and the standard curve is drawn by the degree of protein degradation in the gamma radiation field, the radiation dose Xi corresponding to a certain degree of protein degradation is calculated by the biological dosimeter is the relative radiation dose D.sub.i of the protein in the gamma radiation field, wherein D.sub.i=M.sub.j+N.sub.j. Wherein, M.sub.j is the gamma dose, N.sub.j is the equivalent dose of neutrons relative to gamma, wherein the gamma dose M.sub.j can be calculated by Monte Carlo, and the neutron dose actually received by the protein is the ratio of the equivalent dose of neutrons relative to gamma to the conversion coefficient (Ki) at the protein degradation concentration.

<Embodiment 3> Neutron Capture Therapy System Comprising Biological Dosimeter

(42) The biological dosimeter provided by the embodiment of the present disclosure is used for detecting radiation dose, and can be used not only to detect radiation pollution in the environment, but also to estimate the intensity or dose of the neutron beam in the neutron capture therapy system to guide treatment process.

(43) Neutron capture therapy (NCT) has been increasingly practiced as an effective cancer curing means in recent years, and BNCT is the most common. Neutrons for NCT may be supplied by nuclear reactors or accelerators. Take AB-BNCT for example, its principal components comprise, in general, an accelerator for accelerating charged particles (such as protons and deuterons), a target, a heat removal system and a beam shaping assembly. The accelerated charged particles interact with the metal target to produce the neutrons, and suitable nuclear reactions are always determined according to such characteristics as desired neutron yield and energy, available accelerated charged particle energy and current and materialization of the metal target, among which the most discussed two are .sup.7Li (p, n) .sup.7Be and .sup.9Be (p, n).sup.9B and both are endothermic reaction. Their energy thresholds are 1.881 MeV and 2.055 MeV respectively. Epithermal neutrons at a keV energy level are considered ideal neutron sources for BNCT. Theoretically, bombardment with lithium target using protons with energy slightly higher than the thresholds may produce neutrons relatively low in energy, so the neutrons may be used clinically without many moderations. However, Li (lithium) and Be (beryllium) and protons of threshold energy exhibit not high action cross section. In order to produce sufficient neutron fluxes, high-energy protons are usually selected to trigger the nuclear reactions.

(44) The target, considered perfect, is supposed to have the advantages of high neutron yield, a produced neutron energy distribution near the epithermal neutron energy range (see details thereinafter), little strong-penetration radiation, safety, low cost, easy accessibility, high temperature resistance etc. But in reality, no nuclear reactions may satisfy all requests. The target in these embodiments of the present disclosure is made of lithium. However, well known by those skilled in the art, the target materials may be made of other metals besides the above-mentioned.

(45) Requirements for the heat removal system differ as the selected nuclear reactions. .sup.7Li (p, n) .sup.7Be asks for more than .sup.9Be (p, n).sup.9B does because of low melting point and poor thermal conductivity coefficient of the metal (lithium) target. In these embodiments of the present disclosure is .sup.7Li (p, n) .sup.7Be.

(46) No matter BNCT neutron sources are from the nuclear reactor or the nuclear reactions between the accelerator charged particles and the target, only mixed radiation fields are produced, that is, beams comprise neutrons and photons having energies from low to high. As for BNCT in the depth of tumors, except the epithermal neutrons, the more the residual quantity of radiation ray is, the higher the proportion of nonselective dose deposition in the normal tissue is. Therefore, radiation causing unnecessary dose should be lowered down as much as possible. Besides air beam quality factors, dose is calculated using a human head tissue prosthesis in order to understand dose distribution of the neutrons in the human body. The prosthesis beam quality factors are later used as design reference to the neutron beams, which is elaborated hereinafter.

(47) The International Atomic Energy Agency (IAEA) has given five suggestions on the air beam quality factors for the clinical BNCT neutron sources. The suggestions may be used for differentiating the neutron sources and as reference for selecting neutron production pathways and designing the beam shaping assembly, and are shown as follows:

(48) Epithermal neutron flux >1×10.sup.9 n/cm.sup.2s

(49) Fast neutron contamination <2×10.sup.−13 Gy-cm.sup.2/n

(50) Photon contamination <2×10.sup.−13 Gy-cm.sup.2/n

(51) Thermal to epithermal neutron flux ratio <0.05

(52) Epithermal neutron current to flux ratio >0.7

(53) Note: the epithermal neutron energy range is between 0.5 eV and 40 keV, the thermal neutron energy range is lower than 0.5 eV, and the fast neutron energy range is higher than 40 keV.

(54) 1. Epithermal Neutron Flux

(55) The epithermal neutron flux and the concentration of the boronated pharmaceuticals at the tumor site codetermine clinical therapy time. If the boronated pharmaceuticals at the tumor site are high enough in concentration, the epithermal neutron flux may be reduced. On the contrary, if the concentration of the boronated pharmaceuticals in the tumors is at a low level, it is required that the epithermal neutrons in the high epithermal neutron flux should provide enough doses to the tumors. The given standard on the epithermal neutron flux from IAEA is more than 10.sup.9 epithermal neutrons per square centimeter per second. In this flux of neutron beams, therapy time may be approximately controlled shorter than an hour with the boronated pharmaceuticals. Thus, except that patients are well positioned and feel more comfortable in shorter therapy time, and limited residence time of the boronated pharmaceuticals in the tumors may be effectively utilized.

(56) 2. Fast Neutron Contamination

(57) Unnecessary dose on the normal tissue produced by fast neutrons are considered as contamination. The dose exhibit positive correlation to neutron energy, hence, the quantity of the fast neutrons in the neutron beams should be reduced to the greatest extent. Dose of the fast neutrons per unit epithermal neutron flux is defined as the fast neutron contamination, and according to IAEA, it is supposed to be less than 2*.sup.10-13Gy-cm.sup.2/n.

(58) 3. Photon Contamination (Gamma-Ray Contamination)

(59) Gamma-ray long-range penetration radiation will selectively result in dose deposit of all tissues in beam paths, so that lowering the quantity of gamma-ray is also the exclusive requirement in neutron beam design. Gamma-ray dose accompanied per unit epithermal neutron flux is defined as gamma-ray contamination which is suggested being less than 2*10.sup.−13Gy-cm.sup.2/n according to IAEA.

(60) 4. Thermal to Epithermal Neutron Flux Ratio

(61) The thermal neutrons are so fast in rate of decay and poor in penetration that they leave most of energy in skin tissue after entering the body. Except for skin tumors like melanocytoma, the thermal neutrons serve as neutron sources of BNCT, in other cases like brain tumors, the quantity of the thermal neutrons has to be lowered. The thermal to epithermal neutron flux ratio is recommended at lower than 0.05 in accordance with IAEA.

(62) 5. Epithermal Neutron Current to Flux Ratio

(63) The epithermal neutron current to flux ratio stands for beam direction, the higher the ratio is, the better the forward direction of the neutron beams is, and the neutron beams in the better forward direction may reduce dose surrounding the normal tissue resulted from neutron scattering. In addition, treatable depth as well as positioning posture is improved. The epithermal neutron current to flux ratio is better of larger than 0.7 according to IAEA.

(64) The prosthesis beam quality factors are deduced by virtue of the dose distribution in the tissue obtained by the prosthesis according to a dose-depth curve of the normal tissue and the tumors. The three parameters as follows may be used for comparing different neutron beam therapy effects.

(65) 1. Advantage Depth

(66) Tumor dose is equal to the depth of the maximum dose of the normal tissue. Dose of the tumor cells at a position behind the depth is less than the maximum dose of the normal tissue, that is, boron neutron capture loses its advantages. The advantage depth indicates penetrability of neutron beams. Calculated in cm, the larger the advantage depth is, the larger the treatable tumor depth is.

(67) 2. Advantage Depth Dose Rate

(68) The advantage depth dose rate is the tumor dose rate of the advantage depth and also equal to the maximum dose rate of the normal tissue. It may have effects on length of the therapy time as the total dose on the normal tissue is a factor capable of influencing the total dose given to the tumors. The higher it is, the shorter the irradiation time for giving a certain dose on the tumors is, calculated by cGy/mA-min.

(69) 3. Advantage Ratio

(70) The average dose ratio received by the tumors and the normal tissue from the brain surface to the advantage depth is called as advantage ratio. The average ratio may be calculated using dose-depth curvilinear integral. The higher the advantage ratio is, the better the therapy effect of the neutron beams is.

(71) To provide comparison reference to design of the beam shaping assembly, we also provide the following parameters for evaluating expression advantages and disadvantages of the neutron beams in the embodiments of the present disclosure except the air beam quality factors of IAEA and the abovementioned parameters.

(72) 1. Irradiation time <=30 min (proton current for accelerator is 10 mA)

(73) 2. 30.0RBE-Gy treatable depth >=7 cm

(74) 3. The maximum tumor dose >=60.0RBE-Gy

(75) 4. The maximum dose of normal brain tissue <=12.5RBE-Gy

(76) 5. The maximum skin dose <=11.0RBE-Gy

(77) Note: RBE stands for relative biological effectiveness. Since photons and neutrons express different biological effectiveness, the dose above should be multiplied with RBE of different tissues to obtain equivalent dose.

(78) The neutron capture treatment system including the biological dosimeter is further described below with reference to the drawings: the neutron source in the neutron capture treatment system shown in FIG. 5 is an accelerator neutron source, wherein the charged particles generated by the accelerator 10 form a charged particle beam P, the charged particle beam impinges on the target T in the neutron generating device 20 to form a mixed radiation field containing thermal neutrons, fast neutrons, and epithermal neutrons. The mixed radiation field reflects the neutrons diffused to the surroundings back into the mixed radiation field by the reflector 31 in the beam shaping body 30, then retarded by the slow speed body 32, and the thermal neutron absorber 33 absorbs the lower energy thermal neutrons. Thereafter, a neutron beam N mainly composed of superthermal neutrons is formed, and the neutron beam flows are concentrated by the collimator 40 to accurately illuminate the portion to be irradiated of the patient, and further, in order to prevent the radiation in the beam shaping body 30 from diffusing out, a radiation shield 34 is disposed adjacent the beam exit at the rear of the beam shaping body 30.

(79) Preventing radiation from damaging other normal tissues of the body during treatment often requires positioning the patient within the irradiation chamber prior to illuminating the neutron beam. As shown in FIG. 5, before the neutron irradiation, the portion to be irradiated of the patient is pre-positioned according to the direction of the neutron beam passing through the collimator to the intersection of the X-axis and the Y-axis in the neutron beam direction to achieve precise illumination.

(80) In order to evaluate the neutron radiation dose of the neutron beam at the site to be treated of the patient within the irradiation chamber, it is needed to provide a biological dosimeter A at the predetermined position in the irradiation chamber, which is used to measure the radiation dose at the intersection of the X-axis and the Y-axis in the direction of the neutron beam, and the radiation field in which the biological dosimeter is located is a mixed radiation field of neutron and gamma. The dose calculated by the biological dosimeter based on substituting the degree of protein degradation at the intersection into the standard curve is a relative radiation dose of the protein in the radiation filed used to draw the standard curve, and the neutron dose and the gamma dose in the mixed radiation field need to be separately calculated according to the method of <Embodiment 2>.

(81) The biological dosimeter A can be located at other locations in the illumination chamber in addition to the location shown in FIG. 5 for measuring the dose of the radiation field at the location of the biological dosimeter. Since the biological dosimeter is simple and light to use, it can be located at any position in the irradiation chamber to evaluate the radiation dose at the position, and further determine and control the radiation pollution in the irradiation chamber, thereby showing that the biological dosimeter is of great significance in the neutron capture system.

(82) are not limited to the contents described in the above embodiments and the structures represented in the drawings. Any obvious changes, substitutions, or modifications made on the basis of the present disclosure shall be within the scope of protection claimed by the present disclosure.