Radiation dose measuring device, gel dosimeter, and radiation dose measuring system

Abstract

To put a gel dosimeter to practical use.SOLUTION: A radiation dose measuring device uses a gel dosimeter 4 including a reactive substance 8 that reacts with a radical generated by an ionization action by energy imparted from a radiation 3, a measuring instrument 5 for acquiring a measurement value of a reaction amount of the reactive substance 8 reacting with the radical, and one or more computers 6. The computers 6 perform at least one of the processing for correcting the measurement value and obtaining a dose of the radiation 3 on the basis of a correction coefficient obtained beforehand, and the processing for checking whether or not the measurement value is correct.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present invention relate to radiation dosimetry techniques. [Background technology]

[0002] Cancer therapy with radiation achieves efficient treatment by concentrating therapeutic radiation on cancer tumors. When radiation is irradiated into the human body, the radiation imparts energy to the substance, ionizing the substance and generating radicals. These radicals act on DNA, destroying the tumor's ability to proliferate. Cancer therapy with X-rays involves irradiating the human body with X-rays generated by irradiating a target material with an electron beam.

[0003] On the other hand, cancer treatment using particle beams involves irradiating the human body with charged particles accelerated to a certain energy by an accelerator. When the charged particles are irradiated to the human body, the energy of the charged particles is transferred to the substance through Coulomb interaction. The amount of energy transferred reaches a steep maximum value at a specific depth in the body corresponding to the incident energy of the charged particles. This phenomenon is called the Bragg peak. Cancer treatment using particle beams applies the principle of the manifestation of this Bragg peak, concentrating the transferred energy on the tumor while suppressing the transfer of energy to healthy cells.

[0004] There are two methods for forming the radiation field in particle beam therapy: passive and scanning. In the passive method, the particle beam transported from the accelerator is expanded in the plane and depth directions using scatterers, electromagnets, and ridge filters. In the plane direction, the shape of the beam is adjusted using a collimator to match the shape of the tumor. In the depth direction, the shape of the beam is adjusted using a compensation filter made of a polyethylene block or other material excavated to match the shape of the tumor. By irradiating the patient with the particle beam adjusted in this way, it is possible to reduce the dose given to normal organs and irradiate the tumor locally. In the scanning method, the particle beam is narrowed down to a thin beam called a pencil beam, and irradiation is performed according to the shape of the tumor. In the scanning method, the particle beam is first irradiated two-dimensionally on a surface perpendicular to the emission axis while changing the emission direction of the particle beam. Next, the energy of the particle beam is changed, and the position where the Bragg peak occurs is changed in the depth direction of the human body, and irradiation is performed in the same two-dimensional manner. By repeating this process, the particle beam is irradiated three-dimensionally according to the shape of the tumor, minimizing irradiation damage to healthy tissue.

[0005] The amount of microscopic energy transferred when radiation such as X-rays and charged particles ionize and excite molecules in a substance is called Linear Energy Transfer (LET). This LET is about 2 keV / μm for photon beams. On the other hand, for carbon ion beams ( 12 C 6+ ) is approximately 10 keV / μm at the point of incidence into the human body, and several hundred keV / μm at the point where the Bragg peak occurs. In other words, cancer therapy with particle beams is known as a form of radiation therapy with high LET radiation quality.

[0006] In particle beam therapy, in order to accurately irradiate a cancer target in human tissue with particle beams, it is necessary to optimize the dose distribution at each three-dimensional position of the cancer target in the living tissue. For this purpose, X-ray images or computed tomography (CT) images of the patient are obtained in advance, and information such as the type of cancer tumor, its spatial coordinates, and the surrounding organs is identified. Based on this information, a treatment plan is created using a computer program in order to provide treatment instructions to the treatment device, such as the irradiation direction of the particle beam to be given to the patient, the spatial coordinates where the Bragg peak occurs, and the number of particle beams to be irradiated.

[0007] Here, in order to confirm whether the particle beam is accurately irradiated to the targeted position in the human tissue, it is necessary to perform regular confirmation inspections regarding the irradiation accuracy of the particle beam irradiation device. Specifically, it is necessary to confirm the relationship between the energy of the particle beam and its irradiation depth, that is, the position where the Bragg peak appears. Furthermore, when irradiating the particle beam two-dimensionally, three-dimensionally, or four-dimensionally, it is necessary to confirm that the irradiation field is within the range set at the time of treatment planning. Furthermore, in order to reduce the patient's radiation exposure and to confirm whether the radiation is reliably irradiated to the shape of the tumor, the distribution of the radiation dose is measured using a material called a phantom that simulates the human body and a container filled with water. Currently, a method is adopted in which a dosimeter such as an ionization chamber or a radiochromic film is placed in the phantom to measure the two-dimensional distribution of the radiation dose, and then the two-dimensional distribution is converted into three dimensions for evaluation. However, three-dimensional analysis has the disadvantage of being time-consuming and laborious.

[0008] In recent years, development of three-dimensional gel dosimeters using reactive substances with radiation sensitivity has been promoted to easily measure three-dimensional radiation dose distribution. Types of gel dosimeters include polymer gel dosimeters, Fricke gel dosimeters, and micellar gel dosimeters. Polymer gel dosimeters utilize the polymerization reaction of vinyl monomers caused by radicals generated by radiation. Fricke gel dosimeters utilize the oxidation reaction of iron ions caused by radicals. Micellar gel dosimeters utilize the color development of radiation-sensitive dyes caused by radicals. These dosimeters measure the intensity distribution of radiation given to a medium by measuring the amount of reaction that occurs when radicals generated in the gel dosimeter react with the substance of the gel dosimeter due to radiation irradiation. For example, polymer gel dosimeters use the principle that the amount of polymerization of vinyl monomers affects the spin of hydrogen atoms, and measure the amount of spin change using magnetic resonance imaging (MRI). Fricke gel dosimeters measure the amount of change from divalent iron to trivalent iron caused by radicals. The micellar gel dosimeter measures the absorbance and color intensity of the color produced by the radiation-sensitive dye due to radicals, both of which are proportional to the amount of radicals produced by the amount of energy imparted by radiation to the medium. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 6212695 [Patent Document 2] Patent No. 6296230 [Patent Document 3] Special Publication No. 58-501091 Summary of the Invention [Problem to be solved by the invention]

[0010] The problem with conventional gel dosimeters is that the dose response of each measurement, such as MRI, the amount of change in charge, and the amount of dye coloring, depends on the radiation quality. One of the typical radiation qualities is LET, and in particular, in areas where the LET increases locally, such as at the end of the charged particle's range, a phenomenon occurs in which the measured value is no longer proportional to the energy deposition. As a result, the relationship between the deposited energy and the measured value cannot be maintained, and it is impossible to confirm whether the measured value correctly represents the deposited energy. For these reasons, gel dosimeters have not been applicable to measuring three-dimensional dose distributions by charged particles, and they have long been unable to be put to practical use.

[0011] The embodiments of the present invention have been made in consideration of the above circumstances, and have an object to make the gel dosimeter practical. [Means for solving the problem]

[0012] A radiation dose measurement method according to an embodiment of the present invention is a method that uses a gel dosimeter containing a reactive substance that reacts with radicals generated by ionization due to energy imparted from radiation, a measuring device that obtains a measurement value of the reaction amount of the reactive substance that has reacted with the radical, and one or more computers, and the computer performs at least one of a process of correcting the measurement value based on a predetermined correction coefficient to obtain the radiation dose, and a process of confirming whether the measurement value is correct. Effect of the Invention

[0013] According to the embodiment of the present invention, it is possible to put gel dosimeters into practical use. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a configuration diagram showing a radiation dosimetry system. [Diagram 2] FIG. 2 is an image showing the gel dosimeter of Example 1. [Diagram 3] 1 is a graph showing the relationship between the measured absorbed dose and the depth in Example 1. [Figure 4] 13 is a graph showing the relationship between the correction coefficient and the depth in the first embodiment. [Diagram 5] 13 is a graph showing the relationship between the corrected measurement value and the depth in Example 1. [Figure 6] Graph showing the relationship between dose and depth of a 170 MeV / u beam in Example 2. [Figure 7] Graph showing the relationship between dose and depth of a 200 MeV / u beam in Example 2. [Figure 8] Graph showing the relationship between dose and depth of a 230 MeV / u beam in Example 2. [Figure 9] Graph showing the relationship between dose and depth of a 260 MeV / u beam in Example 2. [Figure 10] Graph showing the relationship between dose and depth of a 320 MeV / u beam in Example 2. [Figure 11] FIG. 11 is a side view showing the gel dosimeter of Example 3. [Figure 12] FIG. 12 is a cross-sectional view taken along the line XII-XII of FIG. 11 according to the third embodiment. [Figure 13] FIG. 12 is an image diagram showing a gel dosimeter corresponding to FIG. 11 during treatment planning in Example 3. [Figure 14] FIG. 13 is an image diagram showing a gel dosimeter corresponding to FIG. 12 during treatment planning in Example 3. [Figure 15] FIG. 12 is an image showing a gel dosimeter corresponding to FIG. 11 during actual measurement in Example 3. [Figure 16] FIG. 13 is an image showing a gel dosimeter corresponding to FIG. 12 during actual measurement in Example 3. [Figure 17] Graph showing gel absorbance for each beam in Example 3. [Figure 18] 13 is a graph showing the correction coefficients of the beams in the third embodiment. [Figure 19] 13 is a graph showing the relationship between absorbed dose and depth in Example 3. [Figure 20] 13 is a graph showing the absorbed dose distribution of the beam in Example 4. [Figure 21] 13 is a graph showing the conversion coefficients of each beam in the fourth embodiment. [Figure 22] 13 is a graph showing the relationship between absorbed dose and depth in Example 4. [Diagram 23] FIG. 13 is a side view showing a gel dosimeter placed on a rotating gantry in Example 5. [Figure 24] 24 is a graph showing the relationship between dose and depth corresponding to FIG. 23 in Example 5. [Diagram 25] FIG. 13 is a side view showing the gel dosimeter when the rotating gantry of Example 5 is rotated. [Figure 26] 26 is a graph showing the relationship between dose and depth corresponding to FIG. 25 in Example 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments of a radiation dosimetry method, a gel dosimeter, and a radiation dosimetry system will be described in detail with reference to the drawings.

[0016] 1, reference numeral 1 denotes a radiation dosimetry system of this embodiment. This radiation dosimetry system 1 is used to perform quality assurance (QA) of radiation 3 irradiated from a treatment device 2.

[0017] The treatment device 2 may be, for example, a particle beam cancer treatment device that performs treatment by irradiating a charged particle beam such as carbon ions as therapeutic radiation 3 to a lesion tissue (cancer) of a patient as an irradiation target.

[0018] This type of radiation therapy technology is called heavy ion cancer therapy technology. This technology uses carbon ions to pinpoint the cancer lesion (affected area), damaging the cancer lesion while minimizing damage to normal cells. Charged particle beams are defined as radiation3 that is heavier than electrons. Charged particles include proton beams and heavy particle beams. Of these, heavy particle beams are defined as those heavier than helium atoms.

[0019] In this embodiment, the charged particle beam uses carbon as the therapeutic radiation 3, but other configurations are also possible. For example, the charged particle beam may use helium, oxygen, or neon. Also, a proton beam may be used as the charged particle beam.

[0020] Compared to conventional cancer treatments using X-rays, gamma rays, or proton beams, heavy ion beam cancer treatments have a higher ability to kill cancer lesions, and have the characteristic that the dose is weak on the surface of the patient's body and peaks at the cancer lesions. This allows for fewer irradiations, fewer side effects, and a shorter treatment period.

[0021] For example, when a charged particle beam passes through a patient's body, it loses kinetic energy and decreases in speed, and encounters resistance that is approximately inversely proportional to the square of the speed, and suddenly stops when it reaches a certain speed. This stopping point is called the Bragg peak, and high energy is released. The treatment device 2 can annihilate only the diseased tissue while suppressing damage to normal tissue by aligning this Bragg peak with the position of the patient's diseased tissue (affected area).

[0022] The radiation dosimetry system 1 is used, for example, to measure or confirm the dose distribution of the dose or spread out Bragg peak (SOBP) of radiation 3 irradiated from the treatment device 2. This measurement or confirmation work may be performed during maintenance of the treatment device 2, or may be performed for each patient before starting treatment.

[0023] The radiation dosimetry system 1 includes a gel dosimeter 4 , a measuring device 5 , and a computer 6 .

[0024] The gel dosimeter 4 includes a colorless and transparent cylindrical container 7 and a colorless and transparent reactive substance 8 contained in the container 7. The gel dosimeter 4 is a type of so-called QA phantom. Note that the colorless and transparent cylindrical container 7 is only one example, and depending on the content of the QA, the container 7 may have another shape, such as a rectangular parallelepiped shape.

[0025] Before being irradiated with radiation 3, the reactive material 8 is colorless and transparent. However, when the reactive material 8 is irradiated with radiation 3, the color of that portion changes. By checking this colored portion 9 of the reactive material 8, the user can determine whether radiation 3 of an appropriate intensity is being irradiated to an appropriate position.

[0026] When measuring the dose of radiation 3 irradiated from the treatment device 2, the gel dosimeter 4 is usually provided at the position of the isocenter, which is the reference point of the treatment device 2. For example, the gel dosimeter 4 is provided on a table (not shown) on which a patient is placed. In addition, when the treatment device 2 includes a rotating gantry (not shown), the gel dosimeter 4 is usually provided at the center of rotation of the rotating gantry.

[0027] The reactant 8 reacts with the radicals generated by ionization caused by the energy imparted by the radiation 3. The radicals in this embodiment are, for example, OH radicals generated by excitation of water molecules.

[0028] The reactive substance 8 includes a gelling agent that gels the aqueous solution, and a color-developing agent that reacts with radicals generated by ionizing water by radiation 3, and the molecular bonding groups in the reaction product selectively absorb light in a specific wavelength range and develop color.

[0029] In the case of a polymer gel dosimeter, the reactant 8 is a vinyl monomer. In the case of a Fricke gel dosimeter, the reactant 8 is an iron ion. In this way, any substance that changes by reacting with a radical corresponds to the reactant 8.

[0030] The measuring device 5 is, for example, a camera that photographs the gel dosimeter 4 and an imaging device such as an optical CT device. The measuring device 5 photographs the colored portion 9 of the reactant 8 in the gel dosimeter 4 and obtains a measurement value of the reaction amount of the reactant 8 that has reacted with the radical. This measurement value is absorbance (amount of color). The measuring device 5 is connected to a computer 6 and is controlled by the computer 6. The information obtained by the measuring device 5 may be pixel data, voxel data, or a tomographic image.

[0031] In addition, when measuring the spin relaxation rate of hydrogen atoms due to the polymerization amount of vinyl monomers or the spin relaxation rate due to the change in valence of iron ions, for example, MRI (Magnetic Resonance Imaging) is used as the measuring device 5. In addition, when measuring the change in the polymerization amount of vinyl monomers, for example, X-ray CT is used as the measuring device 5.

[0032] The computer 6 acquires the measurement values ​​(actual measurements) from the measuring device 5. The computer 6 performs at least one of a process of correcting the measurement values ​​to obtain the dose of the radiation 3 based on a correction coefficient obtained in advance, and a process of confirming whether the measurement values ​​are correct.

[0033] The radiation dosimetry system 1 of this embodiment is configured with a computer 6 having hardware resources such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a HDD (Hard Disk Drive), and an SSD (Solid State Drive), and the CPU executes various programs to realize information processing by software using the hardware resources. Furthermore, the radiation dosimetry method of this embodiment is realized by making the computer 6 execute the various programs.

[0034] Each component of the radiation dosimetry system 1 does not necessarily have to be provided in one computer 6. For example, one radiation dosimetry system 1 may be realized by a plurality of computers 6 connected to each other via a network. For example, a function for calculating a correction coefficient, a function for acquiring a measured value, and a function for correcting the measured value with the correction coefficient may each be provided in an individual computer 6.

[0035] In order to put the gel dosimeter 4 into practical use, the inventors studied the relationship between the amount of radicals generated due to changes in linear energy transfer (LET) and the amount of reaction between the radicals and the reactant 8 in the gel dosimeter 4. As a result, the inventors clarified the mechanism by which the measured value does not reflect the energy transferred by radiation 3.

[0036] For example, when a certain medium is irradiated with radiation 3, radicals in an amount proportional to the applied energy are generated within a microscopic region of a few nanometers centered on the irradiation position of the radiation 3. This phenomenon is called spurring. Within this microscopic region, the radicals disappear by reacting with elements constituting the surrounding medium and with other radicals generated by the radiation 3. Furthermore, some of the radicals react with the reactant 8 of the gel dosimeter 4. The results of these simultaneous reactions can be obtained by measuring the amount of reacted material using various measuring instruments 5.

[0037] Here, the relationship between the rate of radical production due to radiation 3, the rate of radical disappearance, and the reaction rate between the radical and the reactant 8 of the gel dosimeter 4 is expressed by the following relational expression (1).

[0038] Radical production rate > Radical disappearance rate > Reaction rate of radicals and reactants … (1)

[0039] The amount of radicals produced in the spar is proportional to the energy imparted by radiation 3. The rate at which radicals are produced is high, as shown in the above-mentioned relational expression (1), so the amount of radicals reaches a value that reflects the amount of energy imparted by radiation 3 about 1 picosecond after radiation exposure.

[0040] The amount of radicals lost in the spar depends on the amount of radicals present in a unit volume. If the amount of radicals is large, the amount of radicals lost is large, and if the amount of radicals is small, the amount of radicals lost is also small. Since the rate at which radicals disappear is smaller than the rate at which radicals are generated, as shown in the above-mentioned relational equation (1), the value becomes constant at about 1 μs after radiation exposure.

[0041] The amount of reaction between the radicals and the reactant 8 in the gel dosimeter 4 depends on the concentration of radicals present in the spar after 1 μs. Since the reaction rate is small as shown in the above-mentioned relational expression (1), the amount of reaction between the gel dosimeter 4 and the reactant 8 depends on the amount of radicals present about 1 μs after irradiation with radiation 3.

[0042] Here, when radiation 3 with a low LET is irradiated, the amount of radicals generated by the energy transfer of the radiation 3 is small. Therefore, the amount of radicals lost is also small, and the effect of the amount of lost radicals on the amount of radicals reacting with the reactant 8 is small. Therefore, the amount of reaction between the reactant 8 and radicals after 1 μs depends on the amount of radicals generated by the energy transfer.

[0043] On the other hand, in the case of charged particles with a large LET, especially in the case of a region where the LET is high at a pinpoint such as the Bragg peak, a large amount of radicals are generated in this small region in a short time. This causes a large amount of radicals to disappear, and the disappearance speed also becomes fast. As a result, the amount of radicals is rapidly decreased, so the amount of radicals for about 1 μs does not reflect the amount of radicals generated by the energy deposition of radiation 3.

[0044] Therefore, the amount of radicals reacting with the reactant 8 in the gel dosimeter 4 decreases. Therefore, the measurement value of the reactant 8 does not reflect the amount of radicals generated by the energy deposition of the radiation 3. This is the reason why the gel dosimeter 4 does not show a measurement value corresponding to the dose when irradiated with high LET radiation 3.

[0045] This phenomenon is particularly noticeable with charged particles that generate Bragg peaks. For example, as shown in the graph of Figure 5, the measured value (actual measured value) becomes a small value that is significantly different from the actual absorbed dose at the Bragg peak. In the following explanation, this sudden decrease in the measured value is referred to as the deviation phenomenon D.

[0046] The radiation dosimetry system 1 of this embodiment has been developed based on the elucidation of such a reaction mechanism, and detects the energy imparted by charged particles simply and with high accuracy.

[0047] The method invented by the inventors relates to a gel dosimeter 4 including a reactant 8 that reacts with radicals generated by ionization caused by energy deposition from radiation 3. First, a correction coefficient is calculated from the amount of radicals that includes the amount of radicals that has been reduced by irradiation with radiation 3. Then, the amount of reactant 8 that has reacted with radicals corresponding to the energy deposition from radiation 3 is calculated by multiplying the measured amount of reactant 8 that has reacted with radicals generated by irradiation with radiation 3 by the correction coefficient.

[0048] There are various types of reactive substances 8 used in gel dosimeters 4. For example, vinyl monomers are used in polymer gel dosimeters. Iron ions are used in Fricke gel dosimeters. Radiation-sensitive dyes such as leuco dyes are used in micellar gel dosimeters. These reactive substances 8 react with OH radicals generated by the ionization of water upon irradiation with radiation 3, and the amount of energy transferred is measured based on the amount of reaction.

[0049] The inventors also conducted detailed research into the mechanism of radical generation and extinction described above. As a result, they found that the value obtained by multiplying the amount of reactant 8 measured by the gel dosimeter 4 by a correction coefficient calculated from the amount of OH radicals 1 nanosecond after irradiation matches the energy imparted by the charged particles, i.e., the absorbed dose. This embodiment was made based on such findings.

[0050] For example, the correction coefficient is obtained by dividing the OH radical concentration distribution 1 nanosecond after radiation exposure at each coordinate in the traveling direction of the radiation 3 on the gel dosimeter 4 by the OH radical concentration value 1 nanosecond after radiation exposure at the starting point of the radiation 3 exposure on the gel dosimeter 4. The corrected value obtained by multiplying the value of the reactive substance 8 on the gel dosimeter 4 measured on the same coordinate by this correction coefficient is used as the radiation dose value.

[0051] This method can calculate the dose distribution value in the traveling direction of a charged particle having a single energy using the measured value by the gel dosimeter 4. Furthermore, it can also be used to measure the dose distribution of a spread-out Bragg peak generated by using charged particles having multiple energies.

[0052] Furthermore, this method can be used to confirm the dose distribution calculated in the treatment plan. For example, the treatment plan can be confirmed by comparing the dose distribution obtained by multiplying the absorbed dose distribution for each beam of charged particles shown in the treatment plan by the reciprocal of the correction coefficient with the reaction amount of the reactant 8 with the radicals in the gel dosimeter 4, with the measured value.

[0053] This embodiment is applicable to a method for accurately measuring absorbed dose with a chemical dosimeter, and also to a QA method for checking whether a dose distribution to be administered is correctly realized by the treatment device 2.

[0054] The reactive substance 8 of the gel dosimeter 4 exemplified in the following description is composed mainly of water containing a leuco dye. This reactive substance 8 reacts with OH radicals generated when water is irradiated with radiation 3, and turns purple (absorption wavelength 490 nm). The amount of coloring in this colored portion 9 is measured, for example, using an optical CT device as the measuring device 5. This optical CT device photographs the colored portion 9 of the reactive substance 8 from various directions and reconstructs the color distribution in three dimensions, making it possible to measure the three-dimensional distribution of the reaction amount.

[0055] In this embodiment, the aforementioned gel dosimeter 4 is exemplified, but this embodiment can be applied to a measurement method based on the principle of reacting via radicals upon receiving radiation 3, or a measurement method in which a reaction proceeds directly upon receiving radiation 3. EXAMPLES

[0056] A first embodiment carried out by the inventors will be described with reference to Figures 2 to 5. Note that Figure 1 may be referred to.

[0057] The cause of the measurement value deviation phenomenon D (FIG. 5) is that the amount of generated radicals decreases due to a recombination reaction, resulting in a deviation from the absorbed dose value. Example 1 focuses on this principle. First, the amount of radicals is found assuming that the generated radicals do not recombine. Then, the difference with the amount of radicals that have undergone a recombination reaction is calculated as a correction coefficient. Here, the measurement value of the gel dosimeter 4 is multiplied by the correction coefficient. This makes it possible to calculate the reaction amount of the reactant 8 in the case where the radical dissociation phenomenon D due to radiation 3 does not occur, and the absorbed dose of radiation 3 can be determined.

[0058] The inventors applied this embodiment to the measurement of the absorbed dose distribution of a single energy beam of 290 MeV / u irradiated from a particle beam cancer treatment device serving as the treatment device 2, using a gel dosimeter 4.

[0059] As shown in Fig. 2, the inventors placed the material (reactant 8) of the gel dosimeter 4 in a horizontally elongated transparent cell (container 7) with a scale, and irradiated it with a carbon ion beam (radiation 3) of the aforementioned energy. The irradiation conditions were adjusted in advance using the shape of the gel dosimeter 4 and treatment planning software so that a Bragg peak would be generated within the range of the gel dosimeter 4.

[0060] The inventors confirmed that after irradiation, in the reaction material 8, a colored portion 9 that turned blue in the beam traveling direction was formed. The inventors measured the amount of color development at each coordinate in the beam traveling direction using an ultraviolet-visible spectrophotometer, and obtained measured values ​​(actual measured values).

[0061] The graph in Figure 3 shows the measured values ​​(actual measurements) at this time. As shown in this graph, an event called the deviation phenomenon D (Figure 5) occurs in the measured values ​​of the reactant 8. Specifically, the position of the Bragg peak is unclear over the entire direction of beam propagation, and the area where the absorbed dose is typically high near the Bragg peak cannot be identified.

[0062] The inventors calculated the OH radical concentration distribution in the beam traveling direction by using a computer 6 under the same beam conditions as in the irradiation test and with the shape of the gel dosimeter 4. The OH radical concentration was determined as the concentration at which no recombination reaction occurred.

[0063] As shown in Fig. 4, the OH radical concentration at each coordinate was normalized by the OH radical concentration at the entrance of the gel dosimeter 4, and the value of each coordinate was used as the correction coefficient for the traveling direction of the beam. In other words, when the starting point of irradiation of the radiation 3 in the gel dosimeter 4 is set to the origin P0 (Fig. 2) and a one-dimensional coordinate that coincides with the traveling direction of the radiation 3 is specified, the inventors determined the correction coefficient for each coordinate by setting the OH radical concentration at this origin P0 to "1.0". Then, the predetermined position P1 (Fig. 2) becomes the position of the Bragg peak.

[0064] The inventors multiplied the absorbance distribution (Fig. 3) of each coordinate in the gel dosimeter 4 by the distribution of correction coefficients (Fig. 4) of the same coordinate to calculate the corrected absorbance in the beam propagation direction. The inventors were able to confirm the unclear Bragg peak position P1 (Fig. 2) and a typical dose distribution around it. As a result of comparing these distributions with the distributions according to the treatment plan, the inventors confirmed that the overall absorbance distribution and the position of the Bragg peak were consistent. It was then proven that the radiation dose measurement method of this embodiment is effective in confirming the position of the Bragg peak (Fig. 5).

[0065] As described above, when the first embodiment is applied to the radiation dosimetry system 1, the computer 6 determines the correction coefficient from the relationship between the amount of radicals generated and lost, and the amount of reaction. The computer 6 then determines the dose of radiation 3 by multiplying the measured value of the amount of reaction obtained by the measuring device 5 (FIG. 1) by the correction coefficient. In this way, the position of the Bragg peak can be confirmed. EXAMPLES

[0066] Next, a second embodiment will be described with reference to Figures 6 to 10. Note that Figure 1 may be referred to.

[0067] The inventors applied the radiation dosimetry method of this embodiment to quality assurance of a beam irradiated from a particle beam cancer treatment device serving as the treatment device 2.

[0068] The beam energy of the particle beam cancer therapy device is verified by monobeam irradiation for quality control of the irradiation device. Here, the monobeam is adjusted so that the energy becomes 170, 200, 230, 260, 290, and 320 MeV / u. In addition, when planning treatment, the absorbed dose distribution including the Bragg peak when irradiating the gel dosimeter 4 is obtained in advance.

[0069] FIG. 6 is a graph of a monobeam of 170 MeV / u. FIG. 7 is a graph of a monobeam of 200 MeV / u. FIG. 8 is a graph of a monobeam of 230 MeV / u. FIG. 9 is a graph of a monobeam of 260 MeV / u. FIG. 10 is a graph of a monobeam of 320 MeV / u. Note that the graph of 290 MeV / u is omitted here since it is described in Example 1 (FIG. 5).

[0070] The inventors prepared a gel dosimeter 4 in a transparent cell similar to that in Example 1, irradiated it under each of the beam conditions described above, and measured the color development distribution in the irradiation direction using an ultraviolet-visible spectrophotometer. The inventors calculated the OH radical concentration distribution in the beam traveling direction using a computer 6 under the same beam conditions as in each irradiation test and with the shape of the gel dosimeter 4. As in Example 1, the OH radical concentration at each coordinate was normalized by the OH radical concentration at the origin P0 (FIG. 2), which is the entrance of the gel dosimeter 4, and the value of each coordinate was used as a correction coefficient in the beam traveling direction.

[0071] The inventors multiplied the absorbance at each coordinate by the correction coefficient at the same coordinate to calculate the corrected absorbance in the beam direction. The inventors compared the distribution of this value with the treatment plan values ​​and confirmed that the absorbance distribution and the position of the Bragg peak matched the treatment plan under all monobeam conditions.

[0072] This makes it possible to know whether the heavy ion beam irradiation is being carried out as planned under the irradiation conditions established in the treatment plan. The radiation dosimetry method of this embodiment has been proven to be capable of confirming the beam position and distribution required for QA of the treatment plan. EXAMPLES

[0073] Next, a third embodiment will be described with reference to Figures 11 to 19. Note that Figure 1 may be referred to.

[0074] In cancer treatment using heavy ion beams, the energy of the charged particle beam (radiation 3) is changed discretely to form a spread-out Bragg peak (SOBP) that matches the shape of the tumor, allowing the dose to be delivered accurately to the tumor (Figure 19).

[0075] For the QA of the treatment plan, it is necessary to measure the energy imparted to the medium by irradiating the medium with a charged particle beam and to confirm that the spread-out Bragg peak (SOBP) is formed as planned under the irradiation conditions set in the treatment plan. Here, the radiation dosimetry method of the present embodiment is applied to a method for measuring a charged particle beam that forms a spread-out Bragg peak.

[0076] The spread-out Bragg peak (SOBP) is formed by multiplying the beam by the number of charged particles (beam intensity) and adding up all the beams. When the absorbed dose of the spread-out Bragg peak is measured by a gel dosimeter 4, a deviation phenomenon D (FIG. 5) occurs in the measured value for each beam. Therefore, a measured value (actual value) reflecting the reaction amount of the reactant 8 in the state in which the deviation phenomenon D occurs is obtained. Based on this principle, the reaction amount in which the deviation phenomenon D occurs in each beam is corrected by the radiation dose measurement method of this embodiment, and the corrected measured value in the case in which the deviation phenomenon D does not occur is obtained. Based on this, the spread-out Bragg peak can be reconstructed, and the absorbed dose at the time of the formation of the spread-out Bragg peak can be correctly evaluated.

[0077] 11 and 12, the inventors set a target 10 simulating a tumor in a gel dosimeter 4. This target 10 is assumed to be, for example, a cubic tumor with one side measuring 34 mm located at a depth of 46 mm from the surface of a patient's body. A charged particle beam (radiation 3) is irradiated toward this target 10.

[0078] As shown in Fig. 13 and Fig. 14, the inventors created a treatment plan for irradiating a target 10 with a charged particle beam (radiation 3). For example, a plurality of irradiation ranges 11 are set corresponding to a plurality of charged particle beams with different intensities. In other words, these irradiation ranges 11 are set in order to form a spread-out Bragg peak (SOBP) according to the shape of the target 10. The inventors irradiated a gel dosimeter 4 with the charged particle beam according to this treatment plan.

[0079] As shown in Figures 15 and 16, the inventors measured the colored portion 9 of a gel dosimeter 4 in the direction of propagation of a charged particle beam (radiation 3) using an optical CT device as a measuring instrument 5 (Figure 1) and obtained a three-dimensional absorbance distribution.

[0080] The inventors also previously measured the distribution of the colored portion 9 of the gel dosimeter 4 irradiated with 23 types of charged particle beams (FIG. 17).Then, the inventors calculated the OH radical concentration distribution under the same irradiation conditions in the same manner as in the above-mentioned Examples 1 and 2, and used it as a correction coefficient (FIG. 18).

[0081] 19, the inventors calculated the distribution of the absorbance of the reactive substance 8 multiplied by the OH radical concentration on the same coordinates of the gel dosimeter 4. It was found that this corrected measurement value (corrected value) was in good agreement with the treatment plan value, which is the distribution of the dose in the treatment plan.

[0082] In this way, it was found that the spread-out Bragg peak (SOBP) corresponding to the tumor size determined in the treatment plan coincided with the absorbance distribution calculated by correcting the measured value of the absorbance of the colored part 9 of the gel dosimeter 4. Therefore, it was confirmed that the spread-out Bragg peak assumed in the treatment plan was formed by irradiation with a charged particle beam (radiation 3), and that the radiation dose measurement method of this embodiment can be applied to QA of the treatment plan.

[0083] As described above, Example 3 is a method for forming a spread-out Bragg peak (SOBP) by irradiating multiple types of charged particles with different acceleration energies, which are radiation 3, and measuring the dose distribution of the spread-out Bragg peak in a treatment device 2 (Figure 1) that performs radiation therapy.

[0084] When this Example 3 is applied to the radiation dosimetry system 1, first, the starting point of irradiation of the charged particles in the gel dosimeter 4 is set as the origin P0 (FIG. 2), and a one-dimensional coordinate that coincides with the traveling direction of the charged particles is specified. The measuring device 5 (FIG. 1) obtains the measured values ​​(actual measured values) of the reaction amount at each coordinate.

[0085] The computer 6 calculates the amount of radicals generated for each charged particle with different acceleration energies at the same coordinates. The computer 6 also calculates a correction coefficient corresponding to each coordinate, which is obtained by dividing the amount of radicals generated at each coordinate by the amount of radicals generated at the origin P0 (FIG. 2). The computer 6 also calculates a correction value for the reaction amount by multiplying the measured value of the reaction amount at each coordinate by the corresponding correction coefficient. The computer 6 also calculates the dose distribution of the spread-out Bragg peak by adding up the multiple correction values ​​calculated for each charged particle with different acceleration energies. In this way, the dose distribution of the spread-out Bragg peak can be measured using the gel dosimeter 4.

[0086] The correction coefficient is the concentration value of OH radicals 1 nanosecond after irradiation with radiation 3 at each coordinate of the gel dosimeter 4 divided by the concentration value of OH radicals 1 nanosecond after irradiation with radiation 3 at the origin P0 (Figure 2). EXAMPLES

[0087] Next, a fourth embodiment will be described with reference to Figures 20 to 22. Note that Figure 1 may be referred to.

[0088] In radiation therapy, the dose distribution is calculated in advance by a computer 6 based on the results of diagnosing the patient with a computed tomography (CT) device, and the dose to be administered according to the shape of the tumor is calculated. The treatment device 2 (Fig. 1) is then controlled based on the calculated dose distribution. In heavy ion cancer therapy, this dose distribution is the sum of the intensity distributions of the discretely formed beams, so by multiplying this dose distribution by the reciprocal (conversion coefficient) of the correction coefficient calculated by the above-mentioned method, the radical distribution in the case where the deviation phenomenon D (Fig. 5) occurs can be calculated.

[0089] During QA of the treatment device 2, a gel dosimeter 4 (Fig. 1) is irradiated with a charged particle beam (radiation 3) to obtain the distribution of the reaction amount of the reactant 8. Then, by comparing the obtained distribution of the reaction amount with the distribution obtained by multiplying the absorbed dose in the treatment plan by the back-calculated value of the correction coefficient, it is possible to easily check whether the treatment device 2 is correctly administering the dose (Fig. 22).

[0090] In Example 4, as in Example 3, a cubic tumor with one side of 34 mm is assumed to be located at a depth of 40 mm from the surface of the patient's body (FIGS. 11 and 12). The inventors created a treatment plan for irradiating this cube with a charged particle beam (radiation 3) (FIGS. 13 and 14). The inventors irradiated a gel dosimeter 4 with the charged particle beam in accordance with this treatment plan. Then, the inventors measured the colored portion 9 of the gel dosimeter 4 in the traveling direction of the charged particle beam (radiation 3) with an optical CT device as the measuring device 5 (FIG. 1) and obtained a three-dimensional absorbance distribution (FIGS. 15 and 16).

[0091] The inventors multiplied the absorbed dose distribution in the traveling direction of the 23 types of charged particle beams calculated in the treatment plan (FIG. 20) by the reciprocal of the correction coefficient (conversion coefficient) calculated from the OH radical concentration obtained by the method of Example 1 and Example 2 (FIG. 21). Note that the value of the corresponding coordinate is used for the reciprocal of the correction coefficient. This result represents the absorbed dose when recombination of OH radicals occurs when a charged particle beam is irradiated. In other words, this value represents the measurement value (correction value) of the reactant 8 itself (FIG. 22).

[0092] The inventors compared this calculation result (corrected value) with the measurement value (actual measurement value) of the gel dosimeter 4 and found that the two were in good agreement. Therefore, it was found that the validity of a treatment plan can be proven by comparing the distribution in which the absorbed dose assumed in the treatment plan has been corrected with the absorbance distribution obtained by measurement with the gel dosimeter 4. In other words, it was confirmed that the radiation dose measurement method of this embodiment can be applied to QA of a treatment plan.

[0093] The sum of the correction values ​​corresponds to the dose distribution. The sum of the correction values ​​is used as a verification value to compare with the dose distribution in the treatment plan, and it can be confirmed whether the dose distribution established in the treatment plan is reproduced.

[0094] As described above, Example 4 is a method for forming a spread-out Bragg peak (SOBP) by irradiating multiple types of charged particles with different acceleration energies, which are radiation 3, and confirming the dose distribution of the spread-out Bragg peak in a treatment device 2 (Figure 1) that performs radiation therapy.

[0095] When applying this embodiment 4 to the radiation dosimetry system 1, first, the starting point of irradiation of the charged particles in the gel dosimeter 4 is set to the origin P0 (Figure 2), and a one-dimensional coordinate that coincides with the traveling direction of the charged particles is defined.

[0096] The computer 6 calculates the amount of radicals generated for each charged particle with different acceleration energy at the same coordinate based on the planned value of the dose for each coordinate for each charged particle with different acceleration energy, which is previously formulated in the treatment plan. The computer 6 also calculates a correction coefficient corresponding to each coordinate, which is obtained by dividing the amount of radicals generated at each coordinate by the amount of radicals generated at the origin P0 (FIG. 2). The computer 6 also calculates a correction value by multiplying the planned value of the dose at each coordinate by the corresponding conversion coefficient, assuming that the inverse of the correction coefficient is a conversion coefficient corresponding to each coordinate. The computer 6 also calculates a confirmation value by adding up the multiple correction values ​​calculated for each charged particle with different acceleration energy. The computer 6 also compares the measured value of the reaction amount at each coordinate obtained by the measuring device 5 (FIG. 1) with the confirmation value, and checks whether the dose distribution formulated in the treatment plan is reproduced. In this way, it is possible to check whether the spread-out Bragg peak set at the time of treatment plan is correctly realized.

[0097] The correction coefficient is the concentration value of OH radicals 1 nanosecond after irradiation with radiation 3 at each coordinate of the gel dosimeter 4 divided by the concentration value of OH radicals 1 nanosecond after irradiation with radiation 3 at the origin P0 (Figure 2). EXAMPLES

[0098] Next, a fifth embodiment will be described with reference to Figures 23 to 26. Note that Figure 1 may be referred to.

[0099] Example 5 is intended to irradiate from any direction, such as when the treatment device 2 (FIG. 1) is required to irradiate while avoiding important organs. Example 5 is intended to include a rotating gantry (not shown). FIGS. 23 and 25 are cross-sectional views of the gel dosimeter 4 placed at the center of rotation of the rotating gantry. FIG. 23 shows the initial position of the gel dosimeter 4, and FIG. 25 shows the state in which the rotating gantry has rotated 90 degrees. In reality, the gel dosimeter 4 does not rotate, and only the rotating gantry rotates, but to facilitate understanding, the orientation of the gel dosimeter 4 in FIG. 23 is rotated 90 degrees and is shown in FIG. 25.

[0100] When performing heavy particle cancer therapy using a rotating gantry (not shown), it is necessary to check whether the rotation of the rotating gantry causes a shift in the irradiation axis of the charged particle beam (radiation 3). It is also necessary to check whether the spread-out Bragg peak (SOBP) created in the treatment plan is formed inside the patient's body without being affected by the rotation of the rotating gantry.

[0101] The inventors have considered application of this embodiment to QA of charged particle beam irradiation using a rotating gantry. The inventors have simulated a rotating gantry and performed irradiation tests of charged particle beams in a horizontal direction and in a different direction, for example, a vertical direction.

[0102] The inventors developed a treatment plan in which irradiation was first performed from a horizontal direction, and the gel dosimeter 4 was fixed in its position, and then the irradiation angle of the charged particle beam (radiation 3) was changed to irradiate the gel dosimeter 4 from a vertical direction.

[0103] The inventors irradiated the gel dosimeter 4 with 36 charged particle beams of 260 to 140 MeV / u from the vertical direction and with 36 charged particle beams of 260 to 170 MeV / u from the horizontal direction. The inventors made a treatment plan in which a spread-out Bragg peak (SOBP) as shown in the graphs of Fig. 24 and Fig. 26 is formed on the gel dosimeter 4. For example, the treatment plan was made assuming a cubic tumor (target 10) with one side of 60 mm.

[0104] The inventors irradiated a gel dosimeter 4 with a charged particle beam (radiation 3) in accordance with this treatment plan, and measured the distribution of absorbance after irradiation using an optical CT device as a measuring device 5 (FIG. 1).

[0105] In the first irradiation, a distribution of colored areas 9 was observed in the horizontal direction of the gel dosimeter 4, and when irradiation was performed in the vertical direction, an overlapping distribution of colored areas 9 was observed. The inventors confirmed that this matched the area of ​​the assumed cubic tumor (target 10).

[0106] The inventors multiplied the absorbed dose (treatment plan value) of each spatial coordinate of 36 types of charged particle beams vertically and 36 types of charged particle beams horizontally by the conversion coefficient of the same coordinates obtained from the OH radical concentration in the same manner as in the method of Example 4 to calculate the value of the spread-out Bragg peak (SOBP) (corrected value: confirmed value). The inventors then compared this value with the measurement value (actual measurement value) of the gel dosimeter 4. As a result, the total value from both directions assumed in the treatment plan (corrected value: confirmed value) and the measurement value (actual measurement value) of the gel dosimeter 4 matched. This confirmed that by using the radiation dose measurement method of this embodiment, it is possible to verify the treatment plan when the irradiation direction of the charged particle beam is rotated by the rotating gantry (FIGS. 24 and 26).

[0107] As described above, this embodiment has been described based on Examples 1 to 5, but the configuration applied in any of the examples may be applied to other examples, and the configurations applied in the respective examples may be combined.

[0108] The computer 6 described above includes a control device, a storage device, an output device, an input device, and a communication interface. Here, the control device includes a highly integrated processor such as a central processing unit (CPU), a graphics processing unit (GPU), a field programmable gate array (FPGA), or a dedicated chip. The storage device includes a read only memory (ROM), a random access memory (RAM), a hard disk drive (HDD), a solid state drive (SSD), and the like. The output device includes a display panel, a head mounted display, a projector, a printer, and the like. The input device includes a mouse, a keyboard, a touch panel, and the like. The radiation dosimetry system 1 described above can be realized by a hardware configuration using a normal computer 6.

[0109] The program executed by the computer 6 is provided by being pre-installed in a ROM or the like. Additionally or alternatively, the program is provided by being stored in a non-transitory storage medium readable by the computer 6 as a file in an installable or executable format. Examples of the storage medium include a CD-ROM, a CD-R, a memory card, a DVD, a flexible disk (FD), and the like.

[0110] The programs executed by the computer 6 may be stored in a predetermined server connected to a network such as the Internet and provided by downloading them via the network. The computer 6 may also be configured by combining separate modules that independently perform the functions of the components and are mutually connected via a network or dedicated lines.

[0111] In the above embodiment, a human patient is exemplified as an object of irradiation with a charged particle beam in the treatment device 2, but other aspects may be used. For example, animals such as dogs and cats may be irradiated. The treatment device 2 may be used when administering radiation therapy to these animals.

[0112] According to the embodiment described above, the computer 6 performs at least one of the following: a process of correcting the measurement value based on a previously obtained correction coefficient to obtain the dose of the radiation 3; and a process of confirming whether the measurement value is correct. In this way, the gel dosimeter 4 can be put to practical use.

[0113] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations can be made without departing from the spirit of the invention. These embodiments or modifications thereof are within the scope of the invention and its equivalents as described in the claims, as well as within the scope and spirit of the invention. [Explanation of symbols]

[0114] 1...radiation dosimetry system, 2...treatment device, 3...radiation, 4...gel dosimeter, 5...measuring equipment, 6...computer, 7...container, 8...reactant, 9...coloring part, 10...target, 11...irradiation range, D...deviation phenomenon.

Claims

1. a gel dosimeter containing a reactant that reacts with radicals generated by ionization caused by energy imparted by radiation; a measurement device for obtaining a measurement of the amount of reactant reacted with the radical; one or more computers; This is a method using the computer performs at least one of a process of correcting the measurement value based on a previously obtained correction coefficient to obtain the radiation dose, and a process of confirming whether the measurement value is correct. Radiation dose measurement method.

2. The computer includes: determining the correction coefficient from the relationship between the amount of radicals produced and the amount of radicals lost and the amount of reaction; multiplying the measurement value of the reaction amount obtained by the measuring device by the correction coefficient to obtain the dose of the radiation; The radiation dose measuring method according to claim 1 .

3. a method for measuring a dose distribution of the spread-out Bragg peak in a treatment device for performing radiation therapy by irradiating a plurality of types of charged particles having different acceleration energies, the radiation being the radiation; When the irradiation start point of the charged particle in the gel dosimeter is defined as the origin and the coordinate of the one-dimensional direction that coincides with the traveling direction of the charged particle is defined, the measurement device obtains the measurements of the reaction amounts at each of the coordinates; The computer includes: calculating the amount of radicals generated for each of the charged particles having different acceleration energies at the same coordinates; determining the correction coefficient corresponding to each of the coordinates by dividing the amount of radical generation at each of the coordinates by the amount of radical generation at the origin; multiplying the measured value of the reaction amount at each of the coordinates by the corresponding correction coefficient to obtain a correction value of the reaction amount; calculating the dose distribution of the spread-out Bragg peak by summing the correction values ​​obtained for the charged particles having different acceleration energies; The radiation dose measuring method according to claim 1 .

4. a method for forming a spread-out Bragg peak by irradiating a plurality of types of charged particles having different acceleration energies, which are the radiation, and for confirming a dose distribution of the spread-out Bragg peak of a treatment device for performing radiation therapy, When the irradiation start point of the charged particle in the gel dosimeter is defined as the origin and the coordinate of the one-dimensional direction that coincides with the traveling direction of the charged particle is defined, The computer includes: calculating the amount of radicals generated for each of the charged particles having different acceleration energies at the same coordinates based on a planned value of the dose for each of the charged particles having different acceleration energies that is determined in advance in a treatment plan; determining the correction coefficient corresponding to each of the coordinates by dividing the amount of radical generation at each of the coordinates by the amount of radical generation at the origin; a reciprocal of the correction coefficient is set as a conversion coefficient corresponding to each of the coordinates, and a correction value is obtained by multiplying the planned value of the dose at each of the coordinates by the corresponding conversion coefficient; A confirmation value is obtained by adding up the correction values ​​obtained for the charged particles having different acceleration energies; comparing the measured values ​​of the reaction amount at each of the coordinates acquired by the measuring device with the confirmation values ​​to confirm whether the dose distribution determined in the treatment plan is reproduced; The radiation dose measuring method according to claim 1 .

5. the correction coefficient is a value obtained by dividing a concentration value of the OH radical 1 nanosecond after irradiation of the radiation at each of the coordinates of the gel dosimeter by the concentration value of the OH radical 1 nanosecond after irradiation of the radiation at the origin. The method for measuring radiation dose according to claim 3 or 4.

6. The radical is an OH radical produced by excitation of a water molecule. The method for measuring radiation dose according to any one of claims 1 to 4.

7. A gel dosimeter used in the radiation dose measurement method according to any one of claims 1 to 4, The reactants are A gelling agent that gels the aqueous solution; a color former that is cleaved by the radicals generated by ionizing water by the radiation and that has an oxidized molecular bond group that selectively absorbs light in a specific wavelength range and develops a color; Including, Gel dosimeter.

8. A gel dosimeter used in the radiation dose measurement method according to any one of claims 1 to 4, The reactants are A gelling agent that gels the aqueous solution; at least one of a vinyl monomer and an iron ion that is changed by the radical generated by ionization of water by the radiation; Including, Gel dosimeter.

9. a gel dosimeter containing a reactant that reacts with radicals generated by ionization caused by energy imparted by radiation; a measurement device for obtaining a measurement of the amount of reactant reacted with the radical; one or more computers; Equipped with The computer is configured to perform at least one of a process of correcting the measurement value based on a previously obtained correction coefficient to obtain the radiation dose, and a process of confirming whether the measurement value is correct. Radiation dosimetry system.

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