Dose Evaluation System

Abstract

This dose evaluation system evaluates, after treatment, an administered dose that is a dose administered to a tumor of a patient in the treatment by a boron neutron capture therapy system, wherein an actual value R1 indicating a value of an actual proton beam current in the executed treatment, and an actual value R2 of an actual blood boron concentration in the executed treatment are acquired, and an administered dose estimation value is acquired on the basis of information about the acquired values.

Description

[Technical field]

[0001] The present invention relates to a dose evaluation system. [Background technology]

[0002] Conventionally, as a technology in this field, a boron neutron capture therapy system described in the following Patent Document 1 is known. In this boron neutron capture therapy system, a neutron beam detection system for detecting neutron beams is provided at the opening of the collimator, which is the outlet of the neutron beam. This neutron beam detection system can measure the amount of neutron beams output from the boron neutron capture therapy system toward the patient. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-146298 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, while the boron neutron capture therapy system can measure the amount of neutron radiation irradiated toward the patient as described above, it is not possible to know the dose that the patient actually receives, and it is not possible to evaluate whether or not treatment for the patient has been performed appropriately. An object of the present invention is to provide a dose evaluation system that can evaluate the dose actually administered to a patient's tumor in treatment by boron neutron capture therapy. [Means for solving the problem]

[0005] The dose evaluation system of the present invention is a dose evaluation system that evaluates an administration dose, which is the dose administered to a patient's tumor in treatment with a boron neutron capture therapy system, after treatment, and is equipped with a dose estimation unit that acquires a first parameter actual value representing an actual value in the performed treatment for a first parameter related to radiation during treatment, and a second parameter actual value representing an actual value in the performed treatment for a second parameter related to boron concentration in the patient's body during treatment, and acquires an administration dose estimate value that estimates the administration dose in the performed treatment based on the first parameter actual value and the second parameter actual value.

[0006] The dose estimation unit may further acquire a first parameter planned value planned in a treatment plan created in advance for the first parameter, and a second parameter planned value planned in the treatment plan for the second parameter, and acquire an administration dose estimate value based on the first parameter planned value, the first parameter actual value, the second parameter planned value, and the second parameter actual value.

[0007] The dose estimation unit may further acquire an administration dose planned value, which is a planned value of the administration dose planned in the treatment plan, and acquire an administration dose estimated value by correcting the administration dose planned value based on the first parameter planned value, the first parameter actual value, the second parameter planned value, and the second parameter actual value.

[0008] The planned administration dose value includes a planned reaction-derived dose value J1, which is the dose derived from the reaction between neutrons of the neutron beam irradiated to the patient and boron in the patient's body, and a planned neutron-derived dose value J2, which is the dose derived from the neutrons themselves of the neutron beam irradiated to the patient, and the estimated administration dose value may be expressed by the following formula (1). Estimated dose = J1 (∫(R1 R2) / ∫(P1 P2)) +J2·(∫R1 / ∫P1) …Equation (1) however, ∫(R1·R2) is the time integral of the product of the actual value of the first parameter and the actual value of the second parameter from the start time of treatment to the end time of treatment, ∫(P1·P2) is the time integral of the product of the first parameter planning value and the second parameter planning value from the treatment start time to the treatment end time, ∫R1 is the time integral of the actual value of the first parameter from the treatment start time to the treatment end time, ∫P1 is the time integral of the first parameter planning value from the treatment start time to the treatment end time.

[0009] In addition, the first parameter actual value may be obtained based on an actual measurement value of a beam current of a charged particle beam generated by a boron neutron capture therapy system, or an actual measurement value of the amount of neutrons irradiated to a patient by a boron neutron capture therapy system, and the second parameter actual value may be obtained based on an actual measurement value of a boron concentration in the patient's blood. Effect of the Invention

[0010] According to the present invention, it is possible to provide a dose evaluation system capable of evaluating the dose actually administered to a tumor in a patient in treatment by boron neutron capture therapy. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 illustrates a boron neutron capture therapy system. [Diagram 2] FIG. 2 is a diagram showing the vicinity of a neutron beam output section of the system of FIG. 1. [Diagram 3] FIG. 1 is a block diagram showing a dose evaluation system. [Figure 4] FIG. 2 is a diagram showing the vicinity of a neutron detector installed in the system of FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, the same or corresponding elements are given the same reference numerals, and duplicated explanations will be omitted. In addition, the terms "upstream" and "downstream" refer to the upstream (accelerator side) and downstream (patient side) of the emitted charged particle beam and neutron beam, respectively.

[0013] The boron neutron capture therapy system 1 shown in Figure 1 is a device that performs cancer treatment using boron neutron capture therapy (BNCT). 10 A neutron beam N is irradiated to a patient (irradiated subject) 40 to which a boron neutron capture therapy agent (B) has been administered. The boron neutron capture therapy system 1 includes an accelerator 10 (e.g., a cyclotron), which accelerates charged particles (e.g., protons) to generate a charged particle beam P (e.g., a proton beam) and emits it. The accelerator 10 here has the ability to generate a charged particle beam P with a beam radius of 40 mm and 60 kW (=30 MeV×2 mA), for example.

[0014] The charged particle beam P extracted from the accelerator 10 passes through the horizontal steering 12, the four-way slit 14, the horizontal-vertical steering 16, the quadrupole electromagnets 18, 19, and 20, the 90-degree bending electromagnet 22, the quadrupole electromagnet 24, the horizontal-vertical steering 26, the quadrupole electromagnet 28, the four-way slit 30, the current monitor 32, and the charged particle beam scanning unit 34 in sequence, and is guided to a neutron beam output unit 36. The neutron beam output unit 36 ​​extracts (outputs) a neutron beam N generated by irradiating the target T with the charged particle beam P, and the neutron beam N is irradiated to a patient 40 on a treatment table 38.

[0015] The horizontal steering 12 and the horizontal / vertical steering 16, 26 use, for example, electromagnets to adjust the beam axis of the charged particle beam P. Similarly, the quadrupole electromagnets 18, 19, 20, 24, 28 use, for example, electromagnets to suppress divergence of the charged particle beam P. The four-way slits 14, 30 cut off the beam at the ends to shape the charged particle beam P.

[0016] The 90-degree deflection electromagnet 22 deflects the traveling direction of the charged particle beam P by 90 degrees. The 90-degree deflection electromagnet 22 is provided with a switching unit 42, which can deflect the charged particle beam P from the normal trajectory and guide it to a beam dump 44. The beam dump 44 can check the output of the charged particle beam P before treatment, etc.

[0017] The current monitor 32 measures in real time the beam current value (i.e., charge, exposure dose rate) of the charged particle beam P irradiated onto the target T of the neutron beam output unit 36. The current monitor 32 uses a non-destructive DCCT (DC Current Transformer) that can measure current without affecting the charged particle beam P. A predetermined controller is connected to this current monitor 32. Note that "dose rate" means the dose per unit time (the same applies below).

[0018] The charged particle beam scanning unit 34 scans the charged particle beam P and controls the irradiation of the charged particle beam P on the target T. The charged particle beam scanning unit 34 here controls, for example, the irradiation position of the charged particle beam P on the target T, the beam diameter of the charged particle beam P, and the like.

[0019] As shown in FIG. 2, the neutron beam output section 36 includes a target T arranged at the downstream end of a beam duct 48 through which the charged particle beam P passes, a moderator 50 for decelerating the neutron beam N generated at the target T, a shielding body 52 arranged to cover these, and a collimator 46 attached to the downstream end of the shielding body 52.

[0020] The target T generates a neutron beam N when irradiated with the charged particle beam P. The target T here is made of, for example, beryllium (Be) and has a disk shape with a diameter of 160 mm. The type of target T is set according to the energy of the charged particle beam P of the accelerator 10.

[0021] The moderator 50 decelerates the neutron beam N emitted from the target T and reduces its energy so that it is suitable for treatment. The moderator 50 has a laminated structure made of a plurality of different materials, for example. The material of the moderator 50 is appropriately selected depending on various conditions such as the energy of the charged particle beam.

[0022] The shield 52 is attached to the floor of the treatment room to block the neutron beam N and gamma rays and the like generated by the generation of the neutron beam N from being emitted to the outside. The collimator 46 has a circular opening 46a which serves as an output port for the neutron beam N and defines the irradiation field of the neutron beam N.

[0023] An example of boron neutron capture therapy performed in this boron neutron capture therapy system 1 will be described. Here, the charged particle beam P emitted from the accelerator 10 is a proton beam. In the treatment, 10 A drug containing B is administered to the patient 40 and accumulates in the tumor of the patient 40. Meanwhile, based on a treatment plan created in advance by a treatment planning system 55, under the control of a control unit 57, a proton beam emitted from the accelerator 10 is scanned by the charged particle beam scanning unit 34 and irradiated onto the target T. A neutron beam N is generated by the collision of the proton beam with the target T, and the generated neutron beam N is decelerated by a moderator 50 and irradiated onto the patient 40 through an opening 46a of a collimator 46. This neutron beam N and the charged particle beams accumulated in the tumor of the patient 40 are then irradiated onto the patient 40. 10 B reacts with 4 He nucleus (alpha ray) 7 Li nuclei are generated, and these 4 He nucleus (alpha ray) 7 The Li nuclei cause damage to the tumor. The neutron radiation N itself also causes damage to the tumor.

[0024] Next, the dose evaluation system 61 will be described with reference to Fig. 3. The dose evaluation system 61 is a system for evaluating the dose actually administered to the tumor of the patient 40 in the above-mentioned boron neutron capture therapy after the treatment. The dose evaluation system 61 includes a communication unit 61a, a calculation unit 61b (dose estimation unit), and a display unit 61c.

[0025] The communication unit 61a establishes communication with the control unit 57, the treatment planning system 55, etc., and executes data transmission and reception. The control unit 57 comprehensively controls the operation of the boron neutron capture therapy system 1, and performs, for example, processing such as feedback control of the output of the accelerator 10 based on the measurement value by the current monitor 32. The calculation unit 61b executes various calculations related to the administration dose. The display unit 61c displays the calculation results by the calculation unit 61b on a screen and presents them to the user. The display unit 61c is, for example, a display monitor.

[0026] The dose evaluation system 61 is physically configured as a computer system including a CPU, RAM and ROM as main storage devices, auxiliary storage devices such as a hard disk, input devices such as a keyboard and a mouse as input devices, an output device such as a display, a communication module as a data transmission / reception device such as a network card, etc. Each function of the communication unit 61a, the calculation unit 61b, the display unit 61c, etc., provided in the dose evaluation system 61 is realized by loading predetermined computer software onto hardware such as the CPU and RAM, operating the communication module, the input device, and the output device under the control of the CPU, and reading and writing data from and to the RAM and auxiliary storage device.

[0027] The dose evaluation system 61 performs calculations based on input information in accordance with a predetermined program, and estimates the administration dose actually administered to the tumor of the patient 40 during treatment (calculates an administration dose estimate). Input information required for the dose evaluation system 61 to calculate the administration dose estimate is planned value J1, planned value J2, planned value P1, planned value P2, actual value R1, and actual value R2, which will be described below.

[0028] [Planned value J1] The treatment plan 55a created by the treatment planning system 55 includes neutrons of the neutron beam N and a tumor in the patient 40. 10 It is generated by reacting with B (hereinafter simply referred to as "boron") 4 He nucleus (alpha ray) 7The planned value J1 of the dose derived from the Li nucleus (hereinafter referred to as the “reaction-derived dose”) is included. The planned value J1 is transmitted from the treatment planning system 55, received by the communication unit 61a, and input to the dose evaluation system 61. [Planned value J2] The treatment plan 55a also includes a planned value J2 of the dose (hereinafter simply referred to as the “neutron-derived dose”) originating from the neutron beam N itself. The planned value J2 is transmitted from the treatment planning system 55, received by the communication unit 61a, and input to the dose evaluation system 61.

[0029] In the treatment plan 55a, the total dose of the planned value J1 and the planned value J2 is planned as the dose to be administered to the tumor of the patient 40 (hereinafter referred to as the "administered dose planned value"). That is, The dose plan value = J1 + J2.

[0030] [Planned value P1] Furthermore, the treatment plan 55a includes a planned value P1 (first parameter planned value) of the proton beam current (first parameter) extracted from the accelerator 10 at each time (e.g., every second) during treatment. The planned value P1 is transmitted from the treatment planning system 55, received by the communication unit 61a, and input to the dose evaluation system 61. [Planned value P2] Furthermore, the treatment plan 55a includes a planned value P2 (planned second parameter value) of the blood boron concentration (second parameter) of the patient 40 at each time (e.g., every second) during treatment. The planned value P2 is transmitted from the treatment planning system 55, received by the communication unit 61a, and input to the dose evaluation system 61.

[0031] [Real value R1] In the control unit 57 (see FIG. 1) of the boron neutron capture therapy system 1 after the treatment, the actual value R1 of the proton beam current actually emitted from the accelerator 10 at each time (for example, every second) during the treatment is stored as log data. That is, the proton beam current is measured by the current monitor 32 at intervals of, for example, one second, and the measured value, for example, every second from the treatment start time to the treatment end time, is accumulated and stored in the control unit 57 as the actual value R1 (actual value of the first parameter). The treatment start time is the time when the irradiation of the neutron beam N to the patient 40 is started, and the treatment end time is the time when the irradiation of the neutron beam N to the patient 40 is ended. For example, the control unit 57 also reflects information such as the proton beam being temporarily stopped during the treatment. The actual value R1 is transmitted from the control unit 57, received by the communication unit 61a, and input to the dose evaluation system 61. Also, instead of actually measuring the proton beam current with the current monitor 32 as described above, the proton beam current value may be assumed to be constant from the treatment start time to the treatment end time, and this constant value may be used as the actual value R1.

[0032] [Real value R2] The actual value of the blood boron concentration of the patient 40 at each time (for example, every second) during treatment can be estimated or measured by a predetermined method. The estimated or measured actual blood boron concentration is set as the actual value R2 (the actual value of the second parameter). For example, when the drug administration to the patient 40 is performed by a decelerated continuous administration protocol, the blood boron concentration may be measured immediately before the start of irradiation with the neutron beam N and immediately after the end of irradiation, and the blood boron concentration during irradiation may be estimated by linear interpolation based on the measured value. Also, for example, when the drug administration to the patient 40 is performed by an irradiation protocol after the administration is stopped, the blood boron concentration during irradiation may be estimated by assuming that the blood boron concentration decreases exponentially after administration. Also, it may be assumed that the blood boron concentration was constant throughout the entire irradiation with the neutron beam N.

[0033] Alternatively, the blood boron concentration of the patient 40 may be measured in real time (e.g., every second) during irradiation with the neutron beam N, and this measured value may be used as the actual value R2. As a specific method, for example, the blood boron concentration may be derived by measuring gamma rays generated by a reaction between neutrons and boron using a measuring device installed near the patient 40. That is, by measuring the gamma rays in real time during treatment, the amount of boron in the patient 40 consumed in the reaction with neutrons can be known in real time, and the blood boron concentration remaining in the patient 40 can be derived in real time. The actual value R2 derived by these methods may be input into the dose evaluation system 61 manually by an operator, for example.

[0034] The calculation unit 61b of the dose evaluation system 61 calculates an administration dose estimate value based on the planned values ​​J1, J2, P1, and P2 received from the treatment planning system 55, the actual value R1 received from the control unit 57, and the actual value R2 input separately. Specifically, the calculation unit 61b calculates the administration dose estimate value by the calculation of the following formula (1). Estimated dose = J1 (∫(R1 R2) / ∫(P1 P2)) +J2·(∫R1 / ∫P1) …Equation (1)

[0035] Here, in equation (1), ∫(R1 R2) is the time integral of the product of the actual value R1 and the actual value R2 from the treatment start time to the treatment end time, ∫(P1 P2) is a value obtained by integrating the product of planned value P1 and planned value P2 over time from the treatment start time to the treatment end time. ∫R1 is the time integral of the actual value R1 from the treatment start time to the treatment end time, ∫P1 is the time integral of the planned value P1 from the treatment start time to the treatment end time.

[0036] As mentioned above, Dose planning value = J1 + J2 Therefore, it can be said that the dose evaluation system 61 derives an administration dose estimate value by correcting the administration dose plan value according to the treatment plan 55a based on the actual value R1, the actual value R2, the planned value P1, and the planned value P2 by calculating equation (1).

[0037] The display unit 61c of the dose evaluation system 61 displays the above calculation result (administration dose estimate value) by the calculation unit 61b on a screen and presents it to the user. The calculation unit 61b may also compare the administration dose estimate value with the administration dose plan value, and the comparison result may be further displayed on the screen by the display unit 61c. The user can check the calculation result and the comparison result to verify whether the treatment has been achieved according to the prior treatment plan.

[0038] Here, the formula (1) includes ∫(R1 R2) Consider the following. The actual dose administered to the tumor of patient 40 at a certain time is considered to be proportional to the amount of neutron radiation at that time and the amount of boron present in the tumor of patient 40 at that time. The amount of neutron radiation at a certain time is considered to be correlated with the proton beam current extracted from accelerator 10 at that time. The amount of boron present in the tumor of patient 40 at a certain time is considered to be correlated with the blood boron concentration of patient 40 at that time.

[0039] Then, at a certain time (R1 R2) is considered to be correlated with the actual dose administered to the tumor of patient 40 at that time, and is integrated over time to obtain ∫(R1 R2) is considered to indicate the magnitude of the actual dose administered to the tumor of patient 40 from the start time to the end time of treatment. During actual treatment, fluctuations in the proton beam current extracted from accelerator 10 and fluctuations in the blood boron concentration of patient 40 may occur independently, and the calculation of ∫(R1·R2) also reflects the effects of the above-mentioned independent fluctuations.

[0040] Similarly, the compound included in formula (1) ∫(P1 P2) is considered to indicate the magnitude of the planned dose administered to the tumor of patient 40 from the start time to the end time of treatment.

[0041] Therefore, ∫(R1 R2) and ∫(P1 P2) and By using the ratio as a correction coefficient for the planned value J1, the first term of the formula (1) is J1 (∫(R1 R2) / ∫(P1 P2)) It is considered that the reaction-derived dose in the treatment plan has been corrected to approach the true value based on actual measurement results, etc.

[0042] Similarly, ∫R1 and ∫P1 and By using the ratio as a correction coefficient for the planned value J2, the second term of equation (1) is J2 (∫R1 / ∫P1) It is believed that the neutron-derived dose in the treatment plan has been corrected to approach the true value based on actual measurement results, etc.

[0043] Therefore, the estimated dose derived by formula (1) is obtained by dividing the planned dose value into planned value J1 and planned value J2 and correcting them based on the actual values ​​obtained by actual measurements, etc., and is considered to be close to the true dose. In other words, the dose evaluation system 61 of this embodiment can accurately evaluate the dose of the actual treatment after the fact.

[0044] The actual value R1 and the planned value P1 may be values ​​indicating the amount of neutrons irradiated to the patient 40, instead of the proton beam current value. In this case, for example, the amount of neutrons irradiated to the patient 40 at each time is actually measured by the neutron detector 65 shown in Fig. 4, and this actual measurement value is accumulated as the actual value R1 in the control unit 57 and stored as log data. Also in this case, the treatment plan 55a includes a planned value of the amount of neutrons irradiated to the patient 40 at each time (e.g., every second) during treatment, and this planned value may be adopted as the planned value P1.

[0045] The neutron beam detector 65 has a scintillator 65a, an optical fiber 65b, and a photodetector 65c, as shown in Fig. 4. The scintillator 65a is provided in a through hole 46b of the collimator 46 (see Fig. 2) and is exposed to an opening 46a of the collimator 46. The scintillator 65a receives the neutron beam N or gamma rays in the opening 46a and generates scintillation light. This scintillation light is incident on the photodetector 65c through the optical fiber 65b. The photodetector 65c is a light detecting device such as a photomultiplier tube or a phototube, and outputs an electric signal (detection signal) to the control unit 57 when light is detected.

[0046] The amount of neutrons irradiated to the patient 40 may be measured by the following method. For example, a gold wire is placed near the patient 40 during treatment, and the activation of the gold wire is measured after the treatment, thereby deriving the amount of neutrons irradiated to the patient 40. In this case, it may be assumed that the amount of neutrons is constant throughout the treatment.

[0047] The present invention can be embodied in various forms, including the above-described embodiment, with various modifications and improvements based on the knowledge of those skilled in the art. In addition, it is possible to configure modified examples by utilizing the technical matters described in the above-described embodiment. The configurations of each embodiment may be used in appropriate combination.

[0048] For example, some of the values ​​of the proton beam current, blood boron concentration, etc. contained in planned values ​​J1, J2, planned values ​​P1, P2, actual values ​​R1, and actual values ​​R2 may be assumed to be constant from the start time of treatment to the end time of treatment, thereby simplifying the calculations as appropriate.

[0049] In addition, in the above embodiment, the dose evaluation system 61 is a system separate from the treatment planning system 55, but the dose evaluation system 61 may be included in the treatment planning system 55. In other words, the function of the dose evaluation system 61 may be realized on the hardware constituting the treatment planning system 55, and the dose evaluation process may be executed. [Explanation of symbols]

[0050] 1...boron neutron capture therapy system, 32...current monitor, 40...patient, 61...dose evaluation system, 61b...calculation unit (dose estimation unit), 65...neutron radiation detector.

Claims

1. A dose evaluation system for evaluating an administered dose, which is a dose administered to a tumor of a patient in a treatment using a boron neutron capture therapy system, after the treatment, comprising: a first parameter actual value representing an actual value of a first parameter related to radiation during the treatment; and obtaining a second parameter actual value representing an actual value of a second parameter related to a boron concentration in the patient's body during the treatment; a dose estimator that obtains an administration dose estimate value that estimates the administration dose in the performed treatment based on the first parameter actual value and the second parameter actual value; The dose estimation unit is A first parameter planned value planned in a treatment plan created in advance for the first parameter; and further acquiring a second parameter planned value planned in the treatment plan for the second parameter; obtaining the administered dose estimate based on the first planned parameter value, the first actual parameter value, the second planned parameter value, and the second actual parameter value; The dose estimation unit is Further acquiring a dose plan value which is a planned value of the dose planned in the treatment plan; correcting the administration dose plan value based on the first parameter plan value, the first parameter actual value, the second parameter plan value, and the second parameter actual value to obtain the administration dose estimate value; The dose schedule value is A planned value J1 of a reaction-derived dose which is a dose resulting from a reaction between neutrons of a neutron beam irradiated to the patient and boron in the body of the patient; A planned value J2 of a neutron-derived dose, which is a dose derived from the neutrons themselves of the neutron beam irradiated to the patient, The dose assessment system, in which the administration dose estimate is expressed by the following equation (1). Estimated dose = J1・(∫(R1・R2) / ∫(P1・P2)) +J2・(∫R1 / ∫P1) ...Formula (1) however, ∫(R1·R2) is a value obtained by integrating the product of the first parameter actual value and the second parameter actual value over time from the treatment start time to the treatment end time, ∫(P1·P2) is a value obtained by integrating the product of the first parameter planning value and the second parameter planning value over time from the treatment start time to the treatment end time; ∫R1 is a value obtained by integrating the actual value of the first parameter over time from the treatment start time to the treatment end time, ∫P1 is a value obtained by integrating the first parameter planning value over time from the treatment start time to the treatment end time.

2. The first parameter actual value is is obtained based on an actual measurement value of a beam current of a charged particle beam generated by the boron neutron capture therapy system, The second parameter actual value is The dose evaluation system according to claim 1 , wherein the dose evaluation is obtained based on an actual measurement value of the blood boron concentration of the patient.

Images