JP2011007733A - Radiation irradiation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a γ-ray/neutron-beam irradiation device for medical use having easy handleability and excellent work efficiency, capable of obtaining a desired radiation flux distribution shape.SOLUTION: This radiation irradiation device includes: an irradiation source part 30 for irradiating an irradiation object with a radiation; a reactor 10; a neutron irradiation capsule 20 installed in the reactor 10; an introduction pipe 40 for connecting the irradiation source part 30 to the neutron irradiation capsule 20, and introducing radioactive isotope-including solution into the neutron irradiation capsule 20; and a lead-out pipe 50 for connecting the irradiation source part 30 to the neutron irradiation capsule 20, and leading out the radioactive isotope-including solution after being subjected to neutron irradiation from the neutron irradiation capsule 20. In the device, the radioactive isotope-including solution subjected to neutron irradiation in the reactor 10 is conveyed to the irradiation source part 30 through the introduction pipe 40, and is used as an irradiation source for irradiating the irradiation object 108 with a radiation, and thereafter, the radioactive isotope-including solution is returned into the neutron irradiation capsule 20 through the lead-out pipe 50, and is subjected again to neutron irradiation.

Description

  The present invention relates to a radiation irradiation apparatus, and more particularly to a radiation irradiation apparatus that directly uses a neutron-irradiated radioisotope-containing solution useful as a medical radiation irradiation apparatus as an irradiation radiation source.

Radioactive isotope (radio isotope, hereinafter also referred to as "RI") is, industrial applications, medical applications, has been used in a wide range of fields, such as research and development, and of these, cobalt ^{60 (60} Co) and iridium ^{192 (192} A relatively long-life RI such as Ir) is manufactured by irradiating a solid target (metal pellet) with a nuclear reactor (Non-patent Document 1). RI production by these reactor irradiations is performed individually for every several target metal pellets, and many target metal pellets cannot be produced by one reactor irradiation. Moreover, when irradiating the target metal pellet with neutrons in the nuclear reactor, in order to manufacture RI having as uniform radioactivity as possible, only a part of the vertical core position with a high neutron flux could be used.

  For this reason, in order to achieve the desired radiation flux distribution using the manufactured RI, the RIs having different activities irradiated with neutrons in the reactor individually in multiple times are enclosed in sealed containers one by one. After that, it is necessary to arrange them on the substrate, and there is a problem that handling is complicated, work time becomes long, and the exposure dose of the worker increases. In addition, the operation of individually enclosing the container in a sealed container is difficult to manage because there is a risk of loss due to handling of individual RI in the form of a small pellet.

For example, in a gamma knife used for head cancer treatment, 201 RIs ( ⁶⁰ Co: for example, a cylindrical shape having a diameter of 8 mm and a length of 27 mm) are mounted on a hemispherical helmet. In order to equalize the radioactivity of 201 RIs, the neutron irradiation conditions for the Co metal target must be the same. In order to realize the same neutron irradiation conditions by the conventional reactor irradiation method, it was necessary to use only a limited part of the core position, so 201 RIs were produced by one neutron irradiation. However, several Co metal targets were enclosed in an irradiation container, and neutron irradiation was performed in the reactor individually or in multiple times. In this case, 201 ⁶⁰ Co [(1.11 TBq (30 Ci) / piece)] obtained by neutron irradiation were individually enclosed in a sealed container and arranged one by one in a gamma knife helmet. For this reason, the work is complicated and the exposure control of the worker is a problem.

A manufacturing procedure of ¹⁹² Ir widely used for RI for nondestructive inspection is shown below.
1) For example, a cylindrical Ir metal having a diameter of 2 mm and a length of 2 mm and an aluminum spacer are alternately enclosed in a sample holder, and then set in an inner capsule.
2) Put the inner capsule into the aluminum basket capsule, introduce it into the reactor, and use it for neutron irradiation. At this time, in order to obtain a target dose, the neutron irradiation to the inner capsule is about one at a time.
3) Remove the aluminum basket capsule from the reactor, unlock the mechanical lock of the capsule, and remove the inner capsule.
4) After transporting the inner capsule to the RI manufacturing facility, disassemble the inner capsule and measure the radioactivity of Ir metal.
5) Using a special device, Ir metal is individually sealed in a sealed container to check the quality.

  RI is mostly used as a point-like or rod-like fixed source. As the use of the moving radiation source, there is medical irradiation or the like that irradiates the lesion intensively while moving the RI radiation source with a high-precision robot arm or the like and reduces the irradiation to the normal tissue as much as possible. However, an RI that can be used as a plane line source has not been manufactured in a single operation.

The present inventors have found that after a ^{98 Mo} by neutron irradiation was converted into by activation ^{99 Mo} in Mo solution in the reactor was proposed a method for recovering Mo solution containing ^{99 Mo} (Patent Document 1). However, a method and apparatus for directly using a neutron-irradiated liquid as a medical radiation source has not yet been proposed.

  Medical radiation irradiation devices include gamma knives and heavy particle / proton therapy devices.

The gamma knife is formed by arranging a large number of ⁶⁰ Co (1.11 TBq (30 Ci) / piece) obtained by neutron irradiation of Co metal or the like in a nuclear reactor in the irradiation source section. In particular, the head-irradiating gamma knife is a helmet type, and ⁶⁰ Co is attached one by one and a total of 201 ⁶⁰ Co is attached to the inside of the helmet, and an irradiation amount of about 200 Sv / h is obtained at the center position of the helmet. . However, in order to produce a large amount of activation of ⁶⁰ Co equally, it is necessary to manufacture under the same irradiation conditions, and irradiation at a limited core position is necessary. Moreover, in order to make the integrated dose to the affected area sufficient (40 to 70 Gy), irradiation time to the affected area as long as about 20 minutes is required, but long-time radiation irradiation is a burden on the patient. . In addition, in order to increase the irradiation position accuracy, it is necessary to anesthetize the patient and fix a special jig for fixing the helmet to the head with a bolt, which is a burden on the patient.

  The heavy particle / proton beam treatment apparatus enables irradiation with a large dose to the affected part in the deep part of the body using a heavy particle beam such as carbon or the black peak of the proton beam. However, it is necessary to manufacture a bolus (a jig for beam shaping) according to the shape of the affected part, and it is possible to irradiate about 3 people by dividing the beam into multiple parts. In other words, there are problems such as being unable to treat more patients simultaneously and being difficult to adapt to the vicinity of the body surface. In addition, the construction cost of heavy particle / proton therapy equipment is very expensive, on the scale of several tens of billion yen, and as a result, the treatment cost is also expensive.

JP 2008-102078 A

"Isotope Production 35 Years Magazine" edited by Isotope Production 35 Years Editorial Board, published by Tokai Research Institute, Japan Atomic Energy Research Institute, March 31, 1995 New Energy and Industrial Technology Development Organization (Outsourced Chemical Substance Evaluation and Research Organization, Outsourced National Institute for Product Evaluation Technology), Manganese and its compounds, Hazard Assessment Report Ver.1.0, No.116, Chemical Substances Emission Control Management Promotion Law Decree No .: 1-311

  An object of the present invention is to provide a medical γ-ray / neutron beam irradiation apparatus that is easy to handle, excellent in workability, and capable of realizing a desired radiation irradiation rate.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by adopting an apparatus configuration that directly uses a RI solution irradiated with neutrons in a nuclear reactor as a medical radiation source. Thus, the present invention has been completed.

  That is, according to the present invention, there is provided a radiation irradiation apparatus that directly uses an RI solution irradiated with neutrons in a nuclear reactor as a radiation source.

The radiation irradiation apparatus according to the present invention comprises:
An irradiation source unit for irradiating the irradiated object with radiation;
A nuclear reactor,
A neutron irradiation capsule installed in the reactor,
Connecting the radiation source section and the neutron irradiation capsule in fluid communication, and introducing a radioisotope-containing solution into the neutron irradiation capsule;
Connecting the radiation source section and the neutron irradiation capsule in fluid communication, and from the neutron irradiation capsule, a lead-out pipe for deriving the radioisotope-containing solution after neutron irradiation;
Comprising
Irradiation through which the radioactive isotope-containing solution irradiated with neutrons in the nuclear reactor is transported to the irradiation source unit through the introduction pipe and the lead-out pipe, and the irradiated object is irradiated with the radioactive isotope-containing solution. The radioisotope-containing solution is used as a radiation source, and then the neutron irradiation is performed by returning the radioisotope-containing solution from the radiation source section again into the neutron capsule.

  The irradiation source unit is arranged with a pipe through which the neutron-irradiated radioisotope-containing solution flows between the shuttered shields, and irradiates the irradiated object by opening and closing the shutters with the shutters. It is preferable to control.

  In addition, the irradiation source section includes a plurality of small-diameter short-length pipes through which the neutron-irradiated radioisotope-containing solution flows, and is arranged in series so that one end of each pipe faces the irradiated body It is preferable to have a configuration formed by Specifically, for example, a plurality of small and short pipes having a diameter of 2 mm and a height of 10 cm are arranged in series, and the end portions of the pipes and the positions of the shutters are aligned. The amount of radiation to the irradiated object can be adjusted by opening and closing the shutter. If the piping through which the radioactive isotope-containing solution is circulated is too long, the amount of γ-rays attenuates and the amount of irradiation reaching the irradiated object decreases, whereas if the piping is too short, the amount of solution to circulate decreases and the amount of γ-ray irradiation decreases. Less.

  Furthermore, a radioisotope-containing solution irradiated with neutron is provided with a collimator window portion made of beryllium between a pipe through which the neutron-irradiated radioactive isotope-containing solution flows and a shutter of the shield with shutter. The structure which converts the gamma ray radiated | emitted from into a neutron beam may be sufficient.

The radioisotope-containing solution used in the radiation irradiation apparatus of the present invention preferably contains a short half-life radioisotope selected from Mn, Na, Al, K, and Mo. For example, an MnCl ₂ aqueous solution, an NaCl aqueous solution, or a K ₂ MoO ₄ aqueous solution can be preferably used. Since these short half-life radioactive isotopes are used, neutron irradiation in the nuclear reactor can be performed in a short time, and since it attenuates in a short time, handling becomes easy.

  In the radiation irradiation apparatus of the present invention, the amount of radiation source can be controlled by adjusting the concentration of the radioisotope in the radioisotope-containing solution in addition to the arrangement of the pipes and the opening and closing of the shutter. In order to shorten the irradiation time, the concentration of the radioisotope is preferably as high as possible. However, in order to avoid clogging of the piping due to precipitation or the like, the concentration is preferably about 80 to 90 wt%. .

  It is preferable that the piping used in the radiation irradiation apparatus of the present invention is manufactured from a metal such as stainless steel and titanium having high corrosion resistance and an alloy containing these as a main component. It is more preferable to use a double-structured pipe in order to prevent leakage of the radioactive solution.

  Moreover, it can also be set as the structure which connects a some irradiation source part with respect to 1 nuclear reactor. In this case, a large number of irradiated objects can be irradiated simultaneously.

  Further, a stirring device may be provided in the neutron irradiation capsule in the nuclear reactor. As the stirring device, it is preferable to provide a baffle plate for imparting turbulent flow in the flow path of the neutron irradiation capsule. In this case, since the radioactive isotope solution is irradiated with neutrons while stirring in the neutron irradiation capsule, a homogeneous radioisotope-containing solution can be obtained.

  According to the radiation irradiation apparatus of the present invention, since the radioactive isotope-containing solution irradiated with neutrons in the reactor is used as a direct irradiation source, it is taken out from the reactor as in the case of using conventional radioisotopes. Since it is not necessary, the risk of exposure to the operator can be minimized, and handling is easy. In addition, production of radioactive isotopes and use of irradiation can be realized almost simultaneously. Furthermore, the irradiation rate can be easily adjusted by adjusting the concentration of the radioisotope in the radioisotope-containing solution.

  Since the irradiation source section has a simple structure including a pipe for circulating the radioisotope-containing solution and a shutter provided between the pipe and the irradiated object, maintenance is easy. In addition, since the irradiation source section has such a configuration, a desired radiation flux distribution shape can be easily realized and easily adjusted by arranging the piping and opening / closing the shutter.

  Since a short half-life element is used as a radioisotope, a large amount of a short-lived radioisotope-containing solution can be prepared by short-time neutron irradiation, and a powerful irradiation source can be used. Furthermore, since the radioisotope used in this apparatus has a short life and decays within a few days, the apparatus is easily maintained.

  By adopting a configuration in which a plurality of irradiation source units are connected to one nuclear reactor, a large number of irradiated objects can be irradiated simultaneously. In the case of a conventional heavy particle accelerated medical irradiation apparatus or the like using heavy particle beam irradiation, simultaneous irradiation to three irradiated objects was the limit. However, according to the apparatus of the present invention, a conventional heavy particle accelerated medical irradiation apparatus is used. It is possible to simultaneously irradiate 10 to 20 irradiated objects by taking advantage of the characteristics of a nuclear reactor that can secure a much larger irradiation volume than that of an accelerator used for the above.

  In addition, in the case of conventional heavy particle beam irradiation, the dose of the body surface part where irradiation is not desirable could not be suppressed low, but with the device of the present invention, only the affected part existing in any place in the body Irradiation can reduce the dose of normal tissue (see FIG. 3).

  Further, by attaching beryllium or an alloy containing beryllium to the window of the collimator, the radiation species can be changed from γ rays to neutron rays by (γ, n) reaction. By changing the radiation type to neutron radiation, it can be applied to the boron neutron trapping method. That is, by using a tumor marker containing boron, it is possible to irradiate boron delivered to the tumor portion with neutron rays, and to kill only cancer cells by α rays.

  The present invention can be used for various applications, but is particularly useful for medical applications such as a medical gamma ray / neutron beam irradiation apparatus.

FIG. 1 is a configuration diagram showing a schematic configuration of a radiation irradiation apparatus of the present invention. FIG. 2 is a block diagram showing the structure of the radiation source part of the radiation irradiation apparatus of the present invention. FIG. 3 is a graph showing the relationship between the depth from the body surface of each radiation type and the relative dose.

  Hereinafter, the present invention will be described in more detail with reference to the drawings, but the present invention is not limited thereto.

  An apparatus configuration of an example in which the radiation irradiation apparatus of the present invention is applied to a medical treatment apparatus is shown in FIG. The medical radiation irradiation apparatus 1 according to this embodiment is configured to irradiate a nuclear reactor 10, a neutron irradiation capsule 20 provided in the nuclear reactor 10, and an irradiation object (a patient in this embodiment) 108. Radiation source unit 30. Between the irradiation source section 30 and the neutron irradiation capsule 20, both are connected in fluid communication, and an introduction pipe 40 for introducing a radioactive isotope-containing solution into the neutron irradiation capsule 20, and the neutron irradiation capsule A lead-out pipe 50 for leading out the radioisotope-containing solution after neutron irradiation from 20 is provided. The irradiation line source unit 30 includes a shield with shutter 107 having a shutter opening 107 a and a pipe 106 disposed between the shutter with shield 107. An inlet pipe 40 and a lead-out pipe 50 are connected to the pipe 106. The irradiation source unit 30 further includes means for confirming the position of a pathological site such as a γ camera, MRI, and X-ray CT.

  The upper part of FIG. 1 is an example of a concentrated irradiation apparatus, and the lower part of FIG. 1 is an example of a uniform irradiation apparatus. An example of the concentrated irradiation apparatus shown in the upper part of FIG. 1 includes a mounting table 110 on which a patient 108 is placed, a moving table 111 that moves the mounting table 110 in the X-axis direction, the Y-axis direction, and the Z-axis direction. The radiation irradiation unit is arranged so as to cover the lower side and the upper side of the mounting table 110 at a position, and is provided with a through hole so that a patient can pass therethrough. The irradiation source unit 30 is configured to be able to irradiate concentratedly on the irradiation affected part of the patient 108. The example of the uniform irradiation apparatus shown in the lower part of FIG. 1 is configured such that the irradiation source unit 30 is embedded in the mounting table 110 and the whole body can be irradiated from below the patient 108.

In this embodiment, the nuclear reactor 10 is a nuclear reactor (JMTR) that can irradiate with a thermal neutron flux 2 × 10 ¹⁸ n / m ² · s and a fast neutron flux 1 × 10 ¹⁸ n / m ² · s. Twelve irradiation positions are used. After introducing a radioactive isotope-containing solution (MnCl ₂ saturated aqueous solution) containing 1 g of Mn into the neutron irradiation capcel 20 and irradiating it for one day sufficiently longer than the half-life of ⁵⁶ Mn (2.579 hours), 20 is sent to the irradiation source unit 30 via the outlet pipe 50. In this embodiment, the conveyance time from the neutron irradiation capsule 20 to the irradiation source unit 30 is set to 6 minutes. In this condition, 28.1TBq / g radioisotope-containing solution containing (759Ci / g) of ⁵⁶ Mn (MnCl ₂ aqueous saturated _solution; MnCl 2 773 g / water 1 kg) can be prepared. The dose equivalent rate of this radioisotope-containing solution to the irradiated object (patient) 108 located 0.6 m away from the irradiation source unit 30 is 18 Sv / h (calculated by the RASC code). In this embodiment, as shown in FIG. 2A, a small diameter short pipe 106 having a diameter of 2 mm and a height of 10 cm is arranged in series on the irradiation source unit 30, so that the irradiation source unit 30 as a whole is irradiated. Since the area was 3.0144 m ² and an amount of MnCl ₂ aqueous solution corresponding to about 100 mg Mn was flowed, a dose equivalent of 18144 Sv / h × 3014 from a radioisotope of an amount corresponding to 30144 × 0.1 = 3014 g of Mn Become. This value is 289 times that of the conventional gamma knife device. In addition, when the irradiation time was 20 minutes in the conventional gamma knife device, the irradiation was completed in a very short time of about 4 seconds in the device of the present invention. The irradiated radioisotope-containing solution after irradiation is returned again into the neutron irradiation capsule 20 through the introduction pipe 40 and is subjected to neutron irradiation in the reactor 10.

  Further, as shown in FIG. 2B, a beryllium window having a thickness of about 10 cm to 15 cm is provided between the shutter opening 107a facing one end of the small-diameter short and long pipe 106 and the pipe 106, and γ It is also possible to irradiate by converting the rays into neutron rays. If the beryllium window is too thin, the amount of neutron generation becomes small. Conversely, if the beryllium window is too thick, there is no space for accommodating the irradiated object.

  Unlike conventional gamma knives, the radiation irradiation apparatus of the present invention can be used as a direct irradiation source as it is as a direct irradiation source of neutrons irradiated in a nuclear reactor, so that handling is easy and there is little risk of exposure to workers. . In addition, the number of RI radiation sources is many orders of magnitude higher than that of conventional gamma knives, and a sufficient amount of radiation can be irradiated in a short irradiation time. There are few. In addition, since it is possible to adjust the irradiation dose only to the affected area, it is possible to irradiate even with an irradiation dose that could not be used in consideration of exposure to the non-affected area in the conventional treatment method, so the conventional method does not kill it. Cancer can be killed. Furthermore, in contrast to conventional gamma knives that emit in a hemispherical shape, the radiation irradiation apparatus of the present invention can irradiate in a nearly spherical shape, thereby reducing the exposure dose to normal tissue near the body surface. High doses can be given to tumors such as cancer. Moreover, although the conventional gamma knife is limited to the head, irradiation can be performed at any position on the human body.

Claims (5)

An irradiation source unit for irradiating the irradiated object with radiation;
A nuclear reactor,
A neutron irradiation capsule installed in the reactor,
Connecting the radiation source section and the neutron irradiation capsule in fluid communication, and introducing a radioisotope-containing solution into the neutron irradiation capsule;
Connecting the radiation source section and the neutron irradiation capsule in fluid communication, and from the neutron irradiation capsule, a lead-out pipe for deriving the radioisotope-containing solution after neutron irradiation;
Comprising
Irradiation through which the radioactive isotope-containing solution irradiated with neutrons in the nuclear reactor is transported to the irradiation source unit through the introduction pipe and the lead-out pipe, and the irradiated object is irradiated with the radioactive isotope-containing solution. A radiation irradiation apparatus characterized by being used as a radiation source, and thereafter irradiating the radioactive isotope-containing solution again from the irradiation radiation source section into the neutron capsule and neutron irradiation.   The irradiation source unit is arranged with a pipe through which the neutron-irradiated radioisotope-containing solution flows between the shuttered shields, and irradiates the irradiated object by opening and closing the shutters with the shutters. The radiation irradiation apparatus according to claim 1, wherein the radiation irradiation apparatus is controlled.   The irradiation source section includes a plurality of small-diameter, short-and-long pipes through which the neutron-irradiated radioisotope-containing solution flows, and is arranged in series so that one end of each pipe faces the irradiated object. The radiation irradiation apparatus according to claim 2, wherein   Between the pipe through which the neutron-irradiated radioisotope-containing solution circulates and the shutter of the shield with shutter, further comprising a collimator window portion made of beryllium, from the neutron-irradiated radioisotope-containing solution The radiation irradiation apparatus according to claim 2, wherein the emitted γ-ray is converted into a neutron beam.   The radiation irradiation according to claim 1, wherein the radioisotope-containing solution contains a short half-life radioisotope selected from Mn, Na, Al, K, and Mo. apparatus.

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