JP2024081254A - Radioisotope manufacturing method and manufacturing device - Google Patents

Abstract

[Problem] To provide a radioisotope production method and production device capable of efficiently producing volatile radioisotopes such as astatine isotopes. [Solution] The method and device include a pretreatment step of attaching a soluble substance to a collection section, a heating step of heating a target to vaporize and separate the radioisotopes, a collection step of collecting the radioisotopes separated in the heating step in the collection section that has been subjected to the pretreatment step, and a cleaning and recovery step of cleaning and recovering the radioactive substances collected in the collection step. [Selected Figure] Figure 1

Description

Embodiments of the present invention relate to a method and apparatus for producing radioisotopes.

In recent years, cancer treatment using alpha rays has been attracting attention. Because alpha rays have a short range, it is possible to selectively attack targeted cancer cells using drugs that emit alpha rays. Therefore, cancer treatment using alpha rays has the advantage of causing less damage to normal cells.

Various radioisotopes are being considered as drugs that emit alpha rays. Astatine-211 in particular is one of the most promising radioisotopes, as it has a short half-life and decays quickly into stable nuclides. However, because its half-life is only 7.2 hours, if separation takes too long, the amount of astatine-211 produced will decrease.

Therefore, there is a demand for a method for quickly separating the produced astatine-211. A known quick and simple separation method is a separation technology that utilizes the difference in melting and boiling points with the target material, bismuth. However, with this conventional separation technology, astatine-211 adheres to the walls of the pipes in the recovery or transport section, making it necessary to elute or recover the adhered astatine-211 using an organic solvent or alkaline solution.

The inventors have therefore developed a new separation technology using aerosols. This new separation technology reduces the adhesion of astatine-211 to the walls of pipes and other structures.

International Publication No. 2015/195042 International Publication No. 2019/088113 International Publication No. 2019/112034

E. A. Anheim, “Automated astationation of biomolecules - a stepping stone towards multicenter clinical trials,” Science Reports, 2015.

As mentioned above, when volatile radioisotopes such as astatine isotopes are gasified and collected using a filter, there is a problem that some radioisotopes cannot be washed and recovered from the filter, resulting in a low recovery rate of the radioisotopes.

The present invention was made to address the above-mentioned conventional problems, and the problem it aims to solve is to provide a radioisotope production method and production device that can efficiently produce volatile radioisotopes, including astatine isotopes.

The method for producing a radioisotope according to an embodiment of the present invention is characterized by comprising a pretreatment process in which a soluble substance is attached to a collection section, a heating process in which the target is heated to vaporize and separate the radioisotopes, a collection process in which the radioisotopes separated in the heating process are collected in the collection section in which the pretreatment process has been carried out, and a cleaning and recovery process in which the radioactive substance collected in the collection process is cleaned and recovered.

The radioisotope manufacturing device according to an embodiment of the present invention is characterized by having a heating section that heats a target and vaporizes and separates the radioisotopes, a collection section that collects the radioisotopes separated by the heating section, and a pre-processing section that attaches a soluble substance to the collection section.

Embodiments of the present invention provide a method and apparatus for producing radioisotopes that can efficiently produce volatile radioisotopes, including astatine isotopes.

FIG. 2 is a flow chart showing a method for producing a radioisotope according to the first embodiment. FIG. 1 is a diagram illustrating a schematic configuration of a radioisotope production apparatus according to a first embodiment. 1 is a graph showing the recovery rate of astatine-211 according to the first embodiment in comparison with the conventional technique. 4 is a graph showing the relationship between the amount of adhesion to a filter and pressure. FIG. 13 is a diagram illustrating a schematic configuration of a radioisotope production apparatus according to a second embodiment. FIG. 13 is a diagram illustrating a schematic configuration of a radioisotope production apparatus according to a modified example of the second embodiment.

Below, the radioisotope manufacturing method and manufacturing apparatus according to the embodiment will be described with reference to the drawings.

First Embodiment
First, a description will be given of the first embodiment. Fig. 1 is a flow diagram showing the steps of a method for producing a radioisotope according to the first embodiment, and Fig. 2 is a diagram showing a schematic configuration of an apparatus for producing a radioisotope according to the first embodiment.

As shown in FIG. 2, the radioisotope manufacturing apparatus according to the first embodiment includes a carrier gas cylinder 1, a carrier gas flow control valve 2, a differential pressure gauge 3, an aerosol generator 4, a radioisotope-containing target heating furnace 5, and a filter housing 6. The aerosol generator 4 generates aerosols such as KCl, NaCl, NaOH, etc. The aerosols are particles with a particle size of, for example, about 1 nm to about 1 mm. By attaching radioisotopes to these aerosols, the amount of radioisotopes lost due to attachment to piping during transport of the radioisotopes can be reduced.

As shown in FIG. 1, in the first embodiment, first, filter pretreatment is performed (step 1). That is, the collection filter is attached to the filter housing 6, and aerosol containing a gas containing soluble salts such as KCl as soluble substances is generated in the aerosol generator 4, which is then passed through the filter housing 6 for a predetermined period of time to cause the soluble substances (soluble salts) to adhere to the surface of the collection filter. Alternatively, a collection filter that has been pretreated in advance may be attached to the filter housing 6.

The soluble salt may be any salt that dissolves in a liquid solvent at room temperature and pressure, such as water or an organic solvent, used in the cleaning and recovery process described below. In addition to KCl, other salts such as NaOH, NaCl, and KI can be used.

Then, in the radioisotope-containing target heating furnace 5, a target containing a volatile radioactive substance such as astatine-211 is heated, and the astatine-211 present in the target is gasified (step 2). In the radioisotope-containing target heating furnace 5, for example, a bismuth target is irradiated with accelerated helium ions (alpha rays), and the bismuth target is heated by a heating mechanism (not shown) to a predetermined temperature, for example, a temperature of 337°C or higher, which is the boiling point of astatine, and a temperature below the boiling point of the bismuth target, for example, about 500°C.

The gasified astatine-211 is then attached to the aerosol generated in the aerosol generator 4, transported by the flow of carrier gas from the carrier gas cylinder 1, and collected by a collection filter attached to the filter housing 6 installed downstream (step 3).

After performing the above steps for a predetermined time, the collection filter is then removed from the filter housing 6, and the collection filter is washed with a solution such as water, and the astatine-211 captured on the collection filter is recovered (step 4).

As described above, in this embodiment, in step 1, a pretreatment is performed on the collection filter. This pretreatment causes a soluble salt, which is a soluble substance, to adhere to the surface of the collection filter in advance. By performing this pretreatment, astatine-211 becomes easier to remove from the collection filter in the cleaning and recovery step, allowing it to be recovered efficiently. Note that a filter made of glass fiber, for example, can be used as the collection filter.

Figure 3 shows the graph of the results of comparing the recovery of astatine-211 when the collection filter is pretreated with KCl and NaOH as shown in Figure 1 with the recovery of astatine-211 when the collection filter is not pretreated. In the case of KCl, the collection filter was pretreated with He carrier gas containing KCl aerosol. In the case of NaOH, ten filters were immersed in 250 ml of NaOH water of the specified concentration (0.5, 5 wt%), immersed in fresh NaOH water after 10 minutes, and immersed in fresh NaOH water after another 10 minutes, for a total of three immersions, and then dried in a vacuum dryer (room temperature, minimum pressure).

Also, while flowing He carrier gas containing KCl aerosol at 3 L/min, about 250 kBq of astatine-211 was separated and collected, and the radioactivity of astatine-211 attached to the repair filter before and after cleaning was measured with a Ge semiconductor detector when the filter was washed and collected with about 10 ml of 0.01 M NaOH aqueous solution. The separation and recovery rate when the collection filter was pretreated and 30 mg of KCl was attached in advance (shown in the center of Figure 3) was improved from 40% to about 90% compared to the case where the collection filter was not pretreated (shown on the left side of Figure 3). The separation and recovery rate when NaOH was attached in advance (shown on the right side of Figure 3) was improved from 40% to about 75% compared to the case where the collection filter was not pretreated (shown on the left side of Figure 3).

As in the above-described embodiment, soluble salts and the like attached to the collection filter by pretreatment of the collection filter are mixed into the washed and recovered material, and may become impurities depending on the use of the washed and recovered material. Therefore, in order to more efficiently recover astatine-211 from the collection filter, it is desirable to manage the amount of soluble salts and the like attached to the collection filter.

In this case, as shown in Figure 2, the amount of soluble salts attached to the collection filter can be measured online (without removing it from the device) by measuring the differential pressure applied to the collection filter using a differential pressure gauge 3 installed upstream of the device. Figure 4 shows the relationship between the weight of potassium (K) attached to the collection filter on the vertical axis and the pressure measured by the differential pressure gauge 3 on the horizontal axis.

As shown in Figure 4, there is a certain relationship between the pressure value measured by the differential pressure gauge 3 and the weight of soluble salt attached to the collection filter, and the amount of soluble salt attached can be estimated by measuring the pressure with the differential pressure gauge 3. Therefore, by adjusting the pretreatment time for the collection filter while measuring the pressure with the differential pressure gauge 3, the amount of soluble salt attached can be controlled to an appropriate amount. Note that the amount of soluble salt attached to the collection filter can be managed not only by measuring the pressure, but also by measuring the weight of the filter and the electrical resistance caused by the material attached to the filter.

Second Embodiment
Next, a second embodiment will be described with reference to Fig. 5. Note that parts corresponding to those of the radioisotope production apparatus of the first embodiment shown in Fig. 2 are given the same reference numerals, and duplicated explanations will be omitted.

As shown in FIG. 5, in the radioisotope manufacturing apparatus according to the second embodiment, a chemical tank 7 and a switching valve 8 for injecting a chemical containing a soluble salt into the filter housing 6 are provided downstream of the radioisotope-containing target heating furnace 5, and a dryer 9 is provided in the filter housing 6. The chemical tank 7, switching valve 8, and dryer 9 correspond to a pretreatment section that performs a pretreatment process on the collection filter.

In the second embodiment of the above configuration, the pretreatment process for the collection filter can be performed by switching the switching valve 8, injecting a chemical containing a soluble salt from the chemical tank 7 into the filter housing 6, and drying in the dryer 9. In addition to drying in the dryer 9 that performs heating or the like, drying can also be performed by passing a carrier gas for drying from the carrier gas cylinder 1.

In the second embodiment of the above configuration, a pretreatment process for the collection filter can be carried out by injecting a chemical containing a soluble salt from the chemical tank 7 into the filter housing 6. Therefore, the aerosol generator 4 that carried out the pretreatment process for the collection filter in the first embodiment is not necessarily required. However, as shown in FIG. 6, a configuration including the aerosol generator 4 may be used in the separation and recovery process of astatine-211.

Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents as set forth in the claims.

1...Carrier gas cylinder, 2...Carrier gas flow rate control valve, 3...Differential pressure gauge, 4...Aerosol generator, 5...Radioisotope-containing target heating furnace, 6...Filter housing, 7...Chemical solution tank, 8...Switching valve, 9...Dryer.

Claims (8)

A pretreatment step of attaching soluble substances to a collection section;
a heating step of heating the target to vaporize and separate the radioisotopes;
a collection step of collecting the radioisotopes separated in the heating step in the collection unit in which the pretreatment step has been carried out;
a cleaning and recovery step of cleaning and recovering the radioactive material captured in the capture step;
A method for producing a radioisotope, comprising:
A method for producing a radioisotope according to claim 1, comprising the steps of:
The radioisotope separated in the heating step is transported to the collection section by an aerosol generated by an aerosol generator.
A method for producing a radioisotope according to claim 2, comprising the steps of:
a pretreatment step of attaching the soluble substance to the collection section by the aerosol generated by the aerosol generator.
A method for producing a radioisotope according to claim 3, comprising the steps of:
a differential pressure of a carrier gas that sends the aerosol generated by the aerosol generator to the collection section is detected, and an amount of the soluble substance that is attached to the collection section by the pretreatment process is controlled.
A method for producing the radioisotope according to claim 1 or 2, comprising the steps of:
a chemical solution containing the soluble substance is injected into the collection section, and the chemical solution is dried to carry out the pretreatment step.
A method for producing the radioisotope according to claim 1 or 2, comprising the steps of:
A method for producing a radioisotope, comprising the steps of: producing astatine-211.
a heating section for heating the target and vaporizing and separating the radioisotopes;
A collection unit that collects the radioisotopes separated in the heating unit;
a pre-treatment section for attaching a soluble substance to the collection section,
The radioisotope production apparatus according to claim 7,
The radioisotope manufacturing apparatus according to claim 1, wherein the pretreatment section has a chemical injection mechanism for injecting a chemical solution containing the soluble substance into the collection section.

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