JP2024082887A - Radioisotope manufacturing method and manufacturing device - Google Patents

Abstract

[Problem] To provide a radioisotope manufacturing method and device capable of efficiently separating and recovering radioisotopes including astatine isotopes. [Solution] The method includes a target heating step of heating a target to gasify the radioisotopes, a transport step of generating an aerosol flow, attaching the radioisotopes gasified in the target heating step to the aerosol and transporting it, and a filter collection step of collecting the aerosol and radioisotopes transported in the transport step with a collection filter, and the transport step and the filter collection step are performed while heating is performed. [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. Compared to other types of radiation, alpha rays use up all their energy over a short distance, so when used on cancer cells, they have the advantage of causing greater damage to the cancer cells while causing less damage to normal cells. By combining a radioactive nuclide that emits alpha rays with a targeted drug, it is possible to selectively attack cancer cells and achieve high effectiveness. For this reason, various radioisotopes that emit alpha rays are being considered for use as medicines.

Astatine-211 has a short half-life of 7.2 hours and decays quickly into a stable nuclide, which has the advantage of shortening treatment time. For this reason, it is one of the radioisotopes most likely to be used as a medicine.

Astatine-211 has a short half-life, so it is produced using an accelerator. Considering the availability and ease of handling of the raw materials, it is mainly produced by irradiating bismuth with accelerated helium ions. Astatine-211 is separated and recovered from bismuth, and then synthesized into a pharmaceutical product. However, because astatine-211 has a short half-life of 7.2 hours, if separation, recovery, pharmaceutical production, etc. take a long time, the amount of astatine-211 produced will decrease, increasing production costs. For this reason, there is a demand for separation, recovery, and pharmaceutical production in a short time.

A separation technique that takes advantage of the difference in melting and boiling points between the target material, bismuth, is used as a quick and simple separation method. The following method is known as a conventional separation and recovery method. An aerosol is introduced, the target material is heated, and astatine-211 is evaporated and then attached to the aerosol. This astatine-211-adhered aerosol is transported via piping or the like to a filter at room temperature, where the astatine-211-adhered aerosol is captured and recovered.

However, even in the above method using aerosols, there is a need to further reduce the amount of astatine-211 adhering to the tube walls of the recovery and transport sections, and to increase the recovery rate. In addition, since bismuth also evaporates and is transported together with astatine-211, there is an issue that a large amount of bismuth is mixed into the product. If the amount of bismuth mixed in is large, there is a possibility that the synthesis rate will decrease when labeling the targeted drug, which is undesirable.

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 astatine isotopes and other radioisotopes are heated, gasified, separated, and recovered, there is a need to reduce the amount of adhesion to the tube walls and increase the recovery rate. There is also the issue of increased contamination with target materials such as bismuth.

The present invention was made to address these conventional problems, and its purpose is to provide a method and apparatus for producing radioisotopes that can efficiently separate and recover radioisotopes, including astatine isotopes.

The radioisotope manufacturing method according to the embodiment of the present invention includes a target heating process for heating a target to gasify the radioisotope, a transport process for generating an aerosol flow and attaching the radioisotope gasified in the target heating process to the aerosol and transporting it, and a filter collection process for collecting the aerosol and radioisotope transported in the transport process with a collection filter, and is characterized in that the transport process and the filter collection process are performed while heating is being performed.

The radioisotope manufacturing apparatus and method according to the present invention are characterized by comprising a target heating unit that heats a target to gasify the radioisotope, a transport mechanism that generates an aerosol flow and transports the aerosol to which the radioisotope gasified by the target heating mechanism is attached, a collection unit that collects the aerosol and the radioisotope using a collection filter, and a heating mechanism that heats the collection unit and the aerosol passage between the target heating unit and the collection unit.

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

FIG. 2 is a flow chart showing steps of 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. 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 third embodiment. FIG. 1 is a diagram showing a schematic configuration of a conventional radioisotope production apparatus.

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. 1, the steps of the radioisotope production method according to the first embodiment include an aerosol generation step (step 1), a target heating step (step 2), a transport step (step 3), and a filter collection step (step 4). In addition, the target heating step (step 2), the transport step (step 3), and the filter collection step (step 4) are performed in a heated, high-temperature state.

As shown in FIG. 2, the radioisotope manufacturing apparatus 100 according to the first embodiment includes a target heating unit 101 that heats a target to gasify the radioisotope. The target heating unit 101 heats a target containing a volatile radioactive substance such as astatine-211, and gasifies the astatine-211 and other substances present in the target. In this target heating unit 101, for example, a bismuth target is irradiated with accelerated helium ions (alpha rays), and the bismuth target is heated by a heating mechanism 102 to a predetermined temperature, for example, a temperature of 337°C or higher, which is the boiling point of astatine, and a temperature of about 500°C or lower, which is lower than the boiling point of the bismuth target.

A collection section 103 housing a collection filter is provided downstream of the target heating section 101 (right side in FIG. 2). On the other hand, an aerosol generator 104 and a carrier gas supply device 105 are provided upstream of the target heating section 101 (left side in FIG. 2).

The aerosol generator 104 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, it is possible to reduce the amount of radioisotopes lost due to attachment to piping during transport. In addition, the carrier gas supply device 105 supplies a carrier gas such as nitrogen gas, and the flow of this carrier gas transports the aerosols and the radioisotopes attached to the aerosols.

In this embodiment, the collection section 103 is configured to be heated by a heating mechanism 102 for heating the target heating section 101, and the passage for the aerosol and the radioisotopes attached to the aerosol that connects the target heating section 101 and the collection section 103 is also configured to be heated by the heating mechanism 102. In this embodiment, the heating temperature of the collection section 103 and the passage that connects the target heating section 101 and the collection section 103 is the same as the heating temperature of the target heating section 101 (e.g., about 500°C). However, this heating temperature does not necessarily have to be the same as the heating temperature of the target heating section 101, and may be a lower temperature (e.g., about 300°C).

As described above, since the collection unit 103 is heated to a high temperature, the collection filter housed in the collection unit 103 must be heat resistant. Examples of such collection filters that can be used include sintered metal filters, ceramic filters, glass fiber filters, and heat resistant resin filters.

In addition, pressure gauges 106 and 107 are provided between the carrier gas supply device 105 and the aerosol generator 104, and downstream of the collection section 103, respectively.

For comparison, FIG. 5 shows the configuration of a conventional radioisotope manufacturing apparatus 500. As shown in FIG. 5, in the conventional radioisotope manufacturing apparatus 500, only the target heating section 101 is heated by the heating mechanism 102, and the collection section 103 and the flow path connecting the target heating section 101 and the collection section 103 are not heated. This is because, from the viewpoint of the handling of the collection filter, the temperature is kept at room temperature to facilitate removal, etc. However, when the collection filter is used at room temperature as in the conventional radioisotope manufacturing apparatus 500, a temperature gradient occurs from the high-temperature target heating section 101 to the collection section 103 at room temperature and the path connecting them, and aerosols to which radioisotopes are attached adhere to the tube walls, etc. due to thermophoresis, which may reduce the recovery rate.

In this embodiment, the collection section 103 and the passage connecting the target heating section 101 and the collection section 103 are heated by the heating mechanism 102 to a temperature approximately equal to the heating temperature of the target heating section 101, thereby preventing a decrease in the recovery rate due to the adhesion of aerosol to the tube wall, etc., caused by thermophoresis as described above.

There are no particular restrictions on the heating method for the collection section 103 and the passage connecting the target heating section 101 and the collection section 103, and the method may be a furnace such as an electric furnace or heater heating. The heating method may be the same as that for the target, or a different heating method. It is also preferable to install the collection section 103 immediately after the target heating section 101, but it is also possible to install the heated collection section 103 a certain distance after the transport path.

In addition, by bringing the collection section 103 to a temperature equal to or higher than that of the target material, the gas-phase bismuth generated in the target heating section 101 also exists in the gas phase in the collection section 103 due to the vapor pressure relationship. As a result, aerosols and aerosols with radioactive nuclides attached are collected in the collection section 103, but the bismuth in the gas phase flows to the subsequent stage without being collected by the collection filter. This makes it possible to significantly reduce the amount of bismuth collected in the collection section 103.

When the heating temperature of the collection unit 103, etc. is set to a temperature lower than the target temperature, the temperature difference and residence time are appropriately set to reduce thermophoresis. Also, the vapor pressure of bismuth must be taken into consideration.

As described above, according to the first embodiment, when radioisotopes such as astatine-211 are heated, gasified, separated, and recovered, the amount of adhesion to the tube walls and the like can be reduced, and the recovery rate can be increased. In addition, the amount of contaminating target materials such as bismuth can be significantly reduced.

Before starting to heat the target in the target heating section, an aerosol of a soluble salt such as KCl, NaCl, NaOH, or KI can be circulated in the collection section 103 to cause the soluble salt to adhere to the surface of the collection filter in the collection section 103. This makes it easier to clean and recover the collected radioisotopes such as astatine-211 from the collection filter.

Second Embodiment
Next, a second embodiment will be described with reference to Fig. 3. Note that parts corresponding to those in the first embodiment shown in Fig. 2 are given the same reference numerals and duplicated explanations will be omitted.

In the first embodiment, since the collection section 103 is heated to a high temperature, depending on the configuration of the device, it may take time to remove the collection filter from the collection section 103, and the amount of collected radionuclides may decrease due to decay. For this reason, as shown in FIG. 3, the radioisotope production device 200 according to the second embodiment is provided with a cooling device 108 to quickly remove the collection filter from the collection section 103. By using this cooling device 108 to cool the collection section 103 after collection is completed, the time required for cooling can be shortened and the separation and collection efficiency can be improved. Note that the cooling device 108 may be of any configuration, and for example, a water-cooled cooling device or the like can be used.

Third Embodiment
Next, a third embodiment will be described with reference to Fig. 4. Note that parts corresponding to those in the first embodiment shown in Fig. 2 are given the same reference numerals and repeated explanations will be omitted.

In the first embodiment, since the collection section 103 is heated to a high temperature, depending on the device configuration, it may take time to remove the collection filter from the collection section 103, and the amount of collected radioactive nuclides may decrease due to decay. For this reason, as shown in FIG. 4, the radioisotope production device 300 according to the third embodiment is provided with a cooling device 108 as in the second embodiment, and is also provided with a collection mechanism for collecting astatine-211 and the like from the collection filter in the collection section 103.

This recovery mechanism can be composed of a cleaning liquid supply device 109 for supplying cleaning liquid such as water or an organic solvent, a cleaning liquid recovery section 110, and two three-way valves 111 provided on the inlet and outlet sides of the collection section for switching the flow path. By providing a recovery mechanism in this way, astatine-211 and the like can be recovered from within the collection section 103 without removing the collection filter, shortening the time required for recovery and improving separation and recovery efficiency.

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 implemented 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 described in the claims.

100...Radioisotope manufacturing apparatus, 101...Target heating section, 102...Heating mechanism, 103...Collection section, 104...Aerosol generator, 105...Carrier gas supplying apparatus, 106...Pressure gauge, 107...Pressure gauge, 108...Cooling apparatus, 109...Cleaning liquid supplying apparatus, 110...Cleaning liquid recovery section, 111...Three-way valve, 200...Radioisotope manufacturing apparatus, 300...Radioisotope manufacturing apparatus, 500...Radioisotope manufacturing apparatus.

Claims (8)

a target heating step of heating the target to gasify the radioisotope;
a transport step of generating an aerosol flow, attaching the radioisotope gasified in the target heating step to the aerosol, and transporting the radioisotope;
a filter collection step of collecting the aerosol and the radioisotope transported by the transport step with a collection filter;
Equipped with
The method for producing a radioisotope, wherein the transporting step and the filter collecting step are carried out while heating. A method for producing a radioisotope according to claim 1, comprising the steps of:
4. A method for producing a radioisotope, comprising using any one of a sintered metal filter, a ceramic filter, a glass fiber filter, and a heat-resistant resin filter as the collection filter. A method for producing the radioisotope according to claim 1 or 2, comprising the steps of:
In the target heating step, a bismuth target is heated to gasify astatine-211. a target heating unit that heats the target to gasify the radioisotope;
a transport mechanism that generates an aerosol flow and transports the radioisotope gasified by the target heating mechanism by attaching it to the aerosol;
A collection unit that collects aerosols and radioisotopes using a collection filter;
a heating mechanism for heating the collecting unit and an aerosol passage between the target heating unit and the collecting unit;
A radioisotope manufacturing apparatus comprising: The radioisotope production apparatus according to claim 4,
2. The radioisotope manufacturing apparatus according to claim 1, wherein the collection filter is any one of a sintered metal filter, a ceramic filter, a glass fiber filter, and a heat-resistant resin filter. The radioisotope production apparatus according to claim 4 or 5,
A radioisotope manufacturing apparatus comprising: a cooling mechanism for cooling the collection section. The radioisotope production apparatus according to claim 6,
A radioisotope manufacturing apparatus comprising: a cleaning liquid supplying mechanism for supplying a cleaning liquid to the collection section and recovering the radioisotope from the collection filter. The radioisotope production apparatus according to claim 4 or 5,
A radioisotope manufacturing apparatus, comprising: a bismuth target is heated in the target heating section to gasify astatine-211.

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