Dry-type radioisotope purification device

Abstract

This dry-type radioisotope purification device purifies a radioisotope and comprises: a substrate placement part on which can be placed a solid target substrate to which a radioisotope such as astatine-211 is adhered; a delivery part that communicates with the substrate placement part, is thinner than the substrate placement part, and extends non-linearly; and a tubular furnace that heats the substrate placement part and the delivery part.

Description

Dry radioisotope purification equipment

[0001] The present disclosure relates to a dry radioisotope purification apparatus.

[0002] Radioisotopes (RI) used in radiopharmaceuticals and the like are obtained by extracting RI from a target in which RI is generated and purifying the extracted RI using a purification device. For example, in the technology described in Patent Document 1, a solid target provided in a target irradiation device is first irradiated with a charged particle beam to obtain a solid target in which a radioisotope is generated. Then, the solid target containing the desired radioisotope is recovered from the target irradiation device, and the recovered solid target is vaporized to separate and recover the radioisotope from the solid target.

[0003] Japanese Patent Application Publication No. 10-206594

[0004] In this type of radioisotope refining, the vaporized radioisotope may be chemically reacted with a substance contained in a carrier gas to produce a reaction product that is easier to recover. In this case, if the radioisotope does not react sufficiently with the substance in the carrier gas, the yield of the radioisotope decreases. In view of this problem, the present disclosure aims to provide a dry radioisotope refining apparatus that improves the yield of the radioisotope.

[0005] A dry radioisotope refining apparatus according to one embodiment of the present disclosure is a dry radioisotope refining apparatus for refining radioisotopes, and includes a mounting section on which a substrate having a radioisotope attached thereto can be placed, a flow path that is connected to the mounting section, is narrower than the mounting section, and extends in a non-linear manner, and a heating section that heats the mounting section and the flow path.

[0006] According to the present disclosure, it is possible to provide a dry radioisotope refinement apparatus that improves the yield of radioisotopes.

[0007]

[0023] Figure 1 is a cross-sectional view of a hot cell in which a radioisotope refinery apparatus according to an embodiment is housed, showing a cross section parallel to the front.

[0024] Figure 2 is a schematic side view showing a dry radioisotope refinery apparatus according to an embodiment.

[0025] Figure 3 (a) to (c) are views showing an example of a furnace tube including a non-linear delivery section.

[0026] Figure 4 is a schematic side view showing a dry radioisotope refinery apparatus according to another example.

[0008] Hereinafter, an embodiment of a dry radioisotope refining apparatus according to the present disclosure will be described with reference to the accompanying drawings. In the following description, identical or equivalent elements will be designated by the same reference numerals, and redundant description will be omitted.

[0009] The dry radioisotope refinery apparatus 1 according to an embodiment of the present disclosure refines and produces radioisotopes from materials containing radioisotopes (RI). The dry radioisotope refinery apparatus 1 can be used to refine radioisotopes such as astatine-211, iodine-123, iodine-124, and technetium-99m.

[0010] This type of RI is purified by the dry radioisotope refinery apparatus 1 in the form of an RI derivative, such as astatine oxide or 99mTc-TcO4- (technetium peroxide). For example, the astatine obtained by the dry radioisotope refinery apparatus 1 is reacted with a specific ligand in a subsequent synthesis process to synthesize a drug for alpha-particle therapy. In alpha-particle therapy, when the drug is administered to a subject, it accumulates in cancer cells within the subject. The cancer cells are then destroyed by alpha rays emitted from the astatine-211 contained in the drug. Because alpha rays have a short range, they are minimally invasive to surrounding normal tissue. Furthermore, because astatine-211 is a short-lived nuclide that emits almost no gamma rays, hospitalization in a radiation therapy room is not required. Therefore, alpha-particle therapy is expected to be a treatment that improves patients' quality of life.

[0011] The following description will be given taking the dry radioisotope refinement apparatus 1 as an example, where it is used to refine astatine-211. Astatine-211 is produced by irradiating a substrate with bismuth fixed thereon with alpha rays using a radiation irradiation apparatus (not shown), and is recovered from the radiation irradiation apparatus in a state where it is contained within the bismuth. This substrate is introduced into the dry radioisotope refinement apparatus 1 as a solid target substrate W (FIG. 2), which will be described later.

[0012] 1 includes a dry radioisotope refinery apparatus 1 and a hot cell 110 that houses the dry radioisotope refinery apparatus 1. The hot cell 110 has a radiation shielding wall C that suppresses the transmission of radiation. First, an overview of the hot cell 110 included in the radioisotope refinery system 101 will be described with reference to FIG.

[0013] As shown in FIG. 1 , the hot cell 110 includes a box-shaped hot cell body 111. The hot cell body 111 includes walls 114 to 116. The walls 114 to 116 are formed of radiation-shielding walls that suppress the transmission of radiation. The radiation-shielding walls are formed of, for example, lead. The material of the radiation-shielding walls may be changed as appropriate depending on the radioactive material contained in the hot cell body 111. The hot cell body 111 has a front door (not shown) at the front opening and a rear wall (not shown) that is a wall disposed opposite the front wall. The front door and rear wall are formed of radiation-shielding walls, just like the walls 114 to 116.

[0014] The front opening of the hot cell body 111 is used to load and unload the object 100 housed inside the hot cell body 111. The object 100 housed inside the hot cell body 111 is a radiopharmaceutical handling device (radioactive material handling device) similar to those that handle radiopharmaceuticals used in PET diagnosis and the like. Examples of the object 100 include the dry radioisotope refining device 1 according to this embodiment, a synthesis device that labels a radioactive substance with another substance (synthesizes a radiopharmaceutical from a radioactive substance), a quality inspection device that inspects the quality of a radiopharmaceutical, or a dispensing device that dispenses a liquid containing a radiopharmaceutical to a desired liquid volume.

[0015] The hot cell body 111 is formed with a positive pressure chamber 121, which is a space capable of accommodating a radiopharmaceutical handling device. The hot cell body 111 includes partitions 124 and 125 that divide the interior, and has multiple positive pressure chambers 121 via the partitions 124 and 125. The partitions 124 and 125 may be formed of radiation-shielding walls or radiation-transmitting walls. The objects 100 within the positive pressure chambers 121 may be connected to each other by pipes (not shown), allowing radioisotope or radiopharmaceutical samples to be transferred between the objects 100. Since astatine, which is handled in this embodiment, is particularly susceptible to gasification, the outside of the positive pressure chamber 121 must be under negative pressure or must be actively evacuated. Therefore, the hot cell 110 includes an exhaust pipe 130 for the above-mentioned active evacuation.

[0016] Next, a dry radioisotope refinery apparatus 1 according to this embodiment will be described with reference to FIG. 2 . The dry radioisotope refinery apparatus 1 is accommodated in one chamber of a hot cell 110 as the aforementioned target object 100 in a radioisotope production system 101 (see FIG. 1 ). FIG. 2 is a schematic side view showing the dry radioisotope refinery apparatus 1 according to an embodiment of the present disclosure. The dry radioisotope refinery apparatus 1 of this embodiment separates and refines astatine-211, a radioisotope contained in a solid target substrate W. The solid target substrate W is obtained by irradiating a solid substrate having bismuth fixed thereon with a charged particle beam using a charged particle beam irradiation device or the like, and contains astatine-211 produced by a nuclear reaction of the bismuth and remaining unreacted bismuth.

[0017] As shown in FIG. 2 , the dry radioisotope refining apparatus 1 according to this embodiment includes a furnace tube 3, a tubular furnace 2 (heating unit), an insertion tube 4, a rodless cylinder 44, a gas supply unit 50, a control unit 60, and an RI recovery unit 70.

[0018] The furnace tube 3 is a container in which the solid target substrate W is placed. The furnace tube 3 has a substrate placement section 7 (placement section) and a delivery section 8 (flow path). The furnace tube 3 is, for example, a quartz tube. The substrate placement section 7 is placed inside the tubular furnace 2. The substrate placement section 7 extends approximately horizontally. One end of the substrate placement section 7 is open, and has a diameter that allows the insertion tube 4 to be inserted. The insertion tube 4 on which the solid target substrate W is placed is inserted from one end of the substrate placement section 7. In this way, the substrate placement section 7 introduces the solid target substrate W into its interior.

[0019] The other end of the substrate mounting part 7 has an inverted tapered shape with a smaller diameter than the one end, and is connected to the delivery part 8. The delivery part 8 is disposed inside the tubular furnace 2, is composed of a tube thinner than the substrate mounting part 7, and extends non-linearly from the other end of the substrate mounting part 7. The delivery part 8 has a diameter that does not allow the insertion tube 4 to be inserted therein. In other words, the delivery part 8 has a smaller diameter than the substrate mounting part 7. The other end of the delivery part 8 is connected to the RI recovery part 70, which will be described later.

[0020] The tubular furnace 2 is an electric furnace that heats the muffle tube 3 under the control of the control unit 60. The tubular furnace 2 is substantially cylindrical and has a columnar heating space 5 in its center. The tubular furnace 2 is disposed around the muffle tube 3 so as to surround the substrate placement unit 7 and the delivery unit 8 of the muffle tube 3. That is, the substrate placement unit 7 and the delivery unit 8 are housed within the heating space 5 of the tubular furnace 2. The control unit 60 controls the tubular furnace 2 so that the temperatures within the substrate placement unit 7 and the delivery unit 8 heated by the tubular furnace 2 are kept at an appropriate temperature. The appropriate temperature is a temperature at which the radioisotope of the solid target substrate W housed within the substrate placement unit 7 can be vaporized. In this embodiment, the temperature is approximately 800°C, at which astatine-211 can be vaporized. The control unit 60 is provided outside the hot cell 110.

[0021] A solid target substrate W is placed at the tip of the insertion tube 4. The insertion tube 4 is moved approximately horizontally by a rodless cylinder 44, and is able to introduce the solid target substrate W into the substrate placement portion 7 of the furnace tube 3 and to remove the solid target substrate W from the substrate placement portion 7 of the furnace tube 3. The operation of the rodless cylinder 44 is controlled by a control unit 60. When the insertion tube 4 is inserted into the substrate placement portion 7, the insertion tube 4 comes into close contact with the furnace tube 3 and the furnace tube 3 is sealed. As a result, the solid target substrate W placed at the tip of the insertion tube 4 is placed in the substrate placement portion 7 in a sealed state.

[0022] A through-hole (not shown) is formed at the center of the insertion tube 4, penetrating the insertion tube 4 in the axial direction. One end of the through-hole is connected to a gas supply unit 50 via a gas flow pipe (not shown). The gas supply unit 50 operates under the control of a control unit 60 and supplies a carrier gas as a carrier fluid into the substrate mounting unit 7 via the gas flow pipe and the through-hole while the muffle tube 3 is sealed. The carrier gas flows through the muffle tube 3 in a direction from the substrate mounting unit 7 toward the delivery unit 8. The carrier gas used here is, for example, a mixed gas in which oxygen and nitrogen are mixed in a ratio of 2:8. Note that a high oxygen concentration in the mixed gas increases the burden of safety measures, so the oxygen concentration of the mixed gas is preferably about 20%, as described above. Although detailed illustration is omitted, the gas supply unit 50 may include, for example, a gas cylinder and a gas control unit for controlling the delivery of gas from the gas cylinder.

[0023] The RI recovery unit 70 is connected to the downstream end of the delivery unit 8. The RI recovery unit 70 is installed outside the tubular furnace 2. The RI recovery unit 70 includes a three-way valve 21, a trap loop 22 (capture unit), an RI sensor 23, a three-way valve 24, a reagent trap 26, and a vacuum exhaust device 27. The trap loop 22 is formed, for example, of a spirally wound fluororesin pipe. The RI recovery unit 70 also includes a solvent holding loop 28, a liquid delivery pump 29, and a recovery port 31. The three ports of the three-way valve 21 are connected to the downstream end of the delivery unit 8, one end of the trap loop 22, and the recovery port 31, respectively. The three ports of the three-way valve 24 are connected to the other end of the trap loop 22, the upstream end of the reagent trap 26, and one end of the solvent holding loop 28, respectively. A vacuum exhaust device 27 is connected to the downstream end of the reagent trap 26 , and a liquid delivery pump 29 is connected to the other end of the solvent holding loop 28 .

[0024] As described above, the RI collection unit 70 is installed outside the tubular furnace 2, i.e., in a room temperature environment. Alternatively, the RI collection unit 70 may be cooled to room temperature or below by a predetermined cooling means. Alternatively, at least the trap loop 22 of the RI collection unit 70 may be cooled to room temperature or below by a predetermined cooling means. Note that a heat insulating material or a heating device may be installed around the connection portion from the delivery unit 8 to the three-way valve 21 and around the three-way valve 21.

[0025] Next, we will explain the operation of the dry radioisotope refining apparatus 1. The following operation of the dry radioisotope refining apparatus 1 is realized by the operation of each component, such as the rodless cylinder 44, the tubular furnace 2, the three-way valves 21 and 24, the liquid feed pump 29, the vacuum exhaust device 27, and the gas supply unit 50, under the control of the control unit 60.

[0026] First, the solid target substrate W is placed on the insertion tube 4. Then, the rodless cylinder 44 is moved toward the furnace core tube 3, and the solid target substrate W placed on the insertion tube 4 is introduced into the substrate placement portion 7 of the furnace core tube 3. The three-way valve 21 is set to a state connecting the delivery portion 8 and the trap loop 22, and the three-way valve 24 is set to a state connecting the trap loop 22 and the reagent trap 26.

[0027] Thereafter, the tubular furnace 2 is operated to heat the heating space 5, which in turn heats the substrate placement unit 7 and the delivery unit 8 within the heating space 5. The heating in the substrate placement unit 7 vaporizes astatine-211 contained in the solid target substrate W. Furthermore, a carrier gas is supplied from the gas supply unit 50 into the furnace tube 3, and the vacuum exhaust unit 27 is operated. This causes the carrier gas to flow from the substrate placement unit 7 through the delivery unit 8, trap loop 22, and reagent trap 26 toward the vacuum exhaust unit 27. Accompanying this flow of carrier gas, the astatine-211 gas vaporized from the solid target substrate W also flows. Note that the bismuth contained in the solid target substrate W is liquefied on the substrate by heating, but remains in the insertion tube 4.

[0028] As the astatine-211 flows through the substrate support unit 7 and the delivery unit 8, which are both in a high-temperature environment, it chemically reacts with oxygen contained in the carrier gas and converts into astatine oxide, which has a higher boiling point. Astatine is easily oxidized and can take on various oxidation states, such as At(0), AtO+, AtO2-, AtO3-, and AtO4-. Adding oxygen to the carrier gas and oxidizing it during purification is thought to increase the tendency for astatine oxide to become a high-boiling-point compound, such as AtO3- or AtO4-.

[0029] The astatine oxide then liquefies (or solidifies) as its temperature drops within the trap loop 22, which is kept at room temperature, and adheres to the tube wall of the trap loop 22. The amount of radiation from the astatine-211 thus captured in the trap loop 22 is measured by the RI sensor 23, making it possible to detect the amount of astatine-211 accumulated in the trap loop 22.

[0030] On the other hand, astatine-211 that has not reacted with oxygen is thought to have a lower boiling point than astatine oxide, and therefore has a strong tendency to pass through trap loop 22 in a gaseous state. Unreacted astatine-211 that has passed through trap loop 22 and a portion of astatine oxide that has not liquefied (or solidified) in trap loop 22 are captured in reagent trap 26, which has a predetermined structure to prevent it from entering vacuum exhaust device 27.

[0031] Thereafter, when astatine oxide is sufficiently trapped in the trap loop 22, the operation of the tubular furnace 2 and the vacuum exhaust device 27 is stopped. The three-way valve 21 is set to a state connecting the trap loop 22 and the recovery port 31, and the three-way valve 24 is set to a state connecting the solvent holding loop 28 and the trap loop 22. From this state, the liquid feed pump 29 is operated, and the solvent previously stored in the pipe of the solvent holding loop 28 is pumped toward the three-way valve 24. This solvent flows through the three-way valve 24, the trap loop 22, and the three-way valve 21 to the recovery port 31. At this time, the astatine oxide trapped in the trap loop 22 as described above dissolves in the solvent passing through the trap loop 22 and reaches the recovery port 31. The solvent discharged from the recovery port 31 is recovered, and the astatine oxide dissolved in the solvent is recovered. That is, astatine-211 separated and purified from the solid target substrate W is recovered from the recovery port 31 in the form of astatine oxide dissolved in the solvent.

[0032] As can be seen from the operation of the dry radioisotope refining apparatus 1 described above, in order to improve the yield of astatine-211, it is necessary to increase the amount of astatine-211 captured in the trap loop 22. As described above, low-boiling-point astatine-211 that has not reacted with oxygen tends to pass through the trap loop 22 as a gas and not be captured, so it is important that most of the astatine-211 that reaches the trap loop 22 is in the form of astatine oxide, which has a high boiling point and is easily captured by the trap loop 22. Therefore, it is important to convert most of the astatine-211 vaporized from the solid target substrate W into astatine oxide, which has a high boiling point, by reacting it with oxygen in the carrier gas.

[0033] Based on this finding, the delivery section 8 of the furnace tube 3 in the dry radioisotope refinery apparatus 1 of this embodiment extends nonlinearly within the heating space 5. This configuration increases the gas flow path length in the delivery section 8 compared to when the delivery section 8 extends linearly. This increases the reaction time between astatine-211 and oxygen in the carrier gas, increasing the proportion of astatine-211 that converts to astatine oxide. Furthermore, since such astatine oxide has a higher boiling point than unreacted astatine-211, it is more likely to liquefy in the low-temperature trap loop 22 and be captured by the trap loop 22 than unreacted astatine-211. Therefore, a large amount of astatine-211 is captured in the trap loop 22 in the form of astatine oxide. As a result, a large amount of astatine-211 is recovered from the recovery port 31 in the form of astatine oxide dissolved in the solvent, thereby improving the yield of astatine-211.

[0034] Furthermore, the substrate placement unit 7 of the dry radioisotope refinery apparatus 1 can directly introduce and accommodate the solid target substrate W. Therefore, compared to other types of refinery apparatuses that grind the solid target and accommodate it in a furnace tube, this is advantageous in that it avoids problems such as scattering of cuttings containing radioactive materials. However, since the substrate placement unit 7 must be thick to accommodate the solid target substrate W, the heating efficiency of the solid target substrate W by the tubular furnace 2 is lower than that of the other refinery apparatuses described above, and this may also result in a lower reaction efficiency between astatine-211 and oxygen. To address this issue, the dry radioisotope refinery apparatus 1 has a non-linear delivery unit 8, which increases the length of the gas flow path, allowing astatine oxide and oxygen to react sufficiently in the delivery unit 8.

[0035] As mentioned above, astatine is an element that can take on various oxidation states, but it is more likely to become AtO3- or AtO4- when it sufficiently reacts with oxygen in the carrier gas in the tubular furnace 2. Therefore, it is believed that the oxidation of astatine, which is ultimately obtained as a product from the dry radioisotope refinery apparatus 1, progresses, and astatine oxide with a higher oxidation state is obtained.

[0036] As described above, examples of the non-linearly extending delivery section 8 include those shown in FIGS. 3( a) to 3(c). The delivery section 8 shown in FIG. 3(a) extends in a spiral shape with the cylindrical axis of the heating space 5 as its central axis within the heating space 5 of the tubular furnace 2. The delivery section 8 shown in FIG. 3(b) has a complex shape that is randomly bent within the heating space 5. Furthermore, it is not essential that the entire delivery section 8 be located closer to the RI collection section 70 than the substrate placement section 7 within the heating space 5. That is, as shown in FIG. 3(c), for example, a portion of the delivery section 8 may pass through a portion of the heating space 5 closer to the rodless cylinder 44 than the substrate placement section 7. The shape of the delivery section 8 is not limited to the examples shown in FIGS. 3(a) to 3(c), and may be any shape that is non-linear.

[0037] The present disclosure can be implemented in various forms, including the above-described embodiments, with various modifications and improvements based on the knowledge of those skilled in the art. Furthermore, it is also possible to configure modified examples by utilizing the technical matters described in the above-described embodiments. The configurations of the respective embodiments may be used in appropriate combination.

[0038] For example, in the above embodiment, a single tubular furnace 2 that houses the substrate mounting part 7 and the delivery part 8 together within the heating space 5 is used as the heating part that heats the substrate mounting part 7 and the delivery part 8, but this is not limited to this. This heating part may, for example, be provided with a heating device (e.g., a tubular furnace) that heats the substrate mounting part 7 and a heating device (e.g., a tubular furnace) that heats the delivery part 8 separately.

[0039] The present disclosure may also be applied to a dry radioisotope refinery apparatus 201 using an aerosol method, as shown in Fig. 4. In this dry radioisotope refinery apparatus 201, components that are the same as or equivalent to those in the dry radioisotope refinery apparatus 1 described above are designated by the same reference numerals, and redundant explanations will be omitted.

[0040] In the aerosol method, helium gas mixed with an aerosol is used as the carrier fluid instead of an oxygen-nitrogen gas mixture. The dry radioisotope refining apparatus 81 includes a carrier supply unit 203 for supplying a carrier fluid to the furnace tube 3 instead of the gas supply unit 50. The carrier supply unit 203 includes an aerosol source housing 207 communicating with the substrate mounting unit 7 and housing an aerosol source 205, a heating unit 209 for heating the aerosol source housing 207, and a gas cylinder 213 for supplying helium gas to the aerosol source housing 207. Examples of the aerosol source 205 include NaCl and KCl. Furthermore, a filter 215 for capturing a product formed by adsorption of astatine-211 onto the aerosol components is provided downstream of the furnace tube 3 instead of the RI recovery unit 70.

[0041] In this dry radioisotope refinery apparatus 201, the aerosol source 205 in the aerosol source housing 207 is heated by the heating unit 209, thereby generating an aerosol. This aerosol flows toward the substrate placement unit 7 together with helium gas delivered from the gas cylinder 213. That is, in the dry radioisotope refinery apparatus 201, a mixture of helium gas and aerosol is supplied to the furnace tube 3 as a carrier fluid. Then, in the delivery unit 8 of the furnace tube 3, a component (adsorbent) in the aerosol contained in the carrier fluid adsorbs to astatine-211 vaporized in the substrate placement unit 7, forming a product that is more easily captured by the filter 215. That is, this product has physical properties that make it more easily captured by the filter 215 than unreacted astatine-211. In this dry radioisotope refinery apparatus 201, the delivery unit 8 has a non-linear extension.

[0042] 1, 201... dry radioisotope purification apparatus, W... solid target substrate (base material), 2... tubular furnace (heating section), 50... gas supply section (carrier supply section), 7... substrate placement section (placement section), 8... delivery section (flow path), 22... trap loop (capture section), 203... carrier supply section, 215... filter (capture section).

Claims

1. A dry type radioisotope refining apparatus for refining a radioisotope, comprising: a mounting section capable of mounting a substrate having a radioisotope attached thereto; a flow path communicating with the mounting section, the flow path being narrower than the mounting section and extending in a non-linear manner; and a heating section for heating the mounting section and the flow path.

2. A dry radioisotope refining apparatus as described in claim 1, comprising a carrier supply section that supplies a carrier fluid flowing in a direction from the mounting section toward the flow path, the carrier fluid including a reactant that reacts with the radioisotope or an adsorbent that adsorbs to the radioisotope.

3. A dry radioisotope refining apparatus as described in claim 2, further comprising a capture section provided downstream of the carrier fluid from the flow path, for capturing a product produced by the reaction between the radioisotope and the reactant or by adsorption of the radioisotope and the adsorption material.

4. A dry radioisotope refining apparatus as described in claim 3, wherein the product has physical properties that make it more easily captured in the capture section than the unreacted radioisotope.

5. A dry radioisotope refining apparatus as described in claim 3, wherein the boiling point of the product produced by reaction with the radioisotope is higher than the boiling point of the radioisotope, and the capture section is at a lower temperature than the flow path.

6. The dry radioisotope purification apparatus of claim 2, wherein the carrier fluid includes a reactant that reacts with the radioisotope, the radioisotope being astatine-211 and the reactant being oxygen.

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