RU114260U1 - TARGET DEVICE FOR CYCLOTRON WITH 18 MeV PROTON ENERGY FOR OBTAINING RADIO NUCLIDE FTOR-18 IN THE FORM OF FLUORIDE ANION - Google Patents

Abstract

A target device for the SS-18/9 cyclotron with a proton energy of 18 MeV to obtain the fluorine-18 radionuclide in the form of a fluoride anion, containing a target body with a cavity for the irradiated material located in the central part of the front surface of the target body, a flange, its rear wall and foil, characterized in that the target device additionally contains a clamping plate, the target body is made of one piece of niobium, has threads 10-32 UNF from above and below, the height of the cavity for the irradiated material is 41 mm, the cavity has an oval shape, its bottom is beveled at an angle 45º, the rear wall of the target body has ribbing, in shape and location coinciding with the oval cavity on the front surface of the target body, the flange has a recess for fixing the target body, located in such a way that the center of the target is located 11 mm above the center of the hole for the proton beam of the flange, the rear wall of the flange has a recess for circulating cooling water, in the upper and lower parts of which there are p The threads are G1 / 4, the foils are located one between the target body and the flange, the other between the flange and the clamping plate.

Description

The utility model (PM) relates to medical equipment, namely to means for producing a radionuclide for the production of radiopharmaceuticals (RFPs) used to diagnose a wide range of diseases using positron emission tomography.

Positron emission tomography (PET) is one of the most rapidly developing areas of modern nuclear medicine. It allows detecting malignant neoplasms, foci of inflammation and other pathological processes, and visualizing myocardial metabolism.

The use of PET requires the use of radiopharmaceuticals (RFPs) labeled with ultrashort-lived positron-emitting radionuclides, which are produced using cyclotrons. The half-lives of such radionuclides are minutes or tens of minutes. The most widely used radionuclide for PET imaging is fluorine-18 (more than 90% of patient examinations are performed with radiopharmaceuticals labeled with fluorine-18).

The fluorine-18 radionuclide is produced by the nuclear reaction ¹⁸ O (p, n) ¹⁸ F when irradiated with 18-18 MeV protons of oxygen enriched in the ¹⁸ O isotope in the chemical form H ₂ ¹⁸ O. Water is used with an enrichment of 97% of the ¹⁸ isotope O. The radionuclide has a half-life of 109 minutes. The exposure time, optimal in terms of effective yield, is approximately equal to two hours.

Fluorine-18 can be obtained using various cyclotrons with a preferred energy of 12-18 MeV. The most famous cyclotron models are foreign IBA Cyclone 18/9 (18 MeV, 100 μA, 9 Ki fluorine-18 in 2 hours), GE PetTrace (16.5 MeV, 100 μA, 10 Ki fluorine-18 in 2 hours), Siemens Eclipse (11 MeV, 40 μA, 2.5 Ki fluorine-18 in 2 hours). These cyclotrons are equipped with high-performance targets for producing fluorine-18. Each cyclotron requires an individually designed target station. Domestic cyclotrons with an energy of 18 MeV (SS-18/9, MGC-20) are supplied by the manufacturer, NIIEFA named after Efremov (St. Petersburg), without target devices. The target device for producing fluorine-18 to the SS-18/9 and MGC-20 cyclotrons is manufactured at the Research Institute of Positron (FSBEI HPE SPbSPU) and is not commercially available [Radionuclide imaging methods: Textbook / B.V. Zabrodin, V.N. .Lomasov, A.V. Motorny - St. Petersburg: St. Petersburg State University, 2006.].

This target device was selected as a prototype. The target device includes: a flange, its rear wall, 2 foils and a composite tantalum target body, having a cavity 2 mm deep and a rear wall.

For a better understanding, we present the scheme of the target device presented in the prototype. Figure 1 shows the target body (1a is a side view, a section and 1b is a top view), where 1 is the foil, 2 is the disk with a cavity for the irradiated material, 3 is the fluoroplastic gaskets, 4 is the rear wall of the target body, 5 is the hole for creating a cavity for the irradiated material.

In accordance with the description of the prototype, the radionuclide ¹⁸ F is produced by the nuclear reaction ¹⁸ O (p, n) ¹⁸ F when irradiated with protons with an energy of 15 MeV of oxygen enriched in the ¹⁸ O isotope in the chemical form of H ₂ ¹⁸ O. Most often, water is used, with enrichment 95% ¹⁸ O isotope, the cost of which is quite high. In order to save the target substance, the minimum size of the target water cavity was chosen - diameter 25 mm, water layer thickness 2 mm, which provides proton energy losses in the region of the largest cross sections of the nuclear reaction ¹⁸ O (p, n) ¹⁸ F. Irradiated water volume ~ 1 cm ³ .

The target is irradiated with a proton beam with an energy of 15 MeV. The beam current is 20 μA. The beam diameter on the target is 25 mm. The uneven distribution of the beam is not higher than 15%.

At the end of the irradiation of the target, a fluorine-18 radionuclide with an activity of more than 30 GBq is obtained.

Tantalum was selected as the target body material. Structurally, the housing is made of a disk and a ring 2 mm thick. From the side of the beam entrance, the target volume is closed by a titanium foil 50 μm thick. The working volume of the target is sealed with 20 μm thick fluoroplastic gaskets. The selected materials do not interact with fluorine ions formed in water and practically do not introduce impurity contaminants.

Water in the target is irradiated at an excess pressure created by helium. The target withstands excess pressure in a volume of at least 6 kg / cm ² at a working pressure of 2 kg / cm ² .

From this description and the scheme (target body) it is difficult to imagine the complete design of this target device. In our opinion, the target device contains the target body, a flange, its back wall and two foils.

This target device allows you to get up to 0.8 Ki fluorine-18 in 2 hours of exposure.

The target device has a number of disadvantages, namely:

1. a shallow depth of the cavity of the target body for the irradiated material (2 mm) leads to incomplete absorption of protons and thereby to a decrease in the productivity of the target device;

2. since, as follows from the description, the target body is composite and compacted using fluoroplastic rings, this leads, as we have shown, to the products of fluoroplast degradation in the radiation field entering the irradiated water and lowering the radiochemical yield of the radiopharmaceutical when using the radionuclide obtained using this target device;

3. the design of the target body is performed as follows (a small condensation surface of the chamber for the irradiated material, the absence of fins, a gasket between the rear wall of the target and the target body), which does not provide sufficient cooling for it and reduces the performance of the target device;

The above disadvantages lead to the fact that this target device has a low productivity and does not allow to obtain more than 0.8 Ki fluorine-18 in 2 hours of exposure.

The technical result of this PM is to increase the performance of the target device.

This result is achieved by the fact that in the known target device containing the target body with a cavity for the irradiated material located in the central part of the front surface of the body, the flange, its back wall and foils, according to the PM, the target device further comprises a clamping plate, the target body is solid , from niobium, it has threads 10-32 UNF above and below, the height of the cavity for the irradiated material is 41 mm, the cavity is oval, its bottom is beveled at an angle of 45 degrees, the back wall of the target body is it has a fin that matches the shape and location of the oval cavity on the front surface of the target body, the flange has a recess for attaching the target body, so that the center of the target body is 11 mm above the center of the hole for the proton beam, the back wall of the flange has a recess for circulation of cooling water, in the upper and lower parts of which there are G1 / 4 threads, foils are located one between the target body and the flange, the other between the flange and the clamping plate.

The execution of the target body integral allows you to abandon the use of gaskets in the target body, which allows you to get fluorine-18 without impurities in the form of degradation products of the seal material in the radiation field.

The height of the cavity 41 mm provides an increase in the area of the cavity for the irradiated material, which leads to improved heat dissipation and increased productivity.

The use of niobium as the target body material allows one to reduce the cost of the target device without compromising its performance and the quality of the obtained fluorine-18.

The oval shape of the cavity for the irradiated material allows you to increase the area of the condensation surface of the cavity for the irradiated material, which leads to an increase in the productivity of the target device.

The execution of the bottom of the cavity for the irradiated material beveled at an angle of 45 degrees gives a decrease in the dead volume of the target body and allows you to get the irradiated material with less loss.

The location of the center of the target body 11 mm above the center of the hole for the proton beam in the flange provides an increase in the area of the condensation surface of the target body and an increase in the area of the back cooled fin surface while maintaining the size of the target body, which saves the expensive material of which the body is made.

Finning of the rear surface of the target body improves cooling of the target body, which leads to an increase in the performance of the target device.

The presence of 10-32 UNF threads in the target body improves the tightness of the target body and simplifies maintenance of the target device.

The G1 / 4 threads in the back wall of the flange allow the use of large-diameter fittings to supply cooling water to the target body, which improves cooling and thus improves the performance of the target device.

The presence of the clamping plate allows the creation of a closed cavity for helium cooling of the foil located between the target body and the flange.

For a better understanding of PM, we give the schemes:

flange, Fig. 2 (2a - top view, from the recess for mounting the target body, 2b - side view, section, 2c - bottom view, from the side of the recess for mounting the clamping plate), where 1 is the hole for the entrance of the beam, 2 - recess for attaching the target body, 3 - recesses for fittings, 4 - threads for attaching the rear wall, 5 - holes for attaching the flange to the cyclotron ion line, 6 - recess for installing the clamping plate, 7 - recess for installing the foil creating the helium cooling cavity 8 - helium cooling channel; 9 - G1 / 4 threads; 10 - f lga, 11 - foil;

of the target body, which is the main part of the target device, Fig. 3 (3a - rear view, 3b - side view, section, 3c - front view, from the entrance side of the proton beam), where 1 is the ribbing on the back wall of the body, 2 - channels for filling and emptying the target, 3 - threads 10-32 UNF, 4 - cavity of the target, 5 - recess at an angle of 45 degrees;

the back wall, Fig. 4 (4a is a rear view, 4b is a side view, section), where 1 is a G1 / 4 thread for attaching fittings supplying cooling water, 2 is a chamber for water cooling the rear surface of the target body, 3 are mounting holes;

clamping plate, Fig. 5, where 1 is the hole for mounting on the front surface of the flange of the target device, 2 is the hole for the entrance of the proton beam, 3 is the surface that clamps the foil.

The assembly is carried out as follows: a foil is attached to the flange of the target device (Fig. 2) with an opening for the entrance of the proton beam (Fig. 2, p. 1) from the side of the proton beam inlet (Fig. 5) (Fig. 2, p. 10), which is placed in the recess (Fig. 2, p. 7), and the clamping plate in the recess for its installation (Fig. 2, p. 6). The clamping plate is attached to the front surface of the flange through the holes (Fig. 5, p. 1) and clamps the foil with a protrusion (Fig. 5, p. 3). Then the second foil is installed (Fig. 2, item 11), clamped by the target body. By means of bolts screwed into 6 threaded holes (Fig. 2, p. 4), its back wall is fastened to the flange through mounting holes (Fig. 4, p. 3), which clamps the target body in the recess of the flange (Fig. 2, item 2). Fittings with capillaries are screwed into the body of the target in threads 10-32 UNF (Fig. 3, 3), while the fittings are placed in the recesses of the flange (Fig. 2, item 3). Then, fittings G1 / 4 for supplying helium and cooling water, respectively, are attached to the flange through the threads (Fig. 2, item 9) and its back wall (Fig. 4, item 1). The target device is mounted on the cyclotron’s ion line using 4 mounting holes in the flange (Fig. 2, item 5). Refueling of the target is carried out through fittings screwed into the threads 10-32 UNF (Fig. 3, p. 3) and channels of the target body (Fig. 3, p. 2).

The operation of the target device is as follows: a proton beam with a diameter of 20 mm passes through the hole (Fig. 5, p. 2) in the clamping plate and enters the foil (Fig. 2, p. 10), passes through it, then through the helium cooling cavity (Fig. 2, p. 8) in the flange, and passing through the second foil (Fig. 2, p. 11), it enters the irradiated material (water enriched in oxygen-18 isotope) located in the target cavity (Fig. 3, p. 4), where it completely dissipates with the formation of fluorine-18. Cooling water is located in the cavity (Fig. 4, item 2) and cools the finned back surface of the target body.

The proposed PM in comparison with well-known analogues has several advantages:

1. provides up to 5 Ki fluorine-18 at a proton beam current of up to 50 μA, which is not inferior in performance to foreign target devices and more than 6 times greater than the prototype;

2. allows you to get fluorine-18 without impurities, which ensures a high technological yield of the radiopharmaceutical, while when using the prototype target, according to the experience of using in the Russian Science and Technology Center, the technological yield of the radiopharmaceutical can be reduced by 50 or more percent due to the presence of impurities in irradiated material; as a result of this, the total RFP yield when using this PM is 12 times higher than in the prototype.

The proposed target device was developed in the department of cyclotron radiopharmaceuticals of the Federal State Budget Scientific Center of the Russian Center for Scientific and Technical Research and passed clinical testing with 80 radiopharmaceutical syntheses, with a positive result.

Claims (1)

A target device for the SS-18/9 cyclotron with 18 MeV proton energy for producing a fluorine-18 radionuclide in the form of a fluoride anion, containing a target body with a cavity for the irradiated material located in the central part of the front surface of the target body, a flange, its rear wall and foil, characterized in that the target device further comprises a clamping plate, the target body is made of niobium, has threads 10-32 UNF on the top and bottom, the cavity height for the irradiated material is 41 mm, the cavity has an oval shape, its bottom it is filled with a bevel at an angle of 45 °, the back wall of the target body has a ribbing that matches the shape and location of the oval cavity on the front surface of the target body, the flange has a recess for attaching the target body, located so that the center of the target is 11 mm above the center of the hole for proton beam of the flange, the back wall of the flange has a recess for cooling water circulation, in the upper and lower parts of which there are G1 / 4 threads, the foils are located one between the target body and the flange, the other between the flange and the clamping plate Stina.