DE2939282A1 - Prepn. of purest rubidium-81 for medicinal use - by irradiating krypton and protons or deuterons, electromagnetic isotope sepn. and implanting rubidium-81 in common salt - Google Patents

Abstract

Prepn. of Rb-81 suitable for medical purposes comprises producing Rb-81 by chain reactions and then sepg. the impurities using an electromagnetic isotope sepn. (16) and then implanting the sepd. Rb-81 atoms in common salt. Auxiliary appts. for carrying out this prepn. is also claimed. It comprises a gas target chamber (3) in which the chain reactions can be carried out, and which can be inserted into the ion source (15) of the electromagnetic isotope separator (16). There is very low loss of surface ionisation in the hollow chamber. The Rb-activity produced after irradiation of krypton collects on the cylindrical walls of the gas-target chamber. The radioisotope obtd. is practically free from all radioactive impurities. Final stages of prepn. are simple. Common salt is easily dissolved in water and therefore produces (together with the homogeneously distributed Rb-81 in milli curie amts), a physiological soln. suitable e.g. for injections.

Description

Process for the purest preparation of Rb-81

for medical applications Description: The invention relates to a method and an auxiliary device for the purest display of Rb-81 for medical applications, after which the Rb-81 is generated by nuclear reactions and / is separated from impurities.

For the purest preparation of rubidium-81, the method of B.

Rich et al known ("Radiopharmaceuticals", edited by G. Subramanian, B. Rhodes, J. Cooper, and V. Sodd, published by The Society of Nuclear Medicine, Inc. ", New York (1975) at p. 174).

In this process, krypton with a high concentration of 80 Kr and a small proportion of the heavier krypton isotopes with deuterons of only 7.4 MeV irradiated. Practically only (d, n), (d, p) and (d, xn) processes can run here, and since there is no stable 81Kr, contamination by 82 (m) Kr is avoided. The remaining radioactive contaminants are removed by waiting five hours (conversion des 79R # in 79Kr) and largely removed by chemical separation. Residual impurities, especially through 83Rb, which significantly increases the patient's exposure to radiation can, but remain present. Furthermore, the bond to a nuclear reaction with relatively low values for effective cross-section and usable target thickness are necessary.

The object of the invention is now to make 81Rb Krypton with subsequent separation of radioactive impurities - in particular des 82mRb-- without major losses of 81Rb, with nuclear reactions with large Effective cross-section and (or) large usable target thickness despite the then unavoidable Mitprodllation of the 82mRb can be used and the Rb-81 is obtained so that it can be used for medical purposes without much ado.

According to the invention, this object is achieved by the features of the claim 1 solved. Claim 2 specifies an advantageous development of the method and claim 3 a suitable auxiliary device for carrying out the method.

The particular advantages of the invention are that by the electromagnetic isotope separation with low-loss surface ionization in the cavity, wherein the cylindrical wall of the gas target chamber, on which after the irradiation the generated rubidium activity then adheres to the ion source of the separator can be used, a radioisotope required in medicine is generated that is practical completely separated from all radioactive impurities and a simple final preparation permitted. The table salt can easily be dissolved in water and is therefore (together with the homogeneously distributed Rb-81 in Millicurie-Menger) as a physiological solution (e.g. injection).

The invention is illustrated below using an exemplary embodiment explained in more detail by means of FIGS. 1 and 2. Figure 1 gives an example for a gas target chamber and FIG. 2 for an ion source for the electromagnetic Isotope separator again.

FIG. 1 shows a structural implementation in a schematic section for the manufacturing step of Rb-81 by nuclear reactions. The Deuteron or krypton 2 interspersed with proton beam 1 is a 30 mm long tantalum tube 3 (5.5 mm inner #), which collects the rubidium formed and that after the Irradiation in the isotope separator ion source (5. Figure 2) can be used. It is fitted into a two-part, water-cooled copper block 4, one of the two copper block parts 5 is removable. For better heat transfer is A soft indium foil is placed between the tantalum tube 3 and the copper block 4, 5. Before the irradiation, about 3 ~ 10 ~ 1 ° g is applied to the inner surface of the tube 3 Rubidium nitrate distributed by means of a drop of solution to be dried. This makes it easier the subsequent isotope separation. Ray 1 enters and leaves the Krypton volume 2 through window 6 made of 10 p thick damaged film.

These are as double windows with 3 - 4 mm wide atmospheric Gap formed. During the irradiation, in fine rays directed at the window 6 Cooling compressed air 7 blown. The target volume 2 can be evacuated through a channel 8 with 5 mm ~ and fill it with krypton.

The krypton storage vessel 9 forms with the cold finger 10, the manometer 11 and valve 12 a detachable unit. It can be made with natural krypton or for Increasing the yield and reducing the required acceleration beam energy filled with enriched krypton-82. The storage unit 9 itself has a Volume of approx. 6 cm3 (largely determined by the manometer). Storage unit 9 and target chamber 2, 3 together give a volume of approx. 11 cm3. With 70 cm3 Normal pressure krypton is thus achieved in target 2 a pressure of approx. 6 1/2 bar. Higher filling pressures are possible. Located directly in front of the double entry window 6 a diaphragm 13 delimiting the beam 1 with a diameter of 5 mm and - if necessary the beryllium absorber 14 for reducing the energy of the beam 1. Both are screwed onto a water-cooled block. The short distance between absorbers 14 and target 2 does not allow the beam expansion caused by the absorber to take effect. Behind the target 2, the part of the beam 1 passing through the krypton re-enters Vacuum so that he can be measured in a Faraday cage or for the generation of others Isotopes can be used. It is generally 60 to 80% of the current strength in front of the target 2. Immediately after the irradiation, a small Dewar vessel can be inserted into the the cold finger 10 of the storage vessel 9 is immersed via a remote-controlled filling mechanism filled with liquid nitrogen. This will be done within three minutes Krypton completely frozen out of the target (a similar arrangement for the The generation of barium radioisotopes from xenon has already been described in B. Feurer and A. Hanser, KFK 2686, P. 72, 1978).

The one used for isotope separation in the second process step Ion source 15 (see Figure 2) is described, for example, in A. Latuszynski et al, Nucl. Instr. and meth. 125 (1975) 61.

Surface ionization in the cavity can lead to significantly higher ionization yields lead than the Langmuir equation indicates. This is due to the space charge effect that of the hot cavity walls glow electrons emitted inwards. The negative space charge keeps positively ionized atoms away from the walls and prevents their re-discharge, while neutral atoms until their ionization can continue to hit the wall. Furthermore, the ionization yield is reversed proportional to the ion density in the cavity and increasing monotonically with temperature. From this it can be seen that an ion source 15 with surface ionization in the cavity for the present case, in which only a very small amount of substance is the source must enforce and the ion density will therefore be low, is particularly suitable, and that tantalum, which is easy to work with and has a high melting point, despite its relatively low value Electron work function (4.2 ev) can be used as ionizer material.

FIG. 2 now shows a section through the ion source 15 as well as schematically the isotope separator 16 and the saline target 17. Two attachable Caps 18, 19 made of tantalum have the tube 3, which is also made of tantalum enclosed the krypton during the irradiation and the rubidium formed on his Has collected the inner wall, added to the insertable inner furnace cartridge. One the cap 19 is attached to a support rod 20, the other 18 tapers and has a small opening 21 (0.7 mm ~) at the front end for axial extraction of ions. Precisely turned conical surfaces (60 cone angles) ensure that the three parts of the furnace cartridge 3, 18, 19 are tightly and tightly joined together can. With the help of two separately heatable tungsten wire windings 22, 23 (1 mm ~) the furnace cartridge 3 can be brought to high temperatures by electron impact. The main requirement for ionization is the heating of the part near the ion extraction port 21 important. As a result of the small diameter, temperatures can easily be reached there close to the melting point of tantalum (30000C). With the heating of the middle and rear part is mainly the continuous thermal release of the initially regulated by the action of air after the irradiation of oxidic rubidium. To effect electron impact heating, the two tungsten wire turns are made 22 23 connected to the furnace cartridge 3 at -800 V voltage. Flows when fully heated an electron current of approx.

1 A. Oven cartridge 3 and electron impact cathodes are from three heat shields 24 to 26 surrounded. The innermost shield 24 is mounted insulated and serves at the same time as an electron reflector.

Since there is no gas discharge in this ion source 15 and thus also no There is material removal by ion bombardment, the wear is high despite the high Temperatures very low. The three parts 3.18, 19 that make up the furnace cartridge 3, can be removed from each other again after a mass separation with the help of a pull-off device be separated without the conical surfaces important for a tight fit suffer.

The purest Rb-81 ion beam 27 generated in the isotope separator 16 becomes directed at the target 17 (third method step) and stored there. That Target 17 is preferably made of common salt (single crystal, polycrystalline), which brought directly to medical use as an injection medium through solution in e.g. H20 can be. The product of the first method step is in the ion source 15 heated to 20000C for technical reasons, which is indicative of the medicinal purity of Meaning is.

Claims (3)

Claims: rs method for the purest preparation of Rb-81 for medical applications where the Rb-81 is generated by nuclear reactions and thereafter is separated from impurities, characterized in that the separation by means of an electromagnetic isotope separation (16) takes place and the separated Rb-81 atoms implanted in saline. 2. The method according to claim 1, characterized in that the table salt (17) can be polycrystalline. 3. Auxiliary device for performing the method according to claim 1 and 2, characterized by a gas target chamber (3) in which the nuclear reactions are feasible and which is designed such that it can be used as an insert in the ion source (15) of the electromagnetic isotope separator (16) is suitable.