Patent Number: 047822317
Section: description

DETAILED DESCRIPTION The invention is further described with reference to a number of examples. It will be understood by skilled practitioners that these examples are illustrative, and do not limit the scope of the invention or the appended claims. EXAMPLE 1 With reference to FIG. 1, the main generator column 1 is cylindrical and has a ratio of diameter to height of 1:3-5. The main column 1 is made of zirconium or aluminum, and has an upper flange 2 and a lower flange 3 of the same material. Each flange is affixed to the column as shown, and each is welded shut at the end opposite the column, to form a hermetic seal. Upper flange 2 is provided with a narrower and slightly conical extension tube 22. The lower flange 3 is threaded and has an extension tube 23. The column is filled with a target material 6, such as zirconium molybdate dried at 50.degree. C. and dispersed in particles ranging in size from 50 to 100 .mu.m (270 to 140 mesh). The target material is sealed within the column by sinter 4, of porous aluminum or zirconium oxide, at the lower end of the main column 1 near flange 3; and by a plug 5 of quartz, aluminum composite, or graphite felt an the upper end of column 1 within flange 2. Prior to irradiation, as discussed above, the entire main column assembly is wrapped in aluminum foil to prevent contamination, particularly of the flanges 2 and 3. After irradiation, the foil is removed from the column assembly under sterile conditions, and the welded ends of flanges 2 and 3 are opened by grinding or filing. The threaded lower flange 3 is then connected to a threaded end-piece 8 into which a seat 7 of silicon rubber is inserted. The end-piece 8 is connected to an L-shaped discharge tube 12. A supply tube 11 is affixed to flange 2. EXAMPLE 2 FIG. 2 shows a cylindrical main column 1 made of aluminum or zirconium as in FIG. 1. The column 1 is provided at its lower end with a flange 3. The flange 3 is slightly conical at the interior, where it meets column 1, and contains a discharge tube 24 that terminates with a widened part and a conical internal opening 25. The flange 3 and discharge tube 24 are closed by cap 9 and aluminum foil 21 having no conical recess on the internal side. The column is filled with zirconium molybdate particles 6, which have been dried for several days at room temperature. The particles range in size from 10-150 .mu.m (100-200 mesh). The lower end of column 1 is sealed by a porous sinter 4 of silicon dioxide. The upper end is sealed by plug 5 of graphite felt, beyond which is another cap 9 and foil 21. The column is irradiated according to the invention and is then transferred to a sterile environment. The caps 9 and foil 21 are treated with a disinfecting solution. The column 1 is then connected to sterile supply tube 11 and sterile discharge tube 12 at its opposite ends by piercing the foil 21 at each end, and firmly inserting the respective tube 11 or 12 to achieve a tight fit. EXAMPLE 3 FIG. 3 shows a symmetrically closed embodiment. Main column 1 is aluminum or zirconium and has a diameter to height ratio of 1:2-5. Identical threaded flanges 2 and 3 are welded to column 1, flange 2 at the upper end and flange 3 at the lower end. Within each flange are tubes 27 closed by caps 9 packed internally with aluminum foil 21. Target material 6, such as titanium molybdate dried at 40.degree. C. and having a particle size of 70-150 .mu.m (100-200 mesh), is placed within the column. The target material is sealed within the column by plugs 5. After irradiation, caps 9 are removed in a sterile environment and supply tube 11 and discharge tube 12, each with an end-piece 8, are screwed in place. EXAMPLE 4 FIG. 4 shows an assembled generator of the invention. The main column 1 with supply and discharge tubes 11 and 12, as described in Examples 1-3 and 6 and as shown in FIGS. 1-3, is placed within a primary transport container 13 made of lead or depleted uranium. The tubes 11 and 12 are placed within openings in the container 13 during transport, and their ends are aseptically sealed against bacterial contamination by plugs and/or wrapping. Container 13 has a cover 14 with a spherical handle 28 to facilitate manipulation of cover 14. The cover 14 is held securely in place by at least two screws, or by some other known method, such as rectangular hoops or friction clamps secured around the container 13. For transportation to the end user, these components are placed in a protective sheet container (not shown). Upon arrival at the use-site, the column 1 and container 13 assembly are removed from the protective container and placed in a laboratory container 15. Lab container 15 is a thick-walled vessel made of lead or depleted uranium. The sealed outer end of supply tube 11 is broken and, without loss of sterility, is connected to vessel 16, which contains a sterile apyrogenous physiological solution. The sealed outer end of discharge tube 12 is broken and, without loss of sterility, is connected to protective column 17, which contains a sorbent, such as hydrated zirconium oxide. The protecting column 17 in turn is connected to the piercing head of evacuated, flanged, and sterilized penicillin-type bottles 18. The bottles 18 are situated in a thin-walled lead container 19. The components are placed within a cylindrical enclosure 20 that is provided with cavities to house them. Enclosure 20 itself fits within a circular recess of lab container 15. Each elution is performed by placing an evacuated bottle 18 on the piercing head. In response, a corresponding volume of solution is sucked from vessel 16, passes in through supply tube 11, through main column 1, out through discharge tube 12, into column 17 and finally into bottle 18. The eluate, having passed through the sorption material 6, contains .sup.99m Tc radionuclides when it reaches bottle 18. When elution is complete, the sterile seal is maintained by placing a non-evacuated bottle 18 over the piercing head. EXAMPLE 5 In another embodiment of the invention, the elution generator may be supplied to the user in an assembled version, substantially as shown in FIG. 4. The main column 1 is stored in lab container 15 by the manufacturer and the entire device is shipped to the user. This embodiment requires a stronger connection between enclosure 20 and cover 14, such as a heavy threaded bar. EXAMPLE 6 In its simplest embodiment, not illustrated, the main column can be made of a quartz tube narrowed conically at both extremities, containing target material (ie, zirconium molybdate particles 100-150 .mu.m in size; dried at 60.degree. C.), and fused closed. The target material is packed tightly in the narrow ends of the column by quartz wadding. Prior to irradiation, the sealed column is wrapped in aluminum foil. After irradiation, the narrow ends of the column are cut and broken close to each end by a vidium knife or a file. Bacterial infection is prevented by careful flaming of the ends. Supply and discharge hoses, preferably of silicon rubber, are affixed to the ends of the column. The column is shielded by a simple coiled lead sheet within a laboratorium arrangement and is connected to a vessel, such as a birette or a separating funnel, containing the elution solution. In yet another embodiment, the quartz column can be used in a more complex apparatus as shown in Example 4. In operation, the elution generator of the invention, comprising primarily the main generator column, can produce a standard .sup.99m Tc elution of several GBq for a medium intensity neutron flux of 2 to 5.times.10.sup.17 n/m.sup.2 s. The columns of the invention are manufactured in a nonactivated state, which makes their manufacture much easier and safer. Later activation of the column also permits a single activation and sterilization step. The apparatus as a whole may be manufactured and delivered as components which are readily interconnected for use. In addition, the main column can be supplied separately, and through and independent delivery chain, whereby it may be activated by irradiation in a local reactor. This is a particularly important consideration in developing countries. Activation of the column itself and its contaminants (if any) is not a problem, nor is safe transport after irradiation, because the "extra" activity is always equal to or less than that of .sup.99 Mo. The invention as a whole is advantageous because it permits the use of a reactor with a medium intensity neutron flux which are more readily available than these which provide the high intensity activation required by conventional generators; it benefits from a simple and elegant design in manufacture, delivery and use; it achieves simultaneous sterilization and activation of the main elution column; and it permits independent delivery of activated and nonactivated components.