Patent Number: 
Section: description

By means of FIGS. 1-6 an illustrative embodiment of the present invention will be described. This embodiment forms the xe2x80x9cMINItracexe2x80x9d Integrated Radiation Shield: A primary object of the invention is to create a radiation shield for a PET isotope production system, which presents a single unit having a limited size making it suited to be operated at an adequate floor size available for instance at a regular hospital utilising radioactive tracers in the form of short-lived isotopes. Another object of the invention is to still achieve a design of the,radiation shield, which also presents an aesthetic timeless design. Therefore the radiation shield and its integrated subsystems are housed in a carefully shaped shell, which is still offering the full desirable radiation protection shield. An overall picture of the apparatus according to the present invention is disclosed in FIG. 1 and consists of four moulded sections, two fixed section 1 and 2 and two additional movable sections 3 and 4 forming doors. The installation of a PET isotope production system normally includes rigging work of a relatively heavy cyclotron device. Being able to, in a simple way, move, i.e. open, the additional radiation shield sections 3 and 4 constituting the doors provides an effective method to quickly access and service the PET isotope production system. The match casting technology makes the fitting between the sections almost perfect, i.e. no slots, and close fitting to floor surface due to tight casting tolerances. The no time consuming alignment of shield sections is valuable when installing the PET isotope production system. To achieve a simple opening of the radiation shield the sections 3 and 4, according to FIGS. 3 and 4, are forming doors on heavy-duty hinges taking up the load of the weight of the sections 3 and 4. Such a door section in a preferred embodiment has a weight of the order 7-8 tons, and thus the entire radiation shield has a mass corresponding to 10 m3 of special concrete. Correspondingly each section 1 and 2 has a weight of 10-11 tons. A portion of each of the hinges 5 is fixedly moulded into the sections forming the concrete constituting the radiation shield, thereby eliminating all risks for having to perform adjustments over time (i.e. the hinges in fact forming an integral part of the shield) Furthermore these doors 3, 4 are suspended on roller bearings in the hinges 5 forming a virtually xe2x80x9czero friction systemxe2x80x9d making door motion possible with a very low driving force which also is beneficial for eventual pinch hazards. Additionally the hinges 5 are adjustable in all directions facilitating all the options for the necessary final fine adjustment, to obtain a non-leakage radioactive and an almost airtight closure of the casing design enclosing the cyclotron device. The casing according to the invention does not need any floor penetrations for installation of this xe2x80x9cMINItracexe2x80x9d Integrated Radiation Shield. The user will be able to use an existing floor surface and there will be no time consuming preplanning and surface breaking needed for cable ducts, radiation shield rails and driving systems. Preferably before installation of the xe2x80x9cMINItracexe2x80x9d Integrated Radiation Shield the floor surface may be treated with a self levelling low viscosity resin making the floor surface perfectly flat and levelled and ready to use after one night of hardening. On top of the section 2 there are situated a number of intake openings for the externally separated circuits, for instance for the wiring. Each radiation shield section as well as the cyclotron device are equipped with lifting fittings for hydraulic jack rollers making lifting and movement of these heavy components quick and easy during the installation phase. The xe2x80x9cMINItracexe2x80x9d radiation shield consists of a dense concrete body especially designed to balance attenuation properties and the volume/weight ratio of the shield. The heavy ballast is chosen to be mainly iron ore for good gamma radiation attenuation with additional Boron and Hydrogen components to strengthen the neutron radiation attenuation capacity. In a preferred embodiment the radiation shield is having a hydrogen radiation protection mass of the order 25 kg/M3 and 5-10 kg/M3 of pure Boron and maximising the density by means of a magnetite (black ore Fe3O4) content for obtaining a final density of the order 3.5. Furthermore, the targets are surrounded by a shielding of sandwich type containing PE plastics and lead (Pb). Finally the xe2x80x9cMINItracexe2x80x9d radiation shield will form a virtually air-tight container which prevents accidental leakage of radioactivity from the xe2x80x9cMINItracexe2x80x9d interior system to the outside of the casing to create a low radiation environment in a room where the system is operating. Connections are easily provided for creating an under-pressure inside the shield (if regulations call for this). Also note that no air circulation from the surrounding air outside the shield is necessary for cooling purposes of the interior systems of the radiation shields, which assists in keeping the external environment of the casing at very low radiation hazard. Inside the radiation shield there is a space 7 housing a cyclotron with its internal subsystems like ion source, radio frequency electrode system and beam extraction elements and the visible subsystems such as vacuum case and pumps, targets with cooling water, and target window cooling. For easy maintenance of the cyclotron its magnet coils and poles are positioned such that the plane of the ion beam is vertical. Due to this design and the movable sections 3 and 4 the vacuum chamber of the cyclotron can even be divided in this vertical plane for simple access of its interior containing the closely spaced electromagnetic poles forming the acceleration gap for the ion beam and the other internal subsystems. This cyclotron is particularly designed for acceleration of a negative hydrogen ion beam then particularly used for production of short lived radioactive diagnostic tracers for medical applications. Also integrated in the radiation shield there is provided a Waste Gas Delay Line 8 positioned within the concrete portion 1, which is indicated in FIG. 2. It consists of a xe2x80x9clongxe2x80x9d plastic tube embedded in the concrete in such a way that the concrete will provide full radiation shielding for potential radioactivity loaded into the Waste Gas Delay Line 8. At the left side of the concrete casing portion 1 there is created a further compartment 9 (indicated in FIGS. 1 and 5). The compartment 9 offers target media handling 10 for the gas targets (e.g., isotopes 11C, and 15O) consisting of valves and pressure gauges and water dispensing systems 11 for the water targets (e.g., isotopes 13N, and 18F), the processing systems 12 for tracers 15O and processing systems 14 for tracers 11C. The compartment 9 further contains a lead radiation shield 13 embracing the 15O processing system 12 and a similar lead radiation shield 15 for the 11C processing system 14. The lead shields 13, 15 are furnished with doors supported by hinges for easy access of the gas processing systems. At the right shield side of the xe2x80x9cMINItracexe2x80x9d casing there is also, still a compartment 16 (indicated in FIGS. 1 and 6) containing the secondary cooling system 17, mains power distribution 18, vacuum system controller 19 and the ion gas source controller 20. Further at the top of the radiation shield created by the four portions 1-4 there are arranged shield surface driving motors for motions for doors as well as warning signs, e.g. indicating xe2x80x9cMagnet field activexe2x80x9d, xe2x80x9cBeam onxe2x80x9d. Thus, the disclosed apparatus according to the present invention forms an integrated closed radiation-proof system for PET isotope production, which can easily be housed in connection to a main hospital for an easy access of short-lived radioactive tracers for medical diagnostic purposes. The advantages of the present disclosed system primary lies in the design of the compact self-supporting radiation-proof casing which then easily can be applied as a localised facility.