Patent Number: 048517020
Section: summary

BACKGROUND OF THE INVENTION This invention relates to radiation-blocking containers for shielding of radioactive solutions stored within substantially non-shielding vessels. Generally, small vials or microcentrifuge vessels (microtubes) are commonly used to store and transfer small amounts of radioactive material such as .sup.32 P and .sup.125 I isotopes, which produce high energy .beta.-particles. These radioactive materials are often combined with other chemical and biochemical ingredients and the resulting mixtures within these microtubes are subjected to incubations at a variety of temperatures. Microtubes are typically made of polyethylene or polypropylene and include a lid which snaps shut. These vessels have thin walls and provide little shielding from the emitted radiation for the laboratory worker manipulating the samples. Existing radiation shields specifically designed to hold these microtubes consist of a heavy block of radiopaque material such as Plexiglass.TM. which may include multiple drilled-out cylindrical holes for holding several microtubes. Heavy radiopaque cannisters with lids are also used to store single microtubes. SUMMARY OF THE INVENTION The invention features a radiation shield suitable for preventing radiation or radioisotopes from reaching a person using one or more sample vessels holding a radioactive solution. The shield includes a radiopaque container, having a top and a bottom opening, and a means for supporting the vessel within the container. The container blocks .beta.-radiation emitted through the sides of the vessel while allowing continued contact between the vessel and the environment via the bottom opening of the container. In preferred embodiments, the container permits incubation liquid to enter the bottom opening of the container and surround that portion of the vessel holding radioactive solution; the container is a sleeve into which the vessel fits; the sleeve has a substantially flat bottom surface which allows it to rest in a free-standing position on a flat surface; the sleeve has a flange which allows it to be suspended in a rack, and permits incubation liquid to enter the bottom opening of the sleeve when it is suspended in the rack, and surround that portion of the vessel containing the radioactive solution; the container includes a rack for supporting a plurality of vessels, and a radiopaque shield is formed along the perimeter of the rack leaving the bottom of the rack open; the container includes a radiopaque cover for shielding radiation emanating through the top opening. In yet another embodiment, the container is a block of radiopaque material having a plurality of bores, which traverse the block, and the container is transparent. This invention provides radiation shielding for vessels, microtubes, and other small vessels, with the sleeves or racks extending from the lid of a microtube to a point some distance below the microtube to minimize lateral exposure of radiation to the laboratory worker. For example, the laboratory worker can safely hold a sleeve by its sides without significant exposure of the hand to radioactivity. The geometry of the sleeves (open at the bottom) permits liquid in any incubator bath to directly enter the sleeve and surround at least the lower part of the microtube housed within the sleeve to allow accurate temperature control of the radioactive sample. Thus, the sleeve simultaneously provides an individual a portable shield which permits safe hand-manipulation of the vessel as well as direct liquid incubation of the shielded vessel. Hand and finger exposure to radioactivity often occurs during pipeting operations involving hand-held microtubes and other small vessels. Such exposure is encountered in formulating radioactive cocktails for DNA sequencing reactions, conducting immuno precipitation reactions with radio-iodinated reagents, and hand-loading samples into various analytical devices to separate various radioactive molecular species. Manipulations of these sorts are almost impossible to complete without hand and finger contact with the small vessels bearing the radioactive solutions even when proper .beta.-radiation shielding is being utilized. For these operations, the transparent sleeve provides both lateral radiation shielding of the microtube and physical separation between the lid of a microtube and the fingers holding the outer sleeve. This separation minimizes the risk of radioactive contamination to the hand caused by liquid residue on the lid of the microtubes accidentally contacting the gloved hand. Using the sleeves during microtube vortexing and other microtube manipulation steps further reduces radiation exposure of the fingers and the hands. Thus, although narrow columns of radiation are permitted to escape upward and/or downward from the vessels, these columns do not create any great risk of exposure to radiation. On the contrary the shields allow easier manipulation of vessels and thus lower the risk of radioactive spills from the vessels caused by the awkwardness of other types of shielding. Transparent shielding also makes manipulation of the vessels easier since the user need not guess when he is touching the radioactive solution with, for example, a pipetting device. Other features and advantages of the invention will be apprent from the following description of the preferred embodiments, and from the claims. DESCRIPTION OF THE PREFERRED EMBODIMENTS The Figures are first briefly described.