Patent Number: 048088315
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A container for radioactive samples is generally designated 10 in FIG. 1. Container 10 comprises a laminate type of structure including a carrier 12, spacer 14, window 16, window spacer 18 and a tab 20, see also FIGS. 2 and 3. Carrier 12, also referred to as a carrier member or a carrier layer, is a generally planar, disk-shaped member having a thickness of about 0.014 inches and is preferably formed of a synthetic material such as the plastic film sold under the trademark Mylar. Carrier 12 includes opposed surfaces 22, 24, an outer periphery 26 and has at least one aperture 28 formed therein. For some applications, another aperture 30 is provided. Spacer 14, also referred to as a spacer member, volume spacer and a first spacer layer, is a generally planar, disk-shaped member having a total thickness of about 0.020 inches and may be formed of two layers of laminated, double-sided tape or a single layer of suitable non-porous material. Spacer 14 includes an outer periphery 38 and an inner periphery 40 defining an opening 41 formed therethrough. Opposed surfaces 34, 36 include an adhesive 42 thereon. Surface 34 of spacer 14 is adhered to surface 24 of carrier 12 by adhesive 42. Window 16, also referred to as a window member or a transparent window layer, is a generally disk-shaped member preferably formed of a synthetic material such as the plastic film commonly known as 6C or 12C Mylar sold by the DuPont Company of Wilmington, Del., and is of a thickness sufficient to contain a sample and to permit beta or other low energy radiation to pass therethrough. Window 16 is attached to surface 36 of spacer 14 by adhesive 42. In this manner a cavity 44 is defined by surface 24 of carrier 12, inner periphery 40 of spacer 14 and window 16. Cavity 44 is accessible via aperture 28 of carrier 12. Window 16 therefore functions as a means for retaining a radioactive sample in container 10 and simultaneously for permitting beta and other low energy radiation from the sample to exit therethrough. Window spacer 18, also referred to as spacer means or a second spacer layer, is a generally disk-shaped member having a total thickness of about 0.010 inches and is preferably formed of two laminated layers. One of the layers being a synthetic material such as the plastic film sold under the trademark Mylar and the other layer being the double-sided tape mentioned above which includes adhesive 42. Window spacer 18 includes opposed surfaces 46, 48, an outer periphery 50 and an inner periphery 52 defining an opening 54 formed therethrough. Surface 46 of window spacer 18 is adhered to window 16 and to surface 36 of spacer 14 by adhesive 42. Tab 20 includes an adhesive on a surface 21 thereof for permitting tab 20 to function as a well-known means to be removably attached to surface 22 of carrier 14 for sealing aperture 28, or in some cases to simultaneously seal apertures 28 and 30. A blotter 60, FIG. 4, may be placed in cavity 44. Blotter 60 is generally disk-shaped and sized to fit within cavity 44, and may be formed of a suitable wicking material such as a blotter paper, mesh, or fibrous material. In the embodiment of FIGS. 6 and 6A, blotter 60 is illustrated as having an aperture 62 formed therein. Blotter 60 is preferably any suitable material that exhibits capillary wicking and has some thickness, such as a hydrophilic material. In this manner, samples can be evenly distributed in cavity 44 and spacing is maintained between window 16 and carrier 12. In one embodiment, FIG. 3, a large volume sample container includes carrier 12 which is sufficiently rigid to provide structure. Spacer 14 includes inner periphery 40, determined by the dimensions of an associated detector for measuring radioactivity. Window 16 is chemically compatible with most solvents, thin enough to transmit low energy betas and has low permeability to keep a sample from evaporating during a measurement (which would change the counting efficiency). Carrier 12 is provided with two apertures 28, 30 adjacent periphery 40 of spacer 14 to take advantage of capillary wicking to draw a sample into cavity 44 and to simultaneously allow air to be displaced by a liquid sample. These apertures 28, 30 can be sealed with adhesive backed tab 20 to limit evaporative losses which would change the counting efficiency. Sealing tabs 20 also completely enclose the radioactivity in cavity 44 to limit hazardous handling. The sample volume is determined by the diameter of periphery 40 and the thickness of spacer 14. The diameter is selected to correspond with the associated detector. The thickness of spacer 14 is chosen to make a sample volume of a desired size. In FIG. 4, carrier 12 includes one central sample access aperture 28. Contained inside cavity 44 is blotter 60. The characteristics of blotter 60 are chosen to: a) controllably and uniformly disperse the liquid sample throughout the internal volume of cavity 44; b) to uniformly and controllably space window 16 away from carrier 12; and c) to have as low a density as possible to maximize transmission of the low energy betas while still maintaining features a and b mentioned above. Aperture 28 is sealed by tab 20. If desired, blotter 60 may be adhered to carrier 12 with a light adhesive. Spacers 14, 18 and window 16 are substantially the same as described above. In FIG. 5 a high efficiency dry sample container 10 includes a modified carrier 12 having a greater thickness than in the above-mentioned embodiments. Carrier 12 is further modified in such a way as to maximize the deposition of the low energy isotope containing sample near the central region of the container and to provide an optimum emission solid angle into the detector, see also FIG. 5A. This is accomplished by a modified aperture 28 so as to gradually enlarge via a curved peripheral wall 71 as aperture 28 extends from surface 22 to opposed surface 24 of carrier 12. Thus, radio labelled material deposited on wall 71 of carrier 12 will have a greater exposure to an associated detector than would occur with a straight walled aperture as discussed above. Aperture 28 is sealed by tab 20 adhered to surface 22. Spacer 18 and window 16 are substantially the same as described above. In FIG. 6, a DNA liquid sample container includes carrier 12 having a single aperture 28. However, blotter 60 in cavity 44, is modified to include aperture 62 formed therein coaxially with aperture 28 of carrier 12. DNA or other molecules which strongly bind to blotter 60 will preferentially bind to the edges of central aperture 62 thus minimizing the absorption of the betas by the main body of blotter 60. Aperture 28 is sealed by tab 20. Spacers 14, 18 and window 16 are substantially the same as described above. In the embodiments illustrated herein, a preferred construction includes carrier 12, volume spacer 14, blotter 60, window 16 and window spacer 18 being interconnected so as to have a common centroidal axis designated A. Furthermore, carrier aperture 28, spacer opening 41, blotter aperture 62 and window spacer opening 54 also have the same centroidal axis A as illustrated in the drawing. From the foregoing it can be seen that dimensions of volume spacer 14 function to maintain a space, or cavity 44, between carrier 12 and window 16. In FIGS. 7-10A, it is illustrated that a suitable container 10 can include means other than spacer 14 to provide the desired cavity 44. In FIG. 7 a window 16 is suitably tensioned and adhered directly to surface 24 of carrier 12 in a manner sufficient to define a cavity 44 therebetween. Tab 20 is attached to surface 22 of carrier 12 for sealing aperture 28. Several projections 81, FIGS. 8, 8A, may extend from side 24 of carrier 12. Such projections can be of any suitable structure and only one of which is illustrated as exemplary. Projections 81, in this example, are formed as plurality of radial ribs of ridges which may be formed, such as by injection molding, with carrier 12 or attached thereto. Window 16 extends over projections 81 and is suitably attached to carrier 12. Thus, cavity 44 having uniform thickness, is provided between window 16 and surface 24 of carrier 12. Tab 20 seals aperture 28 on side 22 of carrier 12. Blotter 60, discussed above, may also function to maintain a space between carrier 12 and window 16. As illustrated in FIG. 9, blotter 60 is mounted between carrier 12 and window 16. Attachment of window 16 to carrier 12 defines cavity 44 having blotter 16 mounted therein functioning to provide capillary wicking and as a space maintainer. Tab 20 is provided to seal aperture 28. A further example, FIGS. 10, 10A, illustrates a mesh member 83 mounted between window 16 and carrier 12. A mesh of a suitable size, e.g. well-known window screen, may be utilized for this purpose. Although mesh member 83 of this type does not provide capillary wicking as with blotter 60, it is suitable to provide the desired space between carrier 12 and window 16, defining cavity 44, and assists in providing an even distribution of a liquid sample in cavity 44. Carrier 12, FIGS. 11, 12, may be molded to include a first circumferential raised ring 93 functioning as volume spacer 14 and, alternatively, to include a second circumferential raised ring 95 superimposed, in a stepped manner, on ring 93 to function as window spacer 18. A surface 97 of ring 93 provides a land for adhering window 16 thereto thus defining cavity 44 between surface 24 of carrier 12, inner periphery 40 of ring 93 and window 16. Containers 10 may be conveniently packaged on a suitable carrier tape 87 illustrated in FIGS. 13, 13A. Prior to insertion of a sample, containers 10 and tabs 20 are separately mounted on tape 87, with carrier 12 facing upwardly and spacer 14 or spacers 14, 18 facing downwardly so as to provide a space 89 between carrier 12 and carrier tape 87. Once a sample is placed into container 10, tab 20 is adhered to carrier 12 to seal aperture 28 and container 10 may be mechanically manipulated to another work station such as a detector, a drying operation, or the like, depending on the particular sample. Space 89 provides a convenient gripping point for a mechanical manipulator, e.g. robotic arm, (FIG. 15) to grip container 10 and transfer the same to another work station. An exemplary detector may include the well-known planchette counter 91 such as that diagrammatically illustrated in FIG. 14. An advantage of container 10 is that a liquid sample, being sealed in container 10, may be immediately introduced to the counter 91 since the sealed liquid sample cannot interfere with the sensitive gas volume of planchette counter 91. Another exemplary detector, FIG. 15, may include the currently available bench top radiation detection device 101, wherein sample containers 10 are placed in a sample holder well 103 and positioned on a surface 115 at a fixed distance from a solid state detection element 105. In order to maintain containers 10 centered in well 103, a mechanical manipulator 107, such as that described above for gripping and removing container 10 from tape 87, may include a suitable fixture 109 having a circumferential surface 111 which slips fits into associated surface 113 of well 103. In this manner, containers 10 can be delivered to detection device 101, the samples tested, and the container 10 removed entirely by mechanical manipulation. The present invention eliminates or reduces many problems associated with previously used sample containers. First, the sample containers are very small reducing the amount of radioactive waste which must be disposed. Second, the samples once introduced into the sample containers require no further handling, mixing, or other toxic chemicals in order to be counted. They retain their biological activity and can be recovered for use in further biological experimentation if necessary. Third, these sample containers can be presented to a direct ionization detector and have a sufficiently thin exit window that significant amounts of the radioactive emissions from carbon-14 and sulfur-35 can penetrate out of the sample containers and into the detector. Appropriate ionization detectors include solid state detectors and gas proportional or Geiger counters. The major advantage of the present invention sample containers is that the samples can be sealed inside thereby preventing mechanical contact with the radioactivity, and furthermore that liquid samples as well as dry samples can be accurately counted. With the ability to count liquid samples, drying requirements can be eliminated for faster analysis.