Abstract:
A low cost specimen holder for accurately positioning an animal or other specimen in an imaging machine is constructed from two thin sheets of formed plastic. Each sheet can be formed with a half cavity corresponding to the size and shape of a rodent or other laboratory animal or specimen. To minimize diffraction of imaging beams, one of the sheets can be formed to accommodate the entire specimen, and the other sheet can be substantially planar. The two sheets may be snap-fit or press-fit together to closely hold or encapsulate a specimen with the resulting cavity.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates in general to a low cost preformed retainer for securely holding a specimen in position during any of various imaging procedures including X-ray, CT, MRI and PET. 
   2. Description of Prior Developments 
   Laboratory research animals such as rats, mice and other rodents are commonly scanned and imaged with virtually every type of imaging apparatus available. During imaging, it is important to accurately position a specimen in an imaging field. It is also desirable to be able to repeatably place the same specimen in the same position over varying time periods to monitor various physiological developments in the specimen such as tumor growth and to duplicate and verify previous imaging results. 
   Prior positioning devices have been developed for holding specimens in place during imaging, however these devices are typically complex in structure and quite costly. What is needed is a low cost specimen holder having a simple construction which eliminates many of the complex structures found in prior specimen holders. 
   SUMMARY OF THE INVENTION 
   The present invention has been developed to satisfy the needs noted above. A simple, inexpensive and potentially disposable specimen holder has been designed as a hollow plastic transparent retainer having a shaped recess generally matching the contours and profile of an animal or specimen being imaged. The retainer can be molded from optically clear or optically transparent plastic materials such as polycarbonate. 
   Instead of encapsulating the specimen within a body-shaped cavity, a molded support structure can alternatively be formed on the specimen retainer for anchoring portions of a specimen in a fixed predetermined position. For example, a tooth bar can be shaped on the retainer for positioning the specimen&#39;s head, and contoured complementary holders can be formed to wedge and hold the specimen&#39;s legs and body in a predetermined fixed position. 
   The specimen retainer can include a pair of matched mating plastic moldings which can be snapped, pressed, folded or otherwise secured together so as to sandwich, wedge and/or clamp a specimen between the moldings in a preferred orientation. A gasket can be mounted around the perimeter of the specimen holder to provide a hermetic seal against contamination. It is also possible to form a filter in the shape of a porous perimeter gasket around the junction or interface between the mating halves of the specimen retainer so as to surround the specimen and allow the specimen to breath without contamination to or from the surrounding environment. 
   A further enhancement of the invention includes the incorporation of a connector portion on the specimen retainer. The connector portion communicates with the internal cavity within which the specimen is held. This allows for the passage of anesthesia gasses into and/or out of the cavity, as well as passage of electrical leads for sensors connected to the specimen. 
   In some forms of optical imaging, light must pass freely and without distortion through the specimen holder in order to cause the specimen to glow or fluoresce. In this case, it is desirable for the outer surface of the specimen holder to be planar. This can be achieved with a two-piece specimen holder having one half formed as a planar sheet for uniformly transmitting or passing light and the other half deeply contoured to receive the entire specimen. 
   Pockets can be formed in the specimen holder for receiving sensors such as ECG pads and respiratory sensors known as “pillows”. Grooves or channels can also be formed in the specimen holder for accommodating electrical leads and fluid tubing communicating with the sensors. A living hinge can be formed between the two portions of the mold so as to provide a one-piece molding. This economical one-piece construction can be produced as a single-use disposable retainer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various other objects, features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description when considered in connection with the accompanying drawings, in which like reference characters designate like or corresponding parts through the several views and wherein: 
       FIG. 1  is an exploded perspective view of a first embodiment of the invention; 
       FIG. 2  is an exploded perspective view of a second embodiment of the invention; 
       FIG. 3  is an exploded perspective view of a third embodiment of the invention; 
       FIG. 4  is a top plan view of the upper retainer portion of  FIG. 3 ; 
       FIG. 5  is a bottom perspective view of another embodiment of the invention wherein the bottom or lower retainer is contoured to receive the bottom or lower portion of a specimen; 
       FIG. 6  is an exploded perspective view of a mounting tray for mounting a specimen holder to a connector; 
       FIG. 7  is an enlarged perspective view of the mounting tray of  FIG. 6 ; and 
       FIGS. 8 and 9  are schematic top plan views of one-piece specimen holders formed with plastic hinges and surface coils. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention will now be described in conjunction with the drawings, beginning with  FIG. 1  which shows a first embodiment of a specimen holder  10  having an upper or first shroud or retainer portion  12  and a lower or second shroud or retainer portion  14 . Each retainer portion  12 ,  14  can be formed of an inexpensive plastic sheet material and vacuum formed over a heated mold having a shape resembling each respective portion of a specimen to be retained in holder  10 . The retainer portions  12 ,  14  can alternatively be formed by a stamping operation, injection molding or even using light-activated liquid plastic forming techniques such as SLA and SLS. 
   As further seen in  FIG. 1 , one of the retainer portions  12  is formed with a pocket or recess  16  shaped similar to the upper half portion of a rodent, such as a mouse or rat. The other retainer portion  14  is formed with a pocket or recess  18  shaped similar to the lower half portion of a rodent. While rodent shapes are used as examples in the drawing figures, any desired specimen shape can be formed on portions  12 ,  14 , such as a small monkey or other small animal. Together, the upper and lower retainer portions  12 ,  14 , when properly aligned against one another, define an internal retention cavity  15  having a shape substantially the same as or at least analogous or similar to that of a specimen to be placed therein. 
   The retention portions  12 ,  14  include respective upper and lower head half cavities  20 ,  22 , upper and lower front leg half cavities  24 ,  26 , upper and lower body half cavities  28 ,  30 , upper and lower rear leg half cavities  32 ,  34  and upper and lower tail half cavities  36 ,  38 . In order to properly and accurately align the pockets or recesses  16 ,  18  to form a single matched complementary specimen cavity  15 , keying sockets or holes  39  and keying lower retainer portions  12 ,  14 . Notched edges  41  and/or formed hollow pegs  43  can also be used for aligning the holder  10  in a complementary mounting structure in an imaging bracket or mounting assembly in an imaging machine. 
   That is, when the specimen holder  10  is assembled as an integral unit in which a specimen is tightly secured, encapsulated and clamped between the upper and lower retainer portions  12 ,  14 , the holder  10  may be accurately mounted on an imaging machine by placing the keying holes  39 , and/or optional matching alignment notches  41  and/or pegs  43  on complementary registration features or forms on an imaging machine. Of course, any other type of keying and alignment features may be cut or formed on the specimen holder  10  to engage complementary keying features on an imaging machine or mounting assembly of an imaging machine. 
   The upper and lower retainer portions  12 ,  14  may be further secured and locked tightly together with molded or formed pegs provided on one retainer portion  12 . Enlarged heads on the pegs can be sized to permanently snap fit into matching pockets on the other retainer portion  14 . This arrangement is primarily intended for single use disposable holders wherein the specimen can be permanently encapsulated and discarded within the specimen holder  10  after imaging. Any other type of connection may be used such as tongue and groove or adhesively bonded connections which may surround the internal cavity  15  and the entire periphery of the planar edge portions  42 . 
   If needed, intake breathing and exhale and exhaust ports  48 ,  50  may be formed within a semi cylindrical internal nose cavity or trough  52  leading from the front portion of half portion  12  into the head half cavities  20 ,  22 . Air or anesthesia gas may be admitted or pumped into the head cavities  20 ,  22  through one or more ports  48 ,  50  to provide oxygen and other gasses to the specimen and to extract spent gasses from the head cavities. 
   Another embodiment of the invention is shown in  FIG. 2  wherein the specimen holder  10  does not form an internal cavity  15  shaped substantially in the same form as the intended specimen, but instead is formed with supporting, retaining and positioning structures that limit the movement of the specimen between the retainer portions  12 ,  14 . In this example, a pair of parallel raised hollow sidewalls  60  form or define between them a longitudinal channel  62  which serves as a walled bed within which a specimen may be tightly and accurately wedged. Channel  62  transversely centers and aligns a specimen within the holder  10 . 
   Cutout recesses or openings  64  are formed through opposed sides of each sidewall  60  for snugly receiving the arms and legs of a specimen, thereby accurately fixing the specimen longitudinally within the holder  10 . Additional positioning accuracy can be achieved by forming a small transverse wall or ridge  66  at the front end portion of the lower portion  14 . Ridge  66  serves as a bite bar over which a rodent&#39;s front or incisor teeth may be placed in the manner of a tensioned hook to fix the rodent&#39;s head in a predetermined position. 
   That is, the head of the specimen may be held tightly in place, with its teeth hooked over the bite bar on ridge  66 , by a somewhat semi-conical or wedge-shaped head cavity  68  formed on the upper half portion  12 . This somewhat half-conical cavity  68  pushes or wedges down on the head of the specimen when the two half portions  12 ,  14  are superimposed and connected together. The remainder of the specimen is tightly constrained within the grooved bed (defined by channel  62 ) by a clamping force applied by a shallow upper body arched recess  70  that extends longitudinally rearwardly from cavity  68 . Recess  70  is dimensioned to press against the back and rump of the specimen and hold it tightly within channel  62 , while extending over and around sidewalls  60 . 
   If desired, a circular opening  72  may be molded in the leading end of the lower half portion  14  for receiving a plug-type connector of the type having various gas and electrical connections for treating and monitoring the specimen. A HEPA or other type of filter may also be mounted in opening  72 . Alternatively, or in addition to opening  72 , an arched cavity defining a nose and mouth chamber  52  can be formed in the upper retainer portion  12  adjacent the front end of the holder  10  to receive a filter cartridge and/or a plug-type connector. One or more ports  48 ,  50  can be formed through the front wall  77  of the cavity  52  for receiving fluid flow tubing for administering anesthesia and other gasses to a specimen. Additional tubing can be connected to additional ports for inhalation and exhalation of gas as well as for heating and cooling air for stabilizing a live specimen. Additional ports  79  may be formed through the front wall  77  for electrical wires and leads for sensors and the like which can pass through opening  72  in the lower retainer portion  14 . 
   As further seen in  FIG. 2 , a gasket  74  may be mounted around the entire peripheral edge  42  of either the upper or lower retainer portions  12 ,  14 , (here shown on the lower portion). Gasket  74  may form a hermetic seal between the upper and lower retaining portions  12 ,  14  so as to prevent ambient contamination and internal cavity contamination to or from the specimen. 
   In some cases, the gasket  74  can be formed as a loop-shaped circumferential HEPA filter extending around, between and adjacent to the entire perimeter and interface of the upper and lower retainer portions. Alternatively, a circumferential bead of plastic, rubber or caulk-type material may be applied to one of the portions  12 ,  14  to form a circumferential seal or gasket. A tacky adhesive bead may alternatively be applied in the manner of a pre-gummed self-sealing envelope to form an interface seal when the two portions  12  and  14  are pressed together around a specimen. 
   Another embodiment of the invention is shown in  FIGS. 3 and 4  where the lower portion  14  is simply a flat rectangular sheet and the upper portion  12  is formed with a cavity  15  sufficiently large to tightly accommodate the entire specimen. This embodiment is particularly well suited for optical imaging, wherein uniform light transmission is facilitated by the uniformly thick, smooth, flat, planar lower portion  14 , through which the imaging light is transmitted with minimal or uniform diffraction. 
   As further seen in  FIGS. 3 and 4 , the upper retainer portion  12  is adapted to receive and position various monitoring sensors that can be connected to remote monitors for measuring various physiological parameters of a live rodent or other specimen. 
   For example, a hollow cylindrical electrocardiogram (ECG) pocket  84  over one or both upper rear leg cavities  32  is sized to closely fit and position a standard circular ECG sensor pad. A narrow channel  86  communicates with and extends rearwardly from each pocket  84  to the rear edge  88  of the upper retainer portion  12  for accommodating, positioning and retaining the electrical wires or leads connected to the ECG sensor pads. 
   A somewhat larger channel  90  extends rearwardly from the rump and hip region  80  to the rear edge  88  for accommodating, positioning and retaining a hollow air tube. Such an air tube is typically connected to a respiratory sensor which typically takes the form of a small pillow or bladder positioned against or under the chest of the rodent. As further seen in  FIG. 4 , an electrical lead channel  86  from one of the rear leg ECG pockets  84  can enter the larger channel  90  and exit the upper retainer portion  12  through channel  90 . 
   An additional ECG pocket  84  can be formed over one or both of the upper front leg cavities  24 . An electrical lead channel  86  can extend from this front pocket  84  to a rear ECG pocket  84 , and then run rearwardly to rear edge  88  through channel  90 , as shown. 
   A nose and mouth chamber  73  in the form of a semi cylindrical arch is formed on and openly communicates with the front end of the head cavity  20  for receiving hollow tubing and electrical leads as discussed above. As seen in  FIG. 3 , holes or ports  75 ,  79  are formed through front wall  77  of chamber  73  for the passage of such tubing and/or wires. 
   The upper retainer portion  12  of  FIG. 4  is further formed with an injection port  94  leading through a channel  96  to the base of tail cavity  36 . A hypodermic needle can be inserted through port  94  and channel  96  to administer various injections to a specimen within the specimen holder  10 . 
   One or more hollow, tubular cylindrical sockets  98  are formed in the upper retainer portion  12  for receiving, with a snug sliding press fit, one or more complementary-shaped hollow plugs or pegs  100  provided on the lower retainer portion  14 . Plugs  100  can be formed with chamfered top edges  102  to facilitate insertion into the cylindrical sockets  98 . Because the plug  100  and socket  98  interconnection is typically designed with a tight fit, notches  104  ( FIG. 3 ) are formed in the front  105  and rear  106  peripheral edges of the lower retainer  14 . Notches  104  allow the front edge  107  and rear edge  88  of the upper retainer portion  12  to be grasped and peeled upwardly and somewhat inwardly to separate the plugs  100  from the sockets  98  and thereby gain access to the internal cavity  15  and any specimen positioned within the cavity  15 . 
   While the embodiment of  FIGS. 3 and 4  includes a substantially planar lower retainer portion  14 , the embodiment of  FIG. 5  includes a lower retainer portion  14  formed with a contoured lower cavity  18  for receiving the lower portion of a rodent or other specimen. A cylindrical pocket  108  is formed in the central portion of the lower retainer portion  14  for receiving and positioning a respiratory sensor against the chest of a rodent or other specimen. 
   As seen in  FIG. 6 , a fixture in the form of a slotted tray  112  is provided to slidably and removably receive a complete holder  10  with a slotted or tongue-and-groove interconnection. Tray  112  includes a pair of parallel side rails  114  each having a groove or slot  116  formed therein for tightly receiving the lateral edges  118  of holder  10 . A rear support platform  120  extends between the rear ends of side rails  114  to rigidify the tray  112 . 
   One or more channels  122  are formed in the top surface of platform  120 . Channels  122  extend rearwardly through rear wall  124  which serves, to abut and accurately seat holder  10  within tray  112 . Channels  122  are positioned to communicate with fluid ports formed on a specialized male connector  126 . 
   Various gasses such as warm air can be introduced into the internal cavity  15  of holder  10  via connector  126  and channels  122 . As best seen in  FIG. 7 , a pair of eyelets  128  is formed on opposite sides of an electrical lead wire support trough  130  extending rearwardly from rear wall  124 . Plastic screws or other fasteners can be inserted through eyelets  128  and threaded into the connector  126  to anchor and fix the tray  112  to the connector  126 . Connector  126  is adapted to accurately connect to a positioning assembly in an imaging machine. 
   As seen in  FIGS. 8 and 9 , the two retainer portions  12 ,  14  may be formed integrally and homogenously from a single sheet of plastic in a single mold. A flexible living hinge  132  can be formed between longitudinal end portions  88 ,  134  as shown in  FIG. 8 . This provides for an economical one-piece construction which can be opened and closed in the manner of a clamshell. 
   A similar flexible living hinge  136  as shown in  FIG. 9  can be formed between side edges  138 ,  140  of retainer portions  12 ,  14 . A simple pivoting or folding action along hinge  136  serves to open and close cavity  15 . 
   As further seen in  FIGS. 8 and 9 , one or more surface coils  142  can be carried by one or both of the retainer portions  12 ,  14  on either the interior or exterior surfaces thereof. Surface coils  142  can be located to align over any particular area of the specimen, such as the heart or brain, to increase the clarity of the image produced in that area. The surface coils  142  can be applied as a thin non-ferrous metal foil, such as a copper foil, either individually or in a pattern or array of coils over the retainer  10 . Adhesives can be used to bond the surface coils  142  to the plastic retainer portions  12 ,  14  or virtually any metal deposition technique can be used. 
   For example, thick and thin film deposition can be used, as well as other vapor deposition techniques. Etching techniques such as those used in the fabrication of circuit boards and computer chips can also be used. While the surface coils  142  are shown as annular hoops, such as circles and ovals, virtually any shape of surface coil can be mounted or formed on the retainer portions  12 ,  14 . 
   Because each half portion  12 ,  14  can be molded or otherwise formed from inexpensive plastic materials such as polycarbonate, the specimen holders  10  may, if desired, be economically discarded after use. This eliminates cleaning and decontamination of the holder  10  and reduces the chance of contact and contamination between the specimen and laboratory technicians. The internal cavities  15  may be formed in standard incremental sizes (lengths, widths and heights) in the manner of shoe sizes to nominally fit corresponding sized specimens. 
   There has been disclosed heretofore the best embodiment of the invention presently contemplated. Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.