Abstract:
The present disclosure relates to collimator storage devices, exchange devices and carts. According to an aspect of the present disclosure, a collimator change cart for operation with a nuclear camera of a nuclear medicine gantry and a patient handling system is provided and includes a cart assembly; and a collimator drawer assembly supported on the cart assembly. The collimator drawer assembly includes a housing; a plurality of collimator drawers slidably supported in housing, wherein each drawer is supported on a rail provided on opposed sides of said drawer; a damper operatively connected to each drawer; and a drawer locking mechanism movable from a first position in which all the drawers are prevented from sliding out of the housing and a second position in which all of the drawers are free to slide out of the housing. The collimator drawer assembly further includes an anti-tip over feature.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     The present application claims the benefit of and priority to U.S. Provisional Application Ser. No. 60/691,324, filed on Jun. 16, 2005, the entire content of which is incorporated herein by reference. 
     
    
     BACKGROUND  
       [0002]     1. Technical Field  
         [0003]     The present disclosure relates to the field of gamma cameras used in the area of nuclear medicine and, more particularly to collimator storage devices, exchange devices and carts.  
         [0004]     2. Background of Related Art  
         [0005]     Nuclear or scintillation cameras (also called gamma cameras) are responsive to radiation emitted from a radiopharmaceutical injected into a patient during an imaging study. A radiopharmaceutical is typically selected that will target a particular organ or tissue of interest. In computed tomography studies, a detector head (or pair of heads) revolves around the patient and collects the emissions at various angles in order to generate an image of the targeted organ or tissue. In total body studies, the detectors may translate at a fixed or variable altitude along the patient.  
         [0006]     In Emission Computed Tomography (ECT) studies, the image data collected at each angle is merged together into a database that is representative of a three dimensional image of the targeted organ or tissue by a mathematical procedure called reconstruction tomography. A computer process and system perform the image data collection and tomography, and the resultant images may be displayed in a variety of fashions on a computer controlled display screen. Gamma camera detectors are also used in many types of studies that do not employ tomography for image generation, such as total body studies.  
         [0007]     Each detector head of a gamma camera utilizes a collimator placed in front of the detector mechanism to respond to the incident emissions. The collimator is a device for collimating the incident radiation emissions and for filtering out certain types of unwanted radiation emissions. A collimator is typically manufactured from lead material and is composed of an array of parallel tubes and as such resembles a lead “honey comb.” Each individual collimator may weigh from 100 to 250 pounds or more and is mounted on the receiving end of the gamma camera detector to cover the imaging surface. Each collimator must be securely fastened to the detector head during gamma camera studies to prevent collimator separation from the imaging surface as the detector heads revolve or rotate.  
         [0008]     Different collimators have particular characteristics suited to the patient study and the energy of the radiation emissions from the ingested radiopharmaceutical. For instance, some collimators are better suited for gamma studies of a given energy range, a given emission exposure duration, or a given radiophamaceutical.  
         [0009]     Typically, a nuclear camera includes a family of collimators. Relatively thicker collimators with small bores provide higher resolution. Relatively thinner collimators and collimators with larger bores provide higher count rates. Collimators whose bores are angled are used for magnification and reduction imaging. Specialized collimators that focus on two displaced regions of the subject are also used.  
         [0010]     In many instances, the collimators need to be changed depending on the particular procedure being performed and to maintenance purposes. To change the collimators, the operator moves the detector heads to the appropriate collimator changing position. The operator then rolls in a collimator holding cart, which supports the currently installed collimators as they are disconnected. The cart is then used to transport the collimators to a storage location where it is further used to pick-up the proper set of collimators. The appropriate set of collimators on the cart are wheeled up to the detector heads and manually mechanically coupled. This operation typically requires 10-15 minutes of operator time.  
         [0011]     Accordingly, a continuing need exists for carts or carriages for facilitating the removal, replacement and/or exchange of collimators from a nuclear camera and the like.  
       SUMMARY  
       [0012]     The present disclosure relates to collimator storage devices, exchange devices and carts.  
         [0013]     According to an aspect of the present disclosure, a collimator change cart for operation with a nuclear camera of a nuclear medicine gantry and a patient handling system is provided. The collimator change cart includes a cart assembly; and a collimator drawer assembly supported on the cart assembly. The collimator drawer assembly includes a housing, a plurality of collimator drawers slidably supported in housing, wherein each drawer is supported on a rail provided on opposed sides of said drawer; and a damper operatively connected to each drawer. The damper functions to slow extension and retraction of drawers into and out of the housing.  
         [0014]     The collimator drawer assembly may further include a pusher operatively associated with each drawer. The pusher may cause the drawer to extend uniformly from the housing. Each damper may be a hydraulic fluid damper. Each velocity damper may include a first end connected to a respective drawer and a second end connected to the housing.  
         [0015]     The collimator drawer assembly may include a drawer locking mechanism movable from a first position in which all the drawers are prevented from sliding out of the housing and a second position in which all of the drawers are free to slide out of the housing. The drawer locking mechanism may include an actuator bar supporting a plurality of tabs thereon. The actuator bar may be movable between the drawer locking mechanism first position and second position. The tabs may be movable between the drawer locking mechanism first position and second position as the actuator bar is moved between the drawer locking mechanism first position and second position. Each tab may engage a respective drawer when the drawer locking mechanism is in the first position.  
         [0016]     The drawer locking mechanism may include a lock plunger extending from a bottom of the housing. The lock plunger may be actuatable to move the drawer locking mechanism between the first and second positions. The lock plunger may engage a lock receptacle on the patient handling system and may inhibit tipping of the collimator change cart when the collimator change cart is docked.  
         [0017]     The collimator change cart may further include an anti-tip over feature supported on the patient handling system and configured to engage the cart assembly when the collimator change cart is docked. The anti-tip over feature may include a channeled rail supported on the patient handling system and configured and dimensioned to selectively receive at least a portion of the cart assembly therein. The anti-tip over feature may further include a plunger extending from a bottom surface of the housing of the collimator change cart. The plunger may operatively engage a pallet of the patient handling system when the pallet is in a raised position.  
         [0018]     The collimator change cart may further include a drawer locking mechanism movable from a first position in which all the drawers are prevented from sliding out of the housing and a second position in which all of the drawers are free to slide out of the housing. The drawer locking mechanism may include an actuator bar supporting a plurality of tabs thereon, wherein the actuator bar may be movable between the drawer locking mechanism first position and second position. The plunger may be connected to the drawer locking mechanism such that the plunger may be actuatable to move the drawer locking mechanism between the first and second positions.  
         [0019]     The cart assembly may include a pair of spaced apart lower rails supports on casters. The cart assembly may further include an upper platform cantilevered with respect to an upright extending from the lower rails.  
         [0020]     According to another aspect of the present disclosure, a collimator change cart for operation with a nuclear camera of a nuclear medicine gantry and a patient handling system is provided. The collimator change cart includes a cart assembly; and a collimator drawer assembly supported on the cart assembly. The collimator drawer assembly includes a housing; a plurality of collimator drawers slidably supported in housing, wherein each drawer is supported on a rail provided on opposed sides of said drawer; a damper operatively connected to each drawer, wherein the damper slows extension and retraction of drawers into and out of the housing; and a drawer locking mechanism movable from a first position in which all the drawers are prevented from sliding out of the housing and a second position in which all of the drawers are free to slide out of the housing. The collimator change cart further includes an anti-tip over feature supported on the patient handling system and configured to engage the cart assembly when the collimator change cart is in an operative position relative to the nuclear medicine gantry and the patient handling system. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]     The invention may take physical form in certain parts and arrangements of parts, a preferred embodiment of which will be described in detail herein and illustrated in the accompanying drawings which form a part hereof and wherein:  
         [0022]      FIG. 1  is a schematic, perspective view of a collimator change cart of the present disclosure as used with a nuclear medicine gantry and a patient handling system;  
         [0023]      FIG. 2  is an enlarged perspective view of the collimator change cart of  FIG. 1 , illustrating the collimator change cart in a first condition;  
         [0024]      FIG. 3  is an enlarged view of the collimator change cart of  FIG. 2 , illustrating the collimator change cart in a second condition;  
         [0025]      FIG. 4  is a further enlarged view of the indicated area of detail of  FIG. 3 , illustrating a drawer pusher assembly of the collimator change cart of  FIGS. 1-3 ;  
         [0026]      FIG. 4A  is a perspective view of the drawer pusher assembly of  FIG. 4 ;  
         [0027]      FIG. 4B  is an elevational view of the drawer pusher assembly of  FIG. 4A ;  
         [0028]      FIG. 4C  is a cross-sectional view of the drawer pusher assembly of  FIG. 4B , as taken through  4 C- 4 C thereof;  
         [0029]      FIG. 5  is an enlarged, perspective view of the indicated area of detail of  FIG. 3 , illustrating an end of a velocity damper of the collimator change cart of  FIGS. 1-3 ;  
         [0030]      FIG. 6  is a rear view of a collimator drawer assembly of the collimator change cart of  FIGS. 1-3 ;  
         [0031]      FIG. 7  is a partial perspective view of the nuclear medicine gantry operatively engaged with a lock plunger of the collimator change cart of  FIGS. 1-3 ;  
         [0032]      FIG. 8  is a partial perspective view of collimator drawer assembly of the collimator change cart of  FIGS. 1-3 , illustrating a drawer thereof and a corresponding velocity damper thereof in an extended condition;  
         [0033]      FIG. 9  is a partial perspective view of a locking mechanism of the collimator chance cart of  FIGS. 1-3 , shown in an unlocked position;  
         [0034]      FIG. 10  is a partial perspective view of a drawer locking assembly of the collimator change cart of  FIGS. 1-3 ;  
         [0035]      FIG. 11  is an enlarged perspective view of a collimator change cart alignment guide operatively associated with the nuclear medicine gantry and the patient handling system;  
         [0036]      FIG. 12  is a partial perspective view of the nuclear medicine gantry and patient handling system of  FIG. 1 , shown in a “home” position;  
         [0037]      FIG. 13  is a partial perspective view of the nuclear medicine gantry and patient handling system of  FIGS. 1 and 12 , illustrating a relative positioning of the collimator change cart of  FIGS. 1-3  thereto prior to docking therewith;  
         [0038]      FIG. 14  is a further partial perspective view of the nuclear medicine gantry and patient handling system of  FIGS. 1 and 12 , illustrating a relative positioning of the collimator change cart of  FIGS. 1-3  thereto prior to docking therewith;  
         [0039]      FIG. 15  is a partial perspective view of the nuclear medicine gantry and patient handling system of  FIGS. 1 and 12 , illustrating a relative positioning of the collimator chance cart of  FIGS. 1-3  thereto following docking therewith;  
         [0040]      FIG. 16  is a perspective view of the patient handling system of  FIGS. 1 and 12 , illustrating the collimator change cart of  FIGS. 1-3  docket therewith and a collimator change drawer thereof extended over the nuclear camera of the nuclear medicine gantry of  FIGS. 1 and 12 ;  
         [0041]      FIG. 17  is an enlarged, perspective view of the indicated area of detail of  FIG. 16 , illustrating the anti-tip over feature of the present disclosure;  
         [0042]      FIG. 18  is an enlarged, perspective view of the indicated area of detail of  FIG. 16 , illustrating the collimator change drawer of the collimator change cart of  FIGS. 1-3  extended over the nuclear camera;  
         [0043]      FIG. 19  is an elevational view of the collimator change cart of  FIGS. 1-3  docket with the patient handling system;  
         [0044]      FIG. 20  is an enlarged view of the indicated area of detail of  FIG. 19 ;  
         [0045]      FIG. 21  is a perspective view of the collimator change cart of  FIGS. 1-3  docket with the patient handling system;  
         [0046]      FIG. 22  is an enlarged view of the indicated area of detail of  FIG. 21 ;  
         [0047]      FIG. 23  is an enlarged view of the indicated area of detail of  FIG. 21 ;  
         [0048]      FIG. 24  is a side, elevational view of the collimator change cart of  FIGS. 1-3  docket with the patient handling system;  
         [0049]      FIG. 25  is an enlarged view of the indicated area of detail of  FIG. 24 ; and  
         [0050]      FIG. 26  is an enlarged view of the indicated area of detail of  FIG. 24 . 
     
    
     DETAILED DESCRIPTION OF EMBODIMENTS  
       [0051]     The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the preferred embodiments will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. Thus, the present invention is not intended to be limited to the embodiment shown but is to be accorded the widest scope consistent with the principles and features described herein.  
         [0052]     Referring now to the drawings, and first to  FIG. 1 , a nuclear medicine gantry  100  and patient handling system  200  are shown. Nuclear medicine gantry  100  includes a ring  102  operatively connected to and supported on a stand  104 . Nuclear medicine gantry  100  further includes a first nuclear camera  110  and a second nuclear camera  112 , each, operatively associated with and/or mounted to ring  102 .  
         [0053]     Patient handling system  200  includes a lower frame  202  supported on floor “F”, a lift mechanism  204  operatively supported on lower frame  202 , an upper frame  206  operatively supported on lift mechanism  204  and a pallet  208  translatably supported on upper frame  206 . Patient handling system  200  may be oriented such that pallet  208  is translatable in directions parallel to a central axis of ring  102 . Lift mechanism  204  (e.g., parallelogram style, scissors style, etc.) provides the up and down motion of upper frame  206  and pallet  208  for patient loading and positioning.  
         [0054]     As seen in  FIG. 1 , nuclear medicine gantry  100  and patient handling system  200  can accommodate use of a collimator change cart  300 . With reference to  FIGS. 2-6 , Collimator change cart  300  includes a cart assembly  310  supporting a collimator drawer assembly  320  housing and/or storing a plurality of collimators  132  therein. Cart assembly  310  includes a pair of spaced apart lower rails  312   a ,  312   b  supported on casters  314  or the like and an upper platform  316  connected to lower rails  312   a ,  312   b  by a pair of uprights  318 . Upper platform  316  is cantilevered with respect to uprights  318  and is configured and adapted to support collimator drawer assembly  320  thereon.  
         [0055]     As seen in  FIGS. 2-6 , collimator drawer assembly  320  includes a housing  322  having at least a pair of spaced apart side walls  322   a ,  322   b , and optionally a top wall  322   c . In one embodiment, the pair of spaced apart side walls  322   a ,  322   b  are oriented orthogonal to lower rails  312   a ,  312   b  of cart  310 . Collimator drawer assembly  320  is configured and adapted to support at least one drawer  330  thereon, between side walls  322   a ,  322   b . Each drawer  330  is slidably mounted within housing  322  and has a fist position fully retracted within housing  322  and a second position extending from housing  322  in a cantilevered manner. Collimator drawer assembly  320  may be configured to support any number of drawers  330  therein.  
         [0056]     Each drawer  330  may be operatively connected to rails  332  supported on side walls  322   a ,  322   b . Each rail  332  may consist of a linear rail system having a first component thereof supported on a side wall and a second component thereof supported on the drawer, wherein the first and second components of the linear rail system are slidably supported relative to one another. Each drawer  330  is configured to support a collimator  132  (see  FIG. 1 ) thereon. It is contemplated that each drawer  330  may support a different collimator thereon as compared to the other drawers.  
         [0057]     As seen in  FIGS. 3, 5 ,  6 ,  8 ,  9 ,  14 ,  15 ,  22  and  23 , collimator drawer assembly  320  includes a velocity damper  334  connected to each drawer  330 . Velocity damper  334  may be a hydraulic fluid damper including a first end connected to a drawer  330  and a second end connected to housing  322 , wherein the first end and the second end of each damper  334  is fluidly connected to one another. In this manner, as drawer  330  is pulled from housing  322 , damper  334  functions to maintain exert a consistent damping force on drawer  330  to prevent drawer  330  from opening and/or closing too quickly.  
         [0058]     As seen in FIGS.  3 ,  4 - 4 C and  23 , collimator drawer assembly  320  further includes a drawer pusher assembly  336  operatively associated with each drawer  330  and with each respective rail  332  thereof (i.e., the right-side rail and the left side rail). Drawer pusher assembly  336  functions to move drawer  330  out from housing  322  in a uniform manner with respect to the pair of juxtaposed rails  332 . In other words, since right-side and left-side rails  332  are independent of one another, drawer pusher assembly  336  functions to move right-side and left-side rails  332  in unison with one another to ensure that drawer  330  is withdrawn uniformly from housing  322 .  
         [0059]     As seen in  FIGS. 4A-4C , drawer pusher assembly  336  includes block pusher  336   a  connected to a portion of rail  332  connected to drawer  330 . Drawer pusher assembly  336  further includes a pusher arm  336   c  pivotally connected to block pusher  336   a  via a pivot shaft  336   d . Drawer pusher assembly  336  includes a biasing member  336   e  supported on pivot shaft  336   d  and operative engaged with block pusher  336   a  and pusher arm  336   c.    
         [0060]     In operation, when drawer  330  is fully retained within housing  322 , pusher arm  336   c  is in an upright condition, as seen in  FIGS. 4A-4C  and biasing member  336   e  is in a biased condition. As drawer  330  is withdrawn from housing  322 , pusher arm  336   c  is pivoted about pivot shaft  336   d  by the spring force and the unwinding of biasing member  336   e . As pusher arm  336   c  is pivoted about pivot shaft  336   d , block pusher  336   a  moves the portion of rail  332  attached to drawer  330  to facilitate withdrawal of drawer  330  from housing  322  and ensure uniform simultaneous extension of the right-side and left-side rails.  
         [0061]     In particular, in one embodiment, a pair of through-bores  336   f  are formed through block pusher  336   a  for slidably receiving a pair of shafts or guides  337  therethrough. Accordingly, as pusher arm  336   c  is pivoted about pivot shaft  336   d , block pusher  336   a  is moved axially along the pair of shafts or guides.  
         [0062]     As seen in  FIGS. 6, 7  and  9 , collimator drawer assembly  320  includes a drawer locking mechanism  340 . Drawer locking mechanism  340  includes a respective locking tab  342   a - 342   c  for each drawer  330 . Drawer locking mechanism  340  is movable between a first position in which locking tabs  342   a - 342   c  are engaged with a respective aperture  343  formed in drawer  330  and a second position in which locking tabs  342   a - 342   c  are disengaged from a respective drawer  330 . Locking tabs  342   a - 342   c  are supported on an actuator bar  344  and are capable of moving simultaneously. Drawer locking mechanism  340  further includes a lock plunger  346  operatively connected to actuator bar  344  and extending beneath housing  322 , and preferably, platform  316 . Drawer locking mechanism  340  may be biased to the first position by a spring member  345 .  
         [0063]     In operation, as will be discussed in greater detail below, lock plunger  346  includes an extended position wherein drawer locking mechanism  340  is in the first position and locking tabs  342   a - 342   c  are in operative locking engagement in respective apertures  343  of drawers  330 , and a retracted position, as seen in  FIG. 9 , wherein drawer locking mechanism  340  is in the second position and locking tabs  342   a - 342   c  are out of operative locking engagement with respective apertures  343  of drawers  330 .  
         [0064]     As seen in  FIG. 10 , collimator drawer assembly  320  further includes a drawer lock  350  operatively associated with each drawer  330 . Each drawer lock  350  includes a handle  352  supported on each drawer  330   a - 330   d  and a resilient tab  354  extending from each handle  352  and snap-fit engaging a side wall  322 ,  322   b  of housing  322  when drawers  330  are in a fully closed position. In operation, in order to release a drawer  330 , resilient tab  354  is deflected away from a corresponding tab (not shown) on housing  322  and handle  352  is used to pull said drawer  330  from housing  322 .  
         [0065]     As seen in  FIGS. 6, 7 ,  11  and  14 - 17 , collimator change cart  300  includes an anti-tip over element  360  which is secured to the floor, nuclear medicine gantry  100  or patient handling system  200 . In the present embodiment, anti-tip over element  360  includes a channeled rail  362 , or the functional equivalent thereof operatively connected to patient handling system  200 , at a location in close proximity to the floor. Channeled rail  362  is configured and dimensioned such that at least one of lower rails  312   a ,  312   b  of cart assembly  310  is introducible therein. In operation, when a lower rail  312   a ,  312   b  of cart assembly  310  is operatively inserted into channeled rail  362 , channeled rail  362  functions to anchor lower rail  312   a  or  312   b  of cart assembly  310  to the ground and thus functions to inhibit and/or prevent cart assembly  310  from tipping over during use and/or operation of collimator change cart  300 .  
         [0066]     Turning now to  FIGS. 12-26 , a method of using collimator change cart  300  to change and/or replace a collimator of nuclear camera  112  of nuclear medicine gantry  100  is described. Typically, as seen in  FIG. 12 , pallet  208  is lowered relative to nuclear medicine gantry  100  to a collimator change position. As seen throughout  FIGS. 12-26 , with pallet  208  in the collimator change position, collimator change cart  300  is moved into a collimator change or docked position wherein one of lower rails  312   a ,  312   b  of cart assembly  310  is aligned with and introduced into channeled rail  362  of anti-tip over element  360 . When collimator change cart  300  is in the docked position with respect to patient handling system  200  and nuclear medicine gantry  100 , collimator drawer assembly  320  is oriented such that drawers  330  thereof are extendable over nuclear camera  112 .  
         [0067]     In order to ensure that collimator change cart  300  is in the docked position, as seen in  FIG. 11 , a sensor pad  260  may be secured to floor “F” at a known location relative to patient handling system  200  and nuclear medicine gantry  100 . In this manner, collimator change cart  300  is configured and dimensioned such that when collimator change cart  300  is properly docked, a caster  314  thereof operatively engages sensor pad  260  (i.e., an optical sensor, a pressure sensor, etc.), as shown in  FIGS. 16 and 21 .  
         [0068]     With collimator change cart  300  in the docked position, with respect to patient handling system  200  and nuclear medicine gantry  100 , as seen in  FIGS. 6 and 7 , lock plunger  346  of drawer locking mechanism  340  is aligned with a lock receptacle  246  provided on pallet  208  of patient handling system  200 . With collimator change cart  300  in the docked position, pallet  208  of patient handling system  200  is raised until lock receptacle  246  thereof engages lock plunger  346  of drawer locking mechanism  340  and forces lock plunger  346  in an upward direction to the retracted position. In so doing, locking tabs  342   a - 342   c  of drawer locking mechanism  340  are moved out of locking engagement with respect to drawers  330 , as shown in  FIG. 9  and as discussed above. Additionally, lock receptacle  246  captures lock plunger  346  therein and thus further fixes collimator change cart  300  in the docked position.  
         [0069]     With collimator change cart  300  in a fixed docked position, nuclear camera  112  is moved from its “home” position (i.e., a fully lowered position), upwardly until a detector  112   a  of nuclear camera  112  detects a “home flag”  370  (i.e., a sensor, an optical recognition symbol, etc.) provided on collimator change cart  300 , see  FIG. 25 . In one method, once the “home flag”  370  is located, the desired drawer  330  is opened to a fully extended position and switches (not shown) located on the clamp arms (not shown) are closed, as seen in  FIG. 26 . {Please indicate where the clamp arms are located in the drawings}. The closing of the switches located on the clamp arms indicates to a central processor which of drawers  330  has been opened and the additional distance required for nuclear camera  112  to move in order to be in a proper collimator change position/location. As such, nuclear camera  112  is further raised or moved upwardly said known distance until nuclear camera  112  is in the proper collimator change or release position. When nuclear camera  112  is in the proper collimator change or release position, collimator  132  is lifted off of drawer  330  and drawer  330  is free to be retracted into housing  322 .  
         [0070]     In another method, once the “home flag”  370  is located, the distance to the desired drawer  330  is known and as such, nuclear camera  112  may be further raised or moved to the location of said drawer  330 .  
         [0071]     In one embodiment, it is envisioned that when nuclear camera  112  is moved to the desired position, as seen in  FIG. 19 , the drawer lock  350  may be automatically actuated to unlock a respective one of drawers  330   a - 330   d  and allow for the respective one of drawers  330   a - 330   d  to be opened. As seen in  FIGS. 17 and 20 , with drawer lock  350  of a respective one of drawers  330   a - 330   d  unlocked, the respective one of drawers  330   a - 330   d  is withdrawn from housing  322  of collimator drawer assembly  320  to overlie nuclear camera  112 .  
         [0072]     As discussed above, drawer pusher assembly  336  ensures that the respective one of drawers  330  is withdrawn from housing  322  of collimator drawer assembly  320  in a uniform manner, and damper  334  ensures that the respective one of drawers  330  is not withdrawn from housing  322  of collimator drawer assembly  320  too quickly.  
         [0073]     With the respective one of drawers  330  extended over nuclear camera  112 , the collimator of nuclear camera  112  may be removed, a collimator may be attached to nuclear camera  112  and/or the collimator of nuclear camera  111  may be replaced as needed and/or desired.  
         [0074]     Once the collimator has been removed from nuclear camera  112 , attached to nuclear camera  112  and/or replaced, the respective one of the drawers  330  is retracted into housing  322  of collimator drawer assembly  320 , nuclear camera  112  is lowered to the “home” position and pallet  208  of patient handling system  200  is also lowered. When pallet  208  is lowered, lock receptacle  246  disengages lock plunger  346  of drawer locking mechanism  340  which returns to an extended condition and which moves locking tabs  342   a - 342   c  of drawer locking mechanism  340  into locking engagement with respect to drawers  330 . With lock plunger  346  disengaged from lock receptacle  246 , collimator change cart  300  is free to be moved out of operative engagement with nuclear medicine gantry  100  and patient handling system  200 .  
         [0075]     Although the present invention has been described in accordance with the embodiments shown, one of ordinary skill in the art will readily recognize that there could be variations to the embodiment and these variations would be within the spirit and scope of the present invention. Accordingly, many modifications may be made by one of ordinary skill in the art without departing from the spirit and scope of the appended claims.