Abstract:
Apparatus and method for simulating tracer interaction with living tissue. A chamber receives a fluid therein, and includes an inlet conduit for conducting the fluid into the chamber, an outlet conduit for conducting the fluid out of the chamber, a medium disposed within the chamber for modulating fluid flow, and a valve assembly for conducting the fluid into the inlet conduit. In some aspects, the fluid is a radiative tracer or a radiative washout fluid and the medium is configured to mimic a tissue, e.g., the heart, and portions thereof are capable of mimicking both normal and diseased tissues.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to nuclear imaging devices, and more particularly, to phantoms for use therewith for purposes of simulating anatomical conditions. 
       BACKGROUND OF THE INVENTION 
       [0002]    Nuclear medicine is a unique medical specialty wherein radiation is used to acquire images which show the function and anatomy of organs, bones or tissues of the body. Generally, low-level radiopharmaceuticals are ingested or injected into the body and carried to the specific organs, bones or tissues. Gamma photon emitted by the radiopharmaceuticals are then captured by a gamma camera of the imaging device and used to prepare images of the target. In this way, specific organs, bones or tissues and/or functions thereof can be studied with minimal impact upon the patient or subject being studied. 
         [0003]    In order to prepare images, however, it is necessary to calibrate and ensure the accuracy and proper working order of the nuclear imaging device to be used. This is commonly performed by the use of calibration instruments, known as phantoms. Generally, phantoms are structures having known parameters, which can include, but are not limited to, specific dimensions and/or radiation levels. Accordingly, an image of a phantom produced by a nuclear imaging device can be compared with the actual phantom to determine, for example, image quality, background radiation levels, attenuation information, etc. 
         [0004]    In addition to their use as calibration devices, phantoms can also be used for other purposes such as, for example, simulating anatomical conditions for purposes of training individuals to properly use a medical imaging device and/or for training individuals how to read images and/or render diagnoses from the images produced by a medical imaging device. Accordingly, there are various types of phantom and the particular phantom to be used in a simulation depends on a number of factors, which include but are not limited to: specific anatomical area to be studied, e.g., heart, lungs, etc., specific anatomical condition/anomaly to be studied, e.g., normal vs. diseased tissue, etc., and environment, e.g., calibration vs. training. Indeed, phantoms currently range from mere computer software programs, to simple cylindrical devices primarily used for calibration purposes, to more complex mechanical devices that can include pumping mechanisms for mimicking moving body parts, e.g., the human heart. 
         [0005]    While there are known several types of phantom for simulating anatomical conditions, one mechanical-type is described in U.S. Pat. App. Pub. No. 2003/0220718 A1, which published application is incorporated herein by reference in its entirety. The phantom disclosed in that application generally relates to a dynamic cardiac phantom for simulating the beating of a human heart and includes inner and outer elastomeric members defining a void therebetween; the void is intended to mimic the myocardium of the human heart and is capable of being filled with a radiative tracer. The dynamic cardiac phantom, thus, can be used to simulate and image the systolic and diastolic functions of the human heart. Another dynamic cardiac phantom is disclosed in U.S. Pat. App. Pub. No. 2003/0045803 A1 which published application is also incorporated herein by reference in its entirety. 
         [0006]    While the dynamic cardiac phantoms described in U.S. Pat. App. Pub. Nos. 2003/0220718 A1 and 2003/0045803 A1 may be useful for accomplishing their intended purposes, it is also desirable to simulate other anatomical functions and/or characteristics of organs, tissues or bones. For example, because diseased or abnormal tissue can tend to more rapidly “wash-in” or more rapidly “wash-out” certain tracers when compared with normal, non-diseased tissue, it can be desirable to monitor tracer wash-in and wash-out for diagnostic purposes. Accordingly, it is also desirable to simulate wash-in and wash-out. 
         [0007]    What is needed then is a phantom that is capable of simulating tracer wash-in and washout, e.g., radiative tracer, uptake, residence, and/or processing by organs, tissues or bones. 
       SUMMARY OF THE INVENTION 
       [0008]    An apparatus for simulating tracer interaction with a tissue generally comprises a chamber for receiving a fluid therein, an inlet conduit for conducting the fluid into the chamber, an outlet conduit for conducting the fluid out of the chamber, a medium disposed within the chamber for modulating fluid flow, and a valve assembly for conducting the fluid into the inlet conduit. In some aspects, the fluid is a radiative tracer or a radiative washout fluid and the medium is configured to mimic a tissue, e.g., the heart, and portions thereof are capable of mimicking both normal and diseased tissues. 
         [0009]    In some aspects the medium comprises an aggregate-type material and has an attenuation characteristic similar to that of water. In some aspects, the medium comprises Lucite, which can be granular or beaded form. In some aspects, the chamber includes a distribution assembly for uniformly distributing fluid into the chamber. In some aspects, the chamber includes an inner chamber wall and an outer chamber wall, and the inner chamber wall and the outer chamber wall are disposed relative to one another to thereby form a chamber conduit therebetween. 
         [0010]    In some aspects the chamber conduit fluidly connects to the inlet conduit and the outlet conduit, the inner chamber wall includes a plurality of apertures for conducting the fluid to the medium, and the medium is disposed in the chamber conduit. In other aspects, the medium is disposed inward of said inner chamber wall. In some aspects, chamber comprises an expandable chamber wall, for example, for mimicking organs such as the human heart. 
         [0011]    A method for simulating radiative tracer interaction with a tissue generally comprises issuing a first fluid into a chamber comprising a medium via of a valve connected to an input conduit, bathing the medium with the first fluid and allowing the first fluid to exit the chamber via an outlet conduit, monitoring the chamber with a medical imaging device, e.g. to monitor the uptake of a radiative tracer by the medium, issuing a second fluid, e.g. a radiative wash, into the chamber via the input conduit, bathing the medium with the second fluid and allowing the second fluid to exit the chamber, and monitoring the chamber with the medical imaging device, e.g. to monitor egress of the radiative tracer from the medium. 
         [0012]    In some aspects of the method, the medium has an attenuation characteristic substantially similar to water and/or comprises an aggregate-type material, which can be beads, or Lucite beads. In some aspects of the method, the medium is disposed within the chamber, which can comprise inner and outer chamber walls thereby forming a chamber conduit. In some aspects of the method, the medium is disposed within the chamber conduit, which can be fluidly connected to the inlet an inlet and outlet conduit of the chamber. In some aspects of the method, the chamber can comprise an expandable chamber wall. 
         [0013]    These and other aspects, features and advantages of the present invention will become readily apparent to those having ordinary skill in the art upon a reading of the following detailed description of the invention in view of the drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The invention will now be more fully described by way of example with reference to the accompanying drawings in which: 
           [0015]      FIG. 1  is a perspective view of a known dynamic cardiac phantom; 
           [0016]      FIG. 2  is a schematic illustration of a flow drive for a dynamic phantom according to the invention; 
           [0017]      FIG. 3  is a schematic illustration of a phantom according to the invention; 
           [0018]      FIG. 4  is a schematic illustration of a phantom according to the invention; 
           [0019]      FIG. 5  is a schematic illustration of another phantom according to the invention; 
           [0020]      FIG. 6  is a schematic illustration of a dynamic cardiac phantom according to the invention; and, 
           [0021]      FIG. 7   a  and  7   b  are schematic illustrations of the dynamic phantom of  FIG. 5  in collapsed and expanded configurations, respectively. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    The present invention will now be described and disclosed in further detail. It is to be understood, however, that the disclosed embodiments are merely exemplary of the invention and that the invention may be embodied in various and alternative forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting the scope of the claims, but are merely provided as an example to teach one having ordinary skill in the art to make and use the invention. Also, it should be appreciated that, in the detailed description of the invention that follows, like reference numbers on different drawing views are intended to identify like structural elements, and/or functionally equivalent elements, of the invention in the respective views. 
         [0023]    Referring now to  FIG. 1 , which is a view of a known dynamic cardiac phantom as described in U.S. Pat. App. Pub. No. 2003/0220718 A1, known dynamic cardiac phantom  10  includes elastomeric heart portion  12  formed from a first, outer elastomeric sleeve  14  and a second, inner elastomeric sleeve  16 . First outer elastomeric sleeve  14  and second inner elastomeric sleeve  16  are separated from one another by void  18 , which is intended to simulate the myocardium of the human heart. Valve assembly  20  is provided for introducing a radiative fluid into void  18  such that the simulated myocardium can be imaged using a nuclear imaging device when the phantom is operated, for example, contracted and/or expanded to simulate systolic and diastolic functions of a human heart. As may be appreciated from  FIG. 1 , dynamic cardiac phantom  10  is not configured for first introducing a flow in and out of the myocardial void so as to simulate/monitor tracer wash-in and wash-out. 
         [0024]    Referring now to  FIG. 2 , which illustrates an example of a flow drive  100  for a dynamic phantom according to an example embodiment of the invention, flow drive  100  broadly comprises phantom chamber  102 , medium  104 , one or more valve assemblies  106 , one or more pump assemblies  108 , one or more fluid reservoirs  110 , conduits  112 , and system controller  114 . 
         [0025]    In the embodiment illustrated in  FIG. 2 , phantom chamber  102 , which is shown as comprising a hollow sphere, is essentially fluid tight, except for inlet  116  and outlet  118 , which connect to inlet conduit  112   a , and outlet conduit  112   b  respectively. Phantom chamber  102  is configured for receiving medium  104  therein, which in the illustrated embodiment can comprises Lucite® beads or other granulated-type flowing material for substantially filling the volume of the phantom chamber. Accordingly, phantom chamber  104  can be configured to be openable and sealably closable for purposes of filling the volume thereof with a medium. Phantom chamber  102  and is also illustrated as being communicatively connected to system controller  114 , which can comprise a programmable computer and software therefor for controlling/monitoring the phantom. It should be appreciated by those having skill in the art that while phantom chamber  102  is illustrated as comprising a hollow spherical shape, as discussed hereinafter the phantom chamber can comprise a number of shapes and configurations. Similarly, while phantom chamber  102  is preferably formed from Lucite®, or other material having an attenuation substantially equivalent to that of water, materials other than Lucite® can be used, e.g., elastomeric materials. 
         [0026]    Medium  104  is generally provided for modulating flow through the phantom chamber by creating a tortuous path therethrough, which tends to hinder fluid flow through the chamber to thereby simulate tracer uptake. Medium  104  can further be configured for binding/releasing tracer constituents in, for example, the manner of ion attraction/exchange mechanisms, protein receptor/binder type mechanisms, etc. Depending upon the simulation to be performed, the size of beads and/or granular-type material can range from between &lt;1 mm-10 mm. Additionally, as shown in  FIG. 3 , medium  104  can be configured to simulate a “diseased” tissue portion, which can comprise a phantom sub-chamber for receiving a different tracer, tracer with a different concentration, or another medium having a different affinity for the tracer being used. In some embodiments, one or more of chamber  102  or medium  104 , can be configured to include assemblies such as screen members, to prevent the egress of medium  104  from the chamber. In some embodiments, medium  104  can comprise gels or cellular-type material, e.g. sponge-like material. 
         [0027]    Inlet  116  is fluidly connected to inlet conduit  112   a  and outlet  120  is fluidly connected to outlet conduit  112   b  . In the illustrated embodiment, inlet conduit  112   a  can be fluidly connected to one or more fluid reservoirs  110   a - c  via valve  106   a  and/or a pump  108   a  for pumping fluid into the phantom chamber. 
         [0028]    Outlet  120  is connected to outlet conduit  112   b  , which can be connected to valve assembly  106   b  for directing an outlet fluid to waste reservoir  110   d  or recycling an outlet fluid back to one of fluid reservoirs  110   a ,  110   b  and  110   c . In the illustrated embodiment, outlet conduit  112  is fluidly connected to pump  108   b  for purposes of drawing fluid through the phantom chamber. 
         [0029]    Valve assembly  106   a  is provided for dispensing fluid from one of fluid reservoirs  110   a - c  into inlet conduit  112   a  for purposes of being delivered to the phantom chamber by one or more of pumps  108   a,b . Alternatively, fluids can be delivered to phantom chamber  102  by manual means, for example, injection thereof with a syringe through a conduit. The advantage, however, of delivering fluids via valves  106  and pumps  108   a,b  is that each of valve  106   a,b  and pumps  108   a,b  can be controlled by system controller  114  to dispense/deliver fluids  110   a - c  as may be desired and from a remote location. Similarly, valve  106   b  is provided for directing fluid having passed through the phantom chamber to one of waste reservoir  110   d  or back to one of reservoirs  110   a - c . Valve  106   b  can also be controlled via controller system  114 . 
         [0030]    Reservoirs  110   a - d  are provided for storing fluid for delivery to the phantom chamber. Generally, one each of fluid reservoirs  110   a - c  can contain one of a neutral fluid (water) ( 110   a ), a radiative tracer ( 110   b ), and a radiative tracer wash ( 110   c ), e.g. Radiac Wash™, for purposes of neutralizing/removing the radiative tracer from the phantom chamber and medium. 
         [0031]    System controller  114  is generally provided for directing fluid flow into and out of the phantom chamber  102  and comprises a programmable computer and software therefor for controlling the opening and closing valves  106   a, b  and pumps  108   b . System controller  114  can also be configured for controlling/monitoring contraction/expansion of a dynamic cardiac phantom of the type disclosed in U.S. Pat. App. Pub. No. 2003/0220718 A1. 
         [0032]    Accordingly, flow drive for a dynamic phantom  100  can be used in the following manner for simulating tissue uptake: phantom chamber  102  is filled with medium  104  and connected to inlet  116  and outlet  118 , as appropriate, valve  106   b  and pump  108   a,b  are then directed to issue a neutral fluid from fluid reservoir  110   a  into the phantom chamber, which neutral fluid can then be returned to the reservoir  110   a , or directed to waste reservoir  110   d  via valve  108   b  as directed by system controller  114 . Monitoring of the phantom chamber  102  can then begin using a medical imaging device. Valve  106   a  can then be directed by the system controller to begin issuing tracer from fluid reservoir  110   b  into the phantom chamber. After passing through the phantom chamber and/or binding with medium, the used up tracer can then be returned to fluid reservoir  110   b  or directed to waste reservoir  110 d. Monitoring of the phantom chamber by the medical imaging device is continued for a desired time period to observe wash-in of the tracer. At the end of wash-in, valve  106   a  can then be directed to issue a radiative tracer wash in fluid reservoir  110   c  into the phantom chamber. The phantom chamber can then be monitored using the medical imaging device. After passing through the phantom chamber, the radiative wash can be returned to reservoir  110   c  or directed to waste reservoir  110   d  by means of valve  108   b.    
         [0033]    Referring now to  FIGS. 3-7   a,b , the flow drive for a dynamic phantom  100  can be configured for use with various types of phantom chamber and/or medium. As illustrated in  FIG. 3 , medium  104  can comprise sub-medium  118 , which has a different affinity for a tracer and/or, in the case of a radiative tracer, a radiation level different from medium  104 , for purposes of representing or simulating abnormal tissue. 
         [0034]    As illustrated in  FIG. 4 , phantom chamber  102   b  is illustrated as comprising chamber conduit  121  including a plurality of apertures  122  for uniformly distributing a fluid into the medium. 
         [0035]    As shown in  FIG. 5 , phantom chamber  102   c  is illustrated as comprising chamber conduit  121  including a plurality of apertures  122  for uniformly distributing a fluid into the medium as well as outlet conduit  112   c  and outlet portion  120   c  including a plurality of apertures disposed within a portion of the medium. 
         [0036]    As shown in  FIG. 6 , phantom chamber  102   d  is illustrated as comprising core area  124  (which can be solid or hollow) which thereby forms chamber conduit  121 . Medium  104  can be disposed within the conduit chamber, e.g., to simulate the myocardium of the human heart. Finally, as shown in  FIGS. 7A and 7B , phantom chamber  102   e  is illustrated as being configured for simulating systolic and diastolic functions of the heart. In this embodiment, phantom chamber  102   e  comprises first, outer elastomeric sleeve  126  and a second, inner elastomeric sleeve  128 , which both surround hollow core area  124 . First outer elastomeric sleeve  126  and second inner elastomeric sleeve  128  are separated from one another to form chamber conduit  121  whose volume can be filled with medium  104  for purposes of simulating the myocardium of the human heart. A pump can be used to pump a fluid into/out of hollow core area  124  to cause the inner and outer elastomeric sleeves to expand/contract as may be desired to mimic the beating of a heart. Action of the mechanism used to expand/contract the hollow core can be controlled via the system controller. 
         [0037]    Thus, it is seen that an improved flow drive for a dynamic phantom is provided by the present invention, which thereby allows tracer wash-in and washout to be more precisely simulated.