Abstract:
An apparatus and method for simulating cardiac motion for use with an imaging system are provided. The apparatus includes an expandable balloon-like member having a number of protrusions fluidly connected thereto. Fluid is circulated between the pump and a fluid reservoir by a pump which is controlled by a programmable controller. Imaging data is acquired during circulation of the fluid between the reservoir and the phantom and subsequently analyzed to determine the effectacy and efficiency of the imaging protocol.

Description:
BACKGROUND OF INVENTION  
         [0001]    The present invention relates generally to simulating anatomical conditions of a patient and, more particularly, to an apparatus and method for simulating cardiac motion.  
           [0002]    To properly develop and test imaging protocols and techniques it is necessary for researchers, software design engineers, and technicians to accurately and precisely simulate imaging conditions including general anatomical conditions of a typical patient, commonly referred to as “phantomming”. Known phantomming techniques include the use of animals to simulate the anatomical conditions of a human patient. Using animals to create a sample test condition has a number of disadvantages.  
           [0003]    First, acquisition and care of animals often requires extensive and continual expenditures. Animals must be properly cared for and fed to maintain the health of the animal but also to be compliant with a number of regulations associated with animal testing. Further, in the absence of a well-trained animal, it is often necessary to sedate the animal, otherwise the animal may be uncooperative in simulating the test conditions. Moreover, the social climate associated with using animals and testing laboratories may be such that a company or research group may be publicly adversely affected by the use of animals in medical testing.  
           [0004]    Additionally, researchers and design engineers forfeit a certain amount of control over the testing conditions by using animals to simulate human anatomical conditions. For example, without using expensive and potentially detrimental drugs to simulate precise human anatomical patterns, researchers and software designers are unable to exactly define and control the anatomical conditions, such as, defining cardiac motion. That is, researchers cannot reasonably force data to precisely mimic phase data taken from an echocardiograph (EKG) exam. Further, it is considerably more difficult for researchers and software engineers to repeat particular conditions using live animals.  
           [0005]    Therefore, it would be desirable to design an apparatus and method for simulating cardiac motion that is repeatable, controllable, and cost efficient.  
         SUMMARY OF INVENTION  
         [0006]    A method and apparatus for simulating cardiac motion overcoming the aforementioned drawbacks are provided.  
           [0007]    In accordance with one aspect of the present invention, a dynamic cardiac phantom is provided and includes a hollow chamber made of a pliable material to expand and contract based on an injection and discharge of fluid therein. The dynamic cardiac phantom further includes at least one inlet connected to the hollow chamber at one end and having another end connectable to a fluid source to inject and discharge fluid into the hollow chamber in a manner to simulate cardiac motion.  
           [0008]    In accordance with another aspect of the present invention, a cardiac motion simulator for use with an imaging system is provided and includes a balloon having an inlet and a plurality of outlets. The inlet is configured to at least receive fluid. A plurality of tubes corresponding in number to the plurality of outlets of the balloon is also provided. Each tube includes an inlet connected to an outlet of the balloon wherein the plurality of tubes is further configured to receive fluid exiting the plurality of balloon outlets. Further, the balloon expands upon receipt of fluid and retracts upon discharge of fluid to mimic cardiac motion.  
           [0009]    In accordance with another aspect of the present invention, a computer program for mimicking cardiac motion has instructions to supply fluid to an expandable chamber having a number of expandable tubes connected thereto. The computer program further includes instructions to slowly empty fluid from the expandable chamber and rapidly empty fluid from the expandable chamber. The computer program has further instructions to rapidly supply fluid to the expandable chamber and slowly supply fluid to the expandable chamber.  
           [0010]    In accordance with a further aspect of the present invention, a method of phantomming cardiac motion for use with a scanner is provided. The method includes the step of connecting a balloon having an inlet and a number of tubular protrusions to a fluid reservoir. The method further includes the steps of filling the balloon with fluid and circulating fluid to and fro the balloon. Imaging data is then acquired of the balloon during circulation of the fluid to and from.  
           [0011]    In accordance with yet a further aspect of the present invention, a computer tomography system having a rotatable gantry having an opening is provided. The CT system further includes a high frequency electromagnetic energy projection source configured to project high frequency energy toward an object and a scintillator array having a plurality of scintillators to receive high frequency electromagnetic energy attenuated by the object. A photodiode ray is also provided and includes a plurality of photodiodes wherein the photodiode ray is coupled to the scintillator ray and configured to detect light energy emitted there from. A plurality of electrical interconnects are configured to transmit photodiode outputs to a data processing system and a computer is also provided to produce a visual display based upon the photodiode outputs transmitted to the data processing system. The object is defined to include an expandable balloon having a number of tubular protrusions and an inlet configured to receive circulating fluid such that circulation of the fluid simulates cardiac motion.  
           [0012]    Various other features, objects and advantages of the present invention will be made apparent from the following detailed description and the drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0013]    The drawings illustrate one preferred embodiment presently contemplated for carrying out the invention.  
         [0014]    In the drawings:  
         [0015]    [0015]FIG. 1 is a pictorial view of a CT imaging system;  
         [0016]    [0016]FIG. 2 is a block diagram of the system illustrated in FIG. 1;  
         [0017]    [0017]FIG. 3 is a schematic representation of a dynamic cardiac phantom in accordance with the present invention.  
         [0018]    [0018]FIG. 4 is a flow chart for simulating dynamic cardiac motion in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0019]    The operating environment of the present invention is described with respect to a four-slice computed tomography (CT) system. However, it will be appreciated by those of ordinary skill in the art that the present invention is equally applicable for use with single-slice or other multi-slice configurations. Moreover, the present invention will be described with respect to the detection and conversion of x-rays. However, one of ordinary skill in the art will further appreciate, that the present invention is equally applicable for use with other imaging modalities, such as Magnetic Resonance Imaging (MRI), Positron Emission Tomography (PET), or x-ray.  
         [0020]    Referring to FIGS. 1 and 2, a computed tomography (CT) imaging system  10  is shown as including a gantry  12  representative of a “third generation” CT scanner. Gantry  12  has an x-ray source  14  that projects a beam of x-rays  16  toward a detector array  18  on the opposite side of the gantry  12 . Detector array  18  is formed by a plurality of detectors  20  which together sense the projected x-rays that pass through a medical patient  22 . Each detector  20  produces an electrical signal that represents the intensity of an impinging x-ray beam and hence the attenuated beam as it passes through the patient  22 . During a scan to acquire x-ray projection data, gantry  12  and the components mounted thereon rotate about a center of rotation  24 .  
         [0021]    Rotation of gantry  12  and the operation of x-ray source  14  are governed by a control mechanism  26  of CT system  10 . Control mechanism  26  includes an x-ray controller  28  that provides power and timing signals to an x-ray source  14  and a gantry motor controller  30  that controls the rotational speed and position of gantry  12 . A data acquisition system (DAS)  32  in control mechanism  26  samples analog data from detectors  20  and converts the data to digital signals for subsequent processing. An image reconstructor  34  receives sampled and digitized x-ray data from DAS  32  and performs high speed reconstruction. The reconstructed image is applied as an input to a computer  36  which stores the image in a mass storage device  38 .  
         [0022]    Computer  36  also receives commands and scanning parameters from an operator via console  40  that has a keyboard. An associated cathode ray tube display  42  allows the operator to observe the reconstructed image and other data from computer  36 . The operator supplied commands and parameters are used by computer  36  to provide control signals and information to DAS  32 , x-ray controller  28  and gantry motor controller  30 . In addition, computer  36  operates a table motor controller  44  which controls a motorized table  46  to position patient  22  and gantry  12 . Particularly, table  46  moves portions of patient  22  through a gantry opening  48 .  
         [0023]    The present invention provides an apparatus and method of simulating cardiac motion for use with an imaging scanner, such as a CT system. Referring to FIG. 3, the cardiac motion simulator  100  includes a phantom  102 . Phantom  102  is formed of an expandable material and includes a hollowed center region  104  and a number of tubular protrusions  106 . In a preferred embodiment, there are four tubular protrusions  106  corresponding to the four chambers of a human heart. Protrusions  106  may be fastenly connected to an outer surface of the center region  104  or seamlessly connected, i.e., the protrusions  106  and the center region  104  formed as a single unitized structure. However, the inlets  108  of the tubular protrusions must be in fluid communication with the outlets  110  of the center region  104 . Phantom  102  further includes a fluid inlet  112  that fluidly communicates with center region  104 .  
         [0024]    Simulator  100  further includes a pump  114  configured to supply fluid to the phantom  102  from a fluid reservoir  116  via supply/discharge pipe  118 . To mimic cardiac motion, the pump cyclically circulates fluid between the phantom  102  and the reservoir  116 . In a preferred embodiment, the cyclical circulation of fluid between phantom  102  and reservoir  116  are such that the volume changing phases of the heart are simulated. That is, the pump circulates the fluid to mimic a slow empty phase, a rapid empty phase, a change-over to filling phase or pause phase, a rapid filling phase, a slow filling phase, and a change-over to empty phase or pause phase. Typically, the rapid filling phase fills the phantom with fluid at a speed twice that of the slow filling phase. Conversely, the rapid empty phase discharges fluid from the phantom at a speed 50% slower than the fast filling phase. These values are simply one preferred embodiment and are used for illustrative purposes only and are not intended to limit the scope nor the breadth of the present invention.  
         [0025]    Simulator  100  further includes a controller  118  configured to transmit modulating signals to the pump thereby instructing the pump to circulate fluid between phantom  102  and reservoir  116 . The controller  118  may include a computer program that automatically causes the pump to circulate fluid to the phantom and reservoir, but also may transmit operator entered parameters to the pump  114 . For example, controller  118  may include a computer program that automatically randomly varies the aforementioned phases to more accurately reflect cardiac motion. Additionally, a user such as a researcher or design engineer may wish to simulate varied cardiac motion and therefore may input cardiac motion data directly to the controller using a keypad and/or keyboard. Other known data input techniques and modules are contemplated and are within the scope of the present application.  
         [0026]    Accordingly, the present invention includes an algorithm for simulating cardiac motion for use with an imaging system. The present invention contemplates both a method of simulating cardiac motion and a computer program implementing the steps of the method, and both will be discussed with reference to FIG. 4. The algorithm begins at  150  with positioning of the phantom within a field-of-view of the scanner  152 . Once positioned in the scanner  152 , the phantom is filled with fluid such as water at  154 . A data acquisition sequence is then initialized at  156  followed by a slow emptying of the water from the phantom at  158 . In a preferred embodiment the slow emptying phase  158  lasts for 100 ms. per 1,000 ms. of total phase time. Following the slow emptying phase  158 , water is rapidly drained fromm the phantom at  160  for a period of 150 ms. per 1,000 ms. After rapidly emptying the phantom at  160 , the algorithm pauses at  162  for a period of 50 ms. per 1,000 ms. as the algorithm changes over fromm the emptying phase to the filling phase. Thereafter at  164 , the phantom is rapidly filled with water for a period of 100 ms. per 1,000 ms. followed at  166  by a slow filling phase lasting 500 ms. per 1,000 ms. At  168 , the algorithm determines if simulation of cardiac motion is to continue. That is, if simulation is complete  168 ,  170 , an image is reconstructed of the phantom at  172  in accordance with known imaging techniques whereupon the algorithm ends at  174 . However, if cardiac motion simulation is not complete and is to be repeated  168 ,  176 , the algorithm pauses at  178  for a period of 100 ms. per 1,000 ms. to accommodate changing over to the emptying phase fromm the filling phase. Following pausing  178 , the algorithm begins anew at  158  with the slowly emptying of water from the phantom. It should be noted that imaging data is continuously acquired during emptying/filling phases  158 - 166 .  
         [0027]    The time period associated with each phase  158 - 166  is for illustrative purposes only and is not intended to limit the scope or breadth of the instant application. Moreover, the present invention contemplates varying of circulation phases  158 - 166  fromm cycle to cycle, and such variation may be as much as 20% in a preferred embodiment to more precisely simulate cardiac motion of a patient&#39;s heart. The amount of variation however is preferably random and based upon a uniform distribution. Additionally, the algorithm of FIG. 4 contemplates using analyzed EKG traces from a real patient to determine the phase times for acts  158 - 166 . By using actual EKG data, the algorithm may more accurately reflect actual cardiac motion thereby providing more reliable and resourceful data for image reconstruction and subsequent software development.  
         [0028]    That is, the final reconstructed image of the cardiac phantom is analyzed to determine what changes, if any, should be made to the imaging protocol so that artifact free images result. The present invention contemplates evaluation of the imaging protocols using the cardiac phantom during the protocol development stage as well as during onsite clinical trials of the imaging protocol.  
         [0029]    In accordance with one embodiment of the present invention, a dynamic cardiac phantom is provided and includes a hollow chamber made of a pliable material to expand and contract based on an injection and discharge of fluid therein. The dynamic cardiac phantom further includes at least one inlet connected to the hollow chamber at one end and having another end connectable to a fluid source to inject and discharge fluid into the hollow chamber in a manner to simulate cardiac motion.  
         [0030]    In accordance with another embodiment of the present invention, a cardiac motion simulator for use with an imaging system is provided and includes a balloon having an inlet and a plurality of outlets. The inlet is configured to at least receive fluid and preferably discharge fluid as well. A plurality of tubes corresponding in number to the plurality of outlets of the balloon is also provided. Each tube includes an inlet connected to an outlet of the balloon wherein the plurality of tubes is further configured to receive fluid exiting the plurality of balloon outlets. Further, the balloon is configured to expend upon receipt of fluid and retract upon discharge of fluid to mimic cardiac motion.  
         [0031]    In accordance with yet another embodiment of the present invention, a computer program for mimicking cardiac motion has instructions to supply fluid to an expandable chamber having a number of expandable tubes connected thereto. The computer program further includes instructions to slowly empty fluid from the expandable chamber and rapidly empty fluid from the expandable chamber. The computer program has further instructions to rapidly supply fluid to the expandable chamber and slowly supply fluid to the expandable chamber.  
         [0032]    In a further embodiment of the present invention, a method of phantomming cardiac motion for use with a scanner is provided. The method includes the step of connecting a balloon having an inlet and a number of tubular protrusions to a fluid reservoir. The method further includes the steps of filling the balloon with fluid and circulating fluid to and fro the balloon. Imaging data is then acquired of the balloon during circulation of the fluid to and from.  
         [0033]    In yet a further embodiment of the present invention, a computer tomography system having a rotatable gantry having an opening is provided. The CT system further includes a high frequency electromagnetic energy projection source configured to project high frequency energy toward an object and a scintillator ray having a plurality of scintillators to receive high frequency electromagnetic energy attenuated by the object. A photodiode ray is also provided and includes a plurality of photodiodes wherein the photodiode ray is coupled to the scintillator ray and configured to detect light energy emitted therefrom. A plurality of electrical interconnects are configured to transmit photodiode outputs to a data processing system and a computer is also provided to produce a visual display based upon the photodiode outputs transmitted to the data processing system. The object is defined to include an expandable balloon having a number of tubular protrusions and an inlet configured to receive circulating fluid such that circulation of the fluid simulates cardiac motion.  
         [0034]    The present invention has been described in terms of the preferred embodiment, and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims.