Patent Publication Number: US-2005117706-A1

Title: Cooling and power system for a medical imaging system

Description:
BACKGROUND OF THE INVENTION  
      Embodiments of the present invention generally relate to a cooling and/or power system for a medical imaging system, and more particularly to an auxiliary module for cooling, and/or providing power to, an x-ray imaging system.  
      X-ray imaging systems typically include an x-ray tube, a detector, and a positioning arm, such as a C-arm, supporting the x-ray tube and the detector. In operation, an imaging table, on which a patient is positioned, is located between the x-ray tube and the detector. The x-ray tube typically emits radiation, such as X-rays, toward the patient. The radiation typically passes through the patient positioned on the imaging table and impinges on the detector. As the radiation passes through the patient, anatomical structures inside the patient cause spatial variances in the radiation received at the detector. The detector then translates the radiation variances into an image, which may be employed for clinical evaluations.  
      X-rays are produced when high-speed electrons are suddenly decelerated, for example, when a metal target, is struck by electrons that have been accelerated through a potential difference of several thousand volts. Typically, x-ray emitters include an anode, which may be fixed or rotatable, and a cathode. If the anode is rotatable, the anode may be rotated at a high rate of speed in order to manage the resulting heat on the target from the cathode during the x-ray emission process.  
      Some procedures require extended periods of imaging, such as through x-rays, in order to properly diagnose, treat, and/or assess the condition of, a patient. Often, during extended imaging, the imaging element, such as an x-ray tube, overheats such that an operator has to interrupt the imaging procedure in order to allow the imaging element to cool. In mobile x-ray systems in particular, fans and rotating elements within the x-ray tube may not adequately dissipate the heat produced by the x-ray tube. Thus, imaging bay be interrupted for extended periods of time. Further, during periods of extended imaging, the imaging system may not be supplied with adequate power. That is, during periods of extended imaging, power levels within the imaging device may be depleted to the point in which further imaging is precluded.  
      Thus, a need exists for a more efficient system and method of cooling an imaging element of a medical imaging system. Additionally, a need exists for a system and method for providing additional power to a medical imaging system during periods of intense and/or extended imaging.  
     SUMMARY OF THE INVENTION  
      Embodiments of the present invention provide a medical imaging system including a medical imaging device having a main body and an imaging element, and an auxiliary module having a cooling unit configured to circulate chilled liquid to and from the imaging element. As the chilled liquid circulates or passes around the imaging element, the chilled liquid absorbs heat produced by the imaging element during an imaging procedure. The imaging element may be an x-ray tube, included within a mobile x-ray C-arm device.  
      A cooling duct surrounds at least a portion of the imaging element. The cooling duct includes a fluid inlet and a fluid outlet, which are in fluid communication with a fluid input line (or supply tube) and a fluid return line (or return tube), respectively. The chilled liquid is supplied to the cooling duct from the cooling unit through the fluid input line. The chilled liquid is returned to the cooling unit through the fluid return line. The cooling unit includes a pump, or other such component, which acts to circulate the chilled liquid between the cooling unit and the cooling duct.  
      The cooling duct may be permanently or removably connected to the imaging element. For example, the cooling duct may be configured to be positioned over the imaging element during periods of imaging; but, when the imaging device is not in operation, the cooling duct may be removed from the imaging element and stored with the auxiliary module. The auxiliary module may be mobile and/or remotely located from the imaging device. For example the auxiliary module may include a cart having wheels (e.g., caster assemblies) that allow it to be conveniently moved between various locations. Optionally, the auxiliary module may be permanently fixed to the imaging device, or another structure such as a wall, a floor, or another stationary structure.  
      The auxiliary module may also include a booster battery pack, which is configured to be electrically connected to the medical imaging device in order to provide additional power to the medical imaging device during periods of intense and/or extended imaging. The main body of the imaging device includes a power boost receptacle electrically connected to a power supply system within the imaging device. A power cable electrically connected to the booster battery pack may be removably connected (e.g., a plug and socket relationship) to the power boost receptacle so that the power supply system may draw power from the booster battery pack.  
      Embodiments of the present invention also provide a method of operationally supporting an imaging device, such as a mobile x-ray device. The method includes operatively connecting an auxiliary module having a cooling unit to the imaging device, cooling liquid with the cooling unit thereby producing chilled liquid, passing the chilled liquid from the cooling unit to an imaging element, such as an x-ray tube, of the imaging device, and circulating the chilled liquid around at least a portion of the imaging element such that the chilled liquid absorbs heat produced by the imaging element during an imaging procedure.  
      Additionally, the method may also include providing a cooling duct around at least a portion of the x-ray tube, such that the passing includes passing the chilled liquid from the cooling unit to the x-ray tube through a first tube that is in fluid communication with the cooling unit and the cooling duct, and returning the chilled liquid back to the cooling unit through a second tube that is in fluid communication with the cooling unit and the cooling duct.  
      The method may also include providing a booster battery pack in the auxiliary module, and electrically connecting the booster battery pack to the x-ray device so that the x-ray device draws power from the booster battery pack.  
    
    
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS  
       FIG. 1  illustrates a medical imaging system according to an embodiment of the present of the present invention.  
       FIG. 2  illustrates an interior side view of an x-ray tube according to an embodiment of the present invention.  
       FIG. 3  illustrates an auxiliary module according to an alternative embodiment of the present invention.  
       FIG. 4  illustrates an auxiliary module according to another alternative embodiment of the present invention. 
    
    
      The foregoing summary, as well as the following detailed description of certain embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings, certain embodiments. It should be understood, however, that the present invention is not limited to the arrangements and instrumentalities shown in the attached drawings.  
     DETAILED DESCRIPTION OF THE INVENTION  
       FIG. 1  illustrates a medical imaging system  10  according to an embodiment of the present invention. The medical imaging system  10  includes an x-ray device  11 , which includes a base member  12  having wheels  14  (e.g., caster assemblies), a main body  16 , a positioning arm  18 , such as a C arm, an x-ray tube  20 , and a detector  22 . The medical imaging system  10  also includes an auxiliary module, such as a remote cooling and power system,  24  and a workstation  25  operatively connected to the x-ray device  11 . The positioning arm  18  includes a first end, or first prong  26 , and a second end, or second prong  28 .  
      The base member  12  supports the entire structure of the x-ray device  11 . The base member  12  is integrally connected to the main body  16 , which is in turn connected to the positioning arm, or C-arm  18 . The x-ray tube  20  is located at a distal end of the first prong  26 , while the detector  22  is located at a distal end of the second prong  28 . The x-ray tube  20  and the detector  22  are oriented such that the x-ray tube  20  emits radiation toward the detector  22 . Examples of x-ray C-arms are further described in U.S. Pat. No. 6,104,780, entitled “Mobile bi-planar fluoroscopic imaging apparatus,” U.S. Pat. No. 5,802,719, entitled “One piece C-arm for x-ray diagnostic equipment,” and U.S. Pat. No. 5,627,873, entitled “Mini C-arm assembly for mobile x-ray imaging system,” all of which are hereby incorporated by reference in their entireties.  
      The x-ray device  11  is also operatively connected to a workstation  25 . The workstation  25  may be a mobile workstation, such that it may be moved between various locations. The workstation  25  includes a housing  27  that supports a central processing unit (CPU)  29 , an input device  31  (such as a keyboard, mouse, or touch sensitive monitor), and a display unit  33 . The input device  31  and the display unit  33  are in electrical communication with the CPU  29 . The workstation  25  allows a user to operate the x-ray device  11  and monitor the operation thereof.  
      In operation, a patient is positioned on an x-ray positioning table (not shown) between the x-ray tube  20  and the x-ray detector  22 . After the patient is positioned, the imaging process may begin. To begin the imaging process, the x-ray tube  20  is activated. During imaging, the x-ray tube  20  emits radiation that passes through the patient and is received by the detector  22 .  
      The auxiliary module  24  includes a cart  30  housing a cooling unit  32  and a booster battery pack  34 . The cooling unit  32  may be a cold plate, an ice reservoir, a fluid condensing/evaporating system such as in an air conditioning and/or refrigeration unit, a series of heat transfer tubes and pipes, thermionic cooling devices, or various other known cooling systems that are capable of cooling and circulating fluid. The cart  30  is supported by wheels  36 , e.g., caster wheel assemblies, such that the auxiliary module  24  may be conveniently moved to and from various imaging or operating environments. A power input  38  operatively connected to a power cable  40  provides electrical power to the cooling unit  32  (in order to operate the cooling unit  32 ) and the booster battery pack  34  (in order to recharge the booster battery pack  34  with electrical power). The power cable  40  may be removably connected to a source of power, such as a standard AC current wall input. Optionally, the power cable  40  may be removably connectable to various other known sources of power known in the art.  
      The cooling unit  32  is operatively connected to a cooling fluid output  42  and a return fluid input  44 . The cooling unit  32  is configured to pump, or otherwise supply, cooled (i.e., chilled) fluid from the cooling unit  32  through the cooling fluid output  42 . Further, the cooling unit  32  is configured to receive fluid through the return fluid input  44 . The fluid may be water, oil, antifreeze, or various other appropriate liquids that may be circulated within the x-ray tube  20 .  
      A tube  46  is operatively connected to the fluid output  42  at a first end  48  such that chilled fluid may pass from the cooling unit  32 , through the cooling fluid output  42 , and into the tube  46 . A second end  50  of the tube  46  is removably connected to a cooling duct  52 , by way of a fluid inlet  54 , positioned around the x-ray tube  20 . The cooling duct  52  may be an air/fluid-tight tube-like structure that overlies a portion of the x-ray tube  20 . Optionally, the cooling duct  52  may be an air/fluid-tight membrane, sack or pouch that surrounds all, or substantially all, of the x-ray tube  20 . The cooling duct  52  also includes a fluid outlet  56 . A tube  58  is removably connected to the fluid outlet  56  to allow fluid to pass from the cooling duct  52  back to the cooling unit  32  through the return fluid input  44 . The fluid outlets  48 ,  56  and the fluid inlets  44  and  54  include structures, such as check valves, to ensure that fluid does not escape when the cooling unit  32  is not in operation and/or when the tubes  46  and  58  are not connected thereto. Prior to imaging, the tubes  46  and  56  are connected to the fluid inlets  54  and fluid outlet  56 , respectively, so that the x-ray tube  20  may be cooled by chilled fluid circulated by the cooling unit  32 .  
      As shown in  FIG. 1 , the tubes  46  and  58  are removably connected to the cooling duct  52  at the fluid inlet  54  and outlet  56 , respectively. Alternatively, the fluid inlet  54  and the fluid outlet  56  may be positioned on the main body  16  of the x-ray imaging device  11 . Pipes, ducts, or other such structures may be positioned within the main body  12  and the positioning arm  18  in order to allow fluid to pass from the cooling unit  32  to the cooling duct  52 . That is, the x-ray imaging device  11  may include interior piping, ducts, passages, channels and the like that are adapted to allow fluid to pass between the cooling duct  52  and the cooling unit  32 . Also, alternatively, the x-ray imaging device  11  may include exterior piping, ducts, passages, channels and the like that are adapted to allow fluid to pass between the cooling duct  52  and the cooling unit  32 . Thus, instead of constructing the x-ray imaging device  11  to have channels, ducts, and the like within the x-ray imaging device  11 , these components may be positioned on the outside of the main body  16  and the positioning arm  18 .  
      Also, alternatively, the cooling duct  52  may not be permanently attached to the x-ray tube  20 . Instead, the tubes  46 ,  56  and the cooling duct  52  may be a single, unitary, integrally-formed structure. In this case, the fluid inlet  54  and fluid outlet  56  are unnecessary due to the fact that the tubes  46 ,  58  and cooling duct  52  are a unitary structure. The structure defined by the tubes  46 ,  58  and the cooling duct  52  may be configured to be removably wrapped, draped, or otherwise positioned over, the x-ray tube  20 . Thus, when the x-ray imaging device  11  is not in operation, the cooling structure is removed from the x-ray tube  20 . Prior to imaging, however, the cooling structure may be operatively connected to (e.g., draped, shrouded, enveloped, etc., around) the x-ray tube  20 . Optionally, a removable cooling structure may be positioned within the x-ray tube  20 , while another removable cooling structure may be positioned outside the x-ray tube  20 . Further, the removable cooling structure may include a portion positioned within the x-ray tube  20  and another portion positioned outside the x-ray tube  20 .  
      The x-ray imaging device  11  also includes a power boost receptacle  60 . Further, the booster battery pack  34  is electrically connected to a power cable  62  that extends from the cart  30 . The booster battery pack  34  may include various types of batteries, such as are known in the art, depending on the amount of power required for a certain imaging session. The booster battery pack  34  may include one or more primary and/or secondary power sources. For example, the booster battery pack  34  may include one or more of the following battery types: Nickel Metal Hydride; Nickel Cadmium; Lead-Acid; Lithium Ion; Lithium Polymer; Sodium Nickel Chloride; Zinc-Air; Vanadium Redox; Carbon-Zinc; Zinc-Chloride; Alkaline; Mercuric Oxide; Zinc Bromide; and/or various other battery types known in the art.  
      The booster battery pack  34  may be electrically connected to the main power system (not shown) of the x-ray imaging device  11  through the interface between the power cable  62  and the power boost input  60 . The booster battery pack  34  is configured to supply additional power to the x-ray imaging device  11  for extended periods of imaging and/or particularly intense imaging. The booster battery pack  34  is adapted to be charged and recharged through the interface between the power cable  40  and a source of power, such as a through standard AC current wall input. While the x-ray imaging device  11  is typically connected to a source of power separate and distinct from the booster battery pack  34 , the x-ray imaging device  11  may also be powered solely through the booster battery pack  34  in order to facilitate imaging in an environment where power receptacles are scarce (e.g., operatively connected to other devices). Further, the booster battery pack  34  may also be used to supply power to operate the cooling unit  32 .  
      Additionally, the workstation  25  may be electrically connected to the auxiliary module  24  to monitor characteristics of the auxiliary module  24 . For example, the CPU  29  may be configured to receive data from the auxiliary unit  24  regarding cooling liquid temperature, battery power level, and the like. The CPU  29  may then display information regarding these characteristics to an operator on the display  33 . Further, the CPU  29  may automatically operate the auxiliary unit  24  based on predetermined parameters. For example, if the cooling fluid within the auxiliary module  24  is low, or is too warm, the CPU  29  may cease operation of the auxiliary module  24  and/or the x-ray device  11 . Once fluid levels reach an acceptable level (in terms of amount and temperature), the CPU  29  may activate use of the auxiliary module  24  and/or x-ray device  11 .  
      Additionally, the x-ray device  11  may include sensors (not shown) that measure power levels and the like. The CPU  29  may monitor sensed power levels to determine whether additional power from the auxiliary module  24  is needed. The CPU  29  may automatically direct the auxiliary module  24  to provide additional power to the x-ray device  11 , or the CPU  29  may display a message on the display  33  alerting an operator that additional power is needed. Similarly, the temperature of the x-ray tube  20  may be monitored by a thermometer (not shown), or other such device, which is in electrical communication with the CPU  29  or a processing unit within the x-ray device  11  itself. Data regarding x-ray tube temperature may be relayed to the workstation  25 , where it is subsequently displayed.  
      While the imaging system  11  is shown as a mobile imaging system, embodiments of the present invention may also be used with permanent, non-mobile imaging systems. For example, the auxiliary module  24  may be used with a fixed x-ray C-arm imaging system. Additionally, the auxiliary module  24  does not necessarily need to include both the cooling unit  32  and the booster battery pack  34 . That is, the auxiliary module  24  may include either the cooling unit  32  or the battery pack  34 , but not both. Optionally, the auxiliary module  23  may not be mobile, but may rather be mounted to a wall, floor, or a structure within an imaging room. Further, embodiments of the present invention may provide a cooling and/or power boost system that is not mobile. The cooling and/or power boost system may be affixed to the main body  16  or the positioning arm  18 , instead of being remotely located thereform.  
       FIG. 2  illustrates an interior side view of the x-ray tube  20 . The x-ray tube  20  includes a casing  64 , a radiation emission passage  66  formed within the casing  64  and a mounting plate  68  on the side of the x-ray tube  20  opposite that of the emission passage  66 . The casing  64  encloses an insert, or emitter  70 , which houses the internal components of the x-ray tube  20 . The internal components include an anode  72 , an extension rod  74 , such as an axle, a cathode  76 , and a bearing  75  within a vacuum  78 . The cathode  76  and anode  72  are mounted within the interior of the insert  70 . The anode  72  connects to the extension rod  74 . The opposite end of the extension rod  74  is retained by the bearing  75 . The bearing is in turn retained by an additional structure, such as a motor mounted within the insert  70 . The insert  70  is in turn mounted within the casing  64 . While the x-ray tube  20  includes a rotatable anode  72 , the x-ray tube  20  may alternatively include a fixed anode.  
      As mentioned above, x-rays are produced when high-speed electrons are suddenly decelerated, for example, when a metal target, i.e., the anode  72 , is struck by electrons that have been accelerated through a potential difference of more than 80 thousand volts. The x-rays are then emitted through the radiation emission passage  66  toward the detector  22 . As stated above, the anode  72  is connected to the axle, i.e., extension rod  74 . The extension rod  74  is rotated through the bearing  75 , which is activated by the motor. The rotation of the bearing  75  causes the extension rod  74  to rotate. The rotation of the extension rod  74  causes the anode  72  to rotate. The bearing  75  rotates the anode  72  at a high rate, for example 125 Hz.  
      The cooling unit  32  circulates chilled fluid through the cooling duct  52  in the direction of arrow A. As discussed above, chilled fluid is passed into the cooling duct  52  through the tube  46  and fluid inlet  54 . As the fluid passes through the cooling duct  52 , the fluid absorbs heat produced within the x-ray tube  20 . Heat flows from hotter, i.e., higher energy, sources, to cooler, i.e., lower energy sources. Thus, heat produced within the x-ray tube  20  radiates and/or conducts outwardly toward the chilled water within the cooling duct  52 . As the chilled fluid absorbs heat, the temperature of the chilled fluid increases. The fluid is passed through the cooling duct  52  through the fluid outlet  56  and into the tube  58 . The fluid is then returned to the cooling unit  32 , which re-chills the fluid so that it may be re-circulated into the cooling duct  52 . Thus, embodiments of the present invention provide a system and method for cooling the x-ray tube  20 .  
      While the cooling duct  52  is shown outside of the casing  64 , the cooling duct  52  may optionally be located within the interior of the x-ray tube  20  under the casing  64 . Additionally, instead of being in direct contact with the casing  64 , the cooling duct  52  may be positioned directly over the emitter  70 , or other components of the x-ray tube  20 .  
       FIG. 3  illustrates an auxiliary module  80  according to an alternative embodiment of the present invention. The auxiliary module  80  includes the cooling unit  32 , but not a booster battery pack.  
       FIG. 4  illustrates an auxiliary module  82  according to another alternative embodiment of the present invention. The auxiliary module  82  includes the booster battery pack  34 , but not a cooling unit  32 .  
      The cooling and power boost systems discussed above may be used with other imaging devices. For example, embodiments of the present invention may be used with ultrasound systems to cool ultrasound probes and provide additional power thereto. Overall, embodiments of the present invention may be used with any system in which heat is produced as a by-product of the imaging process and/or a system that may benefit from additional power.  
      For example, embodiments of the present invention may be used with various imaging modalities, such as Computed Tomography (CT), X-ray (film-based and digital x-ray systems), Positron Emission Tomography (PET), such as shown and described in U.S. Pat. No. 6,337,481, entitled “Data binning method and apparatus for PET tomography including remote services over a network,” which is hereby incorporated by reference in its entirety, Single Photon Emission Computed Tomography (SPECT), such as shown and described in U.S. Pat. No. 6,194,725, entitled “SPECT system with reduced radius detectors,” which is hereby incorporated by reference in its entirety, Electron Beam Tomography (EBT), such as shown and described in U.S. Pat. No. 5,442,673, entitled “Fixed septum collimator for electron beam tomography,” which is hereby incorporated by reference in its entirety, and Magnetic Resonance (MR), such as described in U.S. Pat. No. 6,462,544, entitled “Magnetic resonance imaging apparatus,” which is also hereby incorporated by reference in its entirety, and various other imaging systems. Additionally, embodiments of the present invention may also be used with navigation and tracking systems, such as those described in U.S. Pat. No. 5,803,089, entitled “Position Tracking and Imaging System for Use in Medical Applications,” which is hereby incorporated by reference in its entirety.  
      Thus, embodiments of the present invention provide an efficient system and method of cooling imaging elements. Further, embodiments of the present invention provide a system and method of supplying additional power to an imaging system.  
      While the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.