Abstract:
A computed tomography system is disclosed herein. The computed tomography system includes a detector module and a rail in contact with the detector module. The rail at least partially defines a passageway adapted to transfer a coolant

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to a computed tomography system. The computed tomography system is adapted to transfer a coolant in order to remove heat from a detector assembly. 
         [0002]    Typically, in computed tomography (CT) systems, an x-ray source emits an x-ray beam toward a subject or object, such as a patient or a piece of luggage, positioned on a support. The x-ray beam, after being attenuated by the object, impinges upon the detector assembly. The intensity of the attenuated x-ray beam received at the detector assembly is typically dependent upon the attenuation of the x-ray beam by the object. 
         [0003]    In known third generation CT systems, the x-ray source and the detector assembly are rotated on a rotatable gantry portion around the object to be imaged so that a gantry angle at which the x-ray beam intersects the object constantly changes. The detector assembly typically includes a plurality of detector modules. Each detector module typically comprises a substrate, a scintillator, a photodiode layer, and a plurality of electronic components. Additionally, the detector module is typically divided into a plurality of detector elements. Data representing the intensity of the received x-ray beam at each of the detector elements are collected across a range of gantry angles. The data are ultimately processed to form an image. 
         [0004]    The electronic components produce heat that may cause a degradation in image quality through multiple mechanisms. For example, the gain of the photodiode layer is highly temperature dependent and operating the detector module at too high of a temperature may lead to image artifacts such as spots or rings. Also, the amount of pixel-to-pixel leakage between photodiodes increases with temperature. A high level of pixel-to-pixel leakage negatively impacts the signal-to-noise ratio within the detector module and results in reduced image quality. Also, an increase in the temperature of the detector module may result in problems with the mechanical alignment of the detector assembly and a collimator. Third generation CT imaging systems rely on an accurately aligned collimator to effectively block scattered x-rays. However, the mechanical alignment of the detector assembly and the collimator may change as the temperature increases outside of an optimal operating range. If the collimator is not properly aligned with the detector assembly, the result may be additional image artifacts. 
         [0005]    The problem is that excessive heat within the detector assembly may lead to image artifacts from multiple sources, resulting in images of diminished quality. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0006]    The above-mentioned shortcomings, disadvantages and problems are addressed herein which will be understood by reading and understanding the following specification. 
         [0007]    In an embodiment, a computed tomography system includes a detector module and a rail in contact with the detector module, the rail at least partially defining a passageway adapted to transfer a coolant. 
         [0008]    In another embodiment, a computed tomography system includes a detector module and a rail attached to the detector module. The computed tomography system also includes a member attached to the rail, the member at least partially defining a passageway adapted to transfer a coolant. 
         [0009]    In another embodiment, a computed tomography system includes a detector module including an electronic component. The computed tomography system includes a coolant in direct contact with the electronic component. The computed tomography system also includes a housing at least partially surrounding the electronic component, the housing adapted to transfer the coolant. 
         [0010]    Various other features, objects, and advantages of the invention will be made apparent to those skilled in the art from the accompanying drawings and detailed description thereof. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a schematic diagram illustrating a CT system in accordance with an embodiment; 
           [0012]      FIG. 2  is a schematic diagram illustrating a portion of a detector assembly attached to a pair of rails and a heat exchanger in accordance with an embodiment; 
           [0013]      FIG. 3  is a schematic diagram illustrating a portion of a detector assembly attached to a pair of rails and a heat exchanger in accordance with another embodiment; and 
           [0014]      FIG. 4  is a schematic diagram illustrating a cross section of a detector assembly attached to a pair of rails in accordance with another embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments that may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical and other changes may be made without departing from the scope of the embodiments. The following detailed description is, therefore, not to be taken as limiting the scope of the invention. 
         [0016]    Referring to  FIG. 1 , a schematic representation of a computed tomography (CT) system  10  according to an embodiment is shown. The CT system  10  includes a gantry  12 , a rotatable gantry portion  14 , and a support  16 . The rotatable gantry portion  14  is adapted to retain an x-ray source  18  and a detector assembly  20 . The x-ray source  18  is configured to emit an x-ray beam  22  towards the detector assembly  20 . The support  16  is configured to support a subject  24  being scanned. Hereinafter, the terms “subject” and “object” shall include anything capable of being imaged. The support  16  is capable of translating the subject  24  along a z-direction with respect to the gantry  12  as indicated by a coordinate axis  26 . 
         [0017]    Referring to  FIG. 2 , a schematic representation of a portion of the detector assembly  20  attached to a pair of rails  28  and a heat exchanger  29  is shown in accordance with an embodiment. The detector assembly  20  is comprised of a plurality of detector modules  30 . There are four detector modules  30  schematically represented in  FIG. 2 . Each detector module  30  includes a scintillator  32 , a photodiode layer  34 , a substrate  36 , and one or more electronic components  38 . The scintillator  32  converts received x-rays into visible light. The photodiode layer  34  is mounted radially outward of the scintillator  32  and converts the visible light from the scintillator  32  into an electrical signal. The substrate  36  provides a generally rigid mounting surface for the scintillator  32 , the photodiode layer  34  and the electronic component  38 . The scintillator  32  and the photodiode layer  34  are mounted to the radially inner side of the substrate  36 . The electronic component  38  may comprise a component from the following nonlimiting list: an analog-to-digital converter (not shown) for converting the analog electrical signals from the photodiode into digital signals, a field-programmable gate-array (not shown), a power supply (not shown), and a voltage regulator (not shown). The analog-to-digital converter, the field-programmable gate-array, and the power supply are all well-known by those skilled in the art. The electronic component  38  is mounted radially outward from the substrate  36  for each detector module  30 . 
         [0018]    The substrate  36  of each detector module is attached to the rails  28 .  FIG. 2  schematically represents an embodiment where each rail  28  defines an inner passageway  40  and an outer passageway  42  through which a coolant  44  may flow. While this embodiment shows the inner passageway  40  and the outer passageway  42  defined by each of the rails  28 , it should be appreciated that embodiments may include only one passageway  40 ,  42  defined by one of the rails  28  and embodiments may also include more than two passageways  40 ,  42  defined by each of the rails  28 . The passageways  40 ,  42  are conductively coupled to the detector modules  30 . For the purposes of this disclosure, the term “conductively coupled” is defined to include two components that are connected by a material that conducts heat. It should be understood that while the inner passageway  40  and the outer passageway  42  shown in  FIG. 2  are round in cross-section and generally parallel to the rails  28 , the passageways  40 ,  42  could be of any shape. A non-limiting list of passageway  40 ,  42  shapes includes: generally parallel to the rail  28 ; generally straight; serpentine; and shapes that vary in cross-section throughout the length of the rail  28 . Additionally, it should be understood that the inner passageway  40  does not need to be of the same size and shape as the outer passageway  42 . 
         [0019]    The passageways  40 ,  42  defined by the rails  28  are in fluid communication with the heat exchanger  29 . The coolant  44  is caused to circulate by a mechanical device such as a pump (not shown). For example, according to an embodiment, heat originating in the electronic components  38  conductively travels through the substrate  36  into the rail  28 . After reaching the rail  28 , heat from the electronic components  38  is absorbed by the coolant  44  circulating through the outer passageway  42 . After absorbing heat, the coolant  44  flows from the outer passageway  42  to the inner passageway  40  through a connecting piece of hose (not shown). The coolant  44  then flows through the inner passageway  40  in generally the opposite direction as the coolant  44  had flowed in the outer passageway  42 . While flowing through the inner passageway  40 , the coolant  44  absorbs additional heat from the electronic components  38 . The coolant  44  then flows to the heat exchanger  29  mounted to the rotatable gantry portion  14  (shown in  FIG. 1 ). The heat exchanger  29  contains a structure with a large surface area to facility heat transfer as is well-known by those skilled in the art. The temperature of the coolant  44  is lowered while passing through the heat exchanger  29 . After the coolant  44  has been cooled, it is pumped back through the outer passageway  42 , where it can absorb more heat from the detector modules  30 . 
         [0020]    While the embodiment shown in  FIG. 2  depicts the inner passageway  40  and the outer passageway  42  defined by the rail  28 , embodiments may also be envisioned where the rail  28  only partially defines the passageways  40 ,  42 . One example of an embodiment where the rail  28  only partially defines the passageways  40 ,  42  is where one side of the passageways  40 ,  42  is defined by a plate or cover (not shown) mounted to the rail  28 . Additionally, it should be understood that embodiments may use a different layout in terms of how the coolant  44  is circulated through the rails  28 . Considerations such as the expected temperature of the detector module  30 , cost, and ease of manufacturing may be taken into account when determining the exact design of the one or more passageways  40 ,  42 . 
         [0021]    Referring to  FIG. 3 , a schematic representation of a portion of the detector assembly  20  attached to a pair of rails  45  and a heat exchanger  29  is shown in accordance with an embodiment. Common reference numbers are used to identify components that are generally identical to those of  FIG. 2 . 
         [0022]      FIG. 3  shows a section of the detector assembly  20  with schematic representations of four detector modules  30 . The pair of generally parallel rails  45  are attached to the substrate  36 . Attached to the outer side of each rail  45  is a member  46 . The member  46  is configured to define a passageway  48  that is adapted to transfer the coolant  44 . Each member  46  may be permanently attached to the rail  45  by a process such as bonding or welding, or the member  46  may be removably attached by a bolt, fastener, or other type of removable mounting mechanism (not shown) to facilitate servicing of the detector assembly  20 . The passageway  48  is conductively coupled to the detector modules  30 . It should be understood that while the passageway  48  shown in the embodiment schematically illustrated in  FIG. 3  is generally oval in cross-section and generally parallel to the rails  45 , the passageway  48  could be of any shape. A non-limiting list of passageway  48  shapes includes: generally parallel to the rail  45 ; generally straight; serpentine; and shapes that vary in cross-section along the length of the member  46 . 
         [0023]    While the embodiment shown in  FIG. 3  shows one passageway  48  defined by each of the members  46 , it should be appreciated by those skilled in the art that embodiments could include either one passageway  48  defined by only one of the members  46  or embodiments could also include a plurality of passageways  48  defined by each of the members  46 . The passageways  48  defined by the members  46  in  FIG. 3  are in fluid communication with the heat exchanger  29 . The coolant  44  is caused to circulate by a mechanical device such as a pump (not shown). For example, according to an embodiment, heat originating in the electronic components  38  conductively travels through the substrate  36 . Once in the substrate  36 , the heat travels either directly into the member  46 , or else the heat travels through the rail  45  and then into the member  46 . After reaching the member  46 , heat from the electronic components  38  is absorbed by the coolant  44  circulating through the passageway  48 , thus lowering the temperature of the electronic components  38 . After absorbing heat, the coolant  44  flows through a hose  47  to the heat exchanger  29 . The heat exchanger  29  contains a structure with a large surface area to facility heat transfer as is well-known by those skilled in the art. The temperature of the coolant  44  is lowered after passing through the heat exchanger  29 . After the coolant  44  has been cooled, it is pumped back through a hose  49  and then back into the passageway  48  defined by the member  46 , where it can absorb more heat from the electronic components  38 . The connection between the hose  49  and the passageway  48  is not shown in  FIG. 3 . The heat exchanger is mounted to the rotatable gantry portion  14  (shown in  FIG. 1 ). It should be understood that embodiments may circulate the coolant in a manner other than that shown in  FIG. 3 . 
         [0024]    Referring to  FIG. 4 , a schematic representation of the cross section of the detector module  30  attached to a pair of rails  31  is shown in accordance with an embodiment. The embodiment shown in  FIG. 4  is intended to be a non-limiting exemplary embodiment for illustrative purposes. Common reference numbers are used to identify components that are generally identical to those of  FIG. 2  and  FIG. 3 . 
         [0025]    The embodiment shown in  FIG. 4  includes a housing  50  attached to the substrate  36  and partially surrounding the electronic component  38 . The housing  50  is shaped in a manner so that the housing  50  and the substrate  36  define a passageway  52  adapted to transfer the coolant  44 . Additionally, it should be understood that the electronic component  38  may not be mounted directly to the substrate  36 . For example, according to an embodiment, the electronic component  38  may be mounted to the housing  50  instead of the substrate  36 . 
         [0026]    The embodiment shown in  FIG. 4  also includes a first member  54  and a second member  56  attached to the pair of rails  31 . The first member  54  defines an inflow passageway  58  and the second member  56  defines an outflow passageway  60 . The inflow passageway  58  and the outflow passageway  60  are in fluid communication with the passageway  52  via a first hose  62  and a second hose  63 . Coolant  44  is supplied to the inflow passageway  58 . The coolant  44  flows from the inflow passageway  58  through the first hose  62  and into the passageway  52 . Once in the passageway  52 , the coolant  44  absorbs heat from the electronic component  38 . After absorbing heat, the coolant  44  flows through the second hose  63  and into the outflow passageway  60  defined by the second member  56 . In the embodiment illustrated in  FIG. 4 , the housing  50  defines a separate passageway  52  over each of the detector modules  30 . However, it should be appreciated that the housing  50  may be shaped so that the electronic components  38  from multiple detector modules  30  fit inside a single passageway  52  according to an embodiment. Also, according to another embodiment, the coolant  44  may enter directly into the passageway  52  defined by the housing  50 . Additionally, the coolant  44  may pass through a passageway (not shown) defined by the rail  31 . After the coolant  44  has absorbed heat from the electronic component  38  and flowed to the outflow passageway  60  defined by the second member  56 , the coolant  44  flows to a heat exchanger (not shown) where the coolant  44  is cooled before entering back into the inflow passageway  58  defined by member  54 . The portion of the hydraulic circuit connecting the outflow passageway  60  to the heat exchanger and the heat exchanger to the inflow passageway  58  is not shown as it is well-known by those skilled in the art. Additionally, it should be understood that embodiments may circulate the coolant  44  through the passageway  52  defined by the housing  50  in a manner other than that shown in  FIG. 4 . 
         [0027]    Referring now to  FIGS. 2 ,  3 , and  4 , the coolant  44  may comprise any one of a number of well-known coolants. A non-limiting list of a well-known coolants includes water glycol, mineral oil, and dielectric fluids such as dielectric oil and perfluorocarbon fluid. Other coolants may be employed as well. The particular coolant  44  chosen may depend on the specifics of the application. For example, the range of operating temperatures, the materials used for the rails  28 ,  45 ,  31 , the substrate  36 , or the member  46 ,  54 ,  56  may also affect the choice of coolant  44 . Additionally, for embodiments where the coolant  44  is in direct contact with the electronic component  38  such as that shown in  FIG. 4 , it may be desirable to choose a coolant  44  with dielectric properties to prevent a short-circuit. Additionally, using a coolant  44  and a heat exchanger  29  may manage the temperature of the detector modules  30  and the rails  28 ,  45 ,  31  more effectively, enabling the use of a less expensive material to build the rails  28 ,  45 ,  31 . For example, if the operating temperature of the CT system  10  (shown in  FIG. 1 ) is more closely controlled, it may be possible to use a rail material with a higher coefficient of thermal expansion. For example, conventional CT systems typically use rails made from steel. Embodiments may be able to use a material such as an aluminum alloy, or an aluminum silicon carbide. Some of these rail materials may provide an additional advantage by having a higher stiffness-to-weight ratio than steel, thus enabling a lighter rotatable gantry portion  14  (shown in  FIG. 1 ). 
         [0028]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.