Abstract:
An X-ray tube housing with integrated cooling passages in the walls of the X-ray tube housing, through which a liquid or gas coolant is circulated and the heat is transferred from the X-ray tube housing to an external cooler. The integrated cooling passages are created around the perimeter of the X-ray tube housing as the X-ray tube housing is formed. For a rotating anode X-ray tube using an oil coolant, the path of heat transfer is from the anode to the glass insert and oil by the means of radiation. The oil that is in contact with the glass insert conducts heat away form the insert to the X-ray tube housing which is then cooled by the integrated cooling passages located within the X-ray tube housing through which fluid is passed to an external fluid cooling system.

Description:
FIELD OF THE INVENTION 
   This invention relates generally to medical imaging systems, and more particularly to cooling of portable of medical imaging devices. 
   BACKGROUND OF THE INVENTION 
   Through-put and turnaround of patients is a key economic metric of the productivity of X-ray imaging devices. X-ray imaging devices have a high fixed cost that the owners and operators of the X-ray imaging devices seek to either reduce and/or the owners and operators seek to derive the greatest amount of productivity from the devices, in order to obtain the greatest return-on-investment from the X-ray imaging device. 
   One way to derive the greatest amount of productivity from the X-ray imaging device is to increase the number of subjects or patients that are imaged in an amount of time. However, the amount of time needed to image a subject is limited to some extent by the amount of time that is required in between imaging sessions to cool the X-ray tube that is in the X-ray imaging device. 
   An X-ray tube typically converts more than 99% of all the energy supplied to the X-ray tube into heat as an unwanted by-product of producing the desired X-rays. The effective management of X-ray tube heat is a key element in the design of X-ray tube housings. 
   Improving the transfer of heat energy away from the X-ray tube facilitates increased use of the system and is more efficient for the user since less time is spent waiting for the X-ray tube to cool. 
   Conventional liquid cooled X-ray tube designs include a pump and a heat exchanger mounted on the X-ray tube. The pump circulates oil from inside the X-ray tube housing through a heat exchanger that cools the oil by either forced air convection or by an external liquid cooler. 
   Other conventional solutions have incorporated secondary external or internal plumbing lines into the X-ray tube housing, through which a coolant is circulated. The cooling lines typically route the coolant to a radiator near the X-ray tube and a fan cools the plumbing lines in or on the X-ray tube housing. 
   Mobile X-ray equipment needs to minimize weight and power requirements. Existing cooling solutions have resulted in increased weight and power requirements at the X-ray tube. Any increased weight at the X-ray tube is particularly undesirable due to the counter balancing required for the gantry, and the use of a fan restricts use of the system in some surgical environments. 
   Conventional X-ray tube housings require a complex design with many parts to integrate the secondary plumbing and customized cooling solutions within the X-ray tube housing which result in high manufacturing and assembly costs. 
   For the reasons stated above, and for other reasons stated, there is a need in the art for an X-ray tube cooling system that has the weight at the X-ray head. There is also a need to reduce the use of fans at the X-ray tube; to reduce the power requirements at the X-ray tube; and to improve the heat transfer from the X-ray tube housing. 
   BRIEF DESCRIPTION OF THE INVENTION 
   The above-mentioned shortcomings, disadvantages, and problems are addressed herein, which will be understood by reading and studying the following specification. 
   In one aspect, passages are integrated into the walls of the X-ray tube housing, through which a substance having a temperature that is less than the operating temperature of the X-ray tube is circulated, and the heat is transferred from the X-ray tube housing to an external cooler. In some embodiments, the substance is liquid. 
   In another aspect, the integrated cooling passages are included about the perimeter of the X-ray tube housing as the X-ray tube housing is formed. In some embodiments using a rotating anode X-ray tube and an oil coolant, the path of heat transfer is from the anode to the glass insert and oil by the means of radiation. The oil that is in contact with the glass insert conducts heat away form the insert to the X-ray tube housing which is then cooled by the integrated cooling passages located within the X-ray tube housing through which fluid is passed to an external fluid cooling system. 
   Apparatus, systems, and methods of varying scope are described herein. In addition to the aspects and advantages described in this summary, further aspects and advantages will become apparent by reference to the drawings and by reading the detailed description that follows. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an overview diagram of an illustrative X-ray tube housing four coolant passages. 
       FIG. 2  is a diagram of an illustrative X-ray tube housing showing the connections between coolant passages, an illustrative X-ray tube mounted within, and the connections to the external cooler. 
       FIG. 3  is a conceptual diagram of the new method of cooling the X-ray tube. 
       FIG. 4  is a diagram of an illustrative end-view of an X-ray tube housing showing the connections between coolant passages, an illustrative X-ray tube mounted within, and the connections to the external cooler. 
       FIG. 5  is a diagram of an illustrative end-view of an X-ray tube housing. 
       FIG. 6  is a diagram of an illustrative side-view of an X-ray tube housing showing the connections between coolant passages, an illustrative X-ray tube mounted within, and the connections to the external cooler. 
       FIG. 7  is a diagram of an illustrative side-view of an X-ray tube housing showing the connections between coolant passages, an illustrative X-ray tube mounted within, and the connections to the external cooler. 
       FIG. 8  is a flowchart showing the movement of heat through the system. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   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 which 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 in a limiting sense. 
   The detailed description is divided into four sections. In the first section, a system level overview is described. In the second section, apparatus of embodiments are described. In the third section, embodiments of methods are described. Finally, in the fourth section, a conclusion of the detailed description is provided. 
   System Level Overview 
     FIG. 1  is an overview diagram of an illustrative X-ray tube housing  100  using four coolant passages  102 - 108  running through the X-ray tube housing  100 . The coolant passage  102  extends from opening  110  to opening  112 ; coolant passage  104  extends from opening  114  to opening  116 ; coolant passage  106  extends from opening  118  to opening  120 ; and coolant passage  108  extends from opening  122 . In this illustrative embodiment, X-ray tube housing  100  is manufactured using an extrusion former as a single unit requiring no assembly and obviates mounting secondary plumbing within the X-ray tube housing  100 . 
   By integrating cooling passages  102 - 108  directly into the walls of the X-ray tube housing  100 , a liquid or gas coolant heat exchange can be externally mounted and connected by flexible pipe to the X-ray tube, avoiding excessive weight and power requirements at the X-ray tube and allowing any fan to be safely situated far from the X-ray tube. 
   Building cooling passages  102 - 108  directly into the X-ray tube housing  100  allows efficient heat exchange from the internal coolant surrounding the X-ray tube inside the X-ray tube housing  100  to an externally-located liquid or gas coolant heat exchange. 
   In this illustrative embodiment, cooling passages  102 - 108  are built into the X-ray tube housing  100  using an extrusion former to enable the manufacture of the X-ray tube housing  100  and cooling passages  102 - 108  as a single form. The number of cooling passages is limited only by the capability of the extrusion former and the design of the housing. 
   Integrating the cooling passages  102 - 108  into the X-ray tube housing  100  simplifies the complexity of the X-ray tube housing assembly by obviating separate secondary plumbing and assists in the external lactation of the heat exchanger. The internal plumbing in this invention is built into the walls of the housing and thus gives the required strength from the metalwork being used to provide the main housing. Integrating plumbing within the X-ray tube housing gives strength to allow the external piping to an external cooling system by increasing the strength of the X-ray tube housing  100  and including the cooling passages  102 - 108  permits the external mounting of the heat exchanger and cooling system. The X-ray tube housing  100  also obviates mounting a cooling fan at the X-ray tube that allows the use in more surgical environments. 
   The X-ray tube housing  100 , by integrating coolant passages  102 - 108 , also obviates many separate cooling parts within the X-ray tube housing, thereby lowering assembly cost by removing the requirement for additional pipework that needs to be separately manufactured. Not only is the additional miniature pipework not required, but the required mounting problems are avoided and the corresponding assembly issues previously involved in connecting the pipework to the external cooler are eliminated because the housing already contains the pipe within the single piece. 
   The X-ray tube housing  100  also solves the need in the art to mount the cooling unit directly at the X-ray tube and allows the use of an external cooler not on the gantry holding the X-ray tube, thus reducing the weight of that cooler and removing the need for additional power lines to the X-ray tube housing. The integration of the coolant pipes into the housing avoids the need to minimize stress upon that pipework because the housing itself provides the superior strength such that any torque applied at the connection point to the external cooler can be distributed across the entire housing. This resistance to torque allows the use of external tubing, which will exert such force, whereas the prior art use of internal, discrete, piping would place all such torque upon the mounting point which would not be able to withstand the strain and thus require the use of a cooling unit directly attached to the X-ray tube housing. 
   While the integration of the cooling passages  102 - 108  into the X-ray tube housing  100  is not limited to any particular number of coolant passages, for sake of clarity a simplified design using four passages is described. Depending upon the competing requirements of the strength, weight, and coolant flow any number of passages could be used from a single larger passage with high coolant flow through to a large number of passages that would allow more uniform heat dissipation. 
   Apparatus Embodiments 
     FIG. 2  is a diagram of X-ray tube  100  housing showing the connections between coolant passages, an illustrative X-ray tube mounted within, and the connections to the external cooling unit. The X-ray tube housing  100  is connected to the external cooling unit through fittings  202  and  204  in openings  112  ( FIG. 1) and 116 , respectively. 
   Openings  110  and  122  are coupled to one another through fittings  206  ( FIG. 2) and 208  and a pipe  210  coupled there between. A pipe  212  connects an opening at the hidden end of coolant passage  108  ( FIG. 1 ) to opening  202  at a fitting  216  ( FIG. 2 ). A pipe  218  couples fittings  214  and  220  to thereby couple opening  118  ( FIG. 1 ) to opening  114 . 
   Flow within the X-ray tube housing  100  is directed as follows: coolant from an externally located coolant heat exchange (i) enters through fitting  202 ; (ii) passes through fitting  116  and though coolant passage  102 ; (iii) passes through fitting  206 , pipe  210 , and fitting  208  to coolant passage  108 ; (iv) through coolant passage  108 , pipe  212 , and fitting  106  to coolant passage  106 ; (v) through coolant passage  106 , fitting  214 , pipe  218 , and fitting  220  into coolant passage  104 ; and (vi) out fitting  204  to the externally located heat exchange. 
   In an alternative embodiment, the flow of coolant through the X-ray tube housing  100  is in the opposite direction. Within the X-ray tube housing  100  is sealed the primary coolant  222  which is oil in this illustration. The actual X-ray tube  224  is mounted within the X-ray tube housing  100  in a conventional manner. 
     FIG. 3  is a block diagram of the new method of cooling the X-ray tube. The X-ray tube housing  100  contains the X-ray tube  224  but is created with integral cooling passages that are attached by external lines  302  and  304  to an external coolant heat exchange  306 . 
     FIG. 4  is a diagram of an illustrative end-view of an X-ray tube housing showing the connections between coolant passages, an illustrative X-ray tube mounted within, and the connections to the external cooler. 
     FIG. 5  is a diagram of an illustrative end-view of an X-ray tube housing. 
     FIG. 6  is a diagram of an illustrative side-view of an X-ray tube housing showing the connections between coolant passages, an illustrative X-ray tube mounted within, and the connections to the external cooler. 
     FIG. 7  is a diagram of an illustrative side-view of an X-ray tube housing showing the connections between coolant passages, an illustrative X-ray tube mounted within, and the connections to the external cooler. 
   Method Embodiments 
   In the previous section, embodiments of apparatus are described. In this section, embodiments of methods are described. 
     FIG. 8  is a flowchart showing an illustrative flow of heat through the system when using a rotating anode X-ray tube using an oil coolant. Unwanted heat is generated by the X-ray tube  802  which in the illustrative embodiment is surrounded by oil to absorb that heat  804 ; the oil is contained in an X-ray housing that is heat conductive  806  and is cooled by coolant fluid caused to flow through one or more passages in the X-ray housing  808 ; the fluid circulates outside the X-ray tube housing  810  and is removed from the fluid by an external cooling system  812 . 
   CONCLUSION 
   An X-ray tube housing with integrated cooling passages is described. Although specific embodiments are illustrated and described herein, any arrangement that is calculated to achieve the same purpose may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations. For example, although described as using four cooling passages within the X-ray tube housing, implementations can be made using 1, 2, 6, 8, or any other number of cooling passages that provides the required function. 
   In particular, the names of the methods and apparatus are not intended to limit embodiments. Furthermore, additional methods and apparatus can be added to the components, functions can be rearranged among the components, and new components to correspond to future enhancements and physical devices used in embodiments can be introduced without departing from the scope of embodiments. Embodiments are applicable to future imaging devices, different medical devices, and new examination equipment. 
   The terminology used in this application with respect to X-ray tube housing tubes is meant to include all imaging housings and secondary cooling environments and alternate technologies which provide the same functionality as described herein.