Abstract:
An integrated x-ray imaging detector assembly is provided for use in an x-ray imaging system. An x-ray detector module is supported by a frame and receives a beam of x-rays emitted from an x-ray source and passed through a target along a detector axis. The x-ray detector is further operable to produce electrical signals in response to the received beam of x-rays. A display terminal is supported by the frame and disposed behind the detector module with respect to the direction of x-ray beam travel. The display terminal is configured to receive the electrical signals and produce an output image corresponding to the electrical signals.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional patent application Serial No. 60/334,745 and entitled “X-RAY POSITIONER WITH SIDE-MOUNTED, INDEPENDENTLY ARTICULATED ARMS” filed on Nov. 15, 2001, the disclosure of which is hereby incorporated by reference as if set forth in its entirety herein. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     BACKGROUND OF THE INVENTION 
     This application relates to medical x-ray positioners and in particular to a positioner using independently articulated arms to support the x-ray source and x-ray detector. 
     Conventional x-ray positioners provide mechanical supports to hold an x-ray source and x-ray detector in opposition about a patient for a limited number of specific procedures. For procedures in which the patient is standing, the x-ray source may be attached to a pillar allowing adjustment in its height as directed toward an x-ray detector attached to an opposing wall or a second similar pillar. For procedures in which the patient is supine, the x-ray source and detector may be attached to opposite sides of a patient table. Alternatively the x-ray source and the detector may be attached to opposite ends of a C-arm which-is supported by a sliding collar allowing the angle of the x-rays through the patient to be varied. 
     Multi-axis robotic arms, positioned above and below the patient table, have been proposed to provide support for the x-ray source and x-ray detector such as may reduce interference between the support structure and other equipment and personnel. See, for example, U.S. Pat. No. 6,200,024 to Negrelli citing U.S. Pat. No. 4,894,855 to Kresse. 
     Such systems require complex multi-axis movement for simple adjustments of the x-ray tube and detector in angulation or translation, and appear to have limited utility for certain common x-ray procedures such as those requiring the patient to stand. Further such systems make it difficult or impossible to swap the location of the x-ray source from beneath the patient to above the patient, when the patient is supine, and an improved image might thereby be obtained. Moreover, such systems provide a display located remote from the x-ray detector, thus causing difficulty to an attending operator who is manipulating the arms while attempting to view the image. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides an integrated x-ray detector assembly for use in an x-ray imaging system. The detector assembly includes a support frame that supports an x-ray detector module that is operable to receive a beam of x-rays emitted from an x-ray source and passed through a target along a detector axis. The detector assembly is further operable to produce electrical signals in response to the received beam of x-rays. A display terminal is also supported by the frame and disposed behind the detector module with respect to the direction of x-ray beam travel. The display terminal is configured to receive the electrical signals and produce an output image corresponding to the electrical signals. In at least one configuration, the image is viewable while the display terminal extends normally with respect to the detector axis and is aligned with the detector module. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of one embodiment of the positioner of the present invention showing offset mounting of two independently articulated arms holding an x-ray source and x-ray detector assembly, respectively; 
     FIG. 2 is a perspective view of the detector of FIG. 1 showing a tilting upward of an integral display of the detector assembly and axes of movement of a control handle supported by the detector assembly; 
     FIG. 3 is a cross-sectional view of the detector assembly of FIG. 2 taken along lines  3 — 3  of FIG. 2 showing the normal registration of an x-ray detector and the display; 
     FIG. 4 is a view (top or side) of the articulated arms of the FIG. 1 showing, in phantom, arm movement implementing an increased source-to-detector distance; 
     FIG. 5 is a side elevational viewing of the articulated arms of FIG. 1 showing positioning of the arms for lateral imaging; 
     FIG. 6 is an exploded perspective diagram showing various options for adding common axes to the articulated arms of FIG. 1 for different procedures; 
     FIG. 7 is a schematic block diagram of the servo motors associated with the axis of FIGS. 1 and 6 and a controller for controlling the axes as well as the x-ray detector and x-ray source according to the present invention; 
     FIG. 8 is a functional diagram of tasks implemented by the controller of FIG. 7 to control the axes according to one embodiment of the invention; 
     FIG. 9 is a functional diagram task implemented by the controller of FIG. 7 to automatically or semi-automatically track a bolus according to one embodiment of the invention; 
     FIG. 10 is a front elevational view of a supine patient showing the x-ray detector and x-ray source positioned by the present invention in the offset opposition; and 
     FIG. 11 is a perspective view of the x-ray detector and x-ray source of FIG. 10 showing offset collimation of the x-ray source and a region of interest display shown on the display x-ray detector assembly. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, a multi-mode x-ray positioner  10  per the present invention provides an x-ray source  12  and an x-ray detector  14 . The x-ray source  12  generally includes an x-ray tube, the necessary cooling components, collimators, and shielding as will be understood to those of ordinary skill in the art. The x-ray detector  14  may be a lightweight flat panel detector such as may be fabricated as an array of detectors, an amorphous silicon detector panel or other imaging device. The x-ray detector is part of a detector assembly  16  to be described in greater detail below. 
     The x-ray source  12  directs an x-ray beam generally along a central ray  13  whereas the x-ray detector  14  receives x-rays generally along a central ray  15  normal to the surface thereof. A patient  50  may be supported supine on a table  56  so as to be aligned with the.central rays  13  and  15 . For this purpose, the table  56  is composed of a radiotranslucent material of a type well known in the art. 
     Referring also to FIG. 4, each of the x-ray source  12  and the x-ray detector  14  are held, respectively, on separate articulated robot arms  18  and  20 . The arms  18  and  20  are attached at a first end to a base  22 , the latter preferably supported against a vertical surface with the arms extending laterally therefrom. 
     The arms  18  and  20  attach to the base  22  at shoulder axes  26  and  24 , respectively. Each shoulder axes  26  and  24  provides angulation of its respective arm  18  or  20  about parallel axes extending generally along the plane of the base  22 , the latter being parallel to a vertical plane defining the surface to which the base  22  is attached. Generally the term “axis” henceforth will refer both to a mechanical joint and the mathematical vector describing movement of that joint. The particular meaning will be evident from context. 
     Attached to and extending from shoulder axes  24  and  26  are upper arms  30  and  32 , respectively, which terminate in elbow axes  34  and  36 , respectively, each also providing for angulation along parallel axes also parallel to axes  24  and  26 . Forearms  38  and  40  extend-from elbow axes  34  and  36 , respectively, and the latter which provide telescoping extension axes  42  and  44  permitting translation movement of wrist axes  46  and  48  along the length of the forearms  38  and  40 . 
     Wrist axes  46  and  48  provide angulation about parallel axes also parallel to axes  24  and  26  and connect, respectively, to the x-ray detector assembly  16  and x-ray source  12 . It is to be understood that the x-ray source and x-ray detector assembly are not limited to mounting on a particular arm and may be replaced by other devices to meet other clinical needs. 
     It will be understood from this description that each of the arms has four axes of motion comprised of shoulder axes  24 , elbow axis  34  and wrist axis  46  and extension axis  42 , for arm  20  and shoulder axes  26 , elbow axis  36 , and wrist axis  48 , and extension axis  44  for arm  18 . Generally, motion of shoulder axes  24  and  26  control the angle of upper arms  30  and  32  and the position of elbow axes  34  and  36  with respect to shoulder axes  24  and  26 . Likewise, motion of elbow axes  34  and  36  control the angle of forearms  38  and  40  and the position of wrist axes  46  and  48  with respect to the elbow axes  34  and  36 . Motion of extension axes  42  and  44  control the separation of elbow axis  34  and wrist axis  46  and elbow axis  36  and wrist axis  48 , respectively, and motion of wrist axes  46  and  48  control the angle of detector  14  and x-ray source  12 . 
     Each of axes  24 ,  26 ,  34 ,  36 ,  42 ,  44 ,  46 , and  48  are enabled for servo control meaning that they may be moved electronically in response to a position and/or motion signal received from the axis so that precise positioning and/or velocity control of each axis may be had through a central controller or group of interconnected controllers as will be described below. 
     Referring again to FIGS. 1 and 4, the arms  18  and  20  may be maneuvered to position the x-ray source  12  and detector assembly  16  in alignment on opposite sides of a patient  50  at a first source-to-detector distance  52 . Subsequently, the arms  20  may be maneuvered, through a combined motion of their axes, to provide a source-to-detector distance  54  substantially greater than source-to-detector distance  52 , while maintaining alignment. Such separation is accomplished principally by a combined angulation and extension of the axes  24 ,  26 ,  34 ,  36 ,  42 ,  44 ,  46 , and  48  and notably does not require an axis of translation aligned with the central rays  13  and  15  of the source and detector as is typical of conventional x-ray positioners. 
     Referring again to FIGS. 1 and 4, the base  22  may be mounted on a waist axis  64  providing rotation about a line that is horizontal and perpendicular  60  to the plane of the base  22 , the rotation as indicated by arrow  62 . Thus, the arms  18  and  20  in their various source-to-detector separations  52  and  54  shown in FIG. 4 may be opposed about a substantially vertical axis (as depicted in FIG. 1) or about a horizontal axis. The horizontal axis is useful for procedures such as chest x-rays or other situations where the patient is best imaged while standing or seated. In these cases, the table  56  would be moved to a vertical configuration or moved out of the way altogether. The rotation of the base  22  about the waist axis  64 , as with the other axes, is under servo control and provides single axis cranial-caudal angular adjustment. 
     Alternatively as shown in FIG. 5, the arms  18  and  20  may be manipulated to provide central rays  13  and  15  perpendicular to the plane of the base  22 . In this case, the arms  18  and  20  are not deployed symmetrically but elbow axis  34  is moved to an acute position whereas elbow axis  36  is moved to an obtuse position with extension axis  44  fully extended and extension axis, 42  fully retracted. This degree of flexibility is accomplished because each of the axes  24 ,  26 ,  34 ,  36 ,  44 ,  42 ,  46  and  48  are independently controllable. 
     Referring to FIG. 6, the base  22  may be mounted directly on a wall or the like by means of stationary collar  70  receiving the waist axis  64 . Alternatively, and as also shown in FIG. 6, the base  22  may be attached to a vertically translating collar  72  also receiving the waist axis  64  but providing for vertical translation along tracks  74  also under servo control to form translation axis  81 . Opposed ends  76  of the track  74  may be held against the wall or vertical surface by stationary collars  78  (only one of which is shown for clarity) similar to stationary collar  70 . The translation axis  81  allows single axis elevation of the x-ray source  12  and x-ray detector  16 . 
     Alternatively, the end  76  may be received by horizontally translating collars  80  moving horizontally along tracks  82  so as to provide a horizontal servo control translation axis  85  for the tracks  74 , the base  22 , and thus the arms  18  and  20 . 
     In an alternative configuration, the base  22  may be mounted to horizontally translating collar  90  of the tracks  92  positioned to extend horizontally along axis  91 . The ends  94  of the tracks  92  may be attached either to a stationary collar  96 , similar to stationary collars  78  or to horizontally vertically collars  98  but with the track  100  positioned to move along vertical axis  83 , the latter having its ends  102  fixed to a stationary surface such as a wall or the like. The translation axis  91  allows single axis horizontal repositioning of the x-ray source  12  and x-ray detector  16 . 
     While the two configurations represented in tree fashion by the branches ending with the axis  85  and  83  of FIG. 6 result in the same degrees of freedom, they provide alternate evolution paths allowing the positioner  10  to be upgraded from a base system having only base  22  and arms  18  and  20  to a full featured system through the addition, respectively, of various components of vertically translating collar  72 , or horizontally translating collars  90 . A wiring harness system (not shown) allows each of these axes to be added to an axis controller to provide improved functionality as will be described below. 
     Referring now to FIGS. 1,  2  and  3 , the detector assembly  16  includes a flat panel x-ray detector  14  on a first surface normally facing the x-ray source  12  and held within a supporting frame  106 . The flat panel x-ray detector  14  is sized to receive a collimated beam of x-rays  104  from the x-ray source  12  and positioned immediately behind the flat panel x-ray detector  14  is a blocking lead shield  1   10 . This may be followed by processing circuit cards  112  and  114 . Following the circuit cards  112  and  114  is a flat panel display  116 . 
     The flat panel display  116  may receive an image registered with the image received by the x-ray detector  14  for display to a human operator viewing the image from the top side of the detector assembly  16 . In this configuration, the image displayed by the flat panel display  116  remains in perfect registration with the x-ray detector  14  thus eliminating confusion that can result in normal fluoroscopy systems where the image may rotate on a stationary monitor with respect to the patient as the positioner is moved. As shown in FIG. 2, in order to provide for oblique viewing angles, the flat panel display  116  may hinge upward about one of two perpendicular hinge axes  128  or  130  so as to provide better viewing for the user while still maintaining rotational registration with the patient&#39;s anatomy. 
     Accordingly, a user, such as an attending physician, need not adjust the position of an x-ray source based on images from a display that is located remotely from the source, as in conventional systems. The present invention is thus particularly useful during a medical procedure, whereby the user may attend to his/her task while viewing-the x-ray image of the patient in one field of vision. 
     Also supported on the top side of the frame  106  is a touch screen panel  118  providing for basic level control of the x-ray system including x-ray tube voltage, exposure time, and other techniques. The front portion of the frame  106  also supports a multi-axis control handle  120  providing a number of signals depending on movement of the handle by the operator either vertically, horizontally or in rotation as shown by arrows  124  and shown also in FIG. 2. A second blocking lead shield  108  may be attached to a portion of the supporting frame  106  positioned toward the operator during normal use as shown in FIG.  1 . 
     The circuit cards  112  collect data from the x-ray detector  14  for a control system to be described. The circuit card  114  provides an interface for the control system with the touch screen panel  118  and a multi-axis control handle  120 . 
     Referring now to FIG. 7, each of the different axes  24 ,  26 ,  34 ,  36 ,  42 ,  44 ,  46 ,  48 ,  64 ,  81 , and  84  provides feedback signals and receives a command signals from an axis control interface  132  so as to provide for servo control of each axis according to techniques well known in the art. The axis control interface  132  connects to a central bus  134  of a controller  136 . The controller  136  is constructed according to conventional computer architecture and includes a processor  138  communicating with the bus  134  and with memory  140  which may include both random access and magnetic disk memory or other mass storage devices. A modem  142  and/or device such as a network interface card also communicating with the bus provide pathways for downloading of information and programs into the memory  140  as will be described. The controller  136  may be a single computer or a number of interconnected computers providing the various functions and services. 
     The controller  136  also provides a signal through port interface  144  (also attached to bus  134 ) to a high voltage power supply  146  feeding the x-ray source  12  so as to provide control over current and x-ray tube voltage and on and off duty cycle. Diagnostic signals may also be received from the power supply  146  via this port interface. Additional ports interfaces  150 ,  152 , and  154  provide communication between the central bus  134  and the control handle  120 , the x-ray detector  14 , the flat panel display  116 , and the touch screen panel  118  described above. 
     During operation, the processor  138  runs a control program  170  held in memory  140  to control the various axes  24 ,  26 ,  34 ,  36 ,  42 ,  44 ,  46 ,  48 ,  64 ,  81 , and  84  and to control the x-ray exposure of a patient and to receive and process the image data for display on the flat panel display  116  according to commands received through the control handle  120  and touch screen panel  118 . 
     The memory  140  may also hold a hardware configuration file  160  and one or more personality files  162 . The hardware configuration file  160  stores data on the various components as shown in FIG. 6 that have been assembled together to produce the particular positioner  10 . The personality files  162  contain models for how the x-ray system will operate, for example, emulating a fluoroscopy system with a spot film device or C-arm type configuration. Each of the personality files  162  includes a zero configuration variable describing how the positioner  10  should be initialized prior to patient scan. More generally, the personality files  162  may include one or more predefined procedures involving dynamic movement of the arms  18  and  20  for a particular procedure such as tomography. The personality files  162  also define how the control handle  120  will be interpreted to axes movement. 
     For example, it may be desired to operate the positioner to emulate a fluoroscopy machine with a C-arm type structure. In this case, fluoroscopy C-arm type personality files  162  would be loaded and invoked through touch screen panel  118 . 
     Referring now to FIG. 8, the control program  170  makes use of the configuration file  160  and the personality files  162  to implement control function blocks for the operation of the positioner  10 . A first function block provides a control map  172  mapping movements of the control handle  120  to movements in a room coordinate system. For example, if the positioner  10  is programmed to emulate a C-arm type device, rotation of the control handle  120  may cause angulation of the C-arm effectively rotating the central rays  13  and  15  about a center point  174  shown in FIG.  7 . The center point may be defined by the center of the base  22  or be arbitrarily located through multiple axis motion as determined by the personality file  162 . Vertical and horizontal movement of the control handle  120  may raise or move laterally the virtual C-arm simultaneously moving the x-ray source  12  and x-ray detector  14  as if they were connected by a rigid bar. The assignment of the control handle  120  to particular room coordinates is arbitrary and even in this case, for example, they may be assigned differently with vertical movement of the control handle  120  changing source-to-detector distance rather than raising or lowering the x-ray detector  14  and x-ray source  12  in unison. Likewise, the motion of the positioner components with respect to each other may be arbitrarily defined to simulate positioners of varying geometries. 
     The control map  172  produces commands  178  in room coordinates or virtual machine coordinates (the latter which describe motion of machine components, such as a C-arm which do not in fact exist). The commands  178  are received by axis parsing and translation module  180  which interrogates the hardware configuration file  160  to see what axes are available in order to realize the coordinate commands  178 . Generally there will be more than one combination of different axes movements and the axis parsing and translation module  180  will select among these looking at other considerations, for example, accessibility and the avoidance of collision within the patient space. 
     The axis parsing and translation module  180  translates the commands  178  into positioner axes commands  182  which are provided to one of the arms, preferably  20 . The second arm  18  will receive positioner axis coordinates  184  from a virtual axis link  186 . The virtual axis link  186  receiving as inputs the positioner axes commands  182  from the axis parsing and translation module  180  and providing corresponding positioner axis commands  184  to achieve the desired virtual linkage between the x-ray source  12  and x-ray detector  14  as defined by the configuration file  160  and the personality files  162 . Generally this linkage will amount to simulation of a virtual structure directly connecting the x-ray source  12  and x-ray detector  14  together such as a bar or C-arm or the like. 
     Because the arms  18  and  20  are not so connected, a variety of other personalities may be adopted including those which provide for complex independent movement of the x-ray source  12  and x-ray detector  14  for tomography and the like. 
     As mentioned, a zero configuration variable may be read by the control program  170  to determine the starting position of the positioner  10 , e.g., whether the x-ray source  12  and x-ray detector  14  are positioned horizontally with respect to each other or laterally or for a standing patient or the like. Zero configuration task  190  handles this initialization of the axes making use of the hardware configuration file  160  and the particular machine model in personality files  162 . The program  170  may also implement a procedure engine  192  which records particular procedures including techniques, exposure times, motion and positioning of the arms that may be collected and exchanged by physicians or skilled practitioners. These procedures may be invoked through the touch screen panel  118 . 
     Referring momentarily to FIG. 7, the hardware configuration file  160  and the various personality files  162  may be loaded via the modem  142  and thus the positioner  10  may be configured remotely and users of the positioner  10  may trade different configurations, personality modules and procedures with each other as they are developed. 
     Referring now to FIG. 9, one such procedure may receive image data from the x-ray detector  14  into a summing unit  193  implemented by the program  170  and also into an image buffer  194 . A subtraction of a previously buffered image and the current image yields motion data  195  which may be operated on by a morphometric filter  196  to identify, for example, a moving bolus of contrast medium in certain types of studies. The morphometric filter may be initialized by user parameters  202  that may be part of a procedure engine module being one of personality files  162 . 
     The location of the bolus relative to the position of the x-ray detector  14  may be extracted as position coordinates  200  in the room or machine frame of reference. The position coordinates  200  may be fed directly to the control map  172  so as to provide for automatic bolus tracking in which the arms  18  and  20  are automatically moved so as to maintain a bolus of contrast medium within the x-ray beam. Memory  140  may also store images including video sequences and the like, user parameter data and other data well known in the art. 
     Referring now to FIG. 10, the small profile of the detector assembly  16  allows for more flexible positioning with respect to patient  50  than would be obtained with a comparable apertured image intensifier  210  shown in dotted outline. This flexibility is further enhanced by the ability to offset the central ray  13  of the x-ray source  12  with respect to the axis  15  of the x-ray detector  14  by displacement of the x-ray source or by offset collimation of the x-ray beam. In either case, when a small beam of x-rays is required, that beam may be directed to a desired area of the x-ray detector  14  rather than to the center of the x-ray detector  14  and that area preferentially scanned. This capability allows improved positioning with respect to the patient  50  without obstruction by the unused areas of the detector assembly  16  for large apertured x-ray detectors  14  or  210  such as may be desirable in particular positioning situations. 
     Referring to FIG. 11, as mentioned, the displacement of the central ray  13  may be performed by angulation of the x-ray source  12  through additional axes (not shown) or by adjustment of a collimator  212  to collimate the x-ray beam to less than the area of the detector but also to offset the center of the beam toward a detector edge. Control of a collimator  212  to control the exit aperture of the x-ray beam is well known in the art, and is modified only to displace the central ray  13  of the beam. Positioning of the detector assembly  16  may be enhanced by the generation of an x-ray reception pattern  214  on the face of the flat panel display  116 , showing the operator the active area of the x-ray detector  14  on the opposite side of the detector assembly  16  prior to exposure. 
     It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but that modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments also be included as come within the scope of the following claims.