Abstract:
A mobile C-arm fluoroscopy unit comprising a self-contained radial coordinate or vector movement mechanism utilizing at least one motor-driven wheel, wherein the at least one motor-driven wheel is individually continuously steerable around a generally vertical steering axis.

Description:
REFERENCE TO PENDING PRIOR PATENT APPLICATION 
       [0001]    This patent application claims benefit of pending prior U.S. Provisional Patent Application Ser. No. 61/880,213, filed Sep. 20, 2013 by John K. Grady for MOTORIZED DRIVE FOR MOBILE FLUOROSCOPY UNITS (Attorney&#39;s Docket No. GRADY-1 PROV), which patent application is hereby incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to precision operator control and setting of the location of the center of a mobile X-ray unit beam, such as where X-ray fluoroscopy is used in the operating room on mobile or “portable” self-contained fluoro or C-arm units, particularly in the “Digital OR” or surgical navigation environment. 
       BACKGROUND OF THE INVENTION 
       [0003]    Prior approaches to X-ray positioning of mobile C-arms have required the use of a second carriage or “X” motion element mounted on the wheeled unit base to provide one axis of an X-Y system, the wheels on the floor providing the other or “Y” axis motion. The “Y” axis motion also provides travel mobility from room to room. Such a design is inherently limited in the amount of X-axis travel the second carriage provides as its cross-travel support bearings must overload if placed too close together; and such a carriage increases the width of the mobile unit, and can cause tipping instability, if the travel beyond the base footprint is made as large as it might be desired. 
         [0004]    The prior art such as Galando (U.S. Pat. No. 6,374,937) and patents cited therein provide extensive detail of this approach, which can be summarized as providing a means to scan a patient in the operating room with a small field C-shaped X-ray viewer using X-Y drives. However, the units described in Galando (U.S. Pat. No. 6,374,937) consist of a mobile base often with swiveling or power driven castors or indexable wheels on the floor, always combined with an upper slide or carriage for the other (i.e., cross table) motion. The upper carriage motion is intended to be used at 90 degrees to the direction of travel of the wheels on the floor when the unit is in a position to be used on the patient, thus forming an X-Y coordinate system. The floor wheels provide the long travel (head to foot, or “Y” travel) and the second upper carriage provides the motion across the patient&#39;s width (or “X” travel). 
         [0005]    See, for example,  FIGS. 1 and 2 , which show a mobile fluoroscopy unit  5  which generally comprises a mobile base  10  movable on powered wheels  15  so as to provide “Y” travel, and comprising a secondary carriage  20  movable on mobile base  10  so as to provide “X” travel, wherein a C-arm  25  is mounted to secondary carriage  20 . Casters  30  provide support for mobile base  10 . As a result of this construction, mobile base  10  may be moved on powered wheels  15  (and casters  30 ) so as to provide Y travel for the unit (and hence Y travel for C-arm  25 ) and secondary carriage  20  may be moved on mobile base  10  so as to provide X travel for C-arm  25 . 
         [0006]    The other prior art do not actively address steerable wheels at all, and depend on “grocery store-type” casters for steering. 
         [0007]    With Galando (U.S. Pat. No. 6,374,937), the main travel wheels  15  of mobile base  10  may also be indexed to a “straight” position for moving mobile fluoroscopy unit  5  over substantial distances, e.g., throughout the hospital. Thus, with Galando (U.S. Pat. No. 6,374,937), the two indexed main travel wheel positions (and resulting travel motions) are “straight ahead” for moving the mobile fluoroscopy unit throughout the hospital, and 90 degrees from that when used with an X-ray stretcher or table. In other words, with Galando (U.S. Pat. No. 6,374,937), powered wheels  15  can be set for X travel while moving the unit into position, or for Y travel during positioning of C-arm  25  along the length of the patient (and with C-arm  25  then being set for X travel across the width of the patient using secondary carriage  20 ). 
         [0008]    While this works reasonably well conceptually, there are serious limitations: the extent of cross-travel motion (i.e., the degree of X travel) is inherently limited to the width or length of the secondary carriage  20  (or traveling member) in the X direction, minus its support bearing spacing. This means a wide base is necessary (i.e., side-to-side, or 90 degrees from patient&#39;s long axis in use), but even if a wide base is provided, the overhanging mass of such a design will eventually cause the unit to fall over if the travel is made large. 
         [0009]    For instance, in Galando (U.S. Pat. No. 6,374,937), at column 5, lines 31-43, the construction is described as a “preferred embodiment” and is in fact the only embodiment shown: the upper carriage (i.e., secondary carriage  20 ) construction is inherent to all the methods of use described in the patent. 
         [0010]    Further, in Galando (U.S. Pat. No. 6,374,937), at column 6, lines 14-24, the invention is described as positioning the floor drive wheels into two positions 90 degrees from each other. In one position the wheels are pointed generally “straight ahead” for moving down a hospital corridor, while in the other position they are turned 90 degrees so that the unit travels along the long axis of the patient with the C-arm hanging to one side, over the patient&#39;s anatomy. Then, to position the X-ray beam across the patient, the second, limited travel upper carriage  20  is invoked in the X-direction. There is no other way to use the system described therein. 
         [0011]    Again, in Galando (U.S. Pat. No. 6,374,937), at column 6, lines 56-58, the indexed wheels  15  are described as being pivoted from a “traveling position” to an “operating position”, clearly describing the intention of the vertical axis as indexing between two discrete positions. 
         [0012]    In contrast, in the present invention discussed below, this vertical or steering axis is connected to a steering lever or steering input which is configured to direct the wheels in any arbitrary or vector direction, combined with a speed input control (preferably on the same lever or hand control). Using this input and mechanical arrangement, the entire upper “X” carriage motion described in Galando (and others) can be dispensed with or omitted; with the present invention, it is replaced with computer-operated servos vectoring the powered wheels in response to the operator&#39;s input. 
         [0013]    Galando (U.S. Pat. No. 6,374,937) also calls out an X-Y joystick input device (see FIG. 2 of Galando) further indicative of the design intent of independent X-Y motions, even if actuated together. 
         [0014]    Various known combinations of power-driven steerable castors, clutches and belts (such as are used in airport sweeping machines, ice rink conditioners, etc.) can accomplish this end goal of moving the X-ray C-arm centerline in a system of radial coordinates under the control a unique operator input device that communicates direction and velocity; an automotive steering wheel and throttle is a good example. However, the computer-assisted vector drive as described hereinbelow has not previously been applied to mobile X-ray units and requires unique solutions due to the overhanging C-arm mass. 
         [0015]    Further, in Galando (U.S. Pat. No. 6,374,937), at column 9, lines 28-31, it is stated that “the apparatus of this invention, uses two distinct and separate chassis or carriages”. The invention discussed hereinbelow specifically disclaims use of two carriages for X-Y motion and is based on eliminating the X motion carriage entirely; instead, the present invention depends on a vector direction steering, and motion along that vector, to move the X-ray beam on the patient. 
         [0016]    Further elaboration the X-Y approach of Galando (U.S. Pat. No. 6,374,937) is disclosed at: column 9, lines 32-97; column 10, lines 1-22; column 11, lines 43-51; column 12, lines 53-56; column 18, lines 39-41; and column 23, lines 17-23. 
         [0017]    In Pejerski (U.S. Pat. No. 4,097,661), the intent is to steer a heavy device (an X-ray machine) by force sensors and a dual wheel drive, similar to a forklift truck. The system of the present invention described hereinbelow uses no force sensors and may only have a single driven wheel, such as a powered “ball” wheel, although two “motor-in-hub” wheels mounted (approximately at the center of gravity) to powered vertical steering axis pivots is the preferred method. The caster(s) used to stabilize the unit may also be actively steered, eliminating the need for offset axis or “tracking” casters. 
       SUMMARY OF THE INVENTION 
       [0018]    The present invention uses a precision “radial coordinate” drive concept on the main wheels (i.e., the powered wheels), which are used for all motions, including corridor travel and precision positioning at the patient, by selecting a “vector direction” (or steering direction), and speed, by using a suitable user interface, such as a lever which the operator points in a given direction and can “lift up” to start forward motion or “push down” for backup motion. The motion can be X, Y or any direction in between, by providing precision computer control of the wheel direction vector in a continuous manner. The position of the mobile fluoroscopy unit is known in a precise way and is intended to interact with a surgical navigation system in the operating room. 
         [0019]    Combinations of wheel angles and speeds can be computer driven to accomplish the user goals. 
         [0020]    Because of the various C-arm angling motions required for imaging at an angle, all mobile C-arm prior art using sliding collars on the C-arm will cause the beam tilt motions to interact in 3D space and are not generally isocentric. As a result, it becomes difficult to integrate a prior art “sliding collar” mobile C-arm into a surgical navigation system. For this reason, the present invention preferably uses the isocentric C-arm structure disclosed in U.S. Pat. No. 7,300,205 with such a navigation system, while supported on the novel wheeled system described herein. 
         [0021]    It is also necessary to consider coordinated turns of the mobile fluoroscopy unit while being transported within the hospital. With the present invention, independent steering positioning servos for all the vectored wheels allows computer coordination of each wheel angle to the desired turn radius. 
         [0022]    In one preferred form of the present invention, there is provided a mobile C-arm fluoroscopy unit comprising a self-contained radial coordinate or vector movement mechanism utilizing at least one motor-driven wheel, wherein the at least one motor-driven wheel is individually continuously steerable around a generally vertical steering axis. 
         [0023]    In another preferred form of the present invention, there is provided a mobile C-arm fluoroscopy unit comprising: 
         [0024]    a base; 
         [0025]    at least one two powered wheels for moving the base relative to the floor; and 
         [0026]    a C-arm mounted to the base; 
         [0027]    wherein the each of the at least two powered wheels is (i) rotatable about a vertical axis, such that the wheel may be aimed in a given direction, and (ii) powered about a horizontal axis, such that the wheel may be driven in the given direction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts, and further wherein: 
           [0029]      FIGS. 1 and 2  are schematic views showing prior art mobile systems with indexable wheels; 
           [0030]      FIGS. 3-5 ,  5 A,  5 B,  6  and  6 A are schematic views showing the use of a vector drive or circular coordinates to position the X-ray beam on the patient, also incorporating straight-ahead drive and steering—many actual steering algorithms are known, such as allowing turning within its own footprint, once independence of direction and velocity are available at each vectored wheel; and 
           [0031]      FIGS. 7-9  are schematic views showing a ¼-of-a-sphere cutout section on the side of the main body of the mobile fluoroscopy unit to allow full steering rotation in a vertical axis of a large main drive wheel. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0032]    Looking now at  FIGS. 3-6 , the present invention comprises a mobile fluoroscopy unit  105  having a base  110 , at least two powered wheels  115  for moving base  110  relative to the floor, and a C-arm  120  cantilevered relative to base  110 . In accordance with the present invention, each of the at least two powered wheels  115  is configured to be rotated about a vertical axis  123  (e.g., via a vertical rotation mechanism  124 ) such that each of the at least two powered wheels  115  is directable in any direction. Each of the powered wheels  115  is configured to be rotated about a horizontal axis  124 A (e.g., via a horizontal rotation mechanism  124 B) such that each of the at least two powered wheels  115  can be driven in a given direction. A steering input  125  (e.g., a vertical or steering axis, such as a joystick or wheel) may be used to selectively aim powered wheels  115  in any arbitrary, or vector, direction. In one preferred form of the present invention, steering input  125  further comprises a speed input control on the same lever or hand control for controlling the speed movement of mobile fluoroscopy unit  105 . By way of example but not limitation, a servo system  126  may be used to connect steering input  125  to vertical rotation mechanism  124 , and horizontal rotation mechanism  124 B, so that powered wheels  115  can be aimed, and driven, respectively, in a coordinated fashion, whereby to precisely position base  110 , and hence C-arm  120 , relative to a patient. 
         [0033]    By virtue of this construction, the entire secondary carriage, which is necessary in the prior art to provide movement along the X-axis, can be eliminated. Instead, movement of mobile fluoroscopy unit  105  along the Y-axis and X-axis is provided by computer-operated servos which aim powered wheels  115  (i.e., by moving the wheels about vertical axis  123 ) and drive powered wheels  115  (i.e., by causing powered wheels  115  to move about a horizontal axle) and are attentive to the operator&#39;s input (e.g., via steering input  125 ). 
         [0034]    If desired, casters  130  (free-wheeling or powered) may also be provided to help support base  110 . 
         [0035]    The present invention specifically eschews the prior art&#39;s use of a secondary carriage for X-axis movement (i.e., secondary carriage  20  of  FIGS. 1 and 2 ) and instead relies solely on vector direction steering of powered wheels  115 , and motion along that vector, to move the X-ray beam relative to the patient. 
         [0036]    The present invention does not use force sensors, and, in one construction, utilizes only a single driven wheel  115 , such as a powered “ball” wheel (although two “motor-in-hub” wheels  115 , mounted approximately at the center of gravity to powered vertical steering axis pivots, is the preferred construction for the present invention). Caster(s)  130 , which are used to stabilize base  110 , may also be actively steered (in the same manner as powered wheels  115 ), thereby eliminating the need for offset axis or “tracking” casters. 
         [0037]    The present invention comprises a precision “radial coordinate” drive concept on the main wheels  115 , which are used for all motions, including corridor travel, by selecting a “vector direction” or steering direction, and a speed, using a suitable user interface (e.g., steering input  125 ). In use, an operator uses steering input  125  to point mobile fluoroscopy unit  105  in a desired direction and uses steering input  125  to move mobile fluoroscopy unit  105  (e.g., by “lifting up” on steering input  125  to start forward motion, or “pressing down” on steering input  125  to back up mobile fluoroscopy unit  105 ). Movement of mobile fluoroscopy unit  105  can be effected along the X-axis, along the Y-axis, or in any direction in between, by precision computer control of the wheel direction vector in a continuous way. The position of the mobile fluoroscopy unit  105  is known in a precise way and is intended to interact with a surgical navigation system in the operating room. 
         [0038]    It will be appreciated that, if desired, combinations of wheel angles and speeds can be computer driven so as to effectively scan a patient using C-arm  125 . 
         [0039]    The various angling motions of C-arm  125 , using sliding collars on the C-arm, causes the beam tilt motions to interact in 3D space and therefore the X-ray beam is not generally isocentric. Thus it becomes difficult to integrate the sliding collar mobile C-arms of the prior art into a surgical navigation system. The present invention uses an isocentric C-arm  125  (such as the isocentric C-arm disclosed in U.S. Pat. No. 7,300,205) in combination with a surgical navigation system, while the C-arm  125  is supported on the novel wheel system discussed above. 
         [0040]    It should further be appreciated that, by providing independent steering positioning servos for all the powered wheels  115 , the present invention allows computer coordination of each wheel angle to a desired turn radius, whereby to better navigate turning of mobile fluoroscopy unit  105  when moving mobile fluoroscopy unit  105  over long distances and/or tortured paths (e.g., such as hallways in a hospital). 
         [0041]    The present invention uses vector drive and/or circular coordinates to position the X-ray beam on the patient, while also incorporating straight-ahead drive and steering. Many actual steering algorithms are known, such as steering algorithms which allow turning mobile fluoroscopy unit  105  within its own footprint, independent of direction and velocity, at each powered wheel  115 . 
         [0042]    If desired, and looking now at  FIGS. 7-9 , wheels  115  may be provided in a ¼-of-a-sphere cutout section  135  on the side of the base  10  of mobile fluoroscopy unit  105  so as to allow full steering rotation in a vertical axis of a large main drive wheel  115 . Furthermore, if desired, wheels  115  may be mounted on C-arm  120 . 
       MODIFICATIONS OF THE PREFERRED EMBODIMENTS 
       [0043]    It should be understood that many additional changes in the details, materials, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the present invention, may be made by those skilled in the art while still remaining within the principles and scope of the invention.