Patent Publication Number: US-2017360372-A1

Title: Robotic Surgical System

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a division of U.S. application Ser. No. 11/647,300, filed 29 Dec. 2006 (the &#39;300 application), now pending, which claims the benefit of U.S. provisional application No. 60/851,042, filed 12 Oct. 2006, (the &#39;042 application); the &#39;300 application is a continuation-in-part of U.S. application Ser. No. 11/139,908, filed 27 May 2005 (the &#39;908 application), now U.S. Pat. No. 7,632,265, which claims the benefit of U.S. provisional application No. 60/575,741, filed 28 May 2004 (the &#39;741 application). The foregoing applications are hereby expressly incorporated by reference as though fully set forth herein. 
    
    
     BACKGROUND OF THE INVENTION 
     a. Field of the Invention 
     The instant invention relates to robotically controlled medical devices. In particular, the instant invention relates to a robotic surgical system for navigating a medical device through a patient&#39;s body for diagnostic and therapeutic purposes. 
     b. Background Art 
     Catheters are used for an ever growing number of medical procedures. To name just a few examples, catheters are used for diagnostic, therapeutic, and ablation procedures. Typically, the user manually manipulates the catheter through the patient&#39;s vasculature to the intended site, such as a site within the patient&#39;s heart. The catheter typically carries one or more electrodes or other diagnostic or therapeutic devices, which may be used for ablation, diagnosis, cardiac mapping, or the like. 
     It is well known that, to facilitate manipulation of the catheter through the patient&#39;s vasculature to the intended site, portions of the catheter shaft, especially the distal regions thereof, may be made steerable. For example, the catheter may be manufactured such that the user can translate, rotate, and deflect the distal end of the catheter as necessary and desired to negotiate the tortuous paths of the patient&#39;s vasculature en route to the target site. Navigating a catheter reliably through the patient&#39;s body to a precise location, however, is an extremely tedious process requiring a substantial amount of time and skill and potentially causing a high degree of fatigue in the physician, especially where actuation forces are transmitted over large distances. 
     BRIEF SUMMARY OF THE INVENTION 
     It is thus desirable to be able to navigate a medical device accurately and precisely through a patient&#39;s body to the locations of diagnostic or therapeutic interest. 
     It is also desirable to be able to reduce the fatigue factor associated with navigating a medical device through a patient&#39;s body. 
     It is further desirable to be able to preserve the ability to manually navigate a medical device when so desired. 
     According to a first aspect of the invention, a robotic surgical system includes: a track; a catheter holding device translatably associated with the track and including a catheter receiving portion; a translation servo mechanism operatively coupled to the catheter holding device and adapted to control translation of the catheter holding device relative to the track; a catheter deflection control mechanism; a deflection servo mechanism operatively coupled to and adapted to control the catheter deflection control mechanism; and a controller operatively coupled to and adapted to control at least one of the translation and deflection servo mechanisms. Preferably, the catheter receiving portion is adapted for quick installation and removal of a catheter. Optionally, the catheter holding device includes the catheter deflection control mechanism. 
     The catheter holding device may be slidable relative to the track or may be translatably associated with the track via a screw mechanism such as a worm gear, a lead screw, or a ball screw. Preferably, the catheter holding device can translate relative to the track a total distance of about 10 cm. The catheter holding device itself may be mounted on the track. Alternatively, a carriage may be translatably mounted on the track, with the catheter holding device mounted on the carriage such that the catheter holding device translates relative to the track with the carriage. Optionally, either or both of the catheter deflection control mechanism and the deflection servo mechanism may be mounted on the carriage. 
     In some embodiments of the invention, the catheter receiving portion is rotatable, preferably by at least about 360°, with a rotation servo mechanism operatively coupled to and adapted to control the rotatable catheter receiving portion. The rotation servo mechanism may also be carriage-mounted. Further, the controller may be operatively coupled to both the rotation servo mechanism and the deflection servo mechanism and adapted to control at least one of, and optionally both, the rotation servo mechanism and the deflection servo mechanism to maintain a substantially constant catheter deflection as the catheter receiving portion rotates. 
     A catheter having a distal end and a proximal end, a catheter control handle near the proximal end, and at least one pull wire extending from the catheter control handle to the distal end may be received in the catheter receiving portion such that it translates relative to the track with the catheter holding device, thereby providing a first degree of freedom to the catheter. In addition, the catheter may be operatively coupled to the catheter deflection control mechanism such that actuation of the catheter deflection control mechanism causes the distal end of the catheter to deflect, thereby providing a second degree of freedom to the catheter. The catheter control handle may include a catheter deflection actuator operatively coupled to the catheter deflection control mechanism to selectively tension at least one pull wire, and optionally at least four pull wires. In embodiments with a rotating catheter receiving portion, the catheter may rotate with the catheter receiving portion, thereby providing a third degree of freedom to the catheter. 
     To provide a substantially sterile field about the catheter outside the patient&#39;s body, an expandable, collapsible tube may surround at least a portion of the catheter. The expandable, collapsible tube may be constructed of a plurality of telescoping tubular elements. 
     An introducer, which extends into a patient such that a distal end of the introducer is proximate a target site, may also be provided as part of the robotic surgical system. A proximal end of the introducer may be stationary, while the distal end may be steerable via a robotic control system including at least one servo mechanism adapted to control the distal end of the introducer in at least one degree of freedom. Optionally, the robotic control system for the introducer includes three servo mechanisms adapted to control the distal end of the introducer in three degrees of freedom. 
     In another embodiment of the invention, a robotic surgical system includes: a track; a carriage mounted on the track; a translation servo mechanism operatively coupled to the carriage and adapted to control movement of the carriage relative to the track; a catheter holding device including a catheter deflection mechanism and a rotatable catheter receiving portion, wherein the catheter holding device is mounted on the carriage such that the catheter holding device moves relative to the track with the carriage; a rotation servo mechanism operatively coupled to the catheter holding device and adapted to control rotation of the catheter receiving portion; a deflection servo mechanism operatively coupled to the catheter deflection mechanism and adapted to control deflection of a catheter that may be received in the catheter receiving portion; a controller coupled to at least the rotation servo mechanism and the deflection servo mechanism, wherein the controller simultaneously controls the deflection servo mechanism and the rotation servo mechanism to maintain a substantially constant catheter deflection during rotation of the catheter receiving portion; an introducer designed to extend into a patient such that a distal end of the introducer is proximate a target site; and a telescoping tube for creating a sterile field between the catheter holding device and a proximal end of the introducer. A catheter received in the catheter receiving portion translates relative to the track with the catheter holding device and rotates about its axis as the catheter receiving portion rotates. The catheter is operatively coupled to the catheter deflection mechanism such that actuation of the catheter deflection mechanism causes a distal end of the catheter to deflect. 
     According to yet another aspect of the invention, a method of manufacturing a surgical system includes the steps of: translatably associating a catheter holding device including a rotatable catheter holding device with a track; operatively coupling a translation servo mechanism to the catheter holding device to control translation of the catheter holding device relative to the track; operatively coupling a rotation servo mechanism to the catheter holding device for controlling rotation of the catheter receiving portion about its axis; providing a catheter deflection control mechanism; operatively coupling a deflection servo mechanism to the catheter deflection control mechanism to control the catheter deflection control mechanism; and coupling a controller to at least the deflection servo mechanism and the rotation servo mechanism, wherein the controller controls at least one of the deflection servo mechanism and the rotation servo mechanism in order to maintain a substantially constant catheter deflection as the catheter receiving portion rotates. Optionally, the controller simultaneously controls both the deflection servo mechanism and the rotation servo mechanism. 
     In still another aspect of the invention, a method of controlling a catheter to treat tissue includes the steps of: providing a robotic catheter control system including a translatable catheter holding device including a catheter receiving portion, a translation mechanism adapted to control translation of the catheter holding device, a deflection mechanism adapted to control deflection of the catheter, and a robotic controller operatively coupled to and adapted to control the translation mechanism and the deflection mechanism; receiving the catheter in the catheter receiving portion such that the catheter translates with the catheter holding device; operatively coupling the catheter to the deflection mechanism such that actuation of the deflection control mechanism causes deflection of the catheter; and robotically navigating the catheter to one or more locations within a patient by actuating one or more of the translation mechanism and the deflection mechanism. Optionally, the method further includes operatively coupling a rotation mechanism to the catheter receiving portion to control rotation thereof, wherein robotically navigating the catheter may also include actuating the rotation mechanism. The deflection mechanism may be actuated to maintain a substantially constant deflection of the catheter distal end during rotation of the catheter. 
     Also disclosed is a robotic surgical system to control a first medical device in at least two degrees of freedom and a second medical device in at least two degrees of freedom. The robotic surgical system includes: a first holding device adapted to receive the first medical device therein; a second holding device adapted to receive the second medical device therein; a first robotic control system, including at least two servo mechanisms, that is operatively coupled to the first holding device and adapted to control the first medical device in at least two degrees of freedom; a second robotic control system, including at least two servo mechanisms, that is operatively coupled to the second holding device and adapted to control the second medical device in at least two degrees of freedom; and at least one controller operatively coupled to said first robotic control system and said second robotic control system to cooperatively control the first and second medical devices in at least two degrees of freedom each. 
     A method of calibrating a robotically controlled catheter is also disclosed. The method includes the following steps: providing a robotic control input to the catheter to deflect the distal end of the catheter; measuring a deflection of the distal end of the catheter; associating the measured deflection of the distal end of the catheter with the robotic control input; and generating a calibration data set, the calibration data set comprising a plurality of associated measured deflections and robotic control inputs. Typically, the distal end of the catheter will be deflected between a first extreme and a second extreme. In addition, the distal end of the catheter may be advanced beyond a distal end of an introducer, in which instance the calibration data set includes a plurality of associated measured deflections and robotic control inputs for a given advancement of the distal end of the catheter beyond the distal end of the introducer. 
     An advantage of the present invention is a reduced exposure to radiation for both the patient and the physician, since the present invention reduces the time required to navigate the catheter to a target location and minimizes the need for fluoroscopy to locate the catheter within the patient. 
     Another advantage of the present invention is the ability to easily switch between automated robotic control and manual control of the catheter. 
     Still another advantage of the present invention is the ability to remotely interact with the robotic surgical system controlling the catheter. 
     The foregoing and other aspects, features, details, utilities, and advantages of the present invention will be apparent from reading the following description and claims, and from reviewing the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of an embodiment of a robotic surgical system. 
         FIG. 2  is a perspective view of one embodiment of a catheter holding device with a catheter placed therein. 
         FIG. 3  is an end view of the catheter holding device of  FIG. 2 . 
         FIG. 4  is a perspective view of one embodiment of a catheter holding device with a catheter secured therein. 
         FIG. 5  is an end view of the catheter holding device of  FIG. 4 . 
         FIG. 6  illustrates an exemplary steerable catheter such as may be used in the robotic surgical system. 
         FIG. 7  depicts automatic control of the robotic surgical system according to a predetermined program. 
         FIG. 8  depicts a user manually controlling the robotic surgical system via an input device. 
         FIG. 9  depicts the user of  FIG. 8  manually controlling the steerable catheter after having removed it from the robotic surgical system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  schematically illustrates an embodiment of a robotic surgical system  10  for robotic manipulation and control of a medical device  12 . Medical device  12  is preferably a catheter, which may be any type of catheter, including, by way of example only and without limitation, an ablation catheter, a guide wire catheter, an introducer catheter, a probe, or a stylet. It should be understood, however, that any other therapeutic, diagnostic, or assistive medical device may be controlled by robotic surgical system  10  without departing from the scope of the present invention. Such other devices include, but are not limited to, syringes, electrophoresis devices, iontophoresis devices, transdermal pharmaceutical delivery devices, myoblast delivery devices, stem cell delivery devices, ablation devices, stents, and pacemaker leads, which may be carried on or delivered by a catheter. It should further be understood that robotic surgical system  10  may be used to manipulate and control more than one medical device  12  in accordance with the quick installation and removal feature described herein. Accordingly, the terms “medical device,” “probe,” “therapeutic device,” and “catheter” are used interchangeably herein. 
     Robotic surgical system  10  generally includes a track  14 , a catheter holding device  16 , a translation servo mechanism  18 , a catheter deflection control mechanism  20 , a deflection servo mechanism  22 , and a controller  24  operatively coupled to at least one of translation servo mechanism  18  and deflection servo mechanism  22 . Translation and deflection servo mechanisms  18 ,  22  may be any type of device for providing mechanical control at a distance, including continuous motors, stepper motors, hydraulic actuators, pulley systems, and other devices known to those of ordinary skill in the art. Catheter deflection control mechanism  20  and deflection servo mechanism  22  are collectively referred to herein as a “catheter deflection mechanism.” 
     Catheter holding device  16  includes a catheter receiving portion  26 . Catheter receiving portion  26  is configured to receive catheter  12  by installing a catheter control handle  28 , located near a proximal end  30  of catheter  12 , into catheter receiving portion  26 . Preferably, catheter receiving portion  26  is adapted for quick installation and removal of any type of catheter  12  (or, as noted above, another medical device), thereby facilitating the installation of device  12  for control by robotic surgical system  10  and removal of device  12  for manual control (e.g., user manipulation of catheter control handle  28 ). Accordingly, catheter control handle  28  may be secured in catheter receiving portion  26  by a frictional fit or with one or more quick-release fasteners. Alternatively, the inner surface of catheter receiving portion  26  and the outer surface of catheter control handle  28  may include mating threaded portions to permit catheter control handle  28  to be screwed into catheter holding device  16 . In other embodiments of robotic surgical system  10 , catheter control handle  28  is clamped or strapped in place in catheter receiving portion  26 . An adapter may also be used to facilitate the reception of catheter control handle  28  within catheter receiving portion  26 . 
     One embodiment of catheter holding device  16  is illustrated in  FIGS. 2 and 3  with catheter control handle  28  placed, but not secured, therein. Catheter holding device  16  includes a base plate  32  and a plurality of upstanding support plates  34 . Support plates  34  support cams  36 , which are connected to pulley systems  38 . 
     Catheter control handle  28  is received downwardly through an opening  40  into the catheter receiving portion  26  and onto belts  40  of pulley systems  38 . As catheter control handle is urged downwardly, belts  40  rotate upper and lower pulleys  38   a,    38   b  in the direction of arrows a. This, in turn, urges cams  36  downwards via links  42  and draws upper pulleys  38   a,    38   b  towards one another via links  44 , while simultaneously wrapping the belts  40  about catheter control handle  28 . Catheter control handle  28  is thereby secured within catheter receiving portion  26  as shown in  FIGS. 4 and 5 . To remove catheter control handle  28  from catheter holding device  16 , the user need only release cams  26 , which reverses the process described above and opens catheter receiving portion  26 . 
     Catheter holding device  16  is translatably associated with track  14 . The phrase “translatably associated with” encompasses all types of relative lateral motion between catheter holding device  16  and track  14 . For example, catheter holding device  16  may slide relative to track  14 . Alternatively, catheter holding device  16  may move laterally along a screw mechanism  46 , such as a worm gear, a lead screw, or a ball screw, attached to track  14 . Preferably, catheter holding device  16  has a translation range relative to track  14  (i.e., the lateral distance that catheter holding device  16  can travel relative to track  14  between extremes) of at least about 5 cm, the approximate width of a human heart. More preferably, the translation range of catheter holding device  16  relative to track  14  is at least about 10 cm. 
     In the preferred embodiment of the invention, a carriage  48  is translatably mounted on track  14  via screw mechanism  46 . Catheter holding device  16  is mounted on carriage  48  such that catheter holding device  16  translates relative to track  14  with carriage  48 . For example, base plate  32  may be fixedly or removably mounted on carriage  48 . Alternatively, catheter holding device  16  may be integrally formed with carriage  48  as a single assembly (i.e., base plate  32  and carriage  48  may be a single, unitary component). Likewise, in some embodiments of the invention, catheter holding device  16  may be translatably mounted directly on track  14  without an intervening carriage. 
     Translation servo mechanism  18  is operatively coupled to catheter holding device  16  and adapted to control translation of catheter holding device  16  relative to track  14  in order to adjust the lateral position of catheter holding device  16  along track  14 . Preferably, translation servo mechanism  18  is operatively coupled to carriage  48  in order to move carriage  48 , and therefore catheter holding device  16  mounted thereon, laterally along track  14 . In the embodiment shown in  FIG. 1 , translation servo mechanism  18  drives screw mechanism  46 , thereby moving carriage  48  laterally therealong. 
     Deflection servo mechanism  22  is operatively coupled to and adapted to control catheter deflection control mechanism  20 . In the preferred embodiment of the invention, deflection servo mechanism  22  is operatively coupled to catheter deflection control mechanism  20  such that deflection servo mechanism  22  can rotate catheter deflection control mechanism  20 . Either or both of deflection servo mechanism  22  and catheter deflection control mechanism  20  may be mounted on carriage  48  in order to simplify the transmission system linking deflection servo mechanism  22  and catheter deflection control mechanism  20 . In some embodiments of robotic surgical system  10 , catheter deflection control mechanism  20  is incorporated in catheter holding device  16 , for example by utilizing pulley systems  38 , and in particular belts  40 , as further described below. One of ordinary skill in the art will appreciate, however, that catheter deflection control mechanism  20  may also be separated from catheter holding device  16  without departing from the spirit and scope of the present invention. 
     Controller  24  is adapted to control at least one of translation servo mechanism  18  and deflection servo mechanism  22  in order to navigate catheter  12  received in catheter holding device  16 . It should also be noted that the use of multiple controllers to control translation servo mechanism  18  and deflection servo mechanism  22  is regarded as within the scope of the present invention. Throughout this disclosure, the term “controller” refers to a device that controls the movement or actuation of one or more robotic systems (that is, the component responsible for providing command inputs to the servo mechanisms). One of ordinary skill in the art will understand how to select an appropriate controller for any particular mechanism within robotic surgical system  10 . Further, the term “controller” should be regarded as encompassing both a singular, integrated controller and a plurality of controllers for actuating one or more robotic systems. 
     As shown in  FIG. 6 , catheter  12  is preferably a steerable catheter including at least one pull wire  50  extending from catheter control handle  28  near proximal end  30  of catheter  12  to a distal end  52  of catheter  12 . Pull wires  50  may be coupled to at least one pull ring  54 , also located near distal end  52  of catheter  12 . When placed in tension, pull wires  50  deflect distal end  52  of catheter  12  into various configurations. As one of skill in the art will understand, additional pull wires  50  will enhance the deflection versatility of distal end  52  of catheter  12 . For example, a single pull wire  50  with a single point of attachment to pull ring  54  will permit distal end  52  of catheter  12  to deflect on a single axis, and perhaps in only one direction, for example upwards relative to  FIG. 6 . By adding a second pull wire  50  (as shown in  FIG. 6 ), or by looping a single pull wire  50  to have two points of attachment  56  to pull ring  54 , distal end  52  of catheter  12  may be deflected in two directions, for example both upwards and downwards relative to  FIG. 6 . A catheter  12  with four pull wires  50  attached to pull ring  54  at about 90° intervals can deflect in four directions, for example upwards, downwards, and into and out of the plane of the paper relative to  FIG. 6 . 
     One or more catheter deflection actuators  58  may be provided on catheter control handle  28  to selectively tension one or more pull wires  50 , thereby controlling the direction and degree of deflection of distal end  52  of catheter  12 . In some embodiments, one or more knobs may be provided, rotation of which selectively tension one or more pull wires  50 . It should be understood, however, that catheter deflection actuators  58  may take many other forms, including, but not limited to, sliders and switches, without departing from the spirit and scope of the present invention. Additionally, it is contemplated that rotating catheter control handle  28  itself may selectively tension pull wires  50  and deflect distal end  52  of catheter  12 . 
     Returning to  FIG. 1 , when catheter control handle  28  is received within catheter receiving portion  26 , catheter  12  translates relative to track  14  with catheter holding device  16 , thereby providing a first degree of freedom permitting catheter  12  to be advanced into and retracted from a patient&#39;s body. Additionally, catheter  12  is operatively coupled to catheter deflection control mechanism  20  such that actuation of catheter deflection control mechanism  20  causes distal end  52  of catheter  12  to deflect, thereby providing a second degree of freedom to catheter  12 . In particular, catheter deflection actuator  58  may be operatively coupled to catheter deflection control mechanism  20  such that catheter deflection control mechanism  20  can actuate catheter deflection actuator  58  to selectively tension one or more pull wires  50  and deflect the distal end  52  of catheter  12  by a desired amount in a desired direction. 
     In some embodiments of the invention, rotating catheter deflection control mechanism  20  will rotate catheter deflection actuator  58  in turn, thereby selectively tensioning one or more pull wires  50  within catheter  12 . The transmission system between catheter deflection control mechanism  20  and catheter deflection actuator  58  may be a frictional fit provided, for example, by rubberized coatings surrounding catheter deflection control mechanism  20  and catheter deflection actuator  58 . Alternatively, catheter deflection control mechanism  20  and catheter deflection actuator  58  may be coupled with mating gear teeth or knurling. 
     Referring specifically to the embodiment of catheter holding device  16  depicted in  FIGS. 2-5 , when catheter  12  is secured in catheter receiving portion  26 , belts  40  frictionally engage catheter control handle  28 . They may also engage catheter deflection actuator  58 . Thus, if pulley system  38  is driven by deflection servo mechanism  22 , belts  40  may rotate catheter control handle  28 , catheter deflection actuator  58 , or both, in order to selectively tension one or more pull wires  50  and deflect distal end  52  of catheter  12 . 
     It should be understood that the particular configurations of catheter deflection control mechanism  20  and catheter deflection actuator  58  described above are merely exemplary and can be modified without departing from the spirit and scope of the invention. For example, if catheter deflection actuator  58  is a slider rather than a knob, catheter deflection control mechanism  20  may be suitably modified, or even replaced as a modular unit, to actuate a slider. This facilitates the quick connect/disconnect operation of robotic surgical system  10  by allowing easy installation and interconnection between off-the-shelf medical devices of varying construction and robotic surgical system  10 . 
     As described above, the inclusion of additional pull wires  50  in catheter  12  increases the number of directions in which distal end  52  of catheter  12  can deflect. This is referred to herein as “deflection versatility.” Where relatively few pull wires  50  (e.g., fewer than about four pull wires  50 ) are used, however, compensation for lost deflection versatility may be had by rotating catheter  12  about its axis. For example, in a catheter using only a single pull wire  50  with a single point of attachment to pull ring  54 , permitting the catheter to deflect only in one direction, the catheter may be deflected in the opposite direction simply by rotating it 180° about its axis. Similarly, a catheter that can deflect in two directions 180° apart can be deflected in the directions midway therebetween by rotating the catheter 90° about its axis. 
     Accordingly, in some embodiments of the invention, catheter receiving portion  26  is rotatable. An example of such a rotatable catheter receiving portion is catheter receiving portion  26  defined by pulley system  38  depicted in  FIGS. 2-5 . A rotation servo mechanism  60  is operatively coupled to rotatable catheter receiving portion  26  and adapted to control rotatable catheter receiving portion  26 . Thus, pulley system  38  may be driven by rotation servo mechanism  60 , thereby engaging belts  40  to rotate catheter  12  about its axis. 
     If desired, rotation servo mechanism  60  may be mounted on carriage  48  or affixed to catheter holding device  16  such that rotation servo mechanism  60  translates relative to track  14  with catheter holding device  16 . This arrangement creates a fixed-distance relationship between rotation servo mechanism  60  and catheter holding device  16 , which can simplify the transmission system coupling rotation servo mechanism  60  to catheter holding device  16 . 
     When installed in catheter holding device  16 , catheter  12  rotates with catheter receiving portion  26 , thereby providing a third degree of freedom to catheter  12  and compensating for low deflection versatility attributable to a relatively lower number of pull wires  50 . Catheter receiving portion  26  is preferably rotatable at least about 360° about its axis, such that catheter  12  received therein is also rotatable at least about 360° about its axis, thereby facilitating deflection of distal end  52  of catheter  12  in substantially any direction, significantly enhancing the deflection versatility of the distal end  52  of the catheter  12 . Catheter receiving portion  26  may also be designed to rotate about 720° or more about its axis. 
     Rotating catheter  12  by rotating catheter receiving portion  26  may cause inadvertent deflection of distal end  52  of catheter  12 . As one skilled in the art will recognize from this disclosure, as catheter receiving portion  26  and catheter  12  rotate, catheter deflection actuator  58  may remain stationary, rather than rotating with catheter control handle  28 , if the torque applied by rotation servo mechanism  60  is insufficient to overcome the inertia of catheter deflection control mechanism  20 . That is, catheter deflection actuator  58  may bind against catheter deflection control mechanism  20 , causing relative rotation between catheter control handle  28  and catheter deflection actuator  58 . This relative rotation may result in uncommanded tensioning of one or more pull wires  50 , inadvertently deflecting distal end  52  of catheter  12 . 
     To maintain a substantially constant deflection as catheter  12  rotates, therefore, controller  24  may be operatively coupled to both rotation servo mechanism  60  and deflection servo mechanism  22 . Controller  24  is adapted to control at least one of deflection servo mechanism  22  and rotation servo mechanism  60 , and preferably to simultaneously control both deflection servo mechanism  22  and rotation servo mechanism  60 , to maintain a substantially constant deflection of distal end  52  as catheter receiving portion  26  and catheter  12  rotate. For example, as controller  24  commands rotation servo mechanism  60  to rotate catheter receiving portion  26 , controller  24  may simultaneously command deflection servo mechanism  22  to actuate catheter deflection control mechanism  20  to counter-rotate, thereby substantially eliminating relative rotation between the catheter deflection actuator  58  and catheter control handle  28 , helping to maintain a substantially constant deflection of catheter  12 . Alternatively, as controller  24  commands rotation servo mechanism  60  to rotate catheter receiving portion  26 , it may simultaneously command deflection servo mechanism  22  to decouple catheter deflection control mechanism  20  from catheter deflection actuator  58 , thereby permitting catheter deflection actuator  58  to rotate freely with catheter control handle  28 . In either case, controller  24  may be configured to eliminate the need to couple deflection servo mechanism  22  and rotation servo mechanism  60  through a mechanical transmission system such as a differential. Further, though described herein as a single controller adapted to control the translation, deflection, and rotation servo mechanisms  18 ,  22 ,  60 , multiple controllers may be used without departing from the spirit and scope of the present invention. 
     An introducer  62 , preferably a steerable introducer, and most preferably an Agilis™ steerable introducer, may be provided as part of robotic surgical system  10 . A proximal end  64  of introducer  62  is preferably stationary, while a distal end  66  of introducer  62  extends into a patient (not shown for clarity) to a location proximate a target site (the term “target” is used herein to refer to a location at which treatment or diagnosis occurs). Introducer  62  may be steerable via a robotic control system  68  including at least one servo mechanism  70  adapted to control distal end  66  of introducer  62  in at least one degree of freedom. Preferably, robotic control system  68  includes three servo mechanisms  70  adapted to control distal end  66  of the introducer  62  in three degrees of freedom (translation, deflection, and rotation), resulting in a total of six degrees of freedom for robotic surgical system  10 , and at least one controller  72  adapted to control servo mechanisms  70 . Similar control principles may be applied to steerable introducer  62  as are described herein with respect to robotic surgical system  10  and medical device  12 . 
     One of ordinary skill in the art will appreciate that the deflection of distal end  52  of catheter  12  is a function not only of the input to catheter deflection actuator  58  (i.e., the selective tensioning of one or more pull wires  50 ), but also of the extent to which catheter  12  is advanced beyond a generally rigid sheath, such as introducer  62 . That is, the further distal end  52  of catheter  12  is advanced beyond distal end  66  of introducer  62 , the greater the deflection of distal end  52  of catheter  12  will be for a given input at catheter deflection actuator  58 . 
     It is therefore desirable to calibrate the deflection of distal end  52  of catheter  12  in terms of both catheter deflection control mechanism inputs and extensions of catheter  12  beyond distal end  66  of introducer  62 . By robotically actuating catheter deflection control mechanism  20  between extremes (e.g., commanding a complete rotation of catheter deflection actuator  58 ) and measuring the resulting deflection of distal end  52  of catheter  12  (e.g., using a localization system), catheter deflection control mechanism inputs may be correlated with deflections of distal end  52  for a given extension of catheter  12  beyond distal end  66  of introducer  62 . A similar process may be performed for a multiple different extensions of catheter  12  beyond distal end  66  of introducer  62 , resulting in a family of calibration curves relating catheter deflection control mechanism inputs to deflections of distal end  52  of catheter  12 . Each curve corresponds to a particular extension of catheter  12  beyond distal end  66  of introducer  62 ; the amount of extension of catheter  12  beyond distal end  66  of introducer  62  may be derived, at least in part, from the amount of translation of catheter holding device  16  relative to track  14 . 
     To create a substantially sterile field around catheter  12  outside the patient&#39;s body, an expandable and collapsible tubular shaft  74  substantially surrounds at least a portion of catheter  12 , such as the region of catheter  12  between catheter holding device  16  and proximal end  64  of introducer  62 . Preferably, shaft  74  is sterilized before use along with other relevant components of robotic surgical system  10 . As catheter holding device  16  translates to advance catheter  12  into the patient (i.e., to the right in  FIG. 1 ), tubular shaft  74  collapses upon itself. Contrarily, as catheter holding device  16  translates to retract catheter  12  from the patient (i.e., to the left in  FIG. 1 ), tubular shaft  74  expands. Preferably, tubular shaft  74  is assembled from a plurality of telescoping tubular elements  76 . It is contemplated, however, that tubular shaft  74  may alternatively be an accordion-pleated or other expandable and collapsible structure. 
     As depicted in  FIGS. 7 and 8 , robotic surgical system  10  may be employed to robotically navigate catheter  12  into and through the patient and to one or more sites, which may be target sites, within the patient&#39;s body by actuating one or more of translation servo mechanism  18 , deflection servo mechanism  22 , and rotation servo mechanism  60  (if present) via controller  24 . Robotic surgical system  10  may operate automatically according to a computerized program as executed by controller  24  ( FIG. 7 ). It is also contemplated that the user, who may be a surgeon, cardiologist, or other physician, may control robotic surgical system  10  through an appropriate set of controls  78 , such as a three-dimensional joystick (e.g., a joystick with three input axes), a steering yoke, or another suitable input device or collection of such devices permitting the user to robotically steer catheter  12  ( FIG. 8 ). 
     As described above, catheter  12  can be quickly and easily disconnected from catheter holding device  16 . Thus, if the user desires to manually control catheter  12  at any point during the procedure, the user may disconnect catheter  12  from the catheter holding device  16  as described above. The user may navigate catheter  12  manually for as long as desired, and then replace it into catheter holding device  16  and resume robotic control.  FIG. 9  illustrates the user manually operating catheter  12  after having removed it from catheter holding device  16 . 
     In some embodiments of the invention, multiple robotic surgical systems controlling multiple medical devices may be employed during a procedure. For example, a first robotic surgical system may control an ultrasonic imaging transducer, while a second robotic surgical system may control an ablation catheter. A single controller, or multiple cooperating controllers, may coordinate the multiple medical devices and the multiple robotic surgical systems, for example in conjunction with a single localization system, or alternatively by utilizing data from the ultrasonic imaging transducer to control the movement of the ablation catheter. 
     Robotic surgical system  10  facilitates precise and accurate navigation of medical device  12  within the patient&#39;s body. In addition, since medical device  12  is manipulated primarily robotically, the physician will experience considerably less fatigue during the surgical procedure. Furthermore, robotic control permits a substantially increased degree of complexity in the control and actuation mechanisms that may be incorporated into medical device  12  over those that may be used in a medical device  12  intended solely for human control, enabling an increase in the versatility of medical device  12 . 
     It is also contemplated that the user operating robotic surgical system  10  may be remote from robotic surgical system  10 . For example, an expert physician in one city may control robotic surgical system  10  located in a second city via a computer network, such as the Internet. 
     Although several embodiments of this invention have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this invention. For example, the robotic surgical system  10  may be modified to incorporate additional servo mechanisms and controllers operating on additional degrees of freedom. 
     In addition, one of ordinary skill in the art will appreciate that, though the devices and methods disclosed herein have been described in connection with the treatment of atrial fibrillation, and in particular in connection with the creation of lesions of ablated tissue, they may be used to administer other therapies or to perform other diagnostic procedures. 
     Further, the devices and methods disclosed herein are capable of use both epicardially and endocardially. 
     All directional references (e.g., upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are only used for identification purposes to aid the reader&#39;s understanding of the present invention, and do not create limitations, particularly as to the position, orientation, or use of the invention. Joinder references (e.g., attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other. 
     It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure may be made without departing from the spirit of the invention as defined in the appended claims.