Abstract:
A robotic system includes a bedside system comprising an axial drive mechanism and a rotational drive mechanism. An engagement mechanism engages and disengages a percutaneous device from at least one of the axial drive mechanism and rotational drive mechanism. A remote work station includes a user interface and a control system operatively coupled to the user interface. The control system is configured to communicate a control signal to the engagement mechanism to engage and disengage the percutaneous device from one of the axial drive mechanism and rotational drive mechanism.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the U.S. Provisional Application No. 61/537,030, filed Sep. 20, 2011 and PCT/US2012/056336 entitled VARIABLE DRIVE FORCE APPARATUS AND METHOD FOR ROBOTIC CATHETER SYSTEM filed Sep. 20, 2012 both of which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to the field of catheter systems for performing diagnostic and/or intervention procedures. The present invention relates specifically to catheter systems including a mechanism for controlling and varying the driving force applied to a percutaneous device. 
     Vascular disease, and in particular cardiovascular disease, may be treated in a variety of ways. Surgery, such as cardiac bypass surgery, is one method for treating cardiovascular disease. However, under certain circumstances, vascular disease may be treated with a catheter based intervention procedure, such as angioplasty. Catheter based intervention procedures are generally considered less invasive than surgery. If a patient shows symptoms indicative of cardiovascular disease, an image of the patient&#39;s heart may be taken to aid in the diagnosis of the patient&#39;s disease and to determine an appropriate course of treatment. For certain disease types, such as atherosclerosis, the image of the patient&#39;s heart may show a lesion that is blocking one or more coronary arteries. Following the diagnostic procedure, the patient may undergo a catheter based intervention procedure. During one type of intervention procedure, a catheter is inserted into the patient&#39;s femoral artery and moved through the patient&#39;s arterial system until the catheter reaches the site of the lesion. In some procedures, the catheter is equipped with a balloon or a stent that when deployed at the site of a lesion allows for increased blood flow through the portion of the coronary artery that is affected by the lesion. In addition to cardiovascular disease, other diseases (e.g., hypertension, etc.) may be treated using catheterization procedures. 
     SUMMARY OF THE INVENTION 
     In one embodiment, a robotic system includes a bedside system comprising an axial drive mechanism and a rotational drive mechanism. An engagement mechanism engages and disengages a percutaneous device from at least one of the axial drive mechanism and rotational drive mechanism. A remote work station includes a user interface and a control system operatively coupled to the user interface. The control system is configured to communicate a control signal to the engagement mechanism to engage and disengage the percutaneous device from one of the axial drive mechanism and rotational drive mechanism. 
     In a further feature, the control system is configured to communicate a control signal to the engagement mechanism to disengage the rotational drive mechanism from the percutaneous device when a user provides an instruction through the user interface to the axial drive mechanism to axially translate the percutaneous device. 
     In a further feature, the control system is configured to communicate a control signal to the engagement mechanism to disengage the axial drive mechanism from the percutaneous device when a user provides an instruction through the user interface to the rotational drive mechanism to rotate the percutaneous device. 
     In a further feature, the control system is configured to communicate a control signal to the engagement mechanism to alternatively disengage the axial drive mechanism and rotational drive mechanism from the percutaneous device when a user provides an instruction through the user interface to both axially translate and rotate the percutaneous device. 
     In a further feature, the engagement mechanism engages and disengages the percutaneous device at least ten times per second. 
     In a further feature, the control system is configured to communicate a control signal to the engagement mechanism to disengage the rotational drive mechanism from the percutaneous device when a user provides an instruction through the user interface and control system to the axial drive mechanism to axially translate the percutaneous device where the percutaneous device is slipping relative to the axial drive mechanism. 
     In another feature, an axial sensor is configured to detect the axial translation of the percutaneous device and communicate a signal to the controller representative of the speed of the axial translation of the percutaneous device. The controller is configured to compare output of the axial sensor with the axial drive mechanism and determine whether the percutaneous device is slipping relative to the axial drive mechanism. 
     In a further feature, a rotational sensor is configured to detect the rotational speed of the percutaneous device and communicate a signal to the control system representative of the rotational speed of the percutaneous device. The control system is configured to compare the output of the rotational sensor with the rotational drive mechanism and determine whether the percutaneous device is rotationally slipping relative to the rotational translational drive mechanism. 
     In a further feature, the control system is configured to communicate a control signal to the engagement mechanism to disengage the axial drive mechanism from the percutaneous device when a user provides an instruction through the user interface and control system to the rotational drive mechanism to rotate the percutaneous device where the percutaneous device is slipping relative to the rotational drive mechanism. 
     In a further feature, the axial drive mechanism includes a drive wheel and roller defining axial engagement surfaces, the percutaneous device being engaged and disengaged between the drive wheel and roller, the engagement mechanism including a linear engagement mechanism configured to move drive wheel and roller toward and away from one another to respectively engage and disengage the percutaneous device. 
     In a further feature, the rotational drive mechanism includes a pair of rollers. The percutaneous device being engaged and disengaged between the rollers, the engagement mechanism including a rotational engagement mechanism configured to move the rollers toward and away from one another to respectively engage and disengage the percutaneous device. 
     In a further feature, the control system is configured to communicate a control signal to a motor operatively coupled to the drive wheel to reduce a rotational speed of the drive wheel when the control system detects linear slippage of the percutaneous device relative to the drive wheel until the percutaneous device is not slipping relative to the drive wheel. 
     In still a further feature, the control system is configured to communicate a control signal to the motor to increase the speed of the drive wheel when slippage is no longer detected. 
     In a further feature, the speed of the drive wheel is increased in a step wise function. 
     In a further feature, the control system is configured to communicate a control signal to a motor operatively coupled to the drive wheel to increase a rotational speed of the drive wheel when the control system detects linear slippage of the percutaneous device relative to the drive wheel until the percutaneous device is moving linearly at a required speed. 
     In a further feature, the axial engagement mechanism is configured to vary the distance between a rotational axis of the drive wheel and a rotational axis of the roller to vary the force applied to the percutaneous device in a direction perpendicular to the rotational axes of the drive wheel and roller. 
     Alternative exemplary embodiments relate to other features and combinations of features as may be generally recited in the claims. 
     In a further feature, the control system is configured to reduce the distance between the drive wheel and roller when the percutaneous device is slipping relative to the drive wheel. 
     In a further feature the percutaneous device is one of a guide wire, working catheter and a guide catheter. 
     In another embodiment, a method for controlling a percutaneous device, includes providing a bedside system comprising, an axial drive mechanism, a rotational drive mechanism, and an engagement mechanism to engage and disengage a percutaneous device from at least one of the axial drive mechanism and rotational drive mechanism; providing a remote work station comprising a user interface and control system operatively coupled to the user interface, and providing a control signal from the control system to the engagement mechanism engaging and disengaging the percutaneous device from one of the axial drive mechanism and rotational drive mechanism. 
     Another feature includes disengaging the percutaneous device from the rotational drive mechanism when the axial drive mechanism is axially driving the percutaneous device. 
     Another feature includes disengaging the percutaneous device from the axial drive mechanism when the rotational drive mechanism is rotationally driving the percutaneous device. 
     Another feature includes alternatively disengaging and engaging the percutaneous device from the axial drive mechanism and rotational drive mechanism. 
     Another feature includes sensing the axial movement of the percutaneous device and comparing the movement of the axial drive mechanism to determine if the percutaneous device is slipping relative to the axial drive mechanism. 
     Another feature includes reducing the speed of a drive motor in the axial drive mechanism until the percutaneous device is no longer slipping relative to the axial drive mechanism. 
     Another feature includes subsequently increasing the speed of a drive motor in the axial drive mechanism so long as the percutaneous device is no longer slipping relative to the axial drive mechanism. 
     Another feature includes increasing the speed of a drive motor in the axial drive mechanism until the percutaneous device is moving at a desired rate. The features noted above may be combined in a number of different combinations all of which are contemplated. 
     Alternative exemplary embodiments relate to other features and combinations of features as may be generally recited in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       This application will become more fully understood from the following detailed description, taken in conjunction with the accompanying figures, wherein like reference numerals refer to like elements in which: 
         FIG. 1  is a perspective view of a catheter procedure system according to an exemplary embodiment; 
         FIG. 2  is a block diagram of a catheter procedure system according to an exemplary embodiment; 
         FIG. 3  is a perspective view of a bedside system showing a cassette prior to being attached to a motor drive base according to an exemplary embodiment; 
         FIG. 4  is a perspective view of a bedside system showing the cassette of  FIG. 3  following attachment to the motor drive base according to an exemplary embodiment; 
         FIG. 5  is a perspective view of a cassette according to an exemplary embodiment; 
         FIG. 6  is a top view showing an axial drive assembly of a cassette in the “engaged” position according to an exemplary embodiment; 
         FIG. 7  is a block diagram of a controller for controlling a robotic catheter system according to an exemplary embodiment; and 
         FIG. 8  is a block diagram of a catheter procedure system showing motors located within a motor drive base according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Before turning to the figures, which illustrate the exemplary embodiments in detail, it should be understood that the present application is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology is for the purpose of description only and should not be regarded as limiting. 
     Referring to  FIG. 1 , a catheter procedure system  10  is shown. Catheter procedure system  10  may be used to perform catheter based medical procedures (e.g., percutaneous intervention procedures). Percutaneous intervention procedures may include diagnostic catheterization procedures during which one or more catheters are used to aid in the diagnosis of a patient&#39;s disease. For example, during one embodiment of a catheter based diagnostic procedure, a contrast media is injected into one or more coronary arteries through a catheter and an image of the patient&#39;s heart is taken. Percutaneous intervention procedures may also include catheter based therapeutic procedures (e.g., balloon angioplasty, stent placement, treatment of peripheral vascular disease, etc.) during which a catheter is used to treat a disease. It should be noted, however, that one skilled in the art would recognize that, certain specific percutaneous intervention devices or components (e.g., type of guide wire, type of catheter, etc.) will be selected based on the type of procedure that is to be performed. Catheter procedure system  10  is capable of performing any number of catheter based medical procedures with minor adjustments to accommodate the specific percutaneous devices to be used in the procedure. In particular, while the embodiments of catheter procedure system  10  described herein are explained primarily in relation to the diagnosis and/or treatment of coronary disease, catheter procedure system  10  may be used to diagnose and/or treat any type of disease or condition amenable to diagnosis and/or treatment via a catheter based procedure. 
     Catheter procedure system  10  includes lab unit  11  and workstation  14 . Catheter procedure system  10  includes a robotic catheter system, shown as bedside system  12 , located within lab unit  11  adjacent patient  21 . Generally, bedside system  12  may be equipped with the appropriate percutaneous devices (e.g., guide wires, guide catheters, working catheters, catheter balloons, stents, diagnostic catheters, etc.) or other components (e.g., contrast media, medicine, etc.) to allow the user to perform a catheter based medical procedure. A robotic catheter system, such as bedside system  12 , may be any system configured to allow a user to perform a catheter-based medical procedure via a robotic system by operating various controls such as the controls located at workstation  14 . Bedside system  12  may include any number and/or combination of components to provide bedside system  12  with the functionality described herein. Various embodiments of bedside system  12  are described in detail in P.C.T. International Application No. PCT/US2009/042720, filed May 4, 2009, which is incorporated herein by reference in its entirety. 
     In one embodiment, bedside system  12  may be equipped to perform a catheter based diagnostic procedure, and in another embodiment, bedside system  12  may be equipped to perform a catheter based therapeutic procedure. Bedside system  12  may be equipped with one or more of a variety of catheters for the delivery of contrast media to the coronary arteries. In one embodiment, bedside system  12  may be equipped with a first catheter shaped to deliver contrast media to the coronary arteries on the left side of the heart, a second catheter shaped to deliver contrast media to the coronary arteries on the right side of the heart, and a third catheter shaped to deliver contrast media into the chambers of the heart. In other embodiments, bedside system  12  may be equipped with a guide catheter, a guide wire, and a working catheter (e.g., a balloon catheter, a stent delivery catheter, ablation catheter, etc.). In one embodiment, bedside system  12  may equipped with a working catheter that includes a secondary lumen that is threaded over the guide wire during a procedure. In another embodiment, bedside system  12  may be equipped with an over-the-wire working catheter that includes a central lumen that is threaded over the guide wire during a procedure. In another embodiment, bedside system  12  may be equipped with an intravascular ultrasound (IVUS) catheter. In another embodiment, any of the percutaneous devices of bedside system  12  may be equipped with positional sensors that indicate the position of the component within the body. 
     Bedside system  12  is in communication with workstation  14 , allowing signals generated by the user inputs and control system of workstation  14  to be transmitted to bedside system  12  to control the various functions of beside system  12 . Bedside system  12  also may provide feedback signals (e.g., operating conditions, warning signals, error codes, etc.) to workstation  14 . Bedside system  12  may be connected to workstation  14  via a communication link  38  that may be a wireless connection, cable connectors, or any other means capable of allowing communication to occur between workstation  14  and beside system  12 . 
     Workstation  14  includes a user interface  30 . User interface  30  includes controls  16 . Controls  16  allow the user to control bedside system  12  to perform a catheter based medical procedure. For example, controls  16  may be configured to cause bedside system  12  to perform various tasks using the various percutaneous devices with which bedside system  12  may be equipped (e.g., to advance, retract, or rotate a guide wire, advance, retract, or rotate a working catheter, advance, retract, or rotate a guide catheter, inflate or deflate a balloon located on a catheter, position and/or deploy a stent, inject contrast media into a catheter, inject medicine into a catheter, or to perform any other function that may be performed as part of a catheter based medical procedure, etc.). 
     In one embodiment, controls  16  include a touch screen  18 , a dedicated guide catheter control  29 , a dedicated guide wire control  23 , and a dedicated working catheter control  25 . In this embodiment, guide wire control  23  is a joystick configured to cause bedside system  12  to advance, retract, or rotate a guide wire, working catheter control  25  is a joystick configured to cause bedside system  12  to advance, retract, or rotate a working catheter, and guide catheter control  29  is a joystick configured to cause bedside system  12  to advance, retract, or rotate a guide catheter. In addition, touch screen  18  may display one or more icons (such as icons  162 ,  164 , and  166 ) that control movement of one or more percutaneous devices via bedside system  12 . Controls  16  may also include a balloon or stent control that is configured to inflate or deflate a balloon and/or a stent. Each of the controls may include one or more buttons, joysticks, touch screens, etc., that may be desirable to control the particular component to which the control is dedicated. 
     Controls  16  may include an emergency stop button  31  and a multiplier button  33 . When emergency stop button  31  is pushed a relay is triggered to cut the power supply to bedside system  12 . Multiplier button  33  acts to increase or decrease the speed at which the associated component is moved in response to a manipulation of guide catheter control  29 , guide wire control  23 , and working catheter control  25 . For example, if operation of guide wire control  23  advances the guide wire at a rate of 1 mm/sec, pushing multiplier button  33  may cause operation of guide wire control  23  to advance the guide wire at a rate of 2 mm/sec. Multiplier button  33  may be a toggle allowing the multiplier effect to be toggled on and off. In another embodiment, multiplier button  33  must be held down by the user to increase the speed of a component during operation of controls  16 . 
     User interface  30  may include a first monitor  26  and a second monitor  28 . First monitor  26  and second monitor  28  may be configured to display information or patient specific data to the user located at workstation  14 . For example, first monitor  26  and second monitor  28  may be configured to display image data (e.g., x-ray images, MRI images, CT images, ultrasound images, etc.), hemodynamic data (e.g., blood pressure, heart rate, etc.), patient record information (e.g., medical history, age, weight, etc.). In addition, first monitor  26  and second monitor  28  may be configured to display procedure specific information (e.g., duration of procedure, catheter or guide wire position, volume of medicine or contrast agent delivered, etc.). Monitor  26  and monitor  28  may be configured to display information regarding the position and/or bend of the distal tip of a steerable guide catheter. Further, monitor  26  and monitor  28  may be configured to display information to provide the functionalities associated with the various modules of controller  40  discussed below. In another embodiment, user interface  30  includes a single screen of sufficient size to display one or more of the display components and/or touch screen components discussed herein. 
     Catheter procedure system  10  also includes an imaging system  32  located within lab unit  11 . Imaging system  32  may be any medical imaging system that may be used in conjunction with a catheter based medical procedure (e.g., non-digital x-ray, digital x-ray, CT, MRI, ultrasound, etc.). In an exemplary embodiment, imaging system  32  is a digital x-ray imaging device that is in communication with workstation  14 . As shown in  FIG. 1 , imaging system  32  may include a C-arm that allows imaging system  32  to partially or completely rotate around patient  21  in order to obtain images at different angular positions relative to patient  21  (e.g., sagital views, caudal views, cranio-caudal views, etc.). 
     Imaging system  32  is configured to take x-ray images of the appropriate area of patient  21  during a particular procedure. For example, imaging system  32  may be configured to take one or more x-ray images of the heart to diagnose a heart condition. Imaging system  32  may also be configured to take one or more x-ray images during a catheter based medical procedure (e.g., real-time images) to assist the user of workstation  14  to properly position a guide wire, guide catheter, working catheter, stent, etc. during the procedure. The image or images may be displayed on first monitor  26  and/or second monitor  28 . 
     In addition, the user of workstation  14  may be able to control the angular position of imaging system  32  relative to the patient to obtain and display various views of the patient&#39;s heart on first monitor  26  and/or second monitor  28 . Displaying different views at different portions of the procedure may aid the user of workstation  14  properly move and position the percutaneous devices within the 3D geometry of the patient&#39;s heart. In an exemplary embodiment, imaging system  32  may be any 3D imaging modality of the past, present, or future, such as an x-ray based computed tomography (CT) imaging device, a magnetic resonance imaging device, a 3D ultrasound imaging device, etc. In this embodiment, the image of the patient&#39;s heart that is displayed during a procedure may be a 3D image. In addition, controls  16  may also be configured to allow the user positioned at workstation  14  to control various functions of imaging system  32  (e.g., image capture, magnification, collimation, c-arm positioning, etc.). 
     Referring to  FIG. 2 , a block diagram of catheter procedure system  10  is shown according to an exemplary embodiment. Catheter procedure system  10  may include a control system, shown as controller  40 . As shown in  FIG. 2 , controller  40  may be part of workstation  14 . Controller  40  is in communication with one or more bedside systems  12 , controls  16 , monitors  26  and  28 , imaging system  32 , and patient sensors  35  (e.g., electrocardiogram (“ECG”) devices, electroencephalogram (“EEG”) devices, blood pressure monitors, temperature monitors, heart rate monitors, respiratory monitors, etc.). In addition, controller  40  may be in communication with a hospital data management system or hospital network  34 , one or more additional output devices  36  (e.g., printer, disk drive, cd/dvd writer, etc.), and a hospital inventory management system  37 . 
     Communication between the various components of catheter procedure system  10  may be accomplished via communication links  38 . Communication links  38  may be dedicated wires or wireless connections. Communication links  38  may also represent communication over a network. Catheter procedure system  10  may be connected or configured to include any other systems and/or devices not explicitly shown. For example, catheter procedure system  10  may include IVUS systems, image processing engines, data storage and archive systems, automatic balloon and/or stent inflation systems, contrast media and/or medicine injection systems, medicine tracking and/or logging systems, user logs, encryption systems, systems to restrict access or use of catheter procedure system  10 , robotic catheter systems of the past, present, or future, etc. 
     Referring to  FIG. 3-6 , an exemplary embodiment of bedside system  12  is shown that is configured to allow a user to advance, retract and rotate a guide wire and to advance and retract a working catheter by operating controls  16  located at workstation  14 . In the embodiment shown, bedside system  12  includes a cassette  300  and a motor drive base  302 . Cassette  300  is equipped with a guide wire  301  and with a working catheter  303  to allow a user to perform a catheterization procedure utilizing cassette  300 . In this embodiment, cassette  300  is configured to be mounted to motor drive base  302 .  FIG. 3  shows a bottom perspective view of cassette  300  prior to mounting to motor drive base  302 . Motor drive base  302  includes a first capstan  304 , a second capstan  306 , and a third capstan  308 . Cassette  300  includes a first capstan socket  310 , a second capstan socket  312 , and a third capstan socket  314 . Cassette  300  includes a housing  316 , and housing  316  includes a base plate  318 . 
     Each of the capstan sockets is configured to receive one of the capstans of motor drive base  302 . In the embodiment shown, base plate  318  includes a hole or aperture aligned with each of the capstan sockets  310 ,  312 , and  314  to allow each capstan to engage with the appropriate capstan socket. As discussed in more detail below, the engagement between the capstans and capstan sockets allows the transfer of energy (e.g., rotational movement) generated by one or more actuators (e.g., motors) located within motor drive base  302  to each of the drive mechanisms within cassette  300 . In one embodiment, a single actuator provides energy to each of the drive mechanisms. In another embodiment, there is an actuator that drives capstan  304 , an actuator that drives capstan  306 , and an actuator that drives capstan  308 . Further, the positioning of the capstans and capstan sockets helps the user to align cassette  300  relative to motor drive base  302  by allowing cassette  300  to be mounted to motor drive base  302  only when all three capstan sockets are aligned with the proper capstan. 
     In one embodiment, the motors that drive capstans  304 ,  306 , and  308  are located within motor drive base  302 . In another embodiment, the motors that drive capstans  304 ,  306 , and  308  may be located outside of base  302  connected to cassette  300  via an appropriate transmission device (e.g., shaft, cable, etc.). In yet another embodiment, cassette  300  includes motors located within the housing of cassette  300 . In another embodiment, cassette  300  does not include capstan sockets  310 ,  312 , and  314 , but includes an alternative mechanism for transferring energy (e.g., rotational motion) from an actuator external to the cassette to each of the cassette drive mechanisms. For example, rotational movement may be transferred to the drive mechanisms of cassette  300  via alternating or rotating magnets or magnetic fields located within motor drive base  302 . 
     In the embodiment shown, cassette  300  also includes a guide catheter support  311  that supports guide catheter  317  at a position spaced from cassette  300 . As shown, guide catheter support  311  is attached to cassette  300  by a rod  313 . Rod  313  and guide catheter support  311  are strong enough to support guide catheter  317  without buckling. Guide catheter support  311  supports guide catheter  317  at a position spaced from the cassette, between the patient and the cassette to prevent buckling, bending, etc. of the portion of guide catheter  317  between the cassette and the patient. 
     Referring to  FIG. 4 , cassette  300  is shown mounted to motor drive base  302 . As shown in  FIG. 4 , cassette  300  includes an outer cassette cover  320  that may be attached to housing  316 . When attached to housing  316 , outer cassette cover  320  is positioned over and covers each of the drive mechanisms of cassette  300 . By covering the drive assemblies of cassette  300 , outer cassette cover  320  acts to prevent accidental contact with the drive mechanisms of cassette  300  while in use. 
     Referring to  FIG. 5 , cassette  300  is shown in the “loading” configuration with outer cassette cover  320  removed. Cassette  300  includes a y-connector support assembly  322 , an axial drive assembly  324 , and a rotational drive assembly  326 . Generally, the various portions of cassette  300  are placed in the loading configuration to allow the user to load or install a guide wire and/or working catheter into cassette  300 . Cassette  300  includes a Y-connector  338  supported by y-connector support assembly  322 . Y-connector  338  includes a first leg  340 , a second leg  342 , and a third leg  344 . First leg  340  is configured to attach to a guide catheter such that the central lumen of the y-connector is in fluid communication with the central lumen of the guide catheter. Second leg  342  is angled away from the longitudinal axis of y-connector  338 . Second leg  342  of y-connector  338  allows introduction of a contrast agent or medicine into the lumen of the guide catheter. A one way valve prohibits bodily fluid from exiting second leg  342 . Third leg  344  extends away from the guide catheter toward axial drive assembly  324 . In use, guide wire  301  and working catheter  303  are inserted into third leg  344  of y-connector  338  via opening  346  and may be advanced through y-connector  338  into the lumen of the guide catheter. The third leg also includes a one way valve that permits insertion and removal of the working catheter and guide wire but prohibits bodily fluids from exiting third leg  344 . 
     Cassette  300  also includes an axial drive assembly  324 . Axial drive assembly  324  includes a first axial drive mechanism, shown as guide wire axial drive mechanism  350 , and a second axial drive mechanism, shown as working catheter axial drive mechanism  352 . Axial drive assembly  324  also includes a top deck  354  and a cover  356 . 
     Generally, in use, a guide wire, such as guide wire  301 , is placed within guide wire channel  364  formed in top deck  354 , and guide wire axial drive mechanism  350  is configured to releasably engage and drive (e.g., to impart motion to) guide wire  301  along its longitudinal axis. In this manner, guide wire axial drive mechanism  350  provides for advancement and/or retraction of guide wire  301 . In use, a working catheter, such as working catheter  303 , is placed within working catheter channel  366  formed in top deck  354 , and working catheter axial drive mechanism  352  is configured to releasably engage and drive (e.g., to impart motion to) working catheter  303  along its longitudinal axis. In this manner, working catheter axial drive mechanism  352  provides for advancement and/or retraction of working catheter  303 . 
     Cassette  300  also includes a rotational drive assembly  326 . Rotational drive assembly  326  includes a rotational drive mechanism, shown as guide wire rotational drive mechanism  380 , a cover  384 , and a journal  388 . Guide wire rotational drive mechanism  380  includes a chassis  382  and an engagement structure  386 . Rotational drive assembly  326  is configured to cause guide wire  301  to rotate about its longitudinal axis. Engagement structure  386  is configured to releasably engage guide wire  301  and to apply sufficient force to guide wire  301  such that guide wire  301  is allowed to rotate about its longitudinal axis while permitting guide wire  301  to be moved axially by guide wire axial drive mechanism  350 . In the embodiment shown, rotational drive assembly  326  is supported within housing  316  such that rotation drive assembly  326  is permitted to rotate within and relative to housing  316 . In use, the guide wire, such as guide wire  301 , is received within guide wire channel  390  defined in chassis  382 , and engagement structure  386  engages guide wire  301  applying sufficient force to guide wire  301  such that the rotation of rotational drive assembly  326  causes guide wire  301  to rotate about its longitudinal axis as rotational drive assembly  326  rotates. Rotational drive mechanism  380  includes a rotation bevel gear  518  that is configured to be coupled to capstan  308  of motor drive base  302  such that rotational drive assembly  326  rotates in response to rotation of capstan  308 . 
       FIG. 5  shows cover  356  and cover  384  in the open positions. When cover  356  and cover  384  are in the open positions, guide wire axial drive mechanism  350 , working catheter axial drive mechanism  352 , and rotational drive mechanism  380  are exposed allowing the user to load cassette  300  with a guide wire and working catheter. Once the guide wire and working catheter are positioned within guide wire channel  364 , guide wire channel  390  and working catheter channel  366 , respectively, engagement surfaces of guide wire axial drive mechanism  350 , rotational drive mechanism  380  and working catheter axial drive mechanism  352  are brought into engagement with the guide wire and working catheter respectively. With the engagement structures of the respective drive mechanisms engaged, a user may operate controls  16  at workstation  14  to cause movement the guide wire and the working catheter. 
     Guide wire axial drive mechanism  350  includes a drive element  400 , a first roller assembly  402 , a second roller assembly  404 , and a guide wire axial motion sensor assembly, shown as encoder assembly  406  (first roller assembly  402  and second roller assembly  404  are shown in broken lines in  FIG. 5 ). Drive element  400  includes a drive shaft  408  and a drive wheel  410 . Drive shaft  408  is configured to engage second capstan  306  of motor drive base  302  such that drive shaft  408  and drive wheel  410  rotate in response to rotation of second capstan  306 . First roller assembly  402  includes an idler wheel or roller  418 . Second roller assembly  404  includes an idler wheel or roller  430 , and encoder assembly  406  includes shaft  438 , idler wheel or roller  442  and a magnetic coupling located at the lower end of shaft  438 . 
     Drive wheel  410  includes an outer or engagement surface, and roller  418  includes an outer or engagement surface. Generally, when guide wire axial drive mechanism  350  is placed in the “use” or “engaged” position (shown in  FIG. 6 ), guide wire  301  is positioned between drive wheel  410  and roller  418  such that the outer surface of drive wheel  410  and the outer surface of roller  418  engage the guide wire. In this embodiment, the outer surfaces of drive wheel  410  and roller  418  define a pair of engagement surfaces. The force applied to guide wire  301  by drive wheel  410  and roller  418  is such that drive wheel  410  is able to impart axial motion to guide wire  301  in response to the rotation of drive shaft  408  caused by rotation of second capstan  306 . This axial motion allows a user to advance and/or retract a guide wire via manipulation of controls  16  located at workstation  14 . Roller  418  is rotatably mounted within wheel housing  420  and rotates freely as drive wheel  410  rotates to drive guide wire  301 . 
     In the “engaged” position, guide wire  301  is positioned between roller  430  and roller  442  such that the outer surfaces of roller  430  and of roller  442  engage the guide wire. In this embodiment, the outer surfaces of roller  430  and of roller  442  define a pair of engagement surfaces. Both rollers  430  and  442  are mounted to rotate freely as drive wheel  410  imparts axial motion to guide wire  301 , and the force applied to guide wire  301  by the outer surfaces of roller  430  and of roller  442  is such that drive wheel  410  is able to pull guide wire  301  past roller  430  and  442 . In this way, the pair of non-active or idle rollers  430  and  442  help support guide wire  301  and maintain alignment of guide wire  301  along the longitudinal axis of cassette  300 . 
     Encoder assembly  406  includes magnetic coupling at the base of shaft  438  that engages a magnetic encoder located within motor drive base  302 . The magnetic encoder is configured to measure an aspect (e.g., speed, position, acceleration, etc.) of axial movement of the guide wire. As roller  442  rotates, shaft  438  rotates causing the magnetic coupling to rotate. The rotation of magnetic coupling causes rotation of the magnetic encoder within motor drive base  302 . Because rotation of roller  442  is related to the axial movement of guide wire  301 , the magnetic encoder within motor drive base  302  is able to provide a measurement of the amount of axial movement experienced by guide wire  301  during a procedure. This information may be used for a variety of purposes. For example, this information may be displayed to a user at workstation  14 , may be used in a calculation of or estimated position of the guide wire within the vascular system of a patient, may trigger an alert or alarm indicating a problem with guide wire advancement, etc. Further, as discussed below, this information may be used by procedure control module  98  to calculate and to vary the amount of force or torque being applied to guide wire  301  by drive wheel  410 . 
     Axial drive assembly  324  also includes working catheter axial drive mechanism  352 . Working catheter axial drive mechanism  352  includes a drive element  452  and a working catheter axial motion sensor assembly, shown as working catheter encoder assembly  454 . Drive element  452  includes a drive shaft  456  and a drive wheel  458 . Drive shaft  456  is configured to engage first capstan  304  of motor drive base  302  such that drive shaft  456  and drive wheel  458  rotate in response to rotation of first capstan  304 . Encoder assembly  454  includes shaft  464  and a roller  466 , and a magnetic coupling located at the lower end of shaft  464 . 
     Drive wheel  458  includes an outer surface and roller  466  includes an outer surface. When working catheter axial drive mechanism  352  is in the “engaged” position, working catheter  303  is positioned between drive wheel  458  and roller  466 , such that outer surfaces of drive wheel  458  and roller  466  engage working catheter  303 . In this embodiment, the outer surfaces of drive wheel  458  and roller  466  define a pair of engagement surfaces. The force applied to working catheter  303  by the outer surfaces of drive wheel  458  and roller  466  is such that drive wheel  458  is able to impart axial motion to the working catheter in response to the rotation of drive shaft  456  caused by rotation of first capstan  304 . This axial motion allows a user to advance and/or retract a working catheter via manipulation of controls  16  located at workstation  14 . Roller  466  is rotatably mounted to shaft  464  and rotates freely as drive wheel  458  rotates to drive the working catheter. 
     Encoder assembly  454  includes a magnetic coupling located at the lower end of shaft  464  that engages a magnetic encoder located within motor drive base  302 . The magnetic encoder is configured to measure an aspect (e.g., speed, position, acceleration, etc.) of axial movement of the working catheter. As roller  466  rotates, shaft  464  rotates causing the magnetic coupling to rotate. The rotation of the magnetic coupling causes rotation of the magnetic encoder within motor drive base  302 . Because rotation of roller  466  is related to the axial movement of working catheter  303 , the magnetic encoder within motor drive base  302  is able to provide a measurement of the amount of axial movement experienced by the working catheter during a procedure. This information may be used for a variety of purposes. For example, this information may be displayed to a user at workstation  14 , may be used in a calculation of or estimated position of the working catheter within the vascular system of a patient, may trigger an alert or alarm indicating a problem with working catheter advancement, etc. Further, as discussed below in relation to the guide wire motor, this information may be used by procedure control module  98  to calculate and to vary the amount of force or torque being applied to working catheter  303  by drive wheel  458 . 
     Referring to  FIG. 7 , a block diagram of controller  40  is shown according to an exemplary embodiment. Controller  40  may generally be an electronic control unit suitable to provide catheter procedure system  10  with the various functionalities described herein. For example, controller  40  may be an embedded system, a dedicated circuit, a general purpose system programmed with the functionality described herein, etc. Controller  40  includes a processing circuit  90 , memory  92 , communication module or subsystem  94 , communication interface  96 , procedure control module or subsystem  98 , simulation module or subsystem  100 , assist control module or subsystem  102 , mode selection module or subsystem  104 , inventory module or subsystem  106 , GUI module or subsystem  108 , data storage module or subsystem  110 , and record module or subsystem  112 . 
     Processing circuit  90  may be a general purpose processor, an application specific processor (ASIC), a circuit containing one or more processing components, a group of distributed processing components, a group of distributed computers configured for processing, etc., configured provide the functionality of module or subsystem components  94 ,  98 - 112 . Memory  92  (e.g., memory unit, memory device, storage device, etc.) may be one or more devices for storing data and/or computer code for completing and/or facilitating the various processes described in the present disclosure. Memory  92  may include volatile memory and/or non-volatile memory. Memory  92  may include database components, object code components, script components, and/or any other type of information structure for supporting the various activities described in the present disclosure. 
     According to an exemplary embodiment, any distributed and/or local memory device of the past, present, or future may be utilized with the systems and methods of this disclosure. According to an exemplary embodiment, memory  92  is communicably connected to processing circuit  90  and module components  94 ,  98 - 112  (e.g., via a circuit or any other wired, wireless, or network connection) and includes computer code for executing one or more processes described herein. A single memory unit may include a variety of individual memory devices, chips, disks, and/or other storage structures or systems. 
     Module or subsystem components  94 ,  98 - 112  may be computer code (e.g., object code, program code, compiled code, script code, executable code, or any combination thereof), hardware, software, or any combination thereof, for conducting each module&#39;s respective functions. Module components  94 ,  98 - 112  may be stored in memory  92 , or in one or more local, distributed, and/or remote memory units configured to be in communication with processing circuit  90  or another suitable processing system. 
     Communication interface  96  includes one or more component for communicably coupling controller  40  to the other components of catheter procedure system  10  via communication links  38 . Communication interface  96  may include one or more jacks or other hardware for physically coupling communication links  38  to controller  40 , an analog to digital converter, a digital to analog converter, signal processing circuitry, and/or other suitable components. Communication interface  96  may include hardware configured to connect controller  40  with the other components of catheter procedure system  10  via wireless connections. Communication module  94  is configured to support the communication activities of controller  40  (e.g., negotiating connections, communication via standard or proprietary protocols, etc.). 
     Data storage module  110  is configured to support the storage and retrieval of information by controller  40 . In one embodiment, data storage module  110  is a database for storing patient specific data, including image data. In another embodiment, data storage module  110  may be located on hospital network  34 . Data storage module  110  and/or communication module  94  may also be configured to import and/or export patient specific data from hospital network  34  for use by controller  40 . 
     Controller  40  also includes simulation module or subsystem  100 , assist module or subsystem  102 , mode selection module or subsystem  104 , inventory module or subsystem  106 , GUI module or subsystem  108 , data storage module or subsystem  110 , and record module or subsystem  112 . Generally, simulation module  100  is configured to run a simulated catheterization procedure based upon stored vascular image data and also based upon a user&#39;s manipulation of controls  16 . Generally, assist module  102  is configured to provide information to the user located at workstation  14  during a real and/or simulated catheterization procedure to assist the user with the performance of the procedure. Specific embodiments of controller  40 , including specific embodiments of simulation module  100 , and assist module  102 , are described in detail in P.C.T. International Application No. PCT/US2009/055318, filed Aug. 28, 2009, which is incorporated herein by reference in its entirety. Other specific embodiments of controller  40 , including specific embodiments of GUI module  108 , are described in P.C.T. International Application No. PCT/US2009/055320, filed Aug. 28, 2009, which is incorporated herein by reference in its entirety. 
     Controller  40  also includes a procedure control module  98  configured to support the control of bedside system  12  during a catheter based medical procedure. Procedure control module  98  allows the user to operate bedside system  12  by manipulating controls  16 . In various embodiments, procedure control module  98  is configured to generate one or more control signals  116  based upon the user&#39;s manipulation of controls  16  and, some embodiments, also based various data and information available to procedure control module  98 . As shown in  FIG. 8 , control signals  116  generated by procedure control module  98  are communicated from controller  40  to the actuators or motors of bedside system  12 . In response to control signals  116 , the motors of bedside system  12  drive the drive mechanisms of cassette  300  (e.g., guide wire axial drive mechanism  350 , working catheter axial drive mechanism  352 , guide wire rotational drive mechanism  380 , etc.) to cause movement of the guide wire or working catheter in accordance with the manipulation of controls  16  by the user. Procedure control module  98  may also cause data appropriate for a particular procedure to be displayed on monitors  26  and  28 . Procedure control module  98  may also cause various icons (e.g., icons  162 ,  164 ,  166 , etc.) to be displayed on touch screen  18  that the user may interact with to control the use of bedside system  12 . 
     Referring to  FIG. 8 , a block diagram of catheter procedure system  10  is shown according to an exemplary embodiment. In the exemplary embodiment of  FIG. 8 , motor drive base  302  includes working catheter axial drive motor  600 , guide wire axial drive motor  602 , a guide wire rotational drive motor  604 , and a power supply  606 . Working catheter axial drive motor  600  drives capstan  304 , guide wire axial drive motor  602  drives capstan  306  and guide wire rotational drive motor  604  drives capstan  308  to cause movement of working catheter  303  and guide wire  301  as discussed above. Motors  600 ,  602  and  604  are in communication with controller  40  such that control signals  116  may be received by motors  600 ,  602  and  604 . Motors  600 ,  602  and  604  respond to control signals  116  by varying the rotation of capstans  304 ,  306  and  308  thereby varying the movement of working catheter  303  and guide wire  301  caused by drive mechanisms  352 ,  350  and  380 . As shown, motor drive base  302  also includes a power supply  606  that may be, for example, a battery, the AC building power supply, etc. 
     In various embodiments, procedure control module  98  and guide wire axial drive motor  602  may be configured to provide for variability and control of the force applied to guide wire  301  by drive wheel  410  during advancement and retraction of guide wire  301 . Variability and control of the force applied to guide wire  301  may be desirable for various reasons including, providing improved ability to traverse a partial occlusion or chronic total occlusion (collectively referred to as “CTO”), etc. In various embodiments, variability and control of the force applied to guide wire  301  is achieved by varying the current and/or voltage supplied to guide wire axial drive motor  602  from power supply  606 . This control of guide wire axial drive motor  602  acts to vary the rotational speed and/or torque that guide wire axial drive motor  602  imparts to guide wire  301  via capstan  306  and drive wheel  410 . In some embodiments, variation of current and/or voltage supplied to guide wire axial drive motor  602  from power supply  606  (and the corresponding variation in the rotational speed and/or torque that guide wire axial drive motor  602  imparts to guide wire  301 ) occurs in response to control signals  116  generated by procedure control module  98 . As discussed in more detail below, control signals  116  may be based upon a user input (e.g., the user&#39;s operation of controls  16 ) and based upon a second input (e.g., other information or data available to procedure control module  98 ), and the actuator may provide torque to a percutaneous device (e.g., the guide wire) via a drive mechanism (as discussed above) in response to the control signal. As discussed below, procedure control module  98  is described as being configured to control, limit, vary, etc. the torque provided an actuator, such as guide wire axial drive motor  602 , based on various inputs (e.g., information, data, operating conditions, etc.) and/or based upon user inputs received by a user interface (e.g., controls  16 ). It should be understood that, in one embodiment, the functionalities provided by control module  98  discussed below are provided by generating control signals  116  based upon the various inputs, and the control signals  116  are transmitted or communicated to an actuator (e.g., guide wire actuator  602 ). In this embodiment, the actuator then provides or generates a torque to a drive mechanism in response to the control signal. 
     During some intervention procedures, it is necessary that the guide wire traverse a partial or total occlusion of the coronary arteries. During these procedures, the guide wire must be advanced with enough force such that the guide wire pushes through the occlusion. However once the guide wire is through the occlusion it may be desirable to reduce the amount of torque the motor provides to drive the guide wire. Thus, in various embodiment, guide wire axial drive motor  602  is a motor having torque and speed characteristics such that it provides increased torque during traversal of the occlusion. For example, in one embodiment, guide wire axial drive motor  602  is configured to deliver sufficient torque via its output shaft such that the force imparted to guide wire  301  is great enough to allow guide wire  301  to traverse a total occlusion. In another embodiment, guide wire axial drive motor  602  is configured such that the maximum torque that may be delivered via its output shaft is such that the force imparted to guide wire  301  is not sufficient to traverse the occlusion. In another embodiment, guide wire axial drive motor  602  is selected to have a relatively low maximum output shaft speed (i.e., the no-load speed of the motor) to prevent sudden unwanted acceleration of guide wire  301 . For example, the output speed of the motor shaft may be varied so as to not provide sufficient force to traverse the occlusion. This lower force may be useful when navigating the guide wire to the occlusion, or CTO. In one embodiment, the torque applied by the motor to the wheels driving the guide wire may be varied to maintain a constant rotational speed of the wheels driving the guide wire. In one embodiment a user may reduce the speed of the guide wire as the tip of the guide wire is about to fully traverse the lesion or CTO. Additionally, a user may reverse the direction of the guide wire upon fully traversing a lesion or CTO to remove any buckling in the guide wire that may have occurred prior to fully traversing the lesion or CTO. This potential unwanted acceleration of guide wire  301  can be minimized by selecting a guide wire axial drive motor  602  with a low maximum output shaft speed or with a controller that controls the speed to constant speed at a given input by the operator. For example if the operator moves a joy stick a certain distance from a neutral position, the speed will remain constant even if the torque is modified for a portion of the travel distance of the guide wire. In one embodiment, the speed of the guide wire may be kept constant, and the torque is varied by moving the joy stick from the neutral position. In this embodiment, as the joy stick is moved further from its neutral position increased torque is provided to the wheels driving the guide wire. As a guide wire is inhibited from moving forward due to frictional forces and/or a CTO, increased torque may be needed from the drive to move the guide wire forward. In one implementation a user may select to move the guide wire or rotate the guide wire at a constant speed while using the joy stick to vary the torque applied to the mechanisms used to linearly and rotating move the guide wire. A user may set the speed of the linear drive or the rotation drive for a certain time or distance be set by controls  16  at workstation  14 . The joy stick in this mode then may be used to vary the torque applied to the drive mechanisms, allowing the user to modify the torque during a procedure. For example it may be desirable to increase the torque during navigation of a lesion or CTO and then to reduce the torque once the guide wire or working catheter has fully traversed the lesion or CTO. Alternatively, the speed is controlled by the joy stick and the controller adjusts the motor torque to obtain the speed required by the user. 
     In other embodiments, procedure control module  98  is configured to control the voltage and/or current supplied to guide wire axial drive motor  602  by power supply  606  in order to control and vary the force applied to guide wire  301  by drive wheel  410 . In one embodiment, procedure control module  98  is configured to limit the maximum speed and maximum torque supplied by guide wire axial drive motor  602  based upon the current location of the tip of the guide wire within the patient&#39;s vascular system. Thus, in this embodiment, control signal  116  generated by procedure control module  98  may be based upon information related to the location of the tip of the guide wire within the patient and based upon the user&#39;s operation of controls  16 . For example, procedure control module  98  may be configured such that the maximum speed and/or maximum torque supplied by guide wire axial drive motor  602  is set higher when the tip of the guide wire is located with the large arteries (e.g., aorta, femoral artery, etc.) and the maximum speed and/or maximum torque supplied by guide wire axial drive motor  602  is set lower when the tip of the guide wire is located with the smaller arteries (e.g., coronary arteries, etc.). In such embodiments, procedure control module  98  may be configured to determine the information related to the location of the tip of the guide wire in various way. For example, procedure control module  98  may prompt the user to input the current location of the tip of the guide wire via controls  16  (e.g., touch screen  18 ), location of the guide wire tip may be determined by image processing of images captured via imaging system  32 , or the location may be determined via the distance information captured by a guide wire axial motion sensor assembly, such as encoder assembly  406 , discussed above. 
     In another embodiment, procedure control module  98  is configured to limit the maximum speed and/or maximum torque supplied by guide wire axial drive motor  602  based upon the type of movement being performed by the guide wire. Thus, in one embodiment, control signal  116  generated by procedure control module  98  may be based upon information related to the direction of movement of the guide wire and based upon the user&#39;s operation of controls  16 . For example, procedure control module  98  may be configured such that the maximum torque and/or speed supplied by guide wire axial drive motor  602  is set lower when the guide wire is being advanced and the maximum torque and/or speed supplied by the guide wire axial drive motor  602  is set higher when the guide wire is being retracted. This arrangement may be desirable because the risk of blood vessel perforation is lower when the guide wire is being retracted. 
     In other embodiments, procedure control module  98  may be configured to control the torque and speed supplied by guide wire axial drive motor  602  to assist in traversal of an occlusion such as a CTO. Thus, in one embodiment, control signal  116  generated by procedure control module  98  may be based upon information related to whether the tip of the percutaneous device is traversing an occluded portion of a vessel of the patient&#39;s vascular system and based upon the user&#39;s operation of controls  16 . For example, procedure control module  98  may be configured such that the maximum torque supplied by guide wire axial drive motor  602  is set higher and the maximum speed supplied by guide wire axial drive motor  602  is set lower during traversal of a CTO. In this embodiment, controls  16  (e.g., touch screen  18 ) may include a button that the user selects when occlusion or CTO traversal is about to start thereby activating the occlusion or CTO traversal limits discussed above. In other embodiments, procedure control module  98  may determine that occlusion or CTO traversal is occurring by identifying the position of the guide wire relative to the occlusion or CTO from image information captured by imaging system  32 . In another embodiment, procedure control module  98  may be configured to determine the extent of occlusion or CTO traversal that has occurred (i.e., how far through the occlusion or CTO the guide wire has traveled), and to control the torque and speed supplied by guide wire axial drive motor  602  based on the extent of occlusion or CTO traversal. For example, procedure control module  98  may be configured to decrease the torque supplied by guide wire axial drive motor  602  as the guide wire nears the end of the occlusion or CTO. In one such embodiment, the extent of occlusion or CTO traversal by the guide wire is determined from image information captured by imaging system  32 . 
     In another embodiment, procedure control module  98  is configured to limit the maximum torque supplied by guide wire axial drive motor  602  such that the force imparted to guide wire  301  is low enough that guide wire  301  is capable of navigating through the blood vessels needed during a procedure at a proper force level. In one such embodiment, procedure control module  98  is configured with a set or non-variable maximum torque threshold such that the torque supplied by guide wire axial drive motor  602  remains below the threshold under all operating conditions. In this embodiment, the set or non-variable maximum torque threshold is selected such that the force applied to the guide wire is optimized for the type of blood vessel to be traversed during a particular procedure. 
     In another embodiment, procedure control module  98  is configured with a variable maximum torque threshold that is determined based upon various data or information accessible by procedure control module  98 . In this embodiment, the torque supplied by guide wire axial drive motor  602  remains below the variable threshold during the procedure. In one such embodiment, the variable maximum torque threshold is determined from image data captured by imaging system  32 . Thus, in this embodiment the maximum torque threshold may be determined based upon the thickness of the blood vessel walls at a certain location identified from the image data, and procedure control module  98  is configured to utilize the determined torque threshold to limit the maximum allowable torque of guide wire axial drive motor  602  as the guide wire traverses that portion of the blood vessel. In another embodiment, the maximum torque threshold utilized by procedure control module  98  is based upon the characteristics of the particular guide wire being used. For example, the maximum torque threshold may be set higher for a larger diameter guide wire than for a smaller diameter guide wire. 
     In another embodiment, procedure control module  98  may be configured to allow the user to set the maximum torque and maximum speed supplied by guide wire axial drive motor  602 . In one embodiment, procedure control module  98  may display a button on touch screen  18  prompting the user to set the maximum torque and maximum speed. In another embodiment, controls  16  may include a set of controls (e.g., dials, sliders, etc.) allowing the user to set the maximum torque and maximum speed supplied by guide wire axial drive motor  602 . In various embodiments, the user may be able to adjust the maximum torque and maximum speed as desired throughout the procedure. 
     In one embodiment, bedside system  12  may include a sensor configured to determine the amount of force applied to guide wire  301  by guide wire axial drive motor  602  as guide wire axial drive mechanism  350  advances and retracts the guide wire. In another embodiment, procedure control module  98  may be configured to determine the amount of force applied to guide wire  301  by guide wire axial drive motor  602  as guide wire axial drive mechanism  350  advances and retracts the guide wire by monitoring the operating state of guide wire axial drive motor  602 . In one embodiment, procedure control module  98  is configured to display information related to determined amount of force to the user via a display device, such as monitors  26  and  28 . For example, the display may be a bar display that fills in as force increase or a dial display with a needle that indicates the determined force. The display may also provide an indication of the force that would result in blood vessel perforation during the procedure. This indication may be an approximation based on location of the guide wire (e.g., in the aorta, in the coronary arteries, etc.) or this indication may be calculated from the image information of the patient&#39;s vascular system. 
     In various embodiments, procedure control module  98  and working catheter axial drive motor  600  may be configured to provide for variability and control of the force applied to working catheter  303  by drive wheel  458  during advancement and retraction of working catheter  303 . Variability and control of the force applied to working catheter  303  may be desirable for various reasons including, lowering the risk of blood vessel perforation, providing improved ability to traverse a partial occlusion or chronic total occlusion (CTO), etc. It should be noted that, while the above disclosure related to primarily to variable control of force and speed imparted to a guide wire by guide wire axial drive motor  602 , the same variable force and speed concepts may be applied to working catheter axial drive motor  600 . 
     In one embodiment, guide wire  301  is translated axially by axial drive assembly  324  and rotational drive assembly  326 . When both axial drive assembly  324  and rotational drive assembly are actively engaged with guide wire  302  a force is applied to the guide wire by both axial drive assembly  324  and rotational drive assembly  326 . As discussed above, guide wire rotational drive mechanism  380  includes a chassis  382  and an engagement structure  386 . Rotational drive assembly  326  is configured to cause guide wire  301  to rotate about its longitudinal axis. Engagement structure  386  is configured to releasably engage guide wire  301  and to apply sufficient force to guide wire  301  such that guide wire  301  is allowed to rotate about its longitudinal axis while permitting guide wire  301  to be moved axially by guide wire axial drive mechanism  350 . However, the force required by the drive wheels  410  of the axial drive assembly to overcome the frictional force applied by the engagement structure of the 386 is greater than the force that would be required if the axial drive assembly were not so engaged. As a result a greater force is applied to the drive wheels and idler wheels of the axial drive mechanism. Similarly, the force required to securely engage guide wire  302  in the rotational drive mechanism to overcome the friction applied by the axial drive assembly is greater than if the axial drive assembly were not engaged. 
     Controller  40  may include instructions to selectively disengage the drive wheels of the axial drive assembly from the guide wire when the rotational drive mechanism is actively rotating the guide wire. Similarly, controller  40  may include instructions to selectively disengage the engagement structure of the rotational drive assembly from guide wire the when the axial drive assembly is actively engaged. This selective disengagement reduces the pressure applied to the guide wire thereby requiring less force to overcome the frictional force of the non-engaged drive mechanism. Similarly, when a user provides instructions to both rotate and axially drive the guide wire, controller  40  may include instructions to alternatively engage and disengage the rotational drive mechanism and the axial drive mechanism. If the instructions are provide rapidly, such as greater than 10 times per second, or 20 or more times per second such that impact will not be perceptible to a physician operating the system and will provide greater control of the rotational and axial drive assemblies as the frictional force of the other drive assembly will be significantly reduced and/or eliminated. 
     In addition to employing the rapid engage and disengage system to alternatingly engage and disengage the rotational and axial drive mechanisms when both rotational and axial drive mechanisms are in use. The engage and disengage feature may be used on each of the axial drive and rotational drive mechanisms. For example, in order to provide greater traction of the drive wheels  410  and idler wheels  418  the force applied to the drive wheels  410  may be rapidly and repeatedly increased and decreased to minimize slipping of the guide wire relative to the drive wheels  410 . In one embodiment both drive wheels  410  are rapidly and repeatedly engaged and disengaged by controller  40  without the need for the physician or operator to repeatedly and rapidly turn a switch on and off. In another embodiment each pair of drive wheel  410  and idler wheel  418  may alternatively engage and disengage so that only one pair of drive wheel  410  and idler wheel  418  are engaged at one time. In another embodiment, if a sensor detects one idler wheel  410  is rotating more slowly than the other idler wheel, controller  40  may automatically provide instructions to disengage and reengage the idler wheel that is slipping to improve contact and engagement. Alternatively, controller  40  may reduce the speed and/or force of the non-drive wheel  410  associated with the non-slipping idler wheel until both idler wheels are rotating together and/or reduce the speed and/or force of both drive wheels. 
     In another embodiment, the force applied between the drive wheels and respective idler wheels maybe varied, so that the pinch force may be varied. Where the pinch force may be varied it may not be necessary to completely disengage the drive wheels and idler wheels or engagement surfaces of the rotational drive assembly, but rather it may be sufficient to reduce and increase the pinch force to achieve the desired result of enhanced control. By reducing the force of the drive wheel against the idler wheels or by reducing the force between the engagement surfaces in the rotational drive assembly, the deformation of the drive wheel surface and engagement surface is reduced thereby providing enhanced repeatable performance to the system. 
     In a further embodiment, controller  40  may provide instructions to adjust the speed and/or force between the drive wheel and idler wheel to decrease and/or increase the speed. A step function or a ramp function of increased speed and/or pressure between the drive wheel and idler wheels will provide enhanced control of the guide wire. In one embodiment, using a joy stick or other input device, a user may move the joy stick from its neutral position to request that a guide wire move a certain speed. If the actual speed of the guide wire being driven or rated is less than the speed requested by the user as a result of slippage of the guide wire with respect to the wheels, the controller may increase the speed of the wheels until the actual linear or rotational speed of the guide wire is equal to the speed requested by the user. 
     Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only. The construction and arrangements of the robotic catheter device, as shown in the various exemplary embodiments, are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Some elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. The order or sequence of any process, logical algorithm, or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present invention.