Patent Publication Number: US-11639847-B2

Title: System and method for detecting a position of a guide catheter support

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. application Ser. No. 15/739,031, filed Dec. 21, 2017, entitled SYSTEM AND METHOD FOR DETECTING A POSITION OF A GUIDE CATHETER SUPPORT, which is a 371 National Stage Entry of PCT/US2016/040262, filed Jun. 30, 2016, entitled SYSTEM AND METHOD FOR DETECTING A POSITION OF A GUIDE CATHETER SUPPORT, which claims the benefit of U.S. Provisional Application No. 62/186,832, filed Jun. 30, 2015, entitled ABSOLUTE LINEAR POSITION SENSING WITH PHOTO DIODES, herein incorporated by reference in their entireties. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to the field of robotic catheter systems for performing diagnostic and/or therapeutic procedures and in particular, to an apparatus and method for detecting a position of a guide catheter support. 
     BACKGROUND OF THE INVENTION 
     Catheters may be used for many medical procedures, including inserting a guide wire, delivering a stent and delivering and inflating a balloon. Catheterization procedures are commonly performed for diagnosis and treatment of diseases of the heart and vascular systems. The catheterization procedure is generally initiated by inserting a guide wire into a blood vessel in the patient&#39;s body. The guide wire is then guided to the desired location, most commonly in one of the heart vessels or elsewhere in the vascular system. At this point, the catheter is slid over the guide wire into the blood vessel and/or heart. In some procedures, the catheter is equipped with a balloon or stent that when deployed at the site of the lesion allows for increased blood flow through the portion of the coronary artery that is affected by the lesion. 
     For manual insertion of a catheter, the physician applies torque and axial push force on the proximal end of a guide wire to effect tip direction and axial advancement at the distal end. Robotic catheter system have been developed that may be used to aid a physician in performing a catheterization procedure such as a percutaneous coronary intervention (PCI). The physician uses a robotic catheter system to precisely steer a coronary guide wire, balloon catheter or stent delivery system in order to, for example, widen an obstructed artery. In order to perform PCI, the various elongated medical devices (e.g., guide wire, guide catheter, working catheter) must be navigated through the coronary anatomy to a target lesion. While observing the coronary anatomy using fluoroscopy, the physician manipulates the elongated medical device into the appropriate vessels toward the lesion and avoid advancing into side branches. A robotic catheter procedure system includes drive mechanisms to drive various elongated medical devices (e.g., guide wire, guide catheter, working catheter) used in catheterization procedures to provide linear and rotational movement of the elongated medical device. 
     During one type of intervention procedure, a guide catheter is inserted into either a patient&#39;s femoral or radial artery through an introducer and the guide catheter is positioned proximate the coronary ostium of a patient&#39;s heart. During the procedure, the guide catheter is used to guide other elongated medical devices such as a guide wire and balloon catheter into a patient. If during a PCI procedure the guide catheter begins to slip out of the ostium, an operator may wish to relocate the end of the guide catheter robotically. A guide catheter support structure, such as a flexible track, may be used to provide support to the guide catheter while it is moved. 
     It would be desirable to provide a system and method for detecting a position of a guide catheter support. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In accordance with an embodiment, a catheter procedure system includes a base and a robotic mechanism having a longitudinal axis and being movable relative to the base along the longitudinal axis, the robotic mechanism includes a robotic drive base including at least one drive mechanism, a cassette operatively secured to the robotic drive base, a rigid guide coupled to the cassette and fixed relative to the robotic mechanism, a flexible track having a distal end, a proximal end and a plurality of reflective sections, wherein at least a portion of the flexible track is disposed within the rigid guide and a position detector mounted to the robotic drive base and positioned beneath the flexible track, the position detector configured detect light reflected off of the reflective sections of the flexible track and to determine the position of the distal end of the flexible track based on the detected reflected light. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will become more fully understood from the following detailed description, taken in conjunction with the accompanying drawings, wherein the reference numerals refer to like parts in which: 
         FIG.  1    is a perspective view of an exemplary catheter procedure system in accordance with an embodiment; 
         FIG.  2    a schematic block diagram of a catheter procedure system in accordance with an embodiment; 
         FIG.  3    is an isometric view of a bedside system of a catheter procedure system in accordance with an embodiment; 
         FIG.  4    is an isometric view of the front portion of the catheter procedure system of  FIG.  3    with Y-connector support cover in a raised position in accordance with an embodiment; 
         FIG.  5    is a top plan view of the front portion of the catheter procedure system of  FIG.  3    with the guide catheter in an engaged position in accordance with an embodiment; 
         FIG.  6    is an isometric view of the front portion of the catheter procedure system of  FIG.  3    with the flexible track in an extended position in accordance with an embodiment; 
         FIG.  7    is a top plan view of the catheter procedure system with the flexible track in the fully retracted position in accordance with an embodiment; 
         FIG.  8    is a top plan view of the catheter procedure system with the flexible track in an extended position in accordance with an embodiment; 
         FIG.  9    is a top plan view of the catheter procedure system with the robotic mechanism in a first position in accordance with an embodiment; 
         FIG.  10    is a top plan view of the catheter procedure system with the robotic mechanism in a second extended position in accordance with an embodiment; 
         FIG.  11    is a rear isometric view of the catheter procedure system with a linear drive in accordance with an embodiment; 
         FIG.  12    is a perspective view of the catheter procedure system with the cassette in a pre-assembly position relative to the robotic drive base in accordance with an embodiment; 
         FIG.  13    is a perspective view of the cassette mounted to the robotic drive base in accordance with an embodiment; 
         FIG.  14    is a front side cross sectional view of the robotic drive base and cassette showing the position detector in accordance with an embodiment 
         FIG.  15    is a perspective view of a position detector in accordance with an embodiment; 
         FIG.  16    is a cross-sectional view of the position detector in accordance with an embodiment; 
         FIG.  17    is a close-up front-side cross-sectional view of the robotic drive base, cassette and position detector in accordance with an embodiment; 
         FIG.  18    is a schematic block diagram of a position detector in accordance with an embodiment; 
         FIG.  19    is a cross-sectional view of a proximal end of the flexible track and rigid guide in accordance with an embodiment; and 
         FIG.  20    is a close up top view of a proximal end of the rigid guide in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    is a perspective view of an exemplary catheter procedure system in accordance with an embodiment. In  FIG.  1   , a catheter procedure system  100  may be used to perform catheter based medical procedures (e.g., a percutaneous intervention procedure). Catheter based medical 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 onto one or more coronary arteries through a catheter and an image of the patient&#39;s heart is taken. Catheter based medical procedures may also include catheter based therapeutic procedures (e.g., 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  100  is capable of performing any number of catheter based medical procedures with minor adjustments to accommodate the specific percutaneous intervention devices to be used in the procedure. In particular, while the embodiments of catheter procedure system  100  describe herein are explained primarily in relation to the diagnosis and/or treatment of coronary disease, catheter procedure system  100  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  100  includes lab unit  106  and workstation  116 . Catheter procedure system  100  includes a robotic catheter system, shown as bedside system  110 , located within lab unit  106  adjacent a patient  102 . Patient  102  is supported on a table  108 . Generally, bedside system  110  may be equipped with the appropriate percutaneous intervention devices or other components (e.g., guide wires, guide catheters, working catheters such as balloon catheters and stent delivery system, contrast media, medicine, diagnostic catheters, etc.) to allow the user to perform a catheter based medical procedure via a robotic system by operating various controls such as the controls located at workstation  116 . Bedside system  110  may include any number and/or combination of components to provide bedside system  110  with the functionality described herein. Bedside system  110  includes, among other elements, a cassette  114  supported by a robotic arm  112  which is used to automatically feed a guide wire into a guide catheter seated in an artery of the patient  102 . 
     Bedside system  110  is in communication with workstation  116 , allowing signals generated by the user inputs of workstation  116  to be transmitted to bedside system  110  to control the various functions of bedside system  110 . Bedside system  110  may also provide feedback signals (e.g., operating conditions, warning signals, error codes, etc.) to workstation  116 . Bedside system  110  may be connected to workstation  116  via a communication link  140  (shown in  FIG.  4   ) that may be a wireless connection, cable connections, or any other means capable of allowing communication to occur between workstation  116  and bedside system  110 . 
     Workstation  116  includes a user interface  126  configured to receive user inputs to operate various components or systems of catheter procedure system  100 . User interface  126  includes controls  118  that allow the user to control bedside system  110  to perform a catheter based medical procedure. For example, controls  118  may be configured to cause bedside system  110  to perform various tasks using the various percutaneous intervention devices with which bedside system  110  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). Cassette  114  includes various drive mechanisms to cause movement (e.g., axial and rotational movement) of the components of the bedside system  110  including the percutaneous intervention devices. 
     In one embodiment, controls  118  include a touch screen  124 , one or more joysticks  128  and buttons  130 ,  132 . The joystick  128  may be configured to advance, retract, or rotate various components and percutaneous intervention devices such as, for example, a guide wire, a guide catheter or a working catheter. Buttons  130 ,  132  may include, for example, an emergency stop button and a multiplier button. When an emergency stop button is pushed a relay is triggered to cut the power supply to bedside system  110 . Multiplier button acts to increase or decrease the speed at which the associated component is moved in response to a manipulation of controls  118 . In one embodiment, controls  118  may include one or more controls or icons (not shown) displayed on touch screen  124 , that, when activated, causes operation of a component of the catheter procedure system  100 . Controls  118  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 screen, etc. that may be desirable to control the particular component to which the control is dedicated. In addition, touch screen  124  may display one or more icons (not shown) related to various portions of controls  118  or to various components of catheter procedure system  100 . 
     User interface  126  may include a first monitor or display  120  and a second monitor or display  122 . First monitor  120  and second monitor  122  may be configured to display information or patient specific data to the user located at workstation  116 . For example, first monitor  120  and second monitor  122  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  120  and second monitor  122  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  120  and monitor  122  may be configured to display information regarding the position the guide catheter. Further, monitor  120  and monitor  122  may be configured to display information to provide the functionalities associated with controller  134  (shown in  FIG.  4   ) discussed below. In another embodiment, user interface  126  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  100  also includes an imaging system  104  located within lab unit  106 . Imaging system  104  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  104  is a digital x-ray imaging device that is in communication with workstation  116 . In one embodiment, imaging system  104  may include a C-arm (not shown) that allows imaging system  104  to partially or completely rotate around patient  102  in order to obtain images at different angular positions relative to patient  102  (e.g., sagittal views, caudal views, anterior-posterior views, etc.). 
     Imaging system  104  may be configured to take x-ray images of the appropriate area of patient  102  during a particular procedure. For example, imaging system  104  may be configured to take one or more x-ray images of the heart to diagnose a heart condition. Imaging system  104  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  116  to properly position a guide wire, guide catheter, stent, etc. during the procedure. The image or images may be displayed on first monitor  120  and/or second monitor  122 . In particular, images may be displayed on first monitor  120  and/or second monitor  122  to allow the user to, for example, accurately move a guide catheter into the proper position. 
     Referring to  FIG.  2   , a block diagram of catheter procedure system  100  is shown according to an exemplary embodiment. Catheter procedure system  100  may include a control system, shown as controller  134 . Controller  134  may be part of workstation  116 . Controller  134  may generally be an electronic control unit suitable to provide catheter procedure system  100  with the various functionalities described herein. For example, controller  134  may be an embedded system, a dedicated circuit, a general purpose system programed with the functionality described herein, etc. Controller  134  is in communication with one or more bedside systems  110 , controls  118 , monitors  120  and  122 , imaging system  104  and patient sensors  136  (e.g., electrocardiogram (“ECG”) devices, electroencephalogram (“EEG”) devices, blood pressure monitors, temperature monitors, heart rate monitors, respiratory monitors, etc.). In various embodiments, controller  134  is configured to generate control signals based on the user&#39;s interaction with controls  118  and/or based upon information accessible to controller  134  such that a medical procedure may be performed using catheter procedure system  100 . In addition, controller  134  may be in communication with a hospital data management system or hospital network  142  and one or more additional output devices  138  (e.g., printer, disk drive, cd/dvd writer, etc.). 
     Communication between the various components of catheter procedure system  100  may be accomplished via communication links  140 . Communication links  140  may be dedicated wires or wireless connections. Communication links  140  may also represent communication over a network. Catheter procedure system  100  may be connected or configured to include any other systems and/or devices not explicitly shown. For example, catheter procedure system  100  may include IVUS systems, image processing engines, data storage and archive systems, automatic balloon and/or stent inflation systems, medicine injection systems, medicine tracking and/or logging systems, user logs, encryption systems, systems to restrict access or use of catheter procedure system  100 , etc. 
     As mentioned, controller  134  is in communication with bedside system  110  and may provide control signals to the bedside system  110  to control the operation of the motors and drive mechanisms used to drive the percutaneous intervention devices (e.g., guide wire, catheter, etc.). The bedside system  110  may include, for example, a guide wire axial drive mechanism that provides for advancement and/or retraction of a guide wire, a working catheter axial drive mechanism that provides for advancement and/or retraction of a working catheter and a guide wire rotational drive mechanism that is configured to cause a guide wire to rotate about its longitudinal axis. In one embodiment, the various drive mechanism are housed in a cassette  114  (shown in  FIG.  1   ). 
       FIG.  3    is an isometric view of a bedside system of a catheter procedure system in accordance with an embodiment. In  FIG.  3   , a bedside system  210  includes a robotic mechanism  212  that may be used to robotically move an elongated medical device. The robotic mechanism  212  is movable relative to a base  214 . The robotic mechanism  212  includes a robotic drive base  220  movable relative to base  214  and a cassette  222  that is operatively secured to robotic drive base  220 . In one embodiment, base  214  is secured to an articulating arm  224  that allows a user to position robotic mechanism  212  proximate a patient. In an embodiment, base  214  is the distal portion of the articulating arm  224 . Articulating arm  224  is secured to a patient bed by a rail clamp or a bed clamp  226 . In this manner, base  214  is secured to a patient bed. By manipulation of articulated arm  224 , the base  214  is placed in a fixed location relative to a patient that lies upon the patient bed. The arms of articulated arm can be fixed once the desired location of robotic mechanism  212  is set relative to the patient. 
     As used herein, the direction distal is the direction toward the patient and the direction proximal is the direction away from the patient. The term up and upper refers to the general direction away from the direction of gravity and the term bottom, lower and down refers to the general direction of gravity. The term front refers to the side of the robotic mechanism that faces a user and away from the articulating arm. The term rear refers to the side of the robotic mechanism that is closest to the articulating arm. The term inwardly refers to the inner portion of a feature. The term outwardly refers to the outward portion of a feature. 
     Bedside system  210  also includes a flexible track  216  that is movable along a rigid guide track  218  having a non-linear portion. The flexible track  216  includes a proximal end  228  and a distal end  230 . The flexible track  216  supports an elongated medical device such as a guide catheter so that the guide catheter can be advanced into the patient without buckling. In one embodiment, cassette  222  includes structure that defines rigid guide  218 . In another embodiment, base  214  alone or in combination with cassette  222  includes structure that defines rigid guide  218 . 
     Referring to  FIGS.  4  and  5   , an elongated medical device such as a guide catheter  238  is operatively secured to the robotic mechanism  212  through the cassette  222 , Guide catheter  238  includes a proximal end  240  and an opposing distal end  242 . In one embodiment, the proximal end  240  of guide catheter  238  may be operatively secured to a Y-connector  244  and a Y-connector engagement mechanism  246 . The Y-connector  244  may be, for example, a hemostasis valve that is secured to cassette  222  by the Y-connector engagement mechanism  246 . The y-connector engagement mechanism  246  includes a Y-connector base  248  that is part of cassette  222  and an enclosure member  252  that includes a lid  250  and a support member  254 . The y-connector base  248  includes a guide catheter drive mechanism (not shown) located in the cassette  222  which in turn is operatively connected to robotic base  220 . The guide catheter drive mechanism includes a drive mechanism that operatively engages and rotates guide catheter  238  along its longitudinal axis based on commands provided by a controller (such as controller  134  shown in  FIG.  2   ). 
     Referring to  FIG.  5   , the guide catheter  238  maintains a linear position along its longitudinal axis  256  within cassette  222  and for at least a certain distance distal cassette  222 . In one embodiment, longitudinal axis  256  corresponds to the longitudinal axis of cassette  222 . During a medical procedure such as a percutaneous coronary intervention (PCI), guide catheter  238  is used to guide other elongated medical devices such as a guide wire and balloon stent catheter into a patient to conduct, for example, an exploratory diagnosis or to treat a stenosis within a patient&#39;s vascular system. In one such procedure, the distal end  242  of the guide catheter  238  is seated within the ostium of a patient&#39;s heart. Robotic mechanism  212  drives a guide wire and/or a working catheter such as a balloon stent catheter in an out of a patient. The guide wire and working catheter are driven within the guide catheter  238  between the distal end of the robotic mechanism  212  and the patient. In one embodiment, longitudinal axis  256  is the axis  3  about which cassette  222  causes rotation of a guide wire and the axis along which cassette  222  drives the guide wire along its longitudinal axis and drives a working catheter such as a balloon stent catheter along its longitudinal axis. 
     Referring to  FIGS.  5  and  6   , a collar  258  is formed at the distal end  260  of rigid guide  218 . The terminal end  230  of flexible track  216  is secured to a sheath clip  232  which is releasably connected to cassette  222 . The rigid guide  218  includes an inner channel through which the flexible track  216  moves relative to rigid guide  218 . The flexible track  216  includes an opening  264  located adjacent the terminal distal end  230  of flexible track  216 . When distal end  230  of flexible track  216  is positioned adjacent collar  258 , the opening  264  extends from collar  258  toward the area in which rigid guide  218  begins an arcuate path away from longitudinal axis  248 . In one embodiment, the arcuate path forms an s-curve having at least one point of inflection along the arcuate path. The opening  264  provides a path for guide catheter  238  to be placed into the hollow cavity of flexible track  216 . Opening  264  tapers to a slit  266  that extends substantially the entire length of flexible track  216 . In one embodiment, slit  266  extends from opening  264  a distance sufficient to allow guide catheter  238  to enter and exit an interior portion of flexible track  216  throughout the entire intended operation of the robotic catheter system. 
     Referring to  FIG.  3   , the flexible tack  216  is initially positioned within the rigid guide  218  by feeding distal end  230  of flexible track  216  into proximal opening  234  of rigid guide  218  until the distal end  230  of flexible track  216  extends beyond collar  258  of rigid guide  218 . The distal end  230  of flexible track  216  is operatively connected to the sheath clip  232 . The rigid guide includes a linear portion beginning at proximal opening  234  and a non-linear portion. In one embodiment, the non-linear portion is an arcuate portion having at least one point of inflection.  FIG.  6    shows a portion of the flexible track  216  extending beyond collar  258 . Since flexible track  216  is formed of a flexible material having a modulus of elasticity that is less than the modulus of elasticity of the rigid guide material, flexible track  216  moves along the curved non-linear portion of the channel defined by rigid guide  218 . 
     Referring to  FIGS.  7  and  8   , to perform a procedure the sheath clip  232  is pulled by a user away from cassette  222  in a direction along longitudinal axis  256  until the distal end  262  of sheath clip  232  is proximate the patient. In one embodiment, an introducer (not shown) is secured to the distal end  262  of sheath clip  232 . The introducer is a device that is secured to a patient to positively position the introducer to the patient to allow insertion and removal of elongated medical devices such as a guide catheter, guide wire and/or working catheter into the patient with minimal tissue damage to the patient. Once the operator has pulled the sheath clip  232  and accompanying flexible track  216  toward the patient such that the introducer is proximate the patient, the flexible track  216  is locked in position by a locking clamp  236 . The locking clamp  236  secures the flexible track  216  to base  214  such that a portion of flexible track  216  is in a fixed position relative to the patient bed and the patient to the extent the patient lies still on the patient bed. 
     Referring to  FIG.  11   , robotic mechanism  212  includes a linear drive mechanism  276 . The linear drive mechanism  276  shown in  FIG.  11    includes a linear slide that is robotically controlled by a user through a remote workstation (for example, workstation  116  shown in  FIG.  1   ). The linear drive mechanism  276  drives robotic mechanism  212  along longitudinal axis  256 . Since rigid guide  218  is fixed relative to robotic mechanism  212 , the rigid guide  218  and robotic mechanism  212  move relative to the flexible track  216  as the robotic mechanism  212  moves along the longitudinal axis  256 . 
     Referring to  FIG.  7    and  FIG.  8   , the operation and movement of flexible track  215  relative to rigid guide  218  will be described. Referring to  FIG.  7   , flexible track  216  is shown in the installation first position in which guide catheter  238  is positioned within sheath clip  232  and flexible track opening  264  as described above. Referring to  FIG.  8   , once sheath clip  232  has been released from the cassette  222 , the sheath clip  232  and distal end  230  of the flexible track  216  are pulled by a user away from cassette  222  such that the distal end  262  of the sheath clip  232  is proximate the entry point of the patient in which a percutaneous intervention will occur. The locking clamp  236  operatively clamps a portion of flexible track  216  so that flexible track  216  is fixed relative to base  214 . 
     Referring to  FIGS.  7  and  8   , the portion of flexible track  216  that is positioned within the arcuate portion of rigid guide  218  is pulled out of the distal end  262  of rigid guide  218  in a direction generally along longitudinal axis  256 . Similarly, a portion  268  of flexible track  216  that was external to and not located within the arcuate portion of rigid guide  218  is pulled into the arcuate portion of rigid guide  218  and depending on how far the terminal distal end  230  of the flexible track  216  is pulled toward the patient, portion  268  of flexible track  216  will enter the arcuate portion of rigid guide and may extend therefrom. Stated another way, flexible track  216  includes three general regions that change with the operation of the guide catheter system. First, a proximal region that includes the flexible track portion from the proximal end  228  of flexible track  216  to the proximal end  270  of the arcuate portion of rigid guide  218 . Flexible track  216  includes a second portion located between the proximal end  270  of the arcuate portion of rigid guide  218  and the distal end  272  of the arcuate portion of rigid guide  218  proximate collar  258 . Flexible track  216  includes a third region that extends from collar  258  of rigid guide  218  in a direction defined by a vector generally along longitudinal axis  256 , where the vector has a beginning at the Y-connector and extends in a direction toward collar  258 . The first region and second region of flexible track  216  as described above is offset from and not in line with longitudinal axis  256 . The third portion of flexible track  216  is generally coaxial with longitudinal axis  256  as flexible track  216  exits collar  258  of rigid guide  218 . 
     During one type of intervention procedure, guide catheter  238  is inserted into a patient&#39;s femoral artery through an introducer and positioned proximate the coronary ostium of a patient&#39;s heart. An operator may wish to relocate the distal end of the guide catheter robotically. Referring to  FIGS.  9  and  10   , the control of the distal end of guide catheter  238  and the movement of the robotic mechanism  212  and rigid guides  218  relative to the flexible track  216  will be described. Referring to  FIG.  9   , guide catheter  238  has a distal portion which extends beyond the distal end  262  of sheath clip  232  in order to extend the terminal end of guide catheter  238  in a direction away from the terminal distal end  262  of the sheath clip  232 . As noted above, the distal end of guide catheter  238  may be placed proximate the ostium of a patient. The robotic control of the distal end of the guide catheter  238  is accomplished by movement of robotic drive mechanism  212  relative to base  214  and flexible track  216  by linear drive  276 . The guide catheter  238  is located within the channel of the flexible track  216  from cassette  222  until the sheath clip  232 . 
     If during a PCI procedure the guide catheter begins to slip out of the ostium, it is possible to extend the distal end of guide catheter  238  back into the patient ostium by robotically moving the robotic mechanism  212  towards the patient. In doing so, the distal end of guide catheter  238  is moved toward the patient reinserting or seating the distal end of the guide catheter into the patient&#39;s ostium as one example. As the robotic drive mechanism  212  is moved along longitudinal axis  256 , the rigid guide  218  is moved relative to the flexible track  216 . The portion of flexible track  216  that is located within the arcuate section of rigid guide  216  changes as the robotic mechanism  212  and rigid guide  218  are moved. The portion of the flexible track  218  that is located in the rigid guide is moved toward and away from longitudinal axis  256  depending on the direction that the robotic drive mechanism  212  is moving. Guide catheter  238  moves into or out of the section of flexible track  216  that is moving in and out of the arcuate portion of rigid guide  218 . In this manner, the portion of guide catheter  238  between cassette  222  and the sheath clip  232  is always located within the channel of flexible track  216 . In this manner, guide catheter  238  may be manipulated within flexible track  216  without buckling or causing other non-desirable movement during a percutaneous intervention procedure. 
     Referring to  FIGS.  9  and  10   , the position of the flexible track  216  with respect to rigid guide  218  will be described as it related to a single section A on flexible track  216 . In one example, section A on flexible track  216  is located distal collar  258  of rigid guide  218 . When an operator determines to insert guide catheter  238  further into or toward a patient in a direction away from collar  258 , an input device is manipulated by the user at a remote workstation that drives robotic drive  212  distally along longitudinal axis  256  by activating linear drive  276 . The proximal end of guide catheter  238  is longitudinally fixed in cassette  222  so that as the robotic drive  212  including cassette  222  is moved relative to base  214  and flexible track  216  by linear drive  276  in a direction toward the patient, the guide catheter  238  moves distally along longitudinal axis  256 . As a result, the distal end of guide catheter  238  moves toward and/or into the patient. 
     As the robotic mechanism  212  is moved along longitudinal axis  256 , section A of flexible track  216  moves into the arcuate portion of rigid guide  218  through collar  258  and along the arcuate portion of rigid guide until section A of the flexible track  216  is adjacent the proximal end of rigid guide  218 . In this manner, distal end  230  of flexible track  216  remains in a constant position but section A of flexible track  216  is moved out of or offset to the longitudinal axis  256 . As section A moves into the arcuate channel defined by the rigid guide  218 , the guide catheter  238  enters the channel or hollow lumen of the flexible track  216  through the slit adjacent in the engagement zone proximal to collar  258 . In this manner, flexible track  216  provides continual support and guidance for the guide catheter  238  between the collar  258  and the patient as the distal end of guide catheter  238  is moved toward and away from the patient. 
     Similarly, if the operator desires to retract the distal end of the guide catheter  238  from within the patient, the user provides a command to the linear drive  276  through the remote workstation to move robotic drive mechanism  212  in a direction away from the patient. In this way, section A of the flexible track  216  would enter the proximal end of the arcuate portion of the rigid guide and be guided within the channel of the rigid guide  218  until section A exits the distal end of the rigid guide  218 . The guide catheter  238  would enter the slit at section A or stated another way, a portion of the guide catheter  238  would enter the flexible track  216  via the portion of the slit that is located within the concentric circle taken at section A of the flexible track  216 . Note that although sections of the flexible track are positioned in different regions of the rigid guide as the robotic mechanism is moved toward and away from the patient the proximal end and the distal end of the flexible track remain in a fixed location as the robotic mechanism is moved along the longitudinal axis. 
     Robotic mechanism  212  may also include a position sensor to determine the distance the distal end  230  of the flexible track  216  has been pulled away from the cassette  222  (e.g., the distance from collar  258 ) along the longitudinal axis  256 . The position information regarding the distal end  230  of the flexible track  216  may be used to control or limit the distance the robotic mechanism  212  moves along the longitudinal axis  256  toward the patient.  FIG.  12    is an exploded view of a bedside system with a cassette in a pre-assembly position relative to the robotic drive base in accordance with an embodiment. A front side of the robotic mechanism  312  is generally designated by  396  and a rear side of the robotic mechanism  312  is generally designated by  398 . A position detector  380  is coupled to the robotic drive base  320  of the robotic mechanism  312 . Position detector  380  is located at a proximal end  394  of the robotic drive base  320 . The position detector  380  is positioned on the robotic drive base  320  so that it sits beneath a proximal portion of flexible track  316  when the cassette  322  is mounted on the robotic drive base  320 .  FIG.  13    shows the cassette  322  mounted on the robotic drive base  320  and disposed over the position detector  380 .  FIG.  14    is a front side cross sectional view of the robotic drive base and cassette showing the position detector in accordance with an embodiment. In  FIG.  14   , a front cross-sectional view of the position detector  380  is shown. Position detector  380  is mounted on the robotic drive base  320  and located beneath the flexible track  316 . As discussed above, flexible track  316  passes through the rigid guide  318 . As the flexible track is moved towards or away from the patient, the position detector  380  is configured to determine the amount of displacement of the distal end  230  (shown in  FIG.  8   ) of the flexible track  316  from the cassette  322 . 
     Position detector  380  may be, for example, an optical detector. Accordingly, the flexible track may include a pattern of reflective and non-reflective sections. Referring to  FIG.  13   , the flexible track  316  includes reflective lines or stripes  395  on at least a proximal portion of the flexible track  316 . The reflective lines  395  are separated by non-reflective lines or section  397 . The reflective lines may be created on the flexible track by, for example, printing white lines on a track formed from translucent material. In another example, the flexible track has a highly reflective opaque surface (e.g., a surface with titanium dioxide) and the non-reflective lines are added by laser etching. In another embodiment, the flexible track  316  is formed from a reflective material that is translucent and the non-reflective lines or sections may be etched on the flexible track  316  using a laser. In another embodiment, the flexible track  316  is formed from a non-reflective material and the reflective lines may be added by, for example, a printing or etching process. In an embodiment, the reflective lines  395  are evenly spaced from one another along the proximal portion of the flexible track  316  such that the reflective line width (t r ) equals the non-reflective line width (t s ). In this embodiment, the resulting resolution of the position detector  380  is B units in which the reflective line width and the non-reflective line width are equal to 2B (i.e., t r =t s =2B). Referring to  FIG.  14   , the position detector  380  is configured as an optical sensor that detects light reflected off of the reflective stripes or lines  395  as the flexible track  316  passes over the position detector  380 . In an embodiment, the reflected light can be enhanced by providing a reflective target within proximal end of the rigid guide.  FIG.  19    is a cross-sectional view of a proximal end of the flexible track and rigid guide in accordance with an embodiment. In  FIG.  19   , a reflective target  381  is shown located within the rigid guide  318  and flexible track  316  and above the position detector  380 . The reflective target  381  is formed from a reflective material. The flexible track  316 , for example, a laser etched translucent track, passes over the reflective target as the track  316  passes over the position detector  380 .  FIG.  20    is a close up top view of a proximal end of the rigid guide in accordance with an embodiment. In  FIG.  20   , the reflective target  381  may be mounted to the rigid guide  318  using a tab  399 . As discussed above, the flexible track  316  includes a lengthwise slit  266  (shown in  FIG.  6   ). The slit slides over the tab  399  as the flexible track is moved towards and away from a patient. 
       FIGS.  15  and  16    illustrate an exemplary position detector assembly in accordance with an embodiment. Position detector  380  includes a housing  384 , windows and/or slits  382  and a reed switch  386 . In one embodiment, the windows and/or slits have a width that is less than or equal to B units. The windows  382  include a transparent material such as, for example, glass with or without an anti-reflective coating. In various embodiments, the position detector may include one or more windows  382 . Position detector  380  includes at least one optical detector disposed within the housing  384 .  FIG.  16    is a cross-sectional view of a position detector in accordance with an embodiment. The optical detector includes a light emitting diode (LED)  388  and a photo-diode  390  disposed within the housing  384  below the windows  382 . The LED  388  is positioned so that light from the LED passes through the window  382  onto the flexible track  316 . The photo-diode  390  is positioned so that it may detect light reflected off of the reflective lines of the flexible track  316 . The LED  388  and the photo-diode  390  are coupled to a circuit board (e.g., a printed circuit board)  392 . While one optical detector (i.e., the pair of LED  388  and photo diode  392 ) is shown in  FIG.  16   , in various embodiments, the position detector  380  may include more than one optical detector.  FIG.  17    is a close up cross-sectional view of a robotic mechanism with a position detector in accordance with an embodiment. In  FIG.  17   , position detector  370  includes four optical detectors. The cross-sectional view of position detector  380  shows the LED of each of the four optical detectors, namely, a first optical detector  383 , a second optical detector  385 , a third optical detector  387  and a fourth optical detector  389 . As discussed above, as the distal end of the flexible track  316  is moved away from or toward the cassette, the proximal end of the flexible track passes over the position sensor  380 . 
     Returning to  FIG.  16   , the circuit board  392  may include circuitry configured to generated signals indicating the distance the distal end of the flexible track has moved based on the reflected light detected by the photo diode  390 . In one embodiment, the position detector is configured to realize a two-bit Gray Code. In one embodiment, position sensor  380  includes two optical detectors, as shown in  FIG.  18    which is a block diagram of a position detector in accordance with an embodiment. In  FIG.  18   , a position detector  480  includes a first optical detector  491  and a second optical detector  493  disposed in a housing  484 . The first optical detector  491  includes an LED and a photo diode and the second optical detector  493  includes an LED and a photo diode. To realize a two bit Gray code, the first optical detector  491  is positioned at a distal end of the housing  484  and may be designated as the most significant bit (MSB). The second optical detector  493  is positioned a distance, l (for example, l={B, 5B,9B, . . . }), from the first optical detector  487  and may be designated as the least significant bit (LSB). The flexible track  416  includes reflective lines  495  and non-reflective lines  497 . Each reflective line  495  has the same width t r  and are evenly spaced from one another by a distance t s  (for example, t s =2B units wide). In one embodiment, the reflective line width and the non-reflective line width are equal (i.e., t r =t s ). The first optical detector  491  and the second optical detector  493  each generate an output voltage that increases when the photo diode detects light from the LED reflected off of the reflective lines  495  of the flexible track  416 . The reflected light is used to detect the presence or absence of a reflective line  495 . 
     When the output voltage of the first  491  or the second  493  optical detector is greater than a predetermined value (i.e., the presence of a reflective line is detected), the respective optical detector may be assigned a logic value of 1. When an output voltage of the first  491  or second  493  optical detector is less than a predetermined value (i.e., a reflective line is not detected), the optical detector may be assigned a logic value of 0. As the distal end of the flexible track  416  is moved away from or toward the cassette and the proximal portion of the flexible track  416  passes over the position detector  480 , the first optical detector  491  and the second optical detector  493  will transition between logic 1 and logic 0. The distance that the distal end of the flexible track  416  is moved away from or toward the cassette may be determined based on the transitions of first  491  and second  493  optical detectors and the reflective lines  495  detected. In one embodiment, the first  491  and second  493  optical detectors will transition from (0,0)→(0,1)→(1,1)→(1,0)→(0,0) after each displacement, B units, of the distal end of the flexible track away from the cassette, The first  491  and second  493  optical detectors will transition from (1,0)→(1,1)→(0,1)→(0,0)→(1,0) after each displacement, -B units, of the distal end of the flexible track toward the cassette. 
     In another embodiment, four optical detectors may be used to realize a two-bit Gray Code. Referring to  FIG.  17   , the second optical detector  385  and the third optical detector  387  represent the LSB and MSB optical detectors, respectively. In this embodiment, the first optical detector  383  (designated as ˜LSB) and the fourth optical detector  389  (designated as ˜MSB) are located within the position detector  380  so that the ˜LSB optical detector  383  is closest to a proximal end of the position detector  380  and the ˜MSB optical detector  389  is closest to a distal end of the position detector  380 . In other words, denoted from the proximal end towards the distal end of the position detector  380 , the first optical detector  383  is designated as ˜LSB, the second optical detector  385  is designated as LSB, the third optical detector  387  is designated as MSB and the fourth optical detector  389  is designated as ˜MSB. The third optical detector  387  is positioned a distance, l (for example, l={B, 5B, 9B . . . }), from the second optical detector  385 . The ˜LSB optical detector  383  may be located a distance of  l ={2B, 6B, 8B, . . . } units from the LSB detector  385  so that when the LSB optical detector  385  is centered on a reflective line the corresponding ˜LSB optical detector  383  is centered on a non-reflective line. The ˜MSB optical detector  389  may be located a distance of  l ={2B, 6B, 8B, . . . } units from the MSB optical detector  387  so that when the MSB optical detector  387  is centered on a reflective line the corresponding ˜MSB optical detector  389  is centered on a non-reflective line. In one embodiment the distances l and  l  are minimized. As discussed above with respect to  FIG.  16   , each reflective line  495  has the same width t r  and are evenly spaced from one another by a distance t s  (for example, t s =2B units wide). In one embodiment, the reflective line width and the non-reflective line width are equal (i.e., t r =t s ). When the difference between the output voltage of the MSB optical detector  387  and the ˜MSB optical detector  389  or the difference between the output voltage of LSB optical detector  385  and the ˜LSB optical detector  383  is greater than a predetermined value, the respective optical detector may be assigned a logic value of 1. When the difference between the output voltage of the MSB optical detector  387  and the ˜MSB optical detector  389  or the difference between the output voltage of the LSB optical detector  385  and the ˜LSB optical detector  383  less than a predetermined value (i.e., a reflective line is not detected), the optical detector may be assigned a logic value of 0. As discussed above, the distance that the distal end of the flexible track  416  is moved away from or toward the cassette may be determined based on the transitions of the optical detectors between logic 1 and logic 0. 
     The signal to noise ratio may be increased by taking a difference between the output voltage of the MSB optical detector  387  and the output voltage of the ˜MSB optical detector  389  and a difference between the LSB optical detector  385  and the output voltage of the ˜LSB optical detector  383 . In addition, the system is self-balancing because it is centered on the difference between a reflective line and a non-reflective line of the flexible track  316 . This embodiment allows for compensation of offsets due to the optical assembly and to gradual irregularities in the surface of the flexible track  316 . 
     Computer-executable instructions for determining the position of a flexible track according to the above-described method may be stored on a form of computer readable media. Computer readable media includes volatile and nonvolatile, removable, and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer readable media includes, but is not limited to, random access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory or other memory technology, compact disk ROM (CD-ROM), digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired instructions and which may be accessed by system  10  (shown in  FIG.  1   ), including by internet or other computer network form of access. 
     This written description used examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims. The order and sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. 
     Many other changes and modifications may be made to the present invention without departing from the spirit thereof. The scope of these and other changes will become apparent from the appended claims.