Abstract:
An apparatus is disclosed for use with a surgical navigation system. The apparatus comprises a universal instrument attachment device. The universal instrument attachment device preferably includes a tracking body onto which a position tracking array is fixedly mountable, and an instrument attachment body removably and adjustably mounted to the tracking body. The instrument attachment body further includes a flexible clamping band having a circumference for adaptably conforming around a variety of instruments having different circumferential shapes and clamping the instrument to the instrument attachment body itself.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a system that assists in the performance of a surgical procedure by generating images to illustrate the relative position of various body parts and instruments during the surgical procedure, and, more particularly, to an image guided system that employs a position tracking device that is adjustably mounted to an instrument. 
     2. Description of the Related Art 
     In recent years, a variety of different types of surgical navigation systems have been introduced in order to improve the performance of surgical procedures. For instance, U.S. Pat. Nos. 5,383,454; 5,851,183; 5,871,445; and 5,891,034 to Bucholz; PCT Application No. PCT/US94/04530 (Publication No. WO 94/24933) to Bucholz; and PCT Application No. PCT/US95/12894 (Publication No. WO 95/11624) to Bucholz et al., the entire disclosures of each of which is incorporated herein by reference, disclose surgical navigation systems that illustrate the position of medical instruments during surgical procedures. 
     A typical navigation system employs a scanner to generate images for indicating the position of a medical instrument relative to a predetermined body part, for example. Moreover, such surgical navigation systems typically include position tracking devices, such as for example, a position indicating LED and/or reflector array arranged about a body part as well as position indicating LEDs and/or reflectors mounted on a medical instrument, which are part of a position sensing device further including a digitizer camera to track the positions of the selected body parts and medical instruments, and a display for illustrating the relative positions of the body party and the medical instrument during the medical procedure. 
     Although these types of systems can be effective, additional improvements are desirable to facilitate the mating of medical instruments to position tracking devices. For example, accurate illustration of the precise position of a medical instrument is of paramount importance in virtually any image guided medical procedure. This is true because a primary purpose of utilizing a navigation system is to allow an operator to perceive accurately the precise location of a body part relative to the location of the medical instrument being implemented. If a medical instrument is not adequately mounted to the position tracking device, then the navigation system may lose information about the precise location of the medical instrument relative to the position tracking device. Consequently, an inaccurate illustration of the location of the medical instrument relative to a body part may result. 
     With this in mind, typical surgical navigation systems employing known mounting devices can suffer from several important drawbacks. In conventional navigation systems, for example, rigid clamping brackets, e.g., in the form of a “C” clamp, and associated clamping screws may be used to attach medical instruments to respective position tracking devices. As such, the amount of frictional clamping force available in such conventional clamping bracket designs may be inherently limited. This is so because the contact area between conventional brackets and medical instruments is restricted to a point or along a line. Thus, conventional bracket mechanisms may increase the likelihood that an inaccurate illustration of the position of a medical instrument will occur, as discussed above, because the stability of conventional position tracking mounting devices may be compromised. 
     As another example, known position tracking mounting devices are not capable of satisfactorily accommodating a wide variety of medical instrument shapes and sizes. Indeed, known clamping devices may need to be replaced each time a medical instrument having a different shape and/or size is desired. In particular, known mounting designs contemplate the use of custom made position tracking mounting mechanisms for medical instruments that are of a different size or shape. Moreover, when using a plurality of different instruments in a single surgical procedure, known position tracking mounting arrangements can fail to facilitate efficient replacement of a variety of medical instruments having different sizes and shapes. As a result, known position tracking mounting devices require unnecessary time, expense and inconvenience. 
     Additionally, conventional surgical navigation systems employ position tracking mounting devices that can fail to adequately address the hazards of introducing new medical instruments into a surgical field prior to and/or during a surgical procedure. Namely, if a new medical instrument is introduced into a surgical procedure without re-calibrating the position of the newly introduced instrument relative to a known reference point, then inaccurate illustration of the position of the medical instrument on the display can result as discussed above. Accordingly, a simple and reliable way to require an operator to properly re-calibrate and/or re-register the position of a newly introduced medical instrument is desirable. 
     As a further example, typical surgical navigation systems employ known position tracking devices that are not always adjustably mounted in a stable manner to a medical instrument in a variety of geometric configurations. Adjustably mounting a medical instrument to a position tracking device is advantageous for a number of important reasons. For instance, a clear line of sight between the digitizer camera and the emitters and/or reflectors of the position tracking should be maintained throughout the medical procedure, itself. If this line of sight is interrupted, then inaccurate illustration of the position of the medical instrument can result, as discussed above. In practice, it is advantageous for a surgeon to be able to position the medical instrument in a particular orientation. In order to position the medical instrument as such, the emitters and/or reflectors of the conventional position tracking device may be forced to point away from the digitizer camera. However, if the position tracking device is adjustably mounted relative to the medical instrument in a stable manner, then the emitters and/or reflectors can be controlled to be continuously directed toward the digitizer camera while the medical instrument is placed in a particular orientation. 
     In light of the foregoing, there are a need for an improved image guided universal attachment device in surgical navigation systems. 
     SUMMARY OF THE INVENTION 
     The advantages and purpose of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Moreover, the advantages and purposes of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. 
     To attain the advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the present invention is directed to an image guided system for use in performing operative procedures with an instrument comprising 
     a computer controlled navigation arrangement having a controller in communication with a sensor array for interacting with a position tracking array and tracking positions of the instrument in three dimensional space relative to a known reference point, a tracking head supporting the position tracking array, an instrument mounting assembly attachable to the instrument, and a quick release coupling for connecting the tracking head to the instrument mounting assembly. 
     In another aspect, the advantages and purpose of the present invention are attained by an instrument attachment device for use with a computer controlled surgical navigation system employing a controller in communication with a sensor array for interacting with an instrument mounted position tracking array and tracking positions of an instrument in three dimensional space relative to a known reference point. The instrument attachment device comprises a tracking head carrying the position tracking array, and an instrument mounting assembly having a compliant clamping band attachable to the instrument, and a head connector enabling adjustment of the angle between the tracking head and the instrument. 
     In yet another aspect, the advantages and purpose of the present invention are realized by a method of computer controlled surgical instrument navigation in which a controller communicates with a sensor array for interacting with an instrument mounted position tracking array on a tracking head and tracks positions of an instrument in three dimensional space relative to a known reference point. The method comprises the steps of fixedly mounting an instrument mounting assembly to each of a plurality of surgical instruments to be used in a surgical procedure, providing for a quick release coupling of the tracking head to the mounting assembly on each of the plurality of surgical instruments, and signalling the controller for each connection and disconnection of the tracking head to each surgical instrument. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and together with the description, serve to explain the principles of the invention. In the drawings, 
     FIG. 1 is a schematic diagram of one preferred embodiment of a surgical navigation system with an image guided universal instrument adapter; 
     FIG. 2 is a exploded perspective view of an instrument attachment device according to a first embodiment of the present invention; 
     FIG. 3 is a assembled perspective view of an instrument attachment body according to the present invention; and 
     FIG. 4 is a schematic cross-section depicting a signal switch arrangement of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     The present invention provides an image guided system for use in performing surgical or other medical procedures with an instrument. The image guided system includes computer controlled navigation arrangement having a controller in communication with a sensor array for interacting with a position tracking head and for tracking positions of the instrument in three dimensional space relative to a known reference point. 
     In the illustrated embodiment, as shown in FIG. 1, a computer assisted image guided surgery system, designated generally by the reference numeral  10 , generates an image for display on a monitor  12  representing the position of one or more body elements, such as a cranium represented by circle  14  fixedly held in a well-known clamping device such as a Mayfield clamp assembly  16 . A reference arc  18 , bearing tracking means such as LED emitters or reflectors  20 , for example, is mounted to the Mayfield clamp  16 . The image is generated from an image data set, usually pre-operatively by a CAT scanner for example, which image has reference points for at least one body element, such as cranium  14 . The reference points of the particular body element have a fixed spatial relation to the particular body element. 
     The illustrated system  10  further includes a Position Sensing Unit (PSU), such as a digitizer camera  24  on a support  26  for identifying, during a surgical procedure, for example, the relative position of each of the reference points to be displayed by tracking the position of emitters/reflectors  20  on arc  18  as shown in FIG.  1 . The system  10  also includes a processor  28 , such as PC or other suitable workstation processor, with an associated controller  30  for modifying the image data set according to the identified relative position of each of the reference points during the procedure, as identified by digitizer camera  24 . The processor  28  can then, for example, generate a displaced image data set representing the position of the body elements during the procedure for display on monitor  12 . An instrument  32 , which may be any of a wide assortment of medical instruments, is fitted with a tracking head  34  in a manner to be further described in detail below. The instrument  32  is used during the medical or surgical procedure and thus positioned relative to a body part, such as cranium  14 , to be tracked by the digital camera or suitable sensor array  24  and may be a drill, probe, catheter, biopsy guide, or any other suitable medical instrument having any particular shape and/or size capable of carrying out any desired procedure. A further description of the operation of the surgical navigation system  10  is found in the above-cited PCT/US95/12894, the entire disclosure of which is incorporated herein by reference. 
     In accordance with the present invention, the described image guided system includes an instrument tracking head and instrument mounting assembly by which the tracking head is fixed to the medical instrument of the system. The mounting assembly provides for a quick release and/or replacement of the tracking head and the instrument as well as adjustment of relative positional orientation between the tracking head and the instrument. Additionally, the instrument attachment body preferably comprises a flexible clamping band arrangement assuring a firm connection of the tracking head and the instrument and which is adaptable to a wide variety of instrument sizes and shapes. 
     In a preferred embodiment illustrated in FIG. 2, tracking head  34  includes a generally U-shaped body  36  having a top surface  38  on which an array of light emitting/reflecting elements  40 , is presented. Where the elements  40  are light emitting, light emitting diodes are preferably used. Alternatively, various forms of light reflective elements may be used. Tracking head  34  is supported on a mounting column  42  depending from the bottom thereof for connection to a instrument mounting assembly generally designated by the reference numeral  44 . 
     Instrument mounting assembly  44  includes as separate components, a clamping band  46 , a mounting post  48 , a saddle collar  50 , a clamp nut  52 , a bolt  54  and a head connector  56 . 
     Mounting post  48  includes a base portion  58  at one end, a central threaded portion  60 , and a radially serrated coupling portion  62  at the other end. The periphery of base portion  58  is preferably of a chamfered rectangular or square configuration but may be of other non-circular peripheral configurations. A bore  64  extends diametrically through base portion  58  and opens through the bottom thereof via a slot  66  parallel to bore  64 . 
     Clamping band  46  is preferably formed from a strip of low carbon stainless steel foil of a thickness in the range of 5 mils to 50 mils, preferably in the range of 10 mils to 30 mils, and more preferably 20 mils, and of a width approximating 0.25 inch to provide a compliant and yet suitably strong clamping band. As shown in FIG. 2, opposite ends of clamping band  46  are folded on themselves and brought together against each other to form an enlarged anchoring bead  68  spaced by a neck portion  69  from a closed loop portion  71  of clamping band  46  . Enlarged anchoring bead  68  is receivable in the bore  64  of mounting post base portion  58  with neck portion  69  in slot  66 , bead  68  being incapable of passing though slot  66 . The construction of clamping band  46  enables customizing of the length of the band to fit any instrument diameter simply by cutting the appropriate length of strip and folding the ends to provide the enlarged anchoring bead  68 . It is preferred, however, that the clamping bands are preformed and made available in sets with bands within each set having varying length to accommodate anticipated variations in instrument diameter. For example, a set may include four clamping band sizes where a first clamping band size fits a range of instruments  32 , such as for example, between 0.125 inches and 0.25 inches in circumference; a second clamping band size accommodates a second range of instruments  32  between 0.25 and 0.375 inches in circumference; a third clamping band size fits a range of instruments  32  between 0.375 and 0.5 inches in diameter; and a fourth clamping band size is customly sized to be within 0.25 inches of the circumference of a given instrument  32 . 
     As shown in FIG. 2, the upper end  70  of saddle collar  50  is circular to provide an annular nut bearing top surface  72 . A major lower portion  74  of saddle collar  50  is of chamfered rectangular of square configuration so that the inside of lower portion  74  complements the shape of base portion  58  on mounting post  48  to prevent relative rotation of mounting post  48  and saddle collar  50  and guide relative axial movement of mounting post  48  within saddle collar  50 . The bottom end of saddle collar  50  is defined by opposite arcuate or saddle-shaped edges  76  in one orthogonal direction, by the bottoms of chamfered corners  77 , and by linear band clamp guiding edges  78  in the other orthogonal direction. As shown in FIGS. 2 and 3, linear guiding edges  78  are preferably elevated above the bottoms of chamfered corners  77  to allow free sliding movement of clamping band  46  without binding between linear guiding edges  78  and the peripheral surface of instrument  32 . The radius of the arcuate edges  76  is selected to approximate one half of the anticipated largest diameter of instrument  32  on which the mounting assembly  44  will used to assure that linear guiding edges  78  will be spaced from the peripheral surface of instrument  38 . Notches  79  are provided in the center of each arcuate edge  76  to provide stable engagement of saddle collar with the smallest diameter instrument  38  to be used, and to provide for proper engagement of rectangular flat instruments, such as forceps. 
     An assembled state of clamping band  46 , mounting post  48 , saddle collar  50 , and clamp nut  52  is shown in FIG.  3 . The assembly is accomplished by inserting enlarged anchoring bead  68  into bore  64  of mounting post base  58  with neck  69  in slot  66 . Saddle collar  50  is then placed over mounting post  48  and located axially thereon so that at least a leading thread at the top of threaded portion  60  is exposed above top surface  72  of saddle collar  50 . Clamp nut  52  is then engaged with the leading threads of threaded portion  60  to secure the assembly in an initial loose condition with base  58  within lower portion  74  of saddle collar  50  and loop portion  71  of clamping band  46  hanging loosely from base portion  58  of mounting post  48 . In practice, bolt  54  is preferably captured in threaded hole  84  to prevent complete separation of it, head connector  56 , and coupling portion  62 . 
     In the initial loosely assembled condition of band clamp  46 , mounting post  48 , saddle collar  50  and clamp nut  52 , radially serrated coupling portion  62  on mounting post  48  projects above clamp nut  52  to be fully accessible. Head connector  56 , which includes a coupling portion  80  having a radially serrated face  82  that complements radial serrated coupling portion  62 , and a threaded hole  84  to receive the threaded shank of bolt  54 , may be mounted by bolt  54  to coupling portion  62 . 
     The loosely interconnected mounting assembly  44  may be connected to instrument  32  by advancing loop portion  71  of clamping band  46  over one end of and axially relative to instrument  32  to a position of attachment to the latter. Clamp nut  52  is then tightened to draw loop portion  71  of clamping band  46  snugly about instrument  32  by applying tension to clamping band  46  as a result threaded movement of mounting post  48  against a compressive reaction in saddle collar  50 . Alternatively, if the shape of instrument  32  does not permit the loose loop portion  71  of clamping band  46  to fit over an end of instrument  32  and/or be advanced axially to the position of clamping band attachment, clamping band  46  may be opened by separating the opposite ends thereof and placed directly about instrument  32  at the position of attachment. The opposite ends of clamping band  46  are then closed on each other to provide the anchoring bead  68 . Mounting post  48  is manipulated to locate anchoring bead  68  of the preplaced clamping band  46  in bore  64  and the assembly of saddle collar  50  and clamp nut  52  is effected as described above. 
     Preferably, and as shown in FIG. 2, the periphery of clamp nut  52  is formed with opposed spanner flats  85  to enable application of tightening or loosening torque by hand or by using a conventional spanner wrench. Bolt  54  is preferably provided with a socket head to enable threaded placement, removal or adjustment using a conventional alien wrench. To enable application of tightening or loosening torque to both clamp nut  52  and bolt  54  by the same tool, a modified alien wrench  86  is supplied. As shown in FIG. 2, wrench  86  is an L-shaped cylindrical rod having an alien wrench head  88  on one end for application to bolt  54 . Clamp nut  52  is provided with at least one, preferably four, chord oriented holes  90  opening through equally spaced spanner flats  85 . Holes  90  are sized to receive the end of wrench  86  in a manner so that torque may be applied to clamping nut  52  in either direction of rotation by using wrench  86 . 
     In the illustrated embodiment, tracking head  34  is secured to instrument mounting assembly  44  for quick connect/disconnect coupling of mounting column  42  on tracking head  34  and head connector  56  of the described instrument mounting assembly  44 . In particular, the bottom end of mounting column  42 , as shown in FIG. 2, is provided with an upwardly extending cylindrical socket  92  having diametrically oriented bayonet slots  94  opening through the periphery of mounting column  42 . Head connector  56 , in turn is provided with a cylindrical plug portion  96  having diametrically extending lugs  98  and a convex, spring-biased, ball detent projection  100  located centrally on a radial end face  102  of the plug portion  96 . 
     To install track head  34  on a particular instrument  32  to which mounting assembly  44  has been fixed in the manner described, during a surgical procedure, an operator preferably aligns plug portion  96  with cylindrical socket  92 , or vice versa, inserts plug portion  96  into socket  92 , and rotates mounting column  42  relative to plug portion  96  of head connector  56  so that lugs  98  engage in bayonet slots  94 . Engagement of ball detent projection  100  with the base end of cylindrical socket  92  will impart a biased retention of lugs  98  in bayonet slots  94 . Removal of track head  34  involves only a reversal of the relative rotation of mounting column  42  and head connector  56  in a pull and twist mode of manipulation. Thus, the quick disconnect mounting arrangement allows an operator to remove an instrument  32  attached to tracking head  34  and replace it with another in a convenient and rapid fashion. 
     Also the angular position of tracking head  34  and instrument  32  may be adjusted to position instrument  32  in a desirable orientation without interrupting a line of sight between the array of light emitting/reflecting elements  40  and digitizer camera  24 . Such adjustment is accomplished in the illustrated embodiment by loosening bolt  54  to release engagement of the radial serrations on the respective coupling portions  62  and  80 , rotating the coupling portions about the axis of bolt  54  and tightening bolt  54  using wrench  86 . 
     Where tracking head  34  includes electric circuitry associated with controller  30 , mounting column may include a sensing device capable of providing a signal in response to the attachment or detachment of mounting column  42  to instrument mounting assembly  44  so that a signal is sent to the controller  30  indicating that a calibration and/or registration procedure needs to be performed. Such a calibration and/or registration procedure is effected to assure that information transmitted to controller  30  from tracking head  34  via digitizer camera  24  includes a precise relation of the working portion of instrument  32  relative to tracking head  34 . 
     In the illustrated embodiment, and as shown very schematically in FIG. 4, a switch  104  having an actuator  106  is positioned in mounting column  42  so that actuator  106  is presented at the inner end of cylindrical socket  92 . As the cylindrical plug portion  96  of head connector  56  is introduced into cylindrical socket  92 , ball detent projection  100  will engage actuator  106  and change the state of switch  104 . Correspondingly, removal of tracking head  34  from instrument mounting assembly  44 , causing withdrawal of plug portion  96 , will return switch  104  to its initial state. 
     In use, the mounting assembly of the invention, may be mounted to each of a plurality of surgical instruments to be used in a surgical procedure, for example. As each such instrument is needed during the procedure, the quick release coupling of the tracking head to the mounting assembly on each of the plurality of surgical instruments minimizes the time required for each instrument change. Also controller  30  will be informed of each change by the state of switch  104  of tracking head  34 . 
     Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.