Patent Publication Number: US-2004059260-A1

Title: Method and device for deflecting a probe

Description:
FIELD  
       [0001] This invention relates to inserting a probe into a biological subject, and more particularly to inserting a probe into a difficult to reach area in a biological subject.  
       BACKGROUND  
       [0002] A probe is a small object that can be inserted into a biological subject. Probes perform a variety functions. For example, some probes detect energy in a target area of a biological subject. Other probes deliver energy to a target area. Leads including electrodes inserted into a human heart provide a conductive path to the heart. Leads including electrodes inserted into a human brain provide a conductive path to the brain. Fiber optic cables inserted into a biological subject provide an optical path for viewing or ablating a target area.  
       [0003] One method of inserting a probe into a biological subject includes inserting a straight tube or cannula into the biological subject. The distal end of the cannula is positioned near a target area. A probe is inserted into the cannula and pushed into the target area. Finally, the cannula is removed from the biological subject leaving the inserted probe positioned in the target area.  
       [0004] This method is useful for inserting a probe into a target area that lies on an unobstructed straight line path from the surface of the biological subject to the target area. Unfortunately, this method is not suitable for inserting a probe into a target area in which the straight line path includes biological structures that are damaged by the insertion of a cannula or in which the target&#39;s orientation is different than the preferred trajectory of the probe.  
       [0005] Many areas of interest in a biological subject are located in the subject such that a straight line path from the surface of the subject passes through a biological structure that would be damaged by the insertion of the cannula. For example, the straight line path from the surface of a human subject that passes through the subthalamic nucleus along its longitudinal axis includes the lower forehead and occipital orbit. Aside from cosmetic reasons, many critical structures lie along the path and would damaged by an incision.  
       [0006] For these and other reasons there is a need for the present invention.  
       SUMMARY  
       [0007] The present invention provides a device for deflecting a probe. The device includes an outer tube having an opening at or near the distal end and an inner tube capable of sliding within the outer tube. The inner tube has material properties such that as the inner tube slides beyond the distal end of the outer tube, the inner tube follows a desired travel path. The distal end of the outer tube may be designed to encourage deflection of the inner tube as the inner tube moves beyond the distal end of the outer tube. This and many other embodiments are described in more detail below. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0008]FIG. 1A is an illustration of a cross-sectional view of one embodiment of a probe deflection device including a stylet inserted into a biological subject;  
     [0009]FIG. 1B is an illustration of a cross-sectional view of one embodiment of a smooth blunt tip formed when a stylet is fully inserted into an inner tube.  
     [0010]FIG. 1C is an illustration of a cross-sectional view of one embodiment of a probe embedded in a biological subject;  
     [0011]FIG. 2 is a cross-sectional illustration of one embodiment of a probe deflection device including a probe;  
     [0012]FIGS. 3A, 3B,  3 C, and  3 D are cross-sectional illustrations of an alternate embodiment of a probe deflection device;  
     [0013]FIG. 3E is an exploded perspective view of the proximal end of the alternate embodiment of the probe deflection device shown in FIGS. 3A, 3B,  3 C, and  3 D;  
     [0014]FIG. 4A is a partially cutaway perspective view of an alternate embodiment of a probe deflection device including a closure;  
     [0015]FIG. 4B is a side view of one embodiment of an outer tube showing a channel;  
     [0016]FIG. 4C is a perspective view of one embodiment of the closure shown in FIG. 4A showing the closure in the open state;  
     [0017]FIG. 4D is an illustration showing a cutaway top view of one embodiment of the closure shown in FIG. 4A illustrating the closure in the open state; and  
     [0018]FIG. 5 is a cross-sectional view one embodiment of a stylet including marker reservoir for use in connection with the probe deflection device of FIG. 4A. 
    
    
     DESCRIPTION  
     [0019] In the following detailed description of the invention reference is made to the accompanying drawings which form a part hereof, and in which is shown, by way of illustration, specific embodiments in which the invention may be practiced. In the drawings, like numerals describe substantially similar components throughout the several views. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the present invention.  
     [0020] The present invention provides a device for deflecting a probe during the insertion of the probe into a difficult to reach target area of a biological subject. The present invention also provides a method for accurately orienting a probe deflection device in a biological subject and a method for deflecting a probe in a biological subject.  
     [0021]FIG. 1A is an illustration of a cross-sectional view of one embodiment of probe deflection device  103  inserted into biological subject  105 . Biological subject  105  includes subthalamic nucleus  107  located in the interior of skull  109 . In this example, subthalamic nucleus  107  is a target area for probe deflection device  103 . In one embodiment, probe deflection device  103  includes outer tube  111  and inner tube  113 . Stylet  112  is shown inserted in inner tube  113 . Outer tube  111  is typically a cannula suitable for insertion into a human brain. Outer tube  111  is inserted into biological subject  105  through a hole in skull  109  using a stylet. The distal end of outer tube  111  is located at a distance of about 1.3 centimeters from an axial end of subthalamic nucleus  107 . The longitudinal axis of subthalamic nucleus  107  makes an angle  115  of about thirty degrees with longitudinal axis  117  of outer tube  111 .  
     [0022] Inner tube  113  is fabricated from a material having material properties that permit inner tube  113  to follow a desired travel path. For example, inner tube  113 , in one embodiment, is fabricated from a resilient material having a memory. To position inner tube  113  in subthalamic nucleus  107 , in one embodiment, a sequence of operations is performed. First, inner tube  113  is shaped to have a bend of about 150 degrees at a point located 1.3 centimeters from the distal end of outer tube  111 . Second, stylet  112  is inserted into inner tube  113 . Stylet  112  has a blunt tip such that when fully inserted into inner tube  113 , the inner tube distal end and the blunt tip form smooth blunt tip  119  as shown in FIG. 1B. Third, stylet  112  and inner tube  113  are inserted into outer tube  111  and pushed into subthalamic nucleus  107 .  
     [0023] To position probe  119 , shown in FIG. 2, in biological subject  105 , a second sequence of operations is performed. First, stylet  112  is extracted from inner tube  113 . Second, probe  119  is inserted into inner tube  113 , effectively replacing stylet  112  in FIG. 1A. This positions probe  119  along the longitudinal axis of subthalamic nucleus  107 . Third, inner tube  113  is retracted from the subthalamic nucleus into outer tube  111 . Finally, inner tube  113  and outer tube  111  are retracted together from biological subject  105 , leaving probe  119  embedded in biological subject  105  and subthalamic nucleus  107 , as shown in FIG. 1C.  
     [0024] Any imaging system capable of imaging a biological subject may be used in positioning probe deflection device  103 . For example, computerized tomography (CT) systems and magnetic resonance (MR) systems may be used in positioning deflection device  103  in biological subjects.  
     [0025]FIG. 2 is a cross-sectional illustration of one embodiment of probe deflection device  103  including probe  119 . Probe deflection device  103  includes outer tube  111  and inner tube  113 . In one embodiment illustrated in FIG. 2, inner tube  113  and probe  119  are shown extending beyond distal end  121  of outer tube  111 .  
     [0026] Outer tube  111 , after insertion into a biological subject, provides a path or channel from the surface of the biological subject to a target area. Outer tube  111  is preferably a tube, such as a cannula, suitable for insertion into a biological subject. The dimensions of outer tube  111  are selected to be compatible with the dimensions of probe  1119  selected for insertion into the biological subject. For example, for the insertion of a deep brain stimulator (DBS) having a diameter of about 0.050 inches, outer tube  111  has an inside diameter of about 0.074 inches and an outside diameter of about 0.088 inches. These dimensions permit the insertion of inner tube  113  and probe  119  into outer tube  111 . Outer tube  111 , in one embodiment, is fabricated from a magnetic resonance (MR) compatible material, such as titanium. Alternatively, outer tube  111  is fabricated from a ceramic material. Fabricating outer tube  111  from an MR compatible material makes outer tube  111  suitable for use in connection with MR imaging systems.  
     [0027] Inner tube  113  is slidable and rotatable within outer tube  111 , and when introduced into a biological subject, inner tube  113  extends from distal end  121  of outer tube  111  into the target area of the biological subject. The target area is the intended location in the biological subject for the distal end of probe  119 . Inner tube  113  is fabricated from a flexible material. In one embodiment, inner tube  113  is fabricated from a resilient material having a memory. Nitinol is one example of a material suitable for use in connection with the present invention. Fabricating inner tube  113  from a resilient material having a memory allows programming inner tube  113  prior to insertion into outer tube  111 . Preprogramming inner tube  113  involves bending inner tube  113  to a shape that defines a travel path for inner tube  113  as it emerges from the distal end of outer tube  111 . For example, if the desired travel path is 1.3 centimeters at an angle of thirty degrees from the longitudinal axis of outer tube  111 , then a one-hundred and fifty degree bend is formed in inner tube  113  at a point located about 1.3 centimeters from the distal end of inner tube  113 . In this way, after inner tube  113  is inserted in outer tube  111  such that the distal end of inner tube  113  extends about 1.3 centimeters beyond the distal end of inner tube  113 , inner tube  113  defines a deflected travel path for probe  119  of about thirty degrees from the longitudinal axis of outer tube  111 .  
     [0028] Inner tube  113 , in one embodiment, is inserted into a biological subject along with stylet  112  shown in FIG. 1A. To avoid cutting tissue in the biological subject, the distal end of inner tube  113  is shaped to provide a smooth surface when combined with the blunt tip stylet. The outer edges of the distal end of inner tube  113  are shaped by smoothing, rounding, or beveling. A smooth surface allows inner tube  113  to tunnel through the tissue of biological subject  105  without damaging the tissue.  
     [0029] A probe is a small object that can be inserted into a biological subject. Probes are not limited to a particular type of object. Probes are also not limited to a class of objects that perform a particular function. For example, leads, catheters, and fiber optic cables are all probes. Probe  119 , in one embodiment, is a thin strand of material. Any material capable of being extended to the distal end of inner tube  113  is capable of being inserted into a biological subject using probe deflection device  103 . In one embodiment, probe  119  is a deep brain stimulator (DBS). In an alternate embodiment, probe  119  is a fiber optic cable. In still another alternate embodiment, probe  119  is a conductive element combined with a fiber optic cable.  
     [0030] Probe  119 , in an alternate embodiment, is shaped to replace a stylet for the insertion of inner tube  113  into a biological subject. For probe  119  having sufficient stiffness to function as a stylet, the distal tip of probe  119  is shaped to provide a smooth surface when combined with inner tube  113 . Using probe  119  to replace a stylet reduces the number of steps and the time required to insert probe  119  into a biological subject.  
     [0031] Probe deflection device  103  is useful for inserting a probe into a target area of a biological subject when the target area is located off axis from the longitudinal axis of outer tube  111 . For example, FIG. 1 shows subthalamic nucleus  107  located off axis from longitudinal axis  117  of outer tube  111 . To provide a channel or path to the off axis target area, a bend is formed in inner tube  113 . In one embodiment, the bend is formed having an angle of about one-hundred and fifty degrees at a point about 1.3 centimeters from the end of the inner tube. Inner tube  113  is inserted in outer tube  111  such that the bend extends beyond the distal end of the outer tube  111 . Probe  119  is inserted in inner tube  113  such that probe  119  extends beyond the end of the outer tube  111  and into the target area. Finally, inner tube  113  is removed from outer tube  111  without deflecting probe  119 .  
     [0032] In an alternate embodiment, the method described above is modified when probe  119  is required to be precisely positioned in a target area. After insertion into the biological subject, the relationship between inner tube  113  and the target area is viewed using an imaging method, such as MR imaging. Any alignment error is identified by comparing the actual location of probe  119  with the expected location. If the alignment error exceeds a predetermined value, then inner tube  113  is at least partially retracted into outer tube  111 , rotated to correct the alignment error, and reinserted into the target area. If necessary, the MR image is examined after reinsertion to verify that inner tube  113  is properly aligned. The process is repeated as many times as necessary to achieve the proper alignment of probe  119  in the target area.  
     [0033]FIGS. 3A, 3B, and  3 C are cross-sectional illustrations of alternate embodiments of probe deflection device  103 . FIG. 3A shows a cross-sectional side view of stylet  301  inserted in outer tube  111 . In this embodiment, outer tube  111  is more oval than round and includes a curved distal tip  303  for deflecting inner tube  113  along a travel path located off the longitudinal axis of outer tube  111 . Curved distal tip  303  is preferably shaped such that when stylet  301  is fully inserted in outer tube  111 , the blunt tip of stylet  301  and curved distal tip  303  form a smooth blunt tip  305 . Smooth blunt tip  305  allows outer tube  111  to be inserted into a biological subject without damaging the tissue of the subject.  
     [0034]FIG. 3B shows a cross-sectional side view of inner tube  113  extending beyond curved distal tip  303  along an off-axis travel path. During the insertion of inner tube  113  into outer tube  111 , spacer  307  is positioned to force inner tube  113  against the curved section of curved distal tip  303 . Spacer  307  is preferably fabricated from an MR compatible material, such as titanium. Alternatively, spacer  307  is fabricated from a ceramic material. In one embodiment, spacer  307  has a crescent shape cross-sectional profile.  
     [0035]FIG. 3C shows a cross-sectional side view of inner tube  113  prior to the retraction of inner tube  113  into outer tube  111 . Spacer  307  is positioned to force inner tube  113  against the straight section of curved distal tip  303 . Forcing inner tube against the straight section of curved distal tip  303  permits the retraction of inner tube  113  into outer tube  111  without altering the position of a probe inserted into inner tube  113 .  
     [0036]FIG. 3D shows a cross-sectional side view of inner tube  113  retracted into outer tube  111  leaving probe  119  embedded in the target area.  
     [0037]FIG. 3E is an exploded perspective view of an alternate embodiment of the proximal end of probe deflection device  103  shown in FIGS. 3A, 3B, and  3 C. Outer tube  111  includes a pair of slots  309  cut into the proximal end of outer tube  111 . Inner tube  113  includes a pair of fins  311  extending out from the surface of inner tube  113 . As inner tube  113  slides into outer tube  111 , the pair of fins  311  fit into the pair of slots  309  and fix the rotational position of inner tube  113  within outer tube  111 . Fixing the rotation position of inner tube  113  with respect to outer tube  111  permits registration of the bend in inner tube  113  with curved distal tip  303  as shown in FIG. 3B. The present invention is not limited to a slotted rotational locking system. An mechanism capable of securing inner tube  113  within outer tube  111  is suitable for use in connection with the present invention.  
     [0038]FIG. 4A is a partially cutaway perspective view of an alternate embodiment of probe deflection device  103 . Probe deflection device  103  includes outer tube  111 , inner tube  113 , and closure  405  including actuator arm  406 . In one embodiment, outer tube  111 , inner tube  113 , closure  405 , and actuator arm  406  are fabricated from an MR-compatible material, such as titanium. Closure  405  includes exit hole  407  having center line  409  defining travel path  411  for inner tube  113 . Exit hole  407  of closure  405  may be covered by a thin outer sheath during the insertion of outer tube  111  into a biological subject. FIG. 4B is a side view of probe deflection device  103  showing the hidden lines of channel  409  that feed inner tube  113  into travel path  411 .  
     [0039]FIG. 4C is a perspective view of closure  405  of FIG. 4A showing closure  405  in the open position. As can be seen in FIG. 4D, actuator arm  405 , in one embodiment, is accessible at the proximal end of outer tube  403 . Actuator arm  406  controls the opening and closing of closure  405 , and as outer tube  403  is pulled away from closure  405 , closure  405  moves to an open position. Referring again to FIG. 4C, in the open position, closure  405  includes slot  415  which intersects exit hole  407 . Slot  415  provides an enhanced path for inner tube  113  during the retraction of inner tube  113  into outer tube  111 . The enhanced path enables the retraction of inner tube  113  into outer tube  111  without deflecting a probe introduced into inner tube  113 .  
     [0040]FIG. 5 is a cross-sectional side view of one embodiment of stylet  501  including imaging marker reservoir  503 . Stylet  501  is suitable for use in connection with the probe deflection device  103  of FIG. 4A. In one embodiment, stylet  501  is fabricated from a flexible material, such as plastic, that is compatible with imaging systems. Imaging marker reservoir  503  is located near the tip of stylet  501  and is shaped to indicate the orientation of stylet  503 . In one embodiment, imaging marker reservoir  503  has an elongated shape extending along the longitudinal axis of stylet  501 . Imaging marker reservoir  503  also encapsulates an imaging contrast media, such as an iodinated contrast media for use with a CT imaging system or a paramagnetic contract media, such as gadolinium for use with an MR imaging system. Stylet  501  is not limited to the embodiment described above. In an alternate embodiment, stylet  501  is a flexible catheter filled with an imaging contrast media.  
     [0041] Stylet  501  is useful in orienting exit hole  507  of closure  505 , as shown in FIG. 5A, in a biological subject. Outer tube  503  is inserted into the biological subject. Stylet  501  is inserted into outer tube  111  directly, or inserted into inner tube  113  before insertion into outer tube  111 . As the tip of stylet  501  reaches exit hole  407 , imaging marker reservoir  503  points along travel path  411 . Travel path  411  is identified by examining an image of stylet  501 . After identifying the projected travel path of stylet  501 , outer tube  403  is rotated to correct for any error detected in the image. If the detected error is less than a predetermined value, then the orientation of outer tube  111  is left unchanged.  
     [0042] Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of the present invention. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.