Method and system for navigating a catheter probe

Abstract

A system for navigating a catheter probe through a body cavity includes a sensing coil affixed to a distal end of the probe. Magnetic fields are projected into the body cavity to induce voltage signals in the sensing coil that are sufficient to describe the orientation and position of the probe. A set of magnetic coils each generates a substantially uniform field in a single respective dimension. The orientation angles of the sensing coil may be determined from known values of the unidirectional fields and the measured induced voltage signals. Gradient magnetic fields with components in two dimensions are projected into the body cavity to induce another group of voltage signals. The geometrical intersection of constant voltage surfaces developed by certain gradient fields that produce the measured induced voltage signals is a set of lines on which the catheter is located. The point of intersection of such lines yields the positional coordinates.

What is claimed is:  
     
       1. A method of determining the location of a magnetically-sensitive, electrically conductive sensing coil affixed to a distal end of a catheter probe partially inserted into a body cavity within a navigational domain, comprising the steps of:
 inducing within said sensing coil a set of orientation signal values each representative of an orientation of said sensing coil and independent of a position of said sensing coil;    determining the orientation of said sensing coil using said induced orientation signal values;    inducing within said sensing coil a set of positional signal values each representative of the position of said sensing coil; and    determining the position of said sensing coil using said positional signal values and said determined orientation.    
     
     
       2. The method as recited in  claim 1 , wherein the step of inducing said set of orientation signal values comprises the steps of:
 generating from outside said body a series of magnetic fields each penetrating at least said navigational domain and characterized substantially by a principal magnetic component in one axial dimension and relatively smaller magnetic components in two other axial dimensions.    
     
     
       3. The method as recited in  claim 1 , wherein the step of inducing said set of positional signal values comprises the steps of:
 generating from outside said body a series of magnetic fields each penetrating at least said navigational domain and characterized substantially by two principal gradient magnetic components in respective axial dimensions and a relatively smaller magnetic components in a third axial dimension.    
     
     
       4. The method as recited in  claim 3 , wherein said generating step further includes the steps of:
 generating said fields to provide a plurality of constant signal surfaces for the sensing coil such that an intersection between two such surfaces with components in the same axial dimensions produces a line along which said sensing coil is located;    wherein said two such surfaces are identified from among said plurality of constant signal surfaces by their ability to induce one of said positional signal values.    
     
     
       5. The method as recited in  claim 4 , further comprises the steps of:
 weighting each line in accordance with a signal strength of said corresponding constant signal surface; and    determining an intersection of said weighted lines.    
     
     
       6. The method as recited in  claim 5 , wherein six constant signal surfaces are generated to produce three intersection lines. 
     
     
       7. A system for determining the location of a magnetically-sensitive, electrically conductive sensing coil affixed to a distal end of a catheter probe partially inserted into a body cavity within a navigational domain, comprising:
 first transmit means for projecting into said navigational domain magnetic energy that is sufficient to induce signal values within said sensing coil representative of an orientation of said sensing coil and independent of the position of said sensing coil;    second transmit means for projecting into said navigational domain magnetic energy that is sufficient to induce signal values within said sensing coil representative of the position of said sensing coil; and    analysis means, coupled to said first transmit means and said second transmit means, for determining the position and orientation of said sensing coil from said induced signal values.    
     
     
       8. A system for determining the location of a magnetically-sensitive, electrically conductive sensing coil affixed to a distal end of a catheter probe partially inserted into a body cavity within a navigational domain, comprising:
 first signal-inducing means for inducing within said sensing coil orientation signals that are representative of the orientation of said sensing coil;    analysis means, coupled to said first signal-inducing means, for determining the orientation of said sensing coil using said induced orientation signals and independent from a position of said sensing coil;    second signal-inducing means for inducing within said sensing coil position signals that are representative of the position of said sensing coil; and    analysis means, coupled to said second signal-inducing means, for determining the position of said sensing coil using said determined orientation and said induced position signals.    
     
     
       9. The system as recited in  claim 8 , wherein the first signal-inducing means comprises:
 field generation means for successively generating magnetic field patterns projected into said navigational domain, each characterized substantially by a principal magnetic field component in one direction and relatively smaller magnetic components in two other directions.    
     
     
       10. The system as recited in  claim 9 , wherein said field generation means comprises a set of magnetic coils. 
     
     
       11. The system as recited in  claim 10 , wherein said magnetic coils are disposed in a planar top of an examination deck upon which a patient is disposed during a surgical procedure. 
     
     
       12. The system as recited in  claim 10 , wherein said magnetic coils are disposed in a planar top and in rail members edge supported by said planar top for an examination deck upon which a patient is disposed during a surgical procedure. 
     
     
       13. The system as recited in  claim 8 , wherein the second signal-inducing means comprises:
 field generation means for successively generating magnetic field patterns each characterized by a first and second gradient field component in respective directions and a relatively smaller third component in another direction.    
     
     
       14. The system as recited in  claim 13 , wherein the field generation means comprises a magnetic coil assembly. 
     
     
       15. A method of determining the location of a magnetically-sensitive, electrically conductive sensing coil affixed to a distal end of a catheter probe partially inserted into a body cavity within a navigational domain, comprising the steps of:
 defining the location of said sensing coil with a set of independent location parameters; and    sequentially generating within said navigational domain a sequence of magnetic fields for inducing within said sensing coil a corresponding sequence of induced signals each defined by an induced signal expression that functionally relates said induced signal to certain ones of said location parameters, such that said set of location parameters is determinable by sequentially solving individual signal expression groups each including certain ones of said induced signal expressions and sufficient to represent a subset of said location parameters.    
     
     
       16. The method as recited in  claim 15 , wherein said sequence of magnetic fields comprises:
 a series of unidirectional magnetic fields each characterized substantially by a principal magnetic field component in one direction and relatively smaller magnetic components in two other directions; and    a series of gradient magnetic fields each characterized by a first and second gradient field component in respective directions and a relatively smaller third component in another direction.    
     
     
       17. The method as recited in  claim 16 , wherein said signal expression groups include:
 an orientation group including induced signal expressions each functionally related to a respective one of said unidirectional magnetic fields and an orientation of said sensing coil, and independent of a position of said sensing coil; and    a position group including induced signal expressions each functionally related to a respective one of said gradient magnetic fields, the orientation of said sensing coil, and the position of said sensing coil.    
     
     
       18. The method as recited in  claim 17 , wherein the step of sequentially solving said individual signal expression groups includes the steps of:
 initially solving the induced signal expressions of said orientation group; and    next solving the induced signal expressions of said position group.    
     
     
       19. A system for determining the location of a magnetically-sensitive, electrically conductive sensing coil affixed to a distal end of a catheter probe partially inserted into a body cavity within a navigational domain, comprising:
 means for defining the location of said sensing coil with a set of independent location parameters; and    field generation means for sequentially generating within said navigational domain a sequence of magnetic fields for inducing within said sensing coil a corresponding sequence of induced signals each defined by an induced signal expression that functionally relates said induced signal to certain ones of said location parameters, such that said set of location parameters is determinable by sequentially solving individual signal expression groups each including certain ones of said induced signal expressions and sufficient to represent a subset of said location parameters.    
     
     
       20. The system as recited in  claim 19 , wherein said sequence of magnetic fields comprises:
 a series of unidirectional magnetic fields each characterized substantially by a principal magnetic field component in one direction and relatively smaller magnetic components in two other directions; and    a series of gradient magnetic fields each characterized by a first and second gradient field component in respective directions and a relatively smaller third component in another direction.    
     
     
       21. The system as recited in  claim 20 , wherein said signal expression groups include:
 an orientation group including induced signal expressions each functionally related to a respective one of said unidirectional magnetic fields and an orientation of said sensing coil, and independent of a position of said sensing coil; and    a position group including induced signal expressions each functionally related to a respective one of said gradient magnetic fields, the orientation of said sensing coil, and the position of said sensing coil.    
     
     
       22. The system as recited in  claim 21 , wherein said field generation means comprises:
 analysis means for solving the induced signal expressions of said orientation group; and    analysis means for solving the induced signal expressions of said position group.    
     
     
       23. A method of determining the location of a magnetically- sensitive, electrically conductive sensing coil in a navigational domain within a body, comprising the steps of:      inducing within said sensing coil a set of orientation signal values each representative of an orientation of said sensing coil and independent of a position of said sensing coil;        determining the orientation of said sensing coil using said induced orientation signal values;        inducing within said sensing coil a set of positional signal values each representative of the position of said sensing coil by generating from outside said body a series of magnetic fields each penetrating at least said navigational domain and characterized substantially by two principal gradient magnetic components in respective axial dimensions and a relatively smaller magnetic component in a third axial dimension;        generating said fields to provide a plurality of constant signal surfaces for the sensing coil such that an intersection between two such surfaces with components in the same axial dimensions produces a line along which said sensing coil is located;        wherein said two such surfaces are identified from among said plurality of constant signal surfaces by their ability to induce one of said positional signal values; and,        determining the position of said sensing coil using said positional signal values and said determined orientation.     
     
     
       24. The method as recited in  claim 23 , wherein the step of inducing said set of orientation signal values comprises the steps of:
   generating from outside said body a series of magnetic fields each penetrating at least said navigational domain and characterized substantially by a principal magnetic component in one axial dimension and relatively smaller magnetic components in two other axial dimensions.     
     
     
       25. The method as recited in  claim 23 , further comprises the steps of:
   weighting each line in accordance with a signal strength of said corresponding constant signal surface; and        determining an intersection of said weighted lines.     
     
     
       26. The method as recited in  claim 25 , wherein six constant signal surfaces are generated to produce three intersection lines. 
     
     
       27. A system for determining the location of a magnetically- sensitive, electrically conductive sensing coil in a navigational domain within a body, comprising:      first signal - inducing means for inducing within said sensing coil orientation signals that are representative of the orientation of said sensing coil, including field generation means for successively generating magnetic field patterns projected into said navigational domain, wherein said field generation means comprises a set of magnetic coils and said magnetic coils are disposed in a planar top of an examination deck upon which a patient is disposed during a surgical procedure;        analysis means, coupled to said first signal - inducing means, for determining the orientation of said sensing coil using said induced orientation signals and independent from a position of said sensing coil;        second signal - inducing means for inducing within said sensing coil position signals that are representative of the position of said sensing coil; and,        analysis means, coupled to said second signal - inducing means, for determining the position of said sensing coil using said determined orientation and said induced position signals.     
     
     
       28. The system as recited in  claim 27 , wherein each of the magnetic field patterns projected into said navigational domain is characterized substantially by a principal magnetic field component in one direction and relatively smaller magnetic components in two other directions. 
     
     
       29. The system as recited in  claim 27 , wherein the second signal- inducing means comprises:      field generation means for successively generating magnetic field patterns each characterized by a first and second gradient field component in respective directions and a relatively smaller third component in another direction.     
     
     
       30. The system as recited in  claim 29 , wherein the field generation means comprises a magnetic coil assembly. 
     
     
       31. A system for determining the location of a magnetically- sensitive, electrically conductive sensing coil in a navigational domain within a body, comprising:      first signal - inducing means for inducing within said sensing coil orientation signals that are representative of the orientation of said sensing coil, including field generation means for successively generating magnetic field patterns projected into said navigational domain, wherein said field generation means comprises a set of magnetic coils and said magnetic coils are disposed in a planar top and in rail members edge supported by said planar top for an examination deck upon which a patient is disposed during a surgical procedure;        analysis means, coupled to said first signal - inducing means, for determining the orientation of said sensing coil using said induced orientation signals and independent from a position of said sensing coil;        second signal - inducing means for inducing within said sensing coil position signals that are representative of the position of said sensing coil; and,        analysis means, coupled to said second signal - inducing means, for determining the position of said sensing coil using said determined orientation and said induced position signals.     
     
     
       32. A system for determining the location of a magnetically- sensitive, electrically conductive sensing coil affixed to a distal end of a catheter probe partially inserted into a body cavity within a navigational domain, comprising:      first signal - inducing means for inducing within said sensing coil orientation signals that are representative of the orientation of said sensing coil, including field generation means for successively generating magnetic field patterns projected into said navigational domain, wherein said field generation means comprises a set of magnetic coils disposed in a planar top of an examination deck upon which a patient is disposed during a surgical procedure;        analysis means, coupled to said first signal - inducing means, for determining the orientation of said sensing coil using said induced orientation signals and independent from a position of said sensing coil;        second signal - inducing means for inducing within said sensing coil position signals that are representative of the position of said sensing coil; and        analysis means, coupled to said second signal - inducing means, for determining the position of said sensing coil using said determined orientation and said induced position signals.     
     
     
       33. The system as recited in  claim 32 , wherein the second signal- inducing means comprises:      field generation means for successively generating magnetic field patterns each characterized by a first and second gradient field component in respective directions and a relatively smaller third component in another direction.     
     
     
       34. The system as recited in  claim 33 , wherein the field generation means comprises a magnetic coil assembly. 
     
     
       35. A system for determining the location of a magnetically- sensitive, electrically conductive sensing coil affixed to a distal end of a catheter probe partially inserted into a body cavity within a navigational domain, comprising:      first signal - inducing means for inducing within said sensing coil orientation signals that are representative of the orientation of said sensing coil, including field generation means for successively generating magnetic field patterns projected into said navigational domain, wherein said field generation means comprises a set of magnetic coils disposed in a planar top and in rail members edge supported by said planar top for an examination deck upon which a patient is disposed during a surgical procedure;        analysis means, coupled to said first signal - inducing means, for determining the orientation of said sensing coil using said induced orientation signals and independent from a position of said sensing coil;        second signal - inducing means for inducing within said sensing coil position signals that are representative of the position of said sensing coil; and        analysis means, coupled to said second signal - inducing means, for determining the position of said sensing coil using said determined orientation and said induced position signals.