Catheter navigation within an MR imaging device

Abstract

A method of magnetically manipulating a medical device within a body part of a human patient in conjunction with MR imaging includes applying a navigating magnetic field with magnets from the MR imaging device, and changing the magnetic moment of the medical device to change the orientation of the medical device within the body part

1 . A method of navigating a medical device having a variable magnetic moment within an operating region within a patient, using an MR imaging device, the method comprising: 
 applying a static magnetic field to the operating region with an external magnet of an MR imaging device;    creating temporary magnetic moments in the medical device to change the orientation of the medical device with respect to the static magnetic field, and orient the medical device in a selected direction within the operating region.    
   
   
       2 . The method according to  claim 1  further comprising the step of varying the direction of the static magnetic field applied to the operating region by the external magnet of an MR imaging device to change the orientation of the medical device.  
   
   
       3 . The method according to  claim 1  wherein the medical device comprises at least one electromagnetic coil, and wherein the step of creating temporary magnetic moments in the medical device comprises energizing the at least one electromagnetic coil.  
   
   
       4 . The method according to  claim 1  wherein the MR imaging device is used to image the operating region in the patient's body between navigations.  
   
   
       5 . The method according to  claim 1  in which the medical device comprises at least one set of three current carrying coils, and the step of creating temporary magnetic moments in the medical device comprises apply current to one or more of the current carrying coils  
   
   
       6 . The method according to  claim 5  wherein there are at least two sets of three current carrying coils.  
   
   
       7 . The method according to  claim 1  in which the medical device comprises at least one set of three current carrying coils, and wherein the coils are used to receive signals during MR imaging to determine at least one of the location and orientation of the medical device.  
   
   
       8 . The method according to  claim 1  in which the medical device comprises at least one set of three current carrying coils, and wherein the coils are used to transmit and/or receive signals during MR imaging to enhance imaging adjacent the medical device.  
   
   
       9 . The method according to  claim 5  wherein the coils are mutually orthogonal.  
   
   
       10 . The method according to  claim 5  further comprising actively removing heat from the medical device generated by the current carrying coils.  
   
   
       11 . The method according to  claim 10  wherein heat is removed by circulating a cooling medium with the medical device.  
   
   
       12 . The method according  claim 10  wherein heat is removed using thermoelectric devices.  
   
   
       13 . The method according to  claim 10  wherein heat is removed using a heat pipe.  
   
   
       14 . A method of navigating a medical device within an operating region in the body of a patient, the medical device having at least one coil therein, the method comprising: 
 establishing a navigating magnetic field in the operating region with an MR imaging device outside of the patient's body;    selectively energizing the at least one coil in the medical device to create a magnetic moment in the medical device and creating a torque tending to align the magnetic moment of the magnetic medical device with the applied magnetic field.    
   
   
       15 . The method according to  claim 14  further comprising varying the direction and/or intensity of the applied magnetic field applied by the MR imaging device to orient the medical device  
   
   
       16 . The method according to  claim 14  wherein the step of selectively energizing the at least one coil comprises applying electrical energy in pulses to the at least one coil in the medical device.  
   
   
       17 . The method according to  claim 16  wherein the medical device is flexible and has a characteristic recovery time in which the device recovers from being flexed, and wherein the time between pulses in less than the characteristic recovery time of the medical device.  
   
   
       18 . In a method of navigating a medical device by applying a static magnetic field and selectively changing the magnetic moment of the medical device to change the orientation of the medical device, a method of turning the medical device on a plane perpendicular to local applied field direction in two steps comprising applying a magnet current to the medical device to bend the medical device out of the plane of the desired turn and subsequently applying a magnet moment to the medical device to cause the medical device to turn back into the plane of the desired turn, in the desired orientation.  
   
   
       19 . A system for navigating a medical device within an MRI consisting of a medical device containing at least one set of three orthogonal current carrying coils, power supplies for energizing said coils, a computer for controlling said power supplies, and an MRI images of the local environment of the coils, said images used by an operator to guide the movements of said medical device through a computer interface.  
   
   
       20 . The system of  claim 19  in which local visualization of tissues is additionally provided to guide navigation.  
   
   
       21 . The system of  claim 20  in which visualization is optical.  
   
   
       22 . The system of  claim 20  in which visualization is through an ultrasonic image.  
   
   
       23 . The system of  claim 19  in which said coils are energized with pulses of currents, the root-mean-square values of which exceed direct current levels that overheat the catheter.  
   
   
       24 . The system of  claim 19  in which currents are applied to the coils to produce oscillatory or periodic movements of the catheter tip.  
   
   
       25 . A method for rotating a catheter tip containing a variable magnetic moment about the direction of an external magnetic field with which the moment interacts, the method consisting of directing the magnetic moment vector in a series of directions which successively rotate the catheter tip out of and into the plane perpendicular to the field direction.  
   
   
       26 . A method of navigating an elongate medical device within an operating region in the body of a patient, the medical device having a proximal end, a distal end, and at least one coil adjacent the distal end, the method comprising: 
 introducing the distal end of the medical device into the operating region in the patient's body;    establishing a navigating magnetic field in the operating region with a magnet of an MR imaging system;    selectively energizing the at least one coil adjacent the distal end of the elongate medical device to create a magnetic moment at the distal end of the elongate medical device to turn the distal end of the elongate medical device in the desired direction.    
   
   
       27 . The method according to  claim 26  further comprising varying the direction and or intensity of the navigating magnetic field applied by the MR imaging device to orient the elongate medical device.  
   
   
       28 . The method according to  claim 26  wherein the step of selectively energizing the at least one coil comprises applying electrical energy in pulses to the at least one coil in the medical device.  
   
   
       29 . The method according to  claim 26  wherein the elongate medical device is flexible, and has a characteristic recovery time in which the device returns to its normal configuration from a deflected configuration, and wherein the at least one coil is energized at a pulse rate faster than the characteristic recovery time of the elongate medical device  
   
   
       30 . The method according to  claim 29  wherein the coil is pulsed to retain the coils below a temperature that is harmful to tissue.  
   
   
       31 . The method according to  claim 29  wherein the at least one coil is pulsed to retain a temperature below about 45° C.  
   
   
       32 . The method according to  claim 29  wherein the at least one coil is pulsed to retain a balance between the heat generated in the coil and the heat conducted from the coil by the flow of body fluids past the coils.  
   
   
       33 . The method according to  claim 26  wherein there are at least two coils adjacent the distal end of the magnetic medical device.  
   
   
       34 . The method according to  claim 33  wherein there are at least three coils adjacent the distal end of the magnetic medical device.  
   
   
       35 . The method according to  claim 26  wherein there are three coils spaced around the circumference of the magnetic medical device.  
   
   
       36 . The method according to  claim 26  wherein at least one coil extends around the circumference of the magnetic medical device.  
   
   
       37 . The method according to  claim 26  wherein the coils are used to locate the magnetic medical device.