Magnetic resonance probes

Abstract

A magnetic resonance probe may include a plurality of center conductors, at least some center conductors including a conductive core and an insulator disposed at least partially about the core along at least a portion of the core, a first dielectric layer disposed at least partially about the plurality of center conductors in a proximal portion of the probe, an outer conductive layer at least partially disposed about the first dielectric layer, and a plurality of electrodes, at least one electrode being coupled to one of the center conductors and disposed at least partly on a probe surface.

1. A magnetic resonance probe, comprising:
 a plurality of center conductors, at least some center conductors;
 including a conductive core and an insulator disposed at least partially about the core along at least a portion of the core; and 
 forming a first pole of a magnetic resonance dipole antenna; 
 
 a first dielectric layer disposed at least partially about the plurality of center conductors in a proximal portion of the probe; 
 an outer conductive layer at least partially disposed about the first dielectric layer and forming a second pole of the magnetic resonance dipole antenna; and 
 a plurality of electrodes, at least one electrode being coupled to one of the center conductors and disposed at least partly on a probe surface. 
 
     
     
       2. The probe of  claim 1 , further comprising a second dielectric layer at least partially disposed about the outer conductive layer. 
     
     
       3. The probe of  claim 1 , further comprising a lubricious coating at least partially disposed about the outer conductive layer. 
     
     
       4. The probe of  claim 1 , wherein the plurality of center conductors are magnetic resonance-compatible. 
     
     
       5. The probe of  claim 1 , wherein at least one insulator has a thickness equal to or less than about 100 microns. 
     
     
       6. The probe of  claim 1 , wherein at least some center conductors comprise at least one of a magnetic resonance compatible material, a super elastic material, copper, silver-copper, gold, silver, platinum, iridium, MP35N, tantalum, titanium, Nitinol, L605, gold-platinum-iridium, gold-copper-iridium, and gold-platinum. 
     
     
       7. The probe of  claim 1 , further comprising a connection to a high-pass filter through which the probe is coupleable to a magnetic resonance scanner. 
     
     
       8. The probe of  claim 1 , further comprising a connection to a low-pass filter through which the probe is coupleable to at least one of an electrophysiological recording system, a tissue stimulator, and an ablation energy source. 
     
     
       9. The probe of  claim 1 , further comprising:
 a ribbon disposed in a distal portion of the probe; and 
 a pull wire coupled to the ribbon. 
 
     
     
       10. The probe of  claim 9 , wherein the pull wire is disposed in a lumen in the probe. 
     
     
       11. The probe of  claim 1 , further comprising a coolant lumen. 
     
     
       12. The probe of  claim 1 , further comprising a plurality of radially expandable arms, wherein at least one electrode is at least partly disposed on one arm. 
     
     
       13. The probe of  claim 12 , further comprising a tubing that is slideably displaceable between at least two positions to transition the expandable arms between a retracted position and an expanded position. 
     
     
       14. The probe of  claim 12 , further comprising a tubing that is slideably displaceable between at least two positions to transition the expandable arms between a retracted position and an expanded position. 
     
     
       15. The probe of  claim 1 , further comprising an ablation electrode disposed at a distal tip of the probe. 
     
     
       16. The probe of  claim 1 , further comprising an interface circuit coupled to the probe, the interface circuit including:
 a signal splitter that directs a signal received from the probe to a magnetic resonance pathway and an electrophysiology pathway; 
 a high-pass filter disposed in the magnetic resonance pathway; 
 a low-pass filter disposed in the electrophysiology pathway; 
 a connector disposed in the magnetic resonance pathway for connecting to a magnetic resonance scanner; and 
 a connector disposed in the electrophysiology pathway for connecting to at least one of a tissue stimulator, a biopotential recording system, and an ablation energy source. 
 
     
     
       17. The probe of  claim 1 , wherein the probe has an outer diameter of less than about 15 French. 
     
     
       18. The probe of  claim 1 , wherein the probe has an outer diameter of less than about 4 French. 
     
     
       19. The probe of  claim 1 , further comprising a connector portion disposed at a proximal end of the probe, the connector portion including:
 an outer conductor contact coupled to the outer conductive layer; 
 extended sections of at least some center conductors extending proximally beyond the outer conductor contact, at least one extended section having a center conductor contact coupled to one center conductor; and 
 an insulated area interposed between the outer conductor contact and the at least one center conductor contact. 
 
     
     
       20. The probe of  claim 1 , defining at least one lumen. 
     
     
       21. The probe of  claim 20 , further comprising a pull wire disposed in the lumen, coupled to a distal portion of the probe, and longitudinally displaceable. 
     
     
       22. The probe of  claim 1 , wherein at least one center conductor is coupled to a distal portion of the probe and longitudinally displaceable. 
     
     
       23. The probe of  claim 1 , wherein all of the center conductors collectively form the first pole of the magnetic resonance dipole antenna. 
     
     
       24. A method of performing a magnetic resonance-guided procedure, comprising:
 placing a subject in a magnetic resonance scanner; 
 identifying a target site in the subject using data about the subject obtained from the scanner; 
 introducing into the patient subject, a magnetic resonance probe as defined by  claim 1 ; 
 advancing the probe to the target site; and 
 performing the procedure using the magnetic resonance probe. 
 
     
     
       25. The method of  claim 24 , wherein the target site is located in the subject's brain, and the probe is introduced by employing a stereotactic frame. 
     
     
       26. The method of  claim 24 , wherein the target site comprises at least one of the subject's thalamus, globus pallidum internus, and subthalamic nucleus. 
     
     
       27. The method of  claim 24 , further comprising anchoring at least one of the probe's electrodes in the subject. 
     
     
       28. The method of  claim 24 , further comprising electrically connecting at least one of the probe's electrodes to a pacemaker. 
     
     
       29. The method of  claim 24 , wherein the target site is located in the subject's heart. 
     
     
       30. The method of  claim 29 , wherein at least one probe electrode is an RF ablation electrode, and the method further comprises ablating heart tissue. 
     
     
       31. The method of  claim 30 , wherein ablating comprises creating a plurality of linear ablations in the subject's left and/or right atrium. 
     
     
       32. A combined magnetic resonance imaging and electrophysiology probe, comprising:
 a plurality of center conductors, at least some center conductors including a conductive core and an insulator disposed at least partially about the core along at least a portion of the core, the insulator having a thickness equal to or less than about 100 microns; 
 a first dielectric layer disposed at least partially about the plurality of center conductors in a proximal portion of the probe; 
 an outer conductive layer at least partially disposed about the first dielectric layer; 
 a second dielectric layer disposed at least partially about the outer conductive layer; and 
 a plurality of electrodes, at least one electrode coupled to one of the center conductors and disposed at least partly on the probe surface. 
 
     
     
       33. A system for magnetic resonance imaging, comprising:
 a magnetic resonance probe, including:
 a plurality of center conductors, at least some center conductors:
 including a conductive core and an insulator disposed at least partially about the core along at least a portion of the core; and 
 forming a first pole of a magnetic resonance dipole antenna; 
 
 a first dielectric layer disposed at least partially about the plurality of center conductors in a proximal portion of the probe; 
 an outer conductive layer disposed at least partially about the first dielectric layer and forming a second pole of the magnetic resonance dipole antenna; and 
 a plurality of electrodes, at least one electrode coupled to one of the center conductors and disposed at least partly on the probe surface; and 
 
 a interface electrically coupled to the probe, the interface including:
 a signal splitter that directs a signal received from the probe to a magnetic resonance pathway and an electrophysiology pathway; 
 a high-pass filter disposed in the magnetic resonance pathway; 
 a low-pass filter disposed in the electrophysiology pathway; 
 a connector disposed in the magnetic resonance pathway for connecting to a magnetic resonance scanner; and 
 a connector disposed in the electrophysiology pathway for connecting to at least one of a tissue stimulator, a electrophysiological recording system, and an ablation energy source. 
 
 
     
     
       34. A magnetic resonance (MR) probe, comprising:
 a plurality of center conductors residing closely spaced together in a medial portion of an MR probe body, each conductor having a conductive core and an insulator disposed over the conductive core;   a first dielectric layer residing over the plurality of center conductors;   a conductive shield layer residing over the first dielectric layer; and   a plurality of electrodes, at least one attached to a respective one of the plurality of conductors,   wherein the plurality of center conductors define a first pole and the conductive shield defines a second pole of a loopless magnetic resonance dipole antenna.   
     
     
       35. A probe according to claim 34, wherein the insulator has a thickness equal to or less than about 100 microns. 
     
     
       36. A probe according to claim 34, wherein the closely spaced plurality of center conductors permit electrical coupling of magnetic resonance energy at a frequency above 10 MHz to thereby define a single electrical entity to define an antenna that receives MR signals. 
     
     
       37. A probe according to claim 34, wherein the closely spaced plurality of center conductors inhibit coupling of low-frequency energy between the center conductors below 0.5 MHz. 
     
     
       38. A probe according to claim 34, wherein the probe is devoid of reactive elements between center conductors proximate the electrodes. 
     
     
       39. A probe according to claim 37, further comprising a decoupling circuit in communication with the center conductors and outer conductive layer whereby the antenna is decoupled from RF transmitted by the MRI system so that tissue adjacent the probe electrodes do not receive undue RF energy deposition at the MRI system operating frequency during the transmit operation of the MRI system. 
     
     
       40. A probe according to claim 38, wherein the loopless antenna defines an MRI visualization length that extends from a portion of the shield and the conductors extending outwardly there from about a distal portion of the probe, such that the first pole has a length between about 3-15 cm. 
     
     
       41. A probe according to claim 40, wherein the electrodes can detect EP signals independent of the transmit/receive operation of the MRI system. 
     
     
       42. A probe according to claim 41, wherein tissue stimulation or ablation energy can be delivered through one or more of the electrodes independent of the transmit/receive operation of the MRI system. 
     
     
       43. A probe according to claim 34, wherein some of the center conductors contact each other. 
     
     
       44. A probe according to claim 43, wherein the insulator is a thin insulator. 
     
     
       45. A probe according to claim 34, wherein the probe body has a flexible distal end whereby the probe body is deflectable. 
     
     
       46. A probe according to claim 34, wherein the plurality of conductors with an outer insulator are at least four insulated wires that connect to a respective one of at least four spaced apart electrodes. 
     
     
       47. A probe according to claim 34, further comprising an interface circuit in communication with the center conductors, wherein the interface circuit has a signal splitter defining an MR pathway with a high pass filter and an EP pathway with a low pass filter, the signal splitter in communication with the plurality of conductors to define a simultaneous EP recording and MR imaging catheter. 
     
     
       48. A probe according to claim 34, wherein at least one of the center conductors defines a combination pull wire and center conductor. 
     
     
       49. A probe according to claim 34, wherein the probe electrodes are sized and configured for deep brain stimulation and recording, and wherein the plurality of center conductors cooperate with the probe conductive shield to function as a magnetic resonance receive antenna. 
     
     
       50. A probe according to claim 34, wherein the probe has a deflectable flexible distal tip portion holding at least some of the electrodes, wherein the probe is a cardiac EP probe with the electrodes configured to ablate cardiac tissue.