Self-expanding multi-channel rf receiver coil for high resolution intra-cardiac mri and method of use

Abstract

A system and method of use for a probe is disclosed that includes a self-expanding housing constructed to permit fluid flow therethrough and constructed for insertion into a subject to be imaged. A plurality of RF coils is attached to the housing to acquire MR data.

What is claimed is: 
     
         1 . A magnetic resonance (MR) imaging apparatus comprising:
 an intra-cardiac catheter comprising a self-expanding housing insertable into a subject to be imaged, the housing constructed to permit fluid flow therethrough and comprising a memory-type material moveable between an expanded position and a compressed position; and   a plurality of RF coils attached to the self-expanding housing and configured to acquire MR data, the intra-cardiac catheter configured to automatically expand the plurality of RF coils to an expanded position from a compressed position;   wherein a gap formed between the plurality of RF coils and the self-expanding housing is configured to increase RF sensitivity away from the intra-cardiac catheter.   
     
     
         2 . The MR imaging apparatus of  claim 1  wherein the gap is filled with an insulating dielectric material. 
     
     
         3 . The MR imaging apparatus of  claim 2  wherein the insulating dielectric material comprises heat-shrink tubing. 
     
     
         4 . The MR imaging apparatus of  claim 1  wherein the gap has a uniform thickness. 
     
     
         5 . The MR imaging apparatus of  claim 1  further comprising:
 a first layer of insulating material wrapped about the self-expanding housing and defining a thickness of the gap between the plurality of RF coils and the self-expanding housing; and 
 a second layer of insulating material coupling the plurality of RF coils to the self-expanding housing. 
 
     
     
         6 . The MR imaging apparatus of  claim 5  wherein the second layer of insulating material hermetically seals the plurality of RF coils. 
     
     
         7 . The MR imaging apparatus of  claim 1  wherein the self-expanding housing comprises at least one bar assembly having a pair of expandable bars. 
     
     
         8 . The MR imaging apparatus of  claim 7  comprising a first bar assembly having a first pair of expandable bars and a second bar assembly having a second pair of expandable bars, the second pair of expandable bars oriented orthogonal to the first pair of expandable bars. 
     
     
         9 . The MR imaging apparatus of  claim 7  further comprising an insulating material wrapped about each of the pair of expandable bars and defining a thickness of the gap. 
     
     
         10 . The MR imaging apparatus of  claim 7  wherein an RF coil is coupled to an edge of one bar of the pair of expandable bars that faces away from the other bar of the pair of expandable bars. 
     
     
         11 . The MR imaging apparatus of  claim 1  further comprising a tracking coil configured to actively track movement of the intra-cardiac catheter during MR imaging. 
     
     
         12 . The MR imaging apparatus of  claim 11  wherein the tracking coil is further configured to transmit tracking signals for gating data acquisition independent of expansion or compression of the plurality of RF coils. 
     
     
         13 . The MR imaging apparatus of  claim 1  further comprising at least one tuning capacitor connected to the plurality RF coils, the at least one tuning capacitor configured to tune the plurality RF coils. 
     
     
         14 . The MR imaging apparatus of  claim 1  further comprising a retractable sheath constructed to enclose the self-expanding housing during insertion into the subject and translation to a target tissue to be imaged and further constructed to be retracted by a user to allow the self-expanding housing to automatically expand when proximity to the target tissue is reached. 
     
     
         15 . A method of using an MR imaging device, the method comprising:
 inserting an intra-cardiac MR imaging device into a sheath configured for insertion into an imaging subject to be scanned, wherein the intra-cardiac MR imaging device comprises a pair of RF coils attached to an auto-expandable housing and separated therefrom by a gap defined by a thickness of heat-shrink tubing;   positioning the intra-cardiac MR imaging device within the imaging subject to be scanned; and   retracting the sheath to allow the auto-expandable housing to automatically expand and to cause the pair of RF coils to transition from a compressed position to an expanded position.   
     
     
         16 . The method of  claim 15  further comprising:
 acquiring tracking data from a MR tracking coil representing position and movement of the imaging device during imaging, the MR tracking coil positioned within the sheath when the pair of RF coils is in the compressed and expanded positions; and 
 gating data acquisition during imaging based on the tracking data to reduce imaging artifacts. 
 
     
     
         17 . The method of  claim 16  further comprising the step of receiving tracking feedback from the MR tracking coil while navigating to a target anatomy prior to retracting the sheath therefrom. 
     
     
         18 . The method of  claim 15  wherein retracting the sheath causes a pair of bar assemblies of the auto-expandable housing to automatically expand to a non-deformed position that permits fluid passage therethrough, each of the pair of bar assemblies comprising a pair of expandable bars. 
     
     
         19 . The method of  claim 18  wherein retracting the sheath causes one expandable bar of a respective bar assembly of the pair of bar assemblies to expand away from the other expandable bar of the respective bar assembly; and
 wherein an RF coil is coupled to an edge of the expandable bar that faces away from the other expandable bar. 
 
     
     
         20 . The method of  claim 15  wherein the pair of RF coils is electrically isolated from the imaging subject to be scanned via heat-shrink tubing disposed around the pair of RF coil elements.