Volume 14 Supplement 1
MRI guided electrophysiological intervention with a voltage-based electro-anatomic mapping system
© Tse et al; licensee BioMed Central Ltd. 2012
Published: 1 February 2012
MRI visualizes luminal & vessel-wall anatomy, and identifies edema & scar tissue, contributing to improved electrophysiological (EP) ablative procedures for treatment of Ventricular Tachycardia & Atrial Fibrillation. MRI-guided EP interventions will be performed for the foreseeable future partially in & outside MRI, due to the need for X-ray/Ultrasound-compliant devices. Electromagnetically tracked catheter procedures, today’s norm for most EP procedure phases; vascular navigation, Electro-Anatomic-Mapping (EAM, the diagnostic and therapeutic phases), can only be performed outside MRI. Separate MRI tracking is required in MRI, complicating EP procedures which require moving in & out of the bore [1, 2]. Continuous catheter tracking using a single system would allow registration-free EAM in & outside MRI. The goal was developing an MR-compatible St. Jude Medical (SJM) EnSite NavX (ESN) voltage-based tracking . ESN applies 5.8/8.0 kHz voltage bursts between 3 pairs of electrodes on the chest, detecting a catheter’s position , so a challenge for intra-MRI use is MR gradient ramps which interfere with ESN operation. Minimal MR Image Quality (IQ) reduction also needs to be insured, as well as <2oC patient-skin heating due to components in MRI.
Fig.1(5) shows simultaneous ESN & MR tracking of the dual ESN&MR-tracked catheter in the phantom, verifying the lack of interference between the 2 methods. 3 EAM & MRI imaging experiments were performed in swine, also equipped with sensors to measure temperature at the surface ESN electrodes. Fig.1(6) shows EAM during imaging where catheter tracking of 2 catheters (reference catheter in the Coronary Sinus (CS) & mapping catheter in the Left Atrium) was performed simultaneously on the ESN , with <5% positional error of the CS catheter relative to its position outside MRI. IQ Reduction was <5% in both SE & GRE, with tracking updated during 60-80% of sequence duration. TR elongation was required in TR<4ms sequences. Electrode temperature rise was <1oC with 4 Watt/kg SAR sequences. Surface burns did not occur.
An MR-compatible ESN system permits registration-free, minimal-heating, EAM for EP procedure in & outside MRI, with simultaneous imaging possible.
- Dukkipati : Circulation’08.
- Schmidt : Circulation A&E’09.
- Nademanee : JACC ’04.
- Early : Eur. Heart J ’06.
- Tse: ISMRM & SCMR ‘10&’11.
This article is published under license to BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.