Feasibility of real-time MR thermal dose mapping for predicting radiofrequency ablation outcome in the myocardium in vivo

Abstract

BackgroundClinical treatment of cardiac arrhythmia by radiofrequency ablation (RFA) currently lacks quantitative and precise visualization of lesion formation in the myocardium during the procedure. This study aims at evaluating thermal dose (TD) imaging obtained from real-time magnetic resonance (MR) thermometry on the heart as a relevant indicator of the thermal lesion extent.MethodsMR temperature mapping based on the Proton Resonance Frequency Shift (PRFS) method was performed at 1.5 T on the heart, with 4 to 5 slices acquired per heartbeat. Respiratory motion was compensated using navigator-based slice tracking. Residual in-plane motion and related magnetic susceptibility artifacts were corrected online. The standard deviation of temperature was measured on healthy volunteers (N = 5) in both ventricles. On animals, the MR-compatible catheter was positioned and visualized in the left ventricle (LV) using a bSSFP pulse sequence with active catheter tracking. Twelve MR-guided RFA were performed on three sheep in vivo at various locations in left ventricle (LV). The dimensions of the thermal lesions measured on thermal dose images, on 3D T1-weighted (T1-w) images acquired immediately after the ablation and at gross pathology were correlated.ResultsMR thermometry uncertainty was 1.5 °C on average over more than 96% of the pixels covering the left and right ventricles, on each volunteer. On animals, catheter repositioning in the LV with active slice tracking was successfully performed and each ablation could be monitored in real-time by MR thermometry and thermal dosimetry. Thermal lesion dimensions on TD maps were found to be highly correlated with those observed on post-ablation T1-w images (R = 0.87) that also correlated (R = 0.89) with measurements at gross pathology.ConclusionsQuantitative TD mapping from real-time rapid CMR thermometry during catheter-based RFA is feasible. It provides a direct assessment of the lesion extent in the myocardium with precision in the range of one millimeter. Real-time MR thermometry and thermal dosimetry may improve safety and efficacy of the RFA procedure by offering a reliable indicator of therapy outcome during the procedure.Electronic supplementary materialThe online version of this article (doi:10.1186/s12968-017-0323-0) contains supplementary material, which is available to authorized users.

Assessment of left ventricle magnetic resonance temperature stability in patients in the presence of arrhythmias

“…Previously, we developed and validated a processing pipeline in a large animal model. 15,16 Here, we transferred this pipeline to a clinical environment and applied it to patients as a complement to a routine clinical MR scan. The raw data were streamed in real-time to a separate workstation and the images were reconstructed and processed online using the Gadgetron framework.…”

“…Pacing of the heart during RFA may also help to improve the performance of thermometry, as suggested in a previous preclinical study. 16 Both retrospective strategies operate on different data streams and information. The G phase metric uses the phase image quality, while the arrhythmia rejection uses the RR interval duration.…”

“…Previous studies using using a similar thermometry pipeline showed that reliable temperature and thermal dose mapping could be achieved during RF ablation in sheep in vivo. 15,16 A second potential issue is related to small local contrast changes on magnitude images associated with temperature increase. These can be attributed to changes in T1 and/or reduction of signal intensity due to intravoxel dephasing in the case of nonuniform temperature distribution within a voxel.…”

MRI-guided pulmonary vein isolation for atrial fibrillation: what is good enough? An early health technology assessment

“…In animal experiments, MRI has been shown to be able to predict histological lesion size and even identify gaps in ablation lines 16. If MRI is able to assess lesion quality in real-time, or can help predict lesion durability, for example, using thermography,17 it seems plausible that MR guidance can improve effectiveness of catheter ablation.…”

MR-guided Cardiac Interventions

“…Small errors in registration mean that either a very broad region must be ablated or critical targets are left untouched, with consequent impact on safety, time and efficacy. [59][60][61] . The work of the Bordeaux group is particularly promising 61 , and implementation within a real-time interface appears to be feasible in the near future.…”