- Oral presentation
- Open Access
Acute and chronic cardiac radio frequency ablation lesion visualisation using magnetic resonance imaging
© Knowles et al; licensee BioMed Central Ltd. 2009
- Published: 28 January 2009
- Visualisation Method
- Radio Frequency Ablation
- Late Enhancement
- Ablation Lesion
- Healthy Myocardium
The use of electro-anatomical mapping systems (EAMS) for catheter guidance and ablation point recording is widespread for the treatment of atrial arrhythmias using radio frequency ablation (RFA). Also, the evolution of RFA lesions over time may be an important factor in the reoccurrence of arrhythmias. In this study, we use late enhancement (LE) magnetic resonance imaging (MRI) as a tool to measure RFA lesions and present a novel visualisation method to represent this information in an intuitive way. This allows the validation of the in-vivo accuracy of EAMS and the examination of the evolution of RFA lesions from the acute to the chronic timescales.
Six patients with either atrial fibrillation (AF, 5 cases) or flutter (AFL, 1 case) underwent RFA. Prior to the procedure, each patient underwent a MRI examination that included administration of a double dose of Gd-DTPA contrast agent followed by MR angiography (MRA) and a T2-prepared balanced-SSFP (bSSFP) sequence. Approximately 20 minutes after contrast administration, a free-breathing, cardiac triggered, 3D LE scan was performed. The scan was inversion recovery-prepared with a resolution of 1.3 × 1.3 × 2 mm3 and TR/TE/á of 6.2 ms/3.0 ms/30°. Signal was acquired using Turbo Field Echo (TFE) with a 100 ms window and a low-high K-space ordering. Inversion time was determined from a Look-Locker scan. All scans were performed using a 1.5 T Philips Achieva MR scanner. During the procedure, ablation points from various EAMS (NavX, CARTO, XMR-EAMS ) were recorded. Post ablation, the patient returned to the MR scanner for a further examination including the bSSFP and LE scans. Approximately 6 weeks later, the patient returned for follow-up MR imaging. Offline, an atrial surface model was generated from the MRA scan, and was transformed into the coordinate system of each of the LE images. Integration of the LE image along the normal vector at each of the surface vertices was performed. This integral was used to colour code the surface model. Areas of LE were defined by integral values higher than the mean of the healthy myocardium plus three standard deviations. EAMS data from NavX and CARTO were exported. The EAMS-derived and the MR-derived cardiac surfaces were registered using a landmark-based registration. Using this registration, the EAMS lesions were transformed onto the MR-derived cardiac surface and repositioned at the nearest vertex.
We have presented a technique based on LE MRI coupled to a novel visualisation method to measure RFA lesions. This technique has been applied to six patients undergoing RFA and used to assess the accuracy of EAMS and to monitor the evolution of lesions over time. We envisage that such an approach will have potential benefit in understanding the causes of arrhythmia reoccurrence and also in the guidance of redo ablations.