Background: The proximity of the esophagus to the left atrium (LA) is of major concern during RF frequency ablation due to the possibility of a left atrial-esophageal fistula. While various imaging modalities are used for visualization and guidance, some differences have been noted in the proximity, thickness and other physical properties among the various modalities. We compared the differences in visualization of the esophageal walls and the location left atrium (LA) in relationship to the esophagus using MRI and CT.

Methods: Delayed gadolinium enhancement MRI (Siemens 1.5 T) scans were obtained on 18 patients to assess atrial anatomy. These images were the also underwent CT (Siemens Definition) images acquired within 3 to 5 months of the MRI acquisition. The distance from the esophagus to the posterior wall of the left atrium was compared on all patients. In addition, anterior and posterior esophageal wall thicknesses were also compared.

Results: The clarity of the esophagus and LA wall was better in MRI techniques. The anterior esophageal wall thicknesses using MRI and CT were 2.4±0.8 mm (mean±stdev) and 2.6±0.9 mm respectively. The average posterior wall thickness was 2.4±0.8 mm on MRI images and 2.7±.9 mm on CT. Esophageal proximity to the posterior wall of the left atrium using was 0.7±0.4 mm on MRI and 1±0.6 mm. None of the observed differences were statistically significant. It should also be noted that the differences approached the pixel resolution of both modalities.

Conclusion: The distances between the LA and CT were similar in both modalities. In general, the definition of the LA wall was clearer using MRI. Given the apparent equivalency, MRI may hold advantages over CT in determining patient anatomy prior to patient procedures due to its lack of ionizing radiation.