B-PO05-076 REPRODUCIBILITY OF LEFT ATRIAL ENDO AND EPICARDIAL WALL EXTRACTION FROM CTA

Abstract

LA wall thickness (LAWT) is a major determinant of lesion transmurality in AF ablation. Computed tomography angiography (CTA) provides sub-millimetric resolution allowing reliable 3D LAWT segmentation. To analyze the intra and inter-user reproducibility of 3D CTA LAWT segmentations. Three observers with different levels of expertise performed, using ADAS 3D, complete LAWT segmentation of CTA (0.5x0.5x0.6mm) once for thirty patients and twice for ten. The endocardial layer was generated by a semi-automatic threshold-based segmentation. The epicardial, by manual contouring of key transverse slices followed by automatic interpolation. Finally, the user adjusted the 3D reconstructions. LAWT, presented as a discretized color map, was generated assigning at each point of the endocardium the distance to the epicardium. Reproducibility was calculated as the point to surface distance between different analyses of the same patient. Pulmonary veins, LAA and mitral annulus were excluded from analysis. Endocardial segmentations were closer than 1mm in 99.38%±0.86 of the vertices for intra and 95.12%±5.07 for inter-user variability, with a mean distance between meshes of 0.17mm±0.08 and 0.30mm±0.18, respectively. For the epicardium, mean distances between meshes were 0.54mm±0.17 for intra and 0.72mm±0.16 for inter-observer, and closer than 1 mm in 82.38%±9.89 of points for intra and 77.68%±7.16 for inter-user analyses. Reproducibility improved significantly (p<0.05) with user expertise. Obtaining reliable CTA-derived 3D LAWT maps by means of endo and epicardial segmentation of the LA wall is feasible with high reproducibility.