Comparison of 2D Echocardiography and Cardiac Cine MRI in the Assessment of Regional Left Ventricular Wall Thickness

The generation of kinematic models of the heart using 3D echocardiography (echo) can be difficult due to poor image contrast and signal dropout, particularly at the epicardial surface. 2D echo images generally have a better contrast-to-noise ratio compared to 3D echo images, thus wall thickness (WT) estimates from 2D echo may provide a reliable means to constrain model fits to 3D echo images. WT estimates were calculated by solving a pair of differential equations guided by a vector field, which is constructed from the solution of Laplace's equation on binary segmentations of the left ventricular myocardium. We compared 2D echo derived WT estimates against values calculated using gold-standard cardiac cine magnetic resonance imaging (MRI) to assess reliability. We found that 2D echo WT estimates were higher compared to WT values from MRI at end-diastole with a mean difference of 1.3mm (95% CI: 0.74-1.8 mm), 1.5mm (95% CI: 0.91-2.1mm) and 2.1mm (95% CI: 1.6-2.6mm) for basal, mid-ventricular and apical segments respectively. At end-systole, the WT estimates from MRI were higher compared to those derived from 2D echo with a mean difference of 2.6mm (95% CI: 2.0-3.1 mm), 2.1mm (95% CI: 1.5-2.7mm) and 1.1mm (95% CI: 0.49-1.7mm) for basal, mid-ventricular and apical segments, respectively. The quantitative WT comparison in this study will contribute to the ongoing efforts to better translate kinematic modelling analyses from gold-standard cardiac MRI to the more widely accessible echocardiography.