Large scale left ventricular shape atlas using automated model fitting to contours

We demonstrate that large legacy databases of manually segmented cardiac MR images can be used to build a shape atlas based on 3D left-ventricular finite-element models. We make use of the Cardiac Atlas Project database to build an atlas of 2,045 asymptomatic cases from the MESA study. Manually placed anatomical landmarks on long-axis and short-axis magnetic resonance images were combined with manually drawn contours on the short axis images which were corrected for breath-hold mis-registration using an automated method. The contours were then fitted by the model using linear least squares optimisation. The fitting error was 0.5 ±0.4 mm at end-diastole and 0.5 ±0.6 mm at end-systole (mean ± std. dev.). Results were validated against 3D models created by experts in a sub-sample of 253 cases using manual breath-hold registration. The atlas surface error was 1.3 ±0.8 mm at end-diastole and 1.2 ±0.9 mm at end-systole. The end-diastolic volume error was 9.0 ±8.7 ml; the end-systolic volume error was 0.8 ±6.3 ml; and the mass error 5.9 ±12.9 g. These differences arose mainly at the base and apex because long-axis images were used in the validation models, but were only used in the automated models to define basal fiducial markers. All models were aligned and scaled, and finally analysed by principal component analysis. Significant differences were found in the first mode shape (sphericity) by gender, smoking, and hypertension.