Three-dimensional left ventricular segmentation from magnetic resonance imaging for patient-specific modelling purposes

Aims: To propose a nearly automated left ventricular (LV) three-dimensional (3D) surface segmentation procedure, based on active shape modelling (ASM) and built on a database of 3D echocardiographic (3DE) LV surfaces, for cardiac magnetic resonance (CMR) images, and to test its accuracy for LV volumes computation compared with 'gold standard' manual tracings and discs-summation method. Methods and results: TheASMwas created based on segmented LVsurfaces (4D LVanalysis,Tomtec) from3DEdatasets of 205 patients. Then, it was applied to the cardiac magnetic resonance imaging short-axis (SAX) images stack of 12 consecutive patients. After proper realignment using two- and four-chambersCMRlong-axis views both as reference and for initializing LV apex and base (six points in total), theASMwas iteratively and automatically updated to match the information of all theSAXplanes contemporaneously, resulting in an endocardial LV 3D mesh from which volume was directly derived. The same CMR imageswere analysed by an experienced cardiologist to derive end-diastolic and end-systolic volumes. Linear correlation and Bland-Altman analyses were applied vs. the manual 'gold standard'. Active shape modelling results showed high correlations with manual values both for LV volumes (r² > 0.98) and ejection fraction (EF) (r² > 0.90), non-significant biases and narrow limits of agreement. Conclusion: The proposed method resulted in accurate detection of 3D LV endocardial surfaces, which lead to fast and reliable measurements of LV volumes and EF when compared with manual tracing of CMR SAX images. The segmented 3D mesh, including a realistic LV apex and base, could constitute a novel starting point for more realistic patient-specific finite element modelling.