Three-dimensional cardiac motion and strain estimation: A validation study in thick-walled univentricular phantoms

Automatic quantification of regional left ventricular function in volumetric ultrasound data remains challenging. Our lab previously presented such an approach based on elastic registration of subsequent volumes using a b-spline representation of the underlying transformation field. Good results were obtained for the assessment of global function, but a thorough validation on a regional level was still lacking. For this purpose, univentricular thick-walled cardiac phantoms were designed and mounted in an experimental setup to (i) locally assess strain accuracy against two reference methods: sonomicrometry and simulations through finite element modeling (FEM); and (ii) to assess whether regions containing stiff inclusions could be detected. Our method showed good correlations against sonomicrometry: R² was 0.95, 0.92 and 0.84 in the radial (R), longitudinal (L) and circumferential (C) direction respectively. Furthermore, the predicted apex-base gradients by FEM were best resolved in the circumferential direction. Finally, the discriminative power of our methodology was adequate to resolve inclusions up to 17mm in diameter, although enough stiffness difference with the surrounding tissue was needed.