A kinematic model for simulating physiological left ventricular deformation patterns - a tool for evaluation of myocardial strain imaging

In this study, we have developed a kinematic model of the left ventricle (LV) with physiological wall thickening, short and long axes deformation and torsion. This was done by approximating the LV as a thick-walled ellipsoid. Since the model is described analytically, it is possible to calculate the velocity vector, the Lagrangian strain tensor and the deformation gradient tensor everywhere within the wall. The true strain can then be obtained in any direction from the Lagrangian strain tensor, whereas "Doppler-based" strain rate (and thereby strain) can be obtained in the beam direction from the deformation gradient tensor. LV diameter, wall thickness and base-to-apex length were measured in 15 healthy individuals, averaged to obtain a representative cardiac cycle and used as input to the model. The deformation patterns of the model were in qualitative agreement with published observation. The model enables researchers to study geometrical artifacts in strain imaging, such as angle dependence and the use of fixed versus moving sample volumes. Furthermore, the model can simulate the motion of a set of point scatterers, and thereby give input to ultrasound simulators for evaluation of strain imaging artifacts.