The main goal of this paper is the description of a computer based system for medical applications to estimate the half-ellipsoid model that fits the left ventricle on its two phases of cardiac cycle: diastole and systole. Techniques for registration and rendering of ultrasound images will be presented using 2D freehand spatial calibrated echocardiography images in order to represent the 3D reconstructed data equivalent to the scanned volume. The 3D reconstruction will be used to estimate and measure parameters of the half-ellipsoid model fitted to the left ventricle.