Robotized ultrasound examination offers on one hand more accuracy for the medical diagnostic and on the other hand a suitable assistance to radiologists. In the literature, very few researches deal with ultrasound image-based control of a medical robot holding the ultrasound probe. This paper presents a new visual servoing approach allowing the automatic guidance of the ultrasound probe. This technique is based on the modeling of the coupling between the ultrasound probe and egg shaped objects. The robotic task consists in reaching a desired image from an arbitrary initial position. The aim of this task is to assist the radiologist diagnostic by automatically moving the ultrasound probe in order to find the ultrasound image view of a tumour cross-section registered in a previous date. This work presents simulation results of the proposed ultrasound vision-based control scheme.