1. A method for simulating an imaging process for an organ, said method comprising: retrieving from a memory a 3D volume model of said organ, said 3D volume model describing a 3D structure of said organ and a distribution of density within said 3D structure, said 3D structure representing a surface and internal features of said organ; generating a slice of said 3D model according to a position and an orientation of an imaging device, said slice including a cross-section of said surface and said internal features; generating a 3D surface model of said organ; distributing position points within said 3D surface model, each one of said points having a 3D spatial coordinate; associating a density value to each one of said position points, thereby obtaining a cloud of data points; storing said cloud of data points in said memory as said 3D volume model; rendering an image in accordance with said slice; and displaying said image.