  We describe an efficient rigorous model suitable for calculating the
properties of finite metamaterial samples, which takes into account the
discrete structure of metamaterials based on capacitively loaded ring
resonators. We illustrate how this model applies specifically to a metamaterial
lens employed in magnetic resonant imaging. We show that the discrete model
reveals the effects which can be missed by a continuous model based on
effective parameters, and that the results are in close agreement with the
experimental data.
