In this work is studied the microwave imaging using an (Ultra-Wideband) UWB antenna, for detection of lesions in tissues as an alternative for the use of X-ray. This paper describes the necessary procedure to realize the target (tumor) detection using microwave imaging. Despite the difference in the materials of the target and the surrounding medium, the
procedure is the same as that used for phantoms that mimic the tissue and tumor. To simplify the understanding of the
procedure, the target is a metallic sphere and the environment is the air. The Kirchhoff migration algorithm was implemented for the image reconstruction.