Apparatus for detecting a discontinuity within a non-biological element located within a biological structure, the apparatus comprising: a microwave energy source; a first antenna coupled to the microwave energy source and arranged to transmit the microwave energy into the biological structure; a second antenna arranged to receive at least a portion of the transmitted microwave energy; an antenna carrier arranged to have the first and second antenna affixed thereon and including means for moving the first and second antenna with respect to the biological structure; and a signal processing unit coupled to the second antenna arranged to determine the phase and/or magnitude response of the received microwave energy as a function of the position of the antennas with respect to the biological structure and provide an indication of the location of the discontinuity within the non-biological element according to the phase and/or magnitude response.