Microwave antenna apparatus, systems, and methods for localizing markers or tissue structures within a body

A system for identifying or locating a tag implanted within a target tissue region within a patient's body, the tag comprising an energy converter configured to transform light pulses from an energy source into electrical energy, and a switch coupled to the energy converter, the system comprising:

• a probe comprising one or more antennas for transmitting electromagnetic signals into a patient's body and receiving electromagnetic signals from the patient's body, the probe further comprising a light source for delivering light pulses into a patient's body such that the light pulses cause the switch to open and close to modulate the electromagnetic signals received by the probe, the probe comprising a processor configured to analyze the modulated electromagnetic signals received by the probe to at least one of identify and locate the tag within the patient's body.

A method for localization of a target tissue region within a patient's body, comprising:

• implanting a tag within a patient's body;
• placing a probe adjacent the patient's body oriented towards the tag;
• activating the probe to a) transmit electromagnetic signals into the patient's body, b) receive electromagnetic signals from the patient's body, c) deliver light energy pulses into a patient's body such that the tag transforms the energy pulses into electrical energy to open and close a switch in the tag to modulate the electromagnetic signals received by the probe, and d) analyze the modulated signals to at least one of identify and locate the tag within the patient's body.