Markers, probes, and related systems and methods are provided for localizing locations within a patient's body, e.g., a lesion within a breast. The marker includes an energy converter e.g., one or more photodiodes, for transforming light energy striking the marker into electrical energy, a storage device coupled to the energy converter for storing the electrical energy, a threshold element that closes a switch when the electrical energy reaches a predetermined threshold to discharge the electrical energy and cause the antenna to transmit a radio frequency (RF) signal. The system includes a probe that transmits light into the patient's body and a processor that correlate the frequency of the RF signals to a distance from the probe to the marker.
