Systems and methods are provided for identifying and locating a plurality of reflector markers implanted within a target tissue region within a patient's body. A probe is provided that is activated to transmit electromagnetic signals into the patient's body, receive reflected signals from the patient's body, and in synchronization with transmitting the electromagnetic signals, deliver light pulses into the patient's body. The markers reflector tags modulate reflected signals from the respective markers based on orthogonal code sequences opening and closing respective switches of the markers to modulate the reflective properties of the markers. The probe processes the return signals to separate the reflected signals based at least in part on the code sequences to identify and locate each of the plurality of reflector tags substantially simultaneously.
