Systems for identifying and locating reflectors using orthogonal sequences of reflector switching

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

• a probe comprising one or more antennas for transmitting electromagnetic signals into the patient's body and receiving reflected signals from the patient's body, the probe further comprising a light source for delivering light pulses into the patient's body synchronized with the electromagnetic signals;
• and
• a plurality of markers sized for implantation within the patient's body, each marker comprising:
• a) an energy converter configured to transform light from the light source into electrical energy;
• b) a clock circuit coupled to the energy converter to identify frames and clock pulses from the light pulses;
• c) one or more elongate members coupled to a switch to provide one or more marker antennas;
• d) a sequence generator coupled to the clock circuit to generate a code sequence based, at least in part, on the frames identified by the clock circuit and the identified clock pulses, the sequence generator coupled to the switch to open and close the switch to modulate electromagnetic signals from the probe reflected by the respective marker of the plurality of markers based on the code sequence;
• and
• e) a power harvesting block coupled to the energy converter to harvest the electrical energy from the light to operate electrical components of the respective marker of the plurality of markers,
• wherein code sequences generated by sequence generators of the plurality of markers are orthogonal to one another, wherein the code sequences cause each of the plurality of markers to open and close the switch of each marker in an orthogonal pattern relative to the other markers of the plurality of markers across a series of clock pulses, the probe further comprising a processor configured to analyze the reflected signals to identify and locate each of the plurality of markers,
• wherein the light source is configured to generate the light pulses in spaced apart frames, each frame comprising a predetermined set of N light pulses separated from one another, wherein the frames are separated by an extended period of light transmission longer than a lighted duration of each of the N light pulses, wherein the light from the light source is on during the extended period of light transmission,
• wherein the power harvesting block harvests the electrical energy from the energy converter during the extended period of light transmission to provide the electrical energy to the sequence generator for generating the code sequence, and
• wherein the clock circuit of each marker is configured to detect a frame event by identifying a first light pulse of the predetermined set of N light pulses after the extended period of light transmission, wherein the frame event indicates to each of the plurality of markers a beginning of each frame, wherein the clock circuit of each of the plurality of markers resets the sequence generator of the respective marker of the plurality of markers to an initial state upon detection of the frame event to generate the respective code sequence to open and close the switch a predetermined number of times not more than N, such that initial states of the code sequences generated by the plurality of markers are aligned at the beginning of each frame, and
• wherein each switch opens and closes the switch according to the respective code sequence during the N light pulses, and the N light pulses corresponded to the clock pulses across which the code sequence occurs.