System for marking a location for treatment within the gastrointestinal tract

A system for the delivery of a drug to a gastrointestinal tract, the system comprising:

• a capsule sized to pass through an intestinal tract of a patient;
• an acoustic transmitter coupled to the capsule, the acoustic transmitter configured to transmit an acoustic tracking signal between the capsule and a location external to a patient's body to track a linear position of the capsule within the patient's intestinal tract as the capsule is passing through the intestinal tract;
• a reference signal generator coupled to the capsule, the reference signal generator configured to generate and transmit a reference signal for identifying a time of tracking signal origination;
• a drug delivery device configured to deliver drug to the intestinal tract;
• and
• a controller configured to actuate the drug delivery device as the capsule is passing through the intestinal tract at a desired position in the intestinal tract based on the capsule position within the intestinal tract.