A marker delivery device is described which has an obturator with an elongated shaft, an inner lumen, a proximal end, and a substantially sealed distal end. One or more tissue markers are deployed within the inner lumen of the elongated shaft of the obturator. Preferably, the tissue marker(s) is disposed within an inner lumen of a marker delivery tube which is disposed within the inner lumen of the elongated shaft of the obturator. The marker delivery tube has an opening for discharging the tissue markers into a body (e.g. biopsy) cavity. The distal tip of the marker delivery tube is configured to penetrate the substantially sealed distal end of the obturator so that tissue markers can be delivered while the obturator is in place within the body. Preferably, the obturator includes a detectable element capable of producing a relatively significant image signature during MRI.