Abstract: A method for detecting a site of interest in a gastrointestinal tract, wherein the method includes sensing a length traveled by a sensor in a gastrointestinal tract from a reference point to a site of interest in the gastrointestinal tract.

Abstract: A method of stereotactic therapy. A frame including at least three markers that are imaged by a structural imaging modality such as CT or MRI, is rigidly secured to a patient and a structural image, of a target inside the patient including diseased tissue, and of a part of the frame including the markers, is acquired. A functional image, such as a SPECT image or a PET image, of the diseased tissue is acquired and registered with the structural image to produce a combined image. A stereotactic guide is rigidly attached to the frame and is used to guide an instrument such as a biopsy needle or a brachytherapy needle to the diseased tissue, with reference to the combined image.