Method and system for guiding a diagnostic or therapeutic instrument towards a target region inside the patient's body

A method for accessing a target in a patient's body with an instrument, the method comprising the steps of:

• (a) providing a guiding device having a frame to be secured to the patient and a stereotactic guide assembly, wherein the frame carries an indicator in the form of at least three markers;
• (b) rigidly securing said frame to the patient;
• (c) imaging at least a portion of the patient's body including the target, using a structural imaging modality, to produce a structural image of the at least portion of the patient's body, and acquiring a series of images to image all the markers and estimate their location in said structural image;
• (d) imaging the at least portion of the patient's body using a functional imaging modality to produce a functional image of the at least portion of the patient's body;
• and
• (e) registering the functional image with the structural image to produce a combined image,
• (f) rigidly attaching said stereotactic guide assembly to said frame, and
• (g) directing the instrument to the target, using the stereotactic guide, with reference to said markers as imaged in the combined image.