A system for tracking a patient is provided. The system can include a first reference frame coupled to a first portion of an anatomical structure. The system can include a second reference frame, which can be coupled to a second portion of the anatomical structure. The system can also include a first...http://www.google.com/patents/US20090281417?utm_source=gb-gplus-sharePatent US20090281417 - Method and apparatus for tracking a patient
