A non-invasive method and apparatus for sensing relative blood flow to extremities, such as using photoelectric dermachromography to measure differential blood flow between extremities, for the purpose of diagnosing cardiovascular conditions, employs reflective colorimeters for performing comparative...http://www.google.ca/patents/US5365924?utm_source=gb-gplus-sharePatent US5365924 - Method and apparatus for non-invasive cardiovascular diagnosis
