Colin H Self1, Stephen Thompson2. 1. Diagnostic and Therapeutic Technologies, School of Clinical and Laboratory Sciences, Medical School, University of Newcastle upon Tyne, Newcastle upon Tyne, NE2 4HH, UK. Electronic address: C.H.Self@ncl.ac.uk. 2. Diagnostic and Therapeutic Technologies, School of Clinical and Laboratory Sciences, Medical School, University of Newcastle upon Tyne, Newcastle upon Tyne, NE2 4HH, UK.