This report is my own composition and has not been accepted in any previous application for a degree. I have carried out the work, of which this is a record, at the Department of Bio-Medical Physics and Bio-Engineering, University of Aberdeen and the Radiotherapy Department of Aberdeen Royal Infirmary during the summer of 1996. All verbatim extracts have been distinguished by quotation marks and the sources of all information specifically acknowledged.

Jonathan A. Buzzard

August 1996